Effects of spatial structure of population size on the population dynamics of barnacles across their elevational range.

PubMed

Fukaya, Keiichi; Okuda, Takehiro; Nakaoka, Masahiro; Noda, Takashi

2014-11-01

Explanations for why population dynamics vary across the range of a species reflect two contrasting hypotheses: (i) temporal variability of populations is larger in the centre of the range compared to the margins because overcompensatory density dependence destabilizes population dynamics and (ii) population variability is larger near the margins, where populations are more susceptible to environmental fluctuations. In both of these hypotheses, positions within the range are assumed to affect population variability. In contrast, the fact that population variability is often related to mean population size implies that the spatial structure of the population size within the range of a species may also be a useful predictor of the spatial variation in temporal variability of population size over the range of the species. To explore how population temporal variability varies spatially and the underlying processes responsible for the spatial variation, we focused on the intertidal barnacle Chthamalus dalli and examined differences in its population dynamics along the tidal levels it inhabits. Changes in coverage of barnacle populations were monitored for 10.5 years at 25 plots spanning the elevational range of this species. Data were analysed by fitting a population dynamics model to estimate the effects of density-dependent and density-independent processes on population growth. We also examined the temporal mean-variance relationship of population size with parameters estimated from the population dynamics model. We found that the relative variability of populations tended to increase from the centre of the elevational range towards the margins because of an increase in the magnitude of stochastic fluctuations of growth rates. Thus, our results supported hypothesis (2). We also found that spatial variations in temporal population variability were well characterized by Taylor's power law, the relative population variability being inversely related to the mean population size. Results suggest that understanding the population dynamics of a species over its range may be facilitated by taking the spatial structure of population size into account as well as by considering changes in population processes as a function of position within the range of the species. © 2014 The Authors. Journal of Animal Ecology © 2014 British Ecological Society.

French Sizing of Medical Devices is not Fit for Purpose

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

Kibriya, Nabil, E-mail: nabskib@yahoo.co.uk; Hall, Rebecca; Powell, Steven

PurposeThe purpose of the study is to quantify the variation in the metric equivalent of French size in a range of medical devices, from various manufacturers, used in interventional radiology.MethodsThe labelling of a range of catheters, introducers, drains, balloons, stents, and endografts was examined. Products were chosen to achieve a broad range of French sizes from several manufacturers. To assess manufacturing accuracy, eight devices were selected for measurement using a laser micrometer. The external diameters of three specimens of each device were measured at centimeter intervals along the length of the device to ensure uniformity.ResultsA total of 200 labels ofmore » interventional radiology equipment were scrutinized. The results demonstrate a wide variation in the metric equivalent of French sizing. Labelled products can vary in diameter across the product range by up to 0.79 mm.The devices selected for measurement with the non-contact laser micrometer demonstrate acceptable manufacturing consistency. The external diameter differed by 0.05 mm on average.ConclusionsOur results demonstrate wide variation in the interpretation of the French scale by different manufacturers of medical devices. This has the potential to lead to problems using coaxial systems especially when the products are from different manufacturers. It is recommended that standard labelling should be employed by all manufacturers conveying specific details of the equipment. Given the wide variation in the interpretation of the French scale, our opinion is that this scale either needs to be abandoned or be strictly defined and followed.« less

Intraspecific variation in reproductive traits of burrowing owls

USGS Publications Warehouse

Conway, Meaghan; Nadeau, Christopher P.; Conway, Courtney J.

2012-01-01

Reviews of hatching asynchrony in birds recommended more studies on intraspecific variation in the extent of hatching asynchrony. We examined intraspecific variation in clutch size, laying chronology, onset of incubation, incubation period, and hatching asynchrony in burrowing owls (Athene cunicularia) in the Imperial Valley of California. Mean clutch size was 7.4 eggs and owls averaged 0.5 eggs laid per day. Females varied considerably in laying interval and onset of incubation (range = 1st to 9th egg in the clutch). The mean incubation period was 21.9 days. Hatching interval also varied greatly among females (x = 0.8, range 0.1-2.0 days between successively hatched eggs). Past burrowing owl studies have largely overlooked the substantial intraspecific variation in these traits or have reported estimates that differ from ours. Future studies designed to identify the environmental factors that explain the large intraspecific variation in these traits will likely provide insights into the constraints on local abundance.

Variations in the size of focal nodular hyperplasia on magnetic resonance imaging.

PubMed

Ramírez-Fuentes, C; Martí-Bonmatí, L; Torregrosa, A; Del Val, A; Martínez, C

2013-01-01

To evaluate the changes in the size of focal nodular hyperplasia (FNH) during long-term magnetic resonance imaging (MRI) follow-up. We reviewed 44 FNHs in 30 patients studied with MRI with at least two MRI studies at least 12 months apart. We measured the largest diameter of the lesion (inmm) in contrast-enhanced axial images and calculated the percentage of variation as the difference between the maximum diameter in the follow-up and the maximum diameter in the initial study. We defined significant variation in size as variation greater than 20%. We also analyzed predisposing hormonal factors. The mean interval between the two imaging studies was 35±2 months (range: 12-94). Most lesions (80%) remained stable during follow-up. Only 9 of the 44 lesions (20%) showed a significant variation in diameter: 7 (16%) decreased in size and 2 (4%) increased, with variations that reached the double of the initial size. The change in size was not related to pregnancy, menopause, or the use of birth control pills or corticoids. Changes in the size of FNHs during follow-up are relatively common and should not lead to a change in the diagnosis. These variations in size seem to be independent of hormonal factors that are considered to predispose. Copyright © 2011 SERAM. Published by Elsevier Espana. All rights reserved.

Factor associated variations in the home range of a resident Adriatic common bottlenose dolphin population.

PubMed

Rako-Gospić, Nikolina; Radulović, Marko; Vučur, Tihana; Pleslić, Grgur; Holcer, Draško; Mackelworth, Peter

2017-11-15

This study investigates the influence of the most dominant factors (association patterns, gender, natal philopatry and anthropogenic pressure) on the home range size of the 44 most resident common bottlenose dolphins (Tursiops truncatus) inhabiting the waters of the Cres-Lošinj archipelago (north Adriatic Sea, Croatia), a recently declared NATURA 2000 SCI. Results show that variations in home range patterns (MCP, 95% KDE and 50% KDE home range size) among the individual resident dolphins are primarily related to differences in gender and reflect the way in which different genders respond to external stressors. In addition, results confirm the seasonal influence of nautical tourism on both female and male dolphins through changes in their home range sizes. The overall results improve current knowledge of the main anthropogenic threats that should be taken into consideration when developing conservation measures to be applied to this Cres and Lošinj SCI. Copyright © 2017 Elsevier Ltd. All rights reserved.

Variation in polyp size estimation among endoscopists and impact on surveillance intervals.

PubMed

Chaptini, Louis; Chaaya, Adib; Depalma, Fedele; Hunter, Krystal; Peikin, Steven; Laine, Loren

2014-10-01

Accurate estimation of polyp size is important because it is used to determine the surveillance interval after polypectomy. To evaluate the variation and accuracy in polyp size estimation among endoscopists and the impact on surveillance intervals after polypectomy. Web-based survey. A total of 873 members of the American Society for Gastrointestinal Endoscopy. Participants watched video recordings of 4 polypectomies and were asked to estimate the polyp sizes. Proportion of participants with polyp size estimates within 20% of the correct measurement and the frequency of incorrect surveillance intervals based on inaccurate size estimates. Polyp size estimates were within 20% of the correct value for 1362 (48%) of 2812 estimates (range 39%-59% for the 4 polyps). Polyp size was overestimated by >20% in 889 estimates (32%, range 15%-49%) and underestimated by >20% in 561 (20%, range 4%-46%) estimates. Incorrect surveillance intervals because of overestimation or underestimation occurred in 272 (10%) of the 2812 estimates (range 5%-14%). Participants in a private practice setting overestimated the size of 3 or of all 4 polyps by >20% more often than participants in an academic setting (difference = 7%; 95% confidence interval, 1%-11%). Survey design with the use of video clips. Substantial overestimation and underestimation of polyp size occurs with visual estimation leading to incorrect surveillance intervals in 10% of cases. Our findings support routine use of measurement tools to improve polyp size estimates. Copyright © 2014 American Society for Gastrointestinal Endoscopy. Published by Elsevier Inc. All rights reserved.

Ecological and evolutionary influences on body size and shape in the Galápagos marine iguana (Amblyrhynchus cristatus).

PubMed

Chiari, Ylenia; Glaberman, Scott; Tarroso, Pedro; Caccone, Adalgisa; Claude, Julien

2016-07-01

Oceanic islands are often inhabited by endemic species that have undergone substantial morphological evolutionary change due to processes of multiple colonizations from various source populations, dispersal, and local adaptation. Galápagos marine iguanas are an example of an island endemic exhibiting high morphological diversity, including substantial body size variation among populations and sexes, but the causes and magnitude of this variation are not well understood. We obtained morphological measurements from marine iguanas throughout their distribution range. These data were combined with genetic and local environmental data from each population to investigate the effects of evolutionary history and environmental conditions on body size and shape variation and sexual dimorphism. Our results indicate that body size and shape are highly variable among populations. Sea surface temperature and island perimeter, but not evolutionary history as depicted by phylogeographic patterns in this species, explain variation in body size among populations. Conversely, evolutionary history, but not environmental parameters or island size, was found to influence variation in body shape among populations. Finally, in all populations except one, we found strong sexual dimorphism in body size and shape in which males are larger, with higher heads than females, while females have longer heads than males. Differences among populations suggest that plasticity and/or genetic adaptation may shape body size and shape variation in marine iguanas. This study will help target future investigations to address the contribution of plasticity versus genetic adaptation on size and shape variation in marine iguanas.

Climatic and geographic predictors of life history variation in Eastern Massasauga (Sistrurus catenatus): A range-wide synthesis.

PubMed

Hileman, Eric T; King, Richard B; Adamski, John M; Anton, Thomas G; Bailey, Robyn L; Baker, Sarah J; Bieser, Nickolas D; Bell, Thomas A; Bissell, Kristin M; Bradke, Danielle R; Campa, Henry; Casper, Gary S; Cedar, Karen; Cross, Matthew D; DeGregorio, Brett A; Dreslik, Michael J; Faust, Lisa J; Harvey, Daniel S; Hay, Robert W; Jellen, Benjamin C; Johnson, Brent D; Johnson, Glenn; Kiel, Brooke D; Kingsbury, Bruce A; Kowalski, Matthew J; Lee, Yu Man; Lentini, Andrew M; Marshall, John C; Mauger, David; Moore, Jennifer A; Paloski, Rori A; Phillips, Christopher A; Pratt, Paul D; Preney, Thomas; Prior, Kent A; Promaine, Andrew; Redmer, Michael; Reinert, Howard K; Rouse, Jeremy D; Shoemaker, Kevin T; Sutton, Scott; VanDeWalle, Terry J; Weatherhead, Patrick J; Wynn, Doug; Yagi, Anne

2017-01-01

Elucidating how life history traits vary geographically is important to understanding variation in population dynamics. Because many aspects of ectotherm life history are climate-dependent, geographic variation in climate is expected to have a large impact on population dynamics through effects on annual survival, body size, growth rate, age at first reproduction, size-fecundity relationship, and reproductive frequency. The Eastern Massasauga (Sistrurus catenatus) is a small, imperiled North American rattlesnake with a distribution centered on the Great Lakes region, where lake effects strongly influence local conditions. To address Eastern Massasauga life history data gaps, we compiled data from 47 study sites representing 38 counties across the range. We used multimodel inference and general linear models with geographic coordinates and annual climate normals as explanatory variables to clarify patterns of variation in life history traits. We found strong evidence for geographic variation in six of nine life history variables. Adult female snout-vent length and neonate mass increased with increasing mean annual precipitation. Litter size decreased with increasing mean temperature, and the size-fecundity relationship and growth prior to first hibernation both increased with increasing latitude. The proportion of gravid females also increased with increasing latitude, but this relationship may be the result of geographically varying detection bias. Our results provide insights into ectotherm life history variation and fill critical data gaps, which will inform Eastern Massasauga conservation efforts by improving biological realism for models of population viability and climate change.

SU-F-R-32: Evaluation of MRI Acquisition Parameter Variations On Texture Feature Extraction Using ACR Phantom

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

Xie, Y; Wang, J; Wang, C

Purpose: To investigate the sensitivity of classic texture features to variations of MRI acquisition parameters. Methods: This study was performed on American College of Radiology (ACR) MRI Accreditation Program Phantom. MR imaging was acquired on a GE 750 3T scanner with XRM explain gradient, employing a T1-weighted images (TR/TE=500/20ms) with the following parameters as the reference standard: number of signal average (NEX) = 1, matrix size = 256×256, flip angle = 90°, slice thickness = 5mm. The effect of the acquisition parameters on texture features with and without non-uniformity correction were investigated respectively, while all the other parameters were keptmore » as reference standard. Protocol parameters were set as follows: (a). NEX = 0.5, 2 and 4; (b).Phase encoding steps = 128, 160 and 192; (c). Matrix size = 128×128, 192×192 and 512×512. 32 classic texture features were generated using the classic gray level run length matrix (GLRLM) and gray level co-occurrence matrix (GLCOM) from each image data set. Normalized range ((maximum-minimum)/mean) was calculated to determine variation among the scans with different protocol parameters. Results: For different NEX, 31 out of 32 texture features’ range are within 10%. For different phase encoding steps, 31 out of 32 texture features’ range are within 10%. For different acquisition matrix size without non-uniformity correction, 14 out of 32 texture features’ range are within 10%; for different acquisition matrix size with non-uniformity correction, 16 out of 32 texture features’ range are within 10%. Conclusion: Initial results indicated that those texture features that range within 10% are less sensitive to variations in T1-weighted MRI acquisition parameters. This might suggest that certain texture features might be more reliable to be used as potential biomarkers in MR quantitative image analysis.« less

Sizing ocean giants: patterns of intraspecific size variation in marine megafauna

PubMed Central

Balk, Meghan A.; Benfield, Mark C.; Branch, Trevor A.; Chen, Catherine; Cosgrove, James; Dove, Alistair D.M.; Gaskins, Lindsay C.; Helm, Rebecca R.; Hochberg, Frederick G.; Lee, Frank B.; Marshall, Andrea; McMurray, Steven E.; Schanche, Caroline; Stone, Shane N.; Thaler, Andrew D.

2015-01-01

What are the greatest sizes that the largest marine megafauna obtain? This is a simple question with a difficult and complex answer. Many of the largest-sized species occur in the world’s oceans. For many of these, rarity, remoteness, and quite simply the logistics of measuring these giants has made obtaining accurate size measurements difficult. Inaccurate reports of maximum sizes run rampant through the scientific literature and popular media. Moreover, how intraspecific variation in the body sizes of these animals relates to sex, population structure, the environment, and interactions with humans remains underappreciated. Here, we review and analyze body size for 25 ocean giants ranging across the animal kingdom. For each taxon we document body size for the largest known marine species of several clades. We also analyze intraspecific variation and identify the largest known individuals for each species. Where data allows, we analyze spatial and temporal intraspecific size variation. We also provide allometric scaling equations between different size measurements as resources to other researchers. In some cases, the lack of data prevents us from fully examining these topics and instead we specifically highlight these deficiencies and the barriers that exist for data collection. Overall, we found considerable variability in intraspecific size distributions from strongly left- to strongly right-skewed. We provide several allometric equations that allow for estimation of total lengths and weights from more easily obtained measurements. In several cases, we also quantify considerable geographic variation and decreases in size likely attributed to humans. PMID:25649000

Variation in reproductive life history traits between two populations of Blackbanded Darters (Percina nigrofasciata)

USGS Publications Warehouse

Hughey, Myra C.; Heins, David C.; Jelks, Howard L.; Ory, Bridget A.; Jordan, Frank

2012-01-01

We examined the life history of Blackbanded Darters (Percina nigrofasciata) from two streams in the Choctawhatchee River drainage, Florida, over a three-year study period. Blackbanded Darters from Turkey Creek were longer than fish from Ten Mile Creek; however, size-adjusted clutch and egg sizes were similar between populations. Larger females produced larger clutches, whereas egg size did not vary with female body size. Seasonally, clutch sizes were greater in May than in August. When contrasted with previous studies of Blackbanded Darters in Alabama and Louisiana, the reproductive season of Blackbanded Darters in Florida was unusually long, ceasing for only a few months in late fall. The reproductive season was longer in Turkey Creek than in Ten Mile Creek. Differences in thermal regime among streams may explain differences in life history traits among local and distant populations of Blackbanded Darters. This research, alone and in combination with previous studies of this species, emphasizes two main points. First, it reaffirms that life history studies based on a single locality or conducted at a single point in time may fail to capture the full range of variation in life history traits. Second, it highlights the extensive phenotypic variation found in species with broad geographic ranges. Such species lend themselves to comparative and experimental research on patterns and causes of life history variation.

Genome size evolution at the speciation level: the cryptic species complex Brachionus plicatilis (Rotifera).

PubMed

Stelzer, Claus-Peter; Riss, Simone; Stadler, Peter

2011-04-07

Studies on genome size variation in animals are rarely done at lower taxonomic levels, e.g., slightly above/below the species level. Yet, such variation might provide important clues on the tempo and mode of genome size evolution. In this study we used the flow-cytometry method to study the evolution of genome size in the rotifer Brachionus plicatilis, a cryptic species complex consisting of at least 14 closely related species. We found an unexpectedly high variation in this species complex, with genome sizes ranging approximately seven-fold (haploid '1C' genome sizes: 0.056-0.416 pg). Most of this variation (67%) could be ascribed to the major clades of the species complex, i.e. clades that are well separated according to most species definitions. However, we also found substantial variation (32%) at lower taxonomic levels--within and among genealogical species--and, interestingly, among species pairs that are not completely reproductively isolated. In one genealogical species, called B. 'Austria', we found greatly enlarged genome sizes that could roughly be approximated as multiples of the genomes of its closest relatives, which suggests that whole-genome duplications have occurred early during separation of this lineage. Overall, genome size was significantly correlated to egg size and body size, even though the latter became non-significant after controlling for phylogenetic non-independence. Our study suggests that substantial genome size variation can build up early during speciation, potentially even among isolated populations. An alternative, but not mutually exclusive interpretation might be that reproductive isolation tends to build up unusually slow in this species complex.

Genome size evolution at the speciation level: The cryptic species complex Brachionus plicatilis (Rotifera)

PubMed Central

2011-01-01

Background Studies on genome size variation in animals are rarely done at lower taxonomic levels, e.g., slightly above/below the species level. Yet, such variation might provide important clues on the tempo and mode of genome size evolution. In this study we used the flow-cytometry method to study the evolution of genome size in the rotifer Brachionus plicatilis, a cryptic species complex consisting of at least 14 closely related species. Results We found an unexpectedly high variation in this species complex, with genome sizes ranging approximately seven-fold (haploid '1C' genome sizes: 0.056-0.416 pg). Most of this variation (67%) could be ascribed to the major clades of the species complex, i.e. clades that are well separated according to most species definitions. However, we also found substantial variation (32%) at lower taxonomic levels - within and among genealogical species - and, interestingly, among species pairs that are not completely reproductively isolated. In one genealogical species, called B. 'Austria', we found greatly enlarged genome sizes that could roughly be approximated as multiples of the genomes of its closest relatives, which suggests that whole-genome duplications have occurred early during separation of this lineage. Overall, genome size was significantly correlated to egg size and body size, even though the latter became non-significant after controlling for phylogenetic non-independence. Conclusions Our study suggests that substantial genome size variation can build up early during speciation, potentially even among isolated populations. An alternative, but not mutually exclusive interpretation might be that reproductive isolation tends to build up unusually slow in this species complex. PMID:21473744

The Effects of Environmental Characteristics on the Structure of Hospital Clusters.

ERIC Educational Resources Information Center

Fennell, Mary L.

1980-01-01

The population ecology view that variation in sets or clusters of organizations should be isomorphic with variation in cluster environment was used to explain structural variation among hospital clusters. Cluster differentiation seems to be casually affected by range of services, average hospital size, and the periodic closing of hospitals.…

Genome Size Variation in the Genus Carthamus (Asteraceae, Cardueae): Systematic Implications and Additive Changes During Allopolyploidization

PubMed Central

GARNATJE, TERESA; GARCIA, SÒNIA; VILATERSANA, ROSER; VALLÈS, JOAN

2006-01-01

• Background and Aims Plant genome size is an important biological characteristic, with relationships to systematics, ecology and distribution. Currently, there is no information regarding nuclear DNA content for any Carthamus species. In addition to improving the knowledge base, this research focuses on interspecific variation and its implications for the infrageneric classification of this genus. Genome size variation in the process of allopolyploid formation is also addressed. • Methods Nuclear DNA samples from 34 populations of 16 species of the genus Carthamus were assessed by flow cytometry using propidium iodide. • Key Results The 2C values ranged from 2·26 pg for C. leucocaulos to 7·46 pg for C. turkestanicus, and monoploid genome size (1Cx-value) ranged from 1·13 pg in C. leucocaulos to 1·53 pg in C. alexandrinus. Mean genome sizes differed significantly, based on sectional classification. Both allopolyploid species (C. creticus and C. turkestanicus) exhibited nuclear DNA contents in accordance with the sum of the putative parental C-values (in one case with a slight reduction, frequent in polyploids), supporting their hybrid origin. • Conclusions Genome size represents a useful tool in elucidating systematic relationships between closely related species. A considerable reduction in monoploid genome size, possibly due to the hybrid formation, is also reported within these taxa. PMID:16390843

Combined use of leaf size and economics traits allows direct comparison of hydrophyte and terrestrial herbaceous adaptive strategies.

PubMed

Pierce, Simon; Brusa, Guido; Sartori, Matteo; Cerabolini, Bruno E L

2012-04-01

Hydrophytes generally exhibit highly acquisitive leaf economics. However, a range of growth forms is evident, from small, free-floating and rapidly growing Lemniden to large, broad-leaved Nymphaeiden, denoting variability in adaptive strategies. Traits used to classify adaptive strategies in terrestrial species, such as canopy height, are not applicable to hydrophytes. We hypothesize that hydrophyte leaf size traits and economics exhibit sufficient overlap with terrestrial species to allow a common classification of plant functional types, sensu Grime's CSR theory. Leaf morpho-functional traits were measured for 61 species from 47 water bodies in lowland continental, sub-alpine and alpine bioclimatic zones in southern Europe and compared against the full leaf economics spectrum and leaf size range of terrestrial herbs, and between hydrophyte growth forms. Hydrophytes differed in the ranges and mean values of traits compared with herbs, but principal components analysis (PCA) demonstrated that both groups shared axes of trait variability: PCA1 encompassed size variation (area and mass), and PCA2 ranged from relatively dense, carbon-rich leaves to nitrogen-rich leaves of high specific leaf area (SLA). Most growth forms exhibited trait syndromes directly equivalent to herbs classified as R adapted, although Nymphaeiden ranged between C and SR adaptation. Our findings support the hypothesis that hydrophyte adaptive strategy variation reflects fundamental trade-offs in economics and size that govern all plants, and that hydrophyte adaptive strategies can be directly compared with terrestrial species by combining leaf economics and size traits.

Evolutionary and Taxonomic Implications of Variation in Nuclear Genome Size: Lesson from the Grass Genus Anthoxanthum (Poaceae)

PubMed Central

Chumová, Zuzana; Krejčíková, Jana; Mandáková, Terezie; Suda, Jan; Trávníček, Pavel

2015-01-01

The genus Anthoxanthum (sweet vernal grass, Poaceae) represents a taxonomically intricate polyploid complex with large phenotypic variation and its evolutionary relationships still poorly resolved. In order to get insight into the geographic distribution of ploidy levels and assess the taxonomic value of genome size data, we determined C- and Cx-values in 628 plants representing all currently recognized European species collected from 197 populations in 29 European countries. The flow cytometric estimates were supplemented by conventional chromosome counts. In addition to diploids, we found two low (rare 3x and common 4x) and one high (~16x–18x) polyploid levels. Mean holoploid genome sizes ranged from 5.52 pg in diploid A. alpinum to 44.75 pg in highly polyploid A. amarum, while the size of monoploid genomes ranged from 2.75 pg in tetraploid A. alpinum to 9.19 pg in diploid A. gracile. In contrast to Central and Northern Europe, which harboured only limited cytological variation, a much more complex pattern of genome sizes was revealed in the Mediterranean, particularly in Corsica. Eight taxonomic groups that partly corresponded to traditionally recognized species were delimited based on genome size values and phenotypic variation. Whereas our data supported the merger of A. aristatum and A. ovatum, eastern Mediterranean populations traditionally referred to as diploid A. odoratum were shown to be cytologically distinct, and may represent a new taxon. Autopolyploid origin was suggested for 4x A. alpinum. In contrast, 4x A. odoratum seems to be an allopolyploid, based on the amounts of nuclear DNA. Intraspecific variation in genome size was observed in all recognized species, the most striking example being the A. aristatum/ovatum complex. Altogether, our study showed that genome size can be a useful taxonomic marker in Anthoxathum to not only guide taxonomic decisions but also help resolve evolutionary relationships in this challenging grass genus. PMID:26207824

Evolutionary and Taxonomic Implications of Variation in Nuclear Genome Size: Lesson from the Grass Genus Anthoxanthum (Poaceae).

PubMed

Chumová, Zuzana; Krejčíková, Jana; Mandáková, Terezie; Suda, Jan; Trávníček, Pavel

2015-01-01

The genus Anthoxanthum (sweet vernal grass, Poaceae) represents a taxonomically intricate polyploid complex with large phenotypic variation and its evolutionary relationships still poorly resolved. In order to get insight into the geographic distribution of ploidy levels and assess the taxonomic value of genome size data, we determined C- and Cx-values in 628 plants representing all currently recognized European species collected from 197 populations in 29 European countries. The flow cytometric estimates were supplemented by conventional chromosome counts. In addition to diploids, we found two low (rare 3x and common 4x) and one high (~16x-18x) polyploid levels. Mean holoploid genome sizes ranged from 5.52 pg in diploid A. alpinum to 44.75 pg in highly polyploid A. amarum, while the size of monoploid genomes ranged from 2.75 pg in tetraploid A. alpinum to 9.19 pg in diploid A. gracile. In contrast to Central and Northern Europe, which harboured only limited cytological variation, a much more complex pattern of genome sizes was revealed in the Mediterranean, particularly in Corsica. Eight taxonomic groups that partly corresponded to traditionally recognized species were delimited based on genome size values and phenotypic variation. Whereas our data supported the merger of A. aristatum and A. ovatum, eastern Mediterranean populations traditionally referred to as diploid A. odoratum were shown to be cytologically distinct, and may represent a new taxon. Autopolyploid origin was suggested for 4x A. alpinum. In contrast, 4x A. odoratum seems to be an allopolyploid, based on the amounts of nuclear DNA. Intraspecific variation in genome size was observed in all recognized species, the most striking example being the A. aristatum/ovatum complex. Altogether, our study showed that genome size can be a useful taxonomic marker in Anthoxathum to not only guide taxonomic decisions but also help resolve evolutionary relationships in this challenging grass genus.

Geographic variation in body size and its relationship with environmental gradients in the Oriental Garden Lizard, Calotes versicolor.

PubMed

Wei, Xiaomei; Yan, Linmiao; Zhao, Chengjian; Zhang, Yueyun; Xu, Yongli; Cai, Bo; Jiang, Ni; Huang, Yong

2018-05-01

Patterns of geographic variation in body size are predicted to evolve as adaptations to local environmental gradients. However, many of these clinal patterns in body size, such as Bergmann's rule, are controversial and require further investigation into ectotherms such as reptiles on a regional scale. To examine the environmental variables (temperature, precipitation, topography and primary productivity) that shaped patterns of geographic variation in body size in the reptile Calotes versicolor , we sampled 180 adult specimens (91 males and 89 females) at 40 locations across the species range in China. The MANOVA results suggest significant sexual size dimorphism in C. versicolor ( F 23,124  = 11.32, p  < .001). Our results showed that C. versicolor failed to fit the Bergmann's rule. We found that the most important predictors of variation in body size of C. versicolor differed for males and females, but mechanisms related to heat balance and water availability hypotheses were involved in both sexes. Temperature seasonality, precipitation of the driest month, precipitation seasonality, and precipitation of the driest quarter were the most important predictors of variation in body size in males, whereas mean precipitation of the warmest quarter, mean temperature of the wettest quarter, precipitation seasonality, and precipitation of the wettest month were most important for body size variation in females. The discrepancy between patterns of association between the sexes suggested that different selection pressures may be acting in males and females.

Speckle size in optical Fourier domain imaging

NASA Astrophysics Data System (ADS)

Lamouche, G.; Vergnole, S.; Bisaillon, C.-E.; Dufour, M.; Maciejko, R.; Monchalin, J.-P.

2007-06-01

As in conventional time-domain optical coherence tomography (OCT), speckle is inherent to any Optical Fourier Domain Imaging (OFDI) of biological tissue. OFDI is also known as swept-source OCT (SS-OCT). The axial speckle size is mainly determined by the OCT resolution length and the transverse speckle size by the focusing optics illuminating the sample. There is also a contribution from the sample related to the number of scatterers contained within the probed volume. In the OFDI data processing, there is some liberty in selecting the range of wavelengths used and this allows variation in the OCT resolution length. Consequently the probed volume can be varied. By performing measurements on an optical phantom with a controlled density of discrete scatterers and by changing the probed volume with different range of wavelengths in the OFDI data processing, there is an obvious change in the axial speckle size, but we show that there is also a less obvious variation in the transverse speckle size. This work contributes to a better understanding of speckle in OCT.

A comparison of certain methods of measuring ranges of small mammals

USGS Publications Warehouse

Stickel, L.F.

1954-01-01

SUMMARY: A comparison is made of different methods of determining size of home range from grid trapping data. Studies of artificial populations show that a boundary strip method of measuring area and an adjusted range length give sizes closer to the true range than do minimum area or observed range length methods. In simulated trapping of artificial populations, the known range size increases with successive captures until a level is reached that approximates the true range. The same general pattern is followed whether traps are visited at random or traps nearer the center of the range are favored; but when central traps are favored the curve levels more slowly. Range size is revealed with fewer captures when traps are far apart than when they are close together. The curve levels more slowly for oblong ranges than for circular ranges of the same area. Fewer captures are required to determine range length than to determine range area. Other examples of simulated trapping in artificial populations are used to provide measurements of distances from the center of activity and distances between successive captures. These are compared with similar measurements taken from Peromyscus trapping data. The similarity of range sizes found in certain field comparisons of area trapping, colored scat collections, and trailing is cited. A comparison of home range data obtained by area trapping and nest box studies is discussed. It is shown that when traps are set too far apart to include two or more in the range of each animal, calculation of average range size gives biased results. The smaller ranges are not expressed and cannot be included in the averages. The result is that range estimates are smaller at closer spacings and greater at wider spacings, purely as a result of these erroneous calculations and not reflecting any varying behavior of the animals. The problem of variation in apparent home range with variation in trap spacing is considered further by trapping in an artificial population. It is found that trap spacing can alter the apparent size of range even when biological factors are excluded and trap visiting is random. The desirability of excluding travels outside the normal range from home range calculations is discussed. Effects of varying the trapping plan by setting alternate rows of traps, or setting two traps per site, are discussed briefly.

Variation in ejecta size with ejection velocity

NASA Technical Reports Server (NTRS)

Vickery, Ann M.

1987-01-01

The sizes and ranges of over 25,000 secondary craters around twelve large primaries on three different planets were measured and used to infer the size-velocity distribution of that portion of the primary crater ejecta that produced the secondaries. The ballistic equation for spherical bodies was used to convert the ranges to velocities, and the velocities and crater sizes were used in the appropriate Schmidt-Holsapple scaling relation of estimate ejecta sizes, and the velocity exponent was determined. The latter are generally between -1 and -13, with an average value of about -1.9. Problems with data collection made it impossible to determine a simple, unique relation between size and velocity.

Navigating aerial transects with a laptop computer

USGS Publications Warehouse

Anthony, R. Michael; Stehn, R.A.

1994-01-01

SUMMARY: A comparison is made of different methods of determining size of home range from grid trapping data. Studies of artificial populations show that a boundary strip method of measuring area and an adjusted range length give sizes closer to the true range than do minimum area or observed range length methods. In simulated trapping of artificial populations, the known range size increases with successive captures until a level is reached that approximates the true range. The same general pattern is followed whether traps are visited at random or traps nearer the center of the range are favored; but when central traps are favored the curve levels more slowly. Range size is revealed with fewer captures when traps are far apart than when they are close together. The curve levels more slowly for oblong ranges than for circular ranges of the same area. Fewer captures are required to determine range length than to determine range area. Other examples of simulated trapping in artificial populations are used to provide measurements of distances from the center of activity and distances between successive captures. These are compared with similar measurements taken from Peromyscus trapping data. The similarity of range sizes found in certain field comparisons of area trapping, colored scat collections, and trailing is cited. A comparison of home range data obtained by area trapping and nest box studies is discussed. It is shown that when traps are set too far apart to include two or more in the range of each animal, calculation of average range size gives biased results. The smaller ranges are not expressed and cannot be included in the averages. The result is that range estimates are smaller at closer spacings and greater at wider spacings, purely as a result of these erroneous calculations and not reflecting any varying behavior of the animals. The problem of variation in apparent home range with variation in trap spacing is considered further by trapping in an artificial population. It is found that trap spacing can alter the apparent size of range even when biological factors are excluded and trap visiting is random. The desirability of excluding travels outside the normal range from home range calculations is discussed. Effects of varying the trapping plan by setting alternate rows of traps, or setting two traps per site, are discussed briefly.

DNA barcoding as a tool for elucidating species delineation in wide-ranging species as illustrated by owls (Tytonidae and Strigidae).

PubMed

Nijman, Vincent; Aliabadian, Mansour

2013-11-01

The mitochondrial cytochrome c-oxidase subunit I (cox1) can serve as a fast and accurate marker for the identification of animal species, and for the discovery of new species across the tree of life. Distinguishing species using this universal molecular marker, a technique known as DNA barcoding, relies on the identifying the gap between intra- and interspecific divergence. One of the difficulties could be wide-ranging, cosmopolitan species that show large amounts of morphological variation. The barn owl Tyto alba is a case in point. It occurs worldwide and varies morphologically, leading to the recognition of many subspecies or, more recently, species. We analysed data from the cox1 gene for 31 individuals of seven subspecies, and compared this with 214 sequences from 29 other owl species. Phylogenetic analysis of the T. alba samples gives very strong support for an Old World alba-clade (three subspecies) and a New World furcata-clade (four subspecies) that are genetically equidistant. The amount of intraspecific variation within each of these clades ranges from 0.66-0.99%, but variation among these clades ranges from 5.33-6.20%. Combined these data suggest that barn owl of the Old World is indeed best considered a separate species different from that of the New World. For combined dataset, sample size of owl species (n between 1 and 21 sequences) increased with geographic range size but we did not find significant relationships between interspecific divergence and sample size or between interspecific divergence and geographic range. For 21/24 species of owls with sample sizes of n ≥4 the maximum interspecific divergences was ≤ 3.00%. However, similar to those found in barn owls, the largest amount of divergence (3.23-4.09%) was present in two other wide-ranging species (Strix nebulosa and Aegolius funereus) raising the possibility of multiple species in other wide-ranging owls as well.

Effects of recruitment, growth, and exploitation on walleye population size structure in northern Wisconsin lakes

USGS Publications Warehouse

Hansen, Michael J.; Nate, Nancy A.

2014-01-01

We evaluated the dynamics of walleye Sander vitreus population size structure, as indexed by the proportional size distribution (PSD) of quality-length fish, in Escanaba Lake during 1967–2003 and in 204 other lakes in northern Wisconsin during 1990–2011. We estimated PSD from angler-caught walleyes in Escanaba Lake and from spring electrofishing in 204 other lakes, and then related PSD to annual estimates of recruitment to age-3, length at age 3, and annual angling exploitation rate. In Escanaba Lake during 1967–2003, annual estimates of PSD were highly dynamic, growth (positively) explained 35% of PSD variation, recruitment explained only 3% of PSD variation, and exploitation explained only 7% of PSD variation. In 204 other northern Wisconsin lakes during 1990–2011, PSD varied widely among lakes, recruitment (negatively) explained 29% of PSD variation, growth (positively) explained 21% of PSD variation, and exploitation explained only 4% of PSD variation. We conclude that population size structure was most strongly driven by recruitment and growth, rather than exploitation, in northern Wisconsin walleye populations. Studies of other species over wide spatial and temporal ranges of recruitment, growth, and mortality are needed to determine which dynamic rate most strongly influences population size structure of other species. Our findings indicate a need to be cautious about assuming exploitation is a strong driver of walleye population size structure.

Playing by the rules? Phenotypic adaptation to temperate environments in an American marsupial

PubMed Central

Harrigan, Ryan J.; Wayne, Robert K.

2018-01-01

Phenotypic variation along environmental gradients can provide evidence suggesting local adaptation has shaped observed morphological disparities. These differences, in traits such as body and extremity size, as well as skin and coat pigmentation, may affect the overall fitness of individuals in their environments. The Virginia opossum (Didelphis virginiana) is a marsupial that shows phenotypic variation across its range, one that has recently expanded into temperate environments. It is unknown, however, whether the variation observed in the species fits adaptive ecogeographic patterns, or if phenotypic change is associated with any environmental factors. Using phenotypic measurements of over 300 museum specimens of Virginia opossum, collected throughout its distribution range, we applied regression analysis to determine if phenotypes change along a latitudinal gradient. Then, using predictors from remote-sensing databases and a random forest algorithm, we tested environmental models to find the most important variables driving the phenotypic variation. We found that despite the recent expansion into temperate environments, the phenotypic variation in the Virginia opossum follows a latitudinal gradient fitting three adaptive ecogeographic patterns codified under Bergmann’s, Allen’s and Gloger’s rules. Temperature seasonality was an important predictor of body size variation, with larger opossums occurring at high latitudes with more seasonal environments. Annual mean temperature predicted important variation in extremity size, with smaller extremities found in northern populations. Finally, we found that precipitation and temperature seasonality as well as low temperatures were strong environmental predictors of skin and coat pigmentation variation; darker opossums are distributed at low latitudes in warmer environments with higher precipitation seasonality. These results indicate that the adaptive mechanisms underlying the variation in body size, extremity size and pigmentation are related to the resource seasonality, heat conservation, and pathogen-resistance hypotheses, respectively. Our findings suggest that marsupials may be highly susceptible to environmental changes, and in the case of the Virginia opossum, the drastic phenotypic evolution in northern populations may have arisen rapidly, facilitating the colonization of seasonal and colder habitats of temperate North America. PMID:29607255

Body-size trends of the extinct giant shark Carcharocles megalodon: a deep-time perspective on marine apex predators.

PubMed

Pimiento, Catalina; Balk, Meghan A

2015-06-01

The extinct shark Carcharocles megalodon is one of the largest marine apex predators ever to exist. Nonetheless, little is known about its body-size variations through time and space. Here, we studied the body-size trends of C. megalodon through its temporal and geographic range to better understand its ecology and evolution. Given that this species was the last of the megatooth lineage, a group of species that shows a purported size increase through time, we hypothesized that C. megalodon also displayed this trend, increasing in size over time and reaching its largest size prior to extinction. We found that C. megalodon body-size distribution was left-skewed (suggesting a long-term selective pressure favoring larger individuals), and presented significant geographic variation (possibly as a result of the heterogeneous ecological constraints of this cosmopolitan species) over geologic time. Finally, we found that stasis was the general mode of size evolution of C. megalodon (i.e., no net changes over time), contrasting with the trends of the megatooth lineage and our hypothesis. Given that C. megalodon is a relatively long-lived species with a widely distributed fossil record, we further used this study system to provide a deep-time perspective to the understanding of the body-size trends of marine apex predators. For instance, our results suggest that (1) a selective pressure in predatory sharks for consuming a broader range of prey may favor larger individuals and produce left-skewed distributions on a geologic time scale; (2) body-size variations in cosmopolitan apex marine predators may depend on their interactions with geographically discrete communities; and (3) the inherent characteristics of shark species can produce stable sizes over geologic time, regardless of the size trends of their lineages.

Body size and lean mass of brown bears across and within four diverse ecosystems

USGS Publications Warehouse

Hilderbrand, Grant V.; Gustine, David; Mangipane, Buck A.; Joly, Kyle; Leacock, William; Mangipane, Lindsey S.; Erlenbach, Joy; Sorum, Mathew; Cameron, Matthew; Belant, Jerrold L.; Cambier, Troy

2018-01-01

Variation in body size across populations of brown bears (Ursus arctos) is largely a function of the availability and quality of nutritional resources while plasticity within populations reflects utilized niche width with implications for population resiliency. We assessed skull size, body length, and lean mass of adult female and male brown bears in four Alaskan study areas that differed in climate, primary food resources, population density, and harvest regime. Full body-frame size, as evidenced by asymptotic skull size and body length, was achieved by 8 to 14 years of age across populations and sexes. Lean body mass of both sexes continued to increase throughout their life. Differences between populations existed for all morphological measures in both sexes, bears in ecosystems with abundant salmon were generally larger. Within all populations, broad variation was seen in body size measures of adults with females displaying roughly a 2-fold difference in lean mass and males showing a 3- to 4-fold difference. The high level of intraspecific variation seen across and within populations suggests the presence of multiple life-history strategies and niche variation relative to resource partitioning, risk tolerance or aversion, and competition. Further, this level of variation indicates broad potential to adapt to changes within a given ecosystem and across the species’ range.

Intrapopulational body size variation and cranial capacity variation in Middle Pleistocene humans: the Sima de los Huesos sample (Sierra de Atapuerca, Spain).

PubMed

Lorenzo, C; Carretero, J M; Arsuaga, J L; Gracia, A; Martínez, I

1998-05-01

A sexual dimorphism more marked than in living humans has been claimed for European Middle Pleistocene humans, Neandertals and prehistoric modern humans. In this paper, body size and cranial capacity variation are studied in the Sima de los Huesos Middle Pleistocene sample. This is the largest sample of non-modern humans found to date from one single site, and with all skeletal elements represented. Since the techniques available to estimate the degree of sexual dimorphism in small palaeontological samples are all unsatisfactory, we have used the bootstraping method to asses the magnitude of the variation in the Sima de los Huesos sample compared to modern human intrapopulational variation. We analyze size variation without attempting to sex the specimens a priori. Anatomical regions investigated are scapular glenoid fossa; acetabulum; humeral proximal and distal epiphyses; ulnar proximal epiphysis; radial neck; proximal femur; humeral, femoral, ulnar and tibial shaft; lumbosacral joint; patella; calcaneum; and talar trochlea. In the Sima de los Huesos sample only the humeral midshaft perimeter shows an unusual high variation (only when it is expressed by the maximum ratio, not by the coefficient of variation). In spite of that the cranial capacity range at Sima de los Huesos almost spans the rest of the European and African Middle Pleistocene range. The maximum ratio is in the central part of the distribution of modern human samples. Thus, the hypothesis of a greater sexual dimorphism in Middle Pleistocene populations than in modern populations is not supported by either cranial or postcranial evidence from Sima de los Huesos.

Genome size variation in deep-sea amphipods

PubMed Central

Jamieson, A. J.; Piertney, S. B.

2017-01-01

Genome size varies considerably across taxa, and extensive research effort has gone into understanding whether variation can be explained by differences in key ecological and life-history traits among species. The extreme environmental conditions that characterize the deep sea have been hypothesized to promote large genome sizes in eukaryotes. Here we test this supposition by examining genome sizes among 13 species of deep-sea amphipods from the Mariana, Kermadec and New Hebrides trenches. Genome sizes were estimated using flow cytometry and found to vary nine-fold, ranging from 4.06 pg (4.04 Gb) in Paralicella caperesca to 34.79 pg (34.02 Gb) in Alicella gigantea. Phylogenetic independent contrast analysis identified a relationship between genome size and maximum body size, though this was largely driven by those species that display size gigantism. There was a distinct shift in the genome size trait diversification rate in the supergiant amphipod A. gigantea relative to the rest of the group. The variation in genome size observed is striking and argues against genome size being driven by a common evolutionary history, ecological niche and life-history strategy in deep-sea amphipods. PMID:28989783

Combined use of leaf size and economics traits allows direct comparison of hydrophyte and terrestrial herbaceous adaptive strategies

PubMed Central

Pierce, Simon; Brusa, Guido; Sartori, Matteo; Cerabolini, Bruno E. L.

2012-01-01

Background and Aims Hydrophytes generally exhibit highly acquisitive leaf economics. However, a range of growth forms is evident, from small, free-floating and rapidly growing Lemniden to large, broad-leaved Nymphaeiden, denoting variability in adaptive strategies. Traits used to classify adaptive strategies in terrestrial species, such as canopy height, are not applicable to hydrophytes. We hypothesize that hydrophyte leaf size traits and economics exhibit sufficient overlap with terrestrial species to allow a common classification of plant functional types, sensu Grime's CSR theory. Methods Leaf morpho-functional traits were measured for 61 species from 47 water bodies in lowland continental, sub-alpine and alpine bioclimatic zones in southern Europe and compared against the full leaf economics spectrum and leaf size range of terrestrial herbs, and between hydrophyte growth forms. Key Results Hydrophytes differed in the ranges and mean values of traits compared with herbs, but principal components analysis (PCA) demonstrated that both groups shared axes of trait variability: PCA1 encompassed size variation (area and mass), and PCA2 ranged from relatively dense, carbon-rich leaves to nitrogen-rich leaves of high specific leaf area (SLA). Most growth forms exhibited trait syndromes directly equivalent to herbs classified as R adapted, although Nymphaeiden ranged between C and SR adaptation. Conclusions Our findings support the hypothesis that hydrophyte adaptive strategy variation reflects fundamental trade-offs in economics and size that govern all plants, and that hydrophyte adaptive strategies can be directly compared with terrestrial species by combining leaf economics and size traits. PMID:22337079

Seed size variation in the palm Euterpe edulis and the effects of seed predators on germination and seedling survival

NASA Astrophysics Data System (ADS)

Pizo, Marco A.; Von Allmen, Christiane; Morellato, L. Patricia C.

2006-05-01

Intraspecific variation in seed size is common in wild plant populations and has important consequences for the reproductive success of individual plants. Multiple, often conflicting evolutionary forces mediated by biotic as well as abiotic agents may maintain such a variation. In this paper we assessed seed size variation in a population of the threatened, commercially important palm Euterpe edulis in southeast Brazil. We investigated (i) how this variation affects the probability of attack by vertebrate and invertebrate post-dispersal seed predators, and (ii) if seed size influences the outcome of seeds damaged by beetles in terms of seed germination and early survival of seedlings. Euterpe edulis seeds varied in diameter from 8.3 to 14.1 mm. Neither insects nor rodents selected the seeds they preyed upon based on seed size. Seed germination and total, shoot and root biomasses of one-year seedlings were significantly and positively affected by seed size. Root biomass and seedling survival were negatively affected by seed damage caused by a scolytid beetle ( Coccotrypes palmarum) whose adults bore into seeds to consume part of the endosperm, but do not oviposit on them. Seed size had a marginally significant effect on seedling survival. Therefore, if any advantage is accrued by E. edulis individuals producing large seeds, this is because of greater seed germination success and seedling vigor. If this is so, even a relatively narrow range of variation in seed size as observed in the E. edulis population studied may translate into differential success of individual plants.

Space use of wintering waterbirds in India: Influence of trophic ecology on home-range size

USGS Publications Warehouse

Namgail, Tsewang; Takekawa, John Y.; Balachandran, Sivananinthaperumal; Sathiyaselvam, Ponnusamy; Mundkur, Taej; Newman, Scott H.

2014-01-01

Relationship between species' home range and their other biological traits remains poorly understood, especially in migratory birds due to the difficulty associated with tracking them. Advances in satellite telemetry and remote sensing techniques have proved instrumental in overcoming such challenges. We studied the space use of migratory ducks through satellite telemetry with an objective of understanding the influence of body mass and feeding habits on their home-range sizes. We marked 26 individuals, representing five species of migratory ducks, with satellite transmitters during two consecutive winters in three Indian states. We used kernel methods to estimate home ranges and core use areas of these waterfowl, and assessed the influence of body mass and feeding habits on home-range size. Feeding habits influenced the home-range size of the migratory ducks. Carnivorous ducks had the largest home ranges, herbivorous ducks the smallest, while omnivorous species had intermediate home-ranges. Body mass did not explain variation in home-range size. To our knowledge, this is the first study of its kind on migratory ducks, and it has important implications for their conservation and management.

Laboratory measurements of selected optical, physical, chemical, and remote-sensing properties of five water mixtures containing Calvert clay and a nonfluorescing dye

NASA Technical Reports Server (NTRS)

Usry, J. W.; Whitlock, C. H.; Poole, L. R.; Witte, W. G., Jr.

1981-01-01

Total suspended solids concentrations ranged from 6.1 ppm to 24.3 ppm and sizes ranged between 1.5 micrometers and 10 micrometers with the most frequently occurring size less than 2 micrometers. Iron concentration was less than 1 percent of the total suspended solids. Nonfluorescing dye concentrations of the two mixtures were 20 ppm and 40 ppm. Attenuation coefficient for the five mixtures ranged from 4.8/m to 21.3/m. Variations in volume scattering function with phase angle were typical. Variations in attenuation and absorption coefficient with wavelength were similar for the mixtures without the dye. Attenuation coefficient of the mixtures with the dye increased for wavelengths less than 600 nm due to the dye's strong absorption peak near 500 nm. Reflectance increased as the concentration of Calvert clay increased and peaked near 600 nm. The nonfluorescent dye decreased the magnitude of the peak, but had practically no effect on the variation for wavelengths greater than 640 nm. At wavelengths less than 600 nm, the spectral variations of the mixtures with the dye were significantly different from those mixtures without the dye.

The evolution of island gigantism and body size variation in tortoises and turtles

PubMed Central

Jaffe, Alexander L.; Slater, Graham J.; Alfaro, Michael E.

2011-01-01

Extant chelonians (turtles and tortoises) span almost four orders of magnitude of body size, including the startling examples of gigantism seen in the tortoises of the Galapagos and Seychelles islands. However, the evolutionary determinants of size diversity in chelonians are poorly understood. We present a comparative analysis of body size evolution in turtles and tortoises within a phylogenetic framework. Our results reveal a pronounced relationship between habitat and optimal body size in chelonians. We found strong evidence for separate, larger optimal body sizes for sea turtles and island tortoises, the latter showing support for the rule of island gigantism in non-mammalian amniotes. Optimal sizes for freshwater and mainland terrestrial turtles are similar and smaller, although the range of body size variation in these forms is qualitatively greater. The greater number of potential niches in freshwater and terrestrial environments may mean that body size relationships are more complicated in these habitats. PMID:21270022

Climate and topography explain range sizes of terrestrial vertebrates

NASA Astrophysics Data System (ADS)

Li, Yiming; Li, Xianping; Sandel, Brody; Blank, David; Liu, Zetian; Liu, Xuan; Yan, Shaofei

2016-05-01

Identifying the factors that influence range sizes of species provides important insight into the distribution of biodiversity, and is crucial for predicting shifts in species ranges in response to climate change. Current climate (for example, climate variability and climate extremes), long-term climate change, evolutionary age, topographic heterogeneity, land area and species traits such as physiological thermal limits, dispersal ability, annual fecundity and body size have been shown to influence range size. Yet, few studies have examined the generality of each of these factors among different taxa, or have simultaneously evaluated the strength of relationships between range size and these factors at a global scale. We quantify contributions of these factors to range sizes of terrestrial vertebrates (mammals, birds and reptiles) at a global scale. We found that large-ranged species experience greater monthly extremes of maximum or minimum temperature within their ranges, or occur in areas with higher long-term climate velocity and lower topographic heterogeneity or lower precipitation seasonality. Flight ability, body mass and continent width are important only for particular taxa. Our results highlight the importance of climate and topographic context in driving range size variation. The results suggest that small-range species may be vulnerable to climate change and should be the focus of conservation efforts.

Suspended sediment transport in an estuarine tidal channel within San Francisco Bay, California

USGS Publications Warehouse

Sternberg, R.W.; Cacchione, D.A.; Drake, D.E.; Kranck, K.

1986-01-01

Size distributions of the suspended sediment samples, estimates of particle settling velocity (??s), friction velocity (U*), and reference concentration (Ca) at z = 20 cm were used in the suspended sediment distribution equations to evaluate their ability to predict the observed suspended sediment profiles. Three suspended sediment particle conditions were evaluated: (1) individual particle sizes in the 4-11 ?? (62.5-0.5 ??m) size range with the reference concentration Ca at z = 20 cm (C??); (2) individual particle sizes in the 4-6 ?? size range, flocs representing the 7-11 ?? size range with the reference concentration Ca at z = 20 cm (Cf); and (3) individual particle sizes in the 4-6 ?? size range, flocs representing the 7-11 ?? size range with the reference concentration predicted as a function of the bed sediment size distribution and the square of the excess shear stress. An analysis was also carried out on the sensitivity of the suspended sediment distribution equation to deviations in the primary variables ??s, U*, and Ca. In addition, computations of mass flux were made in order to show vertical variations in mass flux for varying flow conditions. ?? 1986.

Density-dependent home-range size revealed by spatially explicit capture–recapture

USGS Publications Warehouse

Efford, M.G.; Dawson, Deanna K.; Jhala, Y.V.; Qureshi, Q.

2016-01-01

The size of animal home ranges often varies inversely with population density among populations of a species. This fact has implications for population monitoring using spatially explicit capture–recapture (SECR) models, in which both the scale of home-range movements σ and population density D usually appear as parameters, and both may vary among populations. It will often be appropriate to model a structural relationship between population-specific values of these parameters, rather than to assume independence. We suggest re-parameterizing the SECR model using kp = σp √Dp, where kp relates to the degree of overlap between home ranges and the subscript p distinguishes populations. We observe that kp is often nearly constant for populations spanning a range of densities. This justifies fitting a model in which the separate kp are replaced by the single parameter k and σp is a density-dependent derived parameter. Continuous density-dependent spatial variation in σ may also be modelled, using a scaled non-Euclidean distance between detectors and the locations of animals. We illustrate these methods with data from automatic photography of tigers (Panthera tigris) across India, in which the variation is among populations, from mist-netting of ovenbirds (Seiurus aurocapilla) in Maryland, USA, in which the variation is within a single population over time, and from live-trapping of brushtail possums (Trichosurus vulpecula) in New Zealand, modelling spatial variation within one population. Possible applications and limitations of the methods are discussed. A model in which kp is constant, while density varies, provides a parsimonious null model for SECR. The parameter k of the null model is a concise summary of the empirical relationship between home-range size and density that is useful in comparative studies. We expect deviations from this model, particularly the dependence of kp on covariates, to be biologically interesting.

Transposable element distribution, abundance and role in genome size variation in the genus Oryza.

PubMed

Zuccolo, Andrea; Sebastian, Aswathy; Talag, Jayson; Yu, Yeisoo; Kim, HyeRan; Collura, Kristi; Kudrna, Dave; Wing, Rod A

2007-08-29

The genus Oryza is composed of 10 distinct genome types, 6 diploid and 4 polyploid, and includes the world's most important food crop - rice (Oryza sativa [AA]). Genome size variation in the Oryza is more than 3-fold and ranges from 357 Mbp in Oryza glaberrima [AA] to 1283 Mbp in the polyploid Oryza ridleyi [HHJJ]. Because repetitive elements are known to play a significant role in genome size variation, we constructed random sheared small insert genomic libraries from 12 representative Oryza species and conducted a comprehensive study of the repetitive element composition, distribution and phylogeny in this genus. Particular attention was paid to the role played by the most important classes of transposable elements (Long Terminal Repeats Retrotransposons, Long interspersed Nuclear Elements, helitrons, DNA transposable elements) in shaping these genomes and in their contributing to genome size variation. We identified the elements primarily responsible for the most strikingly genome size variation in Oryza. We demonstrated how Long Terminal Repeat retrotransposons belonging to the same families have proliferated to very different extents in various species. We also showed that the pool of Long Terminal Repeat Retrotransposons is substantially conserved and ubiquitous throughout the Oryza and so its origin is ancient and its existence predates the speciation events that originated the genus. Finally we described the peculiar behavior of repeats in the species Oryza coarctata [HHKK] whose placement in the Oryza genus is controversial. Long Terminal Repeat retrotransposons are the major component of the Oryza genomes analyzed and, along with polyploidization, are the most important contributors to the genome size variation across the Oryza genus. Two families of Ty3-gypsy elements (RIRE2 and Atlantys) account for a significant portion of the genome size variations present in the Oryza genus.

The evolution of environmental tolerance and range size: a comparison of geographically restricted and widespread Mimulus.

PubMed

Sheth, Seema N; Angert, Amy L

2014-10-01

The geographic ranges of closely related species can vary dramatically, yet we do not fully grasp the mechanisms underlying such variation. The niche breadth hypothesis posits that species that have evolved broad environmental tolerances can achieve larger geographic ranges than species with narrow environmental tolerances. In turn, plasticity and genetic variation in ecologically important traits and adaptation to environmentally variable areas can facilitate the evolution of broad environmental tolerance. We used five pairs of western North American monkeyflowers to experimentally test these ideas by quantifying performance across eight temperature regimes. In four species pairs, species with broader thermal tolerances had larger geographic ranges, supporting the niche breadth hypothesis. As predicted, species with broader thermal tolerances also had more within-population genetic variation in thermal reaction norms and experienced greater thermal variation across their geographic ranges than species with narrow thermal tolerances. Species with narrow thermal tolerance may be particularly vulnerable to changing climatic conditions due to lack of plasticity and insufficient genetic variation to respond to novel selection pressures. Conversely, species experiencing high variation in temperature across their ranges may be buffered against extinction due to climatic changes because they have evolved tolerance to a broad range of temperatures. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

Does Intraspecific Size Variation in a Predator Affect Its Diet Diversity and Top-Down Control of Prey?

PubMed Central

Ingram, Travis; Stutz, William E.; Bolnick, Daniel I.

2011-01-01

It has long been known that intraspecific variation impacts evolutionary processes, but only recently have its potential ecological effects received much attention. Theoretical models predict that genetic or phenotypic variance within species can alter interspecific interactions, and experiments have shown that genotypic diversity in clonal species can impact a wide range of ecological processes. To extend these studies to quantitative trait variation within populations, we experimentally manipulated the variance in body size of threespine stickleback in enclosures in a natural lake environment. We found that body size of stickleback in the lake is correlated with prey size and (to a lesser extent) composition, and that stickleback can exert top-down control on their benthic prey in enclosures. However, a six-fold contrast in body size variance had no effect on the degree of diet variation among individuals, or on the abundance or composition of benthic or pelagic prey. Interestingly, post-hoc analyses revealed suggestive correlations between the degree of diet variation and the strength of top-down control by stickleback. Our negative results indicate that, unless the correlation between morphology and diet is very strong, ecological variation among individuals may be largely decoupled from morphological variance. Consequently we should be cautious in our interpretation both of theoretical models that assume perfect correlations between morphology and diet, and of empirical studies that use morphological variation as a proxy for resource use diversity. PMID:21687670

Does intraspecific size variation in a predator affect its diet diversity and top-down control of prey?

PubMed

Ingram, Travis; Stutz, William E; Bolnick, Daniel I

2011-01-01

It has long been known that intraspecific variation impacts evolutionary processes, but only recently have its potential ecological effects received much attention. Theoretical models predict that genetic or phenotypic variance within species can alter interspecific interactions, and experiments have shown that genotypic diversity in clonal species can impact a wide range of ecological processes. To extend these studies to quantitative trait variation within populations, we experimentally manipulated the variance in body size of threespine stickleback in enclosures in a natural lake environment. We found that body size of stickleback in the lake is correlated with prey size and (to a lesser extent) composition, and that stickleback can exert top-down control on their benthic prey in enclosures. However, a six-fold contrast in body size variance had no effect on the degree of diet variation among individuals, or on the abundance or composition of benthic or pelagic prey. Interestingly, post-hoc analyses revealed suggestive correlations between the degree of diet variation and the strength of top-down control by stickleback. Our negative results indicate that, unless the correlation between morphology and diet is very strong, ecological variation among individuals may be largely decoupled from morphological variance. Consequently we should be cautious in our interpretation both of theoretical models that assume perfect correlations between morphology and diet, and of empirical studies that use morphological variation as a proxy for resource use diversity.

Extensive Natural Intraspecific Variation in Stoichiometric (C:N:P) Composition in Two Terrestrial Insect Species

PubMed Central

Bertram, S. M.; Bowen, M.; Kyle, M.; Schade, J. D.

2008-01-01

Heterotrophic organisms must obtain essential elements in sufficient quantities from their food. Because plants naturally exhibit extensive variation in their elemental content, it is important to quantify the within-species stoichiometric variation of consumers. If extensive stoichiometric variation exists, it may help explain consumer variation in life-history strategy and fitness. To date, however, research on stoichiometric variation has focused on interspecific differences and assumed minimal intraspecific differences. Here this assumption is tested. Natural variation is quantified in body stoichiometry of two terrestrial insects: the generalist field cricket, Gryllus texensis Cade and Otte (Orthoptera: Gryllidae) and a specialist curculionid weevil, Sabinia setosa (Le Conte) (Coleoptera: Curculionidae). Both species exhibited extensive intraspecific stoichiometric variation. Cricket body nitrogen content ranged from 8–12% and there was a four-fold difference in body phosphorus content, ranging from 0.32–1.27%. Body size explained half this stoichiometric variation, with larger individuals containing less nitrogen and phosphorus. Weevils exhibited an almost three-fold difference in body phosphorus content, ranging from 0.38–0.97%. Overall, the variation observed within each of these species is comparable to the variation previously observed across almost all terrestrial insect species. PMID:20298114

Factors associated with variation in home-range size of Appilachian Ruffed Grouse (Bonasa Umbellus)

Treesearch

Darroch M. Whitaker; Dean F. Stauffer; Gary W. Norman; Patrick K. Devers; John Edwards; William M. Giuliano; Craig Harper; William Igo; Harry Spiker; Brian Tefft

2007-01-01

From 1996 to 2001, researchers at 10 Appalachian study sites collected radio tracking data sufficient to delineate 1,054 seasonal home ranges of Ruffed Grouse (Banasa umbellus; hereafter "grouse"). Using information-theoretic model selection and paired comparison of home ranges from individual grouse, we evaluated individual, local, and...

Threatened species richness along a Himalayan elevational gradient: quantifying the influences of human population density, range size, and geometric constraints.

PubMed

Paudel, Prakash Kumar; Sipos, Jan; Brodie, Jedediah F

2018-02-07

A crucial step in conserving biodiversity is to identify the distributions of threatened species and the factors associated with species threat status. In the biodiversity hotspot of the Himalaya, very little is known about which locations harbour the highest diversity of threatened species and whether diversity of such species is related to area, mid-domain effects (MDE), range size, or human density. In this study, we assessed the drivers of variation in richness of threatened birds, mammals, reptiles, actinopterygii, and amphibians along an elevational gradient in Nepal Himalaya. Although geometric constraints (MDE), species range size, and human population density were significantly related to threatened species richness, the interaction between range size and human population density was of greater importance. Threatened species richness was positively associated with human population density and negatively associated with range size. In areas with high richness of threatened species, species ranges tend to be small. The preponderance of species at risk of extinction at low elevations in the subtropical biodiversity hotspot could be due to the double impact of smaller range sizes and higher human density.

Functionality of bismuth sulfide quantum dots/wires-glass nanocomposite as an optical current sensor with enhanced Verdet constant

NASA Astrophysics Data System (ADS)

Panmand, Rajendra P.; Kumar, Ganapathy; Mahajan, Satish M.; Kulkarni, Milind V.; Amalnerkar, D. P.; Kale, Bharat B.; Gosavi, Suresh. W.

2011-02-01

We report optical studies with magneto-optic properties of Bi2S3 quantum dot/wires-glass nanocomposite. The size of the Q-dot was observed to be in the range 3-15 nm along with 11 nm Q-wires. Optical study clearly demonstrated the size quantization effect with drastic band gap variation with size. Faraday rotation tests on the glass nanocomposites show variation in Verdet constant with Q-dot size. Bi2S3 Q-dot/wires glass nanocomposite demonstrated 190 times enhanced Verdet constant compared to the host glass. Prima facie observations exemplify the significant enhancement in Verdet constant of Q-dot glass nanocomposites and will have potential application in magneto-optical devices.

Phenotypic plasticity of life-history traits of a calanoid copepod in a tropical lake: Is the magnitude of thermal plasticity related to thermal variability?

PubMed

Ortega-Mayagoitia, Elizabeth; Hernández-Martínez, Osvaldo; Ciros-Pérez, Jorge

2018-01-01

According to the Climatic Variability Hypothesis [CVH], thermal plasticity should be wider in organisms from temperate environments, but is unlikely to occur in tropical latitudes where temperature fluctuations are narrow. In copepods, food availability has been suggested as the main driver of phenotypic variability in adult size if the range of temperature change is less than 14°C. Leptodiaptomus garciai is a calanoid copepod inhabiting Lake Alchichica, a monomictic, tropical lake in Mexico that experiences regular, narrow temperature fluctuations but wide changes in phytoplankton availability. We investigated whether the seasonal fluctuations of temperature and food produce phenotypic variation in the life-history traits of this tropical species. We sampled L. garciai throughout a year and measured female size, egg size and number, and hatching success, along with temperature and phytoplankton biomass. The amplitude of the plastic responses was estimated with the Phenotypic Plasticity Index. This index was also computed for a published dataset of 84 copepod populations to look if there is a relationship between the amplitude of the phenotypic plasticity of adult size and seasonal change in temperature. The temperature annual range in Lake Alchichica was 3.2°C, whereas phytoplankton abundance varied 17-fold. A strong pattern of thermal plasticity in egg size and adult female size followed the inverse relationship with temperature commonly observed in temperate environments, although its adaptive value was not demonstrated. Egg number, relative reproductive effort and number of nauplii per female were clearly plastic to food availability, allowing organisms to increase their fitness. When comparing copepod species from different latitudes, we found that the magnitude of thermal plasticity of adult size is not related to the range of temperature variation; furthermore, thermal plasticity exists even in environments of limited temperature variation, where the response is more intense compared to temperate populations.

Phenotypic plasticity of life-history traits of a calanoid copepod in a tropical lake: Is the magnitude of thermal plasticity related to thermal variability?

PubMed Central

Hernández-Martínez, Osvaldo; Ciros-Pérez, Jorge

2018-01-01

According to the Climatic Variability Hypothesis [CVH], thermal plasticity should be wider in organisms from temperate environments, but is unlikely to occur in tropical latitudes where temperature fluctuations are narrow. In copepods, food availability has been suggested as the main driver of phenotypic variability in adult size if the range of temperature change is less than 14°C. Leptodiaptomus garciai is a calanoid copepod inhabiting Lake Alchichica, a monomictic, tropical lake in Mexico that experiences regular, narrow temperature fluctuations but wide changes in phytoplankton availability. We investigated whether the seasonal fluctuations of temperature and food produce phenotypic variation in the life-history traits of this tropical species. We sampled L. garciai throughout a year and measured female size, egg size and number, and hatching success, along with temperature and phytoplankton biomass. The amplitude of the plastic responses was estimated with the Phenotypic Plasticity Index. This index was also computed for a published dataset of 84 copepod populations to look if there is a relationship between the amplitude of the phenotypic plasticity of adult size and seasonal change in temperature. The temperature annual range in Lake Alchichica was 3.2°C, whereas phytoplankton abundance varied 17-fold. A strong pattern of thermal plasticity in egg size and adult female size followed the inverse relationship with temperature commonly observed in temperate environments, although its adaptive value was not demonstrated. Egg number, relative reproductive effort and number of nauplii per female were clearly plastic to food availability, allowing organisms to increase their fitness. When comparing copepod species from different latitudes, we found that the magnitude of thermal plasticity of adult size is not related to the range of temperature variation; furthermore, thermal plasticity exists even in environments of limited temperature variation, where the response is more intense compared to temperate populations. PMID:29708999

Microstructure characterization of 316L deformed at high strain rates using EBSD

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

Yvell, K., E-mail: kyv@du.se

2016-12-15

Specimens from split Hopkinson pressure bar experiments, at strain rates between ~ 1000–9000 s{sup −1} at room temperature and 500 °C, have been studied using electron backscatter diffraction. No significant differences in the microstructures were observed at different strain rates, but were observed for different strains and temperatures. Size distribution for subgrains with boundary misorientations > 2° can be described as a bimodal lognormal area distribution. The distributions were found to change due to deformation. Part of the distribution describing the large subgrains decreased while the distribution for the small subgrains increased. This is in accordance with deformation being heterogeneousmore » and successively spreading into the undeformed part of individual grains. The variation of the average size for the small subgrain distribution varies with strain but not with strain rate in the tested interval. The mean free distance for dislocation slip, interpreted here as the average size of the distribution of small subgrains, displays a variation with plastic strain which is in accordance with the different stages in the stress-strain curves. The rate of deformation hardening in the linear hardening range is accurately calculated using the variation of the small subgrain size with strain. - Highlights: •Only changes in strain, not strain rate, gave differences in the microstructure. •A bimodal lognormal size distribution was found to describe the size distribution. •Variation of the subgrain fraction sizes agrees with models for heterogeneous slip. •Variation of subgrain size with strain describes part of the stress strain curve.« less

Impact of range shifter material on proton pencil beam spot characteristics.

PubMed

Shen, Jiajian; Liu, Wei; Anand, Aman; Stoker, Joshua B; Ding, Xiaoning; Fatyga, Mirek; Herman, Michael G; Bues, Martin

2015-03-01

To quantitatively investigate the effect of range shifter materials on single-spot characteristics of a proton pencil beam. An analytic approximation for multiple Coulomb scattering ("differential Moliere" formula) was adopted to calculate spot sizes of proton spot scanning beams impinging on a range shifter. The calculations cover a range of delivery parameters: six range shifter materials (acrylonitrile butadiene styrene, Lexan, Lucite, polyethylene, polystyrene, and wax) and water as reference material, proton beam energies ranging from 75 to 200 MeV, range shifter thicknesses of 4.5 and 7.0 g/cm(2), and range shifter positions from 5 to 50 cm. The analytic method was validated by comparing calculation results with the measurements reported in the literature. Relative to a water-equivalent reference, the spot size distal to a wax or polyethylene range shifter is 15% smaller, while the spot size distal to a range shifter made of Lexan or Lucite is about 6% smaller. The relative spot size variations are nearly independent of beam energy and range shifter thickness and decrease with smaller air gaps. Among the six material investigated, wax and polyethylene are desirable range shifter materials when the spot size is kept small. Lexan and Lucite are the desirable range shifter materials when the scattering power is kept similar to water.

Unifying latitudinal gradients in range size and richness across marine and terrestrial systems

PubMed Central

Tomašových, Adam; Kennedy, Jonathan D.; Betzner, Tristan J.; Kuehnle, Nicole Bitler; Edie, Stewart; Kim, Sora; Supriya, K.; White, Alexander E.; Rahbek, Carsten; Huang, Shan; Price, Trevor D.; Jablonski, David

2016-01-01

Many marine and terrestrial clades show similar latitudinal gradients in species richness, but opposite gradients in range size—on land, ranges are the smallest in the tropics, whereas in the sea, ranges are the largest in the tropics. Therefore, richness gradients in marine and terrestrial systems do not arise from a shared latitudinal arrangement of species range sizes. Comparing terrestrial birds and marine bivalves, we find that gradients in range size are concordant at the level of genera. Here, both groups show a nested pattern in which narrow-ranging genera are confined to the tropics and broad-ranging genera extend across much of the gradient. We find that (i) genus range size and its variation with latitude is closely associated with per-genus species richness and (ii) broad-ranging genera contain more species both within and outside of the tropics when compared with tropical- or temperate-only genera. Within-genus species diversification thus promotes genus expansion to novel latitudes. Despite underlying differences in the species range-size gradients, species-rich genera are more likely to produce a descendant that extends its range relative to the ancestor's range. These results unify species richness gradients with those of genera, implying that birds and bivalves share similar latitudinal dynamics in net species diversification. PMID:27147094

Impact of the definition of peak standardized uptake value on quantification of treatment response.

PubMed

Vanderhoek, Matt; Perlman, Scott B; Jeraj, Robert

2012-01-01

PET-based treatment response assessment typically measures the change in maximum standardized uptake value (SUV(max)), which is adversely affected by noise. Peak SUV (SUV(peak)) has been recommended as a more robust alternative, but its associated region of interest (ROI(peak)) is not uniquely defined. We investigated the impact of different ROI(peak) definitions on quantification of SUV(peak) and tumor response. Seventeen patients with solid malignancies were treated with a multitargeted receptor tyrosine kinase inhibitor resulting in a variety of responses. Using the cellular proliferation marker 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT), whole-body PET/CT scans were acquired at baseline and during treatment. (18)F-FLT-avid lesions (∼2/patient) were segmented on PET images, and tumor response was assessed via the relative change in SUV(peak). For each tumor, 24 different SUV(peaks) were determined by changing ROI(peak) shape (circles vs. spheres), size (7.5-20 mm), and location (centered on SUV(max) vs. placed in highest-uptake region), encompassing different definitions from the literature. Within each tumor, variations in the 24 SUV(peaks) and tumor responses were measured using coefficient of variation (CV), standardized deviation (SD), and range. For each ROI(peak) definition, a population average SUV(peak) and tumor response were determined over all tumors. A substantial variation in both SUV(peak) and tumor response resulted from changing the ROI(peak) definition. The variable ROI(peak) definition led to an intratumor SUV(peak) variation ranging from 49% above to 46% below the mean (CV, 17%) and an intratumor SUV(peak) response variation ranging from 49% above to 35% below the mean (SD, 9%). The variable ROI(peak) definition led to a population average SUV(peak) variation ranging from 24% above to 28% below the mean (CV, 14%) and a population average SUV(peak) response variation ranging from only 3% above to 3% below the mean (SD, 2%). The size of ROI(peak) caused more variation in intratumor response than did the location or shape of ROI(peak). Population average tumor response was independent of size, shape, and location of ROI(peak). Quantification of individual tumor response using SUV(peak) is highly sensitive to the ROI(peak) definition, which can significantly affect the use of SUV(peak) for assessment of treatment response. Clinical trials are necessary to compare the efficacy of SUV(peak) and SUV(max) for quantification of response to therapy.

Weight and volume variation in truckloads of logs hauled in the central Appalachians

Treesearch

Floyd G. Timson

1974-01-01

Variation in volume and weight was found among loaded log trucks even when such factors as truck type, logging job, and driver influence were eliminated. A load range of 10,000 pounds or 1,000 board feet was commonplace for the same truck, driver, and cutting site. Differences in log size, shape, weight, and species caused a major share of this variation. Yet,...

Spatial and temporal variation of the gill rakers of gizzard shad and silver carp in three Midwestern rivers

USGS Publications Warehouse

Walleser, Liza R.; Sandheinrich, Mark B.; Howard, David R.; Gaikowski, Mark P.; Amberg, Jon J.

2014-01-01

Improved management of invasive Silver Carp Hypophthalmichthys molitrix in the upper Mississippi River basin may be possible by better understanding the feeding abilities of this population. Food collection for filter-feeding fishes, such as Silver Carp, is influenced by the species-specific structure of their gill rakers. To investigate structural variation in gill rakers of Silver Carp, the morphology of gill rakers was quantified and compared with that of a native filter-feeding fish species which may compete with Silver Carp for food resources, Gizzard Shad Dorosoma cepedianum. Intra- and interspecies variation of gill rakers was examined in both species collected from three locations among four months. Interspecies analysis indicated the size of pores in gill rakers of Silver Carp were much larger than the interraker spacings of Gizzard Shad (95% CI ranged from 80.69 to 185.75 μm versus 16.72 to 47.36 μm, respectively). Intraspecies variation of gill rakers from Silver Carp was related to the overall size of fish and occurred only among sites where dissimilar sizes of fish were collected. This suggested the size of particles filtered by Silver Carp may be dependent upon ontogenic development rather than phenotypic plasticity in response to spatial or temporal factors. Intraspecies variation of gill rakers from Gizzard Shad occurred among site and monthly sampling data; however, variation was only attributable to overall size of fish for monthly sampling data. This suggested ontogeny may influence the filter-feeding ability of this species within a habitat. However, variation noted among sites, which was not attributable to size of fish, may indicate gill rakers are phenotypically plastic among Gizzard Shad populations of various river systems of the upper Mississippi River basin.

Home ranges of lions in the Kalahari, Botswana exhibit vast sizes and high temporal variability.

PubMed

Zehnder, André; Henley, Stephen; Weibel, Robert

2018-06-01

The central Kalahari region in Botswana is one of the few remaining ecosystems with a stable lion population. Yet, relatively little is known about the ecology of the lions there. As an entry point, home range estimations provide information about the space utilization of the studied animals. The home ranges of eight lions in this region were determined to investigate their spatial overlaps and spatiotemporal variations. We found that, except for MCP, all home range estimators yielded comparable results regarding size and shape. The home ranges of all individuals were located predominantly inside the protected reserves. Their areas were among the largest known for lions with 1131 - 4314km 2 (95%), with no significant differences between males and females. Numerous overlaps between lions of different sexes were detected, although these originate from different groups. A distance chart confirmed that most of these lions directly encountered each other once or several times. Strong temporal variations of the home ranges were observed that did not match a seasonal pattern. The exceptionally large home ranges are likely to be caused by the sparse and dynamic prey populations. Since the ungulates in the study area move in an opportunistic way, too, strong spatiotemporal home range variations emerge. This can lead to misleading home ranges. We therefore recommend clarifying the stability of the home ranges by applying several levels of temporal aggregation. The lack of strict territoriality is likely an adaptation to the variable prey base and the high energetic costs associated with defending a large area. Copyright © 2018 Elsevier GmbH. All rights reserved.

Size-frequency distributions along a latitudinal gradient in Middle Permian fusulinoideans.

PubMed

Zhang, Yichun; Payne, Jonathan L

2012-01-01

Geographic gradients in body size within and among living species are commonly used to identify controls on the long-term evolution of organism size. However, the persistence of these gradients over evolutionary time remains largely unknown because ancient biogeographic variation in organism size is poorly documented. Middle Permian fusulinoidean foraminifera are ideal for investigating the temporal persistence of geographic gradients in organism size because they were diverse and abundant along a broad range of paleo-latitudes during this interval (~275-260 million years ago). In this study, we determined the sizes of Middle Permian fusulinoidean fossils from three different paleo-latitudinal zones in order to examine the relationship between the size of foraminifers and regional environment. We recovered the following results: keriothecal fusulinoideans are substantially larger than nonkeriothecal fusulinoideans; fusulinoideans from the equatorial zone are typically larger than those from the north and south transitional zones; neoschwagerinid specimens within a single species are generally larger in the equatorial zone than those in both transitional zones; and the nonkeriothecal fusulinoideans Staffellidae and Schubertellidae have smaller size in the north transitional zone. Fusulinoidean foraminifers differ from most other marine taxa in exhibiting larger sizes closer to the equator, contrary to Bergmann's rule. Meridional variation in seasonality, water temperature, nutrient availability, and carbonate saturation level are all likely to have favored or enabled larger sizes in equatorial regions. Temporal variation in atmospheric oxygen concentrations have been shown to account for temporal variation in fusulinoidean size during Carboniferous and Permian time, but oxygen availability appears unlikely to explain biogeographic variation in fusulinoidean sizes, because dissolved oxygen concentrations in seawater typically increase away from the equator due to declining seawater temperatures. Consequently, our findings highlight the fact that spatial gradients in organism size are not always controlled by the same factors that govern temporal trends within the same clade.

Size-Frequency Distributions along a Latitudinal Gradient in Middle Permian Fusulinoideans

PubMed Central

Zhang, Yichun; Payne, Jonathan L.

2012-01-01

Geographic gradients in body size within and among living species are commonly used to identify controls on the long-term evolution of organism size. However, the persistence of these gradients over evolutionary time remains largely unknown because ancient biogeographic variation in organism size is poorly documented. Middle Permian fusulinoidean foraminifera are ideal for investigating the temporal persistence of geographic gradients in organism size because they were diverse and abundant along a broad range of paleo-latitudes during this interval (∼275–260 million years ago). In this study, we determined the sizes of Middle Permian fusulinoidean fossils from three different paleo-latitudinal zones in order to examine the relationship between the size of foraminifers and regional environment. We recovered the following results: keriothecal fusulinoideans are substantially larger than nonkeriothecal fusulinoideans; fusulinoideans from the equatorial zone are typically larger than those from the north and south transitional zones; neoschwagerinid specimens within a single species are generally larger in the equatorial zone than those in both transitional zones; and the nonkeriothecal fusulinoideans Staffellidae and Schubertellidae have smaller size in the north transitional zone. Fusulinoidean foraminifers differ from most other marine taxa in exhibiting larger sizes closer to the equator, contrary to Bergmann's rule. Meridional variation in seasonality, water temperature, nutrient availability, and carbonate saturation level are all likely to have favored or enabled larger sizes in equatorial regions. Temporal variation in atmospheric oxygen concentrations have been shown to account for temporal variation in fusulinoidean size during Carboniferous and Permian time, but oxygen availability appears unlikely to explain biogeographic variation in fusulinoidean sizes, because dissolved oxygen concentrations in seawater typically increase away from the equator due to declining seawater temperatures. Consequently, our findings highlight the fact that spatial gradients in organism size are not always controlled by the same factors that govern temporal trends within the same clade. PMID:22685590

Modeling grain size variations of aeolian gypsum deposits at White Sands, New Mexico, using AVIRIS imagery

USGS Publications Warehouse

Ghrefat, H.A.; Goodell, P.C.; Hubbard, B.E.; Langford, R.P.; Aldouri, R.E.

2007-01-01

Visible and Near-Infrared (VNIR) through Short Wavelength Infrared (SWIR) (0.4-2.5????m) AVIRIS data, along with laboratory spectral measurements and analyses of field samples, were used to characterize grain size variations in aeolian gypsum deposits across barchan-transverse, parabolic, and barchan dunes at White Sands, New Mexico, USA. All field samples contained a mineralogy of ?????100% gypsum. In order to document grain size variations at White Sands, surficial gypsum samples were collected along three Transects parallel to the prevailing downwind direction. Grain size analyses were carried out on the samples by sieving them into seven size fractions ranging from 45 to 621????m, which were subjected to spectral measurements. Absorption band depths of the size fractions were determined after applying an automated continuum-removal procedure to each spectrum. Then, the relationship between absorption band depth and gypsum size fraction was established using a linear regression. Three software processing steps were carried out to measure the grain size variations of gypsum in the Dune Area using AVIRIS data. AVIRIS mapping results, field work and laboratory analysis all show that the interdune areas have lower absorption band depth values and consist of finer grained gypsum deposits. In contrast, the dune crest areas have higher absorption band depth values and consist of coarser grained gypsum deposits. Based on laboratory estimates, a representative barchan-transverse dune (Transect 1) has a mean grain size of 1.16 ??{symbol} (449????m). The error bar results show that the error ranges from - 50 to + 50????m. Mean grain size for a representative parabolic dune (Transect 2) is 1.51 ??{symbol} (352????m), and 1.52 ??{symbol} (347????m) for a representative barchan dune (Transect 3). T-test results confirm that there are differences in the grain size distributions between barchan and parabolic dunes and between interdune and dune crest areas. The t-test results also show that there are no significant differences between modeled and laboratory-measured grain size values. Hyperspectral grain size modeling can help to determine dynamic processes shaping the formation of the dunes such as wind directions, and the relative strengths of winds through time. This has implications for studying such processes on other planetary landforms that have mineralogy with unique absorption bands in VNIR-SWIR hyperspectral data. ?? 2006 Elsevier B.V. All rights reserved.

On prediction of crack in different orientations in pipe using frequency based approach

NASA Astrophysics Data System (ADS)

Naniwadekar, M. R.; Naik, S. S.; Maiti, S. K.

2008-04-01

A technique based on measurement of change in natural frequencies and modeling of crack by rotational spring is employed to detect a crack with straight front in different orientations in a section of straight horizontal steel hollow pipe (outer diameter 0.0378 m and inner diameter 0.0278 m). Crack orientations in the range 0-60° with the vertical have been examined and sizes/depths in the range 1-4 mm through the wall of thickness 5 mm have been studied. Variation of rotational spring stiffness with crack size and orientation has been obtained experimentally by deflection and vibration methods. The spring stiffness reduces as expected, with an increase in crack size; it increases with an increase in the crack orientation angle. The crack location has been predicted with a maximum error of 7.29%. The sensitivity of the method for prediction of crack location on variations in experimental data has been examined by changing the difference between the frequencies of pipes with and without crack by ±10%. The method is found to be very robust; the maximum variation in location is 2.68%, which is much less than the change in frequency difference introduced.

Variations in interior morphology of 15-20 km lunar craters - Implications for a major subsurface discontinuity

NASA Technical Reports Server (NTRS)

De Hon, R. A.

1980-01-01

Craters vary in morphology as a function of crater diameter, age, and mode of origin. This study concentrates on the morphology of young lunar impact craters within a limited size range. Elimination of morphologic variations generally attributed to crater size or age leaves a small population which should nearly reflect the varying properties of the lunar substrate. The sample consists of 17 craters 15-20 km in diameter with both simple and complex morphologies. While depth/diameter ratios do not obviously differ between mare and highland subsets, apparent depth, rim height, and profile data do differ distinctly. Highland craters tend to be deep, simple, and bowl-shaped. Mare craters tend to be shallow and flat-floored. Rim heights of complex mare craters are typically greater than those of simple craters. Differences of highland and mare crater morphologies are attributed to variations in the thickness of the lunar megaregolith. Highland craters in this size range do not penetrate the megaregolith. The depth and morphology of complex craters are controlled by the discontinuity at the transition from highly brecciated megaregolith to more coherent crystalline material of the upper crust.

Allogenic sedimentary components of Bear Lake, Utah and Idaho

USGS Publications Warehouse

Rosenbaum, J.G.; Dean, W.E.; Reynolds, R.L.; Reheis, M.C.

2009-01-01

Bear Lake is a long-lived lake filling a tectonic depression between the Bear River Range to the west and the Bear River Plateau to the east, and straddling the border between Utah and Idaho. Mineralogy, elemental geochemistry, and magnetic properties provide information about variations in provenance of allogenic lithic material in last-glacial-age, quartz-rich sediment in Bear Lake. Grain-size data from the siliciclastic fraction of late-glacial to Holocene carbonate-rich sediments provide information about variations in lake level. For the quartz-rich lower unit, which was deposited while the Bear River fl owed into and out of the lake, four source areas are recognized on the basis of modern fluvial samples with contrasting properties that reflect differences in bedrock geology and in magnetite content from dust. One of these areas is underlain by hematite-rich Uinta Mountain Group rocks in the headwaters of the Bear River. Although Uinta Mountain Group rocks make up a small fraction of the catchment, hematite-rich material from this area is an important component of the lower unit. This material is interpreted to be glacial fl our. Variations in the input of glacial flour are interpreted as having caused quasi-cyclical variations in mineralogical and elemental concentrations, and in magnetic properties within the lower unit. The carbonate-rich younger unit was deposited under conditions similar to those of the modern lake, with the Bear River largely bypassing the lake. For two cores taken in more than 30 m of water, median grain sizes in this unit range from ???6 ??m to more than 30 ??m, with the coarsest grain sizes associated with beach or shallow-water deposits. Similar grain-size variations are observed as a function of water depth in the modern lake and provide the basis for interpreting the core grain-size data in terms of lake level. Copyright ?? 2009 The Geological Society of America.

A theoretical approach to study the melting temperature of metallic nanowires

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

Arora, Neha; Joshi, Deepika P.

2016-05-23

The physical properties of any material change with the change of its size from bulk range to nano range. A theoretical study to account for the size and shape effect on melting temperature of metallic nanowires has been done. We have studied zinc (Zn), indium (In), lead (Pb) and tin (Sn) nanowires with three different cross sectional shapes like regular triangular, square and regular hexagonal. Variation of melting temperature with the size and shape is graphically represented with the available experimental data. It was found that melting temperature of the nanowires decreases with decrement in the size of nanowire, duemore » to surface effect and at very small size the most probable shape also varies with material.« less

Lack of robustness of textural measures obtained from 3D brain tumor MRIs impose a need for standardization.

PubMed

Molina, David; Pérez-Beteta, Julián; Martínez-González, Alicia; Martino, Juan; Velasquez, Carlos; Arana, Estanislao; Pérez-García, Víctor M

2017-01-01

Textural measures have been widely explored as imaging biomarkers in cancer. However, their robustness under dynamic range and spatial resolution changes in brain 3D magnetic resonance images (MRI) has not been assessed. The aim of this work was to study potential variations of textural measures due to changes in MRI protocols. Twenty patients harboring glioblastoma with pretreatment 3D T1-weighted MRIs were included in the study. Four different spatial resolution combinations and three dynamic ranges were studied for each patient. Sixteen three-dimensional textural heterogeneity measures were computed for each patient and configuration including co-occurrence matrices (CM) features and run-length matrices (RLM) features. The coefficient of variation was used to assess the robustness of the measures in two series of experiments corresponding to (i) changing the dynamic range and (ii) changing the matrix size. No textural measures were robust under dynamic range changes. Entropy was the only textural feature robust under spatial resolution changes (coefficient of variation under 10% in all cases). Textural measures of three-dimensional brain tumor images are not robust neither under dynamic range nor under matrix size changes. Standards should be harmonized to use textural features as imaging biomarkers in radiomic-based studies. The implications of this work go beyond the specific tumor type studied here and pose the need for standardization in textural feature calculation of oncological images.

Population biology of Avena : IX. Gene flow and neighborhood size in relation to microgeographic variation in Avena barbata.

PubMed

Rai, Kedar N; Jain, Subodh K

1982-06-01

Pollen and seed dispersal patterns were analyzed in both natural and experimental populations of Avena barbata. Localized estimates of gene flow rates and plant densities gave estimates of neighborhood size in the range of 40 to 400 plants; the estimates of mean rate and distance of gene flow seemed to vary widely due to variable wind direction, rodent activity, microsite heterogeneity, etc. The relative sizes of neighborhoods in several populations were correlated with the patchy distribution of different genotypes (scored for lemma color and leaf sheath hairiness) within short distances, but patch sizes had a wide range among different sites. Highly localized gene flow patterns seemed to account for the observed pattern of highly patchy variation even when the dispersal curves for both pollen and seed were platykurtic in many cases. Measures of the stability of patches in terms of their size, dispersion in space and genetic structure in time are needed in order to sort out the relative roles of founder effects, random drift (due to small neighborhood size), and highly localized selection. However, our observations suggest that many variables and stochastic processes are involved in such studies so as to allow only weak inference about the underlying role of natural selection, drift and factors of population regulatien.

Martian planetwide crater distributions - Implications for geologic history and surface processes

NASA Technical Reports Server (NTRS)

Soderblom, L. A.; Condit, C. D.; West, R. A.; Herman, B. M.; Kreidler, T. J.

1974-01-01

Three different diameter size ranges are considered in connection with the Martian crater distribution, taking into account small craters from 0.6 to 1.2 km, intermediate-sized craters from 4 to 10 km, and large craters with diameters exceeding 20 km. One of the objectives of the investigation reported is to establish the effects of eolian processes in the modification of craters in the different size ranges. Another objective is concerned with a description of the genetic relationships among the three size ranges of craters. Observables related to the relative age of geologic provinces are to be separated from observables related to geographic variations in eolian transport and deposition. Lunar and Martian cratering histories are compared as a basis for establishing relative and absolute time scales for the geological evolution of Mars.

Canonical Visual Size for Real-World Objects

PubMed Central

Konkle, Talia; Oliva, Aude

2012-01-01

Real-world objects can be viewed at a range of distances and thus can be experienced at a range of visual angles within the visual field. Given the large amount of visual size variation possible when observing objects, we examined how internal object representations represent visual size information. In a series of experiments which required observers to access existing object knowledge, we observed that real-world objects have a consistent visual size at which they are drawn, imagined, and preferentially viewed. Importantly, this visual size is proportional to the logarithm of the assumed size of the object in the world, and is best characterized not as a fixed visual angle, but by the ratio of the object and the frame of space around it. Akin to the previous literature on canonical perspective, we term this consistent visual size information the canonical visual size. PMID:20822298

Exploring the universal ecological responses to climate change in a univoltine butterfly.

PubMed

Fenberg, Phillip B; Self, Angela; Stewart, John R; Wilson, Rebecca J; Brooks, Stephen J

2016-05-01

Animals with distinct life stages are often exposed to different temperatures during each stage. Thus, how temperature affects these life stages should be considered for broadly understanding the ecological consequences of climate warming on such species. For example, temperature variation during particular life stages may affect respective change in body size, phenology and geographic range, which have been identified as the "universal" ecological responses to climate change. While each of these responses has been separately documented across a number of species, it is not known whether each response occurs together within a species. The influence of temperature during particular life stages may help explain each of these ecological responses to climate change. Our goal was to determine if monthly temperature variation during particular life stages of a butterfly species can predict respective changes in body size and phenology. We also refer to the literature to assess if temperature variability during the adult stage influences range change over time. Using historical museum collections paired with monthly temperature records, we show that changes in body size and phenology of the univoltine butterfly, Hesperia comma, are partly dependent upon temporal variation in summer temperatures during key stages of their life cycle. June temperatures, which are likely to affect growth rate of the final larval instar, are important for predicting adult body size (for males only; showing a positive relationship with temperature). July temperatures, which are likely to influence the pupal stage, are important for predicting the timing of adult emergence (showing a negative relationship with temperature). Previous studies show that August temperatures, which act on the adult stage, are linked to range change. Our study highlights the importance of considering temperature variation during each life stage over historic time-scales for understanding intraspecific response to climate change. Range edge studies of ectothermic species that have annual life cycles, long time-series occurrence data, and associated temperature records (ideally at monthly resolutions) could be useful model systems for intraspecific tests of the universal ecological responses to climate change and for exploring interactive effects. © 2016 The Authors. Journal of Animal Ecology © 2016 British Ecological Society.

Geoelectrohydraulic investigation of the surficial aquifer units and corrosivity in parts of Uyo L. G. A., Akwa Ibom State, Southern Nigeria

NASA Astrophysics Data System (ADS)

Ibuot, Johnson C.; Obiora, Daniel N.; Ekpa, Moses M. M.; Okoroh, Doris O.

2017-12-01

This study was carried out employing vertical electrical sounding (VES) with Schlumberger electrode configuration. The objectives were to investigate the distribution of the geohydraulic parameters and the corrosivity of the aquifer layer within the study area. The sand-to-coarse grain sands aquifer have resistivity ranging from 8.1 to 2204 Ωm, while the thickness ranged from 7.4 to 55.3 m. These parameters were used in computing the geohydraulic parameters. Hydraulic conductivity was estimated using the Heigold equation, and its values ranged from 1.42 to 54.90 m/day. Estimated hydraulic conductivity values were employed in determining the aquifer transmissivity which ranged from 11.28 to 812.00 m2/day, fractional porosities ranged from 0.0351 to 0.0598. The longitudinarl conductance also varies from 0.01 to 1.83 Ω-1. The contour plots generated from the SURFER software package show the variation of these parameters. The ranges of these estimated parameters indicate variation in grain sizes, magnitude of pore sizes and facies changes. The corrosivity rating indicates that most of the VES points were practically non-corrosive.

Analysis of variability in additive manufactured open cell porous structures.

PubMed

Evans, Sam; Jones, Eric; Fox, Pete; Sutcliffe, Chris

2017-06-01

In this article, a novel method of analysing build consistency of additively manufactured open cell porous structures is presented. Conventionally, methods such as micro computed tomography or scanning electron microscopy imaging have been applied to the measurement of geometric properties of porous material; however, high costs and low speeds make them unsuitable for analysing high volumes of components. Recent advances in the image-based analysis of open cell structures have opened up the possibility of qualifying variation in manufacturing of porous material. Here, a photogrammetric method of measurement, employing image analysis to extract values for geometric properties, is used to investigate the variation between identically designed porous samples measuring changes in material thickness and pore size, both intra- and inter-build. Following the measurement of 125 samples, intra-build material thickness showed variation of ±12%, and pore size ±4% of the mean measured values across five builds. Inter-build material thickness and pore size showed mean ranges higher than those of intra-build, ±16% and ±6% of the mean material thickness and pore size, respectively. Acquired measurements created baseline variation values and demonstrated techniques suitable for tracking build deviation and inspecting additively manufactured porous structures to indicate unwanted process fluctuations.

Wing morphometrics of Aedes (Ochlerotatus) albifasciatus (Macquart, 1838) (Diptera: Culicidae) from different climatic regions of Argentina.

PubMed

Garzón, Maximiliano J; Schweigmann, Nicolás

2018-05-16

Gene flow restrictions between populations of Aedes albifasciatus, the vector of Western equine encephalitis and Dirophilaria immitis, have been described in the central region of Argentina. Genetic and eco-physiological variations usually result in local forms reflecting the climatic regions. Mosquito wings and their different parts have ecological functions in flight and communication. Therefore, wing shape could be considered an aspect of sexual dimorphism, and its eco-physiological responses can be expressed as morphological changes induced by the environment. To compare the geographical and sexual variations with respect to wing shape and size in two Ae. albifasciatus populations from contrasting climates of Argentina (temperate: Buenos Aires, and the arid steppe of Patagonia: Sarmiento), the wings of adults reared in thermal trays at different constant temperatures (10-29 °C) were analyzed. The wing size of Ae. albifasciatus showed inverse linear relationships with the rearing thermal condition and higher slope for Buenos Aires. In the cool range (10-17 °C), geographical size variations responded to the converse Bergmann's rule, where Buenos Aires individuals were larger than those from Sarmiento. Sexual shape dimorphism occurred in both populations while geographical variation in shape was observed in both sexes. Buenos Aires individuals showed greater response sensitivity with respect to the size-temperature relation than those from Sarmiento. The converse Bergmann's rule in size variation could be due to a higher development rate in Sarmiento to produce more cohorts in the limited favorable season. The shape could be more relevant with respect to the size in the study of population structures due to the size being more liable to vary due to changes in the environment. The geographical variations with respect to morphology could be favored by the isolation between populations and adaptations to the environmental conditions. Our results demonstrate that the shape and size of wing provide useful phenotypic information for studies related to sexual and environmental adaptations.

Species' Traits as Predictors of Range Shifts Under Contemporary Climate Change: A Meta-analysis

NASA Astrophysics Data System (ADS)

MacLean, S. A.; Beissinger, S. R.

2016-12-01

A growing body of literature seeks to explain variation in range shifts using species' ecological and life history traits, with expectations that shifts should be greater in species with greater dispersal ability, reproductive potential, and ecological generalization. If trait-based arguments, hold, then traits would provide valuable evidence-based tools for conservation and management that could increase the accuracy of future range projections, vulnerability assessments, and predictions of novel community assemblages. However, empirical support is limited in extent and consensus, and trait-based relationships remain largely unvalidated. We conducted a comprehensive literature review of species' traits as predictors of range shifts, collecting results from over 11,000 species' responses across multiple taxa from studies that directly compared 20th century and contemporary distributions for multispecies assemblages. We then performed a meta-analysis to calculate the mean study-level effects of body size, fecundity, diet breadth, habitat breadth, and historic range limit, while directly controlling for ecological and methodological heterogeneity across studies that could bias reported effect sizes. We show that ecological and life history traits have had limited success in accounting for variation among species in range shifts over the past century. Of the five traits analyzed, only habitat breadth and historic range limit consistently supported range shift predictions across multiple studies. Fecundity, body size, and diet breadth showed no clear relationship with range shifts, and some traits identified in our literature review (e.g. migratory ecology) have consistently contradicted range shift predictions. Current understanding of species' traits as predictors of range shifts is limited, and standardized study is needed before traits can be reliably incorporated into projections of climate change impacts.

Quantitative Genetic Architecture at Latitudinal Range Boundaries: Reduced Variation but Higher Trait Independence.

PubMed

Paccard, Antoine; Van Buskirk, Josh; Willi, Yvonne

2016-05-01

Species distribution limits are hypothesized to be caused by small population size and limited genetic variation in ecologically relevant traits, but earlier studies have not evaluated genetic variation in multivariate phenotypes. We asked whether populations at the latitudinal edges of the distribution have altered quantitative genetic architecture of ecologically relevant traits compared with midlatitude populations. We calculated measures of evolutionary potential in nine Arabidopsis lyrata populations spanning the latitudinal range of the species in eastern and midwestern North America. Environments at the latitudinal extremes have reduced water availability, and therefore plants were assessed under wet and dry treatments. We estimated genetic variance-covariance (G-) matrices for 10 traits related to size, development, and water balance. Populations at southern and northern distribution edges had reduced levels of genetic variation across traits, but their G-matrices were more spherical; G-matrix orientation was unrelated to latitude. As a consequence, the predicted short-term response to selection was at least as strong in edge populations as in central populations. These results are consistent with genetic drift eroding variation and reducing the effectiveness of correlational selection at distribution margins. We conclude that genetic variation of isolated traits poorly predicts the capacity to evolve in response to multivariate selection and that the response to selection may frequently be greater than expected at species distribution margins because of genetic drift.

Ecological significance of microsatellite variation in western North American populations of Bromus tectorum

Treesearch

Alisa P. Ramakrishnan; Susan Meyer; Daniel J. Fairbanks; Craig E. Coleman

2006-01-01

Bromus tectorum (cheatgrass or downy brome) is an exotic annual weed that is abundant in western USA. We examined variation in six microsatellite loci for 17 populations representing a range of habitats in Utah, Idaho, Nevada and Colorado (USA) and then intensively sampled four representative populations, for a total sample size of approximately 1000 individuals. All...

The fall and rise of the Icelandic Arctic fox (Vulpes lagopus): a 50-year demographic study on a non-cyclic Arctic fox population.

PubMed

Unnsteinsdottir, E R; Hersteinsson, P; Pálsson, S; Angerbjörn, A

2016-08-01

In territorial species, observed density dependence is often manifest in lowered reproductive output at high population density where individuals have fewer resources or are forced to inhabit low-quality territories. The Arctic fox (Vulpes lagopus) in Iceland is territorial throughout the year and feeds mostly on birds, since lemmings are absent from the country. Thus, the population does not exhibit short-term population cycles that are evident in most of the species' geographical range. The population has, however, gone through a major long-term fluctuation in population size. Because of the stability in hunting effort and reliable hunting records since 1958, the total number of adult foxes killed annually can be used as an index of population size (N t ). An index of carrying capacity (K) from population growth data for five separate time blocks during 1958-2007 revealed considerable variation in K and allowed a novel definition of population density in terms of K, or N t /K. Correlation analysis suggested that the reproductive rate was largely determined by the proportion of territorial foxes in the population. Variation in litter size and cub mortality was, on the other hand, related to climatic variation. Thus, Arctic foxes in Iceland engage in typical contest competition but can adapt their territory sizes in response to both temporal and spatial variation in carrying capacity, resulting in surprisingly little variation in litter size.

Laboratory Reflectance Spectra in the Middle-infrared: Effects of Grain Size on Spectral Features

NASA Astrophysics Data System (ADS)

Le Bras, A.; Erard, S.; Fulchignoni, M.

2000-10-01

Since spectral mineral features are sensitive to surface parameters, interpretation of remote-sensing asteroids spectra in terms of mineral composition is not easy nor unique, and laboratory spectra are needed in order to understand the influence of each parameter. We developped an experimental program at IAS, using the 2.5-120 microns interferometer spectrometer, to study the influence of surface parameters on mineral features. We present here the results obtained variing the grain size. We studied grain size effects with two types of terrestrial rocks: anorthosite (bright) and basalte (dark) in the 2-40 microns range. We observed variations of the spectral contrast with grain size, shifts in wavelengths and variations of the intensity of some characteristic spectral features, and appearence of transparency features at wavelengths longer than 8 microns.

When things go pear shaped: contour variations of contacts

NASA Astrophysics Data System (ADS)

Utzny, Clemens

2013-04-01

Traditional control of critical dimensions (CD) on photolithographic masks considers the CD average and a measure for the CD variation such as the CD range or the standard deviation. Also systematic CD deviations from the mean such as CD signatures are subject to the control. These measures are valid for mask quality verification as long as patterns across a mask exhibit only size variations and no shape variation. The issue of shape variations becomes especially important in the context of contact holes on EUV masks. For EUV masks the CD error budget is much smaller than for standard optical masks. This means that small deviations from the contact shape can impact EUV waver prints in the sense that contact shape deformations induce asymmetric bridging phenomena. In this paper we present a detailed study of contact shape variations based on regular product data. Two data sets are analyzed: 1) contacts of varying target size and 2) a regularly spaced field of contacts. Here, the methods of statistical shape analysis are used to analyze CD SEM generated contour data. We demonstrate that contacts on photolithographic masks do not only show size variations but exhibit also pronounced nontrivial shape variations. In our data sets we find pronounced shape variations which can be interpreted as asymmetrical shape squeezing and contact rounding. Thus we demonstrate the limitations of classic CD measures for describing the feature variations on masks. Furthermore we show how the methods of statistical shape analysis can be used for quantifying the contour variations thus paving the way to a new understanding of mask linearity and its specification.

Movement is the glue connecting home ranges and habitat selection.

PubMed

Van Moorter, Bram; Rolandsen, Christer M; Basille, Mathieu; Gaillard, Jean-Michel

2016-01-01

Animal space use has been studied by focusing either on geographic (e.g. home ranges, species' distribution) or on environmental (e.g. habitat use and selection) space. However, all patterns of space use emerge from individual movements, which are the primary means by which animals change their environment. Individuals increase their use of a given area by adjusting two key movement components: the duration of their visit and/or the frequency of revisits. Thus, in spatially heterogeneous environments, animals exploit known, high-quality resource areas by increasing their residence time (RT) in and/or decreasing their time to return (TtoR) to these areas. We expected that spatial variation in these two movement properties should lead to observed patterns of space use in both geographic and environmental spaces. We derived a set of nine predictions linking spatial distribution of movement properties to emerging space-use patterns. We predicted that, at a given scale, high variation in RT and TtoR among habitats leads to strong habitat selection and that long RT and short TtoR result in a small home range size. We tested these predictions using moose (Alces alces) GPS tracking data. We first modelled the relationship between landscape characteristics and movement properties. Then, we investigated how the spatial distribution of predicted movement properties (i.e. spatial autocorrelation, mean, and variance of RT and TtoR) influences home range size and hierarchical habitat selection. In landscapes with high spatial autocorrelation of RT and TtoR, a high variation in both RT and TtoR occurred in home ranges. As expected, home range location was highly selective in such landscapes (i.e. second-order habitat selection); RT was higher and TtoR lower within the selected home range than outside, and moose home ranges were small. Within home ranges, a higher variation in both RT and TtoR was associated with higher selectivity among habitat types (i.e. third-order habitat selection). Our findings show how patterns of geographic and environmental space use correspond to the two sides of a coin, linked by movement responses of individuals to environmental heterogeneity. By demonstrating the potential to assess the consequences of altering RT or TtoR (e.g. through human disturbance or climatic changes) on home range size and habitat selection, our work sets the basis for new theoretical and methodological advances in movement ecology. © 2015 The Authors. Journal of Animal Ecology © 2015 British Ecological Society.

Investigation of Kodak extended dose range (EDR) film for megavoltage photon beam dosimetry.

PubMed

Chetty, Indrin J; Charland, Paule M

2002-10-21

We have investigated the dependence of the measured optical density on the incident beam energy, field size and depth for a new type of film, Kodak extended dose range (Kodak EDR). Film measurements have been conducted over a range of field sizes (3 x 3 cm2 to 25 x 25 cm2) and depths (d(max) to 15 cm), for 6 MV and 15 MV photons within a solid water phantom, and the variation in sensitometric response (net optical density versus dose) has been reported. Kodak EDR film is found to have a linear response with dose, from 0 to 350 cGy, which is much higher than that typically seen for Kodak XV film (0-50 cGy). The variation in sensitometric response for Kodak EDR film as a function of field size and depth is observed to be similar to that of Kodak XV film; the optical density varied in the order of 2-3% for field sizes of 3 x 3 cm2 and 10 x 10 cm2 at depths of d(max), 5 cm and 15 cm in the phantom. Measurements for a 25 x 25 cm2 field size showed consistently higher optical densities at depths of d(max), 5 cm and 15 cm, relative to a 10 x 10 cm2 field size at 5 cm depth, with 4-5% differences noted at a depth of 15 cm. Fractional depth dose and profiles conducted with Kodak EDR film showed good agreement (2%/2 mm) with ion chamber measurements for all field sizes except for the 25 x 25 cm2 at depths greater than 15 cm, where differences in the order of 3-5% were observed. In addition, Kodak EDR film measurements were found to be consistent with those of Kodak XV film for all fractional depth doses and profiles. The results of this study indicate that Kodak EDR film may be a useful tool for relative dosimetry at higher dose ranges.

Relation of Body Size on Ecological Modes

NASA Astrophysics Data System (ADS)

Ivanov, A.; Ngo, A.; Heim, N.; Payne, J.

2016-12-01

Body size in the manner of total biovolume is a useful metric for determining the way an organism interacts with its environment. Body sizes of an organism determines behavior and its life mode, the way an organism lives and survives defined by motility, depth of habitat, and feeding mode. To build on that, we hypothesize that the body size of organisms determines the amount of unique life modes an organism is capable of utilizing. the We categorized the ecological life modes of marine organisms in the phyla Arthropoda, Mollusca, Chordata, and Brachiopoda. After organizing body sizes into bins of 10,000 mm3 per x-value through R, a trend displaying a decrease in the amount of unique life modes per body size bin is visible with increasing size. Chordates however do not display as consistent of a trend as do the rest of the phyla. We hypothesize that this could be because most chordates have a backbone allowing more variation in life modes and behaviors which in turn are capable sustain larger body sizes. A boxplot regarding the range of unique life modes for all body sizes for all phyla also shows that a majority of life mode ranges range from the median size organisms from data collected to the smallest. Which means that with all of the unique life modes that were taken into consideration, the possible body sizes they ranged into were mostly into smaller organisms as there was a majority in life modes that did not range into the realm of larger body size organisms that were greater than the median sizes of the organisms.

Lack of robustness of textural measures obtained from 3D brain tumor MRIs impose a need for standardization

PubMed Central

Pérez-Beteta, Julián; Martínez-González, Alicia; Martino, Juan; Velasquez, Carlos; Arana, Estanislao; Pérez-García, Víctor M.

2017-01-01

Purpose Textural measures have been widely explored as imaging biomarkers in cancer. However, their robustness under dynamic range and spatial resolution changes in brain 3D magnetic resonance images (MRI) has not been assessed. The aim of this work was to study potential variations of textural measures due to changes in MRI protocols. Materials and methods Twenty patients harboring glioblastoma with pretreatment 3D T1-weighted MRIs were included in the study. Four different spatial resolution combinations and three dynamic ranges were studied for each patient. Sixteen three-dimensional textural heterogeneity measures were computed for each patient and configuration including co-occurrence matrices (CM) features and run-length matrices (RLM) features. The coefficient of variation was used to assess the robustness of the measures in two series of experiments corresponding to (i) changing the dynamic range and (ii) changing the matrix size. Results No textural measures were robust under dynamic range changes. Entropy was the only textural feature robust under spatial resolution changes (coefficient of variation under 10% in all cases). Conclusion Textural measures of three-dimensional brain tumor images are not robust neither under dynamic range nor under matrix size changes. Standards should be harmonized to use textural features as imaging biomarkers in radiomic-based studies. The implications of this work go beyond the specific tumor type studied here and pose the need for standardization in textural feature calculation of oncological images. PMID:28586353

Genome expansion and gene loss in powdery mildew fungi reveal functional tradeoffs in extreme parasitism

USDA-ARS?s Scientific Manuscript database

Eukaryotic genomes vary in size over five orders of magnitude ranging from microsporidia (~2.9Mb) to the lung-fish (~1.2Tb). This extraordinary variation is largely a result of the proliferation of mobile DNA elements also referred to as “genomic parasites.” The constraints on genome size may be imp...

COMPARISON OF ORGAN DOSES IN HUMAN PHANTOMS: VARIATIONS DUE TO BODY SIZE AND POSTURE.

PubMed

Feng, Xu; Xiang-Hong, Jia; Qian, Liu; Xue-Jun, Yu; Zhan-Chun, Pan; Chun-Xin, Yang

2017-04-20

Organ dose calculations performed using human phantoms can provide estimates of astronauts' health risks due to cosmic radiation. However, the characteristics of such phantoms strongly affect the estimation precision. To investigate organ dose variations with body size and posture in human phantoms, a non-uniform rational B-spline boundary surfaces model was constructed based on cryosection images. This model was used to establish four phantoms with different body size and posture parameters, whose organs parameters were changed simultaneously and which were voxelised with 4 × 4 × 4 mm3 resolution. Then, using Monte Carlo transport code, the organ doses caused by ≤500 MeV isotropic incident protons were calculated. The dose variations due to body size differences within a certain range were negligible, and the doses received in crouching and standing-up postures were similar. Therefore, a standard Chinese phantom could be established, and posture changes cannot effectively protect astronauts during solar particle events. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Generating Color from Polydisperse, Near Micron-Sized TiO2 Particles.

PubMed

Alam, Al-Mahmnur; Baek, Kyungnae; Son, Jieun; Pei, Yi-Rong; Kim, Dong Ha; Choy, Jin-Ho; Hyun, Jerome K

2017-07-19

Single particle Mie calculations of near micron-sized TiO 2 particles predict strong light scattering dominating the visible range that would give rise to a white appearance. We demonstrate that a polydisperse collection of these "white" particles can result in the generation of visible colors through ensemble scattering. The weighted averaging of the scattering over the particle size distribution modifies the sharp, multiple, high order scattering modes from individual particles into broad variations in the collective extinction. These extinction variations are apparent as visible colors for particles suspended in organic solvent at low concentration, or for a monolayer of particles supported on a transparent substrate viewed in front of a white light source. We further exploit the color variations on optical sensitivity to the surrounding environment to promote micron-sized TiO 2 particles as stable and robust agents for detecting the optical index of homogeneous media with high contrast sensitivities. Such distribution-modulated scattering properties provide TiO 2 particles an intriguing opportunity to impart color and optical sensitivity to their widespread electronic and chemical platforms such as antibacterial windows, catalysis, photocatalysis, optical sensors, and photovoltaics.

Population size, center-periphery, and seed dispersers' effects on the genetic diversity and population structure of the Mediterranean relict shrub Cneorum tricoccon.

PubMed

Lázaro-Nogal, Ana; Matesanz, Silvia; García-Fernández, Alfredo; Traveset, Anna; Valladares, Fernando

2017-09-01

The effect of population size on population genetic diversity and structure has rarely been studied jointly with other factors such as the position of a population within the species' distribution range or the presence of mutualistic partners influencing dispersal. Understanding these determining factors for genetic variation is critical for conservation of relict plants that are generally suffering from genetic deterioration. Working with 16 populations of the vulnerable relict shrub Cneorum tricoccon throughout the majority of its western Mediterranean distribution range, and using nine polymorphic microsatellite markers, we examined the effects of periphery (peripheral vs. central), population size (large vs. small), and seed disperser (introduced carnivores vs. endemic lizards) on the genetic diversity and population structure of the species. Contrasting genetic variation ( H E : 0.04-0.476) was found across populations. Peripheral populations showed lower genetic diversity, but this was dependent on population size. Large peripheral populations showed high levels of genetic diversity, whereas small central populations were less diverse. Significant isolation by distance was detected, indicating that the effect of long-distance gene flow is limited relative to that of genetic drift, probably due to high selfing rates ( F IS  = 0.155-0.887), restricted pollen flow, and ineffective seed dispersal. Bayesian clustering also supported the strong population differentiation and highly fragmented structure. Contrary to expectations, the type of disperser showed no significant effect on either population genetic diversity or structure. Our results challenge the idea of an effect of periphery per se that can be mainly explained by population size, drawing attention to the need of integrative approaches considering different determinants of genetic variation. Furthermore, the very low genetic diversity observed in several small populations and the strong among-population differentiation highlight the conservation value of large populations throughout the species' range, particularly in light of climate change and direct human threats.

Spatial Autocorrelation Can Generate Stronger Correlations between Range Size and Climatic Niches Than the Biological Signal - A Demonstration Using Bird and Mammal Range Maps.

PubMed

Boucher-Lalonde, Véronique; Currie, David J

2016-01-01

Species' geographic ranges could primarily be physiological tolerances drawn in space. Alternatively, geographic ranges could be only broadly constrained by physiological climatic tolerances: there could generally be much more proximate constraints on species' ranges (dispersal limitation, biotic interactions, etc.) such that species often occupy a small and unpredictable subset of tolerable climates. In the literature, species' climatic tolerances are typically estimated from the set of conditions observed within their geographic range. Using this method, studies have concluded that broader climatic niches permit larger ranges. Similarly, other studies have investigated the biological causes of incomplete range filling. But, when climatic constraints are measured directly from species' ranges, are correlations between species' range size and climate necessarily consistent with a causal link? We evaluated the extent to which variation in range size among 3277 bird and 1659 mammal species occurring in the Americas is statistically related to characteristics of species' realized climatic niches. We then compared how these relationships differed from the ones expected in the absence of a causal link. We used a null model that randomizes the predictor variables (climate), while retaining their broad spatial autocorrelation structure, thereby removing any causal relationship between range size and climate. We found that, although range size is strongly positively related to climatic niche breadth, range filling and, to a lesser extent, niche position in nature, the observed relationships are not always stronger than expected from spatial autocorrelation alone. Thus, we conclude that equally strong relationships between range size and climate would result from any processes causing ranges to be highly spatially autocorrelated.

Spatial Autocorrelation Can Generate Stronger Correlations between Range Size and Climatic Niches Than the Biological Signal — A Demonstration Using Bird and Mammal Range Maps

PubMed Central

Boucher-Lalonde, Véronique; Currie, David J.

2016-01-01

Species’ geographic ranges could primarily be physiological tolerances drawn in space. Alternatively, geographic ranges could be only broadly constrained by physiological climatic tolerances: there could generally be much more proximate constraints on species’ ranges (dispersal limitation, biotic interactions, etc.) such that species often occupy a small and unpredictable subset of tolerable climates. In the literature, species’ climatic tolerances are typically estimated from the set of conditions observed within their geographic range. Using this method, studies have concluded that broader climatic niches permit larger ranges. Similarly, other studies have investigated the biological causes of incomplete range filling. But, when climatic constraints are measured directly from species’ ranges, are correlations between species’ range size and climate necessarily consistent with a causal link? We evaluated the extent to which variation in range size among 3277 bird and 1659 mammal species occurring in the Americas is statistically related to characteristics of species’ realized climatic niches. We then compared how these relationships differed from the ones expected in the absence of a causal link. We used a null model that randomizes the predictor variables (climate), while retaining their broad spatial autocorrelation structure, thereby removing any causal relationship between range size and climate. We found that, although range size is strongly positively related to climatic niche breadth, range filling and, to a lesser extent, niche position in nature, the observed relationships are not always stronger than expected from spatial autocorrelation alone. Thus, we conclude that equally strong relationships between range size and climate would result from any processes causing ranges to be highly spatially autocorrelated. PMID:27855201

Estimating home-range size: when to include a third dimension?

PubMed Central

Monterroso, Pedro; Sillero, Neftalí; Rosalino, Luís Miguel; Loureiro, Filipa; Alves, Paulo Célio

2013-01-01

Most studies dealing with home ranges consider the study areas as if they were totally flat, working only in two dimensions, when in reality they are irregular surfaces displayed in three dimensions. By disregarding the third dimension (i.e., topography), the size of home ranges underestimates the surface actually occupied by the animal, potentially leading to misinterpretations of the animals' ecological needs. We explored the influence of considering the third dimension in the estimation of home-range size by modeling the variation between the planimetric and topographic estimates at several spatial scales. Our results revealed that planimetric approaches underestimate home-range size estimations, which range from nearly zero up to 22%. The difference between planimetric and topographic estimates of home-ranges sizes produced highly robust models using the average slope as the sole independent factor. Moreover, our models suggest that planimetric estimates in areas with an average slope of 16.3° (±0.4) or more will incur in errors ≥5%. Alternatively, the altitudinal range can be used as an indicator of the need to include topography in home-range estimates. Our results confirmed that home-range estimates could be significantly biased when topography is disregarded. We suggest that study areas where home-range studies will be performed should firstly be scoped for its altitudinal range, which can serve as an indicator for the need for posterior use of average slope values to model the surface area used and/or available for the studied animals. PMID:23919170

Optimal egg size in a suboptimal environment: reproductive ecology of female Sonora mud turtles (Kinosternon sonoriense) in central Arizona, USA

USGS Publications Warehouse

Lovich, Jeffrey E.; Madrak, Sheila V.; Drost, Charles A.; Monatesti, Anthony J.; Casper, Dennis; Znari, Mohammed

2012-01-01

We studied the reproductive ecology of female Sonora mud turtles (Kinosternon sonoriense) at Montezuma Well, a chemically-challenging natural wetland in central Arizona, USA. Females matured between 115.5 and 125 mm carapace length (CL) and 36-54% produced eggs each year. Eggs were detected in X-radiographs from 23 April-28 September (2007-2008) and the highest proportion (56%) of adult females with eggs occurred in June and July. Clutch frequency was rarely more than once per year. Clutch size was weakly correlated with body size, ranged from 1-8 (mean = 4.96) and did not differ significantly between years. X-ray egg width ranged from 17.8-21.7 mm (mean 19.4 mm) and varied more among clutches than within. Mean X-ray egg width of a clutch did not vary significantly with CL of females, although X-ray pelvic aperture width increased with CL. We observed no evidence of a morphological constraint on egg width. In addition, greater variation in clutch size, relative to egg width, suggests that egg size is optimized in this hydrologically stable but chemically-challenging habitat. We suggest that the diversity of architectures exhibited by the turtle pelvis, and their associated lack of correspondence to taxonomic or behavioral groupings, explains some of the variation observed in egg size of turtles.

Operating manual: Fast response solar array simulator

NASA Technical Reports Server (NTRS)

Vonhatten, R.; Weimer, A.; Zerbel, D. W.

1971-01-01

The fast response solar array simulator (FRSAS) is a universal solar array simulator which features an AC response identical to that of a real array over a large range of DC operating points. In addition, short circuit current (I sub sc) and open circuit voltage (V sub oc) are digitally programmable over a wide range for use not only in simulating a wide range of array sizes, but also to simulate (I sub sc) and (V sub oc) variations with illumination and temperature. A means for simulation of current variations due to spinning is available. Provisions for remote control and monitoring, automatic failure sensing and warning, and a load simulator are also included.

Peromyscus ranges at high and low population densities

USGS Publications Warehouse

Stickel, L.F.

1960-01-01

Live-trapping studies at the Patuxent Wildlife Research Center, Maryland, showed that the ranges of wood mice were larger when the population density was lower and smaller when the population density was higher. When the population density was about 1.3 male mice per acre in June 1954, the average distance recorded between traps after four or more captures was 258 feet. When the population density was about 4.1 male mice per acre in June 1957, the average distance was 119 feet. Differences were statistically significant. Females were so scarce at the low that comparisons could not be made for them. Examples from the literature also show that home range of a species may vary with population density. Other examples show that the range may vary with habitat, breeding condition and food supply. These variations in range size reduce the reliability of censuses in which relative methods are used: Lines of traps sample the population of a larger area when ranges are large than they do when ranges are small. Direct comparisons therefore will err in some degree. Error may be introduced also when line-trap data are transformed to per acre figures on the basis of home-range estimates made by area-trapping at another place or time. Variation in range size also can make it necessary to change area-trapping plans, for larger quadrants are needed when ranges are larger. It my be necessary to set traps closer together when ranges are small than when ranges are large.

A Macrophysiological Analysis of Energetic Constraints on Geographic Range Size in Mammals

PubMed Central

Ceballos, Gerardo; Steele, Michael A.

2013-01-01

Physiological processes are essential for understanding the distribution and abundance of organisms, and recently, with widespread attention to climate change, physiology has been ushered back to the forefront of ecological thinking. We present a macrophysiological analysis of the energetics of geographic range size using combined data on body size, basal metabolic rate (BMR), phylogeny and range properties for 574 species of mammals. We propose three mechanisms by which interspecific variation in BMR should relate positively to geographic range size: (i) Thermal Plasticity Hypothesis, (ii) Activity Levels/Dispersal Hypothesis, and (iii) Energy Constraint Hypothesis. Although each mechanism predicts a positive correlation between BMR and range size, they can be further distinguished based on the shape of the relationship they predict. We found evidence for the predicted positive relationship in two dimensions of energetics: (i) the absolute, mass-dependent dimension (BMR) and (ii) the relative, mass-independent dimension (MIBMR). The shapes of both relationships were similar and most consistent with that expected from the Energy Constraint Hypothesis, which was proposed previously to explain the classic macroecological relationship between range size and body size in mammals and birds. The fact that this pattern holds in the MIBMR dimension indicates that species with supra-allometric metabolic rates require among the largest ranges, above and beyond the increasing energy demands that accrue as an allometric consequence of large body size. The relationship is most evident at high latitudes north of the Tropics, where large ranges and elevated MIBMR are most common. Our results suggest that species that are most vulnerable to extinction from range size reductions are both large-bodied and have elevated MIBMR, but also, that smaller species with elevated MIBMR are at heightened risk. We also provide insights into the global latitudinal trends in range size and MIBMR and more general issues of phylogenetic and geographic scale. PMID:24058444

Reproductive biology, family conflict, and size of offspring in marine invertebrates.

PubMed

Kamel, Stephanie J; Oyarzun, Fernanda X; Grosberg, Richard K

2010-10-01

All organisms face two fundamental trade-offs in the allocation of energetic resources: one between many small versus a few large offspring, and the second between present and future reproduction. Nowhere are these trade-offs more apparent than in the vast range of variation in the sizes of eggs and offspring exhibited among species of marine invertebrates. It has become increasingly clear that, in many taxa of marine organisms, there is also substantial intraspecific variation in the size of eggs and hatchings. This variation has largely been attributed to adaptive maternal effects. In theory, however, the inevitable conflicts of interest that arise in families of sexually reproducing organisms over the optimal distribution of parental resources among siblings could also account for much of this variation in egg and offspring size. Here, we explore the potential impacts of family conflict on offspring traits by comparing the life histories of two exemplar species of marine organisms, the polychaete Boccardia proboscidea and the gastropod Solenosteira macrospira, emphasizing how differences in modes of fertilization and parental care might influence the phenotype and, consequently, the fitness of offspring. © The Author 2010. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved.

Comparative morphology among northern populations of breeding Cooper's Hawks

USGS Publications Warehouse

Rosenfield, Robert N.; Rosenfield, Laura J.; Bielefeldt, John; Murphy, Robert K.; Stewart, Andrew C.; Stout, William E.; Driscoll, Timothy G.; Bozek, Michael A.

2010-01-01

Few studies at a broad geographical scale have characterized intraspecific variation in morphology of woodland hawks in the genus Accipiter. From 1999 to 2007 we investigated morphological variation in large samples of live Cooper's Hawks (A. cooperii) nesting in four study areas: coniferous woodland around Victoria, British Columbia, Canada, isolated deciduous woodlands in short-grass prairies of northwestern North Dakota, towns and rural deciduous woodlands along the border of North Dakota and Minnesota, and urban and rural mixed deciduous and coniferous landscapes of Wisconsin. These sites span 2660 km across the northern part of the species' breeding range. We measured body mass (i.e., size), wing chord, tail length, tarsus diameter, hallux length, and culmen length of breeding adults, finding significant and clinal variation in body mass (or size). The smallest and most similar-sized birds occurred in British Columbia and western North Dakota, larger birds along the border between North Dakota and Minnesota, and the largest birds in Wisconsin. Several other characters varied significantly when mass was used as a covariate. Variation by study site in mean indices of sexual size dimorphism was negligible and not significant. We speculate that the morphological differences we found, in part, are the result of geographic isolation, where diets, migratory behavior, and structural characteristics of nesting habitats vary across landscape types.

Climatic and geographic predictors of life history variation in Eastern Massasauga (Sistrurus catenatus): A range-wide synthesis

PubMed Central

King, Richard B.; Adamski, John M.; Anton, Thomas G.; Bailey, Robyn L.; Baker, Sarah J.; Bieser, Nickolas D.; Bell, Thomas A.; Bissell, Kristin M.; Bradke, Danielle R.; Campa, Henry; Casper, Gary S.; Cedar, Karen; Cross, Matthew D.; DeGregorio, Brett A.; Dreslik, Michael J.; Faust, Lisa J.; Harvey, Daniel S.; Hay, Robert W.; Jellen, Benjamin C.; Johnson, Brent D.; Johnson, Glenn; Kiel, Brooke D.; Kingsbury, Bruce A.; Kowalski, Matthew J.; Lee, Yu Man; Lentini, Andrew M.; Marshall, John C.; Mauger, David; Moore, Jennifer A.; Paloski, Rori A.; Phillips, Christopher A.; Pratt, Paul D.; Preney, Thomas; Prior, Kent A.; Promaine, Andrew; Redmer, Michael; Reinert, Howard K.; Rouse, Jeremy D.; Shoemaker, Kevin T.; Sutton, Scott; VanDeWalle, Terry J.; Weatherhead, Patrick J.; Wynn, Doug; Yagi, Anne

2017-01-01

Elucidating how life history traits vary geographically is important to understanding variation in population dynamics. Because many aspects of ectotherm life history are climate-dependent, geographic variation in climate is expected to have a large impact on population dynamics through effects on annual survival, body size, growth rate, age at first reproduction, size–fecundity relationship, and reproductive frequency. The Eastern Massasauga (Sistrurus catenatus) is a small, imperiled North American rattlesnake with a distribution centered on the Great Lakes region, where lake effects strongly influence local conditions. To address Eastern Massasauga life history data gaps, we compiled data from 47 study sites representing 38 counties across the range. We used multimodel inference and general linear models with geographic coordinates and annual climate normals as explanatory variables to clarify patterns of variation in life history traits. We found strong evidence for geographic variation in six of nine life history variables. Adult female snout-vent length and neonate mass increased with increasing mean annual precipitation. Litter size decreased with increasing mean temperature, and the size–fecundity relationship and growth prior to first hibernation both increased with increasing latitude. The proportion of gravid females also increased with increasing latitude, but this relationship may be the result of geographically varying detection bias. Our results provide insights into ectotherm life history variation and fill critical data gaps, which will inform Eastern Massasauga conservation efforts by improving biological realism for models of population viability and climate change. PMID:28196149

Egg size and asymmetric sibling rivalry in red-winged blackbirds.

PubMed

Forbes, Scott; Wiebe, Mark

2010-06-01

How big to make an egg is a life history decision that in birds is made coincident with a series of other similar decisions (how many eggs to have, whether to fortify them with maternally derived hormones or immune system boosters, whether to hatch the eggs synchronously or asynchronously). Though within-population variation in egg size in birds has been well studied, its adaptive significance, if any, is unclear. Here we examine within-population variation in egg size in relation to asymmetric sibling rivalry in a 17-year study of red-winged blackbirds (Agelaius phoeniceus), an altricial songbird. Egg mass showed a twofold range of variation, with roughly 80% of the variation occurring across clutches. By commencing incubation before the clutch is complete, mothers create advantaged core and disadvantaged marginal elements within their brood. Previous work on this system has shown that sibling competition is asymmetric, and that core offspring enjoy priority access to food, and as a consequence show higher growth and lower mortality than marginal offspring. Here we examine the effect of initial egg size on nestling growth and survival in relation to these competitive asymmetries. Egg mass was strongly linked to hatchling mass, and remained significantly related to the mass of both core and marginal nestlings; the effect of egg size was stronger for core offspring early in the nestling period, but the disparity between core and marginal nestlings narrowed as they approached fledging age, and slower growing marginals fell victim to brood reduction. The effect of egg mass on survival differed dramatically between core and marginal nestlings. Egg mass was significantly related to the survival of marginal but not core nestlings: below average egg mass was associated primarily with very early mortality. Asymmetric sibling competition is clearly a strong determinant of the consequences of egg size variation.

Community variations in infant and child mortality in Peru.

PubMed Central

Edmonston, B; Andes, N

1983-01-01

Data from the national Peru Fertility Survey are used to estimate infant and childhood mortality ratios, 1968--77, for 124 Peruvian communities, ranging from small Indian hamlets in the Andes to larger cities on the Pacific coast. Significant mortality variations are found: mortality is inversely related to community population size and is higher in the mountains than in the jungle or coast. Multivariate analysis is then used to assess the influence of community population size, average female education, medical facilities, and altitude on community mortality. Finally, this study concludes that large-scale sample surveys, which include maternal birth history, add useful data for epidemiological studies of childhood mortality. PMID:6886581

Occupancy in continuous habitat

USGS Publications Warehouse

Efford, Murray G.; Dawson, Deanna K.

2012-01-01

The probability that a site has at least one individual of a species ('occupancy') has come to be widely used as a state variable for animal population monitoring. The available statistical theory for estimation when detection is imperfect applies particularly to habitat patches or islands, although it is also used for arbitrary plots in continuous habitat. The probability that such a plot is occupied depends on plot size and home-range characteristics (size, shape and dispersion) as well as population density. Plot size is critical to the definition of occupancy as a state variable, but clear advice on plot size is missing from the literature on the design of occupancy studies. We describe models for the effects of varying plot size and home-range size on expected occupancy. Temporal, spatial, and species variation in average home-range size is to be expected, but information on home ranges is difficult to retrieve from species presence/absence data collected in occupancy studies. The effect of variable home-range size is negligible when plots are very large (>100 x area of home range), but large plots pose practical problems. At the other extreme, sampling of 'point' plots with cameras or other passive detectors allows the true 'proportion of area occupied' to be estimated. However, this measure equally reflects home-range size and density, and is of doubtful value for population monitoring or cross-species comparisons. Plot size is ill-defined and variable in occupancy studies that detect animals at unknown distances, the commonest example being unlimited-radius point counts of song birds. We also find that plot size is ill-defined in recent treatments of "multi-scale" occupancy; the respective scales are better interpreted as temporal (instantaneous and asymptotic) rather than spatial. Occupancy is an inadequate metric for population monitoring when it is confounded with home-range size or detection distance.

Urbanization disrupts latitude-size rule in 17-year cicadas.

PubMed

Beasley, DeAnna E; Penick, Clint A; Boateng, Nana S; Menninger, Holly L; Dunn, Robert R

2018-03-01

Many ectotherms show a decrease in body size with increasing latitude due to changes in climate, a pattern termed converse Bergmann's rule. Urban conditions-particularly warmer temperatures and fragmented landscapes-may impose stresses on development that could disrupt these body size patterns. To test the impact of urbanization on development and latitudinal trends in body size, we launched a citizen science project to collect periodical cicadas ( Magicicada septendecim ) from across their latitudinal range during the 2013 emergence of Brood II. Periodical cicadas are long-lived insects whose distribution spans a broad latitudinal range covering both urban and rural habitats. We used a geometric morphometric approach to assess body size and developmental stress based on fluctuating asymmetry in wing shape. Body size of rural cicadas followed converse Bergmann's rule, but this pattern was disrupted in urban habitats. In the north, urban cicadas were larger than their rural counterparts, while southern populations showed little variation in body size between habitats. We detected no evidence of differences in developmental stress due to urbanization. To our knowledge, this is the first evidence that urbanization disrupts biogeographical trends in body size, and this pattern highlights how the effects of urbanization may differ over a species' range.

Seasonal body size reductions with warming covary with major body size gradients in arthropod species.

PubMed

Horne, Curtis R; Hirst, Andrew G; Atkinson, David

2017-03-29

Major biological and biogeographical rules link body size variation with latitude or environmental temperature, and these rules are often studied in isolation. Within multivoltine species, seasonal temperature variation can cause substantial changes in adult body size, as subsequent generations experience different developmental conditions. Yet, unlike other size patterns, these common seasonal temperature-size gradients have never been collectively analysed. We undertake the largest analysis to date of seasonal temperature-size gradients in multivoltine arthropods, including 102 aquatic and terrestrial species from 71 global locations. Adult size declines in warmer seasons in 86% of the species examined. Aquatic species show approximately 2.5-fold greater reduction in size per °C of warming than terrestrial species, supporting the hypothesis that greater oxygen limitation in water than in air forces aquatic species to exhibit greater plasticity in body size with temperature. Total percentage change in size over the annual cycle appears relatively constant with annual temperature range but varies between environments, such that the overall size reduction in aquatic-developing species (approx. 31%) is almost threefold greater than in terrestrial species (approx. 11%). For the first time, we show that strong correlations exist between seasonal temperature-size gradients, laboratory responses and latitudinal-size clines, suggesting that these patterns share common drivers. © 2017 The Author(s).

Mitigating Large Fires in Drossel-Schwabl Forest Fire Models

NASA Astrophysics Data System (ADS)

Yoder, M.; Turcotte, D.; Rundle, J.; Morein, G.

2008-12-01

We employ variations of the traditional Drossel-Schwabl cellular automata Forest Fire Models (FFM) to study wildfire dynamics. The traditional FFM produces a very robust power law distribution of events, as a function of size, with frequency-size slope very close to -1. Observed data from Australia, the US and northern Mexico suggest that real wild fires closely follow power laws in frequency size with slopes ranging from close to -2 to -1.3 (B.D. Malamud et al. 2005). We suggest two models that, by fracturing and trimming large clusters, reduce the number of large fires while maintaining scale invariance. These fracturing and trimming processes can be justified in terms of real physical processes. For each model, we achieve slopes in the frequency-size relation ranging from approximately -1.77 to -1.06.

Desiccation tolerance in Anopheles coluzzii: the effects of spiracle size and cuticular hydrocarbons

PubMed Central

Arcaz, Arthur C.; Huestis, Diana L.; Dao, Adama; Yaro, Alpha S.; Diallo, Moussa; Andersen, John; Blomquist, Gary J.; Lehmann, Tovi

2016-01-01

ABSTRACT The African malaria mosquitoes Anopheles gambiae and Anopheles coluzzii range over forests and arid areas, where they withstand dry spells and months-long dry seasons, suggesting variation in their desiccation tolerance. We subjected a laboratory colony (G3) and wild Sahelian mosquitoes during the rainy and dry seasons to desiccation assays. The thoracic spiracles and amount and composition of cuticular hydrocarbons (CHCs) of individual mosquitoes were measured to determine the effects of these traits on desiccation tolerance. The relative humidity of the assay, body water available, rate of water loss and water content at death accounted for 88% of the variation in desiccation tolerance. Spiracle size did not affect the rate of water loss or desiccation tolerance of the colony mosquitoes, as was the case for the total CHCs. However, six CHCs accounted for 71% of the variation in desiccation tolerance and three accounted for 72% of the variation in the rate of water loss. Wild A. coluzzii exhibited elevated desiccation tolerance during the dry season. During that time, relative thorax and spiracle sizes were smaller than during the rainy season. A smaller spiracle size appeared to increase A. coluzzii's desiccation tolerance, but was not statistically significant. Seasonal changes in CHC composition were detected in Sahelian A. coluzzii. Stepwise regression models suggested the effect of particular CHCs on desiccation tolerance. In conclusion, the combination of particular CHCs along with the total amount of CHCs is a primary mechanism conferring desiccation tolerance in A. coluzzii, while variation in spiracle size might be a secondary mechanism. PMID:27207644

Desiccation tolerance in Anopheles coluzzii: the effects of spiracle size and cuticular hydrocarbons.

PubMed

Arcaz, Arthur C; Huestis, Diana L; Dao, Adama; Yaro, Alpha S; Diallo, Moussa; Andersen, John; Blomquist, Gary J; Lehmann, Tovi

2016-06-01

The African malaria mosquitoes Anopheles gambiae and Anopheles coluzzii range over forests and arid areas, where they withstand dry spells and months-long dry seasons, suggesting variation in their desiccation tolerance. We subjected a laboratory colony (G3) and wild Sahelian mosquitoes during the rainy and dry seasons to desiccation assays. The thoracic spiracles and amount and composition of cuticular hydrocarbons (CHCs) of individual mosquitoes were measured to determine the effects of these traits on desiccation tolerance. The relative humidity of the assay, body water available, rate of water loss and water content at death accounted for 88% of the variation in desiccation tolerance. Spiracle size did not affect the rate of water loss or desiccation tolerance of the colony mosquitoes, as was the case for the total CHCs. However, six CHCs accounted for 71% of the variation in desiccation tolerance and three accounted for 72% of the variation in the rate of water loss. Wild A. coluzzii exhibited elevated desiccation tolerance during the dry season. During that time, relative thorax and spiracle sizes were smaller than during the rainy season. A smaller spiracle size appeared to increase A. coluzzii's desiccation tolerance, but was not statistically significant. Seasonal changes in CHC composition were detected in Sahelian A. coluzzii Stepwise regression models suggested the effect of particular CHCs on desiccation tolerance. In conclusion, the combination of particular CHCs along with the total amount of CHCs is a primary mechanism conferring desiccation tolerance in A. coluzzii, while variation in spiracle size might be a secondary mechanism. © 2016. Published by The Company of Biologists Ltd.

Seasonal movements and Home-range use by female pronghorns in sagebrush-steppe communities of western South Dakota

USGS Publications Warehouse

Jacques, C.N.; Jenks, J.A.; Klaver, R.W.

2009-01-01

Knowledge of seasonal movements by pronghorns (Antilocapra americana) within the easternmost extension of sagebrush-steppe communities is limited. Current hypotheses regarding movement patterns suggest that pronghorns initiate seasonal movements in response to severe winter weather, snowfall patterns, spatial and temporal variation in forage abundance, and availability of water. From January 2002 to August 2005, we monitored movements of 76 adult (≥1.5 years) female pronghorns on 2 study areas (Harding and Fall River counties) in western South Dakota. We collected 8,750 visual locations, calculated 204 home ranges, and documented 17 seasonal movements. Eighty-four percent (n = 55) of pronghorns were nonmigratory and 10% (n = 6) were conditional migrators. Mean distance between summer and winter range was 23.1 km (SE = 2.8 km, n = 13). Five adult pronghorns (8%) dispersed a mean distance of 37.6 km (SE = 12.4 km); of which 1 female moved a straight-line distance of 75.0 km. Winter and summer home-range size varied (P < 0.0001) between study sites. Mean 95% adaptive kernel winter and summer home-range size of pronghorns was 55.5 and 19.7 km2, respectively, in Harding County and 127.2 and 65.9 km2, respectively, in Fall River County. Nonmigratory behavior exhibited by pronghorns was likely associated with minimal snow cover and moderate temperatures during winter 2002–2004. Variation in size of adult seasonal home ranges between sites was likely associated with differences in forage distribution and availability between regions.

cm-scale variations of crystal orientation fabric in cold Alpine ice core from Colle Gnifetti

NASA Astrophysics Data System (ADS)

Kerch, Johanna; Weikusat, Ilka; Eisen, Olaf; Wagenbach, Dietmar; Erhardt, Tobias

2015-04-01

Analysis of the microstructural parameters of ice has been an important part of ice core analyses so far mainly in polar cores in order to obtain information about physical processes (e.g. deformation, recrystallisation) on the micro- and macro-scale within an ice body. More recently the influence of impurities and climatic conditions during snow accumulation on these processes has come into focus. A deeper understanding of how palaeoclimate proxies interact with physical properties of the ice matrix bears relevance for palaeoclimatic interpretations, improved geophysical measurement techniques and the furthering of ice dynamical modeling. Variations in microstructural parameters e.g. crystal orientation fabric or grain size can be observed on a scale of hundreds and tens of metres but also on a centimetre scale. The underlying processes are not necessarily the same on all scales. Especially for the short-scale variations many questions remain unanswered. We present results from a study that aims to investigate following hypotheses: 1. Variations in grain size and fabric, i.e. strong changes of the orientation of ice crystals with respect to the vertical, occur on a centimetre scale and can be observed in all depths of an ice core. 2. Palaeoclimate proxies like dust and impurities have an impact on the microstructural processes and thus are inducing the observed short-scale variations in grain size and fabric. 3. The interaction of proxies with the ice matrix leads to depth intervals that show correlating behaviour as well as ranges with anticorrelation between microstructural parameters and palaeoclimatic proxies. The respective processes need to be identified. Fabric Analyser measurements were conducted on more than 80 samples (total of 8 m) from different depth ranges of a cold Alpine ice core (72 m length) drilled in 2013 at Colle Gnifetti, Switzerland/Italy. Results were obtained by automatic image processing, providing estimates for grain size distributions and crystal orientation fabric, and comparison with data from continuous flow analysis of chemical impurities. A microstructural characterisation of the analysed core is presented with emphasis on the observed variations in crystal orientation fabric. The relevance of these results for palaeoclimate reconstruction and geophysical applications in ice are discussed.

Speckle pattern sequential extraction metric for estimating the focus spot size on a remote diffuse target.

PubMed

Yu, Zhan; Li, Yuanyang; Liu, Lisheng; Guo, Jin; Wang, Tingfeng; Yang, Guoqing

2017-11-10

The speckle pattern (line by line) sequential extraction (SPSE) metric is proposed by the one-dimensional speckle intensity level crossing theory. Through the sequential extraction of received speckle information, the speckle metrics for estimating the variation of focusing spot size on a remote diffuse target are obtained. Based on the simulation, we will give some discussions about the SPSE metric range of application under the theoretical conditions, and the aperture size will affect the metric performance of the observation system. The results of the analyses are verified by the experiment. This method is applied to the detection of relative static target (speckled jitter frequency is less than the CCD sampling frequency). The SPSE metric can determine the variation of the focusing spot size over a long distance, moreover, the metric will estimate the spot size under some conditions. Therefore, the monitoring and the feedback of far-field spot will be implemented laser focusing system applications and help the system to optimize the focusing performance.

The influence of landscape characteristics and home-range size on the quantification of landscape-genetics relationships

Treesearch

Tabitha A. Graves; Tzeidle N. Wasserman; Milton Cezar Ribeiro; Erin L. Landguth; Stephen F. Spear; Niko Balkenhol; Colleen B. Higgins; Marie-Josee Fortin; Samuel A. Cushman; Lisette P. Waits

2012-01-01

A common approach used to estimate landscape resistance involves comparing correlations of ecological and genetic distances calculated among individuals of a species. However, the location of sampled individuals may contain some degree of spatial uncertainty due to the natural variation of animals moving through their home range ormeasurement error in plant or animal...

The Smallest Lunar Grains: Analytical TEM Characterization of the Sub-micron Size Fraction of a Mare Soil

NASA Technical Reports Server (NTRS)

Thompson, M.; Christoffersen, R.

2010-01-01

The chemical composition, mineralogical type, and morphology of lunar regolith grains changes considerably with decreasing size, and below the approx.25 m size range the correlation between these parameters and remotely-sensed lunar surface properties connected to space weathering increases significantly. Although trends for these parameters across grain size intervals greater than 20 m are now well established, the 0 to 20 m size interval remains relatively un-subdivided with respect to variations in grain modal composition, chemistry and microstructure. Of particular interest in this size range are grains in the approximate < 1 m diameter class, whose fundamental properties are now the focus of lunar research pertaining to electrostatic grain transport, dusty plasmas, and lunar dust effects on crew health and exploration systems. In this study we have used analytical transmission electron microscopy (TEM) to characterize the mineralogy, microstructure and major element composition of grains below the 1 m size threshold in lunar soil 10084.

An analysis of beak shape variation in two ages of domestic turkeys (Meleagris gallopavo) using landmark-based geometric morphometrics.

PubMed

Dalton, Hillary A; Wood, Benjamin J; Widowski, Tina M; Guerin, Michele T; Torrey, Stephanie

2017-01-01

The objective of this study was to assess beak shape variation in domestic turkeys (Meleagris gallopavo) and determine the effects of age, sex, and beak size on beak shape variation using geometric morphometrics. Dorsal and right lateral images were taken of 2442 turkeys at 6 and 18.5 weeks of age. Landmarks were digitized in tpsDig in three analyses of the dorsal upper mandible, lateral upper mandible, and lateral lower mandible shape of each turkey at both ages. The coordinate data were then subjected to a principal components analysis (PCA), multivariate regression, and a canonical variates analysis (CVA) with a Procrustes ANOVA in MorphoJ. For the dorsal images, three principal components (PCs) showed beak shape variation ranged from long, narrow, and pointed to short, wide, and blunt upper mandibles at both ages (6 weeks: 95.36%, 18.5 weeks: 92.21%). Three PCs showed the lateral upper mandible shape variation ranged from long, wide beaks with long, curved beak tips to short, narrow beaks with short, pointed beak tips at both ages (6 weeks: 94.91%, 18.5 weeks: 94.33%). Three PCs also explained 97.80% (6 weeks) and 97.11% (18.5 weeks) of the lateral lower mandible shape variation ranging from wide and round to narrow and thin lower mandibles with superior/inferior beak tip shifts. Beak size accounted for varying proportions of the beak shape variation (0.96-54.76%; P < 0.0001) in the three analyses of each age group. For all the analyses, the CVA showed sexual dimorphism in beak shape (P < 0.0001) with female upper mandibles appearing wider and blunter dorsally with long, curved beak tips laterally. Whereas male turkey upper mandibles had a narrow, pointed dorsal appearance and short, pointed beak tips laterally. Future applications of beak shape variability could have a genetic and welfare value by incorporating beak shape variation to select for specific turkey beak phenotypes as an alternative to beak treatment.

An analysis of beak shape variation in two ages of domestic turkeys (Meleagris gallopavo) using landmark-based geometric morphometrics

PubMed Central

Widowski, Tina M.; Guerin, Michele T.

2017-01-01

The objective of this study was to assess beak shape variation in domestic turkeys (Meleagris gallopavo) and determine the effects of age, sex, and beak size on beak shape variation using geometric morphometrics. Dorsal and right lateral images were taken of 2442 turkeys at 6 and 18.5 weeks of age. Landmarks were digitized in tpsDig in three analyses of the dorsal upper mandible, lateral upper mandible, and lateral lower mandible shape of each turkey at both ages. The coordinate data were then subjected to a principal components analysis (PCA), multivariate regression, and a canonical variates analysis (CVA) with a Procrustes ANOVA in MorphoJ. For the dorsal images, three principal components (PCs) showed beak shape variation ranged from long, narrow, and pointed to short, wide, and blunt upper mandibles at both ages (6 weeks: 95.36%, 18.5 weeks: 92.21%). Three PCs showed the lateral upper mandible shape variation ranged from long, wide beaks with long, curved beak tips to short, narrow beaks with short, pointed beak tips at both ages (6 weeks: 94.91%, 18.5 weeks: 94.33%). Three PCs also explained 97.80% (6 weeks) and 97.11% (18.5 weeks) of the lateral lower mandible shape variation ranging from wide and round to narrow and thin lower mandibles with superior/inferior beak tip shifts. Beak size accounted for varying proportions of the beak shape variation (0.96–54.76%; P < 0.0001) in the three analyses of each age group. For all the analyses, the CVA showed sexual dimorphism in beak shape (P < 0.0001) with female upper mandibles appearing wider and blunter dorsally with long, curved beak tips laterally. Whereas male turkey upper mandibles had a narrow, pointed dorsal appearance and short, pointed beak tips laterally. Future applications of beak shape variability could have a genetic and welfare value by incorporating beak shape variation to select for specific turkey beak phenotypes as an alternative to beak treatment. PMID:28934330

High spatial variation in population size and symbiotic performance of Rhizobium leguminosarum bv. trifolii with white clover in New Zealand pasture soils.

PubMed

Wakelin, Steven; Tillard, Guyléne; van Ham, Robert; Ballard, Ross; Farquharson, Elizabeth; Gerard, Emily; Geurts, Rene; Brown, Matthew; Ridgway, Hayley; O'Callaghan, Maureen

2018-01-01

Biological nitrogen fixation through the legume-rhizobia symbiosis is important for sustainable pastoral production. In New Zealand, the most widespread and valuable symbiosis occurs between white clover (Trifolium repens L.) and Rhizobium leguminosarum bv. trifolii (Rlt). As variation in the population size (determined by most probable number assays; MPN) and effectiveness of N-fixation (symbiotic potential; SP) of Rlt in soils may affect white clover performance, the extent in variation in these properties was examined at three different spatial scales: (1) From 26 sites across New Zealand, (2) at farm-wide scale, and (3) within single fields. Overall, Rlt populations ranged from 95 to >1 x 108 per g soil, with variation similar at the three spatial scales assessed. For almost all samples, there was no relationship between rhizobia population size and ability of the population to fix N during legume symbiosis (SP). When compared with the commercial inoculant strain, the SP of soils ranged between 14 to 143% efficacy. The N-fixing ability of rhizobia populations varied more between samples collected from within a single hill country field (0.8 ha) than between 26 samples collected from diverse locations across New Zealand. Correlations between SP and calcium and aluminium content were found in all sites, except within a dairy farm field. Given the general lack of association between SP and MPN, and high spatial variability of SP at single field scale, provision of advice for treating legume seed with rhizobia based on field-average MPN counts needs to be carefully considered.

High spatial variation in population size and symbiotic performance of Rhizobium leguminosarum bv. trifolii with white clover in New Zealand pasture soils

PubMed Central

Tillard, Guyléne; van Ham, Robert; Ballard, Ross; Farquharson, Elizabeth; Gerard, Emily; Geurts, Rene; Brown, Matthew; Ridgway, Hayley; O’Callaghan, Maureen

2018-01-01

Biological nitrogen fixation through the legume-rhizobia symbiosis is important for sustainable pastoral production. In New Zealand, the most widespread and valuable symbiosis occurs between white clover (Trifolium repens L.) and Rhizobium leguminosarum bv. trifolii (Rlt). As variation in the population size (determined by most probable number assays; MPN) and effectiveness of N-fixation (symbiotic potential; SP) of Rlt in soils may affect white clover performance, the extent in variation in these properties was examined at three different spatial scales: (1) From 26 sites across New Zealand, (2) at farm-wide scale, and (3) within single fields. Overall, Rlt populations ranged from 95 to >1 x 108 per g soil, with variation similar at the three spatial scales assessed. For almost all samples, there was no relationship between rhizobia population size and ability of the population to fix N during legume symbiosis (SP). When compared with the commercial inoculant strain, the SP of soils ranged between 14 to 143% efficacy. The N-fixing ability of rhizobia populations varied more between samples collected from within a single hill country field (0.8 ha) than between 26 samples collected from diverse locations across New Zealand. Correlations between SP and calcium and aluminium content were found in all sites, except within a dairy farm field. Given the general lack of association between SP and MPN, and high spatial variability of SP at single field scale, provision of advice for treating legume seed with rhizobia based on field-average MPN counts needs to be carefully considered. PMID:29489845

Species traits and climate velocity explain geographic range shifts in an ocean-warming hotspot.

PubMed

Sunday, Jennifer M; Pecl, Gretta T; Frusher, Stewart; Hobday, Alistair J; Hill, Nicole; Holbrook, Neil J; Edgar, Graham J; Stuart-Smith, Rick; Barrett, Neville; Wernberg, Thomas; Watson, Reg A; Smale, Dan A; Fulton, Elizabeth A; Slawinski, Dirk; Feng, Ming; Radford, Ben T; Thompson, Peter A; Bates, Amanda E

2015-09-01

Species' ranges are shifting globally in response to climate warming, with substantial variability among taxa, even within regions. Relationships between range dynamics and intrinsic species traits may be particularly apparent in the ocean, where temperature more directly shapes species' distributions. Here, we test for a role of species traits and climate velocity in driving range extensions in the ocean-warming hotspot of southeast Australia. Climate velocity explained some variation in range shifts, however, including species traits more than doubled the variation explained. Swimming ability, omnivory and latitudinal range size all had positive relationships with range extension rate, supporting hypotheses that increased dispersal capacity and ecological generalism promote extensions. We find independent support for the hypothesis that species with narrow latitudinal ranges are limited by factors other than climate. Our findings suggest that small-ranging species are in double jeopardy, with limited ability to escape warming and greater intrinsic vulnerability to stochastic disturbances. © 2015 John Wiley & Sons Ltd/CNRS.

Coupling mammalian demography to climate through satellite time series of plant phenology

NASA Astrophysics Data System (ADS)

Stoner, D.; Sexton, J. O.; Nagol, J. R.; Ironside, K.; Choate, D.; Longshore, K.; Edwards, T., Jr.

2016-12-01

The seasonality of plant productivity governs the demography of primary and secondary consumers, and in arid ecosystems primary production is constrained by water availability. We relate the behavior, demography, and spatial distribution of large mammalian herbivores and their principal predator to remotely sensed indices of climate and vegetation across the western United States from 2000-2014. Terrain and plant community composition moderate the effects of climatological drought on primary productivity, resulting in spatial variation in ecosystem susceptibility to water stress. Herbivores track these patterns through habitat selection during key periods such as birthing and migration. Across a broad climatological gradient, timing of the start of growing season explains 75% of the variation in herbivore birth timing and 56% of the variation in neonatal survival rates. Initiation of autumn migration corresponds with the end of the growing season. Although indirectly coupled to primary production, carnivore home range size and population density are strongly correlated with plant productivity and growing-season length. Satellite measures of green reflectance during the peak of the growing season explain over 84% of the variation in carnivore home range size and 59% of the variation in density. Climate projections for the western United States predict warming temperatures and shifts in the timing and form of precipitation. Our analyses suggest that increased climatological variability will contribute to fluctuations in the composition and phenology of plant communities. These changes will propagate through consumer trophic levels, manifesting as increased home range area, shifts in the timing of migration, and greater volatility in large mammal populations. Combined with expansion and amplification of human land uses, these changes will likely have economic implications stemming from increased human-wildlife conflict and loss of ecosystem services.

Unique inhibitory cascade pattern of molars in canids contributing to their potential to evolutionary plasticity of diet

PubMed Central

Asahara, Masakazu

2013-01-01

Developmental origins that guide the evolution of dental morphology and dental formulae are fundamental subjects in mammalian evolution. In a previous study, a developmental model termed the inhibitory cascade model was established. This model could explain variations in relative molar sizes and loss of the lower third molars, which sometimes reflect diet, in murine rodents and other mammals. Here, I investigated the pattern of relative molar sizes (inhibitory cascade pattern) in canids, a taxon exhibiting a wide range of dietary habits. I found that interspecific variation in canid molars suggests a unique inhibitory cascade pattern that differs from that in murine rodents and other previously reported mammals, and that this variation reflects dietary habits. This unique variability in molars was also observed in individual variation in canid species. According to these observations, canid species have greater variability in the relative sizes of first molars (carnassials), which are functionally important for dietary adaptation in the Carnivora. In conclusion, an inhibitory cascade that differs from that in murine rodents and other mammals may have contributed to diverse dietary patterns and to their parallel evolution in canids. PMID:23467478

A quality-by-design study for an immediate-release tablet platform: examining the relative impact of active pharmaceutical ingredient properties, processing methods, and excipient variability on drug product quality attributes.

PubMed

Kushner, Joseph; Langdon, Beth A; Hicks, Ian; Song, Daniel; Li, Fasheng; Kathiria, Lalji; Kane, Anil; Ranade, Gautam; Agarwal, Kam

2014-02-01

The impact of filler-lubricant particle size ratio variation (3.4-41.6) on the attributes of an immediate-release tablet was compared with the impacts of the manufacturing method used (direct compression or dry granulation) and drug loading (1%, 5%, and 25%), particle size (D[4,3]: 8-114 μm), and drug type (theophylline or ibuprofen). All batches were successfully manufactured, except for direct compression of 25% drug loading of 8 μm (D[4,3]) drug, which exhibited very poor flow properties. All manufactured tablets possessed adequate quality attributes: tablet weight uniformity <4% RSD, tablet potency: 94%-105%, content uniformity <6% RSD, acceptance value ≤ 15, solid fraction: 0.82-0.86, tensile strength >1 MPa, friability ≤ 0.2% weight loss, and disintegration time < 4 min. The filler-lubricant particle size ratio exhibited the greatest impact on blend and granulation particle size and granulation flow, whereas drug property variation dominated blend flow, ribbon solid fraction, and tablet quality attributes. Although statistically significant effects were observed, the results of this study suggest that the manufacturability and performance of this immediate-release tablet formulation is robust to a broad range of variation in drug properties, both within-grade and extra-grade excipient particle size variations, and the choice of manufacturing method. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association.

MO-F-CAMPUS-T-04: Utilization of Optical Dosimeter for Modulated Spot-Scanning Particle Beam

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

Hsi, W; Li, Y; Huang, Z

Purpose: To present the utilization of an optical dosimeter for modulated spot-scanning carbon-ion and proton beams during the acceptance test of Siemens IONTRIS system. Method and Materials: An optical dosimeter using phosphor scintillation was developed to map and interactively analyze the shapes and sizes of spots over 190 energies for ProTom modulated-scanning system. The dose response to proton had been characterized with proper pixel calibration at ProTom system. The dose response was further studied at 0.7 cm depths by uniform 8cm in-diameter fields of 424.89 MeV/u (E290) carbon-ions and 215.18MeV (E282) protons at IONTRIS system. The virtual source axial distancesmore » (vSAD) of carbonions and protons of IONTRIS system was investigated by measuring either variations of spot position or field size at five different locations to Isocenter. By measuring lateral profiles of uniform doses with varied thin-thicknesses of chest-board pattern and placing the scintillation plate at near to the distal edge, range variations at different off-axis-distances (rOAD) were examined. Relative accuracy and reproducibility of beam range were measured for three beam ranges with a ramping block at front of scintillation plate. Results: Similar dose response was observed for high energies of carbon ions and protons. Mean vSAD at X and Y axes were 744.1 cm and 807.4cm with deviation of 7.4cm and 7.7cm, respectively. Variation of rOAD was within 0.35 mm over 10cm for both protons and carbon ions. Accuracy of measuring relative distal range using the ramping block was 0.2mm. Measured range over repeated three times for each range were within 0.25mm at same room, and within 1.0mm between four rooms. Conclusions: The optical dosimeter could efficiently measure the virtual source distance. And, to measure small range variation at different off-axial locations, and for the relative beam range between rooms during acceptance test of a modulated spot-scanning particle system.« less

Individual variation in nest size and nest site features of the Bornean orangutans (Pongo pygmaeus).

PubMed

Rayadin, Yaya; Saitoh, Takashi

2009-05-01

Nest construction is a daily habit of independent orangutans for sleeping or resting. Data on their nests have been used in various ecological studies (e.g., density estimation, ranging behavior, evolution of material culture) because they are the most observable field signs. We investigated nest size and nest site features of Bornean orangutans in the wild during 10 months' fieldwork at three sites in East Kalimantan, Indonesia: Kutai National Park, Birawa, and Meratus. To examine individual variation, we followed 31 individual orangutans and recorded the 92 nests they made for nest size (diameter) and nest site features (height of nest above ground, tree species used for the nest site, the diameter and height of the tree, whether the nest was new or reused, and nest location within the tree). Analyses taking age-sex classes of the focal individuals into consideration showed significant age-sex differences in nest size and location, but not in nest height or nest tree features (diameter, height of tree, and height of lowest branch). Mature orangutans (adult females, unflanged and flanged males) made larger nests than immatures (juveniles and adolescents). Flanged male orangutans with larger nests used stable locations for nesting sites and reused old nests more frequently than immatures. The overall proportion of nests in open (exposed) locations was higher than in closed (sheltered) locations. Flanged males and immatures frequently made open nests, whereas adult females with an infant preferred closed locations. The good correspondence between nest size and age-sex classes indicates that nest size variation may reflect body size and therefore age-sex variation in the population. (c) 2009 Wiley-Liss, Inc.

Climate and local abundance in freshwater fishes

PubMed Central

Knouft, Jason H.; Anthony, Melissa M.

2016-01-01

Identifying factors regulating variation in numbers of individuals among populations across a species' distribution is a fundamental goal in ecology. A common prediction, often referred to as the abundant-centre hypothesis, suggests that abundance is highest near the centre of a species' range. However, because of the primary focus on the geographical position of a population, this framework provides little insight into the environmental factors regulating local abundance. While range-wide variation in population abundance associated with environmental conditions has been investigated in terrestrial species, the relationship between climate and local abundance in freshwater taxa across species' distributions is not well understood. We used GIS-based temperature and precipitation data to determine the relationships between climatic conditions and range-wide variation in local abundance for 19 species of North American freshwater fishes. Climate predicted a portion of the variation in local abundance among populations for 18 species. In addition, the relationship between climatic conditions and local abundance varied among species, which is expected as lineages partition the environment across geographical space. The influence of local habitat quality on species persistence is well documented; however, our results also indicate the importance of climate in regulating population sizes across a species geographical range, even in aquatic taxa. PMID:27429769

Living in isolation - population structure, reproduction, and genetic variation of the endangered plant species Dianthus gratianopolitanus (Cheddar pink).

PubMed

Putz, Christina M; Schmid, Christoph; Reisch, Christoph

2015-09-01

The endangered plant species Dianthus gratianopolitanus exhibits a highly fragmented distribution range comprising many isolated populations. Based upon this pattern of distribution, we selected a study region in Switzerland with a lower magnitude of isolation (Swiss Jura) and another study region in Germany with a higher degree of isolation (Franconian Jura). In each region, we chose ten populations to analyze population structure, reproduction, and genetic variation in a comparative approach. Therefore, we determined population density, cushion size, and cushion density to analyze population structure, investigated reproductive traits, including number of flowers, capsules, and germination rate, and analyzed amplified fragment length polymorphisms to study genetic variation. Population and cushion density were credibly higher in German than in Swiss populations, whereas reproductive traits and genetic variation within populations were similar in both study regions. However, genetic variation among populations and isolation by distance were stronger in Germany than in Switzerland. Generally, cushion size and density as well as flower and capsule production increased with population size and density, whereas genetic variation decreased with population density. In contrast to our assumptions, we observed denser populations and cushions in the region with the higher magnitude of isolation, whereas reproductive traits and genetic variation within populations were comparable in both regions. This corroborates the assumption that stronger isolation must not necessarily result in the loss of fitness and genetic variation. Furthermore, it supports our conclusion that the protection of strongly isolated populations contributes essentially to the conservation of a species' full evolutionary potential.

Geographic variation in morphology of Alaska-breeding Bar-tailed Godwits (Limosa lapponica) is not maintained on their nonbreeding grounds in New Zealand

USGS Publications Warehouse

Conklin, Jesse R.; Battley, Phil F.; Potter, Murray A.; Ruthrauff, Daniel R.

2011-01-01

Among scolopacid shorebirds, Bar-tailed Godwits (Limosa lapponica) have unusually high intra- and intersexual differences in size and breeding plumage. Despite historical evidence for population structure among Alaska-breeding Bar-tailed Godwits (L. l. baueri), no thorough analysis, or comparison with the population's nonbreeding distribution, has been undertaken. We used live captures, field photography, museum specimens, and individuals tracked from New Zealand to describe geographic variation in size and plumage within the Alaska breeding range. We found a north-south cline in body size in Alaska, in which the smallest individuals of each sex occurred at the highest latitudes. Extent of male breeding plumage (proportion of nonbreeding contour feathers replaced) also increased with latitude, but female breeding plumage was most extensive at mid-latitudes. This population structure was not maintained in the nonbreeding season: morphometrics of captured birds and timing of migratory departures indicated that individuals from a wide range of breeding latitudes occur in each region and site in New Zealand. Links among morphology, phenology, and breeding location suggest the possibility of distinct Alaska breeding populations that mix freely in the nonbreeding season, and also imply that the strongest selection for size occurs in the breeding season.

Intra-class correlation estimates for assessment of vitamin A intake in children.

PubMed

Agarwal, Girdhar G; Awasthi, Shally; Walter, Stephen D

2005-03-01

In many community-based surveys, multi-level sampling is inherent in the design. In the design of these studies, especially to calculate the appropriate sample size, investigators need good estimates of intra-class correlation coefficient (ICC), along with the cluster size, to adjust for variation inflation due to clustering at each level. The present study used data on the assessment of clinical vitamin A deficiency and intake of vitamin A-rich food in children in a district in India. For the survey, 16 households were sampled from 200 villages nested within eight randomly-selected blocks of the district. ICCs and components of variances were estimated from a three-level hierarchical random effects analysis of variance model. Estimates of ICCs and variance components were obtained at village and block levels. Between-cluster variation was evident at each level of clustering. In these estimates, ICCs were inversely related to cluster size, but the design effect could be substantial for large clusters. At the block level, most ICC estimates were below 0.07. At the village level, many ICC estimates ranged from 0.014 to 0.45. These estimates may provide useful information for the design of epidemiological studies in which the sampled (or allocated) units range in size from households to large administrative zones.

Food web structure shaped by habitat size and climate across a latitudinal gradient.

PubMed

Romero, Gustavo Q; Piccoli, Gustavo C O; de Omena, Paula M; Gonçalves-Souza, Thiago

2016-10-01

Habitat size and climate are known to affect the trophic structure and dynamics of communities, but their interactive effects are poorly understood. Organisms from different trophic levels vary in terms of metabolic requirements and heat dissipation. Indeed, larger species such as keystone predators require more stable climatic conditions than their prey. Likewise, habitat size disproportionally affects large-sized predators, which require larger home ranges and are thus restricted to larger habitats. Therefore, food web structure in patchy ecosystems is expected to be shaped by habitat size and climate variations. Here we investigate this prediction using natural aquatic microcosm (bromeliad phytotelmata) food webs composed of litter resources (mainly detritus), detritivores, mesopredators, and top predators (damselflies). We surveyed 240 bromeliads of varying sizes (water retention capacity) across 12 open restingas in SE Brazil spread across a wide range of tropical latitudes (-12.6° to -27.6°, ca. 2,000 km) and climates (Δ mean annual temperature = 5.3°C). We found a strong increase in predator-to-detritivore mass ratio with habitat size, which was representative of a typical inverted trophic pyramid in larger ecosystems. However, this relationship was contingent among the restingas; slopes of linear models were steeper in more stable and favorable climates, leading to inverted trophic pyramids (and top-down control) being more pronounced in environments with more favorable climatic conditions. By contrast, detritivore-resource and mesopredator-detritivore mass ratios were not affected by habitat size or climate variations across latitudes. Our results highlight that the combined effects of habitat size, climate and predator composition are pivotal to understanding the impacts of multiple environmental factors on food web structure and dynamics. © 2016 by the Ecological Society of America.

Rain, prey and predators: climatically driven shifts in frog abundance modify reproductive allometry in a tropical snake.

PubMed

Brown, Gregory P; Shine, Richard

2007-11-01

To predict the impacts of climate change on animal populations, we need long-term data sets on the effects of annual climatic variation on the demographic traits (growth, survival, reproductive output) that determine population viability. One frequent complication is that fecundity also depends upon maternal body size, a trait that often spans a wide range within a single population. During an eight-year field study, we measured annual variation in weather conditions, frog abundance and snake reproduction on a floodplain in the Australian wet-dry tropics. Frog numbers varied considerably from year to year, and were highest in years with hotter wetter conditions during the monsoonal season ("wet season"). Mean maternal body sizes, egg sizes and post-partum maternal body conditions of frog-eating snakes (keelback, Tropidonophis mairii, Colubridae) showed no significant annual variation over this period, but mean clutch sizes were higher in years with higher prey abundance. Larger females were more sensitive to frog abundance in this respect than were smaller conspecifics, so that the rate at which fecundity increased with body size varied among years, and was highest when prey availability was greatest. Thus, the link between female body size and reproductive output varied among years, with climatic factors modifying the relative reproductive rates of larger (older) versus smaller (younger) animals within the keelback population.

Mechanics of Constriction during Cell Division: A Variational Approach

PubMed Central

Almendro-Vedia, Victor G.; Monroy, Francisco; Cao, Francisco J.

2013-01-01

During symmetric division cells undergo large constriction deformations at a stable midcell site. Using a variational approach, we investigate the mechanical route for symmetric constriction by computing the bending energy of deformed vesicles with rotational symmetry. Forces required for constriction are explicitly computed at constant area and constant volume, and their values are found to be determined by cell size and bending modulus. For cell-sized vesicles, considering typical bending modulus of , we calculate constriction forces in the range . The instability of symmetrical constriction is shown and quantified with a characteristic coefficient of the order of , thus evidencing that cells need a robust mechanism to stabilize constriction at midcell. PMID:23990888

Pixel structures to compensate nonuniform threshold voltage and mobility of polycrystalline silicon thin-film transistors using subthreshold current for large-size active matrix organic light-emitting diode displays

NASA Astrophysics Data System (ADS)

Na, Jun-Seok; Kwon, Oh-Kyong

2014-01-01

We propose pixel structures for large-size and high-resolution active matrix organic light-emitting diode (AMOLED) displays using a polycrystalline silicon (poly-Si) thin-film transistor (TFT) backplane. The proposed pixel structures compensate the variations of the threshold voltage and mobility of the driving TFT using the subthreshold current. The simulated results show that the emission current error of the proposed pixel structure B ranges from -2.25 to 2.02 least significant bit (LSB) when the variations of the threshold voltage and mobility of the driving TFT are ±0.5 V and ±10%, respectively.

Thermoregulation of a temperate reptile in a forested habitat.

PubMed

Corkery, Ilse; Bell, Ben D; Nelson, Nicola J

2018-04-01

A major focus in zoology is to understand the phenotypic responses of animals to environmental variation. This is particularly important when dealing with ectotherms in a thermally heterogenous environment. We measured body temperatures of a free-ranging, medium sized temperate reptile, the tuatara, Sphenodon punctatus, to investigate its thermal opportunities and the degree to which the animal actively regulates its body temperature. We found high variation in body temperature between individuals, but this variation could not be attributed to sex or body size. However, variation among individuals in timing of burrow use did affect body temperature and in one of the years studied tuatara were found to be more effective in their thermoregulation when sharing a burrow with a seabird (Pachyptila turtur). The strength of this study is that it includes both biotic and behavioural components of the thermal environment of a temperate reptile, areas which are often missing from thermal studies that focus on the abiotic aspects. Copyright © 2018 Elsevier GmbH. All rights reserved.

Drought stress limits the geographic ranges of two tree species via different physiological mechanisms.

PubMed

Anderegg, Leander D L; HilleRisLambers, Janneke

2016-03-01

Range shifts are among the most ubiquitous ecological responses to anthropogenic climate change and have large consequences for ecosystems. Unfortunately, the ecophysiological forces that constrain range boundaries are poorly understood, making it difficult to mechanistically project range shifts. To explore the physiological mechanisms by which drought stress controls dry range boundaries in trees, we quantified elevational variation in drought tolerance and in drought avoidance-related functional traits of a widespread gymnosperm (ponderosa pine - Pinus ponderosa) and angiosperm (trembling aspen - Populus tremuloides) tree species in the southwestern USA. Specifically, we quantified tree-to-tree variation in growth, water stress (predawn and midday xylem tension), drought avoidance traits (branch conductivity, leaf/needle size, tree height, leaf area-to-sapwood area ratio), and drought tolerance traits (xylem resistance to embolism, hydraulic safety margin, wood density) at the range margins and range center of each species. Although water stress increased and growth declined strongly at lower range margins of both species, ponderosa pine and aspen showed contrasting patterns of clinal trait variation. Trembling aspen increased its drought tolerance at its dry range edge by growing stronger but more carbon dense branch and leaf tissues, implying an increased cost of growth at its range boundary. By contrast, ponderosa pine showed little elevational variation in drought-related traits but avoided drought stress at low elevations by limiting transpiration through stomatal closure, such that its dry range boundary is associated with limited carbon assimilation even in average climatic conditions. Thus, the same climatic factor (drought) may drive range boundaries through different physiological mechanisms - a result that has important implications for process-based modeling approaches to tree biogeography. Further, we show that comparing intraspecific patterns of trait variation across ranges, something rarely done in a range-limit context, helps elucidate a mechanistic understanding of range constraints. © 2015 John Wiley & Sons Ltd.

Day and night variation in chemical composition and toxicological responses of size segregated urban air PM samples in a high air pollution situation

NASA Astrophysics Data System (ADS)

Jalava, P. I.; Wang, Q.; Kuuspalo, K.; Ruusunen, J.; Hao, L.; Fang, D.; Väisänen, O.; Ruuskanen, A.; Sippula, O.; Happo, M. S.; Uski, O.; Kasurinen, S.; Torvela, T.; Koponen, H.; Lehtinen, K. E. J.; Komppula, M.; Gu, C.; Jokiniemi, J.; Hirvonen, M.-R.

2015-11-01

Urban air particulate pollution is a known cause for adverse human health effects worldwide. China has encountered air quality problems in recent years due to rapid industrialization. Toxicological effects induced by particulate air pollution vary with particle sizes and season. However, it is not known how distinctively different photochemical activity and different emission sources during the day and the night affect the chemical composition of the PM size ranges and subsequently how it is reflected to the toxicological properties of the PM exposures. The particulate matter (PM) samples were collected in four different size ranges (PM10-2.5; PM2.5-1; PM1-0.2 and PM0.2) with a high volume cascade impactor. The PM samples were extracted with methanol, dried and thereafter used in the chemical and toxicological analyses. RAW264.7 macrophages were exposed to the particulate samples in four different doses for 24 h. Cytotoxicity, inflammatory parameters, cell cycle and genotoxicity were measured after exposure of the cells to particulate samples. Particles were characterized for their chemical composition, including ions, element and PAH compounds, and transmission electron microscopy (TEM) was used to take images of the PM samples. Chemical composition and the induced toxicological responses of the size segregated PM samples showed considerable size dependent differences as well as day to night variation. The PM10-2.5 and the PM0.2 samples had the highest inflammatory potency among the size ranges. Instead, almost all the PM samples were equally cytotoxic and only minor differences were seen in genotoxicity and cell cycle effects. Overall, the PM0.2 samples had the highest toxic potential among the different size ranges in many parameters. PAH compounds in the samples and were generally more abundant during the night than the day, indicating possible photo-oxidation of the PAH compounds due to solar radiation. This was reflected to different toxicity in the PM samples. Some of the day to night difference may have been caused also by differing wind directions transporting air masses from different emission sources during the day and the night. The present findings indicate the important role of the local particle sources and atmospheric processes on the health related toxicological properties of the PM. The varying toxicological responses evoked by the PM samples showed the importance of examining various particle sizes. Especially the detected considerable toxicological activity by PM0.2 size range suggests they're attributable to combustion sources, new particle formation and atmospheric processes.

Phylogenetic heritability of geographic range size in haematophagous ectoparasites: time of divergence and variation among continents.

PubMed

Krasnov, Boris R; Shenbrot, Georgy I; van der Mescht, Luther; Warburton, Elizabeth M; Khokhlova, Irina S

2018-04-12

To understand existence, patterns and mechanisms behind phylogenetic heritability in the geographic range size (GRS) of parasites, we measured phylogenetic signal (PS) in the sizes of both regional (within a region) and continental (within a continent) geographic ranges of fleas in five regions. We asked whether (a) GRS is phylogenetically heritable and (b) the manifestation of PS varies between regions. We also asked whether geographic variation in PS reflects the effects of the environment's spatiotemporal stability (e.g. glaciation disrupting geographic ranges) or is associated with time since divergence (accumulation differences among species over time). Support for the former hypothesis would be indicated by stronger PS in southern than in northern regions, whereas support for the latter hypothesis would be shown by stronger PS in regions with a large proportion of species belonging to the derived lineages than in regions with a large proportion of species belonging to the basal lineages. We detected significant PS in both regional and continental GRSs of fleas from Canada and in continental GRS of fleas from Mongolia. No PS was found in the GRS of fleas from Australia and Southern Africa. Venezuelan fleas demonstrated significant PS in regional GRS only. Local Indicators of Phylogenetic Association detected significant local positive autocorrelations of GRS in some clades even in regions in which PS has not been detected across the entire phylogeny. This was mainly characteristic of younger taxa.

Size, sex and individual-level behaviour drive intrapopulation variation in cross-ecosystem foraging of a top-predator.

PubMed

Nifong, James C; Layman, Craig A; Silliman, Brian R

2015-01-01

Large-bodied, top-predators are often highly mobile, with the potential to provide important linkages between spatially distinct food webs. What biological factors contribute to variation in cross-ecosystem movements, however, have rarely been examined. Here, we investigated how ontogeny (body size), sex and individual-level behaviour impacts intrapopulation variation in cross-ecosystem foraging (i.e. between freshwater and marine systems), by the top-predator Alligator mississippiensis. Field surveys revealed A. mississippiensis uses marine ecosystems regularly and are abundant in estuarine tidal creeks (from 0·3 to 6·3 individuals per km of creek, n = 45 surveys). Alligator mississippiensis captured in marine/estuarine habitats were significantly larger than individuals captured in freshwater and intermediate habitats. Stomach content analysis (SCA) showed that small juveniles consumed marine/estuarine prey less frequently (6·7% of individuals) than did large juveniles (57·8%), subadult (73%), and adult (78%) size classes. Isotopic mixing model analysis (SIAR) also suggests substantial variation in use of marine/estuarine prey resources with differences among and within size classes between sexes and individuals (range of median estimates for marine/estuarine diet contribution = 0·05-0·76). These results demonstrate the importance of intrapopulation characteristics (body size, sex and individual specialization) as key determinants of the strength of predator-driven ecosystem connectivity resulting from cross-ecosystem foraging behaviours. Understanding the factors, which contribute to variation in cross-ecosystem foraging behaviours, will improve our predictive understanding of the effects of top-predators on community structure and ecosystem function. © 2014 The Authors. Journal of Animal Ecology © 2014 British Ecological Society.

Fluctuating survival selection explains variation in avian group size

PubMed Central

Brown, Charles R.; Brown, Mary Bomberger; Roche, Erin A.; O’Brien, Valerie A.; Page, Catherine E.

2016-01-01

Most animal groups vary extensively in size. Because individuals in certain sizes of groups often have higher apparent fitness than those in other groups, why wide group size variation persists in most populations remains unexplained. We used a 30-y mark–recapture study of colonially breeding cliff swallows (Petrochelidon pyrrhonota) to show that the survival advantages of different colony sizes fluctuated among years. Colony size was under both stabilizing and directional selection in different years, and reversals in the sign of directional selection regularly occurred. Directional selection was predicted in part by drought conditions: birds in larger colonies tended to be favored in cooler and wetter years, and birds in smaller colonies in hotter and drier years. Oscillating selection on colony size likely reflected annual differences in food availability and the consequent importance of information transfer, and/or the level of ectoparasitism, with the net benefit of sociality varying under these different conditions. Averaged across years, there was no net directional change in selection on colony size. The wide range in cliff swallow group size is probably maintained by fluctuating survival selection and represents the first case, to our knowledge, in which fitness advantages of different group sizes regularly oscillate over time in a natural vertebrate population. PMID:27091998

Fluctuating survival selection explains variation in avian group size.

PubMed

Brown, Charles R; Brown, Mary Bomberger; Roche, Erin A; O'Brien, Valerie A; Page, Catherine E

2016-05-03

Most animal groups vary extensively in size. Because individuals in certain sizes of groups often have higher apparent fitness than those in other groups, why wide group size variation persists in most populations remains unexplained. We used a 30-y mark-recapture study of colonially breeding cliff swallows (Petrochelidon pyrrhonota) to show that the survival advantages of different colony sizes fluctuated among years. Colony size was under both stabilizing and directional selection in different years, and reversals in the sign of directional selection regularly occurred. Directional selection was predicted in part by drought conditions: birds in larger colonies tended to be favored in cooler and wetter years, and birds in smaller colonies in hotter and drier years. Oscillating selection on colony size likely reflected annual differences in food availability and the consequent importance of information transfer, and/or the level of ectoparasitism, with the net benefit of sociality varying under these different conditions. Averaged across years, there was no net directional change in selection on colony size. The wide range in cliff swallow group size is probably maintained by fluctuating survival selection and represents the first case, to our knowledge, in which fitness advantages of different group sizes regularly oscillate over time in a natural vertebrate population.

Fluctuating survival selection explains variation in avian group size

USGS Publications Warehouse

Brown, Charles B.; Brown, Mary Bomberger; Roche, Erin A.; O'brien, Valerie A; Page, Catherine E.

2016-01-01

Most animal groups vary extensively in size. Because individuals in certain sizes of groups often have higher apparent fitness than those in other groups, why wide group size variation persists in most populations remains unexplained. We used a 30-y mark–recapture study of colonially breeding cliff swallows (Petrochelidon pyrrhonota) to show that the survival advantages of different colony sizes fluctuated among years. Colony size was under both stabilizing and directional selection in different years, and reversals in the sign of directional selection regularly occurred. Directional selection was predicted in part by drought conditions: birds in larger colonies tended to be favored in cooler and wetter years, and birds in smaller colonies in hotter and drier years. Oscillating selection on colony size likely reflected annual differences in food availability and the consequent importance of information transfer, and/or the level of ectoparasitism, with the net benefit of sociality varying under these different conditions. Averaged across years, there was no net directional change in selection on colony size. The wide range in cliff swallow group size is probably maintained by fluctuating survival selection and represents the first case, to our knowledge, in which fitness advantages of different group sizes regularly oscillate over time in a natural vertebrate population.

Geographic variation of life-history traits in the sand lizard, Lacerta agilis: testing Darwin's fecundity-advantage hypothesis.

PubMed

Roitberg, E S; Eplanova, G V; Kotenko, T I; Amat, F; Carretero, M A; Kuranova, V N; Bulakhova, N A; Zinenko, O I; Yakovlev, V A

2015-03-01

The fecundity-advantage hypothesis (FAH) explains larger female size relative to male size as a correlated response to fecundity selection. We explored FAH by investigating geographic variation in female reproductive output and its relation to sexual size dimorphism (SSD) in Lacerta agilis, an oviparous lizard occupying a major part of temperate Eurasia. We analysed how sex-specific body size and SSD are associated with two putative indicators of fecundity selection intensity (clutch size and the slope of the clutch size-female size relationship) and with two climatic variables throughout the species range and across two widespread evolutionary lineages. Variation within the lineages provides no support for FAH. In contrast, the divergence between the lineages is in line with FAH: the lineage with consistently female-biased SSD (L. a. agilis) exhibits higher clutch size and steeper fecundity slope than the lineage with an inconsistent and variable SSD (L. a. exigua). L. a. agilis shows lower offspring size (egg mass, hatchling mass) and higher clutch mass relative to female mass than L. a. exigua, that is both possible ways to enhance offspring number are exerted. As the SSD difference is due to male size (smaller males in L. a. agilis), fecundity selection favouring larger females, together with viability selection for smaller size in both sexes, would explain the female-biased SSD and reproductive characteristics of L. a. agilis. The pattern of intraspecific life-history divergence in L. agilis is strikingly similar to that between oviparous and viviparous populations of a related species Zootoca vivipara. Evolutionary implications of this parallelism are discussed. © 2015 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2015 European Society For Evolutionary Biology.

Genetic diversity in three endangered pitcher plant species (Sarracenia; Sarraceniaceae) is lower than widespread congeners.

PubMed

Furches, M Steven; Small, Randall L; Furches, Anna

2013-10-01

Narrow-ranging, rare species often exhibit levels of genetic diversity lower than more common or widespread congeners. These taxa are at increased risk of extinction due to threats associated with natural as well as anthropogenic events. We assessed genetic variation in three federally endangered Sarracenia species. We discuss maintenance of genetic diversity and evolutionary implications of rarity. • We analyzed three noncoding chloroplast regions and nine microsatellite loci in populations spanning the geographic ranges of S. oreophila, S. alabamensis, and S. jonesii. The same microsatellite loci were used to examine a single field site of three more widespread species (S. alata, S. leucophylla, and S. rubra subsp. wherryi). • All three endangered species have experienced reductions in population size and numbers. All show considerably less variation than more widespread members of the genus. Sarracenia alabamensis maintains the greatest microsatellite variation but has the fewest remaining populations and may be under the greatest threat. More widespread S. oreophila maintains surprising chloroplast diversity, yet exhibits little microsatellite diversity. Sarracenia jonesii lacks chloroplast diversity, yet maintains greater microsatellite diversity than S. oreophila. • The three endangered species differ in levels and structure of diversity, yet not in predictable ways, emphasizing that unique demographic and ecological histories, rather than current distribution and population size, best explain present patterns of genetic variation. Maintenance of remaining genetic variation is important, but preventing further habitat loss and degradation is critical.

Thriving at the limit: Differential reproductive performance in range-edge populations of a Mediterranean sclerophyll (Olea europaea)

NASA Astrophysics Data System (ADS)

Granado-Yela, Carlos; Balaguer, Luis; García-Verdugo, Carlos; Carrillo, Katty; Méndez, Marcos

2013-10-01

Peripheral populations are often lumped together on the assumption of thriving in marginal habitats where reproductive performance is compromised. We have tested this hypothesis in peripheral populations of wild olive tree (Olea europaea L.) presumably limited by different factors at the westernmost limit of the species range. Additionally, we hypothesized that differences in reproductive outcome among populations are better explained by site-specific environmental conditions (PAR, soil water, soil nutrients, air humidity and air temperature) than by differences in phenotypic traits (tree size and leaf traits). To test these hypotheses, we assessed the number of flowering trees, the flowering intensity, fruit set and seed viability in eight populations for three consecutive years. Our findings provided sufficient evidence to reject the first hypothesis. Peripheral populations that occur under oceanic conditions, resembling the Tertiary subtropical climate, consistently presented higher values for all components of reproductive performance than those at the thermal and rainfall tolerance limits. In support of our second hypothesis, the variation in reproductive performance among populations was primarily accounted for by local environmental conditions. Leaf traits, however, also explained reproductive variation but to a lesser extent. Finally, we found that small changes in tree size may cause large differences in reproductive performance. This close relationship between tree size and reproductive performance suggests that any impact on population size structure would likely jeopardize persistence and expansion at the range edge. Our results suggest that reproductive performance of wild olive trees was not shaped by the population geographic position within the species range, but by the interaction between local environment, as the main driver, and individual phenotypic traits.

Temperature-dependency of Magnetic Susceptibility U Advantages and Limits For Magneto-mineralogical Studies

NASA Astrophysics Data System (ADS)

Kontny, A.

Low-field magnetic susceptibility measurements in the temperature range U192 to 700 C (k(T)) are a widely applied method used for the identification of magnetic phases and characteristic magnetic phase transitions. One of the advantages of this method is the precise determination of titanomagnetite composition independently from grain size. However, the interpretations of k(T)-curves often are discussed controversially because other effects like grain size or the occurrence of more than one magnetic phase complicate the courses. Case studies from the titanomagnetite and titanohe- matite solid solution series including pure magnetite and hematite will be presented and variations in chemical composition, alteration and grain size will be discussed in relation to their geological significance. (1) In subaerially extruded basaltic lava differences in the low-temperature legs of the k(T) curves indicate variations in the degree of high-temperature (deuteric) oxidation of titanomagnetite. This alteration to magnetite-rich titanomagnetite is accompanied by a grain size reduction, which can be correlated with the development of a susceptibility peak at about U160 C. Fur- ther oxidation transforms the titanomagnetite into titanohematite which again results in a characteristic k(T) behavior at low temperatures with a decrease in k with in- creasing temperature (2) Hydrothermal alteration from magnetite to hematite creates a hematite phase that cannot be seen in k(T)-curves. However, hematite that is grown in sediments, can be identified by its Tc. Therefore it is assumed that crystallinity of magnetic phases seems to play a significant role to explain a different behaviour. (3) Submarine basalts rapidly quenched from high temperatures often show wide anti- clines in the k(T)-curves which can be correlated with a range of chemical composition and grain sizes, including small amounts of pure magnetite. This feature is commonly attributed to low-temperature alteration of single domain grains of titanomagnetite and is described for ocean floor basalts. An alternative interpretation is given by composi- tional and grain size variations due to small scale fractionation of melt related to the cooling of the lava. Generally, the high-temperature leg of k(T) curves mostly indi- cates the chemical composition (Tc) and degree of alteration, the low-temperature leg seems to be more sensible for grain size variations.

Annual and semiannual variations of the geomagnetic field at equatorial locations

USGS Publications Warehouse

Campbell, W.H.

1981-01-01

For a year of quiet solar-activity level, geomagnetic records from American hemisphere observatories located between about 0?? and 30?? north geomagnetic latitude were used to compare the annual and semiannual variations of the geomagnetic field associated with three separate contributions: (a) the quiet-day midnight level, MDT; (b) the solar-quiet daily variation, Sq; (c) the quiet-time lunar semidiurnal tidal variation, L(12). Four Fourier spectral constituents (24, 12, 8, 6 h periods) of Sq were individually treated. All three orthogonal elements (H, D and Z) were included in the study. The MDT changes show a dominant semiannual variation having a range of about 7 gammas in H and a dominant annual variation in Z having a range of over 8 gammas. These changes seem to be a seasonal response to the nightside distortions by magnetospheric currents. There is a slow decrease in MDT amplitudes with increasing latitude. The Sq changes follow the patterns expected from an equatorial ionospheric dynamo electrojet current system. The dominant seasonal variations occur in H having a range of over 21 gammas for the 24 h period and over 12 gammas for the 12 h period spectral components. The higher-order components are relatively smaller in size. The Sq(H) amplitudes decrease rapidly with increasing latitude. Magnetospheric contributions to the equatorial Sq must be less than a few per cent of the observed magnitude. The L(12) variation shows the ionospheric electrojet features by the dominance of H and the rapid decrease in amplitude with latitude away from the equator. However, the seasonal variation range of over 7 gammas has a maximum in early February and minimum in late June that is not presently explainable by the known ionospheric conductivity and tidal behavior. ?? 1981.

Infrared variation reduction by simultaneous background suppression and target contrast enhancement for deep convolutional neural network-based automatic target recognition

NASA Astrophysics Data System (ADS)

Kim, Sungho

2017-06-01

Automatic target recognition (ATR) is a traditionally challenging problem in military applications because of the wide range of infrared (IR) image variations and the limited number of training images. IR variations are caused by various three-dimensional target poses, noncooperative weather conditions (fog and rain), and difficult target acquisition environments. Recently, deep convolutional neural network-based approaches for RGB images (RGB-CNN) showed breakthrough performance in computer vision problems, such as object detection and classification. The direct use of RGB-CNN to the IR ATR problem fails to work because of the IR database problems (limited database size and IR image variations). An IR variation-reduced deep CNN (IVR-CNN) to cope with the problems is presented. The problem of limited IR database size is solved by a commercial thermal simulator (OKTAL-SE). The second problem of IR variations is mitigated by the proposed shifted ramp function-based intensity transformation. This can suppress the background and enhance the target contrast simultaneously. The experimental results on the synthesized IR images generated by the thermal simulator (OKTAL-SE) validated the feasibility of IVR-CNN for military ATR applications.

Size-density scaling in protists and the links between consumer-resource interaction parameters.

PubMed

DeLong, John P; Vasseur, David A

2012-11-01

Recent work indicates that the interaction between body-size-dependent demographic processes can generate macroecological patterns such as the scaling of population density with body size. In this study, we evaluate this possibility for grazing protists and also test whether demographic parameters in these models are correlated after controlling for body size. We compiled data on the body-size dependence of consumer-resource interactions and population density for heterotrophic protists grazing algae in laboratory studies. We then used nested dynamic models to predict both the height and slope of the scaling relationship between population density and body size for these protists. We also controlled for consumer size and assessed links between model parameters. Finally, we used the models and the parameter estimates to assess the individual- and population-level dependence of resource use on body-size and prey-size selection. The predicted size-density scaling for all models matched closely to the observed scaling, and the simplest model was sufficient to predict the pattern. Variation around the mean size-density scaling relationship may be generated by variation in prey productivity and area of capture, but residuals are relatively insensitive to variation in prey size selection. After controlling for body size, many consumer-resource interaction parameters were correlated, and a positive correlation between residual prey size selection and conversion efficiency neutralizes the apparent fitness advantage of taking large prey. Our results indicate that widespread community-level patterns can be explained with simple population models that apply consistently across a range of sizes. They also indicate that the parameter space governing the dynamics and the steady states in these systems is structured such that some parts of the parameter space are unlikely to represent real systems. Finally, predator-prey size ratios represent a kind of conundrum, because they are widely observed but apparently have little influence on population size and fitness, at least at this level of organization. © 2012 The Authors. Journal of Animal Ecology © 2012 British Ecological Society.

Intrapopulation Genome Size Variation in D. melanogaster Reflects Life History Variation and Plasticity

PubMed Central

Ellis, Lisa L.; Huang, Wen; Quinn, Andrew M.; Ahuja, Astha; Alfrejd, Ben; Gomez, Francisco E.; Hjelmen, Carl E.; Moore, Kristi L.; Mackay, Trudy F. C.; Johnston, J. Spencer; Tarone, Aaron M.

2014-01-01

We determined female genome sizes using flow cytometry for 211 Drosophila melanogaster sequenced inbred strains from the Drosophila Genetic Reference Panel, and found significant conspecific and intrapopulation variation in genome size. We also compared several life history traits for 25 lines with large and 25 lines with small genomes in three thermal environments, and found that genome size as well as genome size by temperature interactions significantly correlated with survival to pupation and adulthood, time to pupation, female pupal mass, and female eclosion rates. Genome size accounted for up to 23% of the variation in developmental phenotypes, but the contribution of genome size to variation in life history traits was plastic and varied according to the thermal environment. Expression data implicate differences in metabolism that correspond to genome size variation. These results indicate that significant genome size variation exists within D. melanogaster and this variation may impact the evolutionary ecology of the species. Genome size variation accounts for a significant portion of life history variation in an environmentally dependent manner, suggesting that potential fitness effects associated with genome size variation also depend on environmental conditions. PMID:25057905

Selective encapsulation by Janus particles

NASA Astrophysics Data System (ADS)

Li, Wei; Ruth, Donovan; Gunton, James D.; Rickman, Jeffrey M.

2015-06-01

We employ Monte Carlo simulation to examine encapsulation in a system comprising Janus oblate spheroids and isotropic spheres. More specifically, the impact of variations in temperature, particle size, inter-particle interaction range, and strength is examined for a system in which the spheroids act as the encapsulating agents and the spheres as the encapsulated guests. In this picture, particle interactions are described by a quasi-square-well patch model. This study highlights the environmental adaptation and selectivity of the encapsulation system to changes in temperature and guest particle size, respectively. Moreover, we identify an important range in parameter space where encapsulation is favored, as summarized by an encapsulation map. Finally, we discuss the generalization of our results to systems having a wide range of particle geometries.

Diet and gut morphology of male mallards during winter in North Dakota

USGS Publications Warehouse

Olsen, R.E.; Cox, R.R.; Afton, A.D.; Ankney, C.D.

2011-01-01

A free-ranging Mallard (Anas platyrhynchos) population was investigated during winter (December-January 1996-1999) below the Garrison Dam, North Dakota, USA, to relate diet to gut morphology variation in males. Four explanatory variables (fish consumption, male age, winter, and body size) were evaluated as to whether they influenced five response variables associated with gut characteristics of Mallards. Response variables were lower gastro-intestinal tract mass (LGIT), dry liver mass, dry gizzard mass, small intestine length, and ceca length. Diets of Mallards were comprised primarily of Rainbow Smelt (Osmerus mordax) and concomitantly variation in gizzard mass was small. LGIT mass of juveniles was larger than that of adults, greater for those that consumed fish, and greater during the coldest and snowiest winter. Liver mass and small intestine length of Mallards that consumed fish were greater than those that did not. Mallards may maintain lengthy intestines to increase digestive efficiency. Gut size variation was not entirely attributable to dietary composition but also influenced by body size and environmental conditions such that over-winter survival is maximized.

Particle size distribution variance in untreated urban runoff and its implication on treatment selection.

PubMed

Charters, Frances J; Cochrane, Thomas A; O'Sullivan, Aisling D

2015-11-15

Understanding the particle size distribution (PSD) of sediment in urban runoff assists in the selection of appropriate treatment systems for sediment removal as systems vary in their ability to remove sediment across different particle size fractions. Variation in PSD in runoff from individual urban surfaces both during and across multiple rain events is not well understood and it may lead to performance uncertainty in treatment systems. Runoff PSDs in international literature were compiled to provide a comparative summary of PSDs from different urban surfaces. To further assess both intra-event and inter-event PSD variation, untreated runoff was collected from road, concrete roof, copper roof, and galvanized roof surfaces within an urban catchment exposed to the same rainfall conditions and analysed for PSD and total suspended solids (TSS). Road runoff had the highest TSS concentrations, while copper roofs had high initial TSS that reduced to very low levels under steady state conditions. Despite variation in TSS concentrations, the median particle diameter of the TSS was comparable across the surfaces. Intra-event variation was generally not significant, but substantial inter-event variation was observed, particularly for coarser road and concrete roof surfaces. PSD variation for each surface contributed to a wide range in predicted treatment performance and suggests that short-retention treatment devices carry a high performance risk of not being able to achieve adequate TSS removal across all rain events. Copyright © 2015 Elsevier Ltd. All rights reserved.

Gustaf: Detecting and correctly classifying SVs in the NGS twilight zone.

PubMed

Trappe, Kathrin; Emde, Anne-Katrin; Ehrlich, Hans-Christian; Reinert, Knut

2014-12-15

The landscape of structural variation (SV) including complex duplication and translocation patterns is far from resolved. SV detection tools usually exhibit low agreement, are often geared toward certain types or size ranges of variation and struggle to correctly classify the type and exact size of SVs. We present Gustaf (Generic mUlti-SpliT Alignment Finder), a sound generic multi-split SV detection tool that detects and classifies deletions, inversions, dispersed duplications and translocations of ≥ 30 bp. Our approach is based on a generic multi-split alignment strategy that can identify SV breakpoints with base pair resolution. We show that Gustaf correctly identifies SVs, especially in the range from 30 to 100 bp, which we call the next-generation sequencing (NGS) twilight zone of SVs, as well as larger SVs >500 bp. Gustaf performs better than similar tools in our benchmark and is furthermore able to correctly identify size and location of dispersed duplications and translocations, which otherwise might be wrongly classified, for example, as large deletions. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

The problem of scale in planetary geomorphology

NASA Technical Reports Server (NTRS)

Rossbacher, L. A.

1985-01-01

Recent planetary exploration has shown that specific landforms exhibit a significant range in size between planets. Similar features on Earth and Mars offer some of the best examples of this scale difference. The difference in heights of volcanic features between the two planets has been cited often; the Martian volcano Olympus Mons stands approximately 26 km high, but Mauna Loa rises only 11 km above the Pacific Ocean floor. Polygonally fractured ground in the northern plains of Mars has diameters up to 20 km across; the largest terrestrial polygons are only 500 m in diameter. Mars also has landslides, aeolian features, and apparent rift valleys larger than any known on Earth. No single factor can explain the variations in landform size between planets. Controls on variation on Earth, related to climate, lithology, or elevation, have seldom been considered in detail. The size differences between features on Earth and other planets seem to be caused by a complex group of interacting relationships. The major planetary parameters that may affect landform size are discussed.

The influence of leaf size and shape on leaf thermal dynamics: does theory hold up under natural conditions?

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

Leigh, A.; Sevanto, Sanna Annika; Close, J. D.

Laboratory studies on artificial leaves suggest that leaf thermal dynamics are strongly influenced by the two-dimensional size and shape of leaves and associated boundary layer thickness. Hot environments are therefore said to favour selection for small, narrow or dissected leaves. Empirical evidence from real leaves under field conditions is scant and traditionally based on point measurements that do not capture spatial variation in heat load. Here in this study, we used thermal imagery under field conditions to measure the leaf thermal time constant (τ) in summer and the leaf-to-air temperature difference (ΔT) and temperature range across laminae (T range) duringmore » winter, autumn and summer for 68 Proteaceae species. We investigated the influence of leaf area and margin complexity relative to effective leaf width (w e), the latter being a more direct indicator of boundary layer thickness. Normalized difference of margin complexity had no or weak effects on thermal dynamics, but w e strongly predicted τ and ΔT, whereas leaf area influenced T range. Unlike artificial leaves, however, spatial temperature distribution in large leaves appeared to be governed largely by structural variation. Therefore, we agree that small size, specifically we, has adaptive value in hot environments but not with the idea that thermal regulation is the primary evolutionary driver of leaf dissection.« less

The influence of leaf size and shape on leaf thermal dynamics: does theory hold up under natural conditions?

DOE PAGES

Leigh, A.; Sevanto, Sanna Annika; Close, J. D.; ...

2016-11-05

Laboratory studies on artificial leaves suggest that leaf thermal dynamics are strongly influenced by the two-dimensional size and shape of leaves and associated boundary layer thickness. Hot environments are therefore said to favour selection for small, narrow or dissected leaves. Empirical evidence from real leaves under field conditions is scant and traditionally based on point measurements that do not capture spatial variation in heat load. Here in this study, we used thermal imagery under field conditions to measure the leaf thermal time constant (τ) in summer and the leaf-to-air temperature difference (ΔT) and temperature range across laminae (T range) duringmore » winter, autumn and summer for 68 Proteaceae species. We investigated the influence of leaf area and margin complexity relative to effective leaf width (w e), the latter being a more direct indicator of boundary layer thickness. Normalized difference of margin complexity had no or weak effects on thermal dynamics, but w e strongly predicted τ and ΔT, whereas leaf area influenced T range. Unlike artificial leaves, however, spatial temperature distribution in large leaves appeared to be governed largely by structural variation. Therefore, we agree that small size, specifically we, has adaptive value in hot environments but not with the idea that thermal regulation is the primary evolutionary driver of leaf dissection.« less

Effect of Synthesis Parameter on Crystal Structures and Magnetic Properties of Magnesium Nickel Ferrite (Mg0.5Ni0.5Fe2O4) Nanoparticles

NASA Astrophysics Data System (ADS)

Maulia, R.; Putra, R. A.; Suharyadi, E.

2017-05-01

Mg0.5Ni0.5Fe2O4 nanoparticles have been successfully synthesized by using co-precipitation method and varying the synthesis parameter, i.e. synthesis temperature and NaOH concentration. X-ray Diffraction (XRD) pattern showed that nanoparticles have cubic spinel structures with an additional phase of γ-Fe2O3 and particle size varies within the range of 4.3 - 6.7 nm. This variation is due to the effect of various synthesis parameters. Transmission Electron Microscopy (TEM) image showed that the nanoparticles exhibited agglomeration. The observed diffraction ring from selected area electron diffraction showed that the sample was polycrystalline and confirmed the peak appearing in XRD. The coercivities showed an increasing trend with an increase in particle size from 44.7 Oe to 49.6 Oe for variation of NaOH concentration, and a decreasing trend with an increase in particle size from 46.8 to 45.1 Oe for variation of synthesis temperature. The maximum magnetization showed an increasing trend with an increase in the ferrite phase from 3.7 emu/g to 5.4 emu/g possessed in the sample with variations on NaOH concentration. The maximum magnetization for the sample with variations on synthesis temperature varied from 4.4 emu/g to 5.7 emu/g due to its crystal structures.

SU-E-T-374: Evaluation and Verification of Dose Calculation Accuracy with Different Dose Grid Sizes for Intracranial Stereotactic Radiosurgery

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

Han, C; Schultheiss, T

Purpose: In this study, we aim to evaluate the effect of dose grid size on the accuracy of calculated dose for small lesions in intracranial stereotactic radiosurgery (SRS), and to verify dose calculation accuracy with radiochromic film dosimetry. Methods: 15 intracranial lesions from previous SRS patients were retrospectively selected for this study. The planning target volume (PTV) ranged from 0.17 to 2.3 cm{sup 3}. A commercial treatment planning system was used to generate SRS plans using the volumetric modulated arc therapy (VMAT) technique using two arc fields. Two convolution-superposition-based dose calculation algorithms (Anisotropic Analytical Algorithm and Acuros XB algorithm) weremore » used to calculate volume dose distribution with dose grid size ranging from 1 mm to 3 mm with 0.5 mm step size. First, while the plan monitor units (MU) were kept constant, PTV dose variations were analyzed. Second, with 95% of the PTV covered by the prescription dose, variations of the plan MUs as a function of dose grid size were analyzed. Radiochomic films were used to compare the delivered dose and profile with the calculated dose distribution with different dose grid sizes. Results: The dose to the PTV, in terms of the mean dose, maximum, and minimum dose, showed steady decrease with increasing dose grid size using both algorithms. With 95% of the PTV covered by the prescription dose, the total MU increased with increasing dose grid size in most of the plans. Radiochromic film measurements showed better agreement with dose distributions calculated with 1-mm dose grid size. Conclusion: Dose grid size has significant impact on calculated dose distribution in intracranial SRS treatment planning with small target volumes. Using the default dose grid size could lead to under-estimation of delivered dose. A small dose grid size should be used to ensure calculation accuracy and agreement with QA measurements.« less

Lujiatun Psittacosaurids: Understanding Individual and Taphonomic Variation Using 3D Geometric Morphometrics

PubMed Central

Hedrick, Brandon P.; Dodson, Peter

2013-01-01

Psittacosaurus is one of the most abundant and speciose genera in the Dinosauria, with fifteen named species. The genus is geographically and temporally widespread with large sample sizes of several of the nominal species allowing detailed analysis of intra- and interspecific variation. We present a reanalysis of three separate, coeval species within the Psittacosauridae; P. lujiatunensis, P. major, and Hongshanosaurus houi from the Lujiatun beds of the Yixian Formation, northeastern China, using three-dimensional geometric morphometrics on a sample set of thirty skulls in combination with a reevaluation of the proposed character states for each species. Using these complementary methods, we show that individual and taphonomic variation are the joint causes of a large range of variation among the skulls when they are plotted in a morphospace. Our results demonstrate that there is only one species of Psittacosaurus within the Lujiatun beds and that the three nominal species represent different taphomorphotypes of P. lujiatunensis. The wide range of geometric morphometric variation in a single species of Psittacosaurus implies that the range of variation found in other dinosaurian groups may also be related to taphonomic distortion rather than interspecific variation. As the morphospace is driven primarily by variation resulting from taphonomic distortion, this study demonstrates that the geometric morphometric approach can only be used with great caution to delineate interspecific variation in Psittacosaurus and likely other dinosaur groups without a complementary evaluation of character states. This study presents the first application of 3D geometric morphometrics to the dinosaurian morphospace and the first attempt to quantify taphonomic variation in dinosaur skulls. PMID:23950887

Is humanity sustainable?

PubMed Central

Fowler, Charles W; Hobbs, Larry

2003-01-01

The principles and tenets of management require action to avoid sustained abnormal/pathological conditions. For the sustainability of interactive systems, each system should fall within its normal range of natural variation. This applies to individuals (as for fevers and hypertension, in medicine), populations (e.g. outbreaks of crop pests in agriculture), species (e.g. the rarity of endangerment in conservation) and ecosystems (e.g. abnormally low productivity or diversity in 'ecosystem-based management'). In this paper, we report tests of the hypothesis that the human species is ecologically normal. We reject the hypothesis for almost all of the cases we tested. Our species rarely falls within statistical confidence limits that envelop the central tendencies in variation among other species. For example, our population size, CO(2) production, energy use, biomass consumption and geographical range size differ from those of other species by orders of magnitude. We argue that other measures should be tested in a similar fashion to assess the prevalence of such differences and their practical implications. PMID:14728780

Picturing thermal niches and biomass of hydrothermal vent species

NASA Astrophysics Data System (ADS)

Husson, Bérengère; Sarradin, Pierre-Marie; Zeppilli, Daniela; Sarrazin, Jozée

2017-03-01

In community ecology, niche analysis is a classic tool for investigating species' distribution and dynamics. Components of a species' niche include biotic and abiotic factors. In the hydrothermal vent ecosystem, although composition and temporal variation have been investigated since these deep-sea habitats were discovered nearly 40 years ago, the roles and the factors behind the success of the dominant species of these ecosystems have yet to be fully elucidated. In the Lucky Strike vent field on the Mid-Atlantic Ridge (MAR), the dominant species is the mussel Bathymodiolus azoricus. Data on this species and its associated community were collected during four oceanographic cruises on the Eiffel Tower edifice and integrated in a novel statistical framework for niche analysis. We assessed the thermal range, density, biomass and niche similarities of B. azoricus and its associated fauna. Habitat similarities grouped mussels into three size categories: mussels with lengths ranging from 0.5 to 1.5 cm, from 1.5 to 6 cm, and mussels longer than 6 cm. These size categories were consistent with those found in previous studies based on video imagery. The three size categories featured different associated fauna. The thermal range of mussels was shown to change with organism size, with intermediate sizes having a broader thermal niche than small or large mussels. Temperature maxima seem to drive their distribution along the mixing gradient between warm hydrothermal fluids and cold seawater. B. azoricus constitutes nearly 90% of the biomass (in g dry weight /m2) of the ecosystem. Mean individual weights were calculated for 39 of the 79 known taxa on Eiffel Tower and thermal ranges were obtained for all the inventoried species of this edifice. The analysis showed that temperature is a suitable variable to describe density variations among samples for 71 taxa. However, thermal conditions do not suffice to explain biomass variability. Our results provide valuable insights into mussel ecology, biotic interactions and the role of B. azoricus in the community.

Geographical and Temporal Body Size Variation in a Reptile: Roles of Sex, Ecology, Phylogeny and Ecology Structured in Phylogeny

PubMed Central

Aragón, Pedro; Fitze, Patrick S.

2014-01-01

Geographical body size variation has long interested evolutionary biologists, and a range of mechanisms have been proposed to explain the observed patterns. It is considered to be more puzzling in ectotherms than in endotherms, and integrative approaches are necessary for testing non-exclusive alternative mechanisms. Using lacertid lizards as a model, we adopted an integrative approach, testing different hypotheses for both sexes while incorporating temporal, spatial, and phylogenetic autocorrelation at the individual level. We used data on the Spanish Sand Racer species group from a field survey to disentangle different sources of body size variation through environmental and individual genetic data, while accounting for temporal and spatial autocorrelation. A variation partitioning method was applied to separate independent and shared components of ecology and phylogeny, and estimated their significance. Then, we fed-back our models by controlling for relevant independent components. The pattern was consistent with the geographical Bergmann's cline and the experimental temperature-size rule: adults were larger at lower temperatures (and/or higher elevations). This result was confirmed with additional multi-year independent data-set derived from the literature. Variation partitioning showed no sex differences in phylogenetic inertia but showed sex differences in the independent component of ecology; primarily due to growth differences. Interestingly, only after controlling for independent components did primary productivity also emerge as an important predictor explaining size variation in both sexes. This study highlights the importance of integrating individual-based genetic information, relevant ecological parameters, and temporal and spatial autocorrelation in sex-specific models to detect potentially important hidden effects. Our individual-based approach devoted to extract and control for independent components was useful to reveal hidden effects linked with alternative non-exclusive hypothesis, such as those of primary productivity. Also, including measurement date allowed disentangling and controlling for short-term temporal autocorrelation reflecting sex-specific growth plasticity. PMID:25090025

Linkage Disequilibrium Under Recurrent Bottlenecks

PubMed Central

Schaper, E.; Eriksson, A.; Rafajlovic, M.; Sagitov, S.; Mehlig, B.

2012-01-01

To model deviations from selectively neutral genetic variation caused by different forms of selection, it is necessary to first understand patterns of neutral variation. Best understood is neutral genetic variation at a single locus. But, as is well known, additional insights can be gained by investigating multiple loci. The resulting patterns reflect the degree of association (linkage) between loci and provide information about the underlying multilocus gene genealogies. The statistical properties of two-locus gene genealogies have been intensively studied for populations of constant size, as well as for simple demographic histories such as exponential population growth and single bottlenecks. By contrast, the combined effect of recombination and sustained demographic fluctuations is poorly understood. Addressing this issue, we study a two-locus Wright–Fisher model of a population subject to recurrent bottlenecks. We derive coalescent approximations for the covariance of the times to the most recent common ancestor at two loci in samples of two chromosomes. This covariance reflects the degree of association and thus linkage disequilibrium between these loci. We find, first, that an effective population-size approximation describes the numerically observed association between two loci provided that recombination occurs either much faster or much more slowly than the population-size fluctuations. Second, when recombination occurs frequently between but rarely within bottlenecks, we observe that the association of gene histories becomes independent of physical distance over a certain range of distances. Third, we show that in this case, a commonly used measure of linkage disequilibrium, σd2 (closely related to r^2), fails to capture the long-range association between two loci. The reason is that constituent terms, each reflecting the long-range association, cancel. Fourth, we analyze a limiting case in which the long-range association can be described in terms of a Xi coalescent allowing for simultaneous multiple mergers of ancestral lines. PMID:22048021

Distribution and diversity of cytotypes in Dianthus broteri as evidenced by genome size variations.

PubMed

Balao, Francisco; Casimiro-Soriguer, Ramón; Talavera, María; Herrera, Javier; Talavera, Salvador

2009-10-01

Studying the spatial distribution of cytotypes and genome size in plants can provide valuable information about the evolution of polyploid complexes. Here, the spatial distribution of cytological races and the amount of DNA in Dianthus broteri, an Iberian carnation with several ploidy levels, is investigated. Sample chromosome counts and flow cytometry (using propidium iodide) were used to determine overall genome size (2C value) and ploidy level in 244 individuals of 25 populations. Both fresh and dried samples were investigated. Differences in 2C and 1Cx values among ploidy levels within biogeographical provinces were tested using ANOVA. Geographical correlations of genome size were also explored. Extensive variation in chromosomes numbers (2n = 2x = 30, 2n = 4x = 60, 2n = 6x = 90 and 2n = 12x =180) was detected, and the dodecaploid cytotype is reported for the first time in this genus. As regards cytotype distribution, six populations were diploid, 11 were tetraploid, three were hexaploid and five were dodecaploid. Except for one diploid population containing some triploid plants (2n = 45), the remaining populations showed a single cytotype. Diploids appeared in two disjunct areas (south-east and south-west), and so did tetraploids (although with a considerably wider geographic range). Dehydrated leaf samples provided reliable measurements of DNA content. Genome size varied significantly among some cytotypes, and also extensively within diploid (up to 1.17-fold) and tetraploid (1.22-fold) populations. Nevertheless, variations were not straightforwardly congruent with ecology and geographical distribution. Dianthus broteri shows the highest diversity of cytotypes known to date in the genus Dianthus. Moreover, some cytotypes present remarkable internal genome size variation. The evolution of the complex is discussed in terms of autopolyploidy, with primary and secondary contact zones.

Genomic Variation, Host Range, and Infection Kinetics of Closely Related Cyanopodoviruses from New England Coastal Waters

NASA Astrophysics Data System (ADS)

Veglia, A. J.; Milford, C. R.; Marston, M.

2016-02-01

Viruses infecting marine Synechococcus are abundant in coastal marine environments and influence the community composition and abundance of their cyanobacterial hosts. In this study, we focused on the cyanopodoviruses which have smaller genomes and narrower host ranges relative to cyanomyoviruses. While previous studies have compared the genomes of diverse podoviruses, here we analyzed the genomic variation, host ranges, and infection kinetics of podoviruses within the same OTU. The genomes of fifty-five podoviral isolates from the coastal waters of New England were fully sequenced. Based on DNA polymerase gene sequences, these isolates fall into five discrete OTUs (termed RIP - Rhode Island Podovirus). Although all the isolates belonging to the same RIP have very similar DNA polymerase gene sequences (>98% sequence identity), differences in genome content, particularly in regions associated with tail fiber genes, were observed among isolates in the same RIP. Host range tests reveal variation both across and within RIPs. Notably within RIP1, isolates that had similar tail fiber regions also had similar host ranges. Isolates belonging to RIP4 do not contain the host-derived psbA photosynthesis gene, while isolates in the other four RIPs do possess a psbA gene. Nevertheless, infection kinetic experiments suggest that the latent period and burst size for RIP4 isolates are similar to RIP1 isolates. We are continuing to investigate the correlations among genome content, host range, and infection kinetics of isolates belonging to the same OTU. Our results to date suggest that there is substantial genomic variation within an OTU and that this variation likely influences cyanopodoviral - host interactions.

Truly sedentary? The multi-range tactic as a response to resource heterogeneity and unpredictability in a large herbivore.

PubMed

Couriot, Ophélie; Hewison, A J Mark; Saïd, Sonia; Cagnacci, Francesca; Chamaillé-Jammes, Simon; Linnell, John D C; Mysterud, Atle; Peters, Wibke; Urbano, Ferdinando; Heurich, Marco; Kjellander, Petter; Nicoloso, Sandro; Berger, Anne; Sustr, Pavel; Kroeschel, Max; Soennichsen, Leif; Sandfort, Robin; Gehr, Benedikt; Morellet, Nicolas

2018-05-01

Much research on large herbivore movement has focused on the annual scale to distinguish between resident and migratory tactics, commonly assuming that individuals are sedentary at the within-season scale. However, apparently sedentary animals may occupy a number of sub-seasonal functional home ranges (sfHR), particularly when the environment is spatially heterogeneous and/or temporally unpredictable. The roe deer (Capreolus capreolus) experiences sharply contrasting environmental conditions due to its widespread distribution, but appears markedly sedentary over much of its range. Using GPS monitoring from 15 populations across Europe, we evaluated the propensity of this large herbivore to be truly sedentary at the seasonal scale in relation to variation in environmental conditions. We studied movement using net square displacement to identify the possible use of sfHR. We expected that roe deer should be less sedentary within seasons in heterogeneous and unpredictable environments, while migratory individuals should be seasonally more sedentary than residents. Our analyses revealed that, across the 15 populations, all individuals adopted a multi-range tactic, occupying between two and nine sfHR during a given season. In addition, we showed that (i) the number of sfHR was only marginally influenced by variation in resource distribution, but decreased with increasing sfHR size; and (ii) the distance between sfHR increased with increasing heterogeneity and predictability in resource distribution, as well as with increasing sfHR size. We suggest that the multi-range tactic is likely widespread among large herbivores, allowing animals to track spatio-temporal variation in resource distribution and, thereby, to cope with changes in their local environment.

Design of landfill daily cells.

PubMed

Panagiotakopoulos, D; Dokas, I

2001-08-01

The objective of this paper is to study the behaviour of the landfill soil-to-refuse (S/R) ratio when size, geometry and operating parameters of the daily cell vary over realistic ranges. A simple procedure is presented (1) for calculating the cell parameters values which minimise the S/R ratio and (2) for studying the sensitivity of this minimum S/R ratio to variations in cell size, final refuse density, working face length, lift height and cover thickness. In countries where daily soil cover is required, savings in landfill space could be realised following this procedure. The sensitivity of minimum S/R to variations in cell dimensions decreases with cell size. Working face length and lift height affect the S/R ratio significantly. This procedure also offers the engineer an additional tool for comparing one large daily cell with two or more smaller ones, at two different working faces within the same landfill.

Firefighter Hand Anthropometry and Structural Glove Sizing: A New Perspective.

PubMed

Hsiao, Hongwei; Whitestone, Jennifer; Kau, Tsui-Ying; Hildreth, Brooke

2015-12-01

We evaluated the current use and fit of structural firefighting gloves and developed an improved sizing scheme that better accommodates the U.S. firefighter population. Among surveys, 24% to 30% of men and 31% to 62% of women reported experiencing problems with the fit or bulkiness of their structural firefighting gloves. An age-, race/ethnicity-, and gender-stratified sample of 863 male and 88 female firefighters across the United States participated in the study. Fourteen hand dimensions relevant to glove design were measured. A cluster analysis of the hand dimensions was performed to explore options for an improved sizing scheme. The current national standard structural firefighting glove-sizing scheme underrepresents firefighter hand size range and shape variation. In addition, mismatch between existing sizing specifications and hand characteristics, such as hand dimensions, user selection of glove size, and the existing glove sizing specifications, is significant. An improved glove-sizing plan based on clusters of overall hand size and hand/finger breadth-to-length contrast has been developed. This study presents the most up-to-date firefighter hand anthropometry and a new perspective on glove accommodation. The new seven-size system contains narrower variations (standard deviations) for almost all dimensions for each glove size than the current sizing practices. The proposed science-based sizing plan for structural firefighting gloves provides a step-forward perspective (i.e., including two women hand model-based sizes and two wide-palm sizes for men) for glove manufacturers to advance firefighter hand protection. © 2015, Human Factors and Ergonomics Society.

Swift Foxes and Ideal Free Distribution: Relative Influence of Vegetation and Rodent Prey Base on Swift Fox Survival, Density, and Home Range Size

DTIC Science & Technology

2012-01-01

of exploiting a wide range of habitats, reported population parameters such as density and survival vary widely indicating variation in habitat quality...more strongly influenced by the “riskiness” of the habitat than by resource availability [8]. Swift fox population parameters in different landscapes...we explored the effects of landscape heterogeneity on population parameters likely to reflect habitat quality, such as population density, home range

Collagen Fiber Orientation in Primate Long Bones.

PubMed

Warshaw, Johanna; Bromage, Timothy G; Terranova, Carl J; Enlow, Donald H

2017-07-01

Studies of variation in orientation of collagen fibers within bone have lead to the proposition that these are preferentially aligned to accommodate different kinds of load, with tension best resisted by fibers aligned longitudinally relative to the load, and compression best resisted by transversely aligned fibers. However, previous studies have often neglected to consider the effect of developmental processes, including constraints on collagen fiber orientation (CFO), particularly in primary bone. Here we use circularly polarized light microscopy to examine patterns of CFO in cross-sections from the midshaft femur, humerus, tibia, radius, and ulna in a range of living primate taxa with varied body sizes, phylogenetic relationships and positional behaviors. We find that a preponderance of longitudinally oriented collagen is characteristic of both periosteal primary and intracortically remodeled bone. Where variation does occur among groups, it is not simply understood via interpretations of mechanical loads, although prioritized adaptations to tension and/or shear are considered. While there is some suggestion that CFO may correlate with body size, this relationship is neither consistent nor easily explicable through consideration of size-related changes in mechanical adaptation. The results of our study indicate that there is no clear relationship between CFO and phylogenetic status. One of the principle factors accounting for the range of variation that does exist is primary tissue type, where slower depositing bone is more likely to comprise a larger proportion of oblique to transverse collagen fibers. Anat Rec, 300:1189-1207, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Calculations of the variability of ice cloud radiative properties at selected solar wavelengths

NASA Technical Reports Server (NTRS)

Welch, R. M.; Zdunkowski, W. G.; Cox, S. K.

1980-01-01

This study shows that there is surprising little difference in values of reflectance, absorptance, and transmittance for many of the intermediate-size particle spectra. Particle size distributions with mode radii ranging from approximately 50 to 300 microns, irrespective of particle shape and nearly independent of the choice of size distribution representation, give relatively similar flux values. The very small particle sizes, however, have significantly larger values of reflectance and transmittance with corresponding smaller values of absorptance than do the larger particle sizes. The very large particle modes produce very small values of reflectance and transmittance along with very large values of absorptance. Such variations are particularly noticeable when plotted as a function of wavelength.

Data that describe at-a-point temporal variations in the transport rate and particle-size distribution of bedload; East Fork River, Wyoming, and Fall River, Colorado

USGS Publications Warehouse

Gomez, Basil; Emmett, W.W.

1990-01-01

Data from the East Fork River, Wyoming, and the Fall River, Colorado, that document at-a-point temporal variations in the transport rate and particle-size distribution of bedload, associated with the downstream migration of dunes, are presented. Bedload sampling was undertaken, using a 76.2 x 76.2 mm Helley-Smith sampler, on three separate occasions at each site in June 1988. In each instance, the sampling time was 30 seconds and the sampling intervals 5 minutes. The sampling period ranged from 4.92 to 8.25 hours. Water stage did not vary appreciably during any of the sampling periods. (USGS)

Huntingtin gene repeat size variations affect risk of lifetime depression.

PubMed

Gardiner, Sarah L; van Belzen, Martine J; Boogaard, Merel W; van Roon-Mom, Willeke M C; Rozing, Maarten P; van Hemert, Albert M; Smit, Johannes H; Beekman, Aartjan T F; van Grootheest, Gerard; Schoevers, Robert A; Oude Voshaar, Richard C; Roos, Raymund A C; Comijs, Hannie C; Penninx, Brenda W J H; van der Mast, Roos C; Aziz, N Ahmad

2017-12-11

Huntington disease (HD) is a severe neuropsychiatric disorder caused by a cytosine-adenine-guanine (CAG) repeat expansion in the HTT gene. Although HD is frequently complicated by depression, it is still unknown to what extent common HTT CAG repeat size variations in the normal range could affect depression risk in the general population. Using binary logistic regression, we assessed the association between HTT CAG repeat size and depression risk in two well-characterized Dutch cohorts─the Netherlands Study of Depression and Anxiety and the Netherlands Study of Depression in Older Persons─including 2165 depressed and 1058 non-depressed persons. In both cohorts, separately as well as combined, there was a significant non-linear association between the risk of lifetime depression and HTT CAG repeat size in which both relatively short and relatively large alleles were associated with an increased risk of depression (β = -0.292 and β = 0.006 for the linear and the quadratic term, respectively; both P < 0.01 after adjustment for the effects of sex, age, and education level). The odds of lifetime depression were lowest in persons with a HTT CAG repeat size of 21 (odds ratio: 0.71, 95% confidence interval: 0.52 to 0.98) compared to the average odds in the total cohort. In conclusion, lifetime depression risk was higher with both relatively short and relatively large HTT CAG repeat sizes in the normal range. Our study provides important proof-of-principle that repeat polymorphisms can act as hitherto unappreciated but complex genetic modifiers of depression.

Global DNA cytosine methylation as an evolving trait: phylogenetic signal and correlated evolution with genome size in angiosperms

PubMed Central

Alonso, Conchita; Pérez, Ricardo; Bazaga, Pilar; Herrera, Carlos M.

2015-01-01

DNA cytosine methylation is a widespread epigenetic mechanism in eukaryotes, and plant genomes commonly are densely methylated. Genomic methylation can be associated with functional consequences such as mutational events, genomic instability or altered gene expression, but little is known on interspecific variation in global cytosine methylation in plants. In this paper, we compare global cytosine methylation estimates obtained by HPLC and use a phylogenetically-informed analytical approach to test for significance of evolutionary signatures of this trait across 54 angiosperm species in 25 families. We evaluate whether interspecific variation in global cytosine methylation is statistically related to phylogenetic distance and also whether it is evolutionarily correlated with genome size (C-value). Global cytosine methylation varied widely between species, ranging between 5.3% (Arabidopsis) and 39.2% (Narcissus). Differences between species were related to their evolutionary trajectories, as denoted by the strong phylogenetic signal underlying interspecific variation. Global cytosine methylation and genome size were evolutionarily correlated, as revealed by the significant relationship between the corresponding phylogenetically independent contrasts. On average, a ten-fold increase in genome size entailed an increase of about 10% in global cytosine methylation. Results show that global cytosine methylation is an evolving trait in angiosperms whose evolutionary trajectory is significantly linked to changes in genome size, and suggest that the evolutionary implications of epigenetic mechanisms are likely to vary between plant lineages. PMID:25688257

Large-Scale Comparative Analysis Reveals the Mechanisms Driving Plastomic Compaction, Reduction, and Inversions in Conifers II (Cupressophytes).

PubMed

Wu, Chung-Shien; Chaw, Shu-Miaw

2016-12-01

Conifers II (cupressophytes), comprising about 400 tree species in five families, are the most diverse group of living gymnosperms. Their plastid genomes (plastomes) are highly variable in size and organization, but such variation has never been systematically studied. In this study, we assessed the potential mechanisms underlying the evolution of cupressophyte plastomes. We analyzed the plastomes of 24 representative genera in all of the five cupressophyte families, focusing on their variation in size, noncoding DNA content, and nucleotide substitution rates. Using a tree-based method, we further inferred the ancestral plastomic organizations of internal nodes and evaluated the inversions across the evolutionary history of cupressophytes. Our data showed that variation in plastome size is statistically associated with the dynamics of noncoding DNA content, which results in different degrees of plastomic compactness among the cupressophyte families. The degrees of plastomic inversions also vary among the families, with the number of inversions per genus ranging from 0 in Araucariaceae to 1.27 in Cupressaceae. In addition, we demonstrated that synonymous substitution rates are significantly correlated with plastome size as well as degree of inversions. These data suggest that in cupressophytes, mutation rates play a critical role in driving the evolution of plastomic size while plastomic inversions evolve in a neutral manner. © The Author(s) 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Thermodynamics on the nanoscale.

PubMed

Delogu, Francesco

2005-11-24

Classical thermodynamics is applied to the melting of nanometer-sized Sn particles with radii in the range 5-50 nm. Such particles display a depression of both the melting point and the latent heat of fusion depending on the particle size. The size dependence can be explained with the formation of a structurally perturbed layer at the particle surface. The experimental measurement of both melting temperatures and latent heats of fusion allowed for estimation of the thickness of the perturbed layer. This permitted in turn the evaluation of the excess Gibbs free energy associated with the perturbed layer at melting and the determination of its variation with particle size and temperature.

Uniwavelength lidar sensitivity to spherical aerosol microphysical properties for the interpretation of Lagrangian stratospheric observations

NASA Astrophysics Data System (ADS)

Jumelet, Julien; David, Christine; Bekki, Slimane; Keckhut, Philippe

2009-01-01

The determination of stratospheric particle microphysical properties from multiwavelength lidar, including Rayleigh and/or Raman detection, has been widely investigated. However, most lidar systems are uniwavelength operating at 532 nm. Although the information content of such lidar data is too limited to allow the retrieval of the full size distribution, the coupling of two or more uniwavelength lidar measurements probing the same moving air parcel may provide some meaningful size information. Within the ORACLE-O3 IPY project, the coordination of several ground-based lidars and the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) space-borne lidar is planned during measurement campaigns called MATCH-PSC (Polar Stratospheric Clouds). While probing the same moving air masses, the evolution of the measured backscatter coefficient (BC) should reflect the variation of particles microphysical properties. A sensitivity study of 532 nm lidar particle backscatter to variations of particles size distribution parameters is carried out. For simplicity, the particles are assumed to be spherical (liquid) particles and the size distribution is represented with a unimodal log-normal distribution. Each of the four microphysical parameters (i.e. log-normal size distribution parameters, refractive index) are analysed separately, while the three others are remained set to constant reference values. Overall, the BC behaviour is not affected by the initial values taken as references. The total concentration (N0) is the parameter to which BC is least sensitive, whereas it is most sensitive to the refractive index (m). A 2% variation of m induces a 15% variation of the lidar BC, while the uncertainty on the BC retrieval can also reach 15%. This result underlines the importance of having both an accurate lidar inversion method and a good knowledge of the temperature for size distribution retrieval techniques. The standard deviation ([sigma]) is the second parameter to which BC is most sensitive to. Yet, the impact of m and [sigma] on BC variations is limited by the realistic range of their variations. The mean radius (rm) of the size distribution is thus the key parameter for BC, as it can vary several-fold. BC is most sensitive to the presence of large particles. The sensitivity of BC to rm and [sigma] variations increases when the initial size distributions are characterized by low rm and large [sigma]. This makes lidar more suitable to detect particles growing on background aerosols than on volcanic aerosols.

Monthly and diurnal variations in aerosol size distributions, downwind of the Seoul metropolitan area

NASA Astrophysics Data System (ADS)

Kim, B. S.; Choi, Y.; Ghim, Y. S.

2014-12-01

The size distribution of aerosols is a physical property. However, since major aerosol types such as mineral dust, secondary inorganic ions, and carbonaceous aerosols are typically in specific size ranges, we can estimate the chemical composition of aerosols from the size distribution. We measured the mass size distribution of aerosols using an optical particle counter (Grimm Model 1.109) for a year from February 2013 to February 2014 at intervals of 10 minutes. The optical particle counter measures number concentrations between 0.25 and 32 μm in 31 bins and converts them into mass concentrations assuming a sphere and densities of aerosols in urban environment which originate from traffic and other combustion sources and are secondarily formed from photochemical reactions. The measurement site is at the rooftop of the five-story building on the hill (37.34 °N, 127.27 °E, 167 m above sea level), about 35 km southeast of downtown Seoul, the downwind area of which is affected by prevailing northwesterlies. There are no major emission sources nearby except a 4-lane road running about 1.4 km to the west. We tried to characterize the bimodal property of the mass size distribution, consisting of fine and coarse modes, in terms of mass concentration and mean diameter. Monthly and diurnal variations in mass concentration and mean diameter of each mode were investigated to estimate major aerosol types as well as major factors causing those variations.

Effects of plant sex on range distributions and allocation to reproduction.

PubMed

Johnson, Marc T J; Smith, Stacey D; Rausher, Mark D

2010-05-01

Despite an abundance of theory, few empirical studies have explored the ecological and evolutionary consequences of sex. We used a comparative phylogenetic approach to examine whether transitions between sexual and asexual reproduction are associated with changes in the size and distribution of species' geographical ranges, and their investment in reproduction. Here, we reconstructed the phylogeny of the genus Oenothera sections Oenothera and Calylophus (Onagraceae), which contain 35 sexual and 30 functionally asexual species. From each species, we collected data on the geographical distribution and variation in plant traits related to reproduction. Functionally asexual species occurred at higher latitudes, but did not differ in range size, compared with sexual species. Transitions to asexuality were associated with decreased investment in floral structures, including the length of petals, floral tubes and styles. Decreased anther size and increased seed size within asexual species also suggest altered allocation to male and female fitness. The observed range shifts are consistent with superior colonization of environments by asexual species following glaciation, and the observed changes in reproductive allocation support predictions made by models relating to the evolution of selfing. Our results suggest that the evolutionary consequences of asexual reproduction might be less restrictive than previously thought.

SEM Imaging for Observation of Morphological Changes in Anaemic Human Blood Cell

NASA Astrophysics Data System (ADS)

Datta, Triparna; Roychoudhury, Uttam

Scanning Electron Microscopy (SEM) is utilized to elucidate the morphological changes in anaemic human red blood cells. Haemoglobin concentration in human blood is in the range of 11.5-13.5 g/dl in healthy adults. Haemoglobin concentration in anaemic red blood is below the lower limit of normal range. Sometimes, the nature of the abnormal shape of the blood cell determines the cause of anaemia. Normally, there occurs a variation in the diameter of the red blood cell (RBC) for different types of anaemia. Increased variation of size in blood cell is termed anisocytosis (a type of anaemia) (Mohan H, Text book of pathology, New Delhi). In case of anisocytosis, diameter of cells larger than normal cell is observed. The classification of anaemia by the size of blood cell is logical, i.e. common morphological abnormality of human blood cell (Davidson's principle and practice of medicine, Publisher Churchill Livingstone, London). Cells are studied under ZEISS SEM with different magnification and applied potential of kV range. Thus the diameters of RBCs in SEM have been compared with RBCs photographed with light microscope. Anaemic cells are observed overlapped with each other with increasing diameter.

Measuring Snow Grain Size with the Near-Infrared Emitting Reflectance Dome (NERD)

NASA Astrophysics Data System (ADS)

Schneider, A. M.; Flanner, M.

2014-12-01

Because of its high visible albedo, snow plays a large role in Earth's surface energy balance. This role is a subject of intense study, but due to the wide range of snow albedo, variations in the characteristics of snow grains can introduce radiative feedbacks in a snow pack. Snow grain size, for example, is one property which directly affects a snow pack's absorption spectrum. Previous studies model and observe this spectrum, but potential feedbacks induced by these variations are largely unknown. Here, we implement a simple and inexpensive technique to measure snow grain size in an instrument we call the Near-infrared Emitting Reflectance Dome (NERD). A small black styrene dome (~17cm diameter), fitted with two narrowband light-emitting diodes (LEDs) centered around 1300nm and 1550nm and three near-infrared reverse-biased photodiodes, is placed over the snow surface enabling a multi-spectral measurement of the hemispheric directional reflectance factor (HDRF). We illuminate the snow at each wavelength, measure directional reflectance, and infer grain size from the difference in HDRFs measured on the same snow crystals at fixed viewing angles. We validate measurements from the NERD using two different reflectance standards, materials designed to be near perfect Lambertian reflectors, having known, constant reflectances (~99% and ~55%) across a wide range of wavelengths. Using a 3D Monte Carlo model simulating photon pathways through a pack of spherical snow grains, we calculate the difference in HDRFs at 1300nm and 1550nm to predict the calibration curve for a wide range of grain sizes. This theoretically derived curve gives a relationship between effective radius and the difference in HDRFs and allows us to approximate grain sizes using the NERD in just a few seconds. Further calibration requires knowledge of truth values attainable using a previously validated instrument or measurements from an inter-comparison workshop.

Individuals in food webs: the relationships between trophic position, omnivory and among-individual diet variation.

PubMed

Svanbäck, Richard; Quevedo, Mario; Olsson, Jens; Eklöv, Peter

2015-05-01

Among-individual diet variation is common in natural populations and may occur at any trophic level within a food web. Yet, little is known about its variation among trophic levels and how such variation could affect phenotypic divergence within populations. In this study we investigate the relationships between trophic position (the population's range and average) and among-individual diet variation. We test for diet variation among individuals and across size classes of Eurasian perch (Perca fluviatilis), a widespread predatory freshwater fish that undergoes ontogenetic niche shifts. Second, we investigate among-individual diet variation within fish and invertebrate populations in two different lake communities using stable isotopes. Third, we test potential evolutionary implications of population trophic position by assessing the relationship between the proportion of piscivorous perch (populations of higher trophic position) and the degree of phenotypic divergence between littoral and pelagic perch sub-populations. We show that among-individual diet variation is highest at intermediate trophic positions, and that this high degree of among-individual variation likely causes an increase in the range of trophic positions among individuals. We also found that phenotypic divergence was negatively related to trophic position in a population. This study thus shows that trophic position is related to and may be important for among-individual diet variation as well as to phenotypic divergence within populations.

Selective encapsulation by Janus particles

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

Li, Wei, E-mail: wel208@mrl.ucsb.edu; Ruth, Donovan; Gunton, James D.

2015-06-28

We employ Monte Carlo simulation to examine encapsulation in a system comprising Janus oblate spheroids and isotropic spheres. More specifically, the impact of variations in temperature, particle size, inter-particle interaction range, and strength is examined for a system in which the spheroids act as the encapsulating agents and the spheres as the encapsulated guests. In this picture, particle interactions are described by a quasi-square-well patch model. This study highlights the environmental adaptation and selectivity of the encapsulation system to changes in temperature and guest particle size, respectively. Moreover, we identify an important range in parameter space where encapsulation is favored,more » as summarized by an encapsulation map. Finally, we discuss the generalization of our results to systems having a wide range of particle geometries.« less

PMHOME: A DATABASE OF CONTINUOUS PARTICLE MEASUREMENTS IN AN OCCUPIED HOUSE OVER A FOUR-YEAR PERIOD

EPA Science Inventory

Although considerable data exist on 24-hour integrated measurements of fine and coarse particles indoors, much less information is available on moment-to-moment variation for a full range of particle sizes including ultrafine particles. Also, information is limited on the rela...

Case-mix fails to explain variation in mastectomy rates: management of screen-detected breast cancer in a UK region 1997–2003

PubMed Central

Caldon, L J M; Walters, S J; Reed, J A; Murphy, A; Worley, A; Reed, M W R

2004-01-01

Wide variation in the surgical management of breast cancer exists at hospital, regional, national and international level. To demonstrate whether variation in surgical practice observed at aggregate level between breast units persists following adjustment for case-mix, individual patient-level data from the Trent Breast Screening Programme Quality Assurance database (1997–2003) was analysed. Expected case-mix adjusted mastectomy rates were derived by logistic regression using the variables tumour size, site and grade, patient age and year of presentation, employing the region's overall case-mix adjusted practice as the reference population. The region's 11 breast screening units detected 5109 (3989 invasive) surgically managed primary breast cancers over the 6-year period. A total of 1828 mastectomies (Mx) were performed (Mx rate 35.8%, 95% confidence interval: 34.5–37.1%). Significant variation in mastectomy rates were observed between units (range 25–45%, P<0.0001), and persists following case-mix adjustment (P<0.0001). Two-fold variation in observed to expected unit mastectomy rate coefficient is demonstrated overall (range 0.66–1.36), increasing to almost four-fold variation in cancers less than 15 mm diameter (range 0.55–1.95). Significant variation in surgery for screen-detected primary breast cancer is not explained by case-mix. Further research is required to investigate potential patient and professional causative factors. PMID:15611797

Morphological variation in Sarracenia purpurea (Sarraceniaceae): geographic, environmental, and taxonomic correlates.

PubMed

Ellison, Aaron M; Buckley, Hannah L; Miller, Thomas E; Gotelli, Nicholas J

2004-11-01

Geographic variation in morphology reflects phenotypic responses to environmental gradients and evolutionary history of populations and species and may indicate local or regional changes in environmental conditions. The pitcher plant (Sarracenia purpurea) illustrates these principles. At local scales, its morphology reflects nutrient availability. At points along its broad geographic range (from Florida to northern Canada) morphology has been used to distinguish subspecies and varieties, but there has been no detailed study of the continuum of morphological variation across this entire range. Patterns of morphological variation in S. purpurea were characterized as a function of climatic and environmental conditions at 39 sites spanning its range. Differences in pitcher size and shape were strongly correlated with temperature, annual precipitation, and availability of ammonium and calcium in peat pore water. Pitcher shape (lip width, mouth diameter, and pitcher width) in Florida panhandle populations differed significantly from pitcher shape of all other populations, even after accounting for environmental correlations. In contrast, the northern and southern subspecies of S. purpurea (the latter exclusive of the Florida panhandle populations) cannot be distinguished based on these morphological measurements alone. These results support a recent proposal that identifies the Florida populations as a distinct species, Sarracenia rosea.

Predictive models for radial sap flux variation in coniferous, diffuse-porous and ring-porous temperate trees.

PubMed

Berdanier, Aaron B; Miniat, Chelcy F; Clark, James S

2016-08-01

Accurately scaling sap flux observations to tree or stand levels requires accounting for variation in sap flux between wood types and by depth into the tree. However, existing models for radial variation in axial sap flux are rarely used because they are difficult to implement, there is uncertainty about their predictive ability and calibration measurements are often unavailable. Here we compare different models with a diverse sap flux data set to test the hypotheses that radial profiles differ by wood type and tree size. We show that radial variation in sap flux is dependent on wood type but independent of tree size for a range of temperate trees. The best-fitting model predicted out-of-sample sap flux observations and independent estimates of sapwood area with small errors, suggesting robustness in the new settings. We develop a method for predicting whole-tree water use with this model and include computer code for simple implementation in other studies. Published by Oxford University Press 2016. This work is written by (a) US Government employee(s) and is in the public domain in the US.

Drivers of protogynous sex change differ across spatial scales.

PubMed

Taylor, Brett M

2014-01-22

The influence of social demography on sex change schedules in protogynous reef fishes is well established, yet effects across spatial scales (in particular, the magnitude of natural variation relative to size-selective fishing effects) are poorly understood. Here, I examine variation in timing of sex change for exploited parrotfishes across a range of environmental, anthropogenic and geographical factors. Results were highly dependent on spatial scale. Fishing pressure was the most influential factor determining length at sex change at the within-island scale where a wide range of anthropogenic pressure existed. Sex transition occurred at smaller sizes where fishing pressure was high. Among islands, however, differences were overwhelmingly predicted by reefal-scale structural features, a pattern evident for all species examined. For the most abundant species, Chlorurus spilurus, length at sex change increased at higher overall densities and greater female-to-male sex ratios at all islands except where targeted by fishermen; here the trend was reversed. This implies differing selective pressures on adult individuals can significantly alter sex change dynamics, highlighting the importance of social structure, demography and the selective forces structuring populations. Considerable life-history responses to exploitation were observed, but results suggest potential fishing effects on demography may be obscured by natural variation at biogeographic scales.

Identification of copy number variants in horses.

PubMed

Doan, Ryan; Cohen, Noah; Harrington, Jessica; Veazey, Kylee; Veazy, Kylee; Juras, Rytis; Cothran, Gus; McCue, Molly E; Skow, Loren; Dindot, Scott V

2012-05-01

Copy number variants (CNVs) represent a substantial source of genetic variation in mammals. However, the occurrence of CNVs in horses and their subsequent impact on phenotypic variation is unknown. We performed a study to identify CNVs in 16 horses representing 15 distinct breeds (Equus caballus) and an individual gray donkey (Equus asinus) using a whole-exome tiling array and the array comparative genomic hybridization methodology. We identified 2368 CNVs ranging in size from 197 bp to 3.5 Mb. Merging identical CNVs from each animal yielded 775 CNV regions (CNVRs), involving 1707 protein- and RNA-coding genes. The number of CNVs per animal ranged from 55 to 347, with median and mean sizes of CNVs of 5.3 kb and 99.4 kb, respectively. Approximately 6% of the genes investigated were affected by a CNV. Biological process enrichment analysis indicated CNVs primarily affected genes involved in sensory perception, signal transduction, and metabolism. CNVs also were identified in genes regulating blood group antigens, coat color, fecundity, lactation, keratin formation, neuronal homeostasis, and height in other species. Collectively, these data are the first report of copy number variation in horses and suggest that CNVs are common in the horse genome and may modulate biological processes underlying different traits observed among horses and horse breeds.

GCR Modulation by Small-Scale Features in the Interplanetary Medium

NASA Astrophysics Data System (ADS)

Jordan, A. P.; Spence, H. E.; Blake, J. B.; Mulligan, T. L.; Shaul, D. N.; Galametz, M.

2007-12-01

In an effort to uncover the properties of structures in the interplanetary medium (IPM) that modulate galactic cosmic rays (GCR) on short time-scales (from hours to days), we study periods of differing conditions in the IPM. We analyze GCR variations from spacecraft both inside and outside the magnetosphere, using the High Sensitivity Telescope (HIST) on Polar and the Spectrometer for INTEGRAL (SPI). We seek causal correlations between the observed GCR modulations and structures in the solar wind plasma and interplanetary magnetic field, as measured concurrently with ACE and/or Wind. Our analysis spans time-/size-scale variations ranging from classic Forbush decreases (Fds), to substructure embedded within Fds, to much smaller amplitude and shorter duration variations observed during comparatively benign interplanetary conditions. We compare and contrast the conditions leading to the range of different GCR responses to modulating structures in the IPM.

Intra-pulse modulation recognition using short-time ramanujan Fourier transform spectrogram

NASA Astrophysics Data System (ADS)

Ma, Xiurong; Liu, Dan; Shan, Yunlong

2017-12-01

Intra-pulse modulation recognition under negative signal-to-noise ratio (SNR) environment is a research challenge. This article presents a robust algorithm for the recognition of 5 types of radar signals with large variation range in the signal parameters in low SNR using the combination of the Short-time Ramanujan Fourier transform (ST-RFT) and pseudo-Zernike moments invariant features. The ST-RFT provides the time-frequency distribution features for 5 modulations. The pseudo-Zernike moments provide invariance properties that are able to recognize different modulation schemes on different parameter variation conditions from the ST-RFT spectrograms. Simulation results demonstrate that the proposed algorithm achieves the probability of successful recognition (PSR) of over 90% when SNR is above -5 dB with large variation range in the signal parameters: carrier frequency (CF) for all considered signals, hop size (HS) for frequency shift keying (FSK) signals, and the time-bandwidth product for Linear Frequency Modulation (LFM) signals.

Limits to Forecasting Precision for Outbreaks of Directly Transmitted Diseases

PubMed Central

Drake, John M

2006-01-01

Background Early warning systems for outbreaks of infectious diseases are an important application of the ecological theory of epidemics. A key variable predicted by early warning systems is the final outbreak size. However, for directly transmitted diseases, the stochastic contact process by which outbreaks develop entails fundamental limits to the precision with which the final size can be predicted. Methods and Findings I studied how the expected final outbreak size and the coefficient of variation in the final size of outbreaks scale with control effectiveness and the rate of infectious contacts in the simple stochastic epidemic. As examples, I parameterized this model with data on observed ranges for the basic reproductive ratio (R 0) of nine directly transmitted diseases. I also present results from a new model, the simple stochastic epidemic with delayed-onset intervention, in which an initially supercritical outbreak (R 0 > 1) is brought under control after a delay. Conclusion The coefficient of variation of final outbreak size in the subcritical case (R 0 < 1) will be greater than one for any outbreak in which the removal rate is less than approximately 2.41 times the rate of infectious contacts, implying that for many transmissible diseases precise forecasts of the final outbreak size will be unattainable. In the delayed-onset model, the coefficient of variation (CV) was generally large (CV > 1) and increased with the delay between the start of the epidemic and intervention, and with the average outbreak size. These results suggest that early warning systems for infectious diseases should not focus exclusively on predicting outbreak size but should consider other characteristics of outbreaks such as the timing of disease emergence. PMID:16435887

VNIR reflectance spectroscopy of natural carbonate rocks: implication for remote sensing identification of fault damage zones

NASA Astrophysics Data System (ADS)

Traforti, Anna; Mari, Giovanna; Carli, Cristian; Demurtas, Matteo; Massironi, Matteo; Di Toro, Giulio

2017-04-01

Reflectance spectroscopy in the visible and near-infrared (VNIR) is a common technique used to study the mineral composition of Solar System bodies from remote sensed and in-situ robotic exploration. In the VNIR spectral range, both crystal field and vibrational overtone absorptions can be present with spectral characteristics (i.e. albedo, slopes, absorption band with different positions and depths) that vary depending on composition and texture (e.g. grain size, roughness) of the sensed materials. The characterization of the spectral variability related to the rock texture, especially in terms of grain size (i.e., both the size of rock components and the size of particulates), commonly allows to obtain a wide range of information about the different geological processes modifying the planetary surfaces. This work is aimed at characterizing how the grain size reduction associated to fault zone development produces reflectance variations in rock and mineral spectral signatures. To achieve this goal we present VNIR reflectance analysis of a set of fifteen rock samples collected at increasing distances from the fault core of the Vado di Corno fault zone (Campo Imperatore Fault System - Italian Central Apennines). The selected samples had similar content of calcite and dolomite but different grain size (X-Ray Powder Diffraction, optical and scanning electron microscopes analysis). Consequently, differences in the spectral signature of the fault rocks should not be ascribed to mineralogical composition. For each sample, bidirectional reflectance spectra were acquired with a Field-Pro Spectrometer mounted on a goniometer, on crushed rock slabs reduced to grain size <800, <200, <63, <10 μm and on intact fault zone rock slabs. The spectra were acquired on dry samples, at room temperature and normal atmospheric pressure. The source used was a Tungsten Halogen lamp with an illuminated spot area of ca. 0.5 cm2and incidence and emission angles of 30˚ and 0˚ respectively. The spectral analysis of the crushed and intact rock slabs in the VNIR spectral range revealed that in both cases, with increasing grain size: (i) the reflectance decreases (ii) VNIR spectrum slopes (i.e. calculated between wavelengths of 0.425 - 0.605 μm and 2.205 - 2.33 μm, respectively) and (iii) carbonate main absorption band depth (i.e. vibrational absorption band at wavelength of ˜2.3 μm) increase. In conclusion, grain size variations resulting from the fault zone evolution (e.g., cumulated slip or development of thick damage zones) produce reflectance variations in rocks and mineral spectral signatures. The remote sensing analysis in the VNIR spectral range can be applied to identify the spatial distribution and extent of fault core and damage zone domains for industrial and seismic hazard applications. Moreover, the spectral characterization of carbonate-built rocks can be of great interest for the surface investigation of inner planets (e.g. Earth and Mars) and outer bodies (e.g. Galilean icy satellites). On these surfaces, carbonate minerals at different grain sizes are common and usually related to water and carbon distribution, with direct implications for potential life outside Earth (e.g. Mars).

High individual variation in pheromone production by tree-killing bark beetles (Coleoptera: Curculionidae: Scolytinae)

NASA Astrophysics Data System (ADS)

Pureswaran, Deepa S.; Sullivan, Brian T.; Ayres, Matthew P.

2008-01-01

Aggregation via pheromone signalling is essential for tree-killing bark beetles to overcome tree defenses and reproduce within hosts. Pheromone production is a trait that is linked to fitness, so high individual variation is paradoxical. One explanation is that the technique of measuring static pheromone pools overestimates true variation among individuals. An alternative hypothesis is that aggregation behaviour dilutes the contribution of individuals to the trait under selection and reduces the efficacy of natural selection on pheromone production by individuals. We compared pheromone measurements from traditional hindgut extractions of female southern pine beetles with those obtained by aerating individuals till they died. Aerations showed greater total pheromone production than hindgut extractions, but coefficients of variation (CV) remained high (60-182%) regardless of collection technique. This leaves the puzzle of high variation unresolved. A novel but simple explanation emerges from considering bark beetle aggregation behaviour. The phenotype visible to natural selection is the collective pheromone plume from hundreds of colonisers. The influence of a single beetle on this plume is enhanced by high variation among individuals but constrained by large group sizes. We estimated the average contribution of an individual to the pheromone plume across a range of aggregation sizes and showed that large aggregation sizes typical in mass attacks limit the potential of natural selection because each individual has so little effect on the overall plume. Genetic variation in pheromone production could accumulate via mutation and recombination, despite strong effects of the pheromone plume on the fitness of individuals within the aggregation. Thus, aggregation behaviour, by limiting the efficacy of natural selection, can allow the persistence of extreme phenotypes in nature.

Stereoscopic depth perception varies with hues

NASA Astrophysics Data System (ADS)

Chen, Zaiqing; Shi, Junsheng; Tai, Yonghang; Yun, Lijun

2012-09-01

The contribution of color information to stereopsis is controversial, and whether the stereoscopic depth perception varies with chromaticity is ambiguous. This study examined the changes in depth perception caused by hue variations. Based on the fact that a greater disparity range indicates more efficient stereoscopic perception, the effect of hue variations on depth perception was evaluated through the disparity range with random-dot stereogram stimuli. The disparity range was obtained by constant-stimulus method for eight chromaticity points sampled from the CIE 1931 chromaticity diagram. Eight sample points include four main color hues: red, yellow, green, and blue at two levels of chroma. The results show that the disparity range for the yellow hue is greater than the red hue, the latter being greater than the blue hue and the disparity range for green hue is smallest. We conclude that the perceived depth is not the same for different hues for a given size of disparity. We suggest that the stereoscopic depth perception can vary with chromaticity.

Maintenance of phenotypic variation: Repeatability, heritability and size-dependent processes in a wild brook trout population

USGS Publications Warehouse

Letcher, B.H.; Coombs, J.A.; Nislow, K.H.

2011-01-01

Phenotypic variation in body size can result from within-cohort variation in birth dates, among-individual growth variation and size-selective processes. We explore the relative effects of these processes on the maintenance of wide observed body size variation in stream-dwelling brook trout (Salvelinus fontinalis). Based on the analyses of multiple recaptures of individual fish, it appears that size distributions are largely determined by the maintenance of early size variation. We found no evidence for size-dependent compensatory growth (which would reduce size variation) and found no indication that size-dependent survival substantially influenced body size distributions. Depensatory growth (faster growth by larger individuals) reinforced early size variation, but was relatively strong only during the first sampling interval (age-0, fall). Maternal decisions on the timing and location of spawning could have a major influence on early, and as our results suggest, later (>age-0) size distributions. If this is the case, our estimates of heritability of body size (body length=0.25) will be dominated by processes that generate and maintain early size differences. As a result, evolutionary responses to environmental change that are mediated by body size may be largely expressed via changes in the timing and location of reproduction. Published 2011. This article is a US Government work and is in the public domain in the USA.

Beyond body size: muscle biochemistry and body shape explain ontogenetic variation of anti-predatory behaviour in the lizard Salvator merianae.

PubMed

de Barros, Fábio Cury; de Carvalho, José Eduardo; Abe, Augusto Shinya; Kohlsdorf, Tiana

2016-06-01

Anti-predatory behaviour evolves under the strong action of natural selection because the success of individuals avoiding predation essentially defines their fitness. Choice of anti-predatory strategies is defined by prey characteristics as well as environmental temperature. An additional dimension often relegated in this multilevel equation is the ontogenetic component. In the tegu Salvator merianae, adults run away from predators at high temperatures but prefer fighting when it is cold, whereas juveniles exhibit the same flight strategy within a wide thermal range. Here, we integrate physiology and morphology to understand ontogenetic variation in the temperature-dependent shift of anti-predatory behaviour in these lizards. We compiled data for body shape and size, and quantified enzyme activity in hindlimb and head muscles, testing the hypothesis that morphophysiological models explain ontogenetic variation in behavioural associations. Our prediction is that juveniles exhibit body shape and muscle biochemistry that enhance flight strategies. We identified biochemical differences between muscles mainly in the LDH:CS ratio, whereby hindlimb muscles were more glycolytic than the jaw musculature. Juveniles, which often use evasive strategies to avoid predation, have more glycolytic hindlimb muscles and are much smaller when compared with adults 1-2 years old. Ontogenetic differences in body shape were identified but marginally contributed to behavioural variation between juvenile and adult tegus, and variation in anti-predatory behaviour in these lizards resides mainly in associations between body size and muscle biochemistry. Our results are discussed in the ecological context of predator avoidance by individuals differing in body size living at temperature-variable environments, where restrictions imposed by the cold could be compensated by specific phenotypes. © 2016. Published by The Company of Biologists Ltd.

Constraints on the adult-offspring size relationship in protists.

PubMed

Caval-Holme, Franklin; Payne, Jonathan; Skotheim, Jan M

2013-12-01

The relationship between adult and offspring size is an important aspect of reproductive strategy. Although this filial relationship has been extensively examined in plants and animals, we currently lack comparable data for protists, whose strategies may differ due to the distinct ecological and physiological constraints on single-celled organisms. Here, we report measurements of adult and offspring sizes in 3888 species and subspecies of foraminifera, a class of large marine protists. Foraminifera exhibit a wide range of reproductive strategies; species of similar adult size may have offspring whose sizes vary 100-fold. Yet, a robust pattern emerges. The minimum (5th percentile), median, and maximum (95th percentile) offspring sizes exhibit a consistent pattern of increase with adult size independent of environmental change and taxonomic variation over the past 400 million years. The consistency of this pattern may arise from evolutionary optimization of the offspring size-fecundity trade-off and/or from cell-biological constraints that limit the range of reproductive strategies available to single-celled organisms. When compared with plants and animals, foraminifera extend the evidence that offspring size covaries with adult size across an additional five orders of magnitude in organism size. © 2013 The Author(s). Evolution © 2013 The Society for the Study of Evolution.

Time and size resolved Measurement of Mass Concentration at an Urban Site

NASA Astrophysics Data System (ADS)

Karg, E.; Ferron, G. A.; Heyder, J.

2003-04-01

Time- and size-resolved measurements of ambient particles are necessary for modelling of atmospheric particle transport, the interpretation of particulate pollution events and the estimation of particle deposition in the human lungs. In the size range 0.01 - 2 µm time- and size-resolved data are obtained from differential mobility and optical particle counter measurements and from gravimetric filter analyses on a daily basis (PM2.5). By comparison of the time averaged and size integrated particle volume concentration with PM2.5 data, an average density of ambient particles can be estimated. Using this density, the number concentration data can be converted in time- and size-resolved mass concentration. Such measurements were carried out at a Munich downtown crossroads. The spectra were integrated in the size ranges 10 - 100 nm, 100 - 500 nm and 500 - 2000 nm. Particles in these ranges are named ultrafine, fine and coarse particles. These ranges roughly represent freshly emitted particles, aged/accumulated particles and particles entrained by erosive processes. An average number concentration of 80000 1/cm3 (s.d. 67%), a particle volume concentration of 53 µm3/cm3 (s.d. 76%) and a PM2.5 mass concentration of 27 µg/m3 was found. These particle volume- and PM2.5 data imply an average density of 0.51 g/cm3. Average number concentration showed 95.3%, 4.7% and 0.006% of the total particle concentration in the size ranges mentioned above. Mass concentration was 14.7%, 80.2% and 5.1% of the total, assuming the average density to be valid for all particles. The variability in mass concentration was 94%, 75% and 33% for the three size ranges. Nearly all ambient particles were in the ultrafine size range, whereas most of the mass concentration was in the fine size range. However, a considerable mass fraction of nearly 15% was found in the ultrafine size range. As the sampling site was close to the road and traffic emissions were the major source of the particles, 1) the density was very low due to agglomerated and porous structures of freshly emitted combustion particles and 2) the variability was highest in the ultrafine range, obviously correlated to traffic activity and lowest in the micron size range. In conclusion, almost all ambient particles were ultrafine particles, whereas most of the particle mass was associated with fine particles. Nevertheless, a considerable mass fraction was found in the ultrafine size range. These particles had a very low density so that they can be considered as agglomerated and porous particles emitted from vehicles passing the crossroads. Therefore they showed a much higher variation in mass concentration than the fine and coarse particles.

Dust generation in powders: Effect of particle size distribution

NASA Astrophysics Data System (ADS)

Chakravarty, Somik; Le Bihan, Olivier; Fischer, Marc; Morgeneyer, Martin

2017-06-01

This study explores the relationship between the bulk and grain-scale properties of powders and dust generation. A vortex shaker dustiness tester was used to evaluate 8 calcium carbonate test powders with median particle sizes ranging from 2μm to 136μm. Respirable aerosols released from the powder samples were characterised by their particle number and mass concentrations. All the powder samples were found to release respirable fractions of dust particles which end up decreasing with time. The variation of powder dustiness as a function of the particle size distribution was analysed for the powders, which were classified into three groups based on the fraction of particles within the respirable range. The trends we observe might be due to the interplay of several mechanisms like de-agglomeration and attrition and their relative importance.

Infrared spectroscopic ellipsometry of micrometer-sized SiO2 line gratings

NASA Astrophysics Data System (ADS)

Walder, Cordula; Zellmeier, Matthias; Rappich, Jörg; Ketelsen, Helge; Hinrichs, Karsten

2017-09-01

For the design and process control of periodic nano-structured surfaces spectroscopic ellipsometry is already established in the UV-VIS spectral regime. The objective of this work is to show the feasibility of spectroscopic ellipsometry in the infrared, exemplarily, on micrometer-sized SiO2 line gratings grown on silicon wafers. The grating period ranges from 10 to about 34 μm. The IR-ellipsometric spectra of the gratings exhibit complex changes with structure variations. Especially in the spectral range of the oxide stretching modes, the presence of a Rayleigh singularity can lead to pronounced changes of the spectrum with the sample geometry. The IR-ellipsometric spectra of the gratings are well reproducible by calculations with the RCWA method (Rigorous Coupled Wave Analysis). Therefore, infrared spectroscopic ellipsometry allows the quantitative characterization and process control of micrometer-sized structures.

Firefighter Hand Anthropometry and Structural Glove Sizing: A New Perspective

PubMed Central

Hsiao, Hongwei; Whitestone, Jennifer; Kau, Tsui-Ying; Hildreth, Brooke

2015-01-01

Objective We evaluated the current use and fit of structural firefighting gloves and developed an improved sizing scheme that better accommodates the U.S. firefighter population. Background Among surveys, 24% to 30% of men and 31% to 62% of women reported experiencing problems with the fit or bulkiness of their structural firefighting gloves. Method An age-, race/ethnicity-, and gender-stratified sample of 863 male and 88 female firefighters across the United States participated in the study. Fourteen hand dimensions relevant to glove design were measured. A cluster analysis of the hand dimensions was performed to explore options for an improved sizing scheme. Results The current national standard structural firefighting glove-sizing scheme underrepresents firefighter hand size range and shape variation. In addition, mismatch between existing sizing specifications and hand characteristics, such as hand dimensions, user selection of glove size, and the existing glove sizing specifications, is significant. An improved glove-sizing plan based on clusters of overall hand size and hand/finger breadth-to-length contrast has been developed. Conclusion This study presents the most up-to-date firefighter hand anthropometry and a new perspective on glove accommodation. The new seven-size system contains narrower variations (standard deviations) for almost all dimensions for each glove size than the current sizing practices. Application The proposed science-based sizing plan for structural firefighting gloves provides a step-forward perspective (i.e., including two women hand model–based sizes and two wide-palm sizes for men) for glove manufacturers to advance firefighter hand protection. PMID:26169309

New method of extrapolation of the resistance of a model planing boat to full size

NASA Technical Reports Server (NTRS)

Sottorf, W

1942-01-01

The previously employed method of extrapolating the total resistance to full size with lambda(exp 3) (model scale) and thereby foregoing a separate appraisal of the frictional resistance, was permissible for large models and floats of normal size. But faced with the ever increasing size of aircraft a reexamination of the problem of extrapolation to full size is called for. A method is described by means of which, on the basis of an analysis of tests on planing surfaces, the variation of the wetted surface over the take-off range is analytically obtained. The friction coefficients are read from Prandtl's curve for turbulent boundary layer with laminar approach. With these two values a correction for friction is obtainable.

Three-dimensional (3D) geometric morphometric analysis of human premolars to assess sexual dimorphism and biological ancestry in Australian populations.

PubMed

Yong, Robin; Ranjitkar, Sarbin; Lekkas, Dimitra; Halazonetis, Demetrios; Evans, Alistair; Brook, Alan; Townsend, Grant

2018-06-01

This study aimed to investigate size and shape variation of human premolars between Indigenous Australians and Australians of European ancestry, and to assess whether sex and ancestry could be differentiated between these groups using 3D geometric morphometrics. Seventy dental casts from each group, equally subdivided by sex, were scanned using a structured-light scanner. The 3D meshes of upper and lower premolars were processed using geometric morphometric methods. Seventy-two landmarks were recorded for upper premolars and 50 landmarks for lower premolars. For each tooth type, two-way ANOVA was used to assess group differences in centroid size. Shape variations were explored using principal component analysis and visualized using 3D morphing. Two-way Procrustes ANOVA was applied to test group differences for ancestry and sex, and a "leave-one-out" discriminant function was applied to assess group assignment. Centroid size and shape did not display significant difference between the sexes. Centroid size was larger in Indigenous Australians for upper premolars and lower second premolars compared to the Australians of European ancestry. Significant shape variation was noted between the two ancestral groups for upper premolars and the lower first premolar. Correct group assignment of individual teeth to their ancestral groups ranged between 80.0 and 92.8% for upper premolars and 60.0 and 75.7% for lower premolars. Our findings provide evidence of significant size and shape variation in human premolars between the two ancestral groups. High classification rates based on shape analysis of upper premolars highlight potential application of geometric morphometrics in anthropological, bioarcheological and forensic contexts. © 2018 Wiley Periodicals, Inc.

Regulation of water flux through tropical forest canopy trees: do universal rules apply?

PubMed

Meinzer, F C; Goldstein, G; Andrade, J L

2001-01-01

Tropical moist forests are notable for their richness in tree species. The presence of such a diverse tree flora presents potential problems for scaling up estimates of water use from individual trees to entire stands and for drawing generalizations about physiological regulation of water use in tropical trees. We measured sapwood area or sap flow, or both, in 27 co-occurring canopy species in a Panamanian forest to determine the extent to which relationships between tree size, sapwood area and sap flow were species-specific, or whether they were constrained by universal functional relationships between tree size, conducting xylem area, and water use. For the 24 species in which active xylem area was estimated over a range of size classes, diameter at breast height (DBH) accounted for 98% of the variation in sapwood area and 67% of the variation in sapwood depth when data for all species were combined. The DBH alone also accounted for > or = 90% of the variation in both maximum and total daily sap flux density in the outermost 2 cm of sapwood for all species taken together. Maximum sap flux density measured near the base of the tree occurred at about 1,400 h in the largest trees and 1,130 h in the smallest trees studied, and DBH accounted for 93% of the variation in the time of day at which maximum sap flow occurred. The shared relationship between tree size and time of maximum sap flow at the base of the tree suggests that a common relationship between diurnal stem water storage capacity and tree size existed. These results are consistent with a recent hypothesis that allometric scaling of plant vascular systems, and therefore water use, is universal.

Maintenance of phenotypic variation: repeatibility, heritability, and size-dependent processes in a wild brook trout population

Treesearch

Benjamin H. Letcher; Jason A Coombs; Keith H. Nislow

2011-01-01

Phenotypic variation in body size can result from within-cohort variation in birth dates, among-individual growth variation and size-selective processes. We explore the relative effects of these processes on the maintenance of wide observed body size variation in stream-dwelling brook trout (Salvelinus fontinalis). Based on the analyses of multiple...

The potential for adaptive evolution of pollen grain size in Mimulus guttatus.

PubMed

Lamborn, Ellen; Cresswell, James E; Macnair, Mark R

2005-07-01

We tested whether pollen grain size (PGS) shows heritable variation in three independent populations of Mimulus guttatus by imposing artificial selection for this character. In addition, we looked for correlated responses to selection in a range of 15 other floral characters. Heritable variation in PGS was found in all three populations, with heritabilities of between 19 and 40% (average 30%). After three generations, upward and downward lines differed on average by 30% in pollen volume. No consistent patterns of correlated response were found in other characters, indicating that PGS can respond to selective forces acting on PGS alone. Possible selection mechanisms on PGS in this species could include intermale selection, if large pollen grains produce more competitive gametophytes; or optimization of patterns of resource allocation, if local mate competition varies.

Partitioning the factors of spatial variation in regeneration density of shade-tolerant tree species.

PubMed

Gravel, Dominique; Beaudet, Marilou; Messier, Christian

2008-10-01

Understanding coexistence of highly shade-tolerant tree species is a longstanding challenge for forest ecologists. A conceptual model for the coexistence of sugar maple (Acer saccharum) and American beech (Fagus grandibfolia) has been proposed, based on a low-light survival/high-light growth trade-off, which interacts with soil fertility and small-scale spatiotemporal variation in the environment. In this study, we first tested whether the spatial distribution of seedlings and saplings can be predicted by the spatiotemporal variability of light availability and soil fertility, and second, the manner in which the process of environmental filtering changes with regeneration size. We evaluate the support for this hypothesis relative to the one for a neutral model, i.e., for seed rain density predicted from the distribution of adult trees. To do so, we performed intensive sampling over 86 quadrats (5 x 5 m) in a 0.24-ha plot in a mature maple-beech community in Quebec, Canada. Maple and beech abundance, soil characteristics, light availability, and growth history (used as a proxy for spatiotemporal variation in light availability) were finely measured to model variation in sapling composition across different size classes. Results indicate that the variables selected to model species distribution do effectively change with size, but not as predicted by the conceptual model. Our results show that variability in the environment is not sufficient to differentiate these species' distributions in space. Although species differ in their spatial distribution in the small size classes, they tend to correlate at the larger size class in which recruitment occurs. Overall, the results are not supportive of a model of coexistence based on small-scale variations in the environment. We propose that, at the scale of a local stand, the lack of fit of the model could result from the high similarity of species in the range of environmental conditions encountered, and we suggest that coexistence would be stable only at larger spatial scales at which variability in the environment is greater.

Life history dependent morphometric variation in stream-dwelling Atlantic salmon

USGS Publications Warehouse

Letcher, B.H.

2003-01-01

The time course of morphometric variation among life histories for stream-dwelling Atlantic salmon (Salmo salar L.) parr (age-0+ to age-2+) was analyzed. Possible life histories were combinations of parr maturity status in the autumn (mature or immature) and age at outmigration (smolt at age-2+ or later age). Actual life histories expressed with enough fish for analysis in the 1997 cohort were immature/age-2+ smolt, mature/age-2 +smolt, and mature/age-2+ non-smolt. Tagged fish were assigned to one of the three life histories and digital pictures from the field were analyzed using landmark-based geometric morphometrics. Results indicated that successful grouping of fish according to life history varied with fish age, but that fish could be grouped before the actual expression of the life histories. By March (age-1+), fish were successfully grouped using a descriptive discriminant function and successful assignment ranged from 84 to 97% for the remainder of stream residence. A jackknife of the discriminant function revealed an average life history prediction success of 67% from age-1+ summer to smolting. Low sample numbers for one of the life histories may have limited prediction success. A MANOVA on the shape descriptors (relative warps) also indicated significant differences in shape among life histories from age-1+ summer through to smolting. Across all samples, shape varied significantly with size. Within samples, shape did not vary significantly with size for samples from December (age-0+) to May (age-1+). During the age-1+ summer however, shape varied significantly with size, but the relationship between shape and size was not different among life histories. In the autumn (age-1+) and winter (age-2+), life history differences explained a significant portion of the change in shape with size. Life history dependent morphometric variation may be useful to indicate the timing of early expressions of life history variation and as a tool to explore temporal and spatial variation in life history expression.

Small-Size High-Current Generators for X-Ray Backlighting

NASA Astrophysics Data System (ADS)

Chaikovsky, S. A.; Artyomov, A. P.; Zharova, N. V.; Zhigalin, A. S.; Lavrinovich, I. V.; Oreshkin, V. I.; Ratakhin, N. A.; Rousskikh, A. G.; Fedunin, A. V.; Fedushchak, V. F.; Erfort, A. A.

2017-12-01

The paper deals with the soft X-ray backlighting based on the X-pinch as a powerful tool for physical studies of fast processes. Proposed are the unique small-size pulsed power generators operating as a low-inductance capacitor bank. These pulse generators provide the X-pinch-based soft X-ray source (hν = 1-10 keV) of micron size at 2-3 ns pulse duration. The small size and weight of pulse generators allow them to be transported to any laboratory for conducting X-ray backlighting of test objects with micron space resolution and nanosecond exposure time. These generators also allow creating synchronized multi-frame radiographic complexes with frame delay variation in a broad range.

Variation of Strontium (Sr) in the Ferroelectric Material Barium Strontium Titanate (Ba1-xSrxTiO3) by Co precipitation Method

NASA Astrophysics Data System (ADS)

Subarwanti, Y.; Safitri, R. D.; Supriyanto, A.; Iriani, Y.; Jamaludin, A.

2017-02-01

Barium Strontium Titanate (BST) have been made with variation strontium (Sr) 10%, 30% and 50% by co-precipitation method. This study aims to determine influence addition Sr against the crystal structure, crystallite size, lattice parameter, grain size and dielectric constant. Samples have been made by co-precipitation method and then the samples were sintered by furnace at 1100°C with holding time 4 hours. Characterization of BST use X-Ray Diffraction instrument, Scanning Electron Microscopy and Resistance Capacitance Inductance (RCL meter). Based on result obtained, the larger Sr content cause the diffraction angle shift to the right (the greater) and crystallinity increasing. But, the value of dielectric constant, crystallite size and grain size decreasing with additional Sr content. Measurement of dielectric constant (K) performed in the frequency range 1 kHz to 100 kHz and the highest value at Sr content 0.1 i.e. 258.35. The addition of Sr content 30% and 50% change the crystal structure from tetragonal to cubic which has paraelectric phase.

Cavitational synthesis of nanostructured inorganic materials for enhanced heterogeneous catalysis

NASA Astrophysics Data System (ADS)

Krausz, Ivo Michael

The synthesis of nanostructured inorganic materials by hydrodynamic cavitation processing was investigated. The goal of this work was to develop a general synthesis technique for nanostructured materials with a control over crystallite size in the 1--20 nm range. Materials with crystallite sizes in this range have shown enhanced catalytic activity compared to materials with larger crystallite sizes. Several supported and unsupported inorganic materials were studied to understand the effects of cavitation on crystallite size. Cavitation processing of calcium fluoride resulted in more spherical particles, attached to one another by melted necks. This work produced the first evidence of shock wave heating of nanostructured materials by hydrodynamic cavitation processing. Hydrodynamic cavitation synthesis of various catalytic support materials indicated that their phase composition and purity could be controlled by adjustment of the processing parameters. Zirconia/alumina supports synthesized using hydro-dynamic cavitation and calcined to 1368 K retained a high purity cubic zirconia phase, whereas classically prepared samples showed a phase transformation to monoclinic zirconia. Similarly, the synthesis of alumina resulted in materials with varying Bohmite and Bayerite contents as a function of the process parameters. High temperature calcination resulted in stable alumina supports with varying amounts of delta-, and theta-alumina. Synthesis studies of palladium and silver showed modest variations in crystallite size as a function of cavitation process parameters. Calcination resulted in larger grain materials, indicating a disappearance of intergrain boundaries. Based on these results, a new synthesis method was studied involving controlled agglomeration of small silver crystallites by hydrodynamic cavitation processing, followed by deposition on alumina. The optimal pH, concentration, and processing time for controlling the silver crystallite size in the cavitation equipment were determined using a statistical design of experiments approach. Three series of alumina supported silver catalysts were prepared, with silver weight loadings of 1%, 2%, and 5%. Variation of cavitation processing time between 1--64 min allowed the systematic control of silver crystallite size in the range of 3--19 nm. The preferred oxidation of CO in hydrogen (PROX) was chosen as a catalytic test reaction, because of its increasing importance for fuel cell applications. It was found that the catalytic activity was significantly increased for silver crystallite sizes below 5 nm. This work is the first experimental evidence of independent crystallite size control by hydrodynamic cavitation for alumina supported silver catalysts. The synthesis method involving controlled agglomeration and calcination is a general synthesis procedure that can be used to synthesize a wide range of novel catalysts and advanced materials.

Biomass and productivity of three phytoplankton size classes in San Francisco Bay.

USGS Publications Warehouse

Cole, B.E.; Cloern, J.E.; Alpine, A.E.

1986-01-01

The 5-22 mu m size accounted for 40-50% of annual production in each embayment, but production by phytoplanton >22 mu m ranged from 26% in the S reach to 54% of total phytoplankton production in the landward embayment of the N reach. A productivity index is derived that predicts daily productivity for each size class as a function of ambient irradiance and integrated chlorophyll a in the photic zone. For the whole phytoplankton community and for each size class, this index was constant at approx= 0.76 g C m-2 (g chlorophyll a Einstein)-1. The annual means of maximum carbon assimilation numbers were usually similar for the three size classes. Spatial and temporal variations in size-fractionated productivity are primarily due to differences in biomass rather than size-dependent carbon assimilation rates. -from Authors

Spatial and temporal variation in size of polar bear (Ursus maritimus) sexual organs and its use in pollution and climate change studies.

PubMed

Sonne, Christian; Dietz, Rune; Born, Erik W; Riget, Frank F; Leifsson, Pall S; Bechshøft, Thea Ø; Kirkegaard, Maja

2007-11-15

Sexual organs and their development are susceptible to atmospheric transported environmental xenoendocrine pollutants and climate change (food availability). We therefore investigated sexual organs from 55 male and 44 female East Greenland polar bears (Ursus maritimus) to obtain information about growth/size and sexual maturity. Then, the genitalia size was compared with those previously reported from Canadian and Svalbard polar bears. Growth models showed that East Greenland male polar bears reached sexual maturity around 7 years of age and females around 4 years of age. When comparing East Greenland and Svalbard polar bears, the size of baculum and uterus were significantly lower in the East Greenland polar bears (ANOVA: all p < 0.05). Based on previously published baculum mean values from Canadian polar bears, a similar baculum pattern was found for East Greenland vs. Canadian polar bears. It is speculated whether this could be a result of the general high variation in polar bear body size, temporal distribution patterns of anthropogenic long-range transported persistent organic pollutants or climate change (decreasing food availability). The present investigation represents conservation and background data for future spatial and temporal assessments of hunting, pollution and climate change scenarios.

How big should a mammal be? A macroecological look at mammalian body size over space and time

PubMed Central

Smith, Felisa A.; Lyons, S. Kathleen

2011-01-01

Macroecology was developed as a big picture statistical approach to the study of ecology and evolution. By focusing on broadly occurring patterns and processes operating at large spatial and temporal scales rather than on localized and/or fine-scaled details, macroecology aims to uncover general mechanisms operating at organism, population, and ecosystem levels of organization. Macroecological studies typically involve the statistical analysis of fundamental species-level traits, such as body size, area of geographical range, and average density and/or abundance. Here, we briefly review the history of macroecology and use the body size of mammals as a case study to highlight current developments in the field, including the increasing linkage with biogeography and other disciplines. Characterizing the factors underlying the spatial and temporal patterns of body size variation in mammals is a daunting task and moreover, one not readily amenable to traditional statistical analyses. Our results clearly illustrate remarkable regularities in the distribution and variation of mammalian body size across both geographical space and evolutionary time that are related to ecology and trophic dynamics and that would not be apparent without a broader perspective. PMID:21768152

Body frame dimensions are related to obesity and fatness: Lean trunk size, skinfolds, and body mass index.

PubMed

Henneberg, Maciej; Ulijaszek, Stanley J

2010-01-01

We explore relationships between BMI and skinfolds and anthropometric variables reflecting variation in lean body frame. Data on the middle class adult Australian women (n = 1260) collected in 2002 during a National Body Size and Shape Survey were used. Standard measurements of stature, weight, skeletal dimensions (shoulder width, hip width, chest width, and depth, limb lengths), circumferences of head, trunk, limbs and triceps, subscapular and abdominal skinfolds were taken. Techniques for measurements of skeletal frame minimized the inclusion of adipose tissue thickness. Analysis of variance and parametric and nonparametric correlations were used. Vertical dimensions show weak correlations with fatness, while body frame circumferences and transverse dimensions are consistently, significantly, and substantially correlated with fatness, each explaining from 3 to 44% of variation in skinfold thickness. Skeletal dimensions explain up to 50% of variation in skinfold thickness (multiple regression). Especially high correlations with skinfold thickness occur for chest width, depth, and hip width (r range from 0.42 to 0.66). Body frame dimensions reflect largely trunk volume and the trunk/limb proportions. Larger lean trunk size is associated with greater fatness. Since the size of the abdominal cavity, and thus the gastrointestinal system (GI), is reflected in the trunk size, we speculate that larger frame may predispose to obesity in two ways: (1) larger stomachs require greater bulk of food to produce feeling of satiety as mediated through antral distension, (2) larger GIs may absorb more nutrients. Frame size may help to detect the risk of obesity among young adults. 2009 Wiley-Liss, Inc.

What determines species richness of parasitic organisms? A meta-analysis across animal, plant and fungal hosts.

PubMed

Kamiya, Tsukushi; O'Dwyer, Katie; Nakagawa, Shinichi; Poulin, Robert

2014-02-01

Although a small set of external factors account for much of the spatial variation in plant and animal diversity, the search continues for general drivers of variation in parasite species richness among host species. Qualitative reviews of existing evidence suggest idiosyncrasies and inconsistent predictive power for all proposed determinants of parasite richness. Here, we provide the first quantitative synthesis of the evidence using a meta-analysis of 62 original studies testing the relationship between parasite richness across animal, plant and fungal hosts, and each of its four most widely used presumed predictors: host body size, host geographical range size, host population density, and latitude. We uncover three universal predictors of parasite richness across host species, namely host body size, geographical range size and population density, applicable regardless of the taxa considered and independently of most aspects of study design. A proper match in the primary studies between the focal predictor and both the spatial scale of study and the level at which parasite species richness was quantified (i.e. within host populations or tallied across a host species' entire range) also affected the magnitude of effect sizes. By contrast, except for a couple of indicative trends in subsets of the full dataset, there was no strong evidence for an effect of latitude on parasite species richness; where found, this effect ran counter to the general latitude gradient in diversity, with parasite species richness tending to be higher further from the equator. Finally, the meta-analysis also revealed a negative relationship between the magnitude of effect sizes and the year of publication of original studies (i.e. a time-lag bias). This temporal bias may be due to the increasing use of phylogenetic correction in comparative analyses of parasite richness over time, as this correction yields more conservative effect sizes. Overall, these findings point to common underlying processes of parasite diversification fundamentally different from those controlling the diversity of free-living organisms. © 2013 The Authors. Biological Reviews © 2013 Cambridge Philosophical Society.

Feast and famine in plant genomes.

Treesearch

Jonathan F. Wendel; Richard C. Cronn; J. Spencer Jonhston; H. James Price

2002-01-01

Plant genomes vary over several orders of magnitude in size, even among closely related species, yet the origin, genesis and significance of this variation are not clear. Because DNA content varies over a sevenfold range among diploid species in the cotton genus (Gossypium) and its allies, this group offers opportunities for exploring patterns and mechanisms of genome...

7 CFR 51.1437 - Size classifications for halves.

Code of Federal Regulations, 2014 CFR

2014-01-01

... halves per pound shall be based upon the weight of half-kernels after all pieces, particles and dust... specified range. (d) Tolerances for pieces, particles, and dust. In order to allow for variations incident..., particles, and dust: Provided, That not more than one-third of this amount, or 5 percent, shall be allowed...

7 CFR 51.1437 - Size classifications for halves.

Code of Federal Regulations, 2013 CFR

2013-01-01

... halves per pound shall be based upon the weight of half-kernels after all pieces, particles and dust... specified range. (d) Tolerances for pieces, particles, and dust. In order to allow for variations incident..., particles, and dust: Provided, That not more than one-third of this amount, or 5 percent, shall be allowed...

Nuclear DNA content variation within the genus Daucus (Apiaceae) determined by flow cytometry

USDA-ARS?s Scientific Manuscript database

The genus Daucus (Apiaceae) comprises species from around the world, covering a wide climatic range, and showing great morphological plasticity. Both cultivated and wild forms are described within the genus. The aim of the present study was to estimate the genome size variability in the collection o...

Effects of food supplementation on the physiological ecology of female Western diamond-backed rattlesnakes (Crotalus atrox).

PubMed

Taylor, Emily N; Malawy, Michael A; Browning, Dawn M; Lemar, Shea V; DeNardo, Dale F

2005-06-01

Food availability is an important factor in the life histories of organisms because it is often limiting and thus can affect growth, mass change, reproduction, and behaviors such as thermoregulation, locomotion, and mating. Experimental studies in natural settings allow researchers to examine the effects of food on these parameters while animals are free to behave naturally. The wide variation among organisms in energy demands and among environmental food resources suggest that responses to changes in food availability may vary among organisms. Since most supplemental feeding field experiments have been conducted on species with high energy demands, we conducted a supplemental feeding study on free-ranging, female Western diamond-backed rattlesnakes (Crotalus atrox), a species with low energy demands and infrequent reproductive investment. Snakes were offered thawed rodents 1-4 times per week. Over two active seasons, we collected data on surface activity, home range size, growth, mass change, and reproduction of supplementally fed and control snakes. Fed and control snakes did not differ in surface activity levels (proportion of time encountered above versus below ground) or home range size. Fed snakes grew and gained mass faster, and had a dramatically higher occurrence of reproduction than control snakes. Also, fed snakes were in better body condition following reproduction than snakes that were not fed. However, litter characteristics such as offspring number and size were not increased by feeding, suggesting that these characteristics may be fixed. These data experimentally demonstrate that food availability can directly impact some life history traits (i.e., growth and reproduction for C. atrox), but not others (i.e., surface activity and home range size for C. atrox). The relationship between food availability and life history traits is affected in a complex way by ecological traits and physiological constraints, and thus interspecific variation in this relationship is likely to be high.

Potential impacts of climate change on the winter distribution of Afro-Palaearctic migrant passerines

PubMed Central

Barbet-Massin, Morgane; Walther, Bruno A.; Thuiller, Wilfried; Rahbek, Carsten; Jiguet, Frédéric

2009-01-01

We modelled the present and future sub-Saharan winter distributions of 64 trans-Saharan migrant passerines to predict the potential impacts of climate change. These predictions used the recent ensemble modelling developments and the latest IPCC climatic simulations to account for possible methodological uncertainties. Results suggest that 37 species would face a range reduction by 2100 (16 of these by more than 50%); however, the median range size variation is −13 per cent (from −97 to +980%) under a full dispersal hypothesis. Range centroids were predicted to shift by 500±373 km. Predicted changes in range size and location were spatially structured, with species that winter in southern and eastern Africa facing larger range contractions and shifts. Predicted changes in regional species richness for these long-distance migrants are increases just south of the Sahara and on the Arabian Peninsula and major decreases in southern and eastern Africa. PMID:19324660

Spatial and temporal variation of an ice-adapted predator's feeding ecology in a changing Arctic marine ecosystem.

PubMed

Yurkowski, David J; Ferguson, Steven H; Semeniuk, Christina A D; Brown, Tanya M; Muir, Derek C G; Fisk, Aaron T

2016-03-01

Spatial and temporal variation can confound interpretations of relationships within and between species in terms of diet composition, niche size, and trophic position (TP). The cause of dietary variation within species is commonly an ontogenetic niche shift, which is a key dynamic influencing community structure. We quantified spatial and temporal variations in ringed seal (Pusa hispida) diet, niche size, and TP during ontogeny across the Arctic-a rapidly changing ecosystem. Stable carbon and nitrogen isotope analysis was performed on 558 liver and 630 muscle samples from ringed seals and on likely prey species from five locations ranging from the High to the Low Arctic. A modest ontogenetic diet shift occurred, with adult ringed seals consuming more forage fish (approximately 80 versus 60 %) and having a higher TP than subadults, which generally decreased with latitude. However, the degree of shift varied spatially, with adults in the High Arctic presenting a more restricted niche size and consuming more Arctic cod (Boreogadus saida) than subadults (87 versus 44 %) and adults at the lowest latitude (29 %). The TPs of adult and subadult ringed seals generally decreased with latitude (4.7-3.3), which was mainly driven by greater complexity in trophic structure within the zooplankton communities. Adult isotopic niche size increased over time, likely due to the recent circumpolar increases in subarctic forage fish distribution and abundance. Given the spatial and temporal variability in ringed seal foraging ecology, ringed seals exhibit dietary plasticity as a species, suggesting adaptability in terms of their diet to climate change.

Allometric relationship of postmolt net ion uptake, ventilation, and circulation in the freshwater crayfish Procambarus clarkii: intraspecific scaling.

PubMed

Zanotto, F P; Wheatly, M G; Reiber, C L; Gannon, A T; Jalles-Filho, E

2004-01-01

There are few intraspecific studies relating physiological parameters to body mass. This study relates scaling of ionic regulation and respiratory parameters with body mass in crayfish (Procambarus clarkii). These animals were chosen because of their direct development, spanning four orders of magnitude in body mass. Usually, these animals are hyperregulators and must maintain hemolymph electrolyte levels above those in the ambient freshwater. This is especially important in the postmolt, when ion imbalance can occur. Maintaining hemolymph ion levels above ambient involves active processes that are independently related to metabolic rate, ventilation, and circulation. Therefore, this study investigates relationships among size and ionic regulation, heart rate, and ventilation in crayfish, spanning a size range of 0.003-24 g. Postmolt net ion uptake of Ca, titratable base, Na, Cl, and NH4 increase with body mass (positive allometry) with slopes of 0.92, 0.79, 0.90, 0.84, and 0.87, respectively. Between 72% and 97% of variation in ionic regulation was related to body mass. The slopes differed from each other for Ca and titratable base but not for Na, Cl, and NH4. For heart rate and ventilation rate, different relationships were derived for animals smaller and larger than 0.01 g (between first and third instar). Animals larger than 0.01 g show a negative allometric relationship between heart rate and body size ([body mass](0.15)), while smaller animals show positive allometry with body size, but only 29% of variation in heart rate is explained by body size alone. For ventilation rates, the negative allometry with body size for animals larger than 0.01 g is present, but less than 15% of variation in ventilation rate is explained by size, while for smaller animals the size dependency disappears. Based on these results, predictions of physiological parameters such as ionic regulation based on body size are useful in crayfish, but estimates of respiratory parameters and body size should be used with caution.

Particle size effects on viscosity of silver pastes: A manufacturer's view

NASA Technical Reports Server (NTRS)

Provance, J.; Allison, K.

1983-01-01

Particles from a variety of silver powders were investigated by scanning electron microscopy and particle size analyses. Particle size distribution curves and volume population graphs were prepared for these silver powders and for glass powders with optimum, extra fine and coarse particle sizes. The viscosity at a given shear rate and slope of viscosity over a range of shear rates were determined for thick film pastes made with these powders. Because of particle anomalies and variations, the need for flexibility to achieve the best printing qualities for silver pastes was evident. It was established that print quality, dried and fired film density and optimum contact of silver particles with silicon, important for cell electrical output, could be achieved by adjusting the slope of viscosity that fell outside of the range, -0.550 to -0.650. This was accomplished through organic vehicle technology that permitted a change in the slope of viscosity, up or down, while maintaining a constant silver and total solids content.

Parametric study of potential early commercial MHD power plants. Task 3: Parameter variation of plant size

NASA Technical Reports Server (NTRS)

Hals, F. A.

1981-01-01

Plants with a nominal output of 200 and 500 MWe and conforming to the same design configuration as the Task II plant were investigated. This information is intended to permit an assessment of the competitiveness of first generation MHD/steam plants with conventional steam plants over the range of 200 to 1000 MWe. The results show that net plant efficiency of the MHD plant is significantly higher than a conventional steam plant of corresponding size. The cost of electricity is also less for the MHD plant over the entire plant size range. As expected, the cost differential is higher for the larger plant and decreases with plant size. Even at the 200 MWe capacity, however, the differential in COE between the MHD plant and the conventional plant is sufficient attractive to warrant serious consideration. Escalating fuel costs will enhance the competitive position of MHD plants because they can utilize the fuel more efficiently than conventional steam plants.

Relationship of Powder Feedstock Variability to Microstructure and Defects in Selective Laser Melted Alloy 718

NASA Technical Reports Server (NTRS)

Smith, T. M.; Kloesel, M. F.; Sudbrack, C. K.

2017-01-01

Powder-bed additive manufacturing processes use fine powders to build parts layer by layer. For selective laser melted (SLM) Alloy 718, the powders that are available off-the-shelf are in the 10-45 or 15-45 micron size range. A comprehensive investigation of sixteen powders from these typical ranges and two off-nominal-sized powders is underway to gain insight into the impact of feedstock on processing, durability and performance of 718 SLM space-flight hardware. This talk emphasizes an aspect of this work: the impact of powder variability on the microstructure and defects observed in the as-fabricated and full heated material, where lab-scale components were built using vendor recommended parameters. These typical powders exhibit variation in composition, percentage of fines, roughness, morphology and particle size distribution. How these differences relate to the melt-pool size, porosity, grain structure, precipitate distributions, and inclusion content will be presented and discussed in context of build quality and powder acceptance.

Biodiversity and body size are linked across metazoans

PubMed Central

McClain, Craig R.; Boyer, Alison G.

2009-01-01

Body size variation across the Metazoa is immense, encompassing 17 orders of magnitude in biovolume. Factors driving this extreme diversification in size and the consequences of size variation for biological processes remain poorly resolved. Species diversity is invoked as both a predictor and a result of size variation, and theory predicts a strong correlation between the two. However, evidence has been presented both supporting and contradicting such a relationship. Here, we use a new comprehensive dataset for maximum and minimum body sizes across all metazoan phyla to show that species diversity is strongly correlated with minimum size, maximum size and consequently intra-phylum variation. Similar patterns are also observed within birds and mammals. The observations point to several fundamental linkages between species diversification and body size variation through the evolution of animal life. PMID:19324730

Synthesis of Gold Nanoparticles with Buffer-Dependent Variations of Size and Morphology in Biological Buffers.

PubMed

Ahmed, Syed Rahin; Oh, Sangjin; Baba, Rina; Zhou, Hongjian; Hwang, Sungu; Lee, Jaebeom; Park, Enoch Y

2016-12-01

The demand for biologically compatible and stable noble metal nanoparticles (NPs) has increased in recent years due to their inert nature and unique optical properties. In this article, we present 11 different synthetic methods for obtaining gold nanoparticles (Au NPs) through the use of common biological buffers. The results demonstrate that the sizes, shapes, and monodispersity of the NPs could be varied depending on the type of buffer used, as these buffers acted as both a reducing agent and a stabilizer in each synthesis. Theoretical simulations and electrochemical experiments were performed to understand the buffer-dependent variations of size and morphology exhibited by these Au NPs, which revealed that surface interactions and the electrostatic energy on the (111) surface of Au were the determining factors. The long-term stability of the synthesized NPs in buffer solution was also investigated. Most NPs synthesized using buffers showed a uniquely wide range of pH stability and excellent cell viability without the need for further modifications.

Insights into the Evolution of Mitochondrial Genome Size from Complete Sequences of Citrullus lanatus and Cucurbita pepo (Cucurbitaceae)

PubMed Central

Alverson, Andrew J.; Wei, XiaoXin; Rice, Danny W.; Stern, David B.; Barry, Kerrie; Palmer, Jeffrey D.

2010-01-01

The mitochondrial genomes of seed plants are unusually large and vary in size by at least an order of magnitude. Much of this variation occurs within a single family, the Cucurbitaceae, whose genomes range from an estimated 390 to 2,900 kb in size. We sequenced the mitochondrial genomes of Citrullus lanatus (watermelon: 379,236 nt) and Cucurbita pepo (zucchini: 982,833 nt)—the two smallest characterized cucurbit mitochondrial genomes—and determined their RNA editing content. The relatively compact Citrullus mitochondrial genome actually contains more and longer genes and introns, longer segmental duplications, and more discernibly nuclear-derived DNA. The large size of the Cucurbita mitochondrial genome reflects the accumulation of unprecedented amounts of both chloroplast sequences (>113 kb) and short repeated sequences (>370 kb). A low mutation rate has been hypothesized to underlie increases in both genome size and RNA editing frequency in plant mitochondria. However, despite its much larger genome, Cucurbita has a significantly higher synonymous substitution rate (and presumably mutation rate) than Citrullus but comparable levels of RNA editing. The evolution of mutation rate, genome size, and RNA editing are apparently decoupled in Cucurbitaceae, reflecting either simple stochastic variation or governance by different factors. PMID:20118192

Long-term observations of cloud condensation nuclei in the Amazon rain forest – Part 1: Aerosol size distribution, hygroscopicity, and new model parametrizations for CCN prediction

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

Pöhlker, Mira L.; Pöhlker, Christopher; Ditas, Florian

Size-resolved long-term measurements of atmospheric aerosol and cloud condensation nuclei (CCN) concentrations and hygroscopicity were conducted at the remote Amazon Tall Tower Observatory (ATTO) in the central Amazon Basin over a 1-year period and full seasonal cycle (March 2014–February 2015). Our measurements provide a climatology of CCN properties characteristic of a remote central Amazonian rain forest site.The CCN measurements were continuously cycled through 10 levels of supersaturation ( S=0.11 to 1.10 %) and span the aerosol particle size range from 20 to 245 nm. The mean critical diameters of CCN activation range from 43 nm at S = 1.10 % to 172more » nm at S = 0.11 %. Furthermore, the particle hygroscopicity exhibits a pronounced size dependence with lower values for the Aitken mode ( κ Ait = 0.14 ± 0.03), higher values for the accumulation mode ( κ Acc = 0.22 ± 0.05), and an overall mean value of κ mean = 0.17 ± 0.06, consistent with high fractions of organic aerosol.The hygroscopicity parameter, κ, exhibits remarkably little temporal variability: no pronounced diurnal cycles, only weak seasonal trends, and few short-term variations during long-range transport events. In contrast, the CCN number concentrations exhibit a pronounced seasonal cycle, tracking the pollution-related seasonality in total aerosol concentration. Here, we find that the variability in the CCN concentrations in the central Amazon is mostly driven by aerosol particle number concentration and size distribution, while variations in aerosol hygroscopicity and chemical composition matter only during a few episodes.For modeling purposes, we compare different approaches of predicting CCN number concentration and present a novel parametrization, which allows accurate CCN predictions based on a small set of input data.« less

Long-term observations of cloud condensation nuclei in the Amazon rain forest – Part 1: Aerosol size distribution, hygroscopicity, and new model parametrizations for CCN prediction

DOE PAGES

Pöhlker, Mira L.; Pöhlker, Christopher; Ditas, Florian; ...

2016-12-20

Size-resolved long-term measurements of atmospheric aerosol and cloud condensation nuclei (CCN) concentrations and hygroscopicity were conducted at the remote Amazon Tall Tower Observatory (ATTO) in the central Amazon Basin over a 1-year period and full seasonal cycle (March 2014–February 2015). Our measurements provide a climatology of CCN properties characteristic of a remote central Amazonian rain forest site.The CCN measurements were continuously cycled through 10 levels of supersaturation ( S=0.11 to 1.10 %) and span the aerosol particle size range from 20 to 245 nm. The mean critical diameters of CCN activation range from 43 nm at S = 1.10 % to 172more » nm at S = 0.11 %. Furthermore, the particle hygroscopicity exhibits a pronounced size dependence with lower values for the Aitken mode ( κ Ait = 0.14 ± 0.03), higher values for the accumulation mode ( κ Acc = 0.22 ± 0.05), and an overall mean value of κ mean = 0.17 ± 0.06, consistent with high fractions of organic aerosol.The hygroscopicity parameter, κ, exhibits remarkably little temporal variability: no pronounced diurnal cycles, only weak seasonal trends, and few short-term variations during long-range transport events. In contrast, the CCN number concentrations exhibit a pronounced seasonal cycle, tracking the pollution-related seasonality in total aerosol concentration. Here, we find that the variability in the CCN concentrations in the central Amazon is mostly driven by aerosol particle number concentration and size distribution, while variations in aerosol hygroscopicity and chemical composition matter only during a few episodes.For modeling purposes, we compare different approaches of predicting CCN number concentration and present a novel parametrization, which allows accurate CCN predictions based on a small set of input data.« less

Range size heritability and diversification patterns in the liverwort genus Radula.

PubMed

Patiño, Jairo; Wang, Jian; Renner, Matt A M; Gradstein, S Robbert; Laenen, Benjamin; Devos, Nicolas; Shaw, A Jonathan; Vanderpoorten, Alain

2017-01-01

Why some species exhibit larger geographical ranges than others, and to what extent does variation in range size affect diversification rates, remains a fundamental, but largely unanswered question in ecology and evolution. Here, we implement phylogenetic comparative analyses and ancestral area estimations in Radula, a liverwort genus of Cretaceous origin, to investigate the mechanisms that explain differences in geographical range size and diversification rates among lineages. Range size was phylogenetically constrained in the two sub-genera characterized by their almost complete Australasian and Neotropical endemicity, respectively. The congruence between the divergence time of these lineages and continental split suggests that plate tectonics could have played a major role in their present distribution, suggesting that a strong imprint of vicariance can still be found in extant distribution patterns in these highly mobile organisms. Amentuloradula, Volutoradula and Metaradula species did not appear to exhibit losses of dispersal capacities in terms of dispersal life-history traits, but evidence for significant phylogenetic signal in macroecological niche traits suggests that niche conservatism accounts for their restricted geographic ranges. Despite their greatly restricted distribution to Australasia and Neotropics respectively, Amentuloradula and Volutoradula did not exhibit significantly lower diversification rates than more widespread lineages, in contrast with the hypothesis that the probability of speciation increases with range size by promoting geographic isolation and increasing the rate at which novel habitats are encountered. We suggest that stochastic long-distance dispersal events may balance allele frequencies across large spatial scales, leading to low genetic structure among geographically distant areas or even continents, ultimately decreasing the diversification rates in highly mobile, widespread lineages. Copyright © 2016 Elsevier Inc. All rights reserved.

Morphological and genetic divergence in Swedish postglacial stickleback (Pungitius pungitius) populations

PubMed Central

2011-01-01

Background An important objective of evolutionary biology is to understand the processes that govern phenotypic variation in natural populations. We assessed patterns of morphological and genetic divergence among coastal and inland lake populations of nine-spined stickleback in northern Sweden. Coastal populations are either from the Baltic coast (n = 5) or from nearby coastal lakes (n = 3) that became isolated from the Baltic Sea (< 100 years before present, ybp). Inland populations are from freshwater lakes that became isolated from the Baltic approximately 10,000 ybp; either single species lakes without predators (n = 5), or lakes with a recent history of predation (n = 5) from stocking of salmonid predators (~50 ybp). Results Coastal populations showed little variation in 11 morphological traits and had longer spines per unit of body length than inland populations. Inland populations were larger, on average, and showed greater morphological variation than coastal populations. A principal component analysis (PCA) across all populations revealed two major morphological axes related to spine length (PC1, 47.7% variation) and body size (PC2, 32.9% variation). Analysis of PCA scores showed marked similarity in coastal (Baltic coast and coastal lake) populations. PCA scores indicate that inland populations with predators have higher within-group variance in spine length and lower within-group variance in body size than inland populations without predators. Estimates of within-group PST (a proxy for QST) from PCA scores are similar to estimates of FST for coastal lake populations but PST >FST for Baltic coast populations. PST >FST for PC1 and PC2 for inland predator and inland no predator populations, with the exception that PST

Phylogenetic Relationship in Different Commercial Strains of Pleurotus nebrodensis Based on ITS Sequence and RAPD.

PubMed

Alam, Nuhu; Shim, Mi Ja; Lee, Min Woong; Shin, Pyeong Gyun; Yoo, Young Bok; Lee, Tae Soo

2009-09-01

The molecular phylogeny in nine different commercial cultivated strains of Pleurotus nebrodensis was studied based on their internal transcribed spacer (ITS) region and RAPD. In the sequence of ITS region of selected strains, it was revealed that the total length ranged from 592 to 614 bp. The size of ITS1 and ITS2 regions varied among the strains from 219 to 228 bp and 211 to 229 bp, respectively. The sequence of ITS2 was more variable than ITS1 and the region of 5.8S sequences were identical. Phylogenetic tree of the ITS region sequences indicated that selected strains were classified into five clusters. The reciprocal homologies of the ITS region sequences ranged from 99 to 100%. The strains were also analyzed by RAPD with 20 arbitrary primers. Twelve primers were efficient to applying amplification of the genomic DNA. The sizes of the polymorphic fragments obtained were in the range of 200 to 2000 bp. RAPD and ITS analysis techniques were able to detect genetic variation among the tested strains. Experimental results suggested that IUM-1381, IUM-3914, IUM-1495 and AY-581431 strains were genetically very similar. Therefore, all IUM and NCBI gene bank strains of P. nebrodensis were genetically same with some variations.

Distribution and diversity of cytotypes in Dianthus broteri as evidenced by genome size variations

PubMed Central

Balao, Francisco; Casimiro-Soriguer, Ramón; Talavera, María; Herrera, Javier; Talavera, Salvador

2009-01-01

Background and Aims Studying the spatial distribution of cytotypes and genome size in plants can provide valuable information about the evolution of polyploid complexes. Here, the spatial distribution of cytological races and the amount of DNA in Dianthus broteri, an Iberian carnation with several ploidy levels, is investigated. Methods Sample chromosome counts and flow cytometry (using propidium iodide) were used to determine overall genome size (2C value) and ploidy level in 244 individuals of 25 populations. Both fresh and dried samples were investigated. Differences in 2C and 1Cx values among ploidy levels within biogeographical provinces were tested using ANOVA. Geographical correlations of genome size were also explored. Key Results Extensive variation in chromosomes numbers (2n = 2x = 30, 2n = 4x = 60, 2n = 6x = 90 and 2n = 12x =180) was detected, and the dodecaploid cytotype is reported for the first time in this genus. As regards cytotype distribution, six populations were diploid, 11 were tetraploid, three were hexaploid and five were dodecaploid. Except for one diploid population containing some triploid plants (2n = 45), the remaining populations showed a single cytotype. Diploids appeared in two disjunct areas (south-east and south-west), and so did tetraploids (although with a considerably wider geographic range). Dehydrated leaf samples provided reliable measurements of DNA content. Genome size varied significantly among some cytotypes, and also extensively within diploid (up to 1·17-fold) and tetraploid (1·22-fold) populations. Nevertheless, variations were not straightforwardly congruent with ecology and geographical distribution. Conclusions Dianthus broteri shows the highest diversity of cytotypes known to date in the genus Dianthus. Moreover, some cytotypes present remarkable internal genome size variation. The evolution of the complex is discussed in terms of autopolyploidy, with primary and secondary contact zones. PMID:19633312

Suspended sediment transport under estuarine tidal channel conditions

USGS Publications Warehouse

Sternberg, R.W.; Kranck, K.; Cacchione, D.A.; Drake, D.E.

1988-01-01

A modified version of the GEOPROBE tripod has been used to monitor flow conditions and suspended sediment distribution in the bottom boundary layer of a tidal channel within San Francisco Bay, California. Measurements were made every 15 minutes over three successive tidal cycles. They included mean velocity profiles from four electromagnetic current meters within 1 m of the seabed; mean suspended sediment concentration profiles from seven miniature nephelometers operated within 1 m of the seabed; near-bottom pressure fluctuations; vertical temperature gradient; and bottom photographs. Additionally, suspended sediment was sampled from four levels within 1 m of the seabed three times during each successive flood and ebb cycle. While the instrument was deployed, STD-nephelometer measurements were made throughout the water column, water samples were collected each 1-2 hours, and bottom sediment was sampled at the deployment site. From these measurements, estimates were made of particle settling velocity (ws) from size distributions of the suspended sediment, friction velocity (U*) from the velocity profiles, and reference concentration (Ca) was measured at z = 20 cm. These parameters were used in the suspended sediment distribution equations to evaluate their ability to predict the observed suspended sediment profiles. Three suspended sediment particle conditions were evaluated: (1) individual particle size in the 4-11 ?? (62.5-0.5 ??m) range with the reference concentration Ca at z = 20 cm (C??), (2) individual particle size in the 4-6 ?? size range, flocs representing the 7-11 ?? size range with the reference concentration Ca at z = 20 cm (Cf), and (3) individual particle size in the 4-6 ?? size range, flocs representing the 7-11 ?? size range with the reference concentration predicted as a function of the bed sediment size distribution and the square of the excess shear stress. In addition, computations of particle flux were made in order to show vertical variations in horizontal mass flux for varying flow conditions. ?? 1988.

Critical conditions for particle motion in coarse bed materials of nonuniform size distribution

NASA Astrophysics Data System (ADS)

Bathurst, James C.

2013-09-01

Initiation of particle motion in a bed material of nonuniform size distribution may be quantified by (qci/qcr) = (Di/Dr)b, where qci is the critical unit discharge at which particle size Di enters motion, qcr is the critical condition for a reference size Dr unaffected by the hiding/exposure effects associated with nonuniform size distributions, i and r refer to percentiles of the distribution and b varies from 0 (equal mobility in entrainment of all particle sizes) to 1.5-2.5 (full size selective transport). Currently there is no generally accepted method for predicting the value of b. Flume and field data are therefore combined to investigate the above relationship. Thirty-seven sets of flume data quantify the relationship between critical unit discharge and particle size for bed materials with uniform size distributions (used here to approximate full size selective transport). Field data quantify the relationship for bed materials of nonuniform size distribution at 24 sites, with b ranging from 0.15 to 1.3. Intersection of the two relationships clearly demonstrates the hiding/exposure effect; in some but not all cases, Dr is close to the median size D50. The exponent has two clusters of values: b > 1 for sites subject to episodic rain-fed floods and data collected by bedload pit trap and tracers; and b < 0.7 for sites with seasonal snowmelt/glacial melt flow regimes and data collected by bedload sampler and large aperture trap. Field technique appears unlikely to cause variations in b of more than about 0.25. However, the clustering is consistent with possible variations in bed structure distinguishing: for b > 1, sites with relatively infrequent bedload transport where particle embedding and consolidation could reduce the mobility of coarser particles; and, for b < 0.7, a looser bed structure with frequent transport events allowing hiding/exposure and size selection effects to achieve their balance. As yet there is no firm evidence for such a dependency on bed structure but variations in b could potentially be caused by factors outside those determining equal mobility or size selection but appearing to affect b in the same way.

Practice variation in surgical procedures and IUD-insertions among general practitioners in Norway - a longitudinal study.

PubMed

Pahle, Andreas Saxlund; Sørli, Daniel; Kristiansen, Ivar Sønbø; Deraas, Trygve S; Halvorsen, Peder A

2017-01-21

Studies of Primary Health Care (PHC) reveal considerable practice variations in terms of the range of services provided. In Norway, general practitioners (GPs) are traditionally expected to perform IUD-insertions and several surgical procedures as a part of comprehensive PHC. We aimed to investigate variation in the provision of surgical procedures and IUD-insertions across GPs and over time and explore determinants of such variation. Retrospective registry study of Norwegian GPs. From a comprehensive database of GPs' reimbursement claims, we obtained procedure codes and GP characteristics such as age, gender, list size and municipality characteristics from 2006 through 2013. Multivariable logistic regression models were fitted to explore determinants of practice variation. We extracted data from 4,828 GPs. In 2013, 91.0, 76.1 and 74.8% were reimbursed at least once for minor and major surgical procedures and IUD-insertion, respectively. Female GPs had lower odds for performing major surgical procedures (OR 0.38, 95% CI 0.32-0.45) and higher odds for performing IUD-insertions (OR 6.28, 95% CI 4.47-8.82) than male GPs. Older GPs and GPs with shorter patient lists were less likely to perform surgical procedures. GPs with longer patient lists had higher odds for performing IUD-insertions. The proportion of GPs performing surgical procedures increased over time, while the proportion decreased for IUD-insertions. The number of IUD-insertions in specialist care increased from 12,575 in 2011 to 15 216 (+21.0%) in 2014. We observed a large variation in the provision of surgical procedures and IUD-insertions amongst GPs in Norway. The GPs' age, gender, list size and size of municipality were associated with performing the procedures. Our findings suggest a shift of IUD-insertions from primary to specialist care.

Genetic parameters for uniformity of harvest weight and body size traits in the GIFT strain of Nile tilapia.

PubMed

Marjanovic, Jovana; Mulder, Han A; Khaw, Hooi L; Bijma, Piter

2016-06-10

Animal breeding programs have been very successful in improving the mean levels of traits through selection. However, in recent decades, reducing the variability of trait levels between individuals has become a highly desirable objective. Reaching this objective through genetic selection requires that there is genetic variation in the variability of trait levels, a phenomenon known as genetic heterogeneity of environmental (residual) variance. The aim of our study was to investigate the potential for genetic improvement of uniformity of harvest weight and body size traits (length, depth, and width) in the genetically improved farmed tilapia (GIFT) strain. In order to quantify the genetic variation in uniformity of traits and estimate the genetic correlations between level and variance of the traits, double hierarchical generalized linear models were applied to individual trait values. Our results showed substantial genetic variation in uniformity of all analyzed traits, with genetic coefficients of variation for residual variance ranging from 39 to 58 %. Genetic correlation between trait level and variance was strongly positive for harvest weight (0.60 ± 0.09), moderate and positive for body depth (0.37 ± 0.13), but not significantly different from 0 for body length and width. Our results on the genetic variation in uniformity of harvest weight and body size traits show good prospects for the genetic improvement of uniformity in the GIFT strain. A high and positive genetic correlation was estimated between level and variance of harvest weight, which suggests that selection for heavier fish will also result in more variation in harvest weight. Simultaneous improvement of harvest weight and its uniformity will thus require index selection.

Molar intercuspal dimensions: genetic input to phenotypic variation.

PubMed

Townsend, G; Richards, L; Hughes, T

2003-05-01

Molecular studies indicate that epigenetic events are important in determining how the internal enamel epithelium folds during odontogenesis. Since this process of folding leads to the subsequent arrangement of cusps on molar teeth, we hypothesized that intercuspal distances of human molar teeth would display greater phenotypic variation but lower heritabilities than overall crown diameters. Intercuspal distances and maximum crown diameters were recorded from digitized images of dental casts in 100 monozygotic and 74 dizygotic twin pairs. Intercuspal distances displayed less sexual dimorphism in mean values but greater relative variability and fluctuating asymmetry than overall crown measures. Correlations between intercuspal distances and overall crown measures were low. Models incorporating only environmental effects accounted for observed variation in several intercuspal measures. For those intercuspal variables displaying significant additive genetic variance, estimates of heritability ranged from 43 to 79%, whereas those for overall crown size were higher generally, ranging from 60 to 82%. Our finding of high phenotypic variation in intercuspal distances with only moderate genetic contribution is consistent with substantial epigenetic influence on the progressive folding of the internal enamel epithelium, following formation of the primary and secondary enamel knots.

The relative effects of entry parameters on thermal protection system weight. [space shuttle orbiters

NASA Technical Reports Server (NTRS)

Hirasaki, P. N.

1971-01-01

Shielding a spacecraft from the severe thermal environment of an atmospheric entry requires a sophisticated thermal protection system (TPS). Thermal computer program models were developed for two such TPS designs proposed for the space shuttle orbiter. The multilayer systems, a reusable surface insulation TPS, and a re-radiative metallic skin TPS, were sized for a cross-section of trajectories in the entry corridor. This analysis indicates the relative influence of the entry parameters on the weight of each TPS concept. The results are summarized graphically. The trajectory variables considered were down-range, cross-range, orbit inclination, entry interface velocity and flight path angle, maximum heating rate level, angle of attack, and ballistic coefficient. Variations in cross-range and flight path angle over the ranges considered had virtually no effect on the required entry TPS weight. The TPS weight was significantly more sensitive to variations in angle of attack than to dispersions in the other trajectory considered.

Outdoor stocking density in free-range laying hens: radio-frequency identification of impacts on range use.

PubMed

Campbell, D L M; Hinch, G N; Dyall, T R; Warin, L; Little, B A; Lee, C

2017-01-01

The number and size of free-range laying hen (Gallus gallus domesticus) production systems are increasing within Australia in response to consumer demand for perceived improvement in hen welfare. However, variation in outdoor stocking density has generated consumer dissatisfaction leading to the development of a national information standard on free-range egg labelling by the Australian Consumer Affairs Ministers. The current Australian Model Code of Practice for Domestic Poultry states a guideline of 1500 hens/ha, but no maximum density is set. Radio-frequency identification (RFID) tracking technology was used to measure daily range usage by individual ISA Brown hens housed in six small flocks (150 hens/flock - 50% of hens tagged), each with access to one of three outdoor stocking density treatments (two replicates per treatment: 2000, 10 000, 20 000 hens/ha), from 22 to 26, 27 to 31 and 32 to 36 weeks of age. There was some variation in range usage across the sampling periods and by weeks 32 to 36 individual hens from the lowest stocking density on average used the range for longer each day (P<0.001), with fewer visits and longer maximum durations per visit (P<0.001). Individual hens within all stocking densities varied in the percentage of days they accessed the range with 2% of tagged hens in each treatment never venturing outdoors and a large proportion that accessed the range daily (2000 hens/ha: 80.5%; 10 000 hens/ha: 66.5%; 20 000 hens/ha: 71.4%). On average, 38% to 48% of hens were seen on the range simultaneously and used all available areas of all ranges. These results of experimental-sized flocks have implications for determining optimal outdoor stocking densities for commercial free-range laying hens but further research would be needed to determine the effects of increased range usage on hen welfare.

Repeatability and heritability of reproductive traits in free-ranging snakes.

PubMed

Brown, G P; Shine, R

2007-03-01

The underlying genetic basis of life-history traits in free-ranging animals is critical to the effects of selection on such traits, but logistical constraints mean that such data are rarely available. Our long-term ecological studies on free-ranging oviparous snakes (keelbacks, Tropidonophis mairii (Gray, 1841), Colubridae) on an Australian floodplain provide the first such data for any tropical reptile. All size-corrected reproductive traits (egg mass, clutch size, clutch mass and post-partum maternal mass) were moderately repeatable between pairs of clutches produced by 69 female snakes after intervals of 49-1152 days, perhaps because maternal body condition was similar between clutches. Parent-offspring regression of reproductive traits of 59 pairs of mothers and daughters revealed high heritability for egg mass (h2= 0.73, SE=0.24), whereas heritability for the other three traits was low (< 0.37). The estimated heritability of egg mass may be inflated by maternal effects such as differential allocation of yolk steroids to different-sized eggs. High heritability of egg size may be maintained (rather than eroded by stabilizing selection) because selection acts on a trait (hatchling size) that is determined by the interaction between egg size and incubation substrate rather than by egg size alone. Variation in clutch size was mainly because of environmental factors (h2=0.04), indicating that one component of the trade-off between egg size and clutch size is under much tighter genetic control than the other. Thus, the phenotypic trade-off between egg size and egg number in keelback snakes occurs because each female snake must allocate a finite amount of energy into eggs of a genetically determined size.

Morphological variation in Homo erectus and the origins of developmental plasticity

PubMed Central

Antón, Susan C.; Taboada, Hannah G.; Middleton, Emily R.; Rainwater, Christopher W.; Taylor, Andrea B.; Turner, Trudy R.; Turnquist, Jean E.; Weinstein, Karen J.; Williams, Scott A.

2016-01-01

Homo erectus was the first hominin to exhibit extensive range expansion. This extraordinary departure from Africa, especially into more temperate climates of Eurasia, has been variously related to technological, energetic and foraging shifts. The temporal and regional anatomical variation in H. erectus suggests that a high level of developmental plasticity, a key factor in the ability of H. sapiens to occupy a variety of habitats, may also have been present in H. erectus. Developmental plasticity, the ability to modify development in response to environmental conditions, results in differences in size, shape and dimorphism across populations that relate in part to levels of resource sufficiency and extrinsic mortality. These differences predict not only regional variations but also overall smaller adult sizes and lower levels of dimorphism in instances of resource scarcity and high predator load. We consider the metric variation in 35 human and non-human primate ‘populations’ from known environmental contexts and 14 time- and space-restricted paleodemes of H. erectus and other fossil Homo. Human and non-human primates exhibit more similar patterns of variation than expected, with plasticity evident, but in differing patterns by sex across populations. The fossil samples show less evidence of variation than expected, although H. erectus varies more than Neandertals. This article is part of the themed issue ‘Major transitions in human evolution’. PMID:27298467

Seasonal variation of copper and zinc concentrations in the oyster Saccostrea cuccullata from the Dampier Archipelago, Western Australia: implications for pollution monitoring.

PubMed

Talbot, V

1986-12-01

The intertidal rock oyster Saccostrea cuccullata, sampled at eight sites on eight occasions over a 1-year period, contained mean Cu and Zn concentrations ranging between 34 and 267 and 206 and 4078 mg kg-1 dry weight, respectively. In the study area, Cu and Zn emanate from sewage and boat slips (antifouling paints), while Zn probably also originates from coolant water from an electricity power generating station and iron ore exporting facilities. Highest oyster wet weight, Cu and Zn concentrations and loads occurred in January (spawning period), indicating that metal variation was not reciprocating wet weight. Lowest metal concentrations and loads occurred in October (period of onset of gametogenesis), while lowest wet weight occurred in April (post-spawning period). No significant (P less than 0.001) variation in the wet to dry weight ratio was noted temporally. However, significant, though slight, variation was noted between polluted and unpolluted oysters. Results of this study indicate that pollution control monitoring programs should consider: seasonal variation of metal concentrations; portion of the year during which standards are exceeded; oyster size and availability for human consumption; suitability of standards where shellfish are not consumed as a staple diet; appropriate size indicies which can be used for selecting specimens for intersite comparisons; wet to dry weight calculations: techniques, spatial and temporal variations; and the physical dynamics of sites used.

Long‐term trends in fall age ratios of black brant

USGS Publications Warehouse

Ward, David H.; Amundson, Courtney L.; Stehn, Robert A.; Dau, Christian P.

2018-01-01

Accurate estimates of the age composition of populations can inform past reproductive success and future population trajectories. We examined fall age ratios (juveniles:total birds) of black brant (Branta bernicla nigricans; brant) staging at Izembek National Wildlife Refuge near the tip of the Alaska Peninsula, southwest Alaska, USA, 1963 to 2015. We also investigated variation in fall age ratios associated with sampling location, an index of flock size, survey effort, day of season, observer, survey platform (boat‐ or land‐based) and tide stage. We analyzed data using logistic regression models implemented in a Bayesian framework. Mean predicted fall age ratio controlling for survey effort, day of year, and temporal and spatial variation was 0.24 (95% CL = 0.23, 0.25). Overall trend in age ratios was −0.6% per year (95% CL = −1.3%, 0.2%), resulting in an approximate 26% decline in the proportion of juveniles over the study period. We found evidence for variation across a range of variables implying that juveniles are not randomly distributed in space and time within Izembek Lagoon. Age ratios varied by location within the study area and were highly variable among years. They decreased with the number of birds aged (an index of flock size) and increased throughout September before leveling off in early October and declining in late October. Age ratios were similar among tide stages and observers and were lower during boat‐based (offshore) than land‐based (nearshore) surveys. Our results indicate surveys should be conducted annually during early to mid‐October to ensure the entire population is present and available for sampling, and throughout Izembek Lagoon to account for spatiotemporal variation in age ratios. Sampling should include a wide range of flock sizes representative of their distribution and occur in flocks located near and off shore. Further research evaluating the cause of declining age ratios in the fall population is necessary to inform management and predict long‐term population dynamics of brant.

Size variation, growth strategies, and the evolution of modularity in the mammalian skull.

PubMed

Porto, Arthur; Shirai, Leila Teruko; de Oliveira, Felipe Bandoni; Marroig, Gabriel

2013-11-01

Allometry is a major determinant of within-population patterns of association among traits and, therefore, a major component of morphological integration studies. Even so, the influence of size variation over evolutionary change has been largely unappreciated. Here, we explore the interplay between allometric size variation, modularity, and life-history strategies in the skull from representatives of 35 mammalian families. We start by removing size variation from within-species data and analyzing its influence on integration magnitudes, modularity patterns, and responses to selection. We also carry out a simulation in which we artificially alter the influence of size variation in within-taxa matrices. Finally, we explore the relationship between size variation and different growth strategies. We demonstrate that a large portion of the evolution of modularity in the mammalian skull is associated to the evolution of growth strategies. Lineages with highly altricial neonates have adult variation patterns dominated by size variation, leading to high correlations among traits regardless of any underlying modular process and impacting directly their potential to respond to selection. Greater influence of size variation is associated to larger intermodule correlations, less individualized modules, and less flexible responses to natural selection. © 2013 The Author(s). Evolution © 2013 The Society for the Study of Evolution.

Frost and leaf-size gradients in forests: global patterns and experimental evidence.

PubMed

Lusk, Christopher H; Clearwater, Michael J; Laughlin, Daniel C; Harrison, Sandy P; Prentice, Iain Colin; Nordenstahl, Marisa; Smith, Benjamin

2018-05-16

Explanations of leaf size variation commonly focus on water availability, yet leaf size also varies with latitude and elevation in environments where water is not strongly limiting. We provide the first conclusive test of a prediction of leaf energy balance theory that may explain this pattern: large leaves are more vulnerable to night-time chilling, because their thick boundary layers impede convective exchange with the surrounding air. Seedlings of 15 New Zealand evergreens spanning 12-fold variation in leaf width were exposed to clear night skies, and leaf temperatures were measured with thermocouples. We then used a global dataset to assess several climate variables as predictors of leaf size in forest assemblages. Leaf minus air temperature was strongly correlated with leaf width, ranging from -0.9 to -3.2°C in the smallest- and largest-leaved species, respectively. Mean annual temperature and frost-free period were good predictors of evergreen angiosperm leaf size in forest assemblages, but no climate variable predicted deciduous leaf size. Although winter deciduousness makes large leaves possible in strongly seasonal climates, large-leaved evergreens are largely confined to frost-free climates because of their susceptibility to radiative cooling. Evergreen leaf size data can therefore be used to enhance vegetation models, and to infer palaeotemperatures from fossil leaf assemblages. © 2018 The Authors New Phytologist © 2018 New Phytologist Trust.

A Multi-Satellite GRACE-like Mission Using Small Satellites

NASA Astrophysics Data System (ADS)

Stephens, M.; Bender, P. L.; Nerem, R.; Pierce, R.; Wiese, D. N.

2010-12-01

Measurement of global water variation provides information critical to climate change and water resource monitoring. The Gravity Recovery and Climate Experiment II (GRACE II) was chosen as a Tier III mission by National Research Council's decadal survey because of its unique ability to measure the global mass distributions and variations in the mass distribution caused primarily by water variation. We discuss a multi-satellite approach to a GRACE-like mission. Enhanced spatial resolution of mass variations over those provided by the current GRACE mission can be achieved by improving the ranging accuracy; an interferometric ranging concept that improves the ranging accuracy has been demonstrated[1]. However, recent calculations show that to obtain the full science improvement using interferometric ranging, temporal aliasing errors due to modeling and to undersampling of geophysical signals must be mitigated[2]. One approach is to improve the data analysis techniques and validation processes. Another approach is to fly two or more pairs of satellites, thereby sampling the Earth's gravitational field at shorter time intervals[3]. A multiple-pair mission is often dismissed as too expensive, but the mission costs of a multiple-pair GRACE-like mission could be greatly reduced by developing compact ranging systems so that the mass, power, and volume usage is consistent with small spacecraft buses. Such size reduction drastically reduces the launch costs by allowing the spacecraft to be launched as auxiliary payloads. We will discuss the technological challenges that are associated with a GRACE-like mission that uses smallsats to reduce costs of more than one pair of satellites, as well as the scientific benefits of the two or more satellite pairs. The technological challenges include reducing the size of the payload and developing a low-drag, low-pointing jitter spacecraft. [1]Pierce, R., J. Leitch, M. Stephens, P. Bender, and R. Nerem, “Intersatellite range monitoring using optical interferometry”, Appl. Opt. 47 (2008), 5007. [2]P. Visser and E. Pavlis in ”Report from the Workshop on The Future of Satellite Gravimetry”, edited by R. Koop and R. Rummel (ESTEC, Noordwijk, The Netherlands, 12-13 April, 2007), pg. 11. [3]Bender, P. L., D. N. Wiese, and R. S. Nerem, “A possible dual-GRACE mission with 90 degree and 63 degree inclination orbits, Proceedings of the 3rd International Symposium on Formation Flying, Missions and Technologies”, ESA Communication Production Office, ESA-SP-654, 2008.

An Educational Software for Simulating the Sample Size of Molecular Marker Experiments

ERIC Educational Resources Information Center

Helms, T. C.; Doetkott, C.

2007-01-01

We developed educational software to show graduate students how to plan molecular marker experiments. These computer simulations give the students feedback on the precision of their experiments. The objective of the software was to show students using a hands-on approach how: (1) environmental variation influences the range of the estimates of the…

Assessing Live Fuel Moisture For Fire Management Applications

Treesearch

David R. Weise; Roberta A. Hartford; Larry Mahaffey

1998-01-01

The variation associated with sampling live fuel moisture was examined for several shrub and canopy fuels in southern California, Arizona, and Colorado. Ninety-five % confidence intervals ranged from 5 to % . Estimated sample sizes varied greatly. The value of knowing the live fuel moisture content in fire decision making is unknown. If the fuel moisture is highly...

Nanometre-sized pores in coal: Variations between coal basins and coal origin

USGS Publications Warehouse

Sakurovs, Richard; Koval, Lukas; Grigore, Mihaela; Sokolava, Anna; Ruppert, Leslie F.; Melnichenko, Yuri B.

2018-01-01

We have used small angle neutron scattering (SANS) to investigate the differences in methane and hexane penetration in pores in bituminous coal samples from the U.S., Canada, South Africa, and China, and maceral concentrates from Australian coals. This work is an extension of previous work that showed consistent differences between the extent of penetration by methane into 10–20 nm size pores in inertinite in bituminous coals from Australia, North America and Poland.In this study we have confirmed that there are differences in the response of inertinite to methane and hexane penetration in coals sourced from different coal basins. Inertinite in Permian Australian coals generally has relatively high numbers of pores in the 2.5–250 nm size range and the pores are highly penetrable by methane and hexane; coals sourced from Western Canada had similar penetrability to these Australian coals. However, the penetrability of methane and hexane into inertinite from the Australian Illawarra Coal Measures (also Permian) is substantially less than that of the other Australian coals; there are about 80% fewer 12 nm pores in Illawarra inertinite compared to the other Australian coals examined. The inertinite in coals sourced from South Africa and China had accessibility intermediate between the Illawarra coals and the other Australian coals.The extent of hexane penetration was 10–20% less than CD4 penetration into the same coal and this difference was most pronounced in the 5–50 nm pore size range. Hexane and methane penetrability into the coals showed similar trends with inertinite content.The observed variations in inertinite porosity between coals from different coal regions and coal basins may explain why previous studies differ in their observations of the relationships between gas sorption behavior, permeability, porosity, and maceral composition. These variations are not simply a demarcation between Northern and Southern Hemisphere coals.

Design of pressure-sensing diaphragm for MEMS capacitance diaphragm gauge considering size effect

NASA Astrophysics Data System (ADS)

Li, Gang; Li, Detian; Cheng, Yongjun; Sun, Wenjun; Han, Xiaodong; Wang, Chengxiang

2018-03-01

MEMS capacitance diaphragm gauge with a full range of (1˜1000) Pa is considered for its wide application prospect. The design of pressure-sensing diaphragm is the key to achieve balanced performance for this kind of gauges. The optimization process of the pressure-sensing diaphragm with island design of a capacitance diaphragm gauge based on MEMS technique has been reported in this work. For micro-components in micro scale range, mechanical properties are very different from that in the macro scale range, so the size effect should not be ignored. The modified strain gradient elasticity theory considering size effect has been applied to determine the bending rigidity of the pressure-sensing diaphragm, which is then used in the numerical model to calculate the deflection-pressure relation of the diaphragm. According to the deflection curves, capacitance variation can be determined by integrating over the radius of the diaphragm. At last, the design of the diaphragm has been optimized based on three parameters: sensitivity, linearity and ground capacitance. With this design, a full range of (1˜1000) Pa can be achieved, meanwhile, balanced sensitivity, resolution and linearity can be kept.

Enrichment and distribution of 24 elements within the sub-sieve particle size distribution ranges of fly ash from wastes incinerator plants.

PubMed

Raclavská, Helena; Corsaro, Agnieszka; Hartmann-Koval, Silvie; Juchelková, Dagmar

2017-12-01

The management of an increasing amount of municipal waste via incineration has been gaining traction. Fly ash as a by-product of incineration of municipal solid waste is considered a hazardous waste due to the elevated content of various elements. The enrichment and distribution of 24 elements in fly ash from three wastes incinerators were evaluated. Two coarse (>100 μm and <100 μm) and five sub-sieve (12-16, 16-23, 23-34, 34-49, and 49-100 μm) particle size fractions separated on a cyclosizer system were analyzed. An enhancement in the enrichment factor was observed in all samples for the majority of elements in >100 μm range compared with <100 μm range. The enrichment factor of individual elements varied considerably within the samples as well as the sub-sieve particle size ranges. These variations were attributed primarily to: (i) the vaporization and condensation mechanisms, (ii) the different design of incineration plants, (iii) incineration properties, (iv) the type of material being incinerated, and (v) the affinity of elements. Copyright © 2017 Elsevier Ltd. All rights reserved.

A comparative test of adaptive hypotheses for sexual size dimorphism in lizards.

PubMed

Cox, Robert M; Skelly, Stephanie L; John-Alder, Henry B

2003-07-01

It is commonly argued that sexual size dimorphism (SSD) in lizards has evolved in response to two primary, nonexclusive processes: (1) sexual selection for large male size, which confers an advantage in intrasexual mate competition (intrasexual selection hypothesis), and (2) natural selection for large female size, which confers a fecundity advantage (fecundity advantage hypothesis). However, outside of several well-studied lizard genera, the empirical support for these hypotheses has not been examined with appropriate phylogenetic control. We conducted a comparative phylogenetic analysis to test these hypotheses using literature data from 497 lizard populations representing 302 species and 18 families. As predicted by the intrasexual selection hypothesis, male aggression and territoriality are correlated with SSD, but evolutionary shifts in these categorical variables each explain less than 2% of the inferred evolutionary change in SSD. We found stronger correlations between SSD and continuous estimates of intrasexual selection such as male to female home range ratio and female home range size. These results are consistent with the criticism that categorical variables may obscure much of the actual variation in intrasexual selection intensity needed to explain patterns in SSD. In accordance with the fecundity advantage hypothesis, SSD is correlated with clutch size, reproductive frequency, and reproductive mode (but not fecundity slope, reduced major axis estimator of fecundity slope, length of reproductive season, or latitude). However, evolutionary shifts in clutch size explain less than 8% of the associated change in SSD, which also varies significantly in the absence of evolutionary shifts in reproductive frequency and mode. A multiple regression model retained territoriality and clutch size as significant predictors of SSD, but only 16% of the variation in SSD is explained using these variables. Intrasexual selection for large male size and fecundity selection for large female size have undoubtedly helped to shape patterns of SSD across lizards, but the comparative data at present provide only weak support for these hypotheses as general explanations for SSD in this group. Future work would benefit from the consideration of alternatives to these traditional evolutionary hypotheses, and the elucidation of proximate mechanisms influencing growth and SSD within populations.

Variation in the Oral Processing of Everyday Meals Is Associated with Fullness and Meal Size; A Potential Nudge to Reduce Energy Intake?

PubMed

Ferriday, Danielle; Bosworth, Matthew L; Godinot, Nicolas; Martin, Nathalie; Forde, Ciarán G; Van Den Heuvel, Emmy; Appleton, Sarah L; Mercer Moss, Felix J; Rogers, Peter J; Brunstrom, Jeffrey M

2016-05-21

Laboratory studies have demonstrated that experimental manipulations of oral processing can have a marked effect on energy intake. Here, we explored whether variations in oral processing across a range of unmodified everyday meals could affect post-meal fullness and meal size. In Study 1, female participants (N = 12) attended the laboratory over 20 lunchtime sessions to consume a 400-kcal portion of a different commercially available pre-packaged meal. Prior to consumption, expected satiation was assessed. During each meal, oral processing was characterised using: (i) video-recordings of the mouth and (ii) real-time measures of plate weight. Hunger and fullness ratings were elicited pre- and post-consumption, and for a further three hours. Foods that were eaten slowly had higher expected satiation and delivered more satiation and satiety. Building on these findings, in Study 2 we selected two meals (identical energy density) from Study 1 that were equally liked but maximised differences in oral processing. On separate days, male and female participants (N = 24) consumed a 400-kcal portion of either the "fast" or "slow" meal followed by an ad libitum meal (either the same food or a dessert). When continuing with the same food, participants consumed less of the slow meal. Further, differences in food intake during the ad libitum meal were not compensated at a subsequent snacking opportunity an hour later. Together, these findings suggest that variations in oral processing across a range of unmodified everyday meals can affect fullness after consuming a fixed portion and can also impact meal size. Modifying food form to encourage increased oral processing (albeit to a lesser extent than in experimental manipulations) might represent a viable target for food manufacturers to help to nudge consumers to manage their weight.

Rethinking plant functional types in Earth System Models: pan-tropical analysis of tree survival across environmental gradients

NASA Astrophysics Data System (ADS)

Johnson, D. J.; Needham, J.; Xu, C.; Davies, S. J.; Bunyavejchewin, S.; Giardina, C. P.; Condit, R.; Cordell, S.; Litton, C. M.; Hubbell, S.; Kassim, A. R. B.; Shawn, L. K. Y.; Nasardin, M. B.; Ong, P.; Ostertag, R.; Sack, L.; Tan, S. K. S.; Yap, S.; McDowell, N. G.; McMahon, S.

2016-12-01

Terrestrial carbon cycling is a function of the growth and survival of trees. Current model representations of tree growth and survival at a global scale rely on coarse plant functional traits that are parameterized very generally. In view of the large biodiversity in the tropical forests, it is important that we account for the functional diversity in order to better predict tropical forest responses to future climate changes. Several next generation Earth System Models are moving towards a size-structured, trait-based approach to modelling vegetation globally, but the challenge of which and how many traits are necessary to capture forest complexity remains. Additionally, the challenge of collecting sufficient trait data to describe the vast species richness of tropical forests is enormous. We propose a more fundamental approach to these problems by characterizing forests by their patterns of survival. We expect our approach to distill real-world tree survival into a reasonable number of functional types. Using 10 large-area tropical forest plots that span geographic, edaphic and climatic gradients, we model tree survival as a function of tree size for hundreds of species. We found surprisingly few categories of size-survival functions emerge. This indicates some fundamental strategies at play across diverse forests to constrain the range of possible size-survival functions. Initial cluster analysis indicates that four to eight functional forms are necessary to describe variation in size-survival relations. Temporal variation in size-survival functions can be related to local environmental variation, allowing us to parameterize how demographically similar groups of species respond to perturbations in the ecosystem. We believe this methodology will yield a synthetic approach to classifying forest systems that will greatly reduce uncertainty and complexity in global vegetation models.

The effects of host size and temperature on the emergence of Echinoparyphium recurvatum cercariae from Lymnaea peregra under natural light conditions.

PubMed

Morley, N J; Adam, M E; Lewis, J W

2010-09-01

The production of cercariae from their snail host is a fundamental component of transmission success in trematodes. The emergence of Echinoparyphium recurvatum (Trematoda: Echinostomatidae) cercariae from Lymnaea peregra was studied under natural sunlight conditions, using naturally infected snails of different sizes (10-17 mm) within a temperature range of 10-29 degrees C. There was a single photoperiodic circadian cycle of emergence with one peak, which correlated with the maximum diffuse sunlight irradiation. At 21 degrees C the daily number of emerging cercariae increased with increasing host snail size, but variations in cercarial emergence did occur between both individual snails and different days. There was only limited evidence of cyclic emergence patterns over a 3-week period, probably due to extensive snail mortality, particularly those in the larger size classes. Very few cercariae emerged in all snail size classes at the lowest temperature studied (10 degrees C), but at increasingly higher temperatures elevated numbers of cercariae emerged, reaching an optimum between 17 and 25 degrees C. Above this range emergence was reduced. At all temperatures more cercariae emerged from larger snails. Analysis of emergence using the Q10 value, a measure of physiological processes over temperature ranges, showed that between 10 and 21 degrees C (approximately 15 degrees C) Q10 values exceeded 100 for all snail size classes, indicating a substantially greater emergence than would be expected for normal physiological rates. From 14 to 25 degrees C (approximately 20 degrees C) cercarial emergence in most snail size classes showed little change in Q10, although in the smallest size class emergence was still substantially greater than the typical Q10 increase expected over this temperature range. At the highest range of 21-29 degrees C (approximately 25 degrees C), Q10 was much reduced. The importance of these results for cercarial emergence under global climate change is discussed.

Dual influences of ecosystem size and disturbance on food chain length in streams.

PubMed

McHugh, Peter A; McIntosh, Angus R; Jellyman, Phillip G

2010-07-01

The number of trophic transfers occurring between basal resources and top predators, food chain length (FCL), varies widely in the world's ecosystems for reasons that are poorly understood, particularly for stream ecosystems. Available evidence indicates that FCL is set by energetic constraints, environmental stochasticity, or ecosystem size effects, although no single explanation has yet accounted for FCL patterns in a broad sense. Further, whether environmental disturbance can influence FCL has been debated on both theoretical and empirical grounds for quite some time. Using data from sixteen South Island, New Zealand streams, we determined whether the so-called ecosystem size, disturbance, or resource availability hypotheses could account for FCL variation in high country fluvial environments. Stable isotope-based estimates of maximum trophic position ranged from 2.6 to 4.2 and averaged 3.5, a value on par with the global FCL average for streams. Model-selection results indicated that stream size and disturbance regime best explained across-site patterns in FCL, although resource availability was negatively correlated with our measure of disturbance; FCL approached its maximum in large, stable springs and was <3.5 trophic levels in small, fishless and/or disturbed streams. Community data indicate that size influenced FCL, primarily through its influence on local fish species richness (i.e., via trophic level additions and/or insertions), whereas disturbance did so via an effect on the relative availability of intermediate predators (i.e., predatory invertebrates) as prey for fishes. Overall, our results demonstrate that disturbance can have an important food web-structuring role in stream ecosystems, and further imply that pluralistic explanations are needed to fully understand the range of structural variation observed for real food webs.

Ex-Situ Synthesis of Polyvinyl alcohol(PVA)-coated Fe3O4 Nanoparticles by Coprecipitation-Ultrasonication Method

NASA Astrophysics Data System (ADS)

Riva'i, Imam; Oktavia Wulandari, Ika; Sulistyarti, Hermin; Sabarudin, Akhmad

2018-01-01

In this study, the synthesis of Fe3O4 nanoparticles was done with surface modification using PVA with coprecipitation-ultrasonication method. Time variations and PVA concentrations were added to determine the effect on crystallite size and lattice parameters on the synthesis of Fe3O4-PVA nanoparticles. Fe3O4 characterization was done using X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) instruments. FTIR was employed to determine PVA coating on the surface of Fe3O4 nanoparticles. The crystallite size and lattice parameters were analyzed using XRD. From the FTIR data, it is known that the interaction between PVA and Fe3O4 nanoparticles is characterized by Fe-O-C group at 1100 cm-1 region which is characteristic of Fe3O4-PVA nanoparticles, C-H groups of PVA in the range of 2950 cm-1 wave number, C-C of PVA regions of wave number 1405 cm-1, Fe3O4 and Fe3O4-PVA samples are in the range of 565 cm-1. In addition, the variation of ultrasonication time and the addition of PVA concentration have an effect on the crystallite size change and the lattice parameter observed from the XRD data. The use of ultrasonication time will affect the size of the crystallite become smaller and the grating lattice parameters obtained are wider. The effect of addition of PVA showed that higher concentration of PVA resulted in smaller crystallite size and larger lattice parameters. These results indicated that ultrasonication time and addition of PVA concentration greatly affect the characteristics of nanoparticles.

Geographic variation in genetic and demographic performance: new insights from an old biogeographical paradigm.

PubMed

Pironon, Samuel; Papuga, Guillaume; Villellas, Jesús; Angert, Amy L; García, María B; Thompson, John D

2017-11-01

The 'centre-periphery hypothesis' (CPH) is a long-standing postulate in ecology that states that genetic variation and demographic performance of a species decrease from the centre to the edge of its geographic range. This hypothesis is based on an assumed concordance between geographical peripherality and ecological marginality such that environmental conditions become harsher towards the limits of a species range. In this way, the CPH sets the stage for understanding the causes of distribution limits. To date, no study has examined conjointly the consistency of these postulates. In an extensive literature review we discuss the birth and development of the CPH and provide an assessment of the CPH by reviewing 248 empirical studies in the context of three main themes. First, a decrease in species occurrence towards their range limits was observed in 81% of studies, while only 51% demonstrated reduced abundance of individuals. A decline in genetic variation, increased differentiation among populations and higher rates of inbreeding were demonstrated by roughly one in two studies (47, 45 and 48%, respectively). However, demographic rates, size and population performance less often followed CPH expectations (20-30% of studies). We highlight the impact of important methodological, taxonomic, and biogeographical biases on such validation rates. Second, we found that geographic and ecological marginality gradients are not systematically concordant, which casts doubt on the reliability of a main assumption of the CPH. Finally, we attempt to disentangle the relative contribution of geographical, ecological and historical processes on the spatial distribution of genetic and demographic parameters. While ecological marginality gradients explain variation in species' demographic performance better than geographic gradients, contemporary and historical factors may contribute interactively to spatial patterns of genetic variation. We thereby propose a framework that integrates species' ecological niche characteristics together with current and past range structure to investigate spatial patterns of genetic and demographic variation across species ranges. © 2016 Cambridge Philosophical Society.

Postglacial migration supplements climate in determining plant species ranges in Europe

PubMed Central

Normand, Signe; Ricklefs, Robert E.; Skov, Flemming; Bladt, Jesper; Tackenberg, Oliver; Svenning, Jens-Christian

2011-01-01

The influence of dispersal limitation on species ranges remains controversial. Considering the dramatic impacts of the last glaciation in Europe, species might not have tracked climate changes through time and, as a consequence, their present-day ranges might be in disequilibrium with current climate. For 1016 European plant species, we assessed the relative importance of current climate and limited postglacial migration in determining species ranges using regression modelling and explanatory variables representing climate, and a novel species-specific hind-casting-based measure of accessibility to postglacial colonization. Climate was important for all species, while postglacial colonization also constrained the ranges of more than 50 per cent of the species. On average, climate explained five times more variation in species ranges than accessibility, but accessibility was the strongest determinant for one-sixth of the species. Accessibility was particularly important for species with limited long-distance dispersal ability, with southern glacial ranges, seed plants compared with ferns, and small-range species in southern Europe. In addition, accessibility explained one-third of the variation in species' disequilibrium with climate as measured by the realized/potential range size ratio computed with niche modelling. In conclusion, we show that although climate is the dominant broad-scale determinant of European plant species ranges, constrained dispersal plays an important supplementary role. PMID:21543356

Disentangling the effects of species diversity, and intraspecific and interspecific tree size variation on aboveground biomass in dry zone homegarden agroforestry systems.

PubMed

Ali, Arshad; Mattsson, Eskil

2017-11-15

The biodiversity - aboveground biomass relationship has been intensively studied in recent decades. However, no consensus has been arrived to consider the interplay of species diversity, and intraspecific and interspecific tree size variation in driving aboveground biomass, after accounting for the effects of plot size heterogeneity, soil fertility and stand quality in natural forest including agroforests. We tested the full, partial and no mediations effects of species diversity, and intraspecific and interspecific tree size variation on aboveground biomass by employing structural equation models (SEMs) using data from 45 homegarden agroforestry systems in Sri Lanka. The full mediation effect of either species diversity or intraspecific and interspecific tree size variation was rejected, while the partial and no mediation effects were accepted. In the no mediation SEM, homegarden size had the strongest negative direct effect (β=-0.49) on aboveground biomass (R 2 =0.65), followed by strong positive direct effect of intraspecific tree size variation (β=0.32), species diversity (β=0.29) and interspecific tree size variation (β=0.28). Soil fertility had a negative direct effect on interspecific tree size variation (β=-0.31). Stand quality had a significant positive total effect on aboveground biomass (β=0.28), but homegarden size had a significant negative total effect (β=-0.62), while soil fertility had a non-significant total effect on aboveground biomass. Similar to the no mediation SEM, the partial mediation SEMs had explained almost similar variation in aboveground biomass because species diversity, and intraspecific and interspecific tree size variation had non-significant indirect effects on aboveground biomass via each other. Our results strongly suggest that a multilayered tree canopy structure, due to high intraspecific and interspecific tree size variation, increases light capture and efficient utilization of resources among component species, and hence, support the niche complementarity mechanism via plant-plant interactions. Copyright © 2017 Elsevier B.V. All rights reserved.

Abundance and morphometry changes across the high-mountain lake-size gradient in the tropical Andes of Southern Ecuador

NASA Astrophysics Data System (ADS)

Mosquera, Pablo V.; Hampel, Henrietta; Vázquez, Raúl F.; Alonso, Miguel; Catalan, Jordi

2017-08-01

The number, size, and shape of lakes are key determinants of the ecological functionality of a lake district. The lake area scaling relationships with lake number and volume enable upscaling biogeochemical processes and spatially considering organisms' metapopulation dynamics. These relationships vary regionally depending on the geomorphological context, particularly in the range of lake area <1 km2 and mountainous regions. The Cajas Massif (Southern Ecuador) holds a tropical mountain lake district with 5955 water bodies. The number of lakes deviates from a power law relationship with the lake area at both ends of the size range; similarly to the distributions found in temperate mountain ranges. The deviation of each distribution tail does not respond to the same cause. The marked relief limits the size of the largest lakes at high altitudes, whereas ponds are prompt to a complete infilling. A bathymetry survey of 202 lakes, selected across the full-size range, revealed a volume-area scaling coefficient larger than those found for other lake areas of glacial origin but softer relief. Water renewal time is not consistently proportional to the lake area due to the volume-area variation in midsize lakes. The 85% of the water surface is in lakes >104 m2 and 50% of the water resources are held in a few ones (˜10) deeper than 18 m. Therefore, midlakes and large lakes are by far more biogeochemically relevant than ponds and shallow lakes in this tropical mountain lake district.

Low flower-size variation in bilaterally symmetrical flowers: Support for the pollination precision hypothesis.

PubMed

Nikkeshi, Aoi; Kurimoto, Daiki; Ushimaru, Atushi

2015-12-01

The evolutionary shift from radial to bilateral symmetry in flowers is generally associated with the evolution of low flower-size variation. This phenomenon supports the hypothesis that the lower size variation in bilateral flowers can be attributed to low pollinator diversity. In this study, we propose two other hypotheses to explain low flower-size variation in bilateral symmetrical flowers. To test the three hypotheses, we examined the relative importance of pollinator diversity, composition, and bilateral symmetry itself as selective forces on low flower-size variation. We examined pollinator diversity and composition and flower-size variation for 36 species in a seminatural ecosystem with high bee richness and frequent lepidopteran visitation. Bilateral flowers were more frequently visited than radial flowers by larger bees, but functional-group diversity of the pollinators did not differ between symmetry types. Although bilateral flowers had significantly lower flower-size variation than radial flowers, flower-size variation did not vary with pollinator diversity and composition but was instead related to bilateral symmetry. Our results suggest that the lower size variation in bilateral flowers might have evolved under selection favoring the control of pollinator behavior on flowers to enhance the accurate placement of pollen on the body of the pollinator, independent of pollinator type. Because of the limited research on this issue, future work should be conducted in various types of plant-pollinator communities worldwide to further clarify the issue. © 2015 Botanical Society of America.

Population-Based Resequencing of Experimentally Evolved Populations Reveals the Genetic Basis of Body Size Variation in Drosophila melanogaster

PubMed Central

Turner, Thomas L.; Stewart, Andrew D.; Fields, Andrew T.; Rice, William R.; Tarone, Aaron M.

2011-01-01

Body size is a classic quantitative trait with evolutionarily significant variation within many species. Locating the alleles responsible for this variation would help understand the maintenance of variation in body size in particular, as well as quantitative traits in general. However, successful genome-wide association of genotype and phenotype may require very large sample sizes if alleles have low population frequencies or modest effects. As a complementary approach, we propose that population-based resequencing of experimentally evolved populations allows for considerable power to map functional variation. Here, we use this technique to investigate the genetic basis of natural variation in body size in Drosophila melanogaster. Significant differentiation of hundreds of loci in replicate selection populations supports the hypothesis that the genetic basis of body size variation is very polygenic in D. melanogaster. Significantly differentiated variants are limited to single genes at some loci, allowing precise hypotheses to be formed regarding causal polymorphisms, while other significant regions are large and contain many genes. By using significantly associated polymorphisms as a priori candidates in follow-up studies, these data are expected to provide considerable power to determine the genetic basis of natural variation in body size. PMID:21437274

Not my "type": larval dispersal dimorphisms and bet-hedging in opisthobranch life histories.

PubMed

Krug, Patrick J

2009-06-01

When conditions fluctuate unpredictably, selection may favor bet-hedging strategies that vary offspring characteristics to avoid reproductive wipe-outs in bad seasons. For many marine gastropods, the dispersal potential of offspring reflects both maternal effects (egg size, egg mass properties) and larval traits (development rate, habitat choice). I present data for eight sea slugs in the genus Elysia (Opisthobranchia: Sacoglossa), highlighting potentially adaptive variation in traits like offspring size, timing of metamorphosis, hatching behavior, and settlement response. Elysia zuleicae produced both planktotrophic and lecithotrophic larvae, a true case of poecilogony. Both intracapsular and post-hatching metamorphosis occurred among clutches of "Boselia" marcusi, E. cornigera, and E. crispata, a dispersal dimorphism often misinterpreted as poecilogony. Egg masses of E. tuca hatched for up to 16 days but larvae settled only on the adult host alga Halimeda, whereas most larvae of E. papillosa spontaneously metamorphosed 5-7 days after hatching. Investment in extra-capsular yolk may allow mothers to increase larval size relative to egg size and vary offspring size within and among clutches. Flexible strategies of larval dispersal and offspring provisioning in Elysia spp. may represent adaptations to the patchy habitat of these specialized herbivores, highlighting the evolutionary importance of variation in a range of life-history traits.

Among-Population Variation in Microbial Community Structure in the Floral Nectar of the Bee-Pollinated Forest Herb Pulmonaria officinalis L

PubMed Central

Jacquemyn, Hans; Lenaerts, Marijke; Brys, Rein; Willems, Kris; Honnay, Olivier; Lievens, Bart

2013-01-01

Background Microbial communities in floral nectar have been shown to be characterized by low levels of species diversity, yet little is known about among-plant population variation in microbial community composition. Methodology/Principal Findings We investigated the microbial community structure (yeasts and bacteria) in floral nectar of ten fragmented populations of the bee-pollinated forest herb Pulmonaria officinalis. We also explored possible relationships between plant population size and microbial diversity in nectar, and related microbial community composition to the distance separating plant populations. Culturable bacteria and yeasts occurring in the floral nectar of a total of 100 plant individuals were isolated and identified by partially sequencing the 16S rRNA gene and D1/D2 domains of the 26S rRNA gene, respectively. A total of 9 and 11 yeast and 28 and 39 bacterial OTUs was found, taking into account a 3% (OTU0.03) and 1% sequence dissimilarity cut-off (OTU0.01). OTU richness at the plant population level (i.e. the number of OTUs per population) was low for yeasts (mean: 1.7, range: 0–4 OTUs0.01/0.03 per population), whereas on average 6.9 (range: 2–13) OTUs0.03 and 7.9 (range 2–16) OTUs0.01 per population were found for bacteria. Both for yeasts and bacteria, OTU richness was not significantly related to plant population size. Similarity in community composition among populations was low (average Jaccard index: 0.14), and did not decline with increasing distance between populations. Conclusions/Significance We found low similarity in microbial community structure among populations, suggesting that the assembly of nectar microbiota is to a large extent context-dependent. Although the precise factors that affect variation in microbial community structure in floral nectar require further study, our results indicate that both local and regional processes may contribute to among-population variation in microbial community structure in nectar. PMID:23536759

Asynchrony of senescence among phenotypic traits in a wild mammal population

PubMed Central

Hayward, Adam D.; Moorad, Jacob; Regan, Charlotte E.; Berenos, Camillo; Pilkington, Jill G.; Pemberton, Josephine M.; Nussey, Daniel H.

2015-01-01

The degree to which changes in lifespan are coupled to changes in senescence in different physiological systems and phenotypic traits is a central question in biogerontology. It is underpinned by deeper biological questions about whether or not senescence is a synchronised process, or whether levels of synchrony depend on species or environmental context. Understanding how natural selection shapes patterns of synchrony in senescence across physiological systems and phenotypic traits demands the longitudinal study of many phenotypes under natural conditions. Here, we examine the patterns of age-related variation in late adulthood in a wild population of Soay sheep (Ovis aries) that have been the subject of individual-based monitoring for thirty years. We examined twenty different phenotypic traits in both males and females, encompassing vital rates (survival and fecundity), maternal reproductive performance (offspring birth weight, birth date and survival), male rutting behaviour, home range measures, parasite burdens, and body mass. We initially quantified age-related variation in each trait having controlled for annual variation in the environment, among-individual variation and selective disappearance effects. We then standardised our age-specific trait means and tested whether age trajectories could be meaningfully grouped according to sex or the type of trait. Whilst most traits showed age-related declines in later life, we found striking levels of asynchrony both within and between the sexes. Of particular note, female fecundity and reproductive performance declined with age, but male annual reproductive success did not. We also discovered that whilst home range size and quality decline with age in females, home range size increases with age in males. Our findings highlight the complexity of phenotypic ageing under natural conditions and, along with emerging data from other wild populations and laboratory models, suggest that the long-standing hypothesis within evolutionary biology that fitness-related traits should senesce in a synchronous manner is seriously flawed. PMID:26277618

Among-population variation in microbial community structure in the floral nectar of the bee-pollinated forest herb Pulmonaria officinalis L.

PubMed

Jacquemyn, Hans; Lenaerts, Marijke; Brys, Rein; Willems, Kris; Honnay, Olivier; Lievens, Bart

2013-01-01

Microbial communities in floral nectar have been shown to be characterized by low levels of species diversity, yet little is known about among-plant population variation in microbial community composition. We investigated the microbial community structure (yeasts and bacteria) in floral nectar of ten fragmented populations of the bee-pollinated forest herb Pulmonaria officinalis. We also explored possible relationships between plant population size and microbial diversity in nectar, and related microbial community composition to the distance separating plant populations. Culturable bacteria and yeasts occurring in the floral nectar of a total of 100 plant individuals were isolated and identified by partially sequencing the 16S rRNA gene and D1/D2 domains of the 26S rRNA gene, respectively. A total of 9 and 11 yeast and 28 and 39 bacterial OTUs was found, taking into account a 3% (OTU0.03) and 1% sequence dissimilarity cut-off (OTU0.01). OTU richness at the plant population level (i.e. the number of OTUs per population) was low for yeasts (mean: 1.7, range: 0-4 OTUs0.01/0.03 per population), whereas on average 6.9 (range: 2-13) OTUs0.03 and 7.9 (range 2-16) OTUs0.01 per population were found for bacteria. Both for yeasts and bacteria, OTU richness was not significantly related to plant population size. Similarity in community composition among populations was low (average Jaccard index: 0.14), and did not decline with increasing distance between populations. We found low similarity in microbial community structure among populations, suggesting that the assembly of nectar microbiota is to a large extent context-dependent. Although the precise factors that affect variation in microbial community structure in floral nectar require further study, our results indicate that both local and regional processes may contribute to among-population variation in microbial community structure in nectar.

Does increasing daylength control seasonal changes in clutch sizes of Northern Pintails (Anas acuta)?

USGS Publications Warehouse

Krapu, G.L.; Sargeant, G.A.; Perkins, A.E.H.

2002-01-01

We evaluated spatiotemporal variation in clutch sizes of Northern Pintails (pintails; Anas acuta) nesting in California (1985 to 1996), North Dakota (1982 to 1985), Saskatchewan (1982 to 1985) and Alaska (1991 to 1993) to determine whether seasonal declines in clutch size varied in ways that were consistent with a controlling influence of increasing day length. Pintails began nesting in mid-March in California, mid-April in North Dakota and Saskatchewan, and mid-May in Alaska. Observed durations of nesting were 70 ± 2.6 days (SE) in California, 60 ± 6.3 days in North Dakota, 66 ± 1.3 days in Saskatchewan, and 42 ± 0.7 days in Alaska. Annual differences were the principal source of variation in mean clutch sizes (σ̂Y2 = 0.15, SE = 0.049), which varied little among study locations (σ̂A2 = 0.002, SE = 0.013). Predicted rates of seasonal decline in clutch sizes increased with latitude early in the nesting season, but declined as the nesting season progressed, except in California. Rates of decline in clutch sizes thus were not directly related to rates of increase in day length. Predicted declines in numbers of eggs per clutch over the nesting season were similar for all four locations (range, 3.05–3.12) despite wide variation in durations of nesting. Evidence suggests that reduced nutrient availability during nesting contributes to a higher rate of decline in clutch sizes in Alaska than in temperate regions. Pintails that nest early lay large initial clutches, but thereafter clutch sizes decline rapidly and breeding terminates early. This reproductive strategy is adaptive because young that hatch earliest exhibit the highest survival rates; however, the conversion of grassland to cropland on the primary prairie breeding grounds has reduced hatching rates of clutches laid early in the nesting season. Under these conditions, the limited capacity to renest in late spring on their prairie breeding grounds probably has contributed to Pintail population declines.

Individual variation in space use by female spotted hyenas

USGS Publications Warehouse

Boydston, Erin E.; Kapheim, Karen M.; Szykman, Micaela; Holekamp, Kay E.

2003-01-01

Large carnivores range more widely than many other terrestrial mammals, and this behavior tends to bring them into frequent conflict with humans. Within any carnivore population, individual variation in patterns of space use should be expected to make some animals more vulnerable than others to risks of mortality from humans and other sources. In this study, our goal was to document variation among individuals in space use by female spotted hyenas (Crocuta crocuta). We examined predictions of hypotheses suggesting that space use by female hyenas is affected by reproductive state, social rank, and local prey abundance. Home-range size, distance at which females were found from the current communal den, and distance at which they were found from the nearest territorial boundary all varied significantly with the 3 independent variables. Females with den-dwelling cubs had smaller home ranges, were found closer to the communal den, and were found farther from the territorial boundary than were females with no den-dwelling cubs. Neither social rank nor prey availability significantly influenced the space-use patterns of females with den-dwelling cubs. Among females with no den-dwelling cubs, high-ranking females had smaller home ranges, were closer to the communal den, and were farther from the territorial boundary than were low-ranking females. The females ranging most widely were low-ranking individuals with no den-dwelling cubs when they were observed during periods of prey scarcity.

Neocortex expansion is linked to size variations in gene families with chemotaxis, cell-cell signalling and immune response functions in mammals.

PubMed

Castillo-Morales, Atahualpa; Monzón-Sandoval, Jimena; de Sousa, Alexandra A; Urrutia, Araxi O; Gutierrez, Humberto

2016-10-01

Increased brain size is thought to have played an important role in the evolution of mammals and is a highly variable trait across lineages. Variations in brain size are closely linked to corresponding variations in the size of the neocortex, a distinct mammalian evolutionary innovation. The genomic features that explain and/or accompany variations in the relative size of the neocortex remain unknown. By comparing the genomes of 28 mammalian species, we show that neocortical expansion relative to the rest of the brain is associated with variations in gene family size (GFS) of gene families that are significantly enriched in biological functions associated with chemotaxis, cell-cell signalling and immune response. Importantly, we find that previously reported GFS variations associated with increased brain size are largely accounted for by the stronger link between neocortex expansion and variations in the size of gene families. Moreover, genes within these families are more prominently expressed in the human neocortex during early compared with adult development. These results suggest that changes in GFS underlie morphological adaptations during brain evolution in mammalian lineages. © 2016 The Authors.

Neocortex expansion is linked to size variations in gene families with chemotaxis, cell–cell signalling and immune response functions in mammals

PubMed Central

Castillo-Morales, Atahualpa; Monzón-Sandoval, Jimena; de Sousa, Alexandra A.

2016-01-01

Increased brain size is thought to have played an important role in the evolution of mammals and is a highly variable trait across lineages. Variations in brain size are closely linked to corresponding variations in the size of the neocortex, a distinct mammalian evolutionary innovation. The genomic features that explain and/or accompany variations in the relative size of the neocortex remain unknown. By comparing the genomes of 28 mammalian species, we show that neocortical expansion relative to the rest of the brain is associated with variations in gene family size (GFS) of gene families that are significantly enriched in biological functions associated with chemotaxis, cell–cell signalling and immune response. Importantly, we find that previously reported GFS variations associated with increased brain size are largely accounted for by the stronger link between neocortex expansion and variations in the size of gene families. Moreover, genes within these families are more prominently expressed in the human neocortex during early compared with adult development. These results suggest that changes in GFS underlie morphological adaptations during brain evolution in mammalian lineages. PMID:27707894

Can skull form predict the shape of the temporomandibular joint? A study using geometric morphometrics on the skulls of wolves and domestic dogs.

PubMed

Curth, Stefan; Fischer, Martin S; Kupczik, Kornelius

2017-11-01

The temporomandibular joint (TMJ) conducts and restrains masticatory movements between the mammalian cranium and the mandible. Through this functional integration, TMJ morphology in wild mammals is strongly correlated with diet, resulting in a wide range of TMJ variations. However, in artificially selected and closely related domestic dogs, dietary specialisations between breeds can be ruled out as a diversifying factor although they display an enormous variation in TMJ morphology. This raises the question of the origin of this variation. Here we hypothesise that, even in the face of reduced functional demands, TMJ shape in dogs can be predicted by skull form; i.e. that the TMJ is still highly integrated in the dog skull. If true, TMJ variation in the dog would be a plain by-product of the enormous cranial variation in dogs and its genetic causes. We addressed this hypothesis using geometric morphometry on a data set of 214 dog and 60 wolf skulls. We digitized 53 three-dimensional landmarks of the skull and the TMJ on CT-based segmentations and compared (1) the variation between domestic dog and wolf TMJs (via principal component analysis) and (2) the pattern of covariation of skull size, flexion and rostrum length with TMJ shape (via regression of centroid size on shape and partial least squares analyses). We show that the TMJ in domestic dogs is significantly more diverse than in wolves: its shape covaries significantly with skull size, flexion and rostrum proportions in patterns which resemble those observed in primates. Similar patterns in canids, which are carnivorous, and primates, which are mostly frugivorous imply the existence of basic TMJ integration patterns which are independent of dietary adaptations. However, only limited amounts of TMJ variation in dogs can be explained by simple covariation with overall skull geometry. This implies that the final TMJ shape is gained partially independently of the rest of the skull. Copyright © 2017 Elsevier GmbH. All rights reserved.

Interpreting high time resolution galactic cosmic ray observations in a diffusive context

NASA Astrophysics Data System (ADS)

Jordan, A.; Spence, H. E.; Blake, J. B.; Shaul, D. A.

2009-12-01

We interpret galactic cosmic ray (GCR) variations near Earth within a diffusive context. The variations occur on time-/size-scales ranging from Forbush decreases (Fds), to substructure embedded within Fds, to smaller amplitude and shorter duration variations during relatively benign interplanetary conditions. We use high time resolution GCR observations from the High Sensitivity Telescope (HIST) on Polar and from the Spectrometer for INTEGRAL (SPI) and also use solar wind plasma and magnetic field observations from ACE and/or Wind. To calculate the coefficient of diffusion, we combine these datasets with a simple convection-diffusion model for relativistic charged particles in a magnetic field. We find reasonable agreement between our and previous estimates of the coefficient. We also show whether changes in the coefficient of diffusion are sufficient to explain the above GCR variations.

Clan Genomics and the Complex Architecture of Human Disease

PubMed Central

Belmont, John W.; Boerwinkle, Eric

2013-01-01

Human diseases are caused by alleles that encompass the full range of variant types, from single-nucleotide changes to copy-number variants, and these variations span a broad frequency spectrum, from the very rare to the common. The picture emerging from analysis of whole-genome sequences, the 1000 Genomes Project pilot studies, and targeted genomic sequencing derived from very large sample sizes reveals an abundance of rare and private variants. One implication of this realization is that recent mutation may have a greater influence on disease susceptibility or protection than is conferred by variations that arose in distant ancestors. PMID:21962505

The interaction of neutral evolutionary processes with climatically-driven adaptive changes in the 3D shape of the human os coxae.

PubMed

Betti, Lia; von Cramon-Taubadel, Noreen; Manica, Andrea; Lycett, Stephen J

2014-08-01

Differences in the breadth of the pelvis among modern human populations and among extinct hominin species have often been interpreted in the light of thermoregulatory adaptation, whereby a larger pelvic girdle would help preserve body temperature in cold environments while a narrower pelvis would help dissipate heat in tropical climates. There is, however, a theoretical problem in interpreting a pattern of variation as evidence of selection without first accounting for the effects of neutral evolutionary processes (i.e., mutation, genetic drift and migration). Here, we analyse 3D configurations of 27 landmarks on the os coxae of 1494 modern human individuals representing 30 male and 23 female populations from five continents and a range of climatic conditions. We test for the effects of climate on the size and shape of the pelvic bone, while explicitly accounting for population history (i.e., geographically-mediated gene flow and genetic drift). We find that neutral processes account for a substantial proportion of shape variance in the human os coxae in both sexes. Beyond the neutral pattern due to population history, temperature is a significant predictor of shape and size variation in the os coxae, at least in males. The effect of climate on the shape of the pelvic bone, however, is comparatively limited, explaining only a small percentage of shape variation in males and females. In accordance with previous hypotheses, the size of the os coxae tends to increase with decreasing temperature, although the significance of the association is reduced when population history is taken into account. In conclusion, the shape and size of the human os coxae reflect both neutral evolutionary processes and climatically-driven adaptive changes. Neutral processes have a substantial effect on pelvic variation, suggesting such factors will need to be taken into account in future studies of human and fossil hominin coxal variation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Effects of spatial heterogeneity on butterfly species richness in Rocky Mountain National Park, CO, USA

USGS Publications Warehouse

Kumar, S.; Simonson, S.E.; Stohlgren, T.J.

2009-01-01

We investigated butterfly responses to plot-level characteristics (plant species richness, vegetation height, and range in NDVI [normalized difference vegetation index]) and spatial heterogeneity in topography and landscape patterns (composition and configuration) at multiple spatial scales. Stratified random sampling was used to collect data on butterfly species richness from seventy-six 20 ?? 50 m plots. The plant species richness and average vegetation height data were collected from 76 modified-Whittaker plots overlaid on 76 butterfly plots. Spatial heterogeneity around sample plots was quantified by measuring topographic variables and landscape metrics at eight spatial extents (radii of 300, 600 to 2,400 m). The number of butterfly species recorded was strongly positively correlated with plant species richness, proportion of shrubland and mean patch size of shrubland. Patterns in butterfly species richness were negatively correlated with other variables including mean patch size, average vegetation height, elevation, and range in NDVI. The best predictive model selected using Akaike's Information Criterion corrected for small sample size (AICc), explained 62% of the variation in butterfly species richness at the 2,100 m spatial extent. Average vegetation height and mean patch size were among the best predictors of butterfly species richness. The models that included plot-level information and topographic variables explained relatively less variation in butterfly species richness, and were improved significantly after including landscape metrics. Our results suggest that spatial heterogeneity greatly influences patterns in butterfly species richness, and that it should be explicitly considered in conservation and management actions. ?? 2008 Springer Science+Business Media B.V.

The spatial distribution and size of rook (Corvus frugilegus) breeding colonies is affected by both the distribution of foraging habitat and by intercolony competition.

PubMed Central

Griffin, L R; Thomas, C J

2000-01-01

Explanations for the variation in the number of nests at bird colonies have focused on competitive or habitat effects without considering potential interactions between the two. For the rook, a colonial corvid which breeds seasonally but forages around the colony throughout the year, both the amount of foraging habitat and its interaction with the number of competitors from surrounding colonies are important predictors of colony size. The distance over which these effects are strongest indicates that, for rooks, colony size may be limited outside of the breeding season when colony foraging ranges are larger and overlap to a greater extent. PMID:10983832

Diurnal and seasonal variations of concentration and size distribution of nano aerosols (10-1100 nm) enclosing radon decay products in the Postojna Cave, Slovenia.

PubMed

Bezek, M; Gregoric, A; Kávási, N; Vaupotic, J

2012-11-01

At the lowest point along the tourist route in the Postojna Cave, the activity concentration of radon ((222)Rn) short-lived decay products and number concentration and size distribution of background aerosol particles in the size range of 10-1100 nm were measured. In the warm yearly season, aerosol concentration was low (52 cm(-3)) with 21 % particles smaller than 50 nm, while in the cold season, it was higher (1238 cm(-3)) with 8 % of <50 nm particles. Radon activity concentrations were 4489 and 1108 Bq m(-3), and fractions of unattached radon decay products were 0.62 and 0.13, respectively.

Assessment of the within- and between-lot variability of Whatman™ FTA(®) DMPK and 903(®) DBS papers and their suitability for the quantitative bioanalysis of small molecules.

PubMed

Luckwell, Jacquelynn; Denniff, Philip; Capper, Stephen; Michael, Paul; Spooner, Neil; Mallender, Philip; Johnson, Barry; Clegg, Sarah; Green, Mark; Ahmad, Sheelan; Woodford, Lynsey

2013-11-01

To ensure that PK data generated from DBS samples are of the highest quality, it is important that the paper substrate is uniform and does not unduly contribute to variability. This study investigated any within and between lot variations for four cellulose paper types: Whatman™ FTA(®) DMPK-A, -B and -C, and 903(®) (GE Healthcare, Buckinghamshire, UK). The substrates were tested to demonstrate manufacturing reproducibility (thickness, weight, chemical coating concentration) and its effect on the size of the DBS produced, and the quantitative data derived from the bioanalysis of human DBS samples containing six compounds of varying physicochemical properties. Within and between lot variations in paper thickness, mass and chemical coating concentration were within acceptable manufacturing limits. No variation in the spot size or bioanalytical data was observed. Bioanalytical results obtained for DBS samples containing a number of analytes spanning a range of chemical space are not affected by the lot used or by the location within a lot.

Ion beam radiation effects on natural halite crystals

NASA Astrophysics Data System (ADS)

Arun, T.; Ram, S. S.; Karthikeyan, B.; Ranjith, P.; Ray, D. K.; Rout, B.; Krishna, J. B. M.; Sengupta, Pranesh; Parlapalli, Venkata Satyam

2017-10-01

Halites are one of the interesting material due to its color variations. Natural halites whose color ranges from transparent to dark blue were studied by UV-VIS and Raman spectroscopy. The halite crystals were irradiated with 3 MeV proton micro-beam (∼20 μm beam width with ∼80 PA beam current) for 10 and 90 min to study the radiation damage. After 10 mins of irradiation, small spot developed on the surface of transparent halite crystal whereas after 90 mins of irradiation the spot spread inside the bulk leading to a brown coloration (20 μm initial size to ∼2.0 mm final size). The irradiated portion and the un-irradiated portion of the halites was characterized by Raman spectroscopic technique. The variation in the population density was observed from the UV-Vis spectra. The change in the Raman band intensities was observed for transparent, blue colored and proton beam irradiation halites. Such variation of spectroscopic characteristics due to proton irradiation suggests that the halite can be used for the radiation monitoring.

[Geographical variation in the species Montivagum dihumerale and speciation in chigger mites (Acari: Trombiculidae)].

PubMed

Stekol'nikov, A A

2006-01-01

Intraspecific morphological variation of the chigger mite species Montivagum dihumerale (Traub et Nadchatram, 1967) is studied. Eco-geographic rules of the variation are revealed. General size of mites is found to be increased along with the rise of the high-mountain character of the landscape in the collection localities. The numbers of idiosomal setae are varied independently from the size parameters and geographically close populations are proved to be the most similar by these characters. At the same time, numbers of the setae of different types play the leading role in the discrimination of closely related Montivagum species, while the eco-geographical rules have not been found in this genus at the level of interspecific differences. As a result, the hypothesis is set up, that a significant degree of isolation of local populations separated from each other by high mountain ranges of the Central Asia is the main factor of speciation in the genus Montivagum. Regional character of this speciation mode is confirmed by the comparison with other chigger mites taxa.

Understanding and monitoring the consequences of human impacts on intraspecific variation.

PubMed

Mimura, Makiko; Yahara, Tetsukazu; Faith, Daniel P; Vázquez-Domínguez, Ella; Colautti, Robert I; Araki, Hitoshi; Javadi, Firouzeh; Núñez-Farfán, Juan; Mori, Akira S; Zhou, Shiliang; Hollingsworth, Peter M; Neaves, Linda E; Fukano, Yuya; Smith, Gideon F; Sato, Yo-Ichiro; Tachida, Hidenori; Hendry, Andrew P

2017-02-01

Intraspecific variation is a major component of biodiversity, yet it has received relatively little attention from governmental and nongovernmental organizations, especially with regard to conservation plans and the management of wild species. This omission is ill-advised because phenotypic and genetic variations within and among populations can have dramatic effects on ecological and evolutionary processes, including responses to environmental change, the maintenance of species diversity, and ecological stability and resilience. At the same time, environmental changes associated with many human activities, such as land use and climate change, have dramatic and often negative impacts on intraspecific variation. We argue for the need for local, regional, and global programs to monitor intraspecific genetic variation. We suggest that such monitoring should include two main strategies: (i) intensive monitoring of multiple types of genetic variation in selected species and (ii) broad-brush modeling for representative species for predicting changes in variation as a function of changes in population size and range extent. Overall, we call for collaborative efforts to initiate the urgently needed monitoring of intraspecific variation.

Fishing degrades size structure of coral reef fish communities.

PubMed

Robinson, James P W; Williams, Ivor D; Edwards, Andrew M; McPherson, Jana; Yeager, Lauren; Vigliola, Laurent; Brainard, Russell E; Baum, Julia K

2017-03-01

Fishing pressure on coral reef ecosystems has been frequently linked to reductions of large fishes and reef fish biomass. Associated impacts on overall community structure are, however, less clear. In size-structured aquatic ecosystems, fishing impacts are commonly quantified using size spectra, which describe the distribution of individual body sizes within a community. We examined the size spectra and biomass of coral reef fish communities at 38 US-affiliated Pacific islands that ranged in human presence from near pristine to human population centers. Size spectra 'steepened' steadily with increasing human population and proximity to market due to a reduction in the relative biomass of large fishes and an increase in the dominance of small fishes. Reef fish biomass was substantially lower on inhabited islands than uninhabited ones, even at inhabited islands with the lowest levels of human presence. We found that on populated islands size spectra exponents decreased (analogous to size spectra steepening) linearly with declining biomass, whereas on uninhabited islands there was no relationship. Size spectra were steeper in regions of low sea surface temperature but were insensitive to variation in other environmental and geomorphic covariates. In contrast, reef fish biomass was highly sensitive to oceanographic conditions, being influenced by both oceanic productivity and sea surface temperature. Our results suggest that community size structure may be a more robust indicator than fish biomass to increasing human presence and that size spectra are reliable indicators of exploitation impacts across regions of different fish community compositions, environmental drivers, and fisheries types. Size-based approaches that link directly to functional properties of fish communities, and are relatively insensitive to abiotic variation across biogeographic regions, offer great potential for developing our understanding of fishing impacts in coral reef ecosystems. © 2016 John Wiley & Sons Ltd.

MACHINING ELIMINATION THROUGH APPLICATION OF THREAD FORMING FASTENERS IN NET SHAPED CAST HOLES

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

Cleaver, Ryan J; Cleaver, Todd H; Talbott, Richard

The ultimate objective of this work was to eliminate approximately 30% of the machining performed in typical automotive engine and transmission plants by using thread forming fasteners in as-cast holes of aluminum and magnesium cast components. The primary issues at the source of engineers reluctance to implementing thread forming fasteners in lightweight castings are: * Little proof of consistency of clamp load vs. input torque in either aluminum or magnesium castings. * No known data to understand the effect on consistency of clamp load as casting dies wear. The clamp load consistency concern is founded in the fact that amore » portion of the input torque used to create clamp load is also used to create threads. The torque used for thread forming may not be consistent due to variations in casting material, hole size and shape due to tooling wear and process variation (thermal and mechanical). There is little data available to understand the magnitude of this concern or to form the basis of potential solutions if the range of clamp load variation is very high (> +/- 30%). The range of variation that can be expected in as-cast hole size and shape over the full life cycle of a high pressure die casting die was established in previous work completed by Pacific Northwest National Laboratory, (PNNL). This established range of variation was captured in a set of 12 cast bosses by designing core pins at the size and draft angles identified in the sited previous work. The cast bosses were cut into nuts that could be used in the Ford Fastener Laboratory test-cell to measure clamp load when a thread forming fastener was driven into a cast nut. There were two sets of experiments run. First, a series of cast aluminum nuts were made reflecting the range of shape and size variations to be expected over the life cycle of a die casting die. Taptite thread forming fasteners, (a widely used thread forming fastener suitable for aluminum applications), were driven into the various cored, as-cast nuts at a constant input torque and resulting clamp loads were recorded continuously. The clamp load data was used to determine the range of clamp loads to be expected. The bolts were driven to failure. The clamp load corresponding to the target input of 18.5 Nm was recorded for each fastener. In a like fashion, a second set of experiments were run with cast magnesium nuts and ALtracs thread forming fasteners, (a widely used thread forming fastener suitable for magnesium applications). Again all clamp loads were recorded and analyzed similarly to the Taptites in aluminum cast nuts. Results from previous work performed on the same test cell for a Battelle project using standard M8 bolts into standard M8 nuts were included as a comparator for a standard bolt and nut application. The results for the thread forming fasteners in aluminum cast holes were well within industry expectations of +/- 30% for out of the box and robustness range testing. The results for the dry and lubed extreme conditions were only slightly higher than industry expectations at +/- 35.6%. However, when compared to the actual Battelle results (+/- 40%) for a standard bolt and nut the tread forming fasteners performed slightly better. The results for the thread forming fasteners in magnesium cast holes were all well within industry expectations of +/- 30% for all three conditions. The robustness range (.05mm larger and smaller holes than the expected wear pattern of a die casting die at full life cycle) results also fell within the industry expectations for standard threaded fasteners. These results were very encouraging. It was concluded that this work showed that clamp load variation with thread forming fasteners is consistent with industry expectations for standard steel bolts and nuts at +/- 30%. There does not appear to be any significant increase in clamp load variation due to the application of thread forming fasteners in as-cast holes of aluminum or magnesium over the effective life of a die casting mold. The fully implemented potential benefit of thread forming fasteners in as-cast holes of aluminum and magnesium is estimated to be 6 trillion Btu per year for North America. Economic benefit is estimated to be nearly $800 million per year. Environmental benefits and quality improvements will also result from full implementation of this technology.« less

Impact of dynamic distribution of floc particles on flocculation effect.

PubMed

Nan, Jun; He, Weipeng; Song, Xinin; Li, Guibai

2009-01-01

Polyaluminum chloride (PAC) was used as coagulant and suspended particles in kaolin water. Online instruments including turbidimeter and particle counter were used to monitor the flocculation process. An evaluation model for demonstrating the impact on the flocculation effect was established based on the multiple linear regression analysis method. The parameter of the index weight of channels quantitatively described how the variation of floc particle population in different size ranges cause the decrement of turbidity. The study showed that the floc particles in different size ranges contributed differently to the decrease of turbidity and that the index weight of channel could excellently indicate the impact degree of floc particles dynamic distribution on flocculation effect. Therefore, the parameter may significantly benefit the development of coagulation and sedimentation techniques as well as the optimal coagulant selection.

The influence of floral symmetry, dependence on pollinators and pollination generalization on flower size variation

PubMed Central

Lázaro, A.; Totland, Ø.

2014-01-01

Background and Aims The pollinator-mediated stabilizing selection hypothesis suggests that the specialized pollination system of zygomorphic flowers might cause stabilizing selection, reducing their flower size variation compared with actinomorphic flowers. However, the degree of ecological generalization and of dependence on pollinators varies greatly among species of both flower symmetry types and this may also affect flower size variation. Methods Data on 43 species from two contrasting communities (one alpine and one lowland community) were used to test the relationships and interactions between flower size phenotypic variation, floral symmetry, ecological pollination generalization and species' dependence on pollinators. Key Results Contrary to what was expected, higher flower size variation was found in zygomorphic than in actinomorphic species in the lowland community, and no difference in flower size variation was found between symmetry types in the alpine community. The relationship between floral symmetry and flower size variation depended on ecological generalization and species' dependence on pollinators, although the influence of ecological generalization was only detected in the alpine community. Zygomorphic species that were highly dependent on pollinators and that were ecologically specialized were less variable in flower size than ecologically generalist and selfing zygomorphic species, supporting the pollinator-mediated stabilizing selection hypothesis. However, these relationships were not found in actinomorphic species, probably because they are not dependent on any particular pollinator for efficient pollination and therefore their flower size always shows moderate levels of variation. Conclusions The study suggests that the relationship between flower size variation and floral symmetry may be influenced by population-dependent factors, such as ecological generalization and species' dependence on pollinators. PMID:24838838

The influence of floral symmetry, dependence on pollinators and pollination generalization on flower size variation.

PubMed

Lázaro, A; Totland, O

2014-07-01

The pollinator-mediated stabilizing selection hypothesis suggests that the specialized pollination system of zygomorphic flowers might cause stabilizing selection, reducing their flower size variation compared with actinomorphic flowers. However, the degree of ecological generalization and of dependence on pollinators varies greatly among species of both flower symmetry types and this may also affect flower size variation. Data on 43 species from two contrasting communities (one alpine and one lowland community) were used to test the relationships and interactions between flower size phenotypic variation, floral symmetry, ecological pollination generalization and species' dependence on pollinators. Contrary to what was expected, higher flower size variation was found in zygomorphic than in actinomorphic species in the lowland community, and no difference in flower size variation was found between symmetry types in the alpine community. The relationship between floral symmetry and flower size variation depended on ecological generalization and species' dependence on pollinators, although the influence of ecological generalization was only detected in the alpine community. Zygomorphic species that were highly dependent on pollinators and that were ecologically specialized were less variable in flower size than ecologically generalist and selfing zygomorphic species, supporting the pollinator-mediated stabilizing selection hypothesis. However, these relationships were not found in actinomorphic species, probably because they are not dependent on any particular pollinator for efficient pollination and therefore their flower size always shows moderate levels of variation. The study suggests that the relationship between flower size variation and floral symmetry may be influenced by population-dependent factors, such as ecological generalization and species' dependence on pollinators. © The Author 2014. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Freshwater resources in the insular Caribbean: an environmental perspective

Treesearch

T. Heartsill Scalley

2012-01-01

From islands with no permanent flowing streams to those with navigable inland waters, the insular Caribbean contains a great range of conditions regarding the access to freshwater resources. Because of the variation in topography and size, the ability of islands to retain freshwater also varies widely. The usage of freshwater in this region is being led by two major...

Predicting the spread of all invasive forest pests in the United States

Treesearch

Emma J. Hudgins; Andrew M. Liebhold; Brian Leung; Regan Early

2017-01-01

We tested whether a general spread model could capture macroecological patterns across all damaging invasive forest pests in the United States. We showed that a common constant dispersal kernel model, simulated from the discovery date, explained 67.94% of the variation in range size across all pests, and had 68.00% locational accuracy between predicted and observed...

Infrared photometric behavior and opposition effect of Mars

NASA Technical Reports Server (NTRS)

Erard, S.; Bibring, J-P.; Drossart, P.

1992-01-01

Although the instrument wasn't designed for this purpose, data from the imaging spectrometer ISM may be used for studying photometric variations of Mars reflectance, that are related to the surface materials and aerosols physical properties. ISM flew aboard the Phobos-2 spacecraft which orbited Mars from January to March, 1989. About 40,000 spectra were acquired in 128 channels ranging from 0.76 to 3.16 micro-m, with a spatial resolution of 25 km and a signal-to-noise ratio ranging up to 1000. Analysis of the results leads to the following conclusions: width variations of the opposition surge can be related to differences in porosity or grain size distribution on the various domains, with little or no effect from suspended dust. As the biggest effects are observed on dark and bright materials, intermediate behaviors on average-bright regions cannot result from a mixing process, but are more likely to come from either cementation processes or modification of the grain size distribution under the influence of wind, which under Martian conditions preferentially removes the biggest particles. Thus, a surface dust consisting in big bright and small dark grains could explain the observations.

Brightness variation distributions among main belt asteroids from sparse light-curve sampling with Pan-STARRS 1

NASA Astrophysics Data System (ADS)

McNeill, A.; Fitzsimmons, A.; Jedicke, R.; Wainscoat, R.; Denneau, L.; Vereš, P.; Magnier, E.; Chambers, K. C.; Kaiser, N.; Waters, C.

2016-07-01

The rotational state of asteroids is controlled by various physical mechanisms including collisions, internal damping and the Yarkovsky-O'Keefe-Radzievskii-Paddack effect. We have analysed the changes in magnitude between consecutive detections of ˜60 000 asteroids measured by the Panoramic Survey Telescope and Rapid Response System (PanSTARRS) 1 survey during its first 18 months of operations. We have attempted to explain the derived brightness changes physically and through the application of a simple model. We have found a tendency towards smaller magnitude variations with decreasing diameter for objects of 1 < D < 8 km. Assuming the shape distribution of objects in this size range to be independent of size and composition our model suggests a population with average axial ratios 1 : 0.85 ± 0.13 : 0.71 ± 0.13, with larger objects more likely to have spin axes perpendicular to the orbital plane.

Clinical Pathology Reference Intervals for an In-Water Population of Juvenile Loggerhead Sea Turtles (Caretta caretta) in Core Sound, North Carolina, USA

PubMed Central

Kelly, Terra R.; McNeill, Joanne Braun; Avens, Larisa; Hall, April Goodman; Goshe, Lisa R.; Hohn, Aleta A.; Godfrey, Matthew H.; Mihnovets, A. Nicole; Cluse, Wendy M.; Harms, Craig A.

2015-01-01

The loggerhead sea turtle (Caretta caretta) is found throughout the waters of the Atlantic, Pacific, and Indian Oceans. It is a protected species throughout much of its range due to threats such as habitat loss, fisheries interactions, hatchling predation, and marine debris. Loggerheads that occur in the southeastern U.S. are listed as “threatened” on the U.S. Endangered Species List, and receive state and federal protection. As part of an on-going population assessment conducted by the National Marine Fisheries Service, samples were collected from juvenile loggerhead sea turtles in Core Sound, North Carolina, between 2004 and 2007 to gain insight on the baseline health of the threatened Northwest Atlantic Ocean population. The aims of the current study were to establish hematologic and biochemical reference intervals for this population, and to assess variation of the hematologic and plasma biochemical analytes by season, water temperature, and sex and size of the turtles. Reference intervals for the clinical pathology parameters were estimated following Clinical Laboratory Standards Institute guidelines. Season, water temperature, sex, and size of the turtles were found to be significant factors of variation for parameter values. Seasonal variation could be attributed to physiological effects of decreasing photoperiod, cooler water temperature, and migration during the fall months. Packed cell volume, total protein, and albumin increased with increasing size of the turtles. The size-related differences in analytes documented in the present study are consistent with other reports of variation in clinical pathology parameters by size and age in sea turtles. As a component of a health assessment of juvenile loggerhead sea turtles in North Carolina, this study will serve as a baseline aiding in evaluation of trends for this population and as a diagnostic tool for assessing the health and prognosis for loggerhead sea turtles undergoing rehabilitation. PMID:25738772

Clinical pathology reference intervals for an in-water population of juvenile loggerhead sea turtles (Caretta caretta) in Core Sound, North Carolina, USA.

PubMed

Kelly, Terra R; McNeill, Joanne Braun; Avens, Larisa; Hall, April Goodman; Goshe, Lisa R; Hohn, Aleta A; Godfrey, Matthew H; Mihnovets, A Nicole; Cluse, Wendy M; Harms, Craig A

2015-01-01

The loggerhead sea turtle (Caretta caretta) is found throughout the waters of the Atlantic, Pacific, and Indian Oceans. It is a protected species throughout much of its range due to threats such as habitat loss, fisheries interactions, hatchling predation, and marine debris. Loggerheads that occur in the southeastern U.S. are listed as "threatened" on the U.S. Endangered Species List, and receive state and federal protection. As part of an on-going population assessment conducted by the National Marine Fisheries Service, samples were collected from juvenile loggerhead sea turtles in Core Sound, North Carolina, between 2004 and 2007 to gain insight on the baseline health of the threatened Northwest Atlantic Ocean population. The aims of the current study were to establish hematologic and biochemical reference intervals for this population, and to assess variation of the hematologic and plasma biochemical analytes by season, water temperature, and sex and size of the turtles. Reference intervals for the clinical pathology parameters were estimated following Clinical Laboratory Standards Institute guidelines. Season, water temperature, sex, and size of the turtles were found to be significant factors of variation for parameter values. Seasonal variation could be attributed to physiological effects of decreasing photoperiod, cooler water temperature, and migration during the fall months. Packed cell volume, total protein, and albumin increased with increasing size of the turtles. The size-related differences in analytes documented in the present study are consistent with other reports of variation in clinical pathology parameters by size and age in sea turtles. As a component of a health assessment of juvenile loggerhead sea turtles in North Carolina, this study will serve as a baseline aiding in evaluation of trends for this population and as a diagnostic tool for assessing the health and prognosis for loggerhead sea turtles undergoing rehabilitation.

Predator size divergence depends on community context.

PubMed

Okuzaki, Yutaka; Sota, Teiji

2018-05-09

Body size is a multi-functional trait related to various fitness components, but the relative importance of different selection pressures is seldom resolved. In Carabus japonicus beetles, of which the larvae exclusively prey on earthworms, adult body size is related to the presence/absence of a larger congener and habitat temperature. In sympatry, C. japonicus consistently exhibits smaller body size which is effective for avoiding interspecific mating, but in allopatry, it shows size variation unrelated to temperature. Here, we show that this predator-size variation is attributed to prey-size variation, associated with high phylogenetic diversity in earthworm communities. In allopatry, the predator size was larger where larger prey occurred. Larger adult size may have been selected because larger females produce larger larvae, which can subdue larger prey. Thus, in the absence of a larger congener, variation in prey body size had a pronounced effect on geographic body size divergence in C. japonicus. © 2018 John Wiley & Sons Ltd/CNRS.

Particle Transport and Size Sorting in Bubble Microstreaming Flow

NASA Astrophysics Data System (ADS)

Thameem, Raqeeb; Rallabandi, Bhargav; Wang, Cheng; Hilgenfeldt, Sascha

2014-11-01

Ultrasonic driving of sessile semicylindrical bubbles results in powerful steady streaming flows that are robust over a wide range of driving frequencies. In a microchannel, this flow field pattern can be fine-tuned to achieve size-sensitive sorting and trapping of particles at scales much smaller than the bubble itself; the sorting mechanism has been successfully described based on simple geometrical considerations. We investigate the sorting process in more detail, both experimentally (using new parameter variations that allow greater control over the sorting) and theoretically (incorporating the device geometry as well as the superimposed channel flow into an asymptotic theory). This results in optimized criteria for size sorting and a theoretical description that closely matches the particle behavior close to the bubble, the crucial region for size sorting.

Nesting environment may drive variation in eggshell structure and egg characteristics in the Testudinata.

PubMed

Deeming, D Charles

2018-05-14

Testudines exhibit considerable variation in the degree of eggshell calcification, which affects eggshell conductance, water physiology of the embryos, and calcium metabolism of embryos. However, the underlying reason for different shell types has not been explored. Phylogenetically controlled analyses examined relationships between egg size, shell mass, and clutch size in ∼200 turtle species from a range of body sizes and assigned by family as laying either rigid- or pliable-shelled eggs. Shell type affected egg breadth relative to pelvic dimensions, egg mass, and relative shell mass but did not affect size, mass, or total shell mass of the clutch. These results suggest that calcium availability may be a function of body size and the type of shell may reflect in part the interplay between clutch size and egg size. It was further concluded that the eggshell probably evolved as a means of physical protection. Differences in shell calcification may not primarily reflect reproductive parameters but rather correlate with the acidity of a species' nesting environment. Low pH environments may have thicker calcareous layer to counteract the erosion caused by the soil and maintain the integrity of the physical barrier. Limited calcium availability may constrain clutch size. More neutral nesting substrates expose eggshells to less erosion so calcification per egg can be reduced and this allows larger clutch sizes. This pattern is also reflected in thick, calcified crocodilian eggs. Further research is needed to test whether eggshell calcification in the testudines correlates with nest pH in order to verify this relationship. © 2018 Wiley Periodicals, Inc.

Asynchronous spore germination in isogenic natural isolates of Saccharomyces paradoxus.

PubMed

Stelkens, Rike B; Miller, Eric L; Greig, Duncan

2016-05-01

Spores from wild yeast isolates often show great variation in the size of colonies they produce, for largely unknown reasons. Here we measure the colonies produced from single spores from six different wild Saccharomyces paradoxus strains. We found remarkable variation in spore colony sizes, even among spores that were genetically identical. Different strains had different amounts of variation in spore colony sizes, and variation was not affected by the number of preceding meioses, or by spore maturation time. We used time-lapse photography to show that wild strains also have high variation in spore germination timing, providing a likely mechanism for the variation in spore colony sizes. When some spores from a laboratory strain make small colonies, or no colonies, it usually indicates a genetic or meiotic fault. Here, we demonstrate that in wild strains spore colony size variation is normal. We discuss and assess potential adaptive and non-adaptive explanations for this variation. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Latitudinal variation in sensitivity of flower bud formation to high temperature in Japanese Taraxacum officinale.

PubMed

Yoshie, Fumio

2014-05-01

Control of flowering time plays a key role in the successful range expansion of plants. Taraxacum officinale has expanded throughout Japan during the 110 years after it was introduced into a cool temperate region. The present study tested a hypothesis that there is a genetic difference in the bud formation time in relation to temperature along latitudinal gradient of T. officinale populations. In Experiment 1, plants from three populations at different latitudes (26, 36, and 43°N) were grown at three temperatures. Time to flower bud appearance did not significantly differ among the three populations when plants were grown at 14 °C, whereas it increased with increasing latitude when grown at 19 and 24 °C. Rosette diameter was not different among the populations, indicating that the variation in bud formation time reflected a difference in genetic control rather than size variation. The latitudinal variation in bud appearance time was confirmed by Experiment 2 in which plants from 17 population were used. In Experiment 3, the size of plants that exhibited late-flowering was studied to test a hypothesis that the variation in flowering time reflects dormancy of vegetative growth, but the late-flowering plants were found to continue growth, indicating that vegetative dormancy was not the cause of the variation. The results clearly indicate that the degree of suppression of flower bud formation at high temperature decreases with latitude from north to south, which is under genetic control.

Population genetics and the evolution of geographic range limits in an annual plant.

PubMed

Moeller, David A; Geber, Monica A; Tiffin, Peter

2011-10-01

Abstract Theoretical models of species' geographic range limits have identified both demographic and evolutionary mechanisms that prevent range expansion. Stable range limits have been paradoxical for evolutionary biologists because they represent locations where populations chronically fail to respond to selection. Distinguishing among the proposed causes of species' range limits requires insight into both current and historical population dynamics. The tools of molecular population genetics provide a window into the stability of range limits, historical demography, and rates of gene flow. Here we evaluate alternative range limit models using a multilocus data set based on DNA sequences and microsatellites along with field demographic data from the annual plant Clarkia xantiana ssp. xantiana. Our data suggest that central and peripheral populations have very large historical and current effective population sizes and that there is little evidence for population size changes or bottlenecks associated with colonization in peripheral populations. Whereas range limit populations appear to have been stable, central populations exhibit a signature of population expansion and have contributed asymmetrically to the genetic diversity of peripheral populations via migration. Overall, our results discount strictly demographic models of range limits and more strongly support evolutionary genetic models of range limits, where adaptation is prevented by a lack of genetic variation or maladaptive gene flow.

A potential mechanism for allometric trabecular bone scaling in terrestrial mammals.

PubMed

Christen, Patrik; Ito, Keita; van Rietbergen, Bert

2015-03-01

Trabecular bone microstructural parameters, including trabecular thickness, spacing, and number, have been reported to scale with animal size with negative allometry, whereas bone volume fraction is animal size-invariant in terrestrial mammals. As for the majority of scaling patterns described in animals, its underlying mechanism is unknown. However, it has also been found that osteocyte density is inversely related to animal size, possibly adapted to metabolic rate, which shows a negative relationship as well. In addition, the signalling reach of osteocytes is limited by the extent of the lacuno-canalicular network, depending on trabecular dimensions and thus also on animal size. Here we propose animal size-dependent variations in osteocyte density and their signalling influence distance as a potential mechanism for negative allometric trabecular bone scaling in terrestrial mammals. Using an established and tested computational model of bone modelling and remodelling, we run simulations with different osteocyte densities and influence distances mimicking six terrestrial mammals covering a large range of body masses. Simulated trabecular structures revealed negative allometric scaling for trabecular thickness, spacing, and number, constant bone volume fraction, and bone turnover rates inversely related to animal size. These results are in agreement with previous observations supporting our proposal of osteocyte density and influence distance variation as a potential mechanism for negative allometric trabecular bone scaling in terrestrial mammals. The inverse relationship between bone turnover rates and animal size further indicates that trabecular bone scaling may be linked to metabolic rather than mechanical adaptations. © 2015 Anatomical Society.

Effect of Compressive Stresses on Leakage Currents in Microchip Tantalum Capacitors

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander

2012-01-01

Microchip tantalum capacitors are manufactured using new technologies that allow for production of small size capacitors (down to EIA case size 0402) with volumetric efficiency much greater than for regular chip capacitors. Due to a small size of the parts and leadless design they might be more sensitive to mechanical stresses that develop after soldering onto printed wiring boards (PWB) compared to standard chip capacitors. In this work, the effect of compressive stresses on leakage currents in capacitors has been investigated in the range of stresses up to 200 MPa. Significant, up to three orders of magnitude, variations of currents were observed after the stress exceeds a certain critical level that varied from 10 MPa to 180 MPa for capacitors used in this study. A stress-induced generation of electron traps in tantalum pentoxide dielectric is suggested to explain reversible variations of leakage currents in tantalum capacitors. Thermo-mechanical characteristics of microchip capacitors have been studied to estimate the level of stresses caused by assembly onto PWB and assess the risk of stress-related degradation and failures. Keywords: tantalum capacitors, leakage current, soldering, reliability, mechanical stress.

Numbers of genes in the NBS and RLK families vary by more than four-fold within a plant species and are regulated by multiple factors.

PubMed

Zhang, Meiping; Wu, Yen-Hsuan; Lee, Mi-Kyung; Liu, Yun-Hua; Rong, Ying; Santos, Teofila S; Wu, Chengcang; Xie, Fangming; Nelson, Randall L; Zhang, Hong-Bin

2010-10-01

Many genes exist in the form of families; however, little is known about their size variation, evolution and biology. Here, we present the size variation and evolution of the nucleotide-binding site (NBS)-encoding gene family and receptor-like kinase (RLK) gene family in Oryza, Glycine and Gossypium. The sizes of both families vary by numeral fold, not only among species, surprisingly, also within a species. The size variations of the gene families are shown to correlate with each other, indicating their interactions, and driven by natural selection, artificial selection and genome size variation, but likely not by polyploidization. The numbers of genes in the families in a polyploid species are similar to those of one of its diploid donors, suggesting that polyploidization plays little roles in the expansion of the gene families and that organisms tend not to maintain their 'surplus' genes in the course of evolution. Furthermore, it is found that the size variations of both gene families are associated with organisms' phylogeny, suggesting their roles in speciation and evolution. Since both selection and speciation act on organism's morphological, physiological and biological variation, our results indicate that the variation of gene family size provides a source of genetic variation and evolution.

A finite element simulation of sound attenuation in a finite duct with a peripherally variable liner

NASA Technical Reports Server (NTRS)

Watson, W. R.

1977-01-01

Using multimodal analysis, a variational finite element method is presented for analyzing sound attenuation in a three-dimensional finite duct with a peripherally variable liner in the absence of flow. A rectangular element, with cubic shaped functions, is employed. Once a small portion of a peripheral liner is removed, the attenuation rate near the frequency where maximum attenuation occurs drops significantly. The positioning of the liner segments affects the attenuation characteristics of the liner. Effects of the duct termination are important in the low frequency ranges. The main effect of peripheral variation of the liner is a broadening of the attenuation characteristics in the midfrequency range. Because of matrix size limitations of the presently available computer program, the eigenvalue equations should be solved out of core in order to handle realistic sources.

Using effort information with change-in-ratio data for population estimation

USGS Publications Warehouse

Udevitz, Mark S.; Pollock, Kenneth H.

1995-01-01

Most change-in-ratio (CIR) methods for estimating fish and wildlife population sizes have been based only on assumptions about how encounter probabilities vary among population subclasses. When information on sampling effort is available, it is also possible to derive CIR estimators based on assumptions about how encounter probabilities vary over time. This paper presents a generalization of previous CIR models that allows explicit consideration of a range of assumptions about the variation of encounter probabilities among subclasses and over time. Explicit estimators are derived under this model for specific sets of assumptions about the encounter probabilities. Numerical methods are presented for obtaining estimators under the full range of possible assumptions. Likelihood ratio tests for these assumptions are described. Emphasis is on obtaining estimators based on assumptions about variation of encounter probabilities over time.

Repeatability of circadian behavioural variation revealed in free-ranging marine fish.

PubMed

Alós, Josep; Martorell-Barceló, Martina; Campos-Candela, Andrea

2017-02-01

Repeatable between-individual differences in the behavioural manifestation of underlying circadian rhythms determine chronotypes in humans and terrestrial animals. Here, we have repeatedly measured three circadian behaviours, awakening time, rest onset and rest duration, in the free-ranging pearly razorfish, Xyrithchys novacula , facilitated by acoustic tracking technology and hidden Markov models. In addition, daily travelled distance, a standard measure of daily activity as fish personality trait, was repeatedly assessed using a State-Space Model. We have decomposed the variance of these four behavioural traits using linear mixed models and estimated repeatability scores ( R ) while controlling for environmental co-variates: year of experimentation, spatial location of the activity, fish size and gender and their interactions. Between- and within-individual variance decomposition revealed significant R s in all traits suggesting high predictability of individual circadian behavioural variation and the existence of chronotypes. The decomposition of the correlations among chronotypes and the personality trait studied here into between- and within-individual correlations did not reveal any significant correlation at between-individual level. We therefore propose circadian behavioural variation as an independent axis of the fish personality, and the study of chronotypes and their consequences as a novel dimension in understanding within-species fish behavioural diversity.

Cornering characteristics of the nose-gear tire of the space shuttle orbiter

NASA Technical Reports Server (NTRS)

Vogler, W. A.; Tanner, J. A.

1981-01-01

An experimental investigation was conducted to evaluate cornering characteristics of the 32 x 8.8 nose gear tire of the space shuttle orbiter. Data were obtained on a dry concrete runway at nominal ground speeds ranging from 50 to 100 knots and over a range of tire vertical loads and yaw angles which span the expected envelope of loads and yaw angles to be encountered during space shuttle landing operations. The cornering characteristics investigated included side and drag forces and friction coefficients, aligning and overturning torques, friction force moment arm, and the lateral center of pressure shift. Results of this investigation indicate that the cornering characteristics of the space shuttle nose gear tire are insensitive to variations in ground speed over the range tested. The effects on cornering characteristics of variations in the tire vertical load and yaw angle are as expected. Trends observed are consistent with trends observed during previous cornering tests involving other tire sizes.

Morphometric variation in the papionin muzzle and the biochronology of the South African Plio-Pleistocene karst cave deposits.

PubMed

Gilbert, Christopher C; Grine, Frederick E

2010-03-01

Papionin monkeys are widespread, relatively common members of Plio-Pleistocene faunal assemblages across Africa. For these reasons, papionin taxa have been used as biochronological indicators by which to infer the ages of the South African karst cave deposits. A recent morphometric study of South African fossil papionin muzzle shape concluded that its variation attests to a substantial and greater time depth for these sites than is generally estimated. This inference is significant, because accurate dating of the South African cave sites is critical to our knowledge of hominin evolution and mammalian biogeographic history. We here report the results of a comparative analysis of extant papionin monkeys by which variability of the South African fossil papionins may be assessed. The muzzles of 106 specimens representing six extant papionin genera were digitized and interlandmark distances were calculated. Results demonstrate that the overall amount of morphological variation present within the fossil assemblage fits comfortably within the range exhibited by the extant sample. We also performed a statistical experiment to assess the limitations imposed by small sample sizes, such as typically encountered in the fossil record. Results suggest that 15 specimens are sufficient to accurately represent the population mean for a given phenotype, but small sample sizes are insufficient to permit the accurate estimation of the population standard deviation, variance, and range. The suggestion that the muzzle morphology of fossil papionins attests to a considerable and previously unrecognized temporal depth of the South African karst cave sites is unwarranted.

Chromosome Numbers and Genome Size Variation in Indian Species of Curcuma (Zingiberaceae)

PubMed Central

Leong-Škorničková, Jana; Šída, Otakar; Jarolímová, Vlasta; Sabu, Mamyil; Fér, Tomáš; Trávníček, Pavel; Suda, Jan

2007-01-01

Background and Aims Genome size and chromosome numbers are important cytological characters that significantly influence various organismal traits. However, geographical representation of these data is seriously unbalanced, with tropical and subtropical regions being largely neglected. In the present study, an investigation was made of chromosomal and genome size variation in the majority of Curcuma species from the Indian subcontinent, and an assessment was made of the value of these data for taxonomic purposes. Methods Genome size of 161 homogeneously cultivated plant samples classified into 51 taxonomic entities was determined by propidium iodide flow cytometry. Chromosome numbers were counted in actively growing root tips using conventional rapid squash techniques. Key Results Six different chromosome counts (2n = 22, 42, 63, >70, 77 and 105) were found, the last two representing new generic records. The 2C-values varied from 1·66 pg in C. vamana to 4·76 pg in C. oligantha, representing a 2·87-fold range. Three groups of taxa with significantly different homoploid genome sizes (Cx-values) and distinct geographical distribution were identified. Five species exhibited intraspecific variation in nuclear DNA content, reaching up to 15·1 % in cultivated C. longa. Chromosome counts and genome sizes of three Curcuma-like species (Hitchenia caulina, Kaempferia scaposa and Paracautleya bhatii) corresponded well with typical hexaploid (2n = 6x = 42) Curcuma spp. Conclusions The basic chromosome number in the majority of Indian taxa (belonging to subgenus Curcuma) is x = 7; published counts correspond to 6x, 9x, 11x, 12x and 15x ploidy levels. Only a few species-specific C-values were found, but karyological and/or flow cytometric data may support taxonomic decisions in some species alliances with morphological similarities. Close evolutionary relationships among some cytotypes are suggested based on the similarity in homoploid genome sizes and geographical grouping. A new species combination, Curcuma scaposa (Nimmo) Škorničk. & M. Sabu, comb. nov., is proposed. PMID:17686760

Associations between age, body size and nephron number with individual glomerular volumes in urban West African males.

PubMed

McNamara, Bridgette J; Diouf, Boucar; Hughson, Michael D; Hoy, Wendy E; Bertram, John F

2009-05-01

Glomerulomegaly has been associated with an increased risk of renal disease. Few reports have investigated the heterogeneity of glomerular size within kidneys and associated risk factors. This study measured the individual glomerular volume (IGV) of 720 non-sclerotic glomeruli in kidneys of adult West African males, and investigated associations of IGV with age, total glomerular (nephron) number and body surface area (BSA). IGVs were determined in the kidneys of 24 Senegalese males from two age groups (12 subjects aged 20- 30 years and 12 subjects aged 50-70 years). Subjects were randomly chosen at autopsies performed at Le Dantec Hospital in Dakar. Volumes of 30 glomeruli per subject were determined using the disector/Cavalieri stereological method. IGVs ranged from 1.31 x 10(6) microm3 to 12.40 x 10(6) microm3 (a 9.4-fold variation). IGV varied up to 5.3-fold within single kidneys. The trimmed range of IGV within subjects (10th to 90th percentile of IGV) was directly correlated with median glomerular size. The mean and standard deviation (SD) of IGV did not differ significantly between age groups or between subjects with higher (> or =1.78 m2) and lower BSA (<1.78 m2). In older subjects the SD of IGV was significantly and directly correlated with BSA. Kidneys with less than 1 million nephrons had significantly larger mean IGV than kidneys with more than 1 million nephrons, and the trimmed range of IGVs within subjects was inversely correlated with total glomerular number. There was a considerable variation in IGV within kidneys of Senegalese males at autopsy. The heterogeneity of IGV was increased in association with low nephron number and increased BSA, with more pronounced effects in older subjects.

Seed predators exert selection on the subindividual variation of seed size.

PubMed

Sobral, M; Guitián, J; Guitián, P; Larrinaga, A R

2014-07-01

Subindividual variation among repeated organs in plants constitutes an overlooked level of variation in phenotypic selection studies, despite being a major component of phenotypic variation. Animals that interact with plants could be selective agents on subindividual variation. This study examines selective pressures exerted during post-dispersal seed predation and germination on the subindividual variation of seed size in hawthorn (Crataegus monogyna). With a seed offering experiment and a germination test, we estimated phenotypic selection differentials for average and subindividual variation of seed size due to seed predation and germination. Seed size affects germination, growth rate and the probability of an individual seed of escaping predation. Longer seeds showed higher germination rates, but this did not result in significant selection on phenotypes of the maternal trees. On the other hand, seed predators avoided wider seeds, and by doing so exerted phenotypic selection on adult average and subindividual variation of seed size. The detected selection on subindividual variation suggests that the levels of phenotypic variation within individual plants may be, at least partly, the adaptive consequence of animal-mediated selection. © 2013 German Botanical Society and The Royal Botanical Society of the Netherlands.

Individualized statistical learning from medical image databases: application to identification of brain lesions.

PubMed

Erus, Guray; Zacharaki, Evangelia I; Davatzikos, Christos

2014-04-01

This paper presents a method for capturing statistical variation of normal imaging phenotypes, with emphasis on brain structure. The method aims to estimate the statistical variation of a normative set of images from healthy individuals, and identify abnormalities as deviations from normality. A direct estimation of the statistical variation of the entire volumetric image is challenged by the high-dimensionality of images relative to smaller sample sizes. To overcome this limitation, we iteratively sample a large number of lower dimensional subspaces that capture image characteristics ranging from fine and localized to coarser and more global. Within each subspace, a "target-specific" feature selection strategy is applied to further reduce the dimensionality, by considering only imaging characteristics present in a test subject's images. Marginal probability density functions of selected features are estimated through PCA models, in conjunction with an "estimability" criterion that limits the dimensionality of estimated probability densities according to available sample size and underlying anatomy variation. A test sample is iteratively projected to the subspaces of these marginals as determined by PCA models, and its trajectory delineates potential abnormalities. The method is applied to segmentation of various brain lesion types, and to simulated data on which superiority of the iterative method over straight PCA is demonstrated. Copyright © 2014 Elsevier B.V. All rights reserved.

Altitudinal variation of demographic life-history traits does not mimic latitudinal variation in natterjack toads (Bufo calamita).

PubMed

Oromi, Neus; Sanuy, Delfi; Sinsch, Ulrich

2012-02-01

In anuran amphibians, age- and size-related life-history traits vary along latitudinal and altiudinal gradients. In the present study, we tested the hypothesis that altitudinal and latitudinal effects cause similar responses by assessing demographic life-history traits in nine Bufo calamita populations inhabiting elevations from sea level to 2270 m. Skeletochronologically determined age at maturity and longevity increased at elevations exceeding 2000 m, but female potential reproductive lifespan (PRLS) did not increase with altitude, as it did with latitude. Integrating the available evidence, it was found that lifetime fecundity of natterjacks decreased at the upper altitudinal range because PRLS was about the same as in lowland populations but females were smaller. In contrast, small size of northern females was compensated for by increased PRLS which minimised latitudinal variation of lifetime fecundity. Thus, this study provides evidence that altitudinal effects on life-history traits do not mimic latitudinal effects. Life-history trait variation along the altitudinal gradient seems to respond directly to the shortening of the annual activity period. As there is no evidence for increasing mortality in highland populations, reduced lifetime fecundity may be the ultimate reason for the natterjacks' inability to colonise elevations exceeding 2500 m. Copyright © 2011 Elsevier GmbH. All rights reserved.

Individualized Statistical Learning from Medical Image Databases: Application to Identification of Brain Lesions

PubMed Central

Erus, Guray; Zacharaki, Evangelia I.; Davatzikos, Christos

2014-01-01

This paper presents a method for capturing statistical variation of normal imaging phenotypes, with emphasis on brain structure. The method aims to estimate the statistical variation of a normative set of images from healthy individuals, and identify abnormalities as deviations from normality. A direct estimation of the statistical variation of the entire volumetric image is challenged by the high-dimensionality of images relative to smaller sample sizes. To overcome this limitation, we iteratively sample a large number of lower dimensional subspaces that capture image characteristics ranging from fine and localized to coarser and more global. Within each subspace, a “target-specific” feature selection strategy is applied to further reduce the dimensionality, by considering only imaging characteristics present in a test subject’s images. Marginal probability density functions of selected features are estimated through PCA models, in conjunction with an “estimability” criterion that limits the dimensionality of estimated probability densities according to available sample size and underlying anatomy variation. A test sample is iteratively projected to the subspaces of these marginals as determined by PCA models, and its trajectory delineates potential abnormalities. The method is applied to segmentation of various brain lesion types, and to simulated data on which superiority of the iterative method over straight PCA is demonstrated. PMID:24607564

Diversity of the Arabidopsis mitochondrial genome occurs via nuclear-controlled recombination activity.

PubMed

Arrieta-Montiel, Maria P; Shedge, Vikas; Davila, Jaime; Christensen, Alan C; Mackenzie, Sally A

2009-12-01

The plant mitochondrial genome is recombinogenic, with DNA exchange activity controlled to a large extent by nuclear gene products. One nuclear gene, MSH1, appears to participate in suppressing recombination in Arabidopsis at every repeated sequence ranging in size from 108 to 556 bp. Present in a wide range of plant species, these mitochondrial repeats display evidence of successful asymmetric DNA exchange in Arabidopsis when MSH1 is disrupted. Recombination frequency appears to be influenced by repeat sequence homology and size, with larger size repeats corresponding to increased DNA exchange activity. The extensive mitochondrial genomic reorganization of the msh1 mutant produced altered mitochondrial transcription patterns. Comparison of mitochondrial genomes from the Arabidopsis ecotypes C24, Col-0, and Ler suggests that MSH1 activity accounts for most or all of the polymorphisms distinguishing these genomes, producing ecotype-specific stoichiometric changes in each line. Our observations suggest that MSH1 participates in mitochondrial genome evolution by influencing the lineage-specific pattern of mitochondrial genetic variation in higher plants.

Strain Amount Dependent Grain Size and Orientation Developments during Hot Compression of a Polycrystalline Nickel Based Superalloy

PubMed Central

He, Guoai; Tan, Liming; Liu, Feng; Huang, Lan; Huang, Zaiwang; Jiang, Liang

2017-01-01

Controlling grain size in polycrystalline nickel base superalloy is vital for obtaining required mechanical properties. Typically, a uniform and fine grain size is required throughout forging process to realize the superplastic deformation. Strain amount occupied a dominant position in manipulating the dynamic recrystallization (DRX) process and regulating the grain size of the alloy during hot forging. In this article, the high-throughput double cone specimen was introduced to yield wide-range strain in a single sample. Continuous variations of effective strain ranging from 0.23 to 1.65 across the whole sample were achieved after reaching a height reduction of 70%. Grain size is measured to be decreased from the edge to the center of specimen with increase of effective strain. Small misorientation tended to generate near the grain boundaries, which was manifested as piled-up dislocation in micromechanics. After the dislocation density reached a critical value, DRX progress would be initiated at higher deformation region, leading to the refinement of grain size. During this process, the transformations from low angle grain boundaries (LAGBs) to high angle grain boundaries (HAGBs) and from subgrains to DRX grains are found to occur. After the accomplishment of DRX progress, the neonatal grains are presented as having similar orientation inside the grain boundary. PMID:28772514

Genetic variation and bill size dimorphism in a passerine bird, the reed bunting Emberiza schoeniclus.

PubMed

Grapputo, A; Pilastro, A; Marin, G

1998-09-01

In passerine birds morphological differentiation in bill size within species is not commonly observed. Bill size is usually associated with a trophic niche, and strong differences in it may reflect the process of genetic differentiation and, possibly, speciation. We used both mitochondrial DNA (mtDNA) and nuclear microsatellites to study genetic variation between two subspecies of reed bunting, Emberiza schoeniclus schoeniclus and E.s. intermedia, along their distributional boundary in western Europe. These two subspecies are characterized by a high dimorphism in bill size and, although breeding populations of the two subspecies are found very close to each other in northern Italy, apparently no interbreeding occurs. The observed morphological pattern between the two subspecies may be maintained by geographically varying selective forces or, alternatively, may be the result of a long geographical separation followed by a secondary contact. MtDNA sequences of cytochrome b and ND5 (515 bp) showed little variation and did not discriminate between the two subspecies, indicating a divergence time of less than 500 000 years. The analysis of four microsatellite loci suggested a clear, although weak, degree of genetic differentiation in the large- and small-billed populations, as indicated by FST and RST values and genetic distances. The correlation between bill size and genetic distance between populations remained significant after accounting for the geographical distances between sampling localities. Altogether, these results indicate a very recent genetic differentiation between the two bill morphs and suggest that a strong selection for large bills in the southern part of the breeding range is probably involved in maintaining the geographical differentiation of this species.

Predicting nitrogen loading with land-cover composition: how can watershed size affect model performance?

PubMed

Zhang, Tao; Yang, Xiaojun

2013-01-01

Watershed-wide land-cover proportions can be used to predict the in-stream non-point source pollutant loadings through regression modeling. However, the model performance can vary greatly across different study sites and among various watersheds. Existing literature has shown that this type of regression modeling tends to perform better for large watersheds than for small ones, and that such a performance variation has been largely linked with different interwatershed landscape heterogeneity levels. The purpose of this study is to further examine the previously mentioned empirical observation based on a set of watersheds in the northern part of Georgia (USA) to explore the underlying causes of the variation in model performance. Through the combined use of the neutral landscape modeling approach and a spatially explicit nutrient loading model, we tested whether the regression model performance variation over the watershed groups ranging in size is due to the different watershed landscape heterogeneity levels. We adopted three neutral landscape modeling criteria that were tied with different similarity levels in watershed landscape properties and used the nutrient loading model to estimate the nitrogen loads for these neutral watersheds. Then we compared the regression model performance for the real and neutral landscape scenarios, respectively. We found that watershed size can affect the regression model performance both directly and indirectly. Along with the indirect effect through interwatershed heterogeneity, watershed size can directly affect the model performance over the watersheds varying in size. We also found that the regression model performance can be more significantly affected by other physiographic properties shaping nitrogen delivery effectiveness than the watershed land-cover heterogeneity. This study contrasts with many existing studies because it goes beyond hypothesis formulation based on empirical observations and into hypothesis testing to explore the fundamental mechanism.

49 CFR 231.20 - Variation in size permitted.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 4 2010-10-01 2010-10-01 false Variation in size permitted. 231.20 Section 231.20 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RAILROAD SAFETY APPLIANCE STANDARDS § 231.20 Variation in size permitted. To...

[Variability in the relative abundance, size structure and sex ratio of the dolphinfish Coryphaena hippurus (Pisces: Coryphaenidae) in the Gulf of Tehuantepec, México].

PubMed

Alejo-Plata, Carmen; Gómez, José Luis; Serrano-Guzmán, Saúl J

2014-06-01

Variability in the relative abundance, size structure and sex ratio of the dolphinfish Coryphaena hippurus (Pisces: Coryphaenidae) in the Gulf of Tehuantepec, México. The dolphinfish (Coryphaena hippurus), is an oceanic epipelagic fish found worldwide in tropical and subtropical waters, with a high dispersal capability via large-scale migrations. This fast-swimming top-level predator is abundant in the Gulf of Tehuantepec, where it is caught incidentally by artisanal fisheries, and represents a target species for both recreational and commercial fisheries in Mexico, Ecuador, Peru and Central America. Nowadays, local fishery information on this species is scarce, thus our objective was to analyze the size structure by sex and the catch-per-unit-effort (CPUE) tendency of dolphinfish caught in the Gulf of Tehuantepec, from 2000 to 2007. For this, fishery catches information was obtained from the artisanal fleet, at six landing sites in the Gulf, and the sex ratio, fork length (FL) and the catch per unit effort (CPUE) were estimated. From all sampling sites, a total of 3 494 females, and 3 877 males were obtained, and dolphinfish size as fork length (FL) ranged from 20.5 to 152cm. Fish size ranged from 25.5 to 148cm furcal length (FL) in males, and 20.5 to 129cm FL in females. The sex ratio (males:females) was 1:1, except in April-May (1:1.5, p < 0.05) and November (1:0.5, p < 0.05). The sex ratio at different size classes showed a significant bias towards females at smaller sizes (< 75cm FL), whereas the males were predominant in larger size classes (> 100cm FL). The size structure was bimodal, with a variation in the size average; the modes were defined as the small group (FL = 50-55cm) and the large size group (FL = 100-110cm). The CPUE showed seasonal changes: values were high for the November-December period, and values were lower for July-August. The seasonal and inter annual variation in the abundance of dolphinfish is probably related to a pre-spawning migration in close relation to the rain-drought regime characteristic of the region, and the associated wind upwelling season of "Tehuanos" in the Gulf of Tehuantepec.

Identification of human-induced perturbations in Daya Bay, China: Evidence from plankton size structure

NASA Astrophysics Data System (ADS)

Ma, Yan'e.; Ke, Zhixin; Huang, Liangmin; Tan, Yehui

2014-01-01

Plankton size structures were investigated based on estimated individual biovolumes at six typical stations of Daya Bay in the summer (August 2010) and winter (January 2011). The biomass size distribution (BSD) and the number size spectra (NSS) of plankton were established to analyze plankton size structures from taxonomic and ataxonomic perspectives, respectively. In Daya Bay, the phytoplankton individual biovolume was in the range of 64-496,757 μm3, and the zooplankton individual biovolume was in the range of 1.15×106-5.23×1011 μm3. The average biomasses of phytoplankton and zooplankton were 1.60 mg L-1 and 1.19 mg L-1 in the summer, and .42 mg L-1 and .35 mg L-1 in the winter, respectively. The ranges of the NSS slope were -1.94 to -.75, -2.60 to -.69, and -2.11 to -1.64 for phytoplankton, zooplankton, and total plankton, respectively. The ranges of the NSS intercepts were 13.17 to 23.97, -3.19 to 38.88, and 20.14 to 27.86 for phytoplankton, zooplankton, and total plankton, respectively. Our results indicate that the thermal water discharge from nuclear power plants, aquaculture and riverine nutrients significantly influenced the BSD and NSS patterns of plankton in Daya Bay. Moreover, the influence of aquaculture was more significant in the summer, and the influence of thermal water discharge was more significant in the winter. In general, a steeper NSS slope usually suggested more human-induced perturbations. The NSS parameters well reflected the horizontal variations of the environmental characteristics between these stations.

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

Zhang, Y; Giebeler, A; Mascia, A

Purpose: To quantitatively evaluate dosimetric consequence of spot size variations and validate beam-matching criteria for commissioning a pencil beam model for multiple treatment rooms. Methods: A planning study was first conducted by simulating spot size variations to systematically evaluate dosimetric impact of spot size variations in selected cases, which was used to establish the in-air spot size tolerance for beam matching specifications. A beam model in treatment planning system was created using in-air spot profiles acquired in one treatment room. These spot profiles were also acquired from another treatment room for assessing the actual spot size variations between the twomore » treatment rooms. We created twenty five test plans with targets of different sizes at different depths, and performed dose measurement along the entrance, proximal and distal target regions. The absolute doses at those locations were measured using ionization chambers at both treatment rooms, and were compared against the calculated doses by the beam model. Fifteen additional patient plans were also measured and included in our validation. Results: The beam model is relatively insensitive to spot size variations. With an average of less than 15% measured in-air spot size variations between two treatment rooms, the average dose difference was −0.15% with a standard deviation of 0.40% for 55 measurement points within target region; but the differences increased to 1.4%±1.1% in the entrance regions, which are more affected by in-air spot size variations. Overall, our single-room based beam model in the treatment planning system agreed with measurements in both rooms < 0.5% within the target region. For fifteen patient cases, the agreement was within 1%. Conclusion: We have demonstrated that dosimetrically equivalent machines can be established when in-air spot size variations are within 15% between the two treatment rooms.« less

Colour dependence of zodiacal light models

NASA Technical Reports Server (NTRS)

Giese, R. H.; Hanner, M. S.; Leinert, C.

1973-01-01

Colour models of the zodiacal light in the ecliptic have been calculated for both dielectric and metallic particles in the sub-micron and micron size range. Two colour ratios were computed, a blue ratio and a red ratio. The models with a size distribution proportional to s to the -2.5 power ds (where s is the particle radius) generally show a colour close to the solar colour and almost independent of elongation. Especially in the blue colour ratio there is generally no significant dependence on the lower cutoff size (0.1-1 micron). The main feature of absorbing particles is a reddening at small elongations. The models for size distributions proportional to s to the -4 power ds show larger departures from solar colour and more variation with model parameters. Colour measurements, including red and near infra-red, therefore are useful to distinguish between flat and steep size spectra and to verify the presence of slightly absorbing particles.

Age-size relationships in all-aged northern hardwoods

Treesearch

Barton M. Blum

1961-01-01

During the summer of 1960, a series of clearcuttings in small patches were made in an old-growth stand of northern hardwoods on the Bartlett Experimental Forest, Bartlett, New Hampshire. This provided an opportunity to observe the variation in ages of a wide range of trees of different sites and species. The annual rings of over 100 stumps were counted in this stand of...

Growth of ponderosa pine by keen tree class.

Treesearch

Philip A. Briegleb

1943-01-01

Every forester who works in the ponderosa pine woods is impressed by the tremendous range in size, quality, age, and thrift of the trees found in the virgin forest. So great is this variation from tree to tree that stand averages mean little to the timber marker trying to select trees of high value and insect risk for cutting, and at the same time reserve for future...

Computed Tomography Status

DOE R&D Accomplishments Database

Hansche, B. D.

1983-01-01

Computed tomography (CT) is a relatively new radiographic technique which has become widely used in the medical field, where it is better known as computerized axial tomographic (CAT) scanning. This technique is also being adopted by the industrial radiographic community, although the greater range of densities, variation in samples sizes, plus possible requirement for finer resolution make it difficult to duplicate the excellent results that the medical scanners have achieved.

Stony Endocarp Dimension and Shape Variation in Prunus Section Prunus

PubMed Central

Depypere, Leander; Chaerle, Peter; Mijnsbrugge, Kristine Vander; Goetghebeur, Paul

2007-01-01

Background and Aims Identification of Prunus groups at subspecies or variety level is complicated by the wide range of variation and morphological transitional states. Knowledge of the degree of variability within and between species is a sine qua non for taxonomists. Here, a detailed study of endocarp dimension and shape variation for taxa of Prunus section Prunus is presented. Method The sample size necessary to obtain an estimation of the population mean with a precision of 5 % was determined by iteration. Two cases were considered: (1) the population represents an individual; and (2) the population represents a species. The intra-individual and intraspecific variation of Prunus endocarps was studied by analysing the coefficients of variance for dimension and shape parameters. Morphological variation among taxa was assessed using univariate statistics. The influence of the time of sampling and the level of hydration on endocarp dimensions and shape was examined by means of pairwise t-tests. In total, 14 endocarp characters were examined for five Eurasian plum taxa. Key Results All linear measurements and index values showed a low or normal variability on the individual and species level. In contrast, the parameter ‘Vertical Asymmetry’ had high coefficients of variance for one or more of the taxa studied. Of all dimension and shape parameters studied, only ‘Triangle’ differed significantly between mature endocarps of P. insititia sampled with a time difference of 1 month. The level of hydration affected endocarp dimensions and shape significantly. Conclusions Index values and the parameters ‘Perimeter’, ‘Area’, ‘Triangle’, ‘Ellipse’, ‘Circular’ and ‘Rectangular’, based on sample sizes and coefficients of variance, were found to be most appropriate for further taxonomic analysis. However, use of one, single endocarp parameter is not satisfactory for discrimination between Eurasian plum taxa, mainly because of overlapping ranges. Before analysing dried endocarps, full hydration is recommended, as this restores the original dimensions and shape. PMID:17965026

Ecological context of the evolution of self-pollination in Clarkia xantiana: population size, plant communities, and reproductive assurance.

PubMed

Moeller, David A; Geber, Monica A

2005-04-01

The repeated evolutionary transition from outcrossing to self-pollination in flowering plants has been suggested to occur because selfing provides reproductive assurance. Reports from biogeographical and ecological surveys indicate that selfing taxa are often associated with stressful and ephemeral environments, situations in which plant abundance is low (e.g., Baker's law) and with novel plant communities, however experimental tests of ecological hypotheses are few. In this study, we examined the ecological context of selection on mating system traits (herkogamy and protandry) in a California annual, Clarkia xantiana, where natural selfing populations differ from outcrossing populations in that they are often of small size or low density and occur mainly outside the range of pollinator-sharing congeners. We constructed artificial populations of plants with broad genetic variation in floral traits and manipulated two ecological factors, plant population size, and the presence versus absence of pollinator-sharing congeners, in the center of the geographic range of outcrossing populations. We found evidence for context-dependent selection on herkogamy and protandry via female fitness in which reduced traits, which promote autonomous selfing, were favored in small populations isolated from congeners whereas selection was comparatively weak in large populations or when congeners were present. In small, isolated populations, the fertility of plants with low herkogamy or protandry was elevated by 66% and 58%, respectively, compared to those with high herkogamy or protandry. The presence of pollinator-sharing congeners augmented bee visitation rates to C. xantiana flowers by 47% for all bees and by 93% for pollen specialists. By facilitating pollinator visitation, congeners mitigated selection on mating system traits in small populations, where outcross mating success is often low (the Allee effect). We also found support for the hypothesis that pollinator availability directly influenced variation in the strength of selection on herkogamy among populations. The striking parallels between our experimental results and patterns of variation in ecological factors across the geographic range of outcrossing and selfing populations suggest that reproductive assurance may play a central role in directing mating system evolution in C. xantiana.

Modeling intersubject variability of bronchial doses for inhaled radon progeny.

PubMed

Hofmann, Werner; Winkler-Heil, Renate; Hussain, Majid

2010-10-01

The main sources of intersubject variations considered in the present study were: (1) size and structure of nasal and oral passages, affecting extrathoracic deposition and, in further consequence, the fraction of the inhaled activity reaching the bronchial region; (2) size and asymmetric branching of the human bronchial airway system, leading to variations of diameters, lengths, branching angles, etc.; (3) respiratory parameters, such as tidal volume, and breathing frequency; (4) mucociliary clearance rates; and (5) thickness of the bronchial epithelium and depth of target cells, related to airway diameters. For the calculation of deposition fractions, retained surface activities, and bronchial doses, parameter values were randomly selected from their corresponding probability density functions, derived from experimental data, by applying Monte Carlo methods. Bronchial doses, expressed in mGy WLM-1, were computed for specific mining conditions, i.e., for defined size distributions, unattached fractions, and physical activities. Resulting bronchial dose distributions could be approximated by lognormal distributions. Geometric standard deviations illustrating intersubject variations ranged from about 2 in the trachea to about 7 in peripheral bronchiolar airways. The major sources of the intersubject variability of bronchial doses for inhaled radon progeny are the asymmetry and variability of the linear airway dimensions, the filtering efficiency of the nasal passages, and the thickness of the bronchial epithelium, while fluctuations of the respiratory parameters and mucociliary clearance rates seem to compensate each other.

In vivo bone strain in the mandibular corpus of Sapajus during a range of oral food processing behaviors.

PubMed

Ross, Callum F; Iriarte-Diaz, Jose; Reed, David A; Stewart, Thomas A; Taylor, Andrea B

2016-09-01

It has been hypothesized that mandibular corpus morphology of primates is related to the material properties of the foods that they chew. However, chewing foods with different material properties is accompanied by low levels of variation in mandibular strain patterns in macaques. We hypothesized that if variation in primate mandible form reflects adaptations to feeding on foods with different material and geometric properties, then this variation will be driven primarily by differences in oral food processing behavior rather than differences in chewing per se. To test this hypothesis, we recorded in vivo bone strain data from the lateral and medial surfaces of the mandibular corpus during complete feeding sequences in three adult male Sapajus as they fed on foods with a range of sizes and material properties. We assessed whether variation in mandibular corpus strain regimes is associated with variation in feeding behaviors and/or chewing on different foods, and we quantified the relative variation in mandibular corpus strain regimes associated with chewing on foods of different material properties versus a range of oral food processing behaviors (incisor, premolar, and molar biting; pulling on incisors; mastication). Feeding behavior had a significant effect on mandibular corpus strain regimes, as did chewing side and the cycle number in a feeding sequence. However, food type had weaker effects and usually only through interaction effects with chewing side and/or cycle type. Strain regimes varied most across different chew sides, then across different behaviors, and lastly between mastication cycles on different foods. Strain magnitudes associated with premolar, molar, and incisor biting were larger than those recorded during mastication. These data suggest that intra- and inter-specific variation in mandible morphology is a trade-off between performance requirements of different oral food processing behaviors and of variation in chewing side, with direct effects of food type being less important. Copyright © 2016 Elsevier Ltd. All rights reserved.

WE-D-17A-02: Evaluation of a Two-Dimensional Optical Dosimeter On Measuring Lateral Profiles of Proton Pencil Beams

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

Hsi, W; Lee, T; Schultz, T

Purpose: To evaluate the accuracy of a two-dimensional optical dosimeter on measuring lateral profiles for spots and scanned fields of proton pencil beams. Methods: A digital camera with a color image senor was utilized to image proton-induced scintillations on Gadolinium-oxysulfide phosphor reflected by a stainless-steel mirror. Intensities of three colors were summed for each pixel with proper spatial-resolution calibration. To benchmark this dosimeter, the field size and penumbra for 100mm square fields of singleenergy pencil-scan protons were measured and compared between this optical dosimeter and an ionization-chamber profiler. Sigma widths of proton spots in air were measured and compared betweenmore » this dosimeter and a commercial optical dosimeter. Clinical proton beams with ranges between 80 mm and 300 mm at CDH proton center were used for this benchmark. Results: Pixel resolutions vary 1.5% between two perpendicular axes. For a pencil-scan field with 302 mm range, measured field sizes and penumbras between two detection systems agreed to 0.5 mm and 0.3 mm, respectively. Sigma widths agree to 0.3 mm between two optical dosimeters for a proton spot with 158 mm range; having widths of 5.76 mm and 5.92 mm for X and Y axes, respectively. Similar agreements were obtained for others beam ranges. This dosimeter was successfully utilizing on mapping the shapes and sizes of proton spots at the technical acceptance of McLaren proton therapy system. Snow-flake spots seen on images indicated the image sensor having pixels damaged by radiations. Minor variations in intensity between different colors were observed. Conclusions: The accuracy of our dosimeter was in good agreement with other established devices in measuring lateral profiles of pencil-scan fields and proton spots. A precise docking mechanism for camera was designed to keep aligned optical path while replacing damaged image senor. Causes for minor variations between emitted color lights will be investigated.« less

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

Kim, C; Seduk, J; Yang, T

Purpose: A prototype actives scanning beam delivery system was designed, manufactured and installed as a part of the Korea Heavy Ion Medical Accelerator Project. The prototype system includes the most components for steering, modulating, detecting incident beam to patient. The system was installed in MC-50 cyclotron beam line and tested to extract the normal operation conditions. Methods: The commissioning process was completed by using 45 MeV of proton beam. To measure the beam position accuracy along the scanning magnet power supply current, 25 different spots were scanning and measured. The scanning results on GaF film were compared with the irradiationmore » plan. Also, the beam size variation and the intensity reduction using range shifter were measured and analyzed. The results will be used for creating a conversion factors for asymmetric behavior of scanning magnets and a dose compensation factor for longitudinal direction. Results: The results show asymmetry operations on both scanning × and y magnet. In case of scanning magnet × operation, the current to position conversion factors were measured 1.69 mm/A for positive direction and 1.74 mm/A for negative direction. The scanning magnet y operation shows 1.38mm/A and 1.48 mm/A for both directions. The size of incoming beam which was 18 mm as sigma becomes larger up to 55 mm as sigma while using 10 mm of the range shifter plate. As the beam size becomes large, the maximum intensity of the was decreased. In case of using 10 mm of range shifter, the maximum intensity was only 52% compared with no range shifter insertion. Conclusion: For the appropriate operation of the prototype active scanning system, the commissioning process were performed to measure the beam characteristics variation. The obtained results would be applied on the irradiation planning software for more precise dose delivery using the active scanning system.« less

Comparison of hand use and forelimb posture during vertical climbing in mountain gorillas (Gorilla beringei beringei) and chimpanzees (Pan troglodytes).

PubMed

Neufuss, Johanna; Robbins, Martha M; Baeumer, Jana; Humle, Tatyana; Kivell, Tracy L

2017-12-01

Studies on grasping and limb posture during arboreal locomotion in great apes in their natural environment are scarce and thus, attempts to correlate behavioral and habitat differences with variation in morphology are limited. The aim of this study is to compare hand use and forelimb posture during vertical climbing in wild, habituated mountain gorillas (Gorilla beringei beringei) and semi-free-ranging chimpanzees (Pan troglodytes) to assess differences in the climbing styles that may relate to variation in hand or forelimb morphology and body size. We investigated hand use and forelimb posture during both ascent and descent vertical climbing in 15 wild mountain gorillas and eight semi-free-ranging chimpanzees, using video records obtained ad libitum. In both apes, forelimb posture was correlated with substrate size during both ascent and descent climbing. While climbing, both apes used power grips and diagonal power grips, including three different thumb postures. Mountain gorillas showed greater ulnar deviation of the wrist during vertical descent than chimpanzees, and the thumb played an important supportive role when gorillas vertically descended lianas. We found that both apes generally had the same grip preferences and used similar forelimb postures on supports of a similar size, which is consistent with their overall similarity in hard and soft tissue morphology of the hand and forelimb. However, some species-specific differences in morphology appear to elicit slightly different grasping strategies during vertical climbing between mountain gorillas and chimpanzees. © 2017 Wiley Periodicals, Inc.

Site Fidelity in Space Use by Spider Monkeys (Ateles geoffroyi) in the Yucatan Peninsula, Mexico

PubMed Central

Ramos-Fernandez, Gabriel; Smith Aguilar, Sandra E.; Schaffner, Colleen M.; Vick, Laura G.; Aureli, Filippo

2013-01-01

Animal home ranges may vary little in their size and location in the short term but nevertheless show more variability in the long term. We evaluated the degree of site fidelity of two groups of spider monkeys (Ateles geoffroyi) over a 10- and 13-year period, respectively, in the northeastern Yucatan peninsula, Mexico. We used the Local Convex Hull method to estimate yearly home ranges and core areas (defined as the 60% probability contour) for the two groups. Home ranges varied from 7.7 to 49.6 ha and core areas varied from 3.1 to 9.2 ha. We evaluated the degree of site fidelity by quantifying the number of years in which different areas were used as either home ranges or core areas. Large tracts were used only as home ranges and only for a few years, whereas small areas were used as either core area or home range for the duration of the study. The sum of the yearly core areas coincided partially with the yearly home ranges, indicating that home ranges contain areas used intermittently. Home ranges, and especially core areas, contained a higher proportion of mature forest than the larger study site as a whole. Across years and only in one group, the size of core areas was positively correlated with the proportion of adult males in the group, while the size of home ranges was positively correlated with both the proportion of males and the number of tree species included in the diet. Our findings suggest that spider monkey home ranges are the result of a combination of long-term site fidelity and year-to-year use variation to enable exploration of new resources. PMID:23675427

Comparative biology of the crab Goniopsis cruentata: geographic variation of body size, sexual maturity, and allometric growth

NASA Astrophysics Data System (ADS)

de Lira, José Jonathas Pereira Rodrigues; Calado, Tereza Cristina dos Santos; Rezende, Carla Ferreira; Silva, José Roberto Feitosa

2015-12-01

Geographic variation of phenotypic traits is common across species and is often associated with variation in environmental conditions. Here, we found larger bodies and larger size at maturity in a northward, lower latitude population of the crab Goniopsis cruentata, which inhabits a hotter, drier environment in comparison with a southward, higher latitude population. Furthermore, the juvenile male gonopods grow more relative to body size in the population characterized by maturation at a smaller size. In contrast, the female abdomen widens at a higher rate among the late maturing population. These results provide further evidence that local environmental conditions play a role in phenotypic variation between populations inhabiting different latitudes. Moreover, they also show that variation in size at maturity and body size can lead to divergent allometric patterns of sexual characteristics that can have a sex-specific response.

Effect of porosity variation on the electrochemical behavior of vertically aligned multi-walled carbon nanotubes.

PubMed

Raut, Akshay S; Parker, Charles B; Stoner, Brian R; Glass, Jeffrey T

2012-06-01

Electrochemical charge storage characteristics of vertically aligned multi-walled carbon nanotubes (MWCNTs) as a function of varying diameter and spacing are reported. It was observed that the specific capacitance of the MWCNTs increased as both diameter and inter-tube spacing decreased. The MWCNT films with 229 nm inter-MWCNT spacing exhibited specific capacitance of 228 F/g versus 70 F/g for 506 nm spacing, when tested in a non-aqueous electrolyte. Further, a trend in specific capacitance versus pore size is proposed. Coupled with previously reported trends observed in the sub-10 nm pore size regime, this is expected to offer better understanding of electrochemical behavior of porous carbon materials over a wide range of pore sizes.

Effect of Feedstock Size and its Distribution on the Properties of Detonation Sprayed Coatings

NASA Astrophysics Data System (ADS)

Suresh Babu, P.; Rao, D. S.; Rao, G. V. N.; Sundararajan, G.

2007-06-01

The detonation spraying is one of the most promising thermal spray variants for depositing wear and corrosion resistant coatings. The ceramic (Al2O3), metallic (Ni-20 wt%Cr) , and cermets (WC-12 wt%Co) powders that are commercially available were separated into coarser and finer size ranges with relatively narrow size distribution by employing centrifugal air classifier. The coatings were deposited using detonation spray technique. The effect of particle size and its distribution on the coating properties were examined. The surface roughness and porosity increased with increasing powder particle size for all the coatings consistently. The feedstock size was also found to influence the phase composition of Al2O3 and WC-Co coatings; however does not influence the phase composition of Ni-Cr coatings. The associated phase change and %porosity of the coatings imparted considerable variation in the coating hardness, fracture toughness, and wear properties. The fine and narrow size range WC-Co coating exhibited superior wear resistance. The coarse and narrow size distribution Al2O3 coating exhibited better performance under abrasion and sliding wear modes however under erosion wear mode the as-received Al2O3 coating exhibited better performance. In the case of metallic (Ni-Cr) coatings, the coatings deposited using coarser powder exhibited marginally lower-wear rate under abrasion and sliding wear modes. However, under erosion wear mode, the coating deposited using finer particle size exhibited considerably lower-wear rate.

Axial Length Variation Impacts on Superficial Retinal Vessel Density and Foveal Avascular Zone Area Measurements Using Optical Coherence Tomography Angiography.

PubMed

Sampson, Danuta M; Gong, Peijun; An, Di; Menghini, Moreno; Hansen, Alex; Mackey, David A; Sampson, David D; Chen, Fred K

2017-06-01

To evaluate the impact of image magnification correction on superficial retinal vessel density (SRVD) and foveal avascular zone area (FAZA) measurements using optical coherence tomography angiography (OCTA). Participants with healthy retinas were recruited for ocular biometry, refraction, and RTVue XR Avanti OCTA imaging with the 3 × 3-mm protocol. The foveal and parafoveal SRVD and FAZA were quantified with custom software before and after correction for magnification error using the Littman and the modified Bennett formulae. Relative changes between corrected and uncorrected SRVD and FAZA were calculated. Forty subjects were enrolled and the median (range) age of the participants was 30 (18-74) years. The mean (range) spherical equivalent refractive error was -1.65 (-8.00 to +4.88) diopters and mean (range) axial length was 24.42 mm (21.27-28.85). Images from 13 eyes were excluded due to poor image quality leaving 67 for analysis. Relative changes in foveal and parafoveal SRVD and FAZA after correction ranged from -20% to +10%, -3% to +2%, and -20% to +51%, respectively. Image size correction in measurements of foveal SRVD and FAZA was greater than 5% in 51% and 74% of eyes, respectively. In contrast, 100% of eyes had less than 5% correction in measurements of parafoveal SRVD. Ocular biometry should be performed with OCTA to correct image magnification error induced by axial length variation. We advise caution when interpreting interocular and interindividual comparisons of SRVD and FAZA derived from OCTA without image size correction.

Pore-Scale Modeling of Pore Structure Effects on P-Wave Scattering Attenuation in Dry Rocks

PubMed Central

Li, Tianyang; Qiu, Hao; Wang, Feifei

2015-01-01

Underground rocks usually have complex pore system with a variety of pore types and a wide range of pore size. The effects of pore structure on elastic wave attenuation cannot be neglected. We investigated the pore structure effects on P-wave scattering attenuation in dry rocks by pore-scale modeling based on the wave theory and the similarity principle. Our modeling results indicate that pore size, pore shape (such as aspect ratio), and pore density are important factors influencing P-wave scattering attenuation in porous rocks, and can explain the variation of scattering attenuation at the same porosity. From the perspective of scattering attenuation, porous rocks can safely suit to the long wavelength assumption when the ratio of wavelength to pore size is larger than 15. Under the long wavelength condition, the scattering attenuation coefficient increases as a power function as the pore density increases, and it increases exponentially with the increase in aspect ratio. For a certain porosity, rocks with smaller aspect ratio and/or larger pore size have stronger scattering attenuation. When the pore aspect ratio is larger than 0.5, the variation of scattering attenuation at the same porosity is dominantly caused by pore size and almost independent of the pore aspect ratio. These results lay a foundation for pore structure inversion from elastic wave responses in porous rocks. PMID:25961729

Tissue-specific methylation differences and cognitive function in fragile X premutation females

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

Allingham-Hawkins, D.J.; Babul, R.; Chitayat, D.

1996-08-09

Tissue-specific variation in (CGG){sub n} repeat size and methylation status of the FMR1 gene was investigated in 17 female premutation carriers. Minor variation in premutation repeat size among leukocyte, lymphoblast, and fibroblast tissues was noted in some subjects. One subject exhibited a premutation size allele of (CGG){sub 64} in leukocyte and fibroblast tissues by polymerase chain reaction analysis but a normal-size allele of (CGG){sub 46} in lymphoblast cells, suggesting low-level mosaicism in blood and clonality of the lymphoblast cell line. Six subjects exhibited differences in methylation pattern between leukocytes and lymphoblasts but not between leukocytes and fibroblasts, whereas 2 subjectsmore » showed large differences in methylation pattern between leukocytes and fibroblasts. Cognitive function was studied in 14 subjects using the Wechsler Adult Intelligence Scale-Revised. Mean Verbal and Performance IQs were well within the average range as was the mean Full Scale IQ; nevertheless, a trend toward lower Performance IQ compared with Verbal IQ was observed. No significant correlation was apparent between Full Scale IQ and (CGG){sub n} repeat size; however, a significant positive correlation was observed between Full Scale IQ and the proportion of the active X carrying the normal FMR1 allele in fibroblasts but not in leukocytes or lymphoblasts. 24 refs., 1 fig., 2 tabs.« less

Synthesis, characterization, and ion-exchange properties of colloidal zeolite nanocrystals

NASA Astrophysics Data System (ADS)

Jawor, Anna; Jeong, Byeong-Heon; Hoek, Eric M. V.

2009-10-01

Here, we present physical-chemical properties of Linde type A (LTA) zeolite crystals synthesized via conventional hydrothermal and microwave heating methods. Both heating methods produced LTA crystals that were sub-micron in size, highly negatively charged, super-hydrophilic, and stable when dispersed in water. However, microwave heating produced relatively narrow crystal size distributions, required much shorter heating times, and did not significantly change composition, crystallinity, or surface chemistry. Moreover, microwave heating allowed systematic variation of crystal size by varying heating temperature and time during the crystallization reaction, thus producing a continuous gradient of crystal sizes ranging from about 90 to 300 nm. In ion-exchange studies, colloidal zeolites exhibited excellent sorption kinetics and capacity for divalent metal ions, suggesting their potential for use in water softening, scale inhibition, and scavenging of toxic metal ions from water.

Kepler constraints on planets near hot Jupiters.

PubMed

Steffen, Jason H; Ragozzine, Darin; Fabrycky, Daniel C; Carter, Joshua A; Ford, Eric B; Holman, Matthew J; Rowe, Jason F; Welsh, William F; Borucki, William J; Boss, Alan P; Ciardi, David R; Quinn, Samuel N

2012-05-22

We present the results of a search for planetary companions orbiting near hot Jupiter planet candidates (Jupiter-size candidates with orbital periods near 3 d) identified in the Kepler data through its sixth quarter of science operations. Special emphasis is given to companions between the 21 interior and exterior mean-motion resonances. A photometric transit search excludes companions with sizes ranging from roughly two-thirds to five times the size of the Earth, depending upon the noise properties of the target star. A search for dynamically induced deviations from a constant period (transit timing variations) also shows no significant signals. In contrast, comparison studies of warm Jupiters (with slightly larger orbits) and hot Neptune-size candidates do exhibit signatures of additional companions with these same tests. These differences between hot Jupiters and other planetary systems denote a distinctly different formation or dynamical history.

Variability in the reported energy, total fat and saturated fat contents in fast-food products across ten countries.

PubMed

Ziauddeen, Nida; Fitt, Emily; Edney, Louise; Dunford, Elizabeth; Neal, Bruce; Jebb, Susan A

2015-11-01

Fast foods are often energy dense and offered in large serving sizes. Observational data have linked the consumption of fast foods to an increased risk of obesity and related diseases. We surveyed the reported energy, total fat and saturated fat contents, and serving sizes, of fast-food items from five major chains across ten countries, comparing product categories as well as specific food items available in most countries. MRC Human Nutrition Research, Cambridge, UK. Data for 2961 food and drink products were collected, with most from Canada (n 550) and fewest from the United Arab Emirates (n 106). There was considerable variability in energy and fat contents of fast foods across countries, reflecting both the portfolio of products and serving size variability. Differences in total energy between countries were particularly noted for chicken dishes (649-1197 kJ/100 g) and sandwiches (552-1050 kJ/100g). When comparing the same product between countries variations were consistently observed in total energy and fat contents (g/100 g); for example, extreme variation in McDonald's Chicken McNuggets with 12 g total fat/100 g in Germany compared with 21·1 g/100 g in New Zealand. These cross-country variations highlight the possibility for further product reformulation in many countries to reduce nutrients of concern and improve the nutritional profiles of fast-food products around the world. Standardisation of serving sizes towards the lower end of the range would also help to reduce the risk of overconsumption.

Variability in the reported energy, total fat and saturated fat content in fast food products across ten countries

PubMed Central

Ziauddeen, Nida; Fitt, Emily; Edney, Louise; Dunford, Elizabeth; Neal, Bruce; Jebb, Susan A.

2016-01-01

Objective Fast foods are often energy dense and offered in large serving sizes. Observational data has linked the consumption of fast food to an increased risk of obesity and related diseases. Design We surveyed the reported energy, total fat and saturated fat contents, and serving sizes, of fast food items from five major chains across 10 countries, comparing product categories as well as specific food items available in most countries. Setting MRC Human Nutrition Research (HNR), Cambridge Subjects Data for 2961 food and drink products were collected, with most from Canada (n=550) and fewest from United Arab Emirates (n=106). Results There was considerable variability in energy and fat content of fast food across countries, reflecting both the portfolio of products, and serving size variability. Differences in total energy between countries were particularly noted for chicken dishes (649-1197kJ/100g) and sandwiches (552-1050kJ/100g). When comparing the same product between countries variations were consistently observed in total energy and fat content (g/100g) with extreme variation in McDonald’s Chicken McNuggets with 12g total fat (g/100g) in Germany compared to 21.1g in New Zealand. Conclusions These cross-country variations highlight the possibility for further product reformulation in many countries to reduce nutrients of concern and improve the nutritional profiles of fast food products around the world. Standardisation of serving sizes towards the lower end of the range would also help to reduce the risk of overconsumption. PMID:25702788

Complex pattern of variation in neurocranial ontogeny revealed by CT-scanning.

PubMed

Anzelmo, Marisol; Ventrice, Fernando; Kelmansky, Diana; Sardi, Marina

2018-05-01

The neurocranium of hominid species has been largely studied with reference to the midsagittal plane, with variations being attributed to brain evolution. By contrast, there is limited information on variation in non-midsagittal regions, which are the points of insertion of muscles and bony structures related to mastication. This work aims to analyze ontogenetic changes and sexual dimorphism (SD) in midsagittal and non-midsagittal neurocranial structures from a contemporary human sample comprising 138 computed tomography (CT) cranial images of individuals ranging from infants to adults. Morphology of the vault and the base was assessed by registering landmarks and semilandmarks, which were analyzed by geometric morphometrics, and the endocranial volume (EV). The results of regressions and Kruskal-Wallis test indicate that the major size and shape changes in both midsagittal and non-midsagittal regions occur during infancy and juvenility; shape changes are also associated with an increase in EV. The size of the midsagittal vault, the shape of the non-midsagittal vault and the size of the base show an extension of ontogenetic trajectories. Sexes show similar changes in shape but different changes in size. We conclude that brain growth appears to be an important factor influencing the morphology of the neurocranium, at least during infancy and childhood. Subsequent changes may be attributed to osteogenic activity and the differential growth of the brain lobes. Masticatory-related bony structures and muscles may not be strong enough factors to induce independent modifications in non-midsagittal structures. The small influence of the cranial muscles would explain why the human neurocranium is a quite integrated structure.

Geographic patterns of seed mass are associated with climate factors, but relationships vary between species.

PubMed

Soper Gorden, Nicole L; Winkler, Katharine J; Jahnke, Matthew R; Marshall, Elizabeth; Horky, Joshua; Huddelson, Colton; Etterson, Julie R

2016-01-01

Seed size is a critical life history attribute with fitness effects that cascade throughout the lifespan of plants. Interspecific studies repeatedly report a negative correlation between seed mass and latitude. Yet, despite its importance, little is known about geographic variation in seed size within species' ranges. To improve our understanding of intraspecific geographic variation in seed size, we collected and weighed seeds by maternal line from 8 to 17 populations of seven herbaceous plant species spanning large geographic areas, and measured a dispersal trait, awn length, for two grass species. We examined the overall relationship between seed mass and latitude, then divided the data into species-specific subsets to compare the fit of three models to explain seed mass and awn length: (1) latitude and longitude, (2) long-term climate, and (3) collection-year weather. Like previous work, we found a negative relationship between interspecific seed mass and latitude. However, the best-fit models explaining seed size and awn length differed between individual species and often included significant interaction terms. For all species, the best model was either long-term or collection-year climate data instead of latitude and longitude. Intraspecific geographic patterns for seed traits were remarkably inconsistent, covarying both negatively and positively with temperature and precipitation. The only apparent generalization is that annual species' seed mass corresponded more with collection-year weather while perennial species covaried more with long-term climate. Overall, this study suggests that the scale of climate variation that molds seed traits is highly species-specific. © 2016 Botanical Society of America.

Potential environmental influences on variation in body size and sexual size dimorphism among Arizona populations of the western diamond-backed rattlesnake (Crotalus atrox)

USGS Publications Warehouse

Amarello, Melissa; Nowak, Erica M.; Taylor, Emily N.; Schuett, Gordon W.; Repp, Roger A.; Rosen, Philip C.; Hardy, David L.

2010-01-01

Differences in resource availability and quality along environmental gradients are important influences contributing to intraspecific variation in body size, which influences numerous life-history traits. Here, we examined variation in body size and sexual size dimorphism (SSD) in relation to temperature, seasonality, and precipitation among 10 populations located throughout Arizona of the western diamond-backed rattlesnake (Crotalus atrox). Specifically, in our analyses we addressed the following questions: (i) Are adult males larger in cooler, wetter areas? (ii) Does female body size respond differently to environmental variation? (iii) Is seasonality a better predictor of body size variation? (iv) Is SSD positively correlated with increased resources? We demonstrate that male and female C. atrox are larger in body size in cooler (i.e., lower average annual maximum, minimum, and mean temperature) and wetter areas (i.e., higher average annual precipitation, more variable precipitation, and available surface water). Although SSD in C. atrox appeared to be more pronounced in cooler, wetter areas, this relationship did not achieve statistical significance.

Testing Bergmann's rule and the Rosenzweig hypothesis with craniometric studies of the South American sea lion.

PubMed

Sepúlveda, Maritza; Oliva, Doris; Duran, L René; Urra, Alejandra; Pedraza, Susana N; Majluf, Patrícia; Goodall, Natalie; Crespo, Enrique A

2013-04-01

We tested the validity of Bergmann's rule and Rosenzweig's hypothesis through an analysis of the geographical variation of the skull size of Otaria flavescens along the entire distribution range of the species (except Brazil). We quantified the sizes of 606 adult South American sea lion skulls measured in seven localities of Peru, Chile, Uruguay, Argentina, and the Falkland/Malvinas Islands. Geographical and environmental variables included latitude, longitude, and monthly minimum, maximum, and mean air and ocean temperatures. We also included information on fish landings as a proxy for productivity. Males showed a positive relationship between condylobasal length (CBL) and latitude, and between CBL and the six temperature variables. By contrast, females showed a negative relationship between CBL and the same variables. Finally, female skull size showed a significant and positive correlation with fish landings, while males did not show any relationship with this variable. The body size of males conformed to Bergmann's rule, with larger individuals found in southern localities of South America. Females followed the converse of Bergmann's rule at the intraspecific level, but showed a positive relationship with the proxy for productivity, thus supporting Rosenzweig's hypothesis. Differences in the factors that drive body size in females and males may be explained by their different life-history strategies. Our analyses demonstrate that latitude and temperature are not the only factors that explain spatial variation in body size: others such as food availability are also important for explaining the ecogeographical patterns found in O. flavescens.

Understanding the direction of evolution in Burkholderia glumae through comparative genomics.

PubMed

Lee, Hyun-Hee; Park, Jungwook; Kim, Jinnyun; Park, Inmyoung; Seo, Young-Su

2016-02-01

Members of the genus Burkholderia occupy remarkably diverse niches, with genome sizes ranging from ~3.75 to 11.29 Mbp. The genome of Burkholderia glumae ranges in size from ~5.81 to 7.89 Mbp. Unlike other plant pathogenic bacteria, B. glumae can infect a wide range of monocot and dicot plants. Comparative genome analysis of B. glumae strains can provide insight into genome variation as well as differential features of whole metabolism or pathways between multiple strains of B. glumae infecting the same host. Comparative analysis of complete genomes among B. glumae BGR1, B. glumae LMG 2196, and B. glumae PG1 revealed the largest departmentalization of genes onto separate replicons in B. glumae BGR1 and considerable downsizing of the genome in B. glumae LMG 2196. In addition, the presence of large-scale evolutionary events such as rearrangement and inversion and the development of highly specialized systems were found to be related to virulence-associated features in the three B. glumae strains. This connection may explain why this bacterium broadens its host range and reinforces its interaction with hosts.

Relative gut lengths of coral reef butterflyfishes (Pisces: Chaetodontidae)

NASA Astrophysics Data System (ADS)

Berumen, M. L.; Pratchett, M. S.; Goodman, B. A.

2011-12-01

Variation in gut length of closely related animals is known to generally be a good predictor of dietary habits. We examined gut length in 28 species of butterflyfishes (Chaetodontidae), which encompass a wide range of dietary types (planktivores, omnivores, and corallivores). We found general dietary patterns to be a good predictor of relative gut length, although we found high variation among groups and covariance with body size. The longest gut lengths are found in species that exclusively feed on the living tissue of corals, while the shortest gut length is found in a planktivorous species. Although we tried to control for phylogeny, corallivory has arisen multiple times in this family, confounding our analyses. The butterflyfishes, a speciose family with a wide range of dietary habits, may nonetheless provide an ideal system for future work studying gut physiology associated with specialization and foraging behaviors.

Latitude Variation for Pluto's Crater Distribution

NASA Astrophysics Data System (ADS)

Dwivedi, A. K.; Binzel, R. P.; Earle, A. M.; Singer, K. N.; Stern, A.; Olkin, C.; Weaver, H. A., Jr.; Ennico Smith, K.; Young, L. A.

2017-12-01

The crater population distribution on Pluto and Charon have been studied to infer the size distribution of objects in the Kuiper belt (Singer et al. 2017; submitted). In this talk, we will look at the variation in crater distribution with latitude. To circumvent possible bias effects in the analysis, we focus our analysis on a region having the most consistent imaging resolution afforded by the flyby geometry. The longitudinal extent of our study region is 90E to 150E, and the latitudinal extent is 0°N to 90°N. Our preliminary analysis shows crater population peaks in the latitude range 30°N to 60°N and drops off sharply toward the north pole. Here we describe how we quantify the crater distribution in this region and explore a range of processes for volatile transport over both orbital timescales and perihelion precession timescales, including million year Milankovitch cycles for obliquity oscillations.

Testing the 'island rule' for a tenebrionid beetle (Coleoptera, Tenebrionidae)

NASA Astrophysics Data System (ADS)

Palmer, Miquel

2002-05-01

Insular populations and their closest mainland counterparts commonly display body size differences that are considered to fit the island rule, a theoretical framework to explain both dwarfism and gigantism in isolated animal populations. The island rule is used to explain the pattern of change of body size at the inter-specific level. But the model implicitly makes also a prediction for the body size of isolated populations of a single species. It suggests that, for a hypothetical species covering a wide range of island sizes, there exists a specific island size where this species reaches the largest body size. Body size would be small (in relative terms) in the smallest islets of the species range. It would increase with island size, and reach a maximum at some specific island size. However, additional increases from such a specific island size would instead promote body size reduction, and small (in relative terms) body sizes would be found again on the largest islands. The biogeographical patterns predicted by the island rule have been described and analysed for vertebrates only (mainly mammals), but remain largely untested for insects or other invertebrates. I analyse here the pattern of body size variation between seven isolated insular populations of a flightless beetle, Asida planipennis (Coleoptera, Tenebrionidae). This is an endemic species of Mallorca, Menorca and a number of islands and islets in the Balearic archipelago (western Mediterranean). The study covers seven of the 15 known populations (i.e., there are only 15 islands or islets inhabited by the species). The populations studied fit the pattern advanced above and we could, therefore, extrapolate the island rule to a very different kind of organism. However, the small sample size of some of the populations invites some caution at this early stage.

Interannual Variations in Ecosystem Oxidative Ratio in Croplands, Deciduous Forest, Coniferous Forest, and Early Successional Forest Ecosystems

NASA Astrophysics Data System (ADS)

Masiello, C. A.; Hockaday, W. C.; Gallagher, M. E.; Calligan, L.

2009-12-01

Ecosystem net primary productivity (NPP) can vary significantly with annual variations in precipitation and temperature. These climate variations can also drive changes in plant carbon allocation patterns. Shifting allocation patterns can lead to variation in net ecosystem biochemical stocks (e.g. kg cellulose, lignin, protein, and lipid/ha), which can in turn lead to shifts in ecosystem oxidative ratio (OR). OR is the molar ratio of O2 released : CO2 fixed during biosynthesis. Major plant biochemicals vary substantially in oxidative ratio, ranging from average organic acid OR values of 0.75 to average lipid OR values of 1.37 (Masiello et al., 2008). OR is a basic property of ecosystem biochemistry, and is also an essential variable needed to constrain the size of the terrestrial biospheric carbon sink (Keeling et al., 1996). OR is commonly assumed to be 1.10 (e.g. Prentice et al., 2001), but small variations in net ecosystem OR can drive large errors in estimates of the size of the terrestrial carbon sink (Randerson et al., 2006). We hypothesized that interannual changes in climate may drive interannual variation in ecosystem OR values. Working at Kellogg Biological Station NSF LTER, we measured the annual average OR of coniferous and deciduous forests, an early successional forest, and croplands under both corn and soy. There are clear distinctions between individual ecosystems (e.g., the soy crops have a higher OR than the corn crops, and the coniferous forests have a higher OR than the deciduous forests), but the ecosystems themselves retained remarkably constant annual OR values between 1998 and 2008.

Chromosome sizes of phytoplasmas composing major phylogenetic groups and subgroups.

PubMed

Marcone, C; Neimark, H; Ragozzino, A; Lauer, U; Seemüller, E

1999-09-01

ABSTRACT Chromosome sizes of 71 phytoplasmas belonging to 12 major phylogenetic groups including several of the aster yellows subgroups were estimated from electrophoretic mobilities of full-length chromosomes in pulsed-field gels. Considerable variation in genome size, from 660 to 1,130 kilobases (kb), was observed among aster yellows phytoplasmas. Chromosome size heterogeneity was also observed in the stolbur phytoplasma group (range 860 to 1,350 kb); in this group, isolate STOLF contains the largest chromosome found in a phytoplasma to date. A wide range of chromosome sizes, from 670 to 1,075 kb, was also identified in the X-disease group. The other phytoplasmas examined, which included members of the apple proliferation, Italian alfalfa witches' broom, faba bean phyllody, pigeon pea witches' broom, sugarcane white leaf, Bermuda grass white leaf, ash yellows, clover proliferation, and elm yellows groups, all have chromosomes smaller than 1 megabase, and the size ranges within each of these groups is narrower than in the aster yellows, stolbur, and X-disease groups. The smallest chromosome, approximately 530 kb, was found in two Bermuda grass white leaf phytoplasma isolates. This not only is the smallest mollicute chromosome found to date, but also is the smallest chromosome known for any cell. More than one large DNA band was observed in several phytoplasma preparations. Possible explanations for the occurrence of more than one band may be infection of the host plant by different phytoplasmas, the presence of more than one chromosome in the same organism, or the presence of large extrachromosomal DNA elements.

Validation of a particle tracking analysis method for the size determination of nano- and microparticles

NASA Astrophysics Data System (ADS)

Kestens, Vikram; Bozatzidis, Vassili; De Temmerman, Pieter-Jan; Ramaye, Yannic; Roebben, Gert

2017-08-01

Particle tracking analysis (PTA) is an emerging technique suitable for size analysis of particles with external dimensions in the nano- and sub-micrometre scale range. Only limited attempts have so far been made to investigate and quantify the performance of the PTA method for particle size analysis. This article presents the results of a validation study during which selected colloidal silica and polystyrene latex reference materials with particle sizes in the range of 20 nm to 200 nm were analysed with NS500 and LM10-HSBF NanoSight instruments and video analysis software NTA 2.3 and NTA 3.0. Key performance characteristics such as working range, linearity, limit of detection, limit of quantification, sensitivity, robustness, precision and trueness were examined according to recommendations proposed by EURACHEM. A model for measurement uncertainty estimation following the principles described in ISO/IEC Guide 98-3 was used for quantifying random and systematic variations. For nominal 50 nm and 100 nm polystyrene and a nominal 80 nm silica reference materials, the relative expanded measurement uncertainties for the three measurands of interest, being the mode, median and arithmetic mean of the number-weighted particle size distribution, varied from about 10% to 12%. For the nominal 50 nm polystyrene material, the relative expanded uncertainty of the arithmetic mean of the particle size distributions increased up to 18% which was due to the presence of agglomerates. Data analysis was performed with software NTA 2.3 and NTA 3.0. The latter showed to be superior in terms of sensitivity and resolution.

GPS-tracking and colony observations reveal variation in offshore habitat use and foraging ecology of breeding Sandwich Terns

NASA Astrophysics Data System (ADS)

Fijn, R. C.; de Jong, J.; Courtens, W.; Verstraete, H.; Stienen, E. W. M.; Poot, M. J. M.

2017-09-01

Breeding success of seabirds critically depends on their foraging success offshore. However, studies combining at-sea tracking and visual provisioning observations are scarce, especially for smaller species of seabirds. This study is the first in which breeding Sandwich Terns were tracked with GPS-loggers to collect detailed data on foraging habitat use in four breeding seasons. The maximum home range of individual Sandwich Terns comprised approximately 1900 km2 and the average foraging range was 27 km. Trip durations were on average 135 min with average trip lengths of 67 km. Actual foraging behaviour comprised 35% of the time budget of a foraging trip. Substantial year-to-year variation was found in habitat use and trip variables, yet with the exception of 2012, home range size remained similar between years. Food availability, chick age and environmental conditions are proposed as the main driving factors between inter- and intra-annual variations in trip variables. Our multi-method approach also provided geo-referenced information on prey presence and we conclude that future combining of colony observations and GPS-loggers deployments can potentially provide a near complete insight into the feeding ecology of breeding Sandwich Terns, including the behaviour of birds at sea.

Epigenetic Potential as a Mechanism of Phenotypic Plasticity in Vertebrate Range Expansions.

PubMed

Kilvitis, Holly J; Hanson, Haley; Schrey, Aaron W; Martin, Lynn B

2017-08-01

During range expansions, organisms are often exposed to multiple pressures, including novel enemies (i.e., predators, competitors and/or parasites) and unfamiliar or limited resources. Additionally, small propagule sizes at range edges can result in genetic founder effects and bottlenecks, which can affect phenotypic diversity and thus selection. Despite these obstacles, individuals in expanding populations often thrive at the periphery of a range, and this success may be mediated by phenotypic plasticity. Increasing evidence suggests that epigenetic mechanisms may underlie such plasticity because they allow for more rapid phenotypic responses to novel environments than are possible via the accumulation of genetic variation. Here, we review how molecular epigenetic mechanisms could facilitate plasticity in range-expanding organisms, emphasizing the roles of DNA methylation and other epigenetic marks in the physiological regulatory networks that drive whole-organism performance. We focus on the hypothalamic-pituitary-adrenal (HPA) axis, arguing that epigenetically-mediated plasticity in the regulation of glucocorticoids in particular might strongly impact range expansions. We hypothesize that novel environments release and/or select for epigenetic potential in HPA variation and hence organismal performance and ultimately fitness. © The Author 2017. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: journals.permissions@oup.com.

Rapid Increase in Genome Size as a Consequence of Transposable Element Hyperactivity in Wood-White (Leptidea) Butterflies

PubMed Central

Talla, Venkat; Suh, Alexander; Kalsoom, Faheema; Dincă, Vlad; Vila, Roger; Friberg, Magne; Wiklund, Christer

2017-01-01

Abstract Characterizing and quantifying genome size variation among organisms and understanding if genome size evolves as a consequence of adaptive or stochastic processes have been long-standing goals in evolutionary biology. Here, we investigate genome size variation and association with transposable elements (TEs) across lepidopteran lineages using a novel genome assembly of the common wood-white (Leptidea sinapis) and population re-sequencing data from both L. sinapis and the closely related L. reali and L. juvernica together with 12 previously available lepidopteran genome assemblies. A phylogenetic analysis confirms established relationships among species, but identifies previously unknown intraspecific structure within Leptidea lineages. The genome assembly of L. sinapis is one of the largest of any lepidopteran taxon so far (643 Mb) and genome size is correlated with abundance of TEs, both in Lepidoptera in general and within Leptidea where L. juvernica from Kazakhstan has considerably larger genome size than any other Leptidea population. Specific TE subclasses have been active in different Lepidoptera lineages with a pronounced expansion of predominantly LINEs, DNA elements, and unclassified TEs in the Leptidea lineage after the split from other Pieridae. The rate of genome expansion in Leptidea in general has been in the range of four Mb/Million year (My), with an increase in a particular L. juvernica population to 72 Mb/My. The considerable differences in accumulation rates of specific TE classes in different lineages indicate that TE activity plays a major role in genome size evolution in butterflies and moths. PMID:28981642

Copy Number Variation in Fungi and Its Implications for Wine Yeast Genetic Diversity and Adaptation

PubMed Central

Steenwyk, Jacob L.; Rokas, Antonis

2018-01-01

In recent years, copy number (CN) variation has emerged as a new and significant source of genetic polymorphisms contributing to the phenotypic diversity of populations. CN variants are defined as genetic loci that, due to duplication and deletion, vary in their number of copies across individuals in a population. CN variants range in size from 50 base pairs to whole chromosomes, can influence gene activity, and are associated with a wide range of phenotypes in diverse organisms, including the budding yeast Saccharomyces cerevisiae. In this review, we introduce CN variation, discuss the genetic and molecular mechanisms implicated in its generation, how they can contribute to genetic and phenotypic diversity in fungal populations, and consider how CN variants may influence wine yeast adaptation in fermentation-related processes. In particular, we focus on reviewing recent work investigating the contribution of changes in CN of fermentation-related genes in yeast wine strains and offer notable illustrations of such changes, including the high levels of CN variation among the CUP genes, which confer resistance to copper, a metal with fungicidal properties, and the preferential deletion and duplication of the MAL1 and MAL3 loci, respectively, which are responsible for metabolizing maltose and sucrose. Based on the available data, we propose that CN variation is a substantial dimension of yeast genetic diversity that occurs largely independent of single nucleotide polymorphisms. As such, CN variation harbors considerable potential for understanding and manipulating yeast strains in the wine fermentation environment and beyond. PMID:29520259

Evaluating the influence of laser wavelength and detection stage geometry on optical detection efficiency in a single-particle mass spectrometer

NASA Astrophysics Data System (ADS)

Marsden, Nicholas; Flynn, Michael J.; Taylor, Jonathan W.; Allan, James D.; Coe, Hugh

2016-12-01

Single-particle mass spectrometry (SPMS) is a useful tool for the online study of aerosols with the ability to measure size-resolved chemical composition with a temporal resolution relevant to atmospheric processes. In SPMS, optical particle detection is used for the effective temporal alignment of an ablation laser pulse with the presence of a particle in the ion source, and it gives the option of aerodynamic sizing by measuring the offset of particle arrival times between two detection stages. The efficiency of the optical detection stage has a strong influence on the overall instrument performance. A custom detection laser system consisting of a high-powered fibre-coupled Nd:YAG solid-state laser with a collimated beam was implemented in the detection stage of a laser ablation aerosol particle time-of-flight (LAAP-TOF) single-particle mass spectrometer without major modifications to instrument geometry. The use of a collimated laser beam permitted the construction of a numerical model that predicts the effects of detection laser wavelength, output power, beam focussing characteristics, light collection angle, particle size, and refractive index on the effective detection radius (R) of the detection laser beam. We compare the model predictions with an ambient data set acquired during the Ice in Clouds Experiment - Dust (ICE-D) project. The new laser system resulted in an order-of-magnitude improvement in instrument sensitivity to spherical particles in the size range 500-800 nm compared to a focussed 405 nm laser diode system. The model demonstrates that the limit of detection in terms of particle size is determined by the scattering cross section (Csca) as predicted by Mie theory. In addition, if light is collected over a narrow collection angle, oscillations in the magnitude of Csca with respect to particle diameter result in a variation in R, resulting in large particle-size-dependent variation in detection efficiency across the particle transmission range. This detection bias is imposed on the aerodynamic size distributions measured by the instrument and accounts for some of the detection bias towards sea salt particles in the ambient data set.

Size-dependent characterization of embedded Ge nanocrystals: Structural and thermal properties

NASA Astrophysics Data System (ADS)

Araujo, L. L.; Giulian, R.; Sprouster, D. J.; Schnohr, C. S.; Llewellyn, D. J.; Kluth, P.; Cookson, D. J.; Foran, G. J.; Ridgway, M. C.

2008-09-01

A combination of conventional and synchrotron-based techniques has been used to characterize the size-dependent structural and thermal properties of Ge nanocrystals (NCs) embedded in a silica (a-SiO2) matrix. Ge NC size distributions with four different diameters ranging from 4.0 to 9.0 nm were produced by ion implantation and thermal annealing as characterized with small-angle x-ray scattering and transmission electron microscopy. The NCs were well represented by the superposition of bulklike crystalline and amorphous environments, suggesting the formation of an amorphous layer separating the crystalline NC core and the a-SiO2 matrix. The amorphous fraction was quantified with x-ray-absorption near-edge spectroscopy and increased as the NC diameter decreased, consistent with the increase in surface-to-volume ratio. The structural parameters of the first three nearest-neighbor shells were determined with extended x-ray-absorption fine-structure (EXAFS) spectroscopy and evolved linearly with inverse NC diameter. Specifically, increases in total disorder, interatomic distance, and the asymmetry in the distribution of distances were observed as the NC size decreased, demonstrating that finite-size effects govern the structural properties of embedded Ge NCs. Temperature-dependent EXAFS measurements in the range of 15-300 K were employed to probe the mean vibrational frequency and the variation of the interatomic distance distribution (mean value, variance, and asymmetry) with temperature for all NC distributions. A clear trend of increased stiffness (higher vibrational frequency) and decreased thermal expansion with decreasing NC size was evident, confirming the close relationship between the variation of structural and thermal/vibrational properties with size for embedded Ge NCs. The increase in surface-to-volume ratio and the presence of an amorphous Ge layer separating the matrix and crystalline NC core are identified as the main factors responsible for the observed behavior, with the surrounding a-SiO2 matrix also contributing to a lesser extent. Such results are compared to previous reports and discussed in terms of the influence of the surface-to-volume ratio in objects of nanometer dimensions.

Personal Exposure to Particulate Matter and Endotoxin in California Dairy Workers

NASA Astrophysics Data System (ADS)

Garcia, Johnny

The average number of cows per dairy has increased over the last thirty years, with little known about how this increase may impact occupational exposure. Thirteen California dairies and 226 workers participated in this study throughout the 2008 summer months. Particulate Matter (PM) and endotoxin concentrations were quantified using ambient area based and personal air samplers. Two size fractions were collected, Total Suspended Particulate matter (TSP) and PM 2.5. Differences across dairies were evaluated by placing area based integrated air samplers in established locations on the dairies, e.g. milking parlor, drylot corral, and freestall barns. The workers occupational exposure was quantified using personal air samplers. We analyzed concentrations along with the time workers spent conducting specific job tasks during their shift to identify high exposure job tasks. Biological and chemical analytical methods were employed to ascertain endotoxin concentrations in personal and area based air samples. Recombinant factor C assays (rFC) were used to analyze biologically active endotoxin and gas chromatography coupled with mass spectrometry in tandem (GC-MS/MS) was used to quantify total endotoxin. The PM2.5 concentrations ranged from 2-116 mug/m3 for ambient area concentration and 7-495 mug/m3 for personal concentrations while TSP concentrations ranged from 74-1690 mug/m3 for area ambient concentrations and 191-4950 mug/m3 for personal concentrations. Biologically active endotoxin concentrations in the TSP size fraction from ambient area based samples ranged from 11-2095 EU/m3 and 45-2061 EU/m3 for personal samples. Total endotoxin in the TSP size fraction ranged from 75-10,166 pmol/m3 for area based samples and 34-11,689 pmol/m3 for personal samples. Drylot corrals were found to have higher sample mean concentrations when compared to other locations on the dairies for PM and endotoxin. Re-bedding, of the freestalls, was found to consistently lead to higher personal sample mean concentrations when compared to other tasks performed on dairies for both endotoxin and PM. In mixed effect regression models, regional ambient concentrations of PM 2.5 helped account for variation in PM2.5 concentration outcomes. We found that while upwind and downwind mean concentrations were not significantly different, central mean concentrations were higher than upwind concentration. Variation in TSP levels was largely explained by dairy-level characteristics such as the age of the dairy and number of animals in the drylot corrals and freestall barns. The different locations within the dairy were found to differ in mean concentrations for TSP. Biologically active and total endotoxin concentration variation was explained by meteorological data, wind speed, relative humidity, and dairy waste management practices. Personal exposure levels where found to be higher than area based concentrations for PM and endotoxin. Endotoxin characteristics differed by particle size and location within the dairy. The chain length proportion for endotoxin in the PM 2.5 size fraction was dominated by C12 and C16 in the TSP size fraction.

Predictions and retrodictions of the hierarchical representation of habitat in heterogeneous environments

USGS Publications Warehouse

Kolasa, Jurek; Allen, Craig R.; Sendzimir, Jan; Stow, Craig A.

2012-01-01

Interaction between habitat and species is central in ecology. Habitat structure may be conceived as being hierarchical, where larger, more diverse, portions or categories contain smaller, more homogeneous portions. When this conceptualization is combined with the observation that species have different abilities to relate to portions of the habitat that differ in their characteristics, a number of known patterns can be derived and new patterns hypothesized. We propose a quantitative form of this habitat–species relationship by considering species abundance to be a function of habitat specialization, habitat fragmentation, amount of habitat, and adult body mass. The model reproduces and explains patterns such as variation in rank–abundance curves, greater variation and extinction probabilities of habitat specialists, discontinuities in traits (abundance, ecological range, pattern of variation, body size) among species sharing a community or area, and triangular distribution of body sizes, among others. The model has affinities to Holling's textural discontinuity hypothesis and metacommunity theory but differs from both by offering a more general perspective. In support of the model, we illustrate its general potential to capture and explain several empirical observations that historically have been treated independently.

Parental investment and the optimization of human family size

PubMed Central

Lawson, David W.; Mace, Ruth

2011-01-01

Human reproductive behaviour is marked by exceptional variation at the population and individual level. Human behavioural ecologists propose adaptive hypotheses to explain this variation as shifting phenotypic optima in relation to local socioecological niches. Here we review evidence that variation in fertility (offspring number), in both traditional and modern industrialized populations, represents optimization of the life-history trade-off between reproductive rate and parental investment. While a reliance on correlational methods suggests the true costs of sibling resource competition are often poorly estimated, a range of anthropological and demographic studies confirm that parents balance family size against offspring success. Evidence of optimization is less forthcoming. Declines in fertility associated with modernization are particularly difficult to reconcile with adaptive models, because fertility limitation fails to enhance offspring reproductive success. Yet, considering alternative measures, we show that modern low fertility confers many advantages on offspring, which are probably transmitted to future generations. Evidence from populations that have undergone or initiated demographic transition indicate that these rewards to fertility limitation fall selectively on relatively wealthy individuals. The adaptive significance of modern reproductive behaviour remains difficult to evaluate, but may be best understood in response to rising investment costs of rearing socially and economically competitive offspring. PMID:21199838

Biogeographic patterns in life history traits of the Pan-American sandy beach isopod Excirolana braziliensis

NASA Astrophysics Data System (ADS)

Cardoso, Ricardo S.; Defeo, Omar

2004-11-01

Biogeographic patterns in life history traits of the Pan-American sandy beach isopod Excirolana braziliensis were analyzed to determine latitudinal variations along its distribution, from tropical (9°N) to temperate (39°S) sandy beaches in Atlantic and Pacific oceans. Population features exhibited systematic geographical patterns of variation: (1) an increase in individual sizes and growth rates towards temperate beaches, following an inverse relationship with mean water temperature of the surf zone; (2) a shift from almost continuous to seasonal growth from subtropical to temperate Atlantic beaches and a positive relationship between amplitude of intra-annual growth oscillations and temperature range; (3) a linear decrease in life span and an increase in natural mortality from temperate to subtropical beaches; and (4) an increase in the individual mass-at-size (length-mass relationship) from subtropical to temperate beaches. Analyses discriminated by sex were consistent with the patterns illustrated above. Local effects of temperature and beach morphodynamics are discussed. Our results demonstrate that the population dynamics of E. braziliensis is highly plastic over latitudinal gradients, with large-scale variations in temperature and concurrent environmental variables leading to an adjustment of the phenotype-environment relationship.

A general unified framework to assess the sampling variance of heritability estimates using pedigree or marker-based relationships.

PubMed

Visscher, Peter M; Goddard, Michael E

2015-01-01

Heritability is a population parameter of importance in evolution, plant and animal breeding, and human medical genetics. It can be estimated using pedigree designs and, more recently, using relationships estimated from markers. We derive the sampling variance of the estimate of heritability for a wide range of experimental designs, assuming that estimation is by maximum likelihood and that the resemblance between relatives is solely due to additive genetic variation. We show that well-known results for balanced designs are special cases of a more general unified framework. For pedigree designs, the sampling variance is inversely proportional to the variance of relationship in the pedigree and it is proportional to 1/N, whereas for population samples it is approximately proportional to 1/N(2), where N is the sample size. Variation in relatedness is a key parameter in the quantification of the sampling variance of heritability. Consequently, the sampling variance is high for populations with large recent effective population size (e.g., humans) because this causes low variation in relationship. However, even using human population samples, low sampling variance is possible with high N. Copyright © 2015 by the Genetics Society of America.

Effects of variation in coagulation and photochemistry parameters on the particle size distributions in the Venus clouds

NASA Astrophysics Data System (ADS)

McGouldrick, Kevin

2017-12-01

This paper explores the effects that variation in the coalescence efficiency of the Venus cloud particles can have on the structure of the Venus cloud. It is motivated by the acknowledgment of uncertainties in the measured parameters—and the assumptions made to account for them—that define our present knowledge of the particle characteristics. Specifically, we explore the consequence of allowing the coalescence efficiency of supercooled sulfuric acid in the upper clouds to tend to zero. This produces a cloud that occasionally exhibits an enhancement of small particles at altitude (similar to the upper hazes observed by Pioneer Venus and subsequently shown to be somewhat transient). This simulated cloud occasionally exhibits a rapid growth of particle size near cloud base, exhibiting characteristics similar to those seen in the controversial Mode 3 particles. These results demonstrate that a subset of the variations observed as near-infrared opacity variations in the lower and middle clouds of Venus can be explained by microphysical, in addition to dynamical, variations. Furthermore, the existence of a population of particles exhibiting less efficient coalescence efficiencies would support the likelihood of conditions suitable for charge exchange, hence lightning, in the Venus clouds. We recommend future laboratory studies on the coalescence properties of sulfuric acid under the range of conditions experienced in the Venus clouds. We also recommend future in situ measurements to better characterize the properties of the cloud particles themselves, especially composition and particle habits (shapes).[Figure not available: see fulltext.

Seasonal variations in the diversity and abundance of diazotrophic communities across soils.

PubMed

Pereira e Silva, Michele C; Semenov, Alexander V; van Elsas, Jan Dirk; Salles, Joana Falcão

2011-07-01

The nitrogen (N)-fixing community is a key functional community in soil, as it replenishes the pool of biologically available N that is lost to the atmosphere via anaerobic ammonium oxidation and denitrification. We characterized the structure and dynamic changes in diazotrophic communities, based on the nifH gene, across eight different representative Dutch soils during one complete growing season, to evaluate the amplitude of the natural variation in abundance and diversity, and identify possible relationships with abiotic factors. Overall, our results indicate that soil type is the main factor influencing the N-fixing communities, which were more abundant and diverse in the clay soils (n=4) than in the sandy soils (n=4). On average, the amplitude of variation in community size as well as the range-weighted richness were also found to be higher in the clay soils. These results indicate that N-fixing communities associated with sandy and clay soil show a distinct amplitude of variation under field conditions, and suggest that the diazotrophic communities associated with clay soil might be more sensitive to fluctuations associated with the season and agricultural practices. Moreover, soil characteristics such as ammonium content, pH and texture most strongly correlated with the variations observed in the diversity, size and structure of N-fixing communities, whose relative importance was determined across a temporal and spatial scale. © 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

Ureaplasma Species Multiple Banded Antigen (MBA) Variation Is Associated with the Severity of Inflammation In vivo and In vitro in Human Placentae.

PubMed

Sweeney, Emma L; Kallapur, Suhas G; Meawad, Simone; Gisslen, Tate; Stephenson, Sally-Anne; Jobe, Alan H; Knox, Christine L

2017-01-01

Background: The multiple banded antigen (MBA), a surface-exposed lipoprotein, is a proposed virulence factor of Ureaplasma spp. We previously demonstrated that the number of Ureaplasma parvum MBA size variants in amniotic fluid was inversely proportional to the severity of chorioamnionitis in experimentally infected pregnant sheep. However, the effect of ureaplasma MBA size variation on inflammation in human pregnancies has not been reported. Methods: Ureaplasmas isolated from the chorioamnion of pregnant women from a previous study ( n = 42) were speciated/serotyped and MBA size variation was demonstrated by PCR and western blot. Results were correlated with the severity of chorioamnionitis and cord blood cytokines. In vitro , THP-1-derived macrophages were exposed to recombinant-MBA proteins of differing sizes and NF-κB activation and cytokine responses were determined. Results: MBA size variation was identified in 21/32 (65.6%) clinical isolates (in 10 clinical isolates MBA size variation was unable to be determined). Any size variation (increase/decrease) of the MBA (regardless of Ureaplasma species or serovar) was associated with mild or absent chorioamnionitis ( P = 0.023) and lower concentrations of cord blood cytokines IL-8 ( P = 0.04) and G-CSF ( P = 0.008). In vitro , recombinant-MBA variants elicited different cytokine responses and altered expression of NF-κB p65. Conclusion: This study demonstrates that size variation of the ureaplasma MBA protein modulates the host immune response in vivo and in vitro .

Ureaplasma Species Multiple Banded Antigen (MBA) Variation Is Associated with the Severity of Inflammation In vivo and In vitro in Human Placentae

PubMed Central

Sweeney, Emma L.; Kallapur, Suhas G.; Meawad, Simone; Gisslen, Tate; Stephenson, Sally-Anne; Jobe, Alan H.; Knox, Christine L.

2017-01-01

Background: The multiple banded antigen (MBA), a surface-exposed lipoprotein, is a proposed virulence factor of Ureaplasma spp. We previously demonstrated that the number of Ureaplasma parvum MBA size variants in amniotic fluid was inversely proportional to the severity of chorioamnionitis in experimentally infected pregnant sheep. However, the effect of ureaplasma MBA size variation on inflammation in human pregnancies has not been reported. Methods: Ureaplasmas isolated from the chorioamnion of pregnant women from a previous study (n = 42) were speciated/serotyped and MBA size variation was demonstrated by PCR and western blot. Results were correlated with the severity of chorioamnionitis and cord blood cytokines. In vitro, THP-1-derived macrophages were exposed to recombinant-MBA proteins of differing sizes and NF-κB activation and cytokine responses were determined. Results: MBA size variation was identified in 21/32 (65.6%) clinical isolates (in 10 clinical isolates MBA size variation was unable to be determined). Any size variation (increase/decrease) of the MBA (regardless of Ureaplasma species or serovar) was associated with mild or absent chorioamnionitis (P = 0.023) and lower concentrations of cord blood cytokines IL-8 (P = 0.04) and G-CSF (P = 0.008). In vitro, recombinant-MBA variants elicited different cytokine responses and altered expression of NF-κB p65. Conclusion: This study demonstrates that size variation of the ureaplasma MBA protein modulates the host immune response in vivo and in vitro. PMID:28451522

Predicting Achievable Fundamental Frequency Ranges in Vocalization Across Species

PubMed Central

Titze, Ingo; Riede, Tobias; Mau, Ted

2016-01-01

Vocal folds are used as sound sources in various species, but it is unknown how vocal fold morphologies are optimized for different acoustic objectives. Here we identify two main variables affecting range of vocal fold vibration frequency, namely vocal fold elongation and tissue fiber stress. A simple vibrating string model is used to predict fundamental frequency ranges across species of different vocal fold sizes. While average fundamental frequency is predominantly determined by vocal fold length (larynx size), range of fundamental frequency is facilitated by (1) laryngeal muscles that control elongation and by (2) nonlinearity in tissue fiber tension. One adaptation that would increase fundamental frequency range is greater freedom in joint rotation or gliding of two cartilages (thyroid and cricoid), so that vocal fold length change is maximized. Alternatively, tissue layers can develop to bear a disproportionate fiber tension (i.e., a ligament with high density collagen fibers), increasing the fundamental frequency range and thereby vocal versatility. The range of fundamental frequency across species is thus not simply one-dimensional, but can be conceptualized as the dependent variable in a multi-dimensional morphospace. In humans, this could allow for variations that could be clinically important for voice therapy and vocal fold repair. Alternative solutions could also have importance in vocal training for singing and other highly-skilled vocalizations. PMID:27309543

Understanding the uncertainty associated with particle-bound pollutant build-up and wash-off: A critical review.

PubMed

Wijesiri, Buddhi; Egodawatta, Prasanna; McGree, James; Goonetilleke, Ashantha

2016-09-15

Accurate prediction of stormwater quality is essential for developing effective pollution mitigation strategies. The use of models incorporating simplified mathematical replications of pollutant processes is the common practice for determining stormwater quality. However, an inherent process uncertainty arises due to the intrinsic variability associated with pollutant processes, which has neither been comprehensively understood, nor well accounted for in uncertainty assessment of stormwater quality modelling. This review provides the context for defining and quantifying the uncertainty associated with pollutant build-up and wash-off on urban impervious surfaces based on the hypothesis that particle size is predominant in influencing process variability. Critical analysis of published research literature brings scientific evidence together in order to establish the fact that particle size changes with time, and different sized particles exhibit distinct behaviour during build-up and wash-off, resulting in process variability. Analysis of the different adsorption behaviour of particles confirmed that the variations in pollutant load and composition are influenced by particle size. Particle behaviour and variations in pollutant load and composition are related due to the strong affinity of pollutants such as heavy metals and hydrocarbons for specific particle size ranges. As such, the temporal variation in particle size is identified as the key to establishing a basis for assessing build-up and wash-off process uncertainty. Therefore, accounting for pollutant build-up and wash-off process variability, which is influenced by particle size, would facilitate the assessment of the uncertainty associated with modelling outcomes. Furthermore, the review identified fundamental knowledge gaps where further research is needed in relation to: (1) the aggregation of particles suspended in the atmosphere during build-up; (2) particle re-suspension during wash-off; (3) pollutant re-adsorption by different particle size fractions; and (4) development of evidence-based techniques for assessing uncertainty; and (5) methods for translating the knowledge acquired from the investigation of process mechanisms at small scale into catchment scale for stormwater quality modelling. Copyright © 2016 Elsevier Ltd. All rights reserved.

Constraining martian atmospheric dust particle size distributions from MER Navcam observations.

NASA Astrophysics Data System (ADS)

Soderblom, J. M.; Smith, M. D.

2017-12-01

Atmospheric dust plays an important role in atmospheric dynamics by absorbing energy and influencing the thermal structure of the atmosphere [1]. The efficiency by which dust absorbs energy depends on its size and single-scattering albedo. Characterizing these properties and their variability is, thus, important in modeling atmospheric circulation. Near-sun observations of the martian sky from Viking Lander, Mars Pathfinder, and MER Pancam images have been used to characterize the atmospheric scattering phase function. The forward-scattering peak the atmospheric phase function is primarily controlled by the size of aerosol particles and is less sensitive to atmospheric opacity or particle shape and single-scattering albedo [2]. These observations, however, have been limited to scattering angles >5°. We use the MER Navcams, which experience little-to-no debilitating internal instrumental scattered light during near-Sun imaging, enabling measurements of the brightness of the martian sky down to very small scattering angles [3], making them more sensitive to aerosol particle size. Additionally, the Navcams band-pass wavelength is similar to the dust effective particle size, further increasing this sensitivity. These data sample a wide range of atmospheric conditions, including variations in the atmospheric dust loading across the entire martian year, as well as more rapid variations during the onset and dissipation of a global-scale dust storm. General circulation models (GCMs) predict a size-dependence for the transport of dust during dust storms that would result in both spatial (on regional-to-global scales) and temporal (days-to-months) variations in the dust size distribution [4]. The absolute calibration of these data, however, is limited. The instrument temperature measurement is limited to a single thermocouple on the Opportunity left Navcam CCD, and observations of the calibration target by Navcam are infrequent. We discuss ways to mitigate these uncertainties and provide improved recovery of dust particle size distributions from these data. [1] Gierasch and Goody, 1972, J. Atmos. Sci., 29, 400-402. [2] Hansen and Travis, 1974, Space Sci. Rev., 16, 527-610. [3] Soderblom et al., 2008; JGR E06S19. [4] Murphy et al., 1993, JGR 98(E2), 3197-3220.

Variation of mercury in fish from Massachusetts lakes based on ecoregion and lake trophic status

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

Rose, J.; Hutcheson, M.; West, C.R.

1995-12-31

Twenty-four of the state`s least-impacted waterbodies were sampled for sediment, water, physical characteristics and 3 species of fish to determine the extent of, and patterns of variation in, mercury contamination. Sampling effort was apportioned among three different ecological subregions of the state, as defined by EPA, and among lakes of differing trophic status. The authors sought to partition the variance to discover if these broadly defined concepts are suitable predictors of mercury levels in fish. Mean fish mercury was 0.14 ppm wet weight in samples of 168 of the bottom feeding brown bullheads (Ameriurus nebulosus) (range = 0.01--0.79 ppm); 0.3more » ppm in 199 of the omnivorous yellow perch (Perca flavescens) (range = 0.01--0.75 ppm); and 0.4 ppm in samples of 152 of the predaceous largemouth bass (Micropterus salmoides) (range = 0.05--1.1 ppm). Multivariate statistics are employed to determine how mercury concentrations in fish correlate with sediment chemistry, water chemistry, fish trophic status, fish size and age, lake and watershed size, the presence and extent of wetlands in the watershed, and physical characteristics of the lake. The survey design complements ongoing efforts begun in 1983 to test fish in a variety of waters, from which emanated fish advisories for impacted rivers and lakes. The study defines a baseline for fish contamination in Massachusetts lakes and ponds that serves as a template for public health decisions regarding fish consumption.« less

Does Litter Size Variation Affect Models of Terrestrial Carnivore Extinction Risk and Management?

PubMed Central

Devenish-Nelson, Eleanor S.; Stephens, Philip A.; Harris, Stephen; Soulsbury, Carl; Richards, Shane A.

2013-01-01

Background Individual variation in both survival and reproduction has the potential to influence extinction risk. Especially for rare or threatened species, reliable population models should adequately incorporate demographic uncertainty. Here, we focus on an important form of demographic stochasticity: variation in litter sizes. We use terrestrial carnivores as an example taxon, as they are frequently threatened or of economic importance. Since data on intraspecific litter size variation are often sparse, it is unclear what probability distribution should be used to describe the pattern of litter size variation for multiparous carnivores. Methodology/Principal Findings We used litter size data on 32 terrestrial carnivore species to test the fit of 12 probability distributions. The influence of these distributions on quasi-extinction probabilities and the probability of successful disease control was then examined for three canid species – the island fox Urocyon littoralis, the red fox Vulpes vulpes, and the African wild dog Lycaon pictus. Best fitting probability distributions differed among the carnivores examined. However, the discretised normal distribution provided the best fit for the majority of species, because variation among litter-sizes was often small. Importantly, however, the outcomes of demographic models were generally robust to the distribution used. Conclusion/Significance These results provide reassurance for those using demographic modelling for the management of less studied carnivores in which litter size variation is estimated using data from species with similar reproductive attributes. PMID:23469140

Does litter size variation affect models of terrestrial carnivore extinction risk and management?

PubMed

Devenish-Nelson, Eleanor S; Stephens, Philip A; Harris, Stephen; Soulsbury, Carl; Richards, Shane A

2013-01-01

Individual variation in both survival and reproduction has the potential to influence extinction risk. Especially for rare or threatened species, reliable population models should adequately incorporate demographic uncertainty. Here, we focus on an important form of demographic stochasticity: variation in litter sizes. We use terrestrial carnivores as an example taxon, as they are frequently threatened or of economic importance. Since data on intraspecific litter size variation are often sparse, it is unclear what probability distribution should be used to describe the pattern of litter size variation for multiparous carnivores. We used litter size data on 32 terrestrial carnivore species to test the fit of 12 probability distributions. The influence of these distributions on quasi-extinction probabilities and the probability of successful disease control was then examined for three canid species - the island fox Urocyon littoralis, the red fox Vulpes vulpes, and the African wild dog Lycaon pictus. Best fitting probability distributions differed among the carnivores examined. However, the discretised normal distribution provided the best fit for the majority of species, because variation among litter-sizes was often small. Importantly, however, the outcomes of demographic models were generally robust to the distribution used. These results provide reassurance for those using demographic modelling for the management of less studied carnivores in which litter size variation is estimated using data from species with similar reproductive attributes.

Measurement of the Solar Absorptance and Thermal Emittance of Lunar Simulants

NASA Technical Reports Server (NTRS)

Gaier, James R.; Street, Kenneth W.; Gutafson, Robert J.

2010-01-01

The first comparative study of the reflectance spectra of lunar simulants is presented. All of the simulants except one had a wavelength-dependant reflectivity ( ( )) near 0.10 over the wavelength range of 8 to 25 m, so they are highly emitting at room temperature and lower. The 300 K emittance ( ) of all the lunar simulants except one ranged from 0.884 to 0.906. The 300 K of JSC Mars-1 simulant was 0.927. There was considerably more variation in the lunar simulant reflectance in the solar spectral range (250 to 2500 nm) than in the thermal infrared. Larger particle size simulants reflected much less than those with smaller particle size. As expected, the lunar highlands simulants were more reflective in this wavelength range than the lunar mare simulants. The integrated solar absorptance ( ) of the simulants ranged from 0.413 to 0.817 for those with smaller particles, and 0.669 to 0.906 for those with larger particles. Although spectral differences were observed, the for the simulants appears to be similar to that of lunar soils (0.65 to 0.88). These data are now available to be used in modeling the effects of dust on thermal control surfaces.

Measurement of the Solar Absorptance and Thermal Emittance of Lunar Simulants

NASA Technical Reports Server (NTRS)

Gaier, James R.; Street, Kenneth W.; Gustafson, Robert J.

2010-01-01

The first comparative study of the reflectance spectra of lunar simulants is presented. All of the simulants except one had a wavelength-dependent reflectivity, rho(lambda), near 0.10 over the wavelength range of 8 to 25 microns, so they are highly emitting at room temperature and lower. The 300 K emittance, epsilon, of all the lunar simulants except one ranged from 0.884 to 0.906. The 300 K epsilon of JSC Mars-1 simulant was 0.927. There was considerably more variation in the lunar simulant reflectance in the solar spectral range (250 to 2500 nm) than in the thermal infrared. Larger particle size simulants reflected much less than those with smaller particle size. As expected, the lunar highlands simulants were more reflective in this wavelength range than the lunar mare simulants. The alpha of the simulants ranged from 0.413 to 0.817 for those with smaller particles and 0.669 to 0.906 for large particles. Although spectral differences were observed, the total integrated alpha for the simulants appears to be similar to that of lunar soils (0.65 to 0.88). These data are now available to be used in modeling the effects of dust on thermal control surfaces.

Craniodental variation in Paranthropus boisei: a developmental and functional perspective.

PubMed

Wood, B; Lieberman, D E

2001-09-01

What levels and patterns of craniodental variation among a fossil hypodigm are necessary to reject the null hypothesis that only a single species is sampled? We suggest how developmental and functional criteria can be used to predict where in the skeleton of fossil hominins we should expect more, or less, within-species variation. We present and test three hypotheses about the factors contributing to craniodental variation in extant primate taxa, and then apply these results to the interpretation of the P. boisei hypodigm. Within the comparative samples of extant Homo, Pan, Gorilla, Pongo, and Colobus, variables from the cranial base, neurocranium, and face that are not subject to high magnitudes of strain have consistently lower levels of intraspecific variation than variables from regions of the face subject to high levels of strain. Dental size variables are intermediate in terms of their reliability. P. boisei is found to have a low degree of variability relative to extant primates for variables shown to be generally useful for testing taxonomic hypotheses. Contrary to the claims of Suwa et al. ([1997] Nature 389:489-492), the recently discovered material from Konso falls within the range of variation of the "pre-Konso" hypodigm of P. boisei for available conventional metrical variables. Those aspects of the Konso material that appear to extend the range of the P. boisei hypodigm involve regions of the skull predicted to be prone to high levels of within-species variation. The approach used in this study focuses on craniodental data, but it is applicable to other regions of the skeleton. Copyright 2001 Wiley-Liss, Inc.

Experimental study of flow distribution and pressure loss with circumferential inlet and outlet manifolds

NASA Technical Reports Server (NTRS)

Dittrich, R. T.

1972-01-01

Water flow tests with circumferential inlet and outlet manifolds were conducted to determine factors affecting fluid distribution and pressure losses. Various orifice sizes and manifold geometries were tested over a range of flow velocities. With inlet manifolds, flow distribution was related directly to orifice discharge coefficients. A correlation indicated that nonuniform distribution resulted when the velocity head ratio at the orifice was not in the range of constant discharge coefficient. With outlet manifolds, nonuniform flow was related to static pressure variations along the manifold. Outlet manifolds had appreciably greater pressure losses than comparable inlet manifolds.

The geometry of proliferating dicot cells.

PubMed

Korn, R W

2001-02-01

The distributions of cell size and cell cycle duration were studied in two-dimensional expanding plant tissues. Plastic imprints of the leaf epidermis of three dicot plants, jade (Crassula argentae), impatiens (Impatiens wallerana), and the common begonia (Begonia semperflorens) were made and cell outlines analysed. The average, standard deviation and coefficient of variance (CV = 100 x standard deviation/average) of cell size were determined with the CV of mother cells less than the CV for daughter cells and both are less than that for all cells. An equation was devised as a simple description of the probability distribution of sizes for all cells of a tissue. Cell cycle durations as measured in arbitrary time units were determined by reconstructing the initial and final sizes of cells and they collectively give the expected asymmetric bell-shaped probability distribution. Given the features of unequal cell division (an average of 11.6% difference in size of daughter cells) and the size variation of dividing cells, it appears that the range of cell size is more critically regulated than the size of a cell at any particular time.

Spatial and temporal variation of body size among early Homo.

PubMed

Will, Manuel; Stock, Jay T

2015-05-01

The estimation of body size among the earliest members of the genus Homo (2.4-1.5Myr [millions of years ago]) is central to interpretations of their biology. It is widely accepted that Homo ergaster possessed increased body size compared with Homo habilis and Homo rudolfensis, and that this may have been a factor involved with the dispersal of Homo out of Africa. The study of taxonomic differences in body size, however, is problematic. Postcranial remains are rarely associated with craniodental fossils, and taxonomic attributions frequently rest upon the size of skeletal elements. Previous body size estimates have been based upon well-preserved specimens with a more reliable species assessment. Since these samples are small (n < 5) and disparate in space and time, little is known about geographical and chronological variation in body size within early Homo. We investigate temporal and spatial variation in body size among fossils of early Homo using a 'taxon-free' approach, considering evidence for size variation from isolated and fragmentary postcranial remains (n = 39). To render the size of disparate fossil elements comparable, we derived new regression equations for common parameters of body size from a globally representative sample of hunter-gatherers and applied them to available postcranial measurements from the fossils. The results demonstrate chronological and spatial variation but no simple temporal or geographical trends for the evolution of body size among early Homo. Pronounced body size increases within Africa take place only after hominin populations were established at Dmanisi, suggesting that migrations into Eurasia were not contingent on larger body sizes. The primary evidence for these marked changes among early Homo is based upon material from Koobi Fora after 1.7Myr, indicating regional size variation. The significant body size differences between specimens from Koobi Fora and Olduvai support the cranial evidence for at least two co-existing morphotypes in the Early Pleistocene of eastern Africa. Copyright © 2015 Elsevier Ltd. All rights reserved.

Optical Properties of a Semimagnetic Quantum Well in a Proximity of a Superconducting Film

NASA Astrophysics Data System (ADS)

Lebecki, K. M.; Kłopotowski, Ł.; Kossut, J.

2006-11-01

We consider, via numerical calculations, a hybrid structure made of a semimagnetic Cd1-xMnxTe quantum well deposited in a close proximity to superconducting niobium film. We simulate photoluminescence and the Faraday rotation spectra, modified by the presence of vortices in this type II superconductor. The magnitude of the evaluated effects is small - the vortex induced spectral line shape variation is of the order of 1% at 1 K and 0.1% at 3 K and is expected to occur mainly in the field range between 0.03 T and 0.05 T.