bluuebunny/crossref_metadata_2025 huggingface dataset:
Mercury increases water permeability of a plant aquaporin through a non-cysteine-related mechanism
Authors: Frick Anna , Järvå Michael , Ekvall Mikael , Uzdavinys Povilas , Nyblom Maria , Törnroth-Horsefield Susanna
Published: July 2013

Water transport across cellular membranes is mediated by a family of membrane proteins known as AQPs (aquaporins). AQPs were first discovered on the basis of their ability to be inhibited by mercurial compounds, an experiment which has followed the AQP field ever since. Although mercury inhibition is most common, many AQPs are mercury insensitive. In plants, regulation of AQPs is important in order to cope with environmental changes. Plant plasma membrane AQPs are known to be gated by phosphorylation, pH and Ca2+. We have previously solved the structure of the spinach AQP SoPIP2;1 (Spinacia oleracea plasma membrane intrinsic protein 2;1) in closed and open conformations and proposed a mechanism for how this gating can be achieved. To study the effect of mercury on SoPIP2;1 we solved the structure of the SoPIP2;1–mercury complex and characterized the water transport ability using proteoliposomes. The structure revealed mercury binding to three out of four cysteine residues. In contrast to what is normally seen for AQPs, mercury increased the water transport rate of SoPIP2;1, an effect which could not be attributed to any of the cysteine residues. This indicates that other factors might influence the effect of mercury on SoPIP2;1, one of which could be the properties of the lipid bilayer.
Selection of unique gaze direction based on pupil position
Authors: Mohammadi Mohammad Reza , Raie Abolghasem
Published: July 2013

The ‘gaze estimation’ problem, because of its manifold applications including human–computer interaction especially for the handicapped, has been a topic of research for many years. Recently, thanks to technological advances, non‐intrusive methods based on image processing employed in broader applications, are addressed more than before. One of the promising approaches to gaze estimation is based on projective geometry. In projective geometry‐based approaches, an ellipse is fitted to the image of iris boundary and from its parameters, two solutions are obtained, only one of which is valid for the gaze direction. Since the ellipse parameters are not adequate for disambiguation, in a previous work, the accurate coordinates of eye corners in three‐dimensional, as complementary information, is obtained through another system increasing the cost and complexity of the overall system. In this article, a new technique to select the valid solution, based on eye geometry and iris image, is developed. In the proposed technique, relative position of the pupil centre with respect to the iris centre is used as the complementary information and a novel algorithm is proposed for its extraction. The performance of the proposed technique was evaluated on 600 real images and with only one failure on selecting the valid solution demonstrated an accuracy of 99.8% for disambiguation.
Automatic clustering method based on evolutionary optimisation
Authors: Liu Cong , Zhou Aimin , Zhang Guixu
Published: July 2013

How to set the cluster number plays a key role in many clustering applications. To address this issue, this study introduces an automatic clustering method based on evolutionary algorithms (EAs). The basic idea is to convert a clustering problem into a global optimisation problem and tackle it by an EA. A new validity index, which balances the inter‐cluster consistency and the intra‐cluster consistency, is proposed to be the objective function. Three adaptive coding schemes, which can deal with variable‐length optimisation problems by using a fixed‐length chromosome, are designed to detect the cluster number automatically. The validity index and adaptive coding schemes are incorporated in an EA for automatic clustering. The authors approach is compared with some widely used validity indices and an adaptive coding scheme on some artificial data sets and two real‐world problems. The experimental results suggest that their method not only successfully detects the correct cluster numbers but also achieve stable results for most of test problems.
A hybrid method and its applications to analyse the low frequency oscillations in the interconnected power system
Authors: Yang Dechang , Rehtanz Christian , Li Yong , Yang Deyou
Published: July 2013

In this study, a hybrid method is proposed to calculate oscillatory parameters and the approximate mode shapes (AMSs) of low frequency oscillations based on the measured signals from wide area measurement system. This method not only overcomes the limitations of the single algorithm, but also integrates the advantages of the used techniques. First of all, two‐level decomposition is presented to minish the scale‐mixing influence in the empirical mode decomposition. Then, the Gibbs phenomenon of traditional Hilbert transform (HT) is reduced by using the normalised HT. Next, the relative phase calculation algorithm is introduced to realise the generator grouping and mode shape identification. Finally, the AMSs of dominant oscillation at different time ranges and frequency distributions are determined. The EPRI–36 bus simulation model and actual measured signals are used to evaluate the performances and validities of the proposed hybrid method.
Dynamic computing paradigm for comprehensive power flow analysis
Authors: Xie Ning , Torelli Franco , Bompard Ettore , Vaccaro Alfredo
Published: July 2013

In this study, a novel dynamic paradigm aimed at solving the power flow equations in both solvable and unsolvable region is proposed. The challenging idea is to reformulate the power flow equations into a set of ordinary differential equations, whose equilibrium points represent the power flow problem solutions. Starting from the Lyapunov theory, the authors demonstrate that this system of dynamic equations is characterised by an exponential asymptotic convergence to equilibrium points. This feature allows us to overcome the inherent limitations of the traditional iterative minimisation algorithms that can fail to converge because of the highly non‐linearities of the first‐order condition. Extensive simulation studies aimed at demonstrating the effectiveness of the proposed methodology are presented and discussed.
Secondary control of microgrids based on distributed cooperative control of multi‐agent systems
Authors: Bidram Ali , Davoudi Ali , Lewis Frank L. , Qu Zhihua
Published: July 2013

This study proposes a secondary voltage and frequency control scheme based on the distributed cooperative control of multi‐agent systems. The proposed secondary control is implemented through a communication network with one‐way communication links. The required communication network is modelled by a directed graph (digraph). The proposed secondary control is fully distributed such that each distributed generator only requires its own information and the information of its neighbours on the communication digraph. Thus, the requirements for a central controller and complex communication network are obviated, and the system reliability is improved. The simulation results verify the effectiveness of the proposed secondary control for a microgrid test system.
Optimal charge equalisation control for series‐connected batteries
Authors: Chen Woei‐Luen , Cheng Shin‐Rung
Published: July 2013

Batteries play an important role in sustainable energy systems because the energy stored in batteries can be dispatched at any time. Series‐connected batteries can furnish a load with higher voltage and consequently reduce the I2R loss during power conversion and transmission. However, if imbalanced voltage occurs, a battery with high state of charge (SOC) would react more drastically than that with lower SOC under both charging and discharging conditions. Imbalanced charge or discharge would give rise to potential damage to the battery and also shorten the battery life cycle. This study presents a modified charge equaliser (CE) along with an optimal charge equalisation algorithm (CEA). The proposed circuit scheme can distribute an imbalanced charge in a more efficient way without increasing additional circuit cost. To further expedite charge equalisation among a battery string, the activated CE duty ratio is fixed at the upper limits throughout the charge equalisation phase. An optimal CEA with a view towards maximising the final battery string voltage is developed to resolve the CE operating sequence and length. The proposed equalisation strategy is realised using a peripheral interface controller that uses a buck–boost converter as the CE. The experimental results confirm the performance of the proposed strategy.
Parameter‐free Paretian optimisation in electromagnetics: a kinematic formulation
Authors: Di Barba Paolo , Dughiero Fabrizio , Sieni Elisabetta
Published: July 2013

A simple method of parameter‐free Paretian optimisation is proposed in order to explore shapes of the unknown boundary of a synthesis region, in the search for the family of optimal shapes fulfilling a prescribed set of conflicting objective functions. To this end, a velocity‐time law, related to the objective functions, governs the motion of a set of nodes located along the synthesis region boundary. The proposed method of optimal shape design conserves domain connectivity; moreover, because of the kinematic formulation, there is no need to solve the motion equation of the moving boundary. This way, the computational cost of the proposed method is low, and the advantage of a broad search space – inherent in the parameter‐free approach – is preserved. To assess the method, a case study of inverse induction‐heating is considered; the associated field problem is solved by means of finite‐element analysis.
Comparing the trustworthiness of signal‐to‐noise ratio and peak signal‐to‐noise ratio in processing noisy partial discharge signals
Authors: Najafipour Abbas , Babaee Abbas , Shahrtash S. Mohammad
Published: July 2013

In partial discharge (PD) analyses, there is a need to compare the noise level of measured signals in different conditions and/or after applying certain signal processing algorithms (e.g. noise reduction). Moreover, in PD analyses through modelling approaches, whenever noisy signals should be constructed by adding noise with a desired level to the simulated PD signal and/or where de‐noising process is employed, there is a need to evaluate the strength of noise. In all these cases, signal‐to‐noise ratio (SNR) is already used as an indicator of noise level, whereas it is shown that SNR can be deceptive and misleading. Instead, this study recommends employing the proposed peak SNR which is more robust than SNR. The results can be extended to the analysis of any non‐periodic transient signal as well.
Quantum fluid model of coherent stimulated radiation by a dense relativistic cold electron beam
Authors: Monteiro L. F. , Serbeto A. , Tsui K. H. , Mendonça J. T. , Galvão R. M. O.
Published: July 2013

Using a quantum fluid model, the linear dispersion relation for FEL pumped by a short wavelength laser wiggler is deduced. Subsequently, a new quantum corrected resonance condition is obtained. It is shown that, in the limit of low energy electron beam and low frequency pump, the quantum recoil effect can be neglected, recovering the classical FEL resonance condition, ks=4kwγ2. On the other hand, for short wavelength and high energy electron beam, the quantum recoil effect becomes strong and the resonance condition turns into ks=2kw/ƛcγ3/2, with ƛc being the reduced Compton wavelength. As a result, a set of nonlinear coupled equations, which describes the quantum FEL dynamics as a three-wave interaction, is obtained. Neglecting wave propagation effects, this set of equations is solved numerically and results are presented.
Complete positivity of the map from a basis to its dual basis
Authors: Paulsen Vern I. , Shultz Fred
Published: July 2013

The dual of a matrix ordered space has a natural matrix ordering that makes the dual space matrix ordered as well. The purpose of these notes is to give a condition that describes when the linear map taking a basis of Mn to its dual basis is a complete order isomorphism. We exhibit “natural” orthonormal bases for Mn such that this map is an order isomorphism, but not a complete order isomorphism. Included among such bases is the Pauli basis. Our results generalize the Choi matrix by giving conditions under which the role of the standard basis {Eij} can be replaced by other bases.
Tungsten injector for scrape-off layer impurity transport experiments in the Tore Supra tokamak
Authors: Kočan M. , Gunn J. P. , Lunt T. , Meyer O. , Pascal J.-Y.
Published: July 2013

This paper describes the design and operation of a new tungsten (W) injection system for impurity transport experiments in the Tore Supra tokamak. The system is mounted on a reciprocating manipulator and injects a controlled amount of gaseous tungsten hexacarbonyl, W(CO)6 at arbitrary depth in the scrape-off layer, using an inertially activated valve. Injected W(CO)6 is dissociated in the plasma, forming a radially localized plume of W atoms. The injector does not require an external gas feed and can perform a large number of injections from an on-board reservoir of W(CO)6. Some examples of W injections in Tore Supra are included, demonstrating successful operation and discussing some technical issues of the injector prototype.
Reactive molecular dynamics simulations of switching processes of azobenzene-based monolayer on surface
Authors: Tian Ziqi , Wen Jin , Ma Jing
Published: July 2013

It is a challenge to simulate the switching process of functional self-assembled monolayers (SAMs) on metal surfaces, since the systems consist of thousands of atoms and the switching is triggered by quantum-mechanical events. Herein a molecular dynamics simulation with a reactive rotation potential of N=N bond is implemented to investigate the dynamic conformational changes and packing effects on the stimuli-responsive isomerization of the terminally thiol functionalized azobiphenyls (AZOs), which are bound on the Au(111) surface. To, respectively, distinguish the time evolutions that start from cis and trans initial configurations, two different functions are established to model the potential energy curves for cis-to-trans and trans-to-cis transitions, instead of the only one cosine function used in the conventional non-reactive force fields. In order to simulate the conformation transitions of the AZO film on surface, a random switching function, depending on the N=N twisting angle, is constructed to consider both forward and backward cis/trans isomerization events and to trigger the reaction by changing the N atom types automatically. The factors that will influence the isomerization process, including the choice of ensembles and thermostat algorithms, the time intervals separating each switching, and the forms of the switching function, are systematically tested. Most AZO molecules switch from the cis to trans configuration with a coverage of 5.76 × 10−6 mol/m2 on a picosecond time scale, and a low coverage might make the switching irreversible, which is in agreement with the experiments.
Hopping and band mobilities of pentacene, rubrene, and 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) from first principle calculations
Authors: Kobayashi Hajime , Kobayashi Norihito , Hosoi Shizuka , Koshitani Naoki , Murakami Daisuke , Shirasawa Raku , Kudo Yoshihiro , Hobara Daisuke , Tokita Yuichi , Itabashi Masao
Published: July 2013

Hopping and band mobilities of holes in organic semiconductors at room temperature were estimated from first principle calculations. Relaxation times of charge carriers were evaluated using the acoustic deformation potential model. It is found that van der Waals interactions play an important role in determining accurate relaxation times. The hopping mobilities of pentacene, rubrene, and 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) in bulk single crystalline structures were found to be smaller than 4 cm2/Vs, whereas the band mobilities were estimated between 36 and 58 cm2/Vs, which are close to the maximum reported experimental values. This strongly suggests that band conductivity is dominant in these materials even at room temperature.
Guided photoluminescence study of Nd-doped silicon rich silicon oxide and silicon rich silicon nitride waveguides
Authors: Pirasteh Parastesh , Charrier Joël , Dumeige Yannick , Doualan Jean-Louis , Camy Patrice , Debieu Olivier , Liang Chuan-hui , Khomenkova Larysa , Lemaitre Jonathan , Boucher Yann G. , Gourbilleau Fabrice
Published: July 2013

Planar waveguides made of Nd3+-doped silicon rich silicon oxide (SRSO) and silicon rich silicon nitride (SRSN) have been fabricated by reactive magnetron sputtering and characterized with special emphasis on the comparison of the guided photoluminescence (PL) properties of these two matrices. Guided fluorescence excited by top surface pumping at 488 nm on planar waveguides was measured as a function of the distance between the excitation area and the output of the waveguide, as well as a function of the pump power density. The PL intensity increased linearly with pump power without any saturation even at high power. The linear intensity increase of the Nd3+ guided PL under a non-resonant excitation (488 nm) confirms the efficient coupling between either Si-np and rare-earth ions for SRSO or radiative defects and rare earth ions for SRSN. The guided fluorescences at 945 and 1100 nm were observed until 4 mm and 8 mm of the output of the waveguide for Nd3+ doped SRSO and SRSN waveguides, respectively. The guided fluorescence decays of Nd3+-doped-SRSO and -SRSN planar waveguides have been measured and found equal to 97 μs ±7 and 5 μs ± 2, respectively. These results show notably that the Nd3+-doped silicon rich silicon oxide is a very promising candidate on the way to achieve a laser cavity at 1.06 μm.
Optimizing infrared to near infrared upconversion quantum yield of β-NaYF4:Er3+ in fluoropolymer matrix for photovoltaic devices
Authors: Ivaturi Aruna , MacDougall Sean K. W. , Martín-Rodríguez Rosa , Quintanilla Marta , Marques-Hueso Jose , Krämer Karl W. , Meijerink Andries , Richards Bryce S.
Published: July 2013

The present study reports for the first time the optimization of the infrared (1523 nm) to near-infrared (980 nm) upconversion quantum yield (UC-QY) of hexagonal trivalent erbium doped sodium yttrium fluoride (β-NaYF4:Er3+) in a perfluorocyclobutane (PFCB) host matrix under monochromatic excitation. Maximum internal and external UC-QYs of 8.4% ± 0.8% and 6.5% ± 0.7%, respectively, have been achieved for 1523 nm excitation of 970 ± 43 Wm−2 for an optimum Er3+ concentration of 25 mol% and a phosphor concentration of 84.9 w/w% in the matrix. These results correspond to normalized internal and external efficiencies of 0.86 ± 0.12 cm2 W−1 and 0.67 ± 0.10 cm2 W−1, respectively. These are the highest values ever reported for β-NaYF4:Er3+ under monochromatic excitation. The special characteristics of both the UC phosphor β-NaYF4:Er3+ and the PFCB matrix give rise to this outstanding property. Detailed power and time dependent luminescence measurements reveal energy transfer upconversion as the dominant UC mechanism.
Influence of particle-matrix interface, temperature, and agglomeration on heat conduction in dispersions
Authors: Behrang A. , Grmela M. , Dubois C. , Turenne S. , Lafleur P. G.
Published: July 2013

A combination of the effective medium and the phonon approaches is used to investigate heat conduction in heterogeneous media composed of a homogeneous matrix in which spherical particles of micro and nanosizes are dispersed. In particular, we explore the effect of different types of scattering on the particle-matrix interface, temperature dependence of the effective heat conduction coefficient, and the effect of various degrees of agglomeration of the particles. Predictions calculated explicitly for Si nanoparticles dispersed in Ge matrix agree with available Monte Carlo simulations. Our predictions show that the higher is the temperature the lower is the heat conductivity and the smaller is the influence of the details of the particle-matrix interactions. As for the influence of the agglomeration, we predict both decrease and increase of the heat conduction depending on the degree of the agglomeration.
Analysis of size quantization and temperature effects on the threshold voltage of thin silicon film double-gate metal-oxide-semiconductor field-effect transistor (MOSFET)
Authors: Sankar Medury Aditya , Bhat K. N. , Bhat Navakanta
Published: July 2013

In this paper, we analyze the combined effects of size quantization and device temperature variations (T = 50 K to 400 K) on the intrinsic carrier concentration (ni), electron concentration (n) and thereby on the threshold voltage (Vth) for thin silicon film (tsi = 1 nm to 10 nm) based fully-depleted Double-Gate Silicon-on-Insulator MOSFETs. The threshold voltage (Vth) is defined as the gate voltage (Vg) at which the potential at the center of the channel (Φc) begins to saturate (Φc=Φc(sat)). It is shown that in the strong quantum confinement regime (tsi≤3nm), the effects of size quantization far over-ride the effects of temperature variations on the total change in band-gap (ΔEg(eff)), intrinsic carrier concentration (ni), electron concentration (n), Φc(sat) and the threshold voltage (Vth). On the other hand, for tsi≥4 nm, it is shown that size quantization effects recede with increasing tsi, while the effects of temperature variations become increasingly significant. Through detailed analysis, a physical model for the threshold voltage is presented both for the undoped and doped cases valid over a wide-range of device temperatures, silicon film thicknesses and substrate doping densities. Both in the undoped and doped cases, it is shown that the threshold voltage strongly depends on the channel charge density and that it is independent of incomplete ionization effects, at lower device temperatures. The results are compared with the published work available in literature, and it is shown that the present approach incorporates quantization and temperature effects over the entire temperature range. We also present an analytical model for Vth as a function of device temperature (T).
Ultra-low reflectivity polycrystalline silicon surfaces formed by surface structure chemical transfer method
Authors: Imamura Kentaro , Franco Francisco C. , Matsumoto Taketoshi , Kobayashi Hikaru
Published: July 2013

A nanocrystalline Si layer can be formed by the surface structure chemical transfer (SSCT) method in which a platinum mesh is instantaneously contacted with polycrystalline Si wafers immersed in hydrogen peroxide plus hydrofluoric acid solutions. The polycrystalline Si surface after the SSCT method possesses an ultra-low reflectivity. The nanocrystalline Si layer possesses a 100–150 nm thickness, and gives a photoluminescence with a peak maximum at ∼670 nm, indicating band-gap widening. The minority carrier lifetime of as-sliced Si wafers greatly increases after the SSCT method most probably due to the enlargement of the nanocrystalline Si band-gap.
Comparison of isotope effects on thermal conductivity of graphene nanoribbons and carbon nanotubes
Authors: Li Xiuqiang , Chen Jie , Yu Chenxi , Zhang Gang
Published: July 2013

By using molecular dynamics simulation, we explore the isotope effect on thermal conductivity of graphene nanoribbons (GNRs) and carbon nanotubes (CNTs). For both GNRs and CNTs, the lattice thermal conductivity decreases when isotope concentration increases from 0% to 30%. The thermal conductivity reduction ratio in GNRs is less than that in CNTs. For example, thermal conductivity of CNT with 5% 13C concentration is 25% lower than that of pure CNTs; however, the reduction in thermal conductivity of GNRs with the same isotope concentration is only about 12%. Lattice dynamics analysis reveals that these phenomena are related to the phonon localization.
Electrowetting of soap bubbles
Authors: Arscott Steve
Published: July 2013

A proof-of-concept demonstration of the electrowetting-on-dielectric of a sessile soap bubble is reported here. The bubbles are generated using a commercial soap bubble mixture—the surfaces are composed of highly doped, commercial silicon wafers covered with nanometer thick films of Teflon®. Voltages less than 40 V are sufficient to observe the modification of the bubble shape and the apparent bubble contact angle. Such observations open the way to inter alia the possibility of bubble-transport, as opposed to droplet-transport, in fluidic microsystems (e.g., laboratory-on-a-chip)—the potential gains in terms of volume, speed, and surface/volume ratio are non-negligible.
The classic theory of Mexican Transition Zone revisited: the distributional congruence patterns of Passalidae (Coleoptera)
Authors: Gutiérrez-Velázquez Ana , Rojas-Soto Octavio , Reyes-Castillo Pedro , Halffter Gonzalo
Published: July 2013

We incorporated new data to re-evaluate the biogeographical patterns in the Mexican Transition Zone (MTZ) through the recognition of congruence in the geographic distributions of Mexican passalids (Coleoptera : Passalidae). We used three different approaches to parsimony analysis of endemicity (PAE): (1) the use of specific distribution data; (2) the application of a null model of significant co-occurrence to the specific distribution data; and (3) the use of predicted potential distributions through ecological niche modelling. Overall, these approaches sharpened the delimitation of distributions in three general zones. General zone (GZone) 1 includes species of restricted distribution in the state of Chiapas; the grid cells that make up this zone lie mainly in the Chiapas biogeographical province. GZone 2 includes species of restricted distribution located mainly in the states of Veracruz, Puebla, Hidalgo and Queretaro; the grid cells of this zone lie mainly in the Sierra Madre Oriental province. GZone 3 includes species with restricted distribution occurring mainly in the states of Guerrero and Oaxaca; the grid cells of this zone lie mainly in the Sierra Madre del Sur biogeographical province. The patterns of distributional congruence found in this study revealed three important distributional zones for the passalid species within the MTZ highly coincident with patterns proposed by Halffter.
Use of otolith strontium : calcium ratio as an indicator of seasonal displacements of the silverside (Odontesthes bonariensis) in a freshwater–marine environment
Authors: Avigliano E. , Volpedo A. V.
Published: July 2013

Strontium : calcium (Sr : Ca) ratios were measured in sagittal otoliths of silverside (Odontesthes bonariensis) from a freshwater–marine environment (Paraná River Delta and Río de la Plata River, South America) in order to understand its seasonal movements. Conductivity was recorded and the water Sr : Ca ratio was determined by inductively coupled plasma–atomic emission spectrometry (ICP-OES). A calibration curve of water Sr : Ca ratio versus otolith Sr : Ca ratio from four isolated lentic water bodies was made to predict silverside displacements in the lower section of the Plata Basin during summer (lotic water bodies). Otolith Sr : Ca ratio of silversides from the Paraná River Delta was associated with the conductivity of water at the locations where the sample was collected. According to this association and the obtained results in the calibration curve, the silversides were displaced from zones where conductivity was 7.45 (mS cm–1), corresponding to the water Sr : Ca ratio in the outer section of the Río de la Plata River (1.92 mmol mol–1). The high values of otolith Sr : Ca ratio found for some fish may indicate that during summer they moved from estuarine waters where salinity increases gradually to the Argentinian Sea.
Mapping gene clusters within arrayed metagenomic libraries to expand the structural diversity of biomedically relevant natural products
Authors: Owen Jeremy G. , Reddy Boojala Vijay B. , Ternei Melinda A. , Charlop-Powers Zachary , Calle Paula Y. , Kim Jeffrey H. , Brady Sean F.
Published: July 2013

Complex microbial ecosystems contain large reservoirs of unexplored biosynthetic diversity. Here we provide an experimental framework and data analysis tool to facilitate the targeted discovery of natural-product biosynthetic gene clusters from the environment. Multiplex sequencing of barcoded PCR amplicons is followed by sequence similarity directed data parsing to identify sequences bearing close resemblance to biosynthetically or biomedically interesting gene clusters. Amplicons are then mapped onto arrayed metagenomic libraries to guide the recovery of targeted gene clusters. When applied to adenylation- and ketosynthase-domain amplicons derived from saturating soil DNA libraries, our analysis pipeline led to the recovery of biosynthetic clusters predicted to encode for previously uncharacterized glycopeptide- and lipopeptide-like antibiotics; thiocoraline-, azinomycin-, and bleomycin-like antitumor agents; and a rapamycin-like immunosuppressant. The utility of the approach is demonstrated by using recovered eDNA sequences to generate glycopeptide derivatives. The experiments described here constitute a systematic interrogation of a soil metagenome for gene clusters capable of encoding naturally occurring derivatives of biomedically relevant natural products. Our results show that previously undetected biosynthetic gene clusters with potential biomedical relevance are very common in the environment. This general process should permit the routine screening of environmental samples for gene clusters capable of encoding the systematic expansion of the structural diversity seen in biomedically relevant families of natural products.
The counterbend phenomenon in flagellar axonemes and cross-linked filament bundles
Authors: Gadêlha Hermes , Gaffney Eamonn A. , Goriely Alain
Published: July 2013

Recent observations of flagellar counterbend in sea urchin sperm show that the mechanical induction of curvature in one part of a passive flagellum induces a compensatory countercurvature elsewhere. This apparent paradoxical effect cannot be explained using the standard elastic rod theory of Euler and Bernoulli, or even the more general Cosserat theory of rods. Here, we develop a geometrically exact mechanical model to describe the statics of microtubule bundles that is capable of predicting the curvature reversal events observed in eukaryotic flagella. This is achieved by allowing the interaction of deformations in different material directions, by accounting not only for structural bending, but also for the elastic forces originating from the internal cross-linking mechanics. Large-amplitude static configurations can be described analytically, and an excellent match between the model and the observed counterbend deformation was found. This allowed a simultaneous estimation of multiple sperm flagellum material parameters, namely the cross-linking sliding resistance, the bending stiffness, and the sperm head junction compliance ratio. We further show that small variations on the empirical conditions may induce discrepancies for the evaluation of the flagellar material quantities, so that caution is required when interpreting experiments. Finally, our analysis demonstrates that the counterbend emerges as a fundamental property of sliding resistance in cross-linked filamentous polymer bundles, which also suggests that cross-linking proteins may contribute to the regulation of the flagellar waveform in swimming sperm via counterbend mechanics.
Thermodynamic origins of protein folding, allostery, and capsid formation in the human hepatitis B virus core protein
Authors: Alexander Crispin G. , Jürgens Maike C. , Shepherd Dale A. , Freund Stefan M. V. , Ashcroft Alison E. , Ferguson Neil
Published: July 2013

Significance

Hepatitis B virus (HBV) is a major pathogen, yet no fully effective therapies exist. HBc is the multifunctional, capsid-forming protein essential for HBV replication. HBc structural plasticity is reportedly functionally important. We analyzed the folding mechanism of HBc using a multidisciplinary approach, including microscale thermophoresis and ion mobility spectrometry–mass spectrometry. HBc folds in a 3-state transition with a dimeric, helical intermediate. We found evidence of a strained native ensemble wherein the energy landscapes for folding, allostery, and capsid formation are linked. Mutations thermodynamically trapped HBc in conformations unable to form capsids, suggesting chemical chaperones could elicit similar, potentially antiviral, effects.
Endothelial cell junctional adhesion molecule C plays a key role in the development of tumors in a murine model of ovarian cancer
Authors: Leinster David A. , Colom Bartomeu , Whiteford James R. , Ennis Darren P. , Lockley Michelle , McNeish Iain A. , Aurrand‐Lions Michel , Chavakis Triantafyllos , Imhof Beat A. , Balkwill Frances R. , Nourshargh Sussan
Published: July 2013

Junctional adhesion molecule C (JAM‐C) is a transmembrane protein with significant roles in regulation of endothelial cell (EC) functions, including immune cell recruitment and angiogenesis. As these responses are important in promoting tumor growth, the role of EC JAM‐C in tumor development was investigated using the ID8 syngeneic model of ovarian cancer. Within 10–15 wk, intraperitoneally injected ID8 cells form multiple tumor deposits and ascites that resemble human high‐grade serous ovarian cancer. Compared to wild‐type mice, survival in this model was increased in EC JAM‐C knockouts (KOs; 88 vs. 96 d, P=0.04) and reduced in EC JAM‐C transgenics (88 vs. 78.5 d, P=0.03), mice deficient in or overexpressing EC JAM‐C, respectively. While tumor growth was significantly reduced in EC JAM‐C KOs (87% inhibition at 10 wk, P<0.0005), this was not associated with alterations in tumor vessel density or immune cell infiltration. However, tumor microvessels from EC JAM‐C‐deficient mice exhibited reduced pericyte coverage and increased vascular leakage, suggesting a role for EC JAM‐C in the development of functional tumor vessels. These findings provide evidence for a role for EC JAM‐C in tumor growth and aggressiveness as well as recruitment of pericytes to newly formed blood vessels in a model of ovarian cancer.—Leinster, D. A., Colom, B., Whiteford, J. R., Ennis, D. P., Lockley, M., McNeish, I. A., Aurrand‐Lions, M., Chavakis, T., Imhof, B. A., Balkwill, F. R., Nourshargh, S., Endothelial cell junctional adhesion molecule C plays a key role in the development of tumors in a murine model of ovarian cancer. FASEB J. 27, 4244–4253 (2013). www.fasebj.org
N-linked glycan in tick-borne encephalitis virus envelope protein affects viral secretion in mammalian cells, but not in tick cells
Authors: Yoshii Kentaro , Yanagihara Natsumi , Ishizuka Mariko , Sakai Mizuki , Kariwa Hiroaki
Published: July 2013

Tick-borne encephalitis virus (TBEV) is a zoonotic disease agent that causes severe encephalitis in humans. The envelope protein E of TBEV has oneN-linked glycosylation consensus sequence, but little is known about the biological function of theN-linked glycan. In this study, the function of protein E glycosylation was investigated using recombinant TBEV with or without the protein EN-linked glycan. Virion infectivity was not affected after removing theN-linked glycans usingN-glycosidase F. In mammalian cells, loss of glycosylation affected the conformation of protein E during secretion, reducing the infectivity of secreted virions. Mice subcutaneously infected with TBEV lacking protein E glycosylation showed no signs of disease, and viral multiplication in peripheral organs was reduced relative to that with the parental virus. In contrast, loss of glycosylation did not affect the secretory process of infectious virions in tick cells. Furthermore, inhibition of transport to the Golgi apparatus affected TBEV secretion in mammalian cells, but not in tick cells, indicating that TBEV was secreted through an unidentified pathway after synthesis in endoplasmic reticulum in tick cells. These results increase our understanding of the molecular mechanisms of TBEV maturation.
Empirical tests of the Marshall‐Lerner condition: a literature review
Authors: Bahmani Mohsen , Harvey Hanafiah , Hegerty Scott W.
Published: July 2013

Purpose

The Marshall‐Lerner (M‐L) condition, which stipulates that a devaluation or depreciation of its currency will improve a country's trade balance only if the sum of the absolute values of a country's import and export price elasticities are greater than one, is a fundamental tenet of international economics. The purpose of this study is to survey the literature that has tested the M‐L condition, examining in particular whether previous studies' results are statistically significant. The authors then conduct their own estimation of 29 countries' trade elasticities, over the past few decades.

Design/methodology/approach

While mostly a review paper, the paper also applies statistical techniques in two ways. First, the authors use t‐tests on previously‐published statistical results to see if the sums of their elasticities are significantly greater than one. The authors also apply the recently developed ARDL cointegration method, which has a number of attractive statistical properties, to estimate 29 countries' long‐run import and export elasticities and test the M‐L condition using recent data.

Findings

The authors re‐estimation using previous studies' coefficients and standard errors shows that, although the point estimates in many studies suggest that the M‐L condition is met, it really is not met in half of the cases. This lack of evidence is confirmed with the authors' own empirical tests.

Research limitations/implications

Not only does this paper collect the relevant literature in a way that will assist future researchers on the topic, these findings suggest that support for the M‐L condition is much weaker that commonly thought. This therefore makes an important contribution to thinking regarding the potential benefits of devaluation, and to economic theory in general.

Practical implications

Policymakers who hope to improve their countries' competitive position could benefit from learning that this policy is indeed less effective than might be supposed. This could lead to the implementation of more effective economic policies.

Originality/value

As a literature review, the originality of this paper is that it collects relevant studies into one single paper. The statistical analyses allow the reader to re‐interpret these studies' findings in a new light.
A study on next‐generation digital library using context‐awareness technology
Authors: Noh Younghee
Published: July 2013

Purpose

This study seeks to examine the concepts of context, context‐awareness, and context‐awareness technology needed for applying context‐awareness technology to the next‐generation of digital libraries, and proposed context‐aware services that can be applied to any situation by illustrating some library contexts.

Design/methodology/approach

The paper investigated both theoretical research and case analysis studies before suggesting a service model for context‐awareness‐based libraries by examining the context, context‐awareness, and context‐awareness technology in depth.

Findings

This paper derived possible library services which could be provided if context‐awareness services are implemented by examining and analyzing case studies and systems constructed in other fields. A library‐applied context‐aware system could recognize users entering the library and provide optimal services tailored to each situation for both new and existing users. In addition, the context‐awareness‐based library could provide context‐awareness‐based reference services, context‐awareness‐based loan services, and cater to other user needs in the stacks, research space, and a variety of other information spaces. The context‐awareness‐based library could also recognize users in need of emergency assistance by detecting the user's behavior, movement path, and temperature, etc. Comfort or climate‐control services could provide the user with control of the temperature, humidity, illumination and other environmental elements to fit the circumstances of users, books, and instruments through context‐aware technology.

Practical implications

Next‐generation digital libraries apply new concepts such as semantic retrieval, real‐time web, cloud computing, mobile web, linked data, and context‐awareness. Context‐awareness‐based libraries can provide applied context‐awareness access service, reactive space according to the user's access, applied context‐awareness lobbies, applied context‐awareness reference services, and applied context‐awareness safety services, context‐awareness‐based comfort services and so on.

Originality/value

Real instances of libraries applying context‐aware technology are few, according to the investigative results of this study. The study finds that the next‐generation digital library using context‐awareness technology can provide the best possible service for the convenience of its users.
The servicescape as an antecedent to service quality and behavioral intentions
Authors: Hooper Daire , Coughlan Joseph , R. Mullen Michael
Published: July 2013

Purpose

– The purpose of this paper is to examine whether the servicescape should be subsumed as a dimension within service quality conceptualizations or whether it is a unique construct in itself which precedes service quality evaluations and behavioral intentions. The authors both propose and operationalize this model and in doing so make a theoretical contribution by demonstrating how a delineation between these two constructs is necessary in order for theory to progress in this area.

Design/methodology/approach

– A total of 355 customers were intercepted as they exited a retail store and surveyed using a structured questionnaire. The data were then analyzed using structural equation modeling to test the research hypotheses.

Findings

– This paper finds that it is more appropriate to model the servicescape as a separate construct which precedes service quality thus highlighting a need for a demarcation to be made between these important constructs. In addition, the authors find that design is a significant contributor to behavioral intentions further confirming the necessity to manage service environments in order to generate repatronage behaviors.

Practical implications

– Service providers should consider the influence of store environments in shaping service quality perceptions and their subsequent impact on behavioral intentions.

Originality/value

– The paper adds to the existing literature by disentangling the complicated relationships between service environments, service quality and behavioral intentions. Furthermore, the findings indicate to practitioners which aspects of the servicescape require attention so as to maximize repatronage intentions.
Managing customer misbehavior: challenges and strategies
Authors: C. Harris Lloyd , Daunt Kate
Published: July 2013

Purpose

– In this study the authors aim to explore the impact of customer misbehavior on frontline employees and managers and to elucidate the management tactics and strategies that managers employ in an attempt to minimize the impact of customer misbehavior on the workplace.

Design/methodology/approach

– Following a discussion of the research design and methodology employed, the findings of 88 in-depth interviews are presented.

Findings

– These data suggest that customer misbehavior impacts on frontline employees, managers, and managerial strategies. Three main effects of customer misbehavior on customer-contact employees are uncovered: physiological, cognitive, and attitudinal. These are connected with four main management challenges: conflicting pressures, recruitment and retention, counseling and motivation, and time expenditure. Finally, data analysis finds evidence of six main ways in which managers attempted to reduce or to alleviate harmful customer misbehavior: selective recruitment, changes to training and induction procedures, enhanced rewards, work-team design, increase counseling, and alterations to the servicescape.

Practical implications

– The authors recommend that practitioners undertake a misbehavior audit that explores not only the extent of customer misbehavior but also the mechanisms, systems, and procedures the organization has for identifying, recording, and attempting to minimize the effects of dysfunctional customer behavior.

Originality/value

– This study contributes insights into how customer-contact personnel and managers are both affected and cope with customer misbehavior. These insights are helpful for service managers faced with customer misbehavior and academicians interested in how employees respond to contemporary customers.
An examination of consumers
'
resistance to computer-based technologies
Authors: G. Patsiotis Athanasios , Hughes Tim , J. Webber Don
Published: July 2013

Purpose

– This paper aims to provide a better understanding of non-adoption of technological interfaces. The majority of diffusion research on technological innovations does not distinguish clearly between non-adoption and resistance behavior and assumes a symmetrical or linear relationship between the positive and negative influencing factors. As a result, it has not recognized the different types of non-adoption.

Design/methodology/approach

– The determinants of customers
'
propensity to adopt or not to adopt computer-based technologies were examined in the context of internet banking. Several multivariate analysis methods were combined to examine the dimensionality of the constructs involved and their explanatory power on customer intentions and usage behavior.

Findings

– The resulting five dimensions revealed new links that help to explain customer intention in relation to usage behavior. The results reveal that some of the factors explaining non-adoption are not the opposite of those explaining adoption behavior and that others influence positively both behaviors. It is also found that pre-adoption behavior may be different from usage behavior and that delay behavior may be characterized by different phases.

Research limitations/implications

– The findings of this exploratory study suggest new evidence on non-adoption behavior that may stimulate further research inquiry.

Practical implications

– Recognizing these different aspects of customer behavior in relation to adoption/non-adoption has implications for managers involved in utilizing the internet as a channel for customer service.

Originality/value

– This study examined diffusion of innovation from a different angle, looking at non-adoption behavior which may sometimes be the result of some kind of resistance.