Science.gov

Sample records for age class structure

  1. Age-class structure and variability of two populations of the bluemask darter etheostoma (Doration) sp.

    USGS Publications Warehouse

    Simmons, J.W.; Layzer, J.B.; Smith, D.D.

    2008-01-01

    The bluemask darter Etheostoma (Doration) sp. is an endangered fish endemic to the upper Caney Fork system in the Cumberland River drainage in central Tennessee. Darters (Etheostoma spp.) are typically short-lived and exhibit rapid growth that quickly decreases with age. Consequently, estimating age of darters from length-frequency distributions can be difficult and subjective. We used a nonparametric kernel density estimator to reduce subjectivity in estimating ages of bluemask darters. Data were collected from a total of 2926 bluemask darters from the Collins River throughout three growing seasons. Additionally, data were collected from 842 bluemask darters from the Rocky River during one growing season. Analysis of length-frequencies indicated the presence of four age classes in both rivers. In each river, the majority of the population was comprised of fish 0.05). In both rivers, females were more abundant than males.

  2. Divergent patterns of abundance and age-class structure of headwater stream tadpoles in burned and unburned watersheds

    USGS Publications Warehouse

    Hossack, B.R.; Corn, P.S.; Fagre, D.B.

    2006-01-01

    Wildfire is a potential threat to many species with narrow environmental tolerances like the Rocky Mountain tailed frog (Ascaphus montanus Mittleman and Myers, 1949), which inhabits a region where the frequency and intensity of wildfires are expected to increase. We compared pre- and post-fire counts of tadpoles in eight streams in northwestern Montana to determine the effects of wildfire on A. montanus. All streams were initially sampled in 2001, 2 years before four of them burned in a large wildfire, and were resampled during the 2 years following the fire. Counts of tadpoles were similar in the two groups of streams before the fire. After the fire, tadpoles were almost twice as abundant in unburned streams than in burned streams. The fire seemed to have the greatest negative effect on abundance of age-1 tadpoles, which was reflected in the greater variation in same-stream age-class structure compared with those in unburned streams. Despite the apparent effect on tadpoles, we do not expect the wildfire to be an extirpation threat to populations in the streams that we sampled. Studies spanning a chronosequence of fires, as well as in other areas, are needed to assess the effects of fires on streams with A. montanus and to determine the severity and persistence of these effects.

  3. Opportunities for injury reduction in US frontal crashes: an overview by structural engagement, vehicle class, and occupant age.

    PubMed

    Samaha, Randa Radwan; Prasad, Priya; Nix, Lilly

    2013-11-01

    An overview NASS study of US frontal crashes was performed to investigate crash involvement, driver injury distributions and rates in airbag equipped vehicles by vehicle class and structural engagement. Frontal crash bins were based on taxonomy of structural engagement, i.e., Full Engagement, Offset, Between Rails and Corner impact crashes. A new classification of Corner impacts included frontal small overlap impacts with side damage as coded by NASS CDS. Belted drivers of two age groups, between 16 and 50 and over 50 years old, were considered. Vehicles were grouped into light and heavy passenger cars and lights trucks, and vans. A method to identify and address overly influential NASS weights was developed based on considerations of weighting factor statistics. The new taxonomy, with an expanded definition of corner impacts, allowed a more comprehensive classification of frontal crash modes. Results highlight the need to address upper extremities injuries and to better address lower extremities injuries for both the younger and older drivers. For all body regions studied, the vast majority of all serious and moderate injuries occurred in Full Engagement and Offset crash modes for both the younger and older drivers. Corner impacts, which have been the focus of recent research and testing programs, are the smallest contributors to serious and moderate injuries in frontal crashes. Greater opportunities to mitigate injuries in frontal crashes for vehicles have been shown to exist in lower speed full frontal and offset crash modes.

  4. Major Histocompatibility Complex class I proteins are critical for maintaining neuronal structural complexity in the aging brain.

    PubMed

    Lazarczyk, Maciej J; Kemmler, Julia E; Eyford, Brett A; Short, Jennifer A; Varghese, Merina; Sowa, Allison; Dickstein, Daniel R; Yuk, Frank J; Puri, Rishi; Biron, Kaan E; Leist, Marcel; Jefferies, Wilfred A; Dickstein, Dara L

    2016-01-01

    Major histocompatibility complex class I (MHCI) proteins have been implicated in neuronal function through the modulation of neuritogenesis, synaptogenesis, synaptic plasticity, and memory consolidation during development. However, the involvement of MHCI in the aged brain is unclear. Here we demonstrate that MHCI deficiency results in significant dendritic atrophy along with an increase in thin dendritic spines and a reduction in stubby spines in the hippocampus of aged (12 month old) mice. Ultrastructural analyses revealed a decrease in spine head diameter and post synaptic density (PSD) area, as well as an increase in overall synapse density, and non-perforated, small spines. Interestingly, we found that the changes in synapse density and morphology appear relatively late (after the age of 6 months). Finally, we found a significant age dependent increase in the levels of the glutamate receptor, GluN2B in aged MHCI knockout mice, with no change in GluA2/3, VGluT1, PSD95 or synaptophysin. These results indicate that MHCI may be also be involved in maintaining brain integrity at post-developmental stages notably in the modulation of neuronal and spine morphology and synaptic function during non-pathological aging which could have significant implications for cognitive function. PMID:27229916

  5. Chemical structure of cement aged at normal and elevated temperatures and pressures, Part II: Low permeability class G oilwell cement

    SciTech Connect

    Le Saout, Gwenn . E-mail: gwenn.lesaout@epfl.ch; Lecolier, Eric; Rivereau, Alain; Zanni, Helene

    2006-03-15

    Recently, Low Permeability Cement formulation has been developed for oilwell cementing. Therefore, it is important to understand the physical and chemical processes causing cement degradation in the downhole environment. In this study, we have characterised a Low Permeability Class G oilwell Cement immersed for one year in brine at T = 293 K, p = 10{sup 5} Pa and T = 353 K, p = 7 x 10{sup 6} Pa using {sup 29}Si, {sup 27}Al NMR and XRD techniques. Elevated temperature and pressure conditions increase the rate of the pozzolanic reaction and have significant effects on the polymerisation of C-S-H and on the incorporation of Al in the C-S-H structure. Leaching resulted in the formation of calcite and a more polymerised C-S-H with the appearance of tobermorite in the sample cured at elevated temperature and pressure.

  6. Age-class determination of canvasbacks

    USGS Publications Warehouse

    Serie, J.R.; Trauger, D.L.; Doty, H.A.; Sharp, D.E.

    1982-01-01

    A technique was developed to distinguish yearling from adult canvasbacks (Aythya valisineria) in the field during spring on the basis of white flecking on the distal ends of selected wing feathers. Covert feathers from adults had well-defined vermiculation patterns whereas feathers from yearlings lacked such markings. These age-related characters were confirmed by paired comparisons of feathers from the same captive birds in consecutive years and by discriminant analysis of feathers using densitometric measurements from known-age wild birds. Reflective densitometric measurements of greater secondary coverts for females and males were significantly different between 1- and 2-year-old and between 2- and 3-year-old canvasbacks. Greater secondary coverts were the best feathers for recognizing age-classes of males and females. Densitometric values indicate low variability among different observers and within samples.

  7. The Effect of Mixed-Age Classes in Sweden

    ERIC Educational Resources Information Center

    Lindstrom, Elly-Ann; Lindahl, Erica

    2011-01-01

    Mixed-aged (MA) classes are a common phenomenon around the world. In Sweden, these types of classes increased rapidly during the 1980s and 1990s, despite the fact that existing empirical support for MA classes is weak. In this paper, the effect of attending an MA class during grades 4-6 on students' cognitive skills is estimated. Using a unique…

  8. Food item use by coyote sex and age classes

    SciTech Connect

    Cypher, B.L.; Spencer, K.A.; Scrivner, J.H.

    1995-10-01

    Food item use by coyotes was compared between sexes and among age classes at the Naval Petroleum Reserves, California. Item use did not differ significantly between males and females. Although leporid was the item most frequently used by all age classes, item use differed significantly between pups (< 1 year), yearlings (1 year), and adults (> 1 year), probably due to differential use of secondary items. Variation in item use among age classes could potentially bias results of coyote food habit studies.

  9. Dance Class Structure Affects Youth Physical Activity and Sedentary Behavior: A Study of Seven Dance Types

    ERIC Educational Resources Information Center

    Lopez Castillo, Maria A.; Carlson, Jordan A.; Cain, Kelli L.; Bonilla, Edith A.; Chuang, Emmeline; Elder, John P.; Sallis, James F.

    2015-01-01

    Purpose: The study aims were to determine: (a) how class structure varies by dance type, (b) how moderate-to-vigorous physical activity (MVPA) and sedentary behavior vary by dance class segments, and (c) how class structure relates to total MVPA in dance classes. Method: Participants were 291 boys and girls ages 5 to 18 years old enrolled in 58…

  10. Evaluation of Structural Equation Mixture Models: Parameter Estimates and Correct Class Assignment

    ERIC Educational Resources Information Center

    Tueller, Stephen; Lubke, Gitta

    2010-01-01

    Structural equation mixture models (SEMMs) are latent class models that permit the estimation of a structural equation model within each class. Fitting SEMMs is illustrated using data from 1 wave of the Notre Dame Longitudinal Study of Aging. Based on the model used in the illustration, SEMM parameter estimation and correct class assignment are…

  11. Aging evaluation of class 1E batteries: Seismic testing

    SciTech Connect

    Edson, J.L. )

    1990-08-01

    This report presents the results of a seismic testing program on naturally aged class 1E batteries obtained from a nuclear plant. The testing program is a Phase 2 activity resulting from a Phase 1 aging evaluation of class 1E batteries in safety systems of nuclear power plants, performed previously as a part of the US Nuclear Regulatory Commission's Nuclear Plant Aging Research Program and reported in NUREG/CR-4457. The primary purpose of the program was to evaluate the seismic ruggedness of naturally aged batteries to determine if aged batteries could have adequate electrical capacity, as determined by tests recommended by IEEE Standards, and yet have inadequate seismic ruggedness to provide needed electrical power during and after a safe shutdown earthquake (SSE) event. A secondary purpose of the program was to evaluate selected advanced surveillance methods to determine if they were likely to be more sensitive to the aging degradation that reduces seismic ruggedness. The program used twelve batteries naturally aged to about 14 years of age in a nuclear facility and tested them at four different seismic levels representative of the levels of possible earthquakes specified for nuclear plants in the United States. Seismic testing of the batteries did not cause any loss of electrical capacity. 19 refs., 29 figs., 7 tabs.

  12. Population density, biomass, and age-class structure of the invasive clam Corbicula fluminea in rivers of the lower San Joaquin River watershed, California

    USGS Publications Warehouse

    Brown, L.R.; Thompson, J.K.; Higgins, K.; Lucas, L.V.

    2007-01-01

    Corbicula fluminea is well known as an invasive filter-feeding freshwater bivalve with a variety of effects on ecosystem processes. However. C. fluminea has been relatively unstudied in the rivers of the western United States. In June 2003, we sampled C. fluminea at 16 sites in the San Joaquin River watershed of California, which was invaded by C. fluminea in the 1940s. Corbicula fluminea was common in 2 tributaries to the San Joaquin River, reaching densities of 200 clams??m-2, but was rare in the San Joaquin River. Biomass followed a similar pattern. Clams of the same age were shorter in the San Joaquin River than in the tributaries. Distribution of clams was different in the 2 tributaries, but the causes of the difference are unknown. The low density and biomass of clams in the San Joaquin River was likely due to stressful habitat or to water quality, because food was abundant. The success of C. fluminea invasions and subsequent effects on trophic processes likely depends on multiple factors. As C. fluminea continues to expand its range around the world, questions regarding invasion success and effects on ecosystems will become important in a wide array of environmental settings.

  13. Structural aging program status report

    SciTech Connect

    Naus, D.J.; Oland, C.B.; Ellingwood, B.

    1995-04-01

    Research is being conducted at the Oak Ridge National Laboratory (ORNL) under U.S. Nuclear Regulatory Commission (USNRC) sponsorship to address aging management of safety-related concrete structures. Documentation is being prepared to provide the USNRC with potential structural safety issues and acceptance criteria for use in continued service evaluations of nuclear power plants. Program accomplishments have included development of the Structural Materials Information Center containing data and information of the time variation of 144 material properties under the influence of pertinent environmental stressors of aging factors, performance assessments of reinforced concrete structures in several United Kingdom nuclear power facilities, evaluation of European and North American repair practices for concrete, an evaluation of factors affecting the corrosion of metals embedded in concrete, and application of the time-dependent reliability methodology to reinforced concrete flexure and shear structural elements to investigate the role of in-service inspection and repair on their probability of failure.

  14. Aging and the statistical learning of grammatical form classes.

    PubMed

    Schwab, Jessica F; Schuler, Kathryn D; Stillman, Chelsea M; Newport, Elissa L; Howard, James H; Howard, Darlene V

    2016-08-01

    Language learners must place unfamiliar words into categories, often with few explicit indicators about when and how that word can be used grammatically. Reeder, Newport, and Aslin (2013) showed that college students can learn grammatical form classes from an artificial language by relying solely on distributional information (i.e., contextual cues in the input). Here, 2 experiments revealed that healthy older adults also show such statistical learning, though they are poorer than young at distinguishing grammatical from ungrammatical strings. This finding expands knowledge of which aspects of learning vary with aging, with potential implications for second language learning in late adulthood. (PsycINFO Database Record PMID:27294711

  15. Demographic analysis from summaries of an age-structured population

    USGS Publications Warehouse

    Link, W.A.; Royle, J. Andrew; Hatfield, J.S.

    2003-01-01

    Demographic analyses of age-structured populations typically rely on life history data for individuals, or when individual animals are not identified, on information about the numbers of individuals in each age class through time. While it is usually difficult to determine the age class of a randomly encountered individual, it is often the case that the individual can be readily and reliably assigned to one of a set of age classes. For example, it is often possible to distinguish first-year from older birds. In such cases, the population age structure can be regarded as a latent variable governed by a process prior, and the data as summaries of this latent structure. In this article, we consider the problem of uncovering the latent structure and estimating process parameters from summaries of age class information. We present a demographic analysis for the critically endangered migratory population of whooping cranes (Grus americana), based only on counts of first-year birds and of older birds. We estimate age and year-specific survival rates. We address the controversial issue of whether management action on the breeding grounds has influenced recruitment, relating recruitment rates to the number of seventh-year and older birds, and examining the pattern of variation through time in this rate.

  16. Neural network definitions of highly predictable protein secondary structure classes

    SciTech Connect

    Lapedes, A. |; Steeg, E.; Farber, R.

    1994-02-01

    We use two co-evolving neural networks to determine new classes of protein secondary structure which are significantly more predictable from local amino sequence than the conventional secondary structure classification. Accurate prediction of the conventional secondary structure classes: alpha helix, beta strand, and coil, from primary sequence has long been an important problem in computational molecular biology. Neural networks have been a popular method to attempt to predict these conventional secondary structure classes. Accuracy has been disappointingly low. The algorithm presented here uses neural networks to similtaneously examine both sequence and structure data, and to evolve new classes of secondary structure that can be predicted from sequence with significantly higher accuracy than the conventional classes. These new classes have both similarities to, and differences with the conventional alpha helix, beta strand and coil.

  17. Nodal Structure and the Partitioning of Equivalence Classes

    ERIC Educational Resources Information Center

    Fields, Lanny; Watanabe-Rose, Mari

    2008-01-01

    By definition, all of the stimuli in an equivalence class have to be functionally interchangeable with each other. The present experiment, however, demonstrated that this was not the case when using post-class-formation dual-option response transfer tests. With college students, two 4-node 6-member equivalence classes with nodal structures of…

  18. Three separate classes of bacterial ice nucleation structures.

    PubMed Central

    Turner, M A; Arellano, F; Kozloff, L M

    1990-01-01

    Studies of the properties of the ice nucleation structure exposed on the surfaces of various bacteria such as Pseudomonas syringae, Erwinia herbicola, or various strains of Ice+ recombinant Escherichia coli have shown that there are clearly three major related but chemically distinct types of structures on these cells. First, the ability of Ice+ cells to nucleate super-cooled D2O has been examined, and it has been found that this ability (relative to the ability of the same cells to nucleate super-cooled H2O) exhibited three characteristic nucleating patterns. The rarest structure, called class A, is found on only a small fraction of cells in a culture, nucleates H2O at temperatures above -4.4 degrees C, and is an effective nucleator of super-cooled D2O. A second class of structure, called class B, is found on a larger portion of the cells, nucleates H2O between -4.8 and -5.7 degrees C, and is a relatively poor nucleator of super-cooled D2O. The class C structure is found on almost all cells and nucleates at -7.6 degrees C or colder. These three classes of structures were also differentiated by their sensitivities to low concentrations of water-miscible organic solvents such as dioxane or dimethyl sulfoxide. Depending on the specific bacterial strain, the addition of these solvents to bacterial suspensions lowered the nucleation activity of the class A structure by 1,000-fold or more. The nucleation activities of class B structures in the same culture were highly resistant to these compounds and were lowered only by 20 to 40%. The class C structures were more sensitive than Class B structures were, and the nucleation activities decreased 70 to 90%. Finally, the pH sensitivity of these three classes of structures was examined. The class A structure was destroyed in buffers at pH 4.5 lower but was stable in buffers at higher pHs. The class B structure was less sensitive to acidic buffers but was destroyed at pH 5.5 or lower and was stable at higher pHs. However, the

  19. First in the Class? Age and the Education Production Function

    ERIC Educational Resources Information Center

    Cascio, Elizabeth U.; Schanzenbach, Diane Whitmore

    2016-01-01

    We estimate the effects of relative age in kindergarten using data from an experiment where children of the same age were randomly assigned to different kindergarten classmates. We exploit the resulting experimental variation in relative age in conjunction with variation in expected kindergarten entry age based on birth date to account for…

  20. Latent Trajectory Classes for Alcohol-Related Blackouts from Age 15 to 19 in ALSPAC

    PubMed Central

    Schuckit, Marc A.; Smith, Tom L.; Heron, Jon; Hickman, Matthew; Macleod, John; Munafo, Marcus R.; Kendler, Kenneth S.; Dick, Danielle M.; Davey-Smith, George

    2014-01-01

    Background Alcohol-related blackouts (ARBs) are reported by ~50% of drinkers. While much is known about the prevalence of ARBs in young adults and their cross-sectional correlates, there are few prospective studies regarding their trajectories over time during mid-adolescence. This paper reports latent trajectory classes of alcohol-related blackouts between ages 15 and 19, along with predictors of those patterns. Methods Latent Class Growth Analysis (LCGA) was used to evaluate the pattern of occurrence of ARBs across four time points for 1402 drinking adolescents from the Avon Longitudinal Study of Parents and Children (ALSPAC). Multinomial regression analyses evaluated age 15 demography, substance-related items, externalizing characteristics, and estimated peer substance use as predictors of latent class membership. Results ARBs were reported at age 15 in 30% and at age 19 in 74% of these subjects. Four latent trajectory classes were identified: Class 1 (5.1%) reported no blackouts; for Class 2 (29.5%) ARBs rapidly increased with age; for Class 3 (44.9%) blackouts slowly increased; and for Class 4 (20.5%) ARBs were consistently reported. Using Class 2 (rapid increasers) as the reference, predictors of class membership included female sex, higher drinking quantities, smoking, externalizing characteristics, and estimated peer substance involvement (pseudo R2 =.22). Conclusions ARBs were common and repetitive in these young subjects, and predictors of their trajectories over time involved multiple domains representing diverse characteristics. PMID:25516068

  1. Structural and Cultural Factors in Successful Aging Among Older Hispanics

    PubMed Central

    Angel, Ronald J.

    2014-01-01

    Successful or healthful aging are terms that draw attention to life course issues related to individual, physical, and psychologic development and maturation, but they also draw attention to the material basis of successful aging and the social structures that determine one’s place in the social hierarchy. This article focuses on barriers to optimal aging for Hispanics, especially those of Mexican origin, and argues that cultural factors and social class are closely associated. The reduction of health disparities and equity in medical and long-term care requires an understanding of both cultural and material sources of differential health levels. PMID:19065093

  2. On the structure of valiant's complexity classes

    NASA Astrophysics Data System (ADS)

    Bürgisser, Peter

    In [25,27] Valiant developed an algebraic analogue of the theory of NP-completeness for computations with polynomials over a field. We further develop this theory in the spirit of structural complexity and obtain analogues of well-known results by Baker, Gill, and Solovay [1], Ladner [18], and Schöning [23,24].

  3. Age-class separation of blue-winged ducks

    USGS Publications Warehouse

    Hohman, W.L.; Moore, J.L.; Twedt, D.J.; Mensik, John G.; Logerwell, E.

    1995-01-01

    Accurate determination of age is of fundamental importance to population and life history studies of waterfowl and their management. Therefore, we developed quantitative methods that separate adult and immature blue-winged teal (Anas discors), cinnamon teal (A. cyanoptera), and northern shovelers (A. clypeata) during spring and summer. To assess suitability of discriminant models using 9 remigial measurements, we compared model performance (% agreement between predicted age and age assigned to birds on the basis of definitive cloacal or rectral feather characteristics) in different flyways (Mississippi and Pacific) and between years (1990-91 and 1991-92). We also applied age-classification models to wings obtained from U.S. Fish and Wildlife Service harvest surveys in the Mississippi and Central-Pacific flyways (wing-bees) for which age had been determined using qualitative characteristics (i.e., remigial markings, shape, or wear). Except for male northern shovelers, models correctly aged lt 90% (range 70-86%) of blue-winged ducks. Model performance varied among species and differed between sexes and years. Proportions of individuals that were correctly aged were greater for males (range 63-86%) than females (range 39-69%). Models for northern shovelers performed better in flyway comparisons within year (1991-92, La. model applied to Calif. birds, and Calif. model applied to La. birds: 90 and 94% for M, and 89 and 76% for F, respectively) than in annual comparisons within the Mississippi Flyway (1991-92 model applied to 1990-91 data: 79% for M, 50% for F). Exclusion of measurements that varied by flyway or year did not improve model performance. Quantitative methods appear to be of limited value for age separation of female blue-winged ducks. Close agreement between predicted age and age assigned to wings from the wing-bees suggests that qualitative and quantitative methods may be equally accurate for age separation of male blue-winged ducks. We interpret annual

  4. 33 CFR 67.30-1 - Class “C” structures.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Class âCâ structures. 67.30-1... NAVIGATION AIDS TO NAVIGATION ON ARTIFICIAL ISLANDS AND FIXED STRUCTURES Class âCâ Requirements § 67.30-1 Class “C” structures. Class “C” structures shall be the structures erected in an area where Class...

  5. 33 CFR 67.25-1 - Class “B” structures.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Class âBâ structures. 67.25-1... NAVIGATION AIDS TO NAVIGATION ON ARTIFICIAL ISLANDS AND FIXED STRUCTURES Class âBâ Requirements § 67.25-1 Class “B” structures. Class “B” structures shall be the structures erected in an area where Class...

  6. 33 CFR 67.25-1 - Class “B” structures.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Class âBâ structures. 67.25-1... NAVIGATION AIDS TO NAVIGATION ON ARTIFICIAL ISLANDS AND FIXED STRUCTURES Class âBâ Requirements § 67.25-1 Class “B” structures. Class “B” structures shall be the structures erected in an area where Class...

  7. 33 CFR 67.30-1 - Class “C” structures.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Class âCâ structures. 67.30-1... NAVIGATION AIDS TO NAVIGATION ON ARTIFICIAL ISLANDS AND FIXED STRUCTURES Class âCâ Requirements § 67.30-1 Class “C” structures. Class “C” structures shall be the structures erected in an area where Class...

  8. 33 CFR 67.25-1 - Class “B” structures.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false Class âBâ structures. 67.25-1... NAVIGATION AIDS TO NAVIGATION ON ARTIFICIAL ISLANDS AND FIXED STRUCTURES Class âBâ Requirements § 67.25-1 Class “B” structures. Class “B” structures shall be the structures erected in an area where Class...

  9. 33 CFR 67.20-1 - Class “A” structures.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Class âAâ structures. 67.20-1... NAVIGATION AIDS TO NAVIGATION ON ARTIFICIAL ISLANDS AND FIXED STRUCTURES Class âAâ Requirements § 67.20-1 Class “A” structures. Class “A” structures shall be the structures erected in an area where Class...

  10. 33 CFR 67.30-1 - Class “C” structures.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false Class âCâ structures. 67.30-1... NAVIGATION AIDS TO NAVIGATION ON ARTIFICIAL ISLANDS AND FIXED STRUCTURES Class âCâ Requirements § 67.30-1 Class “C” structures. Class “C” structures shall be the structures erected in an area where Class...

  11. 33 CFR 67.20-1 - Class “A” structures.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Class âAâ structures. 67.20-1... NAVIGATION AIDS TO NAVIGATION ON ARTIFICIAL ISLANDS AND FIXED STRUCTURES Class âAâ Requirements § 67.20-1 Class “A” structures. Class “A” structures shall be the structures erected in an area where Class...

  12. 33 CFR 67.20-1 - Class “A” structures.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false Class âAâ structures. 67.20-1... NAVIGATION AIDS TO NAVIGATION ON ARTIFICIAL ISLANDS AND FIXED STRUCTURES Class âAâ Requirements § 67.20-1 Class “A” structures. Class “A” structures shall be the structures erected in an area where Class...

  13. Short-term memory development: differences in serial position curves between age groups and latent classes.

    PubMed

    Koppenol-Gonzalez, Gabriela V; Bouwmeester, Samantha; Vermunt, Jeroen K

    2014-10-01

    In studies on the development of cognitive processes, children are often grouped based on their ages before analyzing the data. After the analysis, the differences between age groups are interpreted as developmental differences. We argue that this approach is problematic because the variance in cognitive performance within an age group is considered to be measurement error. However, if a part of this variance is systematic, it can provide very useful information about the cognitive processes used by some children of a certain age but not others. In the current study, we presented 210 children aged 5 to 12 years with serial order short-term memory tasks. First we analyze our data according to the approach using age groups, and then we apply latent class analysis to form latent classes of children based on their performance instead of their ages. We display the results of the age groups and the latent classes in terms of serial position curves, and we discuss the differences in results. Our findings show that there are considerable differences in performance between the age groups and the latent classes. We interpret our findings as indicating that the latent class analysis yielded a much more meaningful way of grouping children in terms of cognitive processes than the a priori grouping of children based on their ages.

  14. Class I structures license renewal industry report; revision 1. Final report

    SciTech Connect

    Deng, D.; Renfro, J.; Statton, J.

    1994-07-01

    The U.S. nuclear power industry, through coordination by the Nuclear Management and Resources Council (NUMARC), and sponsorship by the U.S. Department of Energy (DOE) and the Electric Power Research Institute (EPRI), has evaluated age-related degradation effects for a number of major plant systems, structures, and components, in the license renewal technical Industry Reports (IRs). License renewal applicants may choose to reference these IRs in support of their plant-specific license renewal applications, as an equivalent to the integrated plant assessment provisions of the license renewal rule (10 CFR Part 54). This IR provides the technical basis for license renewal for U.S. nuclear power plant Class I structures, with the IR evaluating which structures are Class I. Seventeen structures are explicitly described and evaluated in this IR. These structures are not necessarily classified as Class I at all plants, therefore the license renewal applicant should consult this IR for correct identification.

  15. Dance Class Structure Affects Youth Physical Activity and Sedentary Behavior: A Study of Seven Dance Types

    PubMed Central

    Lopez Castillo, Maria A.; Carlson, Jordan A.; Cain, Kelli L.; Bonilla, Edith A.; Chuang, Emmeline; Elder, John P.; Sallis, James F.

    2015-01-01

    Purpose Study aims were to determine: (a) how class structure varies by dance type, (b) how moderate-to-vigorous physical activity (MVPA) and sedentary behavior (SB) vary by dance class segments, and (c) how class structure relates to total MVPA in dance classes. Methods Participants were 291 boys and girls ages 5–18 yr. enrolled in 58 dance classes at 21 dance studios in Southern California. MVPA and SB were assessed with accelerometry, with data aggregated to 15-sec epochs. Percent and minutes of MVPA and SB during dance class segments and percent of class time and minutes spent in each segment were calculated using Freedson age-specific cut points. Differences in MVPA (>3 METS) and SB (<100 counts/min) were examined using mixed effects linear regression. Results The length of each class segment was fairly consistent across dance types, with the exception that in ballet, more time was spent in technique as compared to private jazz/hip-hop classes, and Latin-flamenco and less time was spent in routine/practice as compared to Latin-salsa/ballet folklorico. Segment type accounted for 17% of the variance in the proportion of the segment spent in MVPA. The proportion of the segment in MVPA was higher for routine/practice (44.2%) than technique (34.7%). The proportion of the segment in SB was lowest for routine/practice (22.8%). Conclusion The structure of dance lessons can impact youth’s physical activity. Working with instructors to increase time in routine/practice during dance classes could contribute to physical activity promotion in youth. PMID:25775088

  16. Does 3rd Age + 3rd World = 3rd Class?

    ERIC Educational Resources Information Center

    Tout, Ken

    1992-01-01

    Demographic changes, migration, and industrialization are having drastic effects on older adults in developing nations. Local programs such as Pro Vida in Colombia, supported by Help Age International, rely on the support of volunteers to improve the quality of life for elderly people. (SK)

  17. Spatial and temporal variations in the age structure of Arctic sea ice

    USGS Publications Warehouse

    Belchansky, G.I.; Douglas, D.C.; Platonov, N.G.

    2005-01-01

    Spatial and temporal variations in the age structure of Arctic sea ice are investigated using a new reverse chronology algorithm that tracks ice-covered pixels to their location and date of origin based on ice motion and concentration data. The Beaufort Gyre tends to harbor the oldest (>10 years old) sea ice in the western Arctic while direct ice advection pathways toward the Transpolar Drift Stream maintain relatively young (10 years old (10+ year age class) were observed during 1989-2003. Since the mid-1990s, losses to the 10+ year age class lacked compensation by recruitment due to a prior depletion of all mature (6-10 year) age classes. Survival of the 1994 and 1996-1998 sea ice generations reestablished most mature age classes, and thereby the potential to increase extent of the 10+ year age class during the mid-2000s.

  18. A Way Forward: Nurturing the Imagination at the Intersection of Race, Class, Gender, and Age

    ERIC Educational Resources Information Center

    Lockhart-Gilroy, Annie A.

    2016-01-01

    Those who are oppressed often find themselves internalizing voices that limit their ability. This article focuses on a population that falls on the non-hegemonic side of the intersection of race, class, gender, and age: Black girls from poor and working-class backgrounds. From my work with youth, I have noticed that internalizing these limiting…

  19. Comparison of Statistical Population Reconstruction Using Full and Pooled Adult Age-Class Data

    PubMed Central

    Skalski, John R.; Millspaugh, Joshua J.; Clawson, Michael V.

    2012-01-01

    Background Age-at-harvest data are among the most commonly collected, yet neglected, demographic data gathered by wildlife agencies. Statistical population construction techniques can use this information to estimate the abundance of wild populations over wide geographic areas and concurrently estimate recruitment, harvest, and natural survival rates. Although current reconstruction techniques use full age-class data (0.5, 1.5, 2.5, 3.5, … years), it is not always possible to determine an animal's age due to inaccuracy of the methods, expense, and logistics of sample collection. The ability to inventory wild populations would be greatly expanded if pooled adult age-class data (e.g., 0.5, 1.5, 2.5+ years) could be successfully used in statistical population reconstruction. Methodology/Principal Findings We investigated the performance of statistical population reconstruction models developed to analyze full age-class and pooled adult age-class data. We performed Monte Carlo simulations using a stochastic version of a Leslie matrix model, which generated data over a wide range of abundance levels, harvest rates, and natural survival probabilities, representing medium-to-big game species. Results of full age-class and pooled adult age-class population reconstructions were compared for accuracy and precision. No discernible difference in accuracy was detected, but precision was slightly reduced when using the pooled adult age-class reconstruction. On average, the coefficient of variation increased by 0.059 when the adult age-class data were pooled prior to analyses. The analyses and maximum likelihood model for pooled adult age-class reconstruction are illustrated for a black-tailed deer (Odocoileus hemionus) population in Washington State. Conclusions/Significance Inventorying wild populations is one of the greatest challenges of wildlife agencies. These new statistical population reconstruction models should expand the demographic capabilities of wildlife agencies

  20. Class I Microcins: Their Structures, Activities, and Mechanisms of Resistance

    NASA Astrophysics Data System (ADS)

    Severinov, Konstantin; Semenova, Ekaterina; Kazakov, Teymur

    Microcin J25, microcin B17, and microcin C7-C51 are the three known members of class I posttranslationally modified microcins (heavily posttranslationally modified antibacterial peptides produced by Enterobacteriaceae with molecular weights of less than 5 kDa). The three microcins are unrelated to each other; they have structures that are highly atypical for ribosomally synthesized peptides and target essential molecular machines that are validated drug targets. In this chapter, available data on mechanisms of action, structure-activity relationships, and immunity mechanisms for class I microcins and related compounds are discussed.

  1. Class structure in a deeply divided society: class and ethnic inequality in Israel, 1974-1991.

    PubMed

    Yaish, M

    2001-09-01

    Despite the fact that in many societies ethnicity plays an important role in stratification processes, a common view held by students of stratification argues that the role of ascriptive criteria in stratification processes is diminishing, and that the main axis of the modern stratification system is rooted in the division of labour in the marketplace. Despite this, most Israeli sociologists have taken the ethnic and national cleavages to be the main axes of stratification in Israel. This paper utilizes the 1974 and 1991 mobility surveys in Israel to examine changes over time in the association between ethnicity/nationality (i.e., Ashkenazi-Jews, Sephardi-Jews and Israeli-Arabs) and class position in the Israeli stratification structure. It also examines the extent to which inequality of opportunity within the Israeli class structure is affected by ethnicity/nationality. Here it is found that the ethnic/national cleavage in Israel appears to have played a less important role over time in the allocation of Israeli men to class positions. It is shown that class crystallization processes that result from the differentiation of employment contracts in the marketplace produce a relatively common level of inequality of opportunity in Israel, across sub-populations and over time. Any difference in the level of inequality of opportunity between the various sub-populations would appear to result, in part, from different historical process of, and government policy towards, the three sub-populations. PMID:11578003

  2. Discriminating between Survivors and Nonsurvivors among Working Class Aged Living in the Community.

    ERIC Educational Resources Information Center

    Harel, Zev

    1979-01-01

    The predictive significance of select variables on survival was ascertained among community-living aged of working class background. Sex and performance of daily routines were found to be better initial discriminators, while age and a perceptual style variable termed field dependence/independence were found to have better long-range predictive…

  3. Structural and Functional Aspects of Class A Carbapenemases.

    PubMed

    Naas, Thierry; Dortet, Laurent; Iorga, Bogdan I

    2016-01-01

    The fight against infectious diseases is probably one of the greatest public health challenges faced by our society, especially with the emergence of carbapenem-resistant gram-negatives that are in some cases pan-drug resistant. Currently,β-lactamase-mediated resistance does not spare even the newest and most powerful β-lactams (carbapenems), whose activity is challenged by carbapenemases. The worldwide dissemination of carbapenemases in gram-negative organisms threatens to take medicine back into the pre-antibiotic era since the mortality associated with infections caused by these "superbugs" is very high, due to limited treatment options. Clinically-relevant carbapenemases belong either to metallo-β- lactamases (MBLs) of Ambler class B or to serine-β-lactamases (SBLs) of Ambler class A and D enzymes. Class A carbapenemases may be chromosomally-encoded (SME, NmcA, SFC-1, BIC-1, PenA, FPH-1, SHV-38), plasmid-encoded (KPC, GES, FRI-1) or both (IMI). The plasmid-encoded enzymes are often associated with mobile elements responsible for their mobilization. These enzymes, even though weakly related in terms of sequence identities, share structural features and a common mechanism of action. They variably hydrolyse penicillins, cephalosporins, monobactams, carbapenems, and are inhibited by clavulanate and tazobactam. Three-dimensional structures of class A carbapenemases, in the apo form or in complex with substrates/inhibitors, together with site-directed mutagenesis studies, provide essential input for identifying the structural factors and subtle conformational changes that influence the hydrolytic profile and inhibition of these enzymes. Overall, these data represent the building blocks for understanding the structure-function relationships that define the phenotypes of class A carbapenemases and can guide the design of new molecules of therapeutic interest. PMID:26960341

  4. Structural and Functional Aspects of Class A Carbapenemases.

    PubMed

    Naas, Thierry; Dortet, Laurent; Iorga, Bogdan I

    2016-01-01

    The fight against infectious diseases is probably one of the greatest public health challenges faced by our society, especially with the emergence of carbapenem-resistant gram-negatives that are in some cases pan-drug resistant. Currently,β-lactamase-mediated resistance does not spare even the newest and most powerful β-lactams (carbapenems), whose activity is challenged by carbapenemases. The worldwide dissemination of carbapenemases in gram-negative organisms threatens to take medicine back into the pre-antibiotic era since the mortality associated with infections caused by these "superbugs" is very high, due to limited treatment options. Clinically-relevant carbapenemases belong either to metallo-β- lactamases (MBLs) of Ambler class B or to serine-β-lactamases (SBLs) of Ambler class A and D enzymes. Class A carbapenemases may be chromosomally-encoded (SME, NmcA, SFC-1, BIC-1, PenA, FPH-1, SHV-38), plasmid-encoded (KPC, GES, FRI-1) or both (IMI). The plasmid-encoded enzymes are often associated with mobile elements responsible for their mobilization. These enzymes, even though weakly related in terms of sequence identities, share structural features and a common mechanism of action. They variably hydrolyse penicillins, cephalosporins, monobactams, carbapenems, and are inhibited by clavulanate and tazobactam. Three-dimensional structures of class A carbapenemases, in the apo form or in complex with substrates/inhibitors, together with site-directed mutagenesis studies, provide essential input for identifying the structural factors and subtle conformational changes that influence the hydrolytic profile and inhibition of these enzymes. Overall, these data represent the building blocks for understanding the structure-function relationships that define the phenotypes of class A carbapenemases and can guide the design of new molecules of therapeutic interest.

  5. Cooperation and age structure in spatial games.

    PubMed

    Wang, Zhen; Wang, Zhen; Zhu, Xiaodan; Arenzon, Jeferson J

    2012-01-01

    We study the evolution of cooperation in evolutionary spatial games when the payoff correlates with the increasing age of players (the level of correlation is set through a single parameter, α). The demographic heterogeneous age distribution, directly affecting the outcome of the game, is thus shown to be responsible for enhancing the cooperative behavior in the population. In particular, moderate values of α allow cooperators not only to survive but to outcompete defectors, even when the temptation to defect is large and the ageless, standard α=0 model does not sustain cooperation. The interplay between age structure and noise is also considered, and we obtain the conditions for optimal levels of cooperation.

  6. Continuous Age-Structured Model for Bovine Tuberculosis in African buffalo

    NASA Astrophysics Data System (ADS)

    Anguelov, R.; Kojouharov, H.

    2009-10-01

    The paper deals with a model of the spread of bovine tuberculosis in the buffalo population in the Kruger National Park in South Africa. The model uses continuous age structure and it is formulated in terms of partial differential equations using eight epidemiological classes (compartments). More precisely, the age density for each class at time t satisfies a one way wave equation, where the age is the space variable. The continuous age model discussed here is derived from a 2006 age groups model by P. C. Cross and W. M. Getz.

  7. Age structure and income distribution policy.

    PubMed

    Von Weizsacker, R K

    1988-01-01

    The dependence of earnings on age is a firmly established empirical fact. A simple microeconomic model of educational choice, being consistent with this observation, is designed. The model lends itself readily to aggregation over individuals and age groups. Thus, relations can be set up between economic variables influencing the aggregate distribution of labor incomes and demographic variables determining the age structure of the population. The main results of the present study are: 1) overall earnings inequality is shown to be an increasing function of life expectancy and a decreasing function of fertility. 2) The effectiveness of redistributive policies is sensitive to the age composition. In particular, the inequality-reducing effect of a 1% income tax rise is shown to be smaller the older the population.

  8. Normal and aging hair biology and structure 'aging and hair'.

    PubMed

    Goodier, Molly; Hordinsky, Maria

    2015-01-01

    Much like an individual's hairstyle, hair fibers along the scalp see a number of changes over the course of one's lifetime. As the decades pass, the shine and volume synonymous with youthful hair may give way to thin, dull, and brittle hair commonly associated with aging. These changes are a result of a compilation of genetic and environmental elements influencing the cells of the hair follicle, specifically the hair follicle stem cells and melanocytes. Telomere shortening, decrease in cell numbers, and particular transcription factors have all been implicated in this process. In turn, these molecular alterations lead to structural modifications of the hair fiber, decrease in melanin production, and lengthening of the telogen phase of the hair cycle. Despite this inevitable progression with aging, there exists an array of treatments such as light therapy, minoxidil, and finasteride which have been designed to mitigate the effects of aging, particularly balding and thinning hair. Although each works through a different mechanism, all aim to maintain or potentially restore the youthful quality of hair.

  9. Normal and aging hair biology and structure 'aging and hair'.

    PubMed

    Goodier, Molly; Hordinsky, Maria

    2015-01-01

    Much like an individual's hairstyle, hair fibers along the scalp see a number of changes over the course of one's lifetime. As the decades pass, the shine and volume synonymous with youthful hair may give way to thin, dull, and brittle hair commonly associated with aging. These changes are a result of a compilation of genetic and environmental elements influencing the cells of the hair follicle, specifically the hair follicle stem cells and melanocytes. Telomere shortening, decrease in cell numbers, and particular transcription factors have all been implicated in this process. In turn, these molecular alterations lead to structural modifications of the hair fiber, decrease in melanin production, and lengthening of the telogen phase of the hair cycle. Despite this inevitable progression with aging, there exists an array of treatments such as light therapy, minoxidil, and finasteride which have been designed to mitigate the effects of aging, particularly balding and thinning hair. Although each works through a different mechanism, all aim to maintain or potentially restore the youthful quality of hair. PMID:26370639

  10. Social Skills Expression of Senior High School Age Students in Physical Education Classes

    ERIC Educational Resources Information Center

    Akelaitis, Arturas V.

    2015-01-01

    The main purpose of the present study is to reveal the peculiarities of social skills expression of senior high school age students in physical education classes. The independent random sample consisted of 244 (15-16 years old) students and 258 (17-18 years old) students, of which there were 224 boys and 278 girls. L. Bulotaite and V. Gudžinskiene…

  11. Effects of Age, Gender, School Class on Cardiopulmonary Resuscitation Skills of Nigerian Secondary School Students

    ERIC Educational Resources Information Center

    Onyeaso, Adedamola Olutoyin; Onyeaso, Chukwudi Ochi

    2016-01-01

    Background: The need for training of schoolchildren on cardiopulmonary resuscitation (CPR) as potential bystander CPR providers is growing globally but Nigeria is still behind and lacks basic necessary data. Purpose: The purpose of this study was to investigate the effects of age, gender and school class on CPR skills of Nigerian secondary school…

  12. A realistic age structured transmission model for dengue hemorrhagic fever in Thailand.

    PubMed

    Pongsumpun, P; Tang, I M

    2001-06-01

    The influence of age structure in the susceptible class of the Susceptible-Infected Recovered (SIR) model used to describe the transmission of dengue hemorrhagic fever (DHF) was studied. This was done by first dividing all of the population classes into cohorts and then writing a set of coupled SIR equations for each cohort. The consequences of assuming different behavior of the transmission rates on the age structure in the DHF incidence rates were determined. In order for the predicted incidence rates to be similar to the DHF incidence patterns observed in several provinces in Thailand during the DHF epidemic in 1998, the transmission rates should be age dependent.

  13. Dynamic analysis of a hepatitis B model with three-age-classes

    NASA Astrophysics Data System (ADS)

    Zhang, Suxia; Zhou, Yicang

    2014-07-01

    Based on the fact that the likelihood of becoming chronically infected is dependent on age at primary infection Kane (1995) [2], Edmunds et al. (1993) [3], Medley et al. (2001) [4], and Ganem and Prince (2004) [6], we formulate a hepatitis B transmission model with three age classes. The reproduction number, R0 is defined and the dynamical behavior of the model is analyzed. It is proved that the disease-free equilibrium is globally stable if R0<1, and there exists at least one endemic equilibrium and that the disease is uniformly persistent if R0>1. The unique endemic equilibrium and its global stability is obtained in a special case. Simulations are also conducted to compare the dynamical behavior of the model with and without age classes.

  14. Relative Age Effects in Mathematics and Reading: Investigating the Generalizability across Students, Time and Classes

    PubMed Central

    Thoren, Katharina; Heinig, Elisa; Brunner, Martin

    2016-01-01

    A child's age in comparison to the age of her or his classmates (relative age) has been found to be an influential factor on academic achievement, particularly but not exclusively at the beginning of formal schooling. However, few studies have focused on the generalizability of relative age effects. To close this gap, the present study analyzes the generalizability across students with and without immigrant backgrounds, across three student cohorts that entered school under a changing law of school enrollment, and across classes. To this end, we capitalized on representative large-scale data sets from three student cohorts attending public schools in Berlin, the capital of Germany. We analyzed the data using a multilevel framework. Our results for the overall student sample indicate relative age effects for reading and mathematics in favor of the relatively older students in Grade 2 that become somewhat smaller in size in Grade 3. By Grade 8, relative age effects had vanished in reading and had even reversed in favor of the relatively young in mathematics. Furthermore, relative age effects were not found to be systematically different among students with and without immigrant backgrounds, student cohorts, or across classes. Taken together, these results empirically underscore the broad generalizability of the findings as found for the overall student population and replicate the pattern of findings on relative effects as identified by the majority of previous studies. PMID:27242593

  15. Relative Age Effects in Mathematics and Reading: Investigating the Generalizability across Students, Time and Classes.

    PubMed

    Thoren, Katharina; Heinig, Elisa; Brunner, Martin

    2016-01-01

    A child's age in comparison to the age of her or his classmates (relative age) has been found to be an influential factor on academic achievement, particularly but not exclusively at the beginning of formal schooling. However, few studies have focused on the generalizability of relative age effects. To close this gap, the present study analyzes the generalizability across students with and without immigrant backgrounds, across three student cohorts that entered school under a changing law of school enrollment, and across classes. To this end, we capitalized on representative large-scale data sets from three student cohorts attending public schools in Berlin, the capital of Germany. We analyzed the data using a multilevel framework. Our results for the overall student sample indicate relative age effects for reading and mathematics in favor of the relatively older students in Grade 2 that become somewhat smaller in size in Grade 3. By Grade 8, relative age effects had vanished in reading and had even reversed in favor of the relatively young in mathematics. Furthermore, relative age effects were not found to be systematically different among students with and without immigrant backgrounds, student cohorts, or across classes. Taken together, these results empirically underscore the broad generalizability of the findings as found for the overall student population and replicate the pattern of findings on relative effects as identified by the majority of previous studies.

  16. Relative Age Effects in Mathematics and Reading: Investigating the Generalizability across Students, Time and Classes.

    PubMed

    Thoren, Katharina; Heinig, Elisa; Brunner, Martin

    2016-01-01

    A child's age in comparison to the age of her or his classmates (relative age) has been found to be an influential factor on academic achievement, particularly but not exclusively at the beginning of formal schooling. However, few studies have focused on the generalizability of relative age effects. To close this gap, the present study analyzes the generalizability across students with and without immigrant backgrounds, across three student cohorts that entered school under a changing law of school enrollment, and across classes. To this end, we capitalized on representative large-scale data sets from three student cohorts attending public schools in Berlin, the capital of Germany. We analyzed the data using a multilevel framework. Our results for the overall student sample indicate relative age effects for reading and mathematics in favor of the relatively older students in Grade 2 that become somewhat smaller in size in Grade 3. By Grade 8, relative age effects had vanished in reading and had even reversed in favor of the relatively young in mathematics. Furthermore, relative age effects were not found to be systematically different among students with and without immigrant backgrounds, student cohorts, or across classes. Taken together, these results empirically underscore the broad generalizability of the findings as found for the overall student population and replicate the pattern of findings on relative effects as identified by the majority of previous studies. PMID:27242593

  17. Structural prediction of peptides bound to MHC class I.

    PubMed

    Fagerberg, Theres; Cerottini, Jean-Charles; Michielin, Olivier

    2006-02-17

    An ab initio structure prediction approach adapted to the peptide-major histocompatibility complex (MHC) class I system is presented. Based on structure comparisons of a large set of peptide-MHC class I complexes, a molecular dynamics protocol is proposed using simulated annealing (SA) cycles to sample the conformational space of the peptide in its fixed MHC environment. A set of 14 peptide-human leukocyte antigen (HLA) A0201 and 27 peptide-non-HLA A0201 complexes for which X-ray structures are available is used to test the accuracy of the prediction method. For each complex, 1000 peptide conformers are obtained from the SA sampling. A graph theory clustering algorithm based on heavy atom root-mean-square deviation (RMSD) values is applied to the sampled conformers. The clusters are ranked using cluster size, mean effective or conformational free energies, with solvation free energies computed using Generalized Born MV 2 (GB-MV2) and Poisson-Boltzmann (PB) continuum models. The final conformation is chosen as the center of the best-ranked cluster. With conformational free energies, the overall prediction success is 83% using a 1.00 Angstroms crystal RMSD criterion for main-chain atoms, and 76% using a 1.50 Angstroms RMSD criterion for heavy atoms. The prediction success is even higher for the set of 14 peptide-HLA A0201 complexes: 100% of the peptides have main-chain RMSD values < or =1.00 Angstroms and 93% of the peptides have heavy atom RMSD values < or =1.50 Angstroms. This structure prediction method can be applied to complexes of natural or modified antigenic peptides in their MHC environment with the aim to perform rational structure-based optimizations of tumor vaccines.

  18. [Spatial patterns of different age-class individuals in Pinus tabulaeformis forest in Songshan Nature Reserve of Beijing, China].

    PubMed

    Niu, Li-Li; Yu, Xin-Xiao; Yue, Yong-Jie

    2008-07-01

    By the method of point pattern analysis, this paper studied the spatial patterns of different age-class individuals in the Pinus tabulaeformis forest in Songshan Nature Reserve of Beijing, and the spatial association between the individuals. The results showed that there existed greater differences in the densities of different age-class P. tabulaeformis individuals, e.g., age-class I had the density of 15 plants per hectare, while age-class III had the density of 924 plants per hectare. The spatial patterns of different age-class individuals and the spatial association between the individuals had a close relationship with the spatial scale. In the scale of < 40 m, the individuals of all age-classes tended to clump, and there was a stronger spatial association between the individuals of different age-classes. When the scale was larger than 30 m or 40 m, the individuals of all age-classes would disperse randomly, and their spatial association would be weakened greatly. PMID:18839896

  19. Circadian variation in salivary testosterone across age classes in Ache Amerindian males of Paraguay.

    PubMed

    Bribiescas, Richard G; Hill, Kim R

    2010-01-01

    Testosterone levels exhibit a circadian rhythm in healthy men, with morning levels tending to be higher compared to evening titers. However, circadian rhythms wane with age. Although this has been described in males living within industrialized settings, age-related changes have not received similar attention in populations outside these contexts. Because many nonindustrialized populations, such as Ache Amerindians of Paraguay, exhibit testosterone levels that are lower than what is commonly reported in the clinical literature and lack age-associated variation in testosterone, it was hypothesized that Ache men would not show age-related variation in testosterone circadian rhythms. Diurnal rhythmicity in testosterone within and between Ache men in association with age (n = 52; age range, 18-64) was therefore examined. A significant negative association was evident between the ratio of morning and evening salivary testosterone and age (r = -0.28, P = 0.04). Men in their third decade of life exhibited significant diurnal variation (P = 0.0003), whereas older and younger age classes did not. Men between the ages of 30 and 39 also exhibited a higher AM:PM testosterone ratio compared to 40-49 and 50< year old men (P = 0.002, 0.006). Overall, declines in testosterone with aging may not be universal among human males, however, within-individual analyses of diurnal variation capture age-related contrasts in daily testosterone fluctuations. Circadian rhythmicity differs with age among the Ache and may be a common aspect of reproductive senescence among men regardless of ecological context.

  20. AGE-STRUCTURAL TRANSITION IN INDONESIA

    PubMed Central

    Kreager, Philip; Schröder-Butterfill, Elisabeth

    2016-01-01

    This paper responds to recent calls for empirical study of the impact of age-structural transition. It begins by reviewing evidence of cohort oscillations in twentieth-century Indonesia, which indicates that current older generations are likely to have smaller numbers of children on whom they may rely than generations before and after them. However, to assess whether the imbalances implied by this situation are actually influencing people’s lives, attention to further factors shaping the availability and reliability of younger generations, notably differences in socio-economic status and in patterns of inter-generational support flows, is required. Community-level Indonesian data confirm that elders in the lower social strata are child-poor. Social structural and family network patterns, however, have a greater influence on the availability of inter-generational support than cohort differentials. PMID:27158254

  1. Evaluation of bursal depth as an indicator of age class of harlequin ducks

    USGS Publications Warehouse

    Mather, D.D.; Esler, Daniel

    1999-01-01

    We contrasted the estimated age class of recaptured Harlequin Ducks (Histrionicus histrionicus) (n = 255) based on bursal depth with expected age class based on bursal depth at first capture and time since first capture. Although neither estimated nor expected ages can be assumed to be correct, rates of discrepancies between the two for within-year recaptures indicate sampling error, while between-year recaptures test assumptions about rates of bursal involution. Within-year, between-year, and overall discrepancy rates were 10%, 24%, and 18%, respectively. Most (86%) between-year discrepancies occurred for birds expected to be after-third-year (ATY) but estimated to be third-year (TY). Of these ATY-TY discrepancies, 22 of 25 (88%) birds had bursal depths of 2 or 3 mm. Further, five of six between-year recaptures that were known to be ATY but estimated to be TY had 2 mm bursas. Reclassifying birds with 2 or 3 mm bursas as ATY resulted in reduction in between-year (24% to 10%) and overall (18% to 11%) discrepancy rates. We conclude that age determination of Harlequin Ducks based on bursal depth, particularly using our modified criteria, is a relatively consistent and reliable technique.

  2. Neighborhood Age Structure and its Implications for Health

    PubMed Central

    2006-01-01

    Age structure at the neighborhood level is rarely considered in contextual studies of health. However, age structure can play a critical role in shaping community life, the availability of resources, and the opportunities for social engagement—all factors that, research suggests, have direct and indirect effects on health. Age structure can be theorized as a compositional effect and as a contextual effect. In addition, the dynamic nature of age structure and the utility of a life course perspective as applied to neighborhood effects research merits attention. Four Chicago neighborhoods are summarized to illustrate how age structure varies across small space, suggesting that neighborhood age structure should be considered a key structural covariate in contextual research on health. Considering age structure implies incorporating not only meaningful cut points for important age groups (e.g., proportion 65 years and over) but attention to the shape of the distribution as well. PMID:16865558

  3. Effects of predation and oxygen deficiency on different age classes of the amphipod Monoporeia affinis

    NASA Astrophysics Data System (ADS)

    Sandberg, E.; Bonsdorff, E.

    1996-06-01

    Predation by the big brackish-water isopod Saduria entomon on two age-classes (juveniles and adults) of the small deposit-feeding amphipod Monoporeia (syn. Pontoporeia) affinis was studied at different oxygen conditions (normoxia>11 mg/l O 2, and moderate hypoxia 4 mg/l O 2). Vulnerability of juvenile and adult M. affinis was studied in single and mixed age-class treatments. The proportions of juveniles and adults were varied at one total numerical density. The predatory effects were measured as numbers of individuals consumed and of total biomass intake (mg ash-free dry weight). The highest predation rate (in numbers) was detected in the single-prey treatment with juvenile M. affinis, both in normoxia and moderate hypoxia. No preference for any of the two size classes was found in the treatment with equal numbers of adults and juveniles. In normoxia, the total number of prey consumed decreased with increasing proportions of adults, while intake increased in terms of biomass. In moderate hypoxia, high proportions of adults reduced the predation rate of S. entomon to such an extent that also the intake in terms of biomass was significantly negatively affected.

  4. Affluence, Class Structure, and Working-Class Consciousness in Modern Spain

    ERIC Educational Resources Information Center

    Logan, John R.

    1977-01-01

    A survey of textile workers in Barcelona indicates that the growing proportion of affluent workers in Spain has become a major source of class consciousness, militancy, and politicization. A theoretical framework is presented which interprets the survey findings in terms of the relationship between affluence and class consciousness. (Author/DB)

  5. Structural Basis for Activation of Class Ib Ribonucleotide Reductase

    SciTech Connect

    Boal, Amie K.; Cotruvo, Jr., Joseph A.; Stubbe, JoAnne; Rosenzweig, Amy C.

    2010-12-03

    The class Ib ribonucleotide reductase of Escherichia coli can initiate reduction of nucleotides to deoxynucleotides with either a Mn{sub 2}{sup III}-tyrosyl radical (Y{sm_bullet}) or a Fe{sub 2}{sup III}-Y{sm_bullet} cofactor in the NrdF subunit. Whereas Fe{sub 2}{sup III}-Y{sm_bullet} can self-assemble from Fe{sub 2}{sup II}-NrdF and O{sub 2}, activation of Mn{sub 2}{sup II}-NrdF requires a reduced flavoprotein, NrdI, proposed to form the oxidant for cofactor assembly by reduction of O{sub 2}. The crystal structures reported here of E. coli Mn{sub 2}{sup II}-NrdF and Fe{sub 2}{sup II}-NrdF reveal different coordination environments, suggesting distinct initial binding sites for the oxidants during cofactor activation. In the structures of Mn{sub 2}{sup II}-NrdF in complex with reduced and oxidized NrdI, a continuous channel connects the NrdI flavin cofactor to the NrdF Mn{sub 2}{sup II} active site. Crystallographic detection of a putative peroxide in this channel supports the proposed mechanism of Mn{sub 2}{sup III}-Y{sm_bullet} cofactor assembly.

  6. Structural health management for aging aircraft

    NASA Astrophysics Data System (ADS)

    Ikegami, Roy; Haugse, Eric D.

    2001-06-01

    An effective structural health management (SHM) system can be a useful tool for making aircraft fleet management decisions ranging from individual aircraft maintenance scheduling and usage restrictions to fleet rotation strategies. This paper discusses the end-user requirements for the elements and architecture of an effective SHM system for application to both military and commercial aging aircraft fleets. The elements discussed include the sensor systems for monitoring and characterizing the health of the structure, data processing methods for interpreting sensor data and converting it into useable information, and automated methods for erroneous data detection, data archiving and information dissemination. Current and past SHM technology development/maturation efforts in these areas at the Boeing Company will be described. An evolutionary technology development strategy is developed in which the technologies needed will be matured, integrated into a vehicle health management system, and benefits established without requiring extensive changes to the end-user's existing operation and maintenance infrastructure. Issues regarding the end-user customer acceptance of SHM systems are discussed and summarized.

  7. Restoration of Retarded Influenza Virus-specific Immunoglobulin Class Switch in Aged Mice

    PubMed Central

    Zhang, Yongxin; Wang, Ying; Zhang, Monica; Liu, Lin; Mbawuike, Innocent N

    2016-01-01

    Objective The declined immune response to infection causes significant higher morbidity and mortality in aging in spite of the coexisted hyperimmunoglobulinemia (HIG). This study is to reveal the cellular basis of HIG and mechanism of weakened HA-specific IgG response in aged mice and to test cell therapy in the treatment of age-related IgG antibody production deficiency with immunocyte adoptive transfer. Methods BALB/c mice was immunized with Influenza A/Taiwan vaccine and challenged with the same strain of virus. ELISA was used to assess the levels of total immunoglobulins and antigen specific antibody response. The flow cytometry and ELISPOT were used to evaluate the frequencies of total immunoglobulin- and specific antibody-producing and secreting B lymphocytes. In vitro expanded mononuclear cells, CD4+ T lymphocytes and CD20+ B lymphocytes from old and young mice were adoptively transferred into influenza virus-challenged aged mice, and HA-specific IgG responses were observed. Results It is found that old mice exhibited higher levels of total serum IgG, IgM and IgA, higher frequencies of IgG+, IgM+ and IgA+ cells, and greater antigen-specific IgM and IgA responses to influenza infection, in comparison to young mice. However, influenza antigen- specific IgG and its subclass responses in old mice were significantly lower. Conclusion The retarded specific IgG response could be attributed to an insufficiency of immunoglobulin class switch in aging. Correlation analysis indicated that HIG and deficient specific IgG production in aged mice could be independent to each other in their pathogenesis. Correction of deficient specific IgG production by adoptive transfer of in vitro expanded and unexpanded CD4+ cells from immunized young mice suggests the CD4+ cell dysfunction contributes to the insufficiency of immunoglobulin class switch in aged mice. The transfusion of in vitro expanded lymphocytes could be a potential effective therapy for the age

  8. Geophagy in chacma baboons: patterns of soil consumption by age class, sex, and reproductive state.

    PubMed

    Pebsworth, Paula A; Bardi, Massimo; Huffman, Michael A

    2012-01-01

    Despite baboons' widespread distribution across Africa, geophagy among all subspecies has been poorly documented. We used video camera traps and soil analyses to investigate geophagy in chacma baboons (Papio cynocephalus ursinus) inhabiting the Western Cape of South Africa. During an 18-month study, from August 2009 to January 2011, we continually monitored the largest and most frequently visited geophagy sites with camera traps for 545 days and captured soil consumption at one or more sites on 266 of those days (49%). In 3,500 baboon visits to geophagy sites, video camera traps captured 58.6 hr of geophagy. From these data, we evaluated site preference based on time spent consuming soil among these four geophagy sites. One hundred and seventy days of soil consumption data from the most frequently visited geophagy site allowed us to look for demographic trends in geophagy. Selected consumed soils from geophagy sites were analyzed for mineral, physical, and chemical properties. The baboons spent more time consuming white alkaline soils with high percentages of clay and fine silt, which contained higher concentrations of sodium than non-white acidic soils that contained higher concentrations of iron. Our data indicate that pregnant chacma baboons spent more time consuming soil at monitored geophagy sites than baboons of any other age class, sex, or reproductive state. Based on analytical results, the soils consumed would be effective at alleviating gastrointestinal distress and possibly supplementing minerals for all age/sex classes, but potentially for different age/sex requirements. PMID:21969111

  9. Common structural requirements for heptahelical domain function in class A and class C G protein-coupled receptors.

    PubMed

    Binet, Virginie; Duthey, Béatrice; Lecaillon, Jennifer; Vol, Claire; Quoyer, Julie; Labesse, Gilles; Pin, Jean-Philippe; Prézeau, Laurent

    2007-04-20

    G protein-coupled receptors (GPCRs) are key players in cell communication. Several classes of such receptors have been identified. Although all GPCRs possess a heptahelical domain directly activating G proteins, important structural and sequence differences within receptors from different classes suggested distinct activation mechanisms. Here we show that highly conserved charged residues likely involved in an interaction network between transmembrane domains (TM) 3 and 6 at the cytoplasmic side of class C GPCRs are critical for activation of the gamma-aminobutyric acid type B receptor. Indeed, the loss of function resulting from the mutation of the conserved lysine residue into aspartate or glutamate in the TM3 of gamma-aminobutyric acid type B(2) can be partly rescued by mutating the conserved acidic residue of TM6 into either lysine or arginine. In addition, mutation of the conserved lysine into an acidic residue leads to a nonfunctional receptor that displays a high agonist affinity. This is reminiscent of a similar ionic network that constitutes a lock stabilizing the inactive state of many class A rhodopsin-like GPCRs. These data reveal that despite their original structure, class C GPCRs share with class A receptors at least some common structural feature controlling G protein activation.

  10. Equivalent Structures on Sets: Equivalence Classes, Partitions and Fiber Structures of Functions

    ERIC Educational Resources Information Center

    Hamdan, May

    2006-01-01

    This study reports on how students can be led to make meaningful connections between such structures on a set as a partition, the set of equivalence classes determined by an equivalence relation and the fiber structure of a function on that set (i.e., the set of preimages of all sets {b} for b in the range of the function). In this paper, I first…

  11. Neighborhood Age Structure and Support Networks.

    ERIC Educational Resources Information Center

    Ward, Russell A.; And Others

    Studies conducted in specifically age-segregated housing for older persons suggest that such age-homogeneous settings encourage networks of friendships and mutual assistance. Since patterns of age segregation exist within communities, such segregation may result in similar social benefits. Interviews (N=1,185) assessing social networks were…

  12. Differential Range Use between Age Classes of Southern African Bearded Vultures Gypaetus barbatus

    PubMed Central

    Krüger, Sonja; Reid, Timothy; Amar, Arjun

    2014-01-01

    Bearded Vulture Gypaetus barbatus movements were investigated in southern Africa to determine whether an individual's age, sex or breeding status influenced its ranging behaviour and to provide the information required to guide conservation activities. Data from satellite transmitters fitted to 18 individuals of four age classes were used to determine range size and use. Because of the nature of the movements of marked individuals, these data could be used to determine the overall foraging range of the entire population, which was estimated to be 51 767 km2. Although juvenile, immature and sub-adult birds used different parts of the overall range, their combined foraging range was 65% (33 636 km2) of the overall range. Average adult home ranges (286 km2) were only around 1% the size of the average foraging ranges of non-adults (10 540 –25 985 km2), with those of breeding adults being even smaller (95 km2). Home ranges of breeding adults did not vary in size between seasons but adults utilized their home range more intensively whilst breeding, moving greater distances during the incubation and chick hatching period. Range size and use increased as non-adults aged. Immatures and sub-adults had larger range sizes during winter, but range use of non-adults did not vary seasonally. Range size and use did not differ between the sexes in any of the age classes. Information on home range size and use enables specific areas within the species' range to be targeted for management planning, education and conservation action. PMID:25551614

  13. Differential range use between age classes of southern African Bearded Vultures Gypaetus barbatus.

    PubMed

    Krüger, Sonja; Reid, Timothy; Amar, Arjun

    2014-01-01

    Bearded Vulture Gypaetus barbatus movements were investigated in southern Africa to determine whether an individual's age, sex or breeding status influenced its ranging behaviour and to provide the information required to guide conservation activities. Data from satellite transmitters fitted to 18 individuals of four age classes were used to determine range size and use. Because of the nature of the movements of marked individuals, these data could be used to determine the overall foraging range of the entire population, which was estimated to be 51 767 km(2). Although juvenile, immature and sub-adult birds used different parts of the overall range, their combined foraging range was 65% (33 636 km(2)) of the overall range. Average adult home ranges (286 km(2)) were only around 1% the size of the average foraging ranges of non-adults (10 540 -25 985 km(2)), with those of breeding adults being even smaller (95 km(2)). Home ranges of breeding adults did not vary in size between seasons but adults utilized their home range more intensively whilst breeding, moving greater distances during the incubation and chick hatching period. Range size and use increased as non-adults aged. Immatures and sub-adults had larger range sizes during winter, but range use of non-adults did not vary seasonally. Range size and use did not differ between the sexes in any of the age classes. Information on home range size and use enables specific areas within the species' range to be targeted for management planning, education and conservation action. PMID:25551614

  14. Differential range use between age classes of southern African Bearded Vultures Gypaetus barbatus.

    PubMed

    Krüger, Sonja; Reid, Timothy; Amar, Arjun

    2014-01-01

    Bearded Vulture Gypaetus barbatus movements were investigated in southern Africa to determine whether an individual's age, sex or breeding status influenced its ranging behaviour and to provide the information required to guide conservation activities. Data from satellite transmitters fitted to 18 individuals of four age classes were used to determine range size and use. Because of the nature of the movements of marked individuals, these data could be used to determine the overall foraging range of the entire population, which was estimated to be 51 767 km(2). Although juvenile, immature and sub-adult birds used different parts of the overall range, their combined foraging range was 65% (33 636 km(2)) of the overall range. Average adult home ranges (286 km(2)) were only around 1% the size of the average foraging ranges of non-adults (10 540 -25 985 km(2)), with those of breeding adults being even smaller (95 km(2)). Home ranges of breeding adults did not vary in size between seasons but adults utilized their home range more intensively whilst breeding, moving greater distances during the incubation and chick hatching period. Range size and use increased as non-adults aged. Immatures and sub-adults had larger range sizes during winter, but range use of non-adults did not vary seasonally. Range size and use did not differ between the sexes in any of the age classes. Information on home range size and use enables specific areas within the species' range to be targeted for management planning, education and conservation action.

  15. The Impact of Ignoring the Level of Nesting Structure in Nonparametric Multilevel Latent Class Models

    ERIC Educational Resources Information Center

    Park, Jungkyu; Yu, Hsiu-Ting

    2016-01-01

    The multilevel latent class model (MLCM) is a multilevel extension of a latent class model (LCM) that is used to analyze nested structure data structure. The nonparametric version of an MLCM assumes a discrete latent variable at a higher-level nesting structure to account for the dependency among observations nested within a higher-level unit. In…

  16. Normative and Structural Perspectives on Age in a Work Organization.

    ERIC Educational Resources Information Center

    Lawrence, Barbara S.

    Age grading, the differentiation of social groups by members' age judgments, is widely regarded to be a universal aspect of social life. Most studies have examined age structurally (demographically), rather than normatively (modally). This study presents survey data measuring employees' age judgments of managerial careers collected from an…

  17. Multiple endemic states in age-structured SIR epidemic models.

    PubMed

    Franceschetti, Andrea; Pugliese, Andrea; Breda, Dmitri

    2012-07-01

    SIR age-structured models are very often used as a basic model of epidemic spread. Yet, their behaviour, under generic assumptions on contact rates between different age classes, is not completely known, and, in the most detailed analysis so far, Inaba (1990) was able to prove uniqueness of the endemic equilibrium only under a rather restrictive condition. Here, we show an example in the form of a 3x3 contact matrix in which multiple non-trivial steady states exist. This instance of non-uniqueness of positive equilibria differs from most existing ones for epidemic models, since it arises not from a backward transcritical bifurcation at the disease free equilibrium, but through two saddle-node bifurcations of the positive equilibrium. The dynamical behaviour of the model is analysed numerically around the range where multiple endemic equilibria exist; many other features are shown to occur, from coexistence of multiple attractive periodic solutions, some with extremely long period, to quasi-periodic and chaotic attractors. It is also shown that, if the contact rates are in the form of a 2x2 WAIFW matrix, uniqueness of non-trivial steady states always holds, so that 3 is the minimum dimension of the contact matrix to allow for multiple endemic equilibria.

  18. Structural, Functional, and Taxonomic Diversity of Three PreQ1 Riboswitch Classes

    PubMed Central

    Weinberg, Zasha; Breaker, Ronald R.

    2014-01-01

    SUMMARY Previously, two riboswitch classes have been identified that sense and respond to the hypermodified nucleobase called pre-queuosine1 (preQ1). The enormous expansion of available genomic DNA sequence data creates new opportunities to identify additional representatives of the known riboswitch classes and to discover novel classes. We conducted bioinformatics searches on microbial genomic DNA datasets to discover numerous additional examples belonging to the two previously known riboswitch classes for preQ1 (classes preQ1-I and preQ1-II), including some structural variants that further restrict ligand specificity. Additionally, we discovered a third preQ1-binding riboswitch class (preQ1-III) that is structurally distinct from previously known classes. These findings demonstrate that numerous organisms monitor the concentrations of this modified nucleobase by exploiting one or more riboswitch classes for this widespread compound. PMID:25036777

  19. Age Differences Explain Social Class Differences in Students' Friendship at University: Implications for Transition and Retention

    ERIC Educational Resources Information Center

    Rubin, Mark; Wright, Chrysalis L.

    2015-01-01

    The present research tested the hypotheses that (a) working-class students have fewer friends at university than middle-class students and (b) this social class difference occurs because working-class students tend to be older than middle-class students. A sample of 376 first-year undergraduate students from an Australian university completed an…

  20. Rigor and academic achievement: Career academies versus traditional class structure

    NASA Astrophysics Data System (ADS)

    Kyees, Linda L.

    The purpose of this study was to determine if students who attended high school Career Academy classes, as part of Career and Technical Education, showed greater academic achievement than students who attended traditional high school classes. While all participants attended schools in the same school district, and were seeking the same goal of graduation with a standard diploma, the Career Academy students had the benefit of all classes being directed by a team of teachers who helped them connect their learning to their desired career through collaborative learning projects and assignments. The traditional high school classes taught each subject independent of other subjects and did not have specific connections to desired career goals of the students. The study used a causal-comparative research design and the participants included 1,142 students from 11th and 12th grades who attended 9 high schools in a diversely populated area of central Florida with 571 enrolled in the Career Academies and 571 enrolled in traditional classes. The 10th-grade FCAT scores served as the dependent variable. All students attended similar classes with similar content, making the primary variable the difference in academic gains between students participating in the Career Academy design and the traditional design classes. Using the Man-Whitney U Test resulted in the Career Academy group achieving the higher scores overall. This resulted in rejection of the first null-hypothesis. Further examination determined that the 10th-grade FCAT scores were greater for the average students group, which comprised the largest portion of the participant group, also resulted in rejection of the second null-hypothesis. The gifted and at-risk student group scores resulted in failure to reject the third and fourth null-hypotheses.

  1. Aging IQ Intervention with Older Korean Americans: A Comparison of Internet-Based and In-Class Education

    ERIC Educational Resources Information Center

    Jang, Yuri; Yoon, Hyunwoo; Marti, C. Nathan; Kim, Miyong T.

    2015-01-01

    Using the translated contents of the National Institute on Aging (NIA)'s Aging IQ, an educational intervention was delivered to older Korean Americans. The educational program was delivered via two different modalities, Internet-based education (n = 12) and in-class education (n = 11), and the overall feasibility and efficacy were evaluated by the…

  2. Spatio-Temporal Variation in Age Structure and Abundance of the Endangered Snail Kite: Pooling across Regions Masks a Declining and Aging Population

    PubMed Central

    Kendall, William L.; Fletcher, Robert J.; Kitchens, Wiley M.

    2016-01-01

    While variation in age structure over time and space has long been considered important for population dynamics and conservation, reliable estimates of such spatio-temporal variation in age structure have been elusive for wild vertebrate populations. This limitation has arisen because of problems of imperfect detection, the potential for temporary emigration impacting assessments of age structure, and limited information on age. However, identifying patterns in age structure is important for making reliable predictions of both short- and long-term dynamics of populations of conservation concern. Using a multistate superpopulation estimator, we estimated region-specific abundance and age structure (the proportion of individuals within each age class) of a highly endangered population of snail kites for two separate regions in Florida over 17 years (1997–2013). We find that in the southern region of the snail kite—a region known to be critical for the long-term persistence of the species—the population has declined significantly since 1997, and during this time, it has increasingly become dominated by older snail kites (> 12 years old). In contrast, in the northern region—a region historically thought to serve primarily as drought refugia—the population has increased significantly since 2007 and age structure is more evenly distributed among age classes. Given that snail kites show senescence at approximately 13 years of age, where individuals suffer higher mortality rates and lower breeding rates, these results reveal an alarming trend for the southern region. Our work illustrates the importance of accounting for spatial structure when assessing changes in abundance and age distribution and the need for monitoring of age structure in imperiled species. PMID:27681854

  3. 33 CFR 67.20-1 - Class “A” structures.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Class âAâ structures. 67.20-1 Section 67.20-1 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY AIDS TO NAVIGATION AIDS TO NAVIGATION ON ARTIFICIAL ISLANDS AND FIXED STRUCTURES Class âAâ Requirements §...

  4. 33 CFR 67.30-1 - Class “C” structures.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Class âCâ structures. 67.30-1 Section 67.30-1 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY AIDS TO NAVIGATION AIDS TO NAVIGATION ON ARTIFICIAL ISLANDS AND FIXED STRUCTURES Class âCâ Requirements §...

  5. 33 CFR 67.25-1 - Class “B” structures.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Class âBâ structures. 67.25-1 Section 67.25-1 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY AIDS TO NAVIGATION AIDS TO NAVIGATION ON ARTIFICIAL ISLANDS AND FIXED STRUCTURES Class âBâ Requirements §...

  6. Evolution of a plastic quantitative trait in an age-structured population in a fluctuating environment.

    PubMed

    Engen, Steinar; Lande, Russell; Saether, Bernt-Erik

    2011-10-01

    We analyze weak fluctuating selection on a quantitative character in an age-structured population not subject to density regulation. We assume that early in the first year of life before selection, during a critical state of development, environments exert a plastic effect on the phenotype, which remains constant throughout the life of an individual. Age-specific selection on the character affects survival and fecundity, which have intermediate optima subject to temporal environmental fluctuations with directional selection in some age classes as special cases. Weighting individuals by their reproductive value, as suggested by Fisher, we show that the expected response per year in the weighted mean character has the same form as for models with no age structure. Environmental stochasticity generates stochastic fluctuations in the weighted mean character following a first-order autoregressive model with a temporally autocorrelated noise term and stationary variance depending on the amount of phenotypic plasticity. The parameters of the process are simple weighted averages of parameters used to describe age-specific survival and fecundity. The "age-specific selective weights" are related to the stable distribution of reproductive values among age classes. This allows partitioning of the change in the weighted mean character into age-specific components.

  7. Middle-Class Mythology in an Age of Immigration and Segmented Assimilation: Implication for Counseling Psychology

    ERIC Educational Resources Information Center

    Lee, Richard M.; Dean, Brooke L.

    2004-01-01

    W. M. Liu, S. R. Ali, et al. (2004) provide a useful framework to understand the relevance of social class to counseling psychology research, but they overlook the intersection of race and social class in their review. The authors critique the middle-class mythology that pervades social class research in psychology and introduce segmented…

  8. Choosing Colleges. How Social Class and Schools Structure Opportunity.

    ERIC Educational Resources Information Center

    McDonough, Patricia M.

    This study examines the ways in which social class and high school guidance operations combine to shape a high school student's perceptions of her opportunities for a college education. It is also an analysis of the intersection of family, friends, and school network effects and how they create an individual's biography. Students connect with…

  9. Crystal structure of cod liver class I alcohol dehydrogenase: substrate pocket and structurally variable segments.

    PubMed Central

    Ramaswamy, S.; el Ahmad, M.; Danielsson, O.; Jörnvall, H.; Eklund, H.

    1996-01-01

    The structural framework of cod liver alcohol dehydrogenase is similar to that of horse and human alcohol dehydrogenases. In contrast, the substrate pocket differs significantly, and main differences are located in three loops. Nevertheless, the substrate pocket is hydrophobic like that of the mammalian class I enzymes and has a similar topography in spite of many main-chain and side-chain differences. The structural framework of alcohol dehydrogenase is also present in a number of related enzymes like glucose dehydrogenase and quinone oxidoreductase. These enzymes have completely different substrate specificity, but also for these enzymes, the corresponding loops of the substrate pocket have significantly different structures. The domains of the two subunits in the crystals of the cod enzyme further differ by a rotation of the catalytic domains by about 6 degrees. In one subunit, they close around the coenzyme similarly as in coenzyme complexes of the horse enzyme, but form a more open cleft in the other subunit, similar to the situation in coenzyme-free structures of the horse enzyme. The proton relay system differs from the mammalian class I alcohol dehydrogenases. His 51, which has been implicated in mammalian enzymes to be important for proton transfer from the buried active site to the surface is not present in the cod enzyme. A tyrosine in the corresponding position is turned into the substrate pocket and a water molecule occupies the same position in space as the His side chain, forming a shorter proton relay system. PMID:8845755

  10. Body build classes as a method for systematization of age-related anthropometric changes in girls aged 7-8 and 17-18 years.

    PubMed

    Kasmel, Jaan; Kaarma, Helje; Koskel, Säde; Tiit, Ene-Margit

    2004-03-01

    A total of 462 schoolgirls aged 7-8 and 17-18 years were examined anthropometrically (45 body measurements and 10 skinfolds) in a cross-sectional study. The data were processed in two age groups: 7-8-year-olds (n = 205) and 17-18-year-olds (n = 257). Relying on average height and weight in the groups, both groups were divided into five body build classes: small, medium, large, pyknomorphous and leptomorphous. In these classes, the differences in all other body measurements were compared, and in both age groups, analogous systematic differences were found in length, width and depth measurements and circumferences. This enabled us to compare proportional changes in body measurements during ten years, using for this ratios of averages of basic measurements and measurement groups in the same body build classes. Statistical analysis by the sign test revealed statistically significant differences between various body build classes in the growth of averages. Girls belonging to the small class differed from the girls of the large class by an essentially greater increase in their measurements. Our results suggest that the growth rate of body measurements of girls with different body build can be studied by the help of body build classification.

  11. Class Anxiety in Secondary Education: Exploring Structural Relations with Perceived Control, Engagement, Disaffection, and Performance.

    PubMed

    González, Antonio; Faílde Garrido, José María; Rodríguez Castro, Yolanda; Carrera Rodríguez, María Victoria

    2015-09-14

    The aim of this study was to assess the relationships between class-related anxiety with perceived control, teacher-reported behavioral engagement, behavioral disaffection, and academic performance. Participants were 355 compulsory secondary students (9th and 10th grades; Mean age = 15.2 years; SD = 1.8 years). Structural equation models revealed performance was predicted by perceived control, anxiety, disaffection, and engagement. Perceived control predicted anxiety, disaffection, and engagement. Anxiety predicted disaffection and engagement, and partially mediated the effects from control on disaffection (β = -.277, p < .005; CI = -.378, -.197) and engagement (β = .170, p < .002; CI = .103 .258). The negative association between anxiety and performance was mediated by engagement and disaffection (β = -.295, p < .002; CI = -.439, -.182). Anxiety, engagement, and disaffection mediated the effects of control on performance (β = .352, p < .003; CI = .279, .440). The implications of these results are discussed in the light of current theory and educational interventions.

  12. Structural aging program -- a summary of activities, results, and conclusions

    SciTech Connect

    Naus, D.J.; Oland, C.B.; Ellingwood, B.R.

    1997-01-01

    Research has been conducted by the Oak Ridge National Laboratory to address aging management of nuclear power plant concrete structures. The purpose was to identify potential structural safety issues and acceptance criteria for use in continued service assessments. Primary program accomplishments have included formulation of a Structural Materials Information Center that contains data and information on the time variation of material properties under the influence of pertinent environmental stressors and aging factors for 144 materials, an aging assessment methodology to identify critical structures and degradation factors that can potentially impact their performance, guidelines and evaluation criteria for use in condition assessments of reinforced concrete structures, and a reliability-based methodology for current condition assessments and estimations of future performance of reinforced concrete nuclear power plant structures. In addition, the Structural Aging Program conducted in-depth evaluations of several nondestructive evaluation and repair-related technologies to develop guidance on their applicability.

  13. Lipid composition of the Antarctic fish Pleuragramma antarcticum. Influence of age class

    NASA Astrophysics Data System (ADS)

    Mayzaud, P.; Chevallier, J.; Tavernier, E.; Moteki, M.; Koubbi, P.

    2011-08-01

    Larvae and juvenile stages of Pleuragramma antarcticum have been collected in the Dumont D’Urville Sea (East Antarctica) during summer 2008 on board the TRV Umitaka Maru during the CEAMARC survey. Detailed analyses of their lipid class and fatty acid compositions were carried out. P. antarcticum showed a pronounced ontogenic lipid accumulation with increasing size. Larvae displayed a dominance of polar lipids (83% of total lipids) and low percentage of triglycerides (7%). Conversely juveniles showed an increasing accumulation of triglycerides (up to 72.4%). The fatty acid composition of polar lipids remained rather stable between stages with 22:6n-3 and 20:5n-3 as dominant contributors. The relatively minor ontogenic changes, e.g. increase of monounsaturated and decrease of C18 polyunsaturated fatty acids, may reflect the influence of differences in diet. Triglycerides showed that all three age classes are well segregated in term of fatty acid composition. Larvae triglycerides are characterized by significant percentages of 16:0, 20:5n-3, 20:6n-3 and to a minor extent 18:4n-3, which suggest a prymnesiophyte based diet. Juveniles are characterized by larger percentages of C20:1 and C22:1 acids, considered as markers of Calanus type copepods. The increasing contribution of 18:1n-9 in the triglycerides of the older juveniles suggests a gradual and increasing shift from a copepod dominant diet to an euphausiid dominant diet. Fatty acid trophic markers pattern suggests a shift from a phytophagous and omnivorous diet for larvae to a carnivorous diet for juveniles.

  14. The effect of small class sizes on mortality through age 29 years: evidence from a multicenter randomized controlled trial.

    PubMed

    Muennig, Peter; Johnson, Gretchen; Wilde, Elizabeth Ty

    2011-06-15

    Limiting the number of students per classroom in the early years has been shown to improve educational outcomes. Improved education is, in turn, hypothesized to improve health. The authors examined whether smaller class sizes affect mortality through age 29 years and whether cognitive factors play a role. They used data from the Project Student Teacher Achievement Ratio, a 4-year multicenter randomized controlled trial of reduced class sizes in Tennessee involving 11,601 students between 1985 and 1989. Children randomized to small classes (13-17 students) experienced improved measures of cognition and academic performance relative to those assigned to regular classes (22-25 students). As expected, these cognitive measures were significantly inversely associated with mortality rates (P < 0.05). However, through age 29 years, students randomized to small class size nevertheless experienced higher mortality rates than those randomized to regular size classes (hazard ratio (HR) = 1.58, 95% confidence interval (CI): 1.07, 2.32). The groups at risk included males (HR = 1.73, 95% CI: 1.05, 2.85), whites/Asians (HR = 1.68, 95% CI: 1.04, 2.72), and higher income students (HR = 2.20, 95% CI: 1.06, 4.57). The authors speculate that small classes might produce behavior changes that increase mortality through young adulthood that are stronger than the protective effects of enhanced cognition. PMID:21540326

  15. The effect of small class sizes on mortality through age 29 years: evidence from a multicenter randomized controlled trial.

    PubMed

    Muennig, Peter; Johnson, Gretchen; Wilde, Elizabeth Ty

    2011-06-15

    Limiting the number of students per classroom in the early years has been shown to improve educational outcomes. Improved education is, in turn, hypothesized to improve health. The authors examined whether smaller class sizes affect mortality through age 29 years and whether cognitive factors play a role. They used data from the Project Student Teacher Achievement Ratio, a 4-year multicenter randomized controlled trial of reduced class sizes in Tennessee involving 11,601 students between 1985 and 1989. Children randomized to small classes (13-17 students) experienced improved measures of cognition and academic performance relative to those assigned to regular classes (22-25 students). As expected, these cognitive measures were significantly inversely associated with mortality rates (P < 0.05). However, through age 29 years, students randomized to small class size nevertheless experienced higher mortality rates than those randomized to regular size classes (hazard ratio (HR) = 1.58, 95% confidence interval (CI): 1.07, 2.32). The groups at risk included males (HR = 1.73, 95% CI: 1.05, 2.85), whites/Asians (HR = 1.68, 95% CI: 1.04, 2.72), and higher income students (HR = 2.20, 95% CI: 1.06, 4.57). The authors speculate that small classes might produce behavior changes that increase mortality through young adulthood that are stronger than the protective effects of enhanced cognition.

  16. Nuclear Structure Data for the Present Age

    NASA Astrophysics Data System (ADS)

    Baglin, Coral M.

    2005-05-01

    The US Nuclear Data Program maintains and provides easy and free access to several comprehensive databases that assist scientists to sift through and assess the vast quantity of published nuclear structure and decay data. These databases are an invaluable asset for nuclear-science experimentalists and theorists alike, and the recommended values provided for nuclear properties such as decay modes, level energies and lifetimes, and radiation properties can also be of great importance to specialists in other fields such as medicine, geophysics, and reactor design. The Evaluated Nuclear Structure Data File (ENSDF) contains experimental nuclear structure data for all known nuclides, evaluated by the US nuclear data program evaluators in collaboration with a number of international data groups; the Nuclear Science Reference (NSR) database provides complementary bibliographic information; the Experimental Unevaluated Nuclear Data Listing (XUNDL) exists to enable rapid access to experimental nuclear-structure data compiled from the most recent publications (primarily in high-spin physics). This paper presents an overview of the nuclear structure and decay data available through these databases, with emphasis on recent and forthcoming additions to and presentations of the available material.

  17. Size, longevity and cancer: age structure

    PubMed Central

    2016-01-01

    There is significant recent interest in Peto's paradox and the related problem of the evolution of large, long-lived organisms in terms of cancer robustness. Peto's paradox refers to the expectation that large, long-lived organisms have a higher lifetime cancer risk, which is not the case: a paradox. This paradox, however, is circular: large, long-lived organisms are large and long-lived because they are cancer robust. Lifetime risk, meanwhile, depends on the age distributions of both cancer and competing risks: if cancer strikes before competing risks, then lifetime risk is high; if not, not. Because no set of competing risks is generally prevalent, it is instructive to temporarily dispose of competing risks and investigate the pure age dynamics of cancer under the multistage model of carcinogenesis. In addition to augmenting earlier results, I show that in terms of cancer-free lifespan large organisms reap greater benefits from an increase in cellular cancer robustness than smaller organisms. Conversely, a higher cellular cancer robustness renders cancer-free lifespan more resilient to an increase in size. This interaction may be an important driver of the evolution of large, cancer-robust organisms. PMID:27629030

  18. Size, longevity and cancer: age structure.

    PubMed

    Wensink, Maarten J

    2016-09-14

    There is significant recent interest in Peto's paradox and the related problem of the evolution of large, long-lived organisms in terms of cancer robustness. Peto's paradox refers to the expectation that large, long-lived organisms have a higher lifetime cancer risk, which is not the case: a paradox. This paradox, however, is circular: large, long-lived organisms are large and long-lived because they are cancer robust. Lifetime risk, meanwhile, depends on the age distributions of both cancer and competing risks: if cancer strikes before competing risks, then lifetime risk is high; if not, not. Because no set of competing risks is generally prevalent, it is instructive to temporarily dispose of competing risks and investigate the pure age dynamics of cancer under the multistage model of carcinogenesis. In addition to augmenting earlier results, I show that in terms of cancer-free lifespan large organisms reap greater benefits from an increase in cellular cancer robustness than smaller organisms. Conversely, a higher cellular cancer robustness renders cancer-free lifespan more resilient to an increase in size. This interaction may be an important driver of the evolution of large, cancer-robust organisms. PMID:27629030

  19. Evaluation of aging degradation of structural components

    SciTech Connect

    Chopra, O.K.; Shack, W.J.

    1992-03-01

    Irradiation embrittlement of the neutron shield tank (NST) A212 Grade B steel from the Shippingport reactor, as well as thermal embrittlement of CF-8 cast stainless steel components from the Shippingport and KRB reactors, has been characterized. Increases in Charpy transition temperature (CTT), yield stress, and hardness of the NST material in the low-temperature low-flux environment are consistent with the test reactor data for irradiations at < 232{degrees}C. The shift in CTT is not as severe as that observed in surveillance samples from the High Flux Isotope Reactor (HFIR): however, it shows very good agreement with the results for HFIR A212-B steel irradiated in the Oak Ridge Research Reactor. The results indicate that fluence rate has not effect on radiation embrittlement at rates as low as 2 {times} 10{sup 8} n/cm{sup 2}{center_dot}s at the low operating temperature of the Shippingport NST, i.e., 55{degrees}C. This suggest that radiation damage in Shippingport NST and HFIR surveillance samples may be different because of the neutron spectra and/or Cu and Ni content of the two materials. Cast stainless steel components show relatively modest decreases in fracture toughness and Charpy-impact properties and a small increase in tensile strength. Correlations for estimating mechanical properties of cast stainless steels predict accurate or slightly conservative values for Charpy-impact energy, tensile flow stress, fracture toughness J-R curve, and J{sub IC} of the materials. The kinetics of thermal embrittlement and degree of embrittlement at saturation, i.e., the minimum impact energy achieved after long-term aging, were established from materials that were aged further in the laboratory. The results were consistent with the estimates. The correlations successfully predict the mechanical properties of the Ringhals 2 reactor hot- and crossover-leg elbows (CF-8M steel) after service of {approx}15 y.

  20. Evaluation of aging degradation of structural components

    SciTech Connect

    Chopra, O.K.; Shack, W.J.

    1992-03-01

    Irradiation embrittlement of the neutron shield tank (NST) A212 Grade B steel from the Shippingport reactor, as well as thermal embrittlement of CF-8 cast stainless steel components from the Shippingport and KRB reactors, has been characterized. Increases in Charpy transition temperature (CTT), yield stress, and hardness of the NST material in the low-temperature low-flux environment are consistent with the test reactor data for irradiations at < 232{degrees}C. The shift in CTT is not as severe as that observed in surveillance samples from the High Flux Isotope Reactor (HFIR): however, it shows very good agreement with the results for HFIR A212-B steel irradiated in the Oak Ridge Research Reactor. The results indicate that fluence rate has not effect on radiation embrittlement at rates as low as 2 {times} 10{sup 8} n/cm{sup 2}{center dot}s at the low operating temperature of the Shippingport NST, i.e., 55{degrees}C. This suggest that radiation damage in Shippingport NST and HFIR surveillance samples may be different because of the neutron spectra and/or Cu and Ni content of the two materials. Cast stainless steel components show relatively modest decreases in fracture toughness and Charpy-impact properties and a small increase in tensile strength. Correlations for estimating mechanical properties of cast stainless steels predict accurate or slightly conservative values for Charpy-impact energy, tensile flow stress, fracture toughness J-R curve, and J{sub IC} of the materials. The kinetics of thermal embrittlement and degree of embrittlement at saturation, i.e., the minimum impact energy achieved after long-term aging, were established from materials that were aged further in the laboratory. The results were consistent with the estimates. The correlations successfully predict the mechanical properties of the Ringhals 2 reactor hot- and crossover-leg elbows (CF-8M steel) after service of {approx}15 y.

  1. Measurement and Structural Model Class Separation in Mixture CFA: ML/EM versus MCMC

    ERIC Educational Resources Information Center

    Depaoli, Sarah

    2012-01-01

    Parameter recovery was assessed within mixture confirmatory factor analysis across multiple estimator conditions under different simulated levels of mixture class separation. Mixture class separation was defined in the measurement model (through factor loadings) and the structural model (through factor variances). Maximum likelihood (ML) via the…

  2. 49 CFR 176.172 - Structural serviceability of freight containers and vehicles carrying Class 1 (explosive...

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 2 2013-10-01 2013-10-01 false Structural serviceability of freight containers... serviceability of freight containers and vehicles carrying Class 1 (explosive) materials on ships. (a) Except for Division 1.4 materials, a freight container may not be offered for the carriage of Class 1...

  3. 49 CFR 176.172 - Structural serviceability of freight containers and vehicles carrying Class 1 (explosive...

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 2 2012-10-01 2012-10-01 false Structural serviceability of freight containers... serviceability of freight containers and vehicles carrying Class 1 (explosive) materials on ships. (a) Except for Division 1.4 materials, a freight container may not be offered for the carriage of Class 1...

  4. 49 CFR 176.172 - Structural serviceability of freight containers and vehicles carrying Class 1 (explosive...

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 2 2014-10-01 2014-10-01 false Structural serviceability of freight containers... serviceability of freight containers and vehicles carrying Class 1 (explosive) materials on ships. (a) Except for Division 1.4 materials, a freight container may not be offered for the carriage of Class 1...

  5. The Relationship between Professional Preparation and Class Structure on Health Instruction in the Secondary Classroom

    ERIC Educational Resources Information Center

    Hammig, Bart; Ogletree, Roberta; Wycoff-Horn, Marcie R.

    2011-01-01

    Background: The aim of the present study was to examine the impact of professional preparation and class structure on health content delivery and time spent delivering content among required health education classes in the United States. Methods: Data from the classroom-level file of the 2006 School Health Policies and Programs Study were…

  6. Influence of Professional Preparation and Class Structure on Sexuality Topics Taught in Middle and High Schools

    ERIC Educational Resources Information Center

    Rhodes, Darson L.; Kirchofer, Gregg; Hammig, Bart J.; Ogletree, Roberta J.

    2013-01-01

    Background: This study examined the impact of professional preparation and class structure on sexuality topics taught and use of practice-based instructional strategies in US middle and high school health classes. Methods: Data from the classroom-level file of the 2006 School Health Policies and Programs were used. A series of multivariable…

  7. Undergraduates Improve upon Published Crystal Structure in Class Assignment

    ERIC Educational Resources Information Center

    Horowitz, Scott; Koldewey, Philipp; Bardwell, James C.

    2014-01-01

    Recently, 57 undergraduate students at the University of Michigan were assigned the task of solving a crystal structure, given only the electron density map of a 1.3 Å crystal structure from the electron density server, and the position of the N-terminal amino acid. To test their knowledge of amino acid chemistry, the students were not given the…

  8. Communication Breakdown: The Impact of Ageing on Synapse Structure

    PubMed Central

    Petralia, Ronald S.; Mattson, Mark P.; Yao, Pamela J.

    2014-01-01

    Impaired synaptic plasticity is implicated in the functional decline of the nervous system associated with ageing. Understanding the structure of ageing synapses is essential to understanding the functions of these synapses and their role in the ageing nervous system. In this review, we summarize studies on ageing synapses in vertebrates and invertebrates, focusing on changes in morphology and ultrastructure. We cover different parts of the nervous system, including the brain, the retina, the cochlea, and the neuromuscular junction. The morphological characteristics of aged synapses could shed light on the underlying molecular changes and their functional consequences. PMID:24495392

  9. The age structure of selected countries in the ESCAP region.

    PubMed

    Hong, S

    1982-01-01

    The study objective was to examine the age structure of selected countries in the Economic and Social Commission for Asia and the Pacific (ESCAP) region, using available data and frequently applied indices such as the population pyramid, aged-child ratio, and median age. Based on the overall picture of the age structure thus obtained, age trends and their implication for the near future were arrived at. Countries are grouped into 4 types based on the fertility and mortality levels. Except for Japan, Hong Kong, and Singapore, the age structure in the 18 ESCAP region countries changed comparatively little over the 1950-80 period. The largest structural change occurred in Singapore, where the proportion of children under age 15 in the population declined significantly from 41-27%, while that of persons 65 years and older more than doubled. This was due primarily to the marked decline in fertility from a total fertility rate (TFR) of 6.7-1.8 during the period. Hong Kong also had a similar major transformation during the same period: the proportion of the old age population increased 2 1/2 times, from 2.5-6.3%. The age structures of the 18 ESCAP countries varied greatly by country. 10 countries of the 2 high fertility and mortality types showed a similar young age structural pattern, i.e., they have higher dependency ratios, a higher proportion of children under 15 years, a lower proportion of population 65 years and older, lower aged-child ratios, and younger median ages than the average countries in the less developed regions of the world. With minimal changes over the 1950-80 period, the gap between these countries and the average of the less developed regions widened. Unlike these 10 (mostly South Asian) countries, moderately low fertility and mortality countries (China, Korea, and Sri Lanka) are located between the world average and the less developed region in most of the indices, particularly during the last decade. Although their rate of population aging is not

  10. Age class differences in the feeding behavior of captive Japanese macaques (Macaca fuscataia) in the forested and nonvegetated enclosure groups.

    PubMed

    Jaman, M Firoj; Huffman, Michael A

    2011-01-01

    Age class differences in feeding behavior of primates are affected by many factors, including feeding competition, foraging skills, habitat type, food abundance and distribution, body mass, and food types. Two captive groups of Japanese macaques (Macaca fuscata), one housed in a forested enclosure and the other in a nonvegetated enclosure, were studied to examine the effect of environmental enrichment on age class differences in feeding behavior. Although there was no significant age class difference in time spent feeding on provisioned foods in either enclosure, the feeding rate (intake of unit food/minute) of adults consuming provisioned monkey chow was significantly higher than that of immatures in both enclosures, and was faster for both age groups in the nonvegetated than in the forested enclosure. Overall, feeding time was greatly extended for individuals of both age classes in the forested enclosure compared with their counterparts in the nonvegetated enclosure. Immatures in the forested enclosure utilized a significantly greater number of plant species and food items, exploiting many food items available among the terminal branches, and spent significantly more time feeding than adults. Perhaps constrained by larger body size, adults fed more often on the ground or middle height of the trees, likely reducing competition over plant food resources between adults and immatures. The natural vegetation played an important role in extending feeding time and segregating substrate use during feeding by adults and immatures. This study revealed the benefits concerning environmental enrichment of a naturally forested enclosure, which provides captive primates the opportunity to exhibit age class and species-typical feeding behaviors of importance for their dietary maintenance and general health.

  11. Age, occupational class and sickness absence during pregnancy: a retrospective analysis study of the Norwegian population registry

    PubMed Central

    Ariansen, Anja M S

    2014-01-01

    Objective Western women increasingly delay having children to advance their career, and pregnancy is considered to be riskier among older women. In Norway, this development surprisingly coincides with increased sickness absence among young pregnant women, rather than their older counterparts. This paper tests the hypothesis that young pregnant women have a higher number of sick days because this age group includes a higher proportion of working class women, who are more prone to sickness absence. Design A zero-inflated Poisson regression was conducted on the Norwegian population registry. Participants All pregnant employees giving birth in 2004–2008 were included in the study. A total number of 216 541 pregnancies were observed among 180 483 women. Outcome measure Number of sick days. Results Although the association between age and number of sick days was U-shaped, pregnant women in their early 20s had a higher number of sick days than those in their mid-40s. This was particularly the case for pregnant women with previous births. In this group, 20-year-olds had 12.6 more sick days than 45-year-olds; this age difference was reduced to 6.3 after control for class. Among women undergoing their first pregnancy, 20-year-olds initially had 1.2 more sick days than 45-year-olds, but control for class altered this age difference. After control for class, 45-year-old first-time pregnant women had 2.9 more sick days than 20-year-olds with corresponding characteristics. Conclusions The negative association between age and sickness absence was partly due to younger age groups including more working class women, who were more prone to sickness absence. Young pregnant women's needs for job adjustments should not be underestimated. PMID:24793246

  12. Mammalian class IV alcohol dehydrogenase (stomach alcohol dehydrogenase): structure, origin, and correlation with enzymology.

    PubMed Central

    Parés, X; Cederlund, E; Moreno, A; Hjelmqvist, L; Farrés, J; Jörnvall, H

    1994-01-01

    The structure of a mammalian class IV alcohol dehydrogenase has been determined by peptide analysis of the protein isolated from rat stomach. The structure indicates that the enzyme constitutes a separate alcohol dehydrogenase class, in agreement with the distinct enzymatic properties; the class IV enzyme is somewhat closer to class I (the "classical" liver alcohol dehydrogenase; approximately 68% residue identities) than to the other classes (II, III, and V; approximately 60% residue identities), suggesting that class IV might have originated through duplication of an early vertebrate class I gene. The activity of the class IV protein toward ethanol is even higher than that of the classical liver enzyme. Both Km and kcat values are high, the latter being the highest of any class characterized so far. Structurally, these properties are correlated with replacements at the active site, affecting both substrate and coenzyme binding. In particular, Ala-294 (instead of valine) results in increased space in the middle section of the substrate cleft, Gly-47 (instead of a basic residue) results in decreased charge interactions with the coenzyme pyrophosphate, and Tyr-363 (instead of a basic residue) may also affect coenzyme binding. In combination, these exchanges are compatible with a promotion of the off dissociation and an increased turnover rate. In contrast, residues at the inner part of the substrate cleft are bulky, accounting for low activity toward secondary alcohols and cyclohexanol. Exchanges at positions 259-261 involve minor shifts in glycine residues at a reverse turn in the coenzyme-binding fold. Clearly, class IV is distinct in structure, ethanol turnover, stomach expression, and possible emergence from class I. PMID:8127901

  13. Structural insights into ligand recognition and selectivity for class A, B, and C GPCRs

    PubMed Central

    Lee, Sang-Min; Booe, Jason M.; Pioszak, Augen A.

    2015-01-01

    The G protein-coupled receptor (GPCR) superfamily constitutes the largest collection of cell surface signaling proteins with approximately 800 members in the human genome. GPCRs regulate virtually all aspects of physiology and they are an important class of drug targets with ~30% of drugs on the market targeting a GPCR. Breakthroughs in GPCR structural biology in recent years have significantly expanded our understanding of GPCR structure and function and ushered in a new era of structure-based drug design for GPCRs. Crystal structures for nearly thirty distinct GPCRs are now available including receptors from each of the major classes, A, B, C, and F. These structures provide a foundation for understanding the molecular basis of GPCR pharmacology. Here, we review structural mechanisms of ligand recognition and selectivity of GPCRs with a focus on selected examples from classes A, B, and C, and we highlight major unresolved questions for future structural studies. PMID:25981303

  14. Effects of age and sex on the structural, chemical and technological characteristics of mule duck meat.

    PubMed

    Baeza, E; Salichon, M R; Marche, G; Wacrenier, N; Dominguez, B; Culioli, J

    2000-07-01

    1. The aim of the study was to analyse the effect of age and sex on the chemical, structural and technological characteristics of mule duck meat. 2. Ten males and 10 females were weighed and slaughtered at 8, 10, 11, 12 and 13 weeks of age. Weight, pH value, colour, tenderness and juice loss of breast muscle were determined. 3. The activities of 3 enzymes (citrate synthase, beta-hydroxyacyl CoA dehydrogenase, lactate dehydrogenase) which indicate muscular metabolic activity were assayed. 4. Chemical composition (moisture, lipids, proteins, minerals, lipid and phospholipid classes, fatty acid composition) of breast muscle was analysed. 5. Fibre type, fibre type percentage and cross-sectional areas were determined using histochemistry and an image analysis system. 6. For growth performance and muscular structure, the ideal slaughter age of mule ducks is 10 weeks of age. Chemical and technological analysis indicated that muscular maturity in Pectoralis major was reached at 11 weeks of age, but, at this age, breast lipid content is high. Moreover, after 10 weeks of age, food costs rapidly increased. 7. Lastly, sexual dimorphism for body weight is minor. In this study, at any given age, no significant differences between males and females were shown. Thus, it is possible to rear both sexes together and to slaughter them at the same age.

  15. Predictors of Adult Men's Gender-Role Conflict: Race, Class, Unemployment, Age, Instrumentality-Expressiveness, and Personal Strain.

    ERIC Educational Resources Information Center

    Stillson, Richard W.; And Others

    1991-01-01

    Men (n=134) of different ages, races, classes, personality characteristics, and work statuses were assessed with Gender Role Conflict Scale, Personal Strain Questionnaire, and Personal Attributes Questionnaire. Two meaningful and independent male constellations linking 9 of 13 demographic, psychological, and strain variables with 3 patterns of…

  16. Effect of rabbit age on sperm chromatin structure.

    PubMed

    Gogol, P; Bochenek, M; Smorag, Z

    2002-04-01

    The aim of this study was to determine the relationship between the age of male rabbits and the sperm chromatin structure. The studies involved the semen of New Zealand White rabbits between 5 and 28 months of age. A flow cytometry and sperm chromatin structure assay (SCSA) method was used to determine chromatin structure. The results of cytometric chromatin structure assay suggested a relatively high stability of sperm chromatin in the rabbit. Between 6 and 16 months of age, the mean percentage of sperm with damaged chromatin was the lowest and ranged from 1.7 to 2.4%. Decreased sperm chromatin stability was found in ejaculates taken from male rabbits less than 5 months and more than 20 months of age. PMID:11975746

  17. Localizing Age-Related Individual Differences in a Hierarchical Structure

    ERIC Educational Resources Information Center

    Salthouse, Timothy A.

    2004-01-01

    Data from 33 separate studies were combined to create an aggregate data set consisting of 16 cognitive variables and 6832 different individuals who ranged between 18 and 95 years of age. Analyses were conducted to determine where in a hierarchical structure of cognitive abilities individual differences associated with age, gender, education, and…

  18. Agency Amidst Formidable Structures: How Girls Perform Gender in Science Class

    ERIC Educational Resources Information Center

    Carlone, Heidi B.; Johnson, Angela; Scott, Catherine M.

    2015-01-01

    Larger social structures such as race, class, gender, and sexuality and classroom structures like narrowly defined participation practices constrain individuals' agency to engage in untroubled and sustained science identity work. This article explores the central dilemma of attending to structure and agency in settings where inequities are…

  19. Euler Teaches a Class in Structural Steel Design

    ERIC Educational Resources Information Center

    Boyajian, David M.

    2009-01-01

    Even before steel was a topic of formal study for structural engineers, the brilliant eighteenth century Swiss mathematician and physicist, Leonhard Euler (1707-1783), investigated the theory governing the elastic behaviour of columns, the results of which are incorporated into the American Institute of Steel Construction's (AISC's) Bible: the…

  20. Aging management of containment structures in nuclear power plants

    SciTech Connect

    Naus, D.J.; Oland, C.B.; Ellingwood, B.R.; Graves, H.L. III; Norris, W.E.

    1994-12-31

    Research is being conducted by ORNL under US Nuclear Regulatory Commission (USNRC) sponsorship to address aging management of nuclear power plant containment and other safety-related structures. Documentation is being prepared to provide the USNRC with potential structural safety issues and acceptance criteria for use in continued service evaluations of nuclear power plants. Accomplishments include development of a Structural Materials Information Center containing data and information on the time variation of 144 material properties under the influence of pertinent environmental stressors or aging factors, evaluation of models for potential concrete containment degradation factors, development of a procedure to identify critical structures and degradation factors important to aging management, evaluations of nondestructive evaluation techniques. assessments of European and North American repair practices for concrete, review of parameters affecting corrosion of metals embedded in concrete, and development of methodologies for making current condition assessments and service life predictions of new or existing reinforced concrete structures in nuclear power plants.

  1. Buying into the Computer Age: A Look at the Hispanic Middle Class.

    ERIC Educational Resources Information Center

    Wilhelm, Anthony G.

    The Tomas Rivera Policy Institute conducted focus groups in the summer of 1997 to gain insight into why there is a gap in computer ownership between Hispanic middle-class families and non-Hispanic families of the same middle class income bracket (between 25 and 50 thousand dollars). Results from 6 focus groups of 15 to 20 heads of household each…

  2. Age-structured optimal control in population economics.

    PubMed

    Feichtinger, Gustav; Prskawetz, Alexia; Veliov, Vladimir M

    2004-06-01

    This paper brings both intertemporal and age-dependent features to a theory of population policy at the macro-level. A Lotka-type renewal model of population dynamics is combined with a Solow/Ramsey economy. We consider a social planner who maximizes an aggregate intertemporal utility function which depends on per capita consumption. As control policies we consider migration and saving rate (both age-dependent). By using a new maximum principle for age-structured control systems we derive meaningful results for the optimal migration and saving rate in an aging population. The model used in the numerical calculations is calibrated for Austria.

  3. Leaf area and light use efficiency patterns of Norway spruce under different thinning regimes and age classes

    PubMed Central

    Gspaltl, Martin; Bauerle, William; Binkley, Dan; Sterba, Hubert

    2013-01-01

    Silviculture focuses on establishing forest stand conditions that improve the stand increment. Knowledge about the efficiency of an individual tree is essential to be able to establish stand structures that increase tree resource use efficiency and stand level production. Efficiency is often expressed as stem growth per unit leaf area (leaf area efficiency), or per unit of light absorbed (light use efficiency). We tested the hypotheses that: (1) volume increment relates more closely with crown light absorption than leaf area, since one unit of leaf area can receive different amounts of light due to competition with neighboring trees and self-shading, (2) dominant trees use light more efficiently than suppressed trees and (3) thinning increases the efficiency of light use by residual trees, partially accounting for commonly observed increases in post-thinning growth. We investigated eight even-aged Norway spruce (Picea abies (L.) Karst.) stands at Bärnkopf, Austria, spanning three age classes (mature, immature and pole-stage) and two thinning regimes (thinned and unthinned). Individual leaf area was calculated with allometric equations and absorbed photosynthetically active radiation was estimated for each tree using the three-dimensional crown model Maestra. Absorbed photosynthetically active radiation was only a slightly better predictor of volume increment than leaf area. Light use efficiency increased with increasing tree size in all stands, supporting the second hypothesis. At a given tree size, trees from the unthinned plots were more efficient, however, due to generally larger tree sizes in the thinned stands, an average tree from the thinned treatment was superior (not congruent in all plots, thus only partly supporting the third hypothesis). PMID:25540477

  4. Travelling Wave Solutions in Multigroup Age-Structured Epidemic Models

    NASA Astrophysics Data System (ADS)

    Ducrot, Arnaut; Magal, Pierre; Ruan, Shigui

    2010-01-01

    Age-structured epidemic models have been used to describe either the age of individuals or the age of infection of certain diseases and to determine how these characteristics affect the outcomes and consequences of epidemiological processes. Most results on age-structured epidemic models focus on the existence, uniqueness, and convergence to disease equilibria of solutions. In this paper we investigate the existence of travelling wave solutions in a deterministic age-structured model describing the circulation of a disease within a population of multigroups. Individuals of each group are able to move with a random walk which is modelled by the classical Fickian diffusion and are classified into two subclasses, susceptible and infective. A susceptible individual in a given group can be crisscross infected by direct contact with infective individuals of possibly any group. This process of transmission can depend upon the age of the disease of infected individuals. The goal of this paper is to provide sufficient conditions that ensure the existence of travelling wave solutions for the age-structured epidemic model. The case of two population groups is numerically investigated which applies to the crisscross transmission of feline immunodeficiency virus (FIV) and some sexual transmission diseases.

  5. Solar Array Structures for 300 kW-Class Spacecraft

    NASA Technical Reports Server (NTRS)

    Pappa, Richard; Rose, Geoff; Mann, Troy O.; Warren, Jerry E.; Mikulas, Martin M., Jr.; Kerslake, Tom; Kraft, Tom; Banik, Jeremy

    2013-01-01

    State-of-the-art solar arrays for spacecraft provide on the order of 20 kW of electrical power, and they usually consist of 3J solar cells bonded to hinged rigid panels about 1 inch in thickness. This structural construction allows specific mass and packaging volumes of up to approximately 70 W/kg and 15 kW/m3 to be achieved. Significant advances in solar array structures are required for future very-high-power spacecraft (300+ kW), such as those proposed for pre-positioning heavy cargo on or near the Moon, Mars, or asteroids using solar electric propulsion. These applications will require considerable increases in both W/kg and kW/m3, and will undoubtedly require the use of flexible-substrate designs. This presentation summarizes work sponsored by NASA's Game Changing Development Program since Oct. 2011 to address the challenge of developing 300+ kW solar arrays. The work is primarily being done at NASA Langley, NASA Glenn, and two contractor teams (ATK and DSS), with technical collaboration from AFRL/Kirtland. The near-tem objective of the project is design, analysis, and testing of 30-50 kW solar array designs that are extensible to the far-term objective of 300+ kW. The work is currently focused on three designs: the MegaFlex concept by ATK, the Mega-ROSA concept by DSS, and an in-house 300-kW Government Reference Array concept. Each of these designs will be described in the presentation. Results obtained to date by the team, as well as future work plans, for the design, analysis, and testing of these large solar array structures will be summarized.

  6. Mathematical modeling of a class of multibody flexible spacecraft structures

    NASA Technical Reports Server (NTRS)

    Kelkar, Atul, G.

    1994-01-01

    A mathematical model for a general multibody flexible spacecraft is obtained. The generic spacecraft considered consists of a flexible central body to which a number of flexible multibody structures are attached. The coordinate systems used in the derivation allow effective decoupling of the translational motion of the entire spacecraft from its rotational motion about its center of mass. The derivation assumes that the deformations in the bodies are only due to elastic motions. The dynamic model derived is a closed-form vector-matrix differential equation. The model developed can be used for analysis and simulation of many realistic spacecraft configurations.

  7. Aging and demographic plasticity in response to experimental age structures in honeybees (Apis mellifera L).

    PubMed

    Rueppell, Olav; Linford, Robyn; Gardner, Preston; Coleman, Jennifer; Fine, Kari

    2008-08-01

    Honeybee colonies are highly integrated functional units characterized by a pronounced division of labor. Division of labor among workers is mainly age-based, with younger individuals focusing on in-hive tasks and older workers performing the more hazardous foraging activities. Thus, experimental disruption of the age composition of the worker hive population is expected to have profound consequences for colony function. Adaptive demography theory predicts that the natural hive age composition represents a colony-level adaptation and thus results in optimal hive performance. Alternatively, the hive age composition may be an epiphenomenon, resulting from individual life history optimization. We addressed these predictions by comparing individual worker longevity and brood production in hives that were composed of a single age cohort, two distinct age cohorts, and hives that had a continuous, natural age distribution. Four experimental replicates showed that colonies with a natural age composition did not consistently have a higher life expectancy and/or brood production than the single cohort or double cohort hives. Instead, a complex interplay of age structure, environmental conditions, colony size, brood production, and individual mortality emerged. A general trade-off between worker life expectancy and colony productivity was apparent, and the transition from in-hive tasks to foraging was the most significant predictor of worker lifespan irrespective of the colony age structure. We conclude that the natural age structure of honeybee hives is not a colony-level adaptation. Furthermore, our results show that honeybees exhibit pronounced demographic plasticity in addition to behavioral plasticity to react to demographic disturbances of their societies.

  8. A class of Poisson Nijenhuis structures on a tangent bundle

    NASA Astrophysics Data System (ADS)

    Sarlet, W.; Vermeire, F.

    2004-06-01

    Equipping the tangent bundle TQ of a manifold with a symplectic form coming from a regular Lagrangian L, we explore how to obtain a Poisson-Nijenhuis structure from a given type (1, 1) tensor field J on Q. It is argued that the complete lift Jc of J is not the natural candidate for a Nijenhuis tensor on TQ, but plays a crucial role in the construction of a different tensor R, which appears to be the pullback under the Legendre transform of the lift of J to T*Q. We show how this tangent bundle view brings new insights and is capable also of producing all important results which are known from previous studies on the cotangent bundle, in the case when Q is equipped with a Riemannian metric. The present approach further paves the way for future generalizations.

  9. Aging of safety class 1E transformers in safety systems of nuclear power plants

    SciTech Connect

    Roberts, E.W.; Edson, J.L.; Udy, A.C.

    1996-02-01

    This report discusses aging effects on safety-related power transformers in nuclear power plants. It also evaluates maintenance, testing, and monitoring practices with respect to their effectiveness in detecting and mitigating the effects of aging. The study follows the US Nuclear Regulatory Commission`s (NRC`s) Nuclear Plant-Aging Research approach. It investigates the materials used in transformer construction, identifies stressors and aging mechanisms, presents operating and testing experience with aging effects, analyzes transformer failure events reported in various databases, and evaluates maintenance practices. Databases maintained by the nuclear industry were analyzed to evaluate the effects of aging on the operation of nuclear power plants.

  10. Structural and Functional Changes With the Aging Kidney.

    PubMed

    Denic, Aleksandar; Glassock, Richard J; Rule, Andrew D

    2016-01-01

    Senescence or normal physiologic aging portrays the expected age-related changes in the kidney as compared to a disease that occurs in some but not all individuals. The microanatomical structural changes of the kidney with older age include a decreased number of functional glomeruli from an increased prevalence of nephrosclerosis (arteriosclerosis, glomerulosclerosis, and tubular atrophy with interstitial fibrosis), and to some extent, compensatory hypertrophy of remaining nephrons. Among the macroanatomical structural changes, older age associates with smaller cortical volume, larger medullary volume until middle age, and larger and more numerous kidney cysts. Among carefully screened healthy kidney donors, glomerular filtration rate (GFR) declines at a rate of 6.3 mL/min/1.73 m(2) per decade. There is reason to be concerned that the elderly are being misdiagnosed with CKD. Besides this expected kidney function decline, the lowest risk of mortality is at a GFR of ≥75 mL/min/1.73 m(2) for age <55 years but at a lower GFR of 45 to 104 mL/min/1.73 m(2) for age ≥65 years. Changes with normal aging are still of clinical significance. The elderly have less kidney functional reserve when they do actually develop CKD, and they are at higher risk for acute kidney injury.

  11. Forest age influences oak insect herbivore community structure, richness, and density.

    PubMed

    Jeffries, June M; Marquis, Robert J; Forkner, Rebecca E

    2006-06-01

    Plant succession is one of many factors that may affect the composition and structure of herbivorous insect communities. However, few studies have examined the effect of forest age on the diversity and abundance of insect communities. If forest age influences insect diversity, then the schedule of timber harvest rotation may have consequent effects on biodiversity. The insect herbivore community on Quercus alba (white oak) in the Missouri Ozarks was sampled in a chronoseries, from recently harvested (2 yr) to old-growth (approximately 313 yr) forests. A total of nine sites and 39 stands within those sites were sampled in May and August 2003. Unique communities of plants and insects were found in the oldest forests (122-313 yr). Density and species richness of herbivores were positively correlated with increasing forest age in August but not in May. August insect density was negatively correlated with heat load index; in addition, insect density and richness increased over the chronoseries, but not on the sunniest slopes. Forest structural diversity (number of size classes) was positively correlated with forest age, but woody plant species richness was not. In sum, richness, density, and community structure of white oak insect herbivores are influenced by variation in forest age, forest structure, relative abundance of plant species, and abiotic conditions. These results suggest that time between harvests of large, long-lived, tree species such as white oak should be longer than current practice in order to maintain insect community diversity. PMID:16826990

  12. Aviation Structural Mechanic, Second Class, 2-13. Military Curriculum Materials for Vocational and Technical Education.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. National Center for Research in Vocational Education.

    This self-paced, individualized course, adapted from military curriculum materials for use in vocational and technical education, teaches students the skills needed to become aviation structural mechanics (second class). The course materials consist of five pamphlets covering the structural maintenance and repair of aircraft. The first pamphlet…

  13. Structure and Function of Four Classes of the 4Fe-4S Protein, IspH.

    PubMed

    Rao, Guodong; Oldfield, Eric

    2016-07-26

    IspH, (E)-1-hydroxy-2-methyl-but-2-enyl 4-diphosphate reductase, is an essential enzyme in isoprenoid biosynthesis and an important drug/herbicide target. Using X-ray crystallographic, bioinformatics, mutagenesis/kinetics/stability, and electron paramagnetic resonance (EPR) results, we show that organisms from different environments ultilize one of four main IspH classes. The classes are based on the arrangement of the aromatic residues near the 4Fe-4S cluster and the presence or absence of N- and C-terminal extensions. Class A enzymes are found primarily in anaerobic and microaerophilic bacteria. Class B enzymes are found in aerobic bacteria. Class C enzymes are found in cyanobacteria and plants. Class D enzymes are found in apicomplexan parasites. Using mutagenesis, we show that the cluster-associated aromatic groups in class A and class B IspHs enhance cluster oxidative stability. Y198A, F302A, and a C-terminal truncation mutant of the class B (Escherichia coli) IspH have catalytic activity lower than that of the wild-type protein when using methyl viologen as the electron donor, but higher activity with dithionite as the electron donor, due to ready access of the small reductant to the cluster, consistent with their increased oxygen and H2O2 sensitivity. F302A has the largest effect on the reaction rates, and EPR studies indicate this residue affects Fe-S cluster structure. Similar effects on cluster stability are seen with class A (F14A and Y98A) mutants; however, effects on ET rates are smaller, and there are no differences between the EPR spectra of mutant and wild-type proteins. Overall, the results are of general interest because they show, for the first time, that there are multiple IspH classes that have evolved to allow organisms to survive in diverse oxidative-stress environments. PMID:27357244

  14. Class-level relationships in the phylum Cnidaria: evidence from mitochondrial genome structure.

    PubMed Central

    Bridge, D; Cunningham, C W; Schierwater, B; DeSalle, R; Buss, L W

    1992-01-01

    The phylogenetic relationships of the Recent cnidarian classes remain one of the classic problems in invertebrate zoology. We survey the structure of the mitochondrial genome in representatives of the four extant cnidarian classes and in the phylum Ctenophora. We find that all anthozoan species tested possess mtDNA in the form of circular molecules, whereas all scyphozoan, cubozoan, and hydrozoan species tested display mtDNA in the form of linear molecules. Because ctenophore and all other known metazoan mtDNA is circular, the shared occurrence of linear mtDNA in three of the four cnidarian classes suggests a basal position for the Anthozoa within the phylum. Images PMID:1356268

  15. Stochastic Demography and the Neutral Substitution Rate in Class-Structured Populations

    PubMed Central

    Lehmann, Laurent

    2014-01-01

    The neutral rate of allelic substitution is analyzed for a class-structured population subject to a stationary stochastic demographic process. The substitution rate is shown to be generally equal to the effective mutation rate, and under overlapping generations it can be expressed as the effective mutation rate in newborns when measured in units of average generation time. With uniform mutation rate across classes the substitution rate reduces to the mutation rate. PMID:24594520

  16. Structural Aging Program approach to providing an improved basis for aging management of safety-related concrete structures

    SciTech Connect

    Naus, D.J.; Oland, C.B.; Ellingwood, B.

    1993-11-01

    The Structural Aging (SAG) Program is being conducted at the Oak Ridge National Laboratory (ORNL) for the United States Nuclear Regulatory Commission (USNRC). The SAG Program is addressing the aging management of safety-related concrete structures in nuclear power plants for the purpose of providing improved technical bases for their continued service. The program is organized into four tasks: Program Management, Materials Property Data Base, Structural Component Assessment/Repair Technologies, and Quantitative Methodology for Continued Service Determinations. Objectives and a summary of recent accomplishments under each of these tasks are presented.

  17. Who tweets? Deriving the demographic characteristics of age, occupation and social class from twitter user meta-data.

    PubMed

    Sloan, Luke; Morgan, Jeffrey; Burnap, Pete; Williams, Matthew

    2015-01-01

    This paper specifies, designs and critically evaluates two tools for the automated identification of demographic data (age, occupation and social class) from the profile descriptions of Twitter users in the United Kingdom (UK). Meta-data data routinely collected through the Collaborative Social Media Observatory (COSMOS: http://www.cosmosproject.net/) relating to UK Twitter users is matched with the occupational lookup tables between job and social class provided by the Office for National Statistics (ONS) using SOC2010. Using expert human validation, the validity and reliability of the automated matching process is critically assessed and a prospective class distribution of UK Twitter users is offered with 2011 Census baseline comparisons. The pattern matching rules for identifying age are explained and enacted following a discussion on how to minimise false positives. The age distribution of Twitter users, as identified using the tool, is presented alongside the age distribution of the UK population from the 2011 Census. The automated occupation detection tool reliably identifies certain occupational groups, such as professionals, for which job titles cannot be confused with hobbies or are used in common parlance within alternative contexts. An alternative explanation on the prevalence of hobbies is that the creative sector is overrepresented on Twitter compared to 2011 Census data. The age detection tool illustrates the youthfulness of Twitter users compared to the general UK population as of the 2011 Census according to proportions, but projections demonstrate that there is still potentially a large number of older platform users. It is possible to detect "signatures" of both occupation and age from Twitter meta-data with varying degrees of accuracy (particularly dependent on occupational groups) but further confirmatory work is needed.

  18. Who Tweets? Deriving the Demographic Characteristics of Age, Occupation and Social Class from Twitter User Meta-Data

    PubMed Central

    Sloan, Luke; Morgan, Jeffrey; Burnap, Pete; Williams, Matthew

    2015-01-01

    This paper specifies, designs and critically evaluates two tools for the automated identification of demographic data (age, occupation and social class) from the profile descriptions of Twitter users in the United Kingdom (UK). Meta-data data routinely collected through the Collaborative Social Media Observatory (COSMOS: http://www.cosmosproject.net/) relating to UK Twitter users is matched with the occupational lookup tables between job and social class provided by the Office for National Statistics (ONS) using SOC2010. Using expert human validation, the validity and reliability of the automated matching process is critically assessed and a prospective class distribution of UK Twitter users is offered with 2011 Census baseline comparisons. The pattern matching rules for identifying age are explained and enacted following a discussion on how to minimise false positives. The age distribution of Twitter users, as identified using the tool, is presented alongside the age distribution of the UK population from the 2011 Census. The automated occupation detection tool reliably identifies certain occupational groups, such as professionals, for which job titles cannot be confused with hobbies or are used in common parlance within alternative contexts. An alternative explanation on the prevalence of hobbies is that the creative sector is overrepresented on Twitter compared to 2011 Census data. The age detection tool illustrates the youthfulness of Twitter users compared to the general UK population as of the 2011 Census according to proportions, but projections demonstrate that there is still potentially a large number of older platform users. It is possible to detect “signatures” of both occupation and age from Twitter meta-data with varying degrees of accuracy (particularly dependent on occupational groups) but further confirmatory work is needed. PMID:25729900

  19. Likelihood analysis of spatial capture-recapture models for stratified or class structured populations

    USGS Publications Warehouse

    Royle, J. Andrew; Sutherland, Christopher S.; Fuller, Angela K.; Sun, Catherine C.

    2015-01-01

    We develop a likelihood analysis framework for fitting spatial capture-recapture (SCR) models to data collected on class structured or stratified populations. Our interest is motivated by the necessity of accommodating the problem of missing observations of individual class membership. This is particularly problematic in SCR data arising from DNA analysis of scat, hair or other material, which frequently yields individual identity but fails to identify the sex. Moreover, this can represent a large fraction of the data and, given the typically small sample sizes of many capture-recapture studies based on DNA information, utilization of the data with missing sex information is necessary. We develop the class structured likelihood for the case of missing covariate values, and then we address the scaling of the likelihood so that models with and without class structured parameters can be formally compared regardless of missing values. We apply our class structured model to black bear data collected in New York in which sex could be determined for only 62 of 169 uniquely identified individuals. The models containing sex-specificity of both the intercept of the SCR encounter probability model and the distance coefficient, and including a behavioral response are strongly favored by log-likelihood. Estimated population sex ratio is strongly influenced by sex structure in model parameters illustrating the importance of rigorous modeling of sex differences in capture-recapture models.

  20. The lumbar extradural structure changes with increasing age.

    PubMed

    Igarashi, T; Hirabayashi, Y; Shimizu, R; Saitoh, K; Fukuda, H; Mitsuhata, H

    1997-02-01

    We have examined the extradural space using a flexible extraduroscope in 74 patients undergoing extradural anaesthesia at the L2-3 interspace. Extraduroscopy showed that the extradural space becomes widely patent and the fatty tissue in the extradural space diminishes with increasing age. We postulate that these age-related structural changes may affect the spread of local anaesthetic in the extradural space. PMID:9068330

  1. Report on aging of nuclear power plant reinforced concrete structures

    SciTech Connect

    Naus, D.J.; Oland, C.B.; Ellingwood, B.R.

    1996-03-01

    The Structural Aging Program provides the US Nuclear Regulatory Commission with potential structural safety issues and acceptance criteria for use in continued service assessments of nuclear power plant safety-related concrete structures. The program was organized under four task areas: Program Management, Materials Property Data Base, Structural Component Assessment/Repair Technology, and Quantitative Methodology for Continued Service Determinations. Under these tasks, over 90 papers and reports were prepared addressing pertinent aspects associated with aging management of nuclear power plant reinforced concrete structures. Contained in this report is a summary of program results in the form of information related to longevity of nuclear power plant reinforced concrete structures, a Structural Materials Information Center presenting data and information on the time variation of concrete materials under the influence of environmental stressors and aging factors, in-service inspection and condition assessments techniques, repair materials and methods, evaluation of nuclear power plant reinforced concrete structures, and a reliability-based methodology for current and future condition assessments. Recommendations for future activities are also provided. 308 refs., 61 figs., 50 tabs.

  2. Exploring the vertical age structure of the Galactic disc

    NASA Astrophysics Data System (ADS)

    Casagrande, Luca

    While in external or high-redshift galaxies we can only measure integrated stellar properties at best, the Milky Way offers us the unique opportunity to study its individual baryonic components, including stars. We use oscillations measured in red giant stars by the Kepler satellite to derive stellar ages and explore the vertical age structure across few kpc of the Milky Way disc. We find that old stars dominate at increasing Galactic heights, whereas closer to the plane a rich zoology of ages exists. The age distribution of stars shows a smooth distribution over the last 10 Gyr, which together with a flat age-metallicity relation is consistent with a quiescent evolution for the Milky Way disc since a redshift of about two.

  3. Exploring the vertical age structure of the Galactic disc

    NASA Astrophysics Data System (ADS)

    Casagrande, Luca; Silva Aguirre, Victor; Schlesinger, Katharine J.; Stello, Dennis; Huber, Daniel; Serenelli, Aldo; Schoenrich, Ralph; Asplund, Martin; Feltzing, Sofia

    2015-08-01

    While in external or high-redshift galaxies we can only measure integrated stellar properties at best, the Milky Way offers us the unique opportunity to study its individual baryonic components, including stars. We use oscillations measured in giant stars by the Kepler satellite to derive stellar ages and explore the vertical age structure across few kpc of the Milky Way disc. We find that old stars dominate at increasing Galactic heights, whereas closer to the plane a rich zoology of ages exists. The age distribution of stars shows a smooth decline over the last 10 Gyr, which together with a flat age-metallicity relation is consistent with a quiescent evolution for the Milky Way disc since a redshift of about two.

  4. [Age-related characteristics of structural support for ovarian function].

    PubMed

    Koval'skiĭ, G B

    1984-12-01

    Histoenzymological assay was used to investigate various structures of the ovaries of rats of two groups aged 3-4 and 12-14 months during estral cycle. The activity of 3 beta-, 17 beta- and 20 alpha-steroid dehydrogenases, glucose-6-phosphate dehydrogenase, NAD and NADP-diaphorases, esterase, acid and alkaline phosphatases was studied. It has been shown that transport alterations in the microcirculation including the hematofollicular barrier play, the leading part in age-dependent depression of reproductive and endocrine functions. Ageing rats demonstrated no linkage between endothelial, thecal and granular cells, which points to the injury of the histophysiological mechanisms of the follicular system integration.

  5. Age or stage structure? A comparison of dynamic outcomes from discrete age- and stage-structured population models.

    PubMed

    Wikan, Arild

    2012-06-01

    Discrete stage-structured density-dependent and discrete age-structured density-dependent population models are considered. Regarding the former, we prove that the model at hand is permanent (i.e., that the population will neither go extinct nor exhibit explosive oscillations) and given density dependent fecundity terms we also show that species with delayed semelparous life histories tend to be more stable than species which possess precocious semelparous life histories. Moreover, our findings together with results obtained from other stage-structured models seem to illustrate a fairly general ecological principle, namely that iteroparous species are more stable than semelparous species. Our analysis of various age-structured models does not necessarily support the conclusions above. In fact, species with precocious life histories now appear to possess better stability properties than species with delayed life histories, especially in the iteroparous case. We also show that there are dynamical outcomes from semelparous age-structured models which we are not able to capture in corresponding stage-structured cases. Finally, both age- and stage-structured population models may generate periodic dynamics of low period (either exact or approximate). The important prerequisite is to assume density-dependent survival probabilities. PMID:22297621

  6. Structural Insights into Substrate Binding of Brown Spider Venom Class II Phospholipases D.

    PubMed

    Coronado, M A; Ullah, A; da Silva, L S; Chaves-Moreira, D; Vuitika, L; Chaim, O M; Veiga, S S; Chahine, J; Murakami, M T; Arni, R K

    2015-01-01

    Phospholipases D (PLDs), the major dermonecrotic factors from brown spider venoms, trigger a range of biological reactions both in vitro and in vivo. Despite their clinical relevance in loxoscelism, structural data is restricted to the apo-form of these enzymes, which has been instrumental in understanding the functional differences between the class I and II spider PLDs. The crystal structures of the native class II PLD from Loxosceles intermedia complexed with myo-inositol 1-phosphate and the inactive mutant H12A complexed with fatty acids indicate the existence of a strong ligand-dependent conformation change of the highly conserved aromatic residues, Tyr 223 and Trp225 indicating their roles in substrate binding. These results provided insights into the structural determinants for substrate recognition and binding by class II PLDs.

  7. Structural characterization of the catalytic site of a Nilaparvata lugens delta-class glutathione transferase.

    PubMed

    Yamamoto, Kohji; Higashiura, Akifumi; Hossain, Md Tofazzal; Yamada, Naotaka; Shiotsuki, Takahiro; Nakagawa, Atsushi

    2015-01-15

    Glutathione transferases (GSTs) are a major class of detoxification enzymes that play a central role in the defense against environmental toxicants and oxidative stress. Here, we studied the crystal structure of a delta-class glutathione transferase from Nilaparvata lugens, nlGSTD, to gain insights into its catalytic mechanism. The structure of nlGSTD in complex with glutathione, determined at a resolution of 1.7Å, revealed that it exists as a dimer and its secondary and tertiary structures are similar to those of other delta-class GSTs. Analysis of a complex between nlGSTD and glutathione showed that the bound glutathione was localized to the glutathione-binding site. Site-directed mutagenesis of nlGSTD mutants indicated that amino acid residues Ser11, His52, Glu66, and Phe119 contribute to catalytic activity.

  8. HIV Structural Database using Chem BLAST for all classes of AIDS inhibitors

    National Institute of Standards and Technology Data Gateway

    SRD 155 HIV Structural Database using Chem BLAST for all classes of AIDS inhibitors (Web, free access)   The HIV structural database (HIVSDB) is a comprehensive collection of the structures of HIV protease, both of unliganded enzyme and of its inhibitor complexes. It contains abstracts and crystallographic data such as inhibitor and protein coordinates for 248 data sets, of which only 141 are from the Protein Data Bank (PDB).

  9. Mind-Reading Ability and Structural Connectivity Changes in Aging.

    PubMed

    Cabinio, Monia; Rossetto, Federica; Blasi, Valeria; Savazzi, Federica; Castelli, Ilaria; Massaro, Davide; Valle, Annalisa; Nemni, Raffaello; Clerici, Mario; Marchetti, Antonella; Baglio, Francesca

    2015-01-01

    The Mind-Reading ability through the eyes is an important component of the affective Theory of Mind (ToM), which allows people to infer the other's mental state from the eye gaze. The aim of the present study was to investigate to which extent age-associated structural brain changes impact this ability and to determine if this association is related to executive functions in elderly subjects. For this purpose, Magnetic Resonance Imaging was used to determine both gray matter and white matter (WM) areas associated with aging. The resulting areas have been included in a subsequent correlation analysis to detect the brain regions whose structure was associated with the Mind-Reading ability through the eyes, assessed with the Italian version of the "Reading the Mind in the Eyes" (RME) test, in a sample of 36 healthy subjects ranging from 24 to 79 years of age. The analysis resulted in three important findings: (1) the performance to the RME test is relatively stable across the decades 20-70 (despite a slight decrease of this ability with aging) and independent from executive functions; (2) structural brain imaging demonstrated the involvement of a great number of cortical ToM areas for the execution of the RME test: the bilateral precentral gyrus, the bilateral posterior insula, the left superior temporal gyrus and the left inferior frontal gyrus, which also showed a significant volume decrease with age; (3) an age and task-related decline in WM connectivity on left fronto-temporal portion of the brain. Our results confirm the age-related structural modifications of the brain and show that these changes have an influence on the Mind-Reading ability through the eyes. PMID:26635702

  10. Mind-Reading Ability and Structural Connectivity Changes in Aging

    PubMed Central

    Cabinio, Monia; Rossetto, Federica; Blasi, Valeria; Savazzi, Federica; Castelli, Ilaria; Massaro, Davide; Valle, Annalisa; Nemni, Raffaello; Clerici, Mario; Marchetti, Antonella; Baglio, Francesca

    2015-01-01

    The Mind-Reading ability through the eyes is an important component of the affective Theory of Mind (ToM), which allows people to infer the other’s mental state from the eye gaze. The aim of the present study was to investigate to which extent age-associated structural brain changes impact this ability and to determine if this association is related to executive functions in elderly subjects. For this purpose, Magnetic Resonance Imaging was used to determine both gray matter and white matter (WM) areas associated with aging. The resulting areas have been included in a subsequent correlation analysis to detect the brain regions whose structure was associated with the Mind-Reading ability through the eyes, assessed with the Italian version of the “Reading the Mind in the Eyes” (RME) test, in a sample of 36 healthy subjects ranging from 24 to 79 years of age. The analysis resulted in three important findings: (1) the performance to the RME test is relatively stable across the decades 20–70 (despite a slight decrease of this ability with aging) and independent from executive functions; (2) structural brain imaging demonstrated the involvement of a great number of cortical ToM areas for the execution of the RME test: the bilateral precentral gyrus, the bilateral posterior insula, the left superior temporal gyrus and the left inferior frontal gyrus, which also showed a significant volume decrease with age; (3) an age and task-related decline in WM connectivity on left fronto-temporal portion of the brain. Our results confirm the age-related structural modifications of the brain and show that these changes have an influence on the Mind-Reading ability through the eyes. PMID:26635702

  11. Mind-Reading Ability and Structural Connectivity Changes in Aging.

    PubMed

    Cabinio, Monia; Rossetto, Federica; Blasi, Valeria; Savazzi, Federica; Castelli, Ilaria; Massaro, Davide; Valle, Annalisa; Nemni, Raffaello; Clerici, Mario; Marchetti, Antonella; Baglio, Francesca

    2015-01-01

    The Mind-Reading ability through the eyes is an important component of the affective Theory of Mind (ToM), which allows people to infer the other's mental state from the eye gaze. The aim of the present study was to investigate to which extent age-associated structural brain changes impact this ability and to determine if this association is related to executive functions in elderly subjects. For this purpose, Magnetic Resonance Imaging was used to determine both gray matter and white matter (WM) areas associated with aging. The resulting areas have been included in a subsequent correlation analysis to detect the brain regions whose structure was associated with the Mind-Reading ability through the eyes, assessed with the Italian version of the "Reading the Mind in the Eyes" (RME) test, in a sample of 36 healthy subjects ranging from 24 to 79 years of age. The analysis resulted in three important findings: (1) the performance to the RME test is relatively stable across the decades 20-70 (despite a slight decrease of this ability with aging) and independent from executive functions; (2) structural brain imaging demonstrated the involvement of a great number of cortical ToM areas for the execution of the RME test: the bilateral precentral gyrus, the bilateral posterior insula, the left superior temporal gyrus and the left inferior frontal gyrus, which also showed a significant volume decrease with age; (3) an age and task-related decline in WM connectivity on left fronto-temporal portion of the brain. Our results confirm the age-related structural modifications of the brain and show that these changes have an influence on the Mind-Reading ability through the eyes.

  12. Some bounds in classes of {open_quotes}aging{close_quotes} distributions

    SciTech Connect

    Kotlyar, V.Yu.

    1995-03-01

    Reliability of technical systems is closely linked with {open_quotes}aging{close_quotes} properties of the components. So-called monotone systems whose components have certain aging characteristics are of considerable importance in this field of research. Efficient bounds of reliability, mean time to failure, and other parameters can be obtained for such systems. The bounds in literature were obtained under the least restrictive assumptions on aging. In this paper, we generalize some results of literature to the case of even more general aging principles, specifically, when the system components are HNBUE, HNWUE, NBAFR, NWAFR in terms of their reliability properties. We start with a definition of these properties.

  13. A New Class of Risk-Importance Measures to Support Reactor Aging Management and the Prioritization of Materials Degradation Research

    SciTech Connect

    Unwin, Stephen D.; Lowry, Peter P.; Toyooka, Michael Y.

    2010-06-07

    As the US fleet of light water reactors ages, the risks of operation might be expected to increase. Although probabilistic risk assessment has proven a critical resource in risk-informed regulatory decision-making, limitations in current methods and models have constrained their prospective value in reactor aging management. These limitations stem principally from the use of static component failure rate models (which do not allow the impact of component aging on failure rates to be represented) and a very limited treatment of passive components (which would be expected to have an increasingly significant risk contribution in an aging system). Yet, a PRA captures a substantial knowledge base that could be of significant value in addressing plant aging. In this paper we will describe a methodology and a new class of risk importance measures that allow the use of an existing PRA model to support the management of plant aging, the prioritization of improvements to non-destructive examination and monitoring techniques, and the establishment of research emphases in materials science. This methodology makes use of data resources generated under the USNRC Proactive Management of Materials Degradation program which addresses the anticipated effects of numerous aging degradation mechanisms on a wide variety of component types.

  14. Identity, Age, Proportion of Online Classes, and Success among Students in a Predominantly Online Degree Program

    ERIC Educational Resources Information Center

    Carlsen-Landy, Bev

    2012-01-01

    Most colleges and universities in the US offer at least some classes online, and a significant number of colleges and universities offer degree programs either all online or predominantly online. Many of the distance learning courses and programs emerge from traditional courses and programs; however, in the past decade we have seen the emergence…

  15. Gene-drive in age-structured insect populations.

    PubMed

    Huang, Yunxin; Lloyd, Alun L; Legros, Mathieu; Gould, Fred

    2009-05-01

    To date, models of gene-drive mechanisms proposed for replacing wild-type mosquitoes with transgenic strains that cannot transmit diseases have assumed no age or mating structure. We developed a more detailed model to analyze the effects of age and mating-related factors on the number of engineered insects that must be introduced into a wild population to achieve successful gene-drive based on the Medea and engineered underdominance mechanisms. We found that models without age-structure and mating details can substantially overestimate or underestimate the numbers of engineered insects that must be introduced. In general, introduction thresholds are lowest when young adults are introduced. When both males and females are introduced, assortative mating by age has little impact on the introduction threshold unless the introduced females have diminished reproductive ability because of their age. However, when only males are introduced, assortative mating by age is generally predicted to increase introduction thresholds. In most cases, introduction thresholds are much higher for male-only introductions than for both-sex introductions, but when mating is nearly random and the introduced insects are adults with Medea constructs, male-only introductions can have somewhat lower thresholds than both-sex introductions. Results from this model suggest specific parameters that should be measured in field experiments.

  16. Domain structures and molecular evolution of class I and class II major histocompatibility gene complex (MHC) products deduced from amino acid and nucleotide sequence homologies

    NASA Astrophysics Data System (ADS)

    Ohnishi, Koji

    1984-12-01

    Domain structures of class I and class II MHC products were analyzed from a viewpoint of amino acid and nucleotide sequence homologies. Alignment statistics revealed that class I (transplantation) antigen H chains consist of four mutually homologous domains, and that class II (HLA-DR) antigen β and α chains are both composed of three mutually homologous ones. The N-terminal three and two domains of class I and class II (both β and α) gene products, respectively, all of which being ˜90 residues long, were concluded to be homologous to β2-microglobulin (β2M). The membraneembedded C-terminal shorter domains of these MHC products were also found to be homologous to one another and to the third domain of class I H chains. Class I H chains were found to be more closely related to class II α chains than to class II β chains. Based on these findings, an exon duplication history from a common ancestral gene encoding a β2M-like primodial protein of one-domain-length up to the contemporary MHC products was proposed.

  17. Age-related changes in human vitreous structure.

    PubMed

    Sebag, J

    1987-01-01

    Changes in vitreous structure that occur with aging are important in the pathogenesis of vitreous liquefaction (synchisis senilis), vitreous detachment, and retinal disease. Vitreous morphology was studied in 59 human eyes post-mortem using dark-field horizontal slit illumination of the entire dissected vitreous. In many individuals younger than 30 years, the vitreous was homogeneous in structure. Middle-aged individuals had macroscopic fibers in the central vitreous, which coursed anteroposteriorly and inserted into the vitreous base and the vitreous cortex, posteriorly. During senescence, the vitreous volume was reduced, the vitreous body was collapsed (syneresis), and the fibers were thickened, tortuous, and surrounded by liquid vitreous. This sequence of age-related changes probably results from a progressive reorganization of the hyaluronic acid and collagen molecular networks. Characterization of the molecular events underlying these changes will elucidate the mechanisms of the phenomena of synchisis, syneresis, and detachment, and may provide methods with which to prevent or induce vitreous detachment prophylactically.

  18. Towards universal structure-based prediction of class II MHC epitopes for diverse allotypes.

    PubMed

    Bordner, Andrew J

    2010-01-01

    The binding of peptide fragments of antigens to class II MHC proteins is a crucial step in initiating a helper T cell immune response. The discovery of these peptide epitopes is important for understanding the normal immune response and its misregulation in autoimmunity and allergies and also for vaccine design. In spite of their biomedical importance, the high diversity of class II MHC proteins combined with the large number of possible peptide sequences make comprehensive experimental determination of epitopes for all MHC allotypes infeasible. Computational methods can address this need by predicting epitopes for a particular MHC allotype. We present a structure-based method for predicting class II epitopes that combines molecular mechanics docking of a fully flexible peptide into the MHC binding cleft followed by binding affinity prediction using a machine learning classifier trained on interaction energy components calculated from the docking solution. Although the primary advantage of structure-based prediction methods over the commonly employed sequence-based methods is their applicability to essentially any MHC allotype, this has not yet been convincingly demonstrated. In order to test the transferability of the prediction method to different MHC proteins, we trained the scoring method on binding data for DRB1*0101 and used it to make predictions for multiple MHC allotypes with distinct peptide binding specificities including representatives from the other human class II MHC loci, HLA-DP and HLA-DQ, as well as for two murine allotypes. The results showed that the prediction method was able to achieve significant discrimination between epitope and non-epitope peptides for all MHC allotypes examined, based on AUC values in the range 0.632-0.821. We also discuss how accounting for peptide binding in multiple registers to class II MHC largely explains the systematically worse performance of prediction methods for class II MHC compared with those for class I MHC

  19. Seismic-fragility tests of new and accelerated-aged Class 1E battery cells

    SciTech Connect

    Bonzon, L.L.; Janis, W.J.; Black, D.A.; Paulsen, G.A.

    1987-01-01

    The seismic-fragility response of naturally-aged nuclear station safety-related batteries is of interest for two reasons: (1) to determine actual failure modes and thresholds and (2) to determine the validity of using the electrical capacity of individual cells as an indicator of the potential survivability of a battery given a seismic event. Prior reports in this series discussed the seismic-fragility tests and results for three specific naturally-aged cell types: 12-year old NCX-2250, 10-year old LCU-13, and 10-year old FHC-19. This report focuses on the complementary approach, namely, the seismic-fragility response of accelerated-aged batteries. Of particular interest is the degree to which such approaches accurately reproduce the actual failure modes and thresholds. In these tests the significant aging effects observed, in terms of seismic survivability, were: embrittlement of cell cases, positive bus material and positive plate grids; and excessive sulphation of positive plate active material causing hardening and expansion of positive plates. The IEEE Standard 535 accelerated aging method successfully reproduced seismically significant aging effects in new cells but accelerated grid embrittlement an estimated five years beyond the conditional age of other components.

  20. The leader peptide of mutacin 1140 has distinct structural components compared to related class I lantibiotics.

    PubMed

    Escano, Jerome; Stauffer, Byron; Brennan, Jacob; Bullock, Monica; Smith, Leif

    2014-12-01

    Lantibiotics are ribosomally synthesized peptide antibiotics composed of an N-terminal leader peptide that promotes the core peptide's interaction with the post translational modification (PTM) enzymes. Following PTMs, mutacin 1140 is transported out of the cell and the leader peptide is cleaved to yield the antibacterial peptide. Mutacin 1140 leader peptide is structurally unique compared to other class I lantibiotic leader peptides. Herein, we further our understanding of the structural differences of mutacin 1140 leader peptide with regard to other class I leader peptides. We have determined that the length of the leader peptide is important for the biosynthesis of mutacin 1140. We have also determined that mutacin 1140 leader peptide contains a novel four amino acid motif compared to related lantibiotics. PTM enzyme recognition of the leader peptide appears to be evolutionarily distinct from related class I lantibiotics. Our study on mutacin 1140 leader peptide provides a basis for future studies aimed at understanding its interaction with the PTM enzymes.

  1. Structure of a class C GPCR metabotropic glutamate receptor 1 bound to an allosteric modulator#

    PubMed Central

    Wu, Huixian; Wang, Chong; Gregory, Karen J.; Han, Gye Won; Cho, Hyekyung P.; Xia, Yan; Niswender, Colleen M.; Katritch, Vsevolod; Meiler, Jens; Cherezov, Vadim; Conn, P. Jeffrey; Stevens, Raymond C.

    2014-01-01

    The excitatory neurotransmitter glutamate induces modulatory actions via the metabotropic glutamate receptors (mGlus), which are class C G protein-coupled receptors (GPCRs). We determined the 2.8 Å resolution structure of the human mGlu1 receptor seven-transmembrane (7TM) domain bound to a negative allosteric modulator FITM. The modulator binding site partially overlaps with the orthosteric binding sites of class A GPCRs, but is more restricted compared to most other GPCRs. We observed a parallel 7TM dimer, mediated by cholesterols, suggesting that signaling initiated by glutamate’s interaction with the extracellular domain might be mediated via 7TM interactions within the full-length receptor dimer. A combination of crystallography, structure-activity relationships, mutagenesis, and full-length dimer modeling provides insights on the allosteric modulation and activation mechanism of class C GPCRs. PMID:24603153

  2. The relation between overweight and subjective health according to age, social class, slimming behavior and smoking habits in Dutch adults.

    PubMed Central

    Seidell, J C; Bakx, K C; Deurenberg, P; Burema, J; Hautvast, J G; Huygen, F J

    1986-01-01

    Subjective health status was assessed in relation to overweight by administering a list of 51 health complaints to adult men and women who were either chronically overweight as defined by Body Mass Index (BMI) or not overweight, in a continuous morbidity registration in four general practices during the period 1967-83. Responses were received from 455 men (182 overweight) and 790 women (386 overweight), ages 26-66 years. Response rate (71 per cent) and age distribution (mean age 48) were similar in overweight and non-overweight groups of both sexes. BMI was correlated with the total number of complaints in women (r = 0.15) but not in men (r = 0.07). Multiple regression analysis revealed, however, that age was an effect modifier in this relation, there being a negative association between BMI and subjective health in younger men and a positive association in older men, whereas in women the association between BMI and subjective health was much more pronounced at younger ages than at older ages. In addition, current smoking habits and social class (in men and women) and reported slimming behavior (in women) had an independent relation to the total number of health complaints. BMI was also related to specific complaints and groups of complaints, particularly in women. PMID:3777287

  3. Three-dimensional structure of a Bombyx mori Omega-class glutathione transferase.

    PubMed

    Yamamoto, Kohji; Suzuki, Mamoru; Higashiura, Akifumi; Nakagawa, Atsushi

    2013-09-01

    Glutathione transferases (GSTs) are major phase II detoxification enzymes that play central roles in the defense against various environmental toxicants as well as oxidative stress. Here we report the crystal structure of an Omega-class glutathione transferase of Bombyx mori, bmGSTO, to gain insight into its catalytic mechanism. The structure of bmGSTO complexed with glutathione determined at a resolution of 2.5Å reveals that it exists as a dimer and is structurally similar to Omega-class GSTs with respect to its secondary and tertiary structures. Analysis of a complex between bmGSTO and glutathione showed that bound glutathione was localized to the glutathione-binding site (G-site). Site-directed mutagenesis of bmGSTO mutants indicated that amino acid residues Leu62, Lys65, Lys77, Val78, Glu91 and Ser92 in the G-site contribute to catalytic activity.

  4. Aviation Structural Mechanic, First Class, 2-12. Military Curriculum Materials for Vocational and Technical Education.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. National Center for Research in Vocational Education.

    This self-paced, individualized course, adapted from military curriculum materials for use in vocational and technical education, teaches students the skills needed to become aviation structural mechanics (first class). The course materials consist of three pamphlets. The first pamphlet covers aircraft maintenance management, records, and reports…

  5. Influence of Professional Preparation and Class Structure on HIV, STD, and Pregnancy Prevention Education

    ERIC Educational Resources Information Center

    Rhodes, Darson L.; Jozkowski, Kristen N.; Hammig, Bart J.; Ogletree, Roberta J.; Fogarty, Erin C.

    2014-01-01

    Objective: The purpose of this study was to determine if education about human immunodeficiency virus (HIV)/sexually transmitted disease (STD) and pregnancy prevention is dependent on professional preparation and/or class structure. Design: A secondary data analysis of the 2006 School Health Policies and Programmes Study (SHPPS) was conducted.…

  6. Second Stiefel-Whitney class and spin structures on flat manifolds of diagonal type

    NASA Astrophysics Data System (ADS)

    Console, Sergio; Rossetti, Juan Pablo; Miatello, Roberto J.

    2011-07-01

    In this note, using previous works of Miatello and Podestá and of the authors, we provide simple, explicit combinatorial conditions for the existence of a spin structure on a diagonal flat manifold. We show in an elementary way that the above conditions are equivalent to the vanishing of the second Stiefel-Whitney class.

  7. Embedded Learning Strategy Instruction: Story-Structure Pedagogy in Heterogeneous Secondary Literature Classes

    ERIC Educational Resources Information Center

    Faggella-Luby, Michael; Schumaker, Jean S.; Deshler, Donald D.

    2007-01-01

    The effects of using the Embedded Story-Structure (ESS) Routine in a literature course were investigated. A heterogeneous group of 79 ninth graders, including 14 students with LD, were randomly assigned to one of two conditions, with instruction occurring in groups of 12 to 14 students in general education literature classes over a nine-day…

  8. [Method of Calculating the Distance Between the Classes of the Structural Components of the Forebrain Birds].

    PubMed

    Voronov, L N; Konstantinov, V Y

    2016-01-01

    The method of calculating the distance between the classes of the structural components of the brain of birds. Compared interclass distances of glia, neurons and neuroglial complexes in the forebrain hooded crow (Corvus cornix) (a bird with a highly rational activity) and common crossbill (Loxia curvirostra) (birds with a medium level of rational activity). PMID:27263281

  9. A class of unsteady, three-dimensional flow structures in turbulent boundary layers

    NASA Technical Reports Server (NTRS)

    Ash, R. L.

    1981-01-01

    A restricted class of mathematically admissible, unsteady, three dimensional flows was identified which may constitute part of the structure observed in turbulent boundary layers. The development of the model and some general results are discussed. The resulting solution has characteristics which suggest how upwelling low speed flow can trigger a downward jetting of irrotational high speed fluid into the boundary layer.

  10. iProClass: an integrated database of protein family, function and structure information.

    PubMed

    Huang, Hongzhan; Barker, Winona C; Chen, Yongxing; Wu, Cathy H

    2003-01-01

    The iProClass database provides comprehensive, value-added descriptions of proteins and serves as a framework for data integration in a distributed networking environment. The protein information in iProClass includes family relationships as well as structural and functional classifications and features. The current version consists of about 830 000 non-redundant PIR-PSD, SWISS-PROT, and TrEMBL proteins organized with more than 36 000 PIR superfamilies, 145 000 families, 4000 domains, 1300 motifs and 550 000 FASTA similarity clusters. It provides rich links to over 50 database of protein sequences, families, functions and pathways, protein-protein interactions, post-translational modifications, protein expressions, structures and structural classifications, genes and genomes, ontologies, literature and taxonomy. Protein and superfamily summary reports present extensive annotation information and include membership statistics and graphical display of domains and motifs. iProClass employs an open and modular architecture for interoperability and scalability. It is implemented in the Oracle object-relational database system and is updated biweekly. The database is freely accessible from the web site at http://pir.georgetown.edu/iproclass/ and searchable by sequence or text string. The data integration in iProClass supports exploration of protein relationships. Such knowledge is fundamental to the understanding of protein evolution, structure and function and crucial to functional genomic and proteomic research.

  11. Age structured dynamical model for an endangered lizard Eulamprus leuraensis

    NASA Astrophysics Data System (ADS)

    Supriatna, A. K.; Rachmadani, Q.; Ilahi, F.; Anggriani, N.; Nuraini, N.

    2014-02-01

    The Blue Mountains Water Skink, Eulamprus leuraensis, is listed as an endangered species under the IUCN Red List. This lizard species has a typical characteristic of growth with a low fecundity. It is known that the offspring quality may decline with maternal age of the parents despite they can grow rapidly from neonatal size to adult size within two to three years. It is also believed that low adult survival rates and specialization on rare and fragmented type of habitat are the main cause leading to the endangered status of the lizard. A mathematical model with age structure for Eulamprus leuraensis, taking into account the variation of survival rate in each structure and the declining of offspring quality with respect to maternal age is considered here. Stable coexistence of non-trivial equilibriumis shown. It is also shown that an endangered status is due to combination oflow reproductive output and low rates of adult survival. Further, understanding the age structure within populations can facilitate efective management of the endangered species.

  12. The unitary completion and QR iterations for a class of structured matrices

    NASA Astrophysics Data System (ADS)

    Bini, D. A.; Eidelman, Y.; Gemignani, L.; Gohberg, I.

    2008-03-01

    We consider the problem of completion of a matrix with a specified lower triangular part to a unitary matrix. In this paper we obtain the necessary and sufficient conditions of existence of a unitary completion without any additional constraints and give a general formula for this completion. The paper is mainly focused on matrices with the specified lower triangular part of a special form. For such a specified part the unitary completion is a structured matrix, and we derive in this paper the formulas for its structure. Next we apply the unitary completion method to the solution of the eigenvalue problem for a class of structured matrices via structured QR iterations.

  13. Some Remarks on the Choice of Ductility Class for Earthquake-Resistant Steel Structures

    NASA Astrophysics Data System (ADS)

    Matejčeková-Farhat, Miroslava; Ároch, Rudolf

    2013-09-01

    The implementation of the Eurocodes in current structural design practice has brought about a new emphasis on the design of earthquake-resistant structures. In some European countries, new earthquake zones have been defined; henceforth, the design requirements of many ongoing projects have changed as well. The choice of the ductility class of steel structures as one of the key design parameters, the consequences of this choice on design procedure, and some applications of the Eurocode 8 design criteria by comparing French and Slovak national practice are discussed, using a practical example of a structure.

  14. [Age changes of the connective tissue structures of human penis].

    PubMed

    Klimachev, V V; Neĭmark, A I; Gerval'd, V Ia; Bobrov, I P; Avdalian, A M; Muzalevskaia, N I; Gerval'd, I V; Aliev, R T; Cherdantseva, T M

    2011-01-01

    This investigation was aimed at the study of age changes of penis connective tissue structures. Tissue fragments of penis were obtained from 20 cadavers of men at the age of 20-38 years in group I, and from 20 cadavers of men at the age of 41-59 years in group II. The criteria for the exclusion of material from the research were arterial hypertension, diabetes mellitus, atherosclerosis of internal iliac arteries, Peyronie's disease, and anomalies of genital organ development. It was shown that in the cavernous body of penis, aging was associated with the increased amount and thickening of collagen and argyrophilic fibers, decreased content and thinning of elastic fibers, and the reduced amount of smooth muscle cells (SMC). The average area of fibroblast and SMC nucleolus was not different in both groups studied. The average area of endotheliocyte nucleolus was equal to 1.9+/-0.9 microm2 in group II, being lower than that one in group I, in which this index was equal to 2.1+/-0.9 microm2. No differences in the content of type III and IV collagen were found between the study groups. Age-associated decrease in the average area of endothelial cell nucleolus in the cavernous bodies may reflect the reduction of the activity of these cells and may indicate the development of endothelial dysfunction, which is one of the most important steps in the morphogenesis of age-related male erectile dysfunction.

  15. Active-Site Structure of Class IV Adenylyl Cyclase and Transphyletic Mechanism

    SciTech Connect

    D Gallagher; S Kim; H Robinson; P Reddy

    2011-12-31

    Adenylyl cyclases (ACs) belonging to three nonhomologous classes (II, III, and IV) have been structurally characterized, enabling a comparison of the mechanisms of cyclic adenosine 3',5'-monophosphate biosynthesis. We report the crystal structures of three active-site complexes for Yersinia pestis class IV AC (AC-IV) - two with substrate analogs and one with product. Mn{sup 2+} binds to all three phosphates, and to Glu12 and Glu136. Electropositive residues Lys14, Arg63, Lys76, Lys111, and Arg113 also form hydrogen bonds to phosphates. The conformation of the analogs is suitable for in-line nucleophilic attack by the ribose O3' on {alpha}-phosphate (distance {approx} 4 {angstrom}). In the product complex, a second Mn ion is observed to be coordinated to both ribose 2' oxygen and ribose 3' oxygen. Observation of both metal sites, together with kinetic measurements, provides strong support for a two-cation mechanism. Eleven active-site mutants were also made and kinetically characterized. These findings and comparisons with class II and class III enzymes enable a detailed transphyletic analysis of the AC mechanism. Consistent with its lack of coordination to purine, Y. pestis AC-IV cyclizes both ATP and GTP. As in other classes of AC, the ribose is loosely bound, and as in class III, no base appears to ionize the O3' nucleophile. Different syn/anti conformations suggest that the mechanism involves a conformational transition, and further evidence suggests a role for ribosyl pseudorotation. With resolutions of 1.6-1.7 {angstrom}, these are the most detailed active-site ligand complexes for any class of this ubiquitous signaling enzyme.

  16. Active-Site Structure of Class IV Adenylyl Cyclase and Transphyletic Mechanism

    SciTech Connect

    Gallagher, D.T.; Robinson, H.; Kim, S.-K.; Reddy, P. T.

    2011-01-21

    Adenylyl cyclases (ACs) belonging to three nonhomologous classes (II, III, and IV) have been structurally characterized, enabling a comparison of the mechanisms of cyclic adenosine 3',5'-monophosphate biosynthesis. We report the crystal structures of three active-site complexes for Yersinia pestis class IV AC (AC-IV)-two with substrate analogs and one with product. Mn{sup 2+} binds to all three phosphates, and to Glu12 and Glu136. Electropositive residues Lys14, Arg63, Lys76, Lys111, and Arg113 also form hydrogen bonds to phosphates. The conformation of the analogs is suitable for in-line nucleophilic attack by the ribose O3' on {alpha}-phosphate (distance {approx} 4 {angstrom}). In the product complex, a second Mn ion is observed to be coordinated to both ribose 2' oxygen and ribose 3' oxygen. Observation of both metal sites, together with kinetic measurements, provides strong support for a two-cation mechanism. Eleven active-site mutants were also made and kinetically characterized. These findings and comparisons with class II and class III enzymes enable a detailed transphyletic analysis of the AC mechanism. Consistent with its lack of coordination to purine, Y. pestis AC-IV cyclizes both ATP and GTP. As in other classes of AC, the ribose is loosely bound, and as in class III, no base appears to ionize the O3' nucleophile. Different syn/anti conformations suggest that the mechanism involves a conformational transition, and further evidence suggests a role for ribosyl pseudorotation. With resolutions of 1.6-1.7 {angstrom}, these are the most detailed active-site ligand complexes for any class of this ubiquitous signaling enzyme.

  17. Early-age monitoring of cement structures using FBG sensors

    NASA Astrophysics Data System (ADS)

    Wang, Chuan; Zhou, Zhi; Zhang, Zhichun; Ou, Jinping

    2006-03-01

    With more and more broad applications of the cement-based structures such as neat cement paste, cement mortar and concrete in civil engineering, people hope to find out what their performances should like. The in-service performances of cement-based structures are highly affected by their hardening process during the early-age. But it is still a big problem for traditional sensors to be used to monitor the early curing of cement-based structures due to such disadvantages as difficulties to install sensors inside the concrete, limited measuring points, poor durability and interference of electromagnetic wave and so on. In this paper, according to the sensing properties of the Fiber Bragg Grating sensors and self-characters of the cement-based structures, we have successfully finished measuring and monitoring the early-age inner-strain and temperature changes of the neat cement paste, concrete with and without restrictions, mass concrete structures and negative concrete, respectively. Three types of FBG-based sensors have been developed to monitor the cement-based structures. Besides, the installation techniques and the embedding requirements of FBG sensors in cement-based structures are also discussed. Moreover, such kind of technique has been used in practical structure, 3rd Nanjing Yangtze Bridge, and the results show that FBG sensors are well proper for measuring and monitoring the temperature and strain changes including self-shrinkage, dry shrinkage, plastic shrinkage, temperature expansion, frost heaving and so on inside different cement-based structures. This technique provides us a new useful measuring method on early curing monitoring of cement-based structures and greater understanding of details of their hardening process.

  18. Effects of the Age Structure of the Kindergarten on Altruistic Behavior

    ERIC Educational Resources Information Center

    Bizman, Aharon; And Others

    1978-01-01

    It was hypothesized that children in age-heterogeneous kindergartens would be more prone to behave altruistically than would children in age-homogeneous kindergartens. It was found that children who were studying in heterogeneous classes were more altruistic than were children from homogeneous classes. (Author)

  19. Long-term frequency aging for unpowered space-class oscillators.

    PubMed

    Bloch, Martin; Ho, John; Mancini, Oleandro; Terracciano, Louis; Mallette, Leo A

    2009-10-01

    Very little data exists regarding the long-term aging performance of space-rated oscillators in the non-operating mode. This paper provides empirical evidence that may be used to estimate the performance of unpowered oscillators for long-term space missions, as well as an aid in validating the worst-case analyses that are routinely performed on these oscillators. The proper operation of any space vehicle is dependent on the performance of the onboard master oscillator. For maximum reliability, the onboard clock is often provided as a dual-or triple-redundant ensemble, with one active oscillator. The backup oscillator(s) are usually powered off and may be off for a significant percentage of the mission. A significant parameter of importance for oscillator performance is the aging rate. Papers have been presented on the aging performance of active oscillators in space, but very little data exists regarding the long-term aging performance of oscillators in the nonoperating mode. The aging rate data are extremely important for predicting the expected performance of these backup oscillators after 10 or 15 years in of non-operation in space. This paper presents performance data derived from temperature controlled crystal oscillators and oven controlled crystal oscillators that have been dormant for decades.

  20. Social Orders and Interactions among Children in Age-Mixed Classes in Primary Schools--New Perspectives from a Synthesis of Ethnographic Data

    ERIC Educational Resources Information Center

    Huf, Christina; Raggl, Andrea

    2015-01-01

    The article synthesises data from two ethnographic projects, which both explore interactions of children in age-mixed groups in primary schools. It illuminates critical perspectives on social orders and children's interactions in age-mixed classes by showing how pupils in age-mixed groups become involved in power relations and how the teacher's…

  1. Cephalometric effects of face mask/expansion therapy in Class III children: a comparison of three age groups.

    PubMed

    Kapust, A J; Sinclair, P M; Turley, P K

    1998-02-01

    The purpose of this investigation was to determine the skeletal, dental, and soft tissue effects of face mask/expansion therapy and to examine the effect of age on treatment response. Pretreatment and posttreatment cephalometric radiographs from 63 subjects (4 to 13 years) who had a Class III malocclusion were analyzed. Serial cephalometric tracings of 32 subjects with Class I occlusion made at 4, 6, 8, 10, 12, and 14 years were used as controls. Landmarks were digitized on each tracing and treatment effects were measured by using cranial base and maxillary superimposition techniques. Annual rate differences were compared with t tests for the combined treated group (N = 63) and between stratified treated groups (4 to 7 years N = 15, 7 to 10 years N = 32, 10 to 14 years N = 16). The treated group (N = 63) demonstrated significant (p < 0.001) hard and soft tissue changes that resulted from treatment. Skeletal change was primarily a result of anterior and vertical movement of the maxillae. Mandibular position was directed in a downward and backward vector. Orthodontic changes contributed to the correction, and soft tissue effects resulted in a more convex profile. Minimal significant differences were observed between age groups when comparing angular and linear measurements alone. However, when analyzing the algebraic sum of treatment effects (Johnston analysis), significantly (p < 0.01) greater differences were observed in apical base change (ABCH) and total molar correction (6/6) in the younger age groups. This study demonstrates that face mask/expansion therapy produces dentofacial changes that combine to improve the Class III malocclusion. Although early treatment may be most effective, face mask therapy can provide a viable option for older children as well.

  2. Topology of Type II REases revisited; structural classes and the common conserved core.

    PubMed

    Niv, Masha Y; Ripoll, Daniel R; Vila, Jorge A; Liwo, Adam; Vanamee, Eva S; Aggarwal, Aneel K; Weinstein, Harel; Scheraga, Harold A

    2007-01-01

    Type II restriction endonucleases (REases) are deoxyribonucleases that cleave DNA sequences with remarkable specificity. Type II REases are highly divergent in sequence as well as in topology, i.e. the connectivity of secondary structure elements. A widely held assumption is that a structural core of five beta-strands flanked by two alpha-helices is common to these enzymes. We introduce a systematic procedure to enumerate secondary structure elements in an unambiguous and reproducible way, and use it to analyze the currently available X-ray structures of Type II REases. Based on this analysis, we propose an alternative definition of the core, which we term the alphabetaalpha-core. The alphabetaalpha-core includes the most frequently observed secondary structure elements and is not a sandwich, as it consists of a five-strand beta-sheet and two alpha-helices on the same face of the beta-sheet. We use the alphabetaalpha-core connectivity as a basis for grouping the Type II REases into distinct structural classes. In these new structural classes, the connectivity correlates with the angles between the secondary structure elements and with the cleavage patterns of the REases. We show that there exists a substructure of the alphabetaalpha-core, namely a common conserved core, ccc, defined here as one alpha-helix and four beta-strands common to all Type II REase of known structure.

  3. Minority group status and healthful aging: social structure still matters.

    PubMed

    Angel, Jacqueline L; Angel, Ronald J

    2006-07-01

    During the last 4 decades, a rapid increase has occurred in the number of survey-based and epidemiological studies of the health profiles of adults in general and of the causes of disparities between majority and minority Americans in particular. According to these studies, healthful aging consists of the absence of disease, or at least of the most serious preventable diseases and their consequences, and findings consistently reveal serious African American and Hispanic disadvantages in terms of healthful aging. We (1) briefly review conceptual and operational definitions of race and Hispanic ethnicity, (2) summarize how ethnicity-based differentials in health are related to social structures, and (3) emphasize the importance of attention to the economic, political, and institutional factors that perpetuate poverty and undermine healthful aging among certain groups.

  4. Ageing management of french NPP civil work structures

    NASA Astrophysics Data System (ADS)

    Gallitre, E.; Dauffer, D.

    2011-04-01

    This paper presents EDF practice about concrete structure ageing management, from the mechanisms analysis to the formal procedure which allows the French company to increase 900 MWe NPP lifetime until 40 years; it will also introduce its action plan for 60 years lifetime extension. This practice is based on a methodology which identifies every ageing mechanism; both plants feedback and state of the art are screened and conclusions are drawn up into an "ageing analysis data sheet". That leads at first to a collection of 57 data sheets which give the mechanism identification, the components that are concerned and an analysis grid which is designed to assess the safety risk. This analysis screens the reference documents describing the mechanism, the design lifetime hypotheses, the associated regulation or codification, the feedback experiences, the accessibility, the maintenance actions, the repair possibility and so one. This analysis has to lead to a conclusion about the risk taking into account monitoring and maintenance. If the data sheet conclusion is not clear enough, then a more detailed report is launched. The technical document which is needed, is a formal detailed report which summarizes every theoretical knowledge and monitoring data: its objective is to propose a solution for ageing management: this solution can include more inspections or specific research development, or additional maintenance. After a first stage on the 900 MWe units, only two generic ageing management detailed reports have been needed for the civil engineering part: one about reactor building containment, and one about other structures which focuses on concrete inflating reactions. The second stage consists on deriving this generic analysis (ageing mechanism and detailed reports) to every plant where a complete ageing report is required (one report for all equipments and structures of the plant, but specific for each reactor). This ageing management is a continuous process because the

  5. Stratified at Seven: In-Class Ability Grouping and the Relative Age Effect

    ERIC Educational Resources Information Center

    Campbell, Tammy

    2014-01-01

    There is an established body of evidence indicating that a pupil's relative age within their school year cohort is associated with academic attainment throughout compulsory education. In England, autumn-born pupils consistently attain at higher levels than summer-born pupils. Analysis here investigates a possible channel of this relative age…

  6. First in the Class? Age and the Education Production Function. NBER Working Paper No. 13663

    ERIC Educational Resources Information Center

    Cascio, Elizabeth; Schanzenbach, Diane Whitmore

    2007-01-01

    Older children outperform younger children in a school-entry cohort well into their school careers. The existing literature has provided little insight into the causes of this phenomenon, leaving open the possibility that school-entry age is zero-sum game, where relatively young students lose what relatively old students gain. In this paper, we…

  7. Middle-Aged Working Class Americans at Home. Changing Expectations of Manhood

    ERIC Educational Resources Information Center

    Shostak, Arthur B.

    1972-01-01

    Describes the changing role expectations of the middle-aged blue-collar male as a husband, lover, father, and son, from a formerly stereotyped Archie Bunker" type of role model to one that is aware of improved performance needed in these family roles. (AG)

  8. Sweepnet captures of Lygus hesperus (Hemiptera:Miridae) adult genders and age-classes in cotton

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Management of the western tarnished plant bug, Lygus hesperus Knight, in cotton usually relies on population estimates obtained using the sweepnet. Recent studies indicated adult L. hesperus gender and physiological age influence feeding behavior, within-plant distribution, and injury to cotton. W...

  9. The role of harvesting in age-structured populations: disentangling dynamic and age truncation effects.

    PubMed

    Wikström, Anders; Ripa, Jörgen; Jonzén, Niclas

    2012-12-01

    Understanding the processes generating fluctuations of natural populations lies at the very heart of academic ecology. It is also very important for applications such as fisheries management and pest control. We are interested in the effect of harvesting on population fluctuations and for that purpose we develop and analyze an age-structured model where recruitment is a stochastic process and the adult segment of the population is harvested. When a constant annual harvest is taken the coefficient of variation of the adult population increases for most parameter values due to the age truncation effect, i.e. an increased variability in a juvenescent population due to the removal of older individuals. However, if a constant proportion of the adults is harvested the age truncation effect is sometimes counteracted by a stabilizing dynamic effect of harvesting. Depending on parameter values mirroring different life histories, proportional harvest can either increase or decrease the relative fluctuations of an exploited population. When there is a demographic Allee effect the ratio of juveniles to adults may actually decrease with harvesting. We conclude that, depending on life history and harvest strategy, harvesting can either reinforce or dampen population fluctuations due to the relative importance of stabilizing dynamic effects and the age truncation effect. The strength of the latter is highly dependent on the fished population's endogenous, age-structured dynamics. More specifically, we predict that populations with strong and positively autocorrelated dynamics will show stronger age truncation effect, a testable prediction that offers a simple rule-of-thumb assessment of a population's vulnerability to exploitation.

  10. Crystal structure of class III chitinase from pomegranate provides the insight into its metal storage capacity.

    PubMed

    Masuda, Taro; Zhao, Guanghua; Mikami, Bunzo

    2015-01-01

    Chitinase hydrolyzes the β-1,4-glycosidic bond in chitin. In higher plants, this enzyme has been regarded as a pathogenesis-related protein. Recently, we identified a class III chitinase, which functions as a calcium storage protein in pomegranate (Punica granatum) seed (PSC, pomegranate seed chitinase). Here, we solved a crystal structure of PSC at 1.6 Å resolution. Although its overall structure, including the structure of catalytic site and non-proline cis-peptides, was closely similar to those of other class III chitinases, PSC had some unique structural characteristics. First, there were some metal-binding sites with coordinated water molecules on the surface of PSC. Second, many unconserved aspartate residues were present in the PSC sequence which rendered the surface of PSC negatively charged. This acidic electrostatic property is in contrast to that of hevamine, well-characterized plant class III chitinase, which has rather a positively charged surface. Thus, the crystal structure provides a clue for metal association property of PSC.

  11. Length-independent structural similarities enrich the antibody CDR canonical class model

    PubMed Central

    Nowak, Jaroslaw; Baker, Terry; Georges, Guy; Kelm, Sebastian; Klostermann, Stefan; Shi, Jiye; Sridharan, Sudharsan; Deane, Charlotte M.

    2016-01-01

    ABSTRACT Complementarity-determining regions (CDRs) are antibody loops that make up the antigen binding site. Here, we show that all CDR types have structurally similar loops of different lengths. Based on these findings, we created length-independent canonical classes for the non-H3 CDRs. Our length variable structural clusters show strong sequence patterns suggesting either that they evolved from the same original structure or result from some form of convergence. We find that our length-independent method not only clusters a larger number of CDRs, but also predicts canonical class from sequence better than the standard length-dependent approach. To demonstrate the usefulness of our findings, we predicted cluster membership of CDR-L3 sequences from 3 next-generation sequencing datasets of the antibody repertoire (over 1,000,000 sequences). Using the length-independent clusters, we can structurally classify an additional 135,000 sequences, which represents a ∼20% improvement over the standard approach. This suggests that our length-independent canonical classes might be a highly prevalent feature of antibody space, and could substantially improve our ability to accurately predict the structure of novel CDRs identified by next-generation sequencing. PMID:26963563

  12. Computer Simulation of Sexual Selection on Age-Structured Populations

    NASA Astrophysics Data System (ADS)

    Martins, S. G. F.; Penna, T. J. P.

    Using computer simulations of a bit-string model for age-structured populations, we found that sexual selection of older males is advantageous, from an evolutionary point of view. These results are in opposition to a recent proposal of females choosing younger males. Our simulations are based on findings from recent studies of polygynous bird species. Since secondary sex characters are found mostly in males, we could make use of asexual populations that can be implemented in a fast and efficient way.

  13. Universality class of the structural phase transition in the normal phase of cuprate superconductors.

    PubMed

    Najafi, M N; Tavana, A

    2016-08-01

    The tetragonal-orthorhombic structural phase transition of oxygen atoms in the basal plane of YBa_{2}Cu_{3}O_{6+δ} high-T_{C} cuprate superconductors is studied numerically. By mapping the system onto the asymmetric next-nearest-neighbor Ising model, we characterize this phase transition. Results indicate the degrees of critical behavior. We show that this phase transition occurs at the temperature T_{C}≃0.148eV in the thermodynamic limit. By analyzing the critical exponents, it is found that this universality class displays some common features, with the two-dimensional three-state Potts model universality class, although the possibility of other universality classes cannot be ruled out. Conformal invariance at T=T_{c} is investigated using the Schramm-Loewner evolution (SLE) technique, and it is found that the SLE diffusivity parameter for this system is 3.34±0.01. PMID:27627249

  14. Universality class of the structural phase transition in the normal phase of cuprate superconductors

    NASA Astrophysics Data System (ADS)

    Najafi, M. N.; Tavana, A.

    2016-08-01

    The tetragonal-orthorhombic structural phase transition of oxygen atoms in the basal plane of YBa2Cu3O6 +δ high-TC cuprate superconductors is studied numerically. By mapping the system onto the asymmetric next-nearest-neighbor Ising model, we characterize this phase transition. Results indicate the degrees of critical behavior. We show that this phase transition occurs at the temperature TC≃0.148 eV in the thermodynamic limit. By analyzing the critical exponents, it is found that this universality class displays some common features, with the two-dimensional three-state Potts model universality class, although the possibility of other universality classes cannot be ruled out. Conformal invariance at T =Tc is investigated using the Schramm-Loewner evolution (SLE) technique, and it is found that the SLE diffusivity parameter for this system is 3.34 ±0.01 .

  15. [Age structure and growth characteristic of Castanopsis fargesii population].

    PubMed

    Song, Kun; Da, Liang-jun; Yang, Tong-hui; Yang, Xu-feng

    2007-02-01

    In this paper, the age structure and growth characteristics of Castanopsis fargesii population in a shade-tolerant broadleaved evergreen forest were studied, aimed to understand more about the regeneration patterns and dynamics of this population. The results showed that the age structure of C. fargesii population was of sporadic type, with two death peaks of a 30-year gap. This population had a good plasticity in growth to light condition. Because there were no significant differences in light condition under the canopy in vertical, the saplings came into their first suppression period when they were 5-8 years old, with a height growth rate less than 0. 1 m x a(-1) lasting for 10 years. The beginning time of the first growth suppression period was by the end of the first death peak of the population, and the ending time of the first growth suppression period was at the beginning of the second death peak of the population, demonstrating that growth characteristic was the key factor affecting the age structure of C. fargesii.

  16. Age structure and disturbance legacy of North American forests

    NASA Astrophysics Data System (ADS)

    Pan, Y.; Chen, J. M.; Birdsey, R.; McCullough, K.; He, L.; Deng, F.

    2010-02-01

    Most forests of the world are recovering from a past disturbance. It is well known that forest disturbances profoundly affect carbon stock and fluxes in forest ecosystems, yet it has been a great challenge to assess disturbance impacts in estimates of forest carbon budgets. Net sequestration or loss of CO2 by forests after disturbance follows a predictable pattern with forest recovery. Forest age, which is related to time since disturbance, is the most available surrogate variable for various forest carbon analyses that concern the impact of disturbance. In this study, we compiled the first continental forest age map of North America by combining forest inventory data, historical fire data, optical satellite data and the dataset from NASA's LEDAPS project. Mexico and interior Alaska are excluded from this initial map due to unavailability of all required data sets, but work is underway to develop some different methodology for these areas. We discuss the significance of disturbance legacy from the past, as represented by current forest age structure in different regions of the US and Canada, tracking back disturbances caused by human and nature over centuries and at various scales. We also show how such information can be used with inventory data for analyzing carbon management opportunities, and other modeling applications. By combining geographic information about forest age with estimated C dynamics by forest type, it is possible to conduct a simple but powerful analysis of the net CO2 uptake by forests, and the potential for increasing (or decreasing) this rate as a result of direct human intervention in the disturbance/age status. The forest age map may also help address the recent concern that the terrestrial C sink from forest regrowth in North America may saturate in the next few decades. Finally, we describe how the forest age data can be used in large-scale carbon modeling, both for land-based biogeochemistry models and atmosphere-based inversion models

  17. Age structure and disturbance legacy of North American forests

    NASA Astrophysics Data System (ADS)

    Pan, Y.; Chen, J. M.; Birdsey, R.; McCullough, K.; He, L.; Deng, F.

    2011-03-01

    Most forests of the world are recovering from a past disturbance. It is well known that forest disturbances profoundly affect carbon stocks and fluxes in forest ecosystems, yet it has been a great challenge to assess disturbance impacts in estimates of forest carbon budgets. Net sequestration or loss of CO2 by forests after disturbance follows a predictable pattern with forest recovery. Forest age, which is related to time since disturbance, is a useful surrogate variable for analyses of the impact of disturbance on forest carbon. In this study, we compiled the first continental forest age map of North America by combining forest inventory data, historical fire data, optical satellite data and the dataset from NASA's Landsat Ecosystem Disturbance Adaptive Processing System (LEDAPS) project. A companion map of the standard deviations for age estimates was developed for quantifying uncertainty. We discuss the significance of the disturbance legacy from the past, as represented by current forest age structure in different regions of the US and Canada, by analyzing the causes of disturbances from land management and nature over centuries and at various scales. We also show how such information can be used with inventory data for analyzing carbon management opportunities. By combining geographic information about forest age with estimated C dynamics by forest type, it is possible to conduct a simple but powerful analysis of the net CO2 uptake by forests, and the potential for increasing (or decreasing) this rate as a result of direct human intervention in the disturbance/age status. Finally, we describe how the forest age data can be used in large-scale carbon modeling, both for land-based biogeochemistry models and atmosphere-based inversion models, in order to improve the spatial accuracy of carbon cycle simulations.

  18. Molecular structure and baking performance of individual glycolipid classes from lecithins.

    PubMed

    Selmair, Patrick L; Koehler, Peter

    2009-06-24

    The potential of individual glycolipid classes from lecithins (soybean, rapeseed, and sunflower) in breadmaking was determined in comparison to classical surfactants such as diacetyltartaric acid esters of mono- and diacylglycerides (DATEM), monoacylglycerides, sodium stearoyl-2-lactylate (SSL), and two synthetic glycolipids by means of rheological and baking tests on a microscale. A highly glycolipid-enriched sample containing the entire glycolipid moiety of the lecithin was obtained using an optimized batch procedure with silica gel. This sample was subsequently used to gain individual glycolipid classes through column chromatography on silica gel. The major glycolipid classes in the lecithins, digalactosyl diacylglycerides (1), sterol glucosides (2), acylated sterol glucosides (3), and cerebrosides (4), were identified and characterized. All isolated glycolipid classes displayed excellent baking performance. A better baking activity than that of the classical surfactants was displayed by 1, 3, and 4 and an equivalent baking activity by 2. The same glycolipid classes, except 3, of different lecithin origin showed only slight differences in their baking activities, due to different fatty acid compositions. Furthermore, the glycolipid classes influenced the crumb structure significantly by improving the crumb softness and grain. Interestingly, none of the glycolipid classes showed significant antistaling effect. A direct effect on the overall rheological behavior of the dough was only found for the commercial surfactants. However, the rheological effect seen on gluten isolated from surfactant-containing dough revealed that the surfactants could be divided into two main groups, one of them directly forming and stabilizing liquid film lamellae through adsorption to interfaces and the other indirectly increasing the surface activity of the endogenous lipids in the flour. The results suggest that in wheat dough, glycolipids seem to have an impact on the dough liquor

  19. Cost-effective age structure and geographical distribution of boreal forest reserves.

    PubMed

    Lundström, Johanna; Ohman, Karin; Perhans, Karin; Rönnqvist, Mikael; Gustafsson, Lena; Bugman, Harald

    2011-02-01

    1. Forest reserves are established to preserve biodiversity, and to maintain natural functions and processes. Today there is heightened focus on old-growth stages, with less attention given to early successional stages. The biodiversity potential of younger forests has been overlooked, and the cost-effectiveness of incorporating different age classes in reserve networks has not yet been studied.2. We performed a reserve selection analysis in boreal Sweden using the Swedish National Forest Inventory plots. Seventeen structural variables were used as biodiversity indicators, and the cost of protecting each plot as a reserve was assessed using the Heureka system. A goal programming approach was applied, which allowed inclusion of several objectives and avoided a situation in which common indicators affected the result more than rare ones. The model was limited either by budget or area.3. All biodiversity indicators were found in all age classes, with more than half having the highest values in ages ≥ 100 years. Several large-tree indicators and all deadwood indicators had higher values in forests 0-14 years than in forests 15-69 years.4. It was most cost-effective to protect a large proportion of young forests since they generally have a lower net present value compared to older forests, but still contain structures of importance for biodiversity. However, it was more area-effective to protect a large proportion of old forests since they have a higher biodiversity potential per area.5. The geographical distribution of reserves selected with the budget-constrained model was strongly biassed towards the north-western section of boreal Sweden, with a large proportion of young forest, whereas the area-constrained model focussed on the south-eastern section, with dominance by the oldest age class.6.Synthesis and applications. We show that young forests with large amounts of structures important to biodiversity such as dead wood and remnant trees are cheap and cost

  20. Inhibitory Control Efficiency in a Piaget-Like Class-Inclusion Task in School-Age Children and Adults: A Developmental Negative Priming Study

    ERIC Educational Resources Information Center

    Borst, G.; Poirel, N.; Pineau, A.; Cassotti, M.; Houdé, O.

    2013-01-01

    Most children under 7 years of age presented with 10 daisies and 2 roses fail to indicate that there are more flowers than daisies. Instead of the appropriate comparison of the relative numerosities of the superordinate class (flowers) to its subordinate class (daisies), they perform a direct perceptual comparison of the extensions of the 2…

  1. Structural basis of the inhibition of class C acid phosphatases by adenosine 5;#8242;-phosphorothioate

    SciTech Connect

    Singh, Harkewal; Reilly, Thomas J.; Tanner, John J.

    2012-01-20

    The inhibition of phosphatases by adenosine 5'-phosphorothioate (AMPS) was first reported in the late 1960s; however, the structural basis for the inhibition has remained unknown. Here, it is shown that AMPS is a submicromolar inhibitor of class C acid phosphatases, a group of bacterial outer membrane enzymes belonging to the haloacid dehalogenase structural superfamily. Furthermore, the 1.35-{angstrom} resolution crystal structure of the inhibited recombinant Haemophilus influenzae class C acid phosphatase was determined; this is the first structure of a phosphatase complexed with AMPS. The conformation of AMPS is identical to that of the substrate 5'-AMP, except that steric factors force a rotation of the thiophosphoryl out of the normal phosphoryl-binding pocket. This conformation is catalytically nonproductive, because the P atom is not positioned optimally for nucleophilic attack by Asp64, and the O atom of the scissile O-P bond is too far from the Asp (Asp66) that protonates the leaving group. The structure of 5'-AMP complexed with the Asp64 {yields} Asn mutant enzyme was also determined at 1.35-{angstrom} resolution. This mutation induces the substrate to adopt the same nonproductive binding mode that is observed in the AMPS complex. In this case, electrostatic considerations, rather than steric factors, underlie the movement of the phosphoryl. The structures not only provide an explanation for the inhibition by AMPS, but also highlight the precise steric and electrostatic requirements of phosphoryl recognition by class C acid phosphatases. Moreover, the structure of the Asp64 {yields} Asn mutant illustrates how a seemingly innocuous mutation can cause an unexpected structural change.

  2. Evaluation of efficacies of different classes of antidepressants in the forced swimming test in mice at different ages.

    PubMed

    Bourin, M; Colombel, M C; Redrobe, J P; Nizard, J; Hascoët, M; Baker, G B

    1998-02-01

    1. The efficacies of different classes of antidepressants were investigated using the forced swimming test with mice at different ages. 2. Imipramine (4-32 mg/kg), desipramine (2-16 mg/kg) and bupropion (32, 64 mg/kg) showed activity in all age groups. 3. The selective serotonin reuptake inhibitors (SSRIs) citalopram (16 and 32 mg) and paroxetine (4 and 8 mg) were inactive in the oldest (40 weeks) group of mice, despite showing activity at the same doses in mice ranging in age from 4-24 weeks old. 4. Both SSRIs showed anti-immobility effects at low doses, (paroxetine: 1 and 2 mg/kg; citalopram: 4 and 8 mg/kg) in the 40-week old mice. These effects were not evident in the three younger groups of mice. 5. Moclobemide, a reversible selective inhibitor of monoamine oxidase-A, showed activity only at a high dose (128 mg/kg) and only in 12-week old animals. 6. Since SSRIs have been reported to have relatively selective effects on 5-HT1B receptors, the present results suggest that further studies comparing the effectiveness of SSRIs and other antidepressants in elderly patients should be done. Studies of the effects of aging on the density and/or affinity of 5-HT1A and 5-HT1B/1D receptors are also warranted.

  3. Eukaryotic class II cyclobutane pyrimidine dimer photolyase structure reveals basis for improved ultraviolet tolerance in plants.

    PubMed

    Hitomi, Kenichi; Arvai, Andrew S; Yamamoto, Junpei; Hitomi, Chiharu; Teranishi, Mika; Hirouchi, Tokuhisa; Yamamoto, Kazuo; Iwai, Shigenori; Tainer, John A; Hidema, Jun; Getzoff, Elizabeth D

    2012-04-01

    Ozone depletion increases terrestrial solar ultraviolet B (UV-B; 280-315 nm) radiation, intensifying the risks plants face from DNA damage, especially covalent cyclobutane pyrimidine dimers (CPD). Without efficient repair, UV-B destroys genetic integrity, but plant breeding creates rice cultivars with more robust photolyase (PHR) DNA repair activity as an environmental adaptation. So improved strains of Oryza sativa (rice), the staple food for Asia, have expanded rice cultivation worldwide. Efficient light-driven PHR enzymes restore normal pyrimidines to UV-damaged DNA by using blue light via flavin adenine dinucleotide to break pyrimidine dimers. Eukaryotes duplicated the photolyase gene, producing PHRs that gained functions and adopted activities that are distinct from those of prokaryotic PHRs yet are incompletely understood. Many multicellular organisms have two types of PHR: (6-4) PHR, which structurally resembles bacterial CPD PHRs but recognizes different substrates, and Class II CPD PHR, which is remarkably dissimilar in sequence from bacterial PHRs despite their common substrate. To understand the enigmatic DNA repair mechanisms of PHRs in eukaryotic cells, we determined the first crystal structure of a eukaryotic Class II CPD PHR from the rice cultivar Sasanishiki. Our 1.7 Å resolution PHR structure reveals structure-activity relationships in Class II PHRs and tuning for enhanced UV tolerance in plants. Structural comparisons with prokaryotic Class I CPD PHRs identified differences in the binding site for UV-damaged DNA substrate. Convergent evolution of both flavin hydrogen bonding and a Trp electron transfer pathway establish these as critical functional features for PHRs. These results provide a paradigm for light-dependent DNA repair in higher organisms. PMID:22170053

  4. Structure of the Class IV Adenylyl Cyclase Reveals a Novel Fold

    SciTech Connect

    Gallagher,D.; Smith, N.; Kim, S.; Heroux, A.; Robinson, H.; Reddy, P.

    2006-01-01

    The crystal structure of the class IV adenylyl cyclase (AC) from Yersinia pestis (Yp) is reported at 1.9 {angstrom} resolution. The class IV AC fold is distinct from the previously described folds for class II and class III ACs. The dimeric AC-IV folds into an antiparallel eight-stranded barrel whose connectivity has been seen in only three previous structures: yeast RNA triphosphatase and two proteins of unknown function from Pyrococcus furiosus and Vibrio parahaemolyticus. Eight highly conserved ionic residues E10, E12, K14, R63, K76, K111, D126, and E136 lie in the barrel core and form the likely binding sites for substrate and divalent cations. A phosphate ion is observed bound to R63, K76, K111, and R113 near the center of the conserved cluster. Unlike the AC-II and AC-III active sites that utilize two-Asp motifs for cation binding, the AC-IV active site is relatively enriched in glutamate and features an ExE motif as its most conserved element. Homologs of Y. pestis AC-IV, including human thiamine triphosphatase, span the three kingdoms of life and delineate an ancient family of phosphonucleotide processing enzymes.

  5. Complex structure of a bacterial class 2 histone deacetylase homologue with a trifluoromethylketone inhibitor

    SciTech Connect

    Nielsen, Tine Kragh; Hildmann, Christian; Riester, Daniel; Wegener, Dennis; Schwienhorst, Andreas; Ficner, Ralf

    2007-04-01

    The crystal structure of HDAH FB188 in complex with a trifluoromethylketone at 2.2 Å resolution is reported and compared to a previously determined inhibitor complex. Histone deacetylases (HDACs) have emerged as attractive targets in anticancer drug development. To date, a number of HDAC inhibitors have been developed and most of them are hydroxamic acid derivatives, typified by suberoylanilide hydroxamic acid (SAHA). Not surprisingly, structural information that can greatly enhance the design of novel HDAC inhibitors is so far only available for hydroxamic acids in complex with HDAC or HDAC-like enzymes. Here, the first structure of an enzyme complex with a nonhydroxamate HDAC inhibitor is presented. The structure of the trifluoromethyl ketone inhibitor 9,9,9-trifluoro-8-oxo-N-phenylnonanamide in complex with bacterial FB188 HDAH (histone deacetylase-like amidohydrolase from Bordetella/Alcaligenes strain FB188) has been determined. HDAH reveals high sequential and functional homology to human class 2 HDACs and a high structural homology to human class 1 HDACs. Comparison with the structure of HDAH in complex with SAHA reveals that the two inhibitors superimpose well. However, significant differences in binding to the active site of HDAH were observed. In the presented structure the O atom of the trifluoromethyl ketone moiety is within binding distance of the Zn atom of the enzyme and the F atoms participate in interactions with the enzyme, thereby involving more amino acids in enzyme–inhibitor binding.

  6. Towards Universal Structure-Based Prediction of Class II MHC Epitopes for Diverse Allotypes

    PubMed Central

    Bordner, Andrew J.

    2010-01-01

    The binding of peptide fragments of antigens to class II MHC proteins is a crucial step in initiating a helper T cell immune response. The discovery of these peptide epitopes is important for understanding the normal immune response and its misregulation in autoimmunity and allergies and also for vaccine design. In spite of their biomedical importance, the high diversity of class II MHC proteins combined with the large number of possible peptide sequences make comprehensive experimental determination of epitopes for all MHC allotypes infeasible. Computational methods can address this need by predicting epitopes for a particular MHC allotype. We present a structure-based method for predicting class II epitopes that combines molecular mechanics docking of a fully flexible peptide into the MHC binding cleft followed by binding affinity prediction using a machine learning classifier trained on interaction energy components calculated from the docking solution. Although the primary advantage of structure-based prediction methods over the commonly employed sequence-based methods is their applicability to essentially any MHC allotype, this has not yet been convincingly demonstrated. In order to test the transferability of the prediction method to different MHC proteins, we trained the scoring method on binding data for DRB1*0101 and used it to make predictions for multiple MHC allotypes with distinct peptide binding specificities including representatives from the other human class II MHC loci, HLA-DP and HLA-DQ, as well as for two murine allotypes. The results showed that the prediction method was able to achieve significant discrimination between epitope and non-epitope peptides for all MHC allotypes examined, based on AUC values in the range 0.632–0.821. We also discuss how accounting for peptide binding in multiple registers to class II MHC largely explains the systematically worse performance of prediction methods for class II MHC compared with those for class I

  7. Active sensors for health monitoring of aging aerospace structures

    SciTech Connect

    GIURGIUTIU,VICTOR; REDMOND,JAMES M.; ROACH,DENNIS P.; RACKOW,KIRK A.

    2000-03-08

    A project to develop non-intrusive active sensors that can be applied on existing aging aerospace structures for monitoring the onset and progress of structural damage (fatigue cracks and corrosion) is presented. The state of the art in active sensors structural health monitoring and damage detection is reviewed. Methods based on (a) elastic wave propagation and (b) electro-mechanical (NM) impedance technique are sighted and briefly discussed. The instrumentation of these specimens with piezoelectric active sensors is illustrated. The main detection strategies (E/M impedance for local area detection and wave propagation for wide area interrogation) are discussed. The signal processing and damage interpretation algorithms are tuned to the specific structural interrogation method used. In the high-frequency EIM impedance approach, pattern recognition methods are used to compare impedance signatures taken at various time intervals and to identify damage presence and progression from the change in these signatures. In the wave propagation approach, the acoustic-ultrasonic methods identifying additional reflection generated from the damage site and changes in transmission velocity and phase are used. Both approaches benefit from the use of artificial intelligence neural networks algorithms that can extract damage features based on a learning process. Design and fabrication of a set of structural specimens representative of aging aerospace structures is presented. Three built-up specimens, (pristine, with cracks, and with corrosion damage) are used. The specimen instrumentation with active sensors fabricated at the University of South Carolina is illustrated. Preliminary results obtained with the E/M impedance method on pristine and cracked specimens are presented.

  8. Active sensors for health monitoring of aging aerospace structures

    SciTech Connect

    GIURGIUTIU,VICTOR; REDMOND,JAMES M.; ROACH,DENNIS P.; RACKOW,KIRK A.

    2000-02-29

    A project to develop non-intrusive active sensors that can be applied on existing aging aerospace structures for monitoring the onset and progress of structural damage (fatigue cracks and corrosion) is presented. The state of the art in active sensors structural health monitoring and damage detection is reviewed. Methods based on (a) elastic wave propagation and (b) electro-mechanical (E/M) impedance technique are cited and briefly discussed. The instrumentation of these specimens with piezoelectric active sensors is illustrated. The main detection strategies (E/M impedance for local area detection and wave propagation for wide area interrogation) are discussed. The signal processing and damage interpretation algorithms are tuned to the specific structural interrogation method used. In the high-frequency E/M impedance approach, pattern recognition methods are used to compare impedance signatures taken at various time intervals and to identify damage presence and progression from the change in these signatures. In the wave propagation approach, the acousto-ultrasonic methods identifying additional reflection generated from the damage site and changes in transmission velocity and phase are used. Both approaches benefit from the use of artificial intelligence neural networks algorithms that can extract damage features based on a learning process. Design and fabrication of a set of structural specimens representative of aging aerospace structures is presented. Three built-up specimens (pristine, with cracks, and with corrosion damage) are used. The specimen instrumentation with active sensors fabricated at the University of South Carolina is illustrated. Preliminary results obtained with the E/M impedance method on pristine and cracked specimens are presented.

  9. Implications of a class of grand unified theories for large scale structure in the universe

    NASA Technical Reports Server (NTRS)

    Shafi, Q.; Stecker, F. W.

    1983-01-01

    A class of grand unified theories in which cosmologicaly significant axion and neutrino energy densities arise naturally is discussed. To obtain large scale structure three scenarios are considered: (1) an inflationary scenario; (2) inflation followed by string production; and (3) a non-inflationary scenario with density fluctuations caused solely by strings. Inflation may be compatible with the recent observational indications that mega 1 on the scale of superclusters, particularly if strings are present.

  10. Verb production in agrammatic aphasia: The influence of semantic class and argument structure properties on generalisation

    PubMed Central

    Schneider, Sandra L.; Thompson, Cynthia K.

    2011-01-01

    Background Some individuals with agrammatic aphasia have difficulty producing verbs when naming and generating sentences (Miceli, Silveri, Villa, & Caramazza, 1984; Saffran, Schwartz, & Marin, 1980; Zingeser & Berndt, 1990). And when verbs are produced there is an over-reliance on verbs requiring simple argument structure arrangements (Thompson, Lange, Schneider, & Shapiro, 1997; Thompson, Shapiro, Schneider, & Tait, 1994). Verbs, as argument-taking elements, show especially complex semantic and argument structure properties. This study investigated the role these properties have on verb production in individuals with agrammatic aphasia. Aim This treatment study examined the extent to which semantic class and argument structure properties of verbs influenced the ability of seven individuals with agrammatic Broca’s aphasia to retrieve verbs and then use them in correct sentence production. Verbs from two semantic classes and two argument structure categories were trained using either a semantic or an argument structure verb retrieval treatment. Specifically, acquisition and generalisation to trained and untrained verbs within and across semantic and argument structure categories was examined. In addition, the influence of verb production on each participant’s sentence production was also examined. Methods & Procedures Utilising a single-subject crossover design in combination with a multiple baseline design across subjects and behaviours, seven individuals with agrammatic aphasia were trained to retrieve verbs with specific argument structures from two semantic classes under two treatment conditions—semantic verb retrieval treatment and verb argument structure retrieval treatment. Treatment was provided on two-place and three-place motion or change of state verbs, counterbalanced across subjects and behaviours. A total of 102 verbs, depicted in black and white drawings, were utilised in the study, divided equally into motion and change of state verbs (semantic

  11. Verb production in agrammatic aphasia: The influence of semantic class and argument structure properties on generalisation.

    PubMed

    Schneider, Sandra L; Thompson, Cynthia K

    2003-01-01

    BACKGROUND: Some individuals with agrammatic aphasia have difficulty producing verbs when naming and generating sentences (Miceli, Silveri, Villa, & Caramazza, 1984; Saffran, Schwartz, & Marin, 1980; Zingeser & Berndt, 1990). And when verbs are produced there is an over-reliance on verbs requiring simple argument structure arrangements (Thompson, Lange, Schneider, & Shapiro, 1997; Thompson, Shapiro, Schneider, & Tait, 1994). Verbs, as argument-taking elements, show especially complex semantic and argument structure properties. This study investigated the role these properties have on verb production in individuals with agrammatic aphasia. AIM: This treatment study examined the extent to which semantic class and argument structure properties of verbs influenced the ability of seven individuals with agrammatic Broca's aphasia to retrieve verbs and then use them in correct sentence production. Verbs from two semantic classes and two argument structure categories were trained using either a semantic or an argument structure verb retrieval treatment. Specifically, acquisition and generalisation to trained and untrained verbs within and across semantic and argument structure categories was examined. In addition, the influence of verb production on each participant's sentence production was also examined. METHODS #ENTITYSTARTX00026; PROCEDURES: Utilising a single-subject crossover design in combination with a multiple baseline design across subjects and behaviours, seven individuals with agrammatic aphasia were trained to retrieve verbs with specific argument structures from two semantic classes under two treatment conditions-semantic verb retrieval treatment and verb argument structure retrieval treatment. Treatment was provided on two-place and three-place motion or change of state verbs, counterbalanced across subjects and behaviours. A total of 102 verbs, depicted in black and white drawings, were utilised in the study, divided equally into motion and change of state

  12. Structures of the Class D Carbapenemase OXA-24 from Acinetobacter baumannii in Complex with Doripenem

    SciTech Connect

    Schneider, Kyle D.; Ortega, Caleb J.; Renck, Nicholas A.; Bonomo, Robert A.; Powers, Rachel A.; Leonard, David A.

    2012-02-08

    The emergence of class D {beta}-lactamases with carbapenemase activity presents an enormous challenge to health practitioners, particularly with regard to the treatment of infections caused by Gram-negative pathogens such as Acinetobacter baumannii. Unfortunately, class D {beta}-lactamases with carbapenemase activity are resistant to {beta}-lactamase inhibitors. To better understand the details of the how these enzymes bind and hydrolyze carbapenems, we have determined the structures of two deacylation-deficient variants (K84D and V130D) of the class D carbapenemase OXA-24 with doripenem bound as a covalent acyl-enzyme intermediate. Doripenem adopts essentially the same configuration in both OXA-24 variant structures, but varies significantly when compared to the non-carbapenemase class D member OXA-1/doripenem complex. The alcohol of the 6a hydroxyethyl moiety is directed away from the general base carboxy-K84, with implications for activation of the deacylating water. The tunnel formed by the Y112/M223 bridge in the apo form of OXA-24 is largely unchanged by the binding of doripenem. The presence of this bridge, however, causes the distal pyrrolidine/sulfonamide group to bind in a drastically different conformation compared to doripenem bound to OXA-1. The resulting difference in the position of the side-chain bridge sulfur of doripenem is consistent with the hypothesis that the tautomeric state of the pyrroline ring contributes to the different carbapenem hydrolysis rates of OXA-1 and OXA-24. These findings represent a snapshot of a key step in the catalytic mechanism of an important class D enzyme, and might be useful for the design of novel inhibitors.

  13. Paleomagnetic Age for the World-class Century Zn-Pb-Ag Deposit, Australia

    NASA Astrophysics Data System (ADS)

    Kawasaki, K.; Symons, D. T.; Dawborn, T.

    2009-05-01

    Paleomagnetic results are reported for the Century Zn-Pb-Ag SEDEX deposit in northwestern Queensland, Australia. The stratiform mineralization occurs in fine parallel lamellae in ˜1595 Ma siderite-rich siltstones and black shales of the upper Lawn Hill Formation in the Proterozoic McNamara Group. Galena from the deposit has given a Pb/Pb model age of ˜1575 Ma. Paleomagnetic analysis of 333 specimens from ore zones (15 sites), and hanging wall (4 sites) and footwall (5 sites) siltstones using mostly thermal and then alternating field step demagnetization, isolates a stable characteristic remanent magnetization (ChRM) for the ore sites only. Step demagnetization, rock magnetic tests and thermomagnetic analyses of ore, Zn and Pb concentrates and tailings show that the main remanence carriers are single- or pseudosingle-domain inclusions of titanomagnetite in sphalerite and gangue, and pyrrhotite in galena with modern goethite and/or hematite from the weathering of siderite. A paleomagnetic fold test using the ore sites is positive, showing that the ore ChRM predates D2 deformation in the ˜1595 to ˜1500 Ma Isan orogeny. The orogeny folded the main-stage mineralization, indicating that the ore retains a primary magnetization. The optimum 80% tilt-corrected unit mean ChRM direction for the ore gives a Mesoproterozoic paleopole at ˜1560 Ma on the northern Australian apparent polar wander path. Thus this result both constrains the timing of mineralization and provides an upper age limit for D2 deformation in the orogeny.

  14. Age structure and cooperation in coevolutionary games on dynamic network

    NASA Astrophysics Data System (ADS)

    Qin, Zilong; Hu, Zhenhua; Zhou, Xiaoping; Yi, Jingzhang

    2015-04-01

    Our proposed model imitates the growth of a population and describes the age structure and the level of cooperation in games on dynamic network with continuous changes of structure and topology. The removal of nodes and links caused by age-dependent attack, together with the nodes addition standing for the newborns of population, badly ruins Matthew effect in this coevolutionary process. Though the network is generated by growth and preferential attachment, it degenerates into random network and it is no longer heterogeneous. When the removal of nodes and links is equal to the addition of nodes and links, the size of dynamic network is maintained in steady-state, so is the low level of cooperation. Severe structure variation, homogeneous topology and continuous invasion of new defection jointly make dynamic network unsuitable for the survival of cooperator even when the probability with which the newborn players initially adopt the strategy cooperation is high, while things change slightly when the connections of newborn players are restricted. Fortunately, moderate interactions in a generation trigger an optimal recovering process to encourage cooperation. The model developed in this paper outlines an explanation of the cohesion changes in the development process of an organization. Some suggestions for cooperative behavior improvement are given in the end.

  15. Multiple plumage traits convey information about age and within-age-class qualities of a canopy-dwelling songbird, the Cerulean Warbler

    USGS Publications Warehouse

    Boves, Than J.; Buehler, David A.; Wood, Petra Bohall; Rodewald, Amanda D.; Larkin, Jeffrey L.; Keyser, Patrick D.; Wigley, T. Ben

    2014-01-01

    Colorful plumage traits in birds may convey multiple, redundant, or unreliable messages about an individual. Plumage may reliably convey information about disparate qualities such as age, condition, and parental ability because discrete tracts of feathers may cause individuals to incur different intrinsic or extrinsic costs. Few studies have examined the information content of plumage in a species that inhabits forest canopies, a habitat with unique light environments and selective pressures. We investigated the information content of four plumage patches (blue-green crown and rump, tail white, and black breast band) in a canopy-dwelling species, the Cerulean Warbler (Setophaga cerulea), in relation to age, condition, provisioning, and reproduction. We found that older males displayed wider breast bands, greater tail white, and crown and rump feathers with greater blue-green (435–534 nm) chroma and hue than males in their first potential breeding season. In turn, older birds were in better condition (short and long term) and were reproductively superior to younger birds. We propose that these age-related plumage differences (i.e. delayed plumage maturation) were not a consequence of a life history strategy but instead resulted from constraints during early feather molts. Within age classes, we found evidence to support the multiple messages hypothesis. Birds with greater tail white molted tails in faster, those with more exaggerated rump plumage (lower hue, greater blue-green chroma) provisioned more, and those with lower rump blue-green chroma were in better condition. Despite evidence of reliable signaling in this species, we found no strong relationships between plumage and reproductive performance, potentially because factors other than individual differences more strongly influenced fecundity.

  16. Estimating survival of precocial chicks during the prefledging period using a catch-curve analysis and count-based age-class data

    USGS Publications Warehouse

    McGowan, C.P.; Millspaugh, J.J.; Ryan, M.R.; Kruse, C.D.; Pavelka, G.

    2009-01-01

    Estimating reproductive success for birds with precocial young can be difficult because chicks leave nests soon after hatching and individuals or broods can be difficult to track. Researchers often turn to estimating survival during the prefledging period and, though effective, mark-recapture based approaches are not always feasible due to cost, time, and animal welfare concerns. Using a threatened population of Piping Plovers (Charadrius melodus) that breeds along the Missouri River, we present an approach for estimating chick survival during the prefledging period using long-term (1993-2005), count-based, age-class data. We used a modified catch-curve analysis, and data collected during three 5-day sampling periods near the middle of the breeding season. The approach has several ecological and statistical assumptions and our analyses were designed to minimize the probability of violating those assumptions. For example, limiting the sampling periods to only 5 days gave reasonable assurance that population size was stable during the sampling period. Annual daily survival estimates ranged from 0.825 (SD = 0.03) to 0.931 (0.02) depending on year and sampling period, with these estimates assuming constant survival during the prefledging period and no change in the age structure of the population. The average probability of survival to fledging ranged from 0.126 to 0.188. Our results are similar to other published estimates for this species in similar habitats. This method of estimating chick survival may be useful for a variety of precocial bird species when mark-recapture methods are not feasible and only count-based age class data are available. ?? 2009 Association of Field Ornithologists.

  17. Necessity of Periodic Ophthalmological Examinations in Binocular B Class Driving Licence Holders Over 50 Years of Age

    PubMed Central

    Kurt, Ali; Öktem, Çağlar; Karabıçak Acer, Ayşe; Kocamış, Özkan; Taşdemir, Sedat

    2016-01-01

    Objective: To determine whether binocular B class driving licence (BBCDL) holders over 50 years old are in compliance with the BBCDL criteria for visual acuity, to determine the age-based prevalence of ophthalmological disorders reducing visual acuity in this group, and to investigate whether periodic ophthalmological examinations are needed in licence holders over 50 years of age. Materials and Methods: This prospective study enrolled 451 adults over 50 years old having a BBCDL. The study subjects were categorized into 3 age groups as group 1 (51-60 years), group 2 (61-70 years), and group 3 (over 71 years). Results: The mean age of the subjects was 60.02±7.27 years; 338 (74.9%) were male and 113 (25.1%) were female. The BBCDL criteria were met by 353 (78.3%) subjects whereas 98 (21.7%) subjects did not meet them. Eighty-four (85.7%) of 98 patients not meeting BBCDL criteria still drove. The mean age of the subjects meeting BBCDL criteria (58.82±6.77 years) was significantly lower than the subjects not meeting them (64.34±7.40 years) (p<0.001). The most common pathologies in the individuals still driving despite not meeting BBCDL criteria were senile cataract (38.5%) and diabetic retinopathy (23.1%) in group 1, senile cataract (55.3%) and diabetic retinopathy (14.9%) in group 2, and senile cataract (63.6%) and senile macular degeneration+senile cataract (18.2%) in group 3. Conclusion: More than a fifth of individuals over 50 years old did not meet the BBCDL criteria, due predominantly to senile cataract, and the majority of these individuals continue to drive. Therefore, we believe that individuals over 50 years old who have a BBCDL should undergo periodic ophthalmological examinations.

  18. Aging effects on the structure underlying balance abilities tests.

    PubMed

    Urushihata, Toshiya; Kinugasa, Takashi; Soma, Yuki; Miyoshi, Hirokazu

    2010-01-01

    Balance impairment is one of the biggest risk factors for falls reducing inactivity, resulting in nursing care. Therefore, balance ability is crucial to maintain the activities of independent daily living of older adults. Many tests to assess balance ability have been developed. However, few reports reveal the structure underlying results of balance performance tests comparing young and older adults. Covariance structure analysis is a tool that is used to test statistically whether factorial structure fits data. This study examined aging effects on the factorial structure underlying balance performance tests. Participants comprised 60 healthy young women aged 22 ± 3 years (young group) and 60 community-dwelling older women aged 69 ± 5 years (older group). Six balance tests: postural sway, one-leg standing, functional reach, timed up and go (TUG), gait, and the EquiTest were employed. Exploratory factor analysis revealed that three clearly interpretable factors were extracted in the young group. The first factor had high loadings on the EquiTest, and was interpreted as 'Reactive'. The second factor had high loadings on the postural sway test, and was interpreted as 'Static'. The third factor had high loadings on TUG and gait test, and was interpreted as 'Dynamic'. Similarly, three interpretable factors were extracted in the older group. The first factor had high loadings on the postural sway test and the EquiTest and therefore was interpreted as 'Static and Reactive'. The second factor, which had high loadings on the EquiTest, was interpreted as 'Reactive'. The third factor, which had high loadings on TUG and the gait test, was interpreted as 'Dynamic'. A covariance structure model was applied to the test data: the second-order factor was balance ability, and the first-order factors were static, dynamic and reactive factors which were assumed to be measured based on the six balance tests. Goodness-of-fit index (GFI) of the models were acceptable (young group, GFI

  19. Aging Effects on the Structure Underlying Balance Abilities Tests

    PubMed Central

    Kinugasa, Takashi; Soma, Yuki; Miyoshi, Hirokazu

    2010-01-01

    Balance impairment is one of the biggest risk factors for falls reducing inactivity, resulting in nursing care. Therefore, balance ability is crucial to maintain the activities of independent daily living of older adults. Many tests to assess balance ability have been developed. However, few reports reveal the structure underlying results of balance performance tests comparing young and older adults. Covariance structure analysis is a tool that is used to test statistically whether factorial structure fits data. This study examined aging effects on the factorial structure underlying balance performance tests. Participants comprised 60 healthy young women aged 22 ± 3 years (young group) and 60 community-dwelling older women aged 69 ± 5 years (older group). Six balance tests: postural sway, one-leg standing, functional reach, timed up and go (TUG), gait, and the EquiTest were employed. Exploratory factor analysis revealed that three clearly interpretable factors were extracted in the young group. The first factor had high loadings on the EquiTest, and was interpreted as ‘Reactive’. The second factor had high loadings on the postural sway test, and was interpreted as ‘Static’. The third factor had high loadings on TUG and gait test, and was interpreted as ‘Dynamic’. Similarly, three interpretable factors were extracted in the older group. The first factor had high loadings on the postural sway test and the EquiTest and therefore was interpreted as ‘Static and Reactive’. The second factor, which had high loadings on the EquiTest, was interpreted as ‘Reactive’. The third factor, which had high loadings on TUG and the gait test, was interpreted as ‘Dynamic’. A covariance structure model was applied to the test data: the second-order factor was balance ability, and the first-order factors were static, dynamic and reactive factors which were assumed to be measured based on the six balance tests. Goodness-of-fit index (GFI) of the models were

  20. Shock spectra applications to a class of multiple degree-of-freedom structures system

    NASA Technical Reports Server (NTRS)

    Hwang, Shoi Y.

    1988-01-01

    The demand on safety performance of launching structure and equipment system from impulsive excitations necessitates a study which predicts the maximum response of the system as well as the maximum stresses in the system. A method to extract higher modes and frequencies for a class of multiple degree-of-freedom (MDOF) Structure system is proposed. And, along with the shock spectra derived from a linear oscillator model, a procedure to obtain upper bound solutions for maximum displacement and maximum stresses in the MDOF system is presented.

  1. Structural variation of the ribosomal gene cluster within the class Insecta

    SciTech Connect

    Mukha, D.V.; Sidorenko, A.P.; Lazebnaya, I.V.

    1995-09-01

    General estimation of ribosomal DNA variation within the class Insecta is presented. It is shown that, using blot-hybridization, one can detect differences in the structure of the ribosomal gene cluster not only between genera within an order, but also between species within a genera, including sibling species. Structure of the ribosomal gene cluster of the Coccinellidae family (ladybirds) is analyzed. It is shown that cloned highly conservative regions of ribosomal DNA of Tetrahymena pyriformis can be used as probes for analyzing ribosomal genes in insects. 24 refs., 4 figs.

  2. Large volcanoes on Venus: Examples of geologic and structural characteristics from different classes

    NASA Technical Reports Server (NTRS)

    Crumpler, L. S.; Head, J. W.; Aubele, J. C.

    1993-01-01

    Large volcanoes characterized by radial lava flows and similar evidence for a topographic edifice are widely distributed over the surface of Venus and geologically diverse. Based on the global identification of more than 165 examples and preliminary geologic mapping, large volcanoes range from those characterized geologically as simple lava edifices to those bearing evidence of complexly developed volcanic and structural histories. Many large volcanoes exhibit characteristics transitional to other large magnetic center types such as coronae and novae. In this study, we examine the geology and structure of several type examples of large volcanoes not addressed in previous studies which are representative of several of the morphological classes.

  3. Harnessing heredity in Gilded Age America: middle class mores and industrial breeding in a cultural context.

    PubMed

    Thurtle, Phillip

    2002-01-01

    By investigating the practices and beliefs of Gilded Age trotting horse breeders, this article demonstrates the relationship between industrial economic development and the growth of genetic reasoning in the United States. As most historians of biology already know, E. H. Harriman, Leland Stanford, and John D. Rockefeller not only transformed American business practice, they donated heavily to institutions that promoted eugenic research programs. What is not widely known, however, is that these same industrialists were accomplished trotting horse breeders with well-developed theories of inheritance. The article that follows uses these theories to place the rise of eugenic and genetic research into the context of the rapid development of industry in post Civil War America. Specifically, the study identifies how functional utility as defined through the narrow concerns of industrial practices were privileged over form and pedigree in American horse breeding. Even more importantly, this article suggests that the continuity established between the practices of the industrial philanthropists and the scientific research institutions that they established occurred at two levels: through the values privileged by the development of the dynamics of a mass society and through the tools used to process the large amounts of information necessary to understand breeding patterns in slow breeding organisms. PMID:12068894

  4. Nebraska School Facilities: Educational Adequacy of Class III School District Structures

    ERIC Educational Resources Information Center

    Weidner, John M., Sr.

    2009-01-01

    In 2009, a replication of the Pool study was conducted. This study, however, focused on the school systems classified as Class III districts. Nebraska has 252 Class III districts. Compared with Class II (21), Class IV (1), and Class V(1) districts, the Class III districts offer a wide array of school settings, from urban to extremely rural, and…

  5. Age and structure of a model vapour-deposited glass

    PubMed Central

    Reid, Daniel R.; Lyubimov, Ivan; Ediger, M. D.; de Pablo, Juan J.

    2016-01-01

    Glass films prepared by a process of physical vapour deposition have been shown to have thermodynamic and kinetic stability comparable to those of ordinary glasses aged for thousands of years. A central question in the study of vapour-deposited glasses, particularly in light of new knowledge regarding anisotropy in these materials, is whether the ultra-stable glassy films formed by vapour deposition are ever equivalent to those obtained by liquid cooling. Here we present a computational study of vapour deposition for a two-dimensional glass forming liquid using a methodology, which closely mimics experiment. We find that for the model considered here, structures that arise in vapour-deposited materials are statistically identical to those observed in ordinary glasses, provided the two are compared at the same inherent structure energy. We also find that newly deposited hot molecules produce cascades of hot particles that propagate far into the film, possibly influencing the relaxation of the material. PMID:27762262

  6. The leader peptide of mutacin 1140 has distinct structural components compared to related class I lantibiotics

    PubMed Central

    Escano, Jerome; Stauffer, Byron; Brennan, Jacob; Bullock, Monica; Smith, Leif

    2014-01-01

    Lantibiotics are ribosomally synthesized peptide antibiotics composed of an N-terminal leader peptide that promotes the core peptide's interaction with the post translational modification (PTM) enzymes. Following PTMs, mutacin 1140 is transported out of the cell and the leader peptide is cleaved to yield the antibacterial peptide. Mutacin 1140 leader peptide is structurally unique compared to other class I lantibiotic leader peptides. Herein, we further our understanding of the structural differences of mutacin 1140 leader peptide with regard to other class I leader peptides. We have determined that the length of the leader peptide is important for the biosynthesis of mutacin 1140. We have also determined that mutacin 1140 leader peptide contains a novel four amino acid motif compared to related lantibiotics. PTM enzyme recognition of the leader peptide appears to be evolutionarily distinct from related class I lantibiotics. Our study on mutacin 1140 leader peptide provides a basis for future studies aimed at understanding its interaction with the PTM enzymes. PMID:25400246

  7. Apparent inferiority of first-time breeders in the kittiwake: The role of heterogeneity among age classes

    USGS Publications Warehouse

    Cam, E.; Monnat, J.-Y.

    2000-01-01

    1. Many studies have provided evidence that first-time breeders have a lower survival, a lower probability of success, or of breeding, in the following year. Hypotheses based on reproductive costs have often been proposed to explain this. However, because of the intrinsic relationship between age and experience, the apparent inferiority of first-time breeders at the population level may result from selection, and experience may not influence performance within each individual. In this paper we address the question of phenotypic correlations between fitness components. This addresses differences in individual quality, a prerequisite for a selection process to occur. We also test the hypothesis of an influence of experience on these components while taking age and reproductive success into account: two factors likely to play a key role in a selection process. 2. Using data from a long-term study on the kittiwake, we found that first-time breeders have a lower probability of success, a lower survival and a lower probability of breeding in the next year than experienced breeders. However, neither experienced nor inexperienced breeders have a lower survival or a lower probability of breeding in the following year than birds that skipped a breeding opportunity. This suggests heterogeneity in quality among individuals. 3. Failed birds have a lower survival and a lower probability of breeding in the following year regardless of experience. This can be interpreted in the light of the selection hypothesis. The inferiority of inexperienced breeders may be linked to a higher proportion of lower-quality individuals in younger age classes. When age and breeding success are controlled for, there is no evidence of an influence of experience on survival or future breeding probability. 4. Using data from individuals whose reproductive life lasted the same number of years, we investigated the influence of experience on reproductive performance within individuals. There is no strong

  8. Impact of structural aging on seismic risk assessment of reinforced concrete structures in nuclear power plants

    SciTech Connect

    Ellingwood, B.; Song, J.

    1996-03-01

    The Structural Aging Program is addressing the potential for degradation of concrete structural components and systems in nuclear power plants over time due to aging and aggressive environmental stressors. Structures are passive under normal operating conditions but play a key role in mitigating design-basis events, particularly those arising from external challenges such as earthquakes, extreme winds, fires and floods. Structures are plant-specific and unique, often are difficult to inspect, and are virtually impossible to replace. The importance of structural failures in accident mitigation is amplified because such failures may lead to common-cause failures of other components. Structural condition assessment and service life prediction must focus on a few critical components and systems within the plant. Components and systems that are dominant contributors to risk and that require particular attention can be identified through the mathematical formalism of a probabilistic risk assessment, or PRA. To illustrate, the role of structural degradation due to aging on plant risk is examined through the framework of a Level 1 seismic PRA of a nuclear power plant. Plausible mechanisms of structural degradation are found to increase the core damage probability by approximately a factor of two.

  9. Form Follows Function: Structural and Catalytic Variation in the Class A Flavoprotein Monooxygenases

    PubMed Central

    Crozier-Reabe, Karen; Moran, Graham R.

    2012-01-01

    Flavoprotein monooxygenases (FPMOs) exhibit an array of mechanistic solutions to a common chemical objective; the monooxygenation of a target substrate. Each FPMO efficiently couples reduction of a flavin cofactor by NAD(P)H to oxygenation of the target substrate via a (hydro)peroxyflavin intermediate. This purpose of this review is to describe in detail the Class A flavoprotein hydroxylases (FPMO) in the context of the other FPMO classes (B–F). Both one and two component FPMOs are found in nature. Two-component enzymes require, in addition to the monooxygenase, the involvement of a reductase that first catalyzes the reduction of the flavin by NAD(P)H. The Class A and B FPMOs are single-component and manage to orchestrate the same net reaction within a single peptide. The Class A enzymes have, by some considerable margin, the most complete research record. These enzymes use choreographed movements of the flavin ring that facilitate access of the organic substrates to the active site, provide a means for interaction of NADPH with the flavin, offer a mechanism to sequester the dioxygen reduction chemistry from solvent and a means to release the product. The majority of the discrete catalytic events of the catalytic cycle can be observed directly in exquisite detail using spectrophotometric kinetic methods and many of the key mechanistic conclusions are further supported by structural data. This review attempts to compile each of the key observations made for both paradigm and newly discovered examples of Class A FPMOs into a complete catalytic description of one enzymatic turnover. PMID:23443084

  10. Structural and phylogenetic analysis of the MHC class I-like Fc receptor gene

    SciTech Connect

    Kandil, Eman; Ishibashi, Teruo; Kasahara, Masanori

    1995-06-01

    The intestinal epithelium of neonatal mice and rats expresses an Fc receptor that mediates selective uptake of IgG in mothers`milk. This receptor (FcRn), which helps newborn animals to acquire passive immunity, is an MHC class I-like heterodimer made up of a heavy chain and {beta}{sub 2}-microglobulin. In the present study, we determined the genomic structure of a mouse gene (FcRn) encoding the heavy of FcRn. The overall exon-intron organization of the Fcrn gene was similar to that of the Fcrn gene, thus providing structural evidence that Fcrn os a bona fide class I gene. The 5{prime}-flanking region of the Fcrn gene contained the binding motifs for two cytokine-inducible transcription factors, NF-IL6 and NF1. However, regulatory elements found in MHC class I genes (enhancer A, enhancer B, and the IFN response element) were absent. Phylogenetic tree analysis suggested that, like the MICA, AZGP1, and CD1 genes, the Fcrn gene diverged form MHC class I genes after the emergence of amphibians but before the split of placental and marsupial mammals. Consistent with this result, Southern blot analysis with a mouse Fcrn cDNA probe detected cross-hybridizing bands in various mammalian species and chickens. Sequence analysis of the Fcrn gene isolated from eight mouse strains showed that the membrane-distal domain of FcRn has at least three amino acid variants. The fact that Fcrn is a single copy gene indicates that it is expressed in both the neonatal intestine and the fetal yolk sac. 74 refs., 7 figs., 2 tabs.

  11. Experimental validation of an integrated controls-structures design methodology for a class of flexible space structures

    NASA Technical Reports Server (NTRS)

    Maghami, Peiman G.; Gupta, Sandeep; Elliott, Kenny B.; Joshi, Suresh M.; Walz, Joseph E.

    1994-01-01

    This paper describes the first experimental validation of an optimization-based integrated controls-structures design methodology for a class of flexible space structures. The Controls-Structures-Interaction (CSI) Evolutionary Model, a laboratory test bed at Langley, is redesigned based on the integrated design methodology with two different dissipative control strategies. The redesigned structure is fabricated, assembled in the laboratory, and experimentally compared with the original test structure. Design guides are proposed and used in the integrated design process to ensure that the resulting structure can be fabricated. Experimental results indicate that the integrated design requires greater than 60 percent less average control power (by thruster actuators) than the conventional control-optimized design while maintaining the required line-of-sight performance, thereby confirming the analytical findings about the superiority of the integrated design methodology. Amenability of the integrated design structure to other control strategies is considered and evaluated analytically and experimentally. This work also demonstrates the capabilities of the Langley-developed design tool CSI DESIGN which provides a unified environment for structural and control design.

  12. The Atiyah class and complex structure stabilization in heterotic Calabi-Yau compactifications

    NASA Astrophysics Data System (ADS)

    Anderson, Lara B.; Gray, James; Lukas, Andre; Ovrut, Burt

    2011-10-01

    Holomorphic gauge fields in N = 1 supersymmetri cheterotic compactifications can constrain the complex structure moduli of a Calabi-Yau manifold. In this paper, the tools necessary to use holomorphic bundles as a mechanism for moduli stabilization are systematically developed. We review the requisite deformation theory — including the Atiyah class, which determines the deformations of the complex structure for which the gauge bundle becomes non-holomorphic and, hence, non-supersymmetric. In addition, two equivalent approaches to this mechanism of moduli stabilization are presented. The first isan efficient computational algorithm for determining the supersymmetric moduli space, while the second is an F-term potential in the four-dimensional theory associated with vector bundle holomorphy. These three methods are proven to be rigorously equivalent. We present explicit examples in which large numbers of complex structure moduli are stabilized. Finally, higher-order corrections to the moduli space are discussed.

  13. Discovery of a new class of coronal structures in white light eclipse images

    SciTech Connect

    Druckmüller, Miloslav; Habbal, Shadia Rifai; Morgan, Huw

    2014-04-10

    White light images of the solar corona, taken during total solar eclipses, capture the complex dynamic relationship between the coronal plasma and the magnetic field. This relationship can be recorded on timescales of seconds to minutes, within a few solar radii above the solar surface. Rays, large-scale loops, and streamers, which are the brightest structures in these images, have shaped current models of the coronal magnetic field and solar wind flow. We show in this work how the application of novel image processing techniques to unique high-resolution white light eclipse images reveals the presence of a new class of structures, reminiscent of smoke rings, faint nested expanding loops, expanding bubbles, and twisted helical structures. These features are interpreted as snapshots of the dynamical evolution of instabilities developing at prominence-corona interfaces and propagating outward with the solar wind.

  14. Self-Learning Variable Structure Control for a Class of Sensor-Actuator Systems

    PubMed Central

    Chen, Sanfeng; Li, Shuai; Liu, Bo; Lou, Yuesheng; Liang, Yongsheng

    2012-01-01

    Variable structure strategy is widely used for the control of sensor-actuator systems modeled by Euler-Lagrange equations. However, accurate knowledge on the model structure and model parameters are often required for the control design. In this paper, we consider model-free variable structure control of a class of sensor-actuator systems, where only the online input and output of the system are available while the mathematic model of the system is unknown. The problem is formulated from an optimal control perspective and the implicit form of the control law are analytically obtained by using the principle of optimality. The control law and the optimal cost function are explicitly solved iteratively. Simulations demonstrate the effectiveness and the efficiency of the proposed method. PMID:22778633

  15. Distribution of age-classes of striped weakfish ( Cynoscion guatucupa) along an estuarine-marine gradient: Correlations with the environmental parameters

    NASA Astrophysics Data System (ADS)

    Jaureguizar, Andres J.; Ruarte, Claudio; Guerrero, Raúl A.

    2006-03-01

    The age-class distribution of the striped weakfish ( Cynoscion guatucupa) and its relationship with environmental factors were evaluated along the coast between Argentina and Uruguay, including the Río de la Plata estuary (36° S, 56° W). One hundred and seven stations were sampled between 2001 and 2003 during autumn, winter, and spring. Multivariate analyses (Cluster and MDS) were used to define sampling station groups, and a BIO-ENV procedure used to estimate the association of stations with environmental factors (depth, stratification, temperature and salinity of surface and bottom waters). The BIO-ENV procedure indicated that the salinity during autumn-winter and the temperature in spring had a significant influence on the spatial age-class pattern. The proportion of the youngest age-classes decreased from the estuarine area to the marine coastal area, except during spring where it showed the reverse pattern. The older age-classes inhabited the marine coastal area (more saline) toward the deepest zone, while the youngest individuals inhabited the outer estuarine area. Examination of the coastal circulation associated with the spatial distribution, and of the age-class frequency in the estuarine and marine coastal area, suggested that spawning took place in inshore coastal waters at very shallow depths.

  16. Site and age class variation of hematologic parameters for female Greater Sage Grouse (Centrocercus urophasianus) of Northern Nevada.

    PubMed

    Dyer, Kathryn J; Perryman, Barry L; Holcombe, Dale W

    2010-01-01

    Decreases in Greater Sage Grouse (Centrocercus urophasianus) numbers throughout the western United States have been attributed to declining habitat quantity and quality. Improving our understanding of how interannual ecologic site variability affects nutritional status and fitness of different bird age classes will lead to improved land management and conservation strategies. Greater Sage Grouse were sampled from two Population Management Units located in northern Nevada, United States: Tuscarora (TU) and Lone Willow (LW) during 15 March-11 April 2004 and 14-20 March 2005. Twenty (16 yearlings, four adults) and 17 (7 yearlings, 10 adults) female Sage Grouse were captured and bled during 2004, and 12 (four yearlings, eight adults) and 14 (10 yearlings, four adults) were sampled during 2005 in TU and LW, respectively. Samples were evaluated to examine the effect of site, age, and year on specific hematologic and serum chemistry parameters. Several differences between age classes, sites, and years were detected for a number of fitness indicators; however, actual values fell within normal ranges of variation for Sage Grouse or other avian species. Differences were also detected for several parameters more closely related to reproductive fitness, including total plasma and serum proteins, and serum calcium and phosphorus. Yearlings had lower plasma protein (P<0.0001) and lower serum protein than did adults (P=0.0003). In 2004, TU yearlings had lower serum calcium levels than the adults, and in 2005, LW yearlings had lower levels than adults (P=0.008). Females on the TU site had lower serum phosphorus than the LW females (P<0.0001). Overall, adult females weighed more than yearlings (P=0.0004). Lower values found in yearlings, and on the TU management unit, indicate a lower production potential, particularly in unfavorable years. A lower intrinsic ability of yearlings to reproduce, combined with lower nutrition potentials and associated annual variations on certain types

  17. Secondary structure and 3D homology modeling of swine leukocyte antigen class 2 (SLA-2) molecules.

    PubMed

    Gao, Feng-Shan; Xu, Chong-bo; Long, Yi-hou; Xia, Chun

    2009-01-01

    No information to date is available to elucidate the structure of swine leukocyte antigen class I (SLA-I) molecule which is comprised by a heavy chain of SLA-I non-covalently associated with a light chain, beta(2)-microglobulin (beta(2)m) proteins. Presently, one of SLA-I gene SLA-2 and beta(2)m gene were expressed as soluble maltose binding proteins (MBP-proteins) in a pMAL-p2X/Escherichia coli TB1 system and identified by western blotting with anti-MBP polyclonal antibodies. The expressed proteins MBP-SLA-2 and MBP-beta(2)m were purified on amylose affinity columns followed by DEAE-Sepharose. The purified products were cleaved by Factor Xa, respectively, and the interest of proteins SLA-2 and beta(2)m were purified on amylose affinity columns followed by separation from MBP on DEAE-Sepharose. The secondary structures of SLA-2 and beta(2)m were analyzed by circular dichroism (CD) spectrophotometry. The three-dimensional (3D) structure of their peptide-binding domain (PBD) was modeled-based sequence homology. The content of the alpha-helix, beta-sheet, turn, and random coil in the SLA-2 protein were 76, 95, 36, and 67aa, respectively. In the 98aa of beta(2)m, the contents of the alpha-helix, beta-sheet, turn, and random coil were 0, 45, 8, and 45aa, respectively. The SLA-2 protein displayed a typical alpha-helix structure while beta(2)m protein displayed a typical beta-sheet structure. Homology modeling of the SLA-2 and beta(2)m proteins demonstrated similarities with the structure of human and mouse MHC (major histocompatibility complex) class I proteins.

  18. Inhibitory control efficiency in a Piaget-like class-inclusion task in school-age children and adults: a developmental negative priming study.

    PubMed

    Borst, G; Poirel, N; Pineau, A; Cassotti, M; Houdé, O

    2013-07-01

    Most children under 7 years of age presented with 10 daisies and 2 roses fail to indicate that there are more flowers than daisies. Instead of the appropriate comparison of the relative numerosities of the superordinate class (flowers) to its subordinate class (daisies), they perform a direct perceptual comparison of the extensions of the 2 subordinate classes (daisies vs. roses). In our experiment, we investigated whether increasing efficiency in solving the Piagetian class-inclusion task is related to increasing efficiency in the ability to resist (inhibit) this direct comparison of the subordinate classes' extensions. Ten-year-old and young adult participants performed a computerized priming version of a Piaget-like class-inclusion task. The experimental design was such that the misleading perceptual strategy to inhibit on the prime (in which a superordinate class had to be compared with a subordinate class) became a congruent strategy to activate on the probe (in which the two subordinate classes' extensions were directly compared). We found a negative priming effect of 291 ms in children and 129 ms in adults. These results provide evidence for the first time (a) that adults still need to inhibit the comparison of the subordinate classes' extensions in class-inclusion tasks and (b) that the ability to inhibit this heuristic increases with age (resulting in a lower executive cost). Taken together, these findings provide additional support for the neo-Piagetian approach of cognitive development that suggests that the acquisition of increasingly complex knowledge is based on the ability to resist (inhibit) heuristics and previously acquired knowledge. PMID:22889392

  19. Inhibitory control efficiency in a Piaget-like class-inclusion task in school-age children and adults: a developmental negative priming study.

    PubMed

    Borst, G; Poirel, N; Pineau, A; Cassotti, M; Houdé, O

    2013-07-01

    Most children under 7 years of age presented with 10 daisies and 2 roses fail to indicate that there are more flowers than daisies. Instead of the appropriate comparison of the relative numerosities of the superordinate class (flowers) to its subordinate class (daisies), they perform a direct perceptual comparison of the extensions of the 2 subordinate classes (daisies vs. roses). In our experiment, we investigated whether increasing efficiency in solving the Piagetian class-inclusion task is related to increasing efficiency in the ability to resist (inhibit) this direct comparison of the subordinate classes' extensions. Ten-year-old and young adult participants performed a computerized priming version of a Piaget-like class-inclusion task. The experimental design was such that the misleading perceptual strategy to inhibit on the prime (in which a superordinate class had to be compared with a subordinate class) became a congruent strategy to activate on the probe (in which the two subordinate classes' extensions were directly compared). We found a negative priming effect of 291 ms in children and 129 ms in adults. These results provide evidence for the first time (a) that adults still need to inhibit the comparison of the subordinate classes' extensions in class-inclusion tasks and (b) that the ability to inhibit this heuristic increases with age (resulting in a lower executive cost). Taken together, these findings provide additional support for the neo-Piagetian approach of cognitive development that suggests that the acquisition of increasingly complex knowledge is based on the ability to resist (inhibit) heuristics and previously acquired knowledge.

  20. Development of a new class of satellites: a composite lightweight affordable spacecraft structure

    SciTech Connect

    Thompson, T.C.; Parietti, L.

    1996-06-01

    The Los Alamos National Laboratory (LANL) in partnership with Composite Optics Incorporated (COI) has successfully designed and tested a Composite Lightweight Affordable Structure (CLASS). The use of advanced composites in space applications is well developed, but the application of an all-composite satellite structure has not been achieved until now. The development of this low-cost, lightweight, composite technology for use in small satellite structures, in this case, for the Fast On-Orbit Recording of Transient Events (FORT{acute E}) satellite mission will make a considerable contribution to the advanced spacecraft community. A common practice for constructing small spacecraft structures is to use an all-aluminum spacecraft bus. Compared to a composite structure, this reduces the payload capacity significantly; however, the cost of the aluminum structure has historically been lower than one of that uses lightweight components. LANL mission requirements dictate the need for a long term solution that substantially increased the ratio of payload to structural mass while maintaining a low-risk low-cost approach. LANL intends to use the concept developed for FORT{acute E} on future missions requiring similar enhanced payload capacities. 1 fig.

  1. Molecular structure and spectroscopy of a bacteriopurpurin. A new class of bacteriochlorin photosensitizers

    SciTech Connect

    Robinson, B.C.; Barkigia, K.M.; Renner, M.W.; Fajer, J.

    1999-08-26

    Bacteriochlorins mediate energy and electron transfer in vivo and serve as biomimetic models of bacterial photosynthesis. Recently, the same physicochemical properties of the chromophores have made them attractive as photosensitizers for photodynamic therapy, a medical treatment that combines light, porphyrins, and oxygen to attack and destroy malignant tissue. Despite the intense biophysical, chemical, and medicinal interest in bacteriochlorins, very few high precision structures of the chromophores exist to provide the basis for theoretical calculations that seek to predict their extensively studied physicochemical properties. The authors report here the synthesis, spectral characterization, and structural determination of a metal-free bacteriopurpurin 1, a paradigm for a new class of photosensitizers comprised of porphyrins at the saturation level of bacteriochlorins flanked by two annelated, exocyclic cyclopentenyl rings. The molecule exhibits a very red-shifted Qy transition at 843 nm and is readily oxidized (at 0.39V vs SCE) to a {pi} cation radical with a distinctive EPR signal. The crystallographic results for 1 unambiguously identify the bacteriopurpurin, provide the first stereochemical parameters for this new class of expanded bacteriochlorins, extend the high resolution structural database for bacteriochlorins, and form the basis for theoretical calculations which correctly describe the optical features and electron density profile of 1 and its cation radical.

  2. [Anthropometric-nutritional status of a Spanish middle-class juvenile population. Study by age and sex groups].

    PubMed

    Gargallo Fernández, M A; de la Cruz Iglesias, A I; Garrudo Benito, D; de Cos Blanco, A I

    1993-01-01

    To make an initial approach to the current nutritional situation of the Spanish infant population, we carried out an anthropometric study of the children from 6 to 15 years of age in two schools in Fuenlabrada (Madrid) in a middle to lower class social environment. A total of 1,026 children were studied, to determine weight, height, tricipital fold and arm circumference. These parameters were used to calculate the weight/height ratio (w/h) and the muscular circumference of the arm. All these parameters were tabulated in percentile terms for comparison. The sample was divided into groups according to sex and to age (under 9, 9 to 12 and over 12). We found an overall w/h ratio of 108.8 +/- 17.4, more than the theoretical 100% (p < 0.001); 20.6% of the children over 120%. The Tricipital Fold (TFp) percentile was 62.5 +/- 27, with no differences according to age or sex. The percentile for arm muscular circumference (AMCp) was 48.8 +/- 27 for girls and 41.6 +/- 28 for boys (p < 0.001). Finally, we found a positive and significant correlation (p < 0.05) between w/h and AMCp (r = 0.51) and between w/h and TFp (r = 0.57). We conclude that the population studied is significantly overweight, confirming previous studies. Girls showed better nutritional parameters than the boys, apparently less nutritionally affected by the middle to low social environment. Finally, the w/h ratio, as an isolated parameter, is a good overall index of the nutritional state of children.

  3. Antiarrhythmic Drug Use in Patients <65 Years of Age With Atrial Fibrillation and Without Structural Heart Disease

    PubMed Central

    Allen LaPointe, Nancy M.; Dai, Dadi; Thomas, Laine; Piccini, Jonathan P.; Peterson, Eric D.; Al-Khatib, Sana M.

    2014-01-01

    Little is known in clinical practice about antiarrhythmic drug (AAD) use in atrial fibrillation (AF) patients (particularly younger ones) that do not have structural heart disease. Using the MarketScan® database, we identified patients <65 years of age without known coronary artery disease or heart failure who had an AAD prescription claim (Class Ic drug, amiodarone, sotalol, or dronedarone) after their first AF encounter. A multinomial logistic regression model was created to assess factors associated with using each available AAD, compared with using Class Ic drugs before and after dronedarone was marketed in the United States. Additionally, we used the Kaplan Meier method to determine the rates of change in AAD use and discontinuation during the year post-AAD initiation. Of 8562 AF patients, 35% received Class Ic drugs, 34% amiodarone, 24% sotalol, and 7% dronedarone. The median patient age was 56 (IQR 49, 61) and 34% were female. Both before and after dronedarone was marketed, there was a statistically significant lower likelihood of Class Ic drug use versus other AAD use with increasing age, inpatient index AF encounter, and prior or concomitant anticoagulation therapy. During the 1 year post-AAD initiation, the AAD change rate was 14% for Class Ic drugs, 8% amiodarone, 17% sotalol, and 18% dronedarone (p<0.001); the AAD discontinuation rate was 40% for Class Ic drugs, 52% amiodarone, 40% sotalol, and 69% dronedarone (p<0.001). In conclusion, we found extensive use of amiodarone that may be inconsistent with guideline recommendations, and unexpectedly high rates of AAD discontinuation. PMID:25491240

  4. Contextual Land Use Classification: how Detailed can the Class Structure Be?

    NASA Astrophysics Data System (ADS)

    Albert, L.; Rottensteiner, F.; Heipke, C.

    2016-06-01

    The goal of this paper is to investigate the maximum level of semantic resolution that can be achieved in an automated land use change detection process based on mono-temporal, multi-spectral, high-resolution aerial image data. For this purpose, we perform a step-wise refinement of the land use classes that follows the hierarchical structure of most object catalogues for land use databases. The investigation is based on our previous work for the simultaneous contextual classification of aerial imagery to determine land cover and land use. Land cover is determined at the level of small image segments. Land use classification is applied to objects from the geospatial database. Experiments are carried out on two test areas with different characteristics and are intended to evaluate the step-wise refinement of the land use classes empirically. The experiments show that a semantic resolution of ten classes still delivers acceptable results, where the accuracy of the results depends on the characteristics of the test areas used. Furthermore, we confirm that the incorporation of contextual knowledge, especially in the form of contextual features, is beneficial for land use classification.

  5. Inferring Selection Intensity and Allele Age from Multilocus Haplotype Structure

    PubMed Central

    Chen, Hua; Slatkin, Montgomery

    2013-01-01

    It is a challenging task to infer selection intensity and allele age from population genetic data. Here we present a method that can efficiently estimate selection intensity and allele age from the multilocus haplotype structure in the vicinity of a segregating mutant under positive selection. We use a structured-coalescent approach to model the effect of directional selection on the gene genealogies of neutral markers linked to the selected mutant. The frequency trajectory of the selected allele follows the Wright-Fisher model. Given the position of the selected mutant, we propose a simplified multilocus haplotype model that can efficiently model the dynamics of the ancestral haplotypes under the joint influence of selection and recombination. This model approximates the ancestral genealogies of the sample, which reduces the number of states from an exponential function of the number of single-nucleotide polymorphism loci to a quadratic function. That allows parameter inference from data covering DNA regions as large as several hundred kilo-bases. Importance sampling algorithms are adopted to evaluate the probability of a sample by exploring the space of both allele frequency trajectories of the selected mutation and gene genealogies of the linked sites. We demonstrate by simulation that the method can accurately estimate selection intensity for moderate and strong positive selection. We apply the method to a data set of the G6PD gene in an African population and obtain an estimate of 0.0456 (95% confidence interval 0.0144−0.0769) for the selection intensity. The proposed method is novel in jointly modeling the multilocus haplotype pattern caused by recombination and mutation, allowing the analysis of haplotype data in recombining regions. Moreover, the method is applicable to data from populations under exponential growth and a variety of other demographic histories. PMID:23797107

  6. Age- and sex-specific mortality and population structure in sea otters

    USGS Publications Warehouse

    Bodkin, J.L.; Burdin, A.M.; Ryazanov, D.A.

    2000-01-01

    We used 742 beach-cast carcasses to characterize age- and sex-specific sea otter mortality during the winter of 1990-1991 at Bering Island, Russia. We also examined 363 carcasses recovered after the 1989 grounding of the T/V Exxon Valdez, to characterize age and sex composition in the living western Prince William Sound (WPWS) sea otter population. At Bering Island, mortality was male-biased (81%), and 75% were adults. The WPWS population was female-biased (59%) and most animals were subadult (79% of the males and 45% of the females). In the decade prior to 1990-1991 we found increasing sea otter densities (particularly among males), declining prey resources, and declining weights in adult male sea otters at Bering Island. Our findings suggest the increased mortality at Bering Island in 1990-1991 was a density-dependent population response. We propose male-maintained breeding territories and exclusion of juvenile females by adult females, providing a mechanism for potentially moderating the effects of prey reductions on the female population. Increased adult male mortality at Bearing Island in 1990-1991 likely modified the sex and age class structure there toward that observed in Prince William Sound.

  7. Structural basis for a class of nanomolar influenza A neuraminidase inhibitors

    NASA Astrophysics Data System (ADS)

    Kerry, Philip S.; Mohan, Sankar; Russell, Rupert J. M.; Bance, Nicole; Niikura, Masahiro; Pinto, B. Mario

    2013-10-01

    The influenza virus neuraminidase (NA) is essential for the virus life cycle. The rise of resistance mutations against current antiviral therapies has increased the need for the development of novel inhibitors. Recent efforts have targeted a cavity adjacent to the catalytic site (the 150-cavity) in addition to the primary catalytic subsite in order to increase specificity and reduce the likelihood of resistance. This study details structural and in vitro analyses of a class of inhibitors that bind uniquely in both subsites. Crystal structures of three inhibitors show occupation of the 150-cavity in two distinct and novel binding modes. We believe these are the first nanomolar inhibitors of NA to be characterized in this way. Furthermore, we show that one inhibitor, binding within the catalytic site, offers reduced susceptibility to known resistance mutations via increased flexibility of a pendant pentyloxy group and the ability to pivot about a strong hydrogen-bonding network.

  8. How good strong union men line it out: explorations of the structure and dynamics of coal-miners' class consciousness

    SciTech Connect

    Yarrow, M.N.

    1982-01-01

    This study explores how working-class people apprehend and analyze the class dynamics of their social world. As an exploratory empirical study of the structure and dynamics of working-class consciousness, it seeks to develop the theory of actual class consciousness by bringing previous theories into dialogue with the articulated analyses of coal miners in central Appalachia. Although changing conditions are shown to have a powerful effect on class consciousness, the respondents were found to respond differently to the changing context and to remain loyal to important elements of their earlier perspectives. Suggestions are made for how the theory could be developed further. The data for the study are flexibly structured interviews which were conducted with active, retired, and disabled miners in southern West Virginia and western Virginia. A dozen miners were interviewed during the 1978 strike and again the following summer; during the summer of 1978, nineteen additional miners were interviewed.

  9. Structural and thermodynamic properties of kappa class glutathione transferase from Camelus dromedarius.

    PubMed

    Malik, Ajamaluddin; Fouad, Dalia; Labrou, Nikolaos E; Al-Senaidy, Abdulrahman M; Ismael, Mohamed A; Saeed, Hesham M; Ataya, Farid S

    2016-07-01

    The Arabian camel, Camelus dromedarius is naturally adapted to extreme desert climate and has evolved protective mechanisms to limit oxidative stress. The mitochondrial kappa class glutathione transferase enzyme is a member of GST supergene family that represents an important enzyme group in cellular Phase II detoxification machinery and is involved in the protection against oxidative stress and xenobiotics. In the present study, C. dromedarius kappa class glutathione transferase (CdGSTK1-1) was cloned, expressed in E. coli BL21, purified and its structural, thermodynamic and unfolding pathway was investigated. The results showed that CdGSTK1-1 has unique trimeric structure, exhibits low thermostability and a complex equilibrium unfolding profile. It unfolds through three folding states with formation of thinly populated intermediate species. The melting points (Tm) of the first unfolding transition was 40.3±0.2°C and Tm of the second unfolding transition was 49.1±0.1°C. The van't Hoff enthalpy of the first and second transition were 298.7±13.2 and 616.5±2.4kJ/mol, respectively. Moreover, intrinsic fluorescence and near-UV CD studies indicates that substrate binding does not leads to major conformational changes in CdGSTK1-1. PMID:27044344

  10. Characterization of Two Distinct Structural Classes of Selective Aldehyde Dehydrogenase 1A1 Inhibitors

    PubMed Central

    Morgan, Cynthia A.; Hurley, Thomas D.

    2015-01-01

    Aldehyde dehydrogenases (ALDH) catalyze the irreversible oxidation of aldehydes to their corresponding carboxylic acid. Alterations in ALDH1A1 activity are associated with such diverse diseases as cancer, Parkinson’s disease, obesity, and cataracts. Inhibitors of ALDH1A1 could aid in illuminating the role of this enzyme in disease processes. However, there are no commercially available selective inhibitors for ALDH1A1. Here we characterize two distinct chemical classes of inhibitors that are selective for human ALDH1A1 compared to eight other ALDH isoenzymes. The prototypical members of each structural class, CM026 and CM037, exhibit sub-micromolar inhibition constants, but have different mechanisms of inhibition. The crystal structures of these compounds bound to ALDH1A1 demonstrate that they bind within the aldehyde binding pocket of ALDH1A1 and exploit the presence of a unique Glycine residue to achieve their selectivity. These two novel and selective ALDH1A1 inhibitors may serve as chemical tools to better understand the contributions of ALDH1A1 to normal biology and to disease states. PMID:25634381

  11. Self-optimising control for a class of continuous bioreactor via variable-structure feedback

    NASA Astrophysics Data System (ADS)

    Lara-Cisneros, Gerardo; Alvarez-Ramírez, José; Femat, Ricardo

    2016-04-01

    A self-optimising controller is designed for stabilisation of a class of bioreactor exploiting sliding-mode techniques. The stability analysis for the class of bioreactor, in open-loop configuration, suggests that the optimal behaviour, respect to maximal biomass production, occurs in an unstable region (structurally unstable). In this contribution, a variable-structure controller is designed, exploiting the inhibitory effect of substrate concentration under the biomass growth rate, such that the closed-loop system reaches the optimal manifold where the effect induced by the growth rate gradient is compensated (favouring the maximum growth rate). The self-optimising comprises an uncertainty estimator which computes the unknown terms for increasing the robustness issues of the sliding-mode scheme. Numerical experiments illustrate the performance and execution of the control strategy considering different parameter values for biomass growth rate. The robustness and fragility of the proposed controller are also discussed with respect to the modelling uncertainty and small changes in the controller gains, respectively.

  12. Crystal structures and inhibitor binding properties of plant class V chitinases: the cycad enzyme exhibits unique structural and functional features.

    PubMed

    Umemoto, Naoyuki; Kanda, Yuka; Ohnuma, Takayuki; Osawa, Takuo; Numata, Tomoyuki; Sakuda, Shohei; Taira, Toki; Fukamizo, Tamo

    2015-04-01

    A class V (glycoside hydrolase family 18) chitinase from the cycad Cycas revoluta (CrChiA) is a plant chitinase that has been reported to possess efficient transglycosylation (TG) activity. We solved the crystal structure of CrChiA, and compared it with those of class V chitinases from Nicotiana tabacum (NtChiV) and Arabidopsis thaliana (AtChiC), which do not efficiently catalyze the TG reaction. All three chitinases had a similar (α/β)8 barrel fold with an (α + β) insertion domain. In the acceptor binding site (+1, +2 and +3) of CrChiA, the Trp168 side chain was found to stack face-to-face with the +3 sugar. However, this interaction was not found in the identical regions of NtChiV and AtChiC. In the DxDxE motif, which is essential for catalysis, the carboxyl group of the middle Asp (Asp117) was always oriented toward the catalytic acid Glu119 in CrChiA, whereas the corresponding Asp in NtChiV and AtChiC was oriented toward the first Asp. These structural features of CrChiA appear to be responsible for the efficient TG activity. When binding of the inhibitor allosamidin was evaluated using isothermal titration calorimetry, the changes in binding free energy of the three chitinases were found to be similar to each other, i.e. between -9.5 and -9.8 kcal mol(-1) . However, solvation and conformational entropy changes in CrChiA were markedly different from those in NtChiV and AtChiC, but similar to those of chitinase A from Serratia marcescens (SmChiA), which also exhibits significant TG activity. These results provide insight into the molecular mechanism underlying the TG reaction and the molecular evolution from bacterial chitinases to plant class V chitinases.

  13. Structures of Staphylococcus aureus peptide deformylase in complex with two classes of new inhibitors.

    PubMed

    Lee, Sang Jae; Lee, Seung-Jae; Lee, Seung Kyu; Yoon, Hye-Jin; Lee, Hyung Ho; Kim, Kyeong Kyu; Lee, Bong Jin; Lee, Byung Il; Suh, Se Won

    2012-07-01

    Peptide deformylase (PDF) catalyzes the removal of the formyl group from the N-terminal methionine residue in newly synthesized polypeptides, which is an essential process in bacteria. Four new inhibitors of PDF that belong to two different classes, hydroxamate/pseudopeptide compounds [PMT387 (7a) and PMT497] and reverse-hydroxamate/nonpeptide compounds [PMT1039 (15e) and PMT1067], have been developed. These compounds inhibited the growth of several pathogens involved in respiratory-tract infections, such as Streptococcus pneumoniae, Moraxella catarrhalis and Haemophilus influenzae, and leading nosocomial pathogens such as Staphylococcus aureus and Klebsiella pneumoniae with a minimum inhibitory concentration (MIC) in the range 0.1-0.8 mg ml(-1). Interestingly, the reverse-hydroxamate/nonpeptide compounds showed a 250-fold higher antimicrobial activity towards S. aureus, although the four compounds showed similar K(i) values against S. aureus PDF enzymes, with K(i) values in the 11-85 nM range. To provide a structural basis for the discovery of additional PDF inhibitors, the crystal structures of S. aureus PDF in complex with the four inhibitors were determined at resolutions of 1.90-2.30 Å. The inhibitor-bound structures displayed distinct deviations depending on the inhibitor class. The distance between the Zn(2+) ion and the carbonyl O atom of the hydroxamate inhibitors (or the hydroxyl O atom of the reverse-hydroxamate inhibitors) appears to be correlated to S. aureus inhibition activity. The structural information reported in this study should aid in the discovery of new PDF inhibitors that can be used as novel antibacterial drugs. PMID:22751663

  14. Urban groundwater age modeling under unconfined condition - Impact of underground structures on groundwater age: Evidence of a piston effect

    NASA Astrophysics Data System (ADS)

    Attard, Guillaume; Rossier, Yvan; Eisenlohr, Laurent

    2016-04-01

    In this paper, underground structures are shown to have a major influence on the groundwater mean age distribution described as a dispersive piston effect. Urban underground development does not occur without impacts on subsoil resources. In particular, groundwater resources can be vulnerable and generate disturbances when this space is exploited. Groundwater age spatial distribution data are fundamental for resource management as it can provide operational sustainability indicators. However, the application of groundwater age modeling is neglected regarding the potential effect of underground structures in urban areas. A three dimensional modeling approach was conducted to quantify the impact of two underground structures: (1) an impervious structure and (2) a draining structure. Both structures are shown to cause significant mixing processes occurring between shallow and deeper aquifers. The design technique used for draining structures is shown to have the greatest impact, generating a decrease in mean age of more than 80% under the structure. Groundwater age modeling is shown to be relevant for highlighting the role played by underground structures in advective-dispersive flows in urban areas.

  15. The Work of Power and the Power of Work: Teaching for Class Consciousness in the Neo-Liberal Age

    ERIC Educational Resources Information Center

    Weiner, Eric J.

    2004-01-01

    As workers throughout the globe struggle to gain control over the conditions in which they labor as well as the means by which capital is produced, the importance of understanding class struggle, class formation and class consciousness as they relate to education and schooling takes on a new urgency. In the early part of the twenty-first century,…

  16. Optimal lineage principle for age-structured populations

    NASA Astrophysics Data System (ADS)

    Kussell, Edo

    2012-02-01

    Populations whose individuals exhibit age-dependent growth have often been studied using temporal dynamics of age distributions. In this talk, I examine the dynamics of age along lineages. We will see that the lineage point-of-view provides fundamental insights into evolutionary pressures on individuals' aging profiles. I will describe a variational principle that enables exact results for lineage statistics, in a variety of models. I will also discuss measurements on continuously dividing bacterial populations growing in microfluidics devices.

  17. Structural determinants for ligand capture by a class II preQ1 riboswitch

    PubMed Central

    Kang, Mijeong; Eichhorn, Catherine D.; Feigon, Juli

    2014-01-01

    Prequeuosine (preQ1) riboswitches are RNA regulatory elements located in the 5′ UTR of genes involved in the biosynthesis and transport of preQ1, a precursor of the modified base queuosine universally found in four tRNAs. The preQ1 class II (preQ1-II) riboswitch regulates preQ1 biosynthesis at the translational level. We present the solution NMR structure and conformational dynamics of the 59 nucleotide Streptococcus pneumoniae preQ1-II riboswitch bound to preQ1. Unlike in the preQ1 class I (preQ1-I) riboswitch, divalent cations are required for high-affinity binding. The solution structure is an unusual H-type pseudoknot featuring a P4 hairpin embedded in loop 3, which forms a three-way junction with the other two stems. 13C relaxation and residual dipolar coupling experiments revealed interhelical flexibility of P4. We found that the P4 helix and flanking adenine residues play crucial and unexpected roles in controlling pseudoknot formation and, in turn, sequestering the Shine–Dalgarno sequence. Aided by divalent cations, P4 is poised to act as a “screw cap” on preQ1 recognition to block ligand exit and stabilize the binding pocket. Comparison of preQ1-I and preQ1-II riboswitch structures reveals that whereas both form H-type pseudoknots and recognize preQ1 using one A, C, or U nucleotide from each of three loops, these nucleotides interact with preQ1 differently, with preQ1 inserting into different grooves. Our studies show that the preQ1-II riboswitch uses an unusual mechanism to harness exquisite control over queuosine metabolism. PMID:24469808

  18. Structural diversity and transcription of class III peroxidases from Arabidopsis thaliana.

    PubMed

    Welinder, Karen G; Justesen, Annemarie F; Kjaersgård, Inger V H; Jensen, Rikke B; Rasmussen, Søren K; Jespersen, Hans M; Duroux, Laurent

    2002-12-01

    Understanding peroxidase function in plants is complicated by the lack of substrate specificity, the high number of genes, their diversity in structure and our limited knowledge of peroxidase gene transcription and translation. In the present study we sequenced expressed sequence tags (ESTs) encoding novel heme-containing class III peroxidases from Arabidopsis thaliana and annotated 73 full-length genes identified in the genome. In total, transcripts of 58 of these genes have now been observed. The expression of individual peroxidase genes was assessed in organ-specific EST libraries and compared to the expression of 33 peroxidase genes which we analyzed in whole plants 3, 6, 15, 35 and 59 days after sowing. Expression was assessed in root, rosette leaf, stem, cauline leaf, flower bud and cell culture tissues using the gene-specific and highly sensitive reverse transcriptase-polymerase chain reaction (RT-PCR). We predicted that 71 genes could yield stable proteins folded similarly to horseradish peroxidase (HRP). The putative mature peroxidases derived from these genes showed 28-94% amino acid sequence identity and were all targeted to the endoplasmic reticulum by N-terminal signal peptides. In 20 peroxidases these signal peptides were followed by various N-terminal extensions of unknown function which are not present in HRP. Ten peroxidases showed a C-terminal extension indicating vacuolar targeting. We found that the majority of peroxidase genes were expressed in root. In total, class III peroxidases accounted for an impressive 2.2% of root ESTs. Rather few peroxidases showed organ specificity. Most importantly, genes expressed constitutively in all organs and genes with a preference for root represented structurally diverse peroxidases (< 70% sequence identity). Furthermore, genes appearing in tandem showed distinct expression profiles. The alignment of 73 Arabidopsis peroxidase sequences provides an easy access to the identification of orthologous peroxidases

  19. Structural analysis of an epsilon-class glutathione transferase from housefly, Musca domestica.

    PubMed

    Nakamura, Chihiro; Yajima, Shunsuke; Miyamoto, Toru; Sue, Masayuki

    2013-01-25

    Glutathione transferases (GSTs) play an important role in the detoxification of insecticides, and as such, they are a key contributor to enhanced resistance to insecticides. In the housefly (Musca domestica), two epsilon-class GSTs (MdGST6A and MdGST6B) that share high sequence homology have been identified, which are believed to be involved in resistance against insecticides. The structural determinants controlling the substrate specificity and enzyme activity of MdGST6s are unknown. The aim of this study was to crystallize and perform structural analysis of the GST isozyme, MdGST6B. The crystal structure of MdGST6B complexed with reduced glutathione (GSH) was determined at a resolution of 1.8 Å. MdGST6B was found to have a typical GST folding comprised of N-terminal and C-terminal domains. Arg113 and Phe121 on helix 4 were shown to protrude into the substrate binding pocket, and as a result, the entrance of the substrate binding pocket was narrower compared to delta- and epsilon-class GSTs from Africa malaria vector Anopheles gambiae, agGSTd1-6 and agGSTe2, respectively. This substrate pocket narrowing is partly due to the presence of a π-helix in the middle of helix 4. Among the six residues that donate hydrogen bonds to GSH, only Arg113 was located in the C-terminal domain. Ala substitution of Arg113 did not have a significant effect on enzyme activity, suggesting that the Arg113 hydrogen bond does not play a crucial role in catalysis. On the other hand, mutation at Phe108, located just below Arg113 in the binding pocket, reduced the affinity and catalytic activity to both GSH and the electrophilic co-substrate, 1-chloro-2,4-dinitrobenzene.

  20. Structural Insights into a Novel Class of Aspartate Aminotransferase from Corynebacterium glutamicum

    PubMed Central

    Son, Hyeoncheol Francis; Kim, Kyung-Jin

    2016-01-01

    Aspartate aminotransferase from Corynebacterium glutamicum (CgAspAT) is a PLP-dependent enzyme that catalyzes the production of L-aspartate and α-ketoglutarate from L-glutamate and oxaloacetate in L-lysine biosynthesis. In order to understand the molecular mechanism of CgAspAT and compare it with those of other aspartate aminotransferases (AspATs) from the aminotransferase class I, we determined the crystal structure of CgAspAT. CgAspAT functions as a dimer, and the CgAspAT monomer consists of two domains, the core domain and the auxiliary domain. The PLP cofactor is found to be bound to CgAspAT and stabilized through unique residues. In our current structure, a citrate molecule is bound at the active site of one molecule and mimics binding of the glutamate substrate. The residues involved in binding of the PLP cofactor and the glutamate substrate were confirmed by site-directed mutagenesis. Interestingly, compared with other AspATs from aminotransferase subgroup Ia and Ib, CgAspAT exhibited unique binding sites for both cofactor and substrate; moreover, it was found to have unusual structural features in the auxiliary domain. Based on these structural differences, we propose that CgAspAT does not belong to either subgroup Ia or Ib, and can be categorized into a subgroup Ic. The phylogenetic tree and RMSD analysis also indicates that CgAspAT is located in an independent AspAT subgroup. PMID:27355211

  1. The Structure of Genealogies in the Presence of Purifying Selection: A Fitness-Class Coalescent

    PubMed Central

    Walczak, Aleksandra M.; Nicolaisen, Lauren E.; Plotkin, Joshua B.; Desai, Michael M.

    2012-01-01

    Compared to a neutral model, purifying selection distorts the structure of genealogies and hence alters the patterns of sampled genetic variation. Although these distortions may be common in nature, our understanding of how we expect purifying selection to affect patterns of molecular variation remains incomplete. Genealogical approaches such as coalescent theory have proven difficult to generalize to situations involving selection at many linked sites, unless selection pressures are extremely strong. Here, we introduce an effective coalescent theory (a “fitness-class coalescent”) to describe the structure of genealogies in the presence of purifying selection at many linked sites. We use this effective theory to calculate several simple statistics describing the expected patterns of variation in sequence data, both at the sites under selection and at linked neutral sites. Our analysis combines a description of the allele frequency spectrum in the presence of purifying selection with the structured coalescent approach of Kaplan et al. (1988), to trace the ancestry of individuals through the distribution of fitnesses within the population. We also derive our results using a more direct extension of the structured coalescent approach of Hudson and Kaplan (1994). We find that purifying selection leads to patterns of genetic variation that are related but not identical to a neutrally evolving population in which population size has varied in a specific way in the past. PMID:22135349

  2. Structural insights into the dehydroascorbate reductase activity of human omega-class glutathione transferases.

    PubMed

    Zhou, Huina; Brock, Joseph; Liu, Dan; Board, Philip G; Oakley, Aaron J

    2012-07-13

    The reduction of dehydroascorbate (DHA) to ascorbic acid (AA) is a vital cellular function. The omega-class glutathione transferases (GSTs) catalyze several reductive reactions in cellular biochemistry, including DHA reduction. In humans, two isozymes (GSTO1-1 and GSTO2-2) with significant DHA reductase (DHAR) activity are found, sharing 64% sequence identity. While the activity of GSTO2-2 is higher, it is significantly more unstable in vitro. We report the first crystal structures of human GSTO2-2, stabilized through site-directed mutagenesis and determined at 1.9 Å resolution in the presence and absence of glutathione (GSH). The structure of a human GSTO1-1 has been determined at 1.7 Å resolution in complex with the reaction product AA, which unexpectedly binds in the G-site, where the glutamyl moiety of GSH binds. The structure suggests a similar mode of ascorbate binding in GSTO2-2. This is the first time that a non-GSH-based reaction product has been observed in the G-site of any GST. AA stacks against a conserved aromatic residue, F34 (equivalent to Y34 in GSTO2-2). Mutation of Y34 to alanine in GSTO2-2 eliminates DHAR activity. From these structures and other biochemical data, we propose a mechanism of substrate binding and catalysis of DHAR activity.

  3. MAGNETIC STRUCTURE PRODUCING X- AND M-CLASS SOLAR FLARES IN SOLAR ACTIVE REGION 11158

    SciTech Connect

    Inoue, S.; Magara, T.; Choe, G. S.; Hayashi, K.; Shiota, D.

    2013-06-10

    We study the three-dimensional magnetic structure of the solar active region 11158, which produced one X-class and several M-class flares on 2011 February 13-16. We focus on the magnetic twist in four flare events, M6.6, X2.2, M1.0, and M1.1. The magnetic twist is estimated from the nonlinear force-free field extrapolated from the vector fields obtained from the Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory using the magnetohydrodynamic relaxation method developed by Inoue et al. We found that strongly twisted lines ranging from half-turn to one-turn twists were built up just before the M6.6 and X2.2 flares and disappeared after that. Because most of the twists remaining after these flares were less than a half-turn twist, this result suggests that the buildup of magnetic twist over the half-turn twist is a key process in the production of large flares. On the other hand, even though these strong twists were also built up just before the M1.0 and M1.1 flares, most of them remained afterward. Careful topological analysis before the M1.0 and M1.1 flares shows that the strongly twisted lines were surrounded mostly by the weakly twisted lines formed in accordance with the clockwise motion of the positive sunspot, whose footpoints are rooted in strong magnetic flux regions. These results imply that these weakly twisted lines might suppress the activity of the strongly twisted lines in the last two M-class flares.

  4. Sequence-structure based phylogeny of GPCR Class A Rhodopsin receptors.

    PubMed

    Kakarala, Kavita Kumari; Jamil, Kaiser

    2014-05-01

    Current methods of G protein coupled receptors (GPCRs) phylogenetic classification are sequence based and therefore inappropriate for highly divergent sequences, sharing low sequence identity. In this study, sequence structure profile based alignment generated by PROMALS3D was used to understand the GPCR Class A Rhodopsin superfamily evolution using the MEGA 5 software. Phylogenetic analysis included a combination of Neighbor-Joining method and Maximum Likelihood method, with 1000 bootstrap replicates. Our study was able to identify potential ligand association for Class A Orphans and putative/unclassified Class A receptors with no cognate ligand information: GPR21 and GPR52 with fatty acids; GPR75 with Neuropeptide Y; GPR82, GPR18, GPR141 with N-arachidonylglycine; GPR176 with Free fatty acids, GPR10 with Tachykinin & Neuropeptide Y; GPR85 with ATP, ADP & UDP glucose; GPR151 with Galanin; GPR153 and GPR162 with Adrenalin, Noradrenalin; GPR146, GPR139, GPR142 with Neuromedin, Ghrelin, Neuromedin U-25 & Thyrotropin-releasing hormone; GPR171 with ATP, ADP & UDP Glucose; GPR88, GPR135, GPR161, GPR101with 11-cis-retinal; GPR83 with Tackykinin; GPR148 with Prostanoids, GPR109b, GPR81, GPR31with ATP & UTP and GPR150 with GnRH I & GnRHII. Furthermore, we suggest that this study would prove useful in re-classification of receptors, selecting templates for homology modeling and identifying ligands which may show cross reactivity with other GPCRs as signaling via multiple ligands play a significant role in disease modulation.

  5. Sensitivity analysis of the age-structured malaria transmission model

    NASA Astrophysics Data System (ADS)

    Addawe, Joel M.; Lope, Jose Ernie C.

    2012-09-01

    We propose an age-structured malaria transmission model and perform sensitivity analyses to determine the relative importance of model parameters to disease transmission. We subdivide the human population into two: preschool humans (below 5 years) and the rest of the human population (above 5 years). We then consider two sets of baseline parameters, one for areas of high transmission and the other for areas of low transmission. We compute the sensitivity indices of the reproductive number and the endemic equilibrium point with respect to the two sets of baseline parameters. Our simulations reveal that in areas of either high or low transmission, the reproductive number is most sensitive to the number of bites by a female mosquito on the rest of the human population. For areas of low transmission, we find that the equilibrium proportion of infectious pre-school humans is most sensitive to the number of bites by a female mosquito. For the rest of the human population it is most sensitive to the rate of acquiring temporary immunity. In areas of high transmission, the equilibrium proportion of infectious pre-school humans and the rest of the human population are both most sensitive to the birth rate of humans. This suggests that strategies that target the mosquito biting rate on pre-school humans and those that shortens the time in acquiring immunity can be successful in preventing the spread of malaria.

  6. Cooperation-controlled learning for explicit class structure in self-organizing maps.

    PubMed

    Kamimura, Ryotaro

    2014-01-01

    We attempt to demonstrate the effectiveness of multiple points of view toward neural networks. By restricting ourselves to two points of view of a neuron, we propose a new type of information-theoretic method called "cooperation-controlled learning." In this method, individual and collective neurons are distinguished from one another, and we suppose that the characteristics of individual and collective neurons are different. To implement individual and collective neurons, we prepare two networks, namely, cooperative and uncooperative networks. The roles of these networks and the roles of individual and collective neurons are controlled by the cooperation parameter. As the parameter is increased, the role of cooperative networks becomes more important in learning, and the characteristics of collective neurons become more dominant. On the other hand, when the parameter is small, individual neurons play a more important role. We applied the method to the automobile and housing data from the machine learning database and examined whether explicit class boundaries could be obtained. Experimental results showed that cooperation-controlled learning, in particular taking into account information on input units, could be used to produce clearer class structure than conventional self-organizing maps. PMID:25309950

  7. A Class of Rigid Linker-bearing Glucosides for Membrane Protein Structural Study

    PubMed Central

    Sadaf, Aiman; Mortensen, Jonas S.; Capaldi, Stefano; Tikhonova, Elena; Hariharan, Parameswaran; de Castro Ribeiro, Orquidea; Loland, Claus J; Guan, Lan; Byrne, Bernadette

    2015-01-01

    Membrane proteins are amphipathic bio-macromolecules incompatible with the polar environments of aqueous media. Conventional detergents encapsulate the hydrophobic surfaces of membrane proteins allowing them to exist in aqueous solution. Membrane proteins stabilized by detergent micelles are used for structural and functional analysis. Despite the availability of a large number of detergents, only a few agents are sufficiently effective at maintaining the integrity of membrane proteins to allow successful crystallization. In the present study, we describe a novel class of synthetic amphiphiles with a branched tail group and a triglucoside head group. These head and tail groups were connected via an amide or ether linkage by using a tris(hydroxylmethyl)aminomethane (TRIS) or neopentyl glycol (NPG) linker to produce TRIS-derived triglucosides (TDTs) and NPG-derived triglucosides (NDTs), respectively. Members of this class conferred enhanced stability on target membrane proteins compared to conventional detergents. Because of straightforward synthesis of the novel agents and their favourable effects on a range of membrane proteins, these agents should be of wide applicability to membrane protein science. PMID:27110345

  8. Cooperation-controlled learning for explicit class structure in self-organizing maps.

    PubMed

    Kamimura, Ryotaro

    2014-01-01

    We attempt to demonstrate the effectiveness of multiple points of view toward neural networks. By restricting ourselves to two points of view of a neuron, we propose a new type of information-theoretic method called "cooperation-controlled learning." In this method, individual and collective neurons are distinguished from one another, and we suppose that the characteristics of individual and collective neurons are different. To implement individual and collective neurons, we prepare two networks, namely, cooperative and uncooperative networks. The roles of these networks and the roles of individual and collective neurons are controlled by the cooperation parameter. As the parameter is increased, the role of cooperative networks becomes more important in learning, and the characteristics of collective neurons become more dominant. On the other hand, when the parameter is small, individual neurons play a more important role. We applied the method to the automobile and housing data from the machine learning database and examined whether explicit class boundaries could be obtained. Experimental results showed that cooperation-controlled learning, in particular taking into account information on input units, could be used to produce clearer class structure than conventional self-organizing maps.

  9. Quaternary structure defines a large class of amyloid-β oligomers neutralized by sequestration

    PubMed Central

    Liu, Peng; Reed, Miranda N.; Kotilinek, Linda A.; Grant, Marianne K.O.; Forster, Colleen L.; Qiang, Wei; Shapiro, Samantha L.; Reichl, John H.; Chiang, Angie C.A.; Jankowsky, Joanna L.; Wilmot, Carrie M.; Cleary, James P.; Zahs, Kathleen R.; Ashe, Karen H.

    2015-01-01

    Summary The accumulation of amyloid-β (Aβ) as amyloid fibrils and toxic oligomers is an important step in the development of Alzheimer's disease (AD). However, there are numerous potentially toxic oligomers and little is known about their neurological effects when generated in the living brain. Here, we show that Aβ oligomers can be assigned to one of at least two classes (Type 1 and Type 2) based on their temporal, spatial and structural relationships to amyloid fibrils. The Type 2 oligomers are related to amyloid fibrils and represent the majority of oligomers generated in vivo, but remain confined to the vicinity of amyloid plaques and do not impair cognition at levels relevant to AD. Type 1 oligomers are unrelated to amyloid fibrils and may have greater potential to cause global neural dysfunction in AD because they are dispersed. These results refine our understanding of the pathogenicity of Aβ oligomers in vivo. PMID:26051935

  10. Role of post-translational modifications on structure, function and pharmacology of class C G protein-coupled receptors.

    PubMed

    Nørskov-Lauritsen, Lenea; Bräuner-Osborne, Hans

    2015-09-15

    G protein-coupled receptors are divided into three classes (A, B and C) based on homology of their seven transmembrane domains. Class C is the smallest class with 22 human receptor subtypes including eight metabotropic glutamate (mGlu1-8) receptors, two GABAB receptors (GABAB1 and GABAB2), three taste receptors (T1R1-3), one calcium-sensing (CaS) receptor, one GPCR, class C, group 6, subtype A (GPRC6) receptor, and seven orphan receptors. G protein-coupled receptors undergo a number of post-translational modifications, which regulate their structure, function and/or pharmacology. Here, we review the existence of post-translational modifications in class C G protein-coupled receptors and their regulatory roles, with particular focus on glycosylation, phosphorylation, ubiquitination, SUMOylation, disulphide bonding and lipidation.

  11. Variation of Meat Quality Parameters Due to Conformation and Fat Class in Limousin Bulls Slaughtered at 25 to 27 Months of Age

    PubMed Central

    Guzek, Dominika; Głąska, Dominika; Pogorzelski, Grzegorz; Kozań, Karolina; Pietras, Jacek; Konarska, Małgorzata; Sakowska, Anna; Głąski, Krzysztof; Pogorzelska, Ewelina; Barszczewski, Jerzy; Wierzbicka, Agnieszka

    2013-01-01

    The aim of the present study was to determine the influence of age of animal, hot carcass weight, pH, conformation and fat class on basic beef quality attributes (tenderness, sarcomere length, basic chemical composition, marbling and colour) in a group of purebred animals. The object of the study was beef of Limousin bulls (25 to 27 months, hot carcass weight - 432±31 kg, “U” conformation class, “2”–“3” fat class). Analysed cuts were Infraspinatus muscle from the blade and Longissimus dorsi muscle from the cube roll and the striploin. Tenderness was analysed with universal testing machine, colour - chromometer analysis, sarcomere length - microscopic method, basic chemical composition - near-infrared spectroscopy and marbling - computer image analysis. No differences in tenderness and sarcomere length were observed within the age groups of Limousin bulls (age of 25, 26, 27 months) (p>0.05). Moisture (p = 0.0123) and fat (p = 0.0250) content were significantly different for meat of animals slaughtered at the age of 25 and 27 months. No influence of pH value on tenderness was observed, but at the same time, influence on sarcomere length (p = 0.039) and b* component of colour (0.045) was found. For “U” conformation class, in subclasses, as well as for fat classes “2”–“3”, there were no differences in tenderness, sarcomere length and colour components. Higher fat content was observed in the higher fat class, rather than in lower, however this feature was not associated with marbling. PMID:25049844

  12. Novel 3D bio-macromolecular bilinear descriptors for protein science: Predicting protein structural classes.

    PubMed

    Marrero-Ponce, Yovani; Contreras-Torres, Ernesto; García-Jacas, César R; Barigye, Stephen J; Cubillán, Néstor; Alvarado, Ysaías J

    2015-06-01

    In the present study, we introduce novel 3D protein descriptors based on the bilinear algebraic form in the ℝ(n) space on the coulombic matrix. For the calculation of these descriptors, macromolecular vectors belonging to ℝ(n) space, whose components represent certain amino acid side-chain properties, were used as weighting schemes. Generalization approaches for the calculation of inter-amino acidic residue spatial distances based on Minkowski metrics are proposed. The simple- and double-stochastic schemes were defined as approaches to normalize the coulombic matrix. The local-fragment indices for both amino acid-types and amino acid-groups are presented in order to permit characterizing fragments of interest in proteins. On the other hand, with the objective of taking into account specific interactions among amino acids in global or local indices, geometric and topological cut-offs are defined. To assess the utility of global and local indices a classification model for the prediction of the major four protein structural classes, was built with the Linear Discriminant Analysis (LDA) technique. The developed LDA-model correctly classifies the 92.6% and 92.7% of the proteins on the training and test sets, respectively. The obtained model showed high values of the generalized square correlation coefficient (GC(2)) on both the training and test series. The statistical parameters derived from the internal and external validation procedures demonstrate the robustness, stability and the high predictive power of the proposed model. The performance of the LDA-model demonstrates the capability of the proposed indices not only to codify relevant biochemical information related to the structural classes of proteins, but also to yield suitable interpretability. It is anticipated that the current method will benefit the prediction of other protein attributes or functions. PMID:25843214

  13. Novel 3D bio-macromolecular bilinear descriptors for protein science: Predicting protein structural classes.

    PubMed

    Marrero-Ponce, Yovani; Contreras-Torres, Ernesto; García-Jacas, César R; Barigye, Stephen J; Cubillán, Néstor; Alvarado, Ysaías J

    2015-06-01

    In the present study, we introduce novel 3D protein descriptors based on the bilinear algebraic form in the ℝ(n) space on the coulombic matrix. For the calculation of these descriptors, macromolecular vectors belonging to ℝ(n) space, whose components represent certain amino acid side-chain properties, were used as weighting schemes. Generalization approaches for the calculation of inter-amino acidic residue spatial distances based on Minkowski metrics are proposed. The simple- and double-stochastic schemes were defined as approaches to normalize the coulombic matrix. The local-fragment indices for both amino acid-types and amino acid-groups are presented in order to permit characterizing fragments of interest in proteins. On the other hand, with the objective of taking into account specific interactions among amino acids in global or local indices, geometric and topological cut-offs are defined. To assess the utility of global and local indices a classification model for the prediction of the major four protein structural classes, was built with the Linear Discriminant Analysis (LDA) technique. The developed LDA-model correctly classifies the 92.6% and 92.7% of the proteins on the training and test sets, respectively. The obtained model showed high values of the generalized square correlation coefficient (GC(2)) on both the training and test series. The statistical parameters derived from the internal and external validation procedures demonstrate the robustness, stability and the high predictive power of the proposed model. The performance of the LDA-model demonstrates the capability of the proposed indices not only to codify relevant biochemical information related to the structural classes of proteins, but also to yield suitable interpretability. It is anticipated that the current method will benefit the prediction of other protein attributes or functions.

  14. The poplar Phi class glutathione transferase: expression, activity and structure of GSTF1

    PubMed Central

    Pégeot, Henri; Koh, Cha San; Petre, Benjamin; Mathiot, Sandrine; Duplessis, Sébastien; Hecker, Arnaud; Didierjean, Claude; Rouhier, Nicolas

    2014-01-01

    Glutathione transferases (GSTs) constitute a superfamily of enzymes with essential roles in cellular detoxification and secondary metabolism in plants as in other organisms. Several plant GSTs, including those of the Phi class (GSTFs), require a conserved catalytic serine residue to perform glutathione (GSH)-conjugation reactions. Genomic analyses revealed that terrestrial plants have around ten GSTFs, eight in the Populus trichocarpa genome, but their physiological functions and substrates are mostly unknown. Transcript expression analyses showed a predominant expression of all genes both in reproductive (female flowers, fruits, floral buds) and vegetative organs (leaves, petioles). Here, we show that the recombinant poplar GSTF1 (PttGSTF1) possesses peroxidase activity toward cumene hydroperoxide and GSH-conjugation activity toward model substrates such as 2,4-dinitrochlorobenzene, benzyl and phenetyl isothiocyanate, 4-nitrophenyl butyrate and 4-hydroxy-2-nonenal but interestingly not on previously identified GSTF-class substrates. In accordance with analytical gel filtration data, crystal structure of PttGSTF1 showed a canonical dimeric organization with bound GSH or 2-(N-morpholino)ethanesulfonic acid molecules. The structure of these protein-substrate complexes allowed delineating the residues contributing to both the G and H sites that form the active site cavity. In sum, the presence of GSTF1 transcripts and proteins in most poplar organs especially those rich in secondary metabolites such as flowers and fruits, together with its GSH-conjugation activity and its documented stress-responsive expression suggest that its function is associated with the catalytic transformation of metabolites and/or peroxide removal rather than with ligandin properties as previously reported for other GSTFs. PMID:25566286

  15. The Indris Have Got Rhythm! Timing and Pitch Variation of a Primate Song Examined between Sexes and Age Classes

    PubMed Central

    Gamba, Marco; Torti, Valeria; Estienne, Vittoria; Randrianarison, Rose M.; Valente, Daria; Rovara, Paolo; Bonadonna, Giovanna; Friard, Olivier; Giacoma, Cristina

    2016-01-01

    A crucial, common feature of speech and music is that they show non-random structures over time. It is an open question which of the other species share rhythmic abilities with humans, but in most cases the lack of knowledge about their behavioral displays prevents further studies. Indris are the only lemurs who sing. They produce loud howling cries that can be heard at several kilometers, in which all members of a group usually sing. We tested whether overlapping and turn-taking during the songs followed a precise pattern by analysing the temporal structure of the individuals' contribution to the song. We found that both dominants (males and females) and non-dominants influenced the onset timing one another. We have found that the dominant male and the dominant female in a group overlapped each other more frequently than they did with the non-dominants. We then focused on the temporal and frequency structure of particular phrases occurring during the song. Our results show that males and females have dimorphic inter-onset intervals during the phrases. Moreover, median frequencies of the unit emitted in the phrases also differ between the sexes, with males showing higher frequencies when compared to females. We have not found an effect of age on the temporal and spectral structure of the phrases. These results indicate that singing in indris has a high behavioral flexibility and varies according to social and individual factors. The flexible spectral structure of the phrases given during the song may underlie perceptual abilities that are relatively unknown in other non-human primates, such as the ability to recognize particular pitch patterns. PMID:27378834

  16. Tangled up in knots – Structures of inactivated forms of E. coli class Ia Ribonucleotide Reductase

    PubMed Central

    Zimanyi, Christina M.; Ando, Nozomi; Brignole, Edward J.; Asturias, Francisco J.; Stubbe, JoAnne; Drennan, Catherine L.

    2012-01-01

    Summary Successful targets for anti-cancer drugs such as clofarabine and gemcitabine, ribonucleotide reductases (RNRs) provide the precursors for DNA biosynthesis and repair. Recently, we reported that dATP inhibits E. coli class Ia RNR by driving formation of RNR subunits into α4β4 rings. Here, we present the first X-ray structure of gemcitabine-inhibited E. coli RNR and show that the previously described α4β4 rings can interlock to form an unprecedented (α4β4)2 megacomplex. This complex is also seen in a higher-resolution dATP-inhibited RNR structure presented here, which employs a distinct crystal lattice from that observed in the gemcitabine-inhibited case. With few reported examples of protein catenanes, we use data from small-angle X-ray scattering and electron microscopy to both understand the solution conditions that contribute to concatenation in RNR as well as present a mechanism for the formation of these unusual structures. PMID:22727814

  17. Tangled Up in Knots: Structures of Inactivated Forms of E. coli Class Ia Ribonucleotide Reductase

    SciTech Connect

    Zimanyi, Christina M.; Ando, Nozomi; Brignole, Edward J.; Asturias, Francisco J.; Stubbe, JoAnne; Drennan, Catherine L.

    2012-10-23

    Ribonucleotide reductases (RNRs) provide the precursors for DNA biosynthesis and repair and are successful targets for anticancer drugs such as clofarabine and gemcitabine. Recently, we reported that dATP inhibits E. coli class Ia RNR by driving formation of RNR subunits into {alpha}{sub 4}{beta}{sub 4} rings. Here, we present the first X-ray structure of a gemcitabine-inhibited E. coli RNR and show that the previously described {alpha}{sub 4}{beta}{sub 4} rings can interlock to form an unprecedented ({alpha}{sub 4}{beta}{sub 4}){sub 2} megacomplex. This complex is also seen in a higher-resolution dATP-inhibited RNR structure presented here, which employs a distinct crystal lattice from that observed in the gemcitabine-inhibited case. With few reported examples of protein catenanes, we use data from small-angle X-ray scattering and electron microscopy to both understand the solution conditions that contribute to concatenation in RNRs as well as present a mechanism for the formation of these unusual structures.

  18. X-Ray Structure Reveals a New Class and Provides Insight into Evolution of Alkaline Phosphatases

    PubMed Central

    Bihani, Subhash C.; Das, Amit; Nilgiriwala, Kayzad S.; Prashar, Vishal; Pirocchi, Michel; Apte, Shree Kumar; Ferrer, Jean-Luc; Hosur, Madhusoodan V.

    2011-01-01

    The alkaline phosphatase (AP) is a bi-metalloenzyme of potential applications in biotechnology and bioremediation, in which phosphate monoesters are nonspecifically hydrolysed under alkaline conditions to yield inorganic phosphate. The hydrolysis occurs through an enzyme intermediate in which the catalytic residue is phosphorylated. The reaction, which also requires a third metal ion, is proposed to proceed through a mechanism of in-line displacement involving a trigonal bipyramidal transition state. Stabilizing the transition state by bidentate hydrogen bonding has been suggested to be the reason for conservation of an arginine residue in the active site. We report here the first crystal structure of alkaline phosphatase purified from the bacterium Sphingomonas. sp. Strain BSAR-1 (SPAP). The crystal structure reveals many differences from other APs: 1) the catalytic residue is a threonine instead of serine, 2) there is no third metal ion binding pocket, and 3) the arginine residue forming bidentate hydrogen bonding is deleted in SPAP. A lysine and an aspargine residue, recruited together for the first time into the active site, bind the substrate phosphoryl group in a manner not observed before in any other AP. These and other structural features suggest that SPAP represents a new class of APs. Because of its direct contact with the substrate phosphoryl group, the lysine residue is proposed to play a significant role in catalysis. The structure is consistent with a mechanism of in-line displacement via a trigonal bipyramidal transition state. The structure provides important insights into evolutionary relationships between members of AP superfamily. PMID:21829507

  19. Middle and upper cretaceous amber from the Taimyr Peninsula, Siberia: Evidence for a new structural sub-class of resinite

    SciTech Connect

    Anderson, K.B.

    1994-08-01

    Analysis of three amber (resinite) samples collected from Middle and Upper Cretaceous sediments in the Taimyr Peninsula, Siberia, indicates that these materials are based on copolymers of biformene (I) and communol (II). No resinites of similar structural character have previously been described and hence, these samples represent a previously unknown structural sub-class of resinite.

  20. Race/Ethnicity and Social Capital among Middle- and Upper-Middle-Class Elementary School Families: A Structural Equation Model

    ERIC Educational Resources Information Center

    Caldas, Stephen J.; Cornigans, Linda

    2015-01-01

    This study used structural equation modeling to conduct a first and second order confirmatory factor analysis (CFA) of a scale developed by McDonald and Moberg (2002) to measure three dimensions of social capital among a diverse group of middle- and upper-middle-class elementary school parents in suburban New York. A structural path model was…

  1. Geo-structural mapping and age determinations of Rembrandt basin.

    NASA Astrophysics Data System (ADS)

    Ferrari, Sabrina; Massironi, Matteo; Martellato, Elena; Giacomini, Lorenza; Cremonese, Gabriele; Rothery, David; Prockter, Louise M.

    During its second and thirds flybys MESSENGER imaged a new large and well-preserved basin called Rembrandt Basin (Watters et al., 2009) in Mercury's southern hemisphere. Rembrandt is partially filled by volcanic overlay and is crossed by a marked lobate scarp with some similarities to another prominent mercurian lobate scarp, Beagle Rupes. In attempt to reveal Rembrandt Basin evolution, we mapped its geological units inferring -where possible -their stratigraphic relationships. In addition, we performed crater counts on several of these units and derived age estimates by applying Model Production Function (MPF) absolute-model chronology (Marchi et al., 2009). Since Rembrandt basin (in contrast to other well-seen basins) displays evidence of global-scale in addition to basin-localized deformation (Watters et al. 2009), it is characterized by different tectonic features that in some cases may be controlled by rheological layering within the crust. We attempted to map the contractional and extensional local patterns and the global tectonic features. Notably, the pronounced scarp transecting a 60 km crater near the edge of Rembrandt's inner ring and other structural features in the surrounding regions suggest a linked fault system. The apparent bow shape of this feature could be compared with Beagle Rupes, and similarly may imply special conditions of weakness inside the crust (Rothery and Massironi, 2010). Ref. Watters, T. R., Head, J. W., Solomon, S. C., Robinson, M. S., Chapman, C. R., Denevi, B. W., Fassett, C. I., Murchie, S. L., and Strom, R. G., 2009. Evolution of the Rembrandt Impact Basin on Mercury. Science, 324 , 618-621. Marchi, S., Mottola, S., Cremonese, G., Massironi, M., and Martellato, E., 2009. A new Chronology for the Moon and Mercury. Astronomical Journal, 137 , 4936-4948. Rothery, D. A. and Massironi, M., 2010. Beagle Rupes -evidence for a basal decollement of regional extent in Mercury's lithosphere. Icarus (In Press).

  2. Differential Predation by Age and Sex Classes in Blue Wildebeest in Serengeti: Study of a Modern Carnivore Den in Olduvai Gorge (Tanzania)

    PubMed Central

    Arriaza, Mari Carmen; Domínguez-Rodrigo, Manuel; Martínez-Maza, Cayetana; Mabulla, Audax; Baquedano, Enrique

    2015-01-01

    Age and sex selection of prey is an aspect of predator ecology which has been extensively studied in both temperate and African ecosystems. This dimension, along with fecundity, survival rates of prey and mortality factors other than predation are important in laying down the population dynamics of prey and have important implications in the management of species. A carnivore den located in the short-grassland ecological unit of the Serengeti was studied. Sex- and age- class (using five age categories) of the wildebeest remains recovered were analyzed through horn morphology, biometrics of the bones and tooth wear patterns. We compared our results with previous studies from lion and hyaena kills through multivariate analyses. Seasonality of the accumulation was analyzed through tooth histology. PCA and CVA results show that age class selection by predators depends on season, habitat-type, and growth rate of the wildebeest population. Female-biased predation was found to contradict classical hypotheses based on territorial male behaviour. The lion and spotted hyaena showed strong selection on age classes, contrary to previous studies. Migratory wildebeest sex ratio is regulated through differential predation by seasons and female deaths in the wet season are a trade-off for population stability. These data are crucial for an effective management of the species and the new method created may be useful for different carnivore species and their prey. PMID:26017363

  3. Differential predation by age and sex classes in blue wildebeest in Serengeti: study of a modern carnivore den in Olduvai Gorge (Tanzania).

    PubMed

    Arriaza, Mari Carmen; Domínguez-Rodrigo, Manuel; Martínez-Maza, Cayetana; Mabulla, Audax; Baquedano, Enrique

    2015-01-01

    Age and sex selection of prey is an aspect of predator ecology which has been extensively studied in both temperate and African ecosystems. This dimension, along with fecundity, survival rates of prey and mortality factors other than predation are important in laying down the population dynamics of prey and have important implications in the management of species. A carnivore den located in the short-grassland ecological unit of the Serengeti was studied. Sex- and age- class (using five age categories) of the wildebeest remains recovered were analyzed through horn morphology, biometrics of the bones and tooth wear patterns. We compared our results with previous studies from lion and hyaena kills through multivariate analyses. Seasonality of the accumulation was analyzed through tooth histology. PCA and CVA results show that age class selection by predators depends on season, habitat-type, and growth rate of the wildebeest population. Female-biased predation was found to contradict classical hypotheses based on territorial male behaviour. The lion and spotted hyaena showed strong selection on age classes, contrary to previous studies. Migratory wildebeest sex ratio is regulated through differential predation by seasons and female deaths in the wet season are a trade-off for population stability. These data are crucial for an effective management of the species and the new method created may be useful for different carnivore species and their prey. PMID:26017363

  4. Differential predation by age and sex classes in blue wildebeest in Serengeti: study of a modern carnivore den in Olduvai Gorge (Tanzania).

    PubMed

    Arriaza, Mari Carmen; Domínguez-Rodrigo, Manuel; Martínez-Maza, Cayetana; Mabulla, Audax; Baquedano, Enrique

    2015-01-01

    Age and sex selection of prey is an aspect of predator ecology which has been extensively studied in both temperate and African ecosystems. This dimension, along with fecundity, survival rates of prey and mortality factors other than predation are important in laying down the population dynamics of prey and have important implications in the management of species. A carnivore den located in the short-grassland ecological unit of the Serengeti was studied. Sex- and age- class (using five age categories) of the wildebeest remains recovered were analyzed through horn morphology, biometrics of the bones and tooth wear patterns. We compared our results with previous studies from lion and hyaena kills through multivariate analyses. Seasonality of the accumulation was analyzed through tooth histology. PCA and CVA results show that age class selection by predators depends on season, habitat-type, and growth rate of the wildebeest population. Female-biased predation was found to contradict classical hypotheses based on territorial male behaviour. The lion and spotted hyaena showed strong selection on age classes, contrary to previous studies. Migratory wildebeest sex ratio is regulated through differential predation by seasons and female deaths in the wet season are a trade-off for population stability. These data are crucial for an effective management of the species and the new method created may be useful for different carnivore species and their prey.

  5. RSL Class I Genes Controlled the Development of Epidermal Structures in the Common Ancestor of Land Plants.

    PubMed

    Proust, Hélène; Honkanen, Suvi; Jones, Victor A S; Morieri, Giulia; Prescott, Helen; Kelly, Steve; Ishizaki, Kimitsune; Kohchi, Takayuki; Dolan, Liam

    2016-01-11

    The colonization of the land by plants, sometime before 470 million years ago, was accompanied by the evolution tissue systems [1-3]. Specialized structures with diverse functions-from nutrient acquisition to reproduction-derived from single cells in the outermost layer (epidermis) were important sources of morphological innovation at this time [2, 4, 5]. In extant plants, these structures may be unicellular extensions, such as root hairs or rhizoids [6-9], or multicellular structures, such as asexual propagules or secretory hairs (papillae) [10-12]. Here, we show that a ROOTHAIR DEFECTIVE SIX-LIKE (RSL) class I basic helix-loop-helix transcription factor positively regulates the development of the unicellular and multicellular structures that develop from individual cells that expand out of the epidermal plane of the liverwort Marchantia polymorpha; mutants that lack MpRSL1 function do not develop rhizoids, slime papillae, mucilage papillae, or gemmae. Furthermore, we discovered that RSL class I genes are also required for the development of multicellular axillary hairs on the gametophyte of the moss Physcomitrella patens. Because class I RSL proteins also control the development of rhizoids in mosses and root hairs in angiosperms [13, 14], these data demonstrate that the function of RSL class I genes was to control the development of structures derived from single epidermal cells in the common ancestor of the land plants. Class I RSL genes therefore controlled the generation of adaptive morphological diversity as plants colonized the land from the water. PMID:26725198

  6. RSL Class I Genes Controlled the Development of Epidermal Structures in the Common Ancestor of Land Plants

    PubMed Central

    Proust, Hélène; Honkanen, Suvi; Jones, Victor A.S.; Morieri, Giulia; Prescott, Helen; Kelly, Steve; Ishizaki, Kimitsune; Kohchi, Takayuki; Dolan, Liam

    2016-01-01

    Summary The colonization of the land by plants, sometime before 470 million years ago, was accompanied by the evolution tissue systems [1, 2, 3]. Specialized structures with diverse functions—from nutrient acquisition to reproduction—derived from single cells in the outermost layer (epidermis) were important sources of morphological innovation at this time [2, 4, 5]. In extant plants, these structures may be unicellular extensions, such as root hairs or rhizoids [6, 7, 8, 9], or multicellular structures, such as asexual propagules or secretory hairs (papillae) [10, 11, 12]. Here, we show that a ROOTHAIR DEFECTIVE SIX-LIKE (RSL) class I basic helix-loop-helix transcription factor positively regulates the development of the unicellular and multicellular structures that develop from individual cells that expand out of the epidermal plane of the liverwort Marchantia polymorpha; mutants that lack MpRSL1 function do not develop rhizoids, slime papillae, mucilage papillae, or gemmae. Furthermore, we discovered that RSL class I genes are also required for the development of multicellular axillary hairs on the gametophyte of the moss Physcomitrella patens. Because class I RSL proteins also control the development of rhizoids in mosses and root hairs in angiosperms [13, 14], these data demonstrate that the function of RSL class I genes was to control the development of structures derived from single epidermal cells in the common ancestor of the land plants. Class I RSL genes therefore controlled the generation of adaptive morphological diversity as plants colonized the land from the water. PMID:26725198

  7. RSL Class I Genes Controlled the Development of Epidermal Structures in the Common Ancestor of Land Plants.

    PubMed

    Proust, Hélène; Honkanen, Suvi; Jones, Victor A S; Morieri, Giulia; Prescott, Helen; Kelly, Steve; Ishizaki, Kimitsune; Kohchi, Takayuki; Dolan, Liam

    2016-01-11

    The colonization of the land by plants, sometime before 470 million years ago, was accompanied by the evolution tissue systems [1-3]. Specialized structures with diverse functions-from nutrient acquisition to reproduction-derived from single cells in the outermost layer (epidermis) were important sources of morphological innovation at this time [2, 4, 5]. In extant plants, these structures may be unicellular extensions, such as root hairs or rhizoids [6-9], or multicellular structures, such as asexual propagules or secretory hairs (papillae) [10-12]. Here, we show that a ROOTHAIR DEFECTIVE SIX-LIKE (RSL) class I basic helix-loop-helix transcription factor positively regulates the development of the unicellular and multicellular structures that develop from individual cells that expand out of the epidermal plane of the liverwort Marchantia polymorpha; mutants that lack MpRSL1 function do not develop rhizoids, slime papillae, mucilage papillae, or gemmae. Furthermore, we discovered that RSL class I genes are also required for the development of multicellular axillary hairs on the gametophyte of the moss Physcomitrella patens. Because class I RSL proteins also control the development of rhizoids in mosses and root hairs in angiosperms [13, 14], these data demonstrate that the function of RSL class I genes was to control the development of structures derived from single epidermal cells in the common ancestor of the land plants. Class I RSL genes therefore controlled the generation of adaptive morphological diversity as plants colonized the land from the water.

  8. Spatio-temporal variations in age structures of a partially re-established population of northern river otters (Lontra canadensis)

    USGS Publications Warehouse

    Barrett, Dominic A.; Leslie,, David M.

    2012-01-01

    Examination of age structures and sex ratios is useful in the management of northern river otters (Lontra canadensis) and other furbearers. Reintroductions and subsequent recolonizations of river otters have been well documented, but changes in demographics between expanding and established populations have not been observed. As a result of reintroduction efforts, immigration from Arkansas and northeastern Texas, and other efforts, river otters have become partially reestablished throughout eastern and central Oklahoma. Our objective was to examine age structures of river otters in Oklahoma and identify trends that relate to space (watersheds, county) and time (USDA Animal and Plant Health Inspection Service county trapping records). We predicted that river otters in western areas of the state were younger than river otters occurring farther east. From 2005–2007, we obtained salvaged river otter carcasses from federal and state agencies, and we live-captured other river otters using leg hold traps. Seventy-two river otters were sampled. Overall, sex ratios were skewed toward females (1F∶0.8M), but they did not differ among spatiotemporal scales examined. Teeth were removed from salvaged and live-captured river otters (n  =  63) for aging. One-year old river otters represented the largest age class (30.2%). Proportion of juveniles (<1 y old) in Oklahoma (19.0%) was less than other states. Mean age of river otters decreased from east-to-west in the Arkansas River and its tributaries. Mean age of river otters differed between the Canadian River Watershed (0.8 y) and the Arkansas River Watershed (2.9 y) and the Canadian River Watershed and the Red River Watershed (2.4 y). Proportion of juveniles did not differ among spatiotemporal scales examined. Similar to age structure variations in other mammalian carnivores, colonizing or growing western populations of river otters in Oklahoma contained younger ages than more established eastern populations.

  9. 49 CFR 176.172 - Structural serviceability of freight containers and vehicles carrying Class 1 (explosive...

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... and vehicles carrying Class 1 (explosive) materials on ships. 176.172 Section 176.172 Transportation... serviceability of freight containers and vehicles carrying Class 1 (explosive) materials on ships. (a) Except for...) Before a freight container or transport vehicle is packed with Class 1 (explosive) materials, it must...

  10. 49 CFR 176.172 - Structural serviceability of freight containers and vehicles carrying Class 1 (explosive...

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... and vehicles carrying Class 1 (explosive) materials on ships. 176.172 Section 176.172 Transportation... serviceability of freight containers and vehicles carrying Class 1 (explosive) materials on ships. (a) Except for...) Before a freight container or transport vehicle is packed with Class 1 (explosive) materials, it must...

  11. 77 FR 27815 - Aging Management of Stainless Steel Structures and Components in Treated Borated Water

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-11

    ... COMMISSION Aging Management of Stainless Steel Structures and Components in Treated Borated Water AGENCY..., ``Aging Management of Stainless Steel Structures and Components in Treated Borated Water.'' This LR-ISG... stainless steel structures and components exposed to treated borated water. The NRC published Revision 2...

  12. Effects of Aging Structures and Humidity on Fatigue Properties of Maraging Steel

    NASA Astrophysics Data System (ADS)

    Hayashi, Kousuke; Nagano, Takanori; Moriyama, Michihiko; Wang, Xishu; Kawagoishi, Norio

    Effects of aging structures and humidity on fatigue properties of 350 grade 18% Ni maraging steel were investigated under rotating bending in relative humidity of 25% and 85%. Aging conditions tested were a conventional single aging and a double one which was aged at low temperature after the conventional aging. In each aging, under and peak aged steels were prepared. Tensile strength was increased by the double aging without reduction of the ductility. Proportional relation between fatigue limit and Vickers hardness held until 750HV in low humidity. However fatigue strength was largely decreased by high humidity, especially in the peak aged steel at the single aging. The decrease in fatigue strength by high humidity was mainly caused by the acceleration of a crack initiation due to the anodic dissolution. The acceleration of a crack initiation was larger in the steel peak aged at the single aging with larger precipitated particles.

  13. Geometric and electronic structure of the Mn(IV)Fe(III) cofactor in class Ic ribonucleotide reductase: correlation to the class Ia binuclear non-heme iron enzyme.

    PubMed

    Kwak, Yeonju; Jiang, Wei; Dassama, Laura M K; Park, Kiyoung; Bell, Caleb B; Liu, Lei V; Wong, Shaun D; Saito, Makina; Kobayashi, Yasuhiro; Kitao, Shinji; Seto, Makoto; Yoda, Yoshitaka; Alp, E Ercan; Zhao, Jiyong; Bollinger, J Martin; Krebs, Carsten; Solomon, Edward I

    2013-11-20

    The class Ic ribonucleotide reductase (RNR) from Chlamydia trachomatis (Ct) utilizes a Mn/Fe heterobinuclear cofactor, rather than the Fe/Fe cofactor found in the β (R2) subunit of the class Ia enzymes, to react with O2. This reaction produces a stable Mn(IV)Fe(III) cofactor that initiates a radical, which transfers to the adjacent α (R1) subunit and reacts with the substrate. We have studied the Mn(IV)Fe(III) cofactor using nuclear resonance vibrational spectroscopy (NRVS) and absorption (Abs)/circular dichroism (CD)/magnetic CD (MCD)/variable temperature, variable field (VTVH) MCD spectroscopies to obtain detailed insight into its geometric/electronic structure and to correlate structure with reactivity; NRVS focuses on the Fe(III), whereas MCD reflects the spin-allowed transitions mostly on the Mn(IV). We have evaluated 18 systematically varied structures. Comparison of the simulated NRVS spectra to the experimental data shows that the cofactor has one carboxylate bridge, with Mn(IV) at the site proximal to Phe127. Abs/CD/MCD/VTVH MCD data exhibit 12 transitions that are assigned as d-d and oxo and OH(-) to metal charge-transfer (CT) transitions. Assignments are based on MCD/Abs intensity ratios, transition energies, polarizations, and derivative-shaped pseudo-A term CT transitions. Correlating these results with TD-DFT calculations defines the Mn(IV)Fe(III) cofactor as having a μ-oxo, μ-hydroxo core and a terminal hydroxo ligand on the Mn(IV). From DFT calculations, the Mn(IV) at site 1 is necessary to tune the redox potential to a value similar to that of the tyrosine radical in class Ia RNR, and the OH(-) terminal ligand on this Mn(IV) provides a high proton affinity that could gate radical translocation to the α (R1) subunit.

  14. Geometric and Electronic Structure of the Mn(IV)Fe(III) Cofactor in Class Ic Ribonucleotide Reductase: Correlation to the Class Ia Binuclear Non-Heme Iron Enzyme

    PubMed Central

    Kwak, Yeonju; Jiang, Wei; Dassama, Laura M.K.; Park, Kiyoung; Bell, Caleb B.; Liu, Lei V.; Wong, Shaun D.; Saito, Makina; Kobayashi, Yasuhiro; Kitao, Shinji; Seto, Makoto; Yoda, Yoshitaka; Alp, E. Ercan; Zhao, Jiyong; Bollinger, J Martin; Krebs, Carsten; Solomon, Edward I.

    2013-01-01

    The class Ic ribonucleotide reductase (RNR) from Chlamydia trachomatis (Ct) utilizes a Mn/Fe hetero-binuclear cofactor, rather than the Fe/Fe cofactor found in the β (R2) subunit of the class Ia enzymes, to react with O2. This reaction produces a stable MnIVFeIII cofactor that initiates a radical, which transfers to the adjacent α (R1) subunit and reacts with the substrate. We have studied the MnIVFeIII cofactor using nuclear resonance vibrational spectroscopy (NRVS) and absorption (Abs) / circular dichroism (CD) / magnetic CD (MCD) / variable temperature, variable field (VTVH) MCD spectroscopies to obtain detailed insight into its geometric/electronic structure and to correlate structure with reactivity; NRVS focuses on the FeIII, whereas MCD reflects the spin-allowed transitions mostly on the MnIV. We have evaluated 18 systematically varied structures. Comparison of the simulated NRVS spectra to the experimental data shows that the cofactor has one carboxylate bridge, with MnIV at the site proximal to Phe127. Abs/CD/MCD/VTVH MCD data exhibit 12 transitions that are assigned as d-d, and oxo and OH− to metal charge transfer (CT) transitions. Assignments are based on MCD/Abs intensity ratios, transition energies, polarizations, and derivative-shaped pseudo-A term CT transitions. Correlating these results with TD-DFT calculations defines the MnIVFeIII cofactor as having a µ-oxo, µ-hydroxo core and a terminal hydroxo ligand on the MnIV. From DFT calculations, the MnIV at site 1 is necessary to tune the redox potential to a value similar to that of the tyrosine radical in class Ia RNR, and the OH− terminal ligand on this MnIV provides a high proton affinity that could gate radical translocation to the α (R1) subunit. PMID:24131208

  15. Structure Determination and Interception of Biosynthetic Intermediates for the Plantazolicin Class of Highly Discriminating Antibiotics

    PubMed Central

    Molohon, Katie J.; Melby, Joel O.; Lee, Jaeheon; Evans, Bradley S.; Dunbar, Kyle L.; Bumpus, Stefanie B.; Kelleher, Neil L.; Mitchell, Douglas A.

    2011-01-01

    The soil dwelling, plant-growth promoting bacterium, Bacillus amyloliquefaciens FZB42, is a prolific producer of complex natural products. Recently, a new FZB42 metabolite, plantazolicin (PZN), has been described as a member of the growing thiazole/oxazole-modified microcin (TOMM) family. TOMMs are biosynthesized from inactive, ribosomal peptides and undergo a series of cyclodehydrations, dehydrogenations, and other modifications to become bioactive natural products. Using high-resolution mass spectrometry, chemoselective modification, genetic interruptions, and other spectroscopic tools, we have determined the molecular structure of PZN. In addition to two conjugated polyazole moieties, the amino-terminus of PZN has been modified to Nα,Nα-dimethylarginine. PZN exhibited a highly selective antibiotic activity towards Bacillus anthracis, but no other tested human pathogen. By altering oxygenation levels during fermentation, PZN analogs were produced that bear variability in their heterocycle content, which yielded insight into the order of biosynthetic events. Lastly, genome-mining has revealed the existence of four additional PZN-like biosynthetic gene clusters. Given their structural uniqueness and intriguing antimicrobial specificity, the PZN class of antibiotics may hold pharmacological value. PMID:21950656

  16. [Structure and function of class 1 integron in clinical isolates of Klebsiella pneumoniae].

    PubMed

    Yuejin, Zhang; Qingli, Chang; Qian, Wang; Junwan, Lu; Huan, Wang; Peizhen, Li; Jun, Ying; Qiyu, Bao; Yunliang, Hu

    2014-06-01

    To investigate molecular mechanism of multi-resistance of Klebsiella pneumoniae and its spreading, 179 strains isolated from different clinical samples in the period of 2002-2007 with serious resistance to 14 anti-bacterial agents were examined. Among them, 118 (65.9%) were resistant to at least two anti-bacterial agents; 36.3% (65/179) were found to contain class 1 integrons. There was a significant difference for resistance rate between the integron positive and the negative groups, especially for antimicrobial agents of aminoglycosides, quinolones and sulfonamides (P<0.01). Gene cassette structures of the class 1 integrons in these bacteria were analyzed and their resistance genes were further cloned and tested for antibiotic resistance activities. Fifteen gene cassettes were identified with dfrA17-aadA5 being the most popular form. Three recombinant plasmids pET28a-dhfr17, pET28a-dhfr17-orfF and pET28a-dhfr17-orfF-aadA2 were cloned from a gene cassette of dhfr17-orfF-aadA2. When introduced into a recipient E. coli strain BL21, all of them rendered resistance to co-trimoxazole, with minimum inhibitory concentration (MIC) value up to 256 µg/µL. The E. coli BL21 carrying pET28a- dhfr17 or pET28a-dhfr17-orfF had the same MIC value of 8 µg/µL to streptomycin as the recipient strain without plasmid. However, the E. coli carrying pET28a-dhfr17-orfF-aadA2 was resistant to streptomycin with MIC level up to 256 µg/µL. In conclusion, class 1 integrons were regularly identified in Klebsiella pneumoniae. They mainly carry resistance genes against antimicrobial agents of aminoglycosides and sulfonamide. Transferable plasmid carrying integrons with resistance genes may play an important role in resistance spreading among bacterial species.

  17. Semantics, Phrase Structure and Age as Variables in Sentence Recall.

    ERIC Educational Resources Information Center

    Van Every, Harolyn; Rosenberg, Sheldon

    Forty first-grade and 40 seventh-grade children were assigned at random to four groups of 20 each (two at each age level) and were administered four study-test trials involving oral presentation and oral recall of a list of four sentences of the form article-adjective-noun-verb-adverb. Half of the subjects at each level of age were given…

  18. Age of onset of schizophrenia: perspectives from structural neuroimaging studies.

    PubMed

    Gogtay, Nitin; Vyas, Nora S; Testa, Renee; Wood, Stephen J; Pantelis, Christos

    2011-05-01

    Many of the major neuropsychiatric illnesses, including schizophrenia, have a typical age of onset in late adolescence. Late adolescence may reflect a critical period in brain development making it particularly vulnerable for the onset of psychopathology. Neuroimaging studies that focus on this age range may provide unique insights into the onset and course of psychosis. In this review, we examine the evidence from 2 unique longitudinal cohorts that span the ages from early childhood through young adulthood; a study of childhood-onset schizophrenia where patients and siblings are followed from ages 6 through to their early twenties, and an ultra-high risk study where subjects (mean age of 19 years) are studied before and after the onset of psychosis. From the available evidence, we make an argument that subtle, regionally specific, and genetically influenced alterations during developmental age windows influence the course of psychosis and the resultant brain phenotype. The importance of examining trajectories of development and the need for future combined approaches, using multimodal imaging together with molecular studies is discussed. PMID:21505117

  19. Structural evolution in the aging process of supercooled colloidal liquids.

    PubMed

    Kawasaki, Takeshi; Tanaka, Hajime

    2014-06-01

    When a liquid is rapidly quenched to a temperature below the glass-transition point, it is driven out of equilibrium; it then slowly relaxes to a (quasi)equilibrium state. This slow relaxation process is called aging. By definition, any glasses are inevitably in the process of aging and actually slowly evolving with time. Thus the study of aging phenomena is of fundamental importance for understanding not only the nonequilibrium nature of the glass transition, but also the stability of glassy materials. Here we consider aging after a rather shallow quench, for which a system is still able to reach (metastable) equilibrium. By using polydisperse colloidal liquids as a model, we show the validity of dynamical scaling that there is only one relevant length scale not only for a quasiequilibrium supercooled state but also for a nonequilibrium process of aging, which is reminiscent of dynamical critical phenomena. Our finding indicates that the aging toward (metastable) equilibrium may be regarded as the growth process of critical-like fluctuations of static order associated with low-free-energy configurations, further suggesting that this ordering is the origin of cooperative slow dynamics in the systems studied. The generality of this statement for other glass-forming systems remains for a future study. PMID:25019784

  20. Age of Onset of Schizophrenia: Perspectives From Structural Neuroimaging Studies

    PubMed Central

    Gogtay, Nitin; Vyas, Nora S.; Testa, Renee; Wood, Stephen J.; Pantelis, Christos

    2011-01-01

    Many of the major neuropsychiatric illnesses, including schizophrenia, have a typical age of onset in late adolescence. Late adolescence may reflect a critical period in brain development making it particularly vulnerable for the onset of psychopathology. Neuroimaging studies that focus on this age range may provide unique insights into the onset and course of psychosis. In this review, we examine the evidence from 2 unique longitudinal cohorts that span the ages from early childhood through young adulthood; a study of childhood-onset schizophrenia where patients and siblings are followed from ages 6 through to their early twenties, and an ultra-high risk study where subjects (mean age of 19 years) are studied before and after the onset of psychosis. From the available evidence, we make an argument that subtle, regionally specific, and genetically influenced alterations during developmental age windows influence the course of psychosis and the resultant brain phenotype. The importance of examining trajectories of development and the need for future combined approaches, using multimodal imaging together with molecular studies is discussed. PMID:21505117

  1. Structural evolution in the aging process of supercooled colloidal liquids

    NASA Astrophysics Data System (ADS)

    Kawasaki, Takeshi; Tanaka, Hajime

    2014-06-01

    When a liquid is rapidly quenched to a temperature below the glass-transition point, it is driven out of equilibrium; it then slowly relaxes to a (quasi)equilibrium state. This slow relaxation process is called aging. By definition, any glasses are inevitably in the process of aging and actually slowly evolving with time. Thus the study of aging phenomena is of fundamental importance for understanding not only the nonequilibrium nature of the glass transition, but also the stability of glassy materials. Here we consider aging after a rather shallow quench, for which a system is still able to reach (metastable) equilibrium. By using polydisperse colloidal liquids as a model, we show the validity of dynamical scaling that there is only one relevant length scale not only for a quasiequilibrium supercooled state but also for a nonequilibrium process of aging, which is reminiscent of dynamical critical phenomena. Our finding indicates that the aging toward (metastable) equilibrium may be regarded as the growth process of critical-like fluctuations of static order associated with low-free-energy configurations, further suggesting that this ordering is the origin of cooperative slow dynamics in the systems studied. The generality of this statement for other glass-forming systems remains for a future study.

  2. Lake Erie Yellow perch age estimation based on three structures: Precision, processing times, and management implications

    USGS Publications Warehouse

    Vandergoot, C.S.; Bur, M.T.; Powell, K.A.

    2008-01-01

    Yellow perch Perca flavescens support economically important recreational and commercial fisheries in Lake Erie and are intensively managed. Age estimation represents an integral component in the management of Lake Erie yellow perch stocks, as age-structured population models are used to set safe harvest levels on an annual basis. We compared the precision associated with yellow perch (N = 251) age estimates from scales, sagittal otoliths, and anal spine sections and evaluated the time required to process and estimate age from each structure. Three readers of varying experience estimated ages. The precision (mean coefficient of variation) of estimates among readers was 1% for sagittal otoliths, 5-6% for anal spines, and 11-13% for scales. Agreement rates among readers were 94-95% for otoliths, 71-76% for anal spines, and 45-50% for scales. Systematic age estimation differences were evident among scale and anal spine readers; less-experienced readers tended to underestimate ages of yellow perch older than age 4 relative to estimates made by an experienced reader. Mean scale age tended to underestimate ages of age-6 and older fish relative to otolith ages estimated by an experienced reader. Total annual mortality estimates based on scale ages were 20% higher than those based on otolith ages; mortality estimates based on anal spine ages were 4% higher than those based on otolith ages. Otoliths required more removal and preparation time than scales and anal spines, but age estimation time was substantially lower for otoliths than for the other two structures. We suggest the use of otoliths or anal spines for age estimation in yellow perch (regardless of length) from Lake Erie and other systems where precise age estimates are necessary, because age estimation errors resulting from the use of scales could generate incorrect management decisions. ?? Copyright by the American Fisheries Society 2008.

  3. [Structure of the articular cartilage in the middle aged].

    PubMed

    Kop'eva, T N; Mul'diiarov, P Ia; Bel'skaia, O B; Pastel', V B

    1983-10-01

    In persons 17-83 years of age having no articular disorders 39 samples of the patellar articular cartilage, the articulated surface and the femoral head have been studied histochemically, histometrically and electron microscopically. Age involution of the articular cartilage is revealed after 40 years of age as a progressive decrease in chondrocytes density in the superficial and (to a less degree) in the intermediate zones. This is accompanied with a decreasing number of 3- and 4-cellular lacunae and with an increasing number of unicellular and hollow lacunae. In some chondrocytes certain distrophic and necrotic changes are revealed. In the articular matrix the zone with the minimal content of glycosaminoglycans becomes thicker and keratansulfate content in the territorial matrix of the cartilage deep zone grows large.

  4. Structural and Functional Characterization of Methicillin-Resistant Staphylococcus aureus’s Class IIb Fructose 1,6-Bisphosphate Aldolase

    PubMed Central

    2015-01-01

    Staphylococcus aureus is one of the most common nosocomial sources of soft-tissue and skin infections and has more recently become prevalent in the community setting as well. Since the use of penicillins to combat S. aureus infections in the 1940s, the bacterium has been notorious for developing resistances to antibiotics, such as methicillin-resistant Staphylococcus aureus (MRSA). With the persistence of MRSA as well as many other drug resistant bacteria and parasites, there is a growing need to focus on new pharmacological targets. Recently, class II fructose 1,6-bisphosphate aldolases (FBAs) have garnered attention to fill this role. Regrettably, scarce biochemical data and no structural data are currently available for the class II FBA found in MRSA (SaFBA). With the recent finding of a flexible active site zinc-binding loop (Z-Loop) in class IIa FBAs and its potential for broad spectrum class II FBA inhibition, the lack of information regarding this feature of class IIb FBAs, such as SaFBA, has been limiting for further Z-loop inhibitor development. Therefore, we elucidated the crystal structure of SaFBA to 2.1 Å allowing for a more direct structural analysis of SaFBA. Furthermore, we determined the KM for one of SaFBA’s substrates, fructose 1,6-bisphosphate, as well as performed mode of inhibition studies for an inhibitor that takes advantage of the Z-loop’s flexibility. Together the data offers insight into a class IIb FBA from a pervasively drug resistant bacterium and a comparison of Z-loops and other features between the different subtypes of class II FBAs. PMID:25390935

  5. On the dynamics of the age structure, dependency, and consumption

    PubMed Central

    Hock, Heinrich

    2013-01-01

    We examine the effects of population aging due to declining fertility and rising elderly life expectancy on consumption possibilities in the presence of intergenerational transfers. Our analysis is based on a highly tractable continuous-time overlapping generations model in which the population is divided into three groups (youth dependents, workers, and elderly dependents) and lifecourse transitions take place in a probabilistic fashion. We show that the consumption-maximizing response to greater longevity in highly developed countries is an increase in fertility. However, with larger transfer payments, the actual fertility response will likely be the opposite, leading to further population aging. PMID:24353374

  6. A class of promising acaricidal tetrahydroisoquinoline derivatives: synthesis, biological evaluation and structure-activity relationships.

    PubMed

    Yang, Rui; Ruan, Qiao; Zhang, Bing-Yu; Zheng, Zuo-Lue; Miao, Fang; Zhou, Le; Geng, Hui-Ling

    2014-01-01

    As part of our continuing research on isoquinoline acaricidal drugs, this paper reports the preparation of a series of the 2-aryl-1-cyano-1,2,3,4-tetrahydroisoquinolines with various substituents on the N-phenyl ring, their in vitro acaricidal activities against Psoroptes cuniculi, a mange mite, and discusses their SAR as well. The structures of all compounds, including 12 new ones, were elucidated by analysis of UV, IR, NMR, ESI-MS, HR-MS spectra and X-ray diffraction experiments. All target compounds showed varying degrees of activity at 0.4 mg/mL. Compound 1 showed the strongest activity, with a 50% lethal concentration value (LC50) of 0.2421 μg/mL and 50% lethal time value (LT50) of 7.79 h, comparable to the standard drug ivermectin (LC50 = 0.2474 μg/mL; LT50 = 20.9 h). The SAR showed that the substitution pattern on the N-aromatic ring exerted a significant effect on the activity. The substituents 2'-F, 3'-F, 2'-Cl, 2'-Br and 2'-CF3 remarkably enhanced the activity. Generally, for the isomers with the same substituents at different positions, the order of the activity was ortho > meta > para. It was concluded that the target compounds represent a class of novel promising candidates or lead compounds for the development of new tetrahydroisoquinoline acaricidal agents.

  7. Composite Structural Analysis of Flat-Back Shaped Blade for Multi-MW Class Wind Turbine

    NASA Astrophysics Data System (ADS)

    Kim, Soo-Hyun; Bang, Hyung-Joon; Shin, Hyung-Ki; Jang, Moon-Seok

    2014-06-01

    This paper provides an overview of failure mode estimation based on 3D structural finite element (FE) analysis of the flat-back shaped wind turbine blade. Buckling stability, fiber failure (FF), and inter-fiber failure (IFF) analyses were performed to account for delamination or matrix failure of composite materials and to predict the realistic behavior of the entire blade region. Puck's fracture criteria were used for IFF evaluation. Blade design loads applicable to multi-megawatt (MW) wind turbine systems were calculated according to the Germanischer Lloyd (GL) guideline and the International Electrotechnical Commission (IEC) 61400-1 standard, under Class IIA wind conditions. After the post-processing of final load results, a number of principal load cases were selected and converted into applied forces at the each section along the blade's radius of the FE model. Nonlinear static analyses were performed for laminate failure, FF, and IFF check. For buckling stability, linear eigenvalue analysis was performed. As a result, we were able to estimate the failure mode and locate the major weak point.

  8. Structural and quantum chemical studies of 8-aryl-sulfanyl adenine class Hsp90 inhibitors.

    PubMed

    Immormino, Robert M; Kang, Yanlong; Chiosis, Gabriela; Gewirth, Daniel T

    2006-08-10

    Hsp90 chaperones play a critical role in modulating the activity of many cell signaling proteins and are an attractive target for anti-cancer therapeutics. We report here the structures of the water soluble 8-aryl-sulfanyl adenine class Hsp90 inhibitors, 1 (PU-H71) and 2 (PU-H64), in complex with the N-terminal domain of human Hsp90alpha. The conformation of 1 when bound to Hsp90 differs from previously reported 8-aryl adenine Hsp90 inhibitors including 3 (PU24FCl). While the binding mode for 3 places the 2'-halide of the 8-aryl group on top of the adenine ring, for 1 and 2, we show that the 2'-halide is rotated approximately 180 degrees away. This difference explains the opposing trends in Hsp90 inhibitory activity for the 2'-halo derivatives of the 3',4',5'-trimethoxy series where Cl > Br > I compared to the 4',5'-methylenedioxy series where I > Br > Cl. We also present quantum chemical calculations of 2 and its analogues that illuminate their basis for Hsp90 inhibition. The calculated conformation of 2 agreed well with the crystallographically observed conformations of 1 and 2. The predictive nature of the calculations has allowed the exploration of additional derivatives based on the 8-aryl adenine scaffold.

  9. Structural synthesis of a class of 2R2T hybrid mechanisms

    NASA Astrophysics Data System (ADS)

    Tian, Chunxu; Fang, Yuefa; Guo, Sheng

    2016-07-01

    Conventional overconstrained parallel manipulators have been widely studied both in industry and academia, however the structural synthesis of hybrid mechanisms with additional constraints is seldom studied, especially for the four degrees of freedom(DOF) hybrid mechanisms. In order to develop a manipulator with additional constraints, a class of important spatial mechanisms with coupling chains(CCs) whose motion type is two rotations and two translations(2R2T) is presented. Based on screw theory, the combination of different types of limbs which are used to construct parallel mechanisms and coupling chains is proposed. The basic types of the general parallel mechanisms and geometric conditions of the kinematic chains are given using constraint synthesis method. Moreover, the 2R2T motion pattern hybrid mechanisms which are derived by adding coupling chains between different serial kinematic chains(SKCs) of the corresponding parallel mechanisms are presented. According to the constraint analysis of the mechanisms, the movement relationship of the moving platform and the kinematic chains is derived by disassembling the coupling chains. At last, fourteen novel hybrid mechanisms with two or three serial kinematic chains are presented. The proposed novel hybrid mechanisms and construction method enrich the family of the spatial mechanisms and provide an instruction to design more complex hybrid mechanisms.

  10. The recognition of multi-class protein folds by adding average chemical shifts of secondary structure elements

    PubMed Central

    Feng, Zhenxing; Hu, Xiuzhen; Jiang, Zhuo; Song, Hangyu; Ashraf, Muhammad Aqeel

    2015-01-01

    The recognition of protein folds is an important step in the prediction of protein structure and function. Recently, an increasing number of researchers have sought to improve the methods for protein fold recognition. Following the construction of a dataset consisting of 27 protein fold classes by Ding and Dubchak in 2001, prediction algorithms, parameters and the construction of new datasets have improved for the prediction of protein folds. In this study, we reorganized a dataset consisting of 76-fold classes constructed by Liu et al. and used the values of the increment of diversity, average chemical shifts of secondary structure elements and secondary structure motifs as feature parameters in the recognition of multi-class protein folds. With the combined feature vector as the input parameter for the Random Forests algorithm and ensemble classification strategy, we propose a novel method to identify the 76 protein fold classes. The overall accuracy of the test dataset using an independent test was 66.69%; when the training and test sets were combined, with 5-fold cross-validation, the overall accuracy was 73.43%. This method was further used to predict the test dataset and the corresponding structural classification of the first 27-protein fold class dataset, resulting in overall accuracies of 79.66% and 93.40%, respectively. Moreover, when the training set and test sets were combined, the accuracy using 5-fold cross-validation was 81.21%. Additionally, this approach resulted in improved prediction results using the 27-protein fold class dataset constructed by Ding and Dubchak. PMID:26980999

  11. A Latent Class Analysis of Teacher Candidates' Goal Orientation, Perception of Classroom Structure, Motivation, and Self-Regulation

    ERIC Educational Resources Information Center

    Bembenutty, Hefer

    2010-01-01

    The purpose of this study was to examine whether teacher candidates with mastery- and performance-approach orientations would perceived their education courses as depicting a goal structure consistent with their personal orientations, use of self-regulatory strategies, and motivation for learning. A latent class analysis procedure was used to…

  12. 15 CFR 50.5 - Fee structure for age search and citizenship information.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 15 Commerce and Foreign Trade 1 2011-01-01 2011-01-01 false Fee structure for age search and citizenship information. 50.5 Section 50.5 Commerce and Foreign Trade Regulations Relating to Commerce and... THE CENSUS § 50.5 Fee structure for age search and citizenship information. Type of service...

  13. 15 CFR 50.5 - Fee structure for age search and citizenship information.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 15 Commerce and Foreign Trade 1 2014-01-01 2014-01-01 false Fee structure for age search and citizenship information. 50.5 Section 50.5 Commerce and Foreign Trade Regulations Relating to Commerce and... THE CENSUS § 50.5 Fee structure for age search and citizenship information. Type of service...

  14. 15 CFR 50.5 - Fee structure for age search and citizenship information.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 15 Commerce and Foreign Trade 1 2012-01-01 2012-01-01 false Fee structure for age search and citizenship information. 50.5 Section 50.5 Commerce and Foreign Trade Regulations Relating to Commerce and... THE CENSUS § 50.5 Fee structure for age search and citizenship information. Type of service...

  15. 15 CFR 50.5 - Fee structure for age search and citizenship information.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 15 Commerce and Foreign Trade 1 2010-01-01 2010-01-01 false Fee structure for age search and citizenship information. 50.5 Section 50.5 Commerce and Foreign Trade Regulations Relating to Commerce and... THE CENSUS § 50.5 Fee structure for age search and citizenship information. Type of service...

  16. 15 CFR 50.5 - Fee structure for age search and citizenship information.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 15 Commerce and Foreign Trade 1 2013-01-01 2013-01-01 false Fee structure for age search and citizenship information. 50.5 Section 50.5 Commerce and Foreign Trade Regulations Relating to Commerce and... THE CENSUS § 50.5 Fee structure for age search and citizenship information. Type of service...

  17. Structural and functional imaging correlates for age-related changes in the brain.

    PubMed

    Tumeh, Paul C; Alavi, Abass; Houseni, Mohamed; Greenfield, Antje; Chryssikos, Timothy; Newberg, Andrew; Torigian, Drew A; Moonis, Gul

    2007-03-01

    In recent years, investigators have made significant progress in documenting brain structure and function as it relates to aging by using positron emission tomography, conventional magnetic resonance (MR) imaging, advanced MR techniques, and functional MR imaging. This review summarizes the latest advances in understanding physiologic maturation and aging as detected by these neuroimaging modalities. We also present our experience with MR volumetric and positron emission tomography analysis in separate cohorts of healthy subjects in the pediatric and adult age groups respectively. Our results are consistent with previous studies and include the following: total brain volume was found to increase with age (up to 20 years of age). Whole brain metabolism and frontal lobe metabolism both decrease significantly with age (38% and 42%, respectively), whereas cerebellar metabolism does not show a significant decline with age. Defining normal alterations in brain function and structure allows early detection of disorders such as Alzheimer's and Parkinson's diseases, which are commonly associated with normal aging. PMID:17289456

  18. Crystal structures of an archaeal class II DNA photolyase and its complex with UV-damaged duplex DNA

    PubMed Central

    Kiontke, Stephan; Geisselbrecht, Yann; Pokorny, Richard; Carell, Thomas; Batschauer, Alfred; Essen, Lars-Oliver

    2011-01-01

    Class II photolyases ubiquitously occur in plants, animals, prokaryotes and some viruses. Like the distantly related microbial class I photolyases, these enzymes repair UV-induced cyclobutane pyrimidine dimer (CPD) lesions within duplex DNA using blue/near-UV light. Methanosarcina mazei Mm0852 is a class II photolyase of the archaeal order of Methanosarcinales, and is closely related to plant and metazoan counterparts. Mm0852 catalyses light-driven DNA repair and photoreduction, but in contrast to class I enzymes lacks a high degree of binding discrimination between UV-damaged and intact duplex DNA. We solved crystal structures of Mm0852, the first one for a class II photolyase, alone and in complex with CPD lesion-containing duplex DNA. The lesion-binding mode differs from other photolyases by a larger DNA-binding site, and an unrepaired CPD lesion is found flipped into the active site and recognized by a cluster of five water molecules next to the bound 3′-thymine base. Different from other members of the photolyase-cryptochrome family, class II photolyases appear to utilize an unusual, conserved tryptophane dyad as electron transfer pathway to the catalytic FAD cofactor. PMID:21892138

  19. Crystal structures of an archaeal class II DNA photolyase and its complex with UV-damaged duplex DNA.

    PubMed

    Kiontke, Stephan; Geisselbrecht, Yann; Pokorny, Richard; Carell, Thomas; Batschauer, Alfred; Essen, Lars-Oliver

    2011-11-01

    Class II photolyases ubiquitously occur in plants, animals, prokaryotes and some viruses. Like the distantly related microbial class I photolyases, these enzymes repair UV-induced cyclobutane pyrimidine dimer (CPD) lesions within duplex DNA using blue/near-UV light. Methanosarcina mazei Mm0852 is a class II photolyase of the archaeal order of Methanosarcinales, and is closely related to plant and metazoan counterparts. Mm0852 catalyses light-driven DNA repair and photoreduction, but in contrast to class I enzymes lacks a high degree of binding discrimination between UV-damaged and intact duplex DNA. We solved crystal structures of Mm0852, the first one for a class II photolyase, alone and in complex with CPD lesion-containing duplex DNA. The lesion-binding mode differs from other photolyases by a larger DNA-binding site, and an unrepaired CPD lesion is found flipped into the active site and recognized by a cluster of five water molecules next to the bound 3'-thymine base. Different from other members of the photolyase-cryptochrome family, class II photolyases appear to utilize an unusual, conserved tryptophane dyad as electron transfer pathway to the catalytic FAD cofactor. PMID:21892138

  20. Structural Basis for Catalysis of a Tetrameric Class IIa Fructose 1,6-Bisphosphate Aldolase from Mycobacterium tuberculosis

    SciTech Connect

    Pegan, Scott D.; Ruskseree, Kamolchanok; Franzblau, Scott G.; Mesecar, Andrew D. ); )

    2009-03-04

    Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), currently infects one-third of the world's population in its latent form. The emergence of multidrug-resistant and extensive drug-resistant strains has highlighted the need for new pharmacological targets within M. tuberculosis. The class IIa fructose 1,6-bisphosphate aldolase (FBA) enzyme from M. tuberculosis (MtFBA) has been proposed as one such target since it is upregulated in latent TB. Since the structure of MtFBA has not been determined and there is little information available on its reaction mechanism, we sought to determine the X-ray structure of MtFBA in complex with its substrates. By lowering the pH of the enzyme in the crystalline state, we were able to determine a series of high-resolution X-ray structures of MtFBA bound to dihydroxyacetone phosphate, glyceraldehyde 3-phosphate, and fructose 1,6-bisphosphate at 1.5, 2.1, and 1.3 {angstrom}, respectively. Through these structures, it was discovered that MtFBA belongs to a novel tetrameric class of type IIa FBAs. The molecular details at the interface of the tetramer revealed important information for better predictability of the quaternary structures among the FBAs based on their primary sequences. These X-ray structures also provide interesting and new details on the reaction mechanism of class II FBAs. Substrates and products were observed in geometries poised for catalysis; in addition, unexpectedly, the hydroxyl-enolate intermediate of dihydroxyacetone phosphate was also captured and resolved structurally. These concise new details offer a better understanding of the reaction mechanisms for FBAs in general and provide a structural basis for inhibitor design efforts aimed at this class of enzymes.

  1. Structural basis for catalysis of a tetrameric, class IIa fructose 1,6-bisphosphate aldolase from M. tuberculosis

    PubMed Central

    Pegan, Scott D.; Rukseree, Kamolchanok; Franzblau, Scott G.; Mesecar, Andrew D.

    2009-01-01

    Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), currently infects one third of the world’s population in its latent form. The emergence of multidrug resistant strains, MDR-TB and XDR-TB has highlighted the need for new pharmacological targets within M. tuberculosis. The Class IIa fructose 1,6-bisphosphate aldolase (FBA) enzyme from M. tuberculosis (MtFBA) has been proposed as one such target since its upregulated in latent TB. Since the structure of MtFBA had not been determined and since there was little information available on its reaction mechanism, we sought to determine the X-ray structure of MtFBA in complex with its substrates. By lowering the pH of the enzyme in the crystalline state, we were able to determine a series of high-resolution X-ray structures of MtFBA bound to dihydroxyacetonephosphate (DHAP), glyceraldehyde-3-phosphate (G3P), and fructose 1,6-bisphosphate (FBP) at 1.5 Å, 2.1 Å, and 1.3 Å respectively. Through these structures it was discovered that MtFBA belongs to a novel tetrameric class of the type IIa FBAs. The molecular details at the interface of the tetramer revealed important information for being able to better predict the quaternary structures among the FBAs based on their primary sequences. These X-ray structures also provide interesting and new details on the reaction mechanism of class II FBAs. Not only were the substrates and products observed in geometries poised for catalysis, but unexpectedly the hydroxyl enolate intermediate of DHAP was also captured and resolved structurally. These concise new details provide a better understanding of the reaction mechanisms for FBAs in general and provide a structural basis for inhibitor design efforts aimed at this class of enzymes. PMID:19167403

  2. Nanoscale Structure, Dynamics, and Aging Behavior of Metallic Glass Thin Films.

    PubMed

    Burgess, J A J; Holt, C M B; Luber, E J; Fortin, D C; Popowich, G; Zahiri, B; Concepcion, P; Mitlin, D; Freeman, M R

    2016-01-01

    Scanning tunnelling microscopy observations resolve the structure and dynamics of metallic glass Cu100-xHfx films and demonstrate scanning tunnelling microscopy control of aging at a metallic glass surface. Surface clusters exhibit heterogeneous hopping dynamics. Low Hf concentration films feature an aged surface of larger, slower clusters. Argon ion-sputtering destroys the aged configuration, yielding a surface in constant fluctuation. Scanning tunnelling microscopy can locally restore the relaxed state, allowing for nanoscale lithographic definition of aged sections. PMID:27498698

  3. Nanoscale Structure, Dynamics, and Aging Behavior of Metallic Glass Thin Films

    PubMed Central

    Burgess, J. A. J.; Holt, C. M. B.; Luber, E. J.; Fortin, D. C.; Popowich, G.; Zahiri, B.; Concepcion, P.; Mitlin, D.; Freeman, M. R.

    2016-01-01

    Scanning tunnelling microscopy observations resolve the structure and dynamics of metallic glass Cu100−xHfx films and demonstrate scanning tunnelling microscopy control of aging at a metallic glass surface. Surface clusters exhibit heterogeneous hopping dynamics. Low Hf concentration films feature an aged surface of larger, slower clusters. Argon ion-sputtering destroys the aged configuration, yielding a surface in constant fluctuation. Scanning tunnelling microscopy can locally restore the relaxed state, allowing for nanoscale lithographic definition of aged sections. PMID:27498698

  4. Nanoscale Structure, Dynamics, and Aging Behavior of Metallic Glass Thin Films

    NASA Astrophysics Data System (ADS)

    Burgess, J. A. J.; Holt, C. M. B.; Luber, E. J.; Fortin, D. C.; Popowich, G.; Zahiri, B.; Concepcion, P.; Mitlin, D.; Freeman, M. R.

    2016-08-01

    Scanning tunnelling microscopy observations resolve the structure and dynamics of metallic glass Cu100-xHfx films and demonstrate scanning tunnelling microscopy control of aging at a metallic glass surface. Surface clusters exhibit heterogeneous hopping dynamics. Low Hf concentration films feature an aged surface of larger, slower clusters. Argon ion-sputtering destroys the aged configuration, yielding a surface in constant fluctuation. Scanning tunnelling microscopy can locally restore the relaxed state, allowing for nanoscale lithographic definition of aged sections.

  5. Educating Other People's Children: Race, Class, Ethnicity, Aging, and the Politics of School Funding in Long Island, New York.

    ERIC Educational Resources Information Center

    Singer, Alan

    Long Island, New York, including Nassau and Suffolk Counties, is a patchwork of small ethnically, racially, and economically segregated towns organized into 126 school districts. School funding patterns and problems conform to racial, ethnic, and class lines. Predominantly minority school districts generally have higher property tax rates, fewer…

  6. The Relation of Age and Social Class Factors in Children's Social Pretend Play to Cognitive and Symbolic Ability.

    ERIC Educational Resources Information Center

    Doyle, Anna-Beth; And Others

    1991-01-01

    The amount of social pretend play in free-play sessions of small groups of five to seven year olds, and the symbolic features of this play, were noted. Conservation, verbal symbol substitution, and role-playing skills, were assessed as measures of cognitive symbolic skill. Results provide no evidence that these social class differences reflect…

  7. The effect of a senior jazz dance class on static balance in healthy women over 50 years of age: a pilot study.

    PubMed

    Wallmann, Harvey W; Gillis, Carrie B; Alpert, Patricia T; Miller, Sally K

    2009-01-01

    The purpose of this pilot study is to assess the impact of a senior jazz dance class on static balance for healthy women over 50 years of age using the NeuroCom Smart Balance Master System (Balance Master). A total of 12 healthy women aged 54-88 years completed a 15-week jazz dance class which they attended 1 time per week for 90 min per class. Balance data were collected using the Sensory Organization Test (SOT) at baseline (pre), at 7 weeks (mid), and after 15 weeks (post). An equilibrium score measuring postural sway was calculated for each of six different conditions. The composite equilibrium score (all six conditions integrated to 1 score) was used as an overall measure of balance. Repeated measures analyses of variance (ANOVAs) were used to compare the means of each participant's SOT composite equilibrium score in addition to the equilibrium score for each individual condition (1-6) across the 3 time points (pre, mid, post). There was a statistically significant difference among the means, p < .0005. Pairwise (Bonferroni) post hoc analyses revealed the following statistically significant findings for SOT composite equilibrium scores for the pre (67.33 + 10.43), mid (75.25 + 6.97), and post (79.00 + 4.97) measurements: premid (p = .008); prepost (p < .0005); midpost (p = .033). In addition, correlational statistics were used to determine any relationship between SOT scores and age. Results indicated that administration of a 15-week jazz dance class 1 time per week was beneficial in improving static balance as measured by the Balance Master SOT.

  8. Radiostratigraphy and age structure of the Greenland Ice Sheet

    PubMed Central

    MacGregor, Joseph A; Fahnestock, Mark A; Catania, Ginny A; Paden, John D; Prasad Gogineni, S; Young, S Keith; Rybarski, Susan C; Mabrey, Alexandria N; Wagman, Benjamin M; Morlighem, Mathieu

    2015-01-01

    Several decades of ice-penetrating radar surveys of the Greenland and Antarctic ice sheets have observed numerous widespread internal reflections. Analysis of this radiostratigraphy has produced valuable insights into ice sheet dynamics and motivates additional mapping of these reflections. Here we present a comprehensive deep radiostratigraphy of the Greenland Ice Sheet from airborne deep ice-penetrating radar data collected over Greenland by The University of Kansas between 1993 and 2013. To map this radiostratigraphy efficiently, we developed new techniques for predicting reflection slope from the phase recorded by coherent radars. When integrated along track, these slope fields predict the radiostratigraphy and simplify semiautomatic reflection tracing. Core-intersecting reflections were dated using synchronized depth-age relationships for six deep ice cores. Additional reflections were dated by matching reflections between transects and by extending reflection-inferred depth-age relationships using the local effective vertical strain rate. The oldest reflections, dating to the Eemian period, are found mostly in the northern part of the ice sheet. Within the onset regions of several fast-flowing outlet glaciers and ice streams, reflections typically do not conform to the bed topography. Disrupted radiostratigraphy is also observed in a region north of the Northeast Greenland Ice Stream that is not presently flowing rapidly. Dated reflections are used to generate a gridded age volume for most of the ice sheet and also to determine the depths of key climate transitions that were not observed directly. This radiostratigraphy provides a new constraint on the dynamics and history of the Greenland Ice Sheet. Key Points Phase information predicts reflection slope and simplifies reflection tracing Reflections can be dated away from ice cores using a simple ice flow model Radiostratigraphy is often disrupted near the onset of fast ice flow PMID:26213664

  9. Basic Pharmacological and Structural Evidence for Class A G-Protein-Coupled Receptor Heteromerization.

    PubMed

    Franco, Rafael; Martínez-Pinilla, Eva; Lanciego, José L; Navarro, Gemma

    2016-01-01

    Cell membrane receptors rarely work on isolation, often they form oligomeric complexes with other receptor molecules and they may directly interact with different proteins of the signal transduction machinery. For a variety of reasons, rhodopsin-like class A G-protein-coupled receptors (GPCRs) seem an exception to the general rule of receptor-receptor direct interaction. In fact, controversy surrounds their potential to form homo- hetero-dimers/oligomers with other class A GPCRs; in a sense, the field is going backward instead of forward. This review focuses on the convergent, complementary and telling evidence showing that homo- and heteromers of class A GPCRs exist in transfected cells and, more importantly, in natural sources. It is time to decide between questioning the occurrence of heteromers or, alternatively, facing the vast scientific and technical challenges that class A receptor-dimer/oligomer existence pose to Pharmacology and to Drug Discovery.

  10. Basic Pharmacological and Structural Evidence for Class A G-Protein-Coupled Receptor Heteromerization

    PubMed Central

    Franco, Rafael; Martínez-Pinilla, Eva; Lanciego, José L.; Navarro, Gemma

    2016-01-01

    Cell membrane receptors rarely work on isolation, often they form oligomeric complexes with other receptor molecules and they may directly interact with different proteins of the signal transduction machinery. For a variety of reasons, rhodopsin-like class A G-protein-coupled receptors (GPCRs) seem an exception to the general rule of receptor–receptor direct interaction. In fact, controversy surrounds their potential to form homo- hetero-dimers/oligomers with other class A GPCRs; in a sense, the field is going backward instead of forward. This review focuses on the convergent, complementary and telling evidence showing that homo- and heteromers of class A GPCRs exist in transfected cells and, more importantly, in natural sources. It is time to decide between questioning the occurrence of heteromers or, alternatively, facing the vast scientific and technical challenges that class A receptor-dimer/oligomer existence pose to Pharmacology and to Drug Discovery. PMID:27065866

  11. Basic Pharmacological and Structural Evidence for Class A G-Protein-Coupled Receptor Heteromerization.

    PubMed

    Franco, Rafael; Martínez-Pinilla, Eva; Lanciego, José L; Navarro, Gemma

    2016-01-01

    Cell membrane receptors rarely work on isolation, often they form oligomeric complexes with other receptor molecules and they may directly interact with different proteins of the signal transduction machinery. For a variety of reasons, rhodopsin-like class A G-protein-coupled receptors (GPCRs) seem an exception to the general rule of receptor-receptor direct interaction. In fact, controversy surrounds their potential to form homo- hetero-dimers/oligomers with other class A GPCRs; in a sense, the field is going backward instead of forward. This review focuses on the convergent, complementary and telling evidence showing that homo- and heteromers of class A GPCRs exist in transfected cells and, more importantly, in natural sources. It is time to decide between questioning the occurrence of heteromers or, alternatively, facing the vast scientific and technical challenges that class A receptor-dimer/oligomer existence pose to Pharmacology and to Drug Discovery. PMID:27065866

  12. Phylogeny of the moss class Polytrichopsida (BRYOPHYTA): Generic-level structure and incongruent gene trees.

    PubMed

    Bell, Neil E; Hyvönen, Jaakko

    2010-05-01

    Analysis of an extensive new molecular dataset for the moss class Polytrichopsida provides convincing support for many traditionally recognised genera and identifies higher level phylogenetic structure with a strong geographic component. A large apical clade that is most diverse in the northern hemisphere is subtended by a grade of southern temperate and tropical genera, while the earliest diverging lineages have widely separated relictual distributions. However, there is strongly supported topological incongruence between the nuclear 18S rRNA gene tree and the chloroplast and mitochondrial data for the positions of some taxa and notably for the status of Pogonatum. While Pogonatum is unambiguously paraphyletic in the 18S tree, it is well supported as monophyletic by the combined chloroplast and mitochondrial data, this being corroborated by several distinctive morphological synapomorphies and a 51-53 bp deletion in the rps4-trnS spacer. We explore various reticulate historical processes and methodological issues as possible explanations for incongruence, and suggest that either (1) the 18S topology is an artefact created by convergence of substitutions at specific sites due to functional and/or molecular-structural constraints not accounted for by the model, or (2) the incongruence is a product of ancient hybridization events. Under the latter scenario, incongruent topologies for Pogonatum are parsimoniously explained if Polytrichum (including Polytrichastrum sect. Aporotheca) is ultimately descended from a hybridization event involving an extinct maternal taxon derived from the branch ancestral to the combined Pogonatum/Polytrichum s.l. clade, and a paternal taxon belonging to (or ancestral to) the apical Pogonatum group to which the majority of extant species belong. Numerous novel relationships of taxonomic and evolutionary significance are supported. Notably, both Polytrichastrum and Oligotrichum are polyphyletic. While Polytrichastrum sect. Aporotheca is

  13. Varying contributions of growth and ageing to racial and sex differences in femoral neck structure and strength in old age.

    PubMed

    Wang, Xiao-Fang; Duan, Yunbo; Beck, Thomas J; Seeman, Ego

    2005-06-01

    The structural basis of racial and sex differences in femoral neck (FN) fragility in old age was assessed in a cross-sectional study of 829 healthy Chinese and 1181 healthy Caucasian subjects aged 18 to 93 years in Melbourne, Australia. We measured FN bone mineral density (BMD), periosteal diameter, and estimated endocortical diameter, cortical thickness, volumetric BMD (vBMD), section modulus, and buckling ratio using dual X-ray absorptiometry. Racial and sex differences in structural and strength indices were adjusted for age, bone length and body weight and were expressed in standard deviation (SD) unit. In young adulthood, Chinese women had a 0.85 SD narrower FN, a 0.47 SD thinner cortex and a 0.79 SD shorter FN axis length (FNAL) than Caucasian women. Across age, Chinese and Caucasian women had similar increments in endocortical and periosteal diameters and similar decrements in cortical thickness and vBMD (both approximately 20%). In young adult males, FN periosteal diameter did not differ by race, but cortical thickness was 0.35 SD lower in Chinese than Caucasians. Across age, increments in periosteal and endocortical diameters were less in Chinese than Caucasian men so cortical thickness and vBMD diminished less in Chinese than in Caucasian men. In both races, young adult women had narrower FN than men. As Chinese women had a greater increment in periosteal diameter than Chinese men across age, the sex difference in FN periosteal diameter established in young adulthood diminished in old age. As Caucasian men had a greater increment in periosteal diameter than Caucasian women, the sex difference in FN periosteal diameter established in young adulthood increased with age. In old age, for both sexes, Chinese had a higher fracture risk in bending than Caucasians, but a lower fracture risk by buckling. For both races, women had a higher fracture risk in bending than men. Racial and sexual dimorphism in the absolute and relative behavior of the periosteal and

  14. The 1991 International Conference on Aging Aircraft and Structural Airworthiness

    NASA Technical Reports Server (NTRS)

    Harris, Charles E. (Editor)

    1992-01-01

    Technical sessions of the conference included structural performance, nondestructive evaluation, maintenance and repair, international activities, and commuter airlines. Each session was organized to provide a well-rounded view of the subject from the industry, regulatory, and research perspective. Thirty-four presentations were given by the international technical community.

  15. AGE-RELATED DEGRADATION OF NUCLEAR POWER PLANT STRUCTURES AND COMPONENTS.

    SciTech Connect

    BRAVERMAN,J.

    1999-03-29

    This paper summarizes and highlights the results of the initial phase of a research project on the assessment of aged and degraded structures and components important to the safe operation of nuclear power plants (NPPs). A review of age-related degradation of structures and passive components at NPPs was performed. Instances of age-related degradation have been collected and reviewed. Data were collected from plant generated documents such as Licensing Event Reports, NRC generic communications, NUREGs and industry reports. Applicable cases of degradation occurrences were reviewed and then entered into a computerized database. The results obtained from the review of degradation occurrences are summarized and discussed. Various trending analyses were performed to identify which structures and components are most affected, whether degradation occurrences are worsening, and what are the most common aging mechanisms. The paper also discusses potential aging issues and degradation-susceptible structures and passive components which would have the greatest impact on plant risk.

  16. Age-Related Degradation of Nuclear Power Plant Structures and Components

    SciTech Connect

    Braverman, J.; Chang, T.-Y.; Chokshi, N.; Hofmayer, C.; Morante, R.; Shteyngart, S.

    1999-03-29

    This paper summarizes and highlights the results of the initial phase of a research project on the assessment of aged and degraded structures and components important to the safe operation of nuclear power plants (NPPs). A review of age-related degradation of structures and passive components at NPPs was performed. Instances of age-related degradation have been collected and reviewed. Data were collected from plant generated documents such as Licensing Event Reports, NRC generic communications, NUREGs and industry reports. Applicable cases of degradation occurrences were reviewed and then entered into a computerized database. The results obtained from the review of degradation occurrences are summarized and discussed. Various trending analyses were performed to identify which structures and components are most affected, whether degradation occurrences are worsening, and what was the most common aging mechanisms. The paper also discusses potential aging issues and degradation-susceptible structures and passive components which would have the greatest impact on plant risk.

  17. Two-Class Structure of Income Distribution in the Usa:. Exponential Bulk and Power-Law Tail

    NASA Astrophysics Data System (ADS)

    Yakovenko, V. M.; Silva, A. Christian

    2007-07-01

    Personal income distribution in the USA has a well-defined two-class structure. The majority of population (97-99 %) belongs to the lower class characterized by the exponential Boltzmann-Gibbs ("thermal") distribution, whereas the upper class (1-3 % of population) has a Pareto power-law ("superthermal") distribution. By analyzing income data for 1983-2001, we show that the "thermal" part is stationary in time, save for a gradual increase of the effective temperature, whereas the "superthermal" tail swells and shrinks following the stock market. We discuss the concept of equilibrium inequality in a society, based on the principle of maximal entropy, and quantitatively show that it applies to the majority of population.

  18. Aging and perceived event structure as a function of modality.

    PubMed

    Magliano, Joseph; Kopp, Kristopher; McNerney, M Windy; Radvansky, Gabriel A; Zacks, Jeffrey M

    2012-01-01

    The majority of research on situation model processing in older adults has focused on narrative texts. Much of this research has shown that many important aspects of constructing a situation model for a text are preserved and may even improve with age. However, narratives need not be text-based, and little is known as to whether these findings generalize to visually-based narratives. The present study assessed the impact of story modality on event segmentation, which is a basic component of event comprehension. Older and younger adults viewed picture stories or read text versions of them and segmented them into events. There was comparable alignment between the segmentation judgments and a theoretically guided analysis of shifts in situational features across modalities for both populations. These results suggest that situation models provide older adults with a stable basis for event comprehension across different modalities of expereinces.

  19. Crystal Structure of Venezuelan Hemorrhagic Fever Virus Fusion Glycoprotein Reveals a Class 1 Postfusion Architecture with Extensive Glycosylation

    PubMed Central

    Parsy, Marie-Laure; Harlos, Karl; Huiskonen, Juha T.

    2013-01-01

    Guanarito virus (GTOV) is an emergent and deadly pathogen. We present the crystal structure of the glycosylated GTOV fusion glycoprotein to 4.1-Å resolution in the postfusion conformation. Our structure reveals a classical six-helix bundle and presents direct verification that New World arenaviruses exhibit class I viral membrane fusion machinery. The structure provides visualization of an N-linked glycocalyx coat, and consideration of glycan dynamics reveals extensive coverage of the underlying protein surface, following virus-host membrane fusion. PMID:24049182

  20. Structural damages of maxillofacial biopolymers under solar aging.

    PubMed

    Eleni, P N; Krokida, M K; Frangou, M J; Polyzois, G L; Maroulis, Z B; Marinos-Kouris, D

    2007-09-01

    Additional types of silicone biopolymers are widely used in maxillofacial prosthetics. Therefore, the knowledge of the solar radiation's effect on their structural stability is highly important. Four different industrially synthesized biomaterials were examined, called Episil Europe 1, Europe 2, Europe 3 and Africa 3, which were exposed to solar radiation (UVA, UVB) for eight different time periods (from 8 to 168 h). Structural damages due to irradiation exposure were investigated by mechanical tests (compression) and differential scanning calorimetry (DSC) methods. Simple mathematical models were developed, containing parameters with physical meaning such as maximum stress (sigma(max)), maximum strain (epsilon), elasticity parameter (E), and viscoelastic parameter (p), for the compression test, and melting temperature (T (m)) and Enthalpy in melting point (Heat) for DSC. With increasing irradiation time their maximum stress and strain decreased significantly, and the materials lost their elasticity and molecular stability. A decrement in their melting points and heats was observed as irradiation time was increasing. Finally, experimental results demonstrated that solar radiation has a severe effect on the structural stability of the examined biomaterials.

  1. Effects of United States Department of Agriculture carcass maturity on sensory attributes of steaks produced by cattle representing two dental age classes.

    PubMed

    Semler, M L; Woerner, D R; Belk, K E; Enns, K J; Tatum, J D

    2016-05-01

    This study examined the effects of USDA carcass maturity on sensory properties of LM steaks produced by cattle representing 2 dental age classes. Carcasses identified for use in the experiment were produced by steers and heifers classified as either <30 mo of age (MOA) or ≥30 MOA at the time of slaughter using dentition. Within each dental age class, carcasses were selected to represent 2 maturity groups and 3 marbling categories, resulting in 12 dental age × maturity × marbling subclasses, each consisting of 50 carcasses. Maturity groups consisted of carcasses classified by USDA graders as either A to A (A) overall maturity or B to D (B-D) overall maturity; marbling categories consisted of carcasses with instrument marbling scores of Slight to Slight (SL), Small to Small (SM), or Modest to Moderate (MT-MD). Carcasses were selected in pairs so that each carcass chosen to represent the B-D-maturity group was paired with an A-maturity carcass of the same sex and marbling score (±50 marbling units). Strip loin (LM) steaks were obtained from both sides of each carcass. After a 14-d aging period, 1 LM steak was measured for Warner-Bratzler shear force (WBSF) and slice shear force (SSF), whereas the other LM steak was used for sensory analysis by a trained descriptive attribute panel. No differences ( > 0.05) in LM tenderness, juiciness, or flavor were detected between carcass maturity groups in either dental age class. Advanced dental age (≥30 MOA), however, was associated with more intense ( < 0.05) grassy and bloody/serumy flavors and decreased ( < 0.05) tenderness within the SL marbling group. Marbling score effectively stratified carcasses (MT-MD > SM > SL) according to differences ( < 0.0001) in LM tenderness, juiciness, beefy/brothy flavor, and buttery/beef fat flavor. In addition, increased marbling was associated with lesser ( < 0.01) intensities of bloody/serumy, livery/organy, and grassy flavors as well as smaller ( < 0.0001) values for WBSF and SSF

  2. Interplay between Shear Loading and Structural Aging in a Physical Gelatin Gel

    SciTech Connect

    Ronsin, O.; Caroli, C.; Baumberger, T.

    2009-09-25

    We show that the aging of the mechanical relaxation of a gelatin gel exhibits the same scaling phenomenology as polymer and colloidal glasses. In addition, gelatin is known to exhibit logarithmic structural aging (stiffening). We find that stress accelerates this process. However, this effect is definitely irreducible to a mere age shift with respect to natural aging. We suggest that it is interpretable in terms of elastically aided elementary (coil->helix) local events whose dynamics gradually slows down as aging increases geometric frustration.

  3. The 1.4 Å Crystal Structure of the Class D [beta]-Lactamase OXA-1 Complexed with Doripenem

    SciTech Connect

    Schneider, Kyle D.; Karpen, Mary E.; Bonomo, Robert A.; Leonard, David A.; Powers, Rachel A.

    2010-01-12

    The clinical efficacy of carbapenem antibiotics depends on their resistance to the hydrolytic action of {beta}-lactamase enzymes. The structure of the class D {beta}-lactamase OXA-1 as an acyl complex with the carbapenem doripenem was determined to 1.4 {angstrom} resolution. Unlike most class A and class C carbapenem complexes, the acyl carbonyl oxygen in the OXA-1-doripenem complex is bound in the oxyanion hole. Interestingly, no water molecules were observed in the vicinity of the acyl linkage, providing an explanation for why carbapenems inhibit OXA-1. The side chain amine of K70 remains fully carboxylated in the acyl structure, and the resulting carbamate group forms a hydrogen bond to the alcohol of the 6{alpha}-hydroxyethyl moiety of doripenem. The carboxylate attached to the {beta}-lactam ring of doripenem is stabilized by a salt bridge to K212 and a hydrogen bond with T213, in lieu of the interaction with an arginine side chain found in most other {beta}-lactamase-{beta}-lactam complexes (e.g., R244 in the class A member TEM-1). This novel set of interactions with the carboxylate results in a major shift of the carbapenem's pyrroline ring compared to the structure of the same ring in meropenem bound to OXA-13. Additionally, bond angles of the pyrroline ring suggest that after acylation, doripenem adopts the {Delta}{sup 1} tautomer. These findings provide important insights into the role that carbapenems may have in the inactivation process of class D {beta}-lactamases.

  4. Characterization of a Phanerochaete chrysosporium glutathione transferase reveals a novel structural and functional class with ligandin properties.

    PubMed

    Mathieu, Yann; Prosper, Pascalita; Buée, Marc; Dumarçay, Stéphane; Favier, Frédérique; Gelhaye, Eric; Gérardin, Philippe; Harvengt, Luc; Jacquot, Jean-Pierre; Lamant, Tiphaine; Meux, Edgar; Mathiot, Sandrine; Didierjean, Claude; Morel, Mélanie

    2012-11-01

    Glutathione S-transferases (GSTs) form a superfamily of multifunctional proteins with essential roles in cellular detoxification processes. A new fungal specific class of GST has been highlighted by genomic approaches. The biochemical and structural characterization of one isoform of this class in Phanerochaete chrysosporium revealed original properties. The three-dimensional structure showed a new dimerization mode and specific features by comparison with the canonical GST structure. An additional β-hairpin motif in the N-terminal domain prevents the formation of the regular GST dimer and acts as a lid, which closes upon glutathione binding. Moreover, this isoform is the first described GST that contains all secondary structural elements, including helix α4' in the C-terminal domain, of the presumed common ancestor of cytosolic GSTs (i.e. glutaredoxin 2). A sulfate binding site has been identified close to the glutathione binding site and allows the binding of 8-anilino-1-naphtalene sulfonic acid. Competition experiments between 8-anilino-1-naphtalene sulfonic acid, which has fluorescent properties, and various molecules showed that this GST binds glutathionylated and sulfated compounds but also wood extractive molecules, such as vanillin, chloronitrobenzoic acid, hydroxyacetophenone, catechins, and aldehydes, in the glutathione pocket. This enzyme could thus function as a classical GST through the addition of glutathione mainly to phenethyl isothiocyanate, but alternatively and in a competitive way, it could also act as a ligandin of wood extractive compounds. These new structural and functional properties lead us to propose that this GST belongs to a new class that we name GSTFuA, for fungal specific GST class A.

  5. Demography of deep-dwelling red coral populations: Age and reproductive structure of a highly valued marine species

    NASA Astrophysics Data System (ADS)

    Priori, Cristina; Mastascusa, Vincenza; Erra, Fabrizio; Angiolillo, Michela; Canese, Simonpietro; Santangelo, Giovanni

    2013-02-01

    The valuable Mediterranean red coral Corallium rubrum (Octocorallia Gorgonacea) has been harvested for more than 2 thousand years. Although our knowledge on the demographic features of red coral populations living between 10 and 50 m depth has increased considerably in recent years, the main life-history traits of deeper populations (the main target of current harvesting) are still largely unknown. To increase the demographic knowledge of the latter populations, sampling was carried out during early Summer 2010 in the North-Western Mediterranean (Tyrrhenian Sea - Italy), between 50 and 130 m depth. This paper quantifies the main demographic descriptors of this coral population in terms of size/age and sexual structure. Colony age was estimated by counting annual growth rings on thin sections of 69 colonies. A 2-way ANOVA showed no significant difference between the age estimated by three independent observers. The average annual colony growth rate (basal diameter), showing some decrease with colony age increase, was 0.26 mm/yr. The relationship between age and basal diameter derived from a subsample of colonies was then applied to assess the age of a larger sample of the population and showed 38% of the sampled colonies reached the commercial size (≥7 mm of basal diameter), corresponding to about 30 years in this population and a maximum life span of 93 years; about half of them (51.1%) were in the 21-25 and 26-30 age classes. The analysis of the sexual features revealed a balanced sex ratio, a colony fertility of 90.3% and an average fecundity of 0.83 oocytes or planulae per polyp. The knowledge of these life-history descriptors is needed for our understanding of deep dwelling red coral population dynamics and for matching of harvesting to population growth rate.

  6. miR-Explore: Predicting MicroRNA Precursors by Class Grouping and Secondary Structure Positional Alignment

    PubMed Central

    Sebastian, Bram; Aggrey, Samuel E.

    2013-01-01

    MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expressions by targeting the mRNAs especially in the 3′UTR regions. The identification of miRNAs has been done by biological experiment and computational prediction. The computational prediction approach has been done using two major methods: comparative and noncomparative. The comparative method is dependent on the conservation of the miRNA sequences and secondary structure. The noncomparative method, on the other hand, does not rely on conservation. We hypothesized that each miRNA class has its own unique set of features; therefore, grouping miRNA by classes before using them as training data will improve sensitivity and specificity. The average sensitivity was 88.62% for miR-Explore, which relies on within miRNA class alignment, and 70.82% for miR-abela, which relies on global alignment. Compared with global alignment, grouping miRNA by classes yields a better sensitivity with very high specificity for pre-miRNA prediction even when a simple positional based secondary and primary structure alignment are used. PMID:23645986

  7. Geroprotectors.org: a new, structured and curated database of current therapeutic interventions in aging and age-related disease.

    PubMed

    Moskalev, Alexey; Chernyagina, Elizaveta; de Magalhães, João Pedro; Barardo, Diogo; Thoppil, Harikrishnan; Shaposhnikov, Mikhail; Budovsky, Arie; Fraifeld, Vadim E; Garazha, Andrew; Tsvetkov, Vasily; Bronovitsky, Evgeny; Bogomolov, Vladislav; Scerbacov, Alexei; Kuryan, Oleg; Gurinovich, Roman; Jellen, Leslie C; Kennedy, Brian; Mamoshina, Polina; Dobrovolskaya, Evgeniya; Aliper, Alex; Kaminsky, Dmitry; Zhavoronkov, Alex

    2015-09-01

    As the level of interest in aging research increases, there is a growing number of geroprotectors, or therapeutic interventions that aim to extend the healthy lifespan and repair or reduce aging-related damage in model organisms and, eventually, in humans. There is a clear need for a manually-curated database of geroprotectors to compile and index their effects on aging and age-related diseases and link these effects to relevant studies and multiple biochemical and drug databases. Here, we introduce the first such resource, Geroprotectors (http://geroprotectors.org). Geroprotectors is a public, rapidly explorable database that catalogs over 250 experiments involving over 200 known or candidate geroprotectors that extend lifespan in model organisms. Each compound has a comprehensive profile complete with biochemistry, mechanisms, and lifespan effects in various model organisms, along with information ranging from chemical structure, side effects, and toxicity to FDA drug status. These are presented in a visually intuitive, efficient framework fit for casual browsing or in-depth research alike. Data are linked to the source studies or databases, providing quick and convenient access to original data. The Geroprotectors database facilitates cross-study, cross-organism, and cross-discipline analysis and saves countless hours of inefficient literature and web searching. Geroprotectors is a one-stop, knowledge-sharing, time-saving resource for researchers seeking healthy aging solutions. PMID:26342919

  8. Geroprotectors.org: a new, structured and curated database of current therapeutic interventions in aging and age-related disease.

    PubMed

    Moskalev, Alexey; Chernyagina, Elizaveta; de Magalhães, João Pedro; Barardo, Diogo; Thoppil, Harikrishnan; Shaposhnikov, Mikhail; Budovsky, Arie; Fraifeld, Vadim E; Garazha, Andrew; Tsvetkov, Vasily; Bronovitsky, Evgeny; Bogomolov, Vladislav; Scerbacov, Alexei; Kuryan, Oleg; Gurinovich, Roman; Jellen, Leslie C; Kennedy, Brian; Mamoshina, Polina; Dobrovolskaya, Evgeniya; Aliper, Alex; Kaminsky, Dmitry; Zhavoronkov, Alex

    2015-09-01

    As the level of interest in aging research increases, there is a growing number of geroprotectors, or therapeutic interventions that aim to extend the healthy lifespan and repair or reduce aging-related damage in model organisms and, eventually, in humans. There is a clear need for a manually-curated database of geroprotectors to compile and index their effects on aging and age-related diseases and link these effects to relevant studies and multiple biochemical and drug databases. Here, we introduce the first such resource, Geroprotectors (http://geroprotectors.org). Geroprotectors is a public, rapidly explorable database that catalogs over 250 experiments involving over 200 known or candidate geroprotectors that extend lifespan in model organisms. Each compound has a comprehensive profile complete with biochemistry, mechanisms, and lifespan effects in various model organisms, along with information ranging from chemical structure, side effects, and toxicity to FDA drug status. These are presented in a visually intuitive, efficient framework fit for casual browsing or in-depth research alike. Data are linked to the source studies or databases, providing quick and convenient access to original data. The Geroprotectors database facilitates cross-study, cross-organism, and cross-discipline analysis and saves countless hours of inefficient literature and web searching. Geroprotectors is a one-stop, knowledge-sharing, time-saving resource for researchers seeking healthy aging solutions.

  9. Geroprotectors.org: a new, structured and curated database of current therapeutic interventions in aging and age-related disease

    PubMed Central

    Moskalev, Alexey; Chernyagina, Elizaveta; de Magalhães, João Pedro; Barardo, Diogo; Thoppil, Harikrishnan; Shaposhnikov, Mikhail; Budovsky, Arie; Fraifeld, Vadim E.; Garazha, Andrew; Tsvetkov, Vasily; Bronovitsky, Evgeny; Bogomolov, Vladislav; Scerbacov, Alexei; Kuryan, Oleg; Gurinovich, Roman; Jellen, Leslie C.; Kennedy, Brian; Mamoshina, Polina; Dobrovolskaya, Evgeniya; Aliper, Alex; Kaminsky, Dmitry; Zhavoronkov, Alex

    2015-01-01

    As the level of interest in aging research increases, there is a growing number of geroprotectors, or therapeutic interventions that aim to extend the healthy lifespan and repair or reduce aging-related damage in model organisms and, eventually, in humans. There is a clear need for a manually-curated database of geroprotectors to compile and index their effects on aging and age-related diseases and link these effects to relevant studies and multiple biochemical and drug databases. Here, we introduce the first such resource, Geroprotectors (http://geroprotectors.org). Geroprotectors is a public, rapidly explorable database that catalogs over 250 experiments involving over 200 known or candidate geroprotectors that extend lifespan in model organisms. Each compound has a comprehensive profile complete with biochemistry, mechanisms, and lifespan effects in various model organisms, along with information ranging from chemical structure, side effects, and toxicity to FDA drug status. These are presented in a visually intuitive, efficient framework fit for casual browsing or in-depth research alike. Data are linked to the source studies or databases, providing quick and convenient access to original data. The Geroprotectors database facilitates cross-study, cross-organism, and cross-discipline analysis and saves countless hours of inefficient literature and web searching. Geroprotectors is a one-stop, knowledge-sharing, time-saving resource for researchers seeking healthy aging solutions. PMID:26342919

  10. Effects of aging on processing of novel musical structure.

    PubMed

    Lynch, M P; Steffens, M L

    1994-07-01

    Musical processing involves long-term memory representations of invariant properties of auditory patterns and working memory representations of patterns heard in the present moment. Musical scales are formalized sets of pitches on which much of musical composition and improvisation is based, and frequency relations among scale notes are invariant within categorical boundaries. Studies of young adults have indicated that adjustments of frequency relations are better detected when melodies are based on culturally familiar scales than on culturally unfamiliar scales. A proposed account for this finding has been that knowledge about musical frequency relations is stored in long-term memory. In the present study, old and young adults performed equivalently well in detection of frequency relation adjustments in a culturally familiar scale context, but young adults performed better than old adults in culturally unfamiliar scale contexts. The performance of old adults in a culturally unfamiliar scale context was correlated with high-frequency (8 kHz) hearing sensitivity. These findings suggest that influences of aging on processing of auditory events involve relations of auditory cognition and hearing sensitivity.

  11. Socio-occupational class, region of birth and maternal age: influence on time to detection of cryptorchidism (undescended testes): a Danish nationwide register study

    PubMed Central

    2014-01-01

    Background Cryptorchidism (undescended testes) is associated with poor male fertility, but can be alleviated and fertility preserved to some degree by early detection and treatment. Here we assess the influence of socio-occupational class, geographical region, maternal age and birth cohort on time to detection and correction of cryptorchidism. Methods All boys born in Denmark, 1981 to 1987 or 1988 to 1994, with a diagnosis of cryptorchidism were identified in nationwide registers. The boys were followed for a diagnosis until their 16th birthday. The age at first diagnosis was noted and used as proxy for time to detection of cryptorchidism. Parental employment in the calendar year preceding birth was grouped into one of five socio-occupational classes. Geographical region was defined by place of birth in one of 15 Danish counties. Detection rate ratios of cryptorchidism were analyzed as a function of parental socio-occupational group, county, maternal age and birth cohort by use of Poisson regression. Results Some 6,059 boys in the early and 5,947 boys in the late cohort received a diagnosis of cryptorchidism. Time to detection was independent of parental socio-occupational group and maternal age but differed slightly between geographical regions. A similar pattern was obtained for surgical correction after a diagnosis. Age at diagnosis decreased by 2.7 years from the early to the late cohort. Conclusions These results indicate that childhood socio-occupational inequality in detection and correction of cryptorchidism would play a negligible role in male infertility in a life course perspective. Geographical region may have exerted some influence, especially for the oldest cohort. PMID:24581337

  12. Quantum singularity structure of a class of continuously self-similar spacetimes

    NASA Astrophysics Data System (ADS)

    Konkowski, Deborah; Helliwell, Thomas; Wiliams, Jon

    2016-03-01

    The dynamical, classical timelike singularity in a class of continuously self-similar, conformally-static, spherically-symmetric, power-law spacetimes is probed using massless scalar test fields. Ranges of metric parameters for which these classical singularities may be resolved quantum mechanically are determined; however, the wave operator is shown to be not essentially self-adjoint using Weyl's limit point-limit circle criterion. Thus, unfortunately, in this class of spacetimes the wave packet evolution still has the usual ambiguity associated with scattering off singularities. These spacetimes are not healed quantum mechanically.

  13. The Left Hand Second to Fourth Digit Ratio (2D:4D) Does Not Discriminate World-Class Female Gymnasts from Age Matched Sedentary Girls

    PubMed Central

    Peeters, Maarten W.; Claessens, Albrecht L.

    2012-01-01

    Introduction The second to fourth-digit-ratio (2D:4D), a putative marker of prenatal androgen action and a sexually dimorphic trait, has been suggested to be related with sports performance, although results are not univocal. If this relation exists, it is most likely to be detected by comparing extreme groups on the continuum of sports performance. Methods In this study the 2D:4D ratio of world-class elite female artistic gymnasts (n = 129), competing at the 1987 Rotterdam World-Championships was compared to the 2D:4D ratio of sedentary age-matched sedentary girls (n = 129), alongside with other anthropometric characteristics including other sexually dimorphic traits such as an androgyny index (Bayer & Bayley) and Heath-Carter somatotype components (endomorphy, mesomorphy, ectomorphy) using AN(C)OVA. 2D:4D was measured on X-rays of the left hand. Results Left hand 2D:4D digit ratio in world class elite female gymnasts (0.921±0.020) did not differ significantly from 2D:4D in age-matched sedentary girls (0.924±0.018), either with or without inclusion of potentially confounding covariates such as skeletal age, height, weight, somatotype components or androgyny index. Height (161.9±6.4 cm vs 155.4±6.6 cm p<0.01), weight (53.9±7.6 kg vs 46.2 6.3 kg p<0.01), BMI (20.51±2.41 kg/m2 vs 19.05±1.56 kg/m2), skeletal age (15.2±1.1 y vs 14.5±1.2 y p>0.01), somatotype components (4.0/3.0/2.9 vs 1.7/3.7/3.2 for endomorphy (p<0.01), mesomorphy (p<0.01) and ectomorphy (p<0.05) respectively) all differed significantly between sedentary girls and elite gymnasts. As expressed by the androgyny index, gymnasts have, on average, broader shoulders relative to their hips, compared to the reference sample. Correlations between the 2D:4D ratio and chronological age, skeletal age, and the anthropometric characteristics are low and not significant. Conclusion Although other anthropometric characteristics of sexual dimorphism were significantly different between the two samples

  14. Occupational class inequalities in all-cause and cause-specific mortality among middle-aged men in 14 European populations during the early 2000s.

    PubMed

    Toch-Marquardt, Marlen; Menvielle, Gwenn; Eikemo, Terje A; Kulhánová, Ivana; Kulik, Margarete C; Bopp, Matthias; Esnaola, Santiago; Jasilionis, Domantas; Mäki, Netta; Martikainen, Pekka; Regidor, Enrique; Lundberg, Olle; Mackenbach, Johan P

    2014-01-01

    This study analyses occupational class inequalities in all-cause mortality and four specific causes of death among men, in Europe in the early 2000s, and is the most extensive comparative analysis of occupational class inequalities in mortality in Europe so far. Longitudinal data, obtained from population censuses and mortality registries in 14 European populations, from around the period 2000-2005, were used. Analyses concerned men aged 30-59 years and included all-cause mortality and mortality from all cancers, all cardiovascular diseases (CVD), all external, and all other causes. Occupational class was analysed according to five categories: upper and lower non-manual workers, skilled and unskilled manual workers, and farmers and self-employed combined. Inequalities were quantified with mortality rate ratios, rate differences, and population attributable fractions (PAF). Relative and absolute inequalities in all-cause mortality were more pronounced in Finland, Denmark, France, and Lithuania than in other populations, and the same countries (except France) also had the highest PAF values for all-cause mortality. The main contributing causes to these larger inequalities differed strongly between countries (e.g., cancer in France, all other causes in Denmark). Relative and absolute inequalities in CVD mortality were markedly lower in Southern European populations. We conclude that relative and absolute occupational class differences in all-cause and cause specific mortality have persisted into the early 2000's, although the magnitude differs strongly between populations. Comparisons with previous studies suggest that the relative gap in mortality between occupational classes has further widened in some Northern and Western European populations.

  15. Occupational Class Inequalities in All-Cause and Cause-Specific Mortality among Middle-Aged Men in 14 European Populations during the Early 2000s

    PubMed Central

    Toch-Marquardt, Marlen; Menvielle, Gwenn; Eikemo, Terje A.; Kulhánová, Ivana; Kulik, Margarete C.; Bopp, Matthias; Esnaola, Santiago; Jasilionis, Domantas; Mäki, Netta; Martikainen, Pekka; Regidor, Enrique; Lundberg, Olle; Mackenbach, Johan P.

    2014-01-01

    This study analyses occupational class inequalities in all-cause mortality and four specific causes of death among men, in Europe in the early 2000s, and is the most extensive comparative analysis of occupational class inequalities in mortality in Europe so far. Longitudinal data, obtained from population censuses and mortality registries in 14 European populations, from around the period 2000–2005, were used. Analyses concerned men aged 30–59 years and included all-cause mortality and mortality from all cancers, all cardiovascular diseases (CVD), all external, and all other causes. Occupational class was analysed according to five categories: upper and lower non-manual workers, skilled and unskilled manual workers, and farmers and self-employed combined. Inequalities were quantified with mortality rate ratios, rate differences, and population attributable fractions (PAF). Relative and absolute inequalities in all-cause mortality were more pronounced in Finland, Denmark, France, and Lithuania than in other populations, and the same countries (except France) also had the highest PAF values for all-cause mortality. The main contributing causes to these larger inequalities differed strongly between countries (e.g., cancer in France, all other causes in Denmark). Relative and absolute inequalities in CVD mortality were markedly lower in Southern European populations. We conclude that relative and absolute occupational class differences in all-cause and cause specific mortality have persisted into the early 2000's, although the magnitude differs strongly between populations. Comparisons with previous studies suggest that the relative gap in mortality between occupational classes has further widened in some Northern and Western European populations. PMID:25268702

  16. Implications of a class of grand-unified theories for large-scale structure in the universe

    NASA Technical Reports Server (NTRS)

    Shafi, Q.; Stecker, F. W.

    1984-01-01

    A class of grand-unified theories in which cosmologically significant axion and neutrino energy densities arise naturally is considered. To obtain large-scale structure, attention is given to (1) an inflationary scenario, (2) inflation followed by string production, and (3) a noninflationary scenario with density fluctuations caused solely by strings. It is shown that inflation may be compatible with the recent observational indications that Omega less than 1 on the scale of superclusters, particularly if strings are present.

  17. One-Class Support Vector Machines Identify the Language and Default Mode Regions As Common Patterns of Structural Alterations in Young Children with Autism Spectrum Disorders.

    PubMed

    Retico, Alessandra; Gori, Ilaria; Giuliano, Alessia; Muratori, Filippo; Calderoni, Sara

    2016-01-01

    The identification of reliable brain endophenotypes of autism spectrum disorders (ASD) has been hampered to date by the heterogeneity in the neuroanatomical abnormalities detected in this condition. To handle the complexity of neuroimaging data and to convert brain images in informative biomarkers of pathology, multivariate analysis techniques based on Support Vector Machines (SVM) have been widely used in several disease conditions. They are usually trained to distinguish patients from healthy control subjects by making a binary classification. Here, we propose the use of the One-Class Classification (OCC) or Data Description method that, in contrast to two-class classification, is based on a description of one class of objects only. This approach, by defining a multivariate normative rule on one class of subjects, allows recognizing examples from a different category as outliers. We applied the OCC to 314 regional features extracted from brain structural Magnetic Resonance Imaging (MRI) scans of young children with ASD (21 males and 20 females) and control subjects (20 males and 20 females), matched on age [range: 22-72 months of age; mean = 49 months] and non-verbal intelligence quotient (NVIQ) [range: 31-123; mean = 73]. We demonstrated that a common pattern of features characterize the ASD population. The OCC SVM trained on the group of ASD subjects showed the following performances in the ASD vs. controls separation: the area under the receiver operating characteristic curve (AUC) was 0.74 for the male and 0.68 for the female population, respectively. Notably, the ASD vs. controls discrimination results were maximized when evaluated on the subsamples of subjects with NVIQ ≥ 70, leading to AUC = 0.81 for the male and AUC = 0.72 for the female populations, respectively. Language regions and regions from the default mode network-posterior cingulate cortex, pars opercularis and pars triangularis of the inferior frontal gyrus, and transverse temporal gyrus

  18. One-Class Support Vector Machines Identify the Language and Default Mode Regions As Common Patterns of Structural Alterations in Young Children with Autism Spectrum Disorders

    PubMed Central

    Retico, Alessandra; Gori, Ilaria; Giuliano, Alessia; Muratori, Filippo; Calderoni, Sara

    2016-01-01

    The identification of reliable brain endophenotypes of autism spectrum disorders (ASD) has been hampered to date by the heterogeneity in the neuroanatomical abnormalities detected in this condition. To handle the complexity of neuroimaging data and to convert brain images in informative biomarkers of pathology, multivariate analysis techniques based on Support Vector Machines (SVM) have been widely used in several disease conditions. They are usually trained to distinguish patients from healthy control subjects by making a binary classification. Here, we propose the use of the One-Class Classification (OCC) or Data Description method that, in contrast to two-class classification, is based on a description of one class of objects only. This approach, by defining a multivariate normative rule on one class of subjects, allows recognizing examples from a different category as outliers. We applied the OCC to 314 regional features extracted from brain structural Magnetic Resonance Imaging (MRI) scans of young children with ASD (21 males and 20 females) and control subjects (20 males and 20 females), matched on age [range: 22–72 months of age; mean = 49 months] and non-verbal intelligence quotient (NVIQ) [range: 31–123; mean = 73]. We demonstrated that a common pattern of features characterize the ASD population. The OCC SVM trained on the group of ASD subjects showed the following performances in the ASD vs. controls separation: the area under the receiver operating characteristic curve (AUC) was 0.74 for the male and 0.68 for the female population, respectively. Notably, the ASD vs. controls discrimination results were maximized when evaluated on the subsamples of subjects with NVIQ ≥ 70, leading to AUC = 0.81 for the male and AUC = 0.72 for the female populations, respectively. Language regions and regions from the default mode network—posterior cingulate cortex, pars opercularis and pars triangularis of the inferior frontal gyrus, and transverse temporal

  19. Membrane domain structures of three classes of histidine kinase receptors by cell-free expression and rapid NMR analysis

    PubMed Central

    Maslennikov, Innokentiy; Klammt, Christian; Hwang, Eunha; Kefala, Georgia; Okamura, Mizuki; Esquivies, Luis; Mörs, Karsten; Glaubitz, Clemens; Kwiatkowski, Witek; Jeon, Young Ho; Choe, Senyon

    2010-01-01

    NMR structural studies of membrane proteins (MP) are hampered by complications in MP expression, technical difficulties associated with the slow process of NMR spectral peak assignment, and limited distance information obtainable for transmembrane (TM) helices. To overcome the inherent challenges in the determination of MP structures, we have developed a rapid and cost-efficient strategy that combines cell-free (CF) protein synthesis, optimized combinatorial dual-isotope labeling for nearly instant resonance assignment, and fast acquisition of long-distance information using paramagnetic probes. Here we report three backbone structures for the TM domains of the three classes of Escherichia coli histidine kinase receptors (HKRs). The ArcB and QseC TM domains are both two-helical motifs, whereas the KdpD TM domain comprises a four-helical bundle with shorter second and third helices. The interhelical distances (up to 12 Å) reveal weak interactions within the TM domains of all three receptors. Determined consecutively within 8 months, these structures offer insight into the abundant and underrepresented in the Protein Data Bank class of 2–4 TM crossers and demonstrate the efficiency of our CF combinatorial dual-labeling strategy, which can be applied to solve MP structures in high numbers and at a high speed. Our results greatly expand the current knowledge of HKR structure, opening the doors to studies on their widespread and pharmaceutically important bacterial signaling mechanism. PMID:20498088

  20. Structural Revisions of a Class of Natural Products: Scaffolds of Aglycon Analogues of Fusicoccins and Cotylenins Isolated from Fungi.

    PubMed

    Tang, Ying; Xue, Yongbo; Du, Guang; Wang, Jianping; Liu, Junjun; Sun, Bin; Li, Xiao-Nian; Yao, Guangmin; Luo, Zengwei; Zhang, Yonghui

    2016-03-14

    The reisolation and structural revision of brassicicene D is described, and inspired us to reassign the core skeletons of brassicicenes C-H, J and K, ranging from dicyclopenta[a,d]cyclooctane to tricyclo[9.2.1.0(3,7)]tetradecane using quantum-chemical predictions and experimental validation strategies. Three novel, highly modified fusicoccanes, brassicicenes L-N, were also isolated from the fungus Alternaria brassicicola, and their structures were unequivocally established by spectroscopic data, ECD calculations, and crystallography. The reassigned structures represent the first class of bridgehead double-bond-containing natural products with a bicyclo[6.2.1]undecane carbon skeleton. Furthermore, their stabilities were first predicted with olefin strain energy calculations. Collectively, these findings extend our view of the application of computational predictions and biosynthetic logic-based structure elucidation to address problems related to the structure and stability of natural products. PMID:26916098

  1. Association of structural global brain network properties with intelligence in normal aging.

    PubMed

    Fischer, Florian U; Wolf, Dominik; Scheurich, Armin; Fellgiebel, Andreas

    2014-01-01

    Higher general intelligence attenuates age-associated cognitive decline and the risk of dementia. Thus, intelligence has been associated with cognitive reserve or resilience in normal aging. Neurophysiologically, intelligence is considered as a complex capacity that is dependent on a global cognitive network rather than isolated brain areas. An association of structural as well as functional brain network characteristics with intelligence has already been reported in young adults. We investigated the relationship between global structural brain network properties, general intelligence and age in a group of 43 cognitively healthy elderly, age 60-85 years. Individuals were assessed cross-sectionally using Wechsler Adult Intelligence Scale-Revised (WAIS-R) and diffusion-tensor imaging. Structural brain networks were reconstructed individually using deterministic tractography, global network properties (global efficiency, mean shortest path length, and clustering coefficient) were determined by graph theory and correlated to intelligence scores within both age groups. Network properties were significantly correlated to age, whereas no significant correlation to WAIS-R was observed. However, in a subgroup of 15 individuals aged 75 and above, the network properties were significantly correlated to WAIS-R. Our findings suggest that general intelligence and global properties of structural brain networks may not be generally associated in cognitively healthy elderly. However, we provide first evidence of an association between global structural brain network properties and general intelligence in advanced elderly. Intelligence might be affected by age-associated network deterioration only if a certain threshold of structural degeneration is exceeded. Thus, age-associated brain structural changes seem to be partially compensated by the network and the range of this compensation might be a surrogate of cognitive reserve or brain resilience.

  2. Visualizing Communication Structures in Science Classrooms: Tracing Cumulativity in Teacher-Led Whole Class Discussions

    ERIC Educational Resources Information Center

    Lehesvuori, Sami; Viiri, Jouni; Rasku-Puttonen, Helena; Moate, Josephine; Helaakoski, Jussi

    2013-01-01

    Teacher-led whole class discussions are essential when it comes to guiding students' construction of knowledge, and recent studies on teaching and learning emphasize the need for more student-centered teaching methods. In previous studies, the extent to which different types of communication take place in the classroom have been extensively…

  3. A Conflicting View in the Use of Journals for Composition and Literature Classes: Structure versus Freedom.

    ERIC Educational Resources Information Center

    Townsend, Julie E.

    The most powerful and profound thoughts known to humankind are the result of freedom to write whatever it is that the soul must purge; whatever a person is thinking that troubles him or her; anything that hinders his or her ability to be in that particular moment of living. On the first day of class, one writing instructor tells her students that…

  4. Confirming the Structural Validity of the My Class Inventory -- Short Form Revised

    ERIC Educational Resources Information Center

    Mariani, Melissa; Villares, Elizabeth; Sink, Christopher A.; Colvin, Kimberly; Kuba, Summer Perhay

    2015-01-01

    Researchers analyzed data collected from elementary school students (N = 893) to further establish the psychometric soundness of the My Class Inventory--Short Form Revised (MCI-SFR). A confirmatory factor analysis was conducted resulting in a good fit for a four-factor model, which corresponds to the instrument's four scales (Cohesion,…

  5. Estimating survival rates with time series of standing age-structure data.

    PubMed

    Udevitz, Mark S; Gogan, Peter J P

    2012-04-01

    It has long been recognized that age-structure data contain useful information for assessing the status and dynamics of wildlife populations. For example, age-specific survival rates can be estimated with just a single sample from the age distribution of a stable, stationary population. For a population that is not stable, age-specific survival rates can be estimated using techniques such as inverse methods that combine time series of age-structure data with other demographic data. However, estimation of survival rates using these methods typically requires numerical optimization, a relatively long time series of data, and smoothing or other constraints to provide useful estimates. We developed general models for possibly unstable populations that combine time series of age-structure data with other demographic data to provide explicit maximum likelihood estimators of age-specific survival rates with as few as two years of data. As an example, we applied these methods to estimate survival rates for female bison (Bison bison) in Yellowstone National Park, USA. This approach provides a simple tool for monitoring survival rates based on age-structure data.

  6. Structural hippocampal network alterations during healthy aging: a multi-modal MRI study

    PubMed Central

    Pelletier, Amandine; Periot, Olivier; Dilharreguy, Bixente; Hiba, Bassem; Bordessoules, Martine; Pérès, Karine; Amieva, Hélène; Dartigues, Jean-François; Allard, Michèle; Catheline, Gwénaëlle

    2013-01-01

    While hippocampal atrophy has been described during healthy aging, few studies have examined its relationship with the integrity of White Matter (WM) connecting tracts of the limbic system. This investigation examined WM structural damage specifically related to hippocampal atrophy in healthy aging subjects (n = 129), using morphological MRI to assess hippocampal volume and Diffusion Tensor Imaging (DTI) to assess WM integrity. Subjects with Mild Cognitive Impairment (MCI) or dementia were excluded from the analysis. In our sample, increasing age was significantly associated with reduced hippocampal volume and reduced Fractional Anisotropy (FA) at the level of the fornix and the cingulum bundle. The findings also demonstrate that hippocampal atrophy was specifically associated with reduced FA of the fornix bundle, but it was not related to alteration of the cingulum bundle. Our results indicate that the relationship between hippocampal atrophy and fornix FA values is not due to an independent effect of age on both structures. A recursive regression procedure was applied to evaluate sequential relationships between the alterations of these two brain structures. When both hippocampal atrophy and fornix FA values were included in the same model to predict age, fornix FA values remained significant whereas hippocampal atrophy was no longer significantly associated with age. According to this latter finding, hippocampal atrophy in healthy aging could be mediated by a loss of fornix connections. Structural alterations of this part of the limbic system, which have been associated with neurodegeneration in Alzheimer's disease, result at least in part from the aging process. PMID:24367331

  7. Aging Optimization of Aluminum-Lithium Alloy C458 for Application to Cryotank Structures

    NASA Technical Reports Server (NTRS)

    Sova, B. J.; Sankaran, K. K.; Babel, H. W.; Farahmand, B.; Rioja, R.

    2003-01-01

    This viewgraph report presents an examination of the fracture toughness of aluminum-lithium alloy C458 for use in cryotank structures. Topics cover include: cryogenics, alloy composition, strengthing precipitates in C458, cryogenic fracture toughness improvements, design of experiments for measuring aging optimization of C458 plate and effects of aging of properties of C458 plate.

  8. Factor Structure of Attention Deficit Hyperactivity Disorder Symptoms for Children Age 3 to 5 Years

    ERIC Educational Resources Information Center

    McGoey, Kara E.; Schreiber, James; Venesky, Lindsey; Westwood, Wendy; McGuirk, Lindsay; Schaffner, Kristen

    2015-01-01

    The diagnosis of attention deficit hyperactivity disorder (ADHD) distinguishes two dimensions of symptoms, inattention and hyperactivity-impulsivity for ages 3 to adulthood. Currently, no separate classification for preschool-age children exists, whereas preliminary research suggests that the two-factor structure of ADHD may not match the…

  9. Estimating survival rates with time series of standing age-structure data

    USGS Publications Warehouse

    Udevitz, Mark S.; Gogan, Peter J.

    2014-01-01

    It has long been recognized that age-structure data contain useful information for assessing the status and dynamics of wildlife populations. For example, age-specific survival rates can be estimated with just a single sample from the age distribution of a stable, stationary population. For a population that is not stable, age-specific survival rates can be estimated using techniques such as inverse methods that combine time series of age-structure data with other demographic data. However, estimation of survival rates using these methods typically requires numerical optimization, a relatively long time series of data, and smoothing or other constraints to provide useful estimates. We developed general models for possibly unstable populations that combine time series of age-structure data with other demographic data to provide explicit maximum likelihood estimators of age-specific survival rates with as few as two years of data. As an example, we applied these methods to estimate survival rates for female bison (Bison bison) in Yellowstone National Park, USA. This approach provides a simple tool for monitoring survival rates based on age-structure data.

  10. Insights into MHC class I peptide loading from the structure of the Tapasin-ERp57 thiol oxidoreductase heterodimer

    SciTech Connect

    Dong, G.; Wearsch, P.A.; Peaper, D.R.; Cresswell, P.; Reinisch, K.M.

    2009-03-02

    Tapasin is a glycoprotein critical for loading major histocompatibility complex (MHC) class I molecules with high-affinity peptides. It functions within the multimeric peptide-loading complex (PLC) as a disulfide-linked, stable heterodimer with the thiol oxidoreductase ERp57, and this covalent interaction is required to support optimal PLC activity. Here, we present the 2.6 {angstrom} resolution structure of the tapasin-ERp57 core of the PLC. The structure revealed that tapasin interacts with both ERp57 catalytic domains, accounting for the stability of the heterodimer, and provided an example of a protein disulfide isomerase family member interacting with substrate. Mutational analysis identified a conserved surface on tapasin that interacted with MHC class I molecules and was critical for peptide loading and editing functions of the tapasin-ERp57 heterodimer. By combining the tapasin-ERp57 structure with those of other defined PLC components, we present a molecular model that illuminates the processes involved in MHC class I peptide loading.

  11. A highly accurate protein structural class prediction approach using auto cross covariance transformation and recursive feature elimination.

    PubMed

    Li, Xiaowei; Liu, Taigang; Tao, Peiying; Wang, Chunhua; Chen, Lanming

    2015-12-01

    Structural class characterizes the overall folding type of a protein or its domain. Many methods have been proposed to improve the prediction accuracy of protein structural class in recent years, but it is still a challenge for the low-similarity sequences. In this study, we introduce a feature extraction technique based on auto cross covariance (ACC) transformation of position-specific score matrix (PSSM) to represent a protein sequence. Then support vector machine-recursive feature elimination (SVM-RFE) is adopted to select top K features according to their importance and these features are input to a support vector machine (SVM) to conduct the prediction. Performance evaluation of the proposed method is performed using the jackknife test on three low-similarity datasets, i.e., D640, 1189 and 25PDB. By means of this method, the overall accuracies of 97.2%, 96.2%, and 93.3% are achieved on these three datasets, which are higher than those of most existing methods. This suggests that the proposed method could serve as a very cost-effective tool for predicting protein structural class especially for low-similarity datasets.

  12. The Evolution of an Undergraduate Service Course--How To Cope with Success of an Age of Dinosaurs Class.

    ERIC Educational Resources Information Center

    Montgomery, Homer

    2003-01-01

    Discusses how to address the issue of a course becoming too popular. Uses as an example the Age of Dinosaurs course at the University of Texas at Dallas. Describes some issues that can arise such as classroom overflow, overwhelmed labs, cheating, testing methods, and asynchronous instruction. Recommends looking to web-based course management…

  13. Academic Success as a Function of the Gender, Class, Age, Study Habits, and Employment of College Students.

    ERIC Educational Resources Information Center

    Lammers, William J.; Onwuegbuzie, Anthony J.; Slate, John R.

    2001-01-01

    Studied the predominant study skills and weaknesses of college students in a sample of 366 undergraduates. Study skill weaknesses were identified in the areas of note-taking, reading skills, and time management. Study skills were also related to age, grade point average, and the number of hours spent studying each week. (SLD)

  14. The evolution of oscillatory behavior in age-structured species.

    PubMed

    Greenman, J V; Benton, T G; Boots, M; White, A R

    2005-07-01

    A major challenge in ecology is to explain why so many species show oscillatory population dynamics and why the oscillations commonly occur with particular periods. The background environment, through noise or seasonality, is one possible driver of these oscillations, as are the components of the trophic web with which the species interacts. However, the oscillation may also be intrinsic, generated by density-dependent effects on the life history. Models of structured single-species systems indicate that a much broader range of oscillatory behavior than that seen in nature is theoretically possible. We test the hypothesis that it is selection that acts to constrain the range of periods. We analyze a nonlinear single-species matrix model with density dependence affecting reproduction and with trade-offs between reproduction and survival. We show that the evolutionarily stable state is oscillatory and has a period roughly twice the time to maturation, in line with observed patterns of periodicity. The robustness of this result to variations in trade-off function and density dependence is tested.

  15. Does white matter structure or hippocampal volume mediate associations between cortisol and cognitive ageing?

    PubMed Central

    Cox, Simon R.; MacPherson, Sarah E.; Ferguson, Karen J.; Royle, Natalie A.; Maniega, Susana Muñoz; Hernández, Maria del C. Valdés; Bastin, Mark E.; MacLullich, Alasdair M.J.; Wardlaw, Joanna M.; Deary, Ian J.

    2015-01-01

    Elevated glucocorticoid (GC) levels putatively damage specific brain regions, which in turn may accelerate cognitive ageing. However, many studies are cross-sectional or have relatively short follow-up periods, making it difficult to relate GCs directly to changes in cognitive ability with increasing age. Moreover, studies combining endocrine, MRI and cognitive variables are scarce, measurement methods vary considerably, and formal tests of the underlying causal hypothesis (cortisol → brain → cognition) are absent. In this study, 90 men, aged 73 years, provided measures of fluid intelligence, processing speed and memory, diurnal and reactive salivary cortisol and two measures of white matter (WM) structure (WM hyperintensity volume from structural MRI and mean diffusivity averaged across 12 major tracts from diffusion tensor MRI), hippocampal volume, and also cognitive ability at age 11. We tested whether negative relationships between cognitive ageing differences (over more than 60 years) and salivary cortisol were significantly mediated by WM and hippocampal volume. Significant associations between reactive cortisol at 73 and cognitive ageing differences between 11 and 73 (r = −.28 to −.36, p < .05) were partially mediated by both WM structural measures, but not hippocampal volume. Cortisol-WM relationships were modest, as was the degree to which WM structure attenuated cortisol–cognition associations (<15%). These data support the hypothesis that GCs contribute to cognitive ageing differences from childhood to the early 70s, partly via brain WM structure. PMID:26298692

  16. Does white matter structure or hippocampal volume mediate associations between cortisol and cognitive ageing?

    PubMed

    Cox, Simon R; MacPherson, Sarah E; Ferguson, Karen J; Royle, Natalie A; Maniega, Susana Muñoz; Hernández, Maria Del C Valdés; Bastin, Mark E; MacLullich, Alasdair M J; Wardlaw, Joanna M; Deary, Ian J

    2015-12-01

    Elevated glucocorticoid (GC) levels putatively damage specific brain regions, which in turn may accelerate cognitive ageing. However, many studies are cross-sectional or have relatively short follow-up periods, making it difficult to relate GCs directly to changes in cognitive ability with increasing age. Moreover, studies combining endocrine, MRI and cognitive variables are scarce, measurement methods vary considerably, and formal tests of the underlying causal hypothesis (cortisol→brain→cognition) are absent. In this study, 90 men, aged 73 years, provided measures of fluid intelligence, processing speed and memory, diurnal and reactive salivary cortisol and two measures of white matter (WM) structure (WM hyperintensity volume from structural MRI and mean diffusivity averaged across 12 major tracts from diffusion tensor MRI), hippocampal volume, and also cognitive ability at age 11. We tested whether negative relationships between cognitive ageing differences (over more than 60 years) and salivary cortisol were significantly mediated by WM and hippocampal volume. Significant associations between reactive cortisol at 73 and cognitive ageing differences between 11 and 73 (r=-.28 to -.36, p<.05) were partially mediated by both WM structural measures, but not hippocampal volume. Cortisol-WM relationships were modest, as was the degree to which WM structure attenuated cortisol-cognition associations (<15%). These data support the hypothesis that GCs contribute to cognitive ageing differences from childhood to the early 70s, partly via brain WM structure. PMID:26298692

  17. The Coming of age of Low-cost Nanosatellites as Enablers for Constellation-class Space Weather Networks

    NASA Astrophysics Data System (ADS)

    Klumpar, D. M.

    2006-12-01

    Recent progress in the development of satellite-borne space science instrumentation has focused on increased sophistication resulting in a tremendous increase in understanding of microphysical processes in space. These tremendous advancements, however, have been made without sufficient concomitant experimental characterization of the dynamic behavior of the large-scale geospace system. Global theoretical models of the geospace system need distributed measurements for authentication. Thus there is a need to acquire in-situ space weather data at higher spatio-temporal density than currently planned. Nanosatellites (i.e. 1-10 kg spacecraft) have emerged as technically capable carriers for a variety of on-orbit missions. Advances in electronic miniaturization, reductions in power consumption, increased communications capabilities and miniaturized propulsion systems for station-keeping have enabled development of highly capable miniature satellite buses. Led primarily by universities, kg-class satellites have been developed and launched for a variety of purposes. As recently as July 2006, 18 satellites were lost in a launch booster failure in what was billed as the single largest cluster launch of satellites to date. Thirteen of the 14 one kg-class satellites in this cluster launch were designed, developed, and built in university laboratories. They were built at a fraction of the cost of typical satellites. While, in this instance, these 14 satellites had, for the most part, unrelated mission goals it is perfectly reasonable to envision that a launch of several dozen related satellites is technically feasible at a cost much lower than studies based on traditional methods have shown. This paper will review current nanosatellite capabilities and explore the application of constellations of nanosatellies as carriers of relatively unsophisticated space weather instruments where the value lies in the ability to make a network of measurements that provide unprecedented

  18. An agent-based computational model for tuberculosis spreading on age-structured populations

    NASA Astrophysics Data System (ADS)

    Graciani Rodrigues, C. C.; Espíndola, Aquino L.; Penna, T. J. P.

    2015-06-01

    In this work we present an agent-based computational model to study the spreading of the tuberculosis (TB) disease on age-structured populations. The model proposed is a merge of two previous models: an agent-based computational model for the spreading of tuberculosis and a bit-string model for biological aging. The combination of TB with the population aging, reproduces the coexistence of health states, as seen in real populations. In addition, the universal exponential behavior of mortalities curves is still preserved. Finally, the population distribution as function of age shows the prevalence of TB mostly in elders, for high efficacy treatments.

  19. Alcohol dehydrogenase of class IV (sigma sigma-ADH) from human stomach. cDNA sequence and structure/function relationships.

    PubMed

    Farrés, J; Moreno, A; Crosas, B; Peralba, J M; Allali-Hassani, A; Hjelmqvist, L; Jörnvall, H; Parés, X

    1994-09-01

    Human stomach mucosa contains a characteristic alcohol dehydrogenase (ADH) enzyme, sigma sigma-ADH. Its cDNA has been cloned from a human stomach library and sequenced. The deduced amino acid sequence shows 59-70% identities with the other human ADH classes, demonstrating that the stomach enzyme represents a distinct structure, constituting class IV, coded by a separate gene, ADH7. The amino acid identity with the rat stomach class IV ADH is 88%, which is intermediate between constant and variable dehydrogenases. This value reflects higher conservation than for the classical liver enzymes of class I, compatible with a separate functional significance of the class IV enzyme. Its enzymic features can be correlated with its structural characteristics. The residues lining the substrate-binding cleft are bulky and hydrophobic, similar to those of the class I enzyme; this explains the similar specificity of both classes, compatible with the origin of class IV from class I. Position 47 has Arg, in contrast to Gly in the rat class IV enzyme, but this Arg is still associated with an extremely high activity (kcat = 1510 min-1) and weak coenzyme binding (KiaNAD+ = 1.6 mM). Thus, the strong interaction with coenzyme imposed by Arg47 in class I is probably compensated for in class IV by changes that may negatively affect coenzyme binding: Glu230, His271, Asn260, Asn261, Asn363. The still higher activity and weaker coenzyme binding of rat class IV (kcat = 2600 min-1, KiaNAD = 4 mM) can be correlated to the exchanges to Gly47, Gln230 and Tyr363. An important change at position 294, with Val in human and Ala in rat class IV, is probably responsible for the dramatic difference in Km values for ethanol between human (37 mM) and rat (2.4 M) class IV enzymes.

  20. Mathematical Model of Three Age-Structured Transmission Dynamics of Chikungunya Virus

    PubMed Central

    Agusto, Folashade B.; Easley, Shamise; Freeman, Kenneth; Thomas, Madison

    2016-01-01

    We developed a new age-structured deterministic model for the transmission dynamics of chikungunya virus. The model is analyzed to gain insights into the qualitative features of its associated equilibria. Some of the theoretical and epidemiological findings indicate that the stable disease-free equilibrium is globally asymptotically stable when the associated reproduction number is less than unity. Furthermore, the model undergoes, in the presence of disease induced mortality, the phenomenon of backward bifurcation, where the stable disease-free equilibrium of the model coexists with a stable endemic equilibrium when the associated reproduction number is less than unity. Further analysis of the model indicates that the qualitative dynamics of the model are not altered by the inclusion of age structure. This is further emphasized by the sensitivity analysis results, which shows that the dominant parameters of the model are not altered by the inclusion of age structure. However, the numerical simulations show the flaw of the exclusion of age in the transmission dynamics of chikungunya with regard to control implementations. The exclusion of age structure fails to show the age distribution needed for an effective age based control strategy, leading to a one size fits all blanket control for the entire population. PMID:27190548

  1. Benefits of gregarious feeding by aposematic caterpillars depend on group age structure.

    PubMed

    Campbell, Stuart A; Stastny, Michael

    2015-03-01

    Gregarious feeding is a common feature of herbivorous insects and can range from beneficial (e.g. dilution of predation risk) to costly (e.g. competition). Group age structure should influence these costs and benefits, particularly when old and young larvae differ in their feeding mode or apparency to predators. We investigated the relative value of gregarious feeding by aposematic larvae of Uresiphita reversalis that we observed feeding in groups of mixed ages and variable densities on wild Lupinus diffusus. In a manipulative field experiment, the survivorship and growth of young larvae were enhanced in the presence of older conspecifics, but not in large groups of similarly aged larvae. Estimates of insect damage and induced plant responses suggest that mixed-age groups enhance plant quality for young larvae while avoiding competition. We conclude that benefits of gregariousness in this species are contingent on group age structure, a finding of significance for the ecology and evolution of gregariousness and other social behaviours.

  2. Observability coefficients for predicting the class of synchronizability from the algebraic structure of the local oscillators

    NASA Astrophysics Data System (ADS)

    Sendiña-Nadal, Irene; Boccaletti, Stefano; Letellier, Christophe

    2016-10-01

    Understanding the conditions under which a collective dynamics emerges in a complex network is still an open problem. A useful approach is the master stability function—and its related classes of synchronization—which offers a necessary condition to assess when a network successfully synchronizes. Observability coefficients, on the other hand, quantify how well the original state space of a system can be observed given only the access to a measured variable. The question is therefore pertinent: Given a generic dynamical system (represented by a state variable x) and given a generic measure on it h (x) (which may be either an observation of an external agent, or an output function through which the units of a network interact), are classes of synchronization and observability actually related to each other? We explicitly address this issue, and show a series of nontrivial relationships for networks of different popular chaotic systems (Rössler, Lorenz, and Hindmarsh-Rose oscillators). Our results suggest that specific dynamical properties can be evoked for explaining the classes of synchronizability.

  3. Joint effects of social class and community occupational structure on coronary mortality among black men and white men, upstate New York, 1988–92

    PubMed Central

    Armstrong, D; Strogatz, D; Barnett, E; Wang, R

    2003-01-01

    Study objective: Occupational structure represents the unequal geographical distribution of more desirable jobs among communities (for example, white collar jobs). This study examines joint effects of social class, race, and county occupational structure on coronary mortality rates for men, ages 35–64 years, 1988–92, in upstate New York. Design: Upstate New York's 57 counties were classified into three occupational structure categories; counties with the lowest percentages of the labour force in managerial, professional, and technical occupations were classified in category I, counties with the highest percentages were in category III. Age adjusted coronary heart disease (CHD) mortality rates, 35–64 years, (from vital statistics and census data) were calculated for each occupational structure category. Main results: An inverse association between CHD mortality and occupational structure was observed among blue collar and white collar workers, among black men and white men, with the lowest CHD mortality observed among white collar, white men in category III (135/100 000). About two times higher mortality was observed among blue collar than white collar workers. Among blue collar workers, mortality was 1.3–1.8 times higher among black compared with white workers, and the highest rates were observed among black, blue collar workers (689/100 000). Also, high residential race segregation was shown in all areas. Conclusions: Results suggest the importance of community conditions in coronary health of local populations; however, differential impact on subpopulations was shown. Blue collar and black workers may especially lack economic and other resources to use available community services and/or may experience worse working and living conditions compared with white collar and white workers in the same communities. PMID:12700223

  4. Qualitative characteristics of meat from cull cows of different genotypes and age class slaughter under different finishing systems: a meta-analytic approach.

    PubMed

    Pacheco, Rangel F; Mayer, Andrei R; Vaz, Marcos A B; Pötter, Luciana; Cattelam, Jonatas; Callegaro, Álisson M; Pizzuti, Luiz Angelo D; Brondani, Ivan L; Alves Filho, Dari C; Pacheco, Paulo S

    2015-01-01

    The aim of this study was to evaluate, by meta-analysis, the quality of the meat of the cows according to genotype, termination system and age class slaughter. During an online research were identified 15 articles with information related to meat quality of slaughtered cows. The data were grouped according of the genotype of cows being: zebu or continental defined, crossed zebu x british or zebu x continental; according to termination system: feedlot or grassland; according to age of slaughter, where: up to 4 years old (young), 4-8 years old (adult) or more than 8 years old (old). The meat of the continental crossbred cows was softer than the other genotypes, both panel of evaluators and by Shear. The meat of cows finished in feedlot showed higher marbling degree in relation to meat of females finished on grassland. The reduction of the slaughter age of cows improved the meat color. The cow's genotype affects the organoleptic aspects of meat while the finished system and slaughter age affects the sensory aspects of meat.

  5. Intrinsic Nanoscience of δ Pu-Ga Alloys: Local Structure and Speciation, Collective Behavior, Nanoscale Heterogeneity, and Aging Mechanisms

    SciTech Connect

    Conradson, Steven D.; Bock, Nicolas; Castro, Julio M.; Conradson, Dylan R.; Cox, Lawrence E.; Dmowski, Wojtek; Dooley, David E.; Egami, Takeshi; Espinosa-Faller, Francisco J.; Freibert, Franz J.; Garcia-Adeva, Angel J.; Hess, Nancy J.; Holmstrom, Erik; Howell, Rafael C.; Katz, Barbara A.; Lashley, Jason C.; Martinez, Raymond J.; Moore, David P.; Morales, Luis A.; Olivas, J David; Pereyra, Ramiro A.; Ramos, Michael; Terry, Jeff H.; Villella, Phillip M.

    2014-04-24

    Because diffraction measurements are sensitive only to the long range average arrangement of the atoms in the coherent portion of a crystal, complementary local structure measurements are required for a complete understanding of the structure of a complex material. This is particularly an issue in solid solutions where even random distributions of a solute will result in nanometer-scale fluctuations in the local composition. The structure will be further complicated if collective and cooperative phenomena organize the solute distribution via longer range interactions between non-bonded solute sites. If the solute affects the phase stability then the question is raised of whether the atoms in domains with local compositions outside the limits of the bulk phase will rearrange into the structure stable for that composition and temperature or if the resulting stress would prevent such a local phase transition. If the former, then phase separated, heterogeneous structures at or below the diffraction limit will form. This nanometerscale competition between the phase transition and the epitaxial mismatch – exacerbated by the added strain if the transition involves a volume change – raises the potential for the formation of novel structures that do not occur in bulk material, e.g., fcc Fe. This coupling over multiple scales between inhomogeneity ordering, elastic forces, phase competition, and texture in the form of coexisting structures is a hallmark of martensites, a class of complex materials that includes δ-stabilized PuGa and that often exhibit correlated atomic and electronic properties. The enigmatic and extreme nature of Pu is consistent with its exhibiting unusual structural behavior of this type, including nanoscale heterogeneity in δ-stabilized PuGa and its enhanced homogeneity on aging that has been suggested based on earlier X-ray Absorption Fine Structure (XAFS) spectroscopy and x-ray pair distribution function (pdf) measurements. Measurements on a

  6. Quota implementation of the maximum sustainable yield for age-structured fisheries.

    PubMed

    Kanik, Zafer; Kucuksenel, Serkan

    2016-06-01

    One of the main goals stated in the proposals for the Common Fisheries Policy (CFP) reform was achieving maximum sustainable yield (MSY) for all European fisheries. In this paper, we propose a fishing rights allocation mechanism or management system, which specifies catch limits for individual fishing fleets to implement MSY harvesting conditions in an age-structured bioeconomic model. An age-structured model in a single species fishery with two fleets having perfect or imperfect fishing selectivity is studied. If fishing technology or gear selectivity depends on the relative age composition of the mature fish stock, fixed harvest proportions, derived from catchability and bycatch coefficients, is not valid anymore. As a result, not only the age-structure and fishing technology but also the estimated level of MSY is steering the allocation of quota shares. The results also show that allocation of quota shares based on historical catches or auctioning may not provide viable solutions to achieve MSY. PMID:27018447

  7. Quota implementation of the maximum sustainable yield for age-structured fisheries.

    PubMed

    Kanik, Zafer; Kucuksenel, Serkan

    2016-06-01

    One of the main goals stated in the proposals for the Common Fisheries Policy (CFP) reform was achieving maximum sustainable yield (MSY) for all European fisheries. In this paper, we propose a fishing rights allocation mechanism or management system, which specifies catch limits for individual fishing fleets to implement MSY harvesting conditions in an age-structured bioeconomic model. An age-structured model in a single species fishery with two fleets having perfect or imperfect fishing selectivity is studied. If fishing technology or gear selectivity depends on the relative age composition of the mature fish stock, fixed harvest proportions, derived from catchability and bycatch coefficients, is not valid anymore. As a result, not only the age-structure and fishing technology but also the estimated level of MSY is steering the allocation of quota shares. The results also show that allocation of quota shares based on historical catches or auctioning may not provide viable solutions to achieve MSY.

  8. Density-dependent growth rate in an age-structured population: a field study on stream-dwelling brown trout Salmo trutta.

    PubMed

    Kaspersson, R; Höjesjö, J

    2009-07-01

    A field experiment during autumn, winter and spring was performed in a small stream on the west coast of Sweden, aiming to examine the direct and indirect consequences of density-dependent intercohort competition in brown trout Salmo trutta. Individual growth rate, recapture rate and site fidelity were used as response variables in the young-of-the-year (YOY) age class, experiencing two different treatments: presence or absence of yearlings and over-yearlings (age > or = 1+ year individuals). YOY individuals in stream sections with reduced density of age > or = 1+ year individuals grew significantly faster than individuals experiencing natural cohort structure. In the latter, growth rate was negatively correlated with density and biomass of age > or = 1+ year individuals, which may induce indirect effects on year-class strength through, for example, reduced fecundity and survival. Movement of YOY individuals and turnover rate (i.e. proportion of untagged individuals) were used to demonstrate potential effects of intercohort competition on site fidelity. While YOY movement was remarkably restricted (83% recaptured within 50 m from the release points), turnover rate was higher in sections with reduced density of age > or = 1+ year individuals, suggesting that reduced density of age > or = 1+ year individuals may have released favourable microhabitats.

  9. Structural Validity of the Movement ABC-2 Test: Factor Structure Comparisons across Three Age Groups

    ERIC Educational Resources Information Center

    Schulz, Joerg; Henderson, Sheila E.; Sugden, David A.; Barnett, Anna L.

    2011-01-01

    Background: The Movement ABC test is one of the most widely used assessments in the field of Developmental Coordination Disorder (DCD). Improvements to the 2nd edition of the test (M-ABC-2) include an extension of the age range and reduction in the number of age bands as well as revision of tasks. The total test score provides a measure of motor…

  10. Age-structured mark-recapture analysis: A virtual-population-analysis-based model for analyzing age-structured capture-recapture data

    USGS Publications Warehouse

    Coggins, L.G.; Pine, William E.; Walters, C.J.; Martell, S.J.D.

    2006-01-01

    We present a new model to estimate capture probabilities, survival, abundance, and recruitment using traditional Jolly-Seber capture-recapture methods within a standard fisheries virtual population analysis framework. This approach compares the numbers of marked and unmarked fish at age captured in each year of sampling with predictions based on estimated vulnerabilities and abundance in a likelihood function. Recruitment to the earliest age at which fish can be tagged is estimated by using a virtual population analysis method to back-calculate the expected numbers of unmarked fish at risk of capture. By using information from both marked and unmarked animals in a standard fisheries age structure framework, this approach is well suited to the sparse data situations common in long-term capture-recapture programs with variable sampling effort. ?? Copyright by the American Fisheries Society 2006.

  11. Structural Validity of the Professional Development Profile of the LoTi Digital-Age Survey

    ERIC Educational Resources Information Center

    Mehta, Vandhana; Hull, Darrell M.

    2013-01-01

    The present study was used to examine the structural construct validity of the Professional Development Profile of the LoTi Digital-Age Survey, a measure of teacher instructional practices with technology in the classroom. Teacher responses ("N" = 2,840) from across the United States were used to assess factor structure of the instrument using…

  12. Test series 1: seismic-fragility tests of naturally-aged Class 1E Gould NCX-2250 battery cells

    SciTech Connect

    Bonzon, L. L.; Hente, D. B.; Kukreti, B. M.; Schendel, J. S.; Tulk, J. D.; Janis, W. J.; Black, D A; Paulsen, G. D.; Aucoin, B. D.

    1984-09-01

    The seismic-fragility response of naturally-aged, nuclear station, safety-related batteries is of interest for two reasons: (1) to determine actual failure modes and thresholds; and (2) to determine the validity of using the electrical capacity of individual cells as an indicator of the end-of-life of a battery, given a seismic event. This report covers the first test series of an extensive program using 12-year old, lead-calcium, Gould NCX-2250 cells, from the James A. Fitzpatrick Nuclear Power Station operated by the New York Power Authority. Seismic tests with three cell configurations were performed using a triaxial shake table: single-cell tests, rigidly mounted; multi-cell (three) tests, mounted in a typical battery rack; and single-cell tests specifically aimed towards examining propagation of pre-existing case cracks. In general the test philosophy was to monitor the electrical properties including discharge capacity of cells through a graduated series of g-level step increases until either the shake-table limits were reached or until electrical failure of the cells occurred. Of nine electrically active cells, six failed during seismic testing over a range of imposed g-level loads in excess of a 1-g ZPA. Post-test examination revealed a common failure mode, the cracking at the abnormally brittle, positive lead bus-bar/post interface; further examination showed that the failure zone was extremely coarse grained and extensively corroded. Presently accepted accelerated-aging methods for qualifying batteries, per IEEE Std. 535-1979, are based on plate growth, but these naturally-aged 12-year old cells showed no significant plate growth.

  13. Protection of rubbers against aging with the use of structural, diffusion and kinetic effects

    SciTech Connect

    Kablov, V. F.; Zaikov, G. E.

    2014-05-15

    Processes of rubber aging in the different kinetic modes and mathematical models of the processes including aging and destruction processes under extreme conditions have been studied. The aging process for rubbers as thermodynamically open nonlinear systems has also been considered in the paper. It has been revealed that the aging process can be controlled by the internal physical-chemical processes organization and by creation of external influences (by organization of thermodynamic forces and flows). According to the Onsager principle, in certain conditions of aging the conjugation of thermodynamic forces and flows is possible. The diffusion and structural aspects of aging in elastomeric rubbers and articles thereof have been considered. The composite antiaging systems of prolonged action based on the use of microparticles with a saturated solution of the antiagers migrating into an elastomeric matrix at the exploitation have been proposed.

  14. Protection of rubbers against aging with the use of structural, diffusion and kinetic effects

    NASA Astrophysics Data System (ADS)

    Kablov, V. F.; Zaikov, G. E.

    2014-05-01

    Processes of rubber aging in the different kinetic modes and mathematical models of the processes including aging and destruction processes under extreme conditions have been studied. The aging process for rubbers as thermodynamically open nonlinear systems has also been considered in the paper. It has been revealed that the aging process can be controlled by the internal physical-chemical processes organization and by creation of external influences (by organization of thermodynamic forces and flows). According to the Onsager principle, in certain conditions of aging the conjugation of thermodynamic forces and flows is possible. The diffusion and structural aspects of aging in elastomeric rubbers and articles thereof have been considered. The composite antiaging systems of prolonged action based on the use of microparticles with a saturated solution of the antiagers migrating into an elastomeric matrix at the exploitation have been proposed.

  15. The class III cyclobutane pyrimidine dimer photolyase structure reveals a new antenna chromophore binding site and alternative photoreduction pathways.

    PubMed

    Scheerer, Patrick; Zhang, Fan; Kalms, Jacqueline; von Stetten, David; Krauß, Norbert; Oberpichler, Inga; Lamparter, Tilman

    2015-05-01

    Photolyases are proteins with an FAD chromophore that repair UV-induced pyrimidine dimers on the DNA in a light-dependent manner. The cyclobutane pyrimidine dimer class III photolyases are structurally unknown but closely related to plant cryptochromes, which serve as blue-light photoreceptors. Here we present the crystal structure of a class III photolyase termed photolyase-related protein A (PhrA) of Agrobacterium tumefaciens at 1.67-Å resolution. PhrA contains 5,10-methenyltetrahydrofolate (MTHF) as an antenna chromophore with a unique binding site and mode. Two Trp residues play pivotal roles for stabilizing MTHF by a double π-stacking sandwich. Plant cryptochrome I forms a pocket at the same site that could accommodate MTHF or a similar molecule. The PhrA structure and mutant studies showed that electrons flow during FAD photoreduction proceeds via two Trp triads. The structural studies on PhrA give a clearer picture on the evolutionary transition from photolyase to photoreceptor.

  16. Relations between Classroom Goal Structures and Students' Goal Orientations in Mathematics Classes: When Is a Mastery Goal Structure Adaptive?

    ERIC Educational Resources Information Center

    Skaalvik, Einar M.; Federici, Roger A.

    2016-01-01

    The purpose of this study was to test possible interactions between mastery and performance goal structures in mathematics classrooms when predicting students' goal orientations. More specifically, we tested if the degree of performance goal structure moderated the associations between mastery goal structure and students' goal orientations.…

  17. Crystal Structure of Staphylococcal Enterotoxin I (SEI) in Complex with a Human Major Histocompatibility Complex Class II Molecule*

    PubMed Central

    Fernández, Marisa M.; Guan, Rongjin; Swaminathan, Chittoor P.; Malchiodi, Emilio L.; Mariuzza, Roy A.

    2009-01-01

    Superantigens are bacterial or viral proteins that elicit massive T cell activation through simultaneous binding to major histocompatibility complex (MHC) class II and T cell receptors. This activation results in uncontrolled release of inflammatory cytokines, causing toxic shock. A remarkable property of superantigens, which distinguishes them from T cell receptors, is their ability to interact with multiple MHC class II alleles independently of MHC-bound peptide. Previous crystallographic studies have shown that staphylococcal and streptococcal superantigens belonging to the zinc family bind to a high affinity site on the class II β-chain. However, the basis for promiscuous MHC recognition by zinc-dependent superantigens is not obvious, because the β-chain is polymorphic and the MHC-bound peptide forms part of the binding interface. To understand how zinc-dependent superantigens recognize MHC, we determined the crystal structure, at 2.0 Å resolution, of staphylococcal enterotoxin I bound to the human class II molecule HLA-DR1 bearing a peptide from influenza hemagglutinin. Interactions between the superantigen and DR1 β-chain are mediated by a zinc ion, and 22% of the buried surface of peptide·MHC is contributed by the peptide. Comparison of the staphylococcal enterotoxin I·peptide·DR1 structure with ones determined previously revealed that zinc-dependent superantigens achieve promiscuous binding to MHC by targeting conservatively substituted residues of the polymorphic β-chain. Additionally, these superantigens circumvent peptide specificity by engaging MHC-bound peptides at their conformationally conserved N-terminal regions while minimizing sequence-specific interactions with peptide residues to enhance cross-reactivity. PMID:16829512

  18. Extended Aging Theories for Predictions of Safe Operational Life of Critical Airborne Structural Components

    NASA Technical Reports Server (NTRS)

    Ko, William L.; Chen, Tony

    2006-01-01

    The previously developed Ko closed-form aging theory has been reformulated into a more compact mathematical form for easier application. A new equivalent loading theory and empirical loading theories have also been developed and incorporated into the revised Ko aging theory for the prediction of a safe operational life of airborne failure-critical structural components. The new set of aging and loading theories were applied to predict the safe number of flights for the B-52B aircraft to carry a launch vehicle, the structural life of critical components consumed by load excursion to proof load value, and the ground-sitting life of B-52B pylon failure-critical structural components. A special life prediction method was developed for the preflight predictions of operational life of failure-critical structural components of the B-52H pylon system, for which no flight data are available.

  19. Structure and Evolution of Kuiper Belt Objects: The Case for Compositional Classes

    NASA Astrophysics Data System (ADS)

    McKinnon, William B.; Prialnik, D.; Stern, S. A.

    2007-10-01

    Kuiper belt objects (KBOs) accreted from a mélange of ices, carbonaceous matter, and rock of mixed interstellar and solar nebular provenance. The transneptunian region, where this accretion took place, was likely more radially compact than today. This and the influence of gas drag during the solar nebula epoch argue for more rapid KBO accretion than usually considered. Early evolution of KBOs was largely the result of radiogenic heating, with both short-term and long-term contributions being potentially important. Depending on rock content and porous conductivity, KBO interiors may have reached relatively high temperatures. Models suggest that KBOs likely lost very volatile ices during early evolution, whereas less volatile ices should be retained in cold, less altered subsurface layers; initially amorphous ice may have crystallized in the interior as well, releasing trapped volatiles. Generally, KBOs should be stratified in terms of composition and porosity, albeit subject to impact disruption and collisional stripping. KBOs are thus unlikely to be "the most pristine objects in the Solar System.” Large (dwarf planet) KBOs may be fully differentiated. KBO surface color and compositional classes are usually discussed in terms of "nature vs. nurture,” i.e., a generic primordial composition vs. surface processing, but the true nature of KBOs also depends on how they have evolved. The broad range of albedos now found in the Kuiper belt, deep water-ice absorptions on some objects, evidence for differentiation of Pluto and 2003 EL61, and a range of densities incompatible with a single, primordial composition and variable porosity strongly imply significant, intrinsic compositional differences among KBOs. The interplay of formation zone (accretion rate), body size, and dynamical (collisional) history may yield KBO compositional classes (and their spectral correlates) that recall the different classes of asteroids in the inner Solar System, but whose members are

  20. Precision of hard structures used to estimate age of mountain Whitefish (Prosopium williamsoni)

    USGS Publications Warehouse

    Watkins, Carson J.; Ross, Tyler J.; Hardy, Ryan S.; Quist, Michael

    2015-01-01

    The mountain whitefish (Prosopium williamsoni) is a widely distributed salmonid in western North America that has decreased in abundance over portions of its distribution due to anthropogenic disturbances. In this investigation, we examined precision of age estimates derived from scales, pectoral fin rays, and sagittal otoliths from 167 mountain whitefish. Otoliths and pectoral fin rays were mounted in epoxy and cross-sectioned before examination. Scales were pressed onto acetate slides and resulting impressions were examined. Between-reader precision (i.e., between 2 readers), between-reader variability, and reader confidence ratings were compared among hard structures. Coefficient of variation (CV) in age estimates was lowest and percentage of exact agreement (PA-0) was highest for scales (CV = 5.9; PA-0 = 70%) compared to pectoral fin rays (CV =11.0; PA-0 = 58%) and otoliths (CV = 12.3; PA-0 = 55%). Median confidence ratings were significantly different (P ≤ 0.05) among all structures, with scales having the highest median confidence. Reader confidence decreased with fish age for scales and pectoral fin rays, but reader confidence increased with fish age for otoliths. In general, age estimates were more precise and reader confidence was higher for scales compared to pectoral fin rays and otoliths. This research will help fisheries biologists in selecting the most appropriate hard structure to use for future age and growth studies on mountain whitefish. In turn, selection of the most precise hard structure will lead to better estimates of dynamic rate functions.

  1. Test Series 2: seismic-fragility tests of naturally-aged Class 1E Exide FHC-19 battery cells

    SciTech Connect

    Bonzon, L. L.; Hente, D. B.; Kukreti, B. M.; Schendel, J.; Tulk, J. D.; Janis, W. J.; Black, D. A.; Paulsen, G. D.; Aucoin, B. D.

    1985-03-01

    The seismic-fragility of naturally-aged nuclear station safety-related batteries is of interest for two reasons: (1) to determine actual failure modes and their thresholds and (2) to determine the validity of using the electrical capacity of individual cells as an indicator of the ''end-of-life'' of a battery if subjected to a seismic event. This report, the second in a test series of an extensive seismic research program, covers the testing of 10-year old lead-calcium Exide FHC-19 cells from the Calvert Cliffs Nuclear Power Station operated by the Baltimore Gas and Electric Company. The Exide cells were tested in two configurations using a triaxial shake table: single-cell tests, both rigidly and loosely mounted; and multicell (three-cell) tests, mounted in a typical battery rack. A total of six electrically active cells was used in the two different cell configurations.

  2. Supersymmetric gauge theory on a class of cocalibrated G2-structures

    NASA Astrophysics Data System (ADS)

    Lischewski, Andree

    2015-06-01

    Given a seven-dimensional cocalibrated G2-structure that satisfies an additional trace condition, we construct a supersymmetric Yang-Mills-Lagrangian on it, with the supersymmetry parameters being a distinguished generalized Killing spinor of the G2-structure. The construction is based on a reinterpretation of certain generalized Killing spinors as parallel spinors in an ambient space. The results generalize previous attempts for flat G2-structures and those admitting geometric Killing spinors.

  3. A class of fluorescent heterocyclic dyes revisited: Photophysics, structure, and solvent effects

    NASA Astrophysics Data System (ADS)

    Zhu, Lianjie; Becker, Hans-Christian; Henriksen, Lars; Kilså, Kristine

    2009-08-01

    The photophysical behavior of a series of 2-methylthio-5-(Z-carbonyl)thieno-[3,4-e]-3,4-dihydro-1,2,3-triazine-4-ones was investigated by absorption and emission spectroscopy in a range of solvents representing a systematic variation in polarity, polarizability, as well as hydrogen bond donating and accepting capabilities. In all the investigated compounds, the heterocyclic 6-membered ring of the chromophore is involved in interactions between electron donor and acceptor substituents on the thiophene ring. Throughout the series, the charge-donating methylthio group is kept constant, while the acceptor (Z-carbonyl) is varied between amide, ester, and ketone functionalities. The fluorescent first electronically excited state is primarily of intramolecular HOMO-LUMO charge transfer character. All members of the series exhibit solvent-dependent photophysics, although the magnitude of the dependence varies with the nature of the acceptor group. In addition to the solvent-sensitive photophysics, the investigated class of compounds shows high thermal and chemical stability. Among this class of heterocyclic dyes, the amide-substituted compound is superior with respect to high quantum yield and lifetime, and also shows the largest change in emission lifetimes and fluorescence quantum yields upon solvent variation (about 5-fold).

  4. The first structure of a bacterial class B Acid phosphatase reveals further structural heterogeneity among phosphatases of the haloacid dehalogenase fold.

    PubMed

    Calderone, Vito; Forleo, Costantino; Benvenuti, Manuela; Cristina Thaller, Maria; Rossolini, Gian Maria; Mangani, Stefano

    2004-01-16

    AphA is a periplasmic acid phosphatase of Escherichia coli belonging to class B bacterial phosphatases, which is part of the DDDD superfamily of phosphohydrolases. The crystal structure of AphA has been determined at 2.2A and its resolution extended to 1.7A on an AuCl(3) derivative. This represents the first crystal structure of a class B bacterial phosphatase. Despite the lack of sequence homology, the AphA structure reveals a haloacid dehalogenase-like fold. This finding suggests that this fold could be conserved among members of the DDDD superfamily of phosphohydrolases. The active enzyme is a homotetramer built by using an extended N-terminal arm intertwining the four monomers. The active site of the native enzyme, as prepared, hosts a magnesium ion, which can be replaced by other metal ions. The structure explains the non-specific behaviour of AphA towards substrates, while a structure-based alignment with other phosphatases provides clues about the catalytic mechanism.

  5. Benzenediol lactones: a class of fungal metabolites with diverse structural features and biological activities.

    PubMed

    Shen, Weiyun; Mao, Hongqiang; Huang, Qian; Dong, Jinyan

    2015-06-01

    Benzenediol lactones are a structurally variable family of fungal polyketide metabolites possessing a macrolide core structure fused into a resorcinol aromatic ring. These compounds are widespread in fungi mainly in the genera such as Aigialus, Cochliobolus, Curvularia, Fusarium, Humicola, Lasiodiplodia, Penicillium and Pochonia etc. Most of these fungal metabolites were reported to possess several interesting biological activities, such as cytotoxicities, nematicidal properties, inhibition of various kinases, receptor agonists, anti-inflammatory activities, heat shock response and immune system modulatory activities etc. This review summarizes the research on the isolation, structure elucidation, and biological activities of the benzenediol lactones, along with some available structure-activity relationships, biosynthetic studies, first syntheses, and syntheses that lead to the revision of structure or stereochemistry, published up to the year of 2014. More than 190 benzenediol lactones are described, and over 300 references cited. PMID:25559850

  6. Aging Theories for Establishing Safe Life Spans of Airborne Critical Structural Components

    NASA Technical Reports Server (NTRS)

    Ko, William L.

    2003-01-01

    New aging theories have been developed to establish the safe life span of airborne critical structural components such as B-52B aircraft pylon hooks for carrying air-launch drop-test vehicles. The new aging theories use the equivalent-constant-amplitude loading spectrum to represent the actual random loading spectrum with the same damaging effect. The crack growth due to random loading cycling of the first flight is calculated using the half-cycle theory, and then extrapolated to all the crack growths of the subsequent flights. The predictions of the new aging theories (finite difference aging theory and closed-form aging theory) are compared with the classical flight-test life theory and the previously developed Ko first- and Ko second-order aging theories. The new aging theories predict the number of safe flights as considerably lower than that predicted by the classical aging theory, and slightly lower than those predicted by the Ko first- and Ko second-order aging theories due to the inclusion of all the higher order terms.

  7. The end of the line: The relationship between New York City's subway system and residential class structure

    NASA Astrophysics Data System (ADS)

    Rhindress, Mindy

    Public money is necessary to build and maintain this country's vast network of mass transit systems and highways. Thus you would expect class equity in choices of infrastructure location, types of projects and pricing. However, the influence of commercial interests appears to create a contradictory effect, and may negatively influence the settlement patterns where transit serves. New York City and its subway system offered the perfect case study by which to examine the before and after effects of mass transit introduction given the enormous size of the transit system and the grand development of New York City that appeared to occur simultaneous to subway inauguration. The main objective of this study was to determine the relationship between the growth of the New York City subway system and the establishment of class structure in residential patterns. Regional census data covering the first 16-year period of the subway's development was examined along with geographic statistics on subway line expansion and station openings. GIS (Geographic Information Systems) maps were used to illustrate the development of living spaces as a function of subway introduction into communities, and several Indices were computed to demonstrate the population growth and class disparity. The results revealed that the early years of transit development were entrepreneurial efforts coordinated by business interests. This led to transit first providing significant benefits mostly to the middle and upper classes, giving them a reasonable means by which to escape horrible tenement living conditions while turning a profit at the same time. Thus new settlements were stratified by class almost immediately after introduction. The cycle continued until years later when the automobile was introduced and the once expensive and luxurious, but now more reasonably priced and just functional, public transit system finally befit the population much lower on the socioeconomic scale. Class divisions still

  8. Arterial structure and function in vascular ageing: are you as old as your arteries?

    PubMed

    Thijssen, Dick H J; Carter, Sophie E; Green, Daniel J

    2016-04-15

    Advancing age may be the most potent independent predictor of future cardiovascular events, a relationship that is not fully explained by time-related changes in traditional cardiovascular risk factors. Since some arteries exhibit differential susceptibility to atherosclerosis, generalisations regarding the impact of ageing in humans may be overly simplistic, whereas in vivo assessment of arterial function and health provide direct insight. Coronary and peripheral (conduit, resistance and skin) arteries demonstrate a gradual, age-related impairment in vascular function that is likely to be related to a reduction in endothelium-derived nitric oxide bioavailability and/or increased production of vasoconstrictors (e.g. endothelin-1). Increased exposure and impaired ability for defence mechanisms to resist oxidative stress and inflammation, but also cellular senescence processes, may contribute to age-related changes in vascular function and health. Arteries also undergo structural changes as they age. Gradual thickening of the arterial wall, changes in wall content (i.e. less elastin, advanced glycation end-products) and increase in conduit artery diameter are observed with older age and occur similarly in central and peripheral arteries. These changes in structure have important interactive effects on artery function, with increases in small and large arterial stiffness representing a characteristic change with older age. Importantly, direct measures of arterial function and structure predict future cardiovascular events, independent of age or other cardiovascular risk factors. Taken together, and given the differential susceptibility of arteries to atherosclerosis in humans, direct measurement of arterial function and health may help to distinguish between biological and chronological age-related change in arterial health in humans.

  9. Size class structure, growth rates, and orientation of the central Andean cushion Azorella compacta.

    PubMed

    Kleier, Catherine; Trenary, Tim; Graham, Eric A; Stenzel, William; Rundel, Philip W

    2015-01-01

    Azorella compacta (llareta; Apiaceae) forms dense, woody, cushions and characterizes the high elevation rocky slopes of the central Andean Altiplano. Field studies of an elevational gradient of A. compacta within Lauca National Park in northern Chile found a reverse J-shape distribution of size classes of individuals with abundant small plants at all elevations. A new elevational limit for A. compacta was established at 5,250 m. A series of cushions marked 14 years earlier showed either slight shrinkage or small degrees of growth up to 2.2 cm yr(-1). Despite their irregularity in growth, cushions of A. compacta show a strong orientation, centered on a north-facing aspect and angle of about 20° from horizontal. This exposure to maximize solar irradiance closely matches previous observations of a population favoring north-facing slopes at a similar angle. Populations of A. compacta appear to be stable, or even expanding, with young plants abundant.

  10. Size class structure, growth rates, and orientation of the central Andean cushion Azorella compacta

    PubMed Central

    Trenary, Tim; Graham, Eric A.; Stenzel, William; Rundel, Philip W.

    2015-01-01

    Azorella compacta (llareta; Apiaceae) forms dense, woody, cushions and characterizes the high elevation rocky slopes of the central Andean Altiplano. Field studies of an elevational gradient of A. compacta within Lauca National Park in northern Chile found a reverse J-shape distribution of size classes of individuals with abundant small plants at all elevations. A new elevational limit for A. compacta was established at 5,250 m. A series of cushions marked 14 years earlier showed either slight shrinkage or small degrees of growth up to 2.2 cm yr−1. Despite their irregularity in growth, cushions of A. compacta show a strong orientation, centered on a north-facing aspect and angle of about 20° from horizontal. This exposure to maximize solar irradiance closely matches previous observations of a population favoring north-facing slopes at a similar angle. Populations of A. compacta appear to be stable, or even expanding, with young plants abundant. PMID:25802811

  11. The age and genesis of the structures in the Amerasian basin

    NASA Astrophysics Data System (ADS)

    Verzhbitsky, E. V.; Lobkovsky, L. I.; Kononov, M. V.; Byakov, A. F.

    2012-11-01

    An insufficient number of dated native samples and indistinct magnetic anomalies in the Amerasian Basin prevent geophysicists from identifying the exact age of most of its structural elements. Due to this, it is impossible to gain an insight into the evolution of this vast region, which is highly promising in terms of its hydrocarbon potential. Therefore, the geological time of the formation of the structural elements composing the Amerasian Basin is determined either hypothetically or very loosely (for example, Late Cretaceous-Cenozoic). In order to more precisely estimate the time of formation of the structural elements within the Amerasian Basin, we applied the geothermal method, which is highly informative in terms of the age of the lithosphere, its thickness, and the evolution of the basin structures. Besides, this method provides far narrower time constraints for the formation of the structures compared to the geological data. Based on the thermal flow data, we have numerically calculated the age of the structural elements composing the Amerasian Basin: Podvodnikov Basin (97-79 Ma), Makarov Basin (75-61 Ma), Alpha-Mendeleev Ridge (97-79 Ma), and Lomonosov Ridge (69-57 Ma). The age of these structures derived from the geothermal data agrees with the estimates determined from the geological, geomagnetic, seismic, and radiometric data. Based on the age of the structures estimated from the thermal flow data and the analysis of the geological and geophysical evidence, conclusions are made concerning the genesis and character of formation of the Podvodnikov and Makarov basins and the Alpha-Mendeleev and Lomonosov ridges within the Amerasian Basin.

  12. Digital sleep logs reveal potential impacts of modern temporal structure on class performance in different chronotypes.

    PubMed

    Smarr, Benjamin Lee

    2015-02-01

    Stability of sleep and circadian rhythms are important for healthy learning and memory. While experimental manipulations of lifestyle and learning outcomes present major obstacles, the ongoing increase in data sources allows retrospective data mining of people's sleep timing variation. Here I use digital sleep-log data generated by 1109 students in a biology lab course at the University of Washington to test the hypothesis that higher variance in time asleep and later sleep-onset times negatively correlate with class performance, used here as a real-world proxy for learning and memory. I find that sleep duration variance and mean sleep-onset times both significantly correlate with class performance. These correlations are powerful on weeknights but undetectable on Friday and Saturday nights ("free nights"). Finally, although these data come with no demographic information beyond sex, the constructed demographic groups of "larks" and "owls" within the sexes reveal a significant decrease in performance of owls relative to larks in male students, whereas the correlation of performance with sleep-onset time for all male students was only a near-significant trend. This provides a proof of concept that deeper demographic mining of digital logs in the future may identify subgroups for which certain sleep phenotypes have greater predictive value for performance outcomes. The data analyzed are consistent with known patterns, including sleep-timing delays from weeknights to free nights and sleep-timing delays in men relative to women. These findings support the hypothesis that modern schedule impositions on sleep and circadian timing have consequences for real-world learning and memory. This study also highlights the low-cost, large-scale benefits of personal, daily, digital records as an augmentation of sleep and circadian studies.

  13. Class I HDACs Affect DNA Replication, Repair, and Chromatin Structure: Implications for Cancer Therapy

    PubMed Central

    Stengel, Kristy R.

    2015-01-01

    Abstract Significance: The contribution of epigenetic alterations to cancer development and progression is becoming increasingly clear, prompting the development of epigenetic therapies. Histone deacetylase inhibitors (HDIs) represent one of the first classes of such therapy. Two HDIs, Vorinostat and Romidepsin, are broad-spectrum inhibitors that target multiple histone deacetylases (HDACs) and are FDA approved for the treatment of cutaneous T-cell lymphoma. However, the mechanism of action and the basis for the cancer-selective effects of these inhibitors are still unclear. Recent Advances: While the anti-tumor effects of HDIs have traditionally been attributed to their ability to modify gene expression after the accumulation of histone acetylation, recent studies have identified the effects of HDACs on DNA replication, DNA repair, and genome stability. In addition, the HDIs available in the clinic target multiple HDACs, making it difficult to assign either their anti-tumor effects or their associated toxicities to the inhibition of a single protein. However, recent studies in mouse models provide insights into the tissue-specific functions of individual HDACs and their involvement in mediating the effects of HDI therapy. Critical Issues: Here, we describe how altered replication contributes to the efficacy of HDAC-targeted therapies as well as discuss what knowledge mouse models have provided to our understanding of the specific functions of class I HDACs, their potential involvement in tumorigenesis, and how their disruption may contribute to toxicities associated with HDI treatment. Future Directions: Impairment of DNA replication by HDIs has important therapeutic implications. Future studies should assess how best to exploit these findings for therapeutic gain. Antioxid. Redox Signal. 23, 51–65. PMID:24730655

  14. Structure and Function of a New Class of Human Prolactin Antagonists

    PubMed Central

    DePalatis, Laura; Almgren, Colleen M.; Patmastan, Jypji; Troyer, Mark; Woodrich, Todd; Brooks, Charles L.

    2009-01-01

    Summary Δ41-52 hPRL (human prolactin with residues 41-52 removed) is a lead compound for a new class of hPRL antagonists. The deleted sequence contains residues that functionally couple sites 1 and 2, the two hormone surfaces that each bind receptors. Δ41-52 hPRL retains 0.03% agonist activity in FDC-1 cell bioassays, a 3,054-fold reduction in activity, and displays approximately 100-fold less agonist activity than G129R hPRL, an antagonist that reduces the binding of hPRL receptor at site 2 during the formation of the heterotrimeric hormone/receptor complex. Replacement of various numbers and types of residues into the gap created by the deletion of residues 41 through 52 created hPRLs with varying agonist activities, suggested that manipulation of the sequence connecting the C-terminal of helix 1 with the disulfide bond (cysteines 58 with 174) linking helices 1 and 4 modulates articulation of these helices and influences agonist activity. We have compared the antagonist activities of G129R and Δ41-52 hPRLs to induce apoptosis in Jurkat cells, a human lymphoid cell line displaying an autocrine/paracrine hPRL/receptor system. Δ41-52 hPRL induces apoptosis in a time and dose-dependent fashion. Under these same conditions G129R hPRL fails to induce apoptosis. We conclude Δ41-52 hPRL is a lead compound of a new class of hPRL antagonists capable at low concentrations of inducing apoptosis in human cells expressing an autocrine/paracrine hPRL/receptor system. PMID:19236917

  15. Digital sleep logs reveal potential impacts of modern temporal structure on class performance in different chronotypes.

    PubMed

    Smarr, Benjamin Lee

    2015-02-01

    Stability of sleep and circadian rhythms are important for healthy learning and memory. While experimental manipulations of lifestyle and learning outcomes present major obstacles, the ongoing increase in data sources allows retrospective data mining of people's sleep timing variation. Here I use digital sleep-log data generated by 1109 students in a biology lab course at the University of Washington to test the hypothesis that higher variance in time asleep and later sleep-onset times negatively correlate with class performance, used here as a real-world proxy for learning and memory. I find that sleep duration variance and mean sleep-onset times both significantly correlate with class performance. These correlations are powerful on weeknights but undetectable on Friday and Saturday nights ("free nights"). Finally, although these data come with no demographic information beyond sex, the constructed demographic groups of "larks" and "owls" within the sexes reveal a significant decrease in performance of owls relative to larks in male students, whereas the correlation of performance with sleep-onset time for all male students was only a near-significant trend. This provides a proof of concept that deeper demographic mining of digital logs in the future may identify subgroups for which certain sleep phenotypes have greater predictive value for performance outcomes. The data analyzed are consistent with known patterns, including sleep-timing delays from weeknights to free nights and sleep-timing delays in men relative to women. These findings support the hypothesis that modern schedule impositions on sleep and circadian timing have consequences for real-world learning and memory. This study also highlights the low-cost, large-scale benefits of personal, daily, digital records as an augmentation of sleep and circadian studies. PMID:25564433

  16. Relationship of decrease in fecundity with advancing age to structural changes in mouse endometrium

    PubMed Central

    SHIMIZU, KIYOSHI; YAMADA, JINZO

    2000-01-01

    The aim of this study was to determine whether a relationship exists between decrease in fecundity and structural changes in the antimesometrial endometrium of the mouse. Fecundity was calculated as the number of animals showing a placental sign/number of copulated animals ×100 (%). Structural changes in the endometrium were examined by electron microscopy. A negative correlation between age and fecundity was found. Fecundity was 50% at 7 mo of age. At this age, amorphous material appeared in the region between the basement membrane deep to the luminal epithelium and the subepithelial cells. This material was sometimes attached to the basement membrane. It increased in amount with advancing age, as fecundity decreased. The structure of the uterine luminal epithelial cells did not alter with age. The results indicated that decrease in fecundity with advancing age is correlated with the appearance of amorphous material beneath the basal lamina of the endometrial epithelium. It is suggested that this could impair communication between the luminal epithelium and the endometrial stroma, which plays an important role in implantation. PMID:10697293

  17. A kinetic theory for age-structured stochastic birth-death processes

    NASA Astrophysics Data System (ADS)

    Chou, Tom; Greenman, Chris

    Classical age-structured mass-action models such as the McKendrick-von Foerster equation have been extensively studied but they are structurally unable to describe stochastic fluctuations or population-size-dependent birth and death rates. Conversely, current theories that include size-dependent population dynamics (e.g., carrying capacity) cannot be easily extended to take into account age-dependent birth and death rates. In this paper, we present a systematic derivation of a new fully stochastic kinetic theory for interacting age-structured populations. By defining multiparticle probability density functions, we derive a hierarchy of kinetic equations for the stochastic evolution of an aging population undergoing birth and death. We show that the fully stochastic age-dependent birth-death process precludes factorization of the corresponding probability densities, which then must be solved by using a BBGKY-like hierarchy. Our results generalize both deterministic models and existing master equation approaches by providing an intuitive and efficient way to simultaneously model age- and population-dependent stochastic dynamics applicable to the study of demography, stem cell dynamics, and disease evolution. NSF.

  18. Disentangling normal aging from Alzheimer's disease in structural magnetic resonance images.

    PubMed

    Lorenzi, Marco; Pennec, Xavier; Frisoni, Giovanni B; Ayache, Nicholas

    2015-01-01

    The morphology observed in the brains of patients affected by Alzheimer's disease (AD) is a combination of different biological processes, such as normal aging and the pathological matter loss specific to AD. The ability to differentiate between these biological factors is fundamental to reliably evaluate pathological AD-related structural changes, especially in the earliest phase of the disease, at prodromal and preclinical stages. Here we propose a method based on non-linear image registration to estimate and analyze from observed brain morphologies the relative contributions from aging and pathology. In particular, we first define a longitudinal model of the brain's normal aging process from serial T1-weight magnetic resonance imaging scans of 65 healthy participants. The longitudinal model is then used as a reference for the cross-sectional analysis. Given a new brain image, we then estimate its anatomical age relative to the aging model; this is defined as a morphological age shift with respect to the average age of the healthy population at baseline. Finally, we define the specific morphological process as the remainder of the observed anatomy after the removal of the estimated normal aging process. Experimental results from 105 healthy participants, 110 subjects with mild cognitive impairment (MCI), 86 with MCI converted to AD, and 134 AD patients provide a novel description of the anatomical changes observed across the AD time span: normal aging, normal aging at risk, conversion to MCI, and the latest stages of AD. More advanced AD stages are associated with an increased morphological age shift in the brain and with strong disease-specific morphological changes affecting mainly ventricles, temporal poles, the entorhinal cortex, and hippocampi. Our model shows that AD is characterized by localized disease-specific brain changes as well as by an accelerated global aging process. This method may thus represent a more precise instrument to identify potential

  19. The relationship between health expenditures and the age structure of the population in OECD countries.

    PubMed

    O'Connell, J M

    1996-01-01

    The purpose of this study was to analyse national health expenditures of OECD countries relative to their age structures. Using econometric techniques designed to analyse cross-sectional time series data, the ageing of the population was found to affect health spending in several countries while having no effect in others. In addition, the effect of income on health spending was lower than that generally reported in the literature. These findings suggest that unobserved country-specific factors play a major role in determining the amount of resources allocated to health services in a country. Such factors also determine if the ageing of the population with increased health spending.

  20. Neural convergence for language comprehension and grammatical class production in highly proficient bilinguals is independent of age of acquisition.

    PubMed

    Consonni, Monica; Cafiero, Riccardo; Marin, Dario; Tettamanti, Marco; Iadanza, Antonella; Fabbro, Franco; Perani, Daniela

    2013-05-01

    In bilinguals, native (L1) and second (L2) languages are processed by the same neural resources that can be modulated by age of second language acquisition (AOA), proficiency level, and daily language exposure and usage. AOA seems to particularly affect grammar processing, where a complete neural convergence has been shown only in bilinguals with parallel language acquisition from birth. Despite the fact that proficiency-related neuroanatomical differences have been well documented in language comprehension (LC) and production, few reports have addressed the influence of language exposure. A still unanswered question pertains to the role of AOA, when proficiency is comparably high across languages, with respect to its modulator effects both on LC and production. Here, we evaluated with fMRI during sentence comprehension and verb and noun production tasks, two groups of highly proficient bilinguals only differing in AOA. One group learned Italian and Friulian in parallel from birth, whereas the second group learned Italian between 3 and 6 years. All participants were highly exposed to both languages, but more to Italian than Friulian. The results indicate a complete overlap of neural activations for the comprehension of both languages, not only in bilinguals from birth, but also in late bilinguals. A slightly extra activation in the left thalamus for the less-exposed language confirms that exposure may affect language processing. Noteworthy, we report for the first time that, when proficiency and exposure are kept high, noun and verb production recruit the same neural networks for L1 and L2, independently of AOA. These results support the neural convergence hypothesis.

  1. Key Plant Structural and Allocation Traits Depend on Relative Age in the Perennial Herb Pimpinella saxifraga

    PubMed Central

    NIINEMETS, ÜLO

    2005-01-01

    • Background and Aims Perennial plant formations always include a mixture of various-aged individuals of community-creating species, but the physiological and competitive potentials of plants of differing age and the importance on whole community functioning are still not entirely known. The current study tested the hypothesis that ontogenetically old plants have limited biomass investments in leaves and enhanced foliage support costs. • Methods Leaf structure, size and biomass allocation were studied in the perennial herb Pimpinella saxifraga during plant ontogeny from seedling to senile phases to determine age-dependent controls on key plant structural traits. The average duration of the full ontogenetic cycle is approx. 5–10 years in this species. Plants were sampled from shaded and open habitats. • Key Results Leaflet dry mass per unit area (MA) increased, and the fraction of plant biomass in leaflets (FL) decreased with increasing age, leading to a 5- to 11-fold decrease in leaf area ratio (LAR = FL/MA) between seedlings and senescent plants. In contrast, the fraction of below-ground biomass increased with increasing age. Leaflet size and number per leaf increased with increasing age. This was not associated with enhanced support cost in older plants as age-dependent changes in leaf shape and increased foliage packing along the rachis compensated for an overall increase in leaf size. Age-dependent trends were the same in habitats with various irradiance, but the LAR of plants of varying age was approx. 1·5-fold larger in the shade due to lower MA and larger FL. • Conclusions As plant light interception per unit total plant mass scales with LAR, these data demonstrate major age-dependent differences in plant light-harvesting efficiency that are further modified by site light availability. These ontogenetic changes reduce the differences among co-existing species in perennial communities, and therefore need consideration in our understanding of how

  2. Structural architecture supports functional organization in the human aging brain at a regionwise and network level.

    PubMed

    Zimmermann, Joelle; Ritter, Petra; Shen, Kelly; Rothmeier, Simon; Schirner, Michael; McIntosh, Anthony R

    2016-07-01

    Functional interactions in the brain are constrained by the underlying anatomical architecture, and structural and functional networks share network features such as modularity. Accordingly, age-related changes of structural connectivity (SC) may be paralleled by changes in functional connectivity (FC). We provide a detailed qualitative and quantitative characterization of the SC-FC coupling in human aging as inferred from resting-state blood oxygen-level dependent functional magnetic resonance imaging and diffusion-weighted imaging in a sample of 47 adults with an age range of 18-82. We revealed that SC and FC decrease with age across most parts of the brain and there is a distinct age-dependency of regionwise SC-FC coupling and network-level SC-FC relations. A specific pattern of SC-FC coupling predicts age more reliably than does regionwise SC or FC alone (r = 0.73, 95% CI = [0.7093, 0.8522]). Hence, our data propose that regionwise SC-FC coupling can be used to characterize brain changes in aging. Hum Brain Mapp 37:2645-2661, 2016. © 2016 Wiley Periodicals, Inc. PMID:27041212

  3. Structural transition in sputter-deposited amorphous germanium films by aging at ambient temperature

    NASA Astrophysics Data System (ADS)

    Okugawa, M.; Nakamura, R.; Ishimaru, M.; Watanabe, K.; Yasuda, H.; Numakura, H.

    2016-06-01

    The structure of amorphous Ge (a-Ge) films prepared by sputter-deposition and the effects of aging at ambient temperature and pressure were studied by pair-distribution-function (PDF) analysis from electron scattering and molecular dynamics simulations. The PDFs of the as-deposited and aged samples for 3-13 months showed that the major peaks for Ge-Ge bonds decrease in intensity and broaden with aging for up to 7 months. In the PDFs of a-Ge of molecular dynamics simulation obtained by quenching liquid at different rates, the major peak intensities of a slowly cooled model are higher than those of a rapidly cooled model. Analyses on short- and medium-range configurations show that the slowly cooled model includes a certain amount of medium-range ordered (MRO) clusters, while the rapidly cooled model includes liquid-like configurations rather than MRO clusters. The similarity between experimental and computational PDFs implies that as-deposited films are similar in structure to the slowly cooled model, whereas the fully aged films are similar to the rapidly cooled model. It is assumed that as they undergo room-temperature aging, the MRO clusters disintegrate and transform into liquid-like regions in the same matrix. This transition in local configurations is discussed in terms of instability and the non-equilibrium of nanoclusters produced by a vapor-deposition process.

  4. Structure of a Class I Tagatose-1,6-bisphosphate Aldolase - Investigation into an Apparent Loss of Stereospecificity

    SciTech Connect

    LowKam, C.; Liotard, B; Sygusch, J

    2010-01-01

    Tagatose-1,6-bisphosphate aldolase from Streptococcus pyogenes is a class I aldolase that exhibits a remarkable lack of chiral discrimination with respect to the configuration of hydroxyl groups at both C3 and C4 positions. The enzyme catalyzes the reversible cleavage of four diastereoisomers (fructose 1,6-bisphosphate (FBP), psicose 1,6-bisphosphate, sorbose 1,6-bisphosphate, and tagatose 1,6-bisphosphate) to dihydroxyacetone phosphate (DHAP) and d-glyceraldehyde 3-phosphate with high catalytic efficiency. To investigate its enzymatic mechanism, high resolution crystal structures were determined of both native enzyme and native enzyme in complex with dihydroxyacetone-P. The electron density map revealed a ({alpha}/{beta}){sub 8} fold in each dimeric subunit. Flash-cooled crystals of native enzyme soaked with dihydroxyacetone phosphate trapped a covalent intermediate with carbanionic character at Lys{sup 205}, different from the enamine mesomer bound in stereospecific class I FBP aldolase. Structural analysis indicates extensive active site conservation with respect to class I FBP aldolases, including conserved conformational responses to DHAP binding and conserved stereospecific proton transfer at the DHAP C3 carbon mediated by a proximal water molecule. Exchange reactions with tritiated water and tritium-labeled DHAP at C3 hydrogen were carried out in both solution and crystalline state to assess stereochemical control at C3. The kinetic studies show labeling at both pro-R and pro-S C3 positions of DHAP yet detritiation only at the C3 pro-S-labeled position. Detritiation of the C3 pro-R label was not detected and is consistent with preferential cis-trans isomerism about the C2-C3 bond in the carbanion as the mechanism responsible for C3 epimerization in tagatose-1,6-bisphosphate aldolase.

  5. DISK AND ENVELOPE STRUCTURE IN CLASS 0 PROTOSTARS. I. THE RESOLVED MASSIVE DISK IN SERPENS FIRS 1

    SciTech Connect

    Enoch, Melissa L.; Duchene, Gaspard; Corder, Stuartt

    2009-12-10

    We present the first results of a program to characterize the disk and envelope structure of typical Class 0 protostars in nearby low-mass star-forming regions. We use Spitzer Infrared Spectrograph (IRS) mid-infrared spectra, high-resolution Combined Array for Research in Millimeter-wave Astronomy (CARMA) 230 GHz continuum imaging, and two-dimensional radiative transfer models to constrain the envelope structure, as well as the size and mass of the circumprotostellar disk in Serpens FIRS 1. The primary envelope parameters (centrifugal radius, outer radius, outflow opening angle, and inclination) are well constrained by the spectral energy distribution (SED), including Spitzer IRAC and MIPS photometry, IRS spectra, and 1.1 mm Bolocam photometry. These together with the excellent uv-coverage (4.5-500 klambda) of multiple antenna configurations with CARMA allow for a robust separation of the envelope and a resolved disk. The SED of Serpens FIRS 1 is best fit by an envelope with the density profile of a rotating, collapsing spheroid with an inner (centrifugal) radius of approximately 600 AU, and the millimeter data by a large resolved disk with M{sub disk} approx 1.0 M {sub sun} and R{sub disk} approx 300 AU. These results suggest that large, massive disks can be present early in the main accretion phase. Results for the larger, unbiased sample of Class 0 sources in the Perseus, Serpens, and Ophiuchus molecular clouds are needed to determine if relatively massive disks are typical in the Class 0 stage.

  6. Beyond the Schoolyard: The Contributions of Parenting Logics, Financial Resources, and Social Institutions to the Social Class Gap in Structured Activity Participation

    PubMed Central

    Bennett, Pamela R.; Lutz, Amy; Jayaram, Lakshmi

    2014-01-01

    We investigate cultural and structural sources of class differences in youth activity participation with interview, survey, and archival data. We find working- and middle-class parents overlap in parenting logics about participation, though differ in one respect: middle-class parents are concerned with customizing children’s involvement in activities, while working-class parents are concerned with achieving safety and social mobility for children through participation. Second, because of financial constraints, working-class families rely on social institutions for participation opportunities, but few are available. Schools act as an equalizing institution by offering low-cost activities, allowing working-class children to resemble middle-class youth in school activities, but they remain disadvantaged in out-of-school activities. School influences are complex, however, as they also contribute to class differences by offering different activities to working- and middle-class youth. Findings raise questions about the extent to which differences in participation reflect class culture rather than the objective realities parents face. PMID:25328250

  7. Structure and composition of arytenoid cartilage of the bullfrog (Lithobates catesbeianus) during maturation and aging.

    PubMed

    Laureano, Priscila Eliane dos Santos; Oliveira, Kris Daiana Silva; de Aro, Andrea Aparecida; Gomes, Laurecir; Pimentel, Edson Rosa; Esquisatto, Marcelo Augusto Marretto

    2015-10-01

    The aging process induces progressive and irreversible changes in the structural and functional organization of animals. The objective of this study was to evaluate the effects of aging on the structure and composition of the extracellular matrix of the arytenoid cartilage found in the larynx of male bullfrogs (Lithobates catesbeianus) kept in captivity for commercial purposes. Animals at 7, 180 and 1080 days post-metamorphosis (n=10/age) were euthanized and the cartilage was removed and processed for structural and biochemical analysis. For the structural analyses, cartilage sections were stained with picrosirius, toluidine blue, Weigert's resorcin-fuchsin and Von Kossa stain. The sections were also submitted to immunohistochemistry for detection of collagen types I and II. Other samples were processed for the ultrastructural and cytochemical analysis of proteoglycans. Histological sections were used to chondrocyte count. The number of positive stainings for proteoglycans was quantified by ultrastructural analysis. For quantification and analysis of glycosaminoglycans were used the dimethyl methylene blue and agarose gel electrophoresis methods. The chloramine T method was used for hydroxyproline quantification. At 7 days, basophilia was observed in the pericellular and territorial matrix, which decreased in the latter over the period studied. Collagen fibers were arranged perpendicular to the major axis of the cartilaginous plate and were thicker in older animals. Few calcification areas were observed at the periphery of the cartilage specimens in 1080-day-old animals. Type II collagen was present throughout the stroma at the different ages. Elastic fibers were found in the stroma and perichondrium and increased with age in the two regions. Proteoglycan staining significantly increased from 7 to 180 days and reduced at 1080 days. The amount of total glycosaminoglycans was higher in 180-day-old animals compared to the other ages, with marked presence of

  8. Interactive effects of stress and aging on structural plasticity in the prefrontal cortex

    PubMed Central

    Bloss, Erik B.; Janssen, William G.; McEwen, Bruce S.; Morrison, John H.

    2010-01-01

    Neuronal networks in the prefrontal cortex mediate the highest levels of cognitive processing and decision making, and the capacity to perform these functions is among the cognitive features most vulnerable to aging. Despite much research, the neurobiological basis of age-related compromised prefrontal function remains elusive. Many investigators have hypothesized that exposure to stress may accelerate cognitive aging, though few studies have directly tested this hypothesis and even fewer have investigated a neuronal basis for such effects. It is known that in young animals, stress causes morphological remodeling of prefrontal pyramidal neurons that is reversible. The present studies sought to determine whether age influences the reversibility of stress-induced morphological plasticity in rat prefrontal neurons. We hypothesized that neocortical structural resilience is compromised in normal aging. To directly test this hypothesis we utilized a well-characterized chronic restraint stress paradigm, with an additional group allowed to recover from the stress paradigm, in 3, 12 and 20-month old male rats. In young animals, stress induced reductions of apical dendritic length and branch number, which were reversed with recovery; in contrast, middle-aged and aged rats failed to show reversible morphological remodeling when subjected to the same stress and recovery paradigm. The data presented here provide evidence that aging is accompanied by selective impairments in long-term neocortical morphological plasticity. PMID:20463234

  9. Cytochrome c oxidase loses catalytic activity and structural integrity during the aging process in Drosophila melanogaster

    SciTech Connect

    Ren, Jian-Ching; Rebrin, Igor; Klichko, Vladimir; Orr, William C.; Sohal, Rajindar S.

    2010-10-08

    Research highlights: {yields} Cytochrome c oxidase loses catalytic activity during the aging process. {yields} Abundance of seven nuclear-encoded subunits of cytochrome c oxidase decreased with age in Drosophila. {yields} Cytochrome c oxidase is specific intra-mitochondrial site of age-related deterioration. -- Abstract: The hypothesis, that structural deterioration of cytochrome c oxidase (CcO) is a causal factor in the age-related decline in mitochondrial respiratory activity and an increase in H{sub 2}O{sub 2} generation, was tested in Drosophila melanogaster. CcO activity and the levels of seven different nuclear DNA-encoded CcO subunits were determined at three different stages of adult life, namely, young-, middle-, and old-age. CcO activity declined progressively with age by 33%. Western blot analysis, using antibodies specific to Drosophila CcO subunits IV, Va, Vb, VIb, VIc, VIIc, and VIII, indicated that the abundance these polypeptides decreased, ranging from 11% to 40%, during aging. These and previous results suggest that CcO is a specific intra-mitochondrial site of age-related deterioration, which may have a broad impact on mitochondrial physiology.

  10. Aging Optimization of Aluminum-Lithium Alloy L277 for Application to Cryotank Structures

    NASA Technical Reports Server (NTRS)

    Sova, B. J.; Sankaran, K. K.; Babel, H.; Farahmand, B.; Cho, A.

    2003-01-01

    Compared with aluminum alloys such as 2219, which is widely used in space vehicle for cryogenic tanks and unpressurized structures, aluminum-lithium alloys possess attractive combinations of lower density and higher modulus along with comparable mechanical properties and improved damage tolerance. These characteristics have resulted in the successful use of the aluminum-lithium alloy 2195 for the Space Shuttle External Tank, and the consideration of newer U.S. aluminum-lithium alloys such as L277 and C458 for future space vehicles. A design of experiments aging study was conducted for plate and a limited study on extrusions. To achieve the T8 temper, Alloy L277 is typically aged at 290 F for 40 hours. In the study for plate, a two-step aging treatment was developed through a design of experiments study and the one step aging used as a control. Based on the earlier NASA studies on 2195, the first step aging temperature was varied between 220 F and 260 F. The second step aging temperatures was varied between 290 F and 310 F, which is in the range of the single-step aging temperature. For extrusions, two, single-step, and one two-step aging condition were evaluated. The results of the design of experiments used for the T8 temper as well as a smaller set of experiments for the T6 temper for plate and the results for extrusions will be presented.

  11. 11β-Hydroxysteroid dehydrogenase blockade prevents age-induced skin structure and function defects.

    PubMed

    Tiganescu, Ana; Tahrani, Abd A; Morgan, Stuart A; Otranto, Marcela; Desmoulière, Alexis; Abrahams, Lianne; Hassan-Smith, Zaki; Walker, Elizabeth A; Rabbitt, Elizabeth H; Cooper, Mark S; Amrein, Kurt; Lavery, Gareth G; Stewart, Paul M

    2013-07-01

    Glucocorticoid (GC) excess adversely affects skin integrity, inducing thinning and impaired wound healing. Aged skin, particularly that which has been photo-exposed, shares a similar phenotype. Previously, we demonstrated age-induced expression of the GC-activating enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) in cultured human dermal fibroblasts (HDFs). Here, we determined 11β-HSD1 levels in human skin biopsies from young and older volunteers and examined the aged 11β-HSD1 KO mouse skin phenotype. 11β-HSD1 activity was elevated in aged human and mouse skin and in PE compared with donor-matched photo-protected human biopsies. Age-induced dermal atrophy with deranged collagen structural organization was prevented in 11β-HSD1 KO mice, which also exhibited increased collagen density. We found that treatment of HDFs with physiological concentrations of cortisol inhibited rate-limiting steps in collagen biosynthesis and processing. Furthermore, topical 11β-HSD1 inhibitor treatment accelerated healing of full-thickness mouse dorsal wounds, with improved healing also observed in aged 11β-HSD1 KO mice. These findings suggest that elevated 11β-HSD1 activity in aging skin leads to increased local GC generation, which may account for adverse changes occurring in the elderly, and 11β-HSD1 inhibitors may be useful in the treatment of age-associated impairments in dermal integrity and wound healing.

  12. Structural Basis for Enhancement of Carbapenemase Activity in the OXA-51 Family of Class D β-Lactamases.

    PubMed

    Smith, Clyde A; Antunes, Nuno Tiago; Stewart, Nichole K; Frase, Hilary; Toth, Marta; Kantardjieff, Katherine A; Vakulenko, Sergei

    2015-08-21

    Class D β-lactamases of Acinetobacter baumannii are enzymes of the utmost clinical importance, producing resistance to last resort carbapenem antibiotics. Although the OXA-51-like enzymes constitute the largest family of class D β-lactamases, they are poorly studied and their importance in conferring carbapenem resistance is controversial. We present the detailed microbiological, kinetic, and structural characterization of the eponymous OXA-51 β-lactamase. Kinetic studies show that OXA-51 has low catalytic efficiency for carbapenems, primarily due to the low affinity of the enzyme for these substrates. Structural studies demonstrate that this low affinity results from the obstruction of the enzyme active site by the side chain of Trp222, which presents a transient steric barrier to an incoming carbapenem substrate. The Trp222Met substitution relieves this steric hindrance and elevates the affinity of the mutant enzyme for carbapenems by 10-fold, significantly increasing the levels of resistance to these antibiotics. The ability of OXA-51 to evolve into a robust carbapenemase as the result of a single amino acid substitution may, in the near future, elevate the ubiquitous enzymes of the OXA-51 family to the status of the most deleterious A. baumannii carbapenemases, with dire clinical consequences.

  13. Structural basis for stem cell factor–KIT signaling and activation of class III receptor tyrosine kinases

    PubMed Central

    Liu, Heli; Chen, Xiaoyan; Focia, Pamela J; He, Xiaolin

    2007-01-01

    Stem cell factor (SCF) binds to and activates the KIT receptor, a class III receptor tyrosine kinase (RTK), to stimulate diverse processes including melanogenesis, gametogenesis and hematopoeisis. Dysregulation of KIT activation is associated with many cancers. We report a 2.5 Å crystal structure of the functional core of SCF bound to the extracellular ligand-binding domains of KIT. The structure reveals a ‘wrapping' SCF-recognition mode by KIT, in which KIT adopts a bent conformation to facilitate each of its first three immunoglobulin (Ig)-like domains to interact with SCF. Three surface epitopes on SCF, an extended loop, the B and C helices, and the N-terminal segment, contact distinct KIT domains, with two of the epitopes undergoing large conformational changes upon receptor binding. The SCF/KIT complex reveals a unique RTK dimerization assembly, and a novel recognition mode between four-helix bundle cytokines and Ig-family receptors. It serves as a framework for understanding the activation mechanisms of class III RTKs. PMID:17255936

  14. Structural and biochemical studies reveal UbiG/Coq3 as a class of novel membrane-binding proteins.

    PubMed

    Zhu, Yuwei; Wu, Bo; Zhang, Xu; Fan, Xiaojiao; Niu, Liwen; Li, Xu; Wang, Junfeng; Teng, Maikun

    2015-08-15

    UbiG and Coq3 (orthologue in eukaryotes) are SAM-MTases (S-adenosylmethionine-dependent methyltransferases) that catalyse both O-methylation steps in CoQ biosynthesis from prokaryotes to eukaryotes. However, the detailed molecular mechanism by which they function remains elusive. In the present paper, we report that UbiG/Coq3 defines a novel class of membrane-binding proteins. Escherichia coli UbiG binds specifically to liposomes containing PG (phosphatidylglycerol) or CL (cardiolipin, or diphosphatidylglycerol), two major lipid components of the E. coli plasma membrane, whereas human and yeast Coq3 display a strong preference for liposomes enriched with CL, a signature lipid of the mitochondrial membrane. The crystal structure of UbiG from E. coli was determined at 2.1 Å (1 Å = 0.1 nm) resolution. The structure exhibits a typical Class I SAM-MTase fold with several variations, including a unique insertion between strand β5 and helix α10. This insertion is highly conserved and is required for membrane binding. Mutation of the key residues renders UbiG unable to efficiently bind liposome in vitro and the mutant fails to rescue the phenotype of ΔubiG strain in vivo. Taken together, our results shed light on a novel biochemical function of the UbiG/Coq3 protein. PMID:26251450

  15. Kinetic theory of age-structured stochastic birth-death processes.

    PubMed

    Greenman, Chris D; Chou, Tom

    2016-01-01

    Classical age-structured mass-action models such as the McKendrick-von Foerster equation have been extensively studied but are unable to describe stochastic fluctuations or population-size-dependent birth and death rates. Stochastic theories that treat semi-Markov age-dependent processes using, e.g., the Bellman-Harris equation do not resolve a population's age structure and are unable to quantify population-size dependencies. Conversely, current theories that include size-dependent population dynamics (e.g., mathematical models that include carrying capacity such as the logistic equation) cannot be easily extended to take into account age-dependent birth and death rates. In this paper, we present a systematic derivation of a new, fully stochastic kinetic theory for interacting age-structured populations. By defining multiparticle probability density functions, we derive a hierarchy of kinetic equations for the stochastic evolution of an aging population undergoing birth and death. We show that the fully stochastic age-dependent birth-death process precludes factorization of the corresponding probability densities, which then must be solved by using a Bogoliubov--Born--Green--Kirkwood--Yvon-like hierarchy. Explicit solutions are derived in three limits: no birth, no death, and steady state. These are then compared with their corresponding mean-field results. Our results generalize both deterministic models and existing master equation approaches by providing an intuitive and efficient way to simultaneously model age- and population-dependent stochastic dynamics applicable to the study of demography, stem cell dynamics, and disease evolution.

  16. Kinetic theory of age-structured stochastic birth-death processes

    NASA Astrophysics Data System (ADS)

    Greenman, Chris D.; Chou, Tom

    2016-01-01

    Classical age-structured mass-action models such as the McKendrick-von Foerster equation have been extensively studied but are unable to describe stochastic fluctuations or population-size-dependent birth and death rates. Stochastic theories that treat semi-Markov age-dependent processes using, e.g., the Bellman-Harris equation do not resolve a population's age structure and are unable to quantify population-size dependencies. Conversely, current theories that include size-dependent population dynamics (e.g., mathematical models that include carrying capacity such as the logistic equation) cannot be easily extended to take into account age-dependent birth and death rates. In this paper, we present a systematic derivation of a new, fully stochastic kinetic theory for interacting age-structured populations. By defining multiparticle probability density functions, we derive a hierarchy of kinetic equations for the stochastic evolution of an aging population undergoing birth and death. We show that the fully stochastic age-dependent birth-death process precludes factorization of the corresponding probability densities, which then must be solved by using a Bogoliubov--Born--Green--Kirkwood--Yvon-like hierarchy. Explicit solutions are derived in three limits: no birth, no death, and steady state. These are then compared with their corresponding mean-field results. Our results generalize both deterministic models and existing master equation approaches by providing an intuitive and efficient way to simultaneously model age- and population-dependent stochastic dynamics applicable to the study of demography, stem cell dynamics, and disease evolution.

  17. Kinetic theory of age-structured stochastic birth-death processes.

    PubMed

    Greenman, Chris D; Chou, Tom

    2016-01-01

    Classical age-structured mass-action models such as the McKendrick-von Foerster equation have been extensively studied but are unable to describe stochastic fluctuations or population-size-dependent birth and death rates. Stochastic theories that treat semi-Markov age-dependent processes using, e.g., the Bellman-Harris equation do not resolve a population's age structure and are unable to quantify population-size dependencies. Conversely, current theories that include size-dependent population dynamics (e.g., mathematical models that include carrying capacity such as the logistic equation) cannot be easily extended to take into account age-dependent birth and death rates. In this paper, we present a systematic derivation of a new, fully stochastic kinetic theory for interacting age-structured populations. By defining multiparticle probability density functions, we derive a hierarchy of kinetic equations for the stochastic evolution of an aging population undergoing birth and death. We show that the fully stochastic age-dependent birth-death process precludes factorization of the corresponding probability densities, which then must be solved by using a Bogoliubov--Born--Green--Kirkwood--Yvon-like hierarchy. Explicit solutions are derived in three limits: no birth, no death, and steady state. These are then compared with their corresponding mean-field results. Our results generalize both deterministic models and existing master equation approaches by providing an intuitive and efficient way to simultaneously model age- and population-dependent stochastic dynamics applicable to the study of demography, stem cell dynamics, and disease evolution. PMID:26871029

  18. Crystal Structure of Saccharomyces cerevisiae ECM4, a Xi-Class Glutathione Transferase that Reacts with Glutathionyl-(hydro)quinones

    PubMed Central

    Schwartz, Mathieu; Didierjean, Claude; Hecker, Arnaud; Girardet, Jean-Michel; Morel-Rouhier, Mélanie; Gelhaye, Eric; Favier, Frédérique

    2016-01-01

    Glutathionyl-hydroquinone reductases (GHRs) belong to the recently characterized Xi-class of glutathione transferases (GSTXs) according to unique structural properties and are present in all but animal kingdoms. The GHR ScECM4 from the yeast Saccharomyces cerevisiae has been studied since 1997 when it was found to be potentially involved in cell-wall biosynthesis. Up to now and in spite of biological studies made on this enzyme, its physiological role remains challenging. The work here reports its crystallographic study. In addition to exhibiting the general GSTX structural features, ScECM4 shows extensions including a huge loop which contributes to the quaternary assembly. These structural extensions are probably specific to Saccharomycetaceae. Soaking of ScECM4 crystals with GS-menadione results in a structure where glutathione forms a mixed disulfide bond with the cysteine 46. Solution studies confirm that ScECM4 has reductase activity for GS-menadione in presence of glutathione. Moreover, the high resolution structures allowed us to propose new roles of conserved residues of the active site to assist the cysteine 46 during the catalytic act. PMID:27736955

  19. Development of integrated damage detection system for international America's Cup class yacht structures using a fiber optic distributed sensor

    NASA Astrophysics Data System (ADS)

    Akiyoshi, Shimada; Naruse, Hiroshi; Uzawa, Kyoshi; Murayama, Hideaki; Kageyama, Kazuro

    2000-06-01

    We constructed a new health monitoring system to detect damage using a fiber optic distributed sensor, namely a Brillouin optical time domain reflectometer (BOTDR), and installed it in International America's Cup Class (IACC) yachts, the Japanese entry in America's Cup 2000. IACC yachts are designed to be as fast as possible, so it is essential that they are lightweight and encounter minimum water resistance. Advanced composite sandwich structures, made with carbon fiber reinforced plastic (CFRP) skins and a honeycomb core, are used to achieve the lightweight structure. Yacht structure designs push the strength of the materials to their limit and so it is important to detect highly stressed or damaged regions that might cause a catastrophic fracture. The BOTDR measures changes in the Brillouin frequency shift caused by distributed strain along one optical fiber. We undertook two experiments: a pulling test and a four point bending test on a composite beam. The former showed that no slippage occurred between the optical fiber glass and its coating. The latter confirmed that a debonding between the skin and the core of 300 mm length could be found with the BOTDR. Next we examined the effectiveness with which this system can assess the structural integrity of IACC yachts. The results show that our system has the potential for use as a damage detection system for smart structures.

  20. Structural mechanism of ER retrieval of MHC class I by cowpox.

    PubMed

    McCoy, William H; Wang, Xiaoli; Yokoyama, Wayne M; Hansen, Ted H; Fremont, Daved H

    2012-01-01

    One of the hallmarks of viral immune evasion is the capacity to disrupt major histocompatibility complex class I (MHCI) antigen presentation to evade T-cell detection. Cowpox virus encoded protein CPXV203 blocks MHCI surface expression by exploiting the KDEL-receptor recycling pathway, and here we show that CPXV203 directly binds a wide array of fully assembled MHCI proteins, both classical and non-classical. Further, the stability of CPXV203/MHCI complexes is highly pH dependent, with dramatically increased affinities at the lower pH of the Golgi relative to the endoplasmic reticulum (ER). Crystallographic studies reveal that CPXV203 adopts a beta-sandwich fold similar to poxvirus chemokine binding proteins, and binds the same highly conserved MHCI determinants located under the peptide-binding platform that tapasin, CD8, and natural killer (NK)-receptors engage. Mutagenesis of the CPXV203/MHCI interface identified the importance of two CPXV203 His residues that confer low pH stabilization of the complex and are critical to ER retrieval of MHCI. These studies clarify mechanistically how CPXV203 coordinates with other cowpox proteins to thwart antigen presentation.

  1. Structural Mechanism of ER Retrieval of MHC Class I by Cowpox

    PubMed Central

    McCoy, William H.; Wang, Xiaoli; Yokoyama, Wayne M.; Hansen, Ted H.; Fremont, Daved H.

    2012-01-01

    One of the hallmarks of viral immune evasion is the capacity to disrupt major histocompatibility complex class I (MHCI) antigen presentation to evade T-cell detection. Cowpox virus encoded protein CPXV203 blocks MHCI surface expression by exploiting the KDEL-receptor recycling pathway, and here we show that CPXV203 directly binds a wide array of fully assembled MHCI proteins, both classical and non-classical. Further, the stability of CPXV203/MHCI complexes is highly pH dependent, with dramatically increased affinities at the lower pH of the Golgi relative to the endoplasmic reticulum (ER). Crystallographic studies reveal that CPXV203 adopts a beta-sandwich fold similar to poxvirus chemokine binding proteins, and binds the same highly conserved MHCI determinants located under the peptide-binding platform that tapasin, CD8, and natural killer (NK)-receptors engage. Mutagenesis of the CPXV203/MHCI interface identified the importance of two CPXV203 His residues that confer low pH stabilization of the complex and are critical to ER retrieval of MHCI. These studies clarify mechanistically how CPXV203 coordinates with other cowpox proteins to thwart antigen presentation. PMID:23209377

  2. A class of monolayer metal halogenides MX2: Electronic structures and band alignments

    NASA Astrophysics Data System (ADS)

    Lu, Feng; Wang, Weichao; Luo, Xiaoguang; Xie, Xinjian; Cheng, Yahui; Dong, Hong; Liu, Hui; Wang, Wei-Hua

    2016-03-01

    With systematic first principles calculations, a class of monolayer metal halogenides MX2 (M = Mg, Ca, Zn, Cd, Ge, Pb; M = Cl, Br, I) has been proposed. Our study indicates that these monolayer materials are semiconductors with the band gaps ranging from 2.03 eV of ZnI2 to 6.08 eV of MgCl2. Overall, the band gap increases with the increase of the electronegativity of the X atom or the atomic number of the metal M. Meanwhile, the band gaps of monolayer MgX2 (X = Cl, Br) are direct while those of other monolayers are indirect. Based on the band edge curvatures, the derived electron (me) and hole (mh) effective masses of MX2 monolayers are close to their corresponding bulk values except that the me of CdI2 is three times larger and the mh for PbI2 is twice larger. Finally, the band alignments of all the studied MX2 monolayers are provided using the vacuum level as energy reference. These theoretical results may not only introduce the monolayer metal halogenides family MX2 into the emerging two-dimensional materials, but also provide insights into the applications of MX2 in future electronic, visible and ultraviolet optoelectronic devices.

  3. Implications of a Class of Covariance Structure Models for the Development of Measuring Instruments.

    ERIC Educational Resources Information Center

    Bramble, William J.; Wiley, David E.

    The research on covariance structure analysis is reviewed, and various restrictions on the parameter matrices of the general model are delineated. Models employing two particular restrictions (where the matrix of weights is completely specified and is either scaled--by some unknown but estimable matrix of scaling weights--or unscaled) are…

  4. A Study of Enhanced Structured Web-Based Discussion in a Foreign Language Learning Class

    ERIC Educational Resources Information Center

    Chang, Mei-Mei; Lin, Mei-Chen; Tsai, Ming-Jen

    2013-01-01

    This experimental study aimed to investigate the effect of enhanced structured web discussion on EFL students' language production. This effect was measured by the number of T units and by students' use of the cognitive skills identified by Hunt (1965). A total of 27 college students participated in this study. The participants were randomly…

  5. Dimensionality of the Latent Structure and Item Selection via Latent Class Multidimensional IRT Models

    ERIC Educational Resources Information Center

    Bartolucci, F.; Montanari, G. E.; Pandolfi, S.

    2012-01-01

    With reference to a questionnaire aimed at assessing the performance of Italian nursing homes on the basis of the health conditions of their patients, we investigate two relevant issues: dimensionality of the latent structure and discriminating power of the items composing the questionnaire. The approach is based on a multidimensional item…

  6. A Class of Population Covariance Matrices in the Bootstrap Approach to Covariance Structure Analysis

    ERIC Educational Resources Information Center

    Yuan, Ke-Hai; Hayashi, Kentaro; Yanagihara, Hirokazu

    2007-01-01

    Model evaluation in covariance structure analysis is critical before the results can be trusted. Due to finite sample sizes and unknown distributions of real data, existing conclusions regarding a particular statistic may not be applicable in practice. The bootstrap procedure automatically takes care of the unknown distribution and, for a given…

  7. Age-related changes in pial arterial structure and blood flow in mice.

    PubMed

    Kang, Hye-Min; Sohn, Inkyung; Jung, Junyang; Jeong, Joo-Won; Park, Chan

    2016-01-01

    Age-related cerebral blood flow decreases are thought to deteriorate cognition and cause senescence, although the related mechanism is unclear. To investigate the relationships between aging and changes in cerebral blood flow and vasculature, we obtained fluorescence images of young (2-month-old) and old (12-month-old) mice using indocyanine green (ICG). First, we found that the blood flow in old mice's brains is lower than that in young mice and that old mice had more curved pial arteries and fewer pial artery junctions than young mice. Second, using Western blotting, we determined that the ratio of collagen to elastin (related to cerebral vascular wall distensibility) increased with age. Finally, we found that the peak ICG intensity and blood flow index decreased, whereas the mean transit time increased, with age in the middle cerebral artery and superior sagittal sinus. Age-related changes in pial arterial structure and composition, concurrent with the observed changes in the blood flow parameters, suggest that age-related changes in the cerebral vasculature structure and distensibility may induce altered brain blood flow.

  8. [Population structure of soil arthropod in different age Pinus massoniana plantations].

    PubMed

    Tan, Bo; Wu, Fu-zhong; Yang, Wan-qin; Zhang, Jian; Xu, Zhen-feng; Liu, Yang; Gou, Xiao-lin

    2013-04-01

    An investigation was conducted on the population structure of soil arthropod community in the 3-, 8-, 14-, 31-, and 40-years old Pinus massoniana plantations in the upper reaches of the Yangtze River in spring (May) and autumn (October), 2011, aimed to search for the scientific management of the plantation. A total of 4045 soil arthropods were collected, belonging to 57 families. Both the individual density and the taxonomic group number of the soil arthropod community decreased obviously with increasing soil depth, and this trend increased with increasing stand age. The dominant groups and ordinary groups of the soil arthropod community varied greatly with the stand age of P. massoniana plantation, and a significant difference (P<0.05) was observed in the individual density and taxonomic group number among different age P. massoniana plantations. In comparison with other stand age P. massoniana plantations, 3years old P. massoniana plantation had a significant difference in the structure and diversity of soil arthropod community, and the similarity index of the soil arthropod community was lower. The individual density, taxonomic group number, and diversity of soil arthropod community were the highest in 8-years old P. massoniana plantation, and then, decreased obviously with increasing stand age. It was suggested that the land fertility of the P. massoniana plantations could be degraded with increasing stand age, and it would be appropriate to make artificial regulation and restoration in 8-years old P. massoniana plantation.

  9. The relation between structural and functional connectivity depends on age and on task goals

    PubMed Central

    Ford, Jaclyn H.; Kensinger, Elizabeth A.

    2014-01-01

    The last decade has seen an increase in neuroimaging studies examining structural (i.e., structural integrity of white matter tracts) and functional connectivity (e.g., correlations in neural activity throughout the brain). Although structural and functional connectivity changes have often been measured independently, examining the relation between these two measures is critical to understanding the specific function of neural networks and the ways they may differ across tasks and individuals. The current study addressed this question by examining the effect of age (treated as a continuous variable) and emotional valence on the relation between functional and structural connectivity. As prior studies have suggested that prefrontal regions may guide and regulate emotional memory search via functional connections with the amygdala, the current analysis focused on functional connectivity between the left amygdala and the left prefrontal cortex, and structural integrity of the uncinate fasciculus, a white matter tract connecting prefrontal and temporal regions. Participants took part in a scanned retrieval task in which they recalled positive, negative, and neutral images associated with neutral titles. Aging was associated with a significant increase in the relation between measures of structural integrity (specifically, fractional anisotropy, or FA) along the uncinate fasciculus and functional connectivity between the left ventral prefrontal cortex and amygdala during positive event retrieval, but not negative or neutral retrieval. Notably, during negative event retrieval, age was linked to stronger structure-function relations between the amygdala and the dorsal anterior cingulate cortex, such that increased structural integrity predicted stronger negative functional connectivity in older adults only. These findings suggest that young and older adults may utilize a structural pathway to engage different retrieval and regulatory strategies, even when structural

  10. Advances in Structural Integrity Analysis Methods for Aging Metallic Airframe Structures with Local Damage

    NASA Technical Reports Server (NTRS)

    Starnes, James H., Jr.; Newman, James C., Jr.; Harris, Charles E.; Piascik, Robert S.; Young, Richard D.; Rose, Cheryl A.

    2003-01-01

    Analysis methodologies for predicting fatigue-crack growth from rivet holes in panels subjected to cyclic loads and for predicting the residual strength of aluminum fuselage structures with cracks and subjected to combined internal pressure and mechanical loads are described. The fatigue-crack growth analysis methodology is based on small-crack theory and a plasticity induced crack-closure model, and the effect of a corrosive environment on crack-growth rate is included. The residual strength analysis methodology is based on the critical crack-tip-opening-angle fracture criterion that characterizes the fracture behavior of a material of interest, and a geometric and material nonlinear finite element shell analysis code that performs the structural analysis of the fuselage structure of interest. The methodologies have been verified experimentally for structures ranging from laboratory coupons to full-scale structural components. Analytical and experimental results based on these methodologies are described and compared for laboratory coupons and flat panels, small-scale pressurized shells, and full-scale curved stiffened panels. The residual strength analysis methodology is sufficiently general to include the effects of multiple-site damage on structural behavior.

  11. Structural and vibrational relaxations during aging of an ultralow-expansion glass

    NASA Astrophysics Data System (ADS)

    Kobayashi, Hiroshi; Ohtake, Yurie; Hirata, Shu; Morinaga, Atsuo

    2016-05-01

    We accurately measured the aging of an ultralow-expansion (ULE) glass for 1250 days using a diode laser resonated in the glass cavity at -3.3 °C, where the glass has zero thermal expansion coefficient. We observed that the glass shows exponential and linear decreases in length In addition, it is theoretically shown that glass aging is a nonlinear irreversible process with the spontaneous relaxations of a linear contraction and a dissipated heat. The origin for the linear contraction is an osmotic pressure which is spontaneously generated during glass aging, and the origin for the dissipated heat is the irreversibility on thermal vibrations of molecules. The result obtained is a verification of the Glansdorff-Prigogine evolutional criterion, which is first applied to a structural relaxation phenomenon in this paper. We conclude that a glass reaches a steady nonequilibrium state, which has the dissipative structure both in a steady configurational state and in steady irreversible processes.

  12. Unveiling the structural arrangements responsible for the atomic dynamics in metallic glasses during physical aging

    PubMed Central

    Giordano, V. M.; Ruta, B

    2016-01-01

    Understanding and controlling physical aging, that is, the spontaneous temporal evolution of out-of-equilibrium systems, represents one of the greatest tasks in material science. Recent studies have revealed the existence of a complex atomic motion in metallic glasses, with different aging regimes in contrast with the typical continuous aging observed in macroscopic quantities. By combining dynamical and structural synchrotron techniques, here for the first time we directly connect previously identified microscopic structural mechanisms with the peculiar atomic motion, providing a broader unique view of their complexity. We show that the atomic scale is dominated by the interplay between two processes: rearrangements releasing residual stresses related to a cascade mechanism of relaxation, and medium range ordering processes, which do not affect the local density, likely due to localized relaxations of liquid-like regions. As temperature increases, a surprising additional secondary relaxation process sets in, together with a faster medium range ordering, likely precursors of crystallization. PMID:26787443

  13. A Hierarchical Kinetic Theory of Birth, Death and Fission in Age-Structured Interacting Populations

    NASA Astrophysics Data System (ADS)

    Chou, Tom; Greenman, Chris D.

    2016-07-01

    We develop mathematical models describing the evolution of stochastic age-structured populations. After reviewing existing approaches, we formulate a complete kinetic framework for age-structured interacting populations undergoing birth, death and fission processes in spatially dependent environments. We define the full probability density for the population-size age chart and find results under specific conditions. Connections with more classical models are also explicitly derived. In particular, we show that factorial moments for non-interacting processes are described by a natural generalization of the McKendrick-von Foerster equation, which describes mean-field deterministic behavior. Our approach utilizes mixed-type, multidimensional probability distributions similar to those employed in the study of gas kinetics and with terms that satisfy BBGKY-like equation hierarchies.

  14. [Age structure and dynamics of Quercus wutaishanica population in Lingkong Mountain of Shanxi Province, China].

    PubMed

    Zhang, Jie; Shangguan, Tie-Liang; Duan, Yi-Hao; Guo, Wei; Liu, Wei-Hua; Guo, Dong-Gang

    2014-11-01

    Using the plant survivorship theory, the age structure, and the relationship between tree height and diameter (DBH) of Quercus wutaishanica population in Lingkong Mountain were analyzed, and the static life table was compiled and the survival curve plotted. The shuttle shape in age structure of Q. wutaishanica population suggested its temporal stability. The linear regression significantly fitted the positive correlation between tree height and DBH. The maximal life expectancy was observed among the trees beyond the age of the highest mortality and coincided with the lowest point of mortality density, suggesting the strong vitality of the seedlings and young trees that survived in the natural selection and intraspecific competition. The population stability of the Q. wutaishanica population was characterized by the Deevey-II of the survival curve. The dynamic pattern was characterized by the recession in the early phase, growth in the intermediate phase, and stability in the latter phase. PMID:25898607

  15. Unveiling the structural arrangements responsible for the atomic dynamics in metallic glasses during physical aging

    NASA Astrophysics Data System (ADS)

    Giordano, V. M.; Ruta, B.

    2016-01-01

    Understanding and controlling physical aging, that is, the spontaneous temporal evolution of out-of-equilibrium systems, represents one of the greatest tasks in material science. Recent studies have revealed the existence of a complex atomic motion in metallic glasses, with different aging regimes in contrast with the typical continuous aging observed in macroscopic quantities. By combining dynamical and structural synchrotron techniques, here for the first time we directly connect previously identified microscopic structural mechanisms with the peculiar atomic motion, providing a broader unique view of their complexity. We show that the atomic scale is dominated by the interplay between two processes: rearrangements releasing residual stresses related to a cascade mechanism of relaxation, and medium range ordering processes, which do not affect the local density, likely due to localized relaxations of liquid-like regions. As temperature increases, a surprising additional secondary relaxation process sets in, together with a faster medium range ordering, likely precursors of crystallization.

  16. Dissecting simulated disc galaxies - I. The structure of mono-age populations

    NASA Astrophysics Data System (ADS)

    Martig, Marie; Minchev, Ivan; Flynn, Chris

    2014-08-01

    We study seven simulated disc galaxies, three with a quiescent merger history, and four with mergers in their last 9 Gyr of evolution. We compare their structure at z = 0 by decomposing them into `mono-age populations' (MAPs) of stars within 500 Myr age bins. All studied galaxies undergo a phase of merging activity at high redshift, so that stars older than 9 Gyr are found in a centrally concentrated component, while younger stars are mostly found in discs. We find that most MAPs have simple exponential radial and vertical density profiles, with a scaleheight that typically increases with age. Because a large range of merger histories can create populations with simple structures, this suggests that the simplicity of the structure of mono-abundance populations observed in the Milky Way by Bovy et al. is not necessarily a direct indicator of a quiescent history for the Milky Way. Similarly, the anticorrelation between scalelength and scaleheight does not necessarily imply a merger-free history. However, mergers produce discontinuities between thin and thick disc components, and jumps in the age-velocity relation. The absence of a structural discontinuity between thin and thick disc observed in the Milky Way would seem to be a good indicator that no merger with a mass ratio larger than 1:15-1:10 occurred in the last 9 Gyr. Mergers at higher redshift might nevertheless be necessary to produce the thickest, hottest components of the Milky Way's disc.

  17. 76 FR 69292 - Aging Management of Stainless Steel Structures and Components in Treated Borated Water

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-08

    ... COMMISSION Aging Management of Stainless Steel Structures and Components in Treated Borated Water AGENCY... Components in Treated Borated Water.'' This LR-ISG revises the guidance in the Standard Review Plan for... treated borated water. DATES: Submit comments by December 8, 2011. Comments received after this date...

  18. Socio-Demographic Determinants of Economic Growth: Age-Structure, Preindustrial Heritage and Sociolinguistic Integration

    ERIC Educational Resources Information Center

    Crenshaw, Edward; Robison, Kristopher

    2010-01-01

    This study establishes a socio-demographic theory of international development derived from selected classical and contemporary sociological theories. Four hypotheses are tested: (1. population growth's effect on development depends on age-structure; (2. historic population density (used here as an indicator of preindustrial social complexity)…

  19. Developmental Trajectories of Structural and Pragmatic Language Skills in School-Aged Children with Williams Syndrome

    ERIC Educational Resources Information Center

    Van Den Heuvel, E.; Manders, E.; Swillen, A.; Zink, I.

    2016-01-01

    Background: This study aimed to compare developmental courses of structural and pragmatic language skills in school-aged children with Williams syndrome (WS) and children with idiopathic intellectual disability (IID). Comparison of these language trajectories could highlight syndrome-specific developmental features. Method: Twelve monolingual…

  20. Decreased Default Mode Network connectivity correlates with age-associated structural and cognitive changes

    PubMed Central

    Vidal-Piñeiro, Didac; Valls-Pedret, Cinta; Fernández-Cabello, Sara; Arenaza-Urquijo, Eider M.; Sala-Llonch, Roser; Solana, Elisabeth; Bargalló, Núria; Junqué, Carme; Ros, Emilio; Bartrés-Faz, David

    2014-01-01

    Ageing entails cognitive and motor decline as well as brain changes such as loss of gray (GM) and white matter (WM) integrity, neurovascular and functional connectivity alterations. Regarding connectivity, reduced resting-state fMRI connectivity between anterior and posterior nodes of the Default Mode Network (DMN) relates to cognitive function and has been postulated to be a hallmark of ageing. However, the relationship between age-related connectivity changes and other neuroimaging-based measures in ageing is fragmentarily investigated. In a sample of 116 healthy elders we aimed to study the relationship between antero-posterior DMN connectivity and measures of WM integrity, GM integrity and cerebral blood flow (CBF), assessed with an arterial spin labeling sequence. First, we replicated previous findings demonstrating DMN connectivity decreases in ageing and an association between antero-posterior DMN connectivity and memory scores. The results showed that the functional connectivity between posterior midline structures and the medial prefrontal cortex was related to measures of WM and GM integrity but not to CBF. Gray and WM correlates of anterio-posterior DMN connectivity included, but were not limited to, DMN areas and cingulum bundle. These results resembled patterns of age-related vulnerability which was studied by comparing the correlates of antero-posterior DMN with age-effect maps. These age-effect maps were obtained after performing an independent analysis with a second sample including both young and old subjects. We argue that antero-posterior connectivity might be a sensitive measure of brain ageing over the brain. By using a comprehensive approach, the results provide valuable knowledge that may shed further light on DMN connectivity dysfunctions in ageing. PMID:25309433

  1. Decreased Default Mode Network connectivity correlates with age-associated structural and cognitive changes.

    PubMed

    Vidal-Piñeiro, Didac; Valls-Pedret, Cinta; Fernández-Cabello, Sara; Arenaza-Urquijo, Eider M; Sala-Llonch, Roser; Solana, Elisabeth; Bargalló, Núria; Junqué, Carme; Ros, Emilio; Bartrés-Faz, David

    2014-01-01

    Ageing entails cognitive and motor decline as well as brain changes such as loss of gray (GM) and white matter (WM) integrity, neurovascular and functional connectivity alterations. Regarding connectivity, reduced resting-state fMRI connectivity between anterior and posterior nodes of the Default Mode Network (DMN) relates to cognitive function and has been postulated to be a hallmark of ageing. However, the relationship between age-related connectivity changes and other neuroimaging-based measures in ageing is fragmentarily investigated. In a sample of 116 healthy elders we aimed to study the relationship between antero-posterior DMN connectivity and measures of WM integrity, GM integrity and cerebral blood flow (CBF), assessed with an arterial spin labeling sequence. First, we replicated previous findings demonstrating DMN connectivity decreases in ageing and an association between antero-posterior DMN connectivity and memory scores. The results showed that the functional connectivity between posterior midline structures and the medial prefrontal cortex was related to measures of WM and GM integrity but not to CBF. Gray and WM correlates of anterio-posterior DMN connectivity included, but were not limited to, DMN areas and cingulum bundle. These results resembled patterns of age-related vulnerability which was studied by comparing the correlates of antero-posterior DMN with age-effect maps. These age-effect maps were obtained after performing an independent analysis with a second sample including both young and old subjects. We argue that antero-posterior connectivity might be a sensitive measure of brain ageing over the brain. By using a comprehensive approach, the results provide valuable knowledge that may shed further light on DMN connectivity dysfunctions in ageing.

  2. Age at First Episode Modulates Diagnosis-Related Structural Brain Abnormalities in Psychosis.

    PubMed

    Pina-Camacho, Laura; Del Rey-Mejías, Ángel; Janssen, Joost; Bioque, Miquel; González-Pinto, Ana; Arango, Celso; Lobo, Antonio; Sarró, Salvador; Desco, Manuel; Sanjuan, Julio; Lacalle-Aurioles, Maria; Cuesta, Manuel J; Saiz-Ruiz, Jerónimo; Bernardo, Miguel; Parellada, Mara

    2016-03-01

    Brain volume and thickness abnormalities have been reported in first-episode psychosis (FEP). However, it is unclear if and how they are modulated by brain developmental stage (and, therefore, by age at FEP as a proxy). This is a multicenter cross-sectional case-control brain magnetic resonance imaging (MRI) study. Patients with FEP (n = 196), 65.3% males, with a wide age at FEP span (12-35 y), and healthy controls (HC) (n = 157), matched for age, sex, and handedness, were scanned at 6 sites. Gray matter volume and thickness measurements were generated for several brain regions using FreeSurfer software. The nonlinear relationship between age at scan (a proxy for age at FEP in patients) and volume and thickness measurements was explored in patients with schizophrenia spectrum disorders (SSD), affective psychoses (AFP), and HC. Earlier SSD cases (ie, FEP before 15-20 y) showed significant volume and thickness deficits in frontal lobe, volume deficits in temporal lobe, and volume enlargements in ventricular system and basal ganglia. First-episode AFP patients had smaller cingulate cortex volume and thicker temporal cortex only at early age at FEP (before 18-20 y). The AFP group also had age-constant (12-35-y age span) volume enlargements in the frontal and parietal lobe. Our study suggests that age at first episode modulates the structural brain abnormalities found in FEP patients in a nonlinear and diagnosis-dependent manner. Future MRI studies should take these results into account when interpreting samples with different ages at onset and diagnosis. PMID:26371339

  3. Age at First Episode Modulates Diagnosis-Related Structural Brain Abnormalities in Psychosis.

    PubMed

    Pina-Camacho, Laura; Del Rey-Mejías, Ángel; Janssen, Joost; Bioque, Miquel; González-Pinto, Ana; Arango, Celso; Lobo, Antonio; Sarró, Salvador; Desco, Manuel; Sanjuan, Julio; Lacalle-Aurioles, Maria; Cuesta, Manuel J; Saiz-Ruiz, Jerónimo; Bernardo, Miguel; Parellada, Mara

    2016-03-01

    Brain volume and thickness abnormalities have been reported in first-episode psychosis (FEP). However, it is unclear if and how they are modulated by brain developmental stage (and, therefore, by age at FEP as a proxy). This is a multicenter cross-sectional case-control brain magnetic resonance imaging (MRI) study. Patients with FEP (n = 196), 65.3% males, with a wide age at FEP span (12-35 y), and healthy controls (HC) (n = 157), matched for age, sex, and handedness, were scanned at 6 sites. Gray matter volume and thickness measurements were generated for several brain regions using FreeSurfer software. The nonlinear relationship between age at scan (a proxy for age at FEP in patients) and volume and thickness measurements was explored in patients with schizophrenia spectrum disorders (SSD), affective psychoses (AFP), and HC. Earlier SSD cases (ie, FEP before 15-20 y) showed significant volume and thickness deficits in frontal lobe, volume deficits in temporal lobe, and volume enlargements in ventricular system and basal ganglia. First-episode AFP patients had smaller cingulate cortex volume and thicker temporal cortex only at early age at FEP (before 18-20 y). The AFP group also had age-constant (12-35-y age span) volume enlargements in the frontal and parietal lobe. Our study suggests that age at first episode modulates the structural brain abnormalities found in FEP patients in a nonlinear and diagnosis-dependent manner. Future MRI studies should take these results into account when interpreting samples with different ages at onset and diagnosis.

  4. The Knowledge of Memory Aging Questionnaire: Factor Structure and Correlates in a Lifespan Sample

    PubMed Central

    Calamia, Matthew; Reese-Melancon, Celinda; Cherry, Katie E.; Hawley, Karri S.; Jazwinski, S. Michal

    2016-01-01

    The authors examined the factor structure of the Knowledge of Memory Aging Questionnaire (KMAQ) [1] using confirmatory factor analysis in a lifespan sample of 933 individuals who ranged in age from 18 to 101. Participants were college students at Louisiana State University and adults from the community enrolled in the Louisiana Healthy Aging Study (LHAS). A two-factor solution was expected, consistent with the normal and pathological memory aging dimensions that comprise the KMAQ. A bi-factor solution with items loading on a general response bias factor and either a normal or pathological knowledge-specific factor showed good model fit. Knowledge scores were correlated with demographic and cognitive performance variables. Implications of these data for clinical settings and research are considered. PMID:27505021

  5. The role of age structure in the persistence of a chronic pathogen in a fluctuating population.

    PubMed

    Laverty, Sean M; Adler, Frederick R

    2009-03-01

    Small mammal populations exhibit large fluctuations, potentially leading to local extinction of specialist pathogens after bottlenecks. Pathogen persistence in recovering populations depends on the epidemiological characteristics of the hosts that survive the bottlenecks. Sin Nombre virus is a largely asymptomatic infection of deer mice, which creates a chronic lifelong infection. Earlier work on this virus has shown that males play a key role in pathogen persistence through a combination of longer lifespan and higher seroprevalence. Other evidence indicates that mouse age could play an equally important role, as older mice may have higher survivorship and higher contact rates. We use age structured models to examine the relationships among prevalence, age-dependent demographics, and age-dependent epidemiology.

  6. The Knowledge of Memory Aging Questionnaire: Factor Structure and Correlates in a Lifespan Sample.

    PubMed

    Calamia, Matthew; Reese-Melancon, Celinda; Cherry, Katie E; Hawley, Karri S; Jazwinski, S Michal

    2016-03-01

    The authors examined the factor structure of the Knowledge of Memory Aging Questionnaire (KMAQ) [1] using confirmatory factor analysis in a lifespan sample of 933 individuals who ranged in age from 18 to 101. Participants were college students at Louisiana State University and adults from the community enrolled in the Louisiana Healthy Aging Study (LHAS). A two-factor solution was expected, consistent with the normal and pathological memory aging dimensions that comprise the KMAQ. A bi-factor solution with items loading on a general response bias factor and either a normal or pathological knowledge-specific factor showed good model fit. Knowledge scores were correlated with demographic and cognitive performance variables. Implications of these data for clinical settings and research are considered. PMID:27505021

  7. Analysis of relationship between oxidized phospholipid structure and interaction with the class B scavenger receptors.

    PubMed

    Gao, Detao; Sayre, Lawrence M; Podrez, Eugene A

    2015-01-01

    Recognition of specific oxidized phospholipids oxPCCD36 by scavenger receptors CD36 and SR-BI plays a critical role in several pathophysiological processes. The structural basis for the recognition of oxPCCD36 by CD36 and SR-BI is poorly understood. We describe here the design and synthesis of a series of model oxidized phospholipids having various functional groups at sn-1, sn-2, and sn-3 positions. Synthetic methodologies and experimental details for the preparation of specific examples of model oxidized phospholipids are presented. The correlation between their structure and their ability to serve as ligands for CD36 and SR-BI was determined using competitive binding assay on cells overexpressing scavenger receptors, direct binding assay to scavenger receptors expressed as GST-fusion proteins, and cholesterol ester synthesis assay using mouse peritoneal macrophages.

  8. Structural characteristics via SLDV for a class of morphing micro-air-vehicles

    NASA Astrophysics Data System (ADS)

    Diggs, Edward C.; Bilgen, Onur; Kurdila, Andrew; Kochersburger, Kevin; Inman, Dan; Vignola, Joe

    2007-04-01

    Conventional control surfaces have been used in most carbon fiber composite, membrane-wing autonomous micro air vehicles (MAV). In some cases, vehicle morphing is achieved using servo actuators to articulate vehicle kinematic joints, or to deform crucial wing / tail surfaces. However, articulated lifting surfaces and articulated wing sections are difficult to instrument and fabricate in a repeatable fashion. Assembly is complex and time consuming. The goal of this paper is to establish the feasibility of morphing wings on autonomous MAVs that are actuated via active materials. Active actuation is achieved via a type of piezoceramic composite called Macro Fiber Composite (MFC). This paper investigates the structural dynamics of morphing wings on MAVs that are actuated via active composites. This paper continues the work presented in1 by considering structural dynamic characteristics of the morphing vehicle determined through Scanning Laser Doppler Vibrometry (SLDV).

  9. Structure and function of Neisseria gonorrhoeae MtrF illuminates a class of antimetabolite efflux pumps.

    PubMed

    Su, Chih-Chia; Bolla, Jani Reddy; Kumar, Nitin; Radhakrishnan, Abhijith; Long, Feng; Delmar, Jared A; Chou, Tsung-Han; Rajashankar, Kanagalaghatta R; Shafer, William M; Yu, Edward W

    2015-04-01

    Neisseria gonorrhoeae is an obligate human pathogen and the causative agent of the sexually transmitted disease gonorrhea. The control of this disease has been compromised by the increasing proportion of infections due to antibiotic-resistant strains, which are growing at an alarming rate. N. gonorrhoeae MtrF is an integral membrane protein that belongs to the AbgT family of transporters for which no structural information is available. Here, we describe the crystal structure of MtrF, revealing a dimeric molecule with architecture distinct from all other families of transporters. MtrF is a bowl-shaped dimer with a solvent-filled basin extending from the cytoplasm to halfway across the membrane bilayer. Each subunit of the transporter contains nine transmembrane helices and two hairpins, posing a plausible pathway for substrate transport. A combination of the crystal structure and biochemical functional assays suggests that MtrF is an antibiotic efflux pump mediating bacterial resistance to sulfonamide antimetabolite drugs.

  10. Landscape-level variation in forest structure and biogeochemistry across a substrate age gradient in Hawaii.

    PubMed

    Vitousek, Peter; Asner, Gregory P; Chadwick, Oliver A; Hotchkiss, Sara

    2009-11-01

    We compared forest canopy heights and nitrogen concentrations in long-term research sites and in 2 x 2 km landscapes surrounding these sites along a substrate age gradient in the Hawaiian Islands. Both remote airborne and ground-based measurements were used to characterize processes that control landscape-level variation in canopy properties. We integrated a waveform light detection and ranging (LiDAR) system, a high-resolution imaging spectrometer, and a global positioning system/inertial measurement unit to provide highly resolved images of ground topography, canopy heights, and canopy nitrogen concentrations (1) within a circle 50 m in radius focused on a long-term study site in the center of each landscape; (2) for the entire 2 x 2 km landscape regardless of land cover; and (3) after stratification, for our target cover class, native-dominated vegetation on constructional geomorphic surfaces throughout each landscape. Remote measurements at all scales yielded the same overall patterns as did ground-based measurements in the long-term sites. The two younger landscapes supported taller trees than did older landscapes, while the two intermediate-aged landscapes had higher canopy nitrogen (N) concentrations than did either young or old landscapes. However, aircraft-based analyses detected substantial variability in canopy characteristics on the landscape level, even within the target cover class. Canopy heights were more heterogeneous on the older landscapes, with coefficients of variation increasing from 23-41% to 69-78% with increasing substrate age. This increasing heterogeneity was associated with a larger patch size of canopy turnover and with dominance of most secondary successional stands by the mat-forming fern Dicranopteris linearis in the older landscapes. PMID:19967863

  11. An artificial intelligence-based structural health monitoring system for aging aircraft

    NASA Technical Reports Server (NTRS)

    Grady, Joseph E.; Tang, Stanley S.; Chen, K. L.

    1993-01-01

    To reduce operating expenses, airlines are now using the existing fleets of commercial aircraft well beyond their originally anticipated service lives. The repair and maintenance of these 'aging aircraft' has therefore become a critical safety issue, both to the airlines and the Federal Aviation Administration. This paper presents the results of an innovative research program to develop a structural monitoring system that will be used to evaluate the integrity of in-service aerospace structural components. Currently in the final phase of its development, this monitoring system will indicate when repair or maintenance of a damaged structural component is necessary.

  12. Crystal Structure of PnpCD, a Two-subunit Hydroquinone 1,2-Dioxygenase, Reveals a Novel Structural Class of Fe2+-dependent Dioxygenases*

    PubMed Central

    Liu, Shiheng; Su, Tiantian; Zhang, Cong; Zhang, Wen-Mao; Zhu, Deyu; Su, Jing; Wei, Tiandi; Wang, Kang; Huang, Yan; Guo, Liming; Xu, Sujuan; Zhou, Ning-Yi; Gu, Lichuan

    2015-01-01

    Aerobic microorganisms have evolved a variety of pathways to degrade aromatic and heterocyclic compounds. However, only several classes of oxygenolytic fission reaction have been identified for the critical ring cleavage dioxygenases. Among them, the most well studied dioxygenases proceed via catecholic intermediates, followed by noncatecholic hydroxy-substituted aromatic carboxylic acids. Therefore, the recently reported hydroquinone 1,2-dioxygenases add to the diversity of ring cleavage reactions. Two-subunit hydroquinone 1,2-dioxygenase PnpCD, the key enzyme in the hydroquinone pathway of para-nitrophenol degradation, catalyzes the ring cleavage of hydroquinone to γ-hydroxymuconic semialdehyde. Here, we report three PnpCD structures, named apo-PnpCD, PnpCD-Fe3+, and PnpCD-Cd2+-HBN (substrate analog hydroxyenzonitrile), respectively. Structural analysis showed that both the PnpC and the C-terminal domains of PnpD comprise a conserved cupin fold, whereas PnpC cannot form a competent metal binding pocket as can PnpD cupin. Four residues of PnpD (His-256, Asn-258, Glu-262, and His-303) were observed to coordinate the iron ion. The Asn-258 coordination is particularly interesting because this coordinating residue has never been observed in the homologous cupin structures of PnpCD. Asn-258 is proposed to play a pivotal role in binding the iron prior to the enzymatic reaction, but it might lose coordination to the iron when the reaction begins. PnpD also consists of an intriguing N-terminal domain that might have functions other than nucleic acid binding in its structural homologs. In summary, PnpCD has no apparent evolutionary relationship with other iron-dependent dioxygenases and therefore defines a new structural class. The study of PnpCD might add to the understanding of the ring cleavage of dioxygenases. PMID:26304122

  13. Electromechanical and structural alterations in the aging rabbit heart and aorta

    PubMed Central

    Cooper, Leroy L.; Odening, Katja E.; Hwang, Min-Sig; Chaves, Leonard; Schofield, Lorraine; Taylor, Chantel A.; Gemignani, Anthony S.; Mitchell, Gary F.; Forder, John R.; Choi, Bum-Rak

    2012-01-01

    Aging increases the risk for arrhythmias and sudden cardiac death (SCD). We aimed at elucidating aging-related electrical, functional, and structural changes in the heart and vasculature that account for this heightened arrhythmogenic risk. Young (5–9 mo) and old (3.5–6 yr) female New Zealand White (NZW) rabbits were subjected to in vivo hemodynamic, electrophysiological, and echocardiographic studies as well as ex vivo optical mapping, high-field magnetic resonance imaging (MRI), and histochemical experiments. Aging increased aortic stiffness (baseline pulse wave velocity: young, 3.54 ± 0.36 vs. old, 4.35 ± 0.28 m/s, P < 0.002) and diastolic (end diastolic pressure-volume relations: 3.28 ± 0.5 vs. 4.95 ± 1.5 mmHg/ml, P < 0.05) and systolic (end systolic pressure-volume relations: 20.56 ± 4.2 vs. 33.14 ± 8.4 mmHg/ml, P < 0.01) myocardial elastances in old rabbits. Electrophysiological and optical mapping studies revealed age-related slowing of ventricular and His-Purkinje conduction (His-to-ventricle interval: 23 ± 2.5 vs. 31.9 ± 2.9 ms, P < 0.0001), altered conduction anisotropy, and a greater inducibility of ventricular fibrillation (VF, 3/12 vs. 7/9, P < 0.05) in old rabbits. Histochemical studies confirmed an aging-related increased fibrosis in the ventricles. MRI showed a deterioration of the free-running Purkinje fiber network in ventricular and septal walls in old hearts as well as aging-related alterations of the myofibrillar orientation and myocardial sheet structure that may account for this slowed conduction velocity. Aging leads to parallel stiffening of the aorta and the heart, including an increase in systolic stiffness and contractility and diastolic stiffness. Increasingly, anisotropic conduction velocity due to fibrosis and altered myofibrillar orientation and myocardial sheet structure may contribute to the pathogenesis of VF in old hearts. The aging rabbit model represents a useful tool for elucidating age-related changes that

  14. Structural and functional classes of multipolar cells in the ventral cochlear nucleus.

    PubMed

    Doucet, John R; Ryugo, David K

    2006-04-01

    Multipolar cells in the ventral cochlear nucleus (VCN) are a structurally and functionally diverse group of projection neurons. Understanding their role in the ascending pathway involves partitioning multipolar cells into distinct populations and determining where in the brain each sends its coded messages. In this study, we used retrograde labeling techniques in rats to identify multipolar neurons that project their axons to the ipsilateral dorsal cochlear nucleus (DCN), the contralateral CN, or both structures. Three rats received injections of biotinylated dextran amine in the ipsilateral DCN and diamidino yellow in the contralateral CN. Several radiate multipolar neurons (defined by their axonal projections to the ipsilateral DCN and their dendrites that traverse VCN isofrequency sheets) were double-labeled but over 70% were not. This result suggests two distinct populations: (1) radiate-commissural (RC) multipolar cells that project to the ipsilateral DCN and the contralateral CN, and (2) radiate multipolar cells that project exclusively (in this context) to the ipsilateral DCN. In a different group of animals, we retrogradely labeled multipolar neurons that project their axons to the contralateral CN and measured the size of their cell bodies. The mean size of this population (266 +/- 156 microm2) was significantly smaller than those of RC-multipolar cells (418 +/- 140 microm2). We conclude that the CN commissural pathway is composed of at least two components: (1) RC multipolar cells and (2) commissural multipolar cells that are small- and medium-sized neurons that project exclusively (in this context) to the contralateral CN. These results identify separate structural groups of multipolar cells that may correspond to physiological unit types described in the literature. They also provide protocols for isolating and studying different populations of multipolar cells to determine the neural mechanisms that govern their responses to sound.

  15. Diversified Anchoring Features the Peptide Presentation of DLA-88*50801: First Structural Insight into Domestic Dog MHC Class I.

    PubMed

    Xiao, Jin; Xiang, Wangzhen; Chai, Yan; Haywood, Joel; Qi, Jianxun; Ba, Limin; Qi, Peng; Wang, Ming; Liu, Jun; Gao, George F

    2016-09-15

    Canines represent a crucial animal model for studying human diseases and organ transplantation, as well as the evolution of domestic animals. MHCs, with a central role in cellular immunity, are commonly used in the study of dog population genetics and genome evolution. However, the molecular basis for the peptide presentation of dog MHC remains largely unknown. In this study, peptide presentation by canine MHC class I DLA-88*50801 was structurally determined, revealing diversified anchoring modes of the binding peptides. Flexible and large pockets composed of both hydrophobic and hydrophilic residues can accommodate pathogen-derived peptides with diverse anchor residues, as confirmed by thermostability measurements. Furthermore, DLA-88*50801 contains an unusual α2 helix with a large coil in the TCR contact region. These results further our understanding of canine T cell immunity through peptide presentation of MHC class I and shed light on the molecular basis for vaccine development for canine infectious diseases, for example, canine distemper virus. PMID:27511732

  16. Platyhelminth Venom Allergen-Like (VAL) proteins: revealing structural diversity, class-specific features and biological associations across the phylum.

    PubMed

    Chalmers, Iain W; Hoffmann, Karl F

    2012-09-01

    During platyhelminth infection, a cocktail of proteins is released by the parasite to aid invasion, initiate feeding, facilitate adaptation and mediate modulation of the host immune response. Included amongst these proteins is the Venom Allergen-Like (VAL) family, part of the larger sperm coating protein/Tpx-1/Ag5/PR-1/Sc7 (SCP/TAPS) superfamily. To explore the significance of this protein family during Platyhelminthes development and host interactions, we systematically summarize all published proteomic, genomic and immunological investigations of the VAL protein family to date. By conducting new genomic and transcriptomic interrogations to identify over 200 VAL proteins (228) from species in all 4 traditional taxonomic classes (Trematoda, Cestoda, Monogenea and Turbellaria), we further expand our knowledge related to platyhelminth VAL diversity across the phylum. Subsequent phylogenetic and tertiary structural analyses reveal several class-specific VAL features, which likely indicate a range of roles mediated by this protein family. Our comprehensive analysis of platyhelminth VALs represents a unifying synopsis for understanding diversity within this protein family and a firm context in which to initiate future functional characterization of these enigmatic members.

  17. Structure and mechanism of action of the hydroxy aryl aldehyde class of IRE1 endoribonuclease inhibitors

    PubMed Central

    Sanches, Mario; Duffy, Nicole M.; Talukdar, Manisha; Thevakumaran, Nero; Chiovitti, David; Canny, Marella D.; Lee, Kenneth; Kurinov, Igor; Uehling, David; Al-awar, Rima; Poda, Gennadiy; Prakesch, Michael; Wilson, Brian; Tam, Victor; Schweitzer, Colleen; Toro, Andras; Lucas, Julie L.; Vuga, Danka; Lehmann, Lynn; Durocher, Daniel; Zeng, Qingping; Patterson, John B.; Sicheri, Frank

    2014-01-01

    Endoplasmic reticulum (ER) stress activates the unfolded protein response and its dysfunction is linked to multiple diseases. The stress transducer IRE1α is a transmembrane kinase endoribonuclease (RNase) that cleaves mRNA substrates to re-establish ER homeostasis. Aromatic ring systems containing hydroxy-aldehyde moieties, termed hydroxy aryl aldehydes (HAA), selectively inhibit IRE1α RNase and thus represent a novel chemical series for therapeutic development. We solved crystal structures of murine IRE1α in complex with three HAA inhibitors. HAA inhibitors engage a shallow pocket at the RNase active site through pi-stacking interactions with His910 and Phe889, an essential Schiff base with Lys907 and a H-bond with Tyr892. Structure activity studies and mutational analysis of contact residues define the optimal chemical space of inhibitors and validate the inhibitor binding site. These studies lay the foundation for understanding both the biochemical and cellular functions of IRE1α using small molecule inhibitors and suggest new avenues for inhibitor design. PMID:25164867

  18. Aging Optimization of Aluminum-Lithium Alloy C458 for Application to Cryotank Structures

    NASA Technical Reports Server (NTRS)

    Sova, B. J.; Sankaran, K. K.; Babel, H.; Farahmand, B.; Rioja, R.

    2003-01-01

    Compared with aluminum alloys such as 2219, which is widely used in space vehicle for cryogenic tanks and unpressurized structures, aluminum-lithium alloys possess attractive combinations of lower density and higher modulus along with comparable mechanical properties. These characteristics have resulted in the successful use of the aluminum-lithium alloy 2195 (Al-1.0 Li-4.0 Cu-0.4 Mg-0.4 Ag-0.12 Zr) for the Space Shuttle External Tank, and the consideration of newer U.S. aluminum-lithium alloys such as L277 and C458 for future space vehicles. These newer alloys generally have lithium content less than 2 wt. % and their composition and processing have been carefully tailored to increase the toughness and reduce the mechanical property anisotropy of the earlier generation alloys such 2090 and 8090. Alloy processing, particularly the aging treatment, has a significant influence on the strength-toughness combinations and their dependence on service environments for aluminum-lithium alloys. Work at NASA Marshall Space Flight Center on alloy 2195 has shown that the cryogenic toughness can be improved by employing a two-step aging process. This is accomplished by aging at a lower temperature in the first step to suppress nucleation of the strengthening precipitate at sub-grain boundaries while promoting nucleation in the interior of the grains. Second step aging at the normal aging temperature results in precipitate growth to the optimum size. A design of experiments aging study was conducted for plate. To achieve the T8 temper, Alloy C458 (Al-1.8 Li-2.7 Cu-0.3 Mg- 0.08 Zr-0.3 Mn-0.6 Zn) is typically aged at 300 F for 24 hours. In this study, a two-step aging treatment was developed through a comprehensive 24 full factorial design of experiments study and the typical one-step aging used as a reference. Based on the higher lithium content of C458 compared with 2195, the first step aging temperature was varied between 175 F and 250 F. The second step aging temperatures was

  19. Age structure of owned dogs under compulsory culling in a visceral leishmaniasis endemic area.

    PubMed

    Bortoletto, Danielly Vieira; Utsunomiya, Yuri Tani; Perri, Silvia Helena Venturoli; Ferreira, Fernando; Nunes, Cáris Maroni

    2016-01-01

    The age structure of the dog population is essential for planning and evaluating control programs for zoonotic diseases. We analyzed data of an owned-dog census in order to characterize, for the first time, the structure of a dog population under compulsory culling in a visceral leishmaniasis endemic area (Panorama, São Paulo State, Brazil) that recorded a dog-culling rate of 28% in the year of the study. Data on 1,329 households and 1,671 owned dogs revealed an owned dog:human ratio of 1:7. The mean age of dogs was estimated at 1.73 years; the age pyramid indicated high birth and mortality rates at the first year of age with an estimated cumulative mortality of 78% at the third year of age and expected life span of 2.75 years. In spite of the high mortality, a growth projection simulation suggested that the population has potential to grow in a logarithmic scale over the years. The estimated parameters can be further applied in models to maximize the impact and minimize financial inputs of visceral leishmaniasis control measures. PMID:27598014

  20. The effect of gender and age structure on municipal waste generation in Poland

    SciTech Connect

    Talalaj, Izabela Anna Walery, Maria

    2015-06-15

    Highlights: • An effect of gender and age structure on municipal waste generation was presented. • The waste accumulation index is influenced by a number of unemployed women. • Greater share of women in society contributes to greater waste production. • A model describing the analyzed dependences was determined. - Abstract: In this study the effect of gender and age structure on municipal waste generation was investigated. The data from 10-year period, from 2001 to 2010 year, were taken into consideration. The following parameters of gender and age structure were analyzed: men and woman quantity, female to male ratio, number of working, pre-working and post-working age men/women, number of unemployed men/women. The results have showed a strong correlation of annual per capita waste generation rate with number of unemployed women (r = 0.70) and female to male ratio (r = 0.81). This indicates that waste generation rate is more depended on ratio of men and women that on quantitative size of each group. Using the regression analysis a model describing the dependence between female to male ratio, number of unemployed woman and waste quantity was determined. The model explains 70% of waste quantity variation. Obtained results can be used both to improve waste management and to a fuller understanding of gender behavior.

  1. Field theoretic analysis of a class of planar microwave and optoelectronic structures

    NASA Astrophysics Data System (ADS)

    Hahm, Yeon-Chang

    2000-11-01

    With increasing operating frequencies in CMOS RF/microwave integrated circuits, the performance of on- chip interconnects is becoming significantly affected by the lossy substrate. It is the purpose of the first part of this thesis to develop a rigorous field theoretic analysis approach for efficient characterization of single and multiple coupled interconnects on silicon substrate, which is applicable over a wide range of substrate resistivities. The frequency-dependent transmission line parameters of a microstrip on silicon are determined by a new formulation based on a quasi- electrostatic and quasi-magnetostatic spectral domain approach. It is demonstrated that this new quasi-static formulation provides the complete frequency-dependent interconnect characteristics for all three major transmission line modes of operation. In particular, it is shown that in the case of heavily doped CMOS substrates, the distributed series inductance and series resistance parameters are significantly affected by the presence of longitudinal substrate currents giving rise to the substrate skin-effect. The method is further extended to multiple coupled single and multi-level interconnect structures with ground plane and multiple coupled co-planar stripline structures without ground plane. The finite conductor thickness is taken into account in terms of a stacked conductor model. The new quasi-static approach is validated by comparison with results obtained with a full-wave spectral domain method and the commercial planar full-wave electromagnetic field solver HP/Momentum®, as well as published simulation and measurement data. In the second part of this thesis, coupled planar optical interconnect structures are investigated based on a rigorous field theoretic analysis combined with an application of the normal mode theory for coupled transmission lines. A new transfer matrix description for a general optical directional coupler is presented. Based on this transfer matrix formulation

  2. Structural degradation of acrylic bone cements due to in vivo and simulated aging.

    PubMed

    Hughes, Kerry F; Ries, Michael D; Pruitt, Lisa A

    2003-05-01

    Acrylic bone cement is the primary load-bearing material used for the attachment of orthopedic devices to adjoining bone. Degradation of acrylic-based cements in vivo results in a loss of structural integrity of the bone-cement-prosthesis interface and limits the longevity of cemented orthopedic implants. The purpose of this study is to investigate the effect of in vivo aging on the structure of the acrylic bone cement and to develop an in vitro artificial aging protocol that mimics the observed degradation. Three sets of retrievals are examined in this study: Palacos brand cement retrieved from hip replacements, and Simplex brand cement retrieved from both hip and knee replacement surgeries. In vitro aging is performed using oxidative and acidic environments on three acrylic-based cements: Palacos, Simplex, and CORE. Gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FTIR) are used to examine the evolution of molecular weight and chemical species within the acrylic cements due to both in vivo and simulated aging. GPC analysis indicates that molecular weight is degraded in the hip retrievals but not in the knee retrievals. Artificial aging in an oxidative environment best reproduces this degradation mechanism. FTIR analysis indicates that there exists a chemical evolution within the cement due to in vivo and in vitro aging. These findings are consistent with scission-based degradation schemes in the cement. Based on the results of this study, a pathway for structural degradation of acrylic bone cement is proposed. The findings from this investigation have broad applicability to acrylic-based cements and may provide guidance for the development of new bone cements that resist degradation in the body.

  3. Isothiazolopyridones: synthesis, structure, and biological activity of a new class of antibacterial agents.

    PubMed

    Wiles, Jason A; Hashimoto, Akihiro; Thanassi, Jane A; Cheng, Jijun; Incarvito, Christopher D; Deshpande, Milind; Pucci, Michael J; Bradbury, Barton J

    2006-01-12

    We report the syntheses of first-generation derivatives of isothiazolopyridones and their in vitro evaluation as antibacterial agents. These compounds, containing a novel heterocyclic nucleus composed of an isothiazolone fused to a quinolizin-4-one (at C-2 and C-3 of the quinolizin-4-one), were prepared using a sequence of seven synthetic transformations. The solid-state structure of 7-chloro-9-ethyl-1-thia-2,4a-diazacyclopenta[b]naphthalene-3,4-dione was determined by X-ray diffraction. The prepared derivatives of desfluoroisothiazolopyridones exhibited (a) antibacterial activity against Gram-negative and Gram-positive organisms, (b) inhibitory activities against DNA gyrase and topoisomerase IV, and (c) no inhibitory activity against human topoisomerase II.

  4. Motor structures in female volleyball players aged 14-17 according to technique quality and performance.

    PubMed

    Katić, Ratko; Grgantov, Zoran; Jurko, Damir

    2006-03-01

    The aim of the study was to identify motor structures in elite female volleyball players aged 14-17, and to assess the effect of these motor structures on their technical and situation efficiency. For this purpose, a battery of 12 motor tests as predictor variables, and a set of six technical elements and evaluation of performance quality as criterion variables were applied in a sample of 147 female volleyballers aged 14-15 and a sample of 50 female volleyballers aged 16-17. Analysis of variance between subgroups within the groups of volleyballers aged 14-15 and those aged 16-17 showed the results on all motor tests to improve with the increase in situation performance, which was especially pronounced in the tests assessing explosive strength and agility. The same held true for the results on all tests assessing volleyball techniques, spike and block in particular. In both samples, factor analysis of motor tests isolated two factors underlain by the generation and regulation of strength, and the mechanism of speed regulation. Canonical correlation analysis between the motor regulatory mechanisms and technical elements revealed determination of the mechanisms of strength and technical efficiency in both samples. Regression correlation analysis showed the mechanisms of strength regulation and speed to be good predictors of game performance in female volleyballers aged 14-15 and 16-17, whereby the mechanism of strength regulation had greater effect on the game performance than the mechanism of speed regulation. Regression correlation analysis also revealed the set of 6 techniques evaluated to be a good predictor of situation efficiency in both groups of female volleyballers aged 14-15 and 16-17. The block and spike techniques were found to be the best predictors of game performance quality in the former, and the techniques of spike and block in the latter. Based on the results obtained, a possible model of selection for supreme score achievement in female volleyball

  5. Analysing collimator structure effects in head-scatter calculations for IMRT class fields using scatter raytracing.

    PubMed

    Naqvi, S A; Sarfaraz, M; Holmes, T; Yu, C X; Li, X A

    2001-07-01

    The frequent blocking of the irradiated volume in intensity modulated radiation therapy (IMRT) makes the head-scatter fraction of the incident photon fluence more significant than that in conventional therapy with open fields. On the other hand. certain collimator configurations block scatter photons directed to a given observation point while allowing primary photons to be transmitted. The 'anomalous blocking' makes the primary field a poor indicator of the scatter fluence. Since large MU-to-cGy ratios in IMRT can magnify head-scatter uncertainties, it becomes necessary to accurately model both the effective scatter source and the collimator structure that limits the scatter reaching the irradiated volume. First we obtain a dual-source model, using a Taylor series expansion to derive the effective scatter source distribution from the data measured for the Elekta SL20 linac equipped with a multi-leaf collimator (MLC). Then, using a raytracing algorithm, we calculate the transmission of scatter rays from the effective scatter source plane to points in the patient plane. The method can account for the anomalous blocking of scatter by the MLC leaves and the backup diaphragms. For a variety of collimator settings tested, the calculations agree with measurements to an accuracy of 0.002psi10 x 10, where psi10 x 10 is the total (primary + scatter) photon fluence of an open 10 x 10 cm2 field for the same MU delivered. Although the significance of collimator structure in IMRT depends strongly on fields shapes employed for the delivery, potential cumulative errors on the order of a few per cent can be avoided in fluence calculations if the proposed method is used. PMID:11474941

  6. Snooker: a structure-based pharmacophore generation tool applied to class A GPCRs.

    PubMed

    Sanders, Marijn P A; Verhoeven, Stefan; de Graaf, Chris; Roumen, Luc; Vroling, Bas; Nabuurs, Sander B; de Vlieg, Jacob; Klomp, Jan P G

    2011-09-26

    G-protein coupled receptors (GPCRs) are important drug targets for various diseases and of major interest to pharmaceutical companies. The function of individual members of this protein family can be modulated by the binding of small molecules at the extracellular side of the structurally conserved transmembrane (TM) domain. Here, we present Snooker, a structure-based approach to generate pharmacophore hypotheses for compounds binding to this extracellular side of the TM domain. Snooker does not require knowledge of ligands, is therefore suitable for apo-proteins, and can be applied to all receptors of the GPCR protein family. The method comprises the construction of a homology model of the TM domains and prioritization of residues on the probability of being ligand binding. Subsequently, protein properties are converted to ligand space, and pharmacophore features are generated at positions where protein ligand interactions are likely. Using this semiautomated knowledge-driven bioinformatics approach we have created pharmacophore hypotheses for 15 different GPCRs from several different subfamilies. For the beta-2-adrenergic receptor we show that ligand poses predicted by Snooker pharmacophore hypotheses reproduce literature supported binding modes for ∼75% of compounds fulfilling pharmacophore constraints. All 15 pharmacophore hypotheses represent interactions with essential residues for ligand binding as observed in mutagenesis experiments and compound selections based on these hypotheses are shown to be target specific. For 8 out of 15 targets enrichment factors above 10-fold are observed in the top 0.5% ranked compounds in a virtual screen. Additionally, prospectively predicted ligand binding poses in the human dopamine D3 receptor based on Snooker pharmacophores were ranked among the best models in the community wide GPCR dock 2010.

  7. Age and decision strategies in running memory for speech: effects of prosody and linguistic structure.

    PubMed

    Wingfield, A; Lahar, C J; Stine, E A

    1989-07-01

    Young and elderly adults heard recorded passages of English prose spoken with and without normal prosody, and passages that were devoid of either linguistic or prosodic structure. Subjects were instructed to interrupt the speech input at points of their choosing for immediate recall on a segment-by-segment basis. For both age groups segmentation strategies varied with type of speech materials as did their levels of recall accuracy. Age differences in recall performance were diminished by the presence of normal prosody, an effect only partially attributable to the use of prosody to detect linguistic boundaries at the surface level.

  8. Definitions of fitness in age-structured populations: Comparison in the haploid case.

    PubMed

    Lessard, Sabin; Soares, Cintia

    2016-02-21

    Fisher's (1930) Fundamental Theorem of Natural Selection (FTNS), and in particular the development of an explicit age-structured version of the theorem, is of everlasting interest. In a recent paper, Grafen (2015a) argues that Fisher regarded his theorem as justifying individual rather than population fitness maximization. The argument relies on a new definition of fitness in age-structured populations in terms of individual birth and death rates and age-specific reproductive values in agreement with a principle of neutrality. The latter are frequency-dependent and defined without reference to genetic variation. In the same paper, it is shown that the rate of increase in the mean of the breeding values of fitness weighted by the reproductive values, but keeping the breeding values constant as in Price (1972) is equal to the additive genetic variance in fitness. Therefore, this partial change is obtained by keeping constant not only the genotypic birth and death rates but also the mean age-specific birth and death rates from which the age-specific reproductive values are defined. In this paper we reaffirm that the Malthusian parameter which measures the relative rate of increase or decrease in reproductive value of each genotype in a continuous-time age-structured population is the definition of fitness used in Fisher's (1930) FTNS. This is shown by considering an age-structured asexual haploid population with constant age-specific birth and death (or survival) parameters for each type. Although the original statement of the FTNS is for a diploid population, this simplified haploid model allows us to address the definition of fitness meant in this theorem without the complexities and effects of a changing genic environment. In this simplified framework, the rate of change in mean fitness in continuous time is expected to be exactly equal to the genetic variance in fitness (or to the genetic variance in fitness divided by the mean fitness in discrete time), which can

  9. Age-associated differences on structural brain MRI in nondemented individuals from 71 to 103 years.

    PubMed

    Yang, Zixuan; Wen, Wei; Jiang, Jiyang; Crawford, John D; Reppermund, Simone; Levitan, Charlene; Slavin, Melissa J; Kochan, Nicole A; Richmond, Robyn L; Brodaty, Henry; Trollor, Julian N; Sachdev, Perminder S

    2016-04-01

    Successful brain aging in the oldest old (≥90 years) is underexplored. This study examined cross-sectional brain morphological differences from 8th to 11th decades of life in nondemented individuals by high-resolution magnetic resonance imaging. Two hundred seventy-seven nondemented community-dwelling participants (71-103 years) from Sydney Memory and Ageing Study and Sydney Centenarian Study comprised the sample, including a subsample of 160 cognitively high-functioning elders. Relationships between age and magnetic resonance imaging-derived measurements were studied using general linear models; and structural profiles of the ≥90 years were delineated. In full sample and the subsample, significant linear negative relationship of gray matter with age was found, with the greatest age effects in the medial temporal lobe and parietal and occipital cortices. This pattern was further confirmed by comparing directly the ≥90 years to the 71-89 years groups. Significant quadratic age effects on total white matter and white matter hyperintensities were observed. Our study demonstrated heterogeneous differences across brain regions between the oldest old and young old, with an emphasis on hippocampus, temporoposterior cortex, and white matter hyperintensities. PMID:26973107

  10. Age and disease-related structural changes in the retinal pigment epithelium

    PubMed Central

    Bonilha, Vera L

    2008-01-01

    As the retinal pigment epithelium (RPE) ages, a number of structural changes occur, including loss of melanin granules, increase in the density of residual bodies, accumulation of lipofuscin, accumulation of basal deposits on or within Bruch’s membrane, formation of drusen (between the basal lamina of the RPE and the inner collagenous layer of Bruch’s membrane), thickening of Bruch’s membrane, microvilli atrophy and disorganization of the basal infoldings. Although these changes are well known, the basic mechanisms involved in them are frequently poorly understood. These age-related changes progress slowly and vary in severity in different individuals. These changes are also found in age-related macular degeneration (AMD), a late onset disease that severely impacts the RPE, but they are much more pronounced than during normal aging. However, the changes in AMD lead to severe loss of vision. Given the many supporting functions which the RPE serves for the retina, it is important to decipher the age-related changes in this epithelium in order to understand age-related changes in vision. PMID:19668732

  11. [Intergenerational communication by age-integrating structures? Remarks on on gerontologic utopia].

    PubMed

    Amrhein, L

    2002-08-01

    In their "aging and society" paradigm Riley and collaborators conceptualize the ideal type of an age-integrated society in which the social segregation of different age groups is removed. They claim that in the future the life-world areas of education, work and leisure will no longer exclusively follow the triple division of the life course but will be visited repeatedly in different phases of life. Therefore, they argue, age barriers would be dissolved in many areas, which would lead to more contact and cooperation and to a greater solidarity between the generations. This conception shall be rejected as an utopia because it contradicts central functional mechanisms of modern societies; at best it might be imagined as a "reflexive modernization" of age-segregated structures. A certain distance and alienation between the generations remains a direct, though unintended product of the modernization process and cannot be reversed without welfare losses. A dialogue of generations as a societal project, therefore, implies that the functional differentiation into age groups and life stages will be accepted without referring to pre-modern idealizations of generational relationships.

  12. ALPS: The Age-Layered Population Structure for Reducing the Problem of Premature Convergence

    NASA Technical Reports Server (NTRS)

    Hornby, Gregory S.

    2006-01-01

    To reduce the problem of premature convergence we define a new attribute of an individual, its age, and propose the Age-Layered Population Structure (ALPS), in which age is used to restrict competition and breeding between members of the population. ALPS differs from a typical EA by segregating individuals into different age-layers by their age - a measure of how long the genetic material has been in the population - and by regularly replacing all individuals in the bottom layer with randomly generated ones. The introduction of new, randomly generated individuals at regular intervals results in an EA that is never completely converged and is always looking at new parts of the fitness landscape. By using age to restrict competition and breeding search is able to develop promising young individuals without them being dominated by older ones. We demonstrate the effectiveness of the ALPS algorithm on an antenna design problem in which evolution with ALPS produces antennas more than twice as good as does evolution with two other types of EAs. Further analysis shows that the ALPS model does allow the offspring of newly generated individuals to move the population out of mediocre local-optima to better parts of the fitness landscape.

  13. Deciphering the structural code for proteins: helical propensities in domain classes and statistical multiresidue information in alpha-helices.

    PubMed Central

    Negrete, J. A.; Viñuales, Y.; Palau, J.

    1998-01-01

    We made several statistical analyses in a large sample of nearly 4,000 helices (from 546 redundancy-controlled PDB protein subunits), which give new insights into the helical properties of globular proteins. In a first experiment, the amino acid composition of the whole sample was compared with the composition of two helical sample subgroups (the "mainly-alpha" and the "(alpha/beta)8 barrel" domain classes); we reached the conclusion that composition-based helical propensities for secondary structure prediction do not depend on the structural class. Running a five-residue window through the whole sample, the positional composition revealed that positive and negative residues are located throughout the helices and tend to neutralize the macrodipole effect. On this basis, we analyzed charged triplets using a running five-residue window. The conclusion was that only mixed charged residues [positive (+) and negative (-)] located at positions 1-2-5 and 1-4-5 are clearly favored. In these locations the most abundant are (- -..+) and (-..+ +), and this shows the existence of side chain microdipoles, which neutralize the large macrodipole of the helix. We made a systematic statistical analysis of charged, dipolar, and hydrophobic + aromatic residues, which enabled us to work out rules that should be useful for modeling and design purposes. Finally, we analyzed the relative abundance of all the different amphipathic double-arcs that are present in helices formed by octapeptides (8) and nonapeptides (18). All of the double-arcs that make up Schiffer and Edmundson's classical helical wheel are found in abundance in the sample. PMID:9655341

  14. Core and Large-Scale Structure of the 2000 November 24 X-Class Flare and Coronal Mass Ejection

    NASA Technical Reports Server (NTRS)

    Wang, Haimin; Gallagher, Peter; Yurchyshyn, Vasyl; Yang, Guo; Godde, Philip R.

    2002-01-01

    In this paper, we present three important aspects of the XI .8 flare and the associated coronal mass ejection (CME) that occurred on 2000 November 24: (1) The source of the flare is clearly associated with a magnetic channel structure, as was noted in a study by Zirin & Wang , which is due to a combination of flux emergence inside the leading edge of the penumbra of the major leading sunspot and proper motion of the sunspot group. The channel structure provides evidence for twisted flux ropes that can erupt, forming the core of a CME, and may be a common property of several superactive regions that have produced multiple X-class flares in the past. (2) There are actually three flare ribbons visible. The first can be seen moving away from the flare site, while the second and third make up a stationary ribbon near the leader spot. The moving ribbons could be due to a shock associated with the erupting flux rope or due to the interaction of erupting rope and the surrounding magnetic fields. In either case, the ribbon motion does not fit the classical Kopp-Pneuman model, in which the separation of ribbons is due to magnetic reconnection at successively higher and higher coronal altitudes. (3) From the coronal dimming observed with the EUV Imaging Telescope (EIT), the CME involved a much larger region than the initial X-class flare. By comparing high-resolution full-disk Ha and EIT observations, we found that a remote dimming area is cospatial with the enhanced Ha emission. This result is consistent with the recent model of Yokoyama & Shibata that some dimming areas near footpoints may be due to chromospheric evaporation.

  15. Structure and Characterization of Flavolipids, a Novel Class of Biosurfactants Produced by Flavobacterium sp. Strain MTN11

    PubMed Central

    Bodour, Adria A.; Guerrero-Barajas, Claudia; Jiorle, Beth V.; Malcomson, Mark E.; Paull, Amanda K.; Somogyi, Arpad; Trinh, Long N.; Bates, Robert B.; Maier, Raina M.

    2004-01-01

    Herein we report the structure and selected properties of a new class of biosurfactants that we have named the flavolipids. The flavolipids exhibit a unique polar moiety that features citric acid and two cadaverine molecules. Flavolipids were produced by a soil isolate, Flavobacterium sp. strain MTN11 (accession number AY162137), during growth in mineral salts medium, with 2% glucose as the sole carbon and energy source. MTN11 produced a mixture of at least 37 flavolipids ranging from 584 to 686 in molecular weight (MW). The structure of the major component (23%; MW = 668) was determined to be 4-[[5-(7-methyl-(E)-2-octenoylhydroxyamino)pentyl]amino]-2-[2-[[5-(7-methyl-(E)-2-octenoylhydroxyamino)pentyl]amino]-2-oxoethyl]-2-hydroxy-4-oxobutanoic acid. The partially purified flavolipid mixture isolated from strain MTN11 exhibited a critical micelle concentration of 300 mg/liter and reduced surface tension to 26.0 mN/m, indicating strong surfactant activity. The flavolipid mixture was a strong and stable emulsifier even at concentrations as low as 19 mg/liter. It was also an effective solubilizing agent, and in a biodegradation study, it enhanced hexadecane mineralization by two isolates, MTN11 (100-fold) and Pseudomonas aeruginosa ATCC 9027 (2.5-fold), over an 8-day period. The flavolipid-cadmium stability constant was measured to be 3.61, which is comparable to that for organic ligands such as oxalic acid and acetic acid. In summary, the flavolipids represent a new class of biosurfactants that have potential for use in a variety of biotechnological and industrial applications. PMID:14711632

  16. Slipping Magnetic Reconnection of Flux-rope Structures as a Precursor to an Eruptive X-class Solar Flare

    NASA Astrophysics Data System (ADS)

    Li, Ting; Yang, Kai; Hou, Yijun; Zhang, Jun

    2016-10-01

    We present the quasi-periodic slipping motion of flux-rope structures prior to the onset of an eruptive X-class flare on 2015 March 11, obtained by the Interface Region Imaging Spectrograph and the Solar Dynamics Observatory. The slipping motion occurred at the north part of the flux rope and seemed to successively peel off the flux rope. The speed of the slippage was 30‑40 km s‑1, with an average period of 130 ± 30 s. The Si iv λ1402.77 line showed a redshift of 10‑30 km s‑1 and a line width of 50‑120 km s‑1 at the west legs of slipping structures, indicative of reconnection downflow. The slipping motion lasted about 40 minutes, and the flux rope started to rise up slowly at the late stage of the slippage. Then an X2.1 flare was initiated, and the flux rope was impulsively accelerated. One of the flare ribbons swept across a negative-polarity sunspot, and the penumbral segments of the sunspot decayed rapidly after the flare. We studied the magnetic topology at the flaring region, and the results showed the existence of a twisted flux rope, together with quasi-separatrix layer (QSL) structures binding the flux rope. Our observations imply that quasi-periodic slipping magnetic reconnection occurs along the flux-rope-related QSLs in the preflare stage, which drives the later eruption of the flux rope and the associated flare.

  17. Structural Basis for the Presentation of Tumor-Associated MHC Class II-Restricted Phosphopeptides to CD4+ T Cells

    SciTech Connect

    Li, Y.; Depontieu, F; Sidney, J; Salay, T; Engelhard, V; Hunt, D; Sette, A; Topalian, S; Mariuzza, R

    2010-01-01

    Dysregulated protein phosphorylation is a hallmark of malignant transformation. Transformation can generate major histocompatibility complex (MHC)-bound phosphopeptides that are differentially displayed on tumor cells for specific recognition by T cells. To understand how phosphorylation alters the antigenic identity of self-peptides and how MHC class II molecules present phosphopeptides for CD4{sup +} T-cell recognition, we determined the crystal structure of a phosphopeptide derived from melanoma antigen recognized by T cells-1 (pMART-1), selectively expressed by human melanomas, in complex with HLA-DR1. The structure revealed that the phosphate moiety attached to the serine residue at position P5 of pMART-1 is available for direct interactions with T-cell receptor (TCR) and that the peptide N-terminus adopts an unusual conformation orienting it toward TCR. This structure, combined with measurements of peptide affinity for HLA-DR1 and of peptide-MHC recognition by pMART-1-specific T cells, suggests that TCR recognition is focused on the N-terminal portion of pMART-1. This recognition mode appears to be distinct from that of foreign antigen complexes but is remarkably reminiscent of the way autoreactive TCRs engage self- or altered self-peptides, consistent with the tolerogenic nature of tumor-host immune interactions.

  18. Aged nano-structured platinum based catalyst: effect of chemical treatment on adsorption and catalytic activity.

    PubMed

    Shim, Wang Geun; Nahm, Seung Won; Park, Hyuk Ryeol; Yun, Hyung Sun; Seo, Seong Gyu; Kim, Sang Chai

    2011-02-01

    To examine the effect of chemical treatment on the adsorption and catalytic activity of nanostructured platinum based catalyst, the aged commercial Pt/AC catalyst was pretreated with sulfuric acid (H2SO4) and a cleaning agent (Hexane). Several reliable methods such as nitrogen adsorption, X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and inductively coupled plasma (ICP) were employed to characterize the aged Pt/AC catalyst and its chemically pretreated Pt/AC catalysts. The catalytic and adsorption activities of nano-structured heterogeneous Pt/AC catalyst were investigated on the basis of toluene oxidation and adsorption isotherm data. In addition, the adsorption isotherms of toluene were used to calculate the adsorption energy distribution functions for the parent catalyst and its pre-treated nano-structured Pt/AC catalysts. It was found that sulfuric acid aqueous treatment can enhance the catalytic performance of aged Pt/AC catalyst toward catalytic oxidation of toluene. It was also shown that a comparative analysis of the energy distribution functions for nano-structured Pt/AC catalysts as well as the pore size distribution provides valuable information about their structural and energetic heterogeneity.

  19. Structural Basis for Different Substrate Profiles of Two Closely Related Class D β-Lactamases and Their Inhibition by Halogens.

    PubMed

    Stojanoski, Vlatko; Chow, Dar-Chone; Fryszczyn, Bartlomiej; Hu, Liya; Nordmann, Patrice; Poirel, Laurent; Sankaran, Banumathi; Prasad, B V Venkataram; Palzkill, Timothy

    2015-06-01

    OXA-163 and OXA-48 are closely related class D β-lactamases that exhibit different substrate profiles. OXA-163 hydrolyzes oxyimino-cephalosporins, particularly ceftazidime, while OXA-48 prefers carbapenem substrates. OXA-163 differs from OXA-48 by one substitution (S212D) in the active-site β5 strand and a four-amino acid deletion (214-RIEP-217) in the loop connecting the β5 and β6 strands. Although the structure of OXA-48 has been determined, the structure of OXA-163 is unknown. To further understand the basis for their different substrate specificities, we performed enzyme kinetic analysis, inhibition assays, X-ray crystallography, and molecular modeling. The results confirm the carbapenemase nature of OXA-48 and the ability of OXA-163 to hydrolyze the oxyimino-cephalosporin ceftazidime. The crystal structure of OXA-163 determined at 1.72 Å resolution reveals an expanded active site compared to that of OXA-48, which allows the bulky substrate ceftazidime to be accommodated. The structural differences with OXA-48, which cannot hydrolyze ceftazidime, provide a rationale for the change in substrate specificity between the enzymes. OXA-163 also crystallized under another condition that included iodide. The crystal structure determined at 2.87 Å resolution revealed iodide in the active site accompanied by several significant conformational changes, including a distortion of the β5 strand, decarboxylation of Lys73, and distortion of the substrate-binding site. Further studies showed that both OXA-163 and OXA-48 are inhibited in the presence of iodide. In addition, OXA-10, which is not a member of the OXA-48-like family, is also inhibited by iodide. These findings provide a molecular basis for the hydrolysis of ceftazidime by OXA-163 and, more broadly, show how minor sequence changes can profoundly alter the active-site configuration and thereby affect the substrate profile of an enzyme.

  20. Genus age, provincial area and the taxonomic structure of marine faunas

    PubMed Central

    Harnik, Paul G.; Jablonski, David; Krug, Andrew Z.; Valentine, James W.

    2010-01-01

    Species are unevenly distributed among genera within clades and regions, with most genera species-poor and few species-rich. At regional scales, this structure to taxonomic diversity is generated via speciation, extinction and geographical range dynamics. Here, we use a global database of extant marine bivalves to characterize the taxonomic structure of climate zones and provinces. Our analyses reveal a general, Zipf–Mandelbrot form to the distribution of species among genera, with faunas from similar climate zones exhibiting similar taxonomic structure. Provinces that contain older taxa and/or encompass larger areas are expected to be more species-rich. Although both median genus age and provincial area correlate with measures of taxonomic structure, these relationships are interdependent, nonlinear and driven primarily by contrasts between tropical and extra-tropical faunas. Provincial area and taxonomic structure are largely decoupled within climate zones. Counter to the expectation that genus age and species richness should positively covary, diverse and highly structured provincial faunas are dominated by young genera. The marked differences between tropical and temperate faunas suggest strong spatial variation in evolutionary rates and invasion frequencies. Such variation contradicts biogeographic models that scale taxonomic diversity to geographical area. PMID:20534619