bluuebunny/crossref_metadata_2025 huggingface dataset:
On the mode switching timescales of pulsar PSR B0329+54
Authors: Wang Hong-Guang , Chen Jian-Ling , Wen Zhi-Gang , Pi Fei-Peng
Published: March 2013

Chen et al. (2011) found that the durations (timescales) of the normal and abnormal modes of PSR B0329+54 follow a gamma distribution, and constrained the parameters of the distribution function. In this paper, we perform a further analysis on the relationship between the timescales of the two modes. The ratio between the durations of a normal mode and the succeeding abnormal mode is calculated for 54 such pairs. It is found that the cumulative distribution function (CDF) of the ratio is consistent with the CDF obtained by assuming random mode switching, suggesting that the two modes work independently.
Pulsed γ-ray emission from magnetar 1E 2259+586
Authors: Wu J. H. K. , Hui C. Y. , Huang R. H. H. , Kong A. K. H. , Cheng K. S. , Takata J. , Tam P. H. T. , Wu E. M. H. , Liu C.-Y.
Published: March 2013

Anomalous X-ray pulsars (AXPs) are thought to be magnetars which are young isolated neutron stars with extremely strong magnetic fields of >1014 Gauss. Their tremendous magnetic fields inferred from the spin parameters provide a huge energy reservoir to power the observed X-ray emission. High-energy emission above 0.3 MeV has never been detected despite intensive search. Here, we present the possible Fermi Large Area Telescope (LAT) detection of γ-ray pulsations above 200 MeV from the AXP, 1E 2259+586, which puts the current theoretical models of γ-ray emission mechanisms of magnetars into challenge. We speculate that the high-energy γ-rays originate from the outer magnetosphere of the magnetar.
Rotation Measure variations for millisecond pulsars
Authors: Yan Wenming , Manchester R. N. , Wang Na
Published: March 2013

As part of the Parkes Pulsar Timing Array (PPTA) project, frequent observations of 20 millisecond pulsars are made using the Parkes 64-m radio telescope. Variations in the mean position angle of the 20 millisecond pulsars can be studied by the PPTA data being recorded in full-polarization mode. We briefly discuss these results.
Verzweigte Lernumgebungen und Tests mit EFS Survey 8
Authors: Buchwald Florian , Spoden Christian , Fleischer Jens , Leutner Detlev
Published: March 2013

Die kommerzielle Online-Umfragesoftware EFS Survey ermöglicht es, ohne Programmierkenntnisse verzweigte Lerneinheiten und Tests zu erstellen. Der Beitrag stellt Vorteile und Einschränkungen von EFS Survey für diesen neuen Einsatzbereich vor. Anschließend werden verschiedene psychologische Anwendungsszenarien skizziert: Verzweigte Lerneinheiten, das gleitende Testfenster, nicht-adaptive Tests, selbstadaptierte Tests sowie fest verzweigte Tests.
A stochastic Burgers-Zeldovich model for the formation of planetary ring systems and the satellites of Jupiter and Saturn
Authors: Neate Andrew , Truman Aubrey
Published: March 2013

We consider a proto-ring nebula of a gas giant such as Neptune as a cloud of gas/dust particles whose behaviour is governed by the stochastic mechanics associated to the Kepler problem. This leads to a stochastic Burgers-Zeldovich type model for the formation of planetesimals involving a stochastic Burgers equation with vorticity which could help to explain the turbulent behaviour observed in ring systems. The Burgers fluid density and the distribution of the mass M(T) of a spherical planetesimal of radius δ are computed for times T. For circular orbits, sufficient conditions on certain time averages of δ2 are given ensuring that VarM(T) ∼ 0 as T ∼ ∞. Some applications are given to the satellites of Jupiter and Saturn, in particular giving a possible explanation of the equal mass families of satellites.
Optical studies of the surface effects from the luminescence of single GaN/InGaN nanorod light emitting diodes fabricated on a wafer scale
Authors: Chan Christopher C. S. , Reid Benjamin P. L. , Taylor Robert A. , Zhuang YiDing , Shields Philip A. , Allsopp Duncan W. E. , Jia Wei
Published: March 2013

Time-resolved and time-integrated microphotoluminescence studies at 4.2 K were performed on a single InGaN/GaN nanorod light emitting diode, fabricated in an array, on a wafer scale by nanoimprint lithography. Emission properties and carrier dynamics of the single nanorods are presented. Sharp peaks of 2 meV line-width were observed. The single nanorods possess longer decay rates than an unprocessed wafer at delay-times above 50 ns after excitation. The time evolution of the photoluminescence spectra implies that the slower decay times are due to surface related localisation near the perimeter of the nanorods, resulting in a spatial separation of the recombining carriers at low excitation densities.
The influence of pressure on the phase stability of nanocomposite Fe89Zr7B4 during heating from energy dispersive x-ray diffraction
Authors: Leary A. M. , Lucas M. S. , Ohodnicki P. R. , Kernion S. J. , Mauger L. , Park C. , Kenney-Benson C. , McHenry M. E.
Published: March 2013

Nanocomposite materials consisting of small crystalline grains embedded within an amorphous matrix show promise for many soft magnetic applications. The influence of pressure is investigated by in situ diffraction of hammer milled Fe89Zr7B4 during heating through the α → γ Fe transition at 0.5, 2.2, and 4.9 GPa. The changes in primary and secondary crystallization onset are described by diffusion and the energy to form a critical nucleus within the framework of classical nucleation theory.
Local solid phase growth of few-layer graphene on silicon carbide from nickel silicide supersaturated with carbon
Authors: Escobedo-Cousin Enrique , Vassilevski Konstantin , Hopf Toby , Wright Nick , O'Neill Anthony , Horsfall Alton , Goss Jonathan , Cumpson Peter
Published: March 2013

Patterned few-layer graphene (FLG) films were obtained by local solid phase growth from nickel silicide supersaturated with carbon, following a fabrication scheme, which allows the formation of self-aligned ohmic contacts on FLG and is compatible with conventional SiC device processing methods. The process was realised by the deposition and patterning of thin Ni films on semi-insulating 6H-SiC wafers followed by annealing and the selective removal of the resulting nickel silicide by wet chemistry. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to confirm both the formation and subsequent removal of nickel silicide. The impact of process parameters such as the thickness of the initial Ni layer, annealing temperature, and cooling rates on the FLG films was assessed by Raman spectroscopy, XPS, and atomic force microscopy. The thickness of the final FLG film estimated from the Raman spectra varied from 1 to 4 monolayers for initial Ni layers between 3 and 20 nm thick. Self-aligned contacts were formed on these patterned films by contact photolithography and wet etching of nickel silicide, which enabled the fabrication of test structures to measure the carrier concentration and mobility in the FLG films. A simple model of diffusion-driven solid phase chemical reaction was used to explain formation of the FLG film at the interface between nickel silicide and silicon carbide.
Arbitrary waveform generator for quantum information processing with trapped ions
Authors: Bowler R. , Warring U. , Britton J. W. , Sawyer B. C. , Amini J.
Published: March 2013

Atomic ions confined in multi-electrode traps have been proposed as a basis for scalable quantum information processing. This scheme involves transporting ions between spatially distinct locations by use of time-varying electric potentials combined with laser or microwave pulses for quantum logic in specific locations. We report the development of a fast multi-channel arbitrary waveform generator for applying the time-varying electric potentials used for transport and for shaping quantum logic pulses. The generator is based on a field-programmable gate array controlled ensemble of 16-bit digital-to-analog converters with an update frequency of 50 MHz and an output range of ±10 V. The update rate of the waveform generator is much faster than relevant motional frequencies of the confined ions in our experiments, allowing diabatic control of the ion motion. Numerous pre-loaded sets of time-varying voltages can be selected with 40 ns latency conditioned on real-time signals. Here we describe the device and demonstrate some of its uses in ion-based quantum information experiments, including speed-up of ion transport and the shaping of laser and microwave pulses.
Effect of magnetic field annealing on magnetic properties for nanocrystalline (Fe1−xCox)78.4Si9B9Nb2.6Cu1 alloys
Authors: Wen Zhuan-ping , Wang Zhi , Shi Rui-min , Wang Jia , Zhang Hao
Published: March 2013

The crystalline volume fraction Vcry, saturation magnetostriction λs, effective magnetic anisotropy 〈K〉, and temperature dependence of initial permeability (μi-T curves) for magnetic and nonmagnetic annealed (Fe1−xCox)78.4Si9B9Nb2.6Cu1 (x = 0.35, 0.5, 0.65, 1) alloys were investigated. The results showed that the magnetic annealing can enhance the Vcry and significantly reduce the λs. The Co content has an obvious effect on the λs and 〈K〉, the largest 〈K〉 was observed for the x = 0.5 magnetic annealed sample, which can be explained with magnetic atoms pair ordering theory. And the best high-temperature magnetic softness was obtained for x = 0.35 magnetic annealed sample, in which the lower λs and larger Vcry were observed.
Surface acoustic wave guiding in a diffractionless high aspect ratio transducer
Authors: Socié Ludovic , Benchabane Sarah , Robert Laurent , Khelif Abdelkrim , Laude Vincent
Published: March 2013

We demonstrate efficient three-dimensional surface acoustic wave guidance and confinement in a high-aspect ratio electrode transducer. Each electrode acts as an elastic resonator that is evanescently coupled to its neighbors. We observe high amplitude displacement fields confined within the high aspect ratio electrodes. The stored surface waves are found to present a general shear polarization instead of the sagittal polarization expected for classical Rayleigh waves. The elastic energy is mostly distributed in the mass-loaded areas, and waves propagate within the transducer without diffraction, even for very low acoustic apertures.
Ultraviolet light-emitting diodes grown by plasma-assisted molecular beam epitaxy on semipolar GaN (202¯1) substrates
Authors: Sawicka M. , Chèze C. , Turski H. , Muziol G. , Grzanka S. , Hauswald C. , Brandt O. , Siekacz M. , Kucharski R. , Remmele T. , Albrecht M. , Krysko M. , Grzanka E. , Sochacki T. , Skierbiszewski C.
Published: March 2013

Multi-quantum well (MQW) structures and light emitting diodes (LEDs) were grown on semipolar (202¯1) and polar (0001) GaN substrates by plasma-assisted molecular beam epitaxy. The In incorporation efficiency was found to be significantly lower for the semipolar plane as compared to the polar one. The semipolar MQWs exhibit a smooth surface morphology, abrupt interfaces, and a high photoluminescence intensity. The electroluminescence of semipolar (202¯1) and polar (0001) LEDs fabricated in the same growth run peaks at 387 and 462 nm, respectively. Semipolar LEDs with additional (Al,Ga)N cladding layers exhibit a higher optical output power but simultaneously a higher turn-on voltage.
Semitransparent organic solar cells with hybrid monolayer graphene/metal grid as top electrodes
Authors: Lin Peng , Choy Wallace C. H. , Zhang Di , Xie Fengxian , Xin Jianzhuo , Leung C. W.
Published: March 2013

Hybrid transparent monolayer graphene/metal grid is proposed as top electrode of semitransparent organic solar cells. The hybrid electrode using gold grid on flexible polyethylene terephthalate substrate shows very low sheet resistance of 22 ± 3 Ω/□ and high optical transmittance of 81.4%, which is comparable to conventional indium tin oxide/glass electrode. Using lamination process, the layer of poly(3,4-ethylenedioythiophene):poly(styrenesulfonate) doped with D-sorbitol plays an important role in the electrical performance of the laminated devices. In addition, the devices show best power convention efficiency of 3.1% and fill factor of 55.0%, which are much better than those of similar graphene-based semitransparent organic solar cells.
Picosecond amorphization of chalcogenides material: From scattering to ionization
Authors: Wang P. , Ju C. , Chen W. , Huang D. Q. , Guan X. W. , Li Z. , Cheng X. M. , Miao X. S.
Published: March 2013

Phase change memory cells with chalcogenides material of different thicknesses were fabricated to study the picosecond amorphization process. The threshold voltage (Vth) and time (Tth) of the cells were characterized by the picoseconds electric pulses. The model of the impact ionization and carriers multiplication was proposed to describe the non-thermal amorphization process within picoseconds duration, compared with the inelastic scattering model for the thermal amorphization process within nanoseconds duration. First principle calculations based on density functional theory and Ridley luck-drift model confirmed the explanation and gave a quantitative expression for the origins of Vth and Tth.
Variable-temperature Raman spectroscopic study of the hydrogen sensing mechanism in Pt-WO3 nanowire film
Authors: Yi Luo Jian , Xian Chen Xue , Da Li Wei , Yuan Deng Wei , Li Wei , Yuan Wu Hao , Feng Zhu Lian , Guang Zeng Qing
Published: March 2013

Two special properties of Pt coated WO3 (Pt-WO3) nanowire film for sensing hydrogen gas flow in air are reported in this paper, including the large relative resistance change (close to 100%) and the dependence of the millisecond-scale response time on operating temperature. A variable-temperature Raman spectroscopic system is applied to record the structural changes of WO3 nanowires in situ during the input of H2 gas at different operating temperatures. Furthermore, based on the experimental results, two combined models are proposed to be responsible for the hydrogen sensing mechanism in Pt-WO3 nanowire film.
Capacitance–voltage analysis of LaAlO3/SrTiO3 heterostructures
Authors: Keun Kim Seong , Kim Shin-Ik , Hwang Jin-Ha , Kim Jin-Sang , Baek Seung-Hyub
Published: March 2013

We performed capacitance–voltage analysis of 5-nm-thick LaAlO3/SrTiO3 heterostructure containing two-dimensional-electron-gas (2DEG) at the interface. The complex impedance of the heterostructure was measured as a function of frequency for a wide range of gate biases. The impedance spectra showed a different behavior above and below an applied voltage of −1.8 V. The capacitance determined from the impedance was approximately 1.2 nF above −1.8 V and was drastically reduced to ∼0.01 nF below this voltage, owing to depletion of 2DEG and the insulating SrTiO3 underneath it. This suggests that devices utilizing LaAlO3/SrTiO3 can facilitate switching operations in a very small voltage range.
A Design Approach to Forge Visions That Amplify Paths of Peri-Urban Development
Authors: Rauws Ward , van Dijk Terry
Published: March 2013

Peri-urban areas are generally highly dynamic and fragmented zones. This is due not only to their functional and physical diversity and fragmentation, but also because they are the focus of a wide variety of perceptions and interests. This plurality causes on-going planning difficulties, affecting planners' ability to identify and strategically strengthen common interests for future development. In this paper we claim that spatial visioning can be supportive in bridging the gap between contested ‘perceived peri-urban realities’ by revealing shared values and devising innovative ideas that blend seemingly contradictory demands. However, we suggest that visioning processes need designers to spark imagination effectively and make visioning more productive. Designers can bring together unexpected combinations of stakeholders by redefining problems, strengthen the link between process and content, and take responsibility for integral and appealing vision products.
Association of Prescription Drug Misuse with Risky Motor Vehicle Behaviors among Low-Income Young Women
Authors: Laz Tabassum H. , Shemontee Mirza O. , Rahman Mahbubur , Berenson Abbey B.
Published: March 2013

Background

The purpose of this study was to examine the association between prescription drug misuse and risky motor vehicle behaviors among 16–24-year-old women.

Methods

A survey was conducted on misuse of 4 classes of prescription drugs (pain relievers, tranquilizers, stimulants, and sedatives) and past-month risky motor vehicle behaviors among these women during 2008–2010.

Results

Overall, 47.7% (1408/2952) of women reported risky motor vehicle behavior(s) in the past month. Misuse of 1 or more of the 4 classes was 30.1% (lifetime), 15.0% (past year), and 6.7% (past month). Misuse of 1 or more of these prescription drug classes was associated with risky motor vehicle behaviors in their lifetime (odds ratio [OR]: 1.83, 95% confidence interval [CI]: 1.54–2.18), past year (OR: 2.25, 95% CI: 1.80–2.83), and past month (OR: 2.70, 95% CI: 1.94–3.78).

Conclusions

The current finding that misuse of 1 or more of the 4 prescription drug classes, irrespective of when this last occurred, is associated with risky motor vehicle behaviors may help formulate awareness programs.
Necrosis of the Intranasal Structures and Soft Palate as a Result of Heroin Snorting: A Case Series
Authors: Peyrière Hélène , Léglise Yves , Rousseau Arnaud , Cartier Cesar , Gibaja Valérie , Galland Pascal
Published: March 2013

Background

The link between nasal inhalation of cocaine and nasal and palatal necrosis is well documented. In contrast, few data are available concerning nasal mucosa necrosis related to heroin snorting. The authors report here the retrospective analysis of 24 cases of orofacial lesions in patients with nasal heroin usage, collected between 2006 and 2012.

Cases

The cases concern 17 males and 7 females (median age 29.5 (range: 24–42)) with chronic consumption of intranasal heroin (from 2 months to more than 10 years). Six patients had a history of cocaine abuse. The median daily amount of heroin consumption was 5 g (range: 0.5–10). The complications were nasal perforation (11 cases), nasal ulceration or erythema (5 cases), nasal septum necrosis (5 cases), pharyngeal ulceration (3 cases), and palate damages (5 cases). The most common clinical signs and symptoms were nasal pain, purulent sputum, dysphagia, and rhinitis. Maintenance therapy with methadone (19 cases) or buprenorphine (3 cases) was initiated. In 8 cases, the injury improved.

Discussion

The potential of heroin to induce destructive orofacial lesions should be considered when nasal damages are observed in patients with drug abuse. A multidisciplinary approach seems to be the most effective means of managing such patients.
Why Would Khat Chewers Quit? An In-Depth, Qualitative Study on Saudi Khat Quitters
Authors: Alsanusy Rashad , El-Setouhy Maged
Published: March 2013

Background

Khat chewing, which has many adverse health and social consequences, is highly prevalent and socially accepted in the Jazan region of the Kingdom of Saudi Arabia.

Methods

A qualitative study was conducted with 47 adult male former khat users regarding their khat initiation, continuance, and cessation, the amounts of khat they had used, and the health and social consequences of their use and cessation of use.

Results

Participants noted a desire to show maturity, ease of availability of khat, and peer pressure as reasons for initiating khat chewing. Many noted long leisure times with little to do as a reason for continuing use. Negative consequences of khat use were seen in economic, health, familial, and sexual areas of their lives. After quitting khat use, participants saw improvements in all of these areas.

Conclusions

A comprehensive community development program (CCDP) tackling, among other issues, the normalization of khat use, substantial leisure times with few positive activities, and misinformation about the “benefits” of khat use, as well as developing peer and family training programs to help prevent or stop khat use, would be useful to reduce khat chewing in this community.
Predicting the probability of H3K4me3 occupation at a base pair from the genome sequence context
Authors: Ha Misook , Hong Soondo , Li Wen-Hsiung
Published: March 2013

Motivation: Histone modifications regulate chromatin structure and gene expression. Although nucleosome formation is known to be affected by primary DNA sequence composition, no sequence signature has been identified for histone modifications. It is known that dense H3K4me3 nucleosome sites are accompanied by a low density of other nucleosomes and are associated with gene activation. This observation suggests a different sequence composition of H3K4me3 from other nucleosomes.

Approach: To understand the relationship between genome sequence and chromatin structure, we studied DNA sequences at histone modification sites in various human cell types. We found sequence specificity for H3K4me3, but not for other histone modifications. Using the sequence specificities of H3 and H3K4me3 nucleosomes, we developed a model that computes the probability of H3K4me3 occupation at each base pair from the genome sequence context.

Results: A comparison of our predictions with experimental data suggests a high performance of our method, revealing a strong association between H3K4me3 and specific genomic DNA context. The high probability of H3K4me3 occupation occurs at transcription start and termination sites, exon boundaries and binding sites of transcription regulators involved in chromatin modification activities, including histone acetylases and enhancer- and insulator-associated factors. Thus, the human genome sequence contains signatures for chromatin modifications essential for gene regulation and development. Our method may be applied to find new sequence elements functioning by chromatin modulation.

Availability: Software and supplementary data are available at Bioinformatics online.

Contact:  misook.ha@samsung.com or wli@uchicago.edu

Supplementary information:  Supplementary data are available at Bioinformatics online.
Sorad: a systems biology approach to predict and modulate dynamic signaling pathway response from phosphoproteome time-course measurements
Authors: Äijö Tarmo , Granberg Kirsi , Lähdesmäki Harri
Published: March 2013

Motivation: Signaling networks mediate responses to different stimuli using a multitude of feed-forward, feedback and cross-talk mechanisms, and malfunctions in these mechanisms have an important role in various diseases. To understand a disease and to help discover novel therapeutic approaches, we have to reveal the molecular mechanisms underlying signal transduction and use that information to design targeted perturbations.

Results: We have pursued this direction by developing an efficient computational approach, Sorad, which can estimate the structure of signal transduction networks and the associated continuous signaling dynamics from phosphoprotein time-course measurements. Further, Sorad can identify experimental conditions that modulate the signaling toward a desired response. We have analyzed comprehensive phosphoprotein time-course data from a human hepatocellular liver carcinoma cell line and demonstrate here that Sorad provides more accurate predictions of phosphoprotein responses to given stimuli than previously presented methods and, importantly, that Sorad can estimate experimental conditions to achieve a desired signaling response. Because Sorad is data driven, it has a high potential to generate novel hypotheses for further research. Our analysis of the hepatocellular liver carcinoma data predict a regulatory connection where AKT activity is dependent on IKK in TGFα stimulated cells, which is supported by the original data but not included in the original model.

Availability: An implementation of the proposed computational methods will be available at http://research.ics.aalto.fi/csb/software/.

Contact:  tarmo.aijo@aalto.fi or harri.lahdesmaki@aalto.fi

Supplementary information:  Supplementary data are available at Bioinformatics online.
TfReg: calculating DNA and RNA melting temperatures and opening profiles with mesoscopic models
Authors: Weber Gerald
Published: March 2013

Summary: The mesoscopic statistical physics models, known generically as Peyrard–Bishop (PB) models, have found many applications for the study of oligonucleotide properties. Unfortunately, PB models have not reached a wider non-specialized audience for the lack of freely available software implementations. Here we present an extensible C++ implementation of four variants of the PB model, which allows the user to calculate melting temperatures from tested model parameters. Even for a non-specialist, it should be straightforward to change these parameters to reflect different experimental environments or different types of oligonucleotides. For users with some proficiency in C++ programming, it should be feasible to extend the code to other PB models owing to the generic programming implementation adopted for TfReg. Pre-calculated parameters are included that allow the immediate calculation of melting temperatures and thermal equivalence indexes for DNA and RNA.

Availability: C++ source code and compiled binaries for several Linux distributions are available from https://sites.google.com/site/geraldweberufmg/tfreg and from OpenSuse build service at http://build.opensuse.org.

Contact:  gweberbh@gmail.com

Supplementary information:  Supplementary data are available at Bioinformatics online.
Wheat Gluten Polymer Structures: The Impact of Genotype, Environment, and Processing on Their Functionality in Various Applications
Authors: Johansson Eva , Malik Ali Hafeez , Hussain Abrar , Rasheed Faiza , Newson William R. , Plivelic Tomas , Hedenqvist Mikael S. , Gällstedt Mikael , Kuktaite Ramune
Published: March 2013

For a number of applications, gluten protein polymer structures are of the highest importance in determining end‐use properties. The present article focuses on gluten protein structures in the wheat grain, genotype‐ and environment‐related changes, protein structures in various applications, and their impact on quality. Protein structures in mature wheat grain or flour are strongly related to end‐use properties, although influenced by genetic and environment interactions. Nitrogen availability during wheat development and genetically determined plant development rhythm are the most important parameters determining the gluten protein polymer structure, although temperature during plant development interacts with the impact of the mentioned parameters. Glutenin subunits are the main proteins incorporated in the gluten protein polymer in extracted wheat flour. During dough mixing, gliadins are also incorporated through disulfide‐sulfhydryl exchange reactions. Gluten protein polymer size and complexity in the mature grain and changes during dough formation are important for breadmaking quality. When using the gluten proteins to produce plastics, additional proteins are incorporated in the polymer through disulfide‐sulfhydryl exchange, sulfhydryl oxidation, β‐eliminations with lanthionine formation, and isopeptide formation. In promising materials, the protein polymer structure is changed toward β‐sheet structures of both intermolecular and extended type and a hexagonal close‐packed structure is found. Increased understanding of gluten protein polymer structures is extremely important to improve functionality and end‐use quality of wheat‐ and gluten‐based products.
Optimal concentration for sugar transport in plants
Authors: Jensen Kaare H. , Savage Jessica A. , Holbrook N. Michele
Published: March 2013

Vascular plants transport energy in the form of sugars from the leaves where they are produced to sites of active growth. The mass flow of sugars through the phloem vascular system is determined by the sap flow rate and the sugar concentration. If the concentration is low, little energy is transferred from source to sink. If it is too high, sap viscosity impedes flow. An interesting question is therefore at which concentration is the sugar flow optimal. Optimization of sugar flow and transport efficiency predicts optimal concentrations of 23.5 per cent (if the pressure differential driving the flow is independent of concentration) and 34.5 per cent (if the pressure is proportional to concentration). Data from more than 50 experiments (41 species) collected from the literature show an average concentration in the range from 18.2 per cent (all species) to 21.1 per cent (active loaders), suggesting that the phloem vasculature is optimized for efficient transport at constant pressure and that active phloem loading may have developed to increase transport efficiency.
Functional evidence for physiological mechanisms to circumvent neurotoxicity of cardenolides in an adapted and a non-adapted hawk-moth species
Authors: Petschenka Georg , Pick Christian , Wagschal Vera , Dobler Susanne
Published: March 2013

Because cardenolides specifically inhibit the Na+K+-ATPase, insects feeding on cardenolide-containing plants need to circumvent this toxic effect. Some insects such as the monarch butterfly rely on target site insensitivity, yet other cardenolide-adapted lepidopterans such as the oleander hawk-moth,Daphnis nerii, possess highly sensitive Na+K+-ATPases. Nevertheless, larvae of this species and the relatedManduca sextaare insensitive to injected cardenolides. By radioactive-binding assays with nerve cords of both species, we demonstrate that the perineurium surrounding the nervous tissue functions as a diffusion barrier for a polar cardenolide (ouabain). By contrast, for non-polar cardenolides such as digoxin an active efflux carrier limits the access to the nerve cord. This barrier can be abolished by metabolic inhibitors and by verapamil, a specific inhibitor of P-glycoproteins (PGPs). This supports that a PGP-like transporter is involved in the active cardenolide-barrier of the perineurium. Tissue specific RT-PCR demonstrated expression of three PGP-like genes in hornworm nerve cords, and immunohistochemistry further corroborated PGP expression in the perineurium. Our results thus suggest that the lepidopteran perineurium serves as a diffusion barrier for polar cardenolides and provides an active barrier for non-polar cardenolides. This may explain the highin vivoresistance to cardenolides observed in some lepidopteran larvae, despite their highly sensitive Na+K+-ATPases.
Carry-over effects, sequential density dependence and the dynamics of populations in a seasonal environment
Authors: Betini Gustavo S. , Griswold Cortland K. , Norris D. Ryan
Published: March 2013

Most animal populations have distinct breeding and non-breeding periods, yet the implications of seasonality on population dynamics are not well understood. Here, we introduce an experimental model system to study the population dynamics of two important consequences of seasonality: sequential density dependence and carry-over effects (COEs). Using a replicated seasonal population ofDrosophila, we placed individuals at four densities in the non-breeding season and then, among those that survived, placed them to breed at three different densities. We show that COEs arising from variation in non-breeding density negatively impacts individual performance by reducingper capitabreeding output by 29–77%, implying that non-lethal COEs can have a strong influence on population abundance. We then parametrized a bi-seasonal population model from the experimental results, and show that both sequential density dependence and COEs can stabilize long-term population dynamics and that COEs can reduce population size at low intrinsic rates of growth. Our results have important implications for predicting the successful colonization of new habitats, and for understanding the long-term persistence of seasonal populations in a wide range of taxa, including migratory organisms.
Does fish larval dispersal differ between high and low latitudes?
Authors: Leis Jeffrey M. , Caselle Jennifer E. , Bradbury Ian R. , Kristiansen Trond , Llopiz Joel K. , Miller Michael J. , O'Connor Mary I. , Paris Claire B. , Shanks Alan L. , Sogard Susan M. , Swearer Stephen E. , Treml Eric A. , Vetter Russell D. , Warner Robert R.
Published: March 2013

Several factors lead to expectations that the scale of larval dispersal and population connectivity of marine animals differs with latitude. We examine this expectation for demersal shorefishes, including relevant mechanisms, assumptions and evidence. We explore latitudinal differences in (i) biological (e.g. species composition, spawning mode, pelagic larval duration, PLD), (ii) physical (e.g. water movement, habitat fragmentation), and (iii) biophysical factors (primarily temperature, which could strongly affect development, swimming ability or feeding). Latitudinal differences exist in taxonomic composition, habitat fragmentation, temperature and larval swimming, and each difference could influence larval dispersal. Nevertheless, clear evidence for latitudinal differences in larval dispersal at the level of broad faunas is lacking. For example, PLD is strongly influenced by taxon, habitat and geographical region, but no independent latitudinal trend is present in published PLD values. Any trends in larval dispersal may be obscured by a lack of appropriate information, or use of ‘off the shelf’ information that is biased with regard to the species assemblages in areas of concern. Biases may also be introduced from latitudinal differences in taxa or spawning modes as well as limited latitudinal sampling. We suggest research to make progress on the question of latitudinal trends in larval dispersal.
Maize RNA Polymerase IV Definestrans-Generational Epigenetic Variation
Authors: Erhard Karl F. , Parkinson Susan E. , Gross Stephen M. , Barbour Joy-El R. , Lim Jana P. , Hollick Jay B.
Published: March 2013

The maize (Zea mays) RNA Polymerase IV (Pol IV) largest subunit, RNA Polymerase D1 (RPD1 or NRPD1), is required for facilitating paramutations, restricting expression patterns of genes required for normal development, and generating small interfering RNA (siRNAs). Despite this expanded role for maize Pol IV relative to Arabidopsis thaliana, neither the general characteristics of Pol IV–regulated haplotypes, nor their prevalence, are known. Here, we show that specific haplotypes of the purple plant1 locus, encoding an anthocyanin pigment regulator, acquire and retain an expanded expression domain following transmission from siRNA biogenesis mutants. This conditioned expression pattern is progressively enhanced over generations in Pol IV mutants and then remains heritable after restoration of Pol IV function. This unusual genetic behavior is associated with promoter-proximal transposon fragments but is independent of sequences required for paramutation. These results indicate that trans-generational Pol IV action defines the expression patterns of haplotypes using co-opted transposon-derived sequences as regulatory elements. Our results provide a molecular framework for the concept that induced changes to the heterochromatic component of the genome are coincident with heritable changes in gene regulation. Alterations of this Pol IV–based regulatory system can generate potentially desirable and adaptive traits for selection to act upon.
Review of manufacturing cells as they achieve high levels of autonomy and flexibility
Authors: Bloss Richard
Published: March 2013

Purpose

The purpose of this paper is to provide a review of the most recent IMTS show in Chicago with emphasis on the new manufacturing automation innovations and applications on display.

Design/methodology/approach

The paper presents in‐depth interviews with exhibitors of automation equipment and system integrators of automation technology at the show.

Findings

Automation technology continues to address an ever increasing number of manufacturing tasks to improve quality and productivity at every step in the manufacturing and inspection process.

Practical implications

Customers may be surprised at the automation innovations and new applications which are appearing in the manufacturing environment.

Originality/value

The paper offers a review of some of the latest automation innovations and applications that one might have seen if they had been on the exhibition floor at the most recent Chicago IMTS show.
Retail service quality in small retail sector: the Indian experience
Authors: Khare Arpita
Published: March 2013

Purpose

The objective of the research is to understand Indian consumers' definition of retail service quality with respect to small retailers and influence of hedonic and utilitarian shopping values in determining their expectations towards small retail service quality.

Design/methodology/approach

Data were collected through a small retail store‐intercept technique in four cities of Northern India (n=386).

Findings

The results indicate that small retail service quality for Indian consumers comprises ambience, layout, and service/relationships dimensions. Hedonic and utilitarian shopping values influence consumers' service quality evaluations.

Research limitations/implications

The study did not consider demographic variables like income, education, and occupation as factors that might affect consumers' perceptions towards retail service quality.

Practical implications

The findings can help small retailers in improving their service quality by focusing on Indian consumers' hedonic and utilitarian shopping values. The research helps small retailers to combat the competitive pressures of organized retailing in the Indian retail landscape.

Originality/value

There has been limited research on understanding consumers' perceptions towards retail service quality in the Indian setting. Further, there is no research to examine Indian consumers' perceptions towards small retailers' quality attributes.
Ethnic bias in tenant selection in metropolitan Ibadan private rental housing market
Authors: Taiwo Gbadegesin Job , Ojo Olatoye
Published: March 2013

Purpose

The purpose of this study is to investigate the presence of ethnic bias in residential tenancy and the relationship between ethnic bias tendency of property managers/landlords and their demographic features.

Design/methodology/approach

Data for the study were gathered from administration of questionnaires, designed with items measuring bias tendency and the driving factors on the perceived wave of discrimination on residential tenancy. The structured questionnaires were administered on an intact sample of licensed property managers/agents (practicing Estate Surveyors and Valuers) at annual Mandatory Continuing Professional Development Programme (MCPD) held in metropolitan Ibadan, the largest indigenous city in West Africa and one of the commercial nerve‐centres in the country. Data collected were analyzed using descriptive analysis, chi square and factor analysis.

Findings

The study confirmed a significant relationship between the ethnic status of the principal managers (managing directors) who were mainly Yoruba aliens and the tenants selected to fill vacancies, which implies that there is presence of ethnic discrimination in tenant selection in the area. It is also confirmed that landlord/property manager (agents) experience, environmental influence and landlord/property manager preference are the most driving factors for discriminating against tenants in the city. It is further revealed that there is a significant relationship between two demographic features; professional qualifications and ages of the property managers’ firms and bias tendency.

Research limitations/implications

The research is limited to the metropolitan city of Ibadan, a city with expatriates and diverse ethnic groups working at different sectors of the economy. Further research and statistical tests that covers all the 36 capital cities of the country are required to examine the tenancy nature of other classes of property.

Practical implications

The implication of the study to the practice is reinforced by the consensus character of the study with the professional body (property managers). Insight and findings prove useful in developing a blueprint for curbing acts of discrimination which needs to be well addressed in property management practice. It implies that effective property rights that protect the rights and rental market planning policy in the developing nations require further reform.

Originality/value

Emphasis on tenants’ rights, campaign against racism and discrimination in the developing nations which support equal housing right for all races is the feature and uniqueness of this study.
Economic and management perspectives on control of illegal land uses in the leasehold system
Authors: Lam Terence Y.M. , Man Henry K.H.
Published: March 2013

Purpose

Illegal changes of use in aged industrial and residential buildings is now a prevalent problem in Hong Kong. This research aims to develop a strategy for an effective and efficient control of illegal land use in a highly dense environment, with high rise buildings in multiple leasehold ownerships.

Design/methodology/approach

Multiple cases were qualitatively analyzed, based on documentary analysis of the court proceedings.

Findings

In Cases 1 and 2, lease conditions for restriction to industrial purposes on aged industrial buildings were found to be obsolete and not economically viable, thus resulting in illegal conversion of the premises for commercial use. Cases 2 and 3 showed that ambiguity in user clauses in land leases could lead to illegal changes of use from industrial or residential to commercial activities. Most importantly, Cases 1 and 3 demonstrated that limited resources for lease enforcement are the fundamental cause of the problem. Cases 4 and 5 proved that property managers could take effective legal action against changes of use in buildings with multiple ownerships.

Research limitations/implications

The results of this study are derived from five typical cases in Hong Kong, but they form a baseline upon which further research can build to test their significance in many other settings. Ultimately, a more robust strategy can be developed for ensuring an effective and efficient control of illegal land uses in the leasehold system for Hong Kong and for those countries with a similar tenure system.

Practical implications

A total economic and management strategy should be implemented by the government. The land management system should work in partnership with private property managers which are empowered under the Deed of Mutual Covenant (DMC) of multiple occupied buildings to take instant action against individual owners for breaches of lease conditions. The system should also be more flexible to expand the scope of new uses for aged industrial premises, allow affordable premium for lease modifications, as well as review and clarify any ambiguous user clauses in the related land ordinances.

Social implications

The public should be educated that it is important to seek approvals and consents from the government prior to making any changes of land use. The government should also establish a housing policy to provide sufficient affordable housing for the lower income group so that illegal sub‐divisions on buildings for residential purposes can be eliminated.

Originality/value

The improvement measures identified can effectively enforce compliance with lease conditions, which in turn can reduce the enforcement transaction costs, ensure efficient allocation and use of land in the leasehold system, and maintain building safety.
Collective learning in schools: exploring the perceptions of leadership trainees
Authors: Schechter Chen
Published: March 2013

Purpose

The purpose of this paper is to explore leadership trainees’ perceptions of determinants of collective learning in school settings and of the principal's role in collective learning.

Design/methodology/approach

In total, 24 interviews were conducted with all leadership trainees in a university‐based principal preparatory program. Data analysis inductively generated themes that were grounded in the various perspectives articulated by leadership trainees.

Findings

Leadership trainees pointed out three main difficulties facing collective learning: time and place; staff reaction to collective learning; and acceptance atmosphere. Trainees listed four main roles that principals have in shaping the collective learning process: administrator; team leader; collaborator; and visionary.

Research limitations/implications

The findings call for ongoing research on the connection between leadership trainees’ conceptualizations of collective learning and their practical capabilities to initiate these learning processes in schools.

Originality/value

The results of this study can shed light on how to prepare leadership trainees in a university preparation program to initiate and sustain collaborative learning interactions among faculty members.
Characteristics and properties of Bi‐11Ag solder
Authors: Koleňák Roman , Chachula Michal
Published: March 2013

Purpose

The purpose of this paper is to study Bi‐11Ag solder for higher application temperatures. The aim of the research work was to determine the soldering, thermal and mechanical properties of Bi‐11Ag solder.

Design/methodology/approach

To determine the melting point interval of experimental Bi‐11Ag solder, DSC analysis was performed. The contact angles were studied on a copper, nickel and silver substrate by use of a sessile drop method. Wettability tests were realised at a temperature of 380°C in a shielding atmosphere (90% N2+10% H2). Based on experience achieved with wetting angle measurements, the specimens for measurement of shear strength of Cu, Ni and Ag/Bi‐11Ag joints were fabricated. EDX analysis was used for the study of the solder interaction with the surface of the three metallic substrates.

Findings

The best wettability at soldering in a shielding atmosphere was achieved with silver. The wetting angle at 30 min attained the value of 23°. The worst wettability was observed on copper, where at 30 min the wetting angle was 55°. Average shear strength varied from 31 to 45 MPa. The highest strength was obtained with the Cu substrate whereas the lowest was with the Ni substrate. The lowest strength achieved with the Ni substrate was caused by formation of brittle intermetallic phase NiBi3. Joint formation is realised by eutectic reaction at the contact of Bi with the surface of the copper substrate. Similar joint formation by eutectic reaction occurs also at Bi interaction with the surface of the Ag substrate. At Bi interaction with the nickel substrate a new intermetallic phase (NiBi3) is formed.

Originality/value

Wettability of Bi‐11Ag solder on Cu, Ag and Ni substrates was determined at application of a shielding atmosphere (90% N2+10% H2). Wettability was determined also at application of ZnCl2‐NH4Cl flux. The shear strength of Bi‐11Ag on different substrates was determined. The mechanism of joint formation was analysed.
The embeddedness of accounting outsourcing relationships
Authors: Elharidy Ali M. , Nicholson Brian , Scapens Robert
Published: March 2013

Purpose

This paper aims to improve understanding of how management control systems (MCS) are influenced by local contexts in outsourcing relationships, drawing on a multi‐layer analysis of embeddedness.

Design/methodology/approach

Data were gathered through a field study of 15 Egyptian firms that outsourced various forms of accounting services to third party suppliers.

Findings

The findings indicate that managers make their control choices based on the nature of their “embedded relationships” with suppliers. The embeddedness analysis demonstrates the influence of context on MCS implementation.

Research limitations/implications

There is a paucity of studies focussing on how context affects control in outsourcing relationships. The paper provides a detailed framework and a rich empirically‐based explanation of the findings.

Practical implications

The findings have implications for the practice of accounting outsourcing and provide a conceptual framework of relevance to management practice.

Originality/value

A conceptual framework for understanding embeddedness is presented, which is illustrated with empirical evidence from multiple case analyses to illustrate how the implementation of MCS is influenced by context.