title stringlengths 0 1.13k | abstract stringlengths 1 15.7k | PMID int64 22 36.5M |
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[The lipid-lowering and antioxidative effects of marine collagen peptides]. | To determine the relative molecular mass of marine collagen peptides (MCPs) and investigate the effects of MCPs on serum lipids, anti-oxidative enzymes and malondialdehyde (MDA) in hyperlipidemic rats. Sephadex G-25, high performance liquid chromatography (HPLC) and matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) methods were used to determine the relative molecular mass of MCPs. Then 50 healthy male SD rats were divided into 5 groups, which were normal control (NC) group, hyperlipidemic model control (HC) group and 1.0, 3.0, 9.0 g/kgbw MCPs groups, MCPs were orally administered by gavage to rats in MCPs group for 45 consecutive days (2 ml/100 kgbw per day), and the control rats were given vehicle only, all animals (except NC rats) were fed with a high fat diet composed of 79% basic diet, 10% lard, 10% yolk powder and 1% cholesterol. The levels of serum lipids, the content of MDA and activity of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) in serum were measured. The levels of serum total cholesterol (TC) in 1.0, 3.0, 9.0 g/kgbw MCPs groups were 1.89 +/- 0.29, 2.07 +/- 0.39 and 1.99 +/- 0.29 mmol/L respectively, each of which was significantly lower than that in HC group (3.37 +/- 0.24 mmol/L); low-density lipoprotein cholesterol (LDL-C) levels in 1.0, 3.0, 9.0 g/kgbw MCPs groups were 0.83 +/- 0.16, 1.01 +/- 0.35 and 0.91 +/- 0.26 mmol/L respectively, each of which was significantly lower than that in HC group(2.20 +/- 0.34 mmol/L); triglyceride (TG) levels in 3.0 and 9.0 g/kgbw MCPs groups (0.90 +/- 0.15 and 0.86 +/- 0.12 mmol/L) were reduced significantly compared with that in HC group (1.18 +/- 0.18 mmol/L); MDA level in 9.0 g/kgbw MCPs group was 7.1 +/- 4.1 nmol/ml, which was significantly lower than that in HC group ( 15.9 +/- 9.9 nmol/ml); and atherogenic index (AI) in hyperlipidemic rats fed with 1.0, 3.0, 9.0 g/kgbw MCPs were 1.14 +/- 0.22, 1.16 +/- 0.27 and 0.99 +/- 0.31 respectively, each of which was significantly lower than that in HC group (2.27 +/- 0.55). The activities of SOD in 1.0, 3.0, 9.0 g/kgbw MCPs groups (218.6 +/- 33.2, 242.7 +/- 21.4 and 242.1 +/- 44.8 U/ml) were obviously increased compared with that in HC group (119.7 +/- 47.8 U/ml), and anti-atherogenic index (AAI) were also increased significantly (0.47 +/- 0.04, 0.47 +/- 0.06, 0.51 +/- 0.09 vs 0.31 +/- 0.05). MCPs should have antioxidative and lipid-lowering effects, and might play a preventive role in hyperlipidemia and atherogenesis. | 18,763,630 |
[Effects of marine collagen peptide on delaying the skin aging]. | To investigate the protective effect of marine collagen peptides (MCPs) on the skin of aged mice induced by D-galactose. Subchronic toxicity study was conducted while D-galactose induced subacute aging model was established. D-galactose dose of 0.125 g/kg body weight was intraperitoneally injected daily for 90 days. Marine collagen peptide 0.225, 0.450, 1.350 g/kg body weight were administered by oral gavage. Superoxide dismutase (SOD), catalase (CAT) activity and malondialdehyde (MDA) content in blood serum were measured, along with cutaneous histopathology examination. Epidermal thickness was significantly higher in MCPs treated group. Number and activity of fibroblast in MCPs treated dermis was increased prominently. The activity of SOD in 0.225, 0.450, 1.350 g/kgbw MCPs treated groups were 455.52 +/- 11.39, 460.15 +/- 18.09, 468.59 +/- 27.25 U/ml respectively, each of which was significantly higher than that in model control group; the activity of serum CAT in 0.225, 1.350 g/kgbw MCPs treated groups (21.33 +/- 4.82, 21.69 +/- 1.68 U/ml) were obviously increased compared with that in model control group (17.14 +/- 2.81 U/ml); MDA level in 0.450, 1.350 g/kgbw MCPs treated groups were 5.67 +/- 0.93, 5.76 +/- 1.02 nmol/ml respectively, each of which was significantly lower than that in model control group (7.63 +/- 1.37 nmol/ml). The results showed that MCPs might play a protective role on skin aging by improving the activity of antioxidant. | 18,763,632 |
[Study on protective effect of grape procyanidins in radiation injury in radiation-contacted persons]. | To study the protective effect of Grape procyanidins (GPC) on radiation injury in radiation-contacted persons. Sixty radiation-contacted persons were randomly divided into the experimental group and the control group and 15 radiation-uncontacted persons were selected as the normal group. The experimental group was given GPC (100 mg/day), while the control group was given the capsule of starch every day for 60 days. Vein blood samples were taken before and after the study and the total antioxidative capacity (T-AOC), Malondialdehyde (MDA), cell proliferation, expression levels of proliferative cell nuclear antigen (PCNA), Bcl-2 and Bax protein, WBC were measured. The WBC, T-AOC and cell proliferation rate of the experimental group were (5.62 +/- 0.40) 10(9)/L, (17.07 +/- 1.91) U/ml and 0.87 +/- 0.09 respectively, which were significantly higher than those of the control group. The MDA and Bax expression levels were (4.12 +/- 0.37) nmol/L and 28.06% +/- 5.79% respectively that were significantly lower than those of the control group. GPC should have protective effects on radiation injury of the radiation-contacted persons. | 18,763,638 |
Quantifying the burden of chronic viral hepatitis-related cirrhosis hospitalizations in New Haven County, Connecticut. | Chronic viral hepatitis can cause cirrhosis. Viral hepatitis-related cirrhosis may be causing an increasing health burden since exposure to hepatitis B virus and hepatitis C virus in the United States increased starting in the 1960s. Using hospital discharge data, we estimated the number of adult New Haven County residents hospitalized for cirrhosis and examined the proportion caused by chronic viral hepatitis. Data on etiology were obtained from hospital discharge records, death certificate information, and New Haven County Liver Study records. From 1 October 1999 to 30 September 2000, 269 adult New Haven County residents were hospitalized for cirrhosis in a New Haven County hospital, for an incidence of 43.2 per 100,000 population. The burden of viral hepatitis-related cirrhosis was 15.9 per 100,000. Hepatitis C virus was the most common viral etiology. Given the long period between initial infection and clinical decompensation, screening and treatment programs aimed at reducing viral hepatitis-related morbidity should reduce hospitalization rates. | 18,763,666 |
Oral malodor reduction from a zinc-containing toothpaste. | To evaluate the anti-malodor efficacy of toothpaste containing 0.2% zinc sulphate after a single brushing and following extended use. Two clinical studies of common design but different malodor assessment were carried out. In the first study, volatile sulphur compounds (VSC) were measured with a Halimeter; in the second, breath freshness was assessed by odor judges (organoleptic score). At the start of the study, suitable subjects were assigned at random to either the test toothpaste (containing 0.2% zinc sulphate) or the placebo toothpaste (no zinc), and oral breath assessments were made before and two hours after brushing. The same assessments were repeated after allocated toothpastes had been used twice daily for four weeks. Prior to the before-brushing breath assessment, subjects were asked to refrain from eating/drinking and oral hygiene for 12 hours. The results at the start and end of the study showed a significant reduction in mean Halimeter scores and a significant improvement in organoleptic scores two hours after brushing for subjects using the test toothpaste with zinc sulphate. In addition, at the end of the study, subjects using the test toothpaste with zinc sulphate had reduced Halimeter scores and improved organoleptic scores 12 hours after the last brushing compared to the placebo group. The differences between the test and placebo values ranged from 16% to 46% and were all statistically significant (p < 0.0001). Both clinical studies independently support the efficacy of the test toothpaste with 0.2% zinc sulphate in reducing oral malodor after a single brushing, and after four weeks for 12 hours after brushing compared to a toothpaste without zinc ions. | 18,763,690 |
Proteomics of membrane receptors and signaling. | Receptors represent an abundant class of integral membrane proteins that transmit information on various types of signals within the cell. Assemblages of receptors and their interacting proteins (receptor complexes) have emerged as important units of signal transduction for various types of receptors including G protein coupled, ligand-gated ion channel, and receptor tyrosine kinase. This review aims to summarize the major approaches and findings of receptor proteomics. Isolation and characterization of receptor complexes from cells has become common using the methods of immunoaffinity-, ligand-, and tag-based chromatography followed by MS for the analysis of enriched receptor preparations. In addition, tools such as stable isotope labeling have contributed to understanding quantitative properties and PTMs to receptors and their interacting proteins. As data from studies on receptor-protein interactions considerably expands, complementary approaches such as bioinformatics and computational biology will undoubtedly play a significant role in defining cellular and network functions for various types of receptor complexes. Findings from receptor proteomics may also shed light on the mechanism of action for pharmacological drugs and can be of value in understanding molecular pathologies of disease states. | 18,763,708 |
A practical guide for the identification of membrane and plasma membrane proteins in human embryonic stem cells and human embryonal carcinoma cells. | The identification of (plasma) membrane proteins in cells can provide valuable insights into the regulation of their biological processes. Pluripotent cells such as human embryonic stem cells and embryonal carcinoma cells are capable of unlimited self-renewal and share many of the biological mechanisms that regulate proliferation and differentiation. The comparison of their membrane proteomes will help unravel the biological principles of pluripotency, and the identification of biomarker proteins in their plasma membranes is considered a crucial step to fully exploit pluripotent cells for therapeutic purposes. For these tasks, membrane proteomics is the method of choice, but as indicated by the scarce identification of membrane and plasma membrane proteins in global proteomic surveys it is not an easy task. In this minireview, we first describe the general challenges of membrane proteomics. We then review current sample preparation steps and discuss protocols that we found particularly beneficial for the identification of large numbers of (plasma) membrane proteins in human tumour- and embryo-derived stem cells. Our optimized assembled protocol led to the identification of a large number of membrane proteins. However, as the composition of cells and membranes is highly variable we still recommend adapting the sample preparation protocol for each individual system. | 18,763,709 |
Extracellular recordings of rodents in vivo: their contribution to integrative neuroscience. | The prevalent theory in learning and memory processes is that they are underlain by short and long-term changes in synaptic weight, which continuously modulates neural networks during acquisition and recall. This synaptic plasticity has been revealed by recording extracellular field potentials. The enhancement of synaptic transmission was primarily noted in the hippocampus and was named long-term potentiation (LTP). The opposite mechanism, long-term depression (LTD), a reduction of synaptic transmission, was first discovered in the cerebellum. Since then, the LTP-model has been studied mainly using in vitro and acute anesthetized in vivo preparations. This approach has led to remarkable progress in the comprehension of intracellular molecular processes during LTP and LTD. In this review, we focus mainly on what we can learn about molecular events using extracellular field potential recordings with a more ecological model, i.e., studies using the freely behaving animal, with animals that are genetically modified or not, in several behavioral paradigms aimed at gaining insight into some of the conflicting results obtained with in vitro and in vivo preparations. | 18,763,725 |
Experience-consistent modeling for radial basis function neural networks. | We develop a new approach to the design of neural networks, which utilizes a collaborative framework of knowledge-driven experience. In contrast to the "standard" way of developing neural networks, which explicitly exploits experimental data, this approach incorporates a mechanism of knowledge-driven experience. The essence of the proposed scheme of learning is to take advantage of the parameters (connections) of neural networks built in the past for the same phenomenon (which might also exhibit some variability over time or space) for which are interested to construct the network on a basis of currently available data. We establish a conceptual and algorithmic framework to reconcile these two essential sources of information (data and knowledge) in the process of the development of the network. To make a presentation more focused and come up with a detailed quantification of the resulting architecture, we concentrate on the experience-based design of radial basis function neural networks (RBFNNs). We introduce several performance indexes to quantify an effect of utilization of the knowledge residing within the connections of the networks and establish an optimal level of their use. Experimental results are presented for low-dimensional synthetic data and selected datasets available at the Machine Learning Repository. | 18,763,728 |
A modified LAMSTAR neural network and its applications. | This paper describes a modification of the LArge Memory STorage And Retrieval (LAMSTAR) neural network. The purpose of the modification is to allow rare events a larger role in decision-making when they are strongly biased towards a particular decision. As a by-product, the modification also permits the introduction of a confidence measure. This measure allows comparison across different network inputs so that the user may choose the "best" solution. The authors have applied the modified LAMSTAR network to a financial forecasting problem. | 18,763,732 |
Color image segmentation with support vector machines: applications to road signs detection. | In this paper we propose efficient color segmentation method which is based on the Support Vector Machine classifier operating in a one-class mode. The method has been developed especially for the road signs recognition system, although it can be used in other applications. The main advantage of the proposed method comes from the fact that the segmentation of characteristic colors is performed not in the original but in the higher dimensional feature space. By this a better data encapsulation with a linear hypersphere can be usually achieved. Moreover, the classifier does not try to capture the whole distribution of the input data which is often difficult to achieve. Instead, the characteristic data samples, called support vectors, are selected which allow construction of the tightest hypersphere that encloses majority of the input data. Then classification of a test data simply consists in a measurement of its distance to a centre of the found hypersphere. The experimental results show high accuracy and speed of the proposed method. | 18,763,733 |
Kullback-Leibler Markov chain Monte Carlo--a new algorithm for finite mixture analysis and its application to gene expression data. | In this paper, we study Bayesian analysis of nonlinear hierarchical mixture models with a finite but unknown number of components. Our approach is based on Markov chain Monte Carlo (MCMC) methods. One of the applications of our method is directed to the clustering problem in gene expression analysis. From a mathematical and statistical point of view, we discuss the following topics: theoretical and practical convergence problems of the MCMC method; determination of the number of components in the mixture; and computational problems associated with likelihood calculations. In the existing literature, these problems have mainly been addressed in the linear case. One of the main contributions of this paper is developing a method for the nonlinear case. Our approach is based on a combination of methods including Gibbs sampling, random permutation sampling, birth-death MCMC, and Kullback-Leibler distance. | 18,763,739 |
Conserved water molecules in X-ray structures highlight the role of water in intramolecular and intermolecular interactions. | Water molecules immobilized on a protein or DNA surface are known to play an important role in intramolecular and intermolecular interactions. Comparative analysis of related three-dimensional (3D) structures allows to predict the locations of such water molecules on the protein surface. We have developed and implemented the algorithm WLAKE detecting "conserved" water molecules, i.e. those located in almost the same positions in a set of superimposed structures of related proteins or macromolecular complexes. The problem is reduced to finding maximal cliques in a certain graph. Despite exponential algorithm complexity, the program works appropriately fast for dozens of superimposed structures. WLAKE was used to predict functionally significant water molecules in enzyme active sites (transketolases) as well as in intermolecular (ETS-DNA complexes) and intramolecular (thiol-disulfide interchange protein) interactions. The program is available online at http://monkey.belozersky.msu.ru/~evgeniy/wLake/wLake.html. | 18,763,742 |
Large-scale structural modeling of protein complexes at low resolution. | Structural aspects of protein-protein interactions provided by large-scale, genome-wide studies are essential for the description of life processes at the molecular level. A methodology is developed that applies the protein docking approach (GRAMM), based on the knowledge of experimentally determined protein-protein structures (DOCKGROUND resource) and properties of intermolecular energy landscapes, to genome-wide systems of protein interactions. The full sequence-to-structure-of-complex modeling pipeline is implemented in the Genome Wide Docking Database (GWIDD) resource. Protein interaction data are imported to GWIDD from external datasets of experimentally determined interaction networks. Essential information is extracted and unified to form the GWIDD database. Structures of individual interacting proteins in the database are retrieved (if available) or modeled, and protein complex structures are predicted by the docking program. All protein sequence, structure, and docking information is conveniently accessible through a Web interface. | 18,763,743 |
Discovery and evaluation of 4-(2-(4-chloro-1H-pyrazol-1-yl)ethylamino)-3-(6-(1-(3-fluoropropyl)piperidin-4-yl)-4-methyl-1H-benzo[d]imidazol-2-yl)pyridin-2(1H)-one (BMS-695735), an orally efficacious inhibitor of insulin-like growth factor-1 receptor kinase with broad spectrum in vivo antitumor activity. | We previously reported that 1 (BMS-536924), a benzimidazole inhibitor of the insulin-like growth factor-1 receptor, had demonstrated in vivo antitumor activity. This lead compound was found to have potent CYP3A4 inhibition, CYP3A4 induction mediated by PXR transactivation, poor aqueous solubility, and high plasma protein binding. Herein we disclose the evolution of this chemotype to address these issues. This effort led to 10 (BMS-695735), which exhibits improved ADME properties, a low risk for drug-drug interactions, and in vivo efficacy in multiple xenograft models. | 18,763,755 |
Nickel-catalyzed asymmetric cross-couplings of racemic propargylic halides with arylzinc reagents. | A stereoconvergent method for the catalytic asymmetric Negishi cross-coupling of racemic secondary propargylic halides with arylzinc reagents has been developed. Neither family of compounds has previously been shown to be a suitable partner in such coupling processes. From a practical point of view, it is noteworthy that the catalyst components (NiCl2.glyme and pybox ligand 1) are commercially available. | 18,763,769 |
Origin of the regio- and stereoselectivity of allylic substitution of organocopper reagents. | The origin of the contrasting regioselectivities in allylic substitution found for a heterocuprate MeCu(CN)Li and a homocuprate Me2CuLi was studied using density functional calculations. The gamma-selectivity of MeCu(CN)Li is determined at the oxidative addition stage of the reaction, where the different degree of trans effect of the Me and the CN groups dictates the relative orientation of the methyl group and the leaving acetate group. As the result, the transition state where the acetate group leaves trans to the Me group on the copper atom is favored, and the gamma-selectivity results. The homocuprate Me2CuLi is symmetrical by nature and does not show such regioselectivity. | 18,763,774 |
Exploring electronically polarized pentacenes. | Unsymmetrically functionalized pentacenes with electron-rich and/or -poor substituents at the 6- and 13-positions were synthesized. The electronic influence was evaluated by solution-state UV-vis absorption and emission spectroscopies. These materials exhibit good solubility in common organic solvents and are stable in the presence of air and water. | 18,763,787 |
Palladium-catalyzed C-allylation of benzoins and an NHC-catalyzed three component coupling derived thereof: compatibility of NHC- and Pd-catalysts. | A large range of benzoins was successfully applied as C-nucleophiles in the palladium-catalyzed allylic alkylation with several allyl acetates, resulting in functionalized tertiary homoallylic alcohols. A number of unsymmetrical benzoins can be coupled with high levels of regio- and chemoselectivity. Finally, the challenging compatibility of free N-heterocyclic carbenes with a palladium catalyst has been utilized in a number of metal- and organocatalyzed three-component coupling reactions. | 18,763,794 |
LOCUSTRA: accurate prediction of local protein structure using a two-layer support vector machine approach. | Constraint generation for 3d structure prediction and structure-based database searches benefit from fine-grained prediction of local structure. In this work, we present LOCUSTRA, a novel scheme for the multiclass prediction of local structure that uses two layers of support vector machines (SVM). Using a 16-letter structural alphabet from de Brevern et al. (Proteins: Struct., Funct., Bioinf. 2000, 41, 271-287), we assess its prediction ability for an independent test set of 222 proteins and compare our method to three-class secondary structure prediction and direct prediction of dihedral angles. The prediction accuracy is Q16=61.0% for the 16 classes of the structural alphabet and Q3=79.2% for a simple mapping to the three secondary classes helix, sheet, and coil. We achieve a mean phi(psi) error of 24.74 degrees (38.35 degrees) and a median RMSDA (root-mean-square deviation of the (dihedral) angles) per protein chain of 52.1 degrees. These results compare favorably with related approaches. The LOCUSTRA web server is freely available to researchers at http://www.fz-juelich.de/nic/cbb/service/service.php. | 18,763,837 |
Small estuarine fishes feed on large trematode cercariae: lab and field investigations. | In aquatic ecosystems, dense populations of snails can shed millions of digenean trematode cercariae every day. These short-lived, free-living larvae are rich in energy and present a potential resource for consumers. We investigated whether estuarine fishes eat cercariae shed by trematodes of the estuarine snail Cerithidea californica. In aquaria we presented cercariae from 10 native trematode species to 6 species of native estuarine fishes. Many of these fishes readily engorged on cercariae. To determine if fishes ate cercariae in the field, we collected the most common fish species, Fundulus parvipinnis (California killifish), from shallow water on rising tides when snails shed cercariae. Of 61 killifish, 3 had recognizable cercariae in their gut. Because cercariae are common in this estuary, they could be frequent sources of energy for small fishes. In turn, predation on cercariae by fishes (and other predators) could also reduce the transmission success of trematodes. | 18,763,852 |
Bystander/abscopal effects induced in intact Arabidopsis seeds by low-energy heavy-ion radiation. | To date, radiation-induced bystander effects have been observed largely in in vitro single-cell systems; verification of both the effects and the mechanisms in multicellular systems in vivo is important. Previously we showed that bystander/ abscopal effects can be induced by irradiating the shoot apical meristem cells in Arabidopsis embryos. In this study, we investigated the in vivo effects induced by 30 keV 40Ar ions in intact Arabidopsis seeds and traced the postembryonic development of both irradiated and nonirradiated shoot apical meristem and root apical meristem cells. Since the range of 30 keV 40Ar ions in water is about 0.07 microm, which is less than the distance from the testa to shoot apical meristem and root apical meristem in Arabidopsis seeds (about 100 microm), the incident low-energy heavy ions generally stop in the proximal surface. Our results showed that, after the 30 keV 40Ar-ion irradiation of shielded and nonshielded Arabidopsis seeds at a fluence of 1.5 x 10(17) ions/cm2, short- and long-term postembryonic development, including germination, root hair differentiation, primary root elongation, lateral root initiation and survival, was significantly inhibited. Since shoot apical meristem and root apical meristem cells were not damaged directly by radiation, the results suggested that a damage signal(s) is transferred from the irradiated cells to shoot apical meristem and root apical meristem cells and causes the ultimate developmental alterations, indicating that long-distance bystander/ abscopal effects exist in the intact seed. A further study of mechanisms showed that the effects are associated with either enhanced generation of reactive oxygen species (ROS) or decreased auxin-dependent transcription in postembryonic development. Treatment with the ROS scavenger dimethyl sulfoxide (DMSO) or synthetic auxin 2,4-dichlorophenoxyacetic acid (2,4-D) can significantly reverse both the alterations in postembryonic development and auxin-dependent transcription, suggesting that ROS and auxin-dependent transcription processes play essential roles in the low-energy heavy-ion radiation-induced long-distance bystander/abscopal effects in the intact organism. | 18,763,864 |
Early increase in osteoclast number in mice after whole-body irradiation with 2 Gy X rays. | Bone loss is a consequence of exposure to high-dose radiotherapy. While damage to bone vasculature and reduced proliferation of bone-forming osteoblasts has been implicated in this process, the effect of radiation on the number and activity of bone-resorbing osteoclasts has not been characterized. In this study, we exposed mice to a whole-body dose of 2 Gy of X rays to quantify the early effects of radiation on osteoclasts and bone structural properties. Female C57BL/6 mice (13 weeks old) were divided into two groups: irradiated and nonirradiated controls. Animals were killed humanely 3 days after radiation exposure. Analysis of serum chemistry revealed a 14% increase in the concentration of tartrate resistant acid phosphatase (TRAP)-5b, a marker of osteoclast activity, in irradiated mice (P < 0.05). Osteoclast number (+44%; P < 0.05) and osteoclast surface (+213%; P < 0.001) were elevated in TRAP-stained histological sections of tibial metaphyses. No significant change was observed in osteoblast surface or osteocalcin concentration or in trabecular microarchitecture (i.e. bone volume fraction) as measured through microcomputed tomography (P > 0.05). This study provides definitive, quantitative evidence of an early, radiation-induced increase in osteoclast activity and number. Osteoclastic bone resorption may represent a contributor to bone atrophy observed after therapeutic irradiation. | 18,763,868 |
Intact implicit learning of spatial context and temporal sequences in childhood autism spectrum disorder. | Autism spectrum disorder (ASD) is defined by atypicalities in domains that are posited to rely on implicit learning processes such as social communication, language, and motor behavior. The authors examined 2 forms of implicit learning in 14 children with high-functioning ASD (10 of whom were diagnosed with Asperger's syndrome) and 14 control children, learning of spatial context known to be mediated by the medial temporal lobes (using the contextual cueing task) and of sequences known to be mediated by frontal-striatal and frontal-cerebellar circuits (using the alternating serial reaction time task). Both forms of learning were unimpaired in ASD. Spatial contextual implicit learning was spared in ASD despite slower visual search of spatial displays. The present findings provide evidence for the integrity of learning processes dependent on integration of spatial and sequential contextual information in high-functioning children with ASD. | 18,763,876 |
Age-related differences in cognition: the role of distraction control. | The ability to ignore or control the processing of distracting information may underlie many age-related and individual differences in cognitive abilities. Using a large sample of adults aged 18 to 87 years, this article presents data examining the mediating role of distraction control in the relationship between age and higher order cognition. The reading with distraction task (Connelly, Hasher, & Zacks, 1991) has been used as a measure of the access function of distraction control. Results of this study suggest that distraction control, as measured by this paradigm, plays an important role in mediating age-related effects on measures of working memory and matrix reasoning. | 18,763,883 |
Processing segmental and prosodic information in Cantonese word production. | Five experiments were conducted to investigate how subsyllabic, syllabic, and prosodic information is processed in Cantonese monosyllabic word production. A picture-word interference task was used in which a target picture and a distractor word were presented simultaneously or sequentially. In the first 3 experiments with visually presented distractors, null effects on naming latencies were found when the distractor and the picture name shared the onset, the rhyme, the tone, or both the onset and tone. However, significant facilitation effects were obtained when the target and the distractor shared the rhyme + tone (Experiment 2), the segmental syllable (Experiment 3), or the syllable + tone (Experiment 3). Similar results were found in Experiments 4 and 5 with spoken rather than visual distractors. Moreover, a significant facilitation effect was observed in the rhyme-related condition in Experiment 5, and this effect was not affected by the degree of phonological overlap between the target and the distractor. These results are interpreted in an interactive model, which allows feedback sending from the subsyllabic to the lexical level during the phonological encoding stage in Cantonese word production. | 18,763,899 |
Event-related potentials indicate different processes to mediate categorical and associative priming in person recognition. | Whether representations of people are stored in associative networks based on co-occurrence or are stored in terms of more abstract semantic categories is a controversial question. In the present study, participants performed fame decisions to unfamiliar or famous target faces (Experiment 1) or names (Experiment 2), which were primed, either by highly associated celebrity names or by names from the same occupational category, or were unprimed. Reaction times and event-related potentials (ERPs) were recorded. Reaction times yielded significant priming effects for both associated and same category conditions. ERPs to targets in the associated condition were significantly more positive than were ERPs in all other conditions over central and parietal areas (300-600 ms; N400 priming effect). By contrast, a more posterior effect was found for categorical priming. These findings held for both cross-domain (Experiment 1) and within-domain conditions (Experiment 2). Results (a) demonstrate behavioral and ERP evidence for categorical priming in person recognition, consistent with the assumption that shared semantic information units can mediate semantic priming, and (b) suggest that associative and categorical priming are based on mechanisms that are at least partially different. | 18,763,903 |
Diverging curvature correction to the interfacial tension in polymer solutions. | Application of polymer scaling to the problem of Tolman's length, a curvature correction coefficient in the interfacial tension, shows that Tolman's length in polymer solutions may become as large as half of the thickness of the interface. Tolman's length depends on the degree of polymerization N and the distance to the critical point of phase separation, Delta T. In the "critical" regime (N 1/2|Delta T|<<1) Tolman's length diverges upon approach to the critical temperature as approximately N 0.348|Delta T|-0.304. In the "polymer" regime (N 1/2|Delta T|>> 1) Tolman's length does not depend on N , but diverges more strongly, as approximately |Delta T|-1, proportional to the thickness of the interface. | 18,763,917 |
Intelligent tit-for-tat in the iterated prisoner's dilemma game. | We seek a route to the equilibrium where all the agents cooperate in the iterated prisoner's dilemma game on a two-dimensional plane, focusing on the role of tit-for-tat strategy. When a time horizon, within which a strategy can recall the past, is one time step, an equilibrium can be achieved as cooperating strategies dominate the whole population via proliferation of tit-for-tat. Extending the time horizon, we filter out poor strategies by simplified replicator dynamics and observe a similar evolutionary pattern to reach the cooperating equilibrium. In particular, the rise of a modified tit-for-tat strategy plays a central role, which implies how a robust strategy is adopted when provided with an enhanced memory capacity. | 18,763,937 |
Coarse-grained single-particle dynamics in two-dimensional solids and liquids. | We consider the dynamics of a single tagged particle in a two-dimensional system governed by Lennard-Jones interactions. Previous work based on the Mori-Zwanzig projection operator formalism has shown that the single-particles dynamics can be described via a generalized Langevin equation (GLE) which is exact within the harmonic approximation, that is, for a low-temperature solid [J. M. Deutch and R. Silbey, Phys. Rev. A 3, 2049 (1971)]. In the present work we explore to what an extent the GLE reproduces the effective dynamics under thermodynamic conditions where the harmonic approximation is no longer justified. To this end we compute characteristic time autocorrelation functions for the tagged particle in molecular dynamics simulations of the full system and compare these functions with those obtained from solving the GLE. At low temperatures we find excellent agreement between both data sets. Deviations emerge at higher temperatures which are, however, surprisingly small even in the high-temperature liquid phase. | 18,763,941 |
Self-assembling of dry and cohesive non-Brownian spheres. | Numerous experimental and computational studies have been carried out in recent years to understand the mechanisms governing the compaction of granular systems. Here the problem is further investigated from a different perspective. We compact spheres by a vibrational annealing method and show how the interactions between them and the walls determine the final structure. Dry spheres self-assemble only in body-centered-tetragonal structures, while cohesive ones surpass such density and reach the most compact face-centered-cubic phase. We argue that such polymorphism is due to a molecularlike behavior induced by a compensation mechanism between free and vibrational energies. | 18,763,943 |
Viscous decoupling transitions for individually dragged particles in systems with quenched disorder. | We show that when an individual particle is dragged through an assembly of other particles in the presence of quenched disorder, a viscous decoupling transition occurs between the dragged particle and the surrounding particles which is controlled by the quenched disorder. A counterintuitive consequence of this transition is that the velocity of the dragged particle can be increased by increasing the strength or density of the quenched disorder. The decoupling transition can also occur when the external drive on the dragged particle is increased and is observable as a clear signature in the velocity-force response. | 18,763,951 |
Dynamics of charge transport in planar devices. | The Poisson-Nernst-Planck equations describe the dynamics of charge transport in an electric field. Although they are relevant in many applications, a general solution is not known and several aspects are not well understood. In many situations nonlinear effects arise for which no analytical description is available. In this work, we investigate charge transport in a planar device on application of a voltage step. We derive analytical expressions for the dynamical behavior in four extreme cases. In the "geometry limited" regime, applicable at high voltages and low charge contents, we neglect diffusion and the electric field induced by the charges. This leads to a uniform movement of all charges until the bulk is completely depleted. In the "space charge limited" regime, for high voltages and high charge contents, diffusion is still neglected but the electric field is almost completely screened over transient space charge layers. Eventually, however, the bulk becomes depleted of charges and the field becomes homogeneous again. This regime is solved under the assumption of a homogeneous current density, and is characterized by a typical t -3/4 behavior. In the "diffusion limited" regime, valid for low voltages and low charge contents, diffusion is the dominant transport mechanism and prevents the charges from separating. This results in only very small deviations from a homogeneous charge distribution throughout the device. In the "double layer limited" regime, for low voltages and high charge contents, the combination of dominant diffusion and screening of the electric field results in large variations occurring only in thin double layers near the electrodes. Numerical simulations confirm the validity of the derived analytical expressions for each of the four regimes, and allow us to investigate the parameter values for which they are applicable. We present transient current measurements on a nonpolar liquid with surfactant and compare them with the external current predicted by the theoretical description. The agreement of the analytical expressions with the experiments allows us to obtain values for a number of properties of the charges in the liquid, which are consistent with results in other works. The confirmation by simulations and measurements of the derived theoretical expressions gives confidence about their usefulness to understand various aspects of the Poisson-Nernst-Planck equations and the effects they represent in the dynamics of charge transport. | 18,763,956 |
Transition between two dendritic growth mechanisms in electrodeposition. | We report in this paper the observation of a transition between two different dendritic growth mechanisms in the electrodeposition of a metal from a binary electrolyte. Our results, in particular concerning the dendritic growth velocities, enable us to explain this behavior in terms of models previously proposed in the literature. | 18,763,962 |
Landau-de Gennes theory of biaxial nematics reexamined. | Recent experiments report that the long-looked-for thermotropic biaxial nematic phase has been finally detected in some thermotropic liquid crystalline systems. Inspired by these experimental observations, we concentrate on some elementary theoretical issues concerned with the classical sixth-order Landau-de Gennes free energy expansion in terms of the symmetric and traceless tensor order parameter Q alpha beta. In particular, we fully explore the stability of the biaxial nematic phase giving analytical solutions for all distinct classes of the phase diagrams that theory allows. This includes diagrams with triple, critical, and tricritical points and with multiple (reentrant) biaxial and uniaxial phase transitions. A brief comparison with predictions of existing molecular theories is also given. | 18,763,970 |
Prisoner's dilemma on a stochastic nongrowth network evolution model. | We investigate the evolution of cooperation on a nongrowth dynamic network model with a death-birth dynamics based on tournament selection. In the limit of large population size, the equilibrium cooperator density is well described by our mean field approximations and inversely related to the average degree in the system. Small populations are also examined and found to deviate considerably from their expected mean field behavior. An expanded replicator equation incorporating Gaussian fluctuations in the strategy densities is then constructed, with its output agreeing well with our simulation data for all sizes. We also briefly comment on the role of strategy mutation in sustaining polymorphic populations in small systems. | 18,763,979 |
Force-induced stretched state: effects of temperature. | A model of self-avoiding walks with suitable constraint has been developed to study the effect of temperature on a single-stranded DNA (ssDNA) in the constant force ensemble. Our exact calculations for small chains show that the extension (reaction coordinate) may increase or decrease with the temperature depending on the applied force. The simple model developed here, which incorporates semimicroscopic details of base direction, provides an explanation of the force-induced transitions in ssDNA as observed in experiments. | 18,763,982 |
Effective potential of longitudinal interactions between microtubule protofilaments. | An effective potential for longitudinal interactions between adjacent protofilaments in a microtubule is introduced. Our proposed interaction potential is a periodic and continuous function of the offset between two protofilaments, which also incorporates the bending energy of protofilaments. This potential produces the results of atomistic simulations. Further, using the potential, a Monte Carlo simulation gives results for the skew angles of observed structures that are in good agreement with experiments. | 18,763,987 |
Effect of sensory blind zones on milling behavior in a dynamic self-propelled particle model. | Emergent pattern formation in self-propelled particle (SPP) systems is extensively studied because it addresses a range of swarming phenomena that occur without leadership. Here we present a dynamic SPP model in which a sensory blind zone is introduced into each particle's zone of interaction. Using numerical simulations, we discovered that the degradation of milling patterns with increasing blind zone ranges undergoes two distinct transitions, including a spatially non-homogeneous transition that involves cessation of particles' motion caused by broken symmetries in the interaction fields. Our results also show the necessity of nearly complete panoramic sensory ability for milling behavior to emerge in dynamic SPP models, suggesting a possible relationship between collective behavior and the sensory systems of biological organisms. | 18,763,988 |
Errors in estimation of the input signal for integrate-and-fire neuronal models. | Estimation of the input parameters of stochastic (leaky) integrate-and-fire neuronal models is studied. It is shown that the presence of a firing threshold brings a systematic error to the estimation procedure. Analytical formulas for the bias are given for two models, the randomized random walk and the perfect integrator. For the third model considered, the leaky integrate-and-fire model, the study is performed by using Monte Carlo simulated trajectories. The bias is compared with other errors appearing during the estimation, and it is documented that the effect of the bias has to be taken into account in experimental studies. | 18,763,993 |
Long-range interaction effects on calcium-wave propagation. | In this paper, numerical simulation of calcium waves in a network of cells coupled together by a paracrine signaling is investigated. The model takes into account the long-range interaction between cells due to the action of extracellular messengers, which provide links between first-neighbor cells, but also on cells located far away from the excited cell. When considering bidirectional coupling, the long-range interaction influences neither the frequency nor the amplitude of oscillations, contrary to one-directional coupling. The long-range interaction influences the speed of propagation of Ca2+ waves in the network and induces enlargement of the transition zone before the steady regime of propagation is attained. We also investigate the long-range effects on the colonization of a given niche by a pathogenic microorganism signal on calcium wave propagation in the network. | 18,763,997 |
Slip coefficient in nanoscale pore flow. | The hydrodynamic solutions based on Maxwell's boundary conditions include an empirical slip coefficient (SC), which depends on properties of the adsorbate and adsorbent. Existing kinetic theory derivations of the SC are usually formulated for half-space flow and do not include finite-size effects, which dominate the flow in nanopores. We present an expression for the SC applicable to flow in nanoscale pores, which has been verified by nonequilibrium molecular-dynamics simulation. Our results show that the slip coefficient depends strongly on the pore width for small pores tending to a constant value for pores of width >20 molecular diameters for our systems, in contrast to the linear scaling predicted by Maxwell's theory of slip. | 18,764,009 |
Biclique communities. | We present a method for detecting communities in bipartite networks. Based on an extension of the k -clique community detection algorithm, we demonstrate how modular structure in bipartite networks presents itself as overlapping bicliques. If bipartite information is available, the biclique community detection algorithm retains all of the advantages of the k -clique algorithm, but avoids discarding important structural information when performing a one-mode projection of the network. Further, the biclique community detection algorithm provides a level of flexibility by incorporating independent clique thresholds for each of the nonoverlapping node sets in the bipartite network. | 18,764,021 |
Goos-Hänchen shift and localization of optical modes in deformed microcavities. | Recently, an interesting phenomenon of spatial localization of optical modes along periodic ray trajectories near avoided resonance crossings has been observed [Wiersig, Phys. Rev. Lett. 97, 253901 (2006)]. For the case of a microdisk cavity with elliptical cross section, we use the Husimi function to analyze this localization in phase space. Moreover, we present a semiclassical explanation of this phenomenon in terms of the Goos-Hänchen shift, which works very well even deep in the wave regime. This semiclassical correction to the ray dynamics modifies the phase-space structure such that modes can localize either on stable islands or along unstable periodic ray trajectories. | 18,764,029 |
Partially locked states in coupled oscillators due to inhomogeneous coupling. | We investigate coupled identical phase oscillators with scale-free distribution of coupling strength. It is shown that partially locked states can occur due to the inhomogeneity in coupling and some properties of the coupling function. Various quantities of the partially locked states are computed through a self-consistency argument and the values show good agreement with simulation results. | 18,764,031 |
Avoiding escapes in open dynamical systems using phase control. | In this paper we study how to avoid escapes in open dynamical systems in the presence of dissipation and forcing, as it occurs in realistic physical situations. We use as a prototype model the Helmholtz oscillator, which is the simplest nonlinear oscillator with escapes. For some parameter values, this oscillator presents a critical value of the forcing for which all particles escape from its single well. By using the phase control technique, weakly changing the shape of the potential via a periodic perturbation of suitable phase varphi , we avoid the escapes in different regions of the phase space. We provide numerical evidence, heuristic arguments, and an experimental implementation in an electronic circuit of this phenomenon. Finally, we expect that this method might be useful for avoiding escapes in more complicated physical situations. | 18,764,033 |
Dynamics of semiconductor lasers with external multicavities. | Extending a semiconductor laser by means of an external resonator providing a weak optical feedback causes high-dimensional chaotic fluctuations of the light intensity. Adding a second resonator with different round-trip time may turn these fluctuations into more ordered oscillations or even lead back to a stable steady-state operation. The stability range of periodic or continuous wave solutions can be increased by adding a third resonator to the system. This stabilizing effect of multicavities is shown experimentally and theoretically using numerical simulations based on an extended Lang-Kobayashi model and corresponding linear stability analysis of continuous wave solutions. | 18,764,038 |
Wave chaos in rapidly rotating stars. | The effects of rapid stellar rotation on acoustic oscillation modes are poorly understood. We study the dynamics of acoustic rays in rotating polytropic stars and show using quantum chaos concepts that the eigenfrequency spectrum is a superposition of regular frequency patterns and an irregular frequency subset respectively associated with near-integrable and chaotic phase space regions. This opens fresh perspectives for rapidly rotating star seismology and also provides a potentially observable manifestation of wave chaos in a large-scale natural system. | 18,764,043 |
Oscillation-induced sand ripples in a circular geometry. | This study deals with the observation of sand ripples in a circular geometry under oscillatory flow. We characterize the observed patterns as a function of the excitation parameters. We report the time evolution of the corrugated front invading the flat bed. These experiments reveal unambiguously, because of the gradient of shear stress, the existence of two separated thresholds: one for grain motion and the other for the appearance of ripples. In addition, we display the phase diagram of this instability as a function of the Froude number and a Reynolds number. | 18,764,045 |
Simulations of liquid nanocylinder breakup with dissipative particle dynamics. | In this work, we use a dissipative-particle-dynamics-based model for two-phase flows to simulate the breakup of liquid nanocylinders. Rayleigh's criterion for capillary breakup of inviscid liquid cylinders is shown to apply for the cases considered, in agreement with prior molecular dynamics (MD) simulations. Also, as shown previously through MD simulations, satellite drops are not observed, because of the dominant role played by thermal fluctuations which lead to a symmetric breakup of the neck joining the two main drops. The parameters varied in this study are the domain size, cylinder radius, thermal length scale, viscosity, and surface tension. The breakup time does not show the same scaling dependence as in capillary breakup of liquid cylinders at the macroscale. The time variation of the radius at the point of breakup agrees with prior theoretical predictions from expressions derived with the assumption that thermal fluctuations lead to breakup. | 18,764,048 |
Evolution of anisotropic turbulence in nonlinear magnetic reconnection. | The anisotropy properties of magnetohydrodynamic turbulence in a sheared magnetic field are analyzed through a three-dimensional numerical simulation that reproduces the linear and nonlinear stage of a tearing instability. Far from the current sheet, the energy spectrum develops perpendicularly to the local magnetic field, as in homogeneous configurations. Within the current sheet, the spectrum anisotropy is also affected by the structure of unstable modes. With increasing time, the configuration becomes more turbulent, the former effect disappears, and the energy cascade takes place perpendicularly to the local magnetic field. The local spectrum becomes increasingly anisotropic while the spatially integrated spectrum tends to isotropize. There is the possibility that these properties could be used to identify the nonlinear stage of magnetic reconnection in space and laboratory plasmas, as well as to identify the particle transport regime in the considered magnetic configuration. | 18,764,062 |
Unphysical kinetic effects in particle-in-cell modeling of laser wakefield accelerators. | Unphysical heating and macroparticle trapping that arise in the numerical modeling of laser wakefield accelerators using particle-in-cell codes are investigated. A dark current free laser wakefield accelerator stage, in which no trapping of background plasma electrons into the plasma wave should occur, and a highly nonlinear cavitated wake with self-trapping, are modeled. Numerical errors can lead to errors in the macroparticle orbits in both phase and momentum. These errors grow as a function of distance behind the drive laser and can be large enough to result in unphysical trapping in the plasma wake. The resulting numerical heating in intense short-pulse laser-plasma interactions grows much faster and to a higher level than the known numerical grid heating of an initially warm plasma in an undriven system. The amount of heating, at least in the region immediately behind the laser pulse, can, in general, be decreased by decreasing the grid size, increasing the number of particles per cell, or using smoother interpolation methods. The effect of numerical heating on macroparticle trapping is less severe in a highly nonlinear cavitated wake, since trapping occurs in the first plasma wave period immediately behind the laser pulse. | 18,764,064 |
Enhancement of cooperation in highly clustered scale-free networks. | We study the effect of clustering on the organization of cooperation by analyzing the evolutionary dynamics of the "Prisoner's Dilemma" on scale-free networks with a tunable value of clustering. We find, on the one hand, that a high value of the clustering coefficient produces an overall enhancement of cooperation in the network, even for a very high temptation to defect. On the other hand, high clustering homogenizes the process of invasion of degree classes by defectors, decreasing the chances of survival of low densities of cooperators in the network. | 18,764,081 |
Quantitative modeling of bubble competition in Richtmyer-Meshkov instability. | We present a quantitative model for the evolution of single and multiple bubbles in the Richtmyer-Meshkov (RM) instability. The higher-order solutions for a single-mode bubble are obtained, and distinctions between RM and Rayleigh-Taylor bubbles are investigated. The results for multiple-bubble competition from the model shows that the higher-order correction to the solution of the bubble curvature has a large influence on the growth rate of the RM bubble front. The model predicts that the bubble front of RM mixing grows as h approximately ttheta with theta approximately (0.3-0.35)+/-0.02 . | 18,764,086 |
Analytical characterization of oscillon energy and lifetime. | We develop an analytical procedure to compute all relevant physical properties of scalar field oscillons in models with quartic polynomial potentials: energy, radius, frequency, core amplitude, and lifetime. We compare our predictions to numerical simulations of models with symmetric and asymmetric double-well potentials in three spatial dimensions, obtaining excellent agreement. We also explain why oscillons have not been seen to decay in two spatial dimensions. | 18,764,101 |
Order alphas4 QCD corrections to Z and tau decays. | Using recently developed methods for the evaluation of five-loop amplitudes in perturbative QCD, corrections of order alphas4 for the nonsinglet part of the cross section for electron-positron annihilation into hadrons and for the decay rates of the Z boson and the tau lepton into hadrons are evaluated. The new terms lead to a significant stabilization of the perturbative series, to a reduction of the theory uncertainly in the strong coupling constant alphas, as extracted from these measurements, and to a small shift of the central value, moving the two central values closer together. The agreement between two values of alphas measured at vastly different energies constitutes a striking test of asymptotic freedom. Combining the results from Z and tau decays we find alphas(MZ)=0.1198+/-0.0015 as one of the most precise and presently only result for the strong coupling constant in order alphas4. | 18,764,104 |
Liquid optical fibers with a multistable core actuated by light radiation pressure. | We report on spatiotemporal behavior of self-adapted dielectric liquid columns generated and sustained by light radiation pressure. We show that single- or multivalued liquid column diameter depends on the excitation light beam. When the beam diameter is sufficiently small, we observe a well-defined stationary column diameter. In contrast, at a larger beam diameter, the liquid column experiences complex spatiotemporal dynamics whose statistical analysis evidences an underlying multistable structure. Experimental observations are all supported by a full electromagnetic model that accounts for the wave guiding properties of the liquid column viewed as a step-index liquid-core liquid-cladding optical fiber having an optically tunable core diameter. | 18,764,116 |
Strong coupling approach to actinide metals. | We present a strongly correlated approach to the electronic structure of actinide metals by deriving a low-energy Hamiltonian H[over] under the assumption that kinetic energy is small compared to Coulomb and spin-orbit interactions. The H[over]Pu for Pu metal is similar to the models used for Ce and other lanthanides but qualitatively different from the H[over] presented for the rest of the actinides. With H[over]Pu, we computed the photoemission spectrum and specific heat for alpha and delta-Pu and found good agreement with experiment. | 18,764,130 |
Hole localization in the one-dimensional doped Anderson-Hubbard model. | We study an interplay of disorder and correlation in the one-dimensional hole-doped Hubbard-model with disorder (Anderson-Hubbard model) by using the density-matrix renormalization group method. Concentrating on the doped-hole-density profile, we find in a large U/t regime that the clean system exhibits a simple fluidlike behavior whereas finite disorders create locally Mott regions which expand their area with increasing the disorder strength contrary to the conventional sense. We propose that such an anomalous Mott phase formation assisted by disorder is easily observable in atomic Fermi gases by setting up the box-shape trap. | 18,764,134 |
High energy dispersion relations for the high temperature Bi2Sr2CaCu2O8 superconductor from laser-based angle-resolved photoemission spectroscopy. | Laser-based angle-resolved photoemission spectroscopy measurements have been carried out on the high energy electron dynamics in Bi2Sr2CaCu2O8 high temperature superconductor. Our superhigh resolution data, momentum-dependent measurements, and complete analysis provide important information to judge the nature of the high energy dispersion and kink. Our results rule out the possibility that the high energy dispersion from the momentum distribution curve (MDC) may represent the true bare band as believed in previous studies. We also rule out the possibility that the high energy kink represents electron coupling with some high energy modes as proposed before. Through detailed MDC and energy distribution curve analyses, we propose that the high energy MDC dispersion may not represent intrinsic band structure. | 18,764,144 |
Entanglement between two uses of a noisy multipartite quantum channel enables perfect transmission of classical information. | Suppose that m senders want to transmit classical information to n receivers with zero probability of error using a noisy multipartite communication channel. The senders are allowed to exchange classical, but not quantum, messages among themselves, and the same holds for the receivers. If the channel is classical, a single use can transmit information if and only if multiple uses can. In sharp contrast, we exhibit, for each m and n with m>1 or n>1, a quantum channel of which a single use is not able to transmit information yet two uses can. This latter property requires and is enabled by quantum entanglement. | 18,764,166 |
Fully self-consistent ion-drag-force calculations for dust in collisional plasmas with an external electric field. | The ion drag force on a spherical dust particle immersed in a flowing plasma with an external electric field is self-consistently calculated using the particle-in-cell code SCEPTIC in the entire range of charge-exchange collisionality. Our results, not based on questionable approximations, extend prior analytic calculations valid only in a few limiting regimes. Particular attention is given to the force direction, shown never to be directed opposite to the flow except in the continuum limit, where other forces are of a much stronger magnitude. | 18,764,185 |
Equivalence of critical scaling laws for many-body entanglement in the Lipkin-Meshkov-Glick model. | We establish a relation between several entanglement properties in the Lipkin-Meshkov-Glick model, which is a system of mutually interacting spins embedded in a magnetic field. We provide analytical proofs that the single-copy entanglement and the global geometric entanglement of the ground state close to and at criticality behave as the entanglement entropy. These results are in deep contrast to what is found in one- dimensional spin systems where these three entanglement measures behave differently. | 18,764,198 |
Charging of metal adatoms on ultrathin oxide films: Au and Pd on FeO/Pt(111). | We present a combined experimental (STM/scanning tunneling spectroscopy) and theoretical (density functional theory) study on the deposition of Au and Pd metal atoms on FeO/Pt(111) ultrathin films. We show that while the Pd atoms are only slightly oxidized, the Au atoms form positive ions upon deposition, at variance to a charge transfer into the Au atoms as observed for MgO/Ag(100). The modulation of the adsorption properties within the surface Moiré cell and the charging induce the formation a self-assembled array of gold adatoms on FeO/Pt(111), whereas Pd atoms are randomly distributed. | 18,764,201 |
Instability of square vortex lattice in d-wave superconductors is due to paramagnetic depairing. | The effects of paramagnetic depairing on structural transitions between vortex lattices of a quasi-two-dimensional d-wave superconductor are examined. We find that, when the Maki parameter alphaM is of order unity, a square lattice induced by a d-wave pairing is destabilized with increasing fields, and that a reentrant rhombic lattice occurs in higher fields. Further, a weak Fermi surface anisotropy competitive with the pairing symmetry induces another structural transition near Hc2. These results are consistent with the structure changes of the vortex lattice in CeCoIn5 in H parallel c determined from recent neutron scattering data. | 18,764,215 |
Superconductivity in thin films of boron-doped carbon nanotubes. | Superconductivity in carbon nanotubes (CNTs) is attracting considerable attention. However, its correlation with carrier doping has not been reported. We report on the Meissner effect found in thin films consisting of assembled boron (B)-doped single-walled CNTs (B-SWNTs). We find that only B-SWNT films consisting of low boron concentration leads to evident Meissner effect with Tc=12 K and also that a highly homogeneous ensemble of the B-SWNTs is crucial. The first-principles electronic-structure study of the B-SWNTs strongly supports these results. | 18,764,216 |
Entanglement of solid vortex matter: a boomerang-shaped reduction forced by disorder in interlayer phase coherence in Bi2Sr2CaCu2O8+y. | We present evidence for entangled solid vortex matter in a glassy state in a layered superconductor Bi2Sr2CaCu2O8+y containing randomly splayed linear defects. The interlayer phase coherence--probed by the Josephson plasma resonance--is enhanced at high temperatures, reflecting the recoupling of vortex liquid by the defects. At low temperatures in the vortex solid state, the interlayer coherence follows a boomerang-shaped reentrant temperature path with an unusual low-field decrease in coherence, indicative of meandering vortices. We uncover a distinct temperature scaling between in-plane and out-of-plane critical currents with opposing dependencies on field and time, consistent with the theoretically proposed "splayed-glass" state. | 18,764,217 |
Optical signatures of spin polarization of carriers in quantum dots. | We predict theoretically the optical signatures of spin polarization of carriers in self-assembled quantum dots. The emission spectra are mapped out as a function of increasing electron spin polarization for a fixed number of electrons and holes. The spin-polarized spectra are determined using exact diagonalization techniques for up to 12 particles, corresponding to two lowest filled shells. We predict that the spin polarization leads to photon polarization, to redshifts of emission lines due to excess exchange interactions among the spin-polarized electrons, and to a complete breakup of emission lines for spin-polarized electronic shells. | 18,764,224 |
Emission spectrum of a dressed exciton-biexciton complex in a semiconductor quantum dot. | The photoluminescence spectrum of a single quantum dot was recorded as a secondary resonant laser optically dressed either the vacuum-to-exciton or the exciton-to-biexciton transitions. High-resolution polarization-resolved measurements using a scanning Fabry-Pérot interferometer reveal splittings of the linearly polarized fine-structure states that are nondegenerate in an asymmetric quantum dot. These splittings manifest as either triplets or doublets and depend sensitively on laser intensity and detuning. Our approach realizes complete resonant control of a multiexcitonic system in emission, which can be either pulsed or continuous wave, and offers direct access to the emitted photons. | 18,764,226 |
Out-of-equilibrium microrheology inside living cells. | Both forced and spontaneous motions of magnetic microbeads engulfed by Dictyostelium cells have served as experimental probes of intracellular dynamics. The complex shear modulus G*(omega), determined from active oscillatory measurements, has a power-law dynamics and increases with the probe size, reflecting intracellular structural complexity. The combined use of passive microrheology allows one to derive the power spectrum of active forces acting on intracellular phagosomes and to test the validity of the fluctuation-dissipation theorem inside living cells. | 18,764,230 |
Quantum corrections and bound-state effects in the energy relaxation of hot dense hydrogen. | Simple analytic formulas for energy relaxation (ER) in electron-ion systems, with quantum corrections, ion dynamics, and RPA-type screening are presented. ER in the presence of bound electrons is examined in view of recent simulations for ER in hydrogen in the range 10{20}-10{24} electrons/cc. | 18,764,259 |
Electron spin pumping of Rb atoms on He nanodroplets via nondestructive optical excitation. | We measured laser-induced-fluorescence (LIF) and beam-depletion (BD) spectra of rubidium atoms (5S-5P transition) on the surface of superfluid helium nanodroplets (M-He_{N} with M=Rb). It is known that when M is a lighter alkali atom electronic excitation always leads to detachment of the excited atom (M;{*}). The dissociation energy, few tens cm;{-1}, comes either as photon excess energy or from the barrierless formation of a M;{*}-He exciplex. We observe that this picture does not hold when M=Rb and the photon excess energy is small: we are able to excite atoms without detaching them from the droplet, thanks to a barrier preventing formation of the exciplex. This system is ideally suited for optical spin pumping in a He nanodroplet, whose achievement we explicitly demonstrate in a pump-probe magnetic circular dichroism experiment. | 18,764,262 |
Piezospin polarization of currents in nanostructures. | Torsional oscillations of a freestanding semiconductor beam are shown to cause spin-dependent oscillating potentials that spin polarize an applied charge current in the presence of intentional or disorder scattering potentials. We propose several realizations of mechanical spin generators and manipulators based on this piezospintronic effect. | 18,764,268 |
Electric manipulation of spin relaxation using the spin Hall effect. | Using the spin Hall effect, magnetization relaxation in a Ni_{81}Fe_{19}/Pt film is manipulated electrically. An electric current applied to the Pt layer exerts spin torque on the entire magnetization of the Ni81Fe19 layer via the macroscopic spin transfer induced by the spin Hall effect and modulates the magnetization relaxation in the Ni81Fe19 layer. This method allows us to tune the magnetization dynamics regardless of the film size without applying electric currents directly to the magnetic layer. | 18,764,271 |
Dynamic singularity in multicomponent glass-forming metallic liquids. | In the liquid state, glass-forming Ni59.5Nb40.5 and Ni60Nb34.8Sn5.2 alloys exhibit an extraordinarily high packing fraction. The self-correlation functions measured using quasielastic neutron scattering clearly show the slowing down of microscopic dynamics with an increase in packing fraction. The self-diffusivity in liquid Ni60Nb34.8Sn5.2 decreases by about 2 orders of magnitude within a temperature range of 360 K. For these highly fragile systems, the critical packing fraction obtained form the analysis of incoherent data is in excellent agreement with the prediction made by mode-coupling theory. Our results provide the first experimentally observed value for the critical packing fraction in glass-forming metallic liquids. | 18,764,296 |
Eötvös bounds on couplings of fundamental parameters to gravity. | The possible dependence of fundamental couplings and mass ratios on the gravitational potential has been bounded by comparing atomic clock frequencies over Earth's elliptical orbit. Here we evaluate bounds on such a dependence from Eötvös-type experiments that test the weak equivalence principle, including previously neglected contributions from nuclear binding energy. We find that variations of fundamental parameters correlated with the gravitational potential are limited at 10(-8)-10(-9), an improvement of 2-3 orders of magnitude over atomic clock bounds. | 18,764,316 |
Transition-metal-substituted indium thiospinels as novel intermediate-band materials: prediction and understanding of their electronic properties. | Results of density-functional calculations for indium thiospinel semiconductors substituted at octahedral sites with isolated transition metals (M=Ti,V) show an isolated partially filled narrow band containing three t2g-type states per M atom inside the usual semiconductor band gap. Thanks to this electronic structure feature, these materials will allow the absorption of photons with energy below the band gap, in addition to the normal light absorption of a semiconductor. To our knowledge, we demonstrate for the first time the formation of an isolated intermediate electronic band structure through M substitution at octahedral sites in a semiconductor, leading to an enhancement of the absorption coefficient in both infrared and visible ranges of the solar spectrum. This electronic structure feature could be applied for developing a new third-generation photovoltaic cell. | 18,764,346 |
Electron-hole symmetry and magnetic coupling in antiferromagnetic LaFeAsO. | When either electron or hole doped at concentrations x approximately 0.1, the LaFeAsO family displays remarkably high temperature superconductivity with Tc up to 55 K. In the most energetically stable Q-->M=(pi,pi,0) antiferromagnetic (AFM) phase comprised of tetragonal-symmetry breaking alternating chains of aligned spins, there is a deep pseudogap in the Fe 3d states centered at the Fermi energy arising from light carriers (m* approximately 0.25-0.33), and very strong magnetophonon coupling is uncovered. Doping (of either sign) beyond x approximately 0.08 results in heavy carriers per Fe (by roughly an order of magnitude) with a large Fermi surface. Calculated Fe-Fe transverse exchange couplings Jij(R) reveal that exchange coupling is strongly dependent on both the AFM symmetry and on the Fe-As distance. | 18,764,356 |
Quantum order by disorder in frustrated diamond lattice antiferromagnets. | We present a quantum theory of frustrated diamond lattice antiferromagnets. Considering quantum fluctuations as the predominant mechanism relieving spin frustration, we find a rich phase diagram comprising of six phases with coplanar spiral ordering in addition to the Néel phase. By computing the specific heat of these ordered phases, we obtain a remarkable agreement between (k, k, 0) spiral ordering and the experimental specific heat data for the diamond lattice spinel compounds MnSc2S4, Co3O4, and CoRh2O4, i.e., specific heat data is a strong evidence for (k, k, 0) spiral ordering in all of these materials. This prediction can be tested in future neutron scattering experiments on Co3O4 and CoRh2O4, and is consistent with existing neutron scattering data on MnSc2S4. Based on this agreement, we infer a monotonically increasing relationship between frustration and the strength of quantum fluctuations. | 18,764,361 |
Soft swimming: exploiting deformable interfaces for low reynolds number locomotion. | Reciprocal movement cannot be used for locomotion at low Reynolds number in an infinite fluid or near a rigid surface. Here we show that this limitation is relaxed for a body performing reciprocal motions near a deformable interface. Using physical arguments and scaling relationships, we show that the nonlinearities arising from reciprocal flow-induced interfacial deformation rectify the periodic motion of the swimmer, leading to locomotion. Such a strategy can be used to move toward, away from, and parallel to any deformable interface as long as the length scales involved are smaller than intrinsic scales, which we identify. A macroscale experiment of flapping motion near a free surface illustrates this new result. | 18,764,367 |
Collective states of interacting Fibonacci anyons. | We show that chains of interacting Fibonacci anyons can support a wide variety of collective ground states ranging from extended critical, gapless phases to gapped phases with ground-state degeneracy and quasiparticle excitations. In particular, we generalize the Majumdar-Ghosh Hamiltonian to anyonic degrees of freedom by extending recently studied pairwise anyonic interactions to three-anyon exchanges. The energetic competition between two- and three-anyon interactions leads to a rich phase diagram that harbors multiple critical and gapped phases. For the critical phases and their higher symmetry end points we numerically establish descriptions in terms of two-dimensional conformal field theories. A topological symmetry protects the critical phases and determines the nature of gapped phases. | 18,764,375 |
Hidden variable models for quantum theory cannot have any local part. | It was shown by Bell that no local hidden variable model is compatible with quantum mechanics. If, instead, one permits the hidden variables to be entirely nonlocal, then any quantum mechanical predictions can be recovered. In this Letter, we consider general hidden variable models which can have both local and nonlocal parts. We show the existence of (experimentally verifiable) quantum correlations that are incompatible with any hidden variable model having a nontrivial local part, such as the model proposed by Leggett. | 18,764,377 |
Quantum state reconstruction of a rotational wave packet created by a nonresonant intense femtosecond laser field. | We have experimentally determined the amplitudes and phases of a rotational wave packet in an adiabatically cooled benzene molecule, created by a nonresonant intense femtosecond laser field. In this wave-packet reconstruction, the initial wave packet is further interfered by a replica of the first laser pulse, and the resultant modulation in population is observed in a state-resolved manner. Though several states with different nuclear-spin modifications are populated in the initial condition, a single wave packet created from one of them (with J=0) is specifically reconstructed. Phase shifts characteristic of stepwise Raman excitation beyond the perturbative regime are experimentally identified. | 18,764,388 |
Generation of ultrashort coherent vacuum ultraviolet pulses using electron storage rings: a new bright light source for experiments. | We demonstrate for the first time that seeded harmonic generation on electron storage rings can produce coherent optical pulses in the vacuum ultraviolet spectral range. The experiment is performed at Elettra, where coherent pulses are generated at 132 nm, with a duration of about 100 fs. The light source has a repetition rate of 1 kHz and adjustable polarization; it is very bright, with a peak power several orders of magnitude above that of spontaneous synchrotron radiation. Owing to high stability, the source is used in a test photoemission electron microscopy experiment. We anticipate that seeded harmonic generation on storage rings can lead to unprecedented developments in time-resolved femtosecond spectroscopy and microscopy. | 18,764,393 |
Periodicity hub and nested spirals in the phase diagram of a simple resistive circuit. | We report the discovery of a remarkable "periodicity hub" inside the chaotic phase of an electronic circuit containing two diodes as a nonlinear resistance. The hub is a focal point from where an infinite hierarchy of nested spirals emanates. By suitably tuning two reactances simultaneously, both current and voltage may have their periodicity increased continuously without bound and without ever crossing the surrounding chaotic phase. Familiar period-adding current and voltage cascades are shown to be just restricted one-parameter slices of an exceptionally intricate and very regular onionlike parameter surface centered at the focal hub which organizes all the dynamics. | 18,764,395 |
Validation of thermal-transport modeling with direct-drive, planar-foil acceleration experiments on OMEGA. | We present for the first time the experimental validation of the nonlocal thermal-transport model for a National Ignition Facility relevant laser intensity of approximately 10(15) W/cm(2) on OMEGA. The measured thin target trajectories are in good agreement with predictions based on the nonlocal model over the full range of laser intensities from 2 x 10(14) to 10(15) W/cm(2}) The standard local thermal-transport model with a constant flux limiter of 0.06 disagrees with experimental measurements at a high intensity of approximately 10(15) W/cm(2) but agrees at lower intensities. These results show the significance of nonlocal effects for direct-drive ignition designs. | 18,764,399 |
Development of instabilities in wire-array Z pinches. | 3D resistive MHD simulations are used to show how the properties of the "fundamental" mode of modulated ablation in wire-array Z pinches, are consistent with the growth of a modified m=0-like instability. The modulation wavelength, structure, and evolution is found to be governed by the magnetic topology and is largely independent of the initial conditions. The perturbation amplitude as a function of wire number is shown to be consistent with experimental x-ray power scaling. Simulations of an array of helical wires show a substantial reduction in the amplitude of the instability. | 18,764,402 |
Effective temperature in relaxation of Coulomb glasses. | We study relaxation in two-dimensional Coulomb glasses up to macroscopic times. We use a kinetic Monte Carlo algorithm especially designed to escape efficiently from deep valleys around metastable states. We find that, during the relaxation process, the site occupancy follows a Fermi-Dirac distribution with an effective temperature much higher than the real temperature T. Long electron-hole excitations are characterized by T(eff), while short ones are thermalized at T. We argue that the density of states at the Fermi level is proportional to T(eff) and is a good thermometer to measure it. T(eff) decreases extremely slowly, roughly as the inverse of the logarithm of time, and it should affect hopping conductance in many experimental circumstances. | 18,764,413 |
Rate dependence and role of disorder in linearly sheared two-dimensional foams. | The shear flow of two-dimensional foams is probed as a function of shear rate and disorder. Disordered, bidisperse foams exhibit strongly shear rate dependent velocity profiles. This behavior is captured quantitatively in a simple model based on the balance of the time-averaged drag forces in the system, which are found to exhibit power-law scaling with the foam velocity and strain rate. Disorder makes the scaling of the bulk drag forces different from that of the local interbubble drag forces, which we evidence by rheometrical measurements. In monodisperse, ordered foams, rate independent velocity profiles are found, which lends further credibility to this picture. | 18,764,433 |
Quantum circuit architecture. | We present a method for optimizing quantum circuits architecture, based on the notion of a quantum comb, which describes a circuit board where one can insert variable subcircuits. Unexplored quantum processing tasks, such as cloning and storing or retrieving of gates, can be optimized, along with setups for tomography and discrimination or estimation of quantum circuits. | 18,764,438 |
Rainbow and blueshift effect of a dispersive spherical invisibility cloak impinged on by a nonmonochromatic plane wave. | We demonstrate some interesting phenomena associated with a nonmonochromatic plane wave passing through a spherical invisibility cloak whose radial permittivity and permeability are of Drude and Lorentz types. We observe that the frequency center of a quasimonochromatic incident wave will suffer a blueshift in the forward scattering direction. Different frequency components have different depths of penetration, causing a rainbowlike effect within the cloak. The concept of group velocity at the inner boundary of the cloak needs to be revisited. Extremely low scattering can still be achieved within a narrow band. | 18,764,455 |
Resonances near the classical separatrix of a weakly deformed circular microcavity. | We study localized resonance patterns of a weakly deformed circular dielectric microcavity. The dominant pattern among them is detected when the classical motion of the light is on the separatrix of the effective potential. In this case, the topological shape of the pattern is automatically determined by the refractive index of the microcavity n. Also, the pattern can be interpreted as a linear combination of nearly degenerate eigenstates in the circular dielectric microcavity. Applying this analysis to a spiral-shaped microcavity, we generate quasiscarred patterns for n=2 and n=3. | 18,764,456 |
Momentum-transport studies in high E x B shear plasmas in the National Spherical Torus Experiment. | Experiments have been conducted at the National Sperical Torus Experiment (NSTX) to study both steady state and perturbative momentum transport. These studies are unique in their parameter space under investigation, where the low aspect ratio of NSTX results in rapid plasma rotation with ExB shearing rates high enough to suppress low-k turbulence. In some cases, the ratio of momentum to energy confinement time is found to exceed five. Momentum pinch velocities of order 10-40 m/s are inferred from the measured angular momentum flux evolution after nonresonant magnetic perturbations are applied to brake the plasma. | 18,764,464 |
Quantum Differences between Heavy and Light Water. | The structures of heavy and light water at ambient conditions are investigated with the combined techniques of x-ray diffraction, neutron diffraction, and computer simulation. It is found that heavy water is a more structured liquid than light water. We find the OH bond length in H2O is approximately 3% longer than the OD bond length in D2O. This is a much larger change than current predictions. Corresponding to this, the hydrogen bond in light water is approximately 4% shorter than in heavy water, while the intermolecular HH distance is approximately 2% longer. | 18,764,471 |
Short-range-order lifetime and the "boson peak" in a metallic glass model. | We extend the usual static view of short range order in metallic glasses to a dynamical model of local order. We use an atomistic simulation of a NiZr glass to investigate time-dependent fluctuations of the atomic environment. We show that, even in the "frozen" glass, the solute-centered clusters change their identities between distinct polyhedron types. The frequency spectrum of these transitions exhibits a characteristic peak which we show to be related to a universal vibrational anomaly of disordered solids: the controversial boson peak. | 18,764,475 |
Ultrafast dynamic compression technique to study the kinetics of phase transformations in bismuth. | Preheated Bi (296-532 K) was ramp compressed with 15-35 ns rise times to a peak stress of approximately 11 GPa to explore structural phase-transformation kinetics under dynamic loading conditions. At high strain rates, epsilon[over ]>5 x 10;{6} s;{-1}, deviation from equilibrium phase boundaries suggests that compression time scales are comparable to the new phase incubation period. The dependence of DeltaP/kT on epsilon[over ] is consistent with a thermally activated transformation. | 18,764,477 |
Chirality-induced dynamic kohn anomalies in graphene. | We develop a theory for the renormalization of the phonon energy dispersion in graphene due to the combined effects of both Coulomb and electron-phonon (e-ph) interactions. We obtain the renormalized phonon energy spectrum by an exact analytic derivation of the phonon self-energy, finding three distinct Kohn anomalies (KAs) at the phonon wave vector q=omega/v, 2k_{F}+/-omega/v for LO phonons and one at q=omega/v for TO phonons. The presence of these new KAs in graphene, in contrast to the usual KA q=2k_{F} in ordinary metals, originates from the dynamical screening of e-ph interaction (with a concomitant breakdown of the Born-Oppenheimer approximation) and the peculiar chirality of the graphene e-ph coupling. | 18,764,478 |
Bridge between Abelian and non-Abelian fractional quantum Hall states. | We propose a scheme to construct the most prominent Abelian and non-Abelian fractional quantum Hall states from K-component Halperin wave functions. In order to account for a one-component quantum Hall system, these SU(K) colors are distributed over all particles by an appropriate symmetrization. Numerical calculations corroborate the picture that K-component Halperin wave functions may be a common basis for both Abelian and non-Abelian trial wave functions in the study of one-component quantum Hall systems. | 18,764,488 |
Temporal extent of surface potentials between closely spaced metals. | Variations in the electrostatic surface potential between the proof mass and electrode housing in the space-based gravitational wave mission Laser Interferometer Space Antenna (LISA) is one of the largest contributors of noise at frequencies below a few mHz. Torsion balances provide an ideal test bed for investigating these effects in conditions emulative of LISA. Our apparatus consists of a Au coated Cu plate brought near a Au coated Si plate pendulum suspended from a thin W wire. We have measured a white noise level of 30 microV/sqrt Hz above approximately 0.1 mHz, rising at lower frequencies, for the surface potential variations between these two closely spaced metals. | 18,764,520 |
Global analysis of helicity parton densities and their uncertainties. | We present a new analysis of the helicity parton distributions of the nucleon. The analysis takes into account the available data from inclusive and semi-inclusive polarized deep inelastic scattering, as well as from polarized proton-proton (p-p) scattering at RHIC. For the first time, all theoretical calculations are performed fully at next-to-leading order (NLO) of perturbative QCD, using a method that allows incorporation of the NLO corrections in a very fast and efficient way in the analysis. We find evidence for a rather small gluon polarization in the nucleon, over a limited region of momentum fraction, and for interesting flavor patterns in the polarized sea. | 18,764,525 |
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