Climatic and evolutionary drivers of phase shifts in the plague epidemics of colonial India

PubMed Central

Lewnard, Joseph A.

2016-01-01

Immune heterogeneity in wild host populations indicates that disease-mediated selection is common in nature. However, the underlying dynamic feedbacks involving the ecology of disease transmission, evolutionary processes, and their interaction with environmental drivers have proven challenging to characterize. Plague presents an optimal system for interrogating such couplings: Yersinia pestis transmission exerts intense selective pressure driving the local persistence of disease resistance among its wildlife hosts in endemic areas. Investigations undertaken in colonial India after the introduction of plague in 1896 suggest that, only a decade after plague arrived, a heritable, plague-resistant phenotype had become prevalent among commensal rats of cities undergoing severe plague epidemics. To understand the possible evolutionary basis of these observations, we developed a mathematical model coupling environmentally forced plague dynamics with evolutionary selection of rats, capitalizing on extensive archival data from Indian Plague Commission investigations. Incorporating increased plague resistance among rats as a consequence of intense natural selection permits the model to reproduce observed changes in seasonal epidemic patterns in several cities and capture experimentally observed associations between climate and flea population dynamics in India. Our model results substantiate Victorian era claims of host evolution based on experimental observations of plague resistance and reveal the buffering effect of such evolution against environmental drivers of transmission. Our analysis shows that historical datasets can yield powerful insights into the transmission dynamics of reemerging disease agents with which we have limited contemporary experience to guide quantitative modeling and inference. PMID:27791071

Experimental evolution and the dynamics of adaptation and genome evolution in microbial populations.

PubMed

Lenski, Richard E

2017-10-01

Evolution is an on-going process, and it can be studied experimentally in organisms with rapid generations. My team has maintained 12 populations of Escherichia coli in a simple laboratory environment for >25 years and 60 000 generations. We have quantified the dynamics of adaptation by natural selection, seen some of the populations diverge into stably coexisting ecotypes, described changes in the bacteria's mutation rate, observed the new ability to exploit a previously untapped carbon source, characterized the dynamics of genome evolution and used parallel evolution to identify the genetic targets of selection. I discuss what the future might hold for this particular experiment, briefly highlight some other microbial evolution experiments and suggest how the fields of experimental evolution and microbial ecology might intersect going forward.

Experimental investigation of nucleate pool boiling characteristics of high concentrated alumina/water nanofluids

NASA Astrophysics Data System (ADS)

Kshirsagar, Jagdeep M.; Shrivastava, Ramakant

2018-06-01

In Present study, the critical heat flux (CHF) and boiling heat transfer coefficient of alumina nanoparticles with the base fluid as deionised water is measured. The selected concentrations of nanofluids for the experimentation are from 0.3, 0.6, 0.9, 1.2 and 1.5 wt%. The main objective to select higher concentration is that to study the surface morphology of heater surface at higher concentrations and its effect on critical heat flux and heat transfer coefficient. It is observed that the critical heat flux enhancement rate decreases as concentration increases and surface roughness of heater surface decreases after 1.2 wt% concentration of nanofluids.

A naphthalene exciplex based Al3+ selective on-type fluorescent probe for living cells at the physiological pH range: experimental and computational studies.

PubMed

Banerjee, Arnab; Sahana, Animesh; Das, Sudipta; Lohar, Sisir; Guha, Subarna; Sarkar, Bidisha; Mukhopadhyay, Subhra Kanti; Mukherjee, Asok K; Das, Debasis

2012-05-07

2-((Naphthalen-6-yl)methylthio)ethanol (HL) was prepared by one pot synthesis using 2-mercaptoethanol and 2-bromomethylnaphthalene. It was found to be a highly selective fluorescent sensor for Al(3+) in the physiological pH (pH 7.0-8.0). It could sense Al(3+) bound to cells through fluorescence microscopy. Metal ions like Mn(2+), Fe(3+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Ag(+), Cd(2+), Hg(2+), Cr(3+) and Pb(2+) did not interfere. No interference was also observed with anions like Cl(-), Br(-), F(-), SO(4)(2-), NO(3)(-), CO(3)(2-), HPO(4)(2-) and SCN(-). Experimentally observed structural and spectroscopic features of HL and its Al(3+) complex have been substantiated by computational calculations using density functional theory (DFT) and time dependent density functional theory (TDDFT).

A novel method for multifactorial bio-chemical experiments design based on combinational design theory.

PubMed

Wang, Xun; Sun, Beibei; Liu, Boyang; Fu, Yaping; Zheng, Pan

2017-01-01

Experimental design focuses on describing or explaining the multifactorial interactions that are hypothesized to reflect the variation. The design introduces conditions that may directly affect the variation, where particular conditions are purposely selected for observation. Combinatorial design theory deals with the existence, construction and properties of systems of finite sets whose arrangements satisfy generalized concepts of balance and/or symmetry. In this work, borrowing the concept of "balance" in combinatorial design theory, a novel method for multifactorial bio-chemical experiments design is proposed, where balanced templates in combinational design are used to select the conditions for observation. Balanced experimental data that covers all the influencing factors of experiments can be obtianed for further processing, such as training set for machine learning models. Finally, a software based on the proposed method is developed for designing experiments with covering influencing factors a certain number of times.

Dehydrogenation of methanol to formaldehyde catalyzed by pristine and defective ceria surfaces

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

Beste, Ariana; Overbury, Steven H.

We have explored the dehydrogenation of methoxy on pristine and defective (111), (100), and (110) ceria surfaces with density functional methods. Methanol conversion is used as a probe reaction to understand structure sensitivity of the oxide catalysis. Differences in reaction selectivity have been observed experimentally as a function of crystallographically exposed faces and degree of reduction. We find that the barrier for carbon-hydrogen cleavage in methoxy is similar for the pristine and defective (111), (100), and (110) surfaces. However, there are large differences in the stability of the surface intermediates on the different surfaces. The variations in experimentally observed productmore » selectivities are a consequence of the interplay between barrier controlled bond cleavage and desorption processes. Ultimately, subtle differences in activation energies for carbon-hydrogen cleavage on the different crystallographic faces of ceria could not be correlated with structural or electronic descriptors.« less

Dehydrogenation of methanol to formaldehyde catalyzed by pristine and defective ceria surfaces

DOE PAGES

Beste, Ariana; Overbury, Steven H.

2016-03-09

We have explored the dehydrogenation of methoxy on pristine and defective (111), (100), and (110) ceria surfaces with density functional methods. Methanol conversion is used as a probe reaction to understand structure sensitivity of the oxide catalysis. Differences in reaction selectivity have been observed experimentally as a function of crystallographically exposed faces and degree of reduction. We find that the barrier for carbon-hydrogen cleavage in methoxy is similar for the pristine and defective (111), (100), and (110) surfaces. However, there are large differences in the stability of the surface intermediates on the different surfaces. The variations in experimentally observed productmore » selectivities are a consequence of the interplay between barrier controlled bond cleavage and desorption processes. Ultimately, subtle differences in activation energies for carbon-hydrogen cleavage on the different crystallographic faces of ceria could not be correlated with structural or electronic descriptors.« less

Dehydrogenation of methanol to formaldehyde catalyzed by pristine and defective ceria surfaces.

PubMed

Beste, Ariana; Overbury, Steven H

2016-04-21

We have explored the dehydrogenation of methoxy on pristine and defective (111), (100), and (110) ceria surfaces with density functional methods. Methanol conversion is used as a probe reaction to understand structure sensitivity of the oxide catalysis. Differences in reaction selectivity have been observed experimentally as a function of crystallographically exposed faces and degree of reduction. We find that the barrier for carbon-hydrogen cleavage in methoxy is similar for the pristine and defective (111), (100), and (110) surfaces. However, there are large differences in the stability of the surface intermediates on the different surfaces. The variations in experimentally observed product selectivities are a consequence of the interplay between barrier controlled bond cleavage and desorption processes. Subtle differences in activation energies for carbon-hydrogen cleavage on the different crystallographic faces of ceria could not be correlated with structural or electronic descriptors.

The use of computer-assisted image analysis in the evaluation of the effect of management systems on changes in the color, chemical composition and texture of m. longissimus dorsi in pigs.

PubMed

Zapotoczny, Piotr; Kozera, Wojciech; Karpiesiuk, Krzysztof; Pawłowski, Rodian

2014-08-01

The effect of management systems on selected physical properties and chemical composition of m. longissimus dorsi was studied in pigs. Muscle texture parameters were determined by computer-assisted image analysis, and the color of muscle samples was evaluated using a spectrophotometer. Highly significant correlations were observed between chemical composition and selected texture variables in the analyzed images. Chemical composition was not correlated with color or spectral distribution. Subject to the applied classification methods and groups of variables included in the classification model, the experimental groups were identified correctly in 35-95%. No significant differences in the chemical composition of m. longissimus dorsi were observed between experimental groups. Significant differences were noted in color lightness (L*) and redness (a*). Copyright © 2014 Elsevier Ltd. All rights reserved.

An experimental test of density-dependent selection on temperament traits of activity, boldness and sociability.

PubMed

Le Galliard, J-F; Paquet, M; Mugabo, M

2015-05-01

Temperament traits are seen in many animal species, and recent evolutionary models predict that they could be maintained by heterogeneous selection. We tested this prediction by examining density-dependent selection in juvenile common lizards Zootoca vivipara scored for activity, boldness and sociability at birth and at the age of 1 year. We measured three key life-history traits (juvenile survival, body growth rate and reproduction) and quantified selection in experimental populations at five density levels ranging from low to high values. We observed consistent individual differences for all behaviours on the short term, but only for activity and one boldness measure across the first year of life. At low density, growth selection favoured more sociable lizards, whereas viability selection favoured less active individuals. A significant negative correlational selection on activity and boldness existed for body growth rate irrespective of density. Thus, behavioural traits were characterized by limited ontogenic consistency, and natural selection was heterogeneous between density treatments and fitness traits. This confirms that density-dependent selection plays an important role in the maintenance of individual differences in exploration-activity and sociability. © 2015 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2015 European Society For Evolutionary Biology.

Experimental Evaluations of Selected Immersion Hypothermia Protection Equipment.

DTIC Science & Technology

1979-10-12

Temperature Response ............... 30 Figure 1-3 Estimated Survival Times for Average Men ..... 49 Figure 1-4 Metabolic Rate Response :Subject BS...51 Figure 1-5 Metabolic Rate Response : Subject GE ............... 52 Figure 1-6 Selected Elementary Movements ............... 58 Figure 1-7 Fatigue... responses to cold-Immersion, while wearing the test articles, could be observed or-vs over a narrow range of body core temperatures Involving the mildest

A Perspective on Research on Dishonesty: Limited External Validity Due to the Lack of Possibility of Self-Selection in Experimental Designs.

PubMed

Houdek, Petr

2017-01-01

The aim of this perspective article is to show that current experimental evidence on factors influencing dishonesty has limited external validity. Most of experimental studies is built on random assignments, in which control/experimental groups of subjects face varied sizes of the expected reward for behaving dishonestly, opportunities for cheating, means of rationalizing dishonest behavior etc., and mean groups' reactions are observed. The studies have internal validity in assessing the causal influence of these and other factors, but they lack external validity in organizational, market and other environments. If people can opt into or out of diverse real-world environments, an experiment aimed at studying factors influencing real-life degree of dishonesty should permit for such an option. The behavior of such self-selected groups of marginal subjects would probably contain a larger level of (non)deception than the behavior of average people. The article warns that there are not many studies that would enable self-selection or sorting of participants into varying environments, and that limits current knowledge of the extent and dynamics of dishonest and fraudulent behavior. The article focuses on suggestions how to improve dishonesty research, especially how to avoid the experimenter demand bias.

A Perspective on Research on Dishonesty: Limited External Validity Due to the Lack of Possibility of Self-Selection in Experimental Designs

PubMed Central

Houdek, Petr

2017-01-01

The aim of this perspective article is to show that current experimental evidence on factors influencing dishonesty has limited external validity. Most of experimental studies is built on random assignments, in which control/experimental groups of subjects face varied sizes of the expected reward for behaving dishonestly, opportunities for cheating, means of rationalizing dishonest behavior etc., and mean groups’ reactions are observed. The studies have internal validity in assessing the causal influence of these and other factors, but they lack external validity in organizational, market and other environments. If people can opt into or out of diverse real-world environments, an experiment aimed at studying factors influencing real-life degree of dishonesty should permit for such an option. The behavior of such self-selected groups of marginal subjects would probably contain a larger level of (non)deception than the behavior of average people. The article warns that there are not many studies that would enable self-selection or sorting of participants into varying environments, and that limits current knowledge of the extent and dynamics of dishonest and fraudulent behavior. The article focuses on suggestions how to improve dishonesty research, especially how to avoid the experimenter demand bias. PMID:28955279

The performance of sample selection estimators to control for attrition bias.

PubMed

Grasdal, A

2001-07-01

Sample attrition is a potential source of selection bias in experimental, as well as non-experimental programme evaluation. For labour market outcomes, such as employment status and earnings, missing data problems caused by attrition can be circumvented by the collection of follow-up data from administrative registers. For most non-labour market outcomes, however, investigators must rely on participants' willingness to co-operate in keeping detailed follow-up records and statistical correction procedures to identify and adjust for attrition bias. This paper combines survey and register data from a Norwegian randomized field trial to evaluate the performance of parametric and semi-parametric sample selection estimators commonly used to correct for attrition bias. The considered estimators work well in terms of producing point estimates of treatment effects close to the experimental benchmark estimates. Results are sensitive to exclusion restrictions. The analysis also demonstrates an inherent paradox in the 'common support' approach, which prescribes exclusion from the analysis of observations outside of common support for the selection probability. The more important treatment status is as a determinant of attrition, the larger is the proportion of treated with support for the selection probability outside the range, for which comparison with untreated counterparts is possible. Copyright 2001 John Wiley & Sons, Ltd.

Life-history traits and energetic status in relation to vulnerability to angling in an experimentally selected teleost fish.

PubMed

Redpath, Tara D; Cooke, Steven J; Arlinghaus, Robert; Wahl, David H; Philipp, David P

2009-08-01

In recreational fisheries, a correlation has been established between fishing-induced selection pressures and the metabolic traits of individual fish. This study used a population of largemouth bass (Micropterus salmoides) with lines of low vulnerability fish (LVF) and high vulnerability fish (HVF) that were previously established through artificial truncation selection experiments. The main objective was to evaluate if differential vulnerability to angling was correlated with growth, energetics and nutritional condition during the sub-adult stage. Absolute growth rate was found to be between 9% and 17% higher for LVF compared with HVF over a 6-month period in three experimental ponds. The gonadosomatic index in females was lower for LVF compared with HVF in one experimental pond. No significant differences in energy stores (measured using body constituent analysis) were observed between LVF and HVF. In addition, both groups were consuming the same prey items as evidenced by stomach content analysis. The inherent reasons behind differential vulnerability to angling are complex, and selection for these opposing phenotypes appears to select for differing growth rates, although the driving factors remain unclear. These traits are important from a life-history perspective, and alterations to their frequency as a result of fishing-induced selection could alter fish population structure. These findings further emphasize the need to incorporate evolutionary principles into fisheries management activities.

Life-history traits and energetic status in relation to vulnerability to angling in an experimentally selected teleost fish

PubMed Central

Redpath, Tara D; Cooke, Steven J; Arlinghaus, Robert; Wahl, David H; Philipp, David P

2009-01-01

In recreational fisheries, a correlation has been established between fishing-induced selection pressures and the metabolic traits of individual fish. This study used a population of largemouth bass (Micropterus salmoides) with lines of low vulnerability fish (LVF) and high vulnerability fish (HVF) that were previously established through artificial truncation selection experiments. The main objective was to evaluate if differential vulnerability to angling was correlated with growth, energetics and nutritional condition during the sub-adult stage. Absolute growth rate was found to be between 9% and 17% higher for LVF compared with HVF over a 6-month period in three experimental ponds. The gonadosomatic index in females was lower for LVF compared with HVF in one experimental pond. No significant differences in energy stores (measured using body constituent analysis) were observed between LVF and HVF. In addition, both groups were consuming the same prey items as evidenced by stomach content analysis. The inherent reasons behind differential vulnerability to angling are complex, and selection for these opposing phenotypes appears to select for differing growth rates, although the driving factors remain unclear. These traits are important from a life-history perspective, and alterations to their frequency as a result of fishing-induced selection could alter fish population structure. These findings further emphasize the need to incorporate evolutionary principles into fisheries management activities. PMID:25567883

Wavelength selection of rolling-grain ripples in the laboratory

NASA Astrophysics Data System (ADS)

Rousseaux, Germain; Stegner, Alexandre; Wesfreid, José Eduardo

2004-03-01

We have performed an experimental study, at very high resolution, of the wavelength selection and the evolution of rolling-grain ripples. A clear distinction is made between the flat sand bed instability and the ripple coarsening. The observation of the initial wavelength for the rolling-grain ripples is only possible close to the threshold for movement which imposes a constraint on the parameters. Moreover, we have proposed a law for the selection of the unstable wavelength under the latter constraint. Our results suggest that the initial wavelength depends on the amplitude of oscillation, the grain diameter, and the Stokes layer. Besides, during the coarsening, we observe no self-similarity of the ripple shape and for few cases a logarithmic growth of the wavelength.

Thermal and Mechanical Buckling and Postbuckling Responses of Selected Curved Composite Panels

NASA Technical Reports Server (NTRS)

Breivik, Nicole L.; Hyer, Michael W.; Starnes, James H., Jr.

1998-01-01

The results of an experimental and numerical study of the buckling and postbuckling responses of selected unstiffened curved composite panels subjected to mechanical end shortening and a uniform temperature increase are presented. The uniform temperature increase induces thermal stresses in the panel when the axial displacement is constrained. An apparatus for testing curved panels at elevated temperature is described, numerical results generated by using a geometrically nonlinear finite element analysis code are presented. Several analytical modeling refinements that provide more accurate representation of the actual experimental conditions, and the relative contribution of each refinement, are discussed. Experimental results and numerical predictions are presented and compared for three loading conditions including mechanical end shortening alone, heating the panels to 250 F followed by mechanical end shortening, and heating the panels to 400 F. Changes in the coefficients of thermal expansion were observed as temperature was increased above 330 F. The effects of these changes on the experimental results are discussed for temperatures up to 400 F.

Power Analysis of Artificial Selection Experiments Using Efficient Whole Genome Simulation of Quantitative Traits

PubMed Central

Kessner, Darren; Novembre, John

2015-01-01

Evolve and resequence studies combine artificial selection experiments with massively parallel sequencing technology to study the genetic basis for complex traits. In these experiments, individuals are selected for extreme values of a trait, causing alleles at quantitative trait loci (QTL) to increase or decrease in frequency in the experimental population. We present a new analysis of the power of artificial selection experiments to detect and localize quantitative trait loci. This analysis uses a simulation framework that explicitly models whole genomes of individuals, quantitative traits, and selection based on individual trait values. We find that explicitly modeling QTL provides qualitatively different insights than considering independent loci with constant selection coefficients. Specifically, we observe how interference between QTL under selection affects the trajectories and lengthens the fixation times of selected alleles. We also show that a substantial portion of the genetic variance of the trait (50–100%) can be explained by detected QTL in as little as 20 generations of selection, depending on the trait architecture and experimental design. Furthermore, we show that power depends crucially on the opportunity for recombination during the experiment. Finally, we show that an increase in power is obtained by leveraging founder haplotype information to obtain allele frequency estimates. PMID:25672748

An integrated computational and experimental approach to gaining selectivity for MMP-2 within the gelatinase subfamily.

PubMed

Fabre, Benjamin; Filipiak, Kamila; Díaz, Natalia; Zapico, José María; Suárez, Dimas; Ramos, Ana; de Pascual-Teresa, Beatriz

2014-02-10

Looking for water-soluble inhibitors of matrix metalloproteinase-2 (MMP-2 or gelatinase A), we have previously reported compound 1, a potent MMP-2 inhibitor with a promising selectivity over the structurally homologous MMP-9 (gelatinase B). Here we report the results of Molecular Dynamics (MD) simulations for both gelatinases (MMP-2 and MMP-9), and for the corresponding MMP/1 complexes, in an attempt to shed light on the observed selectivity between the two enzymes. These studies indicated a higher plasticity of MMP-2 at the S1' pocket and suggested an induced-fit effect at the "back door" of this pocket. On the basis of these observations, we designed 11 a-d to aid further discrimination between MMP-2 and MMP-9. Those compounds displayed notably lower inhibitory activities against MMP-9; in particular, 11 b proved to be over 100 times more active against MMP-2 than against MMP-9. MD simulations of the MMP/11 b complexes and thermodynamic integration calculations provided structural insight and relative binding energies consistent with the experimentally observed activity data. These findings demonstrate that structural differences in the S1' pocket bottom permit an improvement in selectivity in the inhibition of MMP-2 over that of MMP-9; this is of great relevance for future structure-based drug design because MMP-2 is a validated target for cancer therapy, whereas MMP-9 plays both detrimental and protective roles in cancer. This study also supports the need to consider the dynamics of the S1' pocket in order to achieve selectivity in the inhibition of MMPs. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microsatellite signature of ecological selection for salt tolerance in a wild sunflower hybrid species, Helianthus paradoxus

PubMed Central

EDELIST, CÉCILE; LEXER, CHRISTIAN; DILLMANN, CHRISTINE; SICARD, DELPHINE; RIESEBERG, LOREN H.

2008-01-01

The hybrid sunflower species Helianthus paradoxus inhabits sporadic salt marshes in New Mexico and southwest Texas, USA, whereas its parental species, Helianthus annuus and Helianthus petiolaris, are salt sensitive. Previous studies identified three genomic regions — survivorship quantitative trait loci (QTLs) — that were under strong selection in experimental hybrids transplanted into the natural habitat of H. paradoxus. Here we ask whether these same genomic regions experienced significant selection during the origin and evolution of the natural hybrid, H. paradoxus. This was accomplished by comparing the variability of microsatellites linked to the three survivorship QTLs with those from genomic regions that were neutral in the experimental hybrids. As predicted if one or more selective sweeps had occurred in these regions, microsatellites linked to the survivorship QTLs exhibited a significant reduction in diversity in populations of the natural hybrid species. In contrast, no difference in diversity levels was observed between the two microsatellite classes in parental populations. PMID:17107488

Selective oxidation of dual phase steel after annealing at different dew points

NASA Astrophysics Data System (ADS)

Lins, Vanessa de Freitas Cunha; Madeira, Laureanny; Vilela, Jose Mario Carneiro; Andrade, Margareth Spangler; Buono, Vicente Tadeu Lopes; Guimarães, Juliana Porto; Alvarenga, Evandro de Azevedo

2011-04-01

Hot galvanized steels have been extensively used in the automotive industry. Selective oxidation on the steel surface affects the wettability of zinc on steel and the grain orientation of inhibition layer (Fe-Al-Zn alloy) and reduces the iron diffusion to the zinc layer. The aim of this work is to identify and quantify selective oxidation on the surface of a dual phase steel, and an experimental steel with a lower content of manganese, annealed at different dew points. The techniques employed were atomic force microscopy, X-ray photoelectron spectroscopy, and glow discharge optical emission spectroscopy. External selective oxidation was observed for phosphorus on steel surface annealed at 0 °C dp, and for manganese, silicon, and aluminum at a lower dew point. The concentration of manganese was higher on the dual phase steel surface than on the surface of the experimental steel. The concentration of molybdenum on the surface of both steels increased as the depth increased.

Effects of a Collaborative Science Intervention on High Achieving Students' Learning Anxiety and Attitudes toward Science

NASA Astrophysics Data System (ADS)

Hong, Zuway-R.

2010-10-01

This study investigated the effects of a collaborative science intervention on high achieving students' learning anxiety and attitudes toward science. Thirty-seven eighth-grade high achieving students (16 boys and 21 girls) were selected as an experimental group who joined a 20-week collaborative science intervention, which integrated and utilized an innovative teaching strategy. Fifty-eight eighth-grade high achieving students were selected as the comparison group. The Secondary School Student Questionnaire was conducted to measure all participants' learning anxiety and attitudes toward science. In addition, 12 target students from the experimental group (i.e., six active and six passive students) were recruited for weekly classroom observations and follow-up interviews during the intervention. Both quantitative and qualitative findings revealed that experimental group students experienced significant impact as seen through increased attitudes and decreased anxiety of learning science. Implications for practice and research are provided.

Experimental investigation of heat transfer and fluid flow behaviour in multiple square perforated twisted tape with square wing inserts heat exchanger tube

NASA Astrophysics Data System (ADS)

Suri, Amar Raj Singh; Kumar, Anil; Maithani, Rajesh

2018-01-01

The present work deals with experimental investigation of heat transfer and fluid flow characteristics of multiple square perforated twisted tape with wing inserts in a heat exchanger tube. The range of selected geometrical parameters are, perforation width ratio (a/WT) of 0.083-0.333, twist ratio (TL/WT) of 2.0-3.5, wing depth ratio (Wd/WT) of 0.042-0.167 and number of twisted tapes (TP) of 4. The Reynolds number (Ren) selected for experimentation ranges from 5000 to 27,000. The maximum heat transfer and friction factor enhancement was found to be 6.96 and 8.34 times that of plane tube, respectively. The maximum heat transfer enhancement is observed at a a/WT of 0.250, TL/WT of 2.5, and Wd/WT of 0.167.

Experimental investigation of heat transfer and fluid flow behaviour in multiple square perforated twisted tape with square wing inserts heat exchanger tube

NASA Astrophysics Data System (ADS)

Suri, Amar Raj Singh; Kumar, Anil; Maithani, Rajesh

2018-06-01

The present work deals with experimental investigation of heat transfer and fluid flow characteristics of multiple square perforated twisted tape with wing inserts in a heat exchanger tube. The range of selected geometrical parameters are, perforation width ratio (a/WT) of 0.083-0.333, twist ratio (TL/WT) of 2.0-3.5, wing depth ratio (Wd/WT) of 0.042-0.167 and number of twisted tapes (TP) of 4. The Reynolds number (Ren) selected for experimentation ranges from 5000 to 27,000. The maximum heat transfer and friction factor enhancement was found to be 6.96 and 8.34 times that of plane tube, respectively. The maximum heat transfer enhancement is observed at a a/WT of 0.250, TL/WT of 2.5, and Wd/WT of 0.167.

Defect Characterization in Semiconductors with Positron Annihilation Spectroscopy

NASA Astrophysics Data System (ADS)

Tuomisto, Filip

Positron annihilation spectroscopy is an experimental technique that allows the selective detection of vacancy defects in semiconductors, providing a means to both identify and quantify them. This chapter gives an introduction to the principles of the positron annihilation techniques and then discusses the physics of some interesting observations on vacancy defects related to growth and doping of semiconductors. Illustrative examples are selected from studies performed in silicon, III-nitrides, and ZnO.

The selective processing of emotional visual stimuli while detecting auditory targets: an ERP analysis.

PubMed

Schupp, Harald T; Stockburger, Jessica; Bublatzky, Florian; Junghöfer, Markus; Weike, Almut I; Hamm, Alfons O

2008-09-16

Event-related potential studies revealed an early posterior negativity (EPN) for emotional compared to neutral pictures. Exploring the emotion-attention relationship, a previous study observed that a primary visual discrimination task interfered with the emotional modulation of the EPN component. To specify the locus of interference, the present study assessed the fate of selective visual emotion processing while attention is directed towards the auditory modality. While simply viewing a rapid and continuous stream of pleasant, neutral, and unpleasant pictures in one experimental condition, processing demands of a concurrent auditory target discrimination task were systematically varied in three further experimental conditions. Participants successfully performed the auditory task as revealed by behavioral performance and selected event-related potential components. Replicating previous results, emotional pictures were associated with a larger posterior negativity compared to neutral pictures. Of main interest, increasing demands of the auditory task did not modulate the selective processing of emotional visual stimuli. With regard to the locus of interference, selective emotion processing as indexed by the EPN does not seem to reflect shared processing resources of visual and auditory modality.

Likelihood-based modification of experimental crystal structure electron density maps

DOEpatents

Terwilliger, Thomas C [Sante Fe, NM

2005-04-16

A maximum-likelihood method for improves an electron density map of an experimental crystal structure. A likelihood of a set of structure factors {F.sub.h } is formed for the experimental crystal structure as (1) the likelihood of having obtained an observed set of structure factors {F.sub.h.sup.OBS } if structure factor set {F.sub.h } was correct, and (2) the likelihood that an electron density map resulting from {F.sub.h } is consistent with selected prior knowledge about the experimental crystal structure. The set of structure factors {F.sub.h } is then adjusted to maximize the likelihood of {F.sub.h } for the experimental crystal structure. An improved electron density map is constructed with the maximized structure factors.

Synthesis, spectral and structural characterization of isobutyl 4-(2-chlorophenyl)-5-cyano-6-(((dimethylamino)methylene)amino)-2-methyl-4H-pyran-3-carboxylate

NASA Astrophysics Data System (ADS)

Udhaya Kumar, C.; Velayutham Pillai, M.; Gokula Krishnan, K.; Ramalingan, C.

2017-09-01

A fascinating selectivity in the direction of the formation of the formamidine was observed upon the reaction of isobutyl 6-amino-4-(2-chlorophenyl)-5-cyano-2-methyl-4H-pyran-3-carboxylate with N,N-dimethyl formamide. A development in selectivity is explored and a probable mechanism for the reaction is also proposed. The formamidine has been analyzed by FT-IR, FT-Raman, LC-MS and NMR (1D and 2D (1H-1H COSY, 1H-13C COSY and HMBC)) spectra. The experimental findings are compared with the theoretical data calculated by using DFT-B3LYP with 6-311++G(d,p) basis set. A good agreement has been observed between experimental and theoretical data. Single crystal X-ray structural analysis of isobutyl 4-(2-chlorophenyl)-5-cyano-6-(((dimethylamino)methylene)amino)-2-methyl-4H-pyran-3-carboxylate (PDMF), evidences the conformation of pyran ring as "flattened-boat".

Adaptive Optics Image Restoration Based on Frame Selection and Multi-frame Blind Deconvolution

NASA Astrophysics Data System (ADS)

Tian, Yu; Rao, Chang-hui; Wei, Kai

Restricted by the observational condition and the hardware, adaptive optics can only make a partial correction of the optical images blurred by atmospheric turbulence. A postprocessing method based on frame selection and multi-frame blind deconvolution is proposed for the restoration of high-resolution adaptive optics images. By frame selection we mean we first make a selection of the degraded (blurred) images for participation in the iterative blind deconvolution calculation, with no need of any a priori knowledge, and with only a positivity constraint. This method has been applied to the restoration of some stellar images observed by the 61-element adaptive optics system installed on the Yunnan Observatory 1.2m telescope. The experimental results indicate that this method can effectively compensate for the residual errors of the adaptive optics system on the image, and the restored image can reach the diffraction-limited quality.

A bee-hive frequency selective surface for Wi-Max and GPS applications

NASA Astrophysics Data System (ADS)

Ray, A.; Kahar, M.; Sarkar, P. P.

2013-10-01

The paper presents investigations on a bee-hive cell, concentric aperture frequency selective surface (FSS) tuned to pass 1.5 GHz for global positioning system application and 3.5 GHz for worldwide interoperability for microwave access applications. The designed dual-band FSS screen is easy to fabricate with low cost materials, exhibiting low weight, with two broad transmission bands, where the maximum recorded -10 dB transmission percentage bandwidth is 68.67 %. Due to symmetrical nature of design, FSS is insensitive to variation of RF incidence angle for 60° rotations. A computationally efficient method for analysing this FSS is presented. Experimental investigation is performed using standard microwave test bench. It is observed that the computed and experimental results are in close agreement.

Angular selectivity asymmetry of holograms recorded in near infrared sensitive liquid crystal photopolymerizable materials

NASA Astrophysics Data System (ADS)

Harbour, Steven; Galstian, Tigran; Akopyan, Rafik; Galstyan, Artur

2004-08-01

We have experimentally observed and theoretically explained the angular selectivity asymmetry in polymer dispersed liquid crystal holograms. Experiments are conducted in compounds with near infrared sensitivity. The coupled-wave theory is used to describe the diffraction properties of obtained anisotropic holographic gratings. Furthermore, the comparison of theory and experiments provides information about the optical axis direction that is defined by the average molecular orientation of the liquid crystal in the polymer matrix.

Pattern selection and tip perturbations in the Saffman-Taylor problem

NASA Technical Reports Server (NTRS)

Hong, D. C.; Langer, J. S.

1987-01-01

An analytic approach to the Saffman-Taylor problem of predicting the width of a viscous finger in a Hele-Shaw cell is presented. The first purpose is to provide a systematic description of the way in which the singular perturbation introduced by capillary forces leads to a solvability mechanism for pattern selection. It is then shown how recent experimental observations by Couder et al. (1986) may be interpreted in terms suggested by this mechanism.

UV-tunable laser induced phototransformations of matrix isolated anethole.

PubMed

Krupa, Justyna; Wierzejewska, Maria; Nunes, Cláudio M; Fausto, Rui

2014-03-14

A matrix isolation study of the infrared spectra and structure of anethole (1-methoxy-4-(1-propenyl)benzene) has been carried out, showing the presence of two E conformers (AE1, AE2) of the molecule in the as-deposited matrices. Irradiation using ultraviolet-tunable laser light at 308-307 nm induced conformationally selective phototransformations of these forms into two less stable Z conformers (AZ1, AZ2). The back reactions were also detected upon irradiation at 301 nm. On the whole, the obtained results allow for full assignment of the infrared spectra of all the four experimentally observed anethole isomers and showed that the narrowband UV-induced E-Z photoisomerization is an efficient and selective way to interconvert the two isomers of anethole into each other, with conformational discrimination. Photolysis of anethole was observed as well, with initial methoxyl O-C bond cleavage and formation of CH3 and p-propenylphenoxy (AR) radicals, followed by radical recombination to form 2-methyl-4-propenyl-2,4-cyclohexadienone, which subsequently undergoes ring-opening generating several conformers of long-chain conjugated ketenes. Interpretation of the experimental observations was supported by density functional theory (B3LYP and B2PLYD) calculations.

Non-linear identification of a squeeze-film damper

NASA Technical Reports Server (NTRS)

Stanway, Roger; Mottershead, John; Firoozian, Riaz

1987-01-01

Described is an experimental study to identify the damping laws associated with a squeeze-film vibration damper. This is achieved by using a non-linear filtering algorithm to process displacement responses of the damper ring to synchronous excitation and thus to estimate the parameters in an nth-power velocity model. The experimental facility is described in detail and a representative selection of results is included. The identified models are validated through the prediction of damper-ring orbits and comparison with observed responses.

Outlier Removal in Model-Based Missing Value Imputation for Medical Datasets.

PubMed

Huang, Min-Wei; Lin, Wei-Chao; Tsai, Chih-Fong

2018-01-01

Many real-world medical datasets contain some proportion of missing (attribute) values. In general, missing value imputation can be performed to solve this problem, which is to provide estimations for the missing values by a reasoning process based on the (complete) observed data. However, if the observed data contain some noisy information or outliers, the estimations of the missing values may not be reliable or may even be quite different from the real values. The aim of this paper is to examine whether a combination of instance selection from the observed data and missing value imputation offers better performance than performing missing value imputation alone. In particular, three instance selection algorithms, DROP3, GA, and IB3, and three imputation algorithms, KNNI, MLP, and SVM, are used in order to find out the best combination. The experimental results show that that performing instance selection can have a positive impact on missing value imputation over the numerical data type of medical datasets, and specific combinations of instance selection and imputation methods can improve the imputation results over the mixed data type of medical datasets. However, instance selection does not have a definitely positive impact on the imputation result for categorical medical datasets.

Selective weathering of shocked minerals and chondritic enrichment of the Martian fines

NASA Technical Reports Server (NTRS)

Boslough, M. B.

1987-01-01

In a recent paper, Boslough and Cygan reported the observation of shock-enhanced chemical weathering kinetics of three silicate minerals. Based on the experimental data and on those of Tyburczy and Ahrens for enhanced dehydration kinetics of shocked serpentine, a mechnaism is proposed by which shock-activated minerals are selectively weathered on the surface of Mars. The purpose of the present abstract is to argue on the basis of relative volumes of shocked materials that, as a direct consequence of selective weathering, the composition of the weathered surface units on Mars should be enriched in meteoritic material.

OBSERVATIONS ON THE REGROWTH OF SUBAQUATIC VEGETATION FOLLOWING TRANSPLANTATION: A POTENTIAL METHOD TO ASSESS ENVIRONMENTAL HEALTH OF COASTAL HABITATS

EPA Science Inventory

In 1991, experimental transplantings of Vallisneria americana (tapegrass, vallisneria, or wildcelery) were initiated at selected sites which lacked grass beds along the north shore of Perdido Bay, located on the Alabama-Florida border. Abatement of organic and color-staining comp...

First steps in experimental cancer evolution

PubMed Central

Taylor, Tiffany B; Johnson, Louise J; Jackson, Robert W; Brockhurst, Michael A; Dash, Philip R

2013-01-01

Evolutionary processes play a central role in the development, progression and response to treatment of cancers. The current challenge facing researchers is to harness evolutionary theory to further our understanding of the clinical progression of cancers. Central to this endeavour will be the development of experimental systems and approaches by which theories of cancer evolution can be effectively tested. We argue here that the experimental evolution approach – whereby evolution is observed in real time and which has typically employed microorganisms – can be usefully applied to cancer. This approach allows us to disentangle the ecological causes of natural selection, identify the genetic basis of evolutionary changes and determine their repeatability. Cell cultures used in cancer research share many of the desirable traits that make microorganisms ideal for studying evolution. As such, experimental cancer evolution is feasible and likely to give great insight into the selective pressures driving the evolution of clinically destructive cancer traits. We highlight three areas of evolutionary theory with importance to cancer biology that are amenable to experimental evolution: drug resistance, social evolution and resource competition. Understanding the diversity, persistence and evolution of cancers is vital for treatment and drug development, and an experimental evolution approach could provide strategic directions and focus for future research. PMID:23745144

Intrinsic selectivity and structure sensitivity of Rhodium catalysts for C 2+ oxygenate production [On the intrinsic selectivity and structure sensitivity of Rhodium catalysts for C 2+ oxygenate production

DOE PAGES

Yang, Nuoya; Medford, Andrew J.; Liu, Xinyan; ...

2016-01-31

Synthesis gas (CO + H 2) conversion is a promising route to converting coal, natural gas, or biomass into synthetic liquid fuels. Rhodium has long been studied as it is the only elemental catalyst that has demonstrated selectivity to ethanol and other C 2+ oxygenates. However, the fundamentals of syngas conversion over rhodium are still debated. In this work a microkinetic model is developed for conversion of CO and H 2 into methane, ethanol, and acetaldehyde on the Rh (211) and (111) surfaces, chosen to describe steps and close-packed facets on catalyst particles. The model is based on DFT calculationsmore » using the BEEF-vdW functional. The mean-field kinetic model includes lateral adsorbate–adsorbate interactions, and the BEEF-vdW error estimation ensemble is used to propagate error from the DFT calculations to the predicted rates. The model shows the Rh(211) surface to be ~6 orders of magnitude more active than the Rh(111) surface, but highly selective toward methane, while the Rh(111) surface is intrinsically selective toward acetaldehyde. A variety of Rh/SiO 2 catalysts are synthesized, tested for catalytic oxygenate production, and characterized using TEM. The experimental results indicate that the Rh(111) surface is intrinsically selective toward acetaldehyde, and a strong inverse correlation between catalytic activity and oxygenate selectivity is observed. Furthermore, iron impurities are shown to play a key role in modulating the selectivity of Rh/SiO 2 catalysts toward ethanol. The experimental observations are consistent with the structure-sensitivity predicted from theory. As a result, this work provides an improved atomic-scale understanding and new insight into the mechanism, active site, and intrinsic selectivity of syngas conversion over rhodium catalysts and may also guide rational design of alloy catalysts made from more abundant elements.« less

Intrinsic selectivity and structure sensitivity of Rhodium catalysts for C 2+ oxygenate production [On the intrinsic selectivity and structure sensitivity of Rhodium catalysts for C 2+ oxygenate production

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

Yang, Nuoya; Medford, Andrew J.; Liu, Xinyan

Synthesis gas (CO + H 2) conversion is a promising route to converting coal, natural gas, or biomass into synthetic liquid fuels. Rhodium has long been studied as it is the only elemental catalyst that has demonstrated selectivity to ethanol and other C 2+ oxygenates. However, the fundamentals of syngas conversion over rhodium are still debated. In this work a microkinetic model is developed for conversion of CO and H 2 into methane, ethanol, and acetaldehyde on the Rh (211) and (111) surfaces, chosen to describe steps and close-packed facets on catalyst particles. The model is based on DFT calculationsmore » using the BEEF-vdW functional. The mean-field kinetic model includes lateral adsorbate–adsorbate interactions, and the BEEF-vdW error estimation ensemble is used to propagate error from the DFT calculations to the predicted rates. The model shows the Rh(211) surface to be ~6 orders of magnitude more active than the Rh(111) surface, but highly selective toward methane, while the Rh(111) surface is intrinsically selective toward acetaldehyde. A variety of Rh/SiO 2 catalysts are synthesized, tested for catalytic oxygenate production, and characterized using TEM. The experimental results indicate that the Rh(111) surface is intrinsically selective toward acetaldehyde, and a strong inverse correlation between catalytic activity and oxygenate selectivity is observed. Furthermore, iron impurities are shown to play a key role in modulating the selectivity of Rh/SiO 2 catalysts toward ethanol. The experimental observations are consistent with the structure-sensitivity predicted from theory. As a result, this work provides an improved atomic-scale understanding and new insight into the mechanism, active site, and intrinsic selectivity of syngas conversion over rhodium catalysts and may also guide rational design of alloy catalysts made from more abundant elements.« less

Non-Equilibrium Dynamics Contribute to Ion Selectivity in the KcsA Channel

PubMed Central

Haas, Stephan; Farley, Robert A.

2014-01-01

The ability of biological ion channels to conduct selected ions across cell membranes is critical for the survival of both animal and bacterial cells. Numerous investigations of ion selectivity have been conducted over more than 50 years, yet the mechanisms whereby the channels select certain ions and reject others are not well understood. Here we report a new application of Jarzynski’s Equality to investigate the mechanism of ion selectivity using non-equilibrium molecular dynamics simulations of Na+ and K+ ions moving through the KcsA channel. The simulations show that the selectivity filter of KcsA adapts and responds to the presence of the ions with structural rearrangements that are different for Na+ and K+. These structural rearrangements facilitate entry of K+ ions into the selectivity filter and permeation through the channel, and rejection of Na+ ions. A mechanistic model of ion selectivity by this channel based on the results of the simulations relates the structural rearrangement of the selectivity filter to the differential dehydration of ions and multiple-ion occupancy and describes a mechanism to efficiently select and conduct K+. Estimates of the K+/Na+ selectivity ratio and steady state ion conductance for KcsA from the simulations are in good quantitative agreement with experimental measurements. This model also accurately describes experimental observations of channel block by cytoplasmic Na+ ions, the “punch through” relief of channel block by cytoplasmic positive voltages, and is consistent with the knock-on mechanism of ion permeation. PMID:24465882

Using R in experimental design with BIBD: An application in health sciences

NASA Astrophysics Data System (ADS)

Oliveira, Teresa A.; Francisco, Carla; Oliveira, Amílcar; Ferreira, Agostinho

2016-06-01

Considering the implementation of an Experimental Design, in any field, the experimenter must pay particular attention and look for the best strategies in the following steps: planning the design selection, conduct the experiments, collect observed data, proceed to analysis and interpretation of results. The focus is on providing both - a deep understanding of the problem under research and a powerful experimental process at a reduced cost. Mainly thanks to the possibility of allowing to separate variation sources, the importance of Experimental Design in Health Sciences is strongly recommended since long time. Particular attention has been devoted to Block Designs and more precisely to Balanced Incomplete Block Designs - in this case the relevance states from the fact that these designs allow testing simultaneously a number of treatments bigger than the block size. Our example refers to a possible study of inter reliability of the Parkinson disease, taking into account the UPDRS (Unified Parkinson's disease rating scale) in order to test if there are significant differences between the specialists who evaluate the patients performances. Statistical studies on this disease were described for example in Richards et al (1994), where the authors investigate the inter-rater Reliability of the Unified Parkinson's Disease Rating Scale Motor Examination. We consider a simulation of a practical situation in which the patients were observed by different specialists and the UPDRS on assessing the impact of Parkinson's disease in patients was observed. Assigning treatments to the subjects following a particular BIBD(9,24,8,3,2) structure, we illustrate that BIB Designs can be used as a powerful tool to solve emerging problems in this area. Once a structure with repeated blocks allows to have some block contrasts with minimum variance, see Oliveira et al. (2006), the design with cardinality 12 was selected for the example. R software was used for computations.

Plasma contactor research, 1989

NASA Technical Reports Server (NTRS)

Williams, John D.

1990-01-01

The characteristics of double layers observed by researchers investigating magnetospheric phenomena are contrasted to those observed in plasma contacting experiments. Experiments in the electron collection mode of the plasma contacting process were performed and the results confirm a simple model of this process for current levels ranging to 3 A. Experimental results were also obtained in a study of the process of electron emission from a hollow cathode plasma contactor. High energy ions are observed coming from the cathode in addition to the electrons and a phenomenological model that suggests a mechanism by which this could occur is presented. Experimental results showing the effects of the design parameters of the ambient plasma simulator on the plasma potential, electron temperature, electron density and plasma noise levels induced in plasma contacting experiments are presented. A preferred simulator design is selected on the basis of these results.

Final Report, DOE Early Career Award: Predictive modeling of complex physical systems: new tools for statistical inference, uncertainty quantification, and experimental design

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

Marzouk, Youssef

Predictive simulation of complex physical systems increasingly rests on the interplay of experimental observations with computational models. Key inputs, parameters, or structural aspects of models may be incomplete or unknown, and must be developed from indirect and limited observations. At the same time, quantified uncertainties are needed to qualify computational predictions in the support of design and decision-making. In this context, Bayesian statistics provides a foundation for inference from noisy and limited data, but at prohibitive computional expense. This project intends to make rigorous predictive modeling *feasible* in complex physical systems, via accelerated and scalable tools for uncertainty quantification, Bayesianmore » inference, and experimental design. Specific objectives are as follows: 1. Develop adaptive posterior approximations and dimensionality reduction approaches for Bayesian inference in high-dimensional nonlinear systems. 2. Extend accelerated Bayesian methodologies to large-scale {\\em sequential} data assimilation, fully treating nonlinear models and non-Gaussian state and parameter distributions. 3. Devise efficient surrogate-based methods for Bayesian model selection and the learning of model structure. 4. Develop scalable simulation/optimization approaches to nonlinear Bayesian experimental design, for both parameter inference and model selection. 5. Demonstrate these inferential tools on chemical kinetic models in reacting flow, constructing and refining thermochemical and electrochemical models from limited data. Demonstrate Bayesian filtering on canonical stochastic PDEs and in the dynamic estimation of inhomogeneous subsurface properties and flow fields.« less

Usage of machine learning for the separation of electroweak and strong Zγ production at the LHC experiments

NASA Astrophysics Data System (ADS)

Petukhov, A. M.; Soldatov, E. Yu

2017-12-01

Separation of electroweak component from strong component of associated Zγ production on hadron colliders is a very challenging task due to identical final states of such processes. The only difference is the origin of two leading jets in these two processes. Rectangular cuts on jet kinematic variables from ATLAS/CMS 8 TeV Zγ experimental analyses were improved using machine learning techniques. New selection variables were also tested. The expected significance of separation for LHC experiments conditions at the second datataking period (Run2) and 120 fb-1 amount of data reaches more than 5σ. Future experimental observation of electroweak Zγ production can also lead to the observation physics beyond Standard Model.

[The study and manufacture of spinning counter for experimental animals].

PubMed

Qi, X P; Zhou, C; Liu, F J; Chen, Z; Jiang, L; Yan, Z

1997-09-01

The single-chip microcomputer technique is used in the present study of spinning counter, which has 4 observation tunnels, the spinning behave of four experiment animals can be recorded at same time. The function of this instrument has four selections according to different experiment, and the recording data can be compute processed.

Relaxation Training with Aggressive Mentally Retarded Adults: A Failure to Observe Carry-Over Effects.

ERIC Educational Resources Information Center

Frankenberger, William

The study was designed to determine whether 16 aggressive mentally retarded adults could reduce their resting electromyographic (EMG) levels through relaxation training techniques. Ss were selected from a large state institution. Ss were divided into two groups--the experimental group received six training sessions which included whole body…

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

Cornacchia, Massimo

The VISA (Visible to Infrared SASE Amplifier) SASE free electron laser has been successfully operated at the Accelerator Test Facility (ATF) at BNL. High gain and saturation were observed at 840 nm. We describe here the diagnostic system, experimental procedures and data reduction algorithms, as the FEL performance was measured along the length of the undulator. We also discuss selected spectral radiation measurements.

Selectivity evaluation for two experimental gill-net configurations used to sample Lake Erie walleyes

USGS Publications Warehouse

Vandergoot, Christopher S.; Kocovsky, Patrick M.; Brenden, Travis O.; Liu, Weihai

2011-01-01

We used length frequencies of captured walleyes Sander vitreus to indirectly estimate and compare selectivity between two experimental gill-net configurations used to sample fish in Lake Erie: (1) a multifilament configuration currently used by the Ohio Department of Natural Resources (ODNR) with stretched-measure mesh sizes ranging from 51 to 127 mm and a constant filament diameter (0.37 mm); and (2) a monofilament configuration with mesh sizes ranging from 38 to 178 mm and varying filament diameter (range = 0.20–0.33 mm). Paired sampling with the two configurations revealed that the catch of walleyes smaller than 250 mm and larger than 600 mm was greater in the monofilament configuration than in the multifilament configuration, but the catch of 250–600-mm fish was greater in the multifilament configuration. Binormal selectivity functions yielded the best fit to observed walleye catches for both gill-net configurations based on model deviances. Incorporation of deviation terms in the binormal selectivity functions (i.e., to relax the assumption of geometric similarity) further improved the fit to observed catches. The final fitted selectivity functions produced results similar to those from the length-based catch comparisons: the monofilament configuration had greater selectivity for small and large walleyes and the multifilament configuration had greater selectivity for mid-sized walleyes. Computer simulations that incorporated the fitted binormal selectivity functions indicated that both nets were likely to result in some bias in age composition estimates and that the degree of bias would ultimately be determined by the underlying condition, mortality rate, and growth rate of the Lake Erie walleye population. Before the ODNR switches its survey gear, additional comparisons of the different gill-net configurations, such as fishing the net pairs across a greater range of depths and at more locations in the lake, should be conducted to maintain congruence in the fishery-independent survey time series.

Great apes select tools on the basis of their rigidity.

PubMed

Manrique, Héctor Marín; Gross, Alexandra Nam-Mi; Call, Josep

2010-10-01

Wild chimpanzees select tools according to their rigidity. However, little is known about whether choices are solely based on familiarity with the materials or knowledge about tool properties. Furthermore, it is unclear whether tool manipulation is required prior to selection or whether observation alone can suffice. We investigated whether chimpanzees (Pan troglodytes) (n = 9), bonobos (Pan paniscus) (n = 4), orangutans (Pongo pygmaeus) (n = 6), and gorillas (Gorilla gorilla) (n = 2) selected new tools on the basis of their rigidity. Subjects faced an out-of-reach reward and a choice of three tools differing in color, diameter, material, and rigidity. We used 10 different 3-tool sets (1 rigid, 2 flexible). Subjects were unfamiliar with the tools and needed to select and use the rigid tool to retrieve the reward. Experiment 1 showed that subjects chose the rigid tool from the first trial with a 90% success rate. Experiments 2a and 2b addressed the role of manipulation and observation in tool selection. Subjects performed equally well in conditions in which they could manipulate the tools themselves or saw the experimenter manipulate the tools but decreased their performance if they could only visually inspect the tools. Experiment 3 showed that subjects could select flexible tools (as opposed to rigid ones) to meet new task demands. We conclude that great apes spontaneously selected unfamiliar rigid or flexible tools even after gathering minimal observational information. 2010 APA, all rights reserved

Nanomaterials for the Selective Detection of Hydrogen Sulfide in Air

PubMed Central

Llobet, Eduard; Brunet, Jérôme; Pauly, Alain; Ndiaye, Amadou; Varenne, Christelle

2017-01-01

This paper presents a focused review on the nanomaterials and associated transduction schemes that have been developed for the selective detection of hydrogen sulfide. It presents a quite comprehensive overview of the latest developments, briefly discusses the hydrogen sulfide detection mechanisms, identifying the reasons for the selectivity (or lack of) observed experimentally. It critically reviews performance, shortcomings, and identifies missing or overlooked important aspects. It identifies the most mature/promising materials and approaches for achieving inexpensive hydrogen sulfide sensors that could be employed in widespread, miniaturized, and inexpensive detectors and, suggests what research should be undertaken for ensuring that requirements are met. PMID:28218674

Coordinated ionospheric and magnetospheric observations from the ISIS 2 satellite by the ISIS 2 experimenters. Volume 2: Auroral optical emissions magnetic field perturbations, and plasma characteristics, measured simultaneously on the same magnetic field line

NASA Technical Reports Server (NTRS)

Shepherd, G. G.

1980-01-01

The data set consists of a selected number of passes, each comprising a format combination that is most appropriate for the particular data set. A list of ISIS 2 experimenters, with addresses and telephone numbers is included. A brief description of the ISIS 2 satellite is given, followed by more detailed instrument descriptions, format descriptions, data set descriptions, and the data themselves.

Local hidden-variable model for a recent experimental test of quantum nonlocality and local contextuality

NASA Astrophysics Data System (ADS)

La Cour, Brian R.

2017-07-01

An experiment has recently been performed to demonstrate quantum nonlocality by establishing contextuality in one of a pair of photons encoding four qubits; however, low detection efficiencies and use of the fair-sampling hypothesis leave these results open to possible criticism due to the detection loophole. In this Letter, a physically motivated local hidden-variable model is considered as a possible mechanism for explaining the experimentally observed results. The model, though not intrinsically contextual, acquires this quality upon post-selection of coincident detections.

Finding viable models in SUSY parameter spaces with signal specific discovery potential

NASA Astrophysics Data System (ADS)

Burgess, Thomas; Lindroos, Jan Øye; Lipniacka, Anna; Sandaker, Heidi

2013-08-01

Recent results from ATLAS giving a Higgs mass of 125.5 GeV, further constrain already highly constrained supersymmetric models such as pMSSM or CMSSM/mSUGRA. As a consequence, finding potentially discoverable and non-excluded regions of model parameter space is becoming increasingly difficult. Several groups have invested large effort in studying the consequences of Higgs mass bounds, upper limits on rare B-meson decays, and limits on relic dark matter density on constrained models, aiming at predicting superpartner masses, and establishing likelihood of SUSY models compared to that of the Standard Model vis-á-vis experimental data. In this paper a framework for efficient search for discoverable, non-excluded regions of different SUSY spaces giving specific experimental signature of interest is presented. The method employs an improved Markov Chain Monte Carlo (MCMC) scheme exploiting an iteratively updated likelihood function to guide search for viable models. Existing experimental and theoretical bounds as well as the LHC discovery potential are taken into account. This includes recent bounds on relic dark matter density, the Higgs sector and rare B-mesons decays. A clustering algorithm is applied to classify selected models according to expected phenomenology enabling automated choice of experimental benchmarks and regions to be used for optimizing searches. The aim is to provide experimentalist with a viable tool helping to target experimental signatures to search for, once a class of models of interest is established. As an example a search for viable CMSSM models with τ-lepton signatures observable with the 2012 LHC data set is presented. In the search 105209 unique models were probed. From these, ten reference benchmark points covering different ranges of phenomenological observables at the LHC were selected.

Orbital selective pairing and gap structures of iron-based superconductors

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

Kreisel, Andreas; Andersen, Brian M.; Sprau, P. O.

We discuss the in uence on spin-fluctuation pairing theory of orbital selective strong correlation effects in Fe-based superconductors, particularly Fe chalcogenide systems. We propose that a key ingredient for an improved itinerant pairing theory is orbital selectivity, i.e., incorporating the reduced coherence of quasiparticles occupying specific orbital states. This modifies the usual spin-fluctuation via suppression of pair scattering processes involving those less coherent states and results in orbital selective Cooper pairing of electrons in the remaining states. We show that this paradigm yields remarkably good agreement with the experimentally observed anisotropic gap structures in both bulk and monolayer FeSe, asmore » well as LiFeAs, indicating that orbital selective Cooper pairing plays a key role in the more strongly correlated iron-based superconductors.« less

Orbital selective pairing and gap structures of iron-based superconductors

DOE PAGES

Kreisel, Andreas; Andersen, Brian M.; Sprau, P. O.; ...

2017-05-08

We discuss the in uence on spin-fluctuation pairing theory of orbital selective strong correlation effects in Fe-based superconductors, particularly Fe chalcogenide systems. We propose that a key ingredient for an improved itinerant pairing theory is orbital selectivity, i.e., incorporating the reduced coherence of quasiparticles occupying specific orbital states. This modifies the usual spin-fluctuation via suppression of pair scattering processes involving those less coherent states and results in orbital selective Cooper pairing of electrons in the remaining states. We show that this paradigm yields remarkably good agreement with the experimentally observed anisotropic gap structures in both bulk and monolayer FeSe, asmore » well as LiFeAs, indicating that orbital selective Cooper pairing plays a key role in the more strongly correlated iron-based superconductors.« less

Overview of clinical research design.

PubMed

Hartung, Daniel M; Touchette, Daniel

2009-02-15

Basic concepts and terminology of clinical research design are presented for new clinical investigators. Clinical research, research involving human subjects, can be described as either observational or experimental. The findings of all clinical research can be threatened by issues of bias and confounding. Biases are systematic errors in how study subjects are selected or measured, which result in false inferences. Confounding is a distortion in findings that is attributable to mixing variable effects. Uncontrolled observation research is generally more prone to bias and confounding than experimental research. Observational research includes designs such as the cohort study, case-control study, and cross-sectional study, while experimental research typically involves a randomized controlled trial (RCT). The cohort study, which includes the RCT, defines subject allocation on the basis of exposure interest (e.g., drug, disease-management program) and follows the patients to assess the outcomes. The case-control study uses the primary outcome of interest (e.g., adverse event) to define subject allocation, and different exposures are assessed in a retrospective manner. Cross-sectional research evaluates both exposure and outcome concurrently. Each of these design methods possesses different strengths and weaknesses in answering research questions, as well as underlying many study subtypes. While experimental research is the strongest method for establishing causality, it can be difficult to accomplish under many scenarios. Observational clinical research offers many design alternatives that may be appropriate if planned and executed carefully.

Direct observation of the skyrmion Hall effect

DOE PAGES

Jiang, Wanjun; Zhang, Xichao; Yu, Guoqiang; ...

2016-09-19

The well-known Hall effect describes the transverse deflection of charged particles (electrons/holes) as a result of the Lorentz force. Similarly, it is intriguing to examine if quasi-particles without an electric charge, but with a topological charge, show related transverse motion. Magnetic skyrmions with a well-defined spin texture with a unit topological charge serve as good candidates to test this hypothesis. In spite of the recent progress made on investigating magnetic skyrmions, direct observation of the skyrmion Hall effect has remained elusive. Here, by using a current-induced spin Hall spin torque, we experimentally demonstrate the skyrmion Hall effect, and the resultantmore » skyrmion accumulation, by driving skyrmions from the creep-motion regime (where their dynamics are influenced by pinning defects) into the steady-flow-motion regime. Lastly, the experimental observation of transverse transport of skyrmions due to topological charge may potentially create many exciting opportunities, such as topological selection.« less

Experimental Observation of Near-Field Deterioration Induced by Stimulated Rotational Raman Scattering in Long Air Paths

NASA Astrophysics Data System (ADS)

Wang, Jing; Zhang, Xiao-Min; Han, Wei; Li, Fu-Quan; Zhou, Li-Dan; Feng, Bin; Xiang, Yong

2011-08-01

We report the experimental investigation of a stimulated rotational Raman scattering effect in long air paths on SG-III TIL, with a 1053 nm, 20-cm-diameter, linearly polarized, 3 ns flat-topped laser pulse. An intense speckle pattern of near field with thickly dotted hot spots is observed at the end of propagation with an intensity-length product above 17TW/cm. The Stokes developing from the scattering of the laser beam by quantum fluctuations is characterized by a combination of high spatial frequency components. The observed speckle pattern with small-diameter hot spots results from the combination of the nonlinear Raman amplification and the linear diffraction propagation effect of the Stokes with a noise pattern arising from the spontaneous Raman scattering. A new promising suppression concept based on the special characteristic of the Stokes, called active and selective filtering of Stokes, is proposed.

Direct observation of the skyrmion Hall effect

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

Jiang, Wanjun; Zhang, Xichao; Yu, Guoqiang

The well-known Hall effect describes the transverse deflection of charged particles (electrons/holes) as a result of the Lorentz force. Similarly, it is intriguing to examine if quasi-particles without an electric charge, but with a topological charge, show related transverse motion. Magnetic skyrmions with a well-defined spin texture with a unit topological charge serve as good candidates to test this hypothesis. In spite of the recent progress made on investigating magnetic skyrmions, direct observation of the skyrmion Hall effect has remained elusive. Here, by using a current-induced spin Hall spin torque, we experimentally demonstrate the skyrmion Hall effect, and the resultantmore » skyrmion accumulation, by driving skyrmions from the creep-motion regime (where their dynamics are influenced by pinning defects) into the steady-flow-motion regime. Lastly, the experimental observation of transverse transport of skyrmions due to topological charge may potentially create many exciting opportunities, such as topological selection.« less

Self-Replicating Cracks: A Collaborative Fracture Mode in Thin Films

NASA Astrophysics Data System (ADS)

Marthelot, Joël; Roman, Benoît; Bico, José; Teisseire, Jérémie; Dalmas, Davy; Melo, Francisco

2014-08-01

Straight cracks are observed in thin coatings under residual tensile stress, resulting into the classical network pattern observed in china crockery, old paintings, or dry mud. Here, we present a novel fracture mechanism where delamination and propagation occur simultaneously, leading to the spontaneous self-replication of an initial template. Surprisingly, this mechanism is active below the standard critical tensile load for channel cracks and selects a robust interaction length scale on the order of 30 times the film thickness. Depending on triggering mechanisms, crescent alleys, spirals, or long bands are generated over a wide range of experimental parameters. We describe with a simple physical model, the selection of the fracture path and provide a configuration diagram displaying the different failure modes.

Microbial catabolic activities are naturally selected by metabolic energy harvest rate.

PubMed

González-Cabaleiro, Rebeca; Ofiţeru, Irina D; Lema, Juan M; Rodríguez, Jorge

2015-12-01

The fundamental trade-off between yield and rate of energy harvest per unit of substrate has been largely discussed as a main characteristic for microbial established cooperation or competition. In this study, this point is addressed by developing a generalized model that simulates competition between existing and not experimentally reported microbial catabolic activities defined only based on well-known biochemical pathways. No specific microbial physiological adaptations are considered, growth yield is calculated coupled to catabolism energetics and a common maximum biomass-specific catabolism rate (expressed as electron transfer rate) is assumed for all microbial groups. Under this approach, successful microbial metabolisms are predicted in line with experimental observations under the hypothesis of maximum energy harvest rate. Two microbial ecosystems, typically found in wastewater treatment plants, are simulated, namely: (i) the anaerobic fermentation of glucose and (ii) the oxidation and reduction of nitrogen under aerobic autotrophic (nitrification) and anoxic heterotrophic and autotrophic (denitrification) conditions. The experimentally observed cross feeding in glucose fermentation, through multiple intermediate fermentation pathways, towards ultimately methane and carbon dioxide is predicted. Analogously, two-stage nitrification (by ammonium and nitrite oxidizers) is predicted as prevailing over nitrification in one stage. Conversely, denitrification is predicted in one stage (by denitrifiers) as well as anammox (anaerobic ammonium oxidation). The model results suggest that these observations are a direct consequence of the different energy yields per electron transferred at the different steps of the pathways. Overall, our results theoretically support the hypothesis that successful microbial catabolic activities are selected by an overall maximum energy harvest rate.

Phase-field simulations of GaN growth by selective area epitaxy on complex mask geometries

DOE PAGES

Aagesen, Larry K.; Coltrin, Michael Elliott; Han, Jung; ...

2015-05-15

Three-dimensional phase-field simulations of GaN growth by selective area epitaxy were performed. Furthermore, this model includes a crystallographic-orientation-dependent deposition rate and arbitrarily complex mask geometries. The orientation-dependent deposition rate can be determined from experimental measurements of the relative growth rates of low-index crystallographic facets. Growth on various complex mask geometries was simulated on both c-plane and a-plane template layers. Agreement was observed between simulations and experiment, including complex phenomena occurring at the intersections between facets. The sources of the discrepancies between simulated and experimental morphologies were also investigated. We found that the model provides a route to optimize masks andmore » processing conditions during materials synthesis for solar cells, light-emitting diodes, and other electronic and opto-electronic applications.« less

Experimental and Computational Exploration of para-Selective Silylation with a Hydrogen-Bonded Template.

PubMed

Maji, Arun; Guin, Srimanta; Feng, Sheng; Dahiya, Amit; Singh, Vikas Kumar; Liu, Peng; Maiti, Debabrata

2017-11-20

The regioselective conversion of C-H bonds into C-Si bonds is extremely important owing to the natural abundance and non-toxicity of silicon. Classical silylation reactions often suffer from poor functional group compatibility, low atom economy, and insufficient regioselectivity. Herein, we disclose a template-assisted method for the regioselective para silylation of toluene derivatives. A new template was designed, and the origin of selectivity was analyzed experimentally and computationally. An interesting substrate-solvent hydrogen-bonding interaction was observed. Kinetic, spectroscopic, and computational studies shed light on the reaction mechanism. The synthetic significance of this strategy was highlighted by the generation of a precursor of a potential lipophilic bioisostere of γ-aminobutyric acid (GABA), various late-stage diversifications, and by mimicking enzymatic transformations. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Quantum irreversible decoherence behaviour in open quantum systems with few degrees of freedom: Application to 1H NMR reversion experiments in nematic liquid crystals

NASA Astrophysics Data System (ADS)

Segnorile, H. H.; Zamar, R. C.

2013-10-01

An experimental study of NMR spin decoherence in nematic liquid crystals is presented. Decoherence dynamics can be put in evidence by means of refocusing experiments of the dipolar interactions. The experimental technique used in this work is based on the MREV8 pulse sequence. The aim of the work is to detect the main features of the irreversible quantum decoherence in liquid crystals, on the basis of the theory presented by the authors recently. The focus is laid on experimentally probing the eigen-selection process in the intermediate time scale, between quantum interference of a closed system and thermalization, as a signature of the quantum spin decoherence of the open quantum system, as well as on quantifying the effects of non-idealities as possible sources of signal decays which could mask the intrinsic decoherence. In order to contrast experiment and theory, the theory was adapted to obtain the decoherence function corresponding to the MREV8 reversion experiments. Non-idealities of the experimental setting, like external field inhomogeneity, pulse misadjustments, and the presence of non-reverted spin interaction terms are analysed in detail within this framework, and their effects on the observed signal decay are numerically estimated. It is found that though all these non-idealities could in principle affect the evolution of the spin dynamics, their influence can be mitigated and they do not present the characteristic behaviour of the irreversible spin decoherence. As unique characteristic of decoherence, the experimental results clearly show the occurrence of eigen-selectivity in the intermediate timescale, in complete agreement with the theoretical predictions. We conclude that the eigen-selection effect is the fingerprint of decoherence associated with a quantum open spin system in liquid crystals. Besides, these features of the results account for the quasi-equilibrium states of the spin system, which were observed previously in these mesophases, and lead to conclude that the quasi-equilibrium is a definite stage of the spin dynamics during its evolution towards equilibrium.

(abstract) A Brief, Selective Review of Thermal Cycling Fatigue in Eutectic Tin-Lead Solder

NASA Technical Reports Server (NTRS)

Winslow, J. W.; Silveira, C. de

1993-01-01

This paper reviews selected parts of the current literature relevant to thermo-mechanical fatigue mechanisms in eutectic tin-lead solder, and suggests a general outline to account for some observed failures. The field is found to be complex. One recent experimental study finds some failure modes to be sensitive to joint geometry. Attempts to extrapolate from test environments to service environments have had only limited success. Much work remains to be done before fatigue failures in this material can be considered as under practical control.

Omnidirectional-view three-dimensional display system based on cylindrical selective-diffusing screen.

PubMed

Xia, Xinxing; Zheng, Zhenrong; Liu, Xu; Li, Haifeng; Yan, Caijie

2010-09-10

We utilized a high-frame-rate projector, a rotating mirror, and a cylindrical selective-diffusing screen to present a novel three-dimensional (3D) omnidirectional-view display system without the need for any special viewing aids. The display principle and image size are analyzed, and the common display zone is proposed. The viewing zone for one observation place is also studied. The experimental results verify this method, and a vivid color 3D scene with occlusion and smooth parallax is also demonstrated with the system.

Selecting promising treatments in randomized Phase II cancer trials with an active control.

PubMed

Cheung, Ying Kuen

2009-01-01

The primary objective of Phase II cancer trials is to evaluate the potential efficacy of a new regimen in terms of its antitumor activity in a given type of cancer. Due to advances in oncology therapeutics and heterogeneity in the patient population, such evaluation can be interpreted objectively only in the presence of a prospective control group of an active standard treatment. This paper deals with the design problem of Phase II selection trials in which several experimental regimens are compared to an active control, with an objective to identify an experimental arm that is more effective than the control or to declare futility if no such treatment exists. Conducting a multi-arm randomized selection trial is a useful strategy to prioritize experimental treatments for further testing when many candidates are available, but the sample size required in such a trial with an active control could raise feasibility concerns. In this study, we extend the sequential probability ratio test for normal observations to the multi-arm selection setting. The proposed methods, allowing frequent interim monitoring, offer high likelihood of early trial termination, and as such enhance enrollment feasibility. The termination and selection criteria have closed form solutions and are easy to compute with respect to any given set of error constraints. The proposed methods are applied to design a selection trial in which combinations of sorafenib and erlotinib are compared to a control group in patients with non-small-cell lung cancer using a continuous endpoint of change in tumor size. The operating characteristics of the proposed methods are compared to that of a single-stage design via simulations: The sample size requirement is reduced substantially and is feasible at an early stage of drug development.

Two different approaches in skin cancer therapy: using a photosensitizer/a natural product

NASA Astrophysics Data System (ADS)

Abraham, Annie; Gayathri, Devi D.; Cibin, T. R.; Ramaiah, D.

2010-02-01

This paper deals with two potential modes for the treatment of skin cancer-one a novel approach using a squaraine dye and the other using a natural product- the flavonoid fraction of Saraca asoka. Squaraine dye is a photosensitizing agent, which is preferentially taken up and retained by the tumor cells and when irradiated with high power visible light results in the selective destruction of the tumor cells by photodynamic therapy. The uniqueness of this mode of treatment lies in the selective destruction of tumor cells without affecting the neighbouring normal cells, which is much advantageous over radiation therapy now frequently used. The chemopreventive and therapeutic effects of the plant component are explored as well. The experimental models were Swiss albino mice in which skin tumor was induced by DMBA. Marked reduction in tumor volume and burden in the treated groups were observed. The reversal of biochemical enzyme markers like rhodanese, myeloperoxidase, β-D glucuronidase, lactate dehydrogenase, hexokinase and sialic acid to near normal levels were observed in the PDT and flavonoid fraction treated groups. The live photographs of the experimental animals and histopathological data further support the obtained results. The study assumes importance as it combines a traditional treatment mode and a novel aspect in cancer therapy using the same experimental models. Also this is the first report on PDT using a squaraine dye for skin cancer therapy in vivo.

Magnetoplasmonic nanostructures based on nickel inverse opal slabs

NASA Astrophysics Data System (ADS)

Grunin, A. A.; Sapoletova, N. A.; Napolskii, K. S.; Eliseev, A. A.; Fedyanin, A. A.

2012-04-01

Nanostructured nickel surfaces representing periodically arranged spherical voids in a nickel film are obtained by electrochemical deposition through a self-assembled opaline template. Excitation of surface plasmon-polaritons (SPPs) on the surface of the sample is experimentally observed as the Wood's anomaly in the reflectance spectra. Transversal magneto-optical Kerr effect (TMOKE) spectra are measured at the different angles of incidence and azimuthal angles. The two- to-threefold enhancement of TMOKE caused by the excitation of mixed plasmons in two selected azimuthal configurations is observed.

Experimental Observations on Dynamic Response of Selected Transparent Armor Materials

DTIC Science & Technology

2014-07-01

that is transmitted through the specimen. A cu- boidal calibration specimen made from Ti – 6Al – 4V alloy was used for this purpose. References 9 and...average (Fig. 9). The density is typically 3.67 g/ cm3, but will vary slightly depending on the composition and porosity . The range of grain sizes for

An Analytical Chemistry Experiment in Simultaneous Spectrophotometric Determination of Fe(III) and Cu(II) with Hexacyanoruthenate(II) Reagent.

ERIC Educational Resources Information Center

Mehra, M. C.; Rioux, J.

1982-01-01

Experimental procedures, typical observations, and results for the simultaneous analysis of Fe(III) and Cu(II) in a solution are discussed. The method is based on selective interaction between the two ions and potassium hexacyanoruthenate(II) in acid solution involving no preliminary sample preparations. (Author/JN)

A Step-by-Step Guide to Propensity Score Matching in R

ERIC Educational Resources Information Center

Randolph, Justus J.; Falbe, Kristina; Manuel, Austin Kureethara; Balloun, Joseph L.

2014-01-01

Propensity score matching is a statistical technique in which a treatment case is matched with one or more control cases based on each case's propensity score. This matching can help strengthen causal arguments in quasi-experimental and observational studies by reducing selection bias. In this article we concentrate on how to conduct propensity…

A new Infrared Atmospheric Sounding Interferometer channel selection and assessment of its impact on Met Office NWP forecasts

NASA Astrophysics Data System (ADS)

Noh, Young-Chan; Sohn, Byung-Ju; Kim, Yoonjae; Joo, Sangwon; Bell, William; Saunders, Roger

2017-11-01

A new set of Infrared Atmospheric Sounding Interferometer (IASI) channels was re-selected from 314 EUMETSAT channels. In selecting channels, we calculated the impact of the individually added channel on the improvement in the analysis outputs from a one-dimensional variational analysis (1D-Var) for the Unified Model (UM) data assimilation system at the Met Office, using the channel score index (CSI) as a figure of merit. Then, 200 channels were selected in order by counting each individual channel's CSI contribution. Compared with the operationally used 183 channels for the UM at the Met Office, the new set shares 149 channels, while the other 51 channels are new. Also examined is the selection from the entropy reduction method with the same 1D-Var approach. Results suggest that channel selection can be made in a more objective fashion using the proposed CSI method. This is because the most important channels can be selected across the whole IASI observation spectrum. In the experimental trial runs using the UM global assimilation system, the new channels had an overall neutral impact in terms of improvement in forecasts, as compared with results from the operational channels. However, upper-tropospheric moist biases shown in the control run with operational channels were significantly reduced in the experimental trial with the newly selected channels. The reduction of moist biases was mainly due to the additional water vapor channels, which are sensitive to the upper-tropospheric water vapor.

Effects of Video Game Training on Measures of Selective Attention and Working Memory in Older Adults: Results from a Randomized Controlled Trial.

PubMed

Ballesteros, Soledad; Mayas, Julia; Prieto, Antonio; Ruiz-Marquez, Eloísa; Toril, Pilar; Reales, José M

2017-01-01

Video game training with older adults potentially enhances aspects of cognition that decline with aging and could therefore offer a promising training approach. Although, previous published studies suggest that training can produce transfer, many of them have certain shortcomings. This randomized controlled trial (RCT; Clinicaltrials.gov ID: NCT02796508) tried to overcome some of these limitations by incorporating an active control group and the assessment of motivation and expectations. Seventy-five older volunteers were randomly assigned to the experimental group trained for 16 sessions with non-action video games from Lumosity , a commercial platform (http://www.lumosity.com/) or to an active control group trained for the same number of sessions with simulation strategy games. The final sample included 55 older adults (30 in the experimental group and 25 in the active control group). Participants were tested individually before and after training to assess working memory (WM) and selective attention and also reported their perceived improvement, motivation and engagement. The results showed improved performance across the training sessions. The main results were: (1) the experimental group did not show greater improvements in measures of selective attention and working memory than the active control group (the opposite occurred in the oddball task); (2) a marginal training effect was observed for the N -back task, but not for the Stroop task while both groups improved in the Corsi Blocks task. Based on these results, one can conclude that training with non-action games provide modest benefits for untrained tasks. The effect is not specific for that kind of training as a similar effect was observed for strategy video games. Groups did not differ in motivation, engagement or expectations.

Effects of Video Game Training on Measures of Selective Attention and Working Memory in Older Adults: Results from a Randomized Controlled Trial

PubMed Central

Ballesteros, Soledad; Mayas, Julia; Prieto, Antonio; Ruiz-Marquez, Eloísa; Toril, Pilar; Reales, José M.

2017-01-01

Video game training with older adults potentially enhances aspects of cognition that decline with aging and could therefore offer a promising training approach. Although, previous published studies suggest that training can produce transfer, many of them have certain shortcomings. This randomized controlled trial (RCT; Clinicaltrials.gov ID: NCT02796508) tried to overcome some of these limitations by incorporating an active control group and the assessment of motivation and expectations. Seventy-five older volunteers were randomly assigned to the experimental group trained for 16 sessions with non-action video games from Lumosity, a commercial platform (http://www.lumosity.com/) or to an active control group trained for the same number of sessions with simulation strategy games. The final sample included 55 older adults (30 in the experimental group and 25 in the active control group). Participants were tested individually before and after training to assess working memory (WM) and selective attention and also reported their perceived improvement, motivation and engagement. The results showed improved performance across the training sessions. The main results were: (1) the experimental group did not show greater improvements in measures of selective attention and working memory than the active control group (the opposite occurred in the oddball task); (2) a marginal training effect was observed for the N-back task, but not for the Stroop task while both groups improved in the Corsi Blocks task. Based on these results, one can conclude that training with non-action games provide modest benefits for untrained tasks. The effect is not specific for that kind of training as a similar effect was observed for strategy video games. Groups did not differ in motivation, engagement or expectations. PMID:29163136

Studies of $$\\Lambda n$$ interaction through polarization observables for final-state interactions in exclusive $$\\Lambda$$ photoproduction off the deuteron

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

Ilieva, Yordanka; Cao, Tongtong; Zachariou, Nicholas

2016-06-01

Theoretical studies suggest that experimental observables for hyperon production reactions can place stringent constraints on the free parameters of hyperon-nucleon potentials, which are critical for the understanding of hypernuclear matter and neutron stars. Here we present preliminary experimental results for the polarization observables S, Py, Ox, Oz, Cx, and Cz for final-state interactions (FSI) in exclusive L photoproduction off the deuteron. The observables were obtained from data collected during the E06-103 (g13) experiment with the CEBAF Large Acceptance Spectrometer (CLAS) in Hall B at Jefferson Lab. The g13 experiment ran with unpolarized deuteron target and circularly- and linearly-polarized photon beamsmore » with energies between 0.5 GeV and 2.5 GeV and collected about 51010 events with multiple charged particles in the final state. To select the reaction of interest, the K+ and the L decay products, a proton and a negative pion, were detected in the CLAS. The missing-mass technique was used to identify exclusive hyperon photoproduction events. Final-state interaction events were selected by requesting that the reconstructed neutron has a momentum larger than 200 MeV/c. The large statistics of E06-103 provided statistically meaningful FSI event samples, which allow for the extraction of one- and two-fold differential single- and double-polarization observables. Here we present preliminary results for a set of six observables for photon energies between 0.9 GeV and 2.3 GeV and for several kinematic variables in the Ln center-of-mass frame. Our results are the very first estimates of polarization observables for FSI in hyperon photoproduction and will be used to constrain the free parameters of hyperon-nucleon potentials.« less

Representativeness of direct observations selected using a work-sampling equation.

PubMed

Sharp, Rebecca A; Mudford, Oliver C; Elliffe, Douglas

2015-01-01

Deciding on appropriate sampling to obtain representative samples of behavior is important but not straightforward, because the relative duration of the target behavior may affect its observation in a given sampling interval. Work-sampling methods, which offer a way to adjust the frequency of sampling according to a priori or ongoing estimates of the behavior to achieve a preselected level of representativeness, may provide a solution. Full-week observations of 7 behaviors were conducted for 3 students with autism spectrum disorder and intellectual disabilities. Work-sampling methods were used to select momentary time samples from the full time-of-interest, which produced representative samples. However, work sampling required impractically high numbers of time samples to obtain representative samples. More practical momentary time samples produced less representative samples, particularly for low-duration behaviors. The utility and limits of work-sampling methods for applied behavior analysis are discussed. © Society for the Experimental Analysis of Behavior.

First observation of low energy electron neutrinos in a liquid argon time projection chamber

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

Acciarri, R.; Adams, C.; Asaadi, J.

The capabilities of liquid argon time projection chambers (LArTPCs) to reconstruct the spatial and calorimetric information of neutrino events have made them the detectors of choice in a number of experiments, specically those looking to observe electron neutrino (e) appearance. The LArTPC promises excellent background rejection capabilities, especially in this \\golden" channel for both short and long baseline neutrino oscillation experiments. We present the rst experimental observation of electron neutrinos and anti-neutrinos in the ArgoNeut LArTPC, in the energy range relevant to DUNE and the Fermilab Short Baseline Neutrino Program. We have selected 37 electron candidate events and 274 gammamore » candidate events, and measured an 80% purity of electrons based on a topological selection. Additionally, we present a of separation of electrons from gammas using calorimetric energy deposition, demonstrating further separation of electrons from background gammas.« less

Applying Propensity Score Methods in Medical Research: Pitfalls and Prospects

PubMed Central

Luo, Zhehui; Gardiner, Joseph C.; Bradley, Cathy J.

2012-01-01

The authors review experimental and nonexperimental causal inference methods, focusing on assumptions for the validity of instrumental variables and propensity score (PS) methods. They provide guidance in four areas for the analysis and reporting of PS methods in medical research and selectively evaluate mainstream medical journal articles from 2000 to 2005 in the four areas, namely, examination of balance, overlapping support description, use of estimated PS for evaluation of treatment effect, and sensitivity analyses. In spite of the many pitfalls, when appropriately evaluated and applied, PS methods can be powerful tools in assessing average treatment effects in observational studies. Appropriate PS applications can create experimental conditions using observational data when randomized controlled trials are not feasible and, thus, lead researchers to an efficient estimator of the average treatment effect. PMID:20442340

Cytonuclear genetics of experimental fish hybrid zones inside Biosphere 2

USGS Publications Warehouse

Scribner, K.T.; Avise, John C.

1994-01-01

Two species of mosquitofish (family Poeciliidae) known to hybridize in nature were introduced into freshwater habitats inside Biosphere 2, and their population genetics were monitored after 2 years. Within four to six generations, nuclear and cytoplasmic markers characteristic of Gambusia holbrooki had risen greatly in frequency, although some Gambusia affinis alleles and haplotypes were retained primarily in recombinant genotypes, indicative of introgressive hybridization. The temporal cytonuclear dynamics proved similar to population genetic changes observed in replicated experimental hybrid populations outside of Biosphere 2, thus indicating strong directional selection favoring G. holbrooki genotypes across the range of environments monitored. When interpreted in the context of species-specific population demographies observed previously, results suggest that the extremely rapid evolution in these zones of secondary contact is attributable primarily to species differences in life-history traits.

An experimental evolution study confirms that discontinuous gas exchange does not contribute to body water conservation in locusts.

PubMed

Talal, Stav; Ayali, Amir; Gefen, Eran

2016-12-01

The adaptive nature of discontinuous gas exchange (DGE) in insects is contentious. The classic 'hygric hypothesis', which posits that DGE serves to reduce respiratory water loss (RWL), is still the best supported. We thus focused on the hygric hypothesis in this first-ever experimental evolution study of any of the competing adaptive hypotheses. We compared populations of the migratory locust (Locusta migratoria) that underwent 10 consecutive generations of selection for desiccation resistance with control populations. Selected locusts survived 36% longer under desiccation stress but DGE prevalence did not differ between these and control populations (approx. 75%). Evolved changes in DGE properties in the selected locusts included longer cycle and interburst durations. However, in contrast with predictions of the hygric hypothesis, these changes were not associated with reduced RWL rates. Other responses observed in the selected locusts were higher body water content when hydrated and lower total evaporative water loss rates. Hence, our data suggest that DGE cycle properties in selected locusts are a consequence of an evolved increased ability to store water, and thus an improved capacity to buffer accumulated CO 2 , rather than an adaptive response to desiccation. We conclude that DGE is unlikely to be an evolutionary response to dehydration challenge in locusts. © 2016 The Author(s).

Poisson-Nernst-Planck Models of Nonequilibrium Ion Electrodiffusion through a Protegrin Transmembrane Pore

PubMed Central

Bolintineanu, Dan S.; Sayyed-Ahmad, Abdallah; Davis, H. Ted; Kaznessis, Yiannis N.

2009-01-01

Protegrin peptides are potent antimicrobial agents believed to act against a variety of pathogens by forming nonselective transmembrane pores in the bacterial cell membrane. We have employed 3D Poisson-Nernst-Planck (PNP) calculations to determine the steady-state ion conduction characteristics of such pores at applied voltages in the range of −100 to +100 mV in 0.1 M KCl bath solutions. We have tested a variety of pore structures extracted from molecular dynamics (MD) simulations based on an experimentally proposed octomeric pore structure. The computed single-channel conductance values were in the range of 290–680 pS. Better agreement with the experimental range of 40–360 pS was obtained using structures from the last 40 ns of the MD simulation, where conductance values range from 280 to 430 pS. We observed no significant variation of the conductance with applied voltage in any of the structures that we tested, suggesting that the voltage dependence observed experimentally is a result of voltage-dependent channel formation rather than an inherent feature of the open pore structure. We have found the pore to be highly selective for anions, with anionic to cationic current ratios (ICl−/IK+) on the order of 103. This is consistent with the highly cationic nature of the pore but surprisingly in disagreement with the experimental finding of only slight anionic selectivity. We have additionally tested the sensitivity of our PNP model to several parameters and found the ion diffusion coefficients to have a significant influence on conductance characteristics. The best agreement with experimental data was obtained using a diffusion coefficient for each ion set to 10% of the bulk literature value everywhere inside the channel, a scaling used by several other studies employing PNP calculations. Overall, this work presents a useful link between previous work focused on the structure of protegrin pores and experimental efforts aimed at investigating their conductance characteristics. PMID:19180178

Predator-prey interactions in the plankton: larval fish feeding on evasive copepods

PubMed Central

Jackson, James M.; Lenz, Petra H.

2016-01-01

Capture success and prey selectivity were investigated in clownfish Amphiprion ocellaris larvae using videography. Three prey types were tested using developmental stages (nauplii, copepodites and adults) of the copepod Parvocalanus crassirostris. Predatory abilities improved rapidly between days 1 and 14 post-hatch. Initially, capture success was limited to nauplii with few attacks on larger stages. Captures of copepodites were first observed at 3 dph, and of adults at 8 dph. Consistent strikes at the larger prey were observed on the day prior to successful captures (2 dph for copepodites, 7 dph for adults). Difference in capture success between nauplii and adults at 8 dph was an order of magnitude. Differences in capture success among prey types persisted but decreased to three-fold by 14 dph. Younger A. ocellaris attacked nauplii preferentially and avoided adult prey. Strike selectivity declined with age, and no selectivity was observed after 10 dph. However, numerically 50% of the ingested prey were still nauplii at 14 dph under the experimental conditions. PMID:27658849

Predator-prey interactions in the plankton: larval fish feeding on evasive copepods.

PubMed

Jackson, James M; Lenz, Petra H

2016-09-23

Capture success and prey selectivity were investigated in clownfish Amphiprion ocellaris larvae using videography. Three prey types were tested using developmental stages (nauplii, copepodites and adults) of the copepod Parvocalanus crassirostris. Predatory abilities improved rapidly between days 1 and 14 post-hatch. Initially, capture success was limited to nauplii with few attacks on larger stages. Captures of copepodites were first observed at 3 dph, and of adults at 8 dph. Consistent strikes at the larger prey were observed on the day prior to successful captures (2 dph for copepodites, 7 dph for adults). Difference in capture success between nauplii and adults at 8 dph was an order of magnitude. Differences in capture success among prey types persisted but decreased to three-fold by 14 dph. Younger A. ocellaris attacked nauplii preferentially and avoided adult prey. Strike selectivity declined with age, and no selectivity was observed after 10 dph. However, numerically 50% of the ingested prey were still nauplii at 14 dph under the experimental conditions.

Predator-prey interactions in the plankton: larval fish feeding on evasive copepods

NASA Astrophysics Data System (ADS)

Jackson, James M.; Lenz, Petra H.

2016-09-01

Capture success and prey selectivity were investigated in clownfish Amphiprion ocellaris larvae using videography. Three prey types were tested using developmental stages (nauplii, copepodites and adults) of the copepod Parvocalanus crassirostris. Predatory abilities improved rapidly between days 1 and 14 post-hatch. Initially, capture success was limited to nauplii with few attacks on larger stages. Captures of copepodites were first observed at 3 dph, and of adults at 8 dph. Consistent strikes at the larger prey were observed on the day prior to successful captures (2 dph for copepodites, 7 dph for adults). Difference in capture success between nauplii and adults at 8 dph was an order of magnitude. Differences in capture success among prey types persisted but decreased to three-fold by 14 dph. Younger A. ocellaris attacked nauplii preferentially and avoided adult prey. Strike selectivity declined with age, and no selectivity was observed after 10 dph. However, numerically 50% of the ingested prey were still nauplii at 14 dph under the experimental conditions.

Selectivity in social and asocial learning: investigating the prevalence, effect and development of young children's learning preferences.

PubMed

Flynn, Emma; Turner, Cameron; Giraldeau, Luc-Alain

2016-03-19

Culture evolution requires both modification and faithful replication of behaviour, thus it is essential to understand how individuals choose between social and asocial learning. In a quasi-experimental design, 3- and 5-year-olds (176), and adults (52) were presented individually with two novel artificial fruits, and told of the apparatus' relative difficulty (easy versus hard). Participants were asked if they wanted to attempt the task themselves or watch an experimenter attempt it first; and then had their preference either met or violated. A significant proportion of children and adults (74%) chose to learn socially. For children, this request was efficient, as observing a demonstration made them significantly quicker at the task than learning asocially. However, for 5-year-olds, children who selected asocial learning were also found to be highly efficient at the task, showing that by 5 years children are selective in choosing a learning strategy that is effective for them. Adults further evidenced this trend, and also showed selectivity based on task difficulty. This is the first study to examine the rates, performance outcomes and developmental trajectory of preferences in asocial and social learning, ultimately informing our understanding of innovation. © 2016 The Authors.

Selectivity in social and asocial learning: investigating the prevalence, effect and development of young children's learning preferences

PubMed Central

Turner, Cameron; Giraldeau, Luc-Alain

2016-01-01

Culture evolution requires both modification and faithful replication of behaviour, thus it is essential to understand how individuals choose between social and asocial learning. In a quasi-experimental design, 3- and 5-year-olds (176), and adults (52) were presented individually with two novel artificial fruits, and told of the apparatus' relative difficulty (easy versus hard). Participants were asked if they wanted to attempt the task themselves or watch an experimenter attempt it first; and then had their preference either met or violated. A significant proportion of children and adults (74%) chose to learn socially. For children, this request was efficient, as observing a demonstration made them significantly quicker at the task than learning asocially. However, for 5-year-olds, children who selected asocial learning were also found to be highly efficient at the task, showing that by 5 years children are selective in choosing a learning strategy that is effective for them. Adults further evidenced this trend, and also showed selectivity based on task difficulty. This is the first study to examine the rates, performance outcomes and developmental trajectory of preferences in asocial and social learning, ultimately informing our understanding of innovation. PMID:26926279

Selection for increased voluntary wheel-running affects behavior and brain monoamines in mice

PubMed Central

Waters, R.Parrish; Pringle, R.B.; Forster, G.L.; Renner, K.J.; Malisch, J.L.; Garland, T.; Swallow, J.G.

2013-01-01

Selective-breeding of house mice for increased voluntary wheel-running has resulted in multiple physiological and behavioral changes. Characterizing these differences may lead to experimental models that can elucidate factors involved in human diseases and disorders associated with physical inactivity, or potentially treated by physical activity, such as diabetes, obesity, and depression. Herein, we present ethological data for adult males from a line of mice that has been selectively bred for high levels of voluntary wheel-running and from a non-selected control line, housed with or without wheels. Additionally, we present concentrations of central monoamines in limbic, striatal, and midbrain regions. We monitored wheel-running for 8 weeks, and observed home-cage behavior during the last 5 weeks of the study. Mice from the selected line accumulated more revolutions per day than controls due to increased speed and duration of running. Selected mice exhibited more active behaviors than controls, regardless of wheel access, and exhibited less inactivity and grooming than controls. Selective-breeding also influenced the longitudinal patterns of behavior. We found statistically significant differences in monoamine concentrations and associated metabolites in brain regions that influence exercise and motivational state. These results suggest underlying neurochemical differences between selected and control lines that may influence the observed differences in behavior. Our results bolster the argument that selected mice can provide a useful model of human psychological and physiological diseases and disorders. PMID:23352668

Observation of the 162Dy-164Dy Isotope Shift for the 0 → 16 717.79 cm-1 Optical Transition.

PubMed

Nardin Barreta, Luiz Felipe; Victor, Alessandro Rogério; Bueno, Patrícia; Dos Santos, Jhonatha Ricardo; da Silveira, Carlos Alberto Barbosa; Neri, José Wilson; Neto, Jonas Jakutis; Sbampato, Maria Esther; Destro, Marcelo Geraldo

2017-08-01

In this work, we report a newly observed isotope shift between 162 Dy and 164 Dy isotopes for the 0 → 16 717.79 cm -1 (598.003 nm) optical transition. We compared the newly observed results against two other lines (597.452 nm and 598.859 nm), which we measured in this work, and were already reported in the literature. The newly observed 162-164 Dy isotope shift, shows at least a 20% larger isotope shift than the isotope shifts for the other two lines investigated. The larger 162-164 isotope shift observed for the 598.003 nm line could lead to an increased isotope selectivity for atomic vapor laser isotope separation (AVLIS). Hence, this line could be a good choice for application in AVLIS. Experimental data available in the literature for the 597.452 nm and 598.859 nm lines, enabled us to perform simulations of spectra for both lines, in order to confirm the accuracy of our experimental measurements.

Improved prediction of peptide detectability for targeted proteomics using a rank-based algorithm and organism-specific data.

PubMed

Qeli, Ermir; Omasits, Ulrich; Goetze, Sandra; Stekhoven, Daniel J; Frey, Juerg E; Basler, Konrad; Wollscheid, Bernd; Brunner, Erich; Ahrens, Christian H

2014-08-28

The in silico prediction of the best-observable "proteotypic" peptides in mass spectrometry-based workflows is a challenging problem. Being able to accurately predict such peptides would enable the informed selection of proteotypic peptides for targeted quantification of previously observed and non-observed proteins for any organism, with a significant impact for clinical proteomics and systems biology studies. Current prediction algorithms rely on physicochemical parameters in combination with positive and negative training sets to identify those peptide properties that most profoundly affect their general detectability. Here we present PeptideRank, an approach that uses learning to rank algorithm for peptide detectability prediction from shotgun proteomics data, and that eliminates the need to select a negative dataset for the training step. A large number of different peptide properties are used to train ranking models in order to predict a ranking of the best-observable peptides within a protein. Empirical evaluation with rank accuracy metrics showed that PeptideRank complements existing prediction algorithms. Our results indicate that the best performance is achieved when it is trained on organism-specific shotgun proteomics data, and that PeptideRank is most accurate for short to medium-sized and abundant proteins, without any loss in prediction accuracy for the important class of membrane proteins. Targeted proteomics approaches have been gaining a lot of momentum and hold immense potential for systems biology studies and clinical proteomics. However, since only very few complete proteomes have been reported to date, for a considerable fraction of a proteome there is no experimental proteomics evidence that would allow to guide the selection of the best-suited proteotypic peptides (PTPs), i.e. peptides that are specific to a given proteoform and that are repeatedly observed in a mass spectrometer. We describe a novel, rank-based approach for the prediction of the best-suited PTPs for targeted proteomics applications. By building on methods developed in the field of information retrieval (e.g. web search engines like Google's PageRank), we circumvent the delicate step of selecting positive and negative training sets and at the same time also more closely reflect the experimentalist´s need for selecting e.g. the 5 most promising peptides for targeting a protein of interest. This approach allows to predict PTPs for not yet observed proteins or for organisms without prior experimental proteomics data such as many non-model organisms. Copyright © 2014 Elsevier B.V. All rights reserved.

Microstructure selection in thin-sample directional solidification of an Al-Cu alloy: In situ X-ray imaging and phase-field simulations

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

Clarke, A. J.; Tourret, D.; Song, Y.

We study microstructure selection during during directional solidification of a thin metallic sample. We combine in situ X-ray radiography of a dilute Al-Cu alloy solidification experiments with three-dimensional phase-field simulations. Here we explore a range of temperature gradient G and growth velocity V and build a microstructure selection map for this alloy. We investigate the selection of the primary dendritic spacing Λ and tip radius ρ. While ρ shows a good agreement between experimental measurements and dendrite growth theory, with ρ~V $-$1/2, Λ is observed to increase with V (∂Λ/∂V > 0), in apparent disagreement with classical scaling laws formore » primary dendritic spacing, which predict that ∂Λ/∂V<0. We show through simulations that this trend inversion for Λ(V) is due to liquid convection in our experiments, despite the thin sample configuration. We use a classical diffusion boundary-layer approximation to semi-quantitatively incorporate the effect of liquid convection into phase-field simulations. This approximation is implemented by assuming complete solute mixing outside a purely diffusive zone of constant thickness that surrounds the solid-liquid interface. This simple method enables us to quantitatively match experimental measurements of the planar morphological instability threshold and primary spacings over an order of magnitude in V. Lastly, we explain the observed inversion of ∂Λ/∂V by a combination of slow transient dynamics of microstructural homogenization and the influence of the sample thickness.« less

Microstructure selection in thin-sample directional solidification of an Al-Cu alloy: In situ X-ray imaging and phase-field simulations

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

Clarke, A. J.; Tourret, D.; Song, Y.

We study microstructure selection during directional solidification of a thin metallic sample. We combine in situ X-ray radiography of a dilute Al-Cu alloy solidification experiments with three-dimensional phase-field simulations. We explore a range of temperature gradient G and growth velocity V and build a microstructure selection map for this alloy. We investigate the selection of the primary dendritic spacing Lambda and tip radius rho. While rho shows a good agreement between experimental measurements and dendrite growth theory, with rho similar to V-1/2, Lambda is observed to increase with V (partial derivative Lambda/partial derivative V > 0), in apparent disagreement withmore » classical scaling laws for primary dendritic spacing, which predict that partial derivative Lambda/partial derivative V <0. We show through simulations that this trend inversion for Lambda(V) is due to liquid convection in our experiments, despite the thin sample configuration. We use a classical diffusion boundary-layer approximation to semi-quantitatively incorporate the effect of liquid convection into phase-field simulations. This approximation is implemented by assuming complete solute mixing outside a purely diffusive zone of constant thickness that surrounds the solid-liquid interface. This simple method enables us to quantitatively match experimental measurements of the planar morphological instability threshold and primary spacings over an order of magnitude in V. We explain the observed inversion of partial derivative Lambda/partial derivative V by a combination of slow transient dynamics of microstructural homogenization and the influence of the sample thickness.« less

Microstructure selection in thin-sample directional solidification of an Al-Cu alloy: In situ X-ray imaging and phase-field simulations

DOE PAGES

Clarke, A. J.; Tourret, D.; Song, Y.; ...

2017-05-01

We study microstructure selection during during directional solidification of a thin metallic sample. We combine in situ X-ray radiography of a dilute Al-Cu alloy solidification experiments with three-dimensional phase-field simulations. Here we explore a range of temperature gradient G and growth velocity V and build a microstructure selection map for this alloy. We investigate the selection of the primary dendritic spacing Λ and tip radius ρ. While ρ shows a good agreement between experimental measurements and dendrite growth theory, with ρ~V $-$1/2, Λ is observed to increase with V (∂Λ/∂V > 0), in apparent disagreement with classical scaling laws formore » primary dendritic spacing, which predict that ∂Λ/∂V<0. We show through simulations that this trend inversion for Λ(V) is due to liquid convection in our experiments, despite the thin sample configuration. We use a classical diffusion boundary-layer approximation to semi-quantitatively incorporate the effect of liquid convection into phase-field simulations. This approximation is implemented by assuming complete solute mixing outside a purely diffusive zone of constant thickness that surrounds the solid-liquid interface. This simple method enables us to quantitatively match experimental measurements of the planar morphological instability threshold and primary spacings over an order of magnitude in V. Lastly, we explain the observed inversion of ∂Λ/∂V by a combination of slow transient dynamics of microstructural homogenization and the influence of the sample thickness.« less

Mutualists and antagonists drive among-population variation in selection and evolution of floral display in a perennial herb

PubMed Central

Ågren, Jon; Hellström, Frida; Toräng, Per; Ehrlén, Johan

2013-01-01

Spatial variation in the direction of selection drives the evolution of adaptive differentiation. However, few experimental studies have examined the relative importance of different environmental factors for variation in selection and evolutionary trajectories in natural populations. Here, we combine 8 y of observational data and field experiments to assess the relative importance of mutualistic and antagonistic interactions for spatial variation in selection and short-term evolution of a genetically based floral display dimorphism in the short-lived perennial herb Primula farinosa. Natural populations of this species include two floral morphs: long-scaped plants that present their flowers well above the ground and short-scaped plants with flowers positioned close to the ground. The direction and magnitude of selection on scape morph varied among populations, and so did the frequency of the short morph (median 19%, range 0–100%; n = 69 populations). A field experiment replicated at four sites demonstrated that variation in the strength of interactions with grazers and pollinators were responsible for among-population differences in relative fitness of the two morphs. Selection exerted by grazers favored the short-scaped morph, whereas pollinator-mediated selection favored the long-scaped morph. Moreover, variation in selection among natural populations was associated with differences in morph frequency change, and the experimental removal of grazers at nine sites significantly reduced the frequency of the short-scaped morph over 8 y. The results demonstrate that spatial variation in intensity of grazing and pollination produces a selection mosaic, and that changes in biotic interactions can trigger rapid genetic changes in natural plant populations. PMID:24145439

Mutualists and antagonists drive among-population variation in selection and evolution of floral display in a perennial herb.

PubMed

Agren, Jon; Hellström, Frida; Toräng, Per; Ehrlén, Johan

2013-11-05

Spatial variation in the direction of selection drives the evolution of adaptive differentiation. However, few experimental studies have examined the relative importance of different environmental factors for variation in selection and evolutionary trajectories in natural populations. Here, we combine 8 y of observational data and field experiments to assess the relative importance of mutualistic and antagonistic interactions for spatial variation in selection and short-term evolution of a genetically based floral display dimorphism in the short-lived perennial herb Primula farinosa. Natural populations of this species include two floral morphs: long-scaped plants that present their flowers well above the ground and short-scaped plants with flowers positioned close to the ground. The direction and magnitude of selection on scape morph varied among populations, and so did the frequency of the short morph (median 19%, range 0-100%; n = 69 populations). A field experiment replicated at four sites demonstrated that variation in the strength of interactions with grazers and pollinators were responsible for among-population differences in relative fitness of the two morphs. Selection exerted by grazers favored the short-scaped morph, whereas pollinator-mediated selection favored the long-scaped morph. Moreover, variation in selection among natural populations was associated with differences in morph frequency change, and the experimental removal of grazers at nine sites significantly reduced the frequency of the short-scaped morph over 8 y. The results demonstrate that spatial variation in intensity of grazing and pollination produces a selection mosaic, and that changes in biotic interactions can trigger rapid genetic changes in natural plant populations.

Centrifugal slurry pump wear and hydraulic studies. Phase II report. Experimental studies

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

Mistry, D.; Cooper, P.; Biswas, C.

1983-01-01

This report describes the work performed by Ingersoll-Rand Research, Inc., under Phase II, Experimental Studies for the contract entitled, Centrifugal Slurry Pump Wear and Hydraulic Studies. This work was carried out for the US Department of Energy under Contract No. DE-AC-82PC50035. The basic development approach pursued this phase is presented, followed by a discussion on wear relationships. The analysis, which resulted in the development of a mathematical wear model relating pump life to some of the key design and operating parameters, is presented. The results, observations, and conclusions of the experimental investigation on small scale pumps that led to themore » selected design features for the prototype pump are discussed. The material investigation was performed at IRRI, ORNL and Battelle. The rationale for selecting the materials for testing, the test methods and apparatus used, and the results obtained are presented followed by a discussion on materials for a prototype pump. In addition, the prototype pump test facility description, as well as the related design and equipment details, are presented. 20 references, 53 figures, 13 tables.« less

Behavior analysis and neuroscience: Complementary disciplines.

PubMed

Donahoe, John W

2017-05-01

Behavior analysis and neuroscience are disciplines in their own right but are united in that both are subfields of a common overarching field-biology. What most fundamentally unites these disciplines is a shared commitment to selectionism, the Darwinian mode of explanation. In selectionism, the order and complexity observed in nature are seen as the cumulative products of selection processes acting over time on a population of variants-favoring some and disfavoring others-with the affected variants contributing to the population on which future selections operate. In the case of behavior analysis, the central selection process is selection by reinforcement; in neuroscience it is natural selection. The two selection processes are inter-related in that selection by reinforcement is itself the product of natural selection. The present paper illustrates the complementary nature of behavior analysis and neuroscience through considering their joint contributions to three central problem areas: reinforcement-including conditioned reinforcement, stimulus control-including equivalence classes, and memory-including reminding and remembering. © 2017 Society for the Experimental Analysis of Behavior.

Experimental and numerical investigation of the flow in a centrifugal compressor volute

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

Hagelstein, D.; Hillewaert, K.; Van Den Braembussche, R.A.

2000-01-01

This paper presents the experimental and numerical investigation of an outward volute of rectangular cross section. The investigation is carried out at the level of stage performance, volute performance, and detailed flow field study at selected peripheral positions for various operating points. The objective of the investigation was to gain further knowledge about the flow structure and loss mechanism in the volute. Simultaneously with the experimental investigation, a numerical simulation of the flow in the volute was carried out. A three-dimensional Euler code was used in which a wall friction term and a tuned artificial dissipation term account for viscousmore » effects. A reasonable agreement between the experimental and numerical results is observed. As a result a good and detailed knowledge about the pressure recovery and loss mechanism in the volute is obtained.« less

CD4 expression on EL4 cells as an epiphenomenon of retroviral transduction and selection.

PubMed

Logan, Grant J; Spinoulas, Afroditi; Alexander, Stephen I; Smythe, Jason A; Alexander, Ian E

2004-04-01

The EL4 murine tumour cell line, isolated from a chemically induced lymphoma over 50 years ago, has been extensively exploited in immunological research. The conclusions drawn from many of these studies have been based on the presumption that EL4 cells maintain a stable phenotype during experimental manipulation. To the contrary, we have observed 100-fold greater expression of cell surface CD4 (CD4(high)) on a subpopulation of EL4 cells following retroviral transduction and G418 selection when compared with unmodified populations. Although the mechanism responsible for this effect remains to be elucidated, the unexpected expression of CD4, a molecule that functions as both a coreceptor with the T-cell receptor and ligand for the pro-inflammatory cytokine IL-16, has the potential to influence experimental outcomes. Upregulation of CD4 should be excluded when EL4 cells are utilized in experiments requiring a consistent immuno-phenotype.

Control of morphology and crystal purity of InP nanowires by variation of phosphine flux during selective area MOMBE

NASA Astrophysics Data System (ADS)

Kelrich, A.; Dubrovskii, V. G.; Calahorra, Y.; Cohen, S.; Ritter, D.

2015-02-01

We present experimental results showing how the growth rate, morphology and crystal structure of Au-catalyzed InP nanowires (NWs) fabricated by selective area metal organic molecular beam epitaxy can be tuned by the growth parameters: temperature and phosphine flux. The InP NWs with 20-65 nm diameters are grown at temperatures of 420 and 480 °C with the PH3 flow varying from 1 to 9 sccm. The NW tapering is suppressed at a higher temperature, while pure wurtzite crystal structure is preferred at higher phosphine flows. Therefore, by combining high temperature and high phosphine flux, we are able to fabricate non-tapered and stacking fault-free InP NWs with the quality that other methods rarely achieve. We also develop a model for NW growth and crystal structure which explains fairly well the observed experimental tendencies.

Study of atomic and molecular emission spectra of Sr by laser induced breakdown spectroscopy (LIBS).

PubMed

Bhatt, Chet R; Alfarraj, Bader; Ayyalasomayajula, Krishna K; Ghany, Charles; Yueh, Fang Y; Singh, Jagdish P

2015-12-01

Laser Induced Breakdown Spectroscopy (LIBS) is an ideal analytical technique for in situ analysis of elemental composition. We have performed a comparative study of the quantitative and qualitative analysis of atomic and molecular emission from LIBS spectra. In our experiments, a mixture of SrCl2 and Al2O3 in powder form was used as a sample. The atomic emission from Sr and molecular emission from SrCl and SrO observed in LIBS spectra were analyzed. The optimum laser energies, gate delays, and gate widths for selected atomic lines and molecular bands were determined from spectra recorded at various experimental parameters. These optimum experimental conditions were used to collect calibration data, and the calibration curves were used to predict the Sr concentration. Limits of detection (LODs) for selected atomic and molecular emission spectra were determined.

Contributions of experimental protobiogenesis to the theory of evolution

NASA Technical Reports Server (NTRS)

Fox, S. W.

1976-01-01

Inferences from experiments in protobiogenesis are examined as a forward extension of the theory of evolutionary biology. A nondiscontinuous, intraconsistent theory of general evolution embracing both protobiology and biology is outlined. This overview emphasizes Darwinian selection in the later stages of evolution, and stereochemical molecular selection in some of its earlier stages. It incorporates the concept of limitation of the scope of evolution by internal constraints on variation, based on the argument that internally limiting constraints observed in experiments with molecules are operative in organisms, if chemical processes occur within biological processes and biological processes are assumed to be exponentializations of chemical processes. Major evolutionary events might have occurred by rapid self-assembly processes analogous to those observed in the formation of phase-separated microspheres from amorphous powder or supersaturated solutions.

Instance-Based Learning: Integrating Sampling and Repeated Decisions from Experience

ERIC Educational Resources Information Center

Gonzalez, Cleotilde; Dutt, Varun

2011-01-01

In decisions from experience, there are 2 experimental paradigms: sampling and repeated-choice. In the sampling paradigm, participants sample between 2 options as many times as they want (i.e., the stopping point is variable), observe the outcome with no real consequences each time, and finally select 1 of the 2 options that cause them to earn or…

Effectiveness of fishing gears to assess fish assemblage size structure in small lake ecosystems

Treesearch

T. A. Clement; K. Pangle; D. G. Uzarski; B. A. Murry

2014-01-01

Measurement of fish body-size distributions is increasingly used as a management tool to assess fishery status. However, the effects of gear selection on observed fish size structure has not received sufficient attention. Four different gear types (experimental gill nets, fine mesh bag seine, and two different sized mesh trap nets), which are commonly employed in the...

Effective charge measurements reveal selective and preferential accumulation of anions, but not cations, at the protein surface in dilute salt solutions

PubMed Central

Gokarn, Yatin R; Fesinmeyer, R Matthew; Saluja, Atul; Razinkov, Vladimir; Chase, Susan F; Laue, Thomas M; Brems, David N

2011-01-01

Specific-ion effects are ubiquitous in nature; however, their underlying mechanisms remain elusive. Although Hofmeister-ion effects on proteins are observed at higher (>0.3M) salt concentrations, in dilute (<0.1M) salt solutions nonspecific electrostatic screening is considered to be dominant. Here, using effective charge (Q*) measurements of hen-egg white lysozyme (HEWL) as a direct and differential measure of ion-association, we experimentally show that anions selectively and preferentially accumulate at the protein surface even at low (<100 mM) salt concentrations. At a given ion normality (50 mN), the HEWL Q* was dependent on anion, but not cation (Li+, Na+, K+, Rb+, Cs+, GdnH+, and Ca2+), identity. The Q* decreased in the order F− > Cl− > Br− > NO3− ∼ I− > SCN− > ClO4− ≫ SO42−, demonstrating progressively greater binding of the monovalent anions to HEWL and also show that the SO42− anion, despite being strongly hydrated, interacts directly with the HEWL surface. Under our experimental conditions, we observe a remarkable asymmetry between anions and cations in their interactions with the HEWL surface. PMID:21432935

Stochastic isotropic hyperelastic materials: constitutive calibration and model selection

NASA Astrophysics Data System (ADS)

Mihai, L. Angela; Woolley, Thomas E.; Goriely, Alain

2018-03-01

Biological and synthetic materials often exhibit intrinsic variability in their elastic responses under large strains, owing to microstructural inhomogeneity or when elastic data are extracted from viscoelastic mechanical tests. For these materials, although hyperelastic models calibrated to mean data are useful, stochastic representations accounting also for data dispersion carry extra information about the variability of material properties found in practical applications. We combine finite elasticity and information theories to construct homogeneous isotropic hyperelastic models with random field parameters calibrated to discrete mean values and standard deviations of either the stress-strain function or the nonlinear shear modulus, which is a function of the deformation, estimated from experimental tests. These quantities can take on different values, corresponding to possible outcomes of the experiments. As multiple models can be derived that adequately represent the observed phenomena, we apply Occam's razor by providing an explicit criterion for model selection based on Bayesian statistics. We then employ this criterion to select a model among competing models calibrated to experimental data for rubber and brain tissue under single or multiaxial loads.

Exogenous attention can be counter-selective: onset cues disrupt sensitivity to color changes.

PubMed

Müller-Plath, Gisela; Klöckner, Nils

2014-03-01

In peripheral spatial cueing paradigms, exogenous attentional capture is commonly observed after salient onset cues or with cues contingent on target characteristics. We proposed that exogenously captured attention disrupts the selectivity to target features. We tested this by experimentally emulating the everyday observation that in a viewing situation in which the observer is monitoring a stationary display fort change to occur, the onset of a salient stimulus (onset cue) or a change in a stationary stimulus similar to the expected one (contingent cue) has a distracting effect. As predicted, we found that both types of cues reduced the target detection sensitivity but enhanced the bias to respond in a go-nogo-paradigm. With the onset cue, the sensitivity loss was more pronounced at the side of the cue, whereas the contingent cue affected both sides likewise. Moreover, the effects of the onset cue interacted with the task difficulty: the more selectivity a task required the more immune it was against disruption, but the more likely was a response. We concluded that onset capture disrupts selective attention by adding noise to the processing of the target location. The effects of contingent capture could be explained with cue-target confounding. Finally, we suggest a new model of attentional capture in which exogenous and endogenous components interact in a dynamic way.

Model-based investigation of the circadian clock and cell cycle coupling in mouse embryonic fibroblasts: Prediction of RevErb-α up-regulation during mitosis.

PubMed

Traynard, Pauline; Feillet, Céline; Soliman, Sylvain; Delaunay, Franck; Fages, François

2016-11-01

Experimental observations have put in evidence autonomous self-sustained circadian oscillators in most mammalian cells, and proved the existence of molecular links between the circadian clock and the cell cycle. Some mathematical models have also been built to assess conditions of control of the cell cycle by the circadian clock. However, recent studies in individual NIH3T3 fibroblasts have shown an unexpected acceleration of the circadian clock together with the cell cycle when the culture medium is enriched with growth factors, and the absence of such acceleration in confluent cells. In order to explain these observations, we study a possible entrainment of the circadian clock by the cell cycle through a regulation of clock genes around the mitosis phase. We develop a computational model and a formal specification of the observed behavior to investigate the conditions of entrainment in period and phase. We show that either the selective activation of RevErb-α or the selective inhibition of Bmal1 transcription during the mitosis phase, allow us to fit the experimental data on both period and phase, while a uniform inhibition of transcription during mitosis seems incompatible with the phase data. We conclude on the arguments favoring the RevErb-α up-regulation hypothesis and on some further predictions of the model. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Analogue Study of Actinide Transport at Sites in Russia

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

Novikov, A P; Simmons, A M; Halsey, W G

2003-02-12

The U. S. Department of Energy (DOE) and the Russian Academy of Sciences (RAS) are engaged in a three-year cooperative study to observe the behavior of actinides in the natural environment at selected disposal sites and/or contamination sites in Russia. The purpose is to develop experimental data and models for actinide speciation, mobilization and transport processes in support of geologic repository design, safety and performance analyses. Currently at the mid-point of the study, the accomplishments to date include: evaluation of existing data and data needs, site screening and selection, initial data acquisition, and development of preliminary conceptual models.

Study of TLIPSS formation on different metals and alloys and their selective etching

NASA Astrophysics Data System (ADS)

Dostovalov, Alexandr V.; Korolkov, Victor P.; Terentiev, Vadim S.; Okotrub, Konstantin A.; Dultsev, Fedor N.; Nemykin, Anton; Babin, Sergey A.

2017-02-01

Experimental investigation of thermochemical laser-induced periodic surface structures (TLIPSS) formation on metal films (Ti, Cr, Ni, NiCr) at different processing conditions is presented. The hypothesis that the TLIPSS formation depends significantly on parabolic rate constant for oxide thin film growth is discussed. Evidently, low value of this parameter for Ni is the reason of TLIPSS absence on Ni and NiCr film with low Cr content. The effect of simultaneous ablative (with period ≍λ) and thermochemical (with period ≍λ) LIPSS formation was observed. The formation of structures after TLIPSS selective etching was demonstrated.

A review of covariate selection for non-experimental comparative effectiveness research.

PubMed

Sauer, Brian C; Brookhart, M Alan; Roy, Jason; VanderWeele, Tyler

2013-11-01

This paper addresses strategies for selecting variables for adjustment in non-experimental comparative effectiveness research and uses causal graphs to illustrate the causal network that relates treatment to outcome. Variables in the causal network take on multiple structural forms. Adjustment for a common cause pathway between treatment and outcome can remove confounding, whereas adjustment for other structural types may increase bias. For this reason, variable selection would ideally be based on an understanding of the causal network; however, the true causal network is rarely known. Therefore, we describe more practical variable selection approaches based on background knowledge when the causal structure is only partially known. These approaches include adjustment for all observed pretreatment variables thought to have some connection to the outcome, all known risk factors for the outcome, and all direct causes of the treatment or the outcome. Empirical approaches, such as forward and backward selection and automatic high-dimensional proxy adjustment, are also discussed. As there is a continuum between knowing and not knowing the causal, structural relations of variables, we recommend addressing variable selection in a practical way that involves a combination of background knowledge and empirical selection and that uses high-dimensional approaches. This empirical approach can be used to select from a set of a priori variables based on the researcher's knowledge to be included in the final analysis or to identify additional variables for consideration. This more limited use of empirically derived variables may reduce confounding while simultaneously reducing the risk of including variables that may increase bias. Copyright © 2013 John Wiley & Sons, Ltd.

Mechanism of alkoxy groups substitution by Grignard reagents on aromatic rings and experimental verification of theoretical predictions of anomalous reactions.

PubMed

Jiménez-Osés, Gonzalo; Brockway, Anthony J; Shaw, Jared T; Houk, K N

2013-05-01

The mechanism of direct displacement of alkoxy groups in vinylogous and aromatic esters by Grignard reagents, a reaction that is not observed with expectedly better tosyloxy leaving groups, is elucidated computationally. The mechanism of this reaction has been determined to proceed through the inner-sphere attack of nucleophilic alkyl groups from magnesium to the reacting carbons via a metalaoxetane transition state. The formation of a strong magnesium chelate with the reacting alkoxy and carbonyl groups dictates the observed reactivity and selectivity. The influence of ester, ketone, and aldehyde substituents was investigated. In some cases, the calculations predicted the formation of products different than those previously reported; these predictions were then verified experimentally. The importance of studying the actual system, and not simplified models as computational systems, is demonstrated.

Mechanism of Alkoxy Groups Substitution by Grignard Reagents on Aromatic Rings and Experimental Verification of Theoretical Predictions of Anomalous Reactions

PubMed Central

Jiménez-Osés, Gonzalo; Brockway, Anthony J.; Shaw, Jared T.; Houk, K. N.

2013-01-01

The mechanism of direct displacement of alkoxy groups in vinylogous and aromatic esters by Grignard reagents, a reaction that is not observed with expectedly better tosyloxy leaving groups, is elucidated computationally. The mechanism of this reaction has been determined to proceed through the inner-sphere attack of nucleophilic alkyl groups from magnesium to the reacting carbons via a metalaoxetane transition state. The formation of a strong magnesium chelate with the reacting alkoxy and carbonyl groups dictates the observed reactivity and selectivity. The influence of ester, ketone and aldehyde substituents was investigated. In some cases, the calculations predicted the formation of products different than those previously reported; these predictions were then verified experimentally. The importance of studying the actual system, and not simplified models as computational systems, is demonstrated. PMID:23601086

Accurate Mapping of Multilevel Rydberg Atoms on Interacting Spin-1 /2 Particles for the Quantum Simulation of Ising Models

NASA Astrophysics Data System (ADS)

de Léséleuc, Sylvain; Weber, Sebastian; Lienhard, Vincent; Barredo, Daniel; Büchler, Hans Peter; Lahaye, Thierry; Browaeys, Antoine

2018-03-01

We study a system of atoms that are laser driven to n D3 /2 Rydberg states and assess how accurately they can be mapped onto spin-1 /2 particles for the quantum simulation of anisotropic Ising magnets. Using nonperturbative calculations of the pair potentials between two atoms in the presence of electric and magnetic fields, we emphasize the importance of a careful selection of experimental parameters in order to maintain the Rydberg blockade and avoid excitation of unwanted Rydberg states. We benchmark these theoretical observations against experiments using two atoms. Finally, we show that in these conditions, the experimental dynamics observed after a quench is in good agreement with numerical simulations of spin-1 /2 Ising models in systems with up to 49 spins, for which numerical simulations become intractable.

The impact of retirement on health: quasi-experimental methods using administrative data.

PubMed

Horner, Elizabeth Mokyr; Cullen, Mark R

2016-02-19

Is retirement good or bad for health? Disentangling causality is difficult. Much of the previous quasi-experimental research on the effect of health on retirement used self-reported health and relied upon discontinuities in public retirement incentives across Europe. The current study investigated the effect of retirement on health by exploiting discontinuities in private retirement incentives to test the effect of retirement on health using a quasi-experimental study design. Secondary data (1997-2009) on a cohort of male manufacturing workers in a United States setting. Health status was determined using claims data from private insurance and Medicare. Analyses used employer-based administrative and claims data and claim data from Medicare. Widely used selection on observables models overstate the negative impact of retirement due to the endogeneity of the decision to retire. In addition, health status as measured by administrative claims data provide some advantages over the more commonly used survey items. Using an instrument and administrative health records, we find null to positive effects from retirement on all fronts, with a possible exception of increased risk for diabetes. This study provides evidence that retirement is not detrimental and may be beneficial to health for a sample of manufacturing workers. In addition, it supports previous research indicating that quasi-experimental methodologies are necessary to evaluate the relationship between retirement and health, as any selection on observable model will overstate the negative relationship of retirement on health. Further, it provides a model for how such research could be implemented in countries like the United States that do not have a strong public pension program. Finally, it demonstrates that such research need-not rely upon survey data, which has certain shortcomings and is not always available for homogenous samples.

Selected spectroscopic results on element 115 decay chains

DOE PAGES

Rudolph, D.; Forsberg, U.; Golubev, P.; ...

2014-08-24

We observed thirty correlated α-decay chains in an experiment studying the fusion-evaporation reaction 48Ca + 243Am at the GSI Helmholtzzentrum fur Schwerionenforschung. The decay characteristics of the majority of these 30 chains are consistent with previous observations and interpretations of such chains to originate from isotopes of element Z = 115. High-resolution α-photon coincidence spectroscopy in conjunction with comprehensive Monte-Carlo simulations allow to propose excitation schemes of atomic nuclei of the heaviest elements, thereby probing nuclear structure models near the 'Island of Stability' with unprecedented experimental precision.

Isotope exchange in reactions between D2O and size-selected ionic water clusters containing pyridine, H+ (pyridine)m(H2O)n.

PubMed

Ryding, Mauritz Johan; Zatula, Alexey S; Andersson, Patrik Urban; Uggerud, Einar

2011-01-28

Pyridine containing water clusters, H(+)(pyridine)(m)(H(2)O)(n), have been studied both experimentally by a quadrupole time-of-flight mass spectrometer and by quantum chemical calculations. In the experiments, H(+)(pyridine)(m)(H(2)O)(n) with m = 1-4 and n = 0-80 are observed. For the cluster distributions observed, there are no magic numbers, neither in the abundance spectra, nor in the evaporation spectra from size selected clusters. Experiments with size-selected clusters H(+)(pyridine)(m)(H(2)O)(n), with m = 0-3, reacting with D(2)O at a center-of-mass energy of 0.1 eV were also performed. The cross-sections for H/D isotope exchange depend mainly on the number of water molecules in the cluster and not on the number of pyridine molecules. Clusters having only one pyridine molecule undergo D(2)O/H(2)O ligand exchange, while H(+)(pyridine)(m)(H(2)O)(n), with m = 2, 3, exhibit significant H/D scrambling. These results are rationalized by quantum chemical calculations (B3LYP and MP2) for H(+)(pyridine)(1)(H(2)O)(n) and H(+)(pyridine)(2)(H(2)O)(n), with n = 1-6. In clusters containing one pyridine, the water molecules form an interconnected network of hydrogen bonds associated with the pyridinium ion via a single hydrogen bond. For clusters containing two pyridines, the two pyridine molecules are completely separated by the water molecules, with each pyridine being positioned diametrically opposite within the cluster. In agreement with experimental observations, these calculations suggest a "see-saw mechanism" for pendular proton transfer between the two pyridines in H(+)(pyridine)(2)(H(2)O)(n) clusters.

Color expression in experimentally regrown feathers of an overwintering migratory bird: implications for signaling and seasonal interactions

PubMed Central

Tonra, Christopher M; Marini, Kristen L D; Marra, Peter P; Germain, Ryan R; Holberton, Rebecca L; Reudink, Matthew W

2014-01-01

Plumage coloration in birds plays a critical role in communication and can be under selection throughout the annual cycle as a sexual and social signal. However, for migratory birds, little is known about the acquisition and maintenance of colorful plumage during the nonbreeding period. Winter habitat could influence the quality of colorful plumage, ultimately carrying over to influence sexual selection and social interactions during the breeding period. In addition to the annual growth of colorful feathers, feather loss from agonistic interactions or predator avoidance could require birds to replace colorful feathers in winter or experience plumage degradation. We hypothesized that conditions on the wintering grounds of migratory birds influence the quality of colorful plumage. We predicted that the quality of American redstart (Setophaga ruticilla) tail feathers regrown after experimental removal in Jamaica, West Indies, would be positively associated with habitat quality, body condition, and testosterone. Both yearling (SY) and adult (ASY) males regrew feathers with lower red chroma, suggesting reduced carotenoid content. While we did not observe a change in hue in ASY males, SY males shifted from yellow to orange plumage resembling experimentally regrown ASY feathers. We did not observe any effects of habitat, testosterone, or mass change. Our results demonstrate that redstarts are limited in their ability to adequately replace colorful plumage, regardless of habitat, in winter. Thus, feather loss on the nonbreeding grounds can affect social signals, potentially negatively carrying over to the breeding period. PMID:24834321

Application of Absorbable Hemostatic Materials Observed in Thyroid Operation

NASA Astrophysics Data System (ADS)

Li, Yan-Ming; Liang, Zhen-Zhen; Song, Yan

2016-05-01

To observe the application effects of the absorbable hemostatic materials in thyroid operation. Methods: From May 2014 to January 2015, 100 patients with thyroid surgery in our university affiliated hospital were selected as the research object. Randomly divided into experimental group and control group, 50 cases in each group. Application of absorbable hemostatic hemostatic materials in the experimental group during the operation, the control group using the traditional mechanical methods of hemostasis hemostasis to observe the operation time, bleeding volume, postoperative drainage volume, complications and hospital stay of the two groups. Results: The operation time, bleeding volume, postoperative drainage and hospital stay in the experimental group were significantly lower in the study group than in the control group, and the difference between the two groups was statistically significant (P< 0.05); The satisfaction of patients in the experimental group was significantly higher than that in the control group, the difference was statistically significant in the two groups (P < 0.05); There was no significant difference in the incidence of wound bleeding complications between the study group and the control group (P > 0.05). Conclusion: Absorbable hemostatic materials can effectively shorten the operation time, reduce intraoperative blood loss and postoperative drainage, reduce the length of hospital stay and improve the success rate of surgery and patient satisfaction, which is worthy to be popularized in clinical thyroid surgery.

Divergent adaptation promotes reproductive isolation among experimental populations of the filamentous fungus Neurospora

PubMed Central

2008-01-01

Background An open, focal issue in evolutionary biology is how reproductive isolation and speciation are initiated; elucidation of mechanisms with empirical evidence has lagged behind theory. Under ecological speciation, reproductive isolation between populations is predicted to evolve incidentally as a by-product of adaptation to divergent environments. The increased genetic diversity associated with interspecific hybridization has also been theorized to promote the development of reproductive isolation among independent populations. Using the fungal model Neurospora, we founded experimental lineages from both intra- and interspecific crosses, and evolved them in one of two sub-optimal, selective environments. We then measured the influence that initial genetic diversity and the direction of selection (parallel versus divergent) had on the evolution of reproductive isolation. Results When assayed in the selective environment in which they were evolved, lineages typically had greater asexual fitness than the progenitors and the lineages that were evolved in the alternate, selective environment. Assays for reproductive isolation showed that matings between lineages that were adapted to the same environment had greater sexual reproductive success than matings between lineages that were adapted to different environments. Evidence of this differential reproductive success was observed at two stages of the sexual cycle. For one of the two observed incompatibility phenotypes, results from genetic analyses were consistent with a two-locus, two-allele model with asymmetric (gender-specific), antagonistic epistasis. The effects of divergent adaptation on reproductive isolation were more pronounced for populations with greater initial genetic variation. Conclusion Divergent selection resulted in divergent adaptation and environmental specialization, consistent with fixation of different alleles in different environments. When brought together by mating, these alleles interacted negatively and had detrimental effects on sexual reproductive success, in agreement with the Dobzhansky-Muller model of genetic incompatibilities. As predicted by ecological speciation, greater reproductive isolation was observed among divergent-adapted lineages than among parallel-adapted lineages. These results support that, given adequate standing genetic variation, divergent adaptation can indirectly cause the evolution of reproductive isolation, and eventually lead to speciation. PMID:18237415

Modeling of DNA-Mediated Self-Assembly from Anisotropic Nanoparticles: A Molecular Dynamics Study

NASA Astrophysics Data System (ADS)

Millan, Jaime; Girard, Martin; Brodin, Jeffrey; O'Brien, Matt; Mirkin, Chad; Olvera de La Cruz, Monica

The programmable selectivity of DNA recognition constitutes an elegant scheme to self-assemble a rich variety of superlattices from versatile nanoscale building blocks, where the natural interactions between building blocks are traded by complementary DNA hybridization interactions. Recently, we introduced and validated a scale-accurate coarse-grained model for a molecular dynamics approach that captures the dynamic nature of DNA hybridization events and reproduces the experimentally-observed crystallization behavior of various mixtures of spherical DNA-modified nanoparticles. Here, we have extended this model to robustly reproduce the assembly of nanoparticles with the anisotropic shapes observed experimentally. In particular, we are interested in two different particle types: (i) regular shapes, namely the cubic and octahedral polyhedra shapes commonly observed in gold nanoparticles, and (ii) irregular shapes akin to those exhibited by enzymes. Anisotropy in shape can provide an analog to the atomic orbitals exhibited by conventional atomic crystals. We present results for the assembly of enzymes or anisotropic nanoparticles and the co-assembly of enzymes and nanoparticles.

Direct observation of spin-quadrupolar excitations in Sr2CoGe2O7 by high-field electron spin resonance

NASA Astrophysics Data System (ADS)

Akaki, Mitsuru; Yoshizawa, Daichi; Okutani, Akira; Kida, Takanori; Romhányi, Judit; Penc, Karlo; Hagiwara, Masayuki

2017-12-01

Exotic spin-multipolar ordering in spin transition metal insulators has so far eluded unambiguous experimental observation. A less studied, but perhaps more feasible fingerprint of multipole character emerges in the excitation spectrum in the form of quadrupolar transitions. Such multipolar excitations are desirable as they can be manipulated with the use of light or electric field and can be captured by means of conventional experimental techniques. Here we study single crystals of multiferroic Sr2CoGe2O7 and observe a two-magnon spin excitation appearing above the saturation magnetic field in electron spin resonance (ESR) spectra. Our analysis of the selection rules reveals that this spin excitation mode does not couple to the magnetic component of the light, but it is excited by the electric field only, in full agreement with the theoretical calculations. Due to the nearly isotropic nature of Sr2CoGe2O7 , we identify this excitation as a purely spin-quadrupolar two-magnon mode.

Dendrites Enable a Robust Mechanism for Neuronal Stimulus Selectivity.

PubMed

Cazé, Romain D; Jarvis, Sarah; Foust, Amanda J; Schultz, Simon R

2017-09-01

Hearing, vision, touch: underlying all of these senses is stimulus selectivity, a robust information processing operation in which cortical neurons respond more to some stimuli than to others. Previous models assume that these neurons receive the highest weighted input from an ensemble encoding the preferred stimulus, but dendrites enable other possibilities. Nonlinear dendritic processing can produce stimulus selectivity based on the spatial distribution of synapses, even if the total preferred stimulus weight does not exceed that of nonpreferred stimuli. Using a multi-subunit nonlinear model, we demonstrate that stimulus selectivity can arise from the spatial distribution of synapses. We propose this as a general mechanism for information processing by neurons possessing dendritic trees. Moreover, we show that this implementation of stimulus selectivity increases the neuron's robustness to synaptic and dendritic failure. Importantly, our model can maintain stimulus selectivity for a larger range of loss of synapses or dendrites than an equivalent linear model. We then use a layer 2/3 biophysical neuron model to show that our implementation is consistent with two recent experimental observations: (1) one can observe a mixture of selectivities in dendrites that can differ from the somatic selectivity, and (2) hyperpolarization can broaden somatic tuning without affecting dendritic tuning. Our model predicts that an initially nonselective neuron can become selective when depolarized. In addition to motivating new experiments, the model's increased robustness to synapses and dendrites loss provides a starting point for fault-resistant neuromorphic chip development.

On the Error State Selection for Stationary SINS Alignment and Calibration Kalman Filters—Part II: Observability/Estimability Analysis

PubMed Central

Silva, Felipe O.; Hemerly, Elder M.; Leite Filho, Waldemar C.

2017-01-01

This paper presents the second part of a study aiming at the error state selection in Kalman filters applied to the stationary self-alignment and calibration (SSAC) problem of strapdown inertial navigation systems (SINS). The observability properties of the system are systematically investigated, and the number of unobservable modes is established. Through the analytical manipulation of the full SINS error model, the unobservable modes of the system are determined, and the SSAC error states (except the velocity errors) are proven to be individually unobservable. The estimability of the system is determined through the examination of the major diagonal terms of the covariance matrix and their eigenvalues/eigenvectors. Filter order reduction based on observability analysis is shown to be inadequate, and several misconceptions regarding SSAC observability and estimability deficiencies are removed. As the main contributions of this paper, we demonstrate that, except for the position errors, all error states can be minimally estimated in the SSAC problem and, hence, should not be removed from the filter. Corroborating the conclusions of the first part of this study, a 12-state Kalman filter is found to be the optimal error state selection for SSAC purposes. Results from simulated and experimental tests support the outlined conclusions. PMID:28241494

Morphology and Orientation Selection of Non-metallic Inclusions in Electrified Molten Metal

NASA Astrophysics Data System (ADS)

Zhao, Z. C.; Qin, R. S.

2017-10-01

The effect of electric current on morphology and orientation selection of non-metallic inclusions in molten metal has been investigated using theoretical modeling and numerical calculation. Two geometric factors, namely the circularity ( fc ) and alignment ratio ( fe ) were introduced to describe the inclusions shape and configuration. Electric current free energy was calculated and the values were used to determine the thermodynamic preference between different microstructures. Electric current promotes the development of inclusion along the current direction by either expatiating directional growth or enhancing directional agglomeration. Reconfiguration of the inclusions to reduce the system electric resistance drives the phenomena. The morphology and orientation selection follow the routine to reduce electric free energy. The numerical results are in agreement with our experimental observations.

Innovations in bonding to zirconia-based materials: Part I.

PubMed

Aboushelib, Moustafa N; Matinlinna, Jukka P; Salameh, Ziad; Ounsi, Hani

2008-09-01

Establishing a reliable bond to zirconia-based materials has proven to be difficult which is the major limitation against fabricating adhesive zirconia restorations. This bond could be improved using novel selective infiltration etching conditioning in combination with engineered zirconia primers. Aim of the work was to evaluate resin-to-zirconia bond strength using selective infiltration etching and novel silane-based zirconia primers. Zirconia discs (Procera Zirconia) received selective infiltration etching surface treatment followed by coating with either of five especially engineered experimental zirconia primers. Pre-aged resin-composite discs (Tetric Ivo Ceram) were bonded to the treated surface using an MDP-containing resin-composite (Panavia F 2.0). The bilayered specimens were cut into microbars and the microtensile bond strength (MTBS) was evaluated. 'As-sintered' zirconia discs served as a control (alpha=0.05). The broken microbars were examined using a scanning electron microscope (SEM). The combination of selective infiltration etching with experimental zirconia primers significantly improved (F=3805, P<0.0001) the MTBS values (41+/-5.8 MPa) compared to the 'as-sintered' surface using the same primers which demonstrated spontaneous failure and very low bond strength values (2.6+/-3.1 MPa). SEM analysis revealed that selective infiltration etching surface treatment resulted in a nano-retentive surface where the zirconia primers were able to penetrate and interlock which explained the higher MTBS values observed for the treated specimens.

Promoting middle school students’ abstract-thinking ability through cognitive apprenticeship instruction in mathematics learning

NASA Astrophysics Data System (ADS)

Yusepa, B. G. P.; Kusumah, Y. S.; Kartasasmita, B. G.

2018-01-01

The aim of this study is to get an in-depth understanding of students’ abstract-thinking ability in mathematics learning. This study was an experimental research with pre-test and post-test control group design. The subject of this study was eighth-grade students from two junior high schools in Bandung. In each schools, two parallel groups were selected and assigned into control and experimental groups. The experimental group was exposed to Cognitive Apprenticeship Instruction (CAI) treatment, whereas the control group was exposed to conventional learning. The results showed that abstract-thinking ability of students in experimental group was better than that of those in control group in which it could be observed from the overall and school level. It could be concluded that CAI could be a good alternative learning model to enhance students’ abstract-thinking ability.

Generation of abnormal acoustic noise: Singing of a cavitating tip vortex

NASA Astrophysics Data System (ADS)

Peng, Xiaoxing; Wang, Benlong; Li, Haoyu; Xu, Lianghao; Song, Mingtai

2017-05-01

We present experimental results and a theoretical analysis for the singing of a cavitating tip vortex (SCTV), which has been occasionally observed under special conditions in a few experimental facilities around the world since the 1990s. Due to lack of repeatability, little is known about the generation mechanism of SCTV [R. E. A. Arndt, Annu. Rev. Fluid Mech. 34, 143 (2002), 10.1146/annurev.fluid.34.082301.114957]. In the present work we propose an experimental procedure to produce the SCTV phenomenon at selected flow conditions in the China Ship Scientific Research Center cavitation mechanism tunnel. By analyzing the frequency characteristics of the acoustical signal and the bubble dynamics, it is found that the tone of SCTV matches the natural frequency of radial oscillation of the cylinder bubble and a formulation to predict SCTV is developed. Good agreement is obtained between the proposed formulation and the experimental data from different facilities.

On the Reverse Asymmetric Gas Transport Effect in the Polymer Membranes

NASA Astrophysics Data System (ADS)

Kurchatov, I. M.; Laguntsov, N. I.; Skuridin, I. E.

In this paper, change of gas permeability value, depending on orientation of polymer gas membrane, in a wide pressure range was investigated. Consistent patterns of asymmetric gas transfer through the PVTMS-membrane were established experimentally. Reverse asymmetric transport effect was observed, wherein the permeability from the direction of porous support prevails at the permeability from the direction of selective non-porous layer.

A "Politically Robust" Experimental Design for Public Policy Evaluation, with Application to the Mexican Universal Health Insurance Program

ERIC Educational Resources Information Center

King, Gary; Gakidou, Emmanuela; Ravishankar, Nirmala; Moore, Ryan T.; Lakin, Jason; Vargas, Manett; Tellez-Rojo, Martha Maria; Avila, Juan Eugenio Hernandez; Avila, Mauricio Hernandez; Llamas, Hector Hernandez

2007-01-01

We develop an approach to conducting large-scale randomized public policy experiments intended to be more robust to the political interventions that have ruined some or all parts of many similar previous efforts. Our proposed design is insulated from selection bias in some circumstances even if we lose observations; our inferences can still be…

The restorative logic of punishment: another argument in favor of weak selection.

PubMed

Baumard, Nicolas

2012-02-01

Strong reciprocity theorists claim that punishment has evolved to promote the good of the group and to deter cheating. By contrast, weak reciprocity suggests that punishment aims to restore justice (i.e., reciprocity) between the criminal and his victim. Experimental evidences as well as field observations suggest that humans punish criminals to restore fairness rather than to support group cooperation.

Apparent directional selection by biased pleiotropic mutation.

PubMed

Tanaka, Yoshinari

2010-07-01

Pleiotropic effects of deleterious mutations are considered to be among the factors responsible for genetic constraints on evolution by long-term directional selection acting on a quantitative trait. If pleiotropic phenotypic effects are biased in a particular direction, mutations generate apparent directional selection, which refers to the covariance between fitness and the trait owing to a linear association between the number of mutations possessed by individuals and the genotypic values of the trait. The present analysis has shown how the equilibrium mean value of the trait is determined by a balance between directional selection and biased pleiotropic mutations. Assuming that genes act additively both on the trait and on fitness, the total variance-standardized directional selection gradient was decomposed into apparent and true components. Experimental data on mutation bias from the bristle traits of Drosophila and life history traits of Daphnia suggest that apparent selection explains a small but significant fraction of directional selection pressure that is observed in nature; the data suggest that changes induced in a trait by biased pleiotropic mutation (i.e., by apparent directional selection) are easily compensated for by (true) directional selection.

Discrimination of correlated and entangling quantum channels with selective process tomography

DOE PAGES

Dumitrescu, Eugene; Humble, Travis S.

2016-10-10

The accurate and reliable characterization of quantum dynamical processes underlies efforts to validate quantum technologies, where discrimination between competing models of observed behaviors inform efforts to fabricate and operate qubit devices. We present a protocol for quantum channel discrimination that leverages advances in direct characterization of quantum dynamics (DCQD) codes. We demonstrate that DCQD codes enable selective process tomography to improve discrimination between entangling and correlated quantum dynamics. Numerical simulations show selective process tomography requires only a few measurement configurations to achieve a low false alarm rate and that the DCQD encoding improves the resilience of the protocol to hiddenmore » sources of noise. Lastly, our results show that selective process tomography with DCQD codes is useful for efficiently distinguishing sources of correlated crosstalk from uncorrelated noise in current and future experimental platforms.« less

To qualify as a social partner, humans hide severe punishment, although their observed cooperativeness is decisive.

PubMed

Rockenbach, Bettina; Milinski, Manfred

2011-11-08

Conflicts of interest between the community and its members are at the core of human social dilemmas. If observed selfishness has future costs, individuals may hide selfish acts but display altruistic ones, and peers aim at identifying the most selfish persons to avoid them as future social partners. An interaction involving hiding and seeking information may be inevitable. We staged an experimental social-dilemma game in which actors could pay to conceal information about their contribution, giving, and punishing decisions from an observer who selects her future social partners from the actors. The observer could pay to conceal her observation of the actors. We found sophisticated dynamic strategies on either side. Actors hide their severe punishment and low contributions but display high contributions. Observers select high contributors as social partners; remarkably, punishment behavior seems irrelevant for qualifying as a social partner. That actors nonetheless pay to conceal their severe punishment adds a further puzzle to the role of punishment in human social behavior. Competition between hiding and seeking information about social behavior may be even more relevant and elaborate in the real world but usually is hidden from our eyes.

Statistical density modification using local pattern matching

DOEpatents

Terwilliger, Thomas C.

2007-01-23

A computer implemented method modifies an experimental electron density map. A set of selected known experimental and model electron density maps is provided and standard templates of electron density are created from the selected experimental and model electron density maps by clustering and averaging values of electron density in a spherical region about each point in a grid that defines each selected known experimental and model electron density maps. Histograms are also created from the selected experimental and model electron density maps that relate the value of electron density at the center of each of the spherical regions to a correlation coefficient of a density surrounding each corresponding grid point in each one of the standard templates. The standard templates and the histograms are applied to grid points on the experimental electron density map to form new estimates of electron density at each grid point in the experimental electron density map.

Theoretical modeling of cellular and dendritic solidification microstructures

NASA Astrophysics Data System (ADS)

Song, Younggil

In this dissertation, we use three-dimensional (3D) phase-field (PF) modeling to investigate (i) 3D solid-liquid interface dynamics observed in microgravity experiments, and (ii) array patterns in a thin-sample geometry. In addition, using the two-dimensional (2D) dendritic-needle-network (DNN) model, we explore (iii) secondary sidebranching dynamics. Recently, solidification experiments are carried out in the DSI (Directional Solidification Insert) of the DECLIC (Device for the study of Critical LIquids and Crystallization) facility aboard the International Space Station (ISS). Thus, the directional solidification experiments are achieved under limited convective currents, and the experimental observations reveal unique dynamics of 3D microstructure in a purely diffusive growth regime. In this directional solidification setup, a temperature field between heat sources could evolve due to two main factors: (i) heat transfer within an adiabatic zone and (ii) latent heat rejection at the interface. These two thermal effects are phenomenologically characterized using a time-dependent thermal shift. In addition, we could quantitatively account for these thermal factors using a numerical calculation of the evolution of temperature field. We introduce these phenomenological and quantitative thermal representations into the PF model. The performed simulations using different thermal descriptions are compared to the experimental measurements from the initial planar interface dynamics to the final spacing selection. The DECLIC-DSI experimental observations exhibit complex grain boundary (GB) dynamics between large grains with a small misorientation. In the observations, several large grains with a small misorientation with respect to the temperature gradient are formed during solidification. Specifically, at a convergent GB, a localized group of misoriented cells penetrates into a nearby grain, which yields the morphological instability of grain boundaries. Remarkably, while the invasion process starts with a group of cells, the leader cell can detach itself from the group and grow continuously as a misoriented solitary cell in the other grain with a different misorientation. We use PF simulations to investigate the GB morphology and dynamics of a solitary cell. Solidification experiments on earth are typically performed in a thin-sample geometry to avoid fluid convection. Thus, we consider various influences on cellular and dendritic array patterns in thin samples. First, we explore the influence of crystal orientation. When a grain in a thin-sample geometry is misoriented with respect to the temperature gradient, primary cells and dendrites drift laterally in both experiments and simulations. At the same time, grain boundaries are systematically formed at the edges of the misoriented grain. The misoriented primary branches move away from the divergent grain boundary. At this boundary, cells/dendrites are generated continuously, and their spacings are larger than the dynamically selected spacings. Primary branches run into the other convergent GB, which leads to their elimination. Thus, at a stationary state, a spacing distribution is uniform with the spacing selected at the divergent GB until it decreases near the convergent GB. We perform simulations to illustrate the global evolutions of a primary spacing. In addition, we suggest a simple geometrical model and a nonlinear advection equation for the dynamics of the primary spacing evolution, which can predict the slow evolution of a primary spacing in a quasi-2D array. Experimental observations point out that the primary spacing selection could be affected by the sample thickness; however, the detailed description for the link between the primary spacing selection and a sample thickness is still missing. Here, we use PF simulations to investigate the primary cellular and dendritic spacing selection mechanisms under the influence of a sample thickness. A thin-sample geometry can limit thermal and solutal convective currents effectively. However, as the sample thickness increases, the convective currents can influence the solid- liquid interface dynamics. Then, the microstructure selection mechanisms can be different from the classical theories that are valid in a diffusive regime. We propose a simple approach for the PF model to demonstrate the microstructure selection when liquid convection is present. These simulations are compared to experimental results. Columnar microstructures with cells and dendrites typically form polycrystalline materials during directional solidification. Then, convergent and divergent grain boundaries form systematically between grains, which are misoriented with respect to the temperature gradient. Moreover, the GB is dynamically selected during the competition between two nearby misoriented grains. In order to investigate the GB orientation selection, we carry out 3D PF simulations in a thin-sample geometry. These simulations reveal the influence of the 3D GB bi-crystallography on grain competition. The results highlight the importance of considering the orientation of the orthogonal planes containing secondary branches in addition to the growth direction of primary branches. Finally, we propose three growth steps to demonstrate the secondary sidebranching growth dynamics under isothermal dendritic growth condition. (Abstract shortened by ProQuest.).

Participant-selected music and physical activity in older adults following cardiac rehabilitation: a randomized controlled trial.

PubMed

Clark, Imogen N; Baker, Felicity A; Peiris, Casey L; Shoebridge, Georgie; Taylor, Nicholas F

2017-03-01

To evaluate effects of participant-selected music on older adults' achievement of activity levels recommended in the physical activity guidelines following cardiac rehabilitation. A parallel group randomized controlled trial with measurements at Weeks 0, 6 and 26. A multisite outpatient rehabilitation programme of a publicly funded metropolitan health service. Adults aged 60 years and older who had completed a cardiac rehabilitation programme. Experimental participants selected music to support walking with guidance from a music therapist. Control participants received usual care only. The primary outcome was the proportion of participants achieving activity levels recommended in physical activity guidelines. Secondary outcomes compared amounts of physical activity, exercise capacity, cardiac risk factors, and exercise self-efficacy. A total of 56 participants, mean age 68.2 years (SD = 6.5), were randomized to the experimental ( n = 28) and control groups ( n = 28). There were no differences between groups in proportions of participants achieving activity recommended in physical activity guidelines at Week 6 or 26. Secondary outcomes demonstrated between-group differences in male waist circumference at both measurements (Week 6 difference -2.0 cm, 95% CI -4.0 to 0; Week 26 difference -2.8 cm, 95% CI -5.4 to -0.1), and observed effect sizes favoured the experimental group for amounts of physical activity (d = 0.30), exercise capacity (d = 0.48), and blood pressure (d = -0.32). Participant-selected music did not increase the proportion of participants achieving recommended amounts of physical activity, but may have contributed to exercise-related benefits.

Magnetic field-induced modification of selection rules for Rb D 2 line monitored by selective reflection from a vapor nanocell

NASA Astrophysics Data System (ADS)

Klinger, Emmanuel; Sargsyan, Armen; Tonoyan, Ara; Hakhumyan, Grant; Papoyan, Aram; Leroy, Claude; Sarkisyan, David

2017-08-01

Magnetic field-induced giant modification of the probabilities of five transitions of 5S1 / 2,Fg = 2 → 5P3 / 2,Fe = 4 of 85Rb and three transitions of 5S1 / 2,Fg = 1 → 5P3 / 2,Fe = 3 of 87Rb forbidden by selection rules for zero magnetic field has been observed experimentally and described theoretically for the first time. For the case of excitation with circularly-polarized (σ+) laser radiation, the probability of Fg = 2,mF = - 2 → Fe = 4,mF = - 1 transition becomes the largest among the seventeen transitions of 85Rb Fg = 2 → Fe = 1,2,3,4 group, and the probability of Fg = 1, mF = - 1 → Fe = 3,mF = 0 transition becomes the largest among the nine transitions of 87Rb Fg = 1 → Fe = 0,1,2,3 group, in a wide range of magnetic field 200-1000 G. Complete frequency separation of individual Zeeman components was obtained by implementation of derivative selective reflection technique with a 300 nm-thick nanocell filled with Rb, allowing formation of narrow optical resonances. Possible applications are addressed. The theoretical model is well consistent with the experimental results.

Model for Codon Position Bias in RNA Editing

NASA Astrophysics Data System (ADS)

Liu, Tsunglin; Bundschuh, Ralf

2005-08-01

RNA editing can be crucial for the expression of genetic information via inserting, deleting, or substituting a few nucleotides at specific positions in an RNA sequence. Within coding regions in an RNA sequence, editing usually occurs with a certain bias in choosing the positions of the editing sites. In the mitochondrial genes of Physarum polycephalum, many more editing events have been observed at the third codon position than at the first and second, while in some plant mitochondria the second codon position dominates. Here we propose an evolutionary model that explains this bias as the basis of selection at the protein level. The model predicts a distribution of the three positions rather close to the experimental observation in Physarum. This suggests that the codon position bias in Physarum is mainly a consequence of selection at the protein level.

A model for codon position bias in RNA editing

NASA Astrophysics Data System (ADS)

Bundschuh, Ralf; Liu, Tsunglin

2006-03-01

RNA editing can be crucial for the expression of genetic information via inserting, deleting, or substituting a few nucleotides at specific positions in an RNA sequence. Within coding regions in an RNA sequence, editing usually occurs with a certain bias in choosing the positions of the editing sites. In the mitochondrial genes of Physarum polycephalum, many more editing events have been observed at the third codon position than at the first and second, while in some plant mitochondria the second codon position dominates. Here we propose an evolutionary model that explains this bias as the basis of selection at the protein level. The model predicts a distribution of the three positions rather close to the experimental observation in Physarum. This suggests that the codon position bias in Physarum is mainly a consequence of selection at the protein level.

Selecting among competing models of electro-optic, infrared camera system range performance

USGS Publications Warehouse

Nichols, Jonathan M.; Hines, James E.; Nichols, James D.

2013-01-01

Range performance is often the key requirement around which electro-optical and infrared camera systems are designed. This work presents an objective framework for evaluating competing range performance models. Model selection based on the Akaike’s Information Criterion (AIC) is presented for the type of data collected during a typical human observer and target identification experiment. These methods are then demonstrated on observer responses to both visible and infrared imagery in which one of three maritime targets was placed at various ranges. We compare the performance of a number of different models, including those appearing previously in the literature. We conclude that our model-based approach offers substantial improvements over the traditional approach to inference, including increased precision and the ability to make predictions for some distances other than the specific set for which experimental trials were conducted.

Linear and nonlinear analysis of fluid slosh dampers

NASA Astrophysics Data System (ADS)

Sayar, B. A.; Baumgarten, J. R.

1982-11-01

A vibrating structure and a container partially filled with fluid are considered coupled in a free vibration mode. To simplify the mathematical analysis, a pendulum model to duplicate the fluid motion and a mass-spring dashpot representing the vibrating structure are used. The equations of motion are derived by Lagrange's energy approach and expressed in parametric form. For a wide range of parametric values the logarithmic decrements of the main system are calculated from theoretical and experimental response curves in the linear analysis. However, for the nonlinear analysis the theoretical and experimental response curves of the main system are compared. Theoretical predictions are justified by experimental observations with excellent agreement. It is concluded finally that for a proper selection of design parameters, containers partially filled with viscous fluids serve as good vibration dampers.

Tailored Codes for Small Quantum Memories

NASA Astrophysics Data System (ADS)

Robertson, Alan; Granade, Christopher; Bartlett, Stephen D.; Flammia, Steven T.

2017-12-01

We demonstrate that small quantum memories, realized via quantum error correction in multiqubit devices, can benefit substantially by choosing a quantum code that is tailored to the relevant error model of the system. For a biased noise model, with independent bit and phase flips occurring at different rates, we show that a single code greatly outperforms the well-studied Steane code across the full range of parameters of the noise model, including for unbiased noise. In fact, this tailored code performs almost optimally when compared with 10 000 randomly selected stabilizer codes of comparable experimental complexity. Tailored codes can even outperform the Steane code with realistic experimental noise, and without any increase in the experimental complexity, as we demonstrate by comparison in the observed error model in a recent seven-qubit trapped ion experiment.

Effect of different oral oxytetracycline treatment regimes on selection of antimicrobial resistant coliforms in nursery pigs.

PubMed

Herrero-Fresno, Ana; Zachariasen, Camilla; Nørholm, Nanna; Holm, Anders; Christiansen, Lasse Engbo; Olsen, John Elmerdahl

2017-09-01

A major concern derived from using antimicrobials in pig production is the development of resistance. This study aimed to assess the impact of selected combinations of oral dose and duration of treatment with oxytetracycline (OTC) on selection of tetracycline resistant (TET-R) coliforms recovered from swine feces. The work encompassed two studies: 1) OTC 5mg/kg and 20mg/kg were administered to nursery pigs for 3 and 10days, respectively, under controlled experimental conditions, and 2) 10mg/kg, 20mg/kg and 30mg/kg OTC were given to a higher number of pigs for 6, 3 and 2days, respectively, under field conditions. Statistical modeling was applied to analyze trends in the proportion of TET-R coliforms. In the experimental study, no statistical difference in proportion of TET-R coliforms was observed between treatments at the end of the trial (day 18) and compared to day 0. In the field study, treatment had a significant effect on the proportion of TET-R bacteria two days after the end of treatment (2dAT) with the regimes "low dose-six days" and "medium dose-three days" yielding the highest and lowest proportions of TET-R strains, respectively. No indication of co-selection for ampicillin- and sulphonamide -R bacteria was observed for any treatment at 2dAT. By the end of the nursery period, the proportion of TET-R bacteria was not significantly different between treatments and compared to day 0. Our results suggest that similar resistance levels might be obtained by using different treatment regimes regardless of the combinations of oral dose-duration of treatment. Copyright © 2017 Elsevier B.V. All rights reserved.

Intracavity adaptive optics. 1: Astigmatism correction performance.

PubMed

Spinhirne, J M; Anafi, D; Freeman, R H; Garcia, H R

1981-03-15

A detailed experimental study has been conducted on adaptive optical control methodologies inside a laser resonator. A comparison is presented of several optimization techniques using a multidither zonal coherent optical adaptive technique system within a laser resonator for the correction of astigmatism. A dramatic performance difference is observed when optimizing on beam quality compared with optimizing on power-in-the-bucket. Experimental data are also presented on proper selection criteria for dither frequencies when controlling phase front errors. The effects of hardware limitations and design considerations on the performance of the system are presented, and general conclusions and physical interpretations on the results are made when possible.

Molecular switches from benzene derivatives adsorbed on metal surfaces

PubMed Central

Liu, Wei; Filimonov, Sergey N.; Carrasco, Javier; Tkatchenko, Alexandre

2013-01-01

Transient precursor states are often experimentally observed for molecules adsorbing on surfaces. However, such precursor states are typically rather short-lived, quickly yielding to more stable adsorption configurations. Here we employ first-principles calculations to systematically explore the interaction mechanism for benzene derivatives on metal surfaces, enabling us to selectively tune the stability and the barrier between two metastable adsorption states. In particular, in the case of the tetrachloropyrazine molecule, two equally stable adsorption states are identified with a moderate and conceivably reversible barrier between them. We address the feasibility of experimentally detecting the predicted bistable behaviour and discuss its potential usefulness in a molecular switch. PMID:24157660

Kullback-Leibler information function and the sequential selection of experiments to discriminate among several linear models. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Sidik, S. M.

1972-01-01

A sequential adaptive experimental design procedure for a related problem is studied. It is assumed that a finite set of potential linear models relating certain controlled variables to an observed variable is postulated, and that exactly one of these models is correct. The problem is to sequentially design most informative experiments so that the correct model equation can be determined with as little experimentation as possible. Discussion includes: structure of the linear models; prerequisite distribution theory; entropy functions and the Kullback-Leibler information function; the sequential decision procedure; and computer simulation results. An example of application is given.

Sparsely sampling the sky: a Bayesian experimental design approach

NASA Astrophysics Data System (ADS)

Paykari, P.; Jaffe, A. H.

2013-08-01

The next generation of galaxy surveys will observe millions of galaxies over large volumes of the Universe. These surveys are expensive both in time and cost, raising questions regarding the optimal investment of this time and money. In this work, we investigate criteria for selecting amongst observing strategies for constraining the galaxy power spectrum and a set of cosmological parameters. Depending on the parameters of interest, it may be more efficient to observe a larger, but sparsely sampled, area of sky instead of a smaller contiguous area. In this work, by making use of the principles of Bayesian experimental design, we will investigate the advantages and disadvantages of the sparse sampling of the sky and discuss the circumstances in which a sparse survey is indeed the most efficient strategy. For the Dark Energy Survey (DES), we find that by sparsely observing the same area in a smaller amount of time, we only increase the errors on the parameters by a maximum of 0.45 per cent. Conversely, investing the same amount of time as the original DES to observe a sparser but larger area of sky, we can in fact constrain the parameters with errors reduced by 28 per cent.

Neural and behavioral correlates of selective stopping: Evidence for a different strategy adoption.

PubMed

Sánchez-Carmona, Alberto J; Albert, Jacobo; Hinojosa, José A

2016-10-01

The present study examined the neural and behavioral correlates of selective stopping, a form of inhibition that has scarcely been investigated. The selectivity of the inhibitory process is needed when individuals have to deal with an environment filled with multiple stimuli, some of which require inhibition and some of which do not. The stimulus-selective stop-signal task has been used to explore this issue assuming that all participants interrupt their ongoing responses selectively to stop but not to ignore signals. However, recent behavioral evidence suggests that some individuals do not carry out the task as experimenters expect, since they seemed to interrupt their response non-selectively to both signals. In the present study, we detected and controlled the cognitive strategy adopted by participants (n=57) when they performed a stimulus-selective stop-signal task before comparing brain activation between conditions. In order to determine both the onset and the end of the response cancellation process underlying each strategy and to fully take advantage of the precise temporal resolution of event-related potentials, we used a mass univariate approach. Source localization techniques were also employed to estimate the neural underpinnings of the effects observed at the scalp level. Our results from scalp and source level analysis support the behavioral-based strategy classification. Specific effects were observed depending on the strategy adopted by participants. Thus, when contrasting successful stop versus ignore conditions, increased activation was only evident for subjects who were classified as using a strategy whereby the response interruption process was selective to stop trials. This increased activity was observed during the P3 time window in several left-lateralized brain regions, including middle and inferior frontal gyri, as well as parietal and insular cortices. By contrast, in those participants who used a strategy characterized by stopping non-selectively, no activation differences between successful stop and ignore conditions were observed at the estimated time at which response interruption process occurs. Overall, results from the current study highlight the importance of controlling for the different strategies adopted by participants to perform selective stopping tasks before analyzing brain activation patterns. Copyright © 2016 Elsevier Inc. All rights reserved.

Selective colors reflection from stratified aragonite calcium carbonate plates of mollusk shells.

PubMed

Lertvachirapaiboon, Chutiparn; Parnklang, Tewarak; Pienpinijtham, Prompong; Wongravee, Kanet; Thammacharoen, Chuchaat; Ekgasit, Sanong

2015-08-01

An interaction between the incident light and the structural architecture within the shell of Asian green mussel (Perna viridis) induces observable pearlescent colors. In this paper, we investigate the influence of the structural architecture on the expressed colors. After a removal of the organic binder, small flakes from crushed shells show vivid rainbow reflection under an optical microscope. An individual flake expresses vivid color under a bright-field illumination while become transparent under a dark-field illumination. The expressed colors of the aragonite flakes are directly associated with its structural architecture. The flakes with aragonite thickness of 256, 310, and 353 nm, respectively, appear blue, green, and red under an optical microscope. The spectral simulation corroborates the experimentally observed optical effects as the flakes with thicker aragonite layers selectively reflected color with longer wavelengths. Flakes with multiple aragonite thicknesses expressed multi-color as the upper aragonite layers allow reflected colors from the lower layers to be observed. Copyright © 2015 Elsevier Inc. All rights reserved.

EVOLUTION OF DIVERGENT FEMALE MATING PREFERENCE IN RESPONSE TO EXPERIMENTAL SEXUAL SELECTION

PubMed Central

Debelle, Allan; Ritchie, Michael G; Snook, Rhonda R

2014-01-01

Sexual selection is predicted to drive the coevolution of mating signals and preferences (mating traits) within populations, and could play a role in speciation if sexual isolation arises due to mating trait divergence between populations. However, few studies have demonstrated that differences in mating traits between populations result from sexual selection alone. Experimental evolution is a promising approach to directly examine the action of sexual selection on mating trait divergence among populations. We manipulated the opportunity for sexual selection (low vs. high) in populations of Drosophila pseudoobscura. Previous studies on these experimental populations have shown that sexual selection manipulation resulted in the divergence between sexual selection treatments of several courtship song parameters, including interpulse interval (IPI) which markedly influences male mating success. Here, we measure female preference for IPI using a playback design to test for preference divergence between the sexual selection treatments after 130 generations of experimental sexual selection. The results suggest that female preference has coevolved with male signal, in opposite directions between the sexual selection treatments, providing direct evidence of the ability of sexual selection to drive the divergent coevolution of mating traits between populations. We discuss the implications in the context sexual selection and speciation. PMID:24931497

Prediction uncertainty and optimal experimental design for learning dynamical systems.

PubMed

Letham, Benjamin; Letham, Portia A; Rudin, Cynthia; Browne, Edward P

2016-06-01

Dynamical systems are frequently used to model biological systems. When these models are fit to data, it is necessary to ascertain the uncertainty in the model fit. Here, we present prediction deviation, a metric of uncertainty that determines the extent to which observed data have constrained the model's predictions. This is accomplished by solving an optimization problem that searches for a pair of models that each provides a good fit for the observed data, yet has maximally different predictions. We develop a method for estimating a priori the impact that additional experiments would have on the prediction deviation, allowing the experimenter to design a set of experiments that would most reduce uncertainty. We use prediction deviation to assess uncertainty in a model of interferon-alpha inhibition of viral infection, and to select a sequence of experiments that reduces this uncertainty. Finally, we prove a theoretical result which shows that prediction deviation provides bounds on the trajectories of the underlying true model. These results show that prediction deviation is a meaningful metric of uncertainty that can be used for optimal experimental design.

Long-Wavelength Rupturing Instability in Surface-Tension-Driven Benard Convection

NASA Technical Reports Server (NTRS)

Swift, J. B.; Hook, Stephen J. Van; Becerril, Ricardo; McCormick, W. D.; Swinney, H. L.; Schatz, Michael F.

1999-01-01

A liquid layer with a free upper surface and heated from below is subject to thermocapillary-induced convective instabilities. We use very thin liquid layers (0.01 cm) to significantly reduce buoyancy effects and simulate Marangoni convection in microgravity. We observe thermocapillary-driven convection in two qualitatively different modes, short-wavelength Benard hexagonal convection cells and a long-wavelength interfacial rupturing mode. We focus on the long-wavelength mode and present experimental observations and theoretical analyses of the long-wavelength instability. Depending on the depths and thermal conductivities of the liquid and the gas above it, the interface can rupture downwards and form a dry spot or rupture upwards and form a high spot. Linear stability theory gives good agreement to the experimental measurements of onset as long as sidewall effects are taken into account. Nonlinear theory correctly predicts the subcritical nature of the bifurcation and the selection between the dry spot and high spots.

Experimental demonstration of an Allee effect in microbial populations.

PubMed

Kaul, RajReni B; Kramer, Andrew M; Dobbs, Fred C; Drake, John M

2016-04-01

Microbial populations can be dispersal limited. However, microorganisms that successfully disperse into physiologically ideal environments are not guaranteed to establish. This observation contradicts the Baas-Becking tenet: 'Everything is everywhere, but the environment selects'. Allee effects, which manifest in the relationship between initial population density and probability of establishment, could explain this observation. Here, we experimentally demonstrate that small populations of Vibrio fischeri are subject to an intrinsic demographic Allee effect. Populations subjected to predation by the bacterivore Cafeteria roenbergensis display both intrinsic and extrinsic demographic Allee effects. The estimated critical threshold required to escape positive density-dependence is around 5, 20 or 90 cells ml(-1)under conditions of high carbon resources, low carbon resources or low carbon resources with predation, respectively. This work builds on the foundations of modern microbial ecology, demonstrating that mechanisms controlling macroorganisms apply to microorganisms, and provides a statistical method to detect Allee effects in data. © 2016 The Author(s).

Sodium channel selectivity and conduction: Prokaryotes have devised their own molecular strategy

PubMed Central

Finol-Urdaneta, Rocio K.; Wang, Yibo; Al-Sabi, Ahmed; Zhao, Chunfeng

2014-01-01

Striking structural differences between voltage-gated sodium (Nav) channels from prokaryotes (homotetramers) and eukaryotes (asymmetric, four-domain proteins) suggest the likelihood of different molecular mechanisms for common functions. For these two channel families, our data show similar selectivity sequences among alkali cations (relative permeability, Pion/PNa) and asymmetric, bi-ionic reversal potentials when the Na/K gradient is reversed. We performed coordinated experimental and computational studies, respectively, on the prokaryotic Nav channels NaChBac and NavAb. NaChBac shows an “anomalous,” nonmonotonic mole-fraction dependence in the presence of certain sodium–potassium mixtures; to our knowledge, no comparable observation has been reported for eukaryotic Nav channels. NaChBac’s preferential selectivity for sodium is reduced either by partial titration of its highly charged selectivity filter, when extracellular pH is lowered from 7.4 to 5.8, or by perturbation—likely steric—associated with a nominally electro-neutral substitution in the selectivity filter (E191D). Although no single molecular feature or energetic parameter appears to dominate, our atomistic simulations, based on the published NavAb crystal structure, revealed factors that may contribute to the normally observed selectivity for Na over K. These include: (a) a thermodynamic penalty to exchange one K+ for one Na+ in the wild-type (WT) channel, increasing the relative likelihood of Na+ occupying the binding site; (b) a small tendency toward weaker ion binding to the selectivity filter in Na–K mixtures, consistent with the higher conductance observed with both sodium and potassium present; and (c) integrated 1-D potentials of mean force for sodium or potassium movement that show less separation for the less selective E/D mutant than for WT. Overall, tight binding of a single favored ion to the selectivity filter, together with crucial inter-ion interactions within the pore, suggests that prokaryotic Nav channels use a selective strategy more akin to those of eukaryotic calcium and potassium channels than that of eukaryotic Nav channels. PMID:24420772

Selective preservation of the beat in apperceptive music agnosia: a case study.

PubMed

Baird, Amee D; Walker, David G; Biggs, Vivien; Robinson, Gail A

2014-04-01

Music perception involves processing of melodic, temporal and emotional dimensions that have been found to dissociate in healthy individuals and after brain injury. Two components of the temporal dimension have been distinguished, namely rhythm and metre. We describe an 18 year old male musician 'JM' who showed apperceptive music agnosia with selectively preserved metre perception, and impaired recognition of sad and peaceful music relative to age and music experience matched controls after resection of a right temporoparietal tumour. Two months post-surgery JM underwent a comprehensive neuropsychological evaluation including assessment of his music perception abilities using the Montreal Battery for Evaluation of Amusia (MBEA, Peretz, Champod, & Hyde, 2003). He also completed several experimental tasks to explore his ability to recognise famous songs and melodies, emotions portrayed by music and a broader range of environmental sounds. Five age-, gender-, education- and musical experienced-matched controls were administered the same experimental tasks. JM showed selective preservation of metre perception, with impaired performances compared to controls and scoring below the 5% cut-off on all MBEA subtests, except for the metric condition. He could identify his favourite songs and environmental sounds. He showed impaired recognition of sad and peaceful emotions portrayed in music relative to controls but intact ability to identify happy and scary music. This case study contributes to the scarce literature documenting a dissociation between rhythmic and metric processing, and the rare observation of selectively preserved metric interpretation in the context of apperceptive music agnosia. It supports the notion that the anterior portion of the superior temporal gyrus (STG) plays a role in metric processing and provides the novel observation that selectively preserved metre is sufficient to identify happy and scary, but not sad or peaceful emotions portrayed in music. Crown Copyright © 2014. Published by Elsevier Ltd. All rights reserved.

A phase transition induces chaos in a predator-prey ecosystem with a dynamic fitness landscape.

PubMed

Gilpin, William; Feldman, Marcus W

2017-07-01

In many ecosystems, natural selection can occur quickly enough to influence the population dynamics and thus future selection. This suggests the importance of extending classical population dynamics models to include such eco-evolutionary processes. Here, we describe a predator-prey model in which the prey population growth depends on a prey density-dependent fitness landscape. We show that this two-species ecosystem is capable of exhibiting chaos even in the absence of external environmental variation or noise, and that the onset of chaotic dynamics is the result of the fitness landscape reversibly alternating between epochs of stabilizing and disruptive selection. We draw an analogy between the fitness function and the free energy in statistical mechanics, allowing us to use the physical theory of first-order phase transitions to understand the onset of rapid cycling in the chaotic predator-prey dynamics. We use quantitative techniques to study the relevance of our model to observational studies of complex ecosystems, finding that the evolution-driven chaotic dynamics confer community stability at the "edge of chaos" while creating a wide distribution of opportunities for speciation during epochs of disruptive selection-a potential observable signature of chaotic eco-evolutionary dynamics in experimental studies.

Selective Laser Melting of Pure Copper

NASA Astrophysics Data System (ADS)

Ikeshoji, Toshi-Taka; Nakamura, Kazuya; Yonehara, Makiko; Imai, Ken; Kyogoku, Hideki

2017-12-01

Appropriate building parameters for selective laser melting of 99.9% pure copper powder were investigated at relatively high laser power of 800 W for hatch pitch in the range from 0.025 mm to 0.12 mm. The highest relative density of the built material was 99.6%, obtained at hatch pitch of 0.10 mm. Building conditions were also studied using transient heat analysis in finite element modeling of the liquidation and solidification of the powder layer. The estimated melt pool length and width were comparable to values obtained by observations using a thermoviewer. The trend for the melt pool width versus the hatch pitch agreed with experimental values.

Selective Laser Melting of Pure Copper

NASA Astrophysics Data System (ADS)

Ikeshoji, Toshi-Taka; Nakamura, Kazuya; Yonehara, Makiko; Imai, Ken; Kyogoku, Hideki

2018-03-01

Appropriate building parameters for selective laser melting of 99.9% pure copper powder were investigated at relatively high laser power of 800 W for hatch pitch in the range from 0.025 mm to 0.12 mm. The highest relative density of the built material was 99.6%, obtained at hatch pitch of 0.10 mm. Building conditions were also studied using transient heat analysis in finite element modeling of the liquidation and solidification of the powder layer. The estimated melt pool length and width were comparable to values obtained by observations using a thermoviewer. The trend for the melt pool width versus the hatch pitch agreed with experimental values.

Informing the Historical Record of Experimental Nonhuman Primate Infections with Ebola Virus: Genomic Characterization of USAMRIID Ebola Virus/H.sapiens-tc/COD/1995/Kikwit-9510621 Challenge Stock R4368 and Its Replacement R4415

DTIC Science & Technology

2016-03-20

8U EBOV/Yam-May populations converted to 7U populations 101 in guinea pigs [10]. These changes may be related to selective advantages linked to the... guinea pigs or nonhuman primates [25]. 104 However, the observations described above indicate that there may be selective advantages 105 associated with...culture and 20 infection of guinea pigs . J Infect Dis. 2011;204 Suppl 3:S941-6. Epub 2011/10/19. doi: 21 10.1093/infdis/jir321. PubMed PMID: 21987773. 22

A combined experimental and finite element approach to analyse the fretting mechanism of the head-stem taper junction in total hip replacement.

PubMed

Bitter, Thom; Khan, Imran; Marriott, Tim; Lovelady, Elaine; Verdonschot, Nico; Janssen, Dennis

2017-09-01

Fretting corrosion at the taper interface of modular hip implants has been implicated as a possible cause of implant failure. This study was set up to gain more insight in the taper mechanics that lead to fretting corrosion. The objectives of this study therefore were (1) to select experimental loading conditions to reproduce clinically relevant fretting corrosion features observed in retrieved components, (2) to develop a finite element model consistent with the fretting experiments and (3) to apply more complicated loading conditions of activities of daily living to the finite element model to study the taper mechanics. The experiments showed similar wear patterns on the taper surface as observed in retrievals. The finite element wear score based on Archard's law did not correlate well with the amount of material loss measured in the experiments. However, similar patterns were observed between the simulated micromotions and the experimental wear measurements. Although the finite element model could not be validated, the loading conditions based on activities of daily living demonstrate the importance of assembly load on the wear potential. These findings suggest that finite element models that do not incorporate geometry updates to account for wear loss may not be appropriate to predict wear volumes of taper connections.

Impact of number of repeated scans on model observer performance for a low-contrast detection task in computed tomography.

PubMed

Ma, Chi; Yu, Lifeng; Chen, Baiyu; Favazza, Christopher; Leng, Shuai; McCollough, Cynthia

2016-04-01

Channelized Hotelling observer (CHO) models have been shown to correlate well with human observers for several phantom-based detection/classification tasks in clinical computed tomography (CT). A large number of repeated scans were used to achieve an accurate estimate of the model's template. The purpose of this study is to investigate how the experimental and CHO model parameters affect the minimum required number of repeated scans. A phantom containing 21 low-contrast objects was scanned on a 128-slice CT scanner at three dose levels. Each scan was repeated 100 times. For each experimental configuration, the low-contrast detectability, quantified as the area under receiver operating characteristic curve, [Formula: see text], was calculated using a previously validated CHO with randomly selected subsets of scans, ranging from 10 to 100. Using [Formula: see text] from the 100 scans as the reference, the accuracy from a smaller number of scans was determined. Our results demonstrated that the minimum number of repeated scans increased when the radiation dose level decreased, object size and contrast level decreased, and the number of channels increased. As a general trend, it increased as the low-contrast detectability decreased. This study provides a basis for the experimental design of task-based image quality assessment in clinical CT using CHO.

Impact of number of repeated scans on model observer performance for a low-contrast detection task in computed tomography

PubMed Central

Ma, Chi; Yu, Lifeng; Chen, Baiyu; Favazza, Christopher; Leng, Shuai; McCollough, Cynthia

2016-01-01

Abstract. Channelized Hotelling observer (CHO) models have been shown to correlate well with human observers for several phantom-based detection/classification tasks in clinical computed tomography (CT). A large number of repeated scans were used to achieve an accurate estimate of the model’s template. The purpose of this study is to investigate how the experimental and CHO model parameters affect the minimum required number of repeated scans. A phantom containing 21 low-contrast objects was scanned on a 128-slice CT scanner at three dose levels. Each scan was repeated 100 times. For each experimental configuration, the low-contrast detectability, quantified as the area under receiver operating characteristic curve, Az, was calculated using a previously validated CHO with randomly selected subsets of scans, ranging from 10 to 100. Using Az from the 100 scans as the reference, the accuracy from a smaller number of scans was determined. Our results demonstrated that the minimum number of repeated scans increased when the radiation dose level decreased, object size and contrast level decreased, and the number of channels increased. As a general trend, it increased as the low-contrast detectability decreased. This study provides a basis for the experimental design of task-based image quality assessment in clinical CT using CHO. PMID:27284547

Do females trade copulations for food? An experimental study on kittiwakes (Rissa tridactyla)

USGS Publications Warehouse

Kempenaers, Bart; Lanctot, Richard B.; Gill, V.A.; Hatch, Shyla A.; Valcu, M.

2007-01-01

Females of many species copulate more frequently than necessary to fertilize their eggs despite the potential costs. Several studies, particularly on socially monogamous birds, have suggested that females obtain immediate material benefits by trading copulations for nutrients or other resources. We experimentally tested this hypothesis by manipulating the food resources available to prelaying female black-legged kittiwakes (Rissa tridactyla). If female kittiwakes trade copulations for courtship feeding because they need the extra resources, well-fed females (experimental group) should be less willing to copulate compared with females that are more food limited (control group). Contrary to our predictions, we found that close to the start of laying experimental females copulated more frequently with their mate than control females. We also observed that males from the experimental group fed their mate at least as often as males from the control group. In experimental pairs, we still observed a positive correlation between the rate of copulation and the rate of courtship feeding. Our results thus refute the immediate material benefits hypothesis. Currently available data are consistent with the hypothesis that prelaying courtship feeding is a form of mating effort. We suggest that the rate of courtship feeding might be a sexually selected trait, on which females base decisions about timing and frequency of copulations, but this remains to be tested. ?? The Author 2006. Published by Oxford University Press on behalf of the International Society for Behavioral Ecology. All rights reserved.

Evolution of viral virulence: empirical studies

USGS Publications Warehouse

Kurath, Gael; Wargo, Andrew R.

2016-01-01

The concept of virulence as a pathogen trait that can evolve in response to selection has led to a large body of virulence evolution theory developed in the 1980-1990s. Various aspects of this theory predict increased or decreased virulence in response to a complex array of selection pressures including mode of transmission, changes in host, mixed infection, vector-borne transmission, environmental changes, host vaccination, host resistance, and co-evolution of virus and host. A fundamental concept is prediction of trade-offs between the costs and benefits associated with higher virulence, leading to selection of optimal virulence levels. Through a combination of observational and experimental studies, including experimental evolution of viruses during serial passage, many of these predictions have now been explored in systems ranging from bacteriophage to viruses of plants, invertebrates, and vertebrate hosts. This chapter summarizes empirical studies of viral virulence evolution in numerous diverse systems, including the classic models myxomavirus in rabbits, Marek's disease virus in chickens, and HIV in humans. Collectively these studies support some aspects of virulence evolution theory, suggest modifications for other aspects, and show that predictions may apply in some virus:host interactions but not in others. Finally, we consider how virulence evolution theory applies to disease management in the field.

Face inversion and acquired prosopagnosia reduce the size of the perceptual field of view.

PubMed

Van Belle, Goedele; Lefèvre, Philippe; Rossion, Bruno

2015-03-01

Using a gaze-contingent morphing approach, we asked human observers to choose one of two faces that best matched the identity of a target face: one face corresponded to the reference face's fixated part only (e.g., one eye), the other corresponded to the unfixated area of the reference face. The face corresponding to the fixated part was selected significantly more frequently in the inverted than in the upright orientation. This observation provides evidence that face inversion reduces an observer's perceptual field of view, even when both upright and inverted faces are displayed at full view and there is no performance difference between these conditions. It rules out an account of the drop of performance for inverted faces--one of the most robust effects in experimental psychology--in terms of a mere difference in local processing efficiency. A brain-damaged patient with pure prosopagnosia, viewing only upright faces, systematically selected the face corresponding to the fixated part, as if her perceptual field was reduced relative to normal observers. Altogether, these observations indicate that the absence of visual knowledge reduces the perceptual field of view, supporting an indirect view of visual perception. Copyright © 2014 Elsevier B.V. All rights reserved.

Fruit and vegetable availability and selection: federal food package revisions, 2009.

PubMed

Zenk, Shannon N; Odoms-Young, Angela; Powell, Lisa M; Campbell, Richard T; Block, Daniel; Chavez, Noel; Krauss, Ramona C; Strode, Steven; Armbruster, James

2012-10-01

With nearly 49,000 authorized retailers nationwide, a policy change that added fruits and vegetables (FV) to the U.S. Department of Agriculture's Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) food packages in 2009 had the potential to expand neighborhood FV availability. This study examined changes in availability and selection of commonly consumed and culturally specific FV at authorized retailers (WIC vendors) before and after implementation of the revised WIC food packages. Quasi-experimental, one-group design with two pre-policy observations and one post-policy observation. Trained observers assessed a list of fresh, frozen, and canned FV at each vendor in seven northern Illinois counties. Eight indices of FV availability and selection were derived. Multiple regression estimated relationships. Data were collected in 2008-2010 and analyzed in 2011. Overall, availability and selection of commonly consumed fresh FV and availability of African-American culturally specific fresh FV improved after implementation of the new policy. Modest improvements in the overall availability of canned low-sodium vegetables and frozen FV were observed. Changes differed by vendor type (large vendor, small vendor, and pharmacy). Changes in availability or selection did not differ by neighborhood characteristics (population density, median household income, racial/ethnic composition). Expansion of WIC foods was associated with small positive externalities on the food environment. Larger subsidies to create more demand and more-substantial stocking requirements for retailers may yield significantly larger improvements and thus warrant further investigation. Approaches targeting rural, low-income, and racial/ethnic minority neighborhoods also may be needed. Copyright © 2012 American Journal of Preventive Medicine. Published by Elsevier Inc. All rights reserved.

Activity and selectivity of photocatalysts in photodegradation of phenols.

PubMed

Emeline, A V; Zhang, X; Murakami, T; Fujishima, A

2012-04-15

Photodegradation of phenol and 4-chlorophenol over six different TiO(2) samples was tested in order to establish whether an interconnection between the activity and selectivity of photocatalysts exists. The obtained experimental data were analyzed using correlation analysis. Some correlations between the activity in phenol(s) photodegradation and selectivity toward formation of primary intermediate products were established. The type of correlations depends on the type of studied photoreactions. The discussion of the observed correlations between the activity and selectivity of photocatalysts is given in terms of the difference of surface concentrations of electrons and holes and corresponding surface active sites which might be dependent on the types of dominating surface faces. On the basis of the obtained results of correlation analysis it was assumed that a higher activity of photocatalysts could be achieved provided that both reduction and oxidation reaction pathways occur with equally high efficiency. Copyright © 2011 Elsevier B.V. All rights reserved.

Coordinated ionospheric and magnetospheric observations from the ISIS 2 satellite by the ISIS 2 experimenters. Volume 1: Optical auroral images and related direct measurements

NASA Technical Reports Server (NTRS)

Murphree, J. S.

1980-01-01

A representative set of data from ISIS 2 covering a range of operating modes and geophysical conditions is presented. The data show the typical values and range of ionospheric and magnetospheric characteristics, as viewed from 1400 km with the ISIS 2 instruments. The definition of each data set depends partly on geophysical parameters and partly on satellite operating mode. Preceding the data set is a description of the organizational parameters and a review of the objectives and general characteristics of the data set. The data are shown as a selection from 12 different data formats. Each data has a different selection of formats, but uniformity of a given format selection is preserved throughout each data set.

Selective electron spin resonance measurements of micrometer-scale thin samples on a substrate

NASA Astrophysics Data System (ADS)

Dikarov, Ekaterina; Fehr, Matthias; Schnegg, Alexander; Lips, Klaus; Blank, Aharon

2013-11-01

An approach to the selective observation of paramagnetic centers in thin samples or surfaces with electron spin resonance (ESR) is presented. The methodology is based on the use of a surface microresonator that enables the selective obtention of ESR data from thin layers with minimal background signals from the supporting substrate. An experimental example is provided, which measures the ESR signal from a 1.2 µm polycrystalline silicon layer on a glass substrate used in modern solar-cell technology. The ESR results obtained with the surface microresonator show the effective elimination of background signals, especially at low cryogenic temperatures, compared to the use of a conventional resonator. The surface microresonator also facilitates much higher absolute spin sensitivity, requiring much smaller surfaces for the measurement.

An experimental sample of the field gamma-spectrometer based on solid state Si-photomultiplier

NASA Astrophysics Data System (ADS)

Denisov, Viktor; Korotaev, Valery; Titov, Aleksandr; Blokhina, Anastasia; Kleshchenok, Maksim

2017-05-01

Design of optical-electronic devices and systems involves the selection of such technical patterns that under given initial requirements and conditions are optimal according to certain criteria. The original characteristic of the OES for any purpose, defining its most important feature ability is a threshold detection. Based on this property, will be achieved the required functional quality of the device or system. Therefore, the original criteria and optimization methods have to subordinate to the idea of a better detectability. Generally reduces to the problem of optimal selection of the expected (predetermined) signals in the predetermined observation conditions. Thus the main purpose of optimization of the system when calculating its detectability is the choice of circuits and components that provide the most effective selection of a target.

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

Dumitrescu, Eugene; Humble, Travis S.

The accurate and reliable characterization of quantum dynamical processes underlies efforts to validate quantum technologies, where discrimination between competing models of observed behaviors inform efforts to fabricate and operate qubit devices. We present a protocol for quantum channel discrimination that leverages advances in direct characterization of quantum dynamics (DCQD) codes. We demonstrate that DCQD codes enable selective process tomography to improve discrimination between entangling and correlated quantum dynamics. Numerical simulations show selective process tomography requires only a few measurement configurations to achieve a low false alarm rate and that the DCQD encoding improves the resilience of the protocol to hiddenmore » sources of noise. Lastly, our results show that selective process tomography with DCQD codes is useful for efficiently distinguishing sources of correlated crosstalk from uncorrelated noise in current and future experimental platforms.« less

Substrate Control in Stereoselective Lanthionine Biosynthesis

PubMed Central

Tang, Weixin; Jiménez-Osés, Gonzalo; Houk, K. N.; van der Donk, Wilfred A.

2014-01-01

Enzymes are typically highly stereoselective catalysts that enforce a reactive conformation on their native substrates. We report here a rare example where the substrate controls the stereoselectivity of an enzyme-catalyzed Michael-type addition during the biosynthesis of lanthipeptides. These natural products contain thioether crosslinks formed by cysteine attack on dehydrated Ser and Thr residues. We demonstrate that several lanthionine synthetases catalyze highly selective anti additions in which the substrate (and not the enzyme) determines whether the addition occurs from the Re or Si face. A single point mutation in the peptide substrate completely inverted the stereochemical outcome of the enzymatic modification. Quantum mechanical calculations reproduced the experimentally observed selectivity and suggest that conformational restraints imposed by the amino acid sequence on the transition states determine the face selectivity of the Michael-type cyclization. PMID:25515891

[Social exchange and inference: an experimental study with the Wason selection task].

PubMed

Hayashi, N

2001-04-01

Social contract theory (Cosmides, 1989) posits that the human mind was equipped with inference faculty specialized for cheater detection. Cosmides (1989) conducted a series of experiments employing the Wason selection task to demonstrate that her social contract theory could account for the content effects reported in the literature. The purpose of this study was to investigate the possibility that the results were due to experimental artifacts. In the current experiment, the subject was given two versions of the Wason task that contained no social exchange context, but included an instruction implying him/her to look for something, together with the cassava root and the abstract versions used by Cosmides (1989). Results showed that the two versions with no social exchange context produced the same response pattern observed in the original study. It may be concluded that the subject's perception of the rule as a social contract was not necessary to obtain the original results, and that an instruction implying that he/she should look for something was sufficient.

Epitaxial Relationships between Calcium Carbonate and Inorganic Substrates

PubMed Central

Yang, Taewook; Jho, Jae Young; Kim, Il Won

2014-01-01

The polymorph-selective crystallization of calcium carbonate has been studied in terms of epitaxial relationship between the inorganic substrates and the aragonite/calcite polymorphs with implication in bioinspired mineralization. EpiCalc software was employed to assess the previously published experimental results on two different groups of inorganic substrates: aragonitic carbonate crystals (SrCO3, PbCO3, and BaCO3) and a hexagonal crystal family (α-Al2O3, α-SiO2, and LiNbO3). The maximum size of the overlayer (aragonite or calcite) was calculated for each substrate based on a threshold value of the dimensionless potential to estimate the relative nucleation preference of the polymorphs of calcium carbonate. The results were in good agreement with previous experimental observations, although stereochemical effects between the overlayer and substrate should be separately considered when existed. In assessing the polymorph-selective nucleation, the current method appeared to provide a better tool than the oversimplified mismatch parameters without invoking time-consuming molecular simulation\\. PMID:25226539

PSYCHE Pure Shift NMR Spectroscopy.

PubMed

Foroozandeh, Mohammadali; Morris, Gareth; Nilsson, Mathias

2018-03-13

Broadband homodecoupling techniques in NMR, also known as "pure shift" methods, aim to enhance spectral resolution by suppressing the effects of homonuclear coupling interactions to turn multiplet signals into singlets. Such techniques typically work by selecting a subset of "active" nuclear spins to observe, and selectively inverting the remaining, "passive", spins to reverse the effects of coupling. Pure Shift Yielded by Chirp Excitation (PSYCHE) is one such method; it is relatively recent, but has already been successfully implemented in a range of different NMR experiments. Paradoxically, PSYCHE is one of the trickiest of pure shift NMR techniques to understand but one of the easiest to use. Here we offer some insights into theoretical and practical aspects of the method, and into the effects and importance of the experimental parameters. Some recent improvements that enhance the spectral purity of PSYCHE spectra will be presented, and some experimental frameworks including examples in 1D and 2D NMR spectroscopy, for the implementation of PSYCHE will be introduced. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Measurement of Net Fluxes of Ammonium and Nitrate at the Surface of Barley Roots Using Ion-Selective Microelectrodes 1

PubMed Central

Henriksen, Gordon H.; Raman, D. Raj; Walker, Larry P.; Spanswick, Roger M.

1992-01-01

Net fluxes of NH4+ and NO3− into roots of 7-day-old barley (Hordeum vulgare L. cv Prato) seedlings varied both with position along the root axis and with time. These variations were not consistent between replicate plants; different roots showed unique temporal and spatial patterns of uptake. Axial scans of NH4+ and NO3− net fluxes were conducted along the apical 7 centimeters of seminal roots of intact barley seedlings in solution culture using ion-selective microelectrodes in the unstirred layer immediately external to the root surface. Theoretically derived relationships between uptake and concentration gradients, combined with experimental observations of the conditions existing in our experimental system, permitted evaluation of the contribution of bulk water flow to ion movement in the unstirred layer, as well as a measure of the spatial resolution of the microelectrode flux estimation technique. Finally, a method was adopted to assess the accuracy of this technique. PMID:16668947

Mode-selective vibrational modulation of charge transport in organic electronic devices

PubMed Central

Bakulin, Artem A.; Lovrincic, Robert; Yu, Xi; Selig, Oleg; Bakker, Huib J.; Rezus, Yves L. A.; Nayak, Pabitra K.; Fonari, Alexandr; Coropceanu, Veaceslav; Brédas, Jean-Luc; Cahen, David

2015-01-01

The soft character of organic materials leads to strong coupling between molecular, nuclear and electronic dynamics. This coupling opens the way to influence charge transport in organic electronic devices by exciting molecular vibrational motions. However, despite encouraging theoretical predictions, experimental realization of such approach has remained elusive. Here we demonstrate experimentally that photoconductivity in a model organic optoelectronic device can be modulated by the selective excitation of molecular vibrations. Using an ultrafast infrared laser source to create a coherent superposition of vibrational motions in a pentacene/C60 photoresistor, we observe that excitation of certain modes in the 1,500–1,700 cm−1 region leads to photocurrent enhancement. Excited vibrations affect predominantly trapped carriers. The effect depends on the nature of the vibration and its mode-specific character can be well described by the vibrational modulation of intermolecular electronic couplings. This presents a new tool for studying electron–phonon coupling and charge dynamics in (bio)molecular materials. PMID:26246039

Mode-selective vibrational modulation of charge transport in organic electronic devices

NASA Astrophysics Data System (ADS)

Bakulin, Artem A.; Lovrincic, Robert; Yu, Xi; Selig, Oleg; Bakker, Huib J.; Rezus, Yves L. A.; Nayak, Pabitra K.; Fonari, Alexandr; Coropceanu, Veaceslav; Brédas, Jean-Luc; Cahen, David

2015-08-01

The soft character of organic materials leads to strong coupling between molecular, nuclear and electronic dynamics. This coupling opens the way to influence charge transport in organic electronic devices by exciting molecular vibrational motions. However, despite encouraging theoretical predictions, experimental realization of such approach has remained elusive. Here we demonstrate experimentally that photoconductivity in a model organic optoelectronic device can be modulated by the selective excitation of molecular vibrations. Using an ultrafast infrared laser source to create a coherent superposition of vibrational motions in a pentacene/C60 photoresistor, we observe that excitation of certain modes in the 1,500-1,700 cm-1 region leads to photocurrent enhancement. Excited vibrations affect predominantly trapped carriers. The effect depends on the nature of the vibration and its mode-specific character can be well described by the vibrational modulation of intermolecular electronic couplings. This presents a new tool for studying electron-phonon coupling and charge dynamics in (bio)molecular materials.

Response to Extreme Temperatures of Mesoporous Silica MCM-41: Porous Structure Transformation Simulation and Modification of Gas Adsorption Properties.

PubMed

Zhang, Shenli; Perez-Page, Maria; Guan, Kelly; Yu, Erick; Tringe, Joseph; Castro, Ricardo H R; Faller, Roland; Stroeve, Pieter

2016-11-08

Molecular dynamics (MD) and Monte Carlo (MC) simulations were applied together for the first time to reveal the porous structure transformation mechanisms of mesoporous silica MCM-41 subjected to temperatures up to 2885 K. Silica was experimentally characterized to inform the models and enable prediction of changes in gas adsorption/separation properties. MD simulations suggest that the pore closure process is activated by a collective diffusion of matrix atoms into the porous region, accompanied by bond reformation at the surface. Degradation is kinetically limited, such that complete pore closure is postponed at high heating rates. We experimentally observe decreased gas adsorption with increasing temperature in mesoporous silica heated at fixed rates, due to pore closure and structural degradation consistent with simulation predictions. Applying the Kissinger equation, we find a strong correlation between the simulated pore collapse temperatures and the experimental values which implies an activation energy of 416 ± 17 kJ/mol for pore closure. MC simulations give the adsorption and selectivity for thermally treated MCM-41, for N 2 , Ar, Kr, and Xe at room temperature within the 1-10 000 kPa pressure range. Relative to pristine MCM-41, we observe that increased surface roughness due to decreasing pore size amplifies the difference of the absolute adsorption amount differently for different adsorbate molecules. In particular, we find that adsorption of strongly interacting molecules can be enhanced in the low-pressure region while adsorption of weakly interacting molecules is inhibited. This then results in higher selectivity in binary mixture adsorption in mesoporous silica.

Invited review: study design considerations for clinical research in veterinary radiology and radiation oncology.

PubMed

Scrivani, Peter V; Erb, Hollis N

2013-01-01

High quality clinical research is essential for advancing knowledge in the areas of veterinary radiology and radiation oncology. Types of clinical research studies may include experimental studies, method-comparison studies, and patient-based studies. Experimental studies explore issues relative to pathophysiology, patient safety, and treatment efficacy. Method-comparison studies evaluate agreement between techniques or between observers. Patient-based studies investigate naturally acquired disease and focus on questions asked in clinical practice that relate to individuals or populations (e.g., risk, accuracy, or prognosis). Careful preplanning and study design are essential in order to achieve valid results. A key point to planning studies is ensuring that the design is tailored to the study objectives. Good design includes a comprehensive literature review, asking suitable questions, selecting the proper sample population, collecting the appropriate data, performing the correct statistical analyses, and drawing conclusions supported by the available evidence. Most study designs are classified by whether they are experimental or observational, longitudinal or cross-sectional, and prospective or retrospective. Additional features (e.g., controlled, randomized, or blinded) may be described that address bias. Two related challenging aspects of study design are defining an important research question and selecting an appropriate sample population. The sample population should represent the target population as much as possible. Furthermore, when comparing groups, it is important that the groups are as alike to each other as possible except for the variables of interest. Medical images are well suited for clinical research because imaging signs are categorical or numerical variables that might be predictors or outcomes of diseases or treatments. © 2013 Veterinary Radiology & Ultrasound.

Experimental verification of PSM polarimetry: monitoring polarization at 193nm high-NA with phase shift masks

NASA Astrophysics Data System (ADS)

McIntyre, Gregory; Neureuther, Andrew; Slonaker, Steve; Vellanki, Venu; Reynolds, Patrick

2006-03-01

The initial experimental verification of a polarization monitoring technique is presented. A series of phase shifting mask patterns produce polarization dependent signals in photoresist and are capable of monitoring the Stokes parameters of any arbitrary illumination scheme. Experiments on two test reticles have been conducted. The first reticle consisted of a series of radial phase gratings (RPG) and employed special apertures to select particular illumination angles. Measurement sensitivities of about 0.3 percent of the clear field per percent change in polarization state were observed. The second test reticle employed the more sensitive proximity effect polarization analyzers (PEPA), a more robust experimental setup, and a backside pinhole layer for illumination angle selection and to enable characterization of the full illuminator. Despite an initial complication with the backside pinhole alignment, the results correlate with theory. Theory suggests that, once the pinhole alignment is corrected in the near future, the second reticle should achieve a measurement sensitivity of about 1 percent of the clear field per percent change in polarization state. This corresponds to a measurement of the Stokes parameters after test mask calibration, to within about 0.02 to 0.03. Various potential improvements to the design, fabrication of the mask, and experimental setup are discussed. Additionally, to decrease measurement time, a design modification and double exposure technique is proposed to enable electrical detection of the measurement signal.

Designing functionality in perovskite thin films using ion implantation techniques: Assessment and insights from first-principles calculations

DOE PAGES

Sharma, Vinit K.; Herklotz, Andreas; Ward, Thomas Zac; ...

2017-09-11

Ion implantation has been widely used in the semiconductor industry for decades to selectively control electron/hole doping for device applications. Recently, experimental studies on ion implantation into more structurally and electronically complex materials have been undertaken in which defect generation has been used to control a variety of functional phenomena. Of particular interest, are recent findings demonstrating that low doses of low energy helium ions into single crystal films can be used to tailor the structural properties. These initial experimental studies have shown that crystal symmetry can be continuously controlled by applying increasingly large doses of He ions into amore » crystal. The observed changes in lattice structure were then observed to correlate with functional changes, such as metal-insulator transition temperature2 and optical bandgap3. In these preliminary experimental studies, changes to lattice expansion was proposed to be the direct result of chemical pressure originating predominantly from the implanted He applying chemical pressure at interstitial sites. However, the influence of possible secondary knock-on damage arising from the He atoms transferring energy to the lattice through nuclear-nuclear collision with the crystal lattice remains largely unaddressed. In this work, we focus on a SrRuO3 model system to provide a comprehensive examination of the impact of common defects on structural and electronic properties, obtain calculated defect formation energies, and define defect migration barriers. Our model indicates that, while interstitial He can modify the crystal properties, a dose significantly larger than those reported in experimental studies would be required. The true origin of the observed structural changes is likely the result of a combination of secondary defects created during He implantation. Of particular importance, we observe that different defect types can generate greatly varied local electronic structures and that the formation energies and migration energy barriers vary by defect type. Thus, we may have identified a new method of selectively inducing controlled defect complexes into single crystal materials. Development of this approach would have a broad impact on both our ability to probe specific defect contributions in fundamental studies and allow a new level of control over functional properties driven by specific defect complexes.« less

Estimating selection through male fitness: three complementary methods illuminate the nature and causes of selection on flowering time

PubMed Central

Austen, Emily J.; Weis, Arthur E.

2016-01-01

Our understanding of selection through male fitness is limited by the resource demands and indirect nature of the best available genetic techniques. Applying complementary, independent approaches to this problem can help clarify evolution through male function. We applied three methods to estimate selection on flowering time through male fitness in experimental populations of the annual plant Brassica rapa: (i) an analysis of mating opportunity based on flower production schedules, (ii) genetic paternity analysis, and (iii) a novel approach based on principles of experimental evolution. Selection differentials estimated by the first method disagreed with those estimated by the other two, indicating that mating opportunity was not the principal driver of selection on flowering time. The genetic and experimental evolution methods exhibited striking agreement overall, but a slight discrepancy between the two suggested that negative environmental covariance between age at flowering and male fitness may have contributed to phenotypic selection. Together, the three methods enriched our understanding of selection on flowering time, from mating opportunity to phenotypic selection to evolutionary response. The novel experimental evolution method may provide a means of examining selection through male fitness when genetic paternity analysis is not possible. PMID:26911957

Mechanosensitive Channel MscS in the Open State: Modeling of the Transition, Explicit Simulations, and Experimental Measurements of Conductance

PubMed Central

Anishkin, Andriy; Kamaraju, Kishore; Sukharev, Sergei

2008-01-01

Mechanosensitive channels of small conductance (MscS) are ubiquitous turgor pressure regulators found in many walled cells and some intracellular organelles. Escherichia coli MscS acting as a tension-activated osmolyte release valve shows a nonsaturable conductance (1.2 nS in a 39 mS/cm electrolyte) and weak preference for anions. Pursuing the transition pathways in this channel, we applied the extrapolated motion protocol (cycles of displacements, minimizations, and short simulations) to the previously generated compact resting conformation of MscS. We observed tilting and straightening of the kinked pore-forming TM3 helices during the barrel expansion. Extended all-atom simulations confirmed the stability of the open conformation in the bilayer. A 53° spontaneous axial rotation of TM3s observed after equilibration increased the width and polarity of the pore allowing for stable voltage-independent hydration and presence of both cations and anions throughout the pore. The resultant open state, characterized by a pore 1.6 nm wide, satisfied the experimental conductance and in-plane expansion. Applied transmembrane electric field (±100 to ±200 mV) in simulations produced a flow of both K+ and Cl−, with Cl− current dominating at higher voltages. Electroosmotic water flux strongly correlated with the chloride current (∼8 waters per Cl−). The selectivity and rectification were in agreement with the experimental measurements performed in the same range of voltages. Among the charged residues surrounding the pore, only K169 was found to contribute noticeably in the rectification. We conclude that (a) the barrel expansion involving tilting, straightening, and rotation of TM3s provides the geometry and electrostatics that accounts for the conductive properties of the open pore; (b) the observed regimen of ion passage through the pore is similar to electrodiffusion, thus macroscopic estimations closely approximate the experimental and molecular dynamics-simulated conductances; (c) increased interaction of the opposing ionic fluxes at higher voltages may result in selectivities stronger than measured near the reversal potential. PMID:18591417

Platelet-rich plasma in orthopedic therapy: a comparative systematic review of clinical and experimental data in equine and human musculoskeletal lesions.

PubMed

Brossi, Patrícia M; Moreira, Juliana J; Machado, Thaís S L; Baccarin, Raquel Y A

2015-04-22

This systematic review aimed to present and critically appraise the available information on the efficacy of platelet rich plasma (PRP) in equine and human orthopedic therapeutics and to verify the influence of study design and methodology on the assumption of PRP's efficacy. We searched Medline, PubMed, Embase, Bireme and Google Scholar without restrictions until July 2013. Randomized trials, human cohort clinical studies or case series with a control group on the use of PRP in tendons, ligaments or articular lesions were included. Equine clinical studies on the same topics were included independently of their design. Experimental studies relevant to the clarification of PRP's effects and mechanisms of action in tissues of interest, conducted in any animal species, were selected. This review included 123 studies. PRP's beneficial effects were observed in 46.7% of the clinical studies, while the absence of positive effects was observed in 43.3%. Among experimental studies, 73% yielded positive results, and 7.9% yielded negative results. The most frequent flaws in the clinical trials' designs were the lack of a true placebo group, poor product characterization, insufficient blinding, small sampling, short follow-up periods, and adoption of poor outcome measures. The methods employed for PRP preparation and administration and the selected outcome measures varied greatly. Poor study design was a common feature of equine clinical trials. From studies in which PRP had beneficial effects, 67.8% had an overall high risk of bias. From the studies in which PRP failed to exhibit beneficial effects, 67.8% had an overall low risk of bias. Most experimental studies revealed positive effects of PRP. Although the majority of equine clinical studies yielded positive results, the human clinical trials' results failed to corroborate these findings. In both species, beneficial results were more frequently observed in studies with a high risk of bias. The use of PRP in musculoskeletal lesions, although safe and promising, has still not shown strong evidence in clinical scenarios.

Evolution of divergent female mating preference in response to experimental sexual selection.

PubMed

Debelle, Allan; Ritchie, Michael G; Snook, Rhonda R

2014-09-01

Sexual selection is predicted to drive the coevolution of mating signals and preferences (mating traits) within populations, and could play a role in speciation if sexual isolation arises due to mating trait divergence between populations. However, few studies have demonstrated that differences in mating traits between populations result from sexual selection alone. Experimental evolution is a promising approach to directly examine the action of sexual selection on mating trait divergence among populations. We manipulated the opportunity for sexual selection (low vs. high) in populations of Drosophila pseudoobscura. Previous studies on these experimental populations have shown that sexual selection manipulation resulted in the divergence between sexual selection treatments of several courtship song parameters, including interpulse interval (IPI) which markedly influences male mating success. Here, we measure female preference for IPI using a playback design to test for preference divergence between the sexual selection treatments after 130 generations of experimental sexual selection. The results suggest that female preference has coevolved with male signal, in opposite directions between the sexual selection treatments, providing direct evidence of the ability of sexual selection to drive the divergent coevolution of mating traits between populations. We discuss the implications in the context sexual selection and speciation. © 2014 The Authors. Evolution published by Wiley Periodicals, Inc. on behalf of The Society for the Study of Evolution.

Online feature selection with streaming features.

PubMed

Wu, Xindong; Yu, Kui; Ding, Wei; Wang, Hao; Zhu, Xingquan

2013-05-01

We propose a new online feature selection framework for applications with streaming features where the knowledge of the full feature space is unknown in advance. We define streaming features as features that flow in one by one over time whereas the number of training examples remains fixed. This is in contrast with traditional online learning methods that only deal with sequentially added observations, with little attention being paid to streaming features. The critical challenges for Online Streaming Feature Selection (OSFS) include 1) the continuous growth of feature volumes over time, 2) a large feature space, possibly of unknown or infinite size, and 3) the unavailability of the entire feature set before learning starts. In the paper, we present a novel Online Streaming Feature Selection method to select strongly relevant and nonredundant features on the fly. An efficient Fast-OSFS algorithm is proposed to improve feature selection performance. The proposed algorithms are evaluated extensively on high-dimensional datasets and also with a real-world case study on impact crater detection. Experimental results demonstrate that the algorithms achieve better compactness and higher prediction accuracy than existing streaming feature selection algorithms.

Rapid bursts and slow declines: on the possible evolutionary trajectories of enzymes

PubMed Central

Newton, Matilda S.; Arcus, Vickery L.; Patrick, Wayne M.

2015-01-01

The evolution of enzymes is often viewed as following a smooth and steady trajectory, from barely functional primordial catalysts to the highly active and specific enzymes that we observe today. In this review, we summarize experimental data that suggest a different reality. Modern examples, such as the emergence of enzymes that hydrolyse human-made pesticides, demonstrate that evolution can be extraordinarily rapid. Experiments to infer and resurrect ancient sequences suggest that some of the first organisms present on the Earth are likely to have possessed highly active enzymes. Reconciling these observations, we argue that rapid bursts of strong selection for increased catalytic efficiency are interspersed with much longer periods in which the catalytic power of an enzyme erodes, through neutral drift and selection for other properties such as cellular energy efficiency or regulation. Thus, many enzymes may have already passed their catalytic peaks. PMID:25926697

Direct Observation of the Surface Segregation of Cu in Pd by Time-Resolved Positron-Annihilation-Induced Auger Electron Spectroscopy

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

Mayer, J.; Hugenschmidt, C.; Schreckenbach, K.

2010-11-12

Density functional theory calculations predict the surface segregation of Cu in the second atomic layer of Pd which has not been unambiguously confirmed by experiment so far. We report measurements on Pd surfaces covered with three and six monolayers of Cu using element selective positron-annihilation-induced Auger electron spectroscopy (PAES) which is sensitive to the topmost atomic layer. Moreover, time-resolved PAES, which was applied for the first time, enables the investigation of the dynamics of surface atoms and hence the observation of the segregation process. The time constant for segregation was experimentally determined to {tau}=1.38(0.21) h, and the final segregated configurationmore » was found to be consistent with calculations. Time-dependent PAES is demonstrated to be a novel element selective technique applicable for the investigation of, e.g., heterogeneous catalysis, corrosion, or surface alloying.« less

Direct Observation of the Surface Segregation of Cu in Pd by Time-Resolved Positron-Annihilation-Induced Auger Electron Spectroscopy

NASA Astrophysics Data System (ADS)

Mayer, J.; Hugenschmidt, C.; Schreckenbach, K.

2010-11-01

Density functional theory calculations predict the surface segregation of Cu in the second atomic layer of Pd which has not been unambiguously confirmed by experiment so far. We report measurements on Pd surfaces covered with three and six monolayers of Cu using element selective positron-annihilation-induced Auger electron spectroscopy (PAES) which is sensitive to the topmost atomic layer. Moreover, time-resolved PAES, which was applied for the first time, enables the investigation of the dynamics of surface atoms and hence the observation of the segregation process. The time constant for segregation was experimentally determined to τ=1.38(0.21)h, and the final segregated configuration was found to be consistent with calculations. Time-dependent PAES is demonstrated to be a novel element selective technique applicable for the investigation of, e.g., heterogeneous catalysis, corrosion, or surface alloying.

Commercial turbofan engine exhaust nozzle flow analyses using PAB3D

NASA Technical Reports Server (NTRS)

Abdol-Hamid, Khaled S.; Uenishi, K.; Carlson, John R.; Keith, B. D.

1992-01-01

Recent developments of a three-dimensional (PAB3D) code have paved the way for a computational investigation of complex aircraft aerodynamic components. The PAB3D code was developed for solving the simplified Reynolds Averaged Navier-Stokes equations in a three-dimensional multiblock/multizone structured mesh domain. The present analysis was applied to commercial turbofan exhaust flow systems. Solution sensitivity to grid density is presented. Laminar flow solutions were developed for all grids and two-equation k-epsilon solutions were developed for selected grids. Static pressure distributions, mass flow and thrust quantities were calculated for on-design engine operating conditions. Good agreement between predicted surface static pressures and experimental data was observed at different locations. Mass flow was predicted within 0.2 percent of experimental data. Thrust forces were typically within 0.4 percent of experimental data.

Evolution of the proportions of two sigma viral types in experimental populations of Drosophila melanogaster in the absence of the allele that is restrictive of viral multiplication.

PubMed Central

Fleuriet, A

1999-01-01

A minority of flies in natural populations of Drosophila melanogaster are endemically infected by a rhabdovirus, sigma. The virus is vertically transmitted through male and female gametes. Two alleles of a fly locus, the ref(2)P locus, are present as a polymorphism in all populations: O permissive, and P restrictive for viral multiplication and transmission. Two viral types are known, Type I, which is very sensitive to the P allele, and Type II, which is more resistant. Previous observations have shown that, in presence of the P allele, viral Type II is selected for, in both natural and experimental populations. The aim of the present study was to determine whether, in the absence of P, Type I is selected for, or whether the two types are equivalent. For this purpose, experimental populations deprived of the P allele and differing in the initial proportions of the two viral types were established. After several generations, and despite a possible bias toward Type I, the frequencies of Type I and Type II clones differed in the various populations, depending on their initial values. These findings do not rule out selective advantage of viral Type I in the absence of P, but suggest that, if any, this advantage is in no way comparable to that displayed by viral Type II in the presence of P. PMID:10581286

Evolution of the proportions of two sigma viral types in experimental populations of Drosophila melanogaster in the absence of the allele that is restrictive of viral multiplication.

PubMed

Fleuriet, A

1999-12-01

A minority of flies in natural populations of Drosophila melanogaster are endemically infected by a rhabdovirus, sigma. The virus is vertically transmitted through male and female gametes. Two alleles of a fly locus, the ref(2)P locus, are present as a polymorphism in all populations: O permissive, and P restrictive for viral multiplication and transmission. Two viral types are known, Type I, which is very sensitive to the P allele, and Type II, which is more resistant. Previous observations have shown that, in presence of the P allele, viral Type II is selected for, in both natural and experimental populations. The aim of the present study was to determine whether, in the absence of P, Type I is selected for, or whether the two types are equivalent. For this purpose, experimental populations deprived of the P allele and differing in the initial proportions of the two viral types were established. After several generations, and despite a possible bias toward Type I, the frequencies of Type I and Type II clones differed in the various populations, depending on their initial values. These findings do not rule out selective advantage of viral Type I in the absence of P, but suggest that, if any, this advantage is in no way comparable to that displayed by viral Type II in the presence of P.

Contrasting epidemic histories reveal pathogen-mediated balancing selection on class II MHC diversity in a wild songbird.

PubMed

Hawley, Dana M; Fleischer, Robert C

2012-01-01

The extent to which pathogens maintain the extraordinary polymorphism at vertebrate Major Histocompatibility Complex (MHC) genes via balancing selection has intrigued evolutionary biologists for over half a century, but direct tests remain challenging. Here we examine whether a well-characterized epidemic of Mycoplasmal conjunctivitis resulted in balancing selection on class II MHC in a wild songbird host, the house finch (Carpodacus mexicanus). First, we confirmed the potential for pathogen-mediated balancing selection by experimentally demonstrating that house finches with intermediate to high multi-locus MHC diversity are more resistant to challenge with Mycoplasma gallisepticum. Second, we documented sequence and diversity-based signatures of pathogen-mediated balancing selection at class II MHC in exposed host populations that were absent in unexposed, control populations across an equivalent time period. Multi-locus MHC diversity significantly increased in exposed host populations following the epidemic despite initial compromised diversity levels from a recent introduction bottleneck in the exposed host range. We did not observe equivalent changes in allelic diversity or heterozygosity across eight neutral microsatellite loci, suggesting that the observations reflect selection rather than neutral demographic processes. Our results indicate that a virulent pathogen can exert sufficient balancing selection on class II MHC to rescue compromised levels of genetic variation for host resistance in a recently bottlenecked population. These results provide evidence for Haldane's long-standing hypothesis that pathogens directly contribute to the maintenance of the tremendous levels of genetic variation detected in natural populations of vertebrates.

Sound settlement: noise surpasses land cover in explaining breeding habitat selection of secondary cavity-nesting birds.

PubMed

Kleist, Nathan J; Guralnick, Robert P; Cruz, Alexander; Francis, Clinton D

2017-01-01

Birds breeding in heterogeneous landscapes select nest sites by cueing in on a variety of factors from landscape features and social information to the presence of natural enemies. We focus on determining the relative impact of anthropogenic noise on nest site occupancy, compared to amount of forest cover, which is known to strongly influence the selection process. We examine chronic, industrial noise from natural gas wells directly measured at the nest box as well as site-averaged noise, using a well-established field experimental system in northwestern New Mexico. We hypothesized that high levels of noise, both at the nest site and in the environment, would decrease nest box occupancy. We set up nest boxes using a geospatially paired control and experimental site design and analyzed four years of occupancy data from four secondary cavity-nesting birds common to the Colorado Plateau. We found different effects of noise and landscape features depending on species, with strong effects of noise observed in breeding habitat selection of Myiarchus cinerascens, the Ash-throated Flycatcher, and Sialia currucoides, the Mountain Bluebird. In contrast, the amount of forest cover less frequently explained habitat selection for those species or had a smaller standardized effect than the acoustic environment. Although forest cover characterization and management is commonly employed by natural resource managers, our results show that characterizing and managing the acoustic environment should be an important tool in protected area management. © 2016 by the Ecological Society of America.

Dissociating action-effect activation and effect-based response selection.

PubMed

Schwarz, Katharina A; Pfister, Roland; Wirth, Robert; Kunde, Wilfried

2018-05-25

Anticipated action effects have been shown to govern action selection and initiation, as described in ideomotor theory, and they have also been demonstrated to determine crosstalk between different tasks in multitasking studies. Such effect-based crosstalk was observed not only in a forward manner (with a first task influencing performance in a following second task) but also in a backward manner (the second task influencing the preceding first task), suggesting that action effect codes can become activated prior to a capacity-limited processing stage often denoted as response selection. The process of effect-based response production, by contrast, has been proposed to be capacity-limited. These observations jointly suggest that effect code activation can occur independently of effect-based response production, though this theoretical implication has not been tested directly at present. We tested this hypothesis by employing a dual-task set-up in which we manipulated the ease of effect-based response production (via response-effect compatibility) in an experimental design that allows for observing forward and backward crosstalk. We observed robust crosstalk effects and response-effect compatibility effects alike, but no interaction between both effects. These results indicate that effect activation can occur in parallel for several tasks, independently of effect-based response production, which is confined to one task at a time. Copyright © 2018 Elsevier B.V. All rights reserved.

Selection and phenotypic characterization of a core collection of Brachypodium distachyon inbred lines.

PubMed

Tyler, Ludmila; Fangel, Jonatan U; Fagerström, Alexandra Dotson; Steinwand, Michael A; Raab, Theodore K; Willats, William Gt; Vogel, John P

2014-01-14

The model grass Brachypodium distachyon is increasingly used to study various aspects of grass biology. A large and genotypically diverse collection of B. distachyon germplasm has been assembled by the research community. The natural variation in this collection can serve as a powerful experimental tool for many areas of inquiry, including investigating biomass traits. We surveyed the phenotypic diversity in a large collection of inbred lines and then selected a core collection of lines for more detailed analysis with an emphasis on traits relevant to the use of grasses as biofuel and grain crops. Phenotypic characters examined included plant height, growth habit, stem density, flowering time, and seed weight. We also surveyed differences in cell wall composition using near infrared spectroscopy (NIR) and comprehensive microarray polymer profiling (CoMPP). In all cases, we observed extensive natural variation including a two-fold variation in stem density, four-fold variation in ferulic acid bound to hemicellulose, and 1.7-fold variation in seed mass. These characterizations can provide the criteria for selecting diverse lines for future investigations of the genetic basis of the observed phenotypic variation.

Iridium-Catalysed ortho-Directed Deuterium Labelling of Aromatic Esters--An Experimental and Theoretical Study on Directing Group Chemoselectivity.

PubMed

Devlin, Jennifer; Kerr, William J; Lindsay, David M; McCabe, Timothy J D; Reid, Marc; Tuttle, Tell

2015-06-25

Herein we report a combined experimental and theoretical study on the deuterium labelling of benzoate ester derivatives, utilizing our developed iridium N-heterocyclic carbene/phosphine catalysts. A range of benzoate esters were screened, including derivatives with electron-donating and -withdrawing groups in the para- position. The substrate scope, in terms of the alkoxy group, was studied and the nature of the catalyst counter-ion was shown to have a profound effect on the efficiency of isotope exchange. Finally, the observed chemoselectivity was rationalized by rate studies and theoretical calculations, and this insight was applied to the selective labelling of benzoate esters bearing a second directing group.

[Studies on extraction process optimization of Panax notogingseng saponins].

PubMed

Qu, Lin-hai; Zheng, Ming; Lou, Yi-jia

2006-06-01

To optimize the conditions for the extraction of panax notogingseng saponins (PNS). After selected extraction solvent and suitable particle, we employed orthogonal experimental design to examine the conditions for the extraction by determination of PNS. Significant effect was observed only in extraction times. The optimum condition for extraction of PNS was to extract panax notogingseng (Burk.) F. H. Chen with 10 times 70% ethanol for 1.5 hours for 3 times.

Tribology experiment. [journal bearings and liquid lubricants

NASA Technical Reports Server (NTRS)

Wall, W. A.

1981-01-01

A two-dimensional concept for Spacelab rack 7 was developed to study the interaction of liquid lubricants and surfaces under static and dynamic conditions in a low-gravity environment fluid wetting and spreading experiments of a journal bearing experiments, and means to accurately measure and record the low-gravity environment during experimentation are planned. The wetting and spreading process of selected commercial lubricants on representative surface are to the observes in a near-zero gravity environment.

Deposition of Size-Selected Cu Nanoparticles by Inert Gas Condensation

PubMed Central

2010-01-01

Nanometer size-selected Cu clusters in the size range of 1–5 nm have been produced by a plasma-gas-condensation-type cluster deposition apparatus, which combines a grow-discharge sputtering with an inert gas condensation technique. With this method, by controlling the experimental conditions, it was possible to produce nanoparticles with a strict control in size. The structure and size of Cu nanoparticles were determined by mass spectroscopy and confirmed by atomic force microscopy (AFM) and scanning electron transmission microscopy (STEM) measurements. In order to preserve the structural and morphological properties, the energy of cluster impact was controlled; the energy of acceleration of the nanoparticles was in near values at 0.1 ev/atom for being in soft landing regime. From SEM measurements developed in STEM-HAADF mode, we found that nanoparticles are near sized to those values fixed experimentally also confirmed by AFM observations. The results are relevant, since it demonstrates that proper optimization of operation conditions can lead to desired cluster sizes as well as desired cluster size distributions. It was also demonstrated the efficiency of the method to obtain size-selected Cu clusters films, as a random stacking of nanometer-size crystallites assembly. The deposition of size-selected metal clusters represents a novel method of preparing Cu nanostructures, with high potential in optical and catalytic applications. PMID:20652132

Optical implementation of spin squeezing

NASA Astrophysics Data System (ADS)

Ono, Takafumi; Sabines-Chesterking, Javier; Cable, Hugo; O'Brien, Jeremy L.; Matthews, Jonathan C. F.

2017-05-01

Quantum metrology enables estimation of optical phase shifts with precision beyond the shot-noise limit. One way to exceed this limit is to use squeezed states, where the quantum noise of one observable is reduced at the expense of increased quantum noise for its complementary partner. Because shot-noise limits the phase sensitivity of all classical states, reduced noise in the average value for the observable being measured allows for improved phase sensitivity. However, additional phase sensitivity can be achieved using phase estimation strategies that account for the full distribution of measurement outcomes. Here we experimentally investigate a model of optical spin-squeezing, which uses post-selection and photon subtraction from the state generated using a parametric downconversion photon source, and we investigate the phase sensitivity of this model. The Fisher information for all photon-number outcomes shows it is possible to obtain a quantum advantage of 1.58 compared to the shot-noise value for five-photon events, even though due to experimental imperfection, the average noise for the relevant spin-observable does not achieve sub-shot-noise precision. Our demonstration implies improved performance of spin squeezing for applications to quantum metrology.

The Experimental Cloud Lidar Pilot Study (ECLIPS) for cloud-radiation research

NASA Technical Reports Server (NTRS)

Platt, C. M.; Young, S. A.; Carswell, A. I.; Pal, S. R.; Mccormick, M. P.; Winker, D. M.; Delguasta, M.; Stefanutti, L.; Eberhard, W. L.; Hardesty, M.

1994-01-01

The Experimental Cloud Lidar Pilot Study (ECLIPS) was initiated to obtain statistics on cloud-base height, extinction, optical depth, cloud brokenness, and surface fluxes. Two observational phases have taken place, in October-December 1989 and April-July 1991, with intensive 30-day periods being selected within the two time intervals. Data are being archived at NASA Langley Research Center and, once there, are readily available to the international scientific community. This article describes the scale of the study in terms of its international involvement and in the range of data being recorded. Lidar observations of cloud height and backscatter coefficient have been taken from a number of ground-based stations spread around the globe. Solar shortwave and infrared longwave fluxes and infrared beam radiance have been measured at the surface wherever possible. The observations have been tailored to occur around the overpass times of the NOAA weather satellites. This article describes in some detail the various retrieval methods used to obtain results on cloud-base height, extinction coefficient, and infrared emittance, paying particular attention to the uncertainties involved.

DC Stark addressing for quantum memory in Tm:YAG

NASA Astrophysics Data System (ADS)

Gerasimov, Konstantin; Minnegaliev, Mansur; Urmancheev, Ravil; Moiseev, Sergey

2017-10-01

We observed a linear DC Stark effect for 3H6 - 3H4 optical transition of Tm3+ ions in Y3Al5O12. We observed that application of electric field pulse suppresses the two-pulse photon echo signal. If we then apply a second electric pulse of opposite polarity the echo signal is restored again, which indicates the linear nature of the observed effect. The effect is present despite the D2 symmetry of the Tm3+ sites that prohibits a linear Stark effect. Experimental data analysis shows that the observed electric field influence can be attributed to defects that break the local crystal field symmetry near Tm3+ ions. Using this effect we demonstrate selective retrieval of light pulses in two-pulse photon echo.

Design and manufacture of customized dental implants by using reverse engineering and selective laser melting technology.

PubMed

Chen, Jianyu; Zhang, Zhiguang; Chen, Xianshuai; Zhang, Chunyu; Zhang, Gong; Xu, Zhewu

2014-11-01

Recently a new therapeutic concept of patient-specific implant dentistry has been advanced based on computer-aided design/computer-aided manufacturing technology. However, a comprehensive study of the design and 3-dimensional (3D) printing of the customized implants, their mechanical properties, and their biomechanical behavior is lacking. The purpose of this study was to evaluate the mechanical and biomechanical performance of a novel custom-made dental implant fabricated by the selective laser melting technique with simulation and in vitro experimental studies. Two types of customized implants were designed by using reverse engineering: a root-analog implant and a root-analog threaded implant. The titanium implants were printed layer by layer with the selective laser melting technique. The relative density, surface roughness, tensile properties, bend strength, and dimensional accuracy of the specimens were evaluated. Nonlinear and linear finite element analysis and experimental studies were used to investigate the stress distribution, micromotion, and primary stability of the implants. Selective laser melting 3D printing technology was able to reproduce the customized implant designs and produce high density and strength and adequate dimensional accuracy. Better stress distribution and lower maximum micromotions were observed for the root-analog threaded implant model than for the root-analog implant model. In the experimental tests, the implant stability quotient and pull-out strength of the 2 types of implants indicated that better primary stability can be obtained with a root-analog threaded implant design. Selective laser melting proved to be an efficient means of printing fully dense customized implants with high strength and sufficient dimensional accuracy. Adding the threaded characteristic to the customized root-analog threaded implant design maintained the approximate geometry of the natural root and exhibited better stress distribution and primary stability. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

A Comparison of Predictive Thermo and Water Solvation Property Prediction Tools and Experimental Data for Selected Traditional Chemical Warfare Agents and Simulants II: COSMO RS and COSMOTherm

DTIC Science & Technology

2017-04-01

A COMPARISON OF PREDICTIVE THERMO AND WATER SOLVATION PROPERTY PREDICTION TOOLS AND EXPERIMENTAL DATA FOR...4. TITLE AND SUBTITLE A Comparison of Predictive Thermo and Water Solvation Property Prediction Tools and Experimental Data for Selected...1  2.  EXPERIMENTAL PROCEDURE

Experimental Study of Hydroxy Gas (HHO) Production with Variation in Current, Voltage and Electrolyte Concentration

NASA Astrophysics Data System (ADS)

Alam, Noor; Pandey, K. M.

2017-08-01

In this paper, work has been carried out experimentally for the investigation of the effects of variation incurrent, voltage, temperature, chemical concentration and reaction time on the amount of hydroxy gas produced. Further effects on the overall electrolysis efficiency of advance alkaline water is also studied. The hydroxy gas (HHO) has been produced experimentally by the electrolysis of alkaline water with parallel plate electrode of 316L-grade stainless steel. The electrode has been selected on the basis of corrosion resistance and inertness with respect to electrolyte (KOH). The process used for the production of HHO is conventional as compared to the other production processes because of reduced energy consumption, less maintenance and low setup cost. From the experimental results, it has been observed that with increase in voltage, temperature and electrolyte concentration of alkaline solution, the production of hydroxy gas has increased about 30 to 40% with reduction in electrical energy consumption.

Experimental evolution and the dynamics of genomic mutation rate modifiers.

PubMed

Raynes, Y; Sniegowski, P D

2014-11-01

Because genes that affect mutation rates are themselves subject to mutation, mutation rates can be influenced by natural selection and other evolutionary forces. The population genetics of mutation rate modifier alleles has been a subject of theoretical interest for many decades. Here, we review experimental contributions to our understanding of mutation rate modifier dynamics. Numerous evolution experiments have shown that mutator alleles (modifiers that elevate the genomic mutation rate) can readily rise to high frequencies via genetic hitchhiking in non-recombining microbial populations. Whereas these results certainly provide an explanatory framework for observations of sporadically high mutation rates in pathogenic microbes and in cancer lineages, it is nonetheless true that most natural populations have very low mutation rates. This raises the interesting question of how mutator hitchhiking is suppressed or its phenotypic effect reversed in natural populations. Very little experimental work has addressed this question; with this in mind, we identify some promising areas for future experimental investigation.

The effect of preferred music genre selection versus preferred song selection on experimentally induced anxiety levels.

PubMed

Walworth, Darcy DeLoach

2003-01-01

The purpose of this study was to investigate the differences of experimentally induced anxiety levels reached by subjects listening to no music (n = 30), subjects listening to music selected by the experimenter from the subject's preferred genre or artist listed as relaxing (n = 30), and subjects listening to a specific song they listed as relaxing (n = 30). Subjects consisted of 90 individuals, male and female, randomly assigned to one of the three groups mentioned above. Subjects in either music group filled out a questionnaire prior to participating in the study indicating their preference of music used for relaxation purposes. Subjects in Experimental Group 1 marked their preferred genres and/or artists, and Experimental Group 2 marked specific songs used for relaxation purposes. While the experimenter hypothesized subjects in Experimental Group 2 would show less anxiety than both the control group and Experimental Group 1, there were no significant differences found between the 2 music groups in anxiety levels reached. However, there was a statistically significant difference between the no music control group and both music groups in the anxiety level reached by subjects. Subjects listening to music, both songs chosen by the experimenter and subject selected songs, showed significantly less anxiety than subjects not listening to music.

The evolutionary legacy of size-selective harvesting extends from genes to populations

PubMed Central

Uusi-Heikkilä, Silva; Whiteley, Andrew R; Kuparinen, Anna; Matsumura, Shuichi; Venturelli, Paul A; Wolter, Christian; Slate, Jon; Primmer, Craig R; Meinelt, Thomas; Killen, Shaun S; Bierbach, David; Polverino, Giovanni; Ludwig, Arne; Arlinghaus, Robert

2015-01-01

Size-selective harvesting is assumed to alter life histories of exploited fish populations, thereby negatively affecting population productivity, recovery, and yield. However, demonstrating that fisheries-induced phenotypic changes in the wild are at least partly genetically determined has proved notoriously difficult. Moreover, the population-level consequences of fisheries-induced evolution are still being controversially discussed. Using an experimental approach, we found that five generations of size-selective harvesting altered the life histories and behavior, but not the metabolic rate, of wild-origin zebrafish (Danio rerio). Fish adapted to high positively size selective fishing pressure invested more in reproduction, reached a smaller adult body size, and were less explorative and bold. Phenotypic changes seemed subtle but were accompanied by genetic changes in functional loci. Thus, our results provided unambiguous evidence for rapid, harvest-induced phenotypic and evolutionary change when harvesting is intensive and size selective. According to a life-history model, the observed life-history changes elevated population growth rate in harvested conditions, but slowed population recovery under a simulated moratorium. Hence, the evolutionary legacy of size-selective harvesting includes populations that are productive under exploited conditions, but selectively disadvantaged to cope with natural selection pressures that often favor large body size. PMID:26136825

Mechanistic differences between methanol and dimethyl ether carbonylation in side pockets and large channels of mordenite.

PubMed

Boronat, Mercedes; Martínez, Cristina; Corma, Avelino

2011-02-21

The activity and selectivity towards carbonylation presented by Brønsted acid sites located inside the 8MR pockets or in the main 12MR channels of mordenite is studied by means of quantum-chemical calculations, and the mechanistic differences between methanol and DME carbonylation are investigated. The selectivity towards carbonylation is higher inside the 8MR pockets, where the competitive formation of DME and hydrocarbons that finally leads to catalyst deactivation is sterically impeded. Moreover, inclusion of dispersion interactions in the calculations leads to agreement between the calculated activation barriers for the rate determining step and the experimentally observed higher reactivity of methoxy groups located inside the 8MR channels.

Assessment of attenuated Salmonella vaccine strains in controlling experimental Salmonella Typhimurium infection in chickens

PubMed Central

Pei, Yanlong; Parreira, Valeria R.; Roland, Kenneth L.; Curtiss, Roy; Prescott, John F.

2014-01-01

Salmonella hold considerable promise as vaccine delivery vectors for heterologous antigens in chickens. Such vaccines have the potential additional benefit of also controlling Salmonella infection in immunized birds. As a way of selecting attenuated strains with optimal immunogenic potential as antigen delivery vectors, this study screened 20 novel Salmonella Typhimurium vaccine strains, differing in mutations associated with delayed antigen synthesis and delayed attenuation, for their efficacy in controlling colonization by virulent Salmonella Typhimurium, as well as for their persistence in the intestine and the spleen. Marked differences were observed between strains in these characteristics, which provide the basis for selection for further study as vaccine vectors. PMID:24396177

Assessment of attenuated Salmonella vaccine strains in controlling experimental Salmonella Typhimurium infection in chickens.

PubMed

Pei, Yanlong; Parreira, Valeria R; Roland, Kenneth L; Curtiss, Roy; Prescott, John F

2014-01-01

Salmonella hold considerable promise as vaccine delivery vectors for heterologous antigens in chickens. Such vaccines have the potential additional benefit of also controlling Salmonella infection in immunized birds. As a way of selecting attenuated strains with optimal immunogenic potential as antigen delivery vectors, this study screened 20 novel Salmonella Typhimurium vaccine strains, differing in mutations associated with delayed antigen synthesis and delayed attenuation, for their efficacy in controlling colonization by virulent Salmonella Typhimurium, as well as for their persistence in the intestine and the spleen. Marked differences were observed between strains in these characteristics, which provide the basis for selection for further study as vaccine vectors.

Observation of hohlraum-wall motion with spectrally selective x-ray imaging at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Izumi, N.; Meezan, N. B.; Divol, L.; Hall, G. N.; Barrios, M. A.; Jones, O.; Landen, O. L.; Kroll, J. J.; Vonhof, S. A.; Nikroo, A.; Jaquez, J.; Bailey, C. G.; Hardy, C. M.; Ehrlich, R. B.; Town, R. P. J.; Bradley, D. K.; Hinkel, D. E.; Moody, J. D.

2016-11-01

The high fuel capsule compression required for indirect drive inertial confinement fusion requires careful control of the X-ray drive symmetry throughout the laser pulse. When the outer cone beams strike the hohlraum wall, the plasma ablated off the hohlraum wall expands into the hohlraum and can alter both the outer and inner cone beam propagations and hence the X-ray drive symmetry especially at the final stage of the drive pulse. To quantitatively understand the wall motion, we developed a new experimental technique which visualizes the expansion and stagnation of the hohlraum wall plasma. Details of the experiment and the technique of spectrally selective x-ray imaging are discussed.

Observation of hohlraum-wall motion with spectrally selective x-ray imaging at the National Ignition Facility.

PubMed

Izumi, N; Meezan, N B; Divol, L; Hall, G N; Barrios, M A; Jones, O; Landen, O L; Kroll, J J; Vonhof, S A; Nikroo, A; Jaquez, J; Bailey, C G; Hardy, C M; Ehrlich, R B; Town, R P J; Bradley, D K; Hinkel, D E; Moody, J D

2016-11-01

The high fuel capsule compression required for indirect drive inertial confinement fusion requires careful control of the X-ray drive symmetry throughout the laser pulse. When the outer cone beams strike the hohlraum wall, the plasma ablated off the hohlraum wall expands into the hohlraum and can alter both the outer and inner cone beam propagations and hence the X-ray drive symmetry especially at the final stage of the drive pulse. To quantitatively understand the wall motion, we developed a new experimental technique which visualizes the expansion and stagnation of the hohlraum wall plasma. Details of the experiment and the technique of spectrally selective x-ray imaging are discussed.

Modeling the concentration-dependent permeation modes of the KcsA potassium ion channel.

PubMed

Nelson, Peter Hugo

2003-12-01

The potassium channel from Streptomyces lividans (KcsA) is an integral membrane protein with sequence similarity to all known potassium channels, particularly in the selectivity filter region. A recently proposed model for ion channels containing either n or (n-1) single-file ions in their selectivity filters [P. H. Nelson, J. Chem. Phys. 177, 11396 (2002)] is applied to published KcsA channel K+ permeation data that exhibit a high-affinity process at low concentrations and a low-affinity process at high concentrations [M. LeMasurier et al., J. Gen. Physiol. 118, 303 (2001)]. The kinetic model is shown to provide a reasonable first-order explanation for both the high- and low-concentration permeation modes observed experimentally. The low-concentration mode ([K+]<200 mM) has a 200-mV dissociation constant of 56 mM and a conductance of 88 pS. The high-concentration mode ([K+]>200 mM) has a 200-mV dissociation constant of 1100 mM and a conductance of 500 pS. Based on the permeation model, and x-ray analysis [J. H. Morais-Cabral et al., Nature (London) 414, 37 (2001)], it is suggested that the experimentally observed K+ permeation modes correspond to an n=3 mechanism at high concentrations and an n=2 mechanism at low concentrations. The ratio of the electrical dissociation distances for the high- and low-concentration modes is 3:2, also consistent with the proposed n=3 and n=2 modes. Model predictions for K+ channels that exhibit asymmetric current-voltage (I-V) curves are presented, and further validation of the kinetic model via molecular simulation and experiment is discussed. The qualitatively distinct I-V characteristics exhibited experimentally by Tl+, NH+4, and Rb+ ions at 100 mM concentration can also be explained using the model, but more extensive experimental tests are required for quantitative validation of the model predictions.

Modeling the concentration-dependent permeation modes of the KcsA potassium ion channel

NASA Astrophysics Data System (ADS)

Nelson, Peter Hugo

2003-12-01

The potassium channel from Streptomyces lividans (KcsA) is an integral membrane protein with sequence similarity to all known potassium channels, particularly in the selectivity filter region. A recently proposed model for ion channels containing either n or (n-1) single-file ions in their selectivity filters [P. H. Nelson, J. Chem. Phys. 177, 11396 (2002)] is applied to published KcsA channel K+ permeation data that exhibit a high-affinity process at low concentrations and a low-affinity process at high concentrations [M. LeMasurier et al., J. Gen. Physiol. 118, 303 (2001)]. The kinetic model is shown to provide a reasonable first-order explanation for both the high- and low-concentration permeation modes observed experimentally. The low-concentration mode ([K+]<200 mM) has a 200-mV dissociation constant of 56 mM and a conductance of 88 pS. The high-concentration mode ([K+]>200 mM) has a 200-mV dissociation constant of 1100 mM and a conductance of 500 pS. Based on the permeation model, and x-ray analysis [J. H. Morais-Cabral et al., Nature (London) 414, 37 (2001)], it is suggested that the experimentally observed K+ permeation modes correspond to an n=3 mechanism at high concentrations and an n=2 mechanism at low concentrations. The ratio of the electrical dissociation distances for the high- and low-concentration modes is 3:2, also consistent with the proposed n=3 and n=2 modes. Model predictions for K+ channels that exhibit asymmetric current-voltage (I-V) curves are presented, and further validation of the kinetic model via molecular simulation and experiment is discussed. The qualitatively distinct I-V characteristics exhibited experimentally by Tl+, NH+4, and Rb+ ions at 100 mM concentration can also be explained using the model, but more extensive experimental tests are required for quantitative validation of the model predictions.

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

Esposito, A.; Pilloni, A.; Polosa, Antonio D.

Multiquark resonances are undoubtedly experimentally observed. The number of states and the amount of details on their properties have been growing over the years. It is very recent the discovery of two pentaquarks and the confirmation of four tetraquarks, two of which had not been observed before. We mainly review the theoretical understanding of this sector of particle physics phenomenology and present some considerations attempting a coherent description of the so called X and Z resonances. The prominent problems plaguing theoretical models, like the absence of selection rules limiting the number of states predicted, motivate new directions in model building.more » Lastly, data are reviewed going through all of the observed resonances with particular attention to their common features and the purpose of providing a starting point to further research.« less

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

Leszczynski, Jerzy; Sponer, Judit; Sponer, Jiri

Recent experimental studies on the Watson Crick type base pairing of triazine and aminopyrimidine derivatives suggest that acid/base properties of the constituent bases might be related to the duplex stabilities measured in solution. Herein we use high-level quantum chemical calculations and molecular dynamics simulations to evaluate the base pairing and stacking interactions of seven selected base pairs, which are common in that they are stabilized by two NH O hydrogen bonds separated by one NH N hydrogen bond. We show that neither the base pairing nor the base stacking interaction energies correlate with the reported pKa data of the basesmore » and the melting points of the duplexes. This suggests that the experimentally observed correlation between the melting point data of the duplexes and the pKa values of the constituent bases is not rooted in the intrinsic base pairing and stacking properties. The physical chemistry origin of the observed experimental correlation thus remains unexplained and requires further investigations. In addition, since our calculations are carried out with extrapolation to the complete basis set of atomic orbitals and with inclusion of higher electron correlation effects, they provide reference data for stacking and base pairing energies of non-natural bases.« less

Rotationally mediated selective adsorption as a probe of isotropic and anisotropic molecule. Surface interaction potentials: HD(J)/Ag(111)

NASA Astrophysics Data System (ADS)

Uy, C. F.; Hogg, C. S.; Cowin, J. P.; Whaley, K. B.; Light, J. C.; Sibener, S. J.

1982-08-01

Rotationally mediated selective adsorption scattering resonances are used to make an experimental and theoretical study of the laterally averaged interaction potential between HD and a weakly corrugated system, Ag(111). The experimentally observed resonances determine the vibrational levels of the HD/Ag(111) physisorption potential as a function of bound rotational state. These vibrational levels show J-dependent shifts due to the orientational anisotropy of the potential. Exact quantum scattering calculations using a full laterally averaged potential of the form V sub o(z,0) = v sub o (z) (1 + beta P sub 2 (cos theta)) have been carried out to obtain rotationally inelastic transition probabilities. Experimental and theoretical resonance energies are compared for two forms of v sub o(z), a Morse and a variable exponent potential, as a function of Beta, and are found to be very close to the first order perturbed energies of a free rotor in bound states of v sub o(z). Both potential forms give equally good fits to the data, yielding an optimum value of the asymmetry parameter, Beta approx. -0.05. The determination of Beta is relatively insensitive to small changes in the v sub o(z) well depth.

Primary standardization of 57Co.

PubMed

Koskinas, Marina F; Moreira, Denise S; Yamazaki, Ione M; de Toledo, Fábio; Brancaccio, Franco; Dias, Mauro S

2010-01-01

This work describes the method developed by the Nuclear Metrology Laboratory in IPEN, São Paulo, Brazil, for the standardization of a (57)Co radioactive solution. Cobalt-57 is a radionuclide used for calibrating gamma-ray and X-ray spectrometers, as well as a gamma reference source for dose calibrators used in nuclear medicine services. Two 4pibeta-gamma coincidence systems were used to perform the standardization, the first used a 4pi(PC) counter coupled to a pair of 76 mm x 76 mm NaI(Tl) scintillators for detecting gamma-rays, the other one used a HPGe spectrometer for gamma detection. The measurements were performed by selecting a gamma-ray window comprising the (122 keV+136 keV) total absorption energy peaks in the NaI(Tl) and selecting the total absorption peak of 122 keV in the germanium detector. The electronic system used the TAC method developed at LMN for registering the observed events. The methodology recently developed by the LMN for simulating all detection processes in a 4pibeta-gamma coincidence system, by means of the Monte Carlo technique, was applied and the behavior of extrapolation curve compared to experimental data. The final activity obtained by the Monte Carlo calculation agrees with the experimental results within the experimental uncertainty. Copyright 2009 Elsevier Ltd. All rights reserved.

A comparative analysis of experimental selection on the stickleback pelvis.

PubMed

Miller, S E; Barrueto, M; Schluter, D

2017-06-01

Mechanisms of natural selection can be identified using experimental approaches. However, such experiments often yield nonsignificant effects and imprecise estimates of selection due to low power and small sample sizes. Combining results from multiple experimental studies might produce an aggregate estimate of selection that is more revealing than individual studies. For example, bony pelvic armour varies conspicuously among stickleback populations, and predation by vertebrate and insect predators has been hypothesized to be the main driver of this variation. Yet experimental selection studies testing these hypotheses frequently fail to find a significant effect. We experimentally manipulated length of threespine stickleback (Gasterosteus aculeatus) pelvic spines in a mesocosm experiment to test whether prickly sculpin (Cottus asper), an intraguild predator of stickleback, favours longer spines. The probability of survival was greater for stickleback with unclipped pelvic spines, but this effect was noisy and not significant. We used meta-analysis to combine the results of our mesocosm experiment with previously published experimental studies of selection on pelvic armour. We found evidence that fish predation indeed favours increased pelvic armour, with a moderate effect size. The same approach found little evidence that insect predation favours reduced pelvic armour. The causes of reduced pelvic armour in many stickleback populations remain uncertain. © 2017 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2017 European Society For Evolutionary Biology.

The Use of Interrupted Case Studies to Enhance Critical Thinking Skills in Biology

PubMed Central

White, Tracy K.; Whitaker, Paul; Gonya, Terri; Hein, Richard; Kroening, Dubear; Lee, Kevin; Lee, Laura; Lukowiak, Andrea; Hayes, Elizabeth

2009-01-01

There has been a dramatic increase in the availability of case studies for use in the biology classroom, and perceptions of the effectiveness of case-study-based learning are overwhelmingly positive. Here we report the results of a study in which we evaluated the ability of interrupted case studies to improve critical thinking in the context of experimental design and the conventions of data interpretation. Students were assessed using further case studies designed to evaluate their ability to recognize and articulate problematic approaches to these elements of experimentation. Our work reveals that case studies have broad utility in the classroom. In addition to demonstrating a small but statistically significant increase in the number of students capable of critically evaluating selected aspects of experimental design, we also observed increased student engagement and documented widespread misconceptions regarding the conventions of data acquisition and analysis. PMID:23653687

Enhancing Ultimate Compressive Strength of Notch Embedded Steel Cylinders Using Overwrap CFRP Patch

NASA Astrophysics Data System (ADS)

Kabir, Mohammad Z.; Nazari, Alireza

2012-06-01

In this study, the application of Fiber Reinforced Polymer (FRP) patch for strengthening of the damaged area in thin walled steel cylinders under compression loading was investigated. In this direction, some experimental tests were carried out on the selected notch induced specimens with unique diameter-to-thickness ratio (D/t). The obtained results were compared to the intact cylinder in order to find out the reduction effect of notch on the buckling load of cylinders. Following that, the notched specimens were treated using externally FRP by wrapping around the notched area and the stability strength of the retrofitted specimens was measured experimentally. The investigation was also carried out in numerical analysis using FEM in order to develop the proposed technique for determination of optimum FRP configurations and also better understanding of the experimental observations considering the nonlinear behavior and failure modes for composite member.

Comparison of experimental and calculated chiroptical spectra for chiral molecular structure determination.

PubMed

Polavarapu, Prasad L; Covington, Cody L

2014-09-01

For three different chiroptical spectroscopic methods, namely, vibrational circular dichroism (VCD), electronic circular dichroism (ECD), and Raman optical activity (ROA), the measures of similarity of the experimental spectra to the corresponding spectra predicted using quantum chemical theories are summarized. In determining the absolute configuration and/or predominant conformations of chiral molecules, these similarity measures provide numerical estimates of agreement between experimental observations and theoretical predictions. Selected applications illustrating the similarity measures for absorption, circular dichroism, and corresponding dissymmetry factor (DF) spectra, in the case of VCD and ECD, and for Raman, ROA, and circular intensity differential (CID) spectra in the case of ROA, are presented. The analysis of similarity in DF or CID spectra is considered to be much more discerning and accurate than that in absorption (or Raman) and circular dichroism (or ROA) spectra, undertaken individually. © 2014 Wiley Periodicals, Inc.

Influence of Problem Based Learning on Critical Thinking Skills and Competence Class VIII SMPN 1 Gunuang Omeh, 2016/2017

NASA Astrophysics Data System (ADS)

Aswan, D. M.; Lufri, L.; Sumarmin, R.

2018-04-01

This research intends to determine the effect of Problem Based Learning models on students' critical thinking skills and competences. This study was a quasi-experimental research. The population of the study was the students of class VIII SMPN 1 Subdistrict Gunuang Omeh. Random sample selection is done by randomizing the class. Sample class that was chosen VIII3 as an experimental class given that treatment study based on problems and class VIII1 as control class that treatment usually given study. Instrument that used to consist of critical thinking test, cognitive tests, observation sheet of affective and psychomotor. Independent t-test and Mann Whitney U test was used for the analysis. Results showed that there was significant difference (sig <0.05) between control and experimental group. The conclusion of this study was Problem Based Learning models affected the students’ critical thinking skills and competences.

Laboratory Measurements of Optical Properties of Micron Size Individual Dust Grains

NASA Technical Reports Server (NTRS)

Abbas, M. M.; Craven, P. D.; Spann, J. F.; Tankosic, D.; LeClair, A.; Witherow, W. K.; Camata, R.; Gerakines, P.

2003-01-01

A laboratory program is being developed at NASA Marshall Space Flight Center for experimental determination of the optical and physical properties individual dust grains in simulated astrophysical environments. The experimental setup is based on an electrodynamic balance that permits levitation of single 0.1 - 10 micron radii dust grains in a cavity evacuated to pressures of approx. 10(exp -6) torr. The experimental apparatus is equipped with observational ports for measurements in the UV, visible, and infrared spectral regions. A cryogenic facility for cooling the particles to temperature of approx. 10-50K is being installed. The current and the planned measurements include: dust charging processes, photoelectric emissions and yields with UV irradiation, radiation pressure measurements, infrared absorption and scattering properties, and condensation processes, involving the analogs of cosmic dust grains. Selected results based on photoemissions, radiation pressure, and other laboratory measurements will be presented.

Valorization of Oleuropein Via Tunable Acid-Promoted Methanolysis.

PubMed

Afonso, Carlos; Cavaca, Lidia A S; Rodrigues, Catarina A B; Simeonov, Svilen P; Gomes, Rafael F A; Coelho, Jaime A S; Romanelli, Gustavo P; Sathicq, Angel G; Martínez, José J

2018-05-28

The acid-promoted methanolysis of Oleuropein was studied using a variety of homogeneous and heterogeneous acid catalysts. Exclusive cleavage of the acetal bond between the glucoside and the monoterpene subunits or further hydrolysis of the hydroxytyrosol ester and subsequent intramolecular rearrangement were observed upon identification of the most efficient catalyst and experimental conditions. Furthermore, selected conditions were tested using Oleuropein under continuous flow and using a crude mixture extracted from olive leaves under batch. Formation of (-) methyl elenolate was also observed in this study, which is a reported precursor for the synthesis of the antihypertensive drug (-) ajmalicine. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Evidence for host genetic regulation of altered lipid metabolism in experimental toxoplasmosis supported with gene data mining results

PubMed Central

2017-01-01

Toxoplasma gondii is one of the most successful parasites on Earth, infecting a wide array of mammals including one third of the global human population. The obligate intracellular protozoon is not capable of synthesizing cholesterol (Chl), and thus depends on uptake of host Chl for its own development. To explore the genetic regulation of previously observed lipid metabolism alterations during acute murine T. gondii infection, we here assessed total Chl and its fractions in serum and selected tissues at the pathophysiological and molecular level, and integrated the observed gene expression of selected molecules relevant for Chl metabolism, including its biosynthetic and export KEGG pathways, with the results of published transcriptomes obtained in similar murine models of T. gondii infection. The serum lipid status as well as the transcript levels of relevant genes in the brain and the liver were assessed in experimental models of acute and chronic toxoplasmosis in wild-type mice. The results showed that acute infection was associated with a decrease in Chl content in both the liver and periphery (brain, peripheral lymphocytes), and a decrease in Chl reverse transport. In contrast, in chronic infection, a return to normal levels of Chl metabolism has been noted. These changes corresponded to the brain and liver gene expression results as well as to data obtained via mining. We propose that the observed changes in Chl metabolism are part of the host defense response. Further insight into the lipid metabolism in T. gondii infection may provide novel targets for therapeutic agents. PMID:28459857

Mutation Induced Conformational Change In CaMKII Peptide Alters Binding Affinity to CaM Through Alternate Binding Site

NASA Astrophysics Data System (ADS)

Ezerski, Jacob; Cheung, Margaret

CaM forms distinct conformation states through modifications in its charge distribution upon binding to Ca2+ ions. The occurrence of protein structural change resulting from an altered charge distribution is paramount in the scheme of cellular signaling. Not only is charge induced structural change observed in CaM, it is also seen in an essential binding target: calmodulin-depended protein kinase II (CaMKII). In order to investigate the mechanism of selectivity in relation to changes in secondary structure, the CaM binding domain of CaMKII is isolated. Experimentally, charged residues of the CaMKII peptide are systematically mutated to alanine, resulting in altered binding kinetics between the peptide and the Ca2+ saturated state of CaM. We perform an all atom simulation of the wildtype (RRK) and mutated (AAA) CaMKII peptides and generate structures from the trajectory. We analyze RRK and AAA using DSSP and find significant structural differences due to the mutation. Structures from the RRK and AAA ensembles are then selected and docked onto the crystal structure of Ca2+ saturated CaM. We observe that RRK binds to CaM at the C-terminus, whereas the 3-residue mutation, AAA, shows increased patterns of binding to the N-terminus and linker regions of CaM. Due to the conformational change of the peptide ensemble from charged residue mutation, a distinct change in the binding site can be seen, which offers an explanation to experimentally observed changes in kinetic binding rates

Effects of self-adjusting file, Mtwo, and ProTaper on the root canal wall.

PubMed

Hin, Ellemieke S; Wu, Min-Kai; Wesselink, Paul R; Shemesh, Hagay

2013-02-01

The purpose of this ex vivo study was to observe the incidence of cracks in root dentin after root canal preparation with hand files, self-adjusting file (SAF), ProTaper, and Mtwo. One hundred extracted mandibular premolars with single canals were randomly selected. Two angulated radiographs were taken for each tooth, and the width of the canal was measured at 9 mm from the apex. Five groups of 20 teeth each were comparable in canal width. The control group was left unprepared. Four experimental groups were instrumented with hand files, ProTaper, Mtwo, and SAF. Roots were then sectioned horizontally and observed under a microscope. The presence of dentinal cracks and their location were noted. The difference between the experimental groups was analyzed with a χ(2) test. No cracks were observed in the control group. In the experimental groups, ProTaper, Mtwo, and SAF caused cracks in 35%, 25%, and 10% of teeth, respectively. The hand-file group did not show any dentinal cracks (P < .0001). ProTaper and Mtwo caused more cracks than hand files (P < .05), but SAF did not (P > .05). Instrumentation of root canals with SAF, Mtwo, and ProTaper could cause damage to root canal dentin. SAF has a tendency to cause less dentinal cracks as compared with ProTaper or Mtwo. Copyright © 2013 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Experimental and theoretical study of the electronic spectrum of the BAr2 complex: Transition to the excited valence B(2s2p2 2D) state

NASA Astrophysics Data System (ADS)

Krumrine, Jennifer R.; Alexander, Millard H.; Yang, Xin; Dagdigian, Paul J.

2000-03-01

The 2s2p22D←2s22p 2P valence transition in the BAr2 cluster is investigated in a collaborative experimental and theoretical study. Laser fluorescence excitation spectra of a supersonic expansion of B atoms entrained in Ar at high source backing pressures display several features not assignable to the BAr complex. Resonance fluorescence is not observed, but instead emission from the lower 3s state. Size-selected fluorescence depletion spectra show that these features in the excitation spectrum are primarily due to the BAr2 complex. This electronic transition within BAr2 is modeled theoretically, similarly to our earlier study of the 3s←2p transition [M. H. Alexander et al., J. Chem. Phys. 106, 6320 (1997)]. The excited potential energy surfaces of the fivefold degenerate B(2s2p22D) state within the ternary complex are computed in a pairwise-additive model employing diatomic BAr potential energy curves which reproduce our previous experimental observations on the electronic states emanating from the B(2D)+Ar asymptote. The simulated absorption spectrum reproduces reasonably well the observed fluorescence depletion spectrum. The theoretical model lends insight into the energetics of the approach of B to multiple Ar atoms, and how the orientation of B p-orbitals governs the stability of the complex.

Separating selection by diurnal and nocturnal pollinators on floral display and spur length in Gymnadenia conopsea.

PubMed

Sletvold, Nina; Trunschke, Judith; Wimmergren, Carolina; Agren, Jon

2012-08-01

Most plants attract multiple flower visitors that may vary widely in their effectiveness as pollinators. Floral evolution is expected to reflect interactions with the most important pollinators, but few studies have quantified the contribution of different pollinators to current selection on floral traits. To compare selection mediated by diurnal and nocturnal pollinators on floral display and spur length in the rewarding orchid Gymnadenia conopsea, we manipulated the environment by conducting supplemental hand-pollinations and selective pollinator exclusions in two populations in central Norway. In both populations, the exclusion of diurnal pollinators significantly reduced seed production compared to open pollination, whereas the exclusion of nocturnal pollinators did not. There was significant selection on traits expected to influence pollinator attraction and pollination efficiency in both the diurnal and nocturnal pollination treatment. The relative strength of selection among plants exposed to diurnal and nocturnal visitors varied among traits and populations, but the direction of selection was consistent. The results suggest that diurnal pollinators are more important than nocturnal pollinators for seed production in the study populations, but that both categories contribute to selection on floral morphology. The study illustrates how experimental manipulations can link specific categories of pollinators to observed selection on floral traits, and thus improve our understanding of how species interactions shape patterns of selection.

Solid-particle jet formation under shock-wave acceleration.

PubMed

Rodriguez, V; Saurel, R; Jourdan, G; Houas, L

2013-12-01

When solid particles are impulsively dispersed by a shock wave, they develop a spatial distribution which takes the form of particle jets whose selection mechanism is still unidentified. The aim of the present experimental work is to study particle dispersal with fingering effects in an original quasi-two-dimensional experiment facility in order to accurately extract information. Shock and blast waves are generated in the carrier gas at the center of a granular medium ring initially confined inside a Hele-Shaw cell and impulsively accelerated. With the present experimental setup, the particle jet formation is clearly observed. From fast flow visualizations, we notice, in all instances, that the jets are initially generated inside the particle ring and thereafter expelled outward. This point has not been observed in three-dimensional experiments. We highlight that the number of jets is unsteady and decreases with time. For a fixed configuration, considering the very early times following the initial acceleration, the jet size selection is independent of the particle diameter. Moreover, the influence of the initial overpressure and the material density on the particle jet formation have been studied. It is shown that the wave number of particle jets increases with the overpressure and with the decrease of the material density. The normalized number of jets as a function of the initial ring acceleration shows a power law valid for all studied configurations involving various initial pressure ratios, particle sizes, and particle materials.

Pen Devices for Insulin Self-Administration Compared With Needle and Vial: Systematic Review of the Literature and Meta-Analysis.

PubMed

Lasalvia, Pieralessandro; Barahona-Correa, Julián Esteban; Romero-Alvernia, Diana Marcela; Gil-Tamayo, Sebastián; Castañeda-Cardona, Camilo; Bayona, Juan Gabriel; Triana, Juan José; Laserna, Andrés Felipe; Mejía-Torres, Miguel; Restrepo-Jimenez, Paula; Jimenez-Zapata, Juliana; Rosselli, Diego

2016-07-01

Pen devices offer advantages compared with vial and syringe (VaS). The purpose of this article was to evaluate efficacy of pen devices compared to VaS. A systematic review of literature was performed in 8 different databases. References were independently screened and selected. Primary observational or experimental studies comparing pen devices with VaS for insulin administrations were included. Studies on specific populations were excluded. Risk of bias was evaluated using appropriate tools. Data on glycosylated hemoglobin (HbA1c), hypoglycemia, adherence, persistence, patient preference, and quality of life (QOL) were collected. Meta-analysis was performed when appropriate. Heterogeneity and risk of publication bias were evaluated. Otherwise, descriptive analyses of the available data was done. In all, 10 348 articles were screened. A total of 17 studies were finally selected: 7 experimental and 10 analytical. The populations of the included articles were mainly composed of adults with type 2 diabetes mellitus. Important risk of bias was found in all of the articles, particularly experimental studies. Meta-analyses were performed for HbA1c, hypoglycemia, adherence and persistence. Pen device showed better results in mean HbA1c change, patients with hypoglycemia, adherence and persistence compared to VaS. No difference was observed in number of patients achieving <7% HbA1c. Preference studies showed a tendency favoring pen devices, however nonvalidated tools were used. One QoL study showed improvements in some subscales of SF-36. There is evidence that pen devices offer benefits in clinical and, less clearly, patient-reported outcomes compared to VaS for insulin administration. However, these results should be taken with caution. © 2016 Diabetes Technology Society.

The effects of a technology-enhanced inquiry instructional model on students' understanding of science in Thailand

NASA Astrophysics Data System (ADS)

Lertwanasiriwan, Chaiwuti

The study examined the effects of a technology-enhanced inquiry instructional model on students' understanding of science in Thailand. A mixed quantitative research design was selected for the research design. A pretest-posttest control-group design was implemented for the experimental research. A causal-comparative design using questionnaire and classroom observation was employed for the non-experimental research. Two sixth-grade classrooms at a medium-sized public school in Bangkok, Thailand were randomly selected for the study - one as the control group and the other as the experimental group. The 34 students in the control group only received the inquiry instructional model, while the 35 students in the experimental group received the technology-enhanced inquiry instructional model. Both groups of students had been taught by the same science teacher for 15 weeks (three periods per week). The results and findings from the study seemed to indicate that both the technology-enhanced inquiry instructional model and the inquiry instructional model significantly improve students' understanding of science. However, it might be claimed that students receiving the technology-enhanced inquiry instructional model gain more than students only receiving the inquiry instructional model. In addition, the technology-enhanced inquiry instructional model seemed to support the assessment during the 5E Model's evaluation stage. Most students appeared to have very good attitudes toward using it in the science classroom suggesting that the technology-enhanced inquiry instructional model motivates students to learn science.

Car-Parrinello molecular dynamics study of the intramolecular vibrational mode-sensitive double proton-transfer mechanisms in porphycene.

PubMed

Walewski, Łukasz; Waluk, Jacek; Lesyng, Bogdan

2010-02-18

Car-Parrinello molecular dynamics simulations were carried out to help interpret proton-transfer processes observed experimentally in porphycene under thermodynamic equilibrium conditions (NVT ensemble) as well as during selective, nonequilibrium vibrational excitations of the molecular scaffold (NVE ensemble). In the NVT ensemble, the population of the trans form in the gas phase at 300 K is 96.5%, and of the cis-1 form is 3.5%, in agreement with experimental data. Approximately 70% of the proton-transfer events are asynchronous double proton transfers. According to the high resolution simulation data they consist of two single transfer events that rapidly take place one after the other. The average time-period between the two consecutive jumps is 220 fs. The gas phase reaction rate estimate at 300 K is 3.6 ps, which is comparable to experimentally determined rates. The NVE ensemble nonequilibrium ab initio MD simulations, which correspond to selective vibrational excitations of the molecular scaffold generated with high resolution laser spectroscopy techniques, exhibit an enhancing property of the 182 cm(-1) vibrational mode and an inhibiting property of the 114 cm(-1) one. Both of them influence the proton-transfer rate, in qualitative agreement with experimental findings. Our ab initio simulations provide new predictions regarding the influence of double-mode vibrational excitations on proton-transfer processes. They can help in setting up future programmable spectroscopic experiments for the proton-transfer translocations.

Modeling and multi-response optimization of pervaporation of organic aqueous solutions using desirability function approach.

PubMed

Cojocaru, C; Khayet, M; Zakrzewska-Trznadel, G; Jaworska, A

2009-08-15

The factorial design of experiments and desirability function approach has been applied for multi-response optimization in pervaporation separation process. Two organic aqueous solutions were considered as model mixtures, water/acetonitrile and water/ethanol mixtures. Two responses have been employed in multi-response optimization of pervaporation, total permeate flux and organic selectivity. The effects of three experimental factors (feed temperature, initial concentration of organic compound in feed solution, and downstream pressure) on the pervaporation responses have been investigated. The experiments were performed according to a 2(3) full factorial experimental design. The factorial models have been obtained from experimental design and validated statistically by analysis of variance (ANOVA). The spatial representations of the response functions were drawn together with the corresponding contour line plots. Factorial models have been used to develop the overall desirability function. In addition, the overlap contour plots were presented to identify the desirability zone and to determine the optimum point. The optimal operating conditions were found to be, in the case of water/acetonitrile mixture, a feed temperature of 55 degrees C, an initial concentration of 6.58% and a downstream pressure of 13.99 kPa, while for water/ethanol mixture a feed temperature of 55 degrees C, an initial concentration of 4.53% and a downstream pressure of 9.57 kPa. Under such optimum conditions it was observed experimentally an improvement of both the total permeate flux and selectivity.

Does Angling Technique Selectively Target Fishes Based on Their Behavioural Type?

PubMed Central

Wilson, Alexander D. M.; Brownscombe, Jacob W.; Sullivan, Brittany; Jain-Schlaepfer, Sofia; Cooke, Steven J.

2015-01-01

Recently, there has been growing recognition that fish harvesting practices can have important impacts on the phenotypic distributions and diversity of natural populations through a phenomenon known as fisheries-induced evolution. Here we experimentally show that two common recreational angling techniques (active crank baits versus passive soft plastics) differentially target wild largemouth bass (Micropterus salmoides) and rock bass (Ambloplites rupestris) based on variation in their behavioural tendencies. Fish were first angled in the wild using both techniques and then brought back to the laboratory and tested for individual-level differences in common estimates of personality (refuge emergence, flight-initiation-distance, latency-to-recapture and with a net, and general activity) in an in-lake experimental arena. We found that different angling techniques appear to selectively target these species based on their boldness (as characterized by refuge emergence, a standard measure of boldness in fishes) but not other assays of personality. We also observed that body size was independently a significant predictor of personality in both species, though this varied between traits and species. Our results suggest a context-dependency for vulnerability to capture relative to behaviour in these fish species. Ascertaining the selective pressures angling practices exert on natural populations is an important area of fisheries research with significant implications for ecology, evolution, and resource management. PMID:26284779

Instance-based learning: integrating sampling and repeated decisions from experience.

PubMed

Gonzalez, Cleotilde; Dutt, Varun

2011-10-01

In decisions from experience, there are 2 experimental paradigms: sampling and repeated-choice. In the sampling paradigm, participants sample between 2 options as many times as they want (i.e., the stopping point is variable), observe the outcome with no real consequences each time, and finally select 1 of the 2 options that cause them to earn or lose money. In the repeated-choice paradigm, participants select 1 of the 2 options for a fixed number of times and receive immediate outcome feedback that affects their earnings. These 2 experimental paradigms have been studied independently, and different cognitive processes have often been assumed to take place in each, as represented in widely diverse computational models. We demonstrate that behavior in these 2 paradigms relies upon common cognitive processes proposed by the instance-based learning theory (IBLT; Gonzalez, Lerch, & Lebiere, 2003) and that the stopping point is the only difference between the 2 paradigms. A single cognitive model based on IBLT (with an added stopping point rule in the sampling paradigm) captures human choices and predicts the sequence of choice selections across both paradigms. We integrate the paradigms through quantitative model comparison, where IBLT outperforms the best models created for each paradigm separately. We discuss the implications for the psychology of decision making. © 2011 American Psychological Association

Use of in vivo Expression Technology for the Identification of Putative Host Adaptation Factors of the Lyme Disease Spirochete.

PubMed

Casselli, Timothy; Bankhead, Troy

2015-01-01

The causative agent of Lyme disease, Borrelia burgdorferi, is an obligate parasite that requires either a tick vector or a mammalian host for survival. Identification of the bacterial genes that are specifically expressed during infection of the mammalian host could provide targets for novel therapeutics and vaccines. In vivo expression technology (IVET) is a reporter-based promoter trap system that utilizes selectable markers to identify promoters of bacterial host-specific genes. Using previously characterized genes for in vivo and in vitro selection, this study utilized an IVET system that allows for selection of B. burgdorferi sequences that act as active promoters only during murine infection. This promoter trap system was able to successfully distinguish active promoter sequences both in vivo and in vitro from control sequences and a library of cloned B. burgdorferi genomic fragments. However, a bottleneck effect during the experimental mouse infection limited the utility for genome-wide promoter screening. Overall, IVET was demonstrated as a tool for the identification of in vivo-induced promoter elements of B. burgdorferi, and the observed infection bottleneck apparent using a polyclonal infection pool provides insight into the dynamics of experimental infection with B. burgdorferi. © 2015 S. Karger AG, Basel.

Experimentally evolved and phenotypically plastic responses to enforced monogamy in a hermaphroditic flatworm.

PubMed

Janicke, T; Sandner, P; Ramm, S A; Vizoso, D B; Schärer, L

2016-09-01

Sexual selection is considered a potent evolutionary force in all sexually reproducing organisms, but direct tests in terms of experimental evolution of sexual traits are still lacking for simultaneously hermaphroditic animals. Here, we tested how evolution under enforced monogamy affected a suite of reproductive traits (including testis area, sex allocation, genital morphology, sperm morphology and mating behaviour) in the outcrossing hermaphroditic flatworm Macrostomum lignano, using an assay that also allowed the assessment of phenotypically plastic responses to group size. The experiment comprised 32 independent selection lines that evolved under either monogamy or polygamy for 20 generations. While we did not observe an evolutionary shift in sex allocation, we detected effects of the selection regime for two male morphological traits. Specifically, worms evolving under enforced monogamy had a distinct shape of the male copulatory organ and produced sperm with shorter appendages. Many traits that did not evolve under enforced monogamy showed phenotypic plasticity in response to group size. Notably, individuals that grew up in larger groups had a more male-biased sex allocation and produced slightly longer sperm than individuals raised in pairs. We conclude that, in this flatworm, enforced monogamy induced moderate evolutionary but substantial phenotypically plastic responses. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

Sexual selection is influenced by both developmental and adult environments.

PubMed

Gillespie, Stephanie R; Scarlett Tudor, M; Moore, Allen J; Miller, Christine W

2014-12-01

Sexual selection is often assumed to be strong and consistent, yet increasing research shows it can fluctuate over space and time. Few experimental studies have examined changes in sexual selection in response to natural environmental variation. Here, we use a difference in resource quality to test for the influence of past environmental conditions and current environmental conditions on male and female mate choice and resulting selection gradients for leaf-footed cactus bugs, Narnia femorata. We raised juveniles on natural high- and low-quality diets, cactus pads with and without ripe cactus fruits. New adults were again assigned a cactus pad with or without fruit, paired with a potential mate, and observed for mating behaviors. We found developmental and adult encounter environments affected mating decisions and the resulting patterns of sexual selection for both males and females. Males were not choosy in the low-quality encounter environment, cactus without fruit, but they avoided mating with small females in the high-quality encounter environment. Females were choosy in both encounter environments, avoiding mating with small males. However, they were the choosiest when they were in the low-quality encounter environment. Female mate choice was also context dependent by male developmental environment. Females were more likely to mate with males that had developed on cactus with fruit when they were currently in the cactus with fruit environment. This pattern disappeared when females were in the cactus without fruit environment. Altogether, these results experimentally demonstrate context-dependent mate choice by both males and females. Furthermore, we demonstrate that simple, seasonal changes in resources can lead to fluctuations in sexual selection. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

Ab initio molecular dynamic study of solid-state transitions of ammonium nitrate

PubMed Central

Yu, Hongyu; Duan, Defang; Liu, Hanyu; Yang, Ting; Tian, Fubo; Bao, Kuo; Li, Da; Zhao, Zhonglong; Liu, Bingbing; Cui, Tian

2016-01-01

High-pressure polymorphism and phase transitions have wide ranging consequences on the basic properties of ammonium nitrate. However, the phase diagram of ammonium nitrate at high pressure and high temperature is still under debate. This study systematically investigates the phase transitions and structural properties of ammonium nitrate at a pressure range of 5–60 GPa and temperature range of 250–400 K by ab initio molecular dynamics simulations. Two new phases are identified: one corresponds to the experimentally observed phase IV’ and the other is named AN-X. Simultaneously, the lattice strains play a significant role in the formation and stabilization of phase IV’, providing a reasonable explanation for experimental observation of phase IV-IV’ transition which only appears under nonhydrostatic pressure. In addition, 12 O atoms neighboring the NH (N atom in ammonium cation) atom are selected as reference system to clearly display the tanglesome rotation of ammonium cation. PMID:26754622

Characterization of azimuthal and longitudinal modes in rolled-up InGaAs/GaAs microtubes at telecom wavelengths.

PubMed

Zhong, Qiuhang; Tian, Zhaobing; Dastjerdi, M Hadi Tavakoli; Mi, Zetian; Plant, David V

2013-08-12

We report on theoretical and experimental investigation of azimuthal and longitudinal modes in rolled-up microtubes at telecom wavelengths. These microtubes are fabricated by selectively releasing a coherently strained InGaAs/GaAs bilayer. We apply planar waveguide method and a quasi-potential model to analyze the azimuthal and longitudinal modes in the microtubes near 1550 nm. Then we demonstrate these modes in transmission spectrum by evanescent light coupling. The experimental observations agree well with the calculated results. Surface-scattering-induced mode splitting is also observed in both transmission and reflection spectra at ~1600 nm. The mode splitting is in essence the non-degeneracy of clockwise and counter-clockwise whispering-gallery modes of the microtubes. This study is significant for understanding the physics of modes in microtubes and other microcavities with three-dimensional optical confinement, as well as for potential applications such as microtube-based photonic integrated devices and sensing purposes.

Sustained State-Independent Quantum Contextual Correlations from a Single Ion

NASA Astrophysics Data System (ADS)

Leupold, F. M.; Malinowski, M.; Zhang, C.; Negnevitsky, V.; Alonso, J.; Home, J. P.; Cabello, A.

2018-05-01

We use a single trapped-ion qutrit to demonstrate the quantum-state-independent violation of noncontextuality inequalities using a sequence of randomly chosen quantum nondemolition projective measurements. We concatenate 53 ×106 sequential measurements of 13 observables, and unambiguously violate an optimal noncontextual bound. We use the same data set to characterize imperfections including signaling and repeatability of the measurements. The experimental sequence was generated in real time with a quantum random number generator integrated into our control system to select the subsequent observable with a latency below 50 μ s , which can be used to constrain contextual hidden-variable models that might describe our results. The state-recycling experimental procedure is resilient to noise and independent of the qutrit state, substantiating the fact that the contextual nature of quantum physics is connected to measurements and not necessarily to designated states. The use of extended sequences of quantum nondemolition measurements finds applications in the fields of sensing and quantum information.

Anomalous behavior in temporal evolution of ripple wavelength under medium energy Ar{sup +}-ion bombardment on Si: A case of initial wavelength selection

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

Garg, Sandeep Kumar; Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110 067; Cuerno, Rodolfo

We have studied the early stage dynamics of ripple patterns on Si surfaces, in the fluence range of 1–3 × 10{sup 18} ions cm{sup −2}, as induced by medium energy Ar{sup +}-ion irradiation at room temperature. Under our experimental conditions, the ripple evolution is found to be in the linear regime, while a clear decreasing trend in the ripple wavelength is observed up to a certain time (fluence). Numerical simulations of a continuum model of ion-sputtered surfaces suggest that this anomalous behavior is due to the relaxation of the surface features of the experimental pristine surface during the initial stage of patternmore » formation. The observation of this hitherto unobserved behavior of the ripple wavelength seems to have been enabled by the use of medium energy ions, where the ripple wavelengths are found to be order(s) of magnitude larger than those at lower ion energies.« less

Selecting Models for Measuring Change When True Experimental Conditions Do Not Exist.

ERIC Educational Resources Information Center

Fortune, Jim C.; Hutson, Barbara A.

1984-01-01

Measuring change when true experimental conditions do not exist is a difficult process. This article reviews the artifacts of change measurement in evaluations and quasi-experimental designs, delineates considerations in choosing a model to measure change under nonideal conditions, and suggests ways to organize models to facilitate selection.…

[Novel artificial lamina for prevention of epidural adhesions after posterior cervical laminectomy].

PubMed

Lü, Chaoliang; Song, Yueming; Liu, Hao; Liu, Limin; Gong, Quan; Li, Tao; Zeng, Jiancheng; Kong, Qingquan; Pei, Fuxing; Tu, Chongqi; Duan, Hong

2013-07-01

To evaluate the application of artificial lamina of multi-amino-acid copolymer (MAACP)/nano-hydroxyapatite (n-HA) in prevention of epidural adhesion and compression of scar tissue after posterior cervical laminectomy. Fifteen 2-year-old male goats [weighing, (30 +/- 2) kg] were randomly divided into experimental group (n=9) and control group (n=6). In the experimental group, C4 laminectomy was performed, followed by MAACP/n-HA artificial lamina implantations; in the control group, only C4 laminectomy was performed. At 4, 12, and 24 weeks after operation, 2, 2, and 5 goats in the experimental group and 2, 2, and 2 goats in the control group were selected for observation of wound infection, artificial laminar fragmentation and displacement, and its shape; Rydell's degree of adhesion criteria was used to evaluate the adhesion degree between 2 groups. X-ray and CT images were observed; at 24 weeks after operation, CT scan was used to measure the spinal canal area and the sagittal diameter of C3, C4, and C5 vertebrea, 2 normal goats served as normal group; and MRI was used to assess adhesion and compression of scar tissue on the dura and the nerve root. Then goats were sacrificed and histological observation was carried out. After operation, the wound healed well; no toxicity or elimination reaction was observed. According to Rydell's degree of adhesion criteria, adhesion in the experimental group was significantly slighter than that in the control group (Z= -2.52, P=0.00). X-ray and CT scan showed that no dislocation of artificial lamina occurred, new cervical bone formed in the defect, and bony spinal canal was rebuilt in the experimental group. Defects of C4 vertebral plate and spinous process were observed in the control group. At 24 weeks, the spinal canal area and sagittal diameter of C4 in the experimental group and normal group were significantly larger than those in the control group (P < 0.05), but no significant difference was found between experimental group and normal group (P > 0.05). MRI showed cerebrospinal fluid signal was unobstructed and no soft tissue projected into the spinal canal in the experimental group; scar tissue projected into the spinal canal and the dura were compressed by scar tissue in the control group. HE staining and Masson trichrome staining showed that artificial lamina had no obvious degradation with high integrity, some new bone formed at interface between the artificial material and bone in the experimental group; fibrous tissue grew into defect in the control group. The MAACP/n-HA artificial lamina could maintaine good biomechanical properties for a long time in vivo and could effectively prevent the epidural scar from growing in the lamina defect area.

Experimental study on the statistic characteristics of a 3x3 RF MIMO channel over a single conventional multimode fiber.

PubMed

Lei, Yi; Li, Jianqiang; Wu, Rui; Fan, Yuting; Fu, Songnian; Yin, Feifei; Dai, Yitang; Xu, Kun

2017-06-01

Based on the observed random fluctuation phenomenon of speckle pattern across multimode fiber (MMF) facet and received optical power distribution across three output ports, we experimentally investigate the statistic characteristics of a 3×3 radio frequency multiple-input multiple-output (MIMO) channel enabled by mode division multiplexing in a conventional 50 µm MMF using non-mode-selective three-dimensional waveguide photonic lanterns as mode multiplexer and demultiplexer. The impacts of mode coupling on the MIMO channel coefficients, channel matrix, and channel capacity have been analyzed over different fiber lengths. The results indicate that spatial multiplexing benefits from the greater fiber length with stronger mode coupling, despite a higher optical loss.

Thermo-mechanical modeling of the gas-tungsten-arc (GTA) welding process

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

Duncan, D.B.

1980-01-18

A fundamental study of gas-tungsten-arc (GTA) welding was undertaken. This was initiated with a review of the GTA welding process which lead to the decision to focus experimental and analytical efforts on stationary welds on a pure material. Pure nickel was selected for the test material. Temperature, strain, and distortion measurements were made during the formation of spot welds on circular plates. Transient thermal data were obtained with thermocouples, a radiation pyrometer, and from motion pictures. Local strain was observed qualitatively from Moire interference fringe patterns. Distortion during welding was measured with displacement gages and residual distortion with a profilometer.more » Experimental measurements are compared with predictions of thermal and mechanical finite element codes.« less

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

Aagesen, Larry K.; Coltrin, Michael Elliott; Han, Jung

Three-dimensional phase-field simulations of GaN growth by selective area epitaxy were performed. Furthermore, this model includes a crystallographic-orientation-dependent deposition rate and arbitrarily complex mask geometries. The orientation-dependent deposition rate can be determined from experimental measurements of the relative growth rates of low-index crystallographic facets. Growth on various complex mask geometries was simulated on both c-plane and a-plane template layers. Agreement was observed between simulations and experiment, including complex phenomena occurring at the intersections between facets. The sources of the discrepancies between simulated and experimental morphologies were also investigated. We found that the model provides a route to optimize masks andmore » processing conditions during materials synthesis for solar cells, light-emitting diodes, and other electronic and opto-electronic applications.« less

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

Aagesen, Larry K.; Thornton, Katsuyo, E-mail: kthorn@umich.edu; Coltrin, Michael E.

Three-dimensional phase-field simulations of GaN growth by selective area epitaxy were performed. The model includes a crystallographic-orientation-dependent deposition rate and arbitrarily complex mask geometries. The orientation-dependent deposition rate can be determined from experimental measurements of the relative growth rates of low-index crystallographic facets. Growth on various complex mask geometries was simulated on both c-plane and a-plane template layers. Agreement was observed between simulations and experiment, including complex phenomena occurring at the intersections between facets. The sources of the discrepancies between simulated and experimental morphologies were also investigated. The model provides a route to optimize masks and processing conditions during materialsmore » synthesis for solar cells, light-emitting diodes, and other electronic and opto-electronic applications.« less

Dynamo Enhancement and Mode Selection Triggered by High Magnetic Permeability.

PubMed

Kreuzahler, S; Ponty, Y; Plihon, N; Homann, H; Grauer, R

2017-12-08

We present results from consistent dynamo simulations, where the electrically conducting and incompressible flow inside a cylinder vessel is forced by moving impellers numerically implemented by a penalization method. The numerical scheme models jumps of magnetic permeability for the solid impellers, resembling various configurations tested experimentally in the von Kármán sodium experiment. The most striking experimental observations are reproduced in our set of simulations. In particular, we report on the existence of a time-averaged axisymmetric dynamo mode, self-consistently generated when the magnetic permeability of the impellers exceeds a threshold. We describe a possible scenario involving both the turbulent flow in the vicinity of the impellers and the high magnetic permeability of the impellers.

Crystal engineering of ibuprofen compounds: From molecule to crystal structure to morphology prediction by computational simulation and experimental study

NASA Astrophysics Data System (ADS)

Zhang, Min; Liang, Zuozhong; Wu, Fei; Chen, Jian-Feng; Xue, Chunyu; Zhao, Hong

2017-06-01

We selected the crystal structures of ibuprofen with seven common space groups (Cc, P21/c, P212121, P21, Pbca, Pna21, and Pbcn), which was generated from ibuprofen molecule by molecular simulation. The predicted crystal structures of ibuprofen with space group P21/c has the lowest total energy and the largest density, which is nearly indistinguishable with experimental result. In addition, the XRD patterns for predicted crystal structure are highly consistent with recrystallization from solvent of ibuprofen. That indicates that the simulation can accurately predict the crystal structure of ibuprofen from the molecule. Furthermore, based on this crystal structure, we predicted the crystal habit in vacuum using the attachment energy (AE) method and considered solvent effects in a systematic way using the modified attachment energy (MAE) model. The simulation can accurately construct a complete process from molecule to crystal structure to morphology prediction. Experimentally, we observed crystal morphologies in four different polarity solvents compounds (ethanol, acetonitrile, ethyl acetate, and toluene). We found that the aspect ratio decreases of crystal habits in this ibuprofen system were found to vary with increasing solvent relative polarity. Besides, the modified crystal morphologies are in good agreement with the observed experimental morphologies. Finally, this work may guide computer-aided design of the desirable crystal morphology.

Immunological characteristics and response to lipopolysaccharide of mouse lines selectively bred with natural and acquired immunities.

PubMed

Narahara, Hiroki; Sakai, Eri; Katayama, Masafumi; Ohtomo, Yukiko; Yamamoto, Kanako; Takemoto, Miki; Aso, Hisashi; Ohwada, Shyuichi; Mohri, Yasuaki; Nishimori, Katsuhiko; Isogai, Emiko; Yamaguchi, Takahiro; Fukuda, Tomokazu

2012-05-01

Genetic improvement of resistance to infectious diseases is a challenging goal in animal breeding. Infection resistance involves multiple immunological characteristics, including natural and acquired immunity. In the present study, we developed an experimental model based on genetic selection, to improve immunological phenotypes. We selectively established three mouse lines based on phagocytic activity, antibody production and the combination of these two phenotypes. We analyzed the immunological characteristics of these lines using a lipopolysaccharide (LPS), which is one of the main components of Gram-negative bacteria. An intense immunological reaction was induced in each of the three mouse lines. Severe loss of body weight and liver damage were observed, and a high level of cytokine messenger RNA was detected in the liver tissue. The mouse line established using a combination of the two selection standards showed unique characteristics relative to the mouse lines selected on the basis of a single phenotype. Our results indicate that genetic selection and breeding is effective, even for immunological phenotypes with a relatively low heritability. Thus, it may be possible to improve resistance to infectious diseases by means of genetic selection. © 2011 The Authors. Animal Science Journal © 2011 Japanese Society of Animal Science.

Adaptive divergence in a scleractinian coral: physiological adaptation of Seriatopora hystrix to shallow and deep reef habitats

PubMed Central

2011-01-01

Background Divergent natural selection across environmental gradients has been acknowledged as a major driver of population and species divergence, however its role in the diversification of scleractinian corals remains poorly understood. Recently, it was demonstrated that the brooding coral Seriatopora hystrix and its algal endosymbionts (Symbiodinium) are genetically partitioned across reef environments (0-30 m) on the far northern Great Barrier Reef. Here, we explore the potential mechanisms underlying this differentiation and assess the stability of host-symbiont associations through a reciprocal transplantation experiment across habitats ('Back Reef', 'Upper Slope' and 'Deep Slope'), in combination with molecular (mtDNA and ITS2-DGGE) and photo-physiological analyses (respirometry and HPLC). Results The highest survival rates were observed for native transplants (measured 14 months after transplantation), indicating differential selective pressures between habitats. Host-symbiont assemblages remained stable during the experimental duration, demonstrating that the ability to "shuffle" or "switch" symbionts is restricted in S. hystrix. Photo-physiological differences were observed between transplants originating from the shallow and deep habitats, with indirect evidence of an increased heterotrophic capacity in native deep-water transplants (from the 'Deep Slope' habitat). Similar photo-acclimatisation potential was observed between transplants originating from the two shallow habitats ('Back Reef' and 'Upper Slope'), highlighting that their genetic segregation over depth may be due to other, non-photo-physiological traits under selection. Conclusions This study confirms that the observed habitat partitioning of S. hystrix (and associated Symbiodinium) is reflective of adaptive divergence along a depth gradient. Gene flow appears to be reduced due to divergent selection, highlighting the potential role of ecological mechanisms, in addition to physical dispersal barriers, in the diversification of scleractinian corals and their associated Symbiodinium. PMID:22004364

Structural hierarchy as a key to complex phase selection in Al-Sm

NASA Astrophysics Data System (ADS)

Ye, Z.; Zhang, F.; Sun, Y.; Nguyen, M. C.; Zhou, S. H.; Zhou, L.; Meng, F.; Ott, R. T.; Park, E.; Besser, M. F.; Kramer, M. J.; Ding, Z. J.; Mendelev, M. I.; Wang, C. Z.; Napolitano, R. E.; Ho, K. M.

2017-10-01

Investigating the unknown structure of the complex cubic phase, previously observed to crystallize from melt-spun amorphous Al-10 at.% Sm alloy, we determine the structure in full site-occupancy detail, highlighting several critical structural features that govern the far-from-equilibrium phase selection pathway. Using an efficient genetic algorithm combining molecular dynamics, density functional theory, and x-ray diffraction, the structure is clearly identified as body-centered cubic I m 3 ¯m (No. 229) with ˜140 atoms per cubic unit cell and a lattice parameter of 1.4 nm. The complex structure is further refined to elucidate the detailed site occupancy, revealing full Sm occupancy on 6b sites and split Sm/Al occupancy on 16f sites. Based on the refined site occupancy associated with the experimentally observed phase, we term this phase ɛ -A l60S m11 (bcc), corresponding to the limiting situation when all 16f sites are occupied by Sm. However, it should be recognized that the range of solubility enabled by split occupancy at Sm sites is an important feature in phase selection under experimental conditions, permitting an avenue for transition with little or no chemical partitioning. Our analysis shows that the ɛ -A l60S m11 (bcc) exhibits a "3-6-6-1" first-shell packing around Sm centers on 16f sites, the same dominant motif exhibited by the undercooled liquid. The coincident motif supports the notion that liquid/glass ordering at high undercooling may give rise to topological invariants between the noncrystalline and crystalline states that provide kinetic pathways to metastable phases that are not accessible during near-equilibrium processing.

Structural hierarchy as a key to complex phase selection in Al-Sm

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

Ye, Z.; Zhang, F.; Sun, Y.

Investigating the unknown structure of the complex cubic phase, previously observed to crystallize from melt-spun amorphous Al–10 at.% Sm alloy, we determine the structure in full site-occupancy detail, highlighting several critical structural features that govern the far-from-equilibrium phase selection pathway. Using an efficient genetic algorithm combining molecular dynamics, density functional theory, and x-ray diffraction, the structure is clearly identified as body-centered cubic Im¯3m (No. 229) with ~140 atoms per cubic unit cell and a lattice parameter of 1.4 nm. The complex structure is further refined to elucidate the detailed site occupancy, revealing full Sm occupancy on 6b sites and splitmore » Sm/Al occupancy on 16f sites. Based on the refined site occupancy associated with the experimentally observed phase, we term this phase ε–Al 60Sm 11(bcc), corresponding to the limiting situation when all 16f sites are occupied by Sm. However, it should be recognized that the range of solubility enabled by split occupancy at Sm sites is an important feature in phase selection under experimental conditions, permitting an avenue for transition with little or no chemical partitioning. Our analysis shows that the ε–Al 60Sm 11(bcc) exhibits a “3-6-6-1” first-shell packing around Sm centers on 16f sites, the same dominant motif exhibited by the undercooled liquid. Here, the coincident motif supports the notion that liquid/glass ordering at high undercooling may give rise to topological invariants between the noncrystalline and crystalline states that provide kinetic pathways to metastable phases that are not accessible during near-equilibrium processing.« less

Structural hierarchy as a key to complex phase selection in Al-Sm

DOE PAGES

Ye, Z.; Zhang, F.; Sun, Y.; ...

2017-10-12

Investigating the unknown structure of the complex cubic phase, previously observed to crystallize from melt-spun amorphous Al–10 at.% Sm alloy, we determine the structure in full site-occupancy detail, highlighting several critical structural features that govern the far-from-equilibrium phase selection pathway. Using an efficient genetic algorithm combining molecular dynamics, density functional theory, and x-ray diffraction, the structure is clearly identified as body-centered cubic Im¯3m (No. 229) with ~140 atoms per cubic unit cell and a lattice parameter of 1.4 nm. The complex structure is further refined to elucidate the detailed site occupancy, revealing full Sm occupancy on 6b sites and splitmore » Sm/Al occupancy on 16f sites. Based on the refined site occupancy associated with the experimentally observed phase, we term this phase ε–Al 60Sm 11(bcc), corresponding to the limiting situation when all 16f sites are occupied by Sm. However, it should be recognized that the range of solubility enabled by split occupancy at Sm sites is an important feature in phase selection under experimental conditions, permitting an avenue for transition with little or no chemical partitioning. Our analysis shows that the ε–Al 60Sm 11(bcc) exhibits a “3-6-6-1” first-shell packing around Sm centers on 16f sites, the same dominant motif exhibited by the undercooled liquid. Here, the coincident motif supports the notion that liquid/glass ordering at high undercooling may give rise to topological invariants between the noncrystalline and crystalline states that provide kinetic pathways to metastable phases that are not accessible during near-equilibrium processing.« less

Predicting the Cosmological Constant from the CausalEntropic Principle

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

Bousso, Raphael; Harnik, Roni; Kribs, Graham D.

2007-02-20

We compute the expected value of the cosmological constant in our universe from the Causal Entropic Principle. Since observers must obey the laws of thermodynamics and causality, it asserts that physical parameters are most likely to be found in the range of values for which the total entropy production within a causally connected region is maximized. Despite the absence of more explicit anthropic criteria, the resulting probability distribution turns out to be in excellent agreement with observation. In particular, we find that dust heated by stars dominates the entropy production, demonstrating the remarkable power of this thermodynamic selection criterion. Themore » alternative approach--weighting by the number of ''observers per baryon''--is less well-defined, requires problematic assumptions about the nature of observers, and yet prefers values larger than present experimental bounds.« less

Low Friction Droplet Transportation on a Substrate with a Selective Leidenfrost Effect.

PubMed

Dodd, Linzi E; Wood, David; Geraldi, Nicasio R; Wells, Gary G; McHale, Glen; Xu, Ben B; Stuart-Cole, Simone; Martin, James; Newton, Michael I

2016-08-31

An energy saving Leidenfrost levitation method is introduced to transport microdroplets with virtually frictionless contact between the liquid and solid substrate. Through microengineering of the heating units, selective areas of the whole substrate can be electrothermally activated. A droplet can be levitated as a result of the Leidenfrost effect and further transported when the substrate is tilted slightly. Selective electroheating produces a uniform temperature distribution on the heating units within 1 s in response to a triggering voltage. Alongside these experimental observations, finite element simulations were conducted to understand the role of substrate thermal conductivity on the temperature profile of the selectively heated substrate. We also generated phase diagrams to verify the Leidenfrost regime for different substrate materials. Finally, we demonstrated the possibility of controlling low friction high speed droplet transportation (∼65 mm/s) when the substrate is tilted (∼7°) by structurally designing the substrate. This work establishes the basis for an entirely new approach to droplet microfluidics.

Stress and selective attention: Immediate and delayed stress effects on inhibition of return.

PubMed

Larra, Mauro F; Pramme, Lisa; Schächinger, Hartmut; Frings, Christian

2016-10-01

The relationship between attention and stress is far from understood. In fact, some studies reported better attentional selection during and after stress, some studies reported worse attentional selection, and some studies reported no effects of stress on attentional selection at all. We argue that given the complexity of both concepts more data are needed as to ultimately understand this relationship. Here we use an established attentional task that yields the inhibition of return (IOR) effect which is assumed to tap attentional control of oculomotor behavior. Participants were stressed with a Cold Pressor Test (CPT) and immediate and delayed effects of stress on hypothalamus-pituitary-adrenal (HPA) axis activation and IOR were analyzed. IOR was neither by immediate nor by delayed after-effects of the CPT stress procedure modulated, instead, we observed reliable and significant IOR in all experimental conditions. Attentional control of oculomotor behavior is therefore not altered after CPT stress, nor related to the post-stress activity of the HPA axis. Copyright © 2016 Elsevier Inc. All rights reserved.

An In Vitro Translation, Selection, and Amplification System for Peptide Nucleic Acids

PubMed Central

Brudno, Yevgeny; Birnbaum, Michael E.; Kleiner, Ralph E.; Liu, David R.

2009-01-01

Methods to evolve synthetic, rather than biological, polymers could significantly expand the functional potential of polymers that emerge from in vitro evolution. Requirements for synthetic polymer evolution include: (i) sequence-specific polymerization of synthetic building blocks on an amplifiable template; (ii) display of the newly translated polymer strand in a manner that allows it to adopt folded structures; (iii) selection of synthetic polymer libraries for desired binding or catalytic properties; and (iv) amplification of template sequences surviving selection in a manner that allows subsequent translation. Here we report the development of such a system for peptide nucleic acids (PNAs) using a set of twelve PNA pentamer building blocks. We validated the system by performing six iterated cycles of translation, selection, and amplification on a library of 4.3 × 108 PNA-encoding DNA templates and observed >1,000,000-fold overall enrichment of a template encoding a biotinylated (streptavidin-binding) PNA. These results collectively provide an experimental foundation for PNA evolution in the laboratory. PMID:20081830

Natural Selection in Large Populations

NASA Astrophysics Data System (ADS)

Desai, Michael

2011-03-01

I will discuss theoretical and experimental approaches to the evolutionary dynamics and population genetics of natural selection in large populations. In these populations, many mutations are often present simultaneously, and because recombination is limited, selection cannot act on them all independently. Rather, it can only affect whole combinations of mutations linked together on the same chromosome. Methods common in theoretical population genetics have been of limited utility in analyzing this coupling between the fates of different mutations. In the past few years it has become increasingly clear that this is a crucial gap in our understanding, as sequence data has begun to show that selection appears to act pervasively on many linked sites in a wide range of populations, including viruses, microbes, Drosophila, and humans. I will describe approaches that combine analytical tools drawn from statistical physics and dynamical systems with traditional methods in theoretical population genetics to address this problem, and describe how experiments in budding yeast can help us directly observe these evolutionary dynamics.

Comparison of probiotic lactobacilli and bifidobacteria effects, immune responses and rotavirus vaccines and infection in different host species

PubMed Central

Vlasova, Anastasia N.; Kandasamy, Sukumar; Chattha, Kuldeep S.; Rajashekara, Gireesh; Saif, Linda J.

2016-01-01

Different probiotic strains of Lactobacillus and Bifidobacterium genera possess significant and widely acknowledged health-promoting and immunomodulatory properties. They also provide an affordable means for prevention and treatment of various infectious, allergic and inflammatory conditions as demonstrated in numerous human and animal studies. Despite the ample evidence of protective effects of these probiotics against rotavirus (RV) infection and disease, the precise immune mechanisms of this protection remain largely undefined, because of limited mechanistic research possible in humans and investigated in the majority of animal models. Additionally, while most human clinical probiotic trials are well-standardized using the same strains, uniform dosages, regimens of the probiotic treatments and similar host age, animal studies often lack standardization, have variable experimental designs, and non-uniform and sometime limited selection of experimental variables or observational parameters. This review presents selected data on different probiotic strains of lactobacilli and bifidobacteria and summarizes the knowledge of their immunomodulatory properties and the associated protection against RV disease in diverse host species including neonates. PMID:26809484

Use of statistical design of experiments for surface modification of Kapton films by CF4sbnd O2 microwave plasma treatment

NASA Astrophysics Data System (ADS)

Grandoni, Andrea; Mannini, Giacomo; Glisenti, Antonella; Manariti, Antonella; Galli, Giancarlo

2017-10-01

A statistical design of experiments (DoE) was used to evaluate the effects of CF4sbnd O2 plasma on Kapton films in which the duration of treatment, volume ratio of plasma gases, and microwave power were selected as effective experimental factors for systematic investigation of surface modification. Static water contact angle (θW), polar component of surface free energy (γSp) and surface O/C atomic ratio were analyzed as response variables. A significant enhancement in wettability and polarity of the treated films compared to untreated Kapton films was observed; depending on the experimental conditions, θW very significantly decreased, showing full wettability, and γSp rose dramatically, up to ten times. Within the DoE the conditions of plasma treatment were identified that resulted in selected optimal values of θW, γSp and O/C responses. Surface chemical changes were detected by XPS and ATR-IR investigations that evidenced both the introduction of fluorinated groups and the opening of the imide ring in the plasma-treated films.

Fitness effects of advantageous mutations in evolving Escherichia coli populations

PubMed Central

Imhof, Marianne; Schlötterer, Christian

2001-01-01

The central role of beneficial mutations for adaptive processes in natural populations is well established. Thus, there has been a long-standing interest to study the nature of beneficial mutations. Their low frequency, however, has made this class of mutations almost inaccessible for systematic studies. In the absence of experimental data, the distribution of the fitness effects of beneficial mutations was assumed to resemble that of deleterious mutations. For an experimental proof of this assumption, we used a novel marker system to trace adaptive events in an evolving Escherichia coli culture and to determine the selective advantage of those beneficial mutations. Ten parallel cultures were propagated for about 1,000 generations by serial transfer, and 66 adaptive events were identified. From this data set, we estimate the rate of beneficial mutations to be 4 × 10−9 per cell and generation. Consistent with an exponential distribution of the fitness effects, we observed a large fraction of advantageous mutations with a small effect and only few with large effect. The mean selection coefficient of advantageous mutations in our experiment was 0.02. PMID:11158603

Functional genomic hypothesis generation and experimentation by a robot scientist.

PubMed

King, Ross D; Whelan, Kenneth E; Jones, Ffion M; Reiser, Philip G K; Bryant, Christopher H; Muggleton, Stephen H; Kell, Douglas B; Oliver, Stephen G

2004-01-15

The question of whether it is possible to automate the scientific process is of both great theoretical interest and increasing practical importance because, in many scientific areas, data are being generated much faster than they can be effectively analysed. We describe a physically implemented robotic system that applies techniques from artificial intelligence to carry out cycles of scientific experimentation. The system automatically originates hypotheses to explain observations, devises experiments to test these hypotheses, physically runs the experiments using a laboratory robot, interprets the results to falsify hypotheses inconsistent with the data, and then repeats the cycle. Here we apply the system to the determination of gene function using deletion mutants of yeast (Saccharomyces cerevisiae) and auxotrophic growth experiments. We built and tested a detailed logical model (involving genes, proteins and metabolites) of the aromatic amino acid synthesis pathway. In biological experiments that automatically reconstruct parts of this model, we show that an intelligent experiment selection strategy is competitive with human performance and significantly outperforms, with a cost decrease of 3-fold and 100-fold (respectively), both cheapest and random-experiment selection.

Functional connectivity experiments reflect routine movement behavior of a tropical hummingbird species.

PubMed

Volpe, Noelia L; Hadley, Adam S; Robinson, W Douglas; Betts, Matthew G

Translocation experiments, in which researchers displace animals and then monitor their movements to return home, are commonly used as tools to assess functional connectivity of fragmented landscapes. Such experiments are purported to have important advantages of being time efficient and of standardizing “motivation” to move across individuals. Yet, we lack tests of whether movement behavior of translocated birds reflects natural behavior of unmanipulated birds. We compared the routine movement behavior of a tropical hummingbird, the Green Hermit (Phaethornis guy), to that of experimentally translocated individuals. We tested for differences in site selection patterns during movement at two spatial scales (point and path levels). We also compared movement rates between treatments. Behaviors documented during translocation experiments reflected those observed during routine movements. At the point level, both translocated and non-translocated birds showed similar levels of preference for mature tropical forest. At the path level, step selection functions showed both translocated and non-translocated hummingbirds avoiding movement across non-forested matrix and selecting streams as movement corridors. Movement rates were generally higher during translocation experiments. However, the negative influence of forest cover on movement rates was proportionately similar in translocation and routine movement treatments. We report the first evidence showing that movement behavior of birds during translocation experiments is similar to their natural movement behavior. Therefore, translocation experiments may be reliable tools to address effects of landscape structure on animal movement. We observed consistent selection of landscape elements between translocated and non-translocated birds, indicating that both routine and translocation movement studies lead to similar conclusions regarding the effect of landscape structure and forest composition on functional connectivity. Our observation that hummingbirds avoid non-forest matrix and select riparian corridors also provides a potential mechanism for pollen limitation in fragmented tropical forest.

Pollinator-mediated selection on flower color, flower scent and flower morphology of Hemerocallis: evidence from genotyping individual pollen grains on the stigma.

PubMed

Hirota, Shun K; Nitta, Kozue; Suyama, Yoshihisa; Kawakubo, Nobumitsu; Yasumoto, Akiko A; Yahara, Tetsukazu

2013-01-01

To trace the fate of individual pollen grains through pollination processes, we determined genotypes of single pollen grains deposited on Hemerocallis stigmas in an experimental mixed-species array. Hemerocallis fulva, pollinated by butterflies, has diurnal, reddish and unscented flowers, and H. citrina, pollinated by hawkmoths, has nocturnal, yellowish and sweet scent flowers. We observed pollinator visits to an experimental array of 24 H. fulva and 12 F2 hybrids between the two species (H. fulva and H. citrina) and collected stigmas after every trip bout of swallowtail butterflies or hawkmoths. We then measured selection by swallowtail butterflies or hawkmoths through male and female components of pollination success as determined by single pollen genotyping. As expected, swallowtail butterflies imposed selection on reddish color and weak scent: the number of outcross pollen grains acquired is a quadratic function of flower color with the maximum at reddish color, and the combined pollination success was maximal at weak scent (almost unrecognizable for human). This explains why H. fulva, with reddish flowers and no recognizable scent, is mainly pollinated by swallowtail butterflies. However, we found no evidence of hawkmoths-mediated selection on flower color or scent. Our findings do not support a hypothesis that yellow flower color and strong scent intensity, the distinctive floral characteristics of H. citrina, having evolved in adaptations to hawkmoths. We suggest that the key trait that triggers the evolution of nocturnal flowers is flowering time rather than flower color and scent.

An Approximate Markov Model for the Wright-Fisher Diffusion and Its Application to Time Series Data.

PubMed

Ferrer-Admetlla, Anna; Leuenberger, Christoph; Jensen, Jeffrey D; Wegmann, Daniel

2016-06-01

The joint and accurate inference of selection and demography from genetic data is considered a particularly challenging question in population genetics, since both process may lead to very similar patterns of genetic diversity. However, additional information for disentangling these effects may be obtained by observing changes in allele frequencies over multiple time points. Such data are common in experimental evolution studies, as well as in the comparison of ancient and contemporary samples. Leveraging this information, however, has been computationally challenging, particularly when considering multilocus data sets. To overcome these issues, we introduce a novel, discrete approximation for diffusion processes, termed mean transition time approximation, which preserves the long-term behavior of the underlying continuous diffusion process. We then derive this approximation for the particular case of inferring selection and demography from time series data under the classic Wright-Fisher model and demonstrate that our approximation is well suited to describe allele trajectories through time, even when only a few states are used. We then develop a Bayesian inference approach to jointly infer the population size and locus-specific selection coefficients with high accuracy and further extend this model to also infer the rates of sequencing errors and mutations. We finally apply our approach to recent experimental data on the evolution of drug resistance in influenza virus, identifying likely targets of selection and finding evidence for much larger viral population sizes than previously reported. Copyright © 2016 by the Genetics Society of America.

Surface stability and the selection rules of substrate orientation for optimal growth of epitaxial II-VI semiconductors

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

Yin, Wan-Jian; Department of Physics & Astronomy, and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Toledo, Ohio 43606; Yang, Ji-Hui

2015-10-05

The surface structures of ionic zinc-blende CdTe (001), (110), (111), and (211) surfaces are systematically studied by first-principles density functional calculations. Based on the surface structures and surface energies, we identify the detrimental twinning appearing in molecular beam epitaxy (MBE) growth of II-VI compounds as the (111) lamellar twin boundaries. To avoid the appearance of twinning in MBE growth, we propose the following selection rules for choosing optimal substrate orientations: (1) the surface should be nonpolar so that there is no large surface reconstructions that could act as a nucleation center and promote the formation of twins; (2) the surfacemore » structure should have low symmetry so that there are no multiple equivalent directions for growth. These straightforward rules, in consistent with experimental observations, provide guidelines for selecting proper substrates for high-quality MBE growth of II-VI compounds.« less

Selecting the Right Varieties in Riau Main Island: Sweet Corn Context

NASA Astrophysics Data System (ADS)

Surtinah; Nurwati, Niken

2018-05-01

The Riau Main island long way known has a unique geographic location and minerals contains in its soils. To help in selecting the best varieties that can help to sustain the food security plan in Riau main island is the aims of this study. Corn is a one of the local food that support the coastal and highland community in Riau and Sumatera Islands. Therefore corn was selected to be the object of this study. This experiment was conducted experimentally using a complete randomized environmental design and the treatment design with eight varieties of sweet corns. Data analysis uses Sidik variety and Duncan 5 % distance tes. The parameter observed is sweet corn which deals with the weight of cobs with cornhusk, the weight of cobs without cornhusk, the length of cobs without cornhusk and the sugar content of the seeds. The result shows that the best varieties are Sweet boy, sweet lady and bonanza.

Vibronic coupling and selectivity of vibrational excitation in the negative ion resonances of ozone

NASA Astrophysics Data System (ADS)

Allan, Michael; Popovic̀, Duška B.

1997-04-01

A recent experimental paper reported two shape resonances in electron impact on ozone, A 1 and B 2, both causing vibrational excitation with a distinct pattern of selectivity. The present Letter attempts to rationalize this selectivity using approximate potential curves, calculated for the A 1 and B 2 resonances by adding the SCF energy of neutral ozone to electron attachment energies calculated from ab initio virtual orbital energies using the Koopmans' theorem and an empirical scaling relation. The slopes of the curves explain the efficient excitation of the symmetric stretch by both resonances and the lack of the bending excitation by the B 2 resonance. The A 1 and B 2 resonances are strongly coupled by the b 2 antisymmetric stretch vibration, causing a double minimum on the lower surface. Nonadiabatic effects caused by the strong vibronic coupling explain the observed excitation of the antisymmetric stretch vibration.

The origin of the bird's beak: new insights from dinosaur incubation periods.

PubMed

Yang, Tzu-Ruei; Sander, P Martin

2018-05-01

The toothless beak of modern birds was considered as an adaption for feeding ecology; however, several recent studies suggested that developmental factors are also responsible for the toothless beak. Neontological and palaeontological studies have progressively uncovered how birds evolved toothless beaks and suggested that the multiple occurrences of complete edentulism in non-avian dinosaurs were the result of selection for specialized diets. Although developmental biology and ecological factors are not mutually exclusive, the conventional hypothesis that ecological factors account for the toothless beak appears insufficient. A recent study on dinosaur incubation period using embryonic teeth posited that tooth formation rate limits developmental speed, constraining toothed dinosaur incubation to slow reptilian rates. We suggest that selection for tooth loss was a side effect of selection for fast embryo growth and thus shorter incubation. This observation would also explain the multiple occurrences of tooth loss and beaks in non-avian dinosaur taxa crownward of Tyrannosaurus Whereas our hypothesis is an observation without any experimental supports, more studies of gene regulation of tooth formation in embryos would allow testing for the trade-off between incubation period and tooth development. © 2018 The Author(s).

The MORPHEUS II protein crystallization screen

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

Gorrec, Fabrice, E-mail: fgorrec@mrc-lmb.cam.ac.uk

2015-06-27

MORPHEUS II is a 96-condition initial crystallization screen formulated de novo. The screen incorporates reagents selected from the Protein Data Bank to yield crystals that are not observed in traditional conditions. In addition, the formulation facilitates the optimization and cryoprotection of crystals. High-quality macromolecular crystals are a prerequisite for the process of protein structure determination by X-ray diffraction. Unfortunately, the relative yield of diffraction-quality crystals from crystallization experiments is often very low. In this context, innovative crystallization screen formulations are continuously being developed. In the past, MORPHEUS, a screen in which each condition integrates a mix of additives selected frommore » the Protein Data Bank, a cryoprotectant and a buffer system, was developed. Here, MORPHEUS II, a follow-up to the original 96-condition initial screen, is described. Reagents were selected to yield crystals when none might be observed in traditional initial screens. Besides, the screen includes heavy atoms for experimental phasing and small polyols to ensure the cryoprotection of crystals. The suitability of the resulting novel conditions is shown by the crystallization of a broad variety of protein samples and their efficiency is compared with commercially available conditions.« less

Restricted interests and teacher presentation of items.

PubMed

Stocco, Corey S; Thompson, Rachel H; Rodriguez, Nicole M

2011-01-01

Restricted and repetitive behavior (RRB) is more pervasive, prevalent, frequent, and severe in individuals with autism spectrum disorders (ASDs) than in their typical peers. One subtype of RRB is restricted interests in items or activities, which is evident in the manner in which individuals engage with items (e.g., repetitious wheel spinning), the types of items or activities they select (e.g., preoccupation with a phone book), or the range of items or activities they select (i.e., narrow range of items). We sought to describe the relation between restricted interests and teacher presentation of items. Overall, we observed 5 teachers interacting with 2 pairs of students diagnosed with an ASD. Each pair included 1 student with restricted interests. During these observations, teachers were free to present any items from an array of 4 stimuli selected by experimenters. We recorded student responses to teacher presentation of items and analyzed the data to determine the relation between teacher presentation of items and the consequences for presentation provided by the students. Teacher presentation of items corresponded with differential responses provided by students with ASD, and those with restricted preferences experienced a narrower array of items.

Characterization of Mitogen-Activated Protein Kinase Expression in Nucleus Accumbens and Hippocampus of Rats Subjected to Food Selection in the Cafeteria Diet Protocol.

PubMed

Sarro-Ramírez, Andrea; Sánchez, Daniel; Tejeda-Padrón, Alma; Buenfil-Canto, Linda Vianey; Valladares-García, Jorge; Pacheco-Pantoja, Elda; Arias-Carrión, Oscar; Murillo-Rodríguez, Eric

2016-01-01

Obesity is a world-wide health problem that requires different experimental perspectives to understand the onset of this disease, including the neurobiological basis of food selection. From a molecular perspective, obesity has been related with activity of several endogenous molecules, including the mitogenactivated protein kinases (MAP-K). The aim of this study was to characterize MAP-K expression in hedonic and learning and memory brain-associated areas such as nucleus accumbens (AcbC) and hippocampus (HIPP) after food selection. We show that animals fed with cafeteria diet during 14 days displayed an increase in p38 MAP-K activity in AcbC if chose cheese. Conversely, a diminution was observed in animals that preferred chocolate in AcbC. Also, a decrease of p38 MAP-K phosphorylation was found in HIPP in rats that selected either cheese or chocolate. Our data demonstrate a putative role of MAP-K expression in food selection. These findings advance our understanding of neuromolecular basis engaged in obesity.

Effects of configuration interaction on photoabsorption spectra in the continuum

NASA Astrophysics Data System (ADS)

Komninos, Yannis; Nicolaides, Cleanthes A.

2004-10-01

It is pointed out that the proper interpretation of a recently published experimental spectrum from the multilaser photoionization of Sr [Eichmann , Phys. Rev. Lett. 90, 233004 (2003)] must account for a radiative transition between two autoionizing states. The application of orthonormality selection rules and of configuration-interaction theory involving the continuous spectrum and the quasicontinuum of the upper part of Rydberg series explains quantitatively the appearance, the shape, and the variation of heights of the observed peaks of resonances.

Bifurcations on Potential Energy Surfaces of Organic Reactions

PubMed Central

Ess, Daniel H.; Wheeler, Steven E.; Iafe, Robert G.; Xu, Lai; Çelebi-Ölçüm, Nihan; Houk, K. N.

2009-01-01

A single transition state may lead to multiple intermediates or products if there is a post-transition state reaction path bifurcation. These bifurcations arise when there are sequential transition states with no intervening energy minimum. For such systems, the shape of the potential energy surface and dynamic effects control selectivity rather than transition state energetics. This minireview covers recent investigations of organic reactions exhibiting reaction pathway bifurcations. Such phenomena are surprisingly general and affect experimental observables such as kinetic isotope effects and product distributions. PMID:18767086

Computation of the intensities of parametric holographic scattering patterns in photorefractive crystals.

PubMed

Schwalenberg, Simon

2005-06-01

The present work represents a first attempt to perform computations of output intensity distributions for different parametric holographic scattering patterns. Based on the model for parametric four-wave mixing processes in photorefractive crystals and taking into account realistic material properties, we present computed images of selected scattering patterns. We compare these calculated light distributions to the corresponding experimental observations. Our analysis is especially devoted to dark scattering patterns as they make high demands on the underlying model.

First experimental assessment of RCS plume-flow field interaction on Hermes leading edge thruster configuration

NASA Astrophysics Data System (ADS)

Poertner, T.

1993-11-01

Glow discharge flow visualization experiments are demonstrated which have been performed to enable a first assessment of the HERMES 1.0 leading edge thruster configuration concerning interference between the thruster plumes of the reaction control system (RCS) and the surrounding flow field. The results of the flow visualization tests are presented in exemplary selected photographs. Additional Pitot pressure measurements support assumptions concerning interference induced pressure changes that may result from the observed significant flow field disturbances.

Rapid bursts and slow declines: on the possible evolutionary trajectories of enzymes.

PubMed

Newton, Matilda S; Arcus, Vickery L; Patrick, Wayne M

2015-06-06

The evolution of enzymes is often viewed as following a smooth and steady trajectory, from barely functional primordial catalysts to the highly active and specific enzymes that we observe today. In this review, we summarize experimental data that suggest a different reality. Modern examples, such as the emergence of enzymes that hydrolyse human-made pesticides, demonstrate that evolution can be extraordinarily rapid. Experiments to infer and resurrect ancient sequences suggest that some of the first organisms present on the Earth are likely to have possessed highly active enzymes. Reconciling these observations, we argue that rapid bursts of strong selection for increased catalytic efficiency are interspersed with much longer periods in which the catalytic power of an enzyme erodes, through neutral drift and selection for other properties such as cellular energy efficiency or regulation. Thus, many enzymes may have already passed their catalytic peaks. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Learning place cells, grid cells and invariances with excitatory and inhibitory plasticity

PubMed Central

2018-01-01

Neurons in the hippocampus and adjacent brain areas show a large diversity in their tuning to location and head direction, and the underlying circuit mechanisms are not yet resolved. In particular, it is unclear why certain cell types are selective to one spatial variable, but invariant to another. For example, place cells are typically invariant to head direction. We propose that all observed spatial tuning patterns – in both their selectivity and their invariance – arise from the same mechanism: Excitatory and inhibitory synaptic plasticity driven by the spatial tuning statistics of synaptic inputs. Using simulations and a mathematical analysis, we show that combined excitatory and inhibitory plasticity can lead to localized, grid-like or invariant activity. Combinations of different input statistics along different spatial dimensions reproduce all major spatial tuning patterns observed in rodents. Our proposed model is robust to changes in parameters, develops patterns on behavioral timescales and makes distinctive experimental predictions. PMID:29465399

Minimal model for a hydrodynamic fingering instability in microroller suspensions

NASA Astrophysics Data System (ADS)

Delmotte, Blaise; Donev, Aleksandar; Driscoll, Michelle; Chaikin, Paul

2017-11-01

We derive a minimal continuum model to investigate the hydrodynamic mechanism behind the fingering instability recently discovered in a suspension of microrollers near a floor [M. Driscoll et al., Nat. Phys. 13, 375 (2017), 10.1038/nphys3970]. Our model, consisting of two continuous lines of rotlets, exhibits a linear instability driven only by hydrodynamic interactions and reproduces the length-scale selection observed in large-scale particle simulations and in experiments. By adjusting only one parameter, the distance between the two lines, our dispersion relation exhibits quantitative agreement with the simulations and qualitative agreement with experimental measurements. Our linear stability analysis indicates that this instability is caused by the combination of the advective and transverse flows generated by the microrollers near a no-slip surface. Our simple model offers an interesting formalism to characterize other hydrodynamic instabilities that have not been well understood, such as size scale selection in suspensions of particles sedimenting adjacent to a wall, or the recently observed formations of traveling phonons in systems of confined driven particles.

Basic concepts and development of an all-purpose computer interface for ROC/FROC observer study.

PubMed

Shiraishi, Junji; Fukuoka, Daisuke; Hara, Takeshi; Abe, Hiroyuki

2013-01-01

In this study, we initially investigated various aspects of requirements for a computer interface employed in receiver operating characteristic (ROC) and free-response ROC (FROC) observer studies which involve digital images and ratings obtained by observers (radiologists). Secondly, by taking into account these aspects, an all-purpose computer interface utilized for these observer performance studies was developed. Basically, the observer studies can be classified into three paradigms, such as one rating for one case without an identification of a signal location, one rating for one case with an identification of a signal location, and multiple ratings for one case with identification of signal locations. For these paradigms, display modes on the computer interface can be used for single/multiple views of a static image, continuous viewing with cascade images (i.e., CT, MRI), and dynamic viewing of movies (i.e., DSA, ultrasound). Various functions on these display modes, which include windowing (contrast/level), magnifications, and annotations, are needed to be selected by an experimenter corresponding to the purpose of the research. In addition, the rules of judgment for distinguishing between true positives and false positives are an important factor for estimating diagnostic accuracy in an observer study. We developed a computer interface which runs on a Windows operating system by taking into account all aspects required for various observer studies. This computer interface requires experimenters to have sufficient knowledge about ROC/FROC observer studies, but allows its use for any purpose of the observer studies. This computer interface will be distributed publicly in the near future.

Utilization of Magnetorheological Finishing as a Diagnostic Tool for Investigating the Three-Dimensional Structure of Fractures in Fused Silica

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

Menapace, J A; Davis, P J; Steele, W A

2005-11-11

We have developed an experimental technique that combines magnetorheological finishing (MRF) and microscopy to examine fractures and/or artifacts in optical materials. The technique can be readily used to provide access to, and interrogation of, a selected segment of a fracture or object that extends beneath the surface. Depth slicing, or cross-sectioning at selected intervals, further allows the observation and measurement of the three-dimensional nature of the sites and the generation of volumetric representations that can be used to quantify shape and depth, and to understand how they were created, how they interact with surrounding material, and how they may bemore » eliminated or mitigated.« less

Observation of hohlraum-wall motion with spectrally selective x-ray imaging at the National Ignition Facility

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

Izumi, N., E-mail: izumi2@llnl.gov; Meezan, N. B.; Divol, L.

The high fuel capsule compression required for indirect drive inertial confinement fusion requires careful control of the X-ray drive symmetry throughout the laser pulse. When the outer cone beams strike the hohlraum wall, the plasma ablated off the hohlraum wall expands into the hohlraum and can alter both the outer and inner cone beam propagations and hence the X-ray drive symmetry especially at the final stage of the drive pulse. To quantitatively understand the wall motion, we developed a new experimental technique which visualizes the expansion and stagnation of the hohlraum wall plasma. Details of the experiment and the techniquemore » of spectrally selective x-ray imaging are discussed.« less

The role of spatial selective attention in working memory for locations: evidence from event-related potentials.

PubMed

Awh, E; Anllo-Vento, L; Hillyard, S A

2000-09-01

We investigated the hypothesis that the covert focusing of spatial attention mediates the on-line maintenance of location information in spatial working memory. During the delay period of a spatial working-memory task, behaviorally irrelevant probe stimuli were flashed at both memorized and nonmemorized locations. Multichannel recordings of event-related potentials (ERPs) were used to assess visual processing of the probes at the different locations. Consistent with the hypothesis of attention-based rehearsal, early ERP components were enlarged in response to probes that appeared at memorized locations. These visual modulations were similar in latency and topography to those observed after explicit manipulations of spatial selective attention in a parallel experimental condition that employed an identical stimulus display.

Structure Optimization of Porous Dental Implant Based on 3D Printing

NASA Astrophysics Data System (ADS)

Ji, Fangqiu; Zhang, Chunyu; Chen, Xianshuai

2018-03-01

In this paper, selective laser melting (SLM) technology is used to process complex structures. In combination with the theory of biomedicine, a porous implant with a porous structure is designed to induce bone cell growth. The mechanical strength advantage of SLM was discussed by observing the metallographic structure of SLM specimen with mechanical microscope and mechanical tensile test. The osseointegration of porous implants was observed and analyzed by biological experiments. By establishing a mechanical model, the mechanical properties of the bone implant combined with the jaw bone were studied by the simple mechanical analysis under static multi loading and the finite element mechanical analysis. According to the experimental observation and mechanical research, the optimization suggestions for the structure design of the implant made by SLM technology were put forward.

Observation of acoustic valley vortex states and valley-chirality locked beam splitting

NASA Astrophysics Data System (ADS)

Ye, Liping; Qiu, Chunyin; Lu, Jiuyang; Wen, Xinhua; Shen, Yuanyuan; Ke, Manzhu; Zhang, Fan; Liu, Zhengyou

2017-05-01

We report an experimental observation of the classical version of valley polarized states in a two-dimensional hexagonal sonic crystal. The acoustic valley states, which carry specific linear momenta and orbital angular momenta, were selectively excited by external Gaussian beams and conveniently confirmed by the pressure distribution outside the crystal, according to the criterion of momentum conservation. The vortex nature of such intriguing bulk crystal states was directly characterized by scanning the phase profile inside the crystal. In addition, we observed a peculiar beam-splitting phenomenon, in which the separated beams are constructed by different valleys and locked to the opposite vortex chirality. The exceptional sound transport, encoded with valley-chirality locked information, may serve as the basis of designing conceptually interesting acoustic devices with unconventional functions.

Multiquark resonances

DOE PAGES

Esposito, A.; Pilloni, A.; Polosa, Antonio D.

2016-12-02

Multiquark resonances are undoubtedly experimentally observed. The number of states and the amount of details on their properties have been growing over the years. It is very recent the discovery of two pentaquarks and the confirmation of four tetraquarks, two of which had not been observed before. We mainly review the theoretical understanding of this sector of particle physics phenomenology and present some considerations attempting a coherent description of the so called X and Z resonances. The prominent problems plaguing theoretical models, like the absence of selection rules limiting the number of states predicted, motivate new directions in model building.more » Lastly, data are reviewed going through all of the observed resonances with particular attention to their common features and the purpose of providing a starting point to further research.« less

Risk Factors for Antimicrobial Resistance in Escherichia coli in Pigs Receiving Oral Antimicrobial Treatment: A Systematic Review.

PubMed

Burow, Elke; Käsbohrer, Annemarie

2017-03-01

The aim of this literature review was to identify risk factors in addition to antimicrobial treatment for antimicrobial resistance (AMR) occurrence in commensal Escherichia coli in pigs. A variety of studies were searched in 2014 and 2015. Studies identified as potentially relevant were assessed against eligibility criteria such as observation or experiment (no review), presentation of risk factors in addition to (single dosage) antimicrobial use, risk factors for but not resulting from AMR, and the same antimicrobial used and tested. Thirteen articles (nine on observational, four on experimental studies) were finally selected as relevant. It was reported that space allowance, production size/stage, cleanliness, entry of animals and humans into herds, dosage/frequency/route of administration, time span between treatment and sampling date, herd size, distance to another farm, coldness, and season had an impact on AMR occurrence. Associations were shown by one to four studies per factor and differed in magnitude, direction, and level of significance. The risk of bias was unclear in nearly half of the information of observational studies and in most of the information from experimental studies. Further research on the effects of specific management practices is needed to develop well-founded management advice.

Longitudinal mode selection in a delay-line homogeneously broadened oscillator with a fast saturable amplifier.

PubMed

Fleyer, Michael; Horowitz, Moshe

2017-05-01

Homogeneously broadened delay-line oscillators such as lasers or optoelectronic oscillators (OEOs) can potentially oscillate in a large number of cavity modes that are supported by their amplifier bandwidth. In a continuous wave operating mode, the oscillating mode is selected between one or few cavity modes that experience the highest small-signal gain. In this manuscript, we show that the oscillation mode of a homogeneously broadened oscillator can be selected from a large number of modes in a frequency region that can be broader than the full width at half maximum of the effective cavity filter. The mode is selected by a short-time injection of an external signal into the oscillator. After the external signal is turned off, the oscillation is maintained in the selected mode even if this mode has a significantly lower small-signal gain than that of other cavity modes. The stability of the oscillation is obtained due to nonlinear saturation effect in the oscillator amplifier. We demonstrate, experimentally and theoretically, mode selection in a long cavity OEO. We could select any desired mode between 400 cavity modes while maintaining ultra-low phase noise in the selected mode and in the non-oscillating modes. No mode-hopping was observed during our maximum measurement duration of about 24 hours.

Treatment of Diabetic Foot Ulcer Using Matriderm In Comparison with a Skin Graft

PubMed Central

Jeon, Hyojin; Yeo, Hyeonjung; Jeong, Hoijoon; Son, Daegu; Han, Kihwan

2013-01-01

Background For patients with neuropathy, vasculopathy, and impairment of wound healing, treatment of a diabetic foot ulcer poses many challenges. A large number of dermal analogues have been invented in an effort to overcome these challenges. Matriderm, a dermal analogue, is made from bovine collagen and elastin. This study was conducted in order to evaluate the effectiveness of Matriderm for treatment of diabetic foot ulcers, in comparison with skin grafting. Methods Sixty patients with diabetic foot ulcer were included in this prospective study. The average age of the patients, who had type II diabetes mellitus, was 58 years old. The patients were allocated to an experimental or control group with their consents. The patients were selected with their consent for inclusion in an experimental group and a control group. Patients in the experimental group received a Matriderm appliance and a split-thickness skin graft, while those in the control group received only a split-thickness skin graft. Results A shorter hospitalization period (7.52 weeks) was observed in the experimental group than in the control group (9.22 weeks), and a shorter period of time (8.61 weeks) was required for complete healing, compared with the control group (12.94 weeks), with statistical significance (P<0.05). A higher elasticity ratio of the affected side to the non-affected side was observed in the experimental group, compared with the control group (P<0.01). Conclusions Matriderm enables effective healing and improves elasticity in treatment of patients with diabetic foot ulcer. PMID:23898439

Comparative analysis of different sensor data (Landsat-TM and MOMS) for earth observation and impact on future sensor development

NASA Technical Reports Server (NTRS)

Bodechtel, J.; Zilger, J.; Salomonson, V. V.

1986-01-01

The missions of the German Modular Optoelectronic Multispectral Scanner (MOMS) aboard two STS flights demonstrated the feasibility of a novel concept with regard to both technical and scientific objectives. On account of the successful missions, a cooperation was agreed between the German Federal Minister for Research nad Technology and NASA for comparing MOMS observations with the more familiar operational Landsat-TM data over selected test sites, as a means of obtaining some relative measure of performance. This paper summarizes the results obtained and presents the MOMS-02, a further experimental representative of the MOMS program aiming at the realization of an operational system for the mid-nineties.

On the orientation of stripes in fish skin patterning.

PubMed

Míguez, David G; Muñuzuri, Alberto P

2006-11-20

This paper is focused on the study of the stripes orientation in the fish skin patterns. Based on microscopic observations of the pigment cells behavior at the embryonic stage, the key aspects of the pigmentation process are implemented in an experimental reaction-diffusion system. The experiment consists of a photosensitive Turing pattern of stripes growing directionally in one direction with controlled velocity. Different growth velocities of the system rearrange the stripes in the same three possible orientations observed in the skin of the colored fishes: parallel, oblique, and perpendicular. Our results suggest that the spreading velocity of the pigment cells in the fish dermis selects the orientation in the patterning processes.

Excess thermodynamics of mixtures involving xenon and light linear alkanes by computer simulation.

PubMed

Carvalho, A J Palace; Ramalho, J P Prates; Martins, Luís F G

2007-06-14

Excess molar enthalpies and excess molar volumes as a function of composition for liquid mixtures of xenon + ethane (at 161.40 K), xenon + propane (at 161.40 K) and xenon + n-butane (at 182.34 K) have been obtained by Monte Carlo computer simulations and compared with available experimental data. Simulation conditions were chosen to closely match those of the corresponding experimental results. The TraPPE-UA force field was selected among other force fields to model all the alkanes studied, whereas the one-center Lennard-Jones potential from Bohn et al. was used for xenon. The calculated H(m)(E) and V(m)(E) for all systems are negative, increasing in magnitude as the alkane chain length increases. The results for these systems were compared with experimental data and with other theoretical calculations using the SAFT approach. An excellent agreement between simulation and experimental results was found for xenon + ethane system, whereas for the remaining two systems, some deviations that become progressively more significant as the alkane chain length increases were observed.

Co-Selection of Resistance to Antibiotics, Biocides and Heavy Metals, and Its Relevance to Foodborne Pathogens

PubMed Central

Wales, Andrew D.; Davies, Robert H.

2015-01-01

Concerns have been raised in recent years regarding co-selection for antibiotic resistance among bacteria exposed to biocides used as disinfectants, antiseptics and preservatives, and to heavy metals (particularly copper and zinc) used as growth promoters and therapeutic agents for some livestock species. There is indeed experimental and observational evidence that exposure to these non-antibiotic antimicrobial agents can induce or select for bacterial adaptations that result in decreased susceptibility to one or more antibiotics. This may occur via cellular mechanisms that are protective across multiple classes of antimicrobial agents or by selection of genetic determinants for resistance to non-antibiotic agents that are linked to genes for antibiotic resistance. There may also be relevant effects of these antimicrobial agents on bacterial community structure and via non-specific mechanisms such as mobilization of genetic elements or mutagenesis. Notably, some co-selective adaptations have adverse effects on fitness in the absence of a continued selective pressure. The present review examines the evidence for the significance of these phenomena, particularly in respect of bacterial zoonotic agents that commonly occur in livestock and that may be transmitted, directly or via the food chain, to human populations. PMID:27025641

On the mechanism of high product selectivity for HCOOH using Pb in CO2 electroreduction.

PubMed

Back, Seoin; Kim, Jun-Hyuk; Kim, Yong-Tae; Jung, Yousung

2016-04-14

While achieving high product selectivity is one of the major challenges of the CO2 electroreduction technology in general, Pb is one of the few examples with high selectivity that produces formic acid almost exclusively (versus H2, CO, or other byproducts). In this work, we study the mechanism of CO2 electroreduction reactions using Pb to understand the origin of high formic acid selectivity. In particular, we first assess the proton-assisted mechanism proposed in the literature using density functional calculations and find that it cannot fully explain the previous selectivity experiments for the Pb electrode. We then suggest an alternative proton-coupled-electron-transfer mechanism consistent with existing observations, and further validate a new mechanism by experimentally measuring and comparing the onset potentials for CO2 reduction vs. H2 production. We find that the origin of a high selectivity of the Pb catalyst for HCOOH production over CO and H2 lies in the strong O-affinitive and weak C-, H-affinitive characteristics of Pb, leading to the involvement of the *OCHO species as a key intermediate to produce HCOOH exclusively and preventing unwanted H2 production at the same time.

Characterization of the stereochemical selectivity of beta-hairpin formation by molecular dynamics simulations.

PubMed

Soto, Patricia; Zangi, Ronen

2005-01-27

The stability of secondary structure motifs found in proteins is influenced by the choice of the configuration of the chiral centers present in the amino acid residues (i.e., D vs L). Experimental studies showed that the structural properties of the tetrapeptide (L)V(L)P(L)A(L)L (all-L) are drastically altered upon mutating the L-proline and the L-alanine by their d-enantiomers [J. Am. Chem. Soc. 1996, 118, 6975]. The all-L diastereomer is unstructured, experiencing little or no beta-hairpin formation, while the (L)V(D)P(D)A(L)L peptide exhibits a substantial population of beta-hairpin conformation. In this study, we perform molecular dynamics simulations to investigate the folding propensity of these two model peptides. The results confirm the experimental findings, namely, that the presence of d-amino acids in the loop region strongly induces beta-hairpin formation (a population increase from about 1.5% to 50% is observed). The major factor determining the different behavior is found to be the large difference in energy between the two diastereomers, approximately 22 kJ/mol, when they adopt a beta-hairpin structure. The higher energy observed for the all-L peptide is a consequence of none-ideal hydrogen bond formation and of steric repulsions. The results suggest that selective incorporation of D-amino acids in proteins can be used to enhance certain secondary structure elements. The kinetic behavior of the folding process observed in the simulations is also investigated. We find that the decay rate of the folded structure fits to a biexponential function, suggesting that the folding/unfolding process of a beta-hairpin is governed by two different mechanisms.

Plant selection and soil legacy enhance long-term biodiversity effects.

PubMed

Zuppinger-Dingley, Debra; Flynn, Dan F B; De Deyn, Gerlinde B; Petermann, Jana S; Schmid, Bernhard

2016-04-01

Plant-plant and plant-soil interactions can help maintain plant diversity and ecosystem functions. Changes in these interactions may underlie experimentally observed increases in biodiversity effects over time via the selection of genotypes adapted to low or high plant diversity. Little is known, however, about such community-history effects and particularly the role of plant-soil interactions in this process. Soil-legacy effects may occur if co-evolved interactions with soil communities either positively or negatively modify plant biodiversity effects. We tested how plant selection and soil legacy influence biodiversity effects on productivity, and whether such effects increase the resistance of the communities to invasion by weeds. We used two plant selection treatments: parental plants growing in monoculture or in mixture over 8 yr in a grassland biodiversity experiment in the field, which we term monoculture types and mixture types. The two soil-legacy treatments used in this study were neutral soil inoculated with live or sterilized soil inocula collected from the same plots in the biodiversity experiment. For each of the four factorial combinations, seedlings of eight species were grown in monocultures or four-species mixtures in pots in an experimental garden over 15 weeks. Soil legacy (live inoculum) strongly increased biodiversity complementarity effects for communities of mixture types, and to a significantly weaker extent for communities of monoculture types. This may be attributed to negative plant-soil feedbacks suffered by mixture types in monocultures, whereas monoculture types had positive plant-soil feedbacks, in both monocultures and mixtures. Monocultures of mixture types were most strongly invaded by weeds, presumably due to increased pathogen susceptibility, reduced biomass, and altered plant-soil interactions of mixture types. These results show that biodiversity effects in experimental grassland communities can be modified by the evolution of positive vs. negative plant-soil feedbacks of plant monoculture vs. mixture types.

Biofilm development in fixed bed biofilm reactors: experiments and simple models for engineering design purposes.

PubMed

Szilágyi, N; Kovács, R; Kenyeres, I; Csikor, Zs

2013-01-01

Biofilm development in a fixed bed biofilm reactor system performing municipal wastewater treatment was monitored aiming at accumulating colonization and maximum biofilm mass data usable in engineering practice for process design purposes. Initially a 6 month experimental period was selected for investigations where the biofilm formation and the performance of the reactors were monitored. The results were analyzed by two methods: for simple, steady-state process design purposes the maximum biofilm mass on carriers versus influent load and a time constant of the biofilm growth were determined, whereas for design approaches using dynamic models a simple biofilm mass prediction model including attachment and detachment mechanisms was selected and fitted to the experimental data. According to a detailed statistical analysis, the collected data have not allowed us to determine both the time constant of biofilm growth and the maximum biofilm mass on carriers at the same time. The observed maximum biofilm mass could be determined with a reasonable error and ranged between 438 gTS/m(2) carrier surface and 843 gTS/m(2), depending on influent load, and hydrodynamic conditions. The parallel analysis of the attachment-detachment model showed that the experimental data set allowed us to determine the attachment rate coefficient which was in the range of 0.05-0.4 m d(-1) depending on influent load and hydrodynamic conditions.

Stereodynamics in NO(X) + Ar inelastic collisions

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

Brouard, M., E-mail: mark.brouard@chem.ox.ac.uk; Chadwick, H.; Gordon, S. D. S.

2016-06-14

The effect of orientation of the NO(X) bond axis prior to rotationally inelastic collisions with Ar has been investigated experimentally and theoretically. A modification to conventional velocity-map imaging ion optics is described, which allows the orientation of hexapole state-selected NO(X) using a static electric field, followed by velocity map imaging of the resonantly ionized scattered products. Bond orientation resolved differential cross sections are measured experimentally for a series of spin-orbit conserving transitions and compared with quantum mechanical calculations. The agreement between experimental results and those from quantum mechanical calculations is generally good. Parity pairs, which have previously been observed inmore » collisions of unpolarized NO with various rare gases, are not observed due to the coherent superposition of the two j = 1/2, Ω = 1/2 Λ-doublet levels in the orienting field. The normalized difference differential cross sections are found to depend predominantly on the final rotational state, and are not very sensitive to the final Λ-doublet level. The differential steric effect has also been investigated theoretically, by means of quantum mechanical and classical calculations. Classically, the differential steric effect can be understood by considering the steric requirement for different types of trajectories that contribute to different regions of the differential cross section. However, classical effects cannot account quantitatively for the differential steric asymmetry observed in NO(X) + Ar collisions, which reflects quantum interference from scattering at either end of the molecule. This quantum interference effect is dominated by the repulsive region of the potential.« less

Vapor tagging of electric blasting caps with perfluorinated compounds. [For crime detection

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

Senum, G I; Gergley, R P; Greene, M

Vapor tagging of electric blasting caps (EBC) is accomplished with the use of perfluorocarbon taggants. These taggants are absorbed in either the present EBC end closures or in substitute fluoroelastomeric end closures to approximately 5 to 10% of the total weight of end closure. The specific taggants have been chosen to allow a 0.5 to 5 nanoliter per minute vapor taggant emission rate from the tagged EBC over a 5 y lifetime. The taggant emission rates from tagged EBC have been experimentally observed to be well described by a taggant emission rate model. This model provides for experimental selection ofmore » the proper taggant for projected lifetimes of ten years based on just several months of observed emission measurements. Another model has been derived which can predict the taggant concentrations in various realistic scenarios such as room, building, lockers, etc. The model takes into consideration the effect of barriers such as boxes, suitcases, etc., in impeding the release of the taggant vapors from the tagged EBC into the scenario and the dilution effect of the scenarios air circulation system. Taggant concentrations have been experimentally determined using a 425 liter sampling chamber with various barriers and the results are used with the model to predict various scenario taggant concentrations.« less

Evaluation of Fentanyl Disposition and Effects in Newborn Piglets as an Experimental Model for Human Neonates

PubMed Central

Valls-i-Soler, Adolfo; Encinas, Esther; Lukas, John C.; Vozmediano, Valvanera; Suárez, Elena

2014-01-01

Background Fentanyl is widely used off-label in NICU. Our aim was to investigate its cerebral, cardiovascular and pulmonary effects as well as pharmacokinetics in an experimental model for neonates. Methods Fentanyl (5 µg/kg bolus immediately followed by a 90 minute infusion of 3 µg/kg/h) was administered to six mechanically ventilated newborn piglets. Cardiovascular, ventilation, pulmonary and oxygenation indexes as well as brain activity were monitored from T = 0 up to the end of experiments (T = 225–300 min). Also plasma samples for quantification of fentanyl were drawn. Results A “reliable degree of sedation” was observed up to T = 210–240 min, consistent with the selected dosing regimen and the observed fentanyl plasma levels. Unlike cardiovascular parameters, which were unmodified except for an increasing trend in heart rate, some of the ventilation and oxygenation indexes as well as brain activity were significantly altered. The pulmonary and brain effects of fentanyl were mostly recovered from T = 210 min to the end of experiment. Conclusion The newborn piglet was shown to be a suitable experimental model for studying fentanyl disposition as well as respiratory and cardiovascular effects in human neonates. Therefore, it could be extremely useful for further investigating the drug behaviour under pathophysiological conditions. PMID:24595018

Observation and experimental investigation of confinement effects on ion transport and electrokinetic flows at the microscale

PubMed Central

Benneker, Anne M.; Wood, Jeffery A.; Tsai, Peichun A.; Lammertink, Rob G. H.

2016-01-01

Electrokinetic effects adjacent to charge-selective interfaces (CSI) have been experimentally investigated in microfluidic platforms in order to gain understanding on underlying phenomena of ion transport at elevated applied voltages. We experimentally investigate the influence of geometry and multiple array densities of the CSI on concentration and flow profiles in a microfluidic set-up using nanochannels as the CSI. Particle tracking obtained under chronoamperometric measurements show the development of vortices in the microchannel adjacent to the nanochannels. We found that the direction of the electric field and the potential drop inside the microchannel has a large influence on the ion transport through the interface, for example by inducing immediate wall electroosmotic flow. In microfluidic devices, the electric field may not be directed normal to the interface, which can result in an inefficient use of the CSI. Multiple vortices are observed adjacent to the CSI, growing in size and velocity as a function of time and dependent on their location in the microfluidic device. Local velocities inside the vortices are measured to be more than 1.5 mm/s. Vortex speed, as well as flow speed in the channel, are dependent on the geometry of the CSI and the distance from the electrode. PMID:27853257

Observation of topological valley transport of sound in sonic crystals

NASA Astrophysics Data System (ADS)

Lu, Jiuyang; Qiu, Chunyin; Ye, Liping; Fan, Xiying; Ke, Manzhu; Zhang, Fan; Liu, Zhengyou

2017-04-01

The concept of valley pseudospin, labelling quantum states of energy extrema in momentum space, is attracting attention because of its potential as a new type of information carrier. Compared with the non-topological bulk valley transport, realized soon after predictions, topological valley transport in domain walls is extremely challenging owing to the inter-valley scattering inevitably induced by atomic-scale imperfections--but an electronic signature was recently observed in bilayer graphene. Here, we report the experimental observation of topological valley transport of sound in sonic crystals. The macroscopic nature of sonic crystals permits a flexible and accurate design of domain walls. In addition to a direct visualization of the valley-selective edge modes through spatial scanning of the sound field, reflection immunity is observed in sharply curved interfaces. The topologically protected interface transport of sound, strikingly different from that in traditional sound waveguides, may serve as the basis for designing devices with unconventional functions.

Phase Transitions of Nanoemulsions Using Ultrasound: Experimental Observations

PubMed Central

Singh, Ram; Husseini, Ghaleb A.; Pitt, William G.

2012-01-01

The ultrasound-induced transformation of perfluorocarbon liquids to gases is of interest in the area of drug and gene delivery. In this study, three independent parameters (temperature, size, and perfluorocarbon species) were selected to investigate the effects of 476-kHz and 20-kHz ultrasound on nanoemulsion phase transition. Two levels of each factor (low and high) were considered at each frequency. The acoustic intensities at gas bubble formation and at the onset of inertial cavitation were recorded and subsequently correlated with the acoustic parameters. Experimental data showed that low frequencies are more effective in forming and collapsing a bubble. Additionally, as the size of the emulsion droplet increased, the intensity required for bubble formation decreased. As expected, perfluorohexane emulsions require greater intensity to form cavitating bubbles than perfluoropentane emulsions. PMID:22444691

Spin coherent states phenomena probed by quantum state tomography in Zeeman perturbed nuclear quadrupole resonance

NASA Astrophysics Data System (ADS)

Teles, João; Auccaise, Ruben; Rivera-Ascona, Christian; Araujo-Ferreira, Arthur G.; Andreeta, José P.; Bonagamba, Tito J.

2018-07-01

Recently, we reported an experimental implementation of quantum information processing (QIP) by nuclear quadrupole resonance (NQR). In this work, we present the first quantum state tomography (QST) experimental implementation in the NQR QIP context. Two approaches are proposed, employing coherence selection by temporal and spatial averaging. Conditions for reduction in the number of cycling steps are analyzed, which can be helpful for larger spin systems. The QST method was applied to the study of spin coherent states, where the alignment-to-orientation phenomenon and the evolution of squeezed spin states show the effect of the nonlinear quadrupole interaction intrinsic to the NQR system. The quantum operations were implemented using a single-crystal sample of KClO3 and observing ^{35}Cl nuclei, which posses spin 3/2.

Effects of trunk stabilization exercise on the local muscle activity and balance ability of normal subjects.

PubMed

Cha, Hyun Gyu

2018-06-01

[Purpose] The purpose of this study was to investigate the effects of trunk stabilization exercise on the transvers abdominalis (TA) and internal oblique (IO) muscle activity and balance ability of normal subjects. [Subjects and Methods] Forty healthy male subjects without orthopedic history of the lower extremity were selected for the present study. The experimental group received a hollowing exercise, curl-up and bridging exercise. The control group received a pelvic tilting exercise in the sitting position for the same period of time. [Results] Significant differences in the post-training gains in Balance index, TA, IO were observed between the experimental group and the control group. [Conclusion] The trunk stabilization exercise improved the balance ability and increased the activity of the TA and IO muscle.

Ab initio and density functional computations of the vibrational spectrum, molecular geometry and some molecular properties of the antidepressant drug sertraline (Zoloft) hydrochloride

NASA Astrophysics Data System (ADS)

Sagdinc, Seda; Kandemirli, Fatma; Bayari, Sevgi Haman

2007-02-01

Sertraline hydrochloride is a highly potent and selective inhibitor of serotonin (5HT). It is a basic compound of pharmaceutical application for antidepressant treatment (brand name: Zoloft). Ab initio and density functional computations of the vibrational (IR) spectrum, the molecular geometry, the atomic charges and polarizabilities were carried out. The infrared spectrum of sertraline is recorded in the solid state. The observed IR wave numbers were analysed in light of the computed vibrational spectrum. On the basis of the comparison between calculated and experimental results and the comparison with related molecules, assignments of fundamental vibrational modes are examined. The X-ray geometry and experimental frequencies are compared with the results of our theoretical calculations.

Study report on interfacing major physiological subsystem models: An approach for developing a whole-body algorithm

NASA Technical Reports Server (NTRS)

Fitzjerrell, D. G.; Grounds, D. J.; Leonard, J. I.

1975-01-01

Using a whole body algorithm simulation model, a wide variety and large number of stresses as well as different stress levels were simulated including environmental disturbances, metabolic changes, and special experimental situations. Simulation of short term stresses resulted in simultaneous and integrated responses from the cardiovascular, respiratory, and thermoregulatory subsystems and the accuracy of a large number of responding variables was verified. The capability of simulating significantly longer responses was demonstrated by validating a four week bed rest study. In this case, the long term subsystem model was found to reproduce many experimentally observed changes in circulatory dynamics, body fluid-electrolyte regulation, and renal function. The value of systems analysis and the selected design approach for developing a whole body algorithm was demonstrated.

Experimental Study on Dissimilar Friction Stir welding of Aluminium Alloys (5083-H111 and 6082-T6) to investigate the mechanical properties

NASA Astrophysics Data System (ADS)

Kumar, H. M. Anil; Venkata Ramana, V.; Pawar, Mayur

2018-03-01

Friction stir welding is an innovative technology in the joining realm of metals and alloys. This technique is highly economical and suitable especially for non ferrous alloys compared to ferrous alloys. It finds many applications in various fields of aeronautics, automobile, ship building industries etc. The paper presents the comparative results of mechanical properties such as tensile strength, microstructure, macro structure and hardness on the similar and dissimilar aluminum alloys AA5083-H111 and AA6082-T6 under certain selected variables - constant tool rotational speed, its tilt angle, welding speed using friction stir welding process. It is observed from the experimental results that joint efficiency of dissimilar aluminium alloys is higher than the similar aluminum alloys.

Generational distribution of a Candida glabrata population: Resilient old cells prevail, while younger cells dominate in the vulnerable host.

PubMed

Bouklas, Tejas; Alonso-Crisóstomo, Luz; Székely, Tamás; Diago-Navarro, Elizabeth; Orner, Erika P; Smith, Kalie; Munshi, Mansa A; Del Poeta, Maurizio; Balázsi, Gábor; Fries, Bettina C

2017-05-01

Similar to other yeasts, the human pathogen Candida glabrata ages when it undergoes asymmetric, finite cell divisions, which determines its replicative lifespan. We sought to investigate if and how aging changes resilience of C. glabrata populations in the host environment. Our data demonstrate that old C. glabrata are more resistant to hydrogen peroxide and neutrophil killing, whereas young cells adhere better to epithelial cell layers. Consequently, virulence of old compared to younger C. glabrata cells is enhanced in the Galleria mellonella infection model. Electron microscopy images of old C. glabrata cells indicate a marked increase in cell wall thickness. Comparison of transcriptomes of old and young C. glabrata cells reveals differential regulation of ergosterol and Hog pathway associated genes as well as adhesion proteins, and suggests that aging is accompanied by remodeling of the fungal cell wall. Biochemical analysis supports this conclusion as older cells exhibit a qualitatively different lipid composition, leading to the observed increased emergence of fluconazole resistance when grown in the presence of fluconazole selection pressure. Older C. glabrata cells accumulate during murine and human infection, which is statistically unlikely without very strong selection. Therefore, we tested the hypothesis that neutrophils constitute the predominant selection pressure in vivo. When we altered experimentally the selection pressure by antibody-mediated removal of neutrophils, we observed a significantly younger pathogen population in mice. Mathematical modeling confirmed that differential selection of older cells is sufficient to cause the observed demographic shift in the fungal population. Hence our data support the concept that pathogenesis is affected by the generational age distribution of the infecting C. glabrata population in a host. We conclude that replicative aging constitutes an emerging trait, which is selected by the host and may even play an unanticipated role in the transition from a commensal to a pathogen state.

Mitochondrial Mutation Rate, Spectrum and Heteroplasmy in Caenorhabditis elegans Spontaneous Mutation Accumulation Lines of Differing Population Size.

PubMed

Konrad, Anke; Thompson, Owen; Waterston, Robert H; Moerman, Donald G; Keightley, Peter D; Bergthorsson, Ulfar; Katju, Vaishali

2017-06-01

Mitochondrial genomes of metazoans, given their elevated rates of evolution, have served as pivotal markers for phylogeographic studies and recent phylogenetic events. In order to determine the dynamics of spontaneous mitochondrial mutations in small populations in the absence and presence of selection, we evolved mutation accumulation (MA) lines of Caenorhabditis elegans in parallel over 409 consecutive generations at three varying population sizes of N = 1, 10, and 100 hermaphrodites. The N =1 populations should have a minimal influence of natural selection to provide the spontaneous mutation rate and the expected rate of neutral evolution, whereas larger population sizes should experience increasing intensity of selection. New mutations were identified by Illumina paired-end sequencing of 86 mtDNA genomes across 35 experimental lines and compared with published genomes of natural isolates. The spontaneous mitochondrial mutation rate was estimated at 1.05 × 10-7/site/generation. A strong G/C→A/T mutational bias was observed in both the MA lines and the natural isolates. This suggests that the low G + C content at synonymous sites is the product of mutation bias rather than selection as previously proposed. The mitochondrial effective population size per worm generation was estimated to be 62. Although it was previously concluded that heteroplasmy was rare in C. elegans, the vast majority of mutations in this study were heteroplasmic despite an experimental regime exceeding 400 generations. The frequencies of frameshift and nonsynonymous mutations were negatively correlated with population size, which suggests their deleterious effects on fitness and a potent role for selection in their eradication. © The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Aerobiological Stabilities of Different Species of Gram-Negative Bacteria, Including Well-Known Biothreat Simulants, in Single-Cell Particles and Cell Clusters of Different Compositions

PubMed Central

Skogan, Gunnar

2017-01-01

ABSTRACT The ability to perform controlled experiments with bioaerosols is a fundamental enabler of many bioaerosol research disciplines. A practical alternative to using hazardous biothreat agents, e.g., for detection equipment development and testing, involves using appropriate model organisms (simulants). Several species of Gram-negative bacteria have been used or proposed as biothreat simulants. However, the appropriateness of different bacterial genera, species, and strains as simulants is still debated. Here, we report aerobiological stability characteristics of four species of Gram-negative bacteria (Pantoea agglomerans, Serratia marcescens, Escherichia coli, and Xanthomonas arboricola) in single-cell particles and cell clusters produced using four spray liquids (H2O, phosphate-buffered saline[PBS], spent culture medium[SCM], and a SCM-PBS mixture). E. coli showed higher stability in cell clusters from all spray liquids than the other species, but it showed similar or lower stability in single-cell particles. The overall stability was higher in cell clusters than in single-cell particles. The highest overall stability was observed for bioaerosols produced using SCM-containing spray liquids. A key finding was the observation that stability differences caused by particle size or compositional changes frequently followed species-specific patterns. The results highlight how even moderate changes to one experimental parameter, e.g., bacterial species, spray liquid, or particle size, can strongly affect the aerobiological stability of Gram-negative bacteria. Taken together, the results highlight the importance of careful and informed selection of Gram-negative bacterial biothreat simulants and also the accompanying particle size and composition. The outcome of this work contributes to improved selection of simulants, spray liquids, and particle size for use in bioaerosol research. IMPORTANCE The outcome of this work contributes to improved selection of simulants, spray liquids, and particle size for use in bioaerosol research. Taken together, the results highlight the importance of careful and informed selection of Gram-negative bacterial biothreat simulants and also the accompanying particle size and composition. The results highlight how even moderate changes to one experimental parameter, e.g., bacterial species, spray liquid, or particle size, can strongly affect the aerobiological stability of Gram-negative bacteria. A key finding was the observation that stability differences caused by particle size or compositional changes frequently followed species-specific patterns. PMID:28687646

[Changes of prostaglandin D2,carboxypeptidase A3 and platelet activating factor in guinea pig in anaphylactic shock].

PubMed

Yang, Kai; Guo, Xiang-jie; Yan, Xue-bin; Gao, Cai-rong

2012-06-01

To detect the changes of leukotriene E4(LTE4), prostaglandin D2(PGD2), carboxypeptidase A3(CPA3) and platelet activating factor (PAF) in guinea pigs died from anaphylactic shock. Guinea pigs were used for establishing anaphylactic shock models. The levels of LTE4, PGD2 and CPA3, and PAF were detected in urine, plasma, and brain tissues with ELISA kit, respectively. The significant biomarkers were selected comparing with control group. The changes of PGD2, CPA3 and PAF in the guinea pigs at time zero, 12 and 24 hours after death were observed and compared respectively. The effect of platelet activating factor acetylhydrolase (PAF-AH) to PAF in guinea pig brain was examined and compared. There were no statistically differences of LTE4 levels in urine observed between experimental group and control group. The levels of CPA3, PGD2 and PAF in the experimental group were significantly higher than that in the control group at 0 h. The levels of PAF at 12 and 24 hours after anaphylactic shock were significantly higher than that in the control group. The levels of PAF decreased significantly after pretreatment with PAF-AH. LTE4 in urine cannot be selected as a biomarker to determine the anaphylactic shock. PGD2 and CPA3 in plasma, and PAF in brain tissue may be used as biomarkers to determine the anaphylactic shock. PAF-AH may be potentially useful for clinical treatment of anaphylactic shock.

Independent priming of location and color in identification of briefly presented letters.

PubMed

Ásgeirsson, Árni Gunnar; Kristjánsson, Árni; Bundesen, Claus

2014-01-01

Attention shifts are facilitated if the items to be attended remain the same across trials. Some researchers argue that this priming effect is perceptual, whereas others propose that priming is postperceptual, involving facilitated response selection. The experimental findings have not been consistent regarding the roles of variables such as task difficulty, response repetition, expectancies, and decision-making. Position priming, when repetition of a target position facilitates responses on a subsequent trial, is another source of disagreement among researchers. Experimental results have likewise been inconsistent as to whether position priming is dependent on the repetition of target features or has an independent effect on attention shifts. We attempted to isolate the perceptual components of priming by presenting brief (10-180 ms) search arrays to eight healthy observers. The task was to identify a color-singleton letter among distractors. All stimulus presentation contingencies were randomized, and responses were unspeeded, to avoid effects of observer expectation and postperceptual effects. Repeating target color and/or position strongly improved performance. The effects of color and position repetition were independent of one another and were stable across participants. The results argue for a strong perceptual component in priming, which biases selection toward recent target features and positions, showing that perceptual mechanisms are sufficient to produce priming in visual search and that such effects can be elicited with limited sensory evidence. The results are the first to demonstrate independent priming of color and position in the identification of briefly presented, postmasked stimuli.

High-resolution IR absorption spectroscopy of polycyclic aromatic hydrocarbons in the 3 μm region: role of hydrogenation and alkylation

NASA Astrophysics Data System (ADS)

Maltseva, Elena; Mackie, Cameron J.; Candian, Alessandra; Petrignani, Annemieke; Huang, Xinchuan; Lee, Timothy J.; Tielens, Alexander G. G. M.; Oomens, Jos; Buma, Wybren Jan

2018-03-01

Aim. We aim to elucidate the spectral changes in the 3 μm region that result from chemical changes in the molecular periphery of polycyclic aromatic hydrocarbons (PAHs) with extra hydrogens (H-PAHs) and methyl groups (Me-PAHs). Methods: Advanced laser spectroscopic techniques combined with mass spectrometry were applied on supersonically cooled 1,2,3,4-tetrahydronaphthalene, 9,10-dihydroanthracene, 9,10-dihydrophenanthrene, 1,2,3,6,7,8-hexahydropyrene, 9-methylanthracene, and 9,10-dimethylanthracene, allowing us to record mass-selective and conformationally selective absorption spectra of the aromatic, aliphatic, and alkyl CH-stretches in the 3.175 - 3.636 µm region with laser-limited resolution. We compared the experimental absorption spectra with standard harmonic calculations and with second-order vibrational perturbation theory anharmonic calculations that use the SPECTRO program for treating resonances. Results: We show that anharmonicity plays an important if not dominant role, affecting not only aromatic, but also aliphatic and alkyl CH-stretch vibrations. The experimental high-resolution data lead to the conclusion that the variation in Me- and H-PAHs composition might well account for the observed variations in the 3 μm emission spectra of carbon-rich and star-forming regions. Our laboratory studies also suggest that heavily hydrogenated PAHs form a significant fraction of the carriers of IR emission in regions in which an anomalously strong 3 μm plateau is observed.

Observation of the Hydrogen Migration in the Cation-Induced Fragmentation of the Pyridine Molecules.

PubMed

Wasowicz, Tomasz J; Pranszke, Bogusław

2016-02-25

The ability to selectively control chemical reactions related to biology, combustion, and catalysis has recently attracted much attention. In particular, the hydrogen atom relocation may be used to manipulate bond-breaking and new bond-forming processes and may hold promise for far-reaching applications. Thus, the hydrogen atom migration preceding fragmentation of the gas-phase pyridine molecules by the H(+), H2(+), He(+), He(2+), and O(+) impact has been studied experimentally in the energy range of 5-2000 eV using collision-induced luminescence spectroscopy. Formation of the excited NH(A(3)Π) radicals was observed among the atomic and diatomic fragments. The structure of the pyridine molecule is lacking of the NH group, therefore observation of its A(3)Π → X(3)Σ(-) emission bands is an evidence of the hydrogen atom relocation prior to the cation-induced fragmentation. The NH(A(3)Π) emission yields indicate that formation of the NH radicals depends on the type of selected projectile and can be controlled by tuning its velocity. The plausible collisional mechanisms as well as fragmentation channels for NH formation in pyridine are discussed.

[Experimental model for metastasis of cecal origin].

PubMed

Bail, J P; Loridon, B; Aillet, G; Poupon, M F; Douillard, J Y

1991-01-01

The pre-selected tumor cells injection in the cecal wall of rat, seems to be a intermediate model between spontaneous evolution of a colon tumor and intrasplenic or direct intraportal injections. From rhabdomyosarcoma cells (RMS S4-MH-) which present the advantage to prudce up lymphatic, pulmonary and hepatic metastases after subcutaneously injection, first subcutaneously (S.C.), intrasplenic (I.S.) and intracecal sites were compared: In the I.C. model, tumor was obtained in 80% of case and the survival was nearly similar to S.C. model's one. The lymphatic metastases were more and more distal as the evolution and the liver metastases were rarely observed. The I.S. model increased quickly and there were always liver metastases; In the two cases, pulmonary metastases were rarely observed (0 and 2/5). With adenocarcinoma colonic cells (Pro b) I.C. injection in the rat, tumor were obtained in 48% of cases without peritoneal dissemination; lymphatic nodes metastases were observed in 80% of cases; liver metastases was obtained in one animal from metastasis pulmonary selection cell lines. The I.C. model allows to estimate the liver and lymphatic nodes part; improved, it would be used to test adjuvant therapies and immunoscintigraphy.

Selection for production-related traits in Pelargonium zonale: improved design and analysis make all the difference

PubMed Central

Molenaar, Heike; Glawe, Martin; Boehm, Robert; Piepho, Hans-Peter

2017-01-01

Ornamental plant variety improvement is limited by current phenotyping approaches and neglected use of experimental designs. The present study was conducted to show the benefits of using an experimental design and corresponding analysis in ornamental breeding regarding simulated response to selection in Pelargonium zonale for production-related traits. This required establishment of phenotyping protocols for root formation and stem cutting counts, with which 974 genotypes were assessed in a two-phase experimental design. The present paper evaluates this protocol. The possibility of varietal improvement through indirect selection on secondary traits such as branch count and flower count was assessed by genetic correlations. Simulated response to selection varied greatly, depending on the genotypic variances of the breeding population and traits. A varietal improvement of over 20% is possible for stem cutting count, root formation, branch count and flower count. In contrast, indirect selection of stem cutting count by branch count or flower count was found to be ineffective. The established phenotypic protocols and two-phase experimental designs are valuable tools for breeding of P. zonale. PMID:28243453

Selection for production-related traits in Pelargonium zonale: improved design and analysis make all the difference.

PubMed

Molenaar, Heike; Glawe, Martin; Boehm, Robert; Piepho, Hans-Peter

2017-01-01

Ornamental plant variety improvement is limited by current phenotyping approaches and neglected use of experimental designs. The present study was conducted to show the benefits of using an experimental design and corresponding analysis in ornamental breeding regarding simulated response to selection in Pelargonium zonale for production-related traits. This required establishment of phenotyping protocols for root formation and stem cutting counts, with which 974 genotypes were assessed in a two-phase experimental design. The present paper evaluates this protocol. The possibility of varietal improvement through indirect selection on secondary traits such as branch count and flower count was assessed by genetic correlations. Simulated response to selection varied greatly, depending on the genotypic variances of the breeding population and traits. A varietal improvement of over 20% is possible for stem cutting count, root formation, branch count and flower count. In contrast, indirect selection of stem cutting count by branch count or flower count was found to be ineffective. The established phenotypic protocols and two-phase experimental designs are valuable tools for breeding of P. zonale .

Folding similarity of the outer pore region in prokaryotic and eukaryotic sodium channels revealed by docking of conotoxins GIIIA, PIIIA, and KIIIA in a NavAb-based model of Nav1.4

PubMed Central

Korkosh, Viacheslav S.; Zhorov, Boris S.

2014-01-01

Voltage-gated sodium channels are targets for many drugs and toxins. However, the rational design of medically relevant channel modulators is hampered by the lack of x-ray structures of eukaryotic channels. Here, we used a homology model based on the x-ray structure of the NavAb prokaryotic sodium channel together with published experimental data to analyze interactions of the μ-conotoxins GIIIA, PIIIA, and KIIIA with the Nav1.4 eukaryotic channel. Using Monte Carlo energy minimizations and published experimentally defined pairwise contacts as distance constraints, we developed a model in which specific contacts between GIIIA and Nav1.4 were readily reproduced without deformation of the channel or toxin backbones. Computed energies of specific interactions between individual residues of GIIIA and the channel correlated with experimental estimates. The predicted complexes of PIIIA and KIIIA with Nav1.4 are consistent with a large body of experimental data. In particular, a model of Nav1.4 interactions with KIIIA and tetrodotoxin (TTX) indicated that TTX can pass between Nav1.4 and channel-bound KIIIA to reach its binding site at the selectivity filter. Our models also allowed us to explain experimental data that currently lack structural interpretations. For instance, consistent with the incomplete block observed with KIIIA and some GIIIA and PIIIA mutants, our computations predict an uninterrupted pathway for sodium ions between the extracellular space and the selectivity filter if at least one of the four outer carboxylates is not bound to the toxin. We found a good correlation between computational and experimental data on complete and incomplete channel block by native and mutant toxins. Thus, our study suggests similar folding of the outer pore region in eukaryotic and prokaryotic sodium channels. PMID:25156117

Observation and theory of reorientation-induced spectral diffusion in polarization-selective 2D IR spectroscopy.

PubMed

Kramer, Patrick L; Nishida, Jun; Giammanco, Chiara H; Tamimi, Amr; Fayer, Michael D

2015-05-14

In nearly all applications of ultrafast multidimensional infrared spectroscopy, the spectral degrees of freedom (e.g., transition frequency) and the orientation of the transition dipole are assumed to be decoupled. We present experimental results which confirm that frequency fluctuations can be caused by rotational motion and observed under appropriate conditions. A theory of the frequency-frequency correlation function (FFCF) observable under various polarization conditions is introduced, and model calculations are found to reproduce the qualitative trends in FFCF rates. The FFCF determined with polarization-selective two-dimensional infrared (2D IR) spectroscopy is a direct reporter of the frequency-rotational coupling. For the solute methanol in a room temperature ionic liquid, the FFCF of the hydroxyl (O-D) stretch decays due to spectral diffusion with different rates depending on the polarization of the excitation pulses. The 2D IR vibrational echo pulse sequence consists of three excitation pulses that generate the vibrational echo, a fourth pulse. A faster FFCF decay is observed when the first two excitation pulses are polarized perpendicular to the third pulse and the echo, 〈XXY Y〉, than in the standard all parallel configuration, 〈XXXX〉, in which all four pulses have the same polarization. The 2D IR experiment with polarizations 〈XY XY〉 ("polarization grating" configuration) gives a FFCF that decays even more slowly than in the 〈XXXX〉 configuration. Polarization-selective 2D IR spectra of bulk water do not exhibit polarization-dependent FFCF decays; spectral diffusion is effectively decoupled from reorientation in the water system.

Observation and theory of reorientation-induced spectral diffusion in polarization-selective 2D IR spectroscopy

NASA Astrophysics Data System (ADS)

Kramer, Patrick L.; Nishida, Jun; Giammanco, Chiara H.; Tamimi, Amr; Fayer, Michael D.

2015-05-01

In nearly all applications of ultrafast multidimensional infrared spectroscopy, the spectral degrees of freedom (e.g., transition frequency) and the orientation of the transition dipole are assumed to be decoupled. We present experimental results which confirm that frequency fluctuations can be caused by rotational motion and observed under appropriate conditions. A theory of the frequency-frequency correlation function (FFCF) observable under various polarization conditions is introduced, and model calculations are found to reproduce the qualitative trends in FFCF rates. The FFCF determined with polarization-selective two-dimensional infrared (2D IR) spectroscopy is a direct reporter of the frequency-rotational coupling. For the solute methanol in a room temperature ionic liquid, the FFCF of the hydroxyl (O-D) stretch decays due to spectral diffusion with different rates depending on the polarization of the excitation pulses. The 2D IR vibrational echo pulse sequence consists of three excitation pulses that generate the vibrational echo, a fourth pulse. A faster FFCF decay is observed when the first two excitation pulses are polarized perpendicular to the third pulse and the echo, , than in the standard all parallel configuration, , in which all four pulses have the same polarization. The 2D IR experiment with polarizations ("polarization grating" configuration) gives a FFCF that decays even more slowly than in the configuration. Polarization-selective 2D IR spectra of bulk water do not exhibit polarization-dependent FFCF decays; spectral diffusion is effectively decoupled from reorientation in the water system.

Experimental and theoretical screening of nanoscale oxide reactivity with LiBH4

NASA Astrophysics Data System (ADS)

Opalka, S. M.; Tang, X.; Laube, B. L.; Vanderspurt, T. H.

2009-05-01

Experimentation, thermodynamic modeling, and atomic modeling were combined to screen the reactivity of SiO2, Al2O3, and ZrO2 nanoscale oxides with LiBH4. Equilibrium thermodynamic modeling showed that the reactions of oxides with LiBH4 could lead to formation of stable Li-bearing oxide and metal boride phases. Experimentation was conducted to evaluate the discharge/recharge reaction products of nanoscale oxide-LiBH4 mixtures. Thermal gravimetric analyses-mass spectroscopy and x-ray diffraction revealed significant SiO2 destabilization of LiBH4 dehydrogenation, resulting in the formation of lithium silicate and boric acid. A smaller amount of lithium metaborate and boric acid was formed with Al2O3. No destabilization products were observed with ZrO2. Density functional theory atomic modeling predicted much stronger LiBH4 interfacial adsorption on the SiO2 and Al2O3 surfaces than on the ZrO2 surface, which was consistent with the experimental findings. Following dehydrogenation, interfacial Li atoms were predicted to strongly adsorb on the oxide surfaces effectively competing with LiH formation. The interfacial Li interactions with Al2O3 and ZrO2 were equal in strength in the fully hydrided and dehydrided states, so that their predicted net effect on LiBH4 dehydrogenation was insignificant. Zirconia was selected for nanoframework development based on the combined observations of compatibility and weaker associative interactions with LiBH4.

Learning to rank atlases for multiple-atlas segmentation.

PubMed

Sanroma, Gerard; Wu, Guorong; Gao, Yaozong; Shen, Dinggang

2014-10-01

Recently, multiple-atlas segmentation (MAS) has achieved a great success in the medical imaging area. The key assumption is that multiple atlases have greater chances of correctly labeling a target image than a single atlas. However, the problem of atlas selection still remains unexplored. Traditionally, image similarity is used to select a set of atlases. Unfortunately, this heuristic criterion is not necessarily related to the final segmentation performance. To solve this seemingly simple but critical problem, we propose a learning-based atlas selection method to pick up the best atlases that would lead to a more accurate segmentation. Our main idea is to learn the relationship between the pairwise appearance of observed instances (i.e., a pair of atlas and target images) and their final labeling performance (e.g., using the Dice ratio). In this way, we select the best atlases based on their expected labeling accuracy. Our atlas selection method is general enough to be integrated with any existing MAS method. We show the advantages of our atlas selection method in an extensive experimental evaluation in the ADNI, SATA, IXI, and LONI LPBA40 datasets. As shown in the experiments, our method can boost the performance of three widely used MAS methods, outperforming other learning-based and image-similarity-based atlas selection methods.

Vibrational spectroscopic, molecular docking and quantum chemical studies on 6-aminonicotinamide

NASA Astrophysics Data System (ADS)

Mohamed Asath, R.; Premkumar, S.; Mathavan, T.; Milton Franklin Benial, A.

2017-04-01

The most stable molecular structure of 6-aminonicotinamide (ANA) molecule was predicted by conformational analysis and vibrational spectral analysis was carried out by experimental and theoretical methods. The calculated and experimentally observed vibrational frequencies were assigned and compared. The π→π* electronic transition of the molecule was predicted by theoretically calculated ultraviolet-visible spectra in gas and liquid phase and further validated experimentally using ethanol as a solvent. Frontier molecular orbitals analysis was carried out to probe the reactive nature of the ANA molecule and further the site selectivity to specific chemical reactions were effectively analyzed by Fukui function calculation. The molecular electrostatic potential surface was simulated to confirm the reactive sites of the molecule. The natural bond orbital analysis was also performed to understand the intra molecular interactions, which confirms the bioactivity of the ANA molecule. Neuroprotective nature of the ANA molecule was analyzed by molecular docking analysis and the ANA molecule was identified as a good inhibitor against Alzheimer's disease.

Experimental Detection of the Intrinsic Difference in Raman Optical Activity of a Photoreceptor Protein under Preresonance and Resonance Conditions.

PubMed

Haraguchi, Shojiro; Hara, Miwa; Shingae, Takahito; Kumauchi, Masato; Hoff, Wouter D; Unno, Masashi

2015-09-21

Raman optical activity (ROA) is an advanced technique capable of detecting structural deformations of light-absorbing molecules embedded in chromophoric proteins. Resonance Raman (RR) spectroscopy is widely used to enhance the band intensities. However, theoretical work has predicted that under resonance conditions the ROA spectrum resembles the shape of the RR spectrum. Herein, we use photoactive yellow protein (PYP) to measure the first experimental data on the effect of changing the excitation wavelength on the ROA spectra of a protein. We observe a close similarity between the shape of the RR spectrum and the resonance ROA spectrum of PYP. Furthermore, we experimentally verify the theoretical prediction concerning the ratio of the amplitudes of the ROA and Raman spectra. Our data demonstrate that selecting an appropriate excitation wavelength is a key factor for extracting structural information on a protein active site using ROA spectroscopy. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Benchmarking comparison and validation of MCNP photon interaction data

NASA Astrophysics Data System (ADS)

Colling, Bethany; Kodeli, I.; Lilley, S.; Packer, L. W.

2017-09-01

The objective of the research was to test available photoatomic data libraries for fusion relevant applications, comparing against experimental and computational neutronics benchmarks. Photon flux and heating was compared using the photon interaction data libraries (mcplib 04p, 05t, 84p and 12p). Suitable benchmark experiments (iron and water) were selected from the SINBAD database and analysed to compare experimental values with MCNP calculations using mcplib 04p, 84p and 12p. In both the computational and experimental comparisons, the majority of results with the 04p, 84p and 12p photon data libraries were within 1σ of the mean MCNP statistical uncertainty. Larger differences were observed when comparing computational results with the 05t test photon library. The Doppler broadening sampling bug in MCNP-5 is shown to be corrected for fusion relevant problems through use of the 84p photon data library. The recommended libraries for fusion neutronics are 84p (or 04p) with MCNP6 and 84p if using MCNP-5.

ROLE OF TIMING IN ASSESSMENT OF NERVE REGENERATION

PubMed Central

BRENNER, MICHAEL J.; MORADZADEH, ARASH; MYCKATYN, TERENCE M.; TUNG, THOMAS H. H.; MENDEZ, ALLEN B.; HUNTER, DANIEL A.; MACKINNON, SUSAN E.

2014-01-01

Small animal models are indispensable for research on nerve injury and reconstruction, but their superlative regenerative potential may confound experimental interpretation. This study investigated time-dependent neuroregenerative phenomena in rodents. Forty-six Lewis rats were randomized to three nerve allograft groups treated with 2 mg/(kg day) tacrolimus; 5 mg/(kg day) Cyclosporine A; or placebo injection. Nerves were subjected to histomorphometric and walking track analysis at serial time points. Tacrolimus increased fiber density, percent neural tissue, and nerve fiber count and accelerated functional recovery at 40 days, but these differences were undetectable by 70 days. Serial walking track analysis showed a similar pattern of recovery. A ‘blow-through’ effect is observed in rodents whereby an advancing nerve front overcomes an experimental defect given sufficient time, rendering experimental groups indistinguishable at late time points. Selection of validated time points and corroboration in higher animal models are essential prerequisites for the clinical application of basic research on nerve regeneration. PMID:18381659

Regioselectivity of intermolecular Pauson-Khand reaction of aliphatic alkynes: experimental and theoretical study of the effect of alkyne polarization.

PubMed

Fager-Jokela, Erika; Muuronen, Mikko; Khaizourane, Héléa; Vázquez-Romero, Ana; Verdaguer, Xavier; Riera, Antoni; Helaja, Juho

2014-11-21

Generally judged poor electronic regioselectivity of alkyne insertion in intermolecular Pauson-Khand reaction (PKR) has severely restricted its synthetic applications. In our previous rational study concerning diarylalkynes (Fager-Jokela, E.; Muuronen, M.; Patzschke, M.; Helaja, J. J. Org. Chem. 2012, 77, 9134-9147), both experimental and theoretical results indicated that purely electronic factors, i.e., alkyne polarization via resonance effect, induced the observed modest regioselectivity. In the present work, we substantiate that the alkyne polarization via inductive effect can result notable, synthetically valuable regioselectivity. Computational study at DFT level was performed to disclose the electronic origin of the selectivity. Overall, the NBO charges of alkynes correlated qualitatively with regioisomer outcome. In a detailed computational PKR case study, the obtained Boltzmann distributions of the transition state (TS) populations correlate closely with experimental regioselectivity. Analysis of the TS-structures revealed that weak interactions, e.g., hydrogen bonding and steric repulsion, affect the regioselectivity and can easily override the electronic guidance.

Large eddy simulation of shock train in a convergent-divergent nozzle

NASA Astrophysics Data System (ADS)

Mousavi, Seyed Mahmood; Roohi, Ehsan

2014-12-01

This paper discusses the suitability of the Large Eddy Simulation (LES) turbulence modeling for the accurate simulation of the shock train phenomena in a convergent-divergent nozzle. To this aim, we selected an experimentally tested geometry and performed LES simulation for the same geometry. The structure and pressure recovery inside the shock train in the nozzle captured by LES model are compared with the experimental data, analytical expressions and numerical solutions obtained using various alternative turbulence models, including k-ɛ RNG, k-ω SST, and Reynolds stress model (RSM). Comparing with the experimental data, we observed that the LES solution not only predicts the "locations of the first shock" precisely, but also its results are quite accurate before and after the shock train. After validating the LES solution, we investigate the effects of the inlet total pressure on the shock train starting point and length. The effects of changes in the back pressure, nozzle inlet angle (NIA) and wall temperature on the behavior of the shock train are investigated by details.

Experimental examination of frequency locking effect in acousto-optic system

NASA Astrophysics Data System (ADS)

Mantsevich, S. N.; Balakshy, V. I.

2018-04-01

The optoelectronic system containing collinear acousto-optic cell fabricated on the base of calcium molybdate crystal and positive electronic feedback circuit was examined. The feedback signal is formed due to the optical heterodyning effect that occurs on the cell output and takes place in the special regime of collinear acousto-optic diffraction. It was discovered that three operation modes that may exist in this system. The boundaries between the modes were determined. The positions of the boundaries depend on the main parameters of the system—the incident light intensity and the feedback gain value. The new for acousto-optics phenomenon of acousto-optic system self-oscillations frequency locking by the RF generator signal was discovered and examined experimentally. Such an effect has never been observed before in the acousto-optic systems. It was experimentally shown that frequency locking effect may be used to select one of the multimode semiconductor laser longitudinal modes to improve laser radiation spectral composition.

Does sex-ratio selection influence nest-site choice in a reptile with temperature-dependent sex determination?

PubMed

Mitchell, Timothy S; Maciel, Jessica A; Janzen, Fredric J

2013-12-07

Evolutionary theory predicts that dioecious species should produce a balanced primary sex ratio maintained by frequency-dependent selection. Organisms with environmental sex determination, however, are vulnerable to maladaptive sex ratios, because environmental conditions vary spatio-temporally. For reptiles with temperature-dependent sex determination, nest-site choice is a behavioural maternal effect that could respond to sex-ratio selection, as mothers could adjust offspring sex ratios by choosing nest sites that will have particular thermal properties. This theoretical prediction has generated decades of empirical research, yet convincing evidence that sex-ratio selection is influencing nesting behaviours remains absent. Here, we provide the first experimental evidence from nature that sex-ratio selection, rather than only viability selection, is probably an important component of nest-site choice in a reptile with temperature-dependent sex determination. We compare painted turtle (Chrysemys picta) neonates from maternally selected nest sites with those from randomly selected nest sites, observing no substantive difference in hatching success or survival, but finding a profound difference in offspring sex ratio in the direction expected based on historical records. Additionally, we leverage long-term data to reconstruct our sex ratio results had the experiment been repeated in multiple years. As predicted by theory, our results suggest that sex-ratio selection has shaped nesting behaviour in ways likely to enhance maternal fitness.

Does sex-ratio selection influence nest-site choice in a reptile with temperature-dependent sex determination?

PubMed Central

Mitchell, Timothy S.; Maciel, Jessica A.; Janzen, Fredric J.

2013-01-01

Evolutionary theory predicts that dioecious species should produce a balanced primary sex ratio maintained by frequency-dependent selection. Organisms with environmental sex determination, however, are vulnerable to maladaptive sex ratios, because environmental conditions vary spatio-temporally. For reptiles with temperature-dependent sex determination, nest-site choice is a behavioural maternal effect that could respond to sex-ratio selection, as mothers could adjust offspring sex ratios by choosing nest sites that will have particular thermal properties. This theoretical prediction has generated decades of empirical research, yet convincing evidence that sex-ratio selection is influencing nesting behaviours remains absent. Here, we provide the first experimental evidence from nature that sex-ratio selection, rather than only viability selection, is probably an important component of nest-site choice in a reptile with temperature-dependent sex determination. We compare painted turtle (Chrysemys picta) neonates from maternally selected nest sites with those from randomly selected nest sites, observing no substantive difference in hatching success or survival, but finding a profound difference in offspring sex ratio in the direction expected based on historical records. Additionally, we leverage long-term data to reconstruct our sex ratio results had the experiment been repeated in multiple years. As predicted by theory, our results suggest that sex-ratio selection has shaped nesting behaviour in ways likely to enhance maternal fitness. PMID:24266033

Near-infrared and ultraviolet induced isomerization of crotonic acid in N{sub 2} and Xe cryomatrices: First observation of two high-energy trans C–O conformers and mechanistic insights

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

Kuş, Nihal; Department of Physics, Anadolu University, 26470 Eskişehir; Fausto, Rui, E-mail: rfausto@ci.uc.pt

2014-12-21

E-crotonic acid was isolated in cryogenic solid N{sub 2} and xenon matrices, and subjected to Laser ultraviolet (UV) and near-infrared (NIR) irradiations. In the deposited matrices, the two low-energy cis C–O E-cc and E-ct conformers, which are the only forms significantly populated in the gas phase, were observed. UV irradiation (λ= 250 nm) of the compound in N{sub 2} matrix allows for experimental detection, not just of the two low-energy cis C–O isomers of Z-crotonic acid previously observed in the experiments carried out in argon matrix [Z-cc and Z-ct; R. Fausto, A. Kulbida, and O. Schrems, J. Chem. Soc., Faradaymore » Trans. 91, 3755–3770 (1995)] but also of the never observed before high-energy forms of both E- and Z-crotonic acids bearing the carboxylic acid group in the trans arrangement (E-tc and Z-tc conformers). In turn, NIR irradiation experiments in the N{sub 2} matrix allow to produce the high-energy E-tc trans C–O conformer in a selective way, from the initially deposited E-cc form. The vibrational signatures of all the 6 rotameric structures of the crotonic acids experimentally observed, including those of the new trans C–O forms, were determined and the individual spectra fully assigned, also with support of theoretically obtained data. On the other hand, as found before for the compound isolated in argon matrix, the experiments performed in xenon matrix failed to experimental detection of the trans C–O forms. This demonstrates that in noble gas matrices these forms are not stable long enough to allow for their observation by steady state spectroscopy techniques. In these matrices, the trans C–O forms convert spontaneously into their cis C–O counterparts, by tunnelling. Some mechanistic details of the studied processes were extracted and discussed.« less

Mendel’s law reveals fatal flaws in Bateman’s 1948 study of mating and fitness

PubMed Central

Gowaty, Patricia Adair; Kim, Yong-Kyu; Anderson, Wyatt W.

2013-01-01

Bateman’s experimental study of Drosophila melanogaster produced conclusions that are now part of the bedrock premises of modern sexual selection. Today it is the most cited experimental study in sexual selection, and famous as the first experimental demonstration of sex differences in the relationship between number of mates and relative reproductive success. We repeated the experimental methodology of the original to evaluate its reliability. The results indicate that Bateman’s methodology of visible mutations to assign parentage and reproductive success to subject adults is significantly biased. When combined in offspring, the mutations decrease offspring survival, so that counts of mate number and reproductive success are mismeasured. Bateman’s method overestimates the number of subjects with no mates and underestimates the number with one or more mates for both sexes. Here we discuss why Bateman’s paper is important and present additional analyses of data from our monogamy trials. Monogamy trials can inform inferences about the force of sexual selection in populations because in monogamy trials male–male competition and female choice are absent. Monogamy trials also would have provided Bateman with an a priori test of the fit of his data to Mendel’s laws, an unstated, but vital assumption of his methodology for assigning parentage from which he inferred the number of mates per individual subject and their reproductive success. Even under enforced monogamous mating, offspring frequencies of double mutant, single mutant and no mutant offspring were significantly different from Mendelian expectations proving that Bateman’s method was inappropriate for answering the questions he posed. Double mutant offspring (those with a mutation from each parent) suffered significant inviability as did single mutant offspring whenever they inherited their mother’s marker but the wild-type allele at their father’s marker locus. These inviability effects produced two important inaccuracies in Bateman’s results and conclusions. (1) Some matings that actually occurred were invisible and (2) reproductive success of some mothers was under-estimated. Both observations show that Bateman’s conclusions about sex differences in number of mates and reproductive success were unwarranted, based on biased observations. We speculate about why Bateman’s classic study remained without replication for so long, and we discuss why repetition almost 60 years after the original is still timely, necessary and critical to the scientific enterprise. We highlight overlooked alternative hypotheses to urge that modern tests of Bateman’s conclusions go beyond confirmatory studies to test alternative hypotheses to explain the relationship between mate number and reproductive success. PMID:23360967

Mendel's law reveals fatal flaws in Bateman's 1948 study of mating and fitness.

PubMed

Gowaty, Patricia Adair; Kim, Yong-Kyu; Anderson, Wyatt W

2013-01-01

Bateman's experimental study of Drosophila melanogaster produced conclusions that are now part of the bedrock premises of modern sexual selection. Today it is the most cited experimental study in sexual selection, and famous as the first experimental demonstration of sex differences in the relationship between number of mates and relative reproductive success. We repeated the experimental methodology of the original to evaluate its reliability. The results indicate that Bateman's methodology of visible mutations to assign parentage and reproductive success to subject adults is significantly biased. When combined in offspring, the mutations decrease offspring survival, so that counts of mate number and reproductive success are mismeasured. Bateman's method overestimates the number of subjects with no mates and underestimates the number with one or more mates for both sexes. Here we discuss why Bateman's paper is important and present additional analyses of data from our monogamy trials. Monogamy trials can inform inferences about the force of sexual selection in populations because in monogamy trials male-male competition and female choice are absent. Monogamy trials also would have provided Bateman with an a priori test of the fit of his data to Mendel's laws, an unstated, but vital assumption of his methodology for assigning parentage from which he inferred the number of mates per individual subject and their reproductive success. Even under enforced monogamous mating, offspring frequencies of double mutant, single mutant and no mutant offspring were significantly different from Mendelian expectations proving that Bateman's method was inappropriate for answering the questions he posed. Double mutant offspring (those with a mutation from each parent) suffered significant inviability as did single mutant offspring whenever they inherited their mother's marker but the wild-type allele at their father's marker locus. These inviability effects produced two important inaccuracies in Bateman's results and conclusions. (1) Some matings that actually occurred were invisible and (2) reproductive success of some mothers was under-estimated. Both observations show that Bateman's conclusions about sex differences in number of mates and reproductive success were unwarranted, based on biased observations. We speculate about why Bateman's classic study remained without replication for so long, and we discuss why repetition almost 60 years after the original is still timely, necessary and critical to the scientific enterprise. We highlight overlooked alternative hypotheses to urge that modern tests of Bateman's conclusions go beyond confirmatory studies to test alternative hypotheses to explain the relationship between mate number and reproductive success.

Pollinator-Mediated Selection on Flower Color, Flower Scent and Flower Morphology of Hemerocallis: Evidence from Genotyping Individual Pollen Grains On the Stigma

PubMed Central

Hirota, Shun K.; Nitta, Kozue; Suyama, Yoshihisa; Kawakubo, Nobumitsu; Yasumoto, Akiko A.; Yahara, Tetsukazu

2013-01-01

To trace the fate of individual pollen grains through pollination processes, we determined genotypes of single pollen grains deposited on Hemerocallis stigmas in an experimental mixed-species array. Hemerocallis fulva, pollinated by butterflies, has diurnal, reddish and unscented flowers, and H. citrina, pollinated by hawkmoths, has nocturnal, yellowish and sweet scent flowers. We observed pollinator visits to an experimental array of 24 H. fulva and 12 F2 hybrids between the two species (H. fulva and H. citrina) and collected stigmas after every trip bout of swallowtail butterflies or hawkmoths. We then measured selection by swallowtail butterflies or hawkmoths through male and female components of pollination success as determined by single pollen genotyping. As expected, swallowtail butterflies imposed selection on reddish color and weak scent: the number of outcross pollen grains acquired is a quadratic function of flower color with the maximum at reddish color, and the combined pollination success was maximal at weak scent (almost unrecognizable for human). This explains why H. fulva, with reddish flowers and no recognizable scent, is mainly pollinated by swallowtail butterflies. However, we found no evidence of hawkmoths-mediated selection on flower color or scent. Our findings do not support a hypothesis that yellow flower color and strong scent intensity, the distinctive floral characteristics of H. citrina, having evolved in adaptations to hawkmoths. We suggest that the key trait that triggers the evolution of nocturnal flowers is flowering time rather than flower color and scent. PMID:24376890

P/Q-type calcium channel modulators

PubMed Central

Nimmrich, V; Gross, G

2012-01-01

P/Q-type calcium channels are high-voltage-gated calcium channels contributing to vesicle release at synaptic terminals. A number of neurological diseases have been attributed to malfunctioning of P/Q channels, including ataxia, migraine and Alzheimer's disease. To date, only two specific P/Q-type blockers are known: both are peptides deriving from the spider venom of Agelenopsis aperta, ω-agatoxins. Other peptidic calcium channel blockers with activity at P/Q channels are available, albeit with less selectivity. A number of low molecular weight compounds modulate P/Q-type currents with different characteristics, and some exhibit a peculiar bidirectional pattern of modulation. Interestingly, there are a number of therapeutics in clinical use, which also show P/Q channel activity. Because selectivity as well as the exact mode of action is different between all P/Q-type channel modulators, the interpretation of clinical and experimental data is complicated and needs a comprehensive understanding of their target profile. The situation is further complicated by the fact that information on potency varies vastly in the literature, which may be the result of different experimental systems, conditions or the splice variants of the P/Q channel. This review attempts to provide a comprehensive overview of the compounds available that affect the P/Q-type channel and should help with the interpretation of results of in vitro experiments and animal models. It also aims to explain some clinical observations by implementing current knowledge about P/Q channel modulation of therapeutically used non-selective drugs. Chances and challenges of the development of P/Q channel-selective molecules are discussed. PMID:22670568

Investigation of heavy-metal accumulation in selected plant samples using laser induced breakdown spectroscopy and laser ablation inductively coupled plasma mass spectrometry

NASA Astrophysics Data System (ADS)

Galiová, M.; Kaiser, J.; Novotný, K.; Novotný, J.; Vaculovič, T.; Liška, M.; Malina, R.; Stejskal, K.; Adam, V.; Kizek, R.

2008-12-01

Single-pulse Laser-Induced Breakdown Spectroscopy (LIBS) and Laser-Ablation Inductively Coupled Plasma Mass-Spectrometry (LA-ICP-MS) were applied for mapping the silver and copper distribution in Helianthus Annuus L. samples treated with contaminant in controlled conditions. For Ag and Cu detection the 328.07 nm Ag(I) and 324.75 nm Cu(I) lines were used, respectively. The LIBS experimental conditions (mainly the laser energy and the observation window) were optimized in order to avoid self-absorption effect in the measured spectra. In the LA-ICP-MS analysis the Ag 107 and Cu 63 isotopes were detected. The capability of these two analytical techniques for high-resolution mapping of selected trace chemical elements was demonstrated.

Semantic Ambiguity: Do Multiple Meanings Inhibit or Facilitate Word Recognition?

PubMed

Haro, Juan; Ferré, Pilar

2018-06-01

It is not clear whether multiple unrelated meanings inhibit or facilitate word recognition. Some studies have found a disadvantage for words having multiple meanings with respect to unambiguous words in lexical decision tasks (LDT), whereas several others have shown a facilitation for such words. In the present study, we argue that these inconsistent findings may be due to the approach employed to select ambiguous words across studies. To address this issue, we conducted three LDT experiments in which we varied the measure used to classify ambiguous and unambiguous words. The results suggest that multiple unrelated meanings facilitate word recognition. In addition, we observed that the approach employed to select ambiguous words may affect the pattern of experimental results. This evidence has relevant implications for theoretical accounts of ambiguous words processing and representation.

Interval sampling methods and measurement error: a computer simulation.

PubMed

Wirth, Oliver; Slaven, James; Taylor, Matthew A

2014-01-01

A simulation study was conducted to provide a more thorough account of measurement error associated with interval sampling methods. A computer program simulated the application of momentary time sampling, partial-interval recording, and whole-interval recording methods on target events randomly distributed across an observation period. The simulation yielded measures of error for multiple combinations of observation period, interval duration, event duration, and cumulative event duration. The simulations were conducted up to 100 times to yield measures of error variability. Although the present simulation confirmed some previously reported characteristics of interval sampling methods, it also revealed many new findings that pertain to each method's inherent strengths and weaknesses. The analysis and resulting error tables can help guide the selection of the most appropriate sampling method for observation-based behavioral assessments. © Society for the Experimental Analysis of Behavior.

Review of research designs and statistical methods employed in dental postgraduate dissertations.

PubMed

Shirahatti, Ravi V; Hegde-Shetiya, Sahana

2015-01-01

There is a need to evaluate the quality of postgraduate dissertations of dentistry submitted to university in the light of the international standards of reporting. We conducted the review with an objective to document the use of sampling methods, measurement standardization, blinding, methods to eliminate bias, appropriate use of statistical tests, appropriate use of data presentation in postgraduate dental research and suggest and recommend modifications. The public access database of the dissertations from Rajiv Gandhi University of Health Sciences was reviewed. Three hundred and thirty-three eligible dissertations underwent preliminary evaluation followed by detailed evaluation of 10% of randomly selected dissertations. The dissertations were assessed based on international reporting guidelines such as strengthening the reporting of observational studies in epidemiology (STROBE), consolidated standards of reporting trials (CONSORT), and other scholarly resources. The data were compiled using MS Excel and SPSS 10.0. Numbers and percentages were used for describing the data. The "in vitro" studies were the most common type of research (39%), followed by observational (32%) and experimental studies (29%). The disciplines conservative dentistry (92%) and prosthodontics (75%) reported high numbers of in vitro research. Disciplines oral surgery (80%) and periodontics (67%) had conducted experimental studies as a major share of their research. Lacunae in the studies included observational studies not following random sampling (70%), experimental studies not following random allocation (75%), not mentioning about blinding, confounding variables and calibrations in measurements, misrepresenting the data by inappropriate data presentation, errors in reporting probability values and not reporting confidence intervals. Few studies showed grossly inappropriate choice of statistical tests and many studies needed additional tests. Overall observations indicated the need to comply with standard guidelines of reporting research.

[RECONSTRUCTION OF LOWER EXTREMITY FUNCTION OF COMPLETE SPINAL CORD INJURY RATS BY FIRST NEURON CONNECTION].

PubMed

Wang, Fangyong; Yuan, Yuan; Li, Jianjun

2015-12-01

To investigate the effects of the first neuron connection for the reconstruction of lower extremity function of complete spinal cord injury rats. Forty adult female Sprague Dawley rats of 300-350 g in weight were selected to prepare the models of L₁ transverse spinal cord injury. After 2 weeks of establishing model, the rats were randomly divided into control group (n = 20) and experimental group (n = 20). In the experimental group, the right hind limb function was reconstructed directly by the first neuron; in the control group, the other treatments were the same to the experimental group except that the distal tibial nerve and the proximal femoral nerve were not sutured. The recovery of motor function of lower extremity was observed by the Basso-Beattie-Bresnahan (BBB) scoring system on bilateral hind limbs at 7, 30, 50, and 70 days after operation. The changes of the spinal cord were observed by HE staining, neurofilament 200 immunohistochemistry staining, and the technique of horseradish peroxidase (HRP) tracing. After establishing models, 6 rats died. The right hind limb had no obvious recovery of the motor function, with the BBB score of 0 in 2 groups; the left hind limb motor function was recovered in different degrees, and there was no significant difference in BBB score between 2 groups (P > 0.05). In the experimental group, HE staining showed that the spinal cord was reconstructed with the sciatic nerve, which was embedded in the spinal cord, and the sciatic nerve membrane was clearly identified, and there was no obvious atrophy in the connecting part of the spinal cord. In the experimental group, the expression of nerve fiber was stained with immunohistochemistry, and the axons of the spinal cord were positively by stained and the peripheral nerve was connected with the spinal cord. HRP labelled synapses were detected by HRP retrograde tracing in the experimental group, while there was no HRP labelled synapse in the control group. Direct reconstruction of the first neurons is sufficient in the regeneration of corresponding neural circuit by the growth of residual axon; but the motor function recovery of the target muscles innervated by peripheral nerve is not observed.

Learning Contrast-Invariant Cancellation of Redundant Signals in Neural Systems

PubMed Central

Bol, Kieran; Maler, Leonard; Longtin, André

2013-01-01

Cancellation of redundant information is a highly desirable feature of sensory systems, since it would potentially lead to a more efficient detection of novel information. However, biologically plausible mechanisms responsible for such selective cancellation, and especially those robust to realistic variations in the intensity of the redundant signals, are mostly unknown. In this work, we study, via in vivo experimental recordings and computational models, the behavior of a cerebellar-like circuit in the weakly electric fish which is known to perform cancellation of redundant stimuli. We experimentally observe contrast invariance in the cancellation of spatially and temporally redundant stimuli in such a system. Our model, which incorporates heterogeneously-delayed feedback, bursting dynamics and burst-induced STDP, is in agreement with our in vivo observations. In addition, the model gives insight on the activity of granule cells and parallel fibers involved in the feedback pathway, and provides a strong prediction on the parallel fiber potentiation time scale. Finally, our model predicts the existence of an optimal learning contrast around 15% contrast levels, which are commonly experienced by interacting fish. PMID:24068898

Theoretical Investigations into Defected Graphene for Electrochemical Reduction of CO 2

DOE PAGES

Siahrostami, Samira; Jiang, Kun; Karamad, Mohammadreza; ...

2017-10-10

Here, despite numerous experimental efforts that have been dedicated to studying carbon-based materials for electrochemical reduction of CO 2, a rationalization of the associated trends in the intrinsic activity of different active motifs has so far been elusive. In the present work, we employ density functional theory calculations to examine a variety of different active sites in N-doped graphene to give a comprehensive outline of the trends in activity. We find that adsorption energies of COOH* and CO* do not follow the linear scaling relationships observed for the pure transition metals, and this unique scaling is rationalized through differences inmore » electronic structure between transition metals and defected graphene. This finding rationalizes most of the experimental observations on the carbon-based materials which present promising catalysts for the two-electron reduction of CO 2 to CO. With this simple thermodynamic analysis, we identify several active sites that are expected to exhibit a comparable or even better activity to the state-of-the-art gold catalyst, and several configurations are suggested to be selective for CO 2RR over HER.« less

Doppler-free satellites of resonances of electromagnetically induced transparency and absorption on the D 2 lines of alkali metals

NASA Astrophysics Data System (ADS)

Sargsyan, A.; Sarkisyan, D.; Staedter, D.; Akulshin, A. M.

2006-11-01

The peculiarities of intra-Doppler structures that are observed in the atomic absorption spectrum of alkali metals with the help of two independent lasers have been studied. These structures accompany ultranarrow coherent resonances of electromagnetically induced transparency and absorption. With the D 2 line of rubidium taken as an example, it is shown that, in the scheme of unidirectional waves, the maximum number of satellite resonances caused by optical pumping selective with respect to the atomic velocity is equal to seven, while only six resonances are observed in the traditional scheme of saturated absorption with counterpropagating waves of the same frequency. The spectral position of the resonances and their polarity depend on the frequency of the saturating radiation, while their number and relative amplitude depend also on the experimental geometry. These features are of general character and should show themselves in the absorption spectrum on the D 2 lines of all alkali metals. An explanation of these features is given. The calculated spectral separations between the resonances are compared to the experimental ones, and their possible application is discussed.

Deformation behavior of HCP titanium alloy: Experiment and Crystal plasticity modeling

DOE PAGES

Wronski, M.; Arul Kumar, Mariyappan; Capolungo, Laurent; ...

2018-03-02

The deformation behavior of commercially pure titanium is studied using experiments and a crystal plasticity model. Compression tests along the rolling, transverse, and normal-directions, and tensile tests along the rolling and transverse directions are performed at room temperature to study the activation of slip and twinning in the hexagonal closed packed titanium. A detailed EBSD based statistical analysis of the microstructure is performed to develop statistics of both {10-12} tensile and {11-22} compression twins. A simple Monte Carlo (MC) twin variant selection criterion is proposed within the framework of the visco-plastic self-consistent (VPSC) model with a dislocation density (DD) basedmore » law used to describe dislocation hardening. In the model, plasticity is accommodated by prismatic, basal and pyramidal slip modes, and {10-12} tensile and {11-22} compression twinning modes. Thus, the VPSC-MC model successfully captures the experimentally observed activation of low Schmid factor twin variants for both tensile and compression twins modes. The model also predicts macroscopic stress-strain response, texture evolution and twin volume fraction that are in agreement with experimental observations.« less

Deformation behavior of HCP titanium alloy: Experiment and Crystal plasticity modeling

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

Wronski, M.; Arul Kumar, Mariyappan; Capolungo, Laurent

The deformation behavior of commercially pure titanium is studied using experiments and a crystal plasticity model. Compression tests along the rolling, transverse, and normal-directions, and tensile tests along the rolling and transverse directions are performed at room temperature to study the activation of slip and twinning in the hexagonal closed packed titanium. A detailed EBSD based statistical analysis of the microstructure is performed to develop statistics of both {10-12} tensile and {11-22} compression twins. A simple Monte Carlo (MC) twin variant selection criterion is proposed within the framework of the visco-plastic self-consistent (VPSC) model with a dislocation density (DD) basedmore » law used to describe dislocation hardening. In the model, plasticity is accommodated by prismatic, basal and pyramidal slip modes, and {10-12} tensile and {11-22} compression twinning modes. Thus, the VPSC-MC model successfully captures the experimentally observed activation of low Schmid factor twin variants for both tensile and compression twins modes. The model also predicts macroscopic stress-strain response, texture evolution and twin volume fraction that are in agreement with experimental observations.« less

Selective C-O Hydrogenolysis and Decarboxylation of Biomass-Derived Heterocyclic Compounds over Heterogeneous Catalysts

NASA Astrophysics Data System (ADS)

Chia, Mei

The catalytic deoxygenation of biomass-derived compounds through selective C-O hydrogenolysis, catalytic transfer hydrogenation and lactonization, and decarboxylation to value-added chemicals over heterogeneous catalysts was examined under liquid phase reaction conditions. The reactions studied involve the conversion or production of heterocyclic compounds, specifically, cyclic ethers, lactones, and 2-pyrones. A bimetallic RhRe/C catalyst was found to be selective for the hydrogenolysis of secondary C-O bonds for a broad range cyclic ethers and polyols. Results from experimentally-observed reactivity trends, NH3 temperature-programmed desorption, fructose dehydration reaction studies, and first-principles density functional theory (DFT) calculations are consistent with the hypothesis of a bifunctional catalyst which facilitates acid-catalyzed ring-opening and dehydration coupled with metal-catalyzed hydrogenation. C-O hydrogenolysis and fructose dehydration activities were observed to decrease with an increase in reduction temperature and a decrease in the number of surface metallic Re atoms measured by in situ X-ray absorption spectroscopy. No C-O hydrogenolysis activity was detected over RhRe/C under water-free conditions. The activation of water molecules by Re atoms on the surface of metallic Rh is suggested to result in the formation of Bronsted acidity over RhRe/C. The catalytic transfer hydrogenation and lactonization of levulinic acid and its esters to gamma-valerolactone was accomplished through the Meerwein-Ponndorf-Verley reaction over metal oxide catalysts using secondary alcohols as the hydrogen donor. ZrO2 was a highly active material for CTH under batch and continuous flow reaction conditions; the initial activity of the catalyst was repeatedly regenerable by calcination in air, with no observable loss in catalytic activity. Lastly, the 2-pyrone, triacetic acid lactone, is shown to be a promising biorenewable platform chemical from which a wide range of chemical intermediates and end products can be obtained using heterogeneous catalysts or by thermal decomposition. Mechanistic insights from experimentally-observed reactivity trends and results from DFT calculations indicate that 2-pyrones undergo reactions unique to their structure such as keto-enol tautomerization, retro Diels-Alder, and nucleophilic attack by water. Ring-opening and decarboxylation reactions were found to be governed by key structural features such as the degree of saturation in the ring (e.g., C4=C5 bond), nature of the solvent, and presence of an acid catalyst.

The Effects of Total Physical Response by Storytelling and the Traditional Teaching Styles of a Foreign Language in a Selected High School

ERIC Educational Resources Information Center

Kariuki, Patrick N. K.; Bush, Elizabeth Danielle

2008-01-01

The purpose of this study was to examine the effects of Total Physical Response by Storytelling and the traditional teaching method on a foreign language in a selected high school. The sample consisted of 30 students who were randomly selected and randomly assigned to experimental and control group. The experimental group was taught using Total…

Effect of Selectively Etched Ferroelectric Thin-Film Layer on the Performance of a Tunable Bandpass Filter

NASA Technical Reports Server (NTRS)

Subramanyam, Guru; Vignesparamoorthy, Sivaruban; Mueller, Carl; VanKeuls, Fred; Warner, Joseph; Miranda, Felix A.

2001-01-01

The main purpose of this work is to study the effect of a selectively etched ferroelectric thin film layer on the performance of an electrically tunable filter. An X-band tunable filter was designed, fabricated and tested on a selectively etched Barium Strontium Titanate (BSTO) ferroelectric thin film layer. Tunable filters with varying lengths of BSTO thin-film in the input and output coupling gaps were modeled, as well as experimentally tested. Experimental results showed that filters with coupling gaps partially filled with BSTO maintained frequency tunability and improved the insertion loss by approx. 2dB. To the best of our knowledge, these results represent the first experimental demonstration of the advantages of selective etching in the performance of thin film ferroelectric-based tunable microwave components.

Low complexity adaptive equalizers for underwater acoustic communications

NASA Astrophysics Data System (ADS)

Soflaei, Masoumeh; Azmi, Paeiz

2014-08-01

Interference signals due to scattering from surface and reflecting from bottom is one of the most important problems of reliable communications in shallow water channels. To solve this problem, one of the best suggested ways is to use adaptive equalizers. Convergence rate and misadjustment error in adaptive algorithms play important roles in adaptive equalizer performance. In this paper, affine projection algorithm (APA), selective regressor APA(SR-APA), family of selective partial update (SPU) algorithms, family of set-membership (SM) algorithms and selective partial update selective regressor APA (SPU-SR-APA) are compared with conventional algorithms such as the least mean square (LMS) in underwater acoustic communications. We apply experimental data from the Strait of Hormuz for demonstrating the efficiency of the proposed methods over shallow water channel. We observe that the values of the steady-state mean square error (MSE) of SR-APA, SPU-APA, SPU-normalized least mean square (SPU-NLMS), SPU-SR-APA, SM-APA and SM-NLMS algorithms decrease in comparison with the LMS algorithm. Also these algorithms have better convergence rates than LMS type algorithm.

An Analysis of the Mode of Gene Action Affecting Pupa Weight in TRIBOLIUM CASTANEUM

PubMed Central

Goodwill, R.

1975-01-01

Triple-testcross experiments (Kearsey and Jinks 1968) were employed to investigate the mode of gene action affecting pupa weight in Tribolium castaneum. Their experimental design involves two inbred lines, the F1 progeny and a segregating population derived from the cross of the inbred lines. In the present experiments, four segregating populations were used. These populations included the F2 generation, a select line (SEL) and two relaxed select lines (RSI and RSII). In addition, all possible reciprocal crosses were made among the RSI, RSII, and SEL populations. It was observed that: (1) additive, dominant and epistatic gene effects all made significant contributions to the pupa weight of the progeny from all four segregating populations; (2) there was no evidence of either accumulation of epistasis as a result of selection in the SEL population or decline in epistasis as a result of removing selection pressure from the RSI and RSII populations; and (3) significant negative heterosis and maternal effects contributed to the pupa weight of the crossbred progeny of the RSI, RSII and SEL populations. PMID:1132679

Mechanisms of selective antitumor action of cold atmospheric plasma

NASA Astrophysics Data System (ADS)

Graves, David; Bauer, Georg

2016-09-01

Transformed (precancerous) cells are known to be subject to elimination through intercellular RONS-dependent apoptosis-inducing signaling. It is a remarkable fact that the chemical species utilized by apoptosis induction in transformed cells are essentially identical to chemical species created by cold atmospheric plasma (CAP) in aqueous solutions. The association between CAP-induced biochemistry and natural cell anti-tumor mechanisms offers the opportunity to establish a rationale for the observed successes of CAP in selectively eliminating tumor cells in vitro and in vivo. In particular, 1O2 appears to act to selectively induce apoptosis in tumor cells, and can also result in self-perpetuating, cell-to-cell apoptotic signaling. Various CAP-generated liquid phase species can react to form 1O2, thus providing a hypothetical mechanism to explain how CAP can trigger therapeutic apoptosis in tumors. The analysis of model experiments performed with defined RONS in vitro implies that CAP-derived 1O2 induces the mechanism through which CAP acts selectively against cancer cells in vitro and tumors in vivo. This hypothesis needs to be tested experimentally in order to establish its validity.

Impaired auditory temporal selectivity in the inferior colliculus of aged Mongolian gerbils.

PubMed

Khouri, Leila; Lesica, Nicholas A; Grothe, Benedikt

2011-07-06

Aged humans show severe difficulties in temporal auditory processing tasks (e.g., speech recognition in noise, low-frequency sound localization, gap detection). A degradation of auditory function with age is also evident in experimental animals. To investigate age-related changes in temporal processing, we compared extracellular responses to temporally variable pulse trains and human speech in the inferior colliculus of young adult (3 month) and aged (3 years) Mongolian gerbils. We observed a significant decrease of selectivity to the pulse trains in neuronal responses from aged animals. This decrease in selectivity led, on the population level, to an increase in signal correlations and therefore a decrease in heterogeneity of temporal receptive fields and a decreased efficiency in encoding of speech signals. A decrease in selectivity to temporal modulations is consistent with a downregulation of the inhibitory transmitter system in aged animals. These alterations in temporal processing could underlie declines in the aging auditory system, which are unrelated to peripheral hearing loss. These declines cannot be compensated by traditional hearing aids (that rely on amplification of sound) but may rather require pharmacological treatment.

Animal evolution during domestication: the domesticated fox as a model

PubMed Central

Trut, Lyudmila; Oskina, Irina; Kharlamova, Anastasiya

2009-01-01

Summary We review the evolution of domestic animals, emphasizing the effect of the earliest steps of domestication on its course. Using the first domesticated species, the dog (Canis familiaris) as an illustration, we describe the evolutionary specificities of the historical domestication, such as the high level and wide range of diversity. We suggest that the process of earliest domestication via unconscious and later conscious selection of human-defined behavioral traits may accelerate phenotypic variations. The review is based on the results of the long-term experiment designed to reproduce early mammalian domestication in the silver fox (Vulpes vulpes) selected for tameability, or amenability to domestication. We describe changes in behavior, morphology and physiology that appeared in the fox during its selection for tameability and that were similar to those observed in the domestic dog. Based on the experimental fox data and survey of relevant data, we discuss the developmental, genetic and possible molecular-genetic mechanisms of these changes. We assign the causative role in evolutionary transformation of domestic animals to selection for behavior and to the neurospecific regulatory genes it affects. PMID:19260016

Flow-assisted single-beam optothermal manipulation of microparticles.

PubMed

Liu, Yangyang; Poon, Andrew W

2010-08-16

An optothermal tweezer was developed with a single-beam laser at 1550 nm for manipulation of colloidal microparticles. Strong absorption in water can thermally induce a localized flow, which exerts a Stokes' drag on the particles that complements the gradient force. Long-range capturing of 6 microm polystyrene particles over approximately 176 microm was observed with a tweezing power of approximately 7 mW. Transportation and levitation, targeted deposition and selective levitation of particles were explored to experimentally demonstrate the versatility of the optothermal tweezer as a multipurpose particle manipulation tool.

Atomistic insight into the adsorption site selectivity of stepped Au(111) surfaces

NASA Astrophysics Data System (ADS)

Gaspari, Roberto; Pignedoli, Carlo A.; Fasel, Roman; Treier, Matthias; Passerone, Daniele

2010-07-01

Using classical and ab initio simulations, we study the interplay between the Au(111) surface reconstruction and monoatomic steps on a vicinal face. The experimentally observed discommensuration line patterns on a specific vicinal are reproduced and explained, and a complete description of the structure is given. An unusual atomic arrangement is shown to be responsible for the lower reactivity of hcp segments of step edges compared to the one of fcc segments. Our results provide an unprecedented understanding of the electronic and geometric properties of the complex Au(111) surface.

Discovery of a meta-stable Al-Sm phase with unknown stoichiometry using a genetic algorithm

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

Zhang, Feng; McBrearty, Ian; Ott, R. T.

Unknown crystalline phases observed during the devitrification process of glassy metal alloys significantly limit our ability to understand and control phase selection in these systems driven far from equilibrium. Here, we report a new meta-stable Al 5Sm phase identified by simultaneously searching Al-rich compositions of the Al–Sm system, using an efficient genetic algorithm. The excellent match between calculated and experimental X-ray diffraction patterns confirms that this new phase appeared in the crystallization of melt-spun Al 90Sm 10 alloys.

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

Kononov, A.; Egorov, S. V.; Kvon, Z. D.

We experimentally investigate spin-polarized electron transport between a permalloy ferromagnet and the edge of a two-dimensional electron system with band inversion, realized in a narrow, 8 nm wide, HgTe quantum well. In zero magnetic field, we observe strong asymmetry of the edge potential distribution with respect to the ferromagnetic ground lead. This result indicates that the helical edge channel, specific for the structures with band inversion even at the conductive bulk, is strongly coupled to the ferromagnetic side contact, possibly due to the effects of proximity magnetization. This allows selective and spin-sensitive contacting of helical edge states.

Magnetic equivalence of terminal nuclei in the azide anion broken by nuclear spin relaxation

NASA Astrophysics Data System (ADS)

Bernatowicz, P.; Szymański, S.

NMR spectra of water solution of sodium azide selectively 15N labelled in the central position were studied using an iterative least-squares method. In agreement with predictions based on Bloch-Wangsness-Redfield nuclear spin relaxation theory, it is demonstrated that quadrupolar relaxation of the magnetically equivalent terminal 14N (spin-1) nuclei in the azide anion renders the J coupling between these nuclei an observable quantity. In isotropic fluids, this seems to be the first experimental evidence of relaxation-broken magnetic equivalence symmetry.

Radiometric evaluation of diglycolamide resins for the chromatographic separation of actinium from fission product lanthanides

DOE PAGES

Radchenko, Valery; Mastren, Tara; Meyer, Catherine A. L.; ...

2017-07-20

Actinium-225 is a potential Targeted Alpha Therapy (TAT) isotope. It can be generated with high energy (≥ 100 MeV) proton irradiation of thorium targets. The main challenge in the chemical recovery of 225Ac lies in the separation from thorium and many fission by-products most importantly radiolanthanides. We recently developed a separation strategy based on a combination of cation exchange and extraction chromatography to isolate and purify 225Ac. In this study, actinium and lanthanide equilibrium distribution coefficients and column elution behavior for both TODGA (N,N,N',N'-tetra- n-octyldiglycolamide) and TEHDGA (N,N,N',N'-tetrakis-2-ethylhexyldiglycolamide) were determined. Density functional theory (DFT) calculations were performed and were inmore » agreement with experimental observations providing the foundation for understanding of the selectivity for Ac and lanthanides on different DGA (diglycolamide) based resins. The results of Gibbs energy (ΔG aq) calculations confirm significantly higher selectivity of DGA based resins for Ln III over Ac III in the presence of nitrate. As a result, DFT calculations and experimental results reveal that Ac chemistry cannot be predicted from lanthanide behavior under comparable circumstances.« less

Comparative Study of Lunar Roughness from Multi - Source Data

NASA Astrophysics Data System (ADS)

Lou, Y.; Kang, Z.

2017-07-01

The lunar terrain can show its collision and volcanic history. The lunar surface roughness can give a deep indication of the effects of lunar surface magma, sedimentation and uplift. This paper aims to get different information from the roughness through different data sources. Besides introducing the classical Root-mean-square height method and Morphological Surface Roughness (MSR) algorithm, this paper takes the area of the Jurassic mountain uplift in the Sinus Iridum and the Plato Crater area as experimental areas. And then make the comparison and contrast of the lunar roughness derived from LRO's DEM and CE-2 DOM. The experimental results show that the roughness obtained by the traditional roughness calculation method reflect the ups and downs of the topography, while the results obtained by morphological surface roughness algorithm show the smoothness of the lunar surface. So, we can first use the surface fluctuation situation derived from RMSH to select the landing area range which ensures the lands are gentle. Then the morphological results determine whether the landing area is suitable for the detector walking and observing. The results obtained at two different scales provide a more complete evaluation system for selecting the landing site of the lunar probe.

A study of marine pollution caused by the release of metals into seawater following acid spills.

PubMed

Cabon, Jean-Yves; Giamarchi, Philippe; Le Floch, Stephane

2010-07-01

This study examined the potential metal pollution induced by the accidental spill of different acids into seawater. The acids sink to the bottom according to their densities and subsequently react with marine sediments. The acids selected for this study were acetic, hydrochloric, nitric, sulfuric, and phosphoric acids; the metallic elements selected were Cr, Cu, Fe, Mn, Pb and Zn. The sediment was collected in Brest Harbour. The percentages of metals released from this sediment in the presence of various concentrations of acids in seawater were important; concentrations of approximately 7 mg L(-1) for Mn and 60 mg L(-1) for Zn were observed under our experimental conditions. We also examined the rate of release of these metals from the sediment into the seawater in the presence of the different acids and under different experimental conditions. We found that most of the metallic elements were released from the sediments into the seawater during the first fifteen minutes of exposure. After this time, a high degree of pollution was induced if acids leached into seawater were not rapidly diluted. Copyright 2010 Elsevier Ltd. All rights reserved.

PSYCHIATRIC MORBIDITY AND PERSONALITY PROFILE IN DIVORCE SEEKING COUPLES

PubMed Central

Batra, Lalit; Gautam, Shiv

1995-01-01

To what extent psychiatric morbidity and personality factors contribute to marital disharmony and decision to divorce is still an unanswered question in Indian setting. This study was undertaken with aims to find out (1) the prevalence of psychiatric morbidity in persons seeking divorce; (2) the prevalence of psychiatric morbidity in persons who had good marital adjustment; (3) the nature of psychiatric morbidity observed in these subjects, and (4) the personality profile of these subjects. Fifty randomly selected divorce seeking couples (n=100) from the matrimonial court of Jaipur City and thirty couples with good marital adjustment (n=60) selected from the community were studied. Probable psychiatric cases identified by administering GHQ (Hindi version) were diagnosed according to ICD-10 and personality profile of all cases was studied by using 16 PF. High psychiatric morbidity (50%) was found among divorce seeking couples in comparison to control group (13%). There was a high prevalence of neurone disorders (22%) and mood disorders (16%) in experimental group. Schizophrenia and related disorders (10%) and substance abuse disorder (2%) were seen only in the experimental group. Specific personality factors related to divorce seeking individuals and persons with stable marriage have been identified. The implications of this study are highlighted. PMID:21743746

Natural history collections as windows on evolutionary processes.

PubMed

Holmes, Michael W; Hammond, Talisin T; Wogan, Guinevere O U; Walsh, Rachel E; LaBarbera, Katie; Wommack, Elizabeth A; Martins, Felipe M; Crawford, Jeremy C; Mack, Katya L; Bloch, Luke M; Nachman, Michael W

2016-02-01

Natural history collections provide an immense record of biodiversity on Earth. These repositories have traditionally been used to address fundamental questions in biogeography, systematics and conservation. However, they also hold the potential for studying evolution directly. While some of the best direct observations of evolution have come from long-term field studies or from experimental studies in the laboratory, natural history collections are providing new insights into evolutionary change in natural populations. By comparing phenotypic and genotypic changes in populations through time, natural history collections provide a window into evolutionary processes. Recent studies utilizing this approach have revealed some dramatic instances of phenotypic change over short timescales in response to presumably strong selective pressures. In some instances, evolutionary change can be paired with environmental change, providing a context for potential selective forces. Moreover, in a few cases, the genetic basis of phenotypic change is well understood, allowing for insight into adaptive change at multiple levels. These kinds of studies open the door to a wide range of previously intractable questions by enabling the study of evolution through time, analogous to experimental studies in the laboratory, but amenable to a diversity of species over longer timescales in natural populations. © 2016 John Wiley & Sons Ltd.

Electronic structure and orientation relationship of Li nanoclusters embedded in MgO studied by depth-selective positron annihilation two-dimensional angular correlation

NASA Astrophysics Data System (ADS)

Falub, C. V.; Mijnarends, P. E.; Eijt, S. W.; van Huis, M. A.; van Veen, A.; Schut, H.

2002-08-01

Quantum-confined positrons are sensitive probes for determining the electronic structure of nanoclusters embedded in materials. In this work, a depth-selective positron annihilation 2D-ACAR (two-dimensional angular correlation of annihilation radiation) method is used to determine the electronic structure of Li nanoclusters formed by implantation of 1016-cm-2 30-keV 6Li ions in MgO (100) and (110) crystals and by subsequent annealing at 950 K. Owing to the difference between the positron affinities of lithium and MgO, the Li nanoclusters act as quantum dots for positrons. 2D-ACAR distributions for different projections reveal a semicoherent fitting of the embedded metallic Li nanoclusters to the host MgO lattice. Ab initio Korringa-Kohn-Rostoker calculations of the momentum density show that the anisotropies of the experimental distributions are consistent with an fcc crystal structure of the Li nanoclusters. The observed reduction of the width of the experimental 2D-ACAR distribution is attributed to positron trapping in vacancies associated with Li clusters. This work proposes a method for studying the electronic structure of metallic quantum dots embedded in an insulating material.

Radiometric evaluation of diglycolamide resins for the chromatographic separation of actinium from fission product lanthanides

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

Radchenko, Valery; Mastren, Tara; Meyer, Catherine A. L.

Actinium-225 is a potential Targeted Alpha Therapy (TAT) isotope. It can be generated with high energy (≥ 100 MeV) proton irradiation of thorium targets. The main challenge in the chemical recovery of 225Ac lies in the separation from thorium and many fission by-products most importantly radiolanthanides. We recently developed a separation strategy based on a combination of cation exchange and extraction chromatography to isolate and purify 225Ac. In this study, actinium and lanthanide equilibrium distribution coefficients and column elution behavior for both TODGA (N,N,N',N'-tetra- n-octyldiglycolamide) and TEHDGA (N,N,N',N'-tetrakis-2-ethylhexyldiglycolamide) were determined. Density functional theory (DFT) calculations were performed and were inmore » agreement with experimental observations providing the foundation for understanding of the selectivity for Ac and lanthanides on different DGA (diglycolamide) based resins. The results of Gibbs energy (ΔG aq) calculations confirm significantly higher selectivity of DGA based resins for Ln III over Ac III in the presence of nitrate. As a result, DFT calculations and experimental results reveal that Ac chemistry cannot be predicted from lanthanide behavior under comparable circumstances.« less

Natural history collections as windows on evolutionary processes

PubMed Central

Holmes, Michael W.; Hammond, Talisin T.; Wogan, Guinevere O.U.; Walsh, Rachel E.; LaBarbera, Katie; Wommack, Elizabeth A.; Martins, Felipe M.; Crawford, Jeremy C.; Mack, Katya L.; Bloch, Luke M.; Nachman, Michael W.

2016-01-01

Natural history collections provide an immense record of biodiversity on Earth. These repositories have traditionally been used to address fundamental questions in biogeography, systematics, and conservation. However, they also hold the potential for studying evolution directly. While some of the best direct observations of evolution have come from long-term field studies or from experimental studies in the lab, natural history collections are providing new insights into evolutionary change in natural populations. By comparing phenotypic and genotypic changes in populations through time, natural history collections provide a window into evolutionary processes. Recent studies utilizing this approach have revealed some dramatic instances of phenotypic change over short time scales in response to presumably strong selective pressures. In some instances evolutionary change can be paired with environmental change, providing a context for potential selective forces. Moreover, in a few cases, the genetic basis of phenotypic change is well understood, allowing for insight into adaptive change at multiple levels. These kinds of studies open the door to a wide range of previously intractable questions by enabling the study of evolution through time, analogous to experimental studies in the laboratory, but amenable to a diversity of species over longer timescales in natural populations. PMID:26757135

Rejection or selection: influence of framing in investment decisions.

PubMed

Cheng, Pi-Yueh; Chiou, Wen-Bin

2010-02-01

According to prospect theory, reflection effects result in preferences for risk-averse choices in gain situations and risk-seeking choices in loss situations. However, relevant literature in regard to decision making has suggested that positive information receives more weight in a selection task, whereas negative information receives more weight in a rejection task. The present study examined whether the nature of a decision task (selection vs rejection) would moderate the reflection effects. Undergraduates (47 men, 49 women; M age = 20.5 yr., SD = 1.1), selected according to specific screening criteria, participated in an experimental study. Typical reflection effects were observed in both selection and rejection task conditions. More importantly, negative information (i.e., the information about probable loss in risky choice of gain situations and the information about certain loss in cautious choice of loss situations) provided in the context of a rejection task received more weight and resulted in more frequent endorsements of the cautious choice in gain situations and of the risky choice in loss situations. Hence, the findings suggest that a decision context characterized by rejection may expand the reflection effects and thereby provide important information about situations in which investment decisions occur in a context characterized by rejection.

Learning to attend: modeling the shaping of selectivity in infero-temporal cortex in a categorization task.

PubMed

Szabo, Miruna; Deco, Gustavo; Fusi, Stefano; Del Giudice, Paolo; Mattia, Maurizio; Stetter, Martin

2006-05-01

Recent experiments on behaving monkeys have shown that learning a visual categorization task makes the neurons in infero-temporal cortex (ITC) more selective to the task-relevant features of the stimuli (Sigala and Logothetis in Nature 415 318-320, 2002). We hypothesize that such a selectivity modulation emerges from the interaction between ITC and other cortical area, presumably the prefrontal cortex (PFC), where the previously learned stimulus categories are encoded. We propose a biologically inspired model of excitatory and inhibitory spiking neurons with plastic synapses, modified according to a reward based Hebbian learning rule, to explain the experimental results and test the validity of our hypothesis. We assume that the ITC neurons, receiving feature selective inputs, form stronger connections with the category specific neurons to which they are consistently associated in rewarded trials. After learning, the top-down influence of PFC neurons enhances the selectivity of the ITC neurons encoding the behaviorally relevant features of the stimuli, as observed in the experiments. We conclude that the perceptual representation in visual areas like ITC can be strongly affected by the interaction with other areas which are devoted to higher cognitive functions.

Continuous selection pressure to improve temperature acclimation of Tisochrysis lutea

PubMed Central

Grimaud, Ghjuvan; Rumin, Judith; Bougaran, Gaël; Talec, Amélie; Gachelin, Manon; Boutoute, Marc; Pruvost, Eric; Bernard, Olivier; Sciandra, Antoine

2017-01-01

Temperature plays a key role in outdoor industrial cultivation of microalgae. Improving the thermal tolerance of microalgae to both daily and seasonal temperature fluctuations can thus contribute to increase their annual productivity. A long term selection experiment was carried out to increase the thermal niche (temperature range for which the growth is possible) of a neutral lipid overproducing strain of Tisochrysis lutea. The experimental protocol consisted to submit cells to daily variations of temperature for 7 months. The stress intensity, defined as the amplitude of daily temperature variations, was progressively increased along successive selection cycles. Only the amplitude of the temperature variations were increased, the daily average temperature was kept constant along the experiment. This protocol resulted in a thermal niche increase by 3°C (+16.5%), with an enhancement by 9% of the maximal growth rate. The selection process also affected T. lutea physiology, with a feature generally observed for ‘cold-temperature’ type of adaptation. The amount of total and neutral lipids was significantly increased, and eventually productivity was increased by 34%. This seven month selection experiment, carried out in a highly dynamic environment, challenges some of the hypotheses classically advanced to explain the temperature response of microalgae. PMID:28902878

Ab Initio Molecular Dynamics Study on the Interactions between Carboxylate Ions and Metal Ions in Water.

PubMed

Mehandzhiyski, Aleksandar Y; Riccardi, Enrico; van Erp, Titus S; Trinh, Thuat T; Grimes, Brian A

2015-08-20

The interaction between a carboxylate anion (deprotonated propanoic acid) and the divalent Mg(2+), Ca(2+), Sr(2+), Ba(2+) metal ions is studied via ab initio molecular dynamics. The main focus of the study is the selectivity of the carboxylate-metal ion interaction in aqueous solution. The interaction is modeled by explicitly accounting for the solvent molecules on a DFT level. The hydration energies of the metal ions along with their diffusion and mobility coefficients are determined and a trend correlated with their ionic radius is found. Subsequently, a series of 16 constrained molecular dynamics simulations for every ion is performed, and the interaction free energy is obtained from thermodynamic integration of the forces between the metal ion and the carboxylate ion. The results indicate that the magnesium ion interacts most strongly with the carboxylate, followed by calcium, strontium, and barium. Because the interaction free energy is not enough to explain the selectivity of the reaction observed experimentally, more detailed analysis is performed on the simulation trajectories to understand the steric changes in the reaction complex during dissociation. The solvent dynamics appear to play an important role during the dissociation of the complex and also in the observed selectivity behavior of the divalent ions.

CMOS compatible electrode materials selection in oxide-based memory devices

NASA Astrophysics Data System (ADS)

Zhuo, V. Y.-Q.; Li, M.; Guo, Y.; Wang, W.; Yang, Y.; Jiang, Y.; Robertson, J.

2016-07-01

Electrode materials selection guidelines for oxide-based memory devices are constructed from the combined knowledge of observed device operation characteristics, ab-initio calculations, and nano-material characterization. It is demonstrated that changing the top electrode material from Ge to Cr to Ta in the Ta2O5-based memory devices resulted in a reduction of the operation voltages and current. Energy Dispersed X-ray (EDX) Spectrometer analysis clearly shows that the different top electrode materials scavenge oxygen ions from the Ta2O5 memory layer at various degrees, leading to different oxygen vacancy concentrations within the Ta2O5, thus the observed trends in the device performance. Replacing the Pt bottom electrode material with CMOS compatible materials (Ru and Ir) further reduces the power consumption and can be attributed to the modification of the Schottky barrier height and oxygen vacancy concentration at the electrode/oxide interface. Both trends in the device performance and EDX results are corroborated by the ab-initio calculations which reveal that the electrode material tunes the oxygen vacancy concentration via the oxygen chemical potential and defect formation energy. This experimental-theoretical approach strongly suggests that the proper selection of CMOS compatible electrode materials will create the critical oxygen vacancy concentration to attain low power memory performance.

A phase transition induces chaos in a predator-prey ecosystem with a dynamic fitness landscape

PubMed Central

2017-01-01

In many ecosystems, natural selection can occur quickly enough to influence the population dynamics and thus future selection. This suggests the importance of extending classical population dynamics models to include such eco-evolutionary processes. Here, we describe a predator-prey model in which the prey population growth depends on a prey density-dependent fitness landscape. We show that this two-species ecosystem is capable of exhibiting chaos even in the absence of external environmental variation or noise, and that the onset of chaotic dynamics is the result of the fitness landscape reversibly alternating between epochs of stabilizing and disruptive selection. We draw an analogy between the fitness function and the free energy in statistical mechanics, allowing us to use the physical theory of first-order phase transitions to understand the onset of rapid cycling in the chaotic predator-prey dynamics. We use quantitative techniques to study the relevance of our model to observational studies of complex ecosystems, finding that the evolution-driven chaotic dynamics confer community stability at the “edge of chaos” while creating a wide distribution of opportunities for speciation during epochs of disruptive selection—a potential observable signature of chaotic eco-evolutionary dynamics in experimental studies. PMID:28678792

Population genetics of the cytoplasm and the units of selection on mitochondrial DNA in Drosophila melanogaster

PubMed Central

2011-01-01

Biological variation exists across a nested set of hierarchical levels from nucleotides within genes to populations within species to lineages within the tree of life. How selection acts across this hierarchy is a long-standing question in evolutionary biology. Recent studies have suggested that genome size is influenced largely by the balance of selection, mutation and drift in lineages with different population sizes. Here we use population cage and maternal transmission experiments to identify the relative strength of selection at an individual and cytoplasmic level. No significant trends were observed in the frequency of large (L) and small (S) mtDNAs across 14 generations in population cages. In all replicate cages, new length variants were observed in heteroplasmic states indicating that spontaneous length mutations occurred in these experimental populations. Heteroplasmic flies carrying L genomes were more frequent than those carrying S genomes suggesting an asymmetric mutation dynamic from larger to smaller mtDNAs. Mother-offspring transmission of heteroplasmy showed that the L mtDNA increased in frequency within flies both between and within generations despite sampling drift of the same intensity as occurred in population cages. These results suggest that selection for mtDNA size is stronger at the cytoplasmic than at the organismal level. The fixation of novel mtDNAs within and between species requires a transient intracellular heteroplasmic stage. The balance of population genetic forces at the cytoplasmic and individual levels governs the units of selection on mtDNA, and has implications for evolutionary inference as well as for the effects of mtDNA mutations on fitness, disease and aging. PMID:21538136

Prey selectivity affects reproductive success of a corallivorous reef fish.

PubMed

Brooker, Rohan M; Jones, Geoffrey P; Munday, Philip L

2013-06-01

Most animals consume a narrower range of food resources than is potentially available in the environment, but the underlying basis for these preferences is often poorly understood. Foraging theory predicts that prey selection should represent a trade-off between prey preferences based on nutritional value and prey availability. That is, species should consume preferred prey when available, but select less preferred prey when preferred prey is rare. We employed both field observation and laboratory experiments to examine the relationship between prey selection and preferences in the obligate coral-feeding filefish, Oxymonacanthus longirostris. To determine the drivers of prey selection, we experimentally established prey preferences in choice arenas and tested the consequences of prey preferences for key fitness-related parameters. Field studies showed that individuals fed almost exclusively on live corals from the genus Acropora. While diet was dominated by the most abundant species, Acropora nobilis, fish appeared to preferentially select rarer acroporids, such as A. millepora and A. hyacinthus. Prey choice experiments confirmed strong preferences for these corals, suggesting that field consumption is constrained by availability. In a longer-term feeding experiment, reproductive pairs fed on non-preferred corals exhibited dramatic reductions to body weight, and in hepatic and gonad condition, compared with those fed preferred corals. The majority of pairs fed preferred corals spawned frequently, while no spawning was observed for any pairs fed a non-preferred species of coral. These experiments suggest that fish distinguish between available corals based on their intrinsic value as prey, that reproductive success is dependent on the presence of particular coral species, and that differential loss of preferred corals could have serious consequences for the population success of these dietary specialists.

Selective concentration for ciprofloxacin resistance in Escherichia coli grown in complex aquatic bacterial biofilms.

PubMed

Kraupner, Nadine; Ebmeyer, Stefan; Bengtsson-Palme, Johan; Fick, Jerker; Kristiansson, Erik; Flach, Carl-Fredrik; Larsson, D G Joakim

2018-04-25

There is concern that antibiotics in the environment can select for and enrich bacteria carrying acquired antibiotic resistance genes, thus increasing the potential of those genes to emerge in a clinical context. A critical question for understanding and managing such risks is what levels of antibiotics are needed to select for resistance in complex bacterial communities. Here, we address this question by examining the phenotypic and genotypic profiles of aquatic communities exposed to ciprofloxacin, also evaluating the within-species selection of resistant E. coli in complex communities. The taxonomic composition was significantly altered at ciprofloxacin exposure concentrations down to 1 μg/L. Shotgun metagenomic analysis indicated that mobile quinolone resistance determinants (qnrD, qnrS and qnrB) were enriched as a direct consequence of ciprofloxacin exposure from 1 μg/L or higher. Only at 5-10 μg/L resistant E.coli increased relative to their sensitive counterparts. These resistant E. coli predominantly harbored non-transferrable, chromosomal triple mutations (gyrA S83 L, D87N and parC S80I), which confer high-level resistance. In a controlled experimental setup such as this, we interpret effects on taxonomic composition and enrichment of mobile quinolone resistance genes as relevant indicators of risk. Hence, the lowest observed effect concentration for resistance selection in complex communities by ciprofloxacin was 1 μg/L and the corresponding no observed effect concentration 0.1 μg/L. These findings can be used to define and implement discharge or surface water limits to reduce risks for selection of antibiotic resistance in the environment. Copyright © 2018 Elsevier Ltd. All rights reserved.

Cation Selectivity in Biological Cation Channels Using Experimental Structural Information and Statistical Mechanical Simulation.

PubMed

Finnerty, Justin John; Peyser, Alexander; Carloni, Paolo

2015-01-01

Cation selective channels constitute the gate for ion currents through the cell membrane. Here we present an improved statistical mechanical model based on atomistic structural information, cation hydration state and without tuned parameters that reproduces the selectivity of biological Na+ and Ca2+ ion channels. The importance of the inclusion of step-wise cation hydration in these results confirms the essential role partial dehydration plays in the bacterial Na+ channels. The model, proven reliable against experimental data, could be straightforwardly used for designing Na+ and Ca2+ selective nanopores.

Virulence and pathogen multiplication: a serial passage experiment in the hypervirulent bacterial insect-pathogen Xenorhabdus nematophila.

PubMed

Chapuis, Élodie; Pagès, Sylvie; Emelianoff, Vanya; Givaudan, Alain; Ferdy, Jean-Baptiste

2011-01-31

The trade-off hypothesis proposes that the evolution of pathogens' virulence is shaped by a link between virulence and contagiousness. This link is often assumed to come from the fact that pathogens are contagious only if they can reach high parasitic load in the infected host. In this paper we present an experimental test of the hypothesis that selection on fast replication can affect virulence. In a serial passage experiment, we selected 80 lines of the bacterial insect-pathogen Xenorhabdus nematophila to multiply fast in an artificial culture medium. This selection resulted in shortened lag phase in our selected bacteria. We then injected these bacteria into insects and observed an increase in virulence. This could be taken as a sign that virulence in Xenorhabdus is linked to fast multiplication. But we found, among the selected lineages, either no link or a positive correlation between lag duration and virulence: the most virulent bacteria were the last to start multiplying. We then surveyed phenotypes that are under the control of the flhDC super regulon, which has been shown to be involved in Xenorhabdus virulence. We found that, in one treatment, the flhDC regulon has evolved rapidly, but that the changes we observed were not connected to virulence. All together, these results indicate that virulence is, in Xenorhabdus as in many other pathogens, a multifactorial trait. Being able to grow fast is one way to be virulent. But other ways exist which renders the evolution of virulence hard to predict.

Progression of Ebola Therapeutics During the 2014-2015 Outbreak.

PubMed

Mendoza, Emelissa J; Qiu, Xiangguo; Kobinger, Gary P

2016-02-01

The recent Ebola virus (EBOV) outbreak in West Africa was the deadliest EBOV epidemic in history, highlighting the need for a safe and efficacious treatment against EBOV disease (EVD). In the absence of an approved treatment, experimental drugs were utilized under compassionate grounds hoping to diminish EVD-associated morbidity and mortality. As more data were collected from safety studies, Phase II/III clinical trials were introduced in Guinea, Sierra Leone, and Liberia to test promising candidates, including small-molecule drugs, RNA-based treatments, and antibody-based therapies. In this review, we summarize the use of, and preliminary observations from, current clinical trials with EVD therapeutics, shedding light on experimental drug selection, emergency clinical evaluation, and the impact these factors may have on future infectious disease outbreaks. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

Broad Feshbach resonance in the 6Li-40K mixture.

PubMed

Tiecke, T G; Goosen, M R; Ludewig, A; Gensemer, S D; Kraft, S; Kokkelmans, S J J M F; Walraven, J T M

2010-02-05

We study the widths of interspecies Feshbach resonances in a mixture of the fermionic quantum gases 6Li and 40K. We develop a model to calculate the width and position of all available Feshbach resonances for a system. Using the model, we select the optimal resonance to study the {6}Li/{40}K mixture. Experimentally, we obtain the asymmetric Fano line shape of the interspecies elastic cross section by measuring the distillation rate of 6Li atoms from a potassium-rich 6Li/{40}K mixture as a function of magnetic field. This provides us with the first experimental determination of the width of a resonance in this mixture, DeltaB=1.5(5) G. Our results offer good perspectives for the observation of universal crossover physics using this mass-imbalanced fermionic mixture.

Optimal control model predictions of system performance and attention allocation and their experimental validation in a display design study

NASA Technical Reports Server (NTRS)

Johannsen, G.; Govindaraj, T.

1980-01-01

The influence of different types of predictor displays in a longitudinal vertical takeoff and landing (VTOL) hover task is analyzed in a theoretical study. Several cases with differing amounts of predictive and rate information are compared. The optimal control model of the human operator is used to estimate human and system performance in terms of root-mean-square (rms) values and to compute optimized attention allocation. The only part of the model which is varied to predict these data is the observation matrix. Typical cases are selected for a subsequent experimental validation. The rms values as well as eye-movement data are recorded. The results agree favorably with those of the theoretical study in terms of relative differences. Better matching is achieved by revised model input data.

Resource and environmental surveys from space with the thematic mapper in the 1980's

NASA Technical Reports Server (NTRS)

1976-01-01

The selection of observation of vegetation is the primary optimization objective of the thematic mapper. The following are aspects of plans for the thematic mapper: (1) to include an appropriately modified first generation MSS in the thematic mapper mission; (2) to provide assured coverage for a minimum of six years to give agencies and other users an opportunity to justify the necessary commitment of resources for the transition into a completely valid operational phase; (3) to provide for global, direct data read-out, without the necessity for on-board data storage or dependence on foreign receiving stations; (4) to recognize the operational character of the thematic mapper after successful completion of its experimental evaluation; and (5) to combine future experimental packages with compatible orbits as part of the operational LANDSAT follow-on payloads.

Déjà vu in unilateral temporal-lobe epilepsy is associated with selective familiarity impairments on experimental tasks of recognition memory.

PubMed

Martin, Chris B; Mirsattari, Seyed M; Pruessner, Jens C; Pietrantonio, Sandra; Burneo, Jorge G; Hayman-Abello, Brent; Köhler, Stefan

2012-11-01

In déjà vu, a phenomenological impression of familiarity for the current visual environment is experienced with a sense that it should in fact not feel familiar. The fleeting nature of this phenomenon in daily life, and the difficulty in developing experimental paradigms to elicit it, has hindered progress in understanding déjà vu. Some neurological patients with temporal-lobe epilepsy (TLE) consistently experience déjà vu at the onset of their seizures. An investigation of such patients offers a unique opportunity to shed light on its possible underlying mechanisms. In the present study, we sought to determine whether unilateral TLE patients with déjà vu (TLE+) show a unique pattern of interictal memory deficits that selectively affect familiarity assessment. In Experiment 1, we employed a Remember-Know paradigm for categorized visual scenes and found evidence for impairments that were limited to familiarity-based responses. In Experiment 2, we administered an exclusion task for highly similar categorized visual scenes that placed both recognition processes in opposition. TLE+ patients again displayed recognition impairments, and these impairments spared their ability to engage recollective processes so as to counteract familiarity. The selective deficits we observed in TLE+ patients contrasted with the broader pattern of recognition-memory impairments that was present in a control group of unilateral patients without déjà vu (TLE-). MRI volumetry revealed that ipsilateral medial temporal structures were less broadly affected in TLE+ than in TLE- patients, with a trend for more focal volume reductions in the rhinal cortices of the TLE+ group. The current findings establish a first empirical link between déjà vu in TLE and processes of familiarity assessment, as defined and measured in current cognitive models. They also reveal a pattern of selectivity in recognition impairments that is rarely observed and, thus, of significant theoretical interest to the memory literature at large. Copyright © 2012 Elsevier Ltd. All rights reserved.

Randomizing Roaches: Exploring the "Bugs" of Randomization in Experimental Design

ERIC Educational Resources Information Center

Wagler, Amy; Wagler, Ron

2014-01-01

Understanding the roles of random selection and random assignment in experimental design is a central learning objective in most introductory statistics courses. This article describes an activity, appropriate for a high school or introductory statistics course, designed to teach the concepts, values and pitfalls of random selection and assignment…

Tuning direct current streaming dielectrophoresis of proteins

PubMed Central

Nakano, Asuka; Camacho-Alanis, Fernanda; Chao, Tzu-Chiao; Ros, Alexandra

2012-01-01

Dielectrophoresis (DEP) of biomolecules has large potential to serve as a novel selectivity parameter for bioanalytical methods such as (pre)concentration, fractionation, and separation. However, in contrast to well-characterized biological cells and (nano)particles, the mechanism of protein DEP is poorly understood, limiting bioanalytical applications for proteins. Here, we demonstrate a detailed investigation of factors influencing DEP of diagnostically relevant immunoglobulin G (IgG) molecules using insulator-based DEP (iDEP) under DC conditions. We found that the pH range in which concentration of IgG due to streaming iDEP occurs without aggregate formation matches the pH range suitable for immunoreactions. Numerical simulations of the electrokinetic factors pertaining to DEP streaming in this range further suggested that the protein charge and electroosmotic flow significantly influence iDEP streaming. These predictions are in accordance with the experimentally observed pH-dependent iDEP streaming profiles as well as the determined IgG molecular properties. Moreover, we observed a transition in the streaming behavior caused by a change from positive to negative DEP induced through micelle formation for the first time experimentally, which is in excellent qualitative agreement with numerical simulations. Our study thus relates molecular immunoglobulin properties to observed iDEP, which will be useful for the future development of protein (pre)concentration or separation methods based on DEP. PMID:23908679

Molecular dynamics simulations reveal that water diffusion between graphene oxide layers is slow

DOE PAGES

Devanathan, Ram; Chase-Woods, Dylan; Shin, Yongsoon; ...

2016-07-08

Membranes made of stacked layers of graphene oxide (GO) hold the tantalizing promise of revolutionizing desalination and water filtration if selective transport of molecules can be controlled. We present the findings of a molecular dynamics simulation study of water intercalated between GO layers that have a C/O ratio of 4. We simulated a range of hydration levels from 1 wt.% to 23.3 wt.% water. The interlayer spacing increased upon hydration from 0.8 nm to 1.1 nm. We also synthesized GO membranes that showed an increase in spacing from about 0.7 nm to 0.8 nm and an increase in mass ofmore » about 14% on hydration. Water diffusion through GO layers is an order of magnitude slower than that in bulk water, because of strong hydrogen bonded interactions. Most of the water molecules are bound to OH groups even at the highest hydration level. We observed large water clusters that could span graphitic regions, oxidized regions and holes that have been experimentally observed in GO. As a result, slow interlayer diffusion can be consistent with experimentally observed water transport in GO if holes lead to a shorter path length than previously assumed and sorption serves as a key rate-limiting step.« less

An inquiry approach to science and language teaching

NASA Astrophysics Data System (ADS)

Rodriguez, Imelda; Bethel, Lowell J.

The purpose of this study was to determine the effectiveness of an inquiry approach to science and language teaching to further develop classification and oral communication skills of bilingual Mexican American third graders. A random sample consisting of 64 subjects was selected for experimental and control groups from a population of 120 bilingual Mexican American third graders. The Solomon Four-Group experimental design was employed. Pre- and posttesting was performed by use of the Goldstein-Sheerer Object Sorting Test, (GSOST) and the Test of Oral Communication Skills, (TOCS). The experimental group participated in a sequential series of science lessons which required manipulation of objects, exploration, peer interaction, and teacher-pupil interaction. The children made observations and comparisons of familiar objects and then grouped them on the basis of perceived and inferred attributes. Children worked individually and in small groups. Analysis of variance procedures was used on the posttest scores to determine if there was a significant improvement in classification and oral communication skills in the experimental group. The results on the posttest scores indicated a significant improvement at the 0.01 level for the experimental group in both classification and oral communication skills. It was concluded that participation in the science inquiry lessons facilitated the development of classification and oral communication skills of bilingual children.

Electronic stopping power of Ti, V and Cr ions in Ge and Au at 150-500 keV/u energies

NASA Astrophysics Data System (ADS)

Linares, R.; Ribas, R. V.; Oliveira, J. R. B.; Medina, N. H.; Santos, H. C.; Seabra, C. C.; Sigaud, L.; Cybulska, E. W.; Seale, W. A.; Allegro, P. R. P.; Touffen, D. L.; Silveira, M. A. G.

2017-12-01

In this paper new experimental data are presented for the stopping power of Ti, V and Cr ions in Ge and Au, in the 150-500 keV/u energy range. The heavy ions at low energies are produced from the elastic scattering between particles of an energetic primary beam (28Si and 16O) directed onto the primary foil of interest (Ti, V or Cr). Measurements were performed using the transmission method. New experimental data points for the stopping power of Ti in Au were compared with previous measurement. The agreement between these two datasets indicates the consistence of the experimental technique. Our experimental data were also compared to some selected theoretical and semi-empirical methods: i) the Unitary Convolution Approximation, ii) the Binary theory, iii) the SRIM code and iv) the Northcliffe & Schilling tables. The experimental data for Ge foil deviate from the theoretical curves possibly due to the effect of band gap structure of the material in the electronic stopping power. For the systems measured here, we observe that the Binary theory exhibits an overall good agreement. The velocity-proportional dependence of the electronic stopping power in the measured energy range is also discussed.

DNA cleavage site selection by Type III restriction enzymes provides evidence for head-on protein collisions following 1D bidirectional motion

PubMed Central

Schwarz, Friedrich W.; van Aelst, Kara; Tóth, Júlia; Seidel, Ralf; Szczelkun, Mark D.

2011-01-01

DNA cleavage by the Type III Restriction–Modification enzymes requires communication in 1D between two distant indirectly-repeated recognitions sites, yet results in non-specific dsDNA cleavage close to only one of the two sites. To test a recently proposed ATP-triggered DNA sliding model, we addressed why one site is selected over another during cleavage. We examined the relative cleavage of a pair of identical sites on DNA substrates with different distances to a free or protein blocked end, and on a DNA substrate using different relative concentrations of protein. Under these conditions a bias can be induced in the cleavage of one site over the other. Monte-Carlo simulations based on the sliding model reproduce the experimentally observed behaviour. This suggests that cleavage site selection simply reflects the dynamics of the preceding stochastic enzyme events that are consistent with bidirectional motion in 1D and DNA cleavage following head-on protein collision. PMID:21724613

Olfactory cues associated with the major histocompatibility complex.

PubMed

Eggert, F; Müller-Ruchholtz, W; Ferstl, R

Besides its immunological function of self/non-self discrimination the major histocompatibility complex (MHC) has been recognized as a possible source of individual specific body odors. Dating back to speculations on the role of the extraordinary polymorphism of the MHC as background of an individual chemosensory identity and to early observations of MHC-dependent mate choice in inbred strains of mice, systematic experimental studies revealed a first evidence for H-2 related body odors in this species. Meanwhile a large number of animal studies with rodents and a series of field studies and experiments with humans have extended our knowledge of MHC-related odor signals and substantiated the hypothesis of immunogenetic associated odor types. These results suggest that the most prominent feature of the MHC, its extraordinary genetic diversity, seems in part to be selectively maintained by behavioral mechanisms which operate in contemporary natural populations. The high degree of heterozygosity found in natural populations of most species seems to be promoted by non-disease-based selection such as mating preferences and selective block of pregnancy.

Running bumps from stealth bosons

NASA Astrophysics Data System (ADS)

Aguilar-Saavedra, J. A.

2018-03-01

For the `stealth bosons' S, light boosted particles with a decay S → A A → q \\bar{q} q \\bar{q} into four quarks and reconstructed as a single fat jet, the groomed jet mass has a strong correlation with groomed jet substructure variables. Consequently, the jet mass distribution is strongly affected by the jet substructure selection cuts when applied on the groomed jet. We illustrate this fact by recasting a CMS search for low-mass dijet resonances and show a few representative examples. The mass distributions exhibit narrow and wide bumps at several locations in the 100-300 GeV range, between the masses of the daughter particles A and the parent particle S, depending on the jet substructure selection. This striking observation introduces several caveats when interpreting and comparing experimental results, for the case of non-standard signatures. The possibility that a single boosted particle decaying hadronically produces multiple bumps, at quite different jet masses, and depending on the event selection, brings the anomaly chasing game to the next level.

Pump and probe spectroscopy with continuous wave quantum cascade lasers.

PubMed

Kirkbride, James M R; Causier, Sarah K; Dalton, Andrew R; Weidmann, Damien; Ritchie, Grant A D

2014-02-07

This paper details infra-red pump and probe studies on nitric oxide conducted with two continuous wave quantum cascade lasers both operating around 5 μm. The pump laser prepares a velocity selected population in a chosen rotational quantum state of the v = 1 level which is subsequently probed using a second laser tuned to a rotational transition within the v = 2 ← v = 1 hot band. The rapid frequency scan of the probe (with respect to the molecular collision rate) in combination with the velocity selective pumping allows observation of marked rapid passage signatures in the transient absorption profiles from the polarized vibrationally excited sample. These coherent transient signals are influenced by the underlying hyperfine structure of the pump and probe transitions, the sample pressure, and the coherent properties of the lasers. Pulsed pump and probe studies show that the transient absorption signals decay within 1 μs at 50 mTorr total pressure, reflecting both the polarization and population dephasing times of the vibrationally excited sample. The experimental observations are supported by simulation based upon solving the optical Bloch equations for a two level system.

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

Kirkbride, James M. R.; Causier, Sarah K.; Dalton, Andrew R.

This paper details infra-red pump and probe studies on nitric oxide conducted with two continuous wave quantum cascade lasers both operating around 5 μm. The pump laser prepares a velocity selected population in a chosen rotational quantum state of the v = 1 level which is subsequently probed using a second laser tuned to a rotational transition within the v = 2 ← v = 1 hot band. The rapid frequency scan of the probe (with respect to the molecular collision rate) in combination with the velocity selective pumping allows observation of marked rapid passage signatures in the transient absorptionmore » profiles from the polarized vibrationally excited sample. These coherent transient signals are influenced by the underlying hyperfine structure of the pump and probe transitions, the sample pressure, and the coherent properties of the lasers. Pulsed pump and probe studies show that the transient absorption signals decay within 1 μs at 50 mTorr total pressure, reflecting both the polarization and population dephasing times of the vibrationally excited sample. The experimental observations are supported by simulation based upon solving the optical Bloch equations for a two level system.« less

[Nursing intervention and evaluation of postoperative pain in preschool children with cleft lip and palate].

PubMed

Gong, Caixia; Yan, Miao; Jiang, Fei; Chen, Zehua; Long, Yuan; Chen, Lixian; Zheng, Qian; Shi, Bing

2014-06-01

This study aimed to observe the postoperative pain rate and degree of pain in preschool children with cleft lip and palate, and investigate the effect of nursing intervention on pain relief. A total of 120 hospitalized cases of three- to seven-year-old preschool children with cleft lip and palate were selected from May to October 2011. The subjects were randomly divided into the control group and experimental groups 1, 2, and 3. The control group used conventional nursing methods, experimental group 1 used analgesic drug treatment, experimental group 2 used psychological nursing interventions, and experimental group 3 used both psychological nursing intervention and analgesic drug treatment. After 6, 12, 24, and 48 h, pain self-assessment, pain parent-assessment, and pain nurse-assessment were calculated for the four groups using the pain assessment forms, and their ratings were compared. The postoperative pain rates of the four groups ranged from 50.0% to 73.3%. The difference among the four groups was statistically significant (P < 0.001). The differences among the control group and experimental groups 1 and 2 were not statistically significant (P = 0.871), whereas the differences among experimental group 3 and the other groups were statistically significant (P < 0.001). Postoperative pain in preschool children with cleft lip and palate is common. Psychological nursing intervention with analgesic treatment is effective in relieving postoperative pain.

Selected clinical chemistry analytes correlate with the pathogenesis of inclusion body hepatitis experimentally induced by fowl aviadenoviruses.

PubMed

Matos, Miguel; Grafl, Beatrice; Liebhart, Dieter; Schwendenwein, Ilse; Hess, Michael

2016-10-01

In the present study, clinical chemistry was applied to assess the pathogenesis and progression of experimentally induced inclusion body hepatitis (IBH). For this, five fowl aviadenovirus (FAdV) strains from recent IBH field outbreaks were used to orally inoculate different groups of day-old specific pathogen-free chickens, which were weighed, sampled and examined during necropsy by sequential killing. Mortalities of 50% and 30% were recorded in two groups between 6 and 9 days post-infection (dpi), along with a decreased weight of 23% and 20%, respectively, compared to the control group. Macroscopical changes were seen in the liver and kidney between 6 and 10 dpi, with no lesions being observed in the other organs. Histological lesions were observed in the liver and pancreas during the same period. Plasma was collected from killed birds of each group at each time point and the following clinical chemistry analytes were investigated: aspartate aminotransferase (AST), glutamate dehydrogenase (GLDH), bile acids, total protein, albumin, uric acid and lipase. Plasma protein profile, AST and GLDH, together with bile acids values paralleled the macroscopical and histopathological lesions in the liver, while plasma lipase activity levels coincided with lesions observed in pancreas. In agreement with the histology and clinical chemistry, viral load in the target organs, liver and pancreas, was highest at 7 dpi. Thus, clinical chemistry was found to be a valuable tool in evaluating and monitoring the progression of IBH in experimentally infected birds, providing a deeper knowledge of the underlying pathophysiological mechanisms of a FAdV infection in chickens.

Effects of environmental change on plant species density: Comparing predictions with experiments

USGS Publications Warehouse

Gough, L.; Grace, J.B.

1999-01-01

Ideally, general ecological relationships may be used to predict responses of natural communities to environmental change, but few attempts have been made to determine the reliability of predictions based on descriptive data. Using a previously published structural equation model (SEM) of descriptive data from a coastal marsh landscape, we compared these predictions against observed changes in plant species density resulting from field experiments (manipulations of soil fertility, flooding, salinity, and mammalian herbivory) in two areas within the same marsh. In general, observed experimental responses were fairly consistent with predictions. The largest discrepancy occurred when sods were transplanted from high- to low-salinity sites and herbivores selectively consumed a particularly palatable plant species in the transplanted sods. Individual plot responses to some treatments were predicted more accurately than others. Individual fertilized plot responses were not consistent with predictions (P > 0.05), nor were fenced plots (herbivore exclosures; R2 = 0.15) compared to unfenced plots (R2 = 0.53). For the remaining treatments, predictions reasonably matched responses (R2 = 0.63). We constructed an SEM for the experimental data; it explained 60% of the variance in species density and showed that fencing and fertilization led to decreases in species density that were not predicted from treatment effects on community biomass or observed disturbance levels. These treatments may have affected the ratio of live to dead biomass, and competitive exclusion likely decreased species density in fenced and fertilized plots. We conclude that experimental validation is required to determine the predictive value of comparative relationships derived from descriptive data.

Allosteric modulation model of the mu opioid receptor by herkinorin, a potent not alkaloidal agonist

NASA Astrophysics Data System (ADS)

Marmolejo-Valencia, A. F.; Martínez-Mayorga, K.

2017-05-01

Modulation of opioid receptors is the primary choice for pain management and structural information studies have gained new horizons with the recently available X-ray crystal structures. Herkinorin is one of the most remarkable salvinorin A derivative with high affinity for the mu opioid receptor, moderate selectivity and lack of nitrogen atoms on its structure. Surprisingly, binding models for herkinorin are lacking. In this work, we explore binding models of herkinorin using automated docking, molecular dynamics simulations, free energy calculations and available experimental information. Our herkinorin D-ICM-1 binding model predicted a binding free energy of -11.52 ± 1.14 kcal mol-1 by alchemical free energy estimations, which is close to the experimental values -10.91 ± 0.2 and -10.80 ± 0.05 kcal mol-1 and is in agreement with experimental structural information. Specifically, D-ICM-1 molecular dynamics simulations showed a water-mediated interaction between D-ICM-1 and the amino acid H2976.52, this interaction coincides with the co-crystallized ligands. Another relevant interaction, with N1272.63, allowed to rationalize herkinorin's selectivity to mu over delta opioid receptors. Our suggested binding model for herkinorin is in agreement with this and additional experimental data. The most remarkable observation derived from our D-ICM-1 model is that herkinorin reaches an allosteric sodium ion binding site near N1503.35. Key interactions in that region appear relevant for the lack of β-arrestin recruitment by herkinorin. This interaction is key for downstream signaling pathways involved in the development of side effects, such as tolerance. Future SAR studies and medicinal chemistry efforts will benefit from the structural information presented in this work.

Considerations for Experimental Animal Models of Concussion, Traumatic Brain Injury, and Chronic Traumatic Encephalopathy—These Matters Matter

PubMed Central

Wojnarowicz, Mark W.; Fisher, Andrew M.; Minaeva, Olga; Goldstein, Lee E.

2017-01-01

Animal models of concussion, traumatic brain injury (TBI), and chronic traumatic encephalopathy (CTE) are widely available and routinely deployed in laboratories around the world. Effective animal modeling requires careful consideration of four basic principles. First, animal model use must be guided by clarity of definitions regarding the human disease or condition being modeled. Concussion, TBI, and CTE represent distinct clinical entities that require clear differentiation: concussion is a neurological syndrome, TBI is a neurological event, and CTE is a neurological disease. While these conditions are all associated with head injury, the pathophysiology, clinical course, and medical management of each are distinct. Investigators who use animal models of these conditions must take into account these clinical distinctions to avoid misinterpretation of results and category mistakes. Second, model selection must be grounded by clarity of purpose with respect to experimental questions and frame of reference of the investigation. Distinguishing injury context (“inputs”) from injury consequences (“outputs”) may be helpful during animal model selection, experimental design and execution, and interpretation of results. Vigilance is required to rout out, or rigorously control for, model artifacts with potential to interfere with primary endpoints. The widespread use of anesthetics in many animal models illustrates the many ways that model artifacts can confound preclinical results. Third, concordance between key features of the animal model and the human disease or condition being modeled is required to confirm model biofidelity. Fourth, experimental results observed in animals must be confirmed in human subjects for model validation. Adherence to these principles serves as a bulwark against flawed interpretation of results, study replication failure, and confusion in the field. Implementing these principles will advance basic science discovery and accelerate clinical translation to benefit people affected by concussion, TBI, and CTE. PMID:28620350

The use of clinical trials in comparative effectiveness research on mental health

PubMed Central

Blanco, Carlos; Rafful, Claudia; Olfson, Mark

2013-01-01

Objectives A large body of research on comparative effectiveness research (CER) focuses on the use of observational and quasi-experimental approaches. We sought to examine the use of clinical trials as a tool for CER, particularly in mental health. Study Design and Setting Examination of three ongoing randomized clinical trials in psychiatry that address issues which would pose difficulties for non-experimental CER methods. Results Existing statistical approaches to non-experimental data appear insufficient to compensate for biases that may arise when the pattern of missing data cannot be properly modeled such as when there are no standards for treatment, when affected populations have limited access to treatment, or when there are high rates of treatment dropout. Conclusions Clinical trials should retain an important role in CER, particularly in cases of high disorder prevalence, large expected effect sizes, difficult to reach populations or when examining sequential treatments or stepped-care algorithms. Progress in CER in mental health will require careful consideration of appropriate selection between clinical trials and non-experimental designs and on allocation of research resources to optimally inform key treatment decisions for each individual patient. PMID:23849150

Supersonic Retropropulsion Experimental Results from the NASA Langley Unitary Plan Wind Tunnel

NASA Technical Reports Server (NTRS)

Berry, Scott A.; Rhode, Matthew N.; Edquist, Karl T.; Player, Charles J.

2011-01-01

A new supersonic retropropulsion experimental effort, intended to provide code validation data, was recently completed in the Langley Research Center Unitary Plan Wind Tunnel Test Section 2 over the Mach number range from 2.4 to 4.6. The experimental model was designed using insights gained from pre-test computations, which were instrumental for sizing and refining the model to minimize tunnel wall interference and internal flow separation concerns. A 5-in diameter 70-deg sphere-cone forebody with a roughly 10-in long cylindrical aftbody was the baseline configuration selected for this study. The forebody was designed to accommodate up to four 4:1 area ratio supersonic nozzles. Primary measurements for this model were a large number of surface pressures on the forebody and aftbody. Supplemental data included high-speed Schlieren video and internal pressures and temperatures. The run matrix was developed to allow for the quantification of various sources of experimental uncertainty, such as random errors due to run-to-run variations and bias errors due to flow field or model misalignments. Preliminary results and observations from the test are presented, while detailed data and uncertainty analyses are ongoing.

Attenuation coefficients and exposure buildup factor of some rocks for gamma ray shielding applications

NASA Astrophysics Data System (ADS)

Obaid, Shamsan S.; Sayyed, M. I.; Gaikwad, D. K.; Pawar, Pravina. P.

2018-07-01

In the present work, the mass attenuation coefficient μ/ρ is investigated experimentally and theoretically for seven rocks (olivine basalt, green marble, jet black granite, telphone black granite, cuddapah limestone, white marble and pink marble). The rock samples were collected from different places of India. The mass attenuation coefficients of the samples were measured experimentally at photon energies of radioisotopes Co57 (122 keV), Ba133 (356 keV), 22Na (511 and 1275 keV), Cs137 (662 keV), Mn54 (840 keV), and Co60 (1330 keV). Theoretically, the simulation results of μ/ρ using both XCOM and MCNP5 codes were compared with experimental results and a satisfactory agreement was observed. Total atomic cross sections (σt,a) electronic cross sections (σt,e), effective atomic number (Zeff), electron density (Ne) and half value layer (HVL) were evaluated using the obtained μ/ρ values for investigated rocks. The HVL values for the selected rocks were compared with some common shielding concretes. Moreover, by Geometric Progression method (G-P) exposure buildup factor (EBF) and energy absorption buildup factor (EABF) values were calculated for incident photon energy 0.015-15 MeV up to penetration depths of 40 mean free paths. The results show that among the studied rocks pink marble possesses superior shielding properties for γ-ray. This work was carried out to explore the advantage of utilizing the selected rocks in engineering structures and building construction to shield gamma-rays.

Weak Value Amplification of a Post-Selected Single Photon

NASA Astrophysics Data System (ADS)

Hallaji, Matin

Weak value amplification (WVA) is a measurement technique in which the effect of a pre- and post-selected system on a weakly interacting probe is magnified. In this thesis, I present the first experimental observation of WVA of a single photon. We observed that a signal photon --- sent through a polarization interferometer and post-selected by photodetection in the almost-dark port --- can act like eight photons. The effect of this single photon is measured as a nonlinear phase shift on a separate laser beam. The interaction between the two is mediated by a sample of laser- cooled 85Rb atoms. Electromagnetically induced transparency (EIT) is used to enhance the nonlinearity and overcome resonant absorption. I believe this work to be the first demonstration of WVA where a deterministic interaction is used to entangle two distinct optical systems. In WVA, the amplification is contingent on discarding a large portion of the original data set. While amplification increases measurement sensitivity, discarding data worsens it. Questioning whether these competing effects conspire to improve or diminish measurement accuracy has resulted recently in controversy. I address this question by calculating the maximum amount of information achievable with the WVA technique. By comparing this information to that achievable by the standard technique, where no post-selection is employed, I show that the WVA technique can be advantageous under a certain class of noise models. Finally, I propose a way to optimally apply the WVA technique.

Large eddy simulation of forced ignition of an annular bluff-body burner

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

Subramanian, V.; Domingo, P.; Vervisch, L.

2010-03-15

The optimization of the ignition process is a crucial issue in the design of many combustion systems. Large eddy simulation (LES) of a conical shaped bluff-body turbulent nonpremixed burner has been performed to study the impact of spark location on ignition success. This burner was experimentally investigated by Ahmed et al. [Combust. Flame 151 (2007) 366-385]. The present work focuses on the case without swirl, for which detailed measurements are available. First, cold-flow measurements of velocities and mixture fractions are compared with their LES counterparts, to assess the prediction capabilities of simulations in terms of flow and turbulent mixing. Timemore » histories of velocities and mixture fractions are recorded at selected spots, to probe the resolved probability density function (pdf) of flow variables, in an attempt to reproduce, from the knowledge of LES-resolved instantaneous flow conditions, the experimentally observed reasons for success or failure of spark ignition. A flammability map is also constructed from the resolved mixture fraction pdf and compared with its experimental counterpart. LES of forced ignition is then performed using flamelet fully detailed tabulated chemistry combined with presumed pdfs. Various scenarios of flame kernel development are analyzed and correlated with typical flow conditions observed in this burner. The correlations between, velocities and mixture fraction values at the sparking time and the success or failure of ignition, are then further discussed and analyzed. (author)« less

[Experimental study on a novel esophageal prosthesis made of composite biomaterials].

PubMed

Qin, Xiong; Xu, Zhi-fei; Shi, Hong-can; Zhao, Xue-wei; Sun, Kang; Gao, Xiang-yang

2003-07-01

To design and develop a novel esophageal prosthesis by selecting appropriate biomaterials, developing special manufacturing techniques, and investigating the feasibility of replacement of cervical esophagus in mongrel dogs. In accordance with the requirements of ideal esophageal substitutes, we designed a new type of esophageal prostheses. The inner stent were made with polyurethane of medical grade, and the outer surface of the prosthesis was coated with collagen-chitosan sponge. The silicone tube was used as a control. Thirteen adult mongrel dogs that were divided into two groups were used to establish the experimental models. In the experimental group (n = 8), the esophageal prostheses were completely incorporated with the native esophagus and adherent to the surrounding host connective tissues. Epithelial linings of varying degrees were formed on the luminal surface, and complete epithelization was seen in 1 month postoperatively. The granulation at the sites of the anastomosis in this group was less significant than that of the control group. One dog has been surviving for 12 months up to now without any complications. In the control group (n = 5), esophageal epithelial was not observed on the luminal surface, constriction of the regenerated esophagus progressed and all the dogs died within 2 months after operation. These observations suggest that this esophageal prosthesis made of composite biomaterials has high biocompatibility and potential for long-segment esophageal reconstruction, which is promising for the clinical repair of esophageal defects.

Turbulent flame spreading mechanisms after spark ignition

NASA Astrophysics Data System (ADS)

Subramanian, V.; Domingo, Pascale; Vervisch, Luc

2009-12-01

Numerical simulation of forced ignition is performed in the framework of Large-Eddy Simulation (LES) combined with a tabulated detailed chemistry approach. The objective is to reproduce the flame properties observed in a recent experimental work reporting probability of ignition in a laboratory-scale burner operating with Methane/air non premixed mixture [1]. The smallest scales of chemical phenomena, which are unresolved by the LES grid, are approximated with a flamelet model combined with presumed probability density functions, to account for the unresolved part of turbulent fluctuations of species and temperature. Mono-dimensional flamelets are simulated using GRI-3.0 [2] and tabulated under a set of parameters describing the local mixing and progress of reaction. A non reacting case was simulated at first, to study the unsteady velocity and mixture fields. The time averaged velocity and mixture fraction, and their respective turbulent fluctuations, are compared against the experimental measurements, in order to estimate the prediction capabilities of LES. The time history of axial and radial components of velocity and mixture fraction is cumulated and analysed for different burner regimes. Based on this information, spark ignition is mimicked on selected ignition spots and the dynamics of kernel development analyzed to be compared against the experimental observations. The possible link between the success or failure of the ignition and the flow conditions (in terms of velocity and composition) at the sparking time are then explored.

Interface Pattern Selection Criterion for Cellular Structures in Directional Solidification

NASA Technical Reports Server (NTRS)

Trivedi, R.; Tewari, S. N.; Kurtze, D.

1999-01-01

The aim of this investigation is to establish key scientific concepts that govern the selection of cellular and dendritic patterns during the directional solidification of alloys. We shall first address scientific concepts that are crucial in the selection of interface patterns. Next, the results of ground-based experimental studies in the Al-4.0 wt % Cu system will be described. Both experimental studies and theoretical calculations will be presented to establish the need for microgravity experiments.

Kinetic Energy Release of the Singly and Doubly Charged Methylene Chloride Molecule: The Role of Fast Dissociation.

PubMed

Alcantara, K F; Rocha, A B; Gomes, A H A; Wolff, W; Sigaud, L; Santos, A C F

2016-09-01

The center of mass kinetic energy release distribution (KERD) spectra of selected ionic fragments, formed through dissociative single and double photoionization of CH2Cl2 at photon energies around the Cl 2p edge, were extracted from the shape and width of the experimentally obtained time-of-flight (TOF) distributions. The KERD spectra exhibit either smooth profiles or structures, depending on the moiety and photon energy. In general, the heavier the ionic fragments, the lower their average KERDs are. In contrast, the light H(+) fragments are observed with kinetic energies centered around 4.5-5.5 eV, depending on the photon energy. It was observed that the change in the photon energy involves a change in the KERDs, indicating different processes or transitions taking place in the breakup process. In the particular case of double ionization with the ejection of two charged fragments, the KERDs present have characteristics compatible with the Coulombic fragmentation model. Intending to interpret the experimental data, singlet and triplet states at Cl 2p edge of the CH2Cl2 molecule, corresponding to the Cl (2p → 10a1*) and Cl (2p → 4b1*) transitions, were calculated at multiconfigurational self-consistent field (MCSCF) level and multireference configuration interaction (MRCI). These states were selected to form the spin-orbit coupling matrix elements, which after diagonalization result in a spin-orbit manifold. Minimum energy pathways for dissociation of the molecule were additionally calculated aiming to give support to the presence of the ultrafast dissociation mechanism in the molecular breakup.

Molecular Preadaptation to Antimony Resistance in Leishmania donovani on the Indian Subcontinent

PubMed Central

Imamura, H.; Zander, D.; D’Haenens, E.; Maes, I.; Domagalska, M. A.; Clos, J.

2018-01-01

ABSTRACT Antimonials (Sb) were used for decades for chemotherapy of visceral leishmaniasis (VL). Now abandoned in the Indian subcontinent (ISC) because of Leishmania donovani resistance, this drug offers a unique model for understanding drug resistance dynamics. In a previous phylogenomic study, we found two distinct populations of L. donovani: the core group (CG) in the Gangetic plains and ISC1 in the Nepalese highlands. Sb resistance was only encountered within the CG, and a series of potential markers were identified. Here, we analyzed the development of resistance to trivalent antimonials (SbIII) upon experimental selection in ISC1 and CG strains. We observed that (i) baseline SbIII susceptibility of parasites was higher in ISC1 than in the CG, (ii) time to SbIII resistance was higher for ISC1 parasites than for CG strains, and (iii) untargeted genomic and metabolomic analyses revealed molecular changes along the selection process: these were more numerous in ISC1 than in the CG. Altogether these observations led to the hypothesis that CG parasites are preadapted to SbIII resistance. This hypothesis was experimentally confirmed by showing that only wild-type CG strains could survive a direct exposure to the maximal concentration of SbIII. The main driver of this preadaptation was shown to be MRPA, a gene involved in SbIII sequestration and amplified in an intrachromosomal amplicon in all CG strains characterized so far. This amplicon emerged around 1850 in the CG, well before the implementation of antimonials for VL chemotherapy, and we discuss here several hypotheses of selective pressure that could have accompanied its emergence. IMPORTANCE The “antibiotic resistance crisis” is a major challenge for scientists and medical professionals. This steady rise in drug-resistant pathogens also extends to parasitic diseases, with antimony being the first anti-Leishmania drug that fell in the Indian subcontinent (ISC). Leishmaniasis is a major but neglected infectious disease with limited therapeutic options. Therefore, understanding how parasites became resistant to antimonials is of commanding importance. In this study, we experimentally characterized the dynamics of this resistance acquisition and show for the first time that some Leishmania populations of the ISC were preadapted to antimony resistance, likely driven by environmental factors or by drugs used in the 19th century. PMID:29669889

Human centromedian-parafascicular complex signals sensory cues for goal-oriented behavior selection.

PubMed

Schepers, Inga M; Beck, Anne-Kathrin; Bräuer, Susann; Schwabe, Kerstin; Abdallat, Mahmoud; Sandmann, Pascale; Dengler, Reinhard; Rieger, Jochem W; Krauss, Joachim K

2017-05-15

Experimental research has shown that the centromedian-parafascicular complex (CM-Pf) of the intralaminar thalamus is activated in attentional orienting and processing of behaviorally relevant stimuli. These observations resulted in the hypothesis that the CM-Pf plays a pivotal role in goal-oriented behavior selection. We here set out to test this hypothesis with electrophysiological recordings from patients with electrodes implanted in CM-Pf for deep brain stimulation (DBS) treatment of chronic neuropathic pain. Six patients participated in (1) an auditory three-class oddball experiment, which required a button press to target tones, but not to standard and deviant tones and in (2) a multi-speaker experiment with a target word that required attention selection and a target image that required response selection. Subjects showed transient neural responses (8-15Hz) to the target tone and the target word. Two subjects additionally showed transient neural responses (15-25Hz) to the target image. All sensory target stimuli were related to an internal goal and required a behavior selection (attention selection, response selection). In group analyses, neural responses were greater to target tones than deviant and standard tones and to target words than other task-relevant words that did not require attention selection. The transient neural responses occurred after the target stimuli but prior to the overt behavioral response. Our results demonstrate that in human subjects the CM-Pf is involved in signaling sensory inputs related to goal-oriented selection of behavior. Copyright © 2017 Elsevier Inc. All rights reserved.

Application of relativistic mean field and effective field theory densities to scattering observables for Ca isotopes

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

Bhuyan, M.; School of Physics, Sambalpur University, Jyotivihar, Burla 768 019; Panda, R. N.

In the framework of relativistic mean field (RMF) theory, we have calculated the density distribution of protons and neutrons for {sup 40,42,44,48}Ca with NL3 and G2 parameter sets. The microscopic proton-nucleus optical potentials for p+{sup 40,42,44,48}Ca systems are evaluated from the Dirac nucleon-nucleon scattering amplitude and the density of the target nucleus using relativistic-Love-Franey and McNeil-Ray-Wallace parametrizations. We have estimated the scattering observables, such as the elastic differential scattering cross section, analyzing power and the spin observables with the relativistic impulse approximation (RIA). The results have been compared with the experimental data for a few selective cases and we findmore » that the use of density as well as the scattering matrix parametrizations are crucial for the theoretical prediction.« less

Thermodynamics of fission products in UO(2 ± x).

PubMed

Nerikar, P V; Liu, X-Y; Uberuaga, B P; Stanek, C R; Phillpot, S R; Sinnott, S B

2009-10-28

The stabilities of selected fission products-Xe, Cs, and Sr-are investigated as a function of non-stoichiometry x in UO(2 ± x). In particular, density functional theory (DFT) is used to calculate the incorporation and solution energies of these fission products at the anion and cation vacancy sites, at the divacancy, and at the bound Schottky defect. In order to reproduce the correct insulating state of UO(2), the DFT calculations are performed using spin polarization and with the Hubbard U term. In general, higher charge defects are more soluble in the fuel matrix and the solubility of fission products increases as the hyperstoichiometry increases. The solubility of fission product oxides is also explored. Cs(2)O is observed as a second stable phase and SrO is found to be soluble in the UO(2) matrix for all stoichiometries. These observations mirror experimentally observed phenomena.

Oral LD50 toxicity modeling and prediction of per- and polyfluorinated chemicals on rat and mouse.

PubMed

Bhhatarai, Barun; Gramatica, Paola

2011-05-01

Quantitative structure-activity relationship (QSAR) analyses were performed using the LD(50) oral toxicity data of per- and polyfluorinated chemicals (PFCs) on rodents: rat and mouse. PFCs are studied under the EU project CADASTER which uses the available experimental data for prediction and prioritization of toxic chemicals for risk assessment by using the in silico tools. The methodology presented here applies chemometrical analysis on the existing experimental data and predicts the toxicity of new compounds. QSAR analyses were performed on the available 58 mouse and 50 rat LD(50) oral data using multiple linear regression (MLR) based on theoretical molecular descriptors selected by genetic algorithm (GA). Training and prediction sets were prepared a priori from available experimental datasets in terms of structure and response. These sets were used to derive statistically robust and predictive (both internally and externally) models. The structural applicability domain (AD) of the models were verified on 376 per- and polyfluorinated chemicals including those in REACH preregistration list. The rat and mouse endpoints were predicted by each model for the studied compounds, and finally 30 compounds, all perfluorinated, were prioritized as most important for experimental toxicity analysis under the project. In addition, cumulative study on compounds within the AD of all four models, including two earlier published models on LC(50) rodent analysis was studied and the cumulative toxicity trend was observed using principal component analysis (PCA). The similarities and the differences observed in terms of descriptors and chemical/mechanistic meaning encoded by descriptors to prioritize the most toxic compounds are highlighted.

Attenders versus Slackers: A Classroom Demonstration of Quasi-Experimentation and Self-Selecting Samples

ERIC Educational Resources Information Center

Stellmack, Mark A.

2013-01-01

Studies of the effects of class attendance on class performance typically are quasi-experimental because students choose whether or not to attend class; that is, the samples are self-selecting. The lack of random assignment prevents one from establishing a causal relationship between attendance and performance. Relating attendance to performance…

Near-optimal experimental design for model selection in systems biology.

PubMed

Busetto, Alberto Giovanni; Hauser, Alain; Krummenacher, Gabriel; Sunnåker, Mikael; Dimopoulos, Sotiris; Ong, Cheng Soon; Stelling, Jörg; Buhmann, Joachim M

2013-10-15

Biological systems are understood through iterations of modeling and experimentation. Not all experiments, however, are equally valuable for predictive modeling. This study introduces an efficient method for experimental design aimed at selecting dynamical models from data. Motivated by biological applications, the method enables the design of crucial experiments: it determines a highly informative selection of measurement readouts and time points. We demonstrate formal guarantees of design efficiency on the basis of previous results. By reducing our task to the setting of graphical models, we prove that the method finds a near-optimal design selection with a polynomial number of evaluations. Moreover, the method exhibits the best polynomial-complexity constant approximation factor, unless P = NP. We measure the performance of the method in comparison with established alternatives, such as ensemble non-centrality, on example models of different complexity. Efficient design accelerates the loop between modeling and experimentation: it enables the inference of complex mechanisms, such as those controlling central metabolic operation. Toolbox 'NearOED' available with source code under GPL on the Machine Learning Open Source Software Web site (mloss.org).

Single isotope fractionation of (16)O(-) implications for early history of solar system

NASA Technical Reports Server (NTRS)

Arrhenius, G.

1980-01-01

Chemical fractionation processes are investigated with emphasis on selective single isotope fractionation in polyisotopic systems, particularly in oxygen. The related temperature parameters of meteoritic condensates and of their source medium are investigated by a thermometric method that is independent of assumptions regarding temperatures and pressures in the solar nebula. The crucial nonlinear chemical fractionation of O-16 was demonstrated experimentally. The effect was achieved in condensed CO2 formed from CO with C-12 O-16 selectively excited by H Ly alpha. The effect was verified by mass spectrometric measurements. The meteorite paleotemperature estimates were advanced from defining only thermal exposure to evaluating time and temperature independently. Grain temperatures at condensation of refractory inclusion materials are indicated to be less than 900 K in agreement with radiation temperature considerations and observations in circumstellar dust shells.

Lavia – an Evaluation of the Potential Safety Benefits of the French Intelligent Speed Adaptation Project

PubMed Central

Driscoll, R.; Page, Y.; Lassarre, S.; Ehrlich, J.

2007-01-01

This paper presents the potential safety benefits of the experimental French LAVIA Intelligent Speed Adaptation system, according to road network and system mode, based on observed driving speeds, distributions of crash severity and crash injury risk. Results are given for car frontal and side impacts that together, represent 80% of all serious and fatal injuries in France. Of the three system modes tested (advisory, driver select, mandatory), our results suggest that driver select would most significantly reduce serious injuries and death. We estimate this 100% utilization of cars equipped with this type of speed adaptation system would decrease injury rates by 6% to 16% over existing conditions depending on the type of crash (frontal or side) and road environment considered. Some limitations associated with the analysis are also identified. PMID:18184509

Optical proposals for controlled delayed-choice experiment based on weak cross-Kerr nonlinearities

NASA Astrophysics Data System (ADS)

Dong, Li; Lin, Yan-Fang; Li, Qing-Yang; Xiu, Xiao-Ming; Dong, Hai-Kuan; Gao, Ya-Jun

2017-05-01

Employing polarization modes of a photon, we propose two theoretical proposals to exhibit the wave-particle duality of the photon with the assistance of weak cross-Kerr nonlinearities. The first proposal is a classical controlled delayed-choice experiment (that is, Wheeler's delayed-choice experiment), where we can observe selectively wave property or particle property of the photon relying on the experimenter's selection, whereas the second proposal is a quantum controlled delayed-choice experiment, by which the mixture phenomenon of a wave and a particle will be exhibited. Both of them can be realized with near-unity probability and embody the charming characteristics of quantum mechanics. The employment of the mature techniques and simple operations (e.g., Homodyne measurement, classical feed forward, and single-photon transformations) provides the feasibility of the delayed-choice experiment proposals presented here.

Response to low-dose herbicide selection in self-pollinated Avena fatua.

PubMed

Busi, Roberto; Girotto, Marcelo; Powles, Stephen B

2016-03-01

When applied at the correct plant stage and dose, herbicides are highly toxic to plants. At reduced, low herbicide doses (below the recommended dose) plants can survive and display continuous and quantitative variation in dose-survival responses. Recurrent (directional) selection studies can reveal whether such a phenotypic variation in plant survival response to low herbicide dose is heritable and leads to herbicide resistance. In a common experimental garden study, we have subjected a susceptible population of self-pollinated hexaploid Avena fatua to low-dose recurrent selection with the ACCase-inhibiting herbicide diclofop-methyl for three consecutive generations. Significant differences in response to low-dose diclofop-methyl selection were observed between the selected progenies and parent plants, with a twofold diclofop-methyl resistance and cross-resistance to ALS-inhibiting herbicides. Thus, the capacity of self-pollinated A. fatua to respond to low-dose herbicide selection is marginal, and it is much lower than in cross-pollinated L. rigidum. Lolium rigidum in the same experiment evolved 40-fold diclofop-methyl resistance by progressive enrichment of quantitative resistance-endowing traits. Cross-pollination rate, genetic variation and ploidy levels are identified as possible drivers affecting the contrasting capacity of Avena versus Lolium plants to respond to herbicide selection and the subsequent likelihood of resistance evolution at low herbicide dose usage. © 2015 Society of Chemical Industry.

Secchi disk observation with spectral-selective glasses in blue and green waters.

PubMed

Lee, Zhongping; Shang, Shaoling; Lin, Gong; Liu, Tongtong; Liu, Yangyang; Du, Keping; Luis, Kelly

2017-08-21

Radiative transfer modeling of Secchi disk observations has historically been based on conjugated signals of eye response and radiance, where water's attenuation in the entire visible band is included in the attenuation when deciding the Secchi disk depth in water. Aas et al. [Ocean Sci.10(2), 177 (2014)Remote Sens. Environ.169, 139 (2015)] hypothesized that it is actually the attenuation in water's transparent window that matters to the observation of a Secchi disk in water. To test this hypothesis, observations of Secchi disks in blue and green waters were conducted via naked eyes, blue-pass glasses, and green-pass glasses. Measurement results indicate that for blue waters, the observed Secchi depths via naked eyes match the depths obtained with blue-pass glasses and much deeper than the depths with green-pass glasses, although the green-pass glasses match the highest response of human eyes. These observations experimentally support the hypothesis that our eye-brain system uses the contrast information in the transparent window to make a judgement decision regarding sighting a Secchi disk in water.

Cation Selectivity in Biological Cation Channels Using Experimental Structural Information and Statistical Mechanical Simulation

PubMed Central

Finnerty, Justin John

2015-01-01

Cation selective channels constitute the gate for ion currents through the cell membrane. Here we present an improved statistical mechanical model based on atomistic structural information, cation hydration state and without tuned parameters that reproduces the selectivity of biological Na+ and Ca2+ ion channels. The importance of the inclusion of step-wise cation hydration in these results confirms the essential role partial dehydration plays in the bacterial Na+ channels. The model, proven reliable against experimental data, could be straightforwardly used for designing Na+ and Ca2+ selective nanopores. PMID:26460827

Stochastic model search with binary outcomes for genome-wide association studies.

PubMed

Russu, Alberto; Malovini, Alberto; Puca, Annibale A; Bellazzi, Riccardo

2012-06-01

The spread of case-control genome-wide association studies (GWASs) has stimulated the development of new variable selection methods and predictive models. We introduce a novel Bayesian model search algorithm, Binary Outcome Stochastic Search (BOSS), which addresses the model selection problem when the number of predictors far exceeds the number of binary responses. Our method is based on a latent variable model that links the observed outcomes to the underlying genetic variables. A Markov Chain Monte Carlo approach is used for model search and to evaluate the posterior probability of each predictor. BOSS is compared with three established methods (stepwise regression, logistic lasso, and elastic net) in a simulated benchmark. Two real case studies are also investigated: a GWAS on the genetic bases of longevity, and the type 2 diabetes study from the Wellcome Trust Case Control Consortium. Simulations show that BOSS achieves higher precisions than the reference methods while preserving good recall rates. In both experimental studies, BOSS successfully detects genetic polymorphisms previously reported to be associated with the analyzed phenotypes. BOSS outperforms the other methods in terms of F-measure on simulated data. In the two real studies, BOSS successfully detects biologically relevant features, some of which are missed by univariate analysis and the three reference techniques. The proposed algorithm is an advance in the methodology for model selection with a large number of features. Our simulated and experimental results showed that BOSS proves effective in detecting relevant markers while providing a parsimonious model.

CO 2 hydrogenation on Pt, Pt/SiO 2 and Pt/TiO 2: Importance of synergy between Pt and oxide support

DOE PAGES

Kattel, Shyam; Yan, Binhang; Chen, Jingguang G.; ...

2016-01-27

In this paper we combined density functional theory (DFT), kinetic Monte Carlo (KMC) simulations and experimental measurements to gain insight into the mechanisms of CO 2 conversion by hydrogen on the Pt nanoparticle (NP). The results show that in spite of the presence of active, low-coordinated sites, Pt NP alone is not able to catalyze the reaction due to the weak CO 2 binding on the catalyst. Once CO 2 is stabilized, the hydrogenation of CO 2 to CO via the reverse-water–gas shift (RWGS) reaction is promoted; in contrast, the enhancement for further *CO hydrogenation to CH 4 is lessmore » significant and no CH 3OH is observed. The selectivity to CO is mainly determined by CO binding energy and the energetics of *CO hydrogenation to *HCO, while that for CH 4 and CH 3OH is determined by the competition between hydrogenation and C–O bond scission reactions of the *H 2COH species. Using SiO 2 and TiO 2 as the support, Pt NP is able to promote the overall CO 2 conversion, while the impact on the selectivity is rather small. The theoretically predicted trend in activity and selectivity is in good agreement with the experimental results. Finally, the enhanced activity of Pt/oxide over Pt is originated from the sites at the Pt–oxide interface, where the synergy between Pt and oxide plays an important role.« less

CO 2 hydrogenation on Pt, Pt/SiO 2 and Pt/TiO 2: Importance of synergy between Pt and oxide support

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

Kattel, Shyam; Yan, Binhang; Chen, Jingguang G.

In this paper we combined density functional theory (DFT), kinetic Monte Carlo (KMC) simulations and experimental measurements to gain insight into the mechanisms of CO 2 conversion by hydrogen on the Pt nanoparticle (NP). The results show that in spite of the presence of active, low-coordinated sites, Pt NP alone is not able to catalyze the reaction due to the weak CO 2 binding on the catalyst. Once CO 2 is stabilized, the hydrogenation of CO 2 to CO via the reverse-water–gas shift (RWGS) reaction is promoted; in contrast, the enhancement for further *CO hydrogenation to CH 4 is lessmore » significant and no CH 3OH is observed. The selectivity to CO is mainly determined by CO binding energy and the energetics of *CO hydrogenation to *HCO, while that for CH 4 and CH 3OH is determined by the competition between hydrogenation and C–O bond scission reactions of the *H 2COH species. Using SiO 2 and TiO 2 as the support, Pt NP is able to promote the overall CO 2 conversion, while the impact on the selectivity is rather small. The theoretically predicted trend in activity and selectivity is in good agreement with the experimental results. Finally, the enhanced activity of Pt/oxide over Pt is originated from the sites at the Pt–oxide interface, where the synergy between Pt and oxide plays an important role.« less

Targeted deletion of MKK4 in cancer cells: a detrimental phenotype manifests as decreased experimental metastasis and suggests a counterweight to the evolution of tumor-suppressor loss.

PubMed

Cunningham, Steven C; Gallmeier, Eike; Hucl, Tomas; Dezentje, David A; Calhoun, Eric S; Falco, Geppino; Abdelmohsen, Kotb; Gorospe, Myriam; Kern, Scott E

2006-06-01

Tumor-suppressors have commanded attention due to the selection for their inactivating mutations in human tumors. However, relatively little is understood about the inverse, namely, that tumors do not select for a large proportion of seemingly favorable mutations in tumor-suppressor genes. This could be explained by a detrimental phenotype accruing in a cell type-specific manner to most cells experiencing a biallelic loss. For example, MKK4, a tumor suppressor gene distinguished by a remarkably consistent mutational rate across diverse tumor types and an unusually high rate of loss of heterozygosity, has the surprisingly low rate of genetic inactivation of only approximately 5%. To explore this incongruity, we engineered a somatic gene knockout of MKK4 in human cancer cells. Although the null cells resembled the wild-type cells regarding in vitro viability and proliferation in plastic dishes, there was a marked difference in a more relevant in vivo model of experimental metastasis and tumorigenesis. MKK4(-/-) clones injected i.v. produced fewer lung metastases than syngeneic MKK4-competent cells (P = 0.0034). These findings show how cell type-specific detrimental phenotypes can offer a paradoxical and yet key counterweight to the selective advantage attained by cells as they experiment with genetic null states during tumorigenesis, the resultant balance then determining the observed biallelic mutation rate for a given tumor-suppressor gene.

Infrasound pulses from lightning and electrostatic field changes: Observation and discussion

NASA Astrophysics Data System (ADS)

Chum, J.; Diendorfer, G.; Å indelářová, T.; Baše, J.; Hruška, F.

2013-10-01

Narrow (~1-2 s) infrasound pulses that followed, with ~11 to ~50 s delays, rapid changes of electrostatic field were observed by a microbarometer array in the Czech Republic during thunderstorm activity. A positive pressure fluctuation (compression phase) always preceded decompression; the compression was usually higher than the decompression. The angles of arrival (azimuth and elevation) were analyzed for selected distinct events. Comparisons of distances and azimuths of infrasound sources from the center of microbarometer array with lightning locations determined by the European Cooperation for Lighting Detection lightning detection network show that most of the selected events can be very likely associated with intracloud (IC) discharges. The preceding rapid changes of electrostatic field, their potential association with IC discharges, and high-elevation angles of arrival for near infrasound sources indicate that an electrostatic mechanism is probably responsible for their generation. It is discussed that distinguishing the relative role of thermal and electrostatic mechanism is difficult and that none of the published models of electrostatic production of infrasound thunder can explain the presented observations precisely. A modification of the current models, based on consideration of at least two charged layers, is suggested. Further theoretical and experimental investigations are however needed to get a better description of the generation mechanism.

Genetic parameters and selection of soybean lines based on selection indexes.

PubMed

Teixeira, F G; Hamawaki, O T; Nogueira, A P O; Hamawaki, R L; Jorge, G L; Hamawaki, C L; Machado, B Q V; Santana, A J O

2017-09-21

Defining selection criteria is important to obtain promising genotypes in a breeding program. The objective of this study was to estimate genetic parameters for agronomic traits and to perform soybean line selection using selection indices. The experiment was conducted at an experimental area located at Capim Branco farm, belonging to the Federal University of Uberlândia. A total of 37 soybean genotypes were evaluated in randomized complete block design with three replicates, in which twelve agronomic traits were evaluated. Analysis of variance, the Scott-Knott test at the 1 and 5% level of probability, and selection index analyses were performed. There was genetic variability for all agronomic traits, with medium to high levels of genotype determination coefficient. Twelve lines with a total cycle up to 110 days were observed and grouped with the cultivars MSOY 6101 and UFUS 7910. Three lines, UFUS FG 03, UFUS FG 20, and UFUS FG 31, were highlighted regarding grain yield with higher values than the national average of 3072 kg/ha. The direct selection enabled the highest trait individual gains. The Williams (1962) index and the Smith (1936) and Hazel (1943) index presented the highest selection gain for the grain yield character. The genotype-ideotype distance index and the index of the sum of ranks of Mulamba and Mock (1978) presented higher values of total selection gain. The lines UFUS FG 12, UFUS FG 14, UFUS FG 18, UFUS FG 25, and UFUS FG 31 were distinguished as superior genotypes by direct selection methods and selection indexes.

Modulating RNA Alignment Using Directional Dynamic Kinks: Application in Determining an Atomic-Resolution Ensemble for a Hairpin using NMR Residual Dipolar Couplings.

PubMed

Salmon, Loïc; Giambaşu, George M; Nikolova, Evgenia N; Petzold, Katja; Bhattacharya, Akash; Case, David A; Al-Hashimi, Hashim M

2015-10-14

Approaches that combine experimental data and computational molecular dynamics (MD) to determine atomic resolution ensembles of biomolecules require the measurement of abundant experimental data. NMR residual dipolar couplings (RDCs) carry rich dynamics information, however, difficulties in modulating overall alignment of nucleic acids have limited the ability to fully extract this information. We present a strategy for modulating RNA alignment that is based on introducing variable dynamic kinks in terminal helices. With this strategy, we measured seven sets of RDCs in a cUUCGg apical loop and used this rich data set to test the accuracy of an 0.8 μs MD simulation computed using the Amber ff10 force field as well as to determine an atomic resolution ensemble. The MD-generated ensemble quantitatively reproduces the measured RDCs, but selection of a sub-ensemble was required to satisfy the RDCs within error. The largest discrepancies between the RDC-selected and MD-generated ensembles are observed for the most flexible loop residues and backbone angles connecting the loop to the helix, with the RDC-selected ensemble resulting in more uniform dynamics. Comparison of the RDC-selected ensemble with NMR spin relaxation data suggests that the dynamics occurs on the ps-ns time scales as verified by measurements of R(1ρ) relaxation-dispersion data. The RDC-satisfying ensemble samples many conformations adopted by the hairpin in crystal structures indicating that intrinsic plasticity may play important roles in conformational adaptation. The approach presented here can be applied to test nucleic acid force fields and to characterize dynamics in diverse RNA motifs at atomic resolution.

Selection of an omnivorous diet by the mangrove tree crab Aratus pisonii in laboratory experiments

NASA Astrophysics Data System (ADS)

Erickson, Amy A.; Feller, Ilka C.; Paul, Valerie J.; Kwiatkowski, Lisa M.; Lee, Woody

2008-02-01

Observational studies on leaf damage, gut content analyses, and crab behaviour have demonstrated that like numerous other mangrove and salt-marsh generalists, the mangrove tree crab Aratus pisonii feeds on a variety of food resources. This study is the first that experimentally tests feeding preferences of A. pisonii, as well as the first to test experimentally whether chemical composition of food resources is responsible for food selection. Feeding preferences were determined among a variety of plant, algal, and animal resources available in the field both in Florida and Belize, using multiple-choice feeding assays, where male and female crabs simultaneously were offered a variety of food items. To test whether chemistry of food resources was responsible for feeding preferences, chemical extracts of food resources were incorporated in an agar-based artificial food, and used in feeding assays. Results of feeding assays suggest that crabs prefer animal matter from ˜ 2.5 to 13× more than other available resources, including leaves of the red mangrove Rhizophora mangle, which contribute the most to their natural diet. Artificial feeding assays also demonstrated that chemical cues were responsible for selection of animal matter, up to 25× more than other available resources. Non-polar extracts (derived from extraction in 1:1 ethyl actetate:methanol) stimulated feeding the most, suggesting that fatty acids, triglycerides, or sterols may be important for growth, reproduction, or survival. Results for both sexes were similar across most assays. While chemical composition of food resources appears to play some role in selection, this does not discount the potential role of other factors, such as resource availability, competition, predation, or reproductive requirements in influencing feeding preferences. Bioassay-guided fractionation of extracts should aid in determining chemical constituents that play the greatest role in determining feeding preferences.

A Robust Adaptive Autonomous Approach to Optimal Experimental Design

NASA Astrophysics Data System (ADS)

Gu, Hairong

Experimentation is the fundamental tool of scientific inquiries to understand the laws governing the nature and human behaviors. Many complex real-world experimental scenarios, particularly in quest of prediction accuracy, often encounter difficulties to conduct experiments using an existing experimental procedure for the following two reasons. First, the existing experimental procedures require a parametric model to serve as the proxy of the latent data structure or data-generating mechanism at the beginning of an experiment. However, for those experimental scenarios of concern, a sound model is often unavailable before an experiment. Second, those experimental scenarios usually contain a large number of design variables, which potentially leads to a lengthy and costly data collection cycle. Incompetently, the existing experimental procedures are unable to optimize large-scale experiments so as to minimize the experimental length and cost. Facing the two challenges in those experimental scenarios, the aim of the present study is to develop a new experimental procedure that allows an experiment to be conducted without the assumption of a parametric model while still achieving satisfactory prediction, and performs optimization of experimental designs to improve the efficiency of an experiment. The new experimental procedure developed in the present study is named robust adaptive autonomous system (RAAS). RAAS is a procedure for sequential experiments composed of multiple experimental trials, which performs function estimation, variable selection, reverse prediction and design optimization on each trial. Directly addressing the challenges in those experimental scenarios of concern, function estimation and variable selection are performed by data-driven modeling methods to generate a predictive model from data collected during the course of an experiment, thus exempting the requirement of a parametric model at the beginning of an experiment; design optimization is performed to select experimental designs on the fly of an experiment based on their usefulness so that fewest designs are needed to reach useful inferential conclusions. Technically, function estimation is realized by Bayesian P-splines, variable selection is realized by Bayesian spike-and-slab prior, reverse prediction is realized by grid-search and design optimization is realized by the concepts of active learning. The present study demonstrated that RAAS achieves statistical robustness by making accurate predictions without the assumption of a parametric model serving as the proxy of latent data structure while the existing procedures can draw poor statistical inferences if a misspecified model is assumed; RAAS also achieves inferential efficiency by taking fewer designs to acquire useful statistical inferences than non-optimal procedures. Thus, RAAS is expected to be a principled solution to real-world experimental scenarios pursuing robust prediction and efficient experimentation.

Entropy-Based Search Algorithm for Experimental Design

NASA Astrophysics Data System (ADS)

Malakar, N. K.; Knuth, K. H.

2011-03-01

The scientific method relies on the iterated processes of inference and inquiry. The inference phase consists of selecting the most probable models based on the available data; whereas the inquiry phase consists of using what is known about the models to select the most relevant experiment. Optimizing inquiry involves searching the parameterized space of experiments to select the experiment that promises, on average, to be maximally informative. In the case where it is important to learn about each of the model parameters, the relevance of an experiment is quantified by Shannon entropy of the distribution of experimental outcomes predicted by a probable set of models. If the set of potential experiments is described by many parameters, we must search this high-dimensional entropy space. Brute force search methods will be slow and computationally expensive. We present an entropy-based search algorithm, called nested entropy sampling, to select the most informative experiment for efficient experimental design. This algorithm is inspired by Skilling's nested sampling algorithm used in inference and borrows the concept of a rising threshold while a set of experiment samples are maintained. We demonstrate that this algorithm not only selects highly relevant experiments, but also is more efficient than brute force search. Such entropic search techniques promise to greatly benefit autonomous experimental design.

An Overview of the Regional Experiments for Land-atmosphere Exchanges 2012 (REFLEX 2012) Campaign

NASA Astrophysics Data System (ADS)

Timmermans, Wim J.; van der Tol, Christiaan; Timmermans, Joris; Ucer, Murat; Chen, Xuelong; Alonso, Luis; Moreno, Jose; Carrara, Arnaud; Lopez, Ramon; de la Cruz Tercero, Fernando; Corcoles, Horacio L.; de Miguel, Eduardo; Sanchez, Jose A. G.; Pérez, Irene; Franch, Belen; Munoz, Juan-Carlos J.; Skokovic, Drazen; Sobrino, Jose; Soria, Guillem; MacArthur, Alasdair; Vescovo, Loris; Reusen, Ils; Andreu, Ana; Burkart, Andreas; Cilia, Chiara; Contreras, Sergio; Corbari, Chiara; Calleja, Javier F.; Guzinski, Radoslaw; Hellmann, Christine; Herrmann, Ittai; Kerr, Gregoire; Lazar, Adina-Laura; Leutner, Benjamin; Mendiguren, Gorka; Nasilowska, Sylwia; Nieto, Hector; Pachego-Labrador, Javier; Pulanekar, Survana; Raj, Rahul; Schikling, Anke; Siegmann, Bastian; von Bueren, Stefanie; Su, Zhongbo (Bob)

2015-12-01

The REFLEX 2012 campaign was initiated as part of a training course on the organization of an airborne campaign to support advancement of the understanding of land-atmosphere interaction processes. This article describes the campaign, its objectives and observations, remote as well as in situ. The observations took place at the experimental Las Tiesas farm in an agricultural area in the south of Spain. During the period of ten days, measurements were made to capture the main processes controlling the local and regional land-atmosphere exchanges. Apart from multi-temporal, multi-directional and multi-spatial space-borne and airborne observations, measurements of the local meteorology, energy fluxes, soil temperature profiles, soil moisture profiles, surface temperature, canopy structure as well as leaf-level measurements were carried out. Additional thermo-dynamical monitoring took place at selected sites. After presenting the different types of measurements, some examples are given to illustrate the potential of the observations made.

Feedback between environment and traits under selection in a seasonal environment: consequences for experimental evolution.

PubMed

Collot, Dorian; Nidelet, Thibault; Ramsayer, Johan; Martin, Olivier C; Méléard, Sylvie; Dillmann, Christine; Sicard, Delphine; Legrand, Judith

2018-04-11

Batch cultures are frequently used in experimental evolution to study the dynamics of adaptation. Although they are generally considered to simply drive a growth rate increase, other fitness components can also be selected for. Indeed, recurrent batches form a seasonal environment where different phases repeat periodically and different traits can be under selection in the different seasons. Moreover, the system being closed, organisms may have a strong impact on the environment. Thus, the study of adaptation should take into account the environment and eco-evolutionary feedbacks. Using data from an experimental evolution on yeast Saccharomyces cerevisiae , we developed a mathematical model to understand which traits are under selection, and what is the impact of the environment for selection in a batch culture. We showed that two kinds of traits are under selection in seasonal environments: life-history traits, related to growth and mortality, but also transition traits, related to the ability to react to environmental changes. The impact of environmental conditions can be summarized by the length of the different seasons which weight selection on each trait: the longer a season is, the higher the selection on associated traits. Since phenotypes drive season length, eco-evolutionary feedbacks emerge. Our results show how evolution in successive batches can affect season lengths and strength of selection on different traits. © 2018 The Author(s).

Sexual selection expedites the evolution of pesticide resistance.

PubMed

Jacomb, Frances; Marsh, Jason; Holman, Luke

2016-12-01

The evolution of insecticide resistance by crop pests and disease vectors causes serious problems for agriculture and health. Sexual selection can accelerate or hinder adaptation to abiotic challenges in a variety of ways, but the effect of sexual selection on resistance evolution is little studied. Here, we examine this question using experimental evolution in the pest insect Tribolium castaneum. The experimental removal of sexual selection slowed the evolution of resistance in populations treated with pyrethroid pesticide, and also reduced the rate at which resistance was lost from pesticide-free populations. These results suggest that selection arising from variance in mating and fertilization success can augment natural selection on pesticide resistance, meaning that sexual selection should be considered when designing strategies to limit the evolution of pesticide resistance. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

Observation of Weyl points

Science.gov Websites

copolymers, liquid crystals. Experimental observation of Weyl points First public annoucement on 11 Feburary Vishwanath from University of California, Berkeley. "Experimental Observation of Weyl Semimetals" ; Published by Science on 16 July, 2015. "Experimental observation of Weyl points" Featured on the

Field-induced exciton condensation in LaCoO3

PubMed Central

Sotnikov, A.; Kuneš, J.

2016-01-01

Motivated by recent observation of magnetic field induced transition in LaCoO3 we study the effect of external field in systems close to instabilities towards spin-state ordering and exciton condensation. We show that, while in both cases the transition can be induced by an external field, temperature dependencies of the critical field have opposite slopes. Based on this result we argue that the experimental observations select the exciton condensation scenario. We show that such condensation is possible due to high mobility of the intermediate spin excitations. The estimated width of the corresponding dispersion is large enough to overrule the order of atomic multiplets and to make the intermediate spin excitation propagating with a specific wave vector the lowest excitation of the system. PMID:27461512

Experimental study of the γ p → π 0 η p reaction with the A2 setup at the Mainz Microtron

DOE PAGES

Sokhoyan, V.; Prakhov, S.; Fix, A.; ...

2018-05-01

The data available from the A2 Collaboration at MAMI were analyzed to select the γp → π0ηp reaction on an event-by-event basis, which allows for partial-wave analyses of three-body final states to obtain more reliable results, compared to fits to measured distributions. These data provide the world’s best statistical accuracy in the energy range from threshold to Eγ = 1.45 GeV, allowing a finer energy binning in the measurement of all observables needed for understanding the reaction dynamics.The results obtained for themeasured observables are compared to existing models, and the impact from the new data is checked by the fitmore » with the revised Mainz model.« less

Being in a "Green" Building Elicits "Greener" Recycling, but Not Necessarily "Better" Recycling.

PubMed

Wu, David W-L; DiGiacomo, Alessandra; Lenkic, Peter J; Wong, Vanessa K; Kingstone, Alan

2016-01-01

Previous observational work revealed that transient populations in a sustainable building disposed of waste more accurately when compared to patrons in a non-sustainable building. The current study uses an experimental design to replicate this observed effect and to investigate whether or not the built environment influences motivational factors to impact behavior. We find support that a building designed and built to communicate an atmosphere of sustainability can influence waste disposal behavior. Participants in the sustainable building used the garbage receptacle significantly less and compensated by tending to select the containers and organics receptacle more, which actually resulted in more errors overall. Our findings suggest that building atmospherics can motivate people to recycle more. However, atmospherics alone do not appear to be sufficient to elicit the desired performance outcome.

Multistage classification of multispectral Earth observational data: The design approach

NASA Technical Reports Server (NTRS)

Bauer, M. E. (Principal Investigator); Muasher, M. J.; Landgrebe, D. A.

1981-01-01

An algorithm is proposed which predicts the optimal features at every node in a binary tree procedure. The algorithm estimates the probability of error by approximating the area under the likelihood ratio function for two classes and taking into account the number of training samples used in estimating each of these two classes. Some results on feature selection techniques, particularly in the presence of a very limited set of training samples, are presented. Results comparing probabilities of error predicted by the proposed algorithm as a function of dimensionality as compared to experimental observations are shown for aircraft and LANDSAT data. Results are obtained for both real and simulated data. Finally, two binary tree examples which use the algorithm are presented to illustrate the usefulness of the procedure.

Experimental study of the γ p →π0η p reaction with the A2 setup at the Mainz Microtron

NASA Astrophysics Data System (ADS)

Sokhoyan, V.; Prakhov, S.; Fix, A.; Abt, S.; Achenbach, P.; Adlarson, P.; Afzal, F.; Aguar-Bartolomé, P.; Ahmed, Z.; Ahrens, J.; Annand, J. R. M.; Arends, H. J.; Bantawa, K.; Bashkanov, M.; Beck, R.; Biroth, M.; Borisov, N. S.; Braghieri, A.; Briscoe, W. J.; Cherepnya, S.; Cividini, F.; Collicott, C.; Costanza, S.; Denig, A.; Dieterle, M.; Downie, E. J.; Drexler, P.; Ferretti Bondy, M. I.; Fil'kov, L. V.; Gardner, S.; Garni, S.; Glazier, D. I.; Gorodnov, I.; Gradl, W.; Günther, M.; Gurevich, G. M.; Hamill, C. B.; Heijkenskjöld, L.; Hornidge, D.; Huber, G. M.; Käser, A.; Kashevarov, V. L.; Kay, S.; Keshelashvili, I.; Kondratiev, R.; Korolija, M.; Krusche, B.; Lazarev, A.; Lisin, V.; Livingston, K.; Lutterer, S.; MacGregor, I. J. D.; Manley, D. M.; Martel, P. P.; McGeorge, J. C.; Middleton, D. G.; Miskimen, R.; Mornacchi, E.; Mushkarenkov, A.; Neganov, A.; Neiser, A.; Oberle, M.; Ostrick, M.; Otte, P. B.; Paudyal, D.; Pedroni, P.; Polonski, A.; Ron, G.; Rostomyan, T.; Sarty, A.; Sfienti, C.; Spieker, K.; Steffen, O.; Strakovsky, I. I.; Strandberg, B.; Strub, Th.; Supek, I.; Thiel, A.; Thiel, M.; Thomas, A.; Unverzagt, M.; Usov, Yu. A.; Wagner, S.; Walford, N. K.; Watts, D. P.; Werthmüller, D.; Wettig, J.; Witthauer, L.; Wolfes, M.; Zana, L. A.; A2 Collaboration at MAMI

2018-05-01

The data available from the A2 Collaboration at MAMI were analyzed to select the γ p →π0η p reaction on an event-by-event basis, which allows for partial-wave analyses of three-body final states to obtain more reliable results, compared to fits to measured distributions. These data provide the world's best statistical accuracy in the energy range from threshold to Eγ=1.45 GeV, allowing a finer energy binning in the measurement of all observables needed for understanding the reaction dynamics. The results obtained for the measured observables are compared to existing models, and the impact from the new data is checked by the fit with the revised Mainz model.

Is Chemically Synthesized Graphene ‘Really’ a Unique Substrate for SERS and Fluorescence Quenching?

NASA Astrophysics Data System (ADS)

Sil, Sanchita; Kuhar, Nikki; Acharya, Somnath; Umapathy, Siva

2013-11-01

We demonstrate observation of Raman signals of different analytes adsorbed on carbonaceous materials, such as, chemically reduced graphene, graphene oxide (GO), multi-walled carbon nanotube (MWCNT), graphite and activated carbon. The analytes selected for the study were Rhodamine 6G (R6G) (in resonant conditions), Rhodamine B (RB), Nile blue (NBA), Crystal Violet (CV) and acetaminophen (paracetamol). All the analytes except paracetamol absorb and fluoresce in the visible region. In this article we provide experimental evidence of the fact that observation of Raman signals of analytes on such carbonaceous materials are more due to resonance effect, suppression of fluorescence and efficient adsorption and that this property in not unique to graphene or nanotubes but prevalent for various type of carbon materials.

Observation of a new vibrational mode of (D{sub 2}O){sub 2} near 68 cm{sup {minus}1} using tunable far-infrared laser spectroscopy

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

Cruzan, J.D.; Loeser, J.G.; Bitten, E.R.

The authors have measured the far-infrared vibration-rotation-tunneling (VRT) spectrum of an intermolecular vibration of (D{sub 2}O){sub 2} near 68 cm{sup -1}. In addition, further transitions of the VRT band of (D{sub 2}O){sub 2} previously reported by Pugliano et al. have been observed. By considering symmetry restraints on the selection rules, these bands have been assigned to the out-of-plane H-bond torsional and in-plane acceptor wagging modes predicted by many theoretical calculations. The experimental-theoretical discrepancy in the measured frequencies of these bands indicates the importance of a fully coupled six-dimensional calculation of the dynamics for the water dimer.

The Fisher-Markov selector: fast selecting maximally separable feature subset for multiclass classification with applications to high-dimensional data.

PubMed

Cheng, Qiang; Zhou, Hongbo; Cheng, Jie

2011-06-01

Selecting features for multiclass classification is a critically important task for pattern recognition and machine learning applications. Especially challenging is selecting an optimal subset of features from high-dimensional data, which typically have many more variables than observations and contain significant noise, missing components, or outliers. Existing methods either cannot handle high-dimensional data efficiently or scalably, or can only obtain local optimum instead of global optimum. Toward the selection of the globally optimal subset of features efficiently, we introduce a new selector--which we call the Fisher-Markov selector--to identify those features that are the most useful in describing essential differences among the possible groups. In particular, in this paper we present a way to represent essential discriminating characteristics together with the sparsity as an optimization objective. With properly identified measures for the sparseness and discriminativeness in possibly high-dimensional settings, we take a systematic approach for optimizing the measures to choose the best feature subset. We use Markov random field optimization techniques to solve the formulated objective functions for simultaneous feature selection. Our results are noncombinatorial, and they can achieve the exact global optimum of the objective function for some special kernels. The method is fast; in particular, it can be linear in the number of features and quadratic in the number of observations. We apply our procedure to a variety of real-world data, including mid--dimensional optical handwritten digit data set and high-dimensional microarray gene expression data sets. The effectiveness of our method is confirmed by experimental results. In pattern recognition and from a model selection viewpoint, our procedure says that it is possible to select the most discriminating subset of variables by solving a very simple unconstrained objective function which in fact can be obtained with an explicit expression.

Basic Navigator Battery: An Experimental Selection Composite for Undergraduate Navigator Training.

ERIC Educational Resources Information Center

Shanahan, Frank M.; Kantor, Jeffrey E.

High rates of attrition among students in Undergraduate Navigator Training (UNT) is a major concern for Air Training Command. The main objective of this research was to evaluate the Basic Navigator Battery (BNB), a multi-test experimental selection instrument, for its potential to increase the validity of the Air Force Officer Qualifying Test…

Effects of Computer-Assisted Instruction on Performance of Senior High School Biology Students in Ghana

ERIC Educational Resources Information Center

Owusu, K. A.; Monney, K. A.; Appiah, J. Y.; Wilmot, E. M.

2010-01-01

This study investigated the comparative efficiency of computer-assisted instruction (CAI) and conventional teaching method in biology on senior high school students. A science class was selected in each of two randomly selected schools. The pretest-posttest non equivalent quasi experimental design was used. The students in the experimental group…

The Effects of Accelerated Math Utilization on Grade Equivalency Score at a Selected Elementary School

ERIC Educational Resources Information Center

Kariuki, Patrick; Gentry, Christi

2010-01-01

The purpose of this study was to examine the effects of Accelerated Math utilization on students' grade equivalency scores. Twelve students for both experimental and control groups were randomly selected from 37 students enrolled in math in grades four through six. The experimental group consisted of the students who actively participated in…

Reverse-engineering of gene networks for regulating early blood development from single-cell measurements.

PubMed

Wei, Jiangyong; Hu, Xiaohua; Zou, Xiufen; Tian, Tianhai

2017-12-28

Recent advances in omics technologies have raised great opportunities to study large-scale regulatory networks inside the cell. In addition, single-cell experiments have measured the gene and protein activities in a large number of cells under the same experimental conditions. However, a significant challenge in computational biology and bioinformatics is how to derive quantitative information from the single-cell observations and how to develop sophisticated mathematical models to describe the dynamic properties of regulatory networks using the derived quantitative information. This work designs an integrated approach to reverse-engineer gene networks for regulating early blood development based on singel-cell experimental observations. The wanderlust algorithm is initially used to develop the pseudo-trajectory for the activities of a number of genes. Since the gene expression data in the developed pseudo-trajectory show large fluctuations, we then use Gaussian process regression methods to smooth the gene express data in order to obtain pseudo-trajectories with much less fluctuations. The proposed integrated framework consists of both bioinformatics algorithms to reconstruct the regulatory network and mathematical models using differential equations to describe the dynamics of gene expression. The developed approach is applied to study the network regulating early blood cell development. A graphic model is constructed for a regulatory network with forty genes and a dynamic model using differential equations is developed for a network of nine genes. Numerical results suggests that the proposed model is able to match experimental data very well. We also examine the networks with more regulatory relations and numerical results show that more regulations may exist. We test the possibility of auto-regulation but numerical simulations do not support the positive auto-regulation. In addition, robustness is used as an importantly additional criterion to select candidate networks. The research results in this work shows that the developed approach is an efficient and effective method to reverse-engineer gene networks using single-cell experimental observations.

[Effect of a tooth-brushing education program on oral health of preschool children].

PubMed

Kang, Bok-Hee; Park, Sun-Nam; Sohng, Kyeong-Yae; Moon, Jung-Soon

2008-12-01

To examine the effect of tooth-brushing education on the oral health of preschoolers. A quasi-experimental design with a non-equivalent control group was used. Two kindergartens were selected and 39 preschoolers from one kindergarten were assigned to the experimental group with tooth-brushing education and 39 from the other kindergarten to the control group. The tooth-brushing education program included 1 session on oral health education, individual tooth-brushing instruction for 1 week and supervised tooth-brushing after lunch for 4 weeks. Oral health behavior including use of tooth paste, tooth-brushing time and method of tooth-brushing, plague, streptococcus mutans, lactobacillus and dental caries were measured before and after the education. Fisher's exact test, t-test and paired t-test with the Window SAS 9.1 program were used to analyze the data. A significant increase in the use of tooth paste, tooth-brushing time and the practice of correct tooth-brushing and a decrease in plague and development of dental caries were observed in the experimental group. This tooth-brushing education was partially effective in improving oral health of preschoolers.

Fantastic plastic? Experimental evaluation of polyurethane bone substitutes as proxies for human bone in trauma simulations.

PubMed

Smith, Martin J; James, Stephen; Pover, Tim; Ball, Nina; Barnetson, Victoria; Foster, Bethany; Guy, Carl; Rickman, John; Walton, Virginia

2015-09-01

Recent years have seen steady improvements in the recognition and interpretation of violence related injuries in human skeletal remains. Such work has at times benefited from the involvement of biological anthropologists in forensic casework and has often relied upon comparison of documented examples with trauma observed in skeletal remains. In cases where no such example exists investigators must turn to experimentation. The selection of experimental samples is problematic as animal proxies may be too dissimilar to humans and human cadavers may be undesirable for a raft of reasons. The current article examines a third alternative in the form of polyurethane plates and spheres marketed as viable proxies for human bone in ballistic experiments. Through subjecting these samples to a range of impacts from both modern and archaic missile weapons it was established that such material generally responds similarly to bone on a broad, macroscopic scale but when examined in closer detail exhibits a range of dissimilarities that call for caution in extrapolating such results to real bone. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Effectiveness of Mindfulness-Based Group Therapy Compared to the Usual Opioid Dependence Treatment.

PubMed

Imani, Saeed; Atef Vahid, Mohammad Kazem; Gharraee, Banafsheh; Noroozi, Alireza; Habibi, Mojtaba; Bowen, Sarah

2015-06-01

This study investigated the effectiveness of mindfulness-based group therapy (MBGT) compared to the usual opioid dependence treatment (TAU).Thirty outpatients meeting the DSM-IV-TR criteria for opioid dependence from Iranian National Center for Addiction Studies (INCAS) were randomly assigned into experimental (Mindfulness-Based Group Therapy) and control groups (the Usual Treatment).The experimental group undertook eight weeks of intervention, but the control group received the usual treatment according to the INCAS program. The Five Factor Mindfulness Questionnaire (FFMQ) and the Addiction Sevier Index (ASI) were administered at pre-treatment and post-treatment assessment periods. Thirteen patients from the experimental group and 15 from the control group completed post-test assessments. The results of MANCOVA revealed an increase in mean scores in observing, describing, acting with awareness, non-judging, non-reacting, and decrease in mean scores of alcohol and opium in MBGT patient group. The effectiveness of MBGT, compared to the usual treatment, was discussed in this paper as a selective protocol in the health care setting for substance use disorders.

Effectiveness of Mindfulness-Based Group Therapy Compared to the Usual Opioid Dependence Treatment

PubMed Central

Imani, Saeed; Atef Vahid, Mohammad Kazem; Gharraee, Banafsheh; Noroozi, Alireza; Habibi, Mojtaba; Bowen, Sarah

2015-01-01

Objective: This study investigated the effectiveness of mindfulness-based group therapy (MBGT) compared to the usual opioid dependence treatment (TAU).Thirty outpatients meeting the DSM-IV-TR criteria for opioid dependence from Iranian National Center for Addiction Studies (INCAS) were randomly assigned into experimental (Mindfulness-Based Group Therapy) and control groups (the Usual Treatment).The experimental group undertook eight weeks of intervention, but the control group received the usual treatment according to the INCAS program. Methods: The Five Factor Mindfulness Questionnaire (FFMQ) and the Addiction Sevier Index (ASI) were administered at pre-treatment and post-treatment assessment periods. Thirteen patients from the experimental group and 15 from the control group completed post-test assessments. Results: The results of MANCOVA revealed an increase in mean scores in observing, describing, acting with awareness, non-judging, non-reacting, and decrease in mean scores of alcohol and opium in MBGT patient group. Conclusion: The effectiveness of MBGT, compared to the usual treatment, was discussed in this paper as a selective protocol in the health care setting for substance use disorders. PMID:26877751

Numerical and Experimental Analysis on Inorganic Phase Change Material Usage in Construction

NASA Astrophysics Data System (ADS)

Muthuvel, S.; Saravanasankar, S.; Sudhakarapandian, R.; Muthukannan, M.

2014-12-01

This work demonstrates the significance of Phase Change Material (PCM) in the construction of working sheds and product storage magazines in fireworks industries to maintain less temperature variation by passive cooling. The inorganic PCM, namely Calcium Chloride Hexahydrate (CCH) is selected in this study. First, the performance of two models with inbuilt CCH was analysed, using computational fluid dynamics. A significant change in the variation of inner wall temperature was observed, particularly during the working hours. This is mainly due to passive cooling, where the heat transfer from the surroundings to the room is partially used for the phase change from solid to liquid. The experiment was carried out by constructing two models, one with PCM packed in hollow brick walls and roof, and the other one as a conventional construction. The experimental results show that the temperature of the room got significantly reduced up to 7 °C. The experimental analysis results had good agreement with the numerical analysis results, and this reveals the advantage of the PCM in the fireworks industry construction.

Optimization of Acid Black 172 decolorization by electrocoagulation using response surface methodology

PubMed Central

2012-01-01

This paper utilizes a statistical approach, the response surface optimization methodology, to determine the optimum conditions for the Acid Black 172 dye removal efficiency from aqueous solution by electrocoagulation. The experimental parameters investigated were initial pH: 4–10; initial dye concentration: 0–600 mg/L; applied current: 0.5-3.5 A and reaction time: 3–15 min. These parameters were changed at five levels according to the central composite design to evaluate their effects on decolorization through analysis of variance. High R2 value of 94.48% shows a high correlation between the experimental and predicted values and expresses that the second-order regression model is acceptable for Acid Black 172 dye removal efficiency. It was also found that some interactions and squares influenced the electrocoagulation performance as well as the selected parameters. Optimum dye removal efficiency of 90.4% was observed experimentally at initial pH of 7, initial dye concentration of 300 mg/L, applied current of 2 A and reaction time of 9.16 min, which is close to model predicted (90%) result. PMID:23369574

Determination of pKa values of new phenacyl-piperidine derivatives by potentiometric titration method in aqueous medium at room temperature (25±0.5oC).

PubMed

Zafar, Shaista; Akhtar, Shamim; Tariq, Talat; Mushtaq, Noushin; Akram, Arfa; Ahmed, Ahsaan; Arif, Muhammad; Naeem, Sabahat; Anwar, Sana

2014-07-01

Dissociation constant (pKa) of ten novel phenacyl derivatives of piperidine were determined by potentiometric titration method in aqueous medium at room temperature (25 ±0.5°C). The sample solutions were prepared in deionized water with ionic strength 0.01M and titrated with 0.1M NaOH solution. In addition, ΔG values were also calculated. Different prediction software programs were used to calculate pKa values too and compared to the experimentally observed pKa values. The experimental and theoretical values were found in close agreement. The results obtained in this research would help to predict the good absorption of the studied compounds and can be selected as lead molecules for the synthesis of CNS active agents because of their lipophilic nature especially compound VII.

Single-Step Laser-Assisted Graphene Oxide Reduction and Nonlinear Optical Properties Exploration via CW Laser Excitation

NASA Astrophysics Data System (ADS)

Ghasemi, Fatemeh; Razi, Sepehr; Madanipour, Khosro

2018-02-01

The synthesis of reduced graphene oxide using pulsed laser irradiation is experimentally investigated. For this purpose, various irradiation conditions were selected and the chemical features of the different products were explored using ultraviolet-visible, Fourier transform infrared and Raman spectroscopy techniques. Moreover, the nonlinear optical properties of the synthesized products were assessed by using open and closed aperture Z-scan techniques, in which continuous wave laser irradiating at 532-nm wavelength was utilized as the exciting source. The results clearly revealed that the degree of graphene oxide reduction not only depends on the amount of the irradiation dose (energy of the laser beam × exposure time) but also on the light source wavelength. Furthermore, strong dependency between the nonlinear optical properties of the products and the amount of the de-oxygenation was observed. The experimental results are discussed in detail.

Site-selective detection of vibrational modes of an iron atom in a trinuclear complex

NASA Astrophysics Data System (ADS)

Faus, Isabelle; Rackwitz, Sergej; Wolny, Juliusz A.; Banerjee, Atanu; Kelm, Harald; Krüger, Hans-Jörg; Schlage, Kai; Wille, Hans-Christian; Schünemann, Volker

2016-12-01

Nuclear inelastic scattering (NIS) experiments on the trinuclear complex [57Fe{L-N4(CH2Fc)2} (CH3CN)2](ClO4)2 have been performed. The octahedral iron ion in the complex was labelled with 57Fe and thereby exclusively the vibrational modes of this iron ion have been detected with NIS. The analysis of nuclear forward scattering (NFS) data yields a ferrous low-spin state for the 57Fe labelled iron ion. The simulation of the partial density of states (pDOS) for the octahedral low-spin iron(II) ion of the complex by density functional theory (DFT) calculations is in excellent agreement with the experimental pDOS of the complex determined from the NIS data obtained at 80 K. Thereby it was possible to assign almost each of the experimentally observed NIS bands to the corresponding molecular vibrational modes.

Experimental modification of interpretation bias about animal fear in young children: effects on cognition, avoidance behavior, anxiety vulnerability, and physiological responding.

PubMed

Lester, Kathryn J; Field, Andy P; Muris, Peter

2011-01-01

This study investigated the effects of experimentally modifying interpretation biases for children's cognitions, avoidance behavior, anxiety vulnerability, and physiological responding. Sixty-seven children (6-11 years) were randomly assigned to receive a positive or negative interpretation bias modification procedure to induce interpretation biases toward or away from threat about ambiguous situations involving Australian marsupials. Children rapidly learned to select outcomes of ambiguous situations, which were congruent with their assigned condition. Furthermore, following positive modification, children's threat biases about novel ambiguous situations significantly decreased, whereas threat biases significantly increased after negative modification. In response to a stress-evoking behavioral avoidance test, positive modification attenuated behavioral avoidance compared to negative modification. However, no significant effects of bias modification on anxiety vulnerability or physiological responses to this stress-evoking Behavioral Avoidance Task were observed.

Effects of Copper Exposure on Photosynthesis and Growth of the Seagrass Cymodocea nodosa: An Experimental Assessment.

PubMed

Llagostera, Izaskun; Cervantes, Daniel; Sanmartí, Neus; Romero, Javier; Pérez, Marta

2016-09-01

Seagrasses form some of the most important coastal habitats. They may be negatively affected by trace metal contamination in certain coastal areas. In this study we experimentally assessed selected morphological and physiological traits of the seagrass Cymodocea nodosa, with increasing concentrations of copper (Cu) under controlled laboratory conditions. Short term (21 days) sub-lethal effects such as decreased maximum quantum yield, increased leaf necrosis and decreased shoot growth and shoot recruitment were clearly observed at the highest Cu exposure (5 mg L(-1)), while the effects were weaker at the intermediate concentration (2.5 mg L(-1)) and almost absent at the lowest concentration (1 mg L(-1)), indicating that this species is highly tolerant to copper exposure, at least in the short term. This fact could help to explain its distribution in relatively polluted coastal waters.

Superhydrophobic nanofluidic channels for enhanced electrokinetic conversion

NASA Astrophysics Data System (ADS)

Checco, Antonio; Al Hossain, Aktaruzzaman; Rahmani, Amir; Black, Charles; Doerk, Gregory; Colosqui, Carlos

2017-11-01

We present current efforts in the development of novel slit nanofluidic channels with superhydrophobic nanostructured surfaces designed to enhance hydrodynamic conductivity and improve selective transport and electrokinetic energy conversion efficiencies (mechanical-electrical energy conversion). The nanochannels are fabricated on silicon wafers using UV lithography, and their internal surface is patterned with conical nanostructures (feature size and spacing 30 nm) defined by block copolymer self-assembly and plasma etching. These nanostructures are rendered superhydrophobic by passivation with a hydrophobic silane monolayer. We experimentally characterize hydrodynamic conductivity, effective zeta potentials, and eletrokinetic flows for the patterned nanochannels, comparing against control channels with bare surfaces. Experimental observations are rationalized using both continuum-based modeling and molecular dynamics simulations. Scientific and technical knowledge produced by this work is particularly relevant for sustainable energy conversion and storage, separation processes and water treatment using nanoporous materials. The ONR Contract # N000141613178 and NSF-CBET award# 1605809.

Identification of new allosteric sites and modulators of AChE through computational and experimental tools.

PubMed

Roca, Carlos; Requena, Carlos; Sebastián-Pérez, Víctor; Malhotra, Sony; Radoux, Chris; Pérez, Concepción; Martinez, Ana; Antonio Páez, Juan; Blundell, Tom L; Campillo, Nuria E

2018-12-01

Allosteric sites on proteins are targeted for designing more selective inhibitors of enzyme activity and to discover new functions. Acetylcholinesterase (AChE), which is most widely known for the hydrolysis of the neurotransmitter acetylcholine, has a peripheral allosteric subsite responsible for amyloidosis in Alzheimer's disease through interaction with amyloid β-peptide. However, AChE plays other non-hydrolytic functions. Here, we identify and characterise using computational tools two new allosteric sites in AChE, which have allowed us to identify allosteric inhibitors by virtual screening guided by structure-based and fragment hotspot strategies. The identified compounds were also screened for in vitro inhibition of AChE and three were observed to be active. Further experimental (kinetic) and computational (molecular dynamics) studies have been performed to verify the allosteric activity. These new compounds may be valuable pharmacological tools in the study of non-cholinergic functions of AChE.

Experimental nanocalorimetry of protonated and deprotonated water clusters

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

Boulon, Julien; Braud, Isabelle; Zamith, Sébastien

2014-04-28

An experimental nanocalorimetric study of mass selected protonated (H{sub 2}O){sub n}H{sup +} and deprotonated (H{sub 2}O){sub n−1}OH{sup −} water clusters is reported in the size range n = 20–118. Water cluster's heat capacities exhibit a change of slope at size dependent temperatures varying from 90 to 140 K, which is ascribed to phase or structural transition. For both anionic and cationic species, these transition temperatures strongly vary at small sizes, with higher amplitude for protonated than for deprotonated clusters, and change more smoothly above roughly n ≈ 35. There is a correlation between bonding energies and transition temperatures, which ismore » split in two components for protonated clusters while only one component is observed for deprotonated clusters. These features are tentatively interpreted in terms of structural properties of water clusters.« less

Experimental verification of position-dependent angular-momentum selection rules for absorption of twisted light by a bound electron

NASA Astrophysics Data System (ADS)

Afanasev, Andrei; Carlson, Carl E.; Schmiegelow, Christian T.; Schulz, Jonas; Schmidt-Kaler, Ferdinand; Solyanik, Maria

2018-02-01

We analyze the multipole excitation of atoms with twisted light, i.e, by a vortex light field that carries orbital angular momentum. A single trapped 40Ca+ ion serves as a localized and positioned probe of the exciting field. We drive the {S}1/2\\to {D}5/2 transition and observe the relative strengths of different transitions, depending on the ion's transversal position with respect to the center of the vortex light field. On the other hand, transition amplitudes are calculated for a twisted light field in form of a Bessel beam, a Bessel-Gauss and a Laguerre-Gauss mode. Analyzing experimental obtained transition amplitudes we find agreement with the theoretical predictions at a level of better than 3%. Finally, we propose measurement schemes with two-ion crystals to enhance the sensing accuracy of vortex modes in future experiments.

Thermophoretically induced large-scale deformations around microscopic heat centers

NASA Astrophysics Data System (ADS)

Puljiz, Mate; Orlishausen, Michael; Köhler, Werner; Menzel, Andreas M.

2016-05-01

Selectively heating a microscopic colloidal particle embedded in a soft elastic matrix is a situation of high practical relevance. For instance, during hyperthermic cancer treatment, cell tissue surrounding heated magnetic colloidal particles is destroyed. Experiments on soft elastic polymeric matrices suggest a very long-ranged, non-decaying radial component of the thermophoretically induced displacement fields around the microscopic heat centers. We theoretically confirm this conjecture using a macroscopic hydrodynamic two-fluid description. Both thermophoretic and elastic effects are included in this theory. Indeed, we find that the elasticity of the environment can cause the experimentally observed large-scale radial displacements in the embedding matrix. Additional experiments confirm the central role of elasticity. Finally, a linearly decaying radial component of the displacement field in the experiments is attributed to the finite size of the experimental sample. Similar results are obtained from our theoretical analysis under modified boundary conditions.

Understanding the NMR properties and conformational behavior of indole vs. azaindole group in protoberberines: NICS and NCS analysis

NASA Astrophysics Data System (ADS)

Kadam, Shivaji S.; Toušek, Jaromír; Maier, Lukáš; Pipíška, Matej; Sklenář, Vladimír; Marek, Radek

2012-11-01

We report here the preparation and the structural investigation into a series of 8-(indol-1-yl)-7,8-dihydroprotoberberine derivatives derived from berberine, palmatine, and coptisine. Structures of these new compounds were characterized mainly by 2D NMR spectroscopy and the conformational behavior was investigated by using methods of density-functional theory (DFT). PBE0/6-311+G** calculated NMR chemical shifts for selected derivatives correlate excellently with the experimental NMR data and support the structural conclusions drawn from the NMR experiments. An interesting role of the nitrogen atom in position N7' of the indole moiety in 8-(7-azaindol-1-yl)-7,8-dihydroprotoberberines as compared to other 8-indolyl derivatives is investigated in detail. The experimentally observed trends in NMR chemical shifts are rationalized by DFT calculations and analysis based on the nucleus-independent chemical shifts (NICS) and natural localized molecular orbitals (NLMOs).

Investigation of singlet oxygen generation in Vit C-Cu2+ -LDL system by chemiluminescence method

NASA Astrophysics Data System (ADS)

Wang, Juan; Xing, Da; Tan, Shici; Tang, Yonghong; He, Yonghong

2002-04-01

In this study, by chemiluminescence method using a Cypridina luciferin analog, 2-methyl-6-(p-methoxyphenyl)-3,7- dihydroimidazo[1,2-a]pyrazin-3-one (MCLA), as a selective and sensitive chemiluminescence probe, singlet oxygen (1O2) formation was observed in the vit C- LDL-Cu2+ reaction system. Another experimental evidence for the generation of 1O2 was the quenching effect of sodium azide (NaN3) on vit C-induced chemiluminescence in the reaction mixture of LDL- Cu2+-MCLA. Analysis based on the experimental results indicated the plausible reaction mechanism is that vit C converts Cu2+ to its reduced state and vit C becomes vit C radical itself, thereby stimulating the formation of peroxyl radicals, and bimolecular reaction of peroxyl radicals results in 1O2 production in the above systems.

A multiscale strength model for tantalum over an extended range of strain rates

NASA Astrophysics Data System (ADS)

Barton, N. R.; Rhee, M.

2013-09-01

A strength model for tantalum is developed and exercised across a range of conditions relevant to various types of experimental observations. The model is based on previous multiscale modeling work combined with experimental observations. As such, the model's parameterization includes a hybrid of quantities that arise directly from predictive sub-scale physics models and quantities that are adjusted to align the model with experimental observations. Given current computing and experimental limitations, the response regions for sub-scale physics simulations and detailed experimental observations have been largely disjoint. In formulating the new model and presenting results here, attention is paid to integrated experimental observations that probe strength response at the elevated strain rates where a previous version of the model has generally been successful in predicting experimental data [Barton et al., J. Appl. Phys. 109(7), 073501 (2011)].

[Experimental study on long-term prevention effect of chitosan electrospun membrane on cerebrospinal fluid leakage].

PubMed

Guo, Xingfeng; Hou, Chunlin; Dou, Yuandong; Lin, Ye; Lei, Deqiao

2014-08-01

To study the long-term prevention effect of self-developed chitosan electrospun membrane on cerebrospinal fluid leakage. Twenty-five healthy adult New Zealand rabbits were selected to prepare the bilateral dural defect (0.8 cem x 0.8 cm in size) via midline incision of head. Defect of the right was repaired with chitosan electrospun membrane as the experimental group; defect of the left was not repaired as the control group. At 2-16 weeks after operation, one rabbit was sacrificed for the general observation of inflammatory response surrounding bone window and absorption of chitosan electrospun membrane; at 3 and 6 weeks after operation, 5 rabbits were sacrificed for sampling to observe histological change and collagen expression by_HE and Masson staining, and to measure the expressions of epidermal growth factor receptor (EGFR) and basic fibroblast growth factor (bFGF) by immunohistochemical staining. No inflammatory reaction of swelling, exudation, and sppuration appeared in the skin and subcutaneous tissue after operation in 2 groups. There was no adhesion around the chitosan electrospun membrane, and new fiber membrane formed under the chitosan electrospun membrane in the experimental group; no cerebrospinal fluid leakage happened; the chitosan electrospun membrane was gradually degraded with time, and was completely absorbed at 16 weeks. There was uneven scar around the dural detect in control group. Histological observation showed less inflammatory cell infiltration in the experimental group, showing significant difference in the number of inflammatory cells compared with control group at 3, 6 weeks (P < 0.05); capillary, granulation tissue and collagen fiber massively proliferated; collagen fiber arranged in line, and there was a clear borderline between chitosan electrospurn membrane and adjacent collagen fiber. The immunohistochemical staining showed that there were high expressions of bFGF and EGFR in the experimental group, and low expressions of bFGF and EGFR in the control group. Chitosan electrospun membrane for dural defect of rabbit can effectively reconstruct the dura, and it has exact long-term prevention effect on cerebrospinal fluid leakage.

Oviductal epithelial cells selected boar sperm according to their functional characteristics

PubMed Central

López-Úbeda, Rebeca; García-Vázquez, Francisco A; Gadea, Joaquín; Matás, Carmen

2017-01-01

The interaction of oviductal epithelial cells (OECs) with the spermatozoa has beneficial effects on the sperm functions. The aim of this study is to evaluate the in vitro fertilizing capacity of incubating spermatozoa previously selected by density gradient in OEC and determinate some sperm characteristics that could explain the results obtained. In this study, we assessed in vitro fertilization (IVF), tyrosine phosphorylation, phosphatidylserine translocation, nuclear DNA fragmentation, and chromatin decondensation. Three experimental sperm groups, previously selected by Percoll gradient, were established according to the origin of the sperm used for IVF: (i) W30 group: spermatozoa were incubated with oocytes in the absence of OEC; (ii) NB group: after sperm incubation in OEC, the unbound spermatozoa were incubated with oocytes, in the absence of OEC; and (iii) B group: after sperm incubation with OEC, the bound spermatozoa were incubated with oocytes in the OEC plates. The results showed that sperm from the NB group led to a lower IVF yield, accompanied by low penetration rates (NB: 19.6%, B: 94.9%, and W30: 62.9%; P < 0.001) and problems of nuclear decondensation. Moreover, higher levels of tyrosine phosphorylation were observed in the NB group compared with the W30 and B groups (NB: 58.7%, B: 2.5%, and W30: 4.5%; P < 0.01). A similar trend was observed in phosphatidylserine translocation (NB: 93.7%, B: 5.7%, and W30: 44.2%; P < 0.01). These results demonstrate that the OEC exerts a rigorous degree of sperm selection, even within an already highly selected population of spermatozoa, and can capture the best functional spermatozoa for fertilization. PMID:27232850

An observation about the relative hardiness of bacterial spores and planetary quarantine

NASA Technical Reports Server (NTRS)

Trauth, C. A., Jr.

1973-01-01

Planetary quarantine objectives are shown to be critically dependent on the deviation in the actual decimal-reduction-time or D values (i.e., the time necessary to reduce the population to one-tenth of its original value) of organisms on spacecraft from the values chosen for spacecraft sterilization that have been selected conservatively relative to defined experimental procedures and bacterial spore stocks. New data indicate that these D values are not conservative when compared with those of naturally occurring organisms. The possible implications of these new data for planetary quarantine are analyzed.

Beyond Self-Report: Emerging Methods for Capturing Individual Differences in Decision-Making Process

PubMed Central

Connors, Brenda L.; Rende, Richard; Colton, Timothy J.

2016-01-01

People vary in the way in which they approach decision-making, which impacts real-world behavior. There has been a surge of interest in moving beyond reliance on self-report measures to capture such individual differences. Particular emphasis has been placed on devising and applying a range of methodologies that include experimental, neuroscience, and observational paradigms. This paper provides a selective review of recent studies that illustrate the methods and yield of these approaches in terms of generating a deeper understanding of decision-making style and the notable differences that can be found across individuals. PMID:26973589