bluuebunny/crossref_metadata_2025 huggingface dataset:
The genetic and environmental etiology of decision‐making: A longitudinal twin study
Authors: Tuvblad Catherine , Gao Yu , Wang Pan , Raine Adrian , Botwick Theodore , Baker Laura A.
Published: December 2012

The present study examined the genetic and environmental etiology of decision‐making (Iowa Gambling Task; Bechara, Damásio, Damásio, & Anderson, 1994), in a sample of twins at ages 11–13, 14–15, and 16–18 years. The variance across five 20‐trial blocks could be explained by a latent “decision‐making’’ factor within each of the three times of IGT administration. This latent factor was modestly influenced by genetic factors, explaining 35%, 20% and 46% of the variance within each of the three times of IGT administration. The remaining variance was explained by the non‐shared environment (65%, 80% and 54%, respectively). Block‐specific non‐shared environmental influences were also observed. The stability of decision‐making was modest across development. Youth showed a trend to choose less risky decks at later ages, suggesting some improvement in task performance across development. These findings contribute to our understanding of decision‐making by highlighting the particular importance of each person's unique experiences on individual differences.
Breaking the amyloidogenicity code: Methods to predict amyloids from amino acid sequence
Authors: Ahmed Abdullah B. , Kajava Andrey V.
Published: December 2012

Numerous studies have shown that the ability to form amyloid fibrils is an inherent property of the polypeptide chain. This has lead to the development of several computational approaches to predict amyloidogenicity by amino acid sequences. Here, we discuss the principles governing these methods, and evaluate them using several datasets. They deliver excellent performance in the tests made using short peptides (∼6 residues). However, there is a general tendency towards a high number of false positives when tested against longer sequences. This shortcoming needs to be addressed as these longer sequences are linked to diseases. Recent structural studies have shown that the core element of the majority of disease‐related amyloid fibrils is a β‐strand‐loop‐β‐strand motif called β‐arch. This insight provides an opportunity to substantially improve the prediction of amyloids produced by natural proteins, ushering in an era of personalized medicine based on genome analysis.
Flow of an Eyring-Powell Fluid with Convective Boundary Conditions
Authors: Hayat T. , Iqbal Z. , Qasim M. , Alsaedi A.
Published: December 2012

The boundary layer flow of an Eyring-Powell fluid over a stretching surface subject to the convective boundary condition is investigated. Nonlinear problem is computed and a comparative study is presented with the existing results in viscous fluid. The constructed differential systems have been solved for homotopic solutions. Convergence of series solutions has been discussed. Special emphasis has been given to the effects of material parameters of fluid (ε), (δ), Biot number (γ) and Prandtl number (Pr) on the velocity and temperature profiles. Tabulated values of Nusselt number and skin friction for different emerging parameters are also illustrated. It is noted that the boundary layer thickness is an increasing function of (ε) and decreasing function of (δ). However the temperature and thermal boundary layer thickness decrease when the values of (ε) and (δ) are increased.
A Study on the Flow Patterns of a Second Grade Viscoe-Lastic Fluid Past a Cavity in a Horizontal Channel
Authors: Hsu C. H. , Hu S. Y. , Kung K. Y. , Kuo C. C. , Chang C. C.
Published: December 2012

This paper studies the behavior of second grade viscoelastic fluid past a cavity in a horizontal channel. The effects of Reynolds number, fluid elasticity and the aspect ratio of the cavity on the flow field are simulated numerically. The equations are converted into the vorticity and stream function equations. The solution is obtained by the finite difference method.

The behavior of viscoelastic fluids is quite different from the Newtonian fluid, due to the effects of fluid elasticity. Only one flow pattern appears when the Newtonian fluid past the cavity. However, three kinds of flow patterns appear while the viscoelastic fluids past the cavity by increasing Reynolds number from 20 to 300. The flow field is affected by the fluid elasticity as well as the aspect ratio of the cavity. The transitional flow pattern appears at lower Reynolds number as the higher elasticity fluid past the cavity with larger aspect ratio.
Dynamic Response and Wave Propagation in Three-Dimensional Framed Structures
Authors: Pao Y.-H. , Nie G.-H. , Keh D.-C.
Published: December 2012

This paper extends the recently developed method of reverberation-ray matrix for planar structures to three-dimensional framed structures. The propagation of steady state axial, flexural and torsional waves, as well as the mode conversions through scattering of all three waves at connecting joints are evaluated in the frequency domain. The transient waves in all members are then determined by the Fourier synthesis. The transient responses of a two-storey framed building subject to a step time loading are calculated in detail. Numerical results are obtained for early time as well as moderately long time records. The results are shown to be accurate in arrival times of all three types of waves and in asymptotic values at times.
The dogs of the Australasian Antarctic Expedition 1911–1914
Authors: Riffenburgh Beau
Published: December 2012

Fifty dogs were ordered from Greenland for use on Douglas Mawson's Australasian Antarctic Expedition (1911–1914). Twenty-one more were later donated to the expedition by Roald Amundsen, when he reached Hobart after his successful attainment of the South Pole. Numerous pups were born during the expedition. This note gives the details of the individual dogs during the expedition, including their names (and why they were so named), descriptions (when known), and fates.
Resting-state functional connectivity in adults with childhood emotional maltreatment
Authors: van der Werff S. J. A. , Pannekoek J. N. , Veer I. M. , van Tol M.-J. , Aleman A. , Veltman D. J. , Zitman F. G. , Rombouts S. A. R. B. , Elzinga B. M. , van der Wee N. J. A.
Published: December 2012

Background

Childhood emotional maltreatment (CEM) has been associated with disturbances in emotional and behavioral functioning, and with changes in regional brain morphology. However, whether CEM has any effect on the intrinsic organization of the brain is not known. In this study, we investigated the effects of CEM on resting-state functional connectivity (RSFC) using seeds in the limbic network, the default-mode network (DMN) and the salience network, and the left dorsomedial prefrontal cortex (dmPFC).

Method

Using 3-T magnetic resonance imaging (MRI), resting-state functional MRI (RS-fMRI) scans were obtained. We defined seeds in the bilateral amygdala, the dorsal anterior cingulate cortex (dACC), the posterior cingulate cortex (PCC) and the left dmPFC, and used these to examine whether individuals reporting CEM (n=44) differed from individuals reporting no CEM (n=44) in RSFC with other brain regions. The two groups were matched for age, gender, handedness and the presence of psychopathology.

Results

CEM was associated with decreased RSFC between the right amygdala and the bilateral precuneus and a cluster extending from the left insula to the hippocampus and putamen. In addition, CEM was associated with decreased RSFC between the dACC and the precuneus and also frontal regions of the brain.

Conclusions

We found that CEM has a profound effect on RSFC in the limbic network and the salience network. Regions that show aberrant connectivity are related to episodic memory encoding, retrieval and self-processing operations.
Social values and the role of law: the use of legal planning tools for old age by privatised and non-privatised Kibbutz members
Authors: MILOE HAMOTAL , DORON ISRAEL
Published: December 2012

Historically, the Kibbutzim in Israel were established as collective, socialist communities. However, since the 1980s, the Kibbutz movement has undergone profound social processes. One of the outcomes of these processes was the privatisation of the Kibbutz. The goal of this study was to examine the relationship between the socio-legal structure of the Kibbutz (i.e.non-privatisedversusprivatised) and the awareness, knowledge and usage of legal planning tools for old age. Using a quantitative research method, a closed questionnaire was designed and distributed to a non-probability convenience sample, consisting of 295 respondents, of them 137 (46%) from traditional Kibbutzim and 158 (54%) from privatised Kibbutzim. Five different legal tools were examined: private pension; private long-term care insurance; advanced health-care directive, will, and organ donation. According to findings, on average, members of privatised Kibbutzim reported higher levels of awareness, knowledge and usage regarding legal planning tools for old age. These findings support other studies that point to the relationships between societal values (collectivistversusindividualistic) and social policies regarding older persons – in general, and legal policies in the field of law and ageing – in specific. It is expected that a shift toward a more individualistic value-based society will increase the awareness and usage of individually based legal planning tools for old age.
Anisotropic diffusion in oriented environments can lead to singularity formation
Authors: HILLEN THOMAS , PAINTER KEVIN J. , WINKLER MICHAEL
Published: December 2012

We consider an anisotropic diffusion equation of the form ut = ∇∇(D(x)u) in two dimensions, which arises in various applications, including the modelling of wolf movement along seismic lines and the invasive spread of certain brain tumours along white matter neural fibre tracts. We consider a degenerate case, where the diffusion tensor D(x) has a zero-eigenvalue for certain values of x. Based on a regularisation procedure and various pointwise and integral a priori estimates, we establish the global existence of very weak solutions to the degenerate limit problem. Moreover, we show that in the large time limit these solutions approach profiles that exhibit a Dirac-type mass concentration phenomenon on the boundary of the region in which diffusion is degenerate, which is quite surprising for a linear diffusion equation. The results are illustrated by numerical examples.
Update on syncope in the older person – a clinical review
Authors: Mappilakkandy Riaz , Edwards Ian
Published: December 2012

Syncope is a common cause of presentation to the emergency department in the older population, who are at increased risk of syncope resulting in serious injury in the form of fractures, adverse cardiac outcomes and death, lack of confidence and mental health issues. Older patients can present diagnostic challenges due to multiple co-morbidities, polypharmacy and the problem of amnesia associated with transient loss of consciousness. The underlying cause of their syncope can be established through a structured approach, and targeted patient selection can limit inappropriate investigations in syncope assessment units and ensure appropriate treatments are instituted. A previous review article in this journal, by Nath and Kenny in 2005, examined the evidence surrounding various aspects of syncope, including prevalence, cause, risks, investigations and treatment. This review updates the evidence and guidelines on the aetiology, investigation and treatments of syncope in the older person, with emphasis on recent advances.
Input frequency and the acquisition of subject-verb agreement in number in spoken and written French
Authors: ÅGREN MALIN , VAN DE WEIJER JOOST
Published: December 2012

The present study focuses on the characteristics of subject-verb agreement in number in spoken and written French, two morphological systems that are very different. In particular, we investigate the impact of frequency of forms and morphological patterns in the input on the acquisition of number agreement in monolingual and bilingual French-speaking children (n = 32). Our results demonstrate an almost perfect fit between the partial and heterogeneous nature of number agreement in the spoken input and the errors found in the children's spoken narratives. However, the influence of a highly systematic written number-agreement on the children's written narratives is weak, mainly due to the lack of phonological cues of number agreement in written French.
Efficacy of olanzapine in comparison with clozapine for treatment-resistant schizophrenia: evidence from a systematic review and meta-analyses
Authors: Souza Juliano S , Kayo Monica , Tassell Ivson , Martins Camila Bertini , Elkis Helio
Published: December 2012

Introduction

Clozapine is considered the gold standard for the treatment of patients with treatment-resistant schizophrenia (TRS); however, randomized controlled trials (RCT) of olanzapine showed efficacy similar to clozapine in patients with TRS.

Methods

A systematic review was conducted comparing clozapine with olanzapine in patients with TRS. Meta-analyses were performed for single outcome measures. Response to treatment was measured by the percentage of responders, or mean change or endpoint values of psychotic symptoms scales. Effect sizes were shown as relative risks (RR), or standardized mean differences, with 95% confidence intervals.

Findings

Seven RCT were included, comprising 648 patients. Five meta-analyses were performed. Olanzapine and clozapine had similar effects on dropout rates (RR = 0.93, CI95%= 0.77–1.12), PANSS total endpoints (SMD = 0.21, CI95%= –0.04–0.46), and PANSS total mean changes (SMD = 0.08, CI95%= –0.01–0.027). Clozapine was superior to olanzapine for PANSS positive (SMD = 0.51, CI95%= 0.17–0.86) and negative (SMD = 0.50, CI95%= 0.16–0.85) subscales. There was a trend toward high doses of olanzapine producing higher effect sizes for this drug.

Conclusions

The results of this study suggest that clozapine is significantly more efficacious than olanzapine in improving positive and negative symptoms in TRS patients.
L1 and L2 picture naming in Mandarin–English bilinguals: A test of Bilingual Dual Coding Theory
Authors: JARED DEBRA , PEI YUN POH REBECCA , PAIVIO ALLAN
Published: December 2012

This study examined the nature of bilinguals’ conceptual representations and the links from these representations to words in L1 and L2. Specifically, we tested an assumption of the Bilingual Dual Coding Theory that conceptual representations include image representations, and that learning two languages in separate contexts can result in differences in referential images for L1 and L2. Mandarin–English participants named aloud culturally-biased images and culturally-unbiased filler images presented on a computer screen in both Mandarin (L1) and English (L2). Culturally-biased images were named significantly faster in the culturally-congruent language than in the incongruent language. These findings indicate that some image representations are more strongly connected to one language than the other, providing support for the Bilingual Dual Coding Theory.
Climate change and animal diseases: making the case for adaptation
Authors: Cáceres Sigfrido Burgos
Published: December 2012

The exponential expansion of the human population has led to overexploitation of resources and overproduction of items that have caused a series of potentially devastating effects, including ocean acidification, ozone depletion, biodiversity loss, the spread of invasive flora and fauna and climatic changes – along with the emergence of new diseases in animals and humans. Climate change occurs as a result of imbalances between incoming and outgoing radiation in the atmosphere. This process generates heat. As concentrations of atmospheric gases reach record levels, global temperatures are expected to increase significantly. The hydrologic cycle will be altered, since warmer air can retain more moisture than cooler air. This means that some geographic areas will have more rainfall, whereas others have more drought and severe weather. The potential consequences of significant and permanent climatic changes are altered patterns of diseases in animal and human populations, including the emergence of new disease syndromes and changes in the prevalence of existing diseases. A wider geographic distribution of known vectors and the recruitment of new strains to the vector pool could result in infections spreading to more and potentially new species of hosts. If these predictions turn out to be accurate, there will be a need for policymakers to consider alternatives, such as adaptation. This review explores the linkages between climate change and animal diseases, and examines interrelated issues that arise from altered biological dynamics. Its aim is to consider various risks and vulnerabilities and to make the case for policies favoring adaptation.
Birds and bornaviruses
Authors: Payne Susan L. , Delnatte Pauline , Guo Jianhua , Heatley J. Jill , Tizard Ian , Smith Dale A.
Published: December 2012

In 2008, avian bornaviruses (ABV) were identified as the cause of proventricular dilatation disease (PDD). PDD is a significant condition of captive parrots first identified in the late 1970s. ABV infection has subsequently been shown to be widespread in wild waterfowl across the United States and Canada where the virus infects 10–20% of some populations of ducks, geese and swans. In most cases birds appear to be healthy and unaffected by the presence of the virus; however, infection can also result in severe non-suppurative encephalitis and lesions similar to those seen in parrots with PDD. ABVs are genetically diverse with seven identified genotypes in parrots and one in canaries. A unique goose genotype (ABV-CG) predominates in waterfowl in Canada and the northern United States. ABV appears to be endemic in North American waterfowl, in comparison to what appears to be an emerging disease in parrots. It is not known whether ABV can spread between waterfowl and parrots. The discovery of ABV infection in North American waterfowl suggests that European waterfowl should be evaluated for the presence of ABV, and also as a possible reservoir species for Borna disease virus (BDV), a related neurotropic virus affecting horses and sheep in central Europe. Although investigations have suggested that BDV is likely derived from a wildlife reservoir, for which the shrew and water vole are currently prime candidates, we suggest that the existence of other mammalian and avian reservoirs should not be discounted.
Hybrid bounds for automorphic forms on ellipsoids over number fields
Authors: Blomer Valentin , Michel Philippe
Published: December 2012

We prove upper bounds for Hecke–Laplace eigenfunctions on certain Riemannian manifolds $X$ of arithmetic type, uniformly in the eigenvalue and the volume of the manifold. The manifolds under consideration are $d$-fold products of $2$-spheres or $3$-spheres, realized as adelic quotients of quaternion algebras over totally real number fields. In the volume aspect we prove a (‘Weyl-type’) saving of $\mathrm{vol} \hspace{0.167em} (X)^{- 1/ 6+ \varepsilon } $.
Soil properties in organic olive orchards following different weed management in a rolling landscape of Andalusia, Spain
Authors: Soriano María-Auxiliadora , Álvarez Sonia , Landa Blanca B. , Gómez José A.
Published: December 2012

This study evaluated the most significant physical, chemical and biological soil properties from a group of organic olive farms located in a typical olive-growing area of Andalusia, Spain, after 5 or more years since the shift from conventional to organic farming, and compared soils with those in nearby undisturbed (U) natural areas. Two soil management systems implemented in these organic olive farms to control weeds, tillage (T), characterized by non-inverting-shallow tillage in spring, and mechanical mowing (M), were compared and evaluated against the U areas. Organic olive orchards showed similar productivity (average fruit yield of 3130 kg ha−1 yr−1) as the conventional, rain-fed olive groves in the same area, with no significant differences due to soil management systems. Soil properties in the olive orchards (i.e. texture, pH, organic carbon (C), organic nitrogen (N), C:N ratio, cation exchange capacity (CEC) and exchangeable potassium) were in the suitable range for olive farming in both soil managements, although organic C and N, saturated hydraulic conductivity and available water-holding capacity (AWC) of the soil were lower than in the U areas. A principal component analysis (PCA) for soil properties in topsoil (0–10 cm depth) distinguished the T from M olive orchards and U areas, and determined organic C and N as the most significant soil properties to characterize them. Average values of soil organic carbon (SOC) stocks for the surface layer (0–10 cm depth) were 18.6, 59.3 and 67.8 Mg ha−1, for T and M soil management systems and U areas, respectively. This indicates that the sustainability of organic olive orchards could be significantly improved by shifting to M soil management to decrease soil erosion and depletion of SOC.
SOME REMARKS ON SUPPLEMENTATION PRINCIPLES IN THE ABSENCE OF ANTISYMMETRY
Authors: OBOJSKA LIDIA
Published: December 2012

In response to the paper by Cotnoir and Bacon published in RSL 2/2012, we would like to add some remarks regarding supplementation principles. It is known that in a classical mereology, the Strong Supplementation Principle (SSP) together with antisymmetry enforces the Weak Supplementation Principle (WSP). Instead, in the nonwellfounded mereology, the failure of extensionality causes the failure of antisymmetry (Cotnoir, 2010), hence the investigated model is also nonantisymmetric. Cotnoir supposes that the failure of antisymmetry implies the failure of (WSP) when (PP1) is applied, however gives no explicit argument, which we would like to supply in this paper. Additionally, when (PP2) is applied, (SSP) implies (WSP), hence the failure of antisymmetry does not necessarily imply the failure of (WSP).
Eastern Religions and Attitude toward Direct Democracy in Taiwan
Authors: Chang Wen-Chun
Published: December 2012

While direct democracy is a practical form of self-determination in the political process, the value system stemming from a given country's social and cultural factors has been argued to be critical in shaping citizens' preferences for a political institution. This article investigates the relationship between religion and the attitude toward direct democracy for the case of Taiwan, an East Asian country where most people are affiliated with Buddhism, Taoism, and folk religions. Unlike Western countries dominated by Judeo-Christianity, some arguments indicate that value systems emphasizing collectivities, social cohesion, and obedience to authorities in East Asian countries are inconsistent with the fundamental value of democratic norms based on individual rights and self-determination. If this is the case, then social and cultural factors are incompatible to democratic development in East Asian societies. Nevertheless, this argument has not been adequately supported by empirical studies. By using data from the Taiwan Social Change Survey 2004, the findings from this study suggest that affiliations with Buddhism, Taoism, and folk religions are positively associated with the agreement of using a referendum in political decision making. The ideological orientation stemming from these Eastern religions plays an important role in enhancing democratic values and the positive attitudes toward referendum.
Faith-based Organizations and Welfare State Retrenchment in Sweden: Substitute or Complement?
Authors: Fridolfsson Charlotte , Elander Ingemar
Published: December 2012

Local governments in Europe are facing difficulties in meeting citizens' demands for welfare provision. This opens new opportunities for profit as well as non-profit providers of social welfare. Faith-based organizations (FBOs) are one type of non-governmental organizations addressed by governments to complement or replace parts of public welfare provision. This article gives some examples of FBOs in action as providers of welfare in a European context, with a particular focus on Sweden. Following the introduction, the second part locates the phenomenon of FBOs within the scholarly debate about secularism/post-secularism as related to multi-level governance. The third part gives an overview of potential roles of FBOs in welfare provision combating poverty and social exclusion, illustrated by a few examples from European contexts. Focus in the fourth part is upon the role of FBO engagement in Sweden as developing after World War II. It is concluded that no system is all encompassing in catering to those who suffer from poverty and social exclusion. There will always be a need for the competence and avant-garde role potentially provided by FBOs. However, due to historical circumstances FBOs in Sweden have been, and still are, complementary rather than an outright alternative to public welfare provision.
Methanotrophic bacteria in oilsands tailings ponds of northern Alberta
Authors: Saidi-Mehrabad Alireza , He Zhiguo , Tamas Ivica , Sharp Christine E , Brady Allyson L , Rochman Fauziah F , Bodrossy Levente , Abell Guy C J , Penner Tara , Dong Xiaoli , Sensen Christoph W , Dunfield Peter F
Published: December 2012

We investigated methanotrophic bacteria in slightly alkaline surface water (pH 7.4–8.7) of oilsands tailings ponds in Fort McMurray, Canada. These large lakes (up to 10 km2) contain water, silt, clay and residual hydrocarbons that are not recovered in oilsands mining. They are primarily anoxic and produce methane but have an aerobic surface layer. Aerobic methane oxidation was measured in the surface water at rates up to 152 nmol CH4 ml−1 water d−1. Microbial diversity was investigated via pyrotag sequencing of amplified 16S rRNA genes, as well as by analysis of methanotroph-specific pmoA genes using both pyrosequencing and microarray analysis. The predominantly detected methanotroph in surface waters at all sampling times was an uncultured species related to the gammaproteobacterial genus Methylocaldum, although a few other methanotrophs were also detected, including Methylomonas spp. Active species were identified via 13CH4 stable isotope probing (SIP) of DNA, combined with pyrotag sequencing and shotgun metagenomic sequencing of heavy 13C-DNA. The SIP-PCR results demonstrated that the Methylocaldum and Methylomonas spp. actively consumed methane in fresh tailings pond water. Metagenomic analysis of DNA from the heavy SIP fraction verified the PCR-based results and identified additional pmoA genes not detected via PCR. The metagenome indicated that the overall methylotrophic community possessed known pathways for formaldehyde oxidation, carbon fixation and detoxification of nitrogenous compounds but appeared to possess only particulate methane monooxygenase not soluble methane monooxygenase.
Biogeography of bacterial communities exposed to progressive long-term environmental change
Authors: Logares Ramiro , Lindström Eva S , Langenheder Silke , Logue Jürg B , Paterson Harriet , Laybourn-Parry Johanna , Rengefors Karin , Tranvik Lars , Bertilsson Stefan
Published: December 2012

The response of microbial communities to long-term environmental change is poorly understood. Here, we study bacterioplankton communities in a unique system of coastal Antarctic lakes that were exposed to progressive long-term environmental change, using 454 pyrosequencing of the 16S rDNA gene (V3–V4 regions). At the time of formation, most of the studied lakes harbored marine-coastal microbial communities, as they were connected to the sea. During the past 20 000 years, most lakes isolated from the sea, and subsequently they experienced a gradual, but strong, salinity change that eventually developed into a gradient ranging from freshwater (salinity 0) to hypersaline (salinity 100). Our results indicated that present bacterioplankton community composition was strongly correlated with salinity and weakly correlated with geographical distance between lakes. A few abundant taxa were shared between some lakes and coastal marine communities. Nevertheless, lakes contained a large number of taxa that were not detected in the adjacent sea. Abundant and rare taxa within saline communities presented similar biogeography, suggesting that these groups have comparable environmental sensitivity. Habitat specialists and generalists were detected among abundant and rare taxa, with specialists being relatively more abundant at the extremes of the salinity gradient. Altogether, progressive long-term salinity change appears to have promoted the diversification of bacterioplankton communities by modifying the composition of ancestral communities and by allowing the establishment of new taxa.
Invariant measures on multimode quantum Gaussian states
Authors: Lupo C. , Mancini S. , De Pasquale A. , Facchi P. , Florio G. , Pascazio S.
Published: December 2012

We derive the invariant measure on the manifold of multimode quantum Gaussian states, induced by the Haar measure on the group of Gaussian unitary transformations. To this end, by introducing a bipartition of the system in two disjoint subsystems, we use a parameterization highlighting the role of nonlocal degrees of freedom—the symplectic eigenvalues—which characterize quantum entanglement across the given bipartition. A finite measure is then obtained by imposing a physically motivated energy constraint. By averaging over the local degrees of freedom we finally derive the invariant distribution of the symplectic eigenvalues in some cases of particular interest for applications in quantum optics and quantum information.
Graphene wrapped multiwalled carbon nanotubes dispersed nanofluids for heat transfer applications
Authors: Jyothirmayee Aravind S. S. , Ramaprabhu S.
Published: December 2012

A two step method is employed for the preparation of graphene wrapped multiwalled carbon nanotubes (MWNT) dispersed nanofluids. Graphene wrapped MWNT composite is prepared by simple chemical vapor deposition technique and further purified prior to the synthesis of nanofluids. The functionalization of MWNT with the poly electrolyte, graphene drives out the need for surfactants or long term harsh chemical treatments as in the case of pristine carbon materials based nanofluids. The enhancement in thermal transport properties of surfactant free graphene wrapped MWNT composite in de-ionized (DI) water and ethylene glycol (EG) base fluids than that of pristine carbon nanomaterial based nanofluids indicates the potential usage of the hybrid composite based nanofluids in heat transfer applications. An enhancement in thermal conductivity of 11.3% and 13.7% has been attained with 0.04% volume fraction of hybrid composite based DI water and EG nanofluids at 25 °C. The nanocomposite possesses extreme stability in a variety of aqueous solvents without any surfactant. Electrical conductivity of the nanofluids analyzed as a function of volume fraction of nanoparticles and temperature shows a positive effect. Further, the analysis of forced convective heat transfer coefficients of the nanofluids flowing through a stain less steel tube shows significant enhancement in heat transfer, attributed to good aspect ratio of graphene wrapped MWNT and synergistic effect of high thermally conducting graphene and MWNT.
An algorithm for the efficient evaluation of two-electron repulsion integrals over contracted Gaussian-type basis functions
Authors: Sandberg Jaime Axel Rosal , Rinkevicius Zilvinas
Published: December 2012

A new algorithm for the evaluation of two-electron repulsion integrals optimized for high contraction degrees is derived. Both the segmented and general contraction versions of the algorithm show significant theoretical performance gains over the asymptotically fastest algorithms published in the literature so far. A preliminary implementation of the algorithm shows good agreement with the theoretical results and demonstrates substantial average speedups in the evaluation of two-electron repulsion integrals over commonly used basis sets with varying degrees of contraction with respect to a mature, highly optimized quantum chemical code.
High-pressure lattice dynamical study of bulk and nanocrystalline In2O3
Authors: Garcia-Domene B. , Ortiz H. M. , Gomis O. , Sans J. A. , Manjón F. J. , Muñoz A. , Rodríguez-Hernández P. , Achary S. N. , Errandonea D. , Martínez-García D. , Romero A. H. , Singhal A. , Tyagi A. K.
Published: December 2012

The effect of pressure on the vibrational properties of bulk and nanocrystalline powders of cubic bixbyite-type In2O3 has been investigated at room temperature by means of Raman spectroscopy up to 31.6 and 30 GPa, respectively. We have been able to follow the pressure dependence of up to sixteen and seven Raman modes in bulk and nanocrystalline cubic In2O3, respectively. The experimental frequencies and pressure coefficients of the Raman-active modes of bulk cubic In2O3 at ambient pressure are in good agreement with those predicted by our theoretical ab initio calculations. Furthermore, a comparison of our experimental data with our calculations for the Raman modes in rhombohedral corundum and orthorhombic Rh2O3-II structures and with already reported Raman modes of rhombohedral corundum-type In2O3 at room pressure indicate that Raman scattering measurements provide no experimental evidence of the cubic to rhombohedral or cubic to orthorhombic phase transitions either in bulk material or in nanocrystals up to 30 GPa.
Propagation of hybrid transverse magnetic-transverse electric plasmons on magnetically biased graphene sheets
Authors: Gómez-Díaz J. S. , Perruisseau-Carrier J.
Published: December 2012

The propagation of plasmons on magnetically biased graphene sheets is addressed. The analysis is based on the transverse resonance method extended to handle the graphene conductivity tensor and allows easily accounting for substrate effects. A transcendental equation is obtained for the propagation constant of the resulting hybrid transverse magnetic-transverse electric mode. A closed-form approximate expression for a graphene layer sandwitched between two different media is also provided. Application of the method shows that the presence of a magnetic field leads to extreme field localization, namely, very small guided wavelength, as compared with usual plasmons in graphene or noble metals. The extent of field localization and its frequency can be dynamically controlled by modifying the applied magnetostatic and electrostatic bias field, respectively. These features could enable extreme device miniaturization and enhanced resolution in sensing applications.
Transport and thermoelectric properties of Sr3(Ti0.95R0.05)2O7 (R = Ta, Nb, W) oxides
Authors: Sun R. R. , Qin X. Y. , Li L. L. , Li D. , Wang N. N. , Zhang J. , Wang Q. Q.
Published: December 2012

The Sr3(Ti0.95R0.05)2O7 (R = Ta, Nb, W) polycrystalline compounds were fabricated, and their transport and thermoelectric properties were investigated. The results indicate that at T > 300 K electrical resistivity ρ for all the doped compounds increases monotonically with temperature, and basically can be described by a relation ρ ∝ TM at T > ∼650 K, with M = 1.39, 1.66, and 1.77 for R = Ta, Nb, and W, respectively, implying that at the high temperatures the acoustic phonon scattering dominates the scattering process. Although the resistivity ρ of Sr3(Ti0.95Ta0.05)2O7 exhibits a metallic-like behavior at the temperature as low as 5 K, a transition from metallic state (dρ/dT > 0) to semiconductor-like state (dρ/dT < 0) was observed at a critical low temperature ∼41 K and ∼79 K for R = Nb and W, respectively. At T < ∼22 K, ∼57 K, and ∼80 K, a relation of σ ∝ T1/2 (here conductivity σ = 1/ρ) holds for the doped compounds with R = Nb, Ta, and W, respectively, suggesting that at the low temperatures the main transport mechanism is electron-electron interaction due to the presence of disorder induced by the dopants. The thermoelectric figure of merit (ZT) for Ta-doped compound increases more steeply with increasing temperature among the three compounds and reaches 0.066 at 1000 K.
On-chip measurements of Brownian relaxation vs. concentration of 40 nm magnetic beads
Authors: Westergaard Østerberg Frederik , Rizzi Giovanni , Fougt Hansen Mikkel
Published: December 2012

We present on-chip Brownian relaxation measurements on a logarithmic dilution series of 40 nm beads dispersed in water with bead concentrations between 16 μg/ml and 4000 μg/ml. The measurements are performed using a planar Hall effect bridge sensor at frequencies up to 1 MHz. No external fields are needed as the beads are magnetized by the field generated by the applied sensor bias current. We show that the Brownian relaxation frequency can be extracted from fitting the Cole-Cole model to measurements for bead concentrations of 64 μg/ml or higher and that the measured dynamic magnetic response is proportional to the bead concentration. For bead concentrations higher than or equal to 500 μg/ml, we extract a hydrodynamic diameter of 47(1) nm for the beads, which is close to the nominal bead size of 40 nm. Furthermore, we study the signal vs. bead concentration at a fixed frequency close to the Brownian relaxation peak and find that the signal from bead suspensions with concentrations down to 16 μg/ml can be resolved.
Description of transport mechanisms in a very long wave infrared quantum cascade detector under strong magnetic field
Authors: Jasnot François-Régis , Maëro Simon , Péré-Laperne Nicolas , de Vaulchier Louis-Anne , Guldner Yves , Carosella Francesca , Ferreira Robson , Delga Alexandre , Doyennette Laetitia , Berger Vincent , Trinité Virginie , Carras Mathieu
Published: December 2012

Measurements of current have been performed on a very long wave infrared quantum cascade detector under strong magnetic field applied parallel to the growth axis, both under dark and light conditions. The analysis of dark current as a function of temperature highlights three regimes of transport involving the different energy levels of the structure. For photocurrent analysis, we developed a model based on a rate equation approach taking into account all the electronic levels of the structure. This model is in agreement with the oscillatory component of the experimental magnetophotocurrent. It allows to identify the key points controlling the electronic transport such as extraction from the upper level of the optically active quantum well, location of ionized impurities, and scattering mechanisms involved in the structure. This work is valuable for the future conception of high-performance quantum cascade detectors in infrared and far infrared range.
Deep levels in a-plane, high Mg-content MgxZn1−xO epitaxial layers grown by molecular beam epitaxy
Authors: Gür Emre , Tabares G. , Arehart A. , Chauveau J. M. , Hierro A. , Ringel S. A.
Published: December 2012

Deep level defects in n-type unintentionally doped a-plane MgxZn1−xO, grown by molecular beam epitaxy on r-plane sapphire were fully characterized using deep level optical spectroscopy (DLOS) and related methods. Four compositions of MgxZn1−xO were examined with x = 0.31, 0.44, 0.52, and 0.56 together with a control ZnO sample. DLOS measurements revealed the presence of five deep levels in each Mg-containing sample, having energy levels of Ec − 1.4 eV, 2.1 eV, 2.6 V, and Ev + 0.3 eV and 0.6 eV. For all Mg compositions, the activation energies of the first three states were constant with respect to the conduction band edge, whereas the latter two revealed constant activation energies with respect to the valence band edge. In contrast to the ternary materials, only three levels, at Ec − 2.1 eV, Ev + 0.3 eV, and 0.6 eV, were observed for the ZnO control sample in this systematically grown series of samples. Substantially higher concentrations of the deep levels at Ev + 0.3 eV and Ec − 2.1 eV were observed in ZnO compared to the Mg alloyed samples. Moreover, there is a general invariance of trap concentration of the Ev + 0.3 eV and 0.6 eV levels on Mg content, while at least and order of magnitude dependency of the Ec − 1.4 eV and Ec − 2.6 eV levels in Mg alloyed samples.
Stochastic model reduction using a modified Hill-type kinetic rate law
Authors: Smadbeck Patrick , Kaznessis Yiannis
Published: December 2012

In the present work, we address a major challenge facing the modeling of biochemical reaction networks: when using stochastic simulations, the computational load and number of unknown parameters may dramatically increase with system size and complexity. A proposed solution to this challenge is the reduction of models by utilizing nonlinear reaction rate laws in place of a complex multi-reaction mechanism. This type of model reduction in stochastic systems often fails when applied outside of the context in which it was initially conceived. We hypothesize that the use of nonlinear rate laws fails because a single reaction is inherently Poisson distributed and cannot match higher order statistics. In this study we explore the use of Hill-type rate laws as an approximation for gene regulation, specifically transcription repression. We matched output data for several simple gene networks to determine Hill-type parameters. We show that the models exhibit inaccuracies when placed into a simple feedback repression model. By adding an additional abstract reaction to the models we account for second-order statistics. This split Hill rate law matches higher order statistics and demonstrates that the new model is able to more accurately describe the mean protein output. Finally, the modified Hill model is shown to be modular and models retain accuracy when placed into a larger multi-gene network. The work as presented may be used in gene regulatory or cell-signaling networks, where multiple binding events can be captured by Hill kinetics. The added benefit of the proposed split-Hill kinetics is the improved accuracy in modeling stochastic effects. We demonstrate these benefits with a few specific reaction network examples
Polarizable force field development and molecular dynamics study of phosphate-based glasses
Authors: Ainsworth Richard I. , Tommaso Devis Di , Christie Jamieson K. , de Leeuw Nora H.
Published: December 2012

Molecular dynamics simulations of phosphate-based glasses P2O5-CaO-Na2O have been carried out, using an interatomic force field that has been parameterized to reproduce the structural and mechanical properties of crystalline phosphorus pentoxide, \documentclass[12pt]{minimal}\begin{document}$\emph {o}^{\prime }$\end{document}o′(P2O5)∞ orthorhombic phase. Polarization effects have been included through the shell-model potential and formal charges have been used to aid transferability. A modification to the \documentclass[12pt]{minimal}\begin{document}${\rm DL}{\_}{\rm POLY}$\end{document} DL _ POLY code (version 2.20) was used to model the high temperature shell dynamics. Structural characterizations of three biomedically applicative molar compositions, (P2O5)0.45(CaO)x(Na2O)0.55−x (x = 0.30, 0.35, and 0.40), have been undertaken. Good agreement with available experimental and ab initio data is obtained. The simulations show that, dependent on composition, the phosphorus atoms are primarily bonded to two or three oxygens that in turn bridge to neighbouring phosphorus atoms. Na+ and Ca2+ modifiers are found to occupy a pseudo-octahedral bonding environment with mean oxygen coordination numbers of 6.55 and 6.85, respectively, across all compositions studied.
Characteristics of built-in polarization potentials in vertically and laterally arranged InGaN/GaN quantum dots
Authors: Park Seoung-Hwan , Hong Woo-Pyo , Kim Jong-Jae
Published: December 2012

Built-in polarization potentials for vertically and laterally arranged InGaN/GaN quantum dot (QD) structures are investigated using the finite-element method based on the theory of continuum elasticity. The potential for vertically arranged QD structures is shown to depend significantly on the number of arranged QD. On the other hand, in the case of laterally arranged QD structures, the potential is shown to be nearly independent of the number of arranged QD. In the case of three vertically arranged QDs, the potential in the central QD is greatly reduced. Similar result is observed in structures with more QDs than three. On the other hand, the reduction effect is not observed in the case of two QDs. The electric field in the central QD region for three vertically arranged QDs is nearly constant and is shown to be smaller compared to that in the left or right QD region. We observe that the potential in the central QD increases with increasing spacer layer thickness.
Nonlinear transmission line based electron beam driver
Authors: French David M. , Hoff Brad W. , Tang Wilkin , Heidger Susan , Allen-Flowers Jordan , Shiffler Don
Published: December 2012

Gated field emission cathodes can provide short electron pulses without the requirement of laser systems or cathode heating required by photoemission or thermionic cathodes. The large electric field requirement for field emission to take place can be achieved by using a high aspect ratio cathode with a large field enhancement factor which reduces the voltage requirement for emission. In this paper, a cathode gate driver based on the output pulse train from a nonlinear transmission line is experimentally demonstrated. The application of the pulse train to a tufted carbon fiber field emission cathode generates short electron pulses. The pulses are approximately 2 ns in duration with emission currents of several mA, and the train contains up to 6 pulses at a frequency of 100 MHz. Particle-in-cell simulation is used to predict the characteristic of the current pulse train generated from a single carbon fiber field emission cathode using the same technique.
Structural and magnetic properties of biaxially textured NiFe2O4 thin films grown on c-plane sapphire
Authors: Seifikar Safoura , Calandro Bridget , Deeb Elisabeth , Sachet Edward , Yang Jijin , Maria Jon-Paul , Bassiri-Gharb Nazanin , Schwartz Justin
Published: December 2012

Chemical solution deposition is used to grow biaxially textured NiFe2O4 (NFO) thin films on (0001) sapphire substrates; a high degree of out-of-plane orientation in the 〈111〉 direction is confirmed by θ–2θ X-ray diffraction and pole figures. X-ray φ-scanning indicates in-plane texture and an epitaxial relationship between NFO (111) and Al2O3 (0001) in two crystallographic variants. The out-of-plane magnetization exhibits improved Mr/Ms from 0.5 in 110 nm-thick films to 0.8 in 60 nm-thick films. Compared to uniaxially textured NFO films on platinized silicon, the out-of-plane coercivity is reduced by 20%. The improved out-of-plane magnetic anisotropy is comparable to epitaxial NFO films of similar thickness deposited by pulsed laser deposition and sputtering.
Annealing induced colossal magnetocapacitance and colossal magnetoresistance in In-doped CdCr2S4
Authors: Xie Y. M. , Yang Z. R. , Li L. , Yin L. H. , Hu X. B. , Huang Y. L. , Jian H. B. , Song W. H. , Sun Y. P. , Zhou S. Q. , Zhang Y. H.
Published: December 2012

The correlation between colossal magnetocapacitance (CMC) and colossal magnetoresistance (CMR) in CdCr2S4 system has been revealed. The CMC is induced in polycrystalline Cd0.97In0.03Cr2S4 by annealing in cadmium vapor. At the same time, an insulator-metal transition and a concomitant CMR are observed near the Curie temperature. In contrast, after the same annealing treatment, CdCr2S4 displays a typical semiconductor behavior and does not show magnetic field dependent dielectric and electric transport properties. The simultaneous occurrence or absence of CMC and CMR effects implies that the CMC in the annealed Cd0.97In0.03Cr2S4 could be explained qualitatively by a combination of CMR and Maxwell-Wagner effect.