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1

Microbial characterization of a JP-4 fuel-contaminated site using a combined lipid biomarker/polymerase chain reaction--denaturing gradient gel electrophoresis (PCR-DGGE)-based approach.  

PubMed

The impact of pollution on soil microbial communities and subsequent bioremediation can be measured quantitatively in situ using direct, non-culture-dependent techniques. Such techniques have advantages over culture-based methods, which often account for less than 1% of the extant microbial community. In 1988, a JP-4 fuel spill contaminated the glacio-fluvial aquifer at Wurtsmith Air Force Base, Michigan, USA. In this study, lipid biomarker characterization of the bacterial and eukaryotic communities was combined with polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis of the eubacterial community to evaluate correlation between contaminant (JP-4 fuel) concentration and community structure shifts. Vadose, capillary fringe and saturated zone samples were taken from cores within and up- and down-gradient from the contaminant plume. Lipid biomarker analysis indicated that samples from within the plume contained increased biomass, with large proportions of typically gram-negative bacteria. Outside the plume, lipid profiles indicated low-biomass microbial communities compared with those within the initial spill site. 16S rDNA sequences derived from DGGE profiles from within the initial spill site suggested dominance of the eubacterial community by a limited number of phylogenetically diverse organisms. Used in tandem with pollutant quantification, these molecular techniques should facilitate significant improvements over current assessment procedures for the determination of remediation end-points. PMID:11207742

Stephen, J R; Chang, Y J; Gan, Y D; Peacock, A; Pfiffner, S M; Barcelona, M J; White, D C; Macnaughton, S J

1999-06-01

2

Polymerase chain reaction denaturing gradient gel electrophoresis analysis of the N2-fixing bacterial diversity in soil under Acacia tortilis ssp. raddiana and Balanites aegyptiaca in the dryland part of Senegal.  

PubMed

Denaturing gradient gel electrophoresis (DGGE) of amplified nifH gene fragments was used to study the diazotrophic community of soil samples under Acacia tortilis ssp. raddiana (legume tree) and Balanites aegyptiaca (non-legume tree), two dominant plant species growing naturally in the dryland part of Senegal. Samples were taken along transects from the stem up to 10 m distance from it, at depths of 0-0.25 m and 0.25-0.50 m. Sampling was done in the dry season (25 June 1999) and in the rainy season (28 August 1999). The community structure and diversity of the bacterial groups from the different samples was analysed further using different techniques, such as statistical analysis and diversity index evaluation of the band patterns. Diazotrophic diversity was lower under B. aegyptiaca than under A. tortilis ssp. raddiana. Multidimensional scaling (MDS) analysis and ANOSIM tests showed a significant effect of the tree on the diazotroph assemblages. SIMPER analysis showed that the major elements responsible for the dissimilarity are a member of the genus Sinorhizobium, which is characteristic of the samples taken under A. tortilis ssp. raddiana and a member of the cluster Bradyrhizobium for the samples taken under B. aegyptiaca. Forty-four major bands were partially sequenced, yielding 33 different nifH sequences, which were used in phylogenetic reconstructions. Most sequences were affiliated with the alpha- beta- and gamma-proteobacteria. Five nifH sequences were identical to those of Pseudomonas stutzeri, and one sequence showed 100% similarity to that of Azotobacter vinelandii. Four bands were affiliated with the Cyanobacteria and a single one with the Firmicutes. For both trees, there were also clear differences between the samples taken in the dry and rainy seasons. Only for the samples taken under A. tortilis ssp. raddiana was a significant difference found between the two sampling depths. PMID:15008817

Demba Diallo, Moudjahidou; Willems, Anne; Vloemans, Nele; Cousin, Sylvie; Vandekerckhove, Tom T; de Lajudie, Philippe; Neyra, Marc; Vyverman, Wim; Gillis, Monique; Van der Gucht, Katleen

2004-04-01

3

Tracking the composition and dominant components of the microbial community via polymerase chain reaction-denaturing gradient gel electrophoresis and fluorescence in situ hybridization during vermiconversion for liquid-state excess sludge stabilization.  

PubMed

To quantitatively explore the microbial community modified by earthworms, a vermifilter (VF, with earthworms) and a conventional biofilter (BF, without earthworms) were continuously operated to stabilize excess sludge. The results demonstrated a positive role imposed by earthworms on compositions and dominant components of microbial community in the VF. For one thing, the phyla Actinobacteria and Acidobacteria were only detected in the VF, which might explain for the higher Shannon index of bacteria in the VF (H = 2.58) than that in the BF (H = 1.99). For another, the total proportion of dominant bacteria in the VF increased by 23% compared to the BF. Moreover, quantification analysis explicitly noted that the dominant bacteria in VF were ?-proteobacteria (27 ± 2%) and ?-proteobacteria (24 ± 1%) while that in BF was Bacteroidetes (21 ± 1%). In conclusion, stimulated by earthworms, a unique microbial community developed in the VF, thus improving the stabilization of excess sludge. PMID:24971951

Xu, Ting; Xing, Meiyan; Yang, Jian; Lv, Baoyi; Duan, Ting; Nie, Jing

2014-09-01

4

Effectiveness of Denaturation Temperature Gradient-Polymerase Chain Reaction for Biased DNAAlgorithms*  

E-print Network

Effectiveness of Denaturation Temperature Gradient- Polymerase Chain Reaction for Biased temperature (Tm): the denaturation temperature gradient-polymerase chain reaction (DTG is the first consideration in the conventional PCR, the denaturation temperature is fixed at a constant

5

Mathematical Modeling and Simulation of Denaturation Temperature Gradient Polymerase Chain Reaction  

E-print Network

Mathematical Modeling and Simulation of Denaturation Temperature Gradient Polymerase Chain Reaction@bi.snu.ac.kr, thpark@plaza.snu.ac.kr Polymerase chain reaction (PCR) is a biochemical process for in vitro. In a previous study, we introduced denaturation temperature gradient polymerase chain reaction (DTG- PCR

Yoo, SukIn

6

Amount of training, deprivation, and variability of chain length as determinants of response-velocity gradients in homogeneous chains  

Microsoft Academic Search

Tested J. Platt and P. Senkowski's model for the acquisition of homogeneous behavior chains in 2 experiments with a total of 66 naive male holtzman rats. Ss were given discrete-trials lever-press training with different chain lengths and deprivation levels. Results of exp. I indicated that with constant chain lengths, response-velocity gradients were of a generally inverted- shape. As training proceeded,

John R. Platt

1972-01-01

7

Ratcheting and transitions: short granular chain in a gradient of vibration.  

PubMed

We report our experimental work on a one-dimensional gradient of vibration with a short granular chain. The system exhibits transitions of ratcheting dynamics from passive monotonic creeping against the gradient, to rapid stochastic head swinging with a reversed bias in its direction, and to seemingly random fluctuations. The spontaneously emerged spatial pattern reflects bifurcations of the state of the chain. Evidence from counterpart experiments using uniform vibrations confirms a nonmonotonic development of accessible modes behind the transitions, whereas the reversed ratcheting reflects an interesting dialogue between the size of the object and the spatial gradient. PMID:24580630

Lin, W-T; Sun, Y-C; Chang, C-C; Lin, Y-C; Peng, C-W; Juan, W-T; Tsai, J-C

2014-02-01

8

Extraordinarily low density of hepatitis C virus estimated by sucrose density gradient centrifugation and the polymerase chain reaction  

Microsoft Academic Search

The genomic RNA of hepatitis C virus (HCV) in the plasma of volunteer blood donors was detected by using the polymerase chain reaction in a fraction of density 1-08 g\\/ml from sucrose density gradient equilibrium centrifugation. When the fraction was treated with the detergent NP40 and recentrifuged in sucrose, the HCV RNA banded at 1.25g\\/ml. Assuming that NP40 removed a

Hideaki Miyamoto; Hiroaki Okamoto; Koei Sato; Takeshi Tanaka; Shunji Mishiro

1992-01-01

9

Thermal denaturation of double-stranded nucleic acids: prediction of temperatures critical for gradient gel electrophoresis and polymerase chain reaction.  

PubMed Central

A program is described which calculates the thermal stability and the denaturation behaviour of double-stranded DNAs and RNAs up to a length of 1000 base pairs. The algorithm is based on recursive generation of conditional and a priori probabilities for base stacking. Output of the program may be compared directly to experimental results; thus the program may be used to optimize the nucleic acid fragments, the primers and the experimental conditions prior to experiments like polymerase chain reactions, temperature-gradient gel electrophoresis, denaturing-gradient gel electrophoresis and hybridizations. The program is available in three versions; the first version runs interactively on VAXstations producing graphics output directly, the second is implemented as part of the HUSAR package at GENIUSnet, the third runs on any computer producing text output which serves as input to available graphics programs. Images PMID:8052531

Steger, G

1994-01-01

10

Molecular dynamics studies on the influences of a gradient electric field on the water chain in a peptide nanotube.  

PubMed

The structure and transportation characteristics of the water chain inside a 8×cyclo-(WL)4 peptide nanotube (PNT) were simulated under a gradient electric (GE) field. The gradient was defined by the ratio of a constant (Ea) and the z-directional length (Lz) of the simulation box. Ea varies from 0.0 to 0.9 V nm(-1). As the gradient increases, the probabilities of finding two water molecules in an ?-plane zone and three in a midplane region increase. To accommodate more water molecules, the axial array of channel water molecules becomes more compact. Meanwhile, the H-bonded network between the channel water is greatly intensified when Ea increases from 0.3 to 0.9 V nm(-1). Nevertheless, the proportion of strong H-bonds does not increase significantly following the formation of a more compact axial array of water molecules. When Ea reaches 0.9 V nm(-1), the water molecule in an ?-plane zone may be dragged by its neighboring water molecules into the midplane region, resulting in a significant deviation from the channel axis. With the augment of the gradient, the dipoles of channel water are gradually oriented along the tube axis in the sequence from gap 1 to 7, namely along the direction of the electric field. Nevertheless, even when E a reaches 0.9 V nm(-1), the dipole orientation of the channel water is not complete, and dipole flips still occur in gap 7. Under a GE field, the rightward and leftward hopping rates of channel water are no longer equal to each other, i.e., channel water performs an asymmetric transportation. PMID:25081606

Li, Hui; Fan, Jianfen F; Li, Rui; Yu, Yi; Yan, Xiliang L

2014-08-01

11

250-GHz electron spin resonance studies of polarity gradients along the aliphatic chains in phospholipid membranes.  

PubMed Central

Rigid-limit 250-GHz electron spin resonance (FIR-ESR) spectra have been studied for a series of phosphatidylcholine spin labels (n-PC, where n = 5, 7, 10, 12, 16) in pure lipid dispersions of dipalmitoylphosphatidylcholine (DPPC) and 1-palmitoyl-2-oleoylphosphatidylcholine (POPC), as well as dispersions of DPPC containing the peptide gramicidin A (GA) in a 1:1 molar ratio. The enhanced g-tensor resolution of 250-GHz ESR for these spin labels permitted a careful study of the nitroxide g-tensor as a function of spin probe location and membrane composition. In particular, as the spin label is displaced from the polar head group, Azz decreases and gxx increases as they assume values typical of a nonpolar environment, appropriate for the hydrophobic alkyl chains in the case of pure lipid dispersions. The field shifts of spectral features due to changes in gxx are an order of magnitude larger than those from changes in Azz. The magnetic tensor parameters measured in the presence of GA were characteristic of a polar environment and showed only a very weak dependence of Azz and gxx on label position. These results demonstrate the significant influence of GA on the local polarity along the lipid molecule, and may reflect increased penetration of water into the alkyl chain region of the lipid in the presence of GA. The spectra from the pure lipid dispersions also exhibit a broad background signal that is most significant for 7-, 10-, and 12-PC, and is more pronounced in DPPC than in POPC. It is attributed to spin probe aggregation yielding spin exchange narrowing. The addition of GA to DPPC essentially suppressed the broad background signal observed in pure DPPC dispersions. PMID:7518705

Earle, K. A.; Moscicki, J. K.; Ge, M.; Budil, D. E.; Freed, J. H.

1994-01-01

12

Culture-based and denaturing gradient gel electrophoresis analysis of the bacterial community structure from the intestinal tracts of earthworms(Eisenia fetida).  

PubMed

The bacterial communities in the intestinal tracts of earthworm were investigated by culture-dependent and - independent approaches. In total, 72 and 55 pure cultures were isolated from the intestinal tracts of earthworms under aerobic and anaerobic conditions, respectively. Aerobic bacteria were classified as Aeromonas (40%), Bacillus (37%), Photobacterium (10%), Pseudomonas (7%), and Shewanella (6%). Anaerobic bacteria were classified as Aeromonas (52%), Bacillus (27%), Shewanella (12%), Paenibacillus (5%), Clostridium (2%), and Cellulosimicrobium (2%). The dominant microorganisms were Aeromonas and Bacillus species under both aerobic and anaerobic conditions. In all, 39 DNA fragments were identified by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis. Aeromonas sp. was the dominant microorganism in feeds, intestinal tracts, and casts of earthworms. The DGGE band intensity of Aeromonas from feeds, intestinal tracts, and casts of earthworms was 12.8%, 14.7%, and 15.1%, respectively. The other strains identified were Bacillus, Clostridium, Enterobacter, Photobacterium, Pseudomonas, Shewanella, Streptomyces, uncultured Chloroflexi bacterium, and uncultured bacterium. These results suggest that PCR-DGGE analysis was more efficient than the culture-dependent approach for the investigation of bacterial diversity and the identification of unculturable microorganisms. PMID:21952364

Hong, Sung Wook; Kim, In Su; Lee, Ju Sam; Chung, Kun Sub

2011-09-01

13

Chain configuration and flexibility gradient in phospholipid membranes. Comparison between spin-label electron spin resonance and deuteron nuclear magnetic resonance, and identification of new conformations.  

PubMed Central

The electron spin resonance spectra of 1-myristoyl-2-[n-(4,4-dimethyloxazolidine-N-oxyl)myristoyl]-sn- glycero-3-phosphocholine spin-label positional isomers (n = 6, 10, and 13) have been studied in oriented, fully hydrated bilayers of dimyristoylphosphatidylcholine, as a function of temperature and magnetic field orientation. The spectra have been simulated using a line-shape model which incorporates chain rotational isomerism, as well as restricted anisotropic motion of the lipid molecules as a whole, and which is valid in all motional regimes of conventional spin-label electron spin resonance (ESR) spectroscopy. At least one component of the lipid motion is found to lie in the slow-motion regime for all label positions, even in the fluid liquid crystalline phase, well above the phase transition. In the gel phase, the chain isomerism lies in the slow-motional regime, and the overall motions are at the rigid-limit. In the fluid phase, the chain isomerism is in the fast-motional regime, and the chain axis motions are in the slow regime. This indicates that the commonly used motional-narrowing theory is not appropriate for the interpretation of spin-label spectra in biological membranes. The simulation parameters yield a consistent description for the chain order and dynamics for all label positions. The correlation times and order parameters for the overall motion are the same at all positions down the chain, whereas the chain conformation and trans-gauche isomerism rate display a characteristic flexibility gradient, with increasing motion towards the terminal methyl end of the chain. Significantly, it is found that all six distinct tetrahedral orientations of the hyperfine tensor at the labeled segment are required for a consistent description of the chain isomerism. For the C-6 segment only the 0 degree (trans) and two 60 degrees (gauche) orientations are significantly populated, for the C-10 position two further 60 degrees orientations are populated, and for the C-13 position all orientations have non-vanishing populations. Detailed comparisons have been made with the results of 2H nuclear magnetic resonance (NMR) measurements on dimyristoylphosphatidylcholine labeled at the same position in the sn-2 chain, and using an identical motional model. The parameters of overall reorientation, both order parameter and correlation times, have very similar values as determined by ESR and NMR. The major difference between the results from the two methods lies in the conformational populations at the labeled chain segment and the trans-gauche isomerization rate in the gel phase. The conformational order is much lower for the spin-labeled chain segments than for the corresponding deuterium-labeled segments, and the isomer interconversion rates in the gel phase(although displaying a mobility gradient in both cases) are found to be much slower in the former case. In addition the spin-label measurements provide information on the macro order (chain tilt), which is only available from oriented samples. These results are consistent between the different spin label positions and are in agreement with the findings from x-ray diffraction. PMID:2539207

Moser, M.; Marsh, D.; Meier, P.; Wassmer, K. H.; Kothe, G.

1989-01-01

14

Evaluation of PCR-DGGE as a method to recapitulate host phylogeny by fecal microbial community fingerprint  

Technology Transfer Automated Retrieval System (TEKTRAN)

Background: Recent studies indicate that host animal could be the primary factor determining the composition of the gastrointestinal microbiome. If host phenotype dictates microbiome composition, then composition should recapitulate host phylogeny. Polymerase chain reaction-denaturing gradient gel ...

15

A gradient Markov chain Monte Carlo algorithm for computing multivariate maximum likelihood estimates and posterior distributions: mixture dose-response assessment.  

PubMed

Multivariate probability distributions, such as may be used for mixture dose-response assessment, are typically highly parameterized and difficult to fit to available data. However, such distributions may be useful in analyzing the large electronic data sets becoming available, such as dose-response biomarker and genetic information. In this article, a new two-stage computational approach is introduced for estimating multivariate distributions and addressing parameter uncertainty. The proposed first stage comprises a?gradient Markov chain Monte Carlo?(GMCMC) technique to find Bayesian posterior mode estimates (PMEs) of parameters, equivalent to maximum likelihood estimates (MLEs) in the absence of subjective information. In the second stage, these estimates are used to initialize a Markov chain Monte Carlo (MCMC) simulation, replacing the conventional burn-in period to allow convergent simulation of the full joint Bayesian posterior distribution and the corresponding unconditional multivariate distribution (not conditional on uncertain parameter values). When the distribution of parameter uncertainty is such a Bayesian posterior, the unconditional distribution is termed?predictive. The method is demonstrated by finding conditional and unconditional versions of the recently proposed emergent dose-response function (DRF). Results are shown for the five-parameter common-mode and seven-parameter dissimilar-mode models, based on published data for eight benzene-toluene dose pairs. The common mode conditional DRF is obtained with a 21-fold reduction in data requirement versus MCMC. Example common-mode unconditional DRFs are then found using synthetic data, showing a 71% reduction in required data. The approach is further demonstrated for a PCB 126-PCB 153 mixture. Applicability is analyzed and discussed. Matlab(®) computer programs are provided. PMID:21906114

Li, Ruochen; Englehardt, James D; Li, Xiaoguang

2012-02-01

16

Application of PCR-denaturing-gradient gel electrophoresis (DGGE) method to examine microbial community structure in asparagus fields with growth inhibition due to continuous cropping.  

PubMed

Growth inhibition due to continuous cropping of asparagus is a major problem; the yield of asparagus in replanted fields is low compared to that in new fields, and missing plants occur among young seedlings. Although soil-borne disease and allelochemicals are considered to be involved in this effect, this is still controversial. We aimed to develop a technique for the biological field diagnosis of growth inhibition due to continuous cropping. Therefore, in this study, fungal community structure and Fusarium community structure in continuously cropped fields of asparagus were analyzed by polymerase chain reaction/denaturing-gradient gel electrophoresis (PCR-DGGE). Soil samples were collected from the Aizu region of Fukushima Prefecture, Japan. Soil samples were taken from both continuously cropped fields of asparagus with growth inhibition and healthy neighboring fields of asparagus. The soil samples were collected from the fields of 5 sets in 2008 and 4 sets in 2009. We were able to distinguish between pathogenic and non-pathogenic Fusarium by using Alfie1 and Alfie2GC as the second PCR primers and PCR-DGGE. Fungal community structure was not greatly involved in the growth inhibition of asparagus due to continuous cropping. By contrast, the band ratios of Fusarium oxysporum f. sp. asparagi in growth-inhibited fields were higher than those in neighboring healthy fields. In addition, there was a positive correlation between the band ratios of Fusarium oxysporum f. sp. asparagi and the ratios of missing asparagus plants. We showed the potential of biological field diagnosis of growth inhibition due to continuous cropping of asparagus using PCR-DGGE. PMID:22200640

Urashima, Yasufumi; Sonoda, Takahiro; Fujita, Yuko; Uragami, Atsuko

2012-01-01

17

Application of PCR-Denaturing-Gradient Gel Electrophoresis (DGGE) Method to Examine Microbial Community Structure in Asparagus Fields with Growth Inhibition due to Continuous Cropping  

PubMed Central

Growth inhibition due to continuous cropping of asparagus is a major problem; the yield of asparagus in replanted fields is low compared to that in new fields, and missing plants occur among young seedlings. Although soil-borne disease and allelochemicals are considered to be involved in this effect, this is still controversial. We aimed to develop a technique for the biological field diagnosis of growth inhibition due to continuous cropping. Therefore, in this study, fungal community structure and Fusarium community structure in continuously cropped fields of asparagus were analyzed by polymerase chain reaction/denaturing-gradient gel electrophoresis (PCR-DGGE). Soil samples were collected from the Aizu region of Fukushima Prefecture, Japan. Soil samples were taken from both continuously cropped fields of asparagus with growth inhibition and healthy neighboring fields of asparagus. The soil samples were collected from the fields of 5 sets in 2008 and 4 sets in 2009. We were able to distinguish between pathogenic and non-pathogenic Fusarium by using Alfie1 and Alfie2GC as the second PCR primers and PCR-DGGE. Fungal community structure was not greatly involved in the growth inhibition of asparagus due to continuous cropping. By contrast, the band ratios of Fusarium oxysporum f. sp. asparagi in growth-inhibited fields were higher than those in neighboring healthy fields. In addition, there was a positive correlation between the band ratios of Fusarium oxysporum f. sp. asparagi and the ratios of missing asparagus plants. We showed the potential of biological field diagnosis of growth inhibition due to continuous cropping of asparagus using PCR-DGGE. PMID:22200640

Urashima, Yasufumi; Sonoda, Takahiro; Fujita, Yuko; Uragami, Atsuko

2012-01-01

18

Detection of Clonal T-Cell Receptor ? Gene Rearrangements in Early Mycosis Fungoides\\/Sezary Syndrome by Polymerase Chain Reaction and Denaturing Gradient Gel Electrophoresis (PCR\\/DGGE)  

Microsoft Academic Search

We used a gene amplification strategy to analyze T-cell receptor (TCR) gene rearrangements in 185 specimens, including mycosis fungoides\\/Sezary syndrome (MF\\/SS), other cutaneous neoplasms, inflammatory dermatoses, reactive lymphoid tissues,and normal skin. Genomic DNA was extracted from lesional tissues and rearrangements of the TCR-? chain gene were amplified using the polymerase chain reaction (PCR) with primers specific for rearrangements involving V?1-8

Gary S. Wood; Rosnn M. Tung; Andreas C. Heaffner; Carol F. Crooks; Shaoyi Liao; Rachaci Orozco; Hendrik Veelken; Marshall E. Kadin; Howard Koh; Peter Heald; Raymond L. Barnhill; Jeffrey Sklar

1994-01-01

19

Geothermal Gradients  

NSDL National Science Digital Library

In this problem set the students use two different equations to calculate a conductive geothermal gradient using a spreadsheet program like Excel. Once they have the geothermal gradient plotted, they are asked to experiment with and comment on the model by changing parameters (e.g. mantle heat flow, thermal conductivity). There is a mix of specific, fill in the blank questions and open-ended questions. This problem set helps develop quantitative problem solving skills using a spreadsheet as a tool, and forces students to think about thermal constraints during igneous and metamorphic processes.

Davidson, Cameron

20

The ecological distribution and comparative photobiology of symbiotic dinoflagellates from reef corals in Belize: Potential implications for coral bleaching  

Microsoft Academic Search

The photobiology and distribution of dinoflagellates in the genus Symbiodinium was investigated for eight common reef coral species over a depth range of 1-25 m on a coral reef in Belize. The genetic identification of symbionts using polymerase chain reaction-denaturing gradient electrophoresis of the internal transcribed spacer 2 region revealed marked differences in host specificity and depth zonation for certain

Mark E. Warner; Todd C. LaJeunesse; Jennifer D. Robison; Rebecca M. Thur

2006-01-01

21

Molecular fingerprinting of bacterial populations in groundwater and bottled mineral water  

Microsoft Academic Search

Monitoring the hygienic quality of drinking waters by determining the concentration of fecal indicators with traditional plate count techniques suffers from important drawbacks. In this work, the potential of PCR-DGGE (polymerase chain reaction - denaturing gradient gel electrophoresis) analysis of 16S rDNA genes to fingerprint the bacterial populations of mineral water and groundwater was investigated. A rapid and simple pretreatment

T. Dewettinck; W. Hulsbosch; K. Van Hege; E. Top; W. Verstraete

2001-01-01

22

Food Chain  

NSDL National Science Digital Library

This video segment from IdahoPTV's D4K describes how energy moves through nature. You will learn about the food chain, and its members: producers, consumers, scavengers. It shows where humans fit into the food chain.

Ptv, Idaho

2011-09-04

23

Food Chains  

NSDL National Science Digital Library

In this project, you will discover the way food chains function by viewing four different types of food chains and designing your favorite one. How is the flow of energy traced through a food chain? Use your cluster organizer to record information for four different food chains and what the consumers, 1st level consumers, 2nd level consumers, and 3rd level consumers are and what they eat. Begin by viewing ecosystems: Introduction to Ecosystems Now that you know what an ...

Hammond, Ms.

2009-10-21

24

PCR-DGGE fingerprinting: novel strategies for detection of microbes in food  

Microsoft Academic Search

Polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) fingerprinting was recently introduced into food microbiology. This paper describes the technique and reports on the state-of-the-art application of this technique to food and food-related ecosystems. Applications of PCR-DGGE in several fields of food microbiology are reviewed: the identification of microorganisms isolated from food, the evaluation of microbial diversity during food fermentation,

Danilo Ercolini

2004-01-01

25

Microbiological study of lactic acid bacteria in kefir grains by culture-dependent and culture-independent methods  

Microsoft Academic Search

Lactic acid bacteria (LAB) in different original kefir grains were first assessed using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) by a culture-dependent way, and were further confirmed by DNA sequencing techniques. Results indicated that a combined method of cultivation with PCR-DGGE and subsequent DNA sequencing could successfully identify four LAB strains from three kefir grains from Taiwan (named Hsinchu,

Hsi-Chia Chen; Sheng-Yao Wang; Ming-Ju Chen

2008-01-01

26

Effect of elevated atmospheric CO2 concentration on ammonia oxidizing bacteria communities inhabiting in rice roots  

Microsoft Academic Search

Recent research suggests that rice root characteristics, particularly growth, are altered by elevated atmospheric CO2. Thus, microbial communities existing in or on rice roots could be greatly influenced by atmospheric CO2 concentration. We investigated the effect of elevated atmospheric CO2 on ammonia oxidizing bacteria (AOB) communities associated with rice roots using polymerase chain reaction–denaturing gradient gel electrophoresis (PCR-DGGE) and sequencing

Saman Bowatte; Susumu Asakawa; Masumi Okada; Kazuhiko Kobayashi; Makoto Kimura

2007-01-01

27

Analysis of bacteria communities in an up-flow fixed-bed (UFB) bioreactor for treating sulfide in hydrocarbon wastewater  

Microsoft Academic Search

An up-flow fixed-bed (UFB) bioreactor with patented functional polyurethane foam (FPUF) carriers was used to treat sulfide in hydrocarbon wastewater. Community compositions of autotrophic and heterotrophic bacteria were analyzed by polymerase chain reaction–denaturing gradient gel electrophoresis (PCR–DGGE). DGGE results showed that a relatively stable bacterial community composed of heterotrophic and autotrophic bacteria formed in the bioreactor by the end of

Guodong Ji; Bo Liao; Huchun Tao; Zhihong Lei

2009-01-01

28

Bulk soil and rhizosphere bacterial community PCR–DGGE profiles and ?-galactosidase activity as indicators of biological quality in soils contaminated by heavy metals and cultivated with Silene vulgaris (Moench) Garcke  

Microsoft Academic Search

The biological quality of two heavy metal contaminated soils (soil C: Typic Calcixerept, pH 8.3 and soil H: Typic Haploxeraf, pH 7.3) was investigated after growing the metal-tolerant plant Silene vulgaris (Moench) Garcke for two vegetative periods. The activity of the enzyme ?-galactosidase, which is sensitive to the presence of contaminants in soil, and the polymerase chain reaction-denaturing gradient gel

M. J. Martínez-Iñigo; A. Pérez-Sanz; I. Ortiz; J. Alonso; R. Alarcón; P. García; M. C. Lobo

2009-01-01

29

Computerized Simulation and Experimental Analysis for Efficient Polymerase Chain Reaction*  

E-print Network

Computerized Simulation and Experimental Analysis for Efficient Polymerase Chain Reaction* Hee@plaza.snu.ac.kr Polymerase chain reaction (PCR) is a useful biochemical operation not only in biological application but also, Effectiveness of Denaturation Temperature Gradient-Polymerase Chain Reaction for Biased DNAAlgorithms

30

Gradient index metamaterials.  

PubMed

Metamaterials--artificially structured materials with tailored electromagnetic response--can be designed to have properties difficult or impossible to achieve with traditional materials fabrication methods. Here we present a structured metamaterial, based on conducting split ring resonators (SRRs), which has an effective index of refraction with a constant spatial gradient. We experimentally confirm the gradient by measuring the deflection of a microwave beam by a planar slab of the composite metamaterial over a range of microwave frequencies. The gradient index metamaterial may prove an advantageous alternative approach to the development of gradient index lenses and similar optics, especially at higher frequencies. In particular, the gradient index metamaterial we propose may be suited for terahertz applications, where the magnetic resonant response of SRRs has recently been demonstrated. PMID:15903607

Smith, D R; Mock, J J; Starr, A F; Schurig, D

2005-03-01

31

Gradient Driven Fluctuations  

NASA Technical Reports Server (NTRS)

We have worked with our collaborators at the University of Milan (Professor Marzio Giglio and his group-supported by ASI) to define the science required to measure gradient driven fluctuations in the microgravity environment. Such a study would provide an accurate test of the extent to which the theory of fluctuating hydrodynamics can be used to predict the properties of fluids maintained in a stressed, non-equilibrium state. As mentioned above, the results should also provide direct visual insight into the behavior of a variety of fluid systems containing gradients or interfaces, when placed in the microgravity environment. With support from the current grant, we have identified three key systems for detailed investigation. These three systems are: 1) A single-component fluid to be studied in the presence of a temperature gradient; 2) A mixture of two organic liquids to be studied both in the presence of a temperature gradient, which induces a steady-state concentration gradient, and with the temperature gradient removed, but while the concentration gradient is dying by means of diffusion; 3) Various pairs of liquids undergoing free diffusion, including a proteidbuffer solution and pairs of mixtures having different concentrations, to allow us to vary the differences in fluid properties in a controlled manner.

Cannell, David

2005-01-01

32

Uniform gradient expansions  

E-print Network

Cosmological singularities are often discussed by means of a gradient expansion that can also describe, during a quasi-de Sitter phase, the progressive suppression of curvature inhomogeneities. While the inflationary event horizon is being formed the two mentioned regimes coexist and a uniform expansion can be conceived and applied to the evolution of spatial gradients across the protoinflationary boundary. It is argued that conventional arguments addressing the preinflationary initial conditions are necessary but generally not sufficient to guarantee a homogeneous onset of the conventional inflationary stage.

Giovannini, Massimo

2014-01-01

33

Gradient enhanced spectroscopy  

NASA Astrophysics Data System (ADS)

This paper provides a brief overview of the personal recollections of the authors regarding their contributions to the introduction of shielded gradient technology into NMR spectroscopy during the late 1980s and early 1990s. It provides some background into early probe design and details some of the early technical progress with the use of shielded magnetic field gradients for coherence selection in high resolution NMR and describes the developments at General Electric, the National Institutes of Health, Georgetown University and Johns Hopkins University School of Medicine that ultimately led to this technology becoming commonplace in modern NMR spectroscopy. Most of this early technical work was published in the Journal of Magnetic Resonance.

van Zijl, Peter C.; Hurd, Ralph E.

2011-12-01

34

Markov Chains  

NSDL National Science Digital Library

Using Mathcad, Maple, Mathmatica, or MatLab, learner should be able to introduce the concepts of transition matrices and Markov chains; to provide motivation for the definition of matrix multiplication in the context of an interesting application; and to lay the groundwork for applied problems that can be solved later with eigenvalues and eigenvectors.

Smith, David

2002-01-11

35

Chain Teleportation  

E-print Network

By means of the idea of measurements on the crossed space-time nonlocal observables, we extend the mechanism for the two-way quantum teleportation to the chain teleportation among N spatially separated spin-1/2 systems. Since in the process only the local interactions are used, the microcausality is automatically satisfied.

Chien-er Lee

2004-09-24

36

Manipulating the Gradient  

ERIC Educational Resources Information Center

We introduce a cooperative learning, group lab for a Calculus III course to facilitate comprehension of the gradient vector and directional derivative concepts. The lab is a hands-on experience allowing students to manipulate a tangent plane and empirically measure the effect of partial derivatives on the direction of optimal ascent. (Contains 7…

Gaze, Eric C.

2005-01-01

37

The biophysical model for accuracy of cellular sensing spatial gradients of multiple chemoattractants  

NASA Astrophysics Data System (ADS)

Spatial gradients of surrounding chemoattractants are the key factors in determining the directionality of eukaryotic cell movement. Thus, it is important for cells to accurately measure the spatial gradients of surrounding chemoattractants. Here, we study the precision of sensing the spatial gradients of multiple chemoattractants using cooperative receptor clusters. Cooperative receptors on cells are modeled as an Ising chain of Monod-Wyman-Changeux clusters subject to multiple chemical-gradient fields to study the physical limits of multiple chemoattractants spatial gradients sensing. We found that eukaryotic cells cannot sense each chemoattractant gradient individually. Instead, cells can only sense a weighted sum of surrounding chemical gradients. Moreover, the precision of sensing one chemical gradient is signicantly affected by coexisting chemoattractant concentrations. These findings can provide a further insight into the role of chemoattractants in immune response and help develop novel treatments for inflammatory diseases.

Chang, Qiang; Zuo, Li

2013-10-01

38

Chain Gang  

NASA Technical Reports Server (NTRS)

6 August 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a chain of clustered and battered craters. These were formed by secondary impact. That is, somewhere to the south (beyond the bottom of this image), a large impact crater formed. When this occurred, material ejected from the crater was thrown tens to hundreds of kilometers away. This material then impacted the martian surface, forming clusters and chains of smaller craters.

Location near: 15.8oN, 35.6oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Northern Spring

2006-01-01

39

Markov Chains  

NSDL National Science Digital Library

Created by Lewis Blake for the Connected Curriculum Project, the purposes of this module are to introduce the concepts of transition matrices and Markov chains; to provide motivation for the definition of matrix multiplication in the context of an interesting application; and to lay the groundwork for applied problems that can be solved later with eigenvalues and eigenvectors. This is part of a larger collection of learning modules hosted by Duke University.

Blake, Lewis

2010-06-01

40

Stress-gradient plasticity.  

PubMed

A new model, stress-gradient plasticity, is presented that provides unique mechanistic insight into size-dependent phenomena in plasticity. This dislocation-based model predicts strengthening of materials when a gradient in stress acts over dislocation source-obstacle configurations. The model has a physical length scale, the spacing of dislocation obstacles, and is validated by several levels of discrete-dislocation simulations. When incorporated into a continuum viscoplastic model, predictions for bending and torsion in polycrystalline metals show excellent agreement with experiments in the initial strengthening and subsequent hardening as a function of both sample-size dependence and grain size, when the operative obstacle spacing is proportional to the grain size. PMID:21911403

Chakravarthy, Srinath S; Curtin, W A

2011-09-20

41

Stress-gradient plasticity  

PubMed Central

A new model, stress-gradient plasticity, is presented that provides unique mechanistic insight into size-dependent phenomena in plasticity. This dislocation-based model predicts strengthening of materials when a gradient in stress acts over dislocation source–obstacle configurations. The model has a physical length scale, the spacing of dislocation obstacles, and is validated by several levels of discrete-dislocation simulations. When incorporated into a continuum viscoplastic model, predictions for bending and torsion in polycrystalline metals show excellent agreement with experiments in the initial strengthening and subsequent hardening as a function of both sample-size dependence and grain size, when the operative obstacle spacing is proportional to the grain size. PMID:21911403

Chakravarthy, Srinath S.; Curtin, W. A.

2011-01-01

42

Interphases of chain molecules: Monolayers and lipid bilayer membranes  

PubMed Central

Using the lattice model for a liquid, we treat the packing of short-chain molecules in interphases such as bilayer membranes. The constant density in the interphase imposes intermolecular constraints on the configurations of the flexible chains. The statistical theory here presented predicts a diffuse distribution of chain ends near the bilayer midplane; no adjustable parameters are required. Inasmuch as some of the chains terminate relatively near the polar interface, the number of chains reaching deeper planar layers is diminished. Consequently, configurational freedom increases with depth. This is the source of the well-known disorder gradient. PMID:16592834

Dill, Ken A.; Flory, Paul J.

1980-01-01

43

Markov Chains  

NSDL National Science Digital Library

Created by Kyle Siegrist of the University of Alabama-Huntsville, this is an online, interactive lesson on Markov chains. The author provides examples, exercises, and applets to introduce the subject. More specifically, the lesson covers: recurrence, transience, periodicity, time reversal, as well as invariant and limiting distributions. In addition, the author has provided links to external resources for further research. Overall, this is a great resource for those interested in this statistical process. It provides basic examples to introduce the topic, but also provides a more in-depth study to further challenge students.

Siegrist, Kyle

2009-03-02

44

technology offer Magnetic Gradient Sensor  

E-print Network

technology offer Magnetic Gradient Sensor magnetic gradient sensor, micromechanical structure The invention concerns a sensor for the magnetic field gradient and applies micromechanical structures. Lorentz are typically measured by Hall- sensors which suffer from a large offset and offset drift. For the measurement

Szmolyan, Peter

45

Energy in density gradient  

NASA Astrophysics Data System (ADS)

Inhomogeneous plasmas and fluids contain energy stored in inhomogeneity and they naturally tend to relax into lower energy states by developing instabilities or by diffusion. But the actual amount of energy in such inhomogeneities has remained unknown. In the present work, the amount of energy stored in a density gradient is calculated for several specific density profiles in a cylindrical configuration. This is of practical importance for drift wave instability in various plasmas, and, in particular, in its application in models dealing with the heating of solar corona because the instability is accompanied with stochastic heating, so the energy contained in inhomogeneity is effectively transformed into heat. It is shown that even for a rather moderate increase of the density at the axis in magnetic structures in the corona by a factor 1.5 or 3, the amount of excess energy per unit volume stored in such a density gradient becomes several orders of magnitude greater than the amount of total energy losses per unit volume (per second) in quiet regions in the corona. Consequently, within the life-time of a magnetic structure such energy losses can easily be compensated by the stochastic drift wave heating.

Vranjes, J.; Kono, M.

2015-01-01

46

Energy in density gradient  

E-print Network

Inhomogeneous plasmas and fluids contain energy stored in inhomogeneity and they naturally tend to relax into lower energy states by developing instabilities or by diffusion. But the actual amount of energy in such inhomogeneities has remained unknown. In the present work the amount of energy stored in a density gradient is calculated for several specific density profiles in a cylindric configuration. This is of practical importance for drift wave instability in various plasmas, and in particular in its application in models dealing with the heating of solar corona because the instability is accompanied with stochastic heating, so the energy contained in inhomogeneity is effectively transformed into heat. It is shown that even for a rather moderate increase of the density at the axis in magnetic structures in the corona by a factor 1.5 or 3, the amount of excess energy per unit volume stored in such a density gradient becomes several orders of magnitude greater than the amount of total energy losses per unit ...

Vranjes, J

2015-01-01

47

The Food Chain  

NSDL National Science Digital Library

In this project you will learn about the food chain. In your notebook, write everything you know about the food chain and what you think goes at the top and bottom of the chain. After you write what you know go here to learn more about the food chain Food Chain Video. Click on "Play Movie." Now after watching the movie you should have ...

Jodi, Miss

2009-07-07

48

Charge gradient microscopy.  

PubMed

Here we present a simple and fast method to reliably image polarization charges using charge gradient microscopy (CGM). We collected the current from the grounded CGM probe while scanning a periodically poled lithium niobate single crystal and single-crystal LiTaO3 thin film on the Cr electrode. We observed current signals at the domains and domain walls originating from the displacement current and the relocation or removal of surface charges, which enabled us to visualize the ferroelectric domains at a scan frequency above 78 Hz over 10 ?m. We envision that CGM can be used in high-speed ferroelectric domain imaging and piezoelectric energy-harvesting devices. PMID:24760831

Hong, Seungbum; Tong, Sheng; Park, Woon Ik; Hiranaga, Yoshiomi; Cho, Yasuo; Roelofs, Andreas

2014-05-01

49

Hierarchically deflated conjugate gradient  

E-print Network

We present a multi-level algorithm for the solution of five dimensional chiral fermion formulations, including domain wall and Mobius Fermions. The algorithm operates on the red-black preconditioned Hermitian operator, and directly accelerates conjugate gradients on the normal equations. The coarse grid representation of this matrix is next-to-next-to-next-to-nearest neighbour and multiple algorithmic advances are introduced, which help minimise the overhead of the coarse grid. The treatment of the coarse grids is purely four dimensional, and the bulk of the coarse grid operations are nearest neighbour. The intrinsic cost of most of the coarse grid operations is therefore comparable to those for the Wilson case. We also document the implementation of this algorithm in the BAGEL/Bfm software package and report on the measured performance gains the algorithm brings to simulations at the physical point on IBM BlueGene/Q hardware.

P A Boyle

2014-02-11

50

Gradient index polymer optics  

NASA Astrophysics Data System (ADS)

The design, fabrication, and properties of one of a new class of gradient-index lenses are reported. The lens is an f/2.25 GRIN singlet based on a nanolayered polymer composite material, designed to correct for spherical aberration. The light gathering and focusing properties of the polymer lens are compared to a homogeneous BK7 glass singlet with a similar f-number. The modulation transfer function of the polymer GRIN lens exceeded that of the homogeneous glass lens at all spatial frequencies and was as much as 3 times better at 5 cyc/mm. The weight of the polymer lens was approximately an order of magnitude less than the homogeneous glass lens.

Beadie, G.; Fleet, E.; Rosenberg, A.; Lane, Paul A.; Shirk, James S.; Kamdar, A. R.; Ponting, M.; Hiltner, A.; Baer, E.

2008-08-01

51

Gradient boosting machines, a tutorial  

PubMed Central

Gradient boosting machines are a family of powerful machine-learning techniques that have shown considerable success in a wide range of practical applications. They are highly customizable to the particular needs of the application, like being learned with respect to different loss functions. This article gives a tutorial introduction into the methodology of gradient boosting methods with a strong focus on machine learning aspects of modeling. A theoretical information is complemented with descriptive examples and illustrations which cover all the stages of the gradient boosting model design. Considerations on handling the model complexity are discussed. Three practical examples of gradient boosting applications are presented and comprehensively analyzed. PMID:24409142

Natekin, Alexey; Knoll, Alois

2013-01-01

52

Supply Chain Management Concentration  

E-print Network

Supply Chain Management Concentration While many rules and specific regulations apply to taking-requisite(s)............................................................Semester(s) Offered Required Course: MGT478............Global Supply Chain Management..............................2 of the following: MGT375............Advanced Supply Chain Management ......................MGT301

Barnes, Elizabeth A.

53

Density Gradients in Chemistry Teaching  

ERIC Educational Resources Information Center

Outlines experiments in which a density gradient might be used to advantage. A density gradient consists of a column of liquid, the composition and density of which varies along its length. The procedure can be used in analysis of solutions and mixtures and in density measures of solids. (Author/TS)

Miller, P. J.

1972-01-01

54

Height and gradient from shading  

Microsoft Academic Search

The method described here for recovering the shape of a surface from a shaded image can deal with complex, wrinkled surfaces. Integrability can be enforced easily because both surface height and gradient are represented (A gra- dient field is integrable if it is the gradient of some surface height function). The robustness of the method stems in part from linearization

Berthold K. P. Horn

1990-01-01

55

Rapid Gradient-Echo Imaging  

PubMed Central

Gradient echo sequences are widely used in magnetic resonance imaging (MRI) for numerous applications ranging from angiography to perfusion to functional MRI. Compared with spin-echo techniques, the very short repetition times of gradient-echo methods enable very rapid 2D and 3D imaging, but also lead to complicated “steady states.” Signal and contrast behavior can be described graphically and mathematically, and depends strongly on the type of spoiling: fully balanced (no spoiling), gradient spoiling, or RF-spoiling. These spoiling options trade off between high signal and pure T1 contrast while the flip angle also affects image contrast in all cases, both of which can be demonstrated theoretically and in image examples. As with spin-echo sequences, magnetization preparation can be added to gradient-echo sequences to alter image contrast. Gradient echo sequences are widely used for numerous applications such as 3D perfusion imaging, functional MRI, cardiac imaging and MR angiography. PMID:23097185

Hargreaves, Brian

2012-01-01

56

Gradient elution in capillary electrochromatography  

SciTech Connect

In analogy to pressure-driven gradient techniques in high-performance liquid chromatography, a system has been developed for delivering electroosmotically-driven solvent gradients for capillary electrochromatography (CEC). Dynamic gradients with sub-mL/min flow rates are generated by merging two electroosmotic flows that are regulated by computer-controlled voltages. These flows are delivered by two fused-silica capillary arms attached to a T-connector, where they mix and then flow into a capillary column that has been electrokinetically packed with 3-mm reversed-phase particles. The inlet of one capillary arm is placed in a solution reservoir containing one mobile phase and the inlet of the other is placed in a second reservoir containing a second mobile phase. Two independent computer-controlled programmable high-voltage power supplies (0-50 kV)--one providing an increasing ramp and the other providing a decreasing ramp--are used to apply variable high-voltage potentials to the mobile phase reservoirs to regulate the electroosmotic flow in each arm. The ratio of the electroosmotic flow rates between the two arms is changed with time according to the computer-controlled voltages to deliver the required gradient profile to the separation column. Experiments were performed to confirm the composition of the mobile phase during a gradient run and to determine the change of the composition in response to the programmed voltage profile. To demonstrate the performance of electroosmotically-driven gradient elution in CEC, a mixture of 16 polycyclic aromatic hydrocarbons (PAHs) was separated in less than 90 minutes. This gradient technique is expected to be well-suited for generating not only solvent gradients in CEC, but also other types of gradients such as pH- and ionic-strength gradients in capillary electrokinetic separations and analyses.

Anex, D.; Rakestraw, D.J. [Sandia National Labs., Livermore, CA (United States); Yan, Chao; Dadoo, R.; Zare, R.N. [Stanford Univ., CA (United States). Dept. of Chemistry

1997-08-01

57

Health supply chain management.  

PubMed

This chapter gives an educational overview of: * The actual application of supply chain practice and disciplines required for service delivery improvement within the current health environment. * A rationale for the application of Supply Chain Management (SCM) approaches to the Health sector. * The tools and methods available for supply chain analysis and benchmarking. * Key supply chain success factors. PMID:20407173

Zimmerman, Rolf; Gallagher, Pat

2010-01-01

58

Molecular dynamics simulation of heat conduction through a molecular chain.  

PubMed

This work deals with a molecular dynamics simulation analysis of the intramolecular vibrational energy transfer in a system of two chromophores, azulene and anthracene, bridged by an aliphatic chain and is motivated by corresponding laser experiments. After selective excitation of the azulene chromophore, the subsequent intramolecular vibrational energy redistribution is monitored by analyzing the transient temperatures of the two chromophores and the chain between them. The main focus concerns the heat conduction process in the chain. Therefore, the chain length was varied from 0 to 19 CH(2) units. In addition, methoxymethyl, 1,2-dimethoxyethyl, and a thiomethoxymethyl chains were studied. The investigation of the intramolecular vibrational energy process was decomposed into a temporal analysis and a spatial analysis. For short alkyl chains, the time constant of energy relaxation increases proportionally to the chain length. However, for longer chains, the time constant characterizing the energy decay of the azulene chromophore saturates and becomes independent of the chain length. This behavior is consistent with experimental findings. The spatial analysis shows more or less exponential decay of the temperature along the chain near the excited chromophore. In additional simulations, the two chromophores were thermostatted at different temperatures to establish a constant heat flux from the azulene to the anthracene side. The steady-state temperature profiles for longer alkyl chains show strong gradients near the two chromophores and constant but weak gradients in the central part of the chain. Both simulation methods indicate that strong Kapitza effects at the boundaries between each chromophore and the molecular chain dominate the intramolecular energy flux. PMID:19928969

Schröder, Christian; Vikhrenko, Vyacheslav; Schwarzer, Dirk

2009-12-24

59

Optimum gradient of mountain paths.  

PubMed

By combining the experiment results of R. Margaria (Atti Accad. Naz. Lincei Memorie 7: 299-368, 1938), regarding the metabolic cost of gradient locomotion, together with recent insights on gait biomechanics, a prediction about the most economical gradient of mountain paths (approximately 25%) is obtained and interpreted. The pendulum-like mechanism of walking produces a waste of mechanical work against gravity within the gradient range of up to 15% (the overall efficiency is dominated by the low transmission efficiency), whereas for steeper values only the muscular efficiency is responsible for the (slight) metabolic change (per meter of vertical displacement) with respect to gradient. The speeds at the optimum gradient turned out to be approximately 0.65 m/s (+0.16 m/s vertical) and 1.50 m/s (-0.36 m/s vertical), for uphill and downhill walking, respectively, and the ascensional energy expenditure was 0.4 and 2.0 ml O2.kg body mass-1.vertical m-1 climbed or descended. When the metabolic power becomes a burden, as in high-altitude mountaineering, the optimum gradient should be reduced. A sample of real mountain path gradients, experimentally measured, mimics the obtained predictions. PMID:8594031

Minetti, A E

1995-11-01

60

High field gradient particle accelerator  

DOEpatents

A high electric field gradient electron accelerator utilizing short duration, microwave radiation, and capable of operating at high field gradients for high energy physics applications or at reduced electric field gradients for high average current intermediate energy accelerator applications is disclosed. Particles are accelerated in a smooth bore, periodic undulating waveguide, wherein the period is so selected that the particles slip an integral number of cycles of the r.f. wave every period of the structure. This phase step of the particles produces substantially continuous acceleration in a traveling wave without transverse magnetic or other guide means for the particle. 10 figs.

Nation, J.A.; Greenwald, S.

1989-05-30

61

High field gradient particle accelerator  

DOEpatents

A high electric field gradient electron accelerator utilizing short duration, microwave radiation, and capable of operating at high field gradients for high energy physics applications or at reduced electric field gradients for high average current intermediate energy accelerator applications. Particles are accelerated in a smooth bore, periodic undulating waveguide, wherein the period is so selected that the particles slip an integral number of cycles of the r.f. wave every period of the structure. This phase step of the particles produces substantially continuous acceleration in a traveling wave without transverse magnetic or other guide means for the particle.

Nation, John A. (Ithaca, NY); Greenwald, Shlomo (Haifa, IL)

1989-01-01

62

Gradient characterization in magnetic resonance imaging  

E-print Network

Special magnetic resonance (MR) scans, such as spiral imaging and echo-planar imaging, require speed and gradient accuracy while putting high demands on the MR gradient system that may cause gradient distortion. Additionally, ...

Cheng, Joseph Yitan

2007-01-01

63

40 CFR 230.25 - Salinity gradients.  

...25 2014-07-01 2014-07-01 false Salinity gradients. 230.25 Section 230.25 ...Characteristics of the Aquatic Ecosystem § 230.25 Salinity gradients. (a) Salinity gradients form where salt water from the...

2014-07-01

64

40 CFR 230.25 - Salinity gradients.  

Code of Federal Regulations, 2013 CFR

...26 2013-07-01 2013-07-01 false Salinity gradients. 230.25 Section 230.25 ...Characteristics of the Aquatic Ecosystem § 230.25 Salinity gradients. (a) Salinity gradients form where salt water from the...

2013-07-01

65

40 CFR 230.25 - Salinity gradients.  

Code of Federal Regulations, 2012 CFR

...26 2012-07-01 2011-07-01 true Salinity gradients. 230.25 Section 230.25 ...Characteristics of the Aquatic Ecosystem § 230.25 Salinity gradients. (a) Salinity gradients form where salt water from the...

2012-07-01

66

40 CFR 230.25 - Salinity gradients.  

Code of Federal Regulations, 2011 CFR

...25 2011-07-01 2011-07-01 false Salinity gradients. 230.25 Section 230.25 ...Characteristics of the Aquatic Ecosystem § 230.25 Salinity gradients. (a) Salinity gradients form where salt water from the...

2011-07-01

67

COMPUTATIONAL COMPLEXITY OF INEXACT GRADIENT ...  

E-print Network

In Figure 5.2 we also plot the evolution of the states and inputs over the simulation .... 80EU/2010); Sectoral Operational Programme Human Resources ... [6] M.R. Hestenes, Multiplier and gradient methods, Journal of Optimization and ...

2012-11-02

68

Application of a food chain model to polychlorinated biphenyl contamination of the lobster and winter flounder food chains in New Bedford Harbor  

Microsoft Academic Search

As part of a Remedial Investigation\\/Feasibility Study for the New Bedford Harbor Superfund site a model of polychlorinated biphenyls (PCBs) in the lobster and winter flounder food chains was developed. This model successfully reproduces tri-, tetra-, penta-, and hexachlorobiphenyl concentrations observed at all levels of the food chain and across the 2 order of magnitude concentration gradient in the system.

John P. Connolly

1991-01-01

69

Laser amplifier chain  

DOEpatents

A laser amplifier chain has a plurality of laser amplifiers arranged in a chain to sequentially amplify a low-power signal beam to produce a significantly higher-power output beam. Overall efficiency of such a chain is improved if high-gain, low efficiency amplifiers are placed on the upstream side of the chain where only a very small fraction of the total pumped power is received by the chain and low-gain, high-efficiency amplifiers are placed on the downstream side where a majority of pumping energy is received by the chain.

Hackel, Richard P. (Livermore, CA)

1992-01-01

70

Laser amplifier chain  

DOEpatents

A laser amplifier chain has a plurality of laser amplifiers arranged in a chain to sequentially amplify a low-power signal beam to produce a significantly higher-power output beam. Overall efficiency of such a chain is improved if high-gain, low efficiency amplifiers are placed on the upstream side of the chain where only a very small fraction of the total pumped power is received by the chain and low-gain, high-efficiency amplifiers are placed on the downstream side where a majority of pumping energy is received by the chain. 6 figs.

Hackel, R.P.

1992-10-20

71

Mechanism of DNA Chain Growth, III. Equal Annealing of T4 Nascent Short DNA Chains with the Separated Complementary Strands of the Phage DNA  

Microsoft Academic Search

Nascent short DNA chains isolated from T4-infected E. coli under a variety of conditions anneal equally to the separated complementary phage DNA strands. The samples examined include: pulse-labeled short chains isolated by alkaline sucrose gradient sedimentation from the T4D (wild type)-infected cells in both the early and late stages of phage DNA synthesis; nascent chains accumulated during ligase inhibition of

Kazunori Sugimoto; Tuneko Okazaki; Yasuo Imae; Reiji Okazaki

1969-01-01

72

Estimation of coastal density gradients  

NASA Astrophysics Data System (ADS)

Density gradients in coastal regions with significant freshwater input are large and variable and are a major control of nearshore circulation. However their measurement is difficult, especially where the gradients are largest close to the coast, with significant uncertainties because of a variety of factors - spatial and time scales are small, tidal currents are strong and water depths shallow. Whilst temperature measurements are relatively straightforward, measurements of salinity (the dominant control of spatial variability) can be less reliable in turbid coastal waters. Liverpool Bay has strong tidal mixing and receives fresh water principally from the Dee, Mersey, Ribble and Conwy estuaries, each with different catchment influences. Horizontal and vertical density gradients are variable both in space and time. The water column stratifies intermittently. A Coastal Observatory has been operational since 2002 with regular (quasi monthly) CTD surveys on a 9 km grid, an situ station, an instrumented ferry travelling between Birkenhead and Dublin and a shore-based HF radar system measuring surface currents and waves. These measurements are complementary, each having different space-time characteristics. For coastal gradients the ferry is particularly useful since measurements are made right from the mouth of Mersey. From measurements at the in situ site alone density gradients can only be estimated from the tidal excursion. A suite of coupled physical, wave and ecological models are run in association with these measurements. The models, here on a 1.8 km grid, enable detailed estimation of nearshore density gradients, provided appropriate river run-off data are available. Examples are presented of the density gradients estimated from the different measurements and models, together with accuracies and uncertainties, showing that systematic time series measurements within a few kilometres of the coast are a high priority. (Here gliders are an exciting prospect for detailed regular measurements to fill this gap.) The consequences for and sensitivity of circulation estimates are presented using both numerical and analytic models.

Howarth, M. J.; Palmer, M. R.; Polton, J. A.; O'Neill, C. K.

2012-04-01

73

Food Chain Game  

NSDL National Science Digital Library

In this outdoor game, learners role play populations linked in a food chain. The resource suggests a chain with plant, grasshopper, frog, and hawk, but other food chains can be role-played, for example plankton, anchovy, salmon, sea lion. The more "animals" (learners!) the merrier for this active game.

Lawrence Hall of Science

1979-01-01

74

Relations in Chains  

ERIC Educational Resources Information Center

The criticisms made against chain indexing are reviewed, and PRECIS briefly considered as a possible (but improbable) general substitute for indexing. The failures of chain indexing arise mainly from an overemphasis on generic relationships. The use of symbols to represent relations between terms is suggested for the chain index. (80 references)…

Mineur, B. W.

1973-01-01

75

Cellular Response of Cardiac Fibroblasts to Amyloidogenic Light Chains  

PubMed Central

Amyloidoses are a group of disorders characterized by abnormal folding of proteins that impair organ function. We investigated the cellular response of primary cardiac fibroblasts to amyloidogenic light chains and determined the corresponding change in proteoglycan expression and localization. The cellular response to 11 urinary immunoglobulin light chains of ?1, ?6, and ? 3 subtypes was evaluated. The localization of the light chains was monitored by conjugating them to Oregon Green 488 and performing live cell confocal microscopy. Sulfation of the proteoglycans was determined after elution over Q1-columns with a single-step salt gradient (1.5 mol/L NaCl) via dimethylmethylene blue. Light chains were detected inside cells within 4 hours and demonstrated perinuclear localization. Over 80% of the cells showed intracellular localization of the amyloid light chains. The light chains induced sulfation of the secreted glycosaminoglycans, but the cell fraction possessed only minimal sulfation. Furthermore, the light chains caused a translocation of heparan sulfate proteoglycan to the nucleus. The conformation and thermal stability of light chains was altered when they were incubated in the presence of heparan sulfate and destabilization of the amyloid light chains was detected. These studies indicate that internalization of the light chains mediates the expression and localization of heparan sulfate proteoglycans. PMID:15632012

Trinkaus-Randall, Vickery; Walsh, Mary T.; Steeves, Shawn; Monis, Grace; Connors, Lawreen H.; Skinner, Martha

2005-01-01

76

Dielectric gradient metasurface optical elements.  

PubMed

Gradient metasurfaces are two-dimensional optical elements capable of manipulating light by imparting local, space-variant phase changes on an incident electromagnetic wave. These surfaces have thus far been constructed from nanometallic optical antennas, and high diffraction efficiencies have been limited to operation in reflection mode. We describe the experimental realization and operation of dielectric gradient metasurface optical elements capable of also achieving high efficiencies in transmission mode in the visible spectrum. Ultrathin gratings, lenses, and axicons have been realized by patterning a 100-nanometer-thick Si layer into a dense arrangement of Si nanobeam antennas. The use of semiconductors can broaden the general applicability of gradient metasurfaces, as they offer facile integration with electronics and can be realized by mature semiconductor fabrication technologies. PMID:25035488

Lin, Dianmin; Fan, Pengyu; Hasman, Erez; Brongersma, Mark L

2014-07-18

77

Refugial isolation versus ecological gradients  

Microsoft Academic Search

Hypotheses for divergence and speciation in rainforests generally fall into two categories: those emphasizing the role of geographic isolation and those emphasizing the role of divergent selection along gradients. While a majority of studies have attempted to infer mechanisms based on the pattern of species richness and congruence of geographic boundaries, relatively few have tried to simultaneously test alternative hypotheses

Thomas B. Smith; Christopher J. Schneider; Karen Holder

2001-01-01

78

Gradient Tempering Of Bearing Races  

NASA Technical Reports Server (NTRS)

Gradient-tempering process increases fracture toughness and resistance to stress-corrosion cracking of ball-bearing races made of hard, strong steels and subject to high installation stresses and operation in corrosive media. Also used in other applications in which local toughening of high-strength/low-toughness materials required.

Parr, Richardson A.

1991-01-01

79

Spatiotemporal Gradient Modeling with Applications  

E-print Network

Quality 3. Airborne Exposure Levels from the Deepwater Horizon Oil Spill #12;Introduction Exposures Data from the Clean-Up of the Deepwater Horizon Oil Spill Discussion #12;Methods Spatiotemporal Gradients in Interval-Censored Airborne Exposures Data from the Clean-Up of the Deepwater Horizon

Carlin, Bradley P.

80

Shape reconstruction from gradient data  

Microsoft Academic Search

We present a novel method for reconstructing the shape of an object from measured gradient data. A certain class of optical sensors does not measure the shape of an object, but its local slope. These sensors display several advantages, including high information efficiency, sensitivity, and robustness. For many applications, however, it is necessary to acquire the shape, which must be

Svenja Ettl; Juergen Kaminski; Markus C. Knauer; Gerd Haeusler

2008-01-01

81

Value Gradient Learning Michael Fairbank  

E-print Network

1 Value Gradient Learning VGL() Michael Fairbank Eduardo Alonso 1 #12;2 What we do and policy fixed VGL when =1 and policy greedy 6 V V x E w R w 6 #12;7 7 An Optimal by the shear of the track is "correct" · Bellman's optimality principle requires that V = R (Watkins' -return

Weyde, Tillman

82

Corrosion in a temperature gradient  

SciTech Connect

High temperature corrosion limits the operation of equipment used in the Power Generation Industry. Some of the more destructive corrosive attack occurs on the surfaces of heat exchangers, boilers, and turbines where the alloys are subjected to large temperature gradients that cause a high heat flux through the accumulated ash, the corrosion product, and the alloy. Most current and past corrosion research has, however, been conducted under isothermal conditions. Research on the thermal-gradient-affected corrosion of various metals and alloys is currently being studied at the Albany Research Center’s SECERF (Severe Environment Corrosion and Erosion Research Facility) laboratory. The purpose of this research is to verify theoretical models of heat flux effects on corrosion and to quantify the differences between isothermal and thermal gradient corrosion effects. The effect of a temperature gradient and the resulting heat flux on corrosion of alloys with protective oxide scales is being examined by studying point defect diffusion and corrosion rates. Fick’s first law of diffusion was expanded, using irreversible thermodynamics, to include a heat flux term – a Soret effect. Oxide growth rates are being measured for the high temperature corrosion of cobalt at a metal surface temperature of 900ºC. Corrosion rates are also being determined for the high temperature corrosion of carbon steel boiler tubes in a simulated waste combustion environment consisting of O2, CO2, N2, and water vapor. Tests are being conducted both isothermally and in the presence of a temperature gradient to verify the effects of a heat flux and to compare to isothermal oxidation.

Covino, Bernard S., Jr.; Holcomb, Gordon R.; Cramer, Stephen D.; Bullard, Sophie J.; Ziomek-Moroz, Margaret; White, M.L. (Convanta)

2003-01-01

83

Magnetic Resonance Imaging with Composite (Dual) Gradients  

PubMed Central

The tradeoff between gradient performance factors, size of the imaging region, and physiological factors such as nerve stimulation typically leads to compromises in gradient design and ultimately suboptimal imaging performance. Local gradient systems can add some performance flexibility, but are cumbersome to set up and remove. In nearly all conventional MRI systems, the use of local gradients precludes the use of the more homogeneous whole body gradients. This paper presents the concept of dynamically selectable composite gradient systems where local gradients and whole body gradients can be selected independently and simultaneously. The relative performance of whole body, insert, and composite gradients is predicted for echoplanar (EPI), turbo spin echo (TSE), and steady state free precession (SSFP). A realization of the concept is presented. PMID:20160925

Parker, Dennis L.; Goodrich, K. Craig; Hadley, J. Rock; Kim, Seong-Eun; Moon, Sung M.; Chronik, Blaine A.; Fontius, Ulrich; Schmitt, Franz

2009-01-01

84

Analysis of Bacterial Communities in Seagrass Bed Sediments by Double-Gradient Denaturing Gradient Gel Electrophoresis  

E-print Network

-Gradient Denaturing Gradient Gel Electrophoresis of PCR-Amplified 16S rRNA Genes J.B. James1 , T.D. Sherman2 and R denaturing gradient gel electrophoresis (DG- DGGE) was used to generate banding patterns from

Sherman, Tim

85

Neuron Chain Tag  

NSDL National Science Digital Library

In this outdoor activity, learners play a game of Tag to discover how neurons attach themselves to each other to form a chain. The game starts with one learner who is "it" and represents the first neuron. When "it" tags another player, the tagger player must hold the hand of "it" and work together to form a long a chain. The game ends when all the players are part of the neuron chain.

2012-06-26

86

Heavy Chain Diseases  

MedlinePLUS

... Blood Cell Disorders Plasma Cell Disorders Leukemias Lymphomas Myeloproliferative Disorders Spleen Disorders ... Heavy chain diseases are plasma cell cancers in which a clone of plasma cells produces ...

87

Bidirectional quantitative force gradient microscopy  

NASA Astrophysics Data System (ADS)

Dynamic operation modes of scanning force microscopy based on probe resonance frequency detection are very successful methods to study force-related properties of surfaces with high spatial resolution. There are well-recognized approaches to measure vertical force components as well as setups sensitive to lateral force components. Here, we report on a concept of bidirectional force gradient microscopy that enables a direct, fast, and quantitative real space mapping of force component derivatives in both the perpendicular and a lateral direction. It relies solely on multiple-mode flexural cantilever oscillations related to vertical probe excitation and vertical deflection sensing. Exploring this concept we present a cantilever-based sensor setup and corresponding quantitative measurements employing magnetostatic interactions with emphasis on the calculation of mode-dependent spring constants that are the foundation of quantitative force gradient studies.

Reiche, Christopher F.; Vock, Silvia; Neu, Volker; Schultz, Ludwig; Büchner, Bernd; Mühl, Thomas

2015-01-01

88

Spatial gradients controlling spindle assembly.  

PubMed

The mitotic spindle is the macromolecular machine utilized to accurately segregate chromosomes in cells. How this self-organized structure assembles is a key aspect of understanding spindle morphogenesis. In the present review, we focus on understanding mechanisms of spindle self-assembly and address how subcellular signalling gradients, such as Ran-GTP and Aurora B, contribute to spindle organization and function. PMID:25619240

Weaver, Lesley N; Walczak, Claire E

2015-02-01

89

Generalized Gradient Approximation Made Simple  

Microsoft Academic Search

Generalized gradient approximations (GGA's) for the exchange-correlation energy improve upon the local spin density (LSD) description of atoms, molecules, and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental constants. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91

John P. Perdew; Kieron Burke; Matthias Ernzerhof

1996-01-01

90

Stellar Population Gradients in WLM  

NASA Astrophysics Data System (ADS)

WLM is one of the most isolated galaxies in the Local Group. From archival HST frames, we look for population gradients using star count ratios from distinct regions of the Color-Magnitude diagram. We find clear evidence for a central concentration of the younger stars. This scenario supports the two-component disk/halo-like structure suggested for dwarf irregular galaxies (Martinez-Delgado, Gallart & Aparicio, 1999).

Noriega-Mendoza, H.; Holtzman, J.

2001-12-01

91

Tropical gradient influences on Caribbean rainfall  

Microsoft Academic Search

Interbasin and intrabasin gradients are important for Caribbean climateThe tropical gradients, the AWP, and the CLLJ modulate Caribbean rainfall variabilityFuture Caribbean drying is linked to a perpetuating midsummer rainfall minimum

Michael A. Taylor; Tannecia S. Stephenson; Albert Owino; A. Anthony Chen; Jayaka D. Campbell

2011-01-01

92

40 CFR 230.25 - Salinity gradients.  

Code of Federal Regulations, 2010 CFR

...the salinity gradient can occur, displacing the maximum sedimentation zone and requiring salinity-dependent aquatic biota...migration of the salinity gradient displacing the maximim sedimentation zone. This migration may affect those organisms that...

2010-07-01

93

Policy Gradient Based Semi-Markov Decision Problems: Approximation and Estimation Errors  

NASA Astrophysics Data System (ADS)

In [1] and [2] we have presented a simulation-based algorithm for optimizing the average reward in a parameterized continuous-time, finite-state semi-Markov Decision Process (SMDP). We approximated the gradient of the average reward. Then, a simulation-based algorithm was proposed to estimate the approximate gradient of the average reward (called GSMDP), using only a single sample path of the underlying Markov chain. GSMDP was proved to converge with probability 1. In this paper, we give bounds on the approximation and estimation errors for GSMDP algorithm. The approximation error of that approximation is the size of the difference between the true gradient and the approximate gradient. The estimation error, the size of the difference between the output of the algorithm and its asymptotic output, arises because the algorithm sees only a finite data sequence.

Vien, Ngo Anh; Lee, Seunggwan; Chung, Taechoong

94

Coordinated supply chain management  

Microsoft Academic Search

Historically, the three fundamental stages of the supply chain, procurement, production and distribution, have been managed independently, buffered by large inventories. Increasing competitive pressures, and market globalization are forcing firms to develop supply chains that can quickly respond to customer needs. To remain competitive, these firms must reduce operating costs while continuously improving customer service. With recent advances in communications

Douglas J. Thomas; Paul M. Griffin

1996-01-01

95

Natural Gradient Works Efficiently in Learning  

Microsoft Academic Search

When a parameter space has a certain underlying structure, the ordinary gradient of a function does not represent its steepest direction, but the natural gradient does. Information geometry is used for calculating the natural gradients in the parameter space of perceptrons, the space of ma- trices (for blind source separation), and the space of linear dynamical systems (for blind source

Shun-ichi Amari

1998-01-01

96

Density Gradient Stabilization of Electron Temperature Gradient Driven Turbulence in a Spherical Tokamak  

E-print Network

Density Gradient Stabilization of Electron Temperature Gradient Driven Turbulence in a Spherical experimental observation of density gradient stabilization of electron temperature gradient driven turbulence in a fusion plasma. It is observed that longer wavelength modes, k?s & 10, are most stabilized by density

Princeton Plasma Physics Laboratory

97

Metallicity Gradients in Simulated Disk Galaxies  

NASA Astrophysics Data System (ADS)

The stellar metallicity and abundance ratio gradients from the fiducial late-type galaxy simulation of Stinson et al. (2010) are presented. Over ˜1-3 scalelengths, gradients are shown to flatten with time, consistent with empirical evidence at high- and low-redshifts. Kinematic effects, including radial migration, though, flatten these intrinsicly steep gradients such that by redshift z=0, the measured gradients of these (now) old stars are flatter than their young counterparts, in contradiction to what is observed locally. Conversely, the stellar [O/Fe] gradient is (to first order) robust against migration, remaining fairly flat for both young and old populations today.

Pilkington, K.; Gibson, B. K.

2012-08-01

98

Protein gradient films of fibroin and gelatine.  

PubMed

Gradients are a natural design principle in biological systems that are used to diminish stress concentration where materials of differing mechanical properties connect. An interesting example of a natural gradient material is byssus, which anchors mussels to rocks and other hard substrata. Building upon previous work with synthetic polymers and inspired by byssal threads, protein gradient films are cast using glycerine-plasticized gelatine and fibroin exhibiting a highly reproducible and smooth mechanical gradient, which encompasses a large range of modulus from 160 to 550?MPa. The reproducible production of biocompatible gradient films represents a first step towards medical applications. PMID:23894133

Claussen, Kai U; Lintz, Eileen S; Giesa, Reiner; Schmidt, Hans-Werner; Scheibel, Thomas

2013-10-01

99

Generalized Gradient Approximation Made Simple  

SciTech Connect

Generalized gradient approximations (GGA{close_quote}s) for the exchange-correlation energy improve upon the local spin density (LSD) description of atoms, molecules, and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental constants. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential. {copyright} {ital 1996 The American Physical Society.}

Perdew, J.P.; Burke, K.; Ernzerhof, M. [Department of Physics and Quantum Theory Group, Tulane University, New Orleans, Louisiana 70118 (United States)] [Department of Physics and Quantum Theory Group, Tulane University, New Orleans, Louisiana 70118 (United States)

1996-10-01

100

Biomolecular gradients in cell culture systems  

PubMed Central

Biomolecule gradients have been shown to play roles in a wide range of biological processes including development, inflammation, wound healing, and cancer metastasis. Elucidation of these phenomena requires the ability to expose cells to biomolecule gradients that are quantifiable, controllable, and mimic those that are present in vivo. Here we review the major biological phenomena in which biomolecule gradients are employed, traditional in vitro gradient-generating methods developed over the past 50 years, and new microfluidic devices for generating gradients. Microfluidic gradient generators offer greater levels of precision, quantitation, and spatiotemporal gradient control than traditional methods, and may greatly enhance our understanding of many biological phenomena. For each method, we outline the salient features, capabilities, and applications. PMID:18094760

Keenan, Thomas M.

2013-01-01

101

Safe Chain Saw Operation.  

E-print Network

and below. Do not cut at chest level or above. ? Keep the chain properly sharpened and tensioned. ? Choose a saw with a chain brake, nose guard, antikickback chain and guide bar and other anti kickback devices. Evaluating or "Sizing-up" Trees... bar or cause the trunk to roll toward you. For lim bing, use a lightweight saw with a short guide bar. This eases holding and maneuvering, decreases fatigue and gives you more control in possible kickback situa tions. Stand at such an angle when...

Nelson, Gary S.

1982-01-01

102

The Global Supply Chain Institute  

E-print Network

of supply chain management. To learn more, contact executive director J. Paul Dittmann at jdittman and Supply Chain Management The University of Tennessee #12;The Global Supply Chain Institute World Class. Worldwide. Looking for ways to expand your supply

Tennessee, University of

103

Nanooptics of gradient dielectric films  

SciTech Connect

The propagation of light through subwave photonic barriers formed by dielectric nanofilms with the refractive indices changing across the films according to the specified law n(z) is considered. Generalised Fresnel formulae depending on the gradient and profile curvature of the refractive index and describing reflection and transmission of such inhomogeneous films are found. For the specified material and thickness, the optical properties of such nanofilms can change from total transmission to total reflection by producing a technologically controlled profile n(z). The obtained results are based on exact analytic solutions of Maxwell's equations for new multiparametric models of inhomogeneous dielectric media. The possibility of producing new subwave dispersion elements, whose action is based on the dependence of the reflection and transmission spectra of gradient photonic barriers on their local dispersion determined by the shape and geometrical parameters of the profile n(z), is shown. The schemes are considered for producing such spectra in the visible and IR regions with the help of periodic nanostructures containing subwave photonic barriers with the normal and anomalous nonlocal dispersion. (nanostructures)

Shvartsburg, Aleksandr B; Agranat, Mikhail B; Chefonov, O V [Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow (Russian Federation)

2009-10-31

104

Improving supply chain resilience  

E-print Network

Due to the global expansion of Company A's supply chain network, it is becoming more vulnerable to many disruptions. These disruptions often incur additional costs; and require time to respond to and recover from these ...

Leung, Elsa Hiu Man

2009-01-01

105

European supply chain study  

E-print Network

Introduction: Supply chain management has been defined as, "..a set of approaches utilized to efficiently integrate suppliers, manufacturers, warehouses and stores, so that merchandise is produced and distributed at the ...

Puri, Mohitkumar

2009-01-01

106

Food Chains: Nature's Restaurant  

NSDL National Science Digital Library

In these life science activities, students will participate in field observations of living things & do research of animals they observe to create a food chain & present it to the class. Students will participate in a food web simulation game.

Schaffran, Jane

107

Polymerase Chain Reaction  

NSDL National Science Digital Library

This interactive activity adapted from the University of Nebraska's Library of Crop Technologies depicts steps in the polymerase chain reaction (PCR) technique and explains how it is used to efficiently copy sections of DNA for analysis.

WGBH Educational Foundation

2009-12-07

108

Supply chain dynamics  

E-print Network

The strong bargaining power of major retailers and the higher requirements for speed, service excellence and customization have significantly contributed to transform the Supply Chain Management. These increasing challenges ...

Barbosa, Ricardo Wagner Lopes, 1976-

2003-01-01

109

Atomic Chain Electronics  

NASA Technical Reports Server (NTRS)

Adatom chains, precise structures artificially created on an atomically regulated surface, are the smallest possible candidates for future nanoelectronics. Since all the devices are created by combining adatom chains precisely prepared with atomic precision, device characteristics are predictable, and free from deviations due to accidental structural defects. In this atomic dimension, however, an analogy to the current semiconductor devices may not work. For example, Si structures are not always semiconducting. Adatom states do not always localize at the substrate surface when adatoms form chemical bonds to the substrate atoms. Transport properties are often determined for the entire system of the chain and electrodes, and not for chains only. These fundamental issues are discussed, which will be useful for future device considerations.

Yamada, Toshishige; Saini, Subhash (Technical Monitor)

1998-01-01

110

Food Chains and Webs  

NSDL National Science Digital Library

In this activity, learners investigate feeding relationships. Learners complete a food web and then make a mobile to represent a food chain. Use this activity to talk about predator/prey relationships and ecosystems.

Council, Biotechnology A.

2012-06-26

111

Green Supply Chain Management  

Microsoft Academic Search

\\u000a In this chapter, we will discuss some of the fundamental aspects of Green Supply Chain Management (GrSCM). First, GrSCM, its\\u000a origins, advantages, barriers, and initiatives will be discussed. Next, we will review green design, green operations, green\\u000a procurement, and GrSCM frameworks. Finally, the role of governments and international organizations in promoting and developing\\u000a green supply chain practices will be analyzed

Ehsan Nikbakhsh

112

Ideal chain (entropic elasticity)  

NSDL National Science Digital Library

In the first video segment, we present a cartoon model of a weighted chain, which can be regarded as an approximation for a polymer under tension (e.g. a strand of DNA being stretched out using optical tweezers). The Hamiltonian and partition function for this system are described in the second segment. Finally, in the third segment, we calculate the average energy and elongation of the chain.

2013-06-21

113

Polymerase Chain Reaction  

NSDL National Science Digital Library

Polymerase chain reaction (PCR) enables researchers to produce millions of copies of a specific DNA sequence in approximately two hours. This automated process bypasses the need to use bacteria for amplifying DNA. This animation from Cold Spring Harbor Laboratory's Dolan DNA Learning Center presents Polymerase Chain Reaction through a series of illustrations of the processes involved. Users may view the animation online (Flash is required) or download it for PC or Mac.

114

New mooring chain designs  

SciTech Connect

The present work introduces the readers to the developments the high technology offshore chain industry has carried out in recent years, in an effort to offer products that meet the needs of petroleum exploration and production. In this manner the industry can continue to regard chain as a fundamental element in its moorings system, whether for projects with a 25 year life, or projects at depths of over 1,000 meters, or in such severe environments as those faced in the Sub-Arctic. Data are presented on Studless Chain and VGW or Variable Geometry and Weight chain. These will allow engineers designers to forget the needs for chains to be circumscribed to rigid guidelines of geometry or dimensions. Instead they can design mooring systems specific for the particular situations they face. No longer shall chain have to meet geometric standardization derived from the middle of the 19th century while meeting the requirements of the 2nd half of the 20th century.

Canada, L.; Vicinay, J.; Sanz, A.; Lopez, E.

1996-12-31

115

MBA Supply Chain Case Competition Center for Supply Chain Management  

E-print Network

MBA Supply Chain Case Competition Center for Supply Chain Management February 1, 2013 1:00 ­ 4:00 p their skills in analyzing a real-world supply chain management case. Provide a chance for sponsoring companies of the Rutgers Center for Supply Chain Management to get to know top talent from RBS. The Schedule The case

Lin, Xiaodong

116

Wnt Secretion and Gradient Formation  

PubMed Central

Concentration gradients formed by the lipid-modified morphogens of the Wnt family are known for their pivotal roles during embryogenesis and adult tissue homeostasis. Wnt morphogens are also implicated in a variety of human diseases, especially cancer. Therefore, the signaling cascades triggered by Wnts have received considerable attention during recent decades. However, how Wnts are secreted and how concentration gradients are formed remains poorly understood. The use of model organisms such as Drosophila melanogaster has provided important advances in this area. For instance, we have previously shown that the lipid raft-associated reggie/flotillin proteins influence Wnt secretion and spreading in Drosophila. Our work supports the notion that producing cells secrete Wnt molecules in at least two pools: a poorly diffusible one and a reggie/flotillin-dependent highly diffusible pool which allows morphogen spreading over long distances away from its source of production. Here we revise the current views of Wnt secretion and spreading, and propose two models for the role of the reggie/flotillin proteins in these processes: (i) reggies/flotillins regulate the basolateral endocytosis of the poorly diffusible, membrane-bound Wnt pool, which is then sorted and secreted to apical compartments for long-range diffusion, and (ii) lipid rafts organized by reggies/flotillins serve as “dating points” where extracellular Wnt transiently interacts with lipoprotein receptors to allow its capture and further spreading via lipoprotein particles. We further discuss these processes in the context of human breast cancer. A better understanding of these phenomena may be relevant for identification of novel drug targets and therapeutic strategies. PMID:23455472

Solis, Gonzalo P.; Lüchtenborg, Anne-Marie; Katanaev, Vladimir L.

2013-01-01

117

Temperature gradient sensor based on CNT composite  

NASA Astrophysics Data System (ADS)

This work describes fabrication and investigation of thin film temperature gradient sensor based on the composite of carbon nano-tubes (CNT) and polymer adhesive. The dependences of the voltage, current and Seebeck coefficient of the sensor upon gradient of temperature were measured. It was observed that with increase of temperature gradient, the voltage and current of the sensor increase while the Seebeck coefficient decreases.

Karimov, Khasan S.; Abid, ?uhammad; Saleem, Muhammad; Akhmedov, Khakim M.; Bashir, Muhammad M.; Shafique, Umar; Ali, Muhammad M.

2014-08-01

118

Chain formation and chain dynamics in a dilute magnetorheological fluid.  

PubMed

Magnetorheological fluids are suspensions of magnetizable particles that reversibly change from liquid to solid when subjected to a magnetic field. A field-induced structure of dipolar chains is responsible for these changes. Our work aimed at understanding chain dynamics and the kinetics of chain formation by using dynamic light scattering. Chain length is determined by measurement of the diffusion coefficient. Chain-length growth shows a Smoluchowski behavior. PMID:18264283

Hagenbüchle, M; Liu, J

1997-10-20

119

Nanofiber Scaffold Gradients for Interfacial Tissue Engineering  

PubMed Central

We have designed a 2-spinnerette device that can directly electrospin nanofiber scaffolds containing a gradient in composition that can be used to engineer interfacial tissues such as ligament and tendon. Two types of nanofibers are simultaneously electrospun in an overlapping pattern to create a nonwoven mat of nanofibers containing a composition gradient. The approach is an advance over previous methods due to its versatility - gradients can be formed from any materials that can be electrospun. A dye was used to characterize the 2-spinnerette approach and applicability to tissue engineering was demonstrated by fabricating nanofibers with gradients in amorphous calcium phosphate nanoparticles (nACP). Adhesion and proliferation of osteogenic cells (MC3T3-E1 murine pre-osteoblasts) on gradients was enhanced on the regions of the gradients that contained higher nACP content yielding a graded osteoblast response. Since increases in soluble calcium and phosphate ions stimulate osteoblast function, we measured their release and observed significant release from nanofibers containing nACP. The nanofiber-nACP gradients fabricated herein can be applied to generate tissues with osteoblast gradients such as ligaments or tendons. In conclusion, these results introduce a versatile approach for fabricating nanofiber gradients that can have application for engineering graded tissues. PMID:22286209

Ramalingam, Murugan; Young, Marian F.; Thomas, Vinoy; Sun, Limin; Chow, Laurence C.; Tison, Christopher K.; Chatterjee, Kaushik; Miles, William C.; Simon, Carl G.

2012-01-01

120

Zonation: Position on Gradient Barnacles: Dessication  

E-print Network

Zonation: Position on Gradient Barnacles: Dessication Many Organisms: Elevation, Depth h: Position Barnacles: Strong Zonation Little Overlap Coexist? Scale #12;Spatial Mosaic Local Disturbance Colonization

Caraco, Thomas

121

Adhesion and friction properties of polymer brushes on rough surfaces: a gradient approach.  

PubMed

The effect of nanoscale surface roughness on the lubrication properties of a polymer brush in a good solvent has been investigated. Friction and adhesion forces were measured by means of polyethylene colloidal-probe AFM across a 12 nm silica particle gradient before and after the adsorption of a poly(L-lysine)-g-poly(ethylene glycol) (PLL-g-PEG) polymer brush. The adsorption and conformation of the polymer chains were studied with multiple transmission and reflection infrared (MTR-IR) spectroscopy. The results show that prior to the adsorption of PLL-g-PEG on the gradient surface, the friction is high at the smooth end of the gradient while it decreases toward the rough end. Moreover, there is a direct correlation between friction and adhesion. Upon adsorption of the brushes, adhesion vanishes. In this case, a higher frictional force between the PEG-coated particle gradient substrate and the polyethylene sphere is observed at the rough end of the gradient in comparison to the smooth end. In spite of the increased adsorbed mass of PLL-g-PEG at the rough end of the gradient, theory and simulations show that the high curvature of the nanoparticles leads to a less swollen PEG brush in comparison to PEG brushes adsorbed on a planar surface, resulting in a lower repulsion, which can explain the observed increase in friction with particle density. PMID:24266663

Ramakrishna, Shivaprakash N; Espinosa-Marzal, Rosa M; Naik, Vikrant V; Nalam, Prathima C; Spencer, Nicholas D

2013-12-10

122

Supply-Chain Optimization Template  

NASA Technical Reports Server (NTRS)

The Supply-Chain Optimization Template (SCOT) is an instructional guide for identifying, evaluating, and optimizing (including re-engineering) aerospace- oriented supply chains. The SCOT was derived from the Supply Chain Council s Supply-Chain Operations Reference (SCC SCOR) Model, which is more generic and more oriented toward achieving a competitive advantage in business.

Quiett, William F.; Sealing, Scott L.

2009-01-01

123

Interim Director Supply Chain Management  

E-print Network

Interim Director Supply Chain Management Rita Neogy Manager Card & Travel Services Tyler Faso-Rae Eisenbeis Vacant Updated: May 28, 2014 SUPPLY CHAIN MANAGEMENT Organizational Chart SCM Administrator Sandra Supply Chain PeopleSoft Master Data Specialist Carllyn Colabella Supply Chain Consultant Customer Service

Habib, Ayman

124

Approximating Markov chains.  

PubMed

A common framework of finite state approximating Markov chains is developed for discrete time deterministic and stochastic processes. Two types of approximating chains are introduced: (i) those based on stationary conditional probabilities (time averaging) and (ii) transient, based on the percentage of the Lebesgue measure of the image of cells intersecting any given cell. For general dynamical systems, stationary measures for both approximating chains converge weakly to stationary measures for the true process as partition width converges to 0. From governing equations, transient chains and resultant approximations of all n-time unit probabilities can be computed analytically, despite typically singular true-process stationary measures (no density function). Transition probabilities between cells account explicitly for correlation between successive time increments. For dynamical systems defined by uniformly convergent maps on a compact set (e.g., logistic, Henon maps), there also is weak continuity with a control parameter. Thus all moments are continuous with parameter change, across bifurcations and chaotic regimes. Approximate entropy is seen as the information-theoretic rate of entropy for approximating Markov chains and is suggested as a parameter for turbulence; a discontinuity in the Kolmogorov-Sinai entropy implies that in the physical world, some measure of coarse graining in a mixing parameter is required. PMID:11607293

Pincus, S M

1992-05-15

125

A micromechanical damage and fracture model for polymers based on fractional strain-gradient elasticity  

NASA Astrophysics Data System (ADS)

We formulate a simple one-parameter macroscopic model of distributed damage and fracture of polymers that is amenable to a straightforward and efficient numerical implementation. We show that the macroscopic model can be rigorously derived, in the sense of optimal scaling, from a micromechanical model of chain elasticity and failure regularized by means of fractional strain-gradient elasticity. In particular, we derive optimal scaling laws that supply a link between the single parameter of the macroscopic model, namely, the critical energy-release rate of the material, and micromechanical parameters pertaining to the elasticity and strength of the polymer chains and to the strain-gradient elasticity regularization. We show how the critical energy-release rate of specific materials can be determined from test data. Finally, we demonstrate the scope and fidelity of the model by means of an example of application, namely, Taylor-impact experiments of polyurea 1000 rods.

Heyden, S.; Li, B.; Weinberg, K.; Conti, S.; Ortiz, M.

2015-01-01

126

Crystalline-gradient polycarbonates prepared from enantioselective terpolymerization of meso-epoxides with CO2  

NASA Astrophysics Data System (ADS)

The development of efficient processes for CO2 transformation into useful products is a long-standing goal for chemists, since CO2 is an abundant, inexpensive and non-toxic renewable C1 resource. Here we describe the enantioselective copolymerization of 3,4-epoxytetrahydrofuran with CO2 mediated by biphenol-linked dinuclear cobalt complex, affording the corresponding polycarbonate with >99% carbonate linkages and excellent enantioselectivity (up to 99% enantiomeric excess). Notably, the resultant isotactic polycarbonate is a typical semicrystalline polymer, possessing a melting point of 271?°C. Furthermore, the enantioselective terpolymerization of 3,4-epoxytetrahydrofuran, cyclopentene oxide and CO2 mediated by this dinuclear cobalt complex gives novel gradient polycarbonates, in which the decrement of one component and the increment of the other component occur sequentially from one chain end to the other end. The resultant terpolymers show perfectly isotactic structure and have unique crystalline-gradient nature, in which the crystallinity continuously varies along the main chain.

Liu, Ye; Ren, Wei-Min; He, Ke-Ke; Lu, Xiao-Bing

2014-12-01

127

Oscillator Chain Model  

NSDL National Science Digital Library

The EJS Oscillator Chain model shows a one-dimensional linear array of coupled harmonic oscillators with fixed ends. This model can be used to study the propagation of waves in a continuous medium and the vibrational modes of a crystalline lattice. The Ejs model shown here contains 31 coupled oscillators equally spaced within the interval [0, 2 pi] with fixed ends. Ejs Oscillator Chain model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_mech_osc_OscillatorChain.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for classical mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Christian, Wolfgang

2008-11-06

128

The adiabatic gradient and the melting point gradient in the core of the earth  

Microsoft Academic Search

The melting gradient and the adiabatic gradient throughout the core of the earth are compared. The temperature of melting of iron at pressures equivalent to the inner core-outer core boundary is estimated to be circa 4250øC with a melting point gradient of approximately 500 ø through the outer core. The adiabatic gradient through the outer core is estimated to be

G. Higgins; G. C. Kennedy

1971-01-01

129

Dinoflagellate community analysis of a fish kill using denaturing gradient gel electrophoresis  

Microsoft Academic Search

A molecular method using the polymerase chain reaction (PCR) amplification of small subunit gene sequences (18S rDNA) and denaturing gradient gel electrophoresis (DGGE) was used to determine both the population complexity and species identification of organisms in harmful algal blooms. Eighteen laboratory cultures of dinoflagellates, including Akashiwo, Gymnodinium, Heterocapsa, Karenia, Karlodinium, Pfiesteria, and Pfiesteria-like species were analyzed using dinoflagellate-specific oligonucleotide

Qian Wang; Jonathan R. Deeds; Robert Belas

2005-01-01

130

Factor-multiple Chains  

NSDL National Science Digital Library

This problem offers opportunities for students to reinforce their understanding of factors and multiples and provides them the chance to justify their solutions. The goal is for the students to create number chains of four whole numbers that can range from 2 to 100 and each consecutive number is a multiple of the previous number. The Teachers' Notes page offers suggestions for implementation, key discussion questions, ideas for extension and support, and a link to a spreadsheet for students to experiment with placing numbers in specific boxes in the chain.

2007-04-01

131

Oscillator Chain JS Model  

NSDL National Science Digital Library

The EJS Oscillator Chain model shows a one-dimensional linear array of coupled harmonic oscillators with fixed ends. This model can be used to study the propagation of waves in a continuous medium and the vibrational modes of a crystalline lattice. The Ejs model shown here contains 31 coupled oscillators equally spaced within the interval [0, 2 pi] with fixed ends. The Oscillator Chain JS Model was developed using the Easy Java Simulations (Ejs) version 5. It is distributed as a ready-to-run html page and requires only a browser with JavaScript support.

Christian, Wolfgang

2013-08-25

132

The impact of gradient strength on in vivo diffusion MRI estimates of axon diameter.  

PubMed

Diffusion magnetic resonance imaging (MRI) methods for axon diameter mapping benefit from higher maximum gradient strengths than are currently available on commercial human scanners. Using a dedicated high-gradient 3T human MRI scanner with a maximum gradient strength of 300mT/m, we systematically studied the effect of gradient strength on in vivo axon diameter and density estimates in the human corpus callosum. Pulsed gradient spin echo experiments were performed in a single scan session lasting approximately 2h on each of three human subjects. The data were then divided into subsets with maximum gradient strengths of 77, 145, 212, and 293mT/m and diffusion times encompassing short (16 and 25ms) and long (60 and 94ms) diffusion time regimes. A three-compartment model of intra-axonal diffusion, extra-axonal diffusion, and free diffusion in cerebrospinal fluid was fitted to the data using a Markov chain Monte Carlo approach. For the acquisition parameters, model, and fitting routine used in our study, it was found that higher maximum gradient strengths decreased the mean axon diameter estimates by two to three fold and decreased the uncertainty in axon diameter estimates by more than half across the corpus callosum. The exclusive use of longer diffusion times resulted in axon diameter estimates that were up to two times larger than those obtained with shorter diffusion times. Axon diameter and density maps appeared less noisy and showed improved contrast between different regions of the corpus callosum with higher maximum gradient strength. Known differences in axon diameter and density between the genu, body, and splenium of the corpus callosum were preserved and became more reproducible at higher maximum gradient strengths. Our results suggest that an optimal q-space sampling scheme for estimating in vivo axon diameters should incorporate the highest possible gradient strength. The improvement in axon diameter and density estimates that we demonstrate from increasing maximum gradient strength will inform protocol development and encourage the adoption of higher maximum gradient strengths for use in commercial human scanners. PMID:25498429

Huang, Susie Y; Nummenmaa, Aapo; Witzel, Thomas; Duval, Tanguy; Cohen-Adad, Julien; Wald, Lawrence L; McNab, Jennifer A

2015-02-01

133

Heat conduction in one-dimensional aperiodic quantum Ising chains.  

PubMed

The heat conductivity of nonperiodic quantum Ising chains whose ends are connected with heat baths at different temperatures are studied numerically by solving the Lindblad master equation. The chains are subjected to a uniform transverse field h, while the exchange coupling J{m} between the nearest-neighbor spins takes the two values J{A} and J{B} arranged in Fibonacci, generalized Fibonacci, Thue-Morse, and period-doubling sequences. We calculate the energy-density profile and energy current of the resulting nonequilibrium steady states to study the heat-conducting behavior of finite but large systems. Although these nonperiodic quantum Ising chains are integrable, it is clearly found that energy gradients exist in all chains and the energy currents appear to scale as the system size ~N{?}. By increasing the ratio of couplings, the exponent ? can be modulated from ? > -1 to ? < -1 corresponding to the nontrivial transition from the abnormal heat transport to the heat insulator. The influences of the temperature gradient and the magnetic field to heat conduction have also been discussed. PMID:21517475

Li, Wenjuan; Tong, Peiqing

2011-03-01

134

Microfluidic gradient PCR (MG-PCR): a new method for microfluidic DNA amplification.  

PubMed

This study develops a new microfluidic DNA amplification strategy for executing parallel DNA amplification in the microfluidic gradient polymerase chain reaction (MG-PCR) device. The developed temperature gradient microfluidic system is generated by using an innovative fin design. The device mainly consists of modular thermally conductive copper flake which is attached onto a finned aluminum heat sink with a small fan. In our microfluidic temperature gradient prototype, a non-linear temperature gradient is produced along the gradient direction. On the copper flake of length 45 mm, width 40 mm and thickness 4 mm, the temperature gradient easily spans the range from 97 to 52 degrees Celsius. By making full use of the hot (90-97 degrees Celsius) and cold (60-70 degrees Celsius) regions on the temperature gradient device, the parallel, two-temperature MG-PCR amplification is feasible. As a demonstration, the MG-PCR from three parallel reactions of 112-bp Escherichia coli DNA fragment is performed in a continuous-flow format, in which the flow of the PCR reagent in the closed loop is induced by the buoyancy-driven nature convection. Although the prototype is not optimized, the MG-PCR amplification can be completed in less than 45 min. However, the MG-PCR thermocycler presented herein can be further scaled-down, and thus the amplification times and reagent consumption can be further reduced. In addition, the currently developed temperature gradient technology can be applied onto other continuous-flow MG-PCR systems or used for other analytical purposes such as parallel and combination measurements, and fluorescent melting curve analysis. PMID:19757072

Zhang, Chunsun; Xing, Da

2010-02-01

135

High Gradient Two-Beam Electron Accelerator  

SciTech Connect

A high-gradient two-beam electron accelerator structure using detuned cavities is described. A self-consistent theory based on a circuit model is presented to calculate idealized acceleration gradient, transformer ratio, and efficiency for energy transfer from the drive beam to the accelerated beam. Experimental efforts are being carried out to demonstrate this acceleration concept.

Jiang, Y. [Beam Physics Laboratory, Yale University, 272 Whitney Ave., New Haven, CT 06511 (United States); Kazakov, S. Yu. [Omega-P, Inc., 258 Bradley St., New Haven, CT 06510 (United States); Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Kuzikov, S. V. [Omega-P, Inc., 258 Bradley St., New Haven, CT 06510 (United States); Institute of Applied Physics, Nizhny Novgorod, 603600 (Russian Federation); Hirshfield, J. L. [Beam Physics Laboratory, Yale University, 272 Whitney Ave., New Haven, CT 06511 (United States); Omega-P, Inc., 258 Bradley St., New Haven, CT 06510 (United States)

2010-11-04

136

Moving thermal gradients in gas chromatography.  

PubMed

This paper examines the separation effects of a moving thermal gradient on a chromatographic column in gas chromatography. This movement of the gradient has a focusing effect on the analyte bands, limiting band broadening in the column. Here we examine the relationship between the slope of this gradient, the velocity of the gradient and the resulting band width. Additionally we examine how transport of analytes along the column at their analyte specific constant temperatures, determined by the gradient slope and velocity, affects resolution. This examination is based primarily on a theoretical model of partitioning and transport of analyte under low concentration conditions. Preliminary predictions indicate that analytes reach near constant temperatures, relative positions and resolutions in less than 100cm of column transport. Use of longer columns produces very little improvement in resolution for any fixed slope. Properties of the thermal gradient determine a fixed solute band width for each analyte. These widths are nearly reached within the first 40-70cm, after which little broadening or narrowing of the bands occur. The focusing effect of the thermal gradient corrects for broad injections, reduces effects of irregular stationary phase coatings and can be used with short columns for fast analysis. Thermal gradient gas chromatographic instrumentation was constructed and used to illustrate some characteristics predicted from the theoretical results. PMID:25435463

Tolley, H Dennis; Tolley, Samuel E; Wang, Anzi; Lee, Milton L

2014-12-29

137

Microinstabilities in weak density gradient tokamak systems  

SciTech Connect

A prominent characteristic of auxiliary-heated tokamak discharges which exhibit improved (''H-mode type'') confinement properties is that their density profiles tend to be much flatter over most of the plasma radius. Depsite this favorable trend, it is emphasized here that, even in the limit of zero density gradient, low-frequency microinstabilities can persist due to the nonzero temperature gradient.

Tang, W.M.; Rewoldt, G.; Chen, L.

1986-04-01

138

Pursuing supply chain gains.  

PubMed

Five hallmarks of an effective supply chain are: A strong relationship is developed with a single GPO. Physicians are involved in supply standardization. Supply contracts are routinely reviewed at time of renewal. Freight costs are understood and negotiated effectively. Products are distributed through an in-house distribution center. PMID:16184962

Long, Gene

2005-09-01

139

The Agile Supply Chain  

Microsoft Academic Search

Turbulent and volatile markets are becoming the norm as life cycles shorten and global economic and competitive forces create additional uncertainty. The risk attached to lengthy and slow-moving logistics “pipelines” has become unsustainable, forcing organizations to look again at how their supply chains are structured and managed. This paper suggests that the key to survival in these changed conditions is

Martin Christopher

2000-01-01

140

Atwood's Heavy Chain  

ERIC Educational Resources Information Center

While perusing various websites in search of a more challenging lab for my students, I came across a number of ideas where replacing the string in an Atwood's machine with a simple ball chain like the kind found in lamp pulls created an interesting system to investigate. The replacement of the string produced a nice nonuniform acceleration, but…

Beeken, Paul

2011-01-01

141

Simplified Chain Inflation  

E-print Network

We propose a simplified chain inflation model and calculate the primordial power spectra of the scalar and tensor fluctuations. The spectral index and the tensor-scalar ratio are respectively 0.972 and 0.089 which are consistent with present cosmological observations.

Qing-Guo Huang

2007-04-25

142

Intracellular chemical gradients: morphing principle in bacteria  

PubMed Central

Advances in computational biology allow systematic investigations to ascertain whether internal chemical gradients can be maintained in bacteria – an open question at the resolution limit of fluorescence microscopy. While it was previously believed that the small bacterial cell size and fast diffusion in the cytoplasm effectively remove any such gradient, a new computational study published in BMC Biophysics supports the emerging view that gradients can exist. The study arose from the recent observation that phosphorylated CtrA forms a gradient prior to cell division in Caulobacter crescentus, a bacterium known for its complicated cell cycle. Tropini et al. (2012) postulate that such gradients can provide an internal chemical compass, directing protein localization, cell division and cell development. More specifically, they describe biochemical and physical constraints on the formation of such gradients and explore a number of existing bacterial cell morphologies. These chemical gradients may limit in vitro analyses, and may ensure timing control and robustness to fluctuations during critical stages in cell development. PMID:22954369

2012-01-01

143

Demand chain management-integrating marketing and supply chain management  

Microsoft Academic Search

This paper endorses demand chain management as a new business model aimed at creating value in today's marketplace, and combining the strengths of marketing and supply chain competencies. Demand chain design is based on a thorough market understanding and has to be managed in such a way as to effectively meet differing customer needs. Based on a literature review as

Uta Jüttner; Martin Christopher; Susan Baker

2007-01-01

144

Markov Chain Monte Carlo Methods Markov Chain Monte Carlo Methods  

E-print Network

Markov Chain Monte Carlo Methods Markov Chain Monte Carlo Methods Christian P. Robert Universit Monte Carlo Methods Outline Motivation and leading example Random variable generation Monte Carlo for variable dimension problems Sequential importance sampling #12;Markov Chain Monte Carlo Methods New [2004

Robert, Christian P.

145

Supply Chain Networks: Challenges and Opportunities  

E-print Network

#12;A General Supply Chain Anna Nagurney Supply Chain Networks #12;Examples of Supply Chains food humanitarian relief healthcare supply chains. Anna Nagurney Supply Chain Networks #12;Food Supply Chains AnnaSupply Chain Networks: Challenges and Opportunities from Analysis to Design Anna Nagurney Isenberg

Nagurney, Anna

146

Supply Chain Networks: Challenges and Opportunities  

E-print Network

Chain Networks #12;Examples of Supply Chains food and food products high tech products automotive energy chains in nature. Anna Nagurney Supply Chain Networks #12;Food Supply Chains Anna Nagurney Supply ChainSupply Chain Networks: Challenges and Opportunities from Analysis to Design Anna Nagurney Isenberg

Nagurney, Anna

147

Measurement of thermodynamics using gradient flow  

E-print Network

We analyze bulk thermodynamics and correlation functions of the energy-momentum tensor in pure Yang-Mills gauge theory using the energy-momentum tensor defined by the gradient flow and small flow time expansion. Our results on thermodynamic observables are consistent with those obtained by the conventional integral method. The analysis of the correlation function of total energy supports the energy conservation. It is also addressed that these analyses with gradient flow require less statistics compared with the previous methods. All these results suggest that the energy-momentum tensor can be successfully defined and observed on the lattice with moderate numerical costs with the gradient flow.

Masakiyo Kitazawa; Masayuki Asakawa; Tetsuo Hatsuda; Takumi Iritani; Etsuko Itou; Hiroshi Suzuki

2014-12-15

148

Algorithm for Image Retrieval Based on Edge Gradient Orientation Statistical Code  

PubMed Central

Image edge gradient direction not only contains important information of the shape, but also has a simple, lower complexity characteristic. Considering that the edge gradient direction histograms and edge direction autocorrelogram do not have the rotation invariance, we put forward the image retrieval algorithm which is based on edge gradient orientation statistical code (hereinafter referred to as EGOSC) by sharing the application of the statistics method in the edge direction of the chain code in eight neighborhoods to the statistics of the edge gradient direction. Firstly, we construct the n-direction vector and make maximal summation restriction on EGOSC to make sure this algorithm is invariable for rotation effectively. Then, we use Euclidean distance of edge gradient direction entropy to measure shape similarity, so that this method is not sensitive to scaling, color, and illumination change. The experimental results and the algorithm analysis demonstrate that the algorithm can be used for content-based image retrieval and has good retrieval results. PMID:24892074

Zeng, Jiexian; Zhao, Yonggang; Li, Weiye

2014-01-01

149

Algorithm for image retrieval based on edge gradient orientation statistical code.  

PubMed

Image edge gradient direction not only contains important information of the shape, but also has a simple, lower complexity characteristic. Considering that the edge gradient direction histograms and edge direction autocorrelogram do not have the rotation invariance, we put forward the image retrieval algorithm which is based on edge gradient orientation statistical code (hereinafter referred to as EGOSC) by sharing the application of the statistics method in the edge direction of the chain code in eight neighborhoods to the statistics of the edge gradient direction. Firstly, we construct the n-direction vector and make maximal summation restriction on EGOSC to make sure this algorithm is invariable for rotation effectively. Then, we use Euclidean distance of edge gradient direction entropy to measure shape similarity, so that this method is not sensitive to scaling, color, and illumination change. The experimental results and the algorithm analysis demonstrate that the algorithm can be used for content-based image retrieval and has good retrieval results. PMID:24892074

Zeng, Jiexian; Zhao, Yonggang; Li, Weiye; Fu, Xiang

2014-01-01

150

Integration of nitrification and denitrification by combining anoxic and aerobic conditions in a membrane bioreactor.  

PubMed

A membrane bioreactor (MBR) was developed to achieve nitrogen removal by combining nitrification and denitrification conditions in one reactor. The activated sludge was alternated between aerobic and anoxic conditions using peristaltic pump. The biomass concentration and floc morphological properties were observed to be similar in anoxic and aerobic compartments. However, the homogeneous properties of the activated sludge did not lead to the failure of oxygen gradient formation in the reactor. Due to the position of the air diffuser, an anoxic compartment at the bottom and an aerobic compartment in the upper part of the reactor were formed after 40 days. The average total nitrogen (TN) removal efficiency was then observed to increase to 77%. The microbial characterization using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis, as well as the specific nitrogen utilization rate measurements, indicated that the nitrogen removal in the reactor occurred via nitrification and denitrification processes. PMID:21099046

Li, Jianfeng; Yang, Fenglin; Ohandja, Dieudonné-Guy; Wong, Fook-Sin

2010-01-01

151

Polymerase Chain Reaction  

NSDL National Science Digital Library

Teachers' Domain presents this interactive, adapted from the University of Nebraska's Library of Crop Technologies, with reading material and animations to help students learn the basic steps of polymerase chain reaction. Following the introduction, the lesson is divided four parts: Finding and Isolating DNA, Creating the DNA Solution, Begin Thermal Cycling, and Replication. Animations help students visualize each step of the processes described. On the site, visitors will also find a supplemental background essay, discussion questions, and standards alignment from Teachers' Domain.

152

Requirements of supply chain management in differentiating European pork chains.  

PubMed

This paper summarizes results obtained by research into pork chain management in the EU Integrated Project Q-Porkchains. Changing demands for intrinsic and extrinsic quality attributes of pork products impact the way supply chain management should be organized from the farmer down to the consumer. The paper shows the importance of Quality Management Systems for integrating supply chains and enhancing consumer confidence. The paper also presents innovations in information system integration for aligning information exchange in the supply chain and logistics concepts based on innovative measurement technologies at the slaughterhouse stage. In the final section research challenges towards sustainable pork supply chains satisfying current consumer demands are presented. PMID:23611335

Trienekens, Jacques; Wognum, Nel

2013-11-01

153

The Tourism Global Value Chain  

E-print Network

The Tourism Global Value Chain ECONOMIC UPGRADING AND WORKFORCE DEVELOPMENT Michelle Christian 2011 CENTER on GLOBALIZATION, GOVERNANCE & COMPETITIVENESS #12;The Tourism Global Value Chain: Economic: November 17, 2011 #12;The Tourism Global Value Chain: Economic Upgrading and Workforce Development i Table

Richardson, David

154

The Supply Chain Management Processes  

Microsoft Academic Search

Increasingly, supply chain management is being recognized as the management of key business processes across the network of organizations that comprise the supply chain. While many have recognized the benefits of a process approach to managing the business and the supply chain, most are vague about what processes are to be considered, what sub-processes and activities are contained in each

Keely L. Croxton; Sebastián J. García-Dastugue; Douglas M. Lambert; Dale S. Rogers

2001-01-01

155

Polymerase Chain Reaction Assay and  

E-print Network

Polymerase Chain Reaction Assay and Bacterial Meningitis Surveillance in Remote Areas, Niger Fati reference laboratory for meningitis in Niger used polymerase chain reaction (PCR) to enhance) and the national reference center for menin- gitis in Niger. The polymerase chain reaction (PCR) method

Paris-Sud XI, Université de

156

Microbial communities involved in anaerobic degradation of unsaturated or saturated long chain fatty acids  

Microsoft Academic Search

Anaerobic long-chain fatty acid (LCFA)-degrading bacteria were identified by combining selective enrichment studies with molecular approaches. Two distinct enrichment cultures growing on unsaturated and saturated LCFAs were obtained by successive transfers in medium containing oleate and palmitate, respectively, as the sole carbon and energy sources. Changes in the microbial composition during enrichment were analyzed by denaturing gradient gel electrophoresis (DGGE)

Diana Z. Sousa; M. Alcina Pereira; Alfons J. M. Stams; M. Madalena Alves; Hauke Smidt

2007-01-01

157

Gradient Clock Synchronization in Wireless Sensor Networks  

E-print Network

Gradient Clock Synchronization in Wireless Sensor Networks Philipp Sommer Computer Engineering clocks are crucial for many ap- plications in sensor networks. Existing time synchro- nization algorithms Keywords Sensor Networks, Time Synchronization, Clock Drift, Implementation, Experiments Permission to make

158

Spin Gradient Demagnetization Cooling of Ultracold Atoms  

E-print Network

We demonstrate a new cooling method in which a time-varying magnetic field gradient is applied to an ultracold spin mixture. This enables preparation of isolated spin distributions at positive and negative effective spin ...

Medley, Patrick M.

159

Regulation of the photosynthetic electron transport chain.  

PubMed

The regulation of electron transport between photosystems II and I was investigated in the plant Silene dioica L. by means of measurement of the kinetics of reduction of P(700) following a light-to-dark transition. It was found that, in this species, the rate constant for P(700) reduction is sensitive to light intensity and to the availability of CO(2). The results indicated that at 25 degrees C the rate of electron transport is down-regulated by approximately 40-50% relative to the maximum rate achievable in saturating CO(2) and that this down-regulation can be explained by regulation of the electron transport chain itself. Measurements of the temperature sensitivity of this rate constant indicated that there is a switch in the rate-limiting step that controls electron transport at around 20 degrees C: at higher temperatures, CO(2) availability is limiting; at lower temperatures some other process regulates electron transport, possibly a diffusion step within the electron transport chain itself. Regulation of electron transport also occurred in response to drought stress and sucrose feeding. Measurements of non-photochemical quenching of chlorophyll fluorescence did not support the idea that electron transport is regulated by the pH gradient across the thylakoid membrane, and the possibility is discussed that the redox potential of a stromal component may regulate electron transport.Keywords: DeltapH. Electron transport. Photosynthesis. Photosynthetic control. Redox regulation. Silene (photosynthesis) PMID:10436228

Ott; Clarke; Birks; Johnson

1999-08-12

160

Gradient approach to the sphaleron barrier  

SciTech Connect

We apply the gradient approach to obtain a path over the sphaleron barrier and to demonstrate the fermionic level crossing phenomenon. Neglecting the mixing angle dependence and assuming that the fermions of a doublet are degenerate in mass we employ spherically symmetric [ital Ansa]$[ital iuml---tze] for the fields. The gradient path over the barrier is smooth, even for large values of the Higgs boson mass or of the fermion mass, where the external energy path bifurcates.

Nolte, G. (Fachbereich Physik, Universitaet Oldenburg, Postfach 2503, D-26111 Oldenburg (Germany)); Kunz, J. (Fachbereich Physik, Universitaet Oldenburg, Postfach 2503, D-26111 Oldenburg (Germany) Instituut voor Theoretische Fysica, Rijksuniversiteit te Utrecht, NL-3508 TA Utrecht (Netherlands))

1995-03-15

161

Topics in Dynamic Meteorology: Pressure Gradient Force  

NSDL National Science Digital Library

This module is a learning object on a foundational aspect of dynamic meteorology, the pressure gradient force. As a learning object, it is meant to supplement other teaching material in a course by elucidating a specific concept. The horizontal pressure gradient force is presented through an interactive tool which allows a student to adjust pressures on an idealized surface map and examine the horizontal accelerations produced in response. Three short exercises are provided to reinforce the concepts.

2014-09-14

162

Medical image registration by combining global and local information: a chain-type diffeomorphic demons algorithm  

NASA Astrophysics Data System (ADS)

The demons algorithm is a popular algorithm for non-rigid image registration because of its computational efficiency and simple implementation. The deformation forces of the classic demons algorithm were derived from image gradients by considering the deformation to decrease the intensity dissimilarity between images. However, the methods using the difference of image intensity for medical image registration are easily affected by image artifacts, such as image noise, non-uniform imaging and partial volume effects. The gradient magnitude image is constructed from the local information of an image, so the difference in a gradient magnitude image can be regarded as more reliable and robust for these artifacts. Then, registering medical images by considering the differences in both image intensity and gradient magnitude is a straightforward selection. In this paper, based on a diffeomorphic demons algorithm, we propose a chain-type diffeomorphic demons algorithm by combining the differences in both image intensity and gradient magnitude for medical image registration. Previous work had shown that the classic demons algorithm can be considered as an approximation of a second order gradient descent on the sum of the squared intensity differences. By optimizing the new dissimilarity criteria, we also present a set of new demons forces which were derived from the gradients of the image and gradient magnitude image. We show that, in controlled experiments, this advantage is confirmed, and yields a fast convergence.

Liu, Xiaozheng; Yuan, Zhenming; Zhu, Junming; Xu, Dongrong

2013-12-01

163

Nucleation modes in sharp concentration gradients  

SciTech Connect

Reaction kinetics in bimetallic multilayers have demonstrated that sharp unidirectional concentration gradient, which develop as interdiffusion proceeds at the interface are able to delay or to suppress nucleation of intermetallics. It has been found that the existence of a critical gradient beyond which nucleation is inhibited is strongly dependent on the mechanism of formation of the embryo. A mechanism of nucleation under concentration gradient ({gradient}c) is proposed and treated on the basis of the Fokker-Planck equation for the distribution in the size space. The influence of the aspect ratio of the embryo on the critical concentration gradient is also studied. Due to the fluctuations of the embryo shape, it is shown that the minimization of the thermodynamic potential leading to the aspect ratio of the embryo is only significant beyond a certain value of the concentration gradient. Application is presented to the nucleation of the compound Ni{sub 10}Zr{sub 7} in an amorphous layer Ni-Zr.

Hodaj, F.; Desre, P.J. [LTPCM-UMR CNRS/INPG/UJF, Saint Martin d`Heres (France); Gusak, A.M.; Kovalchuk, A.O. [Cherkassy State Univ. (Ukraine). Dept. of Theoretical Physics

1998-12-31

164

Translocation of a Polymer Chain across a Nanopore: A Brownian Dynamics Simulation Study  

NASA Technical Reports Server (NTRS)

We carried out Brownian dynamics simulation studies of the translocation of single polymer chains across a nanosized pore under the driving of an applied field (chemical potential gradient). The translocation process can be either dominated by the entropic barrier resulted from restricted motion of flexible polymer chains or by applied forces (or chemical gradient across the wall), we focused on the latter case in our studies. Calculation of radius of gyrations at the two opposite sides of the wall shows that the polymer chains are not in equilibrium during the translocation process. Despite this fact, our results show that the one-dimensional diffusion and the nucleation model provide an excellent description of the dependence of average translocation time on the chemical potential gradients, the polymer chain length and the solvent viscosity. In good agreement with experimental results and theoretical predictions, the translocation time distribution of our simple model shows strong non-Gaussian characteristics. It is observed that even for this simple tubelike pore geometry, more than one peak of translocation time distribution can be generated for proper pore diameter and applied field strengths. Both repulsive Weeks-Chandler-Anderson and attractive Lennard-Jones polymer-nanopore interaction were studied, attraction facilitates the translocation process by shortening the total translocation time and dramatically improve the capturing of polymer chain. The width of the translocation time distribution was found to decrease with increasing temperature, increasing field strength, and decreasing pore diameter.

Tian, Pu; Smith, Grant D.

2003-01-01

165

Synchronized gradient elution in capillary liquid chromatography.  

PubMed

The synchronization of injection valve operation and gradient elution in capillary liquid chromatography (cHPLC) is studied. Focus is placed on the cHPLC systems which rely on the splitting of a primary flow to provide the much smaller secondary flow required at the injection device and analytical column. Owing to the tiny secondary flow rates, synchronization is necessary to achieve proper optimization of gradient elution methods. Otherwise, there is a risk of having the analytes totally or partially eluted in the initial isocratic conditions, and there is no control on the actual gradient profile reaching the column. Synchronization is first achieved by switching back the valve to bypass after injection. This is important to save time, and to avoid the gradient slope to be reduced by mixing within the internal volume of the injector (a 47% of slope reduction, in the conditions used in this work). Valve switching to bypass should be produced immediately after the arrival of the end of the sample plug to the valve (tV). Fine system synchronization is further achieved by starting the gradient at the match time (tM), which is the time required to match the arrival of both the gradient front and the end of the sample plug to the valve, and therefore also to the column inlet. Synchronization of these two events requires starting the gradient either before or even after the injection, thus to prevent a late or an early arrival of the gradient front to the injection valve, respectively. Owing to their dependence with the backpressure, both tV and tM should be measured in the presence of the column at the initial gradient conditions. Simple experiments designed to measure tV and tM are described. With synchronization according to the techniques described in this work, control on the real gradient elution conditions at the column location is maintained, the analysis time is reduced and efficiency improves. The effects of synchronization are illustrated by injecting a mixture of alkylbenzenes. At 1?L min(-1), valve switching to bypass reduced analysis time from ca. 36 to 12min (butylbenzene), and improved peak symmetry (from 2.00 to 0.94 for methylbenzene) and efficiency (the average apparent plate count increased approximately 60%). Synchronization according to the match time further improved efficiency (approximately, up to 120%). PMID:24169041

Carrasco-Correa, Enrique Javier; Acquaviva, Agustín; Herrero-Martínez, José Manuel; Ramis-Ramos, Guillermo

2013-11-29

166

Supply Chain Management Understand and apply essential supply chain management concepts.  

E-print Network

Supply Chain Management Understand and apply essential supply chain management concepts. Gain In Integrated Supply Chain Management Certificate awarded after completion of: · Supply Chain Management Foundation · Supply Chain Relationship Management · Demand Management · Operations Systems Management

Fork, Richard

167

Supply Chain Management and Marketing Sciences Maximizing the Interface between Supply Chain & Marketing  

E-print Network

Supply Chain Management and Marketing Sciences Maximizing the Interface between Supply Chain.Inordertocontinuethetraditionofsuccess,the SCSIleanedonitsconnectionsinthesupplychainindustrymorethanever. SCSImembersareinvolvedinavarietyofstrongSupplyChain professionalorganizations.TheCouncilofSupplyChainManagement.Inaddition,SCSImemberstookpartinmanymeetingsofthese organizationsinordertonetworkandexpandonwhattheylearninthe classroom. TheSCSIalsocontinuedtoworkwiththeRutgersCenterforSupplyChain Management

Lin, Xiaodong

168

Separation of short-chain branched polyolefins by high-temperature gradient adsorption liquid chromatography.  

PubMed

A new separation principle was recently introduced into the analytical characterization of polyolefins by researchers from the German Institute for Polymers in Darmstadt. It was demonstrated that polyolefins can be selectively separated via high-performance liquid chromatography on the basis of their adsorption/desorption behaviours at temperatures as high as 160 °C. A Hypercarb® column packed with porous graphite gave the best results. The mobile phase consisted of a mixture of 1-decanol and 1,2,4-trichlorobenzene. In this work, the same chromatographic system is applied to the separation of ethylene/alkene and ethylene/norbornene copolymers. It was found that the elution volumes of the samples correlate linearly with the average chemical composition of samples. The elution volume is indirectly proportional to the concentration of branches in the ethylene/alkene copolymer. Branching shortens the length of continuous methylene sequences of the polymer backbone, thus decreasing the probability of orientation of a methylene sequence in a flat conformation on the graphite surface, which enables the most intensive van der Waals interactions between the methylene backbone and the carbon surface. An opposite trend in the elution order has been found for ethylene/norbornene copolymers. The elution volume of the ethylene/norbornene copolymers increased with the concentration of norbornene. It indicates pronounced attractive interactions between graphite and the cyclic comonomer. PMID:21046082

Macko, Tibor; Brüll, Robert; Alamo, Rufina G; Stadler, Florian J; Losio, Simone

2011-02-01

169

Assessment of bacterial community structure in soil by polymerase chain reaction and denaturing gradient gel electrophoresis  

Microsoft Academic Search

Bacterial community structure was studied in a Flevo silt loam (FSL) soil microplot, as well as in 15 other soils, by using DNA extraction followed by molecular fingerprinting. Total community DNA was extracted and purified by a direct method, which yielded amplifiable DNA of high molecular weight for all soils. A variable region of the 16S rRNA gene was then

Antonio Gelsomino; Anneke C Keijzer-Wolters; Giovanni Cacco; Jan Dirk van Elsas

1999-01-01

170

Pit Chain on Olympus  

NASA Technical Reports Server (NTRS)

21 April 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a chain of collapse pits on the lower northeast flank of the large martian volcano, Olympus Mons. For these to have formed, something in the subsurface must have been removed or changed volume, such as cooling lava within a subsurface lava tube or extension of the crust by faulting. These pits are located near 20.6oN, 129.4oW. The picture covers an area about 3 km (1.9 mi) across. Sunlight illuminates the scene from the lower left.

2004-01-01

171

Musical Markov Chains  

NASA Astrophysics Data System (ADS)

A system for using dice to compose music randomly is known as the musical dice game. The discrete time MIDI models of 804 pieces of classical music written by 29 composers have been encoded into the transition matrices and studied by Markov chains. Contrary to human languages, entropy dominates over redundancy, in the musical dice games based on the compositions of classical music. The maximum complexity is achieved on the blocks consisting of just a few notes (8 notes, for the musical dice games generated over Bach's compositions). First passage times to notes can be used to resolve tonality and feature a composer.

Volchenkov, Dima; Dawin, Jean René

172

Doping of Semiconducting Atomic Chains  

NASA Technical Reports Server (NTRS)

Due to the rapid progress in atom manipulation technology, atomic chain electronics would not be a dream, where foreign atoms are placed on a substrate to form a chain, and its electronic properties are designed by controlling the lattice constant d. It has been shown theoretically that a Si atomic chain is metallic regardless of d and that a Mg atomic chain is semiconducting or insulating with a band gap modified with d. For electronic applications, it is essential to establish a method to dope a semiconducting chain, which is to control the Fermi energy position without altering the original band structure. If we replace some of the chain atoms with dopant atoms randomly, the electrons will see random potential along the chain and will be localized strongly in space (Anderson localization). However, if we replace periodically, although the electrons can spread over the chain, there will generally appear new bands and band gaps reflecting the new periodicity of dopant atoms. This will change the original band structure significantly. In order to overcome this dilemma, we may place a dopant atom beside the chain at every N lattice periods (N > 1). Because of the periodic arrangement of dopant atoms, we can avoid the unwanted Anderson localization. Moreover, since the dopant atoms do not constitute the chain, the overlap interaction between them is minimized, and the band structure modification can be made smallest. Some tight-binding results will be discussed to demonstrate the present idea.

Toshishige, Yamada; Kutler, Paul (Technical Monitor)

1997-01-01

173

Supply Chain Network Design Under Profit Maximization  

E-print Network

Chain Anna Nagurney Supply Chain Network Design Under Competition #12;Examples of Supply Chains food;Food Supply Chains Anna Nagurney Supply Chain Network Design Under Competition #12;High Tech ProductsSupply Chain Network Design Under Profit Maximization and Oligopolistic Competition Anna Nagurney

Nagurney, Anna

174

Ratio of A Chains to B Chains in Rice Amylopectins  

Microsoft Academic Search

Cereal Chem. 65(5):424-427 The ratio of A chains to B chains of rice amylopectins from two pairs of action of pullulanase on the \\/3-limit dextrin and from A and B chains by the near isogenic lines differing in the waxy gene was determined by the action combined action of \\/3-amylase and pullulanase. Waxy and nonwaxy (low- of pullulanase and of

BENT STIG ENEVOLDSEN

175

Age and metallicity gradients in fossil ellipticals  

NASA Astrophysics Data System (ADS)

Context. Fossil galaxy groups are speculated to be old and highly evolved systems of galaxies that formed early in the universe and had enough time to deplete their L? galaxies through successive mergers of member galaxies, building up one massive central elliptical, but retaining the group X-ray halo. Aims: Considering that fossils are the remnants of mergers in ordinary groups, the merger history of the progenitor group is expected to be imprinted in the fossil central galaxy (FCG). We present for the first time radial gradients of single-stellar population (SSP) ages and metallicites in a sample of FCGs to constrain their formation scenario. We also measure line-strength gradients for the strongest absorption features in these galaxies. Methods: We took deep spectra with the long-slit spectrograph ISIS at the William Herschel Telescope (WHT) for six FCGs. The obtained spectra are fit with Pegase HR SSP models within the full-spectrum fitting package ULySS yielding SSP ages and metallicities of the stellar populations. We measure radial gradients of SSP ages and metallicities along the major axes. Lick indices are measured for the strongest absorption features to determine line-strength gradients and compare with the full-spectrum fitting results. Results: Our sample comprises some of the most massive galaxies in the universe exhibiting an average central velocity dispersion of ?0 = 271 ± 28 km s-1. Metallicity gradients are throughout negative with comparatively flat slopes of ?[Fe/H] = -0.19 ± 0.08 while age gradients are found to be insignificant (?age = 0.00 ± 0.05). All FCGs lie on the fundamental plane, suggesting that they are virialised systems. We find that gradient strengths and central metallicities are similar to those found in cluster ellipticals of similar mass. Conclusions: The comparatively flat metallicity gradients with respect to those predicted by monolithic collapse (?Z = -0.5) suggest that fossils are indeed the result of multiple major mergers. Hence we conclude that fossils are not "failed groups" that formed with a top-heavy luminosity function. The low scatter of gradient slopes suggests a similar merging history for all galaxies in our sample. Figures 3 and 4 are available in electronic form at http://www.aanda.orgReduced spectra are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/553/A99

Eigenthaler, P.; Zeilinger, W. W.

2013-05-01

176

RECONSTITUTION OF 7S MOLECULES FROM L AND H POLYPEPTIDE CHAINS OF ANTIBODIES AND ?-GLOBULINS  

PubMed Central

Admixture of separated L and H polypeptide chains of 7S ?-globulins under appropriate conditions has been found to result in the reconstitution of 7S molecules. The chains were mixed in 0.5 N propionic acid and when dialyzed into neutral aqueous buffers interacted to form reconstituted material in greater than 30 per cent yield. This material had sedimentation coefficients of 6S to 7S, a weight average molecular weight of 160,000, and its antigenic structure and electrophoretic properties were the same as those of 7S ?-globulin. By the use of I131 and I125 labels on the different types of chains, combined with ultracentrifugation of chain mixtures in sucrose density gradients, the 7S product was found to contain both isotopes in ratios consistent with the presence of two L and two H chains. After hydrolysis with papain, the reconstituted material yielded products resembling S and F fragments. All of the isotope corresponding to L chains was found in the counterpart of the S fragment; the isotope corresponding to the H chain fraction was present in both fragments. The activity reconstituted from chains of a purified guinea pig antibody to f1 phage was found to be associated mainly with the 7S material. Hybrid molecules containing rabbit L chains and human H chains and of human L chains and rabbit H chains were formed by the same techniques of reconstitution. It was found that the interchain disulfide bonds of native 7S ?-globulins could be broken and reoxidized, as could those of reconstituted 7S material. Reduced L and H chains mixed in propionic acid, dialyzed against neutral buffers containing mercaptan, then against neutral buffers in the absence of mercaptan, formed stable 7S molecules of molecular weight 160,000, which were dissociable only after reduction. PMID:14157031

Olins, D. E.; Edelman, G. M.

1964-01-01

177

Polarisation effects in gradient nano-optics  

SciTech Connect

The spectra of reflection of s- and p-polarised waves from gradient nanocoatings at arbitrary angles of incidence are found within the framework of two exactly solvable models of such coatings. To use the detected spectra in the visible and IR ranges, for different frequencies and coating thicknesses we present the wave reflection coefficients as functions of dimensionless frequencies related to the refractive index gradient of the coating material. It is shown that reflection from the gradient coatings in question is an order of magnitude weaker than reflection from uniform coatings, other parameters of radiation and the reflection system being equal. We report a new exactly solvable model illustrating the specific effect of gradient film optics – the possibility of non-reflective propagation of an s-wave through such a film (an analogue of the Brewster effect). The prospects are shown for the use of gradient nanostructures with different refractive index profiles to fabricate broadband non-reflective coatings. (nanogradient dielectric coatings and metamaterials)

Erokhin, N S; Shvartsburg, A B [Space Research Institute, Russian Academy of Sciences, Moscow (Russian Federation); Zueva, Yu M [Wave Lab, LLC, CA 91436 (United States)

2013-09-30

178

Population Gradients in Stellar Halos from GHOSTS  

NASA Astrophysics Data System (ADS)

We report on recent results from the Galaxy Halos, Outer disks, Substructure, Thick disks, and Star clusters (GHOSTS) survey, an HST ACS+WFC3 imaging survey to study stellar populations in and around 16 nearby spiral galaxies. By using HST resolution to resolve the stellar halos into individual red giant branch (RGB) stars, we are able to detect distinct stellar populations at several points throughout the halo of the half dozen massive highly-inclined galaxies in the sample. In approximately half of these galaxies, we detect a gradient in the color of the RGB; which we interpret as a metallicity gradient. Stellar halo formation models predict a wide variety of metallicity gradients: those in which the halos are dominated by stars formed in situ predict stronger gradients than we observe, while accretion-dominated halo models predict weaker or nonexistent gradients. Our measurements therefore provide a useful discriminator between stellar halo models, and at first look appear most consistent with the accretion-based model of Cooper et al. (2010).

Bailin, Jeremy; Monachesi, Antonela; Bell, Eric F.; de Jong, Roelof S.; Ghosts Survey

2015-01-01

179

MECHANISM OF DNA CHAIN GROWTH, III. EQUAL ANNEALING OF T4 NASCENT SHORT DNA CHAINS WITH THE SEPARATED COMPLEMENTARY STRANDS OF THE PHAGE DNA*  

PubMed Central

Nascent short DNA chains isolated from T4-infected E. coli under a variety of conditions anneal equally to the separated complementary phage DNA strands. The samples examined include: pulse-labeled short chains isolated by alkaline sucrose gradient sedimentation from the T4D (wild type)-infected cells in both the early and late stages of phage DNA synthesis; nascent chains accumulated during ligase inhibition of T4 ts B20-infected cells; and the single-stranded nascent short chains isolated from T4D-infected cells by mild procedures involving no denaturation treatment. The results are consistent with the hypothesis that both strands of DNA are synthesized discontinuously. PMID:5260937

Sugimoto, Kazunori; Okazaki, Tuneko; Imae, Yasuo; Okazaki, Reiji

1969-01-01

180

Application of denaturing gradient gel electrophoresis (DGGE) and temperature gradient gel electrophoresis (TGGE) in microbial ecology  

Microsoft Academic Search

Here, the state of the art of the application of denaturing gradient gel electrophoresis (DGGE) and temperature gradient gel electrophoresis (TGGE) in microbial ecology will be presented. Furthermore, the potentials and limitations of these techniques will be discussed, and it will be indicated why their use in ecological studies has become so important. Abbreviations: ARDRA - amplified ribosomal DNA restriction

Gerard Muyzer; Kornelia Smalla

1998-01-01

181

Model of separation performance of bilinear gradients in scanning format counter-flow gradient electrofocusing techniques.  

PubMed

Counter-flow gradient electrofocusing allows the simultaneous concentration and separation of analytes by generating a gradient in the total velocity of each analyte that is the sum of its electrophoretic velocity and the bulk counter-flow velocity. In the scanning format, the bulk counter-flow velocity is varying with time so that a number of analytes with large differences in electrophoretic mobility can be sequentially focused and passed by a single detection point. Studies have shown that nonlinear (such as a bilinear) velocity gradients along the separation channel can improve both peak capacity and separation resolution simultaneously, which cannot be realized by using a single linear gradient. Developing an effective separation system based on the scanning counter-flow nonlinear gradient electrofocusing technique usually requires extensive experimental and numerical efforts, which can be reduced significantly with the help of analytical models for design optimization and guiding experimental studies. Therefore, this study focuses on developing an analytical model to evaluate the separation performance of scanning counter-flow bilinear gradient electrofocusing methods. In particular, this model allows a bilinear gradient and a scanning rate to be optimized for the desired separation performance. The results based on this model indicate that any bilinear gradient provides a higher separation resolution (up to 100%) compared to the linear case. This model is validated by numerical studies. PMID:25308774

Shameli, Seyed Mostafa; Glawdel, Tomasz; Ren, Carolyn L

2014-10-13

182

Temperature gradients, not food resource gradients, affect growth rate of migrating Daphnia mendotae in Lake Michigan  

E-print Network

Temperature gradients, not food resource gradients, affect growth rate of migrating Daphnia Michigan. In three laboratory experiments, juvenile Daphnia mendotae, native herbivorous cladocerans, were depended on water temperature, as Daphnia incubated at the epilimnetic temperature (21 °C) grew 42% faster

Peacor, Scott

183

Variable gradient permanent-magnet quadrupole lenses  

SciTech Connect

Rare earth (RE) permanent-magnet quadrupoles (PMQs) have been used for many applications in particle accelerators. They have the advantage over electromagnets of being lightweight and reliable. One difficulty associated with PMQs is that the quadrupole gradient is not easily adjusted. Over a certain range, the magnetization of RE magnets is a reversible function of temperature. We have developed a scheme to use this property to make variable gradient PMQs. The field gradient changes required for tuning are typically on the order of a few percent. For many RE magnets, this requires temperature changes of a few tens of degrees centigrade and is accomplished by actively heating or cooling the quadrupoles. 8 refs., 7 figs.

O'Shea, P.G.; Zaugg, T.J.; Maggs, R.G.; Schafstall, P.; Dyson, J.E.

1989-01-01

184

How receptor diffusion influences gradient sensing.  

PubMed

Chemotaxis, or directed motion in chemical gradients, is critical for various biological processes. Many eukaryotic cells perform spatial sensing, i.e. they detect gradients by comparing spatial differences in binding occupancy of chemosensory receptors across their membrane. In many theoretical models of spatial sensing, it is assumed, for the sake of simplicity, that the receptors concerned do not move. However, in reality, receptors undergo diverse modes of diffusion, and can traverse considerable distances in the time it takes such cells to turn in an external gradient. This sets a physical limit on the accuracy of spatial sensing, which we explore using a model in which receptors diffuse freely over the membrane. We find that the Fisher information carried in binding and unbinding events decreases monotonically with the diffusion constant of the receptors. PMID:25551145

Nguyen, H; Dayan, P; Goodhill, G J

2015-01-01

185

Substrate curvature gradient drives rapid droplet motion.  

PubMed

Making small liquid droplets move spontaneously on solid surfaces is a key challenge in lab-on-chip and heat exchanger technologies. Here, we report that a substrate curvature gradient can accelerate micro- and nanodroplets to high speeds on both hydrophilic and hydrophobic substrates. Experiments for microscale water droplets on tapered surfaces show a maximum speed of 0.42??m/s, 2 orders of magnitude higher than with a wettability gradient. We show that the total free energy and driving force exerted on a droplet are determined by the substrate curvature and substrate curvature gradient, respectively. Using molecular dynamics simulations, we predict nanoscale droplets moving spontaneously at over 100??m/s on tapered surfaces. PMID:25062213

Lv, Cunjing; Chen, Chao; Chuang, Yin-Chuan; Tseng, Fan-Gang; Yin, Yajun; Grey, Francois; Zheng, Quanshui

2014-07-11

186

A novel type of surface gradient coil  

NASA Astrophysics Data System (ADS)

A new surface gradient coil (SGC) consisting of three orthogonal channels and a planar form is described. This coil has been developed for high-resolution imaging which generally requires strong gradient fields. The SGC we have developed can produce strong gradient fields with good linearity within a limited imaging region. To increase the signal-to-noise ratio, we have developed and experimentally examined an integrated surface RF coil-SGC set. In this paper, the geometrical structures and characteristics of the proposed SGC are discussed, and some experimental results obtained by use of the coil set are presented. High-resolution images (50 to 100 ?m) of a water-filled phantom and a volunteer's knee obtained by using the new integrated surface RF coil-SGC set and the KRIS 2.0 T whole-body MRI system are studied and the results are presented.

Cho, Z. H.; Yi, J. H.

187

Using Spatial Gradients to Model Localization Phenomena  

SciTech Connect

We present the final report on a Laboratory-Directed Research and Development project, Using Spatial Gradients to Model Localization Phenomena, performed during the fiscal years 1996 through 1998. The project focused on including spatial gradients in the temporal evolution equations of the state variables that describe hardening in metal plasticity models. The motivation was to investigate the numerical aspects associated with post-bifurcation mesh dependent finite element solutions in problems involving damage or crack propagation as well as problems in which strain Localizations occur. The addition of the spatial gradients introduces a mathematical length scale that eliminates the mesh dependency of the solution. In addition, new experimental techniques were developed to identify the physical mechanism associated with the numerical length scale.

D.J.Bammann; D.Mosher; D.A.Hughes; N.R.Moody; P.R.Dawson

1999-07-01

188

Statistical Methods in Markov Chains  

Microsoft Academic Search

This paper is an expository survey of the mathematical aspects of statistical inference as it applies to finite Markov chains, the problem being to draw inferences about the transition probabilities from one long, unbroken observation $\\\\{x_1, x_2, \\\\cdots, x_n\\\\}$ on the chain. The topics covered include Whittle's formula, chi-square and maximum-likelihood methods, estimation of parameters, and multiple Markov chains. At

Patrick Billingsley

1961-01-01

189

Secure Supply-Chain Protocols  

Microsoft Academic Search

Supply chain interactions have huge economic impor- tance, yet these interactions are managed inefficiently. One of the major sources of inefficiency in supply-chain man- agement is information asymmetry; i.e., information that is available to one or more organizations in the chain (e.g., manufacturer, retailer) is not available to others. There are several causes of information asymmetry, among them fear that

Mikhail J. Atallah; Hicham G. Elmongui; Vinayak Deshpande; Leroy B. Schwarz

2003-01-01

190

Stereo transparency and the disparity gradient limit  

NASA Technical Reports Server (NTRS)

Several studies (Vision Research 15 (1975) 583; Perception 9 (1980) 671) have shown that binocular fusion is limited by the disparity gradient (disparity/distance) separating image points, rather than by their absolute disparity values. Points separated by a gradient >1 appear diplopic. These results are sometimes interpreted as a constraint on human stereo matching, rather than a constraint on fusion. Here we have used psychophysical measurements on stereo transparency to show that human stereo matching is not constrained by a gradient of 1. We created transparent surfaces composed of many pairs of dots, in which each member of a pair was assigned a disparity equal and opposite to the disparity of the other member. For example, each pair could be composed of one dot with a crossed disparity of 6' and the other with uncrossed disparity of 6', vertically separated by a parametrically varied distance. When the vertical separation between the paired dots was small, the disparity gradient for each pair was very steep. Nevertheless, these opponent-disparity dot pairs produced a striking appearance of two transparent surfaces for disparity gradients ranging between 0.5 and 3. The apparent depth separating the two transparent planes was correctly matched to an equivalent disparity defined by two opaque surfaces. A test target presented between the two transparent planes was easily detected, indicating robust segregation of the disparities associated with the paired dots into two transparent surfaces with few mismatches in the target plane. Our simulations using the Tsai-Victor model show that the response profiles produced by scaled disparity-energy mechanisms can account for many of our results on the transparency generated by steep gradients.

McKee, Suzanne P.; Verghese, Preeti

2002-01-01

191

A Method for Calibrating Diffusion Gradients in Diffusion Tensor Imaging  

PubMed Central

Objective To calibrate and correct the gradient errors including gradient amplitude scaling errors, background/imaging gradients, and residual gradients in diffusion tensor imaging (DTI). Methods A calibration protocol using an isotropic phantom was proposed. Gradient errors were estimated by using linear regression analyses on quadratic functions of diffusion gradients along 3 orthogonal directions. A 6-element total effective scaling vector is generated from the calibration protocol to retrospectively correct gradient errors in DTI experiments. Results The accuracy of the calibration protocol was within 1% or less in estimating gradient scaling errors. On both the brain study and the computer simulations, the retrospective correction minimized undesirable estimate biases of DTI measurements due to gradient errors. Conclusion The protocol and retrospective correction are shown to be effective. The method may be used for prospective correction if actual diffusion-gradient waveforms are available. The methodology is expandable to general diffusion imaging schemes. PMID:18043367

Wu, Yu-Chien; Alexander, Andrew L.

2009-01-01

192

Supply Chain Coordination in Hospitals  

NASA Astrophysics Data System (ADS)

This paper presents an innovative approach to support the definition of strategies for the design of alternative configurations of hospital supply chains. This approach was developed around a hybrid Tabu Search / Variable Neighbourhood Search metaheuristic, that uses several neighbourhood structures. The flexibility of the procedure allows its application to supply chains with different topologies and atypical cost characteristics. A preliminary computational experience shows the approach potential in solving large scale supply chain configuration problems. The future incorporation of this approach in a broader Decision Support System (DSS) will provide a tool that can significantly contribute to an increase of healthcare supply chains efficiency and encourage the establishment of collaborative partnerships between their members.

Rego, Nazaré; de Sousa, Jorge Pinho

193

Integrating the healthcare supply chain.  

PubMed

Today's integrated delivery systems (IDSs) require efficient supply chain processes to speed products to users at the lowest possible cost. Most excess costs within the supply chain are a result of inefficient and redundant processes involved in the transport and delivery of supplies from suppliers to healthcare providers. By integrating and assuming control of these supply chain processes, improving supply chain management practices, and organizing and implementing a disciplined redesign plan, IDSs can achieve substantial savings and better focus their organizations on their core patient care mission. PMID:10175103

Brennan, C D

1998-01-01

194

Chains with Fractal Dispersion Law  

E-print Network

Chains with long-range interactions are considered. The interactions are defined such that each nth particle interacts only with chain particles with the numbers n+a(m) and n-a(m), where m=1,2,3,... and a(m) is an integer-valued function. Exponential type functions a(m)=b^m, where b=2,3,.., are discussed. The correspondent pseudodifferential equations of chain oscillations are obtained. Dispersion laws of the suggested chains are described by the Weierstrass and Weierstrass-Mandelbrot functions.

Vasily E. Tarasov

2008-04-03

195

Gravity gradient determination with tethered systems  

NASA Technical Reports Server (NTRS)

A detailed investigation of the Earth's gravity field is needed for application to modern solid earth and oceanic investigations. The use of gravity gradiometers presents a technique to measure the intermediate wavelength components of the gravity field. One configuration of a gradiometer involves a tethered pair of masses orbiting the Earth and stabilized by vertical gravity gradient of the earth. A mesurement of the tension in such a system, called the DUMBBELL system is described. It allows the determination of the vertical gradient of the anomalous component of the Earth's gravtiy field. Preliminary analysis of the dynamics, mechanization, expected signal levels and noise environment indicates that the Dumbbell system is feasible.

Kalaghan, P. M.; Colombo, G.

1978-01-01

196

Short wavelength ion temperature gradient turbulence  

SciTech Connect

The ion temperature gradient (ITG) mode in the high wavenumber regime (k{sub y}{rho}{sub s}>1), referred to as short wavelength ion temperature gradient mode (SWITG) is studied using the nonlinear gyrokinetic electromagnetic code GENE. It is shown that, although the SWITG mode may be linearly more unstable than the standard long wavelength (k{sub y}{rho}{sub s}<1) ITG mode, nonlinearly its contribution to the total thermal ion heat transport is found to be low. We interpret this as resulting from an increased zonal flow shearing effect on the SWITG mode suppression.

Chowdhury, J.; Ganesh, R. [Institute for Plasma Research, Bhat, Gandhinagar (India); Brunner, S.; Lapillonne, X.; Villard, L. [CRPP, Association EURATOM-Confederation Suisse, EPFL, 1015 Lausanne (Switzerland); Jenko, F. [Max-Planck-Institut fuer Plasmaphysik Boltzmannstr. 2, D-85748 Garching (Germany)

2012-10-15

197

Fragment molecular orbital method: analytical energy gradients  

NASA Astrophysics Data System (ADS)

The fragment molecular orbital (FMO) method, which aimed to calculate large molecules such as proteins, was proposed in a previous work. The method divides a molecule into small fragments and performs MO calculations on the fragments and the fragment pairs to obtain the total energy of molecule. The method with the analytical energy gradient at the HF level of theory has been incorporated into the G AUSSIAN 94 (G94) package. Geometry optimization calculations using the energy gradients were successfully performed on a model peptide, methyl-capped glycine trimer.

Kitaura, Kazuo; Sugiki, Sin-Ichirou; Nakano, Tatsuya; Komeiji, Yuto; Uebayasi, Masami

2001-03-01

198

The effect of density gradients on hydrometers  

NASA Astrophysics Data System (ADS)

Hydrometers are simple but effective instruments for measuring the density of liquids. In this work, we studied the effect of non-uniform density of liquid on a hydrometer reading. The effect induced by vertical temperature gradients was investigated theoretically and experimentally. A method for compensating for the effect mathematically was developed and tested with experimental data obtained with the MIKES hydrometer calibration system. In the tests, the method was found reliable. However, the reliability depends on the available information on the hydrometer dimensions and density gradients.

Heinonen, Martti; Sillanpää, Sampo

2003-05-01

199

Relativistic klystron research for high gradient accelerators  

SciTech Connect

Relativistic klystrons are being developed as a power source for high gradient accelerator applications which include large linear electron--positron colliders, compact accelerators, and FEL sources. We have attained 200MW peak power at 11.4 GHz from a relativistic klystron, and 140 MV/m longitudinal gradient in a short 11.4 GHz accelerator section. We report here on the design of our first klystrons, the results of our experiments so far, and some of our plans for the near future. 5 refs., 7 figs.

Allen, M.A.; Callin, R.S.; Deruyter, H.; Eppley, K.R.; Fowkes, W.R.; Herrmannsfeldt, W.B.; Higo, T.; Hoag, H.A.; Lavine, T.L.; Lee, T.G.

1988-06-01

200

Gradient Learning Algorithms for Ontology Computing  

PubMed Central

The gradient learning model has been raising great attention in view of its promising perspectives for applications in statistics, data dimensionality reducing, and other specific fields. In this paper, we raise a new gradient learning model for ontology similarity measuring and ontology mapping in multidividing setting. The sample error in this setting is given by virtue of the hypothesis space and the trick of ontology dividing operator. Finally, two experiments presented on plant and humanoid robotics field verify the efficiency of the new computation model for ontology similarity measure and ontology mapping applications in multidividing setting. PMID:25530752

Gao, Wei; Zhu, Linli

2014-01-01

201

High-pressure liquid chromatographic gradient mixer  

DOEpatents

A gradient mixer effects the continuous mixing of any two miscible solvents without excessive decay or dispersion of the resultant isocratic effluent or of a linear or exponential gradient. The two solvents are fed under low or high pressure by means of two high performance liquid chromatographic pumps. The mixer comprises a series of ultra-low dead volume stainless steel tubes and low dead volume chambers. The two solvent streams impinge head-on at high fluxes. This initial nonhomogeneous mixture is then passed through a chamber packed with spirally-wound wires which cause turbulent mixing thereby homogenizing the mixture with minimum band-broadening.

Daughton, C.G.; Sakaji, R.H.

1982-09-08

202

NNSA TRITIUM SUPPLY CHAIN  

SciTech Connect

Savannah River Site plays a critical role in the Tritium Production Supply Chain for the National Nuclear Security Administration (NNSA). The entire process includes: • Production of Tritium Producing Burnable Absorber Rods (TPBARs) at the Westinghouse WesDyne Nuclear Fuels Plant in Columbia, South Carolina • Production of unobligated Low Enriched Uranium (LEU) at the United States Enrichment Corporation (USEC) in Portsmouth, Ohio • Irradiation of TPBARs with the LEU at the Tennessee Valley Authority (TVA) Watts Bar Reactor • Extraction of tritium from the irradiated TPBARs at the Tritium Extraction Facility (TEF) at Savannah River Site • Processing the tritium at the Savannah River Site, which includes removal of nonhydrogen species and separation of the hydrogen isotopes of protium, deuterium and tritium.

Wyrick, Steven [Savannah River National Laboratory, Aiken, SC, USA; Cordaro, Joseph [Savannah River National Laboratory, Aiken, SC, USA; Founds, Nanette [National Nuclear Security Administration, Albuquerque, NM, USA; Chambellan, Curtis [National Nuclear Security Administration, Albuquerque, NM, USA

2013-08-21

203

Policy Gradient SMDP for Resource Allocation and Routing in Integrated Services Networks  

NASA Astrophysics Data System (ADS)

In this paper, we solve the call admission control (CAC) and routing problem in an integrated network that handles several classes of calls of different values and with different resource requirements. The problem of maximizing the average reward (or cost) of admitted calls per unit time is naturally formulated as a semi-Markov Decision Process (SMDP) problem, but is too complex to allow for an exact solution. Thus in this paper, a policy gradient algorithm, together with a decomposition approach, is proposed to find the dynamic (state-dependent) optimal CAC and routing policy among a parameterized policy space. To implement that gradient algorithm, we approximate the gradient of the average reward. Then, we present a simulation-based algorithm to estimate the approximate gradient of the average reward (called GSMDP algorithm), using only a single sample path of the underlying Markov chain for the SMDP of CAC and routing problem. The algorithm enhances performance in terms of convergence speed, rejection probability, robustness to the changing arrival statistics and an overall received average revenue. The experimental simulations will compare our method's performance with other existing methods and show the robustness of our method.

Vien, Ngo Anh; Viet, Nguyen Hoang; Lee, Seunggwan; Chung, Taechoong

204

Electrochemical fabrication of surface chemical gradients in thiol self-assembled monolayers with tailored work-functions.  

PubMed

The studies on surface chemical gradients are constantly gaining interest both for fundamental studies and for technological implications in materials science, nanofluidics, dewetting, and biological systems. Here we report on a new approach that is very simple and very efficient, to fabricate surface chemical gradients of alkanethiols, which combines electrochemical desorption/partial readsorption, with the withdrawal of the surface from the solution. The gradient is then stabilized by adding a complementary thiol terminated with a hydroxyl group with a chain length comparable to desorbed thiols. This procedure allows us to fabricate a chemical gradient of the wetting properties and the substrate work-function along a few centimeters with a gradient slope higher than 5°/cm. Samples were characterized by cyclic voltammetry during desorption, static contact angle, XPS analysis, and Kelvin probe. Computer simulations based on the Dissipative Particle Dynamics methods were carried out considering a water droplet on a mixed SAM surface. The results help to rationalize the composition of the chemical gradient at different position on the Au surface. PMID:25222857

Fioravanti, Giulia; Lugli, Francesca; Gentili, Denis; Mucciante, Vittoria; Leonardi, Francesca; Pasquali, Luca; Liscio, Andrea; Murgia, Mauro; Zerbetto, Francesco; Cavallini, Massimiliano

2014-10-01

205

Markov Chain Monte Carlo Methods Markov Chain Monte Carlo Methods  

E-print Network

Markov Chain Monte Carlo Methods Markov Chain Monte Carlo Methods Christian P. Robert Universit Monte Carlo Methods Textbook: Monte Carlo Statistical Methods by Christian. P. Robert and George Casella Monte Carlo Methods with R by Christian. P. Robert and George Casella [trad. fran¸caise 2010; japonaise

Robert, Christian P.

206

Chain Dynamics in Magnetorheological Suspensions  

NASA Technical Reports Server (NTRS)

Magnetorheological (MR) suspensions are composed of colloidal particles which acquire dipole moments when subjected to an external magnetic field. At sufficient field strengths and concentrations, the dipolar particles rapidly aggregate to form long chains. Subsequent lateral cross-linking of the dipolar chains is responsible for a rapid liquid-to-solid-like rheological transition. The unique, magnetically-activated rheological properties of MR suspensions make them ideal for interfacing mechanical systems to electronic controls. Additionally, the ability to experimentally probe colloidal suspensions interacting through tunable anisotropic potentials is of fundamental interest. Our current experimental work has focused on understanding the fluctuations of dipolar chains. It has been proposed by Halsey and Toor (HT) that the strong Landau-Peierls thermal fluctuations of dipolar chains could be responsible for long-range attractions between chains. Such interactions will govern the long-time relaxation of MR suspensions. We have synthesized monodisperse neutrally buoyant MR suspensions by density matching stabilized ferrofluid emulsion droplets with D2O. This allows us to probe the dynamics of the dipolar chains using light scattering without gravitational, interfacial, and polydispersity effects to resolve the short-wavelength dynamics of the dipolar chains. We used diffusing wave spectroscopy to measure these dynamics. The particle displacements at short times that show an independence to the field strength, but at long times exhibit a constrained, sub-diffusive motion that slows as the dipole strength is increased. The experiments are in good qualitative agreement with Brownian dynamics simulations of dipolar chains. Although there have been several important and detailed studies of the structure and interactions in MR suspensions, there has not been conclusive evidence that supports or contradicts the HT model prediction that long-range interactions exist between fluctuating chains of dipolar particles. Resolving this issue would contribute greatly to the understanding of these interesting and important materials. We have begun to test the predictions of the HT model by both examining the dynamics of individual chains and by measuring the forces between dipolar chains directly to accurately and quantitatively assess the interactions that they experience. To do so, we employ optical trapping techniques and video-microscopy to manipulate and observe our samples on the microscopic level. With these techniques, it is possible to observe chains that are fluctuating freely in three-dimensions, independent of interfacial effects. More importantly, we are able to controllably observe the interactions of two chains at various separations to measure the force-distance profile. The techniques also allow us to study the mechanical properties of individual chains and chain clusters. Our work to this point has focused on reversibly-formed dipolar chains due to field induced dipoles where the combination of this chaining, the dipolar forces, and the hydrodynamic interactions that dictate the rheology of the suspensions. One can envision, however, many situations where optical, electronic, or rheological behavior may be optimized with magneto-responsive anisotropic particles. Chains of polarizable particles may have the best properties as they can coil and flex in the absence of a field and stiffen and orient when a field is applied. We have recently demonstrated a synthesis of stable, permanent paramagnetic chains by both covalently and physically linking paramagnetic colloidal particles. The method employed allows us to create monodisperse chains of controlled length. We observed the stability, field-alignment, and rigidity of this new class of materials. The chains may exhibit unique rheological properties in an applied magnetic field over isotropic suspensions of paramagnetic particles. They are also useful rheological models as bead-spring systems. These chains form the basis for our current experiments with optical traps.

Gast, A. P.; Furst, E. M.

1999-01-01

207

Axonal Gradient of Arachidonic Acid-containing Phosphatidylcholine and Its Dependence on Actin Dynamics*  

PubMed Central

Phosphatidylcholine (PC) is the most abundant component of lipid bilayers and exists in various molecular forms, through combinations of two acylated fatty acids. Arachidonic acid (AA)-containing PC (AA-PC) can be a source of AA, which is a crucial mediator of synaptic transmission and intracellular signaling. However, the distribution of AA-PC within neurons has not been indicated. In the present study, we used imaging mass spectrometry to characterize the distribution of PC species in cultured neurons of superior cervical ganglia. Intriguingly, PC species exhibited a unique distribution that was dependent on the acyl chains at the sn-2 position. In particular, we found that AA-PC is enriched within the axon and is distributed across a proximal-to-distal gradient. Inhibitors of actin dynamics (cytochalasin D and phallacidin) disrupted this gradient. This is the first report of the gradual distribution of AA-PC along the axon and its association with actin dynamics. PMID:22207757

Yang, Hyun-Jeong; Sugiura, Yuki; Ikegami, Koji; Konishi, Yoshiyuki; Setou, Mitsutoshi

2012-01-01

208

Association with BiP and aggregation of class II MHC molecules synthesized in the absence of invariant chain.  

PubMed Central

Class II molecules of the major histocompatibility complex (MHC) are composed of two polymorphic glycoprotein chains (alpha and beta), that associate in the ER with a third, non-polymorphic glycoprotein known as the invariant chain (Ii). We have examined the relationship between the intracellular transport and physico-chemical characteristics of various combinations of murine alpha, beta and Ii chains. Biochemical and morphological analyses of transfected fibroblasts expressing class II MHC chains show that both unassembled alpha and beta chains, as well as a large fraction of alpha+beta complexes synthesized in the absence of Ii chain, are retained in the ER in association with the immunoglobulin heavy chain binding protein, BiP. Analyses by sedimentation velocity on sucrose gradients show that most incompletely assembled class II MHC species exist as high molecular weight aggregates in both transfected fibroblasts and spleen cells from mice carrying a disruption of the Ii chain gene. This is in contrast to the sedimentation properties of alpha beta Ii complexes from normal mice, which migrate as discrete, stoichiometric complexes of M(r) approximately 200,000-300,000. These observations suggest that assembly with the Ii chain prevents accumulation of aggregated alpha and beta chains in the ER, which might relate to the known ability of the Ii chain to promote exit of class II MHC molecules from the ER. Images PMID:8112308

Bonnerot, C; Marks, M S; Cosson, P; Robertson, E J; Bikoff, E K; Germain, R N; Bonifacino, J S

1994-01-01

209

Cardiolipin biosynthesis and mitochondrial respiratory chain function are interdependent.  

PubMed

Cardiolipin (CL) is an acidic phospholipid present almost exclusively in membranes harboring respiratory chain complexes. We have previously shown that, in Saccharomyces cerevisiae, CL provides stability to respiratory chain supercomplexes and CL synthase enzyme activity is reduced in several respiratory complex assembly mutants. In the current study, we investigated the interdependence of the mitochondrial respiratory chain and CL biosynthesis. Pulse-labeling experiments showed that in vivo CL biosynthesis was reduced in respiratory complexes III (ubiquinol:cytochrome c oxidoreductase) and IV (cytochrome c oxidase) and oxidative phosphorylation complex V (ATP synthase) assembly mutants. CL synthesis was decreased in the presence of CCCP, an inhibitor of oxidative phosphorylation that reduces the pH gradient but not by valinomycin or oligomycin, both of which reduce the membrane potential and inhibit ATP synthase, respectively. The inhibitors had no effect on phosphatidylglycerol biosynthesis or CRD1 gene expression. These results are consistent with the hypothesis that in vivo CL biosynthesis is regulated at the level of CL synthase activity by the DeltapH component of the proton-motive force generated by the functional electron transport chain. This is the first report of regulation of phospholipid biosynthesis by alteration of subcellular compartment pH. PMID:15292198

Gohil, Vishal M; Hayes, Paulette; Matsuyama, Shigemi; Schägger, Hermann; Schlame, Michael; Greenberg, Miriam L

2004-10-01

210

Conjugate Directions for Stochastic Gradient Descent ?  

E-print Network

of Computational Science ETH Zurich, Switzerland fschraudo,graepelg@inf.ethz.ch Abstract. The method of conjugate Stochastic Quadratic Optimization Deterministic bowl. The d-dimensional quadratic bowl provides us, nonlinear problems. The gradient here is #22; g = rf(w) = #22; H(w w #3; ). Stochastic bowl. The stochastic

Schraudolph, Nicol N.

211

Fourier accelerated conjugate gradient lattice gauge fixing  

NASA Astrophysics Data System (ADS)

We provide details of the first implementation of a non-linear conjugate gradient method for Landau and Coulomb gauge fixing with Fourier acceleration. We find clear improvement over the Fourier accelerated steepest descent method, with the average time taken for the algorithm to converge to a fixed, high accuracy, being reduced by a factor of 2 to 4.

Hudspith, R. J.

2015-02-01

212

Fourier Accelerated Conjugate Gradient Lattice Gauge Fixing  

E-print Network

We provide details of the first implementation of a non-linear conjugate gradient method for Landau and Coulomb gauge fixing with Fourier acceleration. We find clear improvement over the Fourier accelerated steepest descent method, with the average time taken for the algorithm to converge to a fixed, high accuracy, being reduced by a factor of 2 to 4.

R. J. Hudspith

2014-05-22

213

Multi-gradient drilling method and system  

DOEpatents

A multi-gradient system for drilling a well bore from a surface location into a seabed includes an injector for injecting buoyant substantially incompressible articles into a column of drilling fluid associated with the well bore. Preferably, the substantially incompressible articles comprises hollow substantially spherical bodies.

Maurer, William C. (Houston, TX); Medley, Jr., George H. (Spring, TX); McDonald, William J. (Houston, TX)

2003-01-01

214

Gradient matrices for output feedback systems  

Microsoft Academic Search

Gradient matrices are formulated for the linear multivariable system with output feedback. The incremental motion of the poles and zeros and the coefficients of the numerator and denominator transfer function polynomials is determined as a function of the elements of an output feedback gain matrix. Also considered is the incremental movement of zeros and the coefficients of the numerator transfer

LOUIS F. GODBOUTJ; DAVID JORDAN

1980-01-01

215

The effect of density gradients on hydrometers  

Microsoft Academic Search

Hydrometers are simple but effective instruments for measuring the density of liquids. In this work, we studied the effect of non-uniform density of liquid on a hydrometer reading. The effect induced by vertical temperature gradients was investigated theoretically and experimentally. A method for compensating for the effect mathematically was developed and tested with experimental data obtained with the MIKES hydrometer

Martti Heinonen; Sampo Sillanpää

2003-01-01

216

Restart procedures for the conjugate gradient method  

Microsoft Academic Search

The conjugate gradient method is particularly useful for minimizing functions of very many variables because it does not require the storage of any matrices. However the rate of convergence of the algorithm is only linear unless the iterative procedure is “restarted” occasionally. At present it is usual to restart everyn or (n + 1) iterations, wheren is the number of

M. J. D. Powell

1977-01-01

217

Stability of Morphogen Gradients & Movement of Molecules  

NSDL National Science Digital Library

A 23 minute QuickTime movie of Nobel Laureate Eric Wieschaus lecture describing the processes that help a fruit fly embryo create morphogen gradients required for normal development. This second part looks at quantitation of maternal protein bicoid and the genes that respond to it. Related lectures cover pattern formation and evolution of patterning.

iBioSeminars (American Society for Cell Biology)

2009-02-05

218

Histograms of Oriented Gradients for Human Detection  

Microsoft Academic Search

We study the question of feature sets for robust visual ob- ject recognition, adopting linear SVM based human detec- tion as a test case. After reviewing existing edge and gra- dient based descriptors, we show experimentally that grids of Histograms of Oriented Gradient (HOG) descriptors sig- nicantly outperform existing feature sets for human detec- tion. We study the inuence of

Navneet Dalal; Bill Triggs

2005-01-01

219

Density Gradient Columns for Chemical Displays.  

ERIC Educational Resources Information Center

Procedures for preparing density gradient columns for chemical displays are presented. They include displays illustrating acid-base reactions, metal ion equilibria, and liquid density. The lifetime of these metastable displays is surprising, some lasting for months in display cabinets. (JN)

Guenther, William B.

1986-01-01

220

Calibration curves for density-gradient columns  

Microsoft Academic Search

Theoretical calibration curves for density-gradient columns at various stages of their development are derived on the assumption that the behaviour is controlled by a Fick's law diffusion. Curves are given for two sets of initial conditions, corresponding to those most commonly used in practice.

D W Budworth

1962-01-01

221

Optimizing the readout of morphogen gradients  

NASA Astrophysics Data System (ADS)

In multicellular organisms, the initial patterns of gene expression are regulated by spatial gradients of biochemical factors, known as morphogen gradients. Because of biochemical noise in the morphogen gradients there are associated spatial errors in the positions of target gene patterns. Using a simple single morphogen and/or single target gene model, we use propagation of error analysis to derive a condition on the amount of morphogen that needs to be produced in order to have precise spatial patterning of the target. We find that there is an optimal morphogen gradient profile that requires the least amount of morphogen to be produced. Experimental results for the Bicoid-Hunchback system in early Drosophila development are consistent with the predictions of this analysis. We also discuss our results in the context of recent work that analyzed this system using mutual information as an organizing principle, and show that minimizing the amount of morphogen produced also leads to a near optimal flow of information between input and target.

Emberly, Eldon

2008-04-01

222

USING SIMPLEX GRADIENTS OF NONSMOOTH FUNCTIONS IN ...  

E-print Network

Our analysis does not require continuous differentiability and can be seen as an ... lation or regression models, which, in turn, are used in derivative-free trust region ... in a sufficient decrease type condition to detect stagnation, and the simplex gradient ... Support for this author was provided by Centro de Matemática da Uni-.

2006-10-26

223

Gradient method for autonomous robot navigation  

Microsoft Academic Search

The analysis of global and local navigation methods for an autonomous mobile robot allowed to select the main lacks of existent methods of navigation. The improved local navigation method based on the use of potential fields for movement taking into account the gradient of direction to the goal is proposed.

Oleh Adamiv; Anatoly Sachenko; Viktor Kapura

2008-01-01

224

Gradient-index lenses as flux concentrators  

NASA Astrophysics Data System (ADS)

While gradient-index lenses are usually analyzed in terms of image fidelity, they are also capable of high flux concentration. In the first part of this presentation, the simplest class of gradient-index problems is revisited. An alterative way to obtain established solution of the refractive index profiles that produce perfect imaging is derived form the method of Fermat's strings and skewness conservation. The degree to which difference classes of such spherical lenses can realize the thermodynamic limit to flux concentration is explored. An answer is also sought to the intriguing question of the extent to which the spherical gradient-index lens of the fish eye is a modified Luneburg lens optimized subject to material constraints. The second half of this presentation addresses gradient-index rod lense. Both analytic methods and computer raytrace simulations are used for a comprehensive evaluation of their concentration and collection efficiency. They appear to be well suited as concentrators for the distal end of laser fiber-optic surgical units.

Gordon, Jeffrey M.

2001-11-01

225

High-gradient continuous-casting furnace  

NASA Technical Reports Server (NTRS)

High gradient allows rapid growth rates in directionally-solidified eutectic alloys. Furnace design permits cost reductions in directional solidification process through its increased solidification rates, which reduces melt/mold interaction. It produces structural engineering materials for any application requiring properties directionally-solidified eutectic materials.

Scheuermann, C. M.; Flemings, M. C.; Neff, M. A.; Rickinson, B. A.; Young, K. P.

1979-01-01

226

USING INEXACT GRADIENTS IN A MULTILEVEL OPTIMIZATION ...  

E-print Network

model is a shifted version of the coarse model that is defined using the value of the gradient on the fine ... analysis of the properties of the models and the behavior of the algorithm. ...... We must first solve the boundary value problem (

2012-04-25

227

Wingless gradient formation in the Drosophila wing  

Microsoft Academic Search

Background: Secreted signaling proteins of the Wingless (Wg)\\/Wnt, Hedgehog and bone morphogenetic protein (BMP)\\/Decapentaplegic (Dpp) families function as morphogens to control growth and pattern formation during development. Although these proteins have been shown to act directly on distant cells in the developing limbs of the fruit fly Drosophila, little is known about how ligand gradients form in vivo. Wg protein

Maura Strigini; Stephen M. Cohen

2000-01-01

228

Escalation of polymerization in a thermal gradient  

PubMed Central

For the emergence of early life, the formation of biopolymers such as RNA is essential. However, the addition of nucleotide monomers to existing oligonucleotides requires millimolar concentrations. Even in such optimistic settings, no polymerization of RNA longer than about 20 bases could be demonstrated. How then could self-replicating ribozymes appear, for which recent experiments suggest a minimal length of 200 nt? Here, we demonstrate a mechanism to bridge this gap: the escalated polymerization of nucleotides by a spatially confined thermal gradient. The gradient accumulates monomers by thermophoresis and convection while retaining longer polymers exponentially better. Polymerization and accumulation become mutually self-enhancing and result in a hyperexponential escalation of polymer length. We describe this escalation theoretically under the conservative assumption of reversible polymerization. Taking into account the separately measured thermophoretic properties of RNA, we extrapolate the results for primordial RNA polymerization inside a temperature gradient in pores or fissures of rocks. With a dilute, nanomolar concentration of monomers the model predicts that a pore length of 5 cm and a temperature difference of 10 K suffice to polymerize 200-mers of RNA in micromolar concentrations. The probability to generate these long RNAs is raised by a factor of >10600 compared with polymerization in a physical equilibrium. We experimentally validate the theory with the reversible polymerization of DNA blocks in a laser-driven thermal trap. The results confirm that a thermal gradient can significantly enlarge the available sequence space for the emergence of catalytically active polymers. PMID:23630280

Mast, Christof B.; Schink, Severin; Gerland, Ulrich; Braun, Dieter

2013-01-01

229

Moving Forward: Mechanisms of Chemoattractant Gradient Sensing  

NSDL National Science Digital Library

Cells use an internal compass to sense the direction of chemoattractant gradients. This is used to bias pseudopod extension at the front of the cell and to orient cell polarization. Recent studies have highlighted the important roles played by phosphoinositide-3,4,5-triphosphate and small G proteins, but many questions remain.

PhD Jonathan Franca-Koh (Johns Hopkins University School of Medicine Department of Cell Biology)

2004-10-01

230

Subspace learning from image gradient orientations.  

PubMed

We introduce the notion of subspace learning from image gradient orientations for appearance-based object recognition. As image data are typically noisy and noise is substantially different from Gaussian, traditional subspace learning from pixel intensities very often fails to estimate reliably the low-dimensional subspace of a given data population. We show that replacing pixel intensities with gradient orientations and the ?? norm with a cosine-based distance measure offers, to some extend, a remedy to this problem. Within this framework, which we coin Image Gradient Orientations (IGO) subspace learning, we first formulate and study the properties of Principal Component Analysis of image gradient orientations (IGO-PCA). We then show its connection to previously proposed robust PCA techniques both theoretically and experimentally. Finally, we derive a number of other popular subspace learning techniques, namely, Linear Discriminant Analysis (LDA), Locally Linear Embedding (LLE), and Laplacian Eigenmaps (LE). Experimental results show that our algorithms significantly outperform popular methods such as Gabor features and Local Binary Patterns and achieve state-of-the-art performance for difficult problems such as illumination and occlusion-robust face recognition. In addition to this, the proposed IGO-methods require the eigendecomposition of simple covariance matrices and are as computationally efficient as their corresponding ?? norm intensity-based counterparts. Matlab code for the methods presented in this paper can be found at http://ibug.doc.ic.ac.uk/resources. PMID:22271825

Tzimiropoulos, Georgios; Zafeiriou, Stefanos; Pantic, Maja

2012-12-01

231

Snakes, shapes, and gradient vector flow  

Microsoft Academic Search

Snakes, or active contours, are used extensively in computer vision and image processing applications, particularly to locate object boundaries. Problems associated with initializa- tion and poor convergence to boundary concavities, however, have limited their utility. This paper presents a new external force for active contours, largely solving both problems. This external force, which we call gradient vector flow (GVF), is

Chenyang Xu; Jerry L. Prince

1998-01-01

232

Practical Markov Chain Monte Carlo  

Microsoft Academic Search

Markov chain Monte Carlo using the Metropolis-Hastings algorithm is a general method for the simulation of stochastic processes having probability densities known up to a constant of proportionality. Despite recent advances in its theory, the practice has remained controversial. This article makes the case for basing all inference on one long run of the Markov chain and estimating the Monte

Charles J. Geyer

1992-01-01

233

Acoustic Chains in Acousmatic Music  

Microsoft Academic Search

The notion of 'acoustic chains' will be posited. It will be argued that 'acoustic chains' link certain acousmatic works at what Denis Smalley terms the 'indicative listening mode' through their common 'affordances' - a term originally used by James Gibson to interpret visual culture and adapted by Luke Windsor to acousmatic music. It will be contended that the listener to

Mathew Adkins

234

Issues in Supply Chain Management  

Microsoft Academic Search

Successful supply chain management requires cross-functional integration and marketing must play a critical role. The challenge is to determine how to successfully accomplish this integration. We present a framework for supply chain management as well as questions for how it might be implemented and questions for future research. Case studies conducted at several companies and involving multiple members of supply

Douglas M Lambert; Martha C Cooper

2000-01-01

235

Issues in Supply Chain Costing  

Microsoft Academic Search

Integration of the supply chain offers many opportunities to improve customer service and eliminate unnecessary costs. However, many firms lack the capability to determine the cost of moving product to market and where potential savings may exist. Supply chain costing provides an approach for measuring the cost of activities spanning the entire channel. Using cost information to evaluate channel performance

Bernard J. LaLonde; Terrance L. Pohlen

1996-01-01

236

Gradient zone-boundary control in salt-gradient solar ponds  

DOEpatents

A method and apparatus for suppressing zone boundary migration in a salt gradient solar pond includes extending perforated membranes across the pond at the boundaries, between the convective and non-convective zones, the perforations being small enough in size to prevent individual turbulence disturbances from penetrating the hole, but being large enough to allow easy molecular diffusion of salt thereby preventing the formation of convective zones in the gradient layer. The total area of the perforations is a sizeable fraction of the membrane area to allow sufficient salt diffusion while preventing turbulent entrainment into the gradient zone.

Hull, J.R.

1982-09-29

237

Quantum reservoirs with ion chains  

NASA Astrophysics Data System (ADS)

Ion chains are promising platforms for studying and simulating quantum reservoirs. One interesting feature is that their vibrational modes can mediate entanglement between two objects which are coupled through the vibrational modes of the chain. In this work we analyze entanglement between the transverse vibrations of two heavy impurity defects embedded in an ion chain, which is generated by the coupling with the chain vibrations. We verify general scaling properties of the defect dynamics and demonstrate that entanglement between the defects can be a stationary feature of these dynamics. We then analyze entanglement in chains composed of tens of ions and propose a measurement scheme which allows one to verify the existence of the predicted entangled state.

Taketani, B. G.; Fogarty, T.; Kajari, E.; Busch, Th.; Morigi, Giovanna

2014-07-01

238

Characterization of Imaging Gradients in Diffusion Tensor Imaging  

PubMed Central

For obtaining a complete model the diffusion tensor imaging (DTI) method is derived in a new linear algebraic framework in order to include the effect of all of the magnetic field gradients on the MRI signal. In the framework, the coefficient matrix of the estimation equations consists of the sum of three matrices corresponding to diffusion gradients, imaging gradients and the cross–terms between them. The derivations demonstrate that there exists modeling incongruities originating from the choice of phase–encoding gradient magnitude and the read–out gradient affecting the entirety of the signal sample points. These reflect on the cross–terms and the imaging gradient coefficient matrix, revealing the DTI's inadequacy for the inclusion of imaging gradients. The linear algebraic framework mitigates the inadequacy by the utilization of center–symmetric gradient schemes. The observations are verified by the experimental results obtained from an isotropic phantom using several existing diffusion gradient schemes. PMID:20810298

Özcan, Alpay

2010-01-01

239

Length selective accumulation of oligonucleotides in thermal gradients  

NASA Astrophysics Data System (ADS)

Central to most Origin-of-Life scenarios is the possibility for pre-biotic organic molecules to interact in order to form increasingly complex, catalytic molecular machinery ultimately capable of autonomous replication. While strong evidence for the spontaneous synthesis of single nucleotides [1] recently arose, concentrations required to allow these building blocks to polymerize [2] and gain functionality, still seem improbable for early earth conditions. Here, we demonstrate experimentally that temperature gradients across pores, as found in rocks near hydrothermal vents [3], are sufficient to accumulate nucleotides efficiently from dilute solutions. In particular we show that depending on the pores' dimensions, it can act as a length-selective molecular filter. We suggest that equivalent systems could have served as meeting points for long and complex molecules, too rare to find each other in a dilute primordial ocean. Furthermore, we discuss under which conditions this selection could have triggered the evolutionary adaptation of molecular replicators, and how polymerase chain reaction assays could nowadays benefit from the presented concept. References: 1. M. Powner et al., Nature 459 (2009), 2. G. Costanzo et al., ChemBioChem 13 (2012), 3. P. Baaske et al., PNAS (2007)

Kreysing, Moritz; Lanzmich, Simon; Braun, Dieter

2013-03-01

240

Mean Gradient Charge: A new definition of atomic charge using induced atomic gradient  

NASA Astrophysics Data System (ADS)

A new definition of atomic charge, Mean Gradient Charge (MGC) is proposed on the basis of 'induced atomic gradient'. Conceptually the connection between electric response to external point charge and Coulomb's law made exact, providing a unique way of extracting atomic charges from quantum mechanical calculations without any numerical ambiguities. Furthermore MGC is relatively invariant with respect to molecular rotation, choices of basis set and even correlation treatments. Preliminary test calculations show that MGC values are in between Mulliken and NPA charges.

Choi, Cheol Ho

2012-02-01

241

Optimisation of gradient elution with serially-coupled columns Part II: Multi-linear gradients.  

PubMed

An interpretive approach is reported for the simultaneous optimisation of resolution and analysis time in the separation of complex samples by reversed-phase liquid chromatography, using serially-coupled columns of different lengths and nature, and multi-linear gradient elution. The results complement those reported in JCA 1350 (2014) 51 for single linear gradients, using combinations of five columns: three C18 columns of different characteristics, a cyano column and a phenyl column. The relationships between the logarithm of the retention factor (lnk) and the organic solvent content (?), and between the peak half-widths and the retention times, for each analyte, were determined using isocratic retention times. From the established correlations, the gradient retention time was predicted using the fundamental equation for gradient elution (modified to be used for serially-coupled columns), and with this information, the peak profile. Two chromatographic goals (maximal peak purity and minimal analysis time) were simultaneously evaluated using the Pareto optimality concept. The rigorous predictive system can be easily applied to columns from different manufacturers and succeeds at different levels: single and combined columns, using isocratic and gradient elution. The computation time for gradient elution optimisation was significantly reduced to practical values with the help of genetic algorithms (GAs). PMID:25465000

Ortiz-Bolsico, C; Torres-Lapasió, J R; García-Alvarez-Coque, M C

2014-12-19

242

Improving supply chain resilience by multi-stage supply chain  

E-print Network

Due to the global expansion of Company A's supply chain network, it is becoming more vulnerable to many disruptions. These disruptions often incur additional costs; and require time to respond to and recover from these ...

Yang, Jingxia, M. Eng, Massachusetts Institute of Technology

2009-01-01

243

Improve supply chain resilience by multi-stage supply chain  

E-print Network

Due to the global expansion of Company A's supply chain network, it is becoming more vulnerable to many disruptions. These disruptions often incur additional costs; and require time to respond to and recover from these ...

Xu, Jie, M. Eng. Massachusetts Institute of Technology

2009-01-01

244

Tuning Surface Microstructure and Gradient Property of Polymer by Photopolymerizable Polysiloxane-modified Nanogels  

PubMed Central

This paper reports a series of photopolymerizable polysiloxane-modified nanogels for regulating surface microstructure and gradient property of polymers, which were synthesized by solution polymerization under different feed ratios of a methacrylate-modified polysiloxane, urethane dimethacrylate (UDMA) and isobornyl methacrylate (IBMA) in the presence of a thiol chain transfer agent. The nanogel structure and composition were characterized by proton nuclear magnetic resonance (1H-NMR), Fourier transform-infrared spectroscopy (FT-IR), transmission electron microscope (TEM), gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The dispersion of these nanogels in triethylene glycol dimethacrylate (TEGDMA) can reduce the onset and magnitude of shrinkage stress during polymerization without compromise to mechanical properties of the resulting polymers. Most importantly, as demonstrated by elemental analysis and X-ray photoelectron spectroscopy (XPS), the nanogels exhibit good self-floating ability in the monomer/polymer matrix and the increase of polysiloxane content in the nanogel can enhance the self-floating capability due to the lower surface tension and energy associated with the polysiloxane component. As a result, the polysiloxane-modified nanogels can spontaneously form a concentration gradient that can be locked in upon photopolymerization leading to a well-controlled heterogeneous polymer that presents a gradient change in thermal stability. With the increase of polysiloxane content, the thermal stability of the polymer was improved significantly. Furthermore, the enrichment of the nanogel on the surface resulting from the good self-floating ability can reduce the dispersion surface energy of gradient polymer film and generate a more hydrophobic surface with altered surface microstructure. These photopolymerizable polysiloxane-modified nanogels are demonstrated to have potential broad application in the preparation of gradient polymer with controlled surface properties. PMID:25045518

Chen, Cong; Liu, JianCheng; Sun, Fang; Stansbury, Jeffrey W.

2014-01-01

245

Food Chain Security and Vulnerability  

NASA Astrophysics Data System (ADS)

In our contemporary societies, the food chain could be defined as a macro-technical system, which depends on a wide variety of actors and risks analysis methods. In this contribution, risks related to the food chain are defined in terms of "modern risks" (Beck 1992). The whole national economic sector of food production/distribution is vulnerable to a local accident, which can affect the functioning of food chain, the export programs and even the political system. Such a complex socio-technical environment is undoubtedly vulnerable to intentional act such as terrorism.

Brunet, Sébastien; Delvenne, Pierre; Claisse, Frédéric

246

Invited Review Supply chain management and advanced  

E-print Network

Invited Review Supply chain management and advanced planning­­basics, overview and challenges Hartmut Stadtler Fachgebiet Produktion & Supply Chain Management, Institut fur Betriebswirtschaftslehre Abstract Literature on supply chain management (SCM) covers several disciplines and is growing rapidly

Grossmann, Ignacio E.

247

Bacterial and archaeal communities in Lake Nyos (Cameroon, Central Africa)  

PubMed Central

The aim of this study was to assess the microbial diversity associated with Lake Nyos, a lake with an unusual chemistry in Cameroon. Water samples were collected during the dry season on March 2013. Bacterial and archaeal communities were profiled using Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) approach of the 16S rRNA gene. The results indicate a stratification of both communities along the water column. Altogether, the physico-chemical data and microbial sequences suggest a close correspondence of the potential microbial functions to the physico-chemical pattern of the lake. We also obtained evidence of a rich microbial diversity likely to include several novel microorganisms of environmental importance in the large unexplored microbial reservoir of Lake Nyos. PMID:25141868

Tiodjio, Rosine E.; Sakatoku, Akihiro; Nakamura, Akihiro; Tanaka, Daisuke; Fantong, Wilson Y.; Tchakam, Kamtchueng B.; Tanyileke, Gregory; Ohba, Takeshi; Hell, Victor J.; Kusakabe, Minoru; Nakamura, Shogo; Ueda, Akira

2014-01-01

248

Sequential sludge digestion after diverse pre-treatment conditions: sludge removal, methane production and microbial community changes.  

PubMed

A lab-scale sequential sludge digestion process which consists of a mesophilic anaerobic digester (MAD) and a thermophilic aerobic digester (TAD) was developed. Thermal, thermal-alkaline and long-term alkaline pre-treatments were applied to the feed sludge to examine their effects on sludge removal and methane production. Especially after thermal-alkaline pre-treatment, high COD removal was maintained; methane production rate was also drastically increased by improving the hydrolysis step of sludge degradation. Polymerase chain reaction-denaturing gel gradient electrophoresis indicated that bacterial communities were represented by three phyla (Firmicutes, Proteobacteria, Actinobacteria) and that Clostridium straminisolvens was the major bacterial species in MAD. Quantitative real-time PCR results indicated that Methanosaeta concilli was the major archaeal species in MAD, and that Ureibacillus sp. was the most abundant bacterial species in TAD. PMID:24768888

Park, Sang Kyu; Jang, Hyun Min; Ha, Jeong Hyub; Park, Jong Moon

2014-06-01

249

Influence of tetracycline on the microbial community composition and activity of nitrifying biofilms.  

PubMed

The present work aims to evaluate the bacterial composition and activity (carbon and nitrogen removal) of nitrifying biofilms exposed to 50?gL(-1) of tetracycline. The tetracycline removal efficiency and the occurrence of tetracycline resistance (tet) genes were also studied. Two sequencing batch biofilm reactors (SBBRs) fed with synthetic wastewater were operated without (SBBR1) and with (SBBR2) the antibiotic. Both SBBRs showed similar organic matter biodegradation and nitrification activity. Tetracycline removal was about 28% and biodegradation was probably the principal removal mechanism of the antibiotic. Polymerase chain reaction-denaturing gradient gel electrophoresis analysis of the bacterial community showed shifts leading to not only the fading of some ribotypes, but also the emergence of new ones in the biofilm with tetracycline. The study of the tet genes showed that tet(S) was only detected in the biofilm with tetracycline, suggesting a relationship between its occurrence and the presence of the antibiotic. PMID:25127228

Matos, Maria; Pereira, Maria A; Parpot, Pier; Brito, António G; Nogueira, Regina

2014-12-01

250

Bacterial and archaeal communities in Lake Nyos (Cameroon, Central Africa)  

NASA Astrophysics Data System (ADS)

The aim of this study was to assess the microbial diversity associated with Lake Nyos, a lake with an unusual chemistry in Cameroon. Water samples were collected during the dry season on March 2013. Bacterial and archaeal communities were profiled using Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) approach of the 16S rRNA gene. The results indicate a stratification of both communities along the water column. Altogether, the physico-chemical data and microbial sequences suggest a close correspondence of the potential microbial functions to the physico-chemical pattern of the lake. We also obtained evidence of a rich microbial diversity likely to include several novel microorganisms of environmental importance in the large unexplored microbial reservoir of Lake Nyos.

Tiodjio, Rosine E.; Sakatoku, Akihiro; Nakamura, Akihiro; Tanaka, Daisuke; Fantong, Wilson Y.; Tchakam, Kamtchueng B.; Tanyileke, Gregory; Ohba, Takeshi; Hell, Victor J.; Kusakabe, Minoru; Nakamura, Shogo; Ueda, Akira

2014-08-01

251

Bacterial and archaeal communities in Lake Nyos (Cameroon, Central Africa).  

PubMed

The aim of this study was to assess the microbial diversity associated with Lake Nyos, a lake with an unusual chemistry in Cameroon. Water samples were collected during the dry season on March 2013. Bacterial and archaeal communities were profiled using Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) approach of the 16S rRNA gene. The results indicate a stratification of both communities along the water column. Altogether, the physico-chemical data and microbial sequences suggest a close correspondence of the potential microbial functions to the physico-chemical pattern of the lake. We also obtained evidence of a rich microbial diversity likely to include several novel microorganisms of environmental importance in the large unexplored microbial reservoir of Lake Nyos. PMID:25141868

Tiodjio, Rosine E; Sakatoku, Akihiro; Nakamura, Akihiro; Tanaka, Daisuke; Fantong, Wilson Y; Tchakam, Kamtchueng B; Tanyileke, Gregory; Ohba, Takeshi; Hell, Victor J; Kusakabe, Minoru; Nakamura, Shogo; Ueda, Akira

2014-01-01

252

Program predicts reservoir temperature and geothermal gradient  

SciTech Connect

This paper reports that a Fortran computer program has been developed to determine static formation temperatures (SFT) and geothermal gradient (GG). A minimum of input data (only two shut-in temperature logs) is required to obtain the values of SFT and GG. Modeling of primary oil production and designing enhanced oil recovery (EOR) projects requires knowing the undisturbed (static) reservoir temperature. Furthermore, the bottom hole circulating temperature (BHCT) is an important factor affecting a cement's thickening time, rheological properties, compressive strength, development, and set time. To estimate the values of BHCT, the geothermal gradient should be determined with accuracy. Recently we obtained an approximate analytical solution which describes the shut-in temperature behavior.

Kutasov, I.M.

1992-06-01

253

Degraded character recognition based on gradient pattern  

NASA Astrophysics Data System (ADS)

Degraded character recognition is a challenging problem in the field of Optical Character Recognition (OCR). The performance of an optical character recognition depends upon printed quality of the input documents. Many OCRs have been designed which correctly identifies the fine printed documents. But, very few reported work has been found on the recognition of the degraded documents. The efficiency of the OCRs system decreases if the input image is degraded. In this paper, a novel approach based on gradient pattern for recognizing degraded printed character is proposed. The approach makes use of gradient pattern of an individual character for recognition. Experiments were conducted on character image that is either digitally written or a degraded character extracted from historical documents and the results are found to be satisfactory.

Babu, D. R. Ramesh; Ravishankar, M.; Kumar, Manish; Wadera, Kevin; Raj, Aakash

2010-02-01

254

Self-similar dynamics of morphogen gradients  

NASA Astrophysics Data System (ADS)

Morphogen gradients are concentration fields of molecules acting as spatial regulators of cell differentiation in developing tissues and play a fundamental role in various aspects of embryonic development. We discovered a family of self-similar solutions in a canonical class of nonlinear reaction-diffusion models describing the formation of morphogen gradients. These solutions are realized in the limit of infinitely high production rate at the tissue boundary and are given by the product of the steady state concentration profile and a function of the diffusion similarity variable. We solved the boundary value problem for the similarity profile numerically and analyzed the implications of the discovered self-similarity on the dynamics of morphogenetic patterning.

Muratov, Cyrill B.; Gordon, Peter V.; Shvartsman, Stanislav Y.

2011-10-01

255

Temperature gradient driven lasing and stimulated cooling  

E-print Network

A laser can be understood as thermodynamic engine converting heat to a coherent single mode field close to Carnot efficiency. From this perspective spectral shaping of the excitation light generates a higher effective temperature on the pump than on the gain transition. Here, using a toy model of a quantum well structure with two suitably designed tunnel-coupled wells kept at different temperature, we study a laser operated on an actual spatial temperature gradient between pump and gain region. We predict gain and narrow band laser emission for a sufficient temperature gradient and resonator quality. Lasing appears concurrent with amplified heat flow and points to a new form of stimulated solid state cooling. Such a mechanism could raise the operating temperature limit of quantum cascade lasers by substituting phonon emission driven injection, which generates intrinsic heat, by an extended model with phonon absorption steps.

K. Sandner; H. Ritsch

2012-05-31

256

The latitudinal biodiversity gradient through deep time.  

PubMed

Today, biodiversity decreases from equatorial to polar regions. This is a fundamental pattern governing the distribution of extant organisms, the understanding of which is critical to predicting climatically driven biodiversity loss. However, its causes remain unresolved. The fossil record offers a unique perspective on the evolution of this latitudinal biodiversity gradient (LBG), providing a dynamic system in which to explore spatiotemporal diversity fluctuations. Deep-time studies indicate that a tropical peak and poleward decline in species diversity has not been a persistent pattern throughout the Phanerozoic, but is restricted to intervals of the Palaeozoic and the past 30 million years. A tropical peak might characterise cold icehouse climatic regimes, whereas warmer greenhouse regimes display temperate diversity peaks or flattened gradients. PMID:24139126

Mannion, Philip D; Upchurch, Paul; Benson, Roger B J; Goswami, Anjali

2014-01-01

257

Automated apparatus for producing gradient gels  

DOEpatents

Apparatus for producing a gradient gel which serves as a standard medium for a two-dimensional analysis of proteins, the gel having a density gradient along its height formed by a variation in gel composition, with the apparatus including first and second pumping means each including a plurality of pumps on a common shaft and driven by a stepping motor capable of providing small incremental changes in pump outputs for the gel ingredients, the motors being controlled, by digital signals from a digital computer, a hollow form or cassette for receiving the gel composition, means for transferring the gel composition including a filler tube extending near the bottom of the cassette, adjustable horizontal and vertical arms for automatically removing and relocating the filler tube in the next cassette, and a digital computer programmed to automatically control the stepping motors, arm movements, and associated sensing operations involving the filling operation.

Anderson, Norman L. (Clarendon Hills, IL)

1986-01-01

258

Image classification with binary gradient contours  

NASA Astrophysics Data System (ADS)

In this work we present a new family of computationally simple texture descriptors, referred to as binary gradient contours (BGC). The BGC methodology relies on computing a set of eight binary gradients between pairs of pixels all along a closed path around the central pixel of a 3×3 grayscale image patch. We developed three different versions of BGC features, namely single-loop, double-loop and triple-loop. To quantitatively assess the effectiveness of the proposed approach we performed an ensemble of texture classification experiments over 10 different datasets. The obtained results make it apparent that the single-loop version is the best performer of the BGC family. Experiments also show that the single-loop BGC texture operator outperforms the well-known LBP. Statistical significance of the achieved accuracy improvement has been demonstrated through the Wilkoxon signed rank test.

Fernández, Antonio; Álvarez, Marcos X.; Bianconi, Francesco

2011-09-01

259

Geothermal temperature gradient core drill, Santiam Pass  

SciTech Connect

DOE is proposing to share in the cost of drilling a 3000-ft core hole to evaluate temperature gradients, subsurface geology and the geothermal potential of an area in the Cascade Mountains. The proposed core hole will be located in the Deschutes National Forest in Oregon, near Santiam Pass. The proposed action has been described in the Environmental Assessment (EA) for Geothermal Temperature Gradient Core Drill Santiam Pass Area (No. OR-050-9-51) prepared by the US Bureau of Land Management (BLM). DOE has determined that the BLM EA adequately addresses the impacts of the proposal and is hereby adopting the EA in partial fulfillment of its NEPA responsibilities. Based upon a review of the EA and an independent analysis, DOE has concluded that the proposed corehole drilling project does not constitute a major federal action significantly affecting the quality of the human environment within the meaning of NEPA. Therefore, an environmental impact statement will not be prepared.

Not Available

1989-01-01

260

Plane mixing layers with streamwise pressure gradient  

NASA Astrophysics Data System (ADS)

Experiments have been conducted to determine the effect of streamwise pressure gradient on the spatial development of a constant density, plane mixing layer. Velocity data and flow visualization images suggest that dP/dx influences the spreading rate of the mixing region indicated by the parameter delta (x), the vorticity thickness, through changes induced in the local value of the ratio of the mean velocities of the two freestreams. There is evidence which suggests that interactions between the primary spanwise vortex structures are enhanced in the presence of an adverse pressure gradient, i.e., dP/dx are O, and are suppressed in an accelerating flow. Application of the Abramovich-Sabin growth law to predict delta (x) appears adequately to account for the trends in measured deviations from linear mixing layer growth. The present data are interpreted on the basis of the vortex pairing model proposed by Winant and Brovand.

Masutani, S. M.; Kobayashi, H.; Azuhata, S.; Miyadera, H.; Hishinuma, Y.

261

Spontaneous wrinkle branching by gradient stiffness.  

PubMed

The concept of coherency loss is proposed to understand wrinkle branching as a pathway toward hierarchical wrinkling pattern formation in a compressed film-substrate system with gradient stiffness of the film or substrate. A simple model indicates that the wrinkle branching arises when the characteristic length of the stiffness inhomogeneity zone is larger than the coherency persistent length, which depends on the amplitude of the stiffness inhomogeneity. Numerical simulations of nonlinear wrinkles based on the model of the Föppl-von Kármán plate on compliant substrates show how regulating the size and amplitude of the stiffness inhomogeneities results in branched wrinkles in striking agreement with the existing observations. The paper reveals the origin of such kinds of branched wrinkles and may provide a guideline for controllable hierarchical wrinkles by patterning the stiffness gradient. PMID:23030926

Ni, Yong; Yang, Dong; He, Linghui

2012-09-01

262

Hydrodynamic gradient expansion in gauge theory plasmas  

E-print Network

We utilize the fluid-gravity duality to investigate the large order behavior of hydrodynamic gradient expansion of the dynamics of a gauge theory plasma system. This corresponds to the inclusion of dissipative terms and transport coefficients of very high order. Using the dual gravity description, we calculate numerically the form of the stress tensor for a boost-invariant flow in a hydrodynamic expansion up to terms with 240 derivatives. We observe a factorial growth of gradient contributions at large orders, which indicates a zero radius of convergence of the hydrodynamic series. Furthermore, we identify the leading singularity in the Borel transform of the hydrodynamic energy density with the lowest nonhydrodynamic excitation corresponding to a `nonhydrodynamic' quasinormal mode on the gravity side.

Michal P. Heller; Romuald A. Janik; Przemyslaw Witaszczyk

2013-05-24

263

Automated apparatus for producing gradient gels  

DOEpatents

Apparatus for producing a gradient gel which serves as a standard medium for a two-dimensional analysis of proteins, the gel having a density gradient along its height formed by a variation in gel composition, with the apparatus including first and second pumping means each including a plurality of pumps on a common shaft and driven by a stepping motor capable of providing small incremental changes in pump outputs for the gel ingredients, the motors being controlled, by digital signals from a digital computer, a hollow form or cassette for receiving the gel composition, means for transferring the gel composition including a filler tube extending near the bottom of the cassette, adjustable horizontal and vertical arms for automatically removing and relocating the filler tube in the next cassette, and a digital computer programmed to automatically control the stepping motors, arm movements, and associated sensing operations involving the filling operation.

Anderson, N.L.

1983-11-10

264

Opinion Formation Models on a Gradient  

PubMed Central

Statistical physicists have become interested in models of collective social behavior such as opinion formation, where individuals change their inherently preferred opinion if their friends disagree. Real preferences often depend on regional cultural differences, which we model here as a spatial gradient g in the initial opinion. The gradient does not only add reality to the model. It can also reveal that opinion clusters in two dimensions are typically in the standard (i.e., independent) percolation universality class, thus settling a recent controversy about a non-consensus model. However, using analytical and numerical tools, we also present a model where the width of the transition between opinions scales , not as in independent percolation, and the cluster size distribution is consistent with first-order percolation. PMID:25474528

Gastner, Michael T.; Markou, Nikolitsa; Pruessner, Gunnar; Draief, Moez

2014-01-01

265

Voltammetry under a Controlled Temperature Gradient  

PubMed Central

Electrochemical measurements are generally done under isothermal conditions. Here we report on the application of a controlled temperature gradient between the working electrode surface and the solution. Using electrochemical sensors prepared on ceramic materials with extremely high specific heat conductivity, the temperature gradient between the electrode and solution was applied here as a second driving force. This application of the Soret phenomenon increases the mass transfer in the Nernst layer and enables more accurate control of the electrode response enhancement by a combination of diffusion and thermal diffusion. We have thus studied the effect of Soret phenomenon by cyclic voltammetry measurements in ferro/ferricyanide. The time dependence of sensor response disappears when applying the Soret phenomenon, and the complicated shape of the cyclic voltammogram is replaced by a simple exponential curve. We have derived the Cotrell-Soret equation describing the steady-state response with an applied temperature difference. PMID:22163578

Krejci, Jan; Sajdlova, Zuzana; Krejci, Jan; Marvanek, Tomas

2010-01-01

266

Markov chain Monte Carlo method for tracking myocardial borders  

NASA Astrophysics Data System (ADS)

Cardiac magnetic resonance studies have led to a greater understanding of the pathophysiology of ischemic heart disease. Manual segmentation of myocardial borders, a major task in the data analysis of these studies, is a tedious and time consuming process subject to observer bias. Automated segmentation reduces the time needed to process studies and removes observer bias. We propose an automated segmentation algorithm that uses an active contour to capture the endo- and epicardial borders of the left ventricle in a mouse heart. The contour is initialized by computing the ellipse corresponding to the maximal gradient inverse of variation (GICOV) value. The GICOV is the mean divided by the normalized standard deviation of the image intensity gradient in the outward normal direction along the contour. The GICOV is maximal when the contour lies along strong, relatively constant gradients. The contour is then evolved until it maximizes the GICOV value subject to shape constraints. The problem is formulated in a Bayesian framework and is implemented using a Markov Chain Monte Carlo technique.

Janiczek, Robert; Ray, N.; Acton, Scott T.; Roy, R. J.; French, Brent A.; Epstein, F. H.

2005-03-01

267

Prediction of gas chromatographic retention times of esters of long chain alcohols and fatty acids.  

PubMed

The linear free energy of solution (DeltaG) relationship (DeltaG=DeltaGo+zdeltaG) for compounds of different carbon atoms (z) in the same homologous series is expanded and modified to cover compounds with two different hydrocarbon side chains. The expanded equation is successfully used to predict the retention times (tR) of standard esters of long chain alcohols and fatty acids of different chain lengths in both isothermal and temperature-programmed gas chromatography (TPGC). Approximately 90% of the 125 predicted tR values have a difference of less than 1.00% from the actual tR and the highest difference is 1.26%. Two different temperature gradients in TPGC are tested. The expanded equation can be used to forecast the tR of TPGC with good accuracy. The highest difference is +/-1.40% and +/-1.00% for the temperature gradients of 2 degrees C and 4 degrees C/min, respectively. However, the increments in free energy per carbon atom (zdeltaG) of the alcohol and acid are approximately equal but have slightly different temperature sensitivities. Therefore, it is very difficult to separate esters of different acid and alcohol chain length but with the same total carbon numbers. Furthermore, the difference in temperature sensitivities for the acid and alcohol side chains renders them to be inversely eluted at different temperatures. PMID:16620510

Katsuwon, Karuna; Aryusuk, Kornkanok; Krisnangkura, Kanit

2006-03-01

268

Parametric study of salt gradient solar ponds  

SciTech Connect

A mathematical model for efficiency of a salt gradient solar pond is described. Heat losses from the bottom of the pond have been calculated, and the results for the effective thermal conductivity with the thicknesses of various insulating materials have been presented. The effect of the ground thermal resistance on the efficiency of the pond for different values of ..delta..T/S/sup 0/ are also shown.

Beniwal, R.S.; Saxena, N.S.; Bhandari, R.C.

1986-02-01

269

Exploration of very high gradient cavities  

SciTech Connect

Several of the 9-cell ILC cavities processed at Jlab within ongoing ILC R&D program have shown interesting behavior at high fields, such as mode mixing and sudden field emission turn-on during quench. Equipped with thermometry and oscillating superleak transducer (OST) system for quench detection, we couple our RF measurements with local dissipation measurements. In this contribution we report on our findings with high gradient SRF cavities.

Grigory Eremeev

2011-07-01

270

M-step preconditioned conjugate gradient methods  

NASA Technical Reports Server (NTRS)

Preconditioned conjugate gradient methods for solving sparse symmetric and positive finite systems of linear equations are described. Necessary and sufficient conditions are given for when these preconditioners can be used and an analysis of their effectiveness is given. Efficient computer implementations of these methods are discussed and results on the CYBER 203 and the Finite Element Machine under construction at NASA Langley Research Center are included.

Adams, L.

1983-01-01

271

Integrated calibration of magnetic gradient tensor system  

NASA Astrophysics Data System (ADS)

Measurement precision of a magnetic gradient tensor system is not only connected with the imperfect performance of magnetometers such as bias, scale factor, non-orthogonality and misalignment errors, but also connected with the external soft-iron and hard-iron magnetic distortion fields when the system is used as a strapdown device. So an integrated scalar calibration method is proposed in this paper. In the first step, a mathematical model for scalar calibration of a single three-axis magnetometer is established, and a least squares ellipsoid fitting algorithm is proposed to estimate the detailed error parameters. For the misalignment errors existing at different magnetometers caused by the installation process and misalignment errors aroused by ellipsoid fitting estimation, a calibration method for combined misalignment errors is proposed in the second step to switch outputs of different magnetometers into the ideal reference orthogonal coordinate system. In order to verify effectiveness of the proposed method, simulation and experiment with a cross-magnetic gradient tensor system are performed, and the results show that the proposed method estimates error parameters and improves the measurement accuracy of magnetic gradient tensor greatly.

Gang, Yin; Yingtang, Zhang; Hongbo, Fan; GuoQuan, Ren; Zhining, Li

2015-01-01

272

High-thermal-gradient Superalloy Crystal Growth  

NASA Technical Reports Server (NTRS)

Single, (001)-oriented crystals of PWA 1480 were processed in alumina/silica shell molds in a laboratory high gradient furnace. The furnace employs a graphite resistance heated element, a radiation baffle, and a water cooled radiation trap below the baffle. All crystals were grown in vacuum (10 torr) and all heat transfer was radiative. The element is constructed with a variable cross section that is tapered just above the baffle to maximize heat input and therefore thermal gradient. A maximum alloy temperature of 1600 C was used. A thermal gradient of 130 deg C/cm was recorded at 1370 C just above the solidus of the PWA 1480 alloys. Crystal bars with 14.4 and 17.5 mm diameters were grown in alumina/silica shell molds. Each crystal was started from a 1.6 mm pencil seed at a rate of 76 mm/hr and slowly accelerated to a rate of 200 mm/hr under computer control. Volume percent porosity and average pore size were measured as functions of distance in representative bars. Low cycle fatigue behavior and stress rupture properties were determined.

Pearson, D. D.; Anton, D. L.; Giamei, A. F.

1985-01-01

273

The Boussinesq Problem in Dipolar Gradient Elasticity  

E-print Network

The three-dimensional axisymmetric Boussinesq problem of an isotropic half-space subjected to a concentrated normal quasi-static load is studied within the framework of linear dipolar gradient elasticity. Our main concern is to determine possible deviations from the predictions of classical linear elastostatics when a more refined theory is employed to attack the problem. Of special importance is the behavior of the new solution near to the point of application of the load where pathological singularities exist in the classical solution. The use of the theory of gradient elasticity is intended here to model the response of materials with microstructure in a manner that the classical theory cannot afford. A linear version of this theory results by considering a linear isotropic expression for the strain-energy density that depends on strain-gradient terms, in addition to the standard strain terms appearing in classical elasticity. Through this formulation, a microstructural material constant is introduced, in addition to the standard Lam\\'e constants. The solution method is based on integral transforms and is exact. The present results show significant departure from the predictions of classical elasticity. Indeed, continuous and bounded displacements are predicted at the points of application of the concentrated load. Such a behavior of the displacement field is, of course, more natural than the singular behavior exhibited in the classical solution.

H. G. Georgiadis; P. A. Gourgiotis; D. S. Anagnostou

2014-03-31

274

Energy Gradient Theory of Hydrodynamic Instability  

E-print Network

A new universal theory for flow instability and turbulent transition is proposed in this study. Flow instability and turbulence transition have been challenging subjects for fluid dynamics for a century. The critical condition of turbulent transition from theory and experiments differs largely from each other for Poiseuille flows. In this paper, a new mechanism of flow instability and turbulence transition is presented for parallel shear flows and the energy gradient theory of hydrodynamic instability is proposed. It is stated that the total energy gradient in the transverse direction and that in the streamwise direction of the main flow dominate the disturbance amplification or decay. A new dimensionless parameter K for characterizing flow instability is proposed for wall bounded shear flows, which is expressed as the ratio of the energy gradients in the two directions. It is thought that flow instability should first occur at the position of Kmax which may be the most dangerous position. This speculation is confirmed by Nishioka et al's experimental data. Comparison with experimental data for plane Poiseuille flow and pipe Poiseuille flow indicates that the proposed idea is really valid. It is found that the turbulence transition takes place at a critical value of Kmax of about 385 for both plane Poiseuille flow and pipe Poiseuille flow, below which no turbulence will occur regardless the disturbance. More studies show that the theory is also valid for plane Couette flows and Taylor-Couette flows between concentric rotating cylinders.

Hua-Shu Dou

2005-01-28

275

Compressive and extensive strain along gradient trajectories  

NASA Astrophysics Data System (ADS)

Based on direct numerical simulations of forced turbulence, shear turbulence, decaying turbulence, a turbulent channel flow as well as a Kolmogorov flow with Taylor based Reynolds numbers Re? between 69 and 295, the normalized probability density function of the length distribution tilde P(tilde l) of dissipation elements, the conditional mean scalar difference < ?k | l > at the extreme points as well as the scaling of the two-point velocity difference along gradient trajectories < ?un> are studied. Using the field of the instantanous turbulent kinetic energy k as a scalar, we find a good agreement between the model equation for tilde P(tilde l) as proposed by Wang and Peters (2008) and the results obtained in the different DNS cases. This confirms the independance of the model solution from both, the Reynolds number and the type of turbulent flow, so that it can be considered universally valid. In addition, we show a 2/3 scaling for the mean conditional scalar difference. In the second part of the paper, we examine the scaling of the conditional two-point velocity difference along gradient trajectories. In particular, we compare the linear s/? scaling, where ? denotes an integral time scale and s the separation arclength along a gradient trajectory in the inertial range as derived by Wang (2009) with the s · a? scaling, where a? denotes the asymtotic value of the conditional mean strain rate of large dissipation elements.

Gampert, Markus; Goebbert, Jens Henrik; Schaefer, Philip; Gauding, Michael; Peters, Norbert; Aldudak, Fettah; Oberlack, Martin

2011-12-01

276

Efficient gradient computation for dynamical models  

PubMed Central

Data assimilation is a fundamental issue that arises across many scales in neuroscience — ranging from the study of single neurons using single electrode recordings to the interaction of thousands of neurons using fMRI. Data assimilation involves inverting a generative model that can not only explain observed data but also generate predictions. Typically, the model is inverted or fitted using conventional tools of (convex) optimization that invariably extremise some functional — norms, minimum descriptive length, variational free energy, etc. Generally, optimisation rests on evaluating the local gradients of the functional to be optimized. In this paper, we compare three different gradient estimation techniques that could be used for extremising any functional in time — (i) finite differences, (ii) forward sensitivities and a method based on (iii) the adjoint of the dynamical system. We demonstrate that the first-order gradients of a dynamical system, linear or non-linear, can be computed most efficiently using the adjoint method. This is particularly true for systems where the number of parameters is greater than the number of states. For such systems, integrating several sensitivity equations – as required with forward sensitivities – proves to be most expensive, while finite-difference approximations have an intermediate efficiency. In the context of neuroimaging, adjoint based inversion of dynamical causal models (DCMs) can, in principle, enable the study of models with large numbers of nodes and parameters. PMID:24769182

Sengupta, B.; Friston, K.J.; Penny, W.D.

2014-01-01

277

Fast computation of satellite gravitational gradient.  

NASA Astrophysics Data System (ADS)

The computation of the Earth's potential function at high order and degree with the method of Cunningham (1970) causes overflow most of the time. The normalized method can eliminate the overflows, but leads to formulae much more involved than those in Cunningham's method; besides, the programming is more complex and the computer time required larger. The method presented has the following features: each component of the satellite gravitational gradient can be computed; the formulae are short and easy to be programmed; the method is much quicker than the normalization method and can be carried out with a microcomputer, without overflow even in the case of Earth's spherical harmonics of order and degree as high as 1025 or higher. This method satisfies the present demand to compute the satellite gravitational gradient with high accuracy. Furthermore, the authors present formulae for the fast computation, without overflow, of the gravitational gradient corresponding to Earth's spherical harmonics up to order and degree of 3170×3170 or higher.

Lin, Qinchang; Yuan, Lin

1998-07-01

278

Crosswind Shear Gradient Affect on Wake Vortices  

NASA Technical Reports Server (NTRS)

Parametric simulations with a Large Eddy Simulation (LES) model are used to explore the influence of crosswind shear on aircraft wake vortices. Previous studies based on field measurements, laboratory experiments, as well as LES, have shown that the vertical gradient of crosswind shear, i.e. the second vertical derivative of the environmental crosswind, can influence wake vortex transport. The presence of nonlinear vertical shear of the crosswind velocity can reduce the descent rate, causing a wake vortex pair to tilt and change in its lateral separation. The LES parametric studies confirm that the vertical gradient of crosswind shear does influence vortex trajectories. The parametric results also show that vortex decay from the effects of shear are complex since the crosswind shear, along with the vertical gradient of crosswind shear, can affect whether the lateral separation between wake vortices is increased or decreased. If the separation is decreased, the vortex linking time is decreased, and a more rapid decay of wake vortex circulation occurs. If the separation is increased, the time to link is increased, and at least one of the vortices of the vortex pair may have a longer life time than in the case without shear. In some cases, the wake vortices may never link.

Proctor, Fred H.; Ahmad, Nashat N.

2011-01-01

279

Efficient gradient computation for dynamical models.  

PubMed

Data assimilation is a fundamental issue that arises across many scales in neuroscience - ranging from the study of single neurons using single electrode recordings to the interaction of thousands of neurons using fMRI. Data assimilation involves inverting a generative model that can not only explain observed data but also generate predictions. Typically, the model is inverted or fitted using conventional tools of (convex) optimization that invariably extremise some functional - norms, minimum descriptive length, variational free energy, etc. Generally, optimisation rests on evaluating the local gradients of the functional to be optimized. In this paper, we compare three different gradient estimation techniques that could be used for extremising any functional in time - (i) finite differences, (ii) forward sensitivities and a method based on (iii) the adjoint of the dynamical system. We demonstrate that the first-order gradients of a dynamical system, linear or non-linear, can be computed most efficiently using the adjoint method. This is particularly true for systems where the number of parameters is greater than the number of states. For such systems, integrating several sensitivity equations - as required with forward sensitivities - proves to be most expensive, while finite-difference approximations have an intermediate efficiency. In the context of neuroimaging, adjoint based inversion of dynamical causal models (DCMs) can, in principle, enable the study of models with large numbers of nodes and parameters. PMID:24769182

Sengupta, B; Friston, K J; Penny, W D

2014-09-01

280

Alternatives to the gradient in optimal transfer line buffer allocation  

E-print Network

This thesis describes several directions to replace the gradient in James Schor's gradient algorithm to solve the dual problem. The alternative directions are: the variance and standard deviation of buffer levels, the ...

Tanizar, Ketty, 1978-

2004-01-01

281

Temperature gradient and electric field driven electrostatic instabilities  

NASA Technical Reports Server (NTRS)

The stability of electrostatic waves to thermodynamic and electric potential gradients was investigated. It is shown that thermodynamic gradients drive instabilities even when the internal electric field vanishes. Skewing of the distribution function is not included in the dielectric.

Morrison, P. J.; Ionson, J. A.

1982-01-01

282

Supply chain management in the cement industry .  

E-print Network

??Traditionally supply chain management has played an operational role within cement and mineral extraction commodity companies. Recently, cost reduction projects have brought supply chain management… (more)

Agudelo, Isabel

2009-01-01

283

JOHN GLENN CENTER Key Chain  

NSDL National Science Digital Library

Brushed Stainless steel key chain with LED light, color engraved with the John Glenn Center for Science Education logo. All proceeds from the sale of this item go to fund the John Glenn Center for Science Education.

1900-01-01

284

Total supply chain cost model  

E-print Network

Sourcing and outsourcing decisions have taken on increased importance within Teradyne to improve efficiency and competitiveness. This project delivered a conceptual framework and a software tool to analyze supply chain ...

Wu, Claudia

2005-01-01

285

Food Chains and Food Webs  

NSDL National Science Digital Library

This lesson explains how energy travels through an ecosystem. This flow can be diagrammed in food chains and food webs as shown in the lesson's illustrations. Key terms are hyperlinked so students can easily view definitions of new concepts.

2012-06-14

286

Quantitative thermal gradient imaging of biological surfaces  

NASA Astrophysics Data System (ADS)

Heat production in biological systems is an obligate consequence of the chemical thermodynamics of the living state. Various cellular and systemic mechanisms exist of the dissipation (or conservation) of this net heat production in a basically aqueous environment to various exchange surfaces. Besides fundamental conduction, and radiation, convective modes of heat transfer are particularly significant, the latter often establishing steady-state thermal gradients particularly at normal or experimental exchange surfaces. Considering the relatively high specific heat of water and the low level of heat generation, the magnitude of such gradients are small and this require methods with sensitivity < 0.1 degree(s)C, with reasonable time response, and ones adaptable to quantitative spatial mapping. To that end, we have developed a calibration procedure and protocols employing a variety of thermotropic liquid crystal (TLC) formats which can quantitatively map both cellular and tissue surface gradients in a reproducible manner. TLC's used in a quantitative mode have the extreme temperature resolution required for basic biological studies, as well as application where altered cellular metabolism and/or vascular flow patterns are manifested as thermal changes in the spatial thermogram. This paper provides preliminary data on the application of the above protocols for the assessment of the dynamic changes in the thermal gradient pattern on the left-ventricular surface of supported, experimental heart preparations. Accordingly, after initial capture of the calibrated TLC images onto videotape using a multichannel plate intensifier (together with A/D conversion of physiological signals), single frame digitization allows for exact quantitative correlations of changes in the thermogram with hemodynamic parameters throughout the cardiac cycles with a time resolution of approximately equals 33 msec. The type of information obtained has potential value in clinical cardiac diagnosis (ie. coronary artery disease, by-pass assessment, etc.) and other biological applications where altered flow and/or heat production leads to changing surface gradients (ie thrombosis, embolism, tumor cell heat production, etc.) which can now be accurately and quantitatively mapped by the use of TLC's.

Swanson, Curtis J.; Wingard, Christopher J.

1991-03-01

287

Light chains and the kidney.  

PubMed Central

Five cases of renal impairment caused by the deposition of light chains in the kidney in association with various immunoproliferative disorders are reported. Light microscopy, immunohistochemistry, and electron microscopy were undertaken and different clinical courses were studied, resulting in variable influences of treatment. Light chain deposition is an important cause of renal impairment and requires special histological techniques for its recognition. Images Fig 1 Fig 2 Fig 3 Fig 4 Fig 5 Fig 6 PMID:3102562

Bradley, J R; Thiru, S; Evans, D B

1987-01-01

288

Bioenergy supply chains and stakeholders  

Microsoft Academic Search

What are the management challenges and opportunities of bio-energy chains for both running their business efficiently and\\u000a effectively and fostering the relationships with most relevant external stakeholders? This question is approached by systematically\\u000a reviewing papers at the interface of bio-energy and supply chain or logistics issues. The review conducted as content analysis\\u000a is based on an analytic framework that conceives

Stefan Gold

2011-01-01

289

Supply chain management and hypercompetition  

Microsoft Academic Search

Firms nowadays face significant challenges in their operating environments, which have been characterised in two different\\u000a ways. From a strategic management perspective these environments are in a state of hypercompetition while from a logistics\\u000a or supply chain perspective these environments require market responsiveness predicated upon agile supply chains. However,\\u000a firms must also rely on many inter-organisational relationships to ensure efficient

Herbert Kotzab; David B. Grant; Christoph Teller; Árni Halldórsson

2009-01-01

290

Osteoradionecrosis of the ossicular chain  

SciTech Connect

Osteoradionecrosis of the temporal bone is a well-known sequela of radiotherapy for neoplasms at the base of the skull. Presenting symptoms include otalgia, chronic aural drainage, and hearing loss, which can be conductive, sensorineural, or mixed. The conductive component has been hypothesized to be caused by radionecrosis of the ossicular chain. This case report documents the existence of osteoradionecrosis of the ossicular chain in a 10-year-old boy operated on for resection of extensive osteoradionecrosis of the temporal bone.

Kveton, J.F.; Sotelo-Avila, C.

1986-11-01

291

Generation of planar kinematic chains  

Microsoft Academic Search

This work presents a completely automated, mathematically rigorous procedure that generates all planar, non-fractionated, pin-jointed kinematic chains having 2–6 independent loops and 1, 2, or 3 degrees of freedom. It also addresses the isomorphism problem and the elimination of rigid subchains. The computer programs can be run on any personal computer (XT or higher); over 6 million kinematic chains and

E. R Tuttle

1996-01-01

292

Application of a food chain model to polychlorinated biphenyl contamination of the lobster and winter flounder food chains in New Bedford Harbor  

SciTech Connect

As part of a Remedial Investigation/Feasibility Study for the New Bedford Harbor Superfund site a model of polychlorinated biphenyls (PCBs) in the lobster and winter flounder food chains was developed. This model successfully reproduces tri-, tetra-, penta-, and hexachlorobiphenyl concentrations observed at all levels of the food chain and across the 2 order of magnitude concentration gradient in the system. The model indicated that PCB concentrations in the flounder and, to a lesser extent, in the lobster are derived from the sediment. Dietary uptake exceeds uptake across the gill for all four homologues and becomes the dominant route at the higher chlorinated homologues. The assimilation efficiency of ingested PCB apparently declines from relatively high values for tri-chlorobiphenyl to relatively low values for hexachlorobiphenyl. Differences in observed lobster and flounder PCB concentrations appear to be due to differences in the importance of the benthic component of the food chains of these animals and differences in whole body lipid content.

Connolly, J.P. (HydroQual, Inc., Mahwah, NJ (United States) Manhattan Coll., Riverdale, NY (United States))

1991-04-01

293

Reinforcement learning in supply chains.  

PubMed

Effective management of supply chains creates value and can strategically position companies. In practice, human beings have been found to be both surprisingly successful and disappointingly inept at managing supply chains. The related fields of cognitive psychology and artificial intelligence have postulated a variety of potential mechanisms to explain this behavior. One of the leading candidates is reinforcement learning. This paper applies agent-based modeling to investigate the comparative behavioral consequences of three simple reinforcement learning algorithms in a multi-stage supply chain. For the first time, our findings show that the specific algorithm that is employed can have dramatic effects on the results obtained. Reinforcement learning is found to be valuable in multi-stage supply chains with several learning agents, as independent agents can learn to coordinate their behavior. However, learning in multi-stage supply chains using these postulated approaches from cognitive psychology and artificial intelligence take extremely long time periods to achieve stability which raises questions about their ability to explain behavior in real supply chains. The fact that it takes thousands of periods for agents to learn in this simple multi-agent setting provides new evidence that real world decision makers are unlikely to be using strict reinforcement learning in practice. PMID:19885962

Valluri, Annapurna; North, Michael J; Macal, Charles M

2009-10-01

294

A Quadratic Gradient Equation for pricing Mortgage-Backed Securities  

E-print Network

A Quadratic Gradient Equation for pricing Mortgage-Backed Securities Marco Papi Institute for Applied Computing - CNR Rome (Italy) A Quadratic Gradient Equation for pricing Mortgage-Backed Securities call option on a corresponding fixed-rate bond. A Quadratic Gradient Equation for pricing Mortgage

Monneau, Régis

295

Crystalline-gradient polycarbonates prepared from enantioselective terpolymerization of meso-epoxides with CO2.  

PubMed

The development of efficient processes for CO2 transformation into useful products is a long-standing goal for chemists, since CO2 is an abundant, inexpensive and non-toxic renewable C1 resource. Here we describe the enantioselective copolymerization of 3,4-epoxytetrahydrofuran with CO2 mediated by biphenol-linked dinuclear cobalt complex, affording the corresponding polycarbonate with >99% carbonate linkages and excellent enantioselectivity (up to 99% enantiomeric excess). Notably, the resultant isotactic polycarbonate is a typical semicrystalline polymer, possessing a melting point of 271?°C. Furthermore, the enantioselective terpolymerization of 3,4-epoxytetrahydrofuran, cyclopentene oxide and CO2 mediated by this dinuclear cobalt complex gives novel gradient polycarbonates, in which the decrement of one component and the increment of the other component occur sequentially from one chain end to the other end. The resultant terpolymers show perfectly isotactic structure and have unique crystalline-gradient nature, in which the crystallinity continuously varies along the main chain. PMID:25477252

Liu, Ye; Ren, Wei-Min; He, Ke-Ke; Lu, Xiao-Bing

2014-01-01

296

Maintaining Optimal Communication Chains in Robotic Sensor Networks using Mobility Control  

Microsoft Academic Search

This paper presents a decentralized mobility control algorithm for the formation and maintenance of an optimal cascaded communication\\u000a chain between a lead sensor-equipped robot and a control station, using a team of robotic vehicles acting as communication\\u000a relays in an unknown and dynamic RF environment. The gradient-based controller presented uses measurements of the signal-to-noise\\u000a ratio (SNR) field of neighbor communication

Cory Dixon; Eric W. Frew

2009-01-01

297

Cationic triple-chain amphiphiles facilitate vesicle fusion compared to double-chain or single-chain analogues  

E-print Network

Cationic triple-chain amphiphiles facilitate vesicle fusion compared to double-chain or single, triple-chain amphiphiles promote vesicle fusion more than structurally related double-chain or single and acid-triggered self-fusion of vesicles composed of cationic amphiphile and anionic cholesteryl

Smith, Bradley D.

298

Effect of Temperature Gradient on Thick Film Selective Emitter Emittance  

NASA Technical Reports Server (NTRS)

A temperature gradient across a thick (greater than or equal to .1 mm) film selective emitter will produce a significant reduction in the spectral emittance from the no temperature gradient case. Thick film selective emitters of rare earth doped host materials such as yttrium-aluminum-garnet (YAG) are examples where temperature gradient effects are important. In this paper a model is developed for the spectral emittance assuming a linear temperature gradient across the film. Results of the model indicate that temperature gradients will result in reductions the order of 20% or more in the spectral emittance.

Chubb, Donald L.; Good, Brian S.; Clark, Eric B.; Chen, Zheng

1997-01-01

299

Spherical integral formulas for upward/downward continuation of gravitational gradients onto gravitational gradients  

NASA Astrophysics Data System (ADS)

New integral formulas for upward/downward continuation of gravitational gradients onto gravitational gradients are derived in this article. They provide more options for continuation of gravitational gradient combinations and extend available mathematical apparatus formulated for this purpose up to now. The starting point represents the analytical solution of the spherical gradiometric boundary value problem in the spatial domain. Applying corresponding differential operators on the analytical solution of the spherical gradiometric boundary value problem, a total of 18 integral formulas are provided. Spatial and spectral forms of isotropic kernels are given and their behaviour for parameters of a GOCE-like satellite is investigated. Correctness of the new integral formulas and the isotropic kernels is tested in a closed-loop simulation. The derived integral formulas and the isotropic kernels form a theoretical basis for validation purposes and geophysical applications of satellite gradiometric data as provided currently by the GOCE mission. They also extend the well-known Meissl scheme.

Šprlák, Michal; Sebera, Josef; Val'ko, Miloš; Novák, Pavel

2014-02-01

300

Ant functional responses along environmental gradients.  

PubMed

Understanding species distributions and diversity gradients is a central challenge in ecology and requires prior knowledge of the functional traits mediating species' survival under particular environmental conditions. While the functional ecology of plants has been reasonably well explored, much less is known about that of animals. Ants are among the most diverse, abundant and ecologically significant organisms on earth, and they perform a great variety of ecological functions. In this study, we analyse how the functional species traits present in ant communities vary along broad gradients in climate, productivity and vegetation type in the south-western Mediterranean. To this end, we compiled one of the largest animal databases to date: it contains information on 211 local ant communities (including eight climate variables, productivity, and vegetation type) and 124 ant species, for which 10 functional traits are described. We used traits that characterize different dimensions of the ant functional niche with respect to morphology, life history and behaviour at both individual and colony level. We calculated two complementary functional trait community indices ('trait average' and 'trait dissimilarity') for each trait, and we analysed how they varied along the three different gradients using generalized least squares models that accounted for spatial autocorrelation. Our results show that productivity, vegetation type and, to a lesser extent, each climate variable per se might play an important role in shaping the occurrence of functional species traits in ant communities. Among the climate variables, temperature and precipitation seasonality had a much higher influence on functional responses than their mean values, whose effects were almost lacking. Our results suggest that strong relationships might exist between the abiotic environment and the distribution of functional traits among south-western Mediterranean ant communities. This finding indicates that functional traits may modulate the responses of ant species to the environment. Since these traits act as the link between species distributions and the environment, they could potentially be used to predict community changes under future global change scenarios. PMID:24720700

Arnan, Xavier; Cerdá, Xim; Retana, Javier

2014-04-11

301

Mass-balance gradients and climatic change  

Microsoft Academic Search

It is generally assumed that the\\u000amass-balance gradient on glaciers is more or less conserved\\u000aunder climatic change. In studies of the dynamic response\\u000aof glaciers to climatic change, one of the following\\u000aassumptions is normally made: (i) the mass-balance\\u000aperturbation is independent of altitude or (ii) the\\u000amass-balance profile does not change - it simply shifts up\\u000aand down.

J. Oerlemans; N. C. Hoogendoorn

1989-01-01

302

New Techniques for Studying Calcium Gradients  

NASA Technical Reports Server (NTRS)

Improved techniques for detecting and manipulating spatial gradients of cytosolic free Ca(2+) concentrations (Ca(2)) sub i and intracellular stores are discussed. Three areas of progress are: (1) development of new fluorescent indicators for Ca(2+) that are the first to be suitable for measuring Ca(2+)) sub i and its inhomogeneities in individual cells; (2) invention of photolabile chelators which shift irreversibly from high to low affinity for Ca(2+) upon illumination, permitting light-controlled jumps in (Ca(2+)) sub i; and (3) fixation methods to trap dynamic intraorganellar Ca stores in a form readily visible by electron microscopy.

Tsien, R. Y.

1985-01-01

303

Unshielded gradient coils design for magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

One of the most important concepts for obtaining an image using MRI is the use of magnetic field gradients. There have been developed different techniques to improve the quality of the magnetic field gradients that allow high strength gradient fields that can be rapidly switched on and off for fast imaging modalities, large homogeneous-gradient-volume or minimum inductance. This work is focused on a comparison between two methods based in the target field method proposed by Turner to build cylindrical unshielded gradient coils. Carlson proposed a current distribution using a Fourier series for a coil of finite length (CAHM). Another solution was proposed by Chronik [4] that adds a set of current constraints forcing the current to lie over a certain length (CCMI). A transverse head gradient coil for imaging application has been implemented in the MATLAB software language and used to create a gradient coil using the CCMI and CAHM methods.

Hidalgo, S. S.; Gadzinski, C.; Rutt, B.

2012-10-01

304

Supply Chain Analysis Center for Transportation Analysis  

E-print Network

exchange and in-transit visibility; Security analysis for supply chains; Business case analysisSupply Chain Analysis Center for Transportation Analysis 2360 Cherahala Boulevard Knoxville, TN experience in supply chain analysis and automated support for supply chain systems. ORNL's Capabilities

305

Knowledge redundancy in supply chains: a framework  

Microsoft Academic Search

Knowledge redundancy is a powerful concept in understanding supply chain performance including supply chain value creation and competitive advantage. This paper argues that knowledge redundancy is not about “redundancy” that might suggest a waste or duplication of knowledge. In contrast, knowledge redundancy between adjacent members of the supply chain is critical to superior supply chain performance. The paper examines the

K. Sivakumar; Subroto Roy

2004-01-01

306

SUPPLY CHAIN MANAGEMENT RAWLS COLLEGE OF BUSINESS  

E-print Network

SUPPLY CHAIN MANAGEMENT RAWLS COLLEGE OF BUSINESS PROGRAM OVERVIEW AND PARTNERSHIP OPPORTUNITIES #12;INNOVATIVE CURRICULUM The Supply Chain Management Program offers an innovative curriculum which of basic supply chain management and the ability to effectively collaborate with other supply chain members

Westfall, Peter H.

307

Simulation for supply Chain management: An Overview  

E-print Network

Chapter 1 Simulation for supply Chain management: An Overview C. THIERRY, A. THOMAS, G. BEL 1.1. Supply chain management In this book we are concerned with the simulation for Supply Chain Management, strategic implications of the tactical activities involved in managing the various flows in a supply chain

Paris-Sud XI, Université de

308

Integrating environmental management and supply chain strategies  

Microsoft Academic Search

The decisions related to managing the supply chain and supply chain strategy are already considered important in many organizations. As more executives adopt envi- ronmental practices, supply chain strategies will only increase in importance. In this paper, we review how companies develop environmental supply chain strategies. Our interviews with companies from The United States, The United Kingdom, Japan and Korea,

Robert Handfield; Robert Sroufe; Steven Walton

2005-01-01

309

Marketing Risk Evaluation of Supply Chain  

Microsoft Academic Search

The supply chain enterprises are interdependent, and must work in coordination. Any problem that occurred in any link would influence the entire supply chain. Authors summarized the main marketing risk sources in the supply chain and constructed evaluation indicators. In the thesis, the risk causes in supply chain marketing are categorized as quantity causes and fuzzy causes, which are also

Liwei Zhang; Yan Chen; Fei Chen

2008-01-01

310

CALCULATING THE CARBON FOOTPRINT SUPPLY CHAIN FOR  

E-print Network

CALCULATING THE CARBON FOOTPRINT SUPPLY CHAIN FOR THE SEMICONDUCTOR INDUSTRY By: Yasser Dessouky #12;Carbon Footprint Supply Chain Carbon Trust defines carbon footprint of a supply chain as follows: "The carbon footprint of a product is the carbon dioxide emitted across the supply chain for a single

Su, Xiao

311

Quality in supply chains: an empirical analysis  

Microsoft Academic Search

Purpose – To analyze the state of supply chain quality management in manufacturing companies by testing several hypotheses regarding the knowledge these companies have about their different supply chain partners, the attributes that characterize customer-supplier relationships and the factors that determine the development of quality specifications in a supply chain, and the effect of supply chain quality management activities of

Ismail Sila; Maling Ebrahimpour; Christiane Birkholz

2006-01-01

312

ENABLING TECHNOLOGIES FOR SUPPLY CHAIN PROCESS MANAGEMENT  

Microsoft Academic Search

Supply chain management deals with the efficient coordination of enterprises along a value chain to provide goods and services to end users. While the operational and strategic aspects of supply chain management have been researched to some extent, one of the questions for enterprises is the management and controlling of supply chain operations on a tactical level. We discuss the

Roland Holten; Alexander Dreiling; Joerg Becker

2002-01-01

313

Data-driven backward chaining  

NASA Technical Reports Server (NTRS)

The C Language Integrated Production System (CLIPS) cannot effectively perform sound and complete logical inference in most real-world contexts. The problem facing CLIPS is its lack of goal generation. Without automatic goal generation and maintenance, forward chaining can only deduce all instances of a relationship. Backward chaining, which requires goal generation, allows deduction of only that subset of what is logically true which is also relevant to ongoing problem solving. Goal generation can be mimicked in simple cases using forward chaining. However, such mimicry requires manual coding of additional rules which can assert an inadequate goal representation for every condition in every rule that can have corresponding facts derived by backward chaining. In general, for N rules with an average of M conditions per rule the number of goal generation rules required is on the order of N*M. This is clearly intractable from a program maintenance perspective. We describe the support in Eclipse for backward chaining which it automatically asserts as it checks rule conditions. Important characteristics of this extension are that it does not assert goals which cannot match any rule conditions, that 2 equivalent goals are never asserted, and that goals persist as long as, but no longer than, they remain relevant.

Haley, Paul

1991-01-01

314

Stellar population gradients in early-type cluster galaxies  

NASA Astrophysics Data System (ADS)

We present a study of internal stellar population gradients in early-type cluster galaxies. Using the Very Large Telescope (VLT) Visible Multi-Object Spectrograph (VIMOS) integral field unit, we observed 19 galaxies in the core of the Shapley supercluster (z = 0.048). The radial trends in nine absorption lines (H?F to Fe5406) were measured to the effective radius for 14 galaxies, from which we derived the gradients in age, total metallicity and ?-element overabundance. We combine these with results from 11 galaxies studied in our previous VIMOS work. We observe a mean metallicity gradient of -0.13 +/- 0.04dex-1 and, in common with the findings of previous studies, galaxies with log? >~ 2.1 have a sizeable intrinsic scatter in metallicity gradient. The mean log(age/Gyr) gradient is -0.02 +/- 0.06dex-1, although several galaxies have significant positive or negative age gradients. The mean gradient in ?-element enhancement is -0.10 +/- 0.04dex-1. We find that stellar population gradients are primarily related to the central metallicity: early-type galaxies with supersolar centres have steep negative metallicity gradients and positive age gradients; those with solar metallicity centres have negligible [Z/H] gradients and negative age gradients. There is a strong observed anticorrelation between the gradients in age and metallicity. While a part of this trend can be attributed to the correlation of measurement errors, we demonstrate that there is an underlying intrinsic relation. For the Shapley galaxies, B - R colour gradients predicted from spectroscopic age and metallicity generally agree well with those measured directly from photometry. Based on observations from the European Organisation for Astronomical Research in the Southern Hemisphere, Chile (programmes: 078.B-0539, 081.B-0539). E-mail: t.d.rawle@durham.ac.uk

Rawle, T. D.; Smith, Russell J.; Lucey, J. R.

2010-01-01

315

GradientOptimizer: an open-source graphical environment for calculating optimized gradients in reversed-phase liquid chromatography.  

PubMed

We here present GradientOptimizer, an intuitive, lightweight graphical user interface to design nonlinear gradients for separation of peptides by reversed-phase liquid chromatography. The software allows to calculate three types of nonlinear gradients, each of them optimizing a certain retention time distribution of interest. GradientOptimizer is straightforward to use, requires minimum processing of the input files, and is supported under Windows, Linux, and OS X platforms. The software is open-source and can be downloaded under an Apache 2.0 license at https://github.com/statisticalbiotechnology/NonlinearGradientsUI. PMID:24700534

Moruz, Luminita; Käll, Lukas

2014-06-01

316

Food web complexity and stability across habitat connectivity gradients.  

PubMed

The effects of habitat connectivity on food webs have been studied both empirically and theoretically, yet the question of whether empirical results support theoretical predictions for any food web metric other than species richness has received little attention. Our synthesis brings together theory and empirical evidence for how habitat connectivity affects both food web stability and complexity. Food web stability is often predicted to be greatest at intermediate levels of connectivity, representing a compromise between the stabilizing effects of dispersal via rescue effects and prey switching, and the destabilizing effects of dispersal via regional synchronization of population dynamics. Empirical studies of food web stability generally support both this pattern and underlying mechanisms. Food chain length has been predicted to have both increasing and unimodal relationships with connectivity as a result of predators being constrained by the patch occupancy of their prey. Although both patterns have been documented empirically, the underlying mechanisms may differ from those predicted by models. In terms of other measures of food web complexity, habitat connectivity has been empirically found to generally increase link density but either reduce or have no effect on connectance, whereas a unimodal relationship is expected. In general, there is growing concordance between empirical patterns and theoretical predictions for some effects of habitat connectivity on food webs, but many predictions remain to be tested over a full connectivity gradient, and empirical metrics of complexity are rarely modeled. Closing these gaps will allow a deeper understanding of how natural and anthropogenic changes in connectivity can affect real food webs. PMID:25227679

LeCraw, Robin M; Kratina, Pavel; Srivastava, Diane S

2014-12-01

317

Achieving consumer focus in supply chains  

Microsoft Academic Search

Purpose – Supply chain performance is two-dimensional: efficiency and effectiveness. The purpose of this paper is to further define and explore the demarcation between supply chain effectiveness and supply chain efficiency. Design\\/methodology\\/approach – A case-study research method is adopted in this paper. This contribution discusses an approach for the improvement of supply chain effectiveness, i.e. Supply Chain Kano-QFD. Findings –

Keivan Zokaei; Peter Hines

2007-01-01

318

Parallelism in planar kinematic chains (manipulators)  

Microsoft Academic Search

Parallelism is an important characteristic of closed kinematic chains particularly for chains with degrees-of-freedom (d.o.f.) greater than one since such chains can be considered for application as robot manipulators. For specified number of links and d.o.f. there exists a large number of distinct chains and hence the designer should have a clue to select the best possible chain for the

A. C. Rao

2004-01-01

319

Asymmetric Uncertainty Expression for High Gradient Aerodynamics  

NASA Technical Reports Server (NTRS)

When the physics of the flow around an aircraft changes very abruptly either in time or space (e.g., flow separation/reattachment, boundary layer transition, unsteadiness, shocks, etc), the measurements that are performed in a simulated environment like a wind tunnel test or a computational simulation will most likely incorrectly predict the exact location of where (or when) the change in physics happens. There are many reasons for this, includ- ing the error introduced by simulating a real system at a smaller scale and at non-ideal conditions, or the error due to turbulence models in a computational simulation. The un- certainty analysis principles that have been developed and are being implemented today do not fully account for uncertainty in the knowledge of the location of abrupt physics changes or sharp gradients, leading to a potentially underestimated uncertainty in those areas. To address this problem, a new asymmetric aerodynamic uncertainty expression containing an extra term to account for a phase-uncertainty, the magnitude of which is emphasized in the high-gradient aerodynamic regions is proposed in this paper. Additionally, based on previous work, a method for dispersing aerodynamic data within asymmetric uncer- tainty bounds in a more realistic way has been developed for use within Monte Carlo-type analyses.

Pinier, Jeremy T

2012-01-01

320

Microtextured surfaces with gradient wetting properties.  

PubMed

Patterned surfaces with microwrinkled surface structures were prepared by thermally evaporating thin aluminum (10-300 nm thick) (Al) layers onto thick prestrained layers of a silicone elastomer and subsequently releasing the strain. This resulted in the formation of sinusoidal periodic surface wrinkles with characteristic wavelengths in the 3-42 ?m range and amplitudes as large as 3.6 ± 0.4 ?m. The Al thickness dependence of the wrinkle wavelengths and amplitudes was determined for different values of the applied prestrain and compared to a recent large-amplitude deflection theory of wrinkle formation. The results were found to be in good agreement with theory. Samples with spatial gradients in wrinkle wavelength and amplitude were also produced by applying mechanical strain gradients to the silicone elastomer layers prior to deposition of the Al capping layers. Sessile water droplets that were placed on these surfaces were found to have contact angles that were dependent upon their position. Moreover, these samples were shown to direct the motion of small water droplets when the substrates were vibrated. PMID:21028810

Langley, Kevin R; Sharp, James S

2010-12-01

321

The phenotypic variance gradient – a novel concept  

PubMed Central

Evolutionary ecologists commonly use reaction norms, which show the range of phenotypes produced by a set of genotypes exposed to different environments, to quantify the degree of phenotypic variance and the magnitude of plasticity of morphometric and life-history traits. Significant differences among the values of the slopes of the reaction norms are interpreted as significant differences in phenotypic plasticity, whereas significant differences among phenotypic variances (variance or coefficient of variation) are interpreted as differences in the degree of developmental instability or canalization. We highlight some potential problems with this approach to quantifying phenotypic variance and suggest a novel and more informative way to plot reaction norms: namely “a plot of log (variance) on the y-axis versus log (mean) on the x-axis, with a reference line added”. This approach gives an immediate impression of how the degree of phenotypic variance varies across an environmental gradient, taking into account the consequences of the scaling effect of the variance with the mean. The evolutionary implications of the variation in the degree of phenotypic variance, which we call a “phenotypic variance gradient”, are discussed together with its potential interactions with variation in the degree of phenotypic plasticity and canalization. PMID:25540685

Pertoldi, Cino; Bundgaard, Jørgen; Loeschcke, Volker; Barker, James Stuart Flinton

2014-01-01

322

Gradient navigation model for pedestrian dynamics  

NASA Astrophysics Data System (ADS)

We present a microscopic ordinary differential equation (ODE)-based model for pedestrian dynamics: the gradient navigation model. The model uses a superposition of gradients of distance functions to directly change the direction of the velocity vector. The velocity is then integrated to obtain the location. The approach differs fundamentally from force-based models needing only three equations to derive the ODE system, as opposed to four in, e.g., the social force model. Also, as a result, pedestrians are no longer subject to inertia. Several other advantages ensue: Model-induced oscillations are avoided completely since no actual forces are present. The derivatives in the equations of motion are smooth and therefore allow the use of fast and accurate high-order numerical integrators. At the same time, the existence and uniqueness of the solution to the ODE system follow almost directly from the smoothness properties. In addition, we introduce a method to calibrate parameters by theoretical arguments based on empirically validated assumptions rather than by numerical tests. These parameters, combined with the accurate integration, yield simulation results with no collisions of pedestrians. Several empirically observed system phenomena emerge without the need to recalibrate the parameter set for each scenario: obstacle avoidance, lane formation, stop-and-go waves, and congestion at bottlenecks. The density evolution in the latter is shown to be quantitatively close to controlled experiments. Likewise, we observe a dependence of the crowd velocity on the local density that compares well with benchmark fundamental diagrams.

Dietrich, Felix; Köster, Gerta

2014-06-01

323

Pumpernickel Valley Geothermal Project Thermal Gradient Wells  

SciTech Connect

The Pumpernickel Valley geothermal project area is located near the eastern edge of the Sonoma Range and is positioned within the structurally complex Winnemucca fold and thrust belt of north-central Nevada. A series of approximately north-northeast-striking faults related to the Basin and Range tectonics are superimposed on the earlier structures within the project area, and are responsible for the final overall geometry and distribution of the pre-existing structural features on the property. Two of these faults, the Pumpernickel Valley fault and Edna Mountain fault, are range-bounding and display numerous characteristics typical of strike-slip fault systems. These characteristics, when combined with geophysical data from Shore (2005), indicate the presence of a pull-apart basin, formed within the releasing bend of the Pumpernickel Valley – Edna Mountain fault system. A substantial body of evidence exists, in the form of available geothermal, geological and geophysical information, to suggest that the property and the pull-apart basin host a structurally controlled, extensive geothermal field. The most evident manifestations of the geothermal activity in the valley are two areas with hot springs, seepages, and wet ground/vegetation anomalies near the Pumpernickel Valley fault, which indicate that the fault focuses the fluid up-flow. There has not been any geothermal production from the Pumpernickel Valley area, but it was the focus of a limited exploration effort by Magma Power Company. In 1974, the company drilled one exploration/temperature gradient borehole east of the Pumpernickel Valley fault and recorded a thermal gradient of 160oC/km. The 1982 temperature data from five unrelated mineral exploration holes to the north of the Magma well indicated geothermal gradients in a range from 66 to 249oC/km for wells west of the fault, and ~283oC/km in a well next to the fault. In 2005, Nevada Geothermal Power Company drilled four geothermal gradient wells, PVTG-1, -2, -3, and -4, and all four encountered geothermal fluids. The holes provided valuable water geochemistry, supporting the geothermometry results obtained from the hot springs and Magma well. The temperature data gathered from all the wells clearly indicates the presence of a major plume of thermal water centered on the Pumpernickel Valley fault, and suggests that the main plume is controlled, at least in part, by flow from this fault system. The temperature data also defines the geothermal resource with gradients >100oC/km, which covers an area a minimum of 8 km2. Structural blocks, down dropped with respect to the Pumpernickel Valley fault, may define an immediate reservoir. The geothermal system almost certainly continues beyond the recently drilled holes and might be open to the east and south, whereas the heat source responsible for the temperatures associated with this plume has not been intersected and must be at a depth greater than 920 meters (depth of the deepest well – Magma well). The geological and structural setting and other characteristics of the Pumpernickel Valley geothermal project area are markedly similar to the portions of the nearby Dixie Valley geothermal field. These similarities include, among others, the numerous, unexposed en echelon faults and large-scale pull-apart structure, which in Dixie Valley may host part of the geothermal field. The Pumpernickel Valley project area, for the majority of which Nevada Geothermal Power Company has geothermal rights, represents a geothermal site with a potential for the discovery of a relatively high temperature reservoir suitable for electric power production. Among locations not previously identified as having high geothermal potential, Pumpernickel Valley has been ranked as one of four sites with the highest potential for electrical power production in Nevada (Shevenell and Garside, 2003). Richards and Blackwell (2002) estimated the total heat loss and the preliminary production capacity for the entire Pumpernickel Valley geothermal system to be at 35MW. A more conservative estimate, for

Z. Adam Szybinski

2006-01-01

324

Determinants of protein side-chain packing.  

PubMed

The problem of protein side-chain packing for a given backbone trace is investigated using 3 different prediction models. The first requires an exhaustive search of all possible combinations of side-chain conformers, using the dead-end elimination theorem. The second considers only side-chain-backbone interactions, whereas the third neglects side-chain-backbone interactions and instead keeps side-chain-side-chain interactions. Predictions of side-chain conformations for 11 proteins using all 3 models show that removal of side-chain-side-chain interactions does not cause a large decrease in the prediction accuracy, whereas the model having only side-chain-side-chain interactions still retains a significant level of accuracy. These results suggest that the 2 classes of interactions, side-chain-backbone and side-chain-side-chain, are consistent with each other and work concurrently to stabilize the native conformations. This is confirmed by analyses of energy spectra of the side-chain conformations derived from the fourth prediction model, the Independent model, which gives almost the same quality of the prediction as the dead-end elimination. The analyses indicate that the 2 classes of interactions simultaneously increase the energy difference between the native and nonnative conformations. PMID:7756990

Tanimura, R; Kidera, A; Nakamura, H

1994-12-01

325

Temperature gradients, not food resource gradients, affect growth rate of migrating Daphnia mendotae in Lake Michigan  

Microsoft Academic Search

Zooplankton production plays a critical role in the Great Lakes ecosystem, and vertical migration, which is exhibited by many zooplankton species, could affect production. We examined the effects of water temperature and food resource gradients on the growth rate of zooplankton undergoing vertical migration in Lake Michigan. In three laboratory experiments, juvenile Daphnia mendotae, native herbivorous cladocerans, were incubated for

Kevin L. Pangle; Scott D. Peacor

2010-01-01

326

Differential evolution Markov chain with snooker updater and fewer chains  

SciTech Connect

Differential Evolution Markov Chain (DE-MC) is an adaptive MCMC algorithm, in which multiple chains are run in parallel. Standard DE-MC requires at least N=2d chains to be run in parallel, where d is the dimensionality of the posterior. This paper extends DE-MC with a snooker updater and shows by simulation and real examples that DE-MC can work for d up to 50--100 with fewer parallel chains (e.g. N=3) by exploiting information from their past by generating jumps from differences of pairs of past states. This approach extends the practical applicability of DE-MC and is shown to be about 5--26 times more efficient than the optimal Normal random walk Metropolis sampler for the 97.5% point of a variable from a 25--50 dimensional Student T{sub 3} distribution. In a nonlinear mixed effects model example the approach outperformed a block-updater geared to the specific features of the model.

Vrugt, Jasper A [Los Alamos National Laboratory; Ter Braak, Cajo J F [NON LANL

2008-01-01

327

Reconciling supply chain vulnerability, risk and supply chain management  

Microsoft Academic Search

Supply chain vulnerability has become a fashionable area of management research. The purpose of this paper is to provide a critique of the extant canon and to review of the positioning of research in the field, together with literature drawn from several relevant and overlapping fields of research and practice. The aim is to foster a more explicit understanding of

H. Peck

2006-01-01

328

Tunnel magnetoresistance of polymeric chains  

E-print Network

Coherent spin-dependent electronic transport is investigated in a molecular junction made of polymeric chain attached to ferromagnetic electrodes (Ni and Co, respectively). Molecular system is described by a simple Huckel model, while the coupling to the electrodes is treated through the use of a broad-band theory. The current flowing through the device is calculated within non-equilibrium Green's function approach. It is shown that tunnel magnetoresistance of molecular junction can be quite large (over 100 %)and strongly depends on: (i) the lenght of the polymeric chain and (ii) the strength of the molecule-to-electrodes coupling.

Kamil Walczak

2004-10-25

329

Gradients of meteorological parameters in convective and nonconvective areas  

NASA Technical Reports Server (NTRS)

Horizontal gradients of geopotential height, temperature, and wind speed were computed at the 850-, 700-, 500-, and 200-mb levels. Mixing ratio gradients also were computed, but only for the 850-, 700-, and 500-mb levels. Rawinsonde data was provided at 3- to 6-h intervals. Cumulative frequency distributions and statistical parameters showed that the variability and magnitude of the gradients decreased as the gradients were computed over progressively longer distances. Most frequency distributions were positively skewed, and the standard deviations of the gradient distributions were roughly half as large as the means. An examination of the differences of gradients observed in convective and nonconvective areas was made after convective areas were determined objectively using Manually Digitized Radar data. The gradients of height, wind speed, and mixing ratio at 850 mb were larger in convective than nonconvective areas. No general relationship held for the meteorological variables at other levels. Intensive examination of the gradients observed near squall lines revealed typical gradient patterns and trends in the magnitudes of the gradients associated with convective systems.

Mccown, M. S.; Scoggins, J. R.

1977-01-01

330

Progress in protein-protein docking: Atomic resolution predictions in the CAPRI experiment using RosettaDock with an improved treatment of side-chain flexibility  

Microsoft Academic Search

RosettaDock uses real-space Monte Carlo minimization (MCM) on both rigid-body and side-chain degrees of freedom to identify the lowest free energy docked arrangement of 2 protein struc- tures. An improved version of the method that uses gradient-based minimization for off-rotamer side- chain optimization and includes information from unbound structures was used to create predictions for Rounds 4 and 5 of

Ora Schueler-Furman; Chu Wang; David Baker

2005-01-01

331

GTEx Chain of Custody Form  

Cancer.gov

GTEx Chain of Custody Form OP-0002-F1 VER. 1.0.1 Effective Date: 08/30/2011 Page 1 of 3 Note: If this is the last part of the form you are completing at this time, please send the form to Study Management Group. Be sure to include the Specimen and

332

Remarks on food chain dynamics  

Microsoft Academic Search

The main modes of behavior of a food chain model, composed of logistic prey and Holling type II predator and superpredator, are discussed in this paper. The study is carried out through bifurcation analysis, alternating between a normal form approach and numerical continuation. The two-parameter bifurcation diagram of the model contains Hopf, fold and transcritical bifurcation curves of equilibria as

Yu. a. Kuznetsov; S. Rinaldi

1995-01-01

333

Remarks on food chain dynamics  

Microsoft Academic Search

The main modes of behavior of a food chain model composed of logistic prey and Holling type II predator and superpredator are discussed in this paper. The study is carried out through bifurcation analysis, alternating between a normal form approach and numerical continuation. The two-parameter bifurcation diagram of the model contains Hopf, fold, and transcritical bifurcation curves of equilibria as

S Rinaldi

1996-01-01

334

The causal chain of loyalty  

Microsoft Academic Search

Loyalty is considered as a key concept in the establishment and maintenance of long term relationships. In this work in progress communication, a theoretical framework is proposed on the basis of the relationship marketing paradigm and commitment trust theory. Loyalty is conceived according to Oliver (1997) as a causal chain composed by cognitive loyalty, affective loyalty, conative loyalty and action

Manel KHADRAOUI; Jamel-Eddine GHARBI; Michel Plaisent

335

Spin chains and string theory  

Microsoft Academic Search

Recently, an impressive agreement was found between anomalous dimen- sions of certain operators in N = 4 SYM and rotating strings with two angular mo- menta in the bulk of AdS5 × S5. A one-loop field theory computation, which involves solving a Heisenberg chain by means of the Bethe ansatz agrees with the large angular momentum limit of a rotating

Martin Kruczenski

336

SUPPLY CHAIN MANAGER CHICAGO, IL  

E-print Network

developing new technology to meet the ever-changing demands of modern industry. The US Headquarters of the organization. Educational credentials should include a degree in logistics, supply chain, industrial lubricants and services to a wide range of industries including the makers of complex metal components

Smilowitz, Karen

337

Measuring supply chain management practices  

Microsoft Academic Search

Purpose – This paper aims to perform an empirical investigation about the constructs and indicators of the supply chain management practices framework. Design\\/methodology\\/approach – The measuring framework proposed is based on a survey that was carried out on 107 Brazilian companies. Statistical techniques were employed to verify, validate, and test the reliability of the constructs and their indicators. To validate

Ana Beatriz Lopes de Sousa Jabbour; Alceu Gomes Alves Filho; Adriana Backx Noronha Viana; Charbel José Chiappetta Jabbour

2011-01-01

338

Determination of gradient elastic tensors: stress and strain dependencies of electric field gradients in cubic and hexagonal systems  

NASA Astrophysics Data System (ADS)

We present ab-initio calculations of the independent components of gradient elastic tensors, so-called gradient elastic constants, which relate electric field gradient tensors to stress or strain tensors. The constants of cubic and hexagonal metals, MAX phases, and zinc oxide were determined within the framework of density functional theory by using the augmented plane waves plus local orbitals method implemented in the WIEN2k code. Comparison with experimental gradient elastic constants and electric field gradients' stress dependencies suggest an accuracy of about 30% of the calculated constants, independent of the probe that detects the field gradient being self- or foreign-atom. Changes in the electric field gradient take place by strain-induced asymmetric occupations of the p and d states in the valence region for all investigated materials. Volume and structural dependencies of the electric field gradient can directly be determined from this fundamental approach and are, for hexagonal closed packed metals, consistent with vanishing electric field gradients around ideal close packing and volume dependencies larger than one. The concept of these calculations is applicable in any hyperfine interaction method and, thus, can be used to gain information about intrinsic strains in systems where the experimental gradient elastic constants are inaccessible.

Brüsewitz, C.; Vetter, U.; Hofsäss, H.

2015-02-01

339

Gradient calculation of the traveltime cost function without ray tracing  

SciTech Connect

Gradient based traveltime tomography algorithms require the computation of the gradient of the traveltime misfit cost function many times. This calculation is customarily done by ray tracing, the path length of the rays being closely related to the gradient. The authors propose in this work an alternative method to compute the gradient of the traveltime cost function without ray tracing. They use upwind finite difference schemes to compute the traveltime field by solving the eikonal equation. Then by adjoint state techniques they derive a closed-form expression of the gradient of the traveltime cost function. This approach allows an accurate computation of the gradient as well as the freedom to change the norm on the model space.

Sei, A.; Symes, W.W. [Rice Univ., Houston, TX (United States)

1994-12-31

340

Thermoacoustic mixture separation with an axial temperature gradient  

SciTech Connect

The theory of thermoacoustic mixture separation is extended to include the effect of a nonzero axial temperature gradient. The analysis yields a new term in the second-order mole flux that is proportional to the temperature gradient and to the square of the volumetric velocity and is independent of the phasing of the wave. Because of this new term, thermoacoustic separation stops at a critical temperature gradient and changes direction above that gradient. For a traveling wave, this gradient is somewhat higher than that predicted by a simple four-step model. An experiment tests the theory for temperature gradients from 0 to 416 K/m in 50-50 He-Ar mixtures.

Geller, Drew W [Los Alamos National Laboratory; Swift, Gregory A [Los Alamos National Laboratory

2008-01-01

341

RRab Lyrae metallicity gradient in the Galactic bulge  

NASA Astrophysics Data System (ADS)

Aims: We revisit the presence and significance of the Galactic bulge metallicity gradients, using the OGlE-III RR Lyrae sample. Methods: We implemented a Monte Carlo simulation to account for observational uncertainties and systematic errors to test the presence, significance, and spatial variation of RR Lyr photometric metallicity gradients within the Galactic bulge. Furthermore, we take special consideration to identify and account for possible observational and statistical biases, which may introduce an apparent metallicity gradient into the sample. Results: We find a mean Galactic bulge RRab metallicity of -0.97 ± 0.29 dex, a global radial metallicity gradient of -0.016 ± 0.008 dex Kpc-1, and a global vertical metallicity gradient of -0.063 ± 0.013 dex Kpc-1. Furthermore, neither the global radial nor vertical gradients can be explained by random chance, unjustified extrapolation of the metallicity calibration law, or induced by a Malmquist bias.

Sans Fuentes, S. A.; De Ridder, J.

2014-11-01

342

Gravity gradient-terrain aided navigation based on particle filter  

NASA Astrophysics Data System (ADS)

Based on Particle Filter, Gravity Gradient-Terrain aided position technology is proposed in this paper. With the sensitivity of gravity gradient to terrain, the gravity gradient reference map can be computed from the local terrain elevation data. The position can be actualized through matching the real-time measured gravity gradient data to the prepared gravity gradient reference map. The most widely used approximate filtering method is the extended Kaman filter (EKF). EKF is computationally simple but, the convergence of the state estimation for the position is not guaranteed. Particle filter (PF) makes use of the non-linear state and measurement functions, no linearization technology is needed. PF can assure the convergence of the state estimation which follows from the classical results on convergence of Bayesian estimators. Simulations have been done and Particle filter has been shown to be a superior alternative to the EKF in the gravity gradient-terrain matching navigation systems.

Xiong, Ling; Ma, Jie; Tian, Jin-Wen

2009-10-01

343

Convection driven generation of long-range material gradients  

PubMed Central

Natural materials exhibit anisotropy with variations in soluble factors, cell distribution, and matrix properties. The ability to recreate the heterogeneity of the natural materials is a major challenge for investigating cell-material interactions and for developing biomimetic materials. Here we present a generic fluidic approach using convection and alternating flow to rapidly generate multi-centimeter gradients of biomolecules, polymers, beads and cells and cross-gradients of two species in a microchannel. Accompanying theoretical estimates and simulations of gradient growth provide design criteria over a range of material properties. A poly(ethyleneglycol) hydrogel gradient, a porous collagen gradient and a composite material with a hyaluronic acid/gelatin cross-gradient were generated with continuous variations in material properties and in their ability to regulate cellular response. This simple yet generic fluidic platform should prove useful for creating anisotropic biomimetic materials and high-throughput platforms for investigating cell-microenvironment interaction. PMID:20035990

Du, Yanan; Hancock, Matthew J.; He, Jiankang; Villa-Uribe, Jose; Wang, Ben; Cropek, Donald M.; Khademhosseini, Ali

2009-01-01

344

High Gradient Wakefields in Dielectric Loaded Structures  

SciTech Connect

Dielectric loaded wakefield structures have potential to be used as high gradient accelerator components. Using the high current drive beam at the Argonne Wakefield Accelerator Facility, we employed cylindrical dielectric loaded wakefield structures to generate accelerating fields of up to 86 MV/m, at 10 GHz. Short electron bunches of up to 86 nC are used to drive these fields, either as single bunches or as bunch trains. The structures consist of cylindrical ceramic tubes (cordierite) with a dielectric constant of 4.76, inserted into cylindrical copper waveguides. These standing-wave structures have a field probe near the outer diameter of the dielectric, in order to sample the RF fields generated by the electron bunches. Monitoring the field probe signal serves to verify the absence of electric breakdown in the structures. MAFIA simulations are used to calculate the amplitude of the fields generated by the traversing electrons bunches.

Conde, M. E.; Franchini, F.; Gai, W.; Konecny, R.; Liu, W.; Power, J. G.; Yusof, Z. [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Antipov, S.; Gao, F.; Wang, H. [Illinois Institute of Technology, 3300 South Federal Street, Chicago, IL 60616 (United States); Jing, C. [Euclid TechLabs, 5900 Harper Road, Solon, OH 44139 (United States)

2006-11-27

345

Constant field gradient planar cavity structure  

SciTech Connect

A cavity structure is described having at least two opposing planar housing members spaced apart to accommodate the passage of a particle beam through the structure between the members. Each of the housing members have a plurality of serially aligned hollows defined therein, and also passages, formed in the members, which interconnect serially adjacent hollows to provide communication between the hollows. The opposing planar housing members are spaced and aligned such that the hollows in one member cooperate with corresponding hollows in the other member to form a plurality of resonant cavities aligned along the particle beam within the cavity structure. To facilitate the obtaining of a constant field gradient within the cavity structure, the passages are configured so as to be incrementally narrower in the direction of travel of the particle beam. In addition, the spacing distance between the opposing housing members is configured to be incrementally smaller in the direction of travel of the beam.

Kang, Yoon W.; Kustom, R.L.

1997-12-01

346

Constant field gradient planar coupled cavity structure  

DOEpatents

A cavity structure having at least two opposing planar housing members spaced apart to accommodate the passage of a particle beam through the structure between the members. Each of the housing members have a plurality of serially aligned hollows defined therein, and also passages, formed in the members, which interconnect serially adjacent hollows to provide communication between the hollows. The opposing planar housing members are spaced and aligned such that the hollows in one member cooperate with corresponding hollows in the other member to form a plurality of resonant cavities aligned along the particle beam within the cavity structure. To facilitate the obtaining of a constant field gradient within the cavity structure, the passages are configured so as to be incrementally narrower in the direction of travel of the particle beam. In addition, the spacing distance between the opposing housing members is configured to be incrementally smaller in the direction of travel of the beam.

Kang, Yoon W. (Naperville, IL); Kustom, Robert L. (Oswego, IL)

1999-01-01

347

Implications of Abundance Gradients in Intracluster Gas  

E-print Network

Analysis of spatially resolved ASCA spectra of the intracluster gas in Abell 496 confirms that metal abundances increase toward the center. We also find spatial gradients in several abundance ratios, indicating that the fraction of iron from SN Ia increases toward the cluster center. The dominant metal enrichment mechanism near the cluster center must therefore be different than in the outer parts. We show that ram pressure stripping of gas from cluster galaxies cannot account for the central abundance enhancement. We suggest that two successive stages of galactic winds contaminate intracluster gas: protogalactic winds driven by SN II, followed by less energetic winds driven by SN Ia, which have longer lived progenitors than SN II. The less energetic secondary wind from a cD galaxy may be suppressed, due to its location at the cluster center, leading to the observed central enhancement of SN Ia ejecta.

Raymond E. White III; Renato A. Dupke

2000-01-18

348

Molecular evolution and the latitudinal biodiversity gradient.  

PubMed

Species density is higher in the tropics (low latitude) than in temperate regions (high latitude) resulting in a latitudinal biodiversity gradient (LBG). The LBG must be generated by differential rates of speciation and/or extinction and/or immigration among regions, but the role of each of these processes is still unclear. Recent studies examining differences in rates of molecular evolution have inferred a direct link between rate of molecular evolution and rate of speciation, and postulated these as important drivers of the LBG. Here we review the molecular genetic evidence and examine the factors that might be responsible for differences in rates of molecular evolution. Critical to this is the directionality of the relationship between speciation rates and rates of molecular evolution. PMID:23486082

Dowle, E J; Morgan-Richards, M; Trewick, S A

2013-06-01

349

Molecular evolution and the latitudinal biodiversity gradient  

PubMed Central

Species density is higher in the tropics (low latitude) than in temperate regions (high latitude) resulting in a latitudinal biodiversity gradient (LBG). The LBG must be generated by differential rates of speciation and/or extinction and/or immigration among regions, but the role of each of these processes is still unclear. Recent studies examining differences in rates of molecular evolution have inferred a direct link between rate of molecular evolution and rate of speciation, and postulated these as important drivers of the LBG. Here we review the molecular genetic evidence and examine the factors that might be responsible for differences in rates of molecular evolution. Critical to this is the directionality of the relationship between speciation rates and rates of molecular evolution. PMID:23486082

Dowle, E J; Morgan-Richards, M; Trewick, S A

2013-01-01

350

High gradient lens for charged particle beam  

DOEpatents

Methods and devices enable shaping of a charged particle beam. A dynamically adjustable electric lens includes a series of alternating a series of alternating layers of insulators and conductors with a hollow center. The series of alternating layers when stacked together form a high gradient insulator (HGI) tube to allow propagation of the charged particle beam through the hollow center of the HGI tube. A plurality of transmission lines are connected to a plurality of sections of the HGI tube, and one or more voltage sources are provided to supply an adjustable voltage value to each transmission line of the plurality of transmission lines. By changing the voltage values supplied to each section of the HGI tube, any desired electric field can be established across the HGI tube. This way various functionalities including focusing, defocusing, acceleration, deceleration, intensity modulation and others can be effectuated on a time varying basis.

Chen, Yu-Jiuan

2014-04-29

351

Transformational acoustic metamaterials based on pressure gradients  

E-print Network

We apply a homogenization process to the acoustic velocity potential wave equation. The study of various examples shows that the resulting effective properties are different from those of the homogenized pressure wave equation for the same underlying acoustic parameters. A careful analysis reveals that a given set of inhomogeneous parameters represents an entirely different physical system depending on the considered equation. Our findings unveil a different way of tailoring acoustic properties through gradients of the static pressure. In contrast to standard metafluids based on isobaric composites, this alternative kind of metafluids is suitable for the implementation of transformational devices designed via the velocity potential equation. This includes acoustic systems in a moving background or arising from general space-time transformations. As an example, we design a device able to cloak the acoustic velocity potential.

C. García-Meca; S. Carloni; C. Barceló; G. Jannes; J. Sánchez-Dehesa; A. Martínez

2014-09-18

352

Constant field gradient planar coupled cavity structure  

DOEpatents

A cavity structure is disclosed having at least two opposing planar housing members spaced apart to accommodate the passage of a particle beam through the structure between the members. Each of the housing members have a plurality of serially aligned hollows defined therein, and also passages, formed in the members, which interconnect serially adjacent hollows to provide communication between the hollows. The opposing planar housing members are spaced and aligned such that the hollows in one member cooperate with corresponding hollows in the other member to form a plurality of resonant cavities aligned along the particle beam within the cavity structure. To facilitate the obtaining of a constant field gradient within the cavity structure, the passages are configured so as to be incrementally narrower in the direction of travel of the particle beam. In addition, the spacing distance between the opposing housing members is configured to be incrementally smaller in the direction of travel of the beam. 16 figs.

Kang, Y.W.; Kustom, R.L.

1999-07-27

353

High-gradient compact linear accelerator  

DOEpatents

A high-gradient linear accelerator comprises a solid-state stack in a vacuum of five sets of disc-shaped Blumlein modules each having a center hole through which particles are sequentially accelerated. Each Blumlein module is a sandwich of two outer conductive plates that bracket an inner conductive plate positioned between two dielectric plates with different thicknesses and dielectric constants. A third dielectric core in the shape of a hollow cylinder forms a casing down the series of center holes, and it has a dielectric constant different that the two dielectric plates that sandwich the inner conductive plate. In operation, all the inner conductive plates are charged to the same DC potential relative to the outer conductive plates. Next, all the inner conductive plates are simultaneously shorted to the outer conductive plates at the outer diameters. The signal short will propagate to the inner diameters at two different rates in each Blumlein module. A faster wave propagates quicker to the third dielectric core across the dielectric plates with the closer spacing and lower dielectric constant. When the faster wave reaches the inner extents of the outer and inner conductive plates, it reflects back outward and reverses the field in that segment of the dielectric core. All the field segments in the dielectric core are then in unipolar agreement until the slower wave finally propagates to the third dielectric core across the dielectric plates with the wider spacing and higher dielectric constant. During such unipolar agreement, particles in the core are accelerated with gradients that exceed twenty megavolts per meter. 10 figs.

Carder, B.M.

1998-05-26

354

High-gradient compact linear accelerator  

DOEpatents

A high-gradient linear accelerator comprises a solid-state stack in a vacuum of five sets of disc-shaped Blumlein modules each having a center hole through which particles are sequentially accelerated. Each Blumlein module is a sandwich of two outer conductive plates that bracket an inner conductive plate positioned between two dielectric plates with different thicknesses and dielectric constants. A third dielectric core in the shape of a hollow cylinder forms a casing down the series of center holes, and it has a dielectric constant different that the two dielectric plates that sandwich the inner conductive plate. In operation, all the inner conductive plates are charged to the same DC potential relative to the outer conductive plates. Next, all the inner conductive plates are simultaneously shorted to the outer conductive plates at the outer diameters. The signal short will propagate to the inner diameters at two different rates in each Blumlein module. A faster wave propagates quicker to the third dielectric core across the dielectric plates with the closer spacing and lower dielectric constant. When the faster wave reaches the inner extents of the outer and inner conductive plates, it reflects back outward and reverses the field in that segment of the dielectric core. All the field segments in the dielectric core are then in unipolar agreement until the slower wave finally propagates to the third dielectric core across the dielectric plates with the wider spacing and higher dielectric constant. During such unipolar agreement, particles in the core are accelerated with gradients that exceed twenty megavolts per meter.

Carder, Bruce M. (205 Rogue River Hwy., Gold Hill, OR 97525)

1998-01-01

355

Velocity prediction in high-gradient channels  

NASA Astrophysics Data System (ADS)

SummaryIn 15 mountain stream reaches containing instream wood, we characterized velocity and flow resistance at bankfull through low flows. These data were: (1) used to assess the accuracy of previously published velocity prediction techniques for high-gradient channels; and (2) were combined with field data from other studies to develop general methodologies for predicting velocity and flow resistance in alluvial and mixed alluvial-bedrock channels both with and without step-forming instream wood. Velocity and flow resistance were poorly predicted by variables characterizing grain size and relative grain submergence. Conversely, methods based on detrended standard deviation of bed elevations (?z) and relative bedform submergence (h/?z) explained up to 84% of the variance in the measured flow resistance coefficients and 97% of the variance in dimensionless velocity. With an average velocity of 0.44 m/s for the collected measurements, velocity was predicted with RMS (root mean square) error as low as 0.071 m/s (16% of average) when discharge and bedform geometry is known and 0.10 m/s (23%) when only bedform geometry is known. Additionally, an empirical relationship indicates V/u?=h/?z, supporting previously-published laboratory findings using a field-based dataset in complex high-gradient channels. Interactions between instream wood and clasts result in substantially enhanced step heights and flow resistance. This compound effect defies description by grain size and relative grain submergence. However, ?z and h/?z quantify variability due to both clasts in combination with wood and clasts alone, providing relatively accurate predictions for the tested dataset and indicating substantial predictive capabilities in channels where bedforms are the primary source of flow resistance.

Yochum, Steven E.; Bledsoe, Brian P.; David, Gabrielle C. L.; Wohl, Ellen

2012-03-01

356

Subduction Plate Characterization from GOCE Gravity Gradients  

NASA Astrophysics Data System (ADS)

The study of subduction zones, i.e. regions where one tectonic plate moves under another and sinks into the mantle, is a fundamental topic in many Earth related sciences. Among others it is required in tectonophysics to model Earthquakes, it is useful in petrology and it is a basic information to study the Earth crust by means of gravity observations. In the present work the possibility of characterizing a subduction zone by exploiting GOCE gravity gradients is investigated. In particular GOCE along orbit-filtered gravity gradients are first reduced for the effect of the oceans, ice sheets and sediments. After that, the subduction zone is approximately delimited and for the observation points falling in this zone, the effect of ';a normal crust', i.e. a crust without subduction anomalies, is estimated by kriging extrapolating the surrounding residual signal. A further reduction for this normal crust effect is performed, thus isolating the gravitational effect of the subducting crust. By using a simulated annealing procedure, the isolated signal is finally fitted with the gravitational effect of a dipping prism, characterized by a set of parameters defining the prism position, size and its dipping and striking angles. The whole procedure has been firstly tested on a close-loop scenario to assess the performance of the simulating annealing algorithm in detecting the parameters used to generate the reference signal; then the procedure has been applied to real data to study the Tonga subduction. The close-loop simulation has shown the good efficiency of the proposed approach that is able of estimating the unknown prism parameters with a relative accuracy lower than 10% even in presence of noise. As for the Tonga subduction, the estimated model seems to confirm the geometry already proposed in literature.

Mansi, A. H.; Reguzzoni, M.; Sampietro, D.

2013-12-01

357

Supply chain challenges. building relationships.  

PubMed

Supply chain management is all about software and systems, right? Put in the best technology, sit back, and watch as your processes run smoothly and the savings roll in? Apparently not. When HBR convened a panel of leading thinkers in the field of supply chain management, technology was not top of mind. People and relationships were the dominant issues of the day. The opportunities and problems created by globalization, for example, are requiring companies to establish relationships with new types of suppliers. The ever-present pressure for speed and cost containment is making it even more important to break down stubbornly high internal barriers and establish more effective cross-functional relationships. The costs of failure have never been higher. The leading supply chain performers are applying new technology, new innovations, and process thinking to far greater advantage than the laggards, reaping tremendous gains in all the variables that affect shareholder value: cost, customer service, asset productivity, and revenue generation. And the gap between the leaders and the losers is growing in almost every industry. This roundtable gathered many of the leading thinkers and doers in the field of supply chain management, including practitioners Scott Beth of Intuit, Sandra Morris of Intel, and Chris Gopal of Unisys. David Burt of the University of San Diego and Stanford's Hau Lee bring the latest research from academia. Accenture's William Copacino and the Warren Company's Robert Porter Lynch offer the consultant's perspectives. Together, they take a wide-ranging view of such topics as developing talent, the role of the chief executive, and the latest technologies, exploring both the tactical and the strategic in the current state of supply chain management. PMID:12858712

Beth, Scott; Burt, David N; Copacino, William; Gopal, Chris; Lee, Hau L; Lynch, Robert Porter; Morris, Sandra

2003-07-01

358

A model of supply chain and supply chain decision-making complexity  

Microsoft Academic Search

Purpose – The objective of this paper is to develop a comprehensive model of supply chain and supply chain decision-making complexity that provides an understanding of the drivers of supply chain complexity and strategies to manage supply chain and supply chain decision-making complexity and outcomes. Design\\/methodology\\/approach – Grounded theory methodology is employed to build a theory of supply chain and

Ila Manuj; Funda Sahin

2011-01-01

359

Observations of Warm Carbon Chain Chemistry in NGC 3576  

NASA Astrophysics Data System (ADS)

We report observations of warm carbon chain chemistry (WCCC) in NGC 3576, including high angular resolution imaging of an ionization source candidate and the first detection of C5H in a massive star-forming region. In order to investigate the environment associated with birthline emergence, we ask how observed chemical conditions relate to Class 0/1 core differentiation: a systemic shift in peak position between species correlates with giant molecular cloud core gradients in turbulence and age. Emission in several molecular lines including HC3N (11-10), NH3 (1, 1), and C5H supports the G291.3-0.7 ionization front—transitional pre-main-sequence core interaction regulating the WCCC environment.

Saul, M.; Tothill, N. F. H.; Purcell, C. R.

2015-01-01

360

Molecules and chains in a strong magnetic field - Statistical treatment  

NASA Astrophysics Data System (ADS)

A Thomas-Fermi-Dirac-Weizsaecker statistical model is developed and employed to investigate diatomic molecules and infinite molecular chains in strong magnetic fields. The standard magnetic Thomas-Fermi-Dirac kinetic, potential, and exchange energy functionals are supplemented by a gradient correction to the kinetic energy. The numerical method used for solving this system in two spatial dimensions is detailed. Numerical solutions for a wide range of magnetic strengths and elements are presented to demonstrate the robustness, as well as the limitations, of the statistical approach. These calculations qualitatively reproduce many of the results of detailed quantum mechanical treatments. For example, the fractional binding energy is greatest for low atomic numbers and for strong magnetic fields.

Abrahams, Andrew M.; Shapiro, Stuart L.

1991-11-01

361

Molecules and chains in a strong magnetic field - Statistical treatment  

NASA Technical Reports Server (NTRS)

A Thomas-Fermi-Dirac-Weizsaecker statistical model is developed and employed to investigate diatomic molecules and infinite molecular chains in strong magnetic fields. The standard magnetic Thomas-Fermi-Dirac kinetic, potential, and exchange energy functionals are supplemented by a gradient correction to the kinetic energy. The numerical method used for solving this system in two spatial dimensions is detailed. Numerical solutions for a wide range of magnetic strengths and elements are presented to demonstrate the robustness, as well as the limitations, of the statistical approach. These calculations qualitatively reproduce many of the results of detailed quantum mechanical treatments. For example, the fractional binding energy is greatest for low atomic numbers and for strong magnetic fields.

Abrahams, Andrew M.; Shapiro, Stuart L.

1991-01-01

362

Chemotactic Gradients Predict Neutrophilic Alveolitis in Endotoxin-treated Rats  

Microsoft Academic Search

We hypothesized that the intensity of neutrophilic alveolitis is related to establishing a gradient of neutrophil attractant chemokines across the alveolar-capillary barrier. In these experiments, a posi- tive chemokine gradient toward the alveoli was induced by intratracheal instillation of endotoxin in rats (IT LPS). Alteration of the chemotactic gradient was induced by combining IT LPS (0.1 mg\\/kg) with an intraperitoneal

TIMOTHY S. BLACKWELL; LISA H. LANCASTER; THOMAS R. BLACKWELL; ANNAPURNA VENKATAKRISHNAN; JOHN W. CHRISTMAN

1999-01-01

363

Using the gradient histogram to analyze the continuous phase plate  

NASA Astrophysics Data System (ADS)

The geometrical optical method has been used to discuss the far-field distribution characteristics of a continuous phase plate. The gradient histogram of the plate’s surface has been calculated. It has been proved that the gradient histogram can be used to show the angular spectrum of a phase plate. The gradient histogram can simplify the analysis process of the angular spectrum and describe the focal spot morphology more intuitively.

Yang, Chunlin

2015-01-01

364

Effects of pressure gradients on turbulent premixed flames  

NASA Technical Reports Server (NTRS)

The influence of a constant acceleration on a turbulent premixed flame is studied by direct numerical simulation. This acceleration induces a mean pressure gradient across the flame brush, leading to a modification of the turbulent flame structure due to differential buoyancy mechanisms between heavy cold fresh and light hot burnt gases. Such a pressure gradient may be encountered in practical applications in ducted flames. A favorable pressure gradient, i.e. the pressure decreases from unburnt to burnt gases, is found to decrease the flame wrinkling, the flame brush thickness, and the turbulent flame speed. A favorable pressure gradient also promotes counter-gradient turbulent transport. On the other hand, adverse pressure gradients tend to increase the flame brush thickness and turbulent flame speed, and promote classical gradient turbulent transport. The balance equation for the turbulent flux of the Favre averaged progress variable is also analyzed. The first results show that the fluctuating pressure term, cannot be neglected as generally assumed in models. Simple models assuming that a high mean pressure gradient may only be balanced by the cross-dissipation term seem too approximate. This analysis has to be continued to compare simulation data and closure schemes proposed for the transport equation. The analysis developed by Veynante et al.(1995) has been extended to imposed acceleration and mean pressure gradients. A simple model for the turbulent flux is proposed and validated from simulation data. Then, a modified criterion is derived to delineate between counter-gradient and gradient turbulent diffusion. In fact, counter-gradient diffusion may occur in most practical applications, especially for ducted flames.

Veynante, D.; Poinsot, T.

1995-01-01

365

Comparison of genetic algorithms with conjugate gradient methods  

NASA Technical Reports Server (NTRS)

Genetic algorithms for mathematical function optimization are modeled on search strategies employed in natural adaptation. Comparisons of genetic algorithms with conjugate gradient methods, which were made on an IBM 1800 digital computer, show that genetic algorithms display superior performance over gradient methods for functions which are poorly behaved mathematically, for multimodal functions, and for functions obscured by additive random noise. Genetic methods offer performance comparable to gradient methods for many of the standard functions.

Bosworth, J. L.; Foo, N. Y.; Zeigler, B. P.

1972-01-01

366

Tailoring exciton dynamics by elastic strain-gradient in semiconductors.  

PubMed

In purely bent ZnO microwires, the excitons can be effectively driven and concentrated by the elastic strain-gradient towards the tensile outer side of the purely bent wire. Experimental and theoretical approaches are combined to investigate the dynamics of excitons in an inhomogeneous strain field with a uniform elastic strain-gradient. Cathodoluminescence spectroscopy analysis on purely bent ZnO microwires verifies that excitons can be effectively driven and concentrated along the elastic strain-gradient. PMID:24470383

Fu, Xuewen; Su, Cong; Fu, Qiang; Zhu, Xinli; Zhu, Rui; Liu, Chuanpu; Liao, Zhimin; Xu, Jun; Guo, Wanlin; Feng, Ji; Li, Ju; Yu, Dapeng

2014-04-23

367

Origin of stress gradients induced in capped, copper metallization  

SciTech Connect

Stress gradients generated near the top surface of Cu thin films by capping layers, as measured using a combination of conventional and glancing incidence x-ray diffraction, exhibit heterogeneous behavior that is directly related to plastic anisotropy within the Cu grains. A comparison of stress gradients measured from several x-ray reflections to their corresponding Schmid factors yields a consistent, critical resolved shear stress. The results experimentally verify that dislocation-mediated plasticity is responsible for the creation of stress gradients at the Cu film/cap interface. Depth-dependent measurements reveal that the observed gradients are localized to within 200?nm of this interface.

Murray, Conal E., E-mail: conal@us.ibm.com [IBM T.J. Watson Research Center, Yorktown Heights, New York 10598 (United States)

2014-02-24

368

Concentration Gradient and Information Energy for Decentralized UAV Control1  

E-print Network

spills, industrial release accidents, or chemical/biological/nuclear terrorist attacks. Depending gradient guidance laws. Guidance potentials are defined to improve sensed data quality in both a scalar

Mohseni, Kamran

369

Better Mini-Batch Algorithms via Accelerated Gradient Methods  

E-print Network

Better Mini-Batch Algorithms via Accelerated Gradient Methods Andrew Cotter Toyota Technological Toyota Technological Institute at Chicago nati@ttic.edu Karthik Sridharan Toyota Technological Institute

370

Determination of Binding Constants by Flow Injection Gradient Technique  

E-print Network

for the determination of binding constants of substrates with cyclodextrins or micelles. The concentration gradient of inclusion complex formation between -cyclodextrin ( -CD) and phenolphthalein and of the incorporation

Reid, Scott A.

371

A molecular dynamics study of the motion of a nanodroplet of pure liquid on a wetting gradient  

NASA Astrophysics Data System (ADS)

The dynamic behavior of a nanodroplet of a pure liquid on a wetting gradient was studied using molecular dynamics simulation. The spontaneous motion of the droplet is induced by a force imbalance at the contact line. We considered a Lennard-Jones system as well as water on a self-assembled monolayer (SAM). The motion of the droplet for the Lennard-Jones case was found to be steady with a simple power law describing its center-of-mass position with time. The behavior of the water droplet was found to depend on the uniformity of the wetting gradient, which was composed of methyl- and hydroxyl-terminated alkanethiol chains on Au(111). When the gradient was nonuniform the droplet was found to become pinned at an intermediate position. However, a uniform gradient with the same overall strength was found to drive a droplet consisting of 2000 water molecules a distance of 25nm or nearly ten times its initial base radius in tens of nanoseconds. A similar result was obtained for a droplet that was twice as large. Despite the many differences between the Lennard-Jones and water-SAM systems, the two show a similar overall behavior for the motion. Fair agreement was seen between the simulation results for the water droplet speed and the theoretical predictions. When the driving force was corrected for contact angle hysteresis, the agreement was seen to improve.

Halverson, Jonathan D.; Maldarelli, Charles; Couzis, Alexander; Koplik, Joel

2008-10-01

372

A molecular dynamics study of the motion of a nanodroplet of pure liquid on a wetting gradient.  

PubMed

The dynamic behavior of a nanodroplet of a pure liquid on a wetting gradient was studied using molecular dynamics simulation. The spontaneous motion of the droplet is induced by a force imbalance at the contact line. We considered a Lennard-Jones system as well as water on a self-assembled monolayer (SAM). The motion of the droplet for the Lennard-Jones case was found to be steady with a simple power law describing its center-of-mass position with time. The behavior of the water droplet was found to depend on the uniformity of the wetting gradient, which was composed of methyl- and hydroxyl-terminated alkanethiol chains on Au(111). When the gradient was nonuniform the droplet was found to become pinned at an intermediate position. However, a uniform gradient with the same overall strength was found to drive a droplet consisting of 2000 water molecules a distance of 25 nm or nearly ten times its initial base radius in tens of nanoseconds. A similar result was obtained for a droplet that was twice as large. Despite the many differences between the Lennard-Jones and water-SAM systems, the two show a similar overall behavior for the motion. Fair agreement was seen between the simulation results for the water droplet speed and the theoretical predictions. When the driving force was corrected for contact angle hysteresis, the agreement was seen to improve. PMID:19045299

Halverson, Jonathan D; Maldarelli, Charles; Couzis, Alexander; Koplik, Joel

2008-10-28

373

Markov chains and embedded Markov chains in geology  

Microsoft Academic Search

Geological data are structured as first-order, discrete-state discrete-time Markov chains in two main ways. In one, observations are spaced equally in time or space to yield transition probability matrices with nonzero elements in the main diagonal; in the other, only state transitions are recorded, to yield matrices with diagonal elements exactly equal to zero. The mathematical differences in these two

W. C. Krumbein; Michael F. Dacey

1969-01-01

374

Coordinated supply chain dynamic production planning model  

NASA Astrophysics Data System (ADS)

Coordination of different and often contradicting interests of individual supply chain members is one of the important issues in supply chain management because the individual members can not succeed without success of the supply chain and vice versa. This paper investigates a supply chain dynamic production planning problem with emphasis on coordination. A planning problem is formally described using a supply chain kernel, which defines supply chain configuration, management policies, available resources and objectives both at supply chain or macro and supply chain member or micro levels. The coordinated model is solved in order to balance decisions made at the macro and micro levels and members' profitability is used as the coordination criterion. The coordinated model is used to determine inventory levels and production capacity across the supply chain. Application of the coordinated model distributes costs burden uniformly among supply chain members and preserves overall efficiency of the supply chain. Influence of the demand series uncertainty is investigated. The production planning model is a part of the integrated supply chain decision modeling system, which is shared among the supply chain members across the Internet.

Chandra, Charu; Grabis, Janis

2001-10-01

375

An integrative framework for architecting supply chains  

E-print Network

This thesis explores the limitations of classic models of supply chain management, and proposes a new view based on the concept of value-driven supply chains, and a method of analysis and design based on the concepts of ...

Cela Díaz, Fernando

2006-01-01

376

Supply chain management in the cement industry  

E-print Network

Traditionally supply chain management has played an operational role within cement and mineral extraction commodity companies. Recently, cost reduction projects have brought supply chain management into the limelight. In ...

Agudelo, Isabel

2009-01-01

377

Managing flexibility in the supply chain  

E-print Network

Supply chain flexibility is introduced and its importance is discussed. This is followed by a review of the flexibility literature in manufacturing, supply chain, economics, strategy, organizational design, and industrial ...

Taylor, James B. (James Boyd), 1975-

2003-01-01

378

Supply chain for mobile network operator  

E-print Network

The purpose of this study is to understand and get insights on the characteristics of mobile device supply chain management for mobile networks operators. The relationship between corporate strategy and supply chain strategy ...

Liu, Kenneth Lap Chi

2010-01-01

379

Soil Fertility Gradient in the Restinga Ecosystem  

NASA Astrophysics Data System (ADS)

The restinga ecosystem (coastal plain vegetation) can be termed as a set of plant communities that suffer strong influenced by fluvial and marine factors and is characterized as an ecosystem of great biological diversity, therefore, represents areas of great importance in the context of ecological preservation. The degradation processes from many forms of anthropogenic disturbances that has taken place since the colonization of the country, made studies on the characterization and dynamics of soil fertility of these areas even more important in relation to the maintenance of its biodiversity and conservation. The sites studied were the Cardoso Island and Comprida Island, and in these, we analyzed four physiognomies, restinga, low restinga, dune and antedune (from continent to ocean). Chemical analyses were performed and soil salinity in these areas in depths 0-5; 0-10; 0-20; 20-40; 40-60 cm. In all soils the cationic exchange capacity was intimately associated with the concentration of soil organic matter, which makes this parameter essential to the maintenance of soil fertility of these areas; in more superficial layers (0-20 cm) there was an increase of pH and base saturation and decline of organic matter, aluminum saturation and cationic exchange capacity in the nearby sea, physiognomies what determines the existence of fertility gradient towards the continent-coast; restinga forests showed a chemical standard that is heavily marked by sandy texture, high degree of leaching, nutrient poverty, low base saturation, high saturation by aluminum and acidity, opposite conditions to soils of the dunes and antedunes, with the exception of sandy texture; despite the existence of a chemical gradient of fertility among the physiognomies studied it is possible to determine the soil acts more strongly as a physical support than as provider of fertility; as for salinity, soil collected in Cardoso Island did not present salinity in any depth, a fact which can be explained due to intense washing these soils are exposed and associated with highly sandy texture what favors the leaching of salts throughout the profile. Comprida Island soils presented salinity in some ante dune that can be explained due to the geographical position that determines a system of frequent wetting of the soil by the sea water and thus facilitating the accumulation of salts in the profile.

América Castelar da Cunha, Joana; Casagrande, José Carlos; Soares, Marcio Roberto; Martins Bonilha, Rodolfo

2013-04-01

380

Thermal Entanglement in Ferrimagnetic Chains  

E-print Network

A formula to evaluate the entanglement in an one-dimensional ferrimagnetic system is derived. Based on the formula, we find that the thermal entanglement in a small size spin-1/2 and spin-s ferrimagnetic chain is rather robust against temperature, and the threshold temperature may be arbitrarily high when s is sufficiently large. This intriguing result answers unambiguously a fundamental question: ``can entanglement and quantum behavior in physical systems survive at arbitrary high temperatures?"

Xiaoguang Wang; Z. D. Wang

2006-04-13

381

Towards biotracing in food chains.  

PubMed

Biotracing is tracing (backward)/tracking (forward) biological contamination in the food/feed chain. Advances in detection technologies, improvements in molecular marker identification, clearer understanding of pathogenicity markers, improved modelling methodologies and, more importantly, the integration of these disciplines will lead to better capability in full-chain tracing and tracking biological contaminations (biotracing). The advantages of improved biotraceability are faster intervention, limited recalls and more targeted remedial action. The project is not dealing with risk assessments but developing tools that can be used in "second-generation" risk assessments involving quantitative microbiology. This concept is the core activity of BIOTRACER, which is an Integrated Project (2007-2011) funded by the EU 6th Framework Programme. The research in biotracing is organised into five Research Areas, and 21 cross-disciplinary work packages that cover tracing and tracking of contamination in feed, meat and dairy chains, in addition to accidental and deliberate contamination of bottled water. The BIOTRACER Consortium consists of 46 partners, including Europe's largest food/feed industries, several SMEs, and relevant International Cooperation (INCO) countries. The Consortium includes experts in predictive microbiology, database developers, software companies, risk assessors, risk managers, system biologists, food and molecular microbiologists, legislative officers, standardization and validation members and food retailers. The outcomes will ensure a more reliable and rapid response to a microbial contamination event. PMID:20627434

Hoorfar, Jeffrey; Wagner, Martin; Jordan, Kieran; Bouquin, Solveig Lind; Skiby, Jeffrey

2011-03-01

382

INFORMS `03, Atlanta GA, October 19-21 A Supply Chain Network EconomyA Supply Chain Network Economy  

E-print Network

INFORMS `03, Atlanta GA, October 19-21 A Supply Chain Network EconomyA Supply Chain Network Economy competition. But a supply chain vs. a supply chain competition in many marketplaces today. #12;INFORMS Atlanta, GA, October 19-22, 2003 Supply Chain EconomySupply Chain Economy Supply Chain Economy (SCE

Nagurney, Anna

383

Machine Learning ! ! ! ! ! Srihari Markov Chain Monte Carlo  

E-print Network

Machine Learning ! ! ! ! ! Srihari 1 Markov Chain Monte Carlo Sampling Methods Sargur Srihari srihari@cedar.buffalo.edu #12;Machine Learning ! ! ! ! ! Srihari 2 Topics 1. Markov Chain Monte Carlo 2 Sampling #12;Machine Learning ! ! ! ! ! Srihari 3 1. Markov Chain Monte Carlo (MCMC) · Rejection sampling

384

WASTE IDENTIFICATION: A SUPPLY CHAIN STRATEGY PERSPECTIVE  

Microsoft Academic Search

The paper deals with the relationship between waste reduction and supply chain strategies and argues that the competitive advantage of a supply chain can be viewed as an ongoing process of acquiring control over different types of waste. The paper orients the managerial thinking to aggregating non-added value activities into waste zones and recognises three waste zones for supply chains;

Latif Al-Hakim

385

Developing Strategies for Green Supply Chain Management  

Microsoft Academic Search

he fi eld of supply chain management has more recently directed its atten- tion to the role of the supply chain in both (a) impacts to the natural environment and (b) the generation of environmental performance change. This shift in our expectations for the supply chain has arisen from growing social pressure, legislative changes around packaging and end-of-life goods, identifi

Dayna Simpson

386

Stretch the Chain and See the Light  

NSDL National Science Digital Library

In this activity, learners use their strength to light a light bulb. A chain made from paper clips is placed in series with a battery and flashlight bulb. When the chain is stretched, the light bulb glows brighter. The explanation lies in decreased electrical resistance due to better contact between the paper clips as the chain is stretched.

2012-06-26

387

Environmental Correlates of Food Chain Length  

Microsoft Academic Search

In 113 community food webs from natural communities, the average and maximal lengths of food chains are independent of primary productivity, contrary to the hypothesis that longer food chains should arise when more energy is available at their base. Environmental variability alone also does not appear to constrain average or maximal chain length. Environments that are three dimensional or solid,

Frederic Briand; Joel E. Cohen

1987-01-01

388

Food Supply Chains with Vertical Integration  

E-print Network

Food Supply Chains with Vertical Integration SOM 822 Research Paper Diogo Souza-Monteiro Dep. of Resource Economics 05/10/2004 #12;Introduction Food Supply chains are becoming increasingly complex in different tiers of food chains. Barkena and Drabenstott (1995) claim that contracts are quickly taking

Nagurney, Anna

389

On a Result for Finite Markov Chains  

ERIC Educational Resources Information Center

In an undergraduate course on stochastic processes, Markov chains are discussed in great detail. Textbooks on stochastic processes provide interesting properties of finite Markov chains. This note discusses one such property regarding the number of steps in which a state is reachable or accessible from another state in a finite Markov chain with M…

Kulathinal, Sangita; Ghosh, Lagnojita

2006-01-01

390

Finite subcategories and heredity chains Bangming Deng  

E-print Network

Finite subcategories and heredity chains Bangming Deng Department of Mathematics, Beijing Normal and define left and right splitting filtrations of S. Heredity chains of A S associated--modules and obtained in this way a heredity chain of ideals of A(\\Lambda). In the present paper we deal with finite

Bielefeld, University of

391

Decorated, Tapered, and Highly Nonlinear Granular Chain  

Microsoft Academic Search

It has been seen that inertial mismatches in 1D granular chains lead to remarkable energy absorption which increases with the number of spheres, N, and tapering, q. Short chains, however, are limited in that regard, and we therefore present one solution which greatly improves performance for any size chain. These strongly nonlinear and scalable systems feature surprisingly complicated dynamics and

Robert Doney; Surajit Sen

2006-01-01

392

Learning to Integrate: Supply Chains Reconceptualised  

ERIC Educational Resources Information Center

This paper introduces and explains a conception of supply chains from a situated learning perspective. This non-conventional supply chain perspective invites the reader to consider supply chain scenarios as "situated learning opportunities involving multiple communities of practice" interacting and participating together. It is argued that by…

Sense, Andrew J.; Clements, Michael D. J.

2007-01-01

393

Visualisation for System Learning in Supply Chains  

ERIC Educational Resources Information Center

Contemporary supply chains are vastly complex, and decisions made by actors have system-wide consequences that these might not be able to foresee. There are gaps between "best practice"-founded theory and actual practice in supply chains. To remedy this, we argue, the supply chain actors need to enhance systems knowledge. There is a need to…

Lindskog, Magnus; Abrahamsson, Mats; Aronsson, Hakan

2007-01-01

394

An empirical investigation into supply chain vulnerability  

Microsoft Academic Search

A growing number of academicians and practitioners have put supply chain risks on their agendas, particularly triggered by a recent series of catastrophic events that have disrupted economies and supply chains around the globe. Given the increasing awareness of this important topic, the purpose of this research was to study supply chain risks in more detail and to investigate the

Stephan M. Wagner; Christoph Bode

2006-01-01

395

Agent-Oriented Supply-Chain Management  

Microsoft Academic Search

The supply chain is a worldwide network of suppliers, factories, warehouses, distribution centers, and retailers through which raw materials are acquired, transformed, and delivered to customers. In recent years, a new software architecture for managing the supply chain at the tactical and operational levels has emerged. It views the supply chain as composed of a set of intelligent software agents,

MARK S. FOX; MIHAI BARBUCEANU; RUNE TEIGEN

2000-01-01

396

Supply Chain Management Jayashankar M. Swaminathan  

E-print Network

1 Supply Chain Management July 2000 Jayashankar M. Swaminathan The Kenan-Flagler Business School work ever in Social and Behavioral Sciences). #12;2 1. Introduction Supply chain management is one management. #12;3 2. Definition Supply chain management is a vast topic as a result people often give

Swaminathan, Jayashankar M.

397

The scope of supply chain management research  

Microsoft Academic Search

Advocates an expanded scope for supply chain management research which accounts for the social function and the political and economic implications of supply chain developments. Argues that the research agenda must not be driven by the notion of efficiency alone, but should also be developed around the concept of the just supply chain. Provides a framework which sets out the

Stephen J. New

1997-01-01

398

Supply Chain Management Degree Curriculum Information Sheet  

E-print Network

Supply Chain Management Degree Curriculum Information Sheet Business Core 33:010:275-Intro to double major in Supply Chain and Finance should take Financial Management for Finance Majors (33 to Project Management will be counted as a Supply Chain elective. #12;SSUUPPPPLLYY CCHHAAIINN AANNDD

Lin, Xiaodong

399

Supply Chain Management Faculty Brian Fugate  

E-print Network

Supply Chain Management Faculty Brian Fugate Brian S. Fugate (Ph.D University of Tennessee) is an Associate Professor of Supply Chain Management at Colorado State University. Brian worked in logistics interests include logistics strategy & performance and managing information flows in the supply chain. His

400

Supply Chain Management Professional Education Review  

E-print Network

Supply Chain Management Professional Education Review A monthly eNewsletter by the Department of Supply Chain Management and Marketing Sciences December 2009 Upcoming Events for Supply Chain Management is providing customized training for a U.S. manufacturing company, a Pharma R

Lin, Xiaodong

401

Performance measurement for green supply chain management  

Microsoft Academic Search

Purpose – To introduce and provide an overview of the various issues related to environmental (green) supply chain management performance measurement. Design\\/methodology\\/approach – The work relies on experiences, case studies and other literature related to performance measurement in environmental supply chains. It seeks to integrate works in supply chain management, environmental management, and performance management into one framework. A systems

Aref A. Hervani; Marilyn M. Helms; Joseph Sarkis

2005-01-01

402

Supply Chain Management Degree Curriculum Information Sheet  

E-print Network

Supply Chain Management Degree Curriculum Information Sheet 33:010:275-Intro. to Managerial (3) 33:630:301-Intro. to Marketing (3) 33:799:301-Intro. to Supply Chain Management (3) 33:630:301) OR 33:799:380-Intro. to Project Management (3)*** 3 Supply Chain electives (9) *Beginning Fall 2013

Lin, Xiaodong

403

Supply Chain Management Strategy PROFESSIONAL DEVELOPMENT SEMINAR  

E-print Network

Supply Chain Management Strategy PROFESSIONAL DEVELOPMENT SEMINAR Saturday, June 14th, and Friday with the College of Business and Economics Graduate Programs Office invites you to attend Supply Chain Management Strategy on June 14 and June 20. WHAT YOU WILL LEARN For many companies, Supply Chain Management has become

Gilchrist, James F.

404

Supply Chain Management Professional Education Review  

E-print Network

Supply Chain Management Professional Education Review A monthly eNewsletter by the Department of Supply Chain Management and Marketing Sciences June 2009 Upcoming Events 2009, it has broader implications for all supply chain managers. How many of us have examined ways

Lin, Xiaodong

405

Methodology for supply chain disruption analysis  

Microsoft Academic Search

Given the size, complexity and dynamic nature of many supply chains, there is a need to understand the impact of disruptions on the operation of the system. This paper presents a network-based modelling methodology to determine how changes or disruptions propagate in supply chains and how those changes or disruptions affect the supply chain system. Understanding the propagation of disruptions

T. Wu; J. Blackhurst; P. O’grady

2007-01-01

406

Policy and the modern food supply chain  

Microsoft Academic Search

The modern food supply chain is assuming many roles traditionally associated with markets. This paper reviews efforts to define food supply chains and define and meas- ure their performance from a commercial and social point of view. It proposes that little thought has been given to the role of government in food supply chains and the degree to which the

Derek Baker

407

Supply chain focus dependent safety stock placement  

Microsoft Academic Search

Increasing globalization, growing product range diversity, and rising consumer awareness are making markets highly competitive, forcing supply chains to adapt constantly to different stimuli. Growing competition between supply chains (as well as players within them) is also warranting a priority for overall supply chain performance over the goals of individual players. It is now well established in the literature that,

Gangaraju Vanteddu; Æ Ratna; Babu Chinnam; Kai Yang; Oleg Gushikin

2008-01-01

408

Tunnel current across linear homocatenated germanium chains  

SciTech Connect

The electronic transport properties of germanium oligomers catenating into linear chains (linear Ge chains) have been theoretically studied using first principle methods. The conduction mechanism of a Ge chain sandwiched between gold electrodes was analyzed based on the density of states and the eigenstates of the molecule in a two-probe environment. Like that of silicon chains (Si chains), the highest occupied molecular orbital of Ge chains contains the extended ?-conjugation of Ge 4p orbitals at energy levels close to the Fermi level; this is in contrast to the electronic properties of linear carbon chains. Furthermore, the conductance of a Ge chain is expected to decrease exponentially with molecular length L. The decay constant ?, which is defined as e{sup ??L}, of a Ge chain is similar to that of a Si chain, whereas the conductance of the Ge chains is higher than that of Si chains even though the Ge–Ge bond length is longer than the Si–Si bond length.

Matsuura, Yukihito, E-mail: matsuura@chem.nara-k.ac.jp [Department of Chemical Engineering, Nara National College of Technology Yatacho 22, Yamato-koriyama, Nara 539-1080 (Japan)

2014-01-28

409

Modeling carbon footprints across the supply chain  

Microsoft Academic Search

Environmental consciousness has become critical in the design and operation of globally integrated supply chain networks. This research examines the carbon footprint across supply chains and thus contributes to the knowledge and practice of green supply chain management. The analytical model uses the long-range Lagrangian and the Eulerian transport methods. Analytical and finite difference methods are used to approximate the

Balan Sundarakani; Robert de Souza; Mark Goh; Stephan M. Wagner; Sushmera Manikandan

2010-01-01

410

Extending the "Knowledge Advantage": Creating Learning Chains  

ERIC Educational Resources Information Center

Purpose: The purpose of this paper is to develop a synergy between the approaches of knowledge management in a learning organisation and supply chain management so that learning chains can be created in order to unleash innovation and creativity by managing knowledge in supply chains. Design/methodology/approach: Through extensive literature…

Maqsood, Tayyab; Walker, Derek; Finegan, Andrew

2007-01-01

411

An integrative framework for supply chain collaboration  

Microsoft Academic Search

Purpose – This paper proposes an integrative framework for supply chain collaboration which is based on the reciprocal approach. Design\\/methodology\\/approach – A reciprocal approach is adopted to capture the interaction phenomenon of different features of collaboration in attaining overall supply chain performance. Findings – A collaborative supply chain framework is composed of five connecting features of collaboration, namely collaborative performance

Togar M. Simatupang; Ramaswami Sridharan

2005-01-01

412

HYDRODYNAMICS INSTABILITIES OF CHOLESTERICS UNDER A THERMAL GRADIENT  

E-print Network

to the conductivity anisotropy of the liquid crystal. The threshold thermal gradient is then much lower a theoretical study of convective instabilities of cholesteric liquid crystal under a thermal gradient. We by heating the sample from the top in cholesteric with a negative thermal conductivity anisotropy Ka (K~ , K

Paris-Sud XI, Université de

413

High gradient acceleration in a 17 GHz photocathode RF gun  

Microsoft Academic Search

The physics and technological issues involved in high gradient particle acceleration at high microwave (RF) frequencies are under study at MIT. The 17 GHz photocathode RF gun has a 1½ cell room temperature copper cavity with a peak accelerating gradient of about 250 MV\\/m. The anticipated beam parameters, when operating with a photoemission cathode, are: energy 2 MeV, normalized emittance

S. C. Chen; J. Gonichon; L. C.-L. Lin; R. J. Temkin; S. Trotz; B. G. Danly; J. S. Wurtele

1993-01-01

414

New Roles for Lysosomal Trafficking in Morphogen Gradient Sensing  

NSDL National Science Digital Library

The way in which cells recognize their position in a gradient of morphogen controls differentiation during embryogenesis. New findings indicate that the rate at which internalized morphogen receptors are trafficked to lysosomes is key to the accurate and precise sensing of morphogen gradients and the appropriate initiation of differentiation programs during development.

Elena Rainero (Beatson Institute for Cancer Research;Integrin Cell Biology Laboratory REV); Jim C. Norman (Beatson Institute for Cancer Research;Integrin Cell Biology Laboratory REV)

2011-05-03

415

Gradient Well-Formedness across the Morpheme Boundary  

ERIC Educational Resources Information Center

Recent theories of phonology hold that phonotactic well-formedness may be gradient, with some legal structures being more well-formed than others. Linguistic and psycholinguistic research has demonstrated that "within" morphemes, speakers encode both categorical (*n/Onset) and gradient (st/Onset greater than sin/Onset) phonotactic restrictions.…

Goldberg, Ariel M.

2010-01-01

416

Polarization of Fucoid Eggs by a Calcium Ionophore Gradient  

Microsoft Academic Search

When the eggs of the brown alga Pelvetia were grown in a gradient of the calcium ionophore A23187, they tended to form their rhizoidal outgrowths on the sides that were exposed to the higher concentration of ionophore. This result supports the hypothesis that the formation of an intracellular calcium gradient is an essential step in the polarization of these eggs;

Kenneth R. Robinson; Roger Cone

1980-01-01

417

Axon initiation and growth cone turning on bound protein gradients.  

PubMed

Extracellular gradients of secreted guidance factors are known to guide axon pathfinding and neuronal migration. These factors are likely to bind to cell surfaces or extracellular matrix, but whether and how they may act in bound gradients remains mostly unclear. In this study, we have developed a new technique for rapid production of stable microscopic gradients of substrate-bound proteins by covalent bonding of the proteins with an epoxy-coated glass substrate while they are diffusing in an agarose gel. Using this method, we found that bound gradients of netrin-1 and brain-derived neurotrophic factor (BDNF) can polarize the initiation and turning of axons in cultured hippocampal neurons. Furthermore, bound BDNF gradient caused attractive and repulsive polarizing response on gradients of low- and high-average density of BDNF, respectively. This novel bidirectional response to BDNF depended on the basal level of cAMP in the neuron. Finally, our data showed that the neuron's attractive response to bound BDNF gradient depended on the absolute difference rather than the relative difference in the BDNF density across the neuron, with a minimal effective difference of 1-2 BDNF molecule/mum(2) on the substrate surface. Thus, substrate-bound guidance factors are highly effective in polarizing axon initiation and growth, and the diffusive printing technique is useful for studying neuronal responses induced by bound protein gradients. PMID:19515913

Mai, Junyu; Fok, Lee; Gao, Hongfeng; Zhang, Xiang; Poo, Mu-Ming

2009-06-10

418

A knowledge-gradient policy for sequential information collection  

E-print Network

A knowledge-gradient policy for sequential information collection Peter I. Frazier, Warren B increment in the value of information in each time period, where the value is measured according to the terminal utility function. We show that the knowledge-gradient policy is optimal both when the horizon

Powell, Warren B.

419

Direct Demonstration of a Growth-lnduced Water Potential Gradient  

Microsoft Academic Search

When transpiration is negligible, water potentials in growing tissues are less than those in mature tissues and have been predicted to form gradients that move water into the enlarging cells. To determine directly whether the gradients exist, we measured water potentials along the radius of stems of intact soybean (G\\/ycine max (L.) Merr.) seedlings growing in vermiculite in a water-saturated

Hiroshi Nonam; John S. Boyer

1993-01-01

420

Image segmentation and analysis via multiscale gradient watershed hierarchies  

Microsoft Academic Search

Multiscale image analysis has been used successfully in a number of applications to classify image features according to their relative scales. As a consequence, much has been learned about the scale-space behavior of intensity extrema, edges, intensity ridges, and grey-level blobs. We investigate the multiscale behavior of gradient watershed regions. These regions are defined in terms of the gradient properties

John M. Gauch

1999-01-01

421

Near-surface temperature gradient in a coastal upwelling regime  

NASA Astrophysics Data System (ADS)

oceanography, a near homogeneous mixed layer extending from the surface to a seasonal thermocline is a common conceptual basis in physics, chemistry, and biology. In a coastal upwelling region 3 km off the coast in the Mexican Pacific, we measured vertical density gradients with a free-rising CTD and temperature gradients with thermographs at 1, 3, and 5 m depths logging every 5 min during more than a year. No significant salinity gradient was observed down to 10 m depth, and the CTD temperature and density gradients showed no pronounced discontinuity that would suggest a near-surface mixed layer. Thermographs generally logged decreasing temperature with depth with gradients higher than 0.2 K m-1 more than half of the time in the summer between 1 and 3 m, 3 and 5 m and in the winter between 1 and 3 m. Some negative temperature gradients were present and gradients were generally highly variable in time with high peaks lasting fractions of hours to hours. These temporal changes were too rapid to be explained by local heating or cooling. The pattern of positive and negative peaks might be explained by vertical stacks of water layers of different temperatures and different horizontal drift vectors. The observed near-surface gradient has implications for turbulent wind energy transfer, vertical exchange of dissolved and particulate water constituents, the interpretation of remotely sensed SST, and horizontal wind-induced transport.

Maske, H.; Ochoa, J.; Almeda-Jauregui, C. O.; Ruiz-de la Torre, M. C.; Cruz-López, R.; Villegas-Mendoza, J. R.

2014-08-01

422

Simple Route to Gradient Concentric Metal and Metal Oxide Rings  

E-print Network

Simple Route to Gradient Concentric Metal and Metal Oxide Rings Suck Won Hong, Supratim Giri on metal and metal oxide have been reported. The rings organized in a concentric mode many offer systems.13 Herein, we report on a simple route to concentric rings of metals or metal oxide. The gradient

Lin, Zhiqun

423

Detection of flowing samples with a selective concentration gradient method  

SciTech Connect

Refractive index gradients generated in the flowing medium are measured with the help of a single probing light beam (Schlieren optics). These gradients are associated with any solute present in the medium. Additionally, excitation energy is introduced to the detection volume. After the relaxation process, the temporal temperature gradient relates closely to the concentration gradient of the adsorbing solute only. Both universal (concentration gradient) and selective (temperature gradient) information associated with the solute can be acquired by monitoring the deflection of the probe light beam in nanoliter detection volume. These data can be utilized to differentiate between samples on the basis of their molar absorption coefficients. A one-dimensional mathematical model was developed to describe the heat transfer associated with the selective concentration gradient method in flowing streams. Theoretical results closely correlate with experimental data. This method has been applied to capillary liquid chromatography detection, characterization of freshness of fruit juices, and contamination of organic solvents (fuels) with water. The detection limit of the selective concentration gradient method is about 6 x 10/sup -6/ absorption unit for 1-mJ excitation pulses. This corresponds to a fraction of fentomole of congo red detected in a few nanoliter volume.

Pawliszyn, J.

1988-04-15

424

Exploiting Matrix Symmetry to Improve FPGA-Accelerated Conjugate Gradient  

E-print Network

the Conjugate Gradient (CG) method using an FPGA co-processor. As in previous approaches, our co-processorExploiting Matrix Symmetry to Improve FPGA- Accelerated Conjugate Gradient Jason D. Bakos, Krishna the upper and lower triangle of the input matrix in parallel. Using a Virtex-2 Pro 100 FPGA, we have

Bakos, Jason D.

425

Leaf litter decomposition and microarthropod abundance along an altitudinal gradient  

Microsoft Academic Search

Mass loss rates of three types of leaf litter were measured along an altitudinal gradient at the Coweeta Hydrologic Laboratory, Macon County, North Carolina. Litterbags containing air dried litter from Quercus prinus L., Lirio- dendron tulipifera L., and Rhododendron maximum L. were placed in five plots along the gradient and sampled monthly. Microarthropods were extracted and sorted, and litter was

Coeli M. Hoover; D. A. Crossley Jr

1995-01-01

426

Accurate Measurement of Magnetic Resonance Imaging Gradient Characteristics  

PubMed Central

Recently, gradient performance and fidelity has become of increasing interest, as the fidelity of the magnetic resonance (MR) image is somewhat dependent on the fidelity of the gradient system. In particular, for high fidelity non-Cartesian imaging, due to non-fidelity of the gradient system, it becomes necessary to know the actual k-space trajectory as opposed to the requested trajectory. In this work we show that, by considering the gradient system as a linear time-invariant system, the gradient impulse response function (GIRF) can be reliably measured to a relatively high degree of accuracy with a simple setup, using a small phantom and a series of simple experiments. It is shown experimentally that the resulting GIRF is able to predict actual gradient performance with a high degree of accuracy. The method captures not only the frequency response but also gradient timing errors and artifacts due to mechanical vibrations of the gradient system. Some discussion is provided comparing the method presented here with other analogous methods, along with limitations of these methods. PMID:25343017

Liu, Hui; Matson, Gerald B.

2014-01-01

427

MECHANISMS CREATING COMMUNITY STRUCTURE ACROSS A FRESHWATER HABITAT GRADIENT  

Microsoft Academic Search

Lentic freshwater habitats in temperate regions exist along a gradient from small ephemeral ponds to large permanent lakes. This environmental continuum is a useful axis for understanding how attributes of individuals ultimately generate structure at the level of the community. Community structure across the gradient is determined by both (a) physical factors, such as pond drying and winter anoxia, that

Gary A. Wellborn; David K. Skelly; Earl E. Werner

1996-01-01

428

Forest bird communities across a gradient of urban development  

E-print Network

that urban and rural bird communities were quite distinct from each other. Rural communities had more longForest bird communities across a gradient of urban development Emily Minor & Dean Urban # Springer across a gradient of urbanization. We used field data and multivariate statistical techniques to examine

Illinois at Chicago, University of

429

Performance of the Electroencephalography Inverse Problem using Electric Potential Gradient  

E-print Network

Performance of the Electroencephalography Inverse Problem using Electric Potential Gradient cases. The spatial covari- ance of the noise is estimated from real EEG measurements. Keywords--Electroencephalography, Cram´er-Rao Bound, gradient sensor. I. INTRODUCTION Electroencephalography (EEG) is used to study

Nehorai, Arye

430

The electric field gradient in heavy rare earth metals  

Microsoft Academic Search

Estimates of the electric field gradient in heavy rare earth metals have been evaluated from experimental hyperfine interaction data. In addition, the magnetic hyperfine fields are analyzed. In the metals the effective radial integrals r-3>4f of the magnetic and quadrupole hyperfine interaction are reduced at most by 10% compared with the free ion values. The electric field gradients due to

J. Pelzl; Fachbereich Physik

1972-01-01

431

Wall Pressure Spectral Model Including the Adverse Pressure Gradient Effects  

E-print Network

Wall Pressure Spectral Model Including the Adverse Pressure Gradient Effects Yannick Rozenberg 1 Sherbrooke, Sherbrooke, QC, J1K2R1, Canada An empirical model to predict the wall-pressure fluctuations spectra beneath ad- verse pressure gradient flows is presented. It is based on Goody's model which already

Paris-Sud XI, Université de

432

Acceleration of conjugate gradient method for circuit simulation using CUDA  

Microsoft Academic Search

The Conjugate Gradient method is a popular iterative method to solve a system of linear equations and is used in a variety of applications. The DC Analyser is a circuit simulator built at IIT Bombay to solve large circuits containing resistances, voltage and current sources and which employs the conjugate gradient method. Current generation of graphics cards offer extremely high

Anirudh Maringanti; Viraj Athavale; Sachin B. Patkar

2009-01-01

433

A gradient expansion for cosmological backreaction  

SciTech Connect

We address the issue of cosmological backreaction from non-linear structure formation by constructing an approximation for the time evolved metric of a dust dominated universe based on a gradient expansion. Our metric begins as a perturbation of a flat Friedmann-Robertson-Walker state described by a nearly scale invariant, Gaussian, power-law distribution, and evolves in time until non-linear structures have formed. After describing and attempting to control for certain complications in the implementation of this approach, this metric then forms a working model of the universe. We numerically calculate the evolution of the average scale factor in this model and hence the backreaction. We argue that, despite its limitations, this model is more realistic than previous models that have confronted the issue of backreaction. We find that the instantaneous effects of backreaction in this model could be as large as ? 10% of the background. This suggests that a proper understanding of the cumulative effects of backreaction could be crucial for precision cosmology and any future exploration of the dark sector.

Enqvist, Kari; Hotchkiss, Shaun [University of Helsinki and Helsinki Institute of Physics, P.O.Box 64, 00014, University of Helsinki (Finland); Rigopoulos, Gerasimos, E-mail: kari.enqvist@helsinki.fi, E-mail: shaun.hotchkiss@helsinki.fi, E-mail: rigopoulos@physik.rwth-aachen.de [Institute for Theoretical Particle Physics and Cosmology, RWTH Aachen, 52056 (Germany)

2012-03-01

434

Passive magnetic shielding in static gradient fields  

NASA Astrophysics Data System (ADS)

The effect of passive magnetic shielding on dc magnetic field gradients imposed by both external and internal sources is studied for two idealized shield models: concentric spherical and infinitely-long cylindrical shells of linear material. It is found that higher-order multipoles of an externally applied magnetic field are always shielded progressively better for either geometry by a factor related to the order of the multipole. In regard to the design of internal coil systems, we determine reaction factors for the general multipole field and provide examples of how one can take advantage of the coupling of the coils to the innermost shell to optimize the uniformity of the field. Furthermore, we provide formulae relevant to active magnetic compensation systems which attempt to stabilize the interior fields by sensing and cancelling the exterior fields close to the outermost shell. Overall this work provides a comprehensive framework that is useful for the analysis and optimization of dc magnetic shields, serving as a theoretical and conceptual design guide as well as a starting point and benchmark for finite-element analysis.

Bidinosti, C. P.; Martin, J. W.

2014-04-01

435

Axial thermal gradients in microchip gas chromatography.  

PubMed

Fabrication technologies for microelectromechanical systems (MEMS) allow miniaturization of conventional benchtop gas chromatography (GC) to portable, palm-sized microfabricated GC (?GC) devices, which are suitable for on-site chemical analysis and remote sensing. The separation performance of ?GC systems, however, has not been on par with conventional GC. Column efficiency, peak symmetry and resolution are often compromised by column defects and non-ideal injections. The relatively low performance of ?GC devices has impeded their further commercialization and broader application. In this work, the separation performance of ?GC columns was improved by incorporating thermal gradient gas chromatography (TGGC). The analysis time was ?20% shorter for TGGC separations compared to conventional temperature-programmed GC (TPGC) when a wide sample band was introduced into the column. Up to 50% reduction in peak tailing was observed for polar analytes, which improved their resolution. The signal-to-noise ratios (S/N) of late-eluting peaks were increased by 3-4 fold. The unique focusing effect of TGGC overcomes many of the previous shortcomings inherent in ?GC analyses. PMID:25476685

Wang, Anzi; Hynynen, Sampo; Hawkins, Aaron R; Tolley, Samuel E; Tolley, H Dennis; Lee, Milton L

2014-12-29

436

The SU(?) twisted gradient flow running coupling  

NASA Astrophysics Data System (ADS)

We measure the running of the SU(?) 't Hooft coupling by performing a step scaling analysis of the Twisted Eguchi-Kawai (TEK) model, the SU( N) gauge theory on a single site lattice with twisted boundary conditions. The computation relies on the conjecture that finite volume effects for SU(N) gauge theories defined on a 4-dimensional twisted torus are controlled by an effective size parameter , with l the torus period. We set the scale for the running coupling in terms of and use the gradient flow to define a renormalized 't Hooft coupling . In the TEK model, this idea allows the determination of the running of the coupling through a step scaling procedure that uses the rank of the group as a size parameter. The continuum renormalized coupling constant is extracted in the zero lattice spacing limit, which in the TEK model corresponds to the large N limit taken at fixed value of . The coupling constant is thus expected to coincide with that of the ordinary pure gauge theory at N = ?. The idea is shown to work and permits us to follow the evolution of the coupling over a wide range of scales. At weak coupling we find a remarkable agreement with the perturbative two-loop formula for the running coupling.

Pérez, Margarita García; González-Arroyo, Antonio; Keegan, Liam; Okawa, Masanori

2015-01-01

437

Evolution of slanted edge gradient SFR measurement  

NASA Astrophysics Data System (ADS)

The well-established Modulation Transfer Function (MTF) is an imaging performance parameter that is well suited to describing certain sources of detail loss, such as optical focus and motion blur. As performance standards have developed for digital imaging systems, the MTF concept has been adapted and applied as the spatial frequency response (SFR). The international standard for measuring digital camera resolution, ISO 12233, was adopted over a decade ago. Since then the slanted edge-gradient analysis method on which it was based has been improved and applied beyond digital camera evaluation. Practitioners have modified minor elements of the standard method to suit specific system characteristics, unique measurement needs, or computational shortcomings in the original method. Some of these adaptations have been documented and benchmarked, but a number have not. In this paper we describe several of these modifications, and how they have improved the reliability of the resulting system evaluations. We also review several ways the method has been adapted and applied beyond camera resolution.

Williams, Don; Burns, Peter D.

2014-01-01

438

A gradient expansion for cosmological backreaction  

E-print Network

We address the issue of cosmological backreaction from non-linear structure formation by constructing an approximation for the time evolved metric of a dust dominated universe based on a gradient expansion. Our metric begins as a perturbation of a flat Friedmann-Robertson-Walker state described by a nearly scale invariant, Gaussian, power-law distribution, and evolves in time until non-linear structures have formed. After describing and attempting to control for certain complications in the implementation of this approach, this metric then forms a working model of the universe. We numerically calculate the evolution of the average scale factor in this model and hence the backreaction. We argue that, despite its limitations, this model is more realistic than previous models that have confronted the issue of backreaction. We find that the effects of backreaction in this model can be as large as $5-10%$ of the background. This suggests that a proper understanding of the effects of backreaction could be important...

Enqvist, Kari; Rigopoulos, Gerasimos

2011-01-01

439

Affinity gradients drive copper to cellular destinations.  

PubMed

Copper is an essential trace element for eukaryotes and most prokaryotes. However, intracellular free copper must be strictly limited because of its toxic side effects. Complex systems for copper trafficking evolved to satisfy cellular requirements while minimizing toxicity. The factors driving the copper transfer between protein partners along cellular copper routes are, however, not fully rationalized. Until now, inconsistent, scattered and incomparable data on the copper-binding affinities of copper proteins have been reported. Here we determine, through a unified electrospray ionization mass spectrometry (ESI-MS)-based strategy, in an environment that mimics the cellular redox milieu, the apparent Cu(I)-binding affinities for a representative set of intracellular copper proteins involved in enzymatic redox catalysis, in copper trafficking to and within various cellular compartments, and in copper storage. The resulting thermodynamic data show that copper is drawn to the enzymes that require it by passing from one copper protein site to another, exploiting gradients of increasing copper-binding affinity. This result complements the finding that fast copper-transfer pathways require metal-mediated protein-protein interactions and therefore protein-protein specific recognition. Together with Cu,Zn-SOD1, metallothioneins have the highest affinity for copper(I), and may play special roles in the regulation of cellular copper distribution; however, for kinetic reasons they cannot demetallate copper enzymes. Our study provides the thermodynamic basis for the kinetic processes that lead to the distribution of cellular copper. PMID:20463663

Banci, Lucia; Bertini, Ivano; Ciofi-Baffoni, Simone; Kozyreva, Tatiana; Zovo, Kairit; Palumaa, Peep

2010-06-01

440

Cubic Gradient-Based Material Interfaces.  

PubMed

Multi-fluid simulations often create volume fraction data, representing fluid volumes per region or cell of a fluid data set. Accurate and visually realistic extraction of fluid boundaries is a challenging and essential task for efficient analysis of multi-fluid data. In this work we present a new material interface reconstruction method for such volume fraction data. Within each cell of the data set, our method utilizes a gradient field approximation based on trilinearly blended Coons-patches to generate a volume-fraction function, representing the change in volume fractions over the cells. A continuously varying isovalue field is applied to this function to produce a smooth interface that preserves the given volume fractions well. Further, the method allows user-controlled balance between volume accuracy and physical plausibility of the interface. The method works on two- and three-dimensional Cartesian grids, and handles multiple materials. Calculations are performed locally and utilize only the one-ring of cells surrounding a given cell, allowing visualizations of the material interfaces to be easily generated on a GPU or in a large-scale distributed parallel environment. Our results demonstrate the robustness, accuracy and flexibility of the developed algorithms. PMID:23420219

Prilepov, Iuri; Obermaier, Harald; Deines, Eduard; Garth, Christoph; Joy, Kenneth I

2013-02-13

441

Cubic gradient-based material interfaces.  

PubMed

Multifluid simulations often create volume fraction data, representing fluid volumes per region or cell of a fluid data set. Accurate and visually realistic extraction of fluid boundaries is a challenging and essential task for efficient analysis of multifluid data. In this work, we present a new material interface reconstruction method for such volume fraction data. Within each cell of the data set, our method utilizes a gradient field approximation based on trilinearly blended Coons-patches to generate a volume fraction function, representing the change in volume fractions over the cells. A continuously varying isovalue field is applied to this function to produce a smooth interface that preserves the given volume fractions well. Further, the method allows user-controlled balance between volume accuracy and physical plausibility of the interface. The method works on two- and three-dimensional Cartesian grids, and handles multiple materials. Calculations are performed locally and utilize only the one-ring of cells surrounding a given cell, allowing visualizations of the material interfaces to be easily generated on a GPU or in a large-scale distributed parallel environment. Our results demonstrate the robustness, accuracy, and flexibility of the developed algorithms. PMID:23929848

Prilepov, Iuri; Obermaier, Harald; Deines, Eduard; Garth, Christoph; Joy, Kenneth I

2013-10-01

442

Relation chain based clustering analysis  

NASA Astrophysics Data System (ADS)

Clustering analysis is currently one of well-developed branches in data mining technology which is supposed to find the hidden structures in the multidimensional space called feature or pattern space. A datum in the space usually possesses a vector form and the elements in the vector represent several specifically selected features. These features are often of efficiency to the problem oriented. Generally, clustering analysis goes into two divisions: one is based on the agglomerative clustering method, and the other one is based on divisive clustering method. The former refers to a bottom-up process which regards each datum as a singleton cluster while the latter refers to a top-down process which regards entire data as a cluster. As the collected literatures, it is noted that the divisive clustering is currently overwhelming both in application and research. Although some famous divisive clustering methods are designed and well developed, clustering problems are still far from being solved. The k - means algorithm is the original divisive clustering method which initially assigns some important index values, such as the clustering number and the initial clustering prototype positions, and that could not be reasonable in some certain occasions. More than the initial problem, the k - means algorithm may also falls into local optimum, clusters in a rigid way and is not available for non-Gaussian distribution. One can see that seeking for a good or natural clustering result, in fact, originates from the one's understanding of the concept of clustering. Thus, the confusion or misunderstanding of the definition of clustering always derives some unsatisfied clustering results. One should consider the definition deeply and seriously. This paper demonstrates the nature of clustering, gives the way of understanding clustering, discusses the methodology of designing a clustering algorithm, and proposes a new clustering method based on relation chains among 2D patterns. In this paper, a new method called relation chain based clustering is presented. The given method demonstrates that arbitrary distribution shape and density are not the essential factors for clustering research, in another words, clusters described by some particular expressions should be considered as a uniform mathematical description which is called "relation chain" emphasized in this paper. The relation chain indicates the relation between each pair of the spatial points and gives the evaluation of the connection between the pair-wise points. This relation chain based clustering algorithm initially assigns the neighborhood evaluation radius of the points, then assesses the clustering result based on inner-cluster variance of each cluster while increasing the radius, adjusting the radius properly and finally gives the clustering result. Some experiments are conducted using the proposed method and the hidden data structure is well explored.

Zhang, Cheng-ning; Zhao, Ming-yang; Luo, Hai-bo

2011-08-01

443

Optimization of torque-balanced asymmetric head gradient coils.  

PubMed

Local gradient coils can improve the performance of echo-planar, diffusion, and short TE imaging in the brain. A modified singular value decomposition algorithm, which allows the rapid optimization and comparison of designs, was employed to optimize head size gradient coils. A theoretical expression for the torque on a cylindrical coil is presented and used to design coils that are free from torque while pulsed within a magnetic field. Gradient coils of various lengths both with and without torque constraints were compared; although torque-free coils do not perform as well as unbalanced coils, asymmetric torque-balanced coils can achieve comparable homogeneity with only a modest increase in inductance and resistance. Both types of coils outperform body size gradient coils by a dramatic margin. A three-axis head gradient designed using these techniques was constructed and used for brain imaging on a clinical scanner. PMID:8744016

Alsop, D C; Connick, T J

1996-06-01

444

Acceleration and radiation processes in controlled gradient gas jets  

NASA Astrophysics Data System (ADS)

The controlled gradient gas jet was designed, constructed and tested at the Naval Research Laboratory. The gas jet is using a laser generated shock wave to control the density gradient between vacuum and neutral gas. The length scale of the density gradient is fully controlled by the strength of the shock wave and can be varied continuously from under 10 ?m in case of strong shock to a 100 ?m for a weak shock wave. To verify the experimental results a simulation was run to model the system using a three-dimensional hydrodynamic code, SPARC, developed at the Naval Research Laboratory. Controlling the gas density gradient is important for electrons and protons acceleration, as well as for optical transition radiation generation. Experiments on using the controlled gradient gas jet and preliminary results on electron acceleration will be presented.

Kaganovich, Dmitri; Helle, Mike; Gordon, Daniel; Xie, Frank; Ting, Antonio

2011-11-01

445

Generalized Hooke's law for isotropic second gradient materials  

E-print Network

In the spirit of Germain the most general objective stored elastic energy for a second gradient material is deduced using a literature result of Fortun\\'e & Vall\\'ee. Linear isotropic constitutive relations for stress and hyperstress in terms of strain and strain-gradient are then obtained proving that these materials are characterized by seven elastic moduli and generalizing previous studies by Toupin, Mindlin and Sokolowski. Using a suitable decomposition of the strain-gradient, it is found a necessary and sufficient condition, to be verified by the elastic moduli, assuring positive definiteness of the stored elastic energy. The problem of warping in linear torsion of a prismatic second gradient cylinder is formulated, thus obtaining a possible measurement procedure for one of the second gradient elastic moduli.

F. dell'Isola; G. Sciarra; S. Vidoli

2010-08-17

446

Mechanical features of the ATS ramped-gradient DTL  

SciTech Connect

At Los Alamos, a short, lightweight drift-tube linac (DTL) has been designed. This accomplishment is possible by varying the accelerating gradient from 2 MV/m at the RFQ end to 4.4 MV/m at the output end, with the gradient rising as a cubic polynomial. The object of raising the gradient to such a high level is to reduce the length of the proposed 50-MeV machine that ultimately will attach to the ramped-gradient drift-tube linac (RGDTL) tank. This is the first proton linac structure to propose such a ramping scheme and the first to attempt reliable long-term operation at such elevated accelerating gradients. It is also the first to attempt to accomplish this with a lightweight aluminum structure designed to operate at 5% duty factor.

Liska, D.J.; McCauley, G.; Carlisle, L.O.

1986-01-01

447

Tailoring magnetic field gradient design to magnet cryostat geometry.  

PubMed

Eddy currents induced within a magnetic resonance imaging (MRI) cryostat bore during pulsing of gradient coils can be applied constructively together with the gradient currents that generate them, to obtain good quality gradient uniformities within a specified imaging volume over time. This can be achieved by simultaneously optimizing the spatial distribution and temporal pre-emphasis of the gradient coil current, to account for the spatial and temporal variation of the secondary magnetic fields due to the induced eddy currents. This method allows the tailored design of gradient coil/magnet configurations and consequent engineering trade-offs. To compute the transient eddy currents within a realistic cryostat vessel, a low-frequency finite-difference time-domain (FDTD) method using total-field scattered-field (TFSF) scheme has been performed and validated. PMID:17945575

Trakic, A; Liu, F; Lopez, H S; Wang, H; Crozier, S

2006-01-01

448

Alternative spring force law for bead-spring chain models of the worm-like chain  

E-print Network

Alternative spring force law for bead-spring chain models of the worm-like chain Patrick T We have developed a new spring force law which can be used in bead-spring chain models of the worm The Society of Rheology. DOI: 10.1122/1.2206713 I. INTRODUCTION The worm-like chain WLC model has been used

Doyle, Patrick S.

449

Supply Chain The effective supply chain has become a new organizational and operational  

E-print Network

MBA in Supply Chain Management #12;The effective supply chain has become a new organizational and operational model for the information age. Supply chain management is a business process that enables­Newark and New Brunswick, which offers an MBA concentration and PhD in supply chain management

Lin, Xiaodong

450

Supply Chain Management and Marketing Sciences Maximizing the Interface between Supply Chain & Marketing  

E-print Network

Supply Chain Management and Marketing Sciences Maximizing the Interface between Supply Chain. Lyons is a research professor in the supply chain environmental management and archaeology departments Highlights Council of Supply Chain Management Professionals gives scholarships to RBS Students p.2 Roundtable

Lin, Xiaodong

451

Supply Chain Management and Marketing Sciences Maximizing the Interface between Supply Chain & Marketing  

E-print Network

Supply Chain Management and Marketing Sciences Maximizing the Interface between Supply Chain-Enhanced Supply Chain Management Program is Key to its Success p.2 Six MBA Students Awarded Scholarships from howmarketinghadtoadapthowitcommunicatedwith #12;Supply Chain Management and Marketing Sciences 2 by Franco Libunao, Neha Mukherjee

Lin, Xiaodong

452

A Network Economic Model for Supply Chain versus Supply Chain Competition  

E-print Network

inequality problem. #12;Introduction To date, the major focus of the supply chain management literature has. This also reflects the philosophy that the firms' cooperation quest in supply chain management is to makeA Network Economic Model for Supply Chain versus Supply Chain Competition Ding Zhang School

Nagurney, Anna

453

Topological superconductivity induced by ferromagnetic metal chains  

NASA Astrophysics Data System (ADS)

Recent experiments have provided evidence that one-dimensional (1D) topological superconductivity can be realized experimentally by placing transition-metal atoms that form a ferromagnetic chain on a superconducting substrate. We address some properties of this type of system by using a Slater-Koster tight-binding model to account for important features of the electronic structure of the transition-metal chains on the superconducting substrate. We predict that topological superconductivity is nearly universal when ferromagnetic transition-metal chains form straight lines on superconducting substrates and that it is possible for more complex chain structures. When the chain is weakly coupled to the substrate and is longer than superconducting coherence lengths, its proximity-induced superconducting gap is ˜? ESO/J where ? is the s -wave pair potential on the chain, ESO is the spin-orbit splitting energy induced in the normal chain state bands by hybridization with the superconducting substrate, and J is the exchange splitting of the ferromagnetic chain d bands. Because of the topological character of the 1D superconducting state, Majorana end modes appear within the gaps of finite length chains. We find, in agreement with the experiment, that when the chain and substrate orbitals are strongly hybridized, Majorana end modes are substantially reduced in amplitude when separated from the chain end by less than the coherence length defined by the p -wave superconducting gap. We conclude that Pb is a particularly favorable substrate material for ferromagnetic chain topological superconductivity because it provides both strong s -wave pairing and strong Rashba spin-orbit coupling, but that there is an opportunity to optimize properties by varying the atomic composition and structure of the chain. Finally, we note that in the absence of disorder, a new chain magnetic symmetry, one that is also present in the crystalline topological insulators, can stabilize multiple Majorana modes at the end of a single chain.

Li, Jian; Chen, Hua; Drozdov, Ilya K.; Yazdani, A.; Bernevig, B. Andrei; MacDonald, A. H.

2014-12-01

454

Bayesian seismic tomography by parallel interacting Markov chains  

NASA Astrophysics Data System (ADS)

The velocity field estimated by first arrival traveltime tomography is commonly used as a starting point for further seismological, mineralogical, tectonic or similar analysis. In order to interpret quantitatively the results, the tomography uncertainty values as well as their spatial distribution are required. The estimated velocity model is obtained through inverse modeling by minimizing an objective function that compares observed and computed traveltimes. This step is often performed by gradient-based optimization algorithms. The major drawback of such local optimization schemes, beyond the possibility of being trapped in a local minimum, is that they do not account for the multiple possible solutions of the inverse problem. They are therefore unable to assess the uncertainties linked to the solution. Within a Bayesian (probabilistic) framework, solving the tomography inverse problem aims at estimating the posterior probability density function of velocity model using a global sampling algorithm. Markov chains Monte-Carlo (MCMC) methods are known to produce samples of virtually any distribution. In such a Bayesian inversion, the total number of simulations we can afford is highly related to the computational cost of the forward model. Although fast algorithms have been recently developed for computing first arrival traveltimes of seismic waves, the complete browsing of the posterior distribution of velocity model is hardly performed, especially when it is high dimensional and/or multimodal. In the latter case, the chain may even stay stuck in one of the modes. In order to improve the mixing properties of classical single MCMC, we propose to make interact several Markov chains at different temperatures. This method can make efficient use of large CPU clusters, without increasing the global computational cost with respect to classical MCMC and is therefore particularly suited for Bayesian inversion. The exchanges between the chains allow a precise sampling of the high probability zones of the model space while avoiding the chains to end stuck in a probability maximum. This approach supplies thus a robust way to analyze the tomography imaging uncertainties. The interacting MCMC approach is illustrated on two synthetic examples of tomography of calibration shots such as encountered in induced microseismic studies. On the second application, a wavelet based model parameterization is presented that allows to significantly reduce the dimension of the problem, making thus the algorithm efficient even for a complex velocity model.

Gesret, Alexandrine; Bottero, Alexis; Romary, Thomas; Noble, Mark; Desassis, Nicolas

2014-05-01

455

Implementing a real-time chain of segmentation of images on a multi-FPGA architecture  

NASA Astrophysics Data System (ADS)

In this paper we present the study and the implementation of an optimized chain of segmentation operators. We implemented this chain in real time, consisting of a Deriche contour detection, double threshold, closing of contours and finally region labeling, on a multi-FPGA architecture. This architecture has four processing FPGAs and four memory modules. Deriche operator, closing of contours and labeling occupy each one an FPGA. Double threshold and detection of the extremities filled partially the forth FPGA. The slowest component of the chain is Deriche operator which can go up to 11.4 Mhz, assuring the process of an image every 40 ms. Deriche operator tries to extract the contours by assuming that a contour is a step super positioned by a white gaussian noise. Our implementation consists of a smoothing part of four second order filters and a Sobel as a derivation part. The second order filters are causal and non-causal horizontal and vertical operators. The gradient image passes through a double threshold filter to select the real contours and the crests and the background pixels. Closing of contours eliminates the false crests and finally the labeling gives a unique label to each closed region. The latency of the chain is in the order of three images. This implementation shows the efficiency of the chain and also it demonstrates the capabilities of our architecture as a prototyping system.

Akil, Mohamed; Zahirazami, Shahram

1998-03-01

456

A comparison of the Monte Carlo and the flux gradient method for atmospheric diffusion  

SciTech Connect

In order to model the dispersal of atmospheric pollutants in the planetary boundary layer, various methods of parameterizing turbulent diffusion have been employed. The purpose of this paper is to use a three-dimensional particle-in-cell transport and diffusion model to compare the Markov chain (Monte Carlo) method of statistical particle diffusion with the deterministic flux gradient (K-theory) method. The two methods are heavily used in the study of atmospheric diffusion under complex conditions, with the Monte Carlo method gaining in popularity partly because of its more direct application of turbulence parameters. The basis of comparison is a data set from night-time drainage flow tracer experiments performed by the US Department of Energy Atmospheric Studies in Complex Terrain (ASCOT) program at the Geysers geothermal region in northern California. The Atmospheric Diffusion Particle-In-Cell (ADPIC) model used is the main model in the Lawrence Livermore National Laboratory emergency response program: Atmospheric Release Advisory Capability (ARAC). As a particle model, it can simulate diffusion in both the flux gradient and Monte Carlo modes. 9 refs., 6 figs.

Lange, R.

1990-05-01

457

Abundance and diversity of organohalide-respiring bacteria in lake sediments across a geographical sulfur gradient.  

PubMed

Across the U.S. Upper Midwest, a natural geographical sulfate gradient exists in lakes. Sediment grab samples and cores were taken to explore whether this sulfur gradient impacted organohalide-respiring Chloroflexi in lake sediments. Putative organohalide-respiring Chloroflexi were detected in 67 of 68 samples by quantitative polymerase chain reaction. Their quantities ranged from 3.5 × 10(4) to 8.4 × 10(10) copies 16S rRNA genes g(-1) dry sediment and increased in number from west to east, whereas lake sulfate concentrations decreased along this west-to-east transect. A terminal restriction fragment length polymorphism (TRFLP) method was used to corroborate this inverse relationship, with sediment samples from lower sulfate lakes containing both a higher number of terminal restriction fragments (TRFs) belonging to the organohalide-respiring Dehalococcoidetes, and a greater percentage of the TRFLP amplification made up by Dehalococcoidetes members. Statistical analyses showed that dissolved sulfur in the porewater, measured as sulfate after oxidation, appeared to have a negative impact on the total number of putative organohalide-respiring Chloroflexi, the number of Dehalococcoidetes TRFs, and the percentage of the TRFLP amplification made up by Dehalococcoidetes. These findings point to dissolved sulfur, presumably present as reduced sulfur species, as a potentially controlling factor in the natural cycling of chlorine, and perhaps as a result, the natural cycling of some carbon as well. PMID:23240654

Krzmarzick, Mark J; McNamara, Patrick J; Crary, Benjamin B; Novak, Paige J

2013-05-01

458

How to improve supply chain flexibility using strategic supply chain networks  

Microsoft Academic Search

In many industries supply chain flexibility is becoming a more and more important concept for gaining competitive advantages.\\u000a By the design and use of strategic supply chain networks significant improvements of supply chain flexibility can be achieved.\\u000a The article identifies resources, objects and parameters of supply chain flexibility and highlights the potentials of a strategic\\u000a supply chain network to realize

Herwig Winkler

2009-01-01

459

Measuring a Small Hydraulic Gradient in the Presence of Noise  

NASA Astrophysics Data System (ADS)

In naturally occurring flow systems the hydraulic gradient may be small, often less than 0.002- 0.001. These small gradients are hard to measure accurately at all scales. On regional flow maps, the accuracy of the head contour lines and the gradient is usually determined by the accuracy of the elevation of the top of the casing and of the well location on the regional map. These limitations on the regional scale accuracy will be improved in the future by the use of Global Positioning System (GPS) technology. However, for the present, some regional gradients and many local gradients - even those based on measurements made at local scales - are problematic in low gradient areas. This paper uses field data to demonstrate some of the problems associated with determining a small natural gradient in the vicinity of a research site, the Geohydrologic Experiment and Monitoring Site (GEMS) at the University of Kansas. The site is contained in an area of about 50 meters by 50 meters near the valley wall in the Kansas River valley north of Lawrence Kansas. The difficulty of determining the natural gradient was discovered about 10 years ago when attempting to design and run a bromide tracer test; the distances between wells at GEMS are too small (about 20m max.) to accurately determine the hydraulic gradient. The task is further complicated by the presence of rural water district wells some distance to the west of the site. Monitoring the water levels at the site reveals a noisy environment, primarily caused by the periodic pumping of the rural water district wells. In 2003 two additional wells were installed near the site, one to the east (96m) and one to the south (147m) of GEMS. With these larger distances between wells, monitored water level differences were more pronounced, permitting reliable gradient estimates to be calculated by accurately surveying the elevations and locations of the wells. Water levels were measured using accurately calibrated pressure transducers recording data at a high frequency over an extended period of time. The amplitude of the noise in the area was found to be larger than the head differences measured between wells; subsequently, techniques for extracting the usable signal were employed and found to be successful. This paper presents the results of our measurement of the natural gradient in the presence of noise, points out some of the pitfalls to avoid when measuring small gradients, and quantifies the uncertainties in flow velocity (magnitude and direction) that can result from gradient measurements in the presence of noise.

McElwee, C. D.; Devlin, J. F.

2004-12-01

460

Hydraulic gradient control for groundwater contaminant removal  

USGS Publications Warehouse

The Rocky Mountain Arsenal near Denver, Colarado, U.S.A., is used as a realistic setting for a hypothetical test of a procedure that plans the hydraulic stabilization and removal of a groundwater contaminant plume. A two-stage planning procedure successfully selects the best wells and their optimal pumping/recharge schedules to contain the plume while a well or system of wells within the plume removes the contaminated water. In stage I, a combined groundwater flow and solute transport model is used to simulate contaminant removal under an assumed velocity field. The result is the approximated plume boundary location as a function of time. In stage II, a linear program, which includes a groundwater flow model as part of the set of constraints, determines the optimal well selection and their optimal pumping/recharge schedules by minimizing total pumping and recharge. The simulation-management model eliminates wells far from the plume perimeter and activates wells near the perimeter as the plume decreases in size. This successfully stablizes the hydraulic gradient during aquifer cleanup.The Rocky Mountain Arsenal near Denver, Colorado, USA, is used as a realistic setting for a hypothetical test of a procedure that plans the hydraulic stabilization and removal of a groundwater contaminant plume. A two-stage planning procedure successfully selects the best wells and their optimal pumping/recharge schedules to contain the plume while a well or system of wells within the plume removes the contaminated water. In stage I, a combined groundwater flow and solute transport model is used to simulate contaminant removal under an assumed velocity field. The result is the approximated plume boundary location as a function of time. In stage II, a linear program, which includes a groundwater flow model as part of the set of constraints, determines the optimal well selection and their optimal pumping/recharge schedules by minimizing total pumping and recharge. Refs.

Fisher, Atwood D.; Gorelick, S.M.

1985-01-01

461

Molecular mechanisms for generating transmembrane proton gradients  

PubMed Central

Membrane proteins use the energy of light or high energy substrates to build a transmembrane proton gradient through a series of reactions leading to proton release into the lower pH compartment (P-side) and proton uptake from the higher pH compartment (N-side). This review considers how the proton affinity of the substrates, cofactors and amino acids are modified in four proteins to drive proton transfers. Bacterial reaction centers (RCs) and photosystem II (PSII) carry out redox chemistry with the species to be oxidized on the P-side while reduction occurs on the N-side of the membrane. Terminal redox cofactors are used which have pKas that are strongly dependent on their redox state, so that protons are lost on oxidation and gained on reduction. Bacteriorhodopsin is a true proton pump. Light activation triggers trans to cis isomerization of a bound retinal. Strong electrostatic interactions within clusters of amino acids are modified by the conformational changes initiated by retinal motion leading to changes in proton affinity, driving transmembrane proton transfer. Cytochrome c oxidase (CcO) catalyzes the reduction of O2 to water. The protons needed for chemistry are bound from the N-side. The reduction chemistry also drives proton pumping from N- to P-side. Overall, in CcO the uptake of 4 electrons to reduce O2 transports 8 charges across the membrane, with each reduction fully coupled to removal of two protons from the N-side, the delivery of one for chemistry and transport of the other to the P-side. PMID:23507617

Gunner, M.R.; Amin, Muhamed; Zhu, Xuyu; Lu, Jianxun

2013-01-01

462

Service Oriented Approach for Autonomous Exception Management in Supply Chains  

E-print Network

Service Oriented Approach for Autonomous Exception Management in Supply Chains Armando Business Process to support Autonomous Exception Management in Supply chains. Keywords: Supply Chain and consequently this triggers a rescheduling task. Current Supply Chain Management Systems lack of systematic

Paris-Sud XI, Université de

463

Density Perturbations in Chain Inflation  

E-print Network

We consider the model of ``Chain Inflation,'' in which the period of inflation in our universe took the form of a long sequence of quantum tunneling events. We find that in the simplest such scenario, in which the tunneling processes are uniform, approximately 10^4 vacua per e-folding of inflation are required in order that the density perturbations produced are of an acceptable size. We arrive at this conclusion through a combination of analytic and numerical techniques, which could also serve as starting points for calculations with more general sets of assumptions.

Brian Feldstein; Brock Tweedie

2006-12-06

464

Evaluation of the peak variance in gradient liquid chromatography.  

PubMed

The peak variance obtained under single stepwise (SS), single linear (SL) and ladder-like (LL) gradient conditions was evaluated by taking into account the variation of plate height with mobile phase composition. LC tests were performed on a C18 column using a mixture of methanol and water as the mobile phase and six aromatic compounds (anisole, o-cresol, biphenyl, phenol, aniline and acetophenone) as the model samples. It was found that the relationship between the retention factor and mobile phase composition could be described by the linear solvent strength model. The plate height that was measured under isocratic conditions varied with mobile phase composition. This variation could be described by a quadratic polynomial in this work. Under gradient conditions, the experimental and predicted values of peak variance were found to be well consistent. The discrepancy between the experimental and predicted values in the SS gradient was larger than that in the SL or LL gradient. This may be ascribed to the distortion of the gradient profile as a result of dispersion that occurred in the mobile phase. By using the dispersive gradient profile that was obtained at the column inlet for the calculation, the discrepancy between the experimental and predicted values in the SS gradient may be minimized. PMID:24471158

Hao, Weiqiang; Di, Bin; Chen, Qiang; Wang, Junde; Yang, Yongbing; Yue, Bangyi

2014-03-21

465

Mesenchymal Stem Cell Durotaxis Depends on Substrate Stiffness Gradient Strength  

PubMed Central

Mesenchymal stem cells (MSCs) respond to niche elasticity, which varies between and within tissues. Stiffness gradients result from pathological conditions but also occur through normal variation, e.g. muscle. MSCs undergo directed migration even in response to shallow stiffness gradients before differentiating. More refined gradients of both stiffness range and strength are needed to better understand mechanical regulation of migration in normal and disease pathologies. We describe polyacrylamide stiffness gradient fabrication using three distinct systems that generate stiffness gradients of physiological (1 Pa/µm), pathological (10 Pa/µm), and step (? 100Pa/um) strength spanning physiologically relevant stiffness for most soft tissue, i.e. 1–12 kPa. MSCs migrated to the stiffest region for each gradient. Time-lapse microscopy revealed that migration velocity scaled directly with gradient strength. Directed migration was reduced in the presence of the contractile agonist lysophosphatidic acid (LPA) and cytoskeletal-perturbing drugs nocodazole and cytochalasin; LPA- and nocodazole-treated cells remained spread and protrusive, while cytochalasin-treated cells did not. Untreated and nocodazole-treated cells spread in a similar manner, but nocodazole-treated cells had greatly diminished traction forces. These data suggest that actin is required for migration whereas microtubules are required for directed migration. The data also imply that in vivo, MSCs may have a more significant contribution to repairs in stiffer regions where they may preferentially accumulate. PMID:23390141

Vincent, Ludovic G.; Choi, Yu Suk; Alonso-Latorre, Baldomero; del Álamo, Juan C.; Engler, Adam J.

2013-01-01

466

Accuracy of direct gradient sensing by single cells  

E-print Network

Many types of cells are able to accurately sense shallow gradients of chemicals across their diameters, allowing the cells to move towards or away from chemical sources. This chemotactic ability relies on the remarkable capacity of cells to infer gradients from particles randomly arriving at cell-surface receptors by diffusion. Whereas the physical limits of concentration sensing by cells have been explored, there is no theory for the physical limits of gradient sensing. Here, we derive such a theory, using as models a perfectly absorbing sphere and a perfectly monitoring sphere, which, respectively, infer gradients from the absorbed surface particle density or the positions of freely diffusing particles inside a spherical volume. We find that the perfectly absorbing sphere is superior to the perfectly monitoring sphere, both for concentration and gradient sensing, since previously observed particles are never remeasured. The superiority of the absorbing sphere helps explain the presence at the surfaces of cells of signal degrading enzymes, such as PDE for cAMP in Dictyostelium discoideum (Dicty) and BAR1 for mating factor alpha in Saccharomyces cerevisiae (budding yeast). Quantitatively, our theory compares favorably to recent measurements of Dicty moving up a cAMP gradient, suggesting these cells operate near the physical limits of gradient detection.

Robert G. Endres; Ned S. Wingreen

2009-06-15

467

Temperature gradient interaction chromatography of polymers: A molecular statistical model.  

PubMed

A new model describing the retention in temperature gradient interaction chromatography of polymers is developed. The model predicts that polymers might elute in temperature gradient interaction chromatography in either an increasing or decreasing order or even nearly independent of molar mass, depending on the rate of the temperature increase relative to the flow rate. This is in contrast to solvent gradient elution, where polymers elute either in order of increasing molar mass or molar mass independent. The predictions of the newly developed model were verified with the literature data as well as new experimental data. PMID:20960449

Radke, Wolfgang; Lee, Sekyung; Chang, Taihyun

2010-11-01

468

Interpretation of restricted diffusion in sandstones with internal field gradients.  

PubMed

We report on experiments to characterize internal magnetic field gradients that are caused by magnetic susceptibility differences between the solid phase and the fluids filling the pore space. Our measurements focus on low-field relaxometry of brine and oil in sandstones from various reservoirs around the world. Our results show the need to understand the dependence of internal field gradients on diffusion length, pore size- and fluid distribution in order to predict the impact of internal gradients on the interpretation of NMR experiments. PMID:11445350

Appel, M; Freeman, J J; Gardner, J S; Hirasaki, G H; Zhang, Q G; Shafer, J L

2001-01-01

469

The global convergence properties of a conjugate gradient method  

NASA Astrophysics Data System (ADS)

Conjugate gradient methods are the most famous methods for solving nonlinear unconstrained optimization problems, especially large scale problems. That is, for its simplicity and low memory requirement. The strong Wolfe line search are usually used in practice for the analyses and implementations of conjugate gradient methods. In this paper, we present a new method of nonlinear conjugate gradient method with strong Wolfe line search for unconstrained optimization problems. Under some assumptions, the sufficient descent property and the global convergence are given. The numerical results show that our new method is efficient for some unconstrained optimization problems.

Omer, Osman; Mamat, Mustafa; Abashar, Abdelrhaman; Rivaie, Mohd

2014-06-01

470

Surface tension corrections in density measurements using density gradient columns  

Microsoft Academic Search

Summary  Surface tension corrections in density measurements using so-called “density gradient columns” are discussed. With application\\u000a of the Antonoff rule the “solidliquid” interface tension gradient along the column, (d?\\u000a \\u000a \\u000a sl\\u000a \\u000a *\\u000a \\/dx) can be replaced by the product of two terms: change of the surface tension of the liquid phase with density (independent\\u000a of the solid examined) and density gradient (a

Andrzej Ziabicki; Andrzej Wasiak

1967-01-01

471

Temperature Gradient Effect on Taylor-Couette Flow  

NASA Astrophysics Data System (ADS)

We have investigated different temperature gradient effect on Taylor-Couette flow. The radius ratio and aspect ratio of the model was 0.825 and 48, respectively. Two heating exchangers were used for generating different temperature gradient. The flow regime in the Taylor-Couette flow was studied by increasing the Reynolds number. The results showed that: as Gr is increased, in helical vortex flow regime, the vortex with the same direction of convection flow increased in size, and the moving velocty also increased. It is also shown that the presence of temperature gradient increased the flow instability obviously as the Richardson number larger than 0.004 5.

Liu, D.; Kim, H. B.

2011-09-01

472

Force-gradient nested multirate methods for Hamiltonian systems  

NASA Astrophysics Data System (ADS)

Force-gradient decomposition methods are used to improve the energy preservation of symplectic schemes applied to Hamiltonian systems. If the potential is composed of different parts with strongly varying dynamics, this multirate potential can be exploited by coupling force-gradient decomposition methods with splitting techniques for multi-time scale problems to further increase the accuracy of the scheme and reduce the computational costs. In this paper, we derive novel force-gradient nested methods and test them numerically. We apply them on the three-body problem, modified for a better observation of the advantageous properties, needed for the future research.

Shcherbakov, Dmitry; Ehrhardt, Matthias; Günther, Michael; Peardon, Michael

2015-02-01

473

A parametric study of thermomechanical behavior of functionally gradient materials  

E-print Network

distance of a functionally gradient cylinder for 5 seconds. . . . . 31 . . . . 36 Temperature distributions through the thickness at the center of the plate. . . . . . . 38 Transverse displacements along the x-direction . 10 Temperature variations... at the ceramic rich end of a functionally gradient Ti-6Al-4V/Zr02 cylinder with various power exponents for 50 seconds. Temperature distributions along the radius of a functionally gradient Ti-6AI-4V/Zr02 cylinder with metal volume fraction, V?, = r, for 20...

Chin, Che-Doong

2012-06-07

474

Continuous chain bit with downhole cycling capability  

DOEpatents

A continuous chain bit for hard rock drilling is capable of downhole cycling. A drill head assembly moves axially relative to a support body while the chain on the head assembly is held in position so that the bodily movement of the chain cycles the chain to present new composite links for drilling. A pair of spring fingers on opposite sides of the chain hold the chain against movement. The chain is held in tension by a spring-biased tensioning bar. A head at the working end of the chain supports the working links. The chain is centered by a reversing pawl and piston actuated by the pressure of the drilling mud. Detent pins lock the head assembly with respect to the support body and are also operated by the drilling mud pressure. A restricted nozzle with a divergent outlet sprays drilling mud into the cavity to remove debris. Indication of the centered position of the chain is provided by noting a low pressure reading indicating proper alignment of drilling mud slots on the links with the corresponding feed branches.

Ritter, Don F. (Albuquerque, NM); St. Clair, Jack A. (Albuquerque, NM); Togami, Henry K. (Albuquerque, NM)

1983-01-01

475

The triple-A supply chain.  

PubMed

Building a strong supply chain is essential for business success. But when it comes to improving their supply chains, few companies take the right approach. Many businesses work to make their chains faster or more cost-effective, assuming that those steps are the keys to competitive advantage. To the contrary: Supply chains that focus on speed and costs tend to deteriorate over time. The author has spent 15 years studying more than 60 companies to gain insight into this and other supply chain dilemmas. His conclusion: Only companies that build supply chains that are agile, adaptable, and aligned get ahead of their rivals. All three components are essential; without any one of them, supply chains break down. Great companies create supply chains that respond to abrupt changes in markets. Agility is critical because in most industries, both demand and supply fluctuate rapidly and widely. Supply chains typically cope by playing speed against costs, but agile ones respond both quickly and cost-efficiently. Great companies also adapt their supply networks when markets or strategies change. The best supply chains allow managers to identify structural shifts early by recording the latest data, filtering out noise, and tracking key patterns. Finally, great companies align the interests of the partners in their supply chains with their own. That's important because every firm is concerned solely with its own interests. If its goals are out of alignment with those of other partners in the supply chain, performance will suffer. When companies hear about the triple-A supply chain, they assume that building one will require increased technology and investment. But most firms already have the infrastructure in place to create one. A fresh attitude alone can go a long way toward making it happen. PMID:15559579

Lee, Hau L

2004-10-01

476

Vibron transport in macromolecular chains  

E-print Network

We study the hopping mechanism of the vibron excitation transport in the simple 1D model of biological macromolecular chains. We supposed that the vibron interaction with thermal oscillations of the macromolecular structural elements will result in vibron self -trapping, and the formation of the partial dressed vibron state. With use of the modified Holstein polaron model, we calculate vibron diffusivity in dependence of the basic system parameters and temperature. We obtain that the vibron diffusivity smoothly decreases in non adiabatic limit when the strength of the vibron-phonon coupling grows. However this dependence becomes by discontinuous one in case of growth of the adiabaticity of the system. The value of the critical point depends of the system temperature, and at room temperatures it belongs to the low or intermediate coupling regime. We discuss an application of these results to study of vibron transport to 3D bundles of such macromolecules chains considering it as polymer nanorods and to 2D polymer films organized from such macromolecules.

D. ?evizovi?; Z. Ivic.; S. Galovi?; A. Chizhov A.; A. Reshetnyak

2014-12-16

477

Covalently immobilized biomolecule gradient on hydrogel surface using a gradient generating microfluidic device for a quantitative mesenchymal stem cell study.  

PubMed

Precisely controlling the spatial distribution of biomolecules on biomaterial surface is important for directing cellular activities in the controlled cell microenvironment. This paper describes a polydimethylsiloxane (PDMS) gradient-generating microfluidic device to immobilize the gradient of cellular adhesive Arg-Gly-Asp (RGD) peptide on poly (ethylene glycol) (PEG) hydrogel. Hydrogels are formed by exposing the mixture of PEG diacrylate (PEGDA), acryloyl-PEG-RGD, and photo-initiator with ultraviolet light. The microfluidic chip was simulated by a fluid dynamic model for the biomolecule diffusion process and gradient generation. PEG hydrogel covalently immobilized with RGD peptide gradient was fabricated in this microfluidic device by photo-polymerization. Bone marrow derived rat mesenchymal stem cells (MSCs) were then cultured on the surface of RGD gradient PEG hydrogel. Cell adhesion of rat MSCs on PEG hydrogel with various RGD gradients were then qualitatively and quantitatively analyzed by immunostaining method. MSCs cultured on PEG hydrogel surface with RGD gradient showed a grated fashion for cell adhesion and spreading that was proportional to RGD concentration. It was also found that 0.107-0.143?mM was the critical RGD concentration range for MSCs maximum adhesion on PEG hydrogel. PMID:22550556

Liu, Zongbin; Xiao, Lidan; Xu, Baojian; Zhang, Yu; Mak, Arthur Ft; Li, Yi; Man, Wing-Yin; Yang, Mo

2012-06-01

478

Skin Membrane Electrical Impedance Properties under the Influence of a Varying Water Gradient  

PubMed Central

The stratum corneum (SC) is an effective permeability barrier. One strategy to increase drug delivery across skin is to increase the hydration. A detailed description of how hydration affects skin permeability requires characterization of both macroscopic and molecular properties and how they respond to hydration. We explore this issue by performing impedance experiments on excised skin membranes in the frequency range 1 Hz to 0.2 MHz under the influence of a varying gradient in water activity (aw). Hydration/dehydration induces reversible changes of membrane resistance and effective capacitance. On average, the membrane resistance is 14 times lower and the effective capacitance is 1.5 times higher when the outermost SC membrane is exposed to hydrating conditions (aw = 0.992), as compared to the case of more dehydrating conditions (aw = 0.826). Molecular insight into the hydration effects on the SC components is provided by natural-abundance 13C polarization transfer solid-state NMR and x-ray diffraction under similar hydration conditions. Hydration has a significant effect on the dynamics of the keratin filament terminals and increases the interchain spacing of the filaments. The SC lipids are organized into lamellar structures with ? 12.6 nm spacing and hexagonal hydrocarbon chain packing with mainly all-trans configuration of the acyl chains, irrespective of hydration state. Subtle changes in the dynamics of the lipids due to mobilization and incorporation of cholesterol and long-chain lipid species into the fluid lipid fraction is suggested to occur upon hydration, which can explain the changes of the impedance response. The results presented here provide information that is useful in explaining the effect of hydration on skin permeability. PMID:23790372

Björklund, Sebastian; Ruzgas, Tautgirdas; Nowacka, Agnieszka; Dahi, Ihab; Topgaard, Daniel; Sparr, Emma; Engblom, Johan

2013-01-01

479

43 CFR 3252.14 - How must I complete a temperature gradient well?  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false How must I complete a temperature gradient well? 3252.14 Section 3252...Operations § 3252.14 How must I complete a temperature gradient well? Complete temperature gradient wells to allow for proper...

2012-10-01

480

43 CFR 3252.14 - How must I complete a temperature gradient well?  

...2014-10-01 false How must I complete a temperature gradient well? 3252.14 Section 3252...Operations § 3252.14 How must I complete a temperature gradient well? Complete temperature gradient wells to allow for proper...

2014-10-01

481

43 CFR 3252.14 - How must I complete a temperature gradient well?  

Code of Federal Regulations, 2011 CFR

...2011-10-01 false How must I complete a temperature gradient well? 3252.14 Section 3252...Operations § 3252.14 How must I complete a temperature gradient well? Complete temperature gradient wells to allow for proper...

2011-10-01

482

43 CFR 3252.13 - How long may I collect information from my temperature gradient well?  

Code of Federal Regulations, 2013 CFR

...long may I collect information from my temperature gradient well? 3252.13 Section...long may I collect information from my temperature gradient well? You may collect information from your temperature gradient well for as long as your...

2013-10-01

483

43 CFR 3252.14 - How must I complete a temperature gradient well?  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false How must I complete a temperature gradient well? 3252.14 Section 3252...Operations § 3252.14 How must I complete a temperature gradient well? Complete temperature gradient wells to allow for proper...

2013-10-01

484

43 CFR 3252.13 - How long may I collect information from my temperature gradient well?  

...long may I collect information from my temperature gradient well? 3252.13 Section...long may I collect information from my temperature gradient well? You may collect information from your temperature gradient well for as long as your...

2014-10-01

485

43 CFR 3252.13 - How long may I collect information from my temperature gradient well?  

Code of Federal Regulations, 2012 CFR

...long may I collect information from my temperature gradient well? 3252.13 Section...long may I collect information from my temperature gradient well? You may collect information from your temperature gradient well for as long as your...

2012-10-01

486

43 CFR 3252.13 - How long may I collect information from my temperature gradient well?  

Code of Federal Regulations, 2011 CFR

...long may I collect information from my temperature gradient well? 3252.13 Section...long may I collect information from my temperature gradient well? You may collect information from your temperature gradient well for as long as your...

2011-10-01

487

Crossover transition in flowing granular chains  

NASA Astrophysics Data System (ADS)

We report on the dynamical and statistical behavior of flowing collections of granular chains confined two-dimensionally (2D) within a rotating tumbler. Experiments are conducted with systems of chains of fixed length, but various lengths are considered. The dynamics are punctuated by cascades of chains along a free-surface cascades, which drive the development of mixed porous/laminar packing arrangements in bulk. We investigate the conformation of the system, as characterized by the porosity of the flow region occupied by the chains and the mean-square end-to-end distance of the chains during flow. Both of these measures show crossover transitions from a 2D self-avoiding walk to a 2D random walk when the chain length becomes long enough to allow self-contact.

Ulrich, Xialing; Fried, Eliot; Shen, Amy Q.

2009-09-01

488

Crossover transition in flowing granular chains.  

PubMed

We report on the dynamical and statistical behavior of flowing collections of granular chains confined two-dimensionally (2D) within a rotating tumbler. Experiments are conducted with systems of chains of fixed length, but various lengths are considered. The dynamics are punctuated by cascades of chains along a free-surface cascades, which drive the development of mixed porous/laminar packing arrangements in bulk. We investigate the conformation of the system, as characterized by the porosity of the flow region occupied by the chains and the mean-square end-to-end distance of the chains during flow. Both of these measures show crossover transitions from a 2D self-avoiding walk to a 2D random walk when the chain length becomes long enough to allow self-contact. PMID:19905048

Ulrich, Xialing; Fried, Eliot; Shen, Amy Q

2009-09-01

489

Conductance of a finite Kitaev chain  

NASA Astrophysics Data System (ADS)

We present a stochastic formulation of the Kadanoff-Baym or Keldysh theory to calculate the conductance of a finite Kitaev chain coupled to two electron reservoirs. We study the dependence of the conductance on the number of sites in the chain and find that only for sufficiently long chains and in the regime that the chain is a topological superconductor the conductance at both ends tends to the universal value 2 e2/h , as expected on the basis of the contact resistance of a single conducting channel provided by the Majorana zero mode. In this topologically nontrivial case we find an exponential decay of the current inside the chain and a simple analytical expression for the decay length. Finally, we also study the differential conductance at nonzero bias and the full current-voltage curves. We find a nonmonotonic behavior of the maximal current through the Kitaev chain as a function of the coupling strength with the reservoirs.

Doornenbal, R. J.; Skantzaris, G.; Stoof, H. T. C.

2015-01-01

490

Control of flexible structures by applied thermal gradients  

NASA Technical Reports Server (NTRS)

Thermal, elastic, and feedback analyses are applied to the case of a beam with a distributed thermal actuator. The actuator is capable of producing a thermal gradient across the section of the beam. One candidate for such an actuator uses the Peltier effect, which appears in certain semiconductors. These devices act as heat pumps when a voltage is applied, causing a temperature gradient. It is shown that the thermal gradients can induce deflection in the beam. If the thermal gradients are applied in the proper sense to a vibrating beam, it is possible to increase the vibration damping exhibited by the structure. Experimental results are given for a cantilever beam, whose first vibrational mode damping ratio was increased from 0.81 to 7.4 percent with simple lead compensation.

Edberg, Donald L.

1987-01-01

491

On the control of flexible structures by applied thermal gradients  

NASA Technical Reports Server (NTRS)

Thermal, elastic, and feedback analyses are applied to the case of a beam with a distributed thermal actuator. The actuator is capable of producing a thermal gradient across the section of the beam. One candidate for such an actuator uses the Peltier effect, which appears in certain semiconductors. These devices act as heat pumps when a voltage is applied, causing a temperature gradient. It is shown that the thermal gradients can induce deflection in the beam. If the thermal gradients are applied in the proper sense to a vibrating beam, it is possible to increase the vibration damping exhibited by the structure. Experimental results are given for a cantilever beam, whose first vibrational mode damping ratio was increased from 0.81 to 7.4 percent with a simple lead compensation.

Edberg, D. L.

1987-01-01

492

Scalings of energetic particle transport by ion temperature gradient microturbulencea...  

E-print Network

Scalings of energetic particle transport by ion temperature gradient microturbulencea... Wenlu 2009; accepted 12 March 2010; published online 7 May 2010 Transport scaling of energetic particles. INTRODUCTION Energetic particles can be created in magnetically con- fined plasmas through fusion reactions

Lin, Zhihong

493