Sample records for high reproductive rates

  1. High rates of pregnancy loss by subordinates leads to high reproductive skew in wild golden lion tamarins (Leontopithecus rosalia)

    PubMed Central

    Henry, MaLinda D.; Hankerson, Sarah J.; Siani, Jennifer M.; French, Jeffrey A.; Dietz, James M.

    2013-01-01

    Across taxa, cooperative breeding has been associated with high reproductive skew. Cooperatively breeding golden lion tamarins (Leontopithecus rosalia) were long thought to have a monogynous mating system in which reproduction was limited to a single dominant female. Subordinates with few reproductive opportunities delayed dispersal and remained in the natal group to provide alloparental care to siblings, thus allowing dominant reproductive females to meet the energetic needs associated with high rates of reproduction and successful infant rearing. The goal of this study was to re-assess monogyny in wild golden lion tamarin groups based upon pregnancy diagnoses that used non-invasive enzyme immunoassay for progesterone and cortisol, combined with weekly data on individual weight gain, bi-annual physical examinations noting pregnancy and lactation status and daily behavioral observations. We established quantitative and qualitative criteria to detect and determine the timing of pregnancies that did not result in the birth of infants. Pregnancy polygyny occurred in 83% of golden lion tamarin groups studied. The loss of 64% of subordinate pregnancies compared to only 15% by dominant females limited reproductive success mainly to dominant females, thus maintaining high reproductive skew in female golden lion tamarins. Pregnancy loss by subordinate adults did not appear to result from dominant interference in subordinate hormonal mechanisms, but more likely resulted from subordinate abandonment of newborn infants to mitigate dominant aggression. PMID:23454002

  2. Reproductive rates in schizophrenic outpatients.

    PubMed

    Nanko, S; Moridaira, J

    1993-06-01

    We investigated the marriage rates, the reproductive rates and the marital reproductivity of schizophrenic outpatients in Japan. A total of 553 patients with DSM-III-R-diagnosed schizophrenia at the Teikyo University Hospital, Tokyo, Japan were compared with age- and sex-matched outpatients at surgical clinics of the same hospital. Our findings indicate that the reproductivity of schizophrenics is reduced, even though the sample consists of outpatient population and modern operational diagnostic criteria have been used. The marriage rate and reproductive rate of the schizophrenics were reduced, especially in men. The number of married men was significantly less than that of married women and the reduced marital reproductivity was found in women but not men. These findings indicate that the reduced reproductivity of men in accounted for largely by a reduced rate of marriage, and that in women is accounted for partly by lower rate of reproductivity within marriage. PMID:8356891

  3. Reproductive investment and somatic growth rates in longear sunfish

    Microsoft Academic Search

    Martin J. Jennings; David P. Philipp

    1992-01-01

    Synopsis Allocation of energy to current reproduction at the expense of other functions, such as growth, can limit future reproductive potential. This cost of reproduction is a central concept of life history theory but has been difficult to verify in comparative field studies. Three levels of comparison of growth rates and reproductive investments were evaluated within and among populations of

  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

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

    2006-01-01

    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

  5. The evolutionary significance of latent reproductive rate in a long-lived vertebrate.

    PubMed

    Cam, Emmanuelle

    2014-09-01

    Kittiwake (Rissa tridactyla) feeding a chick, 4 July 2014, Brittany, France. Chambert, >T., Rotella, J.J. & Garrott, R.A. (2014) An evolutionary perspective on reproductive individual heterogeneity in a marine vertebrate. Journal of Animal Ecology, 83, 1158-1168. Chambert, Rotella & Garrott () used long-term data to assess the evolutionary significance of individual latent reproductive rate in female Weddell seals. Latent reproductive rates capture the differences among individuals in terms of their propensity to breed; they are conceptual and mathematical constructs. Neither recruitment probability nor age of first breeding of daughters was related to the mother's latent reproductive rate, but there was evidence of a weak positive relationship between the latent reproductive rates of mothers and daughters, suggesting some degree of heritability in this trait. Females with a high latent reproductive rate were expected to produce 2·0 times as many recruited females and 2·1 times as many grandchildren as females with a low reproductive rate. There was substantial stochastic variation in the number of offspring and grandchildren produced, but the inter-individual variability in female latent reproductive rate may have important fitness consequences. PMID:26050743

  6. Reproductive rate and longevity in the waterstrider, Gerris buenoi LOCKEROWE' AND G. G. E. SCUDDER

    E-print Network

    Sokolowski, Marla

    reproductive rates and long life spans. Negative relationships between reproductive rate and longev- ityNOTES Reproductive rate and longevity in the waterstrider, Gerris buenoi LOCKEROWE' AND G. G. E December 14, 1988 ROWE,L., and SCUDDER,G. G. E. 1990.Reproductive rate and longevity in the waterstrider

  7. Artificial symbiogenesis and differing reproduction rates.

    PubMed

    Bull, Larry

    2010-01-01

    Symbiosis is the phenomenon in which organisms of different species live together in close association. Symbiogenesis is the name given to the process by which symbiotic partners combine and unify. This letter reconsiders previous work using the NKCS model of coevolution to explore symbiogenesis. In particular, the role of different replication rates between the coevolving partners is considered. This is shown to provide a broader scope for the emergence of endosymbioses and subsequent horizontal gene transfers. PMID:19857143

  8. High Rate Digital Demodulator ASIC

    NASA Technical Reports Server (NTRS)

    Ghuman, Parminder; Sheikh, Salman; Koubek, Steve; Hoy, Scott; Gray, Andrew

    1998-01-01

    The architecture of High Rate (600 Mega-bits per second) Digital Demodulator (HRDD) ASIC capable of demodulating BPSK and QPSK modulated data is presented in this paper. The advantages of all-digital processing include increased flexibility and reliability with reduced reproduction costs. Conventional serial digital processing would require high processing rates necessitating a hardware implementation in other than CMOS technology such as Gallium Arsenide (GaAs) which has high cost and power requirements. It is more desirable to use CMOS technology with its lower power requirements and higher gate density. However, digital demodulation of high data rates in CMOS requires parallel algorithms to process the sampled data at a rate lower than the data rate. The parallel processing algorithms described here were developed jointly by NASA's Goddard Space Flight Center (GSFC) and the Jet Propulsion Laboratory (JPL). The resulting all-digital receiver has the capability to demodulate BPSK, QPSK, OQPSK, and DQPSK at data rates in excess of 300 Mega-bits per second (Mbps) per channel. This paper will provide an overview of the parallel architecture and features of the HRDR ASIC. In addition, this paper will provide an over-view of the implementation of the hardware architectures used to create flexibility over conventional high rate analog or hybrid receivers. This flexibility includes a wide range of data rates, modulation schemes, and operating environments. In conclusion it will be shown how this high rate digital demodulator can be used with an off-the-shelf A/D and a flexible analog front end, both of which are numerically computer controlled, to produce a very flexible, low cost high rate digital receiver.

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

    PubMed

    Peña, Silvia C; Pocsidio, Glorina N

    2007-12-01

    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

  10. Human cleavage-stage embryo vitrification is comparable to slow-rate cryopreservation in cycles of assisted reproduction

    PubMed Central

    Capobianco, Clemente; Montanaro, Nadia; Kabili, Genc; Di Matteo, Loredana; Fusco, Enrico; Dale, Brian

    2010-01-01

    Objectives To compare embryo survival, pregnancy and implantation rates after cryopreservation of human cleavage-stage embryos with slow-rate cryopreservation or vitrification. Study design 262 patients, attending for assisted reproduction, were prepared for oocyte retrieval using standard controlled ovarian hyperstimulation protocols. Excess embryos were cryopreserved on day 3 either by vitrification, or slow-rate cryopreservation in a programmable freezer. Cycles of thawing were monitored for thaw efficiency, pregnancy and implantation rates. Results Clinical pregnancy and implantation rates were highly comparable between cycles in which day 3 embryos were thawed either after slow-rate cryopreservation or vitrification. Conclusions These data suggest that vitrification of human embryos during assisted reproduction cycles achieves comparable success rates to fresh cycles and therefore can be applied in the laboratory of assisted reproduction. PMID:20640501

  11. Individual variation in reproductive costs of reproduction: high-quality females always do better.

    PubMed

    Hamel, Sandra; Côté, Steeve D; Gaillard, Jean-Michel; Festa-Bianchet, Marco

    2009-01-01

    1. Although life-history theory predicts substantial costs of reproduction, individuals often show positive correlations among life-history traits, rather than trade-offs. The apparent absence of reproductive costs may result from heterogeneity in individual quality. 2. Using detailed longitudinal data from three contrasted ungulate populations (mountain goats, Oreamnos americanus; bighorn sheep, Ovis canadensis; and roe deer, Capreolus capreolus), we assessed how individual quality affects the probability of detecting a cost of current reproduction on future reproduction for females. We used a composite measure of individual quality based on variations in longevity (all species), success in the last breeding opportunity before death (goats and sheep), adult mass (all species), and social rank (goats only). 3. In all species, high-quality females consistently had a higher probability of reproduction, irrespective of previous reproductive status. In mountain goats, we detected a cost of reproduction only after accounting for differences in individual quality. Only low-quality female goats were less likely to reproduce following years of breeding than of nonbreeding. Offspring survival was lower in bighorn ewes following years of successful breeding than after years when no lamb was produced, but only for low-quality females, suggesting that a cost of reproduction only occurred for low-quality females. 4. Because costs of reproduction differ among females, studies of life-history evolution must account for heterogeneity in individual quality. PMID:18700872

  12. Low Reproductive Rates of Lake Superior Bald Eagles: Low Food Delivery Rates or Environmental Contaminants?

    Microsoft Academic Search

    Cheryl R. Dykstra; Michael W. Meyer; D. Keith Warnke; William H. Karasov; David E. Andersen; William W. Bowerman IV; John P. Giesy

    1998-01-01

    Reproductive rate (productivity) of bald eagles (Haliaeetus leucocephalus) nesting on the shores of Lake Superior was significantly less than that of neighboring eagles nesting in inland Wisconsin (1.0 vs. 1.3 young per breeding attempt, 1989–1993), and at other inland lake\\/riverine habitats in the Great Lakes Basin. It is possible that the current causes of low productivity on Lake Superior might

  13. A Meta-Analysis of the Habitat Carrying Capacity and Maximum Reproductive Rate of Anadromous Alewife in Eastern North America

    Microsoft Academic Search

    A. JAMIE F. G IBSON; RANSOM A. MYERS

    We analyzed the dynamics of eight populations of anadromous alewife Alosa pseudoharengus to determine their habitat carrying capacity, their maximum reproductive rate, and whether depensation occurs at low abundances. When spawner-recruit models are fit to data sets for individual alewife populations, the resulting parameter estimates are often poorly determined, biologically unrealistic, and highly variable among populations. When the spawner and

  14. Latitudinal compensation in female reproductive rate of a geographically widespread reef fish

    Microsoft Academic Search

    Tomoyuki Kokita

    2004-01-01

    Latitudinal variation in fitness-related traits has often been attributed to local adaptation to climates. In poikilotherms including fishes, lower temperatures and shorter reproductive seasons at high latitudes would be expected to cause a reduction in annual reproductive output of an individual. Theories of latitudinal compensation predict that organisms at high latitudes should evolve compensatory responses for these climatic effects. Therefore,

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

    PubMed Central

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

    2013-01-01

    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

  16. Low Reproductive Rate Predicts Species Sensitivity to Habitat Loss: A Meta-Analysis of Wetland Vertebrates

    PubMed Central

    Quesnelle, Pauline E.; Lindsay, Kathryn E.; Fahrig, Lenore

    2014-01-01

    We tested the hypotheses that species with greater mobility and/or higher reproductive rates are less sensitive to habitat loss than species with lower mobility and/or reproductive rates by conducting a meta-analysis of wetland vertebrate responses to wetland habitat loss. We combined data from 90 studies conducted worldwide that quantified the relationship between wetland amount in a landscape and population abundance of at least one wetland species to determine if mobility (indexed as home range size and body length) and annual reproductive rate influence species responses to wetland loss. When analyzed across all taxa, animals with higher reproductive rates were less sensitive to wetland loss. Surprisingly, we did not find an effect of mobility on response to wetland loss. Overall, wetland mammals and birds were more sensitive to wetland loss than were reptiles and amphibians. Our results suggest that dispersal between habitat patches is less important than species’ reproductive rates for population persistence in fragmented landscapes. This implies that immigration and colonization rate is most strongly related to reproduction, which determines the total number of potential colonists. PMID:24651675

  17. Low reproductive rate predicts species sensitivity to habitat loss: a meta-analysis of wetland vertebrates.

    PubMed

    Quesnelle, Pauline E; Lindsay, Kathryn E; Fahrig, Lenore

    2014-01-01

    We tested the hypotheses that species with greater mobility and/or higher reproductive rates are less sensitive to habitat loss than species with lower mobility and/or reproductive rates by conducting a meta-analysis of wetland vertebrate responses to wetland habitat loss. We combined data from 90 studies conducted worldwide that quantified the relationship between wetland amount in a landscape and population abundance of at least one wetland species to determine if mobility (indexed as home range size and body length) and annual reproductive rate influence species responses to wetland loss. When analyzed across all taxa, animals with higher reproductive rates were less sensitive to wetland loss. Surprisingly, we did not find an effect of mobility on response to wetland loss. Overall, wetland mammals and birds were more sensitive to wetland loss than were reptiles and amphibians. Our results suggest that dispersal between habitat patches is less important than species' reproductive rates for population persistence in fragmented landscapes. This implies that immigration and colonization rate is most strongly related to reproduction, which determines the total number of potential colonists. PMID:24651675

  18. High Redshift Supernova Rates

    E-print Network

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

    2004-06-24

    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 where supernova rates have been estimated from observations. The rate of core collapse supernovae can be used as an independent probe of the cosmic star formation rate. Based on the observations of 17 core collapse supernovae, we measure an increase in the core collapse supernova rate by a factor of 1.6 in the range 0.31 compared to low redshift. At higher redshift (z>1), we find a suggested decrease in the type Ia rate with redshift. This evolution of the Ia rate with redshift is consistent with a type Ia progenitor model where there is a substantial delay between the formation of the progenitor star and the explosion of the supernova. Assuming that the type Ia progenitor stars have initial main sequence masses 3-8 M_Sun, we find that 5-7% of the available progenitors explode as type Ia supernovae.

  19. Spatial distribution of oviposition sites determines variance in the reproductive rate of European bitterling ( Rhodeus amarus )

    Microsoft Academic Search

    Miros?aw Przybylski; Martin Reichard; Rowena Spence; Carl Smith

    2007-01-01

    Summary We investigated reproductive rate in relation to oviposition site distribution and quality in the European bitterling, Rhodeus amarus, a freshwater fish that spawns on the gills of living unionid mussels. In a laboratory experiment male bitterling led females to groups of four mussels at a significantly higher rate than single mussels, irrespective of mussel species. Females spawned significantly more

  20. Ram mating behavior after long-term selection for reproductive rate in Rambouillet ewes.

    PubMed

    Stellflug, J N; Berardinelli, J G

    2002-10-01

    Mating behavior is known to be heritable in several species, but it is not known if selection schemes for ewe reproductive traits affect mating behavior of rams. Therefore, our objectives were to determine if divergent (high vs low index) selection of a female reproductive trait (lambs born divided by age of ewe minus one) affects mating behavior patterns of male offspring during training to service an artificial vagina (AV) in a less than natural setting (Exp. 1) or during serving capacity tests (SCT) in simulated natural mating conditions (Exp. 2). The method for evaluating male mating behavior was a series of serving capacity tests to estimate sexual performance. For Exp. 1, five, 30-min observations were conducted to assess the mating behavior of 29 rams (22 mo old) being trained to service an AV. In Exp. 1, percentages of rams mounting (73 vs 36%) and ejaculating (67 vs 29%) differed (P < 0.05) between rams from high and low Rambouillet ewe selection lines, respectively. In Exp. 2, ram classification consisted of exposing each 22- to 24-mo-old ram (n = 48) to three unrestrained ewes in estrus for 18, 30-min tests. Any ram that had not mounted or ejaculated during SCT was evaluated for sexual orientation in a 30-min preference test in which each ram had access to both restrained estrual ewes and restrained rams. In Exp. 2, there was no difference (P > 0.2) in percentages of rams mounting (92 vs 78%) and ejaculating (88 vs 74%) between rams from high and low Rambouillet ewe selection lines, respectively. There was no difference (P > 0.33) between high and low ewe selection line rams for mounts or ejaculations for 18 SCT. Only one male-oriented ram was identified, which was from the high line. In Exp. 2, six SCT were necessary to obtain 95% reliability in sexual performance scores. Results of these studies indicate that long-term selection of ewes for litter size did not alter ram sexual performance after SCT under simulated natural mating conditions or affect incidence of male-oriented rams. Mating behavior observed during training to service an AV was lower for rams from ewes of the low selection line than for rams from ewes of the high selection line. We concluded that long-term selection for reproductive rate in ewes did not alter mating behavior patterns of male offspring; however, test conditions, such as restrained and unrestrained ewes and number of serving capacity tests, may affect conclusions in studies that evaluate sexual performance of rams. PMID:12413080

  1. Basic Reproductive Rate of a Spatial Epidemic Model Using Computer Algebra Software

    Microsoft Academic Search

    Doracelly Hincapie; Juan Ospina

    2005-01-01

    Phone: (57) 4-311-21-66 Abstract? ? ? ? The use of computer algebra software has many applications in diverse fields like epidemiology. This work pretends to show how computer algebra software applications for symbolic computation have a very promissory future in mathematical epidemiology with a concrete problem of this kind. In this case; the basic reproductive rate, corresponding to the propagation

  2. Human Disturbance Influences Reproductive Success and Growth Rate in California Sea Lions (Zalophus californianus)

    PubMed Central

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

    2011-01-01

    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

  3. Cyclic variations in nitrogen uptake rate in soybean plants: uptake during reproductive growth

    NASA Technical Reports Server (NTRS)

    Vessey, J. K.; Raper, C. D. Jr; Henry, L. T.; Raper CD, J. r. (Principal Investigator)

    1990-01-01

    Net uptake of NO3- by non-nodulated soybean plants [Glycine max (L.) Merr. cv. Ransom] growing in flowing hydroponic culture was measured daily during a 63 d period of reproductive development between the first florally inductive photoperiod and [unknown word] seed growth. Removal of NO3- from a replenished solution containing 1.0 mol m-3 NO3- was determined by ion chromatography. Uptake of NO3- continued throughout reproductive development. The net uptake rate of NO3- cycled between maxima and minima with a periodicity of oscillation of 3 to 7 d during the floral stage and about 6 d during the fruiting stage. Coupled with increasing concentrations of carbon and C : N ratios in tissues, the oscillations in net uptake rates of NO3- are evidence that the demand for carbohydrate by reproductive organs is contingent on the availability of nitrogen in the shoot pool rather than that the demand for nitrogen follows the flux of carbohydrate into reproductive tissues.

  4. High-rate artificial lift

    SciTech Connect

    Clegg, J.D.

    1988-03-01

    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.

  5. High Data Rate Instrument Study

    NASA Technical Reports Server (NTRS)

    Schober, Wayne; Lansing, Faiza; Wilson, Keith; Webb, Evan

    1999-01-01

    The High Data Rate Instrument Study was a joint effort between the Jet Propulsion Laboratory (JPL) and the Goddard Space Flight Center (GSFC). The objectives were to assess the characteristics of future high data rate Earth observing science instruments and then to assess the feasibility of developing data processing systems and communications systems required to meet those data rates. Instruments and technology were assessed for technology readiness dates of 2000, 2003, and 2006. The highest data rate instruments are hyperspectral and synthetic aperture radar instruments which are capable of generating 3.2 Gigabits per second (Gbps) and 1.3 Gbps, respectively, with a technology readiness date of 2003. These instruments would require storage of 16.2 Terebits (Tb) of information (RF communications case of two orbits of data) or 40.5 Tb of information (optical communications case of five orbits of data) with a technology readiness date of 2003. Onboard storage capability in 2003 is estimated at 4 Tb; therefore, all the data created cannot be stored without processing or compression. Of the 4 Tb of stored data, RF communications can only send about one third of the data to the ground, while optical communications is estimated at 6.4 Tb across all three technology readiness dates of 2000, 2003, and 2006 which were used in the study. The study includes analysis of the onboard processing and communications technologies at these three dates and potential systems to meet the high data rate requirements. In the 2003 case, 7.8% of the data can be stored and downlinked by RF communications while 10% of the data can be stored and downlinked with optical communications. The study conclusion is that only 1 to 10% of the data generated by high data rate instruments will be sent to the ground from now through 2006 unless revolutionary changes in spacecraft design and operations such as intelligent data extraction are developed.

  6. Reproductive ecology of tree swallows (Tachycineta bicolor) with high levels of polychlorinated biphenyl contamination

    SciTech Connect

    McCarty, J.P.; Secord, A.L.

    1999-07-01

    Tree swallows(Tachycineta bicolor) breeding along the Hudson River forage extensively on PCB-contaminated insects that emerge from the river. The authors studied the reproductive ecology and behavior of tree swallows breeding at several sites along the Hudson River. Related work has shown that PCB levels in both eggs and chicks were among the highest ever reported in this species, with concentrations comparable to those found in aquatic organisms in the Hudson River. In 1994, reproductive success at PCB-contaminated sites was significantly impaired relative to other sites in New York. Reduced reproductive success was largely due to high levels of nest abandonment during incubation and reduced hatchability of eggs. In 1995, reproductive output was normal, but higher than expected rates of abandonment and supernormal clutches persisted. Growth and development of nestlings was not significantly impaired. Given the levels of contamination in this population, the success of most Hudson River tree swallows reinforces the importance of understanding interspecific differences in the effects of contaminants.

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

    Microsoft Academic Search

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

    2005-01-01

    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

  8. Influence of acupuncture on the pregnancy rate in patients who undergo assisted reproduction therapy

    Microsoft Academic Search

    Wolfgang E. Paulus; Mingmin Zhang; Erwin Strehler; Imam El-Danasouri; Karl Sterzik

    2002-01-01

    Objective: To evaluate the effect of acupuncture on the pregnancy rate in assisted reproduction therapy (ART) by comparing a group of patients receiving acupuncture treatment shortly before and after embryo transfer with a control group receiving no acupuncture.Design: Prospective randomized study.Setting: Fertility center.Patient(s): After giving informed consent, 160 patients who were undergoing ART and who had good quality embryos were

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

    Microsoft Academic Search

    Nicolas Bacaër

    2009-01-01

    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

  10. Honeybees enhance reproduction without affecting the outcrossing rate in endemic Pedicularis densispica (Orobanchaceae).

    PubMed

    Xia, J; Sun, S G; Guo, Y H

    2007-11-01

    There has been substantial debate in recent years surrounding the impact of introduced honeybees on native biota. This study reports on an investigation of Pedicularis densispica, a subalpine annual herb endemic to Southwest China, in an attempt to determine the impact of introduced domestic honeybees on pollen dispersal and thus on their reproductive success and mating system. Honeybees were introduced into the study site in 2004, and a sudden seasonal pollinator shift from bumblebees to honeybees was observed. Intra- and inter-plant visits by different pollinators were recorded in the field in 2003 and 2004. Fruit and seed sets prior to and after the pollinator shift were measured. Experimental pollinations were performed to characterize the breeding system. Outcrossing rates at the seed stage were estimated for both years using RAPD markers. Our results indicated that honeybees foraged between plants more frequently than bumblebees did. Our results also revealed that the introduction of honeybees significantly enhanced reproductive success. However, no significant difference was detected between the outcrossing rates due to bumblebee and honeybee pollination. P. densispica was almost completely outcrossing ( T(m) = 0.956 and 0.967, respectively in 2003 and 2004) but partially self-compatible. This study presents the first report of the outcrossing rate in the genus pedicularis and reveals a limited influence of pollination on the mating system in P. densispica. The pollinator shift did not reduce reproductive success of the plants and honeybees may be used to augment pollinator services for nectariferous P. densispica. PMID:17891702

  11. Individual variation in reproductive costs of reproduction: high-quality females always do better

    Microsoft Academic Search

    Sandra Hamel; Steeve D. Côté; Jean-Michel Gaillard; Marco Festa-Bianchet

    2009-01-01

    Summary 1. Although life-history theory predicts substantial costs of reproduction, individuals often show positive correlations among life-history traits, rather than trade-offs. The apparent absence of reproductive costs may result from heterogeneity in individual quality. 2. Using detailed longitudinal data from three contrasted ungulate populations (mountain goats, Oreamnos americanus ; bighorn sheep, Ovis canadensis ; and roe deer, Capreolus capreolus ),

  12. Cytoplasmically Inherited Reproductive Incompatibility in Tribolium Flour Beetles: The Rate of Spread and Effect on Population Size

    PubMed Central

    Stevens, L.; Wade, M. J.

    1990-01-01

    This paper reports on the effects of a cytoplasmically inherited reproductive incompatibility in different genetic strains of the flour beetle, Tribolium confusum. We measured the rate of spread and the effect of host population size using different initial frequencies of infection with a cytoplasmic factor that mediates reproductive incompatibility. There were two experiments, in one the infected and uninfected lines were from the same genetic strain, b-Yugoslavia. In the other, the infected line was from the ``high cannibalism'' bIV strain and the uninfected line from the ``low cannibalism'' bI strain. We estimate that the fitness ratio of infected to uninfected in b-Yugoslavia is 0.63 and the observed rate of spread for this strain corresponds to a model of cytoplasmic inheritance that takes into account the productivity differences between the infected and cured lines. In the bI-bIV experiment, because the uninfected and infected lines are from different genetic strains, we cannot partition the effects of the cytoplasmic factor from other factors. The rate of spread in the bI-bIV experiment is faster in males and slower in females than predicted from a model of cytoplasmic inheritance. In both experiments, productivity varies with initial infection frequency; however, the relationship is not explained by a simple model that predicts lower population size at intermediate infection frequencies. PMID:2307358

  13. A new method for calculating net reproductive rate from graph reduction with applications to the control of invasive species

    Microsoft Academic Search

    T. de-Camino-Beck; M. A. Lewis

    2007-01-01

    Matrix models are widely used for demographic analysis of age and stage\\u000a structured biological populations. Dynamic properties of the model can\\u000a be summarized by the net reproductive rate R (0). In this paper, we\\u000a introduce a new method to calculate and analyze the net reproductive\\u000a rate directly from the life cycle graph of the matrix. We show, with\\u000a examples, how

  14. Epidemic growth rate and household reproduction number in communities of households, schools and workplaces

    PubMed Central

    Pellis, Lorenzo; Ferguson, Neil M.; Fraser, Christophe

    2013-01-01

    In this paper we present a novel and coherent modelling framework for the characterisation of the real-time growth rate in SIR models of epidemic spread in populations with social structures of increasing complexity. Known results about homogeneous mixing and multitype models are included in the framework, which is then extended to models with households and models with households and schools/workplaces. Efficient methods for the exact computation of the real-time growth rate are presented for the standard SIR model with constant infection and recovery rates (Markovian case). Approximate methods are described for a large class of models with time-varying infection rates (non-Markovian case). The quality of the approximation is assessed via comparison with results from individual-based stochastic simulations. The methodology is then applied to the case of influenza in models with households and schools/workplaces, to provide an estimate of a household-to-household reproduction number and thus asses the effort required to prevent an outbreak by targeting control policies at the level of households. The results highlight the risk of underestimating such effort when the additional presence of schools/workplaces is neglected. Our framework increases the applicability of models of epidemic spread in socially structured population by linking earlier theoretical results, mainly focused on time-independent key epidemiological parameters (e.g. reproduction numbers, critical vaccination coverage, epidemic final size) to new results on the epidemic dynamics. PMID:21120484

  15. Appendicularian ecophysiology I: Food concentration dependent clearance rate, assimilation efficiency, growth and reproduction of Oikopleura dioica

    NASA Astrophysics Data System (ADS)

    Lombard, Fabien; Renaud, Florent; Sainsbury, Christopher; Sciandra, Antoine; Gorsky, Gabriel

    2009-11-01

    Three aspects of the appendicularian O. dioica' s ecophysiology were measured here: 1) morphological parameters over a wide range of appendicularian sizes, including mature animals in order to document the morphological characteristics inducing reproduction; 2) clearance rate and assimilation efficiency using feeding incubations with different algal concentrations and 3) the effect of food concentration on growth, mortality and reproduction. The relationship between the body carbon weight and the clearance rate follows a power function, with an exponent of 0.91 (± 0.07). The rate of particles retention increases with the food concentration following a Michaelis-Menten relationship (half-saturation constant = 151 ± 22 µg C l - 1 , maximum clearance rate = 12 ± 1 µg C µg C - 1 d - 1 ). The carbon assimilation efficiency decreases with the increasing food concentration. As a result, appendicularian growth which is limited in concentrations lower than 50 µg C l - 1 is saturated above 100 µg C l - 1 . In immature animals the gonad represents less than 30% of the body volume whereas in mature individuals, its volume varies between 50% and 87% (mean 63%) suggesting that gonad/total volume ratio can be used as indicator of the maturation stages. The gonad weight in mature animals represents 70.3 (± 4.6)% of the total body carbon weight. Two major maturity stages can explain the changes in energy allocation: i) the somatic growth, when less energy is invested in gonad growth when compared to the rest of the body and ii) the maturation phase where most of the assimilated matter is invested in gonad maturation. This process is rapid, lasting only few hours. For this reason we measured completely mature organisms that are generally not measured during the experimental work with appendicularians. In food-limited conditions, the gonad maturation process starts with smaller individuals and ends with smaller reproductive animals having the same gonad to total volume ratio than in unlimited food conditions. The results obtained in this study were used to model the life cycle of O. dioica (see Lombard, F., Sciandra, A. and Gorsky, G., 2009-this volume. Appendicularian ecophysiology. II. Modeling nutrition, metabolism, growth and reproduction of the appendicularian Oikopleura dioica.).

  16. High Resolution, High Frame Rate Video Technology

    NASA Technical Reports Server (NTRS)

    1990-01-01

    Papers and working group summaries presented at the High Resolution, High Frame Rate Video (HHV) Workshop are compiled. HHV system is intended for future use on the Space Shuttle and Space Station Freedom. The Workshop was held for the dual purpose of: (1) allowing potential scientific users to assess the utility of the proposed system for monitoring microgravity science experiments; and (2) letting technical experts from industry recommend improvements to the proposed near-term HHV system. The following topics are covered: (1) State of the art in the video system performance; (2) Development plan for the HHV system; (3) Advanced technology for image gathering, coding, and processing; (4) Data compression applied to HHV; (5) Data transmission networks; and (6) Results of the users' requirements survey conducted by NASA.

  17. Relationship between body size, provisioning rate, longevity and reproductive success in females of the solitary bee Osmia cornuta

    Microsoft Academic Search

    Jordi Bosch; Narcís Vicens

    2006-01-01

    Body size has often been related to reproductive success in bees and wasps. The objective of this 3-year study was to analyze\\u000a the relationship between nesting female body size, provisioning rate and longevity and their effect on several traits related\\u000a to parental investment and reproductive success in the solitary bee Osmia cornuta. Body size was not correlated to longevity, and

  18. 1995 Assisted Reproductive Technology Success Rates: National Summary and Fertility Clinic Reports

    NSDL National Science Digital Library

    The first national guide to information on the success rate of 281 fertility clinics around the country resides at this site. Issued by the US Centers for Disease Control, the full text of the report offers a clinic-by-clinic guide to summary statistics on the success of numerous methods of assisted reproductive technology (ART) including a variety of in vitro techniques. Based on 59,142 treatments that resulted in 11,315 live births in 1995, the report contains information on percentages of multiple births, information about the diagnoses of patients and age-specific success rates. This report is a response to a 1992 Congressional measure requiring the CDC to publish fertility clinic statistics for consumers.

  19. The effect of stocking rate and calving date on reproductive performance, body state, and metabolic and health parameters of Holstein-Friesian dairy cows.

    PubMed

    McCarthy, B; Pierce, K M; Delaby, L; Brennan, A; Horan, B

    2012-03-01

    Two groups of Holstein-Friesian dairy cows with different mean calving dates (CD) were established from within the existing research herd at Moorepark (Teagasc, Ireland). Animals were assigned to either an early calving (mean CD February 12) treatment or a late calving (mean CD February 25) treatment. Animals within each CD treatment were randomly allocated to 1 of 3 stocking rate (SR) treatments, low (2.51 cows/ha), medium (2.92 cows/ha), or high (3.28 cows/ha), which were designed to represent 3 alternative whole-farm SR in a spring-calving, grass-based milk production system following abolition of the European Union milk quotas. A total of 138 spring-calving dairy cows, comprising 2 strains of Holstein-Friesian, North American (NA) and New Zealand (NZ), were used in each year (2009 and 2010). The effects of CD, SR treatment, genetic strain, and their interactions on reproductive performance, body weight, body condition score, blood metabolites, hormone and immunological parameters, and health status were analyzed. Stocking rate and CD had no effect on pregnancy rates, immunological parameters, or health status, although a tendency was observed for more reproductive intervention as SR increased. Earlier calving and increased SR also resulted in reduced body weight, body condition score, and metabolic status in early lactation. Strain of Holstein-Friesian also affected reproductive performance. The NZ strain tended to have a higher submission rate and 42 d pregnancy rate compared with the NA strain, and a strain by SR interaction was observed for pregnancy rate to first service. Earlier calving and increased SR can be achieved without adverse effects on overall pregnancy rates. The existence of a SR by strain interaction for several reproductive variables suggests that the smaller NZ strain is better adapted to increased SR systems. PMID:22365215

  20. An Optimal Tone Reproduction Curve Operator for the Display of High Dynamic Range Images

    E-print Network

    Aickelin, Uwe

    An Optimal Tone Reproduction Curve Operator for the Display of High Dynamic Range Images Guoping and digital imaging are to develop systems that match or maybe even exceed the capabilities of the human adaptation. Ordinary imaging sensors and reproduction media typically have dynamic ranges spanning a few

  1. Research article Breeding system and reproductive skew in a highly polygynous ant population

    E-print Network

    Alvarez, Nadir

    Research article Breeding system and reproductive skew in a highly polygynous ant population C determinants of nest kin structure, we conducted a detailed analysis of the breeding system of the ant Formica a sub-sample of queens to assess their reproductive status. We also used microsatellites to estimate

  2. Reproductive loss in high-producing dairy cattle: where will it end?

    PubMed

    Lucy, M C

    2001-06-01

    The dairy industry in the United States has changed dramatically in the last decade. Milk production per cow has increased steadily because of a combination of improved management, better nutrition, and intense genetic selection. Dairy farms are larger, and nearly 30% of the dairy cows in the United States are on farms with 500 or more cows. The shift toward more productive cows and larger herds is associated with a decrease in reproductive efficiency. Cows with the greatest milk production have the highest incidence of infertility, but epidemiological studies suggest that, in addition to milk production, other factors are probably decreasing reproductive efficiency in our dairy herds. The reproductive physiology of dairy cows has changed over the past 50 yr, and physiological adaptations to high milk production may explain part of the reproductive decline. Critical areas for new research include control of the estrous cycle, metabolic effects of lactation on reproduction, mechanisms linking disease to reproduction, and early embryonic mortality. Solving reproductive loss in dairy cows will not be easy because only a small number of research groups study reproduction in postpartum dairy cows. Therefore, the present research base will need to be expanded. For this to occur, research funding must be increased above its current level and a renewed emphasis must be placed on solving the emerging crisis of infertility in dairy cows. PMID:11417685

  3. Cumulative live birth rate and assisted reproduction: impact of female age and transfer day

    PubMed Central

    Abuzeid, M.I.; Bolonduro, O.; La Chance, J.; Abozaid, T.; Urich, M.; Ullah, K.; Ali, T.; Ashraf, M.; Khan, I.

    2014-01-01

    Background: Many studies on assisted reproductive technology examine live birth rate per cycle. However, after a cycle fails, couples often want to know what their chances are of having a live birth if they continue treatment. From a patients’ perspective, the cumulative probability of live birth is more informative. Materials and Methods: This study includes patients who underwent fresh, frozen and non-donor ICSI cycles at our IVF unit between 2006-2012. Patients were divided into two groups; Group 1 represented those who underwent only Day 5 transfers, Group 2 represented only Day 3 transfers. Patients who underwent both were excluded. ­Cycles were analyzed until the first live birth or the end of the 3rd cycle. Using Kaplan-Meier analysis, we estimated the cumulative live birth rates for each group and according to female age. Results: The mean age for Group 1 was significantly lower than for Group 2. After 3 cycles, Group 1’s CLBR was 79% versus 66% in Group 2. When analyzing the live births by age and group, there was a significant difference in the CLBR after 3 cycles with the women less than 35 years having the highest CLBR and the women 40 years or older having the lowest CLBR. Conclusion: In women less than 35 years, excellent CLBR can be achieved irrespective of the transfer day. For women 40 years and above, better results of CLBR are observed with Day 5 transfers. Our findings may impact the counseling of couples considering IVF treatment. PMID:25374657

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

    PubMed

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

    2012-08-01

    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 (<25% of pregnancies for the total number of AI), abortion (>18% abortions) and a positive polymerase chain reaction test for Coxiella burnetii in the bulk tank milk with an excretion higher than 10(4)Coxiella /ml for all three herds. Antibodies against C. burnetii were detected in 50.2% of the 781 parous cows analyzed. Coxiella seropositivity was linked to placenta retention, to changes in the interval from parturition to conception (with the lowest interval parturition-conception for cows with low level of seropositivity), early pregnancy (cows becoming pregnant before Day 90 postpartum) and maintenance of gestation during the early fetal period, while it failed to affect rates of abortion after Day 90 of gestation or stillbirth. PMID:21862091

  5. REPRODUCTION AND GROWTH IN A PRECOCIAL SMALL MAMMAL, CAVIA MAGNA

    Microsoft Academic Search

    Cornelia Kraus; Fritz Trillmich; Joachim Künkele

    2005-01-01

    Small mammals usually produce large litters of altricial young, resulting in high reproductive rates. In contrast, cavies give birth to few precocial young after a long gestation. The price of this reproductive strategy is a low intrinsic rate of natural increase. We investigated if the patterns of reproduction in a wild population of Cavia magna are consistent with the hypotheses

  6. Granular Couette Flow at High Shear Rates

    NASA Astrophysics Data System (ADS)

    Voth, Greg; Sundquist, Jamie; Gollub, Jerry

    2002-11-01

    We present an experimental study of couette flow of granular material at very high shear rates. Wall velocities up to 9.4 m/s and shear rates up to 2400 s-1 (based on a shear band that is 4 particle diameters thick) are achieved. We find a surprising non-monotonic dependence of the torque on the shear rate. This effect shows large variability even when the obvious variables such as temperature, humidity and preparation history are controlled. We interpret the variability as arising from particle wear that changes the frictional interactions that dominate the torque at lower shear rates. At very high shear rates, the torque increases monotonically with shear rate and is quite reproducible. We interpret this behavior as reflecting collisional dynamics at high shear rates. Non-dimensional parameters that control the change from friction dominated to collision dominated interactions will be discussed. (Work supported by NSF Division of Materials Research)

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

    Microsoft Academic Search

    Gregory S. Moehrlin; Steven A. Juliano

    1998-01-01

    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

  8. High-rate lithium thionyl chloride cells

    NASA Technical Reports Server (NTRS)

    Goebel, F.

    1982-01-01

    A high-rate C cell with disc electrodes was developed to demonstrate current rates which are comparable to other primary systems. The tests performed established the limits of abuse beyond which the cell becomes hazardous. Tests include: impact, shock, and vibration tests; temperature cycling; and salt water immersion of fresh cells.

  9. High-rate lithium thionyl chloride cells

    NASA Astrophysics Data System (ADS)

    Goebel, F.

    1982-03-01

    A high-rate C cell with disc electrodes was developed to demonstrate current rates which are comparable to other primary systems. The tests performed established the limits of abuse beyond which the cell becomes hazardous. Tests include: impact, shock, and vibration tests; temperature cycling; and salt water immersion of fresh cells.

  10. 2005 Texas High Plains Cotton Variety Ratings

    E-print Network

    Mukhtar, Saqib

    2005 Texas High Plains Cotton Variety Ratings for Verticillium Wilt Dr. Terry Wheeler Research ($) (Loan value x yield) ­ seed + tech fees/acre % Plants with wilt on Aug. 25 (rank) Paymaster 2167RR 909

  11. Effect of Stocking Rate on Pasture Production, Milk Production, and Reproduction of Dairy Cows in Pasture-Based Systems

    Microsoft Academic Search

    K. A. Macdonald; J. W. Penno; J. A. S. Lancaster; J. R. Roche

    2008-01-01

    Ninety-four cows were randomly allocated to 1 of 5 stocking rates (2.2, 2.7, 3.1, 3.7, and 4.3 cows\\/ha) in a completely randomized design for 3 years. Herds were seasonal calving, with only minor differences in grazing management to optimize the profitability of each stock- ingrate(SR).Pastureproductionandqualitydata,milk and milk component data, and reproduction data were collected, averaged for SR treatment, and linear

  12. Hard times in the city – attractive nest sites but insufficient food supply lead to low reproduction rates in a bird of prey

    PubMed Central

    2014-01-01

    Introduction Urbanization is a global phenomenon that is encroaching on natural habitats and decreasing biodiversity, although it is creating new habitats for some species. The Eurasian kestrel (Falco tinnunculus) is frequently associated with urbanized landscapes but it is unclear what lies behind the high densities of kestrels in the urban environment. Results Occupied nest sites in the city of Vienna, Austria were investigated along a gradient of urbanization (percentage of land covered by buildings or used by traffic). Field surveys determined the abundance of potential prey (birds and rodents) and the results were compared to the birds’ diets. A number of breeding parameters were recorded over the course of three years. The majority of kestrels breed in semi-natural cavities in historic buildings. Nearest neighbour distances (NND) were smallest and reproductive success lowest in the city centre. Abundance of potential prey was not found to relate to the degree of urbanization but there was a significant shift in the birds’ diets from a heavy reliance on rodents in the outskirts of the city to feeding more on small birds in the centre. The use of urban habitats was associated with higher nest failure, partly associated with predation and nest desertion, and with significantly lower hatching rates and smaller fledged broods. Conclusions High breeding densities in urban habitats do not necessarily correlate with high habitat quality. The high density of kestrel nests in the city centre is probably due to the ready availability of breeding cavities. Highly urbanized areas in Vienna are associated with unexpected costs for the city dwelling-raptor, in terms both of prey availability and of reproductive success. The kestrel appears to be exploiting the urban environment but given the poor reproductive performance of urban kestrels it is likely that the species is falling into an ecological trap. PMID:24872836

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

    PubMed

    Vitzthum, Virginia J

    2013-01-01

    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. PMID:23382088

  14. THE INFLUENCE OF MODEL TIME STEP ON THE RELATIVE SENSITIVIY OF POPULATION GROWTH RATE TO REPRODUCTION

    EPA Science Inventory

    In recent years there has been an increasing interest in using population models in environmental assessments. Matrix population models represent a valuable tool for extrapolating from life stage-specific stressor effects on survival and reproduction to effects on finite populati...

  15. High rate, high reliability Li/SO2 cells

    NASA Technical Reports Server (NTRS)

    Chireau, R.

    1982-01-01

    The use of the lithium/sulfur dioxide system for aerospace applications is discussed. The high rate density in the system is compared to some primary systems: mercury zinc, silver zinc, and magnesium oxide. Estimates are provided of the storage life and shelf life of typical lithium sulfur batteries. The design of lithium cells is presented and criteria are given for improving the output of cells in order to achieve high rate and high reliability.

  16. High Bit Rate Experiments Over ACTS

    NASA Technical Reports Server (NTRS)

    Bergman, Larry A.; Gary, J. Patrick; Edelsen, Burt; Helm, Neil; Cohen, Judith; Shopbell, Patrick; Mechoso, C. Roberto; Chung-Chun; Farrara, M.; Spahr, Joseph

    1996-01-01

    This paper describes two high data rate experiments chat are being developed for the gigabit NASA Advanced Communications Technology Satellite (ACTS). The first is a telescience experiment that remotely acquires image data at the Keck telescope from the Caltech campus. The second is a distributed global climate application that is run between two supercomputer centers interconnected by ACTS. The implementation approach for each is described along with the expected results. Also. the ACTS high data rate (HDR) ground station is also described in detail.

  17. 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...

  18. The career trajectory of a Black male high school basketball player: A social reproduction perspective

    Microsoft Academic Search

    John N Singer; Reuben A Buford May

    2011-01-01

    Interscholastic sport in the United States is a social institution within which the social relationships and attitudes needed to sustain the existing dominant economic and class relations of the larger society could be perpetuated or reproduced. This single case study allowed us to explore the question of social reproduction by examining the nuances of how a young Black male high

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

    PubMed

    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

    2008-06-01

    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

  20. Understanding High School Graduation Rates in Alabama

    ERIC Educational Resources Information Center

    Alliance for Excellent Education, 2009

    2009-01-01

    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 the…

  1. Baltimore District Tackles High Suspension Rates

    ERIC Educational Resources Information Center

    Maxwell, Lesli A.

    2007-01-01

    This article reports on how the Baltimore District tackles its high suspension rates. Driven by an increasing belief that zero-tolerance disciplinary policies are ineffective, more educators are embracing strategies that do not exclude misbehaving students from school for offenses such as insubordination, disrespect, cutting class, tardiness, and…

  2. Role of high shear rate in thrombosis.

    PubMed

    Casa, Lauren D C; Deaton, David H; Ku, David N

    2015-04-01

    Acute arterial occlusions occur in high shear rate hemodynamic conditions. Arterial thrombi are platelet-rich when examined histologically compared with red blood cells in venous thrombi. Prior studies of platelet biology were not capable of accounting for the rapid kinetics and bond strengths necessary to produce occlusive thrombus under these conditions where the stasis condition of the Virchow triad is so noticeably absent. Recent experiments elucidate the unique pathway and kinetics of platelet aggregation that produce arterial occlusion. Large thrombi form from local release and conformational changes in von Willebrand factor under very high shear rates. The effect of high shear hemodynamics on thrombus growth has profound implications for the understanding of all acute thrombotic cardiovascular events as well as for vascular reconstructive techniques and vascular device design, testing, and clinical performance. PMID:25704412

  3. Reproductive Biology of RareReproductive Biology of Rare PlantsPlants

    E-print Network

    Cruzan, Mitchell B.

    in reproductive success. Mating system.Mating system. Lower with higher rates ofLower with higher ratesReproductive Biology of RareReproductive Biology of Rare PlantsPlants Importance of ReproductionImportance of Reproduction Case StudiesCase Studies #12;Rare Plant ReproductionRare Plant Reproduction Population Viability

  4. Dynamics of high repetition rate regenerative amplifiers

    NASA Astrophysics Data System (ADS)

    Grishin, M.; Gulbinas, V.; Michailovas, A.

    2007-07-01

    Dynamics features of high repetition rate continuously pumped solid-state regenerative amplifiers were studied numerically. A space independent rate equations and discrete-time dynamical system approach were used for system state evolution analysis. Regular single-energy operation, quasi-periodic pulsing and chaotic behavior regions are distinguished in space of control parameters. Diagrams of dynamical regimes comprehensively exhibiting operation features of the system are presented. Seed energy is shown to be an important parameter determining the stability space. Conditions of stable operation are described quantitatively.

  5. A high throughput screening system for predicting chemically-induced reproductive organ deformities.

    PubMed

    van der Burg, Bart; Pieterse, Bart; Buist, Harrie; Lewin, Geertje; van der Linden, Sander C; Man, Hai-Yen; Rorije, Emiel; Piersma, Aldert H; Mangelsdorf, Inge; Wolterbeek, Andre P M; Kroese, E Dinant; van Vugt-Lussenburg, Barbara

    2015-08-01

    There is a great need for alternative testing methods for reproductive toxicants that are practical, fast, cost-effective and easy to interpret. Previously we followed a pragmatic approach using readily available tests, which was successful in predicting reproductive toxicity of chemicals [13]. This initial battery still contained apical tests and is fairly complex and low in its throughput. The current study aimed to simplify this screening battery using a mechanistic approach and a panel of high throughput CALUX reporter gene assays. A mechanistic approach was taken to validate this high throughput test battery. To this end it was challenged with two preselected sets of chemicals addressing two major apical effect classes relevant in reproductive toxicity. We found selectivity in this battery in that 82% of the compounds inducing reproductive organ deformities were predicted correctly, while for compounds inducing neural tube defects this was the case in 47% only. This is consistent with the mechanisms of toxicity covered in the battery. The most informative assays in the battery were ERalpha CALUX to measure estrogenicity and the AR-anti CALUX assay to measure androgen receptor antagonism. PMID:25527862

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

    SciTech Connect

    Boyd, Windy A. [Biomolecular Screening Branch, National Toxicology Program, Research Triangle Park, NC 27709 (United States); McBride, Sandra J.; Rice, Julie R.; Snyder, Daniel W. [Biomolecular Screening Branch, National Toxicology Program, Research Triangle Park, NC 27709 (United States); Freedman, Jonathan H., E-mail: freedma1@niehs.nih.go [Biomolecular Screening Branch, National Toxicology Program, Research Triangle Park, NC 27709 (United States); Laboratory of Toxicology and Pharmacology, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC 27709 (United States)

    2010-06-01

    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. EC{sub 50} values for cadmium for automated measurements (176-192 {mu}M) were comparable to those previously reported for a 72-h exposure using manual counting (151 {mu}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.

  7. Does the silver moss Bryum argenteum exhibit sex-specific patterns in vegetative growth rate, asexual fitness or prezygotic reproductive investment?

    PubMed Central

    Horsley, Kimberly; Stark, Lloyd R.; McLetchie, D. Nicholas

    2011-01-01

    Background and Aims Expected life history trade-offs associated with sex differences in reproductive investment are often undetected in seed plants, with the difficulty arising from logistical issues of conducting controlled experiments. By controlling genotype, age and resource status of individuals, a bryophyte was assessed for sex-specific and location-specific patterns of vegetative, asexual and sexual growth/reproduction across a regional scale. Methods Twelve genotypes (six male, six female) of the dioecious bryophyte Bryum argenteum were subcultured to remove environmental effects, regenerated asexually to replicate each genotype 16 times, and grown over a period of 92 d. Plants were assessed for growth rates, asexual and sexual reproductive traits, and allocation to above- and below-ground regenerative biomass. Key Results The degree of sexual versus asexual reproductive investment appears to be under genetic control, with three distinct ecotypes found in this study. Protonemal growth rate was positively correlated with asexual reproduction and sexual reproduction, whereas asexual reproduction was negatively correlated (appeared to trade-off) with vegetative growth (shoot production). No sex-specific trade-offs were detected. Female sex-expressing shoots were longer than males, but the sexes did not differ in growth traits, asexual traits, sexual induction times, or above- and below-ground biomass. Males, however, had much higher rates of inflorescence production than females, which translated into a significantly higher (24x) prezygotic investment for males relative to females. Conclusions Evidence for three distinct ecotypes is presented for a bryophyte based on regeneration traits. Prior to zygote production, the sexes of this bryophyte did not differ in vegetative growth traits but significantly differed in reproductive investment, with the latter differences potentially implicated in the strongly biased female sex ratio. The disparity between males and females for prezygotic reproductive investment is the highest known for bryophytes. PMID:21320878

  8. Phosphor thermometry at high repetition rates

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

    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.

  9. High temperature electrochemical corrosion rate probes

    SciTech Connect

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

    2005-09-01

    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.

  10. Quasi-Static and High Strain Rates

    Microsoft Academic Search

    I. W. Hall; A. Tasdemird; Ali Kara

    2011-01-01

    Cylindrical samples of a 0\\/90° cross-ply Nextel 610™\\/Al-6061 (?55Vf%) metal matrix composite have been subjected to compression testing at quasi-static and high strain rates over a range of angles between 0° and ±45° with respect to the principal fiber directions. The results, combined with testing in the longitudinal, transverse and through thickness directions, provide a detailed description of the response

  11. High-rate vector quantization for detection

    Microsoft Academic Search

    Riten Gupta; Alfred O. Hero III

    2003-01-01

    We investigate high-rate quantization for various detection and reconstruction loss criteria. A new distortion measure is introduced which accounts for global loss in best attainable binary hypothesis testing performance. The distortion criterion is related to the area under the receiver-operating-characteristic (ROC) curve. Specifically, motivated by Sanov's theorem, we define a performance curve as the trajectory of the pair of optimal

  12. Reproductive and behavioral abnormalities in tree swallows with high levels of PCB contamination

    SciTech Connect

    McCarty, J. [Cornell Univ., Ithaca, NY (United States). Section of Ecology and Systematics; [Fish and Wildlife Service, Cortland, NY (United States); Secord, A. [Fish and Wildlife Service, Cortland, NY (United States); Tillitt, D. [National Biological Service, Columbia, MO (United States)

    1995-12-31

    Tree Swallows (Tachycineta bicolor) breeding along the Hudson River forage extensively on PCB contaminated insects that emerge from the river. The authors studied the reproductive ecology and behavior of tree swallows breeding at several sites along the Hudson River. These sites vary in the severity of PCB contamination. PCB levels in both eggs and chicks were found to be among the highest ever reported in this species, with concentrations comparable to those found in aquatic organisms in the Hudson River. In 1994 reproductive success at PCB contaminated sites was significantly impaired, relative to other sites in New York. Reduced reproductive success was largely attributed to high levels of nest abandonment during incubation and reduced hatchability of eggs. Growth and development of nestlings was not significantly impaired. Abnormal nest building behavior was also noted in 1994, and this was studied in detail in 1995. Nests from contaminated areas are significantly smaller than those at a nearby reference site and at other sites in New York. The authors suggest that the reduced reproductive outputs at these sites are, in large part, a result of effects on the behavior of incubating females. The population-level implications of these patterns are unknown.

  13. The adverse effects of high fat induced obesity on female reproductive cycle and hormones

    NASA Astrophysics Data System (ADS)

    Donthireddy, Laxminarasimha Reddy

    The prevalence of obesity, an established risk and progression factor for abnormal reproductive cycle and tissue damage in female mice. It leads to earlier puberty, menarche in young females and infertility. There are extensive range of consequences of obesity which includes type-2 diabetes, cardiovascular disease and insulin resistance. Obesity is the interaction between dietary intake, genes, life style and environment. The interplay of hormones estrogen, insulin, and leptin is well known on energy homeostasis and reproduction. The aim of this study is to determine the effect of high fat induced obesity on reproductive cycles and its hormonal abnormalities on mice model. Two week, 3 month and 8 month long normal (WT) and very high fat diet (VHFD) diet course is followed. When mice are fed with very high fat diet, there is a drastic increase in weight within the first week later. There was a significant (p<0.001) increase in leptin levels in 6 month VHFD treated animals. 2 week, 3 month and 6 month time interval pap smear test results showed number of cells, length of estrous cycle and phases of the estrous cycle changes with VHFD mice(n=30) compared to normal diet mice(n=10). These results also indicate that the changes in the reproductive cycles in VHFD treated female mice could be due to the changes in hormones. Histo-pathological analyses of kidney, ovary, liver, pancreas, heart and lungs showed remarkable changes in some tissue on exposure to very high fat. Highly deposited fat packets observed surrounding the hepatocytes and nerve cells.

  14. Reproductive Peformance of Great Egrets (Ardea alba) at High Island, Texas

    E-print Network

    McInnes, Andrew

    2012-02-14

    Despite habitat perturbations and seasonal fluctuations in reproduction, many studies report no significant inter-annual variation in Great Egret reproductive performance. I examined the reproductive performance of Great Egrets (Ardea alba) for two...

  15. Length frequency distribution, mortality rate and reproductive biology of kawakawa (Euthynnus affinis-Cantor, 1849) in the coastal waters of Tanzania.

    PubMed

    Johnson, M G; Tamatamah, A R

    2013-11-01

    This study explored important aspect of the basis for the highly complex population of kawakawa (Euthynnus affinis) within the coastal waters of Tanzania; by investigating length frequency distribution, mortality rate and reproductive characteristics. This information is essential for the sustainable management of the regionally-important recreational and economic E. affinis fishery. Fish were sampled on a monthly basis for two monsoon seasons using a ring net and artisanal fishermen boat. Maximum and minimum total length was 85 and 31 cm, respectively. Nonlinear least square fitting provided a complete set of von Bertalanffy growth estimates: L8 = 89.25 cm total length and K = 0.78. The estimated value of total mortality based on length converted catch curve using these growth parameters is Z = 1.78 year(-1). Natural mortality based on growth parameters and mean environmental temperature (T = 26.9 degrees C) is M = 1.09 year(-1). The estimated annual instantaneous fishing mortality (F = 0.69 year(-1)) was considerably grater than the target (Fopt = 0.43 year(-1)) and limit (Flimit = 0.58 year(-1)) biological reference point indicating that E. affinis is heavily overexploited. Reproductive aspects were assessed whereby female E. affinis was reported to reach maturity earlier than males which is an indication of phenotypic response toward a decline in population. Two peaks was revealed by the use of Gonad-Somatic Index (GSI), however an extended spawning period was noticed in a period between November to February following an increased water temperature. Although, these findings presents a snapshot concerning population structure and reproduction of E. affinis, further studies covering the entire coastal waters of Tanzania are recommended to aid the management and conservation strategies. PMID:24511734

  16. A visibility matching tone reproduction operator for high dynamic range scenes

    SciTech Connect

    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

    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.

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

    Microsoft Academic Search

    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

    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

  18. High rate, high reliability Li\\/SO2 cells

    Microsoft Academic Search

    R. Chireau

    1982-01-01

    The use of the lithium\\/sulfur dioxide system for aerospace applications is discussed. The high rate density in the system is compared to some primary systems: mercury zinc, silver zinc, and magnesium oxide. Estimates are provided of the storage life and shelf life of typical lithium sulfur batteries. The design of lithium cells is presented and criteria are given for improving

  19. Study on high rate MRPC for high luminosity experiments

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Huang, X.; Lv, P.; Zhu, W.; Shi, L.; Xie, B.; Cheng, J.; Li, Y.

    2014-08-01

    Multi-gap Resistive Plate Chambers (MRPC) has been used to construct time-of-flight system in the field of nuclear and particle physics, due to their high-precision timing properties, high efficiency, reliability and coverage of large area. With the increase of accelerator luminosity, MRPCs have to withstand particle fluxes up to several tens of kHz/cm2 in view of the next generation physics experiments, such as the SIS-100/300 at FAIR-CBM, SoLID at JLab and NICA at JINR. But the MRPC assembled with float glass has very low rate capability not exceeding some hundreds of Hz/cm2. Two possible solutions for increasing rate capability, one is to reduce the bulk resistivity of glass and the other is to reduce the electrode thickness. Tsinghua University has done R&D on high rate MRPC for many years. A special low resistive glass with bulk resistivity around 1010?.cm was developed. We also studied the rate capability changes with glass thickness. In this paper we describe the performance of low resistive glass and two kinds of high rate MRPC (Pad readout and Strip readout) tested by deuterium beams. The results show that the tolerable particle flux can reach 70 kHz/cm2. In the mean time, MRPCs assembled with three thickness (0.7 mm, 0.5 mm and 0.35 mm) of float glass were also tested with deuteron beams, the results show that the three detectors can afford particle rate up to 500 Hz/cm2, 0.75 kHz/cm2 and 3 kHz/cm2, respectively.

  20. High dose rate brachytherapy for oral cancer

    PubMed Central

    YamazakI, Hideya; Yoshida, Ken; Yoshioka, Yasuo; Shimizutani, Kimishige; Furukawa, Souhei; Koizumi, Masahiko; Ogawa, Kazuhiko

    2013-01-01

    Brachytherapy results in better dose distribution compared with other treatments because of steep dose reduction in the surrounding normal tissues. Excellent local control rates and acceptable side effects have been demonstrated with brachytherapy as a sole treatment modality, a postoperative method, and a method of reirradiation. Low-dose-rate (LDR) brachytherapy has been employed worldwide for its superior outcome. With the advent of technology, high-dose-rate (HDR) brachytherapy has enabled health care providers to avoid radiation exposure. This therapy has been used for treating many types of cancer such as gynecological cancer, breast cancer, and prostate cancer. However, LDR and pulsed-dose-rate interstitial brachytherapies have been mainstays for head and neck cancer. HDR brachytherapy has not become widely used in the radiotherapy community for treating head and neck cancer because of lack of experience and biological concerns. On the other hand, because HDR brachytherapy is less time-consuming, treatment can occasionally be administered on an outpatient basis. For the convenience and safety of patients and medical staff, HDR brachytherapy should be explored. To enhance the role of this therapy in treatment of head and neck lesions, we have reviewed its outcomes with oral cancer, including Phase I/II to Phase III studies, evaluating this technique in terms of safety and efficacy. In particular, our studies have shown that superficial tumors can be treated using a non-invasive mold technique on an outpatient basis without adverse reactions. The next generation of image-guided brachytherapy using HDR has been discussed. In conclusion, although concrete evidence is yet to be produced with a sophisticated study in a reproducible manner, HDR brachytherapy remains an important option for treatment of oral cancer. PMID:23179377

  1. High-Rate Digital Receiver Board

    NASA Technical Reports Server (NTRS)

    Ghuman, Parminder; Bialas, Thomas; Brambora, Clifford; Fisher, David

    2004-01-01

    A high-rate digital receiver (HRDR) implemented as a peripheral component interface (PCI) board has been developed as a prototype of compact, general-purpose, inexpensive, potentially mass-producible data-acquisition interfaces between telemetry systems and personal computers. The installation of this board in a personal computer together with an analog preprocessor enables the computer to function as a versatile, highrate telemetry-data-acquisition and demodulator system. The prototype HRDR PCI board can handle data at rates as high as 600 megabits per second, in a variety of telemetry formats, transmitted by diverse phase-modulation schemes that include binary phase-shift keying and various forms of quadrature phaseshift keying. Costing less than $25,000 (as of year 2003), the prototype HRDR PCI board supplants multiple racks of older equipment that, when new, cost over $500,000. Just as the development of standard network-interface chips has contributed to the proliferation of networked computers, it is anticipated that the development of standard chips based on the HRDR could contribute to reductions in size and cost and increases in performance of telemetry systems.

  2. High counting rate resistive-plate chamber

    SciTech Connect

    Peskov, V.; Anderson, D.F.; Kwan, S.

    1993-05-01

    Parallel-plate avalanche chambers (PPAC) are widely used in physics experiments because they are fast (<1 ns) and have very simple construction: just two parallel metallic plates or mesh electrodes. Depending on the applied voltage they may work either in spark mode or avalanche mode. The advantage of the spark mode of operation is a large signal amplitude from the chamber, the disadvantage is that there is a large dead time (msec) for the entire chamber after an event. The main advantage of the avalanche mode is high rate capability 10{sup 5} counts/mm{sup 2}. A resistive-plate chamber (RPC) is similar to the PPAC in construction except that one or both of the electrodes are made from high resistivity ({ge}10{sup 10} {Omega}{center_dot}cm) materials. In practice RPCs are usually used in the spark mode. Resistive electrodes are charged by sparks, locally reducing the actual electric field in the gap. The size of the charged surface is about 10 mm{sup 2}, leaving the rest of the detector unaffected. Therefore, the rate capability of such detectors in the spark mode is considerably higher than conventional spark counters. Among the different glasses tested the best results were obtained with electron type conductive glasses, which obey Ohm`s law. Most of the work with such glasses was done with high pressure parallel-plate chambers (10 atm) for time-of-flight measurements. Resistive glasses have been expensive and produced only in small quantities. Now resistive glasses are commercially available, although they are still expensive in small scale production. From the positive experience of different groups working with the resistive glasses, it was decided to review the old idea to use this glass for the RPC. This work has investigated the possibility of using the RPC at 1 atm and in the avalanche mode. This has several advantages: simplicity of construction, high rate capability, low voltage operation, and the ability to work with non-flammable gases.

  3. High counting rate resistive-plate chamber

    SciTech Connect

    Peskov, V.; Anderson, D.F.; Kwan, S.

    1993-05-01

    Parallel-plate avalanche chambers (PPAC) are widely used in physics experiments because they are fast (<1 ns) and have very simple construction: just two parallel metallic plates or mesh electrodes. Depending on the applied voltage they may work either in spark mode or avalanche mode. The advantage of the spark mode of operation is a large signal amplitude from the chamber, the disadvantage is that there is a large dead time (msec) for the entire chamber after an event. The main advantage of the avalanche mode is high rate capability 10[sup 5] counts/mm[sup 2]. A resistive-plate chamber (RPC) is similar to the PPAC in construction except that one or both of the electrodes are made from high resistivity ([ge]10[sup 10] [Omega][center dot]cm) materials. In practice RPCs are usually used in the spark mode. Resistive electrodes are charged by sparks, locally reducing the actual electric field in the gap. The size of the charged surface is about 10 mm[sup 2], leaving the rest of the detector unaffected. Therefore, the rate capability of such detectors in the spark mode is considerably higher than conventional spark counters. Among the different glasses tested the best results were obtained with electron type conductive glasses, which obey Ohm's law. Most of the work with such glasses was done with high pressure parallel-plate chambers (10 atm) for time-of-flight measurements. Resistive glasses have been expensive and produced only in small quantities. Now resistive glasses are commercially available, although they are still expensive in small scale production. From the positive experience of different groups working with the resistive glasses, it was decided to review the old idea to use this glass for the RPC. This work has investigated the possibility of using the RPC at 1 atm and in the avalanche mode. This has several advantages: simplicity of construction, high rate capability, low voltage operation, and the ability to work with non-flammable gases.

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

    PubMed Central

    De Mársico, María C; Reboreda, Juan C

    2008-01-01

    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. PMID:18647716

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

    PubMed

    De Mársico, María C; Reboreda, Juan C

    2008-11-01

    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. PMID:18647716

  6. A high-rate fingerprinting code

    NASA Astrophysics Data System (ADS)

    Jourdas, Jean-Francois; Moulin, Pierre

    2008-02-01

    In fingerprinting, a signature, unique to each user, is embedded in each distributed copy of a multimedia content, in order to identify potential illegal redistributors. As an alternative to the vast majority of fingerprinting codes built upon error-correcting codes with a high minimum distance, we propose the construction of a random-like fingerprinting code, intended to operate at rates close to fingerprinting capacity. For such codes, the notion of minimum distance has little relevance. As an example, we present results for a length 288,000 code that can accommodate 33 millions of users and 50 colluders against the averaging attack. The encoding is done by interleaving the users' identifying bitstrings and encoding them multiple times with recursive systematic convolutional codes. The decoding is done in two stages. The first outputs a small set of possible colluders using a bank of list Viterbi decoders. The second stage prunes this set using correlation decoding. We study this scheme and assess its performance through Monte-Carlo simulations. The results show that at rates ranging from 30% to 50% of capacity, we still have a low error probability (e.g. 1%).

  7. High spin rate magnetic controller for nanosatellites

    NASA Astrophysics Data System (ADS)

    Slavinskis, A.; Kvell, U.; Kulu, E.; Sünter, I.; Kuuste, H.; Lätt, S.; Voormansik, K.; Noorma, M.

    2014-02-01

    This paper presents a study of a high rate closed-loop spin controller that uses only electromagnetic coils as actuators. The controller is able to perform spin rate control and simultaneously align the spin axis with the Earth's inertial reference frame. It is implemented, optimised and simulated for a 1-unit CubeSat ESTCube-1 to fulfil its mission requirements: spin the satellite up to 360 deg s-1 around the z-axis and align its spin axis with the Earth's polar axis with a pointing error of less than 3°. The attitude of the satellite is determined using a magnetic field vector, a Sun vector and angular velocity. It is estimated using an Unscented Kalman Filter and controlled using three electromagnetic coils. The algorithm is tested in a simulation environment that includes models of space environment and environmental disturbances, sensor and actuator emulation, attitude estimation, and a model to simulate the time delay caused by on-board calculations. In addition to the normal operation mode, analyses of reduced satellite functionality are performed: significant errors of attitude estimation due to non-operational Sun sensors; and limited actuator functionality due to two non-operational coils. A hardware-in-the-loop test is also performed to verify on-board software.

  8. High-Frame-Rate Oil Film Interferometry

    E-print Network

    White, Jonathan C; Chen, John

    2010-01-01

    The fluid dynamics video to which this abstract relates contains visualization of the response of a laminar boundary layer to a sudden puff from a small hole. The boundary layer develops on a flat plate in a wind tunnel; the hole is located at a streamwise Reynolds number of 100,000. The visualization of the boundary layer response is accomplished using interferometry of a transparent, thin film of oil placed on the surface immediately downstream of the hole and with its leading edge perpendicular to the direction of flow. Through lubrication theory, it is understood that the rate of change of the spacing of the interference fringes is proportional to the skin friction at any instant. For reference, a small disk-shaped protrusion of the type often used to trip the boundary layer in wind model tunnel testing is also shown. Three cases with different puff strengths are included. Using a high-speed commercial camera, frame rates in excess of 1000/sec have been recorded; the video shown here was taken at 24 frame...

  9. High variance in reproductive success generates a false signature of a genetic bottleneck in populations of constant size: a simulation study

    PubMed Central

    2013-01-01

    Background Demographic bottlenecks can severely reduce the genetic variation of a population or a species. Establishing whether low genetic variation is caused by a bottleneck or a constantly low effective number of individuals is important to understand a species’ ecology and evolution, and it has implications for conservation management. Recent studies have evaluated the power of several statistical methods developed to identify bottlenecks. However, the false positive rate, i.e. the rate with which a bottleneck signal is misidentified in demographically stable populations, has received little attention. We analyse this type of error (type I) in forward computer simulations of stable populations having greater than Poisson variance in reproductive success (i.e., variance in family sizes). The assumption of Poisson variance underlies bottleneck tests, yet it is commonly violated in species with high fecundity. Results With large variance in reproductive success (Vk ? 40, corresponding to a ratio between effective and census size smaller than 0.1), tests based on allele frequencies, allelic sizes, and DNA sequence polymorphisms (heterozygosity excess, M-ratio, and Tajima’s D test) tend to show erroneous signals of a bottleneck. Similarly, strong evidence of population decline is erroneously detected when ancestral and current population sizes are estimated with the model based method MSVAR. Conclusions Our results suggest caution when interpreting the results of bottleneck tests in species showing high variance in reproductive success. Particularly in species with high fecundity, computer simulations are recommended to confirm the occurrence of a population bottleneck. PMID:24131797

  10. Filters for High Rate Pulse Processing

    E-print Network

    Alpert, B K; Bennett, D A; Doriese, W B; Fowler, J W; Hoover, A S; Rabin, M W; Ullom, J N

    2012-01-01

    We introduce a filter-construction method for pulse processing that differs in two respects from that in standard optimal filtering, in which the average pulse shape and noise-power spectral density are combined to create a convolution filter for estimating pulse heights. First, the proposed filters are computed in the time domain, to avoid periodicity artifacts of the discrete Fourier transform, and second, orthogonality constraints are imposed on the filters, to reduce the filtering procedure's sensitivity to unknown baseline height and pulse tails. We analyze the proposed filters, predicting energy resolution under several scenarios, and apply the filters to high-rate pulse data from gamma-rays measured by a transition-edge-sensor microcalorimeter.

  11. Filters for High Rate Pulse Processing

    E-print Network

    B. K. Alpert; R. D. Horansky; D. A. Bennett; W. B. Doriese; J. W. Fowler; A. S. Hoover; M. W. Rabin; J. N. Ullom

    2012-12-07

    We introduce a filter-construction method for pulse processing that differs in two respects from that in standard optimal filtering, in which the average pulse shape and noise-power spectral density are combined to create a convolution filter for estimating pulse heights. First, the proposed filters are computed in the time domain, to avoid periodicity artifacts of the discrete Fourier transform, and second, orthogonality constraints are imposed on the filters, to reduce the filtering procedure's sensitivity to unknown baseline height and pulse tails. We analyze the proposed filters, predicting energy resolution under several scenarios, and apply the filters to high-rate pulse data from gamma-rays measured by a transition-edge-sensor microcalorimeter.

  12. High corticosterone, not high energy cost, correlates with reproductive success in the burrow-nesting ancient murrelet.

    PubMed

    Shoji, Akiko; Elliott, Kyle H; O'Reilly, Kathleen M; Gaston, Anthony J

    2013-01-01

    Theory and observations suggest that offspring abandonment in animals may occur when the costs to future reproductive output of current reproductive effort outweigh the fitness benefits of rearing the current brood. While hormonal cues (i.e. corticosterone) or energy reserves are believed to be involved, few studies have directly focused on the proximate cues influencing behaviours directly related to reproductive success. To address this information gap, we determined the incubation metabolic rates and corticosterone (CORT) levels of naturally fasting and freely incubating ancient murrelets (Synthliboramphus antiquus). Respiratory quotient (RQ) increased with date, suggesting that incubating ancient murrelets shifted from strictly lipid-based metabolism towards more protein-based metabolism as incubation progressed. Birds that hatched only one nestling had higher levels of circulating CORT than those which hatched two, suggesting that birds which laid only a single egg found incubation more stressful than those which laid two. However, CORT levels and incubation shift lengths were not correlated, suggesting that birds that undertook prolonged incubation shifts did so only when their energy stores were not jeopardized. PMID:24391929

  13. High Corticosterone, Not High Energy Cost, Correlates with Reproductive Success in the Burrow-Nesting Ancient Murrelet

    PubMed Central

    Shoji, Akiko; Elliott, Kyle H.; O’Reilly, Kathleen M.; Gaston, Anthony J.

    2013-01-01

    Theory and observations suggest that offspring abandonment in animals may occur when the costs to future reproductive output of current reproductive effort outweigh the fitness benefits of rearing the current brood. While hormonal cues (i.e. corticosterone) or energy reserves are believed to be involved, few studies have directly focused on the proximate cues influencing behaviours directly related to reproductive success. To address this information gap, we determined the incubation metabolic rates and corticosterone (CORT) levels of naturally fasting and freely incubating ancient murrelets (Synthliboramphus antiquus). Respiratory quotient (RQ) increased with date, suggesting that incubating ancient murrelets shifted from strictly lipid-based metabolism towards more protein-based metabolism as incubation progressed. Birds that hatched only one nestling had higher levels of circulating CORT than those which hatched two, suggesting that birds which laid only a single egg found incubation more stressful than those which laid two. However, CORT levels and incubation shift lengths were not correlated, suggesting that birds that undertook prolonged incubation shifts did so only when their energy stores were not jeopardized. PMID:24391929

  14. Consideration of wear rates at high velocity

    NASA Astrophysics Data System (ADS)

    Hale, Chad S.

    The development of the research presented here is one in which high velocity relative sliding motion between two bodies in contact has been considered. Overall, the wear environment is truly three-dimensional. The attempt to characterize three-dimensional wear was not economically feasible because it must be analyzed at the micro-mechanical level to get results. Thus, an engineering approximation was carried out. This approximation was based on a metallographic study identifying the need to include viscoplasticity constitutive material models, coefficient of friction, relationships between the normal load and velocity, and the need to understand wave propagation. A sled test run at the Holloman High Speed Test Track (HHSTT) was considered for the determination of high velocity wear rates. In order to adequately characterize high velocity wear, it was necessary to formulate a numerical model that contained all of the physical events present. The experimental results of a VascoMax 300 maraging steel slipper sliding on an AISI 1080 steel rail during a January 2008 sled test mission were analyzed. During this rocket sled test, the slipper traveled 5,816 meters in 8.14 seconds and reached a maximum velocity of 1,530 m/s. This type of environment was never considered previously in terms of wear evaluation. Each of the features of the metallography were obtained through micro-mechanical experimental techniques. The byproduct of this analysis is that it is now possible to formulate a model that contains viscoplasticity, asperity collisions, temperature and frictional features. Based on the observations of the metallographic analysis, these necessary features have been included in the numerical model, which makes use of a time-dynamic program which follows the movement of a slipper during its experimental test run. The resulting velocity and pressure functions of time have been implemented in the explicit finite element code, ABAQUS. Two-dimensional, plane strain models were used to determine the state of stress within the slipper and the pressure distribution along the bottom. Local submodel collisions between the slipper and a 6 mum radius hemispherical asperity were analyzed to determine mechanical and melt wear rates. A simplified damage criterion of maximum Mises stress was used to determine the damaged volume during the slipper and asperity collision. Overall, the model predicts a total wear volume that is approximately 36% of the total wear measured during the metallographic analysis.

  15. Investigating the life-cycle and growth rate of Pediastrum boryanum and the implications for wastewater treatment high rate algal ponds.

    PubMed

    Park, Jason B K; Craggs, Rupert J; Shilton, Andy N

    2014-09-01

    The colonial alga Pediastrum boryanum has beneficial characteristics for wastewater treatment High Rate Algal Ponds (HRAP) including high biomass productivity and settleability. Our previous work has shown that these characteristics are enhanced when a portion of gravity harvested algae is recycled back to the pond. To help understand the mechanisms behind the improved performance of P. boryanum dominated HRAP with algal recycling, this study investigated the life-cycle of P. boryanum. Experiments determined the exact timing and growth rate of P. boryanum life-cycle stages ('juvenile', 'growth' and 'reproductive') under four combinations of light and temperature (250 or 120 ?Mol/m(2)/s; 20 or 10 °C). Single juvenile 16-celled colonies were grown in microcosms on an inverted microscope and photographed every 15 min until reproduction ceased. Two asexual life-cycles and a rarely occurring sexual life-cycle were observed. The time required to achieve asexual reproductive maturity increased from 52 h (high light and temperature) to 307 h (low light and temperature), indicating that the minimum hydraulic retention time or mean cell residence time (MCRT) must be higher than these values to sustain a P. boryanum HRAP culture under ambient conditions. The net growth rate of a P. boryanum colony varied between life-cycle stages (growth > juvenile > reproductive). This suggests that the higher biomass productivity measured in HRAP with algal recycling could be due to both the increased MCRT and an increase in the net growth rate of the HRAP culture by 'seeding' with faster growing colonies. PMID:24852411

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

    SciTech Connect

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

    1994-09-15

    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.

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

    Microsoft Academic Search

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

    2010-01-01

    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

  18. 80 FR 36927 - Determination of Terms and Royalty Rates for Ephemeral Reproductions and Public Performance of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2015-06-29

    The Copyright Royalty Judges publish final regulations that set the rates and terms for the use of sound recordings via digital transmissions made by new subscription services and for the making of ephemeral recordings to facilitate those transmissions during the period commencing January 1, 2016, and ending on December 31,...

  19. In situ high rate growth of high temperature superconductor tapes

    SciTech Connect

    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

    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.

  20. Are low reproductive rates characteristic of New Zealand's native terrestrial birds? Evidence from the allometry of nesting parameters in altricial species

    Microsoft Academic Search

    Donald C. Franklin

    2003-01-01

    We investigate the notion that New Zealand's avifauna exhibits a macro?evolutionary trend towards low reproductive rates by analysing the allometry of nesting parameters for native altricial land birds. We show that egg size, incubation periods, and nestling periods are all strongly correlated with body mass, but clutch size is not. However, egg size more accurately predicts incubation periods, and incubation

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

    Microsoft Academic Search

    Matti T. Leppänen; Jussi V. K. Kukkonen

    1998-01-01

    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

  2. Epidemic growth rate and household reproduction number in communities of households, schools and workplaces

    Microsoft Academic Search

    Lorenzo Pellis; Neil M. Ferguson; Christophe Fraser

    In this paper we present a novel and coherent modelling framework for the characterisation of the real-time growth rate in\\u000a SIR models of epidemic spread in populations with social structures of increasing complexity. Known results about homogeneous\\u000a mixing and multitype models are included in the framework, which is then extended to models with households and models with\\u000a households and schools\\/workplaces.

  3. Endocrine Correlates of Reproductive Status in Breeding and Nonbreeding Wild Female Moustached Tamarins

    Microsoft Academic Search

    Petra Löttker; Maren Huck; Eckhard W. Heymann; Michael Heistermann

    2004-01-01

    In callitrichid primates, reproduction is usually restricted to a single female per group. Reproductive rate is high and the occurrence of a postpartum estrus can lead to simultaneous lactation and pregnancy. In contrast, nonreproductive females often show ovarian inactivity. However, most studies on callitrichid reproductive physiology have been conducted in captivity, where conditions differ considerably from those in the wild,

  4. Tradeoff between offspring mass and subsequent reproduction in a highly iteroparous mammal

    E-print Network

    Festa-Bianchet, Marco

    subsequent reproductive success or survival. We used longitudinal data on marked mountain goatsOreamnos americanus to assess if offspring mass at weaning affected maternal survival and future reproduction

  5. Quantum data locking for high-rate private communication

    E-print Network

    Lupo, Cosmo

    We show that, if the accessible information is used as a security quantifier, quantum channels with a certain symmetry can convey private messages at a tremendously high rate, as high as less than one bit below the rate ...

  6. RAM MATING BEHAVIOR AFTER LONG-TERM SELECTION FOR REPRODUCTIVE RATE IN RAMBOUILLET EWES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Mating behavior is heritable in several species, but it is not known if selection for ewe traits affect ram mating behavior. Our objectives were to determine if divergent (high vs low) selection of a female trait (lambs born) affects mating behavior of male offspring when trained to service an artif...

  7. High-Rate Compression of Polypropylene

    NASA Astrophysics Data System (ADS)

    Okereke, Michael; Buckley, C. Paul

    2008-08-01

    Three grades of polypropylene were tested in compression at room temperature, across an unusually wide range of strain rate: 10-4 to 104 s-1. The quasi-static testing was done in a Hounsfield machine fitted with a digital image acquisition kit, while tests at the highest strain rates were carried out using a compression split Hopkinson pressure bar. The strain rate dependence of compressive yield stress was compared with the Eyring prediction, and found to be a nonlinear function of log10(strain-rate). The nonlinearity is attributed to the presence of two relaxation processes in polypropylene, with differing activation volumes: the ?- and ?-processes. According to the Bauwens two-process model this would lead naturally to curved Eyring plots, where the apparent activation volume decreases with increasing strain-rate. Another prominent feature in the experimental results was the increase in magnitude of post-yield strain-softening with increase in strain-rate. This indicates that the dominant structural relaxation time exceeds the experimental time-scale at the highest strain-rates, but lies below it for the quasi-static tests.

  8. Dislocation Mechanics of High-Rate Deformations

    NASA Astrophysics Data System (ADS)

    Armstrong, Ronald W.; Li, Qizhen

    2015-02-01

    Four topics associated with constitutive equation descriptions of rate-dependent metal plastic deformation behavior are reviewed in honor of previous research accomplished on the same issues by Professor Marc Meyers along with colleagues and students, as follow: (1) increasing strength levels attributed to thermally activated dislocation migration at higher loading rates; (2) inhomogeneous adiabatic shear banding; (3) controlling mechanisms of deformation in shock as compared with shock-less isentropic compression experiments and (4) Hall-Petch-based grain size-dependent strain rate sensitivities exhibited by nanopolycrystalline materials. Experimental results are reviewed on the topics for a wide range of metals.

  9. HIgh Rate X-ray Fluorescence Detector

    SciTech Connect

    Grudberg, Peter Matthew [XIA LLC

    2013-04-30

    The purpose of this project was to develop a compact, modular multi-channel x-ray detector with integrated electronics. This detector, based upon emerging silicon drift detector (SDD) technology, will be capable of high data rate operation superior to the current state of the art offered by high purity germanium (HPGe) detectors, without the need for liquid nitrogen. In addition, by integrating the processing electronics inside the detector housing, the detector performance will be much less affected by the typically noisy electrical environment of a synchrotron hutch, and will also be much more compact than current systems, which can include a detector involving a large LN2 dewar and multiple racks of electronics. The combined detector/processor system is designed to match or exceed the performance and features of currently available detector systems, at a lower cost and with more ease of use due to the small size of the detector. In addition, the detector system is designed to be modular, so a small system might just have one detector module, while a larger system can have many â?? you can start with one detector module, and add more as needs grow and budget allows. The modular nature also serves to simplify repair. In large part, we were successful in achieving our goals. We did develop a very high performance, large area multi-channel SDD detector, packaged with all associated electronics, which is easy to use and requires minimal external support (a simple power supply module and a closed-loop water cooling system). However, we did fall short of some of our stated goals. We had intended to base the detector on modular, large-area detectors from Ketek GmbH in Munich, Germany; however, these were not available in a suitable time frame for this project, so we worked instead with pnDetector GmbH (also located in Munich). They were able to provide a front-end detector module with six 100 m^2 SDD detectors (two monolithic arrays of three elements each) along with associated preamplifiers; these detectors surpassed the performance we expected to get from the Ketek detectors, however they are housed in a sealed module, which does not offer the ease of repair and expandability weâ??d hoped to achieve with the Ketek SDDâ??s. Our packaging efforts were quite successful, as we came up with a very compact way to mount the detector and to house the associated electronics, as well as a very effective way to reliably take out the heat (from the electronics as well as the detectorâ??s Peltier coolers) without risk of condensation and without external airflow or vibration, which could create problems for the target applications. While we were able to design compact processing electronics that fit into the detector assembly, they are still at the prototype stage, and would require a significant redesign to achieve product status. We have not yet tested this detector at a synchrotron facility; we do still plan on working with some close contacts at the nearby Stanford Synchrotron Radiation Laboratory (SSRL) to get some testing with the beam (using existing commercial electronics for readout, as the integrated processor is not ready for use).

  10. Wavefront Correction on High Repetition Rate, High Energy Laser System

    NASA Astrophysics Data System (ADS)

    Liao, Z.

    Diode-pumped solid-state lasers are one of the potential driver technologies for inertial fusion energy power production. The Mercury Laser at Lawrence Livermore National Laboratory is a diode-pumped solid-state laser that will deliver 100 J of energy at 1047 nm with a repetition rate up to 10 Hz and is a scalable prototype of a fusion energy laser driver. As the Mercury laser undergoes proof-of-principal design and activation, high-repetition wavefront correction is one of the advanced components that will be tested within its unique four-pass architecture. High average power operation of the Mercury Laser induces dynamic aberrations to the laser beam wavefront. Analysis of recent data indicates that up to 4 waves of low order aberration (mainly focus error or power, with spatial resolution < 0.5 cm-1) could be expected at each pass. The Mercury laser system uses a custom-designed high-repetition-rate adaptive optics system that consists of a 100-mm diameter bimorph deformable mirror (DM) and a four-way shearing interferometric wavefront sensor capable of running at 10 Hz with very high resolution (100 x 100 sample points). The DM is based on lead zirconate titanate (PZT) technology and is coated with a high-damage threshold antireflection (AR) coating (> 10 J/cm2). The DM has a 5 x 8 actuator configuration with an additional large actuator for power correction (up to 20 waves) for a total of 41 actuators. The DM has a flatness of 0.9 waves peak to valley (PV), which with full correction reduces to 0.17 waves PV and 0.03 waves root mean square (RMS). Placing the deformable mirror (DM) at an image relay point on the laser system between passes allows the DM to be twice as effective in correcting the wavefront. The AO system was able to successfully close the loop on the laser; reducing the wavefront error from 7.2 waves PV and 1.9 waves RMS to 0.83 waves PV and 0.15 waves RMS. Analysis of the residual wavefront shows that all but 0.1 waves PV and 0.04 waves RMS of the residual wavefront errors are high spatial frequency distortions arising from crystal imperfections (which is above and beyond what the current DM can correct).

  11. Foolproof completions for high rate production wells 

    E-print Network

    Tosic, Slavko

    2008-10-10

    Operators, especially those managing production from deepwater reservoirs, are striving to produce hydrocarbons at higher and higher rates without exposing the wells to completion failure risk. To avoid screen failures, recent studies have favored...

  12. Foolproof completions for high rate production wells 

    E-print Network

    Tosic, Slavko

    2009-05-15

    Operators, especially those managing production from deepwater reservoirs, are striving to produce hydrocarbons at higher and higher rates without exposing the wells to completion failure risk. To avoid screen failures, recent studies have favored...

  13. Factors Associated with the Reproductive Health Risk Behavior of High School Students in the Republic of the Marshall Islands

    ERIC Educational Resources Information Center

    Suzuki, Keiko; Motohashi, Yutaka; Kaneko, Yoshihiro

    2006-01-01

    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…

  14. Do highly divergent loci reside in genomic regions affecting reproductive isolation? A test using next-generation sequence data in Timema stick insects

    PubMed Central

    2012-01-01

    Background Genetic divergence during speciation with gene flow is heterogeneous across the genome, with some regions exhibiting stronger differentiation than others. Exceptionally differentiated regions are often assumed to experience reduced introgression, i.e., reduced flow of alleles from one population into another because such regions are affected by divergent selection or cause reproductive isolation. In contrast, the remainder of the genome can be homogenized by high introgression. Although many studies have documented variation across the genome in genetic differentiation, there are few tests of this hypothesis that explicitly quantify introgression. Here, we provide such a test using 38,304 SNPs in populations of Timema cristinae stick insects. We quantify whether loci that are highly divergent between geographically separated (‘allopatric’) populations exhibit unusual patterns of introgression in admixed populations. To the extent this is true, highly divergent loci between allopatric populations contribute to reproductive isolation in admixed populations. Results As predicted, we find a substantial association between locus-specific divergence between allopatric populations and locus-specific introgression in admixed populations. However, many loci depart from this relationship, sometimes strongly so. We also report evidence for selection against foreign alleles due to local adaptation. Conclusions Loci that are strongly differentiated between allopatric populations sometimes contribute to reproductive isolation in admixed populations. However, geographic variation in selection and local adaptation, in aspects of genetic architecture (such as organization of genes, recombination rate variation, number and effect size of variants contributing to adaptation, etc.), and in stochastic evolutionary processes such as drift can cause strong differentiation of loci that do not always contribute to reproductive isolation. The results have implications for the theory of ‘genomic islands of speciation’. PMID:22938057

  15. Effects of folic acid and vitamin B12 supplementation on culling rate, diseases, and reproduction in commercial dairy herds.

    PubMed

    Duplessis, M; Girard, C L; Santschi, D E; Laforest, J-P; Durocher, J; Pellerin, D

    2014-04-01

    This study was undertaken to determine the effect of a combined folic acid and vitamin B12 supplement given in early lactation on culling rate, metabolic disorders and other diseases, and reproduction in commercial dairy herds. A total of 805 cows (271 primiparous and 534 multiparous cows) in 15 commercial dairy herds were involved. Every 2mo from February to December 2010 and within each herd, cows were assigned according to parity, previous 305-d milk production, and calving interval to 5mL of either (1) saline 0.9% NaCl (control group) or (2) 320mg of folic acid + 10mg of vitamin B12 (vitamin group). Treatments were administered weekly by intramuscular injections starting 3wk before the expected calving date until 8wk after parturition. A total of 221 cows were culled before the next dry period. Culling rate was not affected by treatment and was 27.5%; culling rate was greater for multiparous (32.2%) than for primiparous cows (18.8%). Within the first 60d in milk (DIM), 47 cows were culled, representing 21.3% of total culling, and no treatment effect was noted. Ketosis incidence based on a threshold ?100µmol/L of ?-hydroxybutyrate in milk was 38.3±2.9% for the vitamin group and 41.8±3.0% for the control group and was not affected by treatment. The combined supplement of folic acid and vitamin B12 did not decrease incidence of retained placenta, displaced abomasum, milk fever, metritis, or mastitis. However, the incidence of dystocia decreased by 50% in multiparous cows receiving the vitamin supplement, although no effect was observed in primiparous cows. The first breeding postpartum for multiparous cows occurred 3.8d earlier with the vitamin supplement compared with controls, whereas no treatment effect was seen for primiparous cows. Days open, first- and second-breeding conception rates, number of breedings per conception, and percentage of cows pregnant at 150 DIM were not affected by treatment. The reduced percentage of dystocia combined with the earlier DIM at first breeding for multiparous cows receiving the combined supplementation in folic acid and vitamin B12 indicates that the vitamin supplement had a positive effect in older cows. PMID:24485680

  16. High Ratings for Teachers Are Still Seen

    ERIC Educational Resources Information Center

    Sawchuk, Stephen

    2013-01-01

    In Michigan, 98 percent of teachers were rated effective or better under new teacher-evaluation systems recently put in place. In Florida, 97 percent of teachers were deemed effective or better. Principals in Tennessee judged 98 percent of teachers to be "at expectations" or better last school year, while evaluators in Georgia gave good reviews to…

  17. High pressure flow-rate switch

    NASA Technical Reports Server (NTRS)

    Gale, G. P.

    1970-01-01

    Flow-rate switch adjusts easily over a wide switching range and operates uniformly over many cycles. It adapts easily to control of various fluids and has the possibility of introducing multi-point switching. Novel design features include the tapered spool, balanced porting, capillary-bypass lubrication, and capillary-restriction damping.

  18. The American High School Graduation Rate: Trends and Levels

    Microsoft Academic Search

    James J. Heckman; Paul A. LaFontaine

    2008-01-01

    This paper uses multiple data sources and a unified methodology to estimate the trends and levels of the U.S. high school graduation rate. Correcting for important biases that plague previous calculations, we establish that (a) the true high school graduation rate is substantially lower than the official rate issued by the National Center for Educational Statistics; (b) it has been

  19. The American High School Graduation Rate: Trends and Levels

    Microsoft Academic Search

    James J. Heckman; Paul A. LaFontaine

    2007-01-01

    This paper uses multiple data sources and a unified methodology to estimate the trends and levels of the U.S. high school graduation rate. Correcting for important biases that plague previous calculations, we establish that (a) the true high school graduation rate is substantially lower than the official rate issued by the National Center for Educational Statistics; (b) it has been

  20. High rate acoustic link for underwater video transmission

    Microsoft Academic Search

    Costas Pelekanakis; Milica Stojanovic; Lee Freitag

    2003-01-01

    A high bit rate acoustic link for video transmission over an underwater channel is investigated. The key to achieving this objective lies in two approaches: use of efficient data compression algorithms and use of high-level bandwidth-efficient modulation methods. Currently available video encoding standards allow video transmission at bit rates as low as 64 kbps. While this rate is still above

  1. Reproductive strategy, sexual development and attraction to facial characteristics

    Microsoft Academic Search

    R. Elisabeth Cornwell; Miriam J. Law Smith; Lynda G. Boothroyd; Fhionna R. Moore; Hasker P. Davis; Michael Stirrat; Bernard Tiddeman; David I. Perrett

    2006-01-01

    Sexual reproduction strategies vary both between and within species in the level of investment in offspring. Life-history theories suggest that the rate of sexual maturation is critically linked to reproductive strategy, with high investment being associated with few offspring and delayed maturation. For humans, age of puberty and age of first sex are two developmental milestones that have been associated

  2. Controlling the high order multiple birth rate: the European perspective.

    PubMed

    Brinsden, Peter R

    2003-01-01

    The dramatic increase in the incidence of high order multiple pregnancies that has occurred since the mid-1970s is due to three main factors: increasing female age at conception; increasing use of ovulation induction agents and the introduction of sophisticated assisted reproduction techniques. High order multiple pregnancies are at significantly higher risk of complications than singleton pregnancies, for the fetuses, babies and the mothers. The aim of all fertility treatments is to achieve a healthy live child for each couple seeking treatment. Treatment of infertility by IVF and related techniques provides an ideal opportunity to limit the number of high order multiple pregnancies by reducing the number of embryos transferred to the woman. The realization that high order multiple pregnancy can and should be avoided has increasingly led, in most European countries, to a restriction of the number of embryos for transfer to two or even one, without a significant decrease in a couples' chance of achieving a pregnancy. The experience of European countries in reducing the number of embryos transferred is reviewed and a recommendation made that a responsible attitude to embryo transfer is adopted by all practitioners of assisted reproduction. PMID:12735870

  3. High counting rate resistive-plate chamber

    SciTech Connect

    Anderson, D.F.; Kwan, S.; Peskov, V.

    1993-08-01

    Resistive-glass, parallel-plate chambers are studied in both spark and avalanche modes. In the avalanche mode rates of over 10{sup 3}s{sup {minus}1}cm{sup {minus}2} are achievable with a total collected charges per pulse of 10{sup 8} electrons. Operated at low pressure and with secondary-electron emission from a porous CsI surface, a timing resolution of 600 ps has been measured. Future improvements are discussed.

  4. Dose rate in brachytherapy using after-loading machine: pulsed or high-dose rate?

    PubMed

    Hannoun-Lévi, J-M; Peiffert, D

    2014-10-01

    Since February 2014, it is no longer possible to use low-dose rate 192 iridium wires due to the end of industrial production of IRF1 and IRF2 sources. The Brachytherapy Group of the French society of radiation oncology (GC-SFRO) has recommended switching from iridium wires to after-loading machines. Two types of after-loading machines are currently available, based on the dose rate used: pulsed-dose rate or high-dose rate. In this article, we propose a comparative analysis between pulsed-dose rate and high-dose rate brachytherapy, based on biological, technological, organizational and financial considerations. PMID:25195117

  5. High rate data acquisition from Spacelab/Shuttle

    NASA Technical Reports Server (NTRS)

    Coffey, R.

    1978-01-01

    The need for high data rates from a variety of experiments on Spacelab/Shuttle produced the requirement for the Spacelab High Rate Multiplexer/Demultiplexer system. This system acquires serial digital data at asynchronous bit rates from up to sixteen experiments, two data buses, three voice links, two tape recorders, and a universal time channel. Experiment data rates may vary from 200 bps to 16 Mbps while recorded data rates range from 250 Kbps to 32 Mbps. The High Rate Multiplexer (HRM) accepts these data inputs and forms a serial PCM output at flexible rates up to 48 Mbps. This PCM output is transmitted to ground by a Ku-Band RF link via the Tracking and Data Relay Satellite System (TDRSS) or recorded on board for delayed transmission. A complementary ground based High Rate Demultiplexer (HRDM) accepts and demultiplexes the composite PCM data at ground processing locations.

  6. How endangered is sexual reproduction of high-mountain plants by summer frosts? Frost resistance, frequency of frost events and risk assessment.

    PubMed

    Ladinig, Ursula; Hacker, Jürgen; Neuner, Gilbert; Wagner, Johanna

    2013-03-01

    In temperate-zone mountains, summer frosts usually occur during unpredictable cold spells with snow-falls. Earlier studies have shown that vegetative aboveground organs of most high-mountain plants tolerate extracellular ice in the active state. However, little is known about the impact of frost on reproductive development and reproductive success. In common plant species from the European Alps (Cerastium uniflorum, Loiseleuria procumbens, Ranunculus glacialis, Rhododendron ferrugineum, Saxifraga bryoides, S. moschata, S. caesia), differing in growth form, altitudinal distribution and phenology, frost resistance of reproductive and vegetative shoots was assessed in different reproductive stages. Intact plants were exposed to simulated night frosts between -2 and -14 °C in temperature-controlled freezers. Nucleation temperatures, freezing damage and subsequent reproductive success (fruit and seed set, seed germination) were determined. During all reproductive stages, reproductive shoots were significantly less frost resistant than vegetative shoots (mean difference for LT50 -4.2 ± 2.7 K). In most species, reproductive shoots were ice tolerant before bolting and during fruiting (mean LT50 -7 and -5.7 °C), but were ice sensitive during bolting and anthesis (mean LT50 around -4 °C). Only R. glacialis remained ice tolerant during all reproductive stages. Frost injury in reproductive shoots usually led to full fruit loss. Reproductive success of frost-treated but undamaged shoots did not differ significantly from control values. Assessing the frost damage risk on the basis of summer frost frequency and frost resistance shows that, in the alpine zone, low-statured species are rarely endangered as long as they are protected by snow. The situation is different in the subnival and nival zone, where frost-sensitive reproductive shoots may become frost damaged even when covered by snow. Unprotected individuals are at high risk of suffering from frost damage, particularly at higher elevations. It appears that ice tolerance in reproductive structures is an advantage but not an absolute precondition for colonizing high altitudes with frequent frost events. PMID:23386042

  7. High rates of nonbreeding adult bald eagles in southeastern Alaska

    SciTech Connect

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

    1985-01-01

    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.

  8. High strain rate deformation in FCC metals and alloys

    SciTech Connect

    Follansbee, P.S.

    1985-01-01

    The effect of strain rate, and particularly of high strain rates, on deformation mechanisms in materials is of fundamental interest to those who model and analyze dynamic loading. In many materials the strain rate sensitivity is known to increase dramatically when the strain rate is raised above approx.10/sup 3/ s/sup -1/. This increase has been interpreted previously as a transmission in deformation mechanism from thermal activation control at low strain rate to dislocation drag control at high strain rate. In copper, copper-aluminum alloys and stainless steel, recent measurements have shown that the increased rate sensitivity found at high strain rates is not due to a transition in deformation mechanism but rather can be explained with standard thermal activation theory. These findings and their implications regarding the formulation of constitutive behavior are presented.

  9. The vOTU domain of highly-pathogenic porcine reproductive and respiratory syndrome virus displays a differential substrate preference

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Arterivirus genus member Porcine reproductive and respiratory syndrome virus (PRRSV) causes an economically devastating disease that presents global concerns to the pork industry, which have been exacerbated by the emergence of a highly pathogenic PRRSV strain (HP-PRRSV) in China and Southeast Asia....

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

    Microsoft Academic Search

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

    2007-01-01

    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

  11. An empirical test of evolutionary theories for reproductive senescence and reproductive effort in the garter snake Thamnophis elegans

    Microsoft Academic Search

    Amanda M. Sparkman; Stevan J. Arnold; Anne M. Bronikowski

    2007-01-01

    Evolutionary theory predicts that differential reproductive effort and rate of reproductive senescence will evolve under different rates of external mortality. We examine the evolutionary divergence of age-specific reproduction in two life-history ecotypes of the western terrestrial garter snake, Thamnophis elegans. We test for the signature of reproductive senescence (decreasing fecundity with age) and increasing reproductive effort with age (increasing reproductive

  12. Experimentally simulating high-rate behaviour: rate and temperature effects in polycarbonate and PMMA

    PubMed Central

    Kendall, M. J.; Siviour, C. R.

    2014-01-01

    This paper presents results from applying a recently developed technique for experimentally simulating the high-rate deformation response of polymers. The technique, which uses low strain rate experiments with temperature profiles to replicate high-rate behaviour, is here applied to two amorphous polymers, polymethylmethacrylate (PMMA) and polycarbonate, thereby complementing previously obtained data from plasticized polyvinyl chloride. The paper presents comparisons of the mechanical data obtained in the simulation, as opposed to those observed under high-rate loading. Discussion of these data, and the temperature profile required to produce them, gives important information about yield and post-yield behaviour in these materials. PMID:24711491

  13. High power, high efficiency millimeter wavelength traveling wave tubes for high rate communications from deep space

    Microsoft Academic Search

    James A. Dayton Jr.

    1991-01-01

    The high-power transmitters needed for high data rate communications from deep space will require a new class of compact, high efficiency traveling wave tubes (TWT's). Many of the recent TWT developments in the microwave frequency range are generically applicable to mm wave devices, in particular much of the technology of computer aided design, cathodes, and multistage depressed collectors. However, because

  14. High School Graduation Rates: Alternative Methods and Implications

    Microsoft Academic Search

    Jing Miao; Walt Haney

    ABSTRACT The No Child Left Behind Act has brought great attention to the high school graduation rate as one of the mandatory,accountability measures for public school systems. However, there is no consensus on how to calculate the high school graduation rate given the lack of longitudinal databases that track individual students. This study reviews literature on and practices in reporting

  15. HIGH-RATE DISINFECTION TECHNIQUES FOR COMBIND SEWER OVERFLOW

    EPA Science Inventory

    This paper presents high-rate disinfection technologies for combined sewer overflow (CSO). The high-rate disinfection technologies of interest are: chlorination/dechlorination, ultraviolet light irradiation (UV), chlorine dioxide (ClO2 ), ozone (O3), peracetic acid (CH3COOOH )...

  16. Dosimetry errors in endovascular high-dose-rate brachytherapy

    Microsoft Academic Search

    W Schumer; S Wallace; T Wong; G Quong; M Geso

    2000-01-01

    Monte Carlo data were used to demonstrate the dosimetry of the microSelectron high-dose-rate (HDR) iridium 192 (192Ir) stepping source. These data were used to assess the accuracy of the Nucletron brachytherapy planning system (BPS version 13) for peripheral vessel endovascular brachytherapy. Dose rates from the high-dose-rate (HDR) source are calculated using the Monte Carlo code MCNP4A. Calculations are made at

  17. Effects of high tissue concentrations of selenium on reproduction by bluegills

    SciTech Connect

    Gillespie, R.B.; Baumann, P.C.

    1986-03-01

    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, the authors 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 reduced viability of gametes or increased mortality of embryos and larvae. Bluegills with high body concentrations of Se were obtained from Hyco Reservoir (cooling water source of a coal-fired power plant) and those with low body concentrations were obtained from nearby Roxboro City Lake, North Carolina. Neither percent fertilization nor percent hatch of eggs differed significantly among the parent combinations. However, all crosses (8) that included females with high Se body concentrations resulted in larvae with edema; such larvae did not survive to the swim-up stage. Only one of these crosses produced some normal larvae (35%). Mean Se concentrations in the gonads and carcass (body minus gonad) were more than 20 times higher in bluegills from Hyco Reservoir (average = 7.94 mg/kg) than in those from Roxboro City Lake (average = 0.38 mg/kg). The high Se concentrations in ovaries of Hyco Reservoir bluegills and in their progeny suggested that Se was transferred from females to offspring and caused edema in larvae. This abnormality resulted in mortality of affected larval bluegills - and consequently may have caused reductions in the bluegill populations of selenium-enriched reservoirs.

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

    PubMed

    Suzuki, Keiko; Motohashi, Yutaka; Kaneko, Yoshihiro

    2006-04-01

    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

  19. Temperature-driven flower longevity in a high-alpine species of Oxalis influences reproductive assurance.

    PubMed

    Arroyo, Mary T K; Dudley, Leah S; Jespersen, Gus; Pacheco, Diego A; Cavieres, Lohengrin A

    2013-12-01

    How high-alpine plants confront stochastic conditions for animal pollination is a critical question. We investigated the effect of temperature on potential flower longevity (FL) measured in pollinator-excluded flowers and actual FL measured in pollinated flowers in self-incompatible Oxalis compacta and evaluated if plastically prolonged potential FL can ameliorate slow pollination under cool conditions. Pollinator-excluded and hand-pollinated flowers were experimentally warmed with open-top chambers (OTCs) on a site at 3470 m above sea level (asl). Flower-specific temperatures, and pollinator-excluded and open-pollination flower life-spans were measured at six alpine sites between 3100 and 3470 m asl. Fruit set was analyzed in relation to inferred pollination time. Warming reduced potential FL. Variable thermal conditions across the alpine landscape predicted potential and actual FL; flower senescence was pollination-regulated. Actual FL and potential FL were coupled. Prolonged potential FL generally increased fruit set under cooler conditions. Plastic responses permit virgin flowers of O. compacta to remain open longer under cooler temperatures, thereby ameliorating slow pollination, and to close earlier when pollination tends to be faster under warmer conditions. Plastic potential FL provides adaptive advantages in the cold, thermally variable alpine habitat, and has important implications for reproductive success in alpine plants in a warming world. PMID:23952472

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

    PubMed Central

    Firman, Renée C.

    2011-01-01

    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

  1. Quantum data locking for high-rate private communication

    NASA Astrophysics Data System (ADS)

    Lupo, Cosmo; Lloyd, Seth

    2015-03-01

    We show that, if the accessible information is used as a security quantifier, quantum channels with a certain symmetry can convey private messages at a tremendously high rate, as high as less than one bit below the rate of non-private classical communication. This result is obtained by exploiting the quantum data locking effect. The price to pay to achieve such a high private communication rate is that accessible information security is in general not composable. However, composable security holds against an eavesdropper who is forced to measure her share of the quantum system within a finite time after she gets it.

  2. Orientation and rate dependence in high strain-rate compression of single-crystal silicon

    NASA Astrophysics Data System (ADS)

    Smith, R. F.; Minich, R. W.; Rudd, R. E.; Eggert, J. H.; Bolme, C. A.; Brygoo, S. L.; Jones, A. M.; Collins, G. W.

    2012-12-01

    High strain-rate (??˜106-109s-1) compression of single crystal Si reveals strong orientation- and rate-dependent precursor stresses. At these high compression rates, the peak elastic stress, ?E_Peak, for Si [100], [110], and [111] exceeds twice the Hugoniot elastic limit. Near the loading surface, the rate at which Si evolves from uniaxial compression to a three-dimensional relaxed state is exponentially dependent on ?E_Peak and independent of initial crystal orientation. At later times, the high elastic wave speed results in a temporal decoupling of the elastic precursor from the main inelastic wave. A rapid high-?? increase in the measured elastic stress at the onset of inelastic deformation is consistent with a transition from dislocation flow mediated by thermal activation to a phonon drag regime.

  3. Reproductive management of postpartum cows.

    PubMed

    Roche, J F; Mackey, D; Diskin, M D

    2000-07-01

    High reproductive efficiency in the dairy cow requires a disease-free transition period, high submission rates to AI and high pregnancy rates per service. A key risk factor that causes increased incidence of metabolic disease is low negative energy balance (NEB) in the periparturient and early postpartum periods. Low NEB decreases LH pulse frequency, growth rate and diameter of dominant follicle (DF), IGF-I, glucose, insulin concentrations and increases GH and certain blood metabolites; these effects result in greater loss of body condition score (BCS) and a higher percent of anoestrous cows in the herd. It is important to decrease the incidence of metabolic disease by achieving high dry matter intake (DMI) and minimising the period of NEB after calving. Thus, nutritional management of the cow in the transition period has a crucial role to play in improving reproductive efficiency, because acute nutritional deprivation of heifers has immediate deleterious effects on follicular growth and ovulation. To obtain high submission rates, it is necessary to decrease the incidence of anoestrus and to have good oestrous detection rates. Pregnancy rates per service are affected by a variety of factors. NEB can have deleterious effects on the follicle or the corpus luteum (CL) by decreasing IGF-I concentrations and steroidogenesis. High protein diets fed to postpartum cows leads to increased blood urea and lower fertility. Although the mechanism is not clear, the practical implication of feeding the appropriate level of crude protein in the diet is clear. Thus, a coordinated management approach involving herd managers, nutritionists and veterinarians is required to obtain high reproduction efficiency in dairy cows. PMID:10844236

  4. The American High School Graduation Rate: Trends and Levels

    Microsoft Academic Search

    James J. Heckman; Paul A. LaFontaine

    2010-01-01

    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, © majority-minority differentials are substantial and have not converged for 35 years, (d) lower post-1970 rates

  5. Tensile testing of materials at high rates of strain

    Microsoft Academic Search

    Theodore Nicholas

    1981-01-01

    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

  6. An infrared high rate video imager for various space applications

    Microsoft Academic Search

    Hâkan Svedhem; Detlef Koschny

    2010-01-01

    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

  7. Rural and Urban High School Dropout Rates: Are They Different?

    ERIC Educational Resources Information Center

    Jordan, Jeffrey L.; Kostandini, Genti; Mykerezi, Elton

    2012-01-01

    This study estimates the high school dropout rate in rural and urban areas, the determinants of dropping out, and whether the differences in graduation rates have changed over time. We use geocoded data from two nationally representative panel household surveys (NLSY 97 and NLSY 79) and a novel methodology that corrects for biases in graduation…

  8. High Pressure Burn Rate Measurements on an Ammonium Perchlorate Propellant

    Microsoft Academic Search

    E A Glascoe; N Tan

    2010-01-01

    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

  9. High School Dropout Rates for Latino Youth. ERIC Digest.

    ERIC Educational Resources Information Center

    Fry, Richard

    Dropout rates are particularly problematic measures for Hispanic youth. One-third of Hispanic adolescents are foreign-born. Their sending countries tend to have much lower rates of secondary school completion than does the United States. This digest presents recent tabulations on the number of Latino high school dropouts, noting pitfalls in…

  10. Mechanical Properties of Ballistic Gelatin at High Deformation Rates

    Microsoft Academic Search

    C. P. Salisbury; D. S. Cronin

    2009-01-01

    The characterization of soft or low impedance materials is of increasing importance since these materials are commonly used\\u000a in impact and energy absorbing applications. The increasing role of numerical modeling in understanding impact events requires\\u000a high-rate material properties, where the mode of loading is predominantly compressive and large deformations may occur at\\u000a high rates of deformation. The primary challenge in

  11. A General Model of High Frame Rate Imaging System

    Microsoft Academic Search

    Peng Hu; Lu Jianyu; Han Xuemei; Feng Huanqing

    2005-01-01

    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

  12. Performance of High Flow Rate Samplers for Respirable Particle Collection

    PubMed Central

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

    2010-01-01

    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. PMID:20660144

  13. Description of a high rate luminosity monitor installed at CESR

    SciTech Connect

    Jackson, G.P.; Herb, S.W.

    1985-10-01

    In response to a need for a fast, direct measure of luminosity for the purpose of machine optimization, a high rate luminosity monitor has been constructed for CESR. The interaction regions at CESR employ a standard minibeta lattice in which the inner quadrupoles are vertically focussing. Bhabha scattered particles are horizontally defocussed upon traversing these quadrupoles. A beam pipe constricted in the horizontal plane was constructed to detect these high event rate particles. This paper is a description of the luminosity, background, and accidental rates observed with various detector schemes. These results are compared with calculations. Stability and beam steering sensitivies are also explored.

  14. High-mass star-formation rates in M33

    NASA Technical Reports Server (NTRS)

    Wilson, Christine D.; Scoville, Nick; Rice, Walter

    1991-01-01

    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.

  15. High-mass star-formation rates in M33

    SciTech Connect

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

    1991-04-01

    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.

  16. Slow rate of molecular evolution in?high-elevation?hummingbirds

    PubMed Central

    Bleiweiss, Robert

    1998-01-01

    Estimates of relative rates of molecular evolution from a DNA-hybridization phylogeny for 26 hummingbird species provide evidence for a negative association between elevation and rate of single-copy genome evolution. This effect of elevation on rate remains significant even after taking into account a significant negative association between body mass and molecular rate. Population-level processes do not appear to account for these patterns because (i) all hummingbirds breed within their first year and (ii) the more extensive subdivision and speciation of bird populations living at high elevations predicts a positive association between elevation and rate. The negative association between body mass and molecular rate in other organisms has been attributed to higher mutation rates in forms with higher oxidative metabolism. As ambient oxygen tensions and temperature decrease with elevation, the slow rate of molecular evolution in high-elevation hummingbirds also may have a metabolic basis. A slower rate of single-copy DNA change at higher elevations suggests that the dynamics of molecular evolution cannot be separated from the environmental context. PMID:9435240

  17. Teaching Plant Reproduction.

    ERIC Educational Resources Information Center

    Tolman, Marvin N., Ed.; Hardy, Garry R., Ed.

    2000-01-01

    Recommends using Amaryllis hippeastrum to teach young children about plant reproduction. Provides tips for growing these plants, discusses the fast growing rate of the plant, and explains the anatomy. (YDS)

  18. Solidification at the High and Low Rate Extreme

    SciTech Connect

    Halim Meco

    2004-12-19

    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 solidification mechanisms, and thus the final microstructure of the alloy, are governed by these imposed growth rates. At the high rate extreme, for instance, one can have access to novel microstructures that are unattainable at low growth rates. While the low growth rates can be utilized for the study of the intrinsic growth behavior of a certain phase growing from the melt. Although the length scales associated with certain processes, such as capillarity, and the diffusion of heat and solute, are different at low and high rate extremes, the phenomena that govern the selection of a certain microstructural length scale or a growth mode are the same. Consequently, one can analyze the solidification phenomena at both high and low rates by using the same governing principles. In this study, we examined the microstructural control at both low and high extremes. For the high rate extreme, the formation of crystalline products and factors that control the microstructure during rapid solidification by free-jet melt spinning are examined in Fe-Si-B system. Particular attention was given to the behavior of the melt pool at different quench-wheel speeds. Since the solidification process takes place within the melt-pool that forms on the rotating quench-wheel, we examined the influence of melt-pool dynamics on nucleation and growth of crystalline solidification products and glass formation. High-speed imaging of the melt-pool, analysis of ribbon microstructure, and measurement of ribbon geometry and surface character all indicate upper and lower limits for melt-spinning rates for which nucleation can be avoided, and fully amorphous ribbons can be achieved. Comparison of the relevant time scales reveals that surface-controlled melt-pool oscillation may be the dominant factor governing the onset of unsteady thermal conditions accompanied by varying amounts of crystalline nucleation observed near the lower limit. At high quench-wheel velocities, the influence of these oscillations is minimal due to very short melt-pool residence times. However, microstructural evidence suggests that the entrapment of gas pockets at the wheel-metal interface plays a critical role in establishing the upper rate limit. An observed transition in wheel-side surface character with increasing melt-spinning rate supports this conclusion.

  19. Statistical profiles of highly-rated web sites

    Microsoft Academic Search

    Melody Y. Ivory; Marti A. Hearst

    2002-01-01

    We are creating an interactive tool to help non-professional web site builders create high quality designs. We have previously reported that quantitative measures of web page structure can predict whether a site will be highly or poorly rated by experts, with accuracies ranging from 67--80%. In this paper we extend that work in several ways. First, we compute a much

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

    Microsoft Academic Search

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

    1987-01-01

    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

  1. 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

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

    2005-01-01

    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

  2. [A discourse on female nurse job stress and reproductive hazards].

    PubMed

    Chen, Hui-Chuan; Chuang, Chao-Hua

    2011-12-01

    The negative effects of job stress on female reproduction have been receiving greater attention due to rapidly falling fertility rates in recent years. Nurses represent the greatest number of workers in the healthcare system. Nearly all are female and most are of reproductive age. Over half of nurses perceive nursing as a high-pressure occupation, making job stress an important issue. Long-term job stress affects mental and reproductive health. The International Nursing Association's advocacy of high quality, positive medical environments in 2007 highlighted the importance of improving workplace quality. This article reviews references and discusses job stress and its relationship to reproductive hazards for female nurses. We hope it provides valuable information and encourages government and related organizations to improve the medical working environment, recognize job stress in a timely manner, and provide health promotion strategies to reduce reproductive hazards and promote nurse health. PMID:22113640

  3. Evolutionary Dynamics of a Highly Pathogenic Type 2 Porcine Reproductive and Respiratory Syndrome Virus: Analyses of Envelope Protein-Coding Genes.

    PubMed

    Nguyen, V G; Kim, H K; Moon, H J; Park, S J; Chung, H C; Choi, M K; Park, B K

    2015-08-01

    Porcine reproductive and respiratory syndrome virus (PRRSV) has long been an economically devastating swine viral disease. The recent emergence of a highly pathogenic type 2 PRRSV with high mobility and mortality in China, spreading in Vietnam, Laos, and Thailand has placed neighbouring countries at risk. This study applied a codon-based extension of the Bayesian relaxed clock model and the fixed effects maximum-likelihood method to investigate and compare the evolutionary dynamics of type 2 PRRSV for all of known structural envelope protein-coding genes. By comparing the highly pathogenic type 2 PRRSV clade against the typical type 2 PRRSV clade, this study demonstrated that the highly pathogenic clade evolved at high rates in all of the known structural genes but did not display rapid evolutionary dynamics compared with typical type 2 PRRSV. In contrast, the ORF3, ORF5 and ORF6 genes of the highly pathogenic clade evolved in a qualitatively different manner from the genes of the typical clade. At the population level, several codons of the sequence elements that were involved in viral neutralization, as well as codons that were associated with in vitro attenuation/over-attenuation, were predicted to be selected differentially between the typical clade and the highly pathogenic clade. The results of this study suggest that the multigenic factors of the envelope protein-coding genes contribute to diversifying the biological properties (virulence, antigenicity, etc.) of the highly pathogenic clade compared with the typical clade of type 2 PRRSV. PMID:23981823

  4. Improving adolescent sexual and reproductive health. A view from Australia: learning from world's best practice.

    PubMed

    Williams, Henrietta; Davidson, Sandra

    2004-01-01

    There is increasing awareness worldwide of the importance of sexual and reproductive health in adolescents. Australia's high rates of teenage pregnancy and increasing rates of sexually transmitted infections in young people reflect a failure to prioritise adolescent sexual and reproductive health on the public health agenda. This paper reviews adolescent sexual and reproductive health in Australia in comparison with international data, and examines the systemic, social and cultural factors that influence it. Based on comparisons with international best practice, recommendations are included for improvement in adolescent sexual and reproductive health within the Australian context. PMID:16334991

  5. High Strain Rate Behavior of Polymer Matrix Composites Analyzed

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.; Roberts, Gary D.

    2001-01-01

    Procedures for modeling the high-speed impact of composite materials are needed for designing reliable composite engine cases that are lighter than the metal cases in current use. The types of polymer matrix composites that are likely to be used in such an application have a deformation response that is nonlinear and that varies with strain rate. To characterize and validate material models that could be used in the design of impactresistant engine cases, researchers must obtain material data over a wide variety of strain rates. An experimental program has been carried out through a university grant with the Ohio State University to obtain deformation data for a representative polymer matrix composite for strain rates ranging from quasi-static to high rates of several hundred per second. This information has been used to characterize and validate a constitutive model that was developed at the NASA Glenn Research Center.

  6. Long-Life High-Repetition-Rate Triggered Spark Gap

    Microsoft Academic Search

    Harold Watson

    1980-01-01

    A forced-air-blown triggered spark gap (TSG) switch system capable of high-repetition rates on a continuous basis as well as a TSG comparative study is described. The system consists of two TSG's, each discharging its own 30-¿ pulse cable into a common load. The system was operated at 30 kV, 1 kHz, for 39 ?? 106 shots with erosion rates of

  7. Beam test results of high counting rate MRPCs at GSI

    NASA Astrophysics Data System (ADS)

    Zhu, Xianglei; Wang, Yi; Wang, Jingbo; Li, Yuanjing; Cheng, Jianping

    2010-03-01

    The usage of electrodes made of semi-conductive glass is an inspiring way of improving the counting rate capability of resistive plate chamber. We developed 6 and 10-gap multi-gap resistive plate chambers (MRPCs) with low resistive silicate glass electrodes (bulk resistivity ˜1010 ?cm) for applications in time-of-flight (TOF) at high counting rates. These two prototypes were tested with secondary irradiation from 2.5 GeV proton beam at GSI. Time resolutions below 90 ps and efficiencies above 90% were obtained at counting rates up to 28 kHz/cm2 for the 10-gap MRPC.

  8. THE AMERICAN HIGH SCHOOL GRADUATION RATE: TRENDS AND LEVELS*

    PubMed Central

    Heckman, James J.; LaFontaine, Paul A.

    2009-01-01

    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

  9. High-Strain-Rate Compression Testing of Ice

    NASA Technical Reports Server (NTRS)

    Shazly, Mostafa; Prakash, Vikas; Lerch, Bradley A.

    2006-01-01

    In the present study a modified split Hopkinson pressure bar (SHPB) was employed to study the effect of strain rate on the dynamic material response of ice. Disk-shaped ice specimens with flat, parallel end faces were either provided by Dartmouth College (Hanover, NH) or grown at Case Western Reserve University (Cleveland, OH). The SHPB was adapted to perform tests at high strain rates in the range 60 to 1400/s at test temperatures of -10 and -30 C. Experimental results showed that the strength of ice increases with increasing strain rates and this occurs over a change in strain rate of five orders of magnitude. Under these strain rate conditions the ice microstructure has a slight influence on the strength, but it is much less than the influence it has under quasi-static loading conditions. End constraint and frictional effects do not influence the compression tests like they do at slower strain rates, and therefore the diameter/thickness ratio of the samples is not as critical. The strength of ice at high strain rates was found to increase with decreasing test temperatures. Ice has been identified as a potential source of debris to impact the shuttle; data presented in this report can be used to validate and/or develop material models for ice impact analyses for shuttle Return to Flight efforts.

  10. Resolving Vitamin D Deficiency in the Preconception Period among High-Risk Reproductive Women: A Randomized Controlled Trial

    PubMed Central

    Taheri, Mahshid; Baheiraei, Azam; Rahimi Foroushani, Abbas; Modarres, Maryam

    2014-01-01

    Background: Although vitamin D deficiency has been linked to potential complications in reproductive women, the recommended intake dosage of this vitamin in populations with high incidence of deficiency in preconception period has not been defined. Objectives: The study investigated the effect of consuming a dosage of 2000 IU/day oral vitamin D for 105 days, on serum levels of this vitamin in reproductive women. Materials and Methods: 229 women with 18-35 years old, who were confirmed to be vitamin D deficient (vitamin D < 75 nmol/L), were randomized into the intervention and control groups and after 15 weeks consumption of the supplement and placebo, their serum samples were obtained. Results: At baseline the mean serum levels of vitamin D in the control group was 23.34 ± 15.87 nmol/L and in intervention group was 25.13 ± 18.46 nmol/L, that these values didn’t have any significant difference (P = 0.43), while after intervention, significant differences between the two groups was noticed (P < 0.001). The affecting factors to achieve normal range of vitamin D in the intervention group included basal amounts of vitamin D and two underlying factors based on questionnaire data: use of oral supplements (except vitamin D and calcium) in daily life and perfect sun exposure. Conclusion: This study showed positive effect of the 2000 IU/day oral vitamin D on the serum level elevation of this vitamin in reproductive women. PMID:24719700

  11. Safety aspects in primary high-rate lithium cells

    NASA Astrophysics Data System (ADS)

    Eichinger, G.

    1993-03-01

    A comprehensive presentation of the most important features influencing the safety of primary high-rate lithium cells is given. The design of such cells as well as the balance of cathode/electrolyte/anode are the most important features with respect to safety. The reliability of production, however, is of equal importance. The chemical reactions under electrical abuse conditions for the lithium/thionyl chloride system are given. Examples, how lithium/thionyl chloride spirally-wound 'C-size' cells behave under charging and forced overdischarge are presented. There are no indications that in the primary high-rate lithium systems, which are produced in a technical scale, dangerous chemical reactions influence the safety of the systems. Regarding the great number of primary high-rate lithium cells available in the market, the safety of these cells is excellent.

  12. Flexible high-repetition-rate ultrafast fiber laser

    PubMed Central

    Mao, Dong; Liu, Xueming; Sun, Zhipei; Lu, Hua; Han, Dongdong; Wang, Guoxi; Wang, Fengqiu

    2013-01-01

    High-repetition-rate pulses have widespread applications in the fields of fiber communications, frequency comb, and optical sensing. Here, we have demonstrated high-repetition-rate ultrashort pulses in an all-fiber laser by exploiting an intracavity Mach-Zehnder interferometer (MZI) as a comb filter. The repetition rate of the laser can be tuned flexibly from about 7 to 1100?GHz by controlling the optical path difference between the two arms of the MZI. The pulse duration can be reduced continuously from about 10.1 to 0.55?ps with the spectral width tunable from about 0.35 to 5.7?nm by manipulating the intracavity polarization controller. Numerical simulations well confirm the experimental observations and show that filter-driven four-wave mixing effect, induced by the MZI, is the main mechanism that governs the formation of the high-repetition-rate pulses. This all-fiber-based laser is a simple and low-cost source for various applications where high-repetition-rate pulses are necessary. PMID:24226153

  13. High-Strain Rate Mechanical Response of Cured Epoxy Networks

    NASA Astrophysics Data System (ADS)

    Sirk, Timothy; Khare, Ketan; Karim, Mir; Lenhart, Joseph; Khare, Rajesh; Andzelm, Jan

    2013-03-01

    Chemically cross-linked polymer networks are increasingly common in high performance composites, adhesives and other applications involving high-impact loading conditions or ballistic collisions. The mechanical behavior of epoxy and other polymer networks exhibit a strong dependence on strain rate near the glass transition temperature (Tg); however, the elastic modulus at strain rates greater than 105 1/s is difficult to capture with experimental techniques. We present computational results of Di-Glycidyl Ether of Bisphenol A (DGEBA) and Jeffamine diamines (D230) from molecular dynamics simulation, which is intrinsically well-suited to model material deformation at high strain rates. Our results show that the experimental Tg can be reproduced from molecular dynamics, and the Williams-Landel-Ferry equation is useful in rationalizing the shift of Tg due to fast annealing and high strain rates. Temperature sweeps of elastic modulus show the glass-rubber transition to occur over a significantly wider temperature range compared with experimental measurements at low strain rates.

  14. High removal rate laser-based coating removal system

    DOEpatents

    Matthews, Dennis L. (Moss Beach, CA); Celliers, Peter M. (Berkeley, CA); Hackel, Lloyd (Livermore, CA); Da Silva, Luiz B. (Danville, CA); Dane, C. Brent (Livermore, CA); Mrowka, Stanley (Richmond, CA)

    1999-11-16

    A compact laser system that removes surface coatings (such as paint, dirt, etc.) at a removal rate as high as 1000 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.

  15. Male Reproductive Toxicology: Environmental Exposures vs Reproductive Competence

    EPA Science Inventory

    Like the lecture this chapter begins with an overview of male reproductive biology and transitions into male reproductive toxicology. It ends with a brief discussion of the strengths and weaknesses in male reproductive toxicology and epidemiology today. This chapter is highly il...

  16. Ultra High-Rate Germanium (UHRGe) Modeling Status Report

    SciTech Connect

    Warren, Glen A.; Rodriguez, Douglas C.

    2012-06-07

    The Ultra-High Rate Germanium (UHRGe) project at Pacific Northwest National Laboratory (PNNL) is conducting research to develop a high-purity germanium (HPGe) detector that can provide both the high resolution typical of germanium and high signal throughput. Such detectors may be beneficial for a variety of potential applications ranging from safeguards measurements of used fuel to material detection and verification using active interrogation techniques. This report describes some of the initial radiation transport modeling efforts that have been conducted to help guide the design of the detector as well as a description of the process used to generate the source spectrum for the used fuel application evaluation.

  17. High frame rate CCD camera with fast optical shutter

    SciTech Connect

    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

    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.

  18. High-rate quantum cryptography in untrusted networks

    E-print Network

    Stefano Pirandola; Carlo Ottaviani; Gaetana Spedalieri; Christian Weedbrook; Samuel L. Braunstein; Seth Lloyd; Tobias Gehring; Christian S. Jacobsen; Ulrik L. Andersen

    2014-08-01

    We extend the field of continuous-variable quantum cryptography to a network formulation where two honest parties connect to an untrusted relay by insecure quantum links. To generate secret correlations, they transmit coherent states to the relay where a continuous-variable Bell detection is performed and the outcome broadcast. Even though the detection could be fully corrupted and the links subject to optimal coherent attacks, the honest parties can still extract a secret key, achieving high rates when the relay is proximal to one party, as typical in public networks with access points or proxy servers. Our theory is confirmed by an experiment generating key-rates which are orders of magnitude higher than those achievable with discrete-variable protocols. Thus, using the cheapest possible quantum resources, we experimentally show the possibility of high-rate quantum key distribution in network topologies where direct links are missing between end-users and intermediate relays cannot be trusted.

  19. Trends in High School Graduation Rates. Research Brief. Volume 0710

    ERIC Educational Resources Information Center

    Romanik, Dale; Froman, Terry

    2008-01-01

    This Research Brief addresses an outcome measure that is of paramount importance to senior high schools--graduation rate. Nationwide a student drops out of school approximately every nine seconds. The significance of this issue locally is exemplified by a recent American Civil Liberties Union filing of a class action law suit against the Palm…

  20. Transient Simulations of RF and High Data Rate circuits

    Microsoft Academic Search

    Malcolm Edwards; Evgeny Wasserman

    This paper provides an overview of the challenges facing the simulation technology used in modern EDA tools that are employed in the research and design of RF, microwave and high data rate circuits. With the operating frequency of consumer products moving well into the microwave region, attention has to be paid to the way in which dispersive elements, data defined

  1. High Rates of Staphylococcus aureus USA400 Infection, Northern Canada

    PubMed Central

    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

    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. PMID:21470471

  2. Electrical Suppression of Tinnitus with High-Rate Pulse Trains

    Microsoft Academic Search

    Jay T. Rubinstein; Richard S. Tyler; Abigail Johnson; Carolyn J. Brown

    2003-01-01

    Hypothesis: Application of high-rate pulse trains (e.g., 4800 pps) to the cochlea may represent an effective treatment of tinnitus. Background: Tinnitus is a widespread clinical problem with multiple treatments but no cure. A cure for tinnitus would restore the perception of silence. One plausible hypothesis for the origin of tinnitus associated with sensorineural hearing loss is that it is due

  3. Out-of-Favor Reading Plan Rated Highly

    ERIC Educational Resources Information Center

    Viadero, Debra; Manzo, Kathleen Kennedy

    2007-01-01

    Reading Recovery, a popular one-to-one tutoring program that Bush administration officials sought to shut out of a high-profile federal reading program, has gotten a rare thumbs-up from the federal What Works Clearinghouse. The positive rating comes after prominent researchers and federal reading officials tried to dissuade states and districts…

  4. Long-life high-repetition-rate triggered spark gap

    Microsoft Academic Search

    H. Watson

    1979-01-01

    A forced-air-blown triggered spark gap (TSG) switch system is described which is capable of high repetition rates on a continuous basis. Further, a TSG comparative study is presented. It is shown that the system consists of two TSG's, each discharging its own 30-ohm pulse cable into a common load. Switching losses of about 28 percent of the stored cable energy

  5. High Rate of Recent Transposable ElementInduced Adaptation

    E-print Network

    Petrov, Dmitri

    High Rate of Recent Transposable Element­Induced Adaptation in Drosophila melanogaster Josefa Gonza to be potent sources of mutation, their contribution to the generation of recent adaptive changes has never been systematically assessed. In this work, we conduct a genome- wide screen for adaptive TE insertions

  6. Understanding High School Graduation Rates in Rhode Island

    ERIC Educational Resources Information Center

    Alliance for Excellent Education, 2009

    2009-01-01

    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 the…

  7. Making Composite-Material Parts At Moderate To High Rates

    NASA Technical Reports Server (NTRS)

    Farley, Gary L.

    1995-01-01

    Composite-material (matrix/fiber) structural components manufactured at moderate to high rates in production-line-style processes, according to proposal. In method, production lines largely automated and takes advantage of fact matrix resins cured by electron beams in addition to heat. Net result reductions in production times and costs.

  8. Dynamic Strength of Metals at High Pressure and Strain Rate

    Microsoft Academic Search

    Thomas Lorenz

    2006-01-01

    A new approach to materials science at very high pressures and strain rates has been developed on the Omega laser, using a ramped plasma piston drive. A laser drives an ablative shock through a solid plastic reservoir where it unloads at the rear free surface, expands across a vacuum gap, and stagnates on the metal sample under study. This produces

  9. OPTIMAL RATE CONTROL FOR HIGH SPEED TELECOMMUNICATION NETWORKS

    E-print Network

    years to use control theory to design flow controllers with, however, no explicit objective functions in the literature in order to analyze or design controllers [1, 5, 7]. We consider a communication networkOPTIMAL RATE CONTROL FOR HIGH SPEED TELECOMMUNICATION NETWORKS Eitan Altman INRIA B.P. 93 06902

  10. High-sampling-rate pressure transducer has in situ calibration

    NASA Technical Reports Server (NTRS)

    Gross, C.

    1979-01-01

    High-data-rate pressure sensor module can be calibrated after it is attached to an experimental setup. Electrically multiplexed sensor is designed for use in wind-tunnels and other applications requiring accurate measurement of many pressures in a short period of time.

  11. Childhood Onset Schizophrenia: High Rate of Visual Hallucinations

    ERIC Educational Resources Information Center

    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

    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…

  12. High rates of innovation: The Japanese culture shock to Europe

    Microsoft Academic Search

    Christer Karlsson

    1989-01-01

    The analysis in this paper deals with the inherent values and cultures that are used in a Japanese productdevelopment group to create a very high rate of innovation. In order to try to explore the cultures and processes, product development organizations are studied as well as development processes of groups in general. The development group is seen as a fakir's

  13. Statistical Profiles of Highly-Rated Learning Objects

    ERIC Educational Resources Information Center

    Cechinel, Cristian; Sanchez-Alonso, Salvador; Garcia-Barriocanal, Elena

    2011-01-01

    The continuously growth of learning resources available in on-line repositories has raised the concern for the development of automated methods for quality assessment. The current existence of on-line evaluations in such repositories has opened the possibility of searching for statistical profiles of highly-rated resources that can be used as…

  14. Compact solid state high repetition rate variable amplitude pulse generator

    Microsoft Academic Search

    Scott J. Pendleton; Daniel Singleton; Andras Kuthi; Martin A. Gundersen

    2009-01-01

    Presented is a solid state high repetition-rate pulse generator with adjustable output amplitude, together with a resonant LC charger. This pulse generator was designed for transient plasma production for ignition and other aerospace plasma applications. The design of the pulse-forming network makes use of commercially available insulated gate bipolar transistors (IGBT) switching a capacitor bank into a METGLAS transformer together

  15. Adolescent health in Milwaukee: High rates of teenage pregnancy

    E-print Network

    of sexually transmitted diseases ­ Low rates of educational attainment Health education and youth health school students are a captive audience to engage in health education ­ In Milwaukee Public Schools, high school students must pass one class of health education to graduate Project Health (PH) is

  16. Reproductive Hazards

    MedlinePLUS

    ... and female reproductive systems play a role in pregnancy. Problems with these systems can affect fertility and ... a reproductive hazard can cause different effects during pregnancy, depending on when she is exposed. During the ...

  17. Generation of high power, high repetition-rate pulses using erbium-doped fiber ring laser

    E-print Network

    Hinson, Brett Darren

    1998-01-01

    This thesis presents the results obtained from crographics. generation of high repetition rate, high peak power output pulses using an erbium-doped fiber amplifier (EDFA). Two configurations were employed. The first setup used a linear cavity...

  18. Generation of high power, high repetition-rate pulses using erbium-doped fiber ring laser 

    E-print Network

    Hinson, Brett Darren

    1998-01-01

    This thesis presents the results obtained from crographics. generation of high repetition rate, high peak power output pulses using an erbium-doped fiber amplifier (EDFA). Two configurations were employed. The first setup used a linear cavity...

  19. Coal plasticity at high heating rates and temperatures

    SciTech Connect

    Darivakis, G.S.; Peters, W.A.; Howard, J.B.

    1990-01-01

    The broad objective of this project is to obtain improved, quantitative understanding of the transient plasticity of bituminous coals under high heating rates and other reaction and pretreatment conditions of scientific and practical interest. To these ends the research plan is to measure the softening and resolidification behavior of two US bituminous coals with a rapid-heating, fast response, high-temperature coal plastometer, previously developed in this laboratory. Specific measurements planned for the project include determinations of apparent viscosity, softening temperature, plastic period, and resolidificationtime for molten coal: (1) as a function of independent variations in coal type, heating rate, final temperature, gaseous atmosphere (inert, 0{sub 2} or H{sub 2}), and shear rate; and (2) in exploratory runs where coal is pretreated (preoxidation, pyridine extraction, metaplast cracking agents), before heating. The intra-coal inventory and molecular weight distribution of pyridine extractables will also be measured using a rapid quenching, electrical screen heater coal pyrolysis reactor. The yield of extractables is representative of the intra-coal inventory of plasticing agent (metaplast) remaining after quenching. Coal plasticity kinetics will then be mathematically modeled from metaplast generation and depletion rates, via a correlation between the viscosity of a suspension and the concentration of deformable medium (here metaplast) in that suspension. Work during this reporting period has been concerned with re-commissioning the rapid heating rate plastometer apparatus.

  20. Interactions between evolutionary processes at high mutation rates

    PubMed Central

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

    2012-01-01

    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. PMID:22759303

  1. High repetition rate plasma mirror device for attosecond science.

    PubMed

    Borot, A; Douillet, D; Iaquaniello, G; Lefrou, T; Audebert, P; Geindre, J-P; Lopez-Martens, R

    2014-01-01

    This report describes an active solid target positioning device for driving plasma mirrors with high repetition rate ultra-high intensity lasers. The position of the solid target surface with respect to the laser focus is optically monitored and mechanically controlled on the nm scale to ensure reproducible interaction conditions for each shot at arbitrary repetition rate. We demonstrate the target capabilities by driving high-order harmonic generation from plasma mirrors produced on glass targets with a near-relativistic intensity few-cycle pulse laser system operating at 1 kHz. During experiments, residual target surface motion can be actively stabilized down to 47?nm (root mean square), which ensures sub-300-as relative temporal stability of the plasma mirror as a secondary source of coherent attosecond extreme ultraviolet radiation in pump-probe experiments. PMID:24517742

  2. High strain rate behavior of pure metals at elevated temperature

    NASA Astrophysics Data System (ADS)

    Testa, Gabriel; Bonora, Nicola; Ruggiero, Andrew; Iannitti, Gianluca; Domenico, Gentile

    2013-06-01

    In many applications and technology processes, such as stamping, forging, hot working etc., metals and alloys are subjected to elevated temperature and high strain rate deformation process. Characterization tests, such as quasistatic and dynamic tension or compression test, and validation tests, such as Taylor impact and DTE - dynamic tensile extrusion -, provide the experimental base of data for constitutive model validation and material parameters identification. Testing material at high strain rate and temperature requires dedicated equipment. In this work, both tensile Hopkinson bar and light gas gun where modified in order to allow material testing under sample controlled temperature conditions. Dynamic tension tests and Taylor impact tests, at different temperatures, on high purity copper (99.98%), tungsten (99.95%) and 316L stainless steel were performed. The accuracy of several constitutive models (Johnson and Cook, Zerilli-Armstrong, etc.) in predicting the observed material response was verified by means of extensive finite element analysis (FEA).

  3. A High Count Rate Beam Monitor for Thermal Neutrons

    SciTech Connect

    Barnett, Amanda [University of Tennessee, Knoxville (UTK); Crow, Lowell [ORNL; Diawara, Yacouba [ORNL; Funk, Loren L [ORNL; Hayward, J P [University of Tennessee, Knoxville (UTK); Menhard, Kocsis [European Synchrotron Radiation Facility (ESRF); Sedov, Vladislav N [ORNL

    2012-01-01

    Beam monitors are an important diagnostic tool in neutron science facilities. Present beam monitors use either ionization chambers in integration mode, which are slow and have no timing information, or pulse counters which can easily be saturated by high beam intensities. Neutron beam monitors indicate the number of neutrons incident on a scattering sample and allow neutron experimental data to be analyzed even when the source strength varies with time. At high flux neutron scattering facilities, neutron beam monitors with very low efficiency (10-5) are presently selected to keep the counting rate within a feasible range, even when a higher efficiency would improve the counting statistics and yield a better measurement of the incident beam. In this work, we report on a high count rate neutron beam monitor which also offers position sensitivity to provide a beam profile. This beam monitor offers good timing (less than 1 s) in addition to position resolution and will therefore improve the counting statistics at neutron energies up to 10 eV and allow moderator studies. The detector s main characteristics will be presented including its background rate, its count rate capability which is an order of magnitude higher than present counting monitors, and its efficiency for thermal neutrons.

  4. High Strain Rate Characterisation of a Polymer Bonded Sugar

    NASA Astrophysics Data System (ADS)

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

    2006-07-01

    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 at 10-3 s-1. The material behavior is compared to that of other polymer bonded explosives and simulants. In order to further understand the structural deformation mechanisms specimens of both pristine material and that after Instron testing were examined using X-ray microtomography.

  5. A modular high rate data link for small satellites

    NASA Astrophysics Data System (ADS)

    Andelman, Dov; Barak, Ilan; Nissani, Daniel N.

    1992-12-01

    A high performance modular data link operating at rates up to 480 Mbps has been developed for scientific remote sensing satellites to transmit large volumes of data to ground station for further processing. The data link is based on a spaceborne transmitter and a ground based receiving terminal and uses a modular architecture in which data is divided among several frequency multiplexed channels. The step variation of a data rate is performed by changing the number of operating channels. The spaceborne transmitter is attractive for small satellites applications due to its light weight and low power consumption.

  6. High strain-rate model for fiber-reinforced composites

    SciTech Connect

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

    1995-07-01

    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.

  7. High Pressure Burn Rate Measurements on an Ammonium Perchlorate Propellant

    SciTech Connect

    Glascoe, E A; Tan, N

    2010-04-21

    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.

  8. Modeling high strain rate viscoplastic deformations combined with phase changes

    NASA Astrophysics Data System (ADS)

    Roy, Gilles; Montheillet, Frank; CEA Valduc-EMSE Collaboration

    2011-06-01

    Metallic materials submitted to high strain rates upon dynamic loading can undergo phase changes induced by strains, stresses, and/or temperature increase associated with self-heating. Various mechanical and metallurgical assumptions have been proposed and implemented in numerical codes to deal with such complex interactions. In order to assess their respective influences, a simple nearly analytical model was developed and applied to the classical sphere expansion test carried out on a two-phase strain hardening, strain rate and temperature sensitive material. In this paper, classical homogenization assumptions are compared for deriving the overall material flow stress. Strain hardening transfer upon phase transformation is accounted for. Finally, the respective weights of the various contributions to the work rate, associated with stored energy, self-heating, and phase change, are analyzed.

  9. Modeling high strain rate viscoplastic deformations combined with phase changes

    NASA Astrophysics Data System (ADS)

    Montheillet, Frank; Roy, Gilles A.

    2012-03-01

    Metallic materials submitted to high strain rates upon dynamic loading can undergo phase changes induced by strains, stresses, and/or temperature increase associated with self-heating. Various mechanical and metallurgical assumptions have been proposed and implemented in numerical codes to deal with such complex interactions. In order to assess their respective influences, a simple nearly analytical model was developed and applied to the classical sphere expansion test carried out on a twophase strain hardening, strain rate and temperature sensitive material. In this paper, classical homogenization assumptions are compared for deriving the overall material flow stress. Strain hardening transfer upon phase transformation is accounted for. Finally, the respective weights of the various contributions to the work rate, associated with stored energy, self-heating, and phase change, are analyzed.

  10. High data rate recording: Moving to 2 Gbit/s

    NASA Astrophysics Data System (ADS)

    Taratorin, A.; Yuan, S.; Nikitin, V.

    2003-05-01

    High data rate recording can be achieved using fast write drivers and fast heads. Advanced short-yoke write heads and write drivers with 450 ps rise time and programmable current overshoot were used to study recording at data rates up to 2 Gbit/s. The head flux rise time causes shifts of recorded transitions. It is well known that current overshoot helps to overcome bandwidth limitations in the write driver, interconnects, and write head. However, excessive overshoot may cause pattern-dependent transition shifts and significant distortions of recorded transitions. We present the data rate performance of short-yoke recording heads, analysis of nonlinear pattern-dependent distortions, and optimization of the write current wave form in the 1-2 Gbit/s range. Simple dibit and tribit patterns were recorded at 2 Gbit/s. Low-distortion recording for arbitrary data patterns was demonstrated at 1.6 Gbit/s after optimization of write current overshoot.

  11. High rates of organic carbon burial in fjord sediments globally

    NASA Astrophysics Data System (ADS)

    Smith, Richard W.; Bianchi, Thomas S.; Allison, Mead; Savage, Candida; Galy, Valier

    2015-06-01

    The deposition and long-term burial of organic carbon in marine sediments has played a key role in controlling atmospheric O2 and CO2 concentrations over the past 500 million years. Marine carbon burial represents the dominant natural mechanism of long-term organic carbon sequestration. Fjords--deep, glacially carved estuaries at high latitudes--have been hypothesized to be hotspots of organic carbon burial, because they receive high rates of organic material fluxes from the watershed. Here we compile organic carbon concentrations from 573 fjord surface sediment samples and 124 sediment cores from nearly all fjord systems globally. We use sediment organic carbon content and sediment delivery rates to calculate rates of organic carbon burial in fjord systems across the globe. We estimate that about 18 Mt of organic carbon are buried in fjord sediments each year, equivalent to 11% of annual marine carbon burial globally. Per unit area, fjord organic carbon burial rates are one hundred times as large as the global ocean average, and fjord sediments contain twice as much organic carbon as biogenous sediments underlying the upwelling regions of the ocean. We conclude that fjords may play an important role in climate regulation on glacial-interglacial timescales.

  12. HIGH RATES OF EVOLUTION PRECEDED THE ORIGIN OF BIRDS

    PubMed Central

    Puttick, Mark N; Thomas, Gavin H; Benton, Michael J; Polly, P David

    2014-01-01

    The origin of birds (Aves) is one of the great evolutionary transitions. Fossils show that many unique morphological features of modern birds, such as feathers, reduction in body size, and the semilunate carpal, long preceded the origin of clade Aves, but some may be unique to Aves, such as relative elongation of the forelimb. We study the evolution of body size and forelimb length across the phylogeny of coelurosaurian theropods and Mesozoic Aves. Using recently developed phylogenetic comparative methods, we find an increase in rates of body size and body size dependent forelimb evolution leading to small body size relative to forelimb length in Paraves, the wider clade comprising Aves and Deinonychosauria. The high evolutionary rates arose primarily from a reduction in body size, as there were no increased rates of forelimb evolution. In line with a recent study, we find evidence that Aves appear to have a unique relationship between body size and forelimb dimensions. Traits associated with Aves evolved before their origin, at high rates, and support the notion that numerous lineages of paravians were experimenting with different modes of flight through the Late Jurassic and Early Cretaceous. PMID:24471891

  13. Investigation of high-rate lithium-thionyl chloride cells

    NASA Astrophysics Data System (ADS)

    Hayes, Catherine A.; Gust, Steven; Farrington, Michael D.; Lockwood, Judith A.; Donaldson, George J.

    Chemical analysis of a commercially produced high-rate D-size lithium-thionyl cell was carried out, as a function of rate of discharge (1 ohm and 5 ohms), depth of discharge, and temperature (25 C and -40 C), using specially developed methods for identifying suspected minor cell products or impurities which may effect cell performance. These methods include a product-retrieval system which involves solvent extraction to enhance the recovery of suspected semivolatile minor chemicals, and methods of quantitative GC analysis of volatile and semivolatile products. The nonvolatile products were analyzed by wet chemical methods. The results of the analyses indicate that the predominant discharge reaction in this cell is 4Li + 2SOCl2 going to 4LiCl + S + SO2, with SO2 formation decreasing towards the end of cell life (7 to 12 Ah). The rate of discharge had no effect on the product distribution. Upon discharge of the high-rate cell at -40 C, one cell exploded, and all others exhibited overheating and rapid internal pressure rise when allowed to warm up to room temperature.

  14. Optically Stimulated Luminescent Dosimetry for High Dose Rate Brachytherapy

    PubMed Central

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

    2012-01-01

    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

  15. Plastic behavior of aluminum in high strain rate regime

    NASA Astrophysics Data System (ADS)

    Shu, Hua; Fu, Sizu; Huang, Xiuguang; Pan, Hao; Zhang, Fan; Xie, Ziyong; Ye, Junjian; Jia, Guo

    2014-07-01

    The aim of this experiment was to study the plastic response of Al to dynamic loading at high strain rates. Dynamic loading was applied by direct laser ablation of the sample with pulse width of 3 ns long. The free surface velocity histories of shock loaded samples, 60-310 ?m thick at room temperature, and 150 ?m thick with initial temperature from 293 to 893 K, have been recorded using a line velocity interferometer for any reflections (VISAR) system. The line VISAR could measure free surface velocity profile with high temporal resolution (˜100 ps). The measured amplitudes of the elastic precursor waves have been approximated by power functions of the propagation distance with the power index of 0.581, and these data have been converted into relationships between the shear stress at Hugoniot elastic limit and the initial plastic strain rate. The peak longitudinal elastic stress and the strain rate meet a power law dependency with the power index of 0.44. Samples were recovered for post-shot metallographic analysis. The metallographic analysis leads to the conclusion that the spall strength of preheated aluminum is determined more by the rate of void nucleation rather than its growth.

  16. Elastoplastic behavior of copper upon high-strain-rate deformation

    NASA Astrophysics Data System (ADS)

    Chembarisova, R. G.

    2015-06-01

    The deformation behavior of copper under conditions of high-strain-rate deformation has been investigated based on the model of elastoplastic medium with allowance for the kinetics of plastic deformation. Data have been obtained on the evolution of the dislocation subsystem, namely, on the average dislocation density, density of mobile dislocations, velocity of dislocation slip, concentration of deformation-induced vacancies, and density of twins. The coefficient of the annihilation of screw dislocations has been estimated depending on pressure and temperature. It has been shown that severe shear stresses that arise upon high-strain-rate deformation can lead to a significant increase in the concentration of vacancies. The time of the dislocation annihilation upon their nonconservative motion has been estimated. It has been shown that this time is much greater than the time of the deformation process in the samples, which makes it possible to exclude the annihilation of dislocations upon their nonconservative motion from the active mechanisms of deformation.

  17. High removal rate laser-based coating removal system

    SciTech Connect

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

    1999-11-16

    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.

  18. Failure Rate Data Analysis for High Technology Components

    SciTech Connect

    L. C. Cadwallader

    2007-07-01

    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.

  19. ISAP 2012 Brosseaud et al: High modulus asphalt with high rate of recycling 1/13 High modulus asphalt mixes with high rate of RA: what does

    E-print Network

    Paris-Sud XI, Université de

    on motorway), preliminary laboratory mix design, new mixing plant with two separate drums, where one concrete,...), or to reduce the thicknesses of wearing course (very thin or ultra-thin asphalt mixes with high rate of recycling 2/13 laboratory mix design, new mixing plant with two separate drums, where one

  20. Distribution of streaming rates into high-redshift galaxies

    E-print Network

    Goerdt, Tobias; Dekel, Avishai; Teyssier, Romain

    2015-01-01

    We study the accretion along streams from the cosmic web into high-redshift massive galaxies using three sets of AMR hydro-cosmological simulations. We find that the streams keep a roughly constant accretion rate as they penetrate into the halo centre. The mean accretion rate follows the mass and redshift dependence predicted for haloes by the EPS approximation, dM / dt is proportional to Mvir^{1.25} (1 + z)^{2.5}. The distribution of the accretion rates can well be described by a sum of two Gaussians, the primary corresponding to "smooth inflow" and the secondary to "mergers". The same functional form was already found for the distributions of specific star formation rates in observations. The mass fraction in the smooth component is 60 - 90 %, insensitive to redshift or halo mass. The simulations with strong feedback show clear signs of re-accretion due to recycling of galactic winds. The mean accretion rate for the mergers is a factor 2 - 3 larger than that of the smooth component. The standard deviation o...

  1. Development of high burn rate azide polymer propellant

    Microsoft Academic Search

    Yoshino Oyumi; Kikokazu Nagayama

    1997-01-01

    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

  2. Spread Spectrum Watermarking: Zero Rate Embedding to High Payload System

    Microsoft Academic Search

    Santi P. Maity; Claude DELPHA; Amit Phadikar

    2009-01-01

    This article presents a brief review on non-blind and blind spread spectrum (SS) watermarking developed for multimedia signals. The discussion gradually moves from zero-rate embedding to high payload and variable embedding systems that take into consideration the issues of host signal interference rejection, payload problem and decoder structure robust to non-stationary fading like attack. The algorithms have been discussed from

  3. An impulse radio asynchronous transceiver for high data rates

    Microsoft Academic Search

    Stkphane Paquelet; L.-M. Aubert; Bernard Uguen

    2004-01-01

    The purpose of this paper is to provide an operative way of achieving high data rates for impulse radio (IR) transmission based systems. Since applications targeted for ultra wide band (UWB) are liable to be low-cost, we especially focus on simple transceiver design. To that effect, we present an original demodulation scheme adapted to a multi-band ON-OFF keying modulation. From

  4. Determination of temperature rise during high strain rate deformation

    Microsoft Academic Search

    Rajeev Kapoor; Sia Nemat-Nasser

    1998-01-01

    The energy converted to heat during high strain rate plastic deformation is measured directly using an infra-red method for Ta?2.5% W alloy and, indirectly, using UCSD's recovery Hopkinson bar technique for the same alloy, as well as for commercially pure Ti, 1018 steel, 6061 Al and OFHC Cu. The infra-red measurement yields a 70% conversion of work to heat for

  5. Avalanche Photo-Detection for High Data Rate Applications

    E-print Network

    H. B. Coldenstrodt-Ronge; C. Silberhorn

    2007-09-19

    Avalanche photo detection is commonly used in applications which require single photon sensitivity. We examine the limits of using avalanche photo diodes (APD) for characterising photon statistics at high data rates. To identify the regime of linear APD operation we employ a ps-pulsed diode laser with variable repetition rates between 0.5MHz and 80MHz. We modify the mean optical power of the coherent pulses by applying different levels of well-calibrated attenuation. The linearity at high repetition rates is limited by the APD dead time and a non-linear response arises at higher photon-numbers due to multiphoton events. Assuming Poissonian input light statistics we ascertain the effective mean photon-number of the incident light with high accuracy. Time multiplexed detectors (TMD) allow to accomplish photon- number resolution by photon chopping. This detection setup extends the linear response function to higher photon-numbers and statistical methods may be used to compensate for non-linearity. We investigated this effect, compare it to the single APD case and show the validity of the convolution treatment in the TMD data analysis.

  6. Avalanche Photo-Detection for High Data Rate Applications

    E-print Network

    Coldenstrodt-Ronge, H B

    2007-01-01

    Avalanche photo detection is commonly used in applications which require single photon sensitivity. We examine the limits of using avalanche photo diodes (APD) for characterising photon statistics at high data rates. To identify the regime of linear APD operation we employ a ps-pulsed diode laser with variable repetition rates between 0.5MHz and 80MHz. We modify the mean optical power of the coherent pulses by applying different levels of well-calibrated attenuation. The linearity at high repetition rates is limited by the APD dead time and a non-linear response arises at higher photon-numbers due to multiphoton events. Assuming Poissonian input light statistics we ascertain the effective mean photon-number of the incident light with high accuracy. Time multiplexed detectors (TMD) allow to accomplish photon- number resolution by photon chopping. This detection setup extends the linear response function to higher photon-numbers and statistical methods may be used to compensate for non-linearity. We investigate...

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

    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 , ). 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.

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

    PubMed

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

    2013-06-01

    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

  9. Optical communication demonstration and high-rate link facility

    NASA Astrophysics Data System (ADS)

    Sandusky, John; Jeganathan, Muthu; Ortiz, Gerry; Biswas, Abi; Lee, Shinhak; Wilson, Keith; Parker, George; Lesh, James

    1999-01-01

    Motivated by demands for faster, better, cheaper spacecraft, NASA is developing deep-space optical communication technology which promises reduced mass, volume, and power consumption compared to radio-frequency technology. While earth-orbiting optical receivers may eventually be employed, initial deep-space optical communication links are expected to utilize terrestrial telescope receivers. As the communication beam passes through the atmosphere, atmospheric turbulence causes the beam to scintillate, dramatically impacting its temporal and transverse nature. The statistics of these effects must be measured extensively if optical deep-space communication links are to be fully modeled and the design of deep-space communication links optimized. Sponsored by the Engineering Research and Technology Development program, the purposes of the Optical Communication Demonstration and High-Rate Link Facility are to demonstrate a Gbps-class optical downlink, gather extensive link statistics, and provide high-rate downlink capability. The Optical Communication Demonstration and High-Rate Link Facility will be deployed to the International Space Station by flight UF-4, currently scheduled for May 2002.

  10. 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...

  11. 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)

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

    2008-09-01

    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.

  12. Characterization of an infrared detector for high frame rate thermography

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    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.

  13. High Strain Rate Compression Testing of Ceramics and Ceramic Composites.

    SciTech Connect

    Blumenthal, W. R. (William R.)

    2005-01-01

    The compressive deformation and failure behavior of ceramics and ceramic-metal composites for armor applications has been studied as a function of strain rate at Los Alamos National Laboratory since the late 1980s. High strain rate ({approx}10{sup 3} s{sup -1}) uniaxial compression loading can be achieved using the Kolsky-split-Hopkinson pressure bar (SHPB) technique, but special methods must be used to obtain valid strength results. This paper reviews these methods and the limitations of the Kolsky-SHPB technique for this class of materials. The Kolsky-split-Hopkinson pressure bar (Kolsky-SHPB) technique was originally developed to characterize the mechanical behavior of ductile materials such as metals and polymers where the results can be used to develop strain-rate and temperature-dependent constitutive behavior models that empirically describe macroscopic plastic flow. The flow behavior of metals and polymers is generally controlled by thermally-activated and rate-dependent dislocation motion or polymer chain motion in response to shear stresses. Conversely, the macroscopic mechanical behavior of dense, brittle, ceramic-based materials is dominated by elastic deformation terminated by rapid failure associated with the propagation of defects in the material in response to resolved tensile stresses. This behavior is usually characterized by a distribution of macroscopically measured failure strengths and strains. The basis for any strain-rate dependence observed in the failure strength must originate from rate-dependence in the damage and fracture process, since uniform, uniaxial elastic behavior is rate-independent (e.g. inertial effects on crack growth). The study of microscopic damage and fracture processes and their rate-dependence under dynamic loading conditions is a difficult experimental challenge that is not addressed in this paper. The purpose of this paper is to review the methods that have been developed at the Los Alamos National Laboratory to perform valid, uniaxial, dynamic compression experiments on brittle materials using the Kolsky-SHPB technique and to emphasize the limitations of this technique. Kolsky-SHPB results for several ceramic and ceramic-metal(cermet) materials of interest for armor applications have been measured and show little or no strain rate sensitivity compared to quasi-static compression results.

  14. Dynamic Strength of Metals at High Pressure and Strain Rate

    NASA Astrophysics Data System (ADS)

    Lorenz, Thomas

    2006-03-01

    A new approach to materials science at very high pressures and strain rates has been developed on the Omega laser, using a ramped plasma piston drive. A laser drives an ablative shock through a solid plastic reservoir where it unloads at the rear free surface, expands across a vacuum gap, and stagnates on the metal sample under study. This produces a gently increasing ram pressure, compressing the sample nearly isentropically. The peak pressure on the sample, diagnosed with VISAR measurements, can be varied by adjusting the laser energy and pulse length, gap size, and reservoir density, and obeys a simple scaling relation.^1 This has been demonstrated at OMEGA at pressures to 200 GPa in Al foils. In an important application, using in-flight x-ray radiography, the material strength of solid-state samples at high pressure can be inferred by measuring the reductions in the growth rates (stabilization) of Rayleigh-Taylor (RT) unstable interfaces. RT instability measurements of solid of Al-6061-T6 ^2 and vanadium, at pressures of 20-100 GPa, and strain rates of 10^6 to 10^8 s-1, show clear material strength effects. Modelling results for two constitutive strength models -- Steinberg-Guinan and Preston-Tonks-Wallace, show enhanced dynamic strength that may be correlated with a high-strain-rate, phono-drag mechanism. Data, modeling details and future prospects for this project using the National Ignition Facility laser, will be presented. [1] J. Edwards et al., Phys. Rev. Lett., 92, 075002 (2004). [2] K. T. Lorenz et al., Phys. Plasmas 12, 056309 (2005). This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

  15. High temperatures result in smaller nurseries which lower reproduction of pollinators and parasites in a brood site pollination mutualism.

    PubMed

    Krishnan, Anusha; Pramanik, Gautam Kumar; Revadi, Santosh V; Venkateswaran, Vignesh; Borges, Renee M

    2014-01-01

    In a nursery pollination mutualism, we asked whether environmental factors affected reproduction of mutualistic pollinators, non-mutualistic parasites and seed production via seasonal changes in plant traits such as inflorescence size and within-tree reproductive phenology. We examined seasonal variation in reproduction in Ficus racemosa community members that utilise enclosed inflorescences called syconia as nurseries. Temperature, relative humidity and rainfall defined four seasons: winter; hot days, cold nights; summer and wet seasons. Syconium volumes were highest in winter and lowest in summer, and affected syconium contents positively across all seasons. Greater transpiration from the nurseries was possibly responsible for smaller syconia in summer. The 3-5°C increase in mean temperatures between the cooler seasons and summer reduced fig wasp reproduction and increased seed production nearly two-fold. Yet, seed and pollinator progeny production were never negatively related in any season confirming the mutualistic fig-pollinator association across seasons. Non-pollinator parasites affected seed production negatively in some seasons, but had a surprisingly positive relationship with pollinators in most seasons. While within-tree reproductive phenology did not vary across seasons, its effect on syconium inhabitants varied with season. In all seasons, within-tree reproductive asynchrony affected parasite reproduction negatively, whereas it had a positive effect on pollinator reproduction in winter and a negative effect in summer. Seasonally variable syconium volumes probably caused the differential effect of within-tree reproductive phenology on pollinator reproduction. Within-tree reproductive asynchrony itself was positively affected by intra-tree variation in syconium contents and volume, creating a unique feedback loop which varied across seasons. Therefore, nursery size affected fig wasp reproduction, seed production and within-tree reproductive phenology via the feedback cycle in this system. Climatic factors affecting plant reproductive traits cause biotic relationships between plants, mutualists and parasites to vary seasonally and must be accorded greater attention, especially in the context of climate change. PMID:25521512

  16. High Temperatures Result in Smaller Nurseries which Lower Reproduction of Pollinators and Parasites in a Brood Site Pollination Mutualism

    PubMed Central

    Krishnan, Anusha; Pramanik, Gautam Kumar; Revadi, Santosh V.; Venkateswaran, Vignesh; Borges, Renee M.

    2014-01-01

    In a nursery pollination mutualism, we asked whether environmental factors affected reproduction of mutualistic pollinators, non-mutualistic parasites and seed production via seasonal changes in plant traits such as inflorescence size and within-tree reproductive phenology. We examined seasonal variation in reproduction in Ficus racemosa community members that utilise enclosed inflorescences called syconia as nurseries. Temperature, relative humidity and rainfall defined four seasons: winter; hot days, cold nights; summer and wet seasons. Syconium volumes were highest in winter and lowest in summer, and affected syconium contents positively across all seasons. Greater transpiration from the nurseries was possibly responsible for smaller syconia in summer. The 3–5°C increase in mean temperatures between the cooler seasons and summer reduced fig wasp reproduction and increased seed production nearly two-fold. Yet, seed and pollinator progeny production were never negatively related in any season confirming the mutualistic fig–pollinator association across seasons. Non-pollinator parasites affected seed production negatively in some seasons, but had a surprisingly positive relationship with pollinators in most seasons. While within-tree reproductive phenology did not vary across seasons, its effect on syconium inhabitants varied with season. In all seasons, within-tree reproductive asynchrony affected parasite reproduction negatively, whereas it had a positive effect on pollinator reproduction in winter and a negative effect in summer. Seasonally variable syconium volumes probably caused the differential effect of within-tree reproductive phenology on pollinator reproduction. Within-tree reproductive asynchrony itself was positively affected by intra-tree variation in syconium contents and volume, creating a unique feedback loop which varied across seasons. Therefore, nursery size affected fig wasp reproduction, seed production and within-tree reproductive phenology via the feedback cycle in this system. Climatic factors affecting plant reproductive traits cause biotic relationships between plants, mutualists and parasites to vary seasonally and must be accorded greater attention, especially in the context of climate change. PMID:25521512

  17. High Dose-Rate Versus Low Dose-Rate Brachytherapy for Lip Cancer

    SciTech Connect

    Ghadjar, Pirus, E-mail: pirus.ghadjar@insel.ch [Department of Radiation Oncology, Inselspital, Bern University Hospital, and University of Bern (Switzerland); Bojaxhiu, Beat [Department of Radiation Oncology, Inselspital, Bern University Hospital, and University of Bern (Switzerland); Simcock, Mathew [Swiss Group for Clinical Cancer Research Coordinating Center, Bern (Switzerland); Terribilini, Dario; Isaak, Bernhard [Division of Medical Radiation Physics, Inselspital, Bern University Hospital, and University of Bern, Bern (Switzerland); Gut, Philipp; Wolfensberger, Patrick; Broemme, Jens O.; Geretschlaeger, Andreas; Behrensmeier, Frank; Pica, Alessia; Aebersold, Daniel M. [Department of Radiation Oncology, Inselspital, Bern University Hospital, and University of Bern (Switzerland)

    2012-07-15

    Purpose: To analyze the outcome after low-dose-rate (LDR) or high-dose-rate (HDR) brachytherapy for lip cancer. Methods and Materials: One hundred and three patients with newly diagnosed squamous cell carcinoma of the lip were treated between March 1985 and June 2009 either by HDR (n = 33) or LDR brachytherapy (n = 70). Sixty-eight patients received brachytherapy alone, and 35 received tumor excision followed by brachytherapy because of positive resection margins. Acute and late toxicity was assessed according to the Common Terminology Criteria for Adverse Events 3.0. Results: Median follow-up was 3.1 years (range, 0.3-23 years). Clinical and pathological variables did not differ significantly between groups. At 5 years, local recurrence-free survival, regional recurrence-free survival, and overall survival rates were 93%, 90%, and 77%. There was no significant difference for these endpoints when HDR was compared with LDR brachytherapy. Forty-two of 103 patients (41%) experienced acute Grade 2 and 57 of 103 patients (55%) experienced acute Grade 3 toxicity. Late Grade 1 toxicity was experienced by 34 of 103 patients (33%), and 5 of 103 patients (5%) experienced late Grade 2 toxicity; no Grade 3 late toxicity was observed. Acute and late toxicity rates were not significantly different between HDR and LDR brachytherapy. Conclusions: As treatment for lip cancer, HDR and LDR brachytherapy have comparable locoregional control and acute and late toxicity rates. HDR brachytherapy for lip cancer seems to be an effective treatment with acceptable toxicity.

  18. Animal Reproduction

    NSDL National Science Digital Library

    This Topic in Depth takes a look at organizations and educational websites concerned with reproduction in humans and other animals. The Society for the Study of Reproduction (SSR) "is an association of scientists and physicians interested in research in reproduction. Some members are engaged in basic or applied research, while others perform clinical practice." The SSR website (1) contains downloadable copies of the SSR Newsletter; position statements; and information about meetings, awards, and the organization. The Society for Reproduction and Fertility (SRF) "is open to scientists and students worldwide, who work on any aspect of reproductive biology or fertility in man and animals." The SRF website (2) contains sections regarding News, Events, Jobs, Honours, and Grants. SRF makes downloadable copies of its newsletter available as well. The primary aim of the European Society of Human Reproduction & Embryology (ESHRE) "is to promote interest in, and understanding of, reproductive biology and medicine. It does this through facilitating research and subsequent dissemination of research findings in human reproduction and embryology to the general public, scientists, clinicians and patient associations; it also works to inform politicians and policy makers throughout Europe." The ESHRE site (3) contains information about activities, membership, publications, special interest groups, and jobs. The primary function of the Centre for Reproductive Biology in Uppsala (CRU) "is to increase the knowledge about reproduction in animals and humans by applying a more comprehensive view on reproductive biology." CRU is composed of scientists from both Uppsala University and the Swedish University of Agricultural Science. The CRU site (4) contains information about a number of publications, and contact information for CRU members. The Population Council is a nonprofit "organization that conducts biomedical, social science, and public health research." The "Council's reproductive biology and immunology program undertakes fundamental research in the reproductive sciences and immunological processes related to sexually transmitted infections, particularly HIV." This website (5) provides information about different aspects of the research program including Germ Cell Dynamics, Sperm Maturation, and Physiology of Sertoli Cells. From Dr. Michael Gregory of Clinton Community College, the next site (6) is a concise overview of animal reproduction which addresses important aspects of sexual reproduction, and male and female reproductive systems. The final site (7) contains lecture notes regarding avian reproduction from Dr. Gary Ritchison's Ornithology course at Eastern Kentucky University. The lecture notes are interspersed with some especially nice images and diagrams.

  19. High-rate measurement-device-independent quantum cryptography

    NASA Astrophysics Data System (ADS)

    Pirandola, Stefano; Ottaviani, Carlo; Spedalieri, Gaetana; Weedbrook, Christian; Braunstein, Samuel L.; Lloyd, Seth; Gehring, Tobias; Jacobsen, Christian S.; Andersen, Ulrik L.

    2015-06-01

    Quantum cryptography achieves a formidable task—the remote distribution of secret keys by exploiting the fundamental laws of physics. Quantum cryptography is now headed towards solving the practical problem of constructing scalable and secure quantum networks. A significant step in this direction has been the introduction of measurement-device independence, where the secret key between two parties is established by the measurement of an untrusted relay. Unfortunately, although qubit-implemented protocols can reach long distances, their key rates are typically very low, unsuitable for the demands of a metropolitan network. Here we show, theoretically and experimentally, that a solution can come from the use of continuous-variable systems. We design a coherent-state network protocol able to achieve remarkably high key rates at metropolitan distances, in fact three orders of magnitude higher than those currently achieved. Our protocol could be employed to build high-rate quantum networks where devices securely connect to nearby access points or proxy servers.

  20. Homogeneous Nucleation Rate for Highly Supercooled Cirrus Cloud Droplets.

    NASA Astrophysics Data System (ADS)

    Sassen, Kenneth; Dodd, Gregory C.

    1988-04-01

    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 cloud base of two independent data quantities, the aircraft-measured water and ice particle concentrations and the lidar linear depolarization ratio, have been compared to model predictions for both the homogeneous and heterogeneous drop-freezing. modes. It is concluded that, although activated ice nuclei may have contributed to the glaciation of the cloud, homogeneous nucleation was the dominant mode. Accordingly, a homogeneous nucleation rate 106 times greater than that predicted by classical theory, but 103 times less than laboratory measurements would suggest is found to be appropriate at the measured cloud temperatures.

  1. Gas gain stability of MSGCs operating at high rate

    NASA Astrophysics Data System (ADS)

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

    1997-02-01

    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 5 mm -2 s -1 when a semiconductive layer of S8900 glass or polydiamond is applied under or over the strips. The application of such a coating also favours the gain stability at long-term operation. However, the maximum attainable gas gain for coated substrates is 4-10 times smaller than for bare borosilicate glass supports. For the latter substrate type, we observe less ageing when the strips are made of nickel instead of aluminium or copper.

  2. A short pulse, high rep-rate microdischarge VUV source

    NASA Astrophysics Data System (ADS)

    Stephens, Jacob; Fierro, Andrew; Dickens, James; Neuber, Andreas; Center for Pulsed Power; Power Electronics Team

    2013-09-01

    A MOSFET based high voltage pulser is utilized to excite a microdischarge (MD), or microdischarge array (MDA) with pulsed voltages of up to 1 kV, with risetime and FWHM on the order of 10 ns and 30 ns, respectively. Additionally, the pulser is capable of pulsing at rep-rates in excess of 35 MHz. However, for these experiments the rep-rate was set on the order of 1 MHz, so as to limit excess energy deposition into the background gas and optimize the energy efficiency of VUV generation. Using VUV capable spectral diagnostics, the VUV emission of the MDs for various pressures (50-800 + Torr) and gases, focused on argon, argon-hydrogen mixtures, and neon-hydrogen mixtures (all of which provide strong emission at ? < 130 nm) is studied, for pulsed, MHz rep-rated excitation. Using a photomultiplier tube the time dependent behavior of the VUV emission is characterized and compared to results from transient fluid modeling of the MDA. For instance, the MDA turn-on time is recorded to be about 15 ns, which matches the full plasma development time in the model, and the MDA self- capacitance largely determines the turn-off behavior. A MOSFET based high voltage pulser is utilized to excite a microdischarge (MD), or microdischarge array (MDA) with pulsed voltages of up to 1 kV, with risetime and FWHM on the order of 10 ns and 30 ns, respectively. Additionally, the pulser is capable of pulsing at rep-rates in excess of 35 MHz. However, for these experiments the rep-rate was set on the order of 1 MHz, so as to limit excess energy deposition into the background gas and optimize the energy efficiency of VUV generation. Using VUV capable spectral diagnostics, the VUV emission of the MDs for various pressures (50-800 + Torr) and gases, focused on argon, argon-hydrogen mixtures, and neon-hydrogen mixtures (all of which provide strong emission at ? < 130 nm) is studied, for pulsed, MHz rep-rated excitation. Using a photomultiplier tube the time dependent behavior of the VUV emission is characterized and compared to results from transient fluid modeling of the MDA. For instance, the MDA turn-on time is recorded to be about 15 ns, which matches the full plasma development time in the model, and the MDA self- capacitance largely determines the turn-off behavior. This research was supported by an AFOSR grant on the Physics of Distributed Plasma Discharges and fellowships from the National Physical Sciences Consortium, supported by Sandia National Laboratories.

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

    NASA Astrophysics Data System (ADS)

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

    1987-03-01

    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.

  4. High-rate anaerobic composting with biogas recovery

    SciTech Connect

    DeBaere, L.; Verstraete, W.

    1984-03-01

    In Belgium a novel high rate anaerobic composting process with biogas has been developed as an alternative to aerobic systems, producing a commercial dry compost and 60 to 95 cubic metres methane per ton of municipal solid waste. This is a high value energy source simultaneously yielding a stabilized end product. The process was developed so that digestion could take place at 25 to 35% total solids, thus reducing the amount of water needed to dilute the waste, decreasing the digestor volume and cutting transportation costs. The end product is odorless and stable. High rate anaerobic composting of MSW can be combined with sewage sludge stabilization. Manure, vegetable or fruit wastes can be co-treated in certain proportions as required. About 15 to 20% of the energy produced is transformed into electricity and heat and consumed as the waste disposal plant itself. 120 to 140 US $ worth of methane gas and compost can be produced per cubic metre of reactor per year, making anaerobic composting economically attractive.

  5. The high strain-rate behaviour of selected tissue analogues.

    PubMed

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

    2014-05-01

    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

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

    USGS Publications Warehouse

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

    2013-01-01

    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.

  7. Strain rate dependence of dynamic flow stress considering viscous drag for 6061 aluminium alloy at high strain rates

    Microsoft Academic Search

    K. Sakino

    2006-01-01

    In order to evaluate the strain rate dependence of the dynamic flow stress of aluminium alloys, 6061-O and -T6, high strain rate tests are performed at strain rates ranging from about 1000\\/s to 30000\\/s, and strain rate reduction tests are also conducted in the strain rate range from about 10000\\/s to 20000\\/s. A steep increase in the flow stress is

  8. Genome constraint through sexual reproduction: application of 4D-Genomics in reproductive biology.

    PubMed

    Horne, Steven D; Abdallah, Batoul Y; Stevens, Joshua B; Liu, Guo; Ye, Karen J; Bremer, Steven W; Heng, Henry H Q

    2013-06-01

    Assisted reproductive technologies have been used to achieve pregnancies since the first successful test tube baby was born in 1978. Infertile couples are at an increased risk for multiple miscarriages and the application of current protocols are associated with high first-trimester miscarriage rates. Among the contributing factors of these higher rates is a high incidence of fetal aneuploidy. Numerous studies support that protocols including ovulation-induction, sperm cryostorage, density-gradient centrifugation, and embryo culture can induce genome instability, but the general mechanism is less clear. Application of the genome theory and 4D-Genomics recently led to the establishment of a new paradigm for sexual reproduction; sex primarily constrains genome integrity that defines the biological system rather than just providing genetic diversity at the gene level. We therefore propose that application of assisted reproductive technologies can bypass this sexual reproduction filter as well as potentially induce additional system instability. We have previously demonstrated that a single-cell resolution genomic approach, such as spectral karyotyping to trace stochastic genome level alterations, is effective for pre- and post-natal analysis. We propose that monitoring overall genome alteration at the karyotype level alongside the application of assisted reproductive technologies will improve the efficacy of the techniques while limiting stress-induced genome instability. The development of more single-cell based cytogenomic technologies are needed in order to better understand the system dynamics associated with infertility and the potential impact that assisted reproductive technologies have on genome instability. Importantly, this approach will be useful in studying the potential for diseases to arise as a result of bypassing the filter of sexual reproduction. PMID:23294443

  9. Reproductive ecology of female chimpanzees.

    PubMed

    Thompson, Melissa Emery

    2013-03-01

    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

  10. Imploding Liner Material Strength Measurements at High-Strain and High Strain Rate

    Microsoft Academic Search

    R. R. Bartsch; H. Lee; D. Holtkamp; B. Wright; J. Stokes; D. Morgan; W. Anderson; W. Broste

    1998-01-01

    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 â¼1.25 and strain rates of up to â¼10⁶ sec⁻¹ can be readily achieved in a

  11. Imploding Liner Material Strength Measurements at High-Strain and High-Strain Rate

    Microsoft Academic Search

    R. Bartsch; H. Lee; D. Holtkamp; B. Wright; J. Stokes; D. Morgan; W. Anderson; W. Broste

    2004-01-01

    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

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

    Microsoft Academic Search

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

    2004-01-01

    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

  13. Highly Scalable Signals in Space for Future High Data Rate Military Applications

    Microsoft Academic Search

    T. Nicolay; T. Kuhwald; A. Schaefer; T. Detert; T. Langguth

    2006-01-01

    Future military communications systems, on both national and international levels, will demand the capability of transmitting high data rates over self-organising ad-hoc networks. In the work presented in this paper we describe a high data rate signal in space (HDR-SiS) developed by Rohde & Schwarz, that enables the transmission of real time video, voice and data in a mobile ad-hoc

  14. Microsurgical varicocelectomy in the era of assisted reproductive technology: influence of initial semen quality on pregnancy rates

    Microsoft Academic Search

    Khaled M Kamal; Keith Jarvi; Armand Zini

    2001-01-01

    Objective: To evaluate the natural history of infertile couples in whom the man underwent varicocelectomy.Design: Retrospective study.Setting: University infertility clinic.Patient(s): 159 infertile couples.Intervention(s): Microsurgical varicocelectomy.Main Outcome Measures(s): Standard semen parameters and pregnancy rates (assisted and unassisted).Result(s): Postoperative sperm concentration and motility increased significantly compared to before the varicocelectomy (28.9 ± 3.0 vs. 22.5 ± 2.1 × 106\\/mL and 33.9 ±

  15. High Rate Laser Pitting Technique for Solar Cell Texturing

    SciTech Connect

    Hans J. Herfurth; Henrikki Pantsar

    2013-01-10

    High rate laser pitting technique for solar cell texturing Efficiency of crystalline silicon solar cells can be improved by creating a texture on the surface to increase optical absorption. Different techniques have been developed for texturing, with the current state-of-the-art (SOA) being wet chemical etching. The process has poor optical performance, produces surfaces that are difficult to passivate or contact and is relatively expensive due to the use of hazardous chemicals. This project shall develop an alternative process for texturing mc-Si using laser micromachining. It will have the following features compared to the current SOA texturing process: -Superior optical surfaces for reduced front-surface reflection and enhanced optical absorption in thin mc-Si substrates -Improved surface passivation -More easily integrated into advanced back-contact cell concepts -Reduced use of hazardous chemicals and waste treatment -Similar or lower cost The process is based on laser pitting. The objective is to develop and demonstrate a high rate laser pitting process which will exceed the rate of former laser texturing processes by a factor of ten. The laser and scanning technologies will be demonstrated on a laboratory scale, but will use inherently technologies that can easily be scaled to production rates. The drastic increase in process velocity is required for the process to be implemented as an in-line process in PV manufacturing. The project includes laser process development, development of advanced optical systems for beam manipulation and cell reflectivity and efficiency testing. An improvement of over 0.5% absolute in efficiency is anticipated after laser-based texturing. The surface textures will be characterized optically, and solar cells will be fabricated with the new laser texturing to ensure that the new process is compatible with high-efficiency cell processing. The result will be demonstration of a prototype process that is suitable for scale-up to a production tool and process. The developed technique will have an reducing impact on product pricing. As efficiency has a substantial impact on the economics of solar cell production due to the high material cost content; in essence, improved efficiency through cost-effective texturing reduces the material cost component since the product is priced in terms of $/W. The project is a collaboration between Fraunhofer USA, Inc. and a c-Si PV manufacturer.

  16. High rates of nonbreeding adult bald eagles in southeastern Alaska

    Microsoft Academic Search

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

    1985-01-01

    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

  17. Resistance of the boreal forest to high burn rates.

    PubMed

    Héon, Jessie; Arseneault, Dominique; Parisien, Marc-André

    2014-09-23

    Boreal ecosystems and their large carbon stocks are strongly shaped by extensive wildfires. Coupling climate projections with records of area burned during the last 3 decades across the North American boreal zone suggests that area burned will increase by 30-500% by the end of the 21st century, with a cascading effect on ecosystem dynamics and on the boreal carbon balance. Fire size and the frequency of large-fire years are both expected to increase. However, how fire size and time since previous fire will influence future burn rates is poorly understood, mostly because of incomplete records of past fire overlaps. Here, we reconstruct the length of overlapping fires along a 190-km-long transect during the last 200 y in one of the most fire-prone boreal regions of North America to document how fire size and time since previous fire will influence future fire recurrence. We provide direct field evidence that extreme burn rates can be sustained by a few occasional droughts triggering immense fires. However, we also show that the most fire-prone areas of the North American boreal forest are resistant to high burn rates because of overabundant young forest stands, thereby creating a fuel-mediated negative feedback on fire activity. These findings will help refine projections of fire effect on boreal ecosystems and their large carbon stocks. PMID:25201981

  18. High false positive rates in common sensory threshold tests.

    PubMed

    Running, Cordelia A

    2015-02-01

    Large variability in thresholds to sensory stimuli is observed frequently even in healthy populations. Much of this variability is attributed to genetics and day-to-day fluctuation in sensitivity. However, false positives are also contributing to the variability seen in these tests. In this study, random number generation was used to simulate responses in threshold methods using different "stopping rules": ascending 2-alternative forced choice (AFC) with 5 correct responses; ascending 3-AFC with 3 or 4 correct responses; staircase 2-AFC with 1 incorrect up and 2 incorrect down, as well as 1 up 4 down and 5 or 7 reversals; staircase 3-AFC with 1 up 2 down and 5 or 7 reversals. Formulas are presented for rates of false positives in the ascending methods, and curves were generated for the staircase methods. Overall, the staircase methods generally had lower false positive rates, but these methods were influenced even more by number of presentations than ascending methods. Generally, the high rates of error in all these methods should encourage researchers to conduct multiple tests per individual and/or select a method that can correct for false positives, such as fitting a logistic curve to a range of responses. PMID:25407557

  19. Resistance of the boreal forest to high burn rates

    PubMed Central

    Héon, Jessie; Arseneault, Dominique; Parisien, Marc-André

    2014-01-01

    Boreal ecosystems and their large carbon stocks are strongly shaped by extensive wildfires. Coupling climate projections with records of area burned during the last 3 decades across the North American boreal zone suggests that area burned will increase by 30–500% by the end of the 21st century, with a cascading effect on ecosystem dynamics and on the boreal carbon balance. Fire size and the frequency of large-fire years are both expected to increase. However, how fire size and time since previous fire will influence future burn rates is poorly understood, mostly because of incomplete records of past fire overlaps. Here, we reconstruct the length of overlapping fires along a 190-km-long transect during the last 200 y in one of the most fire-prone boreal regions of North America to document how fire size and time since previous fire will influence future fire recurrence. We provide direct field evidence that extreme burn rates can be sustained by a few occasional droughts triggering immense fires. However, we also show that the most fire-prone areas of the North American boreal forest are resistant to high burn rates because of overabundant young forest stands, thereby creating a fuel-mediated negative feedback on fire activity. These findings will help refine projections of fire effect on boreal ecosystems and their large carbon stocks. PMID:25201981

  20. High-rate lithium thionyl-chloride battery development

    SciTech Connect

    Cieslak, W.R.; Weigand, D.E.

    1993-12-31

    We have developed a lithium thionyl-chloride cell for use in a high rate battery application to provide power for a missile computer and stage separation detonators. The battery pack contains 20 high surface area ``DD`` cells wired in a series-parallel configuration to supply a nominal 28 volts with a continuous draw of 20 amperes. The load profile also requires six squib firing pulses of one second duration at a 20 ampere peak. Performance and safety of the cells were optimized in a ``D`` cell configuration before progressing to the longer ``DD` cell. Active surface area in the ``D`` cell is 735 cm{sup 2}, and 1650 cm{sup 2} in the ``DD`` cell. The design includes 1.5M LiAlCl{sub 4}/SOCl{sub 2} electrolyte, a cathode blend of Shawinigan Acetylene Black and Cabot Black Pearls 2000 carbons, Scimat ETFE separator, and photoetched current collectors.

  1. High rate reactive magnetron sputtered tungsten carbide films

    SciTech Connect

    Srivastava, P.K.; Vankar, V.D.; Chopra, K.L.

    1985-11-01

    Tungsten carbide films have been deposited on stainless steel substrates held between 300 to 500 /sup 0/C in a planar rf magnetron sputtering system at rates as high as that of pure tungsten (825 A/sup 0//min). The effect of substrate temperature on formation of WC/sub x/ films has been investigated. A mixture of hexagonal WC, A-15 W/sub 3/C and carbon in graphitic and diamond form have been observed by AES and XRD techniques. The microhardness of these films has been found to be as high as 2365 kgf/mm/sup 2/. The adhesion of these films as measured from indentation crack patterns has been found to depend on substrate temperature as well as on the amount of dispersed carbon in the film.

  2. High rate telemetry for the Spacelab D-2 mission

    NASA Astrophysics Data System (ADS)

    Stubbusch, Hanno

    1990-10-01

    A high rate telemetry handling and data processing system for the German Space Operations Center (GSOC) is described. The system is based on experience gained in previous manned missions such as the First Spacelab Project (FSLP) and Spacelab D-1 CAM. The various requirements for telemetry services to be provided by GSOC as the Payload Operations Control Center (POCC) for the D-2 mission led to a layered implementation of the telemetry system with multiple access points and data gateway functions. The transfer frame format defined by the Consultative Committee on Space Data Systems (CCSDS) is implemented for the data exchange between NASA and GSOC. The hardware and software architecture of the GSOC D-2 system for the POCC functions is shown to demonstrate the handling of high telemetry for a manned mission with Columbus-like requirements.

  3. On the response of rubbers at high strain rates.

    SciTech Connect

    Niemczura, Johnathan Greenberg (University of Texas-Austin)

    2010-02-01

    In this report, we examine the propagation of tensile waves of finite deformation in rubbers through experiments and analysis. Attention is focused on the propagation of one-dimensional dispersive and shock waves in strips of latex and nitrile rubber. Tensile wave propagation experiments were conducted at high strain-rates by holding one end fixed and displacing the other end at a constant velocity. A high-speed video camera was used to monitor the motion and to determine the evolution of strain and particle velocity in the rubber strips. Analysis of the response through the theory of finite waves and quantitative matching between the experimental observations and analytical predictions was used to determine an appropriate instantaneous elastic response for the rubbers. This analysis also yields the tensile shock adiabat for rubber. Dispersive waves as well as shock waves are also observed in free-retraction experiments; these are used to quantify hysteretic effects in rubber.

  4. High strain rate fracture behavior of fused silica

    NASA Astrophysics Data System (ADS)

    Ruggiero, Andrew; Iannitti, Gianluca; Testa, Gabriel; Limido, Jerome; Lacome, Jean; Olovsson, Lars; Ferraro, Mario; Bonora, Nicola

    2013-06-01

    Fused silica is a high purity synthetic amorphous silicon dioxide characterized by low thermal expansion coefficient, excellent optical qualities and exceptional transmittance over a wide spectral range. Because of its wide use in the military industry as window material, it may be subjected to high-energy ballistic impacts. Under such dynamic conditions, post-yield response of the ceramic as well as the strain rate related effects become significant and should be accounted for in the constitutive modeling. In this study, the procedure for constitutive model validation and model parameters identification, is presented. Taylor impact tests and drop weight tests were designed and performed at different impact velocities, from 1 to 100 m/s, and strain rates, from 102 up to 104 s-1. Numerical simulation of both tests was performed with IMPETUS-FEA, a general non-linear finite element software which offers NURBS finite element technology for the simulation of large deformation and fracture in materials. Model parameters were identified by optimization using multiple validation metrics. The validity of the parameters set determined with the proposed procedure was verified comparing numerical predictions and experimental results for an independent designed test consisting in a fused silica tile impacted at prescribed velocity by a steel sphere.

  5. Parasitic heating effects in high frame rate laser imaging experiments

    NASA Astrophysics Data System (ADS)

    Brusnahan, Matthew; Lu, Louise; Sick, Volker

    2013-06-01

    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.

  6. Final Report, Photocathodes for High Repetition Rate Light Sources

    SciTech Connect

    Ben-Zvi, Ilan [Stony Brook University

    2014-04-20

    This proposal brought together teams at Brookhaven National Laboratory (BNL), Lawrence Berkeley National Laboratory (LBNL) and Stony Brook University (SBU) to study photocathodes for high repetition rate light sources such as Free Electron Lasers (FEL) and Energy Recovery Linacs (ERL). The work done under this grant comprises a comprehensive program on critical aspects of the production of the electron beams needed for future user facilities. Our program pioneered in situ and in operando diagnostics for alkali antimonide growth. The focus is on development of photocathodes for high repetition rate Free Electron Lasers (FELs) and Energy Recovery Linacs (ERLs), including testing SRF photoguns, both normal-conducting and superconducting. Teams from BNL, LBNL and Stony Brook University (SBU) led this research, and coordinated their work over a range of topics. The work leveraged a robust infrastructure of existing facilities and the support was used for carrying out the research at these facilities. The program concentrated in three areas: a) Physics and chemistry of alkali-antimonide cathodes b) Development and testing of a diamond amplifier for photocathodes c) Tests of both cathodes in superconducting RF photoguns and copper RF photoguns

  7. Real-Time High-Rate Upgrades of SCIGN Sites

    NASA Astrophysics Data System (ADS)

    Bock, Y.

    2003-12-01

    We are in the process of upgrading sites of the Southern California Integrated GPS Network (SCIGN) to real-time (1 sec latency), high-rate (1 Hz) operations, and have completed the upgrades for more than 25 sites. The normal operation for most of the network includes 30-second sampling with data downloads every 24 hours. The purpose of the upgrades is twofold: (1) to provide data rates useful for measuring strong ground motions to complement traditional seismic instruments in the event of a medium to large earthquake and data latencies useful for seismic response, risk mitigation, and rapid earthquake model determinations based on coseismic displacements; (2) to provide real-time access to high-rate data to surveyors, GIS professionals, structural engineers, transportation engineers and others requiring access to precise positioning and navigation information, under the umbrella of the California Spatial Reference Center (CSRC). We report on the status of upgrades in three sub-networks, each with a distinct focus: (1) the Orange County Real Time Network in collaboration with the County of Orange Public Facilities and Resources Division, (2) the Parkfield region in collaboration with the USGS and UC Berkeley's NCEDC and (3) the Riverside County Real Time Network in collaboration with the Riverside County's Department of Transportation and Flood Control and Water Conservation District. In the latter sub-network, we are developing a real-time displacement meter that will integrate broadband seismic and GPS measurements. We highlight achievements and lessons learned from these upgrades and assess whether it is feasible and desirable for the Earthscope project to pursue a similar approach.

  8. The reproductive cycle of female Ballan wrasse Labrus bergylta in high latitude, temperate waters.

    PubMed

    Muncaster, S; Andersson, E; Kjesbu, O S; Taranger, G L; Skiftesvik, A B; Norberg, B

    2010-08-01

    This 2 year study examined the reproductive cycle of wild female Ballan wrasse Labrus bergylta in western Norway as a precursor to captive breeding trials. Light microscopy of ovarian histology was used to stage gonad maturity and enzyme-linked immuno-absorbent assay (ELISA) to measure plasma concentrations of the sex steroids testosterone (T) and 17beta-oestradiol (E(2)). Ovarian recrudescence began in late autumn to early winter with the growth of previtellogenic oocytes and the formation of cortical alveoli. Vitellogenic oocytes developed from January to June and ovaries containing postovulatory follicles (POF) were present between May and June. These POF occurred simultaneously among other late maturity stage oocytes. Plasma steroid concentration and organo-somatic indices increased over winter and spring. Maximal (mean +/-s.e.) values of plasma T (0.95 +/- 0.26 ng ml(-1)), E(2) (1.75 +/- 0.43 ng ml(-1)) and gonado-somatic index (I(G); 10.71 +/- 0.81) occurred in April and May and decreased greatly in July when only postspawned fish with atretic ovaries occurred. Evidence indicates that L. bergylta are group-synchronous multiple spawners with spawning occurring in spring and peaking in May. A short resting period may occur between late summer and autumn when previtellogenic oocytes predominate and steroid levels are minimal. PMID:20701636

  9. Highly reproductive Escherichia coli cells with no specific assignment to the UAG codon.

    PubMed

    Mukai, Takahito; Hoshi, Hiroko; Ohtake, Kazumasa; Takahashi, Mihoko; Yamaguchi, Atsushi; Hayashi, Akiko; Yokoyama, Shigeyuki; Sakamoto, Kensaku

    2015-01-01

    Escherichia coli is a widely used host organism for recombinant technology, and the bacterial incorporation of non-natural amino acids promises the efficient synthesis of proteins with novel structures and properties. In the present study, we developed E. coli strains in which the UAG codon was reserved for non-natural amino acids, without compromising the reproductive strength of the host cells. Ninety-five of the 273 UAG stop codons were replaced synonymously in the genome of E. coli BL21(DE3), by exploiting the oligonucleotide-mediated base-mismatch-repair mechanism. This genomic modification allowed the safe elimination of the UAG-recognizing cellular component (RF-1), thus leaving the remaining 178 UAG codons with no specific molecule recognizing them. The resulting strain B-95.?A grew as vigorously as BL21(DE3)?in rich medium at 25-42°C, and its derivative B-95.?A?fabR was better adapted to low temperatures and minimal media than B-95.?A. UAG was reassigned to synthetic amino acids by expressing the specific pairs of UAG-reading tRNA and aminoacyl-tRNA synthetase. Due to the preserved growth vigor, the B-95.?A strains showed superior productivities for hirudin molecules sulfonated on a particular tyrosine residue, and the Fab fragments of Herceptin containing multiple azido groups. PMID:25982672

  10. Highly reproductive Escherichia coli cells with no specific assignment to the UAG codon

    PubMed Central

    Mukai, Takahito; Hoshi, Hiroko; Ohtake, Kazumasa; Takahashi, Mihoko; Yamaguchi, Atsushi; Hayashi, Akiko; Yokoyama, Shigeyuki; Sakamoto, Kensaku

    2015-01-01

    Escherichia coli is a widely used host organism for recombinant technology, and the bacterial incorporation of non-natural amino acids promises the efficient synthesis of proteins with novel structures and properties. In the present study, we developed E. coli strains in which the UAG codon was reserved for non-natural amino acids, without compromising the reproductive strength of the host cells. Ninety-five of the 273 UAG stop codons were replaced synonymously in the genome of E. coli BL21(DE3), by exploiting the oligonucleotide-mediated base-mismatch-repair mechanism. This genomic modification allowed the safe elimination of the UAG-recognizing cellular component (RF-1), thus leaving the remaining 178 UAG codons with no specific molecule recognizing them. The resulting strain B-95.?A grew as vigorously as BL21(DE3)?in rich medium at 25–42°C, and its derivative B-95.?A?fabR was better adapted to low temperatures and minimal media than B-95.?A. UAG was reassigned to synthetic amino acids by expressing the specific pairs of UAG-reading tRNA and aminoacyl-tRNA synthetase. Due to the preserved growth vigor, the B-95.?A strains showed superior productivities for hirudin molecules sulfonated on a particular tyrosine residue, and the Fab fragments of Herceptin containing multiple azido groups. PMID:25982672

  11. Anti-D Antibodies Among Women ....... African Journal of Reproductive Health Vol 13 No 3 September 2009

    E-print Network

    Paris-Sud XI, Université de

    Anti-D Antibodies Among Women ....... African Journal of Reproductive Health Vol 13 No 3 September 2009 47 ORIGINAL RESEARCH ARTICLE High Prevalence of Anti-D Antibodies Among Women of Childbearing Age to determine anti-D and D-negative phenotype rates among Cameroonian women of reproductive age (15 ­ 44 years

  12. Bioethical aspects of regenerative and reproductive medicine.

    PubMed

    Yoshimura, Yasunori

    2006-05-01

    The birth announced in 1997 of Dolly, the lamb cloned from the somatic mammary cells of an adult ewe, and the discovery of human embryonic stem cells in 1998 have been the most exciting developments in the biological sciences in the past decade. Reproductive somatic cell nuclear transfer (SCNT) in additional species has been inefficient in that relatively few births, harmful side effects and high fetal and neonatal death rates have resulted from many attempts. Ongoing debates about the ethics of reproductive SCNT have revealed that some researchers regard human reproductive SCNT as morally unacceptable in all circumstances, others see merit in reproductive SCNT in certain circumstances and others await more information before making judgment about the ethical status of the procedure. Regenerative medicine and emerging biotechnologies started to revolutionize the practice of medicine. Advances in stem cell biology, including embryonic and postnatal somatic stem cells, have made the prospect of tissue regeneration a potential reality. Mammal cloning experiments have provided new impetus to the prospect of regenerative medicine through stem cell research. The procedure of SCNT could be used to create the raw material to replace defective or senescent tissue as a natural extension of the biology of stem cells. Researchers working in reproductive medicine should consider the potential hope given to many patients against the requisite and ethically contentious creation of human blastocysts for therapeutic intent. PMID:16879561

  13. SHEAR LOCALIZATION AND CHEMICAL REACTION IN HIGH-STRAIN, HIGH-STRAIN-RATE DEFORMATION OF

    E-print Network

    Meyers, Marc A.

    SHEAR LOCALIZATION AND CHEMICAL REACTION IN HIGH-STRAIN, HIGH-STRAIN-RATE DEFORMATION OF Ti regions can initiate chemical reaction inside a reac- tive powder mixture. The shear band spacing was H0-induced chemical reactions in silicide systems have been investigated in recent years. Vreeland and coworkers [7

  14. Detection of Simian Immunodeficiency Virus in Semen, Urethra, and Male Reproductive Organs during Efficient Highly Active Antiretroviral Therapy

    PubMed Central

    Matusali, G.; Dereuddre-Bosquet, N.; Le Tortorec, A.; Moreau, M.; Satie, A.-P.; Mahé, D.; Roumaud, P.; Bourry, O.; Sylla, N.; Bernard-Stoecklin, S.; Pruvost, A.; Le Grand, R.

    2015-01-01

    ABSTRACT A number of men receiving prolonged suppressive highly active antiretroviral therapy (HAART) still shed human immunodeficiency virus (HIV) in semen. To investigate whether this seminal shedding may be due to poor drug penetration and/or viral production by long-lived cells within male genital tissues, we analyzed semen and reproductive tissues from macaques chronically infected with simian immunodeficiency virus mac251 (SIVmac251) who were treated for 4 months with HAART, which was intensified over the last 7 weeks with an integrase inhibitor. We showed that a subset of treated animals continued shedding SIV in semen despite efficient HAART. This shedding was not associated with low antiretroviral drug concentrations in semen or in testis, epididymis, seminal vesicles, and prostate. HAART had no significant impact on SIV RNA in the urethra, whereas it drastically reduced SIV RNA levels in the prostate and vas deferens and to a lesser extent in the epididymis and seminal vesicle. The only detectable SIV RNA-positive cells within the male genital tract after HAART were urethral macrophages. SIV DNA levels in genital tissues were not decreased by HAART, suggesting the presence throughout the male genital tract of nonproductively infected cells. In conclusion, our results demonstrate that 4 months of HAART induced variable and limited control of viral infection in the male reproductive organs, particularly in the urethra, and suggest that infected long-lived cells in the male genital tract may be involved in persistent seminal shedding during HAART. These results pave the way for further investigations of male genital organ infection in long-term-treated infected individuals. IMPORTANCE A substantial subset of men receiving prolonged HAART suppressing viral loads in the blood still harbor HIV in semen, and cases of sexual transmission have been reported. To understand the origin of this persistence, we analyzed the semen and male reproductive tissues from SIV-infected macaques treated with HAART. We demonstrated that persistent seminal shedding was not linked to poor drug penetration in semen or semen-producing prostate, seminal vesicle, epididymis, and testis. We revealed that HAART decreased SIV RNA to various extents in all male genital organs, with the exception of the urethra, in which SIV RNA+ macrophages were observed despite HAART. Importantly, HAART did not impact SIV DNA levels in the male genital organs. These results suggest that infection of male genital organs, and particularly the urethra, could be involved in the release of virus in semen during HAART. PMID:25833047

  15. Do highly ornamented and less parasitized males have high quality sperm? – an experimental test for parasite-induced reproductive trade-offs in European minnow (Phoxinus phoxinus)

    PubMed Central

    Kekäläinen, Jukka; Pirhonen, Juhani; Taskinen, Jouni

    2014-01-01

    Parasites take their resources from hosts and thus directly reduce available resources for hosts’ own body functions, such as growth and reproduction. Furthermore, parasite infections cause significant indirect costs to their hosts in terms of increased investments on immune defense. In this study, we investigated the impact of parasite infection on the sperm quality and expression of secondary sexual ornamentation (saturation of the red abdominal colouration and number of breeding tubercles) in the Eurasian minnow (Phoxinus phoxinus). We exposed minnows to a high and low dose of common nonspecific fish ectoparasite, the glochidia larvae of duck mussel (Anodonta anatina) and tested whether parasite infection leads to trade-off in sperm quality and/or ornamental expression. We found that glochidia infection reduces the curvature of the sperm swimming trajectory, number of breeding tubercles, and possibly male competitive ability, but does not affect expression of male color ornamentation. Furthermore, glochidia infection was found to reduce sperm motility, but only when all the noninfected individuals were excluded from the model. Supporting one of the predictions by phenotype-linked fertility hypothesis both in high-infection and low-infection group male breeding colouration was positively associated with sperm quality. Our results suggest that although glochidia infection may have negative impact on male reproductive success, parasite-induced costs may not create strong trade-off between breeding colouration and sperm quality or that such trade-off become detectable only in resource-limited conditions. PMID:25540686

  16. Performance of drift-tube detectors at high counting rates for high-luminosity LHC upgrades

    NASA Astrophysics Data System (ADS)

    Bittner, Bernhard; Dubbert, Jörg; Kortner, Oliver; Kroha, Hubert; Manfredini, Alessandro; Nowak, Sebastian; Ott, Sebastian; Richter, Robert; Schwegler, Philipp; Zanzi, Daniele; Biebel, Otmar; Hertenberger, Ralf; Ruschke, Alexander; Zibell, Andre

    2013-12-01

    The performance of pressurized drift-tube detectors at very high background rates has been studied at the Gamma Irradiation Facility (GIF) at CERN and in an intense 20 MeV proton beam at the Munich Van-der-Graaf tandem accelerator for applications in large-area precision muon tracking at high-luminosity upgrades of the Large Hadron Collider (LHC). The ATLAS muon drift-tube (MDT) chambers with 30 mm tube diameter have been designed to cope with ? and neutron background hit rates of up to 500 Hz/cm2. Background rates of up to 14 kHz/cm2 are expected at LHC upgrades. The test results with standard MDT readout electronics show that the reduction of the drift-tube diameter to 15 mm, while leaving the operating parameters unchanged, vastly increases the rate capability well beyond the requirements. The development of new small-diameter muon drift-tube (sMDT) chambers for LHC upgrades is completed. Further improvements of tracking efficiency and spatial resolution at high counting rates will be achieved with upgraded readout electronics employing improved signal shaping for high counting rates.

  17. NEONATAL LOW- AND HIGH-DOSE EXPOSURE TO ESTRADIOL BENZOATE IN THE MALE RAT: II. EFFECTS ON THE MALE PUBERTY AND THE REPRODUCTIVE TRACT

    EPA Science Inventory

    NEONATAL LOW- AND HIGH-DOSE EXPOSURE TO ESTRADIOL BENZOATE IN THE MALE RAT: II. EFFECTS ON MALE PUBERTY AND THE REPRODUCTIVE TRACT. Oliver Putz, Christian B. Schwartz, Gerald A. LeBlanc, Ralph L. Cooper, Gail S. Prins ABSTRACT Environmental contaminants with estrogen...

  18. 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...

  19. 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

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

    2013-02-01

    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

  20. 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 Central

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

    2013-01-01

    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

  1. The addition of high magnifying endoscopy improves rates of high confidence optical diagnosis of colorectal polyps

    PubMed Central

    Iwatate, Mineo; Sano, Yasushi; Hattori, Santa; Sano, Wataru; Hasuike, Noriaki; Ikumoto, Taro; Kotaka, Masahito; Murakami, Yoshitaka; Hewett, David G.; Soetikno, Roy; Kaltenbach, Tonya; Fujimori, Takahiro

    2015-01-01

    Background and study aims: The real-time optical diagnosis of colorectal polyps with high confidence predictions can achieve high levels of accuracy. Increasing the rates of high confidence optical diagnosis can improve the clinical application of real-time optical diagnosis in routine practice. The primary aim of this prospective study was to evaluate whether high magnifying endoscopy improves the rates of high confidence narrow-band imaging (NBI)?–?based optical diagnosis for differentiating between neoplastic and non-neoplastic colorectal lesions according to the NBI international colorectal endoscopic (NICE) classification. Patients and methods: Consecutive adult patients undergoing colonoscopy with a high magnifying (maximum, ×?80) colonoscope between April and August 2012 were recruited. The optical diagnosis for each polyp was evaluated during colonoscopy in two consecutive stages by the same endoscopist, who first used NBI with non-magnifying endoscopy (NBI-NME), then NBI with magnifying endoscopy (NBI-ME). A level of confidence was assigned to each prediction. Results: The analysis included 124 patients (mean age, 56.4 years; male-to-female ratio, 72:52) with 248 polyps smaller than 10?mm. Of the 248 polyps, 210 were 1 to 5?mm in size and 38 were 6 to 9?mm in size; 77 polyps were hyperplastic, 4 were sessile serrated adenomas/polyps, 160 were low grade adenomas, 5 were high grade adenomas, and 2 were deep submucosal invasive carcinomas. The rate of high confidence optical diagnosis when NBI-ME was used was significantly higher than the rate when NBI-NME was used for diminutive (1?–?5?mm) polyps (92.9?% vs 79.5?%, P?High magnifying endoscopy significantly improved the rates of high confidence NBI-based optical diagnosis of diminutive and small colorectal polyps. Study registration: UMIN 000007608

  2. THE DISCOUNTED REPRODUCTIVE NUMBER FOR EPIDEMIOLOGY

    PubMed Central

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

    2013-01-01

    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 PMID:19364158

  3. High rate copper and energy recovery in microbial fuel cells

    PubMed Central

    Rodenas Motos, Pau; ter Heijne, Annemiek; van der Weijden, Renata; Saakes, Michel; Buisman, Cees J. N.; Sleutels, Tom H. J. A.

    2015-01-01

    Bioelectrochemical systems (BESs) are a novel, promising technology for the recovery of metals. The prerequisite for upscaling from laboratory to industrial size is that high current and high power densities can be produced. In this study we report the recovery of copper from a copper sulfate stream (2 g L-1 Cu2+) using a laboratory scale BES at high rate. To achieve this, we used a novel cell configuration to reduce the internal voltage losses of the system. At the anode, electroactive microorganisms produce electrons at the surface of an electrode, which generates a stable cell voltage of 485 mV when combined with a cathode where copper is reduced. In this system, a maximum current density of 23 A m-2 in combination with a power density of 5.5 W m-2 was produced. XRD analysis confirmed 99% purity in copper of copper deposited onto cathode surface. Analysis of voltage losses showed that at the highest current, most voltage losses occurred at the cathode, and membrane, while anode losses had the lowest contribution to the total voltage loss. These results encourage further development of BESs for bioelectrochemical metal recovery.

  4. High rate and stable cycling of lithium metal anode

    PubMed Central

    Qian, Jiangfeng; Henderson, Wesley A.; Xu, Wu; Bhattacharya, Priyanka; Engelhard, Mark; Borodin, Oleg; Zhang, Ji-Guang

    2015-01-01

    Lithium metal is an ideal battery anode. However, dendrite growth and limited Coulombic efficiency during cycling have prevented its practical application in rechargeable batteries. Herein, we report that the use of highly concentrated electrolytes composed of ether solvents and the lithium bis(fluorosulfonyl)imide salt enables the high-rate cycling of a lithium metal anode at high Coulombic efficiency (up to 99.1%) without dendrite growth. With 4?M lithium bis(fluorosulfonyl)imide in 1,2-dimethoxyethane as the electrolyte, a lithium|lithium cell can be cycled at 10?mA?cm?2 for more than 6,000 cycles, and a copper|lithium cell can be cycled at 4?mA?cm?2 for more than 1,000 cycles with an average Coulombic efficiency of 98.4%. These excellent performances can be attributed to the increased solvent coordination and increased availability of lithium ion concentration in the electrolyte. Further development of this electrolyte may enable practical applications for lithium metal anode in rechargeable batteries. PMID:25698340

  5. Advances in high-rate uncooled detector fabrication at Raytheon

    NASA Astrophysics Data System (ADS)

    Black, S. H.; Kraft, R.; Medrano, A.; Kocian, T.; Bradstreet, D.; Williams, R.; Yang, T.

    2010-04-01

    Over the past two years Raytheon has made a major investment aimed at establishing a high volume uncooled manufacturing capability. This effort has addressed three elements of the uncooled value stream, namely bolometer fabrication, packaging and calibration/test. To facilitate a low cost / high volume source of bolometers Raytheon has formed a partnership with a high volume 200mm commercial silicon wafer fabrication. Over a 12 month period Raytheon has installed 200mm VOx deposition equipment, matched the metrology used on the Raytheon 150mm line, transferred the process flow used to fabricate Raytheon's double layer bolometer process and qualified the product. In this paper we will review the process transfer methodology and bolometer performance. To reduce bolometer packaging cost and increase production rates, Raytheon has implemented an automated packaging line. This line utilizes automated adhesive dispense, component pick and place, wire bonding and solder seal. In this paper we will review the process flow, qualification process and line capacity Calibration and test has traditionally been performed using a number of temperature chambers, with increased throughput being obtained by adding more chambers. This comes at the expense of increased test labor required to feed the chambers and an increased energy and floor space foot print. To avoid these collateral costs, Raytheon has implemented an automated robotic calibration cell capable of performing in excess of 5,000 calibrations a month. In this paper we will provide an overview of the calibration cell along with takt time and throughput data.

  6. Dynamic shearing resistance of molten metal films under high pressures and extremely high shearing rates

    Microsoft Academic Search

    Makoto Okada; Nai-Shang Liou; Vikas Prakash

    2002-01-01

    In the present study plate-impact pressureshear experiments have been conducted to study the dynamic shearing resistance of\\u000a molten metal films at shearing rates of approximately 107 s?1. These molten films are generated by pressure-shear impact of relatively low melt-point metals such as 7075-T6 Al alloy with\\u000a high hardness and high flow-strength tool-steel plates. By employing high impact speeds and relatively

  7. Dynamic mathematical model of high rate algal ponds (HRAP).

    PubMed

    Jupsin, H; Praet, E; Vasel, J L

    2003-01-01

    This article presents a mathematical model to describe High-Rate Algal Ponds (HRAPs). The hydrodynamic behavior of the reactor is described as completely mixed tanks in series with recirculation. The hydrodynamic pattern is combined with a subset of River Water Quality Model 1 (RWQM1), including the main processes in liquid phase. Our aim is to develop models for WSPs and aerated lagoons, too, but we focused on HRAPs first for several reasons: Sediments are usually less abundant in HRAP and can be neglected, Stratification is not observed and state variables are constant in a reactor cross section, Due to the system's geometry, the reactor is quite similar to a plugflow type reactor with recirculation, with a simple advection term. The model is based on mass balances and includes the following processes: *Phytoplankton growth with NO3-, NO2- and death, *Aerobic growth of heterotrophs with NO3-, NH4+ and respiration, *Anoxic growth of heterotrophs with NO3-, NO2- and anoxic respiration, *Growth of nitrifiers (two stages) and respiration. The differences with regard to RWQM1 are that we included a limiting term associated with inorganic carbon on the growth rate of algae and nitrifiers, gas transfers are taken into account by the familiar Adeney equation, and a subroutine calculates light intensity at the water surface. This article presents our first simulations. PMID:14510211

  8. Modelling high data rate communication network access protocol

    NASA Technical Reports Server (NTRS)

    Khanna, S.; Foudriat, E. C.; Paterra, Frank; Maly, Kurt J.; Overstreet, C. Michael

    1990-01-01

    Modeling of high data rate communication systems is different from the low data rate systems. Three simulations were built during the development phase of Carrier Sensed Multiple Access/Ring Network (CSMA/RN) modeling. The first was a model using SIMCRIPT based upon the determination and processing of each event at each node. The second simulation was developed in C based upon isolating the distinct object that can be identified as the ring, the message, the node, and the set of critical events. The third model further identified the basic network functionality by creating a single object, the node which includes the set of critical events which occur at the node. The ring structure is implicit in the node structure. This model was also built in C. Each model is discussed and their features compared. It should be stated that the language used was mainly selected by the model developer because of his past familiarity. Further the models were not built with the intent to compare either structure or language but because the complexity of the problem and initial results contained obvious errors, so alternative models were built to isolate, determine, and correct programming and modeling errors. The CSMA/RN protocol is discussed in sufficient detail to understand modeling complexities. Each model is described along with its features and problems. The models are compared and concluding observations and remarks are presented.

  9. Parallel Modem Architectures for High-Data-Rate Space Modems

    NASA Astrophysics Data System (ADS)

    Satorius, E.

    2014-08-01

    Existing software-defined radios (SDRs) for space are limited in data volume by several factors, including bandwidth, space-qualified analog-to-digital converter (ADC) technology, and processor throughput, e.g., the throughput of a space-qualified field-programmable gate array (FPGA). In an attempt to further improve the throughput of space-based SDRs and to fully exploit the newer and more capable space-qualified technology (ADCs, FPGAs), we are evaluating parallel transmitter/receiver architectures for space SDRs. These architectures would improve data volume for both deep-space and particularly proximity (e.g., relay) links. In this article, designs for FPGA implementation of a high-rate parallel modem are presented as well as both fixed- and floating-point simulated performance results based on a functional design that is suitable for FPGA implementation.

  10. Single chain stochastic polymer modeling at high strain rates.

    SciTech Connect

    Harstad, E. N. (Eric N.); Harlow, Francis Harvey,; Schreyer, H. L.

    2001-01-01

    Our goal is to develop constitutive relations for the behavior of a solid polymer during high-strain-rate deformations. In contrast to the classic thermodynamic techniques for deriving stress-strain response in static (equilibrium) circumstances, we employ a statistical-mechanics approach, in which we evolve a probability distribution function (PDF) for the velocity fluctuations of the repeating units of the chain. We use a Langevin description for the dynamics of a single repeating unit and a Lioville equation to describe the variations of the PDF. Moments of the PDF give the conservation equations for a single polymer chain embedded in other similar chains. To extract single-chain analytical constitutive relations these equations have been solved for representative loading paths. By this process we discover that a measure of nonuniform chain link displacement serves this purpose very well. We then derive an evolution equation for the descriptor function, with the result being a history-dependent constitutive relation.

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

    SciTech Connect

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

    1983-01-01

    High-repitition-rate generation of up to 325 mJ of Raman amplified radiation near 615 cm/sup -1/ has been demonstrated in CO/sub 2/-pumped para-H/sub 2/ using a low-power, microwave-shifted CF/sub 4/ 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. Strong conversion was achieved even with no flow at 100 Hz. Details of the overall system design, experimental parameters, and present system limitations are discussed.

  12. Principles of the Electrical Rating of High-Vacuum Power Tubes

    Microsoft Academic Search

    E. E. Spitzer

    1951-01-01

    A rational system of ratings for high-vacuum power tubes has been arrived at, which permits the determination of ratings by calculation, once the radio-frequency power amplifier and oscillator ratings, class C, have been determined by operating test and life test. A summarized tabulation of the rating factors is given. A system for reducing ratings at high frequencies is also developed.

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

    PubMed Central

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

    2013-01-01

    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. PMID:23408525

  14. Epidemiologic study of Holstein dairy cow performance and reproduction near a high-voltage direct - current powerline

    SciTech Connect

    Martin, F.B.; Bender, A.; Steuernagel, G.; Robinson, R.A.; Revsbech, R.; Sorensen, D.K.; Williamson, N.; Williams, A.

    1986-01-01

    The development and operation of a high-voltage direct-current (HVDC) transmission line in rural Minnesota generated public concern over potential adverse effects to nearby residents and their livestock. Electrical parameters near an HVDC line decline rapidly with distance, but effects on ambient space charge have been detected out to 1 mile. To identify potential adverse effects of HVDC line operation on livestock, case-control and cohort study methods were used to examine various indices of Holstein performance in relation to distance from the line and the onset of line operation. It was believed that these indices would reflect changes in physiologic function or overt health effects that might arise from the HVDC environment. High-quality performance data from existing Dairy Herd Improvement Association (DHIA) records were obtained for 97% of qualifying herds located within 10 miles of the line. The large number of animals and years of observation provided high statistical power to detect even small systematic changes in performance. No significant differences in milk production or reproductive capacity were associated with presumed exposure to the HVDC environment. The absence of measurable effects in a large sentinel animal population may have implications for the assessment of human health risks related to HVDC transmission lines.

  15. Epidemiologic study of Holstein dairy cow performance and reproduction near a high-voltage direct-current powerline.

    PubMed

    Martin, F B; Bender, A; Steuernagel, G; Robinson, R A; Revsbech, R; Sorensen, D K; Williamson, N; Williams, A

    1986-01-01

    The development and operation of a high-voltage direct-current (HVDC) transmission line in rural Minnesota generated public concern over potential adverse effects to nearby residents and their livestock. Electrical environmental parameters near an HVDC line decline rapidly with distance, but effects on ambient space charge have been detected out to 1 mile. Previous studies of powerline effects on livestock have involved the more common alternating-current (HVAC) lines, which create a different electrical environment. To identify potential adverse effects of HVDC line operation on livestock, case-control and cohort study methods were used to examine various indices of Holstein performance in relation to distance from the line and the onset of line operation. It was believed that these indices would reflect changes in physiologic function or overt health effects that might arise from the HVDC environment. High-quality performance data from existing Dairy Herd Improvement Association (DHIA) records were obtained for 97% of qualifying herds located within 10 miles of the line. The large number of animals and years of observation provided high statistical power to detect even small systematic changes in performance. No significant differences in milk production or reproductive capacity were associated with presumed exposure to the HVDC environment. The absence of measurable effects in a large "sentinel" animal population may have implications for the assessment of human health risks related to HVDC transmission lines. PMID:3772982

  16. Contributions of vital rates to growth of a protected population of American black bears

    Microsoft Academic Search

    Michael S. Mitchell; Lara B. Pacifici; James B. Grand; Roger A. Powell

    2009-01-01

    Analyses of large, long-lived animals suggest that adult survival generally has the potential to contribute more than reproduction to population growth rate (l), but because survival varies little, high variability in reproduction can have a greater influence. This pattern has been documented for several species of large mammals, but few studies have evaluated such contributions of vital rates to l

  17. High-rate GPS accuracy: its spatio-temporal dependence

    NASA Astrophysics Data System (ADS)

    Elosegui, P.; Davis, J. L.

    2006-12-01

    A device that we built to simulate the ground motions caused by transient geophysical signals such as earthquakes, volcanoes, and glacier flow, enables us to assess the technique of high-rate GPS. We have made extensive measurements with this system while inducing simulated motions on a GPS antenna with a temporal spectrum similar to real seismic events. The difference between the antenna position inferred from GPS observations and the known "true" antenna position yields directly the time-dependent error in the GPS measurements. We have determined that, for a particular test event, 96% of the 1-Hz GPS position estimates were in error by less than 5 mm, and the root-mean-square error of those estimates over the 15-min duration of the simulated seismic event was 2.5 mm. This accuracy was reached when using as a reference a secondary stationary GPS antenna at a distance of just ~10 m, therefore attaining a high degree of error mitigation, and an optimal satellite geometry. Such short baselines are typically not available in realistic geophysical situations. Similarly, the time of an event, and thus satellite geometry, cannot be controlled. We will present an assessment of the dependence of accuracy on baseline and satellite geometry for several simulated seismic motions.

  18. An integrated CMOS high data rate transceiver for video applications

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

    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.

  19. High strain-rate response of injectable PAA hydrogel.

    PubMed

    Lin, Hong-Ru; Wang, Shih-Han; Chiang, Chia-Chin; Juang, Yun-Ching; Yu, Fu-Ann; Tsai, Liren

    2015-06-01

    Hydrogel materials have been widely considered as potential soft tissue replacements because of their high permeability, hydrophilicity, and biocompatibility, as well as their low coefficient of friction. Injectable (thermo-responsive) hydrogels can provide support and cushioning at irregularly shaped disease sites, and are thus suitable for use in treating osteoarthritis or degenerative disc disease. However, while some injectable hydrogels have been proven to sustain human body weight during daily activities, their mechanical properties under harsh dynamic conditions have not been well documented. A specified injectable polyacrylic acid (PAA) hydrogel was prepared for this study. To simulate sudden impacts or unexpected shocks to the PAA hydrogel, the split Hopkinson pressure bar technique was utilized. The dynamic responses of various hydrogels at confined high strain rates (100-2590 s(-1)) were presented. Hydrogel specimens with 3.37, 6.75, and 13.5% acrylic acid (AAc) concentrations were tested in the following three different material conditions: raw, phosphate-buffered saline (PBS) swollen, and PBS swollen with elevated temperature (37 °C). The dynamic bulk moduli of the hydrogels varied from 1.55 to 47.8 MPa depending on the given hydrogel's AAc concentration and swollen condition. PMID:25816201

  20. Preconception care: promoting reproductive planning

    PubMed Central

    2014-01-01

    Introduction Preconception care recognizes that many adolescent girls and young women will be thrust into motherhood without the knowledge, skills or support they need. Sixty million adolescents give birth each year worldwide, even though pregnancy in adolescence has mortality rates at least twice as high as pregnancy in women aged 20-29 years. Reproductive planning and contraceptive use can prevent unintended pregnancies, unsafe abortions and sexually-transmitted infections in adolescent girls and women. Smaller families also mean better nutrition and development opportunities, yet 222 million couples continue to lack access to modern contraception. Method A systematic review and meta-analysis of the evidence was conducted to ascertain the possible impact of preconception care for adolescents, women and couples of reproductive age on MNCH outcomes. A comprehensive strategy was used to search electronic reference libraries, and both observational and clinical controlled trials were included. Cross-referencing and a separate search strategy for each preconception risk and intervention ensured wider study capture. Results Comprehensive interventions can prevent first pregnancy in adolescence by 15% and repeat adolescent pregnancy by 37%. Such interventions should address underlying social and community factors, include sexual and reproductive health services, contraceptive provision; personal development programs and emphasizes completion of education. Appropriate birth spacing (18-24 months from birth to next pregnancy compared to short intervals <6 months) can significantly lower maternal mortality, preterm births, stillbirths, low birth weight and early neonatal deaths. Conclusion Improving adolescent health and preventing adolescent pregnancy; and promotion of birth spacing through increasing correct and consistent use of effective contraception are fundamental to preconception care. Promoting reproductive planning on a wider scale is closely interlinked with the reliable provision of effective contraception, however, innovative strategies will need to be devised, or existing strategies such as community-based health workers and peer educators may be expanded, to encourage girls and women to plan their families. PMID:25415259

  1. High Data Rate Link from DIVA Using a Conformal Antenna

    NASA Astrophysics Data System (ADS)

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

    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.

  2. Asexual Reproduction in Holothurians

    PubMed Central

    Dolmatov, Igor Yu.

    2014-01-01

    Aspects of asexual reproduction in holothurians are discussed. Holothurians are significant as fishery and aquaculture items and have high commercial value. The last review on holothurian asexual reproduction was published 18 years ago and included only 8 species. An analysis of the available literature shows that asexual reproduction has now been confirmed in 16 holothurian species. Five additional species are also most likely capable of fission. The recent discovery of new fissiparous holothurian species indicates that this reproduction mode is more widespread in Holothuroidea than previously believed. New data about the history of the discovery of asexual reproduction in holothurians, features of fission, and regeneration of anterior and posterior fragments are described here. Asexual reproduction is obviously controlled by the integrated systems of the organism, primarily the nervous system. Special molecular mechanisms appear to determine the location where fission occurs along the anterior-posterior axis of the body. Alteration of the connective tissue strength of the body wall may play an important role during fission of holothurians. The basic mechanism of fission is the interaction of matrix metalloproteinases, their inhibitors, and enzymes forming cross-link complexes between fibrils of collagen. The population dynamics of fissiparous holothurians are discussed. PMID:25405228

  3. Observing Outlet Glacier Motion Using High Rate GPS

    NASA Astrophysics Data System (ADS)

    Brown, A.; Howat, I.; Behar, A.; Box, J. E.; Tulaczyk, S.

    2008-12-01

    Observations of short-term variations in the flow speed of marine-terminating outlet glaciers are essential for understanding the dynamics of these systems in relation to changes in surface melting and calving. Due to their inaccessiblity and highly crevassed and unstable surfaces, there is little existing ice motion data for polar outlet glaciers at high-temporal and spatial resolution over multi-week timescales. Here we present the results, successes, and planned improvements of a proof- of-concept study at Store Glacier,West Greenland in 2008 where we deployed both dual frequency and inexpensive L1 single frequency receivers. The dual-frequency system, was deployed roughly 15 km from the ice front near a large supraglacial lake and recorded at 1 s epochs. Three single frequency receivers, recording at 10 s epochs, were installed within 5 km of the ice front and transmitted their data to a base station on the side of the glacier. Dual frequency data was post processed using GAMIT's kinematic software package TRACK. However, multiple attempts at post processing the L1 phase data were unsuccessful due to multipath cycleslip intensity, massive clock drift, and data corruption, so that only the pseudorange data could be utilized. By combining the high-rate motion data with concurrent meteorology,time-lapse photography and seismographic data, we assess how variations in motion correspond with changes in meltwater production, calving and sea ice conditions at the front. Based on this initial deployment, we propose future improvements including increased data collection robustness, use of chokering antennae for multipath mitigation, broadcast GPS clock correction, and dual frequency disposable rover solutions for drastically improved positional analysis at the glacier front.

  4. High Strain Rate Response of Sandwich Composites with Nanophased Cores

    NASA Astrophysics Data System (ADS)

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

    2005-05-01

    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.

  5. Photosynthesis in Relation to Reproductive Success of Cypripedium flavum

    PubMed Central

    ZHANG, SHIBAO; HU, HONG; ZHOU, ZHEKUN; XU, KUN; YAN, NING; LI, SHUYUN

    2005-01-01

    • Background and Aims Cypripedium flavum is a rare, endemic alpine slipper orchid of China, which is under threat from excessive collection and habitat changes. Conservation and re-introduction of C. flavum is restricted by lack of knowledge of the plant's photosynthesis and how that affects reproductive success. The hypothesis is tested that reproductive success is determined by photosynthetic production. • Methods To understand the photosynthetic characteristics and adaptation of C. flavum to alpine environments, and the relation to reproductive success, measurements were made at four field sites with varying degrees of forest cover in the Hengduan Mountains, south-west China. • Key Results Both photosynthetic capacity and reproductive traits of C. flavum are affected by light availability. Photosynthetic rate (A) is greatest around noon, following the pattern of photosynthetically active radiation (PAR) at all sites. Cypripedium flavum has highest daily mean photosynthetic rate (Adaily) and light-saturated photosynthetic rate (Amax) under a half to a third of full sunlight. High radiation decreased A. However, the optimum temperature for photosynthesis was similar (18–20 °C) at all sites. • Conclusions The quotient of daily mean photosynthetic rate to light saturated photosynthesis (Adaily/Amax) is positively correlated with the ramet number m?2 and percentage of fruiting of C. flavum. The Adaily/Amax ratio is a useful proxy for evaluating reproductive success of C. flavum. PMID:15829510

  6. Costs of reproduction in a long-lived bird: large clutch size is associated with low survival in the presence of a highly virulent disease

    PubMed Central

    Descamps, Sébastien; Gilchrist, H. Grant; Bêty, Joël; Buttler, E. Isabel; Forbes, Mark R.

    2009-01-01

    Fitness costs of reproduction are expected to be more pronounced when the environmental conditions deteriorate. We took advantage of a natural experiment to investigate the costs of reproduction among common eiders (Somateria mollissima) nesting at a site in the Arctic, where an avian cholera epizootic appeared at different magnitudes. We tested the predictions that larger reproductive effort (clutch size) is associated with lower survival or breeding probability the following year, and that this relationship was more pronounced under heightened exposure to the disease. Our results indicate that large clutch sizes were associated with lower survival of female eider ducks, but only when there was heightened exposure to avian cholera, as indexed by eider mortality on site. No cost was observed when cholera was absent or when lesser exposure was evident. This supports the hypothesis that fitness costs of high reproductive effort are higher under unfavourable conditions such as a disease epizootic, and further indicates that being a conservative breeder can increase survival probability, given the presence of a highly virulent disease. PMID:19324661

  7. Diagnostic value of sperm DNA fragmentation and sperm high-magnification for predicting outcome of assisted reproduction treatment

    PubMed Central

    López, Gemma; Lafuente, Rafael; Checa, Miguel A; Carreras, Ramón; Brassesco, Mario

    2013-01-01

    Over the last years, major improvements in the field of male infertility diagnosis have been achieved. The aim of this study was to determine the diagnostic usefulness of sperm DNA integrity and sperm vacuolisation for predicting outcome in infertile couples undergoing in vitro fertilisation (IVF) and intracytoplasmic sperm injection (ICSI) treatments. A cohort study from 152 infertile couples undergoing sperm DNA fragmentation and high-magnification tests prior to an assisted reproduction treatment was designed. We found that the most predictive cutoff for pregnancy was 25.5% of DNA fragmentation with a negative predictive value of 72.7% (P=0.02). For the degree of vacuolisation, the best predictor of pregnancy was 73.5% of vacuolated sperm grades III+IV with a negative predictive value of 39.4% (P=0.09), which was not statistically significant. In conclusion, sperm DNA fragmentation greater than 25.5% could be associated with higher probability of failure IVF treatment. Regarding the results of the sperm analysis at high magnification, they do not allow us to predict whether or not patients will become pregnant. PMID:23912311

  8. Diagnostic value of sperm DNA fragmentation and sperm high-magnification for predicting outcome of assisted reproduction treatment.

    PubMed

    López, Gemma; Lafuente, Rafael; Checa, Miguel A; Carreras, Ramón; Brassesco, Mario

    2013-11-01

    Over the last years, major improvements in the field of male infertility diagnosis have been achieved. The aim of this study was to determine the diagnostic usefulness of sperm DNA integrity and sperm vacuolisation for predicting outcome in infertile couples undergoing in vitro fertilisation (IVF) and intracytoplasmic sperm injection (ICSI) treatments. A cohort study from 152 infertile couples undergoing sperm DNA fragmentation and high-magnification tests prior to an assisted reproduction treatment was designed. We found that the most predictive cutoff for pregnancy was 25.5% of DNA fragmentation with a negative predictive value of 72.7% (P=0.02). For the degree of vacuolisation, the best predictor of pregnancy was 73.5% of vacuolated sperm grades III+IV with a negative predictive value of 39.4% (P=0.09), which was not statistically significant. In conclusion, sperm DNA fragmentation greater than 25.5% could be associated with higher probability of failure IVF treatment. Regarding the results of the sperm analysis at high magnification, they do not allow us to predict whether or not patients will become pregnant. PMID:23912311

  9. High-order harmonic generation using a high-repetition-rate turnkey laser.

    PubMed

    Lorek, E; Larsen, E W; Heyl, C M; Carlström, S; Pale?ek, D; Zigmantas, D; Mauritsson, J

    2014-12-01

    We generate high-order harmonics at high pulse repetition rates using a turnkey laser. High-order harmonics at 400 kHz are observed when argon is used as target gas. In neon, we achieve generation of photons with energies exceeding 90 eV (?13 nm) at 20 kHz. We measure a photon flux of up to 4.4 × 10(10) photons per second per harmonic in argon at 100 kHz. Many experiments employing high-order harmonics would benefit from higher repetition rates, and the user-friendly operation opens up for applications of coherent extreme ultra-violet pulses in new research areas. PMID:25554271

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

    SciTech Connect

    Li, Flora M.; Bayer, Bernhard C.; Hofmann, Stephan; Milne, William I.; Flewitt, Andrew J. [Department of Engineering, Electrical Engineering Division, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0FA (United Kingdom); Dutson, James D.; Wakeham, Steve J.; Thwaites, Mike J. [Plasma Quest Ltd., Unit 1B, Rose Estate, Osborn Way, Hook, Hampshire RG27 9UT (United Kingdom)

    2011-06-20

    Amorphous hafnium oxide (HfO{sub x}) is deposited by sputtering while achieving a very high k{approx}30. Structural characterization suggests that the high k is a consequence of a previously unreported cubiclike short range order in the amorphous HfO{sub x} (cubic k{approx}30). The films also possess a high electrical resistivity of 10{sup 14} {Omega} cm, a breakdown strength of 3 MV cm{sup -1}, and an optical gap of 6.0 eV. Deposition at room temperature and a high deposition rate ({approx}25 nm min{sup -1}) makes these high-k amorphous HfO{sub x} films highly advantageous for plastic electronics and high throughput manufacturing.

  11. Reproduction of American robin ( Turdus migratorius) in a suburban environment

    Microsoft Academic Search

    Francois Morneau; Claire Lépine; Robert Décarie; Marc-André Villard; Jean-Luc DesGranges

    1995-01-01

    We compared the breeding biology of the American robin in a suburban population and in populations from less urbanized environments using data from 141 nests from a dense suburb near Montreal, Que., and data from the literature. Our data suggest that robins potentially can have a large clutch size and very high rates of reproductive success in suburban areas and

  12. ABORTED FRUITS OF OPUNTIA MICRODASYS (CACTACEAE): INSURANCE AGAINST REPRODUCTIVE FAILURE

    E-print Network

    Mandujano, María del Carmen

    ABORTED FRUITS OF OPUNTIA MICRODASYS (CACTACEAE): INSURANCE AGAINST REPRODUCTIVE FAILURE 1 N, but plantlet provenance did not. The high fruit abortion rate resulting from environmental and maternal effects provided suitable conditions for establishment of plantlets. Key words: clonal propagation; fruit abortion

  13. Transistor reset preamplifier for high-rate high-resolution spectroscopy

    SciTech Connect

    Landis, D.A.; Cork, C.P.; Madden, N.W.; Goulding, F.S.

    1981-10-01

    Pulsed transistor reset of high resolution charge sensitive preamplifiers used in cooled semiconductor spectrometers can sometimes have an advantage over pulsed light reset systems. Several versions of transistor reset spectrometers using both silicon and germanium detectors have been built. This paper discusses the advantages of the transistor reset system and illustrates several configurations of the packages used for the FET and reset transistor. It also describes the preamplifer circuit and shows the performance of the spectrometer at high rates.

  14. Deposition of Si-DLC films with high hardness, low stress and high deposition rates

    Microsoft Academic Search

    J. C Damasceno; S. S Camargo; F. L Freire; R Carius

    2000-01-01

    In this work silicon-incorporated diamond-like carbon (Si-DLC) films were produced by plasma enhanced chemical vapor deposition (PECVD) from gaseous mixtures of CH4 and SiH4. A study of the influence of self-bias and gas composition on the mechanical and structural properties of the films was carried out. Results show that films deposited at high self-bias present high deposition rates, low stress

  15. Process for High-Rate Fabrication of Alumina Nanotemplates

    NASA Technical Reports Server (NTRS)

    Myung, Nosang; Fleurial, Jean-Pierre; Yun, Minhee; West, William; Choi, Daniel

    2007-01-01

    An anodizing process, at an early stage of development at the time of reporting the information for this article, has shown promise as a means of fabricating alumina nanotemplates integrated with silicon wafers. Alumina nanotemplates are basically layers of alumina, typically several microns thick, in which are formed approximately regular hexagonal arrays of holes having typical diameters of the order of 10 to 100 nm. Interest in alumina nanotemplates has grown in recent years because they have been found to be useful as templates in the fabrication of nanoscale magnetic, electronic, optoelectronic, and other devices. The present anodizing process is attractive for the fabrication of alumina nanotemplates integrated with silicon wafers in two respects: (1) the process involves self-ordering of the holes; that is, the holes as formed by the process are spontaneously arranged in approximately regular hexagonal arrays; and (2) the rates of growth (that is, elongation) of the holes are high enough to make the process compatible with other processes used in the mass production of integrated circuits. In preparation for fabrication of alumina nanotemplates in this process, one first uses electron-beam evaporation to deposit thin films of titanium, followed by thin films of aluminum, on silicon wafers. Then the alumina nanotemplates are formed by anodizing the aluminum layers, as described below. In experiments in which the process was partially developed, the titanium films were 200 A thick and the aluminum films were 5 m thick. The aluminum films were oxidized to alumina, and the arrays of holes were formed by anodizing the aluminum in aqueous solutions of sulfuric and/or oxalic acid at room temperature (see figure). The diameters, spacings, and rates of growth of the holes were found to depend, variously, on the composition of the anodizing solution, the applied current, or the applied potential, as follows: In galvanostatically controlled anodizing, regardless of the chemical composition of the solution, relatively high current densities (50 to 100 mA/cm2) resulted in arrays of holes that were more nearly regular than were those formed at lower current densities. . The rates of elongation of the holes were found to depend linearly on the applied current density: the observed factor of proportionality was 1.2 (m/h)/(mA/cm2). For a given fixed current density and room temperature, the hole diameters were found to depend mainly on the chemical compositions of the anodizing solutions. The holes produced in sulfuric acid solutions were smaller than those produced in oxalic acid solutions. The arrays of holes produced in sulfuric acid were more ordered than were those produced in oxalic acid. . The breakdown voltage was found to decrease logarithmically with increasing concentration of sulfuric acid. The breakdown voltage was also found to decrease with temperature and to be accompanied by a decrease in hole diameter. The hole diameter was found to vary linearly with applied potential, with a slope of 2.1 nm/V. This slope differs from slopes (2.2 and 2.77 nm/V) reported for similar prior measurements on nanotemplates made from bulk aluminum. The differences among these slopes may be attributable to differences among impurities and defects in bulk and electron-beam-evaporated aluminum specimens.

  16. Accuracy of High-Rate GPS for Seismology

    NASA Technical Reports Server (NTRS)

    Elosegui, P.; Davis, J. L.; Oberlander, D.; Baena, R.; Ekstrom, G.

    2006-01-01

    We built a device for translating a GPS antenna on a positioning table to simulate the ground motions caused by an earthquake. The earthquake simulator is accurate to better than 0.1 mm in position, and provides the "ground truth" displacements for assessing the technique of high-rate GPS. We found that the root-mean-square error of the 1-Hz GPS position estimates over the 15-min duration of the simulated seismic event was 2.5 mm, with approximately 96% of the observations in error by less than 5 mm, and is independent of GPS antenna motion. The error spectrum of the GPS estimates is approximately flicker noise, with a 50% decorrelation time for the position error of approx.1.6 s. We that, for the particular event simulated, the spectrum of dependent error in the GPS measurements. surface deformations exceeds the GPS error spectrum within a finite band. More studies are required to determine whether a generally optimal bandwidth exists for a target group of seismic events.

  17. Substrate inhibition and control for high rate biogas production

    SciTech Connect

    Shin, H.S.

    1982-01-01

    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.

  18. Cassini High Rate Detector V5.0

    NASA Astrophysics Data System (ADS)

    Economou, T.; Didonna, P.

    2009-06-01

    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--

  19. Miniature high-resolution laser radar operating at video rates

    NASA Astrophysics Data System (ADS)

    Smithpeter, Colin L.; Nellums, Robert O.; Lebien, Steve M.; Studor, George

    2000-09-01

    We are developing a laser radar to meet the needs of NASA for a 5-lb, 150 in3 image sensor with a pixel range accuracy of 0.1-inch. NASA applications include structural dynamics measurements, navigation guidance in rendezvous and proximity operations, and space vehicle inspection. The sensor is based on the scannerless range imager architecture developed at Sandia. This architecture modulates laser floodlight illumination and a focal plane receiver to phase encode the laser time of flight (TOF) for each pixel. We believe this approach has significant advantages over architectures directly measuring TOF including high data rate, reduced detector bandwidth, and conventional focal plane array (FPA) detection. A limitation of the phase detection technique is its periodic nature, which provides relative range information over a finite ambiguity interval. To extend the operating interval while maintaining a given range resolution, a LADAR sensor using dual modulation frequencies has been developed. The modulation frequency values can be scaled to meet the resolution and range interval requirements of different applications. Results from the miniature NASA sensor illustrate the advantages of the dual-frequency operation and the ability to provide the range images of 640 by 480 pixels at 30 frames per second.

  20. Algal biofuels from wastewater treatment high rate algal ponds.

    PubMed

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

    2011-01-01

    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

  1. Strain rate viscoelastic analysis of soft and highly hydrated biomaterials

    PubMed Central

    Tirella, A; Mattei, G; Ahluwalia, A

    2014-01-01

    Measuring the viscoelastic behavior of highly hydrated biological materials is challenging because of their intrinsic softness and labile nature. In these materials, it is difficult to avoid prestress and therefore to establish precise initial stress and strain conditions for lumped parameter estimation using creep or stress-relaxation (SR) tests. We describe a method ( or epsilon dot method) for deriving the viscoelastic parameters of soft hydrated biomaterials which avoids prestress and can be used to rapidly test degradable samples. Standard mechanical tests are first performed compressing samples using different strain rates. The dataset obtained is then analyzed to mathematically derive the material's viscoelastic parameters. In this work a stable elastomer, polydimethylsiloxane, and a labile hydrogel, gelatin, were first tested using the, in parallel SR was used to compare lumped parameter estimation. After demonstrating that the elastic parameters are equivalent and that the estimation of short-time constants is more precise using the proposed method, the viscoelastic behavior of porcine liver was investigated using this approach. The results show that the constitutive parameters of hepatic tissue can be quickly quantified without the application of any prestress and before the onset of time-dependent degradation phenomena. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 3352–3360, 2014 PMID:23946054

  2. ASIC for High Rate 3D Position Sensitive Detectors

    SciTech Connect

    Vernon, E.; De Geronimo, G.; Ackley, K.; Fried, J.; He, Z.; Herman, C.; Zhang, F.

    2010-06-16

    We report on the development of an application specific integrated circuit (ASIC) for 3D position sensitive detectors (3D PSD). The ASIC is designed to operate with pixelated wide bandgap sensors like Cadmium-Zinc-Telluride (CZT), Mercuric Iodide (Hgl2) and Thallium Bromide (TIBr). It measures the amplitudes and timings associated with an ionizing event on 128 anodes, the anode grid, and the cathode. Each channel provides low-noise charge amplification, high-order shaping with peaking time adjustable from 250 ns to 12 {micro}s, gain adjustable to 20 mV/fC or 120 mV/fC (for a dynamic range of 3.2 MeV and 530 keV in CZT), amplitude discrimination with 5-bit trimming, and positive and negative peak and timing detections. The readout can be full or sparse, based on a flag and single- or multi-cycle token passing. All channels, triggered channels only, or triggered with neighbors can be read out thus increasing the rate capability of the system to more than 10 kcps. The ASIC dissipates 330 mW which corresponds to about 2.5 mW per channel.

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

    SciTech Connect

    Dillon, A. C.

    2012-01-01

    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.

  4. Reproductive Hazards in the Lab Reproductive Hazards

    E-print Network

    de Lijser, Peter

    and pesticides have been shown to have effects on human reproductive systems. Organic solvents, such as xyleneReproductive Hazards in the Lab Reproductive Hazards The term reproductive hazard refers to agents (radiation, x-rays, chemicals or biologicals) that affect the reproductive health of women or men to have

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

    SciTech Connect

    Grunschel, S E; Clifton, R J; Jiao, T

    2010-01-28

    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.

  6. Studies on Nonaluminized High Burning Rate AP-Composite Propellants

    Microsoft Academic Search

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

    2004-01-01

    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

  7. Synergistic effects of sequential infection with highly pathogenic porcine reproductive and respiratory syndrome virus and porcine circovirus type 2

    PubMed Central

    2013-01-01

    Background Porcine reproductive and respiratory syndrome virus (PRRSV) is the causative agent of porcine reproductive and respiratory syndrome (PRRS) and porcine circovirus type 2 (PCV2) is associated with postweaning multisystemic wasting syndrome (PMWS) in pigs. Coinfection with highly pathogenic PRRSV (HP-PRRSV) and PCV2 in the field has recently become extensive in some Asian countries. A synergistic pathogenicity between PRRSV and PCV2 infections has previously been reported. However, the consequences of the sequential infection of pigs with these two viruses are unknown. Methods Thirty 35-day-old piglets were randomly divided into six groups (n = 5 each): HP-PRRSV/PCV2 (group 1, inoculated with HP-PRRSV, then inoculated with PCV2 one week later), PCV2/HP-PRRSV (group 2, inoculated with PCV2, then inoculated with HP-PRRSV one week later), HP-PRRSV+PCV2 (group 3, inoculated with HP-PRRSV and PCV2 concurrently), HP-PRRSV (group 4, inoculated with HP-PRRSV), PCV2 (group 5, inoculated with PCV2), and the control (group 6, uninfected). This experiment lasted 28 days. Clinical symptoms and rectal temperatures were recorded each day after inoculation, body weight was recorded weekly, and serum samples were obtained for viral nucleic acid quantification and antibody titration. Variations in CD3+, CD4+ CD8–, CD3+, CD4–, and CD8+ cells, natural killer (NK) cells, and mononuclear cells were determined by flow cytometry. The serum concentrations of interferon ? (IFN-?), tumor necrosis factor ? (TNF-?), interleukin 10 (IL-10), and macrophage granulocyte-colony stimulating factor (GM-CSF) were determined. Pathological changes in different tissues from the experimentally infected pigs were recorded. Results The piglets in group 1 had the highest viral loads, the lowest antibody titers, the most-severe clinical signs, and the highest mortality (3/5, 60%; the mortality in the other groups was 0%), and interstitial pneumonia was more severe in this group compare to the other HP-PRRSV infected groups. The serum levels of IFN-?, TNF-?, IL-10, and GM-CSF varied (increased or decreased) most widely in group 1, as did each immunocyte subgroup. Conclusions HP-PRRSV infection followed by PCV2 infection enhanced the replication of both viruses in the experimental piglets and led to more-severe clinical signs and lesions, indicating greater synergistic effects during the sequential infection of piglets with HP-PRRSV and then PCV2. PMID:23971711

  8. Genetic Structure Is Associated with Phenotypic Divergence in Floral Traits and Reproductive Investment in a High-Altitude Orchid from the Iron Quadrangle, Southeastern Brazil

    PubMed Central

    Leles, Bruno; Chaves, Anderson V.; Russo, Philip; Batista, João A. N.; Lovato, Maria Bernadete

    2015-01-01

    Knowledge of the role of Neotropical montane landscapes in shaping genetic connectivity and local adaptation is essential for understanding the evolutionary processes that have shaped the extraordinary species diversity in these regions. In the present study, we examined the landscape genetics, estimated genetic diversity, and explored genetic relationships with morphological variability and reproductive strategies in seven natural populations of Cattleya liliputana (Orchidaceae). Nuclear microsatellite markers were used for genetic analyses. Spatial Bayesian clustering and population-based analyses revealed significant genetic structuring and high genetic diversity (He = 0.733 ± 0.03). Strong differentiation was found between populations over short spatial scales (FST = 0.138, p < 0.001), reflecting the landscape discontinuity and isolation. Monmonier´s maximum difference algorithm, Bayesian analysis on STRUCTURE and principal component analysis identified one major genetic discontinuity between populations. Divergent genetic groups showed phenotypic divergence in flower traits and reproductive strategies. Increased sexual reproductive effort was associated with rock outcrop type and may be a response to adverse conditions for growth and vegetative reproduction. Here we discuss the effect of restricted gene flow, local adaptation and phenotypic plasticity as drivers of population differentiation in Neotropical montane rock outcrops. PMID:25756994

  9. Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus Infection Induced Apoptosis and Autophagy in Thymi of Infected Piglets

    PubMed Central

    Tu, Yabin; Tong, Jie; Liu, Yonggang; Zhang, Chong; Chang, Yafei; Wang, Shujie; Jiang, Chenggang; Zhou, En-Min; Cai, Xuehui

    2015-01-01

    Previously, we demonstrated that the highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) HuN4 strain causes obvious thymic atrophy and thymocytes apoptosis in infected piglets after birth, which is more severe than that induced by classical PRRSV. In this study, we investigated apoptosis and autophagy in the thymus of piglets infected with the HP-PRRSV HuN4 strain, and found that both apoptosis and autophagy occurred in the thymus of piglets infected with HP-PRRSV. In addition to a few virus-infected cells, CD14+ cells, the main autophagic cells in the thymus were thymic epithelial cells. These findings demonstrated that HP-PRRSV induces apoptosis in bystander cells, and induces autophagy in both infected and bystander cells in the thymus of infected piglets. Herein, we first present new data on the thymic lesions induced by HP-PRRSV, and show that apoptosis and autophagy are key mechanisms involved in cell survival and determinants of the severity of thymic atrophy in infected piglets. Finally, future studies of the mechanism underlying immune responses are proposed based on our current understanding of PRRSV-host interactions. PMID:26046751

  10. Reproduction of PMWS of high mortality with a porcine circovirus type 2-group 1 isolate

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Introduction In late 2005, sporadic cases of an acute onset of high mortality disease were observed in growing pigs among USA swine herds. PCV2-group 1 (Gp1) virus was consistently detected among the affected animals. Phylogenetic analysis showed that the PCV2 isolates from the United States until l...

  11. 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...

  12. Taking Images in Extremely High Dynamic Range Scenes by Fusing Multiple Exposed Images And Tone Reproduction

    Microsoft Academic Search

    Wen-Chung Kao; Wei-Chi Huang; Lien-Yang Chen; Hong-Shuo Tai; Hung-Hsin Wu

    2008-01-01

    This paper presents an integrated color imaging system for taking images in extremely high dynamic range scenes. The system first fuses five differently exposed images in raw data such that the effective dynamic range of the fused raw data is extended to 256 times. Then it runs several edge detection iterations to extract the image details in different luminance levels

  13. Analyzing network traces to identify long-term high rate flows 

    E-print Network

    Kim, In-Koo

    2001-01-01

    In this thesis we look at a scalable way of identifying long-term high rate flows without maintaining per flow state information proportional to the number of flows. Identification of high-rate flows is useful at the time ...

  14. Women Chemists Mortality Study Finds High Suicide Rate.

    ERIC Educational Resources Information Center

    Chemical and Engineering News, 1984

    1984-01-01

    A study of white women members (N=347) of the American Chemical Society who died between 1925 and 1979 finds five times the expected rate of suicide, a higher risk for some forms of cancer, and a lower rate of heart disease. These and other findings are discussed. (JN)

  15. Characterization of Composites Response at High Rates of Deformation

    NASA Technical Reports Server (NTRS)

    Gilat, Amos

    2001-01-01

    The objective of the proposed research is to experimentally study the effect of strain rate on mechanical response (deformation and failure) of IM-7/977-2 carbon fiber/epoxy matrix composites. The experimental data will provide the information needed for the development of a nonlinear, rate dependent deformation and strength model for this material that can subsequently be used in design.

  16. Development of A Linear Power Amplifier for High Frame Rate Imaging System

    E-print Network

    Lu, Jian-yu

    to obtain RF echo signals for image constructions. Keywords-power amplifier; high frame rate imaging systemDevelopment of A Linear Power Amplifier for High Frame Rate Imaging System Jian-yu Lu and John L@eng.utoledo.edu Abstract -- A linear power amplifier was developed for a high frame rate imaging system. Due

  17. Ionizing radiation promotes protozoan reproduction

    SciTech Connect

    Luckey, T.D.

    1986-11-01

    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.

  18. Your Reproductive Health

    MedlinePLUS

    ... your body Your reproductive health How the female reproductive system works Vaginal infections What is PCOS? Puberty Getting ... Your reproductive health What, exactly, is the female reproductive system? It is all the parts of your body ...

  19. Reproductive Health

    NSDL National Science Digital Library

    BioMed Central contains hundreds of important online journals in its archives, and Reproductive Health is certainly one that visitors will want to look over when they have a few moments. Reproductive Health is the official journal of the Geneva Foundation for Medical Education and Research, and was started in June 2004. It covers all aspects of human reproduction, and recent pieces have dealt with cervical cancer, maternity care, and other related topics. Visitors can view the ten most accessed articles from the journal, sign up to receive an RSS feed of the latest articles, and also email articles to friends and colleagues. For those who might be interested in submitting an article for consideration, they can also do that via this site.

  20. Alternate reproductive strategies in the California gull

    Microsoft Academic Search

    B. H. Pugesek; P. Wood

    1992-01-01

    Summary  We analysed 6 years of reproduction data for 176 California gulls (Larus californicus) surviving from 1980 to 1988. Using a statistical model adapted from Rao's (1958) and Tucker's (1966) generalized growth curve analysis, we reconstructed the reproductive patterns of gulls aged from 0 to 26 years. Individuals were highly consistent in following one of two patterns of reproduction. In a

  1. Seasonal migration to high latitudes results in major reproductive benefits in an insect

    PubMed Central

    Chapman, Jason W.; Bell, James R.; Burgin, Laura E.; Reynolds, Donald R.; Pettersson, Lars B.; Hill, Jane K.; Bonsall, Michael B.; Thomas, Jeremy A.

    2012-01-01

    Little is known of the population dynamics of long-range insect migrants, and it has been suggested that the annual journeys of billions of nonhardy insects to exploit temperate zones during summer represent a sink from which future generations seldom return (the “Pied Piper” effect). We combine data from entomological radars and ground-based light traps to show that annual migrations are highly adaptive in the noctuid moth Autographa gamma (silver Y), a major agricultural pest. We estimate that 10–240 million immigrants reach the United Kingdom each spring, but that summer breeding results in a fourfold increase in the abundance of the subsequent generation of adults, all of which emigrate southward in the fall. Trajectory simulations show that 80% of emigrants will reach regions suitable for winter breeding in the Mediterranean Basin, for which our population dynamics model predicts a winter carrying capacity only 20% of that of northern Europe during the summer. We conclude not only that poleward insect migrations in spring result in major population increases, but also that the persistence of such species is dependent on summer breeding in high-latitude regions, which requires a fundamental change in our understanding of insect migration. PMID:22927392

  2. Models of Evolution of Reproductive Isolation

    PubMed Central

    Nei, Masatoshi; Maruyama, Takeo; Wu, Chung-I

    1983-01-01

    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. PMID:6840540

  3. Sensitive, high-strain, high-rate bodily motion sensors based on graphene-rubber composites.

    PubMed

    Boland, Conor S; Khan, Umar; Backes, Claudia; O'Neill, Arlene; McCauley, Joe; Duane, Shane; Shanker, Ravi; Liu, Yang; Jurewicz, Izabela; Dalton, Alan B; Coleman, Jonathan N

    2014-09-23

    Monitoring of human bodily motion requires wearable sensors that can detect position, velocity and acceleration. They should be cheap, lightweight, mechanically compliant and display reasonable sensitivity at high strains and strain rates. No reported material has simultaneously demonstrated all the above requirements. Here we describe a simple method to infuse liquid-exfoliated graphene into natural rubber to create conducting composites. These materials are excellent strain sensors displaying 10(4)-fold increases in resistance and working at strains exceeding 800%. The sensitivity is reasonably high, with gauge factors of up to 35 observed. More importantly, these sensors can effectively track dynamic strain, working well at vibration frequencies of at least 160 Hz. At 60 Hz, we could monitor strains of at least 6% at strain rates exceeding 6000%/s. We have used these composites as bodily motion sensors, effectively monitoring joint and muscle motion as well and breathing and pulse. PMID:25100211

  4. Versatile high rate plasma deposition and processing with very high frequency excitation

    SciTech Connect

    Heintze, M.

    1997-07-01

    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.

  5. High-speed bit-error-rate measurement system for high-temperature superconducting digital circuits

    Microsoft Academic Search

    Masahiro Horibe; Yoshinobu Tarutani; Keiichi Tanabe

    2003-01-01

    We have investigated and tried to improve the packaging technologies for a bit-error-rate (BER) measurement system for high-Tc superconducting circuits. Signal cables, test fixture, and magnetic shields were specially designed and assembled for the BER measurement system, taking into account electrical losses, signal reflection, heat inflow, and power consumption of a cryocooler. BER was further improved by changing the way

  6. Suppression of anaerobic ammonium oxidizers under high organic content in high-rate Anammox UASB reactor

    Microsoft Academic Search

    Chong-jian Tang; Ping Zheng; Cai-hua Wang; Qaisar Mahmood

    2010-01-01

    The effect of organic matter on the nitrogen removal performance of anaerobic ammonium oxidation (Anammox) process was investigated in an upflow anaerobic sludge blanket (UASB) reactor fed with nitrogen loading rate of 13.92kgNm?3day?1 at an HRT of 0.83h. Mass balance showed that the heterotrophic denitrification prevailed in the UASB reactor, and became the dominant reactions when high influent COD\\/NO2-–N ratios

  7. High-Fidelity Reproduction of Spatiotemporal Visual Signals for Retinal Prosthesis

    PubMed Central

    Jepson, Lauren H.; Hottowy, Pawel; Weiner, Geoffrey A.; Dabrowski, W?adys1aw; Litke, Alan M.; Chichilnisky, E.J.

    2015-01-01

    SUMMARY Natural vision relies on spatiotemporal patterns of electrical activity in the retina. We investigated the feasibility of veridically reproducing such patterns with epiretinal prostheses. Multielectrode recordings and visual and electrical stimulation were performed on populations of identified ganglion cells in isolated peripheral primate retina. Electrical stimulation patterns were designed to reproduce recorded waves of activity elicited by a moving visual stimulus. Electrical responses in populations of ON parasol cells exhibited high spatial and temporal precision, matching or exceeding the precision of visual responses measured in the same cells. Computational readout of electrical and visual responses produced similar estimates of stimulus speed, confirming the fidelity of electrical stimulation for biologically relevant visual signals. These results suggest the possibility of producing rich spatiotemporal patterns of retinal activity with a prosthesis and that temporal multiplexing may aid in reproducing the neural code of the retina. PMID:24910077

  8. A high resolution study of forsterite dissolution rates

    Microsoft Academic Search

    Jodi J. Rosso; J. Donald Rimstidt

    2000-01-01

    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%

  9. Male Reproductive System.

    ERIC Educational Resources Information Center

    Turkington, B. A.

    This autoinstructional lesson deals with the study of the human body with emphasis on the life process of reproduction. It is a learning activity included in high school biology or health education classes. The behavioral objectives are listed and the equipment and materials needed to help the student gain these objectives are also included in the…

  10. Female Reproductive System.

    ERIC Educational Resources Information Center

    Hodge, N. J.

    This autoinstructional lesson can be used with health education and/or biology classes in a high school curriculum. It deals with the study of human development with emphasis on the female reproductive organs and cycles. The behavioral objectives are given, and the materials and equipment needed to gain these objectives are itemized. Fifteen…

  11. Large breasts and narrow waists indicate high reproductive potential in women.

    PubMed Central

    Jasie?ska, Grazyna; Ziomkiewicz, Anna; Ellison, Peter T.; Lipson, Susan F.; Thune, Inger

    2004-01-01

    Physical characteristics, such as breast size and waist-to-hip ratio (WHR), function as important features used by human males to assess female attractiveness. Males supposedly pay attention to these features because they serve as cues to fecundity and health. Here, we document that women with higher breast-to-underbreast ratio (large breasts) and women with relatively low WHR (narrow waists) have higher fecundity as assessed by precise measurements of daily levels of 17-beta-oestradiol (E2) and progesterone. Furthermore, women who are characterized by both narrow waists and large breasts have 26% higher mean E2 and 37% higher mean mid-cycle E2 levels than women from three groups with other combinations of body-shape variables, i.e. low WHR with small breasts and high WHR with either large or small breasts. Such gains in hormone levels among the preferred mates may lead to a substantial rise in the probability of conception, thus providing a significant fitness benefit. PMID:15306344

  12. Age at puberty, ovulation rate, and reproductive tract traits of developing gilts fed two lysine levels and three metabolizable energy levels from 100 to 260 d of age

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this study was to determine the effect of feeding different lysine and metabolizable energy (ME) levels to developing gilts on age at puberty and reproductive tract measurements. Crossbred Large White × Landrace gilts (n = 1221) housed in groups from 100 d of age until slaughter (ap...

  13. Sexual and Reproductive Strategies Among Serbian Gypsies

    Microsoft Academic Search

    Jelena ?rovovi?

    2004-01-01

    This paper deals with a full range of sexual and reproductive behaviors among different “tribes” of Gypsies in Serbia. The examined traits include rates of fertility, mortality, age distribution, education, crime rates, and parental care. In addition, Gypsy traditions of culturally prescribed sexual behavior are also studied. It is found that Gypsy tribes employ different reproductive strategies, ranging from an

  14. Reproductive biology of the isopod Excirolana braziliensis at the southern edge of its geographical range

    NASA Astrophysics Data System (ADS)

    Martínez, Gastón; Defeo, Omar

    2006-12-01

    A full analysis of the reproductive biology of the isopod Excirolana braziliensis Richardson 1912 was conducted in a sandy beach of Uruguay, located at the southernmost edge of its distributional range in the Atlantic Ocean. Reproductive and recruitment periods of E. braziliensis were concentrated in austral summer. Females with oostegites appeared in November, whereas total biomass, individual sizes and fecundity of ovigerous females peaked between December and January. These concurrent traits were responsible for the significant peak of juveniles in January. The size at maturity was 9.88 mm. Four embryonic developmental stages were described and identified: mean length linearly increased from stages I to III, whereas dry weight exponentially decreased from stages I to IV. The high reproductive output (0.41-0.58), reported for the first time in this isopod, exceeds the rates documented for other isopods. Reproduction of E. braziliensis at the southern edge of its range is semelparous: females produce one brood during the reproductive season, exhaust their energy reserves during incubation, and probably die at the end of the reproductive season. A macroscale comparison suggests that E. braziliensis at the southern edge of its range counteracts its narrow reproductive period by a short incubation period with larger individual mature female and embryo sizes, higher fecundity and a higher percentage of ovigerous females than in subtropical and tropical populations. These extreme reproductive indicators could be attributed to the internal retention of embryos that assures offspring survival, coupled with a high adaptation capability to environmental variations across its range.

  15. High strain rate properties of unidirectional composites, part 1

    NASA Technical Reports Server (NTRS)

    Daniel, I. M.

    1991-01-01

    Experimental methods were developed for testing and characterization of composite materials at strain rates ranging from quasi-static to over 500 s(sup -1). Three materials were characterized, two graphite/epoxies and a graphite/S-glass/epoxy. Properties were obtained by testing thin rings 10.16 cm (4 in.) in diameter, 2.54 cm (1 in.) wide, and six to eight plies thick under internal pressure. Unidirectional 0 degree, 90 degree, and 10 degree off-axis rings were tested to obtain longitudinal, transverse, and in-plane shear properties. In the dynamic tests internal pressure was applied explosively through a liquid and the pressure was measured with a calibrated steel ring. Strains in the calibration and specimen rings were recorded with a digital processing oscilloscope. The data were processed and the equation of motion solved numerically by the mini-computer attached to the oscilloscope. Results were obtained and plotted in the form of dynamic stress-strain curves. Longitudinal properties which are governed by the fibers do not vary much with strain rate with only a moderate (up to 20 percent) increase in modulus. Transverse modulus and strength increase sharply with strain rate reaching values up to three times the static values. The in-plane shear modulus and shear strength increase noticeably with strain rate by up to approximately 65 percent. In all cases ultimate strains do not vary significantly with strain rates.

  16. Microstructural Characterization of a High-Strength Aluminum Alloy Subjected to High Strain-Rate Impact

    NASA Astrophysics Data System (ADS)

    Lee, W. M.; Zikry, M. A.

    2011-05-01

    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.

  17. Electrochemical corrosion rate probes for high temperature energy applications

    SciTech Connect

    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

    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.

  18. Highly Divergent Strains of Porcine Reproductive and Respiratory Syndrome Virus Incorporate Multiple Isoforms of Nonstructural Protein 2 into Virions

    PubMed Central

    Kappes, Matthew A.; Miller, Cathy L.

    2013-01-01

    Viral structural proteins form the critical intermediary between viral infection cycles within and between hosts, function to initiate entry, participate in immediate early viral replication steps, and are major targets for the host adaptive immune response. We report the identification of nonstructural protein 2 (nsp2) as a novel structural component of the porcine reproductive and respiratory syndrome virus (PRRSV) particle. A set of custom ?-nsp2 antibodies targeting conserved epitopes within four distinct regions of nsp2 (the PLP2 protease domain [OTU], the hypervariable domain [HV], the putative transmembrane domain [TM], and the C-terminal region [C]) were obtained commercially and validated in PRRSV-infected cells. Highly purified cell-free virions of several PRRSV strains were isolated through multiple rounds of differential density gradient centrifugation and analyzed by immunoelectron microscopy (IEM) and Western blot assays using the ?-nsp2 antibodies. Purified viral preparations were found to contain pleomorphic, predominantly spherical virions of uniform size (57.9 nm ± 8.1 nm diameter; n = 50), consistent with the expected size of PRRSV particles. Analysis by IEM indicated the presence of nsp2 associated with the viral particle of diverse strains of PRRSV. Western blot analysis confirmed the presence of nsp2 in purified viral samples and revealed that multiple nsp2 isoforms were associated with the virion. Finally, a recombinant PRRSV genome containing a myc-tagged nsp2 was used to generate purified virus, and these particles were also shown to harbor myc-tagged nsp2 isoforms. Together, these data identify nsp2 as a virion-associated structural PRRSV protein and reveal that nsp2 exists in or on viral particles as multiple isoforms. PMID:24089566

  19. Data compression techniques applied to high resolution high frame rate video technology

    NASA Technical Reports Server (NTRS)

    Hartz, William G.; Alexovich, Robert E.; Neustadter, Marc S.

    1989-01-01

    An investigation is presented of video data compression applied to microgravity space experiments using High Resolution High Frame Rate Video Technology (HHVT). An extensive survey of methods of video data compression, described in the open literature, was conducted. The survey examines compression methods employing digital computing. The results of the survey are presented. They include a description of each method and assessment of image degradation and video data parameters. An assessment is made of present and near term future technology for implementation of video data compression in high speed imaging system. Results of the assessment are discussed and summarized. The results of a study of a baseline HHVT video system, and approaches for implementation of video data compression, are presented. Case studies of three microgravity experiments are presented and specific compression techniques and implementations are recommended.

  20. High-Rate Punctured Convolutional Codes for Soft Decision Viterbi Decoding

    Microsoft Academic Search

    Y. Yasuda; K. Kashiki; Y. Hirata

    1984-01-01

    The high-rate punctured codes of rates 2\\/3 through 13\\/14 are derived from rate 1\\/2 specific convolutional codes with maximal free distance. Coding gains of derived codes are compared based on their bit error rate performances under soft decision Viterbi decoding.

  1. High Strain Rate Tensile Testing of DOP-26 Iridium

    SciTech Connect

    Schneibel, Joachim H [ORNL; Carmichael Jr, Cecil Albert [ORNL; George, Easo P [ORNL

    2007-11-01

    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.

  2. High strain-rate testing of parachute materials

    SciTech Connect

    Gwinn, K.W.; Totten, J.J.; Waye, D.E.

    1994-12-31

    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 sec{sup {minus}1} 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.

  3. A simulator of PCM stream with high data rate

    NASA Astrophysics Data System (ADS)

    Li, Xian L.; Zhang, Qishan; Yang, Hui

    A simulator of PCM data stream with the data rate up to 30 Mbps was designed. The simulator differs from the traditional ones in the design principle and can bring all potentialities into play. It is more powerful in function, easier to test, and more accurate in control.

  4. A Versatile High Speed Bit Error Rate Testing Scheme

    Microsoft Academic Search

    Yongquan Fan; Zeljko Zilic; Man Wah Chiang

    2004-01-01

    The quality of a digital communication interface can be characterized by its bit error rate (BER) performance. To ensure the quality of the manufactured interface, it is critical to quickly and precisely test its BER behavior. Traditionally, BER is evaluated using software simulations, which are very time-consuming. Though there are some standalone BER test products, they are expensive and none

  5. Simple, fast rise time, high repetition rate Pockels cell driver

    NASA Astrophysics Data System (ADS)

    Plourde, B.; Mack, M. E.; Verro, E.

    1980-04-01

    A thyratron Pockels cell driver capable of optically switching Pockels cells of up to 2.5 cm aperture in 6 ns at repetition rates of up to 1000 Hz is described. The circuit is based on a modified HY-2 thyratron.

  6. Simple, fast rise time, high repetition rate Pockels cell driver

    Microsoft Academic Search

    B. Plourde; M. E. Mack; E. Verro

    1980-01-01

    A thyratron Pockels cell driver capable of optically switching Pockels cells of up to 2.5 cm aperture in 6 ns at repetition rates of up to 1000 Hz is described. The circuit is based on a modified HY-2 thyratron.

  7. Laser cutting of aluminum with high-repetition-rate pulses

    Microsoft Academic Search

    Warren Maher

    1997-01-01

    The precision laser machining (PLM) consortium is developing advanced lasers for machining and investigating process improvements. Recent cutting experiments completed by Boeing at TRW on aluminum alloys included pulse repetition rates up to 220 kHz from a diode-pumped neodymium YAG laser. Overall, cutting speed increased with power over the range tested and results were of a quality and speed to

  8. The American High School Graduation Rate: Trends and Levels. NBER Working Paper No. 13670

    ERIC Educational Resources Information Center

    Heckman, James J.; LaFontaine, Paul A.

    2007-01-01

    This paper uses multiple data sources and a unified methodology to estimate the trends and levels of the U.S. high school graduation rate. Correcting for important biases that plague previous calculations, we establish that (1) the true high school graduation rate is substantially lower than the official rate issued by the National Center for…

  9. Faking giants: the evolution of high prey clearance rates in jellyfishes.

    PubMed

    Acuña, José Luis; López-Urrutia, Ángel; Colin, Sean

    2011-09-16

    Jellyfishes have functionally replaced several overexploited commercial stocks of planktivorous fishes. This is paradoxical, because they use a primitive prey capture mechanism requiring direct contact with the prey, whereas fishes use more efficient visual detection. We have compiled published data to show that, in spite of their primitive life-style, jellyfishes exhibit similar instantaneous prey clearance and respiration rates as their fish competitors and similar potential for growth and reproduction. To achieve this production, they have evolved large, water-laden bodies that increase prey contact rates. Although larger bodies are less efficient for swimming, optimization analysis reveals that large collectors are advantageous if they move through the water sufficiently slowly. PMID:21921197

  10. High-rate systematic recursive convolutional encoders: minimal trellis and code search

    NASA Astrophysics Data System (ADS)

    Benchimol, Isaac; Pimentel, Cecilio; Souza, Richard Demo; Uchôa-Filho, Bartolomeu F.

    2012-12-01

    We consider high-rate systematic recursive convolutional encoders to be adopted as constituent encoders in turbo schemes. Douillard and Berrou showed that, despite its complexity, the construction of high-rate turbo codes by means of high-rate constituent encoders is advantageous over the construction based on puncturing rate-1/2 constituent encoders. To reduce the decoding complexity of high-rate codes, we introduce the construction of the minimal trellis for a systematic recursive convolutional encoding matrix. A code search is conducted and examples are provided which indicate that a more finely grained decoding complexity-error performance trade-off is obtained.

  11. High strength semi-active energy absorbers using shear- and mixedmode operation at high shear rates

    NASA Astrophysics Data System (ADS)

    Becnel, Andrew C.

    This body of research expands the design space of semi-active energy absorbers for shock isolation and crash safety by investigating and characterizing magnetorheological fluids (MRFs) at high shear rates ( > 25,000 1/s) under shear and mixed-mode operation. Magnetorheological energy absorbers (MREAs) work well as adaptive isolators due to their ability to quickly and controllably adjust to changes in system mass or impact speed while providing fail-safe operation. However, typical linear stroking MREAs using pressure-driven flows have been shown to exhibit reduced controllability as impact speed (shear rate) increases. The objective of this work is to develop MREAs that improve controllability at high shear rates by using pure shear and mixed shear-squeeze modes of operation, and to present the fundamental theory and models of MR fluids under these conditions. A proof of concept instrument verified that the MR effect persists in shear mode devices at shear rates corresponding to low speed impacts. This instrument, a concentric cylinder Searle cell magnetorheometer, was then used to characterize three commercially available MRFs across a wide range of shear rates, applied magnetic fields, and temperatures. Characterization results are presented both as flow curves according to established practice, and as an alternate nondimensionalized analysis based on Mason number. The Mason number plots show that, with appropriate correction coefficients for operating temperature, the varied flow curve data can be collapsed to a single master curve. This work represents the first shear mode characterization of MRFs at shear rates over 10 times greater than available with commercial rheometers, as well as the first validation of Mason number analysis to high shear rate flows in MRFs. Using the results from the magnetorheometer, a full scale rotary vane MREA was developed as part of the Lightweight Magnetorheological Energy Absorber System (LMEAS) for an SH-60 Seahawk helicopter crew seat. Characterization tests were carried out on the LMEAS using a 40 vol% MRF used in the previous magnetorheometer tests. These were analyzed using both flow curves and apparent viscosity vs. Mason number diagrams. The nondimensionalized Mason number analysis resulted in data for all conditions of temperature, fluid composition, and shear rate, to collapse onto a single characteristic or master curve. Significantly, the temperature corrected Mason number results from both the bench top magnetorheometer and full scale rotary vane MREA collapse to the same master curve. This enhances the ability of designers of MRFs and MREAs to safely and effectively apply characterization data collected in low shear rate, controlled temperature environments to operational environments that may be completely different. Finally, the Searle cell magnetorheometer was modified with an enforced eccentricity to work in both squeeze and shear modes simultaneously to achieve so called squeeze strengthening of the working MRF, thereby increasing the apparent yield stress and the specific energy absorption. By squeezing the active MR fluid, particles undergo compression-assisted aggregation into stronger, more robust columns which resist shear better than single chains. A hybrid model describing the squeeze strengthening behavior is developed, and recommendations are made for using squeeze strengthening to improve practical MREA devices.

  12. Transmission rates of the bacterial endosymbiont, Neorickettsia risticii, during the asexual reproduction phase of its digenean host, Plagiorchis elegans, within naturally infected lymnaeid snails

    PubMed Central

    2013-01-01

    Background Neorickettsia are obligate intracellular bacterial endosymbionts of digenean parasites present in all lifestages of digeneans. Quantitative information on the transmission of neorickettsial endosymbionts throughout the complex life cycles of digeneans is lacking. This study quantified the transmission of Neorickettsia during the asexual reproductive phase of a digenean parasite, Plagiorchis elegans, developing within naturally parasitized lymnaeid pond snails. Methods Lymnaea stagnalis snails were collected from 3 ponds in Nelson County, North Dakota and screened for the presence of digenean cercariae. Cercariae were identified to species by PCR and sequencing of the 28S rRNA gene. Neorickettsia infections were initially detected using nested PCR and sequencing of a partial 16S rRNA gene of pooled cercariae shed from each parasitized snail. Fifty to 100 single cercariae or sporocysts were isolated from each of six parasitized snails and tested for the presence of Neorickettsia using nested PCR to estimate the efficiency at which Neorickettsia were transmitted to cercariae during asexual development of the digenean. Results A total of 616?L. stagnalis were collected and 240 (39%) shed digenean cercariae. Of these, 18 (8%) were Neorickettsia-positive. Six Neorickettsia infections were selected to determine the transmission efficiency of Neorickettsia from mother to daughter sporocyst and from daughter sporocyst to cercaria. The prevalence of neorickettsiae in cercariae varied from 11 to 91%. The prevalence of neorickettsiae in sporocysts from one snail was 100%. Conclusion Prevalence of Neorickettsia infection in cercariae of Plagiorchis elegans was variable and never reached 100%. Reasons for this are speculative, however, the low prevalence of Neorickettsia observed in some of our samples (11 to 52%) differs from the high prevalence of other, related bacterial endosymbionts, e.g. Wolbachia in Wolbachia-dependent filariid nematodes, where the prevalence among progeny is universally 100%. This suggests that, unlike the Wolbachia-filaria relationship, the Neorickettsia-digenean relationship is not obligatory mutualism. Our study represents the first quantitative estimate of the Neorickettsia transmission through the asexual phase of the digenean life cycle. PMID:24383453

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

    PubMed Central

    2011-01-01

    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. PMID:21651780

  14. Noncancer risk assessment: reproductive toxicology.

    PubMed

    Schwetz, B A

    1996-01-01

    In summary, the concerns that environmental and other agents are causing adverse effects on reproductive function in humans are real, although the risk is not necessarily well characterized. The range of concerns for the types of effect that agents might have on reproduction span the full range of reproductive events. There is a fairly high background of reproductive disease in humans which decreases the sensitivity for identifying agents that have a subtle, but adverse, effect on reproductive performance of humans. Because our animal studies identify a large number of agents that cause some adverse reproductive effect at the dose levels tested, the concern is raised about the oversensitivity of animal models for predicting adverse effects in humans. Until we better understand the biology underlying the reproductive process of humans and animals, it will be difficult to make animal studies more specific in their predictiveness. Continued research to better understand the biology of reproduction in humans and animals should help to identify the types of data generated in animals that are most predictive of an adverse effect in humans. PMID:8744590

  15. Reproductive strategy, sexual development and attraction to facial characteristics

    PubMed Central

    Cornwell, R. Elisabeth; Law Smith, Miriam J; Boothroyd, Lynda G; Moore, Fhionna R; Davis, Hasker P; Stirrat, Michael; Tiddeman, Bernard; Perrett, David I

    2006-01-01

    Sexual reproduction strategies vary both between and within species in the level of investment in offspring. Life-history theories suggest that the rate of sexual maturation is critically linked to reproductive strategy, with high investment being associated with few offspring and delayed maturation. For humans, age of puberty and age of first sex are two developmental milestones that have been associated with reproductive strategies. Stress during early development can retard or accelerate sexual maturation and reproduction. Early age of menarche is associated with absence of younger siblings, absence of a father figure during early life and increased weight. Father absence during early life is also associated with early marriage, pregnancy and divorce. Choice of partner characteristics is critical to successful implementation of sexual strategies. It has been suggested that sexually dimorphic traits (including those evident in the face) signal high-quality immune function and reproductive status. Masculinity in males has also been associated with low investment in mate and offspring. Thus, women's reproductive strategy should be matched to the probability of male investment, hence to male masculinity. Our review leads us to predict associations between the rate of sexual maturation and adult preferences for facial characteristics (enhanced sexual dimorphism and attractiveness). We find for men, engaging in sex at an early age is related to an increased preference for feminized female faces. Similarly, for women, the earlier the age of first sex the greater the preference for masculinity in opposite-sex faces. When we controlled sexual dimorphism in male faces, the speed of sexual development in women was not associated with differences in preference for male facial attractiveness. These developmental influences on partner choice were not mediated by self-rated attractiveness or parental relationships. We conclude that individuals assort in preferences based on the rapidity of their sexual development. Fast developing individuals prefer opposite-sex partners with an increased level of sexually dimorphic facial characteristics. PMID:17118929

  16. Differential immunity in pigs with high and low responses to porcine reproductive and respiratory syndrome virus (PRRSV) infection

    Technology Transfer Automated Retrieval System (TEKTRAN)

    One hundred Hampshire by Duroc crossbred pigs (HD) and 100 NE Index line pigs (I) were infected with porcine reproductive and respiratory syndrome virus (PRRSV) and evaluated for resistance/susceptibility. Controls (100/line) were uninfected littermates to infected pigs. Viremia (V), weight change (...

  17. High School Attrition Rates Across Texas Education Service Center Regions

    ERIC Educational Resources Information Center

    Johnson, Roy

    2008-01-01

    The examination of historical trend data on the number and percent of students lost from public school enrollment prior to graduation from high school is becoming increasingly important since distinct trends are emerging on a regional basis. This study examines regional trends in Texas on the number and percent of students lost from public high…

  18. A new high rate, fast charge, sealed, lead acid battery

    Microsoft Academic Search

    T. Juergens; R. F. Nelson; M. A. Ruderman

    1994-01-01

    A new approach to the design of lead acid batteries has been developed based on the use of very thin lead foil current collectors and very high current carrying capacity. The basic cell construction and the performance characteristics for the new cell are described. Spiral wrap cells based on this electrode concept exhibit extremely high power output with excellent capacity

  19. High Evolutionary Rates in Nuclear Genes of Squamates

    Microsoft Academic Search

    Sandrine Hughes; Dominique Mouchiroud

    2001-01-01

    .   We compared nonsynonymous substitution rates (Ka) of nuclear coding genes between four major groups of living sauropsids\\u000a (reptiles): birds, squamates, crocodiles, and turtles. Since only 9 orthologous genes are known in all the four taxonomic\\u000a groups, we searched for orthologous genes known in chicken and at least one of any representative of poikilotherm sauropsids.\\u000a Thus, we analyzed three additional

  20. An evaluation of chromium deposited by high rate sputtering

    Microsoft Academic Search

    Russell H. Jones

    1976-01-01

    The structure, chemical composition and hardness of 0.005 cm (0.002 in.) thick sputter-deposited chromium coatings produced at deposition rates of 2 to 5 nm\\/s (0.3 to 0.7 mils\\/h), substrate temperatures of 20‡C and 60‡C, and substrate potentials of -30 V (floating) and -50 V, with respect to ground, in a dc-triode sputtering system were examined. The chromium coatings were examined

  1. HIGH DATA RATE TRANSMISSION OVER WIRELESS LOCAL AREA NETWORKS

    Microsoft Academic Search

    Katelijn Vleugels

    This paper discusses new trends in emerging WLAN systems and applications, and their implications on the architecture and circuit implementation of next-generation 802.11 communication ICs. Higher data rates, longer transmission ranges, lower cost and higher system capacity are putting new constraints on the baseband and RF circuits constituting future 802.11 transceivers. Several new circuit techniques drawn from recent publications [2]-[6

  2. Modeling Large-Strain, High-Rate Deformation in Metals

    Microsoft Academic Search

    D R Lesuer; G J Kay; M M LeBlanc

    2001-01-01

    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.

  3. Video-rate high-resolution parallel optical coherence tomography

    Microsoft Academic Search

    Markus Laubscher; Mathieu G. Ducros; Boris Karamata; Theo Lasser

    2002-01-01

    Parallel optical coherence tomography is demonstrated at video rate using a 58 by 58 smart-pixel detector array. A sample volume of 210x210x80 micrometers3 (corresponding to 58x58x58 voxels) was imaged at 25 Hz. A femtosecond mode-locked Ti:Sapphire laser in combination with a free space Michelson interferometer was employed to achieve a 3 micrometer longitudinal resolution. We used 20x microscope objectives in

  4. Study of microvoids in high-rate a-Si:H using positron annihilation

    SciTech Connect

    Zou, X.; Webb, D.P.; Lin, S.H.; Lam, Y.W.; Chan, Y.C.; Hu, Y.F.; Beling, C.D.; Fung, S.

    1997-07-01

    In this paper, the authors have carried out the positron annihilation measurement on high-rate and low-rate a-Si:H thin films deposited by PECVD. By means of the slow positron beam Doppler-broadening technique, the depth profiles of microvoids in a-Si:H have been determined. They have also studied the vacancy-type defect in the surface region in high-rate grown a-Si:H, making comparison between high-rate and low-rate a-Si:H. By plotting S and W parameters in the (S, W) plane, they have shown that the vacancies in all of the high-rate and low-rate deposited intrinsic samples, and in differently doped low-rate samples are of the same nature.

  5. How topography induces reproductive asynchrony and alters gypsy moth invasion dynamics.

    PubMed

    Walter, Jonathan A; Meixler, Marcia S; Mueller, Thomas; Fagan, William F; Tobin, Patrick C; Haynes, Kyle J

    2014-07-17

    Reproductive asynchrony, a temporal mismatch in reproductive maturation between an individual and potential mates, may contribute to mate-finding failure and Allee effects that influence the establishment and spread of invasive species. Variation in elevation is likely to promote variability in maturation times for species with temperature-dependent development, but it is not known how strongly this influences reproductive asynchrony or the population growth of invasive species. We examined whether spatial variation in reproductive asynchrony, due to differences in elevation and local heterogeneity in elevation (hilliness), can explain spatial heterogeneity in the population growth rate of the gypsy moth, Lymantria dispar (L.), along its invasion front in Virginia and West Virginia, USA. We used a spatially explicit model of the effects of reproductive asynchrony on mating success to develop predictions of the influences of elevation and elevational heterogeneity on local population growth rates. Population growth rates declined with increased elevation and more modestly with increased elevational heterogeneity. As in earlier work, we found a positive relationship between the population growth rate and the number of introduced egg masses, indicating a demographic Allee effect. At high elevations and high heterogeneity in elevation, the population growth rate was lowest and the density at which the population tended to replace itself (i.e. the Allee threshold) was highest. An analysis of 22 years of field data also showed decreases in population growth rates with elevation and heterogeneity in elevation that were largely consistent with the model predictions. These results highlight how topographic characteristics can affect reproductive asynchrony and influence mate-finding Allee effects in an invading non-native insect population. Given the dependence of developmental rates on temperature in poikilotherms, topographic effects on reproductive success could potentially be important to the population dynamics of many organisms. PMID:25039257

  6. A tensile impact apparatus for characterization of fibrous composites at high strain rates

    Microsoft Academic Search

    G. H. Majzoobi; F. Fereshteh Saniee; M. Bahrami

    2005-01-01

    A high rate tensile testing apparatus called “flying wedge” for testing fibrous composites at strain rates up to 103s?1 has been described. R2000 glass\\/epoxy composite has been tested at a very low strain rate of 10?3s?1 using the universal Instron tensile testing machine, and at high strain rates up to nearly 850s?1 using flying wedge. The results show significant increase

  7. Unisexual reproduction reverses Muller's ratchet.

    PubMed

    Roach, Kevin C; Heitman, Joseph

    2014-11-01

    Cryptococcus neoformans is a pathogenic basidiomycetous fungus that engages in outcrossing, inbreeding, and selfing forms of unisexual reproduction as well as canonical sexual reproduction between opposite mating types. Long thought to be clonal, >99% of sampled environmental and clinical isolates of C. neoformans are MAT?, limiting the frequency of opposite mating-type sexual reproduction. Sexual reproduction allows eukaryotic organisms to exchange genetic information and shuffle their genomes to avoid the irreversible accumulation of deleterious changes that occur in asexual populations, known as Muller's ratchet. We tested whether unisexual reproduction, which dispenses with the requirement for an opposite mating-type partner, is able to purge the genome of deleterious mutations. We report that the unisexual cycle can restore mutant strains of C. neoformans to wild-type genotype and phenotype, including prototrophy and growth rate. Furthermore, the unisexual cycle allows attenuated strains to purge deleterious mutations and produce progeny that are returned to wild-type virulence. Our results show that unisexual populations of C. neoformans are able to avoid Muller's ratchet and loss of fitness through a unisexual reproduction cycle involving ?-? cell fusion, nuclear fusion, and meiosis. Similar types of unisexual reproduction may operate in other pathogenic and saprobic eukaryotic taxa. PMID:25217049

  8. Genome-wide analysis of alternative reproductive phenotypes in honeybee workers.

    PubMed

    Cardoen, Dries; Wenseleers, Tom; Ernst, Ulrich R; Danneels, Ellen L; Laget, Dries; DE Graaf, Dirk C; Schoofs, Liliane; Verleyen, Peter

    2011-10-01

    A defining feature of social insects is the reproductive division of labour, in which workers usually forego all reproduction to help their mother queen to reproduce. However, little is known about the molecular basis of this spectacular form of altruism. Here, we compared gene expression patterns between nonreproductive, altruistic workers and reproductive, non-altruistic workers in queenless honeybee colonies using a whole-genome microarray analysis. Our results demonstrate massive differences in gene expression patterns between these two sets of workers, with a total of 1292 genes being differentially expressed. In nonreproductive workers, genes associated with energy metabolism and respiration, flight and foraging behaviour, detection of visible light, flight and heart muscle contraction and synaptic transmission were overexpressed relative to reproductive workers. This implies they probably had a higher whole-body energy metabolism and activity rate and were most likely actively foraging, whereas same-aged reproductive workers were not. This pattern is predicted from evolutionary theory, given that reproductive workers should be less willing to compromise their reproductive futures by carrying out high-risk tasks such as foraging or other energetically expensive tasks. By contrast, reproductive workers mainly overexpressed oogenesis-related genes compared to nonreproductive ones. With respect to key switches for ovary activation, several genes involved in steroid biosynthesis were upregulated in reproductive workers, as well as genes known to respond to queen and brood pheromones, genes involved in TOR and insulin signalling pathways and genes located within quantitative trait loci associated with reproductive capacity in honeybees. Overall, our results provide unique insight into the molecular mechanisms underlying alternative reproductive phenotypes in honeybee workers. PMID:21902748

  9. High rate lithium/thionyl chloride bipolar battery development

    NASA Astrophysics Data System (ADS)

    Russell, P. G.; Goebel, F.

    The lithium/thionyl chloride ( {Li}/{SOCl2}) electrochemistry is capable of providing high power and high specific power, especially under pulse discharge conditions, when cells containing thin components are arranged in a bipolar configuration. This paper describes recent work concerned with bipolar cell design, cathode evaluation, component manufacturing methods, and the assembly and testing of bipolar modules containing up to 150 cells for Sonobuoy application.

  10. Power locking of high-repetition-rate chirped pulse amplifiers

    Microsoft Academic Search

    He Wang; Chengquan Li; Jason Tackett; Hiroki Mashiko; Christopher M. Nakamura; Eric Moon; Zenghu Chang

    2007-01-01

    We report a feedback control scheme that minimizes the energy fluctuations of high power femtosecond pulses from a 1 kHz laser\\u000a amplifier. The pulse energy variation in the frequency bandwidth 0–500 Hz was obtained by a photodiode and a low pass filter.\\u000a The measured signal was fed to a proportional-integral-derivative (differential) (PID) controller that changed the amplitude\\u000a of the high voltage pulses

  11. Reproductive Acclimation to Increased Water Temperature in a Tropical Reef Fish

    PubMed Central

    Donelson, Jennifer M.; McCormick, Mark I.; Booth, David J.; Munday, Philip L.

    2014-01-01

    Understanding the capacity of organisms to cope with projected global warming through acclimation and adaptation is critical to predicting their likely future persistence. While recent research has shown that developmental acclimation of metabolic attributes to ocean warming is possible, our understanding of the plasticity of key fitness-associated traits, such as reproductive performance, is lacking. We show that while the reproductive ability of a tropical reef fish is highly sensitive to increases in water temperature, reproductive capacity at +1.5°C above present-day was improved to match fish maintained at present-day temperatures when fish complete their development at the higher temperature. However, reproductive acclimation was not observed in fish reared at +3.0°C warmer than present-day, suggesting limitations to the acclimation possible within one generation. Surprisingly, the improvements seen in reproduction were not predicted by the oxygen- and capacity-limited thermal tolerance hypothesis. Specifically, pairs reared at +1.5°C, which showed the greatest capacity for reproductive acclimation, exhibited no acclimation of metabolic attributes. Conversely, pairs reared at +3.0°C, which exhibited acclimation in resting metabolic rate, demonstrated little capacity for reproductive acclimation. Our study suggests that understanding the acclimation capacity of reproductive performance will be critically important to predicting the impacts of climate change on biological systems. PMID:24823490

  12. Reproduction of radiologic images on plain paper.

    PubMed

    Ibbott, G S; Zhang, Y; Mohiuddin, M; Adams, E

    1998-01-01

    Skyrocketing health care costs and pressures from managed care have combined to promote cost-cutting strategies in radiology and radiation oncology departments. A study was conducted to evaluate the use of a high-resolution laser printer for printing plain-paper images as substitutes for both original and duplicate radiologic film images. A variety of radiologic images were used to evaluate the image reproduction capabilities of the printer in terms of linearity, detail, and contrast. In many cases, printed images had a quality comparable to that of the original images. Six computed tomographic (CT) scans and six radiation therapy simulator radiographs were compared with printed reproductions by each of seven board-certified radiation oncologists, who rated the reproductions as acceptable for documentation, acceptable for diagnostic purposes (CT scans only), or unacceptable. Ninety-five percent of printed CT images and 90% of printed simulation images were rated acceptable for documentation. The quality of printed images of radiation therapy port films was not quantitatively measured but was improved by adjusting image contrast and brightness and using various image enhancement techniques. The use of printed images is less expensive than that of processed film and eliminates the environmental, time, storage, and delivery problems associated with film. Technologic advances in imaging, networking, and printing have made possible the inexpensive duplication of medical images. PMID:9599396

  13. An evaluation of chromium deposited by high rate sputtering

    Microsoft Academic Search

    Russell H. Jones

    1976-01-01

    The structure, chemical composition and hardness of 0.005 cm (0.002 in.) thick sputter-deposited chromium coatings produced\\u000a at deposition rates of 2 to 5 nm\\/s (0.3 to 0.7 mils\\/h), substrate temperatures of 20‡C and 60‡C, and substrate potentials\\u000a of -30 V (floating) and -50 V, with respect to ground, in a dc-triode sputtering system were examined. The chromium coatings\\u000a were examined

  14. Methane conversion efficiency as a simple control parameter for an anaerobic digester at high loading rates.

    PubMed

    Charles, W; Carnaje, N P; Cord-Ruwisch, R

    2011-01-01

    The anaerobic digestion process is globally applied to the treatment of highly concentrated wastes such as industrial and rural effluents, and sewage sludge. However, it is known to be relatively unstable. When loaded with high concentrations of organic material, unwanted volatile fatty acids (VFA) are often produced rather than methane (CH4) gas which can lead to digester acidification and failure. This study investigated digester behaviour under high loading rates, testing the usefulness of stoichiometric methane conversion efficiency as a digester control parameter at high loading rates. Our results show that, in general, the CH4 production rate was proportional to the feed rate (loading rate). However, at very high loading rates, the CH4 production rate was not proportional to the increase in the feeding rate. Consequently, VFA accumulated and the H2 partial pressure increased. The proportionality of the loading rate and gas production rate is stoichiometrically expressed as the conversion efficiency. We found that conversion efficiency was a useful indicator as an early warning of digester imbalance. The digester remained stable at conversion efficiencies above 75%. Dropping below 70% signified the onset of digester failure. As loading rate and methane production data are readily available on-line in most anaerobic digestion plants, the conversion efficiency can be monitored on-line and used as an efficient control technique to maintain safe operation of anaerobic digesters at high loading rates. PMID:22097030

  15. High School Principals' Rating of Success in Implementation of 21st Century Skills

    ERIC Educational Resources Information Center

    Sam, Sonn

    2011-01-01

    The purpose of this quantitative study was to investigate how Rhode Island high school principals rate success in implementing 21st century skills in their schools. Secondly, this study investigated how high school principals rate the influence of implementing of 21st century skills in curriculum and instruction in their schools. The high…

  16. Transmitter diversity for OFDM systems and its impact on high-rate data wireless networks

    Microsoft Academic Search

    Ye Li; J. C. Chuang; N. R. Sollenberger

    1999-01-01

    Transmitter diversity and down-link beamforming can be used in high-rate data wireless networks with orthogonal frequency division multiplexing (OFDM) for capacity improvement. We compare the performance of delay, permutation and space-time coding transmitter diversity for high-rate packet data wireless networks using OFDM modulation. For these systems, relatively high block error rates, such as 10%, are acceptable assuming the use of

  17. Transmitter diversity for OFDM systems and its impacts on high-rate wireless networks

    Microsoft Academic Search

    Y. Li; J. Chuang; N. R. Sollenberger

    1999-01-01

    Transmitter diversity and down-link beamforming can be used in high-rate wireless networks with OFDM for capacity improvement. In this paper, we compare the performance of delay, permutation and space-time coding transmitter diversity for OFDM systems, and its impact on high-rate packet data wireless networks, where relatively high block error rates, such as, 10%, on the wireless links are acceptable using

  18. Analysis of the readout of a high rate MWPC

    NASA Astrophysics Data System (ADS)

    Camerini, P.; Grion, N.; Rui, R.; Sheffer, G.; Openshaw, R.

    1990-06-01

    An analytical method to reduce the raw data supplied by a high-speed multiwire proportional chamber (MWPC) is presented. The results obtained with the MWPC and the associated readout system, LeCroy PCOS III, when monitoring a high-intensity flux of positive pions delivered by the M11 channel at TRIUMF are discussed. The method allows the flux intensity, the beam envelope and the detector efficiency to be determined with little uncertainty (few %) at intense particle beams ( > 10 7 particles/s).

  19. Interactions for pollinator visitation and their consequences for reproduction in a plant community

    NASA Astrophysics Data System (ADS)

    Hegland, Stein Joar; Totland, Ørjan

    2012-08-01

    Competition and facilitation in species interactions attract much attention in ecology, but their relative importance has seldom been evaluated in a community context. We assessed competitive and facilitative interactions for pollinator visitation among co-flowering species in a plant community, investigated the subsequent consequences for plant reproduction, and investigated whether effects could be trait-based. We removed the flowers of two species attractive to pollinators, in two separate experiments and assessed the effects on pollinator visitation rates and components of reproductive success in 11 co-flowering focal herb species. Overall, most focal species appear not to interact with the removal species with respect to pollinator visitation and subsequent reproduction (neutral interactions). Three focal species in the community had significantly higher reproductive responses (fruit production and seed weight) in the presence of the attractive removal species (facilitative interactions), but species interaction effects were less pronounced in species' flower visitation rates. A community-wide meta-analysis demonstrated that the two experiments did not have a significant effect on either facilitation or competition, and that there was no overall correlation between effect sizes for visitation and reproduction. Based on species-specific responses, it seems likely that floral traits such as similar flower colors contribute to interspecific facilitation of pollinator visitation and, in particular, that high pollinator dependence for plant reproduction, and associated pollen limitation, may contribute to subsequent interaction effects on reproduction in the focal species.

  20. The Evolution of Senescence and Post-Reproductive Lifespan in Guppies (Poecilia reticulata)

    PubMed Central

    Reznick, David; Bryant, Michael; Holmes, Donna

    2006-01-01

    The study of post-reproductive lifespan has been of interest primarily with regard to the extended post-menopausal lifespan seen in humans. This unusual feature of human demography has been hypothesized to have evolved because of the “grandmother” effect, or the contributions that post-reproductive females make to the fitness of their children and grandchildren. While some correlative analyses of human populations support this hypothesis, few formal, experimental studies have addressed the evolution of post-reproductive lifespan. As part of an ongoing study of life history evolution in guppies, we compared lifespans of individual guppies derived from populations that differ in their extrinsic mortality rates. Some of these populations co-occur with predators that increase mortality rate, whereas other nearby populations above barrier waterfalls are relatively free from predation. Theory predicts that such differences in extrinsic mortality will select for differences in the age at maturity, allocation of resources to reproduction, and patterns of senescence, including reproductive declines. As part of our evaluation of these predictions, we quantified differences among populations in post-reproductive lifespan. We present here the first formal, comparative study of the evolution of post-reproductive lifespan as a component of the evolution of the entire life history. Guppies that evolved with predators and that experienced high extrinsic mortality mature at an earlier age but also have longer lifespans. We divided the lifespan into three non-overlapping components: birth to age at first reproduction, age at first reproduction to age at last reproduction (reproductive lifespan), and age at last reproduction to age at death (post-reproductive lifespan). Guppies from high-predation environments live longer because they have a longer reproductive lifespan, which is the component of the life history that can make a direct contribution to individual fitness. We found no differences among populations in post-reproductive lifespan, which is as predicted since there can be no contribution of this segment of the life history to an individual's fitness. Prior work on the evolution of post-reproductive lifespan has been dominated by speculation and correlative analyses. We show here that this component of the life history is accessible to formal study as part of experiments that quantify the different segments of an individual's life history. Populations of guppies subject to different mortality pressures from predation evolved differences in total lifespan, but not in post-reproductive lifespan. Rather than showing the direct effects of selection characterizing other life-history traits, post-reproductive lifespan in these fish appears to be a random add-on at the end of the life history. These findings support the hypothesis that differences in lifespan evolving in response to selection are confined to the reproductive lifespan, or those segments of the life history that make a direct contribution to fitness. We also show, for the first time, that fish can have reproductive senescence and extended post-reproductive lifespans despite the general observation that they are capable of producing new primary oocytes throughout their lives. PMID:16363919

  1. Laser balancing system for high material removal rates

    NASA Technical Reports Server (NTRS)

    Jones, M. G.; Georgalas, G.; Ortiz, A. L.

    1984-01-01

    A laser technique to remove material in excess of 10 mg/sec from a spinning rotor is described. This material removal rate is 20 times greater than previously reported for a surface speed of 30 m/sec. Material removal enhancement was achieved by steering a focused laser beam with moving optics to increase the time of laser energy interaction with a particular location on the circumferential surface of a spinning rotor. A neodymium:yttrium aluminum garnet (Nd:YAG) pulse laser was used in this work to evaluate material removal for carbon steel, 347 stainless steel, Inconal 718, and titanium 6-4. This technique is applicable to dynamic laser balancing.

  2. Waiving Away High School Graduation Rate Accountability? Policy Brief

    ERIC Educational Resources Information Center

    Alliance for Excellent Education, 2012

    2012-01-01

    In November 2011, eleven states submitted applications to the U.S. Department of Education (ED) for waivers from key provisions of the No Child Left Behind Act. Although the waiver process presents an opportunity to strengthen college and career readiness among the nation's high school students, this analysis by the Alliance for Excellent…

  3. Single photon detection for high bit rate quantum communication

    Microsoft Academic Search

    J. F. Dynes; Z. L. Yuan; A. W. Sharpe; A. R. Dixon; A. J. Shields

    2011-01-01

    Quantum communication, in particular, quantum key distribution (QKD) is moving ever closer to real world implementation. However, for successful QKD system deployment, the QKD system components must be robustly designed and feature highly reliable operation. In this paper we focus on one important aspect of any quantum communication system: the single photon detector. In particular our interest is centered upon

  4. Modern erosion rates in the High Himalayas of Nepal

    Microsoft Academic Search

    Emmanuel J. Gabet; Douglas W. Burbank; Beth Pratt-Sitaula; Jaakko Putkonen; Bodo Bookhagen

    2008-01-01

    Current theories regarding the connections and feedbacks between surface and tectonic processes are predicated on the assumption that higher rainfall causes more rapid erosion. To test this assumption in a tectonically active landscape, a network of 10 river monitoring stations was established in the High Himalayas of central Nepal across a steep rainfall gradient. Suspended sediment flux was calculated from

  5. Do Ubiquitous Laptop Initiatives Decrease the High School Dropout Rate?

    ERIC Educational Resources Information Center

    Basham, Misty Dawn

    2012-01-01

    In 2007, Mooresville Graded School District developed a strategic plan to infuse twenty-first-century learning skills into the schools by providing staff and students in grades four through twelve with a laptop computer. In late fall of 2007, Mooresville High School deployed laptops to all certified staff and to the entire student body in the…

  6. Power locking of high-repetition-rate chirped pulse amplifiers

    NASA Astrophysics Data System (ADS)

    Wang, He; Li, Chengquan; Tackett, Jason; Mashiko, Hiroki; Nakamura, Christopher M.; Moon, Eric; Chang, Zenghu

    2007-11-01

    We report a feedback control scheme that minimizes the energy fluctuations of high power femtosecond pulses from a 1 kHz laser amplifier. The pulse energy variation in the frequency bandwidth 0-500 Hz was obtained by a photodiode and a low pass filter. The measured signal was fed to a proportional-integral-derivative (differential) (PID) controller that changed the amplitude of the high voltage pulses applied to a Pockels cell. The variation of average power was reduced from 1.33% RMS to 0.28% RMS, which improved the carrier-envelope phase stability from 500 mrad to 200 mrad as measured by two f-to-2f interferometers. The long term stability of the laser was kept to approximately 0.5% RMS.

  7. High-repetition-rate solid state laser for space communications

    Microsoft Academic Search

    Christian Larat; Muriel Schwarz; Jean-Paul Pocholle; Gilles Feugnet; Michel R. Papuchon

    1995-01-01

    The CNES (Centre National d'Etudes Spatiales, French space agency) established the laser system characteristics for Mars-Earth spatial communications using the Pulse Position Modulation technique. Today, diode-pumped solid-state lasers are under intense research and development. Indeed, in comparison with flash-lamp pumped laser, they offer significant advantages in terms of efficiency, compactness, lifetime and high beam quality. We have demonstrated that gain-switch

  8. High Count Rate Neutron Spectrometry With Liquid Scintillation Detectors

    Microsoft Academic Search

    Daniele Marocco; Francesco Belli; Basilio Esposito; Marco Riva; Luca Giacomelli; Marcel Reginatto; Kai Tittelmeier; Andreas Zimbal

    2009-01-01

    Liquid scintillation detectors are widely used in nuclear\\/high-energy physics and nuclear fusion for spectral measurements in mixed radiation fields due to their compactness, fast response and neutron\\/gamma discrimination capabilities. The use of response functions evaluated for the specific system and of appropriate methods of data analysis allows such systems to be used as broadband spectrometers for photons and neutrons. System

  9. An empirical test of evolutionary theories for reproductive senescence and reproductive effort in the garter snake Thamnophis elegans.

    PubMed

    Sparkman, Amanda M; Arnold, Stevan J; Bronikowski, Anne M

    2007-04-01

    Evolutionary theory predicts that differential reproductive effort and rate of reproductive senescence will evolve under different rates of external mortality. We examine the evolutionary divergence of age-specific reproduction in two life-history ecotypes of the western terrestrial garter snake, Thamnophis elegans. We test for the signature of reproductive senescence (decreasing fecundity with age) and increasing reproductive effort with age (increasing reproductive productivity per gram female) in replicate populations of two life-history ecotypes: snakes that grow fast, mature young and have shorter lifespans, and snakes that grow slow, mature late and have long lives. The difference between life-history ecotypes is due to genetic divergence in growth rate. We find (i) reproductive success (live litter mass) increases with age in both ecotypes, but does so more rapidly in the fast-growth ecotype, (ii) reproductive failure increases with age in both ecotypes, but the proportion of reproductive failure to total reproductive output remains invariant, and (iii) reproductive effort remains constant in fast-growth individuals with age, but declines in slow-growth individuals. This illustration of increasing fecundity with age, even at the latest ages, deviates from standard expectations for reproductive senescence, as does the lack of increases in reproductive effort. We discuss our findings in light of recent theories regarding the phenomenon of increased reproduction throughout life in organisms with indeterminate growth and its potential to offset theoretical expectations for the ubiquity of senescence. PMID:17251099

  10. An empirical test of evolutionary theories for reproductive senescence and reproductive effort in the garter snake Thamnophis elegans

    PubMed Central

    Sparkman, Amanda M; Arnold, Stevan J; Bronikowski, Anne M

    2007-01-01

    Evolutionary theory predicts that differential reproductive effort and rate of reproductive senescence will evolve under different rates of external mortality. We examine the evolutionary divergence of age-specific reproduction in two life-history ecotypes of the western terrestrial garter snake, Thamnophis elegans. We test for the signature of reproductive senescence (decreasing fecundity with age) and increasing reproductive effort with age (increasing reproductive productivity per gram female) in replicate populations of two life-history ecotypes: snakes that grow fast, mature young and have shorter lifespans, and snakes that grow slow, mature late and have long lives. The difference between life-history ecotypes is due to genetic divergence in growth rate. We find (i) reproductive success (live litter mass) increases with age in both ecotypes, but does so more rapidly in the fast-growth ecotype, (ii) reproductive failure increases with age in both ecotypes, but the proportion of reproductive failure to total reproductive output remains invariant, and (iii) reproductive effort remains constant in fast-growth individuals with age, but declines in slow-growth individuals. This illustration of increasing fecundity with age, even at the latest ages, deviates from standard expectations for reproductive senescence, as does the lack of increases in reproductive effort. We discuss our findings in light of recent theories regarding the phenomenon of increased reproduction throughout life in organisms with indeterminate growth and its potential to offset theoretical expectations for the ubiquity of senescence. PMID:17251099

  11. Living slow and dying young? Life-history strategy and age-specific survival rates in a precocial small mammal

    Microsoft Academic Search

    CORNELIA KRAUS; DAVID L. THOMSON; JOACHIM KÜNKELE; FRITZ TRILLMICH

    2005-01-01

    1. Mammalian life histories can be ordered along a slowfast continuum from slow-developing, long-lived species with low reproductive rates at one end to rapidly developing, short-lived species with high reproductive rates at the other. Body size and mortality rate are strong correlates of the slowfast axis, whereby juvenile and adult mortality rates correlate positively but are linked to certain life-history

  12. High Rate Deposition of High Quality ZnO:Al by Filtered Cathodic Arc

    SciTech Connect

    Mendelsberg, Rueben J.; Lim, S.H.N.; Milliron, D.J.; Anders, Andre

    2010-11-18

    High quality ZnO:Al (AZO) thin films were prepared on glass substrates by direct current filtered cathodic arc deposition. Substrate temperature was varied from room temperature to 425oC, and samples were grown with and without the assistance of low power oxygen plasma (75W). For each growth condition, at least 3 samples were grown to give a statistical look at the effect of the growth environment on the film properties and to explore the reproducibility of the technique. Growth rate was in the 100-400 nm/min range but was apparently random and could not be easily traced to the growth conditions explored. For optimized growth conditions, 300-600 nm AZO films had resistivities of 3-6 x 10-4 ?Omega cm, carrier concentrations in the range of 2-4 x 1020 cm3, Hall mobility as high as 55 cm2/Vs, and optical transmittance greater than 90percent. These films are also highly oriented with the c-axis perpendicular to the substrate and a surface roughness of 2-4 nm.

  13. Signal simulator model A-111. [signal source for Doppler tracking high data rate receivers

    NASA Technical Reports Server (NTRS)

    Flattau, T.; Mellars, J.

    1974-01-01

    A signal simulator designed to function as a signal source for Doppler tracking high data rate receivers is described. The simulator produces modulated signals whose carrier frequency can be varied between 200 and 900 MHz at rates greater than 20 MHz/sec. The modulation is phase shift keying with data rate up to 300 megabits per second.

  14. Preliminary Findings on Quantitative Measures for Distinguishing Highly Rated Information-Centric Web Pages

    Microsoft Academic Search

    Melody Y. Ivory; Rashmi R. Sinha; Marti A. Hearst

    We present preliminary findings of a quantitative analysis of several attributes of Web page layout and composition and their relation to usability. We compared Web sites that have been favorably rated by experts with those that have not been rated, and found that 6 out of 12 measured attributes were significantly associated with highly rated sites. We also found 2

  15. Heart Rates of High School Physical Education Students during Team Sports, Individual Sports, and Fitness Activities

    ERIC Educational Resources Information Center

    Laurson, Kelly R.; Brown, Dale D.; Cullen, Robert W.; Dennis, Karen K.

    2008-01-01

    This study examined how activity type influenced heart rates and time spent in target heart rate zones of high school students participating in physical education classes. Significantly higher average heart rates existed for fitness (142 plus or minus 24 beats per minute [bpm]) compared to team (118 plus or minus 24 bpm) or individual (114 plus or…

  16. DEVELOPMENT OF A HIGH RATE HIGH RESOLUTION DETECTOR FOR EXAFS EXPERIMENTS.

    SciTech Connect

    DE GERONIMO,G.; O CONNOR,P.; BEUTTENMULLER,R.H.; LI,Z.; KUCZEWSKI,A.J.; SIDDONS,D.P.

    2002-11-10

    A new detector for EXAFS experiments is being developed. It is based on a multi-element Si sensor and dedicated readout ASICs. The sensor is composed of 384 pixels, each having 1 mm{sup 2} area, arranged in four quadrants of 12 x 8 elements, and wire-bonded to 32-channel front-end ASICs. Each channel implements low noise preamplification with self-adaptive continuous reset, high order shaper, band-gap referenced baseline stabilizer, one threshold comparator and two DAC adjustable window comparators, each followed by a 24-bit counter. Fabricated in 0.35{micro}m CMOS dissipates about 8mW per channel. First measurements show at room temperature a resolution of 14 rms electrons without the detector and of 40 rms electrons (340eV) with the detector connected and biased. Cooling at -35C a FWHM of 205eV (167eV from electronics) was measured at the Mn-K{alpha} line. A resolution of about 300eV was measured for rates approaching 100kcps/cm{sup 2} per channel, corresponding to an overall rate in excess of 10MHz/cm{sup 2}. A channel-to-channel threshold dispersion after DACs adjustment of 2.5 rms electrons was also measured.

  17. MELT RATE ENHANCEMENT FOR HIGH ALUMINUM HLW (HIGH LEVEL WASTE) GLASS FORMULATION FINAL REPORT 08R1360-1

    Microsoft Academic Search

    KRUGER AA; MATLACK KS; KOT W; PEGG IL; JOSEPH I; BARDAKCI T; GAN H; GONG W; CHAUDHURI M

    2010-01-01

    This report describes the development and testing of new glass formulations for high aluminum waste streams that achieve high waste loadings while maintaining high processing rates. The testing was based on the compositions of Hanford High Level Waste (HLW) with limiting concentrations of aluminum specified by the Office of River Protection (ORP). The testing identified glass formulations that optimize waste

  18. Principal Transformational Leadership Behaviors, Teachers' Sense of Efficacy, and Student Graduation Rates in High Needs High Schools

    ERIC Educational Resources Information Center

    Lilla, Darlene

    2013-01-01

    This study was an examination of teachers' perceptions of principal leadership behavior, Teaching Efficacy, and Personal Teaching Efficacy in high needs high schools with high and low graduation rates. The participants, one hundred twelve teachers from six high schools on Long Island, New York, responded to a 44-item survey instrument. The six…

  19. Low-dose-rate or high-dose-rate brachytherapy in treatment of prostate cancer – between options

    PubMed Central

    2013-01-01

    Purpose Permanent low-dose-rate (LDR-BT) and temporary high-dose-rate (HDR-BT) brachytherapy are competitive techniques for clinically localized prostate radiotherapy. Although a randomized trial will likely never to be conducted comparing these two forms of brachytherapy, a comparative analysis proves useful in understanding some of their intrinsic differences, several of which could be exploited to improve outcomes. The aim of this paper is to look for possible similarities and differences between both brachytherapy modalities. Indications and contraindications for monotherapy and for brachytherapy as a boost to external beam radiation therapy (EBRT) are presented. It is suggested that each of these techniques has attributes that advocates for one or the other. First, they represent the extreme ends of the spectrum with respect to dose rate and fractionation, and therefore have inherently different radiobiological properties. Low-dose-rate brachytherapy has the great advantage of being practically a one-time procedure, and enjoys a long-term follow-up database supporting its excellent outcomes and low morbidity. Low-dose-rate brachytherapy has been a gold standard for prostate brachytherapy in low risk patients since many years. On the other hand, HDR is a fairly invasive procedure requiring several sessions associated with a brief hospital stay. Although lacking in significant long-term data, it possesses the technical advantage of control over its postimplant dosimetry (by modulating the source dwell time and position), which is absent in LDR brachytherapy. This important difference in dosimetric control allows HDR doses to be escalated safely, a flexibility that does not exist for LDR brachytherapy. Conclusions Radiobiological models support the current clinical evidence for equivalent outcomes in localized prostate cancer with either LDR or HDR brachytherapy, using current dose regimens. At present, all available clinical data regarding these two techniques suggests that they are equally effective, stage for stage, in providing high tumor control rates. PMID:23634153

  20. 31 CFR 356.21 - How are awards at the high yield or discount rate calculated?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...2010-07-01 2010-07-01 false How are awards at the high yield or discount rate calculated...SERIES NO. 1-93) Determination of Auction Awards; Settlement § 356.21 How are awards at the high yield or discount rate...

  1. High repetition-rate wavelength tuning of an extended cavity diode laser for gas phase sensing

    Microsoft Academic Search

    J. Hult; I. S. Burns; C. F. Kaminski

    2005-01-01

    A method for rapid wavelength tuning of an extended cavity diode laser (ECDL) is presented providing for high resolution, narrow bandwidth output over limited spectral regions. The method permits tuning over isolated spectroscopic features at repetition rates of tens of kHz, greatly exceeding conventional ECDL tuning speeds. In this paper we present high repetition rate laser induced fluorescence (LIF) spectroscopy

  2. Retrieving avalanche basal friction law from high rate positioning of avalanches Pulfer G.1

    E-print Network

    Paris-Sud XI, Université de

    Retrieving avalanche basal friction law from high rate positioning of avalanches Pulfer G.1 : The Voellmy avalanche basal friction parameters are retrieved from high rate positioning of artificially released avalanches. Two dense snow avalanches were triggered at the Lautaret full-scale test site

  3. High-Rate Disinfection Techniques for Combined Sewer Overflow (Proceedings Paper)

    EPA Science Inventory

    This paper presents high-rate disinfection technologies for combined sewer overflow (CSO). The high-rate disinfection technologies of interest are: chlorination/dechlorination, ultraviolet light irradiation (UV), chlorine dioxide (ClO2 ), ozone (O3), peracetic acid (CH3COOOH ), a...

  4. High School Dropout, Graduation, and Completion Rates: Better Data, Better Measures, Better Decisions

    ERIC Educational Resources Information Center

    Hauser, Robert M., Ed.; Koenig, Judith Anderson, Ed.

    2011-01-01

    High school graduation and dropout rates have long been used as indicators of educational system productivity and effectiveness and of social and economic well being. While determining these rates may seem like a straightforward task, their calculation is in fact quite complicated. How does one count a student who leaves a regular high school but…

  5. Battery-Supercapacitor Hybrid System for High-Rate Pulsed Load Applications

    E-print Network

    Pedram, Massoud

    Battery-Supercapacitor Hybrid System for High-Rate Pulsed Load Applications Donghwa Shin, Younghyun--Modern batteries (e.g., Li-ion batteries) provide high discharge efficiency, but the rate capacity effect in these batteries drastically decreases the discharge efficiency as the load current increases. Electric double

  6. Evaluation of Gallager Codes for Short Block Length and High Rate Applications

    E-print Network

    MacKay, David J.C.

    for high rate, low block length applications such as magnetic disc drives and compact discs. They have good Gallager codes with high rate and small block length for disc drive applications, a common response bits outperform comparable BCH and Reed-Solomon codes (decoded by a hard input decoder) by more than

  7. Graduation Rates in South Carolina Public High Schools: The Effect of School Size and Socioeconomic Status

    ERIC Educational Resources Information Center

    Rivers, Thomas E., Jr.

    2012-01-01

    This study included a comparison of the graduation rates among high schools in South Carolina closely analyzing school size and socioeconomic status. The purpose for the study was to answer two questions: What patterns and relationships exist between school size and graduation rates at high schools in South Carolina? What patterns and…

  8. High growth rate deposition of oriented InN pillar crystals

    Microsoft Academic Search

    Kikurou Takemoto; Naoyuki Takahashi; Takato Nakamura

    2005-01-01

    High growth rate deposition of highly oriented indium nitride (InN) pillar crystals were successfully grown on Si(100) substrate prepared under atmospheric pressure using a halide CVD method (AP-HCVD). The growth rate of InN pillar crystal can be enhanced threefold by AP-HCVD system with metal halide dual sources zone, and the maximum growth rate of 8.33nm\\/s was achieved. X-ray diffraction and

  9. Neutrino emission rates in highly magnetized neutron stars revisited

    E-print Network

    Mario Riquelme; Andreas Reisenegger; Olivier Espinosa; Claudio Dib

    2005-05-11

    Magnetars are a subclass of neutron stars whose intense soft-gamma-ray bursts and quiescent X-ray emission are believed to be powered by the decay of a strong internal magnetic field. We reanalyze neutrino emission in such stars in the plausibly relevant regime in which the Landau band spacing of both protons and electrons is much larger than kT (where k is the Boltzmann constant and T is the temperature), but still much smaller than the Fermi energies. Focusing on the direct Urca process, we find that the emissivity oscillates as a function of density or magnetic field, peaking when the Fermi level of the protons or electrons lies about 3kT above the bottom of any of their Landau bands. The oscillation amplitude is comparable to the average emissivity when the Landau band spacing mentioned above is roughly the geometric mean of kT and the Fermi energy (excluding mass), i. e., at fields much weaker than required to confine all particles to the lowest Landau band. Since the density and magnetic field strength vary continuously inside the neutron star, there will be alternating surfaces of high and low emissivity. Globally, these oscillations tend to average out, making it unclear whether there will be any observable effects.

  10. WEAK LINE QUASARS AT HIGH REDSHIFT: EXTREMELY HIGH ACCRETION RATES OR ANEMIC BROAD-LINE REGIONS?

    SciTech Connect

    Shemmer, Ohad [Department of Physics, University of North Texas, Denton, TX 76203 (United States); Trakhtenbrot, Benny; Netzer, Hagai [School of Physics and Astronomy and the Wise Observatory, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel-Aviv 69978 (Israel); Anderson, Scott F. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Brandt, W. N.; Schneider, Donald P. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Diamond-Stanic, Aleksandar M.; Fan Xiaohui [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Lira, Paulina [Departamento de Astronomia, Universidad de Chile, Camino del Observatorio 1515, Santiago (Chile); Plotkin, Richard M. [Astronomical Institute 'Anton Pannekoek', University of Amsterdam, Science Park 904, 1098 XH, Amsterdam (Netherlands); Richards, Gordon T. [Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Strauss, Michael A., E-mail: ohad@unt.ed [Princeton University Observatory, Peyton Hall, Princeton, NJ 08544 (United States)

    2010-10-20

    We present Gemini-North K-band spectra of two representative members of the class of high-redshift quasars with exceptionally weak rest-frame ultraviolet emission lines (WLQs), SDSS J114153.34+021924.3 at z = 3.55 and SDSS J123743.08+630144.9 at z = 3.49. In both sources, we detect an unusually weak broad H{beta} line and place tight upper limits on the strengths of their [O III] lines. Virial, H{beta}-based black hole mass determinations indicate normalized accretion rates of L/L {sub Edd}=0.4 for these sources, which is well within the range observed for typical quasars with similar luminosities and redshifts. We also present high-quality XMM-Newton imaging spectroscopy of SDSS J114153.34+021924.3 and find a hard-X-ray photon index of {Gamma} = 1.91{sup +0.24} {sub -0.22}, which supports the virial L/L {sub Edd} determination in this source. Our results suggest that the weakness of the broad emission lines in WLQs is not a consequence of an extreme continuum-emission source but instead due to abnormal broad emission line region properties.

  11. Weak Line Quasars at High Redshift: Extremely High Accretion Rates or Anemic Broad-line Regions?

    NASA Astrophysics Data System (ADS)

    Shemmer, Ohad; Trakhtenbrot, Benny; Anderson, Scott F.; Brandt, W. N.; Diamond-Stanic, Aleksandar M.; Fan, Xiaohui; Lira, Paulina; Netzer, Hagai; Plotkin, Richard M.; Richards, Gordon T.; Schneider, Donald P.; Strauss, Michael A.

    2010-10-01

    We present Gemini-North K-band spectra of two representative members of the class of high-redshift quasars with exceptionally weak rest-frame ultraviolet emission lines (WLQs), SDSS J114153.34+021924.3 at z = 3.55 and SDSS J123743.08+630144.9 at z = 3.49. In both sources, we detect an unusually weak broad H? line and place tight upper limits on the strengths of their [O III] lines. Virial, H?-based black hole mass determinations indicate normalized accretion rates of L/L Edd=0.4 for these sources, which is well within the range observed for typical quasars with similar luminosities and redshifts. We also present high-quality XMM-Newton imaging spectroscopy of SDSS J114153.34+021924.3 and find a hard-X-ray photon index of ? = 1.91+0.24 -0.22, which supports the virial L/L Edd determination in this source. Our results suggest that the weakness of the broad emission lines in WLQs is not a consequence of an extreme continuum-emission source but instead due to abnormal broad emission line region properties.

  12. High gas-transfer velocity in coastal regions with high energy-dissipation rates

    NASA Astrophysics Data System (ADS)

    Tokoro, Tatsuki; Kayanne, Hajime; Watanabe, Atsushi; Nadaoka, Kazuo; Tamura, Hitoshi; Nozaki, Ken; Kato, Ken; Negishi, Akira

    2008-11-01

    We measured the gas-transfer velocity (k) and analyzed factors regulating k at coral reefs and an estuary at Ishigaki Island, Japan, using the floating-chamber method and the measured energy-dissipation rate (?) to represent turbulence in a small-eddy model. We confirmed the validity of the floating-chamber method quantitatively for the first time by the comparing ? values inside and outside the chamber device. We also compared k to ? and empirical parameters such as wind and current speeds. Measured k had a low correlation with the empirical parameters and a high correlation with ?, as indicated by the small-eddy model. The high ? values may have been regulated by topographic conditions, e.g., corals or seagrasses that generate wakes, and complex coastlines or large-scale (on the order of kilometers) topographic factors that generate horizontal current shear. Our measurements indicate that coastal k is regulated by ? and cannot be accurately determined using wind or current speeds. Topographic conditions in coastal regions are important factors that regulate ?; thus, a quantitative analysis of the effects of these conditions is necessary to accurately determine coastal air-water gas flux.

  13. Spectroscopic characterization of high-energy and high fluence rate photon beams

    NASA Astrophysics Data System (ADS)

    Bartol, Laura J.

    High-energy, high fluence rate photon sources are used in radiation oncology for the treatment of a variety of disease sites. Common dosimetry methods for characterizing these sources use energy-integrating devices; however, the most descriptive characterization of these sources are performed with devices that preserve the energy-specific information in the source output. This work used Monte-Carlo- (MC-) and measurement-based spectroscopic methods to characterize two therapeutic-level megavoltage photon sources. MC simulations were performed using the MCNP5 transport code and measurements were performed with a Compton-scattering (CS) technique. Because MC was used extensively in this work, some general MCNP5 investigations were performed to benchmark the techniques used. Limitations in the advanced variance reduction techniques, Doppler-broadening model, and use of phase space files were investigated. Based on the results of these investigations, recommendations were made for using each technique. The validity of the CS technique for use with megavoltage systems was demonstrated using MC simulations of a 6 MV linear accelerator field and measurements of a high dose rate 192Ir source. Following these initial demonstrations, the spectrum of a 60Co teletherapy unit was characterized. Simulations were performed to determine the spectrum's sensitivity to the source model. Multiple measurements were completed using a reverse-electrode germanium (REGe) detector with the CS spectrometry technique. The CS spectra were corrected for detector response and the CS geometry using a novel detector response function that was calculated using MCNP5. The detector response was unfolded using the Gold deconvolution method. Comparisons of the simulated and measured spectra showed agreement in terms of the peak positions, mean spectrum energy, and relative fluences under specific portions of the spectra. The spectrum of a 6 MV photon field from a Varian Clinac iX linear accelerator was also characterized. Simulations were performed to determine the spectrum's sensitivity to changes in the primary electron source parameters of mean energy, spot size, and divergence. In addition, measurements were performed using the CS technique with the REGe detector. These measurements demonstrated that the linac spectrum was detectable above background, and the CS signal was dependent on field size.

  14. Reproductive soundness of captive southern and northern white rhinoceroses ( Ceratotherium simum simum, C.s. cottoni): evaluation of male genital tract morphology and semen quality before and after cryopreservation

    Microsoft Academic Search

    Robert Hermes; Thomas Bernd Hildebrandt; Steffen Blottner; Christian Walzer; Sandra Silinski; Marilyn L. Patton; Gudrun Wibbelt; Franz Schwarzenberger; Frank Göritz

    2005-01-01

    White rhinoceroses suffer from a low rate of reproduction in captivity. This study examines the role of male reproductive function as a contributing factor. We used ultrasonography to image accessory sex glands, testis and epididymis. Electroejaculation provided 36 ejaculates from 21 rhinoceroses. Based on the percentage of progressively motile spermatozoa, semen was categorized in three groups, high (I: >75%), intermediate

  15. One meter square high rate neutron imaging panel based on boron straws

    Microsoft Academic Search

    Jeffrey L. Lacy; Liang Sun; Christopher S. Martin; Athanasios Athanasiades; Tom D. Lyons

    2009-01-01

    In order to fully realize the enhanced potential of the powerful neutron scattering technique provided by high intensity facilities like SNS, large area high rate detectors must be developed that do not depend upon the dwindling stock of 3He. We have developed a neutron detector that offers a large sensitive area (1 m2), 3D spatial resolution, high sensitivity and high

  16. Ka-Band TWT High-Efficiency Power Combiner for High-Rate Data Transmission

    NASA Technical Reports Server (NTRS)

    Wintucky, Edwin G.; Simons, Rainee; Vaden, Karl R.; Lesny, Gary G.; Glass, Jeffrey L.

    2007-01-01

    A four-port magic-T hybrid waveguide junction serves as the central component of a high-efficiency two-way power combiner circuit for transmitting a high-rate phase-modulated digital signal at a carrier frequency in the Ka-band (between 27 and 40 GHz). This power combiner was developed to satisfy a specific requirement to efficiently combine the coherent outputs of two traveling-wavetube (TWT) amplifiers that are typically characterized by power levels on the order of 100 W or more. In this application, the use of a waveguide-based power combiner (instead of a coaxial-cable- or microstrip-based power combiner, for example) is dictated by requirements for low loss, high power-handling capability, and broadband response. Combiner efficiencies were typically 90 percent or more over both the linear and saturated output power regions of operation of the TWTs . Figure 1 depicts the basic configuration of the magic-T hybrid junction. The coherent outputs of the two TWTs enter through ports 1 and 4. As a result of the orientations of the electromagnetic fields, which also provides a needed high port-to-port isolation, of these two input signals and the interior design of the magic-T junction, the input powers are divided so as to add in phase at one output port (port 2), and to be opposite in phase and hence cancel each other at the opposite coplanar output port (port 3). The net result is that the output power at port 2 is essentially double that of the output of one TWT, minus the power lost in the magic-T hybrid junction. Optimum performance as a high-efficiency power combiner thus requires a balance of both power and phase at the input ports of the magic-T. Replicas of this two-way combiner can be arranged in a binary configuration to obtain a 2n-way (where n is an integer) combiner. For example, Figure 2 illustrates the use of three two-way combiners to combine the outputs of four TWTs.

  17. Adult diet affects lifespan and reproduction of the fruit-feeding butterfly Charaxes fulvescens

    PubMed Central

    Molleman, Freerk; Ding, Jimin; Wang, Jane-Ling; Zwaan, Bas J.; Carey, James R.; Brakefield, Paul M.

    2009-01-01

    Fruit-feeding butterflies are among the longest lived Lepidoptera. While the use of pollen-derived amino acids by Heliconius butterflies has been interpreted as important for the evolution of extended lifespans, very little is known about the life-history consequences of frugivory. This issue is addressed by investigating effects of four adult diets (sugar, sugar with amino acids, banana, and moistened banana) on lifespan and reproduction in the fruit-feeding butterfly Charaxes fulvescens Aurivillius (Lepidoptera: Nymphalidae). Female butterflies were collected from Kibale National Park, Uganda, and kept individually in cages near their natural habitat and data were collected on lifespan, oviposition, and hatching of eggs. Lifespan in captivity was longer for the sugar and the amino acid cohort, than for the banana cohorts. The longitudinal pattern of oviposition was erratic, with many days without oviposition and few periods with high numbers of eggs laid. Butterflies typically did not lay eggs during their 1st week in captivity and the length of the period between capture and first reproduction was significantly shorter for butterflies fed moistened banana. The length of the reproduction period (first reproduction–last reproduction in captivity) and the reproduction rate (total number of eggs/length of the reproduction period) did not differ significantly between the diet treatments. Those fed with amino acid and moistened banana had significantly higher egg hatchability than those fed with sugar and banana. We found no evidence for a lifespan cost of reproduction. Our results show that (1) female C. fulvescens can use amino acids in their diet for laying fertile eggs, (2) more wing-wear does correlate with lower survival in captivity (indicating aging in the wild), but not with intensity of reproduction (providing no evidence for reproductive aging), and (3) fruit-feeding butterflies may be dietary restricted in the field. PMID:19774093

  18. Oceanographic drivers of offspring abundance may increase or decrease reproductive variance in a temperate marine fish.

    PubMed

    Lotterhos, Katie E; Markel, Russell W

    2012-10-01

    In species that reproduce into uncertain environments, the relationship between mean reproductive success (the abundance of new recruits) and the variance in reproductive success (whether adults contribute disproportionally more offspring) may not be straightforward because of stochastic environmental processes that create high variance in reproductive success among adults. In this study, we investigated the relationships between oceanography, reproductive success and reproductive variance in the black rockfish, Sebastes melanops, a long-lived temperate reef fish with pelagic larvae. We quantified black rockfish recruitment, genetic diversity and growth rates from otolith microstructure over 5 years (2005-2009) during which oceanographic conditions differed. We used cross-correlations to determine windows of time during which oceanographic variables were significantly correlated with the resulting abundance or genetic diversity of recruits. We found that warmer ocean temperatures were positively correlated with the abundance of recruits, as well as the effective number of breeders. In contrast, the strength of coastal upwelling during settlement was positively correlated with the annual abundance of new recruits, but was negatively correlated with the effective number of breeders. Larval growth rates were explained substantially more by temperature than by upwelling and suggested that temperature affected survival through growth, while upwelling affected survival through transport. Our results indicated that cold ocean temperatures and intense upwelling caused sweepstakes-like processes to operate on black rockfish populations, despite high abundances of recruits. We propose that a decoupling of the mean and variance in reproductive success may be characteristic of organisms that reproduce into uncertain environments. PMID:22978484

  19. The high-strain-rate response of alpha-titanium: Experiments, deformation mechanisms and modeling

    SciTech Connect

    Chichili, D.R.; Ramesh, K.T.; Hemker, K.J. [Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Mechanical Engineering] [Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Mechanical Engineering

    1998-01-23

    The high-strain-rate mechanical response of {alpha}-titanium is examined in terms of the underlying deformation mechanisms that govern its macroscopic behavior. The mechanical behavior of {alpha}-titanium has been evaluated using quasistatic compression testing with servohydraulic machines, dynamic compression testing with a compression Kolsky bar, and high-rate shearing under pressure using the pressure-shear plate impact technique. At the macroscopic level, {alpha}-titanium displays substantial rate sensitivity of the flow stress and pronounced strain hardening. The strain-hardening is greater at high strain rates than at low strain rates, and increases with strain at low strain rates. In an effort to determine the deformation mechanisms underlying this macroscopic behavior, the microstructures developed after low-rate and high-rate deformations have been characterized using both optical and transmission electron microscopy (TEM). At the microscopic level, both dislocations and twins are observed; the density of twins increases with both strain and strain rate and is shown to be a unique function of the flow stress (but not vice versa). Although dislocation motion accounted for the majority of plastic deformation, twin-dislocation interactions play an important role in strain hardening. The Kocks-Mecking model is used in order to describe the mechanical response as a function of the strain, strain rate and temperature; while the model is able to predict the monotonic behavior fairly accurately, it is unable to capture the experimental behavior observed in load-unload-reload tests.

  20. Rates of violence in patients classified as high risk by structured risk assessment instruments

    PubMed Central

    Singh, Jay P.; Fazel, Seena; Gueorguieva, Ralitza; Buchanan, Alec

    2014-01-01

    Background Rates of violence in persons identified as high risk by structured risk assessment instruments (SRAIs) are uncertain and frequently unreported by validation studies. Aims To analyse the variation in rates of violence in individuals identified as high risk by SRAIs. Method A systematic search of databases (1995-2011) was conducted for studies on nine widely used assessment tools. Where violence rates in high-risk groups were not published, these were requested from study authors. Rate information was extracted, and binomial logistic regression was used to study heterogeneity. Results Information was collected on 13 045 participants in 57 samples from 47 independent studies. Annualised rates of violence in individuals classified as high risk varied both across and within instruments. Rates were elevated when population rates of violence were higher, when a structured professional judgement instrument was used and when there was a lower proportion of men in a study. Conclusions After controlling for time at risk, the rate of violence in individuals classified as high risk by SRAIs shows substantial variation. In the absence of information on local base rates, assigning predetermined probabilities to future violence risk on the basis of a structured risk assessment is not supported by the current evidence base. This underscores the need for caution when such risk estimates are used to influence decisions related to individual liberty and public safety. PMID:24590974

  1. Reproductive safety evaluation of L-Ergothioneine.

    PubMed

    Forster, Roy; Spézia, François; Papineau, Dominique; Sabadie, Caroline; Erdelmeier, Irene; Moutet, Marc; Yadan, Jean-Claude

    2015-06-01

    L-Ergothioneine is a naturally occurring histidine-derived betaine (CAS No: 497-30-3) synthesized by bacteria and fungi, and found ubiquitously in plants and animals. It is present in many human foodstuffs. We evaluated the potential reproductive toxicity of L-Ergothioneine in Sprague-Dawley rats. L-Ergothioneine was administered at concentrations of 0.1, 0.3 or 0.9% in diet to F0 males (for 10 weeks before pairing and 3 weeks during pairing) and F0 females (for 13 weeks before pairing, during pairing and gestation, and until day 5 of lactation). Systemic exposure increased with dose-level, but not dose proportionally, suggesting saturation of uptake mechanisms. No clinical signs of toxicity were observed and there were no effects of L-Ergothioneine treatment on mating and reproductive performance or parameters of fertility. All animals mated within a similar number of days and pregnancy rates were uniformly high in control and treated groups. There were no effects of treatment with L-Ergothioneine on the duration of gestation, pre- and post-implantation losses, number of pups delivered and viability index, or on litter parameters (litter size, clinical signs, body weight or sex ratio) and the repartition of found dead/cannibalized pups. In conclusion, L-Ergothioneine was well tolerated and without adverse effects on the reproductive parameters evaluated. PMID:25736892

  2. Pulsed laser deposition with a high average power free electron laser: Benefits of subpicosecond pulses with high repetition rate

    Microsoft Academic Search

    Anne Reilly; Chris Allmond; Shannon Watson; Jason Gammon; Jung Gi Kim

    2003-01-01

    We have conducted experiments exploring pulsed laser deposition of thin films using the high average power Thomas Jefferson National Accelerator Facility Free Electron Laser. The combination of parameters of this laser, including subpicosecond pulses, high average power, high repetition rate, and tunability, makes it a unique tool for the study of the effects of laser characteristics on thin-film quality. When

  3. Materials design and processings for industrial high-strain-rate superplastic forming

    SciTech Connect

    Hosokawa, H.; Higashi, K.

    2000-07-01

    The optimum materials design in microstructural control could be developed for the high-strain-rate superplastic materials in the industrial scale. In the present work, it is reported that the high-performance-engine pistons with near-net-shape can be fabricated by the superplastic forging technology in the high-strain-rate superplastic PM Al-Si based alloy, which is produced by using this optimum materials design.

  4. MEASUREMENTS OF THE FIELD QUALITY IN SUPERCONDUCTING DIPOLES AT HIGH RAMP RATES.

    SciTech Connect

    JAIN, A.; ESCALLIER, J.; GANETIS, G.; LOUIE, W.; MARONE, A.; THOMAS, R.; WANDERER, P.

    2006-09-18

    Several recent applications of superconducting magnets require the magnets to be operated at high ramp rates and at frequencies of several Hertz. Brookhaven National Laboratory (BNL) has recently designed and built prototypes of superconducting dipole magnets that can be ramped at a fairly high rate (1 T/s or more). For accelerator applications, it is also crucial that the magnets maintain good field quality even at high ramp rates. In order to characterize the field quality of magnets at high ramp rates, a measurement system consisting of 16 printed circuit tangential coils has been developed. The coil system is held stationary while the magnet is ramped. This paper describes the techniques used for the measurements and data analysis, and presents the results of measurements at ramp rates of up to 4 T/s in a prototype dipole built at BNL for GSI.

  5. Solid state pulsed lasers with high repetition rate and harmonic generation for laser board systems

    NASA Astrophysics Data System (ADS)

    Pavlovitch, Vladimir L.; Lyashenko, A. I.; Raevsky, Eugene V.; Konovalov, Vladislav A.

    1994-08-01

    Currently flashlamp-pumped Nd:YAG lasers operate at a pulse repetition rate of 10...50 Hz. However, some applications call for increasing pulse repetition rate up to 300...500 Hz. Lasers with high repetition rates may be of practical interest to use in hydrography, lidars, locators, and bathimetric systems. We present the design and the performance of a compact high repetition-rate Nd:YAG oscillator pumped by single flashlamp in electro-optical Q- switched operation with second harmonic generation (SHG).

  6. Data throughput of CDMA-HDR a high efficiency-high data rate personal communication wireless system

    Microsoft Academic Search

    A. Jalali; R. Padovani; R. Pankaj

    2000-01-01

    Forward link data throughput performance of a high data rate wireless access system is presented. On the forward link of the proposed system data is transmitted to different access terminals (AT) in a TDM fashion. The rate transmitted to each AT is variable and depends on each AT's measured SINR. ATs send to the access points (AP) the index of

  7. What Works for Adolescent Reproductive Health: Lessons from Experimental Evaluations of Programs and Interventions. Fact Sheet. Publication #2008-20

    ERIC Educational Resources Information Center

    Ball, Victoria; Moore, Kristin A.

    2008-01-01

    The reproductive health of American adolescents has been, and continues to be, a matter of serious concern. America's teen birth rate--already the highest among developed nations--is again on the rise, and rates of sexually transmitted diseases among American teens are very high. As such, the development and identification of effective…

  8. The Evolution of Human Reproduction

    Microsoft Academic Search

    R. V. Short

    1976-01-01

    Mammals exhibit a variety of density-dependent reproductive variables that enable them to come into equilibrium with their environment. These include the age at puberty, extent of embryonic and foetal death, neonatal mortality rate, and the duration of lactational anoestrus or amenorrhoea. These are all female-oriented mechanisms; most mammals are polygynous, and as the female has the greatest energy investment in

  9. Temperature effects on high strain rate properties of graphite/epoxy composites

    NASA Technical Reports Server (NTRS)

    Yaniv, G.; Daniel, I. M.; Cokeing, S.; Martinez, G. M.

    1991-01-01

    A unidirectional graphite epoxy material (AS4/3501-6) was characterized at strain rates ranging from 5 x 10(exp 6) s(exp -1) to 5(exp -1), at room temperature and at 128 C. Results are presented in the form of stress-strain curves to failure. The longitudinal properties remain nearly unchanged with strain rate and temperature. The transverse modulus increases with strain rate but decreases with temperature. The transverse strength and transverse ultimate tensile strain have a positive rate sensitivity at low rates, which changes to negative at intermediate rates and returns to positive rate sensitivity at the highest rates tested. A temperature-time equivalence principle was applied and master curves were obtained for the transverse mechanical properties. The in-plane shear modulus and in-plane shear strength have a positive rate sensitivity. The ultimate intralaminar shear strain has a positive rate sensitivity at low rates, which changes to negative at high rates. At the elevated temperature of 128 C, the ultimate shear strain is 25 to 30 percent higher than the room temperature value, but its strain rate dependence is moderate.

  10. Temperature dependence of high strain-rate impact fracture behaviour in highly filled polymeric composite and plasticized thermoplastic propellants

    Microsoft Academic Search

    S. Y. Ho; C. W. Fong

    1987-01-01

    The effect of temperature and strain-rate on the fracture behaviour during high strain-rate (~ 103 sec-1) impact of two highly filled polymeric composite propellants (containing segmented polyurethanes based on hydroxy-term inated polybutadiene (HTPB) or glycidyl azide polymer (GAP) filled with ammonium perchlorate (AP) particles) and a plasticized thermoplastic (cast double base (CDB) nitrocellulose-nitroglycerine) propellant have been examined over a wide

  11. Relief-well requirements to kill a high-rate gas blowout from a deepwater reservoir

    SciTech Connect

    Warriner, R.A. (Triton Engineering Services Co. (US)); Cassity, T.G. (Cameron Iron Works (US))

    1988-12-01

    Relief-well requirements were investigated for a dynamic kill of a high-rate gas blowout from a deepwater reservoir to define any necessary special procedures or equipment. Results of the investigation show that a high injection rate and a special-design large-diameter injection riser are required to dynamically kill such a blowout with seawater. The injection riser is necessary to limit surface pump pressure during the high-rate kill operation. Procedures to complete the kill operation hydrostatically with heavy fluid following the dynamic kill are outlined.

  12. Application of high rate, high temperature anaerobic digestion to fungal thermozyme hydrolysates from carbohydrate wastes.

    PubMed

    Forbes, C; O'Reilly, C; McLaughlin, L; Gilleran, G; Tuohy, M; Colleran, E

    2009-05-01

    The objective of this study was to examine the feasibility of using a two-step, fully biological and sustainable strategy for the treatment of carbohydrate rich wastes. The primary step in this strategy involves the application of thermostable enzymes produced by the thermophilic, aerobic fungus, Talaromyces emersonii, to carbohydrate wastes producing a liquid hydrolysate discharged at elevated temperatures. To assess the potential of thermophilic treatment of this hydrolysate, a comparative study of thermophilic and mesophilic digestion of four sugar rich thermozyme hydrolysate waste streams was conducted by operating two high rate upflow anaerobic hybrid reactors (UAHR) at 37 degrees C (R1) and 55 degrees C (R2). The operational performance of both reactors was monitored from start-up by assessing COD removal efficiencies, volatile fatty acid (VFA) discharge and % methane of the biogas produced. Rapid start-up of both R1 and R2 was achieved on an influent composed of the typical sugar components of the organic fraction of municipal solid waste (OFMSW). Both reactors were subsequently challenged in terms of volumetric loading rate (VLR) and it was found that a VLR of 9 gCOD l(-1)d(-1) at a hydraulic retention time (HRT) of 1 day severely affected the thermophilic reactor with instability characterised by a build up of volatile fatty acid (VFA) intermediates in the effluent. The influent to both reactors was changed to a simple glucose and sucrose-based influent supplied at a VLR of 4.5 gCOD l(-1)d(-1) and HRT of 2 days prior to the introduction of thermozyme hydrolysates. Four unique thermozyme hydrolysates were subsequently supplied to the reactors, each for a period of 10 HRTs. The applied hydrolysates were derived from apple pulp, bread, carob powder and cardboard, all of which were successfully and comparably converted by both reactors. The % total carbohydrate removal by both reactors was monitored during the application of the sugar rich thermozyme hydrolysates. This approach offers a sustainable technology for the treatment of carbohydrate rich wastes and highlights the potential of these wastes as substrates for the generation of second-generation biofuels. PMID:19371919

  13. Measurement of High-Strain-Rate Strength of a Metal-Matrix Composite Conductor

    Microsoft Academic Search

    Peter J. Joyce; Lloyd P. Brown; Dwight Landen; Sikhanda Satapathy

    \\u000a Castings of metal matrix composites are of potential interest as high strength, high wear resistance conductors. This paper\\u000a examines the high-strain-rate strength of a tungsten-carbide (WC) filled aluminum bronze alloy (C95400) selected for its good\\u000a combination of good electrical and thermal conductivity and high mechanical strength, toughness, and wear resistance. A functionally\\u000a graded material with high wear resistance at the

  14. The high-strain-rate and spallation response of tantalum, Ta-10W, and T-111

    SciTech Connect

    Gray, G.T. III; Rollett, A.D.

    1991-01-01

    The compressive true stress-true response of tantalum, Ta-10W, and T-111 were found to depend on the applied strain rate, in the range 0.001 to 7000 s{sup {minus}1}. The strain-rate sensitivities of the flow stress of tantalum, Ta-10W, and T-111 a 1% strain are 0.062, 0.031, and 0.024, respectively. The rates of strain hardening in Tantalum, Ta-10W, and T-111 are seen to exhibit differing behavior with increasing strain rate. The calculated average strain-hardening rate in tantalum, {Theta}, for the quasi-static (0.001 s{sup {minus}1}) data at 25{degrees}C is 2080 MPa/unit strain. The hardening rate at 3000s{sup {minus}1} at 25{degrees}C decreases to 846 MPa/unit strain. Normalizing the work hardening rate in tantalum with the Taylor Factor for a random polycrystal, ({Theta} / (3.07){sup 2}), yields work hardening rates of {mu}/276 at quasi-static strain rates and {mu}/680 at high-rates, assuming a shear modulus of 61 GPa for tantalum at room temperature. While the work hardening of all the tantalum-based materials are similar at quasi-static rates, alloying results in a small reduction in hardening rate. With increasing strain rate, the work hardening rate in tantalum decreases by approximately a factor of two compared to the alloys. Alloying tantalum with substitutional or interstitial elements is thought to result in increased edge dislocation storage and screw dislocation cross-slip due to interactions with the alloying elements at high strain rates. 28 refs.

  15. A MODEL FOR EXPERIMENTALLY-OBSERVED HIGH-STRAIN-RATE DYNAMIC STRAIN AGING IN TITANIUM

    E-print Network

    Nemat-Nasser, Sia

    A MODEL FOR EXPERIMENTALLY-OBSERVED HIGH- STRAIN-RATE DYNAMIC STRAIN AGING IN TITANIUM JINGYI CHENG an anomalous response by commercially pure titanium at relatively high temperatures: for a ®xed high strain seems to accurately predict the response of commercially pure titanium, over a broad range of strain

  16. Carbon limitation of biomass production in high-rate oxidation ponds

    Microsoft Academic Search

    Y. Azov; G. Shelef; R. Moraine

    1982-01-01

    Theoretical considerations confirmed by outdoor experiments indicated carbon limitation of biomass production in high-rate oxidation ponds at certain seasonal and operational conditions. Apparently, free carbon dioxide concentration in the pond is the major determinant of carbon-limiting algal photosynthesis. High concentrations of free COâ are provided through bacterial respiration which is the main contributor to algal photosynthesis. At high photosynthetic activities

  17. The Relationships among the Fine Arts, School Culture, and High School Graduation Rates in Georgia

    ERIC Educational Resources Information Center

    Lovett, Andrew, Jr.

    2014-01-01

    High school graduation is the single largest hurdle that students must achieve to prepare for college and career (National Governor's Association, 2011). Fleischman & Heppen (2009) agree that American high schools must address the problem of declining graduation rate. Approximately 1.28 million students drop out of high school annually (Amos,…

  18. Dual-chemistry cathode system for high-rate pulse applications

    Microsoft Academic Search

    Hong Gan; Robert S. Rubino; Esther S. Takeuchi

    2005-01-01

    A novel electrode design was developed and used to construct cells for high-rate pulsing applications. In this electrode design, a cathode material with high energy density, such as carbon monofluoride (CFx), is sandwiched between two layers of current collectors that in turn are sandwiched between two layers of cathode materials with high power capability, such as silver vanadium oxide (SVO).

  19. Patterns of Reproductive Isolation in Toads

    PubMed Central

    2008-01-01

    Understanding the general features of speciation is an important goal in evolutionary biology, and despite significant progress, several unresolved questions remain. We analyzed an extensive comparative dataset consisting of more than 1900 crosses between 92 species of toads to infer patterns of reproductive isolation. This unique dataset provides an opportunity to examine the strength of reproductive isolation, the development and sex ratios of hybrid offspring, patterns of fertility and infertility, and polyploidization in hybrids all in the context of genetic divergence between parental species. We found that the strength of intrinsic postzygotic isolation increases with genetic divergence, but relatively high levels of divergence are necessary before reproductive isolation is complete in toads. Fertilization rates were not correlated to genetic divergence, but hatching success, the number of larvae produced, and the percentage of tadpoles reaching metamorphosis were all inversely related with genetic divergence. Hybrids between species with lower levels of divergence developed to metamorphosis, while hybrids with higher levels of divergence stopped developing in gastrula and larval stages. Sex ratios of hybrid offspring were biased towards males in 70% of crosses and biased towards females in 30% of crosses. Hybrid females from crosses between closely related species were completely fertile, while approximately half (53%) of hybrid males were sterile, with sterility predicted by genetic divergence. The degree of abnormal ploidy in hybrids was positively related to genetic divergence between parental species, but surprisingly, polyploidization had no effect on patterns of asymmetrical inviability. We discuss explanations for these patterns, including the role of Haldane's rule in toads and anurans in general, and suggest mechanisms generating patterns of reproductive isolation in anurans. PMID:19065271

  20. Generation of µW level plateau harmonics at high repetition rate.

    PubMed

    Hädrich, S; Krebs, M; Rothhardt, J; Carstens, H; Demmler, S; Limpert, J; Tünnermann, A

    2011-09-26

    The process of high harmonic generation allows for coherent transfer of infrared laser light to the extreme ultraviolet spectral range opening a variety of applications. The low conversion efficiency of this process calls for optimization or higher repetition rate intense ultrashort pulse lasers. Here we present state-of-the-art fiber laser systems for the generation of high harmonics up to 1 MHz repetition rate. We perform measurements of the average power with a calibrated spectrometer and achieved µW harmonics between 45 nm and 61 nm (H23-H17) at a repetition rate of 50 kHz. Additionally, we show the potential for few-cycle pulses at high average power and repetition rate that may enable water-window harmonics at unprecedented repetition rate. PMID:21996878

  1. Activated carbon derived from melaleuca barks for outstanding high-rate supercapacitors.

    PubMed

    Luo, Qiu-Ping; Huang, Liang; Gao, Xiang; Cheng, Yongliang; Yao, Bin; Hu, Zhimi; Wan, Jun; Xiao, Xu; Zhou, Jun

    2015-07-31

    Activated carbon (AC) was prepared via carbonizing melaleuca bark in an argon atmosphere at 600 °C followed with KOH activation for high-rate supercapacitors. This AC electrode has a high capacitance of 233 F g(-1) at a scan rate of 2 mV s(-1) and an excellent rate capability of ?80% when increasing the sweep rate from 2 to 500 mV s(-1). The symmetric supercapacitor assembled by the above electrode can deliver a high energy density of 4.2 Wh kg(-1) with a power density of 1500 W kg(-1) when operated in the voltage range of 0-1 V in 1 M H2SO4 aqueous electrolyte while maintaining great cycling stability (less than 5% capacitance loss after 10 000 cycles at sweep rate of 100 mV s(-1)). All the outstanding electrochemical performances make this AC electrode a promising candidate for potential energy storage application. PMID:26152815

  2. Rheology and birefringence of Fomblin YR at very high shear rates

    Microsoft Academic Search

    Khaled S. Mriziq; Hank D. Cochran; Mark D. Dadmun

    2007-01-01

    The rheological and structural properties of perfluoropolyether (PFPE) lubricant films including viscosity, shear stress,\\u000a and birefringence were measured at relatively low to extremely high shear rates using a rotational optical rheometer. The\\u000a viscosity of various films with different thicknesses exhibit Newtonian behavior up to a shear rate 1?×?104 s?1, with a transition to shear-thinning behavior obvious at higher shear rates. Birefringence

  3. Extension growth rates in two coral species from high-latitude reefs of Bermuda

    Microsoft Academic Search

    A. Logan; T. Tomascik

    1991-01-01

    Mean annual growth rates (skeletal linear extension) in the hermatypic coralsPorites astreoides Lamarck andDiploria labyrinthiformis (L.) were investigated mainly by X-radiography from a variety of localities at various depths on the high-latitude coral reefs of Bermuda. Growth rates of both species show an inverse curvilinear relationship with depth, with highest growth rates in the shallow inshore waters of Castle Harbour

  4. High Rate Deposition of Microcrystalline Silicon Using Conventional Plasma-Enhanced Chemical Vapor Deposition

    Microsoft Academic Search

    Lihui Guo; Michio Kondo; Makoto Fukawa; Kimihiko Saitoh; Akihisa Matsuda

    1998-01-01

    The deposition of hydrogenated microcrystalline silicon (µc-Si:H) at a relatively high working pressure is performed using a conventional radio-frequency plasma-enhanced chemical vapor deposition method. Correlation of the deposition rate and crystallinity with deposition parameters, such as working pressure, flow rate, dilution ratio and input RF power, are studied. It was found that the deposition rate exhibits a maximum at around

  5. A low-cost time-hopping impulse radio system for high data rate transmission

    Microsoft Academic Search

    Andreas F. Molisch; Yves-Paul Nakache; Philip V. Orlik; Makoto Miyake; Yunnan Wu; Sinan Gezici; Harry Sheng; Sun-yuan Kung; Hisashi Kobayashi; H. Vincent Poor; Alexander M. Haimovich; Jinyun Zhang

    2005-01-01

    We present an efficient, low-cost implementation of time-ho pping impulse radio that fulfills the spectral mask mandated by the FCC and is suitable for high-data-rate, short-range communications. Key features are: (i) all- baseband implementation that obviates the need for passband components, (ii) symbol-rate (not chip rate) sampling, A\\/D conversion, and digital signal processing, (iii) fast a cquisition due to novel

  6. Reproductive soundness of captive southern and northern white rhinoceroses (Ceratotherium simum simum, C.s. cottoni): evaluation of male genital tract morphology and semen quality before and after cryopreservation.

    PubMed

    Hermes, Robert; Hildebrandt, Thomas Bernd; Blottner, Steffen; Walzer, Christian; Silinski, Sandra; Patton, Marilyn L; Wibbelt, Gudrun; Schwarzenberger, Franz; Göritz, Frank

    2005-01-01

    White rhinoceroses suffer from a low rate of reproduction in captivity. This study examines the role of male reproductive function as a contributing factor. We used ultrasonography to image accessory sex glands, testis and epididymis. Electroejaculation provided 36 ejaculates from 21 rhinoceroses. Based on the percentage of progressively motile spermatozoa, semen was categorized in three groups, high (I: >75%), intermediate (II: 50-70%) or low (III: <50%) quality. Only 52% of the males showed high semen quality. Ejaculates in the high motility category also had the highest proportion of morphologically intact spermatozoa. Both semen parameters, sperm motility and morphology, were found to positively correlate with size of the accessory sex glands. The semen category was associated with group size suggesting that the social status influenced functional reproductive parameters. Change of territorial status (n = 1) improved semen quality. Testicular fibrosis was characterized as a sign of reproductive ageing in all males older than 15 years of age (n = 13); although, this ageing process did not notably affect semen parameters. Furthermore, for the benefit of assisted-reproduction and genetic banking programs protocols for the storage of cooled semen and the cryopreservation of spermatozoa were designed using different cryodiluents. This report provides basic data for the evaluation of reproductive components and of breeding management in male rhinoceros. Our results indicate that low rate of reproduction in captivity can be attributed to reduced male reproductive fitness. Changes in management of white rhinoceroses may positively affect male reproductive function. PMID:15589286

  7. An Improved Reaction Rate Equation for Simulating the Ignition and Growth of Reaction in High Explosives

    SciTech Connect

    Murphy, M J

    2010-03-08

    We describe an improved reaction rate equation for simulating ignition and growth of reaction in high explosives. It has been implemented into CALE and ALE3D as an alternate to the baseline the Lee-Tarver reactive flow model. The reactive flow model treats the explosive in two phases (unreacted/reactants and reacted/products) with a reaction rate equation to determine the fraction reacted, F. The improved rate equation has fewer parameters, is continuous with continuous derivative, results in a unique set of reaction rate parameters for each explosive while providing the same functionality as the baseline rate equation. The improved rate equation uses a cosine function in the ignition term and a sine function in the growth and completion terms. The improved rate equation is simpler with fewer parameters.

  8. Effects of high, low, and thinning rates of alternative reinforcement on response elimination and resurgence.

    PubMed

    Sweeney, Mary M; Shahan, Timothy A

    2013-07-01

    A common treatment for operant problem behavior is alternative reinforcement. When alternative reinforcement is removed or reduced, however, resurgence of the target behavior can occur. Shahan and Sweeney (2011) developed a quantitative model of resurgence based on behavioral momentum theory that suggests higher rates of alternative reinforcement result in faster response elimination and greater resurgence when removed, whereas lower rates of alternative reinforcement result in slower response elimination but are followed by less resurgence. Thus, the present study was designed to examine whether faster target response elimination and less resurgence could be achieved by beginning with a high rate of alternative reinforcement and gradually thinning it such that a low rate is ultimately removed during a simulated treatment lapse. Results showed that high rates of alternative reinforcement were more effective than low or thinning rates at target response suppression but resulted in resurgence when discontinued. Low and thinning rates, on the other hand, were less effective at response suppression but target responding did not increase when alternative reinforcement was discontinued. The quantitative model cannot currently account for the finding that lower-rate alternative reinforcement may not effectively disrupt behavior relative to an extinction only control. Relative advantages of high, low, thinning, or no alternative reinforcement are discussed with respect to suppression of target response rate during treatment, resurgence when alternative reinforcement is removed, and alternative response persistence, while taking into account differences between this animal model and modern applied behavior analytic treatments. PMID:23605776

  9. U.S. High School Graduation Rates: Patterns and Explanations. NBER Working Paper No. 18701

    ERIC Educational Resources Information Center

    Murnane, Richard J.

    2013-01-01

    I survey the evidence on patterns in U.S. high school graduation rates over the period 1970-2010 and report the results of new research conducted to fill in holes in the evidence. I begin by pointing out the strengths and limitations of existing data sources. I then describe six striking patterns in graduation rates. They include stagnation over…

  10. Laser welding of stainless steel weld filler metals at high cooling rates

    Microsoft Academic Search

    J. M. Vitek; S. A. David

    1988-01-01

    Several stainless steels were laser welded under conditions resulting in high cooling rates of the welds. Significant changes in the microstructures, compared to those produced by conventional welding techniques, were found. For alloys 304, 308, 309, 316 and 347, a general decrease in ferrite content with increasing cooling rate was found. For three alloys (304, 308, 347), a fully austenitic

  11. A high-rate long-range wireless transmission system for multichannel neural recording applications

    E-print Network

    Shenoy, Krishna V.

    A high-rate long-range wireless transmission system for multichannel neural recording applications-rate, low-power wireless transmission system (named HermesD) to aid the research in neural prosthetics for motor disabilities, by recording and transmitting neural activity from electrode arrays implanted

  12. Solid-state experiments at high pressure and strain rate* D. H. Kalantar,,a)

    E-print Network

    Meyers, Marc A.

    Solid-state experiments at high pressure and strain rate* D. H. Kalantar,,a) B. A. Remington, J. D and strain rates. Details of the target and drive development required for solid-state experiments pressure of 180 GPa and accelerated. A pre-imposed modulation at the embedded Rayleigh­Taylor unstable

  13. NCLB Implementation Report: State Approaches for Calculating High School Graduation Rates.

    ERIC Educational Resources Information Center

    Swanson, Christopher B.

    This review investigated the state accountability Workbooks provisionally approved and publicly reported by the U.S. Department of Education (DOE) as of June 2003. These documents were obtained from the DOE Web site. This report examines state definitions of high school graduation rates and strategies for constructing graduation rate indicators. A…

  14. The Relationship of High School Graduation Exams to Graduation Rates and SAT Scores

    Microsoft Academic Search

    Gregory J. Marchant; Sharon E. Paulson

    The current study examined the effect of high school graduation exams on states' graduation rates, states' aggregated SAT scores, and individual students' SAT scores. Three data sources were used: One source identified states requiring a standardized test for graduation; the NCES provided state aggregated data on graduation rates for the class of 2002; and the College Board provided its 2001

  15. High-repetition-rate ferroelectric-cathode gyrotron M. Einat, E. Jerby,a)

    E-print Network

    Jerby, Eli

    consists of a 7 7 mm2 stainless-steel grid, at- tached to the ceramic plate. The electron gun is activated, a high-repetition-rate microwave oscillator based on a ferroelectric electron gun has been developed of a CRM oscillator with a ferroelectric electron gun is accom- plished in repetition rates of up to 3 MHz

  16. Drop-weight camera system for high-strain-rate mechanical testing

    Microsoft Academic Search

    G. M. Swallowe; S. Hamdan; X. Zeng; W. P. Schiffers

    1997-01-01

    This paper describes a Dropweight-High Speed Camera system designed to measure the uniaxial compressive stress-strain properties of polymers at the strain rates appropriate to ballistic and impact events over time scales of one to tens of milliseconds. The instrument compliments existing techniques and represents a novel development of existing equipment types. It operates at strain rates in the range of

  17. High rate deposition of transparent conducting oxide thin films by vacuum arc plasma evaporation

    Microsoft Academic Search

    Tadatsugu Minami; Satoshi Ida; Toshihiro Miyata

    2002-01-01

    Transparent conducting oxide (TCO) thin films have been deposited at a high rate above 370 nm\\/min by vacuum arc plasma evaporation (VAPE) using sintered oxide fragments as the source material. It was found that the deposition rate of TCO films was strongly dependent on the deposition pressure, whereas the obtained electrical properties were relatively independent of the pressure. Resistivities of

  18. An Analysis of the High Attrition Rates among First Year College Science, Math and Engineering Majors.

    ERIC Educational Resources Information Center

    Daempfle, Peter A.

    Increases in attrition rates among science, mathematics, and engineering (SME) majors have produced a variety of deleterious effects for society. This paper attempts to clarify and interpret the interaction of those characteristics of the structure and culture of undergraduate SME programs that perpetuate high loss rates among their first-year…

  19. Continuous high-repetition-rate operation of collisional soft-x-ray lasers with solid targets

    E-print Network

    Rocca, Jorge J.

    Continuous high-repetition-rate operation of collisional soft-x-ray lasers with solid targets A a laser average output power of 2 W at a wavelength of 13.9 nm by operating a tabletop laser-pumped Ni-like Ag laser at a 5 Hz repetition rate, using a solid helicoidal target that is continuously rotated

  20. Observation of NEOs Having High Apparent Rates with Mobitel Telescope Shulga, O.1

    E-print Network

    Boyer, Edmond

    Observation of NEOs Having High Apparent Rates with Mobitel Telescope Shulga, O.1 , Kozyryev, Y.1 for the small telescopes, but after going away it may become unobservable for the most of telescopes rate causes limitation of exposure time in case if telescope observe in star tracking mode. So

  1. Single Charging of Nanoparticles by UV Photoionization at High Flow Rates

    Microsoft Academic Search

    Esther Hontañón; F. Einar Kruis

    2008-01-01

    The feasibility of UV photoionization for single unipolar charging of nanoparticles at flow rates up to 100 l· min is demonstrated. The charging level of the aerosol particles can be varied by adjusting the intensity of the UV radiation. The suitability of a UV photocharger followed by a DMA to deliver monodisperse nanoparticles at high aerosol flow rates has been

  2. Atomic oxygen photoionization rates computed with high resolution cross sections and solar fluxes

    Microsoft Academic Search

    R. R. Meier; Brendan M. McLaughlin; H. P. Warren; James Bishop

    2007-01-01

    Accurate knowledge of photoionization rates is fundamental for the study and understanding of gases in the solar system. Past calculations of the photoionization rates of atmospheric gases lack the spectral resolution to accommodate highly structured autoionization features in the photoionization cross section. A new theoretical model of the atomic oxygen photoionization cross section combined with a new solar minimum spectral

  3. An Evaluation of a Program Designed to Reduce High School Dropout Rate

    ERIC Educational Resources Information Center

    Lange, Tennille W.

    2012-01-01

    The Pre-GED (General Education Development) and Skills Options Program was a response by one state to the national increase in high school dropout rates. However, more than a decade later dropout rates continued to rise. As a result, an evaluation of the program was needed. Thus, the purpose of this study was to explore the purpose of the program,…

  4. Beyond R0: Demographic Models for Variability of Lifetime Reproductive Output

    PubMed Central

    Caswell, Hal

    2011-01-01

    The net reproductive rate measures the expected lifetime reproductive output of an individual, and plays an important role in demography, ecology, evolution, and epidemiology. Well-established methods exist to calculate it from age- or stage-classified demographic data. As an expectation, provides no information on variability; empirical measurements of lifetime reproduction universally show high levels of variability, and often positive skewness among individuals. This is often interpreted as evidence of heterogeneity, and thus of an opportunity for natural selection. However, variability provides evidence of heterogeneity only if it exceeds the level of variability to be expected in a cohort of identical individuals all experiencing the same vital rates. Such comparisons require a way to calculate the statistics of lifetime reproduction from demographic data. Here, a new approach is presented, using the theory of Markov chains with rewards, obtaining all the moments of the distribution of lifetime reproduction. The approach applies to age- or stage-classified models, to constant, periodic, or stochastic environments, and to any kind of reproductive schedule. As examples, I analyze data from six empirical studies, of a variety of animal and plant taxa (nematodes, polychaetes, humans, and several species of perennial plants). PMID:21738586

  5. Von Willlebrand Adhesion to Surfaces at High Shear Rates Is Controlled by Long-Lived Bonds

    E-print Network

    Sing, Charles E.

    Von Willebrand factor (vWF) adsorbs and immobilizes platelets at sites of injury under high-shear-rate conditions. It has been recently demonstrated that single vWF molecules only adsorb significantly to collagen above a ...

  6. The impact of high inflation rates on the demand for air passenger transportation

    E-print Network

    Vitek, Richard Leo

    1975-01-01

    The impact of high inflation rates on the demand for domestic air passenger transportation is tested in a demand model using time-series data and linear and non-linear least squares regressions with Revenue Passenger Miles ...

  7. ISS Update: High Rate Communications System - Duration: 9 minutes, 26 seconds.

    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 ha...

  8. Why the high attrition rate for computer science students: some thoughts and observations

    Microsoft Academic Search

    Theresa Beaubouef; John Mason

    2005-01-01

    This paper investigates the possible causes for high attrition rates for Computer Science students. It is a serious problem in universities that must be addressed if the need for technologically competent professionals is to be met.

  9. High-strain-rate nanoindentation behavior of fine-grained magnesium alloys

    E-print Network

    Somekawa, Hidetoshi

    The effects of temperature and alloying elements on deformation in the high-strain-rate regime were investigated by testing fine-grained magnesium alloys with an average grain size of 2 ? 3 ?m by a nanoindentation technique. ...

  10. Effects of Data Density of Echo Fourier Domain on Quality of High Frame Rate Imaging

    E-print Network

    Lu, Jian-yu

    ]-[20]. Motion artifacts and phase aberration effects on the HFR imaging have been studied [21) at a high frame rate while dramatically reducing the amount of computations due to the use of Fast Fourier

  11. Statistical Profiles of Highly-Rated Web Sites Melody Y. Ivory

    E-print Network

    Hearst, Marti

    Statistical Profiles of Highly-Rated Web Sites Melody Y. Ivory EECS Department UC Berkeley Berkeley, CA 94720-1776 ivory@cs.berkeley.edu Marti A. Hearst SIMS UC Berkeley Berkeley, CA 94720-4600 hearst

  12. An implementation of a 5.25 GHz transceiver for high data rate wireless applications

    E-print Network

    Matalon, Nir

    2005-01-01

    The desire for transmission of high data rate information across wireless channels has grown immensely over the past decade. Wireless devices available today including mobile phones, wireless local area networks (WLANs) ...

  13. Femtosecond fiber lasers at 1550 nm for high repetition rates and low timing jitter

    E-print Network

    Morse, Jonathan Lee

    2013-01-01

    Femtosecond fiber lasers have become an important enabling technology for advances in many areas including: frequency combs, precise timing distribution, optical arbitrary waveform generation, and high bit rate sampling ...

  14. High repetition rate mode-locked erbium-doped fiber lasers with complete electric field control

    E-print Network

    Sickler, Jason William, 1978-

    2008-01-01

    Recent advances in fully-stabilized mode-locked laser systems are enabling many applications, including optical arbitrary waveform generation (OAWG). In this thesis work, we describe the development of high repetition-rate ...

  15. High Sand Fluxes and Abrasion Rates on Mars Determined from HiRISE Images

    NASA Astrophysics Data System (ADS)

    Bridges, N. T.; Ayoub, F.; Avouac, J.-P.; Leprince, S.; Lucas, A.; Mattson, S.

    2012-03-01

    We derive the reptation and saltation sand fluxes in Nili Patea, Mars. The dunes have unexpectedly high fluxes that are like those in Victoria Valley, Antarctica, implying that rates of landscape modification on Mars and Earth are similar.

  16. Frequency-dependent selection can lead to evolution of high mutation rates.

    PubMed

    Rosenbloom, Daniel I S; Allen, Benjamin

    2014-05-01

    Theoretical and experimental studies have shown that high mutation rates can be advantageous, especially in novel or fluctuating environments. Here we examine how frequency-dependent competition may lead to fluctuations in trait frequencies that exert upward selective pressure on mutation rates. We use a mathematical model to show that cyclical trait dynamics generated by "rock-paper-scissors" competition can cause the mutation rate in a population to converge to a high evolutionarily stable mutation rate, reflecting a trade-off between generating novelty and reproducing past success. Introducing recombination lowers the evolutionarily stable mutation rate but allows stable coexistence between mutation rates above and below the evolutionarily stable rate. Even considering strong mutational load and ignoring the costs of faithful replication, evolution favors positive mutation rates if the selective advantage of prevailing in competition exceeds the ratio of recombining to nonrecombining offspring. We discuss a number of genomic mechanisms that may meet our theoretical requirements for the adaptive evolution of mutation. Overall, our results suggest that local mutation rates may be higher on genes influencing cyclical competition and that global mutation rates in asexual species may be higher in populations subject to strong cyclical competition. PMID:24739203

  17. Poor horse traders: large mammals trade survival for reproduction during the process of feralization

    PubMed Central

    Grange, Sophie; Duncan, Patrick; Gaillard, Jean-Michel

    2009-01-01

    We investigated density dependence on the demographic parameters of a population of Camargue horses (Equus caballus), individually monitored and unmanaged for eight years. We also analysed the contributions of individual demographic parameters to changes in the population growth rates. The decrease in resources caused a loss of body condition. Adult male survival was not affected, but the survival of foals and adult females decreased with increasing density. Prime-aged females maintained high reproductive performance at high density, and their survival decreased. The higher survival of adult males compared with females at high density presumably results from higher investment in reproduction by mares. The high fecundity in prime-aged females, even when at high density, may result from artificial selection for high reproductive performance, which is known to have occurred in all the major domestic ungulates. Other studies suggest that feral ungulates including cattle and sheep, as these horses, respond differently from wild ungulates to increases in density, by trading adult survival for reproduction. As a consequence, populations of feral animals should oscillate more strongly than their wild counterparts, since they should be both more invasive (as they breed faster), and more sensitive to harsh environmental conditions (as the population growth rate of long-lived species is consistently more sensitive to a given proportional change in adult survival than to the same change in any other vital rate). If this principle proves to be general, it has important implications for management of populations of feral ungulates. PMID:19324787

  18. Femtosecond Ti:sapphire cryogenic amplifier with high gain and MHz repetition rate.

    PubMed

    Dantan, Aurélien; Laurat, Julien; Ourjoumtsev, Alexei; Tualle-Brouri, Rosa; Grangier, Philippe

    2007-07-01

    We demonstrate high gain amplification of 160-femtosecond pulses in a compact double-pass cryogenic Ti:sapphire amplifier. The setup involves a negative GVD mirrors recompression stage, and operates with a repetition rate between 0.2 and 4 MHz with a continuous pump laser. Amplification factors as high as 17 and 320 nJ Fourier-limited pulses are obtained at a 800 kHz repetition rate. PMID:19547224

  19. Adaptive coding for high-rate direct-sequence spread spectrum

    Microsoft Academic Search

    Michael B. Pursley

    2005-01-01

    High-rate direct-sequence (DS) spread spectrum is a modulation technique in which most or all of the spreading is provided by nonbinary data modulation. For applications to mobile ad hoc wireless networks, the limited processing gain of high-rate DS spread spectrum gives only modest protection against multiple-access or multipath interference, but increased interference rejection capability can be obtained from error-control coding.

  20. High-Rate Direct-Sequence Spread Spectrum With Error-Control Coding

    Microsoft Academic Search

    Michael B. Pursley; Thomas C. Royster Iv

    2006-01-01

    High-rate direct-sequence spread spectrum is a modulation technique in which most or all of the spreading is provided by nonbinary data modulation. For applications to mobile ad hoc wireless networks, the limited processing gain of high-rate direct-sequence spread spectrum gives only modest protection against multiple access or multipath interference, which limits the applicability of the modulation technique to fairly benign