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1

Variation in the reproductive rate of bats  

Microsoft Academic Search

In many respects, bats have relatively slow life histories. However, the reproductive rate of bats (i.e., the proportion of females that reproduce in any breeding season) has not been critically examined. We compiled data on the reproductive rates of bats to test predictions based on life-history theory. Among 257 samples from 103 species, re - productive rate varied considerably and

Robert M. R. Barclay; Joel Ulmer; Cameron J. A. MacKenzie; Megan S. Thompson; Leif Olson; Julianne McCool; Elvie Cropley; Graeme Poll

2004-01-01

2

Effects of high temperature on reproduction  

Microsoft Academic Search

The significance of seasonal fluctuations in the components of the reproductive cycle is complex. In mammals, high environmental temperature may cause delayed puberty, delayed onset of sexual season, irregularity in cycle length, duration of estrus, ovulation rate, frequency of anovulatory estrus,morphological abnormalities in ova, fetal size and semen characteristics. High temperatures, in birds, may affect rate of egg laying, egg

E. S. E. Hafez

1964-01-01

3

Variable male potential rate of reproduction: high male mating capacity as an adaptation to parasite-induced excess of females?  

PubMed Central

Numerous animals are known to harbour intracytoplasmic symbionts that gain transmission to a new host generation via female eggs and not male sperm. Bacteria of the genus Wolbachia are a typical example. They infect a large range of arthropod species and manipulate host reproduction in several ways. In terrestrial isopods (woodlice), Wolbachia are responsible for converting males into females (feminization (F)) in some species, or for infertility in certain host crosses in other species (cytoplasmic incompatibility (CI)). Wolbachia with the F phenotype impose a strong excess of females on their host populations, while Wolbachia expressing CI do not. Here, we test the possibility that male mating capacity (MC) is correlated with Wolbachia-induced phenotype. We show that males of isopod hosts harbouring F Wolbachia possess a strong MC (i.e. are able to mate with several females in a short time), while those of species harbouring CI Wolbachia possess a weaker MC. This pattern may be explained either by the selection of high MC following the increase in female-biased sex ratios, or because the F phenotype would lead to population extinction in species where MC is not sufficiently high. This last hypotheses is nevertheless more constrained by population structure.

Moreau, Jerome; Rigaud, Thierry

2003-01-01

4

Seasonal variation in the metabolic rate and body composition of female grey seals: fat conservation prior to high-cost reproduction in a capital breeder?  

Microsoft Academic Search

Many animals rely on stored energy through periods of high energy demand or low energy availability or both. A variety of mechanisms may be employed to attain and conserve energy for such periods. Wild grey seals demonstrate seasonal patterns of energy storage and foraging behaviour that appear to maximize the allocation of energy to reproduction—a period characterized by both high

Carol E. Sparling; John R. Speakman; Michael A. Fedak

2006-01-01

5

Ejaculate components delay reproductive senescence while elevating female reproductive rate in an insect  

PubMed Central

Increased female reproductive rates usually result in accelerated senescence. This correlation provides a link between the evolutionary conflict of the sexes and aging when ejaculate components elevate female reproductive rates at the cost of future reproduction. It is not clear whether this female cost is manifest as shorter lifespan or an earlier onset or a steeper rate of reproductive senescence. It also is unclear whether beneficial ejaculates release females from reproductive trade-offs and, if so, which senescence parameters are affected. We examined these issues in the bedbug, Cimex lectularius, a long-lived insect that shows reduced female lifespan as well as female reproductive senescence at the male-determined mating frequency. We demonstrate experimentally that, independently of the mating frequency, females receiving more ejaculate show increased reproductive rates and enter reproductive senescence later than females receiving less ejaculate. The rate of reproductive senescence did not differ between treatments, and reproductive rates did not predict mortality. The ejaculate effects were consistent in inter- and intra-population crosses, suggesting they have not evolved recently and are not caused by inbreeding. Our results suggest that ejaculate components compensate for the costs of elevated female reproductive rates in bedbugs by delaying the onset of reproductive senescence. Ejaculate components that are beneficial to polyandrous females could have arisen because male traits that protect the ejaculate have positive pleiotropic effects and/or because female counteradaptations to antagonistic male traits exceed the neutralization of those traits. That males influence female reproductive senescence has important consequences for trade-offs between reproduction and longevity and for studies of somatic senescence.

Reinhardt, Klaus; Naylor, Richard A.; Siva-Jothy, Michael T.

2009-01-01

6

Estimating Reproductive Rates for Female Bears: Proportions Versus Transition Probabilities.  

National Technical Information Service (NTIS)

Estimating reproductive rate is an important element in understanding the demographic status of any bear population. These rates have been traditionally estimated by marking a sample of individuals with radiocollars and tracking them for the life of the t...

2010-01-01

7

Reproductive Rates in Australian Rodents Are Related to Phylogeny  

PubMed Central

Background The native rodents of Australia are commonly divided into two groups based on the time of their colonization of the Sahulian continent, which encompasses Australia, New Guinea, and the adjacent islands. The first group, the “old endemics,” is a diverse assemblage of 34 genera that are descended from a single colonization of the continent during the Pliocene. A second group, the “new endemics,” is composed of several native Rattus species that are descended from a single colonization during the Pleistocene. Finally, a third group is composed of three non-native species of Rattus and Mus introduced into Australia by humans over the last 200 years. Previous studies have claimed that the three groups differ in their reproductive rates and that this variation in rates is associated with the unique environmental conditions across Australia. We examined these hypotheses using phylogenetically controlled methods. Methodology and Results We examined the relationship between the reproductive rates of the Australian rodents and the environmental variations across the continent, as well as the epoch of their colonization of the continent. Our results revealed no significant correlation with environmental variables but a significant association between colonization age and all the reproductive parameters examined. Discussion Based on a larger phylogeny of the subfamily Murinae, we showed that significant differences in reproductive rates among colonization groups are shared with their closest relatives outside Sahul. Therefore, the lower reproductive rates in the old endemics are more likely to be the result of phylogenetic history and conservation of traits than an adaptation to the Australian environment. In the new endemics, we found a trend of increasing reproductive rates with diversification. We suggest that the differences in reproductive rates of the old endemic rodents and the native Rattus represent alternative adaptive strategies that have allowed them to utilize similar ecological niches across Australia.

Geffen, Eli; Rowe, Kevin C.; Yom-Tov, Yoram

2011-01-01

8

Intraspecific variation in body size and the rate of reproduction in female insects - adaptive allometry or biophysical constraint?  

PubMed

1. A high rate of reproduction may be costly if ecological factors limit immediate reproductive output as a fast metabolism compromises own future survival. Individuals with more reserves need more time and opportunity to realize their reproductive potential. Theory therefore predicts that the reproductive rate, defined as the investment in early reproduction in proportion to total potential, should decrease with body size within species. 2. However, metabolic constraints on body size- and temperature-dependent biological rates may impede biophysical adaptation. Furthermore, the sequential manner resources that are allocated to somatic vs. reproductive tissue during ontogeny may, when juveniles develop in unpredictable environments, further contribute to non-adaptive variation in adult reproductive rates. 3. With a model on female egg laying in insects, we demonstrate how variation in body reserves is predicted to affect reproductive rate under different ecological scenarios. Small females always have higher reproductive rates but shorter lifespans. However, incorporation of female host selectivity leads to more similar reproductive rates among female size classes, and oviposition behaviour is predicted to co-evolve with reproductive rate, resulting in small females being more selective in their choice and gaining relatively more from it. 4. We fed simulations with data on the butterfly Pararge aegeria to compare model predictions with reproductive rates of wild butterflies. However, simulated reproductive allometry was a poor predictor of that observed. Instead, reproductive rates were better explained as a product of metabolic constraints on rates of egg maturation, and an empirically derived positive allometry between reproductive potential and size. However, fitness is insensitive to moderate deviations in reproductive rate when oviposition behaviour is allowed to co-evolve in the simulations, suggesting that behavioural compensation may mitigate putative metabolic and developmental constraints. 5. More work is needed to understand how physiology and development together with compensatory behaviours interact in shaping reproductive allometry. Empirical studies should evaluate adaptive hypotheses against proper null hypotheses, including prediction from metabolic theory, preferentially by studying reproductive physiology in combination with behaviour. Conversely, inferences of constraint explanations on reproductive rates must take into consideration that adaptive scenarios may predict similar allometric exponents. PMID:22702372

Berger, David; Olofsson, Martin; Friberg, Magne; Karlsson, Bengt; Wiklund, Christer; Gotthard, Karl; Gilburn, Andre

2012-06-15

9

Reproductive rate, not dominance status, affects fecal glucocorticoid levels in breeding female meerkats.  

PubMed

Glucocorticoid hormones (GCs) have been studied intensively to understand the associations between physiological stress and reproductive skew in animal societies. However, we have little appreciation of the range of either natural levels within and among individuals, or the associations among dominance status, reproductive rate and GCs levels during breeding. To address these shortcomings, we examined variation in fecal glucocorticoid metabolites (fGC) during breeding periods in free-ranging female meerkats (Suricata suricatta) over 11 years. The vast majority of variation in fGC levels was found within breeding events by the same female (~87%), with the remaining variation arising among breeding events and among females. Concentrations of fGC generally tripled as pregnancy progressed. However, females with a high reproductive rate, defined as those conceiving within a month following parturition (mean = 9 days postpartum), showed significant reductions in fGC in the final 2 weeks before parturition. Despite these reductions, females with a high reproductive rate had higher fGC levels at conception of the following litter than those breeding at a low rate. After controlling for the higher reproductive rate of dominants, we found no association between levels of fGC and either age or dominance status. Our results suggest that one should be cautious about interpreting associations between dominance status, reproductive skew and GCs levels, without knowledge of the natural variation in GCs levels within and among females. PMID:22210199

Barrette, Marie-France; Monfort, Steven L; Festa-Bianchet, Marco; Clutton-Brock, Tim H; Russell, Andrew F

2011-12-22

10

High-resolution color photographic reproductions  

NASA Astrophysics Data System (ADS)

This paper will describe a fine-art reproduction process that: captures painting information with high-resolution color photographs; scans the information into a 300 megabyte digital file; performs a 3D color calibration in a dedicated hardware color-transform circuit; makes a master positive color transparency and makes a reproduction on polaroid color print film. The master transparency can be used to expose a large number of images. This combines the efficiency of instant photography with the color fidelity of digital color transforms.

McCann, John J.

1997-03-01

11

Intrinsic Growth Rates and Net Reproduction Rates in the Presence of Migration  

Microsoft Academic Search

Conventional measures of long-term population growth such as the intrinsic growth rate and the net reproduction rate assume migration rates to be zero. We develop expressions for analogous measures that register the impact of net migration rates, and we develop a simple method of estimating their values. Applying these new measures to data for developed countries shows that allowance for

Samuel H. Preston; Haidong Wang

2007-01-01

12

Exploring individual quality: Basal metabolic rate and reproductive performance in storm-petrels  

USGS Publications Warehouse

Despite evidence that some individuals achieve both superior reproductive performance and high survivorship, the factors underlying variation in individual quality are not well understood. The compensation and increased-intake hypotheses predict that basal metabolic rate (BMR) influences reproductive performance; if so, variation in BMR may be related to differences in individual quality. We evaluated whether BMR measured during the incubation period provides a proximate explanation for variation in individual quality by measuring the BMRs and reproductive performance of Leach's storm-petrels (Oceanodroma leucorhoa) breeding on Kent Island, New Brunswick, Canada, during 2000 and 2001. We statistically controlled for internal (body mass, breeding age, sex) and external (year, date, time of day) effects on BMR. We found that males with relatively low BMRs hatched their eggs earlier in the season and that their chicks' wing growth rates were faster compared to males with relatively high BMRs. Conversely, BMR was not related to egg volume, hatching date, or chick growth rate for females or to lifetime (???23 years) hatching success for either sex. Thus, for males but not for females, our results support the compensation hypothesis. This hypothesis predicts that animals with low BMRs will achieve better reproductive performance than animals with high BMRs because they have lower self-maintenance costs and therefore can apportion more energy to reproduction. These results provide evidence that intraspecific variation in reproductive performance is related to BMR and suggest that BMR may influence individual quality in males. ?? The Author 2005. Published by Oxford University Press on behalf of the International Society for Behavioral Ecology. All rights reserved.

Blackmer, A. L.; Mauck, R. A.; Ackerman, J. T.; Huntington, C. E.; Nevitt, G. A.; Williams, J. B.

2005-01-01

13

Influence of copper on the feeding rate, growth and reproduction of the golden apple snail, Pomacea canaliculata Lamarck.  

PubMed

The influence of copper on feeding rate, growth, and reproduction of Pomacea canaliculata Lamarck was evaluated. Ten days of exposure to copper of relatively high concentration (67.5 microg/L) reduced the snails' feeding rate and retarded their growth. Exposure to 20 microg/L after 36 days increased feeding rate to 28%. After 20 days of exposure at 30 microg/L, snail's growth was significant but thereafter declined. Growth of all snails including control was negligible by day 50 when snails were in the reproductive state. Copper did not affect reproduction. PMID:17999015

Peña, Silvia C; Pocsidio, Glorina N

2007-11-13

14

Age at first reproduction and growth rate are independent of basal metabolic rate in mammals  

Microsoft Academic Search

This study tested an emergent prediction from the Metabolic Theory of Ecology (MTE) that the age at first reproduction (?) of a mammal is proportional to the inverse of its mass-corrected basal metabolic rate: $$ \\\\alpha \\\\propto (B\\/M)^{ - 1}. $$ The hypothesis was tested with multiple regression models of conventional species data and phylogenetically independent contrasts\\u000a of 121 mammal

Barry G. Lovegrove

2009-01-01

15

High survival during hibernation affects onset and timing of reproduction.  

PubMed

The timing of reproduction is one of the most crucial life history traits, with enormous consequences for the fitness of an individual. We investigated the effects of season and timing of birth on local survival probability in a small mammalian hibernator, the common dormouse (Muscardinus avellanarius). Local monthly survival probability was lowest in the early active season (May-August, ?(adult) = 0.75-0.88, ?(juvenile) = 0.61-0.68), increased during the late active season (August-October), and highest during hibernation (October-May, ?(adult) = 0.96-0.98, ?(juvenile) = 0.81-0.94). Consequently, dormice had an extremely high winter survival probability. We observed two peaks in the timing of reproduction (June and August/September, respectively), with the majority of juveniles born late in the active season. Although early investment in reproduction seems the better life history tactic [survival probability until onset of reproduction: ?(born early) = 0.46, 95% confidence interval (CI) 0.28-0.64; ?(born late) = 0.19, 95% CI = 0.09-0.28], only females with a good body condition (significantly higher body mass) invest in reproduction early in the year. We suggest the high over-winter survival in dormice allows for a unique life history pattern (i.e., combining slow and fast life history tactics), which leads to a bimodal seasonal birth pattern: (1) give birth as early as possible to allow even the young to breed before hibernating, and/or (2) give birth as late as possible (leaving just enough time for these young to fatten) and enter directly into a period associated with the highest survival rates (hibernation) until maturity. PMID:22095523

Bieber, Claudia; Juškaitis, Rimvydas; Turbill, Christopher; Ruf, Thomas

2011-11-18

16

High reproductive skew in tropical hover wasps.  

PubMed Central

A plethora of recent models examines how genetic and environmental factors might influence partitioning of reproduction ('skew') in animal societies, but empirical data are sparse. We used three microsatellite loci to estimate skew on 13 nests of the Malaysian hover wasp, Liostenogaster flavolineata. Groups are small in L. flavolineata (1-10 females) and all females are capable of mating and laying eggs. Despite considerable variation between nests in parameters expected to influence skew, skew was uniformly high. On 11 of the 13 nests, all female eggs had been laid by a single dominant female. A second female had laid one to two out of 5-10 eggs respectively on the two remaining nests. A likelihood analysis suggested that on average, 90% of the male eggs had also been laid by the dominant. The slightly lower skew among male eggs might reflect the lower average relatedness of subordinates to male versus female offspring of the dominant. We suggest that high skew in L. flavolineata may result from strong ecological constraints and a relatively high probability that a subordinate will eventually inherit the dominant, egg-laying position.

Sumner, Seirian; Casiraghi, Maurizio; Foster, William; Field, Jeremy

2002-01-01

17

High Growth Rate MOVPE  

NASA Astrophysics Data System (ADS)

In this chapter, growth mechanism of GaN and AlGaN by MOVPE is described in detail. The parasitic reaction that generates particulates in vapor phase is the most probable limiting factor of maximum growth rate of GaN and AlGaN. Both experimental and quantum chemical study of vapor phase reaction between organo-metals and ammonia is described. From the close insight of vapor phase reaction, high flow speed three layered gas injection has been developed. By employing this three-layer gas-injection, GaN was grown with growth rate as high as 28?m/h at atmospheric pressure. As long as the present growth conditions are concerned, SIMS and XRD results suggested that the growth rate of 12?m/h would be a practical limitation of good quality material in terms of electrical and structural properties.

Matsumoto, K.; Tokunaga, H.; Ubukata, A.; Ikenaga, K.; Fukuda, Y.; Yano, Y.; Tabuchi, T.; Kitamura, Y.; Koseki, S.; Yamaguchi, A.; Uematsu, K.

18

The dependence of reproductive rate on cell size and temperature in freshwater ciliated protozoa  

Microsoft Academic Search

Reproductive rates have been calculated for ten species of ciliated protozoa in defined conditions. Interspecific double log regressions of generation time vs. cell volume have been computed at each of three temperatures (8.5° C, 15° C, and 20° C) indicating a significant dependence of reproductive rate on cell size. Recorded generation times varied from 6.38 h in Vorticella microstoma at

Bland J. Finlay

1977-01-01

19

Reproductive performance and mortality rate in Menz and Horro sheep following controlled breeding in Ethiopia  

Microsoft Academic Search

The reproductive and lamb mortality data (n=4890) of Horro and Menz ewes following controlled breeding in Ethiopia were analyzed. Sheep were treated with flugestone acetate (FGA) intravaginal sponges during the wet and dry seasons to compare the reproductive performance of the two indigenous Ethiopian highland sheep breeds. There was a significant (P<0.001) difference in the fertility rate (conception rate) (79%

A. Berhan; J. Van Arendonk

2006-01-01

20

Individual heterogeneity in reproductive rates and cost of reproduction in a long-lived vertebrate.  

PubMed

Individual variation in reproductive success is a key feature of evolution, but also has important implications for predicting population responses to variable environments. Although such individual variation in reproductive outcomes has been reported in numerous studies, most analyses to date have not considered whether these realized differences were due to latent individual heterogeneity in reproduction or merely random chance causing different outcomes among like individuals. Furthermore, latent heterogeneity in fitness components might be expressed differently in contrasted environmental conditions, an issue that has only rarely been investigated. Here, we assessed (i) the potential existence of latent individual heterogeneity and (ii) the nature of its expression (fixed vs. variable) in a population of female Weddell seals (Leptonychotes weddellii), using a hierarchical modeling approach on a 30-year mark-recapture data set consisting of 954 individual encounter histories. We found strong support for the existence of latent individual heterogeneity in the population, with "robust" individuals expected to produce twice as many pups as "frail" individuals. Moreover, the expression of individual heterogeneity appeared consistent, with only mild evidence that it might be amplified when environmental conditions are severe. Finally, the explicit modeling of individual heterogeneity allowed us to detect a substantial cost of reproduction that was not evidenced when the heterogeneity was ignored. PMID:23919151

Chambert, Thierry; Rotella, Jay J; Higgs, Megan D; Garrott, Robert A

2013-05-31

21

Influence of Copper on the Feeding Rate, Growth and Reproduction of the Golden Apple Snail, Pomacea canaliculata Lamarck  

Microsoft Academic Search

The influence of copper on feeding rate, growth, and reproduction of Pomacea canaliculata Lamarck was evaluated. Ten days of exposure to copper of relatively high concentration (67.5 ?g\\/L) reduced the snails’ feeding\\u000a rate and retarded their growth. Exposure to 20 ?g\\/L after 36 days increased feeding rate to 28%. After 20 days of exposure\\u000a at 30 ?g\\/L, snail’s growth was significant but thereafter

Silvia C. Peña; Glorina N. Pocsidio

2007-01-01

22

Estimating Pesticide Effects on Fecundity Rates of Wild Birds Using Current Laboratory Reproduction Tests  

EPA Science Inventory

The manuscript reviews the issues concerning the use of results on pesticide effects from laboratory avian reproduction tests for estimating potential impacts of pesticides on fecundity rates in avian population models....

23

Potential liability of reproductive endocrinologists for high order multiple gestation  

PubMed Central

Background In light of the recent octuplet birth and the accompanying intensive media coverage, there has been much attention on high order multiple births resulting from assisted reproductive technology. Objectives The purpose of this commentary is to review 1) the relative contribution of ART to high order multiple gestation and its impact on infant morbidity, mortality, and health care dollar loss; 2) American Society of Reproductive Medicine’s guidelines for the number of embryos transferred in ART; and 3) how reproductive endocrinologists can lessen their exposure to litigation by following the ASRM guidelines for the number of embryos transferred and documenting proper informed consent in the medical records. Recommendations In situations in which the number of embryos transferred is in excess of the ASRM guidelines, justification for deviating from the ASRM guidelines should be justifiable and documented in the medical records.

Phelps, John

2010-01-01

24

Reproductive effects of sodium borates on male employees: birth rate assessment.  

PubMed Central

OBJECTIVES--The purpose of the study was to investigate potential reproductive effects of sodium borates on occupationally exposed male employees at a large mining and production facility in the Mojave Desert of California. METHODS--The standardised birth ratio (SBR) was used to assess fertility of the male employees. Live births were the measured end point, and the rate of female to male offspring was also assessed. Data were collected through a questionnaire after a series of on site introductory and explanatory meetings with the employees. Initial non-responders were followed up by telephone. Medical insurance records were assessed for those who declined to participate. RESULTS--The questionnaire was a good method of ascertainment for live births. There was no evidence of selection bias in the results. There was a highly significant excess of offspring fathered by the male employees. There was no evidence of a relation between exposure and this excess of offspring, nor were there any temporal differences during the period of observation (> 30 years). Also, there was an excess of the percentage of female offspring fathered by these male employees. This excess of female offspring was not significant. There was no evidence of an exposure relation to sodium borates with this excess of female offspring nor were there any temporal differences. CONCLUSION--Under the conditions studied, there were no adverse reproductive effects of high borate doses as reported from oral ingestion studies in animals.

Whorton, M D; Haas, J L; Trent, L; Wong, O

1994-01-01

25

Patient dropout in an assisted reproductive technology program: implications for pregnancy rates  

Microsoft Academic Search

Objective: To study patient dropout and its impact on crude and cumulative pregnancy rates (PRs) after assisted reproductive technology (ART).Design: Retrospective cohort study.Setting: University hospital-based tertiary care fertility clinic.Patient(s): Two hundred two couples applying for their first ART treatment cycle.Main Outcome Measure(s): Drop-out rate and PR per cycle, cumulative drop-out rate and cumulative PR.Result(s): After three treatment cycles, the cumulative

Jolande A. Land; Dorette A. Courtar; Johannes L. H. Evers

1997-01-01

26

Comparison of Gene Repertoires and Patterns of Evolutionary Rates in Eight Aphid Species That Differ by Reproductive Mode  

PubMed Central

In theory, the loss of sexual reproduction is expected to result in the accumulation of deleterious mutations. In aphids, two main types of life cycle, cyclic and obligate parthenogenesis, represent respectively “sexual” and “asexual” reproductive modes. We used the complete pea aphid genome and previously published expressed sequence tags (ESTs) from two other aphid species. In addition, we obtained 100,000 new ESTs from five more species. The final set comprised four sexual and four asexual aphid species and served to test the influence of the reproductive mode on the evolutionary rates of genes. We reconstructed coding sequences from ESTs and annotated these genes, discovering a novel peptide gene family that appears to be among the most highly expressed transcripts from several aphid species. From 203 genes found to be 1:1 orthologs among the eight species considered, we established a species tree that partly conflicted with taxonomy (for Myzus ascalonicus). We then used this topology to evaluate the dynamics of evolutionary rates and mutation accumulation in the four sexual and four asexual taxa. No significant increase of the nonsynonymous to synonymous ratio or of nonsynonymous mutation numbers was found in any of the four branches for asexual taxa. We however found a significant increase of the synonymous rate in the branch leading to the asexual species Rhopalosiphum maidis, which could be due to a change in the mutation rate or to an increased number of generations implied by its change of life cycle.

Ollivier, M.; Gabaldon, T.; Poulain, J.; Gavory, F.; Leterme, N.; Gauthier, J.-P.; Legeai, F.; Tagu, D.; Simon, J. C.; Rispe, C.

2012-01-01

27

Effects of size and growth rate on vegetative reproduction in Typha  

Microsoft Academic Search

The objective of this study was to separate the effects of plant biomass and growth rate on vegetative reproduction in two species of cat-tail, Typha latifolia and T. angustifolia. Replicate clones of both species were grown under conditions of 100%, 42%, 24%, and 9% full sunlight with harvests at 41, 70, and 91 days after shading. T. angustifolia produced most

James B. Grace; Robert G. Wetzel

1981-01-01

28

The influence of H 2 S on reproduction rate in paramecium caudatum  

Microsoft Academic Search

Conclusion Sulfhydryl in H2S and Na2S in proper concentration, accelerates the reproduction rate ofParamecium caudatum. This fact is further support for the thesis ofHammett that the -SH group is an essential stimulus to growth by increase in cell number.

Margaret J. Sharpe

1930-01-01

29

Ma×imum reproductive rate of fish at low population sizes  

Microsoft Academic Search

We examine a database of over 700 spawner-recruitment series to search for parameters that are constant, or nearly so, at the level of a species or above. We find that the number of spawners produced per spawner each year at low populations, i.e., the maximum annual reproductive rate, is relatively constant within species and that there is relatively little variation

Ransom A. Myers; Keith G. Bowen; Nicholas J. Barrowman

1999-01-01

30

Using potential reproductive rates to predict mating competition among individuals qualified to mate  

Microsoft Academic Search

The potential reproductive rate (PRR), which is the offspring production per unit time each sex would achieve if unconstrained by mate availability, often differs between the sexes. An increasing sexual difference in PRR predicts an intensified mating competition among the sex with the higher PRR. The use of PRR can provide detailed predictions of when, where, and how the intensity

Ingrid Ahnesjo; Charlotta Kvarnemo; Sami Merilaitaa

2001-01-01

31

Pollen flow and effects of population structure on selfing rates and female and male reproductive success in fragmented Magnolia stellata populations  

PubMed Central

Background Fragmentation of plant populations may affect mating patterns and female and male reproductive success. To improve understanding of fragmentation effects on plant reproduction, we investigated the pollen flow patterns in six adjacent local populations of Magnolia stellata, an insect-pollinated, threatened tree species in Japan, and assessed effects of maternal plant (genet) size, local genet density, population size and neighboring population size on female reproductive success (seed production rates), and effects of mating distance, paternal genet size, population size and separation of populations on male reproductive success. Results The seed production rate, i.e. the proportion of ovules that successfully turned into seeds, varied between 1.0 and 6.5%, and increased with increasing population size and neighboring population size, and with decreasing maternal genet size and local genet density. The selfing rate varied between 3.6 and 28.9%, and increased with increasing maternal genet size and with declining local genet density. Male reproductive success increased with increasing paternal genet size, and decreased with increasing mating distance and separation of population. Pollen flow between the populations was low (6.1%) and highly leptocurtic. Conclusions Our results indicate that habitat fragmentation, separation and reduced size of populations, affected mating patterns and reproductive success of M. stellata. Local competition for pollinators and plant display size were likely to alter the reproductive success.

2013-01-01

32

Human disturbance influences reproductive success and growth rate in California sea lions (Zalophus californianus).  

PubMed

The environment is currently undergoing changes at both global (e.g., climate change) and local (e.g., tourism, pollution, habitat modification) scales that have the capacity to affect the viability of animal and plant populations. Many of these changes, such as human disturbance, have an anthropogenic origin and therefore may be mitigated by management action. To do so requires an understanding of the impact of human activities and changing environmental conditions on population dynamics. We investigated the influence of human activity on important life history parameters (reproductive rate, and body condition, and growth rate of neonate pups) for California sea lions (Zalophus californianus) in the Gulf of California, Mexico. Increased human presence was associated with lower reproductive rates, which translated into reduced long-term population growth rates and suggested that human activities are a disturbance that could lead to population declines. We also observed higher body growth rates in pups with increased exposure to humans. Increased growth rates in pups may reflect a density dependent response to declining reproductive rates (e.g., decreased competition for resources). Our results highlight the potentially complex changes in life history parameters that may result from human disturbance, and their implication for population dynamics. We recommend careful monitoring of human activities in the Gulf of California and emphasize the importance of management strategies that explicitly consider the potential impact of human activities such as ecotourism on vertebrate populations. PMID:21436887

French, Susannah S; González-Suárez, Manuela; Young, Julie K; Durham, Susan; Gerber, Leah R

2011-03-16

33

High Repetition Rate Chemical Laser.  

National Technical Information Service (NTIS)

A hydrogen fluoride (HF) chemical laser with an active medium 10 cm in length was constructed for operation at high pulse repetition rates using transverse excitation. The device employed 29 resistively loaded electrodes; open-cycle operation was achieved...

T. V. Jacobson G. H. Kimbell A. R. Lambert D. R. Snelling

1973-01-01

34

Strain-rate effects for high-strain-rate computations  

Microsoft Academic Search

This paper examines the effect of strain rates for computations involving high strain-rates, beyond 103 s - 1. Although it is generally agreed that there is an enhanced rate effect at these higher rates, there is uncertainty regarding the interpretation of dynamic test data, the form of the high-rate effect, and the effect of the high rates on practical problems

G. R. Johnson; T. J. Holmquist; C. E. Anderson Jr.; A. E. Nicholls

2006-01-01

35

Periodic Matrix Population Models: Growth Rate, Basic Reproduction Number, and Entropy  

Microsoft Academic Search

This article considers three different aspects of periodic matrix population models. First, a formula for the sensitivity\\u000a analysis of the growth rate ? is obtained that is simpler than the one obtained by Caswell and Trevisan. Secondly, the formula for the basic reproduction\\u000a number ?0 in a constant environment is generalized to the case of a periodic environment. Some inequalities

Nicolas Bacaër

2009-01-01

36

Contaminant Concentrations and Reproductive Rate of Lake Superior Bald Eagles, 1989–2001  

Microsoft Academic Search

We investigated the trend in contaminant concentrations in Lake Superior bald eagles (Haliaeetus leucocephalus) from 1989–2001, and examined the relationship of contaminant concentrations to eagle reproductive rate during that time. Concentrations of dichloro-diphenyl-dichloroethylene (DDE) and total polychlorinated biphenyls (PCBs) in nestling blood plasma samples decreased significantly from 1989-2001 (p=0.007 for DDE, p=0.004 for total PCBs). Mean contaminant concentrations in eaglet

Cheryl R. Dykstra; Michael W. Meyer; Paul W. Rasmussen; D. Keith Warnke

2005-01-01

37

High-rate artificial lift  

SciTech Connect

This paper summarizes the major considerations in the selection, design, installation, operation, or repair of high-rate artificial-lift systems. The major types of artificial lift - sucker-rod pumps, gas-lift systems, electrical submersible pumps, hydraulic pumps and jets, and hydraulic turbine-driven pumps - will be discussed. An extensive bibliography of artificial-lift papers is included.

Clegg, J.D.

1988-03-01

38

Divergent selection on, but no genetic conflict over, female and male timing and rate of reproduction in a human population.  

PubMed

The sexes often have different phenotypic optima for important life-history traits, and because of a largely shared genome this can lead to a conflict over trait expression. In mammals, the obligate costs of reproduction are higher for females, making reproductive timing and rate especially liable to conflict between the sexes. While studies from wild vertebrates support such sexual conflict, it remains unexplored in humans. We used a pedigreed human population from preindustrial Finland to estimate sexual conflict over age at first and last reproduction, reproductive lifespan and reproductive rate. We found that the phenotypic selection gradients differed between the sexes. We next established significant heritabilities in both sexes for all traits. All traits, except reproductive rate, showed strongly positive intersexual genetic correlations and were strongly genetically correlated with fitness in both sexes. Moreover, the genetic correlations with fitness were almost identical in men and women. For reproductive rate, the intersexual correlation and the correlation with fitness were weaker but again similar between the sexes. Thus, in this population, an apparent sexual conflict at the phenotypic level did not reflect an underlying genetic conflict over the studied reproductive traits. These findings emphasize the need for incorporating genetic perspectives into studies of human life-history evolution. PMID:24107531

Bolund, Elisabeth; Bouwhuis, Sandra; Pettay, Jenni E; Lummaa, Virpi

2013-10-09

39

Diet effects on female reproduction in high growth (hg/hg) mice that are deficient in the Socs-2 gene.  

PubMed

The detrimental effect of larger body size on reproductive performance has been well documented in mouse models of overgrowth, such as Growth Hormone (GH) transgenics. This study describes the reproductive performance of the High Growth (HG) mouse model of overgrowth. The HG mouse model exhibits overgrowth due to a partially recessive autosomal mutation that increases growth rate and mature body size. The HG phenotype results from the lack of expression of Socs-2, which negatively regulates GH signaling. C57BL/6J (C57) and congenic C57BL/6J-hg/hg (HG) female mice were fed four diets differing in protein and energy content, starting at 8 weeks of age. A complete reproductive cycle from mating to weaning was evaluated. HG mice were 40% larger than C57 and had a higher feed intake throughout the experiment. Significant genotype x diet interactions were detected for growth, body composition and reproductive traits. HG females showed poor reproductive performance compared to controls as demonstrated by their lower fertility during mating, which was not overcome by changes in the diet. No differences were detected in litter size, but HG animals exhibited a longer gestation length and heavier pup weaning weights compared to controls. Reproductive impairment in HG seems to be the consequence of the lack of Socs-2 independent of the effects of increased body size on reproduction. PMID:15535462

Corva, Pablo M; Mucci, Nicolás C; Evans, Kristin; Medrano, Juan F

40

Influence of advanced age on the blastocyst development rate and pregnancy rate in assisted reproductive technology  

Microsoft Academic Search

Objective: To evaluate the percentage of blastocysts developing, the pregnancy rate, the implantation rate, and the abortion rate in women >40 years of age using a cell-free culture system for the development of viable human blastocysts.Design: Retrospective clinical study.Setting: Private IVF units.Patient(s): Two hundred ninety-three cycles in patients undergoing IVF treatment for infertility. Sixty-two cycles were in patients ?40 years

Kostas Pantos; Vasilis Athanasiou; Konstantinos Stefanidis; Dimitris Stavrou; Terpsi Vaxevanoglou; Margarita Chronopoulou

1999-01-01

41

[High dose rate prostate brachytherapy].  

PubMed

This article aims at presenting the interest of high dose rate brachytherapy in the radiation treatment of prostatic adenocarcinoma. We will discuss successively the biological and dosimetric specificity of brachytherapy for this particular cancer. Afterwards, we will review the main phase II and III studies, the therapeutic indications in the daily practice from the evidence based medicine as well as the techniques of external beam radiation therapy for the same indications. Finally, the principal avenues of development will be discussed. PMID:23578898

Nickers, P; Blanchard, P; Hannoun-Lévi, J-M; Bossi, A; Chapet, O; Guérif, S

2013-04-08

42

Strain-rate effects for high-strain-rate computations  

NASA Astrophysics Data System (ADS)

This paper examines the effect of strain rates for computations involving high strain-rates, beyond 103 s - 1. Although it is generally agreed that there is an enhanced rate effect at these higher rates, there is uncertainty regarding the interpretation of dynamic test data, the form of the high-rate effect, and the effect of the high rates on practical problems of interest. This article provides an assessment of the high-rate effect for Taylor (cylinder impact) tests, a determination of high-rate constitutive model constants from the Taylor tests, and the effect of the high-rate response on penetration computations. The computations are performed with the Johnson-Cook constitutive model and an enhanced (high-rate) form of the Johnson-Cook model.

Johnson, G. R.; Holmquist, T. J.; Anderson, C. E., Jr.; Nicholls, A. E.

2006-08-01

43

Evolutionary feedbacks between reproductive mode and mutation rate exacerbate the paradox of sex.  

PubMed

Evolutionary theory suggests that low mutation rates should favor the persistence of asexuals. Additionally, given the observation that most nonneutral mutations are deleterious, asexuality may strengthen selection for reduced mutation rates. This reciprocal relationship raises the possibility of a positive feedback loop between sex and mutation rate. We explored the consequences of this evolutionary feedback with an individual-based model in which a sexual population is continually challenged by the introduction of asexual clones. We found that asexuals were more likely to spread in a population when mutation rates were able to evolve relative to a model in which mutation rates were held constant. In fact, under evolving mutation rates, asexuals were able to spread to fixation even when sexuals faced no cost of sex whatsoever. The added success of asexuals was the result of their ability to evolve lower mutation rates and thereby slow the process of mutation accumulation that otherwise limited their spread. Given the existence of ample mutation rate variation in natural populations, our findings show that the evolutionary feedback between sex and mutation rate may intensify the "paradox of sex," supporting the argument that deleterious mutation accumulation alone is likely insufficient to overcome the reproductive advantage of asexual competitors in the short term. PMID:19863589

Sloan, Daniel B; Panjeti, Vijay G

2009-10-23

44

The reproductive and developmental toxicity of High Flash Aromatic Naphtha.  

PubMed

Catalytic reforming is a refining process that converts naphthenes to aromatics by dehydrogenation to make higher octane gasoline blending components. A portion of this wide boiling range hydrocarbon stream can be separated by distillation and used for other purposes. One such application is a mixture of predominantly 9-carbon aromatic molecules (C9 aromatics, primarily isomers of ethyltoluene and trimethylbenzene), which is removed and used as a solvent--High Flash Aromatic Naphtha. A program was initiated to assess the toxicological properties of High Flash Aromatic Naphtha since there may be human exposure through inhalation or external body contact. The current study was conducted to assess the potential for developmental toxicity in the mouse and for reproductive toxicity in the rat. In the developmental toxicity study in CD-1 mice, exposure of dams by inhalation to near lethal levels (1500 ppm) resulted in fetal mortality, reduced weight, delayed ossification, and an increased incidence of cleft palate. At 500 ppm, a level at which maternal weight gain was slightly reduced, fetal weight gain was also reduced, but there was no other evidence of developmental effects. The lowest exposure level (100 ppm) did not cause any maternal or developmental toxicity. There was no consistent evidence of reproductive toxicity in rats, even at exposure levels which resulted in significantly reduced parental weight gain. In addition, when parental exposure was stopped on GD (gestation day) 20, birth weights as well as postnatal survival were generally similar to control values, even in the 1500 ppm exposure group. Postnatal weight gain was also similar to controls early in weaning, but, if maternal exposure was reinitiated, weight gain was reduced in the high exposure group. However, when exposure was continued until delivery, pups in the high exposure group exhibited reduced litter size, birth weight and poor survival. Thus it was likely that the reduction in fetal weight, seen in the developmental toxicity study in mice, was transient and had no postnatal consequences if maternal exposure was terminated at any time prior to delivery. PMID:2237929

McKee, R H; Wong, Z A; Schmitt, S; Beatty, P; Swanson, M; Schreiner, C A; Schardein, J L

45

Male and female differential reproductive rate could explain parental transmission asymmetry of mutation origin in Hirschsprung disease  

PubMed Central

Hirschsprung disease (HSCR, aganglionic megacolon) is a complex and heterogeneous disease with an incidence of 1 in 5000 live births. Despite the multifactorial determination of HSCR in the vast majority of cases, there is a monogenic subgroup for which private rare RET coding sequence mutations with high penetrance are found (45% of HSCR familial cases). An asymmetrical parental origin is observed for RET coding sequence mutations with a higher maternal inheritance. A parent-of-origin effect is usually assumed. Here we show that a differential reproductive rate for males and females also leads to an asymmetrical parental origin, which was never considered as a possible explanation till now. In the case of HSCR, we show a positive association between penetrance of the mutation and parental transmission asymmetry: no parental transmission asymmetry is observed in sporadic RET CDS mutation carrier cases for which penetrance of the mutation is low, whereas a parental transmission asymmetry is observed in affected sib-pairs for which penetrance of the mutation is higher. This allows us to conclude that the explanation for this parental asymmetry is that more severe mutations have resulted in a differential reproductive rate between male and female carriers.

Jannot, Anne-Sophie; Amiel, Jeanne; Pelet, Anna; Lantieri, Francesca; Fernandez, Raquel M; Verheij, Joke B G M; Garcia-Barcelo, Merce; Arnold, Stacey; Ceccherini, Isabella; Borrego, Salud; Hofstra, Robert M W; Tam, Paul K H; Munnich, Arnold; Chakravarti, Aravinda; Clerget-Darpoux, Francoise; Lyonnet, Stanislas

2012-01-01

46

Individualised controlled ovarian stimulation (iCOS): maximising success rates for assisted reproductive technology patients  

PubMed Central

Background In the last two decades, pregnancy rates for patients undergoing in-vitro fertilisation (IVF) have significantly increased. Some of the major advances responsible for this improvement were the introduction of controlled ovarian stimulation (COS) for the induction of multiple follicle development, and the utilisation of mid-luteal gonadotropin-releasing hormone agonists to achieve pituitary down-regulation and full control of the cycle. As a result, a combination of a gonadotropin-releasing hormone agonist with high doses (150-450 IU/day) of recombinant follicle-stimulating hormone has become the current standard approach for ovarian stimulation. However, given the heterogeneity of patients embarking on IVF, and the fact that many different drugs can be used alone or in different combinations (generating multiple potential protocols of controlled ovarian stimulation), we consider the need to identify special populations of patients and adapt treatment protocols accordingly, and to implement a more individualised approach to COS. Discussion Studies on mild, minimal and natural IVF cycles have yielded promising results, but have focused on fresh embryo transfers and included relatively young patient populations who generally have the potential for more favourable outcomes. The efficacy of these protocols in patients with a poorer prognosis remains to be tested. When comparing protocols for COS, it is important to think beyond current primary endpoints, and to consider the ideal quality and quantity of oocytes and embryos being produced per stimulated patient, in order to achieve a pregnancy. We should also focus on the cumulative pregnancy rate, which is based on outcomes from fresh and frozen embryos from the same cycle of stimulation. Individualised COS (iCOS) determined by the use of biomarkers to test ovarian reserve has the potential to optimise outcomes and reduce safety issues by adapting treatment protocols according to each patient's specific characteristics. As new objective endocrine, paracrine, functional and/or genetic biomarkers of response are developed, iCOS can be refined further still, and this will be a significant step towards a personalised approach for IVF. Conclusions A variety of COS protocols have been adopted, with mixed success, but no single approach is appropriate for all patients within a given population. We suggest that treatment protocols should be adapted for individual patients through iCOS; this approach promises to be one of the first steps towards implementing personalised medicine in reproductive science.

2011-01-01

47

High burn rate solid composite propellants  

Microsoft Academic Search

High burn rate propellants help maintain high levels of thrust without requiring complex, high surface area grain geometries. Utilizing high burn rate propellants allows for simplified grain geometries that not only make production of the grains easier, but the simplified grains tend to have better mechanical strength, which is important in missiles undergoing high-g accelerations. Additionally, high burn rate propellants

Timothy D. Manship

2010-01-01

48

Malaria infection and feather growth rate predict reproductive success in house martins.  

PubMed

Carry-over effects take place when events occurring in one season influence individual performance in a subsequent season. Blood parasites (e.g. Plasmodium and Haemoproteus) have strong negative effects on the body condition of their hosts and could slow the rate of feather growth on the wintering grounds. In turn, these winter moult costs could reduce reproductive success in the following breeding season. In house martins Delichon urbica captured and studied at a breeding site in Europe, we used ptilochronology to measure growth rate of tail feathers moulted on the winter range in Africa, and assessed infection status of blood parasites transmitted on the wintering grounds. We found a negative association between haemosporidian parasite infection status and inferred growth rate of tail feathers. A low feather growth rate and blood parasite infections were related to a delay in laying date in their European breeding quarters. In addition, clutch size and the number of fledglings were negatively related to a delayed laying date and blood parasite infection. These results stress the importance of blood parasites and feather growth rate as potentially mechanisms driving carry-over effects to explain fitness differences in wild populations of migratory birds. PMID:22961369

Marzal, Alfonso; Reviriego, Maribel; Hermosell, Ignacio G; Balbontín, Javier; Bensch, Staffan; Relinque, Carmen; Rodríguez, Laura; Garcia-Longoria, Luz; de Lope, Florentino

2012-09-11

49

An Alternative Model of the Reproductive Rate of HIV Infection: Formulation, Evaluation, and Implications for Risk Reduction Interventions.  

ERIC Educational Resources Information Center

Estimates of the reproductive rate of infection with the human immunodeficiency virus (HIV), obtained through a Bernoulli process model, indicate that decreasing the infectivity of the virus, through the use of condoms, for example, is more effective at reducing the infection rate than is limiting the number of sexual partners. (SLD)

Pinkerton, Steven D.; Abramson, Paul R.

1994-01-01

50

High-Redshift Supernova Rates  

Microsoft Academic Search

We use a sample of 42 supernovae detected with the Advanced Camera for Surveys on board the Hubble Space Telescope as part of the Great Observatories Origins Deep Survey to measure the rate of core-collapse supernovae to z~0.7 and Type Ia supernovae to z~1.6. This significantly increases the redshift range at which supernova rates have been estimated from observations. The

Tomas Dahlen; Louis-Gregory Strolger; Adam G. Riess; Bahram Mobasher; Ranga-Ram Chary; Christopher J. Conselice; Andrew S. Fruchter; Mauro Giavalisco; Mario Livio; Piero Madau; Nino Panagia; John L. Tonry

2004-01-01

51

Life table parameters, reproductive rate, intrinsic rate of increase, and estimated cost of rearing Podisus maculiventris (Heteroptera: Pentatomidae) on an artificial diet.  

PubMed

The impact of an insect-free artificial diet provided at nymphal and/or adult stage upon the developmental rate, life table parameters, and fertility table parameters was examined for Podisus maculiventris (Say). This study showed that when fed an insect-free artificial diet during both the nymphal and adult stage, developmental time was prolonged, preoviposition period was extended, and reproductive rate (R0) and intrinsic rate of increase (r) were significantly lower than when fed larval insect prey at both nymphal and adult stages. Additionally, feeding larval prey to adults reared as nymphs on an artificial diet significantly increased the proportion of fertile females, the number of eggs laid by mated females, the reproductive rate and intrinsic rate of increase, but the mean generation time was not significantly different. Likewise, feeding artificial diet to adults reared on larval prey resulted in a significant reduction in reproductive rate and intrinsic rate of increase. The "realized" cost to rear P. maculiventris on the artificial diet was calculated (as the cost to double the population size) using raw material cost, fertility table parameters and doubling time values. Raw material cost for rearing P. maculiventris colony on Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae) was only 1.4 times higher than the cost of artificial diet raw materials required to rear the same size colony. However, the realized cost of rearing was 3.5 times higher when rearing on artificial diet because of the prolonged developmental time and reduced reproductive output. The cost efficiency of rearing a beneficial insect on an artificial diet that decreases the intrinsic rate of increase of a colony is discussed, as well as the advantages and disadvantages of supplementing adult diets with natural prey at the reproductive stage. PMID:11777035

Wittmeyer, J L; Coudron, T A

2001-12-01

52

Effects of subcutaneous transmitters on reproduction, incubation behavior, and annual return rates of female wood ducks  

USGS Publications Warehouse

Radiotransmitters attached externally to breeding waterfowl can have a variety of negative effects. Implanted transmitters can reduce potential deleterious effects; abdominal implants are used most commonly in waterfowl. Methods also have been developed to implant transmitters subcutaneously, but effects of subcutaneous implants on adult ducks have not been evaluated. In this study, we subcutaneously implanted radiotransmitters in pre-laying female wood ducks (Aix sponsa, n = 62) and compared nest initiation date, incubation behavior, body mass, and annual return rates of radiomarked females to a group of females that were not radiomarked. Ninety-six percent (50 of 52) of radiomarked females that were monitored for the entire breeding season initiated nests. Nesting date of radiomarked adult females did not differ from that of adult females without radios, but radiomarked yearling females nested earlier than yearlings not receiving transmitters. We found no differences in early- and late-incubation body mass, incubation constancy, recess frequency, and incubation period between radiomarked females and those without radios. Annual return rates of females that initiated nests did not differ between radiomarked females and those not receiving radios. Data suggest that implanting radiotransmitters subcutaneously in pre-laying female wood ducks did not negatively impact subsequent reproduction, incubation behavior, and survival.

Hepp, G. R.; Folk, T. H.; Hartke, K. M.

2002-01-01

53

The effect of social context and reproductive status on the metabolic rates of dwarf seahorses ( Hippocampus zosterae)  

Microsoft Academic Search

Although we are beginning to understand the conditions in which monogamy is favored over a more promiscuous lifestyle, little is known about the proximate effects of monogamous pair bonding, and subsequent reproduction, on general metabolism. I determined the effects of these factors on the metabolic rates of dwarf seahorses (Hippocampus zosterae), recognized for their monogamous lifestyle and unique male care

Heather D Masonjones

2001-01-01

54

Reproductive responses to varying food supply in a population of Darwin's finches: Clutch size, growth rates and hatching synchrony  

Microsoft Academic Search

I show how food shortage affects reproduction in a population of Darwin's Medium Ground Finches, Geospiza fortis. Despite the common occurrence of starvation and absence of nest predation, hatching is typically nighly synchronous and adaptive brood reductionappears to be absent. Variation in both growth rates and clutch size in association with the varying conditions is documented. This variation is interpreted

Trevor Price

1985-01-01

55

Effects of body mass and reproduction on the basal metabolic rate of brown long-eared bats (Plecotus auritus).  

PubMed

We measured basal metabolic rate (BMR) of nonreproductive and of breeding (pregnant and lactating) female brown long-eared bats (Plecotus auritus) to investigate the effects of intra- and interindividual variation in body mass and of reproduction on metabolism. The BMR of six nonreproductive females was measured between five and seven times at approximately 2-wk intervals over a period of 2.5 mo. There was a highly significant effect (P<0.001) of body mass on BMR of these nonreproductive females. The pooled within-individual scaling exponent (1.88) significantly exceeded the established mammalian interspecific exponent (0.75). In addition, we made single observations on 14 nonreproductive females to establish the effects of differences in mass between individuals. The mean BMR across all 14 individuals was 82 mW (+/-24 SD). There was a significant positive relationship between BMR and body mass across these individuals (r2=0.39), with a between-individual scaling exponent of 0.75. Inter- and intraindividual effects of mass on BMR were combined in a regression analysis that included mean body mass and deviation from mean mass on any given day as predictors. This regression model explained 55% of the variation in BMR. We made longitudinal measurements of BMR throughout reproduction and compared these with the predicted BMR of nonreproductive bats of the same body mass. Reproductive females exhibited temporal flexibility in BMR. BMR during pregnancy increased on a whole-animal basis but was significantly lower (by, on average, 15%) than BMR predicted for nonreproductive females of the same mass. Over a period of 1-75 d following birth, whole-animal BMR was greater than that during pregnancy, even though body mass declined after parturition. Hence, postbirth BMR was greater than the level predicted for nonreproductive females of the same mass. This study indicates that the scaling of BMR with body mass differs significantly within and between individuals and that there is a reduction of BMR in pregnancy and an elevation of BMR during lactation. PMID:10685913

McLean, J A; Speakman, J R

56

High variation in clonal vs. sexual reproduction in populations of the wild strawberry, Fragaria virginiana (Rosaceae)  

PubMed Central

Background and Aims Many plants reproduce both clonally and sexually, and the balance between the two modes of reproduction will vary among populations. Clonal reproduction was characterized in three populations of the wild strawberry, Fragaria virginiana, to determine the extent that reproductive mode varied locally between sites. The study sites were fragmented woodlands in Cook County, Illinois, USA. Methods A total of 95 strawberry ramets were sampled from the three sites via transects. Ramets were mapped and genotyped at five variable microsatellite loci. The variability at these five loci was sufficient to assign plants to clones with high confidence, and the spatial pattern of genets was mapped at each site. Key Results A total of 27 distinct multilocus genotypes were identified. Of these, 18 genotypes were detected only once, with the remaining nine detected in multiple ramets. The largest clone was identified in 16 ramets. No genets were shared between sites, and each site exhibited markedly different clonal and sexual recruitment patterns, ranging from two non-overlapping and widespread genets to 19 distinct genets. Only one flowering genet was female; the remainder were hermaphrodites. Conclusions Local population history or fine-scale ecological differences can result in dramatically different reproductive patterns at small spatial scales. This finding may be fairly widespread among clonal plant species, and studies that aim to characterize reproductive modes in species capable of asexual reproduction need to evaluate reproductive modes in multiple populations and sites.

Wilk, John A.; Kramer, Andrea T.; Ashley, Mary V.

2009-01-01

57

Extensive Pollen Flow but Few Pollen Donors and High Reproductive Variance in an Extremely Fragmented Landscape  

PubMed Central

Analysing pollen movement is a key to understanding the reproductive system of plant species and how it is influenced by the spatial distribution of potential mating partners in fragmented populations. Here we infer parameters related to levels of pollen movement and diversity of the effective pollen cloud for the wind-pollinated shrub Pistacia lentiscus across a highly disturbed landscape using microsatellite loci. Paternity analysis and the indirect KinDist and Mixed Effect Mating models were used to assess mating patterns, the pollen dispersal kernel, the effective number of males (Nep) and their relative individual fertility, as well as the existence of fine-scale spatial genetic structure in adult plants. All methods showed extensive pollen movement, with high rates of pollen flow from outside the study site (up to 73–93%), fat-tailed dispersal kernels and large average pollination distances (??=?229–412 m). However, they also agreed in detecting very few pollen donors (Nep?=?4.3–10.2) and a large variance in their reproductive success: 70% of males did not sire any offspring among the studied female plants and 5.5% of males were responsible for 50% of pollinations. Although we did not find reduced levels of genetic diversity, the adult population showed high levels of biparental inbreeding (14%) and strong spatial genetic structure (Sp?=?0.012), probably due to restricted seed dispersal and scarce safe sites for recruitment. Overall, limited seed dispersal and the scarcity of successful pollen donors can be contributing to generate local pedigrees and to increase inbreeding, the prelude of genetic impoverishment.

Gonzalez-Martinez, Santiago C.; Aparicio, Abelardo

2012-01-01

58

Extensive pollen flow but few pollen donors and high reproductive variance in an extremely fragmented landscape.  

PubMed

Analysing pollen movement is a key to understanding the reproductive system of plant species and how it is influenced by the spatial distribution of potential mating partners in fragmented populations. Here we infer parameters related to levels of pollen movement and diversity of the effective pollen cloud for the wind-pollinated shrub Pistacia lentiscus across a highly disturbed landscape using microsatellite loci. Paternity analysis and the indirect KinDist and Mixed Effect Mating models were used to assess mating patterns, the pollen dispersal kernel, the effective number of males (N(ep)) and their relative individual fertility, as well as the existence of fine-scale spatial genetic structure in adult plants. All methods showed extensive pollen movement, with high rates of pollen flow from outside the study site (up to 73-93%), fat-tailed dispersal kernels and large average pollination distances (??=?229-412 m). However, they also agreed in detecting very few pollen donors (N(ep)?=?4.3-10.2) and a large variance in their reproductive success: 70% of males did not sire any offspring among the studied female plants and 5.5% of males were responsible for 50% of pollinations. Although we did not find reduced levels of genetic diversity, the adult population showed high levels of biparental inbreeding (14%) and strong spatial genetic structure (S(p)?=?0.012), probably due to restricted seed dispersal and scarce safe sites for recruitment. Overall, limited seed dispersal and the scarcity of successful pollen donors can be contributing to generate local pedigrees and to increase inbreeding, the prelude of genetic impoverishment. PMID:23152842

Albaladejo, Rafael G; Guzmán, Beatriz; González-Martínez, Santiago C; Aparicio, Abelardo

2012-11-12

59

Effect of bromocriptine on the severity of ovarian hyperstimulation syndrome and outcome in high responders undergoing assisted reproduction  

PubMed Central

CONTEXT: Ever since ovarian hyperstimulation syndrome (OHSS) was recognized as a clinical entity, various treatment modalities have been tried to prevent its occurrence and reduce its severity. Many recent studies have evaluated the role of dopamine agonists in reducing the incidence of OHSS. OBJECTIVES: To assess the effectiveness of dopamine agonist bromocriptine in reducing the incidence and severity of OHSS in patients undergoing assisted reproduction and its effect on pregnancy rates. SETTINGS AND DESIGN: It was a prospective study in which patients at high risk of developing OHSS undergoing assisted reproduction were recruited. MATERIALS AND METHODS: The study was carried out from August 2008 to August 2009 in patients undergoing assisted reproduction and included 40 patients at high risk for developing OHSS. Tablet bromocriptine 2.5 mg was prescribed for a period of 16 days starting from day of ovum pick up. Patients were analyzed on the basis of incidence of moderate and severe OHSS, timing of onset of OHSS (early/late), hospitalization rate, pregnancy rates and tolerability of medication and were compared with a historical group of high responders matched for age and BMI. STATISTICAL ANALYSIS: Student’s t test and proportion test were used. RESULTS: There was a significant reduction in the incidence of moderate OHSS (P=0.037), early OHSS (P=0.012) as well as the number of admissions (P=0.030). Average duration of hospitalization was also significantly reduced (P=0.036). In the study group, the incidence of clinically significant OHSS was 17.5% as compared to 40.9% in the control group. No difference was detected between the groups in clinical pregnancy rates (P=0.0054). CONCLUSION: Bromocriptine reduced the incidence and severity of clinically significant OHSS in high risk patients without affecting the pregnancy rates.

Sherwal, Vinita; Malik, Sonia; Bhatia, Vandana

2010-01-01

60

The dynamics of reproductive rate, offspring survivorship and growth in the lined seahorse, Hippocampus erectus Perry, 1810  

PubMed Central

Summary Seahorses are the vertebrate group with the embryonic development occurring within a special pouch in males. To understand the reproductive efficiency of the lined seahorse, Hippocampus erectus Perry, 1810 under controlled breeding experiments, we investigated the dynamics of reproductive rate, offspring survivorship and growth over births by the same male seahorses. The mean brood size of the 1-year old pairs in the 1st birth was 85.4±56.9 per brood, which was significantly smaller than that in the 6th birth (465.9±136.4 per brood) (P<0.001). The offspring survivorship and growth rate increased with the births. The fecundity was positively correlated with the length of brood pouches of males and trunk of females. The fecundity of 1-year old male and 2-year old female pairs was significantly higher than that from 1-year old couples (P<0.001). The brood size (552.7±150.4) of the males who mated with females that were isolated for the gamete-preparation, was larger than those (467.8±141.2) from the long-term pairs (P<0.05). Moreover, the offspring from the isolated females had higher survival and growth rates. Our results showed that the potential reproductive rate of seahorses H. erectus increased with the brood pouch development.

Lin, Qiang; Li, Gang; Qin, Geng; Lin, Junda; Huang, Liangmin; Sun, Hushan; Feng, Peiyong

2012-01-01

61

Plasticity of insect reproduction: testing models of flexible and fixed development in response to different growth rates  

Microsoft Academic Search

We tested alternative developmental hypotheses describing when during an insect oviposition cycle reproductive tactics are\\u000a determined. Newly eclosed adult females of the grasshopper Romalea guttata were raised on eight different feeding treatments consisting of a low food diet, a high food diet, and changes from high\\u000a to low food, or low to high food, at different times during the first

Gregory S. Moehrlin; Steven A. Juliano

1998-01-01

62

Alternative Male Reproductive Phenotypes Affect Offspring Growth Rates in Chinook Salmon  

Microsoft Academic Search

Male age at maturity in Chinook salmon Oncorhynchus tshawytscha is a heritable trait in which the physiological “decision” to mature depends on an individual's exceeding a body size or condition threshold at critical developmental periods. In Chinook salmon, high juvenile growth rates promote the so called “jack” male life history. Jack males mature 1 year earlier than the youngest females

Barry A. Berejikian; Donald M. Van Doornik; Jeffrey J. Atkins

2011-01-01

63

A HIGH-THROUGHPUT METHOD FOR ASSESSING CHEMICAL TOXICITY USING A CAENORHABDITIS ELEGANS REPRODUCTION ASSAY  

PubMed Central

The National Research Council has outlined the need for non-mammalian toxicological models to test the potential health effects of a large number of chemicals while also reducing the use of traditional animal models. The nematode Caenorhabditis elegans is an attractive alternative model because of its well-characterized and evolutionarily-conserved biology, low cost, and ability to be used in high-throughput screening. A high-throughput method is described for quantifying the reproductive capacity of C. elegans exposed to chemicals for 48 h from the last larval stage (L4) to adulthood using a COPAS Biosort. Initially, the effects of exposure conditions that could influence reproduction were defined. Concentrations of DMSO vehicle ? 1% did not affect reproduction. Previous studies indicated that C. elegans may be influenced by exposure to low pH conditions. At pHs greater than 4.5, C. elegans reproduction was not affected, however below this pH there was a significant decrease in the number of offspring. Cadmium chloride was chosen as a model toxicant to verify that automated measurements were comparable to those of traditional observational studies. EC50 values for cadmium for automated measurements (176-192 ?M) were comparable to those previously reported for a 72-h exposure using manual counting (151 ?M). The toxicity of seven test toxicants on C. elegans reproduction was highly correlative with rodent lethality suggesting that this assay may be useful in predicting the potential toxicity of chemicals in other organisms.

Boyd, Windy A.; McBride, Sandra J.; Rice, Julie R.; Snyder, Daniel W.; Freedman, Jonathan H.

2010-01-01

64

Effects of High Tissue Concentrations of Selenium on Reproduction by Bluegills  

Microsoft Academic Search

Recent studies have associated high body concentrations of selenium with declines in fish populations inhabiting cooling reservoirs of coal-fired electric power plants. Because some evidence indicated that these declines resulted from reduced reproduction, we made a series of 18 artificial crosses of bluegills Lepomis macrochirus possessing high and low body concentrations of Se to determine whether elevated Se in parents

Robert B. Gillespie; Paul C. Baumann

1986-01-01

65

Assisted Reproductive Technology Success Rates: National Summary and Fertility Clinic Reports, 2004.  

National Technical Information Service (NTIS)

For many people who want to start a family, the dream of having a child is not easily realized; about 12% of women of childbearing age in the United States have received an infertility service. Assisted reproductive technology (ART) has been used in the U...

2006-01-01

66

Selective advantage for sexual reproduction  

NASA Astrophysics Data System (ADS)

This paper develops a simplified model for sexual reproduction within the quasispecies formalism. The model assumes a diploid genome consisting of two chromosomes, where the fitness is determined by the number of chromosomes that are identical to a given master sequence. We also assume that there is a cost to sexual reproduction, given by a characteristic time ?seek during which haploid cells seek out a mate with which to recombine. If the mating strategy is such that only viable haploids can mate, then when ?seek=0 , it is possible to show that sexual reproduction will always out compete asexual reproduction. However, as ?seek increases, sexual reproduction only becomes advantageous at progressively higher mutation rates. Once the time cost for sex reaches a critical threshold, the selective advantage for sexual reproduction disappears entirely. The results of this paper suggest that sexual reproduction is not advantageous in small populations per se, but rather in populations with low replication rates. In this regime, the cost for sex is sufficiently low that the selective advantage obtained through recombination leads to the dominance of the strategy. In fact, at a given replication rate and for a fixed environment volume, sexual reproduction is selected for in high populations because of the reduced time spent finding a reproductive partner.

Tannenbaum, Emmanuel

2006-06-01

67

Understanding High Saving Rate in China  

Microsoft Academic Search

AbstractThis paper presents a detailed analysis of the Chinese saving rate based on the flow of funds data. It finds that the most widely adopted view of precautionary saving, which is regarded as the top reason for maintaining a high saving rate in China, is misleading because this conclusion is drawn from the household survey data. In fact, the household

Xinhua He; Yongfu Cao

2007-01-01

68

A High Rate 4??-? Coincidence Counting System  

Microsoft Academic Search

A high count rate 4??-? coincidence counting system for the determination of absolute disintegration rates of short half-life radionuclides is described. With this system the dead time per pulse is minimized by not stretching any pulses beyond the width necessary to satisfy overlap coincidence requirements. The pulse widths in the beta-ray (?), gamma-ray (?), and coincidence channels are extendable and

L. O. Johnson; R. J. Gehrke

1979-01-01

69

Rate Sensitivity of High Strength Syntactic Foam.  

National Technical Information Service (NTIS)

A series of dynamic experiments was performed on high crush strength syntactic foam to characterize how rate affects the compressive and tensile properties of the material. The Investigation was carried out as part of a larger effort to develop a rate sen...

R. Doleski S. Plunkett W. Tucker

2003-01-01

70

High rate of asthma among immigrants  

Microsoft Academic Search

Articles dealing with the epidemiological aspects of asthma were carefully reviewed in order to support or reject our clinical impression of increased rate of asthma among immigrants. Particular emphasis was put on data on very high or very low rates of asthma. The proposed theories to explain these differences were critically examined.The prevalence of asthma in China and in Africa

A. Ballin; E. Somekh; D. Geva; D. Meytes

1998-01-01

71

Anodic dissolution of metals at high rates  

SciTech Connect

Electrochemical metal shaping and finishing processes involve anodic dissolution of metals at high rates. This paper presents a review of some fundamental aspects related to the understanding of such processes. Included are discussions of the phenomena of passive film breakdown that lead to the transpassive dissolution of metals, some of the available information on anodic reaction stoichiometry, and the role of convective mass transport and salt precipitation layers on metal removal rate and surface finish. The use of pulsating current permits the altering of anodic mass transport rates and transpassive dissolution behavior, thereby making it possible to obtain high dissolution efficiencies even at low average current densities.

Datta, M.

1993-03-01

72

Frequency of multiple paternity in gummy shark, Mustelus antarcticus, and rig, Mustelus lenticulatus, and the implications of mate encounter rate, postcopulatory influences, and reproductive mode.  

PubMed

Elasmobranchs (sharks and rays) show an amazing diversity of reproductive modes and behaviors. Multiple paternity (MP) has been identified in all species where more than 1 litter has been investigated; yet neither direct nor indirect benefits from MP have been determined in elasmobranchs. This has led to the suggestion that MP in this group may simply be a product of convenience polyandry with variation in the frequency of MP driven by differences in mate encounter rates. Here, we use molecular markers to investigate polyandry and MP in 2 closely related and commercially important species of shark, Mustelus antarcticus and Mustelus lenticulatus. In total, 328 M. antarcticus embryos originating from 29 different mothers and 75 M. lenticulatus embryos originating from 19 different mothers were genotyped using 8 microsatellite loci. We find that MP occurs in both species. However, in both species, the majority of litters were sired by a single father. Our results do not support increased fecundity per se as a driver of MP. Further, our results do not suggest that high population densities with resulting high mate encounter rates generated by breeding aggregations necessarily lead to high frequencies of MP. Importantly, we note evidence of reproductive skew within polyandrous litters, which is a predicted outcome of postcopulatory mechanisms. PMID:23505312

Boomer, Jessica J; Harcourt, Robert G; Francis, Malcolm P; Walker, Terence I; Braccini, Juan Matias; Stow, Adam J

2013-03-15

73

High pathogenicity avian influenza virus in the reproductive tract of chickens  

Technology Transfer Automated Retrieval System (TEKTRAN)

Infection with high pathogenicity avian influenza virus (HPAIV) has been associated with a wide range of clinical manifestations in poultry including severe depression in egg production and isolation of HPAIV from eggs laid by infected hens. To evaluate the pathobiology in the reproductive tract of...

74

A Visibility Matching Tone Reproduction Operator for High Dynamic Range Scenes  

Microsoft Academic Search

We present a tone reproduction operator that preserves visibility in high dynamic range scenes. Our method introduces a new histogram adjustment technique, based on the population of local adaptation luminances in a scene. To match subjective viewing experience, the method incorporates models for human contrast sensitivity, glare, spatial acuity and color sensitivity. We compare our results to previous work and

Gregory Ward Larson; Holly E. Rushmeier; Christine D. Piatko

1997-01-01

75

Serological screening for Coxiella burnetii infection and related reproductive performance in high producing dairy cows  

Microsoft Academic Search

The possible relationship between Coxiella-seropositivity and the reproductive performance of cows during the previous year to the serological screening was examined in three high producing dairy herds. The herds had a history of subfertility (18% abortions) and a positive polymerase chain reaction test for Coxiella burnetii in the bulk tank milk with an excretion higher than 104Coxiella \\/ml for all

F. López-Gatius; S. Almeria; I. Garcia-Ispierto

76

Predictive model of rat reproductive toxicity from ToxCast high throughput screening.  

PubMed

The U.S. Environmental Protection Agency's ToxCast research program uses high throughput screening (HTS) for profiling bioactivity and predicting the toxicity of large numbers of chemicals. ToxCast Phase I tested 309 well-characterized chemicals in more than 500 assays for a wide range of molecular targets and cellular responses. Of the 309 environmental chemicals in Phase I, 256 were linked to high-quality rat multigeneration reproductive toxicity studies in the relational Toxicity Reference Database. Reproductive toxicants were defined here as having achieved a reproductive lowest-observed-adverse-effect level of less than 500 mg kg(-1) day(-1). Eight-six chemicals were identified as reproductive toxicants in the rat, and 68 of those had sufficient in vitro bioactivity to model. Each assay was assessed for univariate association with the identified reproductive toxicants. Significantly associated assays were linked to gene sets and used for the subsequent predictive modeling. Using linear discriminant analysis and fivefold cross-validation, a robust and stable predictive model was produced capable of identifying rodent reproductive toxicants with 77% ± 2% and 74% ± 5% (mean ± SEM) training and test cross-validation balanced accuracies, respectively. With a 21-chemical external validation set, the model was 76% accurate, further indicating the model's potential for prioritizing the many thousands of environmental chemicals with little to no hazard information. The biological features of the model include steroidal and nonsteroidal nuclear receptors, cytochrome P450 enzyme inhibition, G protein-coupled receptors, and cell signaling pathway readouts-mechanistic information suggesting additional targeted, integrated testing strategies and potential applications of in vitro HTS to risk assessment. PMID:21565999

Martin, Matthew T; Knudsen, Thomas B; Reif, David M; Houck, Keith A; Judson, Richard S; Kavlock, Robert J; Dix, David J

2011-05-12

77

High doses of dietary zinc induce cytokines, chemokines, and apoptosis in reproductive tissues during regression.  

PubMed

In chickens, high levels of dietary zinc cause molting, and the reproductive system undergoes complete remodeling concomitant to feather replacement. In the present study, the expression profiles of cytokines and chemokines were investigated in the ovary and oviduct of control hens and of hens induced to molt by zinc feeding. The zinc-induced feed-intake suppression, the changes in corticosterone levels, the immune cell populations in the reproductive tract, and the apoptosis of reproductive tissues were analyzed. The expression of mRNAs for interleukin-6 (IL-6), interferon-gamma (IFN-gamma), the avian ortholog of mammalian IL-8 (chCXCLi2), and a chicken MIP-1beta-like chemokine (chCCLi2) in the ovary and of mRNAs for IL-1beta, IL-6, IFN-gamma, transforming growth factor-beta2, chCXCLi2, and chCCLi2 in the oviduct were upregulated significantly during zinc-induced molting. A simultaneous feed-intake reduction was observed with higher expression of cytokines and chemokines. The results of the present investigation also suggested that the upregulation of corticosterone was closely associated with the increased expression of cytokines and chemokines. An increase in apoptosis within reproductive tissue during tissue regression was also noted. We had previously observed the upregulation of these cytokines expression in an earlier study (molting by feed withdrawal). However, the pattern and the level of expression were different among these two methods. These findings indicate that cytokines might be a common mediator of tissue regression during molting induced by diverse methods, although the pattern of induction is different. Thus, a high dose of dietary zinc seems to induce reproductive regression via the upregulation of cytokines and chemokines, the suppression of feed intake, and the increase in serum corticosterone, resulting finally in the apoptosis of reproductive tissues. PMID:18351392

Sundaresan, N R; Anish, D; Sastry, K V H; Saxena, V K; Nagarajan, K; Subramani, J; Leo, M D M; Shit, N; Mohan, J; Saxena, M; Ahmed, K A

2008-03-20

78

High levels of maternally transferred mercury do not affect reproductive output or embryonic survival of northern watersnakes (Nerodia sipedon).  

PubMed

Maternal transfer is an important exposure pathway for contaminants because it can directly influence offspring development. Few studies have examined maternal transfer of contaminants, such as mercury (Hg), in snakes, despite their abundance and high trophic position in many ecosystems where Hg is prevalent. The objectives of the present study were to determine if Hg is maternally transferred in northern watersnakes (Nerodia sipedon) and to evaluate the effects of maternal Hg on reproduction. The authors captured gravid female watersnakes (n?=?31) along the South River in Waynesboro, Virginia, USA, where an extensive Hg-contamination gradient exists. The authors measured maternal tissue and litter Hg concentrations and, following birth, assessed (1) reproductive parameters (i.e., litter size and mass, neonate mass); (2) rates of infertility, death during development, stillbirths, malformations, and runts; and (3) the overall viability of offspring. Mercury concentrations in females were strongly and positively correlated with concentrations in litters, suggesting that N. sipedon maternally transfer Hg in proportion to their tissue residues. Maternal transfer resulted in high concentrations (up to 10.10?mg/kg dry wt total Hg) of Hg in offspring. The authors found little evidence of adverse effects of Hg on these measures of reproductive output and embryonic survival, suggesting that N. sipedon may be more tolerant of Hg than other vertebrate species. Given that this is the first study to examine the effects of maternally transferred contaminants in snakes and that the authors did not measure all reproductive endpoints, further research is needed to better understand factors that influence maternal transfer and associated sublethal effects on offspring. PMID:23233365

Chin, Stephanie Y; Willson, John D; Cristol, Daniel A; Drewett, David V V; Hopkins, William A

2013-03-01

79

The role of sexual and asexual reproduction in structuring high latitude populations of the reef coral Pocillopora damicornis  

Microsoft Academic Search

The genotypic composition of populations of the asexually viviparous coral Pocillopora damicornis varies in a manner that challenges classical models of the roles of sexual and asexual reproduction. On the geographically isolated Hawaiian reefs and high latitude reefs in Western Australia, P. damicornis populations are highly clonal although it has been argued that sexual reproduction via broadcast spawning generates widely

K J Miller; D J Ayre

2004-01-01

80

Micromachined dispenser with high flow rate and high resolution  

Microsoft Academic Search

A micromachined dispenser with a high flow rate and high resolution for chemical analysis is described. The flow rate as a function of the actuation frequency increases linearly up to a frequency of 700 Hz with a final value of about 148 ?l\\/s using water as a pump medium. The dispensing accuracy is better than 1% (coefficient of variance) at

Akira Koide; Yasuhiko Sasaki; Y. Yoshimura; Ryo Miyake; T. Terayama

2000-01-01

81

Late snowmelt delays plant development and results in lower reproductive success in the High Arctic.  

PubMed

In tundra areas where the growing season is short, any delay in the start of summer may have a considerable effect on plant development, growth and reproductive success. Climate models suggest long-term changes in winter precipitation in the Arctic, which may lead to deeper snow cover and a resultant delay in date of snow melt. In this paper, we investigated the role of snow depth and melt out date on the phenological development and reproductive success of vascular plants in Adventdalen, Svalbard (78° 10'N, 16° 06'E). Effects of natural variations in snow accumulation were demonstrated using two vegetation types (snow depth: meadow 21 cm, heath 32 cm), and fences were used to experimentally increase snow depth by over 1m. Phenological delay was greatest directly after snowmelt in the earlier phenological phases, and had the largest effect on the early development of those species which normally green-up early (i.e. Dryas, Papaver, Salix, Saxifraga). Compressed growing seasons and length of the reproductive period led to a reduced reproductive success in some of the study species. There were fewer flowers, fewer plots with dispersing seeds, and lower germination rates. This can have consequences for plant establishment and community composition in the long-term. PMID:21421357

Cooper, Elisabeth J; Dullinger, Stefan; Semenchuk, Philipp

2010-09-25

82

A high-strain-rate superplastic ceramic  

NASA Astrophysics Data System (ADS)

High-strain-rate superplasticity describes the ability of a material to sustain large plastic deformation in tension at high strain rates of the order of 10-2 to 10-1s-1 and is of great technological interest for the shape-forming of engineering materials. High-strain-rate superplasticity has been observed in aluminium-based and magnesium-based alloys. But for ceramic materials, superplastic deformation has been restricted to low strain rates of the order of 10-5 to 10-4s-1 for most oxides and nitrides with the presence of intergranular cavities leading to premature failure. Here we show that a composite ceramic material consisting of tetragonal zirconium oxide, magnesium aluminate spinel and ?-alumina phases exhibits superplasticity at strain rates up to 1s-1. The composite also exhibits a large tensile elongation, exceeding 1,050 per cent for a strain rate of 0.4s-1. The tensile flow behaviour and deformed microstructure of the material indicate that superplasticity is due to a combination of limited grain growth in the constitutive phases and the intervention of dislocation-induced plasticity in the zirconium oxide phase. We suggest that the present results hold promise for the application of shape-forming technologies to ceramic materials.

Kim, B.-N.; Hiraga, K.; Morita, K.; Sakka, Y.

2001-09-01

83

High Resolution Measurement of the Glycolytic Rate  

PubMed Central

The glycolytic rate is sensitive to physiological activity, hormones, stress, aging, and malignant transformation. Standard techniques to measure the glycolytic rate are based on radioactive isotopes, are not able to resolve single cells and have poor temporal resolution, limitations that hamper the study of energy metabolism in the brain and other organs. A new method is described in this article, which makes use of a recently developed FRET glucose nanosensor to measure the rate of glycolysis in single cells with high temporal resolution. Used in cultured astrocytes, the method showed for the first time that glycolysis can be activated within seconds by a combination of glutamate and K+, supporting a role for astrocytes in neurometabolic and neurovascular coupling in the brain. It was also possible to make a direct comparison of metabolism in neurons and astrocytes lying in close proximity, paving the way to a high-resolution characterization of brain energy metabolism. Single-cell glycolytic rates were also measured in fibroblasts, adipocytes, myoblasts, and tumor cells, showing higher rates for undifferentiated cells and significant metabolic heterogeneity within cell types. This method should facilitate the investigation of tissue metabolism at the single-cell level and is readily adaptable for high-throughput analysis.

Bittner, Carla X.; Loaiza, Anitsi; Ruminot, Ivan; Larenas, Valeria; Sotelo-Hitschfeld, Tamara; Gutierrez, Robin; Cordova, Alex; Valdebenito, Rocio; Frommer, Wolf B.; Barros, L. Felipe

2010-01-01

84

High Rate for Type IC Supernovae  

SciTech Connect

Using an automated telescope we have detected 20 supernovae in carefully documented observations of nearby galaxies. The supernova rates for late spiral (Sbc, Sc, Scd, and Sd) galaxies, normalized to a blue luminosity of 10{sup 10} L{sub Bsun}, are 0.4 h{sup 2}, 1.6 h{sup 2}, and 1.1 h{sup 2} per 100 years for SNe type la, Ic, and II. The rate for type Ic supernovae is significantly higher than found in previous surveys. The rates are not corrected for detection inefficiencies, and do not take into account the indications that the Ic supernovae are fainter on the average than the previous estimates; therefore the true rates are probably higher. The rates are not strongly dependent on the galaxy inclination, in contradiction to previous compilations. If the Milky Way is a late spiral, then the rate of Galactic supernovae is greater than 1 per 30 {+-} 7 years, assuming h = 0.75. This high rate has encouraging consequences for future neutrino and gravitational wave observatories.

Muller, R.A.; Marvin-Newberg, H.J.; Pennypacker, Carl R.; Perlmutter, S.; Sasseen, T.P.; Smith, C.K.

1991-09-01

85

High Strain Rate Testing of Solder Interconnections  

Microsoft Academic Search

Understanding the response of the board-to-package (2nd level) interconnections to loading at high strain rates is essential for the design against drop impact failure. To obtain such properties, the impact tester used must provide results for energy to failure and information on impact force and displacement. Knowledge of impact force is essential for quantifying the strength of the interconnection and

K. T. Tsai; F. L. Liu; E. H. Wong; R. Rajoo

2005-01-01

86

High rate vacuum deposition of polymer electrolytes  

Microsoft Academic Search

Two new, high rate, vacuum processes have been developed for the deposition of polymer electrolyte layers on wide web substrates. One method involves the vacuum extrusion of monomer salt solutions followed by e-beam or ultraviolet (UV) curing. The second method involves the vacuum flash evaporation of the monomer salt solution followed by e-beam or UV curing. Each method is compatible

J. D. Affinito; M. E. Gross; C. A. Coronado; G. C. Dunham; P. M. Martin

1996-01-01

87

ISS Update: High Rate Communications System  

NASA Video Gallery

ISS Update Commentator Pat Ryan interviews Diego Serna, Communications and Tracking Officer, about the High Rate Communications System. Questions? Ask us on Twitter @NASA_Johnson and include the hashtag #askStation. For the latest news about the space station, visit http://www.nasa.gov/station.

Mark Garcia

2012-03-27

88

A miniature high repetition rate shock tube  

NASA Astrophysics Data System (ADS)

A miniature high repetition rate shock tube with excellent reproducibility has been constructed to facilitate high temperature, high pressure, gas phase experiments at facilities such as synchrotron light sources where space is limited and many experiments need to be averaged to obtain adequate signal levels. The shock tube is designed to generate reaction conditions of T > 600 K, P < 100 bars at a cycle rate of up to 4 Hz. The design of the apparatus is discussed in detail, and data are presented to demonstrate that well-formed shock waves with predictable characteristics are created, repeatably. Two synchrotron-based experiments using this apparatus are also briefly described here, demonstrating the potential of the shock tube for research at synchrotron light sources.

Tranter, R. S.; Lynch, P. T.

2013-09-01

89

A miniature high repetition rate shock tube.  

PubMed

A miniature high repetition rate shock tube with excellent reproducibility has been constructed to facilitate high temperature, high pressure, gas phase experiments at facilities such as synchrotron light sources where space is limited and many experiments need to be averaged to obtain adequate signal levels. The shock tube is designed to generate reaction conditions of T > 600 K, P < 100 bars at a cycle rate of up to 4 Hz. The design of the apparatus is discussed in detail, and data are presented to demonstrate that well-formed shock waves with predictable characteristics are created, repeatably. Two synchrotron-based experiments using this apparatus are also briefly described here, demonstrating the potential of the shock tube for research at synchrotron light sources. PMID:24089840

Tranter, R S; Lynch, P T

2013-09-01

90

High strain rate behaviour of polypropylene microfoams  

NASA Astrophysics Data System (ADS)

Microcellular materials such as polypropylene foams are often used in protective applications and passive safety for packaging (electronic components, aeronautical structures, food, etc.) or personal safety (helmets, knee-pads, etc.). In such applications the foams which are used are often designed to absorb the maximum energy and are generally subjected to severe loadings involving high strain rates. The manufacture process to obtain polymeric microcellular foams is based on the polymer saturation with a supercritical gas, at high temperature and pressure. This method presents several advantages over the conventional injection moulding techniques which make it industrially feasible. However, the effect of processing conditions such as blowing agent, concentration and microfoaming time and/or temperature on the microstructure of the resulting microcellular polymer (density, cell size and geometry) is not yet set up. The compressive mechanical behaviour of several microcellular polypropylene foams has been investigated over a wide range of strain rates (0.001 to 3000 s-1) in order to show the effects of the processing parameters and strain rate on the mechanical properties. High strain rate tests were performed using a Split Hopkinson Pressure Bar apparatus (SHPB). Polypropylene and polyethylene-ethylene block copolymer foams of various densities were considered.

Gómez-del Río, T.; Garrido, M. A.; Rodríguez, J.; Arencón, D.; Martínez, A. B.

2012-08-01

91

In situ high rate growth of high temperature superconductor tapes  

Microsoft Academic Search

In situ high rate growth of YBa2Cu3O7-? superconducting films has been carried out using e-beam deposition. A deposition flux controller was developed to monitor and control the deposition rates using tunable diode, laser-based, atomic absorption. A wide range of temperatures, deposition rates, and oxygen fluxes including atomic, molecular oxygen, have been explored in order to understand both kinetic and thermodynamic

E. S.-J. Peng; Weizhi Wang; W. Jo; T. Ohnishi; A. F. Marshall; R. H. Hammond; M. R. Beasley; E. J. Peterson; R. E. Ericson

2001-01-01

92

Fifty fertile years: Anthropologists' studies of reproduction in high altitude natives.  

PubMed

Early European colonists of the Andes had difficulties in reproducing, a fact that underpins the hypothesis that reproduction is impaired amongst all humans at high altitudes. Yet a 16th century missionary wrote, "… the Indians are healthiest and where they multiply the most prolifically is in these same cold air-tempers, … [yet most children of the Spaniards] when born in such regions do not survive." These observations suggest that humans at high altitudes are subjected to strong natural selection from hypoxia, cold and limited food sources and, furthermore, that human populations can and have adapted, and continue to adapt, to these conditions. Informed by multiple approaches and theoretical frameworks, anthropologists have investigated to what extent and precisely how high altitude environments impact human reproductive functioning and fertility. Analyses of the proximate determinants of natural fertility suggest that behaviors (breast/infant feeding practices in the Andes, and marriage practices and religious celibacy in the Himalaya) are major determinants of fertility in high altitude populations. Furthermore, data from Project REPA (Reproduction and Ecology in Provincía Aroma), a longitudinal study in rural Bolivia, demonstrate that fecundity is not impaired in this indigenous altiplano population, and that the risk for early pregnancy loss (EPL) is not elevated by environmental hypoxia but does vary seasonally with the agricultural cycle (contra to the assumption that EPLs are due almost entirely to genetically flawed concepti). This review discusses these and other findings that reveal the complex and dynamic adaptations of human reproductive functioning in high altitude environments. Am. J. Hum. Biol., 2013. © 2013 Wiley Periodicals, Inc. PMID:23362150

Vitzthum, Virginia J

2013-01-30

93

Fifty fertile years: anthropologists' studies of reproduction in high altitude natives.  

PubMed

Early European colonists of the Andes had difficulties in reproducing, a fact that underpins the hypothesis that reproduction is impaired amongst all humans at high altitudes. Yet a 16th century missionary wrote, "… the Indians are healthiest and where they multiply the most prolifically is in these same cold air-tempers, … [yet most children of the Spaniards] when born in such regions do not survive." These observations suggest that humans at high altitudes are subjected to strong natural selection from hypoxia, cold and limited food sources and, furthermore, that human populations can and have adapted, and continue to adapt, to these conditions. Informed by multiple approaches and theoretical frameworks, anthropologists have investigated to what extent and precisely how high altitude environments impact human reproductive functioning and fertility. Analyses of the proximate determinants of natural fertility suggest that behaviors (breast/infant feeding practices in the Andes, and marriage practices and religious celibacy in the Himalaya) are major determinants of fertility in high altitude populations. Furthermore, data from Project REPA (Reproduction and Ecology in Provincía Aroma), a longitudinal study in rural Bolivia, demonstrate that fecundity is not impaired in this indigenous altiplano population, and that the risk for early pregnancy loss (EPL) is not elevated by environmental hypoxia but does vary seasonally with the agricultural cycle (contra to the assumption that EPLs are due almost entirely to genetically flawed concepti). This review discusses these and other findings that reveal the complex and dynamic adaptations of human reproductive functioning in high altitude environments. Am. J. Hum. Biol. 25:179-189, 2013. © 2013 Wiley Periodicals, Inc. PMID:23382088

Vitzthum, Virginia J

2013-02-05

94

High strain rate response of an elastomer.  

NASA Astrophysics Data System (ADS)

Pressure-shear plate impact experiments have been conducted to study the mechanical response of an elastomer (polyurea) at very high strain rates: 10^5 - 10^6 s-1. Thin samples are cast between two hard steel plates. Longitudinal waves reverberating through the sample are used to determine the slope of the isentrope at compressive stresses greater than, say, 500 MPa - the pressure at impact. Release wave experiments, combined with plane wave simulations, are used to extend the isentrope into the tensile regime. Because the shearing resistance of polyurea depends strongly on pressure, two approaches are used to investigate the regime of high shearing rate and low pressure. First, an unloading longitudinal wave reflected from the rear surface of the target assembly is made to arrive at the sample midway through its loading by the incident shear wave. As a result, the sample is sheared at high strain rates and both high and low pressure during a single experiment. Second, the thickness of the flyer and front plates are selected such that the compressive pulse passes through the cast-in-place sample before the shear wave arrives, allowing the shearing resistance to be measured at zero pressure. Results of these experiments and their simulation will be presented.

Jiao, Tong; Clifton, Rodney; Grunschel, Stephen

2007-06-01

95

Phosphor thermometry at high repetition rates  

NASA Astrophysics Data System (ADS)

Phosphor thermometry is a semi-invasive surface temperature measurement technique utilizing the luminescence properties of thermographic phosphors. Typically these ceramic materials are coated onto the object of interest and are excited by a short UV laser pulse. Photomultipliers and high-speed camera systems are used to transiently detect the subsequently emitted luminescence decay point wise or two-dimensionally resolved. Based on appropriate calibration measurements, the luminescence lifetime is converted to temperature. Up to now, primarily Q-switched laser systems with repetition rates of 10 Hz were employed for excitation. Accordingly, this diagnostic tool was not applicable to resolve correlated temperature transients at time scales shorter than 100 ms. For the first time, the authors realized a high-speed phosphor thermometry system combining a highly repetitive laser in the kHz regime and a fast decaying phosphor. A suitable material was characterized regarding its temperature lifetime characteristic and precision. Additionally, the influence of laser power on the phosphor coating in terms of heating effects has been investigated. A demonstration of this high-speed technique has been conducted inside the thermally highly transient system of an optically accessible internal combustion engine. Temperatures have been measured with a repetition rate of one sample per crank angle degree at an engine speed of 1000 rpm. This experiment has proven that high-speed phosphor thermometry is a promising diagnostic tool for the resolution of surface temperature transients.

Fuhrmann, N.; Brübach, J.; Dreizler, A.

2013-09-01

96

An abbreviated repeat dose and reproductive/developmental toxicity test for high production volume chemicals  

SciTech Connect

A novel protocol is described for obtaining preliminary data on repeated dose systemic effects and reproductive/developmental toxicity. The test protocol was developed by a group of experts at the request of the U.S. Environmental Protection Agency (EPA) for use as part of a Screening Information Data Set on high production volume chemicals. Interest in this protocol is shared by several regulatory agencies, including the Organization for Economic Cooperation, the European Community, and the EPA. To validate the study protocol, ethylene glycol monomethyl ether (EGME) was used. After a dosing period of approximately 6 weeks, EGME showed both systemic and reproductive/developmental effects similar to those previously reported using standard protocols. Thus, this test protocol may be used as a screening tool for high production volume chemicals.

Scala, R.A.; Bevan, C.; Beyer, B.K. (Exxon Biomedical Sciences, Inc., East Millstone, NJ (United States))

1992-08-01

97

Pathogenicity and distribution of highly pathogenic porcine reproductive and respiratory syndrome virus in pigs.  

PubMed

The pathogenesis of highly pathogenic porcine reproductive and respiratory syndrome virus (PRRSV) strain (HuN4) is poorly understood. Therefore, highly pathogenic PRRSV strain (HuN4) and its derivative strain (HuN4-F112) (obtained by propagation in MARC145 cells for 112 passages) were inoculated into a total of 48 PRRSV-sero-negative pigs (age: 4-5?weeks) by the intranasal route. Virological, pathological and in situ hybridization analyses were performed. The results exhibited that pigs infected with HuN4 showed a loss of appetite, decrease in body weight, raised body temperature and respiratory symptoms, along with interstitial pneumonia lesions. In the HuN4 group, multifocal interstitial pneumonia with macrophage infiltration was found in the lung. The lesions in the lymph node were characterized by collapsed follicles, depletion of germinal centres and reduction in lymphocytes. Perivascular cuffing and glial nodules were observed in the brains of some pigs. By comparison, the HuN4-F112 group had milder lesions. PRRSV was detected in macrophages, alveolar epithelial cells and vascular endothelial cells in the tonsil and lymph nodes. The PRRSV amounts in the pigs infected with HuN4 were 10(5) -10(9) ?copies/ml in the blood and 10(10) -10(11) ?copies/g in the lung tissues, whereas the virus amounts with HuN4-F112 were 10(2.15) -10(3.13) ?copies/ml in the blood and 10(3.0) -10(3.6) ?copies/g in the lung. Our results demonstrate that the PRRS HuN4 virus infects alveolar epithelial cells, macrophages and vascular endothelial cells causing diffuse alveolar damage and lymph node necrosis. Its higher pathogenicity compared with HuN4-F112 virus may be explained in part by higher replication rate in the previously mentioned organs. PMID:22762447

Hu, S P; Zhang, Z; Liu, Y G; Tian, Z J; Wu, D L; Cai, X H; He, X J

2012-07-05

98

A visibility matching tone reproduction operator for high dynamic range scenes  

SciTech Connect

The authors present a tone reproduction operator that preserves visibility in high dynamic range scenes. The method introduces a new histogram adjustment technique, based on the population of local adaptation luminances in a scene. To match subjective viewing experience, the method incorporates models for human contrast sensitivity, glare, spatial acuity and color sensitivity. They compare the results to previous work and present examples the techniques applied to lighting simulation and electronic photography.

Larson, G.W. [Lawrence Berkeley National Lab., CA (United States); Rushmeier, H. [International Business Machines Corp., Yorktown Heights, NY (United States). Thomas J. Watson Research Center; Piatko, C. [National Inst. of Standards and Technology, Gaithersburg, MD (United States)

1997-01-15

99

High doses of dietary zinc induce cytokines, chemokines, and apoptosis in reproductive tissues during regression  

Microsoft Academic Search

In chickens, high levels of dietary zinc cause molting, and the reproductive system undergoes complete remodeling concomitant\\u000a to feather replacement. In the present study, the expression profiles of cytokines and chemokines were investigated in the\\u000a ovary and oviduct of control hens and of hens induced to molt by zinc feeding. The zinc-induced feed-intake suppression, the\\u000a changes in corticosterone levels, the

N. R. Sundaresan; D. Anish; K. V. H. Sastry; V. K. Saxena; K. Nagarajan; J. Subramani; M. D. M. Leo; N. Shit; J. Mohan; M. Saxena; K. A. Ahmed

2008-01-01

100

High temperature electrochemical corrosion rate probes  

SciTech Connect

Corrosion occurs in the high temperature sections of energy production plants due to a number of factors: ash deposition, coal composition, thermal gradients, and low NOx conditions, among others. Electrochemical corrosion rate (ECR) probes have been shown to operate in high temperature gaseous environments that are similar to those found in fossil fuel combustors. ECR probes are rarely used in energy production plants at the present time, but if they were more fully understood, corrosion could become a process variable at the control of plant operators. Research is being conducted to understand the nature of these probes. Factors being considered are values selected for the Stern-Geary constant, the effect of internal corrosion, and the presence of conductive corrosion scales and ash deposits. The nature of ECR probes will be explored in a number of different atmospheres and with different electrolytes (ash and corrosion product). Corrosion rates measured using an electrochemical multi-technique capabilities instrument will be compared to those measured using the linear polarization resistance (LPR) technique. In future experiments, electrochemical corrosion rates will be compared to penetration corrosion rates determined using optical profilometry measurements.

Bullard, Sophie J.; Covino, Bernard S., Jr.; Holcomb, Gordon R.; Ziomek-Moroz, M.

2005-09-01

101

High strain rate damage of Carrara marble  

NASA Astrophysics Data System (ADS)

Several cases of rock pulverization have been observed along major active faults in granite and other crystalline rocks. They have been interpreted as due to coseismic pervasive microfracturing. In contrast, little is known about pulverization in carbonates. With the aim of understanding carbonate pulverization, we investigate the high strain rate (c. 100 s-1) behavior of unconfined Carrara marble through a set of experiments with a Split Hopkinson Pressure Bar. Three final states were observed: (1) at low strain, the sample is kept intact, without apparent macrofractures; (2) failure is localized along a few fractures once stress is larger than 100 MPa, corresponding to a strain of 0.65%; (3) above 1.3% strain, the sample is pulverized. Contrary to granite, the transition to pulverization is controlled by strain rather than strain rate. Yet, at low strain rate, a sample from the same marble displayed only a few fractures. This suggests that the experiments were done above the strain rate transition to pulverization. Marble seems easier to pulverize than granite. This creates a paradox: finely pulverized rocks should be prevalent along any high strain zone near faults through carbonates, but this is not what is observed. A few alternatives are proposed to solve this paradox.

Doan, Mai-Linh; Billi, Andrea

2011-10-01

102

High-shear-rate optical rheometer  

NASA Astrophysics Data System (ADS)

We have developed a parallel-plate rheometer in a magnetic-disk drive configuration constructed of optically transparent materials and operating with a very small gap for measurements at very high shear rates. The friction force at the disk-slider interface has been measured as a function of sliding speed while the film thickness was monitored in situ using a capacitance technique. The shear rate is calculated from the film thickness and the sliding speed. A thin film can be applied on the disk, which allows very high-shear-rate measurements at low sliding speeds with negligible viscous heating. Both disk and slider have been made of optically transparent material to allow optical measurements simultaneously with the rheological measurements. In the present mode, the apparatus is set up for simultaneous rheometery and birefringence measurements on a thin film of polymer lubricant. Rheology and birefringence measurements were made on a perfluoropolyether lubricant over a range of strain rate from 103 s-1 to greater than 106 s-1 with 800 nm, 400 nm, and 200 nm film thicknesses.

Mriziq, K. S.; Dai, H. J.; Dadmun, M. D.; Jellison, G. E.; Cochran, H. D.

2004-06-01

103

High strain rate testing of solder interconnections  

Microsoft Academic Search

Purpose – This paper aims to present a new micro-impact tester developed for characterizing the impact properties of solder joints and micro-structures at high-strain rates, for the microelectronic industry, and the results evaluated for different solder ball materials, pad finishes and thermal histories by using this new tester. Knowledge of impact force is essential for quantifying the strength of the

K. T. Tsai; F. L. Liu; E. H. Wong; R. Rajoo

2006-01-01

104

Reproductive effects of inorganic borates on male employees: birth rate assessment.  

PubMed Central

The purpose of this study was to investigate the potential for reproductive effects of inorganic borate compounds on male employees. The standardized birth ratio (SBR) methodology was used to assess fertility among male employees, using live births as the measured end point. The ratio of female to male births was also assessed. Data were collected via questionnaires and telephone follow-up interviews. Medical insurance records were assessed for nonresponders. Exposures were assessed using three semiquantitative categories. We found a statistically significant increase in fertility as measured by live births among the employees of the inorganic borate facility. There does not appear to be any decrease in fertility due to exposures either as analyzed by the borate exposure categories or over time, which is an indirect measure of exposures. We found a nonstatistically significant increase in the percentage of female offspring. This increase was due, not to a deficiency of male offspring, but rather to a marked increase in the numbers of female offspring. This increase in percentage female offspring does not appear to be related to exposures to inorganic borates. Based on the data, exposures to inorganic borates do not appear to adversely affect fertility in this population.

Whorton, D; Haas, J; Trent, L

1994-01-01

105

Operation of high rate microstrip gas chambers  

NASA Astrophysics Data System (ADS)

We describe recent measurements carried out in well controlled and reproducible conditions to help understanding the factors affecting the short- and long-term behaviour of Microstrip Gas Chambers. Special care has been taken concerning the gas purity and choice of materials used in the system and for the detectors construction. Detectors built on glasses with surface resistivity in the range 1013-1015 ?/? have shown satisfactory performance as they do not show charging-up process at high rate and stand the large doses required for the future high luminosity experiments (~10mCcm-1yr-1). Concerning the lifetime measurements, it has been observed that chambers manufactured on high-resistivity glass are far more susceptible of suffering ageing than detectors made on low resistivity, electron-conducting supports, independently of the metal used for the artwork (chromium or gold) at least in clean gas conditions. The successful operation in the laboratory of detectors manufactured on diamond-coated glass with a surface resistivity around 1015 ?/? confirms the last statement. Results from a long-term, high rate beam test are also reported.

Barr, A.; Boimska, B.; Bouclier, R.; Capeáns, M.; Dominik, W.; Manzin, G.; Million, G.; Hoch, M.; Ropelewski, L.; Sauli, F.; Sharma, A.

1997-02-01

106

Personality and reproductive success in a high-fertility human population.  

PubMed

The existence of interindividual differences in personality traits poses a challenge to evolutionary thinking. Although research on the ultimate consequences of personality differences in nonhuman animals has recently undergone a surge of interest, our understanding of whether and how personality influences reproductive decisions in humans has remained limited and informed primarily by modern societies with low mortality-fertility schedules. Taking an evolutionary approach, we use data from a contemporary polygynous high-fertility human population living in rural Senegal to investigate whether personality dimensions are associated with key life-history traits in humans, i.e., quantity and quality of offspring. We show that personality dimensions predict reproductive success differently in men and women in such societies and, in women, are associated with a trade-off between offspring quantity and quality. In women, neuroticism positively predicts the number of children, both between and within polygynous families. Furthermore, within the low social class, offspring quality (i.e., child nutritional status) decreases with a woman's neuroticism, indicating a reproductive trade-off between offspring quantity and quality. Consistent with this, maximal fitness is achieved by women at an intermediate neuroticism level. In men, extraversion was found to be a strong predictor of high social class and polygyny, with extraverted men producing more offspring than their introverted counterparts. These results have implications for the consideration of alternative adaptive hypotheses in the current debate on the maintenance of personality differences and the role of individual factors in fertility patterns in contemporary humans. PMID:20538974

Alvergne, Alexandra; Jokela, Markus; Lummaa, Virpi

2010-06-10

107

High rate pulse processing algorithms for microcalorimeters  

SciTech Connect

It has been demonstrated that microcalorimeter spectrometers based on superconducting transition-edge-sensor can readily achieve sub-100 eV energy resolution near 100 keV. However, the active volume of a single microcalorimeter has to be small to maintain good energy resolution, and pulse decay times are normally in the order of milliseconds due to slow thermal relaxation. Consequently, spectrometers are typically built with an array of microcalorimeters to increase detection efficiency and count rate. Large arrays, however, require as much pulse processing as possible to be performed at the front end of the readout electronics to avoid transferring large amounts of waveform data to a host computer for processing. In this paper, they present digital filtering algorithms for processing microcalorimeter pulses in real time at high count rates. The goal for these algorithms, which are being implemented in the readout electronics that they are also currently developing, is to achieve sufficiently good energy resolution for most applications while being (a) simple enough to be implemented in the readout electronics and (b) capable of processing overlapping pulses and thus achieving much higher output count rates than the rates that existing algorithms are currently achieving. Details of these algorithms are presented, and their performance was compared to that of the 'optimal filter' that is the dominant pulse processing algorithm in the cryogenic-detector community.

Rabin, Michael [Los Alamos National Laboratory; Hoover, Andrew S [Los Alamos National Laboratory; Bacrania, Mnesh K [Los Alamos National Laboratory; Tan, Hui [XIA-LLC; Breus, Dimitry [XIA-LLC; Henning, Wolfgang [XIA-LLC; Sabourov, Konstantin [XIA-LLC; Collins, Jeff [XAI-LLC; Warburton, William K [XIA-LLC; Dorise, Bertrand [NIST; Ullom, Joel N [NIST; [NON LANL

2009-01-01

108

Glass dynamics at high strain rates  

NASA Astrophysics Data System (ADS)

We present a shear-transformation-zone (STZ) theoretical analysis of molecular-dynamics simulations of a rapidly sheared metallic glass. These simulations are especially revealing because, although they are limited to high strain rates, they span temperatures ranging from well below to well above the glass transition. With one important discrepancy, the simplified STZ theory used here reproduces the simulation data, including the way in which those data can be made to collapse approximately onto simple curves by a scaling transformation. The STZ analysis implies that the system's behavior at high strain rates is controlled primarily by effective-temperature thermodynamics, as opposed to system-specific details of the molecular interactions. The discrepancy between theory and simulations occurs at the lower strain rates for temperatures near the glass transition. We argue that this discrepancy can be resolved by the same multispecies generalization of STZ theory that has been proposed recently for understanding frequency-dependent viscoelastic responses, Stokes-Einstein violations, and stretched-exponential relaxation in equilibrated glassy materials.

Langer, J. S.; Egami, Takeshi

2012-07-01

109

High strain rate behavior of polyurea compositions  

NASA Astrophysics Data System (ADS)

High-strain-rate response of three polyurea compositions with varying molecular weights has been investigated using a Split Hopkinson Pressure Bar arrangement equipped with aluminum bars. Three polyurea compositions were synthesized from polyamines (Versalink, Air Products) with a multi-functional isocyanate (Isonate 143L, Dow Chemical). Amines with molecular weights of 1000, 650, and a blend of 250/1000 have been used in the current investigation. These materials have been tested to strain rates of over 6000/s. High strain rate results from these tests have shown varying trends as a function of increasing strain. While higher molecular weight composition show lower yield, they do not show dominant hardening behavior at lower strain. On the other hand, the blend of 250/1000 show higher load bearing capability but lower strain hardening effects than the 600 and 1000 molecular weight amine based materials. Results indicate that the initial increase in the modulus of the blend of 250/1000 may lead to the loss of strain hardening characteristics as the material is compressed to 50% strain, compared to 1000 molecular weight amine based material.

Joshi, Vasant S.; Milby, Christopher

2012-03-01

110

High Strain Rate Behavior of Polyurea Compositions  

NASA Astrophysics Data System (ADS)

Polyurea has been gaining importance in recent years due to its impact resistance properties. The actual compositions of this viscoelastic material must be tailored for specific use. It is therefore imperative to study the effect of variations in composition on the properties of the material. High-strain-rate response of three polyurea compositions with varying molecular weights has been investigated using a Split Hopkinson Pressure Bar arrangement equipped with titanium bars. The polyurea compositions were synthesized from polyamines (Versalink, Air Products) with a multi-functional isocyanate (Isonate 143L, Dow Chemical). Amines with molecular weights of 1000, 650, and a blend of 250/1000 have been used in the current investigation. The materials have been tested up to strain rates of 6000/s. Results from these tests have shown interesting trends on the high rate behavior. While higher molecular weight composition show lower yield, they do not show dominant hardening behavior. On the other hand, the blend of 250/1000 show higher load bearing capability but lower strain hardening effects than the 600 and 1000 molecular weight amine based materials. Refinement in experimental methods and comparison of results using aluminum Split Hopkinson Bar is presented.

Joshi, Vasant; Milby, Christopher

2011-06-01

111

High Strain Rate Behavior of Nanoporous Tantalum  

NASA Astrophysics Data System (ADS)

Nano-scale failure under extreme conditions is not well understood. In addition to porosity arising from mechanical failure at high strain rates, porous structures also develop due to radiation damage. Therefore, understanding the role of porosity on mechanical behavior is important for the assessment and development of materials like metallic foams, and materials for new fission and fusion reactors, with improved mechanical properties. We carry out molecular dynamics (MD) simulations of a Tantalum (a model body-centered cubic metal) crystal with a collection of nanovoids under compression. The effects of high strain rate, ranging from 10^7s-1 to 10^10s-1, on the stress strain curve and on dislocation activity are examined. We find massive total dislocation densities, and estimate a much lower density of mobile dislocations, due to the formation of junctions. Despite the large stress and strain rate, we do not observe twin formation, since nanopores are effective dislocation production sources. A significant fraction of dislocations survive unloading, unlike what happens in fcc metals, and future experiments might be able to study similar recovered samples and find clues to their plastic behavior during loading.

Ruestes, Carlos J.; Bringa, Eduardo M.; Stukowski, Alexander; Rodriguez Nieva, Joaquin F.; Bertolino, Graciela; Tang, Yizhe; Meyers, Marc A.

2012-02-01

112

Glass dynamics at high strain rates.  

PubMed

We present a shear-transformation-zone (STZ) theoretical analysis of molecular-dynamics simulations of a rapidly sheared metallic glass. These simulations are especially revealing because, although they are limited to high strain rates, they span temperatures ranging from well below to well above the glass transition. With one important discrepancy, the simplified STZ theory used here reproduces the simulation data, including the way in which those data can be made to collapse approximately onto simple curves by a scaling transformation. The STZ analysis implies that the system's behavior at high strain rates is controlled primarily by effective-temperature thermodynamics, as opposed to system-specific details of the molecular interactions. The discrepancy between theory and simulations occurs at the lower strain rates for temperatures near the glass transition. We argue that this discrepancy can be resolved by the same multispecies generalization of STZ theory that has been proposed recently for understanding frequency-dependent viscoelastic responses, Stokes-Einstein violations, and stretched-exponential relaxation in equilibrated glassy materials. PMID:23005420

Langer, J S; Egami, Takeshi

2012-07-12

113

High strain rate deformation of layered nanocomposites.  

PubMed

Insight into the mechanical behaviour of nanomaterials under the extreme condition of very high deformation rates and to very large strains is needed to provide improved understanding for the development of new protective materials. Applications include protection against bullets for body armour, micrometeorites for satellites, and high-speed particle impact for jet engine turbine blades. Here we use a microscopic ballistic test to report the responses of periodic glassy-rubbery layered block-copolymer nanostructures to impact from hypervelocity micron-sized silica spheres. Entire deformation fields are experimentally visualized at an exceptionally high resolution (below 10?nm) and we discover how the microstructure dissipates the impact energy via layer kinking, layer compression, extreme chain conformational flattening, domain fragmentation and segmental mixing to form a liquid phase. Orientation-dependent experiments show that the dissipation can be enhanced by 30% by proper orientation of the layers. PMID:23132014

Lee, Jae-Hwang; Veysset, David; Singer, Jonathan P; Retsch, Markus; Saini, Gagan; Pezeril, Thomas; Nelson, Keith A; Thomas, Edwin L

2012-01-01

114

High strain rate deformation of layered nanocomposites  

NASA Astrophysics Data System (ADS)

Insight into the mechanical behaviour of nanomaterials under the extreme condition of very high deformation rates and to very large strains is needed to provide improved understanding for the development of new protective materials. Applications include protection against bullets for body armour, micrometeorites for satellites, and high-speed particle impact for jet engine turbine blades. Here we use a microscopic ballistic test to report the responses of periodic glassy-rubbery layered block-copolymer nanostructures to impact from hypervelocity micron-sized silica spheres. Entire deformation fields are experimentally visualized at an exceptionally high resolution (below 10?nm) and we discover how the microstructure dissipates the impact energy via layer kinking, layer compression, extreme chain conformational flattening, domain fragmentation and segmental mixing to form a liquid phase. Orientation-dependent experiments show that the dissipation can be enhanced by 30% by proper orientation of the layers.

Lee, Jae-Hwang; Veysset, David; Singer, Jonathan P.; Retsch, Markus; Saini, Gagan; Pezeril, Thomas; Nelson, Keith A.; Thomas, Edwin L.

2012-11-01

115

The oocyte and its role in regulating ovulation rate: a new paradigm in reproductive biology  

Microsoft Academic Search

Ovulation rate in mammals is determined by a complex exchange of hormonal signals between the pituitary gland and the ovary and by a localised exchange of hormones within ovarian follicles between the oocyte and its adjacent somatic cells. From examination of inherited patterns of ovulation rate in sheep, point mutations have been identified in two oocyte- expressed genes, BMP15 (GDF9B)

K P McNatty; L G Moore; N L Hudson; L D Quirke; S B Lawrence; K Reader; J P Hanrahan; P Smith; N P Groome; M Laitinen; O Ritvos; J L Juengel

2004-01-01

116

High frame-rate digital radiographic videography  

SciTech Connect

High speed x-ray imaging can be an important tool for observing internal processes in a wide range of applications. In this paper we describe preliminary implementation of a system having the eventual goal of observing the internal dynamics of bone and joint reactions during loading. Two Los Alamos National Laboratory (LANL) gated and image intensified camera systems were used to record images from an x-ray image convertor tube to demonstrate the potential of high frame-rate digital radiographic videography in the analysis of bone and joint dynamics of the human body. Preliminary experiments were done at LANL to test the systems. Initial high frame-rate imaging (from 500 to 1000 frames/s) of a swinging pendulum mounted to the face of an X-ray image convertor tube demonstrated high contrast response and baseline sensitivity. The systems were then evaluated at the Motion Analysis Laboratory of Henry Ford Health Systems Bone and Joint Center. Imaging of a 9 inch acrylic disk with embedded lead markers rotating at approximately 1000 RPM, demonstrated the system response to a high velocity/high contrast target. By gating the P-20 phosphor image from the X-ray image convertor with a second image intensifier (II) and using a 100-microsecond wide optical gate through the second II, enough prompt light decay from the x-ray image convertor phosphor had taken place to achieve reduction of most of the motion blurring. Measurement of the marker velocity was made by using video frames acquired at 500 frames/s. The data obtained from both experiments successfully demonstrated the feasibility of the technique. Several key areas for improvement are discussed along with salient test results and experiment details.

King, N.S.P.; Cverna, F.H.; Albright, K.L.; Jaramillo, S.A.; Yates, G.J.; McDonald, T.E. [Los Alamos National Lab., NM (United States); Flynn, M.J.; Tashman, S. [Henry Ford Health System, Detroit, MI (United States)

1994-09-01

117

MST-5 high rate mechanical testing facility  

SciTech Connect

Selected aspects of five gun systems in the MST-5 High Rate Mechanical Testing Facility are described. 238 plutonium sources heated by a projectile furnace are impacted in a 7 in. gun system which provides impact containment. Failure strains in sheet metals are determined by a biaxial punch test and a tensile test using a 2 in. bore gun. A similar gun has its target chamber in a glove box for testing radioactive materials. High temperatures (less than or equal to1000/sup 0/C) compression stress-strain curves are obtained by a Hopkinson bar where wave dispersion in the bars is corrected in the data reduction. A 40 mm gun is being set up in a glove box train for determining the shock response of hazardous materials using both instrumental and recovery tests.

Frantz, C.E.

1985-01-01

118

Degradation of the reproduction of the high-order sensation caused by halation  

NASA Astrophysics Data System (ADS)

We are investigating the important physical factors for the reproduction of the high-order sensation, such as 'the sense of existence' and 'the naturalness', in a display of images. In our research, a key assessment word, 'image depth', is a useful indicator for the discovery of new physical factors. Focusing on the faithful reproduction of 'image depth', some physical factors of a display have been discovered. In this report, we will describe the newly discovered physical factor, the halation and the degradation of image quality. After observation of the images on two displays which have different types of coating on the surface of CRT, we have hypothesized that the halation around the surface of CRT might cause a serious degradation of image quality such as 'image depth'. Also we have considered that the coating might be one of important factors related to the halation characteristic. To confirm the above assumption, we prepared three types of CRT picture monitor which have different types of coating: 13 layer AR coating, 4 layer AR + non- glare coating and no-coating. The increase of luminance around a test target of white rectangle caused by the halation have been measured and the relationship between the halation characteristic and the reproduction of 'image depth' has been assessed.

Shirai, Hideki; Kameda, Masashi; Miyahara, Makoto; Taniho, Shuji; Algazi, V. Ralph

1999-04-01

119

Differential reproductive success favours strong host preference in a highly specialized brood parasite  

PubMed Central

Obligate avian brood parasites show dramatic variation in the degree to which they are host specialists or host generalists. The screaming cowbird Molothrus rufoaxillaris is one of the most specialized brood parasites, using a single host, the bay-winged cowbird (Agelaioides badius) over most of its range. Coevolutionary theory predicts increasing host specificity the longer the parasite interacts with a particular avian community, as hosts evolve defences that the parasite cannot counteract. According to this view, host specificity can be maintained if screaming cowbirds avoid parasitizing potentially suitable hosts that have developed effective defences against parasitic females or eggs. Specialization may also be favoured, even in the absence of host defences, if the parasite's reproductive success in alternative hosts is lower than that in the main host. We experimentally tested these hypotheses using as alternative hosts two suitable but unparasitized species: house wrens (Troglodytes aedon) and chalk-browed mockingbirds (Mimus saturninus). We assessed host defences against parasitic females and eggs, and reproductive success of the parasite in current and alternative hosts. Alternative hosts did not discriminate against screaming cowbird females or eggs. Egg survival and hatching success were similarly high in current and alternative hosts, but the survival of parasitic chicks was significantly lower in alternative hosts. Our results indicate that screaming cowbirds have the potential to colonize novel hosts, but higher reproductive success in the current host may favour host fidelity.

De Marsico, Maria C; Reboreda, Juan C

2008-01-01

120

High repetition rate nitrogen ion laser  

SciTech Connect

The average power of a pulsed discharge laser may be increased by increasing the single pulse energy or by pulsing the laser at a higher rate without a substantial loss of single pulse energy. Single pulse energy can be enhanced by increasing the energy deposition to the medium, and by scaling to larger discharge volumes. The realization of high repetition rates (HRR's) is often accomplished by the addition of specialized power supplies, pulse-forming-networks, and laser heads. In this work, a HRR N{sub 2}+ laser has been developed and its output characterized as a function of gas pressure, temperature, velocity, energy deposition, and repetition rate. It is shown that a self-excited superradiant device is more susceptible to HRR failure modes than a similar oscillator-amplifier arrangement, the difference arising from gain and saturation considerations. With this understanding, A HRR N{sub 2}+ oscillator-amplifier was constructed yielding pulse energies of 4.5 mJ and 0.25 W average power at 60 pps, while capable of several hour gas fill lifetimes.

Harshaw, R.C.

1984-01-01

121

High Rate Pulse Processing Algorithms for Microcalorimeters  

NASA Astrophysics Data System (ADS)

It has been demonstrated that microcalorimeter spectrometers based on superconducting transition-edge-sensors can readily achieve sub-100 eV energy resolution near 100 keV. However, the active volume of a single microcalorimeter has to be small in order to maintain good energy resolution, and pulse decay times are normally on the order of milliseconds due to slow thermal relaxation. Therefore, spectrometers are typically built with an array of microcalorimeters to increase detection efficiency and count rate. For large arrays, however, as much pulse processing as possible must be performed at the front end of readout electronics to avoid transferring large amounts of waveform data to a host computer for post-processing. In this paper, we present digital filtering algorithms for processing microcalorimeter pulses in real time at high count rates. The goal for these algorithms, which are being implemented in readout electronics that we are also currently developing, is to achieve sufficiently good energy resolution for most applications while being: a) simple enough to be implemented in the readout electronics; and, b) capable of processing overlapping pulses, and thus achieving much higher output count rates than those achieved by existing algorithms. Details of our algorithms are presented, and their performance is compared to that of the ``optimal filter'' that is currently the predominantly used pulse processing algorithm in the cryogenic-detector community.

Tan, Hui; Breus, Dimitry; Hennig, Wolfgang; Sabourov, Konstantin; Collins, Jeffrey W.; Warburton, William K.; Bertrand Doriese, W.; Ullom, Joel N.; Bacrania, Minesh K.; Hoover, Andrew S.; Rabin, Michael W.

2009-12-01

122

Ecology of reproduction in Sanje mangabeys (Cercocebus sanjei): Dietary strategies and energetic condition during a high fruit period.  

PubMed

The ability to increase energy storage when food is abundant for later use during late gestation and early lactation is often considered the primary benefit of the capital breeding strategy (clustering conceptions during high food periods, HFP) that promotes reproductive success among females living in unpredictable environments. Capital breeding, however, may also enable preconceptive females to increase hormone production for ovulation, which has been linked to energetic condition in capital breeders, and/or allow females entering the subsequent HFP to increase their energetic condition in order to continue nursing unweaned infants. Here, we investigate whether capital breeding provides these additional benefits in 16 female Sanje mangabeys (Cercocebus sanjei) and determine the dietary strategies used to increase energetic condition (measured by urinary C-peptide: UCP) during the HFP. Fecal estradiol (fE2 ) and UCP were negatively correlated with number of cycles before conception (r?=?-0.591, r?=?-0.646, P?rate (FIR) and time spent foraging and feeding did not change over the HFP; however, non-peri-conceptive females exhibited a faster FIR compared to peri-conceptive females (t?=?-2.324, P?reproductive cycle by using capital breeding, which may explain how this strategy promotes female reproductive success. Am. J. Primatol. 75:1196-1208, 2013. © 2013 Wiley Periodicals, Inc. PMID:23897561

McCabe, Gráinne Michelle; Fernández, David; Ehardt, Carolyn L

2013-07-29

123

High divergence of reproductive tract proteins and their association with postzygotic reproductive isolation in Drosophila melanogaster and Drosophila virilis group species  

Microsoft Academic Search

The possible association between gonadal protein divergence and postzygotic reproductive isolation was investigated among species of the Drosophila melanogaster and D. virilis groups. Protein divergence was scored by high-resolution two-dimensional electrophoresis (2DE). Close to 500 protein spots from gonadal tissues (testis and ovary) and nongonadal tissues (malpighian tubules and brain) were analyzed and protein divergence was calculated based on presence

Alberto Civetta; Rama S. Singh

1995-01-01

124

Factors affecting feeding rate, reproduction and growth of an oligochaete Lumbriculus variegatus (Müller)  

Microsoft Academic Search

Worm density of a deposit feeding oligochaete (Lumbriculus variegatus) did not affect egestion whereas both temperature and\\u000a sediment type had a significant influence. The worms egested less actively at the lowest temperature (6 °C). The egestion\\u000a rate, expressed as mg dry feces produced, was highest in the sandy sediment and lowest in the sediment derived almost exclusively\\u000a from decaying plant

Matti T. Leppänen; Jussi V. K. Kukkonen

1998-01-01

125

Individualised controlled ovarian stimulation (iCOS): maximising success rates for assisted reproductive technology patients  

Microsoft Academic Search

Background  In the last two decades, pregnancy rates for patients undergoing in-vitro fertilisation (IVF) have significantly increased.\\u000a Some of the major advances responsible for this improvement were the introduction of controlled ovarian stimulation (COS)\\u000a for the induction of multiple follicle development, and the utilisation of mid-luteal gonadotropin-releasing hormone agonists\\u000a to achieve pituitary down-regulation and full control of the cycle. As a

Ernesto Bosch; Diego Ezcurra

2011-01-01

126

1995 assisted reproductive technology success rates: national summary and fertility clinic report.  

PubMed

Although ART offers important options for the treatment of infertility, the decision to use ART involves many factors in addition to success rates. Going through repeated ART cycles requires substantial commitments of time, effort, money, and emotional energy. Couples and individuals considering ART should carefully examine all related financial, psychologic, ethical, and medical issues before beginning treatment. They should also contact ART clinics to discuss their specific medical situation and potential for success using ART. The next published report will feature 1996 data and provide a listing of clinics that did not submit data. Eventually, the annual report will include information from all U.S. fertility clinics, not just those that are SART members. PMID:9580908

Danel, I A; Green, Y T; Walter, G

1998-04-01

127

Mice lacking Raf kinase inhibitor protein-1 (RKIP-1) have altered sperm capacitation and reduced reproduction rates with a normal response to testicular injury.  

PubMed

Raf kinase inhibitor protein-1 (RKIP-1) belongs to the phosphatidyl ethanolamine-binding family of proteins (PEBP), which are highly conserved throughout evolution and widely expressed in tissues of mammalian organisms. RKIP-1 is a modulator of extracellular signal-regulated kinase (ERK), nuclear factor-kappa B (NF-kappaB), and G protein coupled receptor (GPCR) signaling cascades and is implicated as a factor in numerous physiological processes and disease states including metastasis. Testicular germ cells also express high levels of RKIP mRNA during spermatogenesis, particularly from late pachytene spermatocytes through step 15 elongate spermatids. Therefore, the sensitivity of spermatogenesis to injury was compared in wild-type and RKIP-1(-/-) mice. Unlike what has been described with tumor suppressors such as p53, RKIP-1(-/-) and wild-type mice were equally sensitive to germ cell toxicity by x-irradiation as assessed by terminal deoxynucleotidyl transferase biotin-deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) positivity 9 hours after a 5 Gy exposure and testicular spermatid head counts 15.5 days after 0.5 Gy exposure. Recent findings also indicate that RKIP is a decapacitation factor receptor on sperm. The present study demonstrates that sperm from RKIP-deficient mice are precociously capacitated compared with their wild-type counterparts. Data from mating experiments indicate decreased reproduction rates between crosses of RKIP-1(-/-) male mice and either heterozygous or RKIP-1(-/-) females. Furthermore, RKIP immunolocalization of epididymal sperm supports transfer of the protein from germ cell cytoplasm to the sperm via the cytoplasmic droplet during epididymal transport. Overall, these studies indicate an important role for RKIP in reproduction as a modulator of capacitation but not in the regulation of testicular injury. PMID:17554109

Moffit, Jeffrey S; Boekelheide, Kim; Sedivy, John M; Klysik, Jan

2007-06-06

128

The goitre rate, its association with reproductive failure, and the knowledge of iodine deficiency disorders (IDD) among women in Ethiopia: Cross-section community based study  

Microsoft Academic Search

BACKGROUND: Iodine deficiency is severe public health problem in Ethiopia. Although urinary iodine excretion level (UIE) is a better indicator for IDD the goitre rate is commonly used to mark the public health significance. The range of ill effect of IDD is however beyond goitre in Ethiopia. In this study the prevalence of goitre and its association with reproductive failure,

Cherinet Abuye; Yemane Berhane

2007-01-01

129

Lunar periodicity in catch rate and reproductive condition of adult eastern king prawns, Penaeus plebejus, in coastal waters of south-eastern Queensland, Australia  

Microsoft Academic Search

This study examined the lunar and die1 variation in catch rates and reproductive condition of adult eastern king prawns, Penaeus plebejus, in relatively deep (160 m) coastal waters off south- eastern Queensland. Females numerically dominated catches over most of the lunar cycle and constituted 76% of the weight of the catch. Analysis of variance (ANOVA) revealed an interaction between lunar

A. J. Courtney; DJ Die; JG McGilvray

1996-01-01

130

High rate PLD of diamond-like-carbon utilizing high repetition rate visible lasers  

SciTech Connect

Pulsed Laser Deposition (PLD) has been shown to be an effective method for producing a wide variety of thin films of high-value-added materials. The high average powers and high pulse repetition frequencies of lasers under development at LLNL make it possible to scale-up PLD processes that have been demonstrated in small systems in a number of university, government, and private laboratories to industrially meaningful, economically feasible technologies. A copper vapor laser system at LLNL has been utilized to demonstrate high rate PLD of high quality diamond-like-carbon (DLC) from graphite targets. The deposition rates for PLD obtained with a 100 W laser were {approx} 2000 {mu}m{center_dot}cm{sup 2}/h, or roughly 100 times larger than those reported by chemical vapor deposition (CVD) or physical vapor deposition (PVD) methods. Good adhesion of thin (up to 2 pm) films has been achieved on a small number of substrates that include SiO{sub 2} and single crystal Si. Present results indicate that the best quality DLC films can be produced at optimum rates at power levels and wavelengths compatible with fiber optic delivery systems. If this is also true of other desirable coating systems, this PLD technology could become an extremely attractive industrial tool for high value added coatings.

McLean, W. II; Fehring, E.J.; Dragon, E.P.; Warner, B.E.

1994-09-15

131

Ground based high data rate DVB-S2 demodulator for high data rate AISR transport  

Microsoft Academic Search

The Wideband Global SATCOM system (WGS) block II satellite offers Airborne Intelligence, Surveillance, and Reconnaissance platforms with an unprecedented amount of satellite bandwidth. Unmanned aerial vehicle (UAV) platforms require a new waveform and subsequent modem implementations to fully exploit these new capabilities. To complement the high data rate (HDR) version of the Digital Video Broadcasting, Second Generation Satellite (DVB-S2) standard

Chayil Timmerman; Miles Benson; John Delisle; Justin Delva; Robert Elliott; Jason Hillger; A. Miller; T. Brick; J. Long; N. Humphrey

2010-01-01

132

In situ high rate growth of high temperature superconductor tapes  

SciTech Connect

In situ high rate growth of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} superconducting films has been carried out using e-beam deposition. A deposition flux controller is developed to monitor and control the deposition rates using tunable diode laser based atomic absorption. Wide range of temperatures, deposition rates, and oxygen fluxes including atomic and molecular oxygen, as well as ozone, have been explored in order to understand both kinetic and thermodynamic stability. Critical current density above 1 MA/cm{sup 2} has been achieved on SrTiO{sub 3} substrate samples in growth rate up to 75 {angstrom}/sec. Samples prepared on IBAD YSZ/Ni tapes exhibit similar R(T)s and x-ray diffraction patterns. However, critical current densities of the tapes are around kA/cm{sup 2} or lower. The poor critical current density of the tape is attributed to interaction between the YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} film and the YSZ buffer layer.

Hammond, M. R. B. (Malcom R. Beasley); Peng, L. S. (Luke S.); Wang, W. (Weizhi); Jo, W.; Ohnishi, T. (Tsuyoshi); Marshall, A. F. (Ann F.); Hammond, R. H. (Robert H.); Beasley, M. R. (Malcom R.); Peterson, E. J. (Eric J.); Ericson, R. (Richard)

2001-01-01

133

Nesting ecology and reproductive rate of the red-winged blackbird in tidal marshes of the upper Chesapeake Bay region  

USGS Publications Warehouse

The nesting ecology and reproductive rate of the polygynous red-winged blackbird, Agelaius phoeniceus, were studied in the tidal marshes of Maryland during the period of 1958 through 1961. Sixteen nesting colonies were located in six major marsh communities of the Eastern Shore and were visited approximately twice a week from late April to mid-August. The average clutch size for 537 clutches was 3.3 eggs, with a range of 2 to 5 eggs. The ratio of territorial males to nesting females was 1:1.9. There was direct evidence of double broods by four females. The average number of young produced was 4.2 per breeding female or 8.1 per breeding male. Nesting success for the total of 675 active nests was 57%, with a range from 38% to 69% in the colonies. Robust plants that held constant form throughout the nesting season supported 95% of the nests, and the success of these nests was 58%; in contrast, non-robust plants supported only 5% of the nests, and success of this group of nests was only 26%. Nesting success varied with height from ground: 45% for nests less than 2 feet from the ground, 55% for those 2 to 4 feet, and 62% for those more than 4 feet. Histories of 749 nests were summarized by stages: 749 newly built, 675 with eggs, 424 with nestlings, and 388 with fledging young.

Meanley, B.; Webb, J.S.

1963-01-01

134

Effect of birth litter size, birth parity number, growth rate, backfat thickness and age at first mating of gilts on their reproductive performance as sows  

Microsoft Academic Search

The present study was performed to evaluate retrospectively the influence of birth litter size, birth parity number, performance test parameters (growth rate from birth to 100kg body weight and backfat thickness at 100kg body weight) and age at first mating (AFM) of gilts on their reproductive performance as sows. Traits analysed included remating rate in gilts (RRG), litter size, weaning-to-first-service

P. Tummaruk; N. Lundeheim; S. Einarsson; A.-M. Dalin

2001-01-01

135

The Effect of Minimum Wage Rates on High School Completion  

Microsoft Academic Search

Does increasing the minimum wage reduce the high school completion rate? Previous research has suffered from (1. narrow time horizons, (2. potentially inadequate measures of states’ high school completion rates, and (3. potentially inadequate measures of minimum wage rates. Overcoming each of these limitations, we analyze the impact of changes in state and federal minimum wage rates on state high

John Robert Warren

2010-01-01

136

High dose rate transperineal interstitial brachytherapy for cervical cancer: high pelvic control and low complication rates  

Microsoft Academic Search

Purpose: To report the clinical outcome for cervical carcinoma treated with external beam pelvic radiotherapy and interstitial high dose rate (IS-HDR) brachytherapy.Methods and Materials: Between July 1991 and June 1996, 62 patients with locally advanced stage cervical carcinoma or early stage carcinoma that precluded satisfactory tandem and ovoid insertion were treated. Most patients received 36 Gy (range: 25 Gy–45 Gy)

D. Jeffrey Demanes; Rodney R Rodriguez; Dhananjay D Bendre; Thomas L Ewing

1999-01-01

137

Plastic Flow and Failure Modeling under High Strain Rate Loading.  

National Technical Information Service (NTIS)

High strain rate properties were determined for several metals at room and high temperatures. Split Hopkinson bar (SHB) tests under both tension and compression were performed for obtaining stress-strain curves at different strain rates. Quasistatic tests...

A. M. Rajendran S. J. Bless

1988-01-01

138

Prevention of arsenic-mediated reproductive toxicity in adult female rats by high protein diet.  

PubMed

Abstract Context: The detrimental effects of arsenic on female reproductive functions may involve overt oxidative stress. Casein and pea [Pisum sativum Linn. (Fabaceae)] proteins have antioxidant properties. Objective: To investigate the role of casein- and pea-supplemented high-protein diet (HPD) in utero-ovarian protection from arsenic toxicity. Materials and methods: Adult female Wistar rats were orally gavaged with vehicle (Gr-I) or arsenic at 3?ppm/rat/d (Gr-II and Gr-III) for 30 consecutive days, when they were maintained on either regular diet containing 18% protein (Gr-I and Gr-II), or HPD containing 27% protein in the form of casein (20%) and pea (7%) (Gr-III). Reproductive functions were evaluated using a battery of biochemical and histological techniques. Results: As compared to Gr-I, the Gr-II rats suffered from loss of estrous cyclicity, reduction in weight (mg/100?g body weight) of ovary (Gr-I: 54.3?±?4.2 versus Gr-II: 35.8?±?1.6; p?reproductive damage caused by arsenic. PMID:23859609

Mondal, Srabanti; Mukherjee, Sanjit; Chaudhuri, Keya; Kabir, Syed N; Kumar Mukhopadhyay, Prabir

2013-07-17

139

Declining trends in conception rates in recent birth cohorts of native Danish women: a possible role of deteriorating male reproductive health  

PubMed Central

Recent findings of poor semen quality among at least 20% of normal young men in Denmark prompted us to use unique Danish registers on births and induced abortions to evaluate a possible effect of the poor male fecundity on pregnancy rates among their presumed partners – the younger cohorts of women. We have analysed data from the Danish birth and abortion registries as well as the Danish registry for assisted reproduction (ART) and defined a total natural conception rate (TNCR), which is equal to fertility rate plus induced abortion rate minus ART conception rate. A unique personal identification number allowed the linkage of these databases. Our database included 706 270 native Danish women born between 1960 and 1980. We used projections to estimate the fertility of the later cohorts of women who had not yet finished their reproduction. We found that younger cohorts had progressively lower TNCR and that in terms of their total fertility rate, the declining TNCR is compensated by an increasing use of ART. Our hypothesis of an ongoing birth cohort-related decline in fecundity was also supported by our finding of increasing and substantial use of ART in the management of infertility of relatively young couples in the later cohorts. Furthermore, the lower rates of induced abortion among the younger birth cohorts, often viewed as a success of health education programs, may not be fully explained by improved use of contraception. It seems more likely that decreased fecundity because of widespread poor semen quality among younger cohorts of otherwise normal men may explain some of the observed decline in conception rates. This may imply increasing reproductive health problems and lower fertility in the future, which is difficult to reverse in the short term. The current and projected widespread use of ART in Denmark may be a sign of such an emerging public health problem.

Jensen, Tina Kold; Sobotka, Tomas; Hansen, Martin A; Pedersen, Anette T?nnes; Lutz, Wolfgang; Skakkebaek, Niels E

2008-01-01

140

High Metabolic Rates in Beach Cast Communities  

Microsoft Academic Search

Metabolic hotspots at land–water interfaces are important in supporting biogeochemical processes. Here we confirm the generality\\u000a of land–aquatic interfaces as biogeochemical hot spots by extending this concept to marine beach cast materials. In situ atmospheric\\u000a pCO2, from a respiration chamber (10 cm in diameter and 20 cm high) inserted into wrack deposits, was determined using a high-precision\\u000a (±1 ppm) non-dispersive infrared gas analyzer

Grey T. Coupland; Carlos M. Duarte; Diana I. Walker

2007-01-01

141

Theoretical model of relationship between frame-rate and bit-rate for encoding high frame-rate video signal  

Microsoft Academic Search

Higher frame-rates are being considered to achieve more realistic representations. Since increasing the frame-rate increases the total amount of information, efficient coding methods are required. However, its statistical properties are not clarified. This paper establishes for high frame-rate video a mathematical model of the relationship between frame-rate and bit-rate. A coding experiment confirms the validity of the mathematical model.

Yukihiro Bandoh; Seishi Takamura; Kazuto Kamikura; Yoshiyuki Yashima

2005-01-01

142

Reproductive limits of a late-flowering high-mountain Mediterranean plant along an elevational climate gradient  

Microsoft Academic Search

Summary • Mountain plants are particularly sensitive to climate warming because snowmelt timing exerts a direct control on their reproduction. Current warming is leading to earlier snowmelt dates and longer snow-free periods. Our hypothesis is that high- mountain Mediterranean plants are not able to take advantage of a lengthened snow-free period because this leads to longer drought that truncates the

L. Giménez-Benavides; A. Escudero; J. M. Iriondo

2007-01-01

143

Emergence and pathogenicity of highly pathogenic Porcine reproductive and respiratory syndrome virus in Vientiane, Lao People's Democratic Republic.  

PubMed

Highly pathogenic porcine reproductive and respiratory syndrome (HP-PRRS) characterized by high fever, high morbidity, and high mortality in pigs of all ages emerged in China in 2006 and spread rapidly throughout Southeast Asia. In July 2010, a highly contagious swine disease with clinical signs similar to those of HP-PRRS was observed in the Lao People's Democratic Republic (Lao PDR). A field investigation covering 8 pig farms and 1 slaughterhouse in 7 different districts in the capital city of Vientiane was conducted to identify the disease. Total mortality rates ranged from 6.02% in boars to 91.28% in piglets (mean 54.15%) across the farms investigated. Emergence of the HP-PRRS virus (HP-PRRSV) in Lao PDR was confirmed using real-time reverse transcription polymerase chain reaction as well as virus isolation and identification. An animal inoculation study was performed to characterize the HP-PRRSV responsible for this outbreak. Isolate Laos 1.13 was inoculated into 70-day-old specific pathogen-free pigs to study pathogenicity. Clinical signs of high fever, rubefaction, respiratory distress, nervous symptoms, and diarrhea were observed in inoculated pigs, as well as pathological hemorrhagic lesions consolidated in the lungs. Morbidity and mortality were 100% and 60%, respectively, in inoculated pigs. HP-PRRSV was re-isolated from the inoculated pigs. Results suggested that the newly emerged HP-PRRSV was responsible for recent outbreaks of the swine disease in Lao PDR. The current report highlights the importance of continuous surveillance in neighboring countries to prevent introduction of PRRS to new regions. PMID:22379051

Ni, Jianqiang; Yang, Shibiao; Bounlom, Douangngeun; Yu, Xiuling; Zhou, Zhi; Song, Jianling; Khamphouth, Vongxay; Vatthana, Theppannga; Tian, Kegong

2012-03-01

144

High-rate counting efficiency of VLPC  

SciTech Connect

A simple model is applied to describe dependencies of Visible Light Photon Counter (VLPC) characteristics on temperature and operating voltage. Observed counting efficiency losses at high illumination, improved by operating at higher temperature, are seen to be a consequence of de-biasing within the VLPC structure. A design improvement to minimize internal de-biasing for future VLPC generations is considered. {copyright} {ital 1998 American Institute of Physics.}

Hogue, H.H. [Research and Technology Center, Boeing Electronic Systems and Missile Defense, 3370 Miraloma Ave M/S HB17, Anaheim, California 92803 (United States)

1998-11-01

145

Chinese highly pathogenic porcine reproductive and respiratory syndrome virus exhibits more extensive tissue tropism for pigs  

PubMed Central

Background The highly pathogenic porcine reproductive and respiratory syndrome virus (PRRSV) emerging in China exhibits high fatality to pigs. However, the mechanism related to the increased pathogenicity of the virus remains unclear. In the present study, the differences in tissue tropism between the highly pathogenic PRRSV strain (JXwn06) and the low pathogenic PRRSV strain (HB-1/3.9) were investigated using PRRSV-specific immunohistochemistry (IHC) staining to provide evidence for elucidating possible mechanism of the pathogenicity of Chinese highly pathogenic PRRSV. Findings IHC examination showed that PRRSV antigen in the tissues including spleen, tonsil, thymus, kidney, cerebellum, stomach, small intestine, large intestine, turbinal bone and laryngeal cartilage was positive in more pigs inoculated with JXwn06 than HB-1/3.9, and the tissues including trachea, esophagus, liver, mandibular gland and thyroid gland were positive for viral antigen in the pigs inoculated with JXwn06, but not in the pigs inoculated with HB-1/3.9. Meanwhile, we observed that epithelium in tissues including interlobular bile duct in liver, distal renal tubule of kidney, esophageal gland and tracheal gland were positive for viral antigen only in JXwn06-inoculated pigs, and epithelium of gastric mucosa and fundic gland, and intestinal gland were positive for viral antigen in both JXwn06- and HB-1/3.9-inoculated pigs, using monoclonal antibodies to N and Nsp2 proteins. Conclusions Taken together, these findings indicate that the highly pathogenic PRRSV JXwn06 displays an expanded tissue tropism in vivo, suggesting this may contribute to its high pathogenicity to pigs.

2012-01-01

146

Contrasting hybridization rates between sympatric three-spined sticklebacks highlight the fragility of reproductive barriers between evolutionarily young species  

Microsoft Academic Search

Three-spined sticklebacks ( Gasterosteus aculeatus ) are a powerful evolutionary model system due to the rapid and repeated phenotypic divergence of freshwater forms from a marine ancestor throughout the Northern Hemisphere. Many of these recently derived populations are found in overlapping habitats, yet are reproductively isolated from each other. This scenario provides excellent opportunities to investigate the mechanisms driving speciation

JENNIFER L. G OW; CATHERINE L. P EICHEL; ERIC B. T AYLOR

2006-01-01

147

High rates of nonbreeding adult bald eagles in southeastern Alaska  

SciTech Connect

Present knowledge of bald eagle (Haliaeetus leucocephalus) demography is derived primarily from populations in environments that have been drastically altered by man. Most reproductive studies were done in the 1960's and 1970's when chemical toxins were inhibiting bald eagle productivity. Earlier, the removal of old-growth forests and decimation of anadromous fish runs by Euro-Americans may have greatly reduced bald eagle abundance from presettlement levels. Historical trends in this species are of interest because fundamental differences may exist between populations in pristine and man-altered environments. One difference may be breeding rate. Surpluses of nonbreeding adult bald eagles during the nesting season are rarely mentioned in the literature. Most surveys of reproductive success focus exclusively on eagles at nest sites, which assumes nearly all adults attempt to breed each year. The authors report that a majority of adults in the relatively pristine habitats of southeastern Alaska do not breed annually. This finding is important because if surpluses of non-breeding adults are a natural feature of the population, then hypotheses on density dependent population regulation and the evolution of delayed maturation are suggested. If, on the other hand, the abundance of nonbreeders is an artifact of recent environmental perturbations, serious population declines may occur in southeastern Alaska.

Hansen, A.J.; Hodges, J.I. Jr.

1985-01-01

148

The modern high rate digital cassette recorder  

NASA Astrophysics Data System (ADS)

The magnetic tape recorder has played an essential role in the capture and storage of instrumentation data for more than thirty years. During this time, data recording technology has steadily progressed to meet user demands for more channels, wider bandwidths, and longer recording durations. When acquisition and processing moved from analog to digital techniques, so recorder design followed suit. Milestones marking the evolution of the data recorder through these various stages - multi-track analog, high density longitudinal digital, and more recently rotary digital - have often represented important breakthroughs in the handling of ever-greater quantities of data. Throughout this period there has been a very clear line of demarcation between data storage methods in the 'instrumentation world' on the one hand and the 'computer peripheral world' on the other. This is despite the fact that instrumentation data, whether analog or digital at the point of acquisition, is now likely to be processed on a digital computer at some stage. Regardless of whether the processing device is a small personal computer, a workstation, or the largest supercomputer, system integrators have traditionally been faced with the same basic problem - how to interface what is essentially a manually controlled, continuously running device (the tape recorder) into the fast start/stop computer environment without resorting to an excessive amount of complex custom interfacing and performance compromise. The increasing availability of affordable high power processing equipment throughout the scientific world is forcing recorder manufacturers to make their latest and perhaps most important breakthrough - the computer-friendly data recorder. The operating characteristics of such recorders are discussed and the resultant impact on both data acquisition and data analysis elements of system configuration are considered.

Clemow, Martin

149

HIV prevalence among high school learners - opportunities for schools-based HIV testing programmes and sexual reproductive health services  

PubMed Central

Background Young girls in sub Saharan Africa are reported to have higher rates of human immunodeficiency virus (HIV) infection compared to boys in the same age group. Knowledge of HIV status amongst high schools learners provides an important gateway to prevention and treatment services. This study aimed at determining the HIV prevalence and explored the feasibility of HIV testing among high school learners. Methods Between September 2010 and February 2011, a linked, anonymous cross-sectional survey was conducted in two public sector high schools in the rural KwaZulu-Natal midlands. Following written informed consent, dried blood spot samples (DBS) were collected and tested for HIV. The overall and age-specific HIV prevalence were compared with select demographic variables. Results The HIV prevalence in learners aged 12 to 25 in school A was 4.7% (95% CI 2.8-6.5) compared to 2.5% (95% CI 1.6-3.5) in school B, (p = 0.04). Whilst the HIV prevalence was similar for boys at 1.3% (95% CI 0-2.8) in school A and 1.7% (95% CI 0.5-2.8) in school B, the prevalence in girls was consistently higher and was 7.7% (95% CI 4.5-10.9) in school A and 3.2% (95% CI 1.8-4.6) in school B. The age-specific HIV prevalence in girls increased 1.5 to 2 fold for each two year age category, while for boys the prevalence was stable across all age groups. Conclusions The high HIV prevalence in female learners underscores the importance of sexual reproductive health and schools-based HIV testing programs as an important gateway to prevention and treatment services.

2012-01-01

150

Reproductive success and failure: the role of winter body mass in reproductive allocation in Norwegian moose.  

PubMed

A life history strategy that favours somatic growth over reproduction is well known for long-lived iteroparous species, especially in unpredictable environments. Risk-sensitive female reproductive allocation can be achieved by a reduced reproductive effort at conception, or the subsequent adjustment of investment during gestation or lactation in response to unexpected environmental conditions or resource availability. We investigated the relative importance of reduced investment at conception compared with later in the reproductive cycle (i.e. prenatal, perinatal or neonatal mortality) in explaining reproductive failure in two high-density moose (Alces alces) populations in southern Norway. We followed 65 multiparous, global positioning system (GPS)-collared females throughout the reproductive cycle and focused on the role of maternal nutrition during gestation in determining reproductive success using a quasi-experimental approach to manipulate winter forage availability. Pregnancy rates in early winter were normal (?0.8) in all years while spring calving rates ranged from 0.4 to 0.83, with prenatal mortality accounting for most of the difference. Further losses over summer reduced autumn recruitment rates to 0.23-0.69, despite negligible predation. Over-winter mass loss explained variation in both spring calving and autumn recruitment success better than absolute body mass in early or late winter. Although pregnancy was related to body mass in early winter, overall reproductive success was unrelated to pre-winter body condition. We therefore concluded that reproductive success was limited by winter nutritional conditions. However, we could not determine whether the observed reproductive allocation adjustment was a bet-hedging strategy to maximise reproduction without compromising survival or whether females were simply unable to invest more resources in their offspring. PMID:23223863

Milner, Jos M; van Beest, Floris M; Solberg, Erling J; Storaas, Torstein

2012-12-08

151

Endocrinology of year-round reproduction in a highly seasonal habitat: environmental variability in testosterone and glucocorticoids in baboon males  

PubMed Central

In conditions characterized by energetic constraints, such as in periods of low food availability, some trade-offs between reproduction and self-maintenance may be necessary; even year-round breeders may then be forced to exhibit some reproductive seasonality. Prior research has largely focused on female reproduction and physiology, and few studies have evaluated the impact of environmental factors on males. Here we assessed the effects of season and ambient temperatures on fecal glucocorticoid (fGC) and testosterone (fT) levels in male baboons in Amboseli, Kenya. The Amboseli basin is a highly challenging, semi-arid tropical habitat that is characterized by strongly seasonal patterns of rainfall and by high ambient temperatures. We previously reported that female baboons were impacted by these challenging environmental conditions. We ask here whether male baboons in the same environment and groups as females exhibit similar physiological effects. We found that after accounting for male age and individual variability, males exhibited higher fGC levels and lower fT levels during the dry season than during the wet season. Furthermore, fT but not fGC levels were lower in months of high average daily maximum temperatures, suggesting a direct impact of heat on testes. Our results demonstrate that male baboons, like females, experience ecological stress that alters their reproductive physiology. The impact of the environment on male reproduction deserves more attention both in its own right and because alteration in male physiology may contribute to the reduction in female fertility observed in challenging environments.

Gesquiere, Laurence R.; Onyango, Patrick O.; Alberts, Susan C.; Altmann, Jeanne

2010-01-01

152

Factors associated with the reproductive health risk behavior of high school students in the Republic of the Marshall Islands.  

PubMed

This study revealed factors associated with reproductive health risk behavior among high school students in the Republic of the Marshall Islands. The survey was conducted among high school students from grades 9 through 12 at 2 schools in Majuro, the capital of the Marshall Islands. The questions asked inquired about knowledge, attitude, and behavior related to reproductive health, experience of sexual acts and pregnancy. Multiple logistic regression analysis was performed to assess the association between risk behavior and knowledge, attitude, and other factors. Data obtained from 433 students were used in the analysis. Factors significantly associated with reproductive health risk behavior among both the boys and the girls were a negative attitude toward condom use (odds ratio of the risk group to the low-risk group: boys, 19.54; girls 4.10), not considering receiving public health information and services as a human right (8.10, 3.96), and not knowing where to go for consultation about questions and concerns related to sex (3.32, 4.73). A factor associated with risk behavior in boys alone was acceptance of sexual acts without love (8.46), and factors in girls alone were insufficient knowledge concerning routes of infection by sexually transmitted diseases (6.75) and lack of future life plans (5.00). Neither age nor sex education was a significant predictor. In conclusion, considering reproductive health not to be a personal right was associated with the risk behavior of high school students in the Marshall Islands in regard to reproductive health. PMID:16536853

Suzuki, Keiko; Motohashi, Yutaka; Kaneko, Yoshihiro

2006-04-01

153

Endocrinology of year-round reproduction in a highly seasonal habitat: environmental variability in testosterone and glucocorticoids in baboon males.  

PubMed

In conditions characterized by energetic constraints, such as in periods of low food availability, some trade-offs between reproduction and self-maintenance may be necessary; even year-round breeders may then be forced to exhibit some reproductive seasonality. Prior research has largely focused on female reproduction and physiology, and few studies have evaluated the impact of environmental factors on males. Here we assessed the effects of season and ambient temperatures on fecal glucocorticoid (fGC) and testosterone (fT) levels in male baboons in Amboseli, Kenya. The Amboseli basin is a highly challenging, semiarid tropical habitat that is characterized by strongly seasonal patterns of rainfall and by high ambient temperatures. We previously reported that female baboons were impacted by these challenging environmental conditions. We ask here whether male baboons in the same environment and groups as females exhibit similar physiological effects. We found that after accounting for male age and individual variability, males exhibited higher fGC levels and lower fT levels during the dry season than during the wet season. Furthermore, fT but not fGC levels were lower in months of high average daily maximum temperatures, suggesting a direct impact of heat on testes. Our results demonstrate that male baboons, like females, experience ecological stress that alters their reproductive physiology. The impact of the environment on male reproduction deserves more attention both in its own right and because alteration in male physiology may contribute to the reduction in female fertility observed inchallenging environments. PMID:20721938

Gesquiere, Laurence R; Onyango, Patrick O; Alberts, Susan C; Altmann, Jeanne

2010-08-18

154

What Affects Graduation Rates of Illinois Public High Schools?  

Microsoft Academic Search

This paper attempts to determine: What affects the graduation rates of Illinois public high schools? This question will be answered based on explanatory variables deemed important by previous research. The relationship between Illinois public high school graduation rates and the percentage of low income students in the high school, the percentage of parental involvement within the school, instructional expenditures per

Jazmen Rose

2008-01-01

155

Adverse reproductive and child health outcomes among people living near highly toxic waste water drains in Punjab, India  

Microsoft Academic Search

BackgroundEnvironmental influence plays a major role in determining health status of individuals. Punjab has been reported as having a high degree of water pollution due to heavy metals from untreated industrial effluent discharge and high pesticide consumption in agriculture. The present study ascertained the association of heavy metal and pesticide exposure on reproductive and child health outcomes in Punjab, India.MethodsA

Jarnail Singh Thakur; Shankar Prinja; Dalbir Singh; Arvind Rajwanshi; Rajendra Prasad; Harjinder Kaur Parwana; Rajesh Kumar

2009-01-01

156

Polyandrous females benefit by producing sons that achieve high reproductive success in a competitive environment.  

PubMed

Females of many taxa often copulate with multiple males and incite sperm competition. On the premise that males of high genetic quality are more successful in sperm competition, it has been suggested that females may benefit from polyandry by accruing 'good genes' for their offspring. Laboratory studies have shown that multiple mating can increase female fitness through enhanced embryo viability, and have exposed how polyandry influences the evolution of the ejaculate. However, such studies often do not allow for both female mate choice and male-male competition to operate simultaneously. Here, I took house mice (Mus domesticus) from selection lines that had been evolving with (polygamous) and without (monogamous) sperm competition for 16 generations and, by placing them in free-ranging enclosures for 11 weeks, forced them to compete for access to resources and mates. Parentage analyses revealed that female reproductive success was not influenced by selection history, but there was a significant paternity bias towards males from the polygamous selection lines. Therefore, I show that female house mice benefit from polyandry by producing sons that achieve increased fitness in a semi-natural environment. PMID:21288948

Firman, Renée C

2011-02-02

157

Physiological Ecology of Moose: Nutritional Requirements for Reproduction with Respect to Body Condition Thresholds. Research Performance Report, 1 July 1998-30 June 1999. (Moose Research Center Report).  

National Technical Information Service (NTIS)

We conducted feeding trials with adult female moose (Alces alces) on high and low quality diets to assess the influence of nutrition and reproductive success on body condition and future reproduction. Although dry matter intake rates did not differ betwee...

T. R. Stephenson K. J. Hundertmark J. A. Crouse S. R. Rickabaugh

1999-01-01

158

Grazing willow ( Salix spp.) fodder blocks for increased reproductive rates and internal parasite control in mated hoggets  

Microsoft Academic Search

A grazing experiment, conducted for 116 days from 19 January to 15 May in the late summer\\/autumn of 2006 at Massey University's Riverside dry-land Farm, near Masterton (New Zealand), compared effects of grazing willow (Salix spp.) fodder blocks or perennial ryegrass (Lolium perenne)\\/white clover (Trifolium repens) pasture, during the pre-mating and mating periods, on gastrointestinal nematode parasite control and reproductive

K. Musonda; T. N. Barry; E. L. McWilliam; N. Lopez-Villalobos; W. E. Pomroy

2009-01-01

159

High-resolution laser radar for 3D imaging in artwork cataloging, reproduction, and restoration  

NASA Astrophysics Data System (ADS)

A high resolution Amplitude Modulated Laser Radar (AM-LR) sensor has recently been developed, aimed at accurately reconstructing 3D digital models of real targets, either single objects or complex scenes. The sensor sounding beam can be swept linearly across the object or circularly around it, by placing the object on a controlled rotating platform, enabling to obtain respectively linear and cylindrical range maps. Both amplitude and phase shift of the modulating wave of back-scattered light are collected and processed, providing respectively a shade-free, high resolution, photographic-like picture and accurate range data in the form of a range image. The resolution of range measurements depends mainly on the laser modulation frequency, provided that the power of the backscattered light reaching the detector is at least a few nW (current best performances are ~100 µm). The complete object surface can be reconstructed from the sampled points by using specifically developed software tools. The system has been successfully applied to scan different types of real surfaces (stone, wood, alloys, bones), with relevant applications in different fields, ranging from industrial machining to medical diagnostics, to vision in hostile environments. Examples of artwork reconstructed models (pottery, marble statues) are presented and the relevance of this technology for reverse engineering applied to cultural heritage conservation and restoration are discussed. Final 3D models can be passed to numeric control machines for rapid-prototyping, exported in standard formats for CAD/CAM purposes and made available on the Internet by adopting a virtual museum paradigm, thus possibly enabling specialists to perform remote inspections on high resolution digital reproductions of hardly accessible masterpieces.

Ricci, Roberto; Fantoni, Roberta; Ferri de Collibus, Mario; Fornetti, Giorgio G.; Guarneri, Massimiliano; Poggi, Claudio

2003-10-01

160

High reproduction of Calanus finmarchicus during a diatom-dominated spring bloom  

Microsoft Academic Search

Feeding, egg production, hatching success and early naupliar development of Calanus finmarchicus were measured in three north Norwegian fjords during a spring bloom dominated by diatoms and the haptophyte Phaeocystis pouchetii. Majority of the copepod diet consisted of diatoms, mainly Thalassiosira spp. and Chaetoceros spp., with clearance rates up to 10 ml ind?1 h?1 for individual algae species\\/groups. Egg production rates were high,

Marja Koski

2007-01-01

161

Biodistribution, with high uptake by the reproductive tract, of an intraperitoneally infused radiohalogenated steroidal estrogen-receptor ligand.  

PubMed

We infused [123I]16 alpha-(123I)-iodo-estradiol ([123I]E2) intraperitoneally (i.p.) into swine to study its biodistribution and to explore the i.p. use of radiohalogenated steroid estrogen-receptor (ER) ligands as a potential option for diagnosing and treating intra-abdominal, retroperitoneal, and distant sites of advanced ER-rich malignancies. Fifty to 80% of the radiolabel was absorbed from the peritoneal cavity within 30 minutes, and 30 to 50% of the infused radiolabel was excreted in the urine within 2 hr. The rate of biliary clearance was maximal within 25 minutes. At 3 hr, the ER-rich reproductive tract had greater than 63 times the concentration of radiolabel in blood; the former was blocked by non-labeled competitors for ER. Uptake by non-ER-rich tissues, compared to blood, ranged from 0.7:1 (heart and lungs) to 16:1 (spleen); the omentum, however, exhibited a concentration as high as 64:1, which was not blocked by non-labeled ER ligands. Uptake by ER-rich target tissue remained high when charcoal was used to prevent reabsorption of radiolabel from the digestive tract after its biliary excretion, and when the products of biliary excretion were removed by catheterization of the common bile duct. Neither charcoal nor exteriorization of bile appeared to affect urinary clearance of the radiolabel over the time course of the experiments. Taken together with the recent development of syntheses that yield radiohalogenated sex steroid receptor ligands of high specific activity, our findings are encouraging for the potential application of radiolabeled ligands as i.p. administered pharmaceuticals. The advantage of the i.p. route is that it provides direct uptake of the pharmaceutical by free-floating clusters and individual cancer cells in ascitic fluid, as well as delivery via the circulation to vascularized intra- and/or extraperitoneal metastases. PMID:1995542

Holt, J A; Artwohl, J E; Mercer, L J; Pryde, P G

1991-03-01

162

High Lifetime Pregnancy and Low Contraceptive Usage Among Sex Workers Who Use Drugs- An Unmet Reproductive Health Need  

PubMed Central

Background The objective of this study was to describe levels of pregnancy and contraceptive usage among a cohort of street-based female sex workers (FSWs) in Vancouver. Methods The study sample was obtained from a community-based prospective cohort study (2006-2008) of 211 women in street-based sex work who use drugs, 176 of whom had reported at least one prior pregnancy. Descriptive statistics were used to estimate lifetime pregnancy prevalence, pregnancy outcomes (miscarriage, abortion, adoption, child apprehension, child custody), and contraceptive usage. In secondary analyses, associations between contraceptive usage, individual and interpersonal risk factors and high number of lifetime pregnancies (defined as greater than the sample mean of 4) were examined. Results Among our sample, 84% reported a prior pregnancy, with a mean of 4 lifetime pregnancies (median = 3; IQR: 2-5). The median age of women reporting 5+ pregnancies was 38 years old [interquartile range (IQR): 25.0-39.0] compared to 34 years [IQR: 25.0-39.0] among women reporting 4 or fewer prior pregnancies. 45% were Caucasian and 47% were of Aboriginal ancestry. We observed high rates of previous abortion (median = 1;IQR:1-3), apprehension (median = 2; IQR:1-4) and adoption (median = 1; IQR:1-2) among FSWs who reported prior pregnancy. The use of hormonal and insertive contraceptives was limited. In bivariate analysis, tubal ligation (OR = 2.49; [95%CI = 1.14-5.45]), and permanent contraceptives (e.g., tubal ligation and hysterectomy) (OR = 2.76; [95%CI = 1.36-5.59]) were both significantly associated with having five or more pregnancies. Conclusion These findings demonstrate high levels of unwanted pregnancy in the context of low utilization of effective contraceptives and suggest a need to improve the accessibility and utilization of reproductive health services, including family planning, which are appropriately targeted and tailored for FSWs in Vancouver.

2011-01-01

163

Evaluation of reproductive tract infection during early post-partum period and its relationship with subsequent reproductive performance in high milk producing dairy cows.  

PubMed

Clinically normal Holstein-Friesian cows (n = 43) were used to establish a relationship between the evaluations of the uterine condition by vaginoscopy, Metricheck, endometrial cytology (EC) and ultrasonography (US) during post-partum period (pp), and subsequent reproductive performance. The uterine status of the selected cows was evaluated by EC, Metricheck, US and vaginoscopy on a weekly basis from the third week (W3) to the seventh week (W7) pp. The animals were bred after a voluntary waiting period of 45-60 days pp and diagnosed for pregnancy status at 45 days after breeding by US. First service conception rate (FSCR) of bred animals was 32.6% (14/43). There was no significant difference in polymorphonuclear leucocyte percentage between conceived and non-conceived cows during different weeks post-partum. First service conception rate in animals with normal vaginal discharge as detected by Metricheck was significantly low when compared to those of abnormal discharge during W3 (2.3% vs 30.3%; p?reproductive performance of dairy cattle. PMID:21707786

Senosy, W; Uchiza, M; Tameoka, N; Izaike, Y; Osawa, T

2011-06-24

164

Thermal and reproductive biology of high and low elevation populations of the lizard Sceloporus scalaris : implications for the evolution of viviparity  

Microsoft Academic Search

Viviparity in squamate reptiles is presumed to evolve in cold climates by selection for increasingly longer periods of egg retention. Longer periods of egg retention may require modifications to other reproductive features associated with the evolution of viviparity, including a reduction in eggshell thickness and clutch size. Field studies on the thermal and reproductive biology of high (HE) and low

Tom Mathies; Robin M. Andrews

1995-01-01

165

Adaptive down-sampling of frame-rate for high frame-rate video  

Microsoft Academic Search

Over the past decade, video acquisition rates, which had been 24 Hz (cinema), 30-60 Hz (webcam) or 50-60 Hz (SD\\/HDcam), has broken through to reach 1000 Hz. In order to display these high frame-rate video signals on current display devices in real time, they must be down-sampled first. This study proposes a down-sampling method suitable for high frame-rate video signals.

Yukihiro BANDOH; Seishi TAKAMURA; Kazuto KAMIKURA; Yoshiyuki YASHIMA

2009-01-01

166

Weak interaction rates at high temperatures and densities  

Microsoft Academic Search

Proton-neutron quasiparticle RPA is used for the first time to calculate weak interaction rates for sd- and fp- shell nuclei at high temperatures and densities. Particle emission processes from excited states are taken into account and is found to considerably affect the recommended beta decay rates. The calculated rates take into consideration the latest experimental energy levels and ft value

Jameel-Un Nabi; Hans Volker Klapdor-Kleingrothaus

1999-01-01

167

How States Achieve High Seat Belt Use Rates.  

National Technical Information Service (NTIS)

This study compared States with high seat belt use rates and States with low seat belt use rates using statistical analyses and conducted case studies of 10 high seat belt use States. Primary enforcement seat belt use laws clearly help increase seat belt ...

D. Preusser J. Hedlund K. Ledingham S. H. Gilbert

2008-01-01

168

Plants and Photosynthesis: Level III, Unit 3, Lesson 1; The Human Digestive System: Lesson 2; Functions of the Blood: Lesson 3; Human Circulation and Respiration: Lesson 4; Reproduction of a Single Cell: Lesson 5; Reproduction by Male and Female Cells: Lesson 6; The Human Reproductive System: Lesson 7; Genetics and Heredity: Lesson 8; The Nervous System: Lesson 9; The Glandular System: Lesson 10. Advanced General Education Program. A High School Self-Study Program.  

ERIC Educational Resources Information Center

|This self-study program for the high-school level contains lessons in the following subjects: Plants and Photosynthesis; The Human Digestive System; Functions of the Blood; Human Circulation and Respiration; Reproduction of a Single Cell; Reproduction by Male and Female Cells; The Human Reproductive System; Genetics and Heredity; The Nervous…

Manpower Administration (DOL), Washington, DC. Job Corps.

169

Reverse transcription loop-mediated isothermal amplification for the detection of highly pathogenic porcine reproductive and respiratory syndrome virus  

Microsoft Academic Search

A reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay targeting the open reading frames 1a of highly pathogenic porcine reproductive and respiratory syndrome virus genome was developed. The 10 reference strains, 1 clinical isolation strain and 122 positive samples were tested. Positive reactions were confirmed for all strains and specimens by reverse transcription loop-mediated isothermal amplification and nested reverse transcription polymerase

Hao-tai Chen; Jie Zhang; De-hui Sun; Li-na Ma; Xiang-tao Liu; Kai Quan; Yong-sheng Liu

2008-01-01

170

Laser Driven High Pressure, High Strain-Rate Materials Experiments  

NASA Astrophysics Data System (ADS)

Laser-based experiments are being developed to study the response of solids under high pressure loading. Diagnostic techniques that have been applied include dynamic x-ray diffraction, VISAR wave profile measurements, and post-shock recovery and analysis. These techniques are presented with some results from shocked Si, Al, and Cu experiments.

Kalantar, D. H.; Allen, A. M.; Gregori, F.; Kad, B.; Kumar, M.; Lorenz, K. T.; Loveridge, A.; Meyers, M. A.; Pollaine, S.; Remington, B. A.

2002-07-01

171

High-energy diets may induce a pre-diabetic state altering testicular glycolytic metabolic profile and male reproductive parameters.  

PubMed

Diabetes mellitus is a metabolic disorder that may arise from diet habits and is growing to epidemic proportions. Young male diabetic patients present high infertility/subfertility prevalence resulting from impaired reproductive function and poor semen quality. We aimed to evaluate the effects of a high-energy diet (HED) on glucose tolerance/insulin levels and correlate the observed effects on male reproductive function with overall testicular metabolism. After 1 month, HED fed rats showed increased glycaemic levels, impaired glucose tolerance and hypoinsulinaemia. Moreover, an imbalance of intratesticular and serum testosterone levels was observed, whereas those of 17?-estradiol were not altered. High-energy diet also affected the reproductive parameters, with HED rats exhibiting a significant increase in abnormal sperm morphology. Glycolytic metabolism was favoured in testicles of HED rats with an increased expression of both glucose transporters 1 (GLUT1) and 3 (GLUT3) and the enzyme phosphofrutokinase 1. Moreover, lactate production and the expression of metabolism-associated genes and proteins involved in lactate production and transport were also enhanced by HED. Alanine testicular content was decreased and thus intratesticular lactate/alanine ratio in HED rats was increased, suggesting increased oxidative stress. Other energetic substrates such as acetate and creatine were not altered in testis from HED rats, but intratesticular glycine content was increased in those animals. Taken together, these results suggest that HED induces a pre-diabetic state that may impair reproductive function by modulating overall testicular metabolism. This is the first report on testicular metabolic features and mechanisms related with the onset of a pre-diabetic state. PMID:23495257

Rato, L; Alves, M G; Dias, T R; Lopes, G; Cavaco, J E; Socorro, S; Oliveira, P F

2013-03-14

172

Complicating Power in High-Tech Reproduction: Narratives of Anonymous Paid Egg Donors  

Microsoft Academic Search

This paper is informed by my own participant observation and uses my own ethnography which included conducting in-depth interviews with anonymous paid egg donors and observing a listserv for women considering, pursuing, or having completed egg donation, to illustrate the way that power operates at this particular site of the reproductive center in postmodernity. After outlining who the consumers and

Anne Pollock

2003-01-01

173

Global crop exposure to critical high temperatures in the reproductive period: historical trends and future projections  

NASA Astrophysics Data System (ADS)

Long-term warming trends across the globe have shifted the distribution of temperature variability, such that what was once classified as extreme heat relative to local mean conditions has become more common. This is also true for agricultural regions, where exposure to extreme heat, particularly during key growth phases such as the reproductive period, can severely damage crop production in ways that are not captured by most crop models. Here, we analyze exposure of crops to physiologically critical temperatures in the reproductive stage (Tcrit), across the global harvested areas of maize, rice, soybean and wheat. Trends for the 1980–2011 period show a relatively weak correspondence (r = 0.19) between mean growing season temperature and Tcrit exposure trends, emphasizing the importance of separate analyses for Tcrit. Increasing Tcrit exposure in the past few decades is apparent for wheat in Central and South Asia and South America, and for maize in many diverse locations across the globe. Maize had the highest percentage (15%) of global harvested area exposed to at least five reproductive days over Tcrit in the 2000s, although this value is somewhat sensitive to the exact temperature used for the threshold. While there was relatively little sustained exposure to reproductive days over Tcrit for the other crops in the past few decades, all show increases with future warming. Using projections from climate models we estimate that by the 2030s, 31, 16, and 11% respectively of maize, rice, and wheat global harvested area will be exposed to at least five reproductive days over Tcrit in a typical year, with soybean much less affected. Both maize and rice exhibit non-linear increases with time, with total area exposed for rice projected to grow from 8% in the 2000s to 27% by the 2050s, and maize from 15 to 44% over the same period. While faster development should lead to earlier flowering, which would reduce reproductive extreme heat exposure for wheat on a global basis, this would have little impact for the other crops. Therefore, regardless of the impact of other global change factors (such as increasing atmospheric CO2), reproductive extreme heat exposure will pose risks for global crop production without adaptive measures such as changes in sowing dates, crop and variety switching, expansion of irrigation, and agricultural expansion into cooler areas.

Gourdji, Sharon M.; Sibley, Adam M.; Lobell, David B.

2013-06-01

174

Life Table and Predation of Lemnia biplagiata (Coleoptera: Coccinellidae) Fed on Aphis gossypii (Homoptera: Aphididae) with a Proof on Relationship Among Gross Reproduction Rate, Net Reproduction Rate, and Preadult Survivorship  

Microsoft Academic Search

The life history and predation rate of Lemnia biplagiata (Swartz) fed on Aphis gossypii Glover was studied at 25C in the laboratory. The raw data were analyzed based on the age-stage, two-sex life table to take the variable developmental rate among individuals and both sexes into consideration. The intrinsic rate of increase (r) is 0.1570 d1, the Þnite rate of

Jih-Zu Yu; Hsin Chi; Bing-Huei Chen

2005-01-01

175

High Strain Rate Compressive Tests on Woven Graphite Epoxy Composites  

NASA Astrophysics Data System (ADS)

The behavior of composite materials may be different when they are subjected to high strain rate load. Penetrating split Hopkinson pressure bar (P-SHPB) is a method to impose high strain rate on specimen in the laboratory experiments. This research work studied the response of the thin circular shape specimens, made out of woven graphite epoxy composites, to high strain rate impact load. The stress-strain relationships and behavior of the specimens were investigated during the compressive dynamic tests for strain rates as high as 3200 s-1. One dimensional analysis was deployed for analytical calculations since the experiments fulfilled the ratio of diameter to length of bars condition in impact load experiments. The mechanics of dynamic failure was studied and the results showed the factors which govern the failure mode in high strain deformation via absorbed energy by the specimen. In this paper, the relation of particle velocity with perforation depth was discussed for woven graphite epoxy specimens.

Allazadeh, Mohammad Reza; Wosu, Sylvanus N.

2011-08-01

176

Status of low dose rate and future of high dose rate Cf-252 brachytherapy.  

National Technical Information Service (NTIS)

This work describes the current status of the US low dose rate (LDR) Cf-252 brachytherapy program. The efforts undertaken towards development of a high dose rate (HDR) remotely after loaded Cf-252 source, which can accommodate 1 mg or greater Cf-252, are ...

M. J. Rivard J. G. Wierzbicki F. Van den Heuvel P. J. Chuba J. Fontanesi

1997-01-01

177

The status of low dose rate and future of high dose rate Cf252 brachytherapy  

Microsoft Academic Search

This work describes the current status of the US low dose rate (LDR) Cf-252 brachytherapy program. The efforts undertaken towards development of a high dose rate (HDR) remotely after loaded Cf-252 source, which can accommodate 1 mg or greater Cf-252, are also described. This HDR effort is a collaboration between Oak Ridge National Laboratory (ORNL), commercial remote after loader manufactures,

M. J. Rivard; J. G. Wierzbicki; F. Van den Heuvel; P. J. Chuba; J. Fontanesi; R. C. Martin; R. R. McMahon; R. G. Haire

1997-01-01

178

A comparison of reproductive characteristics of boars generated by somatic cell nuclear transfer to highly related conventionally produced boars.  

PubMed

This study compares the reproductive performance of boars produced by somatic cell nuclear transfer versus conventional breeding. Two different genotypes were selected for comparison: terminal cross line 1 (TX1) and terminal cross line 2 (TX2). The boars selected for comparison from TX1 were three cloned boars, produced by somatic cell nuclear transfer and the conventionally produced progenitor of the clones. The boars selected for comparison from TX2 were a cloned boar produced by somatic cell nuclear transfer and two conventionally produced half sibling boars that were offspring of the progenitor of the clone. Semen from each boar was collected, extended, evaluated and shipped offsite. Upon arrival, the semen was reevaluated and utilized for artificial insemination of 89 commercial gilts, at least 12 gilts per boar, producing 625 piglets. Pregnancy rates were determined at day 30 and 110 of gestation; and farrowing rate and gestation length were recorded. Differences were observed in some of the semen characteristics analyzed with the clones usually possessing superior semen quality to the control, this likely being a result of age differences amongst the clones and controls. Additionally no differences were noted between the clones and controls (progenitor) or between individual boars within genetic line for pregnancy rates, gestation length or any of the litter parameters examined between the clones and controls. These data further support previous reports with limited numbers that the reproductive capabilities of cloned boars are equal to that of conventionally produced boars. PMID:17009889

Williams, N E; Walker, S C; Reeves, D E; Sherrer, E; Galvin, J M; Polejaeva, I; Rampacek, G; Benyshek, L; Christenson, R K; Graves, W M; Pratt, S L

2006-01-01

179

Fast molecular evolution associated with high active metabolic rates in poison frogs.  

PubMed

Molecular evolution is simultaneously paced by mutation rate, genetic drift, and natural selection. Life history traits also affect the speed of accumulation of nucleotide changes. For instance, small body size, rapid generation time, production of reactive oxygen species (ROS), and high resting metabolic rate (RMR) are suggested to be associated with faster rates of molecular evolution. However, phylogenetic correlation analyses failed to support a relationship between RMR and molecular evolution in ectotherms. In addition, RMR might underestimate the metabolic budget (e.g., digestion, reproduction, or escaping predation). An alternative is to test other metabolic rates, such as active metabolic rate (AMR), and their association with molecular evolution. Here, I present comparative analyses of the associations between life history traits (i.e., AMR, RMR, body mass, and fecundity) with rates of molecular evolution of and mitochondrial loci from a large ectotherm clade, the poison frogs (Dendrobatidae). My results support a strong positive association between mass-specific AMR and rates of molecular evolution for both mitochondrial and nuclear loci. In addition, I found weaker and genome-specific covariates such as body mass and fecundity for mitochondrial and nuclear loci, respectively. No direct association was found between mass-specific RMR and rates of molecular evolution. Thus, I provide a mechanistic hypothesis of the link between AMRs and the rate of molecular evolution based on an increase in ROS within germ line cells during periodic bouts of hypoxia/hyperoxia related to aerobic exercise. Finally, I propose a multifactorial model that includes AMR as a predictor of the rate of molecular evolution in ectothermic lineages. PMID:22337863

Santos, Juan C

2012-02-15

180

FAST TRACK COMMUNICATION High rate straining of tantalum and copper  

NASA Astrophysics Data System (ADS)

High strain rate measurements reported recently for several tantalum and copper crystal/polycrystal materials are shown to follow dislocation mechanics-based constitutive relations, first at lower strain rates, for dislocation velocity control of the imposed plastic deformations and, then at higher rates, transitioning to nano-scale dislocation generation control by twinning or slip. For copper, there is the possibility of added-on slip dislocation displacements to be accounted for from the newly generated dislocations.

Armstrong, R. W.; Zerilli, F. J.

2010-12-01

181

Tensile testing of materials at high rates of strain  

Microsoft Academic Search

A tension version of the split Hopkinson bar or Kolsky apparatus is developed for conducting tests in tension at high rates\\u000a of strain up to 103 s?1. A number of aluminum, titanium, and steel alloys tested in tension show increasing degrees of rate sensitivity above 10\\u000a to 102 s?1. Tests on 6061-T651 and 7075-T6 aluminum show measurable strain-rate sensitivity in

Theodore Nicholas

1981-01-01

182

Dual-rate high order hold equivalent controllers  

Microsoft Academic Search

The paper is focused on the computation of a dual-rate high-order-hold discrete equivalent controller. We assume that the continuous-time controller has been already designed in order to meet continuous time-domain and frequency-domain specifications. Dual rate controllers are N-periodic time varying systems, and the lifting technique is utilized to express them as time invariant systems. Several different models are presented (dual-rate

Josep Tornero; M. Tomizuka

2000-01-01

183

Leaving Boys Behind: Public High School Graduation Rates  

ERIC Educational Resources Information Center

This study uses a widely respected method to calculate public high school graduation rates for the nation, for each state, and for the 100 largest school districts in the United States. The authors calculate graduation rates overall, by race, and by gender, using the most recent available data (the class of 2003). While this report builds upon a…

Greene, Jay P.; Winters, Marcus A.

2006-01-01

184

Gas Gain Stability of MSGCs Operating at High Rate.  

National Technical Information Service (NTIS)

Micro Strip Gas Counters (MSGCs) with coated and uncoated borosilicate glass substrates have been investigated on their high rate capability and long term gas gain stability. It is shown that the gain remains almost constant at count rates up to (10 to th...

F. D. van den Berg C. Daum B. van Eijk F. G. Hartjes F. Udo V. Zhukov

1997-01-01

185

The Type Ia Supernova Rate in High Redshift Galaxy Clusters  

Microsoft Academic Search

The type Ia supernova (SN Ia) rate in galaxy clusters can be a powerful probe of both the SN Ia progenitor system and the intracluster medium of the clusters themselves. The cluster SN Ia rate has recently been measured at redshifts below 0.2, but only weak constraints based on one or two SNe exist at high redshift. We report a

Kyle H. Barbary; G. Aldering; R. Amanullah; L. F. Barrientos; M. Brodwin; N. Connolly; K. S. Dawson; A. Dey; M. Doi; M. Donahue; P. Eisenhardt; E. Ellingson; L. Faccioli; V. Fadeyev; H. K. Fakhouri; A. S. Fruchter; D. Gilbank; M. D. Gladders; G. Goldhaber; A. H. Gonzales; A. Goobar; A. Gude; J. Hennawi; H. Hoekstra; E. Hsiao; X. Huang; Y. Ihara; B. T. Jannuzi; B. Koester; M. Kowalski; C. Lidman; E. V. Linder; L. Lubin; J. Meyers; T. Morokuma; S. Perlmutter; M. Postman; J. Rhodes; P. Rosati; D. Rubin; D. J. Schlegel; A. L. Spadafora; S. Stanford; D. Stern; M. Strovink; N. Suzuki; N. Takanashi; N. Yasuda; H. K. Yee; Supernova Cosmology Project

2010-01-01

186

An infrared high rate video imager for various space applications  

Microsoft Academic Search

Modern spacecraft with high data transmission capabilities have opened up the possibility to fly video rate imagers in space. Several fields concerned with observations of transient phenomena can benefit significantly from imaging at video frame rate. Some applications are observations and characterization of bolides\\/meteors, sprites, lightning, volcanic eruptions, and impacts on airless bodies. Applications can be found both on low

Hâkan Svedhem; Detlef Koschny

2010-01-01

187

High frame rate thermal imager for hypersonic wind tunnel applications  

Microsoft Academic Search

Infrared thermography is used to derive heat transfer coefficients from thermal mappings of wind tunnel models. Due to the short duration of the runs in hypersonic F4 facilities, a high frame rate infrared camera is needed to record the thermal variations of the model. In accordance with F4 wind tunnel specifications, a 400 Hz frame rate thermal imager was developed.

Stephane Barbe

1992-01-01

188

Higher Minimum Wage and High School Dropout Rates  

Microsoft Academic Search

We explore whether higher levels of the real minimum wage have differing effects on high school dropout rates across students of various races and ethnicities (whites, African Americans, Hispanics, and Asians). Using a panel of data across Maryland counties and annual observations in 1993-2004, we found higher real minimum wages to be associated with higher dropout rates for Hispanic students,

Stephanie O. Crofton; William L. Anderson; Emily C. Rawe

2009-01-01

189

High Pressure Burn Rate Measurements on an Ammonium Perchlorate Propellant  

Microsoft Academic Search

High pressure deflagration rate measurements of a unique ammonium perchlorate (AP) based propellant are required to design the base burn motor for a Raytheon weapon system. The results of these deflagration rate measurements will be key in assessing safety and performance of the system. In particular, the system may experience transient pressures on the order of 100's of MPa (10's

E A Glascoe; N Tan

2010-01-01

190

High Strain Rate Characterisation of a Polymer Bonded Sugar  

Microsoft Academic Search

The mechanical properties of a polymer bonded sugar consisting of 78% sugar crystals, of modal particle size 310 ?m, dispersed in an HTPB binder have been characterized in a split Hopkinson pressure bar system at a strain rate of 103 s?1 and temperatures from ?100 to +20 °C. These high rate experiments were supplemented by further experiments in an Instron

P. R. Laity; C. R. Siviour; P. D. Church; W. G. Proud

2006-01-01

191

High Strain Rate Characterisation of a Polymer Bonded Sugar  

Microsoft Academic Search

The mechanical properties of a polymer bonded sugar consisting of 78% sugar crystals, of modal particle size 310 mum, dispersed in an HTPB binder have been characterized in a split Hopkinson pressure bar system at a strain rate of 103 s-1 and temperatures from -100 to +20 °C. These high rate experiments were supplemented by further experiments in an Instron

P. R. Laity; C. R. Siviour; P. D. Church; W. G. Proud

2006-01-01

192

Pedalling rate affects endurance performance during high-intensity cycling  

Microsoft Academic Search

The purpose of this study into high-intensity cycling was to: (1) test the hypothesis that endurance time is longest at a freely chosen pedalling rate (FCPR), compared to pedalling rates 25% lower (FCPR-25) and higher (FCPR+25) than FCPR, and (2) investigate how physiological variables, such as muscle fibre type composition and power reserve, relate to endurance time. Twenty males underwent

JensSteen Nielsen; ErnstAlbin Hansen; Gisela Sjøgaard

2004-01-01

193

High Pressure Burning Rates of Multi-Base Propellants.  

National Technical Information Service (NTIS)

Burning rates of multi-base, nitrocellulose propellants at high pressure were measured using recently developed techniques. Since the intended application is in-process control, as-manufactured multi-perforated grains (finished as well as interrupted-proc...

C. R. Felsheim L. H. Caveny L. M. Pokrocos

1977-01-01

194

High Count Rates with Total Internal Reflection Fluorescence Correlation Spectroscopy  

Microsoft Academic Search

We achieved photon count rates per molecule as high as with commonly used confocal fluorescence correlation spectroscopy instruments using a new total internal reflection fluorescence correlation spectroscopy system based on an epi-illumination configuration.

Kai Hassler; Tiemo Anhut; Rudolf Rigler; Michael Gösch; Theo Lasser

2005-01-01

195

High Interest Rates, Spreads, and the Costs of Intermediation.  

National Technical Information Service (NTIS)

Contents: High real interest rates and spreads: An introduction (Spreads and explicit taxes, spreads and implicit taxes on financial intermediation, spreads, operating costs and profits, conclusions and an Agenda for reducing spreads). The costs of interm...

J. A. Hanson R. R. Rocha

1986-01-01

196

Design considerations for high-data-rate chip interconnect systems  

Microsoft Academic Search

Over the past decade, data rates for electrical interconnects in interchip communications systems have experienced a dramatic increase from <;1 Gb\\/s to 10 Gb\\/s and beyond to keep up with ever increasing demands for more I\\/O bandwidth from modern high-capacity storage, networking, and data processing systems. This article presents an overview of the high-data-rate chip interconnect design space, including a

Troy Beukema

2010-01-01

197

A General Model of High Frame Rate Imaging System  

Microsoft Academic Search

A kind of high frame rate (HFR) 2D and 3D imaging method was developed in 1997. Because only one transmission is required to construct an image, this method can reach an ultra high frame rate (about 3750 volumes or frames per second for biological soft tissues at a depth of 200 mm). Compared with conventional delay-and-sum (dynamic focusing) method, the

Peng Hu; Lu Jianyu; Han Xuemei; Feng Huanqing

2005-01-01

198

Identifying High-Rate Flows Based on Sequential Sampling  

NASA Astrophysics Data System (ADS)

We consider the problem of fast identification of high-rate flows in backbone links with possibly millions of flows. Accurate identification of high-rate flows is important for active queue management, traffic measurement and network security such as detection of distributed denial of service attacks. It is difficult to directly identify high-rate flows in backbone links because tracking the possible millions of flows needs correspondingly large high speed memories. To reduce the measurement overhead, the deterministic 1-out-of-k sampling technique is adopted which is also implemented in Cisco routers (NetFlow). Ideally, a high-rate flow identification method should have short identification time, low memory cost and processing cost. Most importantly, it should be able to specify the identification accuracy. We develop two such methods. The first method is based on fixed sample size test (FSST) which is able to identify high-rate flows with user-specified identification accuracy. However, since FSST has to record every sampled flow during the measurement period, it is not memory efficient. Therefore the second novel method based on truncated sequential probability ratio test (TSPRT) is proposed. Through sequential sampling, TSPRT is able to remove the low-rate flows and identify the high-rate flows at the early stage which can reduce the memory cost and identification time respectively. According to the way to determine the parameters in TSPRT, two versions of TSPRT are proposed: TSPRT-M which is suitable when low memory cost is preferred and TSPRT-T which is suitable when short identification time is preferred. The experimental results show that TSPRT requires less memory and identification time in identifying high-rate flows while satisfying the accuracy requirement as compared to previously proposed methods.

Zhang, Yu; Fang, Binxing; Luo, Hao

199

High-rate LDPC codes from unital designs  

Microsoft Academic Search

The paper presents a construction of very high-rate low-density parity-check (LDPC) codes based on incidence matrices of unital designs. Like the projective geometry and oval designs, unital designs exist with incidence matrices which are significantly rank deficient. Thus high-rate LDPC codes with a large number of linearly dependent parity-check equations can be constructed. The LDPC codes from unitals have Tanner

S. J. Johnson; S. R. Weller

2003-01-01

200

Reproductive effects in F1 adult females exposed in utero to moderate to high doses of mono-2-ethylhexylphthalate (MEHP).  

PubMed

Phthalates are widely used as plasticizers in everyday products. Yet, studies on the effects of phthalates on female reproductive health are limited. In this study, pregnant C57/Bl6 mice were exposed via oral gavage to corn oil, 100, 500, or 1000mg/kg MEHP from gestational days 17-19. Reproductive lifespan was decreased by one month in the highest F1 exposure group (9.8±0.4 versus 11.1±0.6 months in control F1 females). F1 females exhibited delayed estrous onset at the two higher exposures and prolonged estrus was observed in all MEHP-exposed females. Serum FSH and estradiol were significantly elevated at the highest exposure and altered mRNA expression was found for the steroidogenic genes LHCGR, aromatase, and StAR. At one year of age, mammary gland hyperplasia was observed in high dose MEHP-exposed females. In summary, late gestational exposure to MEHP leads to multiple latent reproductive effects throughout murine life resulting in premature ovarian senescence and mammary hyperplasia. PMID:22401849

Moyer, Benjamin; Hixon, Mary L

2012-03-06

201

Reproductive Effects in F1 Adult Females Exposed In Utero to Moderate to High Doses of Mono-2-ethylhexylphthalate (MEHP)  

PubMed Central

Phthalates are widely used as plasticizers in everyday products. Yet, studies on the effects of phthalates on female reproductive health are limited. In this study, pregnant C57/Bl6 mice were exposed via oral gavage to corn oil, 100, 500, or 1000mg/kg MEHP from gestational days 17–19. Reproductive lifespan was decreased by one month in the highest F1 exposure group (9.8±0.4 versus 11.1±0.6 months in control F1 females). F1 females exhibited delayed estrous onset at the two higher exposures and prolonged estrus was observed in all MEHP-exposed females. Serum FSH and estradiol were significantly elevated at the highest exposure and altered mRNA expression was found for the steroidogenic genes LHCGR, aromatase, and StAR. At one year of age, mammary gland hyperplasia was observed in high dose MEHP-exposed females. In summary, late gestational exposure to MEHP leads to multiple latent reproductive effects throughout murine life resulting in premature ovarian senescence and mammary hyperplasia.

Moyer, Benjamin; Hixon, Mary L.

2012-01-01

202

Changes in reproductive physiology of lactating dairy cows due to elevated steroid metabolism  

Microsoft Academic Search

This manuscript focuses on potential changes in reproductive physiology that occur due to high milk production in lactating dairy cows. Four reproductive measures are discussed: interval to first ovulation, conception rate, duration of estrus, and multiple ovulation rate. The last two responses have now been closely linked to level of milk production. In contrast, time to first ovulation does not

Milo Wiltbank; Hernando Lopez; Roberto Sartori; Siwat Sangsritavong; Ahmet Gümen

2006-01-01

203

Deformation substructures induced by high-rate deformation  

SciTech Connect

The influence of increasing strain on the deformation substructures in metals and alloys which deform predominately by slip is very similar to that seen following quasi-static deformation at increasingly lower temperatures or due to a decrease in stacking fault energy ({gamma}{sub sf}). For constant strain, deformation at higher rates: (1) produces more uniform dislocation distributions for the same amount of strain, (2) hinders dislocation cell formation, (3) decreases the cell size, and (4) increases misorientaion with more dislocations trapped within the cell interiors. The suppression of thermally-activated dislocation processes in this regime, added to high temperature and strain-rate sensitivity of the yield stress exhibited by many materials, can lead to stresses high enough to nucleate and grow deformation twins even in high stacking fault energy FCC metals such as copper and Al-4.8 wt % Mg. In addition, substructures formed under high-rate conditions differ from those formed under low-rate conditions due to the suppression of dynamic recovery process. Finally, in high-rate deformation such as shock loading, the subsonic restriction on dislocation motion leads to higher dislocation and point defect generation rates, resulting in enhanced hardening when compared to materials deformed to equivalent strains at quasi-static rates. In this paper examples of the deformation substructure evolution observed in aluminum, copper, Ni{sub 3}Al, iron, Ti-6Al-4V, and TiAl at high and shock-loading strain rates will be presented and compared to that seen following low-rate deformation paths. 41 refs., 15 figs.

Gray, G.T. III.

1991-01-01

204

Performance of High Flow Rate Samplers for Respirable Particle Collection  

PubMed Central

The American Conference of Governmental Industrial hygienists (ACGIH) lowered the threshold limit value (TLV) for respirable crystalline silica (RCS) exposure from 0.05 to 0.025 mg m?3 in 2006. For a working environment with an airborne dust concentration near this lowered TLV, the sample collected with current standard respirable aerosol samplers might not provide enough RCS for quantitative analysis. Adopting high flow rate sampling devices for respirable dust containing silica may provide a sufficient amount of RCS to be above the limit of quantification even for samples collected for less than full shift. The performances of three high flow rate respirable samplers (CIP10-R, GK2.69, and FSP10) have been evaluated in this study. Eleven different sizes of monodisperse aerosols of ammonium fluorescein were generated with a vibrating orifice aerosol generator in a calm air chamber in order to determine the sampling efficiency of each sampler. Aluminum oxide particles generated by a fluidized bed aerosol generator were used to test (i) the uniformity of a modified calm air chamber, (ii) the effect of loading on the sampling efficiency, and (iii) the performance of dust collection compared to lower flow rate cyclones in common use in the USA (10-mm nylon and Higgins–Dewell cyclones). The coefficient of variation for eight simultaneous samples in the modified calm air chamber ranged from 1.9 to 6.1% for triplicate measures of three different aerosols. The 50% cutoff size (50dae) of the high flow rate samplers operated at the flow rates recommended by manufacturers were determined as 4.7, 4.1, and 4.8 ?m for CIP10-R, GK2.69, and FSP10, respectively. The mass concentration ratio of the high flow rate samplers to the low flow rate cyclones decreased with decreasing mass median aerodynamic diameter (MMAD) and high flow rate samplers collected more dust than low flow rate samplers by a range of 2–11 times based on gravimetric analysis. Dust loading inside the high flow rate samplers does not appear to affect the particle separation in either FSP10 or GK2.69. The high flow rate samplers overestimated compared to the International Standards Organization/Comité Européen de Normalisation/ACGIH respirable convention [up to 40% at large MMAD (27.5 ?m)] and could provide overestimated exposure data with the current flow rates. However, both cyclones appeared to be able to provide relatively unbiased assessments of RCS when their flow rates were adjusted.

Lee, Taekhee; Kim, Seung Won; Chisholm, William P.; Slaven, James; Harper, Martin

2010-01-01

205

Performance of high flow rate samplers for respirable particle collection.  

PubMed

The American Conference of Governmental Industrial hygienists (ACGIH) lowered the threshold limit value (TLV) for respirable crystalline silica (RCS) exposure from 0.05 to 0.025 mg m(-3) in 2006. For a working environment with an airborne dust concentration near this lowered TLV, the sample collected with current standard respirable aerosol samplers might not provide enough RCS for quantitative analysis. Adopting high flow rate sampling devices for respirable dust containing silica may provide a sufficient amount of RCS to be above the limit of quantification even for samples collected for less than full shift. The performances of three high flow rate respirable samplers (CIP10-R, GK2.69, and FSP10) have been evaluated in this study. Eleven different sizes of monodisperse aerosols of ammonium fluorescein were generated with a vibrating orifice aerosol generator in a calm air chamber in order to determine the sampling efficiency of each sampler. Aluminum oxide particles generated by a fluidized bed aerosol generator were used to test (i) the uniformity of a modified calm air chamber, (ii) the effect of loading on the sampling efficiency, and (iii) the performance of dust collection compared to lower flow rate cyclones in common use in the USA (10-mm nylon and Higgins-Dewell cyclones). The coefficient of variation for eight simultaneous samples in the modified calm air chamber ranged from 1.9 to 6.1% for triplicate measures of three different aerosols. The 50% cutoff size ((50)d(ae)) of the high flow rate samplers operated at the flow rates recommended by manufacturers were determined as 4.7, 4.1, and 4.8 microm for CIP10-R, GK2.69, and FSP10, respectively. The mass concentration ratio of the high flow rate samplers to the low flow rate cyclones decreased with decreasing mass median aerodynamic diameter (MMAD) and high flow rate samplers collected more dust than low flow rate samplers by a range of 2-11 times based on gravimetric analysis. Dust loading inside the high flow rate samplers does not appear to affect the particle separation in either FSP10 or GK2.69. The high flow rate samplers overestimated compared to the International Standards Organization/Comité Européen de Normalisation/ACGIH respirable convention [up to 40% at large MMAD (27.5 microm)] and could provide overestimated exposure data with the current flow rates. However, both cyclones appeared to be able to provide relatively unbiased assessments of RCS when their flow rates were adjusted. PMID:20660144

Lee, Taekhee; Kim, Seung Won; Chisholm, William P; Slaven, James; Harper, Martin

2010-07-21

206

Mate-choice copying when both sexes face high costs of reproduction  

Microsoft Academic Search

Mate choice is linked to costs such as time and energy effort or a higher risk of predation. Furthermore, reproduction with\\u000a a partner of lower than average quality will reduce an individual’s fitness. Copying the mate choice of others is assumed\\u000a to reduce such costs. Most studies dealing with mate-choice copying focused on females, as they are usually expected to

Joachim G. Frommen; Anna K. Rahn; Stefanie H. Schroth; Nadine Waltschyk; Theo C. M. Bakker

2009-01-01

207

Influence of weather on reproductive success of northern fulmars in the Canadian high Arctic  

Microsoft Academic Search

The northern fulmar (Fulmarus glacialis) is a common seabird of the North Atlantic Ocean, with breeding colonies broadly dispersed between 45°N and 80°N. At higher\\u000a latitudes, breeding fulmars experience extensive sea-ice and presumably snow and low temperatures which do not affect fulmars\\u000a in the southern part of the breeding range. We studied the relationship between weather and reproductive success of northern

Mark L. Mallory; Anthony J. Gaston; Mark R. Forbes; H. Grant Gilchrist

2009-01-01

208

High-mass star-formation rates in M33  

SciTech Connect

The H I, CO, and H-alpha data for M33 are analyzed to obtain high-mass star formation rates and efficiencies and to look for variations in these quantities within the inner disk of M33. Star formation rates and efficiencies are calculated using calibrated H-alpha data. The H-alpha emission in this region of the galaxy corresponds to high-mass and total star-formation rates of 0.007 and 0.04 solar mass/yr, respectively. These results agree reasonably well with the rates calculated from the 60 and 100-micron IRAS emission. The star formation rates obtained form FIR and H-alpha luminosities are compared with those obtained from optical photometry. 35 refs.

Wilson, C.D.; Scoville, N.; Rice, W. (California Institute of Technology, Pasadena (USA) JPL, Pasadena, CA (USA))

1991-04-01

209

High Rate Deep Si Etching using Capacitively Coupled Plasma  

NASA Astrophysics Data System (ADS)

High rate deep Si etching using SF6/O2 gas chemistry by Magnetically-Enhanced Reactive Ion Etch (MERIE) system using a Dipole-Ring Magnet (DRM) is studied. It is capable of etching holes 40 ?m in diameter in a Si substrate at etch rates as high as 50 ?m/min. It was found that the Si etch reaction is dominated by the density of fluorine radicals, which is realized at high frequency and pressure. In holes with higher aspect ratios, it was found that the Si etch rate at the bottom of holes is determined not only by the supply of fluorine radicals, but is also influenced by an etch-inhibiting effect related to the sidewall of the hole. Using an 8 ?m square mask, holes with straight sidewalls were etched to a depth of 60 ?m at an etch rate of 24 ?m/min.

Sakai, Itsuko; Sakurai, Noriko; Ohiwa, Tokuhisa

210

High water temperatures impair the reproductive ability of the pejerrey fish Odontesthes bonariensis: effects on the hypophyseal-gonadal axis.  

PubMed

The aim of this research was to study how high water temperatures impair the reproductive activity of pejerrey Odontesthes bonariensis, an inland-water atherinopsid fish species from the pampasic region of Argentina. Adult pejerrey of both sexes were kept under a control-temperature regime (19 degrees C) and two experimental temperatures (23 degrees and 27 degrees C) for 8 d. The effect of elevated temperature on the pituitary-gonad axis was analyzed in terms of the expression of gonadotropin (GtH) subunits: follicle-stimulating hormone beta, luteinizing hormone beta (LH-beta), glycoprotein hormone alpha, and GtH receptors FSH-R and LH-R by semiquantitative reverse transcriptase polymerase chain reaction, plasma levels of sexual steroids by radioimmunoassay, and reproductive status by gonadal histology. The results of this work clearly indicate that short periods of exposure to high water temperatures disrupt pejerrey reproduction. This effect was observed in spawning activity, at the histological level, and in the reduction of plasma estradiol in females and testosterone in males. The mRNA levels of GtH subunits and GtH receptors generally decreased in proportion to the increase in temperature for both sexes. However, the differences between groups were statistically significant only for LH-beta and for FSH-R expression in pejerrey females. Thus, the gonads of pejerrey appear to be the primary target of high water temperature. Analysis of the air temperature in this region over the past 40 yr indicated an increase of 1.74 degrees C in mean annual temperature. This increase, coupled with the mechanism of high-temperature sensitivity shown in this study, may be one of the reasons for the decline in pejerrey populations observed in this region over recent decades. PMID:18922066

Soria, Federico N; Strüssmann, Carlos A; Miranda, Leandro A

211

Reproductive performance of pubertal red deer (Cervus elaphus) hinds: effects of genetic introgression of wapiti subspecies on pregnancy rates at 18 months of age.  

PubMed

Low reproductive productivity of young red deer (Cervus elaphus) hinds on New Zealand deer farms appears to reflect high incidences of puberty failure at 16 months of age. This is despite the general attainment of average liveweights 15-25 kg in excess of the accepted minimum threshold for puberty in subspecies of western European origin (scoticus, elaphus and hippelaphus) that form the basis of the national herd. The present study tests the hypotheses that introgression of the larger North American wapiti subspecies (nelsoni, manitobensis and roosevelti) into breeding herds (1) can be assessed from morphological features of individuals, (2) that there is a relationship between the level of wapiti parentage and non-pregnancy rate at 18 months of age (a proxy for puberty failure) and (3) that minimum liveweight thresholds for puberty increase with increasing levels of wapiti parentage. A total of 4329 18-month-old hinds across four "red" deer farms in southern New Zealand were scanned for pregnancy status. Each hind was assigned a wapiti score (WS) as a subjective assessment of the obviousness of wapiti features. Various body measurements were additionally recorded for each hind. A hair sample was collected for DNA analysis (14 markers) to objectively assign subspecies pedigree (i.e. "Elkmeter") on a subset of 1258 individuals. A total of 506 (11.7%) hinds were not pregnant at 18 months of age with rates varying between 4.1 and 37.3% between farms and years. Mean WS differed significantly between farms and reflected the genetic management policy of each farm. WS was positively correlated to Elkmeter for each farm/year (<0.05) although regression slopes varied significantly. WS was able to be adjusted for these differences to assign a corrected WS (CWS) for all 4329 individuals that estimated the proportion wapiti parentage. Discriminant analysis of morphological variables relative to Elkmeter supported the first hypothesis and showed that shoulder height and body length were good indicators of the degree of wapiti parentage within individuals. This enabled the development of an objective estimate of wapiti parentage (EWP). The actual level of such parentage within herds ranged from <5 to >55%. There was a significant negative association between wapiti parentage and pregnancy, which was strongly influenced by liveweight, supporting the second and third hypotheses. This was manifest as marked displacement of pregnancy probability curves in relation to liveweight between genotype groups, particularly for those groups with >20% wapiti parentage. For example, predicted threshold liveweights required to achieve a 90% pregnancy rate for EWP values that represent 0, 10, 20, 30, 40 and 50% wapiti parentage were 81, 81, 85, 106, 127 and approximately 137 kg, respectively. Within the study herds, the majority of hinds of 0-20% wapiti parentage exceeded the predicted 90% threshold liveweights for their genotype cohort. However, hinds with higher levels of wapiti parentage generally fell below the predicted threshold for their genotype group. The data strongly suggest that under liveweight performance levels measured for red deer, hinds with >20% wapiti parentage are at high risk of puberty failure. PMID:16298276

Asher, G W; Archer, J A; Scott, I C; O'Neill, K T; Ward, J; Littlejohn, R P

2005-12-01

212

Lithium-Ion Battery Pulse/High Rate Demonstration.  

National Technical Information Service (NTIS)

Performance of lithium-ion batteries at low temperatures and/or high rates is relatively poor due to high cell internal impedance. The ac impedance spectroscopy was utilized to determine the impedance characteristics of lithium- ion cells as a function of...

J. P. Fellner

2003-01-01

213

Target delivery system for high repetition rate lasers  

Microsoft Academic Search

We present early prototype of a high repetition target delivery system, designed for nominal operation rate at 1 Hz but with possibility of running at up to 10 Hz. The system is primarily intended to deliver complex solid-state targets, such as composite foils or structured shapes, in vacuum environment into the focus of a high-repetition laser. The system in its

J. Polan; T. Havlicek; B. Rus

2007-01-01

214

High rate electrodes of V 2O 5 aerogel  

Microsoft Academic Search

In the present paper we report on high rate electrodes made from a conventional battery cathode material, vanadium pentoxide. The electrodes were obtained through a sol–gel process by which the active materials were coated in the form of thin, highly porous, layers on appropriate conducting substrates. The composite electrodes are characterized by very short ionic and electronic paths throughout the

S. Passerini; J. J. Ressler; D. B. Le; B. B. Owens; W. H. Smyrl

1999-01-01

215

Magnetic Implosion for Novel Strength Measurements at High Strain Rates  

Microsoft Academic Search

Recently Lee and Preston have proposed to use magnetic implosions as a new method for measuring material strength in a regime of large strains and high strain rates inaccessible to previously established techniques. By its shockless nature, this method avoids the intrinsic difficulties associated with an earlier approach using high explosives. The authors illustrate how the stress-strain relation for an

H. Lee; D. L. Preston; R. R. Bartsch; R. L. Bowers; D. Holtkamp; B. L. Wright

1998-01-01

216

Status of Women Indicators, Infant Mortality Rate and Birth Rate: A study of High Crude Birth Rate Districts of Pakistan  

Microsoft Academic Search

Pakistan, with a population of 139 million in 2000, is the seventh most populous country in the world. The historical trends indicate a continuous and exponentially increasing growth in population because of sustained high fertility and declining mortality. Currently the population is growing at around 2.2 percent per annum, one of the highest rates of growth (after Nigeria) in the

Mohammad Pervez Wasim

2002-01-01

217

Soot-formation rate in premixed combustion at high pressures  

NASA Astrophysics Data System (ADS)

The soot formation rate at high pressures has been studied with a premixed propane-oxygen-inert gas combustion in a specially designed disk-type constant-volume combustion chamber. Premixtures are simultaneously ignited by eight spark plugs located on the circumference of chamber at 45 degree intervals in order to observe the soot formation rate under high pressure. The eight flames being converged compress the end gases to a high pressure. The laser schlieren and direct flame photographs for observation field with 10 mm in diameter are taken to investigate the effects of curvature for the optical path in the flame front and gas flow in the measured position on soot formation rate. The soot formation rate in the chamber center during the final stage of combustion at the highest pressure is measured by the in situ laser extinction technique at the following conditions; 0.4 to 5.0 MPa for pressure, 1600 to 1900 K for temperature and 2.0 to 2.2 for equivalence ratio. The burnt gas temperature is measured by the two-color pyrometry method. The pressure and temperature during soot formation are changed by varying the initial charge pressure and the volume fraction of inert gas in the premixture, respectively. In the present study, it is found that the soot formation rate can be expressed by an empirical pseudo- first-order kinetics for surface growth even at high pressures, and that the rate constant of soot formation is only dependent of the temperature.

Bae, Myung-Whan; Kamimoto, Takeyuki

1995-05-01

218

Evolution of High Tooth Replacement Rates in Sauropod Dinosaurs  

PubMed Central

Background Tooth replacement rate can be calculated in extinct animals by counting incremental lines of deposition in tooth dentin. Calculating this rate in several taxa allows for the study of the evolution of tooth replacement rate. Sauropod dinosaurs, the largest terrestrial animals that ever evolved, exhibited a diversity of tooth sizes and shapes, but little is known about their tooth replacement rates. Methodology/Principal Findings We present tooth replacement rate, formation time, crown volume, total dentition volume, and enamel thickness for two coexisting but distantly related and morphologically disparate sauropod dinosaurs Camarasaurus and Diplodocus. Individual tooth formation time was determined by counting daily incremental lines in dentin. Tooth replacement rate is calculated as the difference between the number of days recorded in successive replacement teeth. Each tooth family in Camarasaurus has a maximum of three replacement teeth, whereas each Diplodocus tooth family has up to five. Tooth formation times are about 1.7 times longer in Camarasaurus than in Diplodocus (315 vs. 185 days). Average tooth replacement rate in Camarasaurus is about one tooth every 62 days versus about one tooth every 35 days in Diplodocus. Despite slower tooth replacement rates in Camarasaurus, the volumetric rate of Camarasaurus tooth replacement is 10 times faster than in Diplodocus because of its substantially greater tooth volumes. A novel method to estimate replacement rate was developed and applied to several other sauropodomorphs that we were not able to thin section. Conclusions/Significance Differences in tooth replacement rate among sauropodomorphs likely reflect disparate feeding strategies and/or food choices, which would have facilitated the coexistence of these gigantic herbivores in one ecosystem. Early neosauropods are characterized by high tooth replacement rates (despite their large tooth size), and derived titanosaurs and diplodocoids independently evolved the highest known tooth replacement rates among archosaurs.

Smith, Kathlyn M.; Fisher, Daniel C.; Wilson, Jeffrey A.

2013-01-01

219

Positron and orthopositronium decay rates in helium at high densities  

Microsoft Academic Search

Positron and orthopositronium (o-Ps) decay rates have been obtained in helium gas over the density ranges 72--200 and 80--520 amagat at gas temperatures 300 and 77 degreeK, respectively. The 77 degreeK o-Ps results exhibit the onset of bubblelike behavior observed by other investigators. The 300 degreeK o-Ps decay rates are in agreement with a linear extrapolation of the high-precision low-density

R. A. Fox; K. F. Canter; M. Fishbein

1977-01-01

220

Progress in testing sheet material at high strain rates  

NASA Astrophysics Data System (ADS)

In this paper the requirements for the evaluation of yield behaviour at high strain rates up to 1000 s^{-1} will be discussed. The main topic is the performance of tests at high strain rates preventing oscillations caused by impact and the use of special solutions for force measurement of sheet material. The importance of obtaining stress-strain curves at high strain rates is increasing due to the need of finite element simulation of higher accuracy, especially in the field of crashworthiness. Finite element codes are now able to use records of stress-strain curves for different strain rates instead of simple models of strain rate dependence of the yield behaviour. The use of light weight metal sheet and newly developed steel sheet material needs the determination of the yield behaviour at high strain rates. Experience in testing and measuring was applied and improved in many tests with round tensile specimens made of steel at strain rates up to 1000 s^{-1}. hall parts connecte with the specimen have to have light weight to reduce the influence of inertia effects. This can be achieved with optical and strain gauge measurements. The time resolution and frequency bandwidth has to be sufficiently in order to obtain reliable data. Because of the low limit frequency, standard force measurement techniques can only be used at strain rates up to 100 s^{-1}. The strain gauge measuring technique for measuring the actual load, approved in many round tensile specimen tests, could not be directly applied to sheet specimens. Based on the experience with round tensile tests a modified procedure has been developed. In order to reduce the experimental effort additional sheets with strain gauges can be connected to the specimen for force measurement. The signal from this force measurement device shows a significant reduction of oscillation. The quality of this method will be demonstrated in test results of different materials. With this method an accurate, reliable and economical test procedure has been established.

Roos, E.; Mayer, U.

2003-09-01

221

Compressive behaviour of concrete at high strain rates  

Microsoft Academic Search

Experimental techniques commonly used for high strain-rate testing of concrete in compression, together with the methods used\\u000a for measurement and recording of stress and strain, are critically assessed in the first part of this paper. The physical\\u000a capability of each loading method is discussed and some consideration is given to the definitions used for specifying the\\u000a loading rate. The second

P. H. Bischoff; S. H. Perry

1991-01-01

222

Study of magnetorheological fluids at high shear rates  

Microsoft Academic Search

The tunable rheological properties of magnetorheological (MR) materials at high shear rates are studied using a piston-driven flow-mode-type rheometer. The proposed method provides measurement of the apparent viscosity and yield stress of MR fluids for a shear rate range of 50 to 40,000 s?1. The rheological properties of a commercial MR fluid, as well as a newly developed MR polymeric gel,

Xiaojie Wang; Faramarz Gordaninejad

2006-01-01

223

High variance in reproductive success of the Pacific oyster ( Crassostrea gigas, Thunberg) revealed by microsatellite-based parentage analysis of multifactorial crosses  

Microsoft Academic Search

Marine bivalves are known to have small Ne\\/N ratios, both in wild and hatchery-propagated populations. This has been interpreted as the consequence of a high variance in reproductive success. However, how much of this variance could be attributed to pre-zygotic reproductive factors or to post-zygotic selection was not yet estimated. To estimate the relative effect of these factors, we have

P Boudry; B Collet; F Cornette; V Hervouet; F Bonhomme

2002-01-01

224

High energy high rate pulsed power processing of materials by powder consolidation and by railgun deposition  

Microsoft Academic Search

This exploratory research program was initiated to investigate the potential of using pulse power sources for powder consolidation, deposition and other High Energy High Rate Processing. The characteristics of the High Energy High Rate (1MJ\\/s) powder consolidation using megampere current pulses from a Homopolar Generator, have been defined. Molybdenum Alloy TZM, A Nickel based metallic glass, Copper graphite composites, and

C. Persad; H. L. Marcus; W. F. Weldon

1987-01-01

225

THE AMERICAN HIGH SCHOOL GRADUATION RATE: TRENDS AND LEVELS.  

PubMed

This paper applies a unified methodology to multiple data sets to estimate both the levels and trends in U.S. high school graduation rates. We establish that (a) the true rate is substantially lower than widely used measures; (b) it peaked in the early 1970s; (c) majority/minority differentials are substantial and have not converged for 35 years; (d) lower post-1970 rates are not solely due to increasing immigrant and minority populations; (e) our findings explain part of the slowdown in college attendance and rising college wage premiums; and (f) widening graduation differentials by gender help explain increasing male-female college attendance gaps. PMID:20625528

Heckman, James J; Lafontaine, Paul A

2010-05-01

226

Behavior of MR Fluids at High Shear Rate  

NASA Astrophysics Data System (ADS)

The high shear rate behavior of MR fluids is investigated using a concentric rotational cylinder viscometer fabricated in-house. The rotational cylinder viscometer is designed such that a high shear rate of up to 30,000 s-1 can be applied to the MR fluid in a pure shear flow mode. As a comparison, the maximum shear rate of a commercially available parallel disk type rheometer is only up to 1,000 s-1. To determine the shear rate of the MR fluid in the viscometer, an exact expression between torque and angular velocity is established. The yield stress and viscosity of the MR fluid is determined by fitting the expression into the measured torque and angular velocities, and the shear stress as a function of the shear rate is further derived. The magnetic filed strength across the fluid gap is determined based on an electromagnetic field analysis, and the yield stress and viscosity of the fluid as a function of the magnetic filed is established. Specifically, the stability of the MR fluid at high shear rate is also evaluated. Two commercially available MR fluids, i.e., Lord's MRF-132DG and MRF-140CG, are investigated using the rotational cylinder viscometer, and the testing results are compared to the manufacturer's data.

Hu, Wei; Wereley, Norman M.

227

[Multifactorial analysis of the blood levels of LH, FSH and estradiol in relation to ovular harvesting rates, fertilization and segmentation in patients undergoing assisted reproduction (GIFT-FIVTE)].  

PubMed

This study shows that there is certain tendency to asssign more value to the observation of follicular growth by ultrasound than to hormonal levels "per se". However, the appreciation of growth is only part of the phenomenon of development and ovarian maturity, for that, surveillance with hormonal monitor of ovarian response keeps with a most important role in Assisted Reproduction Clinica. The basal levels, mainly of FSH and in a less degree LH, inversely correlate with the amount of retrieved ovocytes. Estradiol values should be interpreted with a fixed point of reference, as the day of HCG administration, and a direct relation is seen between estradiol levels and captured ovocytes; however, is of highest usefulness to value the conduct of estradiol level, with the knowledge that the prognosis for good capture rates improves with ascending values and above 700 pg in the day of HCG administration. PMID:1601316

Di Castro Stringher, P; Espinosa de los Monteros Mena, A; Hernández Vazquez, J; Parra Covarrubias, A; Kably Ambe, A; Alvarado Duran, A

1992-04-01

228

High strain rate superplasticity in metals and composites  

SciTech Connect

Superplastic behavior at very high strain rates (at or above 1 s{sup {minus}1}) in metallic-based materials is an area of increasing interest. The phenomenon has been observed quite extensively in metal alloys, metal-matrix composites (MMC), and mechanically-alloyed (MA) materials. In the present paper, experimental results on high strain rate behavior in 2124 Al-based materials, including Zr-modified 2124, SiC-reinforced 2124, MA 2124, and MA 2124 MMC, are presented. Except for the required fine grain size, details of the structural requirements of this phenomenon are not yet understood. Despite this, a systematic approach to produce high strain rate superplasticity (HSRS) in metallic materials is given in this paper. Evidences indicate that the presence of a liquid phase, or a low melting point region, at boundary interfaces is responsible for HSRS.

Nieh, T.G.; Wadsworth, J. [Lawrence Livermore National Lab., CA (United States); Higashi, K. [Osaka Prefecture Univ., Sakai (Japan). Dept. of Mechanicl Systems Engineering

1993-07-01

229

Damage formation during high strain rate deformation of PBS9501  

NASA Astrophysics Data System (ADS)

A key aspect of the response of an explosive formulation to high strain rate loading is damage formation. In addition to the effect on immediate strength properties, damage, once formed, can lead to an undesirable increase in sensitivity and rate of burning. Methodologies for understanding and characterising the damage formed during loading are therefore vital if we are to claim a true understanding of the mechanical properties of these materials. This paper presents results from experiments on stimulant, PBS9501, of a polymer bonded explosive. High strain rate loading was performed in a split Hopkinson pressure bar, using speckle metrology and high speed photography to build up a more complete data-set on the formation of damage in this material. X-ray microtomography was also applied to examine internal damage in recovered specimens.

Siviour, Clive; Proud, William

2007-06-01

230

Microcrystalline silicon solar cells deposited at high rates  

NASA Astrophysics Data System (ADS)

Hydrogenated microcrystalline silicon (?c-Si:H) thin-film solar cells were prepared at high rates by very high frequency plasma-enhanced chemical vapor deposition under high working pressure. The influence of deposition parameters on the deposition rate (RD) and the solar cell performance were comprehensively studied in this paper, as well as the structural, optical, and electrical properties of the resulting solar cells. Reactor-geometry adjustment was done to achieve a stable and homogeneous discharge under high pressure. Optimum solar cells are always found close to the transition from microcrystalline to amorphous growth, with a crystallinity of about 60%. At constant silane concentration, an increase in the discharge power did hardly increase the deposition rate, but did increase the crystallinity of the solar cells. This results in a shift of the ?c-Si:H/a-Si:H transition to higher silane concentration, and therefore leads to a higher RD for the optimum cells. On the other hand, an increase in the total flow rate at constant silane concentration did lead to a higher RD, but lower crystallinity. With this shift of the ?c-Si:H/a-Si:H transition at higher flow rates, the RD for the optimum cells decreased. A remarkable structure development along the growth axis was found in the solar cells deposited at high rates by a ``depth profile'' method, but this does not cause a deterioration of the solar cell performance apart from a poorer blue-light response. As a result, a ?c-Si:H single-junction p-i-n solar cell with a high efficiency of 9.8% was deposited at a RD of 1.1 nm/s.

Mai, Y.; Klein, S.; Carius, R.; Wolff, J.; Lambertz, A.; Finger, F.; Geng, X.

2005-06-01

231

High strain rate deformation of NiAl  

SciTech Connect

NiAl is a potential high temperature structural material. Applications for which NiAl is being considered (such as rotating components in jet engines) requires knowledge of mechanical properties over a wide range of strain rates. Single crystal NiAl (stoichiometric and Ni 49.75Al 0.25Fe) has been deformed in compression along [100] at strain rates of 0.001, 0.1/s and 2000/s and temperatures of 76,298 and 773K. <111> slip was observed after 76K testing at a strain rate of 0.001/s and 298K testing at a strain rate of 2000/s. Kinking was observed after deformation at 298K and a strain rate of 0.001/s and sometimes at 298 K and a strain rate of 0.1/s. Strain hardening rates of 8200 and 4000 MPa were observed after 773 and 298K testing respectively, at a strain rate of 2000/s. Results are discussed in reference to resulting dislocation substructure.

Maloy, S.A.; Gray, G.T. III [Los Alamos National Lab., NM (United States); Darolia, R. [General Electric Co., Cincinnati, OH (United States). Aircraft Engines

1994-07-01

232

Thermal, productive, and reproductive responses of high yielding cows exposed to short-term cooling in summer.  

PubMed

Effect of cooling on body temperature, milk production, estrous behavior, and reproductive performance was examined in 66 estrous-synchronized, Israeli-Holstein dairy cows. Cooling was by an automated system, which actuated sprinkling (30 s) followed by forced ventilation (4.5 min) for 30-min periods. Cows were cooled 9 times/d between 0500 and 2100 h over 10 d, starting 1 d before expected estrus until d 8 post estrus. Cooling reduced typical diurnal rise of body temperature in summer heat-stressed cows by .5 to .9 degrees C, and body temperature was maintained close to normothermic temperature (38.6 degrees C). Milk production of cooled cows was 2.6 kg/d (+8%) above control at end of the cooling period. More cooled cows than noncooled exhibited standing estrous behavior; in noncooled cows, silent ovulations or anestrus were more frequent. Conception rate of cooled cows did not differ from control, suggesting need for a longer than a 10-d cooling period for improvement of fertility. The cooling system has potential to alleviate heat stress in dairy cows and to improve their thermal balance, productive, and reproductive performances. PMID:3392302

Her, E; Wolfenson, D; Flamenbaum, I; Folman, Y; Kaim, M; Berman, A

1988-04-01

233

Low Primary Cesarean Rate and High VBAC Rate With Good Outcomes in an Amish Birthing Center  

PubMed Central

PURPOSE Recent national guidelines encourage a trial of labor after cesarean (TOLAC) as a means of increasing vaginal births after cesarean (VBACs) and decreasing the high US cesarean birth rate and its consequences (2010 National Institute of Health Consensus Statement and American College of Obstetricians and Gynecologists revised guideline). A birthing center serving Amish women in Southwestern Wisconsin offered an opportunity to look at the effects of local culture and practices that support vaginal birth and TOLAC. This study describes childbirth and perinatal outcomes during a 17-year period in LaFarge, Wisconsin. METHODS We undertook a retrospective analysis of the records of all women admitted to the birth center in labor. Main outcome measures include rates of cesarean deliveries, TOLAC and VBAC deliveries, and perinatal outcomes for 927 deliveries between 1993 and 2010. RESULT S The cesarean rate was 4% (35 of 927), the TOLAC rate was 100%, and the VBAC rate was 95% (88 of 92). There were no cases of uterine rupture and no maternal deaths. The neonatal death rate of 5.4 of 1,000 was comparable to that of Wisconsin (4.6 of 1,000) and the United States (4.5 of 1,000). CONCLUSIONS Both the culture of the population served and a number of factors relating to the management of labor at the birthing center have affected the rates of cesarean delivery and TOLAC. The results of the LaFarge Amish study support a low-technology approach to delivery where good outcomes are achieved with low cesarean and high VBAC rates.

Deline, James; Varnes-Epstein, Lisa; Dresang, Lee T.; Gideonsen, Mark; Lynch, Laura; Frey, John J.

2012-01-01

234

Coal plasticity at high heating rates and temperatures  

SciTech Connect

Using a high temperature plastometer with a new cone-shaped shearing disk, the effect of shear rate ({gamma}R) on the apparent viscosity of softened coal was studied. For {gamma}R from 2.01 s{sup {minus}1} to 10.7 s{sup {minus}1}, no shear rate effect on the viscosity of Pittsburgh No. 8 high volatile bituminous coal was observed. Three other coals, each of different ranks ranging from high volatile bituminous to low volatile bituminous, were also studied. Although lower in tar and extractable yields than high volatile bituminous coals, medium and low volatile bituminous coals were found to be very plastic. Their good plastic behavior is therefore hypothesized to arise from their ability to generate higher molecular weight liquid fragments ( macrometaplast'') which are not represented by tar and extractable yields.

Gerjarusak, S.; Peters, W.A.; Howard, J.B.

1992-02-01

235

High frame rate CCD camera with fast optical shutter  

SciTech Connect

A high frame rate CCD camera coupled with a fast optical shutter has been designed for high repetition rate imaging applications. The design uses state-of-the-art microchannel plate image intensifier (MCPII) technology fostered/developed by Los Alamos National Laboratory to support nuclear, military, and medical research requiring high-speed imagery. Key design features include asynchronous resetting of the camera to acquire random transient images, patented real-time analog signal processing with 10-bit digitization at 40--75 MHz pixel rates, synchronized shutter exposures as short as 200pS, sustained continuous readout of 512 x 512 pixels per frame at 1--5Hz rates via parallel multiport (16-port CCD) data transfer. Salient characterization/performance test data for the prototype camera are presented, temporally and spatially resolved images obtained from range-gated LADAR field testing are included, an alternative system configuration using several cameras sequenced to deliver discrete numbers of consecutive frames at effective burst rates up to 5GHz (accomplished by time-phasing of consecutive MCPII shutter gates without overlap) is discussed. Potential applications including dynamic radiography and optical correlation will be presented.

Yates, G.J.; McDonald, T.E. Jr. [Los Alamos National Lab., NM (United States); Turko, B.T. [Lawrence Berkeley National Lab., CA (United States)

1998-09-01

236

Reliability modeling of electronic systems subjected to high strain rates  

Microsoft Academic Search

Electronic products are subjected to high G-levels during mechanical shock and vibration. Failure-modes include solder-joint failures, pad cratering, chip-cracking, copper trace fracture, and underfill fillet failures. The second-level interconnects may be experience high-strain rates and accrue damage during repetitive exposure to mechanical shock. Industry migration to leadfree solders has resulted in proliferation of a wide variety of solder alloy compositions.

Pradeep Lall; Sandeep Shantaram; David Locker

2012-01-01

237

High data-rate atom interferometer for measuring acceleration  

NASA Astrophysics Data System (ADS)

Atom interferometers have the potential to be exceptional broadband inertial sensors in both translational and rotational degrees of freedom. The demonstrated performance of this technology rivals the best ring-laser gyroscopes and falling corner-cube gravimeters. However, compact and field-worthy manifestations of atom interferometers remain elusive using standard approaches. Furthermore, bandwidths have typically been limited to a few Hertz, which is insufficient for a broader application space. We demonstrate a high data-rate light-pulse atom interferometer for measuring acceleration. The device is optimized to operate at rates between 50 Hz to 330 Hz with sensitivities of 0.57 micro-g/rtHz to 36.7 micro-g/rtHz, respectively. Our method offers a dramatic increase in data rate and demonstrates a path to new applications in highly dynamic environments.

Rakholia, Akash; McGuinness, Hayden; Biedermann, Grant

2012-06-01

238

Aspects and Reaction Rates for Pycnonuclear Fusion at High Densities  

Microsoft Academic Search

Pycnonuclear reactions are of great importance in the nuclear astrophysics of high density conditions such as the centers of white dwarf starts, and the deep layers of accreting neutron stars. We present here a single phenomenological expression for the calculation of pycnonuclear reaction rates which is not only valid in mixed component plasma, but can also be extended to cover

Mary Beard; Michael Wiescher; Anatoli Afanasjev; Leandro Gasques; Dima Yakovlev

2008-01-01

239

High data rate quantum noise protected encryption over long distances  

Microsoft Academic Search

We report on a new physical layer optical encryption approach based on quantum noise limited optical signals and M-ary optical phase shift keying that operates at high data rates. In contrast to established encryption methods that rely solely on deterministic algorithms, this system utilizes quantum noise to realize a randomized cipher. Keyed M-ary optical phase modulation is used to encrypt

T. Banwell; P. Toliver; J. C. Young; J. Hodge; M. Rauch; M. S. Goodman; G. Kanter; E. Conrdorf; V. S. Grigoryan; C. Liang; P. Kumar

2005-01-01

240

Vocational maturity ratings of inner-city high school seniors  

Microsoft Academic Search

Compared vocational maturity ratings (VMRs) of 168 inner-city high school seniors who had been exposed to a 2-yr program of structured career-related activities with VMRs of controls (N = 112) using an instrument developed for the study. The experimental groups obtained higher VMRs and higher scores in all vocational maturity component areas. Experimental group seniors in the general curriculum had

John Vriend

1969-01-01

241

Corrected High-Frame Rate Anchored Ultrasound with Software Alignment  

ERIC Educational Resources Information Center

Purpose: To improve lingual ultrasound imaging with the Corrected High Frame Rate Anchored Ultrasound with Software Alignment (CHAUSA; Miller, 2008) method. Method: A production study of the IsiXhosa alveolar click is presented. Articulatory-to-acoustic alignment is demonstrated using a Tri-Modal 3-ms pulse generator. Images from 2 simultaneous…

Miller, Amanda L.; Finch, Kenneth B.

2011-01-01

242

Understanding High School Graduation Rates in West Virginia  

ERIC Educational Resources Information Center

|Graduation rates are a fundamental indicator of whether or not the nation's public school system is doing what it is intended to do: enroll, engage, and educate youth to be productive members of society. Since almost 90 percent of the fastest-growing and highest-paying jobs require some postsecondary education, having a high school diploma and…

Alliance for Excellent Education, 2009

2009-01-01

243

Cassini High Rate Detector V11.0  

NASA Astrophysics Data System (ADS)

The High Rate Detector (HRD) from the University of Chicago is an independent part of the CDA instrument on the Cassini Orbiter that measures the dust flux and particle mass distribution of dust particles hitting the HRD detectors. This data set includes all data from the HRD through December 31, 2011. Please refer to Srama et al. (2004) for a detailed HRD description.

Economou, T.; DiDonna, P.

2012-06-01

244

High Rates of Staphylococcus aureus USA400 Infection, Northern Canada  

PubMed Central

Surveillance of Staphylococcus aureus infections in 3 northern remote communities of Saskatchewan was undertaken. Rates of methicillin-resistant infections were extremely high (146–482/10,000 population), and most (98.2%) were caused by USA400 strains. Although USA400 prevalence has diminished in the United States, this strain is continuing to predominate throughout many northern communities in Canada.

Golding, George R.; Levett, Paul N.; McDonald, Ryan R.; Irvine, James; Quinn, Brian; Nsungu, Mandiangu; Woods, Shirley; Khan, Mohammad; Ofner-Agostini, Marianna

2011-01-01

245

Path Prediction For High Issue-Rate Processors  

Microsoft Academic Search

Rapid developments in the exploitation of instruction-level parallelism are prompting deeper-pipelined, wider machines with high issue rates. Speculative execution has been used to provide the required issue bandwidth. Current methods predict a single branch at a time. Performance improvement is possible by predicting multiple branches in a single cycle. The paper presents a technique to predict paths in a single

Kishore N. Menezes; Sumedh W. Sathaye; T. M. Coate

1997-01-01

246

TROLL HIGH RATE PRODUCTION TEST, PLANNING AND EXECUTION  

Microsoft Academic Search

The high rate production test performed by Norsk Hydro on the Troll East structure during the summer of 1985 with the semi submersible drilling rig Treasure Seeker required that a large number of specially designed, modified or adapted equipment items were used in order to fulfil the objectives and maintain safe operations. These were: Jetting tool for casing cleaning; Gravel

B. H. Nilssen

1987-01-01

247

OPTIMIZATION OF METALLURGICAL PROCESSES USING HIGH RATE BIOTECHNOLOGY  

Microsoft Academic Search

Existing metallurgical operations can be optimized by implementing engineered bioreactor systems in the process configuration. For instance, metals can be recovered safely and economically from process and waste streams using biogenic sulfide. This paper focuses upon possible applications of high rate biotechnology in metallurgy and mining. Metal recovery from liquid streams (process bleed streams, leach water, waste streams), integrated removal

Henk Dijkman; Johannes Boonstra; Rick Lawrence; Cees J. N. Buisman

248

Wastewater treatment high rate algal ponds for biofuel production  

Microsoft Academic Search

While research and development of algal biofuels are currently receiving much interest and funding, they are still not commercially viable at today’s fossil fuel prices. However, a niche opportunity may exist where algae are grown as a by-product of high rate algal ponds (HRAPs) operated for wastewater treatment. In addition to significantly better economics, algal biofuel production from wastewater treatment

J. B. K. Park; R. J. Craggs; A. N. Shilton

2011-01-01

249

High dose rate brachytherapy for superficial cancer of the esophagus  

Microsoft Academic Search

Purpose: We analyzed our experience with external radiotherapy, combined modality treatment, or HDR brachytherapy alone to limited esophageal cancers.Methods and Materials: From 1991 to 1996, 25 patients with limited superficial esophagus carcinomas were treated by high dose rate brachytherapy. The mean age was 63 years (43–86 years). Five patients showed superficial local recurrence after external radiotherapy. Eleven patients without invasion

Philippe Maingon; Anne d’Hombres; Gilles Truc; Isabelle Barillot; Christophe Michiels; Laurent Bedenne; Jean Claude Horiot

2000-01-01

250

Childhood Onset Schizophrenia: High Rate of Visual Hallucinations  

ERIC Educational Resources Information Center

|Objective: To document high rates and clinical correlates of nonauditory hallucinations in childhood onset schizophrenia (COS). Method: Within a sample of 117 pediatric patients (mean age 13.6 years), diagnosed with COS, the presence of auditory, visual, somatic/tactile, and olfactory hallucinations was examined using the Scale for the Assessment…

David, Christopher N.; Greenstein, Deanna; Clasen, Liv; Gochman, Pete; Miller, Rachel; Tossell, Julia W.; Mattai, Anand A.; Gogtay, Nitin; Rapoport, Judith L.

2011-01-01

251

Corrected High-Frame Rate Anchored Ultrasound with Software Alignment  

ERIC Educational Resources Information Center

|Purpose: To improve lingual ultrasound imaging with the Corrected High Frame Rate Anchored Ultrasound with Software Alignment (CHAUSA; Miller, 2008) method. Method: A production study of the IsiXhosa alveolar click is presented. Articulatory-to-acoustic alignment is demonstrated using a Tri-Modal 3-ms pulse generator. Images from 2 simultaneous…

Miller, Amanda L.; Finch, Kenneth B.

2011-01-01

252

A multipurpose high-rate GPS observatory for northwestern Mexico  

Microsoft Academic Search

We describe a proposed joint atmospheric and geophysical high-rate GPS observatory in northwestern Mexico complementing and extending analogous networks in the United Stated. The observatory would measure atmospheric water vapor during the North American Monsoon Experiment (NAME) as well as crustal velocities within and across the Gulf of California and the Mexican Basin and Range region for geodetic applications. The

E. R. Kursinski; R. A. Bennett; A. Hahmann

2003-01-01

253

High Strain-Rate Response of High Purity Aluminum at Temperatures Approaching Melt.  

National Technical Information Service (NTIS)

High-temperature, pressure-shear plate impact experiments were conducted to investigate the rate-controlling mechanisms of the plastic response of high-purity aluminum at high strain rates (10(sup 6) s(sup -1)) and at temperatures approaching melt. Since ...

R. J. Clifton S. E. Grunschel T. Jiao

2010-01-01

254

Demographic and reproductive factors for high seroprevalence of Chlamydia trachomatis among pregnant women in Japan.  

PubMed

In order to elucidate demographic and reproductive factors associated with Chlamydia trachomatis seropositivity, serological screening and questionnaire survey were conducted on pregnant women in Nagasaki Prefecture, Japan. Serum samples were taken from 1718 pregnant women between September and December, 1996, at the cooperative obstetric hospitals and clinics, and tested for the presence of antibodies to C. trachomatis using the enzyme immunoassay. A questionnaire was administered on a sub-sample (n -409), among whom 85 (20.8%) were seropositive. A multiple logistic analysis revealed that four characteristics showed a significant association with the seropositivity: (i) experience of premarital pregnancy, (ii) non use of condoms, (iii) short duration of education, and (iv) more frequent induced abortion. The unsafe sexual behavior of young people lacking proper knowledge of how to prevent STD is the most important intervention target for control of the C. trachomatis epidemic in Japan. PMID:10750735

Kusano, Y; Shibata, Y; Katamine, S; Yamamoto, T; Kurokawa, K; Moriuchi, R; Kubota, K; Masuzaki, H; Honda, S; Moji, K; Takemoto, T

2000-01-01

255

High rate sputter deposition of wear resistant tantalum coatings  

SciTech Connect

The refractory nature and high ductility of body centered cubic (bcc) phase tantalum makes it a suitable material for corrosion- and wear-resistant coatings on surfaces which are subjected to high stresses and harsh chemical and erosive environments. Sputter deposition can produce thick tantalum films but is prone to forming the brittle tetragonal beta phase of this material. Efforts aimed at forming thick bcc phase tantalum coatings in both flat plate and cylindrical geometries by high-rate triode sputtering methods are discussed. In addition to substrate temperature, the bcc-to-beta phase ratio in sputtered tantalum coatings is shown to be sensitive to other substrate surface effects.

Matson, D.W.; Merz, M.D.; McClanahan, E.D.

1991-11-01

256

High-rate mechanical properties of energetic materials  

NASA Astrophysics Data System (ADS)

Compared to the many thousands of studies that have been performed on the energy release mechanisms of high energy materials, relatively few studies have been performed (a few hundred) into their mechanical properties. Since it is increasingly desired to model the high rate deformation of such materials, it is of great importance to gather data on their response so that predictive constitutive models can be constructed. This paper reviews the state of the art concerning what is known about the mechanical response of high energy materials. Examples of such materials are polymer bonded explosives (used in munitions), propellants (used to propel rockets), and pyrotechnics (used to initiate munitions and also in flares).

Walley, S. M.; Siviour, C. R.; Drodge, D. R.; Williamson, D. M.

2010-01-01

257

Magnetic Implosion for Novel Strength Measurements at High Strain Rates  

SciTech Connect

Recently Lee and Preston have proposed to use magnetic implosions as a new method for measuring material strength in a regime of large strains and high strain rates inaccessible to previously established techniques. By its shockless nature, this method avoids the intrinsic difficulties associated with an earlier approach using high explosives. The authors illustrate how the stress-strain relation for an imploding liner can be obtained by measuring the velocity and temperature history of its inner surface. They discuss the physical requirements that lead us to a composite liner design applicable to different test materials, and also compare the code-simulated prediction with the measured data for the high strain-rate experiments conducted recently at LANL. Finally, they present a novel diagnostic scheme that will enable us to remove the background in the pyrometric measurement through data reduction.

Lee, H.; Preston, D.L.; Bartsch, R.R.; Bowers, R.L.; Holtkamp, D.; Wright, B.L.

1998-10-19

258

Magnetic Implosion for Novel Strength Measurements at High Strain Rates  

NASA Astrophysics Data System (ADS)

Recently, Lee and Preston have proposed using magnetic implosions as a new method for measuring material strength in a regime of large strains and high strain rates inaccessible to previously established techniques. By its shockless nature, this method avoids the intrinsic difficulties associated with an earlier approach using high explosives. We illustrate how the stress-strain relation for an imploding liner can be obtained by measuring the velocity and temperature history of its inner surface. We discuss the physical requirements that led us to a composite liner design applicable to different test materials, and also compare the code-simulated prediction with the measured data for the high strain-rate experiments conducted recently at LANL. Finally, we present a novel diagnostic scheme that will enable us to remove the background in the pyrometric measurement through data reduction.

Lee, H.; Preston, D. L.; Bartsch, R. R.; Bowers, R. L.; Holtkamp, D.; Wright, B. L.

2004-11-01

259

Comparison of implantation and pregnancy rates in African American and white women in an assisted reproductive technology practice  

Microsoft Academic Search

Objective: To compare IVF outcomes between infertile African American and white women.Design: Retrospective cohort study.Setting: Hospital-based IVF practice.Patient(s): Women undergoing IVF procedures between November 1996 and June 2000.Intervention(s): None.Main Outcomes Measure(s): Implantation and pregnancy rates.Result(s): There were 24 African American and 273 white women ?40 years of age who underwent 25 and 333 IVF cycles, respectively. African American women were

John E Nichols; H. Lee Higdon; Martin M Crane; William R Boone

2001-01-01

260

Interactions between evolutionary processes at high mutation rates  

PubMed Central

Evolution at high mutation rates is minimally affected by six processes: mutation-selection balance, error catastrophes, Muller’s Ratchet, robustness and compensatory evolution, and clonal interference. Including all of these processes in a tractable, analytical model is difficult, but they can be captured in simulations that utilize realistic genotype-phenotype-fitness maps, as done here by modeling RNA folding. Subjecting finite, asexual populations to a range of mutation rates revealed simple criteria that predict when particular evolutionary processes are important. Populations were initiated with a genotype encoding the most fit phenotype. When purifying selection was strong relative to mutation, the initial genotype was replaced by one more mutationally robust, and the maximally fit phenotype was maintained in a mutation-selection balance where the deleterious mutation rate determined mean fitness. With weaker purifying selection, the most fit genotypes were lost. Although loss of the best genotype was ongoing and might have led to a progressive fitness decline, continual compensatory evolution led to an approximate fitness equilibration. Per total genomic mutation rate, mean fitness was similar for strong and weak purifying selection. These results represent a first step at separating interactions between evolutionary processes at high mutation rate, but additional theory is needed to interpret some outcomes.

Keller, T. E.; Wilke, C. O.; Bull, J. J.

2012-01-01

261

Organic electrodes for high rate capability Lithium-ion batteries  

NASA Astrophysics Data System (ADS)

Lithium-ion batteries (LIBs) for power-intensive applications such as in electric vehicles require high discharge rate, i.e., high Li diffusion rate (or low Li diffusion barrier) in electrode and electrolyte materials. Based on first-principles calculations, we found that organic salt, di-lithium terephthalate (Li2TPA), a promising anode material recently tested in experiment, could have high rate capability. We further predict that di-potassium terephthalate (K2TPA) could exhibit even lower Li diffusion barrier. The calculated Li diffusion barrier in fully lithiated K2TPA is only 150 meV, which yields Li diffusion rate orders of magnitude higher than that in Li-intercalated graphite at room temperature. The calculated anode voltage vs metal lithium and specific energy density are 0.62 V and 209 mAh/g, respectively. In addition, the volume change of K2TPA in charging/discharging is only 5%, much smaller than that in Li-intercalated graphite. These unique advantages call for further investigation of the organic salts, both the TPA-based and beyond, for power-intensive LIB applications either as anode or cathode materials.

Zhang, Y. Y.; Sun, Y. Y.; Du, S. X.; Gao, H. J.; Zhang, S. B.

2012-02-01

262

Pattern recognition in a high-rate GEM-TPC  

NASA Astrophysics Data System (ADS)

A pattern recognition software for a continuously operating high-rate Time Projection Chamber with Gas Electron Multiplier amplification (GEM-TPC) has been designed and tested. Space points are delivered by a track-independent clustering algorithm. A true 3-dimensional track follower combines them to helical tracks, without constraints on the vertex position. Fast helix fits, based on a conformal mapping on the Riemann sphere, are the basis for deciding whether points belong to one track. To assess the performance of the algorithm in a high-rate environment, pp interactions at a rate of 2 × 107 s-1, the maximum rate foreseen for PANDA, have been simulated. The pattern recognition is capable of finding different kinds of track topologies with high efficiency and provides excellent seed values for track fitting or online event selection. The feasibility of event deconvolution has been demonstrated: Different techniques to retain the tracks from an event with known time from other tracks in the TPC are presented in this paper.

Rauch, J.

2012-12-01

263

Vitreous bond CBN high speed and high material removal rate grinding of ceramics  

SciTech Connect

High speed (up to 127 m/s) and high material removal rate (up to 10 mm{sup 3}/s/mm) grinding experiments using a vitreous bond CBN wheel were conducted to investigate the effects of material removal rate, wheel speed, dwell time and truing speed ratio on cylindrical grinding of silicon nitride and zirconia. Experimental results show that the high grinding wheel surface speed can reduce the effective chip thickness, lower grinding forces, enable high material removal rate grinding and achieve a higher G-ratio. The radial feed rate was increased to as high as 0.34 {micro}m/s for zirconia and 0.25 {micro}m/s for silicon nitride grinding to explore the advantage of using high wheel speed for cost-effective high material removal rate grinding of ceramics.

Shih, A.J.; Grant, M.B.; Yonushonis, T.M. [Cummins Engine Co., Inc., Columbus, IN (United States); Morris, T.O.; McSpadden, S.B. [Oak Ridge National Lab., TN (United States)

1998-08-01

264

High strain-rate model for fiber-reinforced composites  

SciTech Connect

Numerical simulations of dynamic uniaxial strain loading of fiber-reinforced composites are presented that illustrate the wide range of deformation mechanisms that can be captured using a micromechanics-based homogenization technique as the material model in existing continuum mechanics computer programs. Enhancements to the material model incorporate high strain-rate plastic response, elastic nonlinearity, and rate-dependent strength degradation due to material damage, fiber debonding, and delamination. These make the model relevant to designing composite structural components for crash safety, armor, and munitions applications.

Aidun, J.B.; Addessio, F.L.

1995-07-01

265

Frequent sexual reproduction and high intraspecific variation in Salix arctica: Implications for a terrestrial feedback to climate change in the High Arctic  

NASA Astrophysics Data System (ADS)

Genetic variation at molecular loci may underlie important variation in the phenotypes of arctic plants. Such intraspecific variation may be a neglected but important component of biological diversity in the Arctic that could impact how arctic ecosystems respond to climate change. Here, we characterized genetic and phenotypic variation in Salix arctica and evaluated the effect of S. arctica on ecosystem CO2 exchange, a process by which terrestrial ecosystems in the Arctic feedback to the global climate system. We found high genetic variation at microsatellite loci of S. arctica collected from an inland and a coastal site in Greenland that indicates sexual reproduction has occurred frequently as the ice sheet has retreated. Across the North American range of S. arctica, ten chloroplast DNA haplotypes were identified. Haplotype diversity and allelic richness were high overall and similar across regions with different glacial histories. Phenotypic variation in ecologically important traits varied substantially in a High Arctic population of S. arctica. In a widespread High Arctic ecosystem, a net loss of CO2 to the atmosphere was observed except where S. arctica was present. We suggest that high genetic variation in S. arctica is in part a result of frequent sexual reproduction, and that the phenotypic variation we observed is likely to be at least partially genetic-based. This would enable a productive High Arctic species to adapt and potentially prosper as climate changes, and thus affect the terrestrial feedback of the Arctic to the climate system.

Steltzer, Heidi; Hufbauer, Ruth A.; Welker, Jeffery M.; Casalis, Maxime; Sullivan, Patrick F.; Chimner, Rodney

2008-09-01

266

High Pressure Burn Rate Measurements on an Ammonium Perchlorate Propellant  

SciTech Connect

High pressure deflagration rate measurements of a unique ammonium perchlorate (AP) based propellant are required to design the base burn motor for a Raytheon weapon system. The results of these deflagration rate measurements will be key in assessing safety and performance of the system. In particular, the system may experience transient pressures on the order of 100's of MPa (10's kPSI). Previous studies on similar AP based materials demonstrate that low pressure (e.g. P < 10 MPa or 1500 PSI) burn rates can be quite different than the elevated pressure deflagration rate measurements (see References and HPP results discussed herein), hence elevated pressure measurements are necessary in order understand the deflagration behavior under relevant conditions. Previous work on explosives have shown that at 100's of MPa some explosives will transition from a laminar burn mechanism to a convective burn mechanism in a process termed deconsolidative burning. The resulting burn rates that are orders-of-magnitude faster than the laminar burn rates. Materials that transition to the deconsolidative-convective burn mechanism at elevated pressures have been shown to be considerably more violent in confined heating experiments (i.e. cook-off scenarios). The mechanisms of propellant and explosive deflagration are extremely complex and include both chemical, and mechanical processes, hence predicting the behavior and rate of a novel material or formulation is difficult if not impossible. In this work, the AP/HTPB based material, TAL-1503 (B-2049), was burned in a constant volume apparatus in argon up to 300 MPa (ca. 44 kPSI). The burn rate and pressure were measured in-situ and used to calculate a pressure dependent burn rate. In general, the material appears to burn in a laminar fashion at these elevated pressures. The experiment was reproduced multiple times and the burn rate law using the best data is B = (0.6 {+-} 0.1) x P{sup (1.05{+-}0.02)} where B is the burn rate in mm/s and P is the pressure in units of MPa. Details of the experimental method, results and data analysis are discussed herein and briefly compared to other AP based materials that have been measured in this apparatus.

Glascoe, E A; Tan, N

2010-04-21

267

Modeling Large-Strain, High-Rate Deformation in Metals  

SciTech Connect

The large strain deformation response of 6061-T6 and Ti-6Al-4V has been evaluated over a range in strain rates from 10{sup -4} s{sup -1} to over 10{sup 4} s{sup -1}. The results have been used to critically evaluate the strength and damage components of the Johnson-Cook (JC) material model. A new model that addresses the shortcomings of the JC model was then developed and evaluated. The model is derived from the rate equations that represent deformation mechanisms active during moderate and high rate loading. Another model that accounts for the influence of void formation on yield and flow behavior of a ductile metal (the Gurson model) was also evaluated. The characteristics and predictive capabilities of these models are reviewed.

Lesuer, D R; Kay, G J; LeBlanc, M M

2001-07-20

268

High strain rate mechanical properties of glassy polymers  

NASA Astrophysics Data System (ADS)

Since the early 1990s, a range of experimental data has been generated describing the response of glassy polymers to high strain rate loading in compression. More recently, research programs that study the combined effects of temperature and strain rate have made significant steps in providing better understanding of the physics behind the observed response, and also in modeling this response. However, limited data are available in tension, and even more limited are data describing both the compressive and tensile response of the same polymer. This paper investigates the compressive and tensile response of glassy polymers, using poly(vinyl chloride) as a representative material, across a range of stain rates from quasi-static to dynamic. The pressure dependant yield in glassy polymers will be discussed through comparison of the tensile and compressive yield stresses.

Jordan, Jennifer L.; Siviour, Clive Richard; Woodworth, Brian

2012-03-01

269

Design constraints of high-bit-rate soliton communication systems  

NASA Astrophysics Data System (ADS)

We have examined the main constraints on the design of single-channel, high-capacity soliton communication systems. In the average soliton regime, the Gordon-Haus timing jitter limits the bit rate to less than 7 Gb/s for transoceanic fiber links, while for shorter transmission distances the main limitation is fiber perturbations arising from discrete in-line amplification. The use of dispersion-decreasing fibers and of periodic optical phase conjugation for jitter control can increase significantly the capacity of soliton communication systems. We found that the third-order dispersion assumes a prominent role in this case. Reducing this effect sufficiently, the main constraint becomes the soliton-soliton interactions and bit rates superior to 110 Gb/s can be achieved for amplifier spacings less than 80 km. For higher amplifier spacings the bit rate is limited by the Raman induced timing jitter.

Ferreira, Mario F.

1999-10-01

270

Methane hydrates with a high capacity and a high formation rate promoted by biosurfactants.  

PubMed

Lignosulfonates, which are byproducts of the pulp and paper industry, can be used as promoters for the formation of methane hydrates with a high capacity up to 170 v/v and a high formation rate. PMID:23073027

Wang, Weixing; Huang, Zhan; Chen, Haoran; Tan, Zhuyan; Chen, Caixing; Sun, Luyi

2012-12-11

271

Spectroscopy of high rate events during active interrogation  

NASA Astrophysics Data System (ADS)

Pulsed accelerators are being used for radiographic inspections in homeland security applications. Adding spectroscopic detection capability enables additional information to be extracted but challenges signal processing hardware. This work compares two approaches to cost-effective digital spectroscopy systems designed to handle these high rate scenarios. In the first system, the signal from a PMT is directly digitized and then deconvolved on a PC using standard techniques. Bypassing the preamplifier, this system can handle high count rates (>106 cps) from an LaCl3 detector with no dead time and an energy resolution of 5% at 1.33 MeV. Spectra acquired from fission product gamma rays between interrogation pulses are shown. At higher rates, this approach is limited by the DAQ transfer rate to the PC. Instead, we tested a fast ADC (125 MSPS) and an FPGA that performed onboard, real-time digital signal processing (DSP). The energy spectrum is generated on the FPGA board during the measurement and transferred later. This system was tested in nuclear resonance fluorescence (NRF) experiments. Resonance peaks from NRF reactions are shown.

Yang, H.; Wehe, D. K.; Bartels, D. M.

2009-01-01

272

High frame rate measurements of semiconductor pixel detector readout IC  

NASA Astrophysics Data System (ADS)

We report on high count rate and high frame rate measurements of a prototype IC named FPDR90, designed for readouts of hybrid pixel semiconductor detectors used for X-ray imaging applications. The FPDR90 is constructed in 90 nm CMOS technology and has dimensions of 4 mm×4 mm. Its main part is a matrix of 40×32 pixels with 100 ?m×100 ?m pixel size. The chip works in the single photon counting mode with two discriminators and two 16-bit ripple counters per pixel. The count rate per pixel depends on the effective CSA feedback resistance and can be set up to 6 Mcps. The FPDR90 can operate in the continuous readout mode, with zero dead time. Due to the architecture of digital blocks in pixel, one can select the number of bits read out from each counter from 1 to 16. Because in the FPDR90 prototype only one data output is available, the frame rate is 9 kfps and 72 kfps for 16 bits and 1 bit readout, respectively (with nominal clock frequency of 200 MHz).

Szczygiel, R.; Grybos, P.; Maj, P.

2012-07-01

273

High dose rate radiation treatment of experimental intramuscular prostate carcinoma  

PubMed Central

Purpose The Dunning R3327-MLL is a well established transplanted tumor line, and as such it makes a desirable model for evaluative studies of therapy. In the current study, the interstitial growth characteristics as well as the response of this tumor to a single fraction of high dose rate radiation is investigated. Materials and Methods The in-vitro response to radiation of the Dunning R3327-MLL was studied via a colony forming assay using a Cs-137 irradiator. In-vitro radiosensitivity was determined on tumors implanted intramuscularly in the left gastrocnemius muscle of the rat and irradiated using an Ir-192 afterloader. Results The results demonstrate a faster growth rate when compared to the reported subcutaneous growth rates. The Dunning R3327-MLL’s radiosensitivity is comparable to that of late response tissues. The dose required to achieve a specific radiobiological response (the ?:? ratio) of the in-vitro cell line is 2.4 Gy, whereas the ratio for the intramuscularly growing tumor was 0.99 Gy. Conclusions These findings signify the intramuscularly implanted Dunning R3327-MLL tumor model as a desirable model for the study of single fraction high dose rate radiation treatments.

Skourou, Christina; Hoopes, P. Jack; Gibbs-Strauss, Summer L.; Gladstone, David J.; Strawbridge, Rendall; Paulsen, Keith D.

2009-01-01

274

Optically stimulated luminescent dosimetry for high dose rate brachytherapy.  

PubMed

Purpose: The objective was to determine whether optically stimulated luminescent dosimeters (OSLDs) were appropriate for in vivo measurements in high dose rate brachytherapy. In order to make this distinction, three dosimetric characteristics were tested: dose linearity, dose rate dependence, and angular dependence. The Landauer nanoDot™ OSLDs were chosen due to their popularity and their availability commercially. Methods: To test the dose linearity, each OSLD was placed at a constant location and the dwell time was varied. Next, in order to test the dose rate dependence, each OSLD was placed at different OLSD-to-source distances and the dwell time was held constant. A curved geometry was created using a circular Accuboost(®) applicator in order to test angular dependence. Results: The OSLD response remained linear for high doses and was independent of dose rate. For doses up to 600?cGy, the linear coefficient of determination was 0.9988 with a response of 725 counts per cGy. The angular dependence was significant only in "edge-on" scenarios. Conclusion: OSLDs are conveniently read out using commercially available readers. OSLDs can be re-read and serve as a permanent record for clinical records or be annealed using conventional fluorescent light. Lastly, OSLDs are produced commercially for $5 each. Due to these convenient features, in conjunction with the dosimetric performance, OSLDs should be considered a clinically feasible and attractive tool for in vivo HDR brachytherapy measurements. PMID:22888476

Tien, Christopher Jason; Ebeling, Robert; Hiatt, Jessica R; Curran, Bruce; Sternick, Edward

2012-08-06

275

Failure Rate Data Analysis for High Technology Components  

SciTech Connect

Understanding component reliability helps designers create more robust future designs and supports efficient and cost-effective operations of existing machines. The accelerator community can leverage the commonality of its high-vacuum and high-power systems with those of the magnetic fusion community to gain access to a larger database of reliability data. Reliability studies performed under the auspices of the International Energy Agency are the result of an international working group, which has generated a component failure rate database for fusion experiment components. The initial database work harvested published data and now analyzes operating experience data. This paper discusses the usefulness of reliability data, describes the failure rate data collection and analysis effort, discusses reliability for components with scarce data, and points out some of the intersections between magnetic fusion experiments and accelerators.

L. C. Cadwallader

2007-07-01

276

High removal rate laser-based coating removal system  

SciTech Connect

A compact laser system is disclosed that removes surface coatings (such as paint, dirt, etc.) at a removal rate as high as 1,000 ft{sup 2}/hr or more without damaging the surface. A high repetition rate laser with multiple amplification passes propagating through at least one optical amplifier is used, along with a delivery system consisting of a telescoping and articulating tube which also contains an evacuation system for simultaneously sweeping up the debris produced in the process. The amplified beam can be converted to an output beam by passively switching the polarization of at least one amplified beam. The system also has a personal safety system which protects against accidental exposures.

Matthews, D.L.; Celliers, P.M.; Hackel, L.; Da Silva, L.B.; Dane, C.B.; Mrowka, S.

1999-11-16

277

High-Transfer-Rate High-Capacity Holographic Disk Data-Storage System  

Microsoft Academic Search

We describe the design and implementation of a high-data-rate high-capacity digital holographic storage disk system. Various system design trade-offs that affect density and data-rate performance are described and analyzed. In the demonstration system that we describe, high-density holographic recording is achieved by use of high-resolution short-focal-length optics and correlation shift multiplexing in photopolymer disk media. Holographic channel decoding at a

Sergei S. Orlov; William Phillips; Eric Bjornson; Yuzuru Takashima; Padma Sundaram; Lambertus Hesselink; Robert Okas; Darren Kwan; Raymond Snyder

2004-01-01

278

Effect of bis(tributyltin) oxide on reproduction and population growth rate of calanoid copepod Schmackeria poplesia  

NASA Astrophysics Data System (ADS)

A full life-cycle toxicity test, combined with histology, on calanoid copepod Schmackeria poplesia was used to study the effect of bis(tributyltin) oxide (TBTO). The results indicate no sex-specific differences in TBTO toxicity. Long-term mortalities of the copepods exposed to concentrations higher than 20 ng TBTO L-1 were significantly elevated compared with that of control, and larval development was inhibited when they were exposed to 40 and 60 ng TBTO L-1. The percentages of ovigerous females were reduced compared with the control ( P<0.01) after 24 days exposure to concentrations higher than 10 ng TBTO L-1. Histological examinations suggest that exposure to TBTO might block the posterior end of the diverticula and inhibits the production of egg sacs. A modified Euler-Lotka equation was used to calculate a population-level endpoint, the intrinsic rate of natural increase ( r m), from individual life-table endpoints, i.e. mortality rate, time of release of first brood, sex ratio, the fraction of ovigerous females among all females as well as the number of nauplii per ovigerous female. Apart from the highest TBTO concentration (60 ng L-1), where all females aborted their egg sacs, 20 ng TBTO L-1 was the only concentration that significantly decreased r m compared with that of control (an effect associated with decreased sex ratio). The results show that the S. poplesia is affected by prolonged exposure to low concentrations of TBTO. The full life-cycle toxicity test combined with histology experiments provides more integral understanding of the toxicity of endocrine disrupters.

Huang, Ying; Zhu, Liyan; Qiu, Xuchun; Zhang, Tianwen

2010-03-01

279

Operation of a high repetition rate intense ion beam diode  

Microsoft Academic Search

Summary form only given, as follows. A magnetically insulated diode has been developed that is capable of pulsing at a high repetition rate for short bursts. This diode has a plasma-anode ion source which originates as an annular puff of H2 or some other gas. The gas puff is preionized and then inductively broken down by a 1 ?s-risetime magnetic

W. A. Noonan; S. C. Glidden; J. B. Greenly; D. A. Hammer; L. Brissette

1990-01-01

280

Homogeneous Nucleation Rate for Highly Supercooled Cirrus Cloud Droplets  

Microsoft Academic Search

A mixed-phase hydrometer growth model has been applied to determining the nucleation mode and rate responsible for the glaciation of a highly supercooled liquid cloud studied jointly by ground-based polarization lidar and aircraft in situ probes. The cloud droplets were detected at the base of an orographically induced cirrus cloud at temperatures between 34.3° and 37.3°C. The vertical distribution above

Kenneth Sassen; Gregory C. Dodd

1988-01-01

281

Development of high burn rate azide polymer propellant  

Microsoft Academic Search

The combustion characteristics of high burn rate azide polymer composite propellant were examined by using ø 70 mm BMI composite rocket motor of L\\/D = 16. Azide polymer propellants have much higher specific impulse than HTPB propellant at below the AP content of 85%. AP\\/B\\/N propellants showed a plateau-mesa burning at a pressure range between 7 MPa and 15 MPa

Yoshino Oyumi; Kikokazu Nagayama

1997-01-01

282

Effect of high dose rate irradiations on COTS optical fibres  

Microsoft Academic Search

Commercial off-the-shelf (COTS) single-mode and multimode germanosilicate optical fibres are intended for use as part of control-command applications in the future Laser Megajoule facility. We evaluated their vulnerability to the radiative environment associated to this project by characterizing their transient radiation responses at infrared wavelengths (1064, 1310 and 1550 nm) after high dose rate exposure (> 108 Gy\\/s). Our results

Sylvain Girard; Jacques Baggio; Martial Martinez

2005-01-01

283

High-repetition-rate amplification of 16 (SIGMA) micron radiation  

Microsoft Academic Search

High repitition rate generation of up to 325 mJ of Raman amplified radiation near 615 cm(+1) was demonstrated in CO2-pumped para-H2 using a low power, microwave shifted CF4 laser as an input Stokes seed source. Experiments were limited to 200 Hz, but single shot Schlieren measurements indicate that our flowing room temperature 44 pass Raman converter should be capable of

N. A. Kurnit; D. E. Watkins; G. W. York

1983-01-01

284

High-repetition-rate Raman amplification of 16-micron radiation  

Microsoft Academic Search

High-repetition-rate generation of up to 325 mJ of Raman amplified radiation near 615\\/cm has been demonstrated in CO2-pumped para-H2 using a low-power, microwave-shifted CF4 laser as an input Stokes seed source. Experiments were limited to 200 Hz, but single-shot Schlieren measurements indicate that the flowing room-temperature 44-pass Raman converter should be capable of the design goal of 1 kHz. Strong

N. A. Kurnit; D. E. Watkins; G. W. York

1983-01-01

285

High-repetition-rate amplification of 16. mu. m radiation  

Microsoft Academic Search

High-repitition-rate generation of up to 325 mJ of Raman amplified radiation near 615 cm⁻¹ has been demonstrated in COâ-pumped para-Hâ using a low-power, microwave-shifted CFâ laser as an input Stokes seed source. Experiments were limited to 200 Hz, but single-shot Schlieren measurements indicate that our flowing room-temperature 44-pass Raman converter should be capable of the design goal of 1 kHz.

N. A. Kurnit; D. E. Watkins; G. W. York

1983-01-01

286

Dropout Prevention: Strategies for Improving High School Graduation Rates  

ERIC Educational Resources Information Center

The reason that the school dropout crisis is now referred to as a "silent epidemic" is because, when we weren't paying attention, the graduation rate in our country slipped to a level that threatens the very health and well-being of our society. Each year, almost one-third of all public high school students--and nearly one-half of all blacks,…

Owen, Jenni, Ed.; Rosch, Joel, Ed.; Muschkin, Clara, Ed.; Alexander, Jana, Ed.; Wyant, Casey, Ed.

2008-01-01

287

High dose rate prostate brachytherapy: the California Endocurietherapy (CET) Method  

Microsoft Academic Search

Background and purpose: To describe the rationale, protocol and procedure for the treatment of prostate cancer using high dose rate brachytherapy (HDR-BT) and a non-fixed template technique.Materials and methods: Between July 1991 and December 1998, 491 patients with carcinoma of the prostate were treated using HDR-BT and a non-fixed template technique. AJC stages T1C–T3B, patients with prior transurethral resections of

D. Jeffrey Demanes; Rodney R Rodriguez; Gillian A Altieri

2000-01-01

288

Adjunct payload for ISS high-rate communications  

NASA Astrophysics Data System (ADS)

An adjunct payload on commercial geosynchronous satellites is developed for ISS and similar high-rate communications. The technical parameters of this payload are set forth and bounds on user fees are established. Depending on the financial arrangements-e.g., development funds, long-term lease agreement, other value offered, commercial subscriptions-the adjunct payload can be a viable option for ISS communications service.

Mitchell, W. Carl; Cleave, Robert; Ford, David

1999-01-01

289

Electrochemical cell with high discharge/charge rate capability  

DOEpatents

A fully charged positive electrode composition for an electrochemical cell includes FeS.sub.2 and NiS.sub.2 in about equal molar amounts along with about 2-20 mole percent of the reaction product Li.sub.2 S. Through selection of appropriate electrolyte compositions, high power output or low operating temperatures can be obtained. The cell includes a substantially constant electrode impedance through most of its charge and discharge range. Exceptionally high discharge rates and overcharge protection are obtainable through use of the inventive electrode composition.

Redey, Laszlo (Downers Grove, IL)

1988-01-01

290

High-data-rate ultrasonic through-metal communication.  

PubMed

A link-adaptive frequency division multiplexing (OFDM) ultrasonic physical layer is proposed for high-data-rate communications through metal walls. The ultrasonic link allows for communication without physical penetration of the metal barrier. Link-adaptive OFDM mitigates the severe frequency- selective fading of the ultrasonic channel and greatly improves throughput over impulse or narrowband communication systems. Throughput improvements of 300% are demonstrated over current narrowband low-frequency techniques, and show improved spectral efficiency over high-frequency techniques found in the literature. PMID:23007780

Wanuga, Kevin; Bielinski, Magda; Primerano, Richard; Kam, Moshe; Dandekar, Kapil R

2012-09-01

291

High-rate electrochemical energy storage through Li+ intercalation pseudocapacitance.  

PubMed

Pseudocapacitance is commonly associated with surface or near-surface reversible redox reactions, as observed with RuO2·xH2O in an acidic electrolyte. However, we recently demonstrated that a pseudocapacitive mechanism occurs when lithium ions are inserted into mesoporous and nanocrystal films of orthorhombic Nb2O5 (T-Nb2O5; refs 1,2). Here, we quantify the kinetics of charge storage in T-Nb2O5: currents that vary inversely with time, charge-storage capacity that is mostly independent of rate, and redox peaks that exhibit small voltage offsets even at high rates. We also define the structural characteristics necessary for this process, termed intercalation pseudocapacitance, which are a crystalline network that offers two-dimensional transport pathways and little structural change on intercalation. The principal benefit realized from intercalation pseudocapacitance is that high levels of charge storage are achieved within short periods of time because there are no limitations from solid-state diffusion. Thick electrodes (up to 40 ?m thick) prepared with T-Nb2O5 offer the promise of exploiting intercalation pseudocapacitance to obtain high-rate charge-storage devices. PMID:23584143

Augustyn, Veronica; Come, Jérémy; Lowe, Michael A; Kim, Jong Woung; Taberna, Pierre-Louis; Tolbert, Sarah H; Abruña, Héctor D; Simon, Patrice; Dunn, Bruce

2013-04-14

292

Factors influencing reproductive performance of northern bobwhite in South Florida  

Microsoft Academic Search

Reproductive success is a critical component of individual fitness, and also an important determinant of growth rates of populations\\u000a characterized by early maturity and high fecundity. We used radiotelemetry data collected during 2003–2008 to estimate reproductive\\u000a parameters in a declining northern bobwhite (Colinus virginianus) population in South Florida, and to test hypotheses regarding factors influencing these parameters. The overall clutch

Virginie Rolland; Jeffrey A. Hostetler; Tommy C. Hines; H. Franklin Percival; Madan K. Oli

293

Characterization of an infrared detector for high frame rate thermography  

NASA Astrophysics Data System (ADS)

The use of a commercially available photodetector based infrared thermography system, operating in the 2–5 µm range, for high frame rate imaging of temperature evolutions in solid materials is investigated. Infrared photodetectors provide a very fast and precise means of obtaining temperature evolutions over a wide range of science and engineering applications. A typical indium antimonide detector will have a thermal resolution of around 4 mK for room temperature measurements, with a noise threshold around 15 to 20 mK. However the precision of the measurement is dependent on the integration time (akin to exposure time in conventional photography). For temperature evolutions that occur at a moderate rate the integration time can be relatively long, enabling a large signal to noise ratio. A matter of increasing importance in engineering is the behaviour of materials at high strain rates, such as those experienced in impact, shock and ballistic loading. The rapid strain evolution in the material is usually accompanied by a temperature change. The temperature change will affect the material constitutive properties and hence it is important to capture both the temperature and the strain evolutions to provide a proper constitutive law for the material behaviour. The present paper concentrates on the capture of the temperature evolutions, which occur at such rates that rule out the use of contact sensors such as thermocouples and electrical resistance thermometers, as their response times are too slow. Furthermore it is desirable to have an indication of the temperature distribution over a test specimen, hence the full-field approach of IRT is investigated. The paper explores the many hitherto unaddressed challenges of IRT when employed at high speed. Firstly the images must be captured at high speeds, which means reduced integration times and hence a reduction in the signal to noise ratio. Furthermore, to achieve the high image capture rates the detector array must be windowed down, therefore there is a compromise made between the extent of the full-field imaging and the temporal resolution of the image capture. In the present work a maximum image capture speed of 15 kHz was achieved with a detector array of 64 × 12 elements and an integration time was 60 µs. Results from initial work on woven E-glass/epoxy tensile specimens are presented.

Fruehmann, R. K.; Crump, D. A.; Dulieu-Barton, J. M.

2013-10-01

294

ASSISTED REPRODUCTIVE TECHNOLOGY REPORTS (ART REPORTS)  

EPA Science Inventory

The Society for Assisted Reproductive Technology (SART), an organization of ART providers affiliated with the American Society for Reproductive Medicine (ASRM), has been collecting data and publishing annual reports of pregnancy success rates for fertility clinics in the United S...

295

Diversification and reproductive isolation: cryptic species in the only New World high-duty cycle bat, Pteronotus parnellii  

PubMed Central

Background Molecular techniques are increasingly employed to recognize the presence of cryptic species, even among commonly observed taxa. Previous studies have demonstrated that bats using high-duty cycle echolocation may be more likely to speciate quickly. Pteronotus parnellii is a widespread Neotropical bat and the only New World species to use high-duty cycle echolocation, a trait otherwise restricted to Old World taxa. Here we analyze morphological and acoustic variation and genetic divergence at the mitochondrial COI gene, the 7th intron region of the y-linked Dby gene and the nuclear recombination-activating gene 2, and provide extensive evidence that P. parnellii is actually a cryptic species complex. Results Central American populations form a single species while three additional species exist in northern South America: one in Venezuela, Trinidad and western Guyana and two occupying sympatric ranges in Guyana and Suriname. Reproductive isolation appears nearly complete (only one potential hybrid individual found). The complex likely arose within the last ~6 million years with all taxa diverging quickly within the last ~1-2 million years, following a pattern consistent with the geological history of Central and northern South America. Significant variation in cranial measures and forearm length exists between three of the four groups, although no individual morphological character can discriminate these in the field. Acoustic analysis reveals small differences (5–10 kHz) in echolocation calls between allopatric cryptic taxa that are unlikely to provide access to different prey resources but are consistent with divergence by drift in allopatric species or through selection for social recognition. Conclusions This unique approach, considering morphological, acoustic and multi-locus genetic information inherited maternally, paternally and bi-parentally, provides strong support to conclusions about the cessation of gene flow and degree of reproductive isolation of these cryptic species.

2013-01-01

296

High rates of nonbreeding adult bald eagles in southeastern Alaska  

Microsoft Academic Search

Present knowledge of bald eagle (Haliaeetus leucocephalus) demography is derived primarily from populations in environments that have been drastically altered by man. Most reproductive studies were done in the 1960's and 1970's when chemical toxins were inhibiting bald eagle productivity. Earlier, the removal of old-growth forests and decimation of anadromous fish runs by Euro-Americans may have greatly reduced bald eagle

A. J. Hansen; J. I. Jr. Hodges

1985-01-01

297

Reproductive ecology of female chimpanzees.  

PubMed

An important adaptive problem for mammals in general, and primates in particular, is how females can manage the high costs of reproduction in the face of fluctuating energetic supplies. For many species, the best solution is to breed seasonally such that high costs are temporally coincident with predictable periods of resource abundance. This is an unreliable strategy for some primates, such as chimpanzees (Pan troglodytes), for which large body size forces an increase in dietary complexity and prolonged reproductive efforts. Here, I review data on reproductive function in chimpanzees, a species that demonstrates a risk-averse reproductive strategy wherein reproductive investment is allocated in accordance with maternal condition. Life history parameters for chimpanzees indicate that most females produce very few surviving offspring. However, comparisons between captive and wild populations and within wild populations illustrate that variation in resource access leads to highly variable reproductive success. Focused hormonal studies have demonstrated these effects at a proximate level, with energetic influences on female dispersal, receptivity, cycle quality, conception success, and lactational amenorrhea. Downstream of these effects, female reproductive function affects sexual attractiveness, and by virtue of males' own optimal reproductive strategies, can lead to coercive aggression and decreased foraging efficiency. Because of their extreme reproductive costs, female chimpanzees utilize a highly conservative reproductive strategy, one that minimizes the costs of ecological variation but makes them vulnerable to sexual conflict and costs of sociality. PMID:23015287

Thompson, Melissa Emery

2012-09-26

298

High pulse rate and pileup handling in precision RBS  

NASA Astrophysics Data System (ADS)

Recording RBS spectra at the fastest possible rate presents obvious advantages. Speed is, moreover, a must when RBS is carried out simultaneously with NRA, when high-Z thick targets are analyzed, like YBaCuO, and a very large number of pulses must be processed for recording with sufficient statistics the narrow high-energy region of interest, when kinetics measurements are carried out in situ, the total time available for the measurements being limited by the physical process under study, etc. We present here the first results of a systematic search for increasing counting rates in RBS while keeping pileup-induced spectrum distortions within acceptable levels. The pileup-handling properties of the fastest available spectroscopy amplifiers were characterized. A probabilistic model was developed of the residual pileup process due to the pairs of pulses not resolved by the pileup rejection system. The corresponding algorithm implemented with the GENPLOT program with RUMP input-output format may be used to clean up the spectra from the residual pileup. We present examples of spectra recorded with counting rates up to 43000 counts/s and treated successfully with this algorithm. The still unsolved problems and possible remedies are discussed.

Amsel, G.; Girard, E.; Vizkelethy, G.; Battistig, G.; Girard, Y.; Szilágyi, E.

1992-02-01

299

Analysis of the strain-rate sensitivity at high strain rates in FCC and BCC metals  

SciTech Connect

The development of a constitutive model based on the use of internal state variables and phenomenological models describing glide kinetics is reviewed. Application of the model to the deformation of fcc metals and alloys is illustrated, with an emphasis on the behavior at high strain rates. Preliminary results in pure iron and 4340 steel are also presented. Deformation twinning is observed in iron samples deformed in the Hopkinson pressure bar. The influence of twinning on the proposed constitutive is discussed. 11 refs., 8 figs.

Follansbee, P.S.

1988-01-01

300

Eighteen-beam gun design for high power, high repetition rate, broadband multiple-beam klystrons  

Microsoft Academic Search

This paper presents the design of a high repetition rate electron gun to be employed in future high-power broadband multiple-beam amplifiers operating in S-band. Special emphasis is placed on the geometric layout of the gun to ensure high repetition rate operation at moderate beam switching voltages, good beam optics, and optimal beam packing for long life, efficient beam-wave interaction and

Khanh T. Nguyen; Dean E. Pershing; David K. Abe; George Miram; Baruch Levush

2005-01-01

301

Modular high frame rate detector for synchrotron applications  

SciTech Connect

The development of detectors often lags the development in X-ray sources. However, advanced detectors are critical for fully utilizing and exploiting the capabilities of the new bright sources. We report on the development of a modular high frame rate detector for synchrotron applications such as small angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS). The detector consists of four modules, each providing an imaging area of 5 x 5 cm{sup 2} and capable of frame rates of 200 frames per second (fps) with full resolution, and 650 fps with smaller region of interest (ROI). Details of the detector design and experiments at synchrotron beamlines are discussed in the paper.

Singh, B.; Yang, L.; Thacker, S.; Gaysinskly, V.; Guo, L.; et. al.

2011-01-27

302

Multianode cylindrical proportional counter for high count rates  

DOEpatents

A cylindrical, multiple-anode proportional counter is provided for counting of low-energy photons (< 60 keV) at count rates of greater than 10/sup 5/ counts/sec. A gas-filled proportional counter cylinder forming an outer cathode is provided with a central coaxially disposed inner cathode and a plurality of anode wires disposed in a cylindrical array in coaxial alignment with and between the inner and outer cathodes to form a virtual cylindrical anode coaxial with the inner and outer cathodes. The virtual cylindrical anode configuration improves the electron drift velocity by providing a more uniform field strength throughout the counter gas volume, thus decreasing the electron collection time following the detection of an ionizing event. This avoids pulse pile-up and coincidence losses at these high count rates. Conventional RC position encoding detection circuitry may be employed to extract the spatial information from the counter anodes.

Hanson, J.A.; Kopp, M.K.

1980-05-23

303

The high strain-rate behaviour of selected tissue analogues.  

PubMed

The high strain-rate response of four readily available tissue simulants has been investigated via plate-impact experiments. Comparison of the shock response of gelatin, ballistic soap (both sub-dermal tissue simulants), lard (adipose layers) and Sylgard(®) (a potential brain simulant) allowed interrogation of the applicability of such monolithic tissue surrogates in the ballistic regime. The gelatin and lard exhibited classic linear Hugoniot equations-of-state in the US-uP plane; while for the ballistic soap and Sylgard(®) a polymer-like non-linear response was observed. In the P/?X-v/v0 plane there was evidence of separation of the simulant materials into distinct groups, suggesting that a single tissue simulant is inadequate to ensure a high-fidelity description of the high strain-rate response of complex mammalian tissue. Gelatin appeared to behave broadly hydrodynamically, while soap, lard and Sylgard(®) were observed to strengthen in a material-dependent manner under specific loading conditions at elevated shock loading pressures/stresses. This strengthening behaviour was tentatively attributed to a further polymeric-like response in the form of a re-arrangement of the molecular chains under loading (a steric effect). In addition, investigation of lateral stress data from the literature showed evidence of operation of a material-independent strengthening mechanism when these materials were stressed above 2.5-3.0GPa, tentatively linked to the generically polymeric-like underlying microstructure of the simulants under consideration. PMID:23778063

Appleby-Thomas, G J; Hazell, P J; Sheldon, R P; Stennett, C; Hameed, A; Wilgeroth, J M

2013-05-30

304

Diamond detector for high rate monitors of fast neutrons beams  

SciTech Connect

A fast neutron detection system suitable for high rate measurements is presented. The detector is based on a commercial high purity single crystal diamond (SDD) coupled to a fast digital data acquisition system. The detector was tested at the ISIS pulsed spallation neutron source. The SDD event signal was digitized at 1 GHz to reconstruct the deposited energy (pulse amplitude) and neutron arrival time; the event time of flight (ToF) was obtained relative to the recorded proton beam signal t{sub 0}. Fast acquisition is needed since the peak count rate is very high ({approx}800 kHz) due to the pulsed structure of the neutron beam. Measurements at ISIS indicate that three characteristics regions exist in the biparametric spectrum: i) background gamma events of low pulse amplitudes; ii) low pulse amplitude neutron events in the energy range E{sub dep}= 1.5-7 MeV ascribed to neutron elastic scattering on {sup 12}C; iii) large pulse amplitude neutron events with E{sub n} < 7 MeV ascribed to {sup 12}C(n,{alpha}){sup 9}Be and 12C(n,n')3{alpha}.

Giacomelli, L.; Rebai, M.; Cippo, E. Perelli; Tardocchi, M.; Fazzi, A.; Andreani, C.; Pietropaolo, A.; Frost, C. D.; Rhodes, N.; Schooneveld, E.; Gorini, G. [Dipartimento di Fisica, Universita degli Studi di Milano-Bicocca, and Istituto di Fisica del Plasma, Associazione EURATOM-ENEA-CNR, Milano (Italy); Energy Department, Politecnico di Milano, Milano (Italy); Dipartimento di Fisica, Centro NAST, Universita degli Studi di Roma Tor Vergata, Roma (Italy); STFC, ISIS facility, Rutherford Appleton Laboratory, Chilton Didcot Oxfordshire (United Kingdom); Dipartimento di Fisica, Universita degli Studi di Milano-Bicocca, and Istituto di Fisica del Plasma, Associazione EURATOM-ENEA-CNR, Milano (Italy)

2012-06-19

305

High Temperature Strain-Rate Dependent Rheology of Strombolian Magmas  

NASA Astrophysics Data System (ADS)

Volcanism at Stromboli generates a variety of products that need to be fully characterized in terms of their rheological behaviour mainly according to phase distribution, volatile content and stress-strain regimes. These eruptive products, similar in overall chemical composition (HK-shoshonitic basalts), strongly differ in terms of crystallinity and vesicularity (from dark holocrystalline scoria to aphiric golden pumice). In order to quantify the effect of crystals on the rheology of basaltic magma from Stromboli, we have investigated the pure liquid viscosity and the strain-rate dependent liquid+crystal rheology of remelted products of nearly aphiric pumices of the 15th March 2007 paroxysmal event. The high T viscosities of fully molten (1225° C- 4 to 5x10-2 s-1. Above the liquidus temperature, viscosity ranges from 100.9 to 101.9 in good agreement with the viscosity model by Giordano et al. (2008). In the subliquidus region, we performed isothermal crystallization experiment to quantify the effect of crystals on the rheology. At T between 1175 and 1205° C viscosities range between 102 and 104 Pa s at rotational rates between 0.2 and 20 rpm. Viscosity increases considerably as a function of crystal content, showing at T=1175° C a maximum relative viscosity of 1.4 log units. Upon cooling from about 1200° C, Fe-oxide and plagioclase form, followed by a late stage crystallization of clinopyroxene at the lowest investigated T, which shows the maximum overall crystal fraction of 23 vol%. In order to evaluate the effect of the strain-rate on the viscosity and the crystallization efficiency with time, we performed at T=1190° C three different rheological measurements starting with different initial strain-rate. The experiments with higher initial strain-rate show lower viscosity increase, associated to lower crystal content. Our experimental data indicate that also at the high temperature regime considered, the viscous response to applied stress and strain rate is highly affected by the presence of even a small amount of crystals. A strong discrepancy between measured data and those obtained by using the Einstein-Roscoe (ER) equation is found already at low crystal fractions. Furthermore, we observe that the measured relative viscosity is significantly more pronounced than predicted by the most recent strain-rate dependent models (Caricchi et al., 2007) and that a weak shear thinning rheological behaviour seems to occur towards the lowest temperatures of investigation. Other than to the crystal volume fraction, we infer such large observed discrepancies as mainly determined by elongated shape of plagioclase, that differs from the more rounded shape of solid particles with which the ER and the Caricchi et al. (2007) were calibrated. Crystal shape and together with it the strain-rate dependence of the rheological properties appears to play a primary role in influencing the transport properties of strombolian basaltic magmas.

Vona, A.; Romano, C.; Dingwell, D. B.; Giordano, D.

2008-12-01

306

High Strain Rate Response of Tungsten Heavy Alloy  

NASA Astrophysics Data System (ADS)

Tungsten heavy alloy (WHA) is studied to investigate the effect of thickness variation on its dynamic behaviors. Exploding Bridgwire (EBW) detonator has been used to drive the alloy plate. The particle velocity at the rear free surface was measured by means of VISAR. The experimental technique in this paper has been introduced to simply obtain the Hugoniot elastic limit and spall strength of materials of small disc plate (diamter of 7mm) with varying thickness. Peak pressure decay is analyzed as a function of the thickness of samples. The fracture behavior of WHA caused by this high strain rate is similar to that due to the conventional tensile test.

Chang, S. N.

1997-07-01

307

Reproductive status, family interactions, and suicidal ideation: Surveys of the general public and high-risk groups  

Microsoft Academic Search

Evolutionary modeling predicts an erosion of self-preservative genetic expression in the conjunction of low reproductive potential and burdensomeness toward kin. Although culture and pathology clearly bear on human suicide, some of its emotional concomitants could reflect such evolution. A survey probing reproductive behavior, quality of family contacts, and suicidal ideation was administered to samples of the general public of Ontario

Denys de Catanzaro

1995-01-01

308

High repetition rate driver circuit for modulation of injection lasers  

SciTech Connect

An injection laser modulator comprises a self-biased field effect transistor (FET) and an injection laser to provide a quiescent state during which lasing of the injection laser occurs in response to a high repetition rate signal of pulse coded modulation (pcm). The modulator is d.c. coupled to an input pulse source of pcm rendering it compatible with an input pulse referenced to ground and not being subject to voltage level shifting of the input pulse. The modulator circuit in its preferred and alternate embodiments provides various arrangements for high impedance input and low impedance output matching. In addition, means are provided for adjusting the bias of the FET as well as the bias of the injection laser.

Dornan, B.R.; Goel, J.; Wolkstein, H.J.

1981-01-06

309

Troll high rate production test, planning and execution  

SciTech Connect

The high rate production test performed by Norsk Hydro on the Troll East structure during the summer of 1985 with the semi submersible drilling rig Treasure Seeker required that a large number of specially designed, modified or adapted equipment items were used in order to fulfil the objectives and maintain safe operations. These were: Jetting tool for casing cleaning; Gravel pack floor manifold to ease operations; Surface read out of downhole pressure and temperature through cable on the outside of the tubing; 3 inch I.D. tester valve; 3.7 inch I.D. annulus pressure operated kill valve; Full bore double gauge carrier; 5 inch I.D. sub-sea test valve; 5 inch I.D. lubricator valve; 5 1/8 inch bore flowhead; Vertical high capacity separator; 32 channel data logger. The use of this equipment together with other more commonly used equipment made the test a success.

Nilssen, B.H.

1987-01-01

310

Driving techniques for high frame rate CCD camera  

NASA Astrophysics Data System (ADS)

This paper describes a high-frame rate CCD camera capable of operating at 100 frames/s. This camera utilizes Kodak KAI-0340, an interline transfer CCD with 640(vertical)×480(horizontal) pixels. Two output ports are used to read out CCD data and pixel rates approaching 30 MHz. Because of its reduced effective opacity of vertical charge transfer registers, interline transfer CCD can cause undesired image artifacts, such as random white spots and smear generated in the registers. To increase frame rate, a kind of speed-up structure has been incorporated inside KAI-0340, then it is vulnerable to a vertical stripe effect. The phenomena which mentioned above may severely impair the image quality. To solve these problems, some electronic methods of eliminating these artifacts are adopted. Special clocking mode can dump the unwanted charge quickly, then the fast readout of the images, cleared of smear, follows immediately. Amplifier is used to sense and correct delay mismatch between the dual phase vertical clock pulses, the transition edges become close to coincident, so vertical stripes disappear. Results obtained with the CCD camera are shown.

Guo, Weiqiang; Jin, Longxu; Xiong, Jingwu

2008-03-01

311

A high load of non-neutral amino-acid polymorphisms explains high protein diversity despite moderate effective population size in a marine bivalve with sweepstakes reproduction.  

PubMed

Marine bivalves show among the greatest allozyme diversity ever reported in Eukaryotes, putting them historically at the heart of the neutralist-selectionist controversy on the maintenance of genetic variation. Although it is now acknowledged that this high diversity is most probably a simple consequence of a large population size, convincing support for this explanation would require a rigorous assessment of the silent nucleotide diversity in natural populations of marine bivalves, which has not yet been done. This study investigated DNA sequence polymorphism in a set of 37 nuclear loci in wild samples of the flat oyster Ostrea edulis. Silent diversity was found to be only moderate (0.7%), and there was no departure from demographic equilibrium under the Wright-Fisher model, suggesting that the effective population size might not be as large as might have been expected. In accordance with allozyme heterozygosity, nonsynonymous diversity was comparatively very high (0.3%), so that the nonsynonymous to silent diversity ratio reached a value rarely observed in any other organism. We estimated that one-quarter of amino acid-changing mutations behave as neutral in O. edulis, and as many as one-third are sufficiently weakly selected to segregate at low frequency in the polymorphism. Finally, we inferred that one oyster is expected to carry more than 4800 non-neutral alleles (or 4.2 cM(-1)). We conclude that a high load of segregating non-neutral amino-acid polymorphisms contributes to high protein diversity in O. edulis. The high fecundity of marine bivalves together with an unpredictable and highly variable success of reproduction and recruitment (sweepstakes reproduction) might produce a greater decoupling between Ne and N than in other organisms with lower fecundities, and we suggest this could explain why a higher segregating load could be maintained for a given silent mutation effective size. PMID:23390609

Harrang, Estelle; Lapègue, Sylvie; Morga, Benjamin; Bierne, Nicolas

2013-02-01

312

Parasitic heating effects in high frame rate laser imaging experiments  

NASA Astrophysics Data System (ADS)

The number of applications using high frame rate imaging in combustion research has grown rapidly in recent years. Enabled by continuous improvements in laser power, a wide range of diagnostics have been developed to measure velocity, species concentration, and temperature. Growing attention is focused on measurements near surfaces, e.g., to gain better insight into transient boundary layer flows in internal combustion engines. During such experiments, laser light is used to illuminate the gas phase region above the surface, but often the laser beam is terminated into the surface directly. Thus, laser operation at several kilohertz and power levels in the range of 10-100 W raise concerns about heating the surface and altering the conditions in the gas phase. In other words, the non-intrusive properties of laser diagnostics might not be guaranteed under such conditions. We have investigated the effect of heating by high repetition rate lasers by measuring the temperature of an exposed metal surface with an infrared sensor and by various simulation approaches. The current results show a modest but noticeable influence of laser heating.

Brusnahan, Matthew; Lu, Louise; Sick, Volker

2013-06-01

313

Arabidopsis thaliana expressing a thermostable chimeric Rubisco activase exhibits enhanced growth and higher rates of photosynthesis at moderately high temperatures.  

PubMed

Temperature is one of the most important factors controlling growth, development, and reproduction in plants. The rate of photosynthesis declines at moderately high temperatures in plants and particularly in temperate species like Arabidopsis thaliana. This can be attributed to a reduced ability of Rubisco activase to achieve optimum activation of Rubisco, leading to reduced Rubisco activity. In order to overcome this problem, we transformed the Arabidopsis rca mutant with a more thermostable, chimeric activase where a Rubisco recognition domain in the more thermostable tobacco activase was replaced with that from Arabidopsis. Transgenic lines expressing this activase showed higher rates of photosynthesis than the wild type after a short exposure to higher temperatures and they also recovered better, when they were returned to the normal temperature. Moreover, under extended exposure to moderately elevated temperature, the transgenic lines had higher biomass and seed yield when compared with the wild type plants. PMID:19507049

Kumar, Anshuman; Li, Cishan; Portis, Archie R

2009-06-09

314

High energy high rate pulsed power processing of materials by powder consolidation and by railgun deposition  

NASA Astrophysics Data System (ADS)

This exploratory research program was initiated to investigate the potential of using pulse power sources for powder consolidation, deposition and other High Energy High Rate Processing. The characteristics of the High Energy High Rate (1MJ/s) powder consolidation using megampere current pulses from a Homopolar Generator, have been defined. Molybdenum Alloy TZM, A Nickel based metallic glass, Copper graphite composites, and P/M Aluminum Alloy X7091 have been investigated. The powder consolidation process produced high densification rates. Density values of 80% to 99% could be obtained with sub second high temperature exposure. Specific energy input and applied pressure were controlling process parameters. Time Temperature Transformation (TTT) concepts underpin a fundamental understanding of pulsed power processing. Deposition experiments were conducted using an exploding foil device (EFD) providing an armature feed to railgun mounted in a vacuum chamber. The material to be deposited - in plasma, gas, liquid or solid state - was accelerated electromagnetically in the railgun and deposited on a substrate.

Persad, C.; Marcus, H. L.; Weldon, W. F.

1987-03-01

315

Analysis of the swine tracheobronchial lymphnode transcriptomic response to infection with a Chinese highly pathogenic strain of porcine reproductive and respiratory syndrome virus  

Technology Transfer Automated Retrieval System (TEKTRAN)

Porcine reproductive and respiratory syndrome virus (PRRSV) is a major pathogen of swine worldwide. Emergence in 2006 of a novel highly pathogenic PRRSV (HP-PRRSV) isolate in China necessitated a comparative investigation into the host transcriptome response in tracheobronchial lymph nodes (TBLN) 14...

316

Secondary infection with Streptococcus suis serotype 7 increases the virulence of highly pathogenic porcine reproductive and respiratory syndrome virus in pigs  

Microsoft Academic Search

BACKGROUND: Porcine reproductive and respiratory syndrome virus (PRRSV) and Streptococcus suis are common pathogens in pigs. In samples collected during the porcine high fever syndrome (PHFS) outbreak in many parts of China, PRRSV and S. suis serotype 7 (SS7) have always been isolated together. To determine whether PRRSV-SS7 coinfection was the cause of the PHFS outbreak, we evaluated the pathogenicity

Min Xu; Shujie Wang; Linxi Li; Liancheng Lei; Yonggang Liu; Wenda Shi; Jiabin Wu; Liqin Li; Fulong Rong; Mingming Xu; Guangli Sun; Hua Xiang; Xuehui Cai

2010-01-01

317

Energetics of growth and reproduction in a high-tidal population of the clam Ruditapes decussatus from Urdaibai Estuary (Basque Country, N. Spain)  

Microsoft Academic Search

Energetics of growth and reproduction were studied in a high-tidal population of the clam Ruditapes decussatus living in the Mundaka Estuary in the Biosphere Reserve of Urdaibai (Basque Country, North Spain). The study included an analysis of growth rings on the shells to establish the growth curve as well as seasonal patterns of growth and body condition, and estimates of

M. B. Urrutia; I. Ibarrola; J. I. P. Iglesias; E. Navarro

1999-01-01

318

Environmental constraints on the growth, photosynthesis and reproductive development of Dryas octopetala at a high Arctic polar semi-desert, Svalbard  

Microsoft Academic Search

Opportunities exist in high Arctic polar semidesert communities for colonisation of unvegetated ground by long-lived clonal plants such as Dryas octopetala. This can be achieved by lateral spread of vegetative ramets, or by sexual reproduction and seedling recruitment. The objectives of this study were (1) to determine whether these two means of proliferation show differential sensitivity to contrasting components of

P. A. Wookey; C. H. Robinson; A. N. Parsons; J. M. Welker; T. V. Callaghan; J. A. Lee

1995-01-01

319

High renesting rates in arctic-breeding Dunlin (Calidris alpina): a clutch-removal experiment  

USGS Publications Warehouse

The propensity to replace a clutch is a complex component of avian reproduction and poorly understood. We experimentally removed clutches from an Arctic-breeding shorebird, the Dunlin (Calidris alpina arcticola), during early and late stages of incubation to investigate replacement clutch rates, renesting interval, and mate and site fidelity between nesting attempts. In contrast to other Arctic studies, we documented renesting by radiotracking individuals to find replacement clutches. We also examined clutch size and mean egg volume to document changes in individual females’ investment in initial and replacement clutches. Finally, we examined the influence of adult body mass, clutch volume, dates of clutch initiation and nest loss, and year on the propensity to renest. We found high (82–95%) and moderate (35–50%) rates of renesting for early and late incubation treatments. Renesting intervals averaged 4.7–6.8 days and were not different for clutches removed early or late in incubation. Most pairs remained together for renesting attempts. Larger females were more likely to replace a clutch; female body mass was the most important parameter predicting propensity to renest. Clutches lost later in the season were less likely to be replaced. We present evidence that renesting is more common in Arctic-breeding shorebirds than was previously thought, and suggest that renesting is constrained by energetic and temporal factors as well as mate availability. Obtaining rates of renesting in species breeding at different latitudes will help determine when this behavior is likely to occur; such information is necessary for demographic models that include individual and population-level fecundity estimates.

Gates, H. River; Lanctot, Richard B.; Powell, Abby N.

2013-01-01

320

Genomic Sequencing Reveals Mutations Potentially Related to the Overattenuation of a Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus  

PubMed Central

Highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) continues to evolve when serially passaged in Marc-145 cells. In this study, we analyzed the genomic and antigenic variants of HP-PRRSV strain JXA1 during in vitro passage. Protective efficacies of JXA1 from passages 100, 110, 120, 140, and 170 against the high-virulence parental virus were evaluated by inoculating pigs with each of these viruses and then challenging with JXA1 from passage 5 at 28 days postimmunization. We found that the antigenicities of JXA1 from passages after 110 were significantly reduced. Inoculation with JXA1 from passages after 110 provided only insufficient protection against the parental strain challenge, indicating that the immunogenicity of JXA1 is significantly decreased when it is in vitro passaged for 110 times and more. To identify the genomic variants that emerged during the overattenuation, eight complete genomes of highly passaged JXA1 were sequenced. One guanine deletion in the 5? untranslated region (UTR), two nucleotide substitutions in the 3? UTR, and 65 amino acid mutations in nonstructural and structural proteins that accompanied with the attenuation and overattenuation were determined. Genomic sequencing of in vitro serially passaged HP-PRRSV first identified the mutations potentially correlated with the overattenuation of a HP-PRRSV strain. These results facilitate the research aimed at elucidating the mechanisms for PRRSV genomic and antigenic changes and may also contribute to developing a safe and effective PRRSV vaccine.

Yu, Xiuling; Chen, Nanhua; Deng, Xiaoyu; Cao, Zhen; Han, Wei; Hu, Dongmei; Wu, Jiajun; Zhang, Shuo; Wang, Baoyue; Gu, Xiaoxue

2013-01-01

321

Montana High School Completion and Graduation Rates for the Graduating Class of 2003  

ERIC Educational Resources Information Center

This report details the graduation rates for the class of 2003 for Montana High Schools. Sections include: Montana High School Completion and Graduation Rate Overview, and Montana High School Completion and Graduation Rates, 2002-03 School Year.

McCulloch, Linda

2004-01-01

322

High Dose Rate Brachytherapy as Prostate Cancer Monotherapy Reduces Toxicity Compared to Low Dose Rate Palladium Seeds  

Microsoft Academic Search

PurposeWe evaluated the potential for differing acute and chronic toxicities between 2 monotherapy methods of image guided conformal brachytherapy, high dose rate (HDR) brachytherapy alone and low dose rate (LDR) permanent palladium seeds.

INGA S. GRILLS; ALVARO A. MARTINEZ; MITCHELL HOLLANDER; RAYWIN HUANG; KENNETH GOLDMAN; PETER Y. CHEN; GARY S. GUSTAFSON

2004-01-01

323

High strain-rate tensile testing and viscoplastic parameter identification using microscopic high-speed photography  

Microsoft Academic Search

A combined experimental\\/numerical method for determination of constitutive parameters in high strain-rate material models is presented. Impact loading, using moderate projectile velocities in combination with small specimens (sub mm) facilitate tensional strain rates in the order of 104–105 s?1. Loading force is measured from one-dimensional wave propagation in a rod using strain gauges and deformation is monitored with a high-speed

J. Kajberg; K. G. Sundin; L. G. Melin; P. Ståhle

2004-01-01

324

Creep behavior of Fe–C alloys at high temperatures and high strain rates  

Microsoft Academic Search

The creep behavior of Fe–C alloys (1–1.8%C) has been studied at high temperatures (0.7–0.9Tm) and high strain rates (1–100 s?1). The dominant deformation resistance has been found to be climb-controlled dislocation creep and thus the creep rates are a function of elastic modulus, lattice diffusivity and stacking fault energy. The self-diffusion coefficient of iron in austenite was found to be

D. R Lesuer; C. K Syn; J. D Whittenberger; M Carsi; O. A Ruano; O. D Sherby

2001-01-01

325

Cryogenic, high-resolution x-ray detector with high count rate capability  

Microsoft Academic Search

A cryogenic, high-resolution X-ray detector with high count rate capability has been invented. The new X-ray detector is based on superconducting tunnel junctions (STJs), and operates without thermal stabilization at or below 500 mK. The X-ray detector exhibits good resolution (.about.5-20 eV FWHM) for soft X-rays in the keV region, and is capable of counting at count rates of more

Matthias Frank; Carl A. Mears; Simon E. Labov; Larry J. Hiller; Andrew T. Barfknecht

2003-01-01

326

High-k (k=30) amorphous hafnium oxide films from high rate room temperature deposition  

NASA Astrophysics Data System (ADS)

Amorphous hafnium oxide (HfOx) is deposited by sputtering while achieving a very high k~30. Structural characterization suggests that the high k is a consequence of a previously unreported cubiclike short range order in the amorphous HfOx (cubic k~30). The films also possess a high electrical resistivity of 1014 ? cm, a breakdown strength of 3 MV cm-1, and an optical gap of 6.0 eV. Deposition at room temperature and a high deposition rate (~25 nm min-1) makes these high-k amorphous HfOx films highly advantageous for plastic electronics and high throughput manufacturing.

Li, Flora M.; Bayer, Bernhard C.; Hofmann, Stephan; Dutson, James D.; Wakeham, Steve J.; Thwaites, Mike J.; Milne, William I.; Flewitt, Andrew J.

2011-06-01

327

Reproductive Timing in Marine Fishes: Variability, Temporal Scales, and Methods  

Microsoft Academic Search

Reproductive timing can be defined as the temporal pattern of reproduction over a lifetime. Although reproductive timing is highly variable in marine fishes, certain traits are universal, including sexual maturity, undergoing one or more reproductive cycles, participating in one or more spawning events within a reproductive cycle, release of eggs or offspring, aging, and death. These traits commonly occur at

Susan K. Lowerre-Barbieri; Konstantinos Ganias; Fran Saborido-Rey; Hilario Murua; John R. Hunter

2011-01-01

328

Reproductive ecology of Caribbean reef corals  

NASA Astrophysics Data System (ADS)

The last decade has seen a resurgence of interest in the processes of sexual reproduction by scleractinian reef corals. Earlier investigations had focused fortuitously on brooding (planulating) species, which resulted in the general misconception that brooding was the main form of larval development of reef corals. More recent work on Indo-Pacific species has shown broadcast spawning and short annual reproductive periods to predominate. This report presents the reproductive patterns of eleven Caribbean coral species and attempts to explain the adaptive features and selective pressures that have led to the evolution of the four reproductive patterns described to date: (a) hermaphroditic broadcasters; (b) gonochoric broadcasters; (c) hermaphroditic broadcasters; (b) gonochoric brooders. Both (a) and (b) correlate with large colony size and short annual spawning periods; and (c) and (d) correlate with small colony size, multiple planulating cycles per year, and occupation of unstable habitats. Selection for outcrossing between long-lived individuals is proposed as the reason for gonochorism and for synchronous spawning of hermaphroditic broadcasters, and also for the large amount of sperm produced by hermaphroditic brooders. Selection for high rates of local recruitment is proposed as the force behind the evolution of brooding by species inhabiting unstable habitats and suffering high rates of adult mortality.

Szmant, Alina M.

1986-08-01

329

Potential and Pitfalls of High-Rate GPS  

NASA Astrophysics Data System (ADS)

With completion of the Plate Boundary Observatory (PBO), we are poised to capture a dense sampling of strong motion displacement time series from significant earthquakes in western North America with High-Rate GPS (HRGPS) data collected at 1 and 5 Hz. These data will provide displacement time series at potentially zero epicentral distance that, if valid, have great potential to contribute to understanding earthquake rupture processes. The caveat relates to whether or not the data are aliased: is the sampling rate fast enough to accurately capture the displacement's temporal history? Using strong motion recordings in the immediate epicentral area of several 6.77.5 events, which can be reasonably expected in the PBO footprint, even the 5 Hz data may be aliased. Some sort of anti-alias processing, currently not applied, will therefore necessary at the closest stations to guarantee the veracity of the displacement time series. We discuss several solutions based on a-priori knowledge of the expected ground motion and practicality of implementation.

Smalley, R.

2008-12-01

330

Coal plasticity at high heating rates and temperatures  

SciTech Connect

Effects of pressure, temperature, and coal type on coal plasticity were investigated. Seven coals, from the Argonne premium sample bank ranging from lignite to low volatile bituminous, were studied. Elevated pressures, up to 10 atm of helium, did not affect coal plasticity, but reducing pressure from atmosphere to vacuum resulted in diminished plasticity, i.e. a shorter plastic period and a higher minimum apparent viscosity. It is hypothesized that high pressure inhibits mass transport of metaplast to tar vapors, but also favors metaplast repolymerization into coke and char. Higher holding temperature decreased the coal plastic period. It is hypothesized that higher temperature increases mass transport of liquid metaplast to tar vapors and metaplast repolymerization to coke and char. Heating rate had essentially no effect on the individual softening temperatures of five different plastic coals. Possible explanations are that, depending on coal type, metaplast generation, by chemical bond breaking or physical melting, or both, is not strongly affected by heating rate. In particular, for medium and low volatile bituminous cools, there is evidence that generation of the metaplast responsible for initial softening involves largely chemical bond breaking as opposed to physical melting.

Gerjarusak, S.; Peters, W.A.; Howard, J.B.

1992-09-01

331

Investigating the confining compressibility of STF at high deformation rate  

NASA Astrophysics Data System (ADS)

The split Hopkinson pressure bar (SHPB) was used to study the compressibility of shear thickening fluid (STF) at high deformation rate. In this study, a steel bulk was introduced into the SHPB system to confine and load the STF. A series of STFs with different particle types (SiO2 and PSt-EA) and volume fractions (63 vol.% and 65 vol.%) were tested and the results were compared. The reliability of the results was proved by repeating the tests and the force balance in suspension. The bulk modulus was used to evaluate the compressibility of STF, which indicated that the SiO2-based STF exhibited a larger compressibility than the PSt-EA-based STF. It was found that the bulk modulus increases with increasing of the strain rate and the volume fraction shows little effect on the bulk modulus. The structure-dependent mechanical property was analyzed and the loading effect of bulk modulus was considered to be originated from the interparticle clustering.

Jiang, Weifeng; Gong, Xinglong; Xu, Yulei; Xuan, Shouhu; Jiang, Wanquan; Zhu, Wei; Li, Xiaofeng; Qin, Lijun

2012-12-01

332

Dynamic behaviour of birch and sequoia at high strain rates  

NASA Astrophysics Data System (ADS)

The paper presents results of experimental analysis for structural woods, i.e. birch and sequoia at high strain rates. Monotonic and cyclic compression testing at room temperature of these materials was performed by experimental Kolsky method, using the 20-mm diameter split Hopkinson pressure bar (SHPB). The cut out specimens were loaded along and across fibers of woods, as well as, in others angles of cutting out from wooden materials. There were obtained dynamic deformation diagrams in various above conditions for these materials. Directions of specimens' cutting out, as well as, confined conditions effect on mechanical dynamic properties of the woods tested. Loading and unloading branches of stress-strain diagrams obtained are nonlinear and strain rates sensitive. Post-failure behavior of woods' specimens tested results from various forms of their fracture, such cracking and spalling. Experimental stress-strain curves showed significant influence of cutting out angles of specimens on fracture stresses' values. Dynamic deformation diagrams at cyclic loading, obtained by original modification of SPHB, are also presented for tested materials. Alongside with the SHPB tests, plane-wave experiments were conducted and the shock adiabates for the wood samples were obtained.

Anatoly, Bragov; Andrey, Lomunov; Ivan, Sergeichev; Gray, George, III

2005-07-01

333

High spontaneous intrachromosomal recombination rates in ataxia-telangiectasia  

SciTech Connect

Ataxia-telangiectasia (A-T) is an inherited human disease associated with neurologic degeneration, immune dysfunctions, and high cancer risk. It has been proposed that the underlying abnormality in A-T is a defect in genetic recombination that interferes with immune gene rearrangements and the repair of DNA damage. Recombination was studied in A-T and control human fibroblast lines by means of two recombination vectors. Unexpectedly, spontaneous intrachromosomal recombination rates were 30 to 200 times higher in A-T fibroblast lines than in normal cells, whereas extrachromosomal recombination frequencies were near normal. Increased recombination is thus a component of genetic instability in A-T and may contribute to the cancer risk seen in A-T patients. 2 refs., 1 fig., 3 tabs.

Meyn, M.S. (Yale Univ., New Haven, CT (United States))

1993-05-28

334

Effect of high dose rate irradiations on COTS optical fibres  

NASA Astrophysics Data System (ADS)

Commercial off-the-shelf (COTS) single-mode and multimode germanosilicate optical fibres are intended for use as part of control-command applications in the future Laser Megajoule facility. We evaluated their vulnerability to the radiative environment associated to this project by characterizing their transient radiation responses at infrared wavelengths (1064, 1310 and 1550 nm) after high dose rate exposure (> 108 Gy/s). Our results showed that these COTS fibres exhibit very different transient responses (10-9 s to 1 s after pulse) and permanent damages (times > 1s), depending on the wavelength of transmitted signal and on their compositions. Presented results could be used to define several choices to ensure the functionality of these applications for both shortest times after a shot (10-9 to 103 s) and during the whole LMJ lifetime (30 years).

Girard, Sylvain; Baggio, Jacques; Martinez, Martial

2005-05-01

335

High strain rate response of a tungsten heavy alloy  

NASA Astrophysics Data System (ADS)

The effect of thickness change of a tungsten heavy alloy (WHA) on its dynamic behaviors has been studied. Exploding bridgwire (EBW) detonator has been used to drive the alloy plate. The particle velocity at the rear free surface of a specimen was measured by means of VISAR. Simple experimental technique has been introduced herein to obtain the Hugoniot elastic limit and spall strength of materials in the form of small disc plate (diameter of ~7 mm) with varying thickness. The peak pressure decay is analyzed as a function of time for traveling of the wave through each specimen. The fracture behavior of WHA caused by the high strain rate herein is similar to that due to the Charpy impact test.

Chang, S. N.; Choi, J. H.

1998-07-01

336

Shock-Less High Rate Compaction of Porous Brittle Materials  

NASA Astrophysics Data System (ADS)

The dynamic behavior of granular materials such as granular silica (sand), technical ceramics, and porous geological substances has importance to a variety of engineering applications. Although the mechanical behaviors of sand and other granular ceramics have been studied extensively for several decades, the dynamic behavior of such materials remains poorly understood. This paper describes how instrumented electromagnetic tube compression driven by capacitive discharge can be used to measure compaction of porous materials at high and controlled strain rates. The technique relies on electromagnetically crushing a powder-filled conductive tube. By measuring the current as a function of time and the tube displacement through Photon Doppler Velocimetry (PDV) sufficient data can be obtained to reveal the behavior of the porous material. The method will be described in detail and example data will be shown for compaction of silica sand.

Fenton, Gregg; Caipen, Terry; Daehn, Glenn; Vogler, Tracy; Grady, Dennis

2009-12-01

337

THE DISCOUNTED REPRODUCTIVE NUMBER FOR EPIDEMIOLOGY  

PubMed Central

The basic reproductive number, , and the effective reproductive number, , are commonly used in mathematical epidemiology as summary statistics for the size and controllability of epidemics. However, these commonly used reproductive numbers can be misleading when applied to predict pathogen evolution because they do not incorporate the impact of the timing of events in the life-history cycle of the pathogen. To study evolution problems where the host population size is changing, measures like the ultimate proliferation rate must be used. A third measure of reproductive success, which combines properties of both the basic reproductive number and the ultimate proliferation rate, is the discounted reproductive number . The discounted reproductive number is a measure of reproductive success that is an individual’s expected lifetime offspring production discounted by the background population growth rate. Here, we draw attention to the discounted reproductive number by providing an explicit definition and a systematic application framework. We describe how the discounted reproductive number overcomes the limitations of both the standard reproductive numbers and proliferation rates, and show that is closely connected to Fisher’s reproductive values for different life-history stages

Reluga, Timothy C.; Medlock, Jan; Galvani, Alison

2013-01-01

338

Why Are U.S. Incarceration Rates So High?  

Microsoft Academic Search

Most explanations of the unprecedented increase in American incarceration rates are inadequate. Crime rate increases, more punitive public attitudes, postmodernist angst, and cynical politics are all only part of the explanation. Those things characterize all Western countries; in some of these countries, imprisonment rates have long been stable or declining, and, where they are rising, absolute levels and rates of

Michael Tonry

1999-01-01

339

A high data rate BPSK receiver implementation in FPGA for high dynamics applications  

Microsoft Academic Search

In this paper we present the implementation of a FPGA based high data rate BPSK receiver specifically designed to withstand the high dynamics of airborne vehicles (i.e. air- craft, sounding rockets, satellites, etc.). The carrier reco- very is implemented through a Costas loop, and a Gardner detector is used for the timing recovery. This architecture was chosen because it provides

Juan Augusto Maya; Nicolas A. Casco; Pedro A. Roncagliolo; Javier G. Garcia

2011-01-01

340

Design and characteristics of high pulse repetition rate and high average power excimer laser systems  

SciTech Connect

This paper describes the design and the performance characteristics of an X-ray preionized discharge pumped XeCl laser system operated at very high repetition rate frequency and high average power (200 W). The laser system is mainly composed of a fast flow subsonic closed cycle wind tunnel, a laser head, a high average power electrical excitation system, and an X-ray preionization source. The laser head design and the dumping of acoustic waves induced by fast electrical energy deposition of 50 J/L bar allow this device to be operated at repetition rate frequencies of up to {approx}1700 Hz.

Sentis, M.L.; Delaporte, P.; Forestier, B.M.; Fontaine, B.L. (Inst. de Mecanique des Fluides de Marseille, UM 34 CRNS, Univ. d'Aix-Marseille, 13003 Marseille (FR))

1991-10-01

341

The status of low dose rate and future of high dose rate Cf-252 brachytherapy  

SciTech Connect

This work describes the current status of the US low dose rate (LDR) Cf-252 brachytherapy program. The efforts undertaken towards development of a high dose rate (HDR) remotely after loaded Cf-252 source, which can accommodate 1 mg or greater Cf-252, are also described. This HDR effort is a collaboration between Oak Ridge National Laboratory (ORNL), commercial remote after loader manufactures, the Gershenson Radiation Oncology Center (ROC), and Wayne State University. To achieve this goal, several advances in isotope chemistry and source preparation at ORNL must be achieved to yield a specific material source loading of greater than or equal 1 mg Cf-252 per mm3. Development work with both radioactive and non-radioactive stand-ins for Cf-252 have indicated the feasibility of fabricating such sources. As a result, the decreased catheter diameter and computer controlled source placement will permit additional sites (e.g. brain, breast, prostate, lung, parotid, etc.) to be treated effectively with Cf-252 sources. Additional work at the Radiochemical Engineering and Development Center (REDC) remains in source fabrication, after loader modification, and safe design. The current LDR Cf-252 Treatment Suite at the ROC is shielded and licensed to hold up to 1 mg of Cf-252. This was designed to maintain cumulative personnel exposure, both external to the room and in direct isotope handling, at less than 20 microSv/hr. However, cumulative exposure may be greatly decreased if a Cf-252 HDR unit is employed which would eliminate direct isotope handling and decrease treatment times from tilde 3 hours to an expected range of 3 to 15 minutes. Such a Cf-252 HDR source will also demonstrate improved dose distributions over current LDR treatments due to the ability to step the point-like source throughout the target volume and weight the dwell time accordingly.

Rivard, M.J.; Wierzbicki, J.G.; Van den Heuvel, F.; Chuba, P.J.; Fontanesi, J. [Wayne State Univ., Detroit, MI (United States). Dept. of Radiation Oncology; Martin, R.C.; McMahon, R.R.; Haire, R.G. [Oak Ridge National Lab., TN (United States)

1997-12-01

342

Diurnal pollen tube growth rate is slowed by high temperature in field-grown Gossypium hirsutum pistils.  

PubMed

For Gossypium hirsutum pollination, germination, and pollen tube growth must occur in a highly concerted fashion on the day of flowering for fertilization to occur. Because reproductive success could be influenced by the photosynthetic activity of major source leaves, we hypothesized that increased temperatures under field conditions would limit fertilization by inhibiting diurnal pollen tube growth through the style and decreasing subtending leaf photosynthesis. To address this hypothesis, G. hirsutum seeds were sown on different dates to obtain flowers exposed to contrasting ambient temperatures while at the same developmental stage (node 8 above the cotyledons). Collection and measurement were conducted at 06:00, 09:00, 12:00, 15:00, and 18:00h on August 4 (34.6°C maximum air temperature) and 14, 2009 (29.9°C maximum air temperature). Microclimate measurements included photosynthetically active radiation, relative humidity, and air temperature. Pistil measurements included pistil surface temperature, pollen germination, pollen tube growth through the style, fertilization efficiency, fertilized ovule number, and total number of ovules per ovary. Subtending leaf measurements included leaf temperature, photosynthesis, and stomatal conductance. Under high temperatures the first measurable pollen tube growth through the style was observed earlier in the day (12:00h) than under cooler conditions (15:00h). Also, high temperature resulted in slower pollen tube growth through the style (2.05mmh(-1)) relative to cooler conditions (3.35mmh(-1)), but there were no differences in fertilization efficiency, number of fertilized ovules, or ovule number. There was no effect of sampling date on diurnal photosynthetic patterns, where the maximum photosynthetic rate was observed at 12:00h on both dates. It is concluded that, of the measured physiological and reproductive processes, pollen tube growth rate showed the greatest sensitivity to high temperature under field conditions. PMID:20832140

Snider, John L; Oosterhuis, Derrick M; Kawakami, Eduardo M

2010-09-15

343

Predictive Model of Rat Reproductive Toxicity from ToxCast High Throughput Screening  

EPA Science Inventory

The EPA ToxCast research program uses high throughput screening for bioactivity profiling and predicting the toxicity of large numbers of chemicals. ToxCast Phase-I tested 309 well-characterized chemicals in over 500 assays for a wide range of molecular targets and cellular respo...

344

The strain-rate sensitivity of high-strength high-toughness steels.  

SciTech Connect

The present study examines the strain-rate sensitivity of four high strength, high-toughness alloys at strain rates ranging from 0.0002 s-1 to 200 s-1: Aermet 100, a modified 4340, modified HP9-4-20, and a recently developed Eglin AFB steel alloy, ES-1c. A refined dynamic servohydraulic method was used to perform tensile tests over this entire range. Each of these alloys exhibit only modest strain-rate sensitivity. Specifically, the strain-rate sensitivity exponent m, is found to be in the range of 0.004-0.007 depending on the alloy. This corresponds to a {approx}10% increase in the yield strength over the 7-orders of magnitude change in strain-rate. Interestingly, while three of the alloys showed a concominant {approx}3-10% drop in their ductility with increasing strain-rate, the ES1-c alloy actually exhibited a 25% increase in ductility with increasing strain-rate. Fractography suggests the possibility that at higher strain-rates ES-1c evolves towards a more ductile dimple fracture mode associated with microvoid coalescence.

Dilmore, M.F. (AFRL/MNMW, Eglin AFB, FL); Crenshaw, Thomas B.; Boyce, Brad Lee

2006-01-01

345

Highly nonlinear defect-induced carrier recombination rates in semiconductors  

NASA Astrophysics Data System (ADS)

Defects in semiconductors can induce recombination of carriers and thus can strongly influence the efficiency and performance of solid-state devices. In the analysis of device performance, defect-induced recombination is often assumed to depend linearly on the carrier concentration or to be given by a sum of Shockley-Read-Hall expressions taken independently for each known defect level. Under these assumptions, defect-induced recombination increases with carrier concentration more slowly than both band-to-band radiative recombination and Auger recombination and becomes relatively less important at higher carrier concentrations. However, we show that defects with multiple defect levels can induce recombination with a highly nonlinear dependence on carrier concentration. For such defects, the usual assumptions about the relative importance of different recombination mechanisms at different carrier concentrations may fail. In order to demonstrate the potential impact of this phenomenon on realistic devices, we incorporate the defect-induced recombination rates obtained from our analysis into a microscopic InGaN/GaN light-emitting diode (LED) model. Our results indicate that a particular class of defects with plausible properties can induce a loss of optical efficiency at carrier concentrations relevant for high-power LED operation.

Modine, N. A.; Armstrong, A. M.; Crawford, M. H.; Chow, W. W.

2013-10-01

346

An integrated CMOS high data rate transceiver for video applications  

NASA Astrophysics Data System (ADS)

This paper presents a 5 GHz CMOS radio frequency (RF) transceiver built with 0.18 ?m RF-CMOS technology by using a proprietary protocol, which combines the new IEEE 802.11n features such as multiple-in multiple-out (MIMO) technology with other wireless technologies to provide high data rate robust real-time high definition television (HDTV) distribution within a home environment. The RF frequencies cover from 4.9 to 5.9 GHz: the industrial, scientific and medical (ISM) band. Each RF channel bandwidth is 20 MHz. The transceiver utilizes a direct up transmitter and low-IF receiver architecture. A dual-quadrature direct up conversion mixer is used that achieves better than 35 dB image rejection without any on chip calibration. The measurement shows a 6 dB typical receiver noise figure and a better than 33 dB transmitter error vector magnitude (EVM) at -3 dBm output power.

Yaping, Liang; Dazhi, Che; Cheng, Liang; Lingling, Sun

2012-07-01

347

A multipurpose high-rate GPS observatory for northwestern Mexico  

NASA Astrophysics Data System (ADS)

We describe a proposed joint atmospheric and geophysical high-rate GPS observatory in northwestern Mexico complementing and extending analogous networks in the United Stated. The observatory would measure atmospheric water vapor during the North American Monsoon Experiment (NAME) as well as crustal velocities within and across the Gulf of California and the Mexican Basin and Range region for geodetic applications. The NOAA-sponsored NAME scheduled for several summers beginning in 2004 addresses the challenging issue of determining and improving the predictability of warm season precipitation in the mountainous region of the Northwestern Mexico and Southwestern US. Much of the rainfall in the region comes during the North American Monsoon each summer. Rainfall in the region is particularly difficult to model and predict because the orography and the complex land-sea geometry of the region with moisture sources in the Gulf of Mexico, Gulf of California and the eastern subtropical Pacific Ocean. The GPS provides accurate, near-continuous observations of water vapor in clear and cloudy air needed to sample the large diurnal variations in the dynamic and thermodynamic properties of the atmosphere. GPS in combination with wind and other measurements scattered in and around the region will provide much needed constraints to determine quantitatively the sources supplying moisture for precipitation within the NAME area. Tectonic applications of this continuous GPS network in Mexico include high-precision determinations of plate boundary deformation in and around the Gulf of California and possible diffuse deformation within the Mexican Basin and Range province. Because of the high sampling rate (1 Hz), the network will also provide data for seismological applications, including surface wave studies (e.g., Larson et al., SCIENCE, 2003) and potential near-field displacement records. Furthermore the network would complement the US-based Plate Boundary Observatory (PBO) facility by extending continuous GPS coverage into northern Mexico and other relatively smaller-scale continuous GPS networks in southern Mexico as well as provide important data for surveying and mapping applications. Several years of observations are required to capture the substantial year-to-year variations in the monsoon and yield accurate estimates of tectonic motion. Both objectives can be accomplished relatively inexpensively with the simple and robust GPS observations made in collaboration with investigators in Mexico.

Kursinski, E. R.; Bennett, R. A.; Hahmann, A.

2003-12-01

348

Juvenile hormone and reproduction in the cricket. II. Effect of rearing temperature on corpus allatum activity (in vitro) in adult females  

Microsoft Academic Search

Summary In the Mediterranean field cricket,Gryllus bimaculatus, reproduction is controlled by temperature and the corpus allatum (CA) hormone JH III. In CA of females reared at 24°?12°C(16?8 h) (high reproduction rate) a first peak in JH III synthesis is reached about 4 days earlier than in those of 20°C females (low reproduction rate). Furthermore, in 20°C animals CA activity is

W. Espig; K. H. Hoffmann

1985-01-01

349

High Data Rate Link from DIVA Using a Conformal Antenna  

NASA Astrophysics Data System (ADS)

Like some other small spinning scientific satellites, DIVA has a fixed position of the spinning axis with respect to sun. Due to this alignment, the earth can appear in any angular position relative to the satellite, which causes the need for an antenna with full spherical coverage to maintain a permanent link to the control facilities on earth. Up to now this coverage usually was achieved by the use of ordinary TT&C-antennas, as they are utilized on communication satellites for telemetry, tracing and command. In this control application there is no need for high-data-rate communication, so this antenna neither offers high bandwidth nor high gain. Especially the low gain of this antenna type results in a bad signal-to-noise ratio (SNR) at the receiving antenna on the earth. As a consequence the low SNR limits the data rate to small values. In scientific missions with a high amount of data needed to be transferred to the earth, the use of these antennas results in a bottle neck in the data link and lowers the efficiency of the scientific mission itself. An increase in SNR at the receiving antenna needs an increase in signal strength because the noise figure of commercially used receiving antennas on the earth is already extremely low and cannot be lowered further without major technical effort. Hence the gain of the transmitting antenna on the satellite has to be increased. In this contribution a broadband conformal antenna concept is presented which yields an average gain of 7.6 dBi over the full sphere for the antenna on the satellite. The antenna consists of 26 elements which are located at different positions on the surface of the satellite. By using the knowledge of the earth's angular position from the satellite's navigation system, the element pointing best towards the earth is used for the link. Technically this problem is solved by using a low-loss switching matrix. Slot spirals are used as single elements. The element consists of an etched slot spiral on an RT/duroid 6002 substrate. A honeycomb structure and a carrier complete the simple mechanical setup of the single element. Using this new antenna there appears to be no limitation in the bandwidth of the data link due to the transmitting antenna, because the bandwidth of the used slot spiral can easily be one octave. Besides the large bandwidth, the pure circular polarisation is a major advantage of the spiral antenna. A usable data rate of 1.2 Mbit/s having a BER of 10^{-5} can be achieved using this switched conformal array antenna and an RF-bandwidth of 2 MHz in S-band.

Loeffler, D.; Wiesbeck, W.; Wiesler, A.; Bastian, U.; Roeser, S.; Mandel, H.; Seifert, W.; Wagner, S.

350

A chicken RAD51 homologue is expressed at high levels in lymphoid and reproductive organs.  

PubMed Central

Comparisons of the amino acid sequences of three yeast RecA-like proteins, Rad51 and DMC1 from S.cerevisiae and Rad51 from S.pombe, revealed several highly conserved regions. Degenerated oligonucleotides encoding two of these regions were used for the polymerase chain reaction to clone a chicken RecA-like gene. The encoded protein shares 68% and 49% identical amino acids with the Rad51 and DMC1 proteins. The strong sequence conservation between the yeast and chicken genes indicates that RecA homologues are conserved throughout evolution from prokaryotes to higher eukaryotes. High expression of the chicken Rad51 gene was found within the organs of lymphoid and germ cell development suggesting its involvement in lymphoid and meiotic recombination. Images

Bezzubova, O; Shinohara, A; Mueller, R G; Ogawa, H; Buerstedde, J M

1993-01-01

351

Reproduction of social class in the teaching and learning of science in urban high schools  

Microsoft Academic Search

The study examines the teaching and learning of science in an urban high school characterised by African American students\\u000a from conditions of relative poverty. An interpretive study was undertaken involving a research team that included the teacher\\u000a in the study and a student from the school. Despite the teacher's effort to enact a curriculum that was transformative the\\u000a students resisted

Kenneth Tobin; Gale Seiler; Edward Walls

1999-01-01

352

A high-throughput method for assessing chemical toxicity using a Caenorhabditis elegans reproduction assay  

Microsoft Academic Search

The National Research Council has outlined the need for non-mammalian toxicological models to test the potential health effects of a large number of chemicals while also reducing the use of traditional animal models. The nematode Caenorhabditis elegans is an attractive alternative model because of its well-characterized and evolutionarily conserved biology, low cost, and ability to be used in high-throughput screening.

Windy A. Boyd; Sandra J. McBride; Julie R. Rice; Daniel W. Snyder; Jonathan H. Freedman

2010-01-01

353

Concurrent highly pathogenic porcine reproductive and respiratory syndrome virus infection accelerates Haemophilus parasuis infection in conventional pigs.  

PubMed

This study was aimed at determining the effect of highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) on Haemophilus parasuis (HPS) in co-infection. A quantitative real-time PCR targeting infB gene, which is conserved among different HPS serotypes, was developed to improve the accuracy and speed of the detection of HPS. A total of 32 four-week-old conventional pigs were distributed randomly into four groups: pigs in group I were intranasally infected with HP-PRRSV first, and were then intraperitoneally inoculated with HPS on 5 days after HP-PRRSV infection; pigs in group II were intranasally inoculated with HP-PRRSV alone; pigs in group III were intraperitoneally inoculated with HPS alone; pigs in group IV were intraperitoneally inoculated with physiological saline. The amount of HPS in serum on 0, 3, 6, 9 and 12 days post-inoculation (dpi) with HPS were detected using the established quantitative real-time PCR. Clinical signs, pathological changes and histopathological lesions were observed. The amount of HPS in serum reached 10(6)copies/?l at 3 dpi with HPS in pigs of group I, while it arrived 10(5.7)copies/?l at 9 dpi with HPS in pigs of group III. The HPS loads in hearts and lungs were much higher than in other tissues. The study showed that HP-PRRSV was able to accelerate HPS infection and loads. PMID:22460022

Yu, Jiang; Wu, Jiaqiang; Zhang, Yuyu; Guo, Lihui; Cong, Xiaoyan; Du, Yijun; Li, Jun; Sun, Wenbo; Shi, Jianli; Peng, Jun; Yin, Feifei; Wang, Dapeng; Zhao, Pengwei; Wang, Jinbao

2012-03-08

354

High Strain Rate Response of Sandwich Composites with Nanophased Cores  

NASA Astrophysics Data System (ADS)

Polyurethane foam materials have been used as core materials in a sandwich construction with S2-Glass/SC-15 facings. The foam material has been manufactured from liquid polymer precursors of polyurethane. The precursors are made of two components; part-A (diphenylmethane diisocyanate) and part-B (polyol). In one set of experiments, part-A was mixed with part-B to manufacture the foam. In another set, TiO2 nanoparticles have been dispersed in part-A through ultrasonic cavitation technique. The loading of nanoparticles was 3% by weight of the total polymer precursor. The TiO2 nanoparticles were spherical in shape, and were about 29 nm in diameter. Sonic cavitation was carried out with a vibrasound liquid processor at 20 kHz frequency with a power intensity of about 100 kW/m2. The two categories of foams manufactured in this manner were termed as neat and nanophased. Sandwich composites were then fabricated using these two categories of core materials using a co-injection resin transfer molding (CIRTM) technique. Test samples extracted from the panel were subjected to quasi-static as well as high strain rate loadings. Rate of loading varied from 0.002 s-1 to around 1300 s-1. It has been observed that infusion of nanoparticles had a direct correlation with the cell geometry. The cell dimensions increased by about 46% with particle infusion suggesting that nanoparticles might have worked as catalysts during the foaming process. Correspondingly, enhancement in thermal properties was also noticed especially in the TGA experiments. There was also a significant improvement in mechanical properties due to nanoparticle infusion. Average increase in sandwich strength and energy absorption with nanophased cores was between 40 60% over their neat counterparts. Details of manufacturing and analyses of thermal and mechanical tests are presented in this paper.

Mahfuz, Hassan; Uddin, Mohammed F.; Rangari, Vijaya K.; Saha, Mrinal C.; Zainuddin, Shaik; Jeelani, Shaik

2005-05-01

355

Solidification at the High and Low Rate Extreme.  

National Technical Information Service (NTIS)

The microstructures formed upon solidification are strongly influenced by the imposed growth rates on an alloy system. Depending on the characteristics of the solidification process, a wide range of growth rates is accessible. The prevailing solidificatio...

H. Meco

2004-01-01

356

An infrared high rate video imager for various space applications  

NASA Astrophysics Data System (ADS)

Modern spacecraft with high data transmission capabilities have opened up the possibility to fly video rate imagers in space. Several fields concerned with observations of transient phenomena can benefit significantly from imaging at video frame rate. Some applications are observations and characterization of bolides/meteors, sprites, lightning, volcanic eruptions, and impacts on airless bodies. Applications can be found both on low and high Earth orbiting spacecraft as well as on planetary and lunar orbiters. The optimum wavelength range varies depending on the application but we will focus here on the near infrared, partly since it allows exploration of a new field and partly because it, in many cases, allows operation both during day and night. Such an instrument has to our knowledge never flown in space so far. The only sensors of a similar kind fly on US defense satellites for monitoring launches of ballistic missiles. The data from these sensors, however, is largely inaccessible to scientists. We have developed a bread-board version of such an instrument, the SPOSH-IR. The instrument is based on an earlier technology development - SPOSH - a Smart Panoramic Optical Sensor Head, for operation in the visible range, but with the sensor replace by a cooled IR detector and new optics. The instrument is using a Sofradir 320x256 pixel HgCdTe detector array with 30µm pixel size, mounted directly on top of a four stage thermoelectric Peltier cooler. The detector-cooler combination is integrated into an evacuated closed package with a glass window on its front side. The detector has a sensitive range between 0.8 and 2.5 µm. The optical part is a seven lens design with a focal length of 6 mm and a FOV 90deg by 72 deg optimized for use at SWIR. The detector operates at 200K while the optics operates at ambient temperature. The optics and electronics for the bread-board has been designed and built by Jena-Optronik, Jena, Germany. This talk will present the design and the strong and the weak points as found through testing will be identified. Possible alternatives for improvements will be discussed and two flight applications will be outlined.

Svedhem, Hâkan; Koschny, Detlef

2010-05-01

357

Burning Rate Studies of HMX Propellants at High Pressures.  

National Technical Information Service (NTIS)

Burning rate studies of some nitramine propellants were conducted at pressures from 2,000 to 50,000 psi. Changes in HMX particle size distribution produced large effects on the burning rates and burning rate exponent at pressures below 7,000 psi, but had ...

B. K. Moy

1975-01-01

358

Comparison of high dose rate, low dose rate, and high dose rate fractionated radiation for optimizing differences in radiosensitivities in vitro.  

PubMed

Radiotherapy is administered with the assumption that all patients respond similarly to radiation although radiosensitivity does vary from patient to patient, resulting in different degrees of early and late effects. Because the dose given to a patient is limited by the response of normal tissue in the treatment field, it would be beneficial to determine the sensitivity of this normal tissue prior to therapy. Previous studies to predict radiosensitivity have used surviving fractions after a single dose given in vitro, however, differences in cell survival at this low level of kill are not easy to resolve. In this study, we set out to evaluate the use of alternative dose regimens which may better resolve differences in radiosensitivity. We have examined several radiation protocols for predictive value, including survival after high doses (6 Gy) at both high (112 cGy/min) and low (.882 cGy/min) dose rates and after fractionated doses of 2 Gy (6 fractions). A sensitive human fibroblast line (S11358) cultured from a patient showing severe effects after therapy is compared with a cell line (OMB1) cultured from an apparently normal subject. Differences between these cell lines have been compared with those between two human melanoma cell lines (SKMEL3 and HT144) which have shown resistant and sensitive response to radiation in vitro respectively. In both fibroblast and melanoma cell lines, the difference in the survival of normal and sensitive cells increased with increasing dose regardless of whether irradiation was delivered as low dose rate, high dose rate, or as fractionated doses. We propose that radiation doses which more closely mimic clinical treatment are more suitable than surviving fraction after 2 Gy (SF2) for in vitro evaluation of relative radiosensitivities of cell populations. PMID:9822167

Wilkins, R C; Ng, C E; Raaphorst, G P

1998-01-01

359

High exposure rates of anticoagulant rodenticides in predatory bird species in intensively managed landscapes in Denmark.  

PubMed

The extensive use of anticoagulant rodenticides (ARs) for rodent control has led to widespread secondary exposure in nontarget predatory wildlife species. We investigated exposure rates and concentrations of five ARs in liver samples from five raptors and six owls from Denmark. A total of 430 birds were analysed. ARs were detected in 84-100 % of individual birds within each species. Multiple AR exposure was detected in 73 % of all birds. Average number of substances detected in individual birds was 2.2 with no differences between owls and raptors. Difenacoum, bromadiolone, and brodifacoum were the most prevalent substances and occurred in the highest concentrations. Second-generation ARs made up 96 % of the summed AR burden. Among the six core species (sample size >30), summed AR concentrations were lower in rough-legged buzzard (Buteo lagopus) and long-eared owl (Asio otus) than in barn owl (Tyto alba), buzzard (B. buteo), kestrel (Falco tinnunculus), and tawny owl (Strix aluco). There was a strong tendency for seasonal variations in the summed AR concentration with levels being lowest during autumn, which is probably related to an influx of less-exposed migrating birds from northern Scandinavia during autumn. High hepatic AR residue concentrations (>100 ng/g wet weight), which have been associated with symptoms of rodenticide poisoning and increased mortality, were recorded high frequencies (12.9-37.4 %) in five of the six core species. The results suggest that the present use of ARs in Denmark, at least locally, may have adverse effects on reproduction and, ultimately, population status in some raptors and owls. PMID:22588365

Christensen, Thomas Kjær; Lassen, Pia; Elmeros, Morten

2012-05-16

360

Cryogenic, high-resolution x-ray detector with high count rate capability  

DOEpatents

A cryogenic, high-resolution X-ray detector with high count rate capability has been invented. The new X-ray detector is based on superconducting tunnel junctions (STJs), and operates without thermal stabilization at or below 500 mK. The X-ray detector exhibits good resolution (.about.5-20 eV FWHM) for soft X-rays in the keV region, and is capable of counting at count rates of more than 20,000 counts per second (cps). Simple, FET-based charge amplifiers, current amplifiers, or conventional spectroscopy shaping amplifiers can provide the electronic readout of this X-ray detector.

Frank, Matthias (Oakland, CA); Mears, Carl A. (Windsor, CA); Labov, Simon E. (Berkeley, CA); Hiller, Larry J. (Livermore, CA); Barfknecht, Andrew T. (Menlo Park, CA)

2003-03-04

361

A high standard metabolic rate constrains juvenile growth.  

PubMed

The allocation of energy to various components of an individual's energy budget is often viewed as a competitive process. As such, a tradeoff may exist between production (growth) and maintenance metabolism. One view of a potential tradeoff, termed "the principle of allocation", suggests that individuals with lower maintenance metabolic expenditures may have higher growth rates. To determine whether such a tradeoff exists, I analyzed the relationship between growth rate and maintenance metabolism of 225 juvenile snapping turtles housed in the laboratory. I measured growth from hatching to 6 months of age, and then measured oxygen consumption and calculated standard metabolic rate. Mean growth rate was 0.19 g d(-) and mean standard metabolic rate (SMR) was 1.41 kJ d(-). Maintenance metabolism and growth were negatively correlated after both were adjusted for body mass. The results support the "principle of allocation" theory: individuals with higher standard metabolic rates tended to have low growth rates. PMID:16351863

Steyermark, Anthony C

2002-01-01

362

Gene expression rate comparison for multiple high-throughput datasets.  

PubMed

Microarray provides genome-wide transcript profiles, whereas RNA-seq is an alternative approach applied for transcript discovery and genome annotation. Both high-throughput techniques show quantitative measurement of gene expression. To explore differential gene expression rates and understand biological functions, the authors designed a system which utilises annotations from Kyoto Encyclopedia of Genes and Genomes (KEGG) biological pathways and Gene Ontology (GO) associations for integrating multiple RNA-seq or microarray datasets. The developed system is initiated by either estimating gene expression levels from mapping next generation sequencing short reads onto reference genomes or performing intensity analysis from microarray raw images. Normalisation procedures on expression levels are evaluated and compared through different approaches including Reads Per Kilobase per Million mapped reads (RPKM) and housekeeping gene selection. Such gene expression levels are shown in different colour shades and graphically displayed in designed temporal pathways. To enhance importance of functional relationships of clustered genes, representative GO terms associated with differentially expressed gene cluster are visually illustrated in a tag cloud representation. PMID:24067413

Chen, Chien-Ming; Shih, Tsan-Huang; Pai, Tun-Wen; Liu, Zhen-Long; Chang, Margaret Dah-Tsyr; Hu, Chin-Hwa

2013-10-01

363

Algal biofuels from wastewater treatment high rate algal ponds.  

PubMed

This paper examines the potential of algae biofuel production in conjunction with wastewater treatment. Current technology for algal wastewater treatment uses facultative ponds, however, these ponds have low productivity (?10 tonnes/ha.y), are not amenable to cultivating single algal species, require chemical flocculation or other expensive processes for algal harvest, and do not provide consistent nutrient removal. Shallow, paddlewheel-mixed high rate algal ponds (HRAPs) have much higher productivities (?30 tonnes/ha.y) and promote bioflocculation settling which may provide low-cost algal harvest. Moreover, HRAP algae are carbon-limited and daytime addition of CO(2) has, under suitable climatic conditions, the potential to double production (to ?60 tonnes/ha.y), improve bioflocculation algal harvest, and enhance wastewater nutrient removal. Algae biofuels (e.g. biogas, ethanol, biodiesel and crude bio-oil), could be produced from the algae harvested from wastewater HRAPs, The wastewater treatment function would cover the capital and operation costs of algal production, with biofuel and recovered nutrient fertilizer being by-products. Greenhouse gas abatement results from both the production of the biofuels and the savings in energy consumption compared to electromechanical treatment processes. However, to achieve these benefits, further research is required, particularly the large-scale demonstration of wastewater treatment HRAP algal production and harvest. PMID:21330711

Craggs, R J; Heubeck, S; Lundquist, T J; Benemann, J R

2011-01-01

364

Cassini High Rate Detector V5.0  

NASA Astrophysics Data System (ADS)

The High Rate Detector (HRD) from the University of Chicago is an independent part of the CDA instrument on the Cassini Orbiter that measures the dust flux and particle mass distribution of dust particles hitting the HRD detectors. This data set includes all data from the HRD through the end of 2008. Please refer to Srama et al. (2004) for a detailed HRD description. --Apple-Mail-2--243167724 Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Content-Transfer-Encoding: 7bit On Aug 5, 2008, at 1:54 PM, Carolyn Stern Grant wrote: >> I am preparing to send you a new batch of publications for >> inclusion in the ADS system. I notice that I never got a response >> from you to the following question. Should I send the publications >> in >> the format we have used in the past, or would you like us to change >> our software to fix this problem? (see your earlier message >> attached.) > > Hi Carol, > > Go ahead and use the format you've used in the past. > > Thanks, > -Carolyn > ************************************************************************* > Carolyn Stern Grant Astrophysics Data System (ADS) > stern@cfa.harvard.edu Center for Astrophysics > 617-495-7154 (voicemail) 60 Garden Street MS 67 > 617-495-7356 fax Cambridge, MA 02138 > ************************************************************************* > > --Apple-Mail-2--243167724--

Economou, T.; Didonna, P.

2009-06-01

365

Substrate inhibition and control for high rate biogas production  

SciTech Connect

This research addresses a critical aspect of the technical feasibility of biogas recovery with poultry manure using anaerobic digestion, namely, inhibition and toxicity factors limiting methane generation under high rate conditions. The research was designed to identify the limiting factors and to examine alternative pretreatment and in situ control methods for the anaerobic digestion of poultry manure as an energy producing system. Biogas production was indicated by the daily gas volume produced per unit digester capacity. Enhanced biogas generation from the anaerobic digester systems using poultry manure was studied in laboratory- and pilot-scale digester operations. It was found that ammonia nitrogen concentration above 4000 mg/l was inhibitory to biogas production. Pretreatment of the manure by elutriation was effective for decreasing inhibitory/toxic conditions. Increased gas production resulted without an indication of serious inhibition by increased volatile acids, indicating a limitation of available carbon sources. For poultry manure digestion, the optimum pH range was 7.1 to 7.6. Annual costs for pretreatment/biogas systems for 10,000, 30,000 and 50,000 birds were estimated and compared with annual surplus energy produced. The economic break-even point was achieved in digesters for greater than 30,000 birds. Capital cost of the digester system was estimated to be $18,300 with annual costs around $4000. It is anticipated that the digester system could be economically applied to smaller farms as energy costs increase.

Shin, H.S.

1982-01-01

366

Bats and birds: Exceptional longevity despite high metabolic rates.  

PubMed

Bats and birds live substantially longer on average than non-flying mammals of similar body size. The combination of small body size, high metabolic rates, and long lifespan in bats and birds would not seem to support oxidative theories of ageing that view senescence as the gradual accumulation of damage from metabolic byproducts. However, large-scale comparative analyses and laboratory studies on a few emerging model species have identified multiple mechanisms for resisting oxidative damage to mitochondrial DNA and cellular structures in both bats and birds. Here we review these recent findings, and suggest areas in which additional progress on ageing mechanisms can be made using bats and birds as novel systems. New techniques for determining the age of free-living, wild individuals, and robustly supported molecular phylogenies, are under development and will improve the efforts of comparative biologists to identify ecological and evolutionary factors promoting long lifespan. In the laboratory, greater development of emerging laboratory models and comparative functional genomic approaches will be needed to identify the molecular pathways of longevity extension in birds and bats. PMID:19643206

Munshi-South, Jason; Wilkinson, Gerald S

2009-07-28

367

Ethnicity and assisted reproductive technologies  

PubMed Central

SUMMARY Racial and ethnic disparities have been reported in every field of medicine. High costs associated with infertility treatment and restricted access to care has made assisted reproductive technologies particularly susceptible and vulnerable to disparity. Despite advances in the field, emerging literature has continued to demonstrate poorer outcomes in minority women receiving treatment with assisted reproductive technologies.

Armstrong, Alicia; Plowden, Torie C

2013-01-01

368

High strain rate and high temperature behaviour of metallic materials for jet engine turbine containment  

NASA Astrophysics Data System (ADS)

This work presents a study on the mechanical characterisation of the materials involved in air jet engine turbines. The final objective is to analyse the phenomenon of a turbine blade off failure, to verify the requirements of the case containment. The materials in the turbine are under high temperatures, ranging from 400circC to 800circC and when the fail of the blade occurs if impacts against the case, reaching strain rates up to 103 s - 1. To obtain the behaviour of the materials, testing at high strain rate and high temperature at one time is necessary. The experimental set-up used was a split Hopkinson pressure bar, with a high temperature furnace adapted. The bars used on the device were high strength nickel alloys with a cooling system to decrease the temperature of the measurement devices. The effect of wave dispersion due to the temperature gradient has been also studied to correct the measurements if necessary. The material tested has been the FV535 stainless steel used on the case. The full stress-strain curves at different temperatures and at strain rates up to 103 s-1 have been obtained. The experimental results show a marked influence of the strain rate and the temperature that cannot be neglected. The Johnson-Cook material model has been used to fit the results of the material tests.

Gálvez, F.; Cendón, D.; Enfedaque, A.; Sánchez-Gálvez, V.

2006-08-01

369

REPRODUCTIVE DEVELOPMENT  

Technology Transfer Automated Retrieval System (TEKTRAN)

Throughout history, humans have celebrated the beauty and fertility of flowering plants. In addition to their aesthetic appeal, flowers contain the reproductive organs of the plant and are therefore essential for sexual propagation of plant life. Our dependence on flowering is illustrated by the die...

370

Dynamic changes in inflammatory cytokines in pigs infected with highly pathogenic porcine reproductive and respiratory syndrome virus.  

PubMed

Porcine reproductive and respiratory syndrome virus (PRRSV) infection induces both humoral and cellular immune responses. In this study, we investigated the changes in cytokine levels in peripheral blood between the highly pathogenic PRRSV HuN4 strain and its derivative strain HuN4-F112 obtained by serial propagation in MARC145 cells to 112 passages. The results demonstrated that pigs infected with HuN4 showed a loss of appetite, decrease in body weight, raised body temperature, and respiratory symptoms, along with interstitial pneumonia lesions. The PRRSV amounts in the pigs infected with HuN4 were 10(5) to 10(9) copies/ml in the blood and 10(10) to 10(11) copies/g in the lung tissues, whereas the virus amounts with HuN4-F112 were 10(2.15) to 10(3.13) copies/ml in the blood and 10(3.0) to 10(3.6) copies/g in the lungs. Moreover, the levels of interleukin 1 (IL-1), IL-6, tumor necrosis factor alpha (TNF-alpha), and alpha interferon (IFN-alpha) in peripheral blood were upregulated 7 days postinoculation with HuN4, which was earlier than in the HuN4-F112 group. Furthermore, cytokine levels in the pigs infected with HuN4 returned to normal on the 21st day postinoculation, while the levels in those infected with HuN4-F112 continued to increase. These results demonstrated that the pigs infected with the highly pathogenic PRRSV HuN4 strain generated earlier and higher levels of inflammatory cytokines, and the results also indicated that HuN4 may aggravate inflammation and damage tissues and organs. The low-pathogenic PRRSV HuN4-F112 strain induced lower levels of inflammatory cytokines, which may enhance the immune responses against the infection. PMID:20631336

Liu, Yonggang; Shi, Wenda; Zhou, Enmin; Wang, Shujie; Hu, Shouping; Cai, Xuehui; Rong, Fulong; Wu, Jiabin; Xu, Min; Xu, Mingming; Li, Liqin

2010-07-14

371

Somos muchos (we are so many): population politics and "reproductive othering" in Mexican fertility clinics.  

PubMed

Although Mexican state officials have long attributed Mexico's "overpopulation problem" to its "high" fertility rate, that rate is almost at replacement level today. Nevertheless, anxieties about overpopulation rooted in reproduction persist. Based on my ethnographic fieldwork in Mexico City fertility clinics, this article examines how overpopulation anxieties affect infertile women as they use assisted reproductive technologies (ARTs) to try to conceive children. I examine how these women attempt to justify their seemingly out-of-place use of ARTs in this "overpopulated" context by evoking discourses of "reproductive othering." Through these discourses they lay claim to a whiter, worthier status than racialized Others on the basis of their purported reproductive practices. I contend that their discourses reveal that infertility and its care are potent sites for the local production and reproduction of personhood, parenthood, and citizenship. PMID:23674326

Braff, Lara

2013-03-01

372

Studies on Nonaluminized High Burning Rate AP-Composite Propellants  

Microsoft Academic Search

This paper discusses the effect of replacement of hydroxyl terminated poly butadiene (HTPB) by butacene on the burning rates of a nonaluminized ammonium perchlorate (AP)–based composite propellant. A remarkable burning rate enhancement (60–100%) was observed on replacement of HTPB by butacene to the extent of 25%. Replacement of 50–75% HTPB by butacene led to further increase in burning rate by

G. M. GORE; A. N. NAZARE; C. N. DIVEKAR; S. K. HAIT; S. N. ASTHANA

2004-01-01

373

High strain-rate fracture and failure of a high strength low alloy steel in compression  

Microsoft Academic Search

The deformation and fracture of quench-hardened and tempered AISI 4340 steel samples at high strain-rates were investigated. The steel samples were quench-hardened and tempered at 205, 315 or 425°C for 1h before they were subjected to high velocity impact testing. Irrespective of the tempered condition of the martensitic steel samples, failure occurred predominantly by ductile shear fracture along the path

A. G. Odeshi; M. N. Bassim

2009-01-01

374

A high-throughput LDPC decoder architecture for high-rate WPAN systems  

Microsoft Academic Search

This paper presents a high-throughput memory- efficient decoder architecture for Quasi-Cyclic Low-Density Parity-Check (QC-LDPC) codes in the high-rate wireless personal area network applications. Two novel techniques which can apply to our selected QC-LDPC codes are proposed, including four-parallel block layered decoding architecture and simplification of the switch networks. The proposed architecture based on a block parallel decoding scheme replaces a

Kyung-Il Baek; Hanho Lee; Chang-Seok Choi; Sangmin Kim; Gerald E. Sobelman

2011-01-01

375

High rep rate high performance plasma focus as a powerful radiation source  

Microsoft Academic Search

Basic operational characteristics of the plasma focus are considered from design perspectives to develop powerful radiation sources. Using these ideas we have developed two compact plasma focus (CPF) devices operating in neon with high performance and high repetition rate capacity for use as an intense soft X-ray (SXR) source for microelectronics lithography. The NX1 is a four-module system with a

Sing Lee; Paul Lee; Guixin Zhang; Xianping Feng; Vladimir A. Gribkov; Mahe Liu; Adrian Serban; Terence K. S. Wong

1998-01-01

376

Effects of Al addition on high strain rate deformation of fully austenitic high Mn steels  

Microsoft Academic Search

The effects of Al addition on dynamic flow response of the fully austenitic high Mn steel were investigated by conducting high strain rate compression tests on Fe–22Mn–xAl–0.6C steels (x=0, 3, 6 in wt.%). While dynamic yield strength of the 0 Al steel and the 3 Al steel were comparable, the 6 Al steel exhibited the highest one. Meanwhile, strain hardenability

Si Woo Hwang; Jung Hoon Ji; Kyung-Tae Park

2011-01-01

377

Response of boron carbide subjected to large strains, high strain rates, and high pressures  

Microsoft Academic Search

This article presents an analysis of the response of boron carbide (B4C) to severe loading conditions that produce large strains, high strain rates, and high pressures. Experimental data from the literature are used to determine and\\/or estimate constants for the JH-2 constitutive model for brittle materials. Because B4C is a very strong material, it is not always possible to determine

Gordon R. Johnson; Tim J. Holmquist

1999-01-01

378

Liquid helium storage at high density and discharge at high flow rates  

Microsoft Academic Search

Equipment to store supercritical helium at high density and to demonstrate pulsed discharge at high flow rates was designed, fabricated, and successfully tested. A storage density of 193 kg\\/cu m (12.03 lb\\/cu ft) at 8.3 MPa (81 atm) was achieved in a 135 liter (35 gal) dewar. Pulsed discharges of 2 seconds and 4 seconds duration were demonstrated at a

D. E. Daney

1976-01-01

379

Steady State Microbunching for High Brilliance and High Repetition Rate Storage Ring-Based Light Sources  

SciTech Connect

Electron-based light sources have proven to be effective sources of high brilliance, high frequency radiation. Such sources are typically either linac-Free Electron Laser (FEL) or storage ring types. The linac-FEL type has high brilliance (because the beam is microbunched) but low repetition rate. The storage ring type has high repetition rate (rapid beam circulation) but comparatively low brilliance or coherence. We propose to explore the feasibility of a microbunched beam in a storage ring that promises high repetition rate and high brilliance. The steady-state-micro-bunch (SSMB) beam in storage ring could provide CW sources for THz, EUV, or soft X-rays. Several SSMB mechanisms have been suggested recently, and in this report, we review a number of these SSMB concepts as promising directions for high brilliance, high repetition rate light sources of the future. The trick of SSMB lies in the RF system, together with the associated synchrotron beam dynamics, of the storage ring. Considering various different RF arrangements, there could be considered a number of scenarios of the SSMB. In this report, we arrange these scenarios more or less in order of the envisioned degree of technical challenge to the RF system, and not in the chronological order of their original references. Once the stored beam is steady-state microbunched in a storage ring, it passes through a radiator repeatedly every turn (or few turns). The radiator extracts a small fraction of the beam energy as coherent radiation with a wavelength corresponding to the microbunched period of the beam. In contrast to an FEL, this radiator is not needed to generate the microbunching (as required e.g. by SASE FELs or seeded FELs), so the radiator can be comparatively simple and short.

Chao, Alex; Ratner, Daniel; /SLAC; Jiao, Yi; /Beijing, Inst. High Energy Phys.

2012-09-06

380

TRP 9904 - Constitutive Behavior of High Strength Multiphase Sheel Steel Under High Strain Rate Deformation  

SciTech Connect

The focus of the research project was to systematically assess the strain rate dependence of strengthening mechanisms in new advanced high strength sheet steels. Data were obtained on specially designed and produced Duel Phase and TRIP steels and compared to the properties of automotive steels currently in use.

David Matlock; John Speer

2005-03-31

381

Strange Quark Decay Rates in Quark Matter at High Temperatures  

Microsoft Academic Search

The rates of the main weak processes involving strange quarks in degenerate quark matter are calculated numerically. The calculations are performed for temperatures up to 100 MeV. Pauli-blocking turns out to be very important. The rates obtained differ by three orders of magnitude from simple estimates in the literature. The results are briefly applied to cosmologically produced quark nuggets, and

Henning Heiselberg; Jes Madsen; Karsten Riisager

1986-01-01

382

High Rates of Inapparent Dengue in Older Adults in Singapore  

PubMed Central

Although the dengue iceberg phenomenon is well known, there is a paucity of data on inapparent dengue. Results from a seroepidemiological study conducted during a dengue epidemic in 2007 in Singapore showed a seroprevalence of 65.9% and an inapparent dengue rate of 78%. Older adults (> 45 years old) had significantly higher rates of inapparent dengue infections (P < 0.05).

Yap, Grace; Li, Chenny; Mutalib, Adeliza; Lai, Yee-Ling; Ng, Lee-Ching

2013-01-01

383

Comparison of RBE values of high- LET ?-particles for the induction of DNA-DSBs, chromosome aberrations and cell reproductive death  

Microsoft Academic Search

Background  Various types of radiation effects in mammalian cells have been studied with the aim to predict the radiosensitivity of tumours\\u000a and normal tissues, e.g. DNA double strand breaks (DSB), chromosome aberrations and cell reproductive inactivation. However,\\u000a variation in correlations with clinical results has reduced general application. An additional type of information is required\\u000a for the increasing application of high-LET radiation

Nicolaas AP Franken; Rosemarie ten Cate; Przemek M Krawczyk; Jan Stap; Jaap Haveman; Jacob Aten; Gerrit W Barendsen

2011-01-01

384

High Rate and High Capacity Li-Ion Electrodes for Vehicular Applications  

SciTech Connect

Significant advances in both energy density and rate capability for Li-ion batteries are necessary for implementation in electric vehicles. We have employed two different methods to improve the rate capability of high capacity electrodes. For example, we previously demonstrated that thin film high volume expansion MoO{sub 3} nanoparticle electrodes ({approx}2 {micro}m thick) have a stable capacity of {approx}630 mAh/g, at C/2 (charge/dicharge in 2 hours). By fabricating thicker conventional electrodes, an improved reversible capacity of {approx}1000 mAh/g is achieved, but the rate capability decreases. To achieve high-rate capability, we applied a thin Al{sub 2}O{sub 3} atomic layer deposition coating to enable the high volume expansion and prevent mechanical degradation. Also, we recently reported that a thin ALD Al{sub 2}O{sub 3} coating can enable natural graphite (NG) electrodes to exhibit remarkably durable cycling at 50 C. Additionally, Al{sub 2}O{sub 3} ALD films with a thickness of 2 to 4 {angstrom} have been shown to allow LiCoO{sub 2} to exhibit 89% capacity retention after 120 charge-discharge cycles performed up to 4.5 V vs. Li/Li{sup +}. Capacity fade at this high voltage is generally caused by oxidative decomposition of the electrolyte or cobalt dissolution. We have recently fabricated full cells of NG and LiCoO{sub 2} and coated both electrodes, one or the other electrode as well as neither electrode. In creating these full cells, we observed some surprising results that lead us to obtain a greater understanding of the ALD coatings. In a different approach we have employed carbon single-wall nanotubes (SWNTs) to synthesize binder-free, high-rate capability electrodes, with 95 wt.% active materials. In one case, Fe{sub 3}O{sub 4} nanorods are employed as the active storage anode material. Recently, we have also employed this method to demonstrate improved conductivity and highly improved rate capability for a LiNi{sub 0.4}Mn{sub 0.4}Co{sub 0.2}O{sub 2} cathode material. Raman spectroscopy was employed to understand how the SWNTs function as a highly flexible conductive additive.

Dillon, A. C.

2012-01-01

385

High invertase activity in tomato reproductive organs correlates with enhanced sucrose import into, and heat tolerance of, young fruit.  

PubMed

Heat stress can cause severe crop yield losses by impairing reproductive development. However, the underlying mechanisms are poorly understood. We examined patterns of carbon allocation and activities of sucrose cleavage enzymes in heat-tolerant (HT) and -sensitive (HS) tomato (Solanum lycopersicum L.) lines subjected to normal (control) and heat stress temperatures. At the control temperature of 25/20 °C (day/night) the HT line exhibited higher cell wall invertase (CWIN) activity in flowers and young fruits and partitioned more sucrose to fruits but less to vegetative tissues as compared to the HS line, independent of leaf photosynthetic capacity. Upon 2-, 4-, or 24-h exposure to day or night temperatures of 5 °C or more above 25/20 °C, cell wall (CWIN) and vacuolar invertases (VIN), but not sucrose synthase (SuSy), activities in young fruit of the HT line were significantly higher than those of the HS line. The HT line had a higher level of transcript of a CWIN gene, Lin7, in 5-day fruit than the HS line under control and heat stress temperatures. Interestingly, heat induced transcription of an invertase inhibitor gene, INVINH1, but reduced its protein abundance. Transcript levels of LePLDa1, encoding phospholipase D, which degrades cell membranes, was less in the HT line than in the HS line after exposure to heat stress. The data indicate that high invertase activity of, and increased sucrose import into, young tomato fruit could contribute to their heat tolerance through increasing sink strength and sugar signalling activities, possibly regulating a programmed cell death pathway. PMID:22105847

Li, Zhimiao; Palmer, William M; Martin, Antony P; Wang, Rongqing; Rainsford, Frederick; Jin, Ye; Patrick, John W; Yang, Yuejian; Ruan, Yong-Ling

2011-11-21

386

High Strain-Rate Response of High Purity Aluminum at Temperatures Approaching Melt  

SciTech Connect

High-temperature, pressure-shear plate impact experiments were conducted to investigate the rate-controlling mechanisms of the plastic response of high-purity aluminum at high strain rates (10{sup 6} s{sup -1}) and at temperatures approaching melt. Since the melting temperature of aluminum is pressure dependent, and a typical pressure-shear plate impact experiment subjects the sample to large pressures (2 GPa-7 GPa), a pressure-release type experiment was used to reduce the pressure in order to measure the shearing resistance at temperatures up to 95% of the current melting temperature. The measured shearing resistance was remarkably large (50 MPa at a shear strain of 2.5) for temperatures this near melt. Numerical simulations conducted using a version of the Nemat-Nasser/Isaacs constitutive equation, modified to model the mechanism of geometric softening, appear to capture adequately the hardening/softening behavior observed experimentally.

Grunschel, S E; Clifton, R J; Jiao, T

2010-01-28

387

High Strain-Rate Response of High-Purity Aluminum at Temperatures Approaching Melt  

NASA Astrophysics Data System (ADS)

High-temperature, pressure-shear plate impact experiments were conducted to investigate the rate-controlling mechanisms of the plastic response of high-purity aluminum at high strain rates (106 s-1) and at temperatures approaching melt. Since the melting temperature of aluminum is pressure dependent, and a typical pressure-shear plate impact experiment subjects the sample to large pressures (2-7 GPa), a pressure-release type experiment was used to reduce the pressure in order to measure the shearing resistance at temperatures up to 95% of the current melting temperature. The measured shearing resistance was remarkably large (50 MPa at a shear strain of 2.5) for temperatures this near melt. Numerical simulations conducted using a version of the Nemat-Nasser/Isaacs [1] constitutive equation, modified to model the mechanism of geometric softening, appear to capture adequately the hardening/softening behavior observed experimentally.

Grunschel, S. E.; Clifton, R. J.; Jiao, T.

2009-12-01

388

A 2 J high-power excimer laser at high pulse repetition rate  

NASA Astrophysics Data System (ADS)

An excimer laser of high pulse energy and high repetition rate was developed. All pulsed power components including the waterline capacitor and the control unit were tested at 100 Hz. A multichannel pseudospark switch operated at 100 kA peak current. An elongated X-ray unit for preionization of the laser gas employing a hollow cathode discharge shows a high reliability and a long service life at repetition rates in excess of 100 Hz. Important design parameters of the XeCl laser are given. In a closed flow-loop the average power of the XeCl laser is measured at 140 W. The temporal evolution of density fluctuations between two consecutive discharges was registered by an interferometer.

Cirkel, Hans-Juergen

1988-03-01

389

Coal plasticity at high heating rates and temperatures  

SciTech Connect

The report elaborates upon our earlier discussion (Technical Progress Report No. 9) of heating rate effects on the plasticity of coals from the Argonne premium sample bank. Apparent viscosity vs. time curves are presented for five of these coals. As reported earlier, heating rate had relatively little effect (typically t 20 K) on the softening temperature of these coals. The results presented here show that as heating rate is increased from 200 to 800 K/s, the plastic period for each of these coals decreases.

Gerjarusak, S.; Peters, W.A.; Howard, J.B.

1992-01-01

390

Strain Rate Sensitivity Estimation from High Velocity Impact Data.  

National Technical Information Service (NTIS)

This experimental study was designed to expand on the work accomplished by Sundararajan and Shewmon in estimating the strain rate sensitivity factors for various materials through the use of simple ballistic impact experiments. The study was divided into ...

M. H. Bednarek

1985-01-01

391

Reproductive Counselling  

PubMed Central

In 1977 a reproductive clinic was started in the Department of Obstetrics, University of British Columbia. This is an account of the 191 couples who attended, with problems related to recurrent abortion, perinatal loss, an abnormality in a live child, family history of an anomaly or exposure of the embryo or fetus to a possible teratogen during early pregnancy. During the counselling session, the possible causes of the pregnancy loss were discussed. The risk of a recurrence of the event was assessed. Ultrasound monitoring and amniocentesis were offered in a subsequent pregnancy where appropriate. We found that following the reproductive counselling session couples developed a much more realistic attitude towards the subsequent pregnancy and their anxiety was considerably lessened.

Poland, Betty J.; Calam, Betty

1980-01-01

392

Development of high strain rate equations for stainless steels  

NASA Astrophysics Data System (ADS)

The dynamic response of four types of stainless steel sheet was investigated at different strain rates from 10-2 up to 103 s-1. The results from the tensile tests were used to evaluate the parameters in three different multiplicative strain rate equations of the type used in crashworthiness calculations. A new type of sigmoid constitutive equation is proposed for one grade of stainless steel.

Andersson, R.; Syk, M.; Powell, J.; Magnusson, G.

2005-10-01

393

The Crush Behavior of Pultruded Tubes at High Strain Rates  

Microsoft Academic Search

The effect of fiber diameter, trigger geometry and section geometry on the crush response of pultruded glass fiber reinforced plastic tubes, made with either polyester or vinyl ester resin, was determined at crush rates from 2.1 x 10-4 m\\/s to — 15 m\\/s. The rate dependence of the specific energy for the polyester resin tubes was positive, whereas that for

P. H. Thornton

1990-01-01

394

A high resolution study of forsterite dissolution rates  

Microsoft Academic Search

The rates of dissolution of olivine (Fo92) were measured over the pH range of 1.8 to 3.8 and from 25 to 45°C using an externally recycled mixed flow reactor. The data were filtered to remove several sources of systematic errors including non-steady state measurements, solution concentrations that were less than 50% above the detection limit, and Mg\\/Si rate ratios 40%

Jodi J. Rosso; J. Donald Rimstidt

2000-01-01

395

High rate properties of porcine skull bone tissue  

NASA Astrophysics Data System (ADS)

Several recent studies have shown the importance of understanding the nature of blast injuries. Traditionally, the lungs and other air filled organs were the focus of these injuries but it is being discovered that some level of brain trauma may result after encountering a blast. These injuries are referred to as traumatic brain injuries, or TBI. There has been many clinical studies and statistical analyses done concerning these injuries, but there is still no physical understanding of the problem. In order to develop a model of how this injury can occur, rate dependent material properties of the tissues the stress wave will travel through are needed. In this study, the compressive response of porcine skull bone through the thickness direction was experimentally determined over a wide range of rates, ranging from 0.001 sec -1 to approximately 3000 sec-1. The results reveal that for most mechanical properties there is a clear rate dependence of the material. However, only one subset of the skull section appeared to have a rate dependent initial modulus, with the rest showing no significant statistical dependence on loading rate. Other mechanical properties appeared to be affected by the loading rate, including the strain energy density.

Herwig, Kyle Jeffry

396

Spectacular Reproduction  

Microsoft Academic Search

Ron Harris captured the popular imagination in October 1999 with a website where he auctioned off the ova of fashion models\\u000a to the highest bidder. This article treats the controversy surrounding Harris’ site within a dual frame of critical theory’s\\u000a approach to reproduction and a folkloristic approach to discourse. The website fuses traditional narrative motifs and structures\\u000a with the logic

Valdimar Tr. Hafstein

2007-01-01

397

Ionizing radiation promotes protozoan reproduction  

SciTech Connect

This experiment was performed to determine whether ionizing radiation is essential for maximum growth rate in a ciliated protozoan. When extraneous ionizing radiation was reduced to 0.15 mrad/day, the reproduction rate of Tetrahymena pyriformis was significantly less (P less than 0.01) than it was at near ambient levels, 0.5 or 1.8 mrad/day. Significantly higher growth rates (P less than 0.01) were obtained when chronic radiation was increased. The data suggest that ionizing radiation is essential for optimum reproduction rate in this organism.

Luckey, T.D.

1986-11-01

398

Life-history traits of Amur sleeper, Perccottus glenii , in the invaded Vistula River: early investment in reproduction but reduced growth rate  

Microsoft Academic Search

In recent decades, Amur sleeper is one of the most invasive fish species in Eastern and Central Europe. Generally, it is assumed\\u000a that success of an invasive species can largely depend on the plasticity of its life-history traits, e.g., indicated by higher\\u000a investment in reproduction in the initial stage of its invasion. On the other hand, such energy allocation to

Grabowska Joanna; Pietraszewski Dariusz; Przybylski Miros?aw; Tarkan Ali Serhan; Marsza? Lidia; Lampart-Ka?u?niacka Magdalena

2011-01-01

399

High-Throughput Sequencing to Reveal Genes Involved in Reproduction and Development in Bactrocera dorsalis (Diptera: Tephritidae)  

Microsoft Academic Search

BackgroundTephritid fruit flies in the genus Bactrocera are of major economic significance in agriculture causing considerable loss to the fruit and vegetable industry. Currently, there is no ideal control program. Molecular means is an effective method for pest control at present, but genomic or transcriptomic data for members of this genus remains limited. To facilitate molecular research into reproduction and

Weiwei Zheng; Tao Peng; Wei He; Hongyu Zhang

2012-01-01

400

Social Rating of Best and Poorest High-school Students  

Microsoft Academic Search

This investigation queried whether (1) there are qualities in addition to intelligence which affect scholarship in high school, and (2) whether the best students do not also possess greater chances of post-school success. The subjects were 165 students of a small high school and the criteria of judgment the estimates of nine high school teachers who were personally acquainted with

P. V. Sangren

1923-01-01

401

Models of Evolution of Reproductive Isolation  

PubMed Central

Mathematical models are presented for the evolution of postmating and premating reproductive isolation. In the case of postmating isolation it is assumed that hybrid sterility or inviability is caused by incompatibility of alleles at one or two loci, and evolution of reproductive isolation occurs by random fixation of different incompatibility alleles in different populations. Mutations are assumed to occur following either the stepwise mutation model or the infinite-allele model. Computer simulations by using Itô's stochastic differential equations have shown that in the model used the reproductive isolation mechanism evolves faster in small populations than in large populations when the mutation rate remains the same. In populations of a given size it evolves faster when the number of loci involved is large than when this is small. In general, however, evolution of isolation mechanisms is a very slow process, and it would take thousands to millions of generations if the mutation rate is of the order of 10-5 per generation. Since gene substitution occurs as a stochastic process, the time required for the establishment of reproductive isolation has a large variance. Although the average time of evolution of isolation mechanisms is very long, substitution of incompatibility genes in a population occurs rather quickly once it starts. The intrapopulational fertility or viability is always very high. In the model of premating isolation it is assumed that mating preference or compatibility is determined by male- and female-limited characters, each of which is controlled by a single locus with multiple alleles, and mating occurs only when the male and female characters are compatible with each other. Computer simulations have shown that the dynamics of evolution of premating isolation mechanism is very similar to that of postmating isolation mechanism, and the mean and variance of the time required for establishment of premating isolation are very large. Theoretical predictions obtained from the present study about the speed of evolution of reproductive isolation are consistent with empirical data available from vertebrate organisms.

Nei, Masatoshi; Maruyama, Takeo; Wu, Chung-I

1983-01-01

402

Imploding Liner Material Strength Measurements at High-Strain and High Strain Rate  

SciTech Connect

Imploding, cylindrical liners provide a unique, shockless means of simultaneously accessing high strain and high-strain-rate for measurement of strength of materials in plastic flow. The radial convergence in the liner geometry results in the liner thickening as the circumference becomes smaller. Strains of up to {approximately}1.25 and strain rates of up to {approximately}10{sup 6} sec{sup -1} can be readily achieved in a material sample placed inside of an aluminum driver liner, using the Pegasus II capacitor bank. This provides yield strength data at conditions where none presently exists. The heating from work done against the yield strength is measured with multichannel pyrometry from infrared radiation emitted by the material sample. The temperature data as a function of liner position are unfolded to give the yield strength along the strain, strain-rate trajectory. Proper design of the liner and sample configuration ensures that the current diffused into the sample adds negligible heating. An important issue, in this type of temperature measurement, is shielding of the pickup optics from other sources of radiation. At strains greater than those achievable on Pegasus, e.g. the LANL Atlas facility, some materials may be heated all the way to melt by this process. Recent data on 6061-T6 Aluminum will be compared with an existing model for strain and strain-rate heating. The liner configuration and pyrometry diagnostic will also be discussed.

Bartsch, R.R.; Lee, H.; Holtkamp, D.; Wright, B.; Stokes, J.; Morgan, D.; Anderson, W.; Broste, W.

1998-10-18

403

Imploding Liner Material Strength Measurements at High-Strain and High-Strain Rate  

NASA Astrophysics Data System (ADS)

Imploding, cylindrical liners provide a unique, shockless means of simultaneously accessing high-strain and high-strain-rate to measure strength of materials in plastic flow. Radial convergence in the liner geometry results in the liner thickening as the circumference decreases. Strains of up to ~1.25 and strain rates of up to ~106 sec-1 can be readily achieved in a material sample placed inside an aluminum driver liner, using the Pegasus II capacitor bank. This can provide yield strength data at conditions where none presently exists. The heating from work done against the yield strength is measured with multichannel pyrometry of infrared radiation emitted by the material sample. The temperature data as a function of liner position can be unfolded to give the yield strength along the strain, strain-rate trajectory. Proper design of the liner and sample configuration ensures that the current diffused into the sample adds negligible heating. An important issue in this type of temperature measurement is shielding the pickup optics from other radiation sources. Recent data on 6061-T6 Aluminum are compared with an existing model for strain and strain-rate heating. Liner configuration and pyrometry diagnostic is also discussed.

Bartsch, R.; Lee, H.; Holtkamp, D.; Wright, B.; Stokes, J.; Morgan, D.; Anderson, W.; Broste, W.

2004-11-01

404

Electrochemical corrosion rate probes for high temperature energy applications  

SciTech Connect

Electrochemical corrosion rate (ECR) probes were constructed and exposed along with mass loss coupons in a N2/O2/CO2/H2O environment to determine ECR probe operating characteristics. Temperatures ranged from 450 to 800 C and both ECR probes and mass loss coupons were coated with ash. Results are presented in terms of the probe response to temperature, the measured zero baseline, and the quantitative nature of the probes. The effect of Stern-Geary constant and the choice of electrochemical technique used to measure the corrosion rate are also discussed. ECR probe corrosion rates were a function of time, temperature, and process environment and were found to be quantitative for some test conditions. Measured Stern-Geary constants averaged 0.0141 V/decade and the linear polarization technique was found to be more quantitative than the electrochemical noise technique.

Covino, Bernard S., Jr.; Bullard, Sophie J.; Cramer, Stephen D.; Holcomb, Gordon R.; Ziomek-Moroz, M.; Cayard, M.S. (InterCorr International Inc.); Eden, D.A. (InterCorr International Inc.)

2004-01-01

405

Versatile high rate plasma deposition and processing with very high frequency excitation  

SciTech Connect

The interest in plasma deposition using very high frequency (VHF) excitation arose after the preparation of a-Si:H at high growth rates was demonstrated. Subsequently the improved process flexibility and the control of material properties offered by the variation of the plasma excitation frequency was recognized. The preparation of amorphous and microcrystalline thin films in a VHF-plasma is described. The increased growth rates have been attributed to an enhancement of film precursor formation at VHF, to the decreased sheath thickness as well as to an enhancement of the surface reactivity by positive ions. Plasma diagnostic investigations show that the parameters mainly affected by the excitation frequency are the ion flux to the electrodes as well as the sheaths potentials and widths, rather than the plasma density. 55 refs., 13 figs.

Heintze, M.

1997-07-01

406

Response of aluminum nitride (including a phase change) to large strains, high strain rates, and high pressures  

Microsoft Academic Search

This article contains a description of a computational constitutive model for brittle materials subjected to large strains, high strain rates, and high pressures. The focus of this model is to determine the response of aluminum nitride under high velocity impact conditions that produce large strains, high strain rates, and high pressures. The strength is expressed as a function of the

Gordon R. Johnson; Timothy J. Holmquist; Stephen R. Beissel

2003-01-01

407

Development of a hermetically sealed, high-energy trigatron switch for high repetition rate applications  

Microsoft Academic Search

Triggered gas switches increase the reliability and repeatability of pulsed power systems. In particular, the performance of high-power, repetitively rated impulse generators is greatly enhanced by including a triggered switch. Impulse generators generally consist of cascaded energy storage elements, and the pulse-to-pulse voltage variations depend, to the first order, on the consistency of the voltage in the first energy storage

Jane M. Lehr; Michael D. Abdalla; Frederick R. Gruner; Brett C. Cockreham; Michael C. Skipper; Sean M. Ahern; William D. Prather

2000-01-01

408

High data rate degradation and medium thermal stability in ultra-high density magnetic recording  

NASA Astrophysics Data System (ADS)

In this dissertation, two major issues in the ultra-high density magnetic recording, the high data rate degradation and the medium thermal stability have been investigated. The high linear density together with the increasing rotational speed makes the high recording data rate inevitable. However, it has been found that the recording performance degrades at high data rates. While in order to maintain a sufficient signal-to-noise ratio (SNR) at high areal density, the grain size in the magnetic layer needs to be reduced, the small grain volume makes the magnetization data pattern in the media become unstable under thermal agitation and affect the lifetime of storage dramatically. By directly measuring the recording bubble footprint, the dynamic recording process was first characterized. In the light of the dynamic recording process, a complete understanding of the overwrite degradation in high speed recording has been obtained. Correlating with the nonlinear head response, the recording degradations at high data rate have been systematically investigated. By comparing the recording characteristics using different drive current waveforms, the effects of the field rise time and the head saturation have been understood. A novel spin-stand based technique has been developed to characterize the thermal stability of recording media. The statistics of effective energy barrier distribution have been obtained by directly measuring the remanent magnetization decay in a short time scale by applying proper reverse fields. The results also indicate that magnetic interactions have significant impact on energy barrier distribution and the magnetization decay process. To study the effect of magnetic interactions on the media thermal stability, a statistical model, which takes into account the magnetic interactions, has been developed. The effective energy barrier has been found to be reduced by the presence of interactions. Increasing the exchange coupling helps to improve the thermal stability of the recording medium. A non-zero weak exchange coupling may be desirable considering both medium SNR and thermal stability. The impacts of the medium orientation and the grain size distribution have also been studied.

Shi, Rick Changqing

409

Development of a high-count-rate neutron detector with position sensitivity and high efficiency  

SciTech Connect

While the neutron scattering community is bombarded with hints of new technologies that may deliver detectors with high-count-rate capability, high efficiency, gamma-ray insensitivity, and high resolution across large areas, only the time-tested, gas-filled {sup 3}He and scintillation detectors are in widespread use. Future spallation sources with higher fluxes simply must exploit some of the advanced detector schemes that are as yet unproved as production systems. Technologies indicating promise as neutron detectors include pixel arrays of amorphous silicon, silicon microstrips, microstrips with gas, and new scintillation materials. This project sought to study the competing neutron detector technologies and determine which or what combination will lead to a production detector system well suited for use at a high-intensity neutron scattering source.

Nelson, R.; Sandoval, J.

1996-10-01

410

High strain-rate testing of parachute materials  

NASA Astrophysics Data System (ADS)

Research at Sandia National Laboratories has shown a strain rate dependence of many materials used in the production of parachutes. Differences in strength of 30% have been found between strain rates of 12/s and slow rates normally used to define material properties for lightweight nylon cloth. These structures are sometimes deployed in a rapid fashion and the loading is experienced in milliseconds; the production of material data in the same loading regime is required for full understanding of material response. Also, material behavior suitable for structural analysis of these structures is required for successful analysis. This is especially important when different materials are used in the same fabric structure. Determining the distribution of load to various portions of a nylon and Kevlar parachute requires the correct moduli and material behavior in the analytical model. The effect of strain rate on the material properties of nylon and Kevlar components commonly used in parachute construction are reported in this paper. These properties are suitable for use in analytical models of these fabric structures.

Gwinn, Kenneth W.; Totten, John J.; Waye, Donald E.

1994-12-01

411

High Strain Rate Tensile Testing of DOP-26 Iridium  

SciTech Connect

The iridium alloy DOP-26 was developed through the Radioisotope Power Systems Program in the Office of Nuclear Energy of the Department of Energy. It is used for clad vent set cups containing radioactive fuel in radioisotope thermoelectric generator (RTG) heat sources which provide electric power for spacecraft. This report describes mechanical testing results for DOP-26. Specimens were given a vacuum recrystallization anneal of 1 hour at 1375 C and tested in tension in orientations parallel and perpendicular to the rolling direction of the sheet from which they were fabricated. The tests were performed at temperatures ranging from room temperature to 1090 C and strain rates ranging from 1 x 10{sup -3} to 50 s{sup -1}. Room temperature testing was performed in air, while testing at elevated temperatures was performed in a vacuum better than 1 x 10{sup -4} Torr. The yield stress (YS) and the ultimate tensile stress (UTS) decreased with increasing temperature and increased with increasing strain rate. Between 600 and 1090 C, the ductility showed a slight increase with increasing temperature. Within the scatter of the data, the ductility did not depend on the strain rate. The reduction in area (RA), on the other hand, decreased with increasing strain rate. The YS and UTS values did not differ significantly for the longitudinal and transverse specimens. The ductility and RA values of the transverse specimens were marginally lower than those of the longitudinal specimens.

Schneibel, Joachim H [ORNL; Carmichael Jr, Cecil Albert [ORNL; George, Easo P [ORNL

2007-11-01

412

Six Habits of the Highly Effective E-Rate Applicant  

ERIC Educational Resources Information Center

Since its inception in 1997, the Schools and Libraries Program of the Federal Communications Commission's Universal Service Fund, more commonly known as E-Rate, has committed more than $30 billion to offset the cost of certain digital and telecommunication services and products that are essential for schools and libraries to receive…

Harrington, John

2011-01-01

413

High strain rate properties and constitutive modeling of glass.  

National Technical Information Service (NTIS)

This paper presents experimental data and computational modeling for a well-defined glass material. The experimental data cover a wide range of strains, strain rates, and pressures that are obtained from quasi-static compression and tension tests, split H...

T. J. Holmquist G. R. Johnson C. M. Lopatin D. E. Grady E. S. Hertel

1995-01-01

414

High Efficiency Gear-Shaping by Controlling Radial Feed Rate,  

National Technical Information Service (NTIS)

Various efforts are being made to achieve a 30-second cycle time for the gear-shaping process in an automobile parts manufacturing line. As one of these, a new method has been developed to shorten the cutting time by controlling the radial feed rate. In t...

T. Rakkaku S. Nakai H. Terai T. Nishimoto

1988-01-01

415

Comparison of RBE values of high- LET ?-particles for the induction of DNA-DSBs, chromosome aberrations and cell reproductive death  

PubMed Central

Background Various types of radiation effects in mammalian cells have been studied with the aim to predict the radiosensitivity of tumours and normal tissues, e.g. DNA double strand breaks (DSB), chromosome aberrations and cell reproductive inactivation. However, variation in correlations with clinical results has reduced general application. An additional type of information is required for the increasing application of high-LET radiation in cancer therapy: the Relative Biological Effectiveness (RBE) for effects in tumours and normal tissues. Relevant information on RBE values might be derived from studies on cells in culture. Methods To evaluate relationships between DNA-DSB, chromosome aberrations and the clinically most relevant effect of cell reproductive death, for ionizing radiations of different LET, dose-effect relationships were determined for the induction of these effects in cultured SW-1573 cells irradiated with gamma-rays from a Cs-137 source or with ?-particles from an Am-241 source. RBE values were derived for these effects. Ionizing radiation induced foci (IRIF) of DNA repair related proteins, indicative of DSB, were assessed by counting gamma-H2AX foci. Chromosome aberration frequencies were determined by scoring fragments and translocations using premature chromosome condensation. Cell survival was measured by colony formation assay. Analysis of dose-effect relations was based on the linear-quadratic model. Results Our results show that, although both investigated radiation types induce similar numbers of IRIF per absorbed dose, only a small fraction of the DSB induced by the low-LET gamma-rays result in chromosome rearrangements and cell reproductive death, while this fraction is considerably enhanced for the high-LET alpha-radiation. Calculated RBE values derived for the linear components of dose-effect relations for gamma-H2AX foci, cell reproductive death, chromosome fragments and colour junctions are 1.0 ± 0.3, 14.7 ± 5.1, 15.3 ± 5.9 and 13.3 ± 6.0 respectively. Conclusions These results indicate that RBE values for IRIF (DNA-DSB) induction provide little valid information on other biologically-relevant end points in cells exposed to high-LET radiations. Furthermore, the RBE values for the induction of the two types of chromosome aberrations are similar to those established for cell reproductive death. This suggests that assays of these aberrations might yield relevant information on the biological effectiveness in high-LET radiotherapy.

2011-01-01

416

Terminal Investment: Individual Reproduction of Ant Queens Increases with Age  

PubMed Central

The pattern of age-specific fecundity is a key component of the life history of organisms and shapes their ecology and evolution. In numerous animals, including humans, reproductive performance decreases with age. Here, we demonstrate that some social insect queens exhibit the opposite pattern. Egg laying rates of Cardiocondyla obscurior ant queens increased with age until death, even when the number of workers caring for them was kept constant. Cardiocondyla, and probably also other ants, therefore resemble the few select organisms with similar age-specific reproductive investment, such as corals, sturgeons, or box turtles (e.g., [1]), but they differ in being more short-lived and lacking individual, though not social, indeterminate growth. Furthermore, in contrast to most other organisms, in which average life span declines with increasing reproductive effort, queens with high egg laying rates survived as long as less fecund queens.

Heinze, Jurgen; Schrempf, Alexandra

2012-01-01

417

The High Cost of South Carolina's Low Graduation Rate. School Choice Issues in the State  

ERIC Educational Resources Information Center

|Research has documented a crisis in South Carolina's high school graduation rate. While state officials report a graduation rate above 70 percent, researchers from South Carolina and elsewhere place the rate just above 50 percent, with rates among minority students lower than 50 percent. South Carolina's graduation rate is the worst of all 50…

Gottlob, Brian J.

2007-01-01

418

Compact plasma focus soft x-ray source with high repetition rate and high intensity  

NASA Astrophysics Data System (ADS)

We have developed two compact plasma focus devices operating in neon with high repetition rate capacity to be used as a repetitive pulse soft x-ray (SXR) source for lithography. A single capacitor module 1-1-1 was used to test high repetitive rate capability and was observed to produce soft x-rays in the wavelength range of 0.8-1.4 nm at up to 10 Hz. The discharge current rises in 1.2 us to peak value of 140 kA at 15 kV charge. The soft x-ray yield varies with the pressure of working gas, the value and polarity of voltage applied to capacitor.On the basis of this module we have designed a our module test system for SXR designated as the NX1. The peak discharge current is 270 kA when the capacitor bank is charged to 12kV. It produces 100J of soft x-ray per shot in single shot mode, in the wavelength range of 0.8 to 1.4nm and a spot size of below 1mm viewed end on. With a repetitive rate of up to 3Hz this gives 300W of average SXR power. The NX2 is a second system that has been designed and constructed. It will be operated at peak currents in excess of 300kA into water-cooled electrodes at repetitive rates up to 20Hz to produce 300W SXR in burst durations of up to 5 minutes. It is estimated that with such a SXR yield into a well designed beamline and a reasonably sensitive resist an exposure could be made in less than 10 seconds. Pushing such x-ray sources further to 2 kW output will make their intensity sufficient for SXR lithography with reasonably high throughput to be of industrial interest.

Lee, Sing; Lee, Paul; Zhang, G. X.; Feng, X.; Serban, A.; Liu, M. H.; Wong, Terence K.; Selvam, C.; Thang, A.

1997-08-01

419

High Cost and Low Survival Rate in High Comorbidity Incident Elderly Hemodialysis Patients  

PubMed Central

Background The comorbidity index is a predictor of mortality in dialysis patients but there are few reports for predicting elderly dialysis mortality and national population-based cost studies on elderly dialysis. The aim of this study was to evaluate the long-term mortality of incident elderly dialysis patients using the Deyo - Charlson comorbidity index (CCI) and to assess the inpatient and outpatient visits along with non-dialysis costs. Methods Data were obtained from catastrophic illness registration of the Taiwan National Health Insurance Research Database. Incident elderly dialysis patients (age >75 years) receiving hemodialysis for more than 90 days between Jan 1, 1998, and dec 31, 2007, were included. Baseline comorbidities were determined one year prior to the first dialysis day according to ICD-9 CM codes. Survival time, mortality rate, hospitalization time, outpatient visit frequency, and costs were calculated for different age and CCI groups. Results In 10,759 incident elderly hemodialysis patients, hazard ratios for all-cause mortality were significantly increased in the different age groups (p < 0.001) and CCI patients (p < 0.001). Death rates increased with both increasing age and CCI score. High comorbidity incident hemodialysis and elderly patients were found to have increased length of hospital stay and total hospitalization costs. Conclusions This population-based cohort study indicated that both age and higher CCI values were predictors of survival in incident elderly hemodialysis. Increased costs and mortality rates were evident in the oldest patients and in those with high CCI scores. Conservative treatment might be considered in high comorbidity and low-survival rate end stage renal disease (ESRD) patients.

Lin, Yi-Ting; Wu, Ping-Hsun; Kuo, Mei-Chuan; Lin, Ming-Yen; Lee, Tzu-Chi; Chiu, Yi-Wen; Hwang, Shang-Jyh; Chen, Hung-Chun

2013-01-01

420

A High Intrinsic Peculiarity Rate among Type IA Supernovae  

Microsoft Academic Search

We have compiled a sample of 45 Type Ia supernovae (SNe Ia) discovered by the Lick Observatory Supernova Search (LOSS) and the Beijing Astronomical Observatory Supernova Survey (BAOSS), and determined the rate of spectroscopically peculiar SNe Ia (i.e., SN 1986G-like, SN 1991bg-like, and SN 1991T-like objects) and the luminosity function of SNe Ia. Because of the nature of the two

Weidong Li; Alexei V. Filippenko; Richard R. Treffers; Adam G. Riess; Jingyao Hu; Yulei Qiu

2001-01-01

421

High data rate fiber systems and their installations  

Microsoft Academic Search

Fiber optic point-to-point links show many advantages over conventional wire systems. These include wide bandwidth, long inter-repeater spacing, secure information transfer, elimination of ground loops and electromagnetic pulse problems. A brief discussion is given of fiber optic components, temporal dispersion, link length, and nuclear hardness. Bit error rate results are given for a 400 Mbps NRZ 200 meter fiber optic

J. Quarato; C. Berner

1978-01-01

422

Modeling Large-Strain, High-Rate Deformation in Metals  

Microsoft Academic Search

The large strain deformation response of 6061-T6 and Ti-6Al-4V has been evaluated over a range in strain rates from 10 s¹ to over 10 s¹. The results have been used to critically evaluate the strength and damage components of the Johnson-Cook (JC) material model. A new model that addresses the shortcomings of the JC model was then developed and evaluated.

D R Lesuer; G J Kay; M M LeBlanc

2001-01-01

423

Microstructural Characterization of a High-Strength Aluminum Alloy Subjected to High Strain-Rate Impact  

NASA Astrophysics Data System (ADS)

The deformation and damage modes associated with the high strain-rate behavior of a high-strength aluminum alloy Al 2139 were analyzed. The microstructure was characterized at different physical scales to determine how the strengthening and toughening mechanisms of the alloy can inhibit and resist failure modes, such as shear localization and bending tensile failure, which occur due to high strain-rate impact. Grain morphology, precipitates (? and ?'), and Mn-bearing dispersed particles and inclusions were characterized by optical microscopy (OM), orientation imaging microscopy (OIM), energy dispersive spectroscopy (EDS), transmission electron microscopy/high-resolution transmission electron microscopy (TEM/HRTEM), selected area diffraction (SAD), and scanning electron microscopy (SEM) investigations of a 38-mm plate impacted by 4340 steel projectiles. Large grain sizes reduce grain boundary (GB) area and allow for more precipitation in the matrix, and these precipitates are shown to play a critical role in the toughening and strengthening of the alloy. Dispersed particles are associated with ductile failure, and inclusions are associated with ductile failure and shear failure. Different deformation modes were observed for the nanoscale precipitates, which affected overall behavior at size scales spanning the nano to the macro.

Lee, W. M.; Zikry, M. A.

2011-05-01

424

Microstructural Characterization of a High-Strength Aluminum Alloy Subjected to High Strain-Rate Impact  

NASA Astrophysics Data System (ADS)

The deformation and damage modes associated with the high strain-rate behavior of a high-strength aluminum alloy Al 2139 were analyzed. The microstructure was characterized at different physical scales to determine how the strengthening and toughening mechanisms of the alloy can inhibit and resist failure modes, such as shear localization and bending tensile failure, which occur due to high strain-rate impact. Grain morphology, precipitates (? and ?'), and Mn-bearing dispersed particles and inclusions were characterized by optical microscopy (OM), orientation imaging microscopy (OIM), energy dispersive spectroscopy (EDS), transmission electron microscopy/high-resolution transmission electron microscopy (TEM/HRTEM), selected area diffraction (SAD), and scanning electron microscopy (SEM) investigations of a 38-mm plate impacted by 4340 steel projectiles. Large grain sizes reduce grain boundary (GB) area and allow for more precipitation in the matrix, and these precipitates are shown to play a critical role in the toughening and strengthening of the alloy. Dispersed particles are associated with ductile failure, and inclusions are associated with ductile failure and shear failure. Different deformation modes were observed for the nanoscale precipitates, which affected overall behavior at size scales spanning the nano to the macro.

Lee, W. M.; Zikry, M. A.

2010-12-01

425

Numerical simulation of plasticity at high strain rate  

SciTech Connect

In numerical simulations of solid dynamics, the total strain rates are calculated from the velocity fields and are input to the constitutive laws. For an elastic-plastic material, the strain rate for a computational cycle may cause the elastic stress to exceed the specified yield surface. This implies that the stress path must move along the yield surface, and some of the strain is realized as plastic (irreversible) strain. The usual numerical method of integrating the elastic-plastic stress-strain relations is a construction procedure due to Wilkins. The virtue of this construction is that it is simple. Sometimes the procedure is inaccurate and leads to incorrect final stress states and plastic strain. In the computer programs, the computational time step is controlled so that the total strain rate can be assumed to be constant over a cycle. With this assumption, it is possible to find a simple yet exact expression for the final stress states for a large variety of yield surfaces. We will derive this expression assuming only that the yield surface does not explicitly depend on the deviator stresses themselves. A numerical program is used to compare the results of Wilkins' construction with new results for particular strain paths. 5 refs., 4 figs.

Margolin, L. (Los Alamos National Lab., NM (USA)); Flower, E.C. (Lawrence Livermore National Lab., CA (USA))

1991-01-01

426

High-rate multiuser communications in shallow water.  

PubMed

Passive multiuser communications in shallow water previously was demonstrated in the 3-4 kHz band using a time reversal approach. This paper extends those experimental results in three respects. First, a larger bandwidth at higher frequency (11-19 kHz) is employed allowing for the use of various symbol rates (or bandwidths). Second, two different shaping pulses are examined: a raised cosine filter and LFM (linear frequency modulation) chirp. Third, the adaptive time reversal approach with spatial nulling is applied to suppress the crosstalk among users. It is shown that the use of a larger bandwidth is beneficial along with the time reversal receiver which can handle significant intersymbol interference with minimal computational complexity. In addition, adding each user degrades the performance by about 4 dB for the benefit of linear increase in data rate. It is demonstrated that an aggregate data rate of 60 kbits/s can be achieved with a 7.5 kHz bandwidth (a spectral efficiency of 8 bits/s?Hz) by three users distributed over 4.2-m depth at a 2.2 km range in shallow water using 16-QAM (quadrature amplitude modulation). PMID:21110587

Song, H C; Kim, J S; Hodgkiss, W S; Kuperman, W A; Stevenson, M

2010-11-01

427

Wear processes in rocks at slow to high slip rates  

NASA Astrophysics Data System (ADS)

Frictional wear experiments are performed on diorite, granite and sandstone at sliding velocities of 0.004-0.27 m/s under normal stresses of 0.21-6.3 MPa using a rotary-shear apparatus, to establish velocity-dependent wear laws of rocks and to determine the partition of frictional work used for gouge generation. Power-laws between normal/shear stresses and steady-state wear rate, defined as (thickness of gouge formed)/(fault displacement), account for our data for diorite and granite at low velocities and most experimental data on wear of rocks reported in the literature. But an exponential law holds for wear of diorite at velocities greater than 0.11 m/s and its wear rate increases dramatically at seismic slip rates. A change from the power-law to the exponential law seems to be caused by frictional heating and thermal fracturing. Both power and exponential laws can describe data for granite. Sandstones exhibit complex wear behavior possibly due to development of shiny slickenside surface that suppresses wear. Our data for diorite indicate that, at the investigated normal stresses, only 0.004% of frictional work is consumed for gouge formation at velocities less than 0.11 m/s, but this fraction increases markedly with increasing velocity. Energy partition for gouge formation is not constant and changes with velocity during earthquakes.

Hirose, Takehiro; Mizoguchi, Kauzo; Shimamoto, Toshihiko

2012-05-01