bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of band offsets and direct current leakage properties of nitrogen doped epitaxial Gd2O3 thin films on Si
Authors: Roy Chaudhuri Ayan , Fissel A. , Osten H. J.
Published: May 2013

Dielectric properties of epitaxial Gd2O3 thin films grown on Si have been found to improve significantly by incorporation of suitable dopants. However, in order to achieve optimum electrical properties from such doped oxides, it is important to understand the correlation between doping and the electronic structure of the material. In the present article, we report about the effect of nitrogen doping on the electronic structure and room temperature dc leakage properties of epitaxial Gd2O3 thin films. Epitaxial Gd2O3:N thin films were grown on p-type Si (111) substrates by solid source molecular beam epitaxy technique using molecular N2O as the nitridation agent. First investigations confirmed the presence of substitutional N in the Gd2O3:N layers. Incorporation of nitrogen did not affect the structural quality of the oxide layers. X ray photoelectron spectroscopy investigations revealed band gap narrowing in epitaxial Gd2O3 due to nitrogen doping, which leads to reduction in the valence band offset of the Gd2O3:N layers with Si. DC leakage current measured at room temperature revealed that despite reduction in the band gap and valence band offsets due to N doping, the Gd2O3:N layers remain sufficiently insulating. A significant reduction of the leakage current densities in the Gd2O3:N layers with increasing nitrogen content suggests that doping of epitaxial Gd2O3 thin films with nitrogen can be an effective route to eliminate the adverse effects of the oxygen vacancy induced defects in the oxide layers.
Surface states effect on photoluminescence of CdS colloidal nanocrystals
Authors: Katsaba A. V. , Ambrozevich S. A. , Vitukhnovsky A. G. , Fedyanin V. V. , Lobanov A. N. , Krivobok V. S. , Vasiliev R. B. , Samatov I. G.
Published: May 2013

CdS colloidal nanocrystals with an average size of 4.5 nm and oleic acid as surfactant were studied using photoluminescence spectroscopy and time-correlated single photon counting technique at different temperatures. Observed spectra revealed three thermally activated luminescence bands at 2.15, 1.76, and 1.37 eV in addition to conventional band edge recombination of the nanocrystals. We present a kinetic model based on concept of single emitters which quantitatively describes the luminescence of the ensemble of the nanocrystals in the temperature range 10–300 K. We determined activation energies (18.2 and 8.6 meV) for transitions responsible for the luminescence. The 1.76 eV band most probably emerges from the intrinsic defects on the surface of CdS, whereas bands at 2.15 and 1.37 eV result from the influence of oleic acid bonded to the surface of the nanocrystals.
Communication: Explicitly-correlated second-order correction to the correlation energy in the random-phase approximation
Authors: Hehn Anna-Sophia , Klopper Wim
Published: May 2013

Within the framework of density-functional theory, the basis-set convergence of energies obtained from the random-phase approximation to the correlation energy is equally slow as in wavefunction theory, as for example in coupled-cluster or many-body perturbation theory. Fortunately, the slow basis-set convergence of correlation energies obtained in the random-phase approximation can be accelerated in exactly the same manner as in wavefunction theory, namely by using explicitly correlated two-electron basis functions that are functions of the interelectronic distances. This is demonstrated in the present work.
Evidence of the semiconductor-metal transition in V2O5 thin films by the pulsed laser photoacoustic method
Authors: Pérez-Pacheco A. , Acosta-Najarro D. R. , Castañeda-Guzmán R. , Cruz-Manjarrez H. , Rodriguez-Fernandez L. , Pineda-Santamaría J. C , Aguilar-Franco M.
Published: May 2013

In this work, the pulsed photoacoustic technique was used to investigate the semiconductor-metal transition of thin vanadium pentoxide films (V2O5) under increasing temperature. The V2O5 thin films were simultaneously deposited by RF magnetron sputtering at room temperature, on corning glass and SnO2:F/glass substrates, in order to compare the photoacoustic response. The elemental and structural analysis of the V2O5 films was performed by Rutherford backscattering spectroscopy and X-ray diffraction. The optical transmission and band gap were determined using UV-Vis spectroscopy. The electrical properties were measured using four-point probe measurements with the Van der Pauw geometry.
Characterization of Al/CuO nanoenergetic multilayer films integrated with semiconductor bridge for initiator applications
Authors: Zhu Peng , Shen Ruiqi , Ye Yinghua , Fu Shuai , Li Dongle
Published: May 2013

This paper describes the ignition characteristics of Al/CuO nanoenergetic multilayer films (nEMFs) integrated with semiconductor bridge (SCB). The as-deposited Al/CuO nEMFs were identified with SEM and differential scanning calorimetry. Results show that distinct Al/CuO nEMFs are sputter deposited in a layered geometry, and the Al/CuO nEMFs gives a reaction heat equal to 2181 J/g. The firing experiments show that Al/CuO nEMFs have no influence on the electrical properties of SCB. Furthermore, the rapid combustion of Al/CuO nEMFs is able to assist SCB generating high-temperature plasma and products, such that enhance the ignition reliability.
Electron transport in quantum dot chains: Dimensionality effects and hopping conductance
Authors: Kunets Vas. P. , Rebello Sousa Dias M. , Rembert T. , Ware M. E. , Mazur Yu. I. , Lopez-Richard V. , Mantooth H. A. , Marques G. E. , Salamo G. J.
Published: May 2013

Detailed experimental and theoretical studies of lateral electron transport in a system of quantum dot chains demonstrate the complicated character of the conductance within the chain structure due to the interaction of conduction channels with different dimensionalities. The one-dimensional character of states in the wetting layer results in an anisotropic mobility, while the presence of the zero-dimensional states of the quantum dots leads to enhanced hopping conductance, which affects the low-temperature mobility and demonstrates an anisotropy in the conductance. These phenomena were probed by considering a one-dimensional model of hopping along with band filling effects. Differences between the model and the experimental results indicate that this system does not obey the simple one-dimensional Mott's law of hopping and deserves further experimental and theoretical considerations.
Thermoelectric and thermospin switch realized by a three-terminal nanojunction
Authors: Wang Yan , Li Zhi-Chao , Gong Wei-Jiang , Sui Xiao-Yan , Chen Xiao-Hui
Published: May 2013

Motivated by the result in the recent work [A. Slachter, F. L. Bakker, J.-P. Adam, and B. J. van Wees, Nature Phys. 6, 879 (2010)], we research the thermally driven electron transport through a quantum dot (QD) coupled to two ferromagnetic leads and one normal-metallic lead. By applying temperature bias between the two ferromagnetic leads, we calculate the charge and spin currents in the normal-metallic lead and the spin accumulation in the QD. As a result, we observe that the charge and pure spin currents in the normal-metallic lead, as well as the spin accumulation in the QD, can be independently driven by the temperature bias. According to these results, we propose this system to be a promising candidate of the nanoswitch for the charge and spin current manipulation.
In-plane electric field effect on a spin-orbit coupled two-dimensional electron system in presence of magnetic field
Authors: Firoz Islam SK , Kanti Ghosh Tarun
Published: May 2013

The effect of in-plane electric field on Landau level spacing, spin splitting energy, average spin polarization, and average spin current in the bulk as well as at the edges of a two-dimensional electron system with Rashba spin-orbit coupling are presented here. The spin splitting energy for a particular magnetic field is found to be reduced by the external in-plane electric field. Unlike the case of a two-dimensional electron system without Rashba spin-orbit interaction, here the Landau level spacing is electric field dependent. This dependency becomes stronger at the edges in comparison to the bulk. The average spin polarization vector rotates anti-clockwise with the increase of electric field. The average spin current also gets influenced significantly by the application of the in-plane electric field.
Reconnection at three dimensional magnetic null points: Effect of current sheet asymmetry
Authors: Wyper P. F. , Jain Rekha
Published: May 2013

Asymmetric current sheets are likely to be prevalent in both astrophysical and laboratory plasmas with complex three dimensional (3D) magnetic topologies. This work presents kinematic analytical models for spine and fan reconnection at a radially symmetric 3D null (i.e., a null where the eigenvalues associated with the fan plane are equal) with asymmetric current sheets. Asymmetric fan reconnection is characterized by an asymmetric reconnection of flux past each spine line and a bulk flow of plasma across the null point. In contrast, asymmetric spine reconnection is characterized by the reconnection of an equal quantity of flux across the fan plane in both directions. The higher modes of spine reconnection also include localized wedges of vortical flux transport in each half of the fan. In this situation, two definitions for reconnection rate become appropriate: a local reconnection rate quantifying how much flux is genuinely reconnected across the fan plane and a global rate associated with the net flux driven across each semi-plane. Through a scaling analysis, it is shown that when the ohmic dissipation in the layer is assumed to be constant, the increase in the local rate bleeds from the global rate as the sheet deformation is increased. Both models suggest that asymmetry in the current sheet dimensions will have a profound effect on the reconnection rate and manner of flux transport in reconnection involving 3D nulls.
Mass dependency of turbulent parameters in stationary glow discharge plasmas
Authors: Titus J. B. , Wiggins D. L. , Alexander A. B. , Johnson J. A.
Published: May 2013

A direct current glow discharge tube is used to determine how mass changes the effects of certain turbulence characteristics in a weakly ionized gas. Helium, neon, argon, and krypton plasmas were created, and an axial magnetic field, varied from 0.0 to 550.0 Gauss, was used to enhance mass dependent properties of turbulence. From the power spectra of light emission variations associated with velocity fluctuations, determination of mass dependency on turbulent characteristic unstable modes, energy associated with turbulence, and the rate at which energy is transferred from scale to scale are measured. The magnetic field strength is found to be too weak to overcome particle diffusion to the walls to affect the turbulence in all four types of plasmas, though mass dependency is still detected. Though the total energy and the rate at which the energy moves between scales are mass invariant, the amplitude of the instability modes that characterize each plasma are dependent on mass.
Wakefield generation via two color laser pulses
Authors: Jha Pallavi , Saroch Akanksha , Kumar Verma Nirmal
Published: May 2013

The analytical study for the evolution of longitudinal as well as transverse electric wakefields, generated via passage of two color laser pulses through uniform plasma, has been presented in the mildly relativistic regime. The frequency difference between the two laser pulses is assumed to be equal to the plasma frequency, in the present analysis. The relative angle between the directions of polarization of the two laser pulses is varied and the wakefield amplitudes are compared. Further, the amplitude of the excited wakes by two color pulses are compared with those generated by a single laser pulse.
Bifurcations of nonlinear ion acoustic travelling waves in the frame of a Zakharov-Kuznetsov equation in magnetized plasma with a kappa distributed electron
Authors: Kumar Samanta Utpal , Saha Asit , Chatterjee Prasanta
Published: May 2013

Bifurcations of nonlinear propagation of ion acoustic waves (IAWs) in a magnetized plasma whose constituents are cold ions and kappa distributed electron are investigated using a two component plasma model. The standard reductive perturbation technique is used to derive the Zakharov-Kuznetsov (ZK) equation for IAWs. By using the bifurcation theory of planar dynamical systems to this ZK equation, the existence of solitary wave solutions and periodic travelling wave solutions is established. All exact explicit solutions of these travelling waves are determined. The results may have relevance in dense space plasmas.
Effect of dust charge fluctuations on current-driven electrostatic ion-cyclotron instability in a collisional magnetized plasma
Authors: Sharma Suresh C. , Sharma Kavita , Gahlot Ajay
Published: May 2013

Current-driven electrostatic ion-cyclotron (EIC) instability is studied in a collisional magnetized dusty plasma. The growth rate and unstable mode frequencies were evaluated based on existing physical parameters relevant to ion cyclotron waves in dusty plasmas. It is found that the unstable mode frequency and growth rate of current-driven EIC instability increase with δ (ion-to-electron density ratio). Moreover, the increase in electron neutral collisional frequency (νe) has no effect on the unstable mode frequency while the normalized growth rate has linear dependence on νe.
Analysis of toroidal phasing of resonant magnetic perturbation effects on edge transport in the DIII-D tokamak
Authors: Wilks T. M. , Stacey W. M. , Evans T. E.
Published: May 2013

Resonant Magnetic Perturbation (RMP) fields produced by external control coils are considered a viable option for the suppression of Edge Localized Modes in present and future tokamaks. In DIII-D, the RMPs are generated by six pairs of I-coils, each spanning 60° in toroidal angle, with the currents flowing in opposite directions in adjacent pairs of I-coils. Reversal of the currents in all I-coils, which produces a 60° toroidal shift in the RMP field configuration, generates uniquely different edge pedestal profiles of the density, temperature, and rotation velocities, implying different effects on the related edge transport phenomena caused by the difference in toroidal phase of the I-coil currents. The diffusive and non-diffusive transport effects of this RMP toroidal phase reversal are analyzed by comparing the ion and electron heat diffusivities, angular momentum transport frequencies, ion diffusion coefficients, and the particle pinch velocities interpreted from the measured profiles for the two phases of the I-coil currents.
Pressure-induced magnetic phase transition in Cr2O3 determined by second harmonic generation measurements
Authors: Bayarjargal Lkhamsuren , Winkler Björn
Published: May 2013

We demonstrate that pressure-induced magnetic phase transitions can be detected by optical second harmonic generation (SHG) measurements in diamond anvil cells and show that the transition from an acentric to a centrosymmetric magnetic structure occurs in Cr2O3 at 10(1) GPa. The pressure dependence of the Néel temperature, dTN/dP = −1.0(5) K/GPa from our SHG measurements, which differs significantly from earlier results where dTN/dP ranged from −16 K/GPa to +15 K/GPa.
Oxygen vacancy enhanced room temperature magnetism in Al-doped MgO nanoparticles
Authors: Mishra Debabrata , Mandal Balaji P. , Mukherjee Rupam , Naik Ratna , Lawes Gavin , Nadgorny Boris
Published: May 2013

We have measured the room temperature magnetization in Al-substituted magnesium oxide, Mg(Al)O nanoparticles with Al fractions of up to 5 at. %. All samples, including undoped MgO nanoparticles, exhibit weak room temperature ferromagnetism, with the saturation magnetization reaching a maximum of 0.023 emu/g at 2 at. % of Al. X-ray photoelectron spectroscopy identifies the presence of oxygen vacancies in both doped and undoped MgO nanoparticles, with the vacancy concentration increasing upon vacuum annealing of Mg(Al)O, resulting in two-fold enhancement of the saturation magnetization for 2 at. % Al-doped MgO. Our results suggest that the oxygen vacancies are largely responsible for the weak room temperature ferromagnetism in MgO.
Atmospheric-pressure microplasmas with high current density confined inside helium-filled hollow-core fibers
Authors: Ji Longfei , Bi Zhenhua , Niu Jinhai , Fan Hongyu , Liu Dongping
Published: May 2013

We report on the generation and confinement of atmospheric-pressure microplasmas inside the 100-to-2000-μm-inner-diameter (i.d.) hollow-core fibers (HCFs) filled with helium gas. The microplasma propagation inside these 10-cm-long HCFs results from the anode-driven pulse discharges with their durations of 30 ns–15 μs. The pulse current density generated at an i.d. of 100 μm is about four magnitudes higher than the glow-like one at an i.d. of 2000 μm. Analysis shows that the generation of the microplasmas with high current density can be explained by the confinement mechanism of HCFs with small i.d. values and low surface recombination rate.
Communication: Excitation band modulation with high-order photonic band gap in PMMA:Eu(TTA)3(TPPO)2 opals
Authors: Xu Wen , Bai Xue , Zhu Yongsheng , Liu Tong , Xu Sai , Dong Biao , Song Hongwei
Published: May 2013

Changes in the excitation spectra of luminescent species inserted in photorefractive crystals as a function of changes in the high-order photonic band gap (PBG) have not been previously observed. In this communication, we present our results monitoring the excitation band of Eu(TTA)3(TPPO)2 inserted in the PMMA opal photonic crystals as a function of the changes in the high-order PBG of the crystals. We find shifts in the complex excitation band and changes in the integrated emission intensity that correlates with shifts in the high-order PBG through coupling to the excitation transition.
Viral DNA tethering domains complement replication-defective mutations in the p12 protein of MuLV Gag
Authors: Schneider William M. , Brzezinski Jonathon D. , Aiyer Sriram , Malani Nirav , Gyuricza Mercedes , Bushman Frederic D. , Roth Monica J.
Published: May 2013

The p12 protein of murine leukemia virus (MuLV) group-specific antigen (Gag) is associated with the preintegration complex, and mutants of p12 (PM14) show defects in nuclear entry or retention. Here we show that p12 proteins engineered to encode peptide sequences derived from known viral tethering proteins can direct chromatin binding during the early phase of viral replication and rescue a lethal p12-PM14 mutant. Peptides studied included segments of Kaposi sarcoma herpesvirus latency-associated nuclear antigen (LANA)
1–23
, human papillomavirus 8 E2, and prototype foamy virus chromatin-binding sequences. Amino acid substitutions in Kaposi sarcoma herpesvirus LANA and prototype foamy virus chromatin-binding sequences that blocked nucleosome association failed to rescue MuLV p12-PM14. Rescue by a larger LANA peptide, LANA
1–32
, required second-site mutations that are predicted to reduce peptide binding affinity to chromosomes, suggesting that excessively high binding affinity interfered with Gag/p12 function. This is supported by confocal microscopy of chimeric p12-GFP fusion constructs showing the reverted proteins had weaker association to condensed mitotic chromosomes. Analysis of the integration-site selection of these chimeric viruses showed no significant change in integration profile compared with wild-type MuLV, suggesting release of the tethered p12 post mitosis, before viral integration.
Ambidextrous objects and trace functions for nonsemisimple categories
Authors: Geer Nathan , Kujawa Jonathan , Patureau-Mirand Bertrand
Published: May 2013

We provide a necessary and sufficient condition for a simple object in a pivotal

k
\Bbbk

-category to be ambidextrous. In turn, these objects imply the existence of nontrivial trace functions in the category. These functions play an important role in low-dimensional topology as well as in studying the category itself. In particular, we prove they exist for factorizable ribbon Hopf algebras, modular representations of finite groups and their quantum doubles, complex and modular Lie (super)algebras, the

(
1
,
p
)

(1,p)

minimal model in conformal field theory, and quantum groups at a root of unity.
Structural Determinants at the Interface of the ARC2 and Leucine-Rich Repeat Domains Control the Activation of the Plant Immune Receptors Rx1 and Gpa2
Authors: Slootweg Erik J. , Spiridon Laurentiu N. , Roosien Jan , Butterbach Patrick , Pomp Rikus , Westerhof Lotte , Wilbers Ruud , Bakker Erin , Bakker Jaap , Petrescu Andrei-José , Smant Geert , Goverse Aska
Published: May 2013

Many plant and animal immune receptors have a modular nucleotide-binding-leucine-rich repeat (NB-LRR) architecture in which a nucleotide-binding switch domain, NB-ARC, is tethered to a LRR sensor domain. The cooperation between the switch and sensor domains, which regulates the activation of these proteins, is poorly understood. Here, we report structural determinants governing the interaction between the NB-ARC and LRR in the highly homologous plant immune receptors Gpa2 and Rx1, which recognize the potato cyst nematode Globodera pallida and Potato virus X, respectively. Systematic shuffling of polymorphic sites between Gpa2 and Rx1 showed that a minimal region in the ARC2 and N-terminal repeats of the LRR domain coordinate the activation state of the protein. We identified two closely spaced amino acid residues in this region of the ARC2 (positions 401 and 403) that distinguish between autoactivation and effector-triggered activation. Furthermore, a highly acidic loop region in the ARC2 domain and basic patches in the N-terminal end of the LRR domain were demonstrated to be required for the physical interaction between the ARC2 and LRR. The NB-ARC and LRR domains dissociate upon effector-dependent activation, and the complementary-charged regions are predicted to mediate a fast reassociation, enabling multiple rounds of activation. Finally, we present a mechanistic model showing how the ARC2, NB, and N-terminal half of the LRR form a clamp, which regulates the dissociation and reassociation of the switch and sensor domains in NB-LRR proteins.
Dynamic Adaption of Metabolic Pathways during Germination and Growth of Lily Pollen Tubes after Inhibition of the Electron Transport Chain
Authors: Obermeyer Gerhard , Fragner Lena , Lang Veronika , Weckwerth Wolfram
Published: May 2013

Investigation of the metabolome and the transcriptome of pollen of lily (Lilium longiflorum) gave a comprehensive overview of metabolic pathways active during pollen germination and tube growth. More than 100 different metabolites were determined simultaneously by gas chromatography coupled to mass spectrometry, and expressed genes of selected metabolic pathways were identified by next-generation sequencing of lily pollen transcripts. The time-dependent changes in metabolite abundances, as well as the changes after inhibition of the mitochondrial electron transport chain, revealed a fast and dynamic adaption of the metabolic pathways in the range of minutes. The metabolic state prior to pollen germination differed clearly from the metabolic state during pollen tube growth, as indicated by principal component analysis of all detected metabolites and by detailed observation of individual metabolites. For instance, the amount of sucrose increased during the first 60 minutes of pollen culture but decreased during tube growth, while glucose and fructose showed the opposite behavior. Glycolysis, tricarbonic acid cycle, glyoxylate cycle, starch, and fatty acid degradation were activated, providing energy during pollen germination and tube growth. Inhibition of the mitochondrial electron transport chain by antimycin A resulted in an immediate production of ethanol and a fast rearrangement of metabolic pathways, which correlated with changes in the amounts of the majority of identified metabolites, e.g. a rapid increase in γ-aminobutyric acid indicated the activation of a γ-aminobutyric acid shunt in the tricarbonic acid cycle, while ethanol fermentation compensated the reduced ATP production after inhibition of the oxidative phosphorylation.
Earnings announcements and the components of the bid‐ask spread
Authors: Gregoriou Andros
Published: May 2013

Purpose

The purpose of this paper is to investigate the impact of the components of the bid‐ask spread around earnings announcements on the London Stock Exchange using intraday data obtained from the ICV Marketeye database. The paper finds that the information asymmetry cost component significantly increases around the earnings announcements, while the inventory holding and order processing cost components significantly decrease around the same period. Specifically, the economic magnitude of the increase in the asymmetric cost component implies that earnings announcements significantly increase the total bid‐ask spread, even when they result in decreased inventory holding and order processing costs.

Design/methodology/approach

Liquidity in financial markets around earnings announcements in the London Stock Exchange obtained by bid‐ask spread decompositions.

Findings

This paper investigates the impact of earnings announcements on the components of the bid‐ask spread on the London Stock Exchange using intraday data. The fundamental conclusion from the empirical findings is that the bid‐ask spread increases once the earnings have been announced, because the market makers' increased concerns about asymmetric information is more pronounced, than the lower inventory and order processing costs due to the higher levels of trading volume. This empirical finding also holds when the earnings announcements are partitioned into positive and negative surprises.

Originality/value

This is the first paper to decompose the bid‐ask spread around earnings announcements on the London Stock Exchange. The paper uses a unique intraday dataset.
The place of the eurozone countries in the international economy
Authors: Maniatis Paraschos
Published: May 2013

Purpose

This study aims to statistically investigate the place of the eurozone countries in the framework of the international economy and particularly within the most advanced non Euro‐currency countries; second it attempts to explain the eventual discrepancies in the performing of the eurozone from the most advanced non‐eurozone countries by the weaknesses of some eurozone members. The discriminant analysis as an investigation tool has been chosen as an as unbiased as possible investigation technique. Of course, every discriminant analysis requires classification criteria. The criteria adopted in this study result to more or less the same conclusions.

Design/methodology/approach

Most econometric studies prefer the popular econometric techniques employing classical regression techniques, while methods of multivariate statistics and non‐linear regressions occupy a minor place as statistical tools. Numerous and multivariate data call for multivariate techniques, which at the cost of losing information and details allow for better a perception of the data structure. Therefore, a great part of the statistical analysis focuses on multivariate techniques and non‐linear regression.

Findings

The study concludes that despite the present budget and debt crisis hitting some major and minor eurozone members the “real” economy of the eurozone posseses a first class place in the World economy – both in relative and absolute terms. During the course of the study effort was paid to balancing the tools of investigation and the fertility of the results, in particular to approach questions such as: what is present condition of the eurozone? How solid are the predictions for a hanging collapse of the euro currency and the eurozone? At the end of the study is given an apercu on the transition of the member countries to the eurozone and their economic status by the end of 2011 tries to soften the fears for the eurozone future.

Originality/value

This study tries to analyze the position of the eurozone countries from an arithmetic/objective perspective, ignoring as much as possible the (geo) political and national interests of the principal countries involved as an effort to check the solidity of the fears. Not all parameters of the economy can enter the study. The author has chosen a few variables, which to their opinion reflect the overall performance of an economy. Parameters relating to financial aspects have nowadays in great degree become autonomous and call for special inquiry. The study seeks to add to econometric studies carried out by national and international institutions and Universities. It mainly concerns the statistical techniques and to treat eurozone as a whole entity vs the rest of the developed non‐eurozone world. Indeed, the study tries to defend the eurozone using objective data against a multitude of gloomy predictions, raised by several world partners, for the performance and the future of the eurozone.
Local damage simulations of printed circuit boards based on in‐plane cohesive zone parameters
Authors: Filipp Fuchs Peter , Fellner Klaus , Pinter Gerald
Published: May 2013

Purpose

The purpose of this paper is to analyse, in a finite element simulation, the failure of a multilayer printed circuit board (PCB), exposed to an impact load, to better evaluate the reliability and lifetime. Thereby the focus was set on failures in the outermost epoxy layer.

Design/methodology/approach

The fracture behaviour of the affected material was characterized. The parameters of a cohesive zone law were determined by performing a double cantilever beam test and a corresponding simulation. The cohesive zone law was used in an enriched finite element local simulation model to predict the crack initiation and crack propagation. Using the determined location of the initial crack, the energy release rate at the crack tip was calculated, allowing an evaluation of the local loading situation.

Findings

A good concurrence between the simulated and the experimentally observed failure pattern was observed. Calculating the energy release rate of two example PCBs, the significant influence of the chosen type on the local failure behaviour was proven.

Originality/value

The work presented in this paper allows for the simulation and evaluation of failure in the outermost epoxy layers of printed circuit boards due to impact loads.
PCB base material qualifications: discrepancies between supplier recommendations, customer expectations and reality
Authors: Ehrler Sylvia
Published: May 2013

Purpose

Today a large variety of printed circuit board (PCB) base materials exists on the market and new ones are added frequently. The base material suppliers, having good original equipment manufacturer (OEM) marketing, usually present the materials in an early development stage to the end customers. The customers, on the other hand, expect from their PCB suppliers that the materials are fully characterized and that qualification samples are available immediately. In many cases, the process recommendations given to the PCB manufacturers are very generic (“like FR4”), insufficient, or not practicable (“8 hours baking time”). However, optimized processing ensures the reliability of the finished PCBs, starting from general leadfree compatibility to CAF testing. This demonstrates the importance of thoroughly verified process parameters and of very specific process recommendations to minimize the number of costly and time‐consuming iterations, and to be able to meet the goal of submitting qualification samples and functional PCBs in minimum time. The purpose of this paper is to show the minimum required PCB processing recommendations, and why these have to be fixed by the material supplier before commercialization of a new base material.

Design/methodology/approach

The paper examines the base material suppliers' situation, customer expectations and reality and the PCB manufacturers' expectations.

Findings

The paper gives the reasons and consequences of early base material marketing.

Originality/value

The paper analyses today's PCB base materials market and shows the reasons and consequences of early base material marketing. Also, the minimum requirements by PCB fabricators concerning processing recommendations are given.
Experimental investigation of microdrilling of printed circuit board
Authors: Zheng Xiaohu , Liu Zhiqiang , An Qinglong , Wang Xibin , Xu Zongwei , Chen Ming
Published: May 2013

Purpose

The purpose of this paper is to investigate the cutting mechanism of drilling printed circuit board (PCB) and to optimize the drilling parameters for decreasing burr size and thrust force.

Design/methodology/approach

An experimental study was carried out to investigate the effect of drilling parameters on thrust force and burr formation. The drilling process of PCB was divided by the variation of drilling force signals. Analysis of variance (ANVONA) was carried out for burr size and thrust force. Desirability function method was used in multiple response optimization, to find the best drilling parameters.

Findings

Enter burr and exit burr have different morphologies and types. The generation of enter burr is mainly caused by burr bending which can be observed in micrographs, whereas the generation of exit burr is more complicated than enter burr; both burr breakup and burr bending are observed in exit burrs. In the selected area, the optimized spindle speed and feed rate for drilling PCB is 12 krev/min and 6 mm/s, respectively.

Research limitations/implications

In this paper, hole wall roughness and tool wear were not considered in the optimization of drilling parameters. The future research work should consider them.

Originality/value

This paper investigates the mechanism of burr formation and thrust force in drilling PCB and then optimizes the drilling parameters to decrease the burr formation and thrust force.
A novel method for colouration of cotton using clay nano‐adsorbent treatment
Authors: Parvinzadeh Gashti Mazeyar , Rashidian Rambod , Almasian Arash , Badakhshan Zohouri Ali
Published: May 2013

Purpose

In recent years, the textile industry has been required to develop new methods and technologies through introduction of some new materials in various processes rather than employing the same conventional chemicals. The aim of this research was to investigate the changes induced on the cotton fibre by the nanoclay treatment using a pre‐treatment method.

Design/methodology/approach

The fibres were dyed with basic and direct dyes after the nanoclay pre‐treatment. Technical measurements were studied including Fourier‐transform infrared spectroscopy (FTIR), UV‐visible spectrophotometer, differential scanning calorimetry (DSC), thermal degradation analysis (TGA), scanning electron microscopy (SEM), moisture regain measurement (MRM), tensile strength test (TST), reflectance spectroscopy (RS) and fastnesses evaluation.

Findings

The intensity of the major peaks in FTIR spectra of the nanoclay treated sample is in favour of the chemical changes of the cellulose functional groups. Basic dyes showed a higher dyeability on the clay pre‐treated samples compared to raw materials. The results of the colour measurements showed that the more concentration of the clay mineral was used, the darker the colour of the dyed sample was. Some interesting results were obtained in the research.

Research limitations/implications

The nanoclay and a dispersing agent used in the present context were used as received. Besides, the type of the dispersing agent is important for preparation of a colloidal dispersion of nanoclay.

Practical implications

The method developed in this research provides a simple and practical solution for improving the dyeability of cotton with direct and basic dyes.

Originality/value

The method for enhancing the dyeability of cotton is novel and can be used in cotton processing with new properties.
Anticorrosive efficiency of ion‐exchanged bentonites in chlorinated rubber paints
Authors: Ahmed Nivin M. , Emira Hassan S. , Tawfik Hesham M.
Published: May 2013

Purpose

Ion‐exchange clays containing sodium such as bentonite and montmorillonite have the ability to exchange their cations. Few studies conducted with this type of ion‐exchange pigments are not conclusive about their anticorrosive efficiency. The present research aims to address the study on the anticorrosive efficiency of this type of pigments in chlorinated rubber paints. Sodium‐bentonite was exchanged with Zn, Sr and Zn‐Sr to be applied on low carbon steel specimens and study the anticorrosive performances of these new ion‐exchanged bentonites (IEBs) in anticorrosive paint formulations.

Design/methodology/approach

The new pigments were characterised using scanning electron microscopy (SEM) and X‐ray fluorescence (XRF) to determine the CEC (cation exchange capacity) of the different exchanged cations. Evaluation of the ion‐exchanged and Na‐bentonite pigments using international standard testing methods (ASTM) was estimated. Paint systems manufactured with these ion‐exchange pigments have been subjected to adhesion, accelerated corrosion laboratory tests, and EIS in order to assess their anticorrosive behaviour.

Findings

The results of this work revealed that the ion‐exchange bentonite (IEBs) pigments showed high anticorrosive performance that can be arranged as follows: Sr‐bentonite was better than Zn‐Bentonite and both were better than the double Zn‐Sr‐bentonite indicating an antagonism behaviour between the two cations when present together.

Practical implications

These pigments can be applied in other polymer composites, e.g. rubber and plastics as reinforcing agent and fillers.

Originality/value

These prepared pigments are environmentally friendly pigments which impart high anticorrosive behaviour to paint films with great economic savings.
Effect of annealing on photochromic performance of (E)‐dicyclopropylmethylene‐(2, 5‐dimethyl‐3‐furylethylidene)‐succinicanhydride doped in polyacrylic acid thin film
Authors: Asiri Abdullah M. , Alamry Khalid A. , Hussein Mahmoud A.
Published: May 2013

Purpose

The purpose of this paper is to investigate the effect of annealing on photochromic performance of (E)‐dicyclopropylmethylene‐(2, 5‐dimethyl‐3‐furylethylid‐ene)‐succinicanhydride doped in polyacrylic acid thin film.

Design/methodology/approach

(E)‐dicyclopropylmethylene‐(2,5‐dimethyl‐3‐furyl‐ethylidene)‐succinic‐anhydride (DMDFS‐E) fulgide doped in polyacrylic acid thin films was prepared. DMDFS‐E fulgide doped in polyacrylic acid thin films was heated at various annealing temperatures. Photocoloration, photobleaching and photochemical fatigue resistance for the desired DMDFS‐E fulgide doped in polyacrylic acid thin films were studied.

Findings

Upon irradiation with UV light (366 nm), fulgide DMDFS‐E undergoes a conrotatory ring closure to the pinkish colored closed form C (523 nm). The later color was switched back to the original color when the films were irradiated with white light. The kinetics of photocoloration and photobleaching processes were followed spectrophotometrically by monitoring the absorbance of the ring closed product DMDFS‐C at its λmax of 523 nm. The first‐order plots of photocoloration reaction showed distinct linear line at different temperatures. The slope of these first‐order lines corresponding to the rate constants k. It was found that for photocoloration reaction, the rate constant of the photocoloration reaction was slower than the photobleaching reaction and both reactions decrease with increasing the annealing temperatures. It was found that there was almost improvement of photochemical fatigue resistance of fulgide DMDFS‐E doped in polyacrylic acid thin film at several of the annealing temperatures.

Originality/value

The results obtained in this work showed that the photochromic properties of DMDFS fulgide E were improved upon annealing the film at 100°C. Therefore, it would be recommended for improvement to apply fulgides as annealed polymer films.
Word‐of‐mouth amongst students at a New Zealand tertiary institution
Authors: Warring Susan
Published: May 2013

Purpose

The aim of this case study was to investigate the extent of word‐of‐mouth influence amongst international students at a New Zealand tertiary institution and to review the literature for a valid and reliable conceptualisation and measurement of word‐of‐mouth.

Design/methodology/approach

Literature suggests that opinion‐leading and seeking scales form a valid and reliable conceptualisation and measurement of word‐of‐mouth. Using these scales, a comparison was made between international students and two groups employing the t‐test, domestic students and decision‐makers for online learning management systems. Analysis of variance was employed to investigate differences in word‐of‐mouth between students of different nationalities.

Findings

Indian students were more likely to give advice, but less likely to seek it, than Chinese students. Also, contrary to expectations, word‐of‐mouth influence was not higher for international than domestic students.

Research limitations/implications

Future research should investigate the relationship between word‐of‐mouth and actual consumption decisions made by students. In addition, a random sample should be conducted with a wider sample frame of institutions so that findings can be generalised.

Practical implications

This study forms a foundation for future research investigating whether and how to harness the potential of word‐of‐mouth amongst different nationalities. For example, internet social networking tools could harness Indian students’ higher propensity to give advice and Chinese students’ higher propensity to seek it.

Originality/value

The development and refinement of opinion leadership scales over time is reviewed to suggest valid and reliable scales which can be adapted to specific contexts.
Assessing leadership knowledge in a principalship preparation programme
Authors: Ng Foo Seong David
Published: May 2013

Purpose

The purpose of this paper is to assess leadership learning in a principalship development programme.

Design/methodology/approach

This case study adopted Popper's three worlds as an analytical framework to assess leadership learning in a principalship development programme. The unit of assessment of learning is knowledge – more specifically subjective and objective knowledge. The study involved participants in a principalship development programme called the Leaders in Education Programme (LEP). The LEP is designed and implemented by the National Institute of Education, Singapore with partnership from the Ministry of Education, Singapore. Since its inception in 2001, the LEP has developed more than 300 school leaders in Singapore schools.

Findings

Through the analyses linking the concepts of complexity theory and Popper's three worlds, valuable insights were gained into how participants developed practical knowledge in leadership and management.

Originality/value

The outcome of the analyses has implications for leadership programme design and for leadership development in countries with similar challenges to prepare a new type of school leaders for the 21st century.
Motivation among public primary school teachers in Mauritius
Authors: Keshwar Seebaluck Ashley , Devi Seegum Trisha
Published: May 2013

Purpose

The purpose of this study was to critically analyse the factors that affect the motivation of public primary school teachers and also to investigate if there is any relationship between teacher motivation and job satisfaction in Mauritius.

Design/methodology/approach

Simple random sampling method was used to collect data from 250 primary teachers who are members of the Government Teachers Union (GTU). Chi‐square test was used to test the hypotheses.

Findings

The findings have shown similar results to the integrated cognitive‐motivational model for the study of teachers’ professional motivation by Jesus and Lens. However, some results seem to contradict the literature review. On the whole, Mauritian primary teachers have a good motivational level.

Research limitations/implications

Owing to time and financial constraints, a larger sample size could not be taken to carry out the survey.

Practical implications

There is a need for educational leaders to take immediate actions pertaining to the improvement of teachers’ motivation.

Originality/value

Despite the fact that many research studies have been carried out on job satisfaction and motivation of teachers worldwide, there is hardly any study that has focused solely on the concept of motivation as far as the Mauritian context is concerned.
The influence of event quality on revisit intention
Authors: Ho Kim Tae , Jae Ko Yong , Min Park Chan
Published: May 2013

Purpose

The purpose of this study is to examine the relationships between spectators’ event quality perceptions and revisit intention in both men's and women's basketball events by focusing on gender influence.

Design/methodology/approach

The study utilizes structural equation modeling (SEM) on data collected by questionnaire survey from a total of 623 spectators of two college men's basketball events (n=292) and two college women's basketball events (n=331).

Findings

The results indicate that for men's basketball events, game performance and staff quality had a significant influence on the revisit intention of spectators, regardless of the spectator's gender. For women's basketball events, game performance and in‐game entertainment were significant determinants of spectator revisit intentions, again regardless of gender.

Research limitations/implications

The current research collected data from division I‐A men's and women's basketball events in only one higher education institution. Further the current research adopted only four salient event quality factors (i.e., game performance, in‐game entertainment, staff quality, and physical surrounding). Finally, current research measured only revisit intention as a dependent variable.

Practical implications

The findings suggest that game performance was found to be the most significant event quality factor regardless of gender in both men’s and women’s sporting events. Furthermore, in‐game entertainment was another critical event quality factor for the revisit intention for women’s basketball events. In addition, females have more sensitive event quality perceptions in both men’s and women’s basketball events.

Originality/value

This study investigated the moderating role of gender in the relationship between specific event quality factors (i.e., game performance, in‐game entertainment, staff quality, and physical surrounding) and revisit intention for both men's and women's college basketball events. The study's findings yield insight into service research and offers meaningful implications to managers for future improvements of their services and development of marketing strategies in this context.