Learning Temporal Statistics for Sensory Predictions in Aging.

PubMed

Luft, Caroline Di Bernardi; Baker, Rosalind; Goldstone, Aimee; Zhang, Yang; Kourtzi, Zoe

2016-03-01

Predicting future events based on previous knowledge about the environment is critical for successful everyday interactions. Here, we ask which brain regions support our ability to predict the future based on implicit knowledge about the past in young and older age. Combining behavioral and fMRI measurements, we test whether training on structured temporal sequences improves the ability to predict upcoming sensory events; we then compare brain regions involved in learning predictive structures between young and older adults. Our behavioral results demonstrate that exposure to temporal sequences without feedback facilitates the ability of young and older adults to predict the orientation of an upcoming stimulus. Our fMRI results provide evidence for the involvement of corticostriatal regions in learning predictive structures in both young and older learners. In particular, we showed learning-dependent fMRI responses for structured sequences in frontoparietal regions and the striatum (putamen) for young adults. However, for older adults, learning-dependent activations were observed mainly in subcortical (putamen, thalamus) regions but were weaker in frontoparietal regions. Significant correlations of learning-dependent behavioral and fMRI changes in these regions suggest a strong link between brain activations and behavioral improvement rather than general overactivation. Thus, our findings suggest that predicting future events based on knowledge of temporal statistics engages brain regions involved in implicit learning in both young and older adults.

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.

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

The zero age main sequence of WIMP burners

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

Fairbairn, Malcolm; Scott, Pat; Edsjoe, Joakim

2008-02-15

We modify a stellar structure code to estimate the effect upon the main sequence of the accretion of weakly-interacting dark matter onto stars and its subsequent annihilation. The effect upon the stars depends upon whether the energy generation rate from dark matter annihilation is large enough to shut off the nuclear burning in the star. Main sequence weakly-interacting massive particles (WIMP) burners look much like proto-stars moving on the Hayashi track, although they are in principle completely stable. We make some brief comments about where such stars could be found, how they might be observed and more detailed simulations whichmore » are currently in progress. Finally we comment on whether or not it is possible to link the paradoxically hot, young stars found at the galactic center with WIMP burners.« less

Mass loss from solar-type stars

NASA Technical Reports Server (NTRS)

Hartmann, L.

1985-01-01

The present picture of mass loss from solar-type (low-mass) stars is described, with special emphasis on winds from pre-main-sequence stars. Attention is given to winds from T Tauri stars and to angular momentum loss. Prospects are good for further advances in our understanding of the powerful mass loss observed from young stars; ultraviolet spectra obtainable with the Space Telescope should provide better estimates of mass loss rates and a clearer picture of physical conditions in the envelopes of these stars. To understand the mass ejection from old, slowly rotating main-sequence stars, we will have to study the sun.

Pre-main sequence variables in young cluster Stock 18

NASA Astrophysics Data System (ADS)

Sinha, Tirthendu; Sharma, Saurabh; Pandey, Rakesh; Pandey, Anil Kumar

2018-04-01

We have carried out multi-epoch deep I band photometry of the open cluster Stock 18 to search for variable stars in star forming regions. In the present study, we identified 65 periodic and 217 non-periodic variable stars. The periods of most of the periodic variables are between 2 hours to 15 days and their magnitude varies between 0.05 to 0.6 mag. We have derived spectral energy distributions for 48 probable pre-main sequence variables. Their average age and mass are 2.7 ± 0.3 Myrs and 2.7 ± 0.2 Mo, respectively.

VizieR Online Data Catalog: NGC 7129 pre-main sequence stars (Stelzer+, 2009)

NASA Astrophysics Data System (ADS)

Stelzer, B.; Scholz, A.

2010-09-01

We make use of X-ray and IR imaging observations to identify the pre-main sequence stars in NGC 7129. We define a sample of young stellar objects based on color-color diagrams composed from IR photometry between 1.6 and 8um, from 2MASS and Spitzer, and based on X-ray detected sources from a Chandra observation. A 22ks long Chandra observation targeting the Herbig star SVS 12 was carried out on Mar 11, 2006 (start of observation UT 14h29m18s). (5 data files).

The effect of starspots on the radii of low-mass pre-main-sequence stars

NASA Astrophysics Data System (ADS)

Jackson, R. J.; Jeffries, R. D.

2014-07-01

A polytropic model is used to investigate the effects of dark photospheric spots on the evolution and radii of magnetically active, low-mass (M < 0.5 M⊙), pre-main-sequence (PMS) stars. Spots slow the contraction along Hayashi tracks and inflate the radii of PMS stars by a factor of (1 - β)-N compared to unspotted stars of the same luminosity, where β is the equivalent covering fraction of dark starspots and N ≃ 0.45 ± 0.05. This is a much stronger inflation than predicted by Spruit & Weiss for main-sequence stars with the same β, where N ˜ 0.2-0.3. These models have been compared to radii determined for very magnetically active K- and M-dwarfs in the young Pleiades and NGC 2516 clusters, and the radii of tidally locked, low-mass eclipsing binary components. The binary components and zero-age main-sequence K-dwarfs have radii inflated by ˜10 per cent compared to an empirical radius-luminosity relation that is defined by magnetically inactive field dwarfs with interferometrically measured radii; low-mass M-type PMS stars, that are still on their Hayashi tracks, are inflated by up to ˜40 per cent. If this were attributable to starspots alone, we estimate that an effective spot coverage of 0.35 < β < 0.51 is required. Alternatively, global inhibition of convective flux transport by dynamo-generated fields may play a role. However, we find greater consistency with the starspot models when comparing the loci of active young stars and inactive field stars in colour-magnitude diagrams, particularly for the highly inflated PMS stars, where the large, uniform temperature reduction required in globally inhibited convection models would cause the stars to be much redder than observed.

ASCA Observations of the T Tauri Star SU Aurigae and the Surrounding L1517 Dark Cloud

NASA Technical Reports Server (NTRS)

Skinner, Stephen L.; Walter, Frederick M.

1998-01-01

We present the results of a approximately equals 40 ks pointed Advanced Satellite for Cosmology and Astrophysics (ASCA) observation of the L1517 star-forming region, centered on the X-ray-bright T Tauri star SU Aurigae. This star has the highest X-ray luminosity of any classical T Tauri star in the Taurus-Auriga region, and its optical spectra show evidence for both mass inflow and outflow. Strong X-ray emission was detected from SU Aur (L(sub x) = 10(exp 30.9) ergs s(exp -1)) as well as weaker emission from five other pre-main-sequence stars. Although no large-amplitude flares were detected, the X-ray emission of SU Aur showed clear variability in the form of a slow decline in count rate during the 1.3 day observation. We provide the first direct comparison of the coronal differential emission measure (DEM) distribution of a classical T Tauri star with that of a young main-sequence star of similar spectral type. The DEM distributions of SU Aur (G2; age 3 Myr) and the young solar-like star EK Draconis (GO V; age 70 Myr) are qualitatively similar, with both showing a bimodal temperature distribution characterized by a cool plasma component peaking at approximately 8-9 MK and a hot component peaking at approximately 20-21 MK. However, there is a striking difference in the relative proportion of plasma at high temperatures in the two stars, with hot plasma (>20 MK) accounting for approximately equals 80% of the volume emission measure of SU Aur, compared to only approximately equals 40% in EK Dra. These results provide new insight into the changes that will occur in the corona of a T Tauri star as it descends onto the main sequence. A sharp decline in the fraction of coronal plasma at flarelike temperatures will occur during the late-T Tauri and post-T Tauri phases, and other recent X-ray studies have shown that this decline will continue after the young solar-like star reaches the main sequence.

Solar Luminosity on the Main Sequence, Standard Model and Variations

NASA Astrophysics Data System (ADS)

Ayukov, S. V.; Baturin, V. A.; Gorshkov, A. B.; Oreshina, A. V.

2017-05-01

Our Sun became Main Sequence star 4.6 Gyr ago according Standard Solar Model. At that time solar luminosity was 30% lower than current value. This conclusion is based on assumption that Sun is fueled by thermonuclear reactions. If Earth's albedo and emissivity in infrared are unchanged during Earth history, 2.3 Gyr ago oceans had to be frozen. This contradicts to geological data: there was liquid water 3.6-3.8 Gyr ago on Earth. This problem is known as Faint Young Sun Paradox. We analyze luminosity change in standard solar evolution theory. Increase of mean molecular weight in the central part of the Sun due to conversion of hydrogen to helium leads to gradual increase of luminosity with time on the Main Sequence. We also consider several exotic models: fully mixed Sun; drastic change of pp reaction rate; Sun consisting of hydrogen and helium only. Solar neutrino observations however exclude most non-standard solar models.

Chromospherically Active Stars in the RAVE Survey. II. Young Dwarfs in the Solar Neighborhood

NASA Astrophysics Data System (ADS)

Žerjal, M.; Zwitter, T.; Matijevič, G.; Grebel, E. K.; Kordopatis, G.; Munari, U.; Seabroke, G.; Steinmetz, M.; Wojno, J.; Bienaymé, O.; Bland-Hawthorn, J.; Conrad, C.; Freeman, K. C.; Gibson, B. K.; Gilmore, G.; Kunder, A.; Navarro, J.; Parker, Q. A.; Reid, W.; Siviero, A.; Watson, F. G.; Wyse, R. F. G.

2017-01-01

A large sample of over 38,000 chromospherically active candidate solar-like stars and cooler dwarfs from the RAVE survey is addressed in this paper. An improved activity identification with respect to the previous study was introduced to build a catalog of field stars in the solar neighborhood with an excess emission flux in the calcium infrared triplet wavelength region. The central result of this work is the calibration of the age-activity relation for main-sequence dwarfs in a range from a few 10 {Myr} up to a few Gyr. It enabled an order of magnitude age estimation of the entire active sample. Almost 15,000 stars are shown to be younger than 1 {Gyr} and ˜2000 younger than 100 {Myr}. The young age of the most active stars is confirmed by their position off the main sequence in the J - K versus {N}{UV}-V diagram showing strong ultraviolet excess, mid-infrared excess in the J - K versus {W}1-{W}2 diagram, and very cool temperatures (J-K> 0.7). They overlap with the reference pre-main-sequence RAVE stars often displaying X-ray emission. The activity level increasing with the color reveals their different nature from the solar-like stars and probably represents an underlying dynamo-generating magnetic fields in cool stars. Of the RAVE objects from DR5, 50% are found in the TGAS catalog and supplemented with accurate parallaxes and proper motions by Gaia. This makes the database of a large number of young stars in a combination with RAVE’s radial velocities directly useful as a tracer of the very recent large-scale star formation history in the solar neighborhood. The data are available online in the Vizier database.

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.

YOUNG STELLAR CLUSTERS CONTAINING MASSIVE YOUNG STELLAR OBJECTS IN THE VVV SURVEY

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

Borissova, J.; Alegría, S. Ramírez; Kurtev, R.

The purpose of this research is to study the connections of the global properties of eight young stellar clusters projected in the Vista Variables in the Via Lactea (VVV) ESO Large Public Survey disk area and their young stellar object (YSO) populations. The analysis is based on the combination of spectroscopic parallax-based reddening and distance determinations with main-sequence and pre-main-sequence ishochrone fitting to determine the basic parameters (reddening, age, distance) of the sample clusters. The lower mass limit estimations show that all clusters are low or intermediate mass (between 110 and 1800  M {sub ⊙}), the slope Γ of themore » obtained present-day mass functions of the clusters is close to the Kroupa initial mass function. The YSOs in the cluster’s surrounding fields are classified using low resolution spectra, spectral energy distribution fits with theoretical predictions, and variability, taking advantage of multi-epoch VVV observations. All spectroscopically confirmed YSOs (except one) are found to be massive (more than 8 M {sub ⊙}). Using VVV and GLIMPSE color–color cuts we have selected a large number of new YSO candidates, which are checked for variability and 57% are found to show at least low-amplitude variations. In few cases it was possible to distinguish between YSO and AGB classifications on the basis of light curves.« less

General properties of magnetic CP stars

NASA Astrophysics Data System (ADS)

Glagolevskij, Yu. V.

2017-07-01

We present the review of our previous studies related to observational evidence of the fossil field hypothesis of formation and evolution of magnetic and non-magnetic chemically peculiar stars. Analysis of the observed data shows that these stars acquire their main properties in the process of gravitational collapse. In the non-stationary Hayashi phase, a magnetic field becomes weakened and its configuration complicated, but the fossil field global orientation remains. After a non-stationary phase, relaxation of young star's tangled field takes place and by the time of joining ZAMS (Zero Age Main Sequence) it is generally restored to a dipole structure. Stability of dipole structures allows them to remain unchanged up to the end of their life on the Main Sequence which is 109 years at most.

Substantial reservoirs of molecular hydrogen in the debris disks around young stars.

PubMed

Thi, W F; Blake, G A; van Dishoeck, E F; van Zadelhoff, G J; Horn, J M; Becklin, E E; Mannings, V; Sargent, A I; van Den Ancker, M E; Natta, A

2001-01-04

Circumstellar accretion disks transfer matter from molecular clouds to young stars and to the sites of planet formation. The disks observed around pre-main-sequence stars have properties consistent with those expected for the pre-solar nebula from which our own Solar System formed 4.5 Gyr ago. But the 'debris' disks that encircle more than 15% of nearby main-sequence stars appear to have very small amounts of gas, based on observations of the tracer molecule carbon monoxide: these observations have yielded gas/dust ratios much less than 0.1, whereas the interstellar value is about 100 (ref. 9). Here we report observations of the lowest rotational transitions of molecular hydrogen (H2) that reveal large quantities of gas in the debris disks around the stars beta Pictoris, 49 Ceti and HD135344. The gas masses calculated from the data are several hundreds to a thousand times greater than those estimated from the CO observations, and yield gas/dust ratios of the same order as the interstellar value.

AN M DWARF COMPANION TO AN F-TYPE STAR IN A YOUNG MAIN-SEQUENCE BINARY

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

Eigmüller, Ph.; Csizmadia, Sz.; Erikson, A.

2016-03-15

Only a few well characterized very low-mass M dwarfs are known today. Our understanding of M dwarfs is vital as these are the most common stars in our solar neighborhood. We aim to characterize the properties of a rare F+dM stellar system for a better understanding of the low-mass end of the Hertzsprung–Russel diagram. We used photometric light curves and radial velocity follow-up measurements to study the binary. Spectroscopic analysis was used in combination with isochrone fitting to characterize the primary star. The primary star is an early F-type main-sequence star with a mass of (1.493 ± 0.073) M{sub ⊙}more » and a radius of (1.474 ± 0.040) R{sub ⊙}. The companion is an M dwarf with a mass of (0.188 ± 0.014) M{sub ⊙} and a radius of (0.234 ± 0.009) R{sub ⊙}. The orbital period is (1.35121 ± 0.00001) days. The secondary star is among the lowest-mass M dwarfs known to date. The binary has not reached a 1:1 spin–orbit synchronization. This indicates a young main-sequence binary with an age below ∼250 Myr. The mass–radius relation of both components are in agreement with this finding.« less

From protostellar to pre-main-sequence evolution

NASA Astrophysics Data System (ADS)

D'Antona, F.

I summarize the status of pre-main-sequence evolutionary tracks starting from the first steps dating back to the concept of Hayashi track. Understanding of the dynamical protostellar phase in the vision of Palla & Stahler, who introduced the concept of the deuterium burning thermostat and of stellar birthline, provided for a long time a link between the dynamical and hydrostatic evolution. Disk accretion however changed considerably the view, but re-introducing some ambiguities which must still be solved. The limitations and uncertainties in the mass and age determination from models for young stellar objects are summarized, but the burning of light elements is still a powerful observational signature.

Are sdAs helium core stars?

NASA Astrophysics Data System (ADS)

Pelisoli, Ingrid; Kepler, S. O.; Koester, Detlev

2017-12-01

Evolved stars with a helium core can be formed by non-conservative mass exchange interaction with a companion or by strong mass loss. Their masses are smaller than 0.5 M⊙. In the database of the Sloan Digital Sky Survey (SDSS), there are several thousand stars which were classified by the pipeline as dwarf O, B and A stars. Considering the lifetimes of these classes on the main sequence, and their distance modulus at the SDSS bright saturation, if these were common main sequence stars, there would be a considerable population of young stars very far from the galactic disk. Their spectra are dominated by Balmer lines which suggest effective temperatures around 8 000-10 000 K. Several thousand have significant proper motions, indicative of distances smaller than 1 kpc. Many show surface gravity in intermediate values between main sequence and white dwarf, 4.75 < log g < 6.5, hence they have been called sdA stars. Their physical nature and evolutionary history remains a puzzle. We propose they are not H-core main sequence stars, but helium core stars and the outcomes of binary evolution. We report the discovery of two new extremely-low mass white dwarfs among the sdAs to support this statement.

ORBITAL SOLUTIONS FOR TWO YOUNG, LOW-MASS SPECTROSCOPIC BINARIES IN OPHIUCHUS

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

Rosero, V.; Prato, L.; Wasserman, L. H.

2011-01-15

We report the orbital parameters for ROXR1 14 and RX J1622.7-2325Nw, two young, low-mass, and double-lined spectroscopic binaries recently discovered in the Ophiuchus star-forming region. Accurate orbital solutions were determined from over a dozen high-resolution spectra taken with the Keck II and Gemini South telescopes. These objects are T Tauri stars with mass ratios close to unity and periods of {approx}5 and {approx}3 days, respectively. In particular, RX J1622.7-2325Nw shows a non-circularized orbit with an eccentricity of 0.30, higher than any other short-period pre-main-sequence (PMS) spectroscopic binary known to date. We speculate that the orbit of RX J1622.7-2325Nw has notmore » yet circularized because of the perturbing action of a {approx}1'' companion, itself a close visual pair. A comparison of known young spectroscopic binaries (SBs) and main-sequence (MS) SBs in the eccentricity-period plane shows an indistinguishable distribution of the two populations, implying that orbital circularization occurs in the first 1 Myr of a star's lifetime. With the results presented in this paper we increase by {approx}4% the small sample of PMS spectroscopic binary stars with known orbital elements.« less

Planets around pulsars - Implications for planetary formation

NASA Technical Reports Server (NTRS)

Bodenheimer, Peter

1993-01-01

Data on planets around pulsars are summarized, and different models intended to explain the formation mechanism are described. Both theoretical and observational evidence suggest that very special circumstances are required for the formation of planetary systems around pulsars, namely, the prior presence of a millisecond pulsar with a close binary companion, probably a low mass main-sequence star. It is concluded that the discovery of two planets around PSR 1257+12 is important for better understanding the problems of dynamics and stellar evolution. The process of planetary formation should be learned through intensive studies of the properties of disks near young objects and application of techniques for detection of planets around main-sequence solar-type stars.

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.

The dot{M}-M_* relation of pre-main-sequence stars: a consequence of X-ray driven disc evolution

NASA Astrophysics Data System (ADS)

Ercolano, B.; Mayr, D.; Owen, J. E.; Rosotti, G.; Manara, C. F.

2014-03-01

We analyse current measurements of accretion rates on to pre-main-sequence stars as a function of stellar mass, and conclude that the steep dependence of accretion rates on stellar mass is real and not driven by selection/detection threshold, as has been previously feared. These conclusions are reached by means of statistical tests including a survival analysis which can account for upper limits. The power-law slope of the dot{M}-M_* relation is found to be in the range of 1.6-1.9 for young stars with masses lower than 1 M⊙. The measured slopes and distributions can be easily reproduced by means of a simple disc model which includes viscous accretion and X-ray photoevaporation. We conclude that the dot{M}-M_* relation in pre-main-sequence stars bears the signature of disc dispersal by X-ray photoevaporation, suggesting that the relation is a straightforward consequence of disc physics rather than an imprint of initial conditions.

Variable stars around selected open clusters in the VVV area: Young Stellar Objects

NASA Astrophysics Data System (ADS)

Medina, Nicolas; Borissova, Jura; Bayo, Amelia; Kurtev, Radostin; Lucas, Philip

2017-09-01

Time-varying phenomena are one of the most substantial sources of astrophysical information, and led to many fundamental discoveries in modern astronomy. We have developed an automated tool to search and analyze variable sources in the near infrared Ks band, using the data from the Vista Variables in the Vía Láctea (VVV) ESO Public Survey ([5, 8]). One of our main goals is to investigate the Young Stellar Objects (YSOs) in the Galactic star forming regions, looking for: •Variability. •New pre-main sequence star clusters. Here we present the newly discovered YSOs within some selected stellar clusters in our Galaxy.

Young Children's Understandings of Length Measurement: Evaluating a Learning Trajectory

ERIC Educational Resources Information Center

Szilagyi, Janka; Clements, Douglas H.; Sarama, Julie

2013-01-01

This study investigated the development of length measurement ideas in students from prekindergarten through 2nd grade. The main purpose was to evaluate and elaborate the developmental progression, or levels of thinking, of a hypothesized learning trajectory for length measurement to ensure that the sequence of levels of thinking is consistent…

A Multi-Fiber Spectroscopic Search for Low-mass Young Stars in Orion OB1

NASA Astrophysics Data System (ADS)

Loerincs, Jacqueline; Briceno, Cesar; Calvet, Nuria; Mateo, Mario L.; Hernandez, Jesus

2017-01-01

We present here results of a low resolution spectroscopic followup of candidate low-mass pre-main sequence stars in the Orion OB1 association. Our targets were selected from the CIDA Variability Survey of Orion (CVSO), and we used the Michigan/Magellan Fiber Spectrograph (M2FS) on the Magellan Clay 6.5m telescope to obtain spectra of 500 candidate T Tauri stars distributed in seven 0.5 deg diameter fields, adding to a total area of ~5.5 deg2. We identify young stars by looking at the distinctive Hα 6563 Å emission and Lithium Li I 6707 Å absorption features characteristic of young low mass pre-main sequence stars. Furthermore, by measuring the strength of their Hα emission lines, confirmed T Tauri stars can be classified as either Classical T Tauris (CTTS) or Weak-line T Tauris (WTTS), which give indication of whether the star is actively accreting material from a gas and dust disk surrounding the star, which may be the precursor of a planetary system. We confirm a total of 90 T Tauri stars, of which 50% are newly identified young members of Orion; out of the 49 new detections,15 are accreting CTTS, and of these all but one are found in the OB1b sub-region. This result is in line with our previous findings that this region is much younger than the more extended Orion OB1a sub-association. The M2FS results add to our growing census of young stars in Orion, that is allowing us to characterize in a systematic and consistent way the distribution of stellar ages across the entire complex, in order to building a complete picture of star formation in this, one of nearest most active sites of star birth.

Circumstellar Material on and off the Main Sequence

NASA Astrophysics Data System (ADS)

Steele, Amy; Debes, John H.; Deming, Drake

2017-06-01

There is evidence of circumstellar material around main sequence, giant, and white dwarf stars that originates from the small-body population of planetary systems. These bodies tell us something about the chemistry and evolution of protoplanetary disks and the planetary systems they form. What happens to this material as its host star evolves off the main sequence, and how does that inform our understanding of the typical chemistry of rocky bodies in planetary systems? In this talk, I will discuss the composition(s) of circumstellar material on and off the main sequence to begin to answer the question, “Is Earth normal?” In particular, I look at three types of debris disks to understand the typical chemistry of planetary systems—young debris disks, debris disks around giant stars, and dust around white dwarfs. I will review the current understanding on how to infer dust composition for each class of disk, and present new work on constraining dust composition from infrared excesses around main sequence and giant stars. Finally, dusty and polluted white dwarfs hold a unique key to our understanding of the composition of rocky bodies around other stars. In particular, I will discuss WD1145+017, which has a transiting, disintegrating planetesimal. I will review what we know about this system through high speed photometry and spectroscopy and present new work on understanding the complex interplay of physics that creates white dwarf pollution from the disintegration of rocky bodies.

THE YOUNG OPEN CLUSTERS KING 12, NGC 7788, AND NGC 7790: PRE-MAIN-SEQUENCE STARS AND EXTENDED STELLAR HALOS

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

Davidge, T. J.

2012-12-20

The stellar contents of the open clusters King 12, NGC 7788, and NGC 7790 are investigated using MegaCam images. Comparisons with isochrones yield an age <20 Myr for King 12, 20-40 Myr for NGC 7788, and 60-80 Myr for NGC 7790 based on the properties of stars near the main-sequence turnoff (MSTO) in each cluster. The reddening of NGC 7788 is much larger than previously estimated. The luminosity functions (LFs) of King 12 and NGC 7788 show breaks that are attributed to the onset of pre-main-sequence (PMS) objects, and comparisons with models of PMS evolution yield ages that are consistentmore » with those measured from stars near the MSTO. In contrast, the r' LF of main-sequence stars in NGC 7790 is matched to r' = 20 by a model that is based on the solar neighborhood mass function. The structural properties of all three clusters are investigated by examining the two-point angular correlation function of blue main-sequence stars. King 12 and NGC 7788 are each surrounded by a stellar halo that extends out to a radius of 5 arcmin ({approx}3.4 pc). It is suggested that these halos form in response to large-scale mass ejection early in the evolution of the clusters, as predicted by models. In contrast, blue main-sequence stars in NGC 7790 are traced out to a radius of {approx}7.5 arcmin ({approx}5.5 pc), with no evidence of a halo. It is suggested that all three clusters may have originated in the same star-forming complex, but not in the same giant molecular cloud.« less

Pre-main-sequence isochrones - II. Revising star and planet formation time-scales

NASA Astrophysics Data System (ADS)

Bell, Cameron P. M.; Naylor, Tim; Mayne, N. J.; Jeffries, R. D.; Littlefair, S. P.

2013-09-01

We have derived ages for 13 young (<30 Myr) star-forming regions and find that they are up to a factor of 2 older than the ages typically adopted in the literature. This result has wide-ranging implications, including that circumstellar discs survive longer (≃ 10-12 Myr) and that the average Class I lifetime is greater (≃1 Myr) than currently believed. For each star-forming region, we derived two ages from colour-magnitude diagrams. First, we fitted models of the evolution between the zero-age main sequence and terminal-age main sequence to derive a homogeneous set of main-sequence ages, distances and reddenings with statistically meaningful uncertainties. Our second age for each star-forming region was derived by fitting pre-main-sequence stars to new semi-empirical model isochrones. For the first time (for a set of clusters younger than 50 Myr), we find broad agreement between these two ages, and since these are derived from two distinct mass regimes that rely on different aspects of stellar physics, it gives us confidence in the new age scale. This agreement is largely due to our adoption of empirical colour-Teff relations and bolometric corrections for pre-main-sequence stars cooler than 4000 K. The revised ages for the star-forming regions in our sample are: ˜2 Myr for NGC 6611 (Eagle Nebula; M 16), IC 5146 (Cocoon Nebula), NGC 6530 (Lagoon Nebula; M 8) and NGC 2244 (Rosette Nebula); ˜6 Myr for σ Ori, Cep OB3b and IC 348; ≃10 Myr for λ Ori (Collinder 69); ≃11 Myr for NGC 2169; ≃12 Myr for NGC 2362; ≃13 Myr for NGC 7160; ≃14 Myr for χ Per (NGC 884); and ≃20 Myr for NGC 1960 (M 36).

A Rapidly Moving Shell in the Orion Nebula

NASA Technical Reports Server (NTRS)

Walter, Donald K.; O'Dell, C. R.; Hu, Xihai; Dufour, Reginald J.

1995-01-01

A well-resolved elliptical shell in the inner Orion Nebula has been investigated by monochromatic imaging plus high- and low-resolution spectroscopy. We find that it is of low ionization and the two bright ends are moving at -39 and -49 km/s with respect to OMC-1. There is no central object, even in the infrared J bandpass although H2 emission indicates a possible association with the nearby very young pre-main-sequence star J&W 352, which is one of the youngest pre-main-sequence stars in the inner Orion Nebula. Many of the characteristics of this object (low ionization, blue shift) are like those of the Herbig-Haro objects, although the symmetric form would make it an unusual member of that class.

Analysis of fundamental parameters for V477 Lyr

NASA Astrophysics Data System (ADS)

Shimansky, V. V.; Pozdnyakova, S. A.; Borisov, N. V.; Bikmaev, I. F.; Galeev, A. I.; Sakhibullin, N. A.; Spiridonova, O. I.

2008-06-01

We analyze the photometric and spectroscopic observations of the young pre-cataclysmic variable (pre-CV) V477 Lyr. The masses of both binary components have been corrected by analyzing their radial velocity curves. We show that agreement between the theoretical and observed light curves of the object is possible for several sets of its physical parameters corresponding to the chosen temperature of the primary component. The final parameters of V477 Lyr have been established by comparing observational data with evolutionary tracks for planetary nebula nuclei. The derived effective temperature of the O subdwarf is higher than that estimated by analyzing the object’s ultraviolet spectra by more than 10000 K. This is in agreement with the analogous results obtained previously for the young pre-CVs V664 Cas and UU Sge. The secondary component of V477 Lyr has been proven to have a more than 25-fold luminosity excess compared to main-sequence stars of similar mass. Comparison of the physical parameters for the cool stars in young pre-CVs indicates that their luminosities do not correlate with the masses of the objects. The observed luminosity excesses in such stars show a close correlation with the post-common-envelope lifetime of the systems and should be investigated within the framework of the theory of their relaxation to the state of main-sequence stars.

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.

DIRECT N-BODY MODELING OF THE OLD OPEN CLUSTER NGC 188: A DETAILED COMPARISON OF THEORETICAL AND OBSERVED BINARY STAR AND BLUE STRAGGLER POPULATIONS

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

Geller, Aaron M.; Hurley, Jarrod R.; Mathieu, Robert D., E-mail: a-geller@northwestern.edu, E-mail: mathieu@astro.wisc.edu, E-mail: jhurley@astro.swin.edu.au

2013-01-01

Following on from a recently completed radial-velocity survey of the old (7 Gyr) open cluster NGC 188 in which we studied in detail the solar-type hard binaries and blue stragglers of the cluster, here we investigate the dynamical evolution of NGC 188 through a sophisticated N-body model. Importantly, we employ the observed binary properties of the young (180 Myr) open cluster M35, where possible, to guide our choices for parameters of the initial binary population. We apply pre-main-sequence tidal circularization and a substantial increase to the main-sequence tidal circularization rate, both of which are necessary to match the observed tidalmore » circularization periods in the literature, including that of NGC 188. At 7 Gyr the main-sequence solar-type hard-binary population in the model matches that of NGC 188 in both binary frequency and distributions of orbital parameters. This agreement between the model and observations is in a large part due to the similarities between the NGC 188 and M35 solar-type binaries. Indeed, among the 7 Gyr main-sequence binaries in the model, only those with P {approx}> 1000 days begin to show potentially observable evidence for modifications by dynamical encounters, even after 7 Gyr of evolution within the star cluster. This emphasizes the importance of defining accurate initial conditions for star cluster models, which we propose is best accomplished through comparisons with observations of young open clusters like M35. Furthermore, this finding suggests that observations of the present-day binaries in even old open clusters can provide valuable information on their primordial binary populations. However, despite the model's success at matching the observed solar-type main-sequence population, the model underproduces blue stragglers and produces an overabundance of long-period circular main-sequence-white-dwarf binaries as compared with the true cluster. We explore several potential solutions to the paucity of blue stragglers and conclude that the model dramatically underproduces blue stragglers through mass-transfer processes. We suggest that common-envelope evolution may have been incorrectly imposed on the progenitors of the spurious long-period circular main-sequence-white-dwarf binaries, which perhaps instead should have gone through stable mass transfer to create blue stragglers, thereby bringing both the number and binary frequency of the blue straggler population in the model into agreement with the true blue stragglers in NGC 188. Thus, improvements in the physics of mass transfer and common-envelope evolution employed in the model may in fact solve both discrepancies with the observations. This project highlights the unique accessibility of open clusters to both comprehensive observational surveys and full-scale N-body simulations, both of which have only recently matured sufficiently to enable such a project, and underscores the importance of open clusters to the study of star cluster dynamics.« less

The young SMC cluster NGC 330

NASA Technical Reports Server (NTRS)

Carney, B. W.; Janes, K. A.; Flower, P. J.

1985-01-01

A color-magnitude diagram has been obtained for the young SMC cluster NGC 330. The diagram shows a well-defined main sequence, a group of blue supergiants, a group of red supergiants between B-V = 1.2 m and 1.6 m about one magnitude fainter, and an empty Hertzsprung gap. The surrounding field is a composite of a very gold population resembling galactic globular clusters and a very young population. DDO and infrared photometry strongly suggest that the cluster is metal-poor, but a definitive measure could not be made because of calibration difficulties. The cluster's age is estimated at 12 million years, with the surrounding field about 50 percent older. The cluster will prove very useful in testing stellar evolution models for young, metal-poor stars if the cluster's metallicity can be established via high-resolution spectroscopy.

The embedded population around Herbig Ae/Be stars

NASA Astrophysics Data System (ADS)

Testi, L.; Stanga, R. M.; Natta, A.; Palla, F.; Prusti, T.; Baffa, C.; Hunt, L. K.; Lisi, F.

Herbig Ae/Be stars are intermediate mass young stars in the pre-main sequence phase of evolution. There are only few stars of this type known so far, and all of them seem to be relatively isolated, in contrast to their low mass counterparts, the T Tauri stars. A possible explanation of this fact is that other young stars formed near the known YSO are deeply embedded in the molecular cloud environment and are not detectable at optical wavelengths. We used the new ARcetri Near Infrared CAmera (ARNICA) to survey in the J, H and K bands the regions of sky around Herbig stars. The aim of this work is to identify embedded YSO and investigate the clustering properties of these young stars.

Accretion shocks in the laboratory: Design of an experiment to study star formation

DOE PAGES

Young, Rachel P.; Kuranz, C. C.; Drake, R. P.; ...

2017-02-13

Here, we present the design of a laboratory-astrophysics experiment to study magnetospheric accretion relevant to young, pre-main-sequence stars. Spectra of young stars show evidence of hotspots created when streams of accreting material impact the surface of the star and create shocks. The structures that form during this process are poorly understood, as the surfaces of young stars cannot be spatially resolved. Our experiment would create a scaled "accretion shock" at a major (several kJ) laser facility. The experiment drives a plasma jet (the "accretion stream") into a solid block (the "stellar surface"), in the presence of a parallel magnetic fieldmore » analogous to the star's local field.« less

WISE Detections of Dust in the Habitable Zones of Planet-Bearing Stars

NASA Technical Reports Server (NTRS)

Morales, Farisa Y.; Padgett, Deborah L.; Bryden, Geoffrey; Werner, M. W.; Furlan, E.

2012-01-01

We use data from the Wide-field Infrared Survey Explorer (WISE) all-sky release to explore the incidence of warm dust in the habitable zones around exoplanet-host stars. Dust emission at 12 and/or 22 microns (T(sub dust) approx.300 and/or approx.150 K) traces events in the terrestrial planet zones; its existence implies replenishment by evaporation of comets or collisions of asteroids, possibly stirred by larger planets. Of the 591 planetary systems (728 extrasolar planets) in the Exoplanet Encyclopedia as of 2012 January 31, 350 are robustly detected by WISE at > or = 5(sigma) level. We perform detailed photosphere subtraction using tools developed for Spitzer data and visually inspect all the WISE images to confirm bona fide point sources. We find nine planet-bearing stars show dust excess emission at 12 and/or 22 microns at > or = 3(sigma) level around young, main-sequence, or evolved giant stars. Overall, our results yield an excess incidence of approx.2.6% for stars of all evolutionary stages, but approx.1% for planetary debris disks around main-sequence stars. Besides recovering previously known warm systems, we identify one new excess candidate around the young star UScoCTIO 108.

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.

Hyperfast pulsars as the remnants of massive stars ejected from young star clusters

NASA Astrophysics Data System (ADS)

Gvaramadze, Vasilii V.; Gualandris, Alessia; Portegies Zwart, Simon

2008-04-01

Recent proper motion and parallax measurements for the pulsar PSR B1508+55 indicate a transverse velocity of ~1100kms-1, which exceeds earlier measurements for any neutron star. The spin-down characteristics of PSR B1508+55 are typical for a non-recycled pulsar, which implies that the velocity of the pulsar cannot have originated from the second supernova disruption of a massive binary system. The high velocity of PSR B1508+55 can be accounted for by assuming that it received a kick at birth or that the neutron star was accelerated after its formation in the supernova explosion. We propose an explanation for the origin of hyperfast neutron stars based on the hypothesis that they could be the remnants of a symmetric supernova explosion of a high-velocity massive star which attained its peculiar velocity (similar to that of the pulsar) in the course of a strong dynamical three- or four-body encounter in the core of dense young star cluster. To check this hypothesis, we investigated three dynamical processes involving close encounters between: (i) two hard massive binaries, (ii) a hard binary and an intermediate-mass black hole (IMBH) and (iii) a single stars and a hard binary IMBH. We find that main-sequence O-type stars cannot be ejected from young massive star clusters with peculiar velocities high enough to explain the origin of hyperfast neutron stars, but lower mass main-sequence stars or the stripped helium cores of massive stars could be accelerated to hypervelocities. Our explanation for the origin of hyperfast pulsars requires a very dense stellar environment of the order of 106- 107starspc-3. Although such high densities may exist during the core collapse of young massive star clusters, we caution that they have never been observed.

THE FORMATION AND EVOLUTION OF YOUNG LOW-MASS STARS WITHIN HALOS WITH HIGH CONCENTRATION OF DARK MATTER PARTICLES

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

Casanellas, Jordi; Lopes, IlIDio, E-mail: jordicasanellas@ist.utl.p, E-mail: ilidio.lopes@ist.utl.p

2009-11-01

The formation and evolution of low-mass stars within dense halos of dark matter (DM) leads to evolution scenarios quite different from the classical stellar evolution. As a result of our detailed numerical work, we describe these new scenarios for a range of DM densities on the host halo, for a range of scattering cross sections of the DM particles considered, and for stellar masses from 0.7 to 3 M {sub sun}. For the first time, we also computed the evolution of young low-mass stars in their Hayashi track in the pre-main-sequence phase and found that, for high DM densities, thesemore » stars stop their gravitational collapse before reaching the main sequence, in agreement with similar studies on first stars. Such stars remain indefinitely in an equilibrium state with lower effective temperatures (|DELTAT{sub eff}|>10{sup 3} K for a star of one solar mass), the annihilation of captured DM particles in their core being the only source of energy. In the case of lower DM densities, these protostars continue their collapse and progress through the main-sequence burning hydrogen at a lower rate. A star of 1 M{sub sun} will spend a time period greater than the current age of the universe consuming all the hydrogen in its core if it evolves in a halo with DM density rho{sub c}hi = 10{sup 9} GeV cm{sup -3}. We also show the strong dependence of the effective temperature and luminosity of these stars on the characteristics of the DM particles and how this can be used as an alternative method for DM research.« less

The Structure of the Young Star Cluster NGC 6231. I. Stellar Population

NASA Astrophysics Data System (ADS)

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

2017-09-01

NGC 6231 is a young cluster (age ˜2-7 Myr) dominating the Sco OB1 association (distance ˜1.59 kpc) with ˜100 O and B stars and a large pre-main-sequence stellar population. We combine a reanalysis of archival Chandra X-ray data with multiepoch near-infrared (NIR) photometry from the VISTA Variables in the Vía Lactéa (VVV) survey and published optical catalogs to obtain a catalog of 2148 probable cluster members. This catalog is 70% larger than previous censuses of probable cluster members in NGC 6231. It includes many low-mass stars detected in the NIR but not in the optical and some B stars without previously noted X-ray counterparts. In addition, we identify 295 NIR variables, about half of which are expected to be pre-main-sequence stars. With the more complete sample, we estimate a total population in the Chandra field of 5700-7500 cluster members down to 0.08 {M}⊙ (assuming a universal initial mass function) with a completeness limit at 0.5 {M}⊙ . A decrease in stellar X-ray luminosities is noted relative to other younger clusters. However, within the cluster, there is little variation in the distribution of X-ray luminosities for ages less than 5 Myr. The X-ray spectral hardness for B stars may be useful for distinguishing between early-B stars with X-rays generated in stellar winds and B-star systems with X-rays from a pre-main-sequence companion (>35% of B stars). A small fraction of catalog members have unusually high X-ray median energies or reddened NIR colors, which might be explained by absorption from thick or edge-on disks or being background field stars.

Intermediate to low-mass stellar content of Westerlund 1

NASA Astrophysics Data System (ADS)

Brandner, W.; Clark, J. S.; Stolte, A.; Waters, R.; Negueruela, I.; Goodwin, S. P.

2008-01-01

We have analysed near-infrared NTT/SofI observations of the starburst cluster Westerlund 1, which is among the most massive young clusters in the Milky Way. A comparison of colour-magnitude diagrams with theoretical main-sequence and pre-main sequence evolutionary tracks yields improved extinction and distance estimates of AKs = 1.13 ± 0.03 mag and d = 3.55 ± 0.17 kpc (DM = 12.75 ± 0.10 mag). The pre-main sequence population is best fit by a Palla & Stahler isochrone for an age of 3.2 Myr, while the main sequence population is in agreement with a cluster age of 3 to 5 Myr. An analysis of the structural parameters of the cluster yields that the half-mass radius of the cluster population increases towards lower mass, indicative of the presence of mass segregation. The cluster is clearly elongated with an eccentricity of 0.20 for stars with masses between 10 and 32 M_⊙, and 0.15 for stars with masses in the range 3 to 10 M_⊙. We derive the slope of the stellar mass function for stars with masses between 3.4 and 27 M_⊙. In an annulus with radii between 0.75 and 1.5 pc from the cluster centre, we obtain a slope of Γ = -1.3. Closer in, the mass function of Westerlund 1 is shallower with Γ = -0.6. The extrapolation of the mass function for stars with masses from 0.08 to 120 M_⊙ yields an initial total stellar mass of ≈52 000 M_⊙, and a present-day mass of 20 000 to 45 000 M_⊙ (about 10 times the stellar mass of the Orion nebula cluster, and 2 to 4 times the mass of the NGC 3603 young cluster), indicating that Westerlund 1 is the most massive starburst cluster identified to date in the Milky Way. Based on observations collected at the European Southern Observatory, La Silla, Chile, and retrieved from the ESO archive (Prog ID 67.C-0514).

Revising Star and Planet Formation Timescales

NASA Astrophysics Data System (ADS)

Bell, Cameron P. M.; Naylor, Tim; Mayne, N. J.; Jeffries, R. D.; Littlefair, S. P.

2013-07-01

We have derived ages for 13 young (<30 Myr) star-forming regions and find that they are up to a factor of 2 older than the ages typically adopted in the literature. This result has wide-ranging implications, including that circumstellar discs survive longer (≃ 10-12 Myr) and that the average Class I lifetime is greater (≃1 Myr) than currently believed. For each star-forming region, we derived two ages from colour-magnitude diagrams. First, we fitted models of the evolution between the zero-age main sequence and terminal-age main sequence to derive a homogeneous set of main-sequence ages, distances and reddenings with statistically meaningful uncertainties. Our second age for each star-forming region was derived by fitting pre-main-sequence stars to new semi-empirical model isochrones. For the first time (for a set of clusters younger than 50 Myr), we find broad agreement between these two ages, and since these are derived from two distinct mass regimes that rely on different aspects of stellar physics, it gives us confidence in the new age scale. This agreement is largely due to our adoption of empirical colour-Teff relations and bolometric corrections for pre-main-sequence stars cooler than 4000 K. The revised ages for the star-forming regions in our sample are: 2 Myr for NGC 6611 (Eagle Nebula; M 16), IC 5146 (Cocoon Nebula), NGC 6530 (Lagoon Nebula; M 8) and NGC 2244 (Rosette Nebula); 6 Myr for σ Ori, Cep OB3b and IC 348; ≃10 Myr for λ Ori (Collinder 69); ≃11 Myr for NGC 2169; ≃12 Myr for NGC 2362; ≃13 Myr for NGC 7160; ≃14 Myr for χ Per (NGC 884); and ≃20 Myr for NGC 1960 (M 36).

The Puzzling Nature OF THE YOUNG MICROQUASAR CIR X-1

NASA Astrophysics Data System (ADS)

Schulz, Norbert

2016-09-01

We propose to observe Cir X-1 for 60 ks within an orbital phase window of 0.96 - 1.04 within its 16.5 day orbit using the HETGS. Cir X-1 is in its more frequent quiescent/flaring state of the late 1970s with respect to its longterm light curve. The binary has recently been identified to be a very young HMXB system with a companion likely still in its pre-main sequence state. The persistent flux has now hit about 20 mCrab, significantly up from our 2008 HETG observation. In this observation we pursue our original goals to study emissions and absorption in accretion feedback plasmas. We specifically search for radiative recombination continua as a telltale for a young HAeBe companion star wind.

Hiding in plain sight

NASA Astrophysics Data System (ADS)

Riedel, Adric Richard

2012-05-01

Since the first successful measurements of stellar trigonometric parallax in the 1830s, the study of nearby stars has focused on the highest proper motion stars (micro > 0.18″ yr-1). Those high proper motion stars have formed the backbone of the last 150 years of study of the Solar Neighborhood and the composition of the Galaxy. Statistically speaking, though, there is a population of stars that will have low proper motions when their space motions have been projected onto the sky. At the same time, over the last twenty years, populations of relatively young stars (less than ˜ 100 Myr), most of them with low proper motions, have been revealed near (< 100 pc) the Sun. This dissertation is the result of two related projects: A photometric search for nearby (< 25pc) southern-hemisphere M dwarf stars with low proper motions (micro < 0.18″ yr-1), and a search for nearby (< 100 pc) pre-main-sequence (< 125 Myr old) M dwarf systems. The projects rely on a variety of photometric, spectroscopic, and astrometric analyses (including parallaxes from our program) using data from telescopes at CTIO via the SMARTS Consortium and at Lowell Observatory. Within this dissertation, I describe the identification and confirmation of 23 new nearby low proper motion M dwarf systems within 25 pc, 8 of which are within 15 pc (50% of the anticipated low-proper-motion 15 pc sample). I also report photometric, spectroscopic, and astrometric parameters and identifications for a selection of 25 known and new candidate nearby young M dwarfs, including new low-mass members of the TW Hydra, beta Pictoris, Tucana-Horologium, Argus, and AB Doradus associations, following the methods of my Riedel et al. (2011) paper and its discovery of AP Col, the closest pre-main-sequence star to the Solar System. These low proper motion and nearby star discoveries are put into the context of the Solar Neighborhood as a whole by means of the new RECONS 25 pc Database, to which I have now added (including my Riedel et al. (2010) paper) 81 star systems (4% of the total). INDEX WORDS: Astronomy, Astrometry, Photometry, Spectroscopy, Kinematics, Proper motion, Parallax, Nearby stars, Low-mass stars, Young stars, Pre-main-sequence stars.

Solar-Type Stars with the Suppression of Convection at an Early Stage of Evolution

NASA Astrophysics Data System (ADS)

Oreshina, A. V.; Baturin, V. A.; Ayukov, S. V.; Gorshkov, A. B.

2017-12-01

The evolution of a solar-mass star before and on the main sequence is analyzed in light of the diminished efficiency of convection in the first 500 Myr. A numerical simulation has been performed with the CESAM2k code. It is shown that the suppression of convection in the early stages of evolution leads to a somewhat higher lithium content than that predicted by the classical solar model. In addition, the star's effective temperature decreases. Ignoring this phenomenon may lead to errors in age and mass determinations for young stars (before the main sequence) from standard evolutionary tracks in the temperature-luminosity diagram. At a later stage of evolution, after 500 Myr, the efficiency of convection tends to the solar value. At this stage, the star's inner structure becomes classical; it does not depend on the previous history. On the contrary, the photospheric lithium abundance contains information about the star's past. In other words, there may exist main-sequence solar-mass stars of the same age (above 500 Myr), radius, and luminosity, yet with different photospheric lithium contents. The main results of this work add considerably to the popular method for determining the age of solar-type stars from lithium abundances.

A M2FS Spectroscopic Study of Low-mass Young Stars in Orion OB1

NASA Astrophysics Data System (ADS)

Kaleida, Catherine C.; Briceno, Cesar; Calvet, Nuria; Mateo, Mario L.; Hernandez, Jesus

2015-01-01

Surveys of pre-main sequence stars in the ~4-10 Myr range provide a window into the decline of the accretion phase of stars and the formation of planets. Nearby star clusters and stellar associations allow for the study of these young stellar populations all the way down to the lowest mass members. One of the best examples of nearby 4-10 Myr old stellar populations is the Orion OB1 association. The CIDA Variability Survey of Orion OB1 (CVSO - Briceño et al. 2001) has used the variability properties of low-mass pre-main-sequence (PMS) stars to identify hundreds of K and M-type stellar members of the Orion OB1 association, a number of them displaying IR-excess emission and thought to be representative of more evolved disk-bearing young stars. Characterizing these young, low-mass objects using spectroscopy is integral to understanding the accretion phase in young stars. We present preliminary results of a spectroscopic survey of candidate and confirmed Orion OB1 low-mass members taken during November 2014 and February 2014 using the Michigan/Magellan Fiber Spectrograph (M2FS), a PI instrument on the Magellan Clay Telescope (PI: M. Matteo). Target fields located in the off-cloud regions of Orion were identified in the CVSO, and observed using the low and high-resolution modes of M2FS. Both low and high-resolution spectra are needed in order to confirm membership and derive masses, ages, kinematics and accretion properties. Initial analysis of these spectra reveal many new K and M-type members of the Orion OB1 association in these low extinction, off-cloud areas. These are the more evolved siblings of the youngest stars still embedded in the molecular clouds, like those in the Orion Nebula Cluster. With membership and spectroscopic indicators of accretion we are building the most comprehensive stellar census of this association, enabling us to derive a robust estimate of the fraction of young stars still accreting at a various ages, a key constraint for the end of accretion and the formation of giant planets.

The Secrets of the Nearest Starburst Cluster. I. Very Large Telescope/ISAAC Photometry of NGC 3603

NASA Astrophysics Data System (ADS)

Stolte, Andrea; Brandner, Wolfgang; Brandl, Bernhard; Zinnecker, Hans; Grebel, Eva K.

2004-08-01

VLT/ISAAC JHKL photometry with subarcsecond resolution of the dense, massive starburst cluster NGC 3603 YC forming the core of the NGC 3603 giant molecular cloud is analyzed to reveal characteristics of the stellar population in unprecedented detail. The color-magnitude plane features a strong pre-main-sequence/main-sequence (PMS/MS) transition region, including the PMS/MS transition point, and reveals a secondary sequence for the first time in a nearby young starburst cluster. Arguments for a possible binary nature of this sequence are given. The resolved PMS/MS transition region allows isochrone fitting below the hydrogen-burning turn-on in NGC 3603 YC, yielding an independent estimate of global cluster parameters. A distance modulus of 13.9 mag, equivalent to d=6.0+/-0.3 kpc, is derived, as well as a line-of-sight extinction of AV=4.5+/-0.6 toward PMS stars in the cluster center. The interpretation of a binary candidate sequence suggests a single age of 1 Myr for NGC 3603 YC, providing evidence for a single burst of star formation without the need to employ an age spread in the PMS population, as argued for in earlier studies. Disk fractions are derived from L-band excesses, indicating a radial increase in the disk frequency from 20% to 40% from the core to the cluster outskirts. The low disk fraction in the cluster core, as compared to the 42% L-band excess fraction found for massive stars in the Trapezium cluster of a comparably young age, indicates strong photoevaporation in the cluster center. The estimated binary fraction of 30%, as well as the low disk fraction, suggest strong impacts on low-mass star formation due to stellar interactions in the dense starburst. The significant differences between NGC 3603 YC and less dense and massive young star clusters in the Milky Way reveal the importance of using local starbursts as templates for massive extragalactic star formation. Based on observations obtained at the ESO VLT on Paranal, Chile, under programs 63.I-0015 and 65.I-0135, and data from the public VLT archive provided by ESO, as well as observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS5-26555.

An intermediate luminosity optical transient (ILOTs) model for the young stellar object ASASSN-15qi

NASA Astrophysics Data System (ADS)

Kashi, Amit; Soker, Noam

2017-07-01

We construct a scenario where the outburst of the young stellar object ASASSN-15qi is an intermediate luminosity optical transient (ILOT). In this scenario, a sub-Jupiter young planet was tidally destructed on to a young main-sequence (MS) star. The system is young, and therefore the radius of the planet is larger than its final value; consequently, its density is smaller. The lower density allows the tidal destruction of the young Saturn-like planet on to the MS star of mass ≈2.4 M⊙, resulting in the formation of a disc and a gravitationally powered ILOT. Unlike the case of the more energetic ILOT V838 Mon, the mass of the destructed planet is too low to inflate a giant envelope, and hence the merger remnant remains hot. If our suggested model holds, this ILOT possesses two interesting properties: (I) its luminosity and total energy are below those of novae; (II) it is not as red as other ILOTs. The unusual outburst of ASASSN-15qi - if indeed is an ILOT - further increases the diversity of the already heterogeneous group of ILOTs. We mark the region on the energy-time diagram occupied by such young ILOTs.

The peculiar dipping events in the disc-bearing young-stellar object EPIC 204278916

NASA Astrophysics Data System (ADS)

Scaringi, S.; Manara, C. F.; Barenfeld, S. A.; Groot, P. J.; Isella, A.; Kenworthy, M. A.; Knigge, C.; Maccarone, T. J.; Ricci, L.; Ansdell, M.

2016-12-01

EPIC 204278916 has been serendipitously discovered from its K2 light curve that displays irregular dimmings of up to 65 per cent for ≈25 consecutive days out of 78.8 d of observations. For the remaining duration of the observations, the variability is highly periodic and attributed to stellar rotation. The star is a young, low-mass (M-type) pre-main-sequence star with clear evidence of a resolved tilted disc from Atacama Large Millimeter/submillimeter Array (ALMA) observations. We examine the K2 light curve in detail and hypothesize that the irregular dimmings are caused by either a warped inner disc edge or transiting cometary-like objects in either circular or eccentric orbits. The explanations discussed here are particularly relevant for other recently discovered young objects with similar absorption dips.

Profiles of Vocal Development in Young Cochlear Implant Recipients

PubMed Central

Ertmer, David J.; Young, Nancy M.; Nathani, Suneeti

2012-01-01

The aim of this study was to examine prelinguistic vocal development in very young cochlear implant recipients. A prospective longitudinal research design was used to observe the sequence and time-course of vocal development in seven children who were implanted between 10 and 36 months of age. Speech samples were collected twice before implant activation and on a monthly basis thereafter for up to 2 years. Children’s vocalizations were classified according to the levels of the Stark Assessment of Early Vocal Development- Revised (SAEVD-R; Nathani, Ertmer, & Stark, in press). The main findings were (a) six of seven children made advancements in vocal development after implantation, (b) children implanted between 12 and 36 months progressed through SAEVD-R levels in the predicted sequence whereas a child implanted at a younger age showed a different sequence, (c) milestones in vocal development were often achieved with fewer months of hearing experience than observed in typically developing infants and appeared to be influenced by age at implantation, and (d) in general, children implanted at younger ages completed vocal development at younger chronological ages than those implanted later in life. Clinical indicators of benefit from implant use were also identified. PMID:17463237

HII 2407: AN ECLIPSING BINARY REVEALED BY K2 OBSERVATIONS OF THE PLEIADES

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

David, Trevor J.; Hillenbrand, Lynne A.; Zhang, Celia

2015-11-20

The star HII 2407 is a member of the relatively young Pleiades star cluster and was previously discovered to be a single-lined spectroscopic binary. It is newly identified here within Kepler/K2 photometric time series data as an eclipsing binary system. Mutual fitting of the radial velocity and photometric data leads to an orbital solution and constraints on fundamental stellar parameters. While the primary has arrived on the main sequence, the secondary is still pre-main sequence and we compare our results for the M/M{sub ⊙} and R/R{sub ⊙} values with stellar evolutionary models. We also demonstrate that the system is likelymore » to be tidally synchronized. Follow-up infrared spectroscopy is likely to reveal the lines of the secondary, allowing for dynamically measured masses and elevating the system to benchmark eclipsing binary status.« less

Pre-main-sequence stars in the young cluster IC 2391

NASA Technical Reports Server (NTRS)

Stauffer, John; Hartmann, Lee W.; Jones, Burton F.; Mcnamara, Brian R.

1989-01-01

Seven or eight new, late-type members of the poor open cluster IC 2391 are identified, and membership is confirmed for two other stars. The new members fall approximately along a 3 x 10 to the 7th yr isochrone, which is the age estimated for the cluster on the basis of it super main-seqence turnoff. Echelle spectra were obtained for the most probable cluster members. Most show H-alpha in emission and a strong Li 6707 A absorption line, and a few are rapid rotators. The Li abundances for cluster stars cooler than the sun are considerably less than the primordial Li abundance, providing the first direct evidence for substantial premain-sequence Li burning. The rotational velocities show a range from about 15 to 150 km/s, with a distribution of rotational velocities not significantly different from that observed for low-mass stars in the Pleiades.

The Problem of Hipparcos Distances to Open Clusters. II. Constraints from Nearby Field Theory. Report 2; ClustersConstraints from nearly Field Stars

NASA Technical Reports Server (NTRS)

Soderblom, David R.; King, Jeremy R.; Hanson, Robert B.; Jones, Burton F.; Fischer, Debra; Stauffer, John R.; Pinsonneault, Marc H.

1998-01-01

This paper examines the discrepancy between distances to nearby open clusters as determined by parallaxes from Hipparcos compared to traditional main-sequence fitting. The biggest difference is seen for the Pleiades, and our hypothesis is that if the Hipparcos distance to the Pleiades is correct, then similar subluminous zero-age main-sequence (ZAMS) stars should exist elsewhere, including in the immediate solar neighborhood. We examine a color-magnitude diagram of very young and nearby solar-type stars and show that none of them lie below the traditional ZAMS, despite the fact that the Hipparcos Pleiades parallax would place its members 0.3 mag below that ZAMS. We also present analyses and observations of solar-type stars that do lie below the ZAMS, and we show that they are subluminous because of low metallicity and that they have the kinematics of old stars.

A possible brown dwarf companion to Gliese 569

NASA Technical Reports Server (NTRS)

Forrest, W. J.; Shure, Mark; Skrutskie, M. F.

1988-01-01

A faint cool companion to Gliese 569, discovered during an IR imaging survey of nearby stars, may be the lowest-mass stellar object yet found. The companion is somewhat cooler in its 1.65-3.75-micron energy distribution than the coolest known main-sequence stars, indicating a low mass. Despite its lower temperature, it is more luminous than similar extremely low-mass stars, suggesting that it is either a young low-mass star evolving toward the main sequence or a cooling substellar brown dwarf. The primary star has emission lines and a low space velocity and exhibits flaring, all of which imply youth for this system. Observations of Gliese 569 and its companion over a period of 2 yr confirm the common proper motion expected of a true binary. The 5-arcsec apparent separation (50 AU) implies an orbital period of roughly 500 yr, which will permit an eventual direct determination of the mass of the companion.

The Zodiacal Exoplanets in Time (ZEIT) Survey

NASA Astrophysics Data System (ADS)

Mann, Andrew; Gaidos, Eric; Newton, Elisabeth R.; Rizzuto, Aaron C.; Vanderburg, Andrew; Mace, Gregory N.; Kraus, Adam L.

2017-01-01

Planets and their host stars evolve with time, and the first few hundred million years are thought to be the most formative. However, the majority of known exoplanets orbit stars older than the timescales of interest (>1 Gyr). We have launched the Zodiacal Exoplanets in Time (ZEIT) survey with the goal of identifying and characterizing young (<1 Gyr) transiting planets. To this end, we have utilized high-precision photometry of nearby young clusters and stellar associations taken as part of the K2 mission. Thus far we have discovered transiting planets in the Hyades and Praesepe clusters (˜800 Myr), and the Upper Scorpius OB association (˜11 Myr), but interestingly none in the Pleiades (˜125 Myr). These discoveries can be used to set limits on the migration timescale, estimate atmosphere loss around young planets, and provide independent tests of pre-main sequence stellar models. Here I overview some key science results from our survey and briefly discuss our plans to identify more young planetary systems.

Reconnaissance of Young M Dwarfs: Locating the Elusive Majority of Nearby Moving Groups

NASA Astrophysics Data System (ADS)

Bowler, Brendan; Liu, Michael; Riaz, Basmah; Gizis, John; Shkolnik, Evgenya

2013-08-01

With ages between ~8-120 Myr and distances lsim;80 pc, young moving group members make excellent targets for detailed studies of pre-main sequence evolution and exoplanet imaging surveys. We propose a multi-semester spectroscopic program to confirm our sample of ~1300 X-ray-selected active M dwarfs, about one-third of which are expected to be members of young moving groups. Our program consists of three parts: a reconnaissance phase of low-resolution spectroscopy to vet unlikely association members, radial velocity observations to confirm group membership, and deep adaptive optics imaging to study the architecture and demographics of giant planets around low-mass stars. We will also exploit our rich sample to study the evolution of chromospheric and coronal activity in low-mass stars with unprecedented precision. Altogether, this program will roughly double the population of M dwarfs in young moving groups, providing new targets for a broad range of star and planet formation studies in the near-future.

UVBY beta photometry of the young southern cluster NGC3293 and comparison with other young clusters

NASA Astrophysics Data System (ADS)

Shobbrook, R. R.

1980-09-01

Stromgren uvby photometry has been obtained for 42 members and beta photometry for 37 members of the young southern galactic cluster NGC 3293. The distance modulus obtained from using Crawford's beta/M(V) calibration is 12.75 mag, corresponding to a distance of 3.55 kpc. Comparison of the colour/colour and the HR diagrams of NGC 3293 with those of the five other young northern and southern clusters reveals large differences between the clusters which may possibly be due to metal abundance variations across the Galaxy. Apparently correlated with this effect is a variation of the luminosities of the lower main sequences over about 1 mag. The fainter stars in the southern clusters appear to be an average of 0.7 mag brighter than those in the northern clusters, but it is not certain at present how much of this difference is due to possible systematic errors in the beta index zero point between the northern and southern hemispheres.

1961-2011: Fifty years of Hayashi tracks

NASA Astrophysics Data System (ADS)

Palla, Francesco

2012-09-01

Fifty years after the seminal paper by Prof. C. Hayashi, the field of pre-main sequence (PMS) evolution still plays a fundamental role in observational and theoretical astrophysics. In this contribution, I highlight the contribution made by Hayashi in establishing the theoretical foundation of early stellar evolution. Then, I discuss the changes of the classical theory introduced by the inclusion of protostellar evolution in PMS models and present selected results on young stars.

Open clusters in Auriga OB2

NASA Astrophysics Data System (ADS)

Marco, Amparo; Negueruela, Ignacio

2016-06-01

We study the area around the H II region Sh 2-234, including the young open cluster Stock 8, to investigate the extent and definition of the association Aur OB2 and the possible role of triggering in massive cluster formation. We obtained Strömgren and J, H, KS photometry for Stock 8 and Strömgren photometry for two other cluster candidates in the area, which we confirm as young open clusters and name Alicante 11 and Alicante 12. We took spectroscopy of ˜33 early-type stars in the area, including the brightest cluster members. We calculate a common distance of 2.80^{+0.27}_{-0.24} kpc for the three open clusters and surrounding association. We derive an age 4-6 Ma for Stock 8, and do not find a significantly different age for the other clusters or the association. The star LS V +34°23, with spectral type O8 II(f), is likely the main source of ionization of Sh 2-234. We observe an important population of pre-main-sequence stars, some of them with discs, associated with the B-type members lying on the main sequence. We interpret the region as an area of recent star formation with some residual and very localized ongoing star formation. We do not find evidence for sequential star formation on a large scale. The classical definition of Aur OB2 has to be reconsidered, because its two main open clusters, Stock 8 and NGC 1893, are not at the same distance. Stock 8 is probably located in the Perseus arm, but other nearby H II regions whose distances also place them in this arm show quite different distances and radial velocities and, therefore, are not connected.

CoRoT-2b: a Tidally Inflated, Young Exoplanet?

NASA Astrophysics Data System (ADS)

Guillot, Tristan; Havel, M.

2009-09-01

CoRoT-2b is among the most anomalously large transiting exoplanet known. Due to its large mass (3.3 Mjup), its large radius ( 1.5 Rjup) cannot be explained by standard evolution models. Recipes that work for other anomalously large exoplanets (e.g. HD209458b), such as invoking kinetic energy transport in the planetary interior or increased opacities, clearly fail for CoRoT-2b. Interestingly, the planet's parent star is an active star with a large fraction (7 to 20%) of spots and a rapid rotation (4.5 days). We first model the star's evolution to accurately constrain the planetary parameters. We find that the stellar activity has little influence on the star's evolution and inferred parameters. However, stellar evolution models point towards two kind of solutions for the star-planet system: (i) a very young system (20-40 Ma) with a star still undergoing pre-main sequence contraction, and a planet which could have a radius as low as 1.4 Rjup, or (ii) a young main-sequence star (40 to 500 Ma) with a planet that is slightly more inflated ( 1.5 Rjup). In either case, planetary evolution models require a significant added internal energy to explain the inferred planet size: from a minimum of 3x1028 erg/s in case (i), to up to 1.5x1029 erg/s in case (ii). We find that evolution models consistently including planet/star tides are able to reproduce the inferred radius but only for a short period of time ( 10 Ma). This points towards a young age for the star/planet system and dissipation by tides due to either circularization or synchronization of the planet. Additional observations of the star (infrared excess due to disk?) and of the planet (precise Rossiter effect, IR secondary eclispe) would be highly valuable to understand the early evolution of star-exoplanet systems.

Investigating ChaMPlane X-Ray Sources in the Galactic Bulge with Magellan LDSS2 Spectra

NASA Astrophysics Data System (ADS)

Koenig, Xavier; Grindlay, Jonathan E.; van den Berg, Maureen; Laycock, Silas; Zhao, Ping; Hong, JaeSub; Schlegel, Eric M.

2008-09-01

We have carried out optical and X-ray spectral analyses on a sample of 136 candidate optical counterparts of X-ray sources found in five Galactic bulge fields included in our Chandra Multiwavelength Plane Survey. We use a combination of optical spectral fitting and quantile X-ray analysis to obtain the hydrogen column density toward each object, and a three-dimensional dust model of the Galaxy to estimate the most probable distance in each case. We present the discovery of a population of stellar coronal emission sources, likely consisting of pre-main-sequence, young main-sequence, and main-sequence stars, as well as a component of active binaries of RS CVn or BY Dra type. We identify one candidate quiescent low-mass X-ray binary with a subgiant companion; we note that this object may also be an RS CVn system. We report the discovery of three new X-ray-detected cataclysmic variables (CVs) in the direction of the Galactic center (at distances lesssim2 kpc). This number is in excess of predictions made with a simple CV model based on a local CV space density of lesssim10-5 pc-3, and a scale height ~200 pc. We discuss several possible reasons for this observed excess.

No Evidence for Protoplanetary Disk Destruction By OB Stars in the MYStIX Sample

NASA Astrophysics Data System (ADS)

Richert, Alexander J. W.; Feigelson, Eric D.; Getman, Konstantin V.; Kuhn, Michael A.

2015-09-01

Hubble Space Telescope images of proplyds in the Orion Nebula, as well as submillimeter/radio measurements, show that the dominant O7 star {θ }1Ori C photoevaporates nearby disks around pre-main-sequence stars. Theory predicts that massive stars photoevaporate disks within distances of the order of 0.1 pc. These findings suggest that young, OB-dominated massive H ii regions are inhospitable to the survival of protoplanetary disks and, subsequently, to the formation and evolution of planets. In the current work, we test this hypothesis using large samples of pre-main-sequence stars in 20 massive star-forming regions selected with X-ray and infrared photometry in the MYStIX survey. Complete disk destruction would lead to a deficit of cluster members with an excess in JHKS and Spitzer/IRAC bands in the vicinity of O stars. In four MYStIX regions containing O stars and a sufficient surface density of disk-bearing sources to reliably test for spatial avoidance, we find no evidence for the depletion of inner disks around pre-main-sequence stars in the vicinity of O-type stars, even very luminous O2-O5 stars. These results suggest that massive star-forming regions are not very hostile to the survival of protoplanetary disks and, presumably, to the formation of planets.

The Exoplant Migration Timescale from K2 Young Clusters

NASA Astrophysics Data System (ADS)

Rizzuto, Aaron C.; Mann, Andrew; Kraus, Adam L.; Ireland, Michael

2017-01-01

Planetary Migration models for close-in exoplanets(a < 0.1 AU, P < 20 days) can be loosely divided into three categories: Disk-driven migration, binary-star planet interaction, and planet-planet interaction. Disk migration, occurs over the lifetime of the protoplanetary disk (<5 Myr), while migration involving dynamical multi-body interactions operate on timescales of ~100’s of Myr to ~1Gyr, a lengthier process than disk migration. It is unclear which of these is the dominating mechanism.The K2 mission has measured planet formation timescales and migration pathways by sampling groups of stars at key pre-main-sequence ages: Over the past 10 campaigns, multiple groups of young stars have been observed by K2, ranging from the 10 Myr Upper Scorpius OB association, through the ˜120 Myr Pleiades, the ˜600-800 Myr Hyades and Praesepe moving groups, to the original Kepler Field. The frequency, orbital and compositional properties of the exoplanet population in these samples of different age, with careful treatment of detection completeness, will be sufficient to address the question of exoplanet migration as their host stars are settling onto the main sequence.We will present the initial results of a program to directly address the question of planet migration with a uniform injection-recovery tests on a new K2 detrending pipeline that is optimized for the particular case of young, rotationally variable stars in K2 to robustly measure the detectability of planets of differing size and orbit. Initial results point towards a migration timescale of 200-700 Myr, which is consistent with the slower planet-planet scattering or Kozai migration models.

The Optical/Near-infrared Extinction Law in Highly Reddened Regions

NASA Astrophysics Data System (ADS)

Hosek, Matthew W., Jr.; Lu, Jessica R.; Anderson, Jay; Do, Tuan; Schlafly, Edward F.; Ghez, Andrea M.; Clarkson, William I.; Morris, Mark R.; Albers, Saundra M.

2018-03-01

A precise extinction law is a critical input when interpreting observations of highly reddened sources such as young star clusters and the Galactic Center (GC). We use Hubble Space Telescope observations of a region of moderate extinction and a region of high extinction to measure the optical and near-infrared extinction law (0.8–2.2 μm). The moderate-extinction region is the young massive cluster Westerlund 1 (Wd1; A Ks ∼ 0.6 mag), where 453 proper-motion selected main-sequence stars are used to measure the shape of the extinction law. To quantify the shape, we define the parameter {{ \\mathcal S }}1/λ , which behaves similarly to a color-excess ratio, but is continuous as a function of wavelength. The high-extinction region is the GC (A Ks ∼ 2.5 mag), where 819 red clump stars are used to determine the normalization of the law. The best-fit extinction law is able to reproduce the Wd1 main-sequence colors, which previous laws misestimate by 10%–30%. The law is inconsistent with a single power law, even when only the near-infrared filters are considered, and has A F125W/A Ks and A F814W/A Ks values that are 18% and 24% higher than the commonly used Nishiyama et al. law, respectively. Using this law, we recalculate the Wd1 distance to be 3905 ± 422 pc from published observations of the eclipsing binary W13. This new extinction law should be used for highly reddened populations in the Milky Way, such as the Quintuplet cluster and Young Nuclear Cluster. A python code is provided to generate the law for future use.

Understanding young stars - A history

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

Stahler, S.W.

1988-12-01

The history of pre-main-sequence theory is briefly reviewed. The paper of Henyey et al. (1955) is seen as an important transitional work, one which abandoned previous simplifying assumptions yet failed to incorporate newer insights into the surface structure of late-type stars. The subsequent work of Hayashi and his contemporaries is outlined, with an emphasis on the underlying physical principles. Finally, the recent impact of protostar theory is discussed, and speculations are offered on future developments. 56 references.

Deciphering the X-ray Emission of the Nearest Herbig Ae Star

NASA Technical Reports Server (NTRS)

Skinner, Stephen L.

2004-01-01

In this research program, we obtained and analyzed an X-ray observation of the young nearby intermediate mass pre-main sequence star HD 104237 using the XMM-Newton space-based observatory. The observation was obtained on 17 Feb. 2002. This observation yielded high-quality X-ray images, spectra, and timing data which provided valuable information on the physical processes responsible for the X-ray emission. This star is a member of the group of so-called Herbig Ae/Be stars, which are young intermediate mass (approx. 2 - 4 solar masses) pre-main sequence (PMS) stars a few million years old that have not yet begun core hydrogen burning. The objective of the XMM-Newton observation was to obtain higher quality data than previously available in order to constrain possible X-ray emission mechanisms. The origin of the X-ray emission from Herbig Ae/Be stars is not yet known. These intermediate mass PMS stars lie on radiative tracks and are not expected to emit X-rays via solar-like magnetic processes, nor are their winds powerful enough to produce X-rays by radiative wind shocks as in more massive O-type stars. The emission could originate in unseen low-mass companions, or it may be intrinsic to the Herbig stars themselves if they still have primordial magnetic fields or can sustain magnetic activity via a nonsolar dynamo.

The Potential Impact of Directionality, Colour Perceptions and Cultural Associations on Disaster Messages During Heatwaves in the UK

PubMed Central

Tang, Chris; Rundblad, Gabriella

2015-01-01

The health risks posed by heatwaves have been well documented. In the UK, before and during a heatwave, alerts are issued to the general public based on a tiered warning system integrating the use of colour and number sequences. There has of yet been no formal assessment of the public response to these messages. Cultural and language barriers make some members of ethnic minority communities particularly hard to reach. These may be less challenging amongst younger community members, who may be well placed to instigate the circulation of warning information to those less able or willing to use conventional channels. This qualitative study assesses the role of age and ethnic and cultural background in the conceptualisation of the number and colour systems used as part of the Heat-Health Watch System (HHWS) and the National Severe Weather Warning Service (NSWWS). Young and older participants were recruited from the Bangladeshi and white British populations of Tower Hamlets. All participants were given a cognitive task that required them to identify and draw associations between 12 cards depicting the four colours and numbers used in the warning system and four pictures providing contextualisation in terms of heatwave risk. A qualitative analysis of the heuristics used in the group discussions provided insights into the conceptualisations basic to interpreting colour and number sequences as representations of risk graduations, and how interpretation might be influenced by age and ethnic and cultural background. There were considerable differences in the interpretation of young Bangladeshi and older white British participants, on the one hand, and older Bangladeshi participants, on the other. Young Bangladeshis and older white British participants conceptualised the colours and numbers as a vertical scale, with the numbers/colours at “the top” corresponding to representations of higher temperature. This conceptualisation was mainly based on strong associations between colour and temperature, with risk only associated with the upper limit of the scale. Older Bangladeshi participants, on the other hand, conceptualised the numbers and pictures as a narrative sequence and disassociated the colours from the other cards. The differences between groups suggest potential cultural barriers to the “intended” interpretation of the colour and number sequences for older Bangladeshis but not for young Bangladeshis. The fact that the predominant association for the colour sequence for both young Bangladeshis and older white British participants was with graduations of temperature rather than risk raises questions about the applicability of using colours in a tiered warning system. PMID:25932346

Trichomonas gallinae: Prevalence and molecular characterization from pigeons in Minoufiya governorate, Egypt.

PubMed

El-Khatam, Ahmed O; AbouLaila, Mahmoud R; Ibrahim, Mahmoud; AbdEl-Gaber, Mostafa M

2016-11-01

Trichomonas gallinae infects the upper digestive tract of pigeons. It is transmitted from mother to young squabs by feeding crop milk. Generally, infection resulted in severe mortalities in young birds. In this study, we examined 3315 pigeons of different ages from the Minoufiya governorate for the clinical infection by T. gallinae. The infection was confirmed in infected birds by microscopical examination of oral swabs, histopathological examination, and PCR of the ITS1/5.8S/ITS2 gene. The prevalence was 63 (1.9%). The parasite was found in 35 (2.04%) from Ashmoun, 15 (1.66%) from Minoof, 8 (1.6%) from Quesna, and 5 (2.5%) from El-Shohada birds. The infection was mainly detected in squabs 60 (1.8%). The sequence of T. gallinae ITS1/5.8S/ITS2 gene from Egypt has high nucleotide sequence identity (up to100%) to T. gallinae from pigeon of USA, Austria, Canada, and Spain. The sequence belongs to genotype B of T. gallinae. Histopathological examination presented the parasites in crop, liver, larynx, and trachea as poorly eosinophilic bodies with severe inflammatory cell infiltration. This is the first study to present the prevalence and genotype of T. gallinae from Minoufiya governorate, Egypt. Copyright © 2016 Elsevier Inc. All rights reserved.

Three years of ULTRASPEC at the Thai 2.4-m telescope: Capabilities and scientific highlights

NASA Astrophysics Data System (ADS)

Yadav, Ram Kesh; Richichi, Andrea; Irawati, Puji; Dhillon, Vikram Singh; Marsh, Thomas R.; Soonthornthum, Boonrucksar

2018-04-01

High temporal resolution observations enable the study of rapid phenomena such as the flux variations in binary system objects, e.g. cataclysmic variables, compact binary systems, the flux variations in young star clusters, stellar occultations and more. The 2.4-m Thai National Telescope (TNT) is ideally suited for this niche research, being the largest facility in Southeast Asia and being equipped with ULTRASPEC, a high-speed imager based on a low-noise frame transfer electron-multiplying CCD. In the sub-window mode, ULTRASPEC can record uninterrupted sequences with frame rates as fast as few milliseconds. We present some of the key results obtained in the area of high time resolution with ULTRASPEC. We also present the results of a recent worldwide campaign to observe the current series of lunar occultations of Aldebaran (α Tauri) carried out in close collaboration with the Devasthal facilities, the out-of-eclipse variations on the post common-envelope system J1021+1744, and pre-main-sequence variables in young open cluster Stock 8.

Multiple stellar populations in Magellanic Cloud clusters - VI. A survey of multiple sequences and Be stars in young clusters

NASA Astrophysics Data System (ADS)

Milone, A. P.; Marino, A. F.; Di Criscienzo, M.; D'Antona, F.; Bedin, L. R.; Da Costa, G.; Piotto, G.; Tailo, M.; Dotter, A.; Angeloni, R.; Anderson, J.; Jerjen, H.; Li, C.; Dupree, A.; Granata, V.; Lagioia, E. P.; Mackey, A. D.; Nardiello, D.; Vesperini, E.

2018-06-01

The split main sequences (MSs) and extended MS turnoffs (eMSTOs) detected in a few young clusters have demonstrated that these stellar systems host multiple populations differing in a number of properties such as rotation and, possibly, age. We analyse Hubble Space Telescope photometry for 13 clusters with ages between ˜40 and ˜1000 Myr and of different masses. Our goal is to investigate for the first time the occurrence of multiple populations in a large sample of young clusters. We find that all the clusters exhibit the eMSTO phenomenon and that MS stars more massive than ˜1.6 M_{⊙} define a blue and a red MS, with the latter hosting the majority of MS stars. The comparison between the observations and isochrones suggests that the blue MSs are made of slow-rotating stars, while the red MSs host stars with rotational velocities close to the breakup value. About half of the bright MS stars in the youngest clusters are H α emitters. These Be stars populate the red MS and the reddest part of the eMSTO, thus supporting the idea that the red MS is made of fast rotators. We conclude that the split MS and the eMSTO are a common feature of young clusters in both Magellanic Clouds. The phenomena of a split MS and an eMSTO occur for stars that are more massive than a specific threshold, which is independent of the host-cluster mass. As a by-product, we report the serendipitous discovery of a young Small Magellanic Cloud cluster, GALFOR 1.

Insufficient Chunk Concatenation May Underlie Changes in Sleep-Dependent Consolidation of Motor Sequence Learning in Older Adults

ERIC Educational Resources Information Center

Bottary, Ryan; Sonni, Akshata; Wright, David; Spencer, Rebecca M. C.

2016-01-01

Sleep enhances motor sequence learning (MSL) in young adults by concatenating subsequences ("chunks") formed during skill acquisition. To examine whether this process is reduced in aging, we assessed performance changes on the MSL task following overnight sleep or daytime wake in healthy young and older adults. Young adult performance…

Observational diagnostics of accretion on young stars and brown dwarfs

NASA Astrophysics Data System (ADS)

Stelzer, Beate; Argiroffi, Costanza

I present a summary of recent observational constraints on the accretion properties of young stars and brown dwarfs with focus on the high-energy emission. In their T Tauri phase young stars assemble a few percent of their mass by accretion from a disk. Various observational signatures of disks around pre-main sequence stars and the ensuing accretion process are found in the IR and optical regime: e.g. excess emission above the stellar photosphere, strong and broad emission lines, optical veiling. At high energies evidence for accretion is less obvious, and the X-ray emission from stars has historically been ascribed to magnetically confined coronal plasmas. While being true for the bulk of the emission, new insight obtained from XMM-Newton and Chandra observations has unveiled contributions from accretion and outflow processes to the X-ray emission from young stars. Their smaller siblings, the brown dwarfs, have been shown to undergo a T Tauri phase on the basis of optical/IR observations of disks and measurements of accretion rates. Most re-cently, first evidence was found for X-rays produced by accretion in a young brown dwarf, complementing the suspected analogy between stars and substellar objects.

Hot H2O Emission and Evidence for Turbulence in the Disk of a Young Star

DTIC Science & Technology

2004-03-01

matter — infrared: stars — planetary systems: protoplanetary disks — stars: formation — stars: pre–main-sequence 1. INTRODUCTION The presence of hot...in disk gaps . Molecules other than CO are expected to exist at the temperatures and densities in the inner few AU of disks . Water should be very... protoplanetary disks . In addition, non-Gaussian line profiles might be ex- pected, given that a characteristic of turbulence seen in both laboratory experiments

Phylogenetic analysis of VP2 gene of canine parvovirus and comparison with Indian and world isolates.

PubMed

Kaur, G; Chandra, M; Dwivedi, P N

2016-03-01

Canine parvovirus (CPV) causes hemorrhagic enteritis, especially in young dogs, leading to high morbidity and mortality. It has four main antigenic types CPV-2, CPV-2a, CPV-2b and CPV-2c. Virus protein 2 (VP2) is the main capsid protein and mutations affecting VP2 gene are responsible for the evolution of various antigenic types of CPV. Full length VP2 gene from field isolates was amplified and cloned for sequence analysis. The sequences were submitted to the GenBank and were assigned Acc. Nos., viz. KP406928.1 for P12, KP406927.1 for P15, KP406930.1 for P32, KP406926.1 for Megavac-6 and KP406929.1 for NobivacDHPPi. Phylogenetic analysis indicated that the samples were forming a separate clad with vaccine strains. When the samples were compared with the world and Indian isolates, it was observed that samples formed a separate node indicating regional genetic variation in CPV.

The Origin Of Cosmic Rays And The Stars Of Berkeley 87

NASA Astrophysics Data System (ADS)

Turner, David G.; Majaess, D. J.; Lane, D. J.; Balam, D. D.

2010-01-01

Spectroscopic observations and the results of photometric monitoring are presented for members of the heavily-reddened, young, 1.2 kpc-distant, open cluster Berkeley 87, which is spatially coincident with the strongest source of cosmic rays in the northern sky. Many cluster members exhibit evidence for extreme loss of mass over their lifetimes: the M3 Ia supergiant BC Cyg has an evolutionary mass half that of stars at the main-sequence turnoff, the B2 Iabe emission-line supergiant HDE 229059 also has an evolutionary mass smaller than that of the main-sequence turnoff, the WO2 star WR 142, the only example of an oxygen sequence Wolf-Rayet star in an open cluster, displays evidence for variable, high velocity winds in its spectrum, the curious object V439 Cyg (B0: Vnne) appears to be an example of a recent binary merger, and Vatican Emission Star VES 203 (B0.5 Ve) displays a strong P Cygni signature in its Balmer line emission. It appears that heavy mass loss is a common factor associated with cluster stars. Could that be associated with the location of a cosmic ray production factory from the vicinity of Berkeley 87?

Functional requirements driving the gene duplication in 12 Drosophila species.

PubMed

Zhong, Yan; Jia, Yanxiao; Gao, Yang; Tian, Dacheng; Yang, Sihai; Zhang, Xiaohui

2013-08-15

Gene duplication supplies the raw materials for novel gene functions and many gene families arisen from duplication experience adaptive evolution. Most studies of young duplicates have focused on mammals, especially humans, whereas reports describing their genome-wide evolutionary patterns across the closely related Drosophila species are rare. The sequenced 12 Drosophila genomes provide the opportunity to address this issue. In our study, 3,647 young duplicate gene families were identified across the 12 Drosophila species and three types of expansions, species-specific, lineage-specific and complex expansions, were detected in these gene families. Our data showed that the species-specific young duplicate genes predominated (86.6%) over the other two types. Interestingly, many independent species-specific expansions in the same gene family have been observed in many species, even including 11 or 12 Drosophila species. Our data also showed that the functional bias observed in these young duplicate genes was mainly related to responses to environmental stimuli and biotic stresses. This study reveals the evolutionary patterns of young duplicates across 12 Drosophila species on a genomic scale. Our results suggest that convergent evolution acts on young duplicate genes after the species differentiation and adaptive evolution may play an important role in duplicate genes for adaption to ecological factors and environmental changes in Drosophila.

Angular Momentum Evolution in Young Low Mass Stars

NASA Astrophysics Data System (ADS)

Pinzón, G.; de La Reza, R.

2006-06-01

During the last decades, the study of rotation in young low mass stars has been one of the more active areas in the field of stellar evolution. Many theoretical efforts have been made to understand the angular momentum evolution and our picture now, reveals the main role of the stellar magnetic field in all pre-main sequence stage (Ghosh & Lamb 1979, ApJ, 234, 296; Cameron & Campbell 1993, A&A, 274, 309; Cameron & Campbell 1995, A&A, 298, 133; Kúker, Henning, & Rúdiger 2003, ApJ, 589, 397; Matt & Pudritz 2005, MNRAS, 356, 167). The mean rotation of most of the cool low mass stars remains roughly constant during the T Tauri stage. This can be explained by the disc locking scenario. This paradigm suggest that star start out as CTTS with periods of 4-14 days, perhaps locked to their disc, and that this disc is eventually lost mainly by accretion. At the current time, it is not clear that this is true for all low mass stars. Some authors have questioned its validity for stars less massive than 0.5 solar masses. Although the reality may eventually turn out to be considerably more complex, a simple consideration of the effects of and limits on disc locking of young low mass stars seems necessary.We have investigated the exchange of angular momentum between a low mass star and an accretion disc during the Hayashi Track (Pinzón, Kúker, & de la Reza 2005, in preparation) and also along the first 100Myr of stellar evolution. The model incorporates changes in the star's moment of inertia, magnetic field strength (Elstner & Rúdiger 2000, A&A, 358, 612), angular momentum loss by a magnetic wind and an exponential decrease of the accretion rate. The lifetime of the accretion disc is a free parameter in our model. The resulting rotation rates are in agreement with observed vsin and photometric periods for young stars belonging to co-moving groups and open young clusters.

ATLASGAL - towards a complete sample of massive star forming clumps

NASA Astrophysics Data System (ADS)

Urquhart, J. S.; Moore, T. J. T.; Csengeri, T.; Wyrowski, F.; Schuller, F.; Hoare, M. G.; Lumsden, S. L.; Mottram, J. C.; Thompson, M. A.; Menten, K. M.; Walmsley, C. M.; Bronfman, L.; Pfalzner, S.; König, C.; Wienen, M.

2014-09-01

By matching infrared-selected, massive young stellar objects (MYSOs) and compact H II regions in the Red MSX Source survey to massive clumps found in the submillimetre ATLASGAL (APEX Telescope Large Area Survey of the Galaxy) survey, we have identified ˜1000 embedded young massive stars between 280° < ℓ < 350° and 10° < ℓ < 60° with | b | < 1.5°. Combined with an existing sample of radio-selected methanol masers and compact H II regions, the result is a catalogue of ˜1700 massive stars embedded within ˜1300 clumps located across the inner Galaxy, containing three observationally distinct subsamples, methanol-maser, MYSO and H II-region associations, covering the most important tracers of massive star formation, thought to represent key stages of evolution. We find that massive star formation is strongly correlated with the regions of highest column density in spherical, centrally condensed clumps. We find no significant differences between the three samples in clump structure or the relative location of the embedded stars, which suggests that the structure of a clump is set before the onset of star formation, and changes little as the embedded object evolves towards the main sequence. There is a strong linear correlation between clump mass and bolometric luminosity, with the most massive stars forming in the most massive clumps. We find that the MYSO and H II-region subsamples are likely to cover a similar range of evolutionary stages and that the majority are near the end of their main accretion phase. We find few infrared-bright MYSOs associated with the most massive clumps, probably due to very short pre-main-sequence lifetimes in the most luminous sources.

Identification of a novel aviadenovirus, designated pigeon adenovirus 2 in domestic pigeons (Columba livia).

PubMed

Teske, L; Rubbenstroth, D; Meixner, M; Liere, K; Bartels, H; Rautenschlein, S

2017-01-02

The young pigeon disease syndrome (YPDS) affects mainly young pigeons of less than one year of age and leads to crop stasis, vomitus, diarrhea, anorexia and occasionally death. This disease is internationally a major health problem because of its seasonal appearance during competitions such as homing pigeon races or exhibitions of ornamental birds. While the etiology of YPDS is still unclear, adenoviruses are frequently discussed as potential causative agents. Electron microscopy of feces from a YPDS outbreak revealed massive shedding of adenovirus-like particles. Whole genome sequencing of this sample identified a novel adenovirus tentatively named pigeon adenovirus 2 (PiAdV-2). Phylogenetic and comparative genome analysis suggest PiAdV-2 to belong to a new species within the genus Aviadenovirus, for which we propose the name Pigeon aviadenovirus B. The PiAdV-2 genome shares 54.9% nucleotide sequence identity with pigeon adenovirus 1 (PiAdV-1). In a screening of further YPDS-affected flocks two variants of PiAdV-2 (variant A and B) were detected which shared 97.6% nucleotide identity of partial polymerase sequences, but only 79.7% nucleotide identity of partial hexon sequences. The distribution of both PiAdV-2 variants was further investigated in fecal samples collected between 2008 and 2015 from healthy or YPDS-affected racing pigeons of different lofts. Independent of their health status, approximately 20% of young and 13% of adult pigeon flocks harbored PiAdV-2 variants. Birds were free of PiAdV-1 or other aviadenoviruses as determined by PCRs targeting the aviadenovirus polymerase or the PiAdV-1 fiber gene, respectively. In conclusion, there is no indication of a correlation between YPDS outbreaks and the presence of PiAdV-2 or other aviadenoviruses, arguing against an causative role in this disease complex. Copyright © 2016 Elsevier B.V. All rights reserved.

51 Eridani and GJ 3305: A 10-15 Myr old Binary Star System at 30 Parsecs

NASA Astrophysics Data System (ADS)

Feigelson, E. D.; Lawson, W. A.; Stark, M.; Townsley, L.; Garmire, G. P.

2006-03-01

Following the suggestion of Zuckerman and coworkers, we consider the evidence that 51 Eri (spectral type F0) and GJ 3305 (M0), historically classified as unrelated main-sequence stars in the solar neighborhood, are instead a wide physical binary system and members of the young β Pic moving group (BPMG). The BPMG is the nearest (d<~50 pc) of several groups of young stars with ages around 10 Myr that are kinematically convergent with the Oph-Sco-Cen association (OSCA), the nearest OB star association. Combining South African Astronomical Observatory optical photometry, Hobby-Eberly Telescope high-resolution spectroscopy, Chandra X-Ray Observatory data, and Second US Naval Observatory CCD Astrograph Catalog kinematics, we confirm with high confidence that the system is indeed extremely young. GJ 3305 itself exhibits very strong magnetic activity but has rapidly depleted most of its lithium. The 51 Eri/GJ 3305 system is the westernmost known member of the OSCA, lying 110 pc from the main subgroups. The system is similar to the BPMG wide binary HD 172555/CD -64 1208 and the HD 104237 quintet, suggesting that dynamically fragile multiple systems can survive the turbulent environments of their natal giant molecular cloud complexes, while still having high dispersion velocities imparted. Nearby young systems such as these are excellent targets for evolved circumstellar disk and planetary studies, having stellar ages comparable to that of the late phases of planet formation.

A sequence analysis of patterns in self-harm in young people with and without experience of being looked after in care.

PubMed

Wadman, Ruth; Clarke, David; Sayal, Kapil; Armstrong, Marie; Harroe, Caroline; Majumder, Pallab; Vostanis, Panos; Townsend, Ellen

2017-11-01

Young people in the public care system ('looked-after' young people) have high levels of self-harm. This paper reports the first detailed study of factors leading to self-harm over time in looked-after young people in England, using sequence analyses of the Card Sort Task for Self-harm (CaTS). Young people in care (looked-after group: n = 24; 14-21 years) and young people who had never been in care (contrast group: n = 21; 13-21 years) completed the CaTS, describing sequences of factors leading to their first and most recent episodes of self-harm. Lag sequential analysis determined patterns of significant transitions between factors (thoughts, feelings, behaviours, events) leading to self-harm across 6 months. Young people in care reported feeling better immediately following their first episode of self-harm. However, fearlessness of death, impulsivity, and access to means were reported most proximal to recent self-harm. Although difficult negative emotions were salient to self-harm sequences in both groups, young people with no experience of being in care reported a greater range of negative emotions and transitions between them. For the contrast group, feelings of depression and sadness were a significant starting point of the self-harm sequence 6 months prior to most recent self-harm. Sequences of factors leading to self-harm can change and evolve over time, so regular monitoring and assessment of each self-harm episode are needed. Support around easing and dealing with emotional distress is required. Restricting access to means to carry out potentially fatal self-harm attempts, particularly for the young persons with experience of being in care, is recommended. Self-harm (and factors associated with self-harm) can change and evolve over time; assessments need to reflect this. Looked-after young people reported feeling better after first self-harm; fearlessness of death, access to means, and impulsivity were reported as key in recent self-harm. Underlying emotional distress, particularly depression and self-hatred were important in both first and most recent self-harm. Looked-after young people should undergo regular monitoring and assessment of each self-harm episode and access to potentially fatal means should be restricted. The CaTS would have clinical utility as an assessment tool Recruiting participants can be a significant challenge in studies with looked-after children and young people. Future research with larger clinical samples would be valuable. © 2017 The British Psychological Society.

Integrative clinical sequencing in the management of children and young adults with refractory or relapsed cancer

PubMed Central

Mody, Rajen J.; Wu, Yi-Mi; Lonigro, Robert J.; Cao, Xuhong; Roychowdhury, Sameek; Vats, Pankaj; Frank, Kevin M.; Prensner, John R.; Asangani, Irfan; Palanisamy, Nallasivam; Dillman, Jonathan R.; Rabah, Raja M.; Kunju, Laxmi Priya; Everett, Jessica; Raymond, Victoria M.; Ning, Yu; Su, Fengyun; Wang, Rui; Stoffel, Elena M.; Innis, Jeffrey W.; Roberts, J. Scott; Robertson, Patricia L.; Yanik, Gregory; Chamdin, Aghiad; Connelly, James A.; Choi, Sung; Harris, Andrew C.; Kitko, Carrie; Rao, Rama Jasty; Levine, John E.; Castle, Valerie P.; Hutchinson, Raymond J.; Talpaz, Moshe; Robinson, Dan R.; Chinnaiyan, Arul M.

2016-01-01

Importance Cancer is caused by a diverse array of somatic and germline genomic aberrations. Advances in genomic sequencing technologies have improved the ability to detect these molecular aberrations with greater sensitivity. However, integrating them into clinical management in an individualized manner has proven challenging. Objective To evaluate the use of integrative clinical sequencing and genetic counseling in the assessment and treatment of children and young adults with cancer. Design, Settings and Participants An observational, consecutive case series (May 2012–October 2014) of 102 children and young adults (mean age, 10.6; median age, 11.5, range: 0–22 years) with relapsed, refractory, or rare cancer at a single major academic medical center. Exposures Each participant underwent integrative clinical exome (tumor and germline DNA) and transcriptome (tumor RNA) sequencing along with genetic counseling. Results were discussed in a multi-disciplinary Precision Medicine Tumor Board (PMTB) and recommendations were reported to treating physicians and families. Main Outcomes and Measures Proportion of patients with potentially actionable findings (PAF), results of clinical actions based on integrative clinical sequencing (ICS), and estimated proportion of patients or their families at risk for future cancer. PAF was defined as any genomic findings discovered during sequencing analysis that could lead to a 1) change in patient management by providing a targetable molecular aberration, 2) change in diagnosis or risk stratification or 3) provides cancer-related germline findings, which inform patients/families about a potential future risk of various cancers; Results We screened 104 patients and enrolled 102 patients of which 91 (89%) had adequate tumor tissue available to complete sequencing and only these patients were included in all subsequent calculations, including 28 (31%) with hematological malignancies and 63 (69%) with solid tumors. Overall, 42 (46%) patients had PAFs which changed patient management including, 54% (15/28) with hematological malignancies and 43% (27/63) with solid tumors. Overall, individualized actions were taken in 23 of the 91 (25%) patients and families based on actionable ICS findings, including change in treatment in 14 (15%) and genetic counseling for future cancer risk in 9 (10%) patients. 9/91 (10%) of these personalized clinical interventions resulted in ongoing partial clinical remission of 8–16 months duration or help sustain complete clinical remission of 6–21 months duration. All 9 (10%) patients and families with actionable incidental genetic findings agreed to formal genetic counseling and screening. Conclusions and Relevance In this single center case series of children and young adults with relapsed or refractory cancer, incorporation of data from integrative clinical sequencing into clinical management was feasible, revealed potentially actionable findings in 46% of patients, and was associated with change in treatment and family genetic counseling in a small proportion of patients. The lack of a control group limited our ability to judge whether better clinical outcomes were achieved compared to standard care. PMID:26325560

Radio and infrared properties of young stars

NASA Technical Reports Server (NTRS)

Panagia, Nino

1987-01-01

Observing young stars, or more appropriately, pre-main-sequence (PMS) stars, in the infrared and at radio frequencies has the advantage over optical observation in that the heavy extinction associated with a star forming region is only a minor problem, so that the whole region can be studied thoroughly. Therefore, it means being able to: (1) search for stars and do statistical studies on the rate of star formation; (2) determine their luminosity, hence, to study luminosity functions and initial mass functions down to low masses; and (3) to study their spectra and, thus, to determine the prevailing conditions at and near the surface of a newly born star and its relations with the surrounding environment. The third point is of principal interest. The report limits itself to a consideration of the observations concerning the processes of outflows from, and accretion onto, PMS stars and the theory necessary to interpret them. Section 2 discusses the radiative processes relevant in stellar outflows. The main observational results are presented in Section 3. A discussion of the statistical properties of stellar winds from PMS stars are given in Section 4.

Detection of extrasolar planets by the large deployable reflector

NASA Technical Reports Server (NTRS)

Hollenbach, D. J.; Takahashi, T.

1984-01-01

The best wavelength for observing Jupiter-size planetary companions to stars other than the Sun is one at which a planet's thermal emission is strongest; typically this would occur in the far-infrared region. It is assumed that the orbiting infrared telescope used is diffraction-limited so that the resolution of the planet from the central star is accomplished in the wings of the star's Airy pattern. Proxima Centauri, Barnard's Star, Wolf 359, and Epsilon Eridani are just a few of the many nearest main-sequence stars that could be studied with the large deployable relfector (LDR). The detectability of a planet improves for warmer planets and less luminous stars; therefore, planets around white dwarfs and those young planets which have sufficient internal gravitational energy release so as to cause a significant increase in their temperatures are considered. If white dwarfs are as old as they are usually assumed to be (5-10 billion yr), then only the nearest white dwarf (Sirius B) is within the range of LDR. The Ursa Major cluster and Perseu cluster are within LDR's detection range mainly because of their proximity and young age, respectively.

An outbreak of food-borne gastroenteritis due to sapovirus among junior high school students.

PubMed

Usuku, Shuzo; Kumazaki, Makoto; Kitamura, Katsuhiko; Tochikubo, Osamu; Noguchi, Yuzo

2008-11-01

The human sapovirus (SaV) causes acute gastroenteritis mainly in infants and young children. A food-borne outbreak of gastroenteritis associated with SaV occurred among junior high school students in Yokohama, Japan, during and after a study trip. The nucleotide sequences of the partial capsid gene derived from the students exhibited 98% homology to a SaV genogroup IV strain, Hu/Angelholm/SW278/2004/SE, which was isolated from an adult with gastroenteritis in Solna, Sweden. An identical nucleotide sequence was detected from a food handler at the hotel restaurant, suggesting that the causative agent of the outbreak was transmitted from the food handler. This is the first description of a food-borne outbreak associated with the SaV genogroup IV strain in Japan.

High-Mass Stars in the Centers of Young Dense Clusters: Mass Segregation, Binary Mergers and Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

Zinnecker, H.

We start by discussing dense, young star-clusters, particularly the 30 Doradus cluster with its core R136. The question of mass segregation and core collapse of the massive stars is addressed. Analytical estimates of relaxation times and collision times predict that the central N=10 subsystem of massive stars in the R136 core will evolve dynamically in such a way and fast enough (i.e. within their main-sequence lifetime of a few Myr) that a dominant massive binary system is formed whose orbit will shrink to a point where merging of the components appears inevitable. The merger product will be spinning rapidly, and we put forward the idea that this rare and very massive object might be the perfect precursor of a gamma-ray burst (collapsar).

The Young Visual Binary Survey

NASA Astrophysics Data System (ADS)

Prato, Lisa; Avilez, Ian; Lindstrom, Kyle; Graham, Sean; Sullivan, Kendall; Biddle, Lauren; Skiff, Brian; Nofi, Larissa; Schaefer, Gail; Simon, Michal

2018-01-01

Differences in the stellar and circumstellar properties of the components of young binaries provide key information about star and disk formation and evolution processes. Because objects with separations of a few to a few hundred astronomical units share a common environment and composition, multiple systems allow us to control for some of the factors which play into star formation. We are completing analysis of a rich sample of about 100 pre-main sequence binaries and higher order multiples, primarily located in the Taurus and Ophiuchus star forming regions. This poster will highlight some of out recent, exciting results. All reduced spectra and the results of our analysis will be publicly available to the community at http://jumar.lowell.edu/BinaryStars/. Support for this research was provided in part by NSF award AST-1313399 and by NASA Keck KPDA funding.

Orbital Motion of Young Binaries in Ophiuchus and Upper Centaurus–Lupus

NASA Astrophysics Data System (ADS)

Schaefer, G. H.; Prato, L.; Simon, M.

2018-03-01

We present measurements of the orbital positions and flux ratios of 17 binary and triple systems in the Ophiuchus star-forming region and the Upper Centaurus–Lupus cluster based on adaptive optics imaging at the Keck Observatory. We report the detection of visual companions in MML 50 and MML 53 for the first time, as well as the possible detection of a third component in WSB 21. For six systems in our sample, our measurements provide a second orbital position following their initial discoveries over a decade ago. For eight systems with sufficient orbital coverage, we analyze the range of orbital solutions that fit the data. Ultimately, these observations will help provide the groundwork toward measuring precise masses for these pre-main-sequence stars and understanding the distribution of orbital parameters in young multiple systems.

A Pan-Carina Young Stellar Object Catalog: Intermediate-mass Young Stellar Objects in the Carina Nebula Identified Via Mid-infrared Excess Emission

NASA Astrophysics Data System (ADS)

Povich, Matthew S.; Smith, Nathan; Majewski, Steven R.; Getman, Konstantin V.; Townsley, Leisa K.; Babler, Brian L.; Broos, Patrick S.; Indebetouw, Rémy; Meade, Marilyn R.; Robitaille, Thomas P.; Stassun, Keivan G.; Whitney, Barbara A.; Yonekura, Yoshinori; Fukui, Yasuo

2011-05-01

We present a catalog of 1439 young stellar objects (YSOs) spanning the 1.42 deg2 field surveyed by the Chandra Carina Complex Project (CCCP), which includes the major ionizing clusters and the most active sites of ongoing star formation within the Great Nebula in Carina. Candidate YSOs were identified via infrared (IR) excess emission from dusty circumstellar disks and envelopes, using data from the Spitzer Space Telescope (the Vela-Carina survey) and the Two-Micron All Sky Survey. We model the 1-24 μm IR spectral energy distributions of the YSOs to constrain physical properties. Our Pan-Carina YSO Catalog (PCYC) is dominated by intermediate-mass (2 M sun < m <~ 10 M sun) objects with disks, including Herbig Ae/Be stars and their less evolved progenitors. The PCYC provides a valuable complementary data set to the CCCP X-ray source catalogs, identifying 1029 YSOs in Carina with no X-ray detection. We also catalog 410 YSOs with X-ray counterparts, including 62 candidate protostars. Candidate protostars with X-ray detections tend to be more evolved than those without. In most cases, X-ray emission apparently originating from intermediate-mass, disk-dominated YSOs is consistent with the presence of low-mass companions, but we also find that X-ray emission correlates with cooler stellar photospheres and higher disk masses. We suggest that intermediate-mass YSOs produce X-rays during their early pre-main-sequence evolution, perhaps driven by magnetic dynamo activity during the convective atmosphere phase, but this emission dies off as the stars approach the main sequence. Extrapolating over the stellar initial mass function scaled to the PCYC population, we predict a total population of >2 × 104 YSOs and a present-day star formation rate (SFR) of >0.008 M sun yr-1. The global SFR in the Carina Nebula, averaged over the past ~5 Myr, has been approximately constant.

Characterizing Intermediate-Mass, Pre-Main-Sequence Stars via X-Ray Emision

NASA Astrophysics Data System (ADS)

Haze Nunez, Evan; Povich, Matthew Samuel; Binder, Breanna Arlene; Broos, Patrick; Townsley, Leisa K.

2018-01-01

The X-ray emission from intermediate-mass, pre-main-sequence stars (IMPS) can provide useful constraints on the ages of very young (${<}5$~Myr) massive star forming regions. IMPS have masses between 2 and 8 $M_{\\odot}$ and are getting power from the gravitational contraction of the star. Main-sequence late-B and A-type stars are not expected to be strong X-ray emitters, because they lack the both strong winds of more massive stars and the magneto-coronal activity of lower-mass stars. There is, however, mounting evidence that IMPS are powerful intrinsic x-ray emitters during their convection-dominated early evolution, before the development and rapid growth of a radiation zone. We present our prime candidates for intrinsic, coronal X-ray emission from IMPS identified in the Chandra Carina Complex Project. The Carina massive star-forming complex is of special interest due to the wide variation of star formation stages within the region. Candidate IMPS were identified using infrared spectral energy distribution (SED) models. X-ray properties, including thermal plasma temperatures and absorption-corrected fluxes, were derived from XSPEC fits performed using absorption ($N_{H}$) constrained by the extinction values returned by the infrared SED fits. We find that IMPS have systematically higher X-ray luminosities compared to their lower-mass cousins, the TTauri stars.This work is supported by the National Science Foundation under grant CAREER-1454334 and by NASA through Chandra Award 18200040.

The detectability of radio emission from exoplanets

NASA Astrophysics Data System (ADS)

Lynch, C. R.; Murphy, Tara; Lenc, E.; Kaplan, D. L.

2018-05-01

Like the magnetised planets in our Solar System, magnetised exoplanets should emit strongly at radio wavelengths. Radio emission directly traces the planetary magnetic fields and radio detections can place constraints on the physical parameters of these features. Large comparative studies of predicted radio emission characteristics for the known population of exoplanets help to identify what physical parameters could be key for producing bright, observable radio emission. Since the last comparative study, many thousands of exoplanets have been discovered. We report new estimates for the radio flux densities and maximum emission frequencies for the current population of known exoplanets orbiting pre-main sequence and main-sequence stars with spectral types F-M. The set of exoplanets predicted to produce observable radio emission are Hot Jupiters orbiting young stars. The youth of these system predicts strong stellar magnetic fields and/or dense winds, which are key for producing bright, observable radio emission. We use a new all-sky circular polarisation Murchison Widefield Array survey to place sensitive limits on 200 MHz emission from exoplanets, with 3σ values ranging from 4.0 - 45.0 mJy. Using a targeted Giant Metre Wave Radio Telescope observing campaign, we also report a 3σ upper limit of 4.5 mJy on the radio emission from V830 Tau b, the first Hot Jupiter to be discovered orbiting a pre-main sequence star. Our limit is the first to be reported for the low-frequency radio emission from this source.

A young star takes centre stage

NASA Image and Video Library

2015-03-02

With its helical appearance resembling a snail’s shell, this reflection nebula seems to spiral out from a luminous central star in this new NASA/ESA Hubble Space Telescope image. The star in the centre, known as V1331 Cyg and located in the dark cloud LDN 981 — or, more commonly, Lynds 981 — had previously been defined as a T Tauri star. A T Tauri is a young star — or Young Stellar Object — that is starting to contract to become a main sequence star similar to the Sun. What makes V1331Cyg special is the fact that we look almost exactly at one of its poles. Usually, the view of a young star is obscured by the dust from the circumstellar disc and the envelope that surround it. However, with V1331Cyg we are actually looking in the exact direction of a jet driven by the star that is clearing the dust and giving us this magnificent view. This view provides an almost undisturbed view of the star and its immediate surroundings allowing astronomers to study it in greater detail and look for features that might suggest the formation of a verylow-mass object in the outer circumstellar disc.

Reconnaissance of Young M Dwarfs: Locating the Elusive Majority of Nearby Moving Groups

NASA Astrophysics Data System (ADS)

Bowler, Brendan; Liu, Michael; Riaz, Basmah; Gizis, John; Shkolnik, Evgenya

2014-02-01

With ages between ~8-120 Myr and distances ≲80 pc, young moving group members make excellent targets for detailed studies of pre-main sequence evolution and exoplanet imaging surveys. We propose to finish a low-resolution spectroscopic program started in 2013B to confirm our sample of ~1300 X-ray-selected active M dwarfs, about one-third of which are expected to be members of young moving groups. Our larger program consists of three parts: an initial reconnaissance phase of low-resolution spectroscopy to vet unlikely association members, radial velocity observations to confirm group membership, and deep adaptive optics imaging to study the architecture and demographics of giant planets around low-mass stars. Our observations in 2014A will finish the phase of low-resolution spectroscopy covering the second half of the sky. We will also exploit our rich sample to study the evolution of chromospheric and coronal activity in low-mass stars with unprecedented precision. Altogether, this program will roughly double the population of M dwarfs in young moving groups, providing new targets for a broad range of star and planet formation studies in the near-future.

Cannibals in the thick disk: the young α-rich stars as evolved blue stragglers

NASA Astrophysics Data System (ADS)

Jofré, P.; Jorissen, A.; Van Eck, S.; Izzard, R. G.; Masseron, T.; Hawkins, K.; Gilmore, G.; Paladini, C.; Escorza, A.; Blanco-Cuaresma, S.; Manick, R.

2016-10-01

Spectro-seismic measurements of red giants enabled the recent discovery of stars in the thick disk that are more massive than 1.4 M⊙. While it has been claimed that most of these stars are younger than the rest of the typical thick disk stars, we show evidence that they might be products of mass transfer in binary evolution, notably evolved blue stragglers. We took new measurements of the radial velocities in a sample of 26 stars from APOKASC, including 13 "young" stars and 13 "old" stars with similar stellar parameters but with masses below 1.2 M⊙ and found that more of the young starsappear to be in binary systems with respect to the old stars.Furthermore, we show that the young stars do not follow the expected trend of [C/H] ratios versus mass for individual stars. However, with a population synthesis of low-mass stars including binary evolution and mass transfer, we can reproduce the observed [C/N] ratios versus mass. Our study shows how asteroseismology of solar-type red giants provides us with a unique opportunity to study the evolution of field blue stragglers after they have left the main-sequence.

STELLAR BORON ABUNDANCES NEAR THE MAIN-SEQUENCE TURNOFF OF THE OPEN CLUSTER NGC 3293 AND IMPLICATIONS FOR THE EFFICIENCY OF ROTATIONALLY DRIVEN MIXING IN STELLAR ENVELOPES

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

Proffitt, Charles R.; Lennon, Daniel J.; Langer, Norbert

2016-06-10

Spectra from the Hubble Space Telescope Cosmic Origins Spectrograph and the Space Telescope Imaging Spectrograph covering the B iii resonance line have been obtained for 10 early-B stars near the turnoff of the young Galactic open cluster NGC 3293. This is the first sample of boron abundance determinations in a single, clearly defined population of early-B stars that also covers a substantial range of projected rotational velocities. In most of these stars we detect partial depletion of boron at a level consistent with that expected for rotational mixing in single stars, but inconsistent with expectations for depletion from close binarymore » evolution. However, our results do suggest that the efficiency of rotational mixing is at or slightly below the low end of the range predicted by the available theoretical calculations. The two most luminous targets observed have a very large boron depletion and may be the products of either binary interactions or post-main-sequence evolution.« less

Capturing the Temporal Sequence of Interaction in Young Siblings

PubMed Central

Steele, Fiona; Jenkins, Jennifer

2015-01-01

We explored whether young children exhibit subtypes of behavioral sequences during sibling interaction. Ten-minute, free-play observations of over 300 sibling dyads were coded for positivity, negativity and disengagement. The data were analyzed using growth mixture modeling (GMM). Younger (18-month-old) children’s temporal behavioral sequences showed a harmonious (53%) and a casual (47%) class. Older (approximately four-year-old) children’s behavior was more differentiated revealing a harmonious (25%), a deteriorating (31%), a recovery (22%) and a casual (22%) class. A more positive maternal affective climate was associated with more positive patterns. Siblings’ sequential behavioral patterns tended to be complementary rather than reciprocal in nature. The study illustrates a novel use of GMM and makes a theoretical contribution by showing that young children exhibit distinct types of temporal behavioral sequences that are related to parenting processes. PMID:25996957

Accuracy and Reproducibility of Adipose Tissue Measurements in Young Infants by Whole Body Magnetic Resonance Imaging

PubMed Central

Bauer, Jan Stefan; Noël, Peter Benjamin; Vollhardt, Christiane; Much, Daniela; Degirmenci, Saliha; Brunner, Stefanie; Rummeny, Ernst Josef; Hauner, Hans

2015-01-01

Purpose MR might be well suited to obtain reproducible and accurate measures of fat tissues in infants. This study evaluates MR-measurements of adipose tissue in young infants in vitro and in vivo. Material and Methods MR images of ten phantoms simulating subcutaneous fat of an infant’s torso were obtained using a 1.5T MR scanner with and without simulated breathing. Scans consisted of a cartesian water-suppression turbo spin echo (wsTSE) sequence, and a PROPELLER wsTSE sequence. Fat volume was quantified directly and by MR imaging using k-means clustering and threshold-based segmentation procedures to calculate accuracy in vitro. Whole body MR was obtained in sleeping young infants (average age 67±30 days). This study was approved by the local review board. All parents gave written informed consent. To obtain reproducibility in vivo, cartesian and PROPELLER wsTSE sequences were repeated in seven and four young infants, respectively. Overall, 21 repetitions were performed for the cartesian sequence and 13 repetitions for the PROPELLER sequence. Results In vitro accuracy errors depended on the chosen segmentation procedure, ranging from 5.4% to 76%, while the sequence showed no significant influence. Artificial breathing increased the minimal accuracy error to 9.1%. In vivo reproducibility errors for total fat volume of the sleeping infants ranged from 2.6% to 3.4%. Neither segmentation nor sequence significantly influenced reproducibility. Conclusion With both cartesian and PROPELLER sequences an accurate and reproducible measure of body fat was achieved. Adequate segmentation was mandatory for high accuracy. PMID:25706876

Accuracy and reproducibility of adipose tissue measurements in young infants by whole body magnetic resonance imaging.

PubMed

Bauer, Jan Stefan; Noël, Peter Benjamin; Vollhardt, Christiane; Much, Daniela; Degirmenci, Saliha; Brunner, Stefanie; Rummeny, Ernst Josef; Hauner, Hans

2015-01-01

MR might be well suited to obtain reproducible and accurate measures of fat tissues in infants. This study evaluates MR-measurements of adipose tissue in young infants in vitro and in vivo. MR images of ten phantoms simulating subcutaneous fat of an infant's torso were obtained using a 1.5T MR scanner with and without simulated breathing. Scans consisted of a cartesian water-suppression turbo spin echo (wsTSE) sequence, and a PROPELLER wsTSE sequence. Fat volume was quantified directly and by MR imaging using k-means clustering and threshold-based segmentation procedures to calculate accuracy in vitro. Whole body MR was obtained in sleeping young infants (average age 67±30 days). This study was approved by the local review board. All parents gave written informed consent. To obtain reproducibility in vivo, cartesian and PROPELLER wsTSE sequences were repeated in seven and four young infants, respectively. Overall, 21 repetitions were performed for the cartesian sequence and 13 repetitions for the PROPELLER sequence. In vitro accuracy errors depended on the chosen segmentation procedure, ranging from 5.4% to 76%, while the sequence showed no significant influence. Artificial breathing increased the minimal accuracy error to 9.1%. In vivo reproducibility errors for total fat volume of the sleeping infants ranged from 2.6% to 3.4%. Neither segmentation nor sequence significantly influenced reproducibility. With both cartesian and PROPELLER sequences an accurate and reproducible measure of body fat was achieved. Adequate segmentation was mandatory for high accuracy.

Clouds, Streams and Bridges. Redrawing the blueprint of the Magellanic System with Gaia DR1

NASA Astrophysics Data System (ADS)

Belokurov, Vasily; Erkal, Denis; Deason, Alis J.; Koposov, Sergey E.; De Angeli, Francesca; Evans, Dafydd Wyn; Fraternali, Filippo; Mackey, Dougal

2017-04-01

We present the discovery of stellar tidal tails around the Large and the Small Magellanic Clouds (LMC and SMC, respectively) in the Gaia DR1 data. In between the Clouds, their tidal arms are stretched towards each other to form an almost continuous stellar bridge. Our analysis relies on the exquisite quality of the Gaia's photometric catalogue to build detailed star-count maps of the Clouds. We demonstrate that the Gaia DR1 data can be used to detect variable stars across the whole sky, and, in particular, RR Lyrae stars in and around the LMC and the SMC. Additionally, we use a combination of Gaia and GALEX to follow the distribution of Young Main Sequence stars in the Magellanic System. Viewed by Gaia, the Clouds show unmistakable signs of interaction. Around the LMC, clumps of RR Lyrae are observable as far as ˜20°, in agreement with the most recent map of Mira-like stars reported in Deason et al. The SMC's outer stellar density contours show a characteristic S-shape, symptomatic of the onset of tidal stripping. Beyond several degrees from the centre of the dwarf, the Gaia RR Lyrae stars trace the Cloud's trailing arm, extending towards the LMC. This stellar tidal tail mapped with RR Lyrae is not aligned with the gaseous Magellanic Bridge, and is shifted by some ˜5° from the Young Main Sequence bridge. We use the offset between the bridges to put constraints on the density of the hot gaseous corona of the Milky Way.

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.

Collision propagation in Papua New Guinea and Solomon Sea

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

Silver, E.A.; Abbott, L.; Kirchoff-Stein, K.

The collision of the Finisterre-New Britain terrane with the Australian continent is propagating eastward at a rate of approximately 125 km/m.y., based on plate motions and the collisional geometry, as well as on the geochemistry of the arc volcanics. A sequence of sedimentary facies is developed from east to west in the modern environment (pelagic sediments, turbidites, marine molasse, and fluvial molasse), and this sequence is accreted from north to south at the front of the terrane collision in the Markham valley. Based on the modern distribution, the authors suggest that the age of the initial marine molasse will predatemore » the passage of the collision point, and that of the fluvial molasse will postdate its passage. Intense erosion in the Markham canyon, located along the suture between the collision point and the coast, appears to be responsible for stripping most of the accreted marine molasse and redepositing it in a basin just east of the collision point. Convergence along the suture zone deceases westward. At Lae, very young deformation is seen, but 80 km to the west undeformed terrace deposits cover the deformation front. Uplift appears active within the range, aided by out-of-sequence thrusting, but still farther west the rocks lack signs of young tectonism. In the region just west of Lae, the main locus of slip between the Australian and south Bismarck plates must transfer southward to the front of the Papuan fold-and-thrust belt.« less

The effect of interference on temporal order memory for random and fixed sequences in nondemented older adults.

PubMed

Tolentino, Jerlyn C; Pirogovsky, Eva; Luu, Trinh; Toner, Chelsea K; Gilbert, Paul E

2012-05-21

Two experiments tested the effect of temporal interference on order memory for fixed and random sequences in young adults and nondemented older adults. The results demonstrate that temporal order memory for fixed and random sequences is impaired in nondemented older adults, particularly when temporal interference is high. However, temporal order memory for fixed sequences is comparable between older adults and young adults when temporal interference is minimized. The results suggest that temporal order memory is less efficient and more susceptible to interference in older adults, possibly due to impaired temporal pattern separation.

NGC 1866: First Spectroscopic Detection of Fast-rotating Stars in a Young LMC Cluster

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

Dupree, A. K.; Dotter, A.; Johnson, C. I.

High-resolution spectroscopic observations were taken of 29 extended main-sequence turnoff (eMSTO) stars in the young (∼200 Myr) Large Magellanic Cloud (LMC) cluster, NGC 1866, using the Michigan/ Magellan Fiber System and MSpec spectrograph on the Magellan -Clay 6.5 m telescope. These spectra reveal the first direct detection of rapidly rotating stars whose presence has only been inferred from photometric studies. The eMSTO stars exhibit H α emission (indicative of Be-star decretion disks), others have shallow broad H α absorption (consistent with rotation ≳150 km s{sup −1}), or deep H α core absorption signaling lower rotation velocities (≲150 km s{sup −1}).more » The spectra appear consistent with two populations of stars—one rapidly rotating, and the other, younger and slowly rotating.« less

A YOUNG ECLIPSING BINARY AND ITS LUMINOUS NEIGHBORS IN THE EMBEDDED STAR CLUSTER Sh 2-252E

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

Lester, Kathryn V.; Gies, Douglas R.; Guo, Zhao, E-mail: lester@chara.gsu.edu, E-mail: gies@chara.gsu.edu, E-mail: guo@chara.gsu.edu

We present a photometric and light curve analysis of an eccentric eclipsing binary in the K2 Campaign 0 field, which resides in Sh 2-252E, a young star cluster embedded in an H ii region. We describe a spectroscopic investigation of the three brightest stars in the crowded aperture to identify which is the binary system. We find that none of these stars are components of the eclipsing binary system, which must be one of the fainter nearby stars. These bright cluster members all have remarkable spectra: Sh 2-252a (EPIC 202062176) is a B0.5 V star with razor sharp absorption lines, Sh 2-252b is amore » Herbig A0 star with disk-like emission lines, and Sh 2-252c is a pre-main-sequence star with very red color.« less

Effect of Sequencing Strength and Endurance Training in Young Male Soccer Players.

PubMed

Makhlouf, Issam; Castagna, Carlo; Manzi, Vincenzo; Laurencelle, Louis; Behm, David G; Chaouachi, Anis

2016-03-01

This study examined the effects of strength and endurance training sequence (strength before or after endurance) on relevant fitness variables in youth soccer players. Fifty-seven young elite-level male field soccer players (13.7 ± 0.5 years; 164 ± 8.3 cm; 53.5 ± 8.6 kg; body fat; 15.6 ± 3.9%) were randomly assigned to a control (n = 14, CG) and 3 experimental training groups (twice a week for 12 weeks) strength before (SE, n = 15), after (ES, n = 14) or on alternate days (ASE, n = 14) with endurance training. A significant (p = 0.001) intervention main effect was detected. There were only trivial training sequence differences (ES vs. SE) for all variables (p > 0.05). The CG showed large squat 1 repetition maximum (1RM) and medium sprint, change of direction ability, and jump improvements. ASE demonstrated a trivial difference in endurance performance with ES and SE (p > 0.05). Large to medium greater improvements for SE and ES were reported compared with ASE for sprinting over 10 and 30 m (p < 0.02). The SE squat 1RM was higher than in ASE (moderate, p < 0.02). Postintervention differences between ES and SE with CG fitness variables were small to medium (p ≤ 0.05) except for a large SE advantage with the Yo-Yo intermittent recovery test (p < 0.001, large). This study showed no effect of intrasession training sequence on soccer fitness-relevant variables. However, combining strength and endurance within a single training session provided superior results vs. training on alternate days. Concurrent training may be considered as an effective and safe training method for the development of the prospective soccer player.

Insufficient chunk concatenation may underlie changes in sleep-dependent consolidation of motor sequence learning in older adults.

PubMed

Bottary, Ryan; Sonni, Akshata; Wright, David; Spencer, Rebecca M C

2016-09-01

Sleep enhances motor sequence learning (MSL) in young adults by concatenating subsequences ("chunks") formed during skill acquisition. To examine whether this process is reduced in aging, we assessed performance changes on the MSL task following overnight sleep or daytime wake in healthy young and older adults. Young adult performance enhancement was correlated with nREM2 sleep, and facilitated by preferential improvement of slowest within-sequence transitions. This effect was markedly reduced in older adults, and accompanied by diminished sigma power density (12-15 Hz) during nREM2 sleep, suggesting that diminished chunk concatenation following sleep may underlie reduced consolidation of MSL in older adults. © 2016 Bottary et al.; Published by Cold Spring Harbor Laboratory Press.

Swallow Event Sequencing: Comparing Healthy Older and Younger Adults.

PubMed

Herzberg, Erica G; Lazarus, Cathy L; Steele, Catriona M; Molfenter, Sonja M

2018-04-23

Previous research has established that a great deal of variation exists in the temporal sequence of swallowing events for healthy adults. Yet, the impact of aging on swallow event sequence is not well understood. Kendall et al. (Dysphagia 18(2):85-91, 2003) suggested there are 4 obligatory paired-event sequences in swallowing. We directly compared adherence to these sequences, as well as event latencies, and quantified the percentage of unique sequences in two samples of healthy adults: young (< 45) and old (> 65). The 8 swallowing events that contribute to the sequences were reliably identified from videofluoroscopy in a sample of 23 healthy seniors (10 male, mean age 74.7) and 20 healthy young adults (10 male, mean age 31.5) with no evidence of penetration-aspiration or post-swallow residue. Chi-square analyses compared the proportions of obligatory pairs and unique sequences by age group. Compared to the older subjects, younger subjects had significantly lower adherence to two obligatory sequences: Upper Esophageal Sphincter (UES) opening occurs before (or simultaneous with) the bolus arriving at the UES and UES maximum distention occurs before maximum pharyngeal constriction. The associated latencies were significantly different between age groups as well. Further, significantly fewer unique swallow sequences were observed in the older group (61%) compared with the young (82%) (χ 2  = 31.8; p < 0.001). Our findings suggest that paired swallow event sequences may not be robust across the age continuum and that variation in swallow sequences appears to decrease with aging. These findings provide normative references for comparisons to older individuals with dysphagia.

Age Spreads and the Temperature Dependence of Age Estimates in Upper Sco

NASA Astrophysics Data System (ADS)

Fang, Qiliang; Herczeg, Gregory J.; Rizzuto, Aaron

2017-06-01

Past estimates for the age of the Upper Sco Association are typically 11–13 Myr for intermediate-mass stars and 4–5 Myr for low-mass stars. In this study, we simulate populations of young stars to investigate whether this apparent dependence of estimated age on spectral type may be explained by the star formation history of the association. Solar and intermediate mass stars begin their pre-main sequence evolution on the Hayashi track, with fully convective interiors and cool photospheres. Intermediate-mass stars quickly heat up and transition onto the radiative Henyey track. As a consequence, for clusters in which star formation occurs on a timescale similar to that of the transition from a convective to a radiative interior, discrepancies in ages will arise when ages are calculated as a function of temperature instead of mass. Simple simulations of a cluster with constant star formation over several Myr may explain about half of the difference in inferred ages versus photospheric temperature; speculative constructions that consist of a constant star formation followed by a large supernova-driven burst could fully explain the differences, including those between F and G stars where evolutionary tracks may be more accurate. The age spreads of low-mass stars predicted from these prescriptions for star formation are consistent with the observed luminosity spread of Upper Sco. The conclusion that a lengthy star formation history will yield a temperature dependence in ages is expected from the basic physics of pre-main sequence evolution, and is qualitatively robust to the large uncertainties in pre-main sequence evolutionary models.

LITHIUM DEPLETION IS A STRONG TEST OF CORE-ENVELOPE RECOUPLING

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

Somers, Garrett; Pinsonneault, Marc H., E-mail: somers@astronomy.ohio-state.edu

2016-09-20

Rotational mixing is a prime candidate for explaining the gradual depletion of lithium from the photospheres of cool stars during the main sequence. However, previous mixing calculations have relied primarily on treatments of angular momentum transport in stellar interiors incompatible with solar and stellar data in the sense that they overestimate the internal differential rotation. Instead, recent studies suggest that stars are strongly differentially rotating at young ages but approach a solid body rotation during their lifetimes. We modify our rotating stellar evolution code to include an additional source of angular momentum transport, a necessary ingredient for explaining the openmore » cluster rotation pattern, and examine the consequences for mixing. We confirm that core-envelope recoupling with a ∼20 Myr timescale is required to explain the evolution of the mean rotation pattern along the main sequence, and demonstrate that it also provides a more accurate description of the Li depletion pattern seen in open clusters. Recoupling produces a characteristic pattern of efficient mixing at early ages and little mixing at late ages, thus predicting a flattening of Li depletion at a few Gyr, in agreement with the observed late-time evolution. Using Li abundances we argue that the timescale for core-envelope recoupling during the main sequence decreases sharply with increasing mass. We discuss the implications of this finding for stellar physics, including the viability of gravity waves and magnetic fields as agents of angular momentum transport. We also raise the possibility of intrinsic differences in initial conditions in star clusters using M67 as an example.« less

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

Fang Qiliang; Herczeg, Gregory J.; Rizzuto, Aaron

Past estimates for the age of the Upper Sco Association are typically 11–13 Myr for intermediate-mass stars and 4–5 Myr for low-mass stars. In this study, we simulate populations of young stars to investigate whether this apparent dependence of estimated age on spectral type may be explained by the star formation history of the association. Solar and intermediate mass stars begin their pre-main sequence evolution on the Hayashi track, with fully convective interiors and cool photospheres. Intermediate-mass stars quickly heat up and transition onto the radiative Henyey track. As a consequence, for clusters in which star formation occurs on amore » timescale similar to that of the transition from a convective to a radiative interior, discrepancies in ages will arise when ages are calculated as a function of temperature instead of mass. Simple simulations of a cluster with constant star formation over several Myr may explain about half of the difference in inferred ages versus photospheric temperature; speculative constructions that consist of a constant star formation followed by a large supernova-driven burst could fully explain the differences, including those between F and G stars where evolutionary tracks may be more accurate. The age spreads of low-mass stars predicted from these prescriptions for star formation are consistent with the observed luminosity spread of Upper Sco. The conclusion that a lengthy star formation history will yield a temperature dependence in ages is expected from the basic physics of pre-main sequence evolution, and is qualitatively robust to the large uncertainties in pre-main sequence evolutionary models.« less

X-Raying the Coronae of HD 155555

NASA Technical Reports Server (NTRS)

Lalitha, S.; Singh, K.P.; Drake, S. A.; Kashyap, V.

2015-01-01

We present an analysis of the high-resolution Chandra observation of the multiple system, HD 155555 (an RS CVn type binary system, HD 155555 AB, and its spatially resolved low-mass companion HD 155555 C). This is an intriguing system which shows properties of both an active pre-main sequence star and a synchronised (main sequence) binary. We obtain the emission measure distribution, temperature structures, plasma densities, and abundances of this system and compare them with the coronal properties of other young/active stars. HD 155555 AB and HD 155555 C produce copious X-ray emission with log L(sub x) of 30.54 and 29.30, respectively, in the 0.3-6.0 kiloelectronvolt energy band. The light curves of individual stars show variability on timescales of few minutes to hours. We analyse the dispersed spectra and reconstruct the emission measure distribution using spectral line analysis. The resulting elemental abundances exhibit inverse first ionisation potential effect in both cases. An analysis of He-like triplets yields a range of coronal electron densities 1010 - 1013 per cubic centimeter. Since HD 155555 AB is classified both as an RS CVn and a PMS star, we compare our results with those of other slightly older active main-sequence stars and T Tauri stars, which indicates that the coronal properties of HD 155555 AB closely resemble that of an older RS CVn binary rather than a younger PMS star. Our results also suggests that the properties of HD 155555 C is very similar to those of other active M dwarfs.

IMPLICATIONS OF RAPID CORE ROTATION IN RED GIANTS FOR INTERNAL ANGULAR MOMENTUM TRANSPORT IN STARS

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

Tayar, Jamie; Pinsonneault, Marc H., E-mail: tayar.1@osu.edu

2013-09-20

Core rotation rates have been measured for red giant stars using asteroseismology. These data, along with helioseismic measurements and open cluster spin-down studies, provide powerful clues about the nature and timescale for internal angular momentum transport in stars. We focus on two cases: the metal-poor red giant KIC 7341231 ({sup O}tto{sup )} and intermediate-mass core helium burning stars. For both, we examine limiting case studies for angular momentum coupling between cores and envelopes under the assumption of rigid rotation on the main sequence. We discuss the expected pattern of core rotation as a function of mass and radius. In themore » case of Otto, strong post-main-sequence coupling is ruled out and the measured core rotation rate is in the range of 23-33 times the surface value expected from standard spin-down models. The minimum coupling timescale (0.17-0.45 Gyr) is significantly longer than that inferred for young open cluster stars. This implies ineffective internal angular momentum transport in early first ascent giants. By contrast, the core rotation rates of evolved secondary clump stars are found to be consistent with strong coupling given their rapid main-sequence rotation. An extrapolation to the white dwarf regime predicts rotation periods between 330 and 0.0052 days, depending on mass and decoupling time. We identify two key ingredients that explain these features: the presence of a convective core and inefficient angular momentum transport in the presence of larger mean molecular weight gradients. Observational tests that can disentangle these effects are discussed.« less

THE YOUNG STELLAR POPULATION OF LYNDS 1340. AN INFRARED VIEW

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

Kun, M.; Moór, A.; Wolf-Chase, G.

We present results of an infrared study of the molecular cloud Lynds 1340, forming three groups of low- and intermediate-mass stars. Our goals are to identify and characterize the young stellar population of the cloud, study the relationships between the properties of the cloud and the emergent stellar groups, and integrate L1340 into the picture of the star-forming activity of our Galactic environment. We selected candidate young stellar objects (YSOs) from the Spitzer and WISE databases using various published color criteria and classified them based on the slope of the spectral energy distribution (SED). We identified 170 Class II, 27more » flat SED, and 45 Class 0/I sources. High angular resolution near-infrared observations of the RNO 7 cluster, embedded in L1340, revealed eight new young stars of near-infrared excess. The surface density distribution of YSOs shows three groups, associated with the three major molecular clumps of L1340, each consisting of ≲100 members, including both pre-main-sequence stars and embedded protostars. New Herbig–Haro objects were identified in the Spitzer images. Our results demonstrate that L1340 is a prolific star-forming region of our Galactic environment in which several specific properties of the intermediate-mass mode of star formation can be studied in detail.« less

Implicit Learning of Predictive Relationships in Three-element Visual Sequences by Young and Old Adults

PubMed Central

Howard, James H.; Howard, Darlene V.; Dennis, Nancy A.; Kelly, Andrew J.

2008-01-01

Knowledge of sequential relationships enables future events to be anticipated and processed efficiently. Research with the serial reaction time task (SRTT) has shown that sequence learning often occurs implicitly without effort or awareness. Here we report four experiments that use a triplet-learning task (TLT) to investigate sequence learning in young and older adults. In the TLT people respond only to the last target event in a series of discrete, three-event sequences or triplets. Target predictability is manipulated by varying the triplet frequency (joint probability) and/or the statistical relationships (conditional probabilities) among events within the triplets. Results revealed that both groups learned, though older adults showed less learning of both joint and conditional probabilities. Young people used the statistical information in both cues, but older adults relied primarily on information in the second cue alone. We conclude that the TLT complements and extends the SRTT and other tasks by offering flexibility in the kinds of sequential statistical regularities that may be studied as well as by controlling event timing and eliminating motor response sequencing. PMID:18763897

SLC52A2 mutations cause SCABD2 phenotype: A second report.

PubMed

Babanejad, Mojgan; Adeli, Omid Ali; Nikzat, Nooshin; Beheshtian, Maryam; Azarafra, Hakimeh; Sadeghnia, Farnaz; Mohseni, Marzieh; Najmabadi, Hossein; Kahrizi, Kimia

2018-01-01

Autosomal recessive cerebellar ataxias (ARCAs) are a large group of neurodegenerative disorders that manifest mainly in children and young adults. Most ARCAs are heterogeneous with respect to age at onset, severity of disease progression, and frequency of extracerebellar and systemic signs. The phenotype of a consanguineous Iranian family was characterized using clinical testing and pedigree analysis. Whole-exome sequencing was used to identify the disease-causing gene in this family. Using whole exome sequencing (WES), a novel missense mutation in SLC52A2 gene is reported in a consanguineous Iranian family with progressive severe hearing loss, optic atrophy and ataxia. This is the second report of the genotype-phenotype correlation between this syndrome named spinocerebellar ataxia with blindness and deafness type 2 (SCABD2) and SLC52A2 gene. Copyright © 2017 Elsevier B.V. All rights reserved.

The Gaia-ESO Survey: the present-day radial metallicity distribution of the Galactic disc probed by pre-main-sequence clusters

NASA Astrophysics Data System (ADS)

Spina, L.; Randich, S.; Magrini, L.; Jeffries, R. D.; Friel, E. D.; Sacco, G. G.; Pancino, E.; Bonito, R.; Bravi, L.; Franciosini, E.; Klutsch, A.; Montes, D.; Gilmore, G.; Vallenari, A.; Bensby, T.; Bragaglia, A.; Flaccomio, E.; Koposov, S. E.; Korn, A. J.; Lanzafame, A. C.; Smiljanic, R.; Bayo, A.; Carraro, G.; Casey, A. R.; Costado, M. T.; Damiani, F.; Donati, P.; Frasca, A.; Hourihane, A.; Jofré, P.; Lewis, J.; Lind, K.; Monaco, L.; Morbidelli, L.; Prisinzano, L.; Sousa, S. G.; Worley, C. C.; Zaggia, S.

2017-05-01

Context. The radial metallicity distribution in the Galactic thin disc represents a crucial constraint for modelling disc formation and evolution. Open star clusters allow us to derive both the radial metallicity distribution and its evolution over time. Aims: In this paper we perform the first investigation of the present-day radial metallicity distribution based on [Fe/H] determinations in late type members of pre-main-sequence clusters. Because of their youth, these clusters are therefore essential for tracing the current interstellar medium metallicity. Methods: We used the products of the Gaia-ESO Survey analysis of 12 young regions (age < 100 Myr), covering Galactocentric distances from 6.67 to 8.70 kpc. For the first time, we derived the metal content of star forming regions farther than 500 pc from the Sun. Median metallicities were determined through samples of reliable cluster members. For ten clusters the membership analysis is discussed in the present paper, while for other two clusters (I.e. Chamaeleon I and Gamma Velorum) we adopted the members identified in our previous works. Results: All the pre-main-sequence clusters considered in this paper have close-to-solar or slightly sub-solar metallicities. The radial metallicity distribution traced by these clusters is almost flat, with the innermost star forming regions having [Fe/H] values that are 0.10-0.15 dex lower than the majority of the older clusters located at similar Galactocentric radii. Conclusions: This homogeneous study of the present-day radial metallicity distribution in the Galactic thin disc favours models that predict a flattening of the radial gradient over time. On the other hand, the decrease of the average [Fe/H] at young ages is not easily explained by the models. Our results reveal a complex interplay of several processes (e.g. star formation activity, initial mass function, supernova yields, gas flows) that controlled the recent evolution of the Milky Way. Based on observations made with the ESO/VLT, at Paranal Observatory, under program 188.B-3002 (The Gaia-ESO Public Spectroscopic Survey).Full 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/601/A70

A spectroscopic and photometric study of the unique pre- main sequence system KH 15D

NASA Astrophysics Data System (ADS)

Hamilton, Catrina Marie

2004-09-01

As a class, T Tauri stars are YSOs, some which are surrounded by circumstellar disks, and are recognized as the final stage of low-mass star formation. They also represent the earliest stage of stellar evolution that is optically visible, and, therefore, can be easily studied in detail. Understanding the processes through which these young stars interact with and eventually disperse their circumstellar disks is critical for understanding how they evolve from the T Tauri phase to the zero age main sequence (ZAMS), and how this affects the formation of planets, as well as their rotational evolution. KH 15D is a unique eclipsing system that could provide invaluable insight into the evolution of circumstellar disk material, as well as clues to the close stellar environment. Discovered in 1997, this star system has been observed to undergo an eclipse every 48 days in which the star's light is diminished by 3.5 magnitudes. What is so unusual about the eclipse is that the length of the eclipse has evolved over time, growing in length from 16 days initially, to ˜25 days in 2002/2003. Evolution of disk material on these timescales has never been observed before, and therefore provides us with a unique opportunity to refine our theories about remnant disks around young stars, how they transition, possibly into planets, and what role they play as the star matures and arrives on the zero age main sequence. Additionally, high resolution spectra obtained at specific phases during the December 2001 eclipse showed that as the obscuring matter cut across the star, dramatic spectral changes in the Hα and Hβ lines were seen. Its unique eclipse produces a “natural coronographic” effect in which the stellar photosphere is occulted, revealing details of its magnetosphere and surroundings during eclipse. There is evidence that the weak-lined T Tauri star (WTTS) central to the system is actively accreting gas, although probably not at the rate of a typical classical T Tauri star, calling into question the common practice of associating WTTS characteristics with the absence of an accretion disk. Here I present an investigation of the photometric and spectroscopic properties of the KH 15D eclipsing system, and discuss the implications that this system holds for the future research of T Tauri stars.

The Structure of the Star-forming Cluster RCW 38

NASA Astrophysics Data System (ADS)

Winston, E.; Wolk, S. J.; Bourke, T. L.; Megeath, S. T.; Gutermuth, R.; Spitzbart, B.

2011-12-01

We present a study of the structure of the high-mass star-forming region RCW 38 and the spatial distribution of its young stellar population. Spitzer Infrared Array Camera (IRAC) photometry (3-8 μm) is combined with Two Micron All Sky Survey near-IR data to identify young stellar objects (YSOs) by IR-excess emission from their circumstellar material. Chandra X-ray data are used to identify class III pre-main-sequence stars lacking circumstellar material. We identify 624 YSOs: 23 class 0/I and 90 flat spectrum protostars, 437 class II stars, and 74 class III stars. We also identify 29 (27 new) O star candidates over the IRAC field. Seventy-two stars exhibit IR-variability, including 7 class 0/I and 12 flat spectrum YSOs. A further 177 tentative candidates are identified by their location in the IRAC [3.6] versus [3.6]-[5.8] color-magnitude diagram. We find strong evidence of subclustering in the region. Three subclusters were identified surrounding the central cluster, with massive and variable stars in each subcluster. The central region shows evidence of distinct spatial distributions of the protostars and pre-main-sequence stars. A previously detected IR cluster, DB2001_Obj36, has been established as a subcluster of RCW 38. This suggests that star formation in RCW 38 occurs over a more extended area than previously thought. The gas-to-dust ratio is examined using the X-ray derived hydrogen column density, N H and the K-band extinction, and found to be consistent with the diffuse interstellar medium, in contrast with Serpens and NGC 1333. We posit that the high photoionizing flux of massive stars in RCW 38 affects the agglomeration of the dust grains.

DETECTION OF A COOL, ACCRETION-SHOCK-GENERATED X-RAY PLASMA IN EX LUPI DURING THE 2008 OPTICAL ERUPTION

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

Teets, William K.; Weintraub, David A.; Kastner, Joel H.

2012-11-20

EX Lupi is the prototype for a class of young, pre-main-sequence stars which are observed to undergo irregular, presumably accretion-generated, optical outbursts that result in a several magnitude rise of the optical flux. EX Lupi was observed to optically erupt in 2008 January, triggering Chandra ACIS Target of Opportunity observations shortly thereafter. We find very strong evidence that most of the X-ray emission in the first few months after the optical outburst is generated by accretion of circumstellar material onto the stellar photosphere. Specifically, we find a strong correlation between the decreasing optical and X-ray fluxes following the peak ofmore » the outburst in the optical, which suggests that these observed declines in both the optical and X-ray fluxes are the result of declining accretion rate. In addition, in our models of the X-ray spectrum, we find strong evidence for a {approx}0.4 keV plasma component, as expected for accretion shocks on low-mass, pre-main-sequence stars. From 2008 March through October, this cool plasma component appeared to fade as EX Lupi returned to its quiescent level in the optical, consistent with a decrease in the overall emission measure of accretion-shock-generated plasma. The overall small increase of the X-ray flux during the optical outburst of EX Lupi is similar to what was observed in previous X-ray observations of the 2005 optical outburst of the EX Lupi-type star V1118 Ori but contrasts with the large increase of the X-ray flux from the erupting young star V1647 Ori during its 2003 and 2008 optical outbursts.« less

An XMM-Newton Observation of the Lagoon Nebula and the Very Young Open Cluster NGC 6530

NASA Technical Reports Server (NTRS)

Rauw, G.; Naze, Y.; Gosset, E.; Stevens, I. R.; Blomme, R.; Corcoran, M. F.; Pittard, J. M.; Runacres, M. C.

2002-01-01

We report the results of an XMM-Newton observation of the Lagoon Nebula (M 8). Our EPIC images of this region reveal a cluster of point sources, most of which have optical counterparts inside the very young open cluster NGC 6530. The bulk of these X-ray sources are probably associated with low and intermediate mass pre-main sequence stars. One of the sources experiences a flare-like increase of its X-ray flux making it the second brightest source in M 8 after the O4 star 9 Sgr. The X-ray spectra of most of the brightest sources can be fitted with thermal plasma models with temperatures of kT approximately a few keV. Only a few of the X-ray selected PMS candidates are known to display H(alpha) emission and were previously classified as classical T Tauri stars. This suggests that most of the X-ray emitting PMS stars in NGC 6530 are weak line T Tauri stars. In addition to 9 Sgr, our EPIC field of view contains also a few early-type stars. The X-ray emission from HD 164816 is found to be typical for an O9.5III-IV star. At least one of the known Herbig Be stars in NGC 6530 (LkH(alpha) 115) exhibits a relatively strong X-ray emission, while most of the main sequence stars of spectral type B1 and later are not detected. We also detect (probably) diffuse X-ray emission from the Hourglass Region that might reveal a hot bubble blown by the stellar wind of Herschel 36, the ionizing star of the Hourglass Region.

Detection of a Cool, Accretion-Shock-Generated X-Ray Plasma in EX Lupi During the 2008 Optical Eruption

NASA Technical Reports Server (NTRS)

Teets, William K.; Weintraub, David A.; Kastner, Joel H.; Grosso, Nicholas; Hamaguchi, Kenji; Richmond, Michael

2012-01-01

EX Lupi is the prototype for a class of young, pre-main-sequence stars which are observed to undergo irregular, presumably accretion-generated, optical outbursts that result in a several magnitude rise of the optical flux. EX Lupi was observed to optically erupt in 2008 January, triggering Chandra ACIS Target of Opportunity observations shortly thereafter. We find very strong evidence that most of the X-ray emission in the first few months after the optical outburst is generated by accretion of circumstellar material onto the stellar photosphere. Specifically, we find a strong correlation between the decreasing optical and X-ray fluxes following the peak of the outburst in the optical, which suggests that these observed declines in both the optical and X-ray fluxes are the result of declining accretion rate. In addition, in our models of the X-ray spectrum, we find strong evidence for an approx 0.4 keV plasma component, as expected for accretion shocks on low-mass, pre-main-sequence stars. From 2008 March through October, this cool plasma component appeared to fade as EX Lupi returned to its quiescent level in the optical, consistent with a decrease in the overall emission measure of accretion-shock-generated plasma. The overall small increase of the X-ray flux during the optical outburst of EX Lupi is similar to what was observed in previous X-ray observations of the 2005 optical outburst of the EX Lupi-type star V1118 Ori but contrasts with the large increase of the X-ray flux from the erupting young star V1647 Ori during its 2003 and 2008 optical outbursts.

Soft X-ray observations of pre-main sequence stars in the chamaeleon dark cloud

NASA Technical Reports Server (NTRS)

Feigelson, Eric D.; Kriss, Gerard A.

1987-01-01

Einstein IPC observations of the nearby Chamaeleon I star forming cloud show 22 well-resolved soft X-ray sources in a 1x2 deg region. Twelve are associated with H-alpha emission line pre-main sequence (PMS) stars, and four with optically selected PMS stars. Several X-ray sources have two or more PMS stars in their error circles. Optical spectra were obtained at CTIO of possible stellar counterparts of the remaining X-ray sources. They reveal 5 probable new cloud members, K7-MO stars with weak or absent emission lines. These naked X-ray selected PMS stars are similar to those found in the Taurus-Auriga cloud. The spatial distributions and H-R diagrams of the X-ray and optically selected PMS stars in the cloud are very similar. Luminosity functions indicate the Chamaeleon stars are on average approximately 5 times more X-ray luminous than Pleiad dwarfs. A significant correlation between L sub x and optical magnitude suggests this trend may continue within the PMS phase of stellar evolution. The relation of increasing X-ray luminosity with decreasing stellar ages is thus extended to stellar ages as young as 1 million years.

The Low Mass IMF in Young Open Clusters

NASA Astrophysics Data System (ADS)

Williams, Douglas M.

1995-01-01

We present the results of the investigation of the Initial Mass Function at the end of the Main Sequence in young open clusters. We find that over a large range in age and environment the IMFs are similar to each other, and to recent determinations of the field star IMF. We have obtained V, I, and K band photometry of fields in the three relatively unembedded open clusters. The photometry reaches down to various masses in each cluster: 0.08{cal M}_⊙ for Praesepe, 0.04{cal M}odot for the Pleiades, and 0.15{cal M}_⊙ for NGC 7160. We compare the methods for estimating the masses of young, embedded stars developed by Comeron et al. (1993 - CRBR) and by Strom, Kepner, & Strom (1995) and show them to be in good agreement. Spectra in the 2 mu m region of six low mass objects from CRBR are also in agreement with the mass estimates using these methods. The spectrum of a brown dwarf candidate is used to place an upper limit on its mass of 60% of the minimum required for hydrogen burning. The IMFs from these four clusters plus NGC 2024 are shown to be in agreement with each other. The composite MF can be fitted with a power law between 0.04 and 0.5 {cal M}_⊙ with a slope of -0.75 +/- 0.3. There is no evidence for a cutoff at the bottom of the main sequence (0.08{cal M}odot); brown dwarfs appear to be abundant in open clusters. However, the slope of the MF is well above the value of _sp {~}<-2 required for very low mass stars and brown dwarfs to contribute a significant portion of the mass of open clusters. The composite cluster MF also is in agreement with recent determinations of the field star IMF for stellar masses. The field star data do not extend into the brown dwarf range; however, if we extrapolate in accordance with the cluster MF, we conclude that brown dwarfs probably do not contribute significantly to the dark matter.

Discussion Starter: The Case for Duplexing without Channel Flow During the Development and Emplacement of the Himalayan Middle Crust

NASA Astrophysics Data System (ADS)

Webb, A. G.; He, D.; Yu, H.

2015-12-01

This presentation and another presentation led by Dawn Kellett will preface a ten-minute open discussion on how the Himalayan middle crust was developed and emplaced. Current hypotheses are transitioning from a set including wedge extrusion, channel flow with focused denudation, and tectonic wedging to a revised dichotomy: models with intense upper plate out-of-sequence activity (i.e., tunneling of channel flow, and critical taper wedge behavior) versus models in which the upper plate mainly records basal accretion of horses (i.e., duplexing). Critical taper and duplexing offer a simple contrast that can be illustrated via food analogies. If a wedge is critical, it churns internally like a pile of CheeriosTM cereal pushed up an inclined plane. Stacking of a duplex acts like a deli meat-slicing machine: slice after slice is cut from the intact block to a stack of slices, but neither the block (~down-going plate) nor the stack (~upper plate) features much internal deformation. Thus critical taper and channel tunneling models predict much processing via out-of-sequence deformation, whereas duplexing predicts in-sequence thrusting. The two concepts may be considered end-members. Recent work shows that the Himalayan middle crust has been assembled along a series of mainly southwards-younging thrust faults. The thrust faults separate 1-5 km thick panels that experienced similar metamorphic cycles during different time periods. Out-of-sequence deformation is rare, with its apparent significance enhanced because of the high throw-to-heave ratio of out-of-sequence thrusting. Flattening fabrics developed prior to thrusting have been interpreted to record either (1) southwards channel tunneling across the upper plate, or (2) fabric development during metamorphism of the down-going plate. We will argue that the thrust faults dominantly represent in-sequence duplexing, and therefore conclude that the Himalaya and analogous hot orogens behave like other accretionary orogens.

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.

Accretion signatures in the X-shooter spectrum of the substellar companion to SR12

NASA Astrophysics Data System (ADS)

Santamaría-Miranda, Alejandro; Cáceres, Claudio; Schreiber, Matthias R.; Hardy, Adam; Bayo, Amelia; Parsons, Steven G.; Gromadzki, Mariusz; Aguayo Villegas, Aurora Belén

2018-04-01

About a dozen substellar companions orbiting young stellar objects or pre-main sequence stars at several hundred au have been identified in the last decade. These objects are interesting both due to the uncertainties surrounding their formation, and because their large separation from the host star offers the potential to study the atmospheres of young giant planets and brown dwarfs. Here, we present X-shooter spectroscopy of SR 12 C, a ˜2 Myr young brown dwarf orbiting SR 12 at an orbital separation of 1083 au. We determine the spectral type, gravity, and effective temperature via comparison with models and observational templates of young brown dwarfs. In addition, we detect and characterize accretion using several accretion tracers. We find SR 12 C to be a brown dwarf of spectral type L0 ± 1, log g = 4 ± 0.5, an effective temperature of 2600 ± 100 K. Our spectra provide clear evidence for accretion at a rate of ˜10-10 M⊙ yr-1. This makes SR 12 one of the few sub-stellar companions with a reliable estimate for its accretion rate. A comparison of the ages and accretion rates of sub-stellar companions with young isolated brown dwarfs does not reveal any significant differences. If further accretion rate measurements of a large number of substellar companions can confirm this trend, this would hint towards a similar formation mechanism for substellar companions at large separations and isolated brown dwarfs.

Alpha Trianguli Australis (K2 II-III) - Hybrid or composite?

NASA Technical Reports Server (NTRS)

Ayres, T. R.

1985-01-01

The prototype hybrid-spectrum giant Alpha Trianguli Australis exhibits a far-ultraviolet continuum which is considerably bluer than would be expected of a star of its optical colors, suggesting the presence of a previously unrecognized companion. If the K-type primary is as luminous as indicated by the widths of its Ca II and H-alpha lines, the companion could be an early F-type dwarf that only recently has arrived on the main sequence. Indeed, the flux of C IV from Alpha TrA - an important measure of hybridness - would not be inconsistent with that expected from a very young chromospherically active F star.

X-ray and Optical Observations of NGC 1788

NASA Astrophysics Data System (ADS)

Alcalá, J. M.; Covino, E.; Wachter, S.; Hoard, D. W.; Sterzik, M. F.; Durisen, R. H.; Freyberg, M.; Cooksey, K.

We report on the results of ROSAT High Resolution Imager (HRI) X-ray observations and optical wide-field spectroscopy and imaging in the star forming region NGC 1788. Several new low mass pre-main sequence (PMS) stars have been found based on intermediate resolution spectroscopy. Many new PMS candidate members of NGC 1788 are selected using the spectroscopically confirmed PMS stars to define the PMS locus in color-magnitude diagrams. Some objects with very red colors detected just above the limiting magnitude of our images, are good candidates for young Brown Dwarfs (BDs). The BD nature of these objects need to be confirmed with subsequent IR observations.

A Panchromatic View of Star-Forming Regions in the Magellanic Clouds: Characterizing Physical and Evolutionary Parameters of 1,000 Young Stellar Objects

NASA Astrophysics Data System (ADS)

Carlson, Lynn R.

2010-01-01

I discuss newly discovered Young Stellar Objects (YSOs) in several star-forming regions in the Magellanic Clouds. I exploit the synergy between infrared photometry from the Spitzer SAGE (Surveying the Agents of Galaxy Evolution) legacy programs, near-infrared and optical photometry from ground-based surveys, and HST imaging to characterize young stellar populations. This reveals a variety of Main Sequence Stars and Proto-Stars over a wide range of evolutionary stages. Through SED fitting, I characterize the youngest, embedded, infrared-bright YSOs. Complementary color-Magnitude analysis and isochrone fitting of optical data allows a statistical description of more evolved, unembedded stellar and protostellar populations within these same regions. I examine the early evolution of Magellanic star clusters, including propagating and triggered star formation, and take a step toward characterizing evolutionary timescales for YSOs. In this talk, I present an overview of the project and exemplify the analysis by focusing on NGC 602 in the SMC and Henize 206 in the LMC as examples. The SAGE Project is supported by NASA/Spitzer grant 1275598 and NASA NAG5-12595.

Early-type objects in NGC 6611 and the Eagle Nebula

NASA Astrophysics Data System (ADS)

Martayan, C.; Floquet, M.; Hubert, A. M.; Neiner, C.; Frémat, Y.; Baade, D.; Fabregat, J.

2008-10-01

Aims: An important question about Be stars is whether they are born as such or whether they have become Be stars during their evolution. It is necessary to observe young clusters to answer this question. Methods: To this end, observations of stars in NGC 6611 and the star-formation region of Eagle Nebula were carried out with the ESO-WFI in slitless spectroscopic mode and at the VLT-GIRAFFE (R ≃ 6400-17 000). The targets for the GIRAFFE observations were pre-selected from the literature and our catalogue of emission-line stars based on the WFI study. GIRAFFE observations allowed us to study the population of the early-type stars accurately both with and without emission lines. For this study, we determined the fundamental parameters of OBA stars thanks to the GIRFIT code. We also studied the status of the objects (main sequence or pre-main sequence stars) by using IR data, membership probabilities, and location in HR diagrams. Results: The nature of the early-type stars with emission-line stars in NGC 6611 and its surrounding environment is derived. The slitless observations with the WFI clearly indicate a small number of emission-line stars in M16. We observed with GIRAFFE 101 OBA stars, among them 9 are emission-line stars with circumstellar emission in Hα. We found that W080 could be a new He-strong star, like W601. W301 is a possible classical Be star, W503 is a mass-transfer eclipsing binary with an accretion disk, and the other ones are possible Herbig Ae/Be stars. We also found that the rotational velocities of main sequence B stars are 18% lower than those of pre-main sequence B stars, in good agreement with theory about the evolution of rotational velocities. Combining adaptive optics, IR data, spectroscopy, and radial velocity indications, we found that 27% of the B-type stars are binaries. We also redetermined the age of NGC 6611 found equal to 1.2-1.8 Myears, in good agreement with the most recent determinations.

The influence of radiative core growth on coronal X-ray emission from pre-main-sequence stars

NASA Astrophysics Data System (ADS)

Gregory, Scott G.; Adams, Fred C.; Davies, Claire L.

2016-04-01

Pre-main-sequence (PMS) stars of mass ≳0.35 M⊙ transition from hosting fully convective interiors to configurations with a radiative core and outer convective envelope during their gravitational contraction. This stellar structure change influences the external magnetic field topology and, as we demonstrate herein, affects the coronal X-ray emission as a stellar analogue of the solar tachocline develops. We have combined archival X-ray, spectroscopic, and photometric data for ˜1000 PMS stars from five of the best studied star-forming regions: the Orion Nebula Cluster, NGC 2264, IC 348, NGC 2362, and NGC 6530. Using a modern, PMS calibrated, spectral type-to-effective temperature and intrinsic colour scale, we de-redden the photometry using colours appropriate for each spectral type, and determine the stellar mass, age, and internal structure consistently for the entire sample. We find that PMS stars on Henyey tracks have, on average, lower fractional X-ray luminosities (LX/L*) than those on Hayashi tracks, where this effect is driven by changes in LX. X-ray emission decays faster with age for higher mass PMS stars. There is a strong correlation between L* and LX for Hayashi track stars but no correlation for Henyey track stars. There is no correlation between LX and radiative core mass or radius. However, the longer stars have spent with radiative cores, the less X-ray luminous they become. The decay of coronal X-ray emission from young early K to late G-type PMS stars, the progenitors of main-sequence A-type stars, is consistent with the dearth of X-ray detections of the latter.

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

The evolution of surface magnetic fields in young solar-type stars II: the early main sequence (250-650 Myr)

NASA Astrophysics Data System (ADS)

Folsom, C. P.; Bouvier, J.; Petit, P.; Lèbre, A.; Amard, L.; Palacios, A.; Morin, J.; Donati, J.-F.; Vidotto, A. A.

2018-03-01

There is a large change in surface rotation rates of sun-like stars on the pre-main sequence and early main sequence. Since these stars have dynamo-driven magnetic fields, this implies a strong evolution of their magnetic properties over this time period. The spin-down of these stars is controlled by interactions between stellar and magnetic fields, thus magnetic evolution in turn plays an important role in rotational evolution. We present here the second part of a study investigating the evolution of large-scale surface magnetic fields in this critical time period. We observed stars in open clusters and stellar associations with known ages between 120 and 650 Myr, and used spectropolarimetry and Zeeman Doppler Imaging to characterize their large-scale magnetic field strength and geometry. We report 15 stars with magnetic detections here. These stars have masses from 0.8 to 0.95 M⊙, rotation periods from 0.326 to 10.6 d, and we find large-scale magnetic field strengths from 8.5 to 195 G with a wide range of geometries. We find a clear trend towards decreasing magnetic field strength with age, and a power law decrease in magnetic field strength with Rossby number. There is some tentative evidence for saturation of the large-scale magnetic field strength at Rossby numbers below 0.1, although the saturation point is not yet well defined. Comparing to younger classical T Tauri stars, we support the hypothesis that differences in internal structure produce large differences in observed magnetic fields, however for weak-lined T Tauri stars this is less clear.

Coronal Properties of X-ray bright stars in young associations: abundances, temperatures and variability

NASA Astrophysics Data System (ADS)

Argiroffi, Costanza

2006-03-01

In this work I have investigated open issues related to the X-ray radiation from young stars, including heating mechanisms of the emitting plasma, its chemical composition, and possible effects due to circumstellar accretion disks. To this aim, I have analyzed observations of young nearby stars taken with the X-ray observatories XMM-Newton and Chandra. For a detailed study of the characteristics of the X-ray emitting plasma, I have selected two X-ray bright young stars, TWA 5 and PZ Tel, for which high-resolution X-ray spectroscopy was achievable, and two regions of the young stellar association Upper Scorpius (USco), for which X-ray images and medium-resolution spectra of individual sources were obtained. TWA 5 is a 10 Myr old star in the TW Hydrae association, which is still accreting material from its circumstellar envelope, while PZ Tel is a ? 12 Myr star in the beta Pictoris moving group, which already dissipated its circumstellar disk. The different evolutionary stages of these two stars allow to probe whether X-ray emission is produced, or affected, by accretion processes. High-resolution X-ray spectra of TWA 5 and PZ Tel were gathered with the grating spectrometers on board XMM-Newton and Chandra, respectively. From the measurements of individual emission line fluxes in their X-ray spectra, I have derived emission measure distributions vs. temperature, abundances, and electron densities of the X-ray emitting plasma. I have found that, in spite of their different evolutionary status, hot (T ? 10 MK) plasma is the main responsible for the observed X-ray emission of both stars. The hot plasma on TWA 5 displays peculiar element abundances with respect to the solar photospheric composition with Ne/Fe ? 10(Ne/Fe), while the coronal plasma on PZ Tel shows Ne/Fe ? 3(Ne/Fe). To explain the strong Fe underabundance (? 0.1 Fe) and the extremely high Ne/Fe ratio of TWA 5 I have considered three different scenarios: (1) coronal plasma may be affected by selective element depletion dependent on the first ionization potential (FIP), similar to the inverse FIP effect usually observed in the coronae of very active stars; (2) the X-ray emitting plasma on TWA 5 may be partially heated by the shock produced by the infall accretion streams onto the stellar photosphere, and hence it may originate from the circumstellar disk, where grain depletion is a possible cause of the metal deficiency; (3) the peculiar abundances on TWA 5 are due to the local chemical composition of the original cloud from which the star formed, and this explains why TWA 5 shares the same abundances with TW Hydrae, another young star located in the same stellar association. The 5 Myr old USco association, due to its vicinity (145 pc) and low circumstellar extinction, is a good laboratory to perform a detailed study of PMS stars of this age. Here I present the results of the analysis of deep XMM-Newton observations of two USco regions covering an area of ?0.4 deg^2 . I have detected 224 X-ray sources among which 22 have been identified with probable USco members on the basis of near infrared and optical photometry. Among these 22 sources, I have recognized 13 sources as USco members for the first time. Except for the intermediate mass star HD 142578, all the detected USco sources are low mass stars of spectral type ranging from G to late M, and including at least one brown dwarf. The X-ray spectral analysis of the most intense USco sources indicates metal depleted plasma with temperature of ? 10 MK, resembling the typical case of active main sequence stars, as already found for TWA 5 and PZ Tel. Strong flares detected from 4 USco members have allowed me to derive coronal lengths of the flaring structures by performing time resolved spectroscopy during the flare decay phases. In all cases the flaring loops have sizes of 10^10 - 10^11 cm, hence smaller than the corresponding stellar radii. These results suggest that, in these very young stars coronal plasma is confined in compact loops. The coronal properties of PZ Tel, TWA 5, and of the USco members indicate that the coronae of pre-main sequence stars become similar to those of older active main-sequence stars on short time scales (? 5 Myr), in terms of average temperature, density, elemental abundances, and loop lengths, even if accretion processes from circumstellar disks are still at work.

Vascular Streak Dieback of cacao in Southeast Asia and Melanesia: in planta detection of the pathogen and a new taxonomy.

PubMed

Samuels, Gary J; Ismaiel, Adnan; Rosmana, Ade; Junaid, Muhammad; Guest, David; McMahon, Peter; Keane, Philip; Purwantara, Agus; Lambert, Smilja; Rodriguez-Carres, Marianela; Cubeta, Marc A

2012-01-01

Vascular Streak Dieback (VSD) disease of cacao (Theobroma cacao) in Southeast Asia and Melanesia is caused by a basidiomycete (Ceratobasidiales) fungus Oncobasidium theobromae (syn. =Thanatephorus theobromae). The most characteristic symptoms of the disease are green-spotted leaf chlorosis or, commonly since about 2004, necrotic blotches, followed by senescence of leaves beginning on the second or third flush behind the shoot apex, and blackening of infected xylem in the vascular traces at the leaf scars resulting from the abscission of infected leaves. Eventually the shoot apex is killed and infected branches die. In susceptible cacao the fungus may grow through the xylem down into the main stem and kill a mature cacao tree. Infections in the stem of young plants prior to the formation of the first 3-4 lateral branches usually kill the plant. Basidiospores released from corticioid basidiomata developed on leaf scars or along cracks in the main vein of infected leaves infect young leaves. The pathogen commonly infects cacao but there are rare reports from avocado. As both crops are introduced to the region, the pathogen is suspected to occur asymptomatically in native vegetation. The pathogen is readily isolated but cultures cannot be maintained. In this study, DNA was extracted from pure cultures of O. theobromae obtained from infected cacao plants sampled from Indonesia. The internal transcribed spacer region (ITS), consisting of ITS1, 5.8S ribosomal RNA and ITS2, and a portion of nuclear large subunit (LSU) were sequenced. Phylogenetic analysis of ITS sequences placed O. theobromae sister to Ceratobasidium anastomosis groups AG-A, AG-Bo, and AG-K with high posterior probability. Therefore the new combination Ceratobasidium theobromae is proposed. A PCR-based protocol was developed to detect and identify C. theobromae in plant tissue of cacao enabling early detection of the pathogen in plants. A second species of Ceratobasidium, Ceratobasidium ramicola, identified through ITS sequence analysis, was isolated from VSD-affected cacao plants in Java, and is widespread in diseased cacao collected from Indonesia. Published by Elsevier Ltd.

Short Communication: Lack of Support for Socially Connected HIV-1 Transmission Among Young Adult Black Men Who Have Sex with Men.

PubMed

Fujimoto, Kayo; Coghill, Lyndon M; Weier, Christopher A; Hwang, Lu-Yu; Kim, Ju Yeong; Schneider, John A; Metzker, Michael L; Brown, Jeremy M

2017-09-01

We explore the phylogenetic relationships among HIV sequences sampled from young adult black men who have sex with men (YAB-MSM), who are connected through peer referral/social ties and who attend common venues. Using 196 viral sequences sampled from the peripheral blood mononuclear cells of 10 individuals, our preliminary phylogenetic results indicate that these socially connected YAB-MSM are infected with distantly related viruses and provide no evidence for viral transmission between network members. Our results suggest that HIV-prevention strategies that target young adult MSM should extend beyond their network members and local community.

Examining Cloud, Metallicity, and Gravity signatures in Brown Dwarfs

NASA Astrophysics Data System (ADS)

Gonzales, Eileen; Faherty, Jacqueline K.; Gagné, Jonathan; Artigau, Étienne; BDNYC

2018-01-01

The nearby solar neighborhood is littered with low mass, low temperature objects called brown dwarfs. This population of ultracool objects do not have enough mass to sustain stable hydrogen burning so they never enter the main sequence and simply cool through time. Brown dwarfs span effective temperatures in the range 250 to 3000K. They also have age dependent observable properties. Young brown dwarfs appear to have redder near infrared colors than field age sources, while old objects tend to have bluer colors. Over the past several years, the research group entitled “Brown Dwarfs in New York City” (BDNYC) has been collecting optical, near and mid-infrared spectra, as well as photometry for sources that have well defined distances. In this poster, I will compare the distance calibrated spectral energy distributions of a sample of old, young, and field age brown dwarfs of the same effective temperature. In so doing, I will discern observables linked to gravity, atmosphere, metallicity and age effects.

Red giants and yellow stragglers in the young open cluster NGC 2447

NASA Astrophysics Data System (ADS)

da Silveira, M. D.; Pereira, C. B.; Drake, N. A.

2018-06-01

In this work we analysed, using high-resolution spectroscopy, a sample of 12 single and 4 spectroscopic binary stars of the open cluster NGC 2447. For the single stars, we obtained atmospheric parameters and chemical abundances of Li, C, N, O, Na, Mg, Al, Ca, Si, Ti, Ni, Cr, Y, Zr, La, Ce, Nd, Eu. Rotational velocities were obtained for all the stars. The abundances of the light elements and Eu and the rotational velocities were derived using spectral synthesis technique. We obtained a mean metallicity of [Fe/H] = -0.17 ± 0.05. We found that the abundances of all elements are similar to field giants and/or giants of open clusters, even for the s-process elements, which are enhanced as in other young open clusters. We show that the spectroscopic binaries NGC 2447-26, 38, and 42 are yellow-straggler stars, of which the primary is a giant star and the secondary a main-sequence A-type star.

The embedded young stars in the Taurus-Auriga molecular cloud. I - Models for spectral energy distributions

NASA Technical Reports Server (NTRS)

Kenyon, Scott J.; Calvet, Nuria; Hartmann, Lee

1993-01-01

We describe radiative transfer calculations of infalling, dusty envelopes surrounding pre-main-sequence stars and use these models to derive physical properties for a sample of 21 heavily reddened young stars in the Taurus-Auriga molecular cloud. The density distributions needed to match the FIR peaks in the spectral energy distributions of these embedded sources suggest mass infall rates similar to those predicted for simple thermally supported clouds with temperatures about 10 K. Unless the dust opacities are badly in error, our models require substantial departures from spherical symmetry in the envelopes of all sources. These flattened envelopes may be produced by a combination of rotation and cavities excavated by bipolar flows. The rotating infall models of Terebey et al. (1984) models indicate a centrifugal radius of about 70 AU for many objects if rotation is the only important physical effect, and this radius is reasonably consistent with typical estimates for the sizes of circumstellar disks around T Tauri stars.

Kinematics and M(sub v) calibration of K and M dwarf stars using Hipparcos data

NASA Technical Reports Server (NTRS)

Upgren, A. R.; Ratnatunga, K. U.; Casertano, S.; Weis, E.

1997-01-01

The luminosities and kinematics of lower main sequence stars in a spectroscopically selected sample covering spectral types K 3 to M 5 are determined using Hipparcos parallaxes and proper motions. The stars separate into two kinematically distinct components, called young disk and old disk components. The young component has velocity dispersion (30, 17, 12) km/s in the U, V and W directions, respectively, and features an asymmetric drift of 8 km/s, a vertex deviation of 10 +/- 3 deg and an absolute magnitude of 10.48 mag at color (R - I)(sub Kron) = 1.0 mag. The respective features of the old component are: (56, 34, 31) km/s, 28 km/s and 0.6 mag at the same color. The slope and intrinsic width of the magnitude calibration of each component are determined. The analysis is used to investigate the possible presence of residual systematic discrepancies of the model with Hipparcos data. There are indications of a possible underestimation of the parallax errors.

A phylo-functional core of gut microbiota in healthy young Chinese cohorts across lifestyles, geography and ethnicities.

PubMed

Zhang, Jiachao; Guo, Zhuang; Xue, Zhengsheng; Sun, Zhihong; Zhang, Menghui; Wang, Lifeng; Wang, Guoyang; Wang, Fang; Xu, Jie; Cao, Hongfang; Xu, Haiyan; Lv, Qiang; Zhong, Zhi; Chen, Yongfu; Qimuge, Sudu; Menghe, Bilige; Zheng, Yi; Zhao, Liping; Chen, Wei; Zhang, Heping

2015-09-01

Structural profiling of healthy human gut microbiota across heterogeneous populations is necessary for benchmarking and characterizing the potential ecosystem services provided by particular gut symbionts for maintaining the health of their hosts. Here we performed a large structural survey of fecal microbiota in 314 healthy young adults, covering 20 rural and urban cohorts from 7 ethnic groups living in 9 provinces throughout China. Canonical analysis of unweighted UniFrac principal coordinates clustered the subjects mainly by their ethnicities/geography and less so by lifestyles. Nine predominant genera, all of which are known to contain short-chain fatty acid producers, co-occurred in all individuals and collectively represented nearly half of the total sequences. Interestingly, species-level compositional profiles within these nine genera still discriminated the subjects according to their ethnicities/geography and lifestyles. Therefore, a phylogenetically diverse core of gut microbiota at the genus level may be commonly shared by distinctive healthy populations as functionally indispensable ecosystem service providers for the hosts.

A phylo-functional core of gut microbiota in healthy young Chinese cohorts across lifestyles, geography and ethnicities

PubMed Central

Zhang, Jiachao; Guo, Zhuang; Xue, Zhengsheng; Sun, Zhihong; Zhang, Menghui; Wang, Lifeng; Wang, Guoyang; Wang, Fang; Xu, Jie; Cao, Hongfang; Xu, Haiyan; Lv, Qiang; Zhong, Zhi; Chen, Yongfu; Qimuge, Sudu; Menghe, Bilige; Zheng, Yi; Zhao, Liping; Chen, Wei; Zhang, Heping

2015-01-01

Structural profiling of healthy human gut microbiota across heterogeneous populations is necessary for benchmarking and characterizing the potential ecosystem services provided by particular gut symbionts for maintaining the health of their hosts. Here we performed a large structural survey of fecal microbiota in 314 healthy young adults, covering 20 rural and urban cohorts from 7 ethnic groups living in 9 provinces throughout China. Canonical analysis of unweighted UniFrac principal coordinates clustered the subjects mainly by their ethnicities/geography and less so by lifestyles. Nine predominant genera, all of which are known to contain short-chain fatty acid producers, co-occurred in all individuals and collectively represented nearly half of the total sequences. Interestingly, species-level compositional profiles within these nine genera still discriminated the subjects according to their ethnicities/geography and lifestyles. Therefore, a phylogenetically diverse core of gut microbiota at the genus level may be commonly shared by distinctive healthy populations as functionally indispensable ecosystem service providers for the hosts. PMID:25647347

Perceiving Goals and Actions in Individuals with Autism Spectrum Disorders

ERIC Educational Resources Information Center

Zalla, Tiziana; Labruyère, Nelly; Georgieff, Nicolas

2013-01-01

In the present study, we investigated the ability to parse familiar sequences of action into meaningful events in young individuals with autism spectrum disorders (ASDs), as compared to young individuals with typical development (TD) and young individuals with moderate mental retardation or learning disabilities (MLDs). While viewing two…

Trends of HIV-1 Subtypes Among Young People in Hangzhou, China.

PubMed

Zhang, Wenjun; Chen, Junfang; Pan, Xiaohong; Zhang, Jiafeng; Guo, Zhihong; Luo, Yan; Yang, Jiezhe; Xia, Yan; He, Lin; Xu, Yun; Xu, Ke; Ding, Xiaobei

2017-03-01

To investigate the HIV-1 molecular epidemiology among young people (18 to 25 years old) in Hangzhou. Plasma samples from 262 newly diagnosed HIV-1-infected patients were collected between 2009 and 2013 from Hangzhou of Zhejiang province. HIV-1 nucleotide sequences of pol gene regions were amplified using a nested polymerase chain reaction method and sequenced. Phylogenetic and recombination analyses were used to determine the HIV-1 genotypes. Based on all sequences generated, the subtype/circulating recombinant forms (CRFs) distribution was as follows: CRF01_AE (68.70%), CRF07_BC (21.54%), subtype B (3.66%), CRF08_BC (2.44%), 01B (2.03%), BC (0.81%), and C (0.41%). We found that the percentage of CRF07_BC was increasing year by year among young people in Hangzhou. Novel CRFs such as CRF67_01B (HZ2011-15 CD4-4516) and CRF68_01B (HZ2011-20 CD4-4530 and HZ2011-29 CD4-4087) were first discovered in the area in this study. Our study presents a molecular epidemiology investigation describing the structure of HIV-1 strains cocirculating in young people in Hangzhou. Increasing CRF07_BC and new CRFs popular in young people are a challenge for future prevention in Hangzhou.

Next Generation Sequencing and Transcriptome Analysis Predicts Biosynthetic Pathway of Sennosides from Senna (Cassia angustifolia Vahl.), a Non-Model Plant with Potent Laxative Properties.

PubMed

Rama Reddy, Nagaraja Reddy; Mehta, Rucha Harishbhai; Soni, Palak Harendrabhai; Makasana, Jayanti; Gajbhiye, Narendra Athamaram; Ponnuchamy, Manivel; Kumar, Jitendra

2015-01-01

Senna (Cassia angustifolia Vahl.) is a world's natural laxative medicinal plant. Laxative properties are due to sennosides (anthraquinone glycosides) natural products. However, little genetic information is available for this species, especially concerning the biosynthetic pathways of sennosides. We present here the transcriptome sequencing of young and mature leaf tissue of Cassia angustifolia using Illumina MiSeq platform that resulted in a total of 6.34 Gb of raw nucleotide sequence. The sequence assembly resulted in 42230 and 37174 transcripts with an average length of 1119 bp and 1467 bp for young and mature leaf, respectively. The transcripts were annotated using NCBI BLAST with 'green plant database (txid 33090)', Swiss Prot, Kyoto Encylcopedia of Genes & Genomes (KEGG), Cluster of Orthologous Gene (COG) and Gene Ontology (GO). Out of the total transcripts, 40138 (95.0%) and 36349 (97.7%) from young and mature leaf, respectively, were annotated by BLASTX against green plant database of NCBI. We used InterProscan to see protein similarity at domain level, a total of 34031 (young leaf) and 32077 (mature leaf) transcripts were annotated against the Pfam domains. All transcripts from young and mature leaf were assigned to 191 KEGG pathways. There were 166 and 159 CDS, respectively, from young and mature leaf involved in metabolism of terpenoids and polyketides. Many CDS encoding enzymes leading to biosynthesis of sennosides were identified. A total of 10,763 CDS differentially expressing in both young and mature leaf libraries of which 2,343 (21.7%) CDS were up-regulated in young compared to mature leaf. Several differentially expressed genes found functionally associated with sennoside biosynthesis. CDS encoding for many CYPs and TF families were identified having probable roles in metabolism of primary as well as secondary metabolites. We developed SSR markers for molecular breeding of senna. We have identified a set of putative genes involved in various secondary metabolite pathways, especially those related to the synthesis of sennosides which will serve as an important platform for public information about gene expression, genomics, and functional genomics in senna.

Next Generation Sequencing and Transcriptome Analysis Predicts Biosynthetic Pathway of Sennosides from Senna (Cassia angustifolia Vahl.), a Non-Model Plant with Potent Laxative Properties

PubMed Central

Rama Reddy, Nagaraja Reddy; Mehta, Rucha Harishbhai; Soni, Palak Harendrabhai; Makasana, Jayanti; Gajbhiye, Narendra Athamaram; Ponnuchamy, Manivel; Kumar, Jitendra

2015-01-01

Senna (Cassia angustifolia Vahl.) is a world’s natural laxative medicinal plant. Laxative properties are due to sennosides (anthraquinone glycosides) natural products. However, little genetic information is available for this species, especially concerning the biosynthetic pathways of sennosides. We present here the transcriptome sequencing of young and mature leaf tissue of Cassia angustifolia using Illumina MiSeq platform that resulted in a total of 6.34 Gb of raw nucleotide sequence. The sequence assembly resulted in 42230 and 37174 transcripts with an average length of 1119 bp and 1467 bp for young and mature leaf, respectively. The transcripts were annotated using NCBI BLAST with ‘green plant database (txid 33090)’, Swiss Prot, Kyoto Encylcopedia of Genes & Genomes (KEGG), Cluster of Orthologous Gene (COG) and Gene Ontology (GO). Out of the total transcripts, 40138 (95.0%) and 36349 (97.7%) from young and mature leaf, respectively, were annotated by BLASTX against green plant database of NCBI. We used InterProscan to see protein similarity at domain level, a total of 34031 (young leaf) and 32077 (mature leaf) transcripts were annotated against the Pfam domains. All transcripts from young and mature leaf were assigned to 191 KEGG pathways. There were 166 and 159 CDS, respectively, from young and mature leaf involved in metabolism of terpenoids and polyketides. Many CDS encoding enzymes leading to biosynthesis of sennosides were identified. A total of 10,763 CDS differentially expressing in both young and mature leaf libraries of which 2,343 (21.7%) CDS were up-regulated in young compared to mature leaf. Several differentially expressed genes found functionally associated with sennoside biosynthesis. CDS encoding for many CYPs and TF families were identified having probable roles in metabolism of primary as well as secondary metabolites. We developed SSR markers for molecular breeding of senna. We have identified a set of putative genes involved in various secondary metabolite pathways, especially those related to the synthesis of sennosides which will serve as an important platform for public information about gene expression, genomics, and functional genomics in senna. PMID:26098898

The population of single and binary white dwarfs of the Galactic bulge

NASA Astrophysics Data System (ADS)

Torres, S.; García-Berro, E.; Cojocaru, R.; Calamida, A.

2018-05-01

Recent Hubble Space Telescope observations have unveiled the white dwarf cooling sequence of the Galactic bulge. Although the degenerate sequence can be well fitted employing the most up-to-date theoretical cooling sequences, observations show a systematic excess of red objects that cannot be explained by the theoretical models of single carbon-oxygen white dwarfs of the appropriate masses. Here, we present a population synthesis study of the white dwarf cooling sequence of the Galactic bulge that takes into account the populations of both single white dwarfs and binary systems containing at least one white dwarf. These calculations incorporate state-of-the-art cooling sequences for white dwarfs with hydrogen-rich and hydrogen-deficient atmospheres, for both white dwarfs with carbon-oxygen and helium cores, and also take into account detailed prescriptions of the evolutionary history of binary systems. Our Monte Carlo simulator also incorporates all the known observational biases. This allows us to model with a high degree of realism the white dwarf population of the Galactic bulge. We find that the observed excess of red stars can be partially attributed to white dwarf plus main sequence binaries, and to cataclysmic variables or dwarf novae. Our best fit is obtained with a higher binary fraction and an initial mass function slope steeper than standard values, as well as with the inclusion of differential reddening and blending. Our results also show that the possible contribution of double degenerate systems or young and thick-discbulge stars is negligible.

Teaching Time Concepts to Young Children.

ERIC Educational Resources Information Center

Muir, Sharon Pray

1986-01-01

Presents many activity ideas for teaching young children about time using chronological events, clocks, and calendars. Jerome Bruner's enactive-iconic-symbolic sequence of concept development is used as a guide for these learning experiences. (LP)

The Rise and Fall of an Evolutionary Innovation: Contrasting Strategies of Venom Evolution in Ancient and Young Animals

PubMed Central

Sunagar, Kartik; Moran, Yehu

2015-01-01

Animal venoms are theorized to evolve under the significant influence of positive Darwinian selection in a chemical arms race scenario, where the evolution of venom resistance in prey and the invention of potent venom in the secreting animal exert reciprocal selection pressures. Venom research to date has mainly focused on evolutionarily younger lineages, such as snakes and cone snails, while mostly neglecting ancient clades (e.g., cnidarians, coleoids, spiders and centipedes). By examining genome, venom-gland transcriptome and sequences from the public repositories, we report the molecular evolutionary regimes of several centipede and spider toxin families, which surprisingly accumulated low-levels of sequence variations, despite their long evolutionary histories. Molecular evolutionary assessment of over 3500 nucleotide sequences from 85 toxin families spanning the breadth of the animal kingdom has unraveled a contrasting evolutionary strategy employed by ancient and evolutionarily young clades. We show that the venoms of ancient lineages remarkably evolve under the heavy constraints of negative selection, while toxin families in lineages that originated relatively recently rapidly diversify under the influence of positive selection. We propose that animal venoms mostly employ a ‘two-speed’ mode of evolution, where the major influence of diversifying selection accompanies the earlier stages of ecological specialization (e.g., diet and range expansion) in the evolutionary history of the species–the period of expansion, resulting in the rapid diversification of the venom arsenal, followed by longer periods of purifying selection that preserve the potent toxin pharmacopeia–the period of purification and fixation. However, species in the period of purification may re-enter the period of expansion upon experiencing a major shift in ecology or environment. Thus, we highlight for the first time the significant roles of purifying and episodic selections in shaping animal venoms. PMID:26492532

A Search for Pulsation in Young Brown Dwarfs and Very Low Mass Stars

NASA Astrophysics Data System (ADS)

Cody, Ann Marie

2012-05-01

In 2005, Palla and Baraffe proposed that brown dwarfs and very low mass stars (<0.1 solar masses) may be unstable to radial oscillations during the pre-main-sequence deuterium burning phase. With associated oscillation periods of 1--4 hours, this potentially new class of pulsation offers unprecedented opportunities to probe the interiors and evolution of low-mass objects in the 1--15 million year age range. Furthermore, several previous reports of short-period variability have suggested that deuterium-burning pulsation is in fact at work in young clusters. For my dissertation, I developed a photometric monitoring campaign to search for low-amplitude periodic variability in young brown dwarfs and very low mass stars using meter-class telescopes from both the ground and space. The resulting high-precision, high-cadence time-series photometry targeted four young clusters and achieved sensitivity to periodic oscillations with photometric amplitudes down to several millimagnitudes. This unprecedented variability census probed timescales ranging from minutes to weeks in a sample of 200 young, low-mass cluster members of IC 348, Sigma Orionis, Chamaeleon I, and Upper Scorpius. While I find a dearth of photometric periods under 10 hours, the campaign's high time resolution and precision have enabled detailed study of diverse light curve behavior in the clusters: rotational spot modulation, accretion signatures, and occultations by surrounding disk material. Analysis of the data has led to the establishment of a lower limit for the timescale of periodic photometric variability in young low-mass and substellar objects, an extension of the rotation period distribution to the brown dwarf regime, as well as insights into the connection between variability and circumstellar disks in the Sigma Orionis and Chamaeleon I clusters.

The Structure of Branching Onsets and Rising Diphthongs: Evidence from the Acquisition of French and Spanish

ERIC Educational Resources Information Center

Kehoe, Margaret; Hilaire-Debove, Geraldine; Demuth, Katherine; Lleo, Conxita

2008-01-01

Consonant-glide-vowel (CGV) sequences are represented differently across languages. In some languages, the CG sequence is represented as a branching onset; in other languages, the GV sequence is represented as a rising diphthong. Given variable syllabification across languages, this study examines how young children represent CGV sequences. In…

Incidental Sequence Learning across the Lifespan

ERIC Educational Resources Information Center

Weiermann, Brigitte; Meier, Beat

2012-01-01

The purpose of the present study was to investigate incidental sequence learning across the lifespan. We tested 50 children (aged 7-16), 50 young adults (aged 20-30), and 50 older adults (aged >65) with a sequence learning paradigm that involved both a task and a response sequence. After several blocks of practice, all age groups slowed down…

PEERING INTO THE GIANT-PLANET-FORMING REGION OF THE TW HYDRAE DISK WITH THE GEMINI PLANET IMAGER

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

Rapson, Valerie A.; Kastner, Joel H.; Millar-Blanchaer, Maxwell A.

2015-12-20

We present Gemini Planet Imager (GPI) adaptive optics near-infrared images of the giant-planet-forming regions of the protoplanetary disk orbiting the nearby (D = 54 pc), pre-main-sequence (classical T Tauri) star TW Hydrae. The GPI images, which were obtained in coronagraphic/polarimetric mode, exploit starlight scattered off small dust grains to elucidate the surface density structure of the TW Hya disk from ∼80 AU to within ∼10 AU of the star at ∼1.5 AU resolution. The GPI polarized intensity images unambiguously confirm the presence of a gap in the radial surface brightness distribution of the inner disk. The gap is centered near ∼23 AU,more » with a width of ∼5 AU and a depth of ∼50%. In the context of recent simulations of giant-planet formation in gaseous, dusty disks orbiting pre-main-sequence stars, these results indicate that at least one young planet with a mass ∼0.2 M{sub J} could be present in the TW Hya disk at an orbital semimajor axis similar to that of Uranus. If this (proto)planet is actively accreting gas from the disk, it may be readily detectable by GPI or a similarly sensitive, high-resolution infrared imaging system.« less

Rosat detections of X-ray emission from young B-type stars

NASA Technical Reports Server (NTRS)

Schmitt, J. H. M. M.; Zinnecker, H.; Cruddace, R.; Harnden, F. R., Jr.

1993-01-01

We present first results of a series of pointings of the Rosat HRI at visual binaries consisting of a B-star with a later-type companion. The binaries selected for this study are very likely physical pairs. Dating of the B-type stars with respect to the zero-age main sequence, as well as spectroscopic observations of the late-type stars, provides evidence for the extreme youth of these systems with ages typically near or below 10 exp 8 yr. Surprisingly, the late-B component was in many cases detected as an X-ray source, in contrast to previous findings that X-ray emission among late-B field stars is rather uncommon.

[Spanish normative studies in a young adult population (NEURONORMA young adults Project): norms for the verbal span, visuospatial span, Letter-Number Sequencing, Trail Making Test and Symbol Digit Modalities Test].

PubMed

Tamayo, F; Casals-Coll, M; Sánchez-Benavides, G; Quintana, M; Manero, R M; Rognoni, T; Calvo, L; Palomo, R; Aranciva, F; Peña-Casanova, J

2012-01-01

Verbal and visuospatial span, Letter-Number Sequencing, Trail Making Test, and Symbol Digit Modalities Test are frequently used in clinical practice to assess attention, executive functions and memory. In the present study, as part of the Spanish normative studies of NEURONORMA young adults Project, normative data adjusted by age and education are provided for digits, Corsi Block-Tapping Task, Letter-Number Sequencing, Trail Making Test, and Symbol Digit Modalities Test. The sample consisted of 179 participants from 18 to 49 years old, who were cognitively normal. Tables to convert raw scores to scaled scores are provided. Age and education adjusted scores are provided by applying linear regressions. Education affected scores in most of the attention tests; age was found to be related to the visuospatial span and to speed of visuomotor tracking, and there was no relationship as regards sex. The data obtained will be useful in the clinical evaluation of young Spanish adults. Copyright © 2011 Sociedad Española de Neurología. Published by Elsevier Espana. All rights reserved.

Physical Activity Is Associated with Reduced Implicit Learning but Enhanced Relational Memory and Executive Functioning in Young Adults

PubMed Central

Watt, Jennifer C.; Grove, George A.; Wollam, Mariegold E.; Uyar, Fatma; Mataro, Maria; Cohen, Neal J.; Howard, Darlene V.; Howard, James H.; Erickson, Kirk I.

2016-01-01

Accumulating evidence suggests that physical activity improves explicit memory and executive cognitive functioning at the extreme ends of the lifespan (i.e., in older adults and children). However, it is unknown whether these associations hold for younger adults who are considered to be in their cognitive prime, or for implicit cognitive functions that do not depend on motor sequencing. Here we report the results of a study in which we examine the relationship between objectively measured physical activity and (1) explicit relational memory, (2) executive control, and (3) implicit probabilistic sequence learning in a sample of healthy, college-aged adults. The main finding was that physical activity was positively associated with explicit relational memory and executive control (replicating previous research), but negatively associated with implicit learning, particularly in females. These results raise the intriguing possibility that physical activity upregulates some cognitive processes, but downregulates others. Possible implications of this pattern of results for physical health and health habits are discussed. PMID:27584059

One-year retention of general and sequence-specific skills in a probabilistic, serial reaction time task.

PubMed

Romano, Jennifer C; Howard, James H; Howard, Darlene V

2010-05-01

Procedural skills such as riding a bicycle and playing a musical instrument play a central role in daily life. Such skills are learned gradually and are retained throughout life. The present study investigated 1-year retention of procedural skill in a version of the widely used serial reaction time task (SRTT) in young and older motor-skill experts and older controls in two experiments. The young experts were college-age piano and action video-game players, and the older experts were piano players. Previous studies have reported sequence-specific skill retention in the SRTT as long as 2 weeks but not at 1 year. Results indicated that both young and older experts and older non-experts revealed sequence-specific skill retention after 1 year with some evidence that general motor skill was retained as well. These findings are consistent with theoretical accounts of procedural skill learning such as the procedural reinstatement theory as well as with previous studies of retention of other motor skills.

SOAR Adaptive Optics Observations of Young Stellar Objects

NASA Astrophysics Data System (ADS)

Briceno, Cesar

2018-01-01

I present results from recent studies of nearby star-forming regions using the SOAR 4.1m telescope Ground-layer Adaptive Optics system.Using narrow-band Hα and [SII] imaging we discovered a spectacular extended Herbig-Haro jet powered by a 26 MJup young brown dwarf located in the vicinity of the σ Orionis cluster. The collimated structure of multiple knots spans 0.26 pc, making it a scaled down version of the parsec-length jets seen in T Tauri stars, and the first substellar analog of an HH jet system.In the ε Chamaeleon stellar group we carried out an Adaptive Optics-aided speckle imaging study of 47 members and candidate members, to characterize the multiplicity of this, one of the nearest groups of young (~3-5 Myr) stars. We resolved 10 new binary pairs, 5 previously know binaries and two triple systems. We find a companion frequency of 0.010±0.04 per decade of separation, in the 4 to 300 AU separation range, a result comparable to main sequence dwarfs in the field. However, the more massive association members, with B and A spectral types, all have companions in this separation range. Finally, we provide new constraints on the orbital elements of the ε Cha triple system.

Disks and Outflows Around Young Stars

NASA Astrophysics Data System (ADS)

Beckwith, Steven; Staude, Jakob; Quetz, Axel; Natta, Antonella

The subject of the book, the ubiquitous circumstellar disks around very young stars and the corresponding jets of outflowing matter, has recently become one of the hottest areas in astrophysics. The disks are thought to be precursors to planetary systems, and the outflows are thought to be a necessary phase in the formation of a young star, helping the star to get rid of angular momentum and energy as it makes its way onto the main sequence. The possible connections to planetary systems and stellar astrophysics makes these topics especially broad, appealing to generalists and specialists alike. The CD not only contains papers that could not be printed in the book but allows the authors to include a fair amount of data, often displayed as color images. The CD-ROM contains all the contributions printed in the corresponding book (Lecture Notes in Physics Vol. 465) and, in addition, those presented exclusively in digital form. Each contribution consists of a file in portable document format (PDF). The electronic version allows full-text searching within each file using Adobe's Acrobat Reader providing instructions for installation on Unix (Sun), PC and Macintosh computers, respectively. All contributions can be printed out; the color diagrams and color frames, which are printed in black and white in the book, can be viewed in color on screen.

Bidirectional Effects of Mother-Young Contact on the Maternal and Neonatal Brains.

PubMed

González-Mariscal, Gabriela; Melo, Angel I

2017-01-01

Adaptive plasticity occurs intensely during the early postnatal period through processes like proliferation, migration, differentiation, synaptogenesis, myelination and apoptosis. Exposure to particular stimuli during this critical period has long-lasting effects on cognition, stress reactivity and behavior. Maternal care is the main source of social, sensory and chemical stimulation to the young and is, therefore, critical to "fine-tune" the offspring's neural development. Mothers providing a low quantity or quality of stimulation produce offspring that will exhibit reduced cognitive performance, impaired social affiliation and increased agonistic behaviors. Transgenerational transmission of such traits occurs epigenetically, i.e., through mechanisms like DNA methylation and post-translational modification of nucleosomal histones, processes that silence or increase gene expression without affecting the DNA sequence. Reciprocally, providing maternal care profoundly affects the behavior, learning, memory and fine neuroanatomy of the adult female. Such effects are in many cases permanent and sometimes they involve the hormones of pregnancy and lactation. The above evidence supports the idea that the mother-young dyad exerts profound and permanent effects on the brains of both adult and developing organisms, respectively. Effects on the latter can be explained by the neural developmental processes taking place during the early postnatal period. In contrast, little is known about the mechanisms mediating the plasticity of the adult maternal brain. The bidirectional effects that mother and young exert on each other's brains exemplify a remarkable plasticity of this organ for organizing itself and provide an immense source of variability for adaptation and evolution in mammals.

Gyrochronology of Low-mass Stars - Age-Rotation-Activity Relations for Young M Dwarfs

NASA Astrophysics Data System (ADS)

Kidder, Benjamin; Shkolnik, E.; Skiff, B.

2014-01-01

New rotation periods for 34 young <300 Myr), early-M dwarfs within 25 parsecs were measured using photometric data collected with telescopes at Lowell Observatory during 2012 and 2013. An additional 25 rotation periods for members of the same sample were found in the literature. Ages were derived from Hα and X-ray emission, lithium absorption, surface gravity, and kinematic association of members of known young moving groups (YMGs). We compared rotation periods with the estimated ages as well as indicators of magnetic activity, with the intention of strengthening age-rotation-activity relations and assessing the possible use of gyrochronology in young, low-mass stars. We compared ages and rotation periods of our target stars to cluster members spanning 1-600 Myr. Rotation periods at every age exhibit a large scatter, with values typically ranging from 0.2 to 15 days. This suggests that gyrochronology for individual field stars will not be possible without a better understanding of the underlying mechanisms that govern angular momentum evolution. Yet, on average, the data still support the predicted trends for spin-up during contraction and spin-down on the main sequence, with the turnover occurring at around 150 Myr for early Ms. This suggests that rotation period distributions can be helpful in evaluating the ages of coeval groups of stars. Many thanks to the National Science Foundation for their support through the Research Experience for Undergraduates Grant AST- 1004107.

Information Topics of Greatest Interest for Return of Genome Sequencing Results among Women Diagnosed with Breast Cancer at a Young Age.

PubMed

Seo, Joann; Ivanovich, Jennifer; Goodman, Melody S; Biesecker, Barbara B; Kaphingst, Kimberly A

2017-06-01

We investigated what information women diagnosed with breast cancer at a young age would want to learn when genome sequencing results are returned. We conducted 60 semi-structured interviews with women diagnosed with breast cancer at age 40 or younger. We examined what specific information participants would want to learn across result types and for each type of result, as well as how much information they would want. Genome sequencing was not offered to participants as part of the study. Two coders independently coded interview transcripts; analysis was conducted using NVivo10. Across result types, participants wanted to learn about health implications, risk and prevalence in quantitative terms, causes of variants, and causes of diseases. Participants wanted to learn actionable information for variants affecting risk of preventable or treatable disease, medication response, and carrier status. The amount of desired information differed for variants affecting risk of unpreventable or untreatable disease, with uncertain significance, and not health-related. Women diagnosed with breast cancer at a young age recognize the value of genome sequencing results in identifying potential causes and effective treatments and expressed interest in using the information to help relatives and to further understand their other health risks. Our findings can inform the development of effective feedback strategies for genome sequencing that meet patients' information needs and preferences.

Theory of Bipolar Outflows from Accreting Hot Stars

NASA Astrophysics Data System (ADS)

Konigl, A.

1996-05-01

There is a growing number of observational indicators for the presence of bipolar outflows in massive, young stellar objects that are still accreting mass as part of their formation process. In particular, there is evidence that the outflows from these objects can attain higher velocities and kinetic luminosities than their lower-mass counterparts. Furthermore, the higher-mass objects appear to smoothly continue the correlation found in T Tauri stars between outflow and accretion signatures, and in several cases there are direct clues to the existence of a disk from optical and infrared spectroscopy. These results suggest that the disk--outflow connection found in low-mass pre--main-sequence stars extends to more massive objects, and that a similar physical mechanism may drive the outflows in both cases. In this presentation, I first critically examine the observational basis for this hypothesis, considering, among other things, the possibility that several low-luminosity outflows might occasionally masquerade as a single flow from a luminous object, and the effects that the radiation field of a hot star could have on the spectroscopic diagnostics of an accretion-driven outflow. I then go on to consider how the commonly invoked centrifugally driven wind models of bipolar outflows in low-mass stars would be affected by the various physical processes (such as photoionization, photoevaporation, radiation pressure, and stellar wind ram pressure) that operate in higher-mass stars. I conclude by mentioning some of the tantalizing questions that one could hope to address as this young field of research continues to develop (for example: is there a high-mass analog of the FU Orionis outburst phenomenon? Could one use observations of progressively more massive, and hence less convective, stars to elucidate the role of stellar magnetic fields in the accretion and outflow processes? Would it be possible to observationally identify massive stars that have reached the main sequence while they were still accreting? Does the evolution of protostellar disks differ in low-mass and high-mass objects?).

Time-series Photometry of the Pre-Main Sequence Binary V4046 Sgr: Testing the Accretion Stream Theory

NASA Astrophysics Data System (ADS)

Tofflemire, Benjamin M.; Mathieu, Robert D.; Ardila, David R.; Ciardi, David R.

2015-01-01

Most stars are born in binaries, and the evolution of protostellar disks in pre-main sequence (PMS) binary stars is a current frontier of star formation research. PMS binary stars can have up to three accretion disks: two circumstellar disks and a circumbinary disk separated by a dynamically cleared gap. Theory suggests that mass may periodically flow in an accretion stream from a circumbinary disk across the gap onto circumstellar disks or stellar surfaces. Thus, accretion in PMS binaries is controlled by not only radiation, disk viscosity, and magnetic fields, but also by orbital dynamics.As part of a larger, ongoing effort to characterize mass accretion in young binary systems, we test the predictions of the binary accretion stream theory through continuous, multi-orbit, multi-color optical and near-infrared (NIR) time-series photometry. Observations such as these are capable of detecting and characterizing these modulated accretion streams, if they are generally present. Broad-band blue and ultraviolet photometry trace the accretion luminosity and photospheric temperature while NIR photometry provide a measurement of warm circumstellar material, all as a function of orbital phase. The predicted phase and magnitude of enhanced accretion are highly dependent on the binary orbital parameters and as such, our campaign focuses on 10 PMS binaries of varying periods and eccentricities. Here we present multi-color optical (U, B,V, R), narrowband (Hα), and multi-color NIR (J, H) lightcurves of the PMS binary V4046 Sgr (P=2.42 days) obtained with the SMARTS 1.3m telescope and LCOGT 1m telescope network. These results act to showcase the quality and breadth of data we have, or are currently obtaining, for each of the PMS binaries in our sample. With the full characterization of our sample, these observations will guide an extension of the accretion paradigm from single young stars to multiple systems.

No large population of unbound or wide-orbit Jupiter-mass planets.

PubMed

Mróz, Przemek; Udalski, Andrzej; Skowron, Jan; Poleski, Radosław; Kozłowski, Szymon; Szymański, Michał K; Soszyński, Igor; Wyrzykowski, Łukasz; Pietrukowicz, Paweł; Ulaczyk, Krzysztof; Skowron, Dorota; Pawlak, Michał

2017-08-10

Planet formation theories predict that some planets may be ejected from their parent systems as result of dynamical interactions and other processes. Unbound planets can also be formed through gravitational collapse, in a way similar to that in which stars form. A handful of free-floating planetary-mass objects have been discovered by infrared surveys of young stellar clusters and star-forming regions as well as wide-field surveys, but these studies are incomplete for objects below five Jupiter masses. Gravitational microlensing is the only method capable of exploring the entire population of free-floating planets down to Mars-mass objects, because the microlensing signal does not depend on the brightness of the lensing object. A characteristic timescale of microlensing events depends on the mass of the lens: the less massive the lens, the shorter the microlensing event. A previous analysis of 474 microlensing events found an excess of ten very short events (1-2 days)-more than known stellar populations would suggest-indicating the existence of a large population of unbound or wide-orbit Jupiter-mass planets (reported to be almost twice as common as main-sequence stars). These results, however, do not match predictions of planet-formation theories and surveys of young clusters. Here we analyse a sample of microlensing events six times larger than that of ref. 11 discovered during the years 2010-15. Although our survey has very high sensitivity (detection efficiency) to short-timescale (1-2 days) microlensing events, we found no excess of events with timescales in this range, with a 95 per cent upper limit on the frequency of Jupiter-mass free-floating or wide-orbit planets of 0.25 planets per main-sequence star. We detected a few possible ultrashort-timescale events (with timescales of less than half a day), which may indicate the existence of Earth-mass and super-Earth-mass free-floating planets, as predicted by planet-formation theories.

From Kissing to Coitus? Sex-of-Partner Differences in the Sexual Milestone Achievement of Young Men

ERIC Educational Resources Information Center

Smiler, Andrew P.; Frankel, Loren B. W.; Savin-Williams, Ritch C.

2011-01-01

Scientific information regarding normative patterns of young men's sexual behavior is insufficient, especially regarding the impact of sex of partner. We explored the age at which 255 young adult men achieved several milestones (e.g., first kiss, manual-genital contact, intercourse) as well as the sequence of milestone achievement and stability in…

Cognitive performance of young and elderly subjects on the free word recall memory test: effect of presentation order on recall order.

PubMed

Santos-Galduróz, R F; Oliveira, F G; Galduróz, J C F; Bueno, O F A

2009-10-01

The influence of aging on memory has been extensively studied, but the importance of short-term memory and recall sequence has not. The objective of the current study was to examine the recall order of words presented on lists and to determine if age affects recall sequence. Physically and psychologically healthy male subjects were divided into two groups according to age, i.e., 23 young subjects (20 to 30 years) and 50 elderly subjects (60 to 70 years) submitted to the Wechsler Adult Intelligence Scale-Revised and the free word recall test. The order of word presentation significantly affected the 3rd and 4th words recalled (P < 0.01; F = 14.6). In addition, there was interaction between the presentation order and the type of list presented (P < 0.05; F = 9.7). Also, both groups recalled the last words presented from each list (words 13-15) significantly more times 3rd and 4th than words presented in all remaining positions (P < 0.01). The order of word presentation also significantly affected the 5th and 6th words recalled (P = 0.05; F = 7.5) and there was a significant interaction between the order of presentation and the type of list presented (P < 0.01; F = 20.8). The more developed the cognitive functions, resulting mainly from formal education, the greater the cognitive reserve, helping to minimize the effects of aging on the long-term memory (episodic declarative).

Genetic Testing of Maturity-Onset Diabetes of the Young Current Status and Future Perspectives

PubMed Central

Firdous, Parveena; Nissar, Kamran; Ali, Sajad; Ganai, Bashir Ahmad; Shabir, Uzma; Hassan, Toyeeba; Masoodi, Shariq Rashid

2018-01-01

Diabetes is a global epidemic problem growing exponentially in Asian countries posing a serious threat. Among diabetes, maturity-onset diabetes of the young (MODY) is a heterogeneous group of monogenic disorders that occurs due to β cell dysfunction. Genetic defects in the pancreatic β-cells result in the decrease of insulin production required for glucose utilization thereby lead to early-onset diabetes (often <25 years). It is generally considered as non-insulin dependent form of diabetes and comprises of 1–5% of total diabetes. Till date, 14 genes have been identified and mutation in them may lead to MODY. Different genetic testing methodologies like linkage analysis, restriction fragment length polymorphism, and DNA sequencing are used for the accurate and correct investigation of gene mutations associated with MODY. The next-generation sequencing has emerged as one of the most promising and effective tools to identify novel mutated genes related to MODY. Diagnosis of MODY is mainly relying on the sequential screening of the three marker genes like hepatocyte nuclear factor 1 alpha (HNF1α), hepatocyte nuclear factor 4 alpha (HNF4α), and glucokinase (GCK). Interestingly, MODY patients can be managed by diet alone for many years and may also require minimal doses of sulfonylureas. The primary objective of this article is to provide a review on current status of MODY, its prevalence, genetic testing/diagnosis, possible treatment, and future perspective. PMID:29867778

Visual Prediction in Infancy: What Is the Association with Later Vocabulary?

ERIC Educational Resources Information Center

Ellis, Erica M.; Gonzalez, Marybel Robledo; Deák, Gedeon O.

2014-01-01

Young infants can learn statistical regularities and patterns in sequences of events. Studies have demonstrated a relationship between early sequence learning skills and later development of cognitive and language skills. We investigated the relation between infants' visual response speed to novel event sequences, and their later receptive and…

Implications of diverse fault orientations imaged in relocated aftershocks of the Mount Lewis, ML 5.7, California, earthquake

NASA Astrophysics Data System (ADS)

Kilb, D.; Rubin, A. M.

2002-11-01

We use seismic waveform cross correlation to determine the relative positions of 2747 microearthquakes near Mount Lewis, California, that have waveforms recorded from 1984 to 1999. These earthquakes include the aftershock sequence of the 1986 ML5.7 Mount Lewis earthquake. Approximately 90% of these aftershocks are located beyond the tips of the approximately north striking main shock, defining an hourglass with the long axis aligned approximately with the main shock. Surprisingly, our relocation demonstrates that many of these aftershocks illuminate a series of near-vertical east-west faults that are ˜0.5-1 km long and separated by as little as ˜200 m. We propose that these structures result from the growth of a relatively young fault in which displacement across a right-lateral approximately north striking fault zone is accommodated by slip on secondary left-lateral approximately east striking faults. We derive the main shock-induced static Coulomb failure function (Δσf) on the dominant fault orientation in our study area using a three-dimensional (3-D) boundary element program. To bound viable friction coefficients, we measure the correlation between the rank ordering of relative amplitudes of Δσf and seismicity rate change. We find that likely friction coefficients are 0.2-0.6 and that the assumed main shock geometry introduces the largest uncertainties in the favored friction values. We obtain similar results from a visual correlation of calculated Δσf contours with the distribution of aftershocks. Viable rate-and-state constitutive parameters bound the observed relationship between magnitude of Δσf and seismicity rate change, and for our favored main shock model a maximum correlation is achieved when Δσf is computed with friction coefficients of 0.3-0.6. These values are below those previously cited for young faults.

Effective Temperatures for Young Stars in Binaries

NASA Astrophysics Data System (ADS)

Muzzio, Ryan; Avilez, Ian; Prato, Lisa A.; Biddle, Lauren I.; Allen, Thomas; Wright-Garba, Nuria Meilani Laure; Wittal, Matthew

2017-01-01

We have observed about 100 multi-star systems, within the star forming regions Taurus and Ophiuchus, to investigate the individual stellar and circumstellar properties of both components in young T Tauri binaries. Near-infrared spectra were collected using the Keck II telescope’s NIRSPEC spectrograph and imaging data were taken with Keck II’s NIRC2 camera, both behind adaptive optics. Some properties are straightforward to measure; however, determining effective temperature is challenging as the standard method of estimating spectral type and relating spectral type to effective temperature can be subjective and unreliable. We explicitly looked for a relationship between effective temperatures empirically determined in Mann et al. (2015) and equivalent width ratios of H-band Fe and OH lines for main sequence spectral type templates common to both our infrared observations and to the sample of Mann et al. We find a fit for a wide range of temperatures and are currently testing the validity of using this method as a way to determine effective temperature robustly. Support for this research was provided by an REU supplement to NSF award AST-1313399.

Exposure to Gambling Advertisements and Gambling Behavior in Young People.

PubMed

Clemens, Franziska; Hanewinkel, Reiner; Morgenstern, Matthis

2017-03-01

A cross-sectional survey of 4617 adolescents and young adults from 38 schools in two German states was conducted in 2014 to assess the association between gambling advertisements and gambling behavior. Exposure to ten gambling advertisements was measured with masked ad images; students indicated contact frequency and brand recall. Main outcomes were several gambling behaviors including probable pathological gambling assessed with the South Oaks Gambling Screen (SOGS ≥ 5). A total of 65.4 % of the students reported gambling at least once in their life; 42.2 % gambled in the last 12 months; 6.9 % gambled in the last week, and 2.8 % reported probable pathological gambling. The average frequency that one of the selected ads had been seen at least once was 29.5 %, the average brand recall rate was 9.4 %. After adjustment for confounding, multilevel mixed-effects logistic regressions revealed that high gambling ad exposure was positively related to all assessed gambling outcomes, with the strongest association for weekly gambling. Future studies need to clarify the temporal sequence and specificity of these associations.

IN-SYNC. II. Virial Stars from Subvirial Cores—the Velocity Dispersion of Embedded Pre-main-sequence Stars in NGC 1333

NASA Astrophysics Data System (ADS)

Foster, Jonathan B.; Cottaar, Michiel; Covey, Kevin R.; Arce, Héctor G.; Meyer, Michael R.; Nidever, David L.; Stassun, Keivan G.; Tan, Jonathan C.; Chojnowski, S. Drew; da Rio, Nicola; Flaherty, Kevin M.; Rebull, Luisa; Frinchaboy, Peter M.; Majewski, Steven R.; Skrutskie, Michael; Wilson, John C.; Zasowski, Gail

2015-02-01

The initial velocity dispersion of newborn stars is a major unconstrained aspect of star formation theory. Using near-infrared spectra obtained with the APOGEE spectrograph, we show that the velocity dispersion of young (1-2 Myr) stars in NGC 1333 is 0.92 ± 0.12 km s-1 after correcting for measurement uncertainties and the effect of binaries. This velocity dispersion is consistent with the virial velocity of the region and the diffuse gas velocity dispersion, but significantly larger than the velocity dispersion of the dense, star-forming cores, which have a subvirial velocity dispersion of 0.5 km s-1. Since the NGC 1333 cluster is dynamically young and deeply embedded, this measurement provides a strong constraint on the initial velocity dispersion of newly formed stars. We propose that the difference in velocity dispersion between stars and dense cores may be due to the influence of a 70 μG magnetic field acting on the dense cores or be the signature of a cluster with initial substructure undergoing global collapse.

New Parallaxes for the Upper Scorpius OB Association

NASA Astrophysics Data System (ADS)

Donaldson, J. K.; Weinberger, A. J.; Gagné, J.; Boss, A. P.; Keiser, S. A.

2017-11-01

Upper Scorpius is a subgroup of the nearest OB association, Scorpius-Centaurus. Its young age makes it an important association to study star and planet formation. We present parallaxes to 52 low-mass stars in Upper Scorpius, 28 of which have full kinematics. We measure ages of the individual stars by combining our measured parallaxes with pre-main-sequence evolutionary tracks. We find a significant difference in the ages of stars with and without circumstellar disks. The stars without disks have a mean age of 4.9 ± 0.8 Myr and those with disks have an older mean age of 8.2 ± 0.9 Myr. This somewhat counterintuitive result suggests that evolutionary effects in young stars can dominate their apparent ages. We also attempt to use the 28 stars with full kinematics (I.e., proper motion, radial velocity (RV), and parallax) to trace the stars back in time to their original birthplace to obtain a trackback age. As expected, given the large measurement uncertainties on available RV measurements, we find that measurement uncertainties alone cause the group to diverge after a few Myr.

The VMC Survey. XXIX. Turbulence-controlled Hierarchical Star Formation in the Small Magellanic Cloud

NASA Astrophysics Data System (ADS)

Sun, Ning-Chen; de Grijs, Richard; Cioni, Maria-Rosa L.; Rubele, Stefano; Subramanian, Smitha; van Loon, Jacco Th.; Bekki, Kenji; Bell, Cameron P. M.; Ivanov, Valentin D.; Marconi, Marcella; Muraveva, Tatiana; Oliveira, Joana M.; Ripepi, Vincenzo

2018-05-01

In this paper we report a clustering analysis of upper main-sequence stars in the Small Magellanic Cloud, using data from the VMC survey (the VISTA near-infrared YJK s survey of the Magellanic system). Young stellar structures are identified as surface overdensities on a range of significance levels. They are found to be organized in a hierarchical pattern, such that larger structures at lower significance levels contain smaller ones at higher significance levels. They have very irregular morphologies, with a perimeter–area dimension of 1.44 ± 0.02 for their projected boundaries. They have a power-law mass–size relation, power-law size/mass distributions, and a log-normal surface density distribution. We derive a projected fractal dimension of 1.48 ± 0.03 from the mass–size relation, or of 1.4 ± 0.1 from the size distribution, reflecting significant lumpiness of the young stellar structures. These properties are remarkably similar to those of a turbulent interstellar medium, supporting a scenario of hierarchical star formation regulated by supersonic turbulence.

Orbital Monitoring of the AstraLux Large M-dwarf Multiplicity Sample

NASA Astrophysics Data System (ADS)

Janson, Markus; Bergfors, Carolina; Brandner, Wolfgang; Bonnefoy, Mickaël; Schlieder, Joshua; Köhler, Rainer; Hormuth, Felix; Henning, Thomas; Hippler, Stefan

2014-10-01

Orbital monitoring of M-type binaries is essential for constraining their fundamental properties. This is particularly useful in young systems, where the extended pre-main-sequence evolution can allow for precise isochronal dating. Here, we present the continued astrometric monitoring of the more than 200 binaries of the AstraLux Large Multiplicity Survey, building both on our previous work, archival data, and new astrometric data spanning the range of 2010-2012. The sample is very young overall—all included stars have known X-ray emission, and a significant fraction (18%) of them have recently also been identified as members of young moving groups in the solar neighborhood. We identify ~30 targets that both have indications of being young and for which an orbit either has been closed or appears possible to close in a reasonable time frame (a few years to a few decades). One of these cases, GJ 4326, is, however, identified as probably being substantially older than has been implied from its apparent moving group membership, based on astrometric and isochronal arguments. With further astrometric monitoring, these targets will provide a set of empirical isochrones, against which theoretical isochrones can be calibrated, and which can be used to evaluate the precise ages of nearby young moving groups. Based on observations collected at the European Southern Observatory, Chile, under observing programs 081.C-0314(A), 082.C-0053(A), and 084.C-0812(A), and on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institute for Astronomy and the Instituto de Astrofísica de Andalucía (CSIC).

What are specialist mental health clinician attitudes to guideline recommendations for the treatment of depression in young people?

PubMed

Hetrick, Sarah E; Simmons, Magenta; Thompson, Andrew; Parker, Alexandra G

2011-11-01

We sought to examine potential barriers to the use of evidence-based guidelines for youth depression in a tertiary specialist mental health service, as part of an initiative to implement evidence based practice within the service. This was a qualitative study adopting a social constructionist perspective using focus groups. The focus groups, conducted with all clinicians (medical and allied health), were audiotaped, transcribed and thematic analysis was undertaken. Clinicians were asked about the barriers to implementing four key recommendations from the National Institute for Health and Clinical Excellence (NICE) guidelines. Barriers existed at (i) the individual clinician level; (ii) the clinical level in terms of the presentation of young people; and (iii) the service level. The key individual clinician level barrier was a stated belief that the guidelines were not relevant to the young people presenting to the service, with little evidence to guide practice. Related, the main barrier with regard to the clinical presentation was the severity and complexity of this presentation, often making the delivery of interventions like cognitive behavioural therapy (CBT) difficult. At the service level, a lack of integration with primary and secondary level care meant sequencing interventions according to guideline recommendations was difficult. There is a clear imperative to develop the evidence base to ensure that effective treatments for young people aged up to 25 years with severe and complex disorders that include comorbid conditions, suicide risk and psychosocial difficulties are investigated and disseminated. Furthermore, this work has highlighted the need for greater investment in models of care that ensure integration between existing primary and secondary care and enhanced specialist early intervention mental health services for young people.

VizieR Online Data Catalog: Structure of young stellar clusters. II. (Kuhn+, 2015)

NASA Astrophysics Data System (ADS)

Kuhn, M. A.; Getman, K. V.; Feigelson, E. D.

2015-07-01

We investigate the intrinsic stellar populations (estimated total numbers of OB and pre-main-sequence stars down to 0.1Mȯ) that are present in 17 massive star-forming regions (MSFRs) surveyed by the MYStIX project. The study is based on the catalog of >31000 MYStIX Probable Complex Members with both disk-bearing and disk-free populations, compensating for extinction, nebulosity, and crowding effects. Correction for observational sensitivities is made using the X-ray luminosity function and the near-infrared initial mass function --a correction that is often not made by infrared surveys of young stars. The resulting maps of the projected structure of the young stellar populations, in units of intrinsic stellar surface density, allow direct comparison between different regions. Several regions have multiple dense clumps, similar in size and density to the Orion Nebula Cluster. The highest projected density of ~34000 stars/pc2 is found in the core of the RCW 38 cluster. Histograms of surface density show different ranges of values in different regions, supporting the conclusion of Bressert et al. (B10; 2010MNRAS.409L..54B) that no universal surface-density threshold can distinguish between clustered and distributed star formation. However, a large component of the young stellar population of MSFRs resides in dense environments of 200-10000 stars/pc2 (including within the nearby Orion molecular clouds), and we find that there is no evidence for the B10 conclusion that such dense regions form an extreme "tail" of the distribution. Tables of intrinsic populations for these regions are used in our companion study of young cluster properties and evolution. (3 data files).

High Contrast X-ray Flares In The Anchors Database

NASA Astrophysics Data System (ADS)

McCleary, Jacqueline; Wolk, S.

2010-01-01

The X-ray light curves of pre-main sequence stars can show variability in the form of flares altering a baseline characteristic activity level; the largest X-ray flares are characterized by a rapid rise to 10 or more times the characteristic count rate, followed by a slower quasi-exponential decay. Analysis of these high-contrast X-ray flares enables the study of the innermost magnetic fields of pre-main sequence stars. We have scanned the ANCHORS database of Chandra observations of star-forming regions to extend the study of flare events on pre-main sequence stars both in sky coverage and in volume. We developed a sample of 30 high-contrast flares out of the 14,000 stars available in ANCHORS at the time of our study. By not biasing our sample by cluster, age, or spectral type, we increased the number of X-ray flare events studied and subsequently the strength of any statements about their properties. Applying the generally accepted methods of time-resolved spectral analysis developed by Reale et al. (1997), we measured the temperatures, confining magnetic field strengths, and loop lengths of these large flares. The results of the flare analysis were compared to the 2MASS and Spitzer data available for the stars in our sample. We found that the longest flare loop lengths (of order several stellar radii) are only seen on stars whose IR data indicates the presence of disks, which suggests that the longest flares may stretch all the way to the disk. Such long flares tend to be more tenuous (rarified) than the other large flares studied. A wide range of loop lengths were observed, indicating that two types of flares may occur on disked young stellar objects: either compact and analogous to flares on evolved stars, or long and the result of star-disk magnetic connections.

The search for extra-solar planetary systems.

PubMed

Paresce, F

1992-01-01

I review the observational evidence for planetary systems around nearby stars and, using our own solar system as a guide, assess the stringent requirements that new searches need to meet in order to unambiguously establish the presence of another planetary system. Basically, these requirements are: 1 milliarcsecond or better positional accuracy for astrometric techniques, 9 orders of magnitude or better star to planet luminosity ratio discrimination at 0.5 to 1" separation in the optical for direct imaging techniques, 10 meters sec-1 or better radial velocity accuracy for reflex motion techniques and +/-1% or better brightness fluctuation accuracy for planet/star occultation measurements. The astrometric accuracy is in reach of HST, direct imaging will require much larger telescopes and/or a 50 times smoother mirror than HST while the reflex motion and occultation techniques best performed on the ground are just becoming viable and promise exciting new discoveries. On the other band, new indirect evidence on the existence of other planetary systems also comes from the observation of large dusty disks around nearby main sequence stars not too dissimilar from our sun. In one particular case, that of Beta Pictoris, a flattened disk seen nearly edge-on has been imaged in the optical and near IR down to almost 70 AU of the star. It probably represents a young planetary system in its clearing out phase as planetesimals collide, erode and are swept out of the inner system by radiation pressure. The hypothesized Kuiper belt around our solar system may be the analogous structure in a later evolutionary stage. Features of this type have been detected in the far IR and sub-millimeter wavelength regions around 50-100 nearby main sequence and pre-main sequence stars. I discuss a battery of new accurate observations planned in the near future of these objects some of which may actually harbour planets or planetesimals that will certainly dramatically improve our knowledge of planetary system formation processes and our peculiar position in this scheme.

Accreting Planets in the Habitable Zones of M-Stars Are Too Hot to Retain Liquid Water

NASA Astrophysics Data System (ADS)

Ramirez, R. M.; Kopparapu, R. K.; Kasting, J. F.

2014-12-01

Previous studies1,2 have shown that young accreting planets in the habitable zones (HZ) of pre-main sequence M-stars face major dynamical hurdles in both the retention and acquisition of volatiles. High collision rates with other bodies, short planetary formation timescales, and inefficient radial mixing are among the major problems encountered. However, another equally-important concern is the high temperatures predicted within the circumstellar disk, greatly hindering volatile delivery. We use a 1-D radiative-convective climate model to demonstrate that the fluxes received by accreting planets orbiting late K-M stars exceed the runaway greenhouse threshold. Given that M-stars are disproportionately brighter in their pre main-sequence lifetimes as compared to Sun-like stars (i.e. G-class insolation), planets orbiting M-stars are especially susceptible to the runaway, with intensity and duration increasing for cooler M-stars. Thus, accreting planetesimals in the HZs of M-stars could be too hot to maintain liquid water on their surfaces. In contrast, accreting planets located at Earth's distance (or farther) from a pre-main sequence solar analogue (i.e. G2 spectral class) receive stellar fluxes well below that of the runaway point. Our results suggest that future missions and surveys can improve their prospects of finding alien life by targeting HZ planets orbiting Sun-like stars. Moreover, our findings support recent claims that Venus may have lost its water during accretion3. REFERENCES1. Lissauer, Jack J. "Planets formed in habitable zones of M dwarf stars probably are deficient in volatiles." The Astrophysical Journal Letters 660.2 (2007): L149. 2. Raymond, Sean N., John Scalo, and Victoria S. Meadows. "A decreased probability of habitable planet formation around low-mass stars." The Astrophysical Journal 669.1 (2007): 606. 3. Hamano, Keiko, Yutaka Abe, and Hidenori Genda. "Emergence of two types of terrestrial planet on solidification of magma ocean." Nature 497.7451 (2013): 607-610.

Isolation and characterization of a cDNA encoding a membrane bound acyl-CoA binding protein from Agave americana L. epidermis.

PubMed

Guerrero, Consuelo; Martín-Rufián, M; Reina, José J; Heredia, Antonio

2006-01-01

A cDNA encoding an acyl-CoA binding protein (ACBP) homologue has been cloned from a cDNA library made from mRNA isolated from epidermis of young leaves of Agave americana L. The derived amino acid sequence reveals a protein corresponding to the membrane-associated form of ACBPs only previously described in Arabidopsis and rice. Northern blot analysis showed that the A. americana ACBP gene is mainly expressed in the epidermis of mature zone of the leaves. The epidermis of A. americana leaves have a well developed cuticle with the highest amounts of the cuticular components waxes, cutin and cutan suggesting a potential role of the protein in cuticle formation.

Ultraviolet studies of O and B stars in the LMC cluster NGC 2100, the SMC cluster NGC 330 and the Galactic cluster NGC 6530

NASA Technical Reports Server (NTRS)

Boehm-Vitense, E.; Hodge, P.

1984-01-01

High-resolution and low-resolution IUE spectra of O and B stars in the LMC cluster NGC 2100, the SMC cluster NGC 330, and the young Galactic cluster NGC 6530 are investigated. Temperatures and luminosities are determined. In the LMC and SMC clusters, the most luminous stars are evolved stars on the horizontal supergiant branch, while in NGC 6530 the stars are all still on the main sequence. Extinction laws were determined. They confirm the known differences between LMC and Galactic extinctions. No mass loss was detected for the evolved B stars in the LMC and SMC clusters, while the high-luminosity stars in NGC 6530 show P Cygni profiles.

The Effect of Interference on Temporal Order Memory for Random and Fixed Sequences in Nondemented Older Adults

ERIC Educational Resources Information Center

Tolentino, Jerlyn C.; Pirogovsky, Eva; Luu, Trinh; Toner, Chelsea K.; Gilbert, Paul E.

2012-01-01

Two experiments tested the effect of temporal interference on order memory for fixed and random sequences in young adults and nondemented older adults. The results demonstrate that temporal order memory for fixed and random sequences is impaired in nondemented older adults, particularly when temporal interference is high. However, temporal order…

VizieR Online Data Catalog: NGC 6802 dwarf cluster members and non-members (Tang+, 2017)

NASA Astrophysics Data System (ADS)

Tang, B.; Geisler, D.; Friel, E.; Villanova, S.; Smiljanic, R.; Casey, A. R.; Randich, S.; Magrini, L.; San, Roman I.; Munoz, C.; Cohen, R. E.; Mauro, F.; Bragaglia, A.; Donati, P.; Tautvaisiene, G.; Drazdauskas, A.; Zenoviene, R.; Snaith, O.; Sousa, S.; Adibekyan, V.; Costado, M. T.; Blanco-Cuaresma, S.; Jimenez-Esteban, F.; Carraro, G.; Zwitter, T.; Francois, P.; Jofre, P.; Sordo, R.; Gilmore, G.; Flaccomio, E.; Koposov, S.; Korn, A. J.; Lanzafame, A. C.; Pancino, E.; Bayo, A.; Damiani, F.; Franciosini, E.; Hourihane, A.; Lardo, C.; Lewis, J.; Monaco, L.; Morbidelli, L.; Prisinzano, L.; Sacco, G.; Worley, C. C.; Zaggia, S.

2016-11-01

The dwarf stars in NGC 6802 observed by GIRAFFE spectrograph are separated into four tables: 1. cluster members in the lower main sequence; 2. cluster members in the upper main sequence; 3. non-member dwarfs in the lower main sequence; 4. non-member dwarfs in the upper main sequence. The star coordinates, V band magnitude, V-I color, and radial velocity are given. (4 data files).

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.

Using Problem Solving to Assess Young Children's Mathematics Knowledge

ERIC Educational Resources Information Center

Charlesworth, Rosalind; Leali, Shirley A.

2012-01-01

Mathematics problem solving provides a means for obtaining a view of young children's understanding of mathematics as they move through the early childhood concept development sequence. Assessment information can be obtained through observations and interviews as children develop problem solutions. Examples of preschool, kindergarten, and primary…

The Stellar Population Associated with the IRAS Source 16132-5039

NASA Astrophysics Data System (ADS)

Roman-Lopes, A.; Abraham, Z.

2004-05-01

We report the discovery of a young massive stellar cluster and infrared nebula in the direction of the CS molecular cloud associated with the IRAS point source 16132-5039. Analysis of mid-infrared images from the more accurate Midcourse Space Experiment catalog reveals that there are two independent components associated with the IRAS source. The integral of the spectral energy distribution for these components between 8.28 and 100 μm gives lower limits for the bolometric luminosity of the embedded objects of 8.7×104 and 9×103 Lsolar, which correspond to zero-age main-sequence O8 and B0.5 stars, respectively. The number of Lyman continuum photons expected from the stars that lie along the reddening line for early-type stars is about 1.7×1049 s-1, enough to produce the detected flux densities at 5 GHz. The near-infrared spectrum of the nebula increases with frequency, implying that free-free emission cannot be the main source of the extended luminosity, from which we conclude that the observed emission must be mainly dust-scattered light. A comparison of the cluster described in this paper with the young stellar cluster associated with the IRAS source 16177-5018, which is located at the same distance and in the same direction, shows that the mean visual absorption of the newly discovered cluster is about 10 mag smaller and that it contains less massive stars, suggesting that it was formed from a less massive molecular cloud. Based on observations made at the Laboratório Nacional de Astrofisica, Ministério da Ciência e Tecnologia, Brazil.

Did A Planet Survive A Post-Main Sequence Evolutionary Event?

NASA Astrophysics Data System (ADS)

Sorber, Rebecca; Jang-Condell, Hannah; Zimmerman, Mara

2018-06-01

The GL86 is star system approximately 10 pc away with a main sequence K- type ~ 0.77 M⊙ star (GL 86A) with a white dwarf ~0.49 M⊙ companion (GL86 B). The system has a ~ 18.4 AU semi-major axis, an orbital period of ~353 yrs, and an eccentricity of ~ 0.39. A 4.5 MJ planet orbits the main sequence star with a semi-major axis of 0.113 AU, an orbital period of 15.76 days, in a near circular orbit with an eccentricity of 0.046. If we assume that this planet was formed during the time when the white dwarf was a main sequence star, it would be difficult for the planet to have remained in a stable orbit during the post-main sequence evolution of GL86 B. The post-main sequence evolution with planet survival will be examined by modeling using the program Mercury (Chambers 1999). Using the model, we examine the origins of the planet: whether it formed before or after the post-main sequence evolution of GL86B. The modeling will give us insight into the dynamical evolution of, not only, the binary star system, but also the planet’s life cycle.

SPIN EVOLUTION OF ACCRETING YOUNG STARS. II. EFFECT OF ACCRETION-POWERED STELLAR WINDS

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

Matt, Sean P.; Pinzon, Giovanni; Greene, Thomas P.

2012-01-20

We present a model for the rotational evolution of a young, solar-mass star interacting magnetically with an accretion disk. As in a previous paper (Paper I), the model includes changes in the star's mass and radius as it descends the Hayashi track, a decreasing accretion rate, and a prescription for the angular momentum transfer between the star and disk. Paper I concluded that, for the relatively strong magnetic coupling expected in real systems, additional processes are necessary to explain the existence of slowly rotating pre-main-sequence stars. In the present paper, we extend the stellar spin model to include the effectmore » of a spin-down torque that arises from an accretion-powered stellar wind (APSW). For a range of magnetic field strengths, accretion rates, initial spin rates, and mass outflow rates, the modeled stars exhibit rotation periods within the range of 1-10 days in the age range of 1-3 Myr. This range coincides with the bulk of the observed rotation periods, with the slow rotators corresponding to stars with the lowest accretion rates, strongest magnetic fields, and/or highest stellar wind mass outflow rates. We also make a direct, quantitative comparison between the APSW scenario and the two types of disk-locking models (namely, the X-wind and Ghosh and Lamb type models) and identify some remaining theoretical issues for understanding young star spins.« less

Spin Evolution of Accreting Young Stars. II. Effect of Accretion-powered Stellar Winds

NASA Astrophysics Data System (ADS)

Matt, Sean P.; Pinzón, Giovanni; Greene, Thomas P.; Pudritz, Ralph E.

2012-01-01

We present a model for the rotational evolution of a young, solar-mass star interacting magnetically with an accretion disk. As in a previous paper (Paper I), the model includes changes in the star's mass and radius as it descends the Hayashi track, a decreasing accretion rate, and a prescription for the angular momentum transfer between the star and disk. Paper I concluded that, for the relatively strong magnetic coupling expected in real systems, additional processes are necessary to explain the existence of slowly rotating pre-main-sequence stars. In the present paper, we extend the stellar spin model to include the effect of a spin-down torque that arises from an accretion-powered stellar wind (APSW). For a range of magnetic field strengths, accretion rates, initial spin rates, and mass outflow rates, the modeled stars exhibit rotation periods within the range of 1-10 days in the age range of 1-3 Myr. This range coincides with the bulk of the observed rotation periods, with the slow rotators corresponding to stars with the lowest accretion rates, strongest magnetic fields, and/or highest stellar wind mass outflow rates. We also make a direct, quantitative comparison between the APSW scenario and the two types of disk-locking models (namely, the X-wind and Ghosh & Lamb type models) and identify some remaining theoretical issues for understanding young star spins.

The Primordial Binary Fraction in Trumpler 14: Frequency and Multiplicity Parameters

NASA Astrophysics Data System (ADS)

Sabbi, Elena

2017-08-01

This is an astrometric proposal designed to identify and characterize the properties of medium- and long-period (orbital periods ranging from 1.8 to 100 years) visual binaries in the mass range between 4 and 20 Mo in the young compact cluster Trumpler 14 in the Carina Nebula. We aim to probe the virtually unexplored population of intermediate- and high-mass binaries that will experience a Roche-lobe overflow during their post-main-sequence evolution. These binaries are of particular interest because they are expected to be the progenitors of supernovae Type Ia, b, and c, X-ray binaries, double neutron stars and double black holes. Multiplicity properties of young stars can be further used to constrain the outcome of the star-formation process and hence distinguish between various formation scenarios. The medium- and long-period binaries (P> 0.5 yr) are hard to detect and expensive to characterize with traditional ground-based spectroscopy. Knowledge of their orbital properties is however crucial to properly estimate the overall fraction of OB stars whose evolution is affected by binary interaction and to predict the outcome of such interaction. Because of the well characterized PSF of WFC3/UVIS and its temporal stability, HST is the only facility able to characterize the properties of OB-type medium-period binaries in Tr14, and Tr14 is the only nearby high-density OB-type young cluster.

Analysis of the optical emission of the young precataclysmic variables HS 1857+5144 and ABELL 65

NASA Astrophysics Data System (ADS)

Shimansky, V. V.; Pozdnyakova, S. A.; Borisov, N. V.; Bikmaev, I. F.; Vlasyuk, V. V.; Spiridonova, O. I.; Galeev, A. I.; Mel'Nikov, S. S.

2009-10-01

We analyze the physical state and the properties of the close binary systems HS 1857+5144 and Abell 65. We took the spectra of both systems over a wide range of orbital phases with the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS) and obtained their multicolor light curves with the RTT150 and Zeiss-1000 telescopes of the SAO RAS. We demonstrate that both Abell 65 and HS 1857+5144 are young precataclysmic variables (PV) with orbital periods of P orb = 1. d 003729 and P orb = 0. d 26633331, respectively. The observed brightness and spectral variations during the orbital period are due to the radiation of the cold component, which absorbs the short-wave radiation of the hot component and reemits it in the visual part of the spectrum. A joint analysis of the brightness and radial velocity curves allowed us to find the possible and optimum sets of their fundamental parameters. We found the luminosity excesses of the secondary components of HS 1857+5144 and Abell 65 with respect to the corresponding Main Sequence stars to be typical for such objects. The excess luminosities of the secondary components of all young PVs are indicative of their faster relaxation rate towards the quiescent state compared to the rates estimated in earlier studies.

Workshop on Physics of Accretion Disks Around Compact and Young Stars

NASA Technical Reports Server (NTRS)

Liang, E (Editor); Stepinski, T. F. (Editor)

1995-01-01

The purpose of the two-day Workshop on Physics of Accretion Disks Around Compact and Young Stars was to bring together workers on accretion disks in the western Gulf region (Texas and Louisiana). Part 2 presents the workshop program, a list of poster presentations, and a list of workshop participants. Accretion disks are believed to surround many stars. Some of these disks form around compact stars, such as white dwarfs, neutron stars, or black holes that are members of binary systems and reveal themselves as a power source, especially in the x-ray and gamma regions of the spectrum. On the other hand, protostellar disks are believed to be accretion disks associated with young, pre-main-sequence stars and manifest themselves mostly in infrared and radio observations. These disks are considered to be a natural outcome of the star formation process. The focus of this workshop included theory and observations relevant to accretion disks around compact objects and newly forming stars, with the primary purpose of bringing the two communities together for intellectual cross-fertilization. The nature of the workshop was exploratory, to see how much interaction is possible between distinct communities and to better realize the local potential in this subject. A critical workshop activity was identification and documentation of key issues that are of mutual interest to both communities.

Few Skewed Disks Found in First Closure-Phase Survey of Herbig Ae/Be Stars

NASA Astrophysics Data System (ADS)

Monnier, J. D.; Berger, J.-P.; Millan-Gabet, R.; Traub, W. A.; Schloerb, F. P.; Pedretti, E.; Benisty, M.; Carleton, N. P.; Haguenauer, P.; Kern, P.; Labeye, P.; Lacasse, M. G.; Malbet, F.; Perraut, K.; Pearlman, M.; Zhao, M.

2006-08-01

Using the three-telescope IOTA interferometer on Mount Hopkins, we report results from the first near-infrared (λ=1.65 μm) closure-phase survey of young stellar objects (YSOs). These closure phases allow us to unambiguously detect departures from centrosymmetry (i.e., skew) in the emission pattern from YSO disks on the scale of ~4 mas, expected from generic ``flared disk'' models. Six of 14 targets showed small, yet statistically significant nonzero closure phases, with largest values from the young binary system MWC 361-A and the (pre-main-sequence?) Be star HD 45677. Our observations are quite sensitive to the vertical structure of the inner disk, and we confront the predictions of the ``puffed-up inner wall'' models of Dullemond, Dominik, & Natta (DDN). Our data support disk models with curved inner rims because the expected emission appears symmetrically distributed around the star over a wide range of inclination angles. In contrast, our results are incompatible with the models possessing vertical inner walls because they predict extreme skewness (i.e., large closure phases) from the near-IR disk emission that is not seen in our data. In addition, we also present the discovery of mysterious H-band ``halos'' (~5%-10% of light on scales 0.01"-0.50") around a few objects, a preliminary ``parametric imaging'' study for HD 45677, and the first astrometric orbit for the young binary MWC 361-A.

Cloning and characterization of the SERK1 gene in triploid Pingyi Tiancha [Malus hupehensis (Pamp.) Rehd. var. pingyiensis Jiang] and a tetraploid hybrid strain.

PubMed

Zhang, L J; Dong, W X; Guo, S M; Wang, Y X; Wang, A D; Lu, X J

2015-11-19

This study aims to explore the roles of somatic embryogenesis receptor-like kinase (SERK) in Malus hupehensis (Pingyi Tiancha). The full-length sequences of SERK1 in triploid Pingyi Tiancha (3n) and a tetraploid hybrid strain 33# (4n) were cloned, sequenced, and designated as MhSERK1 and MhdSERK1, respectively. Multiple alignments of amino acid sequences were conducted to identify similarity between MhSERK1 and MhdSERK1 and SERK sequences in other species, and a neighbor-joining phylogenetic tree was constructed to elucidate their phylogenetic relations. Expression levels of MhSERK1 and MhdSERK1 in different tissues and developmental stages were investigated using quantitative real-time PCR. The coding sequence lengths of MhSERK1 and MhdSERK1 were 1899 bp (encoding 632 amino acids) and 1881 bp (encoding 626 amino acids), respectively. Sequence analysis demonstrated that MhSERK1 and MhdSERK1 display high similarity to SERKs in other species, with a conserved intron/exon structure that is unique to members of the SERK family. Additionally, the phylogenetic tree showed that MhSERK1 and MhdSERK1 clustered with orange CitSERK (93%). Furthermore, MhSERK1 and MhdSERK1 were mainly expressed in the reproductive organs, in particular the ovary. Their expression levels were highest in young flowers and they differed among different tissues and organs. Our results suggest that MhSERK1 and MhdSERK1 are related to plant reproduction, and that MhSERK1 is related to apomixis in triploid Pingyi Tiancha.

Binaries among low-mass stars in nearby young moving groups

NASA Astrophysics Data System (ADS)

Janson, Markus; Durkan, Stephen; Hippler, Stefan; Dai, Xiaolin; Brandner, Wolfgang; Schlieder, Joshua; Bonnefoy, Mickaël; Henning, Thomas

2017-03-01

The solar galactic neighborhood contains a number of young co-moving associations of stars (known as young moving groups) with ages of 10-150 Myr, which are prime targets for a range of scientific studies, including direct imaging planet searches. The late-type stellar populations of such groups still remain in their pre-main sequence phase, and are thus well suited for purposes such as isochronal dating. Close binaries are particularly useful in this regard since they allow for a model-independent dynamical mass determination. Here we present a dedicated effort to identify new close binaries in nearby young moving groups, through high-resolution imaging with the AstraLux Sur Lucky Imaging camera. We surveyed 181 targets, resulting in the detection of 61 companions or candidates, of which 38 are new discoveries. An interesting example of such a case is 2MASS J00302572-6236015 AB, which is a high-probability member of the Tucana-Horologium moving group, and has an estimated orbital period of less than 10 yr. Among the previously known objects is a serendipitous detection of the deuterium burning boundary circumbinary companion 2MASS J01033563-5515561 (AB)b in the z' band, thereby extending the spectral coverage for this object down to near-visible wavelengths. Based on observations collected at the European Southern Observatory, Chile (Programs 096.C-0243 and 097.C-0135).Tables 1-3 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/599/A70

IN-SYNC. IV. The Young Stellar Population in the Orion A Molecular Cloud

NASA Astrophysics Data System (ADS)

Da Rio, Nicola; Tan, Jonathan C.; Covey, Kevin R.; Cottaar, Michiel; Foster, Jonathan B.; Cullen, Nicholas C.; Tobin, John J.; Kim, Jinyoung S.; Meyer, Michael R.; Nidever, David L.; Stassun, Keivan G.; Chojnowski, S. Drew; Flaherty, Kevin M.; Majewski, Steve; Skrutskie, Michael F.; Zasowski, Gail; Pan, Kaike

2016-02-01

We present the results of the Sloan Digital Sky Survey APOGEE INfrared Spectroscopy of Young Nebulous Clusters program (IN-SYNC) survey of the Orion A molecular cloud. This survey obtained high-resolution near-infrared spectroscopy of about 2700 young pre-main-sequence stars on a ˜ 6^\\circ field of view. We have measured accurate stellar parameters ({T}{{eff}}, {log}g, v{sin}I) and extinctions and placed the sources in the Hertzsprung-Russel diagram (HRD). We have also extracted radial velocities for the kinematic characterization of the population. We compare our measurements with literature results to assess the performance and accuracy of the survey. Source extinction shows evidence for dust grains that are larger than those in the diffuse interstellar medium: we estimate an average RV = 5.5 in the region. Importantly, we find a clear correlation between HRD inferred ages and spectroscopic surface-gravity-inferred ages and between extinction and disk presence; this strongly suggests a real spread of ages larger than a few Myr. Focusing on the young population around NGC 1980/ι Ori, which has previously been suggested to be a separate, foreground, older cluster, we confirm its older (˜5 Myr) age and low AV, but considering that its radial velocity distribution is indistinguishable from Orion A’s population, we suggest that NGC 1980 is part of Orion A’s star formation activity. Based on their stellar parameters and kinematic properties, we identify 383 new candidate members of Orion A, most of which are diskless sources in areas of the region poorly studied by previous works.

Hubble Sees a Young Star Take Center Stage

NASA Image and Video Library

2015-03-06

With its helical appearance resembling a snail’s shell, this reflection nebula seems to spiral out from a luminous central star in this NASA/ESA Hubble Space Telescope image. The star in the center, known as V1331 Cyg and located in the dark cloud LDN 981 — or, more commonly, Lynds 981 — had previously been defined as a T Tauri star. A T Tauri is a young star — or Young Stellar Object — that is starting to contract to become a main sequence star similar to the sun. What makes V1331Cyg special is the fact that we look almost exactly at one of its poles. Usually, the view of a young star is obscured by the dust from the circumstellar disc and the envelope that surround it. However, with V1331Cyg we are actually looking in the exact direction of a jet driven by the star that is clearing the dust and giving us this magnificent view. This view provides an almost undisturbed view of the star and its immediate surroundings allowing astronomers to study it in greater detail and look for features that might suggest the formation of a very low-mass object in the outer circumstellar disk. 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

Young, intact and nested retrotransposons are abundant in the onion and asparagus genomes

PubMed Central

Vitte, C.; Estep, M. C.; Leebens-Mack, J.; Bennetzen, J. L.

2013-01-01

Background and Aims Although monocotyledonous plants comprise one of the two major groups of angiosperms and include >65 000 species, comprehensive genome analysis has been focused mainly on the Poaceae (grass) family. Due to this bias, most of the conclusions that have been drawn for monocot genome evolution are based on grasses. It is not known whether these conclusions apply to many other monocots. Methods To extend our understanding of genome evolution in the monocots, Asparagales genomic sequence data were acquired and the structural properties of asparagus and onion genomes were analysed. Specifically, several available onion and asparagus bacterial artificial chromosomes (BACs) with contig sizes >35 kb were annotated and analysed, with a particular focus on the characterization of long terminal repeat (LTR) retrotransposons. Key Results The results reveal that LTR retrotransposons are the major components of the onion and garden asparagus genomes. These elements are mostly intact (i.e. with two LTRs), have mainly inserted within the past 6 million years and are piled up into nested structures. Analysis of shotgun genomic sequence data and the observation of two copies for some transposable elements (TEs) in annotated BACs indicates that some families have become particularly abundant, as high as 4–5 % (asparagus) or 3–4 % (onion) of the genome for the most abundant families, as also seen in large grass genomes such as wheat and maize. Conclusions Although previous annotations of contiguous genomic sequences have suggested that LTR retrotransposons were highly fragmented in these two Asparagales genomes, the results presented here show that this was largely due to the methodology used. In contrast, this current work indicates an ensemble of genomic features similar to those observed in the Poaceae. PMID:23887091

The Discovery of a Low-Mass Binary Companion to HD130948

NASA Astrophysics Data System (ADS)

Potter, D. E.; Cushing, M. C.; Neuhauser, R.

2003-10-01

We report the discovery of a low mass binary companion to the nearby (17.9 pc) main sequence star HD130948 (HR5534, HIP 72567) using the Hokupa'a adaptive optics instrument mounted on the Gemini North 8 meter telescope. Both companions have the same common proper motion as the primary star as seen over a 4 month baseline. The JHK' photometry of the companions, when placed on a near-IR color-magnitude diagram and compared with theoretical models places them at the bottom of the M-dwarf sequence. Preliminary near IR spectra have been obtained with SpeX mounted on the NASA IRTF 3 meter telescope are consistent with the photometric results and show carbon monoxide bandheads and water absorption features indicative of an early L-late M spectral type. The X-ray activity and Lithium abundance of the primary star indicate that the system is probably less than 1 Gyr old. Assuming a young age, these objects are less than 80 Mjupiter. With further astrometric observations carried out over an estimated orbital period of 10-20 years, a dynamical mass will be obtained.

The luminosity function at the end of the main sequence: Results of a deep, large-area, CCD survey for cool dwarfs

NASA Technical Reports Server (NTRS)

Kirkpatrick, J. Davy; Mcgraw, John T.; Hess, Thomas R.; Liebert, James; Mccarthy, Donald W., Jr.

1994-01-01

The luminosity function at the end of the main sequence is determined from V, R, and I data taken by the charge coupled devices (CCD)/Transit Instrument, a dedicated telescope surveying an 8.25 min wide strip of sky centered at delta = +28 deg, thus sampling Galactic latitudes of +90 deg down to -35 deg. A selection of 133 objects chosen via R - I and V - I colors has been observed spectroscopically at the 4.5 m Multiple Mirror Telescope to assess contributions by giants and subdwarfs and to verify that the reddest targets are objects of extremely late spectral class. Eighteen dwarfs of type M6 or later have been discovered, with the latest being of type M8.5. Data used for the determination of the luminosity function cover 27.3 sq. deg down to a completeness limit of R = 19.0. This luminosity function, computed at V, I, and bolometric magnitudes, shows an increase at the lowest luminosities, corresponding to spectral types later than M6- an effect suggested in earlier work by Reid & Gilmore and Legget & Hawkins. When the luminosity function is segregated into north Galactic and south Galactic portions, it is found that the upturn at faint magnitudes exists only in the southern sample. In fact, no dwarfs with M(sub I) is greater than or equal to 12.0 are found within the limiting volume of the 19.4 sq deg northern sample, in stark contrast to the smaller 7.9 sq deg area at southerly latitudes where seven such dwarfs are found. This fact, combined with the fact that the Sun is located approximately 10-40 pc north of the midplane, suggests that the latest dwarfs are part of a young population with a scale height much smaller than the 350 pc value generally adopted for other M dwarfs. These objects comprise a young population either because the lower metallicities prevelant at earlier epochs inhibited the formation of late M dwarfs or because the older counterparts of this population have cooled beyond current detection limits. The latter scenario would hold if these late-type M dwarfs are substellar. The luminosity function data together with an empirical derivation of the mass-luminosity relation (from Henry & McCarthy) are used to compute a mass function independent of theory. This mass function increases toward the end of the main sequence, but the observed density of M dwarfs is still insufficient to account for the missing mass. If the increases seen in the luminosity and mass functions are indicative of a large, unseen, substellar population, brown dwarfs may yet add significantly to the mass of the Galaxy.

Android REST Client Application to View, Collect, and Exploit Video and Image Data

DTIC Science & Technology

2013-09-01

Superresolution Image Reconstruction From a Sequence of Aliased Imagery. Applied Optics 2006, 45 (21), 5073–5085. 3, Driggers, R. G.; Krapels, K. A...Murrill, S.; Young, S. S.; Theilke, M.; Schuler, J. M. Superresolution Performance for Undersampled Imagers. Optical Engineering 2005, 44 (01). 4. Young

The Herbig B0e star HD 53367: circumstellar activity and evidence of binarity

NASA Astrophysics Data System (ADS)

Pogodin, M. A.; Malanushenko, V. P.; Kozlova, O. V.; Tarasova, T. N.; Franco, G. A. P.

2006-06-01

Aims.We investigate the spectroscopic behaviour of the young B0e star HD 53367 within a cooperative observing programme conducted from 1994 to 2005. Methods: .The data include more than 100 high-resolution spectra collected at the Crimean Astronomical Observatory (CrAO) near Hα, Hβ, He i λ 5876, 6678 Å, DNa i, and O ii λ 6641 Å lines. Two spectra obtained at the Observatório do Pico dos Dias (LNA), in the spectral bands λλ 4575-4725 Å and λλ 5625-5775 Å, were used for spectral classification of HD 53367. The temporal behaviour of the circumstellar lines Hα and Hβ as well as the photospheric lines O ii λ 6641 Å and He i λ 6678 Å were investigated during different stages of the photometric activity of this object. Results: .We confirm that the long-term photometric variability of HD 53367 is related to the alternation of two states of this object when the gaseous circumstellar envelope disappears and rises again. Both these processes start near the star and spread to the outlying parts of the envelope. We find that the radial velocities of He i and O ii photospheric lines demonstrate a cyclic variability with a period of P=183.7 days and semi-amplitude K=19 km s-1. The radial velocity change is interpreted in the framework of a model in which the star is a component of an eccentric binary system. An orbital solution is derived and the system's parameters estimated. We find that the orbital eccentricity is e=0.28, and the mean companion separation is 1.7 AU. Conclusions: .Based on the estimated parameters, we conclude that the system consists of a massive (~20 M_⊙) main sequence primary B0e star, and a secondary which is most likely a 5 solar mass pre-main sequence object. We found evidence that the main part of the circumstellar gas in this system is concentrated near the secondary companion. Although the young age of HD 53367, its evolved primary B0e star seems to have already became a classical Be star exhibiting a specific alternation of the B-Be stages.

Young massive star clusters in the era of HST and integral field spectroscopy

NASA Astrophysics Data System (ADS)

Zeidler, Peter; Nota, Antonella; Sabbi, Elena; Grebel, Eva K.; Pasquali, Anna

2018-01-01

With an age of 1 – 2 Myr at a distance of 4 kpc and a total stellar mass of 3.7×104 M⊙, Westerlund 2 (Wd2) is one of the most massive young star clusters in the Milky Way. We present a detailed analysis of its prominent pre-main-sequence population using the data of a high-resolution multi-band survey in the optical and near-infrared with the Hubble Space Telescope (HST), in combination with our spectroscopic survey, observed with the VLT/MUSE integral field unit. With our derived high-resolution extinction map of the region, which is absolutely essential giving the dominating presences of the gas and dust, we derived the spatial dependence of the mass function and quantify the degree of mass segregation down to 0.65 M⊙ with a completeness level better than 50%. Studying the radial dependence of the mass function of Wd2 and quantifying the degree of mass segregation in this young massive star cluster showed that it consists of two sub-clumps, namely the main cluster and the northern clump. From the MUSE data, we can extract individual stellar spectra and spectral energy distributions of the stars, based on the astrometry, provided by our high-resolution HST photometric catalog. This data will provide us with an almost complete spectral classification of a young massive star cluster down to 1.0 M⊙. The combination of the MUSE data, together with 3 more years of approved HST data will allow us to obtain, for the first time, the 3D motions of the stars with an accuracy of 1-2 km s-2 to determine the stellar velocity dispersion in order to study the fate of Wd2. This information is of great importance to adjust the initial conditions in cluster evolution models in order to connect these young massive star clusters and the old globular cluster population. Additionally, the combination of the photometric and spectroscopic datasets allows us to study the stars and their feedback onto the surrounding HII region simultaneously, as well as peculiar objects such as the massive, eclipsing Wolf-Rayet binary, WR20a or a possible Herbig-Haro object in the northern clump.

An analysis of the sequence of the BAD gene among patients with maturity-onset diabetes of the young (MODY).

PubMed

Antosik, Karolina; Gnyś, Piotr; Jarosz-Chobot, Przemysława; Myśliwiec, Małgorzata; Szadkowska, Agnieszka; Małecki, Maciej; Młynarski, Wojciech; Borowiec, Maciej

2017-01-01

Monogenic diabetes is a rare disease caused by single gene mutations. Maturity onset diabetes of the young (MODY) is one of the major forms of monogenic diabetes recognised in the paediatric population. To date, 13 genes have been related to MODY development. The aim of the study was to analyse the sequence of the BCL2-associated agonist of cell death (BAD) gene in patients with clinical suspicion of GCK-MODY, but who were negative for glucokinase (GCK) gene mutations. A group of 122 diabetic patients were recruited from the "Polish Registry for Paediatric and Adolescent Diabetes - nationwide genetic screening for monogenic diabetes" project. The molecular testing was performed by Sanger sequencing. A total of 10 sequence variants of the BAD gene were identified in 122 analysed diabetic patients. Among the analysed patients suspected of MODY, one possible pathogenic variant was identified in one patient; however, further confirmation is required for a certain identification.

Fever of unclear origin and cytopenia because of acute splenic sequestration in a young immunocompetent carrier of beta-globin mutation for Hb Valletta.

PubMed

Parrinello, Gaspare; Torres, Daniele; Paterna, Salvatore; Di Pasquale, Pietro; Licata, Giuseppe

2008-12-01

Fever of unclear origin is a clinical challenge in medical practice. Infectious diseases, neoplasms, and collagen vascular illnesses are its main causes in adults and children. Acute splenic sequestration crises, a known potentially fatal complication of sickle cell disease and sickle beta-thalassemia, are uncommon in beta-heterozygosis. We describe a case of prolonged recurrent episodes of fever with spontaneous resolution, commencing at age 10 in a 15-year-old boy with a history of hypochromic microcytic anemia attributed to a thalassemic trait. He was admitted twice to our university hospital for continuous-remittent fever with a pruritic, macular evanescent Still's skin rash, severe splenomegaly, leucopenia, thrombocytopenia, and sudden aggravation of anemia. Infectious, rheumatologic, autoimmune, and hematologic illnesses were excluded. A genetic-based study revealed heterozygosis of the beta-globin gene for a A>C (Thr>Pro) substitution at position 87 called Hemoglobin Valletta (alpha 2 beta 2 87 PRO) with a C>G transition in homozygosis in beta-globin intronic polymorphism intervening sequence 2 at nucleotide 745. After a follow-up period of 1 year without treatment, the young patient remains apyretic and in good general clinical health with persistent microcythemia and hepatosplenomegaly. Acute splenic sequestration crisis and related cytopenia may be an unusual complication of fever of unclear origin in a beta-thalassemic carrier of a Hemoglobin Valletta mutation and polymorphism in homozygosis of intervening sequence 2 at nucleotide 745. This hemoglobinopathy may predispose to a clinical phenotype of minor or intermediate thalassemia and, during a febrile illness, to hemoglobin instability and splenic sequestration.

Characterization of the faecal bacterial community of wild young South American (Arctocephalus australis) and Subantarctic fur seals (Arctocephalus tropicalis).

PubMed

Medeiros, Aline Weber; Giongo, Adriana; Valdez, Fernanda P; Blaese de Amorin, Derek; Tavares, Maurício; d'Azevedo, Pedro A; Franco, Ana Claudia; Frazzon, Jeverson; Frazzon, Ana P G

2016-03-01

The microbiota of wild marine mammals is poorly understood, perhaps due to the migratory habits of some species and the difficulty in obtaining samples. Using high-throughput sequencing, the present study examines the faecal bacterial community of wild young South American (Arctocephalus australis) and Subantarctic fur seals (A. tropicalis). Faecal samples from South American (n = 6) and Subantarctic fur seals (n = 4) found dead along the south coast of Brazil were collected. Sequences were assigned to taxa using the Ribosomal Database Project-Bayesian classifier. Diversity of the microbiota was assessed by categorization of sequence reads into operational taxonomic units. Results indicate that Firmicutes (88.556%-84.016%) was the predominant phylum in South American and Subantarctic fur seals. The distribution of Actinobacteria and Proteobacteria varied according to the fur seal species. Fusobacteria and Bacteroidetes represented less than 1% of the sequences. The most abundant order in both fur seals was Clostridiales (88.64% and 87.49%). Individual variable incidences were observed in the composition of family among the fur seals, though the families Lachnospiraceae, Peptostreptococcaceae, Ruminococcaceae and Coriobacteriaceae were more prevalent. This study provides insight into the faecal bacterial community of wild young South American and Subantarctic fur seals. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Oculomotor and Manual Indexes of Incidental and Intentional Spatial Sequence Learning during Middle Childhood and Adolescence

ERIC Educational Resources Information Center

Karatekin, Canan; Marcus, David J.; White, Tonya

2007-01-01

The goal of this study was to examine incidental and intentional spatial sequence learning during middle childhood and adolescence. We tested four age groups (8-10 years, 11-13 years, 14-17 years, and young adults [18+ years]) on a serial reaction time task and used manual and oculomotor measures to examine incidental sequence learning.…

Infections with multiple Cryptosporidium species and new genetic variants in young dairy calves on a farm located within a drinking water catchment area in New Zealand.

PubMed

Shrestha, Rima D; Grinberg, Alex; Dukkipati, Venkata S R; Pleydell, Eve J; Prattley, Deborah J; French, Nigel P

2014-05-28

Several Cryptosporidium species are known to infect cattle. However, the occurrence of mixed infections with more than one species and the impact of this phenomenon on animal and human health are poorly understood. Therefore, to detect the presence of mixed Cryptosporidium infections, 15 immunofluorescence-positive specimens obtained from 6-week-old calves' faeces (n=60) on one dairy farm were subjected to PCR-sequencing at multiple loci. DNA sequences of three Cryptosporidium species: C. parvum (15/15), C. bovis (3/15) and C. andersoni (1/15), and two new genetic variants were identified. There was evidence of mixed infections in five specimens. C. parvum, C. bovis and C. andersoni sequences were detected together in one specimen, C. parvum and C. bovis in two specimens, and C. parvum and C. parvum-like variants in the remaining two specimens. Sequencing of gp60 amplicons identified the IIaA19G4R1 (8/15) and IIaA18G3R1 (4/15) C. parvum subgenotypes. This study provides evidence of endemic mixed infections with the three main Cryptosporidium species of cattle and new genetic variants, in calves at the transition age of six weeks. The results add to the body of evidence describing Cryptosporidium isolates as genetically heterogeneous populations, and highlight the need for iterative genotyping to explore their genetic makeup. Copyright © 2014 Elsevier B.V. All rights reserved.

Mutational analysis using Sanger and next generation sequencing in sporadic spindle cell hemangiomas: A study of 19 cases.

PubMed

Ten Broek, Roel W; Bekers, Elise M; de Leng, Wendy W J; Strengman, Eric; Tops, Bastiaan B J; Kutzner, Heinz; Leeuwis, Jan Willem; van Gorp, Joost M; Creytens, David H; Mentzel, Thomas; van Diest, Paul J; Eijkelenboom, Astrid; Flucke, Uta

2017-12-01

Spindle cell hemangioma (SCH) is a distinct vascular soft-tissue lesion characterized by cavernous blood vessels and a spindle cell component mainly occurring in the distal extremities of young adults. The majority of cases harbor heterozygous mutations in IDH1/2 sporadically or rarely in association with Maffucci syndrome. However, based on mosaicism and accordingly a low percentage of lesional cells harboring a mutant allele, detection can be challenging. We tested 19 sporadic SCHs by Sanger sequencing, multiplex ligation-dependent probe amplification (MLPA), conventional next generation sequencing (NGS), and NGS using a single molecule molecular inversion probes (smMIP)-based library preparation to compare their diagnostic value. Out of 10 cases tested by Sanger sequencing and 2 analyzed using MLPA, 4 and 1, respectively, revealed a mutation in IDH1 (p.R132C). The 7 remaining negative cases and additional 6 cases were investigated using smMIP/NGS, showing hot spot mutations in IDH1 (p.R132C) (8 cases) and IDH2 (3 cases; twice p.R172S and once p.R172G, respectively). One case was negative. Owing to insufficient DNA quality and insufficient coverage, 2 cases were excluded. In total, in 16 out of 17 cases successfully tested, an IDH1/2 mutation was found. Given that IDH1/2 mutations were absent in 161 other vascular lesions tested by smMIP/NGS, the mutation can be considered as highly specific for SCH. © 2017 Wiley Periodicals, Inc.

Rotational velocities of newly discovered, low-mass members of the Alpha Persei cluster

NASA Technical Reports Server (NTRS)

Stauffer, John R.; Hartmann, Lee W.; Jones, Burton F.

1989-01-01

About 30 new, low-mass members of the young open cluster Alpha Persei are identified via a proper-motion study and subsequent photometric and spectroscopic observations. Membership in the cluster is confirmed for a number of the fainter proper-motion candidates from Heckman, Dieckvoss, and Kox (1956). Coordinates, finding charts, BVRI photometry, and rotational velocities are provided for most of the stars. At least two of the stars show peculiar H-alpha emission profiles, with weak but very broad emission wings, and relatively narrow absorption reversals. The rotational velocity distribution for low-mass stars in the Alpha Per cluster are compared with recently derived rotational velocity distributions for T Tauri stars, placing strong constraints on the mechanisms for angular momentum loss during pre-main-sequence evolution.

ARC-1989-A89-7028

NASA Image and Video Library

1989-08-25

P-34668 This narrow angled image of Neptune's Triton, part of a sequence recieved from Voyager 2 shows a large flooded basin about 200 km. or 120 miles wide and 400 km. or 240 miles long. It appears to have been formed chiefly by two large, ancient craters. The walls of the basin have retreated, possibly as a consequence of sapping or collapse into the fluid that filled the main floor. The vent from which the flood evidently erupted lies near the right hand end of the basin. The surface of the eruptive material is rough near the vent and along the center of the basin, perhaps as a consequence of the presence of large rafts of ice. The absence of resolved impact craters on the floor of the basin indicatyes a young age for the flood.

A Calibrated H-alpha Index to Monitor Emission Line Objects

NASA Astrophysics Data System (ADS)

Hintz, Eric G.; Joner, M. D.

2013-06-01

Over an 8 year period we have developed a calibrated H-alpha index, similar to the more traditional H-beta index, based on spectrophotometric observations (Joner & Hintz, 2013) from the DAO 1.2-m Telescope. While developing the calibration for this filter set we also obtained spectra of a number of emission line systems such as high mass x-ray binaries (HMXB), Be stars, and young stellar objects. From this work we find that the main sequence stars fill a very tight relation in the H-alpha/H-beta plane and that the emission line objects are easily detected. We will present the overall location of these emission line objects. We will also present the changes experiences by these objects over the course of the years of the project.

Infrared Spectroscopy of Star Formation in Galactic and Extragalactic Regions

NASA Technical Reports Server (NTRS)

Smith, Howard A.; Hasan, Hashima (Technical Monitor)

2002-01-01

This report details work done in a project involving spectroscopic studies, including data analysis and modeling, of star-formation regions using an ensemble of archival space-based data including some from the Infrared Space Observatory's Long Wavelength Spectrometer and Short Wavelength Spectrometer, and other spectroscopic databases. We will include four kinds of regions: (1) disks around more evolved objects; (2) young, low or high mass pre-main sequence stars in star-formation regions; (3) star formation in external, bright IR (infrared) galaxies; and (4) the galactic center. During this period, work proceeded fully on track and on time. Details on workshops and conferences attended and research results are presented. A preprint article entitled 'The Far Infrared Lines of OH as Molecular Cloud Diagnostics' is included as an appendix.

An Unexpected Detection of Bifurcated Blue Straggler Sequences in the Young Globular Cluster NGC 2173

NASA Astrophysics Data System (ADS)

Li, Chengyuan; Deng, Licai; de Grijs, Richard; Jiang, Dengkai; Xin, Yu

2018-03-01

The bifurcated patterns in the color–magnitude diagrams of blue straggler stars (BSSs) have attracted significant attention. This type of special (but rare) pattern of two distinct blue straggler sequences is commonly interpreted as evidence that cluster core-collapse-driven stellar collisions are an efficient formation mechanism. Here, we report the detection of a bifurcated blue straggler distribution in a young Large Magellanic Cloud cluster, NGC 2173. Because of the cluster’s low central stellar number density and its young age, dynamical analysis shows that stellar collisions alone cannot explain the observed BSSs. Therefore, binary evolution is instead the most viable explanation of the origin of these BSSs. However, the reason why binary evolution would render the color–magnitude distribution of BSSs bifurcated remains unclear. C. Li, L. Deng, and R. de Grijs jointly designed this project.

High-Throughput Sequencing of Germline and Tumor From Men with Early-Onset Metastatic Prostate Cancer

DTIC Science & Technology

2016-12-01

AWARD NUMBER: W81XWH-13-1-0371 TITLE: High-Throughput Sequencing of Germline and Tumor From Men with Early- Onset Metastatic Prostate Cancer...DATES COVERED 30 Sep 2013 - 29 Sep 2016 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER High-Throughput Sequencing of Germline and Tumor From Men with...presenting with metastatic prostate cancer at a young age (before age 60 years). Whole exome sequencing identified a panel of germline variants that have

Motion and Structure Estimation of Manoeuvring Objects in Multiple- Camera Image Sequences

DTIC Science & Technology

1992-11-01

and Speckert [23], Gennery [24], Hallman [25], Legters and Young [26], Stuller and Krishnamurthy [27], Wu et al. [381, Matthies, Kanade, and Szeliski...26] G.R. Legters , T.Y. Young, "A mathematical model for computer image track- ing," IEEE Transactions on Pattern Analysis and Machine Intelligence

Evidence-Based and Child-Friendly: Shared Book Reading with Chants Support Young Children's Language and Literacy Development

ERIC Educational Resources Information Center

Richards, Janet C.

2010-01-01

Studies indicate thoughtfully planned chants integrated with shared book reading help young children remember concepts and vocabulary they hear in literature, capture children's imagination, develop their rhyming acuity, and background knowledge, and increase their sense of story structure, understanding of story sequence, phonological awareness,…

Transcriptome profile analysis of young floral buds of fertile and sterile plants from the self-pollinated offspring of the hybrid between novel restorer line NR1 and Nsa CMS line in Brassica napus

PubMed Central

2013-01-01

Background The fertile and sterile plants were derived from the self-pollinated offspring of the F1 hybrid between the novel restorer line NR1 and the Nsa CMS line in Brassica napus. To elucidate gene expression and regulation caused by the A and C subgenomes of B. napus, as well as the alien chromosome and cytoplasm from Sinapis arvensis during the development of young floral buds, we performed a genome-wide high-throughput transcriptomic sequencing for young floral buds of sterile and fertile plants. Results In this study, equal amounts of total RNAs taken from young floral buds of sterile and fertile plants were sequenced using the Illumina/Solexa platform. After filtered out low quality data, a total of 2,760,574 and 2,714,441 clean tags were remained in the two libraries, from which 242,163 (Ste) and 253,507 (Fer) distinct tags were obtained. All distinct sequencing tags were annotated using all possible CATG+17-nt sequences of the genome and transcriptome of Brassica rapa and those of Brassica oleracea as the reference sequences, respectively. In total, 3231 genes of B. rapa and 3371 genes of B. oleracea were detected with significant differential expression levels. GO and pathway-based analyses were performed to determine and further to understand the biological functions of those differentially expressed genes (DEGs). In addition, there were 1089 specially expressed unknown tags in Fer, which were neither mapped to B. oleracea nor to B. rapa, and these unique tags were presumed to arise basically from the added alien chromosome of S. arvensis. Fifteen genes were randomly selected and their expression levels were confirmed by quantitative RT-PCR, and fourteen of them showed consistent expression patterns with the digital gene expression (DGE) data. Conclusions A number of genes were differentially expressed between the young floral buds of sterile and fertile plants. Some of these genes may be candidates for future research on CMS in Nsa line, fertility restoration and improved agronomic traits in NR1 line. Further study of the unknown tags which were specifically expressed in Fer will help to explore desirable agronomic traits from wild species. PMID:23324545

Transcriptome profile analysis of young floral buds of fertile and sterile plants from the self-pollinated offspring of the hybrid between novel restorer line NR1 and Nsa CMS line in Brassica napus.

PubMed

Yan, Xiaohong; Dong, Caihua; Yu, Jingyin; Liu, Wanghui; Jiang, Chenghong; Liu, Jia; Hu, Qiong; Fang, Xiaoping; Wei, Wenhui

2013-01-16

The fertile and sterile plants were derived from the self-pollinated offspring of the F1 hybrid between the novel restorer line NR1 and the Nsa CMS line in Brassica napus. To elucidate gene expression and regulation caused by the A and C subgenomes of B. napus, as well as the alien chromosome and cytoplasm from Sinapis arvensis during the development of young floral buds, we performed a genome-wide high-throughput transcriptomic sequencing for young floral buds of sterile and fertile plants. In this study, equal amounts of total RNAs taken from young floral buds of sterile and fertile plants were sequenced using the Illumina/Solexa platform. After filtered out low quality data, a total of 2,760,574 and 2,714,441 clean tags were remained in the two libraries, from which 242,163 (Ste) and 253,507 (Fer) distinct tags were obtained. All distinct sequencing tags were annotated using all possible CATG+17-nt sequences of the genome and transcriptome of Brassica rapa and those of Brassica oleracea as the reference sequences, respectively. In total, 3231 genes of B. rapa and 3371 genes of B. oleracea were detected with significant differential expression levels. GO and pathway-based analyses were performed to determine and further to understand the biological functions of those differentially expressed genes (DEGs). In addition, there were 1089 specially expressed unknown tags in Fer, which were neither mapped to B. oleracea nor to B. rapa, and these unique tags were presumed to arise basically from the added alien chromosome of S. arvensis. Fifteen genes were randomly selected and their expression levels were confirmed by quantitative RT-PCR, and fourteen of them showed consistent expression patterns with the digital gene expression (DGE) data. A number of genes were differentially expressed between the young floral buds of sterile and fertile plants. Some of these genes may be candidates for future research on CMS in Nsa line, fertility restoration and improved agronomic traits in NR1 line. Further study of the unknown tags which were specifically expressed in Fer will help to explore desirable agronomic traits from wild species.

From CoRoT 102899501 to the Sun. A time evolution model of chromospheric activity on the main sequence

NASA Astrophysics Data System (ADS)

Gondoin, P.; Gandolfi, D.; Fridlund, M.; Frasca, A.; Guenther, E. W.; Hatzes, A.; Deeg, H. J.; Parviainen, H.; Eigmüller, P.; Deleuil, M.

2012-12-01

Aims: The present study reports measurements of the rotation period of a young solar analogue, estimates of its surface coverage by photospheric starspots and of its chromospheric activity level, and derivations of its evolutionary status. Detailed observations of many young solar-type stars, such as the one reported in the present paper, provide insight into rotation and magnetic properties that may have prevailed on the Sun in its early evolution. Methods: Using a model based on the rotational modulation of the visibility of active regions, we analysed the high-accuracy CoRoT lightcurve of the active star CoRoT 102899501. Spectroscopic follow-up observations were used to derive its fundamental parameters. We compared the chromospheric activity level of Corot 102899501 with the R'HK index distribution vs age established on a large sample of solar-type dwarfs in open clusters. We also compared the chromospheric activity level of this young star with a model of chromospheric activity evolution established by combining relationships between the R'HK index and the Rossby number with a recent model of stellar rotation evolution on the main sequence. Results: We measure the spot coverage of the stellar surface as a function of time and find evidence for a tentative increase from 5 - 14% at the beginning of the observing run to 13-29% 35 days later. A high level of magnetic activity on Corot 102899501 is corroborated by a strong emission in the Balmer and Ca ii H and K lines (R'HK ~ -4). The starspots used as tracers of the star rotation constrain the rotation period to 1.625 ± 0.002 days and do not show evidence for differential rotation. The effective temperature (Teff = 5180 ± 80 K), surface gravity (log g = 4.35 ± 0.1), and metallicity ([M/H] = 0.05 ± 0.07 dex) indicate that the object is located near the evolutionary track of a 1.09 ± 0.12 M⊙ pre-main sequence star at an age of 23 ± 10 Myr. This value is consistent with the "gyro-age" of about 8-25 Myr, inferred using a parameterization of the stellar rotation period as a function of colour index and time established for the I-sequence of stars in stellar clusters. Conclusions: We conclude that the high magnetic activity level and fast rotation of CoRoT 102899501 are manifestations of its stellar youth consistent with its estimated evolutionary status and with the detection of a strong Li i λ6707.8 Å absorption line in its spectrum. We argue that a magnetic activity level comparable to that observed on CoRot 102899501 could have been present on the Sun at the time of planet formation. Based on observations obtained with CoRoT, a space project operated by the French Space Agency, CNES, with participation of the Science Programme of ESA, ESTEC/RSSD, Austria, Belgium, Brazil, Germany and Spain.Based on observations made with the Anglo-Australian Telescope; the 2.1-m Otto Struve telescope at McDonald Observatory, Texas, USA; the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, in time allocated by the NOT "Fast-Track" Service Programme, OPTICON, and the Spanish Time Allocation Committee (CAT).The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement number RG226604 (OPTICON).

Emergence of novel domains in proteins

PubMed Central

2013-01-01

Background Proteins are composed of a combination of discrete, well-defined, sequence domains, associated with specific functions that have arisen at different times during evolutionary history. The emergence of novel domains is related to protein functional diversification and adaptation. But currently little is known about how novel domains arise and how they subsequently evolve. Results To gain insights into the impact of recently emerged domains in protein evolution we have identified all human young protein domains that have emerged in approximately the past 550 million years. We have classified them into vertebrate-specific and mammalian-specific groups, and compared them to older domains. We have found 426 different annotated young domains, totalling 995 domain occurrences, which represent about 12.3% of all human domains. We have observed that 61.3% of them arose in newly formed genes, while the remaining 38.7% are found combined with older domains, and have very likely emerged in the context of a previously existing protein. Young domains are preferentially located at the N-terminus of the protein, indicating that, at least in vertebrates, novel functional sequences often emerge there. Furthermore, young domains show significantly higher non-synonymous to synonymous substitution rates than older domains using human and mouse orthologous sequence comparisons. This is also true when we compare young and old domains located in the same protein, suggesting that recently arisen domains tend to evolve in a less constrained manner than older domains. Conclusions We conclude that proteins tend to gain domains over time, becoming progressively longer. We show that many proteins are made of domains of different age, and that the fastest evolving parts correspond to the domains that have been acquired more recently. PMID:23425224

Characterization of Generalized Young Measures Generated by Symmetric Gradients

NASA Astrophysics Data System (ADS)

De Philippis, Guido; Rindler, Filip

2017-06-01

This work establishes a characterization theorem for (generalized) Young measures generated by symmetric derivatives of functions of bounded deformation (BD) in the spirit of the classical Kinderlehrer-Pedregal theorem. Our result places such Young measures in duality with symmetric-quasiconvex functions with linear growth. The "local" proof strategy combines blow-up arguments with the singular structure theorem in BD (the analogue of Alberti's rank-one theorem in BV), which was recently proved by the authors. As an application of our characterization theorem we show how an atomic part in a BD-Young measure can be split off in generating sequences.

Star formation in the outskirts of DDO 154: A top-light IMF in a nearly dormant disc

NASA Astrophysics Data System (ADS)

Watts, Adam B.; Meurer, Gerhardt R.; Lagos, Claudia D. P.; Bruzzese, Sarah M.; Kroupa, Pavel; Jerabkova, Tereza

2018-04-01

We present optical photometry of Hubble Space Telescope (HST) ACS/WFC data of the resolved stellar populations in the outer disc of the dwarf irregular galaxy DDO 154. The photometry reveals that young main sequence stars are almost absent from the outermost HI disc. Instead, most are clustered near the main stellar component of the galaxy. We constrain the stellar initial mass function (IMF) by comparing the luminosity function of the main sequence stars to simulated stellar populations assuming a constant star formation rate over the dynamical timescale. The best-fitting IMF is deficient in high mass stars compared to a canonical Kroupa IMF, with a best-fit slope α = -2.45 and upper mass limit MU = 16 M⊙. This top-light IMF is consistent with predictions of the Integrated Galaxy-wide IMF theory. Combining the HST images with HI data from The HI Nearby Galaxy Survey Treasury (THINGS) we determine the star formation law (SFL) in the outer disc. The fit has a power law exponent N = 2.92 ± 0.22 and zero point A = 4.47 ± 0.65 × 10-7 M⊙ yr-1 kpc-2. This is depressed compared to the Kennicutt-Schmidt Star Formation Law, but consistent with weak star formation observed in diffuse HI environments. Extrapolating the SFL over the outer disc implies that there could be significant star formation occurring that is not detectable in Hα. Last, we determine the Toomre stability parameter Q of the outer disc of DDO 154 using the THINGS HI rotation curve and velocity dispersion map. 72% of the HI in our field has Q ≤ 4 and this incorporates 96% of the observed MS stars. Hence 28% of the HI in the field is largely dormant.

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

Smith, Myron A.; Shiao, Bernard; Bianchi, Luciana, E-mail: myronmeister@gmail.com, E-mail: shiao@stsci.edu, E-mail: bianchi@pha.jhu.edu

We report on intriguing photometric properties of Galactic stars observed in the Galaxy Evolution Explorer (GALEX) satellite's far-UV (FUV) and near-UV (NUV) bandpasses, as well as from the ground-based Sloan Digital Sky Survey (SDSS) and the Kepler Input Catalog. The first property is that the (FUV – NUV) color distribution of stars in the Kepler field consists of two well-separated peaks. A second and more perplexing property is that for stars with spectral types G or later the mean (FUV – NUV) color becomes much bluer, contrary to expectation. Investigating this tendency further, we found in two samples of mid-Fmore » through K type stars that 17%-22% of them exhibit FUV excesses relative to their NUV fluxes and spectral types. A correction for FUV incompleteness of the FUV magnitude-limited star sample brings this ratio to 14%-18%. Nearly the same fractions are also discovered among members of the Kepler Eclipsing Binary Catalog and in the published list of Kepler Objects of Interest. These UV-excess ('UVe') colors are confirmed by the negative UV continuum slopes in GALEX spectra of members of the population. The SDSS spectra of some UVe stars exhibit metallic line weakening, especially in the blue. This suggests an enhanced contribution of UV flux relative to photospheric flux of a solar-type single star. We consider the possibility that the UV excesses originate from various types of hot stars, including white dwarf DA and sdB stars, binaries, and strong chromosphere stars that are young or in active binaries. The space density of compact stars is too low to explain the observed frequency of the UVe stars. Our model atmosphere-derived simulations of colors for binaries with main-sequence pairs with a hot secondary demonstrate that the color loci conflict with the observed sequence. As a preferred alternative we are left with the active chromospheres explanation, whether in active close binaries or young single stars, despite the expected paucity of young, chromospherically active stars in the field. We also address a third perplexing color property, namely, the presence of a prominent island of 'UV red' stars surrounded by 'UV blue' stars in the diagnostic (NUV–g), (g – i) color diagram. We find that the subpopulation composing this island is mainly horizontal branch stars. These objects do not exhibit UV excesses and therefore have UV colors typical for their spectral types. This subpopulation appears 'red' in the UV only because the stars' colors are not pulled to the blue by the inclusion of UVe stars.« less

An Evolutionarily Young Polar Bear (Ursus maritimus) Endogenous Retrovirus Identified from Next Generation Sequence Data.

PubMed

Tsangaras, Kyriakos; Mayer, Jens; Alquezar-Planas, David E; Greenwood, Alex D

2015-11-24

Transcriptome analysis of polar bear (Ursus maritimus) tissues identified sequences with similarity to Porcine Endogenous Retroviruses (PERV). Based on these sequences, four proviral copies and 15 solo long terminal repeats (LTRs) of a newly described endogenous retrovirus were characterized from the polar bear draft genome sequence. Closely related sequences were identified by PCR analysis of brown bear (Ursus arctos) and black bear (Ursus americanus) but were absent in non-Ursinae bear species. The virus was therefore designated UrsusERV. Two distinct groups of LTRs were observed including a recombinant ERV that contained one LTR belonging to each group indicating that genomic invasions by at least two UrsusERV variants have recently occurred. Age estimates based on proviral LTR divergence and conservation of integration sites among ursids suggest the viral group is only a few million years old. The youngest provirus was polar bear specific, had intact open reading frames (ORFs) and could potentially encode functional proteins. Phylogenetic analyses of UrsusERV consensus protein sequences suggest that it is part of a pig, gibbon and koala retrovirus clade. The young age estimates and lineage specificity of the virus suggests UrsusERV is a recent cross species transmission from an unknown reservoir and places the viral group among the youngest of ERVs identified in mammals.

An Evolutionarily Young Polar Bear (Ursus maritimus) Endogenous Retrovirus Identified from Next Generation Sequence Data

PubMed Central

Tsangaras, Kyriakos; Mayer, Jens; Alquezar-Planas, David E.; Greenwood, Alex D.

2015-01-01

Transcriptome analysis of polar bear (Ursus maritimus) tissues identified sequences with similarity to Porcine Endogenous Retroviruses (PERV). Based on these sequences, four proviral copies and 15 solo long terminal repeats (LTRs) of a newly described endogenous retrovirus were characterized from the polar bear draft genome sequence. Closely related sequences were identified by PCR analysis of brown bear (Ursus arctos) and black bear (Ursus americanus) but were absent in non-Ursinae bear species. The virus was therefore designated UrsusERV. Two distinct groups of LTRs were observed including a recombinant ERV that contained one LTR belonging to each group indicating that genomic invasions by at least two UrsusERV variants have recently occurred. Age estimates based on proviral LTR divergence and conservation of integration sites among ursids suggest the viral group is only a few million years old. The youngest provirus was polar bear specific, had intact open reading frames (ORFs) and could potentially encode functional proteins. Phylogenetic analyses of UrsusERV consensus protein sequences suggest that it is part of a pig, gibbon and koala retrovirus clade. The young age estimates and lineage specificity of the virus suggests UrsusERV is a recent cross species transmission from an unknown reservoir and places the viral group among the youngest of ERVs identified in mammals. PMID:26610552

A motivation-based explanatory model of street drinking among young people.

PubMed

Martín-Santana, Josefa D; Beerli-Palacio, Asunción; Fernández-Monroy, Margarita

2014-01-01

This social marketing study focuses on street drinking behavior among young people. The objective is to divide the market of young people who engage in this activity into segments according to their motivations. For the three segments identified, a behavior model is created using the beliefs, attitudes, behavior, and social belonging of young people who engage in street drinking. The methodology used individual questionnaires filled in by a representative sample of young people. The results show that the behavior model follows the sequence of attitudes-beliefs-behavior and that social belonging influences these three variables. Similarly, differences are observed in the behavior model depending on the segment individuals belong to.

Because difficulty is not the same for everyone: the impact of complexity in working memory is associated with cannabinoid 1 receptor genetic variation in young adults.

PubMed

Ruiz-Contreras, Alejandra E; Román-López, Talía V; Caballero-Sánchez, Ulises; Rosas-Escobar, Cintia B; Ortega-Mora, E Ivett; Barrera-Tlapa, Miguel A; Romero-Hidalgo, Sandra; Carrillo-Sánchez, Karol; Hernández-Morales, Salvador; Vadillo-Ortega, Felipe; González-Barrios, Juan Antonio; Méndez-Díaz, Mónica; Prospéro-García, Oscar

2017-03-01

Individual differences in working memory ability are mainly revealed when a demanding challenge is imposed. Here, we have associated cannabinoid 1 (CB1) receptor genetic variation rs2180619 (AA, AG, GG), which is located in a potential CNR1 regulatory sequence, with performance in working memory. Two-hundred and nine Mexican-mestizo healthy young participants (89 women, 120 men, mean age: 23.26 years, SD = 2.85) were challenged to solve a medium (2-back) vs. a high (3-back) difficulty N-back tasks. All subjects responded as expected, performance was better with the medium than the high demand task version, but no differences were found among genotypes while performing each working memory (WM) task. However, the cost of the level of complexity in N-back paradigm was double for GG subjects than for AA subjects. It is noteworthy that an additive-dosage allele relation was found for G allele in terms of cost of level of complexity. These genetic variation results support that the endocannabinoid system, evaluated by rs2180619 polymorphism, is involved in WM ability in humans.

Imaging Forming Planetary Systems: The HST/STIS Legacy and Prospects for Future Missions

NASA Technical Reports Server (NTRS)

Grady, Carol; Woodgate, Bruce E.; Bowers, Charles; Weinberger, Alycia; Schneider, Glenn; Oegerle, William R. (Technical Monitor)

2002-01-01

The first indication that debris and protoplanetary disks associated with other, young planetary systems were sufficiently nearby to image came with the IRAS detection of infrared excesses around $\\beta$ Pic, Vega, Fomalhaut, and $\\epsilon$ Eri. Moving beyond analysis of the infrared excess to optical and near-IR imaging requires access to high Strehl ratio and high contrast imaging techniques, with the ability to efficiently reject the residual scattered and diffracted light from the star to reveal the fainter scattered light and circumstellar emission originating from the vicinity of the star. HST/STIS imaging studies have made use of incomplete Lyot coronagraphic imaging modes to reveal the warped, inner disk of $\\beta$ Pic, provide the highest spatial resolution images of young debris disk systems such as HR 4796A, have revealed the presence of azimuthally symmetric structure in HD 141569 and HD 163296, and have demonstrated that currently active, collimated outflows survive to higher stellar masses than previously expected, and through more of the star's pre-main sequence lifetime than anticipated. The HST/STIS coronagraphic imaging legacy will be discussed, together with the implications for future NIR and optical high contrast imaging capabilities.

Probabilistic HR Diagrams: A New Infrared and X-ray Chronometer for Very Young, Massive Stellar Clusters and Associations

NASA Astrophysics Data System (ADS)

Maldonado, Jessica; Povich, Matthew S.

2016-01-01

We present a novel method for constraining the duration of star formation in very young, massive star-forming regions. Constraints on stellar population ages are derived from probabilistic HR diagrams (pHRDs) generated by fitting stellar model spectra to the infrared (IR) spectral energy distributions (SEDs) of Herbig Ae/Be stars and their less-evolved, pre-main sequence progenitors. Stellar samples for the pHRDs are selected based on the detection of X-ray emission associated with the IR source, and the lack of detectible IR excess emission at wavelengths ≤4.5 µm. The SED model fits were used to create two-dimensional probability distributions of the stellar parameters, specifically bolometric luminosity versus temperature and mass versus evolutionary age. We present first results from the pHRD analysis of the relatively evolved Carina Nebula and the unevolved M17 SWex infrared dark cloud, which reveal the expected, strikingly different star formation durations between these two regions. In the future, we will apply this method to analyze available X-ray and IR data from the MYStIX project on other Galactic massive star forming regions within 3 kpc of the Sun.

ASTEROSEISMIC ANALYSIS OF THE PRE-MAIN-SEQUENCE STARS IN NGC 2264

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

Guenther, D. B.; Casey, M. P.; Kallinger, T.

2009-10-20

NGC 2264 is a young open cluster lying above the Galactic plane in which six variable stars have previously been identified as possible pre-main-sequence (PMS) pulsators. Their oscillation spectra are relatively sparse with each star having from 2 to 12 unambiguous frequency identifications based on Microvariability and Oscillations of Stars satellite and multi-site ground-based photometry. We describe our efforts to find classical PMS stellar models (i.e., models evolved from the Hayashi track) whose oscillation spectra match the observed frequencies. We find model eigenspectra that match the observed frequencies and are consistent with the stars' locations in the HR diagram formore » the three faintest of the six stars. Not all the frequencies found in spectra of the three brightest stars can be matched to classical PMS model spectra possibly because of effects not included in our PMS models such as chemical and angular momentum stratification in the outer layers of the star. All the oscillation spectra contain both radial and nonradial p-modes. We argue that the PMS pulsating stars divide into two groups depending on whether or not they have undergone complete mixing (i.e., have gone through a Hayashi phase). Lower mass stars that do evolve through a Hayashi phase have oscillation spectra predicted by classical PMS models, whereas more massive stars that do not, retain mass infall effects in their surface layers and are not well modeled by classical PMS models.« less

Presupernova Evolution of Differentially Rotating Massive Stars Including Magnetic Fields

NASA Astrophysics Data System (ADS)

Heger, A.; Woosley, S. E.; Spruit, H. C.

2005-06-01

As a massive star evolves through multiple stages of nuclear burning on its way to becoming a supernova, a complex, differentially rotating structure is set up. Angular momentum is transported by a variety of classic instabilities and also by magnetic torques from fields generated by the differential rotation. We present the first stellar evolution calculations to follow the evolution of rotating massive stars including, at least approximately, all these effects, magnetic and nonmagnetic, from the zero-age main sequence until the onset of iron-core collapse. The evolution and action of the magnetic fields is as described by Spruit in 2002, and a range of uncertain parameters is explored. In general, we find that magnetic torques decrease the final rotation rate of the collapsing iron core by about a factor of 30-50 when compared with the nonmagnetic counterparts. Angular momentum in that part of the presupernova star destined to become a neutron star is an increasing function of main-sequence mass. That is, pulsars derived from more massive stars rotate faster and rotation plays a more important role in the star's explosion. The final angular momentum of the core has been determined-to within a factor of 2-by the time the star ignites carbon burning. For the lighter stars studied, around 15 Msolar, we predict pulsar periods at birth near 15 ms, though a factor of 2 range is easily tolerated by the uncertainties. Several mechanisms for additional braking in a young neutron star, especially by fallback, are explored.

Chromospheric variations in main-sequence stars

NASA Technical Reports Server (NTRS)

Baliunas, S. L.; Donahue, R. A.; Soon, J. H.; Horne, J. H.; Frazer, J.; Woodard-Eklund, L.; Bradford, M.; Rao, L. M.; Wilson, O. C.; Zhang, Q.

1995-01-01

The fluxes in passbands 0.1 nm wide and centered on the Ca II H and K emission cores have been monitored in 111 stars of spectral type F2-M2 on or near the main sequence in a continuation of an observing program started by O. C. Wilson. Most of the measurements began in 1966, with observations scheduled monthly until 1980, when observations were schedueld sevral times per week. The records, with a long-term precision of about 1.5%, display fluctuations that can be idntified with variations on timescales similar to the 11 yr cycle of solar activity as well as axial rotation, and the growth and decay of emitting regions. We present the records of chromospheric emission and general conclusions about variations in surface magnetic activity on timescales greater than 1 yr but less than a few decades. The results for stars of spectral type G0-K5 V indicate a pattern of change in rotation and chromospheric activity on an evolutionary timescale, in which (1) young stars exhibit high average levels of activity, rapid rotation rates, no Maunder minimum phase and rarely display a smooth, cyclic variation; (2) stars of intermediate age (approximately 1-2 Gyr for 1 solar mass) have moderate levels of activity and rotation rates, and occasional smooth cycles; and (3) stars as old as the Sun and older have slower rotation rates, lower activity levels and smooth cycles with occasional Maunder minimum-phases.

Discovery and Characterization of Eclipsing Binary Stars and Transiting Planets in Young Benchmark Clusters: The Pleiades and Hyades

NASA Astrophysics Data System (ADS)

Stassun, Keivan; David, Trevor J.; Conroy, Kyle E.; Hillenbrand, Lynne; Stauffer, John R.; Pepper, Joshua; Rebull, Luisa M.; Cody, Ann Marie

2016-06-01

Prior to K2, only one eclipsing binary in the Pleiades was known (HD 23642). We present the discovery and characterization of three additional eclipsing binaries (EBs) in this ~120 Myr old benchmark open cluster. Unlike HD 23642, all three of the new EBs are low mass (Mtot < 1 M⊙) and thus their components are still undergoing pre-main-sequence contraction at the Pleiades age. Low mass EBs are rare, especially in the pre-main-sequence phase, and thus these systems are valuable for constraining theoretical stellar evolution models. One of the three new EBs is single-lined with a K-type primary (HII 2407). The second (HCG 76) comprises two nearly equal-mass 0.3 M⊙ stars, with masses and radii measured with precisions of better than 3% and 5%, respectively. The third (MHO 9) has an M-type primary with a secondary that is possibly quite close to the hydrogen-burning limit, but needs additional follow-up observations to better constrain its parameters. We use the precise parameters of HCG 76 to test the predictions of stellar evolution models, and to derive an independent distance to the Pleiades of 132±5 pc. Finally, we present tentative evidence for differential rotation in the primary component of the newly discovered Pleiades EB HII 2407, and we also characterize a newly discovered transiting Neptune-sized planet orbiting an M-dwarf in the Hyades.

X-ray Emission from Pre-Main-Sequence Stars - Testing the Solar Analogy

NASA Technical Reports Server (NTRS)

Skinner, Stephen L.

2000-01-01

This LTSA award funded my research on the origin of stellar X-ray emission and the validity of the solar-stellar analogy. This research broadly addresses the relevance of our current understanding of solar X-ray physics to the interpretation of X-ray emission from stars in general. During the past five years the emphasis has been on space-based X-ray observations of very young stars in star-forming regions (T Tauri stars and protostars), cool solar-like G stars, and evolved high-mass Wolf-Rayet (WR) stars. These observations were carried out primarily with the ASCA and ROSAT space-based observatories (and most recently with Chandra), supplemented by ground-based observations. This research has focused on the identification of physical processes that are responsible for the high levels of X-ray emission seen in pre-main-sequence (PMS) stars, active cool stars, and WR stars. A related issue is how the X-ray emission of such stars changes over time, both on short timescales of days to years and on evolutionary timescales of millions of years. In the case of the Sun it is known that magnetic fields play a key role in the production of X-rays by confining the coronal plasma in loop-like structures where it is heated to temperatures of several million K. The extent to which the magnetically-confined corona interpretation can be applied to other X-ray emitting stars is the key issue that drives the research summarized here.

Keck Adaptive Optics Imaging of Nearby Young Stars: Detection of Close Multiple Systems

NASA Astrophysics Data System (ADS)

Brandeker, Alexis; Jayawardhana, Ray; Najita, Joan

2003-10-01

Using adaptive optics on the Keck II 10 m telescope on Mauna Kea, we have surveyed 24 of the nearest young stars known in search of close companions. Our sample includes members of the MBM 12 and TW Hydrae young associations and the classical T Tauri binary UY Aurigae in the Taurus star-forming region. We present relative photometry and accurate astrometry for 10 close multiple systems. The multiplicity frequency in the TW Hydrae and MBM 12 groups are high in comparison to other young regions, although the significance of this result is low because of the small number statistics. We resolve S18 into a triple system, including a tight 63 mas (projected separation of 17 AU at a distance of 275 pc) binary, for the first time, with a hierarchical configuration reminiscent of VW Chamaeleontis and T Tauri. Another tight binary in our sample-TWA 5Aab (54 mas or 3 AU at 55 pc)-offers the prospect of dynamical mass measurement using astrometric observations within a few years and thus could be important for testing pre-main-sequence evolutionary models. Our observations confirm with 9 σ confidence that the brown dwarf TWA 5B is bound to TWA 5A. We find that the flux ratio of UY Aur has changed dramatically, by more than a magnitude in the H band, possibly as a result of variable extinction. With the smaller flux difference, the system may once again become detectable as an optical binary, as it was at the time of its discovery in 1944. Taken together, our results demonstrate that adaptive optics on large telescopes is a powerful tool for detecting tight companions and thus exploring the frequency and configurations of close multiple systems.

Is the Young Star RZ Piscium Consuming Its Own (Planetary) Offspring?

NASA Astrophysics Data System (ADS)

Punzi, K. M.; Kastner, J. H.; Melis, C.; Zuckerman, B.; Pilachowski, C.; Gingerich, L.; Knapp, T.

2018-01-01

The erratically variable star RZ Piscium (RZ Psc) displays extreme optical dropout events and strikingly large excess infrared emission. To ascertain the evolutionary status of this intriguing star, we obtained observations of RZ Psc with the European Space Agency’s X-ray Multi-Mirror Mission (XMM-Newton), as well as high-resolution optical spectroscopy with the Hamilton Echelle on the Lick Shane 3 m telescope and with HIRES on the Keck I 10 m telescope. The optical spectroscopy data demonstrate that RZ Psc is a pre-main sequence star with an effective temperature of 5600 ± 75 K and log g of 4.35 ± 0.10. The ratio of X-ray to bolometric luminosity, {log}{L}X/{L}{bol}, lies in the range ‑3.7 to ‑3.2, consistent with ratios typical of young, solar-mass stars, thereby providing strong support for the young star status of RZ Psc. The Li absorption line strength of RZ Psc suggests an age in the range 30–50 Myr, which in turn implies that RZ Psc lies at a distance of ∼170 pc. Adopting this estimated distance, we find the Galactic space velocity of RZ Psc to be similar to the space velocities of stars in young moving groups near the Sun. Optical spectral features indicative of activity and/or circumstellar material are present in our spectra over multiple epochs, which provide evidence for the presence of a significant mass of circumstellar gas associated with RZ Psc. We suggest that the destruction of one or more massive orbiting bodies has recently occurred within 1 au of the star, and we are viewing the aftermath of such an event along the plane of the orbiting debris.

Age-Related Variations in Intestinal Microflora of Free-Range and Caged Hens.

PubMed

Cui, Yizhe; Wang, Qiuju; Liu, Shengjun; Sun, Rui; Zhou, Yaqiang; Li, Yue

2017-01-01

Free range feeding pattern puts the chicken in a mixture of growth materials and enteric bacteria excreted by nature, while it is typically unique condition materials and enteric bacteria in commercial caged hens production. Thus, the gastrointestinal microflora in two feeding patterns could be various. However, it remains poorly understood how feeding patterns affect development and composition of layer hens' intestinal microflora. In this study, the effect of feeding patterns on the bacteria community in layer hens' gut was investigated using free range and caged feeding form. Samples of whole small intestines and cecal digesta were collected from young hens (8-weeks) and mature laying hens (30-weeks). Based on analysis using polymerase chain reaction-denaturing gradient gel electrophoresis and sequencing of bacterial 16S rDNA gene amplicons, the microflora of all intestinal contents were affected by both feeding patterns and age of hens. Firmicutes, Bacteroidetes, Actinobacteria, Proteobacteria, and Fusobacteria were the main components. Additionally, uncultured environmental samples were found too. There were large differences between young hens and adult laying hens, the latter had more Firmicutes and Bacteroidetes, and bacterial community is more abundant in 30-weeks laying hens of all six phyla than 8-weeks young hens of only two phyla. In addition, the differences were also observed between free range and caged hens. Free range hens had richer Actinobacteria, Bacteroidetes, and Proteobacteria. Most of strains found were detected more abundant in small intestines than in cecum. Also the selected Lactic acid bacteria from hens gut were applied in feed and they had beneficial effects on growth performance and jejunal villus growth of young broilers. This study suggested that feeding patterns have an importance effect on the microflora composition of hens, which may impact the host nutritional status and intestinal health.

Assessment of proximal pulmonary arterial stiffness using magnetic resonance imaging: effects of technique, age and exercise

PubMed Central

Kamalasanan, Anu; Cassidy, Deidre B; Struthers, Allan D; Lipworth, Brian J; Houston, J Graeme

2016-01-01

Introduction To compare the reproducibility of pulmonary pulse wave velocity (PWV) techniques, and the effects of age and exercise on these. Methods 10 young healthy volunteers (YHV) and 20 older healthy volunteers (OHV) with no cardiac or lung condition were recruited. High temporal resolution phase contrast sequences were performed through the main pulmonary arteries (MPAs), right pulmonary arteries (RPAs) and left pulmonary arteries (LPAs), while high spatial resolution sequences were obtained through the MPA. YHV underwent 2 MRIs 6 months apart with the sequences repeated during exercise. OHV underwent an MRI scan with on-table repetition. PWV was calculated using the transit time (TT) and flow area techniques (QA). 3 methods for calculating QA PWV were compared. Results PWV did not differ between the two age groups (YHV 2.4±0.3/ms, OHV 2.9±0.2/ms, p=0.1). Using a high temporal resolution sequence through the RPA using the QA accounting for wave reflections yielded consistently better within-scan, interscan, intraobserver and interobserver reproducibility. Exercise did not result in a change in either TT PWV (mean (95% CI) of the differences: −0.42 (−1.2 to 0.4), p=0.24) or QA PWV (mean (95% CI) of the differences: 0.10 (−0.5 to 0.9), p=0.49) despite a significant rise in heart rate (65±2 to 87±3, p<0.0001), blood pressure (113/68 to 130/84, p<0.0001) and cardiac output (5.4±0.4 to 6.7±0.6 L/min, p=0.004). Conclusions QA PWV performed through the RPA using a high temporal resolution sequence accounting for wave reflections yields the most reproducible measurements of pulmonary PWV. PMID:27843548

Conversion of amino-acid sequence in proteins to classical music: search for auditory patterns

PubMed Central

2007-01-01

We have converted genome-encoded protein sequences into musical notes to reveal auditory patterns without compromising musicality. We derived a reduced range of 13 base notes by pairing similar amino acids and distinguishing them using variations of three-note chords and codon distribution to dictate rhythm. The conversion will help make genomic coding sequences more approachable for the general public, young children, and vision-impaired scientists. PMID:17477882

Deconstructing Learning in Science--Young Children's Responses to a Classroom Sequence on Evaporation.

ERIC Educational Resources Information Center

Tytler, Russell; Peterson, Suzanne

2001-01-01

Tracks five-year-old children's ideas by a range of means during and subsequent to a classroom sequence on evaporation. Explores the relationship between social and individual perspectives on learning, and questions some assumptions underlying conceptual change research. Analyzes the children's explanations of various evaporation phenomena over…

Measures of Working Memory, Sequence Learning, and Speech Recognition in the Elderly.

ERIC Educational Resources Information Center

Humes, Larry E.; Floyd, Shari S.

2005-01-01

This study describes the measurement of 2 cognitive functions, working-memory capacity and sequence learning, in 2 groups of listeners: young adults with normal hearing and elderly adults with impaired hearing. The measurement of these 2 cognitive abilities with a unique, nonverbal technique capable of auditory, visual, and auditory-visual…

EFL Learners' Grammatical Awareness through Accumulating Formulaic Sequences of Morphological Structure (-ing)

ERIC Educational Resources Information Center

Kashiwagi, Kazuko; Ito, Yukiko

2017-01-01

Even young EFL learners who have not yet learned L2 grammar will notice language patterns if, when retrieving exemplars ("item-based patterns"), they succeed in making form-meaning connections (FMCs). Item-based patterns, termed formulaic sequences (FS), serve as a basis for creative constructions. Although learners are implicitly…

A unique chromatin complex occupies young α-satellite arrays of human centromeres

PubMed Central

Henikoff, Jorja G.; Thakur, Jitendra; Kasinathan, Sivakanthan; Henikoff, Steven

2015-01-01

The intractability of homogeneous α-satellite arrays has impeded understanding of human centromeres. Artificial centromeres are produced from higher-order repeats (HORs) present at centromere edges, although the exact sequences and chromatin conformations of centromere cores remain unknown. We use high-resolution chromatin immunoprecipitation (ChIP) of centromere components followed by clustering of sequence data as an unbiased approach to identify functional centromere sequences. We find that specific dimeric α-satellite units shared by multiple individuals dominate functional human centromeres. We identify two recently homogenized α-satellite dimers that are occupied by precisely positioned CENP-A (cenH3) nucleosomes with two ~100–base pair (bp) DNA wraps in tandem separated by a CENP-B/CENP-C–containing linker, whereas pericentromeric HORs show diffuse positioning. Precise positioning is largely maintained, whereas abundance decreases exponentially with divergence, which suggests that young α-satellite dimers with paired ~100-bp particles mediate evolution of functional human centromeres. Our unbiased strategy for identifying functional centromeric sequences should be generally applicable to tandem repeat arrays that dominate the centromeres of most eukaryotes. PMID:25927077

Initial Results from the Palomar Adaptive Optics Survey of Young Solar-Type Stars: A Brown Dwarf and Three Stellar Companions

NASA Astrophysics Data System (ADS)

Metchev, Stanimir A.; Hillenbrand, Lynne A.

2004-12-01

We present first results from the Palomar Adaptive Optics Survey of Young Stars conducted at the Hale 5 m telescope. Through direct imaging we have discovered a brown dwarf and two low-mass stellar companions to the young solar-type stars HD 49197, HD 129333 (EK Dra), and V522 Per and confirmed a previously suspected companion to RX J0329.1+0118 (Sterzik et al.), at respective separations of 0.95" (43 AU), 0.74" (25 AU), 2.09" (400 AU), and 3.78" (380 AU). Physical association of each binary system is established through common proper motion and/or low-resolution infrared spectroscopy. Based on the companion spectral types, we estimate their masses at 0.06, 0.20, 0.13, and 0.20 Msolar, respectively. From analysis of our imaging data combined with archival radial velocity data, we find that the spatially resolved companion to HD 129333 is potentially identical to the previously identified spectroscopic companion to this star (Duquennoy & Mayor). However, a discrepancy with the absolute magnitude suggests that the two companions could also be distinct, with the resolved one being the outermost component of a triple system. The brown dwarf HD 49197B is a new member of a growing list of directly imaged substellar companions at 10-1000 AU separations from main-sequence stars, indicating that such brown dwarfs may be more common than initially speculated.

Forming spectroscopic massive protobinaries by disc fragmentation

NASA Astrophysics Data System (ADS)

Meyer, D. M.-A.; Kuiper, R.; Kley, W.; Johnston, K. G.; Vorobyov, E.

2018-01-01

The surroundings of massive protostars constitute an accretion disc which has numerically been shown to be subject to fragmentation and responsible for luminous accretion-driven outbursts. Moreover, it is suspected to produce close binary companions which will later strongly influence the star's future evolution in the Hertzsprung-Russel diagram. We present three-dimensional gravitation-radiation-hydrodynamic numerical simulations of 100 M⊙ pre-stellar cores. We find that accretion discs of young massive stars violently fragment without preventing the (highly variable) accretion of gaseous clumps on to the protostars. While acquiring the characteristics of a nascent low-mass companion, some disc fragments migrate on to the central massive protostar with dynamical properties showing that its final Keplerian orbit is close enough to constitute a close massive protobinary system, having a young high- and a low-mass components. We conclude on the viability of the disc fragmentation channel for the formation of such short-period binaries, and that both processes - close massive binary formation and accretion bursts - may happen at the same time. FU-Orionis-type bursts, such as observed in the young high-mass star S255IR-NIRS3, may not only indicate ongoing disc fragmentation, but also be considered as a tracer for the formation of close massive binaries - progenitors of the subsequent massive spectroscopic binaries - once the high-mass component of the system will enter the main-sequence phase of its evolution. Finally, we investigate the Atacama Large (sub-)Millimeter Array observability of the disc fragments.

Optical photometric variable stars towards the Galactic H II region NGC 2282

NASA Astrophysics Data System (ADS)

Dutta, Somnath; Mondal, Soumen; Joshi, Santosh; Jose, Jessy; Das, Ramkrishna; Ghosh, Supriyo

2018-05-01

We report here CCD I-band time series photometry of a young (2-5 Myr) cluster NGC 2282, in order to identify and understand the variability of pre-main-sequence (PMS) stars. The I-band photometry, down to ˜20.5 mag, enables us to probe the variability towards the lower mass end (˜0.1 M⊙) of PMS stars. From the light curves of 1627 stars, we identified 62 new photometric variable candidates. Their association with the region was established from H α emission and infrared (IR) excess. Among 62 variables, 30 young variables exhibit H α emission, near-IR (NIR)/mid-IR (MIR) excess or both and are candidate members of the cluster. Out of 62 variables, 41 are periodic variables, with a rotation rate ranging from 0.2-7 d. The period distribution exhibits a median period at ˜1 d, as in many young clusters (e.g. NGC 2264, ONC, etc.), but it follows a unimodal distribution, unlike others that have bimodality, with slow rotators peaking at ˜6-8 d. To investigate the rotation-disc and variability-disc connection, we derived the NIR excess from Δ(I - K) and the MIR excess from Spitzer [3.6]-[4.5] μm data. No conclusive evidence of slow rotation with the presence of discs around stars and fast rotation for discless stars is obtained from our periodic variables. A clear increasing trend of the variability amplitude with IR excess is found for all variables.

A Main Sequence For Quasars

NASA Astrophysics Data System (ADS)

Marziani, Paola; Sulentic, J. W.; Dultzin, D.; Negrete, A.; del Olmo, A.; Martínez-Carballo, M. A.; Stirpe, G. M.; D'Onofrio, M.; Perea, J.

2016-10-01

The 4D eigenvector 1 parameter space defined by Sulentic et al. may be seen as a surrogate H-R diagram for quasars. As in the stellar H-R diagram, a source sequence can be easily identified. In the case of quasars, the main sequence appears to be mainly driven by Eddington ratio. A transition Eddington ratio may in part explain the striking observational differences between quasars at opposite ends of the main sequence. The eigenvector-1 approach opens the door towards properly contextualized models of quasar physics, geometry and kinematics. We review some of the progress that has been made over the past 15 years, and point out still unsolved issues.

The CIDA-QUEST large-scale survey of Orion OB1: evidence for rapid disk dissipation in a dispersed stellar population.

PubMed

Briceño, C; Vivas, A K; Calvet, N; Hartmann, L; Pacheco, R; Herrera, D; Romero, L; Berlind, P; Sánchez, G; Snyder, J A; Andrews, P

2001-01-05

We are conducting a large-scale, multiepoch, optical photometric survey [Centro de Investigaciones de Astronomia-Quasar Equatorial Survey Team (CIDA-QUEST)] covering about 120 square degrees to identify the young low-mass stars in the Orion OB1 association. We present results for an area of 34 square degrees. Using photometric variability as our main selection criterion, as well as follow-up spectroscopy, we confirmed 168 previously unidentified pre-main sequence stars that are about 0.6 to 0.9 times the mass of the sun (Mo), with ages of about 1 million to 3 million years (Ori OB1b) and about 3 million to 10 million years (Ori OB1a). The low-mass stars are spatially coincident with the high-mass (at least 3 Mo) members of the associations. Indicators of disk accretion such as Halpha emission and near-infrared emission from dusty disks fall sharply from Ori OB1b to Ori OB1a, indicating that the time scale for disk dissipation and possibly the onset of planet formation is a few million years.

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

Ferraro, F. R.; Dalessandro, E.; Lanzoni, B.

The Galactic bulge is dominated by an old, metal-rich stellar population. The possible presence and the amount of a young (a few gigayears old) minor component is one of the major issues debated in the literature. Recently, the bulge stellar system Terzan 5 was found to harbor three sub-populations with iron content varying by more than one order of magnitude (from 0.2 up to two times the solar value), with chemical abundance patterns strikingly similar to those observed in bulge field stars. Here we report on the detection of two distinct main-sequence turnoff points in Terzan 5, providing the agemore » of the two main stellar populations: 12 Gyr for the (dominant) sub-solar component and 4.5 Gyr for the component at super-solar metallicity. This discovery classifies Terzan 5 as a site in the Galactic bulge where multiple bursts of star formation occurred, thus suggesting a quite massive progenitor possibly resembling the giant clumps observed in star-forming galaxies at high redshifts. This connection opens a new route of investigation into the formation process and evolution of spheroids and their stellar content.« less

Identifying Young, Nearby Stars

NASA Technical Reports Server (NTRS)

Webb, Rich; Song, Inseok; Zuckerman, Ben; Bessell, Mike

2001-01-01

Young stars have certain characteristics, e.g., high atmospheric abundance of lithium and chromospheric activity, fast rotation, distinctive space motion and strong X-ray flux compared to that of older main sequence stars. We have selected a list of candidate young (<100Myr) and nearby (<60pc) stars based on their space motion and/or strong X-ray flux. To determine space motion of a star, one needs to know its coordinates (RA, DEC), proper motion, distance, and radial velocity. The Hipparcos and Tycho catalogues provide all this information except radial velocities. We anticipate eventually searching approx. 1000 nearby stars for signs of extreme youth. Future studies of the young stars so identified will help clarify the formation of planetary systems for times between 10 and 100 million years. Certainly, the final output of this study will be a very useful resource, especially for adaptive optics and space based searches for Jupiter-mass planets and dusty proto-planetary disks. We have begun spectroscopic observations in January, 2001 with the 2.3 m telescope at Siding Spring Observatory (SSO) in New South Wales, Australia. These spectra will be used to determine radial velocities and other youth indicators such as Li 6708A absorption strength and Hydrogen Balmer line intensity. Additional observations of southern hemisphere stars from SSO are scheduled in April and northern hemisphere observations will take place in May and July at the Lick Observatory of the University of California. AT SSO, to date, we have observed about 100 stars with a high resolution spectrometer (echelle) and about 50 stars with a medium spectral resolution spectrometer (the "DBS"). About 20% of these stars turn out to be young stars. Among these, two especially noteworthy stars appear to be the closest T-Tauri stars ever identified. Interestingly, these stars share the same space motions as that of a very famous star with a dusty circumstellar disk--beta Pictoris. This new finding better constrains the age of beta Pictoris to be approx. 10 Myr.

A Survey of Ca II H and K Chromospheric Emission in Southern Solar-Type Stars

NASA Astrophysics Data System (ADS)

Henry, Todd J.; Soderblom, David R.; Donahue, Robert A.; Baliunas, Sallie L.

1996-01-01

More than 800 southern stars within 50 pc have been observed for chromospheric emission in the cores of the Ca II H and K lines. Most of the sample targets were chosen to be G dwarfs on the basis of colors and spectral types. The bimodal distribution in stellar activity first noted in a sample of northern stars by Vaughan and Preston in 1980 is confirmed, and the percentage of active stars, about 30%, is remarkably consistent between the northern and southern surveys. This is especially compelling given that we have used an entirely different instrumental setup and stellar sample than used in the previous study. Comparisons to the Sun, a relatively inactive star, show that most nearby solar-type stars have a similar activity level, and presumably a similar age. We identify two additional subsamples of stars -- a very active group, and a very inactive group. The very active group may be made up of young stars near the Sun, accounting for only a few percent of the sample, and appears to be less than ~0.1 Gyr old. Included in this high-activity tail of the distribution, however, is a subset of very close binaries of the RS CVn or W UMa types. The remaining members of this population may be undetected close binaries or very young single stars. The very inactive group of stars, contributting ~5%--10% to the total sample, may be those caught in a Maunder Minimum type phase. If the observations of the survey stars are considered to be a sequence of snapshots of the Sun during its life, we might expect that the Sun will spend about 10% of the remainder of its main sequence life in a Maunder Minimum phase.

Contribution to the molecular systematics of the genus Capoeta from the south Caspian Sea basin using mitochondrial cytochrome b sequences (Teleostei: Cyprinidae)

PubMed Central

Zareian, Halimeh; Esmaeili, Hamid Reza; Heidari, Adeleh; Khoshkholgh, Majid Reza; Mousavi-Sabet, Hamed

2016-01-01

Traditionally, Capoeta populations from the southern Caspian Sea basin have been considered as Capoeta capoeta gracilis. Study on the phylogenetic relationship of Capoeta species using mitochondrial cytochrome b gene sequences show that Capoeta population from the southern Caspian Sea basin is distinct species and receive well support (posterior probability of 100%). Based on the tree topologies obtained from Bayesian and Maximum Likelihood methods, three main groups for the studied Capoeta were detected: Clade I) Capoeta trutta group (the Mesopotamian Capoeta group) including closely related taxa (e.g. trutta, turani, barroisi) characterized by having numerous irregular black spots on the dorsal half of the body. This clade was the sister group to all other Capoeta species and its separation occurred very early in evolution possess, so we considered it as O ld Evolutionary Group. Clade II) comprises highly diversified and widespread group, Capoeta damascina complex group (small scale capoeta group), the Anatolian-Iranian group (e.g. banarescui, buhsei, damascina, saadii), characterized by small scales and plain body (absence of irregular black spots on the dorsal half of the body, except in some juveniles) with significantly later speciation event so called Young Evolutionary Group. Clade III) Capoeta capoeta complex group (large scale capoeta group, the Aralo-Caspian group) comprises very closely related taxa characterized by large scales and plain body (absence of irregular black spots on the dorsal half of the body) distributed in Aralo-Caspian water bodies (capoeta, ekmekciae, heratensis, gracilis, sevangi) that has been recently diverged and could be considered as Very Young Evolutionary Group. PMID:28097160

Ethnic Identity and Reconciliation: Two Main Tasks for the Young in Bosnia-Herzegovina

ERIC Educational Resources Information Center

Hjort, Hanna; Frisen, Ann

2006-01-01

The saliency of ethnicity and ethnic identity is influenced by contextual circumstances. In Bosnia-Herzegovina, due to the current ethno-political situation, ethnicity and ethnic identity most likely are important aspects of adolescents' lives. The main purpose of this study is to describe a group of young Mostarians in relation to ethnic identity…

The Age of the Young Bulge-like Population in the Stellar System Terzan 5: Linking the Galactic Bulge to the High-z Universe

NASA Astrophysics Data System (ADS)

Ferraro, F. R.; Massari, D.; Dalessandro, E.; Lanzoni, B.; Origlia, L.; Rich, R. M.; Mucciarelli, A.

2016-09-01

The Galactic bulge is dominated by an old, metal-rich stellar population. The possible presence and the amount of a young (a few gigayears old) minor component is one of the major issues debated in the literature. Recently, the bulge stellar system Terzan 5 was found to harbor three sub-populations with iron content varying by more than one order of magnitude (from 0.2 up to two times the solar value), with chemical abundance patterns strikingly similar to those observed in bulge field stars. Here we report on the detection of two distinct main-sequence turnoff points in Terzan 5, providing the age of the two main stellar populations: 12 Gyr for the (dominant) sub-solar component and 4.5 Gyr for the component at super-solar metallicity. This discovery classifies Terzan 5 as a site in the Galactic bulge where multiple bursts of star formation occurred, thus suggesting a quite massive progenitor possibly resembling the giant clumps observed in star-forming galaxies at high redshifts. This connection opens a new route of investigation into the formation process and evolution of spheroids and their stellar content. Based on data obtained with (1) the ESA/NASA HST, under programs GO-14061, GO-12933, GO-10845, (2) the Very Large Telescope of the European Southern Observatory during the Science Verification of the camera MAD; (3) the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and NASA.

Accurate and High-Coverage Immune Repertoire Sequencing Reveals Characteristics of Antibody Repertoire Diversification in Young Children with Malaria

NASA Astrophysics Data System (ADS)

Jiang, Ning

Accurately measuring the immune repertoire sequence composition, diversity, and abundance is important in studying repertoire response in infections, vaccinations, and cancer immunology. Using molecular identifiers (MIDs) to tag mRNA molecules is an effective method in improving the accuracy of immune repertoire sequencing (IR-seq). However, it is still difficult to use IR-seq on small amount of clinical samples to achieve a high coverage of the repertoire diversities. This is especially challenging in studying infections and vaccinations where B cell subpopulations with fewer cells, such as memory B cells or plasmablasts, are often of great interest to study somatic mutation patterns and diversity changes. Here, we describe an approach of IR-seq based on the use of MIDs in combination with a clustering method that can reveal more than 80% of the antibody diversity in a sample and can be applied to as few as 1,000 B cells. We applied this to study the antibody repertoires of young children before and during an acute malaria infection. We discovered unexpectedly high levels of somatic hypermutation (SHM) in infants and revealed characteristics of antibody repertoire development in young children that would have a profound impact on immunization in children.

Supportive Housing in Foster Care: The Views of Young People

ERIC Educational Resources Information Center

Sinkkonen, Hanna-Maija; Kyttälä, Minna

2015-01-01

This study investigated Finnish young people's experiences of supportive housing. Supportive housing is an after-care programme that should support the transition from foster care to independent adulthood. It is directed mainly at young people who have been taken into foster care by social workers. The sample consisted of 39 young people (23…

The fundamental parameters of the chromospherically active K2 dwarf Epsilon Eridani

NASA Technical Reports Server (NTRS)

Drake, Jeremy J.; Smith, Geoffrey

1993-01-01

A silicon array detector was used to record regions exhibiting calcium and iron lines in the spectrum of the chromospherically active K2 dwarf Epsilon Eri at a resolution of 120,000 and with an SNR of not less than 200. The effective temperature, surface gravity, logarithmic iron and calcium abundances, and microturbulence are determined. Three high-excitation lines of Fe I were found to yield anomalously low iron abundances; it is postulated that the origin of the anomaly lies in the nonthermal excitation of the upper photosphere caused by chromospheric emission. It is shown that Epsilon Eri is in an evolutionary stage consistent with an M/solar mass of 0.85 theoretical zero-age main-sequence model. It is suggested that Epsilon Eri is almost certainly a young star of slightly less than one solar mass.

IRAS 22150+6109 - a young B-type star with a large disc

NASA Astrophysics Data System (ADS)

Zakhozhay, Olga V.; Miroshnichenko, Anatoly S.; Kuratov, Kenesken S.; Zakhozhay, Vladimir A.; Khokhlov, Serik A.; Zharikov, Sergey V.; Manset, Nadine

2018-06-01

We present the results of a spectroscopic analysis and spectral energy distribution (SED) modelling of the optical counterpart of the infrared source IRAS 22150+6109. The source was suggested to be a Herbig Be star located in the star-forming region L 1188. Absorption lines in the optical spectrum indicate a spectral type B3, while weak Balmer emission lines reflect the presence of a circumstellar gaseous disc. The star shows no excess radiation in the near-infrared spectral region and a strong excess in the far-infrared that we interpret as radiation from a large disc, the inner edge of which is located very far from the star (550 au) and does not attenuate its radiation. We conclude that IRAS 22150+6109 is an intermediate-mass star that is currently undergoing a short pre-main-sequence evolutionary stage.

A near infrared classification of pre-main sequence stars

NASA Astrophysics Data System (ADS)

Alonso-Martínez, M.; Meeus, G.; Eiroa, C.

2017-03-01

T Tauri stars are young solar analogues (M ≤ 1.5M_{⊙}), harbouring a disc and with ongoing accretion. The T Tauri phase has been estimated to last around 10 Myr. We have obtained J and K band spectra with WHT/LIRIS and NOT/NOTCam of 112 T Tauri stars in the Taurus star forming region. By measuring the equivalent widths of common and strong spectral features, known to follow a tight relation with temperature, we aim at providing a direct and fast method to derive stellar effective temperatures. Line ratios of strong absorption features relatively close in wavelength are used to overcome the effects of veiling. Besides, the Al I (1.313μm) line is strongly gravity-dependent and used to discern between surface gravities. Finally, we estimate accretion rates using the H-lines Pa-β and Br-γ.

Generalization of Learning from Picture Books to Novel Test Conditions by 18- and 24-Month-Old Children

ERIC Educational Resources Information Center

Simcock, Gabrielle; Dooley, Megan

2007-01-01

Researchers know little about whether very young children can recognize objects originally introduced to them in a picture book when they encounter similar looking objects in various real-world contexts. The present studies used an imitation procedure to explore young children's ability to generalize a novel action sequence from a picture book to…

Life With the Alien: Role Casting and Face-Saving Techniques in Family Conversation with Young Children.

ERIC Educational Resources Information Center

Fatigante, Marilena; Fasulo, Alessandra; Pontecorvo, Clotilde

1998-01-01

A qualitative study analyzed the distribution of participation by young children (ages 3-5) in family dinnertime conversation, focusing on "backstage talk," sequences adjacent to those in which the child is involved and within his auditory range, so that the child-projected participation-role alternates between that of addressee and overhearer.…

Dissemination and Implementation of a Financial Management Program for Adult/Young Farmers in Vocational Agriculture Programs in Missouri. Final Report.

ERIC Educational Resources Information Center

Denker, Robert; Stewart, Bob R.

In addition to an eight-page narrative, this final report contains materials and products from phase 2 of a project to develop, disseminate, and implement a three-year sequenced individualized and group instructional program in financial management for adult/young farmers in vocational agriculture. The narrative section discusses the four project…

Resolved photometry of extragalactic young massive star clusters

NASA Astrophysics Data System (ADS)

Larsen, S. S.; de Mink, S. E.; Eldridge, J. J.; Langer, N.; Bastian, N.; Seth, A.; Smith, L. J.; Brodie, J.; Efremov, Yu. N.

2011-08-01

Aims: We present colour-magnitude diagrams (CMDs) of young massive star clusters in several galaxies located well beyond the Local Group. The richness of these clusters allows us to obtain large samples of post-main sequence stars and test how well the observed CMDs are reproduced by canonical stellar isochrones. Methods: We use imaging of seven clusters in the galaxies NGC 1313, NGC 1569, NGC 1705, NGC 5236 and NGC 7793 obtained with the Advanced Camera for Surveys on board the Hubble Space Telescope and carry out PSF-fitting photometry of individual stars in the clusters. The clusters have ages in the range ~(5-50) × 106 years and masses of ~105 M⊙-106 M⊙. Although crowding prevents us from obtaining photometry in the inner regions of the clusters, we are still able to measure up to 30-100 supergiant stars in each of the richest clusters. The resulting CMDs and luminosity functions are compared with photometry of artificially generated clusters, designed to reproduce the photometric errors and completeness as realistically as possible. Results: In agreement with previous studies, our CMDs show no clear gap between the H-burning main sequence and the He-burning supergiant stars, contrary to predictions by common stellar isochrones. In general, the isochrones also fail to match the observed number ratios of red-to-blue supergiant stars, although the difficulty of separating blue supergiants from the main sequence complicates this comparison. In several cases we observe a large spread (1-2 mag) in the luminosities of the supergiant stars that cannot be accounted for by observational errors. We find that this spread can be reproduced by including an age spread of ~(10-30) × 106 years in the models. However, age spreads cannot fully account for the observed morphology of the CMDs and other processes, such as the evolution of interacting binary stars, may also play a role. Conclusions: Colour-magnitude diagrams can be successfully obtained for massive star clusters out to distances of at least 4-5 Mpc. Comparing such CMDs with models based on canonical isochrones we find several areas of disagreement. One interesting possibility is that an age spread of up to ~30 Myr may be present in some clusters. The data presented here may provide useful constraints on models for single and/or binary stellar evolution. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the association of Universities for Research in Astronomy, Inc. under the NASA contract NAS 5-26555Tables 4-10 are only available in electronic form 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/532/A147

Spectral comparison of directly imaged, young substellar companions using integral field spectroscopy - construction of an empiric log g sequence

NASA Astrophysics Data System (ADS)

Schmidt, T.; Neuhaüser, R.; Seifahrt, A.

2010-10-01

About 15 substellar companions with large separations (>∼50 AU) to their young primary stars and brown dwarfs are confirmed by both common proper motion and late-M / early-L type spectra. The origin and early evolution of these objects is still under debate. While often these substellar companions are regarded as brown dwarfs, they could possibly also be massive planets, the mass estimates are very uncertain so far. They are companions to primary stars or brown dwarfs in young associations and star forming regions like the TW Hya association, Upper Scorpius, Taurus, Beta Pic moving group, TucHor association, Lupus, Ophiuchus, and Chamaeleon, hence their ages and distances are well known, in contrast to free-floating brown dwarfs. An empirical classification is not possible, because a spectral sequence that is taking the lower gravity into account, is not existing. This problem leads to an apparent mismatch between spectra of old field type objects and young low-mass companions at the same effective temperature, hampering a determination of temperature and surface gravity independent from models. Now that about 15 such substellar candidates are found in associations of different ages, 1 - 35 Myrs, it is possible to study their spectra in comparison to each other using the advantage of light concentration by an adaptive optics system with their primary as guide star. Therefore we have begun the construction of an empirical log g sequence from beginning to observe all these substellar companions homogeneously using the AO-assisted integral field spectrograph SINFONI at VLT (ESO).

Is a sequence of tests during urethral pressure profilometry correlated with symptoms assessment in women?

PubMed

Valentini, Françoise A; Robain, Gilberte; Marti, Brigitte G

2012-01-01

Our purpose was, applying a strictly defined protocol for urethral profilometry, 1) to test the repeatability of same session rest maximum urethral closure pressure (MUCP) and 2) to search for correlation between women complaint and the changes in MUCP value (rest and dynamic tests). A population of 140 consecutive women referred for evaluation of lower urinary tract dysfunction was stratified in 4 groups according with the urinary symptoms: stress, urge, mixed incontinence and continent and in each group in 3 age groups (young, middle age and old). The sequence of tests recorded in supine position was: urethral pressure profile at rest bladder empty, after bladder filling at 250 mL (reference test), stress profile, fatigability (before (rest) and after 10 successive strong coughs), then in standing position. In all groups, there was no significant difference between the two MUCP values at rest bladder filled. In the three incontinent groups, MUCP was higher bladder empty than bladder filled (p < 0.05) except in the young sub-group. Stress incontinence led to significant decrease of MUCP during dynamic tests in the young group. MUCP was not modified after fatigability test in women with urge complaint whatever age. When recorded following a strictly defined protocol, MUCP at rest bladder filled has a good repeatability in individual. However a complex sequence of tests during urethral pressure profilometry remains discussed in middle-age and old age-groups, it allows specifying the stress component of incontinence in young women and the urgency component in all age-groups.

Determinants of HIV Phylogenetic Clustering in Chicago Among Young Black Men Who Have Sex With Men From the uConnect Cohort.

PubMed

Morgan, Ethan; Nyaku, Amesika N; DʼAquila, Richard T; Schneider, John A

2017-07-01

Phylogenetic analysis determines similarities among HIV genetic sequences from persons infected with HIV, identifying clusters of transmission. We determined characteristics associated with both membership in an HIV transmission cluster and the number of clustered sequences among a cohort of young black men who have sex with men (YBMSM) in Chicago. Pairwise genetic distances of HIV-1 pol sequences were collected during 2013-2016. Potential transmission ties were identified among HIV-infected persons whose sequences were ≤1.5% genetically distant. Putative transmission pairs were defined as ≥1 tie to another sequence. We then determined demographic and risk attributes associated with both membership in an HIV transmission cluster and the number of ties to the sequences from other persons in the cluster. Of 86 available sequences, 31 (36.0%) were tied to ≥1 other sequence. Through multivariable analyses, we determined that those who reported symptoms of depression and those who had a higher number of confidants in their network had significantly decreased odds of membership in transmission clusters. We found that those who had unstable housing and who reported heavy marijuana use had significantly more ties to other individuals within transmission clusters, whereas those identifying as bisexual, those participating in group sex, and those with higher numbers of sexual partners had significantly fewer ties. This study demonstrates the potential for combining phylogenetic and individual and network attributes to target HIV control efforts to persons with potentially higher transmission risk, as well as suggesting some unappreciated specific predictors of transmission risk among YBMSM in Chicago for future study.

The Developmental Sequence of Social-Communicative Skills in Young Children with Autism: A Longitudinal Study

ERIC Educational Resources Information Center

Wu, Chin-Chin; Chiang, Chung-Hsin

2014-01-01

To explore the different developmental trajectories of social-communicative skills in children with autism and typically developing infants, two longitudinal studies were conducted. In Study 1, we examined the developmental sequence of social-communicative skills in 26 typically developing infants when they were 9 months old and reexamined them…

Implicit Learning of Predictive Relationships in Three-Element Visual Sequences by Young and Old Adults

ERIC Educational Resources Information Center

Howard, James H., Jr.; Howard, Darlene V.; Dennis, Nancy A.; Kelly, Andrew J.

2008-01-01

Knowledge of sequential relationships enables future events to be anticipated and processed efficiently. Research with the serial reaction time task (SRTT) has shown that sequence learning often occurs implicitly without effort or awareness. Here, the authors report 4 experiments that use a triplet-learning task (TLT) to investigate sequence…

On the Detection and Characterization of Polluted White Dwarfs

NASA Astrophysics Data System (ADS)

Steele, Amy; Debes, John H.; Deming, Drake

2017-06-01

There is evidence of circumstellar material around main sequence, giant, and white dwarf stars. What happens to this material after the main sequence? With this work, we focus on the characterization of the material around WD 1145+017. The goals are to monitor the white dwarf—which has a transiting, disintegrating planetesimal and determine the composition of the evaporated material for that same white dwarf by looking at high-resolution spectra. We also present preliminary results of follow-up photometric observations of known polluted WDs. If rocky bodies survive red giant branch evolution, then the material raining down on a WD atmosphere is a direct probe of main sequence cosmochemistry. If rocky bodies do not survive the evolution, then this informs the degree of post-main-sequence processing. These case studies will provide the community with further insight about debris disk modeling, the degree of post-main-sequence processing of circumstellar material, and the composition of a disintegrating planetesimal.

Kinematic Modeling of Central Nepal: Thermochronometer Cooling Ages as a Constraint for Balanced Cross Sections

NASA Astrophysics Data System (ADS)

Olree, E.; Robinson, D. M.; McQuarrie, N.; Ghoshal, S.; Olsen, J.

2016-12-01

Using balanced cross sections, one can visualize a valid and admissible interpretation of the surface and subsurface data. Khanal (2014) and Cross (2014) produced two valid and admissible cross sections along the Marsyandi River in central Nepal. However, thermochronologic data adds another dimension that must be adhered to when producing valid and admissible balanced cross sections. Since the previous cross sections were produced, additional zircon-helium (ZHe) cooling ages along the Marsyandi River show ages of 1 Ma near the Main Central thrust in the hinterland to 4 Ma near the Main Boundary thrust closer to the foreland. This distribution of cooling ages requires recent uplift in the hinterland, which is not present in the cross sections. Although a restored version of the Khanal (2014) cross section is sequentially deformed using 2D Move, the kinematic sequence implied in the cross section is inconsistent with the ZHe age distribution. The hinterland dipping duplex proposed by Khanal would require cooling ages that are oldest near the Main Central thrust and young southwards toward the active ramp located 80 km north of the Main Frontal thrust. Instead, the 4 Ma age near the Main Boundary thrust and the increasingly younger ages to the north could be produced by either a foreland-dipping Lesser Himalayan duplex, which would keep active uplift in the north, or by translation of the hinterland dipping duplex southward over the ramp, moving the active thrust ramp northward. To address this problem, a new balanced cross section was produced using both new mapping through the region and the ZHe age distribution as additional constraints. The section was then restored and sequentially deformed in 2D Move. This study illustrates that multiple cross sections can be viable and admissible; however, they can still be incorrect. Thermochronology places additional constraints on the permissible geometries, and thus increases our ability to predict subsurface geometries. The next step of this project is to link the uplift and erosion implied by the kinematic sequence of the new cross section to the measured cooling history by importing the cross section kinematics into advection diffusion modeling software that predicts cooling ages.

A catalog of aftershock sequences in Greece (1971 1997): Their spatial and temporal characteristics

NASA Astrophysics Data System (ADS)

Drakatos, George; Latoussakis, John

A complete catalog of aftershock sequences is provided for main earthquakes with ML 5.0, which occurred in the area of Greece and surrounding regions the last twenty-seven years. The Monthly Bulletins of the Institute of Geodynamics (National Observatory of Athens) have been used as data source. In order to get a homogeneous catalog, several selection criteria have been applied and hence a catalog of 44 aftershock sequences is compiled. The relations between the duration of the sequence, the number of aftershocks, the magnitude of the largest aftershock and its delay time from the main shock as well as the subsurface rupture length versus the magnitude of the main shock are calculated. The results show that linearity exists between the subsurface rupture length and the magnitude of the main shock independent of the slip type, as well as between the magnitude of the main shock (M) and its largest aftershock (Ma). The mean difference M-Ma is almost one unit. In the 40% of the analyzed sequences, the largest aftershock occurred within one day after the main shock.The fact that the aftershock sequences show the same behavior for earthquakes that occur in the same region supports the theory that the spatial and temporal characteristics are strongly related to the stress distribution of the fault area.

Exploring the safety implications of young drivers' behavior, attitudes and perceptions.

PubMed

Hassan, Hany M; Abdel-Aty, Mohamed A

2013-01-01

The present study aims at identifying and quantifying significant factors (i.e., demographic, aberrant driving behavior) associated with young drivers' involvement in at-fault crashes or traffic citations at the ages of 16-17 (while having the Operational License) and 18-24 years old (while having the Full License). A second objective was to investigate the main reason(s) for involvement in risky driving behavior by young drivers. The data used for the analyses were obtained from a self-reported questionnaire survey carried out among 680 young drivers in Central Florida. To achieve these goals, the structural equation modeling approach was adopted. The results revealed that aggressive violations, in-vehicle distractions and demographic characteristics were the significant factors affecting young drivers' involvement in at-fault crashes or traffic violations at the age of 16-17. However, in-vehicle distractions, attitudes toward speeding and demographic characteristics were the significant factors affecting young drivers' crash risk at 18-24. Additionally, the majority of participants reported that "running late" is the main reason for taking risk while driving (i.e., speeding, accept short gaps, or drive so close to the car in front) followed by "racing other cars". Additionally, "exceed speed limits" was the main reason for receiving traffic citations at 16-17 and 18-24 age groups. Practical suggestions on how to reduce crash risk and promote safe driving among young drivers are also discussed. Copyright © 2012 Elsevier Ltd. All rights reserved.

Columbia/Einstein observations of galactic X-ray sources

NASA Technical Reports Server (NTRS)

Long, K. S.

1979-01-01

The imaging observations of galactic clusters are presented. These fall into three categories: pre-main-sequence stars in the Orion nebulae, isolated-main-and-post main-sequence stars, and supernova remnants SNR. In addition to SNR, approximately 30 sources were detected.

X-shooter spectroscopy of young stellar objects. III. Photospheric and chromospheric properties of Class III objects

NASA Astrophysics Data System (ADS)

Stelzer, B.; Frasca, A.; Alcalá, J. M.; Manara, C. F.; Biazzo, K.; Covino, E.; Rigliaco, E.; Testi, L.; Covino, S.; D'Elia, V.

2013-10-01

Context. Traditionally, the chromospheres of late-type stars are studied through their strongest emission lines, Hα and Ca ii HK emission. Our knowledge on the whole emission line spectrum is more elusive as a result of the limited spectral range and sensitivity of most available spectrographs. Aims: We intend to reduce this gap with a comprehensive spectroscopic study of the chromospheric emission line spectrum of a sample of non-accreting pre-main sequence stars (Class III sources). Methods: We analyzed X-shooter/VLT spectra of 24 Class III sources from three nearby star-forming regions (σ Orionis, Lupus III, and TW Hya). We determined the effective temperature, surface gravity, rotational velocity, and radial velocity by comparing the observed spectra with synthetic BT-Settl model spectra. We investigated in detail the emission lines emerging from the stellar chromospheres and combined these data with archival X-ray data to allow for a comparison between chromospheric and coronal emissions. Results: For some objects in the sample the atmospheric and kinematic parameters are presented here for the first time. The effective temperatures are consistent with those derived for the same stars from an empirical calibration with spectral types. Small differences in the surface gravity found between the stars can be attributed to differences in the average age of the three star-forming regions. The strength of lithium absorption and radial velocities confirm the young age of all but one object in the sample (Sz 94). Both X-ray and Hα luminosity as measured in terms of the bolometric luminosity are independent of the effective temperature for early-M stars but decline toward the end of the spectral M sequence. For the saturated early-M stars the average emission level is almost one dex higher for X-rays than for Hα: log (Lx/Lbol) = -2.85 ± 0.36 vs. log (LHα/Lbol) = -3.72 ± 0.21. When all chromospheric emission lines (including the Balmer series up to H11, Ca ii HK, the Ca ii infrared triplet, and several He i lines) are summed up the coronal flux still dominates that of the chromosphere, typically by a factor 2-5. Flux-flux relations between activity diagnostics that probe different atmospheric layers (from the lower chromosphere to the corona) separate our sample of active pre-main sequence stars from the bulk of field M dwarfs studied in the literature. Flux ratios between individual optical emission lines show a smooth dependence on the effective temperature. The Balmer decrements can roughly be reproduced by an NLTE radiative transfer model devised for another young star of similar age. Future, more complete chromospheric model grids can be tested against this data set. Based on observations collected at the Very Large Telescope of the European Southern Observatory under programs 084.C-0269, 085.C-0238, 086.C-0173, 087.C-0244, and 089.C-0143.Tables 2-4 are available in electronic form at http://www.aanda.org

The Effect of Motor Difficulty on the Acquisition of a Computer Task: A Comparison between Young and Older Adults

ERIC Educational Resources Information Center

Fezzani, K.; Albinet, C.; Thon, B.; Marquie, J. -C.

2010-01-01

The present study investigated the extent to which the impact of motor difficulty on the acquisition of a computer task varies as a function of age. Fourteen young and 14 older participants performed 352 sequences of 10 serial pointing movements with a wireless pen on a digitiser tablet. A conditional probabilistic structure governed the…

Prof. Hayashi's work on the pre-main sequence evolution and brown dwarfs

NASA Astrophysics Data System (ADS)

Nakano, Takenori

2012-09-01

Prof. Hayashi's work on the evolution of stars in the pre-main sequence stage is reviewed. The historical background and the process of finding the Hayashi phase are mentioned. The work on the evolution of low-mass stars is also reviewed including the determination of the bottom of the main sequence and evolution of brown dwarfs, and comparison is made with the other works in the same period.

The size evolution of star-forming and quenched galaxies in the IllustrisTNG simulation

NASA Astrophysics Data System (ADS)

Genel, Shy; Nelson, Dylan; Pillepich, Annalisa; Springel, Volker; Pakmor, Rüdiger; Weinberger, Rainer; Hernquist, Lars; Naiman, Jill; Vogelsberger, Mark; Marinacci, Federico; Torrey, Paul

2018-03-01

We analyse scaling relations and evolution histories of galaxy sizes in TNG100, part of the IllustrisTNG simulation suite. Observational qualitative trends of size with stellar mass, star formation rate and redshift are reproduced, and a quantitative comparison of projected r band sizes at 0 ≲ z ≲ 2 shows agreement to much better than 0.25 dex. We follow populations of z = 0 galaxies with a range of masses backwards in time along their main progenitor branches, distinguishing between main-sequence and quenched galaxies. Our main findings are as follows. (i) At M*, z = 0 ≳ 109.5 M⊙, the evolution of the median main progenitor differs, with quenched galaxies hardly growing in median size before quenching, whereas main-sequence galaxies grow their median size continuously, thus opening a gap from the progenitors of quenched galaxies. This is partly because the main-sequence high-redshift progenitors of quenched z = 0 galaxies are drawn from the lower end of the size distribution of the overall population of main-sequence high-redshift galaxies. (ii) Quenched galaxies with M*, z = 0 ≳ 109.5 M⊙ experience a steep size growth on the size-mass plane after their quenching time, but with the exception of galaxies with M*, z = 0 ≳ 1011 M⊙, the size growth after quenching is small in absolute terms, such that most of the size (and mass) growth of quenched galaxies (and its variation among them) occurs while they are still on the main sequence. After they become quenched, the size growth rate of quenched galaxies as a function of time, as opposed to versus mass, is similar to that of main-sequence galaxies. Hence, the size gap is retained down to z = 0.

Multicultural Literature for Children and Young Adults

ERIC Educational Resources Information Center

Bista, Krishna

2012-01-01

In the selection of multicultural literature for children and young adults, educators and researchers focus on two main controversial issues--authority and authenticity--that the authors portray in their writing. What type of author can accurately portray realistic pictures of minority cultures in multicultural literature for young adults? Must it…

The Factors of Design on Playing Equipment in Young Children Schools by Viewpoint of Young Children Behavioral Development

ERIC Educational Resources Information Center

Kuo, Chuen-tzay

2009-01-01

The main purpose of this study was to explore the care-givers of preschool education institutions whose cognition on playing equipment functions, conditions of both setting and using, and the main factors which should beware of design. Besides, not only constructed the factors of design, but also provided suggestions about setting and designing of…

Examining Potential Predictors for Completion of the Gardasil Vaccine Sequence Based on Data Gathered at Clinics of Johns Hopkins Medical Institutions

ERIC Educational Resources Information Center

Barat, Christopher E.; Wright, Courtney; Chou, Betty

2011-01-01

This paper presents categorical data that were gathered at two urban clinics and two suburban clinics of Johns Hopkins in an effort to identify characteristics of young female patients who successfully complete the three-injection sequence of the Gardasil quadrivalent human papillomavirus vaccine (HPV4). Available categorical correlates included…

Lithium Depletion in Solar-like Stars: Effect of Overshooting Based on Realistic Multi-dimensional Simulations

NASA Astrophysics Data System (ADS)

Baraffe, I.; Pratt, J.; Goffrey, T.; Constantino, T.; Folini, D.; Popov, M. V.; Walder, R.; Viallet, M.

2017-08-01

We study lithium depletion in low-mass and solar-like stars as a function of time, using a new diffusion coefficient describing extra-mixing taking place at the bottom of a convective envelope. This new form is motivated by multi-dimensional fully compressible, time-implicit hydrodynamic simulations performed with the MUSIC code. Intermittent convective mixing at the convective boundary in a star can be modeled using extreme value theory, a statistical analysis frequently used for finance, meteorology, and environmental science. In this Letter, we implement this statistical diffusion coefficient in a one-dimensional stellar evolution code, using parameters calibrated from multi-dimensional hydrodynamic simulations of a young low-mass star. We propose a new scenario that can explain observations of the surface abundance of lithium in the Sun and in clusters covering a wide range of ages, from ˜50 Myr to ˜4 Gyr. Because it relies on our physical model of convective penetration, this scenario has a limited number of assumptions. It can explain the observed trend between rotation and depletion, based on a single additional assumption, namely, that rotation affects the mixing efficiency at the convective boundary. We suggest the existence of a threshold in stellar rotation rate above which rotation strongly prevents the vertical penetration of plumes and below which rotation has small effects. In addition to providing a possible explanation for the long-standing problem of lithium depletion in pre-main-sequence and main-sequence stars, the strength of our scenario is that its basic assumptions can be tested by future hydrodynamic simulations.

SEARCHING FOR YOUNG JUPITER ANALOGS AROUND AP COL: L-BAND HIGH-CONTRAST IMAGING OF THE CLOSEST PRE-MAIN-SEQUENCE STAR

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

Quanz, Sascha P.; Avenhaus, Henning; Meyer, Michael R.

2012-08-01

The nearby M-dwarf AP Col was recently identified by Riedel et al. as a pre-main-sequence star (age 12-50 Myr) situated only 8.4 pc from the Sun. The combination of its youth, distance, and intrinsically low luminosity make it an ideal target to search for extrasolar planets using direct imaging. We report deep adaptive optics observations of AP Col taken with VLT/NACO and Keck/NIRC2 in the L band. Using aggressive speckle suppression and background subtraction techniques, we are able to rule out companions with mass m {>=} 0.5-1 M{sub Jup} for projected separations a > 4.5 AU, and m {>=} 2more » M{sub Jup} for projected separations as small as 3 AU, assuming an age of 40 Myr using the COND theoretical evolutionary models. Using a different set of models, the mass limits increase by a factor of {approx}>2. The observations presented here are the deepest mass-sensitivity limits yet achieved within 20 AU on a star with direct imaging. While Doppler radial velocity surveys have shown that Jovian bodies with close-in orbits are rare around M-dwarfs, gravitational microlensing studies predict that 17{sup +6}{sub -9}% of these stars host massive planets with orbital separations of 1-10 AU. Sensitive high-contrast imaging observations, like those presented here, will help to validate results from complementary detection techniques by determining the frequency of gas giant planets on wide orbits around M-dwarfs.« less

Star formation is boosted (and quenched) from the inside-out: radial star formation profiles from MaNGA

NASA Astrophysics Data System (ADS)

Ellison, Sara L.; Sánchez, Sebastian F.; Ibarra-Medel, Hector; Antonio, Braulio; Mendel, J. Trevor; Barrera-Ballesteros, Jorge

2018-02-01

The tight correlation between total galaxy stellar mass and star formation rate (SFR) has become known as the star-forming main sequence. Using ˜487 000 spaxels from galaxies observed as part of the Sloan Digital Sky Survey Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, we confirm previous results that a correlation also exists between the surface densities of star formation (ΣSFR) and stellar mass (Σ⋆) on kpc scales, representing a `resolved' main sequence. Using a new metric (ΔΣSFR), which measures the relative enhancement or deficit of star formation on a spaxel-by-spaxel basis relative to the resolved main sequence, we investigate the SFR profiles of 864 galaxies as a function of their position relative to the global star-forming main sequence (ΔSFR). For galaxies above the global main sequence (positive ΔSFR) ΔΣSFR is elevated throughout the galaxy, but the greatest enhancement in star formation occurs at small radii (<3 kpc, or 0.5Re). Moreover, galaxies that are at least a factor of 3 above the main sequence show diluted gas phase metallicities out to 2Re, indicative of metal-poor gas inflows accompanying the starbursts. For quiescent/passive galaxies that lie at least a factor of 10 below the star-forming main sequence, there is an analogous deficit of star formation throughout the galaxy with the lowest values of ΔΣSFR in the central 3 kpc. Our results are in qualitative agreement with the `compaction' scenario in which a central starburst leads to mass growth in the bulge and may ultimately precede galactic quenching from the inside-out.

Hazardous Early Days In (and Beyond) the Habitable Zones Around Ultra-Low-Mass Stars

NASA Astrophysics Data System (ADS)

Kastner, Joel

Although a majority of stars in the solar neighborhood are of mid- to late-M type, the magnetically-induced coronal (X-ray) and chromospheric (UV, H-alpha) activity of such stars remain essentially unexplored for the important age range 10-100 Myr. Such information on high-energy processes associated with young M stars would provide much-needed constraints on models of the effects of stellar irradiation on the physics and chemistry of planet-forming disks and newborn planets. In addition, X-ray and UV observations of ultra-low-mass young stars can serve to probe the (presently ill-defined) spectral type boundary that determines which very low-mass objects will eventually become M stars -- as opposed to brown dwarfs (BDs) -- following their pre-main sequence evolutionary stages. Via ADAP support, we have developed the GALEX Nearby Young Star Search (GALNYSS), a search method that combines GALEX, 2MASS, WISE and proper motion catalog information to identify nearby, young, lowmass stars. We have applied this method to identify ~2000 candidate young (10-100 Myr), low-mass (M-type) stars within 150 pc. These GALNYSS-identified young star candidates are distributed over the entire GALEX-covered sky, and their spectral types peak in the M3-4 range; followup optical spectroscopic work is ongoing (Rodriguez et al. 2013, ApJ, 774, 101). We now propose an ADA program to determine the X-ray properties of representative stars among these GALNYSS candidates, so as to confirm their youth and investigate the early evolution of coronal activity near the low-mass star/BD boundary and the effects of such activity on planet formation. Specifically, we will exploit the presence in the HEASARC archives of XMM-Newton and (to a lesser extent) Chandra X-ray Observatory data for a few dozen GALNYSS candidates that have been observed serendipitously by one or both of these space observatories. The proposed ADA program will yield the full reduction and analysis of these as-yet unexplored data. The results will be used to constrain models describing the dispersal of protoplanetary disks and evaporation of planetary atmospheres due to intense irradiation by high-energy photons from young, low-mass stars, and to shed new light on the early evolution of magnetic activity of stars with masses down to near the H-burning limit.

A young solar twin in the Rosette cluster NGC 2244 line of sight

NASA Astrophysics Data System (ADS)

Huber, Jeremy M.; Kielkopf, John F.; Mengel, Matthew; Carter, Bradley D.; Ferland, Gary J.; Clark, Frank O.

2018-05-01

Based on prior precision photometry and cluster age analysis, the bright star GSC 00154-01819 is a possible young pre-main sequence member of the Rosette cluster, NGC 2244. As part of a comprehensive study of the large-scale structure of the Rosette and its excitation by the cluster stars, we noted this star as a potential backlight for a probe of the interstellar medium and extinction along the sight line towards a distinctive nebular feature projected on to the cluster centre. New high-resolution spectra of the star were taken with the University College London Echelle Spectrograph of the AAT. They reveal that rather than being a reddened spectral type B or A star within the Mon OB2 association, it is a nearby, largely unreddened, solar twin of spectral type G2V less than 180 Myr old. It is about 219 pc from the Sun with a barycentric radial velocity of +14.35 ± 1.99 km s-1. The spectrum of the Rosette behind it and along this line of sight shows a barycentric radial velocity of +26.0 ± 2.4 km s-1 in H α, and a full width at half-maximum velocity dispersion of 61.94 ± 1.38 km s-1.

Age differences in implicit memory: more apparent than real.

PubMed

Russo, R; Parkin, A J

1993-01-01

Elderly subjects and a group of young subjects identified fragmented picture sequences under conditions of focused attention. Two other groups of young subjects carried out this task under divided-attention conditions. Implicit memory, as measured by item-specific savings, was found in all groups, but this effect was smaller in the elderly group. The young subjects, but not elderly subjects, performed better on new items. The divided-attention conditions equated recall and recognition by the young and the elderly, but only the young subjects showed greater savings for recalled items. The elderly subjects' reduced implicit memory therefore stemmed from their inability to facilitate implicit memory with explicit memory. A second experiment, involving only young subjects tested after delay, produced findings similar to those for the young divided-attention subjects. Implicit memory, as measured by savings in picture completion, does not show an age-related change when the role of explicit memory is considered. Age does, however, reduce skill learning.

UV observations of blue stragglers and population 2 K dwarfs

NASA Technical Reports Server (NTRS)

Carney, B. W.; Bond, H. E.

1986-01-01

Blue stragglers are stars, found usually in either open or globular clusters, that appear to lie on the main sequence, but are brighter and bluer than the cluster turn-off. Currently, two rival models are invoked to explain this apparently pathological behavior: internal mixing (so that fresh fuel is brought into the stellar core); and mass transfer (by which a normal main sequence star acquires mass from an evolving nearby companion and so moves up the main sequence). The latter model predicts that in the absence of complete mass transfer (i.e., coalescence), blue stragglers should be binary systems with the fainter star in a post-main sequence evolutionary state. It is important to ascertain the cause of this phenomenon since stellar evolution models of main sequence stars play such a vital role in astronomy. If mass transfer is involved, one may easily exclude binaries from age determinations of clusters, but if mixing is the cause, our age determinations will be much less accurate unless we can determine whether all stars or only some mix, and what causes the mixing to occur at all.

Toward a Nonspeech Test of Auditory Cognition: Semantic Context Effects in Environmental Sound Identification in Adults of Varying Age and Hearing Abilities

PubMed Central

Sheft, Stanley; Norris, Molly; Spanos, George; Radasevich, Katherine; Formsma, Paige; Gygi, Brian

2016-01-01

Objective Sounds in everyday environments tend to follow one another as events unfold over time. The tacit knowledge of contextual relationships among environmental sounds can influence their perception. We examined the effect of semantic context on the identification of sequences of environmental sounds by adults of varying age and hearing abilities, with an aim to develop a nonspeech test of auditory cognition. Method The familiar environmental sound test (FEST) consisted of 25 individual sounds arranged into ten five-sound sequences: five contextually coherent and five incoherent. After hearing each sequence, listeners identified each sound and arranged them in the presentation order. FEST was administered to young normal-hearing, middle-to-older normal-hearing, and middle-to-older hearing-impaired adults (Experiment 1), and to postlingual cochlear-implant users and young normal-hearing adults tested through vocoder-simulated implants (Experiment 2). Results FEST scores revealed a strong positive effect of semantic context in all listener groups, with young normal-hearing listeners outperforming other groups. FEST scores also correlated with other measures of cognitive ability, and for CI users, with the intelligibility of speech-in-noise. Conclusions Being sensitive to semantic context effects, FEST can serve as a nonspeech test of auditory cognition for diverse listener populations to assess and potentially improve everyday listening skills. PMID:27893791

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

The Monitor project: searching for occultations in young open clusters

NASA Astrophysics Data System (ADS)

Aigrain, S.; Hodgkin, S.; Irwin, J.; Hebb, L.; Irwin, M.; Favata, F.; Moraux, E.; Pont, F.

2007-02-01

The Monitor project is a photometric monitoring survey of nine young (1-200Myr) clusters in the solar neighbourhood to search for eclipses by very low mass stars and brown dwarfs and for planetary transits in the light curves of cluster members. It began in the autumn of 2004 and uses several 2- to 4-m telescopes worldwide. We aim to calibrate the relation between age, mass, radius and where possible luminosity, from the K dwarf to the planet regime, in an age range where constraints on evolutionary models are currently very scarce. Any detection of an exoplanet in one of our youngest targets (<~10Myr) would also provide important constraints on planet formation and migration time-scales and their relation to protoplanetary disc lifetimes. Finally, we will use the light curves of cluster members to study rotation and flaring in low-mass pre-main-sequence stars. The present paper details the motivation, science goals and observing strategy of the survey. We present a method to estimate the sensitivity and number of detections expected in each cluster, using a simple semi-analytic approach which takes into account the characteristics of the cluster and photometric observations, using (tunable) best-guess assumptions for the incidence and parameter distribution of putative companions, and we incorporate the limits imposed by radial velocity follow-up from medium and large telescopes. We use these calculations to show that the survey as a whole can be expected to detect over 100 young low and very low mass eclipsing binaries, and ~3 transiting planets with radial velocity signatures detectable with currently available facilities.

A Continuum of Accretion Burst Behavior in Young Stars Observed by K2

NASA Astrophysics Data System (ADS)

Cody, Ann Marie; Hillenbrand, Lynne A.; David, Trevor J.; Carpenter, John M.; Everett, Mark E.; Howell, Steve B.

2017-02-01

We present 29 likely members of the young ρ Oph or Upper Sco regions of recent star formation that exhibit “accretion burst” type light curves in K2 time series photometry. The bursters were identified by visual examination of their ˜80-day light curves, though all satisfy the M< -0.25 flux asymmetry criterion for burst behavior defined by Cody et al. The burst sources represent ≈9% of cluster members with strong infrared excess indicative of circumstellar material. Higher amplitude burster behavior is correlated with larger inner disk infrared excesses, as inferred from WISE W1-W2 color. The burst sources are also outliers in their large Hα emission equivalent widths. No distinction between bursters and non-bursters is seen in stellar properties such as multiplicity or spectral type. The frequency of bursters is similar between the younger, more compact ρ Oph region, and the older, more dispersed Upper Sco region. The bursts exhibit a range of shapes, amplitudes (˜10%-700%), durations (˜1-10 days), repeat timescales (˜3-80 days), and duty cycles (˜10%-100%). Our results provide important input to models of magnetospheric accretion, in particular, by elucidating the properties of accretion-related variability in the low state between major longer duration events such as EX Lup and FU Ori type accretion outbursts. We demonstrate the broad continuum of accretion burst behavior in young stars—extending the phenomenon to lower amplitudes and shorter timescales than traditionally considered in the theory of pre-main sequence accretion history.

Age-related differences in GABA levels are driven by bulk tissue changes.

PubMed

Maes, Celine; Hermans, Lize; Pauwels, Lisa; Chalavi, Sima; Leunissen, Inge; Levin, Oron; Cuypers, Koen; Peeters, Ronald; Sunaert, Stefan; Mantini, Dante; Puts, Nicolaas A J; Edden, Richard A E; Swinnen, Stephan P

2018-05-02

Levels of GABA, the main inhibitory neurotransmitter in the brain, can be regionally quantified using magnetic resonance spectroscopy (MRS). Although GABA is crucial for efficient neuronal functioning, little is known about age-related differences in GABA levels and their relationship with age-related changes in brain structure. Here, we investigated the effect of age on GABA levels within the left sensorimotor cortex and the occipital cortex in a sample of 85 young and 85 older adults using the MEGA-PRESS sequence. Because the distribution of GABA varies across different brain tissues, various correction methods are available to account for this variation. Considering that these correction methods are highly dependent on the tissue composition of the voxel of interest, we examined differences in voxel composition between age groups and the impact of these various correction methods on the identification of age-related differences in GABA levels. Results indicated that, within both voxels of interest, older (as compared to young adults) exhibited smaller gray matter fraction accompanied by larger fraction of cerebrospinal fluid. Whereas uncorrected GABA levels were significantly lower in older as compared to young adults, this age effect was absent when GABA levels were corrected for voxel composition. These results suggest that age-related differences in GABA levels are at least partly driven by the age-related gray matter loss. However, as alterations in GABA levels might be region-specific, further research should clarify to what extent gray matter changes may account for age-related differences in GABA levels within other brain regions. © 2018 Wiley Periodicals, Inc.

Molecular Epidemiology of HIV-1 Subtype B Reveals Heterogeneous Transmission Risk: Implications for Intervention and Control

PubMed Central

Le Vu, Stephane; Ratmann, Oliver; Tostevin, Anna; Dunn, David; Orkin, Chloe; O’Shea, Siobhan; Delpech, Valerie; Brown, Alison; Gill, Noel; Fraser, Christophe

2018-01-01

Abstract Background The impact of HIV pre-exposure prophylaxis (PrEP) depends on infections averted by protecting vulnerable individuals as well as infections averted by preventing transmission by those who would have been infected if not receiving PrEP. Analysis of HIV phylogenies reveals risk factors for transmission, which we examine as potential criteria for allocating PrEP. Methods We analyzed 6912 HIV-1 partial pol sequences from men who have sex with men (MSM) in the United Kingdom combined with global reference sequences and patient-level metadata. Population genetic models were developed that adjust for stage of infection, global migration of HIV lineages, and changing incidence of infection through time. Models were extended to simulate the effects of providing susceptible MSM with PrEP. Results We found that young age <25 years confers higher risk of HIV transmission (relative risk = 2.52 [95% confidence interval, 2.32–2.73]) and that young MSM are more likely to transmit to one another than expected by chance. Simulated interventions indicate that 4-fold more infections can be averted over 5 years by focusing PrEP on young MSM. Conclusions Concentrating PrEP doses on young individuals can avert more infections than random allocation. PMID:29506269

NEW MEMBERS OF THE SCORPIUS-CENTAURUS COMPLEX AND AGES OF ITS SUB-REGIONS

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

Song, Inseok; Zuckerman, B.; Bessell, M. S.

2012-07-15

We have spectroscopically identified {approx}100 G-, K-, and M-type members of the Scorpius-Centaurus complex. To deduce the age of these young stars we compare their Li {lambda}6708 absorption line strengths against those of stars in the TW Hydrae association and {beta} Pictoris moving group. These line strengths indicate that Sco-Cen stars are younger than {beta} Pic stars whose ages of {approx}12 Myr have previously been derived from a kinematic traceback analysis. Our derived age, {approx}10 Myr, for stars in the Lower Centaurus Crux and Upper Centaurus Lupus subgroups of ScoCen is younger than previously published ages based on the movingmore » cluster method and upper main-sequence fitting. The discrepant ages are likely due to an incorrect (or lack of) cross-calibration between model-dependent and model-independent age-dating methods.« less

Warm Debris Disk Candidates from WISE

NASA Technical Reports Server (NTRS)

Padgett, Deborah; Stapelfeldt, Karl; Liu, Wilson; Leisawitz, David

2011-01-01

The Wide Field Infrared Survey Explorer (WISE) has just completed a sensitive all-sky survey in photometric bands at 3.4, 4.6, 12, and 22 microns. We report on a preliminary investigation of main sequence Hipparcos and Tycho catalog stars with 22 micron emission in excess of photospheric levels. This warm excess emission traces material in the circumstellar region likely to host terrestrial planets and is preferentially found in young systems with ages < 1 Gyr. Nearly a hundred new warm debris disk candidates are detected among FGK stars and 150 A stars within 120 pc. We are in the process of obtaining spectra to determine spectral types and activity level of these stars and are using HST, Herschel and Keck to characterize the dust, multiplicity, and substellar companions of these systems. In this contribution, we will discuss source selection methods and individual examples from among the WISE debris disk candidates.

Warm Debris Disks from WISE

NASA Technical Reports Server (NTRS)

Padgett, Deborah L.

2011-01-01

"The Wide Field Infrared Survey Explorer (WISE) has just completed a sensitive all-sky survey in photometric bands at 3.4, 4.6, 12, and 22 microns. We report on a preliminary investigation of main sequence Hipparcos and Tycho catalog stars with 22 micron emission in excess of photospheric levels. This warm excess emission traces material in the circumstellar region likely to host terrestrial planets and is preferentially found in young systems with ages < 1 Gyr. Nearly a hundred new warm debris disk candidates are detected among FGK stars and a similar number of A stars within 120 pc. We are in the process of obtaining spectra to determine spectral types and activity level of these stars and are using HST, Herschel and Keck to characterize the dust, multiplicity, and substellar companions of these systems. In this contribution, we will discuss source selection methods and individual examples from among the WISE debris disk candidates. "

Photometry, Astrometry, and Discoveries of Ultracool Dwarfs in the Pan-STARRS 3π Survey

NASA Astrophysics Data System (ADS)

Best, William M. J.; Magnier, Eugene A.; Liu, Michael C.; Deacon, Niall; Aller, Kimberly; Zhang, Zhoujian; Pan-STARRS1 Builders

2018-01-01

The Pan-STARRS1 3π Survey (PS1)'s far-red optical sensitivity makes it an exceptional new resource for discovering and characterizing ultracool dwarfs. We present a PS1-based catalog of photometry and proper motions of nearly 10,000 M, L, and T dwarfs, along with our analysis of the kinematics of nearby M6-T9 dwarfs, building a comprehensive picture of the local ultracool population. We highlight some especially interesting ultracool discoveries made with PS1, including brown dwarfs with spectral types in the enigmatic L/T transition, wide companions to main sequence stars that serve as age and metallicity bechmarks for substellar models, and free-floating members of the nearby young moving groups and star-forming regions with masses down to ≈5 MJup. With its public release, PS1 will continue to be a vital tool for studying the ultracool population.

Virulent T4 Acanthamoeba causing keratitis in a patient after swimming while wearing contact lenses in Southern Brazil.

PubMed

Fabres, Laura Fuhrich; Maschio, Vinicius José; Santos, Denise Leal Dos; Kwitko, Sergio; Marinho, Diane Ruschel; Araújo, Bruno Schneider de; Locatelli, Claudete Inês; Rott, Marilise Brittes

2018-06-26

Several strains of free-living amoebae belonging to the genus Acanthamoeba can cause a painful sight-threatening disease of the cornea known as Acanthamoeba keratitis (AK). The numbers of AK cases keep rising worldwide mainly due to an increase in contact lens wearers and lack of hygiene in the maintenance of contact lenses and their cases. We report a case of AK in a healthy young woman admitted to the Hospital de Clinicas in Porto Alegre, southern Brazil. Corneal scrapings were examined for the presence of Acanthamoeba strains. The initial isolate was characterized by morphological and genotypic properties. The isolate belonged to group III according to Pussard and Pons' cyst morphology. Analysis of its 18S rDNA sequence identified the isolate as genotype T4. The T4 genotype is the most commonly reported among keratitis isolates and the most common in environmental samples.

T-ReX Spies the Stars of 30 Doradus

NASA Astrophysics Data System (ADS)

Broos, Patrick; Townsley, Leisa K.; Pollock, Andrew; Crowther, Paul

2017-08-01

30 Doradus (the Tarantula Nebula) is the Local Group's most massive young star-forming complex. At its heart is R136, the most massive resolved stellar cluster; R136 contains, in turn, the most massive stars known. The Chandra X-ray Observatory has recently observed 30 Dor for the 2-megasecond X-ray Visionary Project ``The Tarantula -- Revealed by X-rays'' (T-ReX). This deep observation exploits Chandra's fine spatial resolution to study the full complement of massive stars and the brightest pre-main sequence stars that trace 25 Myrs of star formation in this incomparable nearby starburst. Here we give preliminary results from the ongoing analyses of the data, focusing on the massive stars. While many remain undetected even in this deep ACIS-I observation, a few show dramatic X-ray lightcurves and/or high luminosities befitting this amazing starburst cluster.

Young Adult Outcomes of Children Growing up with Chronic Illness: An analysis of the National Longitudinal Study of Adolescent Health

PubMed Central

Maslow, Gary R.; Haydon, Abigail; Ford, Carol Ann; Halpern, Carolyn Tucker

2012-01-01

Objective To examine young adult outcomes in a nationally representative US cohort of young adults who grew up with a chronic illness. Design Secondary analysis of nationally representative data from Wave III (2001) of the National Longitudinal Study of Adolescent Health. Setting United States Participants The analytic sample included 13,236 young adults 18–28 years old at Wave III. Main Exposure Self-report of a chronic physical illness (asthma, cancer, diabetes or epilepsy) in adolescence. Respondents with (1) asthma or (2) non-asthma chronic illness (cancer, diabetes, or epilepsy) were compared to subjects without these conditions. Main Outcome Measures Self-report of high school graduation, ever having a job, having a current job, living with parents, and ever receiving public assistance. Results Three percent of young adults had non-asthma chronic illness (cancer, diabetes, or epilepsy) and 16% had asthma. The majority of young adults with chronic illness graduated high school (81%) and were currently employed (60%). However, compared to healthy young adults, those with a non-asthma chronic illness were significantly less likely to graduate high school, ever have a job, or have a current job and were more likely to receive public assistance. When compared to young adults with asthma, young adults with non-asthma chronic illness again had significantly worse young adult outcomes on all measures. Conclusions Most young adults growing up with chronic illness graduate high school and are employed. However, these young adults are significantly less likely than their healthy peers to achieve these important educational and vocational milestones. PMID:21383274

Spheres of Influence: What Shapes Young People's Aspirations at Age 12/13 and What Are the Implications for Education Policy?

ERIC Educational Resources Information Center

Archer, Louise; DeWitt, Jennifer; Wong, Billy

2014-01-01

Young people's aspirations remain an enduring focus of education policy interest and concern. Drawing on data from an ongoing five-year study of young people's science and career aspirations (age 10-14), this paper asks what do young people aspire to at age 12/13, and what influences these aspirations? It outlines the main aspirations and sources…

Young Managers' Drive to Thrive: A Personal Work Goal Approach to Burnout and Work Engagement

ERIC Educational Resources Information Center

Hyvonen, Katriina; Feldt, Taru; Salmela-Aro, Katariina; Kinnunen, Ulla; Makikangas, Anne

2009-01-01

This study approaches young managers' occupational well-being through their work-related goal pursuit. The main aim was to identify content categories of personal work goals and investigate their associations with background factors, goal appraisals, burnout, and work engagement. The questionnaire data consisted of 747 young Finnish managers…

The Star-forming Main Sequence of Dwarf Low Surface Brightness Galaxies

NASA Astrophysics Data System (ADS)

McGaugh, Stacy S.; Schombert, James M.; Lelli, Federico

2017-12-01

We explore the star-forming properties of late-type, low surface brightness (LSB) galaxies. The star-forming main sequence ({SFR}-{M}* ) of LSB dwarfs has a steep slope, indistinguishable from unity (1.04 ± 0.06). They form a distinct sequence from more massive spirals, which exhibit a shallower slope. The break occurs around {M}* ≈ {10}10 {M}⊙ , and can also be seen in the gas mass—stellar mass plane. The global Kennicutt-Schmidt law ({SFR}-{M}g) has a slope of 1.47 ± 0.11 without the break seen in the main sequence. There is an ample supply of gas in LSB galaxies, which have gas depletion times well in excess of a Hubble time, and often tens of Hubble times. Only ˜ 3 % of this cold gas needs be in the form of molecular gas to sustain the observed star formation. In analogy with the faint, long-lived stars of the lower stellar main sequence, it may be appropriate to consider the main sequence of star-forming galaxies to be defined by thriving dwarfs (with {M}* < {10}10 {M}⊙ ), while massive spirals (with {M}* > {10}10 {M}⊙ ) are weary giants that constitute more of a turn-off population.

Age Spread in W3 Main: Large Binocular Telescope/LUCI Near-infrared Spectroscopy of the Massive Stellar Content

NASA Astrophysics Data System (ADS)

Bik, A.; Henning, Th.; Stolte, A.; Brandner, W.; Gouliermis, D. A.; Gennaro, M.; Pasquali, A.; Rochau, B.; Beuther, H.; Ageorges, N.; Seifert, W.; Wang, Y.; Kudryavtseva, N.

2012-01-01

We present near-infrared multi-object spectroscopy and JHK s imaging of the massive stellar content of the Galactic star-forming region W3 Main, obtained with LUCI at the Large Binocular Telescope. We confirm 15 OB stars in W3 Main and derive spectral types between O5V and B4V from their absorption line spectra. Three massive young stellar objects are identified by their emission line spectra and near-infrared excess. The color-color diagram of the detected sources allows a detailed investigation of the slope of the near-infrared extinction law toward W3 Main. Analysis of the Hertzsprung-Russell diagram suggests that the Nishiyama extinction law fits the stellar population of W3 Main best (E(J - H)/E(H - K s) = 1.76 and R_{{K_s}} = 1.44). From our spectrophotometric analysis of the massive stars and the nature of their surrounding H II regions, we derive the evolutionary sequence of W3 Main and we find evidence of an age spread of at least 2-3 Myr. While the most massive star (IRS2) is already evolved, indications for high-mass pre-main-sequence evolution are found for another star (IRS N1), deeply embedded in an ultracompact H II (UCH II) region, in line with the different evolutionary phases observed in the corresponding H II regions. We derive a stellar mass of W3 Main of (4 ± 1) × 103 M ⊙ by extrapolating from the number of OB stars using a Kroupa initial mass function and correcting for our spectroscopic incompleteness. We have detected the photospheres of OB stars from the more evolved diffuse H II region to the much younger UCH II regions, suggesting that these stars have finished their formation and cleared away their circumstellar disks very fast. Only in the hyper-compact H II region (IRS5) do the early-type stars seem to be still surrounded by circumstellar material. Based on data acquired using the Large Binocular Telescope (LBT). The LBT is an international collaboration among institutions in Germany, Italy, and the United States. LBT Corporation partners are LBT Beteiligungsgesellschaft, Germany, representing the Max Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; Istituto Nazionale di Astrofisica, Italy; The University of Arizona on behalf of the Arizona university system; The Ohio State University, and The Research Corporation, on behalf of the University of Notre Dame, University of Minnesota, and University of Virginia.

A dehydrin cognate protein from pea (Pisum sativum L.) with an atypical pattern of expression.

PubMed

Robertson, M; Chandler, P M

1994-11-01

Dehydrins are a family of proteins characterised by conserved amino acid motifs, and induced in plants by dehydration or treatment with ABA. An antiserum was raised against a synthetic oligopeptide based on the most highly conserved dehydrin amino acid motif, the lysine-rich (core sequence KIKEK-LPG). This antiserum detected a novel M(r) 40,000 polypeptide and enabled isolation of a corresponding cDNA clone, pPsB61 (B61). The deduced amino acid sequence contained two lysine-rich blocks, however the remainder of the sequenced differed markedly from other pea dehydrins. Surprisingly, the sequence contained a stretch of serine residues, a characteristic common to dehydrins from many plant species but which is missing in pea dehydrin. The expression patterns of B61 mRNA and polypeptide were distinctively different from those of the pea dehydrins during seed development, germination and in young seedlings exposed to dehydration stress or treated with ABA. In particular, dehydration stress led to slightly reduced levels of B61 RNA, and ABA application to young seedlings had no marked effect on its abundance. The M(r) 40,000 polypeptide is thus related to pea dehydrin by the presence of the most highly conserved amino acid sequence motifs, but lacks the characteristic expression pattern of dehydrin. By analogy with heat shock cognate proteins we refer to this protein as a dehydrin cognate.

Infants' statistical learning: 2- and 5-month-olds' segmentation of continuous visual sequences.

PubMed

Slone, Lauren Krogh; Johnson, Scott P

2015-05-01

Past research suggests that infants have powerful statistical learning abilities; however, studies of infants' visual statistical learning offer differing accounts of the developmental trajectory of and constraints on this learning. To elucidate this issue, the current study tested the hypothesis that young infants' segmentation of visual sequences depends on redundant statistical cues to segmentation. A sample of 20 2-month-olds and 20 5-month-olds observed a continuous sequence of looming shapes in which unit boundaries were defined by both transitional probability and co-occurrence frequency. Following habituation, only 5-month-olds showed evidence of statistically segmenting the sequence, looking longer to a statistically improbable shape pair than to a probable pair. These results reaffirm the power of statistical learning in infants as young as 5 months but also suggest considerable development of statistical segmentation ability between 2 and 5 months of age. Moreover, the results do not support the idea that infants' ability to segment visual sequences based on transitional probabilities and/or co-occurrence frequencies is functional at the onset of visual experience, as has been suggested previously. Rather, this type of statistical segmentation appears to be constrained by the developmental state of the learner. Factors contributing to the development of statistical segmentation ability during early infancy, including memory and attention, are discussed. Copyright © 2015 Elsevier Inc. All rights reserved.

Anodal transcranial direct current stimulation enhances the effects of motor imagery training in a finger tapping task.

PubMed

Saimpont, Arnaud; Mercier, Catherine; Malouin, Francine; Guillot, Aymeric; Collet, Christian; Doyon, Julien; Jackson, Philip L

2016-01-01

Motor imagery (MI) training and anodal transcranial direct current stimulation (tDCS) applied over the primary motor cortex can independently improve hand motor function. The main objective of this double-blind, sham-controlled study was to examine whether anodal tDCS over the primary motor cortex could enhance the effects of MI training on the learning of a finger tapping sequence. Thirty-six right-handed young human adults were assigned to one of three groups: (i) who performed MI training combined with anodal tDCS applied over the primary motor cortex; (ii) who performed MI training combined with sham tDCS; and (iii) who received tDCS while reading a book. The MI training consisted of mentally rehearsing an eight-item complex finger sequence for 13 min. Before (Pre-test), immediately after (Post-test 1), and at 90 min after (Post-test 2) MI training, the participants physically repeated the sequence as fast and as accurately as possible. An anova showed that the number of sequences correctly performed significantly increased between Pre-test and Post-test 1 and remained stable at Post-test 2 in the three groups (P < 0.001). Furthermore, the percentage increase in performance between Pre-test and Post-test 1 and Post-test 2 was significantly greater in the group that performed MI training combined with anodal tDCS compared with the other two groups (P < 0.05). As a potential physiological explanation, the synaptic strength within the primary motor cortex could have been reinforced by the association of MI training and tDCS compared with MI training alone and tDCS alone. © 2015 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

A survey of endogenous retrovirus (ERV) sequences in the vicinity of multiple sclerosis (MS)-associated single nucleotide polymorphisms (SNPs).

PubMed

Brütting, Christine; Emmer, Alexander; Kornhuber, Malte; Staege, Martin S

2016-08-01

Although multiple sclerosis (MS) is one of the most common central nervous system diseases in young adults, little is known about its etiology. Several human endogenous retroviruses (ERVs) are considered to play a role in MS. We are interested in which ERVs can be identified in the vicinity of MS associated genetic marker to find potential initiators of MS. We analysed the chromosomal regions surrounding 58 single nucleotide polymorphisms (SNPs) that are associated with MS identified in one of the last major genome wide association studies. We scanned these regions for putative endogenous retrovirus sequences with large open reading frames (ORFs). We observed that more retrovirus-related putative ORFs exist in the relatively close vicinity of SNP marker indices in multiple sclerosis compared to control SNPs. We found very high homologies to HERV-K, HCML-ARV, XMRV, Galidia ERV, HERV-H/env62 and XMRV-like mouse endogenous retrovirus mERV-XL. The associated genes (CYP27B1, CD6, CD58, MPV17L2, IL12RB1, CXCR5, PTGER4, TAGAP, TYK2, ICAM3, CD86, GALC, GPR65 as well as the HLA DRB1*1501) are mainly involved in the immune system, but also in vitamin D regulation. The most frequently detected ERV sequences are related to the multiple sclerosis-associated retrovirus, the human immunodeficiency virus 1, HERV-K, and the Simian foamy virus. Our data shows that there is a relation between MS associated SNPs and the number of retroviral elements compared to control. Our data identifies new ERV sequences that have not been associated with MS, so far.

Molecular and biochemical characterization of caffeine synthase and purine alkaloid concentration in guarana fruit.

PubMed

Schimpl, Flávia Camila; Kiyota, Eduardo; Mayer, Juliana Lischka Sampaio; Gonçalves, José Francisco de Carvalho; da Silva, José Ferreira; Mazzafera, Paulo

2014-09-01

Guarana seeds have the highest caffeine concentration among plants accumulating purine alkaloids, but in contrast with coffee and tea, practically nothing is known about caffeine metabolism in this Amazonian plant. In this study, the levels of purine alkaloids in tissues of five guarana cultivars were determined. Theobromine was the main alkaloid that accumulated in leaves, stems, inflorescences and pericarps of fruit, while caffeine accumulated in the seeds and reached levels from 3.3% to 5.8%. In all tissues analysed, the alkaloid concentration, whether theobromine or caffeine, was higher in young/immature tissues, then decreasing with plant development/maturation. Caffeine synthase activity was highest in seeds of immature fruit. A nucleotide sequence (PcCS) was assembled with sequences retrieved from the EST database REALGENE using sequences of caffeine synthase from coffee and tea, whose expression was also highest in seeds from immature fruit. The PcCS has 1083bp and the protein sequence has greater similarity and identity with the caffeine synthase from cocoa (BTS1) and tea (TCS1). A recombinant PcCS allowed functional characterization of the enzyme as a bifunctional CS, able to catalyse the methylation of 7-methylxanthine to theobromine (3,7-dimethylxanthine), and theobromine to caffeine (1,3,7-trimethylxanthine), respectively. Among several substrates tested, PcCS showed higher affinity for theobromine, differing from all other caffeine synthases described so far, which have higher affinity for paraxanthine. When compared to previous knowledge on the protein structure of coffee caffeine synthase, the unique substrate affinity of PcCS is probably explained by the amino acid residues found in the active site of the predicted protein. Copyright © 2014 Elsevier Ltd. All rights reserved.

Photometric binary stars in Praesepe and the search for globular cluster binaries

NASA Technical Reports Server (NTRS)

Bolte, Michael

1991-01-01

A radial velocity study of the stars which are located on a second sequence above the single-star zero-age main sequence at a given color in the color-magnitude diagram of the open cluster Praesepe, (NGC 2632) shows that 10, and possibly 11, of 17 are binary systems. Of the binary systems, five have full amplitudes for their velocity variations that are greater than 50 km/s. To the extent that they can be applied to globular clusters, these results suggests that (1) observations of 'second-sequence' stars in globular clusters would be an efficient way of finding main-sequence binary systems in globulars, and (2) current instrumentation on large telescopes is sufficient for establishing unambiguously the existence of main-sequence binary systems in nearby globular clusters.

Prelinguistic Vocal Development in Young Cochlear Implant Recipients and Typically Developing Infants: Year 1 of Robust Hearing Experience

PubMed Central

Ertmer, David J.; Jung, Jongmin

2012-01-01

This investigation examined the time course and sequence of prelinguistic vocal development during the first year of cochlear implant (CI) experience. Thirteen children who were implanted between 8 and 35 months and 11 typically developing (TD) infants participated in this longitudinal study. Adult–child play interactions were video- and audio-recorded at trimonthly intervals for each group, and child utterances were classified into categories representing progressively more mature productions: Precanonical Vocalizations, Basic Canonical Syllables, and Advanced Form vocalizations. Young CI recipients met the 20% criterion for establishment of the Basic Canonical Syllables and Advanced Forms levels with fewer months of robust hearing experience than the TD infants. Most CI recipients followed the sequence of development predicted by the Stark Assessment of Early Vocal Development—Revised. The relatively rapid progress of the CI children suggests that an earlier period of auditory deprivation did not have negative consequences for prelinguistic vocal development. It also supports the notion that young CI recipients comparatively advanced maturity facilitated expeditious auditory-guided speech development. PMID:21586617

Young children make their gestural communication systems more language-like: segmentation and linearization of semantic elements in motion events.

PubMed

Clay, Zanna; Pople, Sally; Hood, Bruce; Kita, Sotaro

2014-08-01

Research on Nicaraguan Sign Language, created by deaf children, has suggested that young children use gestures to segment the semantic elements of events and linearize them in ways similar to those used in signed and spoken languages. However, it is unclear whether this is due to children's learning processes or to a more general effect of iterative learning. We investigated whether typically developing children, without iterative learning, segment and linearize information. Gestures produced in the absence of speech to express a motion event were examined in 4-year-olds, 12-year-olds, and adults (all native English speakers). We compared the proportions of gestural expressions that segmented semantic elements into linear sequences and that encoded them simultaneously. Compared with adolescents and adults, children reshaped the holistic stimuli by segmenting and recombining their semantic features into linearized sequences. A control task on recognition memory ruled out the possibility that this was due to different event perception or memory. Young children spontaneously bring fundamental properties of language into their communication system. © The Author(s) 2014.

Metagenomic Sequencing of an Echovirus 30 Genome From Cerebrospinal Fluid of a Patient With Aseptic Meningitis and Orchitis.

PubMed

Piantadosi, Anne; Mukerji, Shibani S; Chitneni, Pooja; Cho, Tracey A; Cosimi, Lisa A; Hung, Deborah T; Goldberg, Marcia B; Sabeti, Pardis C; Kuritzkes, Daniel R; Grad, Yonatan H

2017-01-01

Enteroviruses cause a wide spectrum of clinical disease. In this study, we describe the case of a young man with orchitis and aseptic meningitis who was diagnosed with enterovirus infection. Using unbiased "metagenomic" massively parallel sequencing, we assembled a near-complete viral genome, the first use of this method for full-genome viral sequencing from cerebrospinal fluid. We found that the genome belonged to the subgroup echovirus 30, which is a common cause of aseptic meningitis but has not been previously reported to cause orchitis.

THE EFFECT OF MAGNETIC TOPOLOGY ON THERMALLY DRIVEN WIND: TOWARD A GENERAL FORMULATION OF THE BRAKING LAW

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

Réville, Victor; Brun, Allan Sacha; Strugarek, Antoine

Stellar wind is thought to be the main process responsible for the spin down of main-sequence stars. The extraction of angular momentum by a magnetized wind has been studied for decades, leading to several formulations for the resulting torque. However, previous studies generally consider simple dipole or split monopole stellar magnetic topologies. Here we consider, in addition to a dipolar stellar magnetic field, both quadrupolar and octupolar configurations, while also varying the rotation rate and the magnetic field strength. Sixty simulations made with a 2.5D cylindrical and axisymmetric set-up, and computed with the PLUTO code, were used to find torquemore » formulations for each topology. We further succeed to give a unique law that fits the data for every topology by formulating the torque in terms of the amount of open magnetic flux in the wind. We also show that our formulation can be applied to even more realistic magnetic topologies, with examples of the Sun in its minimum and maximum phases as observed at the Wilcox Solar Observatory, and of a young K-star (TYC-0486-4943-1) whose topology has been obtained by Zeeman-Doppler Imaging.« less

The influence of the magnetic topology on the wind braking of sun-like stars.

NASA Astrophysics Data System (ADS)

Réville, V.; Brun, A. S.; Matt, S. P.; Strugarek, A.; Pinto, R.

2014-12-01

Stellar winds are thought to be the main process responsible for the spin down of main-sequence stars. The extraction of angular momentum by a magnetized wind has been studied for decades, leading to several formulations for the resulting torque. However, previous studies generally consider simple dipole or split monopole stellar magnetic topologies. Here we consider in addition to a dipolar stellar magnetic field, both quadrupolar and octupolar configurations, while also varying the rotation rate and the magnetic field strength. 60 simulations made with a 2.5D, cylindrical and axisymmetric set-up and computed with the PLUTO code were used to find torque formulations for each topology. We further succeed to give a unique law that fits the data for every topology by formulating the torque in terms of the amount of open magnetic flux in the wind. We also show that our formulation can be applied to even more realistic magnetic topologies, with examples of the Sun in its minimum and maximum phase as observed at the Wilcox Solar Observatory, and of a young K-star (TYC-0486-4943-1) whose topology has been obtained by Zeeman-Doppler Imaging (ZDI).

An Unusual Massive Be Star HD 53367: Circumstellar Activity and Evidence for Binarity

NASA Astrophysics Data System (ADS)

Pogodin, M. A.; Malanushenko, V. P.; Kozlova, O. V.; Tarasova, T. N.; Franco, G. A. P.

2006-12-01

We present the results of high-resolution spectroscopy of the young B0e star HD 53367 obtained within the framework of a cooperative observing program in 1994--2005. We confirm that a long-term photometric variability of the object is indeed connected with the alternation of two states of the object when the gaseous circumstellar envelope disappears and arises again. Both these processes start near the star and then spread to remote parts of the envelope. We find that the radial velocities of He I and O II photospheric lines demonstrate a cyclic variability with the period P=183.7 days and the semi-amplitude K=19 km s-1. The radial velocity variation is interpreted in the framework of a model, in which the star is a companion of an eccentric binary system. An orbital solution is derived and the system's parameters are estimated. We find that the orbital eccentricity is e=0.28, the mean companion separation is 1.7 AU, and the secondary companion is most likely to be a 5 solar mass pre-main sequence object. The main part of circumstellar gas in the system is collected near the secondary companion.

X-ray Properties of the Young Open Clusters HM1 and IC 2944-2948

NASA Technical Reports Server (NTRS)

Naze, Y.; Rauw, G.; Sana, H.; Corcoran, Michael F.

2013-01-01

Using XMM-Newton data, we study for the first time the X-ray emission of HM1 and IC 2944/2948. Low-mass, pre-main-sequence objects with an age of a few Myr are detected, as well as a few background or foreground objects. Most massive stars in both clusters display the usual high-energy properties of that type of objects, though with log [L(sub X)/L(sub BOL)] apparently lower in HM1 than in IC2944/2948. Compared with studies of other clusters, it seems that a low signal-to-noise ratio at soft energies, due to the high extinction, may be the main cause of this difference. In HM1, the two Wolf-Rayet stars show contrasting behaviors:WR89 is extremely bright, but much softer than WR87. It remains to be seen whether wind-wind collisions or magnetically confined winds can explain these emissions. In IC 2944/2948, the X-ray sources concentrate around HD 101205; a group of massive stars to the north of this object is isolated, suggesting that there exist two subclusters in the field-of-view.

Intravascular ultrasound and angiographic demonstration of left main stem thrombus-high-risk presentation in a young adult with anabolic steroid abuse.

PubMed

Garg, Pankaj; Davis, Gershan; Wilson, John Ian; Sivananthan, Mohan

2010-01-01

We present a case of acute myocardial infarction in a young adult with a history of anabolic steroid abuse. On diagnostic coronary angiography and intravascular ultrasound, he was found to have a distal left main stem thrombus extending into the proximal left anterior descending artery and a large intermediate vessel. As he was hemodynamically stable and pain-free, he was managed conservatively with triple antiplatelet therapy (aspirin, clopidogrel, and abciximab). This was also to avoid the risk of 'wiring the vessel,' especially if there was underlying dissection. Repeat angiography a few weeks later showed complete thrombus resolution. This is the first reported case of extensive left main stem thrombus in a young patient with anabolic steroid abuse. Management of such cases is not straightforward and our case highlights one approach to both diagnosis and treatment.

Textbook Religion and Lived Religion: A Comparison of the Christian Faith as Expressed in Textbooks and by Young Church Members

ERIC Educational Resources Information Center

Vestøl, Jon Magne

2016-01-01

Drawing on perspectives from sociocultural theory, this article investigates how Christian denominations are represented in Norwegian textbooks of religious education and by young believers. The main finding is that textbooks and young adherents present religion in substantially different ways. While textbooks relate religion to global and…

Representing Young Peoples Sexuality in the "Youth" Media

ERIC Educational Resources Information Center

Batchelor, S. A.; Kitzinger, J.; Burtney, E.

2004-01-01

This paper reports findings from a content analysis of the main messages about sexuality in media outlets consumed by young people. It examines how sexuality is represented and the level of sexual health information provided in some UK magazines and TV programmes targeted at young people. Our findings show that such outlets included a vast range…

Seasonal Patterns in Eastern Equine Encephalitis Virus Antibody in Songbirds in Southern Maine.

PubMed

Elias, Susan P; Keenan, Patrick; Kenney, Joan L; Morris, Sara R; Covino, Kristen M; Robinson, Sara; Foss, Kimberly A; Rand, Peter W; Lubelczyk, Charles; Lacombe, Eleanor H; Mutebi, John-Paul; Evers, David; Smith, Robert P

2017-05-01

The intent of this study was to assess passerine eastern equine encephalitis virus (EEEv) seroprevalence during the breeding season in southern Maine by testing songbird species identified in the literature as amplifying hosts of this virus. In 2013 and 2014, we collected serum samples from songbirds at a mainland site and an offshore island migratory stopover site, and screened samples for EEEv antibodies using plaque reduction neutralization tests. We compared seasonal changes in EEEv antibody seroprevalence in young (hatched in year of capture) and adult birds at the mainland site, and also compared early season seroprevalence in mainland versus offshore adult birds. EEEv seroprevalence did not differ significantly between years at either site. During the early season (May), EEEv antibody seroprevalence was substantially lower (9.6%) in the island migrant adults than in mainland adults (42.9%), 2013-2014. On the mainland, EEEv antibody seroprevalence in young birds increased from 12.9% in midseason (June-August) to 45.6% in late season (September/October), 2013-2014. Seroprevalence in adult birds did not differ between seasons (48.8% vs. 53.3%). EEEv activity in Maine has increased in the past decade as measured by increased virus detection in mosquitoes and veterinary cases. High EEEv seroprevalence in young birds-as compared to that of young birds in other studies-corresponded with two consecutive active EEEv years in Maine. We suggest that young, locally hatched songbirds be sampled as a part of long-term EEEv surveillance, and provide a list of suggested species to sample, including EEEv "superspreaders."

Molecular Gas in Disks around Young Stars with ALMA

NASA Astrophysics Data System (ADS)

Hughes, A. Meredith; Factor, Samuel; Lieman-Sifry, Jesse; Flaherty, Kevin; Daley, Cail; Mann, Rita; Roberge, Aki; Di Francesco, James; Williams, Jonathan; Ricci, Luca; Matthews, Brenda; Bally, John; Johnstone, Doug; Kospal, Agnes; Moor, Attila; Kamp, Inga; Wilner, David; Andrews, Sean; Kastner, Joel H.; Abraham, Peter

2018-01-01

Molecular gas is a critical component of the planet formation process. In this poster, we present two analyses of the molecular gas component of circumstellar disks at extremes (young, old) of the pre-main sequence phase.(1) We characterize the molecular gas content of the disk around d216-0939, a pre-main sequence star in the Orion Nebula Cluster, using ALMA observations of CO(3-2), HCO+(4-3), and HCN(4-3) observed at 0.5" resolution. We model the density and temperature structure of the disk, returning abundances generally consistent with chemical modeling of protoplanetary disks, and obtain a dynamical mass measurement of the central star of 2.2+/-0.4 M_sun, which is inconsistent with the previously determined spectral type of K5. We also report the detection of a spatially unresolved high-velocity blue-shifted excess emission feature with a measurable position offset from the central star, consistent with an object in Keplerian orbit at 60+/-20 au. The feature is due to a local temperature and/or density enhancement consistent with either a hydrodynamic vortex or the expected signature of the envelope of a forming protoplanet within the disk, providing evidence that planet formation is ongoing within this massive and relatively isolated Orion proplyd. This work is published in Factor et al. (2017). (2) We present ~0.4" resolution images of CO(3-2) and associated continuum emission from the gas-bearing debris disk around the nearby A star 49 Ceti, observed with ALMA. We analyze the ALMA visibilities in tandem with the broadband spectral energy distribution to measure the radial surface density profiles of dust and gas emission from the system. The radial extent of the gas disk (~220 au) is smaller than that of the dust disk (~300 au), consistent with recent observations of other gas-bearing debris disks. While there are so far only three broad debris disks with well characterized radial dust profiles at millimeter wavelengths, 49 Ceti’s disk shows a markedly different structure from two radially resolved gas-poor debris disks, implying that the physical processes generating and sculpting the gas and dust are fundamentally different. This work is published in Hughes et al. (2017).

A Spectroscopic Study of Young Stellar Objects in the Serpens Cloud Core and NGC 1333

NASA Astrophysics Data System (ADS)

Winston, E.; Megeath, S. T.; Wolk, S. J.; Hernandez, J.; Gutermuth, R.; Muzerolle, J.; Hora, J. L.; Covey, K.; Allen, L. E.; Spitzbart, B.; Peterson, D.; Myers, P.; Fazio, G. G.

2009-06-01

We present spectral observations of 130 young stellar objects (YSOs) in the Serpens Cloud Core and NGC 1333 embedded clusters. The observations consist of near-IR spectra in the H and K bands from SpeX on the IRTF and far-red spectra (6000-9000 Å) from Hectospec on the Multi-Mirror Telescope. These YSOs were identified in previous Spitzer and Chandra observations, and the evolutionary classes of the YSOs were determined from the Spitzer mid-IR photometry. With these spectra we search for corroborating evidence for the pre-main-sequence nature of the objects, study the properties of the detected emission lines as a function of evolutionary class, and obtain spectral types for the observed YSOs. The temperatures implied by the spectral types are combined with luminosities determined from the near-IR photometry to construct Hertzsprung-Russell (H-R) diagrams for the clusters. By comparing the positions of the YSOs in the H-R diagrams with the pre-main-sequence tracks of Baraffe (1998), we determine the ages of the embedded sources and study the relative ages of the YSOs with and without optically thick circumstellar disks. The apparent isochronal ages of the YSOs in both clusters range from less than 1 Myr to 10 Myr, with most objects below 3 Myr. The observed distributions of ages for the Class II and Class III objects are statistically indistinguishable. We examine the spatial distribution and extinction of the YSOs as a function of their isochronal ages. We find the sources <3 Myr to be concentrated in the molecular cloud gas, while the older sources are spatially dispersed and are not deeply embedded. Nonetheless, the sources with isochronal ages >3 Myr show all the characteristics of YSOs in their spectra, their IR spectral energy distributions, and their X-ray emission; we find no evidence that they are contaminating background giants or foreground dwarfs. However, we find no corresponding decrease in the fraction of sources with infrared excess with isochronal age; this suggests that the older isochronal ages may not measure the true age of the >3 Myr YSOs. Thus, the nature of the apparently older sources and their implications for cluster formation remain unresolved.

Main-sequence magnetic CP stars: II. Physical parameters and chemical composition of the atmosphere

NASA Astrophysics Data System (ADS)

Romanyuk, I. I.

2007-03-01

This paper continues a series of reviews dedicated to magnetic CP stars. The occurrence frequency of CP stars among B5 F0-type main-sequence stars is shown to be equal to about 15 20%. The problems of identification and classification of these objects are addressed. We prefer the classification of Preston, which subdivides chemically peculiar stars into the following groups: Am, λ Boo, Ap/Bp, Hg-Mn, He-weak, and He-strong stars. The main characteristic features of objects of each group are briefly analyzed. The rotation velocities of CP stars are shown to be about three times lower than those of normal stars of the same spectral types (except for λ Boo and He-strong objects). The rotation periods of CP stars range from 0.5 to 100 days, however, there is also a small group of objects with especially long (up to several tens of years) variability periods. All kinds of peculiar stars can be found in visual binaries, with Am-and Hg-Mn-type stars occurring mostly in short-period binaries with P < 10 days, and the binary rate of these stars is close to normal. The percentage of binaries among magnetic stars (20%) is lower than among normal stars. A rather large fraction of CP1-and CP2-type stars was found to occur in young clusters (with ages smaller than 107 years). Photometric and spectral variability of peculiar stars of various types is discussed, and it is shown that only objects possessing magnetic fields exhibit light and spectral variations. The chemical composition of the atmospheres of CP stars of various types is considered. The abundances of various elements are usually determined by comparing the line profiles in the observed spectrum with those of the synthetic spectra computed for various model atmospheres. Different mechanisms are shown to contribute to chemical inhomogeneity at the star’s surface, and the hypothesis of selective diffusion of atoms in a stable atmosphere is developed. Attention is also paid to the problems of the determination of local chemical composition including the stratification of elements. Some of the coolest SrCrEu peculiar stars are found to exhibit fast light variations with periods ranging from 6 to 15 min. These variations are unassociated with rotation, but are due to nonradial pulsations. The final part of the the review considers the fundamental parameters of CP stars. The effective temperatures, luminosities, radii, and masses of these objects are shown to agree with the corresponding physical parameters of normal main-sequence stars of the same spectral types.

Leishmania major infection in a dog with cutaneous manifestations.

PubMed

Baneth, Gad; Nachum-Biala, Yaarit; Shabat Simon, Maytal; Brenner, Ori; Gaier, Sarit; Rojas, Alicia; Yasur-Landau, Daniel

2016-05-10

Leishmania major is a main cause of cutaneous leishmaniasis in humans in an area that stretches from India through Central Asia, the Middle East, to North and West Africa. In Israel, it is a common infection of humans with rodents as the reservoir hosts and Phlebotomus papatasi as its sand fly vector. A 6 months old spayed female mixed breed dog was referred to the Hebrew University Veterinary Teaching Hospital with a large ulcerative dermal lesion on the muzzle, and lesions in the foot pads and left hind leg. Histopathology of a skin biopsy found chronic lymphohistiocytic dermatitis with the presence of Leishmania spp. amastigotes in the muzzle. Physical examination indicated that the dog was overall in a good clinical condition and the main findings were the skin lesions and enlarged prescapular lymph nodes. Complete blood count and serum biochemistry profile were within reference ranges. Serology by ELISA was positive for Leishmania spp. and PCR of the prescapular lymph node was positive by an ITS1 region PCR-high resolution melt analysis. However, the melt curve and subsequent DNA sequencing indicated that infection was caused by L. major and not L. infantum, which is the main causative agent of canine leishmaniosis in the Mediterranean region. DNA was extracted from the paraffin embedded muzzle biopsy and PCR with sequencing also indicated L. major. The dog's young age and the absence of hyperglobulinemia and anemia were not typical of L. infantum infection. The dog was treated with allopurinol and the skin lesions improved and later disappeared when the dog was re-evaluated. This is the first molecularly-confirmed case of L. major infection in a dog. Two previous reports of L. major in dogs originated from Saudi-Arabia and Egypt in 1985 and 1987 were confirmed by enzymatic biochemical techniques. Serology for L. infantum was positive probably due to the well documented serological cross-reactivity between Leishmania spp. Although dogs and wild carnivores are not considered main reservoirs for L. major, the possibility of clinical canine disease and their potential as secondary hosts should be investigated in areas endemic for human L. major infection.

Morphological, molecular and biological characterization of Mehdinema alii (Nematoda: Diplogasterida) from the decorated cricket (Gryllodes sigillatus).

PubMed

Luong, L T; Platzer, E G; De Ley, P; Thomas, W K

1999-12-01

The nematode Mehdinema alii was recovered from the decorated cricket Gryllodes sigillatus (Walker). Morphometric comparisons are presented from 3 populations. The nematode is characterized by dense arrays of spines on the cuticle of the anterior half of the body and a highly elongate, tubular stoma with a dorsal denticle in the glottoid region. Females have a protruding vulva. Young females are amphidelphic, but the anterior ovary disappears in older females bearing multiple developing juveniles. The male is monorchic with asymmetrically placed genital papillae, distally fused spicules, and a highly complex gubernaculum bearing 2 cuticularized thorns that protrude through a separate, postcloacal opening. Adult nematodes are located primarily in the hindgut, whereas juveniles or dauers occur mainly in the genital chamber of both male and female crickets. Male crickets are significantly more likely to be infected than females. This male-biased infection may be linked to the venereal transmission mechanism of the dauers. Although morphologically unusual in many respects, placement of M. alii in Diplogasterida is supported by both the morphology of the anterior digestive tract as well as analysis of its 18S rDNA sequence. These sequence data suggest that M. alii groups most closely with members of the Cylindrocorporidae.

The Microbiome and Metabolites in Fermented Pu-erh Tea as Revealed by High-Throughput Sequencing and Quantitative Multiplex Metabolite Analysis

PubMed Central

Sulyok, Michael; Liu, Xingzhong; Rao, Mingyong

2016-01-01

Pu-erh is a tea produced in Yunnan, China by microbial fermentation of fresh Camellia sinensis leaves by two processes, the traditional raw fermentation and the faster, ripened fermentation. We characterized fungal and bacterial communities in leaves and both Pu-erhs by high-throughput, rDNA-amplicon sequencing and we characterized the profile of bioactive extrolite mycotoxins in Pu-erh teas by quantitative liquid chromatography-tandem mass spectrometry. We identified 390 fungal and 629 bacterial OTUs from leaves and both Pu-erhs. Major findings are: 1) fungal diversity drops and bacterial diversity rises due to raw or ripened fermentation, 2) fungal and bacterial community composition changes significantly between fresh leaves and both raw and ripened Pu-erh, 3) aging causes significant changes in the microbial community of raw, but not ripened, Pu-erh, and, 4) ripened and well-aged raw Pu-erh have similar microbial communities that are distinct from those of young, raw Ph-erh tea. Twenty-five toxic metabolites, mainly of fungal origin, were detected, with patulin and asperglaucide dominating and at levels supporting the Chinese custom of discarding the first preparation of Pu-erh and using the wet tea to then brew a pot for consumption. PMID:27337135

Differential working memory correlates for implicit sequence performance in young and older adults.

PubMed

Bo, Jin; Jennett, S; Seidler, R D

2012-09-01

Our recent work has revealed that visuospatial working memory (VSWM) relates to the rate of explicit motor sequence learning (Bo and Seidler in J Neurophysiol 101:3116-3125, 2009) and implicit sequence performance (Bo et al. in Exp Brain Res 214:73-81, 2011a) in young adults (YA). Although aging has a detrimental impact on many cognitive functions, including working memory, older adults (OA) still rely on their declining working memory resources in an effort to optimize explicit motor sequence learning. Here, we evaluated whether age-related differences in VSWM and/or verbal working memory (VWM) performance relates to implicit performance change in the serial reaction time (SRT) sequence task in OA. Participants performed two computerized working memory tasks adapted from change detection working memory assessments (Luck and Vogel in Nature 390:279-281, 1997), an implicit SRT task and several neuropsychological tests. We found that, although OA exhibited an overall reduction in both VSWM and VWM, both OA and YA showed similar performance in the implicit SRT task. Interestingly, while VSWM and VWM were significantly correlated with each other in YA, there was no correlation between these two working memory scores in OA. In YA, the rate of SRT performance change (exponential fit to the performance curve) was significantly correlated with both VSWM and VWM, while in contrast, OA's performance was only correlated with VWM, and not VSWM. These results demonstrate differential reliance on VSWM and VWM for SRT performance between YA and OA. OA may utilize VWM to maintain optimized performance of second-order conditional sequences.

The K2 M67 Study: A Curiously Young Star in an Eclipsing Binary in an Old Open Cluster

NASA Astrophysics Data System (ADS)

Sandquist, Eric L.; Mathieu, Robert D.; Quinn, Samuel N.; Pollack, Maxwell L.; Latham, David W.; Brown, Timothy M.; Esselstein, Rebecca; Aigrain, Suzanne; Parviainen, Hannu; Vanderburg, Andrew; Stello, Dennis; Somers, Garrett; Pinsonneault, Marc H.; Tayar, Jamie; Orosz, Jerome A.; Bedin, Luigi R.; Libralato, Mattia; Malavolta, Luca; Nardiello, Domenico

2018-04-01

We present an analysis of a slightly eccentric (e = 0.05), partially eclipsing, long-period (P = 69.73 days) main-sequence binary system (WOCS 12009, Sanders 1247) in the benchmark old open cluster M67. Using Kepler K2 and ground-based photometry, along with a large set of new and reanalyzed spectra, we derived highly precise masses (1.111 ± 0.015 and 0.748 ± 0.005 M ⊙) and radii (1.071 ± 0.008 ± 0.003 and 0.713 ± 0.019 ± 0.026 R ⊙, with statistical and systematic error estimates) for the stars. The radius of the secondary star is in agreement with theory. The primary, however, is approximately 15% smaller than reasonable isochrones for the cluster predict. Our best explanation is that the primary star was produced from the merger of two stars, as this can also account for the nondetection of photospheric lithium and its higher temperature relative to other cluster main-sequence stars at the same V magnitude. To understand the dynamical characteristics (low measured rotational line broadening of the primary star and low eccentricity of the current binary orbit), we believe that the most probable (but not the only) explanation is the tidal evolution of a close binary within a primordial triple system (possibly after a period of Kozai–Lidov oscillations), leading to merger approximately 1 Gyr ago. This star appears to be a future blue straggler that is being revealed as the cluster ages and the most massive main-sequence stars die out. Based on observations made at Kitt Peak National Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation; with the Tillinghast Reflector Echelle Spectrograph (TRES) on the 1.5 m Tillinghast telescope, located at the Smithsonian Astrophysical Observatory’s Fred L. Whipple Observatory on Mt. Hopkins in Arizona; the HARPS-N spectrograph on the Italian Telescopio Nazionale Galileo (TNG), operated on the island of La Palma by the INAF Fundacion Galileo Galilei (Spanish Observatory of Roque de los Muchachos of the IAC); and the Las Cumbres Observatory Global Telescope network.

A VLT/NACO survey for triple and quadruple systems among visual pre-main sequence binaries

NASA Astrophysics Data System (ADS)

Correia, S.; Zinnecker, H.; Ratzka, Th.; Sterzik, M. F.

2006-12-01

Aims.This paper describes a systematic search for high-order multiplicity among wide visual Pre-Main Sequence (PMS) binaries. Methods: .We conducted an Adaptive Optics survey of a sample of 58 PMS wide binaries from various star-forming regions, which include 52 T Tauri systems with mostly K- and M-type primaries, with the NIR instrument NACO at the VLT. Results: .Of these 52 systems, 7 are found to be triple (2 new) and 7 quadruple (1 new). The new close companions are most likely physically bound based on their probability of chance projection and, for some of them, on their position on a color-color diagram. The corresponding degree of multiplicity among wide binaries (number of triples and quadruples divided by the number of systems) is 26.9 ± 7.2% in the projected separation range ~0.07 arcsec -12'', with the largest contribution from the Taurus-Auriga cloud. We also found that this degree of multiplicity is twice in Taurus compared to Ophiuchus and Chamaeleon for which the same number of sources are present in our sample. Considering a restricted sample composed of systems at distance 140-190 pc, the degree of multiplicity is 26.8 ± 8.1%, in the separation range 10/14 AU-1700/2300 AU (30 binaries, 5 triples, 6 quadruples). The observed frequency agrees with results from previous multiplicity surveys within the uncertainties, although a significant overabundance of quadruple systems compared to triple systems is apparent. Tentatively including the spectroscopic pairs in our restricted sample and comparing the multiplicity fractions to those measured for solar-type main-sequence stars in the solar neighborhood leads to the conclusion that both the ratio of triples to binaries and the ratio of quadruples to triples seems to be in excess among young stars. Most of the current numerical simulations of multiple star formation, and especially smoothed particles hydrodynamics simulations, over-predict the fraction of high-order multiplicity when compared to our results. The circumstellar properties around the individual components of our high-order multiple systems tend to favor mixed systems (i.e. systems including components of wTTS and cTTS type), which is in general agreement with previous studies of disks in binaries, with the exception of Taurus, where we find a preponderance of similar type of components among the multiples studied.

VizieR Online Data Catalog: VFTS. O-type stellar content of 30 Dor (Walborn+, 2014)

NASA Astrophysics Data System (ADS)

Walborn, N. R.; Sana, H.; Simon-Diaz, S.; Maiz Apellaniz, J.; Taylor, W. D.; Evans, C. J.; Markova, N.; Lennon, D. J.; de Koter, A.

2014-06-01

Detailed spectral classifications are presented for 352 O-B0 stars in the VLT-FLAMES Tarantula Survey ESO Large Programme, of which 213 O-type are judged of sufficiently high quality for further morphological analysis. Among them, six subcategories of special interest are distinguished. (1) Several new examples of the earliest spectral types O2-O3 have been found, while a previously known example has been determined to belong to the nitrogen-rich ON2 class. (2) A group of extremely rapidly rotating main-sequence objects has been isolated, including the largest vsini values known, the spatial and radial-velocity distributions of which suggest ejection from the two principal ionizing clusters NGC 2070 and NGC 2060. (3) Several new examples of the evolved, rapidly rotating Onfp class show similar evidence, although at least some of them are spectroscopic binaries. (4) No fewer than 48 members of the Vz category, hypothesized to be on or near the zero-age main sequence, are found in this sample; in contrast to the rapid rotators, they are strongly concentrated to the ionizing clusters and a newly recognized region of current and recent star formation to the north, supporting their interpretation as very young objects, as do their relatively faint absolute magnitudes. (5) A surprisingly large fraction of the main-sequence spectra belong to the recently recognized V((fc)) class, with CIII emission lines of similar strength to the usual NIII in V((f)) spectra, although a comparable number of the latter are also present, as well as six objects with very high-quality data but no trace of either emission feature, presenting new challenges to physical interpretations. (6) Two mid-O Vz and three late-O giant/supergiant spectra with morphologically enhanced nitrogen lines have been detected. Absolute visual magnitudes have been derived for each star with individual extinction laws, and composite Hertzsprung-Russell diagrams provide evidence of the multiple generations present in this field. Spectroscopic binaries, resolved visual multiples, and possible associations with X-ray sources are noted. Astrophysical and dynamical analyses of this unique dataset underway will provide new insights into the evolution of massive stars and starburst clusters. (2 data files).

Structure, inheritance, and expression of hybrid poplar (Populus trichocarpa x Populus deltoides) phenylalanine ammonia-lyase genes.

PubMed Central

Subramaniam, R; Reinold, S; Molitor, E K; Douglas, C J

1993-01-01

A heterologous probe encoding phenylalanine ammonia-lyase (PAL) was used to identify PAL clones in cDNA libraries made with RNA from young leaf tissue of two Populus deltoides x P. trichocarpa F1 hybrid clones. Sequence analysis of a 2.4-kb cDNA confirmed its identity as a full-length PAl clone. The predicted amino acid sequence is conserved in comparison with that of PAL genes from several other plants. Southern blot analysis of popular genomic DNA from parental and hybrid individuals, restriction site polymorphism in PAL cDNA clones, and sequence heterogeneity in the 3' ends of several cDNA clones suggested that PAL is encoded by at least two genes that can be distinguished by HindIII restriction site polymorphisms. Clones containing each type of PAL gene were isolated from a poplar genomic library. Analysis of the segregation of PAL-specific HindIII restriction fragment-length polymorphisms demonstrated the existence of two independently segregating PAL loci, one of which was mapped to a linkage group of the poplar genetic map. Developmentally regulated PAL expression in poplar was analyzed using RNA blots. Highest expression was observed in young stems, apical buds, and young leaves. Expression was lower in older stems and undetectable in mature leaves. Cellular localization of PAL expression by in situ hybridization showed very high levels of expression in subepidermal cells of leaves early during leaf development. In stems and petioles, expression was associated with subepidermal cells and vascular tissues. PMID:8108506

Color Vision and Hue Categorization in Young Human Infants

ERIC Educational Resources Information Center

Bornstein, Marc H.; And Others

1976-01-01

The main objective of the present investigations was to determine whether or not young human infants see the physical spectrum in a categorical fashion as human adults and animals who possess color vision regularly do. (Author)

Visibility, Immobility and Stigma: Young People's Use of Sexual Health Services in Rural Areas

ERIC Educational Resources Information Center

Craig, Gary; Stanley, Nicky

2006-01-01

Teenage pregnancy has become a major policy issue, for which young people are often publicly held solely responsible. However, a combination of factors substantially increases the risks of conception faced by young people engaging in early sexual activity. This article reports the main findings of a study of teenage pregnancy in linked seaside and…

The Effects of Gesture Use on Young Children's Pitch Accuracy for Singing Tonal Patterns

ERIC Educational Resources Information Center

Liao, Mei-Ying

2008-01-01

The main purpose of this study was to examine the effects of gesture use on young children's singing with regard to improving pitch accuracy. The second purpose was to examine the differences in gesture use among boys and girls and different melodic motions. Eighty Taiwanese young children, five to six years old, participated in this experiment.…

Paired-Associate Learning in Young and Old Adults as Related to Stimulus Concreteness and Presentation Method

ERIC Educational Resources Information Center

Witte, Kenneth L.; Freund, Joel S.

1976-01-01

Investigated the learning of young and old adults as related to two variables, stimulus concreteness (low vs. high) and presentation method (recall vs. multiple choice vs. associate matching). Main findings were: (a) the elderly did not perform as well as young adults, (b) for both groups, performance was better for the pairs with concrete…

The History and Timing of Depression Onset as Predictors of Young Adult Self-Esteem

ERIC Educational Resources Information Center

Gayman, Mathew D.; Lloyd, Donald A.; Ueno, Koji

2011-01-01

Depression often emerges early in the lifecourse and is consistently shown to be associated with poor self-esteem. The 3 main objectives of the current study are to (1) evaluate the association between a history major depression and self-esteem in young adulthood, (2) assess the relationship between timing of depression onset and young adult…

Educating through Sport? Examining HIV/AIDS Education and Sport-for-Development through the Perspectives of Zambian Young People

ERIC Educational Resources Information Center

Jeanes, Ruth

2013-01-01

The sport-for-development movement has grown exponentially in the last decade generating increasing academic attention. However, existing research has rarely sought the views of young people despite them being both the main target audience of initiatives and frequently the deliverers. This paper seeks to address young people's absence within…

Who Are the Persistently NEET Young People? Literature Overview Support Document

ERIC Educational Resources Information Center

Stanwick, John; Forrest, Cameron; Skujins, Peta

2017-01-01

This document was produced by the authors based on their research for the report, "Who Are the Persistently NEET Young People? NCVER Research Report," and is an added resource for further information. The purpose of this document is to review some of the main research and literature on young people aged 15-24 that are not engaged in…

Rules of Engagement: Boys, Young Men and the Challenge of Effective Sex and Relationships Education

ERIC Educational Resources Information Center

Biddulph, Max

2007-01-01

Over the last decade, the relationship between boys, young men and sex and relationships education (SRE) is one that has been characterised by a history of problematising. One of the main difficulties lies with young men's engagement with the subject, and in this article I make a retrospective examination of recent classroom experience with young…

NGC 346: Looking in the Cradle of a Massive Star Cluster

NASA Astrophysics Data System (ADS)

Gouliermis, Dimitrios A.; Hony, Sacha

2017-03-01

How does a star cluster of more than few 10,000 solar masses form? We present the case of the cluster NGC 346 in the Small Magellanic Cloud, still embedded in its natal star-forming region N66, and we propose a scenario for its formation, based on observations of the rich stellar populations in the region. Young massive clusters host a high fraction of early-type stars, indicating an extremely high star formation efficiency. The Milky Way galaxy hosts several young massive clusters that fill the gap between young low-mass open clusters and old massive globular clusters. Only a handful, though, are young enough to study their formation. Moreover, the investigation of their gaseous natal environments suffers from contamination by the Galactic disk. Young massive clusters are very abundant in distant starburst and interacting galaxies, but the distance of their hosting galaxies do not also allow a detailed analysis of their formation. The Magellanic Clouds, on the other hand, host young massive clusters in a wide range of ages with the youngest being still embedded in their giant HII regions. Hubble Space Telescope imaging of such star-forming complexes provide a stellar sampling with a high dynamic range in stellar masses, allowing the detailed study of star formation at scales typical for molecular clouds. Our cluster analysis on the distribution of newly-born stars in N66 shows that star formation in the region proceeds in a clumpy hierarchical fashion, leading to the formation of both a dominant young massive cluster, hosting about half of the observed pre-main-sequence population, and a self-similar dispersed distribution of the remaining stars. We investigate the correlation between stellar surface density (and star formation rate derived from star-counts) and molecular gas surface density (derived from dust column density) in order to unravel the physical conditions that gave birth to NGC 346. A power law fit to the data yields a steep correlation between these two parameters with a considerable scatter. The fraction of stellar over the total (gas plus young stars) mass is found to be systematically higher within the central 15 pc (where the young massive cluster is located) than outside, which suggests variations in the star formation efficiency within the same star-forming complex. This trend possibly reflects a change of star formation efficiency in N66 between clustered and non-clustered star formation. Our findings suggest that the formation of NGC 346 is the combined result of star formation regulated by turbulence and of early dynamical evolution induced by the gravitational potential of the dense interstellar medium.

Dust and gas around young stars

NASA Astrophysics Data System (ADS)

Chen, Christine Hsiao-Ching

To understand how asteroids, planets, and comets form in circumstellar disks of gas and dust, we have carried out a high resolution mid-infrared imaging study and a high resolution ultra violet spectroscopic study of the dust and gas around nearby pre-main sequence Herbig Ae stars and dusty main sequence stars. We have used the Keck I telescope to image at 11.7 μm and 17.9 μm the dust emission around ζ Lep, a main sequence A-type star with an infrared excess, 21.5 pc from the Sun. The excess is at most marginally resolved at 17.9 μm. The dust distance from the star is probably ≤6 AU, although some dust may extend to 9 AU. The mass of observed dust is ˜10 22 g. Since the lifetime of dust particles is about 104 yr because of the Poynting- Robertson effect, we robustly estimate at least 4 × 1026 g must reside in parent bodies which may be asteroids if the system is in a steady state and has an age of ˜300 Myr. This mass is approximately 200 times that contained within the main asteroid belt in our solar system. We have obtained FUSE spectra of σ Her, a nearby binary system, with a main sequence primary, that has a Vega-like infrared excess. We observe absorption in the excited fine structure lines C II* at 1037 Å, N II* at 1085 Å, and N II** at 1086 Å that are blueshifted by as much as ˜30 km/sec with respect to the star. Since these features are considerably narrower than the stellar lines and broader than interstellar features, the C II and N II are circumstellar. Since σ Her has a high luminosity, we suggest that there is a radiatively driven wind, arising from the circumstellar matter, rather than accretion as occurs around β Pic. Assuming that the gas is liberated by collisions between parent bodies at 20 AU, the approximate distance at which blackbody grains are in radiative equilibrium with the star and at which 3-body orbits become unstable, we infer dM/dt ˜6 × 10-12 M⊙ yr-1. This wind depletes the minimum mass of parent bodies in less than the estimated age of the system. Using the Keck I telescope, we have obtained 11.7 μm and 18.7 μm images of the circumstellar dust emission from AB Aur, a Herbig Ae star. We find that AB Aur is probably resolved at 18.7 μm with an angular diameter of 1.2″ at a surface brightness of 3.5 Jy arcsec-2. Most of the dust mass detected at millimeter wavelengths does not contribute to the 18.7 μm emission, which is plausibly explained if the system possesses a relatively cold, massive disk. We find that models with an optically thick, geometrically thin disk, surrounded by an optically thin spherical envelope fit the data somewhat better than flared disk models.

Massive star formation by accretion. II. Rotation: how to circumvent the angular momentum barrier?

NASA Astrophysics Data System (ADS)

Haemmerlé, L.; Eggenberger, P.; Meynet, G.; Maeder, A.; Charbonnel, C.; Klessen, R. S.

2017-06-01

Context. Rotation plays a key role in the star-formation process, from pre-stellar cores to pre-main-sequence (PMS) objects. Understanding the formation of massive stars requires taking into account the accretion of angular momentum during their PMS phase. Aims: We study the PMS evolution of objects destined to become massive stars by accretion, focusing on the links between the physical conditions of the environment and the rotational properties of young stars. In particular, we look at the physical conditions that allow the production of massive stars by accretion. Methods: We present PMS models computed with a new version of the Geneva Stellar Evolution code self-consistently including accretion and rotation according to various accretion scenarios for mass and angular momentum. We describe the internal distribution of angular momentum in PMS stars accreting at high rates and we show how the various physical conditions impact their internal structures, evolutionary tracks, and rotation velocities during the PMS and the early main sequence. Results: We find that the smooth angular momentum accretion considered in previous studies leads to an angular momentum barrier and does not allow the formation of massive stars by accretion. A braking mechanism is needed in order to circumvent this angular momentum barrier. This mechanism has to be efficient enough to remove more than two thirds of the angular momentum from the inner accretion disc. Due to the weak efficiency of angular momentum transport by shear instability and meridional circulation during the accretion phase, the internal rotation profiles of accreting stars reflect essentially the angular momentum accretion history. As a consequence, careful choice of the angular momentum accretion history allows circumvention of any limitation in mass and velocity, and production of stars of any mass and velocity compatible with structure equations.

Star Formation in Galaxies at z ˜ 4-5 from the SMUVS Survey: A Clear Starburst/Main-sequence Bimodality for Hα Emitters on the SFR-M* Plane

NASA Astrophysics Data System (ADS)

Caputi, K. I.; Deshmukh, S.; Ashby, M. L. N.; Cowley, W. I.; Bisigello, L.; Fazio, G. G.; Fynbo, J. P. U.; Le Fèvre, O.; Milvang-Jensen, B.; Ilbert, O.

2017-11-01

We study a large galaxy sample from the Spitzer Matching Survey of the UltraVISTA ultra-deep Stripes (SMUVS) to search for sources with enhanced 3.6 μ {{m}} fluxes indicative of strong Hα emission at z=3.9{--}4.9. We find that the percentage of “Hα excess” sources reaches 37%-40% for galaxies with stellar masses {{log}}10({M}* /{M}⊙ )≈ 9{--}10 and decreases to < 20 % at {{log}}10({M}* /{M}⊙ )˜ 10.7. At higher stellar masses, however, the trend reverses, although this is likely due to active galactic nucleus contamination. We derive star formation rates (SFR) and specific SFR (sSFR) from the inferred Hα equivalent widths of our “Hα excess” galaxies. We show, for the first time, that the “Hα excess” galaxies clearly have a bimodal distribution on the SFR-M* plane: they lie on the main sequence of star formation (with {{log}}10({sSFR}/{{yr}}-1)< -8.05) or in a starburst cloud (with {{log}}10({sSFR}/{{yr}}-1)> -7.60). The latter contains ˜ 15 % of all the objects in our sample and accounts for > 50 % of the cosmic SFR density at z=3.9{--}4.9, for which we derive a robust lower limit of 0.066 {M}⊙ {{yr}}-1 {{Mpc}}-3. Finally, we identify an unusual > 50σ overdensity of z=3.9{--}4.9 galaxies within a 0.20× 0.20 arcmin2 region. We conclude that the SMUVS unique combination of area and depth at mid-IR wavelengths provides an unprecedented level of statistics and dynamic range that are fundamental to revealing new aspects of galaxy evolution in the young universe.

IMPLICATIONS FOR THE FORMATION OF BLUE STRAGGLER STARS FROM HST ULTRAVIOLET OBSERVATIONS OF NGC 188

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

Gosnell, Natalie M.; Mathieu, Robert D.; Geller, Aaron M.

We present results of a Hubble Space Telescope (HST) far-ultraviolet (FUV) survey searching for white dwarf (WD) companions to blue straggler stars (BSSs) in open cluster NGC 188. The majority of NGC 188 BSSs (15 of 21) are single-lined binaries with properties suggestive of mass-transfer formation via Roche lobe overflow, specifically through an asymptotic giant branch star transferring mass to a main sequence secondary, yielding a BSS binary with a WD companion. In NGC 188, a BSS formed by this mechanism within the past 400 Myr will have a WD companion that is hot and luminous enough to be directlymore » detected as a FUV photometric excess with HST. Comparing expected BSS FUV emission to observed photometry reveals four BSSs with WD companions above 12,000 K (younger than 250 Myr) and three WD companions with temperatures between 11,000 and 12,000 K. These BSS+WD binaries all formed through recent mass transfer. The location of the young BSSs in an optical color–magnitude diagram (CMD) indicates that distance from the zero-age main sequence does not necessarily correlate with BSS age. There is no clear CMD separation between mass transfer-formed BSSs and those likely formed through other mechanisms, such as collisions. The seven detected WD companions place a lower limit on the mass-transfer formation frequency of 33%. We consider other possible formation mechanisms by comparing properties of the BSS population to theoretical predictions. We conclude that 14 BSS binaries likely formed from mass transfer, resulting in an inferred mass-transfer formation frequency of approximately 67%.« less

STELLAR POPULATIONS AND THE STAR FORMATION HISTORIES OF LSB GALAXIES. V. WFC3 COLOR–MAGNITUDE DIAGRAMS

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

Schombert, James; McGaugh, Stacy, E-mail: jschombe@uoregon.edu, E-mail: stacy.mcgaugh@case.edu

2015-09-15

We present WFC3 observations of three low surface brightness (LSB) galaxies from the Schombert et al. LSB catalog that are within 11 Mpc of the Milky Way. Deep imaging at F336W, F555W, and F814W allow the construction of the V − I color–magnitude diagrams (CMD) to M{sub I} = −2. Overall 1869, 465, and 501 stellar sources are identified in the three LSB galaxies F415-3, F608-1, and F750-V1, respectively. The spatial distribution of young blue stars matches the Hα maps from ground-based imaging, indicating that star formation in LSB galaxies follows the same style as in other irregular galaxies. Severalmore » star complexes are identified, matching regions of higher surface brightness as seen from ground-based imaging. The CMD for each LSB galaxy has a similar morphology to Local Volume (LV) dwarf galaxies (i.e., a blue main sequence, blue and red He burning branches, and asymptotic giant branch (AGB) stars). The LSB CMD’s distinguish themselves from nearby dwarf CMD’s by having a higher proportion of blue main sequence stars and fewer AGB stars than expected from their mean metallicities. Current [Fe/H] values below −0.6 are deduced from the position of the red helium-burning branch (rHeB) stars in the V − I diagram. The distribution of stars on the blue helium-burning branch (bHeB) and rHeB from the U − V and V − I CMD indicate a history of constant star formation for the last 100 Myr.« less

AB Dor Moving Group Stars Resolved with the CHARA Array

NASA Astrophysics Data System (ADS)

Schaefer, G. H.; White, R. J.; Baines, E. K.; Boyajian, T. S.; ten Brummelaar, T. A.; Farrington, C. D.; Sturmann, J.; Sturmann, L.; Turner, N. H.

2018-05-01

We present interferometric measurements obtained with the CHARA Array of 13 adolescent-age stars in nearby moving groups. The motivation was to spatially resolve the largest stars and to search for binary companions. Nine stars have diameters smaller than the resolution limit and no evidence for companions within 0.5–50 mas and ΔH < 2.0 mag. The diameters of three stars were spatially resolved: GJ 159 (0.582 ± 0.016 mas) and GJ 393 (0.564 ± 0.021 mas) in the AB Dor moving group, and former member HD 89744 (0.556 ± 0.032 mas). Combining the angular diameters with their distances and bolometric fluxes, we measured radii and effective temperatures. The temperatures of GJ 159 (6286 ± 123 K) and GJ 393 (3515 ± 68 K) are consistent with spectroscopic measurements. Comparisons with evolutionary models show that HD 89744 has evolved off the main sequence. GJ 159 and GJ 393 lie within 1.5σ of the zero-age main sequence, complicating their age estimates because it is unclear whether the stars are contracting or expanding. GJ 159 has a mass of 1.2 ± 0.1 {M}ȯ with an age spanning 0.021–3.0 Gyr. Its debris disk and lithium abundance favor a young age. GJ 393 has a mass of 0.42 ± 0.03 {M}ȯ and a lower limit on its age 0.06 Gyr. This overlaps with the age of the moving group; however, an older age would be more consistent with its slow rotation, low activity, and luminosity, suggesting that GJ 393 is a kinematic interloper.

Sulfate Reducing Bacteria and Mycobacteria Dominate the Biofilm Communities in a Chloraminated Drinking Water Distribution System.

PubMed

Gomez-Smith, C Kimloi; LaPara, Timothy M; Hozalski, Raymond M

2015-07-21

The quantity and composition of bacterial biofilms growing on 10 water mains from a full-scale chloraminated water distribution system were analyzed using real-time PCR targeting the 16S rRNA gene and next-generation, high-throughput Illumina sequencing. Water mains with corrosion tubercles supported the greatest amount of bacterial biomass (n = 25; geometric mean = 2.5 × 10(7) copies cm(-2)), which was significantly higher (P = 0.04) than cement-lined cast-iron mains (n = 6; geometric mean = 2.0 × 10(6) copies cm(-2)). Despite spatial variation of community composition and bacterial abundance in water main biofilms, the communities on the interior main surfaces were surprisingly similar, containing a core group of operational taxonomic units (OTUs) assigned to only 17 different genera. Bacteria from the genus Mycobacterium dominated all communities at the main wall-bulk water interface (25-78% of the community), regardless of main age, estimated water age, main material, and the presence of corrosion products. Further sequencing of the mycobacterial heat shock protein gene (hsp65) provided species-level taxonomic resolution of mycobacteria. The two dominant Mycobacteria present, M. frederiksbergense (arithmetic mean = 85.7% of hsp65 sequences) and M. aurum (arithmetic mean = 6.5% of hsp65 sequences), are generally considered to be nonpathogenic. Two opportunistic pathogens, however, were detected at low numbers: M. hemophilum (arithmetic mean = 1.5% of hsp65 sequences) and M. abscessus (arithmetic mean = 0.006% of hsp65 sequences). Sulfate-reducing bacteria from the genus Desulfovibrio, which have been implicated in microbially influenced corrosion, dominated all communities located underneath corrosion tubercules (arithmetic mean = 67.5% of the community). This research provides novel insights into the quantity and composition of biofilms in full-scale drinking water distribution systems, which is critical for assessing the risks to public health and to the water supply infrastructure.

Timing, sequencing, and executive control in repetitive movement production.

PubMed

Krampe, Ralf Th; Mayr, Ulrich; Kliegl, Reinhold

2005-06-01

The authors demonstrate that the timing and sequencing of target durations require low-level timing and executive control. Sixteen young (M-sub(age) = 19 years) and 16 older (M-sub(age) = 70 years) adults participated in 2 experiments. In Experiment 1, individual mean-variance functions for low-level timing (isochronous tapping) and the sequencing of multiple targets (rhythm production) revealed (a) a dissociation of low-level timing and sequencing in both age groups, (b) negligible age differences for low-level timing, and (c) large age differences for sequencing. Experiment 2 supported the distinction between low-level timing and executive functions: Selection against a dominant rhythm and switching between rhythms impaired performances in both age groups and induced pronounced perseveration of the dominant pattern in older adults. ((c) 2005 APA, all rights reserved).

Prospective very young asteroid pairs

NASA Astrophysics Data System (ADS)

Galád, A.; Vokrouhlický, D.; Zizka, J.

2014-07-01

Several tens of asteroid pairs can be discerned from the background main-belt asteroids. The majority of them are thought to have formed within only the last few 10^6 yr. The youngest recognized pairs have formed more than ≈ 10 kyr ago. As some details of pair formation are still not understood well, the study of young pairs is of great importance. It is mainly because the conditions at the time of the pair formation could be deduced much more reliably for young pairs. For example, space weathering on the surfaces of the components, or changes in their rotational properties (in spin rates, tumbling, coordinates of rotational pole) could be negligible since the formation of young pairs. Also, possible strong perturbations by main-belt bodies on pair formation can be reliably studied only for extremely young pairs. Some pairs can quickly blend in with the background asteroids, so even the frequency of asteroid pair formation could be determined more reliably based on young pairs (though only after a statistically significant sample is at disposal). In our regular search for young pairs in the growing asteroid database, only multiopposition asteroids with very similar orbital and proper elements are investigated. Every pair component is represented by a number of clones within orbital uncertainties and drifting in semimajor axis due to the Yarkovsky effect. We found that, if the previously unrecognized pairs (87887) 2000 SS_{286} - 2002 AT_{49} and (355258) 2007 LY_{4} - 2013AF_{40} formed at the recent very close approach of their components, they could become the youngest known pairs. In both cases, the relative encounter velocities of the components were only ˜ 0.1 m s^{-1}. However, the minimum distances between some clones are too large and a few clones of the latter pair did not encounter recently (within ≈ 10 kyr). The age of some prospective young pairs cannot be determined reliably without improved orbital properties (e.g., the second component of a pair (320025) 2007 DT_{76} - 2007 DP_{16}). It is because some components suffered recently repeated close approaches to Ceres or other large main-belt perturbers. In general, the uncertainties in age estimation can be heavily reduced after the physical properties (e.g., sense of rotation, shape, size, binarity) of the pair components are determined.

AK Sco: a tidally induced atmospheric dynamo in a pre-main sequence binary?

NASA Astrophysics Data System (ADS)

Gómez de Castro, A. I.

2009-02-01

AK Sco is a unique source: a 10-30 Myrs old pre-main sequence spectroscopic binary composed by two nearly equal F5 stars that at periastron are separated by barely eleven stellar radii so, the stellar magnetospheres fill the Roche lobe at periastron. The orbit is not yet circularized (e = 0.47) and very strong tides are expected. This makes of AK Sco, the ideal laboratory to study the effect of gravitational tides in the stellar magnetic field building up during pre-main sequence evolution. Evidence of this effect is reported in this contribution.

The Winds of Main Sequence B Stars in NGC 6231, Evidence for Shocks in Weak Winds.

NASA Astrophysics Data System (ADS)

Massa, Derck

1996-07-01

Because the main sequence B stars in NGC 6231 have abnormallystrong C iv wind lines, they are the only main sequence Bstars with distinct edge velocities. Although the underlyingcause for the strong lines remains unknown, these stars doprovide an opportunity to test two important ideas concerningB star winds: 1) that the driving ions in the winds of starswith low mass loss rates decouple from the general flow, and;2) that shocks deep in the winds of main sequence B stars areresponsible for their observed X-rays. In both of thesemodels, the wind accelerates toward a terminal velocity,v_infty, far greater than the observed value, shocking ordecoupling well before it can attain the high v_infty. As aresult, the observable wind accelerates very rapidly, leadingto wind flushing times less than 30 minutes. If theseconjectures are correct, then the winds of main sequence Bstars should be highly variable on time scales of minutes.Model fitting of available IUE data are consistant with thegeneral notion of a rapidly accelerating wind, shocking wellbefore its actual v_infty. However, these are 5 hourexposures, so the fits are to ill-defined mean wind flows.The new GHRS observations will provide adequate spectral andtemporal resolution to observe the expected variability and,thereby, verify the existance of two important astrophysicalprocesses.

Circumstellar disc lifetimes in numerous galactic young stellar clusters

NASA Astrophysics Data System (ADS)

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

2018-07-01

Photometric detections of dust circumstellar discs around pre-main sequence (PMS) stars, coupled with estimates of stellar ages, provide constraints on the time available for planet formation. Most previous studies on disc longevity, starting with Haisch, Lada & Lada, use star samples from PMS clusters but do not consider data sets with homogeneous photometric sensitivities and/or ages placed on a uniform time-scale. Here we conduct the largest study to date of the longevity of inner dust discs using X-ray and 1-8 µm infrared photometry from the MYStIX and SFiNCs projects for 69 young clusters in 32 nearby star-forming regions with ages t ≤ 5 Myr. Cluster ages are derived by combining the empirical AgeJX method with PMS evolutionary models, which treat dynamo-generated magnetic fields in different ways. Leveraging X-ray data to identify disc-free objects, we impose similar stellar mass sensitivity limits for disc-bearing and disc-free young stellar objects while extending the analysis to stellar masses as low as M ˜ 0.1 M⊙. We find that the disc longevity estimates are strongly affected by the choice of PMS evolutionary model. Assuming a disc fraction of 100 per cent at zero age, the inferred disc half-life changes significantly, from t1/2 ˜ 1.3-2 Myr to t1/2 ˜ 3.5 Myr when switching from non-magnetic to magnetic PMS models. In addition, we find no statistically significant evidence that disc fraction varies with stellar mass within the first few Myr of life for stars with masses <2 M⊙, but our samples may not be complete for more massive stars. The effects of initial disc fraction and star-forming environment are also explored.

MYSST: Mapping Young Stars in Space and Time - The HII Complex N44 in the LMC

NASA Astrophysics Data System (ADS)

Gouliermis, Dimitrios

2016-10-01

The stellar initial mass function (IMF), and the timescale and lengthscale of star formation (SF) are critical issues for our understanding of how stars form. Low-mass pre-main-sequence (PMS) stars, having typical contraction times on the order of a few 10 Myr, are the live chronometers of the SF process and primary informants on the low-mass IMF of their host clusters. Our studies show that young star clusters, embedded in star-forming regions of the Large Magellanic Cloud (LMC), encompass rich samples of PMS stars, sufficient to study clustered SF in low-metallicities with optical HST photometry. Yet, the lack of a complete comprehensive stellar sample retains important questions about the universality of the IMF, and the time- and length-scale of SF across a typical molecular cloud unanswered. We propose to address these issues by employing both ACS and WFC3 with their high sensitivity and spatial resolving power to obtain deep photometry (m_555 29 mag) of the LMC star-forming complex N44. We will accomplish a detailed mapping of PMS stars that will trace the whole hierarchy of star formation springing from one giant molecular cloud. Our analysis will provide an unbiased determination of the timescale for SF and the sub-solar IMF down to the hydrogen burning limit in a variety of clustering scales for the first time. Our findings will have a significant impact on our comprehensive understanding of SF in the low-metallicity environment of the LMC. We maximize the HST observing efficiency using both ACS/WFC and WFC3/UVIS in parallel for the simultaneous observations of N44, its ensemble of HII regions and their young stellar clusters in the same F555W and F814W filters.

X-Ray Properties of Low-mass Pre-main Sequence Stars in the Orion Trapezium Cluster

NASA Astrophysics Data System (ADS)

Schulz, Norbert S.; Huenemoerder, David P.; Günther, Moritz; Testa, Paola; Canizares, Claude R.

2015-09-01

The Chandra HETG Orion Legacy Project (HOLP) is the first comprehensive set of observations of a very young massive stellar cluster that provides high-resolution X-ray spectra of very young stars over a wide mass range (0.7-2.3 {M}⊙ ). In this paper, we focus on the six brightest X-ray sources with T Tauri stellar counterparts that are well-characterized at optical and infrared wavelengths. All stars show column densities which are substantially smaller than expected from optical extinction, indicating that the sources are located on the near side of the cluster with respect to the observer as well as that these stars are embedded in more dusty environments. Stellar X-ray luminosities are well above 1031 erg s-1, in some cases exceeding 1032 erg s-1 for a substantial amount of time. The stars during these observations show no flares but are persistently bright. The spectra can be well fit with two temperature plasma components of 10 MK and 40 MK, of which the latter dominates the flux by a ratio 6:1 on average. The total emission measures range between 3-8 × 1054 cm-3 and are comparable to active coronal sources. The fits to the Ne ix He-Like K-shell lines indicate forbidden to inter-combination line ratios consistent with the low-density limit. Observed abundances compare well with active coronal sources underlying the coronal nature of these sources. The surface flux in this sample of 0.6-2.3 {M}⊙ classical T Tauri stars shows that coronal activity increases significantly between ages 0.1 and 10 Myr. The results demonstrate the power of X-ray line diagnostics to study coronal properties of T Tauri stars in young stellar clusters.

Young Cluster Berkeley 59: Properties, Evolution, and Star Formation

NASA Astrophysics Data System (ADS)

Panwar, Neelam; Pandey, A. K.; Samal, Manash R.; Battinelli, Paolo; Ogura, K.; Ojha, D. K.; Chen, W. P.; Singh, H. P.

2018-01-01

Berkeley 59 is a nearby (∼1 kpc) young cluster associated with the Sh2-171 H II region. We present deep optical observations of the central ∼2.5 × 2.5 pc2 area of the cluster, obtained with the 3.58 m Telescopio Nazionale Galileo. The V/(V–I) color–magnitude diagram manifests a clear pre-main-sequence (PMS) population down to ∼0.2 M ⊙. Using the near-infrared and optical colors of the low-mass PMS members, we derive a global extinction of A V = 4 mag and a mean age of ∼1.8 Myr, respectively, for the cluster. We constructed the initial mass function and found that its global slopes in the mass ranges of 0.2–28 M ⊙ and 0.2–1.5 M ⊙ are ‑1.33 and ‑1.23, respectively, in good agreement with the Salpeter value in the solar neighborhood. We looked for the radial variation of the mass function and found that the slope is flatter in the inner region than in the outer region, indicating mass segregation. The dynamical status of the cluster suggests that the mass segregation is likely primordial. The age distribution of the PMS sources reveals that the younger sources appear to concentrate close to the inner region compared to the outer region of the cluster, a phenomenon possibly linked to the time evolution of star-forming clouds. Within the observed area, we derive a total mass of ∼103 M ⊙ for the cluster. Comparing the properties of Berkeley 59 with other young clusters, we suggest it resembles more closely the Trapezium cluster.

Characterisation of monotreme caseins reveals lineage-specific expansion of an ancestral casein locus in mammals.

PubMed

Lefèvre, Christophe M; Sharp, Julie A; Nicholas, Kevin R

2009-01-01

Using a milk-cell cDNA sequencing approach we characterised milk-protein sequences from two monotreme species, platypus (Ornithorhynchus anatinus) and echidna (Tachyglossus aculeatus) and found a full set of caseins and casein variants. The genomic organisation of the platypus casein locus is compared with other mammalian genomes, including the marsupial opossum and several eutherians. Physical linkage of casein genes has been seen in the casein loci of all mammalian genomes examined and we confirm that this is also observed in platypus. However, we show that a recent duplication of beta-casein occurred in the monotreme lineage, as opposed to more ancient duplications of alpha-casein in the eutherian lineage, while marsupials possess only single copies of alpha- and beta-caseins. Despite this variability, the close proximity of the main alpha- and beta-casein genes in an inverted tail-tail orientation and the relative orientation of the more distant kappa-casein genes are similar in all mammalian genome sequences so far available. Overall, the conservation of the genomic organisation of the caseins indicates the early, pre-monotreme development of the fundamental role of caseins during lactation. In contrast, the lineage-specific gene duplications that have occurred within the casein locus of monotremes and eutherians but not marsupials, which may have lost part of the ancestral casein locus, emphasises the independent selection on milk provision strategies to the young, most likely linked to different developmental strategies. The monotremes therefore provide insight into the ancestral drivers for lactation and how these have adapted in different lineages.

Designing a Topic-Based Syllabus for Young Learners

ERIC Educational Resources Information Center

Bourke, James M.

2006-01-01

In recent years there has been a good deal of debate on the teaching of English to young learners. Although the article looks at the teaching of English to lower primary children in an ESL context in Southeast Asia, it is not specific to one region. The young learners in question are aged 6 to 8 years. The main focus of the article is how best to…

What Works for Disconnected Young People: A Scan of the Evidence. MDRC Working Paper

ERIC Educational Resources Information Center

Treskon, Louisa

2016-01-01

The purpose of this paper was to conduct a scan of the current state of the evidence regarding what works in helping disconnected young people, defined as the population of young people ages 16 to 24 who are not connected to work or school. The following four main research questions were investigated: (1) What local, state, and federal policies…

IN-SYNC I: Homogeneous stellar parameters from high-resolution apogee spectra for thousands of pre-main sequence stars

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

Cottaar, Michiel; Meyer, Michael R.; Covey, Kevin R.

2014-10-20

Over two years, 8859 high-resolution H-band spectra of 3493 young (1-10 Myr) stars were gathered by the multi-object spectrograph of the APOGEE project as part of the IN-SYNC ancillary program of the SDSS-III survey. Here we present the forward modeling approach used to derive effective temperatures, surface gravities, radial velocities, rotational velocities, and H-band veiling from these near-infrared spectra. We discuss in detail the statistical and systematic uncertainties in these stellar parameters. In addition, we present accurate extinctions by measuring the E(J – H) of these young stars with respect to the single-star photometric locus in the Pleiades. Finally, wemore » identify an intrinsic stellar radius spread of about 25% for late-type stars in IC 348 using three (nearly) independent measures of stellar radius, namely, the extinction-corrected J-band magnitude, the surface gravity, and the Rsin i from the rotational velocities and literature rotation periods. We exclude that this spread is caused by uncertainties in the stellar parameters by showing that the three estimators of stellar radius are correlated, so that brighter stars tend to have lower surface gravities and larger Rsin i than fainter stars at the same effective temperature. Tables providing the spectral and photometric parameters for the Pleiades and IC 348 have been provided online.« less

Fundamental Parameters of Nearby Young Stars

NASA Astrophysics Data System (ADS)

McCarthy, Kyle; Wilhelm, R. J.

2013-06-01

We present high resolution (R ~ 60,000) spectroscopic data of F and G members of the nearby, young associations AB Doradus and β Pictoris obtained with the Cross-Dispersed Echelle Spectrograph on the 2.7 meter telescope at the McDonald Observatory. Effective temperatures, log(g), [Fe/H], and microturbulent velocities are first estimated using the TGVIT code, then finely tuned using MOOG. Equivalent width (EW) measurements were made using TAME alongside a self-produced IDL routine to constrain EW accuracy and improve computed fundamental parameters. MOOG is also used to derive the chemical abundance of several elements including Mn which is known to be over abundant in planet hosting stars. Vsin(i) are also computed using a χ2 analysis of our observed data to Atlas9 model atmospheres passed through the SPECTRUM spectral synthesis code on lines which do not depend strongly on surface gravity. Due to the limited number of Fe II lines which govern the surface gravity fit in both TGVIT and MOOG, we implement another χ2 analysis of strongly log(g) dependent lines to ensure the values are correct. Coupling the surface gravities and temperatures derived in this study with the luminosities found in the Tycho-2 catalog, we estimate masses for each star and compare these masses to several evolutionary models to begin the process of constraining pre-main sequence evolutionary models.

IN-SYNC I: Homogeneous Stellar Parameters from High-resolution APOGEE Spectra for Thousands of Pre-main Sequence Stars

NASA Astrophysics Data System (ADS)

Cottaar, Michiel; Covey, Kevin R.; Meyer, Michael R.; Nidever, David L.; Stassun, Keivan G.; Foster, Jonathan B.; Tan, Jonathan C.; Chojnowski, S. Drew; da Rio, Nicola; Flaherty, Kevin M.; Frinchaboy, Peter M.; Skrutskie, Michael; Majewski, Steven R.; Wilson, John C.; Zasowski, Gail

2014-10-01

Over two years, 8859 high-resolution H-band spectra of 3493 young (1-10 Myr) stars were gathered by the multi-object spectrograph of the APOGEE project as part of the IN-SYNC ancillary program of the SDSS-III survey. Here we present the forward modeling approach used to derive effective temperatures, surface gravities, radial velocities, rotational velocities, and H-band veiling from these near-infrared spectra. We discuss in detail the statistical and systematic uncertainties in these stellar parameters. In addition, we present accurate extinctions by measuring the E(J - H) of these young stars with respect to the single-star photometric locus in the Pleiades. Finally, we identify an intrinsic stellar radius spread of about 25% for late-type stars in IC 348 using three (nearly) independent measures of stellar radius, namely, the extinction-corrected J-band magnitude, the surface gravity, and the Rsin i from the rotational velocities and literature rotation periods. We exclude that this spread is caused by uncertainties in the stellar parameters by showing that the three estimators of stellar radius are correlated, so that brighter stars tend to have lower surface gravities and larger Rsin i than fainter stars at the same effective temperature. Tables providing the spectral and photometric parameters for the Pleiades and IC 348 have been provided online.

Extreme Radio Flares and Associated X-Ray Variability from Young Stellar Objects in the Orion Nebula Cluster

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

Forbrich, Jan; Reid, Mark J.; Wolk, Scott J.

Young stellar objects are known to exhibit strong radio variability on timescales of weeks to months, and a few reports have documented extreme radio flares with at least an order of magnitude change in flux density on timescales of hours to days. However, there have been few constraints on the occurrence rate of such radio flares or on the correlation with pre-main sequence X-ray flares, although such correlations are known for the Sun and nearby active stars. Here we report simultaneous deep VLA radio and Chandra X-ray observations of the Orion Nebula Cluster, targeting hundreds of sources to look formore » the occurrence rate of extreme radio variability and potential correlation with the most extreme X-ray variability. We identify 13 radio sources with extreme radio variability, with some showing an order of magnitude change in flux density in less than 30 minutes. All of these sources show X-ray emission and variability, but we find clear correlations with extreme radio flaring only on timescales <1 hr. Strong X-ray variability does not predict the extreme radio sources and vice versa. Radio flares thus provide us with a new perspective on high-energy processes in YSOs and the irradiation of their protoplanetary disks. Finally, our results highlight implications for interferometric imaging of sources violating the constant-sky assumption.« less

Reprocessing of Archival Direct Imaging Data of Herbig Ae/Be Stars

NASA Astrophysics Data System (ADS)

Safsten, Emily; Stephens, Denise C.

2017-01-01

Herbig Ae/Be (HAeBe) stars are intermediate mass (2-10 solar mass) pre-main sequence stars with circumstellar disks. They are the higher mass analogs of the better-known T Tauri stars. Observing planets within these young disks would greatly aid in understanding planet formation processes and timescales, particularly around massive stars. So far, only one planet, HD 100546b, has been confirmed to orbit a HAeBe star. With over 250 HAeBe stars known, and several observed to have disks with structures thought to be related to planet formation, it seems likely that there are as yet undiscovered planetary companions within the circumstellar disks of some of these young stars.Direct detection of a low-luminosity companion near a star requires high contrast imaging, often with the use of a coronagraph, and the subtraction of the central star's point spread function (PSF). Several processing algorithms have been developed in recent years to improve PSF subtraction and enhance the signal-to-noise of sources close to the central star. However, many HAeBe stars were observed via direct imaging before these algorithms came out. We present here current work with the PSF subtraction program PynPoint, which employs a method of principal component analysis, to reprocess archival images of HAeBe stars to increase the likelihood of detecting a planet in their disks.

[The future of the European nephrology belongs to the young: the Young Nephrologists' Platform].

PubMed

Bolignano, Davide

2014-01-01

Young people are the future of research, especially in nephrology. The prevalence of young nephrologists within the main scientific European societies varies from the 12% to 34% and the 20% of the ERA-EDTA members are less than 40 years old in 2013. Recently, the ERA-EDTA has launched a new platform, the Young Nephrologists Platform (YNP), which the aim is to become the first modern network of young nephrologists from Europe and beyond. YNP aims at promoting the aggregation of young people through modern communication channels such as social networks, blogs and through the construction of a database collecting information on attitudes and personal experiences of each young nephrologist. A mentorship program, focused and young-oriented clinical courses on hot topics and the direct involvement of young nephrologists in working groups and scientific studies are some of the other interesting initiatives driven by YNP. The future of nephrology belongs to the young and YNP could represent a good springboard for the professional growth of young nephrologists.

Deep near-infrared adaptive-optics observations of a young embedded cluster at the edge of the RCW 41 H II region

NASA Astrophysics Data System (ADS)

Neichel, B.; Samal, M. R.; Plana, H.; Zavagno, A.; Bernard, A.; Fusco, T.

2015-04-01

Aims: We investigate the star formation activity in a young star forming cluster embedded at the edge of the RCW 41 H ii region. As a complementary goal, we aim to demonstrate the gain provided by wide-field adaptive optics (WFAO) instruments to study young clusters. Methods: We used deep, JHKs images from the newly commissioned Gemini-GeMS/GSAOI instrument, complemented with Spitzer IRAC observations, in order to study the photometric properties of the young stellar cluster. GeMS is a WFAO instrument that delivers almost diffraction-limited images over a field of ~2' across. The exquisite angular resolution allows us to reach a limiting magnitude of J ~ 22 for 98% completeness. The combination of the IRAC photometry with our JHKs catalog is used to build color-color diagrams, and select young stellar object (YSO) candidates. The JHKs photometry is also used in conjunction with pre-main sequence evolutionary models to infer masses and ages. The K-band luminosity function is derived, and then used to build the initial mass function (IMF) of the cluster. Results: We detect the presence of 80 YSO candidates. Those YSOs are used to infer the cluster age, which is found to be in the range 1 to 5 Myr. More precisely, we find that 1/3 of the YSOs are in a range between 3 to 5 Myr, while 2/3 of the YSO are ≤3 Myr. When looking at the spatial distribution of these two populations, we find evidence of a potential age gradient across the field that suggests sequential star formation. We construct the IMF and show that we can sample the mass distribution well into the brown dwarf regime (down to ~0.01 M⊙). The logarithmic mass function rises to peak at ~0.3 M⊙, before turning over and declining into the brown dwarf regime. The total cluster mass derived is estimated to be 78 ± 18 M⊙, while the ratio derived of brown dwarfs to star is 18 ± 5%. When comparing it with other young clusters, we find that the IMF shape of the young cluster embedded within RCW 41 is consistent with those of Trapezium, IC 348, or Chamaeleon I, except for the IMF peak, which happens to be at higher mass. This characteristic is also seen in clusters like NGC 6611 or even Taurus. These results suggest that the medium-to-low mass end of the IMF possibly depends on environment.

Capturing Complexities of Relationship-Level Family Planning Trajectories in Malawi.

PubMed

Furnas, Hannah E

2016-09-01

In a transitioning fertility climate, preferences and decisions surrounding family planning are constantly in flux. Malawi provides an ideal case study of family planning complexities as fertility preferences are flexible, the relationship context is unstable, and childbearing begins early. I use intensive longitudinal data from Tsogolo la Thanzi-a research project in Malawi that follows young adults in romantic partnerships through the course of their relationship. I examine two questions: (1) What are the typical patterns of family planning as young adults transition through a relationship? (2) How are family planning trajectories related to individual and relationship-level characteristics? I use sequence analysis to order family planning across time and to contextualize it within each relationship. I generate and cluster the family planning trajectories and find six distinct groups of young adults who engage in family planning in similar ways. I find that family planning is complex, dynamic, and unique to each relationship. I argue that (a) family planning research should use the relationship as the unit of analysis and (b) family planning behaviors and preferences should be sequenced over time for a better understanding of key concepts, such as unmet need. © 2016 The Population Council, Inc.

Capturing Complexities of Relationship-Level Family Planning Trajectories in Malawi

PubMed Central

Furnas, Hannah E.

2017-01-01

In a transitioning fertility climate, preferences and decisions surrounding family planning are constantly in flux. Malawi provides an ideal case study of family planning complexities as fertility preferences are flexible, the relationship context is unstable, and childbearing begins early. I use intensive longitudinal data from Tsogolo la Thanzi—a research project in Malawi that follows young adults in romantic partnerships through the course of their relationship and allows me to ask two questions: (1) What are the typical patterns of family planning as young adults transition through a relationship? (2) How are family planning trajectories related to individual and relationship-level characteristics? I use sequence analysis to order family planning across time and to contextualize it within each relationship. I generate and cluster the family planning trajectories and find six distinct groups of young adults who engage in family planning in similar ways. I find that family planning is complex, dynamic, and unique to each relationship. I argue that (a) family planning research should use the relationship as the unit of analysis and (b) family planning behaviors and preferences should be sequenced over time for a better understanding of key concepts, such as unmet need. PMID:27517867

Perceiving goals and actions in individuals with autism spectrum disorders.

PubMed

Zalla, Tiziana; Labruyère, Nelly; Georgieff, Nicolas

2013-10-01

In the present study, we investigated the ability to parse familiar sequences of action into meaningful events in young individuals with autism spectrum disorders (ASDs), as compared to young individuals with typical development (TD) and young individuals with moderate mental retardation or learning disabilities (MLDs). While viewing two videotaped movies, participants were requested to detect the boundary transitions between component events at both fine and coarse levels of the action hierarchical structure. Overall, reduced accuracy for event detection was found in participants with ASDs, relative to participants with TD, at both levels of action segmentation. The performance was, however, equally diminished in participants with ASDs and MLDs under the course-grained segmentation suggesting that difficulties to detect fine-grained events in ASDs cannot be explained by a general intellectual dysfunction. Reduced accuracy for event detection was related to diminished event recall, memory for event sequence and Theory of Mind abilities. We hypothesized that difficulties with event detection result from a deficit disrupting the on-line processing of kinematic features and physical changes of dynamic human actions. An impairment at the earlier stages of the event encoding process might contribute to deficits in episodic memory and social functioning in individuals with ASDs.

Stratigraphic controls on saltwater intrusion in the Dominguez Gap area of coastal Los Angeles

USGS Publications Warehouse

Edwards, Brian D.; Ehman, Kenneth D.; Ponti, Daniel J.; Reichard, Eric G.; Tinsley, John; Rosenbauer, Robert J.; Land, Michael T.

2009-01-01

The Los Angeles Basin is a densely populated coastal area that significantly depends on groundwater. A part of this groundwater supply is at risk from saltwater intrusion-the impetus for this study. High-resolution seismic-reflection data collected from the Los Angeles-Long Beach Harbor Complex have been combined with borehole geophysical and descriptive geological data from four nearby ??400-m-deep continuously cored wells and with borehole geophysical data from adjacent water and oil wells to characterize the Pliocene to Holocene stratigraphy of the Dominguez Gap coastal aquifer system. The new data are shown as a north-south, two- dimensional, sequence-stratigraphic model that is compared to existing lithostratigraphic models of the Los Angeles Basin in an attempt to better understand pathways of saltwater intrusion into coastal aquifers. Intrusion of saltwater into the coastal aquifer system generally is attributed to over-pumping that caused the hydraulic gradient to reverse during the mid-1920s. Local water managers have used the existing lithostratigraphic model to site closely spaced injection wells of freshwater (barrier projects) attempting to hydraulically control the saltwater intrusion. Improved understanding of the stratigraphic relationships can guide modifications to barrier design that will allow more efficient operation. Allostratigraphic nomenclature is used to define a new sequence-stratigraphic model for the area because the existing lithostratigraphic correlations that have been used to define aquifer systems are shown not to be time-correlative. The youngest sequence, the Holocene Dominguez sequence, contains the Gaspur aquifer at its base. The Gaspur aquifer is intruded with saltwater and consists of essentially flat-lying gravelly sands deposited by the ancestral Los Angeles River as broad channels that occupied a paleovalley incised into the coastal plain during the last glacio-eustatic highstand. The underlying sequences are deformed into a broad anticlinal fold that occurs parallel to, but ??2 km north of, the axis of the Pliocene Wilmington anticline. The Dominguez sequence breaches the crest of the young anticline, cuts through the upper Pleistocene Mesa and Pacific sequences, and into the middle Pleistocene Harbor sequence. Saltwater migrates along channels within the Dominguez sequence and into the underlying sequences (composed mostly of shallow marine and tidal sands, silts, and clays) that contain the classically defined Gage and Lynwood aquifers. The newly recognized Pacific Coast Highway fault cuts through the core of this young fold and is downthrown on the northern side, thereby creating accommodation space for a thick succession of middle Pleistocene sediments that constitute the Upper Wilmington sequence. North of the Pacific Coast Highway fault, the Upper Wilmington sequence contains the classic Silverado aquifer (composed of fluviodeltaic deposits); the Silverado is the primary freshwater aquifer for the West Coast and Central Los Angeles Groundwater Basins. Pore fluid and electric log analyses show the upper part of this aquifer to be saline-intruded near the crest of the young fold. This relationship implies that some saltwater is migrating into deeper aquifers from above, across the regional unconformity that marks the base of the Harbor sequence (ca. 240-270 ka). This sequence-stratigraphic model provides new insight into the potential flow paths for saltwater intrusion, and as such, should allow improved characterization of fluidflow that will aid in transport model studies and in managing groundwater resources. ?? 2009 Geological Society of America.

Sexual identity trajectories among sexual-minority youths: gender comparisons.

PubMed

Savin-Williams, R C; Diamond, L M

2000-12-01

The present investigation explored gender differences in sexual identity development--first same-sex attractions, self-labeling, same-sex sexual contact, and disclosure--among 164 sexual-minority young adults. Based on interviews, results indicated the value of assessing gender differences in the context, timing, spacing, and sequencing of sexual identity milestones. Adolescent males had an earlier onset of all milestones except disclosure. The context for sexual identity milestones were likely to be emotionally oriented for young women and sexually oriented for young men. The gap from first same-sex attractions (8-9 years of age) to first disclosure (around 18 years) averaged 10 years for both sexes. Young women followed label-first developmental trajectories; men were more likely to pursue sex before identifying themselves as gay. In terms of achieving sexual identity milestones, gender mattered, but it was not everything.

Effects of the Affordable Care Act's young adult insurance expansion on prescription drug insurance coverage, utilization, and expenditures.

PubMed

Look, Kevin A; Arora, Prachi

2016-01-01

The US Affordable Care Act (ACA) extended the age of eligibility for young adults to remain on their parents' health insurance plans in order to address the disproportionate number of uninsured young adults in the United States. Effective September 23, 2010, the ACA has required all private health insurance plans to cover dependents until the age of 26. However, it is unknown whether the ACA dependent coverage expansion had an impact on prescription drug insurance or the use of prescription drugs. To evaluate short-term changes in prescription health insurance coverage, prescription drug insurance coverage, prescription drug use, and prescription drug expenditures following implementation of the ACA young adult insurance expansion using national data from 2009 and 2011. Full-year health insurance coverage increased 4.9 percentage points during the study period, which was mainly due to increases in private health insurance among middle- and high-income young adults. In contrast, full-year prescription drug insurance coverage increased 5.5 percentage points and was primarily concentrated among high-income young adults. Although no significant short-term changes in overall prescription drug use were observed, a 30% decrease in out-of-pocket expenditures was seen among young adults. While the main goal of the ACA's young adult insurance expansion was to increase health insurance coverage among young adults, it also had the unintended positive effect of increasing coverage for prescription drug insurance. Additionally, young adults experienced substantial decreases in out-of-pocket spending for prescription drugs. It is important for evaluations of health care policies to assess both intended and unintended outcomes to better understand the implications for the broader health system. Copyright © 2015 Elsevier Inc. All rights reserved.

The effectiveness of using pictures in teaching young children about burn injury accidents.

PubMed

Liu, Hsueh-Fen; Lin, Fang-Suey; Chang, Chien-Ju

2015-11-01

This study utilized the "story grammar" approach (Stein and Glenn, 1979) to analyze the within-corpus differences in recounting of sixty 6- and 7-year-old children, specifically whether illustrations (5-factor accident sequence) were or were not resorted to as a means to assist their narration of a home accident in which a child received a burn injury from hot soup. Our investigation revealed that the message presentation strategy "combining oral and pictures" better helped young children to memorize the story content (sequence of events leading to the burn injury) than "oral only." Specifically, the content of "the dangerous objects that caused the injury", "the unsafe actions that people involved took", and "how the people involved felt about the severity of the accident" differed significantly between the two groups. Copyright © 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.

The dark nemesis of galaxy formation: why hot haloes trigger black hole growth and bring star formation to an end

NASA Astrophysics Data System (ADS)

Bower, Richard G.; Schaye, Joop; Frenk, Carlos S.; Theuns, Tom; Schaller, Matthieu; Crain, Robert A.; McAlpine, Stuart

2017-02-01

Galaxies fall into two clearly distinct types: `blue-sequence' galaxies which are rapidly forming young stars, and `red-sequence' galaxies in which star formation has almost completely ceased. Most galaxies more massive than 3 × 1010 M⊙ follow the red sequence, while less massive central galaxies lie on the blue sequence. We show that these sequences are created by a competition between star formation-driven outflows and gas accretion on to the supermassive black hole at the galaxy's centre. We develop a simple analytic model for this interaction. In galaxies less massive than 3 × 1010 M⊙, young stars and supernovae drive a high-entropy outflow which is more buoyant than any tenuous corona. The outflow balances the rate of gas inflow, preventing high gas densities building up in the central regions. More massive galaxies, however, are surrounded by an increasingly hot corona. Above a halo mass of ˜1012 M⊙, the outflow ceases to be buoyant and star formation is unable to prevent the build-up of gas in the central regions. This triggers a strongly non-linear response from the black hole. Its accretion rate rises rapidly, heating the galaxy's corona, disrupting the incoming supply of cool gas and starving the galaxy of the fuel for star formation. The host galaxy makes a transition to the red sequence, and further growth predominantly occurs through galaxy mergers. We show that the analytic model provides a good description of galaxy evolution in the EAGLE hydrodynamic simulations. So long as star formation-driven outflows are present, the transition mass scale is almost independent of subgrid parameter choice.

"Silent" dissemination of Klebsiella pneumoniae isolates bearing K. pneumoniae carbapenemase in a long-term care facility for children and young adults in Northeast Ohio.

PubMed

Viau, Roberto A; Hujer, Andrea M; Marshall, Steven H; Perez, Federico; Hujer, Kristine M; Briceño, David F; Dul, Michael; Jacobs, Michael R; Grossberg, Richard; Toltzis, Philip; Bonomo, Robert A

2012-05-01

Klebsiella pneumoniae isolates harboring the K. pneumoniae carbapenemase gene (bla(KPC)) are creating a significant healthcare threat in both acute and long-term care facilities (LTCFs). As part of a study conducted in 2004 to determine the risk of stool colonization with extended-spectrum cephalosporin-resistant gram-negative bacteria, 12 isolates of K. pneumoniae that exhibited nonsusceptibility to extended-spectrum cephalosporins were detected. All were gastrointestinal carriage isolates that were not associated with infection. Reassessment of the carbapenem minimum inhibitory concentrations using revised 2011 Clinical Laboratory Standards Institute breakpoints uncovered carbapenem resistance. To further investigate, a DNA microarray assay, PCR-sequencing of bla genes, immunoblotting, repetitive-sequence-based PCR (rep-PCR) and multilocus sequence typing (MLST) were performed. The DNA microarray detected bla(KPC) in all 12 isolates, and bla(KPC-3) was identified by PCR amplification and sequencing of the amplicon. In addition, a bla(SHV-11) gene was detected in all isolates. Immunoblotting revealed "low-level" production of the K. pneumoniae carbapenemase, and rep-PCR indicated that all bla(KPC-3)-positive K. pneumoniae strains were genetically related (≥98% similar). According to MLST, all isolates belonged to sequence type 36. This sequence type has not been previously linked with bla(KPC) carriage. Plasmids from 3 representative isolates readily transferred the bla(KPC-3) to Escherichia coli J-53 recipients. Our findings reveal the "silent" dissemination of bla(KPC-3) as part of Tn4401b on a mobile plasmid in Northeast Ohio nearly a decade ago and establish the first report, to our knowledge, of K. pneumoniae containing bla(KPC-3) in an LTCF caring for neurologically impaired children and young adults.

A DYNAMICAL SIGNATURE OF MULTIPLE STELLAR POPULATIONS IN 47 TUCANAE

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

Richer, Harvey B.; Heyl, Jeremy; Anderson, Jay

2013-07-01

Based on the width of its main sequence, and an actual observed split when viewed through particular filters, it is widely accepted that 47 Tucanae contains multiple stellar populations. In this contribution, we divide the main sequence of 47 Tuc into four color groups, which presumably represent stars of various chemical compositions. The kinematic properties of each of these groups are explored via proper motions, and a strong signal emerges of differing proper-motion anisotropies with differing main-sequence color; the bluest main-sequence stars exhibit the largest proper-motion anisotropy which becomes undetectable for the reddest stars. In addition, the bluest stars aremore » also the most centrally concentrated. A similar analysis for Small Magellanic Cloud stars, which are located in the background of 47 Tuc on our frames, yields none of the anisotropy exhibited by the 47 Tuc stars. We discuss implications of these results for possible formation scenarios of the various populations.« less

Wastewater disposal and the earthquake sequences during 2016 near Fairview, Pawnee, and Cushing, Oklahoma

USGS Publications Warehouse

McGarr, Arthur F.; Barbour, Andrew

2017-01-01

Each of the three earthquake sequences in Oklahoma in 2016—Fairview, Pawnee, and Cushing—appears to have been induced by high-volume wastewater disposal within 10 km. The Fairview M5.1 main shock was part of a 2 year sequence of more than 150 events of M3, or greater; the main shock accounted for about half of the total moment. The foreshocks and aftershocks of the M5.8 Pawnee earthquake were too small and too few to contribute significantly to the cumulative moment; instead, nearly all of the moment induced by wastewater injection was focused on the main shock. The M5.0 Cushing event is part of a sequence that includes 48 earthquakes of M3, or greater, that are mostly foreshocks. The cumulative moment for each of the three sequences during 2016, as well as that for the 2011 Prague, Oklahoma, and nine other sequences representing a broad range of injected volume, are all limited by the total volumes of wastewater injected locally.

A qualitative study of the influence of poor dental aesthetics on the lives of young adults.

PubMed

Josefsson, Eva; Lindsten, Rune; Hallberg, Lillemor R-M

2010-01-01

Although many countries offer some publicly funded orthodontic treatment for children, not all conditions receive treatment and some adolescents enter adulthood with persisting poor dental aesthetics or malocclusions. The aim of this study was to generate a theory highlighting the main concerns of young adults, either native-born or of immigrant background, with poor dental aesthetics and the measures they adopt to manage their condition in everyday life. A qualitative method, classic grounded theory, was applied in order to generate a substantive theory highlighting the main concerns and managing mechanisms of 13 strategically selected 19- and 20-year-olds with poor dental aesthetics. Open interviews were conducted with each participant, the topics covering different aspects of social and dental conditions. A core category and three conceptual categories were generated. The core category was labelled "Being under the pressure of social norms" and was related to categories explaining three different ways in which these young adults handle their main concern: (1) avoiding showing their teeth; (2) minimizing the importance of appearance; and (3) seeking orthodontic treatment. The theory offers the potential for improved understanding of young adults who, despite poor dental aesthetics, are managing well with life, and also of those who have not adjusted well. In early adolescence it may be problematic to make decisions about orthodontic treatment. Undisclosed dental fear can be an important barrier. Some of the young adults in the present study would probably benefit from treatment.

Frequency of MELAS main mutation in a phenotype-targeted young ischemic stroke patient population.

PubMed

Tatlisumak, Turgut; Putaala, Jukka; Innilä, Markus; Enzinger, Christian; Metso, Tiina M; Curtze, Sami; von Sarnowski, Bettina; Amaral-Silva, Alexandre; Jungehulsing, Gerhard Jan; Tanislav, Christian; Thijs, Vincent; Rolfs, Arndt; Norrving, Bo; Fazekas, Franz; Suomalainen, Anu; Kolodny, Edwin H

2016-02-01

Mitochondrial diseases, predominantly mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS), may occasionally underlie or coincide with ischemic stroke (IS) in young and middle-aged individuals. We searched for undiagnosed patients with MELAS in a target subpopulation of unselected young IS patients enrolled in the Stroke in Young Fabry Patients study (sifap1). Among the 3291 IS patients aged 18-55 years recruited to the sifap1 study at 47 centers across 14 European countries, we identified potential MELAS patients with the following phenotypic features: (a) diagnosed cardiomyopathy or (b) presence of two of the three following findings: migraine, short stature (≤165 cm for males; ≤155 cm for females), and diabetes. Identified patients' blood samples underwent analysis of the common MELAS mutation, m.3243A>G in the MTTL1 gene of mitochondrial DNA. Clinical and cerebral MRI features of the mutation carriers were reviewed. We analyzed blood samples of 238 patients (177 with cardiomyopathy) leading to identification of four previously unrecognized MELAS main mutation carrier-patients. Their clinical and MRI characteristics were within the expectation for common IS patients except for severe hearing loss in one patient and hyperintensity of the pulvinar thalami on T1-weighted MRI in another one. Genetic testing for the m.3243A>G MELAS mutation in young patients with IS based on phenotypes suggestive of mitochondrial disease identifies previously unrecognized carriers of MELAS main mutation, but does not prove MELAS as the putative cause.

Statistical theory for protein combinatorial libraries. Packing interactions, backbone flexibility, and the sequence variability of a main-chain structure.

PubMed

Kono, H; Saven, J G

2001-02-23

Combinatorial experiments provide new ways to probe the determinants of protein folding and to identify novel folding amino acid sequences. These types of experiments, however, are complicated both by enormous conformational complexity and by large numbers of possible sequences. Therefore, a quantitative computational theory would be helpful in designing and interpreting these types of experiment. Here, we present and apply a statistically based, computational approach for identifying the properties of sequences compatible with a given main-chain structure. Protein side-chain conformations are included in an atom-based fashion. Calculations are performed for a variety of similar backbone structures to identify sequence properties that are robust with respect to minor changes in main-chain structure. Rather than specific sequences, the method yields the likelihood of each of the amino acids at preselected positions in a given protein structure. The theory may be used to quantify the characteristics of sequence space for a chosen structure without explicitly tabulating sequences. To account for hydrophobic effects, we introduce an environmental energy that it is consistent with other simple hydrophobicity scales and show that it is effective for side-chain modeling. We apply the method to calculate the identity probabilities of selected positions of the immunoglobulin light chain-binding domain of protein L, for which many variant folding sequences are available. The calculations compare favorably with the experimentally observed identity probabilities.

Genome Sequence of Canine Parvovirus Strain SC02/2011, Isolated from a Puppy with Severe Diarrhea in South China

PubMed Central

Cheng, Yi; Ji, Yikuan; Wang, Yu; Sun, Leilei; Huang, Jiaxin

2012-01-01

A widespread hemorrhagic gastroenteritis in young dogs occurred in South China. A virulent field canine parvovirus (CPV) strain, SC02/2011, was isolated from a puppy showing enteric signs in Guangdong, China. The genome of CPV strain SC02/2011 was sequenced and analyzed, which will promote a better understanding of the molecular epidemiology and genetic diversity of CPV field isolates in South China. PMID:23166228

Planning and control of sequential rapid aiming in adults with Parkinson's disease.

PubMed

Smiley-Oyen, A L; Lowry, K A; Kerr, J P

2007-03-01

Eight people with Parkinson's disease (PD), 8 age-matched older adults, and 8 young adults executed 3-dimensional rapid aiming movements to 1, 3, 5, and 7 targets. Reaction time, flight time, and time after peak velocity to the 1st target indicated that both neurologically healthy groups implemented a plan on the basis of anticipation of upcoming targets, whereas the PD group did not. One suggested reason for the PD group's deficiency in anticipatory control is the greater variability in their initial force impulse. Although the PD group scaled peak velocity and time to peak velocity similarly to the other groups, their coefficients of variation were greater, making consistent prediction of the movement outcome difficult and thus making it less advantageous to plan too far in advance. A 2nd finding was that the PD group exhibited increased slowing in time after peak velocity in the final segments of the longest sequence, whereas the other 2 groups did not. The increased slowing could be the result of a different movement strategy, increased difficulty modulating the agonist and antagonist muscle groups later in the sequence, or both. The authors conclude that people with PD use more segmented planning and control strategies than do neurologically healthy older and young adults when executing movement sequences and that the locus of increased bradykinesia in longer sequences is in the deceleration phase of movement.

Expression of young HERV-H loci in the course of colorectal carcinoma and correlation with molecular subtypes

PubMed Central

Naville, Magali; Bressan, Cédric; Hühns, Maja; Gock, Michael; Kühn, Florian; Volff, Jean-Nicolas; Trillet-Lenoir, Véronique

2015-01-01

Background Expression of the human endogenous retrovirus (HERV)-H family has been associated with colorectal carcinomas (CRC), yet no individual HERV-H locus expression has been thoroughly correlated with clinical data. Here, we characterized HERV-H reactivations in clinical CRC samples by integrating expression profiles, molecular patterns and clinical data. Expression of relevant HERV-H sequences was analyzed by qRT-PCR on two well-defined clinical cohorts (n = 139 pairs of tumor and adjacent normal colon tissue) including samples from adenomas (n = 21) and liver metastases (n = 16). Correlations with clinical and molecular data were assessed. Results CRC specific HERV-H sequences were validated and found expressed throughout CRC disease progression. Correlations between HERV-H expression and lymph node invasion of tumor cells (p = 0.0006) as well as microsatellite instable tumors (p < 0.0001) were established. No association with regard to age, tumor localization, grading or common mutations became apparent. Interestingly, CRC expressed elements belonged to specific young HERV-H subfamilies and their 5′ LTR often presented active histone marks. Conclusion These results suggest a functional role of HERV-H sequences in colorectal carcinogenesis. The pronounced connection with microsatellite instability warrants a more detailed investigation. Thus, HERV-H sequences in addition to tumor specific mutations may represent clinically relevant, truly CRC specific markers for diagnostic, prognostic and therapeutic purposes. PMID:26517682

Expression of young HERV-H loci in the course of colorectal carcinoma and correlation with molecular subtypes.

PubMed

Pérot, Philippe; Mullins, Christina Susanne; Naville, Magali; Bressan, Cédric; Hühns, Maja; Gock, Michael; Kühn, Florian; Volff, Jean-Nicolas; Trillet-Lenoir, Véronique; Linnebacher, Michael; Mallet, François

2015-11-24

Expression of the human endogenous retrovirus (HERV)-H family has been associated with colorectal carcinomas (CRC), yet no individual HERV-H locus expression has been thoroughly correlated with clinical data.Here, we characterized HERV-H reactivations in clinical CRC samples by integrating expression profiles, molecular patterns and clinical data. Expression of relevant HERV-H sequences was analyzed by qRT-PCR on two well-defined clinical cohorts (n = 139 pairs of tumor and adjacent normal colon tissue) including samples from adenomas (n = 21) and liver metastases (n = 16). Correlations with clinical and molecular data were assessed. CRC specific HERV-H sequences were validated and found expressed throughout CRC disease progression. Correlations between HERV-H expression and lymph node invasion of tumor cells (p = 0.0006) as well as microsatellite instable tumors (p < 0.0001) were established. No association with regard to age, tumor localization, grading or common mutations became apparent. Interestingly, CRC expressed elements belonged to specific young HERV-H subfamilies and their 5' LTR often presented active histone marks. These results suggest a functional role of HERV-H sequences in colorectal carcinogenesis. The pronounced connection with microsatellite instability warrants a more detailed investigation. Thus, HERV-H sequences in addition to tumor specific mutations may represent clinically relevant, truly CRC specific markers for diagnostic, prognostic and therapeutic purposes.

Listening to "The Thick Bunch": (Mis)Understanding and (Mis)Representation of Young People in Jobs without Training in the South West of England

ERIC Educational Resources Information Center

Lawy, Robert; Quinn, Jocey; Diment, Kim

2009-01-01

Young people in jobs without training are ubiquitous but invisible, working in shops, cafes, and other low-waged, low-status occupations. Commonly elided with young people who are not in education, employment or training, they are positioned as the "thick bunch" with empty and meaningless working lives. The main purpose of the research was to…

Impact of graduated driver licensing restrictions on crashes involving young drivers in New Zealand

PubMed Central

Begg, D; Stephenson, S; Alsop, J; Langley, J

2001-01-01

Objective—To determine the impact on young driver crashes of the three main driving restrictions in the New Zealand graduated driver licensing (GDL) system: night-time curfew, no carrying of young passengers, and a blood alcohol limit of 30 mg/100 ml. Method—The database for this study was created by linking police crash reports to hospital inpatient records (1980–95). Multivariate logistic regression was used to compare car crashes involving a young driver licensed before GDL (n=2252) with those who held a restricted graduated licence (n=980) and with those who held a full graduated licence (n=1273), for each of the main driving restrictions. Results—Compared with the pre-GDL group, the restricted licence drivers had fewer crashes at night (p=0.003), fewer involving passengers of all ages (p=0.018), and fewer where alcohol was suspected (p=0.034), but not fewer involving young casualties (p=0.980). Compared with the pre-GDL drivers, those with the full graduated licence had fewer night crashes (p=0.042) but did not differ significantly for any of the other factors examined. Conclusion—These results suggest that some of the GDL restrictions, especially the night-time curfew, have contributed to a reduction in serious crashes involving young drivers. PMID:11770654

Impact of graduated driver licensing restrictions on crashes involving young drivers in New Zealand.

PubMed

Begg, D J; Stephenson, S; Alsop, J; Langley, J

2001-12-01

To determine the impact on young driver crashes of the three main driving restrictions in the New Zealand graduated driver licensing (GDL) system: night-time curfew, no carrying of young passengers, and a blood alcohol limit of 30 mg/100 ml. The database for this study was created by linking police crash reports to hospital inpatient records (1980-95). Multivariate logistic regression was used to compare car crashes involving a young driver licensed before GDL (n=2,252) with those who held a restricted graduated licence (n=980) and with those who held a full graduated licence (n=1,273), for each of the main driving restrictions. Compared with the pre-GDL group, the restricted licence drivers had fewer crashes at night (p=0.003), fewer involving passengers of all ages (p=0.018), and fewer where alcohol was suspected (p=0.034), but not fewer involving young casualties (p=0.980). Compared with the pre-GDL drivers, those with the full graduated licence had fewer night crashes (p=0.042) but did not differ significantly for any of the other factors examined. These results suggest that some of the GDL restrictions, especially the night-time curfew, have contributed to a reduction in serious crashes involving young drivers.

'Everyone's talking Jadelle': the experiences and attitudes of service providers regarding the use of the contraceptive implant, Jadelle in young people in New Zealand.

PubMed

Sandle, Meghan; Tuohy, P

2017-04-28

The contraceptive implant Jadelle, along with other types of long-acting reversible contraception, is thought to be an ideal choice for young people wanting to avoid pregnancy, however, uptake is low. This study aimed to explore the attitudes and experiences of health professionals regarding the use of Jadelle in teenagers. Semi-structured interviews were carried out with professionals providing contraceptive services to young people. Sampling was by identifying key informants and subsequent snowball sampling. Interviews were transcribed and main themes identified. Ten interviews were done with service providers, including midwives, doctors and nurses. Five main themes were identified: characteristics of young people, contraceptive services, positive features of Jadelle, barriers to contraception and individual choice. Jadelle was seen as a good option due to its effectiveness, discreetness and user independence. Barriers for young people obtaining Jadelle included cost, access, fear of procedure and lack of appropriate services. Health professionals had a range of experiences using the contraceptive implant Jadelle. Most felt that Jadelle was a good choice for young people. Improvements to access were identified, including reduced cost and more youth-friendly services, which may lead to increased Jadelle uptake and a subsequent reduction in unintended teenage pregnancies.

Pre-main Sequence Evolution and the Hydrogen-Burning Minimum Mass

NASA Astrophysics Data System (ADS)

Nakano, Takenori

There is a lower limit to the mass of the main-sequence stars (the hydrogen-burning minimum mass) below which the stars cannot replenish the energy lost from their surfaces with the energy released by the hydrogen burning in their cores. This is caused by the electron degeneracy in the stars which suppresses the increase of the central temperature with contraction. To find out the lower limit we need the accurate knowledge of the pre-main sequence evolution of very low-mass stars in which the effect of electron degeneracy is important. We review how Hayashi and Nakano (1963) carried out the first determination of this limit.

Reconciling mass functions with the star-forming main sequence via mergers

NASA Astrophysics Data System (ADS)

Steinhardt, Charles L.; Yurk, Dominic; Capak, Peter

2017-06-01

We combine star formation along the 'main sequence', quiescence and clustering and merging to produce an empirical model for the evolution of individual galaxies. Main-sequence star formation alone would significantly steepen the stellar mass function towards low redshift, in sharp conflict with observation. However, a combination of star formation and merging produces a consistent result for correct choice of the merger rate function. As a result, we are motivated to propose a model in which hierarchical merging is disconnected from environmentally independent star formation. This model can be tested via correlation functions and would produce new constraints on clustering and merging.

Poison exposures in young Israeli military personnel: a National Poison Center Data analysis.

PubMed

Lavon, Ophir; Bentur, Yedidia

2017-06-01

To characterize poison exposures in young Israeli military personnel as reported to the national poison center. Retrospective poison center chart review over a 14-year period. Cases included were Israeli soldiers aged 18-21 years, the compulsory military service age required by the Israeli law. 1770 records of poison exposures in young military personnel were identified. Most exposed individuals involved males (n = 1268, 71.6%). Main routes of exposure were ingestion (n = 854, 48.3%), inhalation (n = 328, 18.6%) and ocular (n = 211, 11.9%). Accidents or misuse (n = 712, 40.2%) were the most frequently reported circumstances, followed by suicide attempts (370, 20.9%), and bites and stings (161, 9.1%). More than half of the cases involved chemicals (n = 939, 53.1%); hydrocarbons, gases and corrosives were the main causative agents. Pharmaceuticals (mainly analgesics) were involved in 519 (29.3%) cases, venomous animals (mainly scorpions, centipedes, and snakes) in 79 (4.5%). Clinical manifestations were reported in 666 (37.6%) cases, mostly gastrointestinal, neurologic, and respiratory. The vast majority of cases (1634, 92.3%) were asymptomatic or mildly affected; no fatalities were recorded. In 831 (46.9%) cases the clinical toxicologist recommended referral to an emergency department; ambulatory observation was recommended in 563 (31.8%) cases, and hospitalization in 86 (4.9%). Our data show that poison exposures among young soldiers involve mainly males, accidents, misuse and suicides, oral route and chemicals; most exposures were asymptomatic or with mild severity. Repeated evaluations of poison center data pertaining to military personnel is advised for identifying trends in poison exposure and characteristics in this particular population.

The properties and environment of primitive solar nebulae as deduced from observations of solar-type pre-main sequence stars

NASA Technical Reports Server (NTRS)

Strom, Stephen E.; Edwards, Suzan; Strom, Karen M.

1991-01-01

The following topics were discussed: (1) current observation evidence for the presence of circumstellar disks associated with solar type pre-main sequence (PMS) stars; (2) the properties of such disks; and (3) the disk environment.

The evolution of the lithium abundances of solar-type stars. II - The Ursa Major Group

NASA Technical Reports Server (NTRS)

Soderblom, David R.; Pilachowski, Catherine A.; Fedele, Stephen B.; Jones, Burton F.

1993-01-01

We draw upon a recent study of the membership of the Ursa Major Group (UMaG) to examine lithium among 0.3 Gyr old solar-type stars. For most G and K dwarfs, Li confirms the conclusions about membership in UMaG reached on the basis of kinematics and chromospheric activity. G and K dwarfs in UMaG have less Li than comparable stars in the Pleiades. This indicates that G and K dwarfs undergo Li depletion while they are on the main sequence, in addition to any pre-main-sequence depletion they may have experienced. Moreover, the Li abundances of the Pleiades K dwarfs cannot be attributed to main-sequence depletion alone, demonstrating that pre-main-sequence depletion of Li also takes place. The sun's Li abundance implies that the main-sequence mechanism becomes less effective with age. The hottest stars in UMaG have Li abundances like those of hot stars in the Pleiades and Hyades and in T Tauris, and the two genuine UMaG members with temperatures near Boesgaard's Li chasm have Li abundances consistent with that chasm developing fully by 0.3 Gyr for stars with UMaG's metallicity. We see differences in the abundance of Li between UMaG members of the same spectral types, indicating that a real spread in the lithium abundance exists within this group.

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

Ramirez, Ramses M.; Kaltenegger, Lisa

We calculate the pre-main-sequence habitable zone (HZ) for stars of spectral classes F-M. The spatial distribution of liquid water and its change during the pre-main-sequence phase of protoplanetary systems is important for understanding how planets become habitable. Such worlds are interesting targets for future missions because the coolest stars could provide habitable conditions for up to 2.5 billion years post-accretion. Moreover, for a given star type, planetary systems are more easily resolved because of higher pre-main-sequence stellar luminosities, resulting in larger planet-star separation for cool stars than is the case for the traditional main-sequence (MS) HZ. We use one-dimensional radiative-convectivemore » climate and stellar evolutionary models to calculate pre-main-sequence HZ distances for F1-M8 stellar types. We also show that accreting planets that are later located in the traditional MS HZ orbiting stars cooler than a K5 (including the full range of M stars) receive stellar fluxes that exceed the runaway greenhouse threshold, and thus may lose substantial amounts of water initially delivered to them. We predict that M-star planets need to initially accrete more water than Earth did, or, alternatively, have additional water delivered later during the long pre-MS phase to remain habitable. Our findings are also consistent with recent claims that Venus lost its water during accretion.« less

Melatonin Alleviates Liver Apoptosis in Bile Duct Ligation Young Rats.

PubMed

Sheen, Jiunn-Ming; Chen, Yu-Chieh; Hsu, Mei-Hsin; Tain, You-Lin; Huang, Ying-Hsien; Tiao, Mao-Meng; Li, Shih-Wen; Huang, Li-Tung

2016-08-20

Bile duct ligation (BDL)-treated rats display cholestasis and liver damages. The potential protective activity of melatonin in young BDL rats in terms of apoptosis, mitochondrial function, and endoplasmic reticulum (ER) homeostasis has not yet been evaluated. Three groups of young male Sprague-Dawley rats were used: one group received laparotomy (Sham), a second group received BDL for two weeks (BDL), and a third group received BDL and intraperitoneal melatonin (100 mg/day) for two weeks (BDL + M). BDL group rats showed liver apoptosis, increased pro-inflamamtory mediators, caspases alterations, anti-apoptotic factors changes, and dysfunction of ER homeostasis. Melatonin effectively reversed apoptosis, mainly through intrinsic pathway and reversed ER stress. In addition, in vitro study showed melatonin exerted its effect mainly through the melatonin 2 receptor (MT2) in HepG2 cells. In conclusion, BDL in young rats caused liver apoptosis. Melatonin rescued the apoptotic changes via the intrinsic pathway, and possibly through the MT2 receptor. Melatonin also reversed ER stress induced by BDL.

Constraining Source Locations of Shallow Subduction Megathrust Earthquakes in 1-D and 3-D Velocity Models - A Case Study of the 2002 Mw=6.4 Osa Earthquake, Costa Rica

NASA Astrophysics Data System (ADS)

Grevemeyer, I.; Arroyo, I. G.

2015-12-01

Earthquake source locations are generally routinely constrained using a global 1-D Earth model. However, the source location might be associated with large uncertainties. This is definitively the case for earthquakes occurring at active continental margins were thin oceanic crust subducts below thick continental crust and hence large lateral changes in crustal thickness occur as a function of distance to the deep-sea trench. Here, we conducted a case study of the 2002 Mw 6.4 Osa thrust earthquake in Costa Rica that was followed by an aftershock sequence. Initial relocations indicated that the main shock occurred fairly trenchward of most large earthquakes along the Middle America Trench off central Costa Rica. The earthquake sequence occurred while a temporary network of ocean-bottom-hydrophones and land stations 80 km to the northwest were deployed. By adding readings from permanent Costa Rican stations, we obtain uncommon P wave coverage of a large subduction zone earthquake. We relocated this catalog using a nonlinear probabilistic approach using a 1-D and two 3-D P-wave velocity models. The 3-D model was either derived from 3-D tomography based on onshore stations and a priori model based on seismic refraction data. All epicentres occurred close to the trench axis, but depth estimates vary by several tens of kilometres. Based on the epicentres and constraints from seismic reflection data the main shock occurred 25 km from the trench and probably along the plate interface at 5-10 km depth. The source location that agreed best with the geology was based on the 3-D velocity model derived from a priori data. Aftershocks propagated downdip to the area of a 1999 Mw 6.9 sequence and partially overlapped it. The results indicate that underthrusting of the young and buoyant Cocos Ridge has created conditions for interpolate seismogenesis shallower and closer to the trench axis than elsewhere along the central Costa Rica margin.

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.

Young children pause on phrase boundaries in self-paced music listening: The role of harmonic cues.

PubMed

Kragness, Haley E; Trainor, Laurel J

2018-05-01

Proper segmentation of auditory streams is essential for understanding music. Many cues, including meter, melodic contour, and harmony, influence adults' perception of musical phrase boundaries. To date, no studies have examined young children's musical grouping in a production task. We used a musical self-pacing method to investigate (1) whether dwell times index young children's musical phrase grouping and, if so, (2) whether children dwell longer on phrase boundaries defined by harmonic cues specifically. In Experiment 1, we asked 3-year-old children to self-pace through chord progressions from Bach chorales (sequences in which metrical, harmonic, and melodic contour grouping cues aligned) by pressing a computer key to present each chord in the sequence. Participants dwelled longer on chords in the 8th position, which corresponded to phrase endings. In Experiment 2, we tested 3-, 4-, and 7-year-old children's sensitivity to harmonic cues to phrase grouping when metrical regularity cues and melodic contour cues were misaligned with the harmonic phrase boundaries. In this case, 7 and 4 year olds but not 3 year olds dwelled longer on harmonic phrase boundaries, suggesting that the influence of harmonic cues on phrase boundary perception develops substantially between 3 and 4 years of age in Western children. Overall, we show that the musical dwell time method is child-friendly and can be used to investigate various aspects of young children's musical understanding, including phrase grouping and harmonic knowledge. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Work and family transitions and the self-rated health of young women in South Africa.

PubMed

Bennett, Rachel; Waterhouse, Philippa

2018-04-01

Understanding the transition to adulthood has important implications for supporting young adults and understanding the roots of diversity in wellbeing later in life. In South Africa, the end of Apartheid means today's youth are experiencing their transition to adulthood in a changed social and political context which offers opportunities compared to the past but also threats. This paper presents the first national level analysis of the patterning of key transitions (completion of education, entry into the labour force, motherhood and marriage or cohabitation), and the association between the different pathways and health amongst young women. With the use of longitudinal data from the South African National Income Dynamics Study (2008-2015), this paper employs sequence analysis to identify common pathways to adulthood amongst women aged 15-17 years at baseline (n = 429) and logistic regression modelling to examine the association between these pathways and self-rated health. The sequence analysis identified five pathways: 1. 'Non-activity commonly followed by motherhood', 2. 'Pathway from school, motherhood then work', 3. 'Motherhood combined with schooling', 4. 'Motherhood after schooling', and 5. 'Schooling to non-activity'. After controlling for baseline socio-economic and demographic characteristics and health, the regression results show young women who followed pathways characterised by early motherhood and economic inactivity (1, 3 and 4) had poorer self-rated health compared to women whose pathways were characterised by combining motherhood and economic activity (2) and young women who were yet to become economically active or mothers (5). Therefore, policies should seek to prevent adolescent childbearing, support young mothers to continue their educational careers and enable mothers in work and seeking work to balance their work and care responsibilities. Further, the findings highlight the value of taking a holistic approach to health and provide further evidence for the need to consider work-family balance in the development agenda. Copyright © 2018 Elsevier Ltd. All rights reserved.

Kikuchi-Fujimoto disease and systemic lupus erythematosus: the EBV connection?

PubMed

Gionanlis, Lazaros; Katsounaros, Marios; Bamihas, Gerasimos; Fragidis, Stelios; Veneti, Panagiota; Sombolos, Kostas

2009-01-01

Kikuchi-Fujimoto disease (KFD) is a benign and self-limited disease of unknown etiology that affects mainly young women. It presents with localized lymphadenopathy, usually cervical, accompanied with fever, night sweats, and leucopenia. KFD has been rarely described in association with autoimmune disorders, mainly systemic lupus erythematosus (SLE). We report the case of a young patient presenting with KFD coinciding with SLE. The association of KFD and SLE is reviewed. Moreover, a possible pathogenetic role of Ebstein-Barr virus linking the two clinical entities is discussed.

Characterization of Two Novel Polyomaviruses of Birds by Using Multiply Primed Rolling-Circle Amplification of Their Genomes

PubMed Central

Johne, Reimar; Wittig, Walter; Fernández-de-Luco, Daniel; Höfle, Ursula; Müller, Hermann

2006-01-01

Polyomaviruses are small nonenveloped particles with a circular double-stranded genome, approximately 5 kbp in size. The mammalian polyomaviruses mainly cause persistent subclinical infections in their natural nonimmunocompromised hosts. In contrast, the polyomaviruses of birds—avian polyomavirus (APV) and goose hemorrhagic polyomavirus (GHPV)—are the primary agents of acute and chronic disease with high mortality rates in young birds. Screening of field samples of diseased birds by consensus PCR revealed the presence of two novel polyomaviruses in the liver of an Eurasian bullfinch (Pyrrhula pyrrhula griseiventris) and in the spleen of a Eurasian jackdaw (Corvus monedula), tentatively designated as finch polyomavirus (FPyV) and crow polyomavirus (CPyV), respectively. The genomes of the viruses were amplified by using multiply primed rolling-circle amplification and cloned. Analysis of the FPyV and CPyV genome sequences revealed a close relationship to APV and GHPV, indicating the existence of a distinct avian group among the polyomaviruses. The main characteristics of this group are (i) involvement in fatal disease, (ii) the existence of an additional open reading frame in the 5′ region of the late mRNAs, and (iii) a different manner of DNA binding of the large tumor antigen compared to that of the mammalian polyomaviruses. PMID:16537620

[Current international recommendations for pediatric cardiopulmonary resuscitation: the European guidelines].

PubMed

López-Herce, Jesús; Rodríguez Núñez, Antonio; Maconochie, Ian; Van de Voorde, Patric; Biarent, Dominique; Eich, Christof; Bingham, Robert; Rajka, Thomas; Zideman, David; Carrillo, Ángel; de Lucas, Nieves; Calvo, Custodio; Manrique, Ignacio

2017-07-01

This summary of the European guidelines for pediatric cardiopulmonary resuscitation (CPR) emphasizes the main changes and encourages health care professionals to keep their pediatric CPR knowledge and skills up to date. Basic and advanced pediatric CPR follow the same algorithm in the 2015 guidelines. The main changes affect the prevention of cardiac arrest and the use of fluids. Fluid expansion should not be used routinely in children with fever in the abuse of signs of shock because too high a volume can worsen prognosis. Rescue breaths should last around 1 second in basic CPR, making pediatric recommendations consistent with those for adults. Chest compressions should be at least as deep as one-third the anteroposterior diameter of the thorax. Most children in cardiac arrest lack a shockable rhythm, and in such cases a coordinated sequence of breaths, chest compressions, and administration of adrenalin is essential. An intraosseous canula may be the first choice for introducing fluids and medications, especially in young infants. In treating supraventricular tachycardia with cardioversion, an initial dose of 1 J/kg is currently recommended (vs the dose of 0.5 J/kg previously recommended). After spontaneous circulation is recovered, measures to control fever should be taken. The goal is to reach a normal temperature even before arrival to the hospital.

Observation vs. theory: testing the synthetic IR colours of young very low mass stars/brown dwarfs using the evolutionary tracks

NASA Astrophysics Data System (ADS)

Tottle, Jonathan; Mohanty, Subhanjoy

2013-07-01

Our ability to accurately derive stellar properties from spectral energy distributions (SEDs) depends on how well they can be fit with atmospheric models. The AMES-Dusty synthetic spectra (Allard et al., 2001), which incorporate dust grains suspended in the stellar atmosphere, are commonly used to fit SEDs of very low mass stars (VLMS) and brown dwarfs (BDs). Recently, the same group has produced an updated model named BT-Settl (Allard et al., 2012) that allow these grains to gradually settle out of the atmosphere at cooler temperatures. Using these models it is now possible to produce the NIR colours across the main sequence from spectral types M to T. However, one significant area in which these Dusty and Settl models have not been thoroughly tested is in PMS VLMS/BDs. We use empirical IR colours of PMS M-dwarfs to show that both of these models show significant discrepancies with observations. We find that the synthetic spectra imply a temperature up to 500K cooler than expected for these objects from the theoretical evolutionary tracks for their estimated ages. We postulate that the problem lies mainly with the spectra; and if so, we conjecture that an incorrect H2O opacity may be to blame, aided by additional dust effects.

Photometric light curves for seven rapidly-rotating K dwarfs in the Pleiades and Alpha Persei clusters

NASA Technical Reports Server (NTRS)

Stauffer, John R.; Schild, Rudolph A.; Baliunas, Sallie L.; Africano, John L.

1987-01-01

Light curves and period estimates were obtained for several Pleiades and Alpha Persei cluster K dwarfs which were identified as rapid rotators in earlier spectroscopic studies. A few of the stars have previously-published light curves, making it possible to study the long-term variability of the light-curve shapes. The general cause of the photometric variability observed for these stars is an asymmetric distribution of photospheric inhomogeneities (starspots). The presence of these inhomogeneities combined with the rotation of the star lead to the light curves observed. The photometric periods derived are thus identified with the rotation period of the star, making it possible to estimate equatorial rotational velocities for these K dwarfs. These data are of particular importance because the clusters are sufficiently young that stars of this mass should have just arrived on the main sequence. These data could be used to estimate the temperatures and sizes of the spot groups necessary to produce the observed light curves for these stars.

The VMC Survey. XXII. Hierarchical Star Formation in the 30 Doradus-N158-N159-N160 Star-forming Complex

NASA Astrophysics Data System (ADS)

Sun, Ning-Chen; de Grijs, Richard; Subramanian, Smitha; Cioni, Maria-Rosa L.; Rubele, Stefano; Bekki, Kenji; Ivanov, Valentin D.; Piatti, Andrés E.; Ripepi, Vincenzo

2017-02-01

We study the hierarchical stellar structures in a ˜1.5 deg2 area covering the 30 Doradus-N158-N159-N160 star-forming complex with the VISTA Survey of Magellanic Clouds. Based on the young upper main-sequence stars, we find that the surface densities cover a wide range of values, from log({{Σ }}\\cdot pc2) ≲ -2.0 to log({{Σ }}\\cdot pc2) ≳ 0.0. Their distributions are highly non-uniform, showing groups that frequently have subgroups inside. The sizes of the stellar groups do not exhibit characteristic values, and range continuously from several parsecs to more than 100 pc the cumulative size distribution can be well described by a single power law, with the power-law index indicating a projected fractal dimension D2 = 1.6 ± 0.3. We suggest that the phenomena revealed here support a scenario of hierarchical star formation. Comparisons with other star-forming regions and galaxies are also discussed.

Milliarcsecond resolution infrared observations of young stars in Taurus and Ophiuchus

NASA Astrophysics Data System (ADS)

Simon, M.; Howell, R. R.; Longmore, A. J.; Wilking, B. A.; Peterson, D. M.; Chen, W.-P.

1987-09-01

The paper reports K-band lunar occultation observations of 18 stars in the Taurus and Ophiuchus star-forming regions. Four of the systems, HQ Tau, FF Tau, and SR 12 and ROX 31 in Ophiuchus, are binaries. Their separations, as observed in the projection along the directions of their occultations, range from about 5 to 186 milliarcseconds (mas). SR 12 was also observed by the technique of speckle interferometry in the J, H, and K bands. These observations, taken together with the lunar occultation results, show that SR 12 is an about 0.30 arcsec binary system whose components are late-type stars still approaching the main sequence. The lunar occultation observations reveal extended structure associated with two objects. Elias 29 in Ophiuchus contains a central component about 7 mas in diameter, that radiates most of the flux, and a much larger diffuse component. YLW 16A, also in Ophiuchus, is an extended object about 0.5 arcsec in diameter.

Three proposed B-associations in the vicinity of zeta puppis

NASA Technical Reports Server (NTRS)

Upton, E. K. L.

1971-01-01

There appear to be three loose B associations in the general vicinity of zeta Puppis, all at distances of approximately 300 to 400 parsecs from the sun. Their diameters, perpendicular to the line of sight, are 20 to 50 parsecs, and their separations are of similar size. All three are situated in bright areas of the Gum nebula. The proposed associations A and C lie in the two brightest parts of the nebula. The three associations are not all of the same age. Association C is about 50 million years old, whereas A and B are decidedly younger. The ages of A and B cannot be determined from the present data, as their color-magnitude diagrams show no clear turnoff from the main sequence. Association A may be young enough to qualify as the birthplace of zeta Puppis. There is no other identifiable association in which zeta Puppis can have originated, unless its age is substantially greater than the 3 million years assumed.

Analysis of ISO Data

NASA Technical Reports Server (NTRS)

Lambert, David L.

2003-01-01

A block grant supported several astronomers who executed observing programs using the Infrared Space Observatory (ISO). The ISO project in which Harriet Dinerstein participated was a study of sulfur and neon abundances in extragalactic H II regions using the ISO Short Wavelength Spectrometer (SWS). Evans and Jaffe, along with collaborators Ewine van Dishoeck and Wing-Fai Thi, and then graduate student Wenbin Li, carried out an in-depth study of the peripheral region of the molecular cloud L1204/S140, where the far ultraviolet radiation and the density are relatively low. Their observations test theories of photon-dominated regions (PDRs) in a regime that has been little explored. One ISO program was involved with PHT-32 observations of about a dozen young stars to search for extended emission that could be modeled with our dust-modeling-code at UT. The document reports on preliminary analysis of PHT 32 scanning of 10 pre-main-sequence stars at 50 and 100 microns. A small sample of R Coronae Borealis stars was observed with the SWS.

What is Asian Taenia?

PubMed

Eom, Keeseon S

2006-01-01

Asian Taenia is a human tapeworm which was first recognized in Taiwan aborigines and subsequently from Asian countries: Korea, Indonesia, Vietnam, and China. It was originally described as T. asiatica Eom and Rim, 1993 based on the morphology in its adult and larval stage. A taxonomic disagreement on whether it is species or subspecies level is mainly due to the morphological similarity of this tapeworm with T. saginata, but a sympatric distribution of these two tapeworms is also known in China. The life cycle is quite distinct from T. saginata in using the pig as intermediate host and parasitizing visceral organs such as liver, lung and omentum. A long unresolved question in Asian countries concerns the inconsistency between worm ratio and the food preferences was clarified with this viscerotropic tapeworm. Molecular biological differentiation is possible with DNA techniques and a complete genome of mtDNA was sequenced recently which may provide a resource for comparative mitochondrial genomics and systematic studies of parasitic cestodes. This is a young parasite discovered most recently with many research questions yet to be clarified.

The stellar population of the Lupus clouds

NASA Technical Reports Server (NTRS)

Hughes, Joanne; Hartigan, Patrick; Krautter, Joachim; Kelemen, Janos

1994-01-01

We present photometric and spectroscopic observations of the H alpha emission stars in the Lupus dark cloud complex. We estimate the effective temperatures of the stars from their spectral types and calculate the reddening towards each object from the (R-I) colors. From these data, we derive mass and age distributions for the Lupus stars using a new set of pre-main sequence evolutionar tracks. We compare the results for the Lupus stars with those for a similar population of young stellar objects in Taurus-Auriga and Chamaeleon and with the initial mass function for field stars in the solar neighborhood. From the H-R diagrams, Lupus appears to contain older stars than Taurus. The Lupus dark clouds form a greater proportion of low mass stars than the Taurus complex. Also, the proportion of low mass stars in Lupus is higher than that predicted by the Miller-Scalo initial mass function, and the lowest mass stars in Lupus are less active than similar T Tauri stars in other regions.

New Binaries in the ɛ Cha Association

NASA Astrophysics Data System (ADS)

Briceño, César; Tokovinin, Andrei

2017-11-01

We present Adaptive Optics-aided speckle observations of 47 young stars in the ɛ Cha association made at the 4 m Southern Astrophysical Research Telescope in the I-band. We resolved 10 new binary pairs, 5 previously known binaries, and 2 triple systems, also previously known. In the separation range between 4 and 300 au, the 30 association members of spectral types G0 and later host 6 binary companions, leading to the raw companion frequency of 0.010 ± 0.04 per decade of separation, comparable to the main sequence dwarfs in the field. On the other hand, all five massive association members of spectral types A and B have companions in this range. We discuss the newly resolved and known binaries in our sample. Observed motions in the triple system ɛ Cha, composed of three similar B9V stars, can be described by tentative orbits with periods 13 and ˜900 years and a large mutual inclination. Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope.

Calibration of H-alpha/H-beta Indexes for Emission Line Objects

NASA Astrophysics Data System (ADS)

Hintz, Eric G.; Joner, Michael D.

2016-01-01

In Joner and Hintz (2015) they report on a standard star system for calibration of H-alpha and H-beta observations. This work was based on data obtained with the Dominion Astrophysical Observatory 1.2-m telescope. As part of the data acquisition for that project, a large number of emission line objects were also observed. We will report on the preliminary results for the emission line data set. This will include a comparison of equivalent width measurements of each line with the matching index. We will also examine the relation between the absorption line objects previously published and the emission line objects, along with a discussion of the transition point. Object types included are Be stars, high mass x-ray binaries, one low mass x-ray binary, Herbig Ae/Be stars, pre-main sequence stars, T Tauri stars, young stellar objects, and one BY Draconis star. Some of these objects come from Cygnus OB-2, NGC 659, NGC 663, NGC 869 and NGC 884.

Coevality in Young Eclipsing Binaries

NASA Astrophysics Data System (ADS)

Simon, M.; Toraskar, Jayashree

2017-06-01

The ages of the components in very short period pre-main-sequence (PMS) binaries are essential to an understanding of their formation. We considered a sample of seven PMS eclipsing binaries (EBs) with ages 1-6.3 MY and component masses 0.2-1.4 {M}⊙ . The very high precision with which their masses and radii have been measured and the capability provided by the Modules for Experiments in Stellar Astrophysics to calculate their evolutionary tracks at exactly the measured masses allows the determination of age differences of the components independent of their luminosities and effective temperatures. We found that the components of five EBs, ASAS J052821+0338.5, Parenago 1802, JW 380, CoRoT 223992193, and UScoCTIO 5, formed within 0.3 MY of each other. The parameters for the components of V1174 Ori imply an implausible large age difference of 2.7 MY and should be reconsidered. The seventh EB in our sample, RX J0529.4+0041 fell outside the applicability of our analysis.

Lithium Abundances in the Young Open Cluster IC 2602

NASA Technical Reports Server (NTRS)

Randich, S.; Aharpour, N.; Pallavicini, R.; Prosser, C. F.; Stauffer, J. R.

1997-01-01

We have obtained high-resolution spectra for 28 candidate late-type stars in the 30 Myr old cluster IC 2602. NLTE Li abundances have been derived from measured equivalent widths. The log n(Li) - T(sub eff) and log n(Li) - mass distributions for our sample stars have been compared with those of the Pleiades and alpha Persei. Our data show that F stars in the three clusters have the same lithium content, which corresponds to the initial content for Pop. I stars. G and early-K IC 2602 stars are, on average, somewhat more Li-rich than their counterparts in the two slightly older clusters. Finally, the latest-type IC 2602 stars are heavily Li depleted, with their Li content being as low as the lowest measured among the Pleiades. As in the Pleiades and alpha Per, a star-to-star scatter in lithium is observed among 30 Myr old late-K/early-K dwarfs in IC 2602, indicating that this spread develops in the pre-main sequence phases.

Molecular characterization of influenza viruses collected from young children in Uberlandia, Brazil - from 2001 to 2010.

PubMed

de Mattos Silva Oliveira, Thelma Fátima; Yokosawa, Jonny; Motta, Fernando Couto; Siqueira, Marilda Mendonça; da Silveira, Hélio Lopes; Queiróz, Divina Aparecida Oliveira

2015-02-18

Influenza remains a major health problem due to the seasonal epidemics that occur every year caused by the emergence of new influenza virus strains. Hemagglutinin (HA) and neuraminidase (NA) glycoproteins are under selective pressure and subjected to frequent changes by antigenic drift. Therefore, our main objective was to investigate the influenza cases in Uberlândia city, Midwestern Brazil, in order to monitor the appearance of new viral strains, despite the availability of a prophylactic vaccine. Nasopharyngeal samples were collected from 605 children less than five years of age presenting with acute respiratory disease and tested by immunofluorescence assay (IFA) for detection of adenovirus, respiratory syncytial virus, parainfluenza virus types 1, 2, and 3 and influenza virus types A and B. A reverse transcription-PCR (RT-PCR) for influenza viruses A and B was carried out to amplify partial segments of the HA and NA genes. The nucleotide sequences were analyzed and compared with sequences of the virus strains of the vaccine available in the same year of sample collection. Forty samples (6.6%) were tested positive for influenza virus by IFA and RT-PCR, with 39 samples containing virus of type A and one of type B. By RT-PCR, the type A viruses were further characterized in subtypes H3N2, H1N2 and H1N1 (41.0%, 17.9%, and 2.6%, respectively). Deduced amino acid sequence analysis of the partial hemagglutinin sequence compared to sequences from vaccine strains, revealed that all strains found in Uberlândia had variations in the antigenic sites. The sequences of the receptor binding sites were preserved, although substitutions with similar amino acids were observed in few cases. The neuraminidase sequences did not show significant changes. All the H3 isolates detected in the 2001-2003 period had drifted from vaccine strain, unlike the isolates of the 2004-2007 period. These results suggest that the seasonal influenza vaccine effectiveness could be reduced because of A H3N2 variants that circulated in 2001-2003 years. Thus, an early monitoring of variants circulating in the country or in a region may provide important information about the probable efficacy of the vaccine that will be administered in an influenza season.

The Stratigraphy and Lithofacies of the Paleoproterozoic Volcaniclastic Sequences in the Cape Three Points Area- Akodda section of the Southern in Ashanti Belt in the Birimian of southwest Ghana

NASA Astrophysics Data System (ADS)

Yoshimaru, S.; Kiyokawa, S.; Ito, T.; Ikehara, M.; Nyame, F. K.; Tetteh, G. M.

2015-12-01

The Paleoproterozoic Era is thought to have experienced one of the most significant changes in earth's environment during earth history. Early continents started to diverge and collide accompanied by first major oxidation of the atmosphere-oceanic system known as the Great Oxidation Environment (GOE). Due to their well-preserved oceanic sedimentary sequences, Paleoproterozoic belts are usually good targets for studies on the history of earth's past environment. In addition, these belts provide great help to understand the nature of the Paleoproterozoic deeper oceanic environments. Birimian greenstone belt in southwestern Ghana is likely to have made up of subduction of oceanic basin to form a volcanic island arc. Birimian rocks are separated by nonconformity from the Tarkwaian Group which is a younger paleoplacer deposit (Perrouty et al., 2012). The Birimian is made up of island-arc volcanic rocks; foreland basin made up of shale, sandstone, quartzite and turbidities derived from 2.17 Ga granite intrusions during Birimian volcanism. In this study, we focused on the coastal area around Cape Three Points at the southernmost part of the Ashanti (Axim-Konongo) belt in Ghana. In the eastern part of the area, excellently preserved Paleoprotorozoic deeper oceanic sedimentary sequences extensively outcrop for over 4km stretch. This volcano-sedimentary sequence has been affected by greenschist facies metamorphism. Structurally, this region preserves S1 cleavage and asymmetrical synform with west vergence and S0 younging to the east. Provisional stratigraphy is very continuous up to more than 2000m thick and, in addition, suggests at least four different fining upward sequences in the area to the east and west of Atwepo, west of Kwetakora and Akodda. These sub-sequences are mainly composed of volcaniclasitc, sandstone, black shale and rare volcanics such as pillow basalt or massive volcanic lava. In other words, this continuous sequence suggests distal submarine volcaniclastic rocks in an oceanic island arc around the West African Craton. Preliminary δ13C analysis gave values of -23.7~ -36.5 ‰ for black shale occupying the middle to upper part of the whole section. The very light carbon isotope ratios suggest deposition of the black shale under highly euxinic conditions like today's Black sea.

Factors associated with young adults delaying and forgoing driving licenses: results from Britain.

PubMed

Le Vine, Scott; Polak, John

2014-01-01

To identify the reasons that young adults (age 17-29) in Britain delay or forgo driving license acquisition. Using year 2010 British National Travel Survey microdata, we first analyze self-reported reasons (including their prioritisation) for not holding a full car driving license and then estimate a logistic regression model for license-holding to investigate additional factors, several of which extend from previous studies. This study also employs a novel segmentation approach to analyze the sets of reasons that individual young adults cite for not driving. These results show that, despite the lack of a graduated driving license system at present, many young adults indicate that issues associated with the driving license acquisition process are the main reason they do not hold a full driving license. About 3 in 10 young adults can be interpreted as not viewing driving as a priority, though half of those without a license are either learning to drive or are deterred principally by the cost of learning. We calculate that after their 17th birthday (the age of eligibility for a full driving license) young adults spend a mean of 1.7 years learning to drive. Young adults citing the costs of insurance or car purchase are likely to cite them as secondary rather than the main reason for not driving, whereas those citing physical/health difficulties are very likely to cite this as the main reason they do not drive. Two distinct groups of young people are identified that both indicate that costs deter them from driving-one group that is less well off financially and that indicates that costs alone are the primary deterrent and one that reports that other reasons also apply and is better off. Status as an international migrant was found to be an important factor, net of confounding variables, for identifying that a young adult in Britain does not hold a driving license. Further research is needed to understand the relative saliency of plausible causal mechanisms for this finding. We also report that both personal income and household income are independently positively associated with license-holding but that (intuitively) the relationship of license holding with a young adult's own personal income is the much stronger of the two. On the basis of these findings, it can be concluded that a number of previously underappreciated factors appear to be linked with young British adults not acquiring a driving license.

The 2016 Mihoub (north-central Algeria) earthquake sequence: Seismological and tectonic aspects

NASA Astrophysics Data System (ADS)

Khelif, M. F.; Yelles-Chaouche, A.; Benaissa, Z.; Semmane, F.; Beldjoudi, H.; Haned, A.; Issaadi, A.; Chami, A.; Chimouni, R.; Harbi, A.; Maouche, S.; Dabbouz, G.; Aidi, C.; Kherroubi, A.

2018-06-01

On 28 May 2016 at 23:54 (UTC), an Mw5.4 earthquake occurred in Mihoub village, Algeria, 60 km southeast of Algiers. This earthquake was the largest event in a sequence recorded from 10 April to 15 July 2016. In addition to the permanent national network, a temporary network was installed in the epicentral region after this shock. Recorded event locations allow us to give a general overview of the sequence and reveal the existence of two main fault segments. The first segment, on which the first event in the sequence was located, is near-vertical and trends E-W. The second fault plane, on which the largest event of the sequence was located, dips to the southeast and strikes NE-SW. A total of 46 well-constrained focal mechanisms were calculated. The events located on the E-W-striking fault segment show mainly right-lateral strike-slip (strike N70°E, dip 77° to the SSE, rake 150°). The events located on the NE-SW-striking segment show mainly reverse faulting (strike N60°E, dip 70° to the SE, rake 130°). We calculated the static stress change caused by the first event (Md4.9) of the sequence; the result shows that the fault plane of the largest event in the sequence (Mw5.4) and most of the aftershocks occurred within an area of increased Coulomb stress. Moreover, using the focal mechanisms calculated in this work, we estimated the orientations of the main axes of the local stress tensor ellipsoid. The results confirm previous findings that the general stress field in this area shows orientations aligned NNW-SSE to NW-SE. The 2016 Mihoub earthquake sequence study thus improves our understanding of seismic hazard in north-central Algeria.

The Spirituality of Young Australians

ERIC Educational Resources Information Center

Mason, Michael; Singleton, Andrew; Webber, Ruth

2007-01-01

A research project conducted in 2003-2006, the Spirit of Generation Y, using both extended interviews and a nationwide survey, revealed three main strands in the spirituality of young Australians: traditional, alternative and humanist. Their involvement in traditional religions was declining, like that of their parents, and although some adopted…

Real-Life Problem-Solving Thinking and Social Adjustment: Intervention for Preschool and Kindergarten Children.

ERIC Educational Resources Information Center

Shure, Myrna Beth

1979-01-01

Descriptive and evaluative information is presented about the Interpersonal Cognitive Problem Solving (ICPS) program, which utilizes sequenced games and dialogs to teach young children new ways of thinking about and coping with interpersonal difficulties. (SJL)

Youth social behaviour and network therapy (Y-SBNT): adaptation of a family and social network intervention for young people who misuse alcohol and drugs - a randomised controlled feasibility trial.

PubMed

Watson, Judith; Toner, Paul; Day, Ed; Back, Donna; Brady, Louca-Mai; Fairhurst, Caroline; Renwick, Charlotte; Templeton, Lorna; Akhtar, Shabana; Lloyd, Charlie; Li, Jinshuo; Cocks, Kim; Ambegaokar, Sangeeta; Parrott, Steve; McArdle, Paul; Gilvarry, Eilish; Copello, Alex

2017-03-01

Family interventions appear to be effective at treating young people's substance misuse. However, implementation of family approaches in UK services is low. This study aimed to demonstrate the feasibility of recruiting young people to an intervention based on an adaptation of adult social behaviour and network therapy. It also sought to involve young people with experience of using substance misuse services in the research process. To demonstrate the feasibility of recruiting young people to family and social network therapy and to explore ways in which young people with experience of using substance misuse services could be involved in a study of this nature. A pragmatic, two-armed, randomised controlled open feasibility trial. Two UK-based treatment services for young people with substance use problems, with recruitment taking place from May to November 2014. Young people aged 12-18 years, newly referred and accepted for structured interventions for drug and/or alcohol problems. A remote, web-based computer randomisation system allocated young people to adapted youth social behaviour and network therapy (Y-SBNT) or treatment as usual (TAU). Y-SBNT participants were intended to receive up to six 50-minute sessions over a maximum of 12 weeks. TAU participants continued to receive usual care delivered by their service. Feasibility was measured by recruitment rates, retention in treatment and follow-up completion rates. The main clinical outcome was the proportion of days on which the main problem substance was used in the preceding 90-day period as captured by the Timeline Follow-Back interview at 3 and 12 months. In total, 53 young people were randomised (Y-SBNT, n  = 26; TAU, n  = 27) against a target of 60 (88.3%). Forty-two young people attended at least one treatment session [Y-SBNT 22/26 (84.6%); TAU 20/27 (74.1%)]; follow-up rates were 77.4% at month 3 and 73.6% at month 12. Data for nine young people were missing at both months 3 and 12, so the main clinical outcome analysis was based on 24 young people (92.3%) in the Y-SBNT group and 20 young people (74.1%) in the TAU group. At month 12, the average proportion of days that the main problem substance was used in the preceding 90 days was higher in the Y-SBNT group than in the TAU group (0.54 vs. 0.41; adjusted mean difference 0.13, 95% confidence interval -0.12 to 0.39; p  = 0.30). No adverse events were reported. Seventeen young people with experience of substance misuse services were actively involved throughout the study. They informed key elements of the intervention and research process, ensuring that the intervention was acceptable and relevant to our target groups; contributing to the design of key trial documents, ideas for a new model of public involvement and this report. Two parents were also involved. The adapted intervention could be delivered in young people's services, and qualitative interviews found that Y-SBNT was acceptable to young people, family members and staff. Engagement of family and network members proved difficult within the intervention and research aspects. The study proved the feasibility of this work in routine services but outcome measurement based on narrow substance use variables may be limited and may fail to capture other important changes in wider areas of functioning for young people. Validation of the EuroQol-5 Dimensions for young people aged 12-18 years should be considered and flexible models for involvement of young people in research are required to achieve inclusive representation throughout all aspects of the research process. Although recommendation of a full trial of the Y-SBNT intervention compared with TAU is not supported, this study can inform future intervention development and UK research within routine addiction services. Current Controlled Trials ISRCTN93446265. This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment ; Vol. 21, No. 15. See the NIHR Journals Library website for further project information.

Detection of X-ray emission from the young low-mass star Rossiter 137B

NASA Technical Reports Server (NTRS)

Vilhu, O.; Linsky, J. L.

1987-01-01

Rst 137B, a close M-dwarf companion to the active K-star HD 36705, has been detected in a High Resolution Image in the Einstein Observatory Archive. The X-ray surface fluxes (0.2-4 keV) from both stars are close to the empirical saturation level, F(x)/F(bol) of about 0.001, defined by rapid rotators and very young stars. This supports the earlier results of the youthfulness of the system. This young couple is an excellent subject for studies of dependence of early evolution on stellar mass. Rst 137B is one of the latest spectral types and thus lowest-mass premain-sequence stars yet detected as an X-ray source.

Finding the Onset of Convection in Main Sequence Stars

NASA Technical Reports Server (NTRS)

Simon, Theodore

2003-01-01

The primary goal of the work performed under this grant was to locate, if possible, the onset of subphotospheric convection zones in normal main sequence stars by using the presence of emission in high temperature lines in far ultraviolet spectra from the FUSE spacecraft as a proxy for convection. The change in stellar structure represented by this boundary between radiative and convective stars has always been difficult to find by other empirical means. A search was conducted through observations of a sample of A-type stars, which were somewhat hotter and more massive than the Sun, and which were carefully chosen to bridge the theoretically expected radiative/convective boundary line along the main sequence.

Habitable zones around main sequence stars

NASA Technical Reports Server (NTRS)

Kasting, James F.; Whitmire, Daniel P.; Reynolds, Ray T.

1993-01-01

A mechanism for stabilizing climate on the earth and other earthlike planets is described, and the physical processes that define the inner and outer boundaries of the habitable zone (HZ) around the sun and main sequence stars are discussed. Physical constraints on the HZ obtained from Venus and Mars are taken into account. A 1D climate model is used to estimate the width of the HZ and the continuously habitable zone around the sun, and the analysis is extended to other main sequence stars. Whether other stars have planets and where such planets might be located with respect to the HZ is addressed. The implications of the findings for NASA's SETI project are considered.

Rapid DNA Sequencing by Direct Nanoscale Reading of Nucleotide Bases on Individual DNA Chains

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

Lee, James Weifu; Meller, Amit

2007-01-01

Since the independent invention of DNA sequencing by Sanger and by Gilbert 30 years ago, it has grown from a small scale technique capable of reading several kilobase-pair of sequence per day into today's multibillion dollar industry. This growth has spurred the development of new sequencing technologies that do not involve either electrophoresis or Sanger sequencing chemistries. Sequencing by Synthesis (SBS) involves multiple parallel micro-sequencing addition events occurring on a surface, where data from each round is detected by imaging. New High Throughput Technologies for DNA Sequencing and Genomics is the second volume in the Perspectives in Bioanalysis series, whichmore » looks at the electroanalytical chemistry of nucleic acids and proteins, development of electrochemical sensors and their application in biomedicine and in the new fields of genomics and proteomics. The authors have expertly formatted the information for a wide variety of readers, including new developments that will inspire students and young scientists to create new tools for science and medicine in the 21st century. Reviews of complementary developments in Sanger and SBS sequencing chemistries, capillary electrophoresis and microdevice integration, MS sequencing and applications set the framework for the book.« less

18. VIEW TOWARD MAIN ENTRANCE OF AMERICAN TOOL ENGINE LATHE, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

18. VIEW TOWARD MAIN ENTRANCE OF AMERICAN TOOL ENGINE LATHE, JIB CRANE ABOVE-LOOKING NORTH. - W. A. Young & Sons Foundry & Machine Shop, On Water Street along Monongahela River, Rices Landing, Greene County, PA

27. CORNER OF MAIN SHOP SHOWING BELT DRIVE AND BLOWER ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

27. CORNER OF MAIN SHOP SHOWING BELT DRIVE AND BLOWER FOR CUPOLA-LOOKING SOUTHWEST. - W. A. Young & Sons Foundry & Machine Shop, On Water Street along Monongahela River, Rices Landing, Greene County, PA

Release, browse damage, and growth of young white pines

Treesearch

Thomas W. McConkey

1960-01-01

Exactly what happens to young white pine seedlings that have been released from hardwood competition and allowed to grow, subject to browse damage, for a 7-year period? Some indications of the results of such treatment can be seen from recent work on the Massabesic Experimental Forest in Maine.

Digital Natives Come to Preschool: Implications for Early Childhood Practice

ERIC Educational Resources Information Center

Zevenbergen, Robyn

2007-01-01

This article explores the implications of young learners' dispositions towards the use of digital technologies in contemporary early childhood settings. It is proposed that young learners have grown up in very different social conditions from previous generations, mainly through the saturation of digital technologies, in particular computers. This…

Young People with Health Conditions and the Inclusive Education Problematic

ERIC Educational Resources Information Center

Yates, Lyn

2014-01-01

This article revisits debates about inclusive education from the perspective of the "Keeping Connected" project, a qualitative longitudinal research project focusing on young people with health-related disrupted experiences of schooling. Drawing on findings from this project, three main arguments are advanced and illustrated in relation…

[Caring for teenagers with anorexia].

PubMed

Lapp, Aymeric

2015-04-01

Anorexia mainly affects young girls, although more and more boys and adults are also concerned. The consequences of eating disorders have a significant impact on young people's health. Nurses play a key role in the therapeutic contract set up during the hospital treatment. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

NATIONAL SURVEYS OF MULTIPLE ENVIRONMENTAL HAZARDS TO YOUNG CHILDREN IN HOMES AND CHILD CARE CENTERS

EPA Science Inventory

The Department of Housing and Urban Development (HUD) has teamed with other federal agencies to characterize exposure of multiple environmental hazards to young children in two main indoor environments, homes and daycare centers. Under the co-sponsorship of HUD and the Nationa...

A sample of potential disk hosting first ascent red giants

NASA Astrophysics Data System (ADS)

Steele, Amy; Debes, John

2018-01-01

Observations of (sub)giants with planets and disks provide the first set of proof that disks can survive the first stages of post-main-sequence evolution, even though the disks are expected to dissipate by this time. The infrared (IR) excesses present around a number of post-main-sequence (PMS) stars could be due to a traditional debris disk with planets (e.g. kappa CrB), some remnant of enhanced mass loss (e.g. the shell-like structure of R Sculptoris), and/or background contamination. We present a sample of potential disk hosting first ascent red giants. These stars all have infrared excesses at 22 microns, and possibly host circumstellar debris. We summarize the characteristics of the sample to better inform the incidence rates of thermally emitting material around giant stars. A thorough follow-up study of these candidates would serve as the first step in probing the composition of the dust in these systems that have left the main sequence, providing clues to the degree of disk processing that occurs beyond the main-sequence.

Molecular Microbial Analysis of Lactobacillus Strains Isolated from the Gut of Calves for Potential Probiotic Use

PubMed Central

Soto, Lorena P.; Frizzo, Laureano S.; Bertozzi, Ezequiel; Avataneo, Elizabeth; Sequeira, Gabriel J.; Rosmini, Marcelo R.

2010-01-01

The intestinal microbiota has an influence on the growth and health status of the hosts. This is of particular interest in animals reared using intensive farming practices. Hence, it is necessary to know more about complexity of the beneficial intestinal microbiota. The use of molecular methods has revolutionized microbial identification by improving its quality and effectiveness. The specific aim of the study was to analyze predominant species of Lactobacillus in intestinal microbial ecosystem of young calves. Forty-two lactic acid bacteria (LAB) isolated from intestinal tract of young calves were characterized by: Amplified Ribosomal DNA Restriction Analysis (ARDRA), by using Hae III, Msp I, and Hinf I restriction enzymes, and 16S rDNA gene sequencing. ARDRA screening revealed nine unique patterns among 42 isolates, with the same pattern for 29 of the isolates. Gene fragments of 16S rDNA of 19 strains representing different patterns were sequenced to confirm the identification of these species. These results confirmed that ARDRA is a good tool for identification and discrimination of bacterial species isolated from complex ecosystem and between closely related groups. This paper provides information about the LAB species predominant in intestinal tract of young calves that could provide beneficial effects when administered as probiotic. PMID:20445780

The environmental impacts on the star formation main sequence: An Hα study of the newly discovered rich cluster at z = 1.52

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

Koyama, Yusei; Kodama, Tadayuki; Tadaki, Ken-ichi

2014-07-01

We report the discovery of a strong over-density of galaxies in the field of a radio galaxy at z = 1.52 (4C 65.22) based on our broadband and narrow-band (Hα) photometry with the Subaru Telescope. We find that Hα emitters are located in the outskirts of the density peak (cluster core) dominated by passive red-sequence galaxies. This resembles the situation in lower-redshift clusters, suggesting that the newly discovered structure is a well-evolved rich galaxy cluster at z = 1.5. Our data suggest that the color-density and stellar mass-density relations are already in place at z ∼ 1.5, mostly driven bymore » the passive red massive galaxies residing within r{sub c} ≲ 200 kpc from the cluster core. These environmental trends almost disappear when we consider only star-forming (SF) galaxies. We do not find SFR-density or SSFR-density relations amongst SF galaxies, and the location of the SF main sequence does not significantly change with environment. Nevertheless, we find a tentative hint that star-bursting galaxies (up-scattered objects from the main sequence) are preferentially located in a small group at ∼1 Mpc away from the main body of the cluster. We also argue that the scatter of the SF main sequence could be dependent on the distance to the nearest neighboring galaxy.« less

The SAMI Galaxy Survey: spatially resolving the main sequence of star formation

NASA Astrophysics Data System (ADS)

Medling, Anne M.; Cortese, Luca; Croom, Scott M.; Green, Andrew W.; Groves, Brent; Hampton, Elise; Ho, I.-Ting; Davies, Luke J. M.; Kewley, Lisa J.; Moffett, Amanda J.; Schaefer, Adam L.; Taylor, Edward; Zafar, Tayyaba; Bekki, Kenji; Bland-Hawthorn, Joss; Bloom, Jessica V.; Brough, Sarah; Bryant, Julia J.; Catinella, Barbara; Cecil, Gerald; Colless, Matthew; Couch, Warrick J.; Drinkwater, Michael J.; Driver, Simon P.; Federrath, Christoph; Foster, Caroline; Goldstein, Gregory; Goodwin, Michael; Hopkins, Andrew; Lawrence, J. S.; Leslie, Sarah K.; Lewis, Geraint F.; Lorente, Nuria P. F.; Owers, Matt S.; McDermid, Richard; Richards, Samuel N.; Sharp, Robert; Scott, Nicholas; Sweet, Sarah M.; Taranu, Dan S.; Tescari, Edoardo; Tonini, Chiara; van de Sande, Jesse; Walcher, C. Jakob; Wright, Angus

2018-04-01

We present the ˜800 star formation rate maps for the Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey based on H α emission maps, corrected for dust attenuation via the Balmer decrement, that are included in the SAMI Public Data Release 1. We mask out spaxels contaminated by non-stellar emission using the [O III]/H β, [N II]/H α, [S II]/H α, and [O I]/H α line ratios. Using these maps, we examine the global and resolved star-forming main sequences of SAMI galaxies as a function of morphology, environmental density, and stellar mass. Galaxies further below the star-forming main sequence are more likely to have flatter star formation profiles. Early-type galaxies split into two populations with similar stellar masses and central stellar mass surface densities. The main-sequence population has centrally concentrated star formation similar to late-type galaxies, while galaxies >3σ below the main sequence show significantly reduced star formation most strikingly in the nuclear regions. The split populations support a two-step quenching mechanism, wherein halo mass first cuts off the gas supply and remaining gas continues to form stars until the local stellar mass surface density can stabilize the reduced remaining fuel against further star formation. Across all morphologies, galaxies in denser environments show a decreased specific star formation rate from the outside in, supporting an environmental cause for quenching, such as ram-pressure stripping or galaxy interactions.

Not enough time? Individual and environmental implications for workplace physical activity programming among women with and without young children.

PubMed

Tavares, Leonor S; Plotnikoff, Ronald C

2008-03-01

This study sets out to determine the main issues employed women with and without young children voice as influencing their physical activity behaviors, and to identify the environmental dimensions (e.g., physical, social, cultural, organizational, policy) within and outside of the workplace surrounding physical activity promotion that are most pertinent to employed women in Canada. Thirty employed women participated in focus groups, and four senior personnel were interviewed. Worksite observations were carried out and a Workplace Physical Activity Audit Tool was administered. Results indicate that time constraints and demands of personal and work life are barriers to achieving more activity. The issues surrounding family obligations and pressures for women with young children illustrate the main differences between groups. Key environmental factors are addressed and considered for future workplace physical activity programming goals.

A sharp interpolation between the Hölder and Gaussian Young inequalities

NASA Astrophysics Data System (ADS)

da Pelo, Paolo; Lanconelli, Alberto; Stan, Aurel I.

2016-03-01

We prove a very general sharp inequality of the Hölder-Young-type for functions defined on infinite dimensional Gaussian spaces. We begin by considering a family of commutative products for functions which interpolates between the pointwise and Wick products; this family arises naturally in the context of stochastic differential equations, through Wong-Zakai-type approximation theorems, and plays a key role in some generalizations of the Beckner-type Poincaré inequality. We then obtain a crucial integral representation for that family of products which is employed, together with a generalization of the classic Young inequality due to Lieb, to prove our main theorem. We stress that our main inequality contains as particular cases the Hölder inequality and Nelson’s hyper-contractive estimate, thus providing a unified framework for two fundamental results of the Gaussian analysis.

Stellar Kinematic Groups. II. A Reexamination of the Membership, Activity, and Age of the Ursa Major Group

NASA Astrophysics Data System (ADS)

King, Jeremy R.; Villarreal, Adam R.; Soderblom, David R.; Gulliver, Austin F.; Adelman, Saul J.

2003-04-01

Utilizing Hipparcos parallaxes, original radial velocities and recent literature values, new Ca II H and K emission measurements, literature-based abundance estimates, and updated photometry (including recent resolved measurements of close doubles), we revisit the Ursa Major moving group membership status of some 220 stars to produce a final clean list of nearly 60 assured members, based on kinematic and photometric criteria. Scatter in the velocity dispersions and H-R diagram is correlated with trial activity-based membership assignments, indicating the usefulness of criteria based on photometric and chromospheric emission to examine membership. Closer inspection, however, shows that activity is considerably more robust at excluding membership, failing to do so only for <=15% of objects, perhaps considerably less. Our UMa members demonstrate nonzero vertex deviation in the Bottlinger diagram, behavior seen in older and recent studies of nearby young disk stars and perhaps related to Galactic spiral structure. Comparison of isochrones and our final UMa group members indicates an age of 500+/-100 Myr, some 200 Myr older than the canonically quoted UMa age. Our UMa kinematic/photometric members' mean chromospheric emission levels, rotational velocities, and scatter therein are indistinguishable from values in the Hyades and smaller than those evinced by members of the younger Pleiades and M34 clusters, suggesting these characteristics decline rapidly with age over 200-500 Myr. None of our UMa members demonstrate inordinately low absolute values of chromospheric emission, but several may show residual fluxes a factor of >=2 below a Hyades-defined lower envelope. If one defines a Maunder-like minimum in a relative sense, then the UMa results may suggest that solar-type stars spend 10% of their entire main-sequence lives in periods of precipitously low activity, which is consistent with estimates from older field stars. As related asides, we note six evolved stars (among our UMa nonmembers) with distinctive kinematics that lie along a 2 Gyr isochrone and appear to be late-type counterparts to disk F stars defining intermediate-age star streams in previous studies, identify a small number of potentially very young but isolated field stars, note that active stars (whether UMa members or not) in our sample lie very close to the solar composition zero-age main sequence, unlike Hipparcos-based positions in the H-R diagram of Pleiades dwarfs, and argue that some extant transformations of activity indices are not adequate for cool dwarfs, for which Ca II infrared triplet emission seems to be a better proxy than Hα-based values for Ca II H and K indices.

Pathogenesis, Molecular Genetics, and Genomics of Mycobacterium avium subsp. paratuberculosis, the Etiologic Agent of Johne’s Disease

PubMed Central

Rathnaiah, Govardhan; Zinniel, Denise K.; Bannantine, John P.; Stabel, Judith R.; Gröhn, Yrjö T.; Collins, Michael T.; Barletta, Raúl G.

2017-01-01

Mycobacterium avium subsp. paratuberculosis (MAP) is the etiologic agent of Johne’s disease in ruminants causing chronic diarrhea, malnutrition, and muscular wasting. Neonates and young animals are infected primarily by the fecal–oral route. MAP attaches to, translocates via the intestinal mucosa, and is phagocytosed by macrophages. The ensuing host cellular immune response leads to granulomatous enteritis characterized by a thick and corrugated intestinal wall. We review various tissue culture systems, ileal loops, and mice, goats, and cattle used to study MAP pathogenesis. MAP can be detected in clinical samples by microscopy, culturing, PCR, and an enzyme-linked immunosorbent assay. There are commercial vaccines that reduce clinical disease and shedding, unfortunately, their efficacies are limited and may not engender long-term protective immunity. Moreover, the potential linkage with Crohn’s disease and other human diseases makes MAP a concern as a zoonotic pathogen. Potential therapies with anti-mycobacterial agents are also discussed. The completion of the MAP K-10 genome sequence has greatly improved our understanding of MAP pathogenesis. The analysis of this sequence has identified a wide range of gene functions involved in virulence, lipid metabolism, transcriptional regulation, and main metabolic pathways. We also review the transposons utilized to generate random transposon mutant libraries and the recent advances in the post-genomic era. This includes the generation and characterization of allelic exchange mutants, transcriptomic analysis, transposon mutant banks analysis, new efforts to generate comprehensive mutant libraries, and the application of transposon site hybridization mutagenesis and transposon sequencing for global analysis of the MAP genome. Further analysis of candidate vaccine strains development is also provided with critical discussions on their benefits and shortcomings, and strategies to develop a highly efficacious live-attenuated vaccine capable of differentiating infected from vaccinated animals. PMID:29164142

Effects of Main-Sequence Mass Loss on Stellar and Galactic Chemical Evolution.

NASA Astrophysics Data System (ADS)

Guzik, Joyce Ann

1988-06-01

L. A. Willson, G. H. Bowen and C. Struck -Marcell have proposed that 1 to 3 solar mass stars may experience evolutionarily significant mass loss during the early part of their main-sequence phase. The suggested mass-loss mechanism is pulsation, facilitated by rapid rotation. Initial mass-loss rates may be as large as several times 10^{-9}M o/yr, diminishing over several times 10^8 years. We attempted to test this hypothesis by comparing some theoretical implications with observations. Three areas are addressed: Solar models, cluster HR diagrams, and galactic chemical evolution. Mass-losing solar models were evolved that match the Sun's luminosity and radius at its present age. The most extreme viable models have initial mass 2.0 M o, and mass-loss rates decreasing exponentially over 2-3 times 10^8 years. Compared to a constant -mass model, these models require a reduced initial ^4He abundance, have deeper envelope convection zones and higher ^8B neutrino fluxes. Early processing of present surface layers at higher interior temperatures increases the surface ^3He abundance, destroys Li, Be and B, and decreases the surface C/N ratio following first dredge-up. Evolution calculations incorporating main-sequence mass loss were completed for a grid of models with initial masses 1.25 to 2.0 Mo and mass loss timescales 0.2 to 2.0 Gyr. Cluster HR diagrams synthesized with these models confirm the potential for the hypothesis to explain observed spreads or bifurcations in the upper main sequence, blue stragglers, anomalous giants, and poor fits of main-sequence turnoffs by standard isochrones. Simple closed galactic chemical evolution models were used to test the effects of main-sequence mass loss on the F and G dwarf distribution. Stars between 3.0 M o and a metallicity -dependent lower mass are assumed to lose mass. The models produce a 30 to 60% increase in the stars to stars-plus -remnants ratio, with fewer early-F dwarfs and many more late-F dwarfs remaining on the main sequence to the present. The ratio of stars to stellar remnants and the white dwarf age distribution may prove valuable in distinguishing between explanations for the observed bimodal present-day stellar mass function.

40. MAIN DRIVE SHAFT IN CENTER, PATTERN STORAGE IN REAR, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

40. MAIN DRIVE SHAFT IN CENTER, PATTERN STORAGE IN REAR, WATER TANK AT RIGHT-LOOKING EAST. - W. A. Young & Sons Foundry & Machine Shop, On Water Street along Monongahela River, Rices Landing, Greene County, PA

Identifying the Young Low-mass Stars within 25 pc. II. Distances, Kinematics, and Group Membership

NASA Astrophysics Data System (ADS)

Shkolnik, Evgenya L.; Anglada-Escudé, Guillem; Liu, Michael C.; Bowler, Brendan P.; Weinberger, Alycia J.; Boss, Alan P.; Reid, I. Neill; Tamura, Motohide

2012-10-01

We have conducted a kinematic study of 165 young M dwarfs with ages of lsim300 Myr. Our sample is composed of stars and brown dwarfs with spectral types ranging from K7 to L0, detected by ROSAT and with photometric distances of lsim25 pc assuming that the stars are single and on the main sequence. In order to find stars kinematically linked to known young moving groups (YMGs), we measured radial velocities for the complete sample with Keck and CFHT optical spectroscopy and trigonometric parallaxes for 75 of the M dwarfs with the CAPSCam instrument on the du Pont 2.5 m Telescope. Due to their youthful overluminosity and unresolved binarity, the original photometric distances for our sample underestimated the distances by 70% on average, excluding two extremely young (lsim3 Myr) objects found to have distances beyond a few hundred parsecs. We searched for kinematic matches to 14 reported YMGs and identified 10 new members of the AB Dor YMG and 2 of the Ursa Majoris group. Additional possible candidates include six Castor, four Ursa Majoris, two AB Dor members, and one member each of the Her-Lyr and β Pic groups. Our sample also contains 27 young low-mass stars and 4 brown dwarfs with ages lsim150 Myr that are not associated with any known YMG. We identified an additional 15 stars that are kinematic matches to one of the YMGs, but the ages from spectroscopic diagnostics and/or the positions on the sky do not match. These warn against grouping stars together based only on kinematics and that a confluence of evidence is required to claim that a group of stars originated from the same star-forming event. Based on observations collected at the W. M. Keck Observatory, the Canada-France-Hawaii Telescope, the du Pont Telescope at Las Campanas Observatory, and the Subaru Telescope. The Keck Observatory is operated as a scientific partnership between the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W. M. Keck Foundation. The CFHT is operated by the National Research Council of Canada, the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

EIN3-like gene expression during fruit ripening of Cavendish banana (Musa acuminata cv. Grande naine).

PubMed

Mbéguié-A-Mbéguié, Didier; Hubert, Olivier; Fils-Lycaon, Bernard; Chillet, Marc; Baurens, Franc-Christophe

2008-06-01

Ethylene signal transduction initiates with ethylene binding at receptor proteins and terminates in a transcription cascade involving the EIN3/EIL transcription factors. Here, we have isolated four cDNAs homologs of the Arabidopsis EIN3/EIN3-like gene, MA-EILs (Musa acuminata ethylene insensitive 3-like) from banana fruit. Sequence comparison with other banana EIL gene already registered in the database led us to conclude that, at this day, at least five different genes namely MA-EIL1, MA-EIL2/AB266318, MA-EIL3/AB266319, MA-EIL4/AB266320 and AB266321 exist in banana. Phylogenetic analyses included all banana EIL genes within a same cluster consisting of rice OsEILs, a monocotyledonous plant as banana. However, MA-EIL1, MA-EIL2/AB266318, MA-EIL4/AB266320 and AB266321 on one side, and MA-EIL3/AB266319 on the other side, belong to two distant subclusters. MA-EIL mRNAs were detected in all examined banana tissues but at lower level in peel than in pulp. According to tissues, MA-EIL genes were differentially regulated by ripening and ethylene in mature green fruit and wounding in old and young leaves. MA-EIL2/AB266318 was the unique ripening- and ethylene-induced gene; MA-EIL1, MA-EIL4/Ab266320 and AB266321 genes were downregulated, while MA-EIL3/AB266319 presented an unusual pattern of expression. Interestingly, a marked change was observed mainly in MA-EIL1 and MA-EIL3/Ab266319 mRNA accumulation concomitantly with changes in ethylene responsiveness of fruit. Upon wounding, the main effect was observed in MA-EIL4/AB266320 and AB266321 mRNA levels, which presented a markedly increase in both young and old leaves, respectively. Data presented in this study suggest the importance of a transcriptionally step control in the regulation of EIL genes during banana fruit ripening.

Lights and shadows: multi-wavelength analysis of young stellar objects and their protoplanetary discs

NASA Astrophysics Data System (ADS)

Rigon, Laura

2016-03-01

Stars form from the collapse of molecular clouds and evolve in an environment rich in gas and dust before becoming Main Sequence stars. During this phase, characterised by the presence of a protoplanetary disc, stars manifest changes in the structure and luminosity. This thesis performs a multi-wavelength analysis, from optical to mm range, on a sample of young stars (YSOs), mainly Classical T Tauri (CTTS). The purpose is to study optical and infrared variability and its relation with the protoplanetary disc. Longer wavelength, in the mm range, are used instead to investigate the evolution of the disc, in terms of dust growth. In optical, an F-test on a sample of 39 CTTS reveals that 67% of the stars are variable. The variability, quantified through pooled sigma, is visible both in magnitude amplitudes and changes over time. Time series analysis applied on the more variable stars finds the presence of quasi periodicity, with periods longer than two weeks, interpreted either as eclipsing material in the disc happening on a non-regular basis, or as a consequence of star-disc interaction via magnetic field lines. The variability of YSOs is confirmed also in infrared, even if with lower amplitude. No strong correlations are found between optical and infrared variability, which implies a different cause or a time shift in the two events. By using a toy model to explore their origin, I find that infrared variations are likely to stem from emissions in the inner disc. The evolution of discs in terms of dust growth is confirmed in most discs by the analysis of the slope of the spectral energy distribution (SED), after correcting for wind emission and optical depth effects. However, the comparison with a radiative transfer model highlights that a number of disc parameters, in particular disc masses and temperature, dust size distribution and composition, can also affect the slope of the SED.

Aging reduces experience-induced sensorimotor plasticity. A magnetoencephalographic study.

PubMed

Mary, Alison; Bourguignon, Mathieu; Wens, Vincent; Op de Beeck, Marc; Leproult, Rachel; De Tiège, Xavier; Peigneux, Philippe

2015-01-01

Modulation of the mu-alpha and mu-beta spontaneous rhythms reflects plastic neural changes within the primary sensorimotor cortex (SM1). Using magnetoencephalography (MEG), we investigated how aging modifies experience-induced plasticity after learning a motor sequence, looking at post- vs. pre-learning changes in the modulation of mu rhythms during the execution of simple hand movements. Fifteen young (18-30 years) and fourteen older (65-75 years) right-handed healthy participants performed auditory-cued key presses using all four left fingers simultaneously (Simple Movement task - SMT) during two separate sessions. Following both SMT sessions, they repeatedly practiced a 5-elements sequential finger-tapping task (FTT). Mu power calculated during SMT was averaged across 18 gradiometers covering the right sensorimotor region and compared before vs. after sequence learning in the alpha (9/10/11Hz) and the beta (18/20/22Hz) bands separately. Source power maps in the mu-alpha and mu-beta bands were localized using Dynamic Statistical Parametric Mapping (dSPM). The FTT sequence was performed faster at retest than at the end of the learning session, indicating an offline boost in performance. Analyses conducted on SMT sessions revealed enhanced rebound after learning in the right SM1, 3000-3500ms after the initiation of movement, in young as compared to older participants. Source reconstruction indicated that mu-beta is located in the precentral gyrus (motor processes) and mu-alpha is located in the postcentral gyrus (somatosensory processes) in both groups. The enhanced post-movement rebound in young subjects potentially reflects post-training plastic changes in SM1. Age-related decreases in post-training modulatory effects suggest reduced experience-dependent plasticity in the aging brain. Copyright © 2014 Elsevier Inc. All rights reserved.

A surprise at the bottom of the main sequence: Rapid rotation and NO H-alpha emission

NASA Technical Reports Server (NTRS)

Basri, Gibor; Marcy, Geoffrey W.

1995-01-01

We report Kech Observatory high-resolution echelle spectra from 640-850 nm for eight stars near the faint end of the main sequence. These spectra are the highest resolution spectra of such late-type stars, and clearly resolve the TiO, VO, and atomic lines. The sample includes the field brown-dwarf candidate, BRI 0021-0214 (M9.5+). Very unexpectedly, it shows the most rapid rotation in the entire samples, v sin i approximately 40 km/s, which is 20x faster than typical field nonemission M stars. Equally surprising is that BRI 0021 exhibits no emission or absorptionat H-alpha. We argue that this absence is not simply due to its cool photosphere, but that stellar activity declines in a fundamental way at the end of the main sequence. As it is the first very late M dwarf observed at high spectral resolution, BRI 0021 may be signaling a qualitative change in the angular momentum loss rate among the lowest mass stars. Conventionally, its rapid rotation would have marked BRI 0021 as very young, consistent with the selection effect which arises if the latest-type dwarfs are really brown dwarfs on cooling curves. In any case, it is unprecedented to find no sign of stellar activity in such a rapidly rotating convective star. We also discuss the possible conflict between this observation and the extremely strong H-alpha seen in another very cool star, PC 0025+0447. Extrapolation of M-L relations for BRI 0021 yields M approximately 0.065 solar mass, and the other sample objects have expected masses near the H-burning limit. These include two Pleiades brown-dwarf candidates, four field M6 dwarfs and one late-type T Tauri star. The two Pleiades M6 dwarfs have v sin i of 26 and 37 km/s, H-alpha in emission, and radial velocities consistent with Pleiades M6 dwarfs have v sin i of 26 and 37 km/s, H-alpha in emission, and radial velocities consistent with Pleiades membership. Similarly, the late-type T Tauri star has v sin i approximately 30 km/s and H alpha emission indicate of its youth. Two of the four late-type field dMe star also exhibit rotation above 5 km/s, consistent with expectations. BRI 0021 has no measurable absoprtion due to lithium, indicating that it is likely to be more massive than 0.065 solar mass.

Abundant aftershock sequence of the 2015 Mw7.5 Hindu Kush intermediate-depth earthquake

NASA Astrophysics Data System (ADS)

Li, Chenyu; Peng, Zhigang; Yao, Dongdong; Guo, Hao; Zhan, Zhongwen; Zhang, Haijiang

2018-05-01

The 2015 Mw7.5 Hindu Kush earthquake occurred at a depth of 213 km beneath the Hindu Kush region of Afghanistan. While many early aftershocks were missing from the global earthquake catalogues, this sequence was recorded continuously by eight broad-band stations within 500 km. Here we use a waveform matching technique to systematically detect earthquakes around the main shock. More than 3000 events are detected within 35 d after the main shock, as compared with 42 listed in the Advanced National Seismic System catalogue (or 196 in the International Seismological Centre catalogue). The aftershock sequence generally follows the Omori's law with a decay constant p = 0.92. We also apply the recently developed double-pair double-difference technique to relocate all detected aftershocks. Most of them are located to the west of the hypocentre of the main shock, consistent with the westward propagation of the main-shock rupture. The aftershocks outline a nearly vertical southward dipping plane, which matches well with one of the nodal planes of the main shock. We conclude that the aftershock sequence of this intermediate-depth earthquake shares many similarities with those for shallow earthquakes and infer that there are some common mechanisms responsible for shallow and intermediate-depth earthquakes.

Understanding the relationship transitions and associated end of life clinical needs of young adults with life-limiting illnesses: A triangulated longitudinal qualitative study

PubMed Central

Johnston, Bridget; Jindal-Snape, Divya; Pringle, Jan; Gold, Libby; Grant, Jayne; Dempsey, Raymond; Scott, Ros; Carragher, Pat

2016-01-01

Background: Care of young adults with life-limiting illnesses can often be complex due to the fact that they are growing and developing within the continuing presence of their illness. There is little research conducted nationally and internationally, which has examined the life issues of young adults or taken a longitudinal approach to understand such issues over a period of time. Aim: To gain clear understanding of one particular and pertinent life issue—relationship transition—occurring in the context of being a young adult with a life-limiting illness and the clinical needs arising from this. Design: This was a triangulated, longitudinal, qualitative study involving young adults with life-limiting illnesses and their significant others, namely, family members and healthcare professionals. Semi-structured interviews were conducted with participants and analysed using thematic analysis. Clinical case note reviews were also carried out. Setting/participants: A total of 12 young adults (aged between 17 and 23 years) from 2 hospices and 22 nominated significant others participated in a total of 58 interviews. Results: Thematic analysis revealed 4 main themes and 11 subthemes. The main themes were ‘Dependence dichotomy’, ‘In it together’, ‘Biographical uncertainty’, and ‘Conserving integrity’. These themes helped to establish the nature of relationship transitions that the young adult participants from the study experienced and additionally allowed insight into their possible needs at their end of life. Conclusion: This study has identified the nature of relationship transitions pertinent to young adults and has highlighted associated end of life clinical needs. This study can influence further research into the transitions and end of life needs of this particular patient group receiving palliative care, while informing the lacking evidence base which exists internationally. PMID:27781097

A Mumps Outbreak in Vojvodina, Serbia, in 2012 Underlines the Need for Additional Vaccination Opportunities for Young Adults.

PubMed

Nedeljković, Jasminka; Kovačević-Jovanović, Vesna; Milošević, Vesna; Šeguljev, Zorica; Petrovic, Vladimir; Muller, Claude P; Hübschen, Judith M

2015-01-01

In 2012, mumps was introduced from Bosnia and Herzegovina to Vojvodina, causing an outbreak with 335 reported cases. The present manuscript analyses the epidemiological and laboratory characteristics of this outbreak, identifies its main causes and suggests potential future preventive measures. Sera of 133 patients were tested for mumps-specific antibodies by ELISA and 15 nose/throat swabs were investigated for mumps virus RNA by RT-PCR. IgG antibodies were found in 127 patients (95.5%). Mumps infection was laboratory-confirmed in 53 patients, including 44 IgM and 9 PCR positive cases. All other 282 cases were classified as epidemiologically-confirmed. More than half of the patients (n = 181, 54%) were 20-29 years old, followed by the 15-19 age bracket (n = 95, 28.4%). Twice as many males as females were affected (67% versus 33%). Disease complications were reported in 13 cases (3.9%), including 9 patients with orchitis and 4 with pancreatitis. According to medical records or anamnestic data, 190 patients (56.7%) were immunized with two doses and 35 (10.4%) with one dose of mumps-containing vaccine. The Serbian sequences corresponded to a minor genotype G variant detected during the 2011/2012 mumps outbreak in Bosnia and Herzegovina. Vaccine failures, the initial one-dose immunization policy and a vaccine shortage between 1999 and 2002 contributed to the outbreak. Additional vaccination opportunities should be offered to young adults during transition periods in their life trajectories.

A Mumps Outbreak in Vojvodina, Serbia, in 2012 Underlines the Need for Additional Vaccination Opportunities for Young Adults

PubMed Central

Nedeljković, Jasminka; Kovačević-Jovanović, Vesna; Milošević, Vesna; Šeguljev, Zorica; Petrovic, Vladimir; Muller, Claude P.; Hübschen, Judith M.

2015-01-01

In 2012, mumps was introduced from Bosnia and Herzegovina to Vojvodina, causing an outbreak with 335 reported cases. The present manuscript analyses the epidemiological and laboratory characteristics of this outbreak, identifies its main causes and suggests potential future preventive measures. Sera of 133 patients were tested for mumps-specific antibodies by ELISA and 15 nose/throat swabs were investigated for mumps virus RNA by RT-PCR. IgG antibodies were found in 127 patients (95.5%). Mumps infection was laboratory-confirmed in 53 patients, including 44 IgM and 9 PCR positive cases. All other 282 cases were classified as epidemiologically-confirmed. More than half of the patients (n = 181, 54%) were 20–29 years old, followed by the 15–19 age bracket (n = 95, 28.4%). Twice as many males as females were affected (67% versus 33%). Disease complications were reported in 13 cases (3.9%), including 9 patients with orchitis and 4 with pancreatitis. According to medical records or anamnestic data, 190 patients (56.7%) were immunized with two doses and 35 (10.4%) with one dose of mumps-containing vaccine. The Serbian sequences corresponded to a minor genotype G variant detected during the 2011/2012 mumps outbreak in Bosnia and Herzegovina. Vaccine failures, the initial one-dose immunization policy and a vaccine shortage between 1999 and 2002 contributed to the outbreak. Additional vaccination opportunities should be offered to young adults during transition periods in their life trajectories. PMID:26496490

Light-curve Modulation of Low-mass Stars in K2. I. Identification of 481 Fast Rotators in the Solar Neighborhood

NASA Astrophysics Data System (ADS)

Saylor, Dicy; Lepine, Sebastien; Crossfield, Ian; Petigura, Erik A.

2018-01-01

The K2 mission is targeting large numbers of nearby (d < 100 pc) GKM dwarfs selected from the SUPERBLINK proper motion survey (μ > 40 mas yr‑1, V < 20). Additionally, the mission is targeting low-mass, high proper motion stars associated with the local (d < 500 pc) Galactic halo population also selected from SUPERBLINK. K2 campaigns 0 through 8 monitored a total of 26,518 of these cool main-sequence stars. We used the auto-correlation function to search for fast rotators by identifying short-period photometric modulations in the K2 light curves. We identified 481 candidate fast rotators with rotation periods <4 days that show light-curve modulations consistent with starspots. Their kinematics show low average transverse velocities, suggesting that they are part of the young disk population. A subset (13) of the fast rotators is found among those targets with colors and kinematics consistent with the local Galactic halo population and may represent stars spun up by tidal interactions in close binary systems. We further demonstrate that the M dwarf fast rotators selected from the K2 light curves are significantly more likely to have UV excess and discuss the potential of the K2 mission to identify new nearby young GKM dwarfs on the basis of their fast rotation rates. Finally, we discuss the possible use of local halo stars as fiducial, non-variable sources in the Kepler fields.

Young Stellar Object Candidates in the Aquila Rift Region

NASA Astrophysics Data System (ADS)

Zhang, Miao-miao; Wang, Hong-chi; Stecklum, B.

2010-10-01

Using the 2m telescope of the Turingia State Observatory at Tauten-berg (TLS), imaging observations in 3 wavebands (H α, R and I) are performed in the 16 fields in the Aquila Rift region. The observed fields cover about 7 square degrees. Excluding the 3 fields with unqualified data, the photometrical analysis is made for the remaining 13 fields, from which point sources are identified, and finally 7 H α emission-line star candidates are identified by color-color diagrams. The 7 candidates are located in five fields. Three of them are located near the Galactic plane, while the galactic latitudes of the rest are greater than 4°. The 2 M ASS counterparts of the point sources are identified, and the properties of the 7 H α emission-line star candidates are further analyzed by using the two-color diagrams. It is found that the near-infrared radiation from these H α emission-line star candidates has no obvious infrared excess, one of them even falls on the main-sequence branch. This indicates that the H α-emissive young stellar objects (YSOs) are not always accompanied with the infrared excess, and that the results of the H α emission line observation and the infrared excess observation are mutually supplemented. If the 7 H α emission-line star candidates are regarded as YSO candidates, then the number of YSOs in the Aquila Rift region is quite small. The further confirmation of these candidates needs subsequent spectral observations.

Young adults perinatally infected with HIV perform more poorly on measures of executive functioning and motor speed than ethnically matched healthy controls.

PubMed

Willen, Elizabeth J; Cuadra, Anai; Arheart, Kristopher L; Post, M J D; Govind, Varan

2017-03-01

Perinatal HIV is associated with significant neurocognitive morbidities, but few studies have examined cognitive impact of early HIV infection on patients surviving to adulthood. The purpose of this study was to evaluate neurocognitive outcomes among a cohort of perinatally infected young adults. Individuals between the ages of 18 and 24 with perinatal infection were recruited for this cross-sectional study along with similarly aged healthy controls. Participants completed an MRI and brief neuropsychological assessment battery. Multivariate analysis of covariance controlling for age, gender, race/ethnicity, and education was completed to detect differences between the HIV+ and control groups. Multivariable linear regression was performed to assess HIV-associated factors potentially impacting neuropsychological findings among the HIV+ group. Twenty-nine HIV+ young adults and 13 healthy controls were included in the study. After adjusting for age and sociodemographic variables, the HIV+ group scored lower on attention/working memory (Digit Span (p = .008) and Letter-Number Sequencing (p = .038)), set-shifting (DKEFS Trail Making Test Condition 4 (p = .026) and motor speed (DKEFS Trail Making Test Condition 5 (p = .003)). For the HIV+ group, nadir CD4 was associated with better Letter-Number Sequencing score (p = .029) and use of highly active antiretroviral therapy was associated with better performance on Category Fluency (p = .040). After controlling for sociodemographic variables, executive dysfunction persists among young adults with perinatal HIV infection in comparison to controls. Future studies to further elucidate the impact of executive dysfunction on independent living and functional outcomes are indicated.

An Introduction to the Sun and Stars

NASA Astrophysics Data System (ADS)

Green, Simon F.; Jones, Mark H.

2015-02-01

Introduction; 1. Seeing the Sun; 2. The working Sun; 3. Measuring stars; 4. Comparing stars; 5. The formation of stars; 6. The main sequence life of stars; 7. The life of stars beyond the main sequence; 8. The death of stars; 9. The remnants of stars; Conclusion; Answers and comments; Appendices; Glossary; Further reading; Acknowledgements; Figure references; Index.

Mass loss from pre-main-sequence accretion disks. I - The accelerating wind of FU Orionis

NASA Technical Reports Server (NTRS)

Calvet, Nuria; Hartmann, Lee; Kenyon, Scott J.

1993-01-01

We present evidence that the wind of the pre-main-sequence object FU Orionis arises from the surface of the luminous accretion disk. A disk wind model calculated assuming radiative equilibrium explains the differential behavior of the observed asymmetric absorption-line profiles. The model predicts that strong lines should be asymmetric and blueshifted, while weak lines should be symmetric and double-peaked due to disk rotation, in agreement with observations. We propose that many blueshifted 'shell' absorption features are not produced in a true shell of material, but rather form in a differentially expanding wind that is rapidly rotating. The inference of rapid rotation supports the proposal that pre-main-sequence disk winds are rotationally driven.

[The migration and professional characteristics of young people in Medina-Dakar].

PubMed

Badiane, W

1990-01-01

The characteristics of young migrants in the Medina quarter of Dakar, Senegal, are analyzed using data from a survey carried out in 1987 of 300 workers. The author concludes that these migrants are mainly from rural areas and have high levels of professional mobility associated with their search for better-paying jobs.

Physical Activity among Young People in the Context of Lifestyle

ERIC Educational Resources Information Center

Telama, Risto; Nupponen, Heimo; Pieron, Maurice

2005-01-01

The promotion of a healthy lifestyle is the main goal of physical education in many countries. However, very little is known about the relationship between different lifestyles and physical activity patterns among young people. The aim of this study was to investigate the relationship between lifestyle and physical activity among 12- and…

Microcomputers for Young Children: Procedures and Practices in the Laboratory Classroom.

ERIC Educational Resources Information Center

Baker, Betty Ruth

These guidelines are designed to give preservice teachers information to use in selecting techniques and planning learning experiences for young children in the microcomputer laboratory. The main purpose of this laboratory experience is for children to develop computer awareness/literacy and keyboard knowledge, and to improve skills in following…

Exploring the Etiology of Perfectionism and Perceptions of Self-Worth in Young Athletes

ERIC Educational Resources Information Center

McArdle, Siobhain; Duda, Joan L.

2008-01-01

This study assessed the main and interactive effects of perceived parental expectations and perceived parental criticism on 180 young talented athletes' perfectionistic tendencies and level and reported fluctuation in self-esteem. A potential quadratic effect of perceived parental expectations on the targeted dependent variables was also tested.…

Drawing as Social Play: Shared Meaning-Making in Young Children's Collective Drawing Activities

ERIC Educational Resources Information Center

Kukkonen, Tiina; Chang-Kredl, Sandra

2018-01-01

The ability to construct shared meaning with peers is important for young children's social and linguistic development. Previous studies have mainly focused on shared meaning-making within cooperative pretend play with little mention of other childhood activities that might promote intersubjectivity. This study investigated the group play that…

Attachment States of Mind and the Quality of Young Adults' Sibling Relationships

ERIC Educational Resources Information Center

Fortuna, Keren; Roisman, Glenn I.; Haydon, Katherine C.; Groh, Ashley M.; Holland, Ashley S.

2011-01-01

This report examines young adults' states of mind regarding their early attachment experiences in relation to the observed and perceived quality of their sibling relationships. Sixty sibling pairs (18-25 years of age) were (a) administered the Adult Attachment Interview (George, Kaplan, & Main, 1985), (b) videotaped during a conflict…

Involving Parents in Teaching Social Communication Skills to Young Children

ERIC Educational Resources Information Center

Weiss, Amy L.; Theadore, Geraldine

2011-01-01

This article focuses on why and how speech-language pathologists and other professionals can encourage the involvement of parents in teaching social communication skills to their young children. Four main topics are explored: (1) the evidence that many of the children with special needs served by speech-language pathologists and other…

Updating and Not Shifting Predicts Learning Performance in Young and Middle-Aged Adults

ERIC Educational Resources Information Center

Gijselaers, Hieronymus J. M.; Meijs, Celeste; Neroni, Joyce; Kirschner, Paul A.; de Groot, Renate H. M.

2017-01-01

The goal of this study was to investigate whether single executive function (EF) tests were predictive for learning performance in mainly young and middle-aged adults. The tests measured shifting and updating. Processing speed was also measured. In an observational study, cognitive performance and learning performance were measured objectively in…

'A Drink That Makes You Feel Happier, Relaxed and Loving': Young People's Perceptions of Alcohol Advertising on Facebook.

PubMed

Weaver, Emma R N; Wright, Cassandra J C; Dietze, Paul M; Lim, Megan S C

2016-07-01

To explore young people's perceptions of alcohol advertising on Facebook and investigate perceived compliance with the Alcohol Beverages Advertising Code (ABAC). An online cross-sectional survey with 172 Australians aged 16-29 years recruited from a market research website and via Facebook. We compiled advertisements from six popular alcohol brands' Australian Facebook pages and asked respondents for their perceptions and interpretations in open and closed-ended questions. Open-ended responses most commonly indicated that the main messages of the advertisements related to social success. In closed-ended questions, respondents perceived advertisements implied that alcohol facilitated relaxation (67%), improved mood (65%), social success (57%) and confidence (49%). Young people identified the main themes of alcohol advertising on Facebook as related to social success and significant improvement in mood. Young people's interpretations of Facebook alcohol advertising suggest breaches of ABAC guidelines. Strengthening the enforcement and application of the ABAC and social media alcohol advertising policies is justified. © The Author 2016. Medical Council on Alcohol and Oxford University Press. All rights reserved.

Is there a lack of information on HPV vaccination given by health professionals to young women?

PubMed

La Torre, G; De Vito, E; Ficarra, M G; Firenze, A; Gregorio, P; Boccia, A

2013-10-01

The aim of this survey is to compare the main sources of information about vaccination against Human papillomavirus (HPV) of young women aged over-18 and under-18 years. A multicenter study was carried out in Italy through the administration of a questionnaire. Univariate analyses were conducted to evaluate possible differences between age groups and different locations (chi-square test and Fisher test where possible). The sample consisted of 987 young women. The main sources of information about HPV vaccination are represented by magazines/books (23.1%) and TV (20.5%) for the over-18s, while for the under-18s the sources are general practitioners (22.6%) and pediatricians (15.4%). The over-18s with health professionals as parents consult mostly gynecologists (27.7%) and general practitioners (20.5%). This study highlights lack of information on HPV vaccination given by health professionals to young women and underlines the need to improve education about cervical cancer, prevention and HPV vaccination. Copyright © 2013 Elsevier Ltd. All rights reserved.

Empirical Studies of Patterning

ERIC Educational Resources Information Center

Pasnak, Robert

2017-01-01

Young children have been taught simple sequences of alternating shapes and colors, referred to as "patterning", for the past half century in the hope that their understanding of pre-algebra and their mathematics achievement would be improved. The evidence that such patterning instruction actually improves children's academic achievement…

Dreams of Death.

ERIC Educational Resources Information Center

Barrett, Deirdre

1989-01-01

Examined frequency and characteristics of overt dreams of dying among healthy young adults. Dreams of dying were found to be rare but distinctive content category, representing overwhelmingly pleasant dreams. Over one-half of death dreams involved lengthy afterlife sequence, remainder focused on process of death. Death dreams of these healthy…

Chicken parvovirus-induced runting-stunting syndrome in young broilers

USDA-ARS?s Scientific Manuscript database

Previously we identified a novel parvovirus from enteric contents of chickens that were affected by enteric diseases. Comparative sequence analysis showed that the chicken parvovirus (ChPV) represented a new member in the Parvoviridae family. Here, we describe some of the pathogenic characteristics ...

The influence of melting on the kinematic development of the Himalayan crystalline core

NASA Astrophysics Data System (ADS)

Webb, Alexander

2016-04-01

Current hypotheses for the development and emplacement of the Himalayan crystalline core are 1) models with intense upper plate out-of-sequence activity (i.e., tunneling of channel flow, and some modes of critical taper wedge behavior) and 2) models in which the upper plate mainly records basal accretion of horses (i.e., duplexing). The two concepts can be considered end-members. A signal difference between these two models is the role of melting. The intense upper plate deformation envisioned in the first set of models has been hypothesized to be largely a product of partial melting, particularly in channel flow models. Specifically, the persistent presence of melt in the middle crust of the upper plate may dramatically lower the viscosity of these rocks, allowing distributed deformation. The second set of models - duplexing - predicts in-sequence thrusting with only minor out-of-sequence deformation. Stacking of a duplex acts like a deli cheese-slicing machine: slice after slice is cut from the intact block to a stack of slices, but neither the block (~down-going plate) nor the stack (~upper plate) features much internal deformation. In this model, partial melting produces no significant kinematic impact. The dominant preserved structural elements across the Himalayan crystalline core rocks are flattening and L-S fabrics. Structurally high portions of the crystalline core locally display complex outcrop-scale deformation associated with migmatitic rocks, and contain km-scale leucogranite bodies; both features developed in the early to middle Miocene. The flattening and L-S fabrics have been interpreted to record either (A) southwards channel tunneling across the upper plate, or (B) fabric development during metamorphism of the down-going plate, prior to accretion to the upper plate. The deformation of migmatitic rock and emplacement of leucogranite have been interpreted in support of widespread distributed deformation. Alternatively, these features may have accumulated from increments of melting and crystallization which did not produce sufficient melt during any one period to significantly alter viscosity at >100 m scales. Recent work integrating monazite and zircon geochronology with structural records shows that the Himalayan middle crust has been assembled along a series of mainly southwards-younging thrust faults throughout the early to middle Miocene. The thrust faults separate 1-5 km thick panels that experienced similar metamorphic cycles during different time periods. At this scale, out-of-sequence deformation is rare, with its apparent significance enhanced because of the high throw-to-heave ratio of out-of-sequence thrusting. These findings support the duplexing model and indicate that melting did not have a significant impact on the kinematic development of the Himalayan crystalline core.

The relationship between executive function and fine motor control in young and older adults.

PubMed

Corti, Emily J; Johnson, Andrew R; Riddle, Hayley; Gasson, Natalie; Kane, Robert; Loftus, Andrea M

2017-01-01

The present study examined the relationship between executive function (EF) and fine motor control in young and older healthy adults. Participants completed 3 measures of executive function; a spatial working memory (SWM) task, the Stockings of Cambridge task (planning), and the Intra-Dimensional Extra-Dimensional Set-Shift task (set-shifting). Fine motor control was assessed using 3 subtests of the Purdue Pegboard (unimanual, bimanual, sequencing). For the younger adults, there were no significant correlations between measures of EF and fine motor control. For the older adults, all EFs significantly correlated with all measures of fine motor control. Three separate regressions examined whether planning, SWM and set-shifting independently predicted unimanual, bimanual, and sequencing scores for the older adults. Planning was the primary predictor of performance on all three Purdue subtests. A multiple-groups mediation model examined whether planning predicted fine motor control scores independent of participants' age, suggesting that preservation of planning ability may support fine motor control in older adults. Planning remained a significant predictor of unimanual performance in the older age group, but not bimanual or sequencing performance. The findings are discussed in terms of compensation theory, whereby planning is a key compensatory resource for fine motor control in older adults. Copyright © 2016 Elsevier B.V. All rights reserved.

Effects of professional rehabilitation training on the recovery of neurological function in young stroke patients

PubMed Central

Li, Chao-jin-zi; Du, Xiao-xia; Yang, Kun; Song, Lu-ping; Li, Peng-kun; Wang, Qiang; Sun, Rong; Lin, Xiao-ling; Lu, Hong-yu; Zhang, Tong

2016-01-01

Young stroke patients have a strong desire to return to the society, but few studies have been conducted on their rehabilitation training items, intensity, and prognosis. We analyzed clinical data of young and middle-aged/older stroke patients hospitalized in the Department of Neurological Rehabilitation, China Rehabilitation Research Center, Capital Medical University, China from February 2014 to May 2015. Results demonstrated that hemorrhagic stroke (59.6%) was the primary stroke type found in the young group, while ischemic stroke (60.0%) was the main type detected in the middle-aged/older group. Compared with older stroke patients, education level and incidence of hyperhomocysteinemia were higher in younger stroke patients, whereas, incidences of hypertension, diabetes, and heart disease were lower. The average length of hospital stay was longer in the young group than in the middle-aged/older group. The main risk factors observed in the young stroke patients were hypertension, drinking, smoking, hyperlipidemia, hyperhomocysteinemia, diabetes, previous history of stroke, and heart disease. The most accepted rehabilitation program consisted of physiotherapy, occupational therapy, speech therapy, acupuncture and moxibustion. Average rehabilitation training time was 2.5 hours/day. Barthel Index and modified Rankin Scale scores were increased at discharge. Six months after discharge, the degree of occupational and economic satisfaction declined, and there were no changes in family life satisfaction. The degrees of other life satisfaction (such as friendship) improved. The degree of disability and functional status improved significantly in young stroke patients after professional rehabilitation, but the number of patients who returned to society within 6 months after stroke was still small. PMID:28123417

Tidal dissipation in rotating low-mass stars and implications for the orbital evolution of close-in planets. I. From the PMS to the RGB at solar metallicity

NASA Astrophysics Data System (ADS)

Gallet, F.; Bolmont, E.; Mathis, S.; Charbonnel, C.; Amard, L.

2017-08-01

Context. Star-planet interactions must be taken into account in stellar models to understand the dynamical evolution of close-in planets. The dependence of the tidal interactions on the structural and rotational evolution of the star is of particular importance and should be correctly treated. Aims: We quantify how tidal dissipation in the convective envelope of rotating low-mass stars evolves from the pre-main sequence up to the red-giant branch depending on the initial stellar mass. We investigate the consequences of this evolution on planetary orbital evolution. Methods: We couple the tidal dissipation formalism previously described to the stellar evolution code STAREVOL and apply this coupling to rotating stars with masses between 0.3 and 1.4 M⊙. As a first step, this formalism assumes a simplified bi-layer stellar structure with corresponding averaged densities for the radiative core and the convective envelope. We use a frequency-averaged treatment of the dissipation of tidal inertial waves in the convection zone (but neglect the dissipation of tidal gravity waves in the radiation zone). In addition, we generalize a recent work by following the orbital evolution of close-in planets using the new tidal dissipation predictions for advanced phases of stellar evolution. Results: On the pre-main sequence the evolution of tidal dissipation is controlled by the evolution of the internal structure of the contracting star. On the main sequence it is strongly driven by the variation of surface rotation that is impacted by magnetized stellar winds braking. The main effect of taking into account the rotational evolution of the stars is to lower the tidal dissipation strength by about four orders of magnitude on the main sequence, compared to a normalized dissipation rate that only takes into account structural changes. Conclusions: The evolution of the dissipation strongly depends on the evolution of the internal structure and rotation of the star. From the pre-main sequence up to the tip of the red-giant branch, it varies by several orders of magnitude, with strong consequences for the orbital evolution of close-in massive planets. These effects are the strongest during the pre-main sequence, implying that the planets are mainly sensitive to the star's early history.

The effects of progressive muscle relaxation and autogenic relaxation on young soccer players' mood states.

PubMed

Hashim, Hairul Anuar; Hanafi Ahmad Yusof, Hazwani

2011-06-01

This study was designed to compare the effects of two different relaxation techniques, namely progressive muscle relaxation (PMR) and autogenic relaxation (AGR) on moods of young soccer players. sixteen adolescent athletes (mean age: 14.1 ± 1.3) received either PMR or AGR training. Using Profile of Mood States- Adolescents, their mood states were measured one week before relaxation training, before the first relaxation session, and after the twelfth relaxation session. Mixed ANOVA revealed no significant interaction effects and no significant main effects in any of the subscales. However, significant main effects for testing sessions were found for confusion, depression, fatigue, and tension subscales. Post hoc tests revealed post-intervention reductions in the confusion, depression, fatigue, and tension subscale scores. These two relaxation techniques induce equivalent mood responses and may be used to regulate young soccer players' mood states.

The Effects of Progressive Muscle Relaxation and Autogenic Relaxation on Young Soccer Players’ Mood States

PubMed Central

Hashim, Hairul Anuar; Hanafi@Ahmad Yusof, Hazwani

2011-01-01

Purpose This study was designed to compare the effects of two different relaxation techniques, namely progressive muscle relaxation (PMR) and autogenic relaxation (AGR) on moods of young soccer players. Methods Sixteen adolescent athletes (mean age: 14.1 ± 1.3) received either PMR or AGR training. Using Profile of Mood States- Adolescents, their mood states were measured one week before relaxation training, before the first relaxation session, and after the twelfth relaxation session. Results Mixed ANOVA revealed no significant interaction effects and no significant main effects in any of the subscales. However, significant main effects for testing sessions were found for confusion, depression, fatigue, and tension subscales. Post hoc tests revealed post-intervention reductions in the confusion, depression, fatigue, and tension subscale scores. Conclusion These two relaxation techniques induce equivalent mood responses and may be used to regulate young soccer players’ mood states. PMID:22375225

“Silent” Dissemination of Klebsiella pneumoniae Isolates Bearing K. pneumoniae Carbapenemase in a Long-term Care Facility for Children and Young Adults in Northeast Ohio

PubMed Central

Viau, Roberto A.; Hujer, Andrea M.; Marshall, Steven H.; Perez, Federico; Hujer, Kristine M.; Briceño, David F.; Dul, Michael; Jacobs, Michael R.; Grossberg, Richard; Toltzis, Philip

2012-01-01

Background. Klebsiella pneumoniae isolates harboring the K. pneumoniae carbapenemase gene (blaKPC) are creating a significant healthcare threat in both acute and long-term care facilities (LTCFs). As part of a study conducted in 2004 to determine the risk of stool colonization with extended-spectrum cephalosporin-resistant gram-negative bacteria, 12 isolates of K. pneumoniae that exhibited nonsusceptibility to extended-spectrum cephalosporins were detected. All were gastrointestinal carriage isolates that were not associated with infection. Methods. Reassessment of the carbapenem minimum inhibitory concentrations using revised 2011 Clinical Laboratory Standards Institute breakpoints uncovered carbapenem resistance. To further investigate, a DNA microarray assay, PCR-sequencing of bla genes, immunoblotting, repetitive-sequence-based PCR (rep-PCR) and multilocus sequence typing (MLST) were performed. Results. The DNA microarray detected blaKPC in all 12 isolates, and blaKPC-3 was identified by PCR amplification and sequencing of the amplicon. In addition, a blaSHV-11 gene was detected in all isolates. Immunoblotting revealed “low-level” production of the K. pneumoniae carbapenemase, and rep-PCR indicated that all blaKPC-3-positive K. pneumoniae strains were genetically related (≥98% similar). According to MLST, all isolates belonged to sequence type 36. This sequence type has not been previously linked with blaKPC carriage. Plasmids from 3 representative isolates readily transferred the blaKPC-3 to Escherichia coli J-53 recipients. Conclusions. Our findings reveal the “silent” dissemination of blaKPC-3 as part of Tn4401b on a mobile plasmid in Northeast Ohio nearly a decade ago and establish the first report, to our knowledge, of K. pneumoniae containing blaKPC-3 in an LTCF caring for neurologically impaired children and young adults. PMID:22492318

12. VIEW FROM MAIN ENTRANCE OF STOVE, ENGINE LATHE, AND ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

12. VIEW FROM MAIN ENTRANCE OF STOVE, ENGINE LATHE, AND GRINDER (L TO R) IN FOREGROUND, SHAFTING ABOVE LOOKING SOUTH. - W. A. Young & Sons Foundry & Machine Shop, On Water Street along Monongahela River, Rices Landing, Greene County, PA