bluuebunny/crossref_metadata_2025 huggingface dataset:
Altered sciatic nerve fiber morphology and endoneural microvessels in mouse models relevant for obesity, peripheral diabetic polyneuropathy, and the metabolic syndrome
Authors: Nowicki Marcin , Kosacka Joanna , Serke Heike , Blüher Matthias , Spanel‐Borowski Katharina
Published: September 2011

The morphology of sciatic nerves from leptin‐deficient ob/ob mice and leptin receptor‐deficient db/db mice, both models for obesity, peripheral diabetic neuropathy, and the metabolic syndrome, has yet to be examined for changes in nerve fibers and in endoneural microvessels. Sciatic nerves from three groups of 4‐month‐old mice (WT C57BL6, ob/ob, and db/db) were investigated. In ultrathin sections, the thickness of myelin sheaths was significantly reduced in small, medium‐sized, and large axons of db/db mice compared with WT mice. In ob/ob mice, only large fibers showed a decrease in myelin sheath thickness. The number of nonmyelinated nerve fibers was lower in ob/ob mice than in the db/db group. A thickened basal lamina of Schwann cells occurred in the ob/ob group only. In contrast, the basement membrane of endoneural microvessels was thickened in both obese groups. For this reason, laminin expression in Western blot analysis was lower in the db/db group than in the ob/ob one. Endoneural microvessels, which had been injected with fluorescein isothiocyanate, depicted signs of vasodilatation in the ob/ob and vasoconstriction in db/db mice. Endoneural vessels displayed two receptors of oxLDL. LOX‐1 was strongly expressed in db/db mice, whereas TLR4 was at its maximum in the ob/ob group. We conclude that changes in nerve fibers and in endoneural microvessels are present in sciatic nerve of both mouse models of type 2 diabetes. Upregulation of oxLDL‐dependent receptors in endoneural microvessels might be connected to different degrees of oxidative stress in severe diabetic db/db mice and in the mild diabetic ob/ob group. © 2011 Wiley Periodicals, Inc.
Classification and differential metabolite discovery of liver diseases based on plasma metabolic profiling and support vector machines
Authors: Lin Xiaohui , Zhang Yang , Ye Guozhu , Li Xiang , Yin Peiyuan , Ruan Qiang , Xu Guowang
Published: September 2011

Discovery of differential metabolites is the focus of metabonomics study. It has very important applications in pathogenesis and disease classification. The aim of this work is to identify differential metabolites for classifying the patients with hepatocellular carcinoma, cirrhosis and hepatitis based on metabolic profiling data analyzed by gas chromatography‐time of flight mass spectrometry. A two‐stage feature selection algorithm, F‐SVM, combining F‐score in analysis of variance and support vector machine (SVM), was applied in discovering discriminative metabolites for three different types of liver diseases. The results show that the accuracy rate of the double cross‐validation was 73.68±2.98%. 22 important differential metabolites selected by F‐SVM were identified and related pathophysiological process of liver diseases was set forth. We conclude that F‐SVM is quite feasible to be applied in the selection of biologically relevant features in metabonomics.
Silica‐coated La0.75Sr0.25MnO3 nanoparticles for magnetically driven DNA isolation
Authors: Trachtová Štěpánka , Kaman Ondřej , Španová Alena , Veverka Pavel , Pollert Emil , Rittich Bohuslav
Published: September 2011

Magnetic La0.75Sr0.25MnO3 nanoparticles possessing an approximately 20‐nm‐thick silica shell (LSMO(0.25)@SiO2) were characterised and tested for the isolation of PCR‐ready bacterial DNA. The results presented here show that the nanoparticles do not interfere in PCR. DNA was apparently reversibly adsorbed on their silica shell from the aqueous phase system (16% PEG 6000–2 M NaCl). The method proposed was used for DNA isolation from complex food samples (dairy products and probiotic food supplements). The isolated DNA was compatible with PCR. The main advantages of the nanoparticles tested for routine use were their high colloidal stability allowing a more precise dosage and therefore high reproducibility of DNA isolation.
NMR quantitation: influence of RF inhomogeneity
Authors: Mo Huaping , Harwood John , Raftery Daniel
Published: September 2011

The NMR peak integral is ideally linearly dependent on the sine of excitation angle (θ), which has provided unsurpassed flexibility in quantitative NMR by allowing the use of a signal of any concentration as the internal concentration reference. Controlling the excitation angle is particularly critical for solvent proton concentration referencing to minimize the negative impact of radiation damping, and to reduce the risk of receiver gain compression. In practice, due to the influence of RF inhomogeneity for any given probe, the observed peak integral is not exactly proportional to sin θ. To evaluate the impact quantitatively, we introduce a RF inhomogeneity factor I(θ) as a function of the nominal pulse excitation angle and propose a simple calibration procedure. Alternatively, I(θ) can be calculated from the probe's RF profile, which can be readily obtained as a gradient image of an aqueous sample. Our results show that without consideration of I(θ), even for a probe with good RF homogeneity, up to 5% error can be introduced due to different excitation pulse angles used for the analyte and the reference. Hence, a simple calibration of I(θ) can eliminate such errors and allow an accurate description of the observed NMR signal's dependence on the excitation angle in quantitative analysis. Copyright © 2011 John Wiley & Sons, Ltd.
A Case of Dwarfism from the Byzantine City Rehovot‐in‐the‐Negev, Israel
Authors: Slon V. , Nagar Y. , Kuperman T. , Hershkovitz I.
Published: September 2011

Skeletons of dwarfs have been found in many archaeological sites from around the world. Nevertheless, their descriptions (morphologically and metrically) are very limited. We describe herein the skeleton of a male dwarf, approximately 35–50 years old, found in the Byzantine cemetery (5th–8th century CE) of Rehovot‐in‐the‐Negev, southern Israel. Living stature was estimated at 120–125 cm. Detailed morphological skeletal descriptions and morphometric analysis, together with computed tomography (CT) observations, suggest a diagnosis of achondroplasia. The long bones anomalies, in tandem with other features such as hydrocephalus and spinal stenosis, are discussed in regard to their effect on the dwarf's daily life. The putative place of dwarfs in early Christian communities, compared with dwarfs from other times and places, will be addressed. Copyright © 2011 John Wiley & Sons, Ltd.
Flexible polybenzoxazine thermosets containing pendent aliphatic chains
Authors: Agag Tarek , Akelah Ahmed , Rehab Ahmed , Mostafa Salwa
Published: September 2011

The rich chemistry of polybenzoxazines allows a wide range of molecular structure design by using appropriate starting materials. A new class of polybenzoxazines has been developed from benzoxazine monomers containing pendent long aliphatic chains. The monomers have been synthesized by the reaction of phenol or bisphenol A with two different long‐chain aliphatic amines. The chemical structure of the monomers was confirmed by 1H nuclear magnetic resonance and Fourier transform infrared spectroscopy. The polymerization behavior of the monomers studied by differential scanning calorimetry shows exothermic peaks due to the ring‐opening polymerization of benzoxazine monomers centered at 247–255 °C. Dynamic mechanical analysis indicated that the glass transition temperatures Tg were in the range 81–92 °C. The thermal stability of the polymers was also examined by thermogravimetric analysis, demonstrating that the weight loss temperatures decreased in comparison with that of traditional polybenzoxazine. Copyright © 2011 Society of Chemical Industry
Effect of crystallization on barrier properties of formulated polylactide
Authors: Courgneau Cécile , Domenek, Sandra , Lebossé Régis , Guinault Alain , Avérous Luc , Ducruet Violette
Published: September 2011

Polylactide (PLA), a biodegradable polymer obtained from biomass, was formulated with a nucleating agent, talc, and a plasticizer, acetyl tributyl citrate, and cold crystallized in α and α′ form. The barrier properties of crystallized PLA were investigated as a function of the formulation and the crystalline form, thanks to three molecules with increasing polymer interactions, i.e. helium, oxygen and ethyl acetate (EA). Contrary to expectation, the oxygen diffusion coefficient in neat and formulated PLA did not decrease with crystallization. Even an increase of the diffusion coefficient was noticed for the most interacting probe, EA, in formulated PLA. Conditioning of neat and formulated PLA in an atmosphere containing EA vapour caused a modification of the material structure by plasticization and induced crystallization even at small EA activities. The plasticizing effect caused the glass transition temperature Tg to shift to below ambient temperature. In the case of neat PLA induced crystallization in solely the α form was obtained, and in the case of formulated PLA a blend of α and α′ forms was observed. Copyright © 2011 Society of Chemical Industry
Single electron transfer‐living radical polymerization of methyl methacrylate catalyzed by ytterbium powder
Authors: Liu Delong , Ma Jing , Chen Hou , Yin Ping , Ji Naiyi , Zong Guangxi
Published: September 2011

Zerovalent ytterbium (Yb) powder is firstly used as a catalyst in single electron transfer‐living radical polymerization of methyl methacrylate initiated by carbon tetrachloride in N, N‐dimethylformamide (DMF) and dimethyl sulfoxide, respectively. Polymerization proceeds in a “living”/controlled way as evidenced by kinetic studies and chain extension results, producing well‐defined polymers with controlled degree of polymerization and narrow molecular weight distribution. The apparent activation energy of polymerization in DMF is accounted to be 36.2 kJ/mol, and the energy of equilibrium state is calculated to be 13.9 kJ/mol. An increase in the concentration of Yb(0) yields a higher monomer conversion. It is observed that polymerization rate experiments a rapid increase in the presence of more polar solvent water, and increasing in the content of H2O results in an increase in the apparent rate constant of polymerization, and a decrease in the molecular weight distribution. The reaction rate and molecular weight increase along with the decrease of DMF content. The effect of Yb(0) powder content, different ligands and concentration of initiator on the polymerization is also investigated. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
A couple‐based intervention for patients and caregivers facing end‐stage cancer: outcomes of a randomized controlled trial
Authors: McLean Linda M. , Walton Tara , Rodin Gary , Esplen Mary Jane , Jones Jennifer M.
Published: September 2011

Background

We evaluated the effect of Emotionally Focused Therapy (EFT) [intervention (INT)], modified for the advanced cancer population versus standard care [control (CTL)], on marital functioning and psychosocial outcomes among distressed couples. EFT examines the ways couples process patterns of interaction, facilitating change.

Methods

Forty‐two patients with metastatic cancer and their caregivers were assigned randomly to receive eight sessions of EFT delivered by one EFT‐trained psychologist or standard care provided by multidisciplinary clinicians. Partners completed measures of marital functioning, depression, hopelessness, empathic caregiving (patient), and caregiver burden (caregiver) before randomization at baseline (T0), post‐intervention (T1), and 3‐month post‐intervention (T2). Data were analyzed using three‐way analyses of covariance; main effects were treatment, patient status, and sex. Multilevel modeling was also employed.

Results

At T1, INT group led to significant improvement in marital functioning (p ≤ 0.0001) and patients' experience of caregiver empathic care (p = 0.02) versus CTL group. Effect sizes for these differences were in the large range (d = 1.00). In both groups, patients showed a marginally higher mean score for marital functioning compared with caregivers [INT: M = 56.3, standard deviation (SD) = 4.6 vs M = 54.3, SD = 4.5; CTL group: M = 43.4, SD = 10.3 vs M = 42.4, SD = 6.8, respectively]. At T2, results were maintained.

Conclusions

The effectiveness of and adherence to the EFT couple intervention for patients facing advanced cancer were demonstrated in this study. Larger randomized control trials are needed to confirm these findings. Qualitative studies may help to further understand the mechanism by which such an intervention may act. Copyright © 2011 John Wiley & Sons, Ltd.
A multilayer evaluation approach for protein structure prediction and model quality assessment
Authors: Zhang Jingfen , Wang Qingguo , Vantasin Kittinun , Zhang Jiong , He Zhiquan , Kosztin Ioan , Shang Yi , Xu Dong
Published: September 2011

Protein tertiary structures are essential for studying functions of proteins at molecular level. An indispensable approach for protein structure solution is computational prediction. Most protein structure prediction methods generate candidate models first and select the best candidates by model quality assessment (QA). In many cases, good models can be produced, but the QA tools fail to select the best ones from the candidate model pool. Because of incomplete understanding of protein folding, each QA method only reflects partial facets of a structure model and thus has limited discerning power with no one consistently outperforming others. In this article, we developed a set of new QA methods, including two QA methods for evaluating target/template alignments, a molecular dynamics (MD)‐based QA method, and three consensus QA methods with selected references to reveal new facets of protein structures complementary to the existing methods. Moreover, the underlying relationship among different QA methods were analyzed and then integrated into a multilayer evaluation approach to guide the model generation and model selection in prediction. All methods are integrated and implemented into an innovative and improved prediction system hereafter referred to as MUFOLD. In CASP8 and CASP9, MUFOLD has demonstrated the proof of the principles in terms of both QA discerning power and structure prediction accuracy. Proteins 2011; © 2011 Wiley‐Liss, Inc.
Analysis of independent protection layers used in three typical chemical processes
Authors: Meyer Herbert W.H.
Published: September 2011

Independent protection layers (IPLs) used to mitigate the most severe consequences are analyzed for three chemical processes. The IPLs are categorized by type, function, and design. An analysis of management systems that are in place to ensure the integrity of the IPLs is also included. Categorizations for all three plants revealed similar results and suggest that the results extend across the chemical industry. The data show that the chemical plants depend much more heavily on IPLs that prevent an incident rather than respond to an incident once hazardous material is released. The survey also found that there is a significant reliance on administrative safeguards to achieve an acceptable level of risk. Recommendations are made on how administrative safeguards can adapt these systems to improve their robustness. © 2011 American Institute of Chemical Engineers Process Saf Prog, 2011
Testing interruptions in reactive systems
Authors: Andrade Wilkerson L. , Machado Patrícia D. L.
Published: September 2011

Modelling and testing of reactive systems with interruptions are discussed. These systems are commonly found in portable devices, where interruptions to a running application can be demanded at any time, due to concurrent execution of processes sharing a single resource, such as screen, as well as arrival of calls from network distributed services. Since the possible number of combinations of allowed interruptions is large, proper test case selection activities need to be performed. But, in order to systematically investigate and select test cases, it is fundamental to explicitly model interruption behaviour in a compositional way, avoiding the need for explicit enumeration. This work presents a strategy for testing interruptions in reactive systems that covers modelling for testing of systems with interruptions, generation and selection of sound test cases. The strategy is supported by the LTS-BT tool. Moreover, a formal model of an environment devoted to execution of test cases with interruptions is presented. Finally, a case study illustrates its applicability in the mobile phone application domain.
Bioavailability of vitamin C from mashed potatoes and potato chips after oral administration in healthy Japanese men
Authors: Kondo Yoshitaka , Higashi Chihana , Iwama Mizuki , Ishihara Katsuyuki , Handa Setsuko , Mugita Hiroyuki , Maruyama Naoki , Koga Hidenori , Ishigami Akihito
Published: September 2011

Potato (Solanum tuberosum) tubers contain vitamin C (VC) and commercial potato chips have more VC content per wet weight by dehydration during frying. However, intestinal absorption of VC from orally ingested potatoes and its transfer to the blood remains questionable. The present study was designed to determine whether the dietary consumption of potatoes affects VC concentration in plasma and urinary excretion of VC in human subjects. After overnight fasting, five healthy Japanese men between 22 and 27 years of age consumed 87 g mashed potatoes and 282 g potato chips. Each portion contained 50 mg of VC, 50 mg VC in mineral water and mineral water. Before and after a single episode of ingestion, blood and urine samples were collected every 30 min or 1 h for 8 h. When measured by subtraction of the initial baseline value before administration of potatoes from the values measured throughout the 8 h test period, plasma VC concentrations increased almost linearly up to 3 h. Subsequently, the values of potato-fed subjects were higher than those of water, but did not differ significantly from those of VC in water (P = 0·14 andP = 0·5). Less VC tended to be excreted in urine during the 8 h test than VC in water alone (17·0 (sem7·5) and 25·9 (sem8·8)v.47·9 (sem17·9) μmol/mmol creatinine). Upon human consumption, mashed potatoes and potato chips provide VC content that is effectively absorbed in the intestine and transferred to the blood. Clearly, potatoes are a readily available source of dietary VC.
Policy Dynamism: The Case of Aboriginal Australian Education
Authors: MOORE TERRY
Published: September 2011

With reference to an ethnographic study of Aboriginal Australians in formal schooling, this paper focuses on the dynamism of the policy process. It argues that social policy is different in its performance from its formal articulation. It proposes that other discourses complicate policy discourse in its implementation, and that the Aboriginal objects of policy respond creatively to their representation in policy in ways that contribute to that complication. Aboriginal political leaders adopt the subject imagined in policy, elaborate its normativity and pressure their constituency to perform it. The routine performance of this subject works to compromise individuals’ capabilities to negotiate their lived interculturality and multiplicity, and confirms Aborigines in their marginalisation. Thus, policy becomes a central, authoritative catalyst in the real-world constitution of the subject initially imagined. The paper proposes that if social policy engages with this complexity, it can be effective in its aims of contributing to Aboriginal education and development, and management of the emerging condition of diversity. In both cases, it must account for the discursive and performative agency of the objects of policy, making it necessarily context-specific and revisable.
Three-dimensional path planning for unmanned aerial vehicle based on linear programming
Authors: Chen Yang , Han Jianda , Zhao Xingang
Published: September 2011

In this paper, an approach based on linear programming (LP) is proposed for path planning in three-dimensional space, in which an aerial vehicle is requested to pursue a target while avoiding static or dynamic obstacles. This problem is very meaningful for many aerial robots, such as unmanned aerial vehicles. First, the tasks of target-pursuit and obstacle-avoidance are modelled with linear constraints in relative coordination according to LP formulation. Then, two weighted cost functions, representing the optimal velocity resolution, are integrated into the final objective function. This resolution, defined to achieve the optimal velocity, deals with the optimization of a pair of orthogonal vectors. Some constraints, such as boundaries of the vehicle velocity, acceleration, sensor range, and flying height, are considered in this method. A number of simulations, under static and dynamic environments, are carried out to validate the performance of generating optimal trajectory in real time. Compared with ant colony optimization algorithm and genetic algorithm, our method has less parameters to tune and can achieve better performance in real-time application.
Rethinking Solidarity in the EU, from fact to social contract
Authors: WTE  , DN
Published: September 2011

At the time of writing of this editorial, in the high summer of 2011, the ‘market forces” are meeting up for an attack on the first major member of the Eurozone, Italy. It begins, as has now become familiar, with a rise in the rate of interest that a country has to pay for money to service its sovereign debt. Above a critical percentage, around seven in this case, the servicing of its debt, compounded with the loss of tax income due to a slackening economy, will send the country into the downward spiral of ever-increasing debt. The perspective of a possible default in turn will send the interest rate further upward, pushing the country into a more certain default, and so on. It is a self-fulfilling perspective.
The Effect of Foregone Outcomes on Choices From Experience
Authors: Yechiam Eldad , Rakow Tim
Published: September 2011

We examined the relative weight given to obtained and foregone outcomes (i.e., outcomes from the non-chosen options) in repeated choices using cognitive modeling. Previous modeling studies have yielded mixed results. When participants’ choices are analyzed by models that predict the next choice ahead in a sequence of decisions, the results imply that people give less weight to foregone than to obtained outcomes. In contrast, in simulation models of n trials ahead, the results imply that, on average, people give equal weight to foregone and obtained outcomes. Using datasets of experience-based binary choices with fixed (stationary) payoff distributions (Erev & Haruvy, in press) and dynamic (nonstationary) payoff distributions (Rakow & Miler, 2009), we employed generalization tests at the individual level to examine whether the findings derived from the one-step-ahead method are due to overfitting. The results of trial-ahead model fitting implied that for the nonstationary tasks only, foregone outcomes received lower weight. However, when this dataset was assessed via generalization criteria at the individual level, equal weighting of foregone and obtained outcomes was the best assumption. This implies that overfitting is implicated in the superior fit of models that assume discounting of foregone outcomes.
Quorum quenching quandary: resistance to antivirulence compounds
Authors: Maeda Toshinari , García-Contreras Rodolfo , Pu Mingming , Sheng Lili , Garcia Luis Rene , Tomás Maria , Wood Thomas K
Published: September 2011

Quorum sensing (QS) is the regulation of gene expression in response to the concentration of small signal molecules, and its inactivation has been suggested to have great potential to attenuate microbial virulence. It is assumed that unlike antimicrobials, inhibition of QS should cause less Darwinian selection pressure for bacterial resistance. Using the opportunistic pathogen Pseudomonas aeruginosa, we demonstrate here that bacterial resistance arises rapidly to the best-characterized compound that inhibits QS (brominated furanone C-30) due to mutations that increase the efflux of C-30. Critically, the C-30-resistant mutant mexR was more pathogenic to Caenorhabditis elegans in the presence of C-30, and the same mutation arises in bacteria responsible for chronic cystic fibrosis infections. Therefore, bacteria may evolve resistance to many new pharmaceuticals thought impervious to resistance.
Adipokines and Adipocyte Function in Clock Mutant Mice That Retain Melatonin Rhythmicity
Authors: Kennaway David J. , Owens Julie A. , Voultsios Athena , Wight Nicole
Published: September 2011

Clockδ19+MEL mutant mice, which retain melatonin rhythmicity, but lack peripheral tissue rhythmicity have impaired glucose tolerance, but reduced plasma free fatty acids, increased plasma adiponectin, and improved insulin sensitivity. Here, we report their response to a high‐fat diet and adipocyte rhythmicity and function. The diet increased epigonadal fat weight similarly (twofold) in both wild‐type and Clockδ19+MEL mice. The Clockδ19 mutation abolished rhythmicity of Per2, Rev erbα and peroxisome proliferator‐activated receptor‐γ (Pparγ) mRNA in epigonadal fat, but not Bmal1 mRNA, and reduced Rev erbα mRNA by 59 and 70% compared to the wild‐type mice on the control and high‐fat diets, respectively. The mutants had increased Adipoq mRNA expression in epigonadal fat (22%; P < 0.05) on a control diet, but showed no further change on a high‐fat diet, and no change in Lep, Nampt or Retn mRNA on either diet. The Clockδ19 mutation abolished rhythmicity of genes in epigonadal fat that contribute to plasma free fatty acids for mice on both diets, and increased Lipe mRNA expression in those on the high‐fat diet. The persistent melatonin rhythm and reduced plasma free fatty acids in Clockδ19+MEL mutants may contribute to their enhanced insulin sensitivity, ameliorate the extent of impaired glucose homeostasis, and protect against the adverse effects of a high‐fat diet.
Adaptive evolution of drug targets in producer and non-producer organisms
Authors: Hansen Bjarne G. , Sun Xin E. , Genee Hans J. , Kaas Christian S. , Nielsen Jakob B. , Mortensen Uffe H. , Frisvad Jens C. , Hedstrom Lizbeth
Published: September 2011

MPA (mycophenolic acid) is an immunosuppressive drug produced by several fungi in Penicillium subgenus Penicillium. This toxic metabolite is an inhibitor of IMPDH (IMP dehydrogenase). The MPA-biosynthetic cluster of Penicillium brevicompactum contains a gene encoding a B-type IMPDH, IMPDH-B, which confers MPA resistance. Surprisingly, all members of the subgenus Penicillium contain genes encoding IMPDHs of both the A and B types, regardless of their ability to produce MPA. Duplication of the IMPDH gene occurred before and independently of the acquisition of the MPAbiosynthetic cluster. Both P. brevicompactum IMPDHs are MPA-resistant, whereas the IMPDHs from a non-producer are MPA-sensitive. Resistance comes with a catalytic cost: whereas P. brevicompactum IMPDH-B is >1000-fold more resistant to MPA than a typical eukaryotic IMPDH, its kcat/Km value is 0.5% of ‘normal’. Curiously, IMPDH-B of Penicillium chrysogenum, which does not produce MPA, is also a very poor enzyme. The MPA-binding site is completely conserved among sensitive and resistant IMPDHs. Mutational analysis shows that the C-terminal segment is a major structural determinant of resistance. These observations suggest that the duplication of the IMPDH gene in the subgenus Penicillium was permissive for MPA production and that MPA production created a selective pressure on IMPDH evolution. Perhaps MPA production rescued IMPDH-B from deleterious genetic drift.
ASHA and the Evolution of Telepractice
Authors: Brown Janet
Published: September 2011

The American Speech-Language-Hearing Association (ASHA) has been providing information and resources about the appropriate use of telepractice (also called teleaudiology and telespeech) since the late 1990s. In the past 13 years, ASHA has fielded a telepractice survey to its members, disseminated guidance about the use of telepractice through practice policy documents, collaborated with other organizations, and advocated to payers and to state and federal legislators about the reimbursement and regulation of telepractice services. This article describes the key activities in ASHA's role to date and continuing challenges.
Growth and optical properties of CdTe quantum dots in ZnTe nanowires
Authors: Wojnar Piotr , Janik Elżbieta , Baczewski Lech T. , Kret Sławomir , Karczewski G. , Wojtowicz Tomasz , Goryca Mateusz , Kazimierczuk Tomasz , Kossacki Piotr
Published: September 2011

We report on the formation of optically active CdTe quantum dots in ZnTe nanowires. The CdTe/ZnTe nanostructures have been grown by a gold nanocatalyst assisted molecular beam epitaxy in a vapor-liquid solid growth process. The presence of CdTe insertions in ZnTe nanowire results in the appearance of a strong photoluminescence band in the 2.0 eV–2.25 eV energy range. Spatially resolved photoluminescence measurements reveal that this broad emission consists of several sharp lines with the spectral width of about 2 meV. The large degree of linear polarization of these individual emission lines confirms their nanowire origin, whereas the zero-dimensional confinement is proved by photon correlation spectroscopy.
Mechanisms of kinetic trapping in self-assembly and phase transformation
Authors: Hagan Michael F. , Elrad Oren M. , Jack Robert L.
Published: September 2011

In self-assembly processes, kinetic trapping effects often hinder the formation of thermodynamically stable ordered states. In a model of viral capsid assembly and in the phase transformation of a lattice gas, we show how simulations in a self-assembling steady state can be used to identify two distinct mechanisms of kinetic trapping. We argue that one of these mechanisms can be adequately captured by kinetic rate equations, while the other involves a breakdown of theories that rely on cluster size as a reaction coordinate. We discuss how these observations might be useful in designing and optimising self-assembly reactions.
Silicon nanowire - poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) heterojunction solar cells
Authors: Ozdemir Baris , Kulakci Mustafa , Turan Rasit , Emrah Unalan Husnu
Published: September 2011

Radial heterojunctions are known to exhibit magnificent anti-reflectivity and enhanced carrier collectivity due to short carrier diffusion distances. In this work, silicon nanowire-poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) radial heterojunction solar cells are presented. Both layers of the heterojunction are fabricated using simple and cost-effective methods. Radial heterojunctions showed remarkable improvements in solar cell characteristics compared to planar heterojunctions, fabricated under the same conditions. The highest solar cell efficiency of 5.30% is obtained. The cells exhibit external quantum efficiency of 77% at 500 nm wavelength and harvest light over the entire 300-1200 nm spectral bandwidth. The effect of nanowire length on device performance is also determined.
Low-frequency noise of unipolar nanorectifiers
Authors: Balocco Claudio , Kasjoo Shahrir R. , Zhang Linqing Q. , Alimi Yasaman , Song Aimin M.
Published: September 2011

Unipolar nanodiodes, also known as self-switching devices, have recently been demonstrated as terahertz detectors at room temperature. Here, we study their low-frequency noise spectra and noise equivalent power and show that both performance parameters are comparable to those reported for state-of-the-art Schottky diodes. The truly planar nanodiode layout enables building structures with thousands of devices connected in parallel, which reduce low-frequency noise without affecting sensitivity. The observed 1/f noise can be described by Hooge’s mobility fluctuation theory.
Enhanced electrostatic discharge properties of nitride-based light-emitting diodes with inserting Si-delta-doped layers
Authors: Zheng Zhiyuan , Chen Zimin , Xian Yulun , Fan Bingfeng , Huang Shanjin , Jia Weiqing , Wu Zhisheng , Wang Gang , Jiang Hao
Published: September 2011

We report significantly improved electrostatic discharge (ESD) properties of InGaN/GaN-based light-emitting diodes (LEDs) with inserting Si-delta-doped layers between multiple quantum wells and n-cladding layer. The ESD endurance voltage increased from −1200 V to −4000 V with the insertion of delta-doped layers. The mechanism of the enhanced ESD properties was then investigated. According to capacitance-voltage results, the factor of capacitance modulation was ruled out. However, infrared microscopy image proved better current spreading in the LEDs with delta-doped layers. In addition, current-voltage, photoluminescence, and atomic force microscope measurements demonstrated substantial quality improvements. These two reasons were considered as the dominant mechanisms of the enhanced ESD properties.
The role of mobility in bulk heterojunction solar cells
Authors: Xu Feng , Yan Dadong
Published: September 2011

In this letter, we employ a three-dimensional master equation calculation to investigate the mobility dependence of bulk heterojunction (BHJ) solar cell performance. By taking energetic disorder and morphology into consideration, we show mobility-enhanced device efficiency with a remarkable charge transport loss induced by molecular disorder and an open circuit voltage loss in high mobility region due to morphological defect-assisted bimolecular recombination. The result suggests that the description of interfacial processes is crucial in the modeling of BHJ photovoltaic devices.
Improved charge-trapping properties of HfYON film for nonvolatile memory applications in comparison with HfON and Y2O3 films
Authors: Huang X. D. , Liu L. , Xu J. P. , Lai P. T.
Published: September 2011

The charge-trapping properties of HfYON film are investigated by using the Al/HfYON/SiO2/Si structure. The physical features of this film were explored by transmission electron microscopy and x-ray photoelectron spectroscopy. The proposed device shows better charge-trapping characteristics than samples with HfON or Y2O3 as the charge-trapping layer due to its higher trapping efficiency, as confirmed by extracting their charge-trap centroid and charge-trap density. Moreover, the Al/Al2O3/HfYON/SiO2/Si structure shows high program speed (4.5 V at +14 V, 1 ms), large memory window (6.0 V at ±14 V, 1 s), and good retention property, further demonstrating that HfYON is a promising candidate as the charge-trapping layer for nonvolatile memory applications.
Fluxgate based detection of magnetic nanoparticle dynamics in a rotating magnetic field
Authors: Dieckhoff Jan , Schilling Meinhard , Ludwig Frank
Published: September 2011

We have developed a measurement setup allowing the investigation of the dynamics of magnetic nanoparticle suspensions in a rotating magnetic field. To determine the vector of the sample magnetization, sensitive fluxgate magnetometers are utilized detecting the sample’s stray field. The phase lag between sample magnetization and rotating magnetic field vector is determined via the cross correlation spectrum. The phase lag spectra measured for various rotating field amplitudes on aqueous magnetite nanoparticle suspensions show good agreement with theory if the multidispersity of core and hydrodynamic size is taken into account.
Depth
Authors: Koenderink Jan J , van Doorn Andrea J , Wagemans Johan
Published: September 2011

Depth is the feeling of remoteness, or separateness, that accompanies awareness in human modalities like vision and audition. In specific cases depths can be graded on an ordinal scale, or even measured quantitatively on an interval scale. In the case of pictorial vision this is complicated by the fact that human observers often appear to apply mental transformations that involve depths in distinct visual directions. This implies that a comparison of empirically determined depths between observers involves pictorial space as an integral entity, whereas comparing pictorial depths as such is meaningless. We describe the formal structure of pictorial space purely in the phenomenological domain, without taking recourse to the theories of optics which properly apply to physical space—a distinct ontological domain. We introduce a number of general ways to design and implement methods of geodesy in pictorial space, and discuss some basic problems associated with such measurements. We deal mainly with conceptual issues.
Accessing protein conformational ensembles using room-temperature X-ray crystallography
Authors: Fraser James S. , van den Bedem Henry , Samelson Avi J. , Lang P. Therese , Holton James M. , Echols Nathaniel , Alber Tom
Published: September 2011

Modern protein crystal structures are based nearly exclusively on X-ray data collected at cryogenic temperatures (generally 100 K). The cooling process is thought to introduce little bias in the functional interpretation of structural results, because cryogenic temperatures minimally perturb the overall protein backbone fold. In contrast, here we show that flash cooling biases previously hidden structural ensembles in protein crystals. By analyzing available data for 30 different proteins using new computational tools for electron-density sampling, model refinement, and molecular packing analysis, we found that crystal cryocooling remodels the conformational distributions of more than 35% of side chains and eliminates packing defects necessary for functional motions. In the signaling switch protein, H-Ras, an allosteric network consistent with fluctuations detected in solution by NMR was uncovered in the room-temperature, but not the cryogenic, electron-density maps. These results expose a bias in structural databases toward smaller, overpacked, and unrealistically unique models. Monitoring room-temperature conformational ensembles by X-ray crystallography can reveal motions crucial for catalysis, ligand binding, and allosteric regulation.
The Word-length Effect and Disyllabic Words
Authors: Lovatt Peter , Avons S.E. , Masterson Jackie
Published: September 2011

Three experiments compared immediate serial recall of disyllabic words that differed on spoken duration. Two sets of long- and short-duration words were selected, in each case maximizing duration differences but matching for frequency, familiarity, phonological similarity, and number of phonemes, and controlling for semantic associations. Serial recall measures were obtained using auditory and visual presentation and spoken and picture-pointing recall. In Experiments 1a and 1b, using the first set of items, long words were better recalled than short words. In Experiments 2a and 2b, using the second set of items, no difference was found between long and short disyllabic words. Experiment 3 confirmed the large advantage for short-duration words in the word set originally selected by Baddeley, Thomson, and Buchanan (1975). These findings suggest that there is no reliable advantage for short-duration disyllables in span tasks, and that previous accounts of a word-length effect in disyllables are based on accidental differences between list items. The failure to find an effect of word duration casts doubt on theories that propose that the capacity of memory span is determined by the duration of list items or the decay rate of phonological information in short-term memory.
Set-size and Frequency-of-occurrence Judgements in Young and Older Adults: The Role of the Availability Heuristic
Authors: Maley Jennifer E. , Hunt Maree , Parr Wendy
Published: September 2011

Two experiments examined the cognitive processes underlying judgements of set size and judgements of frequency of occurrence in young (Experiments 1 and 2) and older (Experiment 2) adults. Previous research has implicated the availability heuristic in set-size judgements, whereas an automatic processing mechanism has been implicated in judgements of frequency of occurrence. In the current experiments, path analysis was employed to investigate the role of an availability bias in performance on the judgement tasks. In Experiments 1 and 2, both types of judgement were influenced by repetition frequency of words independent of the availability (recall) of specific exemplars. Experiment 2 extended the investigation to include age differences. Although older adults’ recall performance was poorer overall, the availability bias was age invariant, and there were no age differences in either set-size or frequency-of-occurrence judgements. Our results indicate that both set-size and frequency-of-occurrence judgements are independent of the availability bias evident in recall, and they support the notion that an automatic processing mechanism underlies both types of judgement.
Orthographic Repetition Blindness
Authors: Harris Catherine L. , Morris Alison L.
Published: September 2011

Repetition blindness (RB) is the failure to report the second occurrence of a repeated word, when words are sequentially and briefly displayed (Kanwisher, 1987). RB is also observed for non-identical words, such as home, dome. Explanations for non-identity RB assume that similarity at the level of the whole word causes the second word to be suppressed (“similarity inhibition”). Three experiments demonstrate that RB is robust for diverse types of orthographic relatedness, including critical words that share only their first initial letter, their last two letters, first three letters, middle three letters, beginning and final letters, three alternating letters, and three non-aligned letters (as in chance hand). The theoretical construct of similarity inhibition may be able to account for these data, although one mechanism previously proposed in the literature, neighbourhood inhibition, is probably not a useful way to explain the data on RB for words sharing only one or two letters. We introduce an alternative explanation for orthographic RB: Only the repeated letters are suppressed, and amount of RB depends on how easily the perceiver can reconstruct the target word from the non-suppressed letters.
The Effects of Massive Repetition on Speeded Recognition of Faces
Authors: Lewis Michael B. , llis Hadyn D.E
Published: September 2011

Models of face processing suggest that recognizing a person should prime recognition of a consecutive, but different, image of the same person. This prediction is tested in four experiments using large blocks of different views of the same person. The experiments demonstrate that reaction times decreased according to a negative power function as the number of repetitions increased. After sufficient repetitions, however, the reaction times lengthened. The presentation of a different familiar person between blocks of repetitions caused the reaction time for the target to increase to a level equivalent to that with no repetitions. Experiments 2 and 3 investigated the effect of different intervening stimuli (unfamiliar faces and objects). Such stimuli reduced the effect of mass repetition—but the reduction using a familiar face was greater than that with either unfamiliar faces or objects. Experiment 4 confirmed that the effects of massive repetition occur for a face familiarity task as well as for face identification tasks. The results are discussed in terms of the predictions of Burton's (1994) IACL model.
A More Complete Task-Set Reconfiguration in Random than in Predictable Task Switch
Authors: Tornay Francisco J. , Milán Emilio G.
Published: September 2011

Three experiments are presented that compare the cost found when switching from one task to another in two different conditions. In one of them, the tasks switch in predictable sequences. In the other condition, the tasks alternate at random. A smaller time cost is found in the random-switch condition when enough preparation time is allowed. Such an effect is due to the random-switch cost continuing to decrease with preparation time after the predictable-switch cost has reached an asymptote. Although the relationship between number of repetitions of one task and time cost is different in the random- and the predictable-switch conditions, only the latter shows the presence of an “exogenous” component of cost. The implications of this finding are discussed in relationship with the usual distinction between an endogenous component of switch cost that is affected by preparation time and another exogenous, residual component (e.g., Rogers & Monsell, 1995). It is proposed that a different kind of task-set preparation is at work when tasks alternate at random.
Revisiting Scene Primes for Object Locations
Authors: Germeys Filip , d'Ydewalle Géry
Published: September 2011

Sanocki and Epstein (1997) provided evidence that an immediate prior experience of a scene, as a prime, can induce representations of its spatial layout, facilitating the subsequent spatial processing of objects in the target scene. In their experiments, observers responded to target scenes by indicating which of two critical objects was closer in the pictorial space. Reaction times to target scenes that were preceded by same-scene primes without the critical objects were faster than reaction times to target scenes that were preceded by different scene or control primes (geometrical figures). By manipulating the nature of the prime and the interval between prime and target, and by cueing the position of the critical objects, we obtain evidence that the facilitating effect of the same-scene primes can also be explained by the sudden appearance of the critical objects in the target scene. In same-scene conditions, the critical objects cause a local onset, whereas in different-scene and control conditions the entire target scene causes a global onset. As a result, the local onset in the same-scene condition produces a shift of attention towards the critical objects, resulting in faster processing of the critical objects.
On the Strategic Modulation of the Time Course of Facilitation and Inhibition of Return
Authors: Lupiáñez Juan , Milliken Bruce , Solano César , Weaver Bruce , Tipper Steven P.
Published: September 2011

In studies of exogenous attentional orienting, response times for targets at previously cued locations are often longer than those for targets at previously uncued locations. This effect is known widely as inhibition of return (IOR). There has been debate as to whether IOR can be observed in discrimination as well as detection tasks. The experiments reported here confirm that IOR can be observed when target discrimination is required and that the cue-target interval at which IOR is observed is often longer in discrimination than in detection tasks. The results also demonstrate that the later emergence of IOR is related to perceptual discrimination rather than to response selection differences between discrimination and detection tasks. More difficult discrimination tasks lengthen the SOA at which IOR emerges. In contrast, increasing task difficulty by adding a distractor to the location opposite the target shortens the SOA at which IOR emerges. Together, the results reveal an adaptive interaction between exogenous and endogenous attentional systems, in which the action of the orienting (exogenous) system is modulated endogenously in accord with task demands.
De-Confusing the THOG Problem: The Pythagorean Solution
Authors: Griggs Richard A. , Koenig Cynthia S. , Alea Nicole L.
Published: September 2011

Sources of facilitation for Needham and Amado's (1995) Pythagoras version of Wason's THOG problem were systematically examined in three experiments with 174 participants. Although both the narrative structure and figural notation used in the Pythagoras problem independently led to significant facilitation (40–50% correct), pairing hypothesis generation with either factor or pairing the two factors together was found to be necessary to obtain substantial facilitation (> 50% correct). Needham and Amado's original finding for the complete Pythagoras problem was also replicated. These results are discussed in terms of the “confusion theory” explanation for performance on the standard THOG problem. The possible role of labelling as a de-confusing factor in other versions of the THOG problem and the implications of the present findings for human reasoning are also considered.