bluuebunny/crossref_metadata_2025 huggingface dataset:
Heterogeneity and aSociolinguistics of Multilingualism: Reconfiguring French Language Pedagogy
Authors: Clark Julie Byrd
Published: March 2012

This article focuses on the current state of the field of French language pedagogy (FLP) and education in Canada. The author provides a brief history of French as a Second Language (FSL) education and Official bilingualism in Canada to demonstrate the social, historical, political and ideological dimensions that have shaped (and continue to shape) ways of thinking about FLP. In relation to the state of current research, this article highlights some of the contributions sociolinguistic research brings to contemporary thinking about multilingualism as it relates to FLP, by examining what the author refers to as thesociolinguistics of multilingualism. This approach considers the social construction of bi/multilingualism and the everyday practices of multilinguals in diverse contexts, in relation to policy, theory, and professional practice. With the growing number of multilingual students from diverse backgrounds participating in FSL teacher and language education programs, there is a critical need to (re)shape pedagogies that reflect the complex linguistic repertoires and social practices of youth with multiple, heterogeneous identities in today’s classrooms: diversity within Canada’s linguistic duality. From this vein, the author argues for a multidimensional, reflexive, and interdisciplinary approach for FLP and official bilingual education: one that values heterogeneity; as well as fosters a deeper engagement with the teaching (and learning) of languages, namely French.
High temperature oxidation behavior of chromium‐rich alloys containing high carbides fractions. Part I: Nickel‐base alloys
Authors: Berthod P.
Published: March 2012

Six wear‐resistant alloys based on nickel, containing 30 wt.% Cr and from 2.5 to 5.0 wt.% C, were elaborated by foundry and subjected to oxidation by air at 1000, 1100, and 1200 °C, for evaluating the oxidation behavior of hard bulk alloys. Their microstructures are rich in chromium carbides, eutectic, or pro‐eutectic, and they also contain graphite for the highest carbon contents of interest. All the studied alloys obviously display a chromia‐forming behavior, despite the initial low chromium content in the matrix. During oxidation, carbides disappear over an increasing distance from the oxidation front, with the consequence of the enrichment of the neighbor matrix in chromium. The minimal chromium content on the surface after oxidation decreases when the alloy is richer in carbon and increases with the oxidation temperature. The carbide‐free zone tends to be deeper when the oxidation temperature increases, and also when the alloy's carbon content increases, in contrast with low‐C Ni‐30Cr alloys previously studied. The disappearance of carbides means a carbon loss as gaseous oxidized species. This probably disturbs the oxide scales growing on the external surface and may influence the oxidation behavior of the alloys. When present, graphite does not deteriorate dramatically the oxidation resistance of the alloys. The hardness of the alloys are lowered by the exposures to high temperature and by the presence of graphite.
Epoxy‐coated bars as corrosion control in cracked reinforced concrete
Authors: López‐Calvo H. Z. , Montes‐Garcia P. , Kondratova I. , Bremner T. W. , Thomas M. D. A.
Published: March 2012

One of the most common corrosion protection methods in reinforcing concrete bars is the application of fusion‐bonded epoxy coatings. Although considerable research has been carried out on the performance of epoxy‐coated bars (ECR), there are still many uncertainties about their performance in cracked concrete. In this experimental program, reinforcing steel bars with six types of epoxy coatings embedded in concrete slabs with a 0.4 mm wide preformed crack intersecting the reinforcing steel at right angles were tested. Results of corrosion potentials, corrosion current density, coating adhesion tests, chloride content, and visual examination after 68 months of exposure to a simulated marine environment are reported. Results revealed that under the studied conditions the ECR did not provide total protection of steel reinforcement in cracked concrete. Their use however, tended to reduce significantly the damage caused by the chloride‐induced corrosion when compared with the uncoated bars embedded in concrete with similar characteristics.
Influence of various loadings of hydrophilic or hydrophobic silica nanoparticles on water uptake and porosity of a polyurethane coating
Authors: Dolatzadeh F. , Jalili M. M. , Moradian S.
Published: March 2012

In this paper, water uptake, porosity and corrosion behaviours of two‐pack polyurethane coatings separately loaded with two types of silica nanoparticles (i.e. hydrophilic and hydrophobic silica nanoparticles) are presented. Water uptake of such coatings was measured by the aid of electrochemical impedance spectroscopy whereas porosity of the coatings was determined according to the ASTM D 6583 standard. Transmission electron microscopy and Fourier transform infrared spectroscopy were also utilised to examine morphology and chemical structure of the nanoparticles filled coatings. These techniques show that the hydrophobic SiO2 nanoparticles could be easily dispersed throughout the polyurethane matrix while negatively influence the curing process of the coatings. The results reveal that the incorporation of both hydrophilic and hydrophobic silica nanoparticles into the polyurethane matrix, generally, reduces the percent porosity of the resultant coatings. However, obtained results show that the type and content of silica nanoparticles influence the capacitance and therefore water uptake of the coatings to various extents.
Investigation of biodegradation behaviour of an Mg‐1Ca alloy influenced by heat treatment and applying plasma‐chemical oxidation layers
Authors: Schmigalla S. , Bender S. , Heyn A. , Schmidt J. , Hort N.
Published: March 2012

The degradation behaviour of an Mg‐1Ca alloy is investigated in vitro to figure out the possibilities of influencing the degradation behaviour of such an alloy by applying heat treatment as well as the use of a coating system based on plasma‐chemical oxidation. It is shown that an optimised solution annealing (T4‐heat treatment) can reduce the degradation rate while an additional ageing between 240 and 300 °C (T6‐heat treatment) increases it. A coating generated by plasma‐chemical oxidation reduces the degradation rate in the immersion test. Its effect is depending on the former heat treatment of the Mg‐1Ca alloy as well as on the parameter during plasma‐chemical oxidation.
Corrosion of stainless steel grades in H2O/KOH 50% at 120 °C: AISI304 austenitic and 2205 duplex
Authors: Bozzini B. , Bogani F. , Giovannelli G. , Natali S. , Scarselli G. , Boniardi M.
Published: March 2012

We report on the corrosion of austenitic (AISI304) and duplex (2205) stainless steels in H2O/KOH 50% at 120 °C. The research is based on a combination of electrochemical, structural and compositional analyses, aimed at assessing the surface modifications resulting from anodic attack and their impact on corrosion resistance. Linear sweep voltammetry and electrochemical impedance spectrometry measurements were carried out in an air‐tight high‐temperature cell. In‐plane and cross‐sectional SEM micrography, X‐ray diffractometry and EDX profiling were used to characterise samples attacked under electrochemically controlled conditions. Electrochemical results have shown that AISI304 exhibits a complex passivating behaviour, while the anodic electrokinetics of the duplex is characterised by mixed kinetic control. AISI304 was found to fail by intergranular corrosion and to be covered: in passive conditions by acicular compounds and in transpassive conditions by a compact layer of corrosion products. Duplex samples, instead, exhibit an uniform form of corrosion morphology and bear a compact layer of corrosion products both in passive and in transpassive conditions.
Reduction of Graphite Oxide with a Grignard Reagent for Facile In Situ Preparation of Electrically Conductive Polyolefin/Graphene Nanocomposites
Authors: Huang Yingjuan , Qin Yawei , Wang Ning , Zhou Yong , Niu Hui , Dong Jin‐Yong , Hu Jiangpu , Wang Yuexin
Published: March 2012

A Grignard reagent, n‐BuMgCl, is found to be able to reduce graphite oxide to form loosely aggregated graphene sheets immobilized with few Mg–Cl species. Further complexing with TiCl4 leads to a graphene‐based supported catalyst that is ready for in situ olefin polymerization to access electrically conductive polyolefin/graphene nanocomposites. PP/graphene nanocomposites thus prepared possess a rather low electrical percolation threshold (approximately 0.2 vol%) and high conductivities (e.g., 3.92 S·m−1 at 1.2 vol%, 28.5 S·m−1 at 4.1 vol%, and 163.1 S·m−1 at 10.2 vol%).
Bioactive tanshinone I inhibits the growth of lung cancer in part via downregulation of Aurora A function
Authors: Li Yanli , Gong Yi , Li Linglin , Abdolmaleky Hamid M. , Zhou Jin‐Rong
Published: March 2012

Lung cancer is the leading cause of cancer death in the world, and the searching for novel efficacious and safe agents for lung cancer prevention remains the top priority of lung cancer research. In the present study, we evaluated the effect of bioactive tanshinones from a Chinese herb Salvia miltiorrhiza, cryptotanshinone (CT), tanshinone I (T1) and tanshinone IIA (T2A), on the proliferation inhibition of lung cancer cell lines. Tanshinones inhibited the lung cancer cell proliferation in vitro, with T1 the most potent, via cell cycle arrest and apoptosis induction. Gene function assay showed that Aurora A knockdown by siRNA dramatically eliminated the T1 activity in vitro, suggesting that Aurora A is an important functional target for T1. We further evaluated the effectiveness of T1 on the growth of H1299 nonsmall lung cancer cell in a mouse model. Tanshinone I inhibited the growth of H1299 lung tumor in a dose‐dependent manner. Tanshinone I at 200 mg/kg body weight significantly reduced final tumor weight by 34% (P < 0.05) associated with inhibiting proliferation and inducing apoptosis of lung cancer cells by 54% (P < 0.001) and 193% (P < 0.001), respectively, inhibiting lung tumor angiogenesis by 72% (P < 0.001), and reducing Aurora A expression by 67% (P < 0.001). On the other hand, T1 did not significantly alter food intake or body weight. Our results provided experimental evidence to suggest that T1 may be an efficacious and safe agent for the prevention of lung cancer progression and Aurora A may be an important molecular target for T1 action against lung cancer. © 2012 Wiley Periodicals, Inc.
The structure of glibenclamide in the solid state
Authors: Sanz Dionisia , Claramunt Rosa M. , Alkorta Ibon , Sánchez‐Sanz Goar , Elguero José
Published: March 2012

The structure of glibenclamide, 5‐chloro‐N‐(2‐{4‐[(cyclohexylamino)carbonyl] aminosulfonyl}phenyl) ethyl)‐2‐methoxybenzamide, an important antidiabetic drug, has been studied both in solution and in the solid state by a combination of NMR spectroscopy and theoretical calculations. The possibility that glibenclamide suffers a tautomerization under melting to afford a desmotrope was rejected. Copyright © 2012 John Wiley & Sons, Ltd.
Bottleneck links, variable demand, and the tragedy of the commons
Authors: Cole Richard , Dodis Yevgeniy , Roughgarden Tim
Published: March 2012

We study the price of anarchy of selfish routing with variable traffic rates and when the path cost is a nonadditive function of the edge costs. Nonadditive path costs are important, for example, in networking applications, where a key performance metric is the achievable throughput along a path, which is controlled by its bottleneck (most congested) edge. We prove the following results.

In multicommodity networks, the worst‐case price of anarchy under the ℓp path cost with 1 < p ≤∞ can be dramatically larger than under the standard ℓ1 path cost.

In single‐commodity networks, the worst‐case price of anarchy under the ℓp path cost with 1 < p < ∞ is no more than with the standard ℓ1 path norm. (A matching lower bound follows trivially from known results.) This upper bound also applies to the ℓ∞ path cost if and only if attention is restricted to the natural subclass of equilibria generated by distributed shortest path routing protocols.

For a natural cost‐minimization objective function, the price of anarchy with endogenous traffic rates (and under any ℓp path cost) is no larger than that in fixed‐demand networks. Intuitively, the worst‐case inefficiency arising from the “tragedy of the commons” is no more severe than that from routing inefficiencies.

© 2012 Wiley Periodicals, Inc. NETWORKS, 2012
A branch‐and‐cut algorithm for the pickup and delivery traveling salesman problem with multiple stacks
Authors: Côté Jean‐François , Archetti Claudia , Speranza Maria Grazia , Gendreau Michel , Potvin Jean‐Yves
Published: March 2012

This article studies the pickup and delivery traveling salesman problem with multiple stacks. The vehicle contains a number of (horizontal) stacks of finite capacity for loading items from the rear of the vehicle. Each stack must satisfy the last‐in‐first‐out constraint that states that any new item must be loaded on top of a stack and any unloaded item must be on top of its stack. A branch‐and‐cut algorithm is proposed for solving this problem. Computational results are reported on different types of randomly generated instances as well as on classical instances for some well‐known special cases of the problem. © 2012 Wiley Periodicals, Inc. NETWORKS, 2012
Integer programming models and algorithms for the graph decontamination problem with mobile agents
Authors: Penuel John , Cole Smith J. , Shen Siqian
Published: March 2012

This article considers the problem of using synchronous mobile agents to decontaminate the nodes of a graph given a spreading contamination. We begin by considering the problem of minimizing cleaning time, given initial agent, and contamination locations. Then, we take as input a set of all possible locations in which a contamination can start and examine problems in which we strategically preposition agents. In one problem, we minimize the number of agents and prescribe their initial locations, so that the graph can be cleaned within a time limit for any potential initial contamination. We also determine the best initial locations for some predetermined number of agents to minimize expected cleaning time, given probability estimates of potential initial contamination locations. We analyze the complexity of each variant and formulate the problems as mixed‐integer programs. As an alternative method, we also provide a construction heuristic for the cleaning problem and cutting‐plane algorithms for the agent location problems. Computational results using these approaches demonstrate the efficacy of our procedures. © 2012 Wiley Periodicals, Inc. NETWORKS, 2013
Differential Diagnosis of Limb Length Discrepancy in a 19th Century Burial from Southwest Mississippi
Authors: Thompson Andrew R.
Published: March 2012

This paper reports on a 19th century skeleton from southwest Mississippi that displays shortening of several right side bones. Most notable is a 50‐mm discrepancy in leg length involving the tibiae and fibulae. Osseous changes in the right foot suggest limited muscle function was present in this area. However, the shortened tibia and fibula show no signs of atrophy. After considering both osteological features and burial context, it is concluded that the individual was likely exposed to the poliovirus during childhood. While this diagnosis does not conform to the skeletal expectations of polio based on most paleopathological descriptions, the deformities observed fit within the range of what has been reported clinically. Based on this finding, it is suggested that polio should be considered as an etiological source of limb shortening even when signs of diffuse skeletal atrophy are lacking. Copyright © 2012 John Wiley & Sons, Ltd.
Reversed micelle Synthesis of Ag/polyaniline nanocomposites via an in situ ultraviolet photo‐redox mechanism
Authors: Li Zhihua , Lin Wei , Lu Jianti , Laven Jozua , Foyet Adolphe
Published: March 2012

Silver/polyaniline nanocomposites were synthesized in reversed micellar solution, and the reaction was performed via in situ reduction of silver nitrate in aniline by photolysis. The nanocomposites were characterized by ultraviolet‐visible spectroscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, thermo‐gravimetric analysis, differential scanning calorimetric analysis, and electrochemical methods. The results showed that the Ag/polyaniline nanocomposites are composed of nano‐sized particles of 15–30 nm that contain Ag domains of 10–15 nm. The electrical conductivity of an Ag/polyaniline pellet is 95.89 S cm−1, whereas a polyaniline pellet is found to be 3.1 × 10−2 S cm−1. Ag/polyaniline composites also have a higher degradation temperature and specific capacitance, when compared with pure polyaniline. Potentiodynamic polarization showed the anodic shifting of the zero current potential and a lower exchange current density for the Ag/polyaniline composite. Compared with polyaniline, the Ag/polyaniline nanocomposite is a promising candidate for coatings with improved anticorrosion performance. POLYM. COMPOS.,, 2012. © 2012 Society of Plastics Engineers
Effect of SWCNT dispersion on epoxy nanocomposite properties
Authors: Uzunpinar Cihan , Mosiewicki Mirna A. , Auad Maria L.
Published: March 2012

In nanocomposites containing single wall carbon nanotubes (SWCNTs), the final properties strongly depend on the dispersion quality of these fillers. Various methods have been used to improve the dispersion of nanofillers; however, one of the most effective ways is to functionalize carbon nanotubes (CNTs) with covalent and noncovalent functional groups. In this work, the dispersion of SWCNTs in an epoxy system was studied by using surfactants, acid (COOH), and ester groups (PGE)‐modified CNTs. Rheological and scanning electron microscopy analysis showed that functionalization of CNTs helped in improving the dispersion of fillers in the epoxy matrix. Systems with surfactant modified SWCNTs (1 wt%) exhibited the highest storage modulus at low frequencies after 5‐min sonication. This behavior is associated to a stronger network of fillers as a result of a good dispersion. However, longer sonication times lowered the storage modulus, corresponding to a degradation of the tubes. The effect of the dispersion quality on mechanical properties was also studied using a three‐point bending set‐up. POLYM. COMPOS.,, 2012. © 2012 Society of Plastics Engineers
Polysulfones with chelating groups for heavy metals retention
Authors: Albu Raluca Marinica , Avram Ecaterina , Stoica Iuliana , Ioan Silvia
Published: March 2012

The formation conditions of new quaternized polysulfones with chelating groups (methyl 3‐pyridyl ketone) (KQPSF) and the major factors influencing the retention process of copper ions were analyzed by attenuated total reflection Fourier transform infrared spectroscopy, atomic force microscopy, environmental scanning electron microscopy, and differential scanning calorimetry. The investigations showed that the percentage of copper ions retained by KQPSF increases by increasing both the time of immersion in a CuCl2·2H2O aqueous solution, and molarity, the maximum value being attained on immersion for 48 h, at a temperature of 60°C and a molarity of 1.5 M. It can be concluded that methyl 3‐pyridyl ketone might be used for obtaining complex polysulfone structures employed by multiple applications, including wastewater purification. POLYM. COMPOS.,, 2012. © 2012 Society of Plastics Engineers
Comparative study of the thermal and mechanical properties of nanocomposites prepared by in situ polymerization of ε‐caprolactone and functionalized carbon nanotubes
Authors: Antolín‐Cerón Víctor H. , Gómez‐Salazar Sergio , Rabelero Martin , Soto Víctor , Luna‐Bárcenas Gabriel , Katime Issa , Nuño‐Donlucas Sergio M.
Published: March 2012

As an effort to compare the influence of several types of functionalized carbon nanotubes (CNTs) upon the mechanical and thermal properties of nanocomposites prepared with a poly(ε‐caprolactone) (PCL) as matrix and functionalized CNTs as fillers; nanocomposites of PCL–CNTs were studied in this study. CNTs were synthesized by chemical vapor deposition using dry ethanol as the carbon source. High resolution scanning electron microscopy, high resolution transmission electron microscopy, and Raman and infrared spectroscopies were used to characterize the CNTs obtained. Four chemical synthesis routes were exploited to add different types of chemical groups onto the surface of purified CNTs. Specifically, the authors inserted: (i) N‐methylpyrrolidine, (ii) carboxyl and hydroxyl, (iii) urethane, and (iv) phenylmethanol groups onto CNTs surface. Nanocomposites were synthesized by in situ polymerization of ε‐caprolactone (ε‐CL) in presence of 1 wt% of each type of functionalized CNTs. Young's moduli of the nanocomposites prepared with N‐methylpyrrolidine or carboxyl and hydroxyl functionalized CNTs are higher than the one of pure PCL, whereas all the mechanical properties of the nanocomposites containing urethane or phenylmethanol groups evaluated at the break point were higher than those of pure PCL. Thermal stability of all the nanocomposites studied improved with respect to pure PCL. POLYM. COMPOS.,, 2012. © 2012 Society of Plastics Engineers
Investigation of molecular interaction between single‐walled carbon nanotubes and conjugated polymers
Authors: Zaminpayma Esmaeil , Mirabbaszadeh Kavoos
Published: March 2012

Single‐walled carbon nanotubes (SWNTs) have unique properties such as high electrical conductivity and high tensile strength. Their composites with polymers have a great role in new sciences such as organic solar cells and ultrastrong lightweight materials. In this article, molecular dynamic simulations with polymer consistent force field are performed to study the interaction between SWNTs and conjugated polymers including poly(2‐methoxy‐5‐(3‐7‐dimethyloctyloxy)‐1,4‐phenylenevinylene) (MDMO‐PPV), poly(3‐hexythiophene) (P3HT), and poly[(9,9′‐dioctylfluorenyl‐2,7‐diyl)‐co‐bis(N,N′‐(4,butylphenyl))bis(N,N′‐phenyl‐1,4‐phenylene)diamine] (PFB). We computed the interaction energy and morphology of polymers adsorbed to the surface of SWNTs was studied by the radius of gyration (Rg). The influence of important factors such as SWNT radius, chirality, and the temperature on the interfacial adhesion of SWNT–polymer and Rg of polymers were studied. We found that the strongest interaction between the SWNTs and these polymers was, first observed for P3HT, then MDMO‐PPV, and finally PFB. Our results showed that the interaction energy is influenced by SWNT radius and the specific monomer structure of the polymers, but the effects of chirality and temperature are very weak. In addition, we found that the temperature, chirality, and radius have not any important effect on the radius of gyration. POLYM. COMPOS.,, 2012. © 2012 Society of Plastics Engineers
Preparation, characterization and electromagnetic properties of polyaniline/carbon nanotubes/nickel ferrite nanocomposites
Authors: El‐Shishtawy Reda M. , Salam M. Abdel , Gabal M.A. , Asiri Abdullah M.
Published: March 2012

New electromagnetic nanocomposites were prepared from polyaniline (PANI)/oxidized single‐walled carbon nanotubes (OxSWCNTs)/NiFe2O4 by in situ polymerization of aniline using hexanoic acid as a soft template. OxSWCNT and NiFe2O4 were prepared first so as to be used in the formulation of PANI composites. Transmission electron microscope (TEM) results revealed the formation of PANI nanoparticles of 60 nm diameter, OxSWCNT of 24 nm, and NiFe2O4 of 54 nm. Also, TEM image of the ternary composite indicated agglomerative coating of PANI appearing as a gray shells and black core of NiFe2O4 with widening the diameter of OxSWCNT to be around 66 nm. Dc conductivity was measured as a function of temperature. Magnetic susceptibility was measured as a function of temperature and magnetic field intensity. All samples revealed NiFe2O4‐dependent ferromagnetism. The activation energies for dc conductivity suggest that the conductivity is owing to hopping conduction mechanism. A synergistic effect between NiFe2O4 and PANI/OxSWCNT is observed. POLYM. COMPOS.,, 2012. © 2012 Society of Plastics Engineers
Characterizing the Protocol for Early Modified Constraint‐induced Movement Therapy in the EXPLICIT‐Stroke Trial
Authors: Nijland Rinske , van Wegen Erwin , van der Krogt Hanneke , Bakker Chantal , Buma Floor , Klomp Asbjørn , van Kordelaar Joost , Kwakkel Gert ,   on behalf of the EXPLICIT‐stroke consortium
Published: March 2012

Constraint‐induced movement therapy (CIMT) is a commonly used rehabilitation intervention to improve upper limb function after stroke. CIMT was originally developed for patients with a chronic upper limb paresis. Although there are indications that exercise interventions should start as early as possible after stroke, only a few randomized controlled trials have been published on either CIMT or modified forms of CIMT (mCIMT) during the acute phase after stroke. The implementation of (m)CIMT in published studies is very heterogeneous in terms of content, timing and intensity of therapy. Moreover, mCIMT studies often fail to provide a detailed description of the protocol applied. The purpose of the present paper is therefore to describe the essential elements of the mCIMT protocol as developed for the EXplaining PLastICITy after stroke (EXPLICIT‐stroke) study. The EXPLICIT‐stroke mCIMT protocol emphasizes restoring body functions, while preventing the development of compensatory movement strategies. More specifically, the intervention aims to improve active wrist ‐and finger extension, which is assumed to be a key factor for upper limb function. The intervention starts within 2 weeks after stroke onset. The protocol retains two of the three key elements of the original CIMT protocol, that is, repetitive training and the constraining element. Repetitive task training is applied for 1 hour per working day, and the patients wear a mitt for at least 3 hours per day for three consecutive weeks. Copyright © 2012 John Wiley & Sons, Ltd.
Chiral second‐harmonic generation from small organic molecules at surfaces
Authors: Persechini L. , McGilp J. F.
Published: March 2012

The molecules of life are chiral. Advanced materials for heterogeneous enantioselective catalysis and biomolecular sensing and recognition will need nanoscale chiral structures, and methods of characterizing them. Optical circular dichroism (CD) is the main technique for probing chiral molecules in solution. Amino acids are levorotatory, but CD cannot detect chirality in ultrathin films of these small molecules at surfaces, as the response is too weak. Chiral second‐harmonic generation (SHG) from ultrathin layers of larger, more polarizable organic molecules has been detected at silica surfaces, where the presence of electronic resonances enhanced the signal. Here chiral SHG is reported from ultrathin films of 1,1′‐binaphthalene‐2,2′‐diol (binol) and cysteine. The SH response from the different chiral enantiomers was measured away from resonance, using unamplified femtosecond excitation at 800 nm, by rotating a quarter‐wave plate polarizer, and detecting the p‐polarized SH output. The SH response from the molecules is measurable and differs significantly between the enantiomers. Simultaneous fitting of the polarizer rotation plots, using a simple phenomenological model, produces reasonable agreement with the experimental results. This exploratory work shows that SHG has sufficient sensitivity to detect the chirality of small molecules adsorbed on surfaces.
Quantum state tomography measurements on strain‐tuned InxGa1−xAs/GaAs quantum dots
Authors: Jöns K. D. , Hafenbrak R. , Atkinson P. , Rastelli A. , Schmidt O. G. , Michler P.
Published: March 2012

We present quantum state tomography (QST) measurements on strain‐tuned self‐assembled InxGa1−xAs/GaAs quantum dots. By applying uniaxial stress we tune the fine structure splitting (FSS) of the exciton transition and investigate the change in the two‐photon polarization state (TPPS) of the quantum dot. We tune the FSS to a minimum value of 4.7 µeV. The density matrix of the TPPS indicates an onset of the anti‐crossing of the exciton transition. Our experiments show that strain‐tuning is a promising method for the generation of triggered polarization entangled photon pairs.
Magnetic properties in semifluorinated GaN sheet from first principles calculations
Authors: Xiao Wen‐Zhi , Wang Ling‐Ling , Luo Hai‐Jun , Yang Jian‐Yu
Published: March 2012

Based on first‐principles spin‐polarized density functional theory calculations, the relative stability, electronic structures, and magnetic properties of semi‐fluorinated gallium nitride (GaN) sheets are investigated. The most stable conformation exhibits ferromagnetic (FM) ground state with a magnetic moment of about 1.0µB per fluorine. The half‐metallic ferromagnetism is mainly attributed to the charge transfers from N to F atoms. Fluorination leads to unpaired spins in N‐2pz states and unsaturated F‐2p orbitals. The hole‐mediated double exchange is responsible for the ferromagnetism in GaN sheets. In addition, GaN nanoribbons (GaNNRs) fluorinated only Ga edges are FM. This opens a route toward metal‐free magnetic materials which have a huge possibility of making spintronic devices and nanomagnets.
Electronic activity in chelotropic and cycloaddition reactions
Authors: Correa José V. , Jaque Pablo , Geerlings Paul , Toro‐Labbé Alejandro
Published: March 2012

Using the reaction electronic flux, a new tool aimed at identifying and characterizing the electronic activity taking place during a chemical process, the chelotropic and cycloaddition reactions of 1,3–butadiene with sulfur dioxide are revisited. The mechanisms of both reactions were studied within the framework of the reaction force analysis; the electronic activity determined through the reaction electronic flux was rationalized in terms of chemical events, bond forming or breaking processes, and polarization and transfer effects localized on the reactants species. The results show interesting features and differences between both the mechanisms; while the chelotropic path is driven by through space electrostatic interactions, the cycloaddition reaction is mainly driven by through bond electronic activity. The relation between these findings and the experimentally found kinetic (cycloaddition) and thermodynamic (chelotropic reaction) control is discussed. Int J Quantum Chem, 2012. © 2012 Wiley Periodicals, Inc.
A mass spectrometric investigation of isomers of butane
Authors: Yılmaz Alıç Tuğbahan , Kılıç Hamdi Şükür , Durmuş Haziret , Doğan Mevlüt , Ledingham Ken W. D.
Published: March 2012

RATIONALE

Butane is an important industrial chemical in which photo‐processes are very important for the initiation of reactions. Recent advances in nanosecond pulsed laser technology have led to high laser intensities being available to researchers to enable these photo‐processes to be studied in compounds such as butane.

METHODS

The photo‐decomposition, dissociation and combustion mechanisms in the neutral butane molecule have been studied in detail, by investigating the multiphoton (MP) dissociative ionisation of its n‐ and i‐isomers, using a time‐of‐flight mass spectrometer connected to a high power nanosecond laser system. The laser used was a Nd:Yag with a 5 ns pulse width operated at the fundamental wavelength (1064 nm) and the doubled and tripled wavelengths (532 nm and 355 nm). The fragmentation patterns for the isomers were determined for the three wavelengths as a function of laser intensity. Similar laser intensities of between 1010 and 1013 W/cm2 were used at the three wavelengths: 1064, 532 and 355 nm.

RESULTS

The mass spectra of each isomer of the butane molecule display a very weak molecular ion and are dominated by fragment ion peaks. The degree of fragmentation increases as the laser intensity increases.

CONCLUSIONS

Depending on the wavelength some significant differences in the mass spectra of the two isomers were detected and it has been concluded that the isomerisation of i‐butane to n‐butane is a process which is faster than the duration of the laser pulse used. Copyright © 2012 John Wiley & Sons, Ltd.
The Moderating Effects of Stress and Rumination on Depressive Symptoms in Women and Men
Authors: Mezo Peter G. , Baker Robyn M.
Published: March 2012

Although there is an abundance of research linking stress and rumination to depression in women, little is known with respect to the role stress plays in the relationship between rumination and depression. Moreover, the role of stress in the rumination–depression relationship has not been previously investigated separately in women. In the present study, 301 undergraduate women and 109 undergraduate men were administered a questionnaire battery to assess their degrees of stress, depressive symptoms and ruminative tendencies. Individually, both stress and rumination scores were found to account for a large proportion of variance in depressive symptom scores. The interaction of stress and rumination also accounted for a significant proportion of this variance, suggesting a significant moderating effect of stress on the rumination–depressive symptom relationship in women and men. Furthermore, women and men with the highest degrees of stress demonstrated the strongest rumination–depressive symptom relationship. However, low‐stress women and low‐stress men demonstrated divergent patterns of relationships. The alternative model of rumination as a moderator of the stress–depression relationship likewise supported divergent relationships between low‐rumination women and low‐rumination men in the relationship between stress and depression. The implications of these findings regarding vulnerability to depressive symptoms are discussed. Copyright © 2012 John Wiley & Sons, Ltd.
Static and Cyclic Deformation Behavior of the Ferritic Steel 16Mo3 Under Monotonic and Cyclic Loading at High Temperatures
Authors: Hoffmann Markus , Biermann Horst
Published: March 2012

The ferritic steel 16Mo3 is commonly used for heat exchangers and steam generators. The temperature loading conditions for these applications range typically from 200 to 500°C. For a basic characterization of the steel 16Mo3, the properties were determined by means of tensile tests with different strain rates. At 200 and 300°C, a negative strain‐rate sensitivity was observed which is due to dynamic strain ageing (Portevin–LeChâtelier effect). To characterize the low cycle fatigue (LCF) behavior of this steel, isothermal strain‐controlled LCF tests were carried out at 200 and 500°C at different strain amplitudes. The cyclic stress response curves are showing principally different courses at the investigated temperatures. The stress relaxation behavior was obtained by cyclic load enhancement tests at various strain amplitudes with dwell times of 30 and 120 s.
Effect of Isothermal Bainite Treatment on Microstructure and Mechanical Properties of Low‐Carbon TRIP Seamless Steel Tube
Authors: Zhang Zicheng , Manabe Ken‐ichi , Li Yanmei , Zhu Fuxian
Published: March 2012

In this work, a low‐carbon transformation‐induced‐plasticity (TRIP) seamless steel tube (Fe–0.15C–1.34Si–1.45Mn–0.029Nb–0.024Ti, in wt%), having potential in application of hydroforming process, has been successfully manufactured by using piercing, cold‐drawing, and two‐stage heat‐treatment process. The optimal heat‐treatment conditions, inter‐critical annealing (IA), and isothermal bainite treatment (IBT) were firstly obtained to maximize the volume fraction and stability of the retained austenite (RA). The effects of temperature and holding time IBT on the microstructures of the TRIP steel tube were studied via optical microscopy (OM), scanning microscopy (SEM), transmission electron microscopy (TEM), and X‐ray diffractometer (XRD). The mechanical properties in the axial direction and hydroformability were also evaluated by conventional tensile test and flaring test, respectively. Two‐stage heat‐treatment was finally performed to achieve the required mechanical properties for the hydroformed tube. The results shows that the RA volume fraction increased at first and then decreased with the increase of IBT holding time and IBT temperature for a particular set of IA temperature and IA holding time. It was also demonstrated that high tensile strength of 618 MPa, total elongation of 35.5%, n‐value of 0.23, and better hydroformability could be successfully produced in this TRIP steel tube at IA temperature of 800°C, holding for 10 min, and IBT of 410°C for 4 min holding time.
Multipath traffic balancing approach for disconnection reduction in video games over mobile ad hoc networks
Authors: Kaiser Arnaud , Achir Nadjib , Boussetta Khaled
Published: March 2012

In this work, we aim to improve the gameplay of time‐sensitive video games over mobile ad hoc networks (MANETs). We focus on the disconnection problems. Precisely, when the path between a player and the game server fails, the game on the player side freezes and becomes unplayable until the network re‐establishes a new path toward the game server. In MANETs, disconnections occur mainly because of node mobility. To overcome this problem, we propose a multipath approach that we combine with an adaptive traffic balancing algorithm. Precisely, for each source–destination couple, we maintain two Optimized Link State Routing paths using the end‐to‐end delay metric. Each path carries a proportion of the game traffic. Our traffic balancing algorithm relies on path robustness estimation to dynamically balance the game traffic between the two paths. The results of our experiments, which are based on a real implementation of our proposals, show that using multipath routing with traffic balancing among different paths reduces route failures and improves the gameplay experience. Copyright © 2012 John Wiley & Sons, Ltd.
Joint optimization of source and relay precoding in non‐regenerative MIMO relay systems
Authors: Zhang Yang , Li Jiandong , Pang Lihua , Ding Zhi
Published: March 2012

We investigate the problem of precoding optimization in an amplify‐and‐forward multiple‐input‐multiple‐output relay system. Most reported works on this problem focus chiefly on the design of relay precoder without simultaneously optimizing the direct link. In this paper, we propose a method for joint source/relay precoder design, taking both direct and relay links into account. Our design is based on maximizing the mutual information (MI) under limited transmission power constraints at the source and relay, respectively. We first formulate a constrained optimization problem before relaxing the original cost function for tractability and derive a MI lower bound. This elaborate bound can asymptotically approach the exact expression of MI in an iterative fashion. In contrast to previous strategies, we then prove that the optimal structure of the source and relay precoders jointly convert the multiple‐input‐multiple‐output relay channel into a bank of single‐input‐single‐output relay channels without having to assume a beamforming structure to simplify the derivation. Specifically, the linear precoding design problem degenerates into power loading among multiple single‐input‐single‐output relay channels. Applying standard Lagrange technique results in a scalar convex optimization, and it can be readily solved by iterative water filling. Numerical examples demonstrate that the proposed scheme, either exploiting partial or full channel state information, significantly outperforms the existing methods. Copyright © 2012 John Wiley & Sons, Ltd.
Eshelby‐Kröner self‐consistent elastic model: the geometric mean versus the arithmetic mean – A numerical investigation
Authors: Fréour S. , Fajoui J.
Published: March 2012

Scale‐transition models, such as Eshelby‐Kröner self‐consistent framework, which are often used for predicting the effective behavior of heterogeneous materials or estimating the distribution of local states from the knowledge of the corresponding macroscopic quantities, require the extensive use of set averages. The present paper is devoted to the comparison of the numerical results provided in pure elasticity by Eshelby‐Kröner model depending on the average type chosen for achieving set average operations: either the traditional arithmetic mean or the geometric average. Various numerical applications of the model to the case of predicting either the effective stiffness or the lattice strains of single‐phase polycrystals will be provided. The particular case when an extreme grain‐shape occurs will also be investigated.
Evaluation and Interpretation of the Effects of Environmental Enrichment Utilizing Varying Degrees of Sampling Effort
Authors: Quirke Thomas , O'Riordan Ruth M
Published: March 2012

Documenting the effects of novel forms of enrichment is becoming increasingly important within the field of environmental enrichment. Appropriate documentation and evaluation must accompany any enrichment research project in order for accurate results to be obtained. The objective of the present study was to provide an example of how the level of effort in documenting the effect of enrichment is linked to how it is evaluated. This study was carried out on eight cheetahs (Acinonyx jubatus) at Fota Wildlife Park, Ireland. Temporal feeding variation was the enrichment type used during this study. Behavior data were collected in five different ways in order to simulate varying degrees of effort. Randomization tests were utilized to analyze behavior data. Significant behavioral differences were observed in the first four sampling methods with patterns of behavior remaining similar in all five methods. However, only the most time intensive method concurred with findings previously published utilizing this form of enrichment. No significant differences in behavior were detected when the least time intensive method was used. Between 1 and 2 hr of data collection daily is necessary to evaluate temporal feeding variation accurately. However, 30–45 min of data collection also gave an insight into the effectiveness of the enrichment. Methods of evaluation can influence the interpretations of the strength of the enriching effect of the treatment. Appropriate evaluation and accurate reporting of enrichment is crucial for the future development of the environmental enrichment field. Zoo Biol 32:262–268, 2013. © 2012 Wiley Periodicals, Inc.
Sex Identification of Four Penguin Species Using Locus‐Specific PCR
Authors: Zhang Peijun , Han Jiabo , Liu Quansheng , Zhang Junxin , Zhang Xianfeng
Published: March 2012

Traditional methods for sex identification are not applicable to sexually monomorphic species, leading to difficulties in the management of their breeding programs. To identify sex in sexually monomorphic birds, molecular methods have been established. Two established primer pairs (2550F/2718R and p8/p2) amplify the CHD1 gene region from both the Z and W chromosomes. Here, we evaluated the use of these primers for sex identification in four sexually monomorphic penguin species: king penguins (Aptenodytes patagonicus), rockhopper penguins (Eudyptes chrysocome), gentoo penguins (Pygoscelis papua), and Magellanic penguins (Spheniscus magellanicus). For all species except rockhopper penguins, primer pair 2550F/2718R resulted in two distinct CHD1Z and CHD1W PCR bands, allowing for sex identification. For rockhopper penguins, only primer pair p8/p2 yielded different CHD1Z and CHD1W bands, which were faint and similar in size making them difficult to distinguish. As a result, we designed a new primer pair (PL/PR) that efficiently determined the gender of individuals from all four penguin species. Sequencing of the PCR products confirmed that they were from the CHD1 gene region. Primer pair PL/PR can be evaluated for use in sexing other penguin species, which will be crucial for the management of new penguin breeding programs. Zoo Biol 32:257–261, 2013. © 2012 Wiley Periodicals, Inc.
Fortification of Potato Chips with Natural Plant Extracts to Enhance their Sensory Properties and Storage Stability
Authors: Rababah Taha M. , Feng Hao , Yang Wade , Yücel Sevil
Published: March 2012

This study evaluated the effectiveness of grape seed extracts (GSE), green tea extracts (GTE), or butylated hydroxytoluene (BHT) on lipid oxidation reduction of potato chips stored for up to 90 days. The highest (P ≤ 0.05) phenolic contents were detected in GSE (6134.5 mg gallic acid equivalent/100 g) followed by GTE and other plant extracts (oregano, thyme, terebinth, parsley, and bouncing bet). BHT had the greatest antioxidant activity (% inhibition) value (53.0) followed by GSE (42.6) and GTE (31.7). The GSE and GTE exhibited significantly higher antioxidant activities (measured by oxidative stability instrument) than the other plant extracts. The BHT and GSE at 1,000 ppm level was significantly the most effective in minimizing the peroxide value development during 90 days of storage. Descriptive results showed that higher levels of GSE and GTE (750 and 1,000 ppm) prevented the astringency development during 60 days of storage and minimized the off‐notes, i.e., astringency and rancidity, during 90 days of storage. The cardboard attribute was not noticed when GSE and GTE, and BHT were added at 750 and 1,000 ppm levels. The GSE and GTE have a great potential for use as natural antioxidants to preserve the potato chips.
Regulation of Integrin Adhesions by Varying the Density of Substrate-Bound Epidermal Growth Factor
Authors: Shahal Tamar , Geiger Benjamin , Dunlop Iain E. , Spatz Joachim P.
Published: March 2012

Substrates coated with specific bioactive ligands are important for tissue engineering, enabling the local presentation of extracellular stimulants at controlled positions and densities. In this study, we examined the cross-talk between integrin and epidermal growth factor (EGF) receptors following their interaction with surface-immobilized Arg-Gly-Asp (RGD) and EGF ligands, respectively. Surfaces of glass coverslips, modified with biotinylated silane-polyethylene glycol, were functionalized by either biotinylated RGD or EGF (or both) via the biotin–NeutrAvidin interaction. Fluorescent labeling of the adhering A431 epidermoid carcinoma cells for zyxin or actin indicated that EGF had a dual effect on focal adhesions (FA) and stress fibers: at low concentrations (0.1; 1 ng/ml), it stimulated their growth; whereas at higher concentrations, on surfaces with low to intermediate RGD densities, it induced their disassembly, leading to cell detachment. The EGF- dependent dissociation of FAs was, however, attenuated on higher RGD density surfaces. Simultaneous stimulation by both immobilized RGD and EGF suggest a strong synergy between integrin and EGFR signaling, in FA induction and cell spreading. A critical threshold level of EGF was required to induce significant variation in cell adhesion; beyond this critical density, the immobilized molecule had a considerably stronger effect on cell adhesion than did soluble EGF. The mechanisms underlying this synergy between the adhesion ligand and EGF are discussed.