Evaluation of Solute Clusters Associated with Bake-Hardening Response in Isothermal Aged Al-Mg-Si Alloys Using a Three-Dimensional Atom Probe

NASA Astrophysics Data System (ADS)

Aruga, Yasuhiro; Kozuka, Masaya; Takaki, Yasuo; Sato, Tatsuo

2014-12-01

Temporal changes in the number density, size distribution, and chemical composition of clusters formed during natural aging at room temperature and pre-aging at 363 K (90 °C) in an Al-0.62Mg-0.93Si (mass pct) alloy were evaluated using atom probe tomography. More than 10 million atoms were examined in the cluster analysis, in which about 1000 clusters were obtained for each material after various aging treatments. The statistically proven records show that both number density and the average radius of clusters in pre-aged materials are larger than in naturally aged materials. It was revealed that the fraction of clusters with a low Mg/Si ratio after natural aging for a short time is higher than with other aging treatments, regardless of cluster size. This indicates that Si-rich clusters form more easily after short-period natural aging, and that Mg atoms can diffuse into the clusters or possibly form another type of Mg-Si cluster after prolonged natural aging. The formation of large clusters with a uniform Mg/Si ratio is encouraged by pre-aging. It can be concluded that an increase of small clusters with various Mg/Si ratios does not promote the bake-hardening (BH) response, whereas large clusters with a uniform Mg/Si ratio play an important role in hardening during the BH treatment at 443 K (170 °C).

Global survey of star clusters in the Milky Way. VI. Age distribution and cluster formation history

NASA Astrophysics Data System (ADS)

Piskunov, A. E.; Just, A.; Kharchenko, N. V.; Berczik, P.; Scholz, R.-D.; Reffert, S.; Yen, S. X.

2018-06-01

Context. The all-sky Milky Way Star Clusters (MWSC) survey provides uniform and precise ages, along with other relevant parameters, for a wide variety of clusters in the extended solar neighbourhood. Aims: In this study we aim to construct the cluster age distribution, investigate its spatial variations, and discuss constraints on cluster formation scenarios of the Galactic disk during the last 5 Gyrs. Methods: Due to the spatial extent of the MWSC, we have considered spatial variations of the age distribution along galactocentric radius RG, and along Z-axis. For the analysis of the age distribution we used 2242 clusters, which all lie within roughly 2.5 kpc of the Sun. To connect the observed age distribution to the cluster formation history we built an analytical model based on simple assumptions on the cluster initial mass function and on the cluster mass-lifetime relation, fit it to the observations, and determined the parameters of the cluster formation law. Results: Comparison with the literature shows that earlier results strongly underestimated the number of evolved clusters with ages t ≳ 100 Myr. Recent studies based on all-sky catalogues agree better with our data, but still lack the oldest clusters with ages t ≳ 1 Gyr. We do not observe a strong variation in the age distribution along RG, though we find an enhanced fraction of older clusters (t > 1 Gyr) in the inner disk. In contrast, the distribution strongly varies along Z. The high altitude distribution practically does not contain clusters with t < 1 Gyr. With simple assumptions on the cluster formation history, the cluster initial mass function and the cluster lifetime we can reproduce the observations. The cluster formation rate and the cluster lifetime are strongly degenerate, which does not allow us to disentangle different formation scenarios. In all cases the cluster formation rate is strongly declining with time, and the cluster initial mass function is very shallow at the high mass end.

Masturbation Experiences of Swedish Senior High School Students: Gender Differences and Similarities.

PubMed

Driemeyer, Wiebke; Janssen, Erick; Wiltfang, Jens; Elmerstig, Eva

Research about masturbation tends to be limited to the assessment of masturbation incidence and frequency. Consequently, little is known about what people experience connected to masturbation. This might be one reason why theoretical approaches that specifically address the persistent gender gap in masturbation frequency are lacking. The aim of the current study was to explore several aspects of masturbation in young men and women, and to examine possible associations with their social backgrounds and sexual histories. Data from 1,566 women and 1,452 men (ages 18 to 22) from 52 Swedish senior high schools were analyzed. Comparisons between men and women were made regarding incidence of and age at first masturbation, the use of objects (e.g., sex toys), fantasies, and sexual functioning during masturbation, as well as about their attitudes toward masturbation and sexual fantasies. Cluster analysis was carried out to identify similarities between and differences within the gender groups. While overall more men than women reported experience with several of the investigated aspects, cluster analyses revealed that a large proportion of men and women reported similar experiences and that fewer experiences are not necessarily associated with negative attitudes toward masturbation. Implications of these findings are discussed in consideration of particular social backgrounds.

Female cluster headache in the United States of America: what are the gender differences? Results from the United States Cluster Headache Survey.

PubMed

Rozen, Todd D; Fishman, Royce S

2012-06-15

To present results from the United States Cluster Headache Survey regarding gender differences in cluster headache demographics, clinical characteristics, diagnostic delay, triggers, treatment response and personal burden. Very few studies have looked at the gender differences in cluster headache presentation. The United States Cluster Headache Survey is the largest study of cluster headache sufferers ever completed in the United States and it is also the largest study of female cluster headache patients ever presented. The total survey consisted of 187 multiple choice questions which dealt with various issues related to cluster headache including: demographics, clinical characteristics, concomitant medical conditions, family history, triggers, smoking history, diagnosis, treatment response and personal burden. A group of questions were specifically targeted to female cluster headache patients. The survey was placed on a website from October to December 2008. For all survey responders the diagnosis of cluster headache needed to be made by a neurologist but there was no validation of the headache diagnosis by the authors. 1134 individuals completed the survey (816 male, 318 female). Key Points that define the differences between female and male cluster headache include: a. Age of onset: women develop cluster headache at an earlier age than men and are more likely to develop a second peak of cluster headache onset after 50 years of age. b. Family history: woman cluster headache sufferers are more likely to have a family history of both cluster headache and migraine and have an increased familial risk of Parkinson's disease. c. Comorbid conditions: female cluster headaches sufferers are significantly more likely to experience depression and have asthma than males. d. Aura issues: aura with cluster headache is equally common in both sexes, but aura duration is shorter in women. Women are much more likely to experience sensory, language and brainstem auras. e. Pain location: cluster headache pain is typically retro-orbital in location in both sexes but women are significantly more likely to experience cluster headache pain in the jaw, cheek and ear than men. f. Associated symptoms: women with cluster headache develop more “migrainous” associated symptoms than men, especially nausea and they are also more likely to have self-injurious behavior than men. g. Triggers: women with cluster headache are much less likely to have alcohol trigger a headache, but are significantly more likely to have “migrainous” triggers for their cluster headaches than men. h. Smoking issues: women are much less likely to have a smoking history than male cluster headache sufferers, more likely to have never smoked prior to cluster headache onset. i. Cycle issues: spring and fall are the most common time to start a cluster headache cycle in both sexes. Women are statistically significantly less likely to start a cluster headache cycle in the months of October–December than men. Women have more attacks per day and higher pain intensity nighttime attacks than men. j. in regard to acute treatment women statistically were less response to sumatriptan injectable and nasal spray than men, but statistically more likely to respond to inhaled lidocaine. There was equal efficacy in the sexes to inhaled oxygen but slower response in women. For preventive treatment no significant gender differences were noted, but overall women were less responsive to almost all preventives than men. k. Diagnostic delay: there remains a significant diagnostic delay for cluster headache patients in both sexes but women were more likely to be diagnosed after 10 years of symptom onset than males and significantly fewer women were diagnosed correctly at an initial physician visit than men. l. Female specific issues: cluster headache does not appear to be influenced by menses or menopause but 50% of the survey responders stated their headaches improved with pregnancy. Cluster headache does not appear to alter fertility rates in female cluster headache sufferers. m. Personal burden: cluster headache causes significantly more personal burden in women than men with more loss of employment and/or need of disability, as well as more homebound days. Overall women and men with cluster headache have a similar presentation but there are some distinct differences that have been suggested in smaller studies of female cluster headache that we have now verified, while some of our study conclusions have not been shown previously. One major limitation to the study is a lack of validation of diagnosis. A substantial false positive cluster headache diagnosis rate, especially in females, cannot be excluded by the study methods utilized. Copyright © 2012 Elsevier B.V. All rights reserved.

Effects of symptom clusters and depression on the quality of life in patients with advanced lung cancer.

PubMed

Choi, S; Ryu, E

2018-01-01

People with advanced lung cancer experience later symptoms after treatment that is related to poorer psychosocial and quality of life (QOL) outcomes. The purpose of this study was to identify the effect of symptom clusters and depression on the QOL of patients with advanced lung cancer. A sample of 178 patients with advanced lung cancer at the National Cancer Center in Korea completed a demographic questionnaire, the M.D. Anderson Symptom Inventory-Lung Cancer, the Center for Epidemiological Studies Depression Scale, and the Functional Assessment of Cancer Therapy-General scale. The most frequently experienced symptom was fatigue, anguish was the most severe symptom-associated distress, and 28.9% of participants were clinically depressed. Factor analysis was used to identify symptom clusters based on the severity of patients' symptom experiences. Three symptom clusters were identified: treatment-associated, lung cancer and psychological symptom clusters. The regression model found a significant negative impact on QOL for depression and lung cancer symptom cluster. Age as the control variable was found to be significant impact on QOL. Therefore, psychological screening and appropriate intervention is an essential part of advanced cancer care. Both pharmacological and non-pharmacological approaches for alleviating depression may help to improve the QOL of lung cancer patients. © 2016 John Wiley & Sons Ltd.

A Separable Two-Dimensional Random Field Model of Binary Response Data from Multi-Day Behavioral Experiments.

PubMed

Malem-Shinitski, Noa; Zhang, Yingzhuo; Gray, Daniel T; Burke, Sara N; Smith, Anne C; Barnes, Carol A; Ba, Demba

2018-04-18

The study of learning in populations of subjects can provide insights into the changes that occur in the brain with aging, drug intervention, and psychiatric disease. We introduce a separable two-dimensional (2D) random field (RF) model for analyzing binary response data acquired during the learning of object-reward associations across multiple days. The method can quantify the variability of performance within a day and across days, and can capture abrupt changes in learning. We apply the method to data from young and aged macaque monkeys performing a reversal-learning task. The method provides an estimate of performance within a day for each age group, and a learning rate across days for each monkey. We find that, as a group, the older monkeys require more trials to learn the object discriminations than do the young monkeys, and that the cognitive flexibility of the younger group is higher. We also use the model estimates of performance as features for clustering the monkeys into two groups. The clustering results in two groups that, for the most part, coincide with those formed by the age groups. Simulation studies suggest that clustering captures inter-individual differences in performance levels. In comparison with generalized linear models, this method is better able to capture the inherent two-dimensional nature of the data and find between group differences. Applied to binary response data from groups of individuals performing multi-day behavioral experiments, the model discriminates between-group differences and identifies subgroups. Copyright © 2018. Published by Elsevier B.V.

Did a stellar fly-by shape the planetary system around Pr 0211 in the cluster M44?

NASA Astrophysics Data System (ADS)

Pfalzner, Susanne; Bhandare, Asmita; Vincke, Kirsten

2018-02-01

Out of the 3000 exoplanets detected so far, only 14 planets are members of open clusters: one of them is the exoplanet system around Pr 0211 in the cluster M44. The system consists of at least 2 planets, and the outer planet moves on a highly eccentric orbit at 5.5 AU. One hypothesis is that a close fly-by of a neighbouring star was responsible for the eccentric orbit. We test this hypothesis. First we determined the type of fly-by that would lead to the observed parameters, and then we used this result to determine the history of such fly-bys in simulations of the early dynamics in an M44-like environment. We find that although very close fly-bys are required to obtain the observed properties of Pr 0211c, such fly-bys are relatively common as a result of the high stellar density and longevity of the cluster. Such close fly-bys are most frequent during the first 1‑2 Myr after cluster formation, corresponding to a cluster age ≤3 Myr. During the first 2 to 3 Myr, about 6.5% of stars experience a fly-by that would lead to such a small system-size as observed for Pr 0211 or even smaller. It is unclear whether planets generally form on such short timescales. However, after this time, the close fly-by rate is still 0.2‑0.5 Myr‑1, which means that 12‑20% of stars would experience such close fly-bys over this time span when we extrapolate the situation to the age of M44. Our simulations show that the fly-by scenario is a realistic option for the formation of eccentricity orbits of the planets in M44 (Wang et al. 2015). The occurrence of such events is relatively high, leading to the expectation that similar systems are likely common in open clusters in general.

Chronology of the halo globular cluster system formation.

NASA Astrophysics Data System (ADS)

Salaris, M.; Weiss, A.

1997-11-01

Using up-to-date stellar models and isochrones we determine the age of 25 galactic halo clusters. The clusters are distributed into four groups according to metallicity. We measure the absolute age of a reference cluster in each group, and then find the relative ages of the other clusters relative to this one. This combination yields the most reliable results. We find that the oldest cluster group on average is 11.8+/-0.9Gyr or 12.3+/-0.3Gyr old, depending on whether we include Arp 2 and Rup 106. The average age of all clusters is about 10.5Gyr. Questions concerning a common age for all clusters and a relation between metallicity and age are addressed. The groups of lower metallicity appear to be coeval, but our results indicate that globally the sample has an age spread, and age and metallicity are correlated but not with a simple linear relation.

Core-halo age gradients and star formation in the Orion Nebula and NGS 2024 young stellar clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Getman, Konstantin V.; Feigelson, Eric D.; Kuhn, Michael A.

2014-06-01

We analyze age distributions of two nearby rich stellar clusters, the NGC 2024 (Flame Nebula) and Orion Nebula cluster (ONC) in the Orion molecular cloud complex. Our analysis is based on samples from the MYStIX survey and a new estimator of pre-main sequence (PMS) stellar ages, Age{sub JX} , derived from X-ray and near-infrared photometric data. To overcome the problem of uncertain individual ages and large spreads of age distributions for entire clusters, we compute median ages and their confidence intervals of stellar samples within annular subregions of the clusters. We find core-halo age gradients in both the NGC 2024more » cluster and ONC: PMS stars in cluster cores appear younger and thus were formed later than PMS stars in cluster peripheries. These findings are further supported by the spatial gradients in the disk fraction and K-band excess frequency. Our age analysis is based on Age{sub JX} estimates for PMS stars and is independent of any consideration of OB stars. The result has important implications for the formation of young stellar clusters. One basic implication is that clusters form slowly and the apparent age spreads in young stellar clusters, which are often controversial, are (at least in part) real. The result further implies that simple models where clusters form inside-out are incorrect and more complex models are needed. We provide several star formation scenarios that alone or in combination may lead to the observed core-halo age gradients.« less

MASSCLEANage—Stellar Cluster Ages from Integrated Colors

NASA Astrophysics Data System (ADS)

Popescu, Bogdan; Hanson, M. M.

2010-11-01

We present the recently updated and expanded MASSCLEANcolors, a database of 70 million Monte Carlo models selected to match the properties (metallicity, ages, and masses) of stellar clusters found in the Large Magellanic Cloud (LMC). This database shows the rather extreme and non-Gaussian distribution of integrated colors and magnitudes expected with different cluster age and mass and the enormous age degeneracy of integrated colors when mass is unknown. This degeneracy could lead to catastrophic failures in estimating age with standard simple stellar population models, particularly if most of the clusters are of intermediate or low mass, like in the LMC. Utilizing the MASSCLEANcolors database, we have developed MASSCLEANage, a statistical inference package which assigns the most likely age and mass (solved simultaneously) to a cluster based only on its integrated broadband photometric properties. Finally, we use MASSCLEANage to derive the age and mass of LMC clusters based on integrated photometry alone. First, we compare our cluster ages against those obtained for the same seven clusters using more accurate integrated spectroscopy. We find improved agreement with the integrated spectroscopy ages over the original photometric ages. A close examination of our results demonstrates the necessity of solving simultaneously for mass and age to reduce degeneracies in the cluster ages derived via integrated colors. We then selected an additional subset of 30 photometric clusters with previously well-constrained ages and independently derive their age using the MASSCLEANage with the same photometry with very good agreement. The MASSCLEANage program is freely available under GNU General Public License.

Ages of intermediate-age Magellanic Cloud star clusters

NASA Technical Reports Server (NTRS)

Flower, P. J.

1984-01-01

Ages of intermediate-age Large Magellanic Cloud star clusters have been estimated without locating the faint, unevolved portion of cluster main sequences. Six clusters with established color-magnitude diagrams were selected for study: SL 868, NGC 1783, NGC 1868, NGC 2121, NGC 2209, and NGC 2231. Since red giant photometry is more accurate than the necessarily fainter main-sequence photometry, the distributions of red giants on the cluster color-magnitude diagrams were compared to a grid of 33 stellar evolutionary tracks, evolved from the main sequence through core-helium exhaustion, spanning the expected mass and metallicity range for Magellanic Cloud cluster red giants. The time-dependent behavior of the luminosity of the model red giants was used to estimate cluster ages from the observed cluster red giant luminosities. Except for the possibility of SL 868 being an old globular cluster, all clusters studied were found to have ages less than 10 to the 9th yr. It is concluded that there is currently no substantial evidence for a major cluster population of large, populous clusters greater than 10 to the 9th yr old in the Large Magellanic Cloud.

Psychometric properties of the Adolescent Dissociative Experiences Scale in a sample of Italian adolescents.

PubMed

Schimmenti, Adriano

2016-01-01

The purpose of this study was to examine the psychometric properties of the Italian translation of the Adolescent Dissociative Experiences Scale (A-DES). A sample of 1,806 high-school students between the ages of 13 and 18 years, recruited in 6 Italian cities, completed the A-DES. The A-DES showed high internal consistency, excellent item-to-scale homogeneity, good split-half reliability, and a single-factor structure. The scores of the Italian adolescents were comparable to those found in previous research with the measure. No gender differences were found in mean A-DES scores, but boys and girls showed different patterns of responses on A-DES items. Age differences were also found, with 13- and 18-year-old students scoring higher on the measure than the other participants. A cluster analysis showed that participants could be consistently grouped into 2 clusters of low- and high-dissociative adolescents. This study supports the A-DES as a reliable and valid screening measure for dissociative symptoms in adolescents.

Age determination of 15 old to intermediate-age small Magellanic cloud star clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parisi, M. C.; Clariá, J. J.; Piatti, A. E.

2014-04-01

We present color-magnitude diagrams in the V and I bands for 15 star clusters in the Small Magellanic Cloud (SMC) based on data taken with the Very Large Telescope (VLT, Chile). We selected these clusters from our previous work, wherein we derived cluster radial velocities and metallicities from calcium II infrared triplet (CaT) spectra also taken with the VLT. We discovered that the ages of six of our clusters have been appreciably underestimated by previous studies, which used comparatively small telescopes, graphically illustrating the need for large apertures to obtain reliable ages of old and intermediate-age SMC star clusters. Inmore » particular, three of these clusters, L4, L6, and L110, turn out to be among the oldest SMC clusters known, with ages of 7.9 ± 1.1, 8.7 ± 1.2, and 7.6 ± 1.0 Gyr, respectively, helping to fill a possible 'SMC cluster age gap'. Using the current ages and metallicities from Parisi et al., we analyze the age distribution, age gradient, and age-metallicity relation (AMR) of a sample of SMC clusters measured homogeneously. There is a suggestion of bimodality in the age distribution but it does not show a constant slope for the first 4 Gyr, and we find no evidence for an age gradient. Due to the improved ages of our cluster sample, we find that our AMR is now better represented in the intermediate/old period than we had derived in Parisi et al., where we simply took ages available in the literature. Additionally, clusters younger than ∼4 Gyr now show better agreement with the bursting model of Pagel and Tautvaišienė, but we confirm that this model is not a good representation of the AMR during the intermediate/old period. A more complicated model is needed to explain the SMC chemical evolution in that period.« less

MASSCLEANage-STELLAR CLUSTER AGES FROM INTEGRATED COLORS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Popescu, Bogdan; Hanson, M. M., E-mail: popescb@mail.uc.ed, E-mail: margaret.hanson@uc.ed

2010-11-20

We present the recently updated and expanded MASSCLEANcolors, a database of 70 million Monte Carlo models selected to match the properties (metallicity, ages, and masses) of stellar clusters found in the Large Magellanic Cloud (LMC). This database shows the rather extreme and non-Gaussian distribution of integrated colors and magnitudes expected with different cluster age and mass and the enormous age degeneracy of integrated colors when mass is unknown. This degeneracy could lead to catastrophic failures in estimating age with standard simple stellar population models, particularly if most of the clusters are of intermediate or low mass, like in the LMC.more » Utilizing the MASSCLEANcolors database, we have developed MASSCLEANage, a statistical inference package which assigns the most likely age and mass (solved simultaneously) to a cluster based only on its integrated broadband photometric properties. Finally, we use MASSCLEANage to derive the age and mass of LMC clusters based on integrated photometry alone. First, we compare our cluster ages against those obtained for the same seven clusters using more accurate integrated spectroscopy. We find improved agreement with the integrated spectroscopy ages over the original photometric ages. A close examination of our results demonstrates the necessity of solving simultaneously for mass and age to reduce degeneracies in the cluster ages derived via integrated colors. We then selected an additional subset of 30 photometric clusters with previously well-constrained ages and independently derive their age using the MASSCLEANage with the same photometry with very good agreement. The MASSCLEANage program is freely available under GNU General Public License.« less

A person-centered approach to the multifaceted nature of young adult sexual behavior.

PubMed

McGuire, Jenifer K; Barber, Bonnie L

2010-07-01

Young adult sexual relationships were examined using a multifaceted, person-centered approach with data from Wave 7 (aged 20-21; N = 1,126) of the Michigan Study of Adolescent Life Transitions. The study utilized hierarchical cluster analyses based on the following measured variables: frequency of sex, importance of regularly having sex, satisfaction with sex life, experience of coercion for sex, and sexual risk reduction. Five distinct clusters emerged for females (Satisfied, Moderate, Active Unprotected, Pressured, and Inactive) and represented patterns such as more partners paired with less risk reduction (Active Unprotected), high satisfaction paired with frequent sex and high-risk reduction (Satisfied), or higher levels of coercion paired with low satisfaction and low-risk reduction (Pressured). Similar clusters emerged for males, with one additional cluster: the Dissatisfied cluster. Clusters differed with respect to relationship status, marital status, and psychological well-being (both males and females) and parental divorce, living situation, and sexual orientation (females only).

Age and Mass for 920 Large Magellanic Cloud Clusters Derived from 100 Million Monte Carlo Simulations

NASA Astrophysics Data System (ADS)

Popescu, Bogdan; Hanson, M. M.; Elmegreen, Bruce G.

2012-06-01

We present new age and mass estimates for 920 stellar clusters in the Large Magellanic Cloud (LMC) based on previously published broadband photometry and the stellar cluster analysis package, MASSCLEANage. Expressed in the generic fitting formula, d 2 N/dMdtvpropM α t β, the distribution of observed clusters is described by α = -1.5 to -1.6 and β = -2.1 to -2.2. For 288 of these clusters, ages have recently been determined based on stellar photometric color-magnitude diagrams, allowing us to gauge the confidence of our ages. The results look very promising, opening up the possibility that this sample of 920 clusters, with reliable and consistent age, mass, and photometric measures, might be used to constrain important characteristics about the stellar cluster population in the LMC. We also investigate a traditional age determination method that uses a χ2 minimization routine to fit observed cluster colors to standard infinite-mass limit simple stellar population models. This reveals serious defects in the derived cluster age distribution using this method. The traditional χ2 minimization method, due to the variation of U, B, V, R colors, will always produce an overdensity of younger and older clusters, with an underdensity of clusters in the log (age/yr) = [7.0, 7.5] range. Finally, we present a unique simulation aimed at illustrating and constraining the fading limit in observed cluster distributions that includes the complex effects of stochastic variations in the observed properties of stellar clusters.

The Clusters AgeS Experiment (CASE). Variable Stars in the Field of the Globular Cluster NGC 3201

NASA Astrophysics Data System (ADS)

Kaluzny, J.; Rozyczka, M.; Thompson, I. B.; Narloch, W.; Mazur, B.; Pych, W.; Schwarzenberg-Czerny, A.

2016-01-01

The field of the globular cluster NGC 3201 was monitored between 1998 and 2009 in a search for variable stars. BV light curves were obtained for 152 periodic or likely periodic variables, fifty-seven of which are new detections. Thirty-seven newly detected variables are proper motion members of the cluster. Among them we found seven detached or semi-detached eclipsing binaries, four contact binaries, and eight SX Phe pulsators. Four of the eclipsing binaries are located in the turnoff region, one on the lower main sequence and the remaining two slightly above the subgiant branch. Two contact systems are blue stragglers, and another two reside in the turnoff region. In the blue straggler region a total of 266 objects were found, of which 140 are proper motion (PM) members of NGC 3201, and another nineteen are field stars. Seventy-eight of the remaining objects for which we do not have PM data are located within the half-light radius from the center of the cluster, and most of them are likely genuine blue stragglers. Four variable objects in our field of view were found to coincide with X-ray sources: three chromospherically active stars and a quasar at a redshift z≍0.5.

OGLE Collection of Star Clusters. New Objects in the Magellanic Bridge and the Outskirts of the Small Magellanic Cloud

NASA Astrophysics Data System (ADS)

Sitek, M.; Szymański, M. K.; Udalski, A.; Skowron, D. M.; Kostrzewa-Rutkowska, Z.; Skowron, J.; Karczmarek, P.; Cieślar, M.; Wyrzykowski, Ł.; Kozłowski, S.; Pietrukowicz, P.; Soszyński, I.; Mróz, P.; Pawlak, M.; Poleski, R.; Ulaczyk, K.

2017-12-01

The Magellanic System (MS) encompasses the nearest neighbors of the Milky Way, the Large (LMC) and Small (SMC) Magellanic Clouds, and the Magellanic Bridge (MBR). This system contains a diverse sample of star clusters. Their parameters, such as the spatial distribution, chemical composition and age distribution yield important information about the formation scenario of the whole Magellanic System. Using deep photometric maps compiled in the fourth phase of the Optical Gravitational Lensing Experiment (OGLE-IV) we present the most complete catalog of star clusters in the Magellanic System ever constructed from homogeneous, long time-scale photometric data. In this second paper of the series, we show the collection of star clusters found in the area of about 360 square degrees in the MBR and in the outer regions of the SMC. Our sample contains 198 visually identified star cluster candidates, 75 of which were not listed in any of the previously published catalogs. The new discoveries are mainly young small open clusters or clusters similar to associations.

INTER- AND INTRA-CLUSTER AGE GRADIENTS IN MASSIVE STAR FORMING REGIONS AND INDIVIDUAL NEARBY STELLAR CLUSTERS REVEALED BY MYStIX

NASA Astrophysics Data System (ADS)

Getman, Konstantin V.; Feigelson, Eric; Kuhn, Michael A.; Broos, Patrick S; Townsley, Leisa K.; Naylor, Tim; Povich, Matthew S.; Luhman, Kevin; Garmire, Gordon

2014-08-01

The MYStIX (Massive Young Star-Forming Complex Study in Infrared and X-ray) project seeks to characterize 20 OB-dominated young star forming regions (SFRs) at distances <4 kpc using photometric catalogs from the Chandra X-ray Observatory, Spitzer Space Telescope, UKIRT and 2MASS surveys. As part of the MYStIX project, we developed a new stellar chronometer that employs near-infrared and X-ray photometry data, AgeJX. Computing AgeJX averaged over MYStIX (sub)clusters reveals previously unknown age gradients across most of the MYStIX regions as well as within some individual rich clusters. Within the SFRs, the inferred AgeJX ages are youngest in obscured locations in molecular clouds, intermediate in revealed stellar clusters, and oldest in distributed stellar populations. Noticeable intra-cluster gradients are seen in the NGC 2024 (Flame Nebula) star cluster and the Orion Nebula Cluster (ONC): stars in cluster cores appear younger and thus were formed later than stars in cluster halos. The latter result has two important implications for the formation of young stellar clusters. Clusters likely form slowly: they do not arise from a single nearly-instantaneous burst of star formation. The simple models where clusters form inside-out are likely incorrect, and more complex models are needed. We provide several star formation scenarios that alone or in combination may lead to the observed core-halo age gradients.

Classification of patients based on their evaluation of hospital outcomes: cluster analysis following a national survey in Norway

PubMed Central

2013-01-01

Background A general trend towards positive patient-reported evaluations of hospitals could be taken as a sign that most patients form a homogeneous, reasonably pleased group, and consequently that there is little need for quality improvement. The objective of this study was to explore this assumption by identifying and statistically validating clusters of patients based on their evaluation of outcomes related to overall satisfaction, malpractice and benefit of treatment. Methods Data were collected using a national patient-experience survey of 61 hospitals in the 4 health regions in Norway during spring 2011. Postal questionnaires were mailed to 23,420 patients after their discharge from hospital. Cluster analysis was performed to identify response clusters of patients, based on their responses to single items about overall patient satisfaction, benefit of treatment and perception of malpractice. Results Cluster analysis identified six response groups, including one cluster with systematically poorer evaluation across outcomes (18.5% of patients) and one small outlier group (5.3%) with very poor scores across all outcomes. One-Way ANOVA with post-hoc tests showed that most differences between the six response groups on the three outcome items were significant. The response groups were significantly associated with nine patient-experience indicators (p < 0.001), and all groups were significantly different from each of the other groups on a majority of the patient-experience indicators. Clusters were significantly associated with age, education, self-perceived health, gender, and the degree to write open comments in the questionnaire. Conclusions The study identified five response clusters with distinct patient-reported outcome scores, in addition to a heterogeneous outlier group with very poor scores across all outcomes. The outlier group and the cluster with systematically poorer evaluation across outcomes comprised almost one-quarter of all patients, clearly demonstrating the need to tailor quality initiatives and improve patient-perceived quality in hospitals. More research on patient clustering in patient evaluation is needed, as well as standardization of methodology to increase comparability across studies. PMID:23433450

Intracluster age gradients in numerous young stellar clusters

NASA Astrophysics Data System (ADS)

Getman, K. V.; Feigelson, E. D.; Kuhn, M. A.; Bate, M. R.; Broos, P. S.; Garmire, G. P.

2018-05-01

The pace and pattern of star formation leading to rich young stellar clusters is quite uncertain. In this context, we analyse the spatial distribution of ages within 19 young (median t ≲ 3 Myr on the Siess et al. time-scale), morphologically simple, isolated, and relatively rich stellar clusters. Our analysis is based on young stellar object (YSO) samples from the Massive Young Star-Forming Complex Study in Infrared and X-ray and Star Formation in Nearby Clouds surveys, and a new estimator of pre-main sequence (PMS) stellar ages, AgeJX, derived from X-ray and near-infrared photometric data. Median cluster ages are computed within four annular subregions of the clusters. We confirm and extend the earlier result of Getman et al. (2014): 80 per cent of the clusters show age trends where stars in cluster cores are younger than in outer regions. Our cluster stacking analyses establish the existence of an age gradient to high statistical significance in several ways. Time-scales vary with the choice of PMS evolutionary model; the inferred median age gradient across the studied clusters ranges from 0.75 to 1.5 Myr pc-1. The empirical finding reported in the present study - late or continuing formation of stars in the cores of star clusters with older stars dispersed in the outer regions - has a strong foundation with other observational studies and with the astrophysical models like the global hierarchical collapse model of Vázquez-Semadeni et al.

Continuing Education Needs of the Office Oncology Nurse.

ERIC Educational Resources Information Center

Rogers, Miriam P.

1999-01-01

A study determined the learning needs of office oncology nurses (n=290)as a critical first step in planning education programs. Participants ranked cancer-care topics similarly, regardless of age, background, or experience. The highest-ranked needs were clustered in the areas of cancer nursing practice, major cancers, and cancer treatment.…

Temporal features of word-initial /s/+stop clusters in bilingual Mandarin-English children and monolingual English children and adults.

PubMed

Yang, Jing

2018-03-01

This study investigated the durational features of English word-initial /s/+stop clusters produced by bilingual Mandarin (L1)-English (L2) children and monolingual English children and adults. The participants included two groups of five- to six-year-old bilingual children: low proficiency in the L2 (Bi-low) and high proficiency in the L2 (Bi-high), one group of age-matched English children, and one group of English adults. Each participant produced a list of English words containing /sp, st, sk/ at the word-initial position followed by /a, i, u/, respectively. The absolute durations of the clusters and cluster elements and the durational proportions of elements to the overall cluster were measured. The results revealed that Bi-high children behaved similarly to the English monolinguals whereas Bi-low children used a different strategy of temporal organization to coordinate the cluster components in comparison to the English monolinguals and Bi-high children. The influence of language experience and continuing development of temporal features in children were discussed.

Increased Symptom Reporting in Young Athletes Based on History of Previous Concussions.

PubMed

Moser, Rosemarie Scolaro; Schatz, Philip

2017-01-01

Research documents increased symptoms in adolescents with a history of two or more concussions. This study examined baseline evaluations of 2,526 younger athletes, ages 10 to 14. Between-groups analyses examined Post Concussion Symptom Scale symptoms by concussion history group (None, One, Two+) and clusters of Physical, Cognitive, Emotional, and Sleep symptoms. Healthy younger athletes with a concussion history reported greater physical, emotional, and sleep-related symptoms than those with no history of concussion, with a greater endorsement in physical/sleep symptom clusters. Findings suggest younger athletes with a history of multiple concussions may experience residual symptoms.

Accurate age determinations of several nearby open clusters containing magnetic Ap stars

NASA Astrophysics Data System (ADS)

Silaj, J.; Landstreet, J. D.

2014-06-01

Context. To study the time evolution of magnetic fields, chemical abundance peculiarities, and other characteristics of magnetic Ap and Bp stars during their main sequence lives, a sample of these stars in open clusters has been obtained, as such stars can be assumed to have the same ages as the clusters to which they belong. However, in exploring age determinations in the literature, we find a large dispersion among different age determinations, even for bright, nearby clusters. Aims: Our aim is to obtain ages that are as accurate as possible for the seven nearby open clusters α Per, Coma Ber, IC 2602, NGC 2232, NGC 2451A, NGC 2516, and NGC 6475, each of which contains at least one magnetic Ap or Bp star. Simultaneously, we test the current calibrations of Te and luminosity for the Ap/Bp star members, and identify clearly blue stragglers in the clusters studied. Methods: We explore the possibility that isochrone fitting in the theoretical Hertzsprung-Russell diagram (i.e. log (L/L⊙) vs. log Te), rather than in the conventional colour-magnitude diagram, can provide more precise and accurate cluster ages, with well-defined uncertainties. Results: Well-defined ages are found for all the clusters studied. For the nearby clusters studied, the derived ages are not very sensitive to the small uncertainties in distance, reddening, membership, metallicity, or choice of isochrones. Our age determinations are all within the range of previously determined values, but the associated uncertainties are considerably smaller than the spread in recent age determinations from the literature. Furthermore, examination of proper motions and HR diagrams confirms that the Ap stars identified in these clusters are members, and that the presently accepted temperature scale and bolometric corrections for Ap stars are approximately correct. We show that in these theoretical HR diagrams blue stragglers are particularly easy to identify. Conclusions: Constructing the theoretical HR diagram of a nearby open cluster makes possible an accurate age determination, with well defined uncertainty. This diagnostic of a cluster also provides a useful tool for studying unusual stars such as Ap stars and blue stragglers. Table 3 is available in electronic form at http://www.aanda.org

Hierarchical Star Formation in Turbulent Media: Evidence from Young Star Clusters

NASA Astrophysics Data System (ADS)

Grasha, K.; Elmegreen, B. G.; Calzetti, D.; Adamo, A.; Aloisi, A.; Bright, S. N.; Cook, D. O.; Dale, D. A.; Fumagalli, M.; Gallagher, J. S., III; Gouliermis, D. A.; Grebel, E. K.; Kahre, L.; Kim, H.; Krumholz, M. R.; Lee, J. C.; Messa, M.; Ryon, J. E.; Ubeda, L.

2017-06-01

We present an analysis of the positions and ages of young star clusters in eight local galaxies to investigate the connection between the age difference and separation of cluster pairs. We find that star clusters do not form uniformly but instead are distributed so that the age difference increases with the cluster pair separation to the 0.25-0.6 power, and that the maximum size over which star formation is physically correlated ranges from ˜200 pc to ˜1 kpc. The observed trends between age difference and separation suggest that cluster formation is hierarchical both in space and time: clusters that are close to each other are more similar in age than clusters born further apart. The temporal correlations between stellar aggregates have slopes that are consistent with predictions of turbulence acting as the primary driver of star formation. The velocity associated with the maximum size is proportional to the galaxy’s shear, suggesting that the galactic environment influences the maximum size of the star-forming structures.

Physician styles of patient management as a potential source of disparities: cluster analysis from a factorial experiment.

PubMed

Lutfey, Karen E; Gerstenberger, Eric; McKinlay, John B

2013-06-01

To identify styles of physician decision making (as opposed to singular clinical actions) and to analyze their association with variations in the management of a vignette presentation of coronary heart disease (CHD). Primary data were collected from primary care physicians in North and South Carolina. In a balanced factorial experimental design, primary care physicians viewed one of 16 (2(4)) video vignette presentations of CHD and provided detailed information about how they would manage the case. 256 MD primary care physicians were interviewed face-to-face in North and South Carolina. We identify three clusters depicting unique styles of CHD management that are robust to controls for physician (gender and level of experience) and patient characteristics (age, gender, socioeconomic status, and race) as well as key organizational features of physicians' work settings. Physicians in Cluster 1 "Cardiac" (N = 92) were more likely to focus on cardiac issues compared with their counterparts; physicians in Cluster 2 "Talkers" (N = 93) were more likely to give advice and take additional medical history; whereas physicians in Cluster 3 "Minimalists" (N = 71) were less likely than their counterparts to take action on any of the types of management behavior. Variations in styles of decision making, which encompass multiple outcome variables and extend beyond individual-level demographic predictors, may add to our understanding of disparities in health quality and outcomes. © Health Research and Educational Trust.

Clinical Characteristics of Exacerbation-Prone Adult Asthmatics Identified by Cluster Analysis.

PubMed

Kim, Mi Ae; Shin, Seung Woo; Park, Jong Sook; Uh, Soo Taek; Chang, Hun Soo; Bae, Da Jeong; Cho, You Sook; Park, Hae Sim; Yoon, Ho Joo; Choi, Byoung Whui; Kim, Yong Hoon; Park, Choon Sik

2017-11-01

Asthma is a heterogeneous disease characterized by various types of airway inflammation and obstruction. Therefore, it is classified into several subphenotypes, such as early-onset atopic, obese non-eosinophilic, benign, and eosinophilic asthma, using cluster analysis. A number of asthmatics frequently experience exacerbation over a long-term follow-up period, but the exacerbation-prone subphenotype has rarely been evaluated by cluster analysis. This prompted us to identify clusters reflecting asthma exacerbation. A uniform cluster analysis method was applied to 259 adult asthmatics who were regularly followed-up for over 1 year using 12 variables, selected on the basis of their contribution to asthma phenotypes. After clustering, clinical profiles and exacerbation rates during follow-up were compared among the clusters. Four subphenotypes were identified: cluster 1 was comprised of patients with early-onset atopic asthma with preserved lung function, cluster 2 late-onset non-atopic asthma with impaired lung function, cluster 3 early-onset atopic asthma with severely impaired lung function, and cluster 4 late-onset non-atopic asthma with well-preserved lung function. The patients in clusters 2 and 3 were identified as exacerbation-prone asthmatics, showing a higher risk of asthma exacerbation. Two different phenotypes of exacerbation-prone asthma were identified among Korean asthmatics using cluster analysis; both were characterized by impaired lung function, but the age at asthma onset and atopic status were different between the two. Copyright © 2017 The Korean Academy of Asthma, Allergy and Clinical Immunology · The Korean Academy of Pediatric Allergy and Respiratory Disease

The Cluster AgeS Experiment (CASE). Detecting Aperiodic Photometric Variability with the Friends of Friends Algorithm

NASA Astrophysics Data System (ADS)

Rozyczka, M.; Narloch, W.; Pietrukowicz, P.; Thompson, I. B.; Pych, W.; Poleski, R.

2018-03-01

We adapt the friends of friends algorithm to the analysis of light curves, and show that it can be succesfully applied to searches for transient phenomena in large photometric databases. As a test case we search OGLE-III light curves for known dwarf novae. A single combination of control parameters allows us to narrow the search to 1% of the data while reaching a ≍90% detection efficiency. A search involving ≍2% of the data and three combinations of control parameters can be significantly more effective - in our case a 100% efficiency is reached. The method can also quite efficiently detect semi-regular variability. In particular, 28 new semi-regular variables have been found in the field of the globular cluster M22, which was examined earlier with the help of periodicity-searching algorithms.

Ages of Extragalactic Intermediate-Age Star Clusters

NASA Technical Reports Server (NTRS)

Flower, P. J.

1983-01-01

A dating technique for faint, distant star clusters observable in the local group of galaxies with the space telescope is discussed. Color-magnitude diagrams of Magellanic Cloud clusters are mentioned along with the metallicity of star clusters.

THE CLUSTER AGES EXPERIMENT (CASE). VII. ANALYSIS OF TWO ECLIPSING BINARIES IN THE GLOBULAR CLUSTER NGC 6362

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaluzny, J.; Rozyczka, M.; Schwarzenberg-Czerny, A.

2015-11-15

We use photometric and spectroscopic observations of the detached eclipsing binaries V40 and V41 in the globular cluster NGC 6362 to derive masses, radii, and luminosities of the component stars. The orbital periods of these systems are 5.30 and 17.89 days, respectively. The measured masses of the primary and secondary components (M{sub p}, M{sub s}) are (0.8337 ± 0.0063, 0.7947 ± 0.0048) M{sub ⊙} for V40 and (0.8215 ± 0.0058, 0.7280 ± 0.0047) M{sub ⊙} for V41. The measured radii (R{sub p}, R{sub s}) are (1.3253 ± 0.0075, 0.997 ± 0.013) R{sub ⊙} for V40 and (1.0739 ± 0.0048, 0.7307more » ± 0.0046) R{sub ⊙} for V41. Based on the derived luminosities, we find that the distance modulus of the cluster is 14.74 ± 0.04 mag—in good agreement with 14.72 mag obtained from color–magnitude diagram (CMD) fitting. We compare the absolute parameters of component stars with theoretical isochrones in mass–radius and mass–luminosity diagrams. For assumed abundances [Fe/H] = −1.07, [α/Fe] = 0.4, and Y = 0.25 we find the most probable age of V40 to be 11.7 ± 0.2 Gyr, compatible with the age of the cluster derived from CMD fitting (12.5 ± 0.5 Gyr). V41 seems to be markedly younger than V40. If independently confirmed, this result will suggest that V41 belongs to the younger of the two stellar populations recently discovered in NGC 6362. The orbits of both systems are eccentric. Given the orbital period and age of V40, its orbit should have been tidally circularized some ∼7 Gyr ago. The observed eccentricity is most likely the result of a relatively recent close stellar encounter.« less

Exploring dysmenorrhoea and menstrual experiences among Lebanese female adolescents.

PubMed

Santina, T; Wehbe, N; Ziade, F

2012-08-01

Data on menstrual experiences and their impact on quality of life among women in developing countries are scant. The aim of this study was to assess the prevalence of dysmenorrhoea among adolescent girls in Sidon city and suburbs, Lebanon, and to explore its possible relationship with menstrual experience. In a cross-sectional design, 389 post-menarcheal schoolgirls aged 13-19 years were selected using a cluster random sampling method. Of these 161 (41.4%) were regularly or sometimes absent from school due to menstrual problems and 289 (74.3%) experienced dysmenorrhoea. Nevertheless only 7.3% of the girls had consulted a physician about dysmenorrhoea. Three-quarters of these young women (75.2%) had scores indicating negative menstrual experience based on the Menstrual Experience and Behavior Questionnaire. Significant predictors of dysmenorrhoea were negative menstrual experience, younger age of girl, longer duration of bleeding and longer cycle length. Better reproductive health educational programmes focusing on menstruation are needed for female adolescents.

Not-so-simple stellar populations in the intermediate-age Large Magellanic Cloud star clusters NGC 1831 and NGC 1868

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Chengyuan; De Grijs, Richard; Deng, Licai, E-mail: joshuali@pku.edu.cn, E-mail: grijs@pku.edu.cn

2014-04-01

Using a combination of high-resolution Hubble Space Telescope/Wide-Field and Planetary Camera-2 observations, we explore the physical properties of the stellar populations in two intermediate-age star clusters, NGC 1831 and NGC 1868, in the Large Magellanic Cloud based on their color-magnitude diagrams. We show that both clusters exhibit extended main-sequence turn offs. To explain the observations, we consider variations in helium abundance, binarity, age dispersions, and the fast rotation of the clusters' member stars. The observed narrow main sequence excludes significant variations in helium abundance in both clusters. We first establish the clusters' main-sequence binary fractions using the bulk of themore » clusters' main-sequence stellar populations ≳ 1 mag below their turn-offs. The extent of the turn-off regions in color-magnitude space, corrected for the effects of binarity, implies that age spreads of order 300 Myr may be inferred for both clusters if the stellar distributions in color-magnitude space were entirely due to the presence of multiple populations characterized by an age range. Invoking rapid rotation of the population of cluster members characterized by a single age also allows us to match the observed data in detail. However, when taking into account the extent of the red clump in color-magnitude space, we encounter an apparent conflict for NGC 1831 between the age dispersion derived from that based on the extent of the main-sequence turn off and that implied by the compact red clump. We therefore conclude that, for this cluster, variations in stellar rotation rate are preferred over an age dispersion. For NGC 1868, both models perform equally well.« less

Hierarchical Star Formation in Turbulent Media: Evidence from Young Star Clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grasha, K.; Calzetti, D.; Elmegreen, B. G.

We present an analysis of the positions and ages of young star clusters in eight local galaxies to investigate the connection between the age difference and separation of cluster pairs. We find that star clusters do not form uniformly but instead are distributed so that the age difference increases with the cluster pair separation to the 0.25–0.6 power, and that the maximum size over which star formation is physically correlated ranges from ∼200 pc to ∼1 kpc. The observed trends between age difference and separation suggest that cluster formation is hierarchical both in space and time: clusters that are closemore » to each other are more similar in age than clusters born further apart. The temporal correlations between stellar aggregates have slopes that are consistent with predictions of turbulence acting as the primary driver of star formation. The velocity associated with the maximum size is proportional to the galaxy’s shear, suggesting that the galactic environment influences the maximum size of the star-forming structures.« less

Young star clusters in nearby molecular clouds

NASA Astrophysics Data System (ADS)

Getman, K. V.; Kuhn, M. A.; Feigelson, E. D.; Broos, P. S.; Bate, M. R.; Garmire, G. P.

2018-06-01

The SFiNCs (Star Formation in Nearby Clouds) project is an X-ray/infrared study of the young stellar populations in 22 star-forming regions with distances ≲ 1 kpc designed to extend our earlier MYStIX (Massive Young Star-Forming Complex Study in Infrared and X-ray) survey of more distant clusters. Our central goal is to give empirical constraints on cluster formation mechanisms. Using parametric mixture models applied homogeneously to the catalogue of SFiNCs young stars, we identify 52 SFiNCs clusters and 19 unclustered stellar structures. The procedure gives cluster properties including location, population, morphology, association with molecular clouds, absorption, age (AgeJX), and infrared spectral energy distribution (SED) slope. Absorption, SED slope, and AgeJX are age indicators. SFiNCs clusters are examined individually, and collectively with MYStIX clusters, to give the following results. (1) SFiNCs is dominated by smaller, younger, and more heavily obscured clusters than MYStIX. (2) SFiNCs cloud-associated clusters have the high ellipticities aligned with their host molecular filaments indicating morphology inherited from their parental clouds. (3) The effect of cluster expansion is evident from the radius-age, radius-absorption, and radius-SED correlations. Core radii increase dramatically from ˜0.08 to ˜0.9 pc over the age range 1-3.5 Myr. Inferred gas removal time-scales are longer than 1 Myr. (4) Rich, spatially distributed stellar populations are present in SFiNCs clouds representing early generations of star formation. An appendix compares the performance of the mixture models and non-parametric minimum spanning tree to identify clusters. This work is a foundation for future SFiNCs/MYStIX studies including disc longevity, age gradients, and dynamical modelling.

Behavioral and anatomical consequences of early versus late symbol training in macaques.

PubMed

Srihasam, Krishna; Mandeville, Joseph B; Morocz, Istvan A; Sullivan, Kevin J; Livingstone, Margaret S

2012-02-09

Distinct brain regions, reproducible from one person to the next, are specialized for processing different kinds of human expertise, such as face recognition and reading. Here, we explore the relationship between age of learning, learning ability, and specialized brain structures. Specifically, we ask whether the existence of reproducible cortical domains necessarily means that certain abilities are innate, or innately easily learned, or whether reproducible domains can be formed, or refined, by interactions between genetic programs and common early experience. Functional MRI showed that intensive early, but not late, experience caused the formation of category-selective regions in macaque temporal lobe for stimuli never naturally encountered by monkeys. And behaviorally, early training produced more fluent processing of these stimuli than the same training in adults. One explanation for these results is that in higher cortical areas, as in early sensory areas, experience drives functional clustering and functional clustering determines how that information is processed. Copyright © 2012 Elsevier Inc. All rights reserved.

Clustering of trauma and associations with single and co-occurring depression and panic attack over twenty years.

PubMed

McCutcheon, Vivia V; Heath, Andrew C; Nelson, Elliot C; Bucholz, Kathleen K; Madden, Pamela A F; Martin, Nicholas G

2010-02-01

Individuals who experience one type of trauma often experience other types, yet few studies have examined the clustering of trauma. This study examines the clustering of traumatic events and associations of trauma with risk for single and co-occurring major depressive disorder (MDD) and panic attack for 20 years after first trauma. Lifetime histories of MDD, panic attack, and traumatic events were obtained from participants in an Australian twin sample. Latent class analysis was used to derive trauma classes based on each respondent's trauma history. Associations of the resulting classes and of parental alcohol problems and familial effects with risk for a first onset of single and co-occurring MDD and panic attack were examined from the year of first trauma to 20 years later. Traumatic events clustered into three distinct classes characterized by endorsement of little or no trauma, primarily nonassaultive, and primarily assaultive events. Individuals in the assaultive class were characterized by a younger age at first trauma, a greater number of traumatic events, and high rates of parental alcohol problems. Members of the assaultive trauma class had the strongest and most enduring risk for single and co-occurring lifetime MDD and panic attack. Assaultive trauma outweighed associations of familial effects and nonassaultive trauma with risk for 10 years following first trauma.

Cúmulos jóvenes inmersos en campos de edad intermedia en la barra de la Nube Mayor de Magallanes

NASA Astrophysics Data System (ADS)

Piatti, A. E.; Geisler, D.; Bica, E.; Clariá, J. J.

We present Washington system photometry for 11 star clusters immersed in the northwest part of the Large Magellanic Cloud (LMC) bar. The fields are heavily populated by the intermediate-age component of the LMC bar. We succeeded in disentangling cluster colour-magnitude diagrams from those of the fields and in deriving reddening and ages for five clusters - SL 218, BRHT4b, NGC 1839, NGC 1838 and NGC 1863 - with the aid of recent Washington System theoretical isochrones. The resulting cluster ages range between 50 and 125 Myr. Despite their proximity, NGC 1836 and BRHT4b have very different ages. Thus the possibility for these two objects being a binary cluster is very unlikely, although a capture cannot be ruled out a priori. Our results suggest that for each intermediate-age cluster remaining in the LMC bar region, a number of robust young blue star clusters occurs in the same region (Piatti et al. 2003, MNRAS, 343, 851).

Geographic Variation and Factors Associated with Female Genital Mutilation among Reproductive Age Women in Ethiopia: A National Population Based Survey

PubMed Central

Setegn, Tesfaye; Lakew, Yihunie; Deribe, Kebede

2016-01-01

Background Female genital mutilation (FGM) is a common traditional practice in developing nations including Ethiopia. It poses complex and serious long-term health risks for women and girls and can lead to death. In Ethiopia, the geographic distribution and factors associated with FGM practices are poorly understood. Therefore, we assessed the spatial distribution and factors associated with FGM among reproductive age women in the country. Method We used population based national representative surveys. Data from two (2000 and 2005) Ethiopian demographic and health surveys (EDHS) were used in this analysis. Briefly, EDHS used a stratified, two-stage cluster sampling design. A total of 15,367 (from EDHS 2000) and 14,070 (from EDHS 2005) women of reproductive age (15–49 years) were included in the analysis. Three outcome variables were used (prevalence of FGM among women, prevalence of FGM among daughters and support for the continuation of FGM). The data were weighted and descriptive statistics (percentage change), bivariate and multivariable logistic regression analyses were carried out. Multicollinearity of variables was assessed using variance inflation factors (VIF) with a reference value of 10 before interpreting the final output. The geographic variation and clustering of weighted FGM prevalence were analyzed and visualized on maps using ArcGIS. Z-scores were used to assess the statistical difference of geographic clustering of FGM prevalence spots. Result The trend of FGM weighted prevalence has been decreasing. Being wealthy, Muslim and in higher age categories are associated with increased odds of FGM among women. Similarly, daughters from Muslim women have increased odds of experiencing FGM. Women in the higher age categories have increased odds of having daughters who experience FGM. The odds of FGM among daughters decrease with increased maternal education. Mass media exposure, being wealthy and higher paternal and maternal education are associated with decreased odds of women’s support of FGM continuation. FGM prevalence and geographic clustering showed variation across regions in Ethiopia. Conclusion Individual, economic, socio-demographic, religious and cultural factors played major roles in the existing practice and continuation of FGM. The significant geographic clustering of FGM was observed across regions in Ethiopia. Therefore, targeted and integrated interventions involving religious leaders in high FGM prevalence spot clusters and addressing the socio-economic and geographic inequalities are recommended to eliminate FGM. PMID:26741488

Geographic Variation and Factors Associated with Female Genital Mutilation among Reproductive Age Women in Ethiopia: A National Population Based Survey.

PubMed

Setegn, Tesfaye; Lakew, Yihunie; Deribe, Kebede

2016-01-01

Female genital mutilation (FGM) is a common traditional practice in developing nations including Ethiopia. It poses complex and serious long-term health risks for women and girls and can lead to death. In Ethiopia, the geographic distribution and factors associated with FGM practices are poorly understood. Therefore, we assessed the spatial distribution and factors associated with FGM among reproductive age women in the country. We used population based national representative surveys. Data from two (2000 and 2005) Ethiopian demographic and health surveys (EDHS) were used in this analysis. Briefly, EDHS used a stratified, two-stage cluster sampling design. A total of 15,367 (from EDHS 2000) and 14,070 (from EDHS 2005) women of reproductive age (15-49 years) were included in the analysis. Three outcome variables were used (prevalence of FGM among women, prevalence of FGM among daughters and support for the continuation of FGM). The data were weighted and descriptive statistics (percentage change), bivariate and multivariable logistic regression analyses were carried out. Multicollinearity of variables was assessed using variance inflation factors (VIF) with a reference value of 10 before interpreting the final output. The geographic variation and clustering of weighted FGM prevalence were analyzed and visualized on maps using ArcGIS. Z-scores were used to assess the statistical difference of geographic clustering of FGM prevalence spots. The trend of FGM weighted prevalence has been decreasing. Being wealthy, Muslim and in higher age categories are associated with increased odds of FGM among women. Similarly, daughters from Muslim women have increased odds of experiencing FGM. Women in the higher age categories have increased odds of having daughters who experience FGM. The odds of FGM among daughters decrease with increased maternal education. Mass media exposure, being wealthy and higher paternal and maternal education are associated with decreased odds of women's support of FGM continuation. FGM prevalence and geographic clustering showed variation across regions in Ethiopia. Individual, economic, socio-demographic, religious and cultural factors played major roles in the existing practice and continuation of FGM. The significant geographic clustering of FGM was observed across regions in Ethiopia. Therefore, targeted and integrated interventions involving religious leaders in high FGM prevalence spot clusters and addressing the socio-economic and geographic inequalities are recommended to eliminate FGM.

The Effects of Rotation on the Main-sequence Turnoff of Intermediate-age Massive Star Clusters

NASA Astrophysics Data System (ADS)

Yang, Wuming; Bi, Shaolan; Meng, Xiangcun; Liu, Zhie

2013-10-01

The double or extended main-sequence turnoffs (MSTOs) in the color-magnitude diagram (CMD) of intermediate-age massive star clusters in the Large Magellanic Cloud are generally interpreted as age spreads of a few hundred Myr. However, such age spreads do not exist in younger clusters (i.e., 40-300 Myr), which challenges this interpretation. The effects of rotation on the MSTOs of star clusters have been studied in previous works, but the results obtained are conflicting. Compared with previous works, we consider the effects of rotation on the main-sequence lifetime of stars. Our calculations show that rotating models have a fainter and redder MSTO with respect to non-rotating counterparts with ages between about 0.8 and 2.2 Gyr, but have a brighter and bluer MSTO when age is larger than 2.4 Gyr. The spread of the MSTO caused by a typical rotation rate is equivalent to the effect of an age spread of about 200 Myr. Rotation could lead to the double or extended MSTOs in the CMD of the star clusters with ages between about 0.8 and 2.2 Gyr. However, the extension is not significant, and it does not even exist in younger clusters. If the efficiency of the mixing were high enough, the effects of the mixing would counteract the effect of the centrifugal support in the late stage of evolution, and the rotationally induced extension would disappear in the old intermediate-age star clusters, but younger clusters would have an extended MSTO. Moreover, the effects of rotation might aid in understanding the formation of some "multiple populations" in globular clusters.

Large and Small Magellanic Clouds age-metallicity relationships

NASA Astrophysics Data System (ADS)

Perren, G. I.; Piatti, A. E.; Vázquez, R. A.

2017-10-01

We present a new determination of the age-metallicity relation for both Magellanic Clouds, estimated through the homogeneous analysis of 239 observed star clusters. All clusters in our set were observed with the filters of the Washington photometric system. The Automated Stellar cluster Analysis package (ASteCA) was employed to derive the cluster's fundamental parameters, in particular their ages and metallicities, through an unassisted process. We find that our age-metallicity relations (AMRs) can not be fully matched to any of the estimations found in twelve previous works, and are better explained by a combination of several of them in different age intervals.

The Connection Between X-ray Binaries and Star Clusters in the Antennae

NASA Astrophysics Data System (ADS)

Rangelov, Blagoy; Chandar, R.; Prestwich, A.

2011-05-01

High Mass X-ray Binaries (HMXBs) are believed to form in massive, compact star clusters. However the correlation between these young binary star systems and properties of their parent clusters are still poorly known. We compare the locations of 82 X-ray binaries detected in the merging Antennae galaxies by Zezas et al. (2006) based on observations taken with the Chandra Space Telescope, with a catalog of optically selected star clusters presented recently by Whitmore et al. (2010) based on observations taken with the Hubble Space Telescope. We find 22 X-ray binaries coincident or nearly coincident with star clusters. The ages of the clusters were estimated by comparing their UBVIHα colors with predictions from stellar evolutionary models. We find that 14 of the 22 coincident sources (64%) are hosted by star clusters with ages of 6 Myr or less. At these very young ages, only stars initially more massive than M ≥ 30 Msun have evolved into compact remnants, almost certainly black holes. Therefore, these 14 sources are likely to be black hole binaries. Five of the XRBs are hosted by young clusters with ages τ 30-50 Myr, while three are hosted by intermediate age clusters with τ 100-300 Myr. We suggest that these older X-ray binaries likely have neutron stars as the compact object. We conclude that precision age-dating of star clusters, which are spatially coincident with XRBs in nearby star forming galaxies, is a powerful method of constraining the nature of the XRBs.

The Cluster AgeS Experiment (CASE). Variable Stars in the Field of the Globular Cluster M22

NASA Astrophysics Data System (ADS)

Rozyczka, M.; Thompson, I. B.; Pych, W.; Narloch, W.; Poleski, R.; Schwarzenberg-Czerny, A.

2017-09-01

The field of the globular cluster M22 (NGC 6656) was monitored between 2000 and 2008 in a search for variable stars. BV light curves were obtained for 359 periodic, likely periodic, and long-term variables, 238 of which are new detections. 39 newly detected variables, and 63 previously known ones are members or likely members of the cluster, including 20 SX Phe, 10 RRab and 16 RRc type pulsators, one BL Her type pulsator, 21 contact binaries, and 9 detached or semi-detached eclipsing binaries. The most interesting among the identified objects are V112 - a bright multimode SX Phe pulsator, V125 - a β Lyr type binary on the blue horizontal branch, V129 - a blue/yellow straggler with a W UMa-like light curve, located halfway between the extreme horizontal branch and red giant branch, and V134 - an extreme horizontal branch object with P=2.33 d and a nearly sinusoidal light curve. All four of them are proper motion members of the cluster. Among nonmembers, a P=2.83 d detached eclipsing binary hosting a δ Sct type pulsator was found, and a peculiar P=0.93 d binary with ellipsoidal modulation and narrow minimum in the middle of one of the descending shoulders of the sinusoid. We also collected substantial new data for previously known variables. In particular we revise the statistics of the occurrence of the Blazhko effect in RR Lyr type variables of M22.

Stellar Wind Retention and Expulsion in Massive Star Clusters

NASA Astrophysics Data System (ADS)

Naiman, J. P.; Ramirez-Ruiz, E.; Lin, D. N. C.

2018-05-01

Mass and energy injection throughout the lifetime of a star cluster contributes to the gas reservoir available for subsequent episodes of star formation and the feedback energy budget responsible for ejecting material from the cluster. In addition, mass processed in stellar interiors and ejected as winds has the potential to augment the abundance ratios of currently forming stars, or stars which form at a later time from a retained gas reservoir. Here we present hydrodynamical simulations that explore a wide range of cluster masses, compactnesses, metallicities and stellar population age combinations in order to determine the range of parameter space conducive to stellar wind retention or wind powered gas expulsion in star clusters. We discuss the effects of the stellar wind prescription on retention and expulsion effectiveness, using MESA stellar evolutionary models as a test bed for exploring how the amounts of wind retention/expulsion depend upon the amount of mixing between the winds from stars of different masses and ages. We conclude by summarizing some implications for gas retention and expulsion in a variety of compact (σv ≳ 20 kms-1) star clusters including young massive star clusters (105 ≲ M/M⊙ ≲ 107, age ≲ 500 Myrs), intermediate age clusters (105 ≲ M/M⊙ ≲ 107, age ≈ 1 - 4 Gyrs), and globular clusters (105 ≲ M/M⊙ ≲ 107, age ≳ 10 Gyrs).

A Deep Near-Infrared Survey of the N 49 Region around the Soft Gamma-Ray Repeater 0526-66

NASA Technical Reports Server (NTRS)

Klose, S.; Henden, A. A.; Geppert, U.; Greiner, J.; Guetter, H. H.; Hartmann, D. H.; Kouveliotou, C.; Luginbuhl, C. B.; Stecklurn, B.; Vrba, F. J.

2004-01-01

We report the results of a deep near-infrared survey of the vicinity of supernova remnant N49 in the Large Magellanic Cloud (LMC), which contains the soft gamma-ray repeater (SGR) 0526-66. Two of the four confirmed SGRs are potentially associated with compact stellar clusters. We thus searched for a similar association of SGR0526-66, and find the unexplored young stellar cluster SL 463 at a projected distance of approx. 30 pc from the SGR. This constitutes the third cluster-SGR link, and lends support to scenarios in which SGR progenitors originate in young, embedded clusters. If real, the cluster-SGR association constrains the age and thus the initial mass of these stars. In addition, our high-resolution images of the super- nova remnant N49 reveal an area of excess K-band flux in the southeastern part of the SNR. This feature coincides with the maximum flux area at 8.28 microns as detected by the Midcourse Space Experiment (MSX satellite), which we identify with IRAS 052594607.

Kron 3: a fourth intermediate age cluster in the SMC with evidence of multiple populations

NASA Astrophysics Data System (ADS)

Hollyhead, K.; Lardo, C.; Kacharov, N.; Bastian, N.; Hilker, M.; Rejkuba, M.; Koch, A.; Grebel, E. K.; Georgiev, I.

2018-05-01

We present the results of a spectroscopic study of the intermediate age (≈6.5 Gyr) massive cluster Kron 3 in the Small Magellanic Cloud. We measure CN and CH band strengths (at ≃3839 and 4300 Å, respectively) using VLT FORS2 spectra of 16 cluster members and find a sub-population of five stars enriched in nitrogen. We conclude that this is evidence for multiple populations in Kron 3, the fourth intermediate age cluster, after Lindsay 1, NGC 416 and NGC 339 (ages 6-8 Gyr), to display this phenomenon originally thought to be a unique characteristic of old globular clusters. At ≈6.5 Gyr this is one of the youngest clusters with multiple populations, indicating that the mechanism responsible for their onset must operate until a redshift of at least 0.75, much later than the peak of globular cluster formation at redshift ˜3.

Beverage consumption patterns at age 13–17 are associated with weight, height, and BMI at age 17

PubMed Central

Marshall, Teresa A.; Van Buren, John M.; Warren, John J.; Cavanaugh, Joseph E.; Levy, Steven M.

2017-01-01

Background Sugar-sweetened beverages (SSBs) have been associated with obesity in children and adults; however, associations between beverage patterns and obesity are not understood. Objective To describe beverage patterns during adolescence, and the associations between adolescent beverage patterns and age 17 anthropometric measures. Design Cross-sectional analyses of longitudinally-collected data. Participants/setting Participants in the longitudinal Iowa Fluoride Study having at least one beverage questionnaire completed between ages 13.0 and 14.0 years, having a second questionnaire completed between 16.0 and 17.0 years and attending an age 17 clinic exam for weight and height measurements (n=369). Exposure Beverages were collapsed into 4 categories {i.e., 100% juice, milk, water and other sugar-free beverages (water/SFB), and SSBs} for the purpose of clustering. Five beverage clusters were identified from standardized age 13–17 mean daily beverage intakes and named by the authors for the dominant beverage: juice, milk, water/SFB, neutral and SSB. Outcome Age 17 weight, height and BMI. Statistical analyses Ward’s method for clustering of beverage variables. One-way ANOVA and chi-square tests for bivariable associations. Gamma regression for associations of weight or BMI (outcomes) with beverage clusters and demographic variables. Linear regression for associations of height (outcome) with beverage clusters and demographic variables. Results Participants with family incomes < $60,000 trended shorter (1.5±0.8 cm; P=0.070) and were heavier (2.0±0.7 BMI units; P=0.002) than participants with family incomes ≥ 60,000/year. Adjusted mean weight, height and BMI estimates differed by beverage cluster membership. For example, on average, male and female members of the neutral cluster were 4.5 cm (P=0.010) and 4.2 (P=0.034) cm shorter, respectively, than members of the milk cluster. For members of the juice cluster, the mean BMI was lower than for members of the milk cluster (by 2.4 units), water/SFB cluster (3.5 units), neutral cluster (2.2 units) and SSB cluster (3.2 units) (all Ps<0.05). Conclusions Age 13–17 year beverage patterns were associated with age 17 anthropometric measures and BMI in this sample. Beverage patterns might be characteristic of overall food choices and dietary behaviors that influence growth. PMID:28259744

Substance Use Prevention Program for Adolescents with Intellectual Disabilities on Special Education Schools: A Cluster Randomised Control Trial

ERIC Educational Resources Information Center

Kiewik, M.; VanDerNagel, J. E.?L.; Kemna, L. E.?M.; Engels, R. C.?M.?E.; DeJong, C. A.?J.

2016-01-01

Background: Students without intellectual disability (ID) start experimenting with tobacco and alcohol between 12 and 15?years of age. However, data for 12- to 15-year old students with ID are unavailable. Prevention programs, like "prepared on time" (based on the attitude-social influence-efficacy model), are successful, but their…

Symptom clusters in advanced cancer.

PubMed

Jiménez, Ana; Madero, Rosario; Alonso, Alberto; Martínez-Marín, Virginia; Vilches, Yolanda; Martínez, Beatriz; Feliu, Marta; Díaz, Leyre; Espinosa, Enrique; Feliu, Jaime

2011-07-01

Patients with advanced cancer often experience multiple concurrent symptoms. Few studies have explored symptom clusters (SCs) in this population. The aim of the present study was to explore SCs in advanced cancer, evaluate the characteristics associated with various clusters, and determine their relationship to survival. This study included patients in the palliative care program of the Hospital Universitario La Paz from 2003 to 2005. The Edmonton Symptom Assessment System and a supplement including 13 other symptoms were used to detect symptoms. Principal component analysis was performed to determine symptom relationships and compare SCs with associated parameters. In total, 406 patients were included, 61% men and 39% women. The median age was 66.4 (range 18-95). The most common primaries were gastrointestinal (35%), lung (25%), genitourinary (8%), breast (5%), and head and neck (5%) carcinomas. The following clusters were identified: confusion (cognitive impairment, agitation, urinary incontinence), neuropsychological (anxiety, depression, and insomnia), anorexia-cachexia (anorexia, weight loss, and tiredness), and gastrointestinal (nausea and vomiting). The presence of these SCs was influenced by primary cancer site, gender, age, and performance status. Survival was related to the number of SCs present in a given patient: zero SC, 52 days; one SC, 38 days; two SCs, 23 days; and three to four SCs, 19 days; P < 0.001. Different SCs can be identified in patients with advanced cancer. These SCs are influenced by primary cancer site, gender, age, and Eastern Cooperative Oncology Group performance status, and they can have prognostic value. Copyright © 2011 U.S. Cancer Pain Relief Committee. Published by Elsevier Inc. All rights reserved.

X-Ray Binaries and Star Clusters in the Antennae: Optical Cluster Counterparts

NASA Astrophysics Data System (ADS)

Rangelov, Blagoy; Chandar, Rupali; Prestwich, Andrea; Whitmore, Bradley C.

2012-10-01

We compare the locations of 82 X-ray binaries (XRBs) detected in the merging Antennae galaxies by Zezas et al., based on observations taken with the Chandra X-Ray Observatory, with a catalog of optically selected star clusters presented by Whitmore et al., based on observations taken with the Hubble Space Telescope. Within the 2σ positional uncertainty of ≈0farcs8, we find 22 XRBs are coincident with star clusters, where only two to three chance coincidences are expected. The ages of the clusters were estimated by comparing their UBVI, Hα colors with predictions from stellar evolutionary models. We find that 14 of the 22 coincident XRBs (64%) are hosted by star clusters with ages of ≈6 Myr or less. All of the very young host clusters are fairly massive and have M >~ 3 × 104 M ⊙, with many having masses M ≈ 105 M ⊙. Five of the XRBs are hosted by young clusters with ages τ ≈ 10-100 Myr, while three are hosted by intermediate-age clusters with τ ≈ 100-300 Myr. Based on the results from recent N-body simulations, which suggest that black holes are far more likely to be retained within their parent clusters than neutron stars, we suggest that our sample consists primarily of black hole binaries with different ages.

Extended main sequence turnoffs in intermediate-age star clusters: a correlation between turnoff width and early escape velocity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goudfrooij, Paul; Kozhurina-Platais, Vera; Kalirai, Jason S.

2014-12-10

We present a color-magnitude diagram analysis of deep Hubble Space Telescope imaging of a mass-limited sample of 18 intermediate-age (1-2 Gyr old) star clusters in the Magellanic Clouds, including eight clusters for which new data were obtained. We find that all star clusters in our sample feature extended main-sequence turnoff (eMSTO) regions that are wider than can be accounted for by a simple stellar population (including unresolved binary stars). FWHM widths of the MSTOs indicate age spreads of 200-550 Myr. We evaluate the dynamical evolution of clusters with and without initial mass segregation. Our main results are (1) the fractionmore » of red clump (RC) stars in secondary RCs in eMSTO clusters scales with the fraction of MSTO stars having pseudo-ages of ≲1.35 Gyr; (2) the width of the pseudo-age distributions of eMSTO clusters is correlated with their central escape velocity v {sub esc}, both currently and at an age of 10 Myr. We find that these two results are unlikely to be reproduced by the effects of interactive binary stars or a range of stellar rotation velocities. We therefore argue that the eMSTO phenomenon is mainly caused by extended star formation within the clusters; and (3) we find that v {sub esc} ≥ 15 km s{sup –1} out to ages of at least 100 Myr for all clusters featuring eMSTOs, and v {sub esc} ≤ 12 km s{sup –1} at all ages for two lower-mass clusters in the same age range that do not show eMSTOs. We argue that eMSTOs only occur for clusters whose early escape velocities are higher than the wind velocities of stars that provide material from which second-generation stars can form. The threshold of 12-15 km s{sup –1} is consistent with wind velocities of intermediate-mass asymptotic giant branch stars and massive binary stars in the literature.« less

STAR CLUSTERS IN A NUCLEAR STAR FORMING RING: THE DISAPPEARING STRING OF PEARLS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Väisänen, Petri; Barway, Sudhanshu; Randriamanakoto, Zara, E-mail: petri@saao.ac.za

2014-12-20

An analysis of the star cluster population in a low-luminosity early-type galaxy, NGC 2328, is presented. The clusters are found in a tight star forming nuclear spiral/ring pattern and we also identify a bar from structural two-dimensional decomposition. These massive clusters are forming very efficiently in the circumnuclear environment and they are young, possibly all less than 30 Myr of age. The clusters indicate an azimuthal age gradient, consistent with a ''pearls-on-a-string'' formation scenario, suggesting bar-driven gas inflow. The cluster mass function has a robust down turn at low masses at all age bins. Assuming clusters are born with a power-lawmore » distribution, this indicates extremely rapid disruption at timescales of just several million years. If found to be typical, it means that clusters born in dense circumnuclear rings do not survive to become old globular clusters in non-interacting systems.« less

Star Formation in NGC 6531-Evidence From the age Spread and Initial Mass Function

NASA Astrophysics Data System (ADS)

Forbes, Douglas

1996-09-01

The results of a photometric UBV study of the young open cluster NGC 6531 are presented. The cluster is found to have a mean reddening E(B-V)=0.28±0.04 (s.d.) and distance modulus (V0-Mv)=10.70±0.13 (s.e.), and 105±11 likely cluster members have been identified within the cluster coronal radius of 9 arcmin. A comparison of the high-luminosity end of the cluster color-magnitude diagram to the evolutionary models by Maeder & Meynet [A&AS, 76, 411(1988)] suggests a nuclear age of (8±2) Myr. The very clear gap in the distribution of stars with 0≤(B-V)0≤0.20, corresponding to the "burn-off" of 3He in stars contracting to the main sequence [Ulrich, ApJ, 168, 57 (1971)], implies a contraction age of (8±3) Myr. There would seem to be no evidence of a spread in the ages of cluster stars, as has been observed in several other young open clusters [Herbst & Miller, AJ, 87, 1478 (1982)]. The initial mass function (IMF) constructed from the cluster luminosity function and the mass-luminosity relation given by Scab (1986) shows good agreement with the field star IMF, and with the IMFS of a number of clusters of similar age and richness. The relative deficiency of low-mass stars seen by Herbst and Miller in NGC 3293 (a cluster of quite similar age and reddening) is not evident in NGC 6531.

Exploring the nature and synchronicity of early cluster formation in the Large Magellanic Cloud - II. Relative ages and distances for six ancient globular clusters

NASA Astrophysics Data System (ADS)

Wagner-Kaiser, R.; Mackey, Dougal; Sarajedini, Ata; Chaboyer, Brian; Cohen, Roger E.; Yang, Soung-Chul; Cummings, Jeffrey D.; Geisler, Doug; Grocholski, Aaron J.

2017-11-01

We analyse Hubble Space Telescope observations of six globular clusters in the Large Magellanic Cloud (LMC) from programme GO-14164 in Cycle 23. These are the deepest available observations of the LMC globular cluster population; their uniformity facilitates a precise comparison with globular clusters in the Milky Way. Measuring the magnitude of the main-sequence turn-off point relative to template Galactic globular clusters allows the relative ages of the clusters to be determined with a mean precision of 8.4 per cent, and down to 6 per cent for individual objects. We find that the mean age of our LMC cluster ensemble is identical to the mean age of the oldest metal-poor clusters in the Milky Way halo to 0.2 ± 0.4 Gyr. This provides the most sensitive test to date of the synchronicity of the earliest epoch of globular cluster formation in two independent galaxies. Horizontal branch magnitudes and subdwarf fitting to the main sequence allow us to determine distance estimates for each cluster and examine their geometric distribution in the LMC. Using two different methods, we find an average distance to the LMC of 18.52 ± 0.05.

Oldest Known Objects May Be Surprisingly Immature

NASA Astrophysics Data System (ADS)

2008-04-01

Some of the oldest objects in the Universe may still have a long way to go, according to a new study using NASA’s Chandra X-ray Observatory. These new results indicate that globular clusters might be surprisingly less mature in their development than previously thought. Globular clusters, dense bunches of up to millions of stars found in all galaxies, are among the oldest known objects in the Universe, with most estimates of their ages ranging from 9 to 13 billions of years old. As such they contain some of the first stars to form in a galaxy and understanding their evolution is critical to understanding the evolution of galaxies. Animation The Evolution of a Globular Cluster "For many years, globular clusters have been used as wonderful natural laboratories to study the evolution and interaction of stars," said John Fregeau of Northwestern University, who conducted the study. "So, it’s exciting to discover something that may be new and fundamental about the way they evolve." Conventional wisdom is that globular clusters pass through three phases of evolution or development of their structure, corresponding to adolescence, middle age, and old age. These "ages" refer to the evolutionary state of the cluster, not the physical ages of the individual stars. People Who Read This Also Read... Milky Way's Super-efficient Particle Accelerators Caught in The Act Discovery of Most Recent Supernova in Our Galaxy Action Replay of Powerful Stellar Explosion Jet Power and Black Hole Assortment Revealed in New Chandra Image In the adolescent phase, the stars near the center of the cluster collapse inward. Middle age refers to a phase when the interactions of double stars near the center of the cluster prevents it from further collapse. Finally, old age describes when binaries in the center of the cluster are disrupted or ejected, and the center of the cluster collapses inwards. For years, it has been thought that most globular clusters are middle- aged with a few being toward the end of their evolution. However, Chandra data along with theoretical work suggest this may not be the case. When single and double stars interact in the crowded centers of globular clusters, double stars can form that transfer mass and give off X-rays. Since such double stars are expected to mostly be formed in the middle of a globular cluster’s evolution and then lost in old age, the relative number of X-ray sources gives clues about the stage of evolution the cluster is in. A new study by Fregeau of 13 globular clusters in the Milky Way shows that three of them have unusually large number of X-ray sources, or X- ray binaries, suggesting the clusters are middle-aged. Previously, these globular clusters had been classified as being in old age because they had very tight concentrations of stars in their centers, another litmus test of age used by astronomers. The implication is that most globular clusters, including the other ten studied by Fregeau, are not in the middle age of their evolution, as previously thought, but are actually in adolescence. "It’s remarkable that these objects, which are thought to be some of the oldest in the Universe, may really be very immature in their development," said Fregeau whose paper appears in The Astrophysical Journal. "This would represent a major change in thinking about the current evolutionary status of globular clusters." If confirmed, this result would help reconcile other observations with recent theoretical work that suggest the tightness of the central concentration of stars in the most evolved globular clusters is consistent with them being in a middle, rather than an advanced phase of evolution. Other theoretical studies have suggested it can take longer than the current age of the Universe for globular clusters to reach old age. Besides improving the understanding of the basic evolution of globular clusters, this result has implications for understanding stellar interactions in dense environments. It also removes the need for exotic mechanisms - some involving black holes - that were thought to be needed to prevent the many middle-aged clusters from collapsing. "Some exotic scenarios, including some of my own, have been invoked to try to make sense of the observations and save the old theory," said Fregeau. "If this result holds up, we don't have to worry about the exotic scenarios any more." NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the agency’s Science Mission Directorate. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.

Enhanced positron trapping by Ag nanoclusters at low temperatures: A challenge of positron sensitivity to quantum dots

NASA Astrophysics Data System (ADS)

Zou, B.; Qi, N.; Liu, Z. W.; Chen, Z. Q.; Liu, H. Q.; Yi, D. Q.; Tang, Z.

2017-03-01

Microstructure evolution of three Al-Ag alloys with different Ag contents (1 wt. % Ag, 5 wt. % Ag, and 15 wt. % Ag) was studied by positron annihilation spectroscopy during the aging process. In situ measurements of the positron lifetime and Doppler broadening of annihilation radiation indicate the fast formation of Ag-rich clusters during natural aging of the alloys. The formation of Ag-rich clusters was further confirmed by coincidence Doppler broadening measurements. The Ag signal reflected by the Coincidence Doppler broadening spectrum increases with increasing Ag content and is further enhanced after subsequent artificial aging at 140 °C. This might be due to the increase in the size of Ag clusters. The temperature dependence of the Doppler broadening spectra between 10 K and 290 K was measured for the Al-Ag alloys after natural and artificial aging. Detrapping of positrons from Ag clusters with increasing temperature was observed for all the three Al-Ag alloys after natural aging and for the Al-1 wt. % Ag after artificial aging. This indicates that Ag clusters act as shallow positron trapping centers. The thermal detrapping of positrons becomes ambiguous with increasing Ag content in the alloy and is nearly invisible in the artificially aged Al-5 wt. % Ag and Al-15 wt. % Ag. The positron binding energy of the Ag cluster is roughly estimated to be about 18.8 meV and 50 meV in the Al-1 wt. % Ag sample after natural aging and artificial aging at 140 °C, respectively, which suggests that the confinement of positrons in the quantum-dot like state depends on the size or chemical composition of clusters. Theoretical calculations confirm positron trapping by Ag nanoclusters, and the confinement of positrons is enhanced with increasing Ag cluster size.

Bitter experiences of elderly parents of children with intellectual disabilities: A phenomenological study

PubMed Central

Hamedanchi, Arya; Khankeh, Hamid Reza; Fadayevatan, Reza; Teymouri, Robab; Sahaf, Robab

2016-01-01

Background: It is predicted that over the next 30 years, there will be a significant increase in the number of elderly parents who care for their children with intellectual disability. This paper is part of a larger qualitative study which investigated the unpleasant experiences of these parents. Materials and Methods: A phenomenological approach was adopted and data were collected through unstructured in-depth interviews with elderly parents of children with intellectual disability. The data were analyzed using Colaizzi's seven-step method. Results: “Bitterness” is one of the four emergent themes extracted in this study which has five theme clusters: inappropriate behavior toward the child in the society, the society's failure to support the child with intellectual disability, sorrows experienced by parents, the child's problems, and barriers in the care of the child with intellectual disability. One significant barrier in the last theme cluster is limitations due to aging. Conclusions: The findings of this study suggest that the elderly parents of children with intellectual disability experience many sorrows and unpleasant feelings, but they mostly consider the social factors as the cause of problems and not the presence of the child. The results also indicate that older parents cannot look after the child as before in their old age; so, future well-designed studies are required for identification of the process of supporting them. PMID:27186205

A WISE Survey of New Star Clusters in the Central Plane Region of the Milky Way

NASA Astrophysics Data System (ADS)

Ryu, Jinhyuk; Lee, Myung Gyoon

2018-04-01

We present the discovery of new star clusters in the central plane region (| l| < 30^\\circ and | b| < 6^\\circ ) of the Milky Way. In order to overcome the extinction problem and the spatial limit of previous surveys, we use the Wide-field Infrared Survey Explorer (WISE) data to find clusters. We also use other infrared survey data in the archive for additional analysis. We find 923 new clusters, of which 202 clusters are embedded clusters. These clusters are concentrated toward the Galactic plane and show a symmetric distribution with respect to the Galactic latitude. The embedded clusters show a stronger concentration to the Galactic plane than the nonembedded clusters. The new clusters are found more in the first Galactic quadrant, while previously known clusters are found more in the fourth Galactic quadrant. The spatial distribution of the combined sample of known clusters and new clusters is approximately symmetric with respect to the Galactic longitude. We estimate reddenings, distances, and relative ages of the 15 class A clusters using theoretical isochrones. Ten of them are relatively old (age >800 Myr) and five are young (age ≈4 Myr).

Detrital zircon geochronology of some neoproterozoic to triassic rocks in interior alaska

USGS Publications Warehouse

Bradley, D.C.; McClelland, W.C.; Wooden, J.L.; Till, A.B.; Roeske, S.M.; Miller, M.L.; Karl, Susan M.; Abbott, J.G.

2007-01-01

We report 777 U-Pb SHRIMP detrital zircon ages from thirteen sandstones and metasandstones in interior Alaska. About sixty grains per sample were analyzed; typically, half to three-fourths of these were concordant within ?? 10%. Farewell terrane. Two quartzites were collected from Ruby quadrangle and a third from Taylor Mountains quadrangle. All three are interpreted to represent a low stratigraphic level in the Nixon Fork platform succession; the samples from Ruby quadrangle are probably late Neoproterozoic, and the sample from Taylor Mountains quadrangle is probably Cambrian in age. The youngest detrital zircon in any of the three is 851 Ma. The two Ruby quadrangle samples area almost identical: one has a major age cluster at 1980-2087 and minor age clusters at 944-974 and 1366-1383 Ma; the other has a major age cluster at 1993-2095 Ma and minor age clusters at 912-946 and 1366-1395 Ma. The Taylor Mountains sample shows one dominant peak at 1914-2057 Ma. Notably absent are zircons in the range 1800-1900 Ma, which are typical of North American sources. The detrital zircon populations are consistent with paleontological evidence for a peri- Siberian position of the Farewell terrane during the early Paleozoic. Mystic subterrane of the Farewell terrane. Three graywackes from flysch of the Mystic subterrane, Talkeetna quadrangle, were sampled with the expectation that all three were Pennsylvanian. Asample from Pingston Creek is Triassic (as revealed by an interbedded ash dated at ca. 223 Ma) and is dominated by age clusters of 341-359 and 1804-1866 Ma, both consistent with a sediment source in the Yukon-Tanana terrane. Minor age clusters at 848-869 and 1992-2018 Ma could have been sourced in the older part of the Farewell terrane. Still other minor age clusters at 432-461, 620-657, 1509-1536, and 1627-1653 Ma are not readily linked to sources that are now nearby. Asample from Surprise Glacier is mid-Mississippian or younger. Adominant age cluster at 1855-1883 and a minor one at 361-367 Ma could have been sourced in the Yukon-Tanana terrane. Other age clusters at 335-336, 457-472, 510-583, and 1902-1930 have no obvious nearby source. A sample from Ripsnorter Creek is Silurian or younger. The dominant age cluster at 937-981 Ma and a minor one at 2047-2077 Ma could have been sourced in the Farewell terrane. Minor age clusters at 1885-1900 and 2719-2770 Ma could have been sourced in the Yukon-Tanana terrane. Other age clusters at 429 490, 524-555, 644-652, 1023-1057, 1131-1185, and 1436-1445 Ma have no obvious nearby source. The so-called Mystic subterrane is structurally complex and would appear to include more than one Phanerozoic turbidite succession; more mapping and detrital zircon geochronology are needed. Wickersham and Yukon-Tanana terranes. A grit from Wickersham terrane in Tanana quadrangle and a grit from Yukon-Tanana terrane in Talkeetna quadrangle have similar, exclusively Precambrian detrital zircon populations, supporting previous correlations. The Wickersham sample has major age clusters at 1776-1851 and 1930-1964 Ma, and the youngest grain is 1198 Ma. The Yukon-Tanana grit has a major age cluster at 1834-1867 Ma, and the youngest grain is 1789 Ma. A North American source has been previously proposed, and this seems likely based on detrital zircon data. Ruby terrane and Minook Complex. Detrital zircons from quartzites in the Ruby terrane show two quite different age patterns. Asample from the Bear Creek area of Tanana quadrangle has detrital zircon ages that are similar to those from the Wickersham and Yukon-Tanana grits. The dominant age clusters are 1823-1856 and 1887-1931 Ma. In contrast, a quartzite from nearby Senatis Mountain (Tanana quadrangle) yielded a completely different detrital zircon age spectrum, featuring a broad peak with no significant gaps from 1024 to 1499 Ma and a minor age cluster at 1671-1695 Ma. The youngest concordant zircon is 1024 ?? 6 Ma. Aquartzite from the Minook Complex, a sliver along t

Washington photometry of 14 intermediate-age to old star clusters in the Small Magellanic Cloud

NASA Astrophysics Data System (ADS)

Piatti, Andrés E.; Clariá, Juan J.; Bica, Eduardo; Geisler, Doug; Ahumada, Andrea V.; Girardi, Léo

2011-10-01

We present CCD photometry in the Washington system C, T1 and T2 passbands down to T1˜ 23 in the fields of L3, L28, HW 66, L100, HW 79, IC 1708, L106, L108, L109, NGC 643, L112, HW 84, HW 85 and HW 86, 14 Small Magellanic Cloud (SMC) clusters, most of them poorly studied objects. We measured T1 magnitudes and C-T1 and T1-T2 colours for a total of 213 516 stars spread throughout cluster areas of 14.7 × 14.7 arcmin2 each. We carried out an in-depth analysis of the field star contamination of the colour-magnitude diagrams (CMDs) and statistically cleaned the cluster CMDs. Based on the best fits of isochrones computed by the Padova group to the (T1, C-T1) CMDs, as well as from the δ(T1) index and the standard giant branch procedure, we derived ages and metallicities for the cluster sample. With the exception of IC 1708, a relatively metal-poor Hyades-age cluster, the remaining 13 objects are between intermediate and old age (from 1.0 to 6.3 Gyr), their [Fe/H] values ranging from -1.4 to -0.7 dex. By combining these results with others available in the literature, we compiled a sample of 43 well-known SMC clusters older than 1 Gyr, with which we produced a revised age distribution. We found that the present clusters' age distribution reveals two primary excesses of clusters at t˜ 2 and 5 Gyr, which engraves the SMC with clear signs of enhanced formation episodes at both ages. In addition, we found that from the birth of the SMC cluster system until approximately the first 4 Gyr of its lifetime, the cluster formation resembles that of a constant formation rate scenario.

A computational microscopy study of nanostructural evolution in irradiated pressure vessel steels

NASA Astrophysics Data System (ADS)

Odette, G. R.; Wirth, B. D.

1997-11-01

Nanostructural features that form in reactor pressure vessel steels under neutron irradiation at around 300°C lead to significant hardening and embrittlement. Continuum thermodynamic-kinetic based rate theories have been very successful in modeling the general characteristics of the copper and manganese nickel rich precipitate evolution, often the dominant source of embrittlement. However, a more detailed atomic scale understanding of these features is needed to interpret experimental measurements and better underpin predictive embrittlement models. Further, other embrittling features, believed to be subnanometer defect (vacancy)-solute complexes and small regions of modest enrichment of solutes are not well understood. A general approach to modeling embrittlement nanostructures, based on the concept of a computational microscope, is described. The objective of the computational microscope is to self-consistently integrate atomic scale simulations with other sources of information, including a wide range of experiments. In this work, lattice Monte Carlo (LMC) simulations are used to resolve the chemically and structurally complex nature of CuMnNiSi precipitates. The LMC simulations unify various nanoscale analytical characterization methods and basic thermodynamics. The LMC simulations also reveal that significant coupled vacancy and solute clustering takes place during cascade aging. The cascade clustering produces the metastable vacancy-cluster solute complexes that mediate flux effects. Cascade solute clustering may also play a role in the formation of dilute atmospheres of solute enrichment and enhance the nucleation of manganese-nickel rich precipitates at low Cu levels. Further, the simulations suggest that complex, highly correlated processes (e.g. cluster diffusion, formation of favored vacancy diffusion paths and solute scavenging vacancy cluster complexes) may lead to anomalous fast thermal aging kinetics at temperatures below about 450°C. The potential technical significance of these phenomena is described.

Gender differences in climacteric symptoms and associated factors in Korean men and women.

PubMed

Yeom, Hyun-E

2018-06-01

Both men and women may experience multifaceted symptoms that are part of natural aging throughout the climacteric period. This study compared the prevalence and severity of climacteric symptoms between genders and identified the underlying clusters of climacteric symptoms and associated factors in midlife men and women. A cross-sectional study was done with 254 middle-aged Korean men (n = 129, M = 50.4) and women (n = 125, M = 49.5). Data were collected by self-administered surveys and analyzed using t-tests, chi-square tests, exploratory factor analysis, and regression analysis. Significant gender differences in overall climacteric symptoms were not detected except for muscle weakness, weight gain, and hot flashes. Climacteric symptoms were clustered as physical, vasomotor-genital, psychological, and metabolic dimensions, with the physical dimension being the most explanatory cluster. A significant gender effect was found only in the metabolic dimension after adjusting for the relevant covariates, and regular eating was significantly associated with all symptom clusters. This study offers evidence that most climacteric symptoms are shared by both men and women and emphasizes the importance of healthier lifestyles in the climacteric transition period. The findings highlight the critical need for integrated assessments of the multifactorial symptoms and of modifying poor lifestyles in both genders throughout the climacteric transition period. Copyright © 2018 Elsevier Inc. All rights reserved.

Beverage Consumption Patterns at Age 13 to 17 Years Are Associated with Weight, Height, and Body Mass Index at Age 17 Years.

PubMed

Marshall, Teresa A; Van Buren, John M; Warren, John J; Cavanaugh, Joseph E; Levy, Steven M

2017-05-01

Sugar-sweetened beverages (SSBs) have been associated with obesity in children and adults; however, associations between beverage patterns and obesity are not understood. Our aim was to describe beverage patterns during adolescence and associations between adolescent beverage patterns and anthropometric measures at age 17 years. We conducted a cross-sectional analyses of longitudinally collected data. Data from participants in the longitudinal Iowa Fluoride Study having at least one beverage questionnaire completed between ages 13.0 and 14.0 years, having a second questionnaire completed between 16.0 and 17.0 years, and attending clinic examination for weight and height measurements at age 17 years (n=369) were included. Beverages were collapsed into four categories (ie, 100% juice, milk, water and other sugar-free beverages, and SSBs) for the purpose of clustering. Five beverage clusters were identified from standardized age 13 to 17 years mean daily beverage intakes and named by the authors for the dominant beverage: juice, milk, water/sugar-free beverages, neutral, and SSB. Weight, height, and body mass index (BMI; calculated as kg/m 2 ) at age 17 years were analyzed. We used Ward's method for clustering of beverage variables, one-way analysis of variance and χ 2 tests for bivariable associations, and γ-regression for associations of weight or BMI (outcomes) with beverage clusters and demographic variables. Linear regression was used for associations of height (outcome) with beverage clusters and demographic variables. Participants with family incomes <$60,000 trended shorter (1.5±0.8 cm; P=0.070) and were heavier (2.0±0.7 BMI units; P=0.002) than participants with family incomes ≥$60,000/year. Adjusted mean weight, height, and BMI estimates differed by beverage cluster membership. For example, on average, male and female members of the neutral cluster were 4.5 cm (P=0.010) and 4.2 cm (P=0.034) shorter, respectively, than members of the milk cluster. For members of the juice cluster, mean BMI was lower than for members of the milk cluster (by 2.4 units), water/sugar-free beverage cluster (3.5 units), neutral cluster (2.2 units), and SSB cluster (3.2 units) (all P<0.05). Beverage patterns at ages 13 to 17 years were associated with anthropometric measures and BMI at age 17 years in this sample. Beverage patterns might be characteristic of overall food choices and dietary behaviors that influence growth. Copyright © 2017 Academy of Nutrition and Dietetics. Published by Elsevier Inc. All rights reserved.

X-RAY BINARIES AND STAR CLUSTERS IN THE ANTENNAE: OPTICAL CLUSTER COUNTERPARTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rangelov, Blagoy; Chandar, Rupali; Prestwich, Andrea

2012-10-20

We compare the locations of 82 X-ray binaries (XRBs) detected in the merging Antennae galaxies by Zezas et al., based on observations taken with the Chandra X-Ray Observatory, with a catalog of optically selected star clusters presented by Whitmore et al., based on observations taken with the Hubble Space Telescope. Within the 2{sigma} positional uncertainty of Almost-Equal-To 0.''8, we find 22 XRBs are coincident with star clusters, where only two to three chance coincidences are expected. The ages of the clusters were estimated by comparing their UBVI, H{alpha} colors with predictions from stellar evolutionary models. We find that 14 ofmore » the 22 coincident XRBs (64%) are hosted by star clusters with ages of Almost-Equal-To 6 Myr or less. All of the very young host clusters are fairly massive and have M {approx}> 3 Multiplication-Sign 10{sup 4} M {sub Sun }, with many having masses M Almost-Equal-To 10{sup 5} M {sub Sun }. Five of the XRBs are hosted by young clusters with ages {tau} Almost-Equal-To 10-100 Myr, while three are hosted by intermediate-age clusters with {tau} Almost-Equal-To 100-300 Myr. Based on the results from recent N-body simulations, which suggest that black holes are far more likely to be retained within their parent clusters than neutron stars, we suggest that our sample consists primarily of black hole binaries with different ages.« less

GLOBULAR CLUSTER ABUNDANCES FROM HIGH-RESOLUTION, INTEGRATED-LIGHT SPECTROSCOPY. III. THE LARGE MAGELLANIC CLOUD: Fe AND AGES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Colucci, Janet E.; Bernstein, Rebecca A.; Cameron, Scott A.

2011-07-01

In this paper, we refine our method for the abundance analysis of high-resolution spectroscopy of the integrated light of unresolved globular clusters (GCs). This method was previously demonstrated for the analysis of old (>10 Gyr) Milky Way (MW) GCs. Here, we extend the technique to young clusters using a training set of nine GCs in the Large Magellanic Cloud. Depending on the signal-to-noise ratio of the data, we use 20-100 Fe lines per cluster to successfully constrain the ages of old clusters to within a {approx}5 Gyr range, the ages of {approx}2 Gyr clusters to a 1-2 Gyr range, andmore » the ages of the youngest clusters (0.05-1 Gyr) to a {approx}200 Myr range. We also demonstrate that we can measure [Fe/H] in clusters with any age less than 12 Gyr with similar or only slightly larger uncertainties (0.1-0.25 dex) than those obtained for old MW GCs (0.1 dex); the slightly larger uncertainties are due to the rapid evolution in stellar populations at these ages. In this paper, we present only Fe abundances and ages. In the next paper in this series, we present our complete analysis of {approx}20 elements for which we are able to measure abundances. For several of the clusters in this sample, there are no high-resolution abundances in the literature from individual member stars; our results are the first detailed chemical abundances available. The spectra used in this paper were obtained at Las Campanas with the echelle on the du Pont Telescope and with the MIKE spectrograph on the Magellan Clay Telescope.« less

Age as a major factor in the onset of multiple populations in stellar clusters

NASA Astrophysics Data System (ADS)

Martocchia, S.; Cabrera-Ziri, I.; Lardo, C.; Dalessandro, E.; Bastian, N.; Kozhurina-Platais, V.; Usher, C.; Niederhofer, F.; Cordero, M.; Geisler, D.; Hollyhead, K.; Kacharov, N.; Larsen, S.; Li, C.; Mackey, D.; Hilker, M.; Mucciarelli, A.; Platais, I.; Salaris, M.

2018-01-01

It is now well established that globular clusters (GCs) exhibit star-to-star light-element abundance variations (known as multiple populations, MPs). Such chemical anomalies have been found in (nearly) all the ancient GCs (more than 10 Gyr old) of our Galaxy and its close companions, but so far no model for the origin of MPs is able to reproduce all the relevant observations. To gain new insights into this phenomenon, we have undertaken a photometric Hubble Space Telescope survey to study clusters with masses comparable to that of old GCs, where MPs have been identified, but with significantly younger ages. Nine clusters in the Magellanic Clouds with ages between ∼1.5 and 11 Gyr have been targeted in this survey. We confirm the presence of MPs in all clusters older than 6 Gyr and we add NGC 1978 to the group of clusters for which MPs have been identified. With an age of ∼2 Gyr, NGC 1978 is the youngest cluster known to host chemical abundance spreads found to date. We do not detect evident star-to-star variations for slightly younger massive clusters (∼1.7 Gyr), thus pointing towards an unexpected age dependence for the onset of MPs. This discovery suggests that the formation of MPs is not restricted to the early Universe and that GCs and young massive clusters share common formation and evolutionary processes.

Spatial clustering of childhood leukaemia in Switzerland: A nationwide study.

PubMed

Konstantinoudis, Garyfallos; Kreis, Christian; Ammann, Roland A; Niggli, Felix; Kuehni, Claudia E; Spycher, Ben D

2017-10-01

The aetiology of childhood leukaemia remains largely unknown. Several hypotheses involve environmental exposures that could implicate spatial clustering of cases. The evidence from previous clustering studies is inconclusive. Most of them used areal data and thus had limited spatial resolution. We investigated whether childhood leukaemia tends to cluster in space using exact geocodes of place of residence both at the time of birth or diagnosis. We included 1,871 leukaemia cases diagnosed between 1985 and 2015 at age 0-15 years from the Swiss Childhood Cancer Registry. For each case, we randomly sampled 10 age and sex matched controls from national censuses closest in time. We used the difference of k-functions, Cuzick-Edwards' test and Tango's index for point data to assess spatial clustering and Kulldorff's circular scan to detect clusters. We separately investigated acute lymphoid leukaemia (ALL), acute myeloid leukaemia (AML), different age groups at diagnosis (0-4, 5-15 years) and adjusted for multiple testing. After adjusting for multiple testing, we found no evidence of spatial clustering of childhood leukaemia neither around time of birth (p = 0.52) nor diagnosis (p = 0.51). Individual tests indicated spatial clustering for leukaemia diagnosed at age 5-15 years, p k-functions = 0.05 and p Cuzick-Edwards' = 0.04 and a cluster of ALL cases diagnosed at age 0-4 years in a small rural area (p = 0.05). This study provides little evidence of spatial clustering of childhood leukaemia in Switzerland and highlights the importance of accounting for multiple testing in clustering studies. © 2017 UICC.

[Association between adverse experiences in childhood and risk of chronic diseases in adulthood].

PubMed

Nie, Junyan; Yu, Honghui; Wang, Zhiqiang; Wang, Leilei; Han, Juan; Wang, Youjie; Du, Yukai; Shen, Min

2015-09-01

To analyze the prevalence and characteristics of childhood adverse experiences among adults aged 18-59 years and understand the association between childhood adverse experiences and risk of chronic diseases in adulthood. A cross-sectional study was conducted with a questionnaire among adults aged 18-59 years selected through cluster random sampling from 3 communities in Macheng, Hubei province. Uinivariate and multivariate logistic regression analyses were conducted to evaluate the association between adverse experiences in childhood and the risk of chronic diseases in adulthood. A total of 1 767 adults aged 18-59 years were surveyed and 1 501 valid questionnaires were returned. The average age was (36.32± 10.20) years for males and (35.72±9.08) years for females. The prevalence rate of childhood adverse experiences was 66.22%. The risk of chronic disease in adults increased with the increase of the score indicating childhood adverse experiences (Z=-5.902 1, P<0.000 1). Multivariate logistic regression analysis showed that being physically abused (OR=1.93, 95% CI: 1.41-2.64), substance abuse in family (OR=2.82, 95% CI: 1.16-6.80), being bullied (OR=2.59, 95% CI: 1.39-4.80) and parents separation/divorce (OR=1.51, 95% CI: 1.09-2.09) were significantly associated with risk of chronic diseases in adulthood. The prevalence of adverse childhood experiences was high in adults aged 18-59 years, which was significantly associated with the risk of chronic diseases in adulthood. Early prevention of chronic diseases should be conducted in childhood.

Study of Intermediate Age (~10-30 Myr) Open Clusters

NASA Astrophysics Data System (ADS)

Olguin, Lorenzo; Michel, Raul; Contreras, Maria; Hernandez, Jesus; Schuster, William; Chavarria-Kleinhenn, Carlos

2013-07-01

We present the study of a sample of intermediate age open clusters (age ~ 10-30 Myr) using optical (UBVRI) and infrared photometric data. Optical photometry was obtained as part of the San Pedro Martir Open Clusters Project (SPM-OCP, Schuster et al. 2007; Michel et al. 2013). Infrared photometry was retrieved from 2MASS public data archive and WISE database. Open clusters included in the SPM-OCP were selected from catalogues presented by Dias et al. (2002) and Froebrich, Scholz & Raftery (2007). One of the main goals of the SPM-OCP is to compile a self-consistent and homogeneous set of cluster fundamental parameters such as reddening, distance, age, and metallicity whenever possible. In this work, we have analyzed a set of 25 clusters from the SPM-OCP with estimated ages between 10 and 30 Myr. Derived fundamental parameters for each cluster in the sample as well as an example of typical color-color and color-magnitude diagrams are presented. Kinematic membership was established by using proper motion data taken from the literature. Based on infrared photometry, we have searched for candidate stars to posses a circumstellar disk within each clusters. For those selected candidates a follow-up spectroscpic study is being carried out. This work was partially supported by UNAM-PAPIIT grant IN-109311.

Multiple stellar populations in Magellanic Cloud clusters - III. The first evidence of an extended main sequence turn-off in a young cluster: NGC 1856

NASA Astrophysics Data System (ADS)

Milone, A. P.; Bedin, L. R.; Piotto, G.; Marino, A. F.; Cassisi, S.; Bellini, A.; Jerjen, H.; Pietrinferni, A.; Aparicio, A.; Rich, R. M.

2015-07-01

Recent studies have shown that the extended main-sequence turn-off (eMSTO) is a common feature of intermediate-age star clusters in the Magellanic Clouds (MCs). The most simple explanation is that these stellar systems harbour multiple generations of stars with an age difference of a few hundred million years. However, while an eMSTO has been detected in a large number of clusters with ages between ˜1-2 Gyr, several studies of young clusters in both MCs and in nearby galaxies do not find any evidence for a prolonged star formation history, i. e. for multiple stellar generations. These results have suggested alternative interpretation of the eMSTOs observed in intermediate-age star clusters. The eMSTO could be due to stellar rotation mimicking an age spread or to interacting binaries. In these scenarios, intermediate-age MC clusters would be simple stellar populations, in close analogy with younger clusters. Here, we provide the first evidence for an eMSTO in a young stellar cluster. We exploit multiband Hubble Space Telescope photometry to study the ˜300-Myr old star cluster NGC 1856 in the Large Magellanic Cloud and detected a broadened MSTO that is consistent with a prolonged star formation which had a duration of about 150 Myr. Below the turn-off, the main sequence (MS) of NGC 1856 is split into a red and blue component, hosting 33 ± 5 and 67 ± 5 per cent of the total number of MS stars, respectively. We discuss these findings in the context of multiple-stellar-generation, stellar-rotation, and interacting-binary hypotheses.

An improved determination of the lithium depletion boundary age of Blanco 1 and a first look on the effects of magnetic activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Juarez, Aaron J.; Stassun, Keivan G.; Cargile, Phillip A.

2014-11-10

The lithium depletion boundary (LDB) is a robust method for accurately determining the ages of young clusters, but most pre-main-sequence models used to derive LDB ages do not include the effects of magnetic activity on stellar properties. In light of this, we present results from our spectroscopic study of the very-low-mass members of the southern open cluster Blanco 1 using the Gemini-North Telescope, program IDs: GN-2009B-Q-53 and GN-2010B-Q-96. We obtained Gemini Multi-Object Spectrograph spectra at intermediate resolution for cluster candidate members with I ≈ 13-20 mag. From our sample of 43 spectra, we find 14 probable cluster members by consideringmore » proximity to the cluster sequence in an I/I – K {sub s} color-magnitude diagram, agreement with the cluster's systemic radial velocity, and magnetic activity as a youth indicator. We systematically analyze the Hα and Li features and update the LDB age of Blanco 1 to be 126{sub −14}{sup +13} Myr. Our new LDB age for Blanco 1 shows remarkable coevality with the benchmark Pleiades open cluster. Using available empirical activity corrections, we investigate the effects of magnetic activity on the LDB age of Blanco 1. Accounting for activity, we infer a corrected LDB age of 114{sub −10}{sup +9} Myr. This work demonstrates the importance of accounting for magnetic activity on LDB inferred stellar ages, suggesting the need to reinvestigate previous LDB age determinations.« less

Integral field spectroscopy with GEMINI: Extragalactic star cluster in NGC1275

NASA Astrophysics Data System (ADS)

Trancho, Gelys; Miller, Bryan; García-Lorenzo, Begoña; Sánchez, Sebastián F.

2006-01-01

Studies of globular cluster systems play a critical role in our understanding of galaxy formation. Imaging with the Hubble Space Telescope has revealed that young star clusters are formed copiously in galaxy mergers, strengthening theories in which giant elliptical galaxies are formed by the merger of spirals [e.g. Whitmore, B.C., Schweizer, F., Leitherer, C., Borne, K., Robert, C., 1993. Astronomical Journal. 106, 1354; Miller, B.W., Whitmore, B.C., Schweizer, F., Fall, S.M., 1997. Astronomical Journal. 114, 2381; Zepf, S.E., Ashman, K.M., English, J., Freeman, K.C., Sharples, R.M., 1999. Astronomical Journal. 118, 752; Ashman, K.M., Zepf, S.E., 1992. Astrophysical Journal. 384, 50]. However, the formation and evolution of globular cluster systems is still not well understood. Ages and metallicities of the clusters are uncertain either because of degeneracy in the broad-band colors or due to variable reddening. Also, the luminosity function of the young clusters, which depends critically on the metallicities and ages of the clusters, appears to be single power-laws while the luminosity function of old clusters has a well-defined break. Either there is significant dynamical evolution of the cluster systems or metallicity affects the mass function of forming clusters. Spectroscopy of these clusters are needed to improve the metallicity and age measurements and to study the kinematics of young cluster systems. Therefore, we have obtained GMOS IFU data of 4 clusters in NGC1275. We will present preliminary results like metallicities, ages, and velocities of the star clusters from IFU spectroscopy.

OPEN CLUSTERS AS PROBES OF THE GALACTIC MAGNETIC FIELD. I. CLUSTER PROPERTIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoq, Sadia; Clemens, D. P., E-mail: shoq@bu.edu, E-mail: clemens@bu.edu

2015-10-15

Stars in open clusters are powerful probes of the intervening Galactic magnetic field via background starlight polarimetry because they provide constraints on the magnetic field distances. We use 2MASS photometric data for a sample of 31 clusters in the outer Galaxy for which near-IR polarimetric data were obtained to determine the cluster distances, ages, and reddenings via fitting theoretical isochrones to cluster color–magnitude diagrams. The fitting approach uses an objective χ{sup 2} minimization technique to derive the cluster properties and their uncertainties. We found the ages, distances, and reddenings for 24 of the clusters, and the distances and reddenings formore » 6 additional clusters that were either sparse or faint in the near-IR. The derived ranges of log(age), distance, and E(B−V) were 7.25–9.63, ∼670–6160 pc, and 0.02–1.46 mag, respectively. The distance uncertainties ranged from ∼8% to 20%. The derived parameters were compared to previous studies, and most cluster parameters agree within our uncertainties. To test the accuracy of the fitting technique, synthetic clusters with 50, 100, or 200 cluster members and a wide range of ages were fit. These tests recovered the input parameters within their uncertainties for more than 90% of the individual synthetic cluster parameters. These results indicate that the fitting technique likely provides reliable estimates of cluster properties. The distances derived will be used in an upcoming study of the Galactic magnetic field in the outer Galaxy.« less

The panchromatic Hubble Andromeda Treasury. V. Ages and masses of the year 1 stellar clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fouesneau, Morgan; Johnson, L. Clifton; Weisz, Daniel R.

We present ages and masses for 601 star clusters in M31 from the analysis of the six filter integrated light measurements from near-ultraviolet to near-infrared wavelengths, made as part of the Panchromatic Hubble Andromeda Treasury (PHAT). We derive the ages and masses using a probabilistic technique, which accounts for the effects of stochastic sampling of the stellar initial mass function. Tests on synthetic data show that this method, in conjunction with the exquisite sensitivity of the PHAT observations and their broad wavelength baseline, provides robust age and mass recovery for clusters ranging from ∼10{sup 2} to 2 × 10{sup 6}more » M {sub ☉}. We find that the cluster age distribution is consistent with being uniform over the past 100 Myr, which suggests a weak effect of cluster disruption within M31. The age distribution of older (>100 Myr) clusters falls toward old ages, consistent with a power-law decline of index –1, likely from a combination of fading and disruption of the clusters. We find that the mass distribution of the whole sample can be well described by a single power law with a spectral index of –1.9 ± 0.1 over the range of 10{sup 3}-3 × 10{sup 5} M {sub ☉}. However, if we subdivide the sample by galactocentric radius, we find that the age distributions remain unchanged. However, the mass spectral index varies significantly, showing best-fit values between –2.2 and –1.8, with the shallower slope in the highest star formation intensity regions. We explore the robustness of our study to potential systematics and conclude that the cluster mass function may vary with respect to environment.« less

STAR CLUSTERS IN M31. II. OLD CLUSTER METALLICITIES AND AGES FROM HECTOSPEC DATA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Caldwell, Nelson; Schiavon, Ricardo; Morrison, Heather

2011-02-15

We present new high signal-to-noise spectroscopic data on the M31 globular cluster (GC) system, obtained with the Hectospec multifiber spectrograph on the 6.5 m MMT. More than 300 clusters have been observed at a resolution of 5 A and with a median S/N of 75 per A, providing velocities with a median uncertainty of 6 km s{sup -1}. The primary focus of this paper is the determination of mean cluster metallicities, ages, and reddenings. Metallicities were estimated using a calibration of Lick indices with [Fe/H] provided by Galactic GCs. These match well the metallicities of 24 M31 clusters determined frommore » Hubble Space Telescope color-magnitude diagrams, the differences having an rms of 0.2 dex. The metallicity distribution is not generally bimodal, in strong distinction with the bimodal Galactic globular distribution. Rather, the M31 distribution shows a broad peak, centered at [Fe/H] = -1, possibly with minor peaks at [Fe/H] = -1.4, -0.7, and -0.2, suggesting that the cluster systems of M31 and the Milky Way had different formation histories. Ages for clusters with [Fe/H] > - 1 were determined using the automatic stellar population analysis program EZ{sub A}ges. We find no evidence for massive clusters in M31 with intermediate ages, those between 2 and 6 Gyr. Moreover, we find that the mean ages of the old GCs are remarkably constant over about a decade in metallicity (-0.95{approx}< [Fe/H] {approx}<0.0).« less

A QUANTITATIVE ANALYSIS OF DISTANT OPEN CLUSTERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Janes, Kenneth A.; Hoq, Sadia

2011-03-15

The oldest open star clusters are important for tracing the history of the Galactic disk, but many of the more distant clusters are heavily reddened and projected against the rich stellar background of the Galaxy. We have undertaken an investigation of several distant clusters (Berkeley 19, Berkeley 44, King 25, NGC 6802, NGC 6827, Berkeley 52, Berkeley 56, NGC 7142, NGC 7245, and King 9) to develop procedures for separating probable cluster members from the background field. We next created a simple quantitative approach for finding approximate cluster distances, reddenings, and ages. We first conclude that with the possible exceptionmore » of King 25 they are probably all physical clusters. We also find that for these distant clusters our typical errors are about {+-}0.07 in E(B - V), {+-}0.15 in log(age), and {+-}0.25 in (m - M){sub o}. The clusters range in age from 470 Myr to 7 Gyr and range from 7.1 to 16.4 kpc from the Galactic center.« less

WFPC2 Observations of Star Clusters in the Magellanic Clouds. Report 2; The Oldest Star Clusters in the Small Magellanic Cloud

NASA Technical Reports Server (NTRS)

Mighell, Kenneth J.; Sarajedini, Ata; French, Rica S.

1998-01-01

We present our analysis of archival Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2) observations in F45OW ( approximately B) and F555W (approximately V) of the intermediate-age populous star clusters NGC 121, NGC 339, NGC 361, NGC 416, and Kron 3 in the Small Magellanic Cloud. We use published photometry of two other SMC populous star clusters, Lindsay 1 and Lindsay 113, to investigate the age sequence of these seven populous star clusters in order to improve our understanding of the formation chronology of the SMC. We analyzed the V vs B-V and M(sub V) vs (B-V)(sub 0) color-magnitude diagrams of these populous Small Magellanic Cloud star clusters using a variety of techniques and determined their ages, metallicities, and reddenings. These new data enable us to improve the age-metallicity relation of star clusters in the Small Magellanic Cloud. In particular, we find that a closed-box continuous star-formation model does not reproduce the age-metallicity relation adequately. However, a theoretical model punctuated by bursts of star formation is in better agreement with the observational data presented herein.

Photometric Study of Intermediate Age Open Clusters

NASA Astrophysics Data System (ADS)

Contreras, Maria Eugenia; Michel, R.; Schuster, W.; Chavarria-Kleinhenn, C.; Olguin, L.

2011-05-01

We present the study of a sample of intermediate age open clusters (age 10-30 Myr) using optical (UBVRI) and infrared (JHK) photometric data. Optical photometry was obtained as part of the San Pedro Martir Open Clusters Project (SPM-OCP, Schuster et al. 2007; Michel et al. 2011, in preparation) while near-infrared photometry was retrieved from the 2MASS public data archive (ref). Most of the clusters included in SPM-OCP were selected from the Dias et al. (2002). catalog. On one hand, UVRI photometry was used to derive fundamental parameters of each cluster in the sample, such as age, distance and reddening. On the other hand, infrared photometry has allowed us to carry out a preliminary search of candidate stars to posses a circumstellar disk detected via its near-infrared excess. Observational data show that the number of infrared excess detection decreases with stellar age and actually this emission seems to completely disappear in stars with an age of 30 Myr (Strom et al. 1993; Muzerolle et al. 2000). One possible explanation for the lack of infrared emission has been proposed to be grain coagulation where small dust particles grow into larger and larger bodies until forming planetesimals and even planets. In this work we are aimed to analyze a sample of open clusters lying in this crucial age range.

A 10-year population based study of 'opt-out' HIV testing of tuberculosis patients in Alberta, Canada: national implications.

PubMed

Long, Richard; Niruban, Selvanayagam; Heffernan, Courtney; Cooper, Ryan; Fisher, Dina; Ahmed, Rabia; Egedahl, Mary Lou; Fur, Rhonda

2014-01-01

Compliance with the recommendation that all tuberculosis (TB) patients be tested for human immunodeficiency virus (HIV) has not yet been achieved in Canada or globally. The experience of "opt-out" HIV testing of TB patients in the Province of Alberta, Canada is described over a 10-year period, 2003-2012. Testing rates are reported before and after the introduction of the "opt-out" approach. Risk factors for HIV seropositivity are described and demographic, clinical and laboratory characteristics of TB patients who were newly diagnosed versus previously diagnosed with HIV are compared. Genotypic clusters, defined as groups of two or more cases whose isolates of Mycobacterium tuberculosis had identical DNA fingerprints over the 10-year period or within 2 years of one another, were analyzed for their ability to predict HIV co-infection. HIV testing rates were 26% before and 90% after the introduction of "opt-out" testing. During the "opt-out" testing years those <15 or >64 years of age at diagnosis were less likely to have been tested. In those tested the prevalence of HIV was 5.6%. In the age group 15-64 years, risk factors for HIV were: age (35-64 years), Canadian-born Aboriginal or foreign-born sub-Saharan African origin, and combined respiratory and non-respiratory disease. Compared to TB patients previously known to be HIV positive, TB patients newly discovered to be HIV positive had more advanced HIV disease (lower CD4 counts; higher viral loads) at diagnosis. Large cluster size was associated with Aboriginal ancestry. Cluster size predicted HIV co-infection in Aboriginal peoples when clusters included all cases reported over 10 years but not when clusters included cases reported within 2 years of one another. "Opt-out" HIV testing of TB patients is effective and well received. Universal HIV testing of TB patients (>80% of patients tested) has immediate (patients) and longer-term (TB/HIV program planning) benefits.

The Distribution and Ages of Star Clusters in the Small Magellanic Cloud: Constraints on the Interaction History of the Magellanic Clouds

NASA Astrophysics Data System (ADS)

Bitsakis, Theodoros; González-Lópezlira, R. A.; Bonfini, P.; Bruzual, G.; Maravelias, G.; Zaritsky, D.; Charlot, S.; Ramírez-Siordia, V. H.

2018-02-01

We present a new study of the spatial distribution and ages of the star clusters in the Small Magellanic Cloud (SMC). To detect and estimate the ages of the star clusters we rely on the new fully automated method developed by Bitsakis et al. Our code detects 1319 star clusters in the central 18 deg2 of the SMC we surveyed (1108 of which have never been reported before). The age distribution of those clusters suggests enhanced cluster formation around 240 Myr ago. It also implies significant differences in the cluster distribution of the bar with respect to the rest of the galaxy, with the younger clusters being predominantly located in the bar. Having used the same setup, and data from the same surveys as for our previous study of the LMC, we are able to robustly compare the cluster properties between the two galaxies. Our results suggest that the bulk of the clusters in both galaxies were formed approximately 300 Myr ago, probably during a direct collision between the two galaxies. On the other hand, the locations of the young (≤50 Myr) clusters in both Magellanic Clouds, found where their bars join the H I arms, suggest that cluster formation in those regions is a result of internal dynamical processes. Finally, we discuss the potential causes of the apparent outside-in quenching of cluster formation that we observe in the SMC. Our findings are consistent with an evolutionary scheme where the interactions between the Magellanic Clouds constitute the major mechanism driving their overall evolution.

Nuclear Rings in the IR: Hidden Super Star Clusters

NASA Astrophysics Data System (ADS)

Maoz, Dan

1997-07-01

We propose NICMOS broad-band {F160W, F187W} and Paschen Alpha {F187N} imaging of nuclear starburst rings in two nearby galaxies. We already have UV {F220W} FOC data, and are scheduled to obtain WFPC2 images in U, V, I, and Halpha+[NII] of these rings. The rings contain large populations of super star clusters similar to those recently discovered in other types of starburst systems. Nuclear rings contain large numbers of these clusters in relatively unobscured starburst environments. Measurement of the age, size, and stellar contents of the clusters can test the hypothesis that super star clusters are young globular clusters. Together with our UV and optical data, NICMOS images will provide the SED of numerous super star clusters over a decade in wavelength. Our already-approved observations will allow us to estimate, by comparison with evolutionary synthesis models, the masses and ages of the clusters. The proposed IR data will be sensitive to the number of supergiants {1.6 micron} and O-stars {Paschen Alpha} in each of the clusters. The observations will provide an independent determination of the reddening, mass, and age of each cluster. We expect to see in the IR numerous clusters that are obscured in the UV and optical. These clusters may be the younger ones, which are still embedded in their molecular clouds. By measuring the mass, age, and size of a large number of clusters, we can actually obtain an evolutionary picture of these objects at different stages in their lives.

Effects of cluster location and cluster distribution on performance on the traveling salesman problem.

PubMed

MacGregor, James N

2015-10-01

Research on human performance in solving traveling salesman problems typically uses point sets as stimuli, and most models have proposed a processing stage at which stimulus dots are clustered. However, few empirical studies have investigated the effects of clustering on performance. In one recent study, researchers compared the effects of clustered, random, and regular stimuli, and concluded that clustering facilitates performance (Dry, Preiss, & Wagemans, 2012). Another study suggested that these results may have been influenced by the location rather than the degree of clustering (MacGregor, 2013). Two experiments are reported that mark an attempt to disentangle these factors. The first experiment tested several combinations of degree of clustering and cluster location, and revealed mixed evidence that clustering influences performance. In a second experiment, both factors were varied independently, showing that they interact. The results are discussed in terms of the importance of clustering effects, in particular, and perceptual factors, in general, during performance of the traveling salesman problem.

Different disease subtypes with distinct clinical expression in familial Mediterranean fever: results of a cluster analysis.

PubMed

Akar, Servet; Solmaz, Dilek; Kasifoglu, Timucin; Bilge, Sule Yasar; Sari, Ismail; Gumus, Zeynep Zehra; Tunca, Mehmet

2016-02-01

The aim of this study was to evaluate whether there are clinical subgroups that may have different prognoses among FMF patients. The cumulative clinical features of a large group of FMF patients [1168 patients, 593 (50.8%) male, mean age 35.3 years (s.d. 12.4)] were studied. To analyse our data and identify groups of FMF patients with similar clinical characteristics, a two-step cluster analysis using log-likelihood distance measures was performed. For clustering the FMF patients, we evaluated the following variables: gender, current age, age at symptom onset, age at diagnosis, presence of major clinical features, variables related with therapy and family history for FMF, renal failure and carriage of M694V. Three distinct groups of FMF patients were identified. Cluster 1 was characterized by a high prevalence of arthritis, pleuritis, erysipelas-like erythema (ELE) and febrile myalgia. The dosage of colchicine and the frequency of amyloidosis were lower in cluster 1. Patients in cluster 2 had an earlier age of disease onset and diagnosis. M694V carriage and amyloidosis prevalence were the highest in cluster 2. This group of patients was using the highest dose of colchicine. Patients in cluster 3 had the lowest prevalence of arthritis, ELE and febrile myalgia. The frequencies of M694V carriage and amyloidosis were lower in cluster 3 than the overall FMF patients. Non-response to colchicine was also slightly lower in cluster 3. Patients with FMF can be clustered into distinct patterns of clinical and genetic manifestations and these patterns may have different prognostic significance. © The Author 2015. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Classification of frailty using the Kihon checklist: A cluster analysis of older adults in urban areas.

PubMed

Kera, Takeshi; Kawai, Hisashi; Yoshida, Hideyo; Hirano, Hirohiko; Kojima, Motonaga; Fujiwara, Yoshinori; Ihara, Kazushige; Obuchi, Shuichi

2017-01-01

Frailty is an important predictor of the need for long-term care and hospitalization. Our aim was to categorize frailty in community-dwelling older adults. The present study was carried out in 2011-2013, and consisted of 1380 individuals over 65 years of age. Participants completed the Kihon checklist, which is widely used to assess frailty in Japan, and their physical, cognitive and social function was evaluated. Non-hierarchical cluster analysis was used to statistically categorize frailty. The optimum number of clusters was determined as the point at which the external reference values (instrumental activity of daily living score, grip power, 10-m walk time, body mass index, portable fall risk index, occlusal force and Mini-Mental State Examination score) differed. According to the Kihon checklist, 369 (26.7%) of the 1380 study participants were considered frail. When the cluster number was increased from two to six, the scores in each subdomain of the Kihon checklist significantly differed. The estimated minimum number of clusters was five, and each of the five cluster groups had distinct characteristics. The numbers of participants in cluster groups 1-5 were 105, 78, 62, 71 and 53, respectively. We identified five types of frailty in community-dwelling older adults in Japan: "experience of falling," "pre-frailty," "oral frailty," "housebound" and "severe frailty." Geriatr Gerontol Int 2017; 17: 69-77. © 2016 Japan Geriatrics Society.

Cluster Analysis in Sociometric Research: A Pattern-Oriented Approach to Identifying Temporally Stable Peer Status Groups of Girls

ERIC Educational Resources Information Center

Zettergren, Peter

2007-01-01

A modern clustering technique was applied to age-10 and age-13 sociometric data with the purpose of identifying longitudinally stable peer status clusters. The study included 445 girls from a Swedish longitudinal study. The identified temporally stable clusters of rejected, popular, and average girls were essentially larger than corresponding…

Do We Really Have an Age/H_0 Conflict?

NASA Astrophysics Data System (ADS)

Baum, W. A.

1997-12-01

Two independent methods for estimating the age of the universe can both be linked to the absolute magnitudes of the RR Lyrae stars, one based on stellar evolution in globular clusters and the other based on the Hubble Constant derived from globular clusters as distance indicators. The latter has recently been extracted from HST-WFPC2 data for globular clusters in the Coma Cluster galaxy IC 4051 (Baum et al. 1997, AJ, 113, 1483). If RR Lyrae stars are brighter than we have previously thought, the stellar-evolution age estimate is shortened whereas the Hubble age is increased, so we can ask a very simple question: For what RR Lyrae magnitude zero point would the stellar-evolution age coincide with the Hubble age, and is it a reasonable value? Allowing 1 Gyr for globular clusters to have formed, and assuming a classical Einstein-deSitter universe with Lambda = 0, I find the two ages to coincide if M_V(RR) ~ 0.16[Fe/H] + 0.46, which (among other things) puts the Large Magellanic Cloud at (m-M) = 18.78 +/- 0.17 mag. The implied age of the universe is 11.0 +/- 1.4 Gyr, and the corresponding H_0 = 59 +/- 8 km/s per Mpc.

VizieR Online Data Catalog: RAVE open cluster pairs, groups and complexes (Conrad+, 2017)

NASA Astrophysics Data System (ADS)

Conrad, C.; Scholz, R.-D.; Kharchenko, N. V.; Piskunov, A. E.; Roeser, S.; Schilbach, E.; de Jong, R. S.; Schnurr, O.; Steinmetz, M.; Grebel, E. K.; Zwitter, T.; Bienayme, O.; Bland-Hawthorn, J.; Gibson, B. K.; Gilmore, G.; Kordopatis, G.; Kunder, A.; Navarro, J. F.; Parker, Q.; Reid, W.; Seabroke, G.; Siviero, A.; Watson, F.; Wyse, R.

2017-01-01

The presented tables summarize the parameters for the clusters and the mean values for the detected potential cluster groupings. The ages, distances and proper motions were taken from the Catalogue of Open Cluster Data (COCD; Kharchenko et al. 2005, Cat. J/A+A/438/1163, J/A+A/440/403), while additional radial velocities and metallicities were obtained from the Radial Velocity Experiment (RAVE; Kordopatis et al. 2013AJ....146..134K, Cat. III/272 ) and from the online compilation provided by Dias et al. (2002, See B/ocl). A description of the determination for the radial velocities and metallicities can be found in Conrad et al. 2014A&A...562A..54C. The potential groupings were identified using an adapted Friends-of-Friends algorithm with two sets of linking lengths, namely (100pc, 10km/s) and (100pc, 20km/s). The table clupar.dat (combining Tables A.1 and A.2 from the Appendix of our paper): Tables comprises the parameters collected for the final working sample of 432 clusters with available radial velocities, namely coordinates and proper motions in equatorial and galactic coordinates, distances, ages, metallicities, as well as Cartesian coordinates and velocities. The latter were computed through converting the spherical parameters to Cartesian space with the sun as point of origin. The tables grpar10.dat and grpar20.dat (listed as two parts in Table B.1 of the Appendix of our paper) contain the mean values for the identified potential open cluster groupings for two sets of linking lengths, 100pc and 10km/s (19 potential groupings) and 100pc and 20km/s (41 potential groupings), respectively. These were computed as simple mean, while the uncertainties were computed as simple rms. We list the counting number, the number of members, the COCD number and name for each member, The mean Cartesian coordinates and velocities, along with the uncertainties, the mean distances (with uncertainties), the mean logarithmic ages (with uncertainties) and the mean metallicities, where available (with uncertainties, if at least two measurement were used). (4 data files).

Dynamical age differences among coeval star clusters as revealed by blue stragglers.

PubMed

Ferraro, F R; Lanzoni, B; Dalessandro, E; Beccari, G; Pasquato, M; Miocchi, P; Rood, R T; Sigurdsson, S; Sills, A; Vesperini, E; Mapelli, M; Contreras, R; Sanna, N; Mucciarelli, A

2012-12-20

Globular star clusters that formed at the same cosmic time may have evolved rather differently from the dynamical point of view (because that evolution depends on the internal environment) through a variety of processes that tend progressively to segregate stars more massive than the average towards the cluster centre. Therefore clusters with the same chronological age may have reached quite different stages of their dynamical history (that is, they may have different 'dynamical ages'). Blue straggler stars have masses greater than those at the turn-off point on the main sequence and therefore must be the result of either a collision or a mass-transfer event. Because they are among the most massive and luminous objects in old clusters, they can be used as test particles with which to probe dynamical evolution. Here we report that globular clusters can be grouped into a few distinct families on the basis of the radial distribution of blue stragglers. This grouping corresponds well to an effective ranking of the dynamical stage reached by stellar systems, thereby permitting a direct measure of the cluster dynamical age purely from observed properties.

Clues to the Formation of Spiral Structure in M51 from the Ages and Locations of Star Clusters

NASA Astrophysics Data System (ADS)

Chandar, Rupali; Chien, L.-H.; Meidt, Sharon; Querejeta, Miguel; Dobbs, Clare; Schinnerer, Eva; Whitmore, Bradley C.; Calzetti, Daniela; Dinino, Daiana; Kennicutt, Robert C.; Regan, Michael

2017-08-01

We determine the spatial distributions of star clusters at different ages in the grand-design spiral galaxy M51 using a new catalog based on multi-band images taken with the Hubble Space Telescope (HST). These distributions, when compared with the spiral structure defined by molecular gas, dust, young and old stars, show the following sequence in the inner arms: dense molecular gas (and dust) defines the inner edge of the spiral structure, followed by an overdensity of old stars and then young stellar clusters. The offset between gas and young clusters in the inner arms is consistent with the expectations for a density wave. Clusters as old as a few hundred Myr remain concentrated close to the spiral arms, although the distributions are broader than those for the youngest clusters, which is also consistent with predictions from density wave simulations. The outermost portion of the west arm is different from the rest of the spiral structure in that it contains primarily intermediate-age (≈ 100{--}400 {Myr}) clusters; we believe that this is a “material” arm. We have identified four “feathers,” stellar structures beyond the inner arms that have a larger pitch angle than the arms. We do not find age gradients along any of the feathers, but the least coherent feathers appear to have the largest range of cluster ages.

Life history factors, personality and the social clustering of sexual experience in adolescents.

PubMed

van Leeuwen, Abram J; Mace, Ruth

2016-10-01

Adolescent sexual behaviour may show clustering in neighbourhoods, schools and friendship networks. This study aims to assess how experience with sexual intercourse clusters across the social world of adolescents and whether predictors implicated by life history theory or personality traits can account for its between-individual variation and social patterning. Using data on 2877 adolescents from the Avon Longitudinal Study of Parents and Children, we ran logistic multiple classification models to assess the clustering of sexual experience by approximately 17.5 years in schools, neighbourhoods and friendship networks. We examined how much clustering at particular levels could be accounted for by life history predictors and Big Five personality factors. Sexual experience exhibited substantial clustering in friendship networks, while clustering at the level of schools and neighbourhoods was minimal, suggesting a limited role for socio-ecological influences at those levels. While life history predictors did account for some variation in sexual experience, they did not explain clustering in friendship networks. Personality, especially extraversion, explained about a quarter of friends' similarity. After accounting for life history factors and personality, substantial unexplained similarity among friends remained, which may reflect a tendency to associate with similar individuals or the social transmission of behavioural norms.

Life history factors, personality and the social clustering of sexual experience in adolescents

PubMed Central

2016-01-01

Adolescent sexual behaviour may show clustering in neighbourhoods, schools and friendship networks. This study aims to assess how experience with sexual intercourse clusters across the social world of adolescents and whether predictors implicated by life history theory or personality traits can account for its between-individual variation and social patterning. Using data on 2877 adolescents from the Avon Longitudinal Study of Parents and Children, we ran logistic multiple classification models to assess the clustering of sexual experience by approximately 17.5 years in schools, neighbourhoods and friendship networks. We examined how much clustering at particular levels could be accounted for by life history predictors and Big Five personality factors. Sexual experience exhibited substantial clustering in friendship networks, while clustering at the level of schools and neighbourhoods was minimal, suggesting a limited role for socio-ecological influences at those levels. While life history predictors did account for some variation in sexual experience, they did not explain clustering in friendship networks. Personality, especially extraversion, explained about a quarter of friends' similarity. After accounting for life history factors and personality, substantial unexplained similarity among friends remained, which may reflect a tendency to associate with similar individuals or the social transmission of behavioural norms. PMID:27853543

Wide-Field CCD Photometry around Nine Open Clusters

NASA Astrophysics Data System (ADS)

Sharma, Saurabh; Pandey, A. K.; Ogura, K.; Mito, H.; Tarusawa, K.; Sagar, R.

2006-10-01

In this paper we study the evolution of the core and corona of nine open clusters using the projected radial density profiles derived from homogeneous CCD photometric data obtained with the 105 cm Kiso Schmidt telescope. The age and galactocentric distance of the target clusters vary from 16 to 2000 Myr and 9 to 10.8 kpc, respectively. Barring Be 62, which is a young open cluster, other clusters show a uniform reddening across the cluster region. The reddening in Be 62 varies from E(B-V)min=0.70 mag to E(B-V)max=1.00 mag. The coronae of six of the clusters in the present sample are found to be elongated; however, on the basis of the present sample it is not possible to establish any correlation between the age and shape of the core. The elongated core in the case of the young cluster Be 62 may reflect the initial conditions in the parental molecular cloud. The other results of the present study are as follows: (1) Core radius rc and corona size rcn/cluster radius rcl are linearly correlated. (2) The rc, rcn, and rcl are linearly correlated with the number of stars in that region. (3) In the age range 10-1000 Myr, the core and corona shrink with age. (4) We find that in the galactocentric distance range 9-10 kpc, the core and corona/cluster extent of the clusters increase with the galactocentric distance.

MASSCLEANCOLORS-MASS-DEPENDENT INTEGRATED COLORS FOR STELLAR CLUSTERS DERIVED FROM 30 MILLION MONTE CARLO SIMULATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Popescu, Bogdan; Hanson, M. M.

2010-04-10

We present Monte Carlo models of open stellar clusters with the purpose of mapping out the behavior of integrated colors with mass and age. Our cluster simulation package allows for stochastic variations in the stellar mass function to evaluate variations in integrated cluster properties. We find that UBVK colors from our simulations are consistent with simple stellar population (SSP) models, provided the cluster mass is large, M {sub cluster} {>=} 10{sup 6} M {sub sun}. Below this mass, our simulations show two significant effects. First, the mean value of the distribution of integrated colors moves away from the SSP predictionsmore » and is less red, in the first 10{sup 7} to 10{sup 8} years in UBV colors, and for all ages in (V - K). Second, the 1{sigma} dispersion of observed colors increases significantly with lower cluster mass. We attribute the former to the reduced number of red luminous stars in most of the lower mass clusters and the latter to the increased stochastic effect of a few of these stars on lower mass clusters. This latter point was always assumed to occur, but we now provide the first public code able to quantify this effect. We are completing a more extensive database of magnitudes and colors as a function of stellar cluster age and mass that will allow the determination of the correlation coefficients among different bands, and improve estimates of cluster age and mass from integrated photometry.« less

Spectroscopic constraints on the form of the stellar cluster mass function

NASA Astrophysics Data System (ADS)

Bastian, N.; Konstantopoulos, I. S.; Trancho, G.; Weisz, D. R.; Larsen, S. S.; Fouesneau, M.; Kaschinski, C. B.; Gieles, M.

2012-05-01

This contribution addresses the question of whether the initial cluster mass function (ICMF) has a fundamental limit (or truncation) at high masses. The shape of the ICMF at high masses can be studied using the most massive young (<10 Myr) clusters, however this has proven difficult due to low-number statistics. In this contribution we use an alternative method based on the luminosities of the brightest clusters, combined with their ages. The advantages are that more clusters can be used and that the ICMF leaves a distinct pattern on the global relation between the cluster luminosity and median age within a population. If a truncation is present, a generic prediction (nearly independent of the cluster disruption law adopted) is that the median age of bright clusters should be younger than that of fainter clusters. In the case of an non-truncated ICMF, the median age should be independent of cluster luminosity. Here, we present optical spectroscopy of twelve young stellar clusters in the face-on spiral galaxy NGC 2997. The spectra are used to estimate the age of each cluster, and the brightness of the clusters is taken from the literature. The observations are compared with the model expectations of Larsen (2009, A&A, 494, 539) for various ICMF forms and both mass dependent and mass independent cluster disruption. While there exists some degeneracy between the truncation mass and the amount of mass independent disruption, the observations favour a truncated ICMF. For low or modest amounts of mass independent disruption, a truncation mass of 5-6 × 105 M⊙ is estimated, consistent with previous determinations. Additionally, we investigate possible truncations in the ICMF in the spiral galaxy M 83, the interacting Antennae galaxies, and the collection of spiral and dwarf galaxies present in Larsen (2009, A&A, 494, 539) based on photometric catalogues taken from the literature, and find that all catalogues are consistent with having a truncation in the cluster mass functions. However for the case of the Antennae, we find a truncation mass of a few × 106M⊙ , suggesting a dependence on the environment, as has been previously suggested.

The complex star cluster system of NGC 1316 (Fornax A)

NASA Astrophysics Data System (ADS)

Sesto, Leandro A.; Faifer, Favio R.; Forte, Juan C.

2016-10-01

This paper presents Gemini-gri' high-quality photometry for cluster candidates in the field of NGC 1316 (Fornax A) as part of a study that also includes GMOS spectroscopy. A preliminary discussion of the photometric data indicates the presence of four stellar cluster populations with distinctive features in terms of age, chemical abundance and spatial distribution. Two of them seem to be the usually old (metal poor and metal rich) populations typically found in elliptical galaxies. In turn, an intermediate-age (5 Gyr) globular cluster population is the dominant component of the sample (as reported by previous papers). We also find a younger cluster population with a tentative age of ≈ 1 Gyr.

A spin-down clock for cool stars from observations of a 2.5-billion-year-old cluster.

PubMed

Meibom, Søren; Barnes, Sydney A; Platais, Imants; Gilliland, Ronald L; Latham, David W; Mathieu, Robert D

2015-01-29

The ages of the most common stars--low-mass (cool) stars like the Sun, and smaller--are difficult to derive because traditional dating methods use stellar properties that either change little as the stars age or are hard to measure. The rotation rates of all cool stars decrease substantially with time as the stars steadily lose their angular momenta. If properly calibrated, rotation therefore can act as a reliable determinant of their ages based on the method of gyrochronology. To calibrate gyrochronology, the relationship between rotation period and age must be determined for cool stars of different masses, which is best accomplished with rotation period measurements for stars in clusters with well-known ages. Hitherto, such measurements have been possible only in clusters with ages of less than about one billion years, and gyrochronology ages for older stars have been inferred from model predictions. Here we report rotation period measurements for 30 cool stars in the 2.5-billion-year-old cluster NGC 6819. The periods reveal a well-defined relationship between rotation period and stellar mass at the cluster age, suggesting that ages with a precision of order 10 per cent can be derived for large numbers of cool Galactic field stars.

Quantitative evidence of an intrinsic luminosity spread in the Orion nebula cluster

NASA Astrophysics Data System (ADS)

Reggiani, M.; Robberto, M.; Da Rio, N.; Meyer, M. R.; Soderblom, D. R.; Ricci, L.

2011-10-01

Aims: We study the distribution of stellar ages in the Orion nebula cluster (ONC) using accurate HST photometry taken from HST Treasury Program observations of the ONC utilizing the cluster distance estimated by Menten and collaborators. We investigate whether there is an intrinsic age spread in the region and whether the age depends on the spatial distribution. Methods: We estimate the extinction and accretion luminosity towards each source by performing synthetic photometry on an empirical calibration of atmospheric models using the package Chorizos of Maiz-Apellaniz. The position of the sources in the HR-diagram is compared with different theoretical isochrones to estimate the mean cluster age and age dispersion. On the basis of Monte Carlo simulations, we quantify the amount of intrinsic age spread in the region, taking into account uncertainties in the distance, spectral type, extinction, unresolved binaries, accretion, and photometric variability. Results: According to the evolutionary models of Siess and collaborators, the mean age of the Cluster is 2.2 Myr with a scatter of few Myr. With Monte Carlo simulations, we find that the observed age spread is inconsistent with that of a coeval stellar population, but in agreement with a star formation activity between 1.5 and 3.5 Myr. We also observe some evidence that ages depends on the spatial distribution.

Effects of age and body mass index on breast characteristics: A cluster analysis.

PubMed

Coltman, Celeste E; Steele, Julie R; McGhee, Deirdre E

2018-05-24

Limited research has quantified variation in the characteristics of the breasts among women and determined how these breast characteristics are influenced by age and body mass. The aim of this study was to classify the breasts of women in the community into different categories based on comprehensive and objective measurements of the characteristics of their breasts and torsos, and to determine the effect of age and body mass index (BMI) on the prevalence of these breast categories. Four breast characteristic clusters were identified (X-Large, Very-ptotic & Splayed; Large, Ptotic & Splayed; Medium & Mildly-ptotic; and Small & Non-ptotic), with age and BMI shown to significantly affect the breast characteristic clusters. These results highlight the difference in breast characteristics exhibited among women and how these clusters are affected by age and BMI. The breast characteristic clusters identified in this study could be used as a basis for future bra designs and sizing systems in order to improve bra fit for women.

Relative age of Camelot crater and crater clusters near the Apollo 17 landing site

USGS Publications Warehouse

Lucchitta, B.K.

1979-01-01

Topographic profiles and depth-diameter ratios from the crater Camelot and craters of the central cluster in the Apollo 17 landing area suggest that these craters are of the same age. Therefore, layers that can be recognized in the deep-drill core and that can be identified as ejecta deposits from Camelot or from the cluster craters should yield similar emplacement ages. ?? 1979.

Health and disease phenotyping in old age using a cluster network analysis.

PubMed

Valenzuela, Jesus Felix; Monterola, Christopher; Tong, Victor Joo Chuan; Ng, Tze Pin; Larbi, Anis

2017-11-15

Human ageing is a complex trait that involves the synergistic action of numerous biological processes that interact to form a complex network. Here we performed a network analysis to examine the interrelationships between physiological and psychological functions, disease, disability, quality of life, lifestyle and behavioural risk factors for ageing in a cohort of 3,270 subjects aged ≥55 years. We considered associations between numerical and categorical descriptors using effect-size measures for each variable pair and identified clusters of variables from the resulting pairwise effect-size network and minimum spanning tree. We show, by way of a correspondence analysis between the two sets of clusters, that they correspond to coarse-grained and fine-grained structure of the network relationships. The clusters obtained from the minimum spanning tree mapped to various conceptual domains and corresponded to physiological and syndromic states. Hierarchical ordering of these clusters identified six common themes based on interactions with physiological systems and common underlying substrates of age-associated morbidity and disease chronicity, functional disability, and quality of life. These findings provide a starting point for indepth analyses of ageing that incorporate immunologic, metabolomic and proteomic biomarkers, and ultimately offer low-level-based typologies of healthy and unhealthy ageing.

NEW CONSTRAINTS ON MASS-DEPENDENT DISRUPTION OF STAR CLUSTERS IN M51

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chandar, Rupali; Whitmore, Bradley C.; Regan, Michael

2011-02-01

We use UBVI H{alpha} images of the Whirlpool galaxy, M51, taken with the Advanced Camera for Surveys and WFPC2 cameras on the Hubble Space Telescope (HST) to select star clusters, and to estimate their masses and ages by comparing their observed colors with predictions from population synthesis models. We construct the mass function of intermediate-age (1-4 x 10{sup 8} yr) clusters, and find that it is well described by a power law, {psi}(M) {proportional_to} M{sup {beta}}, with {beta} = -2.1 {+-} 0.2, for clusters more massive than M {approx} 6 x 10{sup 3} M{sub sun}. This extends the mass functionmore » of intermediate-age clusters in M51 to masses lower by nearly a factor of five over previous determinations. The mass function does not show evidence for curvature at either the high or low mass end. This shape indicates that there is no evidence for the earlier disruption of lower mass clusters compared with their higher mass counterparts (i.e., no mass-dependent disruption) over the observed range of masses and ages, or for a physical upper mass limit M{sub C} with which clusters in M51 can form. These conclusions differ from previous suggestions based on poorer-quality HST observations. We discuss their implications for the formation and disruption of the clusters. Ages of clusters in two 'feathers', stellar features extending from the outer portion of a spiral arm, show that the feather with a larger pitch angle formed earlier, and over a longer period, than the other.« less

Bullied youth: the impact of bullying through lesbian, gay, and bisexual name calling.

PubMed

Evans, Caroline B R; Chapman, Mimi V

2014-11-01

Bullying is a common experience for many school-aged youth, but the majority of bullying research and intervention does not address the content of bullying behavior, particularly teasing. Understanding the various forms of bullying as well as the language used in bullying is important given that bullying can have persistent consequences, particularly for victims who are bullied through biased-based bullying, such as being called gay, lesbian, or queer. This study examines bullying experiences in a racially and ethnically diverse sample of 3,379 rural elementary-, middle-, and high-school youth. We use latent class analysis to establish clusters of bullying behaviors, including forms of biased-based bullying. The resulting classes are examined to ascertain if and how bullying by biased-based labeling is clustered with other forms of bullying behavior. This analysis identifies 3 classes of youth: youth who experience no bullying victimization, youth who experience social and emotional bullying, and youth who experience all forms of social and physical bullying, including being bullied by being called gay, lesbian, or queer. Youth in Classes 2 and 3 labeled their experiences as bullying. Results indicate that youth bullied by being called gay, lesbian, or queer are at a high risk of experiencing all forms of bullying behavior, highlighting the importance of increased support for this vulnerable group. (c) 2014 APA, all rights reserved.

Kinetics of carbon clustering in detonation of high explosives: Does theory match experiment?

NASA Astrophysics Data System (ADS)

Velizhanin, Kirill; Watkins, Erik; Dattelbaum, Dana; Gustavsen, Richard; Aslam, Tariq; Podlesak, David; Firestone, Millicent; Huber, Rachel; Ringstrand, Bryan; Willey, Trevor; Bagge-Hansen, Michael; Hodgin, Ralph; Lauderbach, Lisa; van Buuren, Tony; Sinclair, Nicholas; Rigg, Paulo; Seifert, Soenke; Gog, Thomas

2017-06-01

Chemical reactions in detonation of carbon-rich high explosives yield carbon clusters as major constituents of the products. Efforts to model carbon clustering as a diffusion-limited irreversible coagulation of carbon clusters go back to the seminal paper by Shaw and Johnson. However, first direct experimental observations of the kinetics of clustering yielded cluster growth one to two orders of magnitude slower than theoretical predictions. Multiple efforts were undertaken to test and revise the basic assumptions of the model in order to achieve better agreement with experiment. We discuss our very recent direct experimental observations of carbon clustering dynamics and demonstrate that these new results are in much better agreement with the modified Shaw-Johnson model. The implications of this much better agreement on our present understanding of detonation carbon clustering processes and possible ways to increase the agreement between theory and experiment even further are discussed.

A First Estimate of the X-Ray Binary Frequency as a Function of Star Cluster Mass in a Single Galactic System

NASA Astrophysics Data System (ADS)

Clark, D. M.; Eikenberry, S. S.; Brandl, B. R.; Wilson, J. C.; Carson, J. C.; Henderson, C. P.; Hayward, T. L.; Barry, D. J.; Ptak, A. F.; Colbert, E. J. M.

2008-05-01

We use the previously identified 15 infrared star cluster counterparts to X-ray point sources in the interacting galaxies NGC 4038/4039 (the Antennae) to study the relationship between total cluster mass and X-ray binary number. This significant population of X-Ray/IR associations allows us to perform, for the first time, a statistical study of X-ray point sources and their environments. We define a quantity, η, relating the fraction of X-ray sources per unit mass as a function of cluster mass in the Antennae. We compute cluster mass by fitting spectral evolutionary models to Ks luminosity. Considering that this method depends on cluster age, we use four different age distributions to explore the effects of cluster age on the value of η and find it varies by less than a factor of 4. We find a mean value of η for these different distributions of η = 1.7 × 10-8 M-1⊙ with ση = 1.2 × 10-8 M-1⊙. Performing a χ2 test, we demonstrate η could exhibit a positive slope, but that it depends on the assumed distribution in cluster ages. While the estimated uncertainties in η are factors of a few, we believe this is the first estimate made of this quantity to "order of magnitude" accuracy. We also compare our findings to theoretical models of open and globular cluster evolution, incorporating the X-ray binary fraction per cluster.

Mid-infrared Integrated-light Photometry Of LMC Star Clusters

NASA Astrophysics Data System (ADS)

Pessev, Peter; Goudfrooij, P.; Puzia, T.; Chandar, R.

2008-03-01

Massive star clusters (Galactic Globular Clusters and Populous Clusters in the Magellanic Clouds) are the best available approximation of Simple Stellar Populations (SSPs). Since the stellar populations in these nearby objects are studied in details, they provide fundamental age/metallicity templates for interpretation of the galaxy properties, testing and calibration of the SSP Models. Magellanic Cloud clusters are particularly important since they populate a region of the age/metallicity parameter space that is not easily accessible in our Galaxy. We present the first Mid-IR integrated-light measurements for six LMC clusters based on our Spitzer IRAC imaging program. Since we are targeting a specific group of intermediate-age clusters, our imaging goes deeper compared to SAGE-LMC survey data. We present a literature compilation of clusters' properties along with multi-wavelength integrated light photometry database spanning from the optical (Johnson U band) to the Mid-IR (IRAC Channel 4). This data provides an important empirical baseline for the interpretation of galaxy colors in the Mid-IR (especially high-z objects whose integrated-light is dominated by TP-AGB stars emission). It is also a valuable tool to check the SSP model predictions in the intermediate-age regime and provides calibration data for the next generation of SSP models.

Gemini Spectra of Star Clusters in the Spiral Galaxy M101

NASA Astrophysics Data System (ADS)

Simanton-Coogan, Lesley A.; Chandar, Rupali; Miller, Bryan; Whitmore, Bradley C.

2017-12-01

We present low resolution, visible light spectra of 41 star clusters in the spiral galaxy M101, taken with the Gemini/GMOS instrument. We measure Lick indices for each cluster and compare with BaSTI models to estimate their ages and metallicities. We also measure the line-of-sight velocities. We find that 25 of the clusters are fairly young massive clusters (YMCs) with ages of hundreds of millions of years, and 16 appear to be older, globular clusters (GCs). There are at least four GCs with best-fit ages of ≈1–3 Gyr and eight with best-fit ages of ≈5–10 Gyr. The mean metallicity of the YMCs is [Fe/H] ≈ ‑0.1 and for the GCs is [Fe/H] ≈ ‑0.9. We find a near-continuous spread in both age and metallicity for our sample, which may indicate that M101 had a more-or-less continuous history of cluster and star formation. From the kinematics, we find that the YMCs rotate with the H I gas fairly well, while the GCs do not. We cannot definitively say whether the GCs sampled here lie in an inner halo, thick disk, or bulge/psuedobulge component, although given the very small bulge in M101, the last seems unlikely. The kinematics and ages of the YMCs suggest that M101 may have undergone heating of its disk or possibly a continuous merger/accretion history for the galaxy.

Methodology and Baseline Results From the Evaluation of a Sexuality Education Activity in Mpumalanga and KwaZulu-Natal, South Africa.

PubMed

Speizer, Ilene S; Mandal, Mahua; Xiong, Khou; Hattori, Aiko; Makina-Zimalirana, Ndinda; Kumalo, Faith; Taylor, Stephen; Ndlovu, Muzi S; Madibane, Mathata; Beke, Andy

2018-04-01

In South Africa, adolescents and young adults (ages 15-24) are at risk of HIV, sexually transmitted infections, and unintended pregnancies. Recently, the Department of Basic Education has revised its sexuality education content and teaching strategies (using scripted lessons plans) as part of its life orientation curriculum. This paper presents the methodology and baseline results from the evaluation of the scripted lesson plans and supporting activities. A rigorous cluster-level randomized design with random assignment of schools as clusters is used for the evaluation. Baseline results from grade 8 female and male learners and grade 10 female learners demonstrate that learners are at risk of HIV and early and unintended pregnancies. Multivariable analyses demonstrate that household-level food insecurity and living with an HIV-positive person are associated with sexual experience and pregnancy experience. Implications are discussed for strengthening the current life orientation program for future scale-up by the government of South Africa.

A Massive Cluster in its Youth: the Fundamental Plane, Kinematics, and Ages for Cluster Galaxies at z = 1.80 in JKCS 041

NASA Astrophysics Data System (ADS)

Prichard, Laura Jane; Davies, Roger L.; Beifiori, Alessandra; Chan, Jeffrey C. C.; Cappellari, Michele; Houghton, Ryan C. W.; Mendel, Trevor; Bender, Ralf; Galametz, Audrey; Saglia, Roberto P.; Smith, Russell; Stott, John P.; Wilman, David J.; Lewis, Ian J.; Sharples, Ray; Wegner, Michael

2018-01-01

Galaxy clusters are the largest gravitationally bound structures in the Universe, and we know that early type galaxies (ETGs) are more common towards their centers. Clusters of galaxies are increasingly rare at early times, but are essential for understanding the formation of these massive structures and how they alter the fate of their member galaxies. However, long integration times are required to constrain the stellar properties of these distant cluster ETGs. Now with the advent of the multiplexed near-infrared integral field instrument, the K-band Multi-Object Spectrograph (KMOS) on the Very Large Telescope, we can target the ETGs in these valuable high-redshift clusters more efficiently than ever. The KMOS guaranteed observing program, the KMOS Cluster Survey (KCS; P.I.s Bender & Davies), has enabled a study of cluster galaxies in overdensities spanning z=1-2 through absorption-line spectroscopy obtained from 20-hour integrations. We will present spectra for 16 galaxies in the furthest KCS overdensity, JKCS 041, an ETG-rich cluster at z=1.80. We measured seven velocity dispersions from the quiescent galaxy spectra, expanding the sample of like measurements in the literature at or above z=1.80 by more than 40%. Through the analysis of Hubble Space Telescope photometry and deep absorption-line spectroscopy, we were able to construct the highest redshift fundamental plane (FP) within a single system for galaxies in JKCS 041. From the redshift evolution of the FP zero-point, we derived a mean age of the galaxies in this cluster of 1.4 +/- 0.2 Gyrs. We determined relative velocities of the galaxies to study the three-dimensional structure of this overdensity. We noticed from the dynamics of JKCS 041 that a group of galaxies was infalling towards the cluster center. When measuring FP ages for the infalling group, we found these galaxies had significantly younger mean ages (0.3 +/- 0.2 Gyrs) than the other galaxies in the cluster (2.0 +0.3/-0.1 Gyrs). Based on the galaxy dynamics, cluster morphology, and galaxy stellar age results, we concluded that JKCS 041 is in formation and consists of two merging groups of galaxies. This could link galaxy ages to large-scale structure for the first time at this redshift.

The Star Cluster System in the Local Group Starburst Galaxy IC 10

NASA Astrophysics Data System (ADS)

Lim, Sungsoon; Lee, Myung Gyoon

2015-05-01

We present a survey of star clusters in the halo of IC 10, a starburst galaxy in the Local Group, based on Subaru R-band images and NOAO Local Group Survey UBVRI images. We find five new star clusters. All of these star clusters are located far from the center of IC 10, while previously known star clusters are mostly located in the main body. Interestingly, the distribution of these star clusters shows an asymmetrical structure elongated along the east and southwest directions. We derive UBVRI photometry of 66 star clusters, including these new star clusters, as well as previously known star clusters. Ages of the star clusters are estimated from a comparison of their UBVRI spectral energy distribution with the simple stellar population models. We find that the star clusters in the halo are all older than 1 Gyr, while those in the main body have various ages, from very young (several Myr) to old (\\gt 1 Gyr). The young clusters (\\lt 10 Myr) are mostly located in the Hα emission regions and are concentrated on a small region at 2\\prime\\prime in the southeast direction from the galaxy center, while the old clusters are distributed in a wider area than the disk. Intermediate-age clusters (∼100 Myr) are found in two groups. One is close to the location of the young clusters and the other is at ∼ 4\\prime\\prime from the location of the young clusters. The latter may be related to past mergers or tidal interaction.

Extended Star Formation or a Range of Stellar Rotation Velocities? The Nature of Extended Main Sequence Turnoffs in Intermediate-Age Star Clusters

NASA Astrophysics Data System (ADS)

Goudfrooij, Paul

2016-10-01

Recently, deep color-magnitude diagrams (CMDs) from HST data revealed that several massive intermediate-age star clusters in the Magellanic Clouds exhibit extended main-sequence turn-offs (eMSTOs), and in some cases also dual red clumps. This poses serious questions regarding the mechanisms responsible for the formation of massive star clusters and their well-known light-element abundance variations. The nature of eMSTOs is currently a hotly debated topic of study. Several recent studies indicate that the eMSTOs are caused by an age spread of about 100-500 Myr among cluster stars, while other studies indicate that eMSTOs can be caused by a coeval population in which the relevant stars span a range of rotation velocities. Formal evidence to (dis-)prove either scenario still remains at large, mainly because the available stellar tracks that incorporate the effects of rotation are only available for masses > 1.7 Msun whereas the stars in the known eMSTOs of intermediate-age clusters are less massive. To circumvent this issue, we identified a massive star cluster in the Large Magellanic Cloud (LMC) that has the right dynamical properties to host an eMSTO along with an age at which the effects of age spreads to CMD morphology are substantially different from those of spreads of rotation rates: the 600 Myr old cluster NGC 1831. We propose to obtain deep WFC3/UVIS imaging with filters F336W and F814W to analyze the morphologies of the MSTO and upper MS regions of NGC 1831 at high precision and compare with model predictions. This will have a lasting impact on our understanding of the eMSTO phenomenon and of star cluster formation in general.

Open clusters in the Kepler field. II. NGC 6866

DOE Office of Scientific and Technical Information (OSTI.GOV)

Janes, Kenneth; Hoq, Sadia; Barnes, Sydney A.

We have developed a maximum-likelihood procedure to fit theoretical isochrones to the observed cluster color-magnitude diagrams of NGC 6866, an open cluster in the Kepler spacecraft field of view. The Markov chain Monte Carlo algorithm permits exploration of the entire parameter space of a set of isochrones to find both the best solution and the statistical uncertainties. For clusters in the age range of NGC 6866 with few, if any, red giant members, a purely photometric determination of the cluster properties is not well-constrained. Nevertheless, based on our UBVRI photometry alone, we have derived the distance, reddening, age, and metallicitymore » of the cluster and established estimates for the binary nature and membership probability of individual stars. We derive the following values for the cluster properties: (m – M) {sub V} = 10.98 ± 0.24, E(B – V) = 0.16 ± 0.04 (so the distance = 1250 pc), age =705 ± 170 Myr, and Z = 0.014 ± 0.005.« less

Star Clusters in the Magellanic Clouds

NASA Astrophysics Data System (ADS)

Gallagher, J. S., III

2014-09-01

The Magellanic Clouds (MC) are prime locations for studies of star clusters covering a full range in age and mass. This contribution briefly reviews selected properties of Magellanic star clusters, by focusing first on young systems that show evidence for hierarchical star formation. The structures and chemical abundance patterns of older intermediate age star clusters in the Small Magellanic Cloud (SMC) are a second topic. These suggest a complex history has affected the chemical enrichment in the SMC and that low tidal stresses in the SMC foster star cluster survival.

Integrated spectral study of small angular diameter galactic open clusters

NASA Astrophysics Data System (ADS)

Clariá, J. J.; Ahumada, A. V.; Bica, E.; Pavani, D. B.; Parisi, M. C.

2017-10-01

This paper presents flux-calibrated integrated spectra obtained at Complejo Astronómico El Leoncito (CASLEO, Argentina) for a sample of 9 Galactic open clusters of small angular diameter. The spectra cover the optical range (3800-6800 Å), with a resolution of ˜14 Å. With one exception (Ruprecht 158), the selected clusters are projected into the fourth Galactic quadrant (282o < l < 345o) near the Galactic plane (∣b∣ ≤ 9o). We performed simultaneous estimates of foreground interstellar reddening and age by comparing the continuum distribution and line strenghts of the cluster spectra with those of template cluster spectra with known parameters. We thus provide spectroscopic information independent from that derived through color-magnitude diagram studies. We found three clusters (Collinder 249, NGC 4463 and Ruprecht 122) younger than ˜40 Myr, four moderately young ones (BH 92, Harvard 5, Hogg 14 and Pismis 23) with ages within 200-400 Myr, and two intermediate-age ones (Ruprecht 158 and ESO 065-SC07) with ages within 1.0-2.2 Gyr. The derived foreground E(B - V) color excesses vary from around 0.0 in Ruprecht 158 to ˜1.1 in Pismis 23. In general terms, the results obtained show good agreement with previous photometric results. In Ruprecht 158 and BH 92, however, some differences are found between the parameters here obtained and previous values in the literature. Individual spectra of some comparatively bright stars located in the fields of 5 out of the 9 clusters here studied, allowed us to evaluate their membership status. The current cluster sample complements that of 46 open clusters previously studied by our group in an effort to gather a spectral library with several clusters per age bin. The cluster spectral library that we have been building is an important tool to tie studies of resolved and unresolved stellar content.

It is not just a meal, it is an emotional experience - a segmentation of older persons based on the emotions that they associate with mealtimes.

PubMed

den Uijl, Louise C; Jager, Gerry; de Graaf, Cees; Waddell, Jason; Kremer, Stefanie

2014-12-01

Worldwide, the group of older persons is growing fast. To aid this important group in their food and meal requirements, a deeper insight into the expectations and experiences of these persons regarding their mealtimes and snack times is needed. In the current study, we aim to identify consumer segments within the group of vital community-dwelling older persons on the basis of the emotions they associate with their mealtimes and snack times (from now on referred to as mealtimes). Participants (n = 392, mean age 65.8 (years) ± 5.9 (SD)) completed an online survey. The survey consisted of three questionnaires: emotions associated with mealtimes, functionality of mealtimes, and psychographic characteristics (health and taste attitudes, food fussiness, and food neophobia). Consumer segments were identified and characterised based on the emotions that the respondents reported to experience at mealtimes, using a hierarchical cluster analysis. Clusters were described using variables previously not included in the cluster analysis, such as functionality of mealtimes and psychographic characteristics. Four consumer segments were identified: Pleasurable averages, Adventurous arousals, Convivial indulgers, and Indifferent restrictives. These segments differed significantly in their emotional associations with mealtimes both in valence and level of arousal. The present study provides actionable insights for the development of products and communication strategies tailored to the needs of vital community-dwelling older persons. Copyright © 2014 Elsevier Ltd. All rights reserved.

Introducing ab initio based neural networks for transition-rate prediction in kinetic Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Messina, Luca; Castin, Nicolas; Domain, Christophe; Olsson, Pär

2017-02-01

The quality of kinetic Monte Carlo (KMC) simulations of microstructure evolution in alloys relies on the parametrization of point-defect migration rates, which are complex functions of the local chemical composition and can be calculated accurately with ab initio methods. However, constructing reliable models that ensure the best possible transfer of physical information from ab initio to KMC is a challenging task. This work presents an innovative approach, where the transition rates are predicted by artificial neural networks trained on a database of 2000 migration barriers, obtained with density functional theory (DFT) in place of interatomic potentials. The method is tested on copper precipitation in thermally aged iron alloys, by means of a hybrid atomistic-object KMC model. For the object part of the model, the stability and mobility properties of copper-vacancy clusters are analyzed by means of independent atomistic KMC simulations, driven by the same neural networks. The cluster diffusion coefficients and mean free paths are found to increase with size, confirming the dominant role of coarsening of medium- and large-sized clusters in the precipitation kinetics. The evolution under thermal aging is in better agreement with experiments with respect to a previous interatomic-potential model, especially concerning the experiment time scales. However, the model underestimates the solubility of copper in iron due to the excessively high solution energy predicted by the chosen DFT method. Nevertheless, this work proves the capability of neural networks to transfer complex ab initio physical properties to higher-scale models, and facilitates the extension to systems with increasing chemical complexity, setting the ground for reliable microstructure evolution simulations in a wide range of alloys and applications.

Latino/a depression and smoking: an analysis through the lenses of culture, gender, and ethnicity.

PubMed

Lorenzo-Blanco, Elma I; Cortina, Lilia M

2013-06-01

Rates of major depressive disorder (MDD) and cigarette smoking increase with Latino/a acculturation, but this varies by gender and ethnic subgroup. We investigated how lived experiences (i.e., discrimination, family conflict, family cohesion, familismo) clustered together in the everyday lives of Latina/os. We further examined associations of cluster profile and Latino/a subgroup with MDD and smoking, and tested whether gender moderated these associations. Data came from the National Latino Asian American Study, which included 2,554 Latino/as (48 % female; mean age = 38.02 years). K-means cluster analysis revealed six profiles of experience, which varied by gender and socio-cultural characteristics. Proportionately more women than men were in groups with problematic family lives. Acculturated Latino/as were disproportionately represented in profiles reporting frequent discrimination, family conflict, and a lack of shared family values and cohesion. Profiles characterized by high discrimination and family problems also predicted elevated risk for MDD and smoking. Findings suggest that Latino/a acculturation comes jointly with increased discrimination, increased family conflict, and reduced family cohesion and shared family values, exacerbating risk for MDD and smoking. This research on pathways to depression and smoking can inform the development of targeted assessment, prevention, and intervention strategies, tailored to the needs of Latino/as.

History of Hubble Space Telescope (HST)

NASA Image and Video Library

2001-09-06

Scientists using NASA's Hubble Space Telescope (HST) are studying the colors of star clusters to determine the age and history of starburst galaxies, a technique somewhat similar to the process of learning the age of a tree by counting its rings. One such galaxy, Galaxy NGC 3310, a hotbed of star formation showcased in this HST photograph, is forming clusters of stars at a prodigious rate. The image shows several hundred star clusters, visible as the bright blue diffuse objects tracing the galaxy's spiral arms. Each of these star clusters represents the formation of up to about a million stars, a process that takes less than 100,000 years. In addition, hundreds of individual young stars can be seen throughout the galaxy. The star clusters become redder with age as the most massive and bluest stars exhaust their fuel and burn out. Measurements in this image of the wide range of cluster colors show their ages range between about one million and more that one hundred million years. This suggests the starburst "turned on" more than 100 million years ago.

EXTENDED STAR FORMATION IN THE INTERMEDIATE-AGE LARGE MAGELLANIC CLOUD STAR CLUSTER NGC 2209

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keller, Stefan C.; Mackey, A. Dougal; Da Costa, Gary S.

2012-12-10

We present observations of the 1 Gyr old star cluster NGC 2209 in the Large Magellanic Cloud made with the GMOS imager on the Gemini South Telescope. These observations show that the cluster exhibits a main-sequence turnoff that spans a broader range in luminosity than can be explained by a single-aged stellar population. This places NGC 2209 amongst a growing list of intermediate-age (1-3 Gyr) clusters that show evidence for extended or multiple epochs of star formation of between 50 and 460 Myr in extent. The extended main-sequence turnoff observed in NGC 2209 is a confirmation of the prediction inmore » Keller et al. made on the basis of the cluster's large core radius. We propose that secondary star formation is a defining feature of the evolution of massive star clusters. Dissolution of lower mass clusters through evaporation results in only clusters that have experienced secondary star formation surviving for a Hubble time, thus providing a natural connection between the extended main-sequence turnoff phenomenon and the ubiquitous light-element abundance ranges seen in the ancient Galactic globular clusters.« less

Highly dynamically evolved intermediate-age open clusters

NASA Astrophysics Data System (ADS)

Piatti, Andrés E.; Dias, Wilton S.; Sampedro, Laura M.

2017-04-01

We present a comprehensive UBVRI and Washington CT1T2 photometric analysis of seven catalogued open clusters, namely: Ruprecht 3, 9, 37, 74, 150, ESO 324-15 and 436-2. The multiband photometric data sets in combination with 2MASS photometry and Gaia astrometry for the brighter stars were used to estimate their structural parameters and fundamental astrophysical properties. We found that Ruprecht 3 and ESO 436-2 do not show self-consistent evidence of being physical systems. The remained studied objects are open clusters of intermediate age (9.0 ≤ log(t yr-1) ≤ 9.6), of relatively small size (rcls ˜ 0.4-1.3 pc) and placed between 0.6 and 2.9 kpc from the Sun. We analysed the relationships between core, half-mass, tidal and Jacoby radii as well as half-mass relaxation times to conclude that the studied clusters are in an evolved dynamical stage. The total cluster masses obtained by summing those of the observed cluster stars resulted to be ˜10-15 per cent of the masses of open clusters of similar age located closer than 2 kpc from the Sun. We found that cluster stars occupy volumes as large as those for tidally filled clusters.

Correlates of root caries experience in middle-aged and older adults in the Northwest Practice-based REsearch Collaborative in Evidence-based DENTistry research network.

PubMed

Chi, Donald L; Berg, Joel H; Kim, Amy S; Scott, JoAnna

2013-05-01

The authors examined the correlates of root caries experience for middle-aged adults (aged 45-64 years) and older adults (65 years and older) to test the hypothesis that the factors related to root caries are different for middle-aged adults than they are for older adults. The authors conducted an observational cross-sectional study that focused on adult patients aged 45 to 97 years recruited from the Northwest Practice-based REsearch Collaborative in Evidence-based DENTistry research network (N = 775). The outcome variable was any root caries experience (no/yes). The authors hypothesized that sociodemographic, intra- oral and behavioral factors were root caries correlates. The authors used Poisson regression models to generate overall and age-stratified prevalence ratios (PRs) of root caries, and they used generalized estimating equations to account for practice-level clustering of participants. A total of 19.6 percent of adults had any root caries. A dentist's assessment that the patient was at high risk of developing any caries was associated with greater prevalence of root caries experience in both middle-aged adults (PR, 2.70; 95 percent confidence interval [CI], 1.63-4.46) and older adults (PR, 1.87; 95 percent CI, 1.19-2.95). The following factors were associated significantly with increased root caries prevalence but only for middle-aged adults: male sex (P = .02), self-reported dry mouth (P < .001), exposed roots (P = .03) and increased frequency of eating or drinking between meals (P = .03). No other covariates were related to root caries experience for older adults. Within a practice-based research network, the factors associated with root caries experience were different for middle-aged adults than they were for older adults. Research is needed to identify relevant root caries correlates for adults 65 years and older. Practical Implications. Interventions aimed at preventing root caries are likely to be different for middle-aged adults than for older adults. Dentists should use root caries prevention programs that address appropriate aged-based risk factors.

Trajectories of acute low back pain: a latent class growth analysis.

PubMed

Downie, Aron S; Hancock, Mark J; Rzewuska, Magdalena; Williams, Christopher M; Lin, Chung-Wei Christine; Maher, Christopher G

2016-01-01

Characterising the clinical course of back pain by mean pain scores over time may not adequately reflect the complexity of the clinical course of acute low back pain. We analysed pain scores over 12 weeks for 1585 patients with acute low back pain presenting to primary care to identify distinct pain trajectory groups and baseline patient characteristics associated with membership of each cluster. This was a secondary analysis of the PACE trial that evaluated paracetamol for acute low back pain. Latent class growth analysis determined a 5 cluster model, which comprised 567 (35.8%) patients who recovered by week 2 (cluster 1, rapid pain recovery); 543 (34.3%) patients who recovered by week 12 (cluster 2, pain recovery by week 12); 222 (14.0%) patients whose pain reduced but did not recover (cluster 3, incomplete pain recovery); 167 (10.5%) patients whose pain initially decreased but then increased by week 12 (cluster 4, fluctuating pain); and 86 (5.4%) patients who experienced high-level pain for the whole 12 weeks (cluster 5, persistent high pain). Patients with longer pain duration were more likely to experience delayed recovery or nonrecovery. Belief in greater risk of persistence was associated with nonrecovery, but not delayed recovery. Higher pain intensity, longer duration, and workers' compensation were associated with persistent high pain, whereas older age and increased number of episodes were associated with fluctuating pain. Identification of discrete pain trajectory groups offers the potential to better manage acute low back pain.

A formal concept analysis approach to consensus clustering of multi-experiment expression data

PubMed Central

2014-01-01

Background Presently, with the increasing number and complexity of available gene expression datasets, the combination of data from multiple microarray studies addressing a similar biological question is gaining importance. The analysis and integration of multiple datasets are expected to yield more reliable and robust results since they are based on a larger number of samples and the effects of the individual study-specific biases are diminished. This is supported by recent studies suggesting that important biological signals are often preserved or enhanced by multiple experiments. An approach to combining data from different experiments is the aggregation of their clusterings into a consensus or representative clustering solution which increases the confidence in the common features of all the datasets and reveals the important differences among them. Results We propose a novel generic consensus clustering technique that applies Formal Concept Analysis (FCA) approach for the consolidation and analysis of clustering solutions derived from several microarray datasets. These datasets are initially divided into groups of related experiments with respect to a predefined criterion. Subsequently, a consensus clustering algorithm is applied to each group resulting in a clustering solution per group. These solutions are pooled together and further analysed by employing FCA which allows extracting valuable insights from the data and generating a gene partition over all the experiments. In order to validate the FCA-enhanced approach two consensus clustering algorithms are adapted to incorporate the FCA analysis. Their performance is evaluated on gene expression data from multi-experiment study examining the global cell-cycle control of fission yeast. The FCA results derived from both methods demonstrate that, although both algorithms optimize different clustering characteristics, FCA is able to overcome and diminish these differences and preserve some relevant biological signals. Conclusions The proposed FCA-enhanced consensus clustering technique is a general approach to the combination of clustering algorithms with FCA for deriving clustering solutions from multiple gene expression matrices. The experimental results presented herein demonstrate that it is a robust data integration technique able to produce good quality clustering solution that is representative for the whole set of expression matrices. PMID:24885407

New clues to the cause of extended main-sequence turnoffs in intermediate-age star clusters in the Magellanic Clouds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Correnti, Matteo; Goudfrooij, Paul; Kalirai, Jason S.

2014-10-01

We use the Wide Field Camera 3 on board the Hubble Space Telescope (HST) to obtain deep, high-resolution images of two intermediate-age star clusters in the Large Magellanic Cloud of relatively low mass (≈10{sup 4} M {sub ☉}) and significantly different core radii, namely NGC 2209 and NGC 2249. For comparison purposes, we also reanalyzed archival HST images of NGC 1795 and IC 2146, two other relatively low-mass star clusters. From the comparison of the observed color-magnitude diagrams with Monte Carlo simulations, we find that the main-sequence turnoff (MSTO) regions in NGC 2209 and NGC 2249 are significantly wider thanmore » that derived from simulations of simple stellar populations, while those in NGC 1795 and IC 2146 are not. We determine the evolution of the clusters' masses and escape velocities from an age of 10 Myr to the present age. We find that differences among these clusters can be explained by dynamical evolution arguments if the currently extended clusters (NGC 2209 and IC 2146) experienced stronger levels of initial mass segregation than the currently compact ones (NGC 2249 and NGC 1795). Under this assumption, we find that NGC 2209 and NGC 2249 have estimated escape velocities, V {sub esc} ≳ 15 km s{sup –1} at an age of 10 Myr, large enough to retain material ejected by slow winds of first-generation stars, while the two clusters that do not feature extended MSTOs have V {sub esc} ≲ 12 km s{sup –1} at that age. These results suggest that the extended MSTO phenomenon can be better explained by a range of stellar ages rather than a range of stellar rotation velocities or interacting binaries.« less

Stellar age spreads in clusters as imprints of cluster-parent clump densities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parmentier, G.; Grebel, E. K.; Pfalzner, S.

2014-08-20

It has recently been suggested that high-density star clusters have stellar age distributions much narrower than that of the Orion Nebula Cluster, indicating a possible trend of narrower age distributions for denser clusters. We show this effect to likely arise from star formation being faster in gas with a higher density. We model the star formation history of molecular clumps in equilibrium by associating a star formation efficiency per free-fall time, ε{sub ff}, to their volume density profile. We focus on the case of isothermal spheres and we obtain the evolution with time of their star formation rate. Our modelmore » predicts a steady decline of the star formation rate, which we quantify with its half-life time, namely, the time needed for the star formation rate to drop to half its initial value. Given the uncertainties affecting the star formation efficiency per free-fall time, we consider two distinct values: ε{sub ff} = 0.1 and ε{sub ff} = 0.01. When ε{sub ff} = 0.1, the half-life time is of the order of the clump free-fall time, τ{sub ff}. As a result, the age distributions of stars formed in high-density clumps have smaller full-widths at half-maximum than those of stars formed in low-density clumps. When the star formation efficiency per free-fall time is 0.01, the half-life time is 10 times longer, i.e., 10 clump free-fall times. We explore what happens if the duration of star formation is shorter than 10τ{sub ff}, that is, if the half-life time of the star formation rate cannot be defined. There, we build on the invariance of the shape of the young cluster mass function to show that an anti-correlation between the clump density and the duration of star formation is expected. We therefore conclude that, regardless of whether the duration of star formation is longer than the star formation rate half-life time, denser molecular clumps yield narrower star age distributions in clusters. Published densities and stellar age spreads of young clusters and star-forming regions actually suggest that the timescale for star formation is of order 1-4τ{sub ff}. We also discuss how the age bin size and uncertainties in stellar ages affect our results. We conclude that there is no need to invoke the existence of multiple cluster formation mechanisms to explain the observed range of stellar age spreads in clusters.« less

Stars caught in the braking stage in young Magellanic Cloud clusters

NASA Astrophysics Data System (ADS)

D'Antona, Francesca; Milone, Antonino P.; Tailo, Marco; Ventura, Paolo; Vesperini, Enrico; di Criscienzo, Marcella

2017-08-01

The colour-magnitude diagrams of many Magellanic Cloud clusters (with ages up to 2 billion years) display extended turnoff regions where the stars leave the main sequence, suggesting the presence of multiple stellar populations with ages that may differ even by hundreds of millions of years 1,2,3 . A strongly debated question is whether such an extended turnoff is instead due to populations with different stellar rotations3,4,5,6 . The recent discovery of a 'split' main sequence in some younger clusters (~80-400 Myr) added another piece to this puzzle. The blue side of the main sequence is consistent with slowly rotating stellar models, and the red side consistent with rapidly rotating models7,8,9,10. However, a complete theoretical characterization of the observed colour-magnitude diagram also seemed to require an age spread9. We show here that, in the three clusters so far analysed, if the blue main-sequence stars are interpreted with models in which the stars have always been slowly rotating, they must be ~30% younger than the rest of the cluster. If they are instead interpreted as stars that were initially rapidly rotating but have later slowed down, the age difference disappears, and this 'braking' also helps to explain the apparent age differences of the extended turnoff. The age spreads in Magellanic Cloud clusters are thus a manifestation of rotational stellar evolution. Observational tests are suggested.

A cross-sectional cluster analysis of the combined association of physical activity and sleep with sociodemographic and health characteristics in mid-aged and older adults.

PubMed

Rayward, Anna T; Duncan, Mitch J; Brown, Wendy J; Plotnikoff, Ronald C; Burton, Nicola W

2017-08-01

This study aimed to identify how different patterns of physical activity, sleep duration and sleep quality cluster together, and to examine how the identified clusters differ in terms of socio-demographic and health characteristics. Participants were adults from Brisbane, Australia, aged 42-72 years who reported their physical activity, sleep duration, sleep quality, socio-demographic and health characteristics in 2011 (n=5854). Two-step Cluster Analyses were used to identify clusters. Cluster differences in socio-demographic and health characteristics were examined using chi square tests (p<0.05). Four clusters were identified: 'Poor Sleepers' (31.2%), 'Moderate Sleepers' (30.7%), 'Mixed Sleepers/Highly Active' (20.5%), and 'Excellent Sleepers/Mixed Activity' (17.6%). The 'Poor Sleepers' cluster had the highest proportion of participants with less-than-recommended sleep duration and poor sleep quality, had the poorest health characteristics and a high proportion of participants with low physical activity. Physical activity, sleep duration and sleep quality cluster together in distinct patterns and clusters of poor behaviours are associated with poor health status. Multiple health behaviour change interventions which target both physical activity and sleep should be prioritised to improve health outcomes in mid-aged adults. Copyright © 2017 Elsevier B.V. All rights reserved.

On the determination of age and mass functions of stars in young open star clusters from the analysis of their luminosity functions

NASA Astrophysics Data System (ADS)

Piskunov, A. E.; Belikov, A. N.; Kharchenko, N. V.; Sagar, R.; Subramaniam, A.

2004-04-01

We construct the observed luminosity functions of the remote young open clusters NGC 2383, 2384, 4103, 4755, 7510 and Hogg 15 from CCD observations of them. The observed LFs are corrected for field star contamination determined with the help of a Galactic star count model. In the case of Hogg 15 and NGC 2383 we also consider the additional contamination from neighbouring clusters NGC 4609 and 2384, respectively. These corrections provide a realistic pattern of cluster LF in the vicinity of the main-sequence (MS) turn-on point and at fainter magnitudes reveal the so-called H-feature arising as a result of the transition of the pre-MS phase to the MS, which is dependent on the cluster age. The theoretical LFs are constructed representing a cluster population model with continuous star formation for a short time-scale and a power-law initial mass function (IMF), and these are fitted to the observed LF. As a result, we are able to determine for each cluster a set of parameters describing the cluster population (the age, duration of star formation, IMF slope and percentage of field star contamination). It is found that in spite of the non-monotonic behaviour of observed LFs, cluster IMFs can be described as power-law functions with slopes similar to Salpeter's value. The present main-sequence turn-on cluster ages are several times lower than those derived from the fitting of theoretical isochrones to the turn-off region of the upper main sequences.

Star clusters: age, metallicity and extinction from integrated spectra

NASA Astrophysics Data System (ADS)

González Delgado, Rosa M.; Cid Fernandes, Roberto

2010-01-01

Integrated optical spectra of star clusters in the Magellanic Clouds and a few Galactic globular clusters are fitted using high-resolution spectral models for single stellar populations. The goal is to estimate the age, metallicity and extinction of the clusters, and evaluate the degeneracies among these parameters. Several sets of evolutionary models that were computed with recent high-spectral-resolution stellar libraries (MILES, GRANADA, STELIB), are used as inputs to the starlight code to perform the fits. The comparison of the results derived from this method and previous estimates available in the literature allow us to evaluate the pros and cons of each set of models to determine star cluster properties. In addition, we quantify the uncertainties associated with the age, metallicity and extinction determinations resulting from variance in the ingredients for the analysis.

Phenotypes determined by cluster analysis in severe or difficult-to-treat asthma.

PubMed

Schatz, Michael; Hsu, Jin-Wen Y; Zeiger, Robert S; Chen, Wansu; Dorenbaum, Alejandro; Chipps, Bradley E; Haselkorn, Tmirah

2014-06-01

Asthma phenotyping can facilitate understanding of disease pathogenesis and potential targeted therapies. To further characterize the distinguishing features of phenotypic groups in difficult-to-treat asthma. Children ages 6-11 years (n = 518) and adolescents and adults ages ≥12 years (n = 3612) with severe or difficult-to-treat asthma from The Epidemiology and Natural History of Asthma: Outcomes and Treatment Regimens (TENOR) study were evaluated in this post hoc cluster analysis. Analyzed variables included sex, race, atopy, age of asthma onset, smoking (adolescents and adults), passive smoke exposure (children), obesity, and aspirin sensitivity. Cluster analysis used the hierarchical clustering algorithm with the Ward minimum variance method. The results were compared among clusters by χ(2) analysis; variables with significant (P < .05) differences among clusters were considered as distinguishing feature candidates. Associations among clusters and asthma-related health outcomes were assessed in multivariable analyses by adjusting for socioeconomic status, environmental exposures, and intensity of therapy. Five clusters were identified in each age stratum. Sex, atopic status, and nonwhite race were distinguishing variables in both strata; passive smoke exposure was distinguishing in children and aspirin sensitivity in adolescents and adults. Clusters were not related to outcomes in children, but 2 adult and adolescent clusters distinguished by nonwhite race and aspirin sensitivity manifested poorer quality of life (P < .0001), and the aspirin-sensitive cluster experienced more frequent asthma exacerbations (P < .0001). Distinct phenotypes appear to exist in patients with severe or difficult-to-treat asthma, which is related to outcomes in adolescents and adults but not in children. The study of the therapeutic implications of these phenotypes is warranted. Copyright © 2013 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.

The Age Related Properties of Solar Type Stars

NASA Technical Reports Server (NTRS)

Soderblom, David

1999-01-01

The studies of lithium in solar-type stars in clusters of a wide range of ages has provided critical information on a tracer of convective processes, especially among very young stars. Our most recent work has been on a pre-main sequence cluster (NGC 2264) that took place after this grant expired, but was founded on it. The spread seen in Li in Zero-Age Main Sequence clusters like the Pleiades is huge and possibly related to rotation. No clear spread in seen in NGC 2264, so it does not have its origins in the conditions of formation but is instead a result of processes occurring during PMS evolution. Our observations of M67 were particularly interesting because this cluster is the same age as the Sun, i.e.,very old. Clear evidence was seen for a spread in Li there too, indicating that the spread seen in very young stars perpetuates itself into old age.

The formation and evolution of M33 as revealed by its star clusters

NASA Astrophysics Data System (ADS)

San Roman, Izaskun

2012-03-01

Numerical simulations based on the Lambda-Cold Dark Matter (Λ-CDM) model predict a scenario consistent with observational evidence in terms of the build-up of Milky Way-like halos. Under this scenario, large disk galaxies derive from the merger and accretion of many smaller subsystems. However, it is less clear how low-mass spiral galaxies fit into this picture. The best way to answer this question is to study the nearest example of a dwarf spiral galaxy, M33. We will use star clusters to understand the structure, kinematics and stellar populations of this galaxy. Star clusters provide a unique and powerful tool for studying the star formation histories of galaxies. In particular, the ages and metallicities of star clusters bear the imprint of the galaxy formation process. We have made use of the star clusters to uncover the formation and evolution of M33. In this dissertation, we have carried out a comprehensive study of the M33 star cluster system, including deep photometry as well as high signal-to-noise spectroscopy. In order to mitigate the significant incompleteness presents in previous catalogs, we have conducted ground-based and space-based photometric surveys of M33 star clusters. Using archival images, we have analyzed 12 fields using the Advanced Camera for Surveys Wide Field Channel onboard the Hubble Space Telescope (ACS/HST) along the major axis of the galaxy. We present integrated photometry and color-magnitude diagrams for 161 star clusters in M33, of which 115 were previously uncataloged. This survey extends the depth of the existing M33 cluster catalogs by ˜ 1 mag. We have expanded our search through a photometric survey in a 1° x 1° area centered on M33 using the MegaCam camera on the 3.6m Canada-France-Hawaii Telescope (CFHT). In this work we discuss the photometric properties of the sample, including color-color diagrams of 599 new candidate stellar clusters, and 204 confirmed clusters. Comparisons with models of simple stellar populations suggest a large range of ages some as old as ˜ 10 Gyr. In addition, we find in the color-color diagrams a significant population of very young clusters (< 10 Myr) possessing nebular emission. Analysis of the radial density distribution suggests that the cluster system of M33 has suffered from significant depletion, possibly due to interactions with M31. To further understand the properties of M33 star clusters, we have carried out a morphological study 161 star clusters in M33 using ACS/HST images. We have obtained, for the first time, ellipticities, position angles, and surface brightness profiles of a statistically significant number of clusters. Ellipticities show that, on average, M33 clusters are more flattened than those of the Milky Way and M31, and more similar to clusters in the Small Magellanic Cloud. The ellipticities do not show any correlation with age or mass, suggesting that rotation is not the main cause of elongation in the M33 clusters. The position angles of the clusters show a bimodality with a strong peak perpendicular to the position angle of the galaxy. These results support the notion that tidal forces are the reason for the cluster flattening. We have fit analytical models to the surface brightness profiles, and derived structural parameters. The overall analysis shows several differences between the structural properties of the M33 cluster system and cluster systems in nearby galaxies. Finally, we have performed a spectroscopic study of star clusters in the above mentioned catalog. We present high-precision velocity measures of 45 star clusters, based on observations from the 10.4m Gran Telescopio Canarias (GTC) using OSIRIS and 4.2m William Herschel Telescope (WHT) using WYFFOS. All the clusters have been previously confirmed using HST imaging, and ages and integrated photometry are known. The velocity of the clusters with respect to local disk motion increases with age for young and intermediate clusters. The mean dispersion velocity for the intermediate age clusters in our sample is significantly larger than in previous studies. Analysis of these velocities along the major axis of the galaxy show no net rotation of the intermediate age subsample. The small number of old clusters in our sample does not allow for any conclusive evidence in that age division.

A prospective study of autistic-like traits in unaffected siblings of probands with autism spectrum disorder.

PubMed

Georgiades, Stelios; Szatmari, Peter; Zwaigenbaum, Lonnie; Bryson, Susan; Brian, Jessica; Roberts, Wendy; Smith, Isabel; Vaillancourt, Tracy; Roncadin, Caroline; Garon, Nancy

2013-01-01

The presence of autistic-like traits in relatives of individuals with autism spectrum disorder (ASD) is well recognized, but, to our knowledge, the emergence of these traits early in development has not been studied. To prospectively investigate the emergence of autistic-like traits in unaffected (no ASD diagnosis) infant siblings of probands diagnosed as having ASD. Two groups of children unaffected with ASD were assessed prospectively-siblings of probands diagnosed as having ASD (high risk [HR]) and control subjects with no family history of ASD (low risk [LR]). Scores on a measure of autistic-like traits at 12 months of age were used in a cluster analysis of the entire sample. A prospective study of infant siblings of probands with ASD from 3 diagnostic centers in Canada. The study included 170 HR and 90 LR children, none of whom was diagnosed as having ASD at age 3 years. The Autism Observation Scale for Infants was used to measure autistic-like traits and derive clusters at 12 months of age. Clusters were compared on ASD symptoms, cognitive abilities, and social-emotional difficulties at age 3 years. Two clusters were identified. Cluster 1 (n = 37; 14.2% of total sample) had significantly higher levels of autistic-like traits compared with cluster 2. Within cluster 1, 33 children came from the siblings (19.4% of HR group) and only 4 came from the control subjects (4.5% of LR group). At age 3 years, children from cluster 1 had more social-communication impairment (effect size > 0.70; P < .001), lower cognitive abilities (effect size = -0.59; P < .005), and more internalizing problems (effect size = 0.55; P = .01). Compared with control subjects, HR siblings had a relative risk of 4.3 (95% CI,1.6-11.9) for membership in cluster 1. Study findings suggest the emergence of autistic-like traits resembling a broader autism phenotype by 12 months of age in approximately 19% of HR siblings who did not meet ASD diagnostic criteria at age 3 years.

Mass to Luminosity Ratios of Some Clusters in the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Sohn, Young-Jong; Chun, Mun-Suk

1990-12-01

Luminosity profiles and dynamical parameters of 12 globular clusters in the Large Magellanic Cloud(SB(s)m) are obtained from the concentric aperture photoelectric photometry of 3 different aged clusters and the collected photometric data of 9 clusters. The total masses of the globular clusters are the calculated using the equation M = Mrt3(4¥Ø2-k2), which is derived from the theoretical rotation curve for the exponential disk(Chun 1987). These masses lie between 0.3 x 104 and 15.8 x 104 M . From the determined total mass and luminosity ratios are also derived. The M/L ratio of a cluster increases with the cluster age; about 0.03 for the youngest clusters(SWB ¥°) and about 0.24 for the oldest clusters(SUB ¥¶). There is a difference in M/L by a factor of 10 between the galactic globular clusters and the old globular clusters in the LCM.

Spatial distribution and cluster analysis of risky sexual behaviours and STDs reported by Chinese adults in Guangzhou, China: a representative population-based study

PubMed Central

Chen, Wen; Zhou, Fangjing; Hall, Brian J; Wang, Yu; Latkin, Carl; Ling, Li; Tucker, Joseph D

2016-01-01

Objectives To assess associations between residences location, risky sexual behaviours and sexually transmitted diseases (STDs) among adults living in Guangzhou, China. Methods Data were obtained from 751 Chinese adults aged 18–59 years in Guangzhou, China, using stratified random sampling by using spatial epidemiological methods. Face-to-face household interviews were conducted to collect self-report data on risky sexual behaviours and diagnosed STDs. Kulldorff’s spatial scan statistic was implemented to identify and detect spatial distribution and clusters of risky sexual behaviours and STDs. The presence and location of statistically significant clusters were mapped in the study areas using ArcGIS software. Results The prevalence of self-reported risky sexual behaviours was between 5.1% and 50.0%. The self-reported lifetime prevalence of diagnosed STDs was 7.06%. Anal intercourse clustered in an area located along the border within the rural–urban continuum (p=0.001). High rate clusters for alcohol or other drugs using before sex (p=0.008) and migrants who lived in Guangzhou <1 year (p=0.007) overlapped this cluster. Excess cases for unprotected sex (p=0.031) overlapped the cluster for college students (p<0.001). Five of nine (55.6%) students who had sexual experience during the last 12 months located in the cluster of unprotected sex. Conclusions Short-term migrants and college students reported greater risky sexual behaviours. Programmes to increase safer sex within these communities to reduce the risk of STDs are warranted in Guangzhou. Spatial analysis identified geographical clusters of risky sexual behaviours, which is critical for optimising surveillance and targeting control measures for these locations in the future. PMID:26843400

ADHD latent class clusters: DSM-IV subtypes and comorbidity

PubMed Central

Elia, Josephine; Arcos-Burgos, Mauricio; Bolton, Kelly L.; Ambrosini, Paul J.; Berrettini, Wade; Muenke, Maximilian

2014-01-01

ADHD (Attention Deficit Hyperactivity Disorder) has a complex, heterogeneous phenotype only partially captured by Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria. In this report, latent class analyses (LCA) are used to identify ADHD phenotypes using K-SADS-IVR (Schedule for Affective Disorders & Schizophrenia for School Age Children-IV-Revised) symptoms and symptom severity data from a clinical sample of 500 ADHD subjects, ages 6–18, participating in an ADHD genetic study. Results show that LCA identified six separate ADHD clusters, some corresponding to specific DSM-IV subtypes while others included several subtypes. DSM-IV comorbid anxiety and mood disorders were generally similar across all clusters, and subjects without comorbidity did not aggregate within any one cluster. Age and gender composition also varied. These results support findings from population-based LCA studies. The six clusters provide additional homogenous groups that can be used to define ADHD phenotypes in genetic association studies. The limited age ranges aggregating in the different clusters may prove to be a particular advantage in genetic studies where candidate gene expression may vary during developmental phases. DSM-IV comorbid mood and anxiety disorders also do not appear to increase cluster heterogeneity; however, longitudinal studies that cover period of risk are needed to support this finding. PMID:19900717

Determining Distance, Age, and Activity in a New Benchmark Cluster: Ruprecht 147

NASA Astrophysics Data System (ADS)

Wright, Jason T.

2009-08-01

This proposal seeks 0.7 night of time on Hectochelle to observe the F, G, and K dwarfs of Ruprecht 147, recently identified as the closest old stellar cluster. At only ~ 200 pc and at an age of ~ 1-2 Gyr, this will be an important benchmark in stellar astrophysics, providing the only sample of spectroscopically accessible old, late-type stars of determinable age. Hectochelle is the ideal instrument to study this cluster, with a FOV, fiber count, and telescope aperture well matched to the cluster's diameter (~ 1°), richness (~ 100 identified members), and distance modulus (6.5-7 mag., putting the G and K dwarfs at B=11-15). Hectochelle will measure the Ca II line strengths of members to establish, for the first time, the chromospheric activity levels of a statistically significant sample of single, G and K dwarfs of this modest age. Hectochelle will also vet background stars for suitability as astrometric reference stars for a forthcoming HST FGS proposal to robustly measure the cluster's distance.

The open cluster IC 4665

NASA Technical Reports Server (NTRS)

Prosser, Charles F.

1993-01-01

The results of a combined astrometric, photometric, and spectroscopic program to identify members of the open cluster IC 4665 are presented. Numerous new proper motion/photometric candidate members and at least 23 M dwarfs with H-alpha emission have been identified. A reanalysis of IC 4665 age using different methods yields conflicting results ranging from about 3 X 10 exp 7 yr to the age of the Pleiades. This study provides a list of candidate cluster members in the intermediate and low-mass regime of this cluster. Future spectroscopic observations of these candidates should eventually identify true cluster members.

Age Differences in Recall and Information Processing in Verbal and Spatial Learning.

ERIC Educational Resources Information Center

Mungas, Dan; And Others

1991-01-01

Three age groups of 24 people each completed verbal word list tasks and spatial learning tasks 5 times each. Significant age differences were found for total recall and type of task. Younger subjects showed increased levels of clustering--organizing information according to semantic or spatial clusters. Age was not related to temporal order of…

Beverage consumption patterns of Canadian adults aged 19 to 65 years.

PubMed

Nikpartow, Nooshin; Danyliw, Adrienne D; Whiting, Susan J; Lim, Hyun J; Vatanparast, Hassanali

2012-12-01

To investigate the beverage intake patterns of Canadian adults and explore characteristics of participants in different beverage clusters. Analyses of nationally representative data with cross-sectional complex stratified design. Canadian Community Health Survey, Cycle 2.2 (2004). A total of 14 277 participants aged 19-65 years, in whom dietary intake was assessed using a single 24 h recall, were included in the study. After determining total intake and the contribution of beverages to total energy intake among age/sex groups, cluster analysis (K-means method) was used to classify males and females into distinct clusters based on the dominant pattern of beverage intakes. To test differences across clusters, χ2 tests and 95 % confidence intervals of the mean intakes were used. Six beverage clusters in women and seven beverage clusters in men were identified. 'Sugar-sweetened' beverage clusters - regular soft drinks and fruit drinks - as well as a 'beer' cluster, appeared for both men and women. No 'milk' cluster appeared among women. The mean consumption of the dominant beverage in each cluster was higher among men than women. The 'soft drink' cluster in men had the lowest proportion of the higher levels of education, and in women the highest proportion of inactivity, compared with other beverage clusters. Patterns of beverage intake in Canadian women indicate high consumption of sugar-sweetened beverages particularly fruit drinks, low intake of milk and high intake of beer. These patterns in women have implications for poor bone health, risk of obesity and other morbidities.

Successful ageing: A study of the literature using citation network analysis.

PubMed

Kusumastuti, Sasmita; Derks, Marloes G M; Tellier, Siri; Di Nucci, Ezio; Lund, Rikke; Mortensen, Erik Lykke; Westendorp, Rudi G J

2016-11-01

Ageing is accompanied by an increased risk of disease and a loss of functioning on several bodily and mental domains and some argue that maintaining health and functioning is essential for a successful old age. Paradoxically, studies have shown that overall wellbeing follows a curvilinear pattern with the lowest point at middle age but increases thereafter up to very old age. To shed further light on this paradox, we reviewed the existing literature on how scholars define successful ageing and how they weigh the contribution of health and functioning to define success. We performed a novel, hypothesis-free and quantitative analysis of citation networks exploring the literature on successful ageing that exists in the Web of Science Core Collection Database using the CitNetExplorer software. Outcomes were visualized using timeline-based citation patterns. The clusters and sub-clusters of citation networks identified were starting points for in-depth qualitative analysis. Within the literature from 1902 through 2015, two distinct citation networks were identified. The first cluster had 1146 publications and 3946 citation links. It focused on successful ageing from the perspective of older persons themselves. Analysis of the various sub-clusters emphasized the importance of coping strategies, psycho-social engagement, and cultural differences. The second cluster had 609 publications and 1682 citation links and viewed successful ageing based on the objective measurements as determined by researchers. Subsequent sub-clustering analysis pointed to different domains of functioning and various ways of assessment. In the current literature two mutually exclusive concepts of successful ageing are circulating that depend on whether the individual himself or an outsider judges the situation. These different points of view help to explain the disability paradox, as successful ageing lies in the eyes of the beholder. Copyright © 2016 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

Cluster Headache Clinical Phenotypes: Tobacco Nonexposed (Never Smoker and No Parental Secondary Smoke Exposure as a Child) versus Tobacco-Exposed: Results from the United States Cluster Headache Survey.

PubMed

Rozen, Todd D

2018-05-01

To present results from the United States Cluster Headache Survey comparing the clinical presentation of tobacco nonexposed and tobacco-exposed cluster headache patients. Cluster headache is uniquely tied to a personal history of tobacco usage/cigarette smoking and, if the individual cluster headache sufferer did not smoke, it has been shown that their parent(s) typically did and that individual had significant secondary smoke exposure as a child. The true nontobacco exposed (no personal or secondary exposure) cluster headache sufferer has never been fully studied. The United States Cluster Headache Survey consisted of 187 multiple choice questions related to cluster headache including: patient demographics, clinical headache characteristics, family history, triggers, smoking history (personal and secondary), and headache-related disability. The survey was placed on a website from October through December 2008. One thousand one hundred thirty-four individuals completed the survey. One hundred thirty-three subjects or 12% of the surveyed population had no personal smoking/tobacco use history and no secondary smoke exposure as an infant/child, thus a nontobacco exposed population. In the nonexposed population, there were 87 males and 46 females with a gender ratio of 1.9:1. Episodic cluster headache occurred in 80% of nonexposed subjects. One thousand and one survey responders or 88% were tobacco-exposed (729 males and 272 females) with a gender ratio of 2.7:1. Eighty-three percent had a personal smoking history, while only 17% just had parents who smoked with secondary smoke exposure. Eighty-five percent of smokers had double exposure with a personal smoking history and secondary exposure as a child. Nonexposed cluster headache subjects are significantly more likely to develop cluster headache at ages 40 years and younger, while the exposed sufferers are significantly more likely to develop cluster headache at 40 years of age and older. Nonexposed patients have a statistically significant higher frequency of a migraine family history. The exposed population is statistically significantly more likely to have a history of head trauma 19% vs the nonexposed population 10% (P = .02). Tobacco exposed are significantly more likely to transition from episodic to chronic cluster headache (23% vs 14%, P = .02). Cranial autonomic symptoms as well as agitation are more common in tobacco exposed. Nonexposed are less likely to have specific cluster headache triggers. Exposed are significantly more likely to be triggered by alcohol. Tobacco exposed are significantly heavier caffeine users than nonexposed. Nonexposed are significantly more likely to have cluster headache cycles that vary throughout the year than exposed (52% vs 40%, P = .02). Exposed are much more likely to develop cluster headache from 12 am to 6 am than non exposed. Exposed experience significantly more frequent attacks per day and longer duration cycles than nonexposed. A significantly larger percent of the exposed population (57%) has suicidal ideations with their syndrome than nonexposed (43%) (P = .003). In regard to disability, both subtypes are disabled by their headaches, but exposed have more work related disability and lost home-days from headache. Both subgroups have a poor overall response to preventive and abortive medication outside of inhaled oxygen and injectable sumatriptan. Cluster headache sufferers who were never exposed to tobacco (personal or secondary as a child) appear to present uniquely compared to the tobacco exposed subgroup. The tobacco exposed clinical phenotype appears to have a more severe syndrome based on attack frequency, cycle duration, and headache related disability. Tobacco exposure is associated with cluster headache chronification. The nonexposed subtype appears to have an earlier age of onset, higher rate of familial migraine, and less circadian periodicity and daytime entrainment, suggesting a possible different underlying pathology than in the tobacco exposed sub-form. © 2018 American Headache Society.

The Gaia-ESO Survey: open clusters in Gaia-DR1 . A way forward to stellar age calibration

NASA Astrophysics Data System (ADS)

Randich, S.; Tognelli, E.; Jackson, R.; Jeffries, R. D.; Degl'Innocenti, S.; Pancino, E.; Re Fiorentin, P.; Spagna, A.; Sacco, G.; Bragaglia, A.; Magrini, L.; Prada Moroni, P. G.; Alfaro, E.; Franciosini, E.; Morbidelli, L.; Roccatagliata, V.; Bouy, H.; Bravi, L.; Jiménez-Esteban, F. M.; Jordi, C.; Zari, E.; Tautvaišiene, G.; Drazdauskas, A.; Mikolaitis, S.; Gilmore, G.; Feltzing, S.; Vallenari, A.; Bensby, T.; Koposov, S.; Korn, A.; Lanzafame, A.; Smiljanic, R.; Bayo, A.; Carraro, G.; Costado, M. T.; Heiter, U.; Hourihane, A.; Jofré, P.; Lewis, J.; Monaco, L.; Prisinzano, L.; Sbordone, L.; Sousa, S. G.; Worley, C. C.; Zaggia, S.

2018-05-01

Context. Determination and calibration of the ages of stars, which heavily rely on stellar evolutionary models, are very challenging, while representing a crucial aspect in many astrophysical areas. Aims: We describe the methodologies that, taking advantage of Gaia-DR1 and the Gaia-ESO Survey data, enable the comparison of observed open star cluster sequences with stellar evolutionary models. The final, long-term goal is the exploitation of open clusters as age calibrators. Methods: We perform a homogeneous analysis of eight open clusters using the Gaia-DR1 TGAS catalogue for bright members and information from the Gaia-ESO Survey for fainter stars. Cluster membership probabilities for the Gaia-ESO Survey targets are derived based on several spectroscopic tracers. The Gaia-ESO Survey also provides the cluster chemical composition. We obtain cluster parallaxes using two methods. The first one relies on the astrometric selection of a sample of bona fide members, while the other one fits the parallax distribution of a larger sample of TGAS sources. Ages and reddening values are recovered through a Bayesian analysis using the 2MASS magnitudes and three sets of standard models. Lithium depletion boundary (LDB) ages are also determined using literature observations and the same models employed for the Bayesian analysis. Results: For all but one cluster, parallaxes derived by us agree with those presented in Gaia Collaboration (2017, A&A, 601, A19), while a discrepancy is found for NGC 2516; we provide evidence supporting our own determination. Inferred cluster ages are robust against models and are generally consistent with literature values. Conclusions: The systematic parallax errors inherent in the Gaia DR1 data presently limit the precision of our results. Nevertheless, we have been able to place these eight clusters onto the same age scale for the first time, with good agreement between isochronal and LDB ages where there is overlap. Our approach appears promising and demonstrates the potential of combining Gaia and ground-based spectroscopic datasets. Based on observations collected with the FLAMES instrument at VLT/UT2 telescope (Paranal Observatory, ESO, Chile), for the Gaia-ESO Large Public Spectroscopic Survey (188.B-3002, 193.B-0936).Additional tables are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/612/A99

X-ray and IR Surveys of the Orion Molecular Clouds and the Cepheus OB3b Cluster

NASA Astrophysics Data System (ADS)

Megeath, S. Thomas; Wolk, Scott J.; Pillitteri, Ignazio; Allen, Tom

2014-08-01

X-ray and IR surveys of molecular clouds between 400 and 700 pc provide complementary means to map the spatial distribution of young low mass stars associated with the clouds. We overview an XMM survey of the Orion Molecular Clouds, at a distance of 400 pc. By using the fraction of X-ray sources with disks as a proxy for age, this survey has revealed three older clusters rich in diskless X-ray sources. Two are smaller clusters found at the northern and southern edges of the Orion A molecular cloud. The third cluster surrounds the O-star Iota Ori (the point of Orion's sword) and is in the foreground to the Orion molecular cloud. In addition, we present a Chandra and Spitzer survey of the Cep OB3b cluster at 700 pc. These data show a spatially variable disk fraction indicative of age variations within the cluster. We discuss the implication of these results for understanding the spread of ages in young clusters and the star formation histories of molecular clouds.

Medium resolution spectroscopy and chemical composition of Galactic globular clusters

NASA Astrophysics Data System (ADS)

Khamidullina, D. A.; Sharina, M. E.; Shimansky, V. V.; Davoust, E.

We used integrated-light medium-resolution spectra of six Galactic globular clusters and model stellar atmospheres to carry out population synthesis and to derive chemical composition and age of the clusters. We used medium-resolution spectra of globular clusters published by Schiavon et al. (2005), as well as our long-slit observations with the 1.93 m telescope of the Haute Provence Observatory. The observed spectra were fitted to the theoretical ones interactively. As an initial approach, we used masses, radii and log g of stars in the clusters corresponding to the best fitting isochrones in the observed color-magnitude diagrams. The computed synthetic blanketed spectra of stars were summed according to the Chabrier mass function. To improve the determination of age and helium content, the shape and depth of the Balmer absorption lines was analysed. The abundances of Mg, Ca, C and several other elements were derived. A reasonable agreement with the literature data both in chemical composition and in age of the clusters is found. Our method might be useful for the development of stellar population models and for a better understanding of extragalactic star clusters.

Transport in the Subtropical Lowermost Stratosphere during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment

NASA Technical Reports Server (NTRS)

Pittman, Jasna V.; Weinstock, Elliot M.; Oglesby, Robert J.; Sayres, David S.; Smith, Jessica B.; Anderson, James G.; Cooper, Owen R.; Wofsy, Steven C.; Xueref, Irene; Gerbig, Cristoph;

X ray studies of the Hyades cluster

NASA Technical Reports Server (NTRS)

Stern, Robert A.

1993-01-01

The Hyades cluster occupies a unique position in both the history of astronomy and at the frontiers of contemporary astronomical research. At a distance of only 45 pc, the Hyades is the nearest star cluster in the Galaxy which is localized in the sky: the UMa cluster, which is closer, but much sparser, essentially surrounds the Solar neighborhood. The Hyades is the prototype cluster for distance determination using the 'moving-cluster' method, and thus serves to define the zero-age main sequence from which the cosmic distance scale is essentially bootstrapped. The Hyades age (0.6-0.7 Gyr), nearly 8 times younger than the Sun, guarantees the Hyades critical importance to studies of stellar evolution. The results of a complete survey of the Hyades cluster using the ROSAT All Sky Survey (RASS) are reported.

Yellow supergiants in open clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sowell, J.R.

1986-01-01

Superluminous giant stars (SLGs) have been reported in young globular clusters in the Large Magellanic Cloud (LMC). These stars appear to be in the post-asymptotic-giant-branch phase of evolution. This program was an investigation of galactic SLG candidates in open clusters, which are more like the LMC young globular clusters. These were chosen because luminosity, mass, and age determinations can be made for members since cluster distances and interstellar reddenings are known. Color magnitude diagrams were searched for candidates, using the same selection criteria as for SLGs in the LMC. Classification spectra were obtained of 115 program stars from McGraw-Hill Observatorymore » and of 68 stars from Cerro Tololo Inter-American Observatory Chile. These stars were visually classified on the MK system using spectral scans of standard stars taken at the respective observations. Published information was combined with this program's data for 83 stars in 30 clusters. Membership probabilities were assigned to these stars, and the clusters were analyzed according to age. It was seen that the intrinsically brightest supergiants are found in the youngest clusters. With increasing cluster age, the absolute luminosities attained by the supergiants decline. Also, it appears that the evolutionary tracks of luminosity class II stars are more similar to those of class I than of class III.« less

The Evolution of Globular Cluster Systems In Early-Type Galaxies

NASA Astrophysics Data System (ADS)

Grillmair, Carl

1999-07-01

We will measure structural parameters {core radii and concentrations} of globular clusters in three early-type galaxies using deep, four-point dithered observations. We have chosen globular cluster systems which have young, medium-age and old cluster populations, as indicated by cluster colors and luminosities. Our primary goal is to test the hypothesis that globular cluster luminosity functions evolve towards a ``universal'' form. Previous observations have shown that young cluster systems have exponential luminosity functions rather than the characteristic log-normal luminosity function of old cluster systems. We will test to see whether such young system exhibits a wider range of structural parameters than an old systems, and whether and at what rate plausible disruption mechanisms will cause the luminosity function to evolve towards a log-normal form. A simple observational comparison of structural parameters between different age cluster populations and between diff er ent sub-populations within the same galaxy will also provide clues concerning both the formation and destruction mechanisms of star clusters, the distinction between open and globular clusters, and the advisability of using globular cluster luminosity functions as distance indicators.

Detecting Subgroups in Children Diagnosed with Pervasive Developmental Disorder--Not Otherwise Specified

ERIC Educational Resources Information Center

Brennan, Laura; Barton, Marianne; Chen, Chi-Ming; Green, James; Fein, Deborah

2015-01-01

Hierarchical cluster analyses were used to detect three subgroups in a sample of children with pervasive developmental disorder--not otherwise specified (PDD-NOS) evaluated at ages 2 and 4. At age 2, Cluster 1 demonstrated few autism symptoms and high cognitive scores; 60% no longer met criteria for PDD at 4. Cluster 2 exhibited more autism…

On the relative ages of galactic globular clusters. A new observable, a semi-empirical calibration and problems with the theoretical isochrones

NASA Astrophysics Data System (ADS)

Buonanno, R.; Corsi, C. E.; Pulone, L.; Fusi Pecci, F.; Bellazzini, M.

1998-05-01

A new procedure is described to derive homogeneous relative ages from the Color-Magnitude Diagrams (CMDs) of Galactic globular clusters (GGCs). It is based on the use of a new observable, Delta V(0.05) , namely the difference in magnitude between an arbitrary point on the upper main sequence (V_{+0.05} -the V magnitude of the MS-ridge, 0.05 mag redder than the Main Sequence (MS) Turn-off, (TO)) and the horizontal branch (HB). The observational error associated to Delta V(0.05) is substantially smaller than that of previous age-indicators, keeping the property of being strictly independent of distance and reddening and of being based on theoretical luminosities rather than on still uncertain theoretical temperatures. As an additional bonus, the theoretical models show that Delta V(0.05) has a low dependence on metallicity. Moreover, the estimates of the relative age so obtained are also sufficiently invariant (to within ~ +/- 1 Gyr) with varying adopted models and transformations. Since the difference in the color difference Delta (B-V)_{TO,RGB} (VandenBerg, Bolte and Stetson 1990 -VBS, Sarajedini and Demarque 1990 -SD) remains the most reliable technique to estimate relative cluster ages for clusters where the horizontal part of the HB is not adequately populated, we have used the differential ages obtained via the "vertical" Delta V(0.05) parameter for a selected sample of clusters (with high quality CMDs, well populated HBs, trustworthy calibrations) to perform an empirical calibration of the "horizontal" observable in terms of [Fe/H] and age. A direct comparison with the corresponding calibration derived from the theoretical models reveals the existence of clear-cut discrepancies, which call into question the model scaling with metallicity in the observational planes. Starting from the global sample of considered clusters, we have thus evaluated, within a homogeneous procedure, relative ages for 33 GGCs having different metallicity, HB-morphologies, and galactocentric distances. These new estimates have also been compared with previous latest determinations (Chaboyer, Demarque and Sarajedini 1996, and Richer {et al. } 1996). The distribution of the cluster ages with varying metallicity and galactocentric distance are briefly discussed: (a) there is no direct indication for any evident age-metallicity relationship; (b) there is some spread in age (still partially compatible with the errors), and the largest dispersion is found for intermediate metal-poor clusters; (c) older clusters populate both the inner and the outer regions of the Milky Way, while the younger globulars are present only in the outer regions, but the sample is far too poor to yield conclusive evidences.

Clustering Coefficients for Correlation Networks.

PubMed

Masuda, Naoki; Sakaki, Michiko; Ezaki, Takahiro; Watanabe, Takamitsu

2018-01-01

Graph theory is a useful tool for deciphering structural and functional networks of the brain on various spatial and temporal scales. The clustering coefficient quantifies the abundance of connected triangles in a network and is a major descriptive statistics of networks. For example, it finds an application in the assessment of small-worldness of brain networks, which is affected by attentional and cognitive conditions, age, psychiatric disorders and so forth. However, it remains unclear how the clustering coefficient should be measured in a correlation-based network, which is among major representations of brain networks. In the present article, we propose clustering coefficients tailored to correlation matrices. The key idea is to use three-way partial correlation or partial mutual information to measure the strength of the association between the two neighboring nodes of a focal node relative to the amount of pseudo-correlation expected from indirect paths between the nodes. Our method avoids the difficulties of previous applications of clustering coefficient (and other) measures in defining correlational networks, i.e., thresholding on the correlation value, discarding of negative correlation values, the pseudo-correlation problem and full partial correlation matrices whose estimation is computationally difficult. For proof of concept, we apply the proposed clustering coefficient measures to functional magnetic resonance imaging data obtained from healthy participants of various ages and compare them with conventional clustering coefficients. We show that the clustering coefficients decline with the age. The proposed clustering coefficients are more strongly correlated with age than the conventional ones are. We also show that the local variants of the proposed clustering coefficients (i.e., abundance of triangles around a focal node) are useful in characterizing individual nodes. In contrast, the conventional local clustering coefficients were strongly correlated with and therefore may be confounded by the node's connectivity. The proposed methods are expected to help us to understand clustering and lack thereof in correlational brain networks, such as those derived from functional time series and across-participant correlation in neuroanatomical properties.

Clustering Coefficients for Correlation Networks

PubMed Central

Masuda, Naoki; Sakaki, Michiko; Ezaki, Takahiro; Watanabe, Takamitsu

2018-01-01

Graph theory is a useful tool for deciphering structural and functional networks of the brain on various spatial and temporal scales. The clustering coefficient quantifies the abundance of connected triangles in a network and is a major descriptive statistics of networks. For example, it finds an application in the assessment of small-worldness of brain networks, which is affected by attentional and cognitive conditions, age, psychiatric disorders and so forth. However, it remains unclear how the clustering coefficient should be measured in a correlation-based network, which is among major representations of brain networks. In the present article, we propose clustering coefficients tailored to correlation matrices. The key idea is to use three-way partial correlation or partial mutual information to measure the strength of the association between the two neighboring nodes of a focal node relative to the amount of pseudo-correlation expected from indirect paths between the nodes. Our method avoids the difficulties of previous applications of clustering coefficient (and other) measures in defining correlational networks, i.e., thresholding on the correlation value, discarding of negative correlation values, the pseudo-correlation problem and full partial correlation matrices whose estimation is computationally difficult. For proof of concept, we apply the proposed clustering coefficient measures to functional magnetic resonance imaging data obtained from healthy participants of various ages and compare them with conventional clustering coefficients. We show that the clustering coefficients decline with the age. The proposed clustering coefficients are more strongly correlated with age than the conventional ones are. We also show that the local variants of the proposed clustering coefficients (i.e., abundance of triangles around a focal node) are useful in characterizing individual nodes. In contrast, the conventional local clustering coefficients were strongly correlated with and therefore may be confounded by the node's connectivity. The proposed methods are expected to help us to understand clustering and lack thereof in correlational brain networks, such as those derived from functional time series and across-participant correlation in neuroanatomical properties. PMID:29599714

Physical properties of star clusters in the outer LMC as observed by the DES

DOE PAGES

Pieres, A.; Santiago, B.; Balbinot, E.; ...

2016-05-26

The Large Magellanic Cloud (LMC) harbors a rich and diverse system of star clusters, whose ages, chemical abundances, and positions provide information about the LMC history of star formation. We use Science Verification imaging data from the Dark Energy Survey to increase the census of known star clusters in the outer LMC and to derive physical parameters for a large sample of such objects using a spatially and photometrically homogeneous data set. Our sample contains 255 visually identified cluster candidates, of which 109 were not listed in any previous catalog. We quantify the crowding effect for the stellar sample producedmore » by the DES Data Management pipeline and conclude that the stellar completeness is < 10% inside typical LMC cluster cores. We therefore develop a pipeline to sample and measure stellar magnitudes and positions around the cluster candidates using DAOPHOT. We also implement a maximum-likelihood method to fit individual density profiles and colour-magnitude diagrams. For 117 (from a total of 255) of the cluster candidates (28 uncatalogued clusters), we obtain reliable ages, metallicities, distance moduli and structural parameters, confirming their nature as physical systems. The distribution of cluster metallicities shows a radial dependence, with no clusters more metal-rich than [Fe/H] ~ -0.7 beyond 8 kpc from the LMC center. Furthermore, the age distribution has two peaks at ≃ 1.2 Gyr and ≃ 2.7 Gyr.« less

Physical properties of star clusters in the outer LMC as observed by the DES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pieres, A.; Santiago, B.; Balbinot, E.

The Large Magellanic Cloud (LMC) harbors a rich and diverse system of star clusters, whose ages, chemical abundances, and positions provide information about the LMC history of star formation. We use Science Verification imaging data from the Dark Energy Survey to increase the census of known star clusters in the outer LMC and to derive physical parameters for a large sample of such objects using a spatially and photometrically homogeneous data set. Our sample contains 255 visually identified cluster candidates, of which 109 were not listed in any previous catalog. We quantify the crowding effect for the stellar sample producedmore » by the DES Data Management pipeline and conclude that the stellar completeness is < 10% inside typical LMC cluster cores. We therefore develop a pipeline to sample and measure stellar magnitudes and positions around the cluster candidates using DAOPHOT. We also implement a maximum-likelihood method to fit individual density profiles and colour-magnitude diagrams. For 117 (from a total of 255) of the cluster candidates (28 uncatalogued clusters), we obtain reliable ages, metallicities, distance moduli and structural parameters, confirming their nature as physical systems. The distribution of cluster metallicities shows a radial dependence, with no clusters more metal-rich than [Fe/H] ~ -0.7 beyond 8 kpc from the LMC center. Furthermore, the age distribution has two peaks at ≃ 1.2 Gyr and ≃ 2.7 Gyr.« less

Paternal age related schizophrenia (PARS): Latent subgroups detected by k-means clustering analysis.

PubMed

Lee, Hyejoo; Malaspina, Dolores; Ahn, Hongshik; Perrin, Mary; Opler, Mark G; Kleinhaus, Karine; Harlap, Susan; Goetz, Raymond; Antonius, Daniel

2011-05-01

Paternal age related schizophrenia (PARS) has been proposed as a subgroup of schizophrenia with distinct etiology, pathophysiology and symptoms. This study uses a k-means clustering analysis approach to generate hypotheses about differences between PARS and other cases of schizophrenia. We studied PARS (operationally defined as not having any family history of schizophrenia among first and second-degree relatives and fathers' age at birth ≥ 35 years) in a series of schizophrenia cases recruited from a research unit. Data were available on demographic variables, symptoms (Positive and Negative Syndrome Scale; PANSS), cognitive tests (Wechsler Adult Intelligence Scale-Revised; WAIS-R) and olfaction (University of Pennsylvania Smell Identification Test; UPSIT). We conducted a series of k-means clustering analyses to identify clusters of cases containing high concentrations of PARS. Two analyses generated clusters with high concentrations of PARS cases. The first analysis (N=136; PARS=34) revealed a cluster containing 83% PARS cases, in which the patients showed a significant discrepancy between verbal and performance intelligence. The mean paternal and maternal ages were 41 and 33, respectively. The second analysis (N=123; PARS=30) revealed a cluster containing 71% PARS cases, of which 93% were females; the mean age of onset of psychosis, at 17.2, was significantly early. These results strengthen the evidence that PARS cases differ from other patients with schizophrenia. Hypothesis-generating findings suggest that features of PARS may include a discrepancy between verbal and performance intelligence, and in females, an early age of onset. These findings provide a rationale for separating these phenotypes from others in future clinical, genetic and pathophysiologic studies of schizophrenia and in considering responses to treatment. Copyright © 2011 Elsevier B.V. All rights reserved.

Unveiling hidden properties of young star clusters: differential reddening, star-formation spread, and binary fraction

NASA Astrophysics Data System (ADS)

Bonatto, C.; Lima, E. F.; Bica, E.

2012-04-01

Context. Usually, important parameters of young, low-mass star clusters are very difficult to obtain by means of photometry, especially when differential reddening and/or binaries occur in large amounts. Aims: We present a semi-analytical approach (ASAmin) that, when applied to the Hess diagram of a young star cluster, is able to retrieve the values of mass, age, star-formation spread, distance modulus, foreground and differential reddening, and binary fraction. Methods: The global optimisation method known as adaptive simulated annealing (ASA) is used to minimise the residuals between the observed and simulated Hess diagrams of a star cluster. The simulations are realistic and take the most relevant parameters of young clusters into account. Important features of the simulations are a normal (Gaussian) differential reddening distribution, a time-decreasing star-formation rate, the unresolved binaries, and the smearing effect produced by photometric uncertainties on Hess diagrams. Free parameters are cluster mass, age, distance modulus, star-formation spread, foreground and differential reddening, and binary fraction. Results: Tests with model clusters built with parameters spanning a broad range of values show that ASAmin retrieves the input values with a high precision for cluster mass, distance modulus, and foreground reddening, but they are somewhat lower for the remaining parameters. Given the statistical nature of the simulations, several runs should be performed to obtain significant convergence patterns. Specifically, we find that the retrieved (absolute minimum) parameters converge to mean values with a low dispersion as the Hess residuals decrease. When applied to actual young clusters, the retrieved parameters follow convergence patterns similar to the models. We show how the stochasticity associated with the early phases may affect the results, especially in low-mass clusters. This effect can be minimised by averaging out several twin clusters in the simulated Hess diagrams. Conclusions: Even for low-mass star clusters, ASAmin is sensitive to the values of cluster mass, age, distance modulus, star-formation spread, foreground and differential reddening, and to a lesser degree, binary fraction. Compared with simpler approaches, including binaries, a decaying star-formation rate, and a normally distributed differential reddening appears to yield more constrained parameters, especially the mass, age, and distance from the Sun. A robust determination of cluster parameters may have a positive impact on many fields. For instance, age, mass, and binary fraction are important for establishing the dynamical state of a cluster or for deriving a more precise star-formation rate in the Galaxy.

Are the gyro-ages of field stars underestimated?

NASA Astrophysics Data System (ADS)

Kovács, Géza

2015-09-01

By using the current photometric rotational data on eight galactic open clusters, we show that the evolutionary stellar model (isochrone) ages of these clusters are tightly correlated with the period shifts applied to the (B - V)0-Prot ridges that optimally align these ridges to the one defined by Praesepe and the Hyades. On the other hand, when the traditional Skumanich-type multiplicative transformation is used, the ridges become far less aligned due to the age-dependent slope change introduced by the period multiplication. Therefore, we employ our simple additive gyro-age calibration on various datasets of Galactic field stars to test its applicability. We show that, in the overall sense, the gyro-ages are systematically greater than the isochrone ages. The difference could exceed several giga years, depending on the stellar parameters. Although the age overlap between the open clusters used in the calibration and the field star samples is only partial, the systematic difference indicates the limitation of the currently available gyro-age methods and suggests that the rotation of field stars slows down with a considerably lower speed than we would expect from the simple extrapolation of the stellar rotation rates in open clusters.

Search For Star Cluster Age Gradients Across Spiral Arms of Three LEGUS Disk Galaxies

NASA Astrophysics Data System (ADS)

Shabani, F.; Grebel, E. K.; Pasquali, A.; D'Onghia, E.; Gallagher, J. S.; Adamo, A.; Messa, M.; Elmegreen, B. G.; Dobbs, C.; Gouliermis, D. A.; Calzetti, D.; Grasha, K.; Elmegreen, D. M.; Cignoni, M.; Dale, D. A.; Aloisi, A.; Smith, L. J.; Tosi, M.; Thilker, D. A.; Lee, J. C.; Sabbi, E.; Kim, H.; Pellerin, A.

2018-05-01

One of the main theories for explaining the formation of spiral arms in galaxies is the stationary density wave theory. This theory predicts the existence of an age gradient across the arms. We use the stellar cluster catalogues of the galaxies NGC 1566, M51a, and NGC 628 from the Legacy Extragalactic UV Survey (LEGUS) program. In order to test for the possible existence of an age sequence across the spiral arms, we quantified the azimuthal offset between star clusters of different ages in our target galaxies. We found that NGC 1566, a grand-design spiral galaxy with bisymmetric arms and a strong bar, shows a significant age gradient across the spiral arms that appears to be consistent with the prediction of the stationary density wave theory. In contrast, M51a with its two well-defined spiral arms and a weaker bar does not show an age gradient across the arms. In addition, a comparison with non-LEGUS star cluster catalogues for M51a yields similar results. We believe that the spiral structure of M51a is not the result of a stationary density wave with a fixed pattern speed. Instead, tidal interactions could be the dominant mechanism for the formation of spiral arms. We also found no offset in the azimuthal distribution of star clusters with different ages across the weak spiral arms of NGC 628.

Clustering of Health Behaviors and Cardiorespiratory Fitness Among U.S. Adolescents.

PubMed

Hartz, Jacob; Yingling, Leah; Ayers, Colby; Adu-Brimpong, Joel; Rivers, Joshua; Ahuja, Chaarushi; Powell-Wiley, Tiffany M

2018-05-01

Decreased cardiorespiratory fitness (CRF) is associated with an increased risk of cardiovascular disease. However, little is known how the interaction of diet, physical activity (PA), and sedentary time (ST) affects CRF among adolescents. By using a nationally representative sample of U.S. adolescents, we used cluster analysis to investigate the interactions of these behaviors with CRF. We hypothesized that distinct clustering patterns exist and that less healthy clusters are associated with lower CRF. We used 2003-2004 National Health and Nutrition Examination Survey data for persons aged 12-19 years (N = 1,225). PA and ST were measured objectively by an accelerometer, and the American Heart Association Healthy Diet Score quantified diet quality. Maximal oxygen consumption (V˙O 2 ​max) was measured by submaximal treadmill exercise test. We performed cluster analysis to identify sex-specific clustering of diet, PA, and ST. Adjusting for accelerometer wear time, age, body mass index, race/ethnicity, and the poverty-to-income ratio, we performed sex-stratified linear regression analysis to evaluate the association of cluster with V˙O 2 ​max. Three clusters were identified for girls and boys. For girls, there was no difference across clusters for age (p = .1), weight (p = .3), and BMI (p = .5), and no relationship between clusters and V˙O 2 ​max. For boys, the youngest cluster (p < .01) had three healthy behaviors, weighed less, and was associated with a higher V˙O 2 ​max compared with the two older clusters. We observed clustering of diet, PA, and ST in U.S. adolescents. Specific patterns were associated with lower V˙O 2 ​max for boys, suggesting that our clusters may help identify adolescent boys most in need of interventions. Published by Elsevier Inc.

AGES OF STAR CLUSTERS IN THE TIDAL TAILS OF MERGING GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mulia, A. J.; Chandar, R.; Whitmore, B. C.

We study the stellar content in the tidal tails of three nearby merging galaxies, NGC 520, NGC 2623, and NGC 3256, using BVI imaging taken with the Advanced Camera for Surveys on board the Hubble Space Telescope. The tidal tails in all three systems contain compact and fairly massive young star clusters, embedded in a sea of diffuse, unresolved stellar light. We compare the measured colors and luminosities with predictions from population synthesis models to estimate cluster ages and find that clusters began forming in tidal tails during or shortly after the formation of the tails themselves. We find amore » lack of very young clusters (≤10 Myr old), implying that eventually star formation shuts off in the tails as the gas is used up or dispersed. There are a few clusters in each tail with estimated ages that are older than the modeled tails themselves, suggesting that these may have been stripped out from the original galaxy disks. The luminosity function of the tail clusters can be described by a single power-law, dN/dL ∝ L{sup α}, with −2.6 < α < −2.0. We find a stellar age gradient across some of the tidal tails, which we interpret as a superposition of (1) newly formed stars and clusters along the dense center of the tail and (2) a sea of broadly distributed, older stellar material ejected from the progenitor galaxies.« less

Reddening and age for 13 southern Galactic open clusters determined from integrated spectra

NASA Astrophysics Data System (ADS)

Ahumada, A. V.; Clariá, J. J.; Bica, E.; Dutra, C. M.; Torres, M. C.

2001-10-01

In this study we present flux-calibrated integrated spectra in the range 3800-6800 Å for 13 concentrated open clusters with Galactic longitudes between 219deg and 316deg, nine of which have not been previously studied. Using the equivalent widths of the Balmer lines and comparing the cluster spectra with template spectra of Magellanic Clouds and Galactic star clusters with known parameters, we derive both foreground interstellar reddening values and age. For nine clusters these two parameters have been determined for the first time, while for the rest of the sample the results show good agreement with previous studies. The present analysis indicates four very young (Hogg 11, NGC 5606, vdB-RN 80 and Pismis 17), seven moderately young (ESO 429-SC13, Hogg 3, Hogg 12, Haffner 7, BH 87, NGC 2368 and Bochum 12) and two intermediate-age (Berkeley 75 and NGC 2635) open clusters. The derived foreground interstellar reddening values are in the range 0.00 <= E(B-V) <= 0.38. The age and reddening distributions of the present sample of relatively faint open clusters match those of open clusters with known parameters in a 90deg sector centered at l = 270deg. Based on observations made at Complejo Astronómico El Leoncito, which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba and San Juan, Argentina.

Physician styles of decision-making for a complex condition: Type 2 diabetes with co-morbid mental illness.

PubMed

Trachtenberg, Felicia L; Pober, David M; Welch, Lisa C; McKinlay, John B

Variation in physician decisions may reflect personal styles of decision-making, as opposed to singular clinical actions and these styles may be applied differently depending on patient complexity. The objective of this study is to examine clusters of physician decision-making for type 2 diabetes, overall and in the presence of a mental health co-morbidity. This randomized balanced factorial experiment presented video vignettes of a "patient" with diagnosed, but uncontrolled type 2 diabetes. "Patients" were systematically varied by age, sex, race and co-morbidity (depression, schizophrenia with normal or bizarre affect, eczema as control). Two hundred and fifty-six primary care physicians, balanced by gender and experience level, completed a structured interview about clinical management. Cluster analysis identified 3 styles of diabetes management. "Minimalists" (n=84) performed fewer exams or tests compared to "middle of the road" physicians (n=84). "Interventionists" (n=88) suggested more medications and referrals. A second cluster analysis, without control for co-morbidities, identified an additional cluster of "information seekers" (n=15) who requested more additional information and referrals. Physicians ranking schizophrenia higher than diabetes on their problem list were more likely "minimalists" and none were "interventionists" or "information seekers". Variations in clinical management encompass multiple clinical actions and physicians subtly shift these decision-making styles depending on patient co-morbidities. Physicians' practice styles may help explain persistent differences in patient care. Training and continuing education efforts to encourage physicians to implement evidence-based clinical practice should account for general styles of decision-making and for how physicians process complicating comorbidities.

Early Results from Star Date: M83 - A Citizen Science Project to Age Date Star Clusters in the Southern Pinwheel Galaxy

NASA Astrophysics Data System (ADS)

Heartley, Jeremy; Whitmore, B. C.; Blair, W. P.; Christian, C. A.; Donaldson, T.; Hammer, D.; Smith, S.; Viana, A.

2014-01-01

The M83 Citizen Science Project is a collaborative effort currently in development between the Space Telescope Science Institute (STScI) and Zooniverse under the guidance of Dr. Brad Whitmore as part of Cy 19 proposal 12513 (PI - Dr. William Blair). This unique citizen science project will allow users to analyze individual star clusters within The Southern Pinwheel Galaxy, M83. The project will show users color-composite images taken with Wide Field Camera 3 (WFC3) aboard the Hubble Space Telescope (HST) and ask them to estimate the age of the star cluster. Through a multistage process, the project will educate and familiarize the user with the appearance of each age category based on the presence and shape of H-alpha emission, degree of resolution of the individual stars, and color of the cluster. (Whitmore et al. 2011). Additionally, the project will involve the actual measurement of the star cluster and H-alpha cloud radii to be used for further assessment and reinforcement of age. The data from this project and the statistics it yields will quantify these ages which can then be used to inform the debate between universal and environmental models of star cluster formation and destruction in galaxies. The tentative launch date is December 2013, therefore early results should be available at the time of the conference.

Observational tests for stellar evolution and pulsation theory. I - The globular clusters M 4 and M 15

NASA Astrophysics Data System (ADS)

Caputo, F.

1987-01-01

It is shown that the pulsational properties of RR Lyrae variables in globular clusters can be used together with the Red Giant Branch location to derive reliable information on the cluster reddening and distance modulus. By demanding full agreement with some key observables, the reddening and distance modulus of the globular clusters M4 and M15 are derived as a function of the mass of the variables and of the adopted cluster metallicity. Thus, from the comparison between observations and theoretical isochrones, the cluster age can be evaluated. A best guess for the age of M4 and M15 can be presented: 16×109yr, with a total uncertainty of 2 billion years.

Evaluating gyrochronology on the zero-age-main-sequence: rotation periods in the southern open cluster Blanco 1 from the Kelt-South survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cargile, P. A.; Pepper, J.; Siverd, R.

2014-02-10

We report periods for 33 members of Blanco 1 as measured from Kilodegree Extremely Little Telescope-South light curves, the first reported rotation periods for this benchmark zero-age-main-sequence open cluster. The distribution of these stars spans from late-A or early-F dwarfs to mid-K with periods ranging from less than a day to ∼8 days. The rotation period distribution has a morphology similar to the coeval Pleiades cluster, suggesting the universal nature of stellar rotation distributions. Employing two different gyrochronology methods, we find an age of 146{sub −14}{sup +13} Myr for the cluster. Using the same techniques, we infer an age ofmore » 134{sub −10}{sup +9} Myr for the Pleiades measured from existing literature rotation periods. These rotation-derived ages agree with independently determined cluster ages based on the lithium depletion boundary technique. Additionally, we evaluate different gyrochronology models and quantify levels of agreement between the models and the Blanco 1/Pleiades rotation period distributions, including incorporating the rotation distributions of clusters at ages up to 1.1 Gyr. We find the Skumanich-like spin-down rate sufficiently describes the rotation evolution of stars hotter than the Sun; however, we find cooler stars rotating faster than predicted by a Skumanich law, suggesting a mass dependence in the efficiency of stellar angular momentum loss rate. Finally, we compare the Blanco 1 and Pleiades rotation period distributions to available nonlinear angular momentum evolution models. We find they require a significant mass dependence on the initial rotation rate of solar-type stars to reproduce the observed range of rotation periods at a given stellar mass and are furthermore unable to predict the observed over-density of stars along the upper envelope of the clusters' rotation distributions.« less

Can Healthcare Assistant Training (CHAT) improve the relational care of older people? Study protocol for a pilot cluster randomised controlled trial.

PubMed

Arthur, Antony; Maben, Jill; Wharrad, Heather; Aldus, Clare; Sarre, Sophie; Schneider, Justine; Nicholson, Caroline; Barton, Garry; Cox, Karen; Clark, Allan

2015-12-09

People aged 75 years and over account for 1 in 4 of all hospital admissions. There has been increasing recognition of problems in the care of older people, particularly in hospitals. Evidence suggests that older people judge the care they receive in terms of kindness, empathy, compassion, respectful communication and being seen as a person not just a patient. These are aspects of care to which we refer when we use the term 'relational care'. Healthcare assistants deliver an increasing proportion of direct care to older people, yet their training needs are often overlooked. This study will determine the acceptability and feasibility of a cluster randomised controlled trial of 'Older People's Shoes' a 2-day training intervention for healthcare assistants caring for older people in hospital. Within this pilot, 2-arm, parallel, cluster randomised controlled trial, healthcare assistants within acute hospital wards are randomised to either the 2-day training intervention or training as usual. Registered nurses deliver 'Older People's Shoes' over 2 days, approximately 1 week apart. It contains three components: experiential learning about ageing, exploration of older people's stories, and customer care. Outcomes will be measured at the level of patient (experience of emotional care and quality of life during their hospital stay), healthcare assistant (empathy and attitudes towards older people), and ward (quality of staff/patient interaction). Semi-structured interviews of a purposive sample of healthcare assistants receiving the intervention, and all trainers delivering the intervention, will be undertaken to gain insights into the experiences of both the intervention and the trial, and its perceived impact on practice. Few training interventions for care staff have been rigorously tested using randomised designs. This study will establish the viability of a definitive cluster randomised controlled trial of a new training intervention to improve the relational care proided by healthcare assistants working with older people in hospital. The study was registered as an International Standard Randomised Controlled Trial ( ISRCTN10385799 ) on 29 December 2014.

Eclipsing Binary V1178 Tau: A Reddening Independent Determination of the Age and Distance to NGC 1817

NASA Astrophysics Data System (ADS)

Hedlund, Anne; Sandquist, Eric L.; Arentoft, Torben; Brogaard, Karsten; Grundahl, Frank; Stello, Dennis; Bedin, Luigi R.; Libralato, Mattia; Malavolta, Luca; Nardiello, Domenico; Molenda-Zakowicz, Joanna; Vanderburg, Andrew

2018-06-01

V1178 Tau is a double-lined spectroscopic eclipsing binary in NGC1817, one of the more massive clusters observed in the K2 mission. We have determined the orbital period (P = 2.20 d) for the first time, and we model radial velocity measurements from the HARPS and ALFOSC spectrographs, light curves collected by Kepler, and ground based light curves using the Eclipsing Light Curve code (ELC, Orosz & Hauschildt 2000). We present masses and radii for the stars in the binary, allowing for a reddening-independent means of determining the cluster age. V1178 Tau is particularly useful for calculating the age of the cluster because the stars are close to the cluster turnoff, providing a more precise age determination. Furthermore, because one of the stars in the binary is a delta Scuti variable, the analysis provides improved insight into their pulsations.

Links between patterns of racial socialization and discrimination experiences and psychological adjustment: a cluster analysis.

PubMed

Ajayi, Alex A; Syed, Moin

2014-10-01

This study used a person-oriented analytic approach to identify meaningful patterns of barriers-focused racial socialization and perceived racial discrimination experiences in a sample of 295 late adolescents. Using cluster analysis, three distinct groups were identified: Low Barrier Socialization-Low Discrimination, High Barrier Socialization-Low Discrimination, and High Barrier Socialization-High Discrimination clusters. These groups were substantively unique in terms of the frequency of racial socialization messages about bias preparation and out-group mistrust its members received and their actual perceived discrimination experiences. Further, individuals in the High Barrier Socialization-High Discrimination cluster reported significantly higher depressive symptoms than those in the Low Barrier Socialization-Low Discrimination and High Barrier Socialization-Low Discrimination clusters. However, no differences in adjustment were observed between the Low Barrier Socialization-Low Discrimination and High Barrier Socialization-Low Discrimination clusters. Overall, the findings highlight important individual differences in how young people of color experience their race and how these differences have significant implications on psychological adjustment. Copyright © 2014 The Foundation for Professionals in Services for Adolescents. Published by Elsevier Ltd. All rights reserved.

Influence of birth cohort on age of onset cluster analysis in bipolar I disorder.

PubMed

Bauer, M; Glenn, T; Alda, M; Andreassen, O A; Angelopoulos, E; Ardau, R; Baethge, C; Bauer, R; Bellivier, F; Belmaker, R H; Berk, M; Bjella, T D; Bossini, L; Bersudsky, Y; Cheung, E Y W; Conell, J; Del Zompo, M; Dodd, S; Etain, B; Fagiolini, A; Frye, M A; Fountoulakis, K N; Garneau-Fournier, J; Gonzalez-Pinto, A; Harima, H; Hassel, S; Henry, C; Iacovides, A; Isometsä, E T; Kapczinski, F; Kliwicki, S; König, B; Krogh, R; Kunz, M; Lafer, B; Larsen, E R; Lewitzka, U; Lopez-Jaramillo, C; MacQueen, G; Manchia, M; Marsh, W; Martinez-Cengotitabengoa, M; Melle, I; Monteith, S; Morken, G; Munoz, R; Nery, F G; O'Donovan, C; Osher, Y; Pfennig, A; Quiroz, D; Ramesar, R; Rasgon, N; Reif, A; Ritter, P; Rybakowski, J K; Sagduyu, K; Scippa, A M; Severus, E; Simhandl, C; Stein, D J; Strejilevich, S; Hatim Sulaiman, A; Suominen, K; Tagata, H; Tatebayashi, Y; Torrent, C; Vieta, E; Viswanath, B; Wanchoo, M J; Zetin, M; Whybrow, P C

2015-01-01

Two common approaches to identify subgroups of patients with bipolar disorder are clustering methodology (mixture analysis) based on the age of onset, and a birth cohort analysis. This study investigates if a birth cohort effect will influence the results of clustering on the age of onset, using a large, international database. The database includes 4037 patients with a diagnosis of bipolar I disorder, previously collected at 36 collection sites in 23 countries. Generalized estimating equations (GEE) were used to adjust the data for country median age, and in some models, birth cohort. Model-based clustering (mixture analysis) was then performed on the age of onset data using the residuals. Clinical variables in subgroups were compared. There was a strong birth cohort effect. Without adjusting for the birth cohort, three subgroups were found by clustering. After adjusting for the birth cohort or when considering only those born after 1959, two subgroups were found. With results of either two or three subgroups, the youngest subgroup was more likely to have a family history of mood disorders and a first episode with depressed polarity. However, without adjusting for birth cohort (three subgroups), family history and polarity of the first episode could not be distinguished between the middle and oldest subgroups. These results using international data confirm prior findings using single country data, that there are subgroups of bipolar I disorder based on the age of onset, and that there is a birth cohort effect. Including the birth cohort adjustment altered the number and characteristics of subgroups detected when clustering by age of onset. Further investigation is needed to determine if combining both approaches will identify subgroups that are more useful for research. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

A Photometric Survey of the Open Clusters NGC 7789 and M67

NASA Astrophysics Data System (ADS)

Janes, Kenneth

2010-01-01

Although there is strong evidence that stellar activity declines as a star ages, beyond about the age of the Hyades (600 Myr) there is little direct confirmation of this decline in stars of known age. This report is an update of an earlier report (Hayes-Gehrke, et al., 2004, AJ, 128, 2862) of a long-term project to explore stellar activity in old open clusters. I have now accumulated 12 years of photometry of the old clusters NGC 7789 (about 1.8 Gyr) and M 67 (about 4 Gyr). An analysis of these data has revealed a substantial number of low-amplitude variable stars in both clusters, including a number of previously-discovered eclipsing binary stars, and several stars near the main sequence turnoff of both clusters that exhibit apparently erratic variations. Some of the M 67 erratics are known X-ray sources. On the main sequence, the large majority of stars show little or no evidence for variability at the 0.1% - 0.2% level, consistent with a regular systematic decline in activity level with age.

Dynamically allocated virtual clustering management system

NASA Astrophysics Data System (ADS)

Marcus, Kelvin; Cannata, Jess

2013-05-01

The U.S Army Research Laboratory (ARL) has built a "Wireless Emulation Lab" to support research in wireless mobile networks. In our current experimentation environment, our researchers need the capability to run clusters of heterogeneous nodes to model emulated wireless tactical networks where each node could contain a different operating system, application set, and physical hardware. To complicate matters, most experiments require the researcher to have root privileges. Our previous solution of using a single shared cluster of statically deployed virtual machines did not sufficiently separate each user's experiment due to undesirable network crosstalk, thus only one experiment could be run at a time. In addition, the cluster did not make efficient use of our servers and physical networks. To address these concerns, we created the Dynamically Allocated Virtual Clustering management system (DAVC). This system leverages existing open-source software to create private clusters of nodes that are either virtual or physical machines. These clusters can be utilized for software development, experimentation, and integration with existing hardware and software. The system uses the Grid Engine job scheduler to efficiently allocate virtual machines to idle systems and networks. The system deploys stateless nodes via network booting. The system uses 802.1Q Virtual LANs (VLANs) to prevent experimentation crosstalk and to allow for complex, private networks eliminating the need to map each virtual machine to a specific switch port. The system monitors the health of the clusters and the underlying physical servers and it maintains cluster usage statistics for historical trends. Users can start private clusters of heterogeneous nodes with root privileges for the duration of the experiment. Users also control when to shutdown their clusters.

Applying Multivariate Adaptive Splines to Identify Genes With Expressions Varying After Diagnosis in Microarray Experiments.

PubMed

Duan, Fenghai; Xu, Ye

2017-01-01

To analyze a microarray experiment to identify the genes with expressions varying after the diagnosis of breast cancer. A total of 44 928 probe sets in an Affymetrix microarray data publicly available on Gene Expression Omnibus from 249 patients with breast cancer were analyzed by the nonparametric multivariate adaptive splines. Then, the identified genes with turning points were grouped by K-means clustering, and their network relationship was subsequently analyzed by the Ingenuity Pathway Analysis. In total, 1640 probe sets (genes) were reliably identified to have turning points along with the age at diagnosis in their expression profiling, of which 927 expressed lower after turning points and 713 expressed higher after the turning points. K-means clustered them into 3 groups with turning points centering at 54, 62.5, and 72, respectively. The pathway analysis showed that the identified genes were actively involved in various cancer-related functions or networks. In this article, we applied the nonparametric multivariate adaptive splines method to a publicly available gene expression data and successfully identified genes with expressions varying before and after breast cancer diagnosis.

A populous intermediate-age open cluster and evidence of an embedded cluster among the FSR globular cluster candidates

NASA Astrophysics Data System (ADS)

Bica, E.; Bonatto, C.

2008-03-01

We study the nature of the globular cluster (GC) candidates FSR 1603 and FSR1755 selected from the catalogue of Froebrich, Scholz & Raftery. Their properties are investigated with Two-Micron All-Sky Survey field-star decontaminated photometry, which is used to build colour-magnitude diagrams (CMDs) and stellar radial density profiles. FSR1603 has the open cluster Ruprecht 101 as optical counterpart, and we show it to be a massive intermediate-age cluster. Relevant parameters of FSR1603 are the age ~1Gyr, distance from the Sun dsolar ~ 2.7kpc, Galactocentric distance RGC ~ 6.4kpc, core radius RC ~ 1.1pc, mass function slope χ ~ 1.8, observed stellar mass (for stars with mass in the range 1.27 <= m <= 2.03Msolar) Mobs ~ 500Msolar and a total (extrapolated to m = 0.08Msolar) stellar mass Mtot ~ 2300Msolar. FSR1755, on the other hand, is not a populous cluster. It may be a sparse young cluster embedded in the HII region Sh2-3, subject to an absorption AV ~ 4.1, located at dsolar ~ 1.3kpc. Important field-star contamination, spatially variable heavy dust obscuration, even in Ks, and gas emission characterize its field. A nearly vertical, sparse blue stellar sequence shows up in the CMDs.

The Mass Function in h+(chi) Persei

NASA Astrophysics Data System (ADS)

Bragg, Ann; Kenyon, Scott

2000-08-01

Knowledge of the stellar initial mass function (IMF) is critical to understanding star formation and galaxy evolution. Past studies of the IMF in open clusters have primarily used luminosity functions to determine mass functions, frequently in relatively sparse clusters. Our goal with this project is to derive a reliable, well- sampled IMF for a pair of very dense young clusters (h+(chi) Persei) with ages, 1-2 × 10^7 yr (e.g., Vogt A& A 11:359), where stellar evolution theory is robust. We will construct the HR diagram using both photometry and spectral types to derive more accurate stellar masses and ages than are possible using photometry alone. Results from the two clusters will be compared to examine the universality of the IMF. We currently have a spectroscopic sample covering an area within 9 arc-minutes of the center of each cluster taken with the FAST Spectrograph. The sample is complete to V=15.4 and contains ~ 1000 stars. We request 2 nights at WIYN/HYDRA to extend this sample to deeper magnitudes, allowing us to determine the IMF of the clusters to a lower limiting mass and to search for a pre-main sequence, theoretically predicted to be present for clusters of this age. Note that both clusters are contained within a single HYDRA field.

Integrated J- and H-band spectra of globular clusters in the LMC: implications for stellar population models and galaxy age dating

NASA Astrophysics Data System (ADS)

Lyubenova, M.; Kuntschner, H.; Rejkuba, M.; Silva, D. R.; Kissler-Patig, M.; Tacconi-Garman, L. E.

2012-07-01

Context. The rest-frame near-IR spectra of intermediate age (1-2 Gyr) stellar populations are dominated by carbon based absorption features offering a wealth of information. Yet, spectral libraries that include the near-IR wavelength range do not sample a sufficiently broad range of ages and metallicities to allow for accurate calibration of stellar population models and thus the interpretation of the observations. Aims: In this paper we investigate the integrated J- and H-band spectra of six intermediate age and old globular clusters in the Large Magellanic Cloud (LMC). Methods: The observations for six clusters were obtained with the SINFONI integral field spectrograph at the ESO VLT Yepun telescope, covering the J (1.09-1.41 μm) and H-band (1.43-1.86 μm) spectral range. The spectral resolution is 6.7 Å in J and 6.6 Å in H-band (FWHM). The observations were made in natural seeing, covering the central 24″ × 24″ of each cluster and in addition sampling the brightest eight red giant branch and asymptotic giant branch (AGB) star candidates within the clusters' tidal radii. Targeted clusters cover the ages of ~1.3 Gyr (NGC 1806, NGC 2162), 2 Gyr (NGC 2173) and ~13 Gyr (NGC 1754, NGC 2005, NGC 2019). Results.H-band C2 and K-band 12CO (2-0) feature strengths for the LMC globular clusters are compared to the models of Maraston (2005). C2 is reasonably well reproduced by the models at all ages, while 12CO (2-0) shows good agreement for older (age ≥ 2 Gyr) populations, but the younger (1.3 Gyr) globular clusters do not follow the models. We argue that this is due to the fact that the empirical calibration of the models relies on only a few Milky Way carbon star spectra, which show different 12CO (2-0) index strengths than the LMC stars. The C2 absorption feature strength correlates strongly with age. It is present essentially only in populations that have 1-2 Gyr old stars, while its value is consistent with zero for older populations. The distinct spectral energy distribution observed for the intermediate age globular clusters in the J- and H-bands agrees well with the model predictions of Maraston for the contribution from the thermally pulsing AGB phase. Conclusions: In this pilot project we present an empirical library of six LMC globular cluster integrated near-IR spectra that are useful for testing stellar population models in this wavelength regime. We show that the H-band C2 absorption feature and the J-, H-band spectral shape can be used as an age indicator for intermediate age stellar populations in integrated spectra of star clusters and galaxies. Based on observation collected at the ESO Paranal La Silla Observatory, Chile, Prog. ID 078.B-0205.Table 2 is available in electronic form at http://www.aanda.orgJ- and H-spectra are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/543/A75

Searching for the birthplaces of open clusters with ages of several billion years

NASA Astrophysics Data System (ADS)

Acharova, I. A.; Shevtsova, E. S.

2016-01-01

We discuss the possibility of finding the birthplaces of open clusters (OC) with ages of several billion years. The proposed method is based on the comparison of the results of the chemical evolution modeling of the Galactic disk with the parameters of the cluster. Five OCs older than 7 Gyr are known: NGC6791, BH176, Collinder 261, Berkeley 17, and Berkeley 39. The oxygen and iron abundances in NGC6791 and the oxygen abundance in BH176 are twice the solar level, the heavy-element abundances in other clusters are close to the corresponding solar values. According to chemical evolution models, at the time of the formation of the objects considered the regions where the oxygen and iron abundances reached the corresponding levels extended out to 5 kpc from the Galactic center.At present time theOCs considered are located several kpc from the Galactic center. Some of these clusters are located extremely high, about 1 kpc above the disk midplane, i.e., they have been subject to some mechanism that has carried them into orbits uncharacteristic of this type of objects. It follows from a comparison with the results of chemical evolution that younger clusters with ages of 4-5 Gyr, e.g., NGC1193,M67, and others, may have formed in a broad range of Galactocentric distances. Their large heights above the disk midplane is sufficient to suggest that these clusters have moved away from their likely birthplaces. Clusters are carried far away from the Galactic disk until the present time: about 40 clusters with ages from 0 to 2 Gyr are observed at heights ranging from 300 to 750 pc.

STAR FORMATION ACROSS THE W3 COMPLEX

DOE Office of Scientific and Technical Information (OSTI.GOV)

Román-Zúñiga, Carlos G.; Ybarra, Jason E.; Tapia, Mauricio

We present a multi-wavelength analysis of the history of star formation in the W3 complex. Using deep, near-infrared ground-based images combined with images obtained with Spitzer and Chandra observatories, we identified and classified young embedded sources. We identified the principal clusters in the complex and determined their structure and extension. We constructed extinction-limited samples for five principal clusters and constructed K-band luminosity functions that we compare with those of artificial clusters with varying ages. This analysis provided mean ages and possible age spreads for the clusters. We found that IC 1795, the centermost cluster of the complex, still hosts amore » large fraction of young sources with circumstellar disks. This indicates that star formation was active in IC 1795 as recently as 2 Myr ago, simultaneous to the star-forming activity in the flanking embedded clusters, W3-Main and W3(OH). A comparison with carbon monoxide emission maps indicates strong velocity gradients in the gas clumps hosting W3-Main and W3(OH) and shows small receding clumps of gas at IC 1795, suggestive of rapid gas removal (faster than the T Tauri timescale) in the cluster-forming regions. We discuss one possible scenario for the progression of cluster formation in the W3 complex. We propose that early processes of gas collapse in the main structure of the complex could have defined the progression of cluster formation across the complex with relatively small age differences from one group to another. However, triggering effects could act as catalysts for enhanced efficiency of formation at a local level, in agreement with previous studies.« less

Reanalysis of 24 Nearby Open Clusters using Gaia data

NASA Astrophysics Data System (ADS)

Yen, Steffi X.; Reffert, Sabine; Röser, Siegfried; Schilbach, Elena; Kharchenko, Nina V.; Piskunov, Anatoly E.

2018-04-01

We have developed a fully automated cluster characterization pipeline, which simultaneously determines cluster membership and fits the fundamental cluster parameters: distance, reddening, and age. We present results for 24 established clusters and compare them to literature values. Given the large amount of stellar data for clusters available from Gaia DR2 in 2018, this pipeline will be beneficial to analyzing the parameters of open clusters in our Galaxy.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jacobson, Heather R.; Pilachowski, Catherine A.; Friel, Eileen D., E-mail: jacob189@msu.edu, E-mail: catyp@astro.indiana.edu, E-mail: edfriel@mac.com

We present a detailed chemical abundance study of evolved stars in 10 open clusters based on Hydra multi-object echelle spectra obtained with the WIYN 3.5 m telescope. From an analysis of both equivalent widths and spectrum synthesis, abundances have been determined for the elements Fe, Na, O, Mg, Si, Ca, Ti, Ni, Zr, and for two of the 10 clusters, Al and Cr. To our knowledge, this is the first detailed abundance analysis for clusters NGC 1245, NGC 2194, NGC 2355, and NGC 2425. These 10 clusters were selected for analysis because they span a Galactocentric distance range R{sub gc}more » {approx} 9-13 kpc, the approximate location of the transition between the inner and outer disks. Combined with cluster samples from our previous work and those of other studies in the literature, we explore abundance trends as a function of cluster R{sub gc}, age, and [Fe/H]. As found previously by us and other studies, the [Fe/H] distribution appears to decrease with increasing R{sub gc} to a distance of {approx}12 kpc and then flattens to a roughly constant value in the outer disk. Cluster average element [X/Fe] ratios appear to be independent of R{sub gc}, although the picture for [O/Fe] is more complicated with a clear trend of [O/Fe] with [Fe/H] and sample incompleteness. Other than oxygen, no other element [X/Fe] exhibits a clear trend with [Fe/H]; likewise, there does not appear to be any strong correlation between abundance and cluster age. We divided clusters into different age bins to explore temporal variations in the radial element distributions. The radial metallicity gradient appears to have flattened slightly as a function of time, as found by other studies. There is also some indication that the transition from the inner disk metallicity gradient to the {approx}constant [Fe/H] distribution of the outer disk occurs at different Galactocentric radii for different age bins. However, interpretation of the time evolution of radial abundance distributions is complicated by the unequal R{sub gc} and [Fe/H] ranges spanned by clusters in different age bins.« less

Hubble Revisits a Globular Cluster’s Age

NASA Image and Video Library

2014-08-13

This new NASA/ESA Hubble Space Telescope image shows the globular cluster IC 4499. Globular clusters are big balls of old stars that orbit around their host galaxy. It has long been believed that all the stars within a globular cluster form at the about same time, a property which can be used to determine the cluster's age. For more massive globulars however, detailed observations have shown that this is not entirely true — there is evidence that they instead consist of multiple populations of stars born at different times. One of the driving forces behind this behavior is thought to be gravity: more massive globulars manage to grab more gas and dust, which can then be transformed into new stars. IC 4499 is a somewhat special case. Its mass lies somewhere between low-mass globulars, which show a single generation build-up, and the more complex and massive globulars which can contain more than one generation of stars. By studying objects like IC 4499 astronomers can therefore explore how mass affects a cluster's contents. Astronomers found no sign of multiple generations of stars in IC 4499 — supporting the idea that less massive clusters in general only consist of a single stellar generation. Hubble observations of IC 4499 have also helped to pinpoint the cluster's age: observations of this cluster from the 1990s suggested a puzzlingly young age when compared to other globular clusters within the Milky Way. However, since those first estimates new Hubble data have been obtained and it has been found to be much more likely that IC 4499 is actually roughly the same age as other Milky Way clusters at approximately 12 billion years old. Credit: ESA and NASA NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

On the mass of dense star clusters in starburst galaxies from spectrophotometry

NASA Astrophysics Data System (ADS)

Fleck, J.-J.; Boily, C. M.; Lançon, A.; Deiters, S.

2006-07-01

The mass of unresolved young star clusters derived from spectrophotometric data may well be off by a factor of 2 or more once the migration of massive stars driven by mass segregation is accounted for. We quantify this effect for a large set of cluster parameters, including variations in the stellar initial mass function (IMF), the intrinsic cluster mass, and mean mass density. Gas-dynamical models coupled with the Cambridge stellar evolution tracks allow us to derive a scheme to recover the real cluster mass given measured half-light radius, one-dimensional velocity dispersion and age. We monitor the evolution with time of the ratio of real to apparent mass through the parameter η. When we compute η for rich star clusters, we find non-monotonic evolution in time when the IMF stretches beyond a critical cut-off mass of 25.5Msolar. We also monitor the rise of colour gradients between the inner and outer volume of clusters: we find trends in time of the stellar IMF power indices overlapping well with those derived for the Large Magellanic Cloud cluster NGC 1818 at an age of 30Myr. We argue that the core region of massive Antennae clusters should have suffered from much segregation despite their low ages. We apply these results to a cluster mass function, and find that the peak of the mass distribution would appear to observers shifted to lower masses by as much as 0.2dex. The star formation rate derived for the cluster population is then underestimated by from 20 to 50 per cent.

Exploring the IMF of star clusters: a joint SLUG and LEGUS effort

NASA Astrophysics Data System (ADS)

Ashworth, G.; Fumagalli, M.; Krumholz, M. R.; Adamo, A.; Calzetti, D.; Chandar, R.; Cignoni, M.; Dale, D.; Elmegreen, B. G.; Gallagher, J. S., III; Gouliermis, D. A.; Grasha, K.; Grebel, E. K.; Johnson, K. E.; Lee, J.; Tosi, M.; Wofford, A.

2017-08-01

We present the implementation of a Bayesian formalism within the Stochastically Lighting Up Galaxies (slug) stellar population synthesis code, which is designed to investigate variations in the initial mass function (IMF) of star clusters. By comparing observed cluster photometry to large libraries of clusters simulated with a continuously varying IMF, our formalism yields the posterior probability distribution function (PDF) of the cluster mass, age and extinction, jointly with the parameters describing the IMF. We apply this formalism to a sample of star clusters from the nearby galaxy NGC 628, for which broad-band photometry in five filters is available as part of the Legacy ExtraGalactic UV Survey (LEGUS). After allowing the upper-end slope of the IMF (α3) to vary, we recover PDFs for the mass, age and extinction that are broadly consistent with what is found when assuming an invariant Kroupa IMF. However, the posterior PDF for α3 is very broad due to a strong degeneracy with the cluster mass, and it is found to be sensitive to the choice of priors, particularly on the cluster mass. We find only a modest improvement in the constraining power of α3 when adding Hα photometry from the companion Hα-LEGUS survey. Conversely, Hα photometry significantly improves the age determination, reducing the frequency of multi-modal PDFs. With the aid of mock clusters, we quantify the degeneracy between physical parameters, showing how constraints on the cluster mass that are independent of photometry can be used to pin down the IMF properties of star clusters.

IDENTIFICATION OF THE LITHIUM DEPLETION BOUNDARY AND AGE OF THE SOUTHERN OPEN CLUSTER BLANCO 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cargile, P. A.; James, D. J.; Jeffries, R. D., E-mail: p.cargile@vanderbilt.ed

2010-12-20

We present results from a spectroscopic study of the very low mass members of the Southern open cluster Blanco 1 using the Gemini-N telescope. We obtained intermediate resolution (R {approx} 4400) GMOS spectra for 15 cluster candidate members with I {approx} 14-20 mag, and employed a series of membership criteria-proximity to the cluster's sequence in an I/I - K{sub s} color-magnitude diagram (CMD), kinematics agreeing with the cluster systemic motion, magnetic activity as a youth indicator-to classify 10 of these objects as probable cluster members. For these objects, we searched for the presence of the Li I 6708 A featuremore » to identify the lithium depletion boundary (LDB) in Blanco 1. The I/I - K{sub s} CMD shows a clear mass segregation in the Li distribution along the cluster sequence; namely, all higher mass stars are found to be Li poor, while lower mass stars are found to be Li rich. The division between Li-poor and Li-rich (i.e., the LDB) in Blanco 1 is found at I = 18.78 {+-} 0.24 and I - K{sub s} = 3.05 {+-} 0.10. Using current pre-main-sequence evolutionary models, we determine an LDB age of 132 {+-} 24 Myr. Comparing our derived LDB age to upper-main-sequence isochrone ages for Blanco 1, as well as for other open clusters with identified LDBs, we find good chronometric consistency when using stellar evolution models that incorporate a moderate degree of convective core overshoot.« less

A Constraint on the Formation Timescale of the Young Open Cluster NGC 2264: Lithium Abundance of Pre-main Sequence Stars

NASA Astrophysics Data System (ADS)

Lim, Beomdu; Sung, Hwankyung; Kim, Jinyoung S.; Bessell, Michael S.; Hwang, Narae; Park, Byeong-Gon

2016-11-01

The timescale of cluster formation is an essential parameter in order to understand the formation process of star clusters. Pre-main sequence (PMS) stars in nearby young open clusters reveal a large spread in brightness. If the spread were considered to be a result of a real spread in age, the corresponding cluster formation timescale would be about 5-20 Myr. Hence it could be interpreted that star formation in an open cluster is prolonged for up to a few tens of Myr. However, difficulties in reddening correction, observational errors, and systematic uncertainties introduced by imperfect evolutionary models for PMS stars can result in an artificial age spread. Alternatively, we can utilize Li abundance as a relative age indicator of PMS star to determine the cluster formation timescale. The optical spectra of 134 PMS stars in NGC 2264 have been obtained with MMT/Hectochelle. The equivalent widths have been measured for 86 PMS stars with a detectable Li line (3500\\lt {T}{eff}[{{K}}]≤slant 6500). Li abundance under the condition of local thermodynamic equilibrium (LTE) was derived using the conventional curve of growth method. After correction for non-LTE effects, we find that the initial Li abundance of NGC 2264 is A({Li})=3.2+/- 0.2. From the distribution of the Li abundances, the underlying age spread of the visible PMS stars is estimated to be about 3-4 Myr and this, together with the presence of embedded populations in NGC 2264, suggests that the cluster formed on a timescale shorter than 5 Myr.

The Immersive Virtual Reality Experience: A Typology of Users Revealed Through Multiple Correspondence Analysis Combined with Cluster Analysis Technique.

PubMed

Rosa, Pedro J; Morais, Diogo; Gamito, Pedro; Oliveira, Jorge; Saraiva, Tomaz

2016-03-01

Immersive virtual reality is thought to be advantageous by leading to higher levels of presence. However, and despite users getting actively involved in immersive three-dimensional virtual environments that incorporate sound and motion, there are individual factors, such as age, video game knowledge, and the predisposition to immersion, that may be associated with the quality of virtual reality experience. Moreover, one particular concern for users engaged in immersive virtual reality environments (VREs) is the possibility of side effects, such as cybersickness. The literature suggests that at least 60% of virtual reality users report having felt symptoms of cybersickness, which reduces the quality of the virtual reality experience. The aim of this study was thus to profile the right user to be involved in a VRE through head-mounted display. To examine which user characteristics are associated with the most effective virtual reality experience (lower cybersickness), a multiple correspondence analysis combined with cluster analysis technique was performed. Results revealed three distinct profiles, showing that the PC gamer profile is more associated with higher levels of virtual reality effectiveness, that is, higher predisposition to be immersed and reduced cybersickness symptoms in the VRE than console gamer and nongamer. These findings can be a useful orientation in clinical practice and future research as they help identify which users are more predisposed to benefit from immersive VREs.

Breast cancer and symptom clusters during radiotherapy.

PubMed

Matthews, Ellyn E; Schmiege, Sarah J; Cook, Paul F; Sousa, Karen H

2012-01-01

Symptom clusters assessment shifts the clinical focus from a specific symptom to the patient's experience as a whole. Few studies have examined breast cancer symptom clusters during treatment, and fewer studies have addressed symptom clusters during radiation therapy (RT). The theoretical underpinning of this study is the Symptoms Experience Model. Research is needed to identify antecedents and consequences of cancer-related symptom clusters. The present study was intended to determine the clustering of symptoms during RT in women with breast cancer and significant correlations among the symptoms, individual characteristics, and mood. A secondary data analysis from a descriptive correlational study of 93 women at weeks 3 to 7 of RT from centers in the mid-Atlantic region of the United States, Symptom Distress Scale, the subscales of the Positive and Negative Affect Scale, Life Orientation Test, and Self-transcendence Scale were completed. Confirmatory factor analysis revealed symptoms grouped into 3 distinct clusters: pain-insomnia-fatigue, cognitive disturbance-outlook, and gastrointestinal. The pain-insomnia-fatigue and cognitive disturbance-outlook clusters were associated with individual characteristics, optimism, self-transcendence, and positive and negative mood. The gastrointestinal cluster correlated significantly only with positive mood. This study provides insight into symptoms that group together and the relationship of symptom clusters to antecedents and mood. These findings underscore the need to define and standardize the measurement of symptom clusters and understand variability in concurrent symptoms. Attention to symptom clusters shifts the clinical focus from a specific symptom to the patient's experience as a whole and helps identify the most effective interventions.

Reddening, distance modulus and age of the globular cluster NGC 6121 (M4) from the properties of RR Lyrae variables

NASA Astrophysics Data System (ADS)

Caputo, F.; Castellani, V.; Quarta, M. L.

1985-02-01

It is shown that pulsational properties of RR Lyrae variables in globular clusters can be used to put theoretical constraints on the values of cluster reddening and distance modulus. By requiring that the HR diagram location of pulsators agrees with the period distribution observed and with the theoretical boundaries of the instability strip, reddening and distance modulus of the globular cluster M4 are derived as a (slow) function of the pulsator masses. Thus, a best guess is presented for the cluster age (t = 12.2 billion years), some evidence for a non-canonical evolutionary having been taken into account.

Semantic Clustering of Search Engine Results

PubMed Central

Soliman, Sara Saad; El-Sayed, Maged F.; Hassan, Yasser F.

2015-01-01

This paper presents a novel approach for search engine results clustering that relies on the semantics of the retrieved documents rather than the terms in those documents. The proposed approach takes into consideration both lexical and semantics similarities among documents and applies activation spreading technique in order to generate semantically meaningful clusters. This approach allows documents that are semantically similar to be clustered together rather than clustering documents based on similar terms. A prototype is implemented and several experiments are conducted to test the prospered solution. The result of the experiment confirmed that the proposed solution achieves remarkable results in terms of precision. PMID:26933673

Measuring galaxy cluster masses with CMB lensing using a Maximum Likelihood estimator: statistical and systematic error budgets for future experiments

NASA Astrophysics Data System (ADS)

Raghunathan, Srinivasan; Patil, Sanjaykumar; Baxter, Eric J.; Bianchini, Federico; Bleem, Lindsey E.; Crawford, Thomas M.; Holder, Gilbert P.; Manzotti, Alessandro; Reichardt, Christian L.

2017-08-01

We develop a Maximum Likelihood estimator (MLE) to measure the masses of galaxy clusters through the impact of gravitational lensing on the temperature and polarization anisotropies of the cosmic microwave background (CMB). We show that, at low noise levels in temperature, this optimal estimator outperforms the standard quadratic estimator by a factor of two. For polarization, we show that the Stokes Q/U maps can be used instead of the traditional E- and B-mode maps without losing information. We test and quantify the bias in the recovered lensing mass for a comprehensive list of potential systematic errors. Using realistic simulations, we examine the cluster mass uncertainties from CMB-cluster lensing as a function of an experiment's beam size and noise level. We predict the cluster mass uncertainties will be 3 - 6% for SPT-3G, AdvACT, and Simons Array experiments with 10,000 clusters and less than 1% for the CMB-S4 experiment with a sample containing 100,000 clusters. The mass constraints from CMB polarization are very sensitive to the experimental beam size and map noise level: for a factor of three reduction in either the beam size or noise level, the lensing signal-to-noise improves by roughly a factor of two.

Chemical evolution of the Magellanic Clouds

NASA Astrophysics Data System (ADS)

Barbuy, B.; de Freitas Pacheco, J. A.; Idiart, T.

We have obtained integrated spectra for 14 clusters in the Magellanic Clouds, on which the spectral indices Hβ, Mg2, Fe5270, Fe5335 were measured. Selecting indices whose behaviour depends essentially on age and metallicity (Hβ and ), together with (B-V) and (V-K) colours, we were able to determine age and metallicities for these clusters, using calibrations based on single stellar population models (Borges et al. 1995). A chemical evolution model which follows a star formation history as indicated by the field population is checked with the age and metallicity data for our sample star clusters.

Compulsive buying disorder clustering based on sex, age, onset and personality traits.

PubMed

Granero, Roser; Fernández-Aranda, Fernando; Baño, Marta; Steward, Trevor; Mestre-Bach, Gemma; Del Pino-Gutiérrez, Amparo; Moragas, Laura; Mallorquí-Bagué, Núria; Aymamí, Neus; Goméz-Peña, Mónica; Tárrega, Salomé; Menchón, José M; Jiménez-Murcia, Susana

2016-07-01

In spite of the revived interest in compulsive buying disorder (CBD), its classification into the contemporary nosologic systems continues to be debated, and scarce studies have addressed heterogeneity in the clinical phenotype through methodologies based on a person-centered approach. To identify empirical clusters of CBD employing personality traits, as well as patients' sex, age and the age of CBD onset as indicators. An agglomerative hierarchical clustering method defining a combination of the Schwarz Bayesian Information Criterion and log-likelihood was used. Three clusters were identified in a sample of n=110 patients attending a specialized CBD unit a) "male compulsive buyers" reported the highest prevalence of comorbid gambling disorder and the lowest levels of reward dependence; b) "female low-dysfunctional" mainly included employed women, with the highest level of education, the oldest age of onset, the lowest scores in harm avoidance and the highest levels of persistence, self-directedness and cooperativeness; and c) "female highly-dysfunctional" with the youngest age of onset, the highest levels of comorbid psychopathology and harm avoidance, and the lowest score in self-directedness. Sociodemographic characteristics and personality traits can be used to determine CBD clusters which represent different clinical subtypes. These subtypes should be considered when developing assessment instruments, preventive programs and treatment interventions. Copyright © 2016 Elsevier Inc. All rights reserved.

Suppression of vacancy cluster growth in concentrated solid solution alloys

DOE PAGES

Zhao, Shijun; Velisa, Gihan; Xue, Haizhou; ...

2016-12-13

Large vacancy clusters, such as stacking-fault tetrahedra, are detrimental vacancy-type defects in ion-irradiated structural alloys. Suppression of vacancy cluster formation and growth is highly desirable to improve the irradiation tolerance of these materials. In this paper, we demonstrate that vacancy cluster growth can be inhibited in concentrated solid solution alloys by modifying cluster migration pathways and diffusion kinetics. The alloying effects of Fe and Cr on the migration of vacancy clusters in Ni concentrated alloys are investigated by molecular dynamics simulations and ion irradiation experiment. While the diffusion coefficients of small vacancy clusters in Ni-based binary and ternary solid solutionmore » alloys are higher than in pure Ni, they become lower for large clusters. This observation suggests that large clusters can easily migrate and grow to very large sizes in pure Ni. In contrast, cluster growth is suppressed in solid solution alloys owing to the limited mobility of large vacancy clusters. Finally, the differences in cluster sizes and mobilities in Ni and in solid solution alloys are consistent with the results from ion irradiation experiments.« less

Theory of Positron Annihilation in Helium-Filled Bubbles in Plutonium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sterne, P A; Pask, J E

2003-02-13

Positron annihilation lifetime spectroscopy is a sensitive probe of vacancies and voids in materials. This non-destructive measurement technique can identify the presence of specific defects in materials at the part-per-million level. Recent experiments by Asoka-Kumar et al. have identified two lifetime components in aged plutonium samples--a dominant lifetime component of around 182 ps and a longer lifetime component of around 350-400ps. This second component appears to increase with the age of the sample, and accounts for only about 5 percent of the total intensity in 35 year-old plutonium samples. First-principles calculations of positron lifetimes are now used extensively to guidemore » the interpretation of positron lifetime data. At Livermore, we have developed a first-principles finite-element-based method for calculating positron lifetimes for defects in metals. This method is capable of treating system cell sizes of several thousand atoms, allowing us to model defects in plutonium ranging in size from a mono-vacancy to helium-filled bubbles of over 1 nm in diameter. In order to identify the defects that account for the observed lifetime values, we have performed positron lifetime calculations for a set of vacancies, vacancy clusters, and helium-filled vacancy clusters in delta-plutonium. The calculations produced values of 143ps for defect-free delta-Pu and 255ps for a mono-vacancy in Pu, both of which are inconsistent with the dominant experimental lifetime component of 182ps. Larger vacancy clusters have even longer lifetimes. The observed positron lifetime is significantly shorter than the calculated lifetimes for mono-vacancies and larger vacancy clusters, indicating that open vacancy clusters are not the dominant defect in the aged plutonium samples. When helium atoms are introduced into the vacancy cluster, the positron lifetime is reduced due to the increased density of electrons available for annihilation. For a mono-vacancy in Pu containing one helium atom, the calculated lifetime is 190 ps, while a di-vacancy containing two helium atoms has a positron lifetime of 205 ps. In general, increasing the helium density in a vacancy cluster or He-filled bubble reduces the positron lifetime, so that the same lifetime value can arise fi-om a range of vacancy cluster sizes with different helium densities. In order to understand the variation of positron lifetime with vacancy cluster size and helium density in the defect, we have performed over 60 positron lifetime calculations with vacancy cluster sizes ranging from 1 to 55 vacancies and helium densities ranging fi-om zero to five helium atoms per vacancy. The results indicate that the experimental lifetime of 182 ps is consistent with the theoretical value of 190 ps for a mono-vacancy with a single helium atom, but that slightly better agreement is obtained for larger clusters of 6 or more vacancies containing 2-3 helium atoms per vacancy. For larger vacancy clusters with diameters of about 3-5 nm or more, the annihilation with helium electrons dominates the positron annihilation rate; the observed lifetime of 180ps is then consistent with a helium concentration in the range of 3 to 3.5 Hehacancy, setting an upper bound on the helium concentration in the vacancy clusters. In practice, the single lifetime component is most probably associated with a family of helium-filled bubbles rather than with a specific unique defect size. The longer 350-400ps lifetime component is consistent with a relatively narrow range of defect sizes and He concentration. At zero He concentration, the lifetime values are matched by small vacancy clusters containing 6-12 vacancies. With increasing vacancy cluster size, a small amount of He is required to keep the lifetime in the 350-400 ps range, until the value saturates for larger helium bubbles of more than 50 vacancies (bubble diameter > 1.3 nm) at a helium concentration close to 1 He/vacancy. These results, taken together with the experimental data, indicate that the features observed in TEM data by Schwartz et al are not voids, but are in fact helium-filled bubbles with a helium pressure of around 2-3 helium atoms per vacancy, depending on the bubble size. This is consistent with the conclusions of recently developed models of He-bubble growth in aged plutonium.« less

X-ray illumination of globular cluster puzzles. [globular cluster X ray sources as clues to Milky Way Galaxy age and evolution

NASA Technical Reports Server (NTRS)

Lightman, A. P.; Grindlay, J. E.

1982-01-01

Globular clusters are thought to be among the oldest objects in the Galaxy, and provide, in this connection, important clues for determining the age and process of formation of the Galaxy. The present investigation is concerned with puzzles relating to the X-ray emission of globular clusters, taking into account questions regarding the location of X-ray emitting clusters (XEGC) unusually near the galactic plane and/or galactic center. An adopted model is discussed for the nature, formation, and lifetime of X-ray sources in globular clusters. An analysis of the available data is conducted in connection with a search for correlations between binary formation time scales, central relaxation times, galactic locations, and X-ray emission. The positive correlation found between distance from galactic center and two-body binary formation time for globular clusters, explanations for this correlation, and the hypothesis that X-ray sources in globular clusters require binary star systems provide a possible explanation of the considered puzzles.

Assessing predicted age-specific breast cancer mortality rates in 27 European countries by 2020.

PubMed

Clèries, R; Rooney, R M; Vilardell, M; Espinàs, J A; Dyba, T; Borras, J M

2018-03-01

We assessed differences in predicted breast cancer (BC) mortality rates, across Europe, by 2020, taking into account changes in the time trends of BC mortality rates during the period 2000-2010. BC mortality data, for 27 European Union (EU) countries, were extracted from the World Health Organization mortality database. First, we compared BC mortality data between time periods 2000-2004 and 2006-2010 through standardized mortality ratios (SMRs) and carrying out a graphical assessment of the age-specific rates. Second, making use of the base period 2006-2012, we predicted BC mortality rates by 2020. Finally, making use of the SMRs and the predicted data, we identified a clustering of countries, assessing differences in the time trends between the areas defined in this clustering. The clustering approach identified two clusters of countries: the first cluster were countries where BC predicted mortality rates, in 2020, might slightly increase among women aged 69 and older compared with 2010 [Greece (SMR 1.01), Croatia (SMR 1.02), Latvia (SMR 1.15), Poland (SMR 1.14), Estonia (SMR 1.16), Bulgaria (SMR 1.13), Lithuania (SMR 1.03), Romania (SMR 1.13) and Slovakia (SMR 1.06)]. The second cluster was those countries where BC mortality rates level off or decrease in all age groups (remaining countries). However, BC mortality rates between these clusters might diminish and converge to similar figures by 2020. For the year 2020, our predictions have shown a converging pattern of BC mortality rates between European regions. Reducing disparities, in access to screening and treatment, could have a substantial effect in countries where a non-decreasing trend in age-specific BC mortality rates has been predicted.

Preference Mapping of Soymilk with Different U.S. Consumers.

PubMed

Lawrence, S E; Lopetcharat, K; Drake, M A

2016-02-01

This study determined and compared drivers of liking for unflavored soymilk with different U.S. consumer groups. A highly trained panel documented appearance, mouthfeel and flavor attributes of 26 commercial soymilks. Twelve representative soymilks were then selected for evaluation by consumers from 3 age/cultural categories (n = 75 each category; Caucasian/African American females aged 18 to 30 y; Asian females aged 18 to 30 y; Caucasian/African American females aged 40 to 64 y). Consumers evaluated overall liking and liking and intensity of specific attributes. Results were evaluated by analysis of variance, followed by internal and external preference mapping. Age had no effect on overall liking, while ethnicity did (Caucasian/African American compared with Asian; P < 0.05). Caucasians/African Americans differentiated soymilks more than Asians and assigned a wider range of liking scores than Asians (2.1 to 7.2 compared with 4.0 to 6.1). Three consumer clusters were identified. Sweet taste with vanilla/vanillin and sweet aromatic flavors and higher viscosity were preferred by most consumers and differences between consumer clusters were primarily in drivers of dislike. Drivers of dislike were not identified for Cluster 1 consumers while Clusters 2 and 3 consumers (n = 84, n = 80) disliked beany, green/grassy and meaty/brothy flavors and astringency. Cluster 3 (n = 80) consumers scored all soymilks higher in liking (P < 0.05) than Cluster 2 consumers, and were willing to overlook disliked attributes with the addition of sweet taste, whereas the Cluster 2 consumers were not. These findings can be utilized to produce soymilks with attributes that are well liked by target consumers and to tailor attributes for segments of the population that have not yet been accommodated. © 2015 Institute of Food Technologists®

Fitness as a determinant of arterial stiffness in healthy adult men: a cross-sectional study.

PubMed

Chung, Jinwook; Kim, Milyang; Jin, Youngsoo; Kim, Yonghwan; Hong, Jeeyoung

2018-01-01

Fitness is known to influence arterial stiffness. This study aimed to assess differences in cardiorespiratory endurance, muscular strength, and flexibility according to arterial stiffness, based on sex and age. We enrolled 1590 healthy adults (men: 1242, women: 348) who were free of metabolic syndrome. We measured cardiorespiratory endurance in an exercise stress test on a treadmill, muscular strength by a grip test, and flexibility by upper body forward-bends from a standing position. The brachial-ankle pulse wave velocity test was performed to measure arterial stiffness before the fitness test. Cluster analysis was performed to divide the patients into groups with low (Cluster 1) and high (Cluster 2) arterial stiffness. According to the k-cluster analysis results, Cluster 1 included 624 men and 180 women, and Cluster 2 included 618 men and 168 women. Men in the middle-aged group with low arterial stiffness demonstrated higher cardiorespiratory endurance, muscular strength, and flexibility than those with high arterial stiffness. Similarly, among men in the old-aged group, the cardiorespiratory endurance and muscular strength, but not flexibility, differed significantly according to arterial stiffness. Women in both clusters showed similar cardiorespiratory endurance, muscular strength, and flexibility regardless of their arterial stiffness. Among healthy adults, arterial stiffness was inversely associated with fitness in men but not in women. Therefore, fitness seems to be a determinant for arterial stiffness in men. Additionally, regular exercise should be recommended for middle-aged men to prevent arterial stiffness.

[High risk groups in health behavior defined by clustering of smoking, alcohol, and exercise habits: National Heath and Nutrition Examination Survey].

PubMed

Kang, Kiwon; Sung, Joohon; Kim, Chang Yup

2010-01-01

We investigated the clustering of selected lifestyle factors (cigarette smoking, heavy alcohol consumption, lack of physical exercise) and identified the population characteristics associated with increasing lifestyle risks. Data on lifestyle risk factors, sociodemographic characteristics, and history of chronic diseases were obtained from 7,694 individuals >/=20 years of age who participated in the 2005 Korea National Health and Nutrition Examination Survey (KNHANES). Clustering of lifestyle risks involved the observed prevalence of multiple risks and those expected from marginal exposure prevalence of the three selected risk factors. Prevalence odds ratio was adopted as a measurement of clustering. Multiple correspondence analysis, Kendall tau correlation, Man-Whitney analysis, and ordinal logistic regression analysis were conducted to identify variables increasing lifestyle risks. In both men and women, increased lifestyle risks were associated with clustering of: (1) cigarette smoking and excessive alcohol consumption, and (2) smoking, excessive alcohol consumption, and lack of physical exercise. Patterns of clustering for physical exercise were different from those for cigarette smoking and alcohol consumption. The increased unhealthy clustering was found among men 20-64 years of age with mild or moderate stress, and among women 35-49 years of age who were never-married, with mild stress, and increased body mass index (>30 kg/m(2)). Addressing a lack of physical exercise considering individual characteristics including gender, age, employment activity, and stress levels should be a focus of health promotion efforts.

Integrated spectral properties of 22 small angular diameter galactic open clusters

NASA Astrophysics Data System (ADS)

Ahumada, A. V.; Clariá, J. J.; Bica, E.

2007-10-01

Aims:Flux-calibrated integrated spectra of a sample of 22 Galactic open clusters of small angular diameter are presented. With one exception (ESO 429-SC2), all objects have Galactic longitudes in the range 208° < l < 33°. The spectra cover the range ≈3600-6800 Å, with a resolution of ≈14 Å. The properties of the present cluster sample are compared with those of well-studied clusters located in two 90° sectors, centred at l = 257° and l = 347°. The dissolution rate of Galactic open clusters in these two sectors is examined. Methods: Using the equivalent widths of the Balmer lines and comparing line intensities and continuum distribution of the cluster spectra with those of template cluster spectra with known properties, we derive both foreground reddening values and ages. Thus, we provide information independent of that determined through colour-magnitude diagrams. Results: The derived E(B-V) values for the whole sample vary from 0.0 in ESO 445-SC74 to 1.90 in Pismis 24, while the ages range from ~3 Myr (NGC 6604 and BH 151) to ~3.5 Gyr (Ruprecht 2). For six clusters (Dolidze 34, ESO 429-SC2, ESO 445-SC74, Ruprecht 2, BH 151 and Hogg 9) the foreground E(B-V) colour excesses and ages are determined for the first time. The results obtained for the remaining clusters show, in general terms, good agreement with previous photometric results. Conclusions: The age and reddening distributions of the present sample match those of known clusters in the two selected Galactic sectors. The present results would favour a major dissolution rate of star clusters in these two sectors. Two new solar-metallicity templates are defined corresponding to the age groups of (4-5) Myr and 30 Myr among those of Piatti et al. (2002, MNRAS, 335, 233). The Piatti et al. templates of 20 Myr and (3-4) Gyr are here redefined. Based on observations made at Complejo Astronómico El Leoncito, which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina (CONICET) and the National Universities of La Plata, Córdoba and San Juan, Argentina. Tables [see full text]- [see full text] and Appendix are only available in electronic form at http://www.aanda.org

Globular Cluster Abundances from High-resolution, Integrated-light Spectroscopy. IV. The Large Magellanic Cloud: α, Fe-peak, Light, and Heavy Elements

NASA Astrophysics Data System (ADS)

Colucci, Janet E.; Bernstein, Rebecca A.; Cameron, Scott A.; McWilliam, Andrew

2012-02-01

We present detailed chemical abundances in eight clusters in the Large Magellanic Cloud (LMC). We measure abundances of 22 elements for clusters spanning a range in age of 0.05-12 Gyr, providing a comprehensive picture of the chemical enrichment and star formation history of the LMC. The abundances were obtained from individual absorption lines using a new method for analysis of high-resolution (R ~ 25,000), integrated-light (IL) spectra of star clusters. This method was developed and presented in Papers I, II, and III of this series. In this paper, we develop an additional IL χ2-minimization spectral synthesis technique to facilitate measurement of weak (~15 mÅ) spectral lines and abundances in low signal-to-noise ratio data (S/N ~ 30). Additionally, we supplement the IL abundance measurements with detailed abundances that we measure for individual stars in the youngest clusters (age < 2 Gyr) in our sample. In both the IL and stellar abundances we find evolution of [α/Fe] with [Fe/H] and age. Fe-peak abundance ratios are similar to those in the Milky Way (MW), with the exception of [Cu/Fe] and [Mn/Fe], which are sub-solar at high metallicities. The heavy elements Ba, La, Nd, Sm, and Eu are significantly enhanced in the youngest clusters. Also, the heavy to light s-process ratio is elevated relative to the MW ([Ba/Y] >+0.5) and increases with decreasing age, indicating a strong contribution of low-metallicity asymptotic giant branch star ejecta to the interstellar medium throughout the later history of the LMC. We also find a correlation of IL Na and Al abundances with cluster mass in the sense that more massive, older clusters are enriched in the light elements Na and Al with respect to Fe, which implies that these clusters harbor star-to-star abundance variations as is common in the MW. Lower mass, intermediate-age, and young clusters have Na and Al abundances that are lower and more consistent with LMC field stars. Our results can be used to constrain both future chemical evolution models for the LMC and theories of globular cluster formation. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

Galaxy evolution in clusters since z~1

NASA Astrophysics Data System (ADS)

Aragon-Salamanca, Alfonso

2010-09-01

Galaxy clusters provide some of the most extreme environments in which galaxies evolve, making them excellent laboratories to study the age old question of "nature" vs. "nurture" in galaxy evolution. Here I review some of the key observational results obtained during the last decade on the evolution of the morphology, structure, dynamics, star-formation history and stellar populations of cluster galaxies since the time when the universe was half its present age. Many of the results presented here have been obtained within the ESO Distant Cluster Survey (EDisCS) and Space Telescope A901/02 Galaxy Evolution Survey (STAGES) collaborations.

Galaxy Evolution in Clusters Since z ~ 1

NASA Astrophysics Data System (ADS)

Aragón-Salamanca, A.

Galaxy clusters provide some of the most extreme environments in which galaxies evolve, making them excellent laboratories to study the age old question of "nature" vs. "nurture" in galaxy evolution. Here I review some of the key observational results obtained during the last decade on the evolution of the morphology, structure, dynamics, star-formation history and stellar populations of cluster galaxies since the time when the Universe was half its present age. Many of the results presented here have been obtained within the ESO Distant Cluster Survey (EDisCS) and Space Telescope A901/02 Galaxy Evolution Survey (STAGES) collaborations.

Rotation Period of Blanco 1 Members from KELT Light Curves: Comparing Rotation-Ages to Various Stellar Chronometers at 100 Myr

NASA Astrophysics Data System (ADS)

Cargile, Phillip; James, D. J.; Pepper, J.; Kuhn, R.; Siverd, R. J.; Stassun, K. G.

2012-01-01

The age of a star is one of its most fundamental properties, and yet tragically it is also the one property that is not directly measurable in observations. We must therefore rely on age estimates based on mostly model-dependent or empirical methods. Moreover, there remains a critical need for direct comparison of different age-dating techniques using the same stars analyzed in a consistent fashion. One chronometer commonly being employed is using stellar rotation rates to measure stellar ages, i.e., gyrochronology. Although this technique is one of the better-understood chronometers, its calibration relies heavily on the solar datum, as well as benchmark open clusters with reliable ages, and also lacks a comprehensive comparative analysis to other stellar chronometers. The age of the nearby (? pc) open cluster Blanco 1 has been estimated using various techniques, including being one of only 7 clusters with an LDB age measurement, making it a unique and powerful comparative laboratory for stellar chronometry, including gyrochronology. Here, we present preliminary results from our light-curve analysis of solar-type stars in Blanco 1 in order to identify and measure rotation periods of cluster members. The light-curve data were obtained during the engineering and calibration phase of the KELT-South survey. The large area on the sky and low number of contaminating field stars makes Blanco 1 an ideal target for the extremely wide field and large pixel scale of the KELT telescope. We apply a period-finding technique using the Lomb-Scargle periodogram and FAP statistics to measure significant rotation periods in the KELT-South light curves for confirmed Blanco 1 members. These new rotation periods allow us to test and inform rotation evolution models for stellar ages at ? Myr, determining a rotation-age for Blanco 1 using gyrochronology, and compare this rotation-age to other age measurements for this cluster.

Paleomagnetically inferred ages of a cluster of Holocene monogenetic eruptions in the Tacámbaro-Puruarán area (Michoacán, México): Implications for volcanic hazards

NASA Astrophysics Data System (ADS)

Mahgoub, Ahmed Nasser; Böhnel, Harald; Siebe, Claus; Salinas, Sergio; Guilbaud, Marie-Noëlle

2017-11-01

The paleomagnetic dating procedure was applied to a cluster of four partly overlapping monogenetic Holocene volcanoes and associated lava flows, namely La Tinaja, La Palma, Mesa La Muerta, and Malpaís de Cutzaróndiro, located in the Tacámbaro-Puruarán area, at the southeastern margin of the Michoacán-Guanajuato volcanic field. For this purpose, 21 sites distributed as far apart as possible from each other were sampled to obtain a well-averaged mean paleomagnetic direction for each single lava flow. For intensity determinations, double-heating Thellier experiments using the IZZI protocol were conducted on 55 selected samples. La Tinaja is the oldest of these flows and was dated by the 14C method at 5115 ± 130 years BP (cal 4184-3655 BCE). It is stratigraphically underneath the other three flows with Malpaís de Cutzaróndiro lava flow being the youngest. The paleomagnetic dating procedure was applied using the Matlab archaeo-dating tool in couple with the geomagnetic field model SHA.DIF.14k. Accordingly, for La Tinaja several possible age ranges were obtained, of which the range 3650-3480 BCE is closest to the 14C age. Paleomagnetic dating on La Palma produced a unique age range of 3220-2880 BCE. Two ages ranges of 2240-2070 BCE and 760-630 BCE were obtained for Mesa La Muerta and a well-constrained age of 420-320 BCE for Malpaís de Cutzaróndiro. Although systematic archaeological excavations have so far not been carried out in this area, it is possible that the younger eruptions were contemporary to local human occupation. Our paleomagnetic dates indicate that all four eruptions, although closely clustered in space, occurred separately in time with varying recurrence intervals ranging between 300 and 2300 years. This finding should be considered when constraining the nature of the magmatic plumbing system and developing a strategy aimed at reducing risk in the volcanically active Michoacán-Guanajuato volcanic field, where several young monogenetic volcano clusters have been identified recently. These enigmatic small "flare-ups" (outbursts of small pods of magma in geologically short periods of time within a small area) have also been encountered in other subduction-related volcanic fields around the globe (e.g. Cascades arc in the western U.S.A.) and still require to be investigated by geophysical and petrological means in order to understand their origin.

Multidimensional assessment of awareness in early-stage dementia: a cluster analytic approach.

PubMed

Clare, Linda; Whitaker, Christopher J; Nelis, Sharon M; Martyr, Anthony; Markova, Ivana S; Roth, Ilona; Woods, Robert T; Morris, Robin G

2011-01-01

Research on awareness in dementia has yielded variable and inconsistent associations between awareness and other factors. This study examined awareness using a multidimensional approach and applied cluster analytic techniques to identify associations between the level of awareness and other variables. Participants were 101 individuals with early-stage dementia (PwD) and their carers. Explicit awareness was assessed at 3 levels: performance monitoring in relation to memory, evaluative judgement in relation to memory, everyday activities and socio-emotional functioning, and metacognitive reflection in relation to the experience and impact of the condition. Implicit awareness was assessed with an emotional Stroop task. Different measures of explicit awareness scores were related only to a limited extent. Cluster analysis yielded 3 groups with differing degrees of explicit awareness. These groups showed no differences in implicit awareness. Lower explicit awareness was associated with greater age, lower MMSE scores, poorer recall and naming scores, lower anxiety and greater carer stress. Multidimensional assessment offers a more robust approach to classifying PwD according to level of awareness and hence to examining correlates and predictors of awareness. Copyright © 2011 S. Karger AG, Basel.

Diary Data Subjected to Cluster Analysis of Intake/Output/Void Habits with Resulting Clusters Compared by Continence Status, Age, Race

PubMed Central

Miller, Janis M; Guo, Ying; Rodseth, Sarah Becker

2011-01-01

Background Data that incorporate the full complexity of healthy beverage intake and voiding frequency do not exist; therefore, clinicians reviewing bladder habits or voiding diaries for continence care must rely on expert opinion recommendations. Objective To use data-driven cluster analyses to reduce complex voiding diary variables into discrete patterns or data cluster profiles, descriptively name the clusters, and perform validity testing. Method Participants were 352 community women who filled out a 3-day voiding diary. Six variables (void frequency during daytime hours, void frequency during nighttime hours, modal output, total output, total intake, and body mass index) were entered into cluster analyses. The clusters were analyzed for differences by continence status, age, race (Black women, n = 196 White women, n = 156), and for those who were incontinent, by leakage episode severity. Results Three clusters emerged, labeled descriptively as Conventional, Benchmark, and Superplus. The Conventional cluster (68% of the sample) demonstrated mean daily intake of 45 ±13 ounces; mean daily output of 37 ± 15 ounces, mean daily voids 5 ± 2 times, mean modal daytime output 10±0.5 ounces, and mean nighttime voids 1±1 times. The Superplus cluster (7% of the sample) showed double or triple these values across the 5 variables, and the Benchmark cluster (25%) showed values consistent with current popular recommendations on intake and output (e.g., meeting or exceeding the 8 × 8 fluid intake rule of thumb). The clusters differed significantly (p < .05) by age, race, amount of irritating beverages consumed, and incontinence status. Discussion Identification of three discrete clusters provides for a potential parsimonious but data-driven means of classifying individuals for additional epidemiological or clinical study. The clinical utility rests with potential for intervening to move an individual from a high risk to low risk cluster with regards to incontinence. PMID:21317828

The Ages of 55 Globular Clusters as Determined Using an Improved \\Delta V^HB_TO Method along with Color-Magnitude Diagram Constraints, and Their Implications for Broader Issues

NASA Astrophysics Data System (ADS)

VandenBerg, Don A.; Brogaard, K.; Leaman, R.; Casagrande, L.

2013-10-01

Ages have been derived for 55 globular clusters (GCs) for which Hubble Space Telescope Advanced Camera for Surveys photometry is publicly available. For most of them, the assumed distances are based on fits of theoretical zero-age horizontal-branch (ZAHB) loci to the lower bound of the observed distributions of HB stars, assuming reddenings from empirical dust maps and metallicities from the latest spectroscopic analyses. The age of the isochrone that provides the best fit to the stars in the vicinity of the turnoff (TO) is taken to be the best estimate of the cluster age. The morphology of isochrones between the TO and the beginning part of the subgiant branch (SGB) is shown to be nearly independent of age and chemical abundances. For well-defined color-magnitude diagrams (CMDs), the error bar arising just from the "fitting" of ZAHBs and isochrones is ≈ ± 0.25 Gyr, while that associated with distance and chemical abundance uncertainties is ~ ± 1.5-2 Gyr. The oldest GCs in our sample are predicted to have ages of ≈13.0 Gyr (subject to the aforementioned uncertainties). However, the main focus of this investigation is on relative GC ages. In conflict with recent findings based on the relative main-sequence fitting method, which have been studied in some detail and reconciled with our results, ages are found to vary from mean values of ≈12.5 Gyr at [Fe/H] <~ - 1.7 to ≈11 Gyr at [Fe/H] >~ -1. At intermediate metallicities, the age-metallicity relation (AMR) appears to be bifurcated: one branch apparently contains clusters with disk-like kinematics, whereas the other branch, which is displaced to lower [Fe/H] values by ≈0.6 dex at a fixed age, is populated by clusters with halo-type orbits. The dispersion in age about each component of the AMR is ~ ± 0.5 Gyr. There is no apparent dependence of age on Galactocentric distance (R G) nor is there a clear correlation of HB type with age. As previously discovered in the case of M3 and M13, subtle variations have been found in the slope of the SGB in the CMDs of other metal-poor ([Fe/H] <~ - 1.5) GCs. They have been tentatively attributed to cluster-to-cluster differences in the abundance of helium. Curiously, GCs that have relatively steep "M13-like" SGBs tend to be massive systems, located at small R G, that show the strongest evidence of in situ formation of multiple stellar populations. The clusters in the other group are typically low-mass systems (with 2-3 exceptions, including M3) that, at the present time, should not be able to retain the matter lost by mass-losing stars due either to the development of GC winds or to ram-pressure stripping by the halo interstellar medium. The apparent separation of the two groups in terms of their present-day gas retention properties is difficult to understand if all GCs were initially ~20 times their current masses. The lowest-mass systems, in particular, may have never been massive enough to retain enough gas to produce a significant population of second-generation stars. In this case, the observed light element abundance variations, which are characteristic of all GCs, were presumably present in the gas out of which the observed cluster stars formed.

Coffee-rings and glasses: Colloids out of equilibrium

NASA Astrophysics Data System (ADS)

Yunker, Peter Joseph

This thesis describes experiments that utilize colloids to explore nonequilibrium phenomena. Specifically, the deposition of particles during evaporation and the glass transition are explored. In the first set of experiments, we found that particle shape has a profound effect on particle deposition. We evaporated drops of colloidal suspensions containing micron-sized particles that range in shape from isotropic spheres to very anisotropic ellipsoids. For sessile drops, i.e., drops sitting on a solid surface, spheres are deposited in a ring-like stain, while ellipsoids are deposited uniformly. We also confined drops between glass plates and allowed them to evaporate. During evaporation, colloidal particles coat the air-water interface, forming colloidal monolayer membranes (CMMs). As particle anisotropy increases, CMM bending rigidity was found to increase. This increase in bending rigidity provides a new mechanism that produces a uniform deposition of ellipsoids and a heterogeneous deposition of spheres. In the second set of experiments, we employed colloidal suspensions to investigate the character of glassy materials. "Anisotropic glasses'' were investigated with ellipsoidal particles confined to two-dimensional chambers at high packing fractions; this system enabled the study of the effects of particle shape on the vibrational properties of colloidal glasses. Low frequency modes in glasses composed of slightly anisotropic particles are found to have predominantly rotational character. Conversely, low frequency modes in glasses of highly anisotropic particles exhibit a mix of rotational and translational character. Aging effects in glasses were explored using suspensions of temperature-sensitive microgel spheres. We devised a method to rapidly quench from liquid to glass states, and then observed the resultant colloidal glasses as they aged. Particle rearrangements in glasses occur collectively, i.e., many particles move in a correlated manner. During aging, we observed that the size of these collective rearrangements increases. Thus, the slowing dynamics of aging appear governed by growing correlated domains of particles required for relaxation. Using the same microgel particles, the transformation of a crystal into a glass due to added disorder was investigated by adding smaller particles into a quasi-two-dimensional colloidal crystal. The crystal-glass transition bears structural signatures similar to those of the crystal-fluid transition, but also exhibits a sharp change in dynamic heterogeneity which ``turns-on'' abruptly as a function of increasing disorder. Finally, we investigated the influence of morphology and size on the vibrational properties of disordered clusters of colloidal particles. Spectral features of cluster vibrational modes are found to depend strongly on the average number of nearest neighbors but only weakly on the number of particles in each glassy cluster. The scaling of the median phonon frequency with nearest neighbor number is reminiscent of athermal simulations of the jamming transition.

Multiwavelength Studies of Young OB Associations

NASA Astrophysics Data System (ADS)

Feigelson, Eric D.

We discuss how contemporary multiwavelength observations of young OB-dominated clusters address long-standing astrophysical questions: Do clusters form rapidly or slowly with an age spread? When do clusters expand and disperse to constitute the field star population? Do rich clusters form by amalgamation of smaller subclusters? What is the pattern and duration of cluster formation in massive star forming regions (MSFRs)? Past observational difficulties in obtaining good stellar censuses of MSFRs have been alleviated in recent studies that combine X-ray and infrared surveys to obtain rich, though still incomplete, censuses of young stars in MSFRs. We describe here one of these efforts, the MYStIX project, that produced a catalog of 31,784 probable members of 20 MSFRs. We find that age spread within clusters is real in the sense that the stars in the core formed after the cluster halo. This is consistent with some recent astrophysical models involving merging star-forming filaments. Cluster expansion is seen in the ensemble of (sub)clusters, and older dispersing populations are found across MSFRs. Long-lived, asynchronous star formation is pervasive across MSFRs.

Spectroscopic determination of fundamental parameters of small angular diameter galactic open clusters

NASA Astrophysics Data System (ADS)

Ahumada, A. V.; Claria, J. J.; Bica, E.; Parisi, M. C.; Torres, M. C.; Pavani, D. B.

We present integrated spectra obtained at CASLEO (Argentina) for 9 galactic open clusters of small angular diameter. Two of them (BH 55 and Rup 159) have not been the target of previous research. The flux-calibrated spectra cover the spectral range approx. 3600-6900 A. Using the equivalent widths (EWs) of the Balmer lines and comparing the cluster spectra with template spectra, we determined E(B-V) colour excesses and ages for the present cluster sample. The parameters obtained for 6 of the clusters show good agreement with previous determinations based mainly on photometric methods. This is not the case, however, for BH 90, a scarcely reddened cluster, for which Moffat and Vogt (1975, Astron. and Astroph. SS, 20, 125) derived E(B-V) = 0.51. We explain and justify the strong discrepancy found for this object. According to the present analysis, 3 clusters are very young (Bo 14, Tr 15 and Tr 27), 2 are moderately young (NGC 6268 and BH 205), 3 are Hyades-like clusters (Rup 164, BH 90 and BH 55) and only one is an intermediate-age cluster (Rup 159).

The phonotactic influence on the perception of a consonant cluster /pt/ by native English and native Polish listeners: A behavioral and event related potential (ERP) study

PubMed Central

Wagner, Monica; Shafer, Valerie L.; Martin, Brett; Steinschneider, Mitchell

2013-01-01

The effect of exposure to the contextual features of the /pt/ cluster was investigated in native-English and native-Polish listeners using behavioral and event-related potential (ERP) methodology. Both groups experience the /pt/ cluster in their languages, but only the Polish group experiences the cluster in the context of word onset examined in the current experiment. The /st/ cluster was used as an experimental control. ERPs were recorded while participants identified the number of syllables in the second word of nonsense word pairs. The results found that only Polish listeners accurately perceived the /pt/ cluster and perception was reflected within a late positive component of the ERP waveform. Furthermore, evidence of discrimination of /pt/ and /pǝt/ onsets in the neural signal was found even for non-native listeners who could not perceive the difference. These findings suggest that exposure to phoneme sequences in highly specific contexts may be necessary for accurate perception. PMID:22867752

High Intensity Femtosecond XUV Pulse Interactions with Atomic Clusters: Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ditmire, Todd

We propose to expand our recent studies on the interactions of intense extreme ultraviolet (XUV) femtosecond pulses with atomic and molecular clusters. The work described follows directly from work performed under BES support for the past grant period. During this period we upgraded the THOR laser at UT Austin by replacing the regenerative amplifier with optical parametric amplification (OPA) using BBO crystals. This increased the contrast of the laser, the total laser energy to ~1.2 J , and decreased the pulse width to below 30 fs. We built a new all reflective XUV harmonic beam line into expanded lab space. This enabled an increase influence by a factor ofmore » 25 and an increase in the intensity by a factor of 50. The goal of the program proposed in this renewal is to extend this class of experiments to available higher XUV intensity and a greater range of wavelengths. In particular we plan to perform experiments to confirm our hypothesis about the origin of the high charge states in these exploding clusters, an effect which we ascribe to plasma continuum lowering (ionization potential depression) in a cluster nano-­plasma. To do this we will perform experiments in which XUV pulses of carefully chosen wavelength irradiate clusters composed of only low-Z atoms and clusters with a mixture of this low-­Z atom with higher Z atoms. The latter clusters will exhibit higher electron densities and will serve to lower the ionization potential further than in the clusters composed only of low Z atoms. This should have a significant effect on the charge states produced in the exploding cluster. We will also explore the transition of explosions in these XUV irradiated clusters from hydrodynamic expansion to Coulomb explosion. The work proposed here will explore clusters of a wider range of constituents, including clusters from solids. Experiments on clusters from solids will be enabled by development we performed during the past grant period in which we constructed and tested a cluster generator based on the Laser Ablation of Microparticles (LAM) method.« less

Cloud computing and validation of expandable in silico livers.

PubMed

Ropella, Glen E P; Hunt, C Anthony

2010-12-03

In Silico Livers (ISLs) are works in progress. They are used to challenge multilevel, multi-attribute, mechanistic hypotheses about the hepatic disposition of xenobiotics coupled with hepatic responses. To enhance ISL-to-liver mappings, we added discrete time metabolism, biliary elimination, and bolus dosing features to a previously validated ISL and initiated re-validated experiments that required scaling experiments to use more simulated lobules than previously, more than could be achieved using the local cluster technology. Rather than dramatically increasing the size of our local cluster we undertook the re-validation experiments using the Amazon EC2 cloud platform. So doing required demonstrating the efficacy of scaling a simulation to use more cluster nodes and assessing the scientific equivalence of local cluster validation experiments with those executed using the cloud platform. The local cluster technology was duplicated in the Amazon EC2 cloud platform. Synthetic modeling protocols were followed to identify a successful parameterization. Experiment sample sizes (number of simulated lobules) on both platforms were 49, 70, 84, and 152 (cloud only). Experimental indistinguishability was demonstrated for ISL outflow profiles of diltiazem using both platforms for experiments consisting of 84 or more samples. The process was analogous to demonstration of results equivalency from two different wet-labs. The results provide additional evidence that disposition simulations using ISLs can cover the behavior space of liver experiments in distinct experimental contexts (there is in silico-to-wet-lab phenotype similarity). The scientific value of experimenting with multiscale biomedical models has been limited to research groups with access to computer clusters. The availability of cloud technology coupled with the evidence of scientific equivalency has lowered the barrier and will greatly facilitate model sharing as well as provide straightforward tools for scaling simulations to encompass greater detail with no extra investment in hardware.

Reconstructing merger timelines using star cluster age distributions: the case of MCG+08-11-002

NASA Astrophysics Data System (ADS)

Davies, Rebecca L.; Medling, Anne M.; U, Vivian; Max, Claire E.; Sanders, David; Kewley, Lisa J.

2016-05-01

We present near-infrared imaging and integral field spectroscopy of the centre of the dusty luminous infrared galaxy merger MCG+08-11-002, taken using the Near InfraRed Camera 2 (NIRC2) and the OH-Suppressing InfraRed Imaging Spectrograph (OSIRIS) on Keck II. We achieve a spatial resolution of ˜25 pc in the K band, allowing us to resolve 41 star clusters in the NIRC2 images. We calculate the ages of 22/25 star clusters within the OSIRIS field using the equivalent widths of the CO 2.3 μm absorption feature and the Br γ nebular emission line. The star cluster age distribution has a clear peak at ages ≲ 20 Myr, indicative of current starburst activity associated with the final coalescence of the progenitor galaxies. There is a possible second peak at ˜65 Myr which may be a product of the previous close passage of the galaxy nuclei. We fit single and double starburst models to the star cluster age distribution and use Monte Carlo sampling combined with two-sided Kolmogorov-Smirnov tests to calculate the probability that the observed data are drawn from each of the best-fitting distributions. There is a >90 per cent chance that the data are drawn from either a single or double starburst star formation history, but stochastic sampling prevents us from distinguishing between the two scenarios. Our analysis of MCG+08-11-002 indicates that star cluster age distributions provide valuable insights into the timelines of galaxy interactions and may therefore play an important role in the future development of precise merger stage classification systems.

The very massive star content of the nuclear star clusters in NGC 5253

NASA Astrophysics Data System (ADS)

Smith, Linda J.; Crowther, Paul A.; Calzetti, Daniela

2017-11-01

The blue compact dwarf galaxy NGC 5253 hosts a very young starburst containing twin nuclear star clusters. Calzetti et al. (2015) find that the two clusters have an age of 1 Myr, in contradiction to the age of 3-5 Myr inferred from the presence of Wolf-Rayet (W-R) spectral features. We use Hubble Space Telescope (HST) far-ultraviolet (FUV) and ground-based optical spectra to show that the cluster stellar features arise from very massive stars (VMS), with masses greater than 100 M⊙, at an age of 1-2 Myr. We discuss the implications of this and show that the very high ionizing flux can only be explained by VMS. We further discuss our findings in the context of VMS contributing to He ii λ1640 emission in high redshift galaxies, and emphasize that population synthesis models with upper mass cut-offs greater than 100 M⊙ are crucial for future studies of young massive clusters.

Determining the Ages and Distances of 4 Open Clusters

NASA Astrophysics Data System (ADS)

Sawczynec, Erica A.; James D. Armstrong, Joe M. Ritter, Jeff Kuhn

2018-01-01

The study of nearby young open clusters can give insight into star formation and potentially the local rate of metal enrichment. Presented is a BVRI photometric analysis of 4 open clusters; NGC 2509, NGC 2483, NGC 2482, and NGC 6705, in order to reevaluate previously published ages and distances using modern CCD photometry, and newer stellar models. Observations were obtained from the Cerro Tololo node of the Las Cumbres Observatory 1.0 meter network. Color magnitude diagrams were compared to modeled isochrones and the updated ages and distances determined. An interesting stellar association was found in the color magnitude diagram of NGC 6705. The structure is suggestive of two epochs of stellar formation. Members of this structure were evaluated using the Gaia Archive in order to explore the possibility of a heterogeneous population. The status of NGC 2483 as an open cluster has been debated; however, it has been noted that there is a high concentration of Be stars found in the region. It is concluded that NGC 2483 is an open cluster.

Color-magnitude diagram of Palomar 4 - CCD photometry

NASA Astrophysics Data System (ADS)

Christian, C. A.; Heasley, J. N.

1986-04-01

Photometry of the globular cluster Pal 4 was obtained with the RCA CCD camera on the 3.6 m Canada-France-Hawaii Telescope on Mauna Kea. The color-magnitude diagram of the cluster shows a well-defined red horizontal branch, typical of outer halo systems, and an asymptotic giant branch well separated from the giant branch. The population of Pal 4 has been sampled to the main-sequence turnoff region (V = 25), allowing a detailed comparison of this distant object with theoretical models. The cluster parameters consistent with the CCD data are (m - M)0 = 20.1 + or - 0.1 mag, E(B - V) = 0.02 + or - 0.02, and Fe/H forbidden line = -1.7 + or - 0.1 with Y =0.2. The age of the cluster, determined by comparison with the isochrones of VandenBerg and Bell (1985) is consistent with an age of 15 + or - 1 Gyr, similar to inner halo globular clusters with ages determined in the same way.

White Dwarfs in Star Clusters: The Initial-Final Mass Relation for Stars from 0.85 to 8 M$_\\odot$

NASA Astrophysics Data System (ADS)

Cummings, Jeffrey; Kalirai, Jason; Tremblay, P.-E.; Ramírez-Ruiz, Enrico

2018-01-01

The spectroscopic study of white dwarfs provides both their mass, cooling age, and intrinsic photometric properties. For white dwarfs in the field of well-studied star clusters, this intrinsic photometry can be used to determine if they are members of that star cluster. Comparison of a member white dwarf's cooling age to its total cluster's age provides the evolutionary timescale of its progenitor star, and hence the mass. This is the initial-final mass relation (IFMR) for stars, which gives critical information on how a progenitor star evolves and loses mass throughout its lifetime, and how this changes with progenitor mass. Our work, for the first time, presents a uniform analysis of 85 white dwarf cluster members spanning from progenitor masses of 0.85 to 8 M$_\\odot$. Comparison of our work to theoretical IFMRs shows remarkable consistency in their shape but differences remain. We will discuss possible explanations for these differences, including the effects of stellar rotation.

Unique relations between counterfactual thinking and DSM-5 PTSD symptom clusters.

PubMed

Mitchell, Melissa A; Contractor, Ateka A; Dranger, Paula; Shea, M Tracie

2016-05-01

Cognitive models of posttraumatic stress disorder (PTSD) propose that rumination about a trauma may increase particular symptom clusters. One type of rumination, termed counterfactual thinking (CFT), refers to thinking of alternative outcomes for an event. CFT centered on a trauma is thought to increase intrusions, negative alterations in mood and cognitions (NAMC), and marked alterations in arousal and reactivity (AAR). The theorized relations between CFT and specific symptom clusters have not been thoroughly investigated. Also, past work has not evaluated whether the relation is confounded by depressive symptoms, age, gender, or number of traumatic events experienced. The current study examined the unique associations between CFT and PTSD symptom clusters according to the Diagnostic and Statistical Manual of Mental Disorders (American Psychiatric Association, 2013) in 51 trauma-exposed treatment-seeking individuals. As predicted, CFT was associated with all PTSD symptom clusters. After controlling for common predictors of PTSD symptom severity (i.e., age, depressive symptoms, and number of traumatic life events endorsed), we found CFT to be significantly associated with the intrusion and avoidance symptom clusters but not the AAR or NAMC symptom clusters. Results from the present study provide further support for the role of rumination in specific PTSD symptom clusters above and beyond symptoms of depression, age, and number of traumatic life events endorsed. Future work may consider investigating interventions to reduce rumination in PTSD. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

The Structure of the Young Star Cluster NGC 6231. II. Structure, Formation, and Fate

NASA Astrophysics Data System (ADS)

Kuhn, Michael A.; Getman, Konstantin V.; Feigelson, Eric D.; Sills, Alison; Gromadzki, Mariusz; Medina, Nicolás; Borissova, Jordanka; Kurtev, Radostin

2017-12-01

The young cluster NGC 6231 (stellar ages ˜2-7 Myr) is observed shortly after star formation activity has ceased. Using the catalog of 2148 probable cluster members obtained from Chandra, VVV, and optical surveys (Paper I), we examine the cluster’s spatial structure and dynamical state. The spatial distribution of stars is remarkably well fit by an isothermal sphere with moderate elongation, while other commonly used models like Plummer spheres, multivariate normal distributions, or power-law models are poor fits. The cluster has a core radius of 1.2 ± 0.1 pc and a central density of ˜200 stars pc-3. The distribution of stars is mildly mass segregated. However, there is no radial stratification of the stars by age. Although most of the stars belong to a single cluster, a small subcluster of stars is found superimposed on the main cluster, and there are clumpy non-isotropic distributions of stars outside ˜4 core radii. When the size, mass, and age of NGC 6231 are compared to other young star clusters and subclusters in nearby active star-forming regions, it lies at the high-mass end of the distribution but along the same trend line. This could result from similar formation processes, possibly hierarchical cluster assembly. We argue that NGC 6231 has expanded from its initial size but that it remains gravitationally bound.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salinas, R.; Pajkos, M. A.; Strader, J.

Intermediate-age star clusters in the Large Magellanic Cloud show extended main sequence turnoffs (MSTOs) that are not consistent with a canonical single stellar population. These broad turnoffs have been interpreted as evidence for extended star formation and/or stellar rotation. Since most of these studies use single frames per filter to do the photometry, the presence of variable stars near the MSTO in these clusters has remained unnoticed and their impact has been totally ignored. We model the influence of Delta Scuti using synthetic CMDs, adding variable stars following different levels of incidence and amplitude distributions. We show that Delta Scutimore » observed at a single phase will produce a broadening of the MSTO without affecting other areas of a CMD such as the upper MS or the red clump; furthermore, the amount of spread introduced correlates with cluster age, as observed. This broadening is constrained to ages ∼1–3 Gyr when the MSTO area crosses the instability strip, which is also consistent with observations. Variable stars cannot explain bifurcarted MSTOs or the extended MSTOs seen in some young clusters, but they can make an important contribution to the extended MSTOs in intermediate-age clusters.« less

Automated detection of case clusters of waterborne acute gastroenteritis from health insurance data - pilot study in three French districts.

PubMed

Rambaud, Loïc; Galey, Catherine; Beaudeau, Pascal

2016-04-01

This pilot study was conducted to assess the utility of using a health insurance database for the automated detection of waterborne outbreaks of acute gastroenteritis (AGE). The weekly number of AGE cases for which the patient consulted a doctor (cAGE) was derived from this database for 1,543 towns in three French districts during the 2009-2012 period. The method we used is based on a spatial comparison of incidence rates and of their time trends between the target town and the district. Each municipality was tested, week by week, for the entire study period. Overall, 193 clusters were identified, 10% of the municipalities were involved in at least one cluster and less than 2% in several. We can infer that nationwide more than 1,000 clusters involving 30,000 cases of cAGE each year may be linked to tap water. The clusters discovered with this automated detection system will be reported to local operators for investigation of the situations at highest risk. This method will be compared with others before automated detection is implemented on a national level.

Investigating Open Clusters Melotte 111 and NGC 6811

NASA Astrophysics Data System (ADS)

Gunshefski, Linda; Paust, Nathaniel E. Q.; van Belle, Gerard

2018-01-01

We present photometry and color-magnitude diagrams for the open clusters Melotte 111 (Coma Bernices) and NGC 6811. These clusters were observed with Lowell Observatory’s Discovery Channel Telescope Large Monolithic Imager in the V and I bands. The images were reduced with IRAF and photometry was performed with DAOPHOT/ALLSTAR. The resulting photometry extends many magnitudes below the main sequence turnoff. Both clusters are located nearby, (Melotte 111 d=86 pc and NGC 6811 d=1,107) and are evolutionarily young (Melotte 111, age=450 Myr and NGC 6811, age=1,000 Myr). This work marks the first step of a project to determine the cluster main sequence mass functions and examine how the mass functions evolve in young stellar populations.

School climate and continuity of adolescent personality disorder symptoms.

PubMed

Kasen, Stephanie; Cohen, Patricia; Chen, Henian; Johnson, Jeffrey G; Crawford, Thomas N

2009-12-01

Schools are key social contexts for shaping development and behavior in youths; yet, little is known of their influence on adolescent personality disturbance. A community-based sample of 592 adolescents was assessed for family and school experiences, Axis I psychiatric disorders, and Axis II personality disorder (PD) symptoms, and followed into young adulthood. Multiple regression analysis was used to estimate associations between adolescent-reported school climate and young adult PD symptoms independent of age, sex, family socioeconomic status; childhood maltreatment; Axis I disorder, PD symptoms, academic grades, and parental punishment in adolescence; and four dimensions of school climate. Schools characterized as high in learning focus were related to cluster B (antisocial, borderline, histrionic, and narcissistic PD) symptom declines, whereas schools characterized as high in opportunities for student autonomy were related to cluster A (paranoid, schizoid, and schizotypal PD) symptom declines. In contrast, schools characterized as conflictual or supporting interpersonal informality/familiarity among students and teachers were related to increases in cluster A symptoms and cluster C (avoidant, dependent, and obsessive-compulsive PD) symptoms. Schools may exert both positive and negative influences on continuity of adolescent personality disturbance. The role of the school in guiding young people toward more favorable developmental pathways and alleviating personality disturbance is discussed.

Upgrading of the LGD cluster at JINR to support DLNP experiments

NASA Astrophysics Data System (ADS)

Bednyakov, I. V.; Dolbilov, A. G.; Ivanov, Yu. P.

2017-01-01

Since its construction in 2005, the Computing Cluster of the Dzhelepov Laboratory of Nuclear Problems has been mainly used to perform calculations (data analysis, simulation, etc.) for various scientific collaborations in which DLNP scientists take an active part. The Cluster also serves to train specialists. Much has changed in the past decades, and the necessity has arisen to upgrade the cluster, increasing its power and replacing the outdated equipment to maintain its reliability and modernity. In this work we describe the experience of performing this upgrading, which can be helpful for system administrators to put new equipment for clusters of this type into operation quickly and efficiently.

The Evolutionary Status of Be Stars: Results from a Photometric Study of Southern Open Clusters

NASA Astrophysics Data System (ADS)

McSwain, M. Virginia; Gies, Douglas R.

2005-11-01

Be stars are a class of rapidly rotating B stars with circumstellar disks that cause Balmer and other line emission. There are three possible reasons for the rapid rotation of Be stars: they may have been born as rapid rotators, spun up by binary mass transfer, or spun up during the main-sequence (MS) evolution of B stars. To test the various formation scenarios, we have conducted a photometric survey of 55 open clusters in the southern sky. Of these, five clusters are probably not physically associated groups and our results for two other clusters are not reliable, but we identify 52 definite Be stars and an additional 129 Be candidates in the remaining clusters. We use our results to examine the age and evolutionary dependence of the Be phenomenon. We find an overall increase in the fraction of Be stars with age until 100 Myr, and Be stars are most common among the brightest, most massive B-type stars above the zero-age main sequence (ZAMS). We show that a spin-up phase at the terminal-age main sequence (TAMS) cannot produce the observed distribution of Be stars, but up to 73% of the Be stars detected may have been spun-up by binary mass transfer. Most of the remaining Be stars were likely rapid rotators at birth. Previous studies have suggested that low metallicity and high cluster density may also favor Be star formation. Our results indicate a possible increase in the fraction of Be stars with increasing cluster distance from the Galactic center (in environments of decreasing metallicity). However, the trend is not significant and could be ruled out due to the intrinsic scatter in our data. We also find no relationship between the fraction of Be stars and cluster density.

The association between content of the elements S, Cl, K, Fe, Cu, Zn and Br in normal and cirrhotic liver tissue from Danes and Greenlandic Inuit examined by dual hierarchical clustering analysis.

PubMed

Laursen, Jens; Milman, Nils; Pind, Niels; Pedersen, Henrik; Mulvad, Gert

2014-01-01

Meta-analysis of previous studies evaluating associations between content of elements sulphur (S), chlorine (Cl), potassium (K), iron (Fe), copper (Cu), zinc (Zn) and bromine (Br) in normal and cirrhotic autopsy liver tissue samples. Normal liver samples from 45 Greenlandic Inuit, median age 60 years and from 71 Danes, median age 61 years. Cirrhotic liver samples from 27 Danes, median age 71 years. Element content was measured using X-ray fluorescence spectrometry. Dual hierarchical clustering analysis, creating a dual dendrogram, one clustering element contents according to calculated similarities, one clustering elements according to correlation coefficients between the element contents, both using Euclidian distance and Ward Procedure. One dendrogram separated subjects in 7 clusters showing no differences in ethnicity, gender or age. The analysis discriminated between elements in normal and cirrhotic livers. The other dendrogram clustered elements in four clusters: sulphur and chlorine; copper and bromine; potassium and zinc; iron. There were significant correlations between the elements in normal liver samples: S was associated with Cl, K, Br and Zn; Cl with S and Br; K with S, Br and Zn; Cu with Br. Zn with S and K. Br with S, Cl, K and Cu. Fe did not show significant associations with any other element. In contrast to simple statistical methods, which analyses content of elements separately one by one, dual hierarchical clustering analysis incorporates all elements at the same time and can be used to examine the linkage and interplay between multiple elements in tissue samples. Copyright © 2013 Elsevier GmbH. All rights reserved.

Stellar Populations and Radial Migrations in Virgo Disk Galaxies

NASA Astrophysics Data System (ADS)

Roediger, Joel C.; Courteau, Stéphane; Sánchez-Blázquez, Patricia; McDonald, Michael

2012-10-01

We present new stellar age profiles, derived from well-resolved optical and near-infrared images of 64 Virgo cluster disk galaxies, whose analysis poses a challenge for current disk galaxy formation models. Our ability to break the age-metallicity degeneracy and the significant size of our sample represent key improvements over complementary studies of field disk galaxies. Our results can be summarized as follows: first, and contrary to observations of disk galaxies in the field, these cluster galaxies are distributed almost equally amongst the three main types of disk galaxy luminosity profiles (I/II/III), indicating that the formation and/or survival of Type II breaks is suppressed within the cluster environment. Second, we find examples of statistically significant inversions ("U-shapes") in the age profiles of all three disk galaxy types, reminiscent of predictions from high-resolution simulations of classically truncated Type II disks in the field. These features characterize the age profiles for only about a third (<=36%) of each disk galaxy type in our sample. An even smaller fraction of cluster disks (~11% of the total sample) exhibit age profiles that decrease outward (i.e., negative age gradients). Instead, flat and/or positive age gradients prevail (>=50%) within our Type I, II, and III subsamples. These observations thus suggest that while stellar migrations and inside-out growth can play a significant role in the evolution of all disk galaxy types, other factors contributing to the evolution of galaxies can overwhelm the predicted signatures of these processes. We interpret our observations through a scenario whereby Virgo cluster disk galaxies formed initially like their brethren in the field but which, upon falling into the cluster, were transformed into their present state through external processes linked to the environment (e.g., ram-pressure stripping and harassment). Current disk galaxy formation models, which have largely focused on field galaxies, fail to reproduce these results, thus calling for adequate hydrodynamical simulations of dense galaxy environments if we are to understand cluster disks. The current paper highlights numerous constraints for such simulations. In the Appendix, we confirm the claim by Erwin et al. that Type II breaks are absent in Virgo cluster S0s and discuss the detection of Type III breaks in such galaxies.

Just the right age: well-clustered exposure ages from a global glacial 10Be compilation

NASA Astrophysics Data System (ADS)

Heyman, Jakob; Margold, Martin

2017-04-01

Cosmogenic exposure dating has been used extensively for defining glacial chronologies, both in ice sheet and alpine settings, and the global set of published ages today reaches well beyond 10,000 samples. Over the last few years, a number of important developments have improved the measurements (with well-defined AMS standards) and exposure age calculations (with updated data and methods for calculating production rates), in the best case enabling high precision dating of past glacial events. A remaining problem, however, is the fact that a large portion of all dated samples have been affected by prior and/or incomplete exposure, yielding erroneous exposure ages under the standard assumptions. One way to address this issue is to only use exposure ages that can be confidently considered as unaffected by prior/incomplete exposure, such as groups of samples with statistically identical ages. Here we use objective statistical criteria to identify groups of well-clustered exposure ages from the global glacial "expage" 10Be compilation. Out of ˜1700 groups with at least 3 individual samples ˜30% are well-clustered, increasing to ˜45% if allowing outlier rejection of a maximum of 1/3 of the samples (still requiring a minimum of 3 well-clustered ages). The dataset of well-clustered ages is heavily dominated by ages <30 ka, showing that well-defined cosmogenic chronologies primarily exist for the last glaciation. We observe a large-scale global synchronicity in the timing of the last deglaciation from ˜20 to 10 ka. There is also a general correlation between the timing of deglaciation and latitude (or size of the individual ice mass), with earlier deglaciation in lower latitudes and later deglaciation towards the poles. Grouping the data into regions and comparing with available paleoclimate data we can start to untangle regional differences in the last deglaciation and the climate events controlling the ice mass loss. The extensive dataset and the statistical analysis enables an unprecedented global view on the last deglaciation.

Star clusters and K2

NASA Astrophysics Data System (ADS)

Dotson, Jessie; Barentsen, Geert; Cody, Ann Marie

2018-01-01

The K2 survey has expanded the Kepler legacy by using the repurposed spacecraft to observe over 20 star clusters. The sample includes open and globular clusters at all ages, including very young (1-10 Myr, e.g. Taurus, Upper Sco, NGC 6530), moderately young (0.1-1 Gyr, e.g. M35, M44, Pleiades, Hyades), middle-aged (e.g. M67, Ruprecht 147, NGC 2158), and old globular clusters (e.g. M9, M19, Terzan 5). K2 observations of stellar clusters are exploring the rotation period-mass relationship to significantly lower masses than was previously possible, shedding light on the angular momentum budget and its dependence on mass and circumstellar disk properties, and illuminating the role of multiplicity in stellar angular momentum. Exoplanets discovered by K2 in stellar clusters provides planetary systems ripe for modeling given the extensive information available about their ages and environment. I will review the star clusters sampled by K2 across 16 fields so far, highlighting several characteristics, caveats, and unexplored uses of the public data set along the way. With fuel expected to run out in 2018, I will discuss the closing Campaigns, highlight the final target selection opportunities, and explain the data archive and TESS-compatible software tools the K2 mission intends to leave behind for posterity.

Clustering performances in the NBA according to players' anthropometric attributes and playing experience.

PubMed

Zhang, Shaoliang; Lorenzo, Alberto; Gómez, Miguel-Angel; Mateus, Nuno; Gonçalves, Bruno; Sampaio, Jaime

2018-04-20

The aim of this study was: (i) to group basketball players into similar clusters based on a combination of anthropometric characteristics and playing experience; and (ii) explore the distribution of players (included starters and non-starters) from different levels of teams within the obtained clusters. The game-related statistics from 699 regular season balanced games were analyzed using a two-step cluster model and a discriminant analysis. The clustering process allowed identifying five different player profiles: Top height and weight (HW) with low experience, TopHW-LowE; Middle HW with middle experience, MiddleHW-MiddleE; Middle HW with top experience, MiddleHW-TopE; Low HW with low experience, LowHW-LowE; Low HW with middle experience, LowHW-MiddleE. Discriminant analysis showed that TopHW-LowE group was highlighted by two-point field goals made and missed, offensive and defensive rebounds, blocks, and personal fouls; whereas the LowHW-LowE group made fewest passes and touches. The players from weaker teams were mostly distributed in LowHW-LowE group, whereas players from stronger teams were mainly grouped in LowHW-MiddleE group; and players that participated in the finals were allocated in the MiddleHW-MiddleE group. These results provide alternative references for basketball staff concerning the process of evaluating performance.

Dating star clusters in the Small Magellanic Cloud by means of integrated spectra

NASA Astrophysics Data System (ADS)

Ahumada, A. V.; Clariá, J. J.; Bica, E.; Dutra, C. M.

2002-10-01

In this study flux-calibrated integrated spectra in the range (3600-6800) Å are presented for 16 concentrated star clusters in the Small Magellanic Cloud (SMC), approximately half of which constitute unstudied objects. We have estimated ages and foreground interstellar reddening values from the comparison of the line strengths and continuum distribution of the cluster spectra with those of template cluster spectra with known parameters. Most of the sample clusters are young blue clusters (6-50 Myr), while L 28, NGC 643 and L 114 are found to be intermediate-age clusters (1-6 Gyr). One well known SMC cluster (NGC 416) was observed for comparison purposes. The sample includes clusters in the surroundings and main body of the SMC, and the derived foreground reddening values are in the range 0.00 <= E(B-V) <= 0.15. The present data also make up a cluster spectral library at SMC metallicity. Based on observations made at Complejo Astronómico El Leoncito, which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba and San Juan, Argentina.

Physically and sexually violent experiences of reproductive-aged women displaced by Hurricane Katrina.

PubMed

Picardo, Carla W; Burton, Shirley; Naponick, John

2010-01-01

Measure the frequency of physical and sexual abuse in a sample of reproductive aged women displaced by Hurricane Katrina, and compare those experiences to the year before Hurricane Katrina. Sixty-six English-speaking women aged 18-49 years residing in Louisiana Federal Emergency Management Agency (FEMA) housing were screened for physical and sexual abuse seven to nine months after Hurricane Katrina, using modified 30x7 cluster sampling methodology. Twenty-three percent (95% confidence interval [CI], 14, 34%) of women reported being hit or verbally threatened since Hurricane Katrina. Abuse had increased for 33% (95% CI, 13, 63%) and decreased for 13% (95% CI, 4, 37%) of women. Twenty percent (95% CI, 6, 51%) of abused women were with a new partner, while 13% (95% CI, 4, 39%) reported new abuse with the same partner. Four women reported sexual abuse since Hurricane Katrina. Compared to before the storm, the frequency of sexual abuse was the same for two women, and one reported new abuse with the same partner. Physical abuse was not uncommon among displaced women following Hurricane Katrina. Increasing and new abuse were the most commonly reported experiences. Violence against women should not be overlooked as a continued, and perhaps escalating, occurrence requiring attention following displacement after disasters of such magnitude as Hurricane Katrina.

Extended Main-sequence Turn-offs in Intermediate-age Star Clusters: Stellar Rotation Diminishes, but Does Not Eliminate, Age Spreads

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goudfrooij, Paul; Correnti, Matteo; Girardi, Léo, E-mail: goudfroo@stsci.edu

Extended main-sequence turn-off (eMSTO) regions are a common feature in color–magnitude diagrams of young- and intermediate-age star clusters in the Magellanic Clouds. The nature of eMSTOs remains debated in the literature. The currently most popular scenarios are extended star formation activity and ranges of stellar rotation rates. Here we study details of differences in main-sequence turn-off (MSTO) morphology expected from spreads in age versus spreads in rotation rates, using Monte Carlo simulations with the Geneva syclist isochrone models that include the effects of stellar rotation. We confirm a recent finding of Niederhofer et al. that a distribution of stellar rotationmore » velocities yields an MSTO extent that is proportional to the cluster age, as observed. However, we find that stellar rotation yields MSTO crosscut widths that are generally smaller than observed ones at a given age. We compare the simulations with high-quality Hubble Space Telescope data of NGC 1987 and NGC 2249, which are the two only relatively massive star clusters with an age of ∼1 Gyr for which such data is available. We find that the distribution of stars across the eMSTOs of these clusters cannot be explained solely by a distribution of stellar rotation velocities, unless the orientations of rapidly rotating stars are heavily biased toward an equator-on configuration. Under the assumption of random viewing angles, stellar rotation can account for ∼60% and ∼40% of the observed FWHM widths of the eMSTOs of NGC 1987 and NGC 2249, respectively. In contrast, a combination of distributions of stellar rotation velocities and stellar ages fits the observed eMSTO morphologies very well.« less

Ages of LMC star clusters using ASAD2

NASA Astrophysics Data System (ADS)

Asa'd, Randa S.; Vazdekis, Alexandre; Zeinelabdin, Sami

2016-04-01

We use ASAD2, the new version of ASAD (Analyzer of Spectra for Age Determination), to obtain the age and reddening of 27 Large Magellanic Cloud (LMC) clusters from full fitting of integrated spectra using different statistical methods [χ2 and Kolmogorov-Smirnov (KS) test] and a set of stellar population models including GALAXEV and MILES. We show that our results are in good agreement with the colour-magnitude diagram (CMD) ages for both models, and that metallicity does not affect the age determination for the full spectrum fitting method regardless of the model used for ages with log (age/year) < 9. We discuss the results obtained by the two statistical results for both GALAXEV and MILES versus three factors: age, signal-to-noise ratio and resolution (full width at half maximum). The predicted reddening values when using the χ2 minimization method are within the range found in the literature for resolved clusters (I.e. <0.35); however the KS test can predict E(B - V) higher values. The sharp spectrum transition originated at ages around the supergiants contribution, at either side of the AGB peak around log (age/year) 9.0 and log (age/year) 7.8 are limiting our ability to provide values in agreement with the CMD estimates and as a result the reddening determination is not accurate. We provide the detailed results of four clusters spanning a wide range of ages. ASAD2 is a user-friendly program available for download on the Web and can be immediately used at http://randaasad.wordpress.com/asad-package/.

Globular cluster chemistry in fast-rotating dwarf stars belonging to intermediate-age open clusters

NASA Astrophysics Data System (ADS)

Pancino, Elena

2018-06-01

The peculiar chemistry observed in multiple populations of Galactic globular clusters is not generally found in other systems such as dwarf galaxies and open clusters, and no model can currently fully explain it. Exploring the boundaries of the multiple-population phenomenon and the variation of its extent in the space of cluster mass, age, metallicity, and compactness has proven to be a fruitful line of investigation. In the framework of a larger project to search for multiple populations in open clusters that is based on literature and survey data, I found peculiar chemical abundance patterns in a sample of intermediate-age open clusters with publicly available data. More specifically, fast-rotating dwarf stars (v sin i ≥ 50 km s-1) that belong to four clusters (Pleiades, Ursa Major, Come Berenices, and Hyades) display a bimodality in either [Na/Fe] or [O/Fe], or both, with the low-Na and high-O peak more populated than the high-Na and low-O peak. Additionally, two clusters show a Na-O anti-correlation in the fast-rotating stars, and one cluster shows a large [Mg/Fe] variation in stars with high [Na/Fe], reaching the extreme Mg depletion observed in NGC 2808. Even considering that the sample sizes are small, these patterns call for attention in the light of a possible connection with the multiple population phenomenon of globular clusters. The specific chemistry observed in these fast-rotating dwarf stars is thought to be produced by a complex interplay of different diffusion and mixing mechanisms, such as rotational mixing and mass loss, which in turn are influenced by metallicity, binarity, mass, age, variability, and so on. However, with the sample in hand, it was not possible to identify which stellar parameters cause the observed Na and O bimodality and Na-O anti-correlation. This suggests that other stellar properties might be important in addition to stellar rotation. Stellar binarity might influence the rotational properties and enhance rotational mixing and mass loss of stars in a dense environment like that of clusters (especially globulars). In conclusion, rotation and binarity appear as a promising research avenue for better understanding multiple stellar populations in globular clusters; this is certainly worth exploring further.

Comorbid personality traits in schizophrenia: prevalence and clinical characteristics.

PubMed

Moore, Elizabeth A; Green, Melissa J; Carr, Vaughan J

2012-03-01

Accumulating evidence suggests high rates of personality disorder (PD) in schizophrenia (Sz), and as such, the implications of PD in this context are beginning to be studied more thoroughly. We examined clinical, cognitive and experiential (i.e., reported childhood adversity) correlates of aberrant personality traits in schizophrenia and healthy controls (HC) as measured by the International Personality Disorder Examination Questionnaire (IPDEQ). Participants were 549 individuals with schizophrenia or schizoaffective disorder, and 572 healthy adults recruited to the Australian Schizophrenia Research Bank (ASRB). Schizophrenia participants were significantly more likely than healthy controls to screen positive for personality disorder across all ICD-10 subtypes, and there was substantial overlap between clusters, with ∼33% of Sz participants screening positive for all 3 personality disorder clusters. Among both Sz and HC groups, cluster B personality characteristics were significantly associated with increased suicidal behaviours, lower cognitive performance, and the experience of childhood adversity. In addition, Cluster C personality features were associated with higher overall ratings of affective blunting in schizophrenia, and Cluster A personality features were associated with childhood 'loss' in HC participants only. The cumulative effects of screening positive for more than one personality disorder in Sz was associated with higher likelihood of suicidal behaviour, earlier age of onset of Sz, and poorer cognitive functioning. The results suggest that abnormal co-occurrence of personality traits across DSM-IV clusters is evident in a significant proportion of individuals with schizophrenia, and that these personality features impact significantly on clinical and cognitive characteristics of Sz. Copyright © 2011 Elsevier Ltd. All rights reserved.

Measuring galaxy cluster masses with CMB lensing using a Maximum Likelihood estimator: statistical and systematic error budgets for future experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raghunathan, Srinivasan; Patil, Sanjaykumar; Bianchini, Federico

We develop a Maximum Likelihood estimator (MLE) to measure the masses of galaxy clusters through the impact of gravitational lensing on the temperature and polarization anisotropies of the cosmic microwave background (CMB). We show that, at low noise levels in temperature, this optimal estimator outperforms the standard quadratic estimator by a factor of two. For polarization, we show that the Stokes Q/U maps can be used instead of the traditional E- and B-mode maps without losing information. We test and quantify the bias in the recovered lensing mass for a comprehensive list of potential systematic errors. Using realistic simulations, wemore » examine the cluster mass uncertainties from CMB-cluster lensing as a function of an experiment's beam size and noise level. We predict the cluster mass uncertainties will be 3 - 6% for SPT-3G, AdvACT, and Simons Array experiments with 10,000 clusters and less than 1% for the CMB-S4 experiment with a sample containing 100,000 clusters. The mass constraints from CMB polarization are very sensitive to the experimental beam size and map noise level: for a factor of three reduction in either the beam size or noise level, the lensing signal-to-noise improves by roughly a factor of two.« less

The Relationship Between Problem Gambling and Attention Deficit Hyperactivity Disorder.

PubMed

Waluk, O R; Youssef, G J; Dowling, N A

2016-06-01

Recent studies indicate that treatment-seeking problem gamblers display elevated rates of ADHD and that adolescents who screen positive for ADHD are more likely to engage in gambling, develop gambling problems, and experience a greater severity in gambling problems. This study aimed to (a) compare the prevalence of ADHD in treatment-seeking problem gamblers to the general population; (b) investigate the relationships between ADHD and problem gambling severity, cluster B personality disorders, motor impulsivity, alcohol use, substance use, gender, and age; and (c) investigate the degree to which these factors moderate the relationship between ADHD and problem gambling severity. Participants included 214 adults (154 males, 58 females, 2 unspecified) who sought treatment for their gambling problems at a specialist gambling agency in Melbourne, Australia. Almost one-quarter (24.9 %) of treatment-seeking problem gamblers screened positively for ADHD, which was significantly higher than the 14 % prevalence in a community sample. ADHD was significantly positively correlated with problem gambling severity, motor impulsivity, and cluster B personality disorders, but was not associated with alcohol and substance use, gender or age. None of the factors significantly moderated the relationship between ADHD and problem gambling severity. These findings suggest that a considerable proportion of treatment-seeking problem gamblers report ADHD and that their clinical profile is complicated by the presence of high impulsivity and cluster B personality disorders. They highlight the need for specialist gambling agencies to develop screening, assessment, and management protocols for co-occurring ADHD to enhance the effectiveness of treatment.

Proposed shade guide for human facial skin and lip: a pilot study.

PubMed

Wee, Alvin G; Beatty, Mark W; Gozalo-Diaz, David J; Kim-Pusateri, Seungyee; Marx, David B

2013-08-01

Currently, no commercially available facial shade guide exists in the United States for the fabrication of facial prostheses. The purpose of this study was to measure facial skin and lip color in a human population sample stratified by age, gender, and race. Clustering analysis was used to determine optimal color coordinates for a proposed facial shade guide. Participants (n=119) were recruited from 4 racial/ethnic groups, 5 age groups, and both genders. Reflectance measurements of participants' noses and lower lips were made by using a spectroradiometer and xenon arc lamp with a 45/0 optical configuration. Repeated measures ANOVA (α=.05), to identify skin and lip color differences, resulting from race, age, gender, and location, and a hierarchical clustering analysis, to identify clusters of skin colors) were used. Significant contributors to L*a*b* facial color were race and facial location (P<.01). b* affected all factors (P<.05). Age affected only b* (P<.001), while gender affected only L* (P<.05) and b* (P<.05). Analyses identified 5 clusters of skin color. The study showed that skin color caused by age and gender primarily occurred within the yellow-blue axis. A significant lightness difference between gender groups was also found. Clustering analysis identified 5 distinct skin shade tabs. Copyright © 2013 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

Young LMC clusters: the role of red supergiants and multiple stellar populations in their integrated light and CMDs

NASA Astrophysics Data System (ADS)

Asa'd, Randa S.; Vazdekis, Alexandre; Cerviño, Miguel; Noël, Noelia E. D.; Beasley, Michael A.; Kassab, Mahmoud

2017-11-01

The optical integrated spectra of three Large Magellanic Cloud young stellar clusters (NGC 1984, NGC 1994 and NGC 2011) exhibit concave continua and prominent molecular bands which deviate significantly from the predictions of single stellar population (SSP) models. In order to understand the appearance of these spectra, we create a set of young stellar population (MILES) models, which we make available to the community. We use archival International Ultraviolet Explorer integrated UV spectra to independently constrain the cluster masses and extinction, and rule out strong stochastic effects in the optical spectra. In addition, we also analyse deep colour-magnitude diagrams of the clusters to provide independent age determinations based on isochrone fitting. We explore hypotheses, including age spreads in the clusters, a top-heavy initial mass function, different SSP models and the role of red supergiant stars (RSG). We find that the strong molecular features in the optical spectra can be only reproduced by modelling an increased fraction of about ˜20 per cent by luminosity of RSG above what is predicted by canonical stellar evolution models. Given the uncertainties in stellar evolution at Myr ages, we cannot presently rule out the presence of Myr age spreads in these clusters. Our work combines different wavelengths as well as different approaches (resolved data as well as integrated spectra for the same sample) in order to reveal the complete picture. We show that each approach provides important information but in combination we can better understand the cluster stellar populations.

X-Ray source populations in old open clusters: Collinder 261

NASA Astrophysics Data System (ADS)

Vats, Smriti; van den Berg, Maureen; Wijnands, Rudy

2014-09-01

We are carrying out an X-ray survey of old open clusters with the Chandra X-ray Observatory. Single old stars, being slow rotators, are very faint in X-rays (L_X < 1×10^27 erg/s). Hence, X-rays produced by mass transfer in cataclysmic variables (CVs) or by rapid rotation of the stars in tidally locked, detached binaries (active binaries; ABs) can be detected, without contamination from single stars. By comparing the properties of various types of interacting binaries in different environments (the Galactic field, old open clusters, globular clusters), we aim to study binary evolution and how it may be affected by dynamical encounters with other cluster stars. Stellar clusters are good targets to study binaries, as age, distance, chemical composition, are well constrained. Collinder (Cr) 261 is an old open cluster (age ~ 7 Gyr), with one of the richest populations inferred of close binaries and blue stragglers of all open clusters and is therefore an obvious target to study the products of close encounters in open clusters. We will present the first results of this study, detailing the low-luminosity X-ray population of Cr 261, in conjunction with other open clusters in our survey (NGC 188, Berkeley 17, NGC 6253, M67, NGC 6791) and in comparison with populations in globular clusters.

EVIDENCE FOR THE UNIVERSALITY OF PROPERTIES OF RED-SEQUENCE GALAXIES IN X-RAY- AND RED-SEQUENCE-SELECTED CLUSTERS AT z ∼ 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Foltz, R.; Wilson, G.; DeGroot, A.

We study the slope, intercept, and scatter of the color–magnitude and color–mass relations for a sample of 10 infrared red-sequence-selected clusters at z ∼ 1. The quiescent galaxies in these clusters formed the bulk of their stars above z ≳ 3 with an age spread Δt ≳ 1 Gyr. We compare UVJ color–color and spectroscopic-based galaxy selection techniques, and find a 15% difference in the galaxy populations classified as quiescent by these methods. We compare the color–magnitude relations from our red-sequence selected sample with X-ray- and photometric-redshift-selected cluster samples of similar mass and redshift. Within uncertainties, we are unable tomore » detect any difference in the ages and star formation histories of quiescent cluster members in clusters selected by different methods, suggesting that the dominant quenching mechanism is insensitive to cluster baryon partitioning at z ∼ 1.« less

Intraclass Correlations and Covariate Outcome Correlations for Planning Two-and Three-Level Cluster-Randomized Experiments in Education

ERIC Educational Resources Information Center

Hedges, Larry V.; Hedberg, E. C.

2013-01-01

Background: Cluster-randomized experiments that assign intact groups such as schools or school districts to treatment conditions are increasingly common in educational research. Such experiments are inherently multilevel designs whose sensitivity (statistical power and precision of estimates) depends on the variance decomposition across levels.…

Intraclass Correlations and Covariate Outcome Correlations for Planning 2 and 3 Level Cluster Randomized Experiments in Education

ERIC Educational Resources Information Center

Hedges, Larry V.; Hedberg, Eric C.

2013-01-01

Background: Cluster randomized experiments that assign intact groups such as schools or school districts to treatment conditions are increasingly common in educational research. Such experiments are inherently multilevel designs whose sensitivity (statistical power and precision of estimates) depends on the variance decomposition across levels.…

MSFC Skylab contamination control systems mission evaluation

NASA Technical Reports Server (NTRS)

1974-01-01

Cluster external contamination control evaluation was made throughout the Skylab Mission. This evaluation indicated that contamination control measures instigated during the design, development, and operational phases of this program were adequate to reduce the general contamination environment external to the Cluster below the threshold senstivity levels for experiments and affected subsystems. Launch and orbit contamination control features included eliminating certain vents, rerouting vents for minimum contamination impact, establishing filters, incorporating materials with minimum outgassing characteristics and developing operational constraints and mission rules to minimize contamination effects. Prior to the launch of Skylab, contamination control math models were developed which were used to predict Cluster surface deposition and background brightness levels throughout the mission. The report summarizes the Skylab system and experiment contamination control evaluation. The Cluster systems and experiments evaluated include Induced Atmosphere, Corollary and ATM Experiments, Thermal Control Surfaces, Solar Array Systems, Windows and Star Tracker.

Bangladesh Midlife Women's Health Study (BMWHS): methods, challenges and experiences.

PubMed

Islam, Rakibul M; Bell, Robin J; Hossain, Mohammad B; Davis, Susan R

2015-01-01

To understand the challenges and experiences encountered during data collection for Bangladesh Midlife Women's Health Study (BMWHS) that investigated the low uptake of cervical cancer (CCa) screening barriers, understanding of breast cancer (BCa) knowledge and practices, the prevalence of urinary and fecal incontinence and menopausal symptoms. A multistage cluster sampling technique was used to recruit women from the 32 districts of Bangladesh that had offered CCa screening. Female interviewers were trained to undertake structured face-to-face interviews that incorporated both non-validated and several validated questionnaires, such as Question for Urinary Incontinence Diagnosis, Pelvic Organ Prolapse Distress Inventory, Colorectal-Anal Distress Inventory and Menopause-Specific Quality of Life. We completed surveys of 1590 women, estimated age 30-59 years, between September 2013 and March 2014. We implemented several strategies to deal with low literacy and used the temporal relationship between marriage and childbirth, and the average age of onset of menarche, to estimate age. Cultural and religious sensitivities and personal security were managed by engaging community leaders, limiting activities to daylight hours, adopting local codes of dress, such as the wearing of head scarves. Our major challenges and experiences included difficulties in age determination, selection of and access to households, interview privacy, lack of basic and health literacy, transportation, political unrest and security of the interviewers. By anticipating challenges, we have been able to comprehensively survey a representative sample of Bangladeshi women. Disseminating information about the field challenges and experiences from the BMWHS should assist other researchers planning to conduct surveys about women's health issues in similar context. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

THE BRIGHTEST YOUNG STAR CLUSTERS IN NGC 5253

DOE Office of Scientific and Technical Information (OSTI.GOV)

Calzetti, D.; Johnson, K. E.; Adamo, A.

2015-10-01

The nearby dwarf starburst galaxy NGC 5253 hosts a number of young, massive star clusters, the two youngest of which are centrally concentrated and surrounded by thermal radio emission (the “radio nebula”). To investigate the role of these clusters in the starburst energetics, we combine new and archival Hubble Space Telescope images of NGC 5253 with wavelength coverage from 1500 Å to 1.9 μm in 13 filters. These include Hα, Pβ, and Pα, and the imaging from the Hubble Treasury Program LEGUS (Legacy Extragalactic UV Survey). The extraordinarily well-sampled spectral energy distributions enable modeling with unprecedented accuracy the ages, masses,more » and extinctions of the nine optically brightest clusters (M{sub V} < −8.8) and the two young radio nebula clusters. The clusters have ages ∼1–15 Myr and masses ∼1 × 10{sup 4}–2.5 × 10{sup 5} M{sub ⊙}. The clusters’ spatial location and ages indicate that star formation has become more concentrated toward the radio nebula over the last ∼15 Myr. The most massive cluster is in the radio nebula; with a mass ∼2.5 × 10{sup 5} M{sub ⊙} and an age ∼1 Myr, it is 2–4 times less massive and younger than previously estimated. It is within a dust cloud with A{sub V} ∼ 50 mag, and shows a clear near-IR excess, likely from hot dust. The second radio nebula cluster is also ∼1 Myr old, confirming the extreme youth of the starburst region. These two clusters account for about half of the ionizing photon rate in the radio nebula, and will eventually supply about 2/3 of the mechanical energy in present-day shocks. Additional sources are required to supply the remaining ionizing radiation, and may include very massive stars.« less

The Brightest Young Star Clusters in NGC 5253.

NASA Astrophysics Data System (ADS)

Calzetti, D.; Johnson, K. E.; Adamo, A.; Gallagher, J. S., III; Andrews, J. E.; Smith, L. J.; Clayton, G. C.; Lee, J. C.; Sabbi, E.; Ubeda, L.; Kim, H.; Ryon, J. E.; Thilker, D.; Bright, S. N.; Zackrisson, E.; Kennicutt, R. C.; de Mink, S. E.; Whitmore, B. C.; Aloisi, A.; Chandar, R.; Cignoni, M.; Cook, D.; Dale, D. A.; Elmegreen, B. G.; Elmegreen, D. M.; Evans, A. S.; Fumagalli, M.; Gouliermis, D. A.; Grasha, K.; Grebel, E. K.; Krumholz, M. R.; Walterbos, R.; Wofford, A.; Brown, T. M.; Christian, C.; Dobbs, C.; Herrero, A.; Kahre, L.; Messa, M.; Nair, P.; Nota, A.; Östlin, G.; Pellerin, A.; Sacchi, E.; Schaerer, D.; Tosi, M.

2015-10-01

The nearby dwarf starburst galaxy NGC 5253 hosts a number of young, massive star clusters, the two youngest of which are centrally concentrated and surrounded by thermal radio emission (the “radio nebula”). To investigate the role of these clusters in the starburst energetics, we combine new and archival Hubble Space Telescope images of NGC 5253 with wavelength coverage from 1500 Å to 1.9 μm in 13 filters. These include Hα, Pβ, and Pα, and the imaging from the Hubble Treasury Program LEGUS (Legacy Extragalactic UV Survey). The extraordinarily well-sampled spectral energy distributions enable modeling with unprecedented accuracy the ages, masses, and extinctions of the nine optically brightest clusters (MV < -8.8) and the two young radio nebula clusters. The clusters have ages ˜1-15 Myr and masses ˜1 × 104-2.5 × 105 M⊙. The clusters’ spatial location and ages indicate that star formation has become more concentrated toward the radio nebula over the last ˜15 Myr. The most massive cluster is in the radio nebula; with a mass ˜2.5 × 105 M⊙ and an age ˜1 Myr, it is 2-4 times less massive and younger than previously estimated. It is within a dust cloud with AV ˜ 50 mag, and shows a clear near-IR excess, likely from hot dust. The second radio nebula cluster is also ˜1 Myr old, confirming the extreme youth of the starburst region. These two clusters account for about half of the ionizing photon rate in the radio nebula, and will eventually supply about 2/3 of the mechanical energy in present-day shocks. Additional sources are required to supply the remaining ionizing radiation, and may include very massive stars. Based on observations obtained with the NASA/ESA Hubble Space Telescope, at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

The effects of bilingual language proficiency on recall accuracy and semantic clustering in free recall output: evidence for shared semantic associations across languages.

PubMed

Francis, Wendy S; Taylor, Randolph S; Gutiérrez, Marisela; Liaño, Mary K; Manzanera, Diana G; Penalver, Renee M

2018-05-19

Two experiments investigated how well bilinguals utilise long-standing semantic associations to encode and retrieve semantic clusters in verbal episodic memory. In Experiment 1, Spanish-English bilinguals (N = 128) studied and recalled word and picture sets. Word recall was equivalent in L1 and L2, picture recall was better in L1 than in L2, and the picture superiority effect was stronger in L1 than in L2. Semantic clustering in word and picture recall was equivalent in L1 and L2. In Experiment 2, Spanish-English bilinguals (N = 128) and English-speaking monolinguals (N = 128) studied and recalled word sequences that contained semantically related pairs. Data were analyzed using a multinomial processing tree approach, the pair-clustering model. Cluster formation was more likely for semantically organised than for randomly ordered word sequences. Probabilities of cluster formation, cluster retrieval, and retrieval of unclustered items did not differ across languages or language groups. Language proficiency has little if any impact on the utilisation of long-standing semantic associations, which are language-general.

Segmentation of bone pixels from EROI Image using clustering method for bone age assessment

NASA Astrophysics Data System (ADS)

Bakthula, Rajitha; Agarwal, Suneeta

2016-03-01

The bone age of a human can be identified using carpal and epiphysis bones ossification, which is limited to teen age. The accurate age estimation depends on best separation of bone pixels and soft tissue pixels in the ROI image. The traditional approaches like canny, sobel, clustering, region growing and watershed can be applied, but these methods requires proper pre-processing and accurate initial seed point estimation to provide accurate results. Therefore this paper proposes new approach to segment the bone from soft tissue and background pixels. First pixels are enhanced using BPE and the edges are identified by HIPI. Later a K-Means clustering is applied for segmentation. The performance of the proposed approach has been evaluated and compared with the existing methods.

Spatial Hotspot Analysis of Acute Myocardial Infarction Events in an Urban Population: A Correlation Study of Health Problems and Industrial Installation

PubMed Central

NAMAYANDE, Motahareh Sadat; NEJADKOORKI, Farhad; NAMAYANDE, Seyedeh Mahdieh; DEHGHAN, Hamidreza

2016-01-01

Background: The current study’s objectives were to find any possible spatial patterns and hotspot of cardiovascular events and to perform a correlation study to find any possible relevance between cardiovascular disease (CVE) and location of industrial installation said above. Methods: We used the Acute Myocardial Infarction (AMI) hospital admission record in three main hospitals in Yazd, Yazd Province, Iran during 2013, because of CVDs and searched for possible correlation between industries as point-source pollutants and non-random distribution of AMI events. Results: MI incidence rate in Yazd was obtained 531 per 100,000 person-year among men, 458 per 100,000 person-year among women and 783/100,000 person-yr totally. We applied a GIS Hotspot analysis to determine feasible clusters and two sets of clusters were observed. Mean age of 56 AMI events occurred in the cluster cells was calculated as 62.21±14.75 yr. Age and sex as main confounders of AMI were evaluated in the cluster areas in comparison to other areas. We observed no significant difference regarding sex (59% in cluster cells versus 55% in total for men) and age (62.21±14.7 in cluster cells versus 63.28±13.98 in total for men). Conclusion: We found proximity of AMI events cluster to industries installations, and a steel industry, specifically. There could be an association between road-related pollutants and the observed sets of cluster due to the proximity exist between rather crowded highways nearby the events cluster. PMID:27057527

Correlates of the categories of adolescent attachment styles: Perceived rearing, family function, early life events, and personality.

PubMed

Tanaka, Nao; Hasui, Chieko; Uji, Masayo; Hiramura, Hidetoshi; Chen, Zi; Shikai, Noriko; Kitamura, Toshinori

2008-02-01

To identify the psychosocial correlates of adolescents. Unmarried university students (n = 4226) aged 18-23 years were examined in a questionnaire survey. Four clusters of people (indifferent, secure, fearful, and preoccupied) identified by cluster analysis were plotted in 2-D using discriminant function analysis with the first function (father's and mother's Care, Cooperativeness, and family Cohesion on the positive end and Harm Avoidance and father's and mother's Overprotection on the negative end) representing the Self-model and the second function (Reward Dependence and experience of Peer Victimization on the positive end and Self-directedness on the negative end) representing the Other model. These findings partially support Bartholomew's notion that adult attachment is based on the good versus bad representations of the self and the other and that it is influenced by psychosocial environments experienced over the course of development.

Recent collisional jet from a primitive asteroid

NASA Astrophysics Data System (ADS)

Novaković, Bojan; Dell'Oro, Aldo; Cellino, Alberto; Knežević, Zoran

2012-09-01

In this paper we show an example of a young asteroid cluster located in a dynamically stable region, which was produced by partial disruption of a primitive body about 30 km in size. We estimate its age to be only 1.9 ± 0.3 Myr; thus, its post-impact evolution should have been very limited. The large difference in size between the largest object and the other cluster members means that this was a cratering event. The parent body had a large orbital inclination and was subject to collisions with typical impact speeds higher by a factor of 2 than in the most common situations encountered in the main belt. For the first time, we have at our disposal the observable outcome of a very recent event to study high-speed collisions involving primitive asteroids, providing very useful constraints to numerical simulations of these events and to laboratory experiments.

Colloidal heteroaggregation: a strategy to prepare composite materials

NASA Astrophysics Data System (ADS)

López-López, J. M.; Schmitt, A.; Moncho-Jordá, A.; Hidalgo-Álvarez, R.

2009-01-01

In this work, we make use of single-cluster light-scattering (SCLS) experiments and Brownian dynamics (BD) simulations in order to investigate the formation of binary clusters of oppositely-charged colloidal particles by heteroaggregation processes. Two parameters determinate the stability, size and structure of the clusters: the relative concentration of both species x and the range of the particle-particle interactions κa. SCLS experiments reveal that stable binary clusters arise in asymmetric systems when particle-particle interactions are long-ranged. These stable aggregates group in bell-shaped distributions that correspond to compact clusters with different orders, i.e., with a given number of minority particles. It is found that x controls the distribution of the clusters among the different orders and κa determine the average size of the clusters belonging to each order. Finally, BD simulations allow us to interpret all these results within the the frame of the classic Hogg-Healy-Fuersternau theory.

The new ClusterTrap setup

NASA Astrophysics Data System (ADS)

Martinez, F.; Marx, G.; Schweikhard, L.; Vass, A.; Ziegler, F.

2011-07-01

ClusterTrap has been designed to investigate properties of atomic clusters in the gas phase with particular emphasis on the dependence on the cluster size and charge state. The combination of cluster source, Penning trap and time-of-flight mass spectrometry allows a variety of experimental schemes including collision-induced dissociation, photo-dissociation, further ionization by electron impact, and electron attachment. Due to the storage capability of the trap extended-delay reaction experiments can be performed. Several recent modifications have resulted in an improved setup. In particular, an electrostatic quadrupole deflector allows the coupling of several sources or detectors to the Penning trap. Furthermore, a linear radio-frequency quadrupole trap has been added for accumulation and ion bunching and by switching the potential of a drift tube the kinetic energy of the cluster ions can be adjusted on their way towards or from the Penning trap. Recently, experiments on multiply negatively charged clusters have been resumed.

Variability of cognitive development in children with Down syndrome: relevance of good reasons for using the cluster procedure.

PubMed

Tsao, R; Kindelberger, C

2009-01-01

The main goal of this cross-sectional study was to demonstrate that, in addition to a main change during childhood, the cognitive development of children with Down syndrome (DS) is characterized by interindividual variability in their cognitive functioning. Eighty-eight French children with DS took part in this experiment. They were divided into six chronological age groups: 6 years (N=9), 7 years (N=19), 8 years (N=18), 9 years (N=19), 10 years (N=14) and 11 years (N=9). They were assessed by means of the Differential Scales of Intellectual Efficiency. This test, composed of six independent scales, measures verbal abilities and nonverbal reasoning abilities. Initial analyses of the verbal and nonverbal subtest scores indicated a main change in cognitive skills. We then used a clustering approach to identify four cognitive profiles that distinguished the children with DS independently of age and gender. The results confirm that there is a growth in the cognitive skills of DS children. They also suggest that the cognitive functioning of DS children is characterized by different individual profiles. Implications for more fine-tuned research and intervention efforts are discussed.

The Psychology of Yoga Practitioners: A Cluster Analysis.

PubMed

Genovese, Jeremy E C; Fondran, Kristine M

2017-11-01

Yoga practitioners (N = 261) completed the revised Expression of Spirituality Inventory (ESI) and the Multidimensional Body-Self Relations Questionnaire. Cluster analysis revealed three clusters: Cluster A scored high on all four spiritual constructs. They had high positive evaluations of their appearance, but a lower orientation towards their appearance. They tended to have a high evaluation of their fitness and health, and higher body satisfaction. Cluster B showed lower scores on the spiritual constructs. Like Cluster A, members of Cluster B tended to show high positive evaluations of appearance and fitness. They also had higher body satisfaction. Members of Cluster B had a higher fitness orientation and a higher appearance orientation than members of Cluster A. Members of Cluster C had low scores for all spiritual constructs. They had a low evaluation of, and unhappiness with, their appearance. They were unhappy with the size and appearance of their bodies. They tended to see themselves as overweight. There was a significant difference in years of practice between the three groups (Kruskall -Wallis, p = .0041). Members of Cluster A have the most years of yoga experience and members of Cluster B have more yoga experience than members of Cluster C. These results suggest the possible existence of a developmental trajectory for yoga practitioners. Such a developmental sequence may have important implications for yoga practice and instruction.

The Psychology of Yoga Practitioners: A Cluster Analysis.

PubMed

Genovese, Jeremy E C; Fondran, Kristine M

2017-03-30

Yoga practitioners (N = 261) completed the revised Expression of Spirituality Inventory (ESI) and the Multidimensional Body-Self Relations Questionnaire. Cluster analysis revealed three clusters: Cluster A scored high on all four spiritual constructs. They had high positive evaluations of their appearance, but a lower orientation towards their appearance. They tended to have a high evaluation of their fitness and health, and higher body satisfaction. Cluster B showed lower scores on the spiritual constructs. Like Cluster A, members of Cluster B tended to show high positive evaluations of appearance and fitness. They also had higher body satisfaction. Members of Cluster B had a higher fitness orientation and a higher appearance orientation than members of Cluster A. Members of Cluster C had low scores for all spiritual constructs. They had a low evaluation of, and unhappiness with, their appearance. They were unhappy with the size and appearance of their bodies. They tended to see themselves as overweight. There was a significant difference in years of practice between the three groups (Kruskall-Wallis, p = .0041). Members of Cluster A have the most years of yoga experience and members of Cluster B have more yoga experience than members of Cluster C. These results suggest the possible existence of a developmental trajectory for yoga practitioners. Such a developmental sequence may have important implications for yoga practice and instruction.

Seizure clusters: characteristics and treatment.

PubMed

Haut, Sheryl R

2015-04-01

Many patients with epilepsy experience 'clusters' or flurries of seizures, also termed acute repetitive seizures (ARS). Seizure clustering has a significant impact on health and quality of life. This review summarizes recent advances in the definition and neurophysiologic understanding of clustering, the epidemiology and risk factors for clustering and both inpatient and outpatient clinical implications. New treatments for seizure clustering/ARS are perhaps the area of greatest recent progress. Efforts have focused on creating a uniform definition of a seizure cluster. In neurophysiologic studies of refractory epilepsy, seizures within a cluster appear to be self-triggering. Clinical progress has been achieved towards a more precise prevalence of clustering, and consensus guidelines for epilepsy monitoring unit safety. The greatest recent advances are in the study of nonintravenous route of benzodiazepines as rescue medications for seizure clusters/ARS. Rectal benzodiazepines have been very effective but barriers to use exist. New data on buccal, intramuscular and intranasal preparations are anticipated to lead to a greater number of approved treatments. Progesterone may be effective for women who experience catamenial clusters. Seizure clustering is common, particularly in the setting of medically refractory epilepsy. Clustering worsens health and quality of life, and the field requires greater focus on clarifying of definition and clinical implications. Progress towards the development of nonintravenous routes of benzodiazepines has the potential to improve care in this area.

K2 eclipsing binaries in the benchmark open cluster Ruprecht 147

NASA Astrophysics Data System (ADS)

Torres, Guillermo

Open clusters are ideal laboratories to study stellar astrophysics. They represent homogeneous collections of hundreds or thousands of stars that were formed together and should therefore have the same age, chemical composition, space motion, and distance. Easily measured properties for member stars such as the brightness and color can be used to infer some of the characteristics of the ensemble including the age and distance, by comparing with model isochrones in the color-magnitude diagram. In recent years space missions such as CoRoT and Kepler have enabled the detection of solar-like oscillations in some of the brighter open cluster members, which can yield asteroseismic estimates of the stellar masses and radii through simple scaling relations anchored on the Sun, and also ages under certain assumptions. Furthermore, when photometric rotation periods of stars can be measured in them, clusters will well-known ages then become essential calibrators for gyrochronology relations, which describe how stars spin down as they get older due to magnetic braking from stellar winds. These relations are important because they provide one of the few empirical ways to age-date field stars. For clusters endowed with detached, double-lined eclipsing binaries amenable to study, even stronger constraints on their properties become available that are of an entirely different nature. The absolute masses and radii of the binary components can be measured very accurately and in a model-independent way, providing an opportunity for stringent tests of stellar evolution theory. The ages that can also be obtained by comparison with models can serve to validate other age estimates mentioned above. Ruprecht 147 is remarkable in that it permits all of these types of studies at the same time. It is the oldest nearby open cluster, with an age of about 3 Gyr and a distance of only 300 pc. This makes it a favorable target for follow-up studies. The metallicity is well determined from previous spectroscopic investigations. It was observed photometrically by the K2 mission for 80 days in late 2015, enabling both asteroseismic and rotation period studies of dozens of members. What makes it truly unique, however, is that it has no less than five eclipsing binaries brighter than 13th magnitude that lend themselves to high-precision mass and radius determinations. No other open cluster has as many, let alone an old one. The brightest binary happens to be at the tip of the turnoff and provides an unusually strong constraint on age. A very special opportunity for study has thus presented itself. This is a proposal to analyze publicly available K2 photometry for the five bright eclipsing binaries discovered in Ruprecht 147, with the goal of fashioning the cluster into an important new benchmark for high-precision testing of stellar astrophysics. We will supplement the K2 light curves, processed with special detrending techniques, with ground-based spectroscopic observations yielding radial velocities for the stars. With these we will derive accurate masses, radii, and temperatures for the components of each binary using well-proven classical methodologies. The impact of the project is that the large number of binaries will allow for an unprecedented and extraordinarily strong test of stellar evolution theory over a range of masses, not available for any other open cluster. The ages we will infer are completely independent of, and of a different nature than other estimates in Ruprecht 147, coming from isochrone fitting in the colormagnitude diagram, asteroseismology of the brighter cluster members, or the use of gyrochronology relations. We will thus have a unique opportunity to cross-validate four different age-dating techniques in the same cluster. Additionally, our accurate eclipsing binary masses and radii will enable crucial tests of the asteroseismic scaling relations, which will improve their use for single stars.

Who are the healthy active seniors? A cluster analysis.

PubMed

Lai, Claudia K Y; Chan, Engle Angela; Chin, Kenny C W

2014-12-01

This paper reports a cluster analysis of a sample recruited from a randomized controlled trial that explored the effect of using a life story work approach to improve the psychological outcomes of older people in the community. 238 subjects from community centers were included in this analysis. After statistical testing, 169 seniors were assigned to the active ageing (AG) cluster and 69 to the inactive ageing (IG) cluster. Those in the AG were younger and healthier, with fewer chronic diseases and fewer depressive symptoms than those in the IG. They were more satisfied with their lives, and had higher self-esteem. They met with their family members more frequently, they engaged in more leisure activities and were more likely to have the ability to move freely. In summary, active ageing was observed in people with better health and functional performance. Our results echoed the limited findings reported in the literature.

Discovery of Extended Main-sequence Turnoffs in Four Young Massive Clusters in the Magellanic Clouds

NASA Astrophysics Data System (ADS)

Li, Chengyuan; de Grijs, Richard; Deng, Licai; Milone, Antonino P.

2017-08-01

An increasing number of young massive clusters (YMCs) in the Magellanic Clouds have been found to exhibit bimodal or extended main sequences (MSs) in their color-magnitude diagrams (CMDs). These features are usually interpreted in terms of a coeval stellar population with different stellar rotational rates, where the blue and red MS stars are populated by non- (or slowly) and rapidly rotating stellar populations, respectively. However, some studies have shown that an age spread of several million years is required to reproduce the observed wide turnoff regions in some YMCs. Here we present the ultraviolet-visual CMDs of four Large and Small Magellanic Cloud YMCs, NGC 330, NGC 1805, NGC 1818, and NGC 2164, based on high-precision Hubble Space Telescope photometry. We show that they all exhibit extended main-sequence turnoffs (MSTOs). The importance of age spreads and stellar rotation in reproducing the observations is investigated. The observed extended MSTOs cannot be explained by stellar rotation alone. Adopting an age spread of 35-50 Myr can alleviate this difficulty. We conclude that stars in these clusters are characterized by ranges in both their ages and rotation properties, but the origin of the age spread in these clusters remains unknown.

Dairy Products, Dietary Calcium and Bone Health: Possibility of Prevention of Osteoporosis in Women: The Polish Experience

PubMed Central

Wadolowska, Lidia; Sobas, Kamila; Szczepanska, Justyna W.; Slowinska, Malgorzata A.; Czlapka-Matyasik, Magdalena; Niedzwiedzka, Ewa

2013-01-01

The objective of the study was to analyze the consumption of dairy products and dietary calcium by women in the context of bone mineral density and to assess opportunities to prevent osteoporosis in a dietary manner. The study was carried out with 712 Polish women. In 170 women aged 32 to 59 bone mineral density (BMD) was measured. The data on the consumption of dairy products and dietary calcium and some other osteoporosis risk factors was collected from 712 women. The average calcium intake from a diet was 507 mg/day. Only 2% of the women met Polish calcium intake recommendations. During adulthood, dairy product consumption or dietary calcium intake did not differ significantly between women with low BMD (below −1 SD) and women with regular BMD (≥−1 SD) (47.4 vs. 44.3 servings/week and 459 vs. 510 mg/day, respectively, p > 0.05). The odds ratios adjusted for age, menstruation and BMI in women with upper BMD tercile in comparison to the reference group (bottom tercile) was 2.73 (95% CI: 1.14, 6.55; p < 0.05) for the daily consumption of dairy products during the pre-school period and 2.40 (95% CI: 1.01, 5.70; p < 0.05) for the daily consumption of dairy products during the school period. Two clusters of women were established. In the S1 cluster, low BMD (below −1 SD) was associated with older age (≥50 years), lack of menstrual cycle. In the S2 cluster, regular BMD (≥−1 SD) was related to younger aged women (<50 years), presence of menstrual cycle, consumption of higher level of dairy products (≥28 servings/week) during adulthood and daily intake of dairy products during childhood and adolescence. The results indicate that good bone health to the large extent depended upon the combined impact of dietary factors and some non-modifiable risk factors of osteoporosis such as age and the presence of menstruation. Consumption of dairy products in childhood and adolescence may improve bone mineral density and reduce the risk of osteoporosis in adult women. PMID:23863825

Open clusters. III. Fundamental parameters of B stars in NGC 6087, NGC 6250, NGC 6383, and NGC 6530 B-type stars with circumstellar envelopes

NASA Astrophysics Data System (ADS)

Aidelman, Y.; Cidale, L. S.; Zorec, J.; Panei, J. A.

2018-02-01

Context. Stellar physical properties of star clusters are poorly known and the cluster parameters are often very uncertain. Methods: Our goals are to perform a spectrophotometric study of the B star population in open clusters to derive accurate stellar parameters, search for the presence of circumstellar envelopes, and discuss the characteristics of these stars. The BCD spectrophotometric system is a powerful method to obtain stellar fundamental parameters from direct measurements of the Balmer discontinuity. To this end, we wrote the interactive code MIDE3700. The BCD parameters can also be used to infer the main properties of open clusters: distance modulus, color excess, and age. Furthermore, we inspected the Balmer discontinuity to provide evidence for the presence of circumstellar disks and identify Be star candidates. We used an additional set of high-resolution spectra in the Hα region to confirm the Be nature of these stars. Results: We provide Teff, log g, Mv, Mbol, and spectral types for a sample of 68 stars in the field of the open clusters NGC 6087, NGC 6250, NGC 6383, and NGC 6530, as well as the cluster distances, ages, and reddening. Then, based on a sample of 230 B stars in the direction of the 11 open clusters studied along this series of three papers, we report 6 new Be stars, 4 blue straggler candidates, and 15 B-type stars (called Bdd) with a double Balmer discontinuity, which indicates the presence of circumstellar envelopes. We discuss the distribution of the fraction of B, Be, and Bdd star cluster members per spectral subtype. The majority of the Be stars are dwarfs and present a maximum at the spectral type B2-B4 in young and intermediate-age open clusters (<40 Myr). Another maximum of Be stars is observed at the spectral type B6-B8 in open clusters older than 40 Myr, where the population of Bdd stars also becomes relevant. The Bdd stars seem to be in a passive emission phase. Conclusions: Our results support previous statements that the Be phenomenon is present along the whole main sequence band and occurs in very different evolutionary states. We find clear evidence of an increase of stars with circumstellar envelopes with cluster age. The Be phenomenon reaches its maximum in clusters of intermediate age (10-40 Myr) and the number of B stars with circumstellar envelopes (Be plus Bdd stars) is also high for the older clusters (40-100 Myr). Observations taken at CASLEO, operating under agreement of CONICET and the Universities of La Plata, Córdoba, and San Juan, Argentina.Tables 1, 2, 9-16 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/610/A30

In vitro analysis of equine, bone marrow-derived mesenchymal stem cells demonstrates differences within age- and gender-matched horses.

PubMed

Carter-Arnold, J L; Neilsen, N L; Amelse, L L; Odoi, A; Dhar, M S

2014-09-01

Stem cell therapies are used routinely in equine practice. Most published reports characterise stem cells derived from younger horses; however, middle-aged horses are often in athletic performance, and experience degenerative medical conditions. Thus, mesenchymal stem cells (MSCs) from this group should be investigated. To describe differences in in vitro adherence, proliferation and potential for differentiation of equine bone marrow-derived MSCs (equine BMMSCs) harvested from middle-aged (10-13 years old) female donors. Descriptive study of stem cell characteristics. Equine BMMSCs from 6 horses were cultured in vitro and evaluated for viability, proliferation, osteogenesis, chondrogenesis, adipogenesis, cluster-of-differentiation markers and gene expression. Equine BMMSCs from all 6 donors demonstrated fibroblastic, cellular morphology, adherence to plastic and expression of cluster-of-differentiation markers. They varied in their rate of proliferation and trilineage differentiation. The equine BMMSCs of one of 6 donors demonstrated a higher rate of proliferation, enhanced ability for cell passaging and a more robust in vitro differentiation. Comparatively, equine BMMSCs from 2 donors demonstrated a lower rate of proliferation and lack of osteogenic and chondrogenic differentiation. The results of this study confirm that donor-to-donor variation in equine BMMSCs exists and this variation can be documented using in vitro assays. Subjective assessment suggests that the rate of proliferation tends to correlate with differentiation potential. © 2013 EVJ Ltd.

Synergistic Effects of Age on Patterns of White and Gray Matter Volume across Childhood and Adolescence1,2,3

PubMed Central

Krongold, Mark; Cooper, Cassandra; Lebel, Catherine

2015-01-01

Abstract The human brain develops with a nonlinear contraction of gray matter across late childhood and adolescence with a concomitant increase in white matter volume. Across the adult population, properties of cortical gray matter covary within networks that may represent organizational units for development and degeneration. Although gray matter covariance may be strongest within structurally connected networks, the relationship to volume changes in white matter remains poorly characterized. In the present study we examined age-related trends in white and gray matter volume using T1-weighted MR images from 360 human participants from the NIH MRI study of Normal Brain Development. Images were processed through a voxel-based morphometry pipeline. Linear effects of age on white and gray matter volume were modeled within four age bins, spanning 4-18 years, each including 90 participants (45 male). White and gray matter age-slope maps were separately entered into k-means clustering to identify regions with similar age-related variability across the four age bins. Four white matter clusters were identified, each with a dominant direction of underlying fibers: anterior–posterior, left–right, and two clusters with superior–inferior directions. Corresponding, spatially proximal, gray matter clusters encompassed largely cerebellar, fronto-insular, posterior, and sensorimotor regions, respectively. Pairs of gray and white matter clusters followed parallel slope trajectories, with white matter changes generally positive from 8 years onward (indicating volume increases) and gray matter negative (decreases). As developmental disorders likely target networks rather than individual regions, characterizing typical coordination of white and gray matter development can provide a normative benchmark for understanding atypical development. PMID:26464999

YSOVAR: The Age of the Cepheus C Star Cluster

NASA Astrophysics Data System (ADS)

Luna, Jessica; Covey, K.; YSOVAR

2014-01-01

We constructed a spectroscopic Hertzsprung-Russell diagram for the Cepheus C (Ceph C) sub-cluster, which we use to generate the first quantitative measurement of this young cluster’s age. Using two TripleSpec spectrographs, on the 3.5m telescope at Apache Point Ob- servatory and the 200” telescope at Palomar Observatory, we obtained near infrared (NIR) spectra for 31 candidate Ceph C members. By comparing our target spectra to a large library of dwarf, sub-giant, and giant star templates, we measured spectral types for candidate Ceph C members ranging from F2 to M2.5. We converted each YSO’s ST into a Teff estimate using the ST to Teff relation recently published by Pecaut et al. (2013). Using our spectroscopically derived extinction estimates to deredden spectral energy distributions constructed from 2MASS and Spitzer photometry, we measured each YSO’s bolometric luminosity. Placing each candidate Ceph C member on an HR Dia- gram, we used Dartmouth pre-main sequence evolutionary tracks to estimate the mass and age of each YSO. We measure a median stellar age for the Ceph C cluster of ˜10 Myrs or less. We also detect a large systematic effect in our ages, however, such that cooler, low mass mem- bers have substantially smaller inferred ages than their higher mass counterparts. We are working to understand the root cause of this systematic effect, but this first estimate of Ceph C’s age will advance our understanding of the cluster’s relationship to other sub clusters in Cepheus, and place the Ceph C cluster in context among other local star forming regions. This research was funded by the NSF through grant number AST-1004107.

Globular cluster ages determined from the Oosterhoff period-metallicity effect using oxygen-enhanced isochrones. III

NASA Astrophysics Data System (ADS)

Sandage, Allan

1993-08-01

The new brighter calibration of absolute luminosities of RR Lyrae stars by about 0.25 mag as a function of metallicity via the Oosterhoff period effect gives a revised age of the Galactic globular cluster system as 14 Gyr when used with the oxygen-enhanced main-sequence termination models of Bergbush and VandenBerg (1992). There is no correlation of cluster age with metallicity. The presence or absence of age differences between any two clusters is neither proof nor disproof of the Eggen-Lynden Bell-Sandage model of the formation of the Galaxy by collapse. If there were different density regimes within the initial density fluctuation that was the protogalaxy, then there has been a hierarchy of collapse times for the various parts of the present Galaxy. The age of the universe is 15 Gyr, based on the age of the Galaxy at 14 Gyr, to which 1 Gyr is added for the gestation time of the galaxies. The ratio of this age to the inverse Hubble constant with H(0) about 45 km/s Mpc, based on a recent concordant determination using supernovae of type Ia, is close to the critical value of 2/3 required if the deceleration is caused by a mean density just equal to that needed for closure. For the first time, these new data give the possibility that Omega = 1 from this timing test.

Using Cluster Analysis to Examine Husband-Wife Decision Making

ERIC Educational Resources Information Center

Bonds-Raacke, Jennifer M.

2006-01-01

Cluster analysis has a rich history in many disciplines and although cluster analysis has been used in clinical psychology to identify types of disorders, its use in other areas of psychology has been less popular. The purpose of the current experiments was to use cluster analysis to investigate husband-wife decision making. Cluster analysis was…

A parsimonious characterization of change in global age-specific and total fertility rates

PubMed Central

2018-01-01

This study aims to understand trends in global fertility from 1950-2010 though the analysis of age-specific fertility rates. This approach incorporates both the overall level, as when the total fertility rate is modeled, and different patterns of age-specific fertility to examine the relationship between changes in age-specific fertility and fertility decline. Singular value decomposition is used to capture the variation in age-specific fertility curves while reducing the number of dimensions, allowing curves to be described nearly fully with three parameters. Regional patterns and trends over time are evident in parameter values, suggesting this method provides a useful tool for considering fertility decline globally. The second and third parameters were analyzed using model-based clustering to examine patterns of age-specific fertility over time and place; four clusters were obtained. A country’s demographic transition can be traced through time by membership in the different clusters, and regional patterns in the trajectories through time and with fertility decline are identified. PMID:29377899

The Spots and Activity of Stars in the Beehive Cluster Observed by the Kepler Space Telescope (K2)

NASA Astrophysics Data System (ADS)

Savanov, I. S.; Kalinicheva, E. S.; Dmitrienko, E. S.

2018-05-01

The spottedness parameters S (the fraction of the visible surface of the star occupied by spots) characterizing the activity of 674 stars in the Beehive Cluster (age 650 Myr) are estimated, together with variations of this parameter as a function of the rotation period, Rossby number Ro and other characteristics of the stars. The activity of the stars in this cluster is lower than the activity of stars in the younger Pleiades (125 Myr). The average S value for the Beehive Cluster stars is 0.014, while Pleiades stars have the much higher average value 0.052. The activity parameters of 61 solar-type stars in the Beehive Cluster, similar Hyades stars (of about the same age), and stars in the younger Pleiades are compared. The average S value of such objects in the Beehive Cluster is 0.014± 0.008, nearly coincident with the estimate obtained for solar-type Hyades stars. The rotation periods of these objects are 9.1 ± 3.4 day, on average, in agreement with the average rotation period of the Hyades stars (8.6 d ). Stars with periods exceeding 3-4 d are more numerous in the Beehive Cluster than in the Pleiades, and their periods have a larger range, 3-30 d . The characteristic dependence with a kink at Ro (saturation) = 0.13 is not observed in the S-Rossby number diagram for the Beehive and Hyades stars, only a clump of objects with Rossby numbers Ro > 0.7. The spottedness data for the Beehive Cluster and Hyades stars are in good agreement with the S values for dwarfs with ages of 600-700 Myr. This provides evidence for the reliability of the results of gyrochronological calibrations. The data for the Beehive and Pleiades stars are used to analyze variations in the spot-forming activity for a large number of stars of the same age that are members of a single cluster. A joint consideration of the data for two clusters can be used to draw conclusions about the time evolution of the activity of stars of different masses (over a time interval of the order of 500 Myr).

The Evolution of Rotation and Activity in Young Open Clusters: the Zero-Age Main Sequence.

NASA Astrophysics Data System (ADS)

Patten, Brian Michael

1995-01-01

I have undertaken a program of ground- and space -based observations to measure photometric rotation periods and X-ray luminosities for late-type stars in the young open clusters IC 2391 and IC 2602. With cluster ages of ~30 Myr, IC 2391 and IC 2602 are ideal sites in which to observe conditions at the ZAMS since the solar-type stars in these clusters have not been on the main sequence long enough to undergo significant magnetic braking. The ROSAT survey of IC 2391 revealed 80 X-ray sources, 44 of which were found to be associated with stars which are now classified as new cluster members. Among the solar-type stars in both IC 2391 and IC 2602, I find a factor of ~25 spread in the distribution of rotation periods, which range from 0.21 to 4.86 day. I also find a factor of ~10-20 spread in the range of LX about a median LX value of ~10^{30 } erg s^{-1} for both clusters. These results show conclusively that stars arrive on the ZAMS with a wide range of rotation rates and coronal activity levels. When compared to data from older clusters, such as the Pleiades and the Hyades, there is an overall decline observed in both the rotation rates and median X-ray luminosity of cluster members with increasing age, however, while the spread in the range of rotation rates decreases to a small value, the spread in the range of LX values as a fraction of the median is observed to increase with age. This behavior is best explained through a dependence of LX on P rot which is weak in the young clusters and strong in the older clusters. The Rossby diagram shows there is a tight correlation between L X/Lbol and the Rossby number, Prot divided by the convective turnover time. Young, rapidly rotating, main sequence stars lie along a plateau of magnetic saturation, where LX has a weak dependence on rotation period, while older, more slowly rotating stars lie in a region on the Rossby diagram where LX has a strong dependence on rotation period.

Vitamin D prenatal programming of childhood metabolomics profiles at age 3 y.

PubMed

Blighe, Kevin; Chawes, Bo L; Kelly, Rachel S; Mirzakhani, Hooman; McGeachie, Michael; Litonjua, Augusto A; Weiss, Scott T; Lasky-Su, Jessica A

2017-10-01

Background: Vitamin D deficiency is implicated in a range of common complex diseases that may be prevented by gestational vitamin D repletion. Understanding the metabolic mechanisms related to in utero vitamin D exposure may therefore shed light on complex disease susceptibility. Objective: The goal was to analyze the programming role of in utero vitamin D exposure on children's metabolomics profiles. Design: First, unsupervised clustering was done with plasma metabolomics profiles from a case-control subset of 245 children aged 3 y with and without asthma from the Vitamin D Antenatal Asthma Reduction Trial (VDAART), in which pregnant women were randomly assigned to vitamin D supplementation or placebo. Thereafter, we analyzed the influence of maternal pre- and postsupplement vitamin D concentrations on cluster membership. Finally, we used the metabolites driving the clustering of children to identify the dominant metabolic pathways that were influential in each cluster. Results: We identified 3 clusters of children characterized by 1 ) high concentrations of fatty acids and amines and low maternal postsupplement vitamin D (mean ± SD; 27.5 ± 11.0 ng/mL), 2 ) high concentrations of amines, moderate concentrations of fatty acids, and normal maternal postsupplement vitamin D (34.0 ± 14.1 ng/mL), and 3 ) low concentrations of fatty acids, amines, and normal maternal postsupplement vitamin D (35.2 ± 15.9 ng/mL). Adjusting for sample storage time, maternal age and education, and both child asthma and vitamin D concentration at age 3 y did not modify the association between maternal postsupplement vitamin D and cluster membership ( P = 0.0014). Maternal presupplement vitamin D did not influence cluster membership, whereas the combination of pre- and postsupplement concentrations did ( P = 0.03). Conclusions: Young children can be clustered into distinct biologically meaningful groups by their metabolomics profiles. The clusters differed in concentrations of inflammatory mediators, and cluster membership was influenced by in utero vitamin D exposure, suggesting a prenatal programming role of vitamin D on the child's metabolome. This trial was registered at clinicaltrials.gov as NCT00920621. © 2017 American Society for Nutrition.

A Photometric Search for Planets in the Open Cluster NGC 7086

NASA Astrophysics Data System (ADS)

Rosvick, Joanne M.; Robb, Russell

2006-12-01

In an attempt to discover short-period, Jupiter-mass planets orbiting solar-type stars in open clusters, we searched for planetary transits in the populous and relatively unstudied open cluster NGC 7086. A color-magnitude diagram constructed from new B and V photometry is presented, along with revised estimates of the cluster's color excess, distance modulus, and age. Several turnoff stars were observed spectroscopically in order to determine a color excess of E(B-V)=0.83+/-0.02. Empirically fitting the main sequences of two young open clusters and the semiempirical zero-age main sequence of Vandenberg and Poll yielded a distance modulus of (V-MV)=13.4+/-0.3 mag. This corresponds to a true distance modulus of (m-M)0=10.8 mag or a distance of 1.5 kpc to NGC 7086. These values were used with isochrones from the Padova group to obtain a cluster age of 100 Myr. Eleven nights of R-band photometry were used to search for planetary transits. Differential magnitudes were constructed for each star in the cluster. Light curves for each star were produced on a night-to-night basis and inspected for variability. No planetary transits were apparent; however, some interesting variable stars were discovered: a pulsating variable that appears to be a member of the γ Dor class and four possible eclipsing binary stars, one of which actually may be a multiple system.

Coping with Stress in Deprived Urban Neighborhoods: What Is the Role of Green Space According to Life Stage?

PubMed

Roe, Jenny J; Aspinall, Peter A; Ward Thompson, Catharine

2017-01-01

This study follows previous research showing how green space quantity and contact with nature (via access to gardens/allotments) helps mitigate stress in people living in deprived urban environments (Ward Thompson et al., 2016). However, little is known about how these environments aid stress mitigation nor how stress levels vary in a population experiencing higher than average stress. This study used Latent Class Analysis (LCA) to, first, identify latent health clusters in the same population ( n = 406) and, second, to relate health cluster membership to variables of interest, including four hypothetical stress coping scenarios. Results showed a three-cluster model best fit the data, with membership to health clusters differentiated by age, perceived stress, general health, and subjective well-being. The clusters were labeled by the primary health outcome (i.e., perceived stress) and age group (1) Low-stress Youth characterized by ages 16-24; (2) Low-stress Seniors characterized by ages 65+ and (3) High-stress Mid-Age characterized by ages 25-44. Next, LCA identified that health membership was significantly related to four hypothetical stress coping scenarios set in people's current residential context: " staying at home " and three scenarios set outwith the home, " seeking peace and quiet," "going for a walk " or " seeking company. " Stress coping in Low stress Youth is characterized by " seeking company " and " going for a walk "; stress coping in Low-stress Seniors and High stress Mid-Age is characterized by " staying at home. " Finally, LCA identified significant relationships between health cluster membership and a range of demographic, other individual and environmental variables including access to, use of and perceptions of local green space. Our study found that the opportunities in the immediate neighborhood for stress reduction vary by age. Stress coping in youth is likely supported by being social and keeping physically active outdoors, including local green space visits. By contrast, local green space appears not to support stress regulation in young-middle aged and older adults, who choose to stay at home. We conclude that it is important to understand the complexities of stress management and the opportunities offered by local green space for stress mitigation by age and other demographic variables, such as gender.

Coping with Stress in Deprived Urban Neighborhoods: What Is the Role of Green Space According to Life Stage?

PubMed Central

Roe, Jenny J.; Aspinall, Peter A.; Ward Thompson, Catharine

2017-01-01

This study follows previous research showing how green space quantity and contact with nature (via access to gardens/allotments) helps mitigate stress in people living in deprived urban environments (Ward Thompson et al., 2016). However, little is known about how these environments aid stress mitigation nor how stress levels vary in a population experiencing higher than average stress. This study used Latent Class Analysis (LCA) to, first, identify latent health clusters in the same population (n = 406) and, second, to relate health cluster membership to variables of interest, including four hypothetical stress coping scenarios. Results showed a three-cluster model best fit the data, with membership to health clusters differentiated by age, perceived stress, general health, and subjective well-being. The clusters were labeled by the primary health outcome (i.e., perceived stress) and age group (1) Low-stress Youth characterized by ages 16–24; (2) Low-stress Seniors characterized by ages 65+ and (3) High-stress Mid-Age characterized by ages 25–44. Next, LCA identified that health membership was significantly related to four hypothetical stress coping scenarios set in people's current residential context: “staying at home” and three scenarios set outwith the home, “seeking peace and quiet,” “going for a walk” or “seeking company.” Stress coping in Low stress Youth is characterized by “seeking company” and “going for a walk”; stress coping in Low-stress Seniors and High stress Mid-Age is characterized by “staying at home.” Finally, LCA identified significant relationships between health cluster membership and a range of demographic, other individual and environmental variables including access to, use of and perceptions of local green space. Our study found that the opportunities in the immediate neighborhood for stress reduction vary by age. Stress coping in youth is likely supported by being social and keeping physically active outdoors, including local green space visits. By contrast, local green space appears not to support stress regulation in young-middle aged and older adults, who choose to stay at home. We conclude that it is important to understand the complexities of stress management and the opportunities offered by local green space for stress mitigation by age and other demographic variables, such as gender. PMID:29093689

Sizing the star cluster population of the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Piatti, Andrés E.

2018-04-01

The number of star clusters that populate the Large Magellanic Cloud (LMC) at deprojected distances <4 deg has been recently found to be nearly double the known size of the system. Because of the unprecedented consequences of this outcome in our knowledge of the LMC cluster formation and dissolution histories, we closely revisited such a compilation of objects and found that only ˜35 per cent of the previously known catalogued clusters have been included. The remaining entries are likely related to stellar overdensities of the LMC composite star field, because there is a remarkable enhancement of objects with assigned ages older than log(t yr-1) ˜ 9.4, which contrasts with the existence of the LMC cluster age gap; the assumption of a cluster formation rate similar to that of the LMC star field does not help to conciliate so large amount of clusters either; and nearly 50 per cent of them come from cluster search procedures known to produce more than 90 per cent of false detections. The lack of further analyses to confirm the physical reality as genuine star clusters of the identified overdensities also glooms those results. We support that the actual size of the LMC main body cluster population is close to that previously known.

The gap in the color-magnitude diagram of NGC 2420: A test of convective overshoot and cluster age

NASA Technical Reports Server (NTRS)

Demarque, Pierre; Sarajedini, Ata; Guo, X.-J.

1994-01-01

Theoretical isochrones have been constructed using the OPAL opacities specifically to study the color-magnitude diagram of the open star cluster NGC 2420. This cluster provides a rare test of core convection in intermediate-mass stars. At the same time, its age is of interest because of its low metallicity and relatively high Galactic latitude for an open cluster. The excellent color-magnitude diagram constructed by Anthony-Twarog et al. (1990) allows a detailed fit of the isochrones to the photometric data. We discuss the importance of convective overshoot at the convective core edge in determining the morphology of the gap located near the main-sequence turnoff. We find that given the assumptions made in the models, a modest amount of overshoot (0.23 H(sub p)) is required for the best fit. Good agreement is achieved with all features of the turnoff gap for a cluster age of 2.4 +/- 0.2 Gyr. We note that a photometrically complete luminosity function near the main-sequence turnoff and subgiant branch would also provide an important test of the overshoot models.

Determination of Fundamental Properties of an M31 Globular Cluster from Main-Sequence Photometry

NASA Astrophysics Data System (ADS)

Ma, Jun; Wu, Zhenyu; Wang, Song; Fan, Zhou; Zhou, Xu; Wu, Jianghua; Jiang, Zhaoji; Chen, Jiansheng

2010-10-01

M31 globular cluster B379 is the first extragalactic cluster whose age was determined by main-sequence photometry. In the main-sequence photometric method, the age of a cluster is obtained by fitting its color-magnitude diagram (CMD) with stellar evolutionary models. However, different stellar evolutionary models use different parameters of stellar evolution, such as range of stellar masses, different opacities and equations of state, and different recipes, and so on. So, it is interesting to check whether different stellar evolutionary models can give consistent results for the same cluster. Brown et al. constrained the age of B379 by comparing its CMD with isochrones of the 2006 VandenBerg models. Using SSP models of Bruzual & Charlot and its multiphotometry, ZMa et al. independently determined the age of B379, which is in good agreement with the determination of Brown et al. The models of Bruzual & Charlot are calculated based on the Padova evolutionary tracks. It is necessary to check whether the age of B379 as determined based on the Padova evolutionary tracks is in agreement with the determination of Brown et al.. In this article, we redetermine the age of B379 using isochrones of the Padova stellar evolutionary models. In addition, the metal abundance, the distance modulus, and the reddening value for B379 are reported. The results obtained are consistent with the previous determinations, which include the age obtained by Brown et al. This article thus confirms the consistency of the age scale of B379 between the Padova isochrones and the 2006 VandenBerg isochrones; i.e., the comparison between the results of Brown et al. and Ma et al. is meaningful. The results reported in this article of values found for B379 are: metallicity [M/H] = log(Z/Z ⊙) = -0.325, age τ = 11.0 ± 1.5 Gyr, reddening E(B - V) = 0.08, and distance modulus (m - M)0 = 24.44 ± 0.10.

Looking for signs of Alzheimer's disease.

PubMed

Hodgson, Lynne Gershenson; Cutler, Stephen J

2003-01-01

This study examined the correlates of symptom-seeking behavior for Alzheimer's disease (AD) among middle-aged persons. Symptom seeking, the tendency to search for signs of disease, is one manifestation of an individual's concern about developing AD. The data were obtained from a survey of two subsamples of 40-60 year old adults: 1) 108 adult children with a living parent with a diagnosis of probable AD; and 2) 150 adults in a matched group with no parental history of AD. Bivariate and multivariate analyses were used to identify significant predictors of symptom seeking, which was measured by a composite index comprised of responses from three questions about checking for signs of AD, interpreting signs as symptoms of AD, and soliciting external validation for concerns. Four clusters of predictors were examined: memory assessment, AD experience, sociodemographics, and well-being. Within these clusters, the constellations of significant predictors varied by subsample, but the most robust predictors were aspects of subjective assessments of memory functioning and AD experience. An understanding of the correlates of symptom seeking for AD has implications for early detection of the disease as well as identifying populations under stress from excessive worry about their own future health.

Students' Changing Attitudes and Aspirations Towards Physics During Secondary School

NASA Astrophysics Data System (ADS)

Sheldrake, Richard; Mujtaba, Tamjid; Reiss, Michael J.

2017-11-01

Many countries desire more students to study science subjects, although relatively few students decide to study non-compulsory physics at upper-secondary school and at university. To gain insight into students' intentions to study non-compulsory physics, a longitudinal sample (covering 2258 students across 88 secondary schools in England) was surveyed in year 8 (age 12/13) and again in year 10 (age 14/15). Predictive modelling highlighted that perceived advice, perceived utility of physics, interest in physics, self-concept beliefs (students' subjective beliefs of their current abilities and performance) and home support specifically orientated to physics were key predictors of students' intentions. Latent-transition analysis via Markov models revealed clusters of students, given these factors at years 8 and 10. Students' intentions varied across the clusters, and at year 10 even varied when accounting for the students' underlying attitudes and beliefs, highlighting that considering clusters offered additional explanatory power and insight. Regardless of whether three-cluster, four-cluster, or five-cluster models were considered, the majority of students remained in the same cluster over time; for those who transitioned clusters, more students changed clusters reflecting an increase in attitudes than changed clusters reflecting a decrease. Students in the cluster with the most positive attitudes were most likely to remain within that cluster, while students in clusters with less positive attitudes were more likely to change clusters. Overall, the cluster profiles highlighted that students' attitudes and beliefs may be more closely related than previously assumed, but that changes in their attitudes and beliefs were indeed possible.

Cardiovascular Risk Factors Among Low-Income Women: A Population-Based Study in China from 1991 to 2011.

PubMed

Lu, Hongyan; Bai, Lingling; Zhan, Changqing; Yang, Li; Tu, Jun; Gu, Hongfei; Shi, Min; Wang, Jinghua; Ning, Xianjia

2016-12-01

Data on long-term trends in the prevalence and clustering of cardiovascular disease (CVD) risk factors among women in China are rare, especially among low-income women. The aim of this study was to investigate the secular trends in the prevalence of CVD risk factors among low-income women in northern China. The prevalence and clustering of CVD risk factors, including hypertension, diabetes, obesity, current smoking status, and alcohol consumption, were assessed and compared in women aged 35-74 years in northern China in 1991 and 2011. The age-adjusted prevalence of cardiovascular risk factors among women was significantly higher in 2011 than in 1991, with increases of 31% (53.6% vs. 41.1%) for hypertension, 148% (20.9% vs. 8.4%) for obesity, 256% (11.7% vs. 3.3%) for diabetes, and 1634% (4.5% vs. 0.3%) for alcohol consumption. Over the 21-year period, there were significant differences in the prevalence of clustering of ≥1, ≥2, and 3 risk factors in all age groups. The greatest increase was observed among women aged 35-44 years, with a 7.3-fold increase in the prevalence of clustering of three risk factors. Simultaneously, the prevalence of clustering of ≥1 risk factors among women aged 35-44 years was 1.7-fold higher in 2011 than in 1991; the prevalence of clustering of ≥2 risk factors was raised by 5.5-fold among elderly women. Our findings suggest that it is crucial to emphasize the prevention and control of cardiovascular risk factors among young women in rural China to reduce the burden of CVDs.

A multitask clustering approach for single-cell RNA-seq analysis in Recessive Dystrophic Epidermolysis Bullosa

PubMed Central

Petegrosso, Raphael; Tolar, Jakub

2018-01-01

Single-cell RNA sequencing (scRNA-seq) has been widely applied to discover new cell types by detecting sub-populations in a heterogeneous group of cells. Since scRNA-seq experiments have lower read coverage/tag counts and introduce more technical biases compared to bulk RNA-seq experiments, the limited number of sampled cells combined with the experimental biases and other dataset specific variations presents a challenge to cross-dataset analysis and discovery of relevant biological variations across multiple cell populations. In this paper, we introduce a method of variance-driven multitask clustering of single-cell RNA-seq data (scVDMC) that utilizes multiple single-cell populations from biological replicates or different samples. scVDMC clusters single cells in multiple scRNA-seq experiments of similar cell types and markers but varying expression patterns such that the scRNA-seq data are better integrated than typical pooled analyses which only increase the sample size. By controlling the variance among the cell clusters within each dataset and across all the datasets, scVDMC detects cell sub-populations in each individual experiment with shared cell-type markers but varying cluster centers among all the experiments. Applied to two real scRNA-seq datasets with several replicates and one large-scale droplet-based dataset on three patient samples, scVDMC more accurately detected cell populations and known cell markers than pooled clustering and other recently proposed scRNA-seq clustering methods. In the case study applied to in-house Recessive Dystrophic Epidermolysis Bullosa (RDEB) scRNA-seq data, scVDMC revealed several new cell types and unknown markers validated by flow cytometry. MATLAB/Octave code available at https://github.com/kuanglab/scVDMC. PMID:29630593

Prevalence and factors related to dental caries among pre-school children of Saddar town, Karachi, Pakistan: a cross-sectional study.

PubMed

Dawani, Narendar; Nisar, Nighat; Khan, Nazeer; Syed, Shahbano; Tanweer, Navara

2012-12-27

Dental caries is highly prevalent and a significant public health problem among children throughout the world. Epidemiological data regarding prevalence of dental caries amongst Pakistani pre-school children is very limited. The objective of this study is to determine the frequency of dental caries among pre-school children of Saddar Town, Karachi, Pakistan and the factors related to caries. A cross-sectional study of 1000 preschool children was conducted in Saddar town, Karachi. Two-stage cluster sampling was used to select the sample. At first stage, eight clusters were selected randomly from total 11 clusters. In second stage, from the eight selected clusters, preschools were identified and children between 3- to 6-years age group were assessed for dental caries. Caries prevalence was 51% with a mean dmft score being 2.08 (±2.97) of which decayed teeth constituted 1.95. The mean dmft of males was 2.3 (±3.08) and of females was 1.90 (±2.90). The mean dmft of 3, 4, 5 and 6-year olds was 1.65, 2.11, 2.16 and 3.11 respectively. A significant association was found between dental caries and following variables: age group of 4-years (p-value < 0.029, RR = 1.248, 95% Bias corrected CI 0.029-0.437) and 5-years (p-value < 0.009, RR = 1.545, 95% Bias corrected CI 0.047-0.739), presence of dental plaque (p-value < 0.003, RR = 0.744, 95% Bias corrected CI (-0.433)-(-0.169)), poor oral hygiene (p-value < 0.000, RR = 0.661, 95% Bias corrected CI (-0.532)-(-0.284)), as well as consumption of non-sweetened milk (p-value < 0.049, RR = 1.232, 95% Bias corrected CI 0.061-0.367). Half of the preschoolers had dental caries coupled with a high prevalence of unmet dental treatment needs. Association between caries experience and age of child, consumption of non-sweetened milk, dental plaque and poor oral hygiene had been established.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barnes, Sydney A.; Weingrill, Joerg; Fritzewski, Dario

We report rotation periods for 20 cool (FGK) main sequence member stars of the 4 Gyr-old open cluster M67 (=NGC 2682), obtained by analyzing data from Campaign 5 of the K2 mission with the Kepler Space Telescope . The rotation periods delineate a sequence in the color–period diagram (CPD) of increasing period with redder color. This sequence represents a cross-section at the cluster age of the surface P = P ( t , M ), suggested in prior work to extend to at least solar age. The current Sun is located marginally (approximately 1 σ ) above M67 in themore » CPD, as its relative age leads us to expect, and lies on the P = P ( t , M ) surface to within measurement precision. We therefore conclude that the solar rotation rate is normal as compared with cluster stars, a fact that strengthens the solar–stellar connection. The agreement between the M67 rotation period measurements and prior predictions further implies that rotation periods, especially when coupled with appropriate supporting work such as spectroscopy, can provide reliable ages via gyrochronology for other similar FGK dwarfs from the early main sequence to solar age and likely until the main sequence turnoff. The M67 rotators have a rotational age of 4.2 Gyr with a standard deviation of 0.7 Gyr, implying that similar field stars can be age-dated to precisions of ∼17%. The rotational age of the M67 cluster as a whole is therefore 4.2 Gyr, but with a lower (averaged) uncertainty of 0.2 Gyr.« less

Evidence for feedback and stellar-dynamically regulated bursty star cluster formation: the case of the Orion Nebula Cluster

NASA Astrophysics Data System (ADS)

Kroupa, Pavel; Jeřábková, Tereza; Dinnbier, František; Beccari, Giacomo; Yan, Zhiqiang

2018-04-01

A scenario for the formation of multiple co-eval populations separated in age by about 1 Myr in very young clusters (VYCs, ages less than 10 Myr) and with masses in the range 600-20 000 M⊙ is outlined. It rests upon a converging inflow of molecular gas building up a first population of pre-main sequence stars. The associated just-formed O stars ionise the inflow and suppress star formation in the embedded cluster. However, they typically eject each other out of the embedded cluster within 106 yr, that is before the molecular cloud filament can be ionised entirely. The inflow of molecular gas can then resume forming a second population. This sequence of events can be repeated maximally over the life-time of the molecular cloud (about 10 Myr), but is not likely to be possible in VYCs with mass <300 M⊙, because such populations are not likely to contain an O star. Stellar populations heavier than about 2000 M⊙ are likely to have too many O stars for all of these to eject each other from the embedded cluster before they disperse their natal cloud. VYCs with masses in the range 600-2000 M⊙ are likely to have such multi-age populations, while VYCs with masses in the range 2000-20 000 M⊙ can also be composed solely of co-eval, mono-age populations. More massive VYCs are not likely to host sub-populations with age differences of about 1 Myr. This model is applied to the Orion Nebula Cluster (ONC), in which three well-separated pre-main sequences in the colour-magnitude diagram of the cluster have recently been discovered. The mass-inflow history is constrained using this model and the number of OB stars ejected from each population are estimated for verification using Gaia data. As a further consequence of the proposed model, the three runaway O star systems, AE Aur, μ Col and ι Ori, are considered as significant observational evidence for stellar-dynamical ejections of massive stars from the oldest population in the ONC. Evidence for stellar-dynamical ejections of massive stars in the currently forming population is also discussed.

Natural course of untreated cluster headache: A retrospective cohort study.

PubMed

Lee, Mi Ji; Choi, Hyun Ah; Shin, Jong Hwa; Park, Hea Ree; Chung, Chin-Sang

2018-04-01

Objective To determine the natural course of cluster headache. Methods We screened patients with cluster headache who were diagnosed at Samsung Medical Center and lost to follow-up for ≥5 years. Eligible patients were interviewed by phone about the longitudinal changes in headache characteristics and disease course. Remission was defined as symptom-free 1) for longer than twice the longest between-bout period and 2) for ≥5 years. Results Forty-two patients lost to follow-up for mean 7.5 (range, 5.0-15.7) years were included. The length of the last bout did not differ from the first one, while the last between-bout period was longer than the first one ( p = 0.012). Characteristics of cluster headache decreased over time: Side-locked unilaterality (from 92.9% to 78.9%), seasonal and circadian rhythmicity (from 63.9% to 60.9% and from 62.2 to 40.5%, respectively), and autonomic symptoms (from 95.2% to 75.0%). Remission occurred in 14 (33.3%) patients at a mean age of 42.3 (range, 27-65) years, which was not different from the age of last bouts in active patients ( p = 0.623). There was a trend for more seasonal and circadian predilection at baseline in the active group ( p = 0.056 and 0.063, respectively) and fewer lifetime bouts and shorter disease duration in patients in remission ( p = 0.063 and 0.090). Conclusions This study first shows the natural courses of cluster headache. Features of cluster headache become less prominent over time. Remission occurred regardless of age. Although no single predictor of remission was found, our data suggest that remission of cluster headache might not be a consequence of more advanced age, longer duration of disease, or accumulation of lifetime bouts.

The Low-mass Population in the Young Cluster Stock 8: Stellar Properties and Initial Mass Function

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jose, Jessy; Herczeg, Gregory J.; Fang, Qiliang

The evolution of H ii regions/supershells can trigger a new generation of stars/clusters at their peripheries, with environmental conditions that may affect the initial mass function, disk evolution, and star formation efficiency. In this paper we study the stellar content and star formation processes in the young cluster Stock 8, which itself is thought to be formed during the expansion of a supershell. We present deep optical photometry along with JHK and 3.6 and 4.5 μ m photometry from UKIDSS and Spitzer -IRAC. We use multicolor criteria to identify the candidate young stellar objects in the region. Using evolutionary models,more » we obtain a median log(age) of ∼6.5 (∼3.0 Myr) with an observed age spread of ∼0.25 dex for the cluster. Monte Carlo simulations of the population of Stock 8, based on estimates for the photometric uncertainty, differential reddening, binarity, and variability, indicate that these uncertainties introduce an age spread of ∼0.15 dex. The intrinsic age spread in the cluster is ∼0.2 dex. The fraction of young stellar objects surrounded by disks is ∼35%. The K -band luminosity function of Stock 8 is similar to that of the Trapezium cluster. The initial mass function (IMF) of Stock 8 has a Salpeter-like slope at >0.5 M {sub ⊙} and flattens and peaks at ∼0.4 M {sub ⊙}, below which it declines into the substellar regime. Although Stock 8 is surrounded by several massive stars, there seems to be no severe environmental effect in the form of the IMF due to the proximity of massive stars around the cluster.« less

Cloud computing and validation of expandable in silico livers

PubMed Central

2010-01-01

Background In Silico Livers (ISLs) are works in progress. They are used to challenge multilevel, multi-attribute, mechanistic hypotheses about the hepatic disposition of xenobiotics coupled with hepatic responses. To enhance ISL-to-liver mappings, we added discrete time metabolism, biliary elimination, and bolus dosing features to a previously validated ISL and initiated re-validated experiments that required scaling experiments to use more simulated lobules than previously, more than could be achieved using the local cluster technology. Rather than dramatically increasing the size of our local cluster we undertook the re-validation experiments using the Amazon EC2 cloud platform. So doing required demonstrating the efficacy of scaling a simulation to use more cluster nodes and assessing the scientific equivalence of local cluster validation experiments with those executed using the cloud platform. Results The local cluster technology was duplicated in the Amazon EC2 cloud platform. Synthetic modeling protocols were followed to identify a successful parameterization. Experiment sample sizes (number of simulated lobules) on both platforms were 49, 70, 84, and 152 (cloud only). Experimental indistinguishability was demonstrated for ISL outflow profiles of diltiazem using both platforms for experiments consisting of 84 or more samples. The process was analogous to demonstration of results equivalency from two different wet-labs. Conclusions The results provide additional evidence that disposition simulations using ISLs can cover the behavior space of liver experiments in distinct experimental contexts (there is in silico-to-wet-lab phenotype similarity). The scientific value of experimenting with multiscale biomedical models has been limited to research groups with access to computer clusters. The availability of cloud technology coupled with the evidence of scientific equivalency has lowered the barrier and will greatly facilitate model sharing as well as provide straightforward tools for scaling simulations to encompass greater detail with no extra investment in hardware. PMID:21129207

Multiple Basinal Fluid Events in the Lower Belt Supergroup, Montana: Constraints From CHIME Ages and REE Patterns of Monazites

NASA Astrophysics Data System (ADS)

Gonzalez-Alvarez, I.; Kusiak, M. A.

2004-05-01

Chemical dates (CHIME) on 105 spots and REE patterns of monazites were obtained from coarse sandstones and siltstones in the Mesoproterozoic siliciclastic Appekunny and Grinnell formations, lower Belt Supergroup, Montana, by EMPA. At least three post-depositional events induced by basinal fluids can be recognized: (a) red coloration accompanied by a major K-addition; (b) a green overprint of red siltstones; and (c) dolomitization. Fluid advection in the unmineralized lower Belt is pervasive and may have been alkaline and oxidizing. These three events progressively modified the primary geochemical characteristics of the siliciclastic rocks. Calculated ages show similar ranges in the fine and coarse-grained facies. For siltstones there are two age clusters: (1) at 1,801 ± 21 to 1,968 ± 26 Ma, as well as (2) at 854 ± 7 to 962 ± 13 Ma. Coarse sandstones show similar age clusters (3) at 1,831 ± 14 to 1,982 ± 12 Ma, and (4) at 803 ± 6 to 944 ± 9 Ma. A wide range of dates plots between the clusters for both facies. Clusters (1) and (3) are interpreted as the result of detrital monazites from a source area ~1.8 to 1.9 Ga old. Mineralogical variations and trace element systematic reveal basinal brines, which mobilized MREE and HREE, locally generating secondary monazites, influencing large domains of the lower Belt. The lower Belt Supergroup is estimated to have been deposited between 1.47 Ga and 1.45 Ga; consequently, the second age cluster for sandstones and siltstones is viewed as constraining the timeframe of a major basinal fluid event at ~0.80 to 0.96 Ga. That event is clearly distinct from the hydrothermal system associated with the Sullivan sedex base metal deposit at the base of the Belt. Ages between the clusters are interpreted either as secondary, formed during additional basinal fluid events or as reset of detrital monazites. Accordingly, the Belt basin was intermittently an open system to fluids from ~1.47 to ~0.80 Ga. Chondrite-normalized REE patterns for both facies display three unusual features: (A) on a linear scale for both facies for clusters (1) and (3) monazites reveal a straight line from La to Sm. For clusters (2) and (4) the profiles between La and Sm are concave or convex; concave profiles are produced mainly because of the Ce values. All reset monazites have convex or concave La-Sm profiles; (B) LREE/HREE and La/Y ratios average values for both facies in clusters (1) and (3) exhibit distinctively lower values than in clusters (2) and (4); (C) on log scale, charts show an unusually heterogeneous MREE and HREE profile for all monazites.

Cluster analysis of obsessive-compulsive spectrum disorders in patients with obsessive-compulsive disorder: clinical and genetic correlates.

PubMed

Lochner, Christine; Hemmings, Sian M J; Kinnear, Craig J; Niehaus, Dana J H; Nel, Daniel G; Corfield, Valerie A; Moolman-Smook, Johanna C; Seedat, Soraya; Stein, Dan J

2005-01-01

Comorbidity of certain obsessive-compulsive spectrum disorders (OCSDs; such as Tourette's disorder) in obsessive-compulsive disorder (OCD) may serve to define important OCD subtypes characterized by differing phenomenology and neurobiological mechanisms. Comorbidity of the putative OCSDs in OCD has, however, not often been systematically investigated. The Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition , Axis I Disorders-Patient Version as well as a Structured Clinical Interview for Putative OCSDs (SCID-OCSD) were administered to 210 adult patients with OCD (N = 210, 102 men and 108 women; mean age, 35.7 +/- 13.3). A subset of Caucasian subjects (with OCD, n = 171; control subjects, n = 168), including subjects from the genetically homogeneous Afrikaner population (with OCD, n = 77; control subjects, n = 144), was genotyped for polymorphisms in genes involved in monoamine function. Because the items of the SCID-OCSD are binary (present/absent), a cluster analysis (Ward's method) using the items of SCID-OCSD was conducted. The association of identified clusters with demographic variables (age, gender), clinical variables (age of onset, obsessive-compulsive symptom severity and dimensions, level of insight, temperament/character, treatment response), and monoaminergic genotypes was examined. Cluster analysis of the OCSDs in our sample of patients with OCD identified 3 separate clusters at a 1.1 linkage distance level. The 3 clusters were named as follows: (1) "reward deficiency" (including trichotillomania, Tourette's disorder, pathological gambling, and hypersexual disorder), (2) "impulsivity" (including compulsive shopping, kleptomania, eating disorders, self-injury, and intermittent explosive disorder), and (3) "somatic" (including body dysmorphic disorder and hypochondriasis). Several significant associations were found between cluster scores and other variables; for example, cluster I scores were associated with earlier age of onset of OCD and the presence of tics, cluster II scores were associated with female gender and childhood emotional abuse, and cluster III scores were associated with less insight and with somatic obsessions and compulsions. However, none of these clusters were associated with any particular genetic variant. Analysis of comorbid OCSDs in OCD suggested that these lie on a number of different dimensions. These dimensions are partially consistent with previous theoretical approaches taken toward classifying OCD spectrum disorders. The lack of genetic validation of these clusters in the present study may indicate the involvement of other, as yet untested, genes. Further genetic and cluster analyses of comorbid OCSDs in OCD may ultimately contribute to a better delineation of OCD endophenotypes.

The Mass Function of Young Star Clusters in the "Antennae" Galaxies.

PubMed

Zhang; Fall

1999-12-20

We determine the mass function of young star clusters in the merging galaxies known as the "Antennae" (NGC 4038/9) from deep images taken with the Wide Field Planetary Camera 2 on the refurbished Hubble Space Telescope. This is accomplished by means of reddening-free parameters and a comparison with stellar population synthesis tracks to estimate the intrinsic luminosity and age, and hence the mass, of each cluster. We find that the mass function of the young star clusters (with ages less, similar160 Myr) is well represented by a power law of the form psi&parl0;M&parr0;~M-2 over the range 104 less, similarM less, similar106 M middle dot in circle. This result may have important implications for our understanding of the origin of globular clusters during the early phases of galactic evolution.

Stochastic Sampling in the IMF of Galactic Open Clusters

NASA Astrophysics Data System (ADS)

Kay, Christina; Hancock, M.; Canalizo, G.; Smith, B. J.; Giroux, M. L.

2010-01-01

We sought observational evidence of the effects of stochastic sampling of the initial mass function by investigating the integrated colors of a sample of Galactic open clusters. In particular we looked for scatter in the integrated (V-K) color as previous research resulted in little scatter in the (U-B) and (B-V) colors. Combining data from WEBDA and 2MASS we determined three different colors for 287 open clusters. Of these clusters, 39 have minimum uncertainties in age and formed a standard set. A plot of the (V-K) color versus age showed much more scatter than the (U-B) versus age. We also divided the sample into two groups based on a lowest luminosity limit which is a function of age and V magnitude. We expected the group of clusters fainter than this limit to show more scatter than the brighter group. Assuming the published ages, we compared the reddening corrected observed colors to those predicted by Starburst99. The presence of stochastic sampling should increase scatter in the distribution of the differences between observed and model colors of the fainter group relative to the brighter group. However, we found that K-S tests cannot rule out that the distribution of color difference for the brighter and fainter sets come from the same parent distribution. This indistinguishabilty may result from uncertainties in the parameters used to define the groups. This result constrains the size of the effects of stochastic sampling of the initial mass function.

Nanoprecipitates and Their Strengthening Behavior in Al-Mg-Si Alloy During the Aging Process

NASA Astrophysics Data System (ADS)

Li, Hui; Liu, Wenqing

2017-04-01

The different nanoprecipitates formed in a 6061 aluminum alloy during aging at 453 K (180 °C), with or without 168 hours of pre-natural aging (NA), and the age-hardening response of the alloy were investigated by atom probe tomography (APT) and hardness testing. A hardness plateau developed between 2 and 8 hours in both the artificial aging (AA) and artificial aging with pre-natural aging (NAAA) samples. The hardness of NAAA samples was lower than that of AA samples when artificially aged for the same time. A 168-hour NA led to the formation of solute atom clusters in the matrix. The NA accelerated the precipitation kinetics of the following AA. The solute atom clusters gave the highest hardness increment per unit volume fraction. The β″ precipitates were dominant in the samples at the hardness plateau. The average normalized Mg:Si ratios of the solute atom clusters and GP zones were near 1. The average Mg:Si ratio of β″ precipitates increased from 1.3 to 1.5 upon aging for 2 hours. The microstructural evolution of samples with or without NA and its influence on the strengthening effects are discussed based on the experimental results.

An extended affinity propagation clustering method based on different data density types.

PubMed

Zhao, XiuLi; Xu, WeiXiang

2015-01-01

Affinity propagation (AP) algorithm, as a novel clustering method, does not require the users to specify the initial cluster centers in advance, which regards all data points as potential exemplars (cluster centers) equally and groups the clusters totally by the similar degree among the data points. But in many cases there exist some different intensive areas within the same data set, which means that the data set does not distribute homogeneously. In such situation the AP algorithm cannot group the data points into ideal clusters. In this paper, we proposed an extended AP clustering algorithm to deal with such a problem. There are two steps in our method: firstly the data set is partitioned into several data density types according to the nearest distances of each data point; and then the AP clustering method is, respectively, used to group the data points into clusters in each data density type. Two experiments are carried out to evaluate the performance of our algorithm: one utilizes an artificial data set and the other uses a real seismic data set. The experiment results show that groups are obtained more accurately by our algorithm than OPTICS and AP clustering algorithm itself.

Effect of binary fraction on color-magnitude diagram of NGC 1904

NASA Astrophysics Data System (ADS)

Li, Zhongmu; Deng, Yangyang

2018-05-01

The age of a southern globular cluster in Milky Way, NGC 1904, was shown to be larger than the typical age of the universe, around 13.7 Gyr, by some photometric studies which assumed all stars as single stars. Besides the uncertainties in photometry, isochrone and fitting technique, the neglect of binary stars possibly distorted the result. We study the effect of binary fraction on the color-magnitude diagram (CMD) of NGC 1904, via a new tool for CMD studies, Powerful CMD, which can determine binary fraction, age, metallicity, distance modulus, color excess, rotating star fraction and star formation history simultaneously. We finally obtain the youngest age of 14.1±2.1 Gyr with a zero-age binary fraction of 60 percent for cluster NGC 1904. The result is consistent with the age of the universe. Although our result suggests that binary fraction affects the determination of age slightly, it can improve the fitting to observed CMD, in particular blue stragglers. This suggests us to consider the effect of binaries in the studies of star clusters.

The microRNA-132 and microRNA-212 cluster regulates hematopoietic stem cell maintenance and survival with age by buffering FOXO3 expression

PubMed Central

Mehta, Arnav; Zhao, Jimmy L.; Sinha, Nikita; Marinov, Georgi K.; Mann, Mati; Kowalczyk, Monika S.; Galimidi, Rachel P.; Du, Xiaomi; Erikci, Erdem; Regev, Aviv; Chowdhury, Kamal; Baltimore, David

2015-01-01

Summary MicroRNAs are critical post-transcriptional regulators of hematopoietic cell-fate decisions, though little remains known about their role in aging hematopoietic stem cells (HSCs). We found that the microRNA-212/132 cluster (Mirc19) is enriched in HSCs and is up-regulated during aging. Both over-expression and deletion of microRNAs in this cluster leads to inappropriate hematopoiesis with age. Enforced expression of miR-132 in the bone marrow of mice led to rapid HSC cycling and depletion. A genetic deletion of Mirc19 in mice resulted in HSCs that had altered cycling, function, and survival in response to growth factor starvation. We found that miR-132 exerted its effect on aging HSCs by targeting the transcription factor FOXO3, a known aging associated gene. Our data demonstrates that Mirc19 plays a role in maintaining balanced hematopoietic output by buffering FOXO3 expression. We have thus identified it as a potential target that may play a role in age-related hematopoietic defects. PMID:26084022

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chandar, Rupali; Fall, S. Michael; Whitmore, Bradley C., E-mail: Rupali.Chandar@utoledo.ed, E-mail: fall@stsci.ed, E-mail: whitmore@stsci.ed

We compare the observed bivariate distribution of masses (M) and ages (tau) of star clusters in the Large Magellanic Cloud (LMC) with the predicted distributions g(M, tau) from three idealized models for the disruption of star clusters: (1) sudden mass-dependent disruption, (2) gradual mass-dependent disruption, and (3) gradual mass-independent disruption. The model with mass-independent disruption provides a good, first-order description of these cluster populations, with g(M, tau) {proportional_to} M {sup beta}tau{sup g}amma, beta = -1.8 +- 0.2 and gamma = -0.8 +- 0.2, at least for clusters with ages tau {approx}< 10{sup 9} yr and masses M {approx}> 10{sup 3}more » M{sub sun} (more specifically, tau {approx}< 10{sup 7}(M/10{sup 2} M{sub sun}){sup 1.3} yr). This model predicts that the clusters should have a power-law luminosity function, dN/dL {proportional_to} L {sup -1.8}, in agreement with observations. The first two models, on the other hand, fare poorly when describing the observations, refuting previous claims that mass-dependent disruption of star clusters is observed in the LMC over the studied M-tau domain. Clusters in the SMC can be described by the same g(M, tau) distribution as for the LMC, but with smaller samples and hence larger uncertainties. The successful g(M, tau) model for clusters in the Magellanic Clouds is virtually the same as the one for clusters in the merging Antennae galaxies, but extends the domain of validity to lower masses and to older ages. This indicates that the dominant disruption processes are similar in these very different galaxies over at least tau {approx}< 10{sup 8} yr and possibly tau {approx}< 10{sup 9} yr. The mass functions for young clusters in the LMC are power laws, while that for ancient globular clusters is peaked. We show that the observed shapes of these mass functions are consistent with expectations from the simple evaporation model presented by McLaughlin and Fall.« less

Dating the Tidal Disruption of Globular Clusters with GAIA Data on Their Stellar Streams

NASA Astrophysics Data System (ADS)

Bose, Sownak; Ginsburg, Idan; Loeb, Abraham

2018-05-01

The Gaia mission promises to deliver precision astrometry at an unprecedented level, heralding a new era for discerning the kinematic and spatial coordinates of stars in our Galaxy. Here, we present a new technique for estimating the age of tidally disrupted globular cluster streams using the proper motions and parallaxes of tracer stars. We evolve the collisional dynamics of globular clusters within the evolving potential of a Milky Way-like halo extracted from a cosmological ΛCDM simulation and analyze the resultant streams as they would be observed by Gaia. The simulations sample a variety of globular cluster orbits, and account for stellar evolution and the gravitational influence of the disk of the Milky Way. We show that a characteristic timescale, obtained from the dispersion of the proper motions and parallaxes of stars within the stream, is a good indicator for the time elapsed since the stream has been freely expanding away due to the tidal disruption of the globular cluster. This timescale, in turn, places a lower limit on the age of the cluster. The age can be deduced from astrometry using a modest number of stars, with the error on this estimate depending on the proximity of the stream and the number of tracer stars used.

Geographic clusters in underimmunization and vaccine refusal.

PubMed

Lieu, Tracy A; Ray, G Thomas; Klein, Nicola P; Chung, Cindy; Kulldorff, Martin

2015-02-01

Parental refusal and delay of childhood vaccines has increased in recent years and is believed to cluster in some communities. Such clusters could pose public health risks and barriers to achieving immunization quality benchmarks. Our aims were to (1) describe geographic clusters of underimmunization and vaccine refusal, (2) compare clusters of underimmunization with different vaccines, and (3) evaluate whether vaccine refusal clusters may pose barriers to achieving high immunization rates. We analyzed electronic health records among children born between 2000 and 2011 with membership in Kaiser Permanente Northern California. The study population included 154,424 children in 13 counties with continuous membership from birth to 36 months of age. We used spatial scan statistics to identify clusters of underimmunization (having missed 1 or more vaccines by 36 months of age) and vaccine refusal (based on International Classification of Diseases, Ninth Revision, Clinical Modification codes). We identified 5 statistically significant clusters of underimmunization among children who turned 36 months old during 2010-2012. The underimmunization rate within clusters ranged from 18% to 23%, and the rate outside them was 11%. Children in the most statistically significant cluster had 1.58 (P < .001) times the rate of underimmunization as others. Underimmunization with measles, mumps, rubella vaccine and varicella vaccines clustered in similar geographic areas. Vaccine refusal also clustered, with rates of 5.5% to 13.5% within clusters, compared with 2.6% outside them. Underimmunization and vaccine refusal cluster geographically. Spatial scan statistics may be a useful tool to identify locations with challenges to achieving high immunization rates, which deserve focused intervention. Copyright © 2015 by the American Academy of Pediatrics.

Symptom clustering and quality of life in patients with ovarian cancer undergoing chemotherapy.

PubMed

Nho, Ju-Hee; Reul Kim, Sung; Nam, Joo-Hyun

2017-10-01

The symptom clusters in patients with ovarian cancer undergoing chemotherapy have not been well evaluated. We investigated the symptom clusters and effects of symptom clusters on the quality of life of patients with ovarian cancer. We recruited 210 ovarian cancer patients being treated with chemotherapy and used a descriptive cross-sectional study design to collect information on their symptoms. To determine inter-relationships among symptoms, a principal component analysis with varimax rotation was performed based on the patient's symptoms (fatigue, pain, sleep disturbance, chemotherapy-induced peripheral neuropathy, anxiety, depression, and sexual dysfunction). All patients had experienced at least two domains of concurrent symptoms, and there were two types of symptom clusters. The first symptom cluster consisted of anxiety, depression, fatigue, and sleep disturbance symptoms, while the second symptom cluster consisted of pain and chemotherapy-induced peripheral neuropathy symptoms. Our subgroup cluster analysis showed that ovarian cancer patients with higher-scoring symptoms had significantly poorer quality of life in both symptom cluster 1 and 2 subgroups, with subgroup-specific patterns. The symptom clusters were different depending on age, age at disease onset, disease duration, recurrence, and performance status of patients with ovarian cancer. In addition, ovarian cancer patients experienced different symptom clusters according to cancer stage. The current study demonstrated that there is a specific pattern of symptom clusters, and symptom clusters negatively influence the quality of life in patients with ovarian cancer. Identifying symptom clusters of ovarian cancer patients may have clinical implications in improving symptom management. Copyright © 2017 Elsevier Ltd. All rights reserved.

Reddenings, Metallicities, and Possible Abundance Anomalies in Young Globular Clusters

NASA Astrophysics Data System (ADS)

Sarajedini, Ata; Layden, Andrew

1997-01-01

We present new photometry in the VI passbands for the ``young'' globular clusters Rup 106, Ter 7, and Arp 2. After formulating the simultaneous reddening and metallicity (SRM) method of Sarajedini (1994) in the BV passbands, we apply it, along with the SRM method in VI, to the red giant branches (RGBs) of these clusters using B-V photometry from the literature and the V-I data presented herein. We find [Fe/H] = -1.90 +/- 0.10, E(B-V) = 0.18 +/- 0.02 for Rup 106, [Fe/H] = -0.82 +/- 0.15, E(B-V) = 0.07 +/- 0.03 for Ter 7, and [Fe/H] = -1.84 +/- 0.09, E(B-V) = 0.10 +/- 0.02 for Arp 2. Furthermore, in light of this new abundance for Ter 7 and recent work on the luminosity of the red horizontal branch, we rederive the age of Ter 7 finding it to be some 6 Gyr younger than 47 Tuc. We show that the SRM method is insensitive to age for clusters with purely red HBs and ages as young as ~ 5 Gyr; for clusters with bluer HBs, the SRM method is only mildly sensitive to age differences between such clusters and the calibrating (standard) clusters. From these metallicity estimates, we conclude that the photometric abundances of the program clusters based on the properties of the RGB are systematically lower (Delta [Fe/H] = 0.1-0.4 dex) than those derived using other indicators, in particular the Ca 2 triplet method. We note that the young globular clusters Pal 12 and possibly IC 4499 also exhibit this behavior. We suggest that this discrepancy is due to systematic differences in the [alpha /Fe] ratios between the young clusters and the ``normal'' Galactic globulars used to calibrate the abundance determination methods. However, we are unable to completely reconcile all the observations of Rup 106 using this approach. Systematic differences in [alpha /Fe] between the young clusters and the rest of the Galactic globulars may indicate differences in their chemical enrichment histories, perhaps due to differing environments at the times of their formation. Interestingly, both Ter 7 and Arp 2 are believed to be memebers of the Sagittarius dwarf galaxy, while Rup 106 and (perhaps) Pal 12 are suspected of being captured from the Magellanic Clouds.

Is sibling rivalry fatal?: siblings and mortality clustering.

PubMed

Kippen, Rebecca; Walters, Sarah

2012-01-01

Evidence drawn from nineteenth-century Belgian population registers shows that the presence of similarly aged siblings competing for resources within a household increases the probability of death for children younger than five, even when controlling for the preceding birth interval and multiple births. Furthermore, in this period of Belgian history, such mortality tended to cluster in certain families. The findings suggest the importance of segmenting the mortality of siblings younger than five by age group, of considering the presence of siblings as a time-varying covariate, and of factoring mortality clustering into analyses.

THE AGES OF 55 GLOBULAR CLUSTERS AS DETERMINED USING AN IMPROVED ΔV{sup HB}{sub TO} METHOD ALONG WITH COLOR-MAGNITUDE DIAGRAM CONSTRAINTS, AND THEIR IMPLICATIONS FOR BROADER ISSUES

DOE Office of Scientific and Technical Information (OSTI.GOV)

VandenBerg, Don A.; Brogaard, K.; Leaman, R.

Ages have been derived for 55 globular clusters (GCs) for which Hubble Space Telescope Advanced Camera for Surveys photometry is publicly available. For most of them, the assumed distances are based on fits of theoretical zero-age horizontal-branch (ZAHB) loci to the lower bound of the observed distributions of HB stars, assuming reddenings from empirical dust maps and metallicities from the latest spectroscopic analyses. The age of the isochrone that provides the best fit to the stars in the vicinity of the turnoff (TO) is taken to be the best estimate of the cluster age. The morphology of isochrones between themore » TO and the beginning part of the subgiant branch (SGB) is shown to be nearly independent of age and chemical abundances. For well-defined color-magnitude diagrams (CMDs), the error bar arising just from the 'fitting' of ZAHBs and isochrones is ≈ ± 0.25 Gyr, while that associated with distance and chemical abundance uncertainties is ∼ ± 1.5-2 Gyr. The oldest GCs in our sample are predicted to have ages of ≈13.0 Gyr (subject to the aforementioned uncertainties). However, the main focus of this investigation is on relative GC ages. In conflict with recent findings based on the relative main-sequence fitting method, which have been studied in some detail and reconciled with our results, ages are found to vary from mean values of ≈12.5 Gyr at [Fe/H] ∼< – 1.7 to ≈11 Gyr at [Fe/H] ∼> –1. At intermediate metallicities, the age-metallicity relation (AMR) appears to be bifurcated: one branch apparently contains clusters with disk-like kinematics, whereas the other branch, which is displaced to lower [Fe/H] values by ≈0.6 dex at a fixed age, is populated by clusters with halo-type orbits. The dispersion in age about each component of the AMR is ∼ ± 0.5 Gyr. There is no apparent dependence of age on Galactocentric distance (R{sub G}) nor is there a clear correlation of HB type with age. As previously discovered in the case of M3 and M13, subtle variations have been found in the slope of the SGB in the CMDs of other metal-poor ([Fe/H] ∼< – 1.5) GCs. They have been tentatively attributed to cluster-to-cluster differences in the abundance of helium. Curiously, GCs that have relatively steep 'M13-like' SGBs tend to be massive systems, located at small R{sub G}, that show the strongest evidence of in situ formation of multiple stellar populations. The clusters in the other group are typically low-mass systems (with 2-3 exceptions, including M3) that, at the present time, should not be able to retain the matter lost by mass-losing stars due either to the development of GC winds or to ram-pressure stripping by the halo interstellar medium. The apparent separation of the two groups in terms of their present-day gas retention properties is difficult to understand if all GCs were initially ∼20 times their current masses. The lowest-mass systems, in particular, may have never been massive enough to retain enough gas to produce a significant population of second-generation stars. In this case, the observed light element abundance variations, which are characteristic of all GCs, were presumably present in the gas out of which the observed cluster stars formed.« less

Comparison of Poisson and Bernoulli spatial cluster analyses of pediatric injuries in a fire district

PubMed Central

Warden, Craig R

2008-01-01

Background With limited resources available, injury prevention efforts need to be targeted both geographically and to specific populations. As part of a pediatric injury prevention project, data was obtained on all pediatric medical and injury incidents in a fire district to evaluate geographical clustering of pediatric injuries. This will be the first step in attempting to prevent these injuries with specific interventions depending on locations and mechanisms. Results There were a total of 4803 incidents involving patients less than 15 years of age that the fire district responded to during 2001–2005 of which 1997 were categorized as injuries and 2806 as medical calls. The two cohorts (injured versus medical) differed in age distribution (7.7 ± 4.4 years versus 5.4 ± 4.8 years, p < 0.001) and location type of incident (school or church 12% versus 15%, multifamily residence 22% versus 13%, single family residence 51% versus 28%, sport, park or recreational facility 3% versus 8%, public building 8% versus 7%, and street or road 3% versus 30%, respectively, p < 0.001). Using the medical incident locations as controls, there was no significant clustering for environmental or assault injuries using the Bernoulli method while there were four significant clusters for all injury mechanisms combined, 13 clusters for motor vehicle collisions, one for falls, and two for pedestrian or bicycle injuries. Using the Poisson cluster method on incidence rates by census tract identified four clusters for all injuries, three for motor vehicle collisions, four for fall injuries, and one each for environmental and assault injuries. The two detection methods shared a minority of overlapping geographical clusters. Conclusion Significant clustering occurs overall for all injury mechanisms combined and for each mechanism depending on the cluster detection method used. There was some overlap in geographic clusters identified by both methods. The Bernoulli method allows more focused cluster mapping and evaluation since it directly uses location data. Once clusters are found, interventions can be targeted to specific geographic locations, location types, ages of victims, and mechanisms of injury. PMID:18808720

Comparison of Poisson and Bernoulli spatial cluster analyses of pediatric injuries in a fire district.

PubMed

Warden, Craig R

2008-09-22

With limited resources available, injury prevention efforts need to be targeted both geographically and to specific populations. As part of a pediatric injury prevention project, data was obtained on all pediatric medical and injury incidents in a fire district to evaluate geographical clustering of pediatric injuries. This will be the first step in attempting to prevent these injuries with specific interventions depending on locations and mechanisms. There were a total of 4803 incidents involving patients less than 15 years of age that the fire district responded to during 2001-2005 of which 1997 were categorized as injuries and 2806 as medical calls. The two cohorts (injured versus medical) differed in age distribution (7.7 +/- 4.4 years versus 5.4 +/- 4.8 years, p < 0.001) and location type of incident (school or church 12% versus 15%, multifamily residence 22% versus 13%, single family residence 51% versus 28%, sport, park or recreational facility 3% versus 8%, public building 8% versus 7%, and street or road 3% versus 30%, respectively, p < 0.001). Using the medical incident locations as controls, there was no significant clustering for environmental or assault injuries using the Bernoulli method while there were four significant clusters for all injury mechanisms combined, 13 clusters for motor vehicle collisions, one for falls, and two for pedestrian or bicycle injuries. Using the Poisson cluster method on incidence rates by census tract identified four clusters for all injuries, three for motor vehicle collisions, four for fall injuries, and one each for environmental and assault injuries. The two detection methods shared a minority of overlapping geographical clusters. Significant clustering occurs overall for all injury mechanisms combined and for each mechanism depending on the cluster detection method used. There was some overlap in geographic clusters identified by both methods. The Bernoulli method allows more focused cluster mapping and evaluation since it directly uses location data. Once clusters are found, interventions can be targeted to specific geographic locations, location types, ages of victims, and mechanisms of injury.

Insight into acid-base nucleation experiments by comparison of the chemical composition of positive, negative, and neutral clusters.

PubMed

Bianchi, Federico; Praplan, Arnaud P; Sarnela, Nina; Dommen, Josef; Kürten, Andreas; Ortega, Ismael K; Schobesberger, Siegfried; Junninen, Heikki; Simon, Mario; Tröstl, Jasmin; Jokinen, Tuija; Sipilä, Mikko; Adamov, Alexey; Amorim, Antonio; Almeida, Joao; Breitenlechner, Martin; Duplissy, Jonathan; Ehrhart, Sebastian; Flagan, Richard C; Franchin, Alessandro; Hakala, Jani; Hansel, Armin; Heinritzi, Martin; Kangasluoma, Juha; Keskinen, Helmi; Kim, Jaeseok; Kirkby, Jasper; Laaksonen, Ari; Lawler, Michael J; Lehtipalo, Katrianne; Leiminger, Markus; Makhmutov, Vladimir; Mathot, Serge; Onnela, Antti; Petäjä, Tuukka; Riccobono, Francesco; Rissanen, Matti P; Rondo, Linda; Tomé, António; Virtanen, Annele; Viisanen, Yrjö; Williamson, Christina; Wimmer, Daniela; Winkler, Paul M; Ye, Penglin; Curtius, Joachim; Kulmala, Markku; Worsnop, Douglas R; Donahue, Neil M; Baltensperger, Urs

2014-12-02

We investigated the nucleation of sulfuric acid together with two bases (ammonia and dimethylamine), at the CLOUD chamber at CERN. The chemical composition of positive, negative, and neutral clusters was studied using three Atmospheric Pressure interface-Time Of Flight (APi-TOF) mass spectrometers: two were operated in positive and negative mode to detect the chamber ions, while the third was equipped with a nitrate ion chemical ionization source allowing detection of neutral clusters. Taking into account the possible fragmentation that can happen during the charging of the ions or within the first stage of the mass spectrometer, the cluster formation proceeded via essentially one-to-one acid-base addition for all of the clusters, independent of the type of the base. For the positive clusters, the charge is carried by one excess protonated base, while for the negative clusters it is carried by a deprotonated acid; the same is true for the neutral clusters after these have been ionized. During the experiments involving sulfuric acid and dimethylamine, it was possible to study the appearance time for all the clusters (positive, negative, and neutral). It appeared that, after the formation of the clusters containing three molecules of sulfuric acid, the clusters grow at a similar speed, independent of their charge. The growth rate is then probably limited by the arrival rate of sulfuric acid or cluster-cluster collision.

The Young Massive Stellar Cluster Sandage-96 after the Explosion of SN 2004DJ in NGC 2403

NASA Technical Reports Server (NTRS)

Vinko, J.; Sarneczky, K.; Balog, Z.; Immler, S.; Sugerman, B.; Brown, P. J.; Misselt, K.; Szabo, Gy. M.; Klagyivik, P.; Kun, M.;

Typology of people with first-episode psychosis.

PubMed

Subramaniam, Mythily; Zheng, Huili; Soh, Pauline; Poon, Lye Yin; Vaingankar, Janhavi A; Chong, Siow Ann; Verma, Swapna

2016-08-01

The aim of the current study was to create a typology of patients with first-episode psychosis based on sociodemographic and clinical characteristics, service use and outcomes using cluster analysis. Data from all respondents who were accepted into the Early Psychosis Intervention Programme (EPIP), Singapore from 2007 to 2011 were analysed. A two-step clustering method was carried out to classify the patients into distinct clusters. Two clusters were identified. Cluster 1 comprised largely of younger people with mean age of 25.5 (6.0) years at treatment contact, who were predominantly male (55.3%), single (98.3%) and living with parents (86.3%). Cluster 1 had a higher proportion of people diagnosed with the schizophrenia spectrum disorder (71.4%) and with a positive family history of psychiatric illness. Patients in cluster 2 were generally older with a mean age of 33.6 (4.7) years and the majority were women (74.2%). Cluster 1 had people with higher Positive and Negative Syndrome Scale (PANSS) scores at baseline as compared with cluster 2. After a 1-year follow up, their scores were still poorer than their counterparts in cluster 2, especially for PANSS negative score. The functioning level of people in cluster 1 showed less improvement than the people in cluster 2 after a year of treatment. There is a compelling need to develop new therapies and intensively treat young people presenting with psychosis as this group tends to have poorer outcomes even after 1 year of treatment. © 2014 Wiley Publishing Asia Pty Ltd.

Integrated spectral properties of 7 galactic open clusters

NASA Astrophysics Data System (ADS)

Ahumada, A. V.; Clariá, J. J.; Bica, E.; Piatti, A. E.

2000-01-01

This paper presents flux-calibrated integrated spectra in the range 3600-9000 Ä for 7 concentrated, relatively populous Galactic open clusters. We perform simultaneous estimates of age and foreground interstellar reddening by comparing the continuum distribution and line strengths of the cluster spectra with those of template cluster spectra with known parameters. For five clusters these two parameters have been determined for the first time (Ruprecht 144, BH 132, Pismis 21, Lyng\\aa 11 and BH 217), while the results here derived for the remaining two clusters (Hogg 15 and Melotte 105) show very good agreement with previous studies based mainly on colour-magnitude diagrams. We also provide metallicity estimates for six clusters from the equivalent widths of CaII triplet and TiO features. The present cluster sample improves the age resolution around solar metal content in the cluster spectral library for population synthesis. We compare the properties of the present sample with those of clusters in similar directions. Hogg 15 and Pismis 21 are among the most reddened clusters in sectors centered at l = 270o and l = 0o, respectively. Besides, the present results would favour an important dissolution rate of star clusters in these zones. Based on observations made at Complejo Astronómico El Leoncito, which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba and San Juan, Argentina.

Dental caries experience among Albanian pre-school children: a national survey.

PubMed

Hysi, D; Caglar, E; Droboniku, E; Toti, C; Kuscu, O O

2017-03-01

To determine the dental caries experience and treatment needs among 5-year-olds in Albania. This cross sectional study was conducted in 2015 by using a cluster sampling technique. The dmft was used to assess dental caries experience and caries prevalence as percentages of children with dmf⟩0. Caries treatment needs were assessed with dt/dmft x 100, missing teeth with mt/dmft x 100 and ft /dmft x 100 as the Care Index. 2,039 five-year-olds, from 17 districts of Albania were selected . Children's residency was divided into 3 main regions (South, West, Central and North). WHO 2013 diagnostic criteria were used and dental caries was recorded at cavity level d3. The mean age was 5.4 (SD 0.5) years. The caries prevalence (dmf⟩0) was 84.1%. The prevalence of children without cavitated lesions (d=0) was 20.1%. The mean dmft index was 4.41 (SD 3.83). The caries treatment needs were 84% (SD 26%). The Albanian 5-year-olds assessed in this survey had a high dental caries experience and untreated cavities in the primary dentition. The national health authorities should introduce preventive programs and improved dental care access for this age group. Copyright© 2017 Dennis Barber Ltd

Investigating Subtypes of Child Development: A Comparison of Cluster Analysis and Latent Class Cluster Analysis in Typology Creation

ERIC Educational Resources Information Center

DiStefano, Christine; Kamphaus, R. W.

2006-01-01

Two classification methods, latent class cluster analysis and cluster analysis, are used to identify groups of child behavioral adjustment underlying a sample of elementary school children aged 6 to 11 years. Behavioral rating information across 14 subscales was obtained from classroom teachers and used as input for analyses. Both the procedures…

Catalog of open clusters and associated interstellar matter

NASA Technical Reports Server (NTRS)

Leisawitz, David

1988-01-01

The Catalog of Open Clusters and Associated Interstellar Matter summarizes observations of 128 open clusters and their associated ionized, atomic, and molecular iinterstellar matter. Cluster sizes, distances, radial velocities, ages, and masses, and the radial velocities and masses of associated interstellar medium components, are given. The database contains information from approximately 400 references published in the scientific literature before 1988.

Hogg 12 and NGC 3590: A New Open Cluster Binary System Candidate

NASA Astrophysics Data System (ADS)

Piatti, Andrés E.; Clariá, Juan J.; Ahumada, Andrea V.

2010-05-01

We have obtained CCD UBVIKC photometry down to V ˜ 22.0 for the open clusters Hogg 12 and NGC 3590 and the fields surrounding them. Based on photometric and morphological criteria, as well as on the stellar density in the region, our evidence is sufficient to confirm that Hogg 12 is a genuine open cluster. NGC 3590 was used as a control cluster. The color-magnitude diagrams of Hogg 12, cleaned from field star contamination, reveal that this is a solar metal content cluster, affected by E(B - V) = 0.40 ± 0.05, located at a heliocentric distance d = 2.0 ± 0.5 kpc, and of an age similar to that of NGC 3590 (t = 30 Myr). Both clusters are surprisingly small objects whose radii are barely ˜1 pc, andthey are separated in the sky by scarcely 3.6 pc. These facts, added to their similar ages, reddenings, and metallicities, allow us to consider them a new open cluster binary system candidate. Of the ˜180 open cluster binary systems estimated to exist in the Galaxy, of which 27 are actually well known, Hogg 12 and NGC 3590 appear to be one of the two closest pairs.

Identification of Clusters of Foot Pain Location in a Community Sample.

PubMed

Gill, Tiffany K; Menz, Hylton B; Landorf, Karl B; Arnold, John B; Taylor, Anne W; Hill, Catherine L

2017-12-01

To identify foot pain clusters according to pain location in a community-based sample of the general population. This study analyzed data from the North West Adelaide Health Study. Data were obtained between 2004 and 2006, using computer-assisted telephone interviewing, clinical assessment, and self-completed questionnaire. The location of foot pain was assessed using a diagram during the clinical assessment. Hierarchical cluster analysis was undertaken to identify foot pain location clusters, which were then compared in relation to demographics, comorbidities, and podiatry services utilization. There were 558 participants with foot pain (mean age 54.4 years, 57.5% female). Five clusters were identified: 1 with predominantly arch and ball pain (26.8%), 1 with rearfoot pain (20.9%), 1 with heel pain (13.3%), and 2 with predominantly forefoot, toe, and nail pain (28.3% and 10.7%). Each cluster was distinct in age, sex, and comorbidity profile. Of the two clusters with predominantly forefoot, toe, and nail pain, one of them had a higher proportion of men and those classified as obese, had diabetes mellitus, and used podiatry services (30%), while the other was comprised of a higher proportion of women who were overweight and reported less use of podiatry services (17.5%). Five clusters of foot pain according to pain location were identified, all with distinct age, sex, and comorbidity profiles. These findings may assist in the identification of individuals at risk for developing foot pain and in the development of targeted preventive strategies and treatments. © 2017, American College of Rheumatology.

Study of II Galactic quadrant of Milky Way Galaxy using open clusters

NASA Astrophysics Data System (ADS)

Bisht, Devendra; Ganesh, Shashikiran; Baliyan, Kiran Singh; Yadav, Ramakant Singh; Durgapal, Alok

2018-04-01

We have made UBV I CCD observations for the open clusters Teutsch 1, Riddle 4 and Czernik 6 using 1.04-m Sampurnanand telescope located at the ARIES observatory (Manora peak, Nainital, India). We have used 2MASS JHKS data for the clusters Teutsch 126, Teutsch 54 and Czernik 3. For the estimation of fundamental parameters, we have plotted radial density profiles, colour-magnitude and colour-colour diagrams. Using these inputs, we have studied the structure of Milky Way Galaxy in the second Galactic quadrant. We have considered the open clusters that are younger than 1 Gyrs and lay in the longitude range from 90 to 180 deg. Our study shows that up to 3.5 Kpc, the Galactic disc bends towards the southern hemisphere while after 3.5 Kpc it bends towards the northern hemisphere. The distribution of reddening with longitude and age shows a decreasing trend with the longitude and age of the clusters. Our study also indicates that younger clusters have more reddening than older ones.

Characteristics of the Variable Star P Cygni Determined from Cluster Membership

NASA Technical Reports Server (NTRS)

Turner, David G.; Welch, Gary; Graham, Marianne; Fairweather, David; Horsford, Andrew; Seymour, Michael; Feibelman, Walter; Fisher, Richard (Technical Monitor)

2001-01-01

Empirical information on the luminosity, reddening, age, and mass of the variable B2 Oe supergiant P Cygni is derived from its assumed membership in the sparse anonymous cluster on which it is projected, as well as its association with the spatially adjacent cluster IC 4996, which forms a double cluster with the P Cyg cluster. Evidence for the high luminosity of P Cyg is confirmed by its derived absolute magnitude of M(sub V)= -8.46 +/- 0.03, which translates to log (L/L(sun)) = 5.54 +/- 0.02 for an effective temperature consistent with the star's derived space reddening (E(sub B-V) = 0.53 +/- 0.02). More surprising is an age for the associated clusters of 6 (+/- 1.5) x 10(exp 6) years, corresponding to a turnoff point mass of 25.1 (+/- 5.5) M(sun). By inference, P Cygni, as a post main-sequence object, should have a mass of no more than approximately 23-35 M(sun).

Not-so-simple stellar populations in nearby, resolved massive star clusters

NASA Astrophysics Data System (ADS)

de Grijs, Richard; Li, Chengyuan

2018-02-01

Around the turn of the last century, star clusters of all kinds were considered ‘simple’ stellar populations. Over the past decade, this situation has changed dramatically. At the same time, star clusters are among the brightest stellar population components and, as such, they are visible out to much greater distances than individual stars, even the brightest, so that understanding the intricacies of star cluster composition and their evolution is imperative for understanding stellar populations and the evolution of galaxies as a whole. In this review of where the field has moved to in recent years, we place particular emphasis on the properties and importance of binary systems, the effects of rapid stellar rotation, and the presence of multiple populations in Magellanic Cloud star clusters across the full age range. Our most recent results imply a reverse paradigm shift, back to the old simple stellar population picture for at least some intermediate-age (˜1-3 Gyr old) star clusters, opening up exciting avenues for future research efforts.

The Open Cluster Chemical Abundances and Mapping (OCCAM) Survey: Galactic Neutron Capture Abundance Gradients

NASA Astrophysics Data System (ADS)

O'Connell, Julia; Frinchaboy, Peter M.; Shetrone, Matthew D.; Melendez, Matthew; Cunha, Katia M. L.; Majewski, Steven R.; Zasowski, Gail; APOGEE Team

2017-01-01

The evolution of elements, as a function or age, throughout the Milky Way disk provides a key constraint for galaxy evolution models. In an effort to provide these constraints, we have conducted an investigation into the r- and s- process elemental abundances for a large sample of open clusters as part of an optical follow-up to the SDSS-III/APOGEE-1 survey. Stars were identified as cluster members by the Open Cluster Chemical Abundance & Mapping (OCCAM) survey, which culls member candidates by radial velocity, metallicity, and proper motion from the observed APOGEE sample. To obtain data for neutron capture elements in these clusters, we conducted a long-term observing campaign covering three years (2013-2016) using the McDonald Observatory Otto Struve 2.1-m telescope and Sandiford Cass Echelle Spectrograph (R ~ 60,000). We present Galactic neutron-capture abundance gradients using 30+ clusters, within 6 kpc of the Sun, covering a range of ages from ~80 Myr to ~10 Gyr .

The Open Cluster Chemical Abundances and Mapping (OCCAM) Survey: Galactic Neutron CaptureAbundance Gradients

NASA Astrophysics Data System (ADS)

O'Connell, Julia; Frinchaboy, Peter M.; Shetrone, Matthew D.; Melendez, Matthew; Cunha, Katia; Majewski, Steven R.; Zasowski, Gail; APOGEE Team

2017-06-01

The evolution of elements, as a function or age, throughout the Milky Way disk provides a key constraint for galaxy evolution models. In an effort to provide these constraints, we have conducted an investigation into the r- and s- process elemental abundances for a large sample of open clusters as part of an optical follow-up to the SDSS-III/APOGEE-1 survey. Stars were identified as cluster members by the Open Cluster Chemical Abundance & Mapping (OCCAM) survey, which culls member candidates by radial velocity, metallicity and proper motion from the observed APOGEE sample. To obtain data for neutron capture elements in these clusters, we conducted a long-term observing campaign covering three years (2013-2016) using the McDonald Observatory Otto Struve 2.1-m telescope and Sandiford Cass Echelle Spectrograph (R ~ 60,000). We present Galactic neutron capture abundance gradients using 30+ clusters, within 6 kpc of the Sun, covering a range of ages from ~80 Myr to ~10 Gyr .

"What Could Have Been Different": A Qualitative Study of Syndemic Theory and HIV Prevention among Young Men Who Have Sex with Men.

PubMed

Lyons, Thomas; Johnson, Amy K; Garofalo, Robert

2013-01-01

Young men who have sex with men (MSM) experience multiple health disparities, including alcohol and drug use, partner violence, victimization due to sexual orientation, and HIV infection. Syndemic theorists explain the clustering of these disparities among adult MSM as a result of cultural marginalization. To date, research on a similar emerging syndemic among young MSM has been limited to quantitative studies. This study seeks to better understand these disparities, and how they may cluster together, via qualitative interviews with 21 ethnically diverse, HIV infected young MSM aged 18-24 years old. These youth report a lack of gay-specific HIV prevention education, absence of role models, and lack of productive future goal-related activities as factors related to their acquisition of HIV, and downplay substance use as a factor. Although not necessarily the components traditionally cited by syndemic theorists, these findings support the notion that multiple factors of cultural marginalization cluster together in the lives of young MSM, and underscore the importance of community-level interventions, such as sexual health education, access to mentors, and assistance with future goal setting and planning.

“What Could Have Been Different”: A Qualitative Study of Syndemic Theory and HIV Prevention among Young Men Who Have Sex with Men

PubMed Central

Lyons, Thomas; Johnson, Amy K.; Garofalo, Robert

2013-01-01

Young men who have sex with men (MSM) experience multiple health disparities, including alcohol and drug use, partner violence, victimization due to sexual orientation, and HIV infection. Syndemic theorists explain the clustering of these disparities among adult MSM as a result of cultural marginalization. To date, research on a similar emerging syndemic among young MSM has been limited to quantitative studies. This study seeks to better understand these disparities, and how they may cluster together, via qualitative interviews with 21 ethnically diverse, HIV infected young MSM aged 18–24 years old. These youth report a lack of gay-specific HIV prevention education, absence of role models, and lack of productive future goal-related activities as factors related to their acquisition of HIV, and downplay substance use as a factor. Although not necessarily the components traditionally cited by syndemic theorists, these findings support the notion that multiple factors of cultural marginalization cluster together in the lives of young MSM, and underscore the importance of community-level interventions, such as sexual health education, access to mentors, and assistance with future goal setting and planning. PMID:24244112

Health risk behaviours of Palestinian youth: findings from a representative survey.

PubMed

Glick, Peter; Al-Khammash, Umaiyeh; Shaheen, Mohammed; Brown, Ryan; Goutam, Prodyumna; Karam, Rita; Linnemayr, Sebastian; Massad, Salwa

2018-05-03

There is little systematic information about health risk behaviours among youth in Middle Eastern countries, leaving public health authorities unprepared to deal with emerging public health threats at a time of major social change. The Palestinian Youth Health Risk study investigates patterns of risk behaviours among Palestinian youth, their perceptions of the risks and benefits of such behaviours, and the relationship of exposure to violence with mental health and engagement in risk behaviours. We conducted a representative survey among 2500 individuals aged 15-24 years in the West Bank and East Jerusalem, permitting reliable comparison across sex and rural-urban divisions. A stratified 2-stage random sample was drawn from the 2007 population census, with strata formed by crossing the 12 governorates with urban, rural and refugee camp locations. Within strata, 208 survey clusters were sampled with probability proportional to size. Within each cluster, 14 households with youth of the appropriate age were sampled. Among youth aged 20-24 years, 22.4% of males and 11.6% of females reported trying alcohol; 10.5% of males and 4.3% of females reported trying drugs. Almost one quarter of unmarried youth aged 20-24 years reported any sexual experience. Tobacco use is high, even among younger youth (45.4% of males and 21.2% of females aged 15-19 smoke). Risk behaviours are higher among males, older youth and in urban areas and refugee camps. While smoking is of particular concern, prevention outreach for all behaviours should be directed at subgroups and areas identified as highest risk. Copyright © World Health Organization (WHO) 2018. Some rights reserved. This work is available under the CC BY-NC-SA 3.0 IGO license (https://creativecommons.org/licenses/by-nc-sa/3.0/igo).

Hubble Space Telescope imaging of the central star forming region in NGC 1140 (exp 1)

NASA Technical Reports Server (NTRS)

Hunter, Deidre A.; O'Connell, Robert W.; Gallagher, John S. Iii

1994-01-01

We present broadband images taken with the Hubble Space Telescope's Planetary Camera of the central supergiant H II region in the amorphous galaxy NGC 1140. These images allow observations to a resolution of about 13 pc at the galaxy, and they reveal that its central 1/2 kpc contains 6-7 blue, luminous, compact super star clusters, many of which would be comparable in luminosity to globular clusters at the same age. A blue arc-shaped structure near the center may be a grouping of less luminous, R136/NGC 2070-sized clusters or a sheet of OB stars. Additional somewhat less luminous and redder clusters are also found farther out from the center. If these clusters are older, they too could have had luminosities comparable to those of the central six clusters at a comparable age. Thus, we find that NGC 1140 is remarkable in the number of extreme clusters that it has formed recently in a relatively small area of the galaxy. Since NGC 1140 exhibits global characteristics that are consistent with a recent merger, these clusters are likely to be a product of that event. This galaxy adds to the number of cases where rapid star formation has evidently produced super star clusters.

College Students' Perceptions of Job Demands, Recommended Retirement Ages, and Age of Optimal Performance in Selected Occupations

ERIC Educational Resources Information Center

Panek, Paul E.; Staats, Sara; Hiles, Amanda

2006-01-01

Two studies were conducted. In study one 100 participants rated 60 occupations on the amount of cognitive/intellectual, physical, sensory-perceptual, and perceptual-motor demands they perceived as required for successful performance in that particular occupation. Results of a cluster analysis determined four clusters of occupations on the basis of…

Clusters and Factors Associated with Complementary Basic Education in Tanzania Mainland

ERIC Educational Resources Information Center

Edwin, Paul; Amina, Msengwa S.; Godwin, Naimani M.

2017-01-01

Complimentary Basic Education in Tanzania (COBET) is a community-based programme initiated in 1999 to provide formal education system opportunity to over aged children or children above school age. The COBET program was analyzed using secondary data collected from 21 regions from 2008 to 2012. Cluster analysis was applied to classify the 21…

Mitochondrial DNA polymorphisms associated with longevity in a Finnish population.

PubMed

Niemi, Anna-Kaisa; Hervonen, Antti; Hurme, Mikko; Karhunen, Pekka J; Jylhä, Marja; Majamaa, Kari

2003-01-01

Sequence variation in mitochondrial DNA (mtDNA) may cause slight differences both in the functioning of the respiratory chain and in free radical production, and an association between certain mtDNA haplogroups and longevity has been suggested. In order to determine further the role of mtDNA in longevity, we studied the frequencies of mtDNA haplogroups and haplogroup clusters among elderly subjects and controls in a Finnish population. Samples were obtained from 225 persons aged 90-91 years (Vitality 90+) and from 400 middle-aged controls and 257 infants. MtDNA haplogroups were determined by restriction fragment length polymorphism. The haplogroup frequencies of the Vitality 90+ group differed from both those of the middle-aged controls ( P=0.01) and the infants ( P=0.00005), haplogroup H being less frequent than among the middle-aged subjects ( P=0.001) and infants ( P=0.00001), whereas haplogroups U and J were more frequent. Haplogroup clusters also differed between Vitality 90+ and both the middle-aged subjects ( P=0.002) and infants ( P=0.00001), the frequency of haplogroup cluster HV being lower in the former and that of UK and WIX being higher. These data suggest an association between certain mtDNA haplogroups or haplogroup clusters and longevity. Furthermore, our data appear to favour the presence of advantageous polymorphisms and support a role for mitochondria and mtDNA in the degenerative processes involved in ageing.

'Theory of Mind', psychotic-like experiences and psychometric schizotypy in adolescents from the general population.

PubMed

Barragan, Marcela; Laurens, Kristin R; Navarro, José Blas; Obiols, Jordi E

2011-04-30

This study examined 'Theory of Mind' (ToM) functioning, its association with psychometric schizotypy and with self-reported psychotic-like experiences (PLEs) and depressive symptoms, in a community sample of adolescents. Seventy-two adolescents (mean age 14.51years) from Barcelona, Spain, completed questionnaires assessing PLEs, depressive symptoms, and schizotypy. A verbal ToM task and a vocabulary test were administered. The effect of symptomatology, vocabulary ability, age, and gender on task performance was explored. Neither total score on schizotypy nor PLEs were associated with ToM performance. A significant effect of vocabulary on adolescent's performance of both ToM and control stories was found. ToM showed significant negative associations with positive schizotypy, and with one cluster of positive PLEs: first-rank experiences. Positive significant associations between ToM and persecutory delusions and the impulsive aspects of schizotypy were found. Depressive symptoms did not affect ToM performance. Positive schizotypal traits and first-rank symptoms are associated with ToM deficits in adolescents. Results support the trait-(versus state-) dependent notion of ToM impairments in schizophrenia. ToM may be a developmental impairment associated with positive schizotypy and PLEs. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

An Intervention to Improve Teachers' Interpersonally Involving Instructional Practices in High School Physical Education: Implications for Student Relatedness Support and In-Class Experiences.

PubMed

Sparks, Cassandra; Lonsdale, Chris; Dimmock, James; Jackson, Ben

2017-04-01

Research grounded in self-determination theory has demonstrated the important role of teachers in shaping students' physical education experiences. Utilizing a cluster-randomized controlled design, this study aimed to examine whether an interpersonally involving training program based on self-determination theory principles could enhance students' in-class experiences. With 18 teachers (males = 8, females = 10, M age  = 32.75, SD = 8.14) and a final sample of 382 students (males = 155, females = 227, M age  = 13.20, SD = 1.66), we implemented linear mixed modeling to investigate the effects on students' (a) perceived relatedness support and (b) enjoyment of physical education, tripartite efficacy beliefs (i.e., self-efficacy, other-efficacy, relation-inferred self-efficacy), self-determined motivation, and amotivation. Relative to those in the control condition, students in the treatment condition reported positive changes in teacher-provided relatedness support, enjoyment, other-efficacy, and peer-focused relation-inferred self-efficacy. These findings demonstrate support for strategies designed to aid physical education teachers' relatedness-supportive instructional behaviors.

Photoinduced intermolecular dynamics and subsequent fragmentation in VUV-ionized acetamide clusters

NASA Astrophysics Data System (ADS)

Tarkanovskaja, Marta; Kooser, Kuno; Levola, Helena; Nõmmiste, Ergo; Kukk, Edwin

2016-09-01

Photofragmentation of small gas-phase acetamide clusters (CH3CONH2)n (n ≤ 10) produced by a supersonic expansion source has been studied using time-of-flight ion mass spectroscopy combined with tunable vacuum-ultraviolet (VUV) synchrotron radiation. Fragmentation channels of acetamide clusters under VUV photoionization resulting in protonated and ammoniated clusters formation were identified with the discussion about the preceding intramolecular rearrangements. Acetamide-2,2,2-d3 clusters were also studied in an experiment with a gas discharge lamp as a VUV light source; comparison with the main experiment gave insights into the mechanism of formation of protonated acetamide clusters, indicating that proton transfer from amino group plays a dominant role in that process. Geometry of the acetamide dimer was discussed and the most stable arrangement was concluded to be achieved when subunits of the dimer are connected via two N—H⋯O —C hydrogen bonds. Also, the influence of the photon energy on the stability of the clusters and their fragmentation channels has been examined.

A New Approach to the General Chemistry Laboratory

NASA Astrophysics Data System (ADS)

Bieron, Joseph F.; McCarthy, Paul J.; Kermis, Thomas W.

1996-11-01

Background Canisius College is a medium-sized liberal arts college with a longstanding tradition of maintaining an excellent chemistry program. We realized a few years ago, however, that this tradition was not being sustained by our General Chemistry laboratory course, which had not changed significantly in years. With the help of a grant from the National Science Foundation, our department has been able to design a new laboratory course built around several guiding principles. The design called for experiments to be grouped in units or clusters. Each cluster has a unifying theme or common thread, which gives some coherence to the experiments. The clusters and experiments are listed in the appendix and briefly explained below. Course Design Cluster A's topic is organic and polymer chemistry, and its main objective is to show that chemistry can be enjoyable and relevant to common experiences. Data collection is minimal and hands-on manipulation with observable products is emphasized. Cluster B is a case study of the chemistry of maintaining a swimming pool. The common theme is solution chemistry, and the experiments are designed to promote critical thinking. Cluster C encompasses both oxidation - reduction reactions and electrochemistry, and attempts to show the commonality of these important topics. Cluster D is a series of experiments on methods and techniques of analytical chemistry; in this group the analysis of unknown materials is undertaken. Cluster E is covered last in the second semester, and it stresses important concepts in chemistry at a slightly more advanced level. The emphasis is on the relationship of experiment to theory, and the cluster involves experiments in kinetics, equilibrium, and synthesis. Other guidelines that we considered important in our design were the use of computers (when appropriate), the introduction of microscale chemistry, and the use of instrumentation whenever possible. A separate cluster, labeled Mac, was developed to provide all students the opportunity to become proficient with Macintosh computers, which are used for data manipulation in some experiments. Another feature of the laboratory design is worthy of note. The experiments do not necessarily follow the topic chronologically as it is presented in the lecture. Instead, each cluster has a fairly extensive introduction, which summarizes the chemistry in that cluster. We had a reason in mind when we did this. In the past we have been content to cover the material in the lectures and to use the laboratory for confirmation of what the student had already learned. The results of laboratory experiments are known beforehand, and the students expect these results. An "unknown" given to the student merely allows the teacher to assess the student's lab technique and/or ability to calculate from the data a particular parameter of the unknown, such as its molar mass or its concentration. This, of course, is not the way science is done; the answers are not known before the experiment. In the normal course of scientific investigation, experiments are carried out to provide information needed for advancing knowledge, and not simply to confirm what is already known. In our design, ideally the students do the experiments to generate useful data. It is clear to them from the outset that there are no "correct answers." Data sampling and statistical analysis of the results are part of the experiments. In the course of developing these clusters, some questions arose that required further research. Several more advanced students have become involved in addressing these problems. One study on the "golden penny" demonstration resulted in a recent publication in this Journal (1). Student Evaluation of the Course An evaluation instrument was developed by two professors of the Psychology Department at Canisius College. It was administered at the end of each semester to all students taking General Chemistry. In addition, at the end of the second semester, the same professors engaged a group of 14 students (representing a cross section of the whole class) in a 75-minute discussion of many aspects of the courses. As presented above, we made no attempt to perfectly synchronize the lecture and lab. In spite of our rationale, students invariably found this unappealing. They clearly prefer to have the matter covered in lecture before they perform an experiment on the particular subject. In general, students expressed a positive view of the lab experiments, particularly the "experiment and observation" component. Somewhat more than half agreed or strongly agreed that the lab course stimulated their interest in chemistry. Most (80%) thought the number of experiments that we attempted to do was "about right", and they considered the experiments well written with clear directions (86%). As regards the use of microscale techniques, the overriding response was neutrality, both in the enjoyment and in the perceptions of this as "new and different". The use of computers in some experiments was not perceived as difficult, nor was it seen as especially helpful in increasing understanding of chemistry. The component of the experiments most disliked by students and considered most difficult was the data-sheet reports. (Because these contain the observed data and the calculated results, this is probably not surprising.) The students were required to keep a notebook, and 68% found this an aid in taking tests on the lab work. Instructors' Observations The instructors consider these experiments to be an improvement over the experiments they replaced. Students showed an interest in doing the experiments without the usual activity of trying to determine from other students the "correct" answers. One prelab presentation can cover an entire cluster, and weekly prelab directions take minimal time. The students learned to keep detailed notebooks, since they could use the notes for the exam at the end of each cluster. In summary, we believe this laboratory course meets most of our objectives. Student dissatisfaction with doing experiments at a time different from lecture coverage of the material must be weighed against their acceptance of other beneficial aspects of the laboratory: doing experiments without predetermined or expected results; keeping a detailed notebook; writing reports that include notations of both precision and accuracy; and relating chemical analyses to everyday common experiences. Acknowledgment The research was supported in part by an NSF grant USE-9150613 (JB), by a Canisius College faculty grant (PM), and by a Hughes Earning Excellence Award (TK). Literature Cited 1. Szczepankiewicz, S. H.; Bieron, J. F.; Kozik, M. J. Chem. Educ. 1995, 72, 386 - 388. Appendix. List of Experiments Cluster A: Carbon is Number One Experiment: A1. Formation of Silicate and Polyvinyl Alcohol Polymers A2. Measurement of the Heat of Reaction of a Hydrocarbon A3. Gas Chromatographic Separation of a Mixture A4. Step-growth (Condensation) Polymerization A5. Chain-growth (Addition) Polymerization Cluster B: Swimming Pool Experiment Experiment: B1. Determination of the pH of Pool Water B2. Determination of the Alkalinity of Pool Water B3. Determination of Chloride Ion Concentration in Pool Water B4. Determination of Free and Total Chlorine in Pool Water B5. Determination of the Total Hardness of Pool Water B6. Analysis of Swimming Pool Data Using a Spreadsheet: Calculation of Saturation Index and [Ca2+][CO32 - ] Ion Product Cluster C: Show Your Metal Experiment: C1. Multiple Oxidation States of Manganese C2. Stoichiometry of a Redox Reaction C3. Determination of the Empirical Formula of a Transition Metal Oxide C4. Iron Determination by Titration with Permanganate C5. The Driving Force of Redox Reactions: Reduction Potentials and Electochemical Cells C6. Concentration Cell C7. Constructing a Commercial Battery C8. Experiments with Pennies Cluster D: The Mystery Module Experiment: D1. Color Additives in Foods: Thin Layer Chromatography D2. The Eight Test Tube Challenge D3. Acid - Base Titration: Classical Analytical Method D4. Acid - Base Titration: Potentiometric Titration D5. The Oxidizing Strength of Household Bleach D6. Analysis of Copper in Brass D7. Analysis of Fluoride Ion in Drinking Water Cluster E: Think Like a Chemist Experiment: E1. Kinetic Study of an Oxidation - Reduction Reaction: A Clock Reaction E2. Determination of the Equilibrium Constant of FeSCN2+ E3. NO2/N2O4 Equilibrium: Variation with Temperature E4. Synthesis of a Coordination Complex of Iron: K3[Fe(C2O4)3] · 3H2O Cluster Mac: Computers in Chemistry Experiment: Mac1. Signing on to the Canisius College Macintosh Network Mac2. Using Excel and Summary of Basic Spreadsheet Operations Mac3. Temperature Conversion and Percent Composition using Excel NOTE: Several experiments will make use of Cricket Graph and Excel for analysis of the data and presentation of the results.

The Gaia-ESO Survey and CSI 2264: Substructures, disks, and sequential star formation in the young open cluster NGC 2264

NASA Astrophysics Data System (ADS)

Venuti, L.; Prisinzano, L.; Sacco, G. G.; Flaccomio, E.; Bonito, R.; Damiani, F.; Micela, G.; Guarcello, M. G.; Randich, S.; Stauffer, J. R.; Cody, A. M.; Jeffries, R. D.; Alencar, S. H. P.; Alfaro, E. J.; Lanzafame, A. C.; Pancino, E.; Bayo, A.; Carraro, G.; Costado, M. T.; Frasca, A.; Jofré, P.; Morbidelli, L.; Sousa, S. G.; Zaggia, S.

2018-01-01

Context. Reconstructing the structure and history of young clusters is pivotal to understanding the mechanisms and timescales of early stellar evolution and planet formation. Recent studies suggest that star clusters often exhibit a hierarchical structure, possibly resulting from several star formation episodes occurring sequentially rather than a monolithic cloud collapse. Aims: We aim to explore the structure of the open cluster and star-forming region NGC 2264 ( 3 Myr), which is one of the youngest, richest and most accessible star clusters in the local spiral arm of our Galaxy; we link the spatial distribution of cluster members to other stellar properties such as age and evolutionary stage to probe the star formation history within the region. Methods: We combined spectroscopic data obtained as part of the Gaia-ESO Survey (GES) with multi-wavelength photometric data from the Coordinated Synoptic Investigation of NGC 2264 (CSI 2264) campaign. We examined a sample of 655 cluster members, with masses between 0.2 and 1.8 M⊙ and including both disk-bearing and disk-free young stars. We used Teff estimates from GES and g,r,i photometry from CSI 2264 to derive individual extinction and stellar parameters. Results: We find a significant age spread of 4-5 Myr among cluster members. Disk-bearing objects are statistically associated with younger isochronal ages than disk-free sources. The cluster has a hierarchical structure, with two main blocks along its latitudinal extension. The northern half develops around the O-type binary star S Mon; the southern half, close to the tip of the Cone Nebula, contains the most embedded regions of NGC 2264, populated mainly by objects with disks and ongoing accretion. The median ages of objects at different locations within the cluster, and the spatial distribution of disked and non-disked sources, suggest that star formation began in the north of the cluster, over 5 Myr ago, and was ignited in its southern region a few Myr later. Star formation is likely still ongoing in the most embedded regions of the cluster, while the outer regions host a widespread population of more evolved objects; these may be the result of an earlier star formation episode followed by outward migration on timescales of a few Myr. We find a detectable lag between the typical age of disk-bearing objects and that of accreting objects in the inner regions of NGC 2264: the first tend to be older than the second, but younger than disk-free sources at similar locations within the cluster. This supports earlier findings that the characteristic timescales of disk accretion are shorter than those of disk dispersal, and smaller than the average age of NGC 2264 (i.e., ≲3 Myr). At the same time, we note that disks in the north of the cluster tend to be shorter-lived ( 2.5 Myr) than elsewhere; this may reflect the impact of massive stars within the region (notably S Mon), that trigger rapid disk dispersal. Conclusions: Our results, consistent with earlier studies on NGC 2264 and other young clusters, support the idea of a star formation process that takes place sequentially over a prolonged span in a given region. A complete understanding of the dynamics of formation and evolution of star clusters requires accurate astrometric and kinematic characterization of its population; significant advance in this field is foreseen in the upcoming years thanks to the ongoing Gaia mission, coupled with extensive ground-based surveys like GES. Full Table B.1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/609/A10

The Formation and Evolution of the Large Magellanic Cloud from Selected Clusters and Star Fields

NASA Astrophysics Data System (ADS)

Olsen, Knut Anders Grova

We have obtained deep Hubble Space Telescope color-magnitude diagrams of fields centered on the six old LMC globular clusters NGC 1754, NGC 1835, WGC 1898, NGC 1916, NGC 2005, and NGC 2019. The data have been carefully calibrated and the effects of crowding on the photometric accuracy have been thoroughly investigated. The observations have been used to produce V-I,V color-magnitude diagrams of the clusters and of the background field stars, which we have separated from each other through a statistical cleaning technique. The cluster color-magnitude diagrams show that the clusters are old, with main sequence turnoffs at V~ 22.5 and well-developed horizontal branches. We used the slopes of the red giant branches to measure the abundances, which we find to be 0.3 dex higher, on average, than previously measured spectroscopic abundances. In two cases there is significant variable reddening across at least part of the image, but only for NGC 1916 does differential reddening preclude accurate measurements of the CMD characteristics. The mean reddenings of the clusters, measured both from the color of the red giant branch and through comparison with Milky Way clusters, are <=0.10 magnitudes in E(B-V) in all cases. By matching tbe color-magnitude diagrams of the clusters to fiducial sequences of the Milky Way globular clusters M3, M5, and M55, we find that the mean difference of the LMC and Milky Way cluster ages is 1.0 ± 1.2 Gyr, calculated such that a positive difference indicates that the LMC clusters are older. Through Monte Carlo simulations, errors in the individual measurements of the ages relative to Milky Way clusters are found to be ~<1.0 Gyr. We find a similar chronology by comparing the horizontal branch morphologies and abundances with HB evolutionary tracks, assuming that age is the 'second parameter'. These results imply that the LMC formed at the same time as the Milky Way Galaxy. The evolution of the LMC following its formation has been studied through an analysis of the field star CMDs. We used an automated technique to disentangle the evolutionary tracks of varying age and composition that are represented in the CMDs. We computed star formation rates as a function of age for a number of models having different initial mass function slopes, distances, and uniform reddenings, assuming that the chemical evolution follows that implied by LMC clusters. Our results show that the LMC has been actively forming stars over the last 4 Gyr, with evidence for a decline in the last 0.5-1 Gyr. While the NGC 1754 field, which lies in the disk, has had only a low level of star formation after the globular cluster formation epoch until 4 Gyr ago, we find that the bar has been actively forming stars for the past 6-8 Gyr. We find that these qualitative results are robust against errors in the model parameters. (Abstract shortened by UMI.)* ftn*Originally published in DAI Vol. 59, No. 6. Reprinted here with corrected author name.

Identification of chronic rhinosinusitis phenotypes using cluster analysis.

PubMed

Soler, Zachary M; Hyer, J Madison; Ramakrishnan, Viswanathan; Smith, Timothy L; Mace, Jess; Rudmik, Luke; Schlosser, Rodney J

2015-05-01

Current clinical classifications of chronic rhinosinusitis (CRS) have been largely defined based upon preconceived notions of factors thought to be important, such as polyp or eosinophil status. Unfortunately, these classification systems have little correlation with symptom severity or treatment outcomes. Unsupervised clustering can be used to identify phenotypic subgroups of CRS patients, describe clinical differences in these clusters and define simple algorithms for classification. A multi-institutional, prospective study of 382 patients with CRS who had failed initial medical therapy completed the Sino-Nasal Outcome Test (SNOT-22), Rhinosinusitis Disability Index (RSDI), Medical Outcomes Study Short Form-12 (SF-12), Pittsburgh Sleep Quality Index (PSQI), and Patient Health Questionnaire (PHQ-2). Objective measures of CRS severity included Brief Smell Identification Test (B-SIT), CT, and endoscopy scoring. All variables were reduced and unsupervised hierarchical clustering was performed. After clusters were defined, variations in medication usage were analyzed. Discriminant analysis was performed to develop a simplified, clinically useful algorithm for clustering. Clustering was largely determined by age, severity of patient reported outcome measures, depression, and fibromyalgia. CT and endoscopy varied somewhat among clusters. Traditional clinical measures, including polyp/atopic status, prior surgery, B-SIT and asthma, did not vary among clusters. A simplified algorithm based upon productivity loss, SNOT-22 score, and age predicted clustering with 89% accuracy. Medication usage among clusters did vary significantly. A simplified algorithm based upon hierarchical clustering is able to classify CRS patients and predict medication usage. Further studies are warranted to determine if such clustering predicts treatment outcomes. © 2015 ARS-AAOA, LLC.

Star cluster formation history along the minor axis of the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Piatti, Andrés E.; Cole, Andrew A.; Emptage, Bryn

2018-01-01

We analysed Washington CMT1 photometry of star clusters located along the minor axis of the Large Magellanic Cloud (LMC), from the LMC optical centre up to ∼39° outwards to the North-West. The data base was exploited in order to search for new star cluster candidates, to produce cluster CMDs cleaned from field star contamination and to derive age estimates for a statistically complete cluster sample. We confirmed that 146 star cluster candidates are genuine physical systems, and concluded that an overall ∼30 per cent of catalogued clusters in the surveyed regions are unlikely to be true physical systems. We did not find any new cluster candidates in the outskirts of the LMC (deprojected distance ≳ 8°). The derived ages of the studied clusters are in the range 7.2 < log(t yr-1) ≤ 9.4, with the sole exception of the globular cluster NGC 1786 (log(t yr-1) = 10.10). We also calculated the cluster frequency for each region, from which we confirmed previously proposed outside-in formation scenarios. In addition, we found that the outer LMC fields show a sudden episode of cluster formation (log(t yr-1) ∼7.8-7.9) which continued until log(t yr-1) ∼7.3 only in the outermost LMC region. We link these features to the first pericentre passage of the LMC to the Milky Way (MW), which could have triggered cluster formation due to ram pressure interaction between the LMC and MW halo.

Biomarker clusters are differentially associated with longitudinal cognitive decline in late midlife

PubMed Central

Racine, Annie M.; Koscik, Rebecca L.; Berman, Sara E.; Nicholas, Christopher R.; Clark, Lindsay R.; Okonkwo, Ozioma C.; Rowley, Howard A.; Asthana, Sanjay; Bendlin, Barbara B.; Blennow, Kaj; Zetterberg, Henrik; Gleason, Carey E.; Carlsson, Cynthia M.

2016-01-01

The ability to detect preclinical Alzheimer’s disease is of great importance, as this stage of the Alzheimer’s continuum is believed to provide a key window for intervention and prevention. As Alzheimer’s disease is characterized by multiple pathological changes, a biomarker panel reflecting co-occurring pathology will likely be most useful for early detection. Towards this end, 175 late middle-aged participants (mean age 55.9 ± 5.7 years at first cognitive assessment, 70% female) were recruited from two longitudinally followed cohorts to undergo magnetic resonance imaging and lumbar puncture. Cluster analysis was used to group individuals based on biomarkers of amyloid pathology (cerebrospinal fluid amyloid-β42/amyloid-β40 assay levels), magnetic resonance imaging-derived measures of neurodegeneration/atrophy (cerebrospinal fluid-to-brain volume ratio, and hippocampal volume), neurofibrillary tangles (cerebrospinal fluid phosphorylated tau181 assay levels), and a brain-based marker of vascular risk (total white matter hyperintensity lesion volume). Four biomarker clusters emerged consistent with preclinical features of (i) Alzheimer’s disease; (ii) mixed Alzheimer’s disease and vascular aetiology; (iii) suspected non-Alzheimer’s disease aetiology; and (iv) healthy ageing. Cognitive decline was then analysed between clusters using longitudinal assessments of episodic memory, semantic memory, executive function, and global cognitive function with linear mixed effects modelling. Cluster 1 exhibited a higher intercept and greater rates of decline on tests of episodic memory. Cluster 2 had a lower intercept on a test of semantic memory and both Cluster 2 and Cluster 3 had steeper rates of decline on a test of global cognition. Additional analyses on Cluster 3, which had the smallest hippocampal volume, suggest that its biomarker profile is more likely due to hippocampal vulnerability and not to detectable specific volume loss exceeding the rate of normal ageing. Our results demonstrate that pathology, as indicated by biomarkers, in a preclinical timeframe is related to patterns of longitudinal cognitive decline. Such biomarker patterns may be useful for identifying at-risk populations to recruit for clinical trials. PMID:27324877

Biomarker clusters are differentially associated with longitudinal cognitive decline in late midlife.

PubMed

Racine, Annie M; Koscik, Rebecca L; Berman, Sara E; Nicholas, Christopher R; Clark, Lindsay R; Okonkwo, Ozioma C; Rowley, Howard A; Asthana, Sanjay; Bendlin, Barbara B; Blennow, Kaj; Zetterberg, Henrik; Gleason, Carey E; Carlsson, Cynthia M; Johnson, Sterling C

2016-08-01

The ability to detect preclinical Alzheimer's disease is of great importance, as this stage of the Alzheimer's continuum is believed to provide a key window for intervention and prevention. As Alzheimer's disease is characterized by multiple pathological changes, a biomarker panel reflecting co-occurring pathology will likely be most useful for early detection. Towards this end, 175 late middle-aged participants (mean age 55.9 ± 5.7 years at first cognitive assessment, 70% female) were recruited from two longitudinally followed cohorts to undergo magnetic resonance imaging and lumbar puncture. Cluster analysis was used to group individuals based on biomarkers of amyloid pathology (cerebrospinal fluid amyloid-β42/amyloid-β40 assay levels), magnetic resonance imaging-derived measures of neurodegeneration/atrophy (cerebrospinal fluid-to-brain volume ratio, and hippocampal volume), neurofibrillary tangles (cerebrospinal fluid phosphorylated tau181 assay levels), and a brain-based marker of vascular risk (total white matter hyperintensity lesion volume). Four biomarker clusters emerged consistent with preclinical features of (i) Alzheimer's disease; (ii) mixed Alzheimer's disease and vascular aetiology; (iii) suspected non-Alzheimer's disease aetiology; and (iv) healthy ageing. Cognitive decline was then analysed between clusters using longitudinal assessments of episodic memory, semantic memory, executive function, and global cognitive function with linear mixed effects modelling. Cluster 1 exhibited a higher intercept and greater rates of decline on tests of episodic memory. Cluster 2 had a lower intercept on a test of semantic memory and both Cluster 2 and Cluster 3 had steeper rates of decline on a test of global cognition. Additional analyses on Cluster 3, which had the smallest hippocampal volume, suggest that its biomarker profile is more likely due to hippocampal vulnerability and not to detectable specific volume loss exceeding the rate of normal ageing. Our results demonstrate that pathology, as indicated by biomarkers, in a preclinical timeframe is related to patterns of longitudinal cognitive decline. Such biomarker patterns may be useful for identifying at-risk populations to recruit for clinical trials. © The Author (2016). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Discovery of Extended Main-sequence Turnoffs in Four Young Massive Clusters in the Magellanic Clouds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Chengyuan; De Grijs, Richard; Deng, Licai

An increasing number of young massive clusters (YMCs) in the Magellanic Clouds have been found to exhibit bimodal or extended main sequences (MSs) in their color–magnitude diagrams (CMDs). These features are usually interpreted in terms of a coeval stellar population with different stellar rotational rates, where the blue and red MS stars are populated by non- (or slowly) and rapidly rotating stellar populations, respectively. However, some studies have shown that an age spread of several million years is required to reproduce the observed wide turnoff regions in some YMCs. Here we present the ultraviolet–visual CMDs of four Large and Smallmore » Magellanic Cloud YMCs, NGC 330, NGC 1805, NGC 1818, and NGC 2164, based on high-precision Hubble Space Telescope photometry. We show that they all exhibit extended main-sequence turnoffs (MSTOs). The importance of age spreads and stellar rotation in reproducing the observations is investigated. The observed extended MSTOs cannot be explained by stellar rotation alone. Adopting an age spread of 35–50 Myr can alleviate this difficulty. We conclude that stars in these clusters are characterized by ranges in both their ages and rotation properties, but the origin of the age spread in these clusters remains unknown.« less

Clustering of health-related behaviors among early and mid-adolescents in Tuscany: results from a representative cross-sectional study

PubMed Central

Lazzeri, Giacomo; Panatto, Donatella; Domnich, Alexander; Arata, Lucia; Pammolli, Andrea; Simi, Rita; Giacchi, Mariano Vincenzo; Amicizia, Daniela; Gasparini, Roberto

2018-01-01

Abstract Background A huge amount of literature suggests that adolescents’ health-related behaviors tend to occur in clusters, and the understanding of such behavioral clustering may have direct implications for the effective tailoring of health-promotion interventions. Despite the usefulness of analyzing clustering, Italian data on this topic are scant. This study aimed to evaluate the clustering patterns of health-related behaviors. Methods The present study is based on data from the Health Behaviors in School-aged Children (HBSC) study conducted in Tuscany in 2010, which involved 3291 11-, 13- and 15-year olds. To aggregate students’ data on 22 health-related behaviors, factor analysis and subsequent cluster analysis were performed. Results Factor analysis revealed eight factors, which were dubbed in accordance with their main traits: ‘Alcohol drinking’, ‘Smoking’, ‘Physical activity’, ‘Screen time’, ‘Signs & symptoms’, ‘Healthy eating’, ‘Violence’ and ‘Sweet tooth’. These factors explained 67% of variance and underwent cluster analysis. A six-cluster κ-means solution was established with a 93.8% level of classification validity. The between-cluster differences in both mean age and gender distribution were highly statistically significant. Conclusions Health-compromising behaviors are common among Tuscan teens and occur in distinct clusters. These results may be used by schools, health-promotion authorities and other stakeholders to design and implement tailored preventive interventions in Tuscany. PMID:27908972

Clustering of health-related behaviors among early and mid-adolescents in Tuscany: results from a representative cross-sectional study.

PubMed

Lazzeri, Giacomo; Panatto, Donatella; Domnich, Alexander; Arata, Lucia; Pammolli, Andrea; Simi, Rita; Giacchi, Mariano Vincenzo; Amicizia, Daniela; Gasparini, Roberto

2018-03-01

A huge amount of literature suggests that adolescents' health-related behaviors tend to occur in clusters, and the understanding of such behavioral clustering may have direct implications for the effective tailoring of health-promotion interventions. Despite the usefulness of analyzing clustering, Italian data on this topic are scant. This study aimed to evaluate the clustering patterns of health-related behaviors. The present study is based on data from the Health Behaviors in School-aged Children (HBSC) study conducted in Tuscany in 2010, which involved 3291 11-, 13- and 15-year olds. To aggregate students' data on 22 health-related behaviors, factor analysis and subsequent cluster analysis were performed. Factor analysis revealed eight factors, which were dubbed in accordance with their main traits: 'Alcohol drinking', 'Smoking', 'Physical activity', 'Screen time', 'Signs & symptoms', 'Healthy eating', 'Violence' and 'Sweet tooth'. These factors explained 67% of variance and underwent cluster analysis. A six-cluster κ-means solution was established with a 93.8% level of classification validity. The between-cluster differences in both mean age and gender distribution were highly statistically significant. Health-compromising behaviors are common among Tuscan teens and occur in distinct clusters. These results may be used by schools, health-promotion authorities and other stakeholders to design and implement tailored preventive interventions in Tuscany.

Deep HST Photometry of NGC 6388: Age and Horizontal Branch Luminosity

NASA Technical Reports Server (NTRS)

Stetson, Peter B.; Catelan, M.; Pritzl, Barton J.; Smith, Horace A.; Kinemuchi, Karen; Layden, Andrew C.; Sweigart, Allen V.; Rich, R. M.

2006-01-01

We present the first deep color-magnitude diagram (CMD) of the Galactic globular cluster NGC 6388, obtained with the Hubble Space Telescope, that is able to reach the main-sequence turnoff point of the cluster. From a detailed comparison between the cluster CMD and that of 47 Tucanae (NGC 104), we find that the bulk of the stars in these two clusters have nearly the same age and chemical composition. On the other hand, our results indicate that the blue horizontal branch and RR Lyrae components in NGC 6388 are intrinsically over-luminous, which must be due to one or more, still undetermined, non-canonical second parameter(s) affecting a relatively minor fraction of the stars in NGC 6388.

Kimberlites of the Man craton, West Africa

NASA Astrophysics Data System (ADS)

Skinner, E. M. W.; Apter, D. B.; Morelli, C.; Smithson, N. K.

2004-09-01

The Man craton in West Africa is an Archaean craton formerly joined to the Guyana craton (South America) that was rifted apart in the Mesozoic. Kimberlites of the Man craton include three Jurassic-aged clusters in Guinea, two Jurassic-aged clusters in Sierra Leone, and in Liberia two clusters of unknown age and one Neoproterozoic cluster recently dated at ∼800 Ma. All of the kimberlites irrespective of age occur as small pipes and prolific dykes. Some of the Banankoro cluster pipes in Guinea, the Koidu pipes in Sierra Leone and small pipes in the Weasua cluster in Liberia contain hypabyssal-facies kimberlite and remnants of the so-called transitional-facies and diatreme-facies kimberlite. Most of the Man craton kimberlites are mineralogically classified as phlogopite kimberlites, although potassium contents are relatively low. They are chemically similar to mica-poor Group 1A Southern African examples. The Jurassic kimberlites are considered to represent one province of kimberlites that track from older bodies in Guinea (Droujba 153 Ma) to progressively younger kimberlites in Sierra Leone (Koidu, 146 Ma and Tongo, 140 Ma). The scarcity of diatreme-facies kimberlites relative to hypabyssal-facies kimberlites and the presence of the so-called transitional-facies indicate that the pipes have been eroded down to the interface between the root and diatreme zones. From this observation, it is concluded that extensive erosion (1-2 km) has occurred since the Jurassic. In addition to erosion, the presence of abundant early crystallizing phlogopite is considered to have had an effect on the relatively small sizes of the Man craton kimberlites.

The young star cluster population of M51 with LEGUS - I. A comprehensive study of cluster formation and evolution

NASA Astrophysics Data System (ADS)

Messa, M.; Adamo, A.; Östlin, G.; Calzetti, D.; Grasha, K.; Grebel, E. K.; Shabani, F.; Chandar, R.; Dale, D. A.; Dobbs, C. L.; Elmegreen, B. G.; Fumagalli, M.; Gouliermis, D. A.; Kim, H.; Smith, L. J.; Thilker, D. A.; Tosi, M.; Ubeda, L.; Walterbos, R.; Whitmore, B. C.; Fedorenko, K.; Mahadevan, S.; Andrews, J. E.; Bright, S. N.; Cook, D. O.; Kahre, L.; Nair, P.; Pellerin, A.; Ryon, J. E.; Ahmad, S. D.; Beale, L. P.; Brown, K.; Clarkson, D. A.; Guidarelli, G. C.; Parziale, R.; Turner, J.; Weber, M.

2018-01-01

Recently acquired WFC3 UV (F275W and F336W) imaging mosaics under the Legacy Extragalactic UV Survey (LEGUS), combined with archival ACS data of M51, are used to study the young star cluster (YSC) population of this interacting system. Our newly extracted source catalogue contains 2834 cluster candidates, morphologically classified to be compact and uniform in colour, for which ages, masses and extinction are derived. In this first work we study the main properties of the YSC population of the whole galaxy, considering a mass-limited sample. Both luminosity and mass functions follow a power-law shape with slope -2, but at high luminosities and masses a dearth of sources is observed. The analysis of the mass function suggests that it is best fitted by a Schechter function with slope -2 and a truncation mass at 1.00 ± 0.12 × 105 M⊙. Through Monte Carlo simulations, we confirm this result and link the shape of the luminosity function to the presence of a truncation in the mass function. A mass limited age function analysis, between 10 and 200 Myr, suggests that the cluster population is undergoing only moderate disruption. We observe little variation in the shape of the mass function at masses above 1 × 104 M⊙ over this age range. The fraction of star formation happening in the form of bound clusters in M51 is ∼ 20 per cent in the age range 10-100 Myr and little variation is observed over the whole range from 1 to 200 Myr.

Opening the Window on Galaxy Assembly: Ages and Structural Parameters of Globular Clusters Towards the Galactic Bulge

NASA Astrophysics Data System (ADS)

Cohen, Roger

2015-10-01

The primary aim of this program is to undertake a systematic investigation of highly reddened Galactic globular clusters (GGCs) located towards the Galactic bulge. These clusters have been excluded from deep space-based photometric surveys due to their severe total and differential extinction. We will exploit the photometric depth and homogeneity of two existing Treasury programs (the ACS GGC Treasury Survey and the WFC3 Bulge Treasury Program) along with the unique optical+IR parallel imaging capabilities of HST to finally place the bulge GGCs in the context of their optically well-studied counterparts. Specifically, by leveraging ACS/WFC together with WFC3/IR, we first exploit the reddening sensitivity at optical wavelengths to map severe, small-scale differential reddening in the cluster cores. Corrected two-color WFC3/IR photometry will then be used to measure cluster ages to better than 1 Gyr relative precision, finally completing the age-metallicity relation of the Milky Way GGC system. Ages are obtained using a demonstrated procedure which is strictly differential, and therefore insensitive to total distance, reddening, reddening law, or photometric calibration uncertainties. At the same time, deep archival Treasury survey imaging of the Galactic bulge will be used to decontaminate cluster luminosity functions, yielding measurements of bulge GGC mass functions and mass segregation on par with results from the ACS GGC Treasury survey. Finally, the imaging which we propose will be combined with existing wide-field near-IR PSF photometry, yielding complete radial number density profiles, structural and morphological parameters.

MYStIX: Dynamical evolution of young clusters

NASA Astrophysics Data System (ADS)

Kuhn, Michael A.

2014-08-01

The spatial structure of young stellar clusters in Galactic star-forming regions provides insight into these clusters’ dynamical evolution---a topic with implications for open questions in star-formation and cluster survival. The Massive Young Star-Forming Complex Study in Infrared and X-ray (MYStIX) provides a sample of >30,000 young stars in star-forming regions (d<3.6 kpc) that contain at least one O-type star. We use the finite mixture model analysis to identify subclusters of stars and determine their properties: including subcluster radii, intrinsic numbers of stars, central density, ellipticity, obscuration, and age. In 17 MYStIX regions we find 142 subclusters, with a diverse radii and densities and age spreads of up to ~1 Myr in a region. There is a strong negative correlation between subcluster radius and density, which indicates that embedded subclusters expand but also gain stars as they age. Subcluster expansion is also shown by a positive radius--age correlation, which indicates that subclusters are expanding at <1 km/s. The subcluster ellipticity distribution and number--density relation show signs of a hierarchical merger scenario, whereby young stellar clusters are built up through mergers of smaller clumps, causing evolution from a clumpy spatial distribution of stars (seen in some regions) to a simpler distribution of stars (seen in other regions). Many of the simple young stellar clusters show signs of dynamically relaxation, even though they are not old enough for this to have occurred through two-body interactions. However, this apparent contradiction might be explained if small subcluster, which have shorter dynamical relaxation times, can produce dynamically relaxed clusters through hierarchical mergers.

A Model-Based Cluster Analysis of Maternal Emotion Regulation and Relations to Parenting Behavior.

PubMed

Shaffer, Anne; Whitehead, Monica; Davis, Molly; Morelen, Diana; Suveg, Cynthia

2017-10-15

In a diverse community sample of mothers (N = 108) and their preschool-aged children (M age  = 3.50 years), this study conducted person-oriented analyses of maternal emotion regulation (ER) based on a multimethod assessment incorporating physiological, observational, and self-report indicators. A model-based cluster analysis was applied to five indicators of maternal ER: maternal self-report, observed negative affect in a parent-child interaction, baseline respiratory sinus arrhythmia (RSA), and RSA suppression across two laboratory tasks. Model-based cluster analyses revealed four maternal ER profiles, including a group of mothers with average ER functioning, characterized by socioeconomic advantage and more positive parenting behavior. A dysregulated cluster demonstrated the greatest challenges with parenting and dyadic interactions. Two clusters of intermediate dysregulation were also identified. Implications for assessment and applications to parenting interventions are discussed. © 2017 Family Process Institute.

UBVI CCD Photometry of the Open Clusters NGC 4609 and Hogg 15

NASA Astrophysics Data System (ADS)

Kook, Seung-Hwa; Sung, Hwankyung; Bessell, M. S.

2010-10-01

{UBVI CCD photometry is obtained for the open clusters NGC 4609 and Hogg 15 in Crux. For NGC 4609, CCD data are presented for the first time. From new photometry we derive the reddening, distance modulus and age of each cluster - NGC 4609 : E(B-V) = 0.37 ± 0.03, V_0 - M_V = 10.60 ± 0.08, log τ= 7.7 ± 0.1; Hogg 15 : E(B-V) = 1.13 ± 0.11, V_0 - M_V = 12.50 ± 0.15, log τ ≲ 6.6. The young age of Hogg 15 strongly implies that WR 47 is a member of the cluster. We also determine the mass function of these clusters and obtain a slope Γ = -1.2 (± 0.3) for NGC 4609 which is normal and a somewhat shallow slope (Γ = -0.95 ± 0.5) for Hogg 15.

Distinguishing Fear Versus Distress Symptomatology in Pediatric OCD.

PubMed

Rozenman, Michelle; Peris, Tara; Bergman, R Lindsey; Chang, Susanna; O'Neill, Joseph; McCracken, James T; Piacentini, John

2017-02-01

Prior research has identified OCD subtypes or "clusters" of symptoms that differentially relate to clinical features of the disorder. Given the high comorbidity between OCD and anxiety, OCD symptom clusters may more broadly associate with fear and/or distress internalizing constructs. This study examines fear and distress dimensions, including physical concerns (fear), separation anxiety (fear), perfectionism (distress), and anxious coping (distress), as predictors of previously empirically-derived OCD symptom clusters in a sample of 215 youth diagnosed with primary OCD (ages 7-17, mean age = 12.25). Self-reported separation fears predicted membership in Cluster 1 (aggressive, sexual, religious, somatic obsessions, and checking compulsions) while somatic/autonomic fears predicted membership in Cluster 2 (symmetry obsessions and ordering, counting, repeating compulsions). Results highlight the diversity of pediatric OCD symptoms and their differential association with fear, suggesting the need to carefully assess both OCD and global fear constructs that might be directly targeted in treatment.

Electronic spectra and excited-state dynamics of acridine and its hydrated clusters

NASA Astrophysics Data System (ADS)

Harthcock, Colin; Zhang, Jie; Kong, Wei; Mitsui, Masaaki; Ohshima, Yasuhiro

2017-04-01

We combine results from several different experiments to investigate the photophysics of acridine (Ac) and its hydrated clusters in the gas phase. Our findings are also compared with results from condensed phase studies. Similar to measurements of Ac dissolved in hydrocarbons, the lifetime of the first electronically excited state of isolated Ac in vacuum is too short for typical resonantly enhanced multiphoton ionization (REMPI) and laser induced fluorescence (LIF) experiments, hence no signal from REMPI and LIF can be attributed to monomeric Ac. Instead, sensitized phosphorescence emission spectroscopy is more successful in revealing the electronic states of Ac. Upon clustering with water, on the other hand, the lifetimes of the excited states are substantially increased to the nanosecond scale, and with two water molecules attached to Ac, the lifetime of the hydrated cluster is essentially the same as that of Ac in aqueous solutions. Detailed REMPI and ultraviolet-ultraviolet hole-burning experiments are then performed to reveal the structural information of the hydrated clusters. Although the formation of hydrogen bonds results in energy level reversal and energy separation between the first two excited states of Ac, its effect on the internal geometry of Ac is minimal, and all clusters with 1-3 water molecules demonstrate consistent intramolecular vibrational modes. Theoretical calculations reveal just one stable structure for each cluster under supersonic molecular beam conditions. Furthermore, different from mono- and di-water clusters, tri-water clusters consist of a linear chain of three water molecules attached to Ac. Consequently, the fragmentation pattern in the REMPI spectrum of tri-water clusters seems to be dominated by water trimer elimination, since the REMPI spectrum of Ac+.W3 is largely reproduced in the Ac+ mass channel, but not in the Ac+.W1 or Ac+.W2 channel.

The evolution of angular momentum among zero-age main-sequence solar-type stars

NASA Technical Reports Server (NTRS)

Soderblom, David R.; Stauffer, John R.; Macgregor, Keith B.; Jones, Burton F.

1993-01-01

We consider a survey of rotation among F, G, and K dwarfs of the Pleiades in the context of other young clusters (Alpha Persei and the Hyades) and pre-main-sequence (PMS) stars (in Taurus-Auriga and Orion) in order to examine how the angular momentum of a star like the sun evolves during its early life on the main sequence. The rotation of PMS stars can be evolved into distributions like those seen in the young clusters if there is only modest, rotation-independent angular momentum loss prior to the ZAMS. Even then, the ultrafast rotators (UFRs, or ZAMS G and K dwarfs with v sin i equal to or greater than 30 km/s) must owe their extra angular momentum to their conditions of formation and to different angular momentum loss rates above a threshold velocity, for it is unlikely that these stars had angular momentum added as they neared the ZAMS, nor can a spread in ages within a cluster account for the range of rotation seen. Only a fraction of solar-type stars are thus capable of becoming UFRs, and it is not a phase that all stars experience. Simple scaling relations (like the Skumanich relation) applied to the observed surface rotation rates of young solar-type stars cannot reproduce the way in which the Pleiades evolve into the Hyades. We argue that invoking internal differential rotation in these ZAMS stars can explain several aspects of the observations and thus can provide a consistent picture of ZAMS angular momentum evolution.

Cosmic-ray exposure history at Taurus-Littrow

NASA Technical Reports Server (NTRS)

Drozd, R. J.; Hohenberg, C. M.; Morgan, C. J.; Podosek, F. A.; Wroge, M. L.

1977-01-01

Recent surface history at Taurus-Littrow is dominated by emplacement of the Central Cluster and Bright Mantle morphological units, both believed to have resulted from arrival of ejecta from a large primary crater, probably Tycho. This paper reports new noble gas data for eight Apollo 17 rocks. Kr-81 - Kr cosmic ray exposure ages for these rocks affirm the observation of a pronounced grouping of ages, reinforcing the photogeologic evidence for the site-wide nature of the Central Cluster event. The consequences of post-cratering shielding changes are considered and it is concluded that the differences can reasonably be attributed to these changes, particularly because of the greater likelihood of rollover and impact fragmentation of the relatively smaller rocks from which most age data have been obtained. These considerations also lead to a more refined age estimate of 109 plus or minus 4 m.y. for Central Cluster, the Bright Mantle, and Tycho.

The metallicity spread and the age-metallicity relation of ω Centauri

DOE Office of Scientific and Technical Information (OSTI.GOV)

Villanova, S.; Geisler, D.; Gratton, R. G.

2014-08-20

ω Centauri is a peculiar globular cluster formed by a complex stellar population. To investigate it, we studied 172 stars belonging to the five SGBs that we can identify in our photometry, in order to measure their [Fe/H] content as well as estimate their age dispersion and the age-metallicity relation. The first important result is that all of these SGBs have a distribution in metallicity with a spread that exceeds the observational errors and typically displays several peaks that indicate the presence of several subpopulations. We were able to identify at least six of them based on their mean [Fe/H]more » content. These metallicity-based subpopulations are seen to varying extents in each of the five SGBs. Taking advantage of the age sensitivity of the SGB, we showed that, first of all, at least half of the subpopulations have an age spread of at least 2 Gyr. Then, we obtained an age-metallicity relation that is the most complete to date for this cluster. Interpretation of the age-metallicity relation is not straightforward, but it is possible that the cluster (or what we can call its progenitor) was initially composed of two populations with different metallicities. Because of their age, it is very unlikely that the most metal-rich derives from the most metal-poor by some kind of chemical evolution process, so they can be assumed to be two independent primordial objects, or perhaps two separate parts of a single larger object, that merged in the past to form the present-day cluster.« less

Characterization of deuterium clusters mixed with helium gas for an application in beam-target-fusion experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bang, W.; Quevedo, H. J.; Bernstein, A. C.

We measured the average deuterium cluster size within a mixture of deuterium clusters and helium gas by detecting Rayleigh scattering signals. The average cluster size from the gas mixture was comparable to that from a pure deuterium gas when the total backing pressure and temperature of the gas mixture were the same as those of the pure deuterium gas. According to these measurements, the average size of deuterium clusters depends on the total pressure and not the partial pressure of deuterium in the gas mixture. To characterize the cluster source size further, a Faraday cup was used to measure themore » average kinetic energy of the ions resulting from Coulomb explosion of deuterium clusters upon irradiation by an intense ultrashort pulse. The deuterium ions indeed acquired a similar amount of energy from the mixture target, corroborating our measurements of the average cluster size. As the addition of helium atoms did not reduce the resulting ion kinetic energies, the reported results confirm the utility of using a known cluster source for beam-target-fusion experiments by introducing a secondary target gas.« less

Characterization of deuterium clusters mixed with helium gas for an application in beam-target-fusion experiments

DOE PAGES

Bang, W.; Quevedo, H. J.; Bernstein, A. C.; ...

2014-12-10

We measured the average deuterium cluster size within a mixture of deuterium clusters and helium gas by detecting Rayleigh scattering signals. The average cluster size from the gas mixture was comparable to that from a pure deuterium gas when the total backing pressure and temperature of the gas mixture were the same as those of the pure deuterium gas. According to these measurements, the average size of deuterium clusters depends on the total pressure and not the partial pressure of deuterium in the gas mixture. To characterize the cluster source size further, a Faraday cup was used to measure themore » average kinetic energy of the ions resulting from Coulomb explosion of deuterium clusters upon irradiation by an intense ultrashort pulse. The deuterium ions indeed acquired a similar amount of energy from the mixture target, corroborating our measurements of the average cluster size. As the addition of helium atoms did not reduce the resulting ion kinetic energies, the reported results confirm the utility of using a known cluster source for beam-target-fusion experiments by introducing a secondary target gas.« less

Cluster AgeS Experiment (CASE): deficiency of observed dwarf novae in globular clusters

NASA Astrophysics Data System (ADS)

Pietrukowicz, P.; Kaluzny, J.; Schwarzenberg-Czerny, A.; Thompson, I. B.; Pych, W.; Krzeminski, W.; Mazur, B.

2008-08-01

We present the results of a search for dwarf novae (DNe) in globular clusters (GCs). It is based on the largest available homogeneous sample of observations, in terms of the time-span, number of observations and number of clusters. It includes 16 Galactic GCs and yielded two new certain DNe: M55-CV1 and M22-CV2. All previously known systems located in our fields were recovered, too. We surveyed M4, M5, M10, M12, M22, M30, M55, NGC 288, NGC 362, NGC 2808, NGC 3201, NGC 4372, NGC 6362, NGC 6752, ω Centauri (NGC 5139) and 47 Tucanae (NGC 104). The discovery of two DNe, namely M55-CV1 and M22-CV2, was already reported by Kaluzny et al. and Pietrukowicz et al., respectively. In the remaining 14 GCs, we found no certain new DNe. Our result raises the total number of known DNe in the Galactic GCs to 12 DNe, distributed among seven clusters. Our survey recovered all three already known erupting cataclysmic variables (CVs) located in our fields, namely M5-V101, M22-CV1, and V4 in the foreground of M30. To assess the efficiency of the survey, we analysed images with inserted artificial stars mimicking outbursts of the prototype DNe SS Cygni and U Geminorum. Depending on the conditions, we recovered between 16-100 per cent of these artificial stars. The efficiency seems to be predominantly affected by duty cycle/time-sampling and much less by distance/magnitude. Except for saturated tiny collapsed cores of M30, NGC 362 and NGC 6752 (and also the dense core of NGC 2808), crowding effects in the V band were avoided by our image subtraction technique augmented with auxiliary unsaturated B-band images. Our results clearly demonstrate that in GCs common types of DNe are very rare indeed. However, great care must be taken before these conclusions can be extended to the CV population in GCs.

N-body experiments and missing mass in clusters of galaxies

NASA Technical Reports Server (NTRS)

Smith, H.; Hintzen, P.; Sofia, S.; Oegerle, W.; Scott, J.; Holman, G.

1979-01-01

It is commonly assumed that the distributions of surface density and radial-velocity dispersion in clusters of galaxies are sensitive tracers of the underlying distribution of any unseen mass. N-body experiments have been used to test this assumption. Calculations with equal-mass systems indicate that the effects of the underlying mass distribution cannot be detected by observations of the surface-density or radial-velocity distributions, and the existence of an extended binding mass in all well-studied clusters would be consistent with available observations.

The Aftermath of a Suicide Cluster in the Age of Online Social Networking: A Qualitative Analysis of Adolescent Grief Reactions

ERIC Educational Resources Information Center

Heffel, Carly J.; Riggs, Shelley A.; Ruiz, John M.; Ruggles, Mark

2015-01-01

Although suicide clusters have been identified in many populations, research exploring the role of online communication in the aftermath of a suicide cluster is extremely limited. This study used the Consensual Qualitative Research method to analyze interviews with ten high school students 1 year after a suicide cluster in a small suburban school…

ABUNDANCES OF RED GIANTS IN OLD OPEN CLUSTERS. V. Be 31, Be 32, Be 39, M 67, NGC 188, AND NGC 1193

DOE Office of Scientific and Technical Information (OSTI.GOV)

Friel, Eileen D.; Jacobson, Heather R.; Pilachowski, Catherine A., E-mail: friel@lowell.ed, E-mail: jacob189@msu.ed, E-mail: catyp@astro.indiana.ed

2010-05-15

We present a detailed abundance analysis based on high resolution spectroscopy for 16 stars in the old open clusters Be 31, Be 32, Be 39, M 67, NGC 188, and NGC 1193. Average cluster metallicities of [Fe/H] = -0.30 {+-} 0.02, -0.21 {+-} 0.01, +0.03 {+-} 0.07, +0.12 {+-} 0.02, and -0.22 {+-} 0.14 (s.d.) have been found for Be 32, Be 39, M 67, NGC 188, and NGC 1193, respectively. The two stars observed in the field of Be 31 have disparate radial velocities and elemental abundance patterns, and also disagree with the possible Be 31 star studied bymore » Yong et al. We conclude that membership has yet to be established for this important cluster, and therefore no element abundances measured here or in previous studies of Be 31 should be taken as definitive cluster abundances. A careful comparison of our results for the clusters M 67 and Be 32 to those of other studies shows general good agreement and identifies systematic differences resulting from different analyses. After combination of our results with those of other studies for clusters spanning the full R{sub gc} range of the thin disk, we explore the abundance distributions as a function of R{sub gc} and age for the elements Fe, O, Na, Mg, Al, Si, Ca, Ti, and Ni. As found in previous work, the [Fe/H] gradient appears to be continuous up to R{sub gc} {approx} 13 kpc before flattening in the outer disk. [X/Fe] ratios show a scatter of 0.2-0.3 dex at all R{sub gc}, for all elements considered. The [X/Fe] values of the six clusters analyzed here are consistent with those of other clusters of similar metallicity and Galactocentric location. Our whole cluster sample shows trends of increasing [O/Fe] and [Al/Fe] with age, although these trends vanish with the inclusion of other clusters from the literature. Larger, homogeneous open cluster samples are necessary to verify the existence and magnitude of abundance trends with age.« less

Typical patterns of modifiable health risk factors (MHRFs) in elderly women in Germany: results from the cross-sectional German Health Update (GEDA) study, 2009 and 2010.

PubMed

Jentsch, Franziska; Allen, Jennifer; Fuchs, Judith; von der Lippe, Elena

2017-04-04

Modifiable health risk factors (MHRFs) significantly affect morbidity and mortality rates and frequently occur in specific combinations or risk clusters. Using five MHRFs (smoking, high-risk alcohol consumption, physical inactivity, low intake of fruits and vegetables, and obesity) this study investigates the extent to which risk clusters are observed in a representative sample of women aged 65 and older in Germany. Additionally, the structural composition of the clusters is systematically compared with data and findings from other countries. A pooled data set of Germany's representative cross-sectional surveys GEDA09 and GEDA10 was used. The cohort comprised 4,617 women aged 65 and older. Specific risk clusters based on five MHRFs are identified, using hierarchical cluster analysis. The MHRFs were defined as current smoking (daily or occasionally), risk alcohol consumption (according to the Alcohol Use Disorders Identification Test, a sum score of 4 or more points), physical inactivity (less active than 5 days per week for at least 30 min and lack of sports-related activity in the last three months), low intake of fruits and vegetables (less than one serving of fruits and one of vegetables per day), and obesity (a body mass index equal to or greater than 30). A total of 4,292 cases with full information on these factors are included in the cluster analysis. Extended analyses were also performed to include the number of chronic diseases by age and socioeconomic status of group members. A total of seven risk clusters were identified. In a comparison with data from international studies, the seven risk clusters were found to be stable with a high degree of structural equivalency. Evidence of the stability of risk clusters across various study populations provides a useful starting point for long-term targeted health interventions. The structural clusters provide information through which various MHRFs can be evaluated simultaneously.

STAR CLUSTERS IN M33: UPDATED UBVRI PHOTOMETRY, AGES, METALLICITIES, AND MASSES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fan, Zhou; De Grijs, Richard, E-mail: zfan@bao.ac.cn, E-mail: grijs@pku.edu.cn

2014-04-01

The photometric characterization of M33 star clusters is far from complete. In this paper, we present homogeneous UBVRI photometry of 708 star clusters and cluster candidates in M33 based on archival images from the Local Group Galaxies Survey, which covers 0.8 deg{sup 2} along the galaxy's major axis. Our photometry includes 387, 563, 616, 580, and 478 objects in the UBVRI bands, respectively, of which 276, 405, 430, 457, and 363 do not have previously published UBVRI photometry. Our photometry is consistent with previous measurements (where available) in all filters. We adopted Sloan Digital Sky Survey ugriz photometry for complementarymore » purposes, as well as Two Micron All Sky Survey near-infrared JHK photometry where available. We fitted the spectral-energy distributions of 671 star clusters and candidates to derive their ages, metallicities, and masses based on the updated PARSEC simple stellar populations synthesis models. The results of our χ{sup 2} minimization routines show that only 205 of the 671 clusters (31%) are older than 2 Gyr, which represents a much smaller fraction of the cluster population than that in M31 (56%), suggesting that M33 is dominated by young star clusters (<1 Gyr). We investigate the mass distributions of the star clusters—both open and globular clusters—in M33, M31, the Milky Way, and the Large Magellanic Cloud. Their mean values are log (M {sub cl}/M {sub ☉}) = 4.25, 5.43, 2.72, and 4.18, respectively. The fraction of open to globular clusters is highest in the Milky Way and lowest in M31. Our comparisons of the cluster ages, masses, and metallicities show that our results are basically in agreement with previous studies (where objects in common are available); differences can be traced back to differences in the models adopted, the fitting methods used, and stochastic sampling effects.« less

Paleoglaciation of the Tibetan Plateau based on exposure ages and ELA depression estimates

NASA Astrophysics Data System (ADS)

Heyman, Jakob

2014-05-01

The Tibetan Plateau holds a major part of all glaciers outside the polar regions and an ample record of past glaciations. The glacial history of the Tibetan Plateau has attracted significant interest, with a large body of research investigating the extent, timing, and climatic implications of past glaciations. Here I present an extensive compilation of exposure ages and equilibrium line altitude (ELA) depression estimates from glacial deposits across the Tibetan Plateau to address the timing and degree of past glaciations. I compiled Be-10 exposure age data for a total of 1877 samples and recalculated exposure ages using an updated (lower) global Be-10 production rate. All samples were organized in groups of individual glacial deposits where each deposit represents one glacial event enabling evaluation of the exposure age clustering. For each glacial deposit I estimated the ELA depression based on a simple toe to headwall ratio approach using Google Earth. To discriminate good (well-clustered) from poor (scattered) exposure age groups the glacial deposits were divided into three groups based on exposure age clustering. A major part of the glacial deposits have scattered exposure ages affected by prior or incomplete exposure, complicating exposure age interpretations. The well-clustered exposure age groups are primarily from mountain ranges along the margins of the Tibetan Plateau with a main peak in age between 10 and 30 ka, indicating glacial advances during the global last glacial maximum (LGM). A large number of exposure ages older than 30 ka indicates maximum glaciation predating the LGM, but the exposure age scatter generally prohibits accurate definition of the glacial chronology. The ELA depression estimates scatter significantly, but a major part is remarkably low. Average ELA depressions of 333 ± 191 m for the LGM and 494 ± 280 m for the pre-LGM exposure indicate restricted glacier expansion and limited glacial cooling.

Effect of Composition and Pre-Ageing on the Natural Ageing and Paint-Baking Behaviour of Al-Mg-Si Alloys

NASA Astrophysics Data System (ADS)

Rometsch, Paul A.; Gao, Sam X.; Couper, Malcolm J.

Two 6xxx series aluminium alloys were designed to have the same total solute content but very different Mg/Si ratios. An excess Mg alloy (Al-1.2Mg-0.5Si) and an excess Si alloy (Al-0.5Mg-1.2Si) were cast and rolled to 1 mm thick sheet. Both were naturally aged for 30 days and then artificially aged for 0.5 h at 170°C to simulate an automotive body panel paint-baking cycle. In order to improve the paint-bake response, pre-ageing treatments of 20 s at 200°C and 2 h at 100°C were tested and evaluated using atom probe tomography, transmission electron microscopy and hardness testing. The results show that the excess Mg alloy tends to have coarser clusters/precipitates than the excess Si alloy, and that the Mg/Si ratio of the smaller clusters is closer to the alloy composition than that of the larger clusters and precipitates. Depending on the pre-ageing treatment, both alloys can give good paint-baking responses.

Cluster reactivity experiments: Employing mass spectrometry to investigate the molecular level details of catalytic oxidation reactions

PubMed Central

Johnson, Grant E.; Tyo, Eric C.; Castleman, A. W.

2008-01-01

Mass spectrometry is the most widely used tool in the study of the properties and reactivity of clusters in the gas phase. In this article, we demonstrate its use in investigating the molecular-level details of oxidation reactions occurring on the surfaces of heterogeneous catalysts via cluster reactivity experiments. Guided ion beam mass spectrometry (GIB-MS) employing a quadrupole–octopole–quadrupole (Q–O–Q) configuration enables mass-selected cluster ions to be reacted with various chemicals, providing insight into the effect of size, stoichiometry, and ionic charge state on the reactivity of catalyst materials. For positively charged tungsten oxide clusters, it is shown that species having the same stoichiometry as the bulk, WO3+, W2O6+, and W3O9+, exhibit enhanced activity and selectivity for the transfer of a single oxygen atom to propylene (C3H6), suggesting the formation of propylene oxide (C3H6O), an important monomer used, for example, in the industrial production of plastics. Furthermore, the same stoichiometric clusters are demonstrated to be active for the oxidation of CO to CO2, a reaction of significance to environmental pollution abatement. The findings reported herein suggest that the enhanced oxidation reactivity of these stoichiometric clusters may be due to the presence of radical oxygen centers (W–O●) with elongated metal–oxygen bonds. The unique insights gained into bulk-phase oxidation catalysis through the application of mass spectrometry to cluster reactivity experiments are discussed. PMID:18687883

Canine parvovirus in Australia: the role of socio-economic factors in disease clusters.

PubMed

Brady, S; Norris, J M; Kelman, M; Ward, M P

2012-08-01

To identify clusters of canine parvoviral related disease occurring in Australia during 2010 and investigate the role of socio-economic factors contributing to these clusters, reported cases of canine parvovirus were extracted from an on-line disease surveillance system. Reported residential postcode was used to locate cases, and clusters were identified using a scan statistic. Cases included in clusters were compared to those not included in such clusters with respect to human socioeconomic factors (postcode area relative socioeconomic disadvantage, economic resources, education and occupation) and dog factors (neuter status, breed, age, gender, vaccination status). During 2010, there were 1187 cases of canine parvovirus reported. Nineteen significant (P<0.05) disease clusters were identified, most commonly located in New South Wales. Eleven (58%) clusters occurred between April and July, and the average cluster length was 5.7 days. All clusters occurred in postcodes with a significantly (P<0.05) greater level of relative socioeconomic disadvantage and a lower rank in education and occupation, and it was noted that clustered cases were less likely to have been neutered (P=0.004). No significant difference (P>0.05) was found between cases reported from cluster postcodes and those not within clusters for dog age, gender, breed or vaccination status (although the latter needs to be interpreted with caution, since vaccination was absent in most of the cases). Further research is required to investigate the apparent association between indicators of poor socioeconomic status and clusters of reported canine parvovirus diseases; however these initial findings may be useful for developing geographically- and temporally-targeted prevention and disease control programs. Copyright © 2012 Elsevier Ltd. All rights reserved.

Cluster headache - clinical pattern and a new severity scale in a Swedish cohort.

PubMed

Steinberg, Anna; Fourier, Carmen; Ran, Caroline; Waldenlind, Elisabet; Sjöstrand, Christina; Belin, Andrea Carmine

2018-06-01

Background The aim of this study was to investigate clinical features of a cluster headache cohort in Sweden and to construct and test a new scale for grading severity. Methods Subjects were identified by screening medical records for the ICD 10 code G44.0, that is, cluster headache. Five hundred participating research subjects filled in a questionnaire including personal, demographic and medical aspects. We constructed a novel scale for grading cluster headache in this cohort: The Cluster Headache Severity Scale, which included number of attacks per day, attack and period duration. The lowest total score was three and the highest 12, and we used the Cluster Headache Severity Scale to grade subjects suffering from cluster headache. We further implemented the scale by defining a cluster headache maximum severity subgroup with a high Cluster Headache Severity Scale score ≥ 9. Results A majority (66.7%) of the patients reported that attacks appear at certain time intervals. In addition, cluster headache patients who were current tobacco users or had a history of tobacco consumption had a later age of disease onset (31.7 years) compared to non-tobacco users (28.5 years). The Cluster Headache Severity Scale score was higher in the patient group reporting sporadic or no alcohol intake than in the groups reporting an alcohol consumption of three to four standard units per week or more. Maximum severity cluster headache patients were characterised by higher age at disease onset, greater use of prophylactic medication, reduced hours of sleep, and lower alcohol consumption compared to the non-cluster headache maximum severity group. Conclusion There was a wide variation of severity grade among cluster headache patients, with a very marked impact on daily living for the most profoundly affected.

Late Life Employment Histories and Their Association With Work and Family Formation During Adulthood: A Sequence Analysis Based on ELSA.

PubMed

Wahrendorf, Morten; Zaninotto, Paola; Hoven, Hanno; Head, Jenny; Carr, Ewan

2017-05-31

To extend research on workforce participation beyond age 50 by describing entire employment histories in later life and testing their links to prior life course conditions. We use data from the English Longitudinal Study of Ageing, with retrospective information on employment histories between age 50 and 70 for 1,103 men and 1,195 women (n = 2,298). We apply sequence analysis and group respondents into eight clusters with similar histories. Using multinomial regressions, we then test their links to labor market participation, partnership, and parenthood histories during early (age 20-34) and mid-adulthood (age 35-49). Three clusters include histories dominated by full-time employees but with varying age of retirement (before, at, and after age 60). One cluster is dominated by self-employment with comparatively later retirement. Remaining clusters include part-time work (retirement around age 60 or no retirement), continuous domestic work (mostly women), or other forms of nonemployment. Those who had strong attachments to the labor market during adulthood are more likely to have histories of full-time work up until and beyond age 60, especially men. Parenthood in early adulthood is related to later retirement (for men only). Continued domestic work was not linked to parenthood. Partnered women tend to work part-time or do domestic work. The findings remain consistent after adjusting for birth cohort, childhood adversity, life course health, and occupational position. Policies aimed at increasing the proportion of older workers not only need to address later stages of the life course but also early and mid-adulthood. © The Author 2017. Published by Oxford University Press on behalf of The Gerontological Society of America.

Classes of Psychotic Experiences in Kenyan Children and Adolescents

PubMed Central

Owoso, Akinkunle; Mbwayo, Anne W.; Mutiso, Victoria N.; Muriungi, Susan K.; Khasakhala, Lincoln I.; Barch, Deanna M.; Ndetei, David M.

2012-01-01

Psychotic-like experiences (PLEs) have been observed worldwide in both adults and children outside the context of a clinical disorder. In the current study, we investigate the prevalence and patterns of PLEs among children and adolescents in Kenya. Among 1,971 students from primary and secondary schools around Nairobi (aged 8–19), 22.1 % reported a lifetime history of a psychotic experience, and 16.3 % reported this unrelated to sleep or drugs. Psychotic experiences were more common in males compared to females. LCA resulted in a three-class model comprised of a normative class (83.3 %), a predominately hallucinatory class (Type 1 psychosis: 9.6 %), and a pan-psychotic class (Type 2 psychosis: 7.2 %). These results indicate that PLEs are prevalent in children and adolescents, and the distributions of symptom clusters are similar to that found in adulthood. The relationship of specific PLEs to the future development of psychotic disorder, functional impairment or distress will require further study. PMID:23065300

Explaining prompts children to privilege inductively rich properties.

PubMed

Walker, Caren M; Lombrozo, Tania; Legare, Cristine H; Gopnik, Alison

2014-11-01

Four experiments with preschool-aged children test the hypothesis that engaging in explanation promotes inductive reasoning on the basis of shared causal properties as opposed to salient (but superficial) perceptual properties. In Experiments 1a and 1b, 3- to 5-year-old children prompted to explain during a causal learning task were more likely to override a tendency to generalize according to perceptual similarity and instead extend an internal feature to an object that shared a causal property. Experiment 2 replicated this effect of explanation in a case of label extension (i.e., categorization). Experiment 3 demonstrated that explanation improves memory for clusters of causally relevant (non-perceptual) features, but impairs memory for superficial (perceptual) features, providing evidence that effects of explanation are selective in scope and apply to memory as well as inference. In sum, our data support the proposal that engaging in explanation influences children's reasoning by privileging inductively rich, causal properties. Copyright © 2014 Elsevier B.V. All rights reserved.

Classes of psychotic experiences in Kenyan children and adolescents.

PubMed

Mamah, Daniel; Owoso, Akinkunle; Mbwayo, Anne W; Mutiso, Victoria N; Muriungi, Susan K; Khasakhala, Lincoln I; Barch, Deanna M; Ndetei, David M

2013-06-01

Psychotic-like experiences (PLEs) have been observed worldwide in both adults and children outside the context of a clinical disorder. In the current study, we investigate the prevalence and patterns of PLEs among children and adolescents in Kenya. Among 1,971 students from primary and secondary schools around Nairobi (aged 8-19), 22.1 % reported a lifetime history of a psychotic experience, and 16.3 % reported this unrelated to sleep or drugs. Psychotic experiences were more common in males compared to females. LCA resulted in a three-class model comprised of a normative class (83.3 %), a predominately hallucinatory class (Type 1 psychosis: 9.6 %), and a pan-psychotic class (Type 2 psychosis: 7.2 %). These results indicate that PLEs are prevalent in children and adolescents, and the distributions of symptom clusters are similar to that found in adulthood. The relationship of specific PLEs to the future development of psychotic disorder, functional impairment or distress will require further study.

HUBBLE PINPOINTS WHITE DWARFS IN GLOBULAR CLUSTER

NASA Technical Reports Server (NTRS)

2002-01-01

Peering deep inside a cluster of several hundred thousand stars, NASA's Hubble Space Telescope uncovered the oldest burned-out stars in our Milky Way Galaxy. Located in the globular cluster M4, these small, dying stars - called white dwarfs - are giving astronomers a fresh reading on one of the biggest questions in astronomy: How old is the universe? The ancient white dwarfs in M4 are about 12 to 13 billion years old. After accounting for the time it took the cluster to form after the big bang, astronomers found that the age of the white dwarfs agrees with previous estimates for the universe's age. In the top panel, a ground-based observatory snapped a panoramic view of the entire cluster, which contains several hundred thousand stars within a volume of 10 to 30 light-years across. The Kitt Peak National Observatory's 0.9-meter telescope took this picture in March 1995. The box at left indicates the region observed by the Hubble telescope. The Hubble telescope studied a small region of the cluster. A section of that region is seen in the picture at bottom left. A sampling of an even smaller region is shown at bottom right. This region is only about one light-year across. In this smaller region, Hubble pinpointed a number of faint white dwarfs. The blue circles pinpoint the dwarfs. It took nearly eight days of exposure time over a 67-day period to find these extremely faint stars. Globular clusters are among the oldest clusters of stars in the universe. The faintest and coolest white dwarfs within globular clusters can yield a globular cluster's age. Earlier Hubble observations showed that the first stars formed less than 1 billion years after the universe's birth in the big bang. So, finding the oldest stars puts astronomers within arm's reach of the universe's age. M4 is 7,000 light-years away in the constellation Scorpius. Hubble's Wide Field and Planetary Camera 2 made the observations from January through April 2001. These optical observations were combined to create the above images. Spectral data were also taken. Credit for Hubble telescope photos: NASA and H. Richer (University of British Columbia) Credit for ground-based photo: NOAO/AURA/NSF

Multimorbidity patterns of and use of health services by Swedish 85-year-olds: an exploratory study

PubMed Central

2013-01-01

Background As life expectancy continues to rise, more elderly are reaching advanced ages (≥80 years). The increasing prevalence of multimorbidity places additional demands on health-care resources for the elderly. Previous studies noted the impact of multimorbidity on the use of health services, but the effects of multimorbidity patterns on health-service use have not been well studied, especially for very old people. This study determines patterns of multimorbidity associated with emergency-room visits and hospitalization in an 85-year-old population. Methods Health and living conditions were reported via postal questionnaire by 496 Linköping residents aged 85 years (189 men and 307 women). Diagnoses of morbidity were reviewed in patients’ case reports, and the local health-care register provided information on the use of health services. Hierarchical cluster analysis was applied to evaluate patterns of multimorbidity with gender stratification. Factors associated with emergency-room visits and hospitalization were analyzed using logistic regression models. Results Cluster analyses revealed five clusters: vascular, cardiopulmonary, cardiac (only for men), somatic–mental (only for men), mental disease (only for women), and three other clusters related to aging (one for men and two for women). Heart failure in men (OR = 2.4, 95% CI = 1–5.7) and women (OR = 3, 95% CI = 1.3–6.9) as a single morbidity explained more variance than morbidity clusters in models of emergency-room visits. Men's cardiac cluster (OR = 1.6; 95% CI = 1–2.7) and women's cardiopulmonary cluster (OR = 1.7, 95% CI = 1.2–2.4) were significantly associated with hospitalization. The combination of the cardiopulmonary cluster with the men’s cardiac cluster (OR = 1.6, 95% CI = 1–2.4) and one of the women’s aging clusters (OR = 0.5, 95% CI = 0.3–0.8) showed interaction effects on hospitalization. Conclusion In this 85-year-old population, patterns of cardiac and pulmonary conditions were better than a single morbidity in explaining hospitalization. Heart failure was superior to multimorbidity patterns in explaining emergency-room visits. A holistic approach to examining the patterns of multimorbidity and their relationships with the use of health services will contribute to both local health care policy and geriatric practice. PMID:24195643

Asymmetries in Phonological Development: The Case of Word-Final Cluster Acquisition in Welsh-English Bilingual Children

ERIC Educational Resources Information Center

Mayr, Robert; Howells, Gwennan; Lewis, Rhonwen

2015-01-01

This study provides the first systematic account of word-final cluster acquisition in bilingual children. To this end, forty Welsh-English bilingual children differing in language dominance and age (2;6 to 5;0) participated in a picture-naming task in English and Welsh. The results revealed significant age and dominance effects on cluster…

The Age of the Inner Halo Globular Cluster NGC 6652

NASA Technical Reports Server (NTRS)

Chaboyer, Brian; Sarajedini, Ata; Armandroff, Taft E.

2000-01-01

Hubble Space Telescope (HST) (V,I) photometry has been obtained for the inner halo globular cluster NGC 6652. The photometry reaches approximately 4 mag below the turn-off and includes a well populated horizontal branch (HB). This cluster is located close to the Galactic center at RGC approximately equal to 2.0 kpc with a reddening of E(V-I) = 0.15 +/- 0.02 and has a metallicity of [Fe/H] approximately equal to -0.85. Based upon DELTA V (sup SGB) (sub HB), NGC 6652 is 11.7 plus or minus 1.6 Gyr old. Using A HB precise differential ages for 47 Tuc (a thick disk globular), M107 and NGC 1851 (both halo clusters) were obtained. NGC 6652 appears to be the same age as 47 Tuc and NGC 1851 (within +/- 1.2 Gyr), while there is a slight suggestion that M107 is older than NGC 6652 by 2.3 +/- 1.5 Gyr. As this is a less than 2 sigma result, this issue needs to be investigated further before a definitive statement regarding the relative age of M107 and NGC 6652 may be made.

Cúmulos estelares de edad intermedia de la Nube Mayor de Magallanes: determinación de parámetros fundamentales a partir de fotometría de Washington

NASA Astrophysics Data System (ADS)

Palma, T.; Clariá, J. J.; Geisler, D.; Piatti, A. E.; Ahumada, A. V.

Based on CCD images obtained in the Washington system at Cerro Tololo Inter-American Observatory, we determine ages and metallicities of 8 unstudied star clusters of the Large Magellanic Cloud (LMC). We find that they are intermediate-age (1-2 Gyr) and relatively metal-poor, although the metallicities are mainly determined from isochrones and are not strongly constrained. The study of this cluster sample will soon be extended to almost a hundred practically unstudied LMC star clusters. FULL TEXT IN SPANISH

Self-consistent physical parameters for five intermediate-age SMC stellar clusters from CMD modelling

NASA Astrophysics Data System (ADS)

Dias, B.; Kerber, L. O.; Barbuy, B.; Santiago, B.; Ortolani, S.; Balbinot, E.

2014-01-01

Context. Stellar clusters in the Small Magellanic Cloud (SMC) are useful probes for studying the chemical and dynamical evolution of this neighbouring dwarf galaxy, enabling inspection of a large period covering over 10 Gyr. Aims: The main goals of this work are the derivation of age, metallicity, distance modulus, reddening, core radius, and central density profiles for six sample clusters, in order to place them in the context of the Small Cloud evolution. The studied clusters are AM 3, HW 1, HW 34, HW 40, Lindsay 2, and Lindsay 3; HW 1, HW 34, and Lindsay 2 are studied for the first time. Methods: Optical colour-magnitude diagrams (V,B - V CMDs) and radial density profiles were built from images obtained with the 4.1 m Southern Astrophysical Research (SOAR) telescope, reaching V ~ 23. The determination of structural parameters were carried out by applying King profile fitting. The other parameters were derived in a self-consistent way by means of isochrone fitting, which uses likelihood statistics to identify the synthetic CMDs that best reproduce the observed ones. Membership probabilities were determined comparing the cluster and control field CMDs. Completeness and photometric uncertainties were obtained by performing artificial star tests. Results: The results confirm that these clusters (except HW 34, identified as a field fluctuation) are intermediate-age clusters, with ages between 1.2 Gyr (Lindsay 3) and ~5.0 Gyr (HW 1). In particular HW 1, Lindsay 2 and Lindsay 3 are located in a region that we called West Halo, where studies of ages and metallicity gradients are still lacking. Moreover, Lindsay 2 was identified as a moderately metal-poor cluster with [Fe/H] = -1.4 ± 0.2 dex, lower than expected from the age-metallicity relation by Pagel & Tautvaisiene (1998). We also found distances varying from ~53 kpc to 66 kpc, compatible with the large depth of the SMC. Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação (MCTI) da República Federativa do Brasil, the US National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).Appendix A is available in electronic form at http://www.aanda.orgThe tables of photometry are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/561/A106

Machine assisted histogram classification

NASA Astrophysics Data System (ADS)

Benyó, B.; Gaspar, C.; Somogyi, P.

2010-04-01

LHCb is one of the four major experiments under completion at the Large Hadron Collider (LHC). Monitoring the quality of the acquired data is important, because it allows the verification of the detector performance. Anomalies, such as missing values or unexpected distributions can be indicators of a malfunctioning detector, resulting in poor data quality. Spotting faulty or ageing components can be either done visually using instruments, such as the LHCb Histogram Presenter, or with the help of automated tools. In order to assist detector experts in handling the vast monitoring information resulting from the sheer size of the detector, we propose a graph based clustering tool combined with machine learning algorithm and demonstrate its use by processing histograms representing 2D hitmaps events. We prove the concept by detecting ion feedback events in the LHCb experiment's RICH subdetector.

Home Environments of Infants From Immigrant Families in the United States: Findings From the New Immigrant Survey

PubMed Central

Bradley, Robert H.; Pennar, Amy; Glick, Jennifer

2014-01-01

Data from the New Immigrant Survey were used to describe the home environments of 638 children ages birth to 3 years whose parents legally immigrated to the United States. Thirty-two indicators of home conditions were clustered into four domains: discipline and socioemotional in support, learning materials, enriching experiences, and family activities. Results revealed variation in how frequently infants from every country (Mexico, El Salvador, India, Philippines) and region (East Asia, Europe, Caribbean, Africa) studied experienced each home environmental condition. There were differences between countries and regions on many indicators as well as differences based on parents' level of education. The experiences documented for children of recent legal immigrants were similar to those documented for children of native-born families in other studies. PMID:25798506

Measuring galaxy cluster masses with CMB lensing using a Maximum Likelihood estimator: statistical and systematic error budgets for future experiments

DOE PAGES

Raghunathan, Srinivasan; Patil, Sanjaykumar; Baxter, Eric J.; ...

2017-08-25

We develop a Maximum Likelihood estimator (MLE) to measure the masses of galaxy clusters through the impact of gravitational lensing on the temperature and polarization anisotropies of the cosmic microwave background (CMB). We show that, at low noise levels in temperature, this optimal estimator outperforms the standard quadratic estimator by a factor of two. For polarization, we show that the Stokes Q/U maps can be used instead of the traditional E- and B-mode maps without losing information. We test and quantify the bias in the recovered lensing mass for a comprehensive list of potential systematic errors. Using realistic simulations, wemore » examine the cluster mass uncertainties from CMB-cluster lensing as a function of an experiment’s beam size and noise level. We predict the cluster mass uncertainties will be 3 - 6% for SPT-3G, AdvACT, and Simons Array experiments with 10,000 clusters and less than 1% for the CMB-S4 experiment with a sample containing 100,000 clusters. The mass constraints from CMB polarization are very sensitive to the experimental beam size and map noise level: for a factor of three reduction in either the beam size or noise level, the lensing signal-to-noise improves by roughly a factor of two.« less

Measuring galaxy cluster masses with CMB lensing using a Maximum Likelihood estimator: statistical and systematic error budgets for future experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raghunathan, Srinivasan; Patil, Sanjaykumar; Baxter, Eric J.

We develop a Maximum Likelihood estimator (MLE) to measure the masses of galaxy clusters through the impact of gravitational lensing on the temperature and polarization anisotropies of the cosmic microwave background (CMB). We show that, at low noise levels in temperature, this optimal estimator outperforms the standard quadratic estimator by a factor of two. For polarization, we show that the Stokes Q/U maps can be used instead of the traditional E- and B-mode maps without losing information. We test and quantify the bias in the recovered lensing mass for a comprehensive list of potential systematic errors. Using realistic simulations, wemore » examine the cluster mass uncertainties from CMB-cluster lensing as a function of an experiment’s beam size and noise level. We predict the cluster mass uncertainties will be 3 - 6% for SPT-3G, AdvACT, and Simons Array experiments with 10,000 clusters and less than 1% for the CMB-S4 experiment with a sample containing 100,000 clusters. The mass constraints from CMB polarization are very sensitive to the experimental beam size and map noise level: for a factor of three reduction in either the beam size or noise level, the lensing signal-to-noise improves by roughly a factor of two.« less

Bright Young Star Clusters in NGC5253 with LEGUS

NASA Astrophysics Data System (ADS)

Calzetti, Daniela; Johnson, Kelsey E.; Adamo, Angela; Gallagher, John S.; Andrews, Jennifer E.; Smith, Linda J.; Clayton, Geoffrey C.; Lee, Janice C.; Sabbi, Elena; Ubeda, Leonardo; Kim, Hwihyun; Ryon, Jenna E.; Thilker, David A.; Bright, Stacey N.; Zackrisson, Erik; Kennicutt, Robert; de Mink, Selma E.; Whitmore, Bradley C.; Aloisi, Alessandra; Chandar, Rupali; Cignoni, Michele; Cook, David; Dale, Daniel A.; Elmegreen, Bruce; Elmegreen, Debra M.; Evans, Aaron S.; Fumagalli, Michele; Gouliermis, Dimitrios; Grasha, Kathryn; Grebel, Eva; Krumholz, Mark R.; Walterbos, Rene A. M.; Wofford, Aida; Brown, Thomas M.; Christian, Carol A.; Dobbs, Claire; Herrero-Davo`, Artemio; Kahre, Lauren; Messa, Matteo; Nair, Preethi; Nota, Antonella; Östlin, Göran; Pellerin, Anne; Sacchi, Elena; Schaerer, Daniel; Tosi, Monica

2016-01-01

Using UV-to-H broad and narrow-band HST imaging, we derive the ages and masses of the 11 brightest star clusters in the dwarf galaxy NGC5253. This galaxy, located at ~3 Mpc, hosts an intense starburst, which includes a centrally-concentrated dusty region with strong thermal radio emission (the `radio nebula'). The HST imaging includes data from the Cycle 21 Treasury Program LEGUS (Legacy ExtraGalactic UV Survey), in addition to narrow--band H-alpha (6563 A), P-beta (12820 A), and P-alpha (18756 A). The bright clusters have ages ~1-15 Myr and masses ~1E4 - 2.5E5 Msun. Two of the 11 star clusters are located within the radio nebula, and suffer from significant dust attenuation. Both are extremely young, with a best-fit age around 1 Myr, and masses ~7.5E4 and ~2.5E5 Msun, respectively. The most massive of the two `radio nebula' clusters is 2-4 times less massive than previously estimated and is embedded within a cloud of dust with A_V~50 mag. The two clusters account for about half of the ionizing photon rate in the radio nebula, and will eventually supply about 2/3 of the mechanical energy in present-day shocks. Additional sources are required to supply the remaining ionizing radiation, and may include very massive stars.

Integration of molecular typing results into tuberculosis surveillance in Germany—A pilot study

PubMed Central

Fiebig, Lena; Priwitzer, Martin; Richter, Elvira; Rüsch-Gerdes, Sabine; Haas, Walter; Niemann, Stefan; Brodhun, Bonita

2017-01-01

An integrated molecular surveillance for tuberculosis (TB) improves the understanding of ongoing TB transmission by combining molecular typing and epidemiological data. However, the implementation of an integrated molecular surveillance for TB is complex and requires thoughtful consideration of feasibility, demand, public health benefits and legal issues. We aimed to pilot the integration of molecular typing results between 2008 and 2010 in the German Federal State of Baden-Württemberg (population 10.88 Million) as preparation for a nationwide implementation. Culture positive TB cases were typed by IS6110 DNA fingerprinting and results were integrated into routine notification data. Demographic and clinical characteristics of cases and clusters were described and new epidemiological links detected after integrating typing data were calculated. Furthermore, a cross-sectional survey was performed among local public health offices to evaluate their perception and experiences. Overall, typing results were available for 83% of notified culture positive TB cases, out of which 25% were clustered. Age <15 years (OR = 4.96, 95% CI: 1.69–14.55) and being born in Germany (OR = 2.01, 95% CI: 1.44–2.80) were associated with clustering. At cluster level, molecular typing information allowed the identification of previously unknown epidemiological links in 11% of the clusters. In 59% of the clusters it was not possible to identify any epidemiological link. Clusters extending over different counties were less likely to have epidemiological links identified among their cases (OR = 11.53, 95% CI: 3.48–98.23). The majority of local public health offices found molecular typing useful for their work. Our study illustrates the feasibility of integrating typing data into the German TB notification system and depicts its added public health value as complementary strategy in TB surveillance, especially to uncover transmission events among geographically separated TB patients. It also emphasizes that special efforts are required to strengthen the communication between local public health offices in different counties to enhance TB control. PMID:29166403

Integration of molecular typing results into tuberculosis surveillance in Germany-A pilot study.

PubMed

Andrés, Marta; Göhring-Zwacka, Elke; Fiebig, Lena; Priwitzer, Martin; Richter, Elvira; Rüsch-Gerdes, Sabine; Haas, Walter; Niemann, Stefan; Brodhun, Bonita

2017-01-01

An integrated molecular surveillance for tuberculosis (TB) improves the understanding of ongoing TB transmission by combining molecular typing and epidemiological data. However, the implementation of an integrated molecular surveillance for TB is complex and requires thoughtful consideration of feasibility, demand, public health benefits and legal issues. We aimed to pilot the integration of molecular typing results between 2008 and 2010 in the German Federal State of Baden-Württemberg (population 10.88 Million) as preparation for a nationwide implementation. Culture positive TB cases were typed by IS6110 DNA fingerprinting and results were integrated into routine notification data. Demographic and clinical characteristics of cases and clusters were described and new epidemiological links detected after integrating typing data were calculated. Furthermore, a cross-sectional survey was performed among local public health offices to evaluate their perception and experiences. Overall, typing results were available for 83% of notified culture positive TB cases, out of which 25% were clustered. Age <15 years (OR = 4.96, 95% CI: 1.69-14.55) and being born in Germany (OR = 2.01, 95% CI: 1.44-2.80) were associated with clustering. At cluster level, molecular typing information allowed the identification of previously unknown epidemiological links in 11% of the clusters. In 59% of the clusters it was not possible to identify any epidemiological link. Clusters extending over different counties were less likely to have epidemiological links identified among their cases (OR = 11.53, 95% CI: 3.48-98.23). The majority of local public health offices found molecular typing useful for their work. Our study illustrates the feasibility of integrating typing data into the German TB notification system and depicts its added public health value as complementary strategy in TB surveillance, especially to uncover transmission events among geographically separated TB patients. It also emphasizes that special efforts are required to strengthen the communication between local public health offices in different counties to enhance TB control.

DIFFERENT DYNAMICAL AGES FOR THE TWO YOUNG AND COEVAL LMC STAR CLUSTERS, NGC 1805 AND NGC 1818, IMPRINTED ON THEIR BINARY POPULATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Geller, Aaron M.; Grijs, Richard de; Li, Chengyuan

2015-05-20

The two Large Magellanic Cloud star clusters, NGC 1805 and NGC 1818, are approximately the same chronological age (∼30 Myr), but show different radial trends in binary frequency. The F-type stars (1.3–2.2 M{sub ⊙}) in NGC 1818 have a binary frequency that decreases toward the core, while the binary frequency for stars of similar mass in NGC 1805 is flat with radius, or perhaps bimodal (with a peak in the core). We show here, through detailed N-body modeling, that both clusters could have formed with the same primordial binary frequency and with binary orbital elements and masses drawn from themore » same distributions (defined from observations of open clusters and the field of our Galaxy). The observed radial trends in binary frequency for both clusters are best matched with models that have initial substructure. Furthermore, both clusters may be evolving along a very similar dynamical sequence, with the key difference that NGC 1805 is dynamically older than NGC 1818. The F-type binaries in NGC 1818 still show evidence of an initial period of rapid dynamical disruptions (which occur preferentially in the core), while NGC 1805 has already begun to recover a higher core binary frequency, owing to mass segregation (which will eventually produce a distribution in binary frequency that rises only toward the core, as is observed in old Milky Way star clusters). This recovery rate increases for higher-mass binaries, and therefore even at one age in one cluster, we predict a similar dynamical sequence in the radial distribution of the binary frequency as a function of binary primary mass.« less

THE VERY MASSIVE STAR CONTENT OF THE NUCLEAR STAR CLUSTERS IN NGC 5253

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, L. J.; Crowther, P. A.; Calzetti, D.

2016-05-20

The blue compact dwarf galaxy NGC 5253 hosts a very young starburst containing twin nuclear star clusters, separated by a projected distance of 5 pc. One cluster (#5) coincides with the peak of the H α emission and the other (#11) with a massive ultracompact H ii region. A recent analysis of these clusters shows that they have a photometric age of 1 ± 1 Myr, in apparent contradiction with the age of 3–5 Myr inferred from the presence of Wolf-Rayet features in the cluster #5 spectrum. We examine Hubble Space Telescope ultraviolet and Very Large Telescope optical spectroscopy ofmore » #5 and show that the stellar features arise from very massive stars (VMSs), with masses greater than 100 M {sub ⊙}, at an age of 1–2 Myr. We further show that the very high ionizing flux from the nuclear clusters can only be explained if VMSs are present. We investigate the origin of the observed nitrogen enrichment in the circumcluster ionized gas and find that the excess N can be produced by massive rotating stars within the first 1 Myr. We find similarities between the NGC 5253 cluster spectrum and those of metal-poor, high-redshift galaxies. We discuss the presence of VMSs in young, star-forming galaxies at high redshift; these should be detected in rest-frame UV spectra to be obtained with the James Webb Space Telescope . We emphasize that population synthesis models with upper mass cutoffs greater than 100 M {sub ⊙} are crucial for future studies of young massive star clusters at all redshifts.« less

Short Communication: Phylogenetic Evidence of HIV-1 Transmission Between Adult and Adolescent Men Who Have Sex with Men.

PubMed

Wolf, Elizabeth; Herbeck, Joshua T; Van Rompaey, Stephen; Kitahata, Mari; Thomas, Katherine; Pepper, Gregory; Frenkel, Lisa

2017-04-01

HIV-1 incidence among youth, especially men who have sex with men (MSM), is increasing in the United States. We aimed to better understand the patterns of adolescent HIV-1 acquisition, to help guide future prevention interventions. We conducted a study combining epidemiologic and HIV-1 pol sequence data from a retrospective cohort of HIV-infected adults and adolescents in Seattle, WA between 2000 and 2013. Adolescents were defined as 13-24 years of age at the time of first HIV-1 care. Maximum-likelihood phylogenetic trees were reconstructed to identify putative viral transmission clusters of two or more individuals, followed by multivariable regression tests of associations between clustering and demographic and clinical parameters. The dataset included 3,102 sequences from 1,953 individuals; 72 putative transmission clusters were identified, representing 168 individuals (8.6%). MSM and MSM/intravenous drug use (IDU) were positively associated with clustering, with aOR 3.18 (95% CI: 1.34-7.55) and 2.59 (95% CI: 1.04-6.49), respectively. African American race was negatively associated with clustering (aOR 0.54 95% CI: 0.32-0.91). Twenty-five clusters contained one adolescent and five clusters contained two adolescents. Other individuals who clustered with adolescents were predominantly male (95%), white (85%), and either MSM (66%) or MSM/IDU (16%), with a greater mean age (34 years vs. 22 years; p < .01). In this Seattle cohort, HIV-1 transmission linkages were identified between white male adolescents and older MSM adults. Interventions aimed at age-discrepant pairs may reduce HIV-1 infections in adolescent males.

Risk for self-reported anorexia or bulimia nervosa based on drive for thinness and negative affect clusters/dimensions during adolescence: A three-year prospective study of the TChAD cohort.

PubMed

Peñas-Lledó, Eva; Bulik, Cynthia M; Lichtenstein, Paul; Larsson, Henrik; Baker, Jessica H

2015-09-01

This study explored the cross-sectional and predictive effect of drive for thinness and/or negative affect scores on the development of self-reported anorexia nervosa (AN) and bulimia nervosa (BN). K-means were used to cluster the Eating Disorder Inventory-Drive for Thinness (DT) and Child Behavior Checklist Anxious/Depressed (A/D) scores from 615 unrelated female twins at age 16-17. Logistic regressions were used to assess the effect of these clusters on self-reported eating disorder diagnosis at ages 16-17 (n = 565) and 19-20 (n = 451). DT and A/D scores were grouped into four clusters: Mild (scores lower than 90th percentile on both scales), DT (higher scores only on DT), A/D (higher scores only on A/D), and DT-A/D (higher scores on both the DT and A/D scales). DT and DT-A/D clusters at age 16-17 were associated cross-sectionally with AN and both cross-sectionally and longitudinally with BN. The DT-A/D cluster had the highest prevalence of AN at follow-up compared with all other clusters. Similarly, an interaction was observed between DT and A/D that predicted risk for AN. Having elevated DT and A/D scores may increase risk for eating disorder symptomatology above and beyond a high score on either alone. Findings suggest that cluster modeling based on DT and A/D may be useful to inform novel and useful intervention strategies for AN and BN in adolescents. © 2015 Wiley Periodicals, Inc.

Risk for self-reported anorexia or bulimia nervosa based on drive for thinness and negative affect clusters/dimensions during adolescence: A three-year prospective study of the TChAD cohort

PubMed Central

Peñas-Lledó, Eva; Bulik, Cynthia M.; Lichtenstein, Paul; Larsson, Henrik; Baker, Jessica H.

2015-01-01

Objective The present study explored the cross-sectional and predictive effect of drive for thinness and/or negative affect scores on the development of self-reported anorexia nervosa (AN) and bulimia nervosa (BN). Method K-means were used to cluster the Eating Disorder Inventory-Drive for Thinness (DT) and Child Behavior Checklist Anxious/Depressed (A/D) scores from 615 unrelated female twins at age 16–17. Logistic regressions were used to assess the effect of these clusters on self-reported eating disorder diagnosis at ages 16–17 (n=565) and 19–20 (n=451). Results DT and A/D scores were grouped into four clusters: Mild (scores lower than 90th percentile on both scales), DT (higher scores only on DT), A/D (higher scores only on A/D), and DT-A/D (higher scores on both the DT and A/D scales). DT and DT-A/D clusters at age 16–17 were associated cross-sectionally with AN and both cross-sectionally and longitudinally with BN. The DT-A/D cluster had the highest prevalence of AN at follow-up compared with all other clusters. Similarly, an interaction was observed between DT and A/D that predicted risk for AN. Discussion Having elevated DT and A/D scores may increase risk for eating disorder symptomatology above and beyond a high score on either alone. Findings suggest that cluster modeling based on DT and A/D may be useful to inform novel and useful intervention strategies for AN and BN in adolescents. PMID:26013185

Effect of a pragmatic, cluster-randomized controlled trial on patient experience with care: The Transforming Outcomes for Patients through Medical home Evaluation and reDesign (TOPMED) study

PubMed Central

Dorr, David A.; Anastas, Tracy; Ramsey, Katrina; Wagner, Jesse; Sachdeva, Bhavaya; Michaels, LeAnn; Fagnan, Lyle

2016-01-01

Background Health reform programs like the Patient-Centered Medical Home (PCMH) are intended to improve the Triple Aim. Previous studies on PCMHs have shown mixed effects, but High Value Elements (HVEs) are expected to improve the Triple Aim. Objective To understand whether focusing on high value elements (HVEs) would improve patient experience with care. Methods Eight clinics were cluster-randomized in a year-long trial. Both arms received practice facilitation, IT-based reporting, and financial incentives. Intervention practices were encouraged to choose HVEs for QI goals. To assess patient experience, 1,597 Consumer Assessment of Healthcare Providers and Systems (CAHPS) surveys were sent pre- and post-trial to a stratified random sample of patients. Difference in difference multivariate analysis was used to compare patient responses from intervention and control practices, adjusting for confounders. Results The response rate was 43% (n=686). Non-respondent analysis showed no difference between arms, although differences were seen by risk status and age. The overall difference in difference was 2.8%, favoring the intervention. The intervention performed better in 9 of 11 composites. The intervention performed significantly better in Follow-up on test results (p=.091) and Patients’ rating of the provider (p=.091), while the control performed better in Access to care (p=.093). Both arms also had decreases, including 4 of 11 composites for the intervention, and 8 of 11 for the control. Discussion Practices that targeted HVEs showed significantly more improvement in patient experience of care. However, contemporaneous trends may have affected results, leading to declines in patient experience in both arms. PMID:27116107

Final Technical Report: The effects of climate, forest age, and disturbance history on carbon and water processes at AmeriFlux sites across gradients in Pacific Northwest forests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Law, Beverly E.

Investigate the effects of disturbance and climate variables on processes controlling carbon and water processes at AmeriFlux cluster sites in semi-arid and mesic forests in Oregon. The observations were made at three existing and productive AmeriFlux research sites that represent climate and disturbance gradients as a natural experiment of the influence of climatic and hydrologic variability on carbon sequestration and resulting atmospheric CO 2 feedback that includes anomalies during the warm/ dry phase of the Pacific Decadal Oscillation.

Determination of the fundamental properties of an M31 globular cluster from main-sequence photometry

NASA Astrophysics Data System (ADS)

Ma, Jun

2013-02-01

We determined the age of the M31 globular cluster B379 using isochrones of the Padova stellar evolutionary models. At the same time, the cluster's metal abundance, its distance modulus, and reddening value were also obtained. The results obtained in this paper are consistent with previous determinations, including the age. Brown et al. constrained the age of B379 by comparing its color-magnitude diagram with isochrones of the 2006 VandenBerg models. Therefore, this paper confirms the consistency of the age scale of B379 between the Padova isochrones and the 2006 VandenBerg isochrones. The results of B379 obtained in this paper are: metallicity [M/H] = log(Z/Z⊙) = -0.325 dex, age τ = 11.0 +/- 1.5 Gyr, reddening E(B - V) = 0.08 mag, and distance modulus (m - M)0 = 24.44 +/- 0.10 mag. Using the metallicity, the reddening value and the distance modulus obtained in this paper, we constrained the age of B379 by comparing its multicolor photometry with theoretical stellar population synthesis models. The age of B379 obtained is 10.6-0.76 +0.92 Gyr, which is in very good agreement with the determination from main-sequence photometry.

Microscopic Electron Variations Measured Simultaneously By The Cluster Spacecraft

NASA Astrophysics Data System (ADS)

Buckley, A. M.; Carozzi, T. D.; Gough, M. P.; Beloff, N.

Data is used from the Particle Correlator experiments running on each of the four Cluster spacecraft so as to determine common microscopic behaviour in the elec- tron population observed over the macroscopic Cluster separations. The Cluster par- ticle correlator experiments operate by forming on board Auto Correlation Functions (ACFs) generated from short time series of electron counts obtained, as a function of electron energy, from the PEACE HEEA sensor. The information on the microscopic variation of the electron flux covers the frequency range DC up to 41 kHz (encom- passing typical electron plasma frequencies and electron gyro frequencies and their harmonics), the electron energy range is that covered by the PEACE HEEA sensor (within the range 1 eV to 26 keV). Results are presented of coherent electron struc- tures observed simultaneously by the four spacecraft in the differing plasma interac- tion regions and boundaries encountered by Cluster. As an aid to understanding the plasma interactions, use is made of numerical simulations which model both the un- derlying statistical properties of the electrons and also the manner in which particle correlator experiments operate.

High energy conformers of M(+)(APE)(H2O)(0-1)Ar(0-1) clusters revealed by combined IR-PD and DFT-MD anharmonic vibrational spectroscopy.

PubMed

Brites, V; Nicely, A L; Sieffert, N; Gaigeot, M-P; Lisy, J M

2014-07-14

IR-PD vibrational spectroscopy and DFT-based molecular dynamics simulations are combined in order to unravel the structures of M(+)(APE)(H2O)0-1 ionic clusters (M = Na, K), where APE (2-amino-1-phenyl ethanol) is commonly used as an analogue for the noradrenaline neurotransmitter. The strength of the synergy between experiments and simulations presented here is that DFT-MD provides anharmonic vibrational spectra that unambiguously help assign the ionic clusters structures. Depending on the interacting cation, we have found that the lowest energy conformers of K(+)(APE)(H2O)0-1 clusters are formed, while the lowest energy conformers of Na(+)(APE)(H2O)0-1 clusters can only be observed through water loss channel (i.e. without argon tagged to the clusters). Trapping of higher energy conformers is observed when the argon loss channel is recorded in the experiment. This has been rationalized by transition state energies. The dynamical anharmonic vibrational spectra unambiguously provide the prominent OH stretch due to the OH···NH2 H-bond, within 10 cm(-1) of the experiment, hence reproducing the 240-300 cm(-1) red-shift (depending on the interacting cation) from bare neutral APE. When this H-bond is not present, the dynamical anharmonic spectra provide the water O-H stretches as well as the rotational motion of the water molecule at finite temperature, as observed in the experiment.

Geospatial clustering in sugar-sweetened beverage consumption among Boston youth.

PubMed

Tamura, Kosuke; Duncan, Dustin T; Athens, Jessica K; Bragg, Marie A; Rienti, Michael; Aldstadt, Jared; Scott, Marc A; Elbel, Brian

2017-09-01

The objective was to detect geospatial clustering of sugar-sweetened beverage (SSB) intake in Boston adolescents (age = 16.3 ± 1.3 years [range: 13-19]; female = 56.1%; White = 10.4%, Black = 42.6%, Hispanics = 32.4%, and others = 14.6%) using spatial scan statistics. We used data on self-reported SSB intake from the 2008 Boston Youth Survey Geospatial Dataset (n = 1292). Two binary variables were created: consumption of SSB (never versus any) on (1) soda and (2) other sugary drinks (e.g., lemonade). A Bernoulli spatial scan statistic was used to identify geospatial clusters of soda and other sugary drinks in unadjusted models and models adjusted for age, gender, and race/ethnicity. There was no statistically significant clustering of soda consumption in the unadjusted model. In contrast, a cluster of non-soda SSB consumption emerged in the middle of Boston (relative risk = 1.20, p = .005), indicating that adolescents within the cluster had a 20% higher probability of reporting non-soda SSB intake than outside the cluster. The cluster was no longer significant in the adjusted model, suggesting spatial variation in non-soda SSB drink intake correlates with the geographic distribution of students by race/ethnicity, age, and gender.

Clustering box office movie with Partition Around Medoids (PAM) Algorithm based on Text Mining of Indonesian subtitle

NASA Astrophysics Data System (ADS)

Alfarizy, A. D.; Indahwati; Sartono, B.

2017-03-01

Indonesia is the largest Hollywood movie industry target market in Southeast Asia in 2015. Hollywood movies distributed in Indonesia targeted people in all range of ages including children. Low awareness of guiding children while watching movies make them could watch any rated films even the unsuitable ones for their ages. Even after being translated into Bahasa and passed the censorship phase, words that uncomfortable for children to watch still exist. The purpose of this research is to cluster box office Hollywood movies based on Indonesian subtitle, revenue, IMDb user rating and genres as one of the reference for adults to choose right movies for their children to watch. Text mining is used to extract words from the subtitles and count the frequency for three group of words (bad words, sexual words and terror words), while Partition Around Medoids (PAM) Algorithm with Gower similarity coefficient as proximity matrix is used as clustering method. We clustered 624 movies from 2006 until first half of 2016 from IMDb. Cluster with highest silhouette coefficient value (0.36) is the one with 5 clusters. Animation, Adventure and Comedy movies with high revenue like in cluster 5 is recommended for children to watch, while Comedy movies with high revenue like in cluster 4 should be avoided to watch.

Fatality rate of pedestrians and fatal crash involvement rate of drivers in pedestrian crashes: a case study of Iran.

PubMed

Kashani, Ali Tavakoli; Besharati, Mohammad Mehdi

2017-06-01

The aim of this study was to uncover patterns of pedestrian crashes. In the first stage, 34,178 pedestrian-involved crashes occurred in Iran during a four-year period were grouped into homogeneous clusters using a clustering analysis. Next, some in-cluster and inter-cluster crash patterns were analysed. The clustering analysis yielded six pedestrian crash groups. Car/van/pickup crashes on rural roads as well as heavy vehicle crashes were found to be less frequent but more likely to be fatal compared to other crash clusters. In addition, after controlling for crash frequency in each cluster, it was found that the fatality rate of each pedestrian age group as well as the fatal crash involvement rate of each driver age group varies across the six clusters. Results of present study has some policy implications including, promoting pedestrian safety training sessions for heavy vehicle drivers, imposing limitations over elderly heavy vehicle drivers, reinforcing penalties toward under 19 drivers and motorcyclists. In addition, road safety campaigns in rural areas may be promoted to inform people about the higher fatality rate of pedestrians on rural roads. The crash patterns uncovered in this study might also be useful for prioritizing future pedestrian safety research areas.

Association between Physical Activity Levels and Physiological Factors Underlying Mobility in Young, Middle-Aged and Older Individuals Living in a City District

PubMed Central

Laudani, Luca; Vannozzi, Giuseppe; Sawacha, Zimi; della Croce, Ugo; Cereatti, Andrea; Macaluso, Andrea

2013-01-01

Maintaining adequate levels of physical activity is known to preserve health status and functional independence as individuals grow older. However, the relationship between determinants of physical activity (volume and intensity) and physiological factors underlying mobility (cardio-respiratory fitness, neuromuscular function and functional abilities) is still unclear. The aim of this study was to investigate the association between objectively quantified physical activity and a spectrum of physiological factors underlying mobility in young, middle-aged and older individuals living in a city district. Experiments were carried out on 24 young (28±2 years), 24 middle-aged (48±2 years) and 24 older (70±3 years) gender-matched volunteers. Physical activity was monitored by a wearable activity monitor to quantify volume and intensity of overall physical activity and selected habitual activities over 24 hours. Ventilatory threshold was assessed during an incremental cycling test. Torque, muscle fiber conduction velocity and agonist-antagonist coactivation were measured during maximal voluntary contraction of knee extensors and flexors. Ground reaction forces were measured during sit-to-stand and counter-movement jump. K-means cluster analysis was used to classify the participants’ physical activity levels based on parameters of volume and intensity. Two clusters of physical activity volume (i.e., high and low volume) and three clusters of physical activity intensity (i.e. high, medium and low intensity) were identified in all participants. Cardio-respiratory fitness was associated with volume of overall physical activity as well as lying, sitting, standing, walking and stair climbing. On the other hand, neuromuscular function and functional abilities showed a significant association with intensity of overall physical activity as well as postural transition, walking and stair climbing. As a practical application, the relative role played by volume and intensity of overall physical activity and selected habitual activities should be taken into account in the design of preventative training interventions to preserve mobility as individuals grow older. PMID:24040209

Quantitative chemical tagging, stellar ages and the chemo-dynamical evolution of the Galactic disc

NASA Astrophysics Data System (ADS)

Mitschang, A. W.; De Silva, G.; Zucker, D. B.; Anguiano, B.; Bensby, T.; Feltzing, S.

2014-03-01

The early science results from the new generation of high-resolution stellar spectroscopic surveys, such as Galactic Archaeology with HERMES (GALAH) and the Gaia European Southern Observatory survey (Gaia-ESO), will represent major milestones in the quest to chemically tag the Galaxy. Yet this technique to reconstruct dispersed coeval stellar groups has remained largely untested until recently. We build on previous work that developed an empirical chemical tagging probability function, which describes the likelihood that two field stars are conatal, that is, they were formed in the same cluster environment. In this work, we perform the first ever blind chemical tagging experiment, i.e. tagging stars with no known or otherwise discernible associations, on a sample of 714 disc field stars with a number of high-quality high-resolution homogeneous metal abundance measurements. We present evidence that chemical tagging of field stars does identify coeval groups of stars, yet these groups may not represent distinct formation sites, e.g. as in dissolved open clusters, as previously thought. Our results point to several important conclusions, among them that group finding will be limited strictly to chemical abundance space, e.g. stellar ages, kinematics, colours, temperature and surface gravity do not enhance the detectability of groups. We also demonstrate that in addition to its role in probing the chemical enrichment and kinematic history of the Galactic disc, chemical tagging represents a powerful new stellar age determination technique.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goudfrooij, Paul, E-mail: goudfroo@stsci.edu

We study mass functions of globular clusters derived from Hubble Space Telescope/Advanced Camera for Surveys images of the early-type merger remnant galaxy NGC 1316, which hosts a significant population of metal-rich globular clusters of intermediate age ({approx}3 Gyr). For the old, metal-poor ({sup b}lue{sup )} clusters, the peak mass of the mass function M{sub p} increases with internal half-mass density {rho}{sub h} as M{sub p}{proportional_to}{rho}{sub h}{sup 0.44}, whereas it stays approximately constant with galactocentric distance R{sub gal}. The mass functions of these clusters are consistent with a simple scenario in which they formed with a Schechter initial mass function andmore » evolved subsequently by internal two-body relaxation. For the intermediate-age population of metal-rich ({sup r}ed{sup )} clusters, the faint end of the previously reported power-law luminosity function of the clusters with R{sub gal} > 9 kpc is due to many of those clusters having radii larger than the theoretical maximum value imposed by the tidal field of NGC 1316 at their R{sub gal}. This renders disruption by two-body relaxation ineffective. Only a few such diffuse clusters are found in the inner regions of NGC 1316. Completeness tests indicate that this is a physical effect. Using comparisons with star clusters in other galaxies and cluster disruption calculations using published models, we hypothesize that most red clusters in the low-{rho}{sub h} tail of the initial distribution have already been destroyed in the inner regions of NGC 1316 by tidal shocking, and that several remaining low-{rho}{sub h} clusters will evolve dynamically to become similar to 'faint fuzzies' that exist in several lenticular galaxies. Finally, we discuss the nature of diffuse red clusters in early-type galaxies.« less

[Prognostic differences of phenotypes in pT1-2N0 invasive breast cancer: a large cohort study with cluster analysis].

PubMed

Wang, Z; Wang, W H; Wang, S L; Jin, J; Song, Y W; Liu, Y P; Ren, H; Fang, H; Tang, Y; Chen, B; Qi, S N; Lu, N N; Li, N; Tang, Y; Liu, X F; Yu, Z H; Li, Y X

2016-06-23

To find phenotypic subgroups of patients with pT1-2N0 invasive breast cancer by means of cluster analysis and estimate the prognosis and clinicopathological features of these subgroups. From 1999 to 2013, 4979 patients with pT1-2N0 invasive breast cancer were recruited for hierarchical clustering analysis. Age (≤40, 41-70, 70+ years), size of primary tumor, pathological type, grade of differentiation, microvascular invasion, estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER-2) were chosen as distance metric between patients. Hierarchical cluster analysis was performed using Ward's method. Cophenetic correlation coefficient (CPCC) and Spearman correlation coefficient were used to validate clustering structures. The CPCC was 0.603. The Spearman correlation coefficient was 0.617 (P<0.001), which indicated a good fit of hierarchy to the data. A twelve-cluster model seemed to best illustrate our patient cohort. Patients in cluster 5, 9 and 12 had best prognosis and were characterized by age >40 years, smaller primary tumor, lower histologic grade, positive ER and PR status, and mainly negative HER-2. Patients in the cluster 1 and 11 had the worst prognosis, The cluster 1 was characterized by a larger tumor, higher grade and negative ER and PR status, while the cluster 11 was characterized by positive microvascular invasion. Patients in other 7 clusters had a moderate prognosis, and patients in each cluster had distinctive clinicopathological features and recurrent patterns. This study identified distinctive clinicopathologic phenotypes in a large cohort of patients with pT1-2N0 breast cancer through hierarchical clustering and revealed different prognosis. This integrative model may help physicians to make more personalized decisions regarding adjuvant therapy.

Where are Low Mass X-ray Binaries Formed?

NASA Astrophysics Data System (ADS)

Kundu, A.; Maccarone, T. J.; Zepf, S. E.

2004-08-01

Chandra images of nearby galaxies reveal large numbers of low mass X-ray binaries (LMXBs). As in the Galaxy, a significant fraction of these are associated with globular clusters. We exploit the LMXB-globular cluster link in order to probe both the physical properties of globular clusters that promote the formation of LMXBs within clusters with specific characteristics, and to study whether the non-cluster field LMXB population was originally formed in clusters and then released into the field. The large population of globular clusters around nearby galaxies and the range of properties such as age, metallicity and host galaxy environment spanned by these objects enables us to identify and probe the link between these characteristics and the formation of LMXBs. We present the results of our study of a large sample of elliptical and S0 galaxies which reveals among other things that bright LMXBs definitively prefer metal-rich cluster hosts and that this relationship is unlikely to be driven by age effects. The ancestry of the non-cluster field LMXBs is a matter of some debate with suggestions that they they might have formed in the field, or created in globular clusters and then subsequently released into the field either by being ejected from clusters by dynamical processes or as remnants of dynamically destroyed clusters. Each of these scenarios has a specific spatial signature that can be tested by our combined optical and X-ray study. Furthermore, these scenarios predict additional statistical variations that may be driven by the specific host galaxy environment. We present a detailed analysis of our sample galaxies and comment on the probability that the field sources were actually formed in clusters.

Menstrual experiences and beliefs: a multicountry study of relationships with fertility and fertility regulating methods.

PubMed

Severy, L J; Thapa, S; Askew, I; Glor, J

1993-01-01

Knowledge is needed about what women generally experience (behavior and beliefs about sexual, personal, social, and dietary factors) during menstruation as baseline data. Data were obtained from a WHO non nationally representative sample of 5322 parous women from 14 cultural groups between 1973 to 1980 and a subsample of 500 women with detailed daily diaries from 10 countries (Egypt, India, Indonesia, jamaica, Korea, Mexico, Pakistan, Philippines, UK, and Yugoslavia). This study identified and analyzed 1) critical variables through principal component analysis and varimax rotation, 2) clusters of types of women with particular menstrual experiences and particular beliefs, and 3) the relationship between demographic variables and the 2 resultant cluster and the relationship between beliefs and experiences. Factor analysis resulted in the identification of 6 factors and 13 variables which accounted for more than 65% of the variance: amount of bleeding, activity during the last menstrual period, mood during last menstrual period, discomfort during last menstrual period, predictability, and blood characteristics (smell and color). Beliefs that explained more than 53% of the estimated variance were bathing behavior during menstruation, fertility and femininity issues, interpretations and implications of menstruation, and beliefs about not washing hair or body during menstruation. Alpha estimates of reliability for the belief ranged from .33 to .73, and for behavior the range was .40 to .59. The cluster analysis of type of persons identified 3 groups of women: type I (26.4%) who experienced low blood loss the first day and had a long duration of bleeding; type II (52.3%) who had a short duration of bleeding; and type III (21.2%) who had the heaviest bleeding and longest duration of bleeding. The cluster analysis of women's belief types indicated 9 profiles. For instance, Type 2 women tended to believe that menstruation is dirty but prefer more blood loss. Belief Profiles 3, 4, 5, 8, and 9 are consistently represented and profiles 1, 2, 6, and 7 show wide variability. 7 demographic factors were found to be significantly related to belief clusters: country of residence, religion, literacy, age, work environment, social status, and rural vs. urban area. There was evidence, for instance, that type 2 women were overrepresented in the use of modern methods, and that Belief Profile 1, which represents 10.23% of the sample, showed 17.86% using modern methods. The findings show that Belief Profile 1 persons who disagreed with many items were the most likely to use modern methods and have smaller family sizes. Beliefs, which reflect socialization according to demographic variables, appear to affect choice of methods and family size.

Astrophysical properties of star clusters in the Magellanic Clouds homogeneously estimated by ASteCA

NASA Astrophysics Data System (ADS)

Perren, G. I.; Piatti, A. E.; Vázquez, R. A.

2017-06-01

Aims: We seek to produce a homogeneous catalog of astrophysical parameters of 239 resolved star clusters, located in the Small and Large Magellanic Clouds, observed in the Washington photometric system. Methods: The cluster sample was processed with the recently introduced Automated Stellar Cluster Analysis (ASteCA) package, which ensures both an automatized and a fully reproducible treatment, together with a statistically based analysis of their fundamental parameters and associated uncertainties. The fundamental parameters determined for each cluster with this tool, via a color-magnitude diagram (CMD) analysis, are metallicity, age, reddening, distance modulus, and total mass. Results: We generated a homogeneous catalog of structural and fundamental parameters for the studied cluster sample and performed a detailed internal error analysis along with a thorough comparison with values taken from 26 published articles. We studied the distribution of cluster fundamental parameters in both Clouds and obtained their age-metallicity relationships. Conclusions: The ASteCA package can be applied to an unsupervised determination of fundamental cluster parameters, which is a task of increasing relevance as more data becomes available through upcoming surveys. A table with the estimated fundamental parameters for the 239 clusters analyzed is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/602/A89

Pathological and non-pathological variants of restrictive eating behaviors in middle childhood: A latent class analysis.

PubMed

Schmidt, Ricarda; Vogel, Mandy; Hiemisch, Andreas; Kiess, Wieland; Hilbert, Anja

2018-08-01

Although restrictive eating behaviors are very common during early childhood, their precise nature and clinical correlates remain unclear. Especially, there is little evidence on restrictive eating behaviors in older children and their associations with children's shape concern. The present population-based study sought to delineate subgroups of restrictive eating patterns in N = 799 7-14 year old children. Using Latent Class Analysis, children were classified based on six restrictive eating behaviors (for example, picky eating, food neophobia, and eating-related anxiety) and shape concern, separately in three age groups. For cluster validation, sociodemographic and objective anthropometric data, parental feeding practices, and general and eating disorder psychopathology were used. The results showed a 3-cluster solution across all age groups: an asymptomatic class (Cluster 1), a class with restrictive eating behaviors without shape concern (Cluster 2), and a class showing restrictive eating behaviors with prominent shape concern (Cluster 3). The clusters differed in all variables used for validation. Particularly, the proportion of children with symptoms of avoidant/restrictive food intake disorder was greater in Cluster 2 than Clusters 1 and 3. The study underlined the importance of considering shape concern to distinguish between different phenotypes of children's restrictive eating patterns. Longitudinal data are needed to evaluate the clusters' predictive effects on children's growth and development of clinical eating disorders. Copyright © 2018 Elsevier Ltd. All rights reserved.

Controlled assembly and single electron charging of monolayer protected Au144 clusters: an electrochemistry and scanning tunneling spectroscopy study

NASA Astrophysics Data System (ADS)

Bodappa, Nataraju; Fluch, Ulrike; Fu, Yongchun; Mayor, Marcel; Moreno-García, Pavel; Siegenthaler, Hans; Wandlowski, Thomas

2014-11-01

Single gold particles may serve as room temperature single electron memory units because of their size dependent electronic level spacing. Here, we present a proof-of-concept study by electrochemically controlled scanning probe experiments performed on tailor-made Au particles of narrow dispersity. In particular, the charge transport characteristics through chemically synthesized hexane-1-thiol and 4-pyridylbenzene-1-thiol mixed monolayer protected Au144 clusters (MPCs) by differential pulse voltammetry (DPV) and electrochemical scanning tunneling spectroscopy (EC-STS) are reported. The pyridyl groups exposed by the Au-MPCs enable their immobilization on Pt(111) substrates. By varying the humidity during their deposition, samples coated by stacks of compact monolayers of Au-MPCs or decorated with individual, laterally separated Au-MPCs are obtained. DPV experiments with stacked monolayers of Au144-MPCs and EC-STS experiments with laterally separated individual Au144-MPCs are performed both in aqueous and ionic liquid electrolytes. Lower capacitance values were observed for individual clusters compared to ensemble clusters. This trend remains the same irrespective of the composition of the electrolyte surrounding the Au144-MPC. However, the resolution of the energy level spacing of the single clusters is strongly affected by the proximity of neighboring particles.Single gold particles may serve as room temperature single electron memory units because of their size dependent electronic level spacing. Here, we present a proof-of-concept study by electrochemically controlled scanning probe experiments performed on tailor-made Au particles of narrow dispersity. In particular, the charge transport characteristics through chemically synthesized hexane-1-thiol and 4-pyridylbenzene-1-thiol mixed monolayer protected Au144 clusters (MPCs) by differential pulse voltammetry (DPV) and electrochemical scanning tunneling spectroscopy (EC-STS) are reported. The pyridyl groups exposed by the Au-MPCs enable their immobilization on Pt(111) substrates. By varying the humidity during their deposition, samples coated by stacks of compact monolayers of Au-MPCs or decorated with individual, laterally separated Au-MPCs are obtained. DPV experiments with stacked monolayers of Au144-MPCs and EC-STS experiments with laterally separated individual Au144-MPCs are performed both in aqueous and ionic liquid electrolytes. Lower capacitance values were observed for individual clusters compared to ensemble clusters. This trend remains the same irrespective of the composition of the electrolyte surrounding the Au144-MPC. However, the resolution of the energy level spacing of the single clusters is strongly affected by the proximity of neighboring particles. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03793f

Volume shift and charge instability of simple-metal clusters

NASA Astrophysics Data System (ADS)

Brajczewska, M.; Vieira, A.; Fiolhais, C.; Perdew, J. P.

1996-12-01

Experiment indicates that small clusters show changes (mostly contractions) of the bond lengths with respect to bulk values. We use the stabilized jellium model to study the self-expansion and self-compression of spherical clusters (neutral or ionized) of simple metals. Results from Kohn - Sham density functional theory are presented for small clusters of Al and Na, including negatively-charged ones. We also examine the stability of clusters with respect to charging.

Model-based recursive partitioning to identify risk clusters for metabolic syndrome and its components: findings from the International Mobility in Aging Study

PubMed Central

Pirkle, Catherine M; Wu, Yan Yan; Zunzunegui, Maria-Victoria; Gómez, José Fernando

2018-01-01

Objective Conceptual models underpinning much epidemiological research on ageing acknowledge that environmental, social and biological systems interact to influence health outcomes. Recursive partitioning is a data-driven approach that allows for concurrent exploration of distinct mixtures, or clusters, of individuals that have a particular outcome. Our aim is to use recursive partitioning to examine risk clusters for metabolic syndrome (MetS) and its components, in order to identify vulnerable populations. Study design Cross-sectional analysis of baseline data from a prospective longitudinal cohort called the International Mobility in Aging Study (IMIAS). Setting IMIAS includes sites from three middle-income countries—Tirana (Albania), Natal (Brazil) and Manizales (Colombia)—and two from Canada—Kingston (Ontario) and Saint-Hyacinthe (Quebec). Participants Community-dwelling male and female adults, aged 64–75 years (n=2002). Primary and secondary outcome measures We apply recursive partitioning to investigate social and behavioural risk factors for MetS and its components. Model-based recursive partitioning (MOB) was used to cluster participants into age-adjusted risk groups based on variabilities in: study site, sex, education, living arrangements, childhood adversities, adult occupation, current employment status, income, perceived income sufficiency, smoking status and weekly minutes of physical activity. Results 43% of participants had MetS. Using MOB, the primary partitioning variable was participant sex. Among women from middle-incomes sites, the predicted proportion with MetS ranged from 58% to 68%. Canadian women with limited physical activity had elevated predicted proportions of MetS (49%, 95% CI 39% to 58%). Among men, MetS ranged from 26% to 41% depending on childhood social adversity and education. Clustering for MetS components differed from the syndrome and across components. Study site was a primary partitioning variable for all components except HDL cholesterol. Sex was important for most components. Conclusion MOB is a promising technique for identifying disease risk clusters (eg, vulnerable populations) in modestly sized samples. PMID:29500203

Integrated K-band spectra of old and intermediate-age globular clusters in the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Lyubenova, M.; Kuntschner, H.; Rejkuba, M.; Silva, D. R.; Kissler-Patig, M.; Tacconi-Garman, L. E.; Larsen, S. S.

2010-02-01

Current stellar population models have arguably the largest uncertainties in the near-IR wavelength range, partly due to a lack of large and well calibrated empirical spectral libraries. In this paper we present a project whose aim it is to provide the first library of luminosity weighted integrated near-IR spectra of globular clusters to be used to test the current stellar population models and serve as calibrators for future ones. Our pilot study presents spatially integrated K-band spectra of three old (≥10 Gyr) and metal poor ([Fe/H] ~ -1.4), and three intermediate age (1-2 Gyr) and more metal rich ([Fe/H] ~ - 0.4) globular clusters in the LMC. We measured the line strengths of the Na I, Ca I and 12CO (2-0) absorption features. The Na I index decreases with increasing age and decreasing metallicity of the clusters. The DCO index, used to measure the 12CO (2-0) line strength, is significantly reduced by the presence of carbon-rich TP-AGB stars in the globular clusters with age ~1 Gyr. This is in contradiction to the predictions of the stellar population models of Maraston (2005, MNRAS, 362, 799). We find that this disagreement is due to the different CO absorption strength of carbon-rich Milky Way TP-AGB stars used in the models and the LMC carbon stars in our sample. For globular clusters with age ≥ 2 Gyr we find DCO index measurements consistent with the model predictions. Based on observation collected at the ESO Paranal La Silla Observatory, Chile, Prog. ID 078.B-0205.Spectra in FITS format are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/510/A19

Symptoms and Symptom Clusters Identified by Adolescents and Young Adults With Cancer Using a Symptom Heuristics App.

PubMed

Ameringer, Suzanne; Erickson, Jeanne M; Macpherson, Catherine Fiona; Stegenga, Kristin; Linder, Lauri A

2015-12-01

Adolescents and young adults (AYAs) with cancer experience multiple distressing symptoms during treatment. Because the typical approach to symptom assessment does not easily reflect the symptom experience of individuals, alternative approaches to enhancing communication between the patient and provider are needed. We developed an iPad-based application that uses a heuristic approach to explore AYAs' cancer symptom experiences. In this mixed-methods descriptive study, 72 AYAs (13-29 years old) with cancer receiving myelosuppressive chemotherapy used the Computerized Symptom Capture Tool (C-SCAT) to create images of the symptoms and symptom clusters they experienced from a list of 30 symptoms. They answered open-ended questions within the C-SCAT about the causes of their symptoms and symptom clusters. The images generated through the C-SCAT and accompanying free-text data were analyzed using descriptive, content, and visual analyses. Most participants (n = 70) reported multiple symptoms (M = 8.14). The most frequently reported symptoms were nausea (65.3%), feeling drowsy (55.6%), lack of appetite (55.6%), and lack of energy (55.6%). Forty-six grouped their symptoms into one or more clusters. The most common symptom cluster was nausea/eating problems/appetite problems. Nausea was most frequently named as the priority symptom in a cluster and as a cause of other symptoms. Although common threads were present in the symptoms experienced by AYAs, the graphic images revealed unique perspectives and a range of complexity of symptom relationships, clusters, and causes. Results highlight the need for a tailored approach to symptom management based on how the AYA with cancer perceives his or her symptom experience. © 2015 Wiley Periodicals, Inc.

Associations of racial discrimination and parental discrimination coping messages with African American adolescent racial identity.

PubMed

Richardson, Bridget L; Macon, Tamarie A; Mustafaa, Faheemah N; Bogan, Erin D; Cole-Lewis, Yasmin; Chavous, Tabbye M

2015-06-01

Research links racial identity to important developmental outcomes among African American adolescents, but less is known about the contextual experiences that shape youths' racial identity. In a sample of 491 African American adolescents (48% female), associations of youth-reported experiences of racial discrimination and parental messages about preparation for racial bias with adolescents' later racial identity were examined. Cluster analysis resulted in four profiles of adolescents varying in reported frequency of racial discrimination from teachers and peers at school and frequency of parental racial discrimination coping messages during adolescents' 8th grade year. Boys were disproportionately over-represented in the cluster of youth experiencing more frequent discrimination but receiving fewer parental discrimination coping messages, relative to the overall sample. Also examined were clusters of adolescents' 11th grade racial identity attitudes about the importance of race (centrality), personal group affect (private regard), and perceptions of societal beliefs about African Americans (public regard). Girls and boys did not differ in their representation in racial identity clusters, but 8th grade discrimination/parent messages clusters were associated with 11th grade racial identity cluster membership, and these associations varied across gender groups. Boys experiencing more frequent discrimination but fewer parental coping messages were over-represented in the racial identity cluster characterized by low centrality, low private regard, and average public regard. The findings suggest that adolescents who experience racial discrimination but receive fewer parental supports for negotiating and coping with discrimination may be at heightened risk for internalizing stigmatizing experiences. Also, the findings suggest the need to consider the context of gender in adolescents' racial discrimination and parental racial socialization.

No Evidence of Chemical Abundance Variations in the Intermediate-age Cluster NGC 1783

NASA Astrophysics Data System (ADS)

Zhang, Hao; de Grijs, Richard; Li, Chengyuan; Wu, Xiaohan

2018-02-01

We have analyzed multi-passband photometric observations, obtained with the Hubble Space Telescope, of the massive (1.8 × 105 M ⊙), intermediate-age (1.8 Gyr-old) Large Magellanic Cloud star cluster NGC 1783. The morphology of the cluster’s red giant branch does not exhibit a clear broadening beyond its intrinsic width; the observed width is consistent with that owing to photometric uncertainties alone and independent of the photometric selection boundaries we applied to obtain our sample of red giant stars. The color dispersion of the cluster’s red giant stars around the best-fitting ridgeline is 0.062 ± 0.009 mag, which is equivalent to the width of 0.080 ± 0.001 mag derived from artificial simple stellar population tests, that is, tests based on single-age, single-metallicity stellar populations. NGC 1783 is comparably as massive as other star clusters that show clear evidence of multiple stellar populations. After incorporating mass-loss recipes from its current age of 1.8 Gyr to an age of 6 Gyr, NGC 1783 is expected to remain as massive as some other clusters that host clear multiple populations at these intermediate ages. If we were to assume that mass is an important driver of multiple population formation, then NGC 1783 should have exhibited clear evidence of chemical abundance variations. However, our results support the absence of any chemical abundance variations in NGC 1783.

Spatio-Temporal Structure, Path Characteristics, and Perceptual Grouping in Immediate Serial Spatial Recall

PubMed Central

De Lillo, Carlo; Kirby, Melissa; Poole, Daniel

2016-01-01

Immediate serial spatial recall measures the ability to retain sequences of locations in short-term memory and is considered the spatial equivalent of digit span. It is tested by requiring participants to reproduce sequences of movements performed by an experimenter or displayed on a monitor. Different organizational factors dramatically affect serial spatial recall but they are often confounded or underspecified. Untangling them is crucial for the characterization of working-memory models and for establishing the contribution of structure and memory capacity to spatial span. We report five experiments assessing the relative role and independence of factors that have been reported in the literature. Experiment 1 disentangled the effects of spatial clustering and path-length by manipulating the distance of items displayed on a touchscreen monitor. Long-path sequences segregated by spatial clusters were compared with short-path sequences not segregated by clusters. Recall was more accurate for sequences segregated by clusters independently from path-length. Experiment 2 featured conditions where temporal pauses were introduced between or within cluster boundaries during the presentation of sequences with the same paths. Thus, the temporal structure of the sequences was either consistent or inconsistent with a hierarchical representation based on segmentation by spatial clusters but the effect of structure could not be confounded with effects of path-characteristics. Pauses at cluster boundaries yielded more accurate recall, as predicted by a hierarchical model. In Experiment 3, the systematic manipulation of sequence structure, path-length, and presence of path-crossings of sequences showed that structure explained most of the variance, followed by the presence/absence of path-crossings, and path-length. Experiments 4 and 5 replicated the results of the previous experiments in immersive virtual reality navigation tasks where the viewpoint of the observer changed dynamically during encoding and recall. This suggested that the effects of structure in spatial span are not dependent on perceptual grouping processes induced by the aerial view of the stimulus array typically afforded by spatial recall tasks. These results demonstrate the independence of coding strategies based on structure from effects of path characteristics and perceptual grouping in immediate serial spatial recall. PMID:27891101

Physical, sexual and emotional abuse during childhood: Experiences of a sample of Sri Lankan Young adults.

PubMed

Chandraratne, Nadeeka K; Fernando, Asvini D; Gunawardena, Nalika

2018-07-01

Abuse during childhood is a human tragedy leading to lifelong adverse health, social, and economic consequences for survivors. This descriptive, cross-sectional study aimed to determine the prevalence of childhood physical, sexual and emotional abusive experiences among students (aged 18-19 years) in a Sri Lankan district. Multistage cluster sampling was used to select a sample of 1500 students. Experiences of physical, sexual and emotional abuse and age at abuse, perpetrators, consequences and severity were assessed using a version of ISPCAN Child Abuse Screening Tool-Retrospective Version (ICAST-R) which was culturally adapted and validated by the authors for use amongst Sinhalese students. The prevalence of the various forms of abuse during childhood was as follows: physical: 45.4% (95% CI: 42.9-7.9); sexual: 9.1% (95% CI: 7.6-10.5); emotional: 27.9% (95% CI: 25.7-30.2). The corresponding percentages of individuals categorized as having experienced severe or very severe abuse were as follows, physical: 0.3% (2/672); sexual: 4.05% (3/135); emotional: 8.8% (36/412). Experience of physical abuse was more prevalent amongst male students (54.8% vs. 38.3%) as was emotional abuse (33.9% vs. 23.2%), whereas experience of sexual abuse was more prevalent amongst female students (11.5% vs. 6.4%). Parents and teachers were the commonest perpetrators of physical and emotional abuse. Most of the sexually abusive acts were committed by neighbors or strangers. Some physically abusive acts were more frequent at earlier ages than emotional and sexual abusive acts, which were more common in late adolescence. The results indicate the necessity of targeted interventions to address this public health issue. Copyright © 2018 Elsevier Ltd. All rights reserved.

Deriving physical parameters of unresolved star clusters. V. M 31 PHAT star clusters

NASA Astrophysics Data System (ADS)

de Meulenaer, P.; Stonkutė, R.; Vansevičius, V.

2017-06-01

Context. This study is the fifth of a series that investigates the degeneracy and stochasticity problems present in the determination of physical parameters such as age, mass, extinction, and metallicity of partially resolved or unresolved star cluster populations in external galaxies when using HST broad-band photometry. Aims: In this work we aim to derive parameters of star clusters using models with fixed and free metallicity based on the HST WFC3+ACS photometric system. The method is applied to derive parameters of a subsample of 1363 star clusters in the Andromeda galaxy observed with the HST. Methods: Following Paper III, we derive the star cluster parameters using a large grid of stochastic models that are compared to the six observed integrated broad-band WFC3+ACS magnitudes of star clusters. Results: We show that the age, mass, and extinction of the M 31 star clusters, derived assuming fixed solar metallicity, are in agreement with previous studies. We also demonstrate the ability of the WFC3+ACS photometric system to derive metallicity of star clusters older than 1 Gyr. We show that the metallicity derived using broad-band photometry of 36 massive M 31 star clusters is in good agreement with the metallicity derived using spectroscopy. Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/602/A112

The Low End of the Initial Mass Function in Young Clusters. II. Evidence for Primordial Mass Segregation in NGC 330 in the Small Magellanic Cloud

NASA Astrophysics Data System (ADS)

Sirianni, Marco; Nota, Antonella; De Marchi, Guido; Leitherer, Claus; Clampin, Mark

2002-11-01

As part of a larger program aimed at investigating the universality of the initial mass function (IMF) at low masses in a number of young clusters in the LMC and SMC, we present a new study of the low end of the stellar IMF of NGC 330, the richest young star cluster in the SMC, from deep broadband V and I images obtained with HST/WFPC2. We detect stars down to a limiting magnitude of m555=24.9, which corresponds to stellar masses of ~0.8Msolar at the distance of the SMC. A comparison of the cluster color-magnitude diagram with theoretical evolutionary tracks indicates an age of ~30 Myr for NGC 330, in agreement with previous published results. We derive the cluster luminosity function, which we correct for background contamination using an adjacent SMC field, and construct the mass function in the 1-7Msolar mass range. Given the young cluster age, the MF can well approximate the IMF. We find that the IMF in the central cluster regions (within 30") is well reproduced by a power law with a slope consistent with Salpeter's. In addition, the richness of the cluster allows us to investigate the IMF as a function of radial distance from the center. We find that the IMF becomes steeper at increasing distances from the cluster center (between 30" and 90"), with the number of massive stars (>5Msolar) decreasing from the core to the outskirts of the cluster 5 times more rapidly than the less-massive objects (~=1Msolar). We believe the observed mass segregation to be of a primordial nature rather than dynamical since the age of NGC 330 is 10 times shorter than the expected relaxation time of the cluster. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by AURA for NASA under contract NAS5-26555.

General Framework for Effect Sizes in Cluster Randomized Experiments

ERIC Educational Resources Information Center

VanHoudnos, Nathan

2016-01-01

Cluster randomized experiments are ubiquitous in modern education research. Although a variety of modeling approaches are used to analyze these data, perhaps the most common methodology is a normal mixed effects model where some effects, such as the treatment effect, are regarded as fixed, and others, such as the effect of group random assignment…

A More Powerful Test in Three-Level Cluster Randomized Designs

ERIC Educational Resources Information Center

Konstantopoulos, Spyros

2011-01-01

Field experiments that involve nested structures frequently assign treatment conditions to entire groups (such as schools). A key aspect of the design of such experiments includes knowledge of the clustering effects that are often expressed via intraclass correlation. This study provides methods for constructing a more powerful test for the…

Photometric and integrated spectral study of the young open clusters Pismis 22, NGC 6178, NGC 6216 and Ruprecht 130

NASA Astrophysics Data System (ADS)

Piatti, A. E.; Clariá, J. J.; Bica, E.

2000-08-01

We present CCD observations in the B, V , and I passbands obtained for stars in the fields of the open clusters Pismis 22, NGC 6178, NGC 6216, and Ruprecht 130, projected not far from the Galactic centre (|l| < 30̂, |b| < 2̂). The sample consists of about 790 stars reaching down to V ~ 18-19 mag. From the analysis of the colour magnitude diagrams, we confirmed the physical reality of the clusters and derived their reddening, distance and age. In addition, we obtained flux-calibrated integrated spectra in the range 3500-9200 Å for the cluster sample. The equivalent widths of the Balmer lines provided us with age estimates, while the comparison with template spectra allowed us to derive both foreground reddening and age. The photometric and spectroscopic results reveal that the four studied objects are young open clusters with ages ranging between 35 and 50 Myr. The clusters, located between 1.0 kpc and 4.3 kpc from the Sun, are affected by different amounts of interstellar visual absorption (0.6 ≃ Av ≃ 6.0). Based on observations made at Complejo Astronómico El Leoncito, which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la Repúbica Argentina and the National Universities of La Plata, Córdoba, and San Juan, Argentina, and at the University of Toronto (David Dunlap Observatory) 24-inch telescope, Las Campanas, Chile. Tables 3-6 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html

Association of Mediterranean diet and other health behaviours with barriers to healthy eating and perceived health among British adults of retirement age.

PubMed

Lara, Jose; McCrum, Leigh-Ann; Mathers, John C

2014-11-01

Health behaviours including diet, smoking, alcohol consumption, and physical activity, predict health risks at the population level. We explored health behaviours, barriers to healthy eating and self-rated health among individuals of retirement age. Study design 82 men and 124 women participated in an observational, cross-sectional online survey. Main outcome measures A 14-item Mediterranean diet score (MDPS), perceived barriers to healthy eating (PBHE), self-reported smoking, physical activity habits, and current and prior perceived health status (PHS) were assessed. A health behaviours score (HBS) including smoking, physical activity, body mass index (BMI) and MDPS was created to evaluate associations with PHS. Two-step cluster analysis identified natural groups based on PBHE. Analysis of variance was used to evaluate between group comparisons. PBHE number was associated with BMI (r=0.28, P<0.001), age (r=-0.19; P=0.006), and MDPS (r=-0.31; P<0.001). PHBE cluster analysis produced three clusters. Cluster-1 members (busy lifestyle) were significantly younger (57 years), more overweight (28kg/m(2)), scored lower on MDPS (4.7) and reported more PBHE (7). Cluster-3 members (no characteristic PBHE) were leaner (25kg/m(2)), reported the lowest number of PBHE (2), and scored higher on HBS (2.7) and MDPS (6.2). Those in PHS categories, bad/fair, good, and very good, reported mean HBS of 2.0, 2.4 and 3.0, respectively (P<0.001). Compared with the previous year, no significant associations between PHS and HBS were observed. PBHE clusters were associated with BMI, MDPS and PHS and could be a useful tool to tailor interventions for those of peri-retirement age. Copyright © 2014 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

Exploration and Validation of Clusters of Physically Abused Children

ERIC Educational Resources Information Center

Ward, Caryn Sabourin; Haskett, Mary E.

2008-01-01

Objective: Cluster analysis was used to enhance understanding of heterogeneity in social adjustment of physically abused children. Method: Ninety-eight physically abused children (ages 5-10) were clustered on the basis of social adjustment, as measured by observed behavior with peers on the school playground and by teacher reports of social…

Dietary patterns and sarcopenia in an urban African American and White population in the United States.

PubMed

Fanelli Kuczmarski, Marie; Mason, Marc A; Beydoun, May A; Allegro, Deanne; Zonderman, Alan B; Evans, Michele K

2013-01-01

The primary objective of this cross-sectional study was to characterize dietary patterns of African Americans and Whites, 30 to 64 years, examined in the Healthy Aging in Neighborhoods of Diversity across the Life Span study. Other objectives of the study were to evaluate micronutrient adequacy of each pattern and to determine the association of diet with sarcopenia. Cluster analysis was used to determine patterns and mean adequacy ratio (MAR) to determine adequacy of 15 micronutrients. Ten clusters were identified: sandwich, sweet drink, pizza, poultry, frozen meal, dessert, alcoholic drink, bread, starchy vegetables, and pasta/rice dish. MAR ranged from 69 for the sweet drink cluster to 82 for the pasta/rice dish cluster. Sarcopenia was present in 6.4% of the sample, ranging from 1.5% in the poultry cluster to 14.1% in the alcoholic drink cluster. This study is the first to report an association between diet and sarcopenia in people younger than 65 years. The identification of presarcopenia has important implications for dietary interventions that might delay age-associated loss of lean mass.

Forming clusters within clusters: how 30 Doradus recollapsed and gave birth again

NASA Astrophysics Data System (ADS)

Rahner, Daniel; Pellegrini, Eric W.; Glover, Simon C. O.; Klessen, Ralf S.

2018-01-01

The 30 Doradus nebula in the Large Magellanic Cloud (LMC) contains the massive starburst cluster NGC 2070 with a massive and probably younger stellar sub clump at its centre: R136. It is not clear how such a massive inner cluster could form several million years after the older stars in NGC 2070, given that stellar feedback is usually thought to expel gas and inhibit further star formation. Using the recently developed 1D feedback scheme WARPFIELD to scan a large range of cloud and cluster properties, we show that an age offset of several million years between the stellar populations is in fact to be expected given the interplay between feedback and gravity in a giant molecular cloud with a density ≳500 cm-3 due to re-accretion of gas on to the older stellar population. Neither capture of field stars nor gas retention inside the cluster have to be invoked in order to explain the observed age offset in NGC 2070 as well as the structure of the interstellar medium around it.

Do entheogen-induced mystical experiences boost the immune system? Psychedelics, peak experiences, and wellness.

PubMed

Roberts, T B

1999-01-01

Daily events that boost the immune system (as indicated by levels of salivary immunoglobulin A), some instances of spontaneous remission, and mystical experiences seem to share a similar cluster of thoughts, feelings, moods, perceptions, and behaviors. Entheogens--psychedelic drugs used in a religious context--can also produce mystical experiences (peak experiences, states of unitive consciousness, intense primary religious experiences) with the same cluster of effects. When this happens, is it also possible that such entheogen-induced mystical experiences strengthen the immune system? Might spontaneous remissions occur more frequently under such conditions? This article advances the so called "Emxis hypothesis"--that entheogen-induced mystical experiences influence the immune system.

The capacity limitations of orientation summary statistics

PubMed Central

Attarha, Mouna; Moore, Cathleen M.

2015-01-01

The simultaneous–sequential method was used to test the processing capacity of establishing mean orientation summaries. Four clusters of oriented Gabor patches were presented in the peripheral visual field. One of the clusters had a mean orientation that was tilted either left or right while the mean orientations of the other three clusters were roughly vertical. All four clusters were presented at the same time in the simultaneous condition whereas the clusters appeared in temporal subsets of two in the sequential condition. Performance was lower when the means of all four clusters had to be processed concurrently than when only two had to be processed in the same amount of time. The advantage for establishing fewer summaries at a given time indicates that the processing of mean orientation engages limited-capacity processes (Experiment 1). This limitation cannot be attributed to crowding, low target-distractor discriminability, or a limited-capacity comparison process (Experiments 2 and 3). In contrast to the limitations of establishing multiple summary representations, establishing a single summary representation unfolds without interference (Experiment 4). When interpreted in the context of recent work on the capacity of summary statistics, these findings encourage reevaluation of the view that early visual perception consists of summary statistic representations that unfold independently across multiple areas of the visual field. PMID:25810160

Effect of palladium doping on the stability and fragmentation patterns of cationic gold clusters

NASA Astrophysics Data System (ADS)

Ferrari, P.; Hussein, H. A.; Heard, C. J.; Vanbuel, J.; Johnston, R. L.; Lievens, P.; Janssens, E.

2018-05-01

We analyze in detail how the interplay between electronic structure and cluster geometry determines the stability and the fragmentation channels of single Pd-doped cationic Au clusters, PdA uN-1+ (N =2 -20 ). For this purpose, a combination of photofragmentation experiments and density functional theory calculations was employed. A remarkable agreement between the experiment and the calculations is obtained. Pd doping is found to modify the structure of the Au clusters, in particular altering the two-dimensional to three-dimensional transition size, with direct consequences on the stability of the clusters. Analysis of the electronic density of states of the clusters shows that depending on cluster size, Pd delocalizes one 4 d electron, giving an enhanced stability to PdA u6 + , or remains with all 4 d10 electrons localized, closing an electronic shell in PdA u9 + . Furthermore, it is observed that for most clusters, Au evaporation is the lowest-energy decay channel, although for some sizes Pd evaporation competes. In particular, PdA u7 + and PdA u9 + decay by Pd evaporation due to the high stability of the A u7 + and A u9 + fragmentation products.

Edades y metalicidades de cinco cúmulos estelares proyectados en dirección a la Nube Menor de Magallanes: implicaciones sobre los procesos de formación y evolución de estos sistemas

NASA Astrophysics Data System (ADS)

Piatti, A. E.; Santos, J. F. C.; Clariá, J. J.; Bica, E.; Sarajedini, A.; Geisler, D.

Washington photometry of the 5 star clusters Lindsay 32, Lindsay 38, Kron 28, Kron 44 and Lindsay 116 and their surrounding fields located towards the Small Magellanic Cloud (SMC) is presented for the first time. From the color-magnitude diagrams, cleaned from field stars contamination, the cluster and SMC field reddenings, ages and metallicities are determined. The ages - derived from the difference in the T1 magnitude betweem the giant clump and the Main Sequence turnoff point - vary between 2 and 6 Gyr, and the metallicities ([Fe/H]) between -1.65 and -1.10. Lindsay 116 is located closer to the Large Magellanic Cloud (LMC) than to the SMC and its fundamental parameters suggests a higher probability of belonging to the LMC. The results obtained in this work, combined with previous estimates of age and metallicity for other seven clusters, allow us to draw the following conclusions: (1) There does not exist an age-position relation in the SMC, but a age-metallicity one. (2) The chemical enrichment in the SMC has been very efficient during the last 5 Gyr. (3) The SMC clusters formation and evolution can be better represented by a bursting star formation process than by a continuum star formation mechanism.

Transmission clustering among newly diagnosed HIV patients in Chicago, 2008 to 2011: using phylogenetics to expand knowledge of regional HIV transmission patterns

PubMed Central

Lubelchek, Ronald J.; Hoehnen, Sarah C.; Hotton, Anna L.; Kincaid, Stacey L.; Barker, David E.; French, Audrey L.

2014-01-01

Introduction HIV transmission cluster analyses can inform HIV prevention efforts. We describe the first such assessment for transmission clustering among HIV patients in Chicago. Methods We performed transmission cluster analyses using HIV pol sequences from newly diagnosed patients presenting to Chicago’s largest HIV clinic between 2008 and 2011. We compared sequences via progressive pairwise alignment, using neighbor joining to construct an un-rooted phylogenetic tree. We defined clusters as >2 sequences among which each sequence had at least one partner within a genetic distance of ≤ 1.5%. We used multivariable regression to examine factors associated with clustering and used geospatial analysis to assess geographic proximity of phylogenetically clustered patients. Results We compared sequences from 920 patients; median age 35 years; 75% male; 67% Black, 23% Hispanic; 8% had a Rapid Plasma Reagin (RPR) titer ≥ 1:16 concurrent with their HIV diagnosis. We had HIV transmission risk data for 54%; 43% identified as men who have sex with men (MSM). Phylogenetic analysis demonstrated 123 patients (13%) grouped into 26 clusters, the largest having 20 members. In multivariable regression, age < 25, Black race, MSM status, male gender, higher HIV viral load, and RPR ≥ 1:16 associated with clustering. We did not observe geographic grouping of genetically clustered patients. Discussion Our results demonstrate high rates of HIV transmission clustering, without local geographic foci, among young Black MSM in Chicago. Applied prospectively, phylogenetic analyses could guide prevention efforts and help break the cycle of transmission. PMID:25321182

LBT/MODS spectroscopy of globular clusters in the irregular galaxy NGC 4449

NASA Astrophysics Data System (ADS)

Annibali, F.; Morandi, E.; Watkins, L. L.; Tosi, M.; Aloisi, A.; Buzzoni, A.; Cusano, F.; Fumana, M.; Marchetti, A.; Mignoli, M.; Mucciarelli, A.; Romano, D.; van der Marel, R. P.

2018-05-01

We present intermediate-resolution (R ˜ 1000) spectra in the ˜3500-10 000 Å range of 14 globular clusters in the Magellanic irregular galaxy NGC 4449 acquired with the Multi-Object Double Spectrograph on the Large Binocular Telescope. We derived Lick indices in the optical and the Ca II triplet index in the near-infrared in order to infer the clusters' stellar population properties. The inferred cluster ages are typically older than ˜9 Gyr, although ages are derived with large uncertainties. The clusters exhibit intermediate metallicities, in the range -1.2 ≲ [Fe/H] ≲ -0.7, and typically sub-solar [α/Fe] ratios, with a peak at ˜-0.4. These properties suggest that (i) during the first few Gyr NGC 4449 formed stars slowly and inefficiently, with galactic winds having possibly contributed to the expulsion of the α-elements, and (ii) globular clusters in NGC 4449 formed relatively `late', from a medium already enriched in the products of Type Ia supernovae. The majority of clusters appear also underabundant in CN compared to Milky Way halo globular clusters, perhaps because of the lack of a conspicuous N-enriched, second generation of stars like that observed in Galactic globular clusters. Using the cluster velocities, we infer the dynamical mass of NGC 4449 inside 2.88 kpc to be M(<2.88 kpc) = 3.15^{+3.16}_{-0.75} × 10^9 M_{\\odot }. We also report the serendipitous discovery of a planetary nebula within one of the targeted clusters, a rather rare event.

Time-dependent risks of cancer clustering among couples: a nationwide population-based cohort study in Taiwan.

PubMed

Wang, Jong-Yi; Liang, Yia-Wen; Yeh, Chun-Chen; Liu, Chiu-Shong; Wang, Chen-Yu

2018-02-21

Spousal clustering of cancer warrants attention. Whether the common environment or high-age vulnerability determines cancer clustering is unclear. The risk of clustering in couples versus non-couples is undetermined. The time to cancer clustering after the first cancer diagnosis is yet to be reported. This study investigated cancer clustering over time among couples by using nationwide data. A cohort of 5643 married couples in the 2002-2013 Taiwan National Health Insurance Research Database was identified and randomly matched with 5643 non-couple pairs through dual propensity score matching. Factors associated with clustering (both spouses with tumours) were analysed by using the Cox proportional hazard model. Propensity-matched analysis revealed that the risk of clustering of all tumours among couples (13.70%) was significantly higher than that among non-couples (11.84%) (OR=1.182, 95% CI 1.058 to 1.321, P=0.0031). The median time to clustering of all tumours and of malignant tumours was 2.92 and 2.32 years, respectively. Risk characteristics associated with clustering included high age and comorbidity. Shared environmental factors among spouses might be linked to a high incidence of cancer clustering. Cancer incidence in one spouse may signal cancer vulnerability in the other spouse. Promoting family-oriented cancer care in vulnerable families and preventing shared lifestyle risk factors for cancer are suggested. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Grid Computing Environment using a Beowulf Cluster

NASA Astrophysics Data System (ADS)

Alanis, Fransisco; Mahmood, Akhtar

2003-10-01

Custom-made Beowulf clusters using PCs are currently replacing expensive supercomputers to carry out complex scientific computations. At the University of Texas - Pan American, we built a 8 Gflops Beowulf Cluster for doing HEP research using RedHat Linux 7.3 and the LAM-MPI middleware. We will describe how we built and configured our Cluster, which we have named the Sphinx Beowulf Cluster. We will describe the results of our cluster benchmark studies and the run-time plots of several parallel application codes that were compiled in C on the cluster using the LAM-XMPI graphics user environment. We will demonstrate a "simple" prototype grid environment, where we will submit and run parallel jobs remotely across multiple cluster nodes over the internet from the presentation room at Texas Tech. University. The Sphinx Beowulf Cluster will be used for monte-carlo grid test-bed studies for the LHC-ATLAS high energy physics experiment. Grid is a new IT concept for the next generation of the "Super Internet" for high-performance computing. The Grid will allow scientist worldwide to view and analyze huge amounts of data flowing from the large-scale experiments in High Energy Physics. The Grid is expected to bring together geographically and organizationally dispersed computational resources, such as CPUs, storage systems, communication systems, and data sources.

Optical Tweezers for Sample Fixing in Micro-Diffraction Experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amenitsch, H.; Rappolt, M.; Sartori, B.

2007-01-19

In order to manipulate, characterize and measure the micro-diffraction of individual structural elements down to single phospholipid liposomes we have been using optical tweezers (OT) combined with an imaging microscope. We were able to install the OT system at the microfocus beamline ID13 at the ESRF and trap clusters of about 50 multi-lamellar liposomes (< 10 {mu}m large cluster). Further we have performed a scanning diffraction experiment with a 1 micrometer beam to demonstrate the fixing capabilities and to confirm the size of the liposome cluster by X-ray diffraction.

Effect Sizes in Cluster-Randomized Designs

ERIC Educational Resources Information Center

Hedges, Larry V.

2007-01-01

Multisite research designs involving cluster randomization are becoming increasingly important in educational and behavioral research. Researchers would like to compute effect size indexes based on the standardized mean difference to compare the results of cluster-randomized studies (and corresponding quasi-experiments) with other studies and to…

Clusters in intense x-ray pulses

NASA Astrophysics Data System (ADS)

Bostedt, Christoph

2012-06-01

Free-electron lasers can deliver extremely intense, coherent x-ray flashes with femtosecond pulse length, opening the door for imaging single nanoscale objects in a single shot. All matter irradiated by these intense x-ray pulses, however, will be transformed into a highly-excited non-equilibrium plasma within femtoseconds. During the x-ray pulse complex electron dynamics and the onset of atomic disorder will be induced, leading to a time-varying sample. We have performed first experiments about x-ray laser pulse -- cluster interaction with a combined spectroscopy and imaging approach at both, the FLASH free electron laser in Hamburg (Germany) and the LCLS x-ray free-electron laser in Stanford (California). Atomic clusters are ideal for investigating the light - matter interaction because their size can be tuned from the molecular to the bulk regime, thus allowing to distinguish between intra and inter atomic processes. Imaging experiments with xenon clusters show power-density dependent changes in the scattering patterns. Modeling the scattering data indicates that the optical constants of the clusters change during the femtosecond pulse due to the transient creation of high charge states. The results show that ultra fast scattering is a promising approach to study transient states of matter on a femtosecond time scale. Coincident recording of time-of-flight spectra and scattering patterns allows the deconvolution of focal volume and particle size distribution effects. Single-shot single-particle experiments with keV x-rays reveal that for the highest power densities an highly excited and hot cluster plasma is formed for which recombination is suppressed. Time resolved infrared pump -- x-ray probe experiments have started. Here, the clusters are pumped into a nanoplasma state and their time evolution is probed with femtosecond x-ray scattering. The data show strong variations in the scattering patterns stemming from electronic reconfigurations in the cluster plasma. The results will be compared to theoretical predictions and discussed in light of current developments at free-electron laser sources.

Positive and negative affectivity as risk factors for heavy drinking in the second half of life: a prospective cohort study.

PubMed

Brunborg, Geir Scott

2017-05-01

To estimate the prospective relations between levels of propensity to experience positive affect (PA) and propensity to experience negative affect (NA) and risk of heavy drinking in a cohort of Norwegians aged 40-80 years. Clustered sampling was used to draw Norwegians aged 40-79 years in 2002/03 (t1). The relationship between PA and NA measured at t1 and heavy drinking measured in 2007/08 (t2) was estimated with random-intercept logistic regression. Norway. A total of 2142 (44.0% men) who consumed mean = 3.07 [standard deviation (SD) = 3.15] UK units of alcohol on average per week and were intoxicated less than once per week at t1. The Brief Measure of Positive and Negative Affect, quantity-frequency measure of alcohol use and frequency of drinking to intoxication. Heavy drinking at t2 (> 14 units per week and/or intoxication ≥ once per week) was regressed on PA and NA at t1. Controlling for alcohol consumption, gender, age, income and level of education (at t1) and change in PA and NA, there was little evidence for an association between level of PA and heavy drinking [odds ratio (OR) = 0.96, 95% confidence interval (CI) = 0.71, 1.29, Bayes factor = 0.15]. The level of NA at t1 was associated with greater risk of heavy drinking at t2 (OR = 1.40, 95% CI = 1.02, 1.93). There is little evidence for an association between the propensity to experience positive affect and heavy drinking among Norwegians aged 40-80 years. Norwegian adults in the second half of life with a high propensity to experience negative affect are at greater risk of heavy drinking approximately 5 years later than those with a low propensity to experience negative affect. © 2016 Society for the Study of Addiction.

VizieR Online Data Catalog: Star clusters distances and extinctions. II. (Buckner+, 2014)

NASA Astrophysics Data System (ADS)

Buckner, A. S. M.; Froebrich, D.

2015-04-01

Until now, it has been impossible to observationally measure how star cluster scaleheight evolves beyond 1Gyr as only small samples have been available. Here, we establish a novel method to determine the scaleheight of a cluster sample using modelled distributions and Kolmogorov-Smirnov tests. This allows us to determine the scaleheight with a 25% accuracy for samples of 38 clusters or more. We apply our method to investigate the temporal evolution of cluster scaleheight, using homogeneously selected sub-samples of Kharchenko et al. (MWSC, 2012, Cat. J/A+A/543/A156, 2013, J/A+A/558/A53 ), Dias et al. (DAML02, 2002A&A...389..871D, Cat. B/ocl), WEBDA, and Froebrich et al. (FSR, 2007MNRAS.374..399F, Cat. J/MNRAS/374/399). We identify a linear relationship between scaleheight and log(age/yr) of clusters, considerably different from field stars. The scaleheight increases from about 40pc at 1Myr to 75pc at 1Gyr, most likely due to internal evolution and external scattering events. After 1Gyr, there is a marked change of the behaviour, with the scaleheight linearly increasing with log(age/yr) to about 550pc at 3.5Gyr. The most likely interpretation is that the surviving clusters are only observable because they have been scattered away from the mid-plane in their past. A detailed understanding of this observational evidence can only be achieved with numerical simulations of the evolution of cluster samples in the Galactic disc. Furthermore, we find a weak trend of an age-independent increase in scaleheight with Galactocentric distance. There are no significant temporal or spatial variations of the cluster distribution zero-point. We determine the Sun's vertical displacement from the Galactic plane as Z⊙=18.5+/-1.2pc. (1 data file).

The globular cluster system of NGC 1316. II. The extraordinary object SH2

NASA Astrophysics Data System (ADS)

Richtler, T.; Kumar, B.; Bassino, L. P.; Dirsch, B.; Romanowsky, A. J.

2012-07-01

Context. SH2 has been described as an isolated HII-region, located about 6.5' south of the nucleus of NGC 1316 (Fornax A), a merger remnant in the the outskirts of the Fornax cluster of galaxies. Aims: We give a first, preliminary description of the stellar content and environment of this remarkable object. Methods: We used photometric data in the Washington system and HST photometry from the Hubble Legacy Archive for a morphological description and preliminary aperture photometry. Low-resolution spectroscopy provides radial velocities of the brightest star cluster in SH2 and a nearby intermediate-age cluster. Results: SH2 is not a normal HII-region, ionized by very young stars. It contains a multitude of star clusters with ages of approximately 108 yr. A ring-like morphology is striking. SH2 seems to be connected to an intermediate-age massive globular cluster with a similar radial velocity, which itself is the main object of a group of fainter clusters. Metallicity estimates from emission lines remain ambiguous. Conclusions: The present data do not yet allow firm conclusions about the nature or origin of SH2. It might be a dwarf galaxy that has experienced a burst of extremely clustered star formation. We may witness how globular clusters are donated to a parent galaxy. Based on observations taken at the European Southern Observatory, Cerro Paranal, Chile, under the programmes 082.B-0680, on observations taken at the Interamerican Observatory, Cerro Tololo, Chile. Furthermore based on observations made with the NASA/ESA Hubble Space Telescope (HST, PI: A. Sandage, Prop.ID: 7504), and obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (ST-ECF/ESA) and the Canadian Astronomy Data Centre (CADC/NRC/CSA).

Identifying the heterogeneity of young adult rhinitis through cluster analysis in the Isle of Wight birth cohort.

PubMed

Kurukulaaratchy, Ramesh J; Zhang, Hongmei; Patil, Veeresh; Raza, Abid; Karmaus, Wilfried; Ewart, Susan; Arshad, S Hasan

2015-01-01

Rhinitis affects many young adults and often shows comorbidity with asthma. We hypothesized that young adult rhinitis, like asthma, exhibits clinical heterogeneity identifiable by means of cluster analysis. Participants in the Isle of Wight birth cohort (n = 1456) were assessed at 1, 2, 4, 10, and 18 years of age. Cluster analysis was performed on those with rhinitis at age 18 years (n = 468) by using 13 variables defining clinical characteristics. Four clusters were identified. Patients in cluster 1 (n = 128 [27.4%]; ie, moderate childhood-onset rhinitis) had high atopy and eczema prevalence and high total IgE levels but low asthma prevalence. They showed the best lung function at 18 years of age, with normal fraction of exhaled nitric oxide (Feno), low bronchial hyperresponsiveness (BHR), and low bronchodilator reversibility (BDR) but high rhinitis symptoms and treatment. Patients in cluster 2 (n = 199 [42.5%]; ie, mild-adolescence-onset female rhinitis) had the lowest prevalence of comorbid atopy, asthma, and eczema. They had normal lung function and low BHR, BDR, Feno values, and total IgE levels plus low rhinitis symptoms, severity, and treatment. Patients in cluster 3 (n = 59 [12.6%]; ie, severe earliest-onset rhinitis with asthma) had the youngest rhinitis onset plus the highest comorbid asthma (of simultaneous onset) and atopy. They showed the most obstructed lung function with high BHR, BDR, and Feno values plus high rhinitis symptoms, severity, and treatment. Patient 4 in cluster 4 (n = 82 [17.5%]; ie, moderate childhood-onset male rhinitis with asthma) had high atopy, intermediate asthma, and low eczema. They had impaired lung function with high Feno values and total IgE levels but intermediate BHR and BDR. They had moderate rhinitis symptoms. Clinically distinctive adolescent rhinitis clusters are apparent with varying sex and asthma associations plus differing rhinitis severity and treatment needs. Copyright © 2014 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

"Everybody Puts Their Whole Life on Facebook": Identity Management and the Online Social Networks of LGBTQ Youth.

PubMed

McConnell, Elizabeth; Néray, Bálint; Hogan, Bernie; Korpak, Aaron; Clifford, Antonia; Birkett, Michelle

2018-05-26

Lesbian, gay, bisexual, transgender, and queer (LGBTQ) youth and young adults almost inevitably "come out", or self-disclose their identity to others. Some LGBTQ youth are more uniformly "out", while others may disclose to some groups but not others. This selective disclosure is complicated on real name social media sites, which tend to encourage a unified presentation of self across social contexts. We explore these complications with a cohort of LBGTQ youth on Facebook ( N = 199, M age = 24.13). Herein we ask: How do LBGTQ youth manage the disclosure of their sexual orientation and/or gender identity to different people in their lives? Further, are there identifiable differences in the online social network structure for LGBTQ youth who manage outness in different ways? Finally, how do LGBTQ young people describe their experiences on Facebook? We answer these questions using a mixed methods approach, combining statistical cluster analysis, network visualization, and qualitative data. Our findings illustrate patterns in network structure by outness cluster type, highlighting both the work involved in managing one's online identity as well as the costs to (semi-) closeted individuals including a considerably lower overall network connectivity. In particular, outness to family characterized LGBTQ young people's experiences on Facebook.

Stability and change of personality across the life course: the impact of age and major life events on mean-level and rank-order stability of the Big Five.

PubMed

Specht, Jule; Egloff, Boris; Schmukle, Stefan C

2011-10-01

Does personality change across the entire life course, and are those changes due to intrinsic maturation or major life experiences? This longitudinal study investigated changes in the mean levels and rank order of the Big Five personality traits in a heterogeneous sample of 14,718 Germans across all of adulthood. Latent change and latent moderated regression models provided 4 main findings: First, age had a complex curvilinear influence on mean levels of personality. Second, the rank-order stability of Emotional Stability, Extraversion, Openness, and Agreeableness all followed an inverted U-shaped function, reaching a peak between the ages of 40 and 60 and decreasing afterward, whereas Conscientiousness showed a continuously increasing rank-order stability across adulthood. Third, personality predicted the occurrence of several objective major life events (selection effects) and changed in reaction to experiencing these events (socialization effects), suggesting that personality can change due to factors other than intrinsic maturation. Fourth, when events were clustered according to their valence, as is commonly done, effects of the environment on changes in personality were either overlooked or overgeneralized. In sum, our analyses show that personality changes throughout the life span, but with more pronounced changes in young and old ages, and that this change is partly attributable to social demands and experiences. 2011 APA, all rights reserved

A tale of two anomalies: Depletion, dispersion, and the connection between the stellar lithium spread and inflated radii on the pre-main sequence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Somers, Garrett; Pinsonneault, Marc H., E-mail: somers@astronomy.ohio-state.edu, E-mail: pinsono@astronomy.ohio-state.edu

2014-07-20

We investigate lithium depletion in standard stellar models (SSMs) and main sequence (MS) open clusters, and explore the origin of the Li dispersion in young, cool stars of equal mass, age, and composition. We first demonstrate that SSMs accurately predict the Li abundances of solar analogs at the zero-age main sequence (ZAMS) within theoretical uncertainties. We then measure the rate of MS Li depletion by removing the [Fe/H]-dependent ZAMS Li pattern from three well-studied clusters, and comparing the detrended data. MS depletion is found to be mass-dependent, in the sense of more depletion at low mass. A dispersion in Limore » abundance at fixed T{sub eff} is nearly universal, and sets in by ∼200 Myr. We discuss mass and age dispersion trends, and the pattern is mixed. We argue that metallicity impacts the ZAMS Li pattern, in agreement with theoretical expectations but contrary to the findings of some previous studies, and suggest Li as a test of cluster metallicity. Finally, we argue that a radius dispersion in stars of fixed mass and age, during the epoch of pre-MS Li destruction, is responsible for the spread in Li abundances and the correlation between rotation and Li in young cool stars, most well known in the Pleiades. We calculate stellar models, inflated to match observed radius anomalies in magnetically active systems, and the resulting range of Li abundances reproduces the observed patterns of young clusters. We discuss ramifications for pre-MS evolutionary tracks and age measurements of young clusters, and suggest an observational test.« less

The search for multiple populations in Magellanic Cloud Clusters IV: Coeval multiple stellar populations in the young star cluster NGC 1978

NASA Astrophysics Data System (ADS)

Martocchia, S.; Niederhofer, F.; Dalessandro, E.; Bastian, N.; Kacharov, N.; Usher, C.; Cabrera-Ziri, I.; Lardo, C.; Cassisi, S.; Geisler, D.; Hilker, M.; Hollyhead, K.; Kozhurina-Platais, V.; Larsen, S.; Mackey, D.; Mucciarelli, A.; Platais, I.; Salaris, M.

2018-04-01

We have recently shown that the ˜2 Gyr old Large Magellanic Cloud star cluster NGC 1978 hosts multiple populations in terms of star-to-star abundance variations in [N/Fe]. These can be seen as a splitting or spread in the sub-giant and red giant branches (SGB and RGB) when certain photometric filter combinations are used. Due to its relative youth, NGC 1978 can be used to place stringent limits on whether multiple bursts of star-formation have taken place within the cluster, as predicted by some models for the origin of multiple populations. We carry out two distinct analyses to test whether multiple star-formation epochs have occurred within NGC 1978. First, we use UV CMDs to select stars from the first and second population along the SGB, and then compare their positions in optical CMDs, where the morphology is dominantly controlled by age as opposed to multiple population effects. We find that the two populations are indistinguishable, with age differences of 1 ± 20 Myr between them. This is in tension with predictions from the AGB scenario for the origin of multiple populations. Second, we estimate the broadness of the main sequence turnoff (MSTO) of NGC 1978 and we report that it is consistent with the observational errors. We find an upper limit of ˜65 Myr on the age spread in the MSTO of NGC 1978. This finding is in conflict with the age spread scenario as origin of the extendend MSTO in intermediate age clusters, while it fully supports predictions from the stellar rotation model.

The search for multiple populations in Magellanic Cloud clusters - IV. Coeval multiple stellar populations in the young star cluster NGC 1978

NASA Astrophysics Data System (ADS)

Martocchia, S.; Niederhofer, F.; Dalessandro, E.; Bastian, N.; Kacharov, N.; Usher, C.; Cabrera-Ziri, I.; Lardo, C.; Cassisi, S.; Geisler, D.; Hilker, M.; Hollyhead, K.; Kozhurina-Platais, V.; Larsen, S.; Mackey, D.; Mucciarelli, A.; Platais, I.; Salaris, M.

2018-07-01

We have recently shown that the ˜2 Gyr old Large Magellanic Cloud star cluster NGC 1978 hosts multiple populations in terms of star-to-star abundance variations in [N/Fe]. These can be seen as a splitting or spread in the subgiant and red giant branches (SGB and RGB) when certain photometric filter combinations are used. Because of its relative youth, NGC 1978 can be used to place stringent limits on whether multiple bursts of star formation have taken place within the cluster, as predicted by some models for the origin of multiple populations. We carry out two distinct analyses to test whether multiple star formation epochs have occurred within NGC 1978. First, we use ultraviolet colour-magnitude diagrams (CMDs) to select stars from the first and second population along the SGB, and then compare their positions in optical CMDs, where the morphology is dominantly controlled by age as opposed to multiple population effects. We find that the two populations are indistinguishable, with age differences of 1 ± 20 Myr between them. This is in tension with predictions from the asymptotic giant branch scenario for the origin of multiple populations. Second, we estimate the broadness of the main-sequence turn-off (MSTO) of NGC 1978 and we report that it is consistent with the observational errors. We find an upper limit of ˜65 Myr on the age spread in the MSTO of NGC 1978. This finding is in conflict with the age spread scenario as origin of the extended MSTO in intermediate-age clusters, while it fully supports predictions from the stellar rotation model.

Looking for Photometric Signatures of Fast Rotation in Intermediate-Age Star Clusters in the Magellanic Clouds

NASA Astrophysics Data System (ADS)

Goudfrooij, Paul

2017-08-01

Recently, deep color-magnitude diagrams from HST data revealed that several massive intermediate-age star clusters in the Magellanic Clouds exhibit extended main-sequence turn-offs (eMSTOs). This discovery posed serious questions regarding the mechanisms responsible for the formation of massive globular clusters and their well-known multiple stellar populations. The nature of eMSTOs is a hotly debated topic of study. Several studies argued that the eMSTOs are caused by an age range of up to a few hundred Myr, while other studies indicate that eMSTOs can instead be caused by a coeval population in which the stars span a range of rotation velocities. Formal evidence to (dis-)prove either scenario still remains at large, in part because stellar tracks that incorporate the effects of rotation have so far only been available for masses > 1.7 Msun whereas the stars in the known eMSTOs of intermediate-age star clusters are less massive. In this proposal we aim to look for photometric signatures of fast rotators in eMSTO clusters that have been observed by HST in three passbands including (at least) F336W and F814W. We will study spreads in different stellar colors, testing against those predicted with the aid of von Zeipel's geometric study for a population of rotating stars with a significant spread in their inclination. Importantly, this spread due to the presence of rotation is predicted to occur along well-defined lines in color-color diagrams, in directions that are distinct from those in color-magnitude diagrams and distinct from the spread predicted for the age range scenario.

Muscle transcriptome profiling in divergent phenotype swine breeds during growth using microarray and RT-PCR tools.

PubMed

D'Andrea, M; Dal Monego, S; Pallavicini, A; Modonut, M; Dreos, R; Stefanon, B; Pilla, F

2011-10-01

Using an array consisting of 10 665 70-mer oligonucleotide probes, the longissimus dorsi muscle tissue expression during growth in nine pigs belonging to Casertana (CT), an autochthonous breed characterized by slow growth and a massive accumulation of backfat, was compared with that of two cosmopolitan breeds, Large White (LW) and a crossbreed (CB; Duroc × Landrace × Large White). The results were validated by real-time PCR. All animals were of the same age and were raised under the same environmental conditions. Muscle tissues were collected at 3, 6, 9 and 11 months of age, and a total of 173 genes showed significant differential expression between CT and the cosmopolitan genetic types at 3 months of age. Time series cluster analysis indicated that the CT breed had a different pattern of gene expression compared with that of the LW and the CB. Four of the eight clusters highlighted the gene differences between CT and the other two breeds, which were further supported by statistical analyses: clusters 4 and 5 contained a total of 71 genes that were underexpressed at 3 months of age, and cluster 3 and cluster 7 included 28 and 42 genes respectively that were overexpressed at 3 months of age. As expected, differentially expressed genes belonged to the category of genes coding for contractile fibres and transcription factors involved in muscle development and differentiation. These findings highlight muscle expression genes during pig growth and are useful to understand the genetic meaning of the different developmental rates. © 2011 The Authors, Animal Genetics © 2011 Stichting International Foundation for Animal Genetics.

Cardiorespiratory instability in monitored step-down unit patients: using cluster analysis to identify patterns of change

PubMed Central

Clermont, Gilles; Chen, Lujie; Dubrawski, Artur W.; Ren, Dianxu; Hoffman, Leslie A.; Pinsky, Michael R.; Hravnak, Marilyn

2018-01-01

Cardiorespiratory instability (CRI) in monitored step-down unit (SDU) patients has a variety of etiologies, and likely manifests in patterns of vital signs (VS) changes. We explored use of clustering techniques to identify patterns in the initial CRI epoch (CRI1; first exceedances of VS beyond stability thresholds after SDU admission) of unstable patients, and inter-cluster differences in admission characteristics and outcomes. Continuous noninvasive monitoring of heart rate (HR), respiratory rate (RR), and pulse oximetry (SpO2) were sampled at 1/20 Hz. We identified CRI1 in 165 patients, employed hierarchical and k-means clustering, tested several clustering solutions, used 10-fold cross validation to establish the best solution and assessed inter-cluster differences in admission characteristics and outcomes. Three clusters (C) were derived: C1) normal/high HR and RR, normal SpO2 (n = 30); C2) normal HR and RR, low SpO2 (n = 103); and C3) low/normal HR, low RR and normal SpO2 (n = 32). Clusters were significantly different based on age (p < 0.001; older patients in C2), number of comorbidities (p = 0.008; more C2 patients had ≥ 2) and hospital length of stay (p = 0.006; C1 patients stayed longer). There were no between-cluster differences in SDU length of stay, or mortality. Three different clusters of VS presentations for CRI1 were identified. Clusters varied on age, number of comorbidities and hospital length of stay. Future study is needed to determine if there are common physiologic underpinnings of VS clusters which might inform clinical decision-making when CRI first manifests. PMID:28229353

The real population of star clusters in the bar of the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Piatti, Andrés E.

2017-09-01

We report results on star clusters located in the south-eastern half of the Large Magellanic (LMC) bar from Washington CT1 photometry. Using appropriate kernel density estimators, we detected 73 star cluster candidates, three of which do not show any detectable trace of star cluster sequences in their colour-magnitude diagrams (CMDs). We did not detect the other 38 previously catalogued clusters, which could not be recognized when visually inspecting the C and T1 images either; the distribution of stars in their respective fields do not resemble that of a stellar aggregate. They represent 33 per cent of all catalogued objects located within the analysed LMC bar field. From matching theoretical isochrones to the cluster CMDs cleaned from field star contamination, we derived ages in the range 7.2 < log(t yr-1) < 10.1. As far as we are aware, this is the first time that homogeneous age estimates based on resolved stellar photometry are obtained for most of the studied clusters. We built the cluster frequency (CF) for the surveyed area, and found that the main star cluster formation activity has taken place during the period log(t yr-1) 8.0-9.0. Since 100 Myr ago, clusters have been formed during a few bursting formation episodes. When comparing the observed CF to that recovered from the star formation rate, we found noticeable differences, which suggests that field star and star cluster formation histories could have been significantly different. Photometric catalogues of the studied star clusters are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/606/A21

A Lithium Abundance Study of Solar-type Stars in Blanco 1 using the 2.1m McDonald Telescope: Developing Undergraduate Research Experiences.

NASA Astrophysics Data System (ADS)

Cargile, Phillip; James, D. J.; Villalon, K.; Girgenti, S.; Mermilliod, J.

2007-12-01

We present a new catalog of lithium equivalent widths for 20 solar-type stars in the young (60-100 Myr), nearby (250 pc) open cluster Blanco 1, measured from high-resolution spectra (R 30,000), taken during an observing run on the 2.1m telescope at McDonald Observatory. These new lithium data, coupled with the 20 or so extant measurements in the literature, are used in combination with the results of a recently completed standardized BVIc CCD survey, and corresponding 2MASS near-infrared colors, to derive precise lithium abundances for solar-type stars in Blanco 1. Comparing these new results with the existing lithium dataset for other open clusters, we investigate the mass- and age-dependent lithium depletion distribution among early-epoch (< 1Gyr) solar-type stars, and specifically, the lithium abundance scatter as a function of mass in Blanco 1. Our scientific project is highly synergystic with a pedagogical philosophy. We have instituted a program whereby undergraduate students - typically majoring in Liberal Arts and performing an independent study in Astronomy - receive hands-on research experience observing with the 2.1m telescope at the McDonald Observatory. After their observing run, these undergraduates take part in the reduction and analysis of the acquired spectra, and their research experience typically culminates in writing an undergraduate thesis and/or giving a professional seminar to the Astronomy group at Vanderbilt University.

Ageing behaviour of an Fe-20Ni-1.8Mn-1.6Ti-0.59Al (wt%) maraging alloy: clustering, precipitation and hardening

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pereloma, E.V.; Shekhter, A.; Miller, M.K.

2004-11-08

Changes in the solute distribution as well as the evolution of precipitation, microstructure and mechanical properties have been studied in an experimental maraging Fe-20Ni-1.8Mn-1.5Ti-0.59Al (wt%) alloy during ageing at 550 deg C. An initial hardening reaction within 5 s is reported, which is remarkable in terms of extent and rapidity. This strengthening was caused by the formation of complex multi-component atomic co-clusters containing primarily Ni-Ti-Al as well as some Mn. This cluster strengthened condition produced the optimum toughness observed throughout the ageing sequence. After 60 s ageing, the appearance of discrete precipitation of needle-shaped {eta}-Ni{sub 3}Ti particles was associated withmore » a second rise in hardness towards an eventual peak at 600 s. This precipitation hardening was accompanied by an increase in tensile strength and a decrease in ductility. A reverse transformation of martensite to austenite occurs progressively during ageing and this contributes to the initial and secondary softening.« less

U-series vs 14C ages of deep-sea corals from the southern Labrador Sea: Sporadic development of corals and geochemical processes hampering estimation of ambient water ventilation ages

NASA Astrophysics Data System (ADS)

Hillaire-Marcel, Claude; Maccali, Jenny; Ménabréaz, Lucie; Ghaleb, Bassam; Blénet, Aurélien; Edinger, Evan

2017-04-01

Deep-sea scleractinian corals were collected with the remotely operated ROPOS vehicle off Newfounland. Fossil specimens of Desmophyllum dianthus were raised from coral graveyards at Orphan Knoll (˜1700m depth) and Flemish cap (˜2200 m depth), while live specimens were collected directly in overlying steep rock slopes. D. dianthus has an aragonitic skeleton and is thus particularly suited for U-Th dating. We obtained > 70 U-series ages along with > 20 14C measurements. Results display a discrete age distribution with two age clusters: a Bølling-Allerød and Holocene cluster with > 20 samples, and a Marine Isotope Stage (MIS) 5c cluster with ˜50 samples. Only two samples lay outside these clusters, at ˜ 64 ka and at ˜181 ka. Contrary to the New England seamounts where coral presence seems to have been continue through the last 70 ka, Orphan Knoll and Flemish Cap graveyards are marked by the absence of preserved specimens from MIS 2 to MIS 4 and throughout MIS 6. For filter-feeding deep-sea corals, access to food-rich waters is essential. Hence the Holocene and MIS 5 clusters observed in the Labrador basin might represent intervals linked to high food availability, either through production in the overlying water column, more effectively in relation to particulate and dissolved organic carbon transport via an active Western Boundary Undercurrent. Comparison of 230Th-ages vs 14C-ages in order to document changes in ventilation ages of the ambient water masses is equivocal due to the presence of some diagenetic and/or initial 230Th-excess. In addition, discrete diagenetic U-fluxes can be documented from 234U/238U vs 230Th/238U data. They point to a recent winnowing of sediment overlying the fossil corals that we link to the Holocene intensification of the Western Boundary Undercurrent, which resulted in driving Fe-Mn coatings.

FIRST OBSERVATIONAL SIGNATURE OF ROTATIONAL DECELERATION IN A MASSIVE, INTERMEDIATE-AGE STAR CLUSTER IN THE MAGELLANIC CLOUDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Xiaohan; Li, Chengyuan; De Grijs, Richard

While the extended main-sequence turnoffs (eMSTOs) found in almost all 1–2 Gyr old star clusters in the Magellanic Clouds are often explained by postulating extended star formation histories (SFHs), the tight subgiant branches (SGBs) seen in some clusters challenge this popular scenario. Puzzlingly, the SGB of the eMSTO cluster NGC 419 is significantly broader at bluer than at redder colors. We carefully assess and confirm the reality of this observational trend. If we would assume that the widths of the features in color–magnitude space were entirely owing to a range in stellar ages, the SFHs of the eMSTO stars andmore » the blue SGB region would be significantly more prolonged than that of the red part of the SGB. This cannot be explained by assuming an internal age spread. We show that rotational deceleration of a population of rapidly rotating stars, a currently hotly debated alternative scenario, naturally explains the observed trend along the SGB. Our analysis shows that a “converging” SGB could be produced if the cluster is mostly composed of rapidly rotating stars that slow down over time owing to the conservation of angular momentum during their evolutionary expansion from main-sequence turnoff stars to red giants.« less

Open star clusters and Galactic structure

NASA Astrophysics Data System (ADS)

Joshi, Yogesh C.

2018-04-01

In order to understand the Galactic structure, we perform a statistical analysis of the distribution of various cluster parameters based on an almost complete sample of Galactic open clusters yet available. The geometrical and physical characteristics of a large number of open clusters given in the MWSC catalogue are used to study the spatial distribution of clusters in the Galaxy and determine the scale height, solar offset, local mass density and distribution of reddening material in the solar neighbourhood. We also explored the mass-radius and mass-age relations in the Galactic open star clusters. We find that the estimated parameters of the Galactic disk are largely influenced by the choice of cluster sample.

Photometric Calibrations of Gemini Images of NGC 6253

NASA Astrophysics Data System (ADS)

Pearce, Sean; Jeffery, Elizabeth

2017-01-01

We present preliminary results of our analysis of the metal-rich open cluster NGC 6253 using imaging data from GMOS on the Gemini-South Observatory. These data are part of a larger project to observe the effects of high metallicity on white dwarf cooling processes, especially the white dwarf cooling age, which have important implications on the processes of stellar evolution. To standardize the Gemini photometry, we have also secured imaging data of both the cluster and standard star fields using the 0.6-m SARA Observatory at CTIO. By analyzing and comparing the standard star fields of both the SARA data and the published Gemini zero-points of the standard star fields, we will calibrate the data obtained for the cluster. These calibrations are an important part of the project to obtain a standardized deep color-magnitude diagram to analyze the cluster. We present the process of verifying our standardization process. With a standardized CMD, we also present an analysis of the cluster's main sequence turn off age.

Effect Sizes in Three-Level Cluster-Randomized Experiments

ERIC Educational Resources Information Center

Hedges, Larry V.

2011-01-01

Research designs involving cluster randomization are becoming increasingly important in educational and behavioral research. Many of these designs involve two levels of clustering or nesting (students within classes and classes within schools). Researchers would like to compute effect size indexes based on the standardized mean difference to…

Psychiatric outcomes after childbirth: can posttraumatic growth protect me from disordered eating symptoms?

PubMed

Ayache, Raphael; Benticha, Sarah; Goutaudier, Nelly; Chabrol, Henri

2016-06-01

While many studies on mood disorder and posttraumatic stress disorder (PTSD) following childbirth have been conducted, little is known regarding posttraumatic growth (PTG) and disordered eating in the postpartum period. This study aims to (a) identify the typology of women following childbirth based on anxiety, depressive, PTSD symptoms and level of PTG and (b) evaluate whether these profiles differ on disordered eating symptoms. Up to 2 years after childbirth, 306 French-speaking mothers [mean age (SD) = 29.4 (4.6) years] completed questionnaires assessing PTSD, depressive, anxiety and disordered-eating symptoms and level of posttraumatic growth. Four profiles were highlighted: a first one labeled growing cluster (22.2 % of the sample, n = 68), a second one labeled low level of symptoms cluster (37.6 % of the sample, n = 115), a third one labeled vulnerable cluster (21.6 % of the sample, n = 66) and a last one labeled anxious-depressed-traumatized cluster (18.6 % of the sample, n = 57). Our findings also highlight an impact of these profiles on disordered eating symptoms, suggesting that disordered eating in postpartum would not be the result of pregnancy. Consistent with our expectation, our findings suggest a potential protective role of posttraumatic growth on the development of disordered eating symptoms. Further researches focusing on traumatic experience, disordered eating and posttraumatic growth in postpartum are warranted.

Mobilization of hematopoietic progenitor cells with granulocyte colony stimulating factors for autologous transplant in hematologic malignancies: a single center experience

PubMed Central

Gabús, Raul; Borelli, Gabriel; Ferrando, Martín; Bódega, Enrique; Citrín, Estela; Jiménez, Constanza Olivera; Álvarez, Ramón

2011-01-01

Background In 2006 the Hematology Service of Hospital Maciel published its experience with peripheral blood progenitor cell harvesting for autologous stem cell transplantation using Filgen JP (Clausen Filgrastim). After mobilization with a mean filgrastim dose of 78 mcg/Kg, 4.7 x 106 CD34+ cells/Kg were obtained by apheresis. Age above 50, multiple myeloma as underlying disease and a malignancy that was not in remission were identified as frequent characteristics among patients showing complex mobilization. Objective The aim of this study was to compare stem cell mobilization using different brands of filgrastim. Methods One hundred and fifty-seven mobilizations performed between 1997 and 2006 were analyzed. This retrospective analysis comparative two groups of patients: those mobilized with different brands of filgrastim (Group A) and those who received Filgen JP (Clausen Filgrastim) as mobilizing agent (Group B). A cluster analysis technique was used to identify four clusters of individuals with different behaviors differentiated by age, total dose of filgrastim required, number of apheresis and harvested CD34+ cells. Results The mean total dose of filgrastim administered was 105 mcg/Kg, the median number of apheresis was 2 procedures and the mean number of harvested stem cells was 4.98 x 106 CD34+ cells/Kg. No significant differences were observed between Groups A and B regarding the number of apheresis, harvested CD34+ cells and number of mobilization failures, however the total dose of filgrastim was significantly lower in Group B. Conclusions Among other factors, the origin of the cytokine used as mobilizing agent is an element to be considered when evaluating CD34+ cell mobilization results. PMID:23049356

Mobilization of hematopoietic progenitor cells with granulocyte colony stimulating factors for autologous transplant in hematologic malignancies: a single center experience.

PubMed

Gabús, Raul; Borelli, Gabriel; Ferrando, Martín; Bódega, Enrique; Citrín, Estela; Jiménez, Constanza Olivera; Alvarez, Ramón

2011-01-01

In 2006 the Hematology Service of Hospital Maciel published its experience with peripheral blood progenitor cell harvesting for autologous stem cell transplantation using Filgen JP (Clausen Filgrastim). After mobilization with a mean filgrastim dose of 78 mcg/Kg, 4.7 x 10(6) CD34(+) cells/Kg were obtained by apheresis. Age above 50, multiple myeloma as underlying disease and a malignancy that was not in remission were identified as frequent characteristics among patients showing complex mobilization. The aim of this study was to compare stem cell mobilization using different brands of filgrastim. One hundred and fifty-seven mobilizations performed between 1997 and 2006 were analyzed. This retrospective analysis comparative two groups of patients: those mobilized with different brands of filgrastim (Group A) and those who received Filgen JP (Clausen Filgrastim) as mobilizing agent (Group B). A cluster analysis technique was used to identify four clusters of individuals with different behaviors differentiated by age, total dose of filgrastim required, number of apheresis and harvested CD34(+) cells. The mean total dose of filgrastim administered was 105 mcg/Kg, the median number of apheresis was 2 procedures and the mean number of harvested stem cells was 4.98 x 10(6) CD34(+) cells/Kg. No significant differences were observed between Groups A and B regarding the number of apheresis, harvested CD34(+) cells and number of mobilization failures, however the total dose of filgrastim was significantly lower in Group B. Among other factors, the origin of the cytokine used as mobilizing agent is an element to be considered when evaluating CD34(+) cell mobilization results.

Constraints on the age and evolution of the Galaxy from the white dwarf luminosity function

NASA Technical Reports Server (NTRS)

Wood, M. A.

1992-01-01

The white dwarf disk luminosity function is explored using observational results of Liebert et al. (1988, 1989) as a template for comparison, and the cooling curves of Wood (1990, 1991) as the input basis functions for the integration. The star formation rate over the history of the Galaxy is found to be constant to within an order of magnitude, and the disk age lies in the range 6-13.5 Gyr, where roughly 40 percent of the uncertainty is due to the observational uncertainties. Using the best current estimates as inputs to the integration, the disk ages range from 7.5 to 11 Gyr, i.e., they are substantially younger than most estimates for the halo globular clusters but in reasonable agreement with those for the disk globular clusters and open clusters. The ages of these differing populations, taken together, are consistent with the pressure-supported collapse models of early spiral Galactic evolution.

Site-Specific Biomolecule Labeling with Gold Clusters

PubMed Central

Ackerson, Christopher J.; Powell, Richard D.; Hainfeld, James F.

2013-01-01

Site-specific labeling of biomolecules in vitro with gold clusters can enhance the information content of electron cryomicroscopy experiments. This chapter provides a practical overview of well-established techniques for forming biomolecule/gold cluster conjugates. Three bioconjugation chemistries are covered: Linker-mediated bioconjugation, direct gold–biomolecule bonding, and coordination-mediated bonding of nickel(II) nitrilotriacetic acid (NTA)-derivatized gold clusters to polyhistidine (His)-tagged proteins. PMID:20887859

The Structure and Stability of Bn(+) Clusters

NASA Technical Reports Server (NTRS)

Ricca, Alessandra; Bauschlicher, Charles W., Jr.; Langhoff, Stephen R. (Technical Monitor)

1995-01-01

The geometries of B+n clusters for n less than 14 have been optimized using density functional theory with the B3LYP functional. The most stable structure for each cluster is planar or quasi-planar. The B3LYP fragmentation energies are calibrated using coupled cluster theory. Overall, our corrected fragmentation energies are in reasonable agreement with experiment. Our results are compared with previous theoretical results.

Integrating IS Curriculum Knowledge through a Cluster-Computing Project--A Successful Experiment

ERIC Educational Resources Information Center

Kitchens, Fred L.; Sharma, Sushil K.; Harris, Thomas

2004-01-01

MIS curricula in business schools are challenged to provide MIS courses that give students a strong practical understanding of the basic technologies, while also providing enough hands-on experience to solve real life problems. As an experimental capstone MIS course, the authors developed a cluster-computing project to expose business students to…

Statistical Clustering and the Contents of the Infant Vocabulary

ERIC Educational Resources Information Center

Swingley, Daniel

2005-01-01

Infants parse speech into word-sized units according to biases that develop in the first year. One bias, present before the age of 7 months, is to cluster syllables that tend to co-occur. The present computational research demonstrates that this statistical clustering bias could lead to the extraction of speech sequences that are actual words,…

Zodiacal Exoplanets in Time: Searching for Young Stars in K2

NASA Astrophysics Data System (ADS)

Morris, Nathan; Mann, Andrew W.

2017-06-01

Nearby young, open clusters such as the Hyades, Pleiades, and Praesepe provide an important reference point for the properties of stellar systems in general. In each cluster, all stars are of the same known age. As such, observations of planetary systems around these stars can be used to gain insight into the early stages of planetary system formation. K2, the revived Kepler mission, has provided a vast number of light curves for young stars in the and elsewhere in the K2 field. We aim to compute rotational periods from sunspot patterns for all K2 target stars and use gyrochronometric relationships derived from cluster stars to determine their ages. From there, we will search for planets around young stars outside the clusters with the ultimate goal of shedding light on how planets and planetary systems evolve with time.

Estudio de cúmulos estelares de la Nube Menor de Magallanes: fotometría de Washington de 14 cúmulos de edad intermedia

NASA Astrophysics Data System (ADS)

Piatti, A. E.; Clariá, J. J.; Bica, E.; Geisler, D.; Ahumada, A. V.; Girardi, L.

We present CCD photometry in the Washington system C and T1 bands of 14 star clusters of the Small Magellanic Cloud (SMC). We determine ages and metallicities using theoretical isochrones, the T1 parameter and the Red Giant Standard method. Excepting IC 1708, all the observed clusters are aged between 1 and 6.3 Gyr, while their metallicities ([Fe/H]) range be- tween -0.7 and -1.4. Two important cluster formation episodes in the SMC, dated at 2 Gyr and 5 Gyr ago, were detected. During approximately the first 4 Gyr in the SMC lifetime, the cluster formation rate turned out to be constant. A detailed version of this work can be seen in Piatti et al. (2011, MNRAS, 417, 1559). FULL TEXT IN SPANISH

Disintegration of the Aged Open Cluster Berkeley 17

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhattacharya, Souradeep; Vaidya, Kaushar; Mishra, Ishan

We present the analysis of the morphological shape of Berkeley 17, the oldest known open cluster (∼10 Gyr), using the probabilistic star counting of Pan-STARRS point sources, and confirm its core-tail shape, plus an antitail, previously detected with the 2MASS data. The stellar population, as diagnosed by the color–magnitude diagram and theoretical isochrones, shows many massive members in the clusters core, whereas there is a paucity of such members in both of the tails. This manifests mass segregation in this aged star cluster with the low-mass members being stripped away from the system. It has been claimed that Berkeley 17more » is associated with an excessive number of blue straggler candidates. A comparison of nearby reference fields indicates that about half of these may be field contamination.« less

Galaxy evolution in clusters since z=1

NASA Astrophysics Data System (ADS)

Aragón-Salamanca, A.

2011-11-01

It is now 30 years since Alan Dressler published his seminal paper onthe morphology-density relation. Although there is still much to learnon the effect of the environment on galaxy evolution, extensive progress has been made since then both observationally and theoretically.Galaxy clusters provide some of the most extreme environments in which galaxies evolve, making them excellent laboratories to study the age old question of "nature'' vs. "nurture'' in galaxy evolution. Here I review some of the key observational results obtained during the last decade on the evolution of the morphology, structure, dynamics, star-formation history and stellar populations of cluster galaxies since the time when the universe was half its present age.Many of the results presented here have been obtainedwithin the ESO Distant Cluster Survey (EDisCS) and Space Telescope A901/02 Galaxy Evolution Survey (STAGES) collaborations.

The dynamical origin of multiple populations in intermediate-age clusters in the Magellanic Clouds

NASA Astrophysics Data System (ADS)

Hong, Jongsuk; de Grijs, Richard; Askar, Abbas; Berczik, Peter; Li, Chengyuan; Wang, Long; Deng, Licai; Kouwenhoven, M. B. N.; Giersz, Mirek; Spurzem, Rainer

2017-11-01

Numerical simulations were carried out to study the origin of multiple stellar populations in the intermediate-age clusters NGC 411 and NGC 1806 in the Magellanic Clouds. We performed NBODY6++ simulations based on two different formation scenarios, an ad hoc formation model where second-generation (SG) stars are formed inside a cluster of first-generation (FG) stars using the gas accumulated from the external intergalactic medium and a minor merger model of unequal mass (MSG/MFG ∼ 5-10 per cent) clusters with an age difference of a few hundred million years. We compared our results such as the radial profile of the SG-to-FG number ratio with observations on the assumption that the SG stars in the observations are composed of cluster members, and confirmed that both the ad hoc formation and merger scenarios reproduce the observed radial trend of the SG-to-FG number ratio, which shows less centrally concentrated SG than FG stars. It is difficult to constrain the formation scenario for the multiple populations by only using the spatial distribution of the SG stars. SG stars originating from the merger scenario show a significant velocity anisotropy and rotational features compared to those from the ad hoc formation scenario. Thus, observations aimed at kinematic properties like velocity anisotropy or rotational velocities for SG stars should be obtained to better understand the formation of the multiple populations in these clusters. This is, however, beyond current instrumentation capabilities.

Improved Gravitation Field Algorithm and Its Application in Hierarchical Clustering

PubMed Central

Zheng, Ming; Sun, Ying; Liu, Gui-xia; Zhou, You; Zhou, Chun-guang

2012-01-01

Background Gravitation field algorithm (GFA) is a new optimization algorithm which is based on an imitation of natural phenomena. GFA can do well both for searching global minimum and multi-minima in computational biology. But GFA needs to be improved for increasing efficiency, and modified for applying to some discrete data problems in system biology. Method An improved GFA called IGFA was proposed in this paper. Two parts were improved in IGFA. The first one is the rule of random division, which is a reasonable strategy and makes running time shorter. The other one is rotation factor, which can improve the accuracy of IGFA. And to apply IGFA to the hierarchical clustering, the initial part and the movement operator were modified. Results Two kinds of experiments were used to test IGFA. And IGFA was applied to hierarchical clustering. The global minimum experiment was used with IGFA, GFA, GA (genetic algorithm) and SA (simulated annealing). Multi-minima experiment was used with IGFA and GFA. The two experiments results were compared with each other and proved the efficiency of IGFA. IGFA is better than GFA both in accuracy and running time. For the hierarchical clustering, IGFA is used to optimize the smallest distance of genes pairs, and the results were compared with GA and SA, singular-linkage clustering, UPGMA. The efficiency of IGFA is proved. PMID:23173043

Prevalence and factors related to dental caries among pre-school children of Saddar town, Karachi, Pakistan: a cross-sectional study

PubMed Central

2012-01-01

Background Dental caries is highly prevalent and a significant public health problem among children throughout the world. Epidemiological data regarding prevalence of dental caries amongst Pakistani pre-school children is very limited. The objective of this study is to determine the frequency of dental caries among pre-school children of Saddar Town, Karachi, Pakistan and the factors related to caries. Methods A cross-sectional study of 1000 preschool children was conducted in Saddar town, Karachi. Two-stage cluster sampling was used to select the sample. At first stage, eight clusters were selected randomly from total 11 clusters. In second stage, from the eight selected clusters, preschools were identified and children between 3- to 6-years age group were assessed for dental caries. Results Caries prevalence was 51% with a mean dmft score being 2.08 (±2.97) of which decayed teeth constituted 1.95. The mean dmft of males was 2.3 (±3.08) and of females was 1.90 (±2.90). The mean dmft of 3, 4, 5 and 6- year olds was 1.65, 2.11, 2.16 and 3.11 respectively. A significant association was found between dental caries and following variables: age group of 4-years (p-value ² 0.029, RR = 1.248, 95% Bias corrected CI 0.029-0.437) and 5-years (p-value ² 0.009, RR = 1.545, 95% Bias corrected CI 0.047-0.739), presence of dental plaque (p-value ² 0.003, RR = 0.744, 95% Bias corrected CI (−0.433)-(−0.169)), poor oral hygiene (p-value ² 0.000, RR = 0.661, 95% Bias corrected CI (−0.532)-(−0.284)), as well as consumption of non-sweetened milk (p-value ² 0.049, RR = 1.232, 95% Bias corrected CI 0.061-0.367). Conclusion Half of the preschoolers had dental caries coupled with a high prevalence of unmet dental treatment needs. Association between caries experience and age of child, consumption of non-sweetened milk, dental plaque and poor oral hygiene had been established. PMID:23270546

Yellow evolved stars in open clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sowell, J.R.

1987-05-01

This paper describes a program in which Galactic cluster post-AGB candidates were first identified and then analyzed for cluster membership via radial velocities, monitored for possible photometric variations, examined for evidence of mass loss, and classified as completely as possible in terms of their basic stellar parameters. The intrinsically brightest supergiants are found in the youngest clusters. With increasing cluster age, the absolute luminosities attained by the supergiants decline. It appears that the evolutionary tracks of luminosity class II stars are more similar to those of class I than of class III. Only two superluminous giant star candidates are foundmore » in open clusters. 154 references.« less

Star Formation in the Orion Nebula Cluster

NASA Astrophysics Data System (ADS)

Palla, Francesco; Stahler, Steven W.

1999-11-01

We study the record of star formation activity within the dense cluster associated with the Orion Nebula. The bolometric luminosity function of 900 visible members is well matched by a simplified theoretical model for cluster formation. This model assumes that stars are produced at a constant rate and distributed according to the field-star initial mass function. Our best-fit age for the system, within this framework, is 2×106 yr. To undertake a more detailed analysis, we present a new set of theoretical pre-main-sequence tracks. These cover all masses from 0.1 to 6.0 Msolar, and start from a realistic stellar birthline. The tracks end along a zero-age main-sequence that is in excellent agreement with the empirical one. As a further aid to cluster studies, we offer an heuristic procedure for the correction of pre-main-sequence luminosities and ages to account for the effects of unresolved binary companions. The Orion Nebula stars fall neatly between our birthline and zero-age main-sequence in the H-R diagram. All those more massive than about 8 Msolar lie close to the main sequence, as also predicted by theory. After accounting for the finite sensitivity of the underlying observations, we confirm that the population between 0.4 and 6.0 Msolar roughly follows a standard initial mass function. We see no evidence for a turnover at lower masses. We next use our tracks to compile stellar ages, also between 0.4 and 6.0 Msolar. Our age histogram reveals that star formation began at a low level some 107 yr ago and has gradually accelerated to the present epoch. The period of most active formation is indeed confined to a few×106 yr, and has recently ended with gas dispersal from the Trapezium. We argue that the acceleration in stellar births, which extends over a wide range in mass, reflects the gravitational contraction of the parent cloud spawning this cluster.

Red giants observed by CoRoT and APOGEE: The evolution of the Milky Way's radial metallicity gradient

NASA Astrophysics Data System (ADS)

Anders, F.; Chiappini, C.; Minchev, I.; Miglio, A.; Montalbán, J.; Mosser, B.; Rodrigues, T. S.; Santiago, B. X.; Baudin, F.; Beers, T. C.; da Costa, L. N.; García, R. A.; García-Hernández, D. A.; Holtzman, J.; Maia, M. A. G.; Majewski, S.; Mathur, S.; Noels-Grotsch, A.; Pan, K.; Schneider, D. P.; Schultheis, M.; Steinmetz, M.; Valentini, M.; Zamora, O.

2017-04-01

Using combined asteroseismic and spectroscopic observations of 418 red-giant stars close to the Galactic disc plane (6 kpc < RGal ≲ 13 kpc, | ZGal| < 0.3 kpc), we measure the age dependence of the radial metallicity distribution in the Milky Way's thin disc over cosmic time. The slope of the radial iron gradient of the young red-giant population (-0.058 ± 0.008 [stat.] ±0.003 [syst.] dex/kpc) is consistent with recent Cepheid measurements. For stellar populations with ages of 1-4 Gyr the gradient is slightly steeper, at a value of -0.066 ± 0.007 ± 0.002 dex/kpc, and then flattens again to reach a value of -0.03 dex/kpc for stars with ages between 6 and 10 Gyr. Our results are in good agreement with a state-of-the-art chemo-dynamical Milky-Way model in which the evolution of the abundance gradient and its scatter can be entirely explained by a non-varying negative metallicity gradient in the interstellar medium, together with stellar radial heating and migration. We also offer an explanation for why intermediate-age open clusters in the solar neighbourhood can be more metal-rich, and why their radial metallicity gradient seems to be much steeper than that of the youngest clusters. Already within 2 Gyr, radial mixing can bring metal-rich clusters from the innermost regions of the disc to Galactocentric radii of 5 to 8 kpc. We suggest that these outward-migrating clusters may be less prone to tidal disruption and therefore steepen the local intermediate-age cluster metallicity gradient. Our scenario also explains why the strong steepening of the local iron gradient with age is not seen in field stars. In the near future, asteroseismic data from the K2 mission will allow for improved statistics and a better coverage of the inner-disc regions, thereby providing tighter constraints on theevolution of the central parts of the Milky Way.

Coulomb Fission in Multiply-Charged Ammonia Clusters: Accurate Measurements of the Rayleigh Instability Limit from Fragmentation Patterns.

PubMed

Harris, Christopher; Stace, Anthony J

2018-03-15

A series of experiments have been undertaken on the fragmentation of multiply charged ammonia clusters, (NH 3 ) n z+ , where z ≤ 8 and n ≤ 850, to establish Rayleigh instability limits, whereby clusters at certain critical sizes become unstable due to Coulomb repulsion between the resident charges. Experimental results on size-selected clusters are found to be in excellent agreement with theoretical predictions of Rayleigh instability limits at all values of the charge. Electrostatic theory has been used to help identify fragmentation patterns on the assumption that the clusters separate into two dielectric spheres, and the predicted Coulomb repulsion energies used to establish pathways and the sizes of cluster fragments. The results show that fragmentation is very asymmetric in terms of both the numbers of molecules involved and the amount of charge each fragment accommodates. For clusters carrying a charge ≤+4, the results show that fragmentation proceeds via the loss of small, singly charged clusters. When clusters carry a charge of +5 or more, the experimental observations suggest a marked switch in behavior. Although the laboratory measurements equate to fragmentation via the loss of a large dication cluster, electrostatic theory supports an interpretation that involves the sequential loss of two smaller, singly charged clusters possibly accompanied by the extensive evaporation of neutral molecules. It is suggested that this change in fragmentation pattern is driven by the channelling of Coulomb repulsion energy into intermolecular modes within these larger clusters. Overall, the results appear to support the ion evaporation model that is frequently used to interpret electrospray experiments.

U.S. consumer demand for restaurant calorie information: targeting demographic and behavioral segments in labeling initiatives.

PubMed

Kolodinsky, Jane; Reynolds, Travis William; Cannella, Mark; Timmons, David; Bromberg, Daniel

2009-01-01

To identify different segments of U.S. consumers based on food choices, exercise patterns, and desire for restaurant calorie labeling. Using a stratified (by region) random sample of the U.S. population, trained interviewers collected data for this cross-sectional study through telephone surveys. Center for Rural Studies U.S. national health survey. The final sample included 580 responses (22% response rate); data were weighted to be representative of age and gender characteristics of the U.S. population. Self-reported behaviors related to food choices, exercise patterns, desire for calorie information in restaurants, and sample demographics. Clusters were identified using Schwartz Bayesian criteria. Impacts of demographic characteristics on cluster membership were analyzed using bivariate tests of association and multinomial logit regression. Cluster analysis revealed three clusters based on respondents' food choices, activity levels, and desire for restaurant labeling. Two clusters, comprising three quarters of the sample, desired calorie labeling in restaurants. The remaining cluster opposed restaurant labeling. Demographic variables significantly predicting cluster membership included region of residence (p < .10), income (p < .05), gender (p < .01), and age (p < .10). Though limited by a low response and potential self-reporting bias in the phone survey, this study suggests that several groups are likely to benefit from restaurant calorie labeling. Specific demographic clusters could be targeted through labeling initiatives.

A comprehensive photometric study of dynamically evolved small van den Bergh-Hagen open clusters

NASA Astrophysics Data System (ADS)

Piatti, Andrés E.

2016-12-01

We present results from Johnson UBV, Kron-Cousins RI and Washington CT1T2 photometries for seven van den Bergh-Hagen (vdBH) open clusters, namely, vdBH 1, 10, 31, 72, 87, 92, and 118. The high-quality, multiband photometric data sets were used to trace the cluster stellar density radial profiles and to build colour-magnitude diagrams and colour-colour diagrams from which we estimated their structural parameters and fundamental astrophysical properties. The clusters in our sample cover a wide age range, from ˜60 Myr up to 2.8 Gyr, are of relatively small size (˜1-6 pc) and are placed at distances from the Sun which vary between 1.8 and 6.3 kpc, respectively. We also estimated lower limits for the cluster present-day masses as well as half-mass relaxation times (tr). The resulting values in combination with the structural parameter values suggest that the studied clusters are in advanced stages of their internal dynamical evolution (age/tr ˜ 20-320), possibly in the typical phase of those tidally filled with mass segregation in their core regions. Compared to open clusters in the solar neighbourhood, the seven vdBH clusters are within more massive (˜80-380 M⊙), with higher concentration parameter values (c ˜ 0.75-1.15) and dynamically evolved ones.

Multilevel Analysis Methods for Partially Nested Cluster Randomized Trials

ERIC Educational Resources Information Center

Sanders, Elizabeth A.

2011-01-01

This paper explores multilevel modeling approaches for 2-group randomized experiments in which a treatment condition involving clusters of individuals is compared to a control condition involving only ungrouped individuals, otherwise known as partially nested cluster randomized designs (PNCRTs). Strategies for comparing groups from a PNCRT in the…

Synthesis and Ligand-Exchange Reactions of a Tri-Tungsten Cluster with Applications in Biomedical Imaging

ERIC Educational Resources Information Center

Noey, Elizabeth; Curtis, Jeff C.; Tam, Sylvia; Pham, David M.; Jones, Ella F.

2011-01-01

In this experiment students are exposed to concepts in inorganic synthesis and various spectroscopies as applied to a tri-tungsten cluster with applications in biomedical imaging. The tungsten-acetate cluster, Na[W[superscript 3](mu-O)[subscript 2](CH[superscript 3]COO)[superscript 9

Prevalence and risk factors of seizure clusters in adult patients with epilepsy.

PubMed

Chen, Baibing; Choi, Hyunmi; Hirsch, Lawrence J; Katz, Austen; Legge, Alexander; Wong, Rebecca A; Jiang, Alfred; Kato, Kenneth; Buchsbaum, Richard; Detyniecki, Kamil

2017-07-01

In the current study, we explored the prevalence of physician-confirmed seizure clusters. We also investigated potential clinical factors associated with the occurrence of seizure clusters overall and by epilepsy type. We reviewed medical records of 4116 adult (≥16years old) outpatients with epilepsy at our centers for documentation of seizure clusters. Variables including patient demographics, epilepsy details, medical and psychiatric history, AED history, and epilepsy risk factors were then tested against history of seizure clusters. Patients were then divided into focal epilepsy, idiopathic generalized epilepsy (IGE), or symptomatic generalized epilepsy (SGE), and the same analysis was run. Overall, seizure clusters were independently associated with earlier age of seizure onset, symptomatic generalized epilepsy (SGE), central nervous system (CNS) infection, cortical dysplasia, status epilepticus, absence of 1-year seizure freedom, and having failed 2 or more AEDs (P<0.0026). Patients with SGE (27.1%) were more likely to develop seizure clusters than patients with focal epilepsy (16.3%) and IGE (7.4%; all P<0.001). Analysis by epilepsy type showed that absence of 1-year seizure freedom since starting treatment at one of our centers was associated with seizure clustering in patients across all 3 epilepsy types. In patients with SGE, clusters were associated with perinatal/congenital brain injury. In patients with focal epilepsy, clusters were associated with younger age of seizure onset, complex partial seizures, cortical dysplasia, status epilepticus, CNS infection, and having failed 2 or more AEDs. In patients with IGE, clusters were associated with presence of an aura. Only 43.5% of patients with seizure clusters were prescribed rescue medications. Patients with intractable epilepsy are at a higher risk of developing seizure clusters. Factors such as having SGE, CNS infection, cortical dysplasia, status epilepticus or an early seizure onset, can also independently increase one's chance of having seizure clusters. Copyright © 2017. Published by Elsevier B.V.

The clustering of diet, physical activity and sedentary behavior in children and adolescents: a review.

PubMed

Leech, Rebecca M; McNaughton, Sarah A; Timperio, Anna

2014-01-22

Diet, physical activity (PA) and sedentary behavior are important, yet modifiable, determinants of obesity. Recent research into the clustering of these behaviors suggests that children and adolescents have multiple obesogenic risk factors. This paper reviews studies using empirical, data-driven methodologies, such as cluster analysis (CA) and latent class analysis (LCA), to identify clustering patterns of diet, PA and sedentary behavior among children or adolescents and their associations with socio-demographic indicators, and overweight and obesity. A literature search of electronic databases was undertaken to identify studies which have used data-driven methodologies to investigate the clustering of diet, PA and sedentary behavior among children and adolescents aged 5-18 years old. Eighteen studies (62% of potential studies) were identified that met the inclusion criteria, of which eight examined the clustering of PA and sedentary behavior and eight examined diet, PA and sedentary behavior. Studies were mostly cross-sectional and conducted in older children and adolescents (≥ 9 years). Findings from the review suggest that obesogenic cluster patterns are complex with a mixed PA/sedentary behavior cluster observed most frequently, but healthy and unhealthy patterning of all three behaviors was also reported. Cluster membership was found to differ according to age, gender and socio-economic status (SES). The tendency for older children/adolescents, particularly females, to comprise clusters defined by low PA was the most robust finding. Findings to support an association between obesogenic cluster patterns and overweight and obesity were inconclusive, with longitudinal research in this area limited. Diet, PA and sedentary behavior cluster together in complex ways that are not well understood. Further research, particularly in younger children, is needed to understand how cluster membership differs according to socio-demographic profile. Longitudinal research is also essential to establish how different cluster patterns track over time and their influence on the development of overweight and obesity.

The clustering of diet, physical activity and sedentary behavior in children and adolescents: a review

PubMed Central

2014-01-01

Diet, physical activity (PA) and sedentary behavior are important, yet modifiable, determinants of obesity. Recent research into the clustering of these behaviors suggests that children and adolescents have multiple obesogenic risk factors. This paper reviews studies using empirical, data-driven methodologies, such as cluster analysis (CA) and latent class analysis (LCA), to identify clustering patterns of diet, PA and sedentary behavior among children or adolescents and their associations with socio-demographic indicators, and overweight and obesity. A literature search of electronic databases was undertaken to identify studies which have used data-driven methodologies to investigate the clustering of diet, PA and sedentary behavior among children and adolescents aged 5–18 years old. Eighteen studies (62% of potential studies) were identified that met the inclusion criteria, of which eight examined the clustering of PA and sedentary behavior and eight examined diet, PA and sedentary behavior. Studies were mostly cross-sectional and conducted in older children and adolescents (≥9 years). Findings from the review suggest that obesogenic cluster patterns are complex with a mixed PA/sedentary behavior cluster observed most frequently, but healthy and unhealthy patterning of all three behaviors was also reported. Cluster membership was found to differ according to age, gender and socio-economic status (SES). The tendency for older children/adolescents, particularly females, to comprise clusters defined by low PA was the most robust finding. Findings to support an association between obesogenic cluster patterns and overweight and obesity were inconclusive, with longitudinal research in this area limited. Diet, PA and sedentary behavior cluster together in complex ways that are not well understood. Further research, particularly in younger children, is needed to understand how cluster membership differs according to socio-demographic profile. Longitudinal research is also essential to establish how different cluster patterns track over time and their influence on the development of overweight and obesity. PMID:24450617