bluuebunny/crossref_metadata_2025 huggingface dataset:
An exploratory study of international strategic choices for exporting firms in Nigeria
Authors: Okpara John O.
Published: June 2012

International markets offer potential opportunities for small and medium‐sized enterprises (SMEs) in developing markets in terms of export growth and performance. Notwithstanding these benefits, many SMEs in Nigeria have not initiated exports or have faced problems in competing in the export markets. The aim of this article is to examine strategic choices available for SME exporting firms in Nigeria. Results of data analysis revealed that the three types of strategy orientations pursued by firms for dealing with competition in export markets are low cost, differentiation, and differentiation focus strategies. Findings also showed that low cost and differentiation strategies are significantly and positively related to export performance. © 2012 Wiley Periodicals, Inc.
Evaluating the contribution of the export sector to real GDP growth rate under structural adjustment programme (SAP): The case of Ghana
Authors: Mmieh Frederick , Owusu‐Frimpong Nana , Mordi Chima
Published: June 2012

This study evaluates the contribution of the export sector to real gross domestic product (GDP) growth rate in the past eight years in Ghana. First, it reviews the main economic policy adopted by the government from 1983 to 2007 to reverse the postindependence economic decline of the Ghanaian economy. Second, it assesses the extent to which the continued reform agenda has facilitated the growth of the export sector during 2000–2007. Third, it presents an evaluation of the contribution of the performance of the export sector as a major stimulus to economic growth. Documentary analysis of available evidence reveals that the implementation of the Structural Adjustment Programme (SAP) has led to a positive export sector performance and subsequent real GDP growth rates during the period under review. However, this study argues that there is little aggregate evidence that the trade policy reforms and liberalization since the late 1980s have produced a very significant export response. Exports have not increased consistently and imports have tended to grow faster than exports following liberalization widening the trade deficit and thus constraining growth. © 2012 Wiley Periodicals, Inc.
Mechanical properties of silicon nanowires
Authors: Furmanchuk Al'ona , Isayev Olexandr , Dinadayalane Tandabany C. , Leszczynska Danuta , Leszczynski Jerzy
Published: June 2012

Silicon nanowires (SiNWs) are at the top of the list of materials used in conventional electromechanical devices as well as in strained nanotechnology. Both experimental and theoretical studies showed the size‐dependent character of mechanical properties of SiNWs. However, the surface contaminations, local surface strains, ‘boundary conditions’, native oxide, equipment‐induced errors, and the errors caused by postprocessing of results lead to softening of Young's modulus and extension of the region where the size dependency is seen by experimentalists. Application of improved potentials or advanced theoretical modeling such as inclusion of explicit treatment of temperature and quantum‐mechanical effects allows to show specificity of Young's modulus to the size and shape in case of small (width <4 nm) nanowires. The ductile‐brittle transitions of SiNWs at different temperatures are revealed. Some suggestions on postprocessing techniques are discussed. © 2012 John Wiley & Sons, Ltd.

This article is categorized under:

Structure and Mechanism > Molecular Structures
Three factors in the design and acquisition of language
Authors: O'Grady William
Published: June 2012

Recent advances in linguistic theory offer new proposals about the factors that are crucial to understanding the design and acquisition of language—the genetic endowment, experience, and principles not specific to the language faculty. Of particular interest is the third of these factors, whose importance is now widely recognized, raising questions about its character, its role in shaping the language faculty, and its impact on the future of linguistic research.WIREs Cogn Sci2012 doi: 10.1002/wcs.1188

This article is categorized under:

Linguistics > Language Acquisition
Tutorial on biological networks
Authors: Vital‐Lopez Francisco G. , Memišević Vesna , Dutta Bhaskar
Published: June 2012

Understanding how the functioning of a biological system emerges from the interactions among its components is a long‐standing goal of network science. Fomented by developments in high‐throughput technologies to characterize biomolecules and their interactions, network science has emerged as one of the fastest growing areas in computational and systems biology research. Although the number of research and review articles on different aspects of network science is increasing, updated resources that provide a broad, yet concise, review of this area in the context of systems biology are few. The objective of this article is to provide an overview of the research on biological networks to a general audience, who have some knowledge of biology and statistics, but are not necessarily familiar with this research field. Based on the different aspects of network science research, the article is broadly divided into four sections: (1) network construction, (2) topological analysis, (3) network and data integration, and (4) visualization tools. We specifically focused on the most widely studied types of biological networks, which are, metabolic, gene regulatory, protein–protein interaction, genetic interaction, and signaling networks. In future, with further developments on experimental and computational methods, we expect that the analysis of biological networks will assume a leading role in basic and translational research. © 2012 Wiley Periodicals, Inc.

This article is categorized under:

Algorithmic Development > Biological Data Mining

Application Areas > Data Mining Software Tools

Application Areas > Science and Technology
Laparoscopic Common Bile Duct Exploration in Patients with Complicated Cholecystitis: a Safety and Feasibility Study
Authors: Lo Hung‐Chieh , Wang Yu‐Chun , Huang Jui‐Chien , Hsu Cheng‐Hsiung , Wu Shih‐Chi , Hsieh Chi‐Hsun
Published: June 2012

Background

Laparoscopic cholecystectomy (LC) with common bile duct exploration (LCBDE) is nowadays a preferred one‐stage treatment. However, the influence of complicated cholecystitis (CC) on LCBDE has rarely been addressed. In the present study we aimed to verify whether severe gallbladder inflammation would adversely affect the outcome of LCBDE.

Material and methods

From 2008 to 2011, all patients undergoing LC and LCBDE at China Medical University Hospital were included. Patients were divided into two groups based on the severity of cholecystitis. Those with unstable hemodynamics and co‐morbidities who were deemed unfit for general anesthesia were excluded. Patient demographics, surgical results, and outcome were compared between the groups.

Results

During the study period, 117 patients diagnosed with cholecystitis were found to have common bile duct (CBD) stones and underwent LC + LCBDE. Of these 117 patients, 87 had uncomplicated cholecystitis (UC) and the remaining 30 patients had CC. There was no demographic difference between the groups, but for patients with CC there were marginally longer operative times (190 vs. 223 min, p = 0.141), more blood loss (10 vs. 150 ml, p < 0.05), and longer postoperative hospital stays (6 vs. 7 days, p < 0.05). The risk of developing major intraoperative complications was not greater for those with CC. Conversion to open cholecystectomy was necessary in a total of 12 cases (10 %) with an overall 1 % mortality rate.

Conclusions

Complicated cholecystitis was not a contraindication for LCBDE. Complete stone clearance can be achieved in a substantial number of cases with an acceptable complication rate. Further prospective randomized studies are required to validate its long‐term safety.
Primary obturator-muscle pyomyositis in immunocompetent children
Authors: García-Mata Serafín , Hidalgo-Ovejero Angel , Esparza-Estaun Joaquín
Published: June 2012

Purpose

Primary pyomyositis in immunocompetent children in non-tropical regions (countries with temperate climates) is very uncommon. It is rarely found in the intrapelvic muscles, and even more rarely in the obturator muscles. We try to draw attention to the potential occurrence in these conditions.

Methods

Five new cases of primary obturator-muscle pyomyositis in immunocompetent children aged between 6 and 11 years in a temperate climate are presented. They present with symptoms as follows: fever, pain (thigh, abdominal, inguinal, and/or hip pain), and limp. Three of them had no hip movement limitation. All of them had tenderness in the perineum zone.

Results

Laboratory tests may reveal high erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) counts, but depend on the length of diagnostic delay. The evolution time oscillated from 1 to 5 days. Fever and limp disappearance depends on the evolution time previous to the onset of the antibiotics administration. In 4 out of 5 patients, Staphylococcus aureus was present in the blood cultures. In all cases of obturator-muscle pyomyositis, diagnosis was confirmed using computed tomography (CT) scan (one) and/or magnetic resonance imaging (MRI) (four).

Conclusions

Obturator-muscle pyomyositis is aimed at emphasizing the diagnostic difficulties associated with the condition, due to its deep location and to the fact that the disease presents with multiple manifestations that may initially cause confusion, since they mimic other conditions occurring in the abdomen, hip (septic arthritis, osteomyelitis), spine, etc. The diagnosis is only confirmed using CT scan and/or MRI. In the five patients with antibiotics treatment, the condition resolves without sequelae, even at long-term follow-up.
Development Disparities in Northeast India
Authors: Bhattacharya Rakhee
Published: June 2012

India's recent reform measures have transformed the socioeconomic landscape of many states; however, it has left a few others behind. Development Disparities in Northeast India attempts to determine Northeast India 's place in the country's economic growth map. It examines whether India's liberalization has infused any hope into the Northeastern states of India. This book objectively analyses Northeast India's intra-regional variations and relates these to a pan-regional analytic grid thereby connecting it to the rest of India. The book opens a debate by examining critical issues like the colossal gap between supply steered policies of the central government and demands of the people in this region. It also addresses the issues of rampant corruption, dismal failure of governance and an insurgent economy that drives a sinister parallel economy within the region. This book will be of interest to graduate students, researchers, academicians and policymakers.
Crustal anisotropy beneath Hudson Bay from ambient noise tomography: Evidence for post‐orogenic lower‐crustal flow?
Authors: Pawlak Agnieszka , Eaton David W. , Darbyshire Fiona , Lebedev Sergei , Bastow Ian D.
Published: June 2012

The crust underlying Hudson Bay, Canada records a long and complex tectonic history. In this study, we investigate this region using tomographic inversion based on continuous ambient noise recordings from 37 broadband seismograph stations that encircle Hudson Bay. The ambient noise data were processed to obtain group‐velocity dispersion measurements from 10–35 s period, which were inverted using an algorithm that incorporates the effects of anisotropy. This work is among the first in which ambient noise data have been used to investigate azimuthal anisotropy. The inversion method uses smoothing and damping to regularize the solution; due to the significantly increased number of model parameters relative to the isotropic case, we performed a careful analysis for parameter selection to determine whether “leakage” occurs between isotropic and anisotropic model parameters. We observe a robust pattern of anisotropic fast directions in the mid‐crust that are consistent with large‐scale tectonic trends based on magnetic‐anomaly patterns. In particular, a distinctive double‐indentor shape for the Superior craton is clearly expressed in both data sets. This pattern breaks down deeper in the crust, suggesting that some degree of lithospheric decoupling in the lower crust, such as channel flow, occurred during orogenesis. Given regional evidence for vertically coherent deformation in the crust and underlying mantle, we interpret this pattern in the lower crust as a tectonic overprint that post‐dates the main phase of Trans‐Hudson deformation. At most levels in the crust, we observe a profound change in direction of anisotropic fast direction across an inferred suture beneath Hudson Bay.
The CLARION Competition and the Scholarship of Teaching and Learning
Authors: Goldberg Lynette R. , Koontz Jennifer Scott , Downs David
Published: June 2012

Advocates of the Scholarship of Teaching and Learning (SoTL) argue that teaching and learning must be student-centered, experiential, collaborative, and interprofessional. Researchers must collect data on the outcomes of such learning systematically and disseminate it. This careful approach to documenting student learning and effective teaching facilitates public recognition of the scholarship involved in teaching and learning. Faculty and students can participate in the national, interprofessional, case-based CLinician/Administrator Relationship Improvement OrganizatioN (CLARION) competition in order to implement SoTL. In this paper, we describe the CLARION experience, present examples of the qualitative and quantitative data researchers can compile to document student learning, and show how participation in such an experience can result in additional collaborative and interprofessional activities for students and faculty.
Role-Playing and its Carryover To Practice in Speech-Language Pathology
Authors: Harten Ana Claudia
Published: June 2012

The value of a graduate course in the field of speech-language pathology is limited when students do not transfer the knowledge and skills they acquire to their clinical practicum. In this article, I describe the implementation of role-playing simulation into classroom instruction about aphasia and explore graduate students’ perceptions of this instructional method’s efficacy and carryover to a clinical practicum.
Are the sunspots really vanishing?
Authors: Clette Frédéric , Lefèvre Laure
Published: June 2012

Context:The elapsed solar cycle (23) ended with an exceptionally long period of low activity and with unprecedented low levels for various series of solar irradiance and particle flux measurements. This unpredicted evolution of solar activity raised multiple questions about a future decline of the solar cycles and launched a quest for precursor signs of this possible deep solar transition over the last decade.

Aim:We present here a review and overall interpretation of most current diagnostics of solar cycle 23, including the recent disagreements that appeared among solar reference indices and standard solar-based geo-indices, the indication of a changed pattern of internal torsional waves (helioseismology) or the announced fading and magnetic weakening of sunspots.

Methods:Based on a statistical analysis of detailed sunspot properties over the last 24 years, we complete the picture with new evidence of a strong global deficit of the smallest sunspots starting around 2000, in order to answer the question: are all sunspots about to disappear?

Results:This global scale-dependent change in sunspot properties is confirmed to be real and not due to uncontrolled biases in some of the indices. It can also explain the recent discrepancies between solar indices by their different sensitivities to small and weak magnetic elements (small spots). The International Sunspot IndexRi, based on unweighted sunspot counts, proved to be particularly sensitive to this particular small-scale solar evolution.

Conclusions:Our results and interpretation show the necessity to look backwards in time, more than 80 years ago. Indeed, the Sun seems to be actually returning to a past and hardly explored activity regime ending before the 1955–1995 Grand Maximum, which probably biased our current space-age view of solar activity.
Oberflächenersatzwechsel in der Knieendoprothetik – eine intraoperative Ursachenanalyse
Authors: Haasper C. , Kendoff D. , Gebauer M. , Gehrke T. , Klauser W.
Published: June 2012

Hintergrund: Wechseloperationen nehmen aufgrund der steigenden Primärimplantationszahlen, durchschnittlich jüngeren Patienten und der dabei immer älter werdenden Bevölkerung auch in der Knieendoprothetik zu. Der technische Anspruch dieser Operationen ist ungleich höher als beim Ersteingriff. Das zu erwartende klinische Ergebnis ist in den meisten Fällen auch schlechter als bei der Primärimplantation. Strategien zur Qualitätssteigerung bei den Primäroperationen sind daher wünschenswert. Patienten/Material: 203 ungekoppelte Knieprothesen wurden 2009 im Rahmen von Wechseloperationen in einem Zentrum explantiert. Bei 150 handelte es sich dabei um einen sogenannten Oberflächenersatz bzw. eine bandgeführte, bikondyläre Prothese. Diese Fälle wurden hinsichtlich der Versagensursache analysiert. Ergebnisse: Die durchschnittliche Standzeit der explantierten Prothesen betrug 55 Monate (Spannweite 0,5–125 Monate). Ursächlich waren intraoperativ 46 Komponenten aseptisch gelockert (30,7 %), 37 Knie klinisch instabil (24,7 %), 26 hatten eine Bewegungseinschränkung (17,3 %), 9 Fehlimplantation (5 femoral, 2 tibial, 2 kombiniert; insg. 6 %), 3 Materialschäden (2 %). In 25 Fällen lagen Infektionen (16,7 %) zugrunde und 4 Patienten hatten einen unspezifischen vorderen Knieschmerz (2,6 %). Drei Prothesen wurden zum mehrzeitigen Vorgehen bei Infekt entfernt, in 5 Fällen erfolgte ein Inlaywechsel, ebenfalls 5-mal wurde konvertiert von kreuzbanderhaltend auf kreuzbandersetzend. In 60 Fällen wurde eine teilgekoppelte Prothese (40 %) und bei 42 eine Scharnierprothese (28 %) implantiert. In 45 Fällen kam ein kondylär geführtes System (30 %) zum Einsatz. Das Bewegungsausmaß wurde verbessert. Schlussfolgerung: Bei der Analyse zeigte sich, dass wahrscheinlich in ⅓ der Fälle aufgrund technischer Fehler bei der Primärimplantation der Wechsel vermeidbar gewesen sein könnte. Infektionen und Arthrofibrose waren neben unklarem Beschwerdebild weniger vertreten, auch wenn sie in der Literatur als Hauptversager aufgeführt werden. Diese Arbeit unterstützt den hohen Qualitätsanspruch an die Primärimplantation, die in die Hände des routinierten Operateurs gegeben werden sollte.
Quantifying intermittency in the open drivebelt billiard
Authors: Dettmann Carl P. , Georgiou Orestis
Published: June 2012

A “drivebelt” stadium billiard with boundary consisting of circular arcs of differing radius connected by their common tangents shares many properties with the conventional “straight” stadium, including hyperbolicity and mixing, as well as intermittency due to marginally unstable periodic orbits (MUPOs). Interestingly, the roles of the straight and curved sides are reversed. Here, we discuss intermittent properties of the chaotic trajectories from the point of view of escape through a hole in the billiard, giving the exact leading order coefficient limt→∞tP(t) of the survival probability P(t) which is algebraic for fixed hole size. However, in the natural scaling limit of small hole size inversely proportional to time, the decay remains exponential. The big distinction between the straight and drivebelt stadia is that in the drivebelt case, there are multiple families of MUPOs leading to qualitatively new effects. A further difference is that most marginal periodic orbits in this system are oblique to the boundary, thus permitting applications that utilise total internal reflection such as microlasers.
Structure and evolution of strange attractors in non-elastic triangular billiards
Authors: Arroyo Aubin , Markarian Roberto , Sanders David P.
Published: June 2012

We study non-elastic billiard dynamics in an equilateral triangular table. In such dynamics, collisions with the walls of the table are not elastic, as in standard billiards; rather, the outgoing angle of the trajectory with the normal vector to the boundary at the point of collision is a uniform factor λ < 1 smaller than the incoming angle. This leads to contraction in phase space for the discrete-time dynamics between consecutive collisions, and hence to attractors of zero Lebesgue measure, which are almost always fractal strange attractors with chaotic dynamics, due to the presence of an expansion mechanism. We study the structure of these strange attractors and their evolution as the contraction parameter λ is varied. For λ∈(0,13), we prove rigorously that the attractor has the structure of a Cantor set times an interval, whereas for larger values of λ gaps arise in the Cantor structure. For λ close to 1, the attractor splits into three transitive components, whose basins of attraction have fractal boundaries.
The effect of surfactant convection and diffusion on the evolution of an axisymmetric pendant droplet
Authors: Weidner D. E.
Published: June 2012

In this work, we consider the evolution of a single axisymmetric droplet as it grows from an initially uniform thin liquid film on the underside of a solid, horizontal substrate. We consider the effects of an insoluble surfactant on the free surface, the concentration of which changes due to convection and diffusion. Employing the lubrication approximations, we derive a linear solution valid in the initial stages of drop growth, and a full nonlinear solution, which we solve numerically using finite differences. Both a linear analysis and a numerical solution show that for sufficiently thin films, corresponding to low Bond numbers, diffusion of surfactant can effectively negate the effects of surfactant convection, and the drop evolves as if there is no surfactant on the free surface. For sufficiently thick films, corresponding to high Bond numbers, gravitational forces are stronger than surface tension gradient forces, and again the droplet evolves as if there is no surfactant present. For intermediate Bond numbers, the convection of surfactant can significantly slow the growth rate and must be included in the analysis to accurately model the time evolution of a typical pendant droplet. The interactions between coating height, flux, and surface velocity are used to explain the physics of this behavior.
Bandgaps in phononic strip waveguides
Authors: Aravantinos-Zafiris N. , Sigalas M. M.
Published: June 2012

In this work, we numerically examine the usage of a sonic strip waveguide having a phononic crystal. This structure could have important applications in acoustic circuits. The well known finite difference time domain (FDTD) method was used for the simulations. Several different matrix materials were considered for the waveguide structure. All three polarizations of the input pulse where examined and the effects of all the geometric parameters of the waveguide structure have been considered in this study.
Influence of channel material properties on performance of nanowire transistors
Authors: Razavi Pedram , Fagas Giorgos , Ferain Isabelle , Yu Ran , Das Samaresh , Colinge Jean-Pierre
Published: June 2012

The performance of germanium and silicon inversion-mode and junctionless nanowire field-effect transistors are investigated using three-dimensional quantum mechanical simulations in the ballistic transport regime and within the framework of effective-mass theory for different channel materials and orientations. Our study shows that junctionless nanowire transistors made using n-type Ge or Si nanowires as a channel material are more immune to short-channel effects than conventional inversion-mode nanowire field-effect transistors. As a result, these transistors present smaller subthreshold swing, less drain-induced barrier-lowering, lower source-to-drain tunneling, and higher Ion/Ioff ratio for the same technology node and low standby power technologies. We also show that the short-channel characteristics of Ge and Si junctionless nanowire transistors, unlike the inversion-mode nanowire transistors, are very similar. The results are explained through a detailed analysis on the effect of the channel crystallographic orientation, effective masses, and dielectric constant on electrical characteristics.
Effect of neighboring perturbations on drop coalescence at an interface
Authors: Bordoloi Ankur Deep , Longmire Ellen K.
Published: June 2012

Coalescence at a quiescent silicone oil/water glycerine interface was investigated for water/glycerine drops with Bond number ∼7 and Ohnesorge number = 0.01 using high-speed imaging and time-resolved tomographic particle image velocimetry. In addition to a single drop case, three perturbation cases were considered corresponding with a second drop, a solid particle wetted in oil, and a solid particle wetted in water/glycerine placed adjacent to the coalescing drop. Each perturbing object caused an initial tilting of the drop, influencing its rupture location and eventual collapse behavior. Once tilted, drops typically ruptured near their lowest vertical position which was located either toward or away from the perturbing object depending on the case. The initial retraction speed of the ruptured film was higher for drops initially tilted at significant angles, and the local variations in retraction speed correlated well with the expected variations in local film thickness. The drop fluid always collapsed away from the drop axis in the direction of the rupture location in all unperturbed or perturbed cases. In the case of a drop next to a particle wetted in water/glycerine, the collapsing fluid travelled away from the particle, and the downward propagating vortex ring which developed was similar to that resulting from an unperturbed drop rupture. By contrast, the drop fluid collapsed toward either a second drop or a particle wetted in oil. The resulting vortex rings were more asymmetric, and viscous interaction between the particle and collapsing fluid hindered the downward motion of the associated ring.
Non-linear luminescent coupling in series-connected multijunction solar cells
Authors: Steiner Myles A. , Geisz John F.
Published: June 2012

The assumption of superposition or linearity of photocurrent with solar flux is widespread for calculations and measurements of solar cells. The well-known effect of luminescent coupling in multijunction solar cells has also been assumed to be linear with excess current. Here we show significant non-linearities in luminescent coupling in III-V multijunction solar cells and propose a simple model based on competition between radiative and nonradiative processes in the luminescent junction to explain these non-linearities. We demonstrate a technique for accurately measuring the junction photocurrents under a specified reference spectrum, that accounts for and quantifies luminescent coupling effects.
Controlling activated processes of nonadiabatically, periodically driven dynamical systems: A multiple scale perturbation approach
Authors: Shit Anindita , Chattopadhyay Sudip , Chaudhuri Jyotipratim Ray
Published: June 2012

We arrive at the escape rate from a metastable state for a system of Brownian particles driven periodically by a space dependent, rapidly oscillating external perturbation (with frequency ω) in one dimension (one of the most important class of nonequilibrium system). Though the problem may seem to be time-dependent, and is poised on the extreme opposite side of adiabaticity, there exists a multiple scale perturbation theory (“Kapitza window”) by means of which the dynamics can be treated in terms of an effective time-independent potential that is derived as an expansion in orders of \documentclass[12pt]{minimal}\begin{document}$\frac{1}{\omega }$\end{document}1ω to the order ω−3. The resulting time-independent equation is then used to calculate the escape rate of physical systems from a metastable state induced by external monochromatic field in the moderate-to-large damping limit and to investigate the effect of ω on the resulting rate in conjunction with the thermal energy. With large value of ω, we find that the environment with moderate-to-large damping impedes the escape process of the particle while high amplitude of the periodic driving force allows the particle to cross the barrier with a large escape rate. A comparison of our theoretical expression with numerical simulation gives a satisfactory agreement.
Doping and defects in YBa2Cu3O7: Results from hybrid density functional theory
Authors: Schwingenschlögl U. , Schuster C.
Published: June 2012

Modified orbital occupation and inhomogeneous charge distribution in high-Tc oxide compounds due to doping and/or defects play a huge role for the material properties. To establish insight into the charge redistribution, we address metallic YBa2Cu3O7 in two prototypical configurations: Ca doped (hole doping) and O deficient (electron doping). By means of first principles calculations for fully relaxed structures, we evaluate the orbital occupations. We find that the change of the charge density, in particular in the CuO2 planes, shows a complex spatial pattern instead of the expected uniform (de-)population of the valence states.
Tuning of terahertz intrinsic oscillations in asymmetric triple-barrier resonant tunneling diodes
Authors: Wójcik Paweł , Spisak Bartłomiej J. , Wołoszyn Maciej , Adamowski Janusz
Published: June 2012

Intrinsic terahertz oscillations of the electronic current in the asymmetric triple-barrier resonant tunneling diode are investigated by means of the time-dependent Wigner-Poisson method. The current-voltage characteristics calculated for the nanodevice exhibits four separate bias voltage windows with the current oscillations, which are caused by two different mechanisms. One of these bias voltage windows, for which the electronic current oscillations stem from the negative feedback between the electronic current and the coupled quasi-bound states in the quantum wells embedded in the active region of the nanodevice, is considered in detail. It is demonstrated that the amplitude and frequency of the current oscillations in this bias voltage window depend on the coupling between the quasi-bound states formed in the quantum wells. Strength of this coupling is controlled by the thickness of the central barrier separating the quantum wells, which allows to tune the amplitude and frequency of the terahertz oscillations. Additionally, it was shown that the amplitude of the current oscillations can be tuned by shifting up or down the energy of the bottom of the wider quantum well. These properties suggest that the considered nanodevice may be of interest because of its possible application as tunable terahertz generator.
Substrate effect on the melting temperature of gold nanoparticles
Authors: Luo Wenhua , Su Kalin , Li Kemin , Liao Gaohua , Hu Nengwen , Jia Ming
Published: June 2012

Previous experimental, molecular dynamics, and thermodynamic researches on the melting temperature of Au nanoparticles on tungsten substrate provide entirely different results. To account for the substrate effect upon the melting point of nanoparticles, three different substrates were tested by using a thermodynamic model: tungsten, amorphous carbon, and graphite. The results reveal that the melting point suppression of a substrate-supported Au nanoparticle is principally ruled by the free surface-to-volume ratio of the particle or the contact angle between the particle and the substrate. When the contact angle θ is less than 90°, a stronger size-dependent melting point depression compared with those for free nanoparticles is predicted; when the contact angle θ is greater than 90°, the melting temperature of the supported Au nanoparticles are somewhat higher than those for free nanoparticles.
Hard x-ray scanning microscopy with coherent radiation: Beyond the resolution of conventional x-ray microscopes
Authors: Schropp A. , Hoppe R. , Patommel J. , Samberg D. , Seiboth F. , Stephan S. , Wellenreuther G. , Falkenberg G. , Schroer C. G.
Published: June 2012

We demonstrate x-ray scanning coherent diffraction microscopy (ptychography) with 10 nm spatial resolution, clearly exceeding the resolution limits of conventional hard x-ray microscopy. The spatial resolution in a ptychogram is shown to depend on the shape (structure factor) of a feature and can vary for different features in the object. In addition, the resolution and contrast are shown to increase with increasing coherent fluence. For an optimal ptychographic x-ray microscope, this implies a source with highest possible brilliance and an x-ray optic with a large numerical aperture to generate the optimal probe beam.
Fabrication of double-walled carbon nanotube film/Cu2O nanoparticle film/TiO2 nanotube array heterojunctions for photosensors
Authors: Yang Mingjie , Xu Jia , Wei Jinquan , Sun Jia-Lin , Liu Wei , Zhu Jia-Lin
Published: June 2012

A structure for visible photosensors based on double-walled carbon nanotube (DWCNT) film/Cu2O nanoparticle (NP) film/TiO2 nanotube array (TNA) heterojunctions has been fabricated. Cu2O nanoparticles reduce dark current and enhance photoresponse of the heterojunctions. Consequently, the optoelectric performance is significantly enhanced compared to that of the heterojunctions without Cu2O nanoparticles. The photocurrent-to-dark current ratio reaches ∼1 × 104 under illumination at 405 nm and ∼3 × 104 under illumination at 532 nm, which is two orders of magnitude higher than the results of double-walled carbon nanotube film/TiO2 nanotube array heterojunctions under the same illumination density. Moreover, the response speed of the heterojunctions is greatly improved.
Appropriate precision agriculture with site-specific cropping system management for marginal and small farmers.
Authors: Dhananjoy Mandal Dhananjoy Mandal , Ghosh P. P. , Dasgupta M. K.
Published: June 2012

As conceived in the 'West', precision agriculture (PA) may be suitable for capital-intensive, high-technology regions in developed countries, monoculture affected by a single major soil-borne plant pathogen or pest in large farms, but not for peasant farming or the pest-complex-ridden unaided agriculture as found in less-developed countries (LDCs). PA is not about an abstract of characterization. Appropriate precision agriculture (APA) as site-specific appropriate precision agriculture (SSAPA) represents cropping system (CS) management with such geoinformatics and agri-informatics as are available for land, soil, water, meteorology and forecasting inputs and outputs by marketing, production, protection and other essential information provided through a decision support system through communication networking. Such management approaches are not ordinarily available to most of the farmers in LDCs. It is a prelude to site-specific cropping system management (SSCSM) as the chosen methodology of PA that is likely to be appropriate for marginal and small farmers (MSFs) of LDCs. Benchmark socio-economic information about the farmers of the district in which the experimental site Senkapur-on-Ajay is located, along with predictable trends of macro-meteorological information for 35 years, surface soil and profile survey data in the experimental site and around were made available. In addition, computation of crop suitability was done by conducting a field experiment in a rice-based CS with annual crop rotation as cropping sequence (cs) and when each cs has been rotated for 3 years it is considered a CS. Nine rice and vegetable-based CSs and 27 cs were compared in terms of cultural practices with improved package (IP) and farmer's package (FP), crop growth and productivity, soil nutrient management systems and nutrient use efficiency, appropriate integrated pest management (AIPM), pest:natural enemies (P:NE) balance, energy use efficiency and economics approximately each with several variables. Further information and advice including pest management decisions were provided through marketing information and intelligence, as well as through a communication networking system (CNS) with farmers reporting on pest intensities, with responses from the researcher together with the farmers by means of visits and mobile telephone connections with some local leading farmers, and a post-experimental survey of the targeted farmers on the utilities and problems, if any, on the perception on APA with SSCSM in a 10 km radius of the experimental site. The farmers were satisfied with the information provided during the experiment. This methodology can be adopted for as many locations as possible, wherever similar trials in different sub-agro-ecosystems in various agro-ecosystems are conducted. The methodologies have to be fine-tuned with continuous and active experimentation and communication networking.
Nutrition labelling - is it effective in encouraging healthy eating?
Authors: Hieke S. , Wills J. M.
Published: June 2012

Nutrition labelling has experienced considerable attention in research, combining the expertise as well as general behavioural insights from disciplines such as the social sciences, human medicine and biology, but also business-oriented fields including marketing, communication and general strategy. With a topic as complex as consumption behaviour and its effects on global well-being and health as substantial as they are, many researchers have undertaken studies of quantitative and qualitative nature to explore these relationships. The resulting proliferation of literature has called for reviewing work at many stages, hoping to provide the informational base for actions to be taken on a public health and policy level. Based on such recent changes and developments in the European nutrition labelling landscape, this paper sets out to give an overview on the topic, the reviewing work that has been done so far and the necessary updates on the most recent work in this field. Looking at the question of whether nutrition labelling so far has been effective in encouraging healthy eating, results of this review may be seen as a base for evaluating future achievements of the new EU regulation.
Who is most susceptible to movie smoking effects? Exploring the impacts of race and socio‐economic status
Authors: Soneji Samir , Lewis Valerie A. , Tanski Susanne , Sargent James D.
Published: June 2012

Aims

This study assesses how race/ethnicity and socio‐economic status modify the relationship between exposure to movie smoking and having tried smoking in adolescents.

Design

Data come from a cross‐sectional telephone survey and were analyzed using logistic regression models. A respondent reporting ever having tried smoking was regressed on exposure to movie smoking, race, socio‐economic status, the interactions of these variables and family and background characteristics.

Setting

National sample of US adolescents.

Participants

A total of 3653 respondents aged 13–18 years.

Measurements

Outcome was if subjects reported ever having tried smoking. Movie smoking exposure was assessed through respondents' reporting having watched a set of movie titles, which were coded for smoking instances.

Findings

The proportion having tried smoking was lower for blacks (32%) compared to Hispanics (41%) and whites (38%). The relationship between movie smoking and having tried smoking varied by race/ethnicity. Among whites and Hispanics exposure to movie smoking positively predicted smoking behavior, but movie smoking had no impact on blacks. Socio‐economic status further modified the relation among whites; high socio‐economic status white adolescents were more susceptible to movie smoking than low socio‐economic status white adolescents.

Conclusions

Exposure to movie smoking is not experienced uniformly as a risk factor for having ever tried smoking among US adolescents. Whites and Hispanics are more likely to try smoking as a function of increased exposure to movie smoking. In addition, higher socio‐economic status increases susceptibility to movie smoking among whites. Youth with fewer risk factors may be more influenced by media messages on smoking.
Differential effects of infliximab on absolute circulating blood leucocyte counts of innate immune cells in early and late rheumatoid arthritis patients
Authors: Coulthard L R , Geiler J , Mathews R J , Church L D , Dickie L J , Cooper D L , Wong C , Savic S , Bryer D , Buch M H , Emery P , Morgan A W , McDermott M F
Published: June 2012

Anti-tumour necrosis factor (TNF) biologics have revolutionized therapy of rheumatoid arthritis (RA). We compared the effects of infliximab on numbers of circulating leucocyte subsets in early RA (disease/symptom duration of ≤1 year) and late RA patients (>1 year). A control group consisted of early RA patients treated with a combination of methotrexate (MTX) and methylprednisolone. Blood samples were obtained at baseline (pre-therapy) from all RA patients, divided into three groups: (i) late RA receiving infliximab/MTX, (ii) early RA–infliximab/MTX, (iii) early RA–steroid/MTX, and also from follow-up patients at 2 and 14 weeks. Significant differences in absolute counts of monocytes and granulocytes were observed between healthy controls and RA patients. At baseline CD14bright monocytes and CD16+ granulocytes were increased in both early RA and late RA patients. CD4+ T cells, CD8+ T cells and B cells were all increased at baseline in early RA, but not in late RA. At 2 weeks following infliximab treatment decreased granulocytes were observed in both early and late RA and decreased natural killer (NK) cells in late RA. CD16+ granulocytes and NK cells were also decreased at 14 weeks post-infliximab in early RA. Biotinylated infliximab was used to detect membrane-associated TNF (mTNF)-expressing leucocytes in RA patients. CD16+ granulocytes, NK cells and CD14dim monocytes all expressed higher levels of mTNF in RA patients. In summary infliximab is associated with decreased CD16+ granulocyte and NK cell counts, possibly through binding of mTNF. Differential effects of infliximab between early and late RA suggest that pathogenic mechanisms change as disease progresses.
Small metacarpal bones of low quality in obese children
Authors: Longhi Silvia , Pasquino Bruno , Calcagno Annalisa , Bertelli Enrica , Olivieri Irene , Di Iorgi Natascia , Radetti Giorgio
Published: June 2012

Objective

It is still not known whether fat mass excess could exert a positive effect on bone. The aim of our study was to evaluate bone strength and quality in a group of overweight and obese children and adolescents by assessing bone geometry at metacarpal bones and ultrasound at phalangeal level.

Design and patients

This is a cross sectional observational study performed in 123 subjects, aged 11·2 ± 2·9 years.

Measurements

Digitalized X‐rays were evaluated at the level of the 2nd metacarpal bone for the determination of the outer (D) and inner (d) diameter, cortical area (CA), medullary endocortical area (EA), metacarpal index (MI) and bone strength (Bending Breaking Resistance Index; BBRI). A total of 98 subjects underwent amplitude dependent speed of sound (Ad‐SOS) and bone transmission time (BTT) assessment by phalangeal ultrasonography.

Results

SDs for each measured parameter were as follows: Males: D = −0·71 ± 0·95, d = −0·29 ± 0·86, CA = −0·69 ± 0·69, EA = −0·32 ± 0·79, Ad‐SOS = −1·14 ± 0·91, BTT = −1·17 ± 1·11 and BBRI (417 ± 151 vs 495 ± 174 mm3) were all significantly lower than in controls (P < 0·05). Females: D = −1·03 ± 1·06, d = −0·38 ± 0·92, CA = −0·91 ± 0·72, EA = −0·46 ± 0·79, Ad‐SOS = −1·08 ± 1·11, BTT = −0·97 ± 1·07 and BBRI (342 ± 117 vs 649 ± 318 mm3) were all significantly lower than in controls (P < 0·05).

Conclusions

Obese children show an unfavourable bone geometry and a bone of low quality and reduced strength compared to controls at a nonweight bearing skeletal site. This finding seems to support a detrimental effect of fat mass on bone and explain the frequent occurrence of wrist fractures in this group of children.
Agronomic value and adaptation across climatically contrasting environments ofItalian red clover landraces and natural populations
Authors: Annicchiarico P. , Pagnotta M. A.
Published: June 2012

This study aimed to support red clover (Trifolium pratenseL.) breeding programmes by investigating germplasm adaptive variation. Four landraces representative of the former commercial ecotypes from northern and centralItaly, thirteen natural populations collected in Italy across a wide latitudinal and altitudinal range in exploited or abandoned old natural grasslands, natural pastures or in the wild, and the varietiesPerseo andDivin were evaluated for 2‐year forage yield, for plant survival and for some morphophysiological traits. Evaluations were made at two sites, one with a subcontinental climate (Lodi) and the other with aMediterranean climate (Viterbo). Specific adaptation was particularly large in natural populations, whose interaction with location implied a widespread inversion of population ranks across sites for forage yield depending on their geographical origin. Forage yield and persistence of the populations were not correlated, owing to the trend of landrace and variety germplasm towards high yield but poor persistence. AtLodi, forage yield was associated with winter hardiness and was maximized by landrace germplasm, whereas persistence depended on various factors and was high only in a set of natural populations collected from pastures. AtViterbo, natural populations that evolved under severe summer drought stress tended towards high yield and persistence, showing no yield disadvantage relative to the best‐performing landrace or variety germplasm.
Mixed‐grass prairie rhizome biomass is influenced by cattle grazing intensity
Authors: Dong X. , Cheng F.‐C. , Wang D. , Wang G. , Patton B. D. , Nyren P. E.
Published: June 2012

This study was conducted on a mixed‐grass prairie in south‐central North Dakota, USA, to test the effect of animal grazing on rhizome biomass. Below‐ground plant biomass samples were collected from pastures with moderate and heavy grazing by beef cattle. Because the biomass data did not meet the normality assumptions, the computer resampling method involving a nested anova was used. A reduction in rhizomes was found under heavy grazing, as compared with moderate grazing. Although rhizomes only accounted for a small fraction of total below‐ground plant biomass, our study suggested that the high rhizome density found in the moderately grazed pastures might be partly responsible for the greater potential of plant regrowth in the moderately grazed pastures than in the heavily grazed pastures on this mixed‐grass prairie.