bluuebunny/crossref_metadata_2025 huggingface dataset:
Symplectic finite‐difference time‐domain scheme based on decomposition technique of the exponential operator for plasma media
Authors: Liu Song , He Zhifang , Cheng Sheng , Zhong Shuang‐ying
Published: October 2015

The electromagnetic waves propagation in dispersive media is modelled using symplectic finite‐difference time‐domain (SFDTD) method based on decomposition technique of the exponential operator. The numerical stability and the dispersion relationships are presented. The numerical dispersion and dissipation errors originated from SFDTD method for non‐magnetised collisional plasma medium are computed by comparing the real part and imaginary of numerical wave number with this analytic wave number. The high accuracy and efficiency is also confirmed by computing the reflection and transmission coefficients for a non‐magnetised collision plasma slab. The numerical results show that the SFDTD method not only improves computational efficiency but also needs less computer memory as compared with the existing FDTD method. It can also be seen clearly that the eigenfrequency of the cavity resonator is filled with plasma media offsets. This conclusion has potential applications in the design of new types of microwave devices.
Auxiliary circuit for zero‐voltage‐transition interleaved pulse‐width modulation buck converter
Authors: Esteki Morteza , Adib Ehsan , Farzanehfard Hosein , Arshadi Sayed Abbas
Published: October 2015

An interleaved zero‐voltage‐transition (ZVT) pulse‐width modulation (PWM) buck converter is proposed in this study. The proposed converter consists of two identical buck converters connected in parallel and an auxiliary circuit. The auxiliary circuit has only one active switch. Zero‐voltage switching condition for main switches and also, zero‐current switching condition for the auxiliary circuit semiconductor components are achieved. Principle of operation and analysis of the proposed converter is provided. Moreover, the extension of the proposed idea to interleaved buck–boost, interleaved flyback and interleaved forward converters are presented. A 160 W prototype of the proposed ZVT PWM buck converter is implemented and the results are presented to verify the validity of theoretical analysis.
Design of synchronous reference frame phase‐locked loop with the presence of dc offsets in the input voltage
Authors: Kulkarni Abhijit , John Vinod
Published: October 2015

A novel small‐signal state‐space model is formulated for the commonly used synchronous reference frame phase‐locked loop (SRF‐PLL). Using this model, the effect of dc offsets as a function of SRF‐PLL design parameters is quantified. It is shown that the unit vectors produced by the phase‐locked loop (PLL) will have dc offsets when the input contains dc offsets. This can result in dc injection to the grid, which is highly undesirable. A systematic design method is proposed which ensures that dc injection to the grid is within the prescribed grid interconnection standards. In this design, SRF‐PLL bandwidth is analytically computed for different levels of dc offsets in the input. The proposed design is compared with conventional pre‐filter‐based designs addressing the dc offset issue. The proposed design method results in the fastest transient response for given worst‐case input dc offset without changing the PLL structure. Such a design for the SRF‐PLL is computationally less intensive and is preferable when low‐end digital controllers are used. The analytical results have been verified experimentally.
Improved Y‐source DC–AC converter with continuous input current
Authors: Ahrabi Rouzbeh Reza , Banaei Mohamad Reza
Published: October 2015

In this study, the structure of Y‐source converter is improved in order to achieve continuous current at the input side of the Y‐source converter. Continuous input current reduces the size and stress of utilised elements. In addition to shoot‐through duty cycle, the proposed converter uses coupled transformer to produce the required voltage gain. The obtained gain can be tuned by varying the turns ratio of the coupled transformer. Shared core is used for all windings. Hence, the cost of transformer is almost fixed in comparison with the related structures, but voltage gain is much higher than similar structures. The operating principles and steady‐state analyses are presented to express the operational concept. Also, experimental results are given to verify the validity of the proposed converter.
Simple scheme to extract maximum power from series connected photovoltaic modules experiencing mismatched operating conditions
Authors: Debnath Dipankar , De Pronoy , Chatterjee Kishore
Published: October 2015

Solar photovoltaic (PV) arrays formed by series combination of several PV modules suffer from considerable reduction in power yield when subjected to mismatched operating conditions. To address this issue several schemes have been reported in the literature. Amongst these schemes, the distributed maximum power point tracking (DMPPT) schemes seem to be the most promising ones. However, majority of the existing DMPPT schemes employ voltage‐equalisation technique, which cannot attain exact MPP for all the modules. To overcome this problem individual power measurement units are employed for each of the module but then it leads to the involvement of large number of sensors. Schemes which do not require modular level sensing have also been reported but they require to employ a very computational intensive control algorithm coupled with the need for precise communication. This study attempts to address these limitations by proposing a simpler DMPPT strategy. It requires only one conventional MPPT algorithm to extract maximum power from the overall system. The implementation of the scheme is carried out by utilising the power circuit configuration of the existing flyback‐converter based standard DMPPT scheme. The viability of the scheme is ascertained through detailed simulation and experimental studies.
Single‐phase multi‐level AC–DC power conversion interface
Authors: Wu Jinn‐Chang , Jou Hurng‐Liahng , Jhang Jian Jyun‐Yi
Published: October 2015

This study proposes a single‐phase multi‐level AC–DC power conversion interface that is composed of a power factor correction stage and a buck power conversion stage. The power factor correction stage is configured using two power factor correctors (PFCs) connected in cascade. Only the power electronic switch in one of the PFCs is switched in high‐frequency pulse‐width modulation to generate a five‐level voltage at the input AC terminals of the power factor correction stage. The input current of the power factor correction stage is controlled to be sinusoidal and in phase with the utility voltage. Accordingly, the voltage stress and switching loss are improved because the change in voltage in each switching operation is reduced. The filter inductance and the electromagnetic interference are also reduced. The buck power conversion stage integrates a buck power converter and a forward power converter that combines the output voltages of the two PFCs in a stable DC voltage that supplies the load. The controllers for the buck power converter and the forward power converter are integrated to simplify the controller for the buck power conversion stage. A hardware prototype is developed to verify the performance of the proposed single‐phase AC–DC power conversion interface.
Optimisation of offshore wind farm cable connection layout considering levelised production cost using dynamic minimum spanning tree algorithm
Authors: Hou Peng , Hu Weihao , Chen Cong , Chen Zhe
Published: October 2015

The approach in this study has been developed to optimise the cable connection layout of large‐scale offshore wind farms. The objective is to minimise the levelised production cost (LPC) of an offshore wind farm by optimising the cable connection configuration. On the basis of the minimum spanning tree (MST) algorithm, an improved algorithm, the dynamic MST algorithm is proposed. The current carrying capacity of the cable is considered to be the main constraint and the cable sectional area is changed dynamically. An irregular shaped wind farm is chosen as the studied case and the results are compared with the layout obtained by a traditional MST algorithm. Simulation results show that the proposed method is an effective way for offshore wind farm collection system layout design.
Review of micro‐Doppler signatures
Authors: Tahmoush Dave
Published: October 2015

Micro‐Doppler signals refer to Doppler scattering returns produced by the motions of the target other than gross translation. The small micro‐motions of a subject, and even just parts of a subject, can be observed through the micro‐Doppler signature it creates in response to an active emitter such as a radar, laser, and even acoustic emitters. These micro‐Doppler signatures are produced by the kinematic properties of the subject's motion and can be used to extract the salient features of the subject's motion, and often, identify the subject. The rapidly declining cost of micro‐Doppler‐capable active sensors like radar with their dramatically improving capabilities, provide significant motivation in developing micro‐Doppler techniques that can improve the exploitation of these sensors. Micro‐Doppler techniques aim at extracting the micro‐motion of the subject that may be unique to a particular subject class or activity in order to distinguish probable false alarms from real detections, as well as to increase the value of the information extracted from the sensor. The source of micro‐motion depends on the subject and can be a rotating propeller on a fixed‐wing aircraft, the multiple spinning rotor blades of a helicopter, or an unmanned aerial vehicle (UAV); the vibrations of an engine shaking a vehicle; an antenna rotating on a ship; the flapping wings of birds; the swinging arms and legs of a walking person; and many other sources. Confuser detections, such as birds for UAVs or animals for humans, can be interpreted as false alarms for a sensor system, so using the available micro‐Doppler returns for classification can significantly reduce the sensor false alarm rate, thereby improving the utility of the sensor system. This study reviews the current research in micro‐Doppler based on subject type, sensor capabilities, as well as environmental effects, and then proposes future research areas for micro‐Doppler.
Sparse electrocardiogram signals recovery based on solving a row echelon‐like form of system
Authors: Cai Pingmei , Wang Guinan , Yu Shiwei , Zhang Hongjuan , Ding Shuxue , Wu Zikai
Published: October 2015

The study of biology and medicine in a noise environment is an evolving direction in biological data analysis. Among these studies, analysis of electrocardiogram (ECG) signals in a noise environment is a challenging direction in personalized medicine. Due to its periodic characteristic, ECG signal can be roughly regarded as sparse biomedical signals. This study proposes a two‐stage recovery algorithm for sparse biomedical signals in time domain. In the first stage, the concentration subspaces are found in advance. Then by exploiting these subspaces, the mixing matrix is estimated accurately. In the second stage, based on the number of active sources at each time point, the time points are divided into different layers. Next, by constructing some transformation matrices, these time points form a row echelon‐like system. After that, the sources at each layer can be solved out explicitly by corresponding matrix operations. It is noting that all these operations are conducted under a weak sparse condition that the number of active sources is less than the number of observations. Experimental results show that the proposed method has a better performance for sparse ECG signal recovery problem.
Quantum size effect across semiconductor‐to‐metal phase transition in vanadium dioxide thin films
Authors: Khan G.R. , Bhat B.A.
Published: October 2015

The phase transition temperature of vanadium dioxide (VO2) thin films shifts to the vicinity of room temperature by reducing the dimensions from microscale to nanoscale without the use of any dopant. This quantum size effect elucidated by studying the structural, optical and electrical properties of nanothin and microthin films of VO2 across their semiconductor–metal phase transitions has been demonstrated in this reported work. The films fabricated on glass substrates via the inorganic sol–gel route were characterised by Rutherford backscattering spectrometry (RBS), X‐ray diffractometery, scanning electron microscopy, ultraviolet–visible spectroscopy and the four‐probe method. The RBS results estimate a layer thickness of 15 and 291 nm for nanothin and microthin films, respectively. The films were polycrystalline in their nature of [011] orientation with regular and irregular crystallites of a cuboidal surface morphology. Estimation of crystallite size revealed that nanothin films attain poor crystallinity as compared with microthin films. The blue shift was observed in nanothin films from microthin films as maximum absorption occurred at wavelengths of 360 and 443 nm, respectively. Optical bandgaps of 2.3 and 1.87 eV were found for nanothin and microthin films, respectively. Depletion in metal‐to‐semiconductor and semiconductor‐to‐metal transition temperatures were experienced from higher temperature regimes of 341 and 335 K for microthin films to lower temperature regimes of 319 and 305 K for nanothin films, respectively.
3D self-consistent modeling of a matrix source of negative hydrogen ions
Authors: Tarnev Kh. , Demerdjiev A. , Shivarova A. , Lishev St.
Published: October 2015

The paper is in the scope of studies on the rf driving of a matrix source of negative hydrogen ions: a matrix of small radius discharges with planar-coil inductive driving and single aperture extraction from each discharge. The results from a three-dimensional model, in which plasma description is coupled to electrodynamics, confirm former conclusion that a single coil driving of the whole matrix by a zigzag coil with an omega-shaped conductor on the bottom of each discharge tube ensures efficient rf power deposition to the plasma. The latter is due to similarities with the rf driving of a single discharge by a single planar coil, shown by the obtained induced current and spatial distribution of the plasma parameters. Distinctions associated with the coil configuration as a single coil for the whole matrix are also discussed.
Far tails of the density of states in amorphous organic semiconductors
Authors: Novikov S. V.
Published: October 2015

Far tails of the density of state (DOS) are calculated for the simple models of organic amorphous material, the model of dipolar glass and model of quadrupolar glass. It was found that in both models far tails are non-Gaussian. In the dipolar glass model, the DOS is symmetric around zero energy, while for the model of quadrupolar glass, the DOS is generally asymmetric and its asymmetry is directly related to the particular geometry of quadrupoles. Far tails of the DOS are relevant for the quasi-equilibrium transport of the charge carriers at low temperature. Asymmetry of DOS in quadrupolar glasses means a principal inequivalence of the random energy landscape for the transport of electrons and holes. Possible effect of the non-Gaussian shape of the far tails of the DOS on the temperature dependence of carrier drift mobility is discussed.
Low field domain wall dynamics in artificial spin-ice basis structure
Authors: Kwon J. , Goolaup S. , Lim G. J. , Kerk I. S. , Chang C. H. , Roy K. , Lew W. S.
Published: October 2015

Artificial magnetic spin-ice nanostructures provide an ideal platform for the observation of magnetic monopoles. The formation of a magnetic monopole is governed by the motion of a magnetic charge carrier via the propagation of domain walls (DWs) in a lattice. To date, most experiments have been on the static visualization of DW propagation in the lattice. In this paper, we report on the low field dynamics of DW in a unit spin-ice structure measured by magnetoresistance changes. Our results show that reversible DW propagation can be initiated within the spin-ice basis. The initial magnetization configuration of the unit structure strongly influences the direction of DW motion in the branches. Single or multiple domain wall nucleation can be induced in the respective branches of the unit spin ice by the direction of the applied field.
Comment on “A novel and facile decay path of Criegee intermediates by intramolecular insertion reactions via roaming transition states” [J. Chem. Phys. 142, 124312 (2015)]
Authors: Harding Lawrence B. , Klippenstein Stephen J.
Published: October 2015

We discuss the recent report of a roaming type mechanism for the decomposition of the Criegee intermediate. We show that the predicted barrier height for this new pathway is too low by ∼30 kcal/mol owing to an inconsistent use of spin-restricted and spin-unrestricted calculations. As a result, this new pathway is not expected to compete significantly with the well-known dioxirane pathways for the decomposition of the Criegee intermediate.
A comparative study of capacitively coupled HBr/He, HBr/Ar plasmas for etching applications: Numerical investigation by fluid model
Authors: Gul Banat , Aman-ur-Rehman
Published: October 2015

Fluid model has been applied to perform a comparative study of hydrogen bromide (HBr)/He and HBr/Ar capacitively coupled plasma discharges that are being used for anisotropic etching process. This model has been used to identify the most dominant species in HBr based plasmas. Our simulation results show that the neutral species like H and Br, which are the key player in chemical etching, have bell shape distribution, while ions like HBr+, Br+, which play a dominant rule in the physical etching, have double humped distribution and show peaks near electrodes. It was found that the dilution of HBr by Ar and/or He results in an increase in electron density and electron temperature, which results in more ionization and dissociation and hence higher densities of neutral and charged species can be achieved. The ratio of positive ion flux to the neutral flux increases with an increase in additive gas fraction. Compare to HBr/He plasma, the HBr/Ar plasma shows a maximum change in the ion density and flux and hence the etching rate can be considered in the ion-assisted and in the ion-flux etch regime in HBr/Ar discharge. The densities of electron and other dominant species in HBr/Ar plasma are higher than those of HBr/He plasma. The densities and fluxes of the active neutrals and positive ions for etching and subsequently chemical etching versus physical sputtering in HBr/Ar and HBr/He plasmas discharge can be controlled by tuning gas mixture ratio and the desire etching can be achieved.
Influence of voltage rise time on microwave generation in relativistic backward wave oscillator
Authors: Wu Ping , Sun Jun , Teng Yan , Deng Yuqun , Shi Yanchao , Chen Changhua
Published: October 2015

In relativistic backward wave oscillators (RBWOs), although the slow wave structure (SWS) and electron beam determine the main characteristics of beam-wave interaction, many other factors can also significantly affect the microwave generation process. This paper investigates the influence of voltage rise time on beam-wave interaction in RBWOs. Preliminary analysis and PIC simulations demonstrate if the voltage rise time is moderately long, the microwave frequency will gradually increase during the startup process until the voltage reaches its amplitude, which can be explained by the dispersion relation. However, if the voltage rise time is long enough, the longitudinal resonance of the finitely-long SWS will force the RBWO to work with unwanted longitudinal modes for a while and then gradually hop to the wanted longitudinal mode, and this will lead to an impure microwave frequency spectrum. Besides, a longer voltage rise time will delay the startup process and thus lead to a longer microwave saturation time. And if unwanted longitudinal modes are excited due to long voltage rise time, the microwave saturation time will be further lengthened. Therefore, the voltage rise time of accelerators adopted in high power microwave technology should not be too long in case unwanted longitudinal modes are excited.
Quantum photonics hybrid integration platform
Authors: Murray E. , Ellis D. J. P. , Meany T. , Floether F. F. , Lee J. P. , Griffiths J. P. , Jones G. A. C. , Farrer I. , Ritchie D. A. , Bennett A. J. , Shields A. J.
Published: October 2015

Fundamental to integrated photonic quantum computing is an on-chip method for routing and modulating quantum light emission. We demonstrate a hybrid integration platform consisting of arbitrarily designed waveguide circuits and single-photon sources. InAs quantum dots (QD) embedded in GaAs are bonded to a SiON waveguide chip such that the QD emission is coupled to the waveguide mode. The waveguides are SiON core embedded in a SiO2 cladding. A tuneable Mach Zehnder interferometer (MZI) modulates the emission between two output ports and can act as a path-encoded qubit preparation device. The single-photon nature of the emission was verified using the on-chip MZI as a beamsplitter in a Hanbury Brown and Twiss measurement.
Fano resonance based optical modulator reaching 85% modulation depth
Authors: Zhao Wenyu , Jiang Huan , Liu Bingyi , Jiang Yongyuan , Tang Chengchun , Li Junjie
Published: October 2015

In this paper, we demonstrate the combination of nematic liquid crystal with a binary silicon nanohole array to realize a high performance Fano resonance based optical modulator. The simulations using a finite difference time domain method reveal that the sharp Fano profile in the binary array originates from the interaction of the in-phased and anti-phased lattice collective resonance hybridized through lattice coupling effects. Experimental results agree very well with the simulations and demonstrate the strong dependence of the Q factor and spectral contrast of the resonance on the radius difference of the two nanohole arrays. Infiltrated with nematic liquid crystal, E7, the Fano profile can be dynamically and continuously tuned by an applied voltage, and an unprecedented modulation depth up to 85% is achieved.
First-principles study on elastic and superconducting properties of Nb3Sn and Nb3Al under hydrostatic pressure
Authors: Zhang Rui , Gao Peifeng , Wang Xingzhe , Zhou Youhe
Published: October 2015

The low temperature superconducting materials, such as Nb3Sn and Nb3Al, have similar crystal structures and elastic properties. However, their critical-temperature degradations always show the distinct way under mechanical stresses. In this study, first-principles calculations for the low temperature superconductors based on plane-wave pseudo-potential density functional theory within the generalized gradient approximation are implemented, and the elastic moduli of Nb3Sn and Nb3Al and those superconductivities in the presence of hydrostatic pressure are evaluated. The Debye temperatures are obtained by the bulk moduli and shear moduli of superconducting materials. The MacMillan equation is further used to acquire the critical temperatures of Nb3Sn and Nb3Al under different hydrostatic pressures. It is found that the elastic constants and bulk moduli of the low temperature superconductors are enhanced by the applied hydrostatic pressure, while the critical temperatures usually are decreased with the pressure. Additionally, the decrease of critical-temperature for Nb3Sn is more sensitive to the hydrostatic pressure than the one for Nb3Al. The prediction results show good agreement with the experimental results in the literatures qualitatively.
Efficient new process for the desulfurization of mixtures of air and hydrogen sulfide via a dielectric barrier discharge plasma
Authors: Dahle S.
Published: October 2015

The efficient removal of hydrogen sulfide, H2S, from streams of H2S in air via a dielectric barrier discharge (DBD) plasma has been investigated using a quadrupole mass spectrometer. A suitable plasma device with a reservoir for storing sorbent powder of various kinds within the plasma region was constructed. Plasma treatments of gas streams with high concentrations of hydrogen sulfide in air yielded a removal of more than 98% of the initial hydrogen sulfide and a deposition of sulfur at the surface of the dielectric, while small amounts of sulfur dioxide were generated. The presence of calcium carbonate within the plasma region of the DBD device resulted in the removal of over 99% of the initial hydrogen sulfide content and the removal of 98% of the initial sulfur dioxide impurities from the gas mixture.
Population reversal driven by unrestrained interactions in molecular dynamics simulations: A dialanine model
Authors: Pullara Filippo , General Ignacio J.
Published: October 2015

Standard Molecular Dynamics simulations (MD) are usually performed under periodic boundary conditions using the well-established “Ewald summation”. This implies that the distance among each element in a given lattice cell and its corresponding element in another cell, as well as their relative orientations, are constant. Consequently, protein-protein interactions between proteins in different cells—important in many biological activities, such as protein cooperativity and physiological/pathological aggregation—are severely restricted, and features driven by protein-protein interactions are lost. The consequences of these restrictions, although conceptually understood and mentioned in the literature, have not been quantitatively studied before. The effect of protein-protein interactions on the free energy landscape of a model system, dialanine, is presented. This simple system features a free energy diagram with well-separated minima. It is found that, in the case of absence of peptide-peptide (p-p) interactions, the ψ = 150° dihedral angle determines the most energetically favored conformation (global free-energy minimum). When strong p-p interactions are induced, the global minimum switches to the ψ = 0° conformation. This shows that the free-energy landscape of an individual molecule is dramatically affected by the presence of other freely interacting molecules of its same type. Results of the study suggest how taking into account p-p interactions in MD allows having a more realistic picture of system activity and functional conformations.
Molecularly Imprinted TiO2/WO3-Coated Magnetic Nanocomposite for Photocatalytic Degradation of 4-Nitrophenol Under Visible Light
Authors: Wei Shoutai , Liu Hualong , He Chiyang , Liang Ying
Published: October 2015

In this paper, a molecularly imprinted TiO2/WO3-coated magnetic Fe3O4@SiO2 nanocomposite was developed for photocatalytic degradation. Fe3O4 nanoparticles were first prepared by a traditional co-precipitation method, and then a SiO2 shell was grown on the surface of the Fe3O4 nanoparticles. Finally, a 4-nitrophenol imprinted TiO2/WO3 coating was obtained on the surface of the Fe3O4@SiO2 nanocomposite via a sol-gel method and subsequent calcination. The new composite was characterised by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high resolution TEM (HRTEM) and vibrating sample magnetometry (VSM). In addition, the adsorption ability and photocatalytic activity of the composite were investigated. Results showed that the imprinted composite had higher adsorption ability for the template than the non-imprinted composite. The imprinted catalyst could degrade 4-nitrophenol under visible light with a first-order reaction rate of 0.1039 h–1, which was ~2.5 times that of the non-imprinted catalyst. The new imprinted catalyst showed good catalytic selectivity, an ease of being recycled by an external magnetic field, good reusability, no need for additional chemicals, and allows the possibility of utilising solar light as energy resource. Therefore, the catalyst can be potentially applied for ‘green’, low-cost and effective degradation of 4-nitrophenol in real wastewater.
Follicular fluid and serum metabolites in Holstein cows are predictive of genetic merit for fertility
Authors: Moore S. G. , O'Gorman A. , Brennan L. , Fair T. , Butler S. T.
Published: October 2015

The aims of the present study were to: (1) characterise the metabolome of follicular fluid and serum in dairy cows with similar genetic merit for milk production but with extremes of good (Fert+) or poor (Fert–) genetic merit for fertility; and (2) identify potential biomarkers of dairy cow fertility. Follicular fluid from the first wave dominant follicle and serum were collected on Day 7 of the oestrous cycle. The most pronounced effect of genotype was noted in the serum, where the abundance of total polyunsaturated fatty acids and n-6 polyunsaturated fatty acids was greater in Fert+ cows, and the abundance of total saturated fatty acids was greater in Fert– cows. The abundance of nine fatty acids (arachidic acid, heneicosanoic acid, myristic acid, behenic acid, myristoleic acid, heptadecenoic acid, cis-11-eicosanoic acid, nervonic acid and γ-linolenic acid) in follicular fluid was affected by genotype. Concentrations of cysteine, leucine, ornithine, proline and tyrosine in follicular fluid, and asparagine, creatinine, cysteine, methionine, proline and valine in serum, were also affected by genotype. Receiver operating characteristic curve analysis indicated that the follicular fluid and serum fatty acids and follicular fluid amino acids that were significantly affected by genotype were highly predictive of fertility genotype.
Measuring wildland fire leadership: the crewmember perceived leadership scale
Authors: Waldron Alexis L. , Schary David P. , Cardinal Bradley J.
Published: October 2015

The aims of this research were to develop and test a scale used to measure leadership in wildland firefighting using two samples of USA wildland firefighters. The first collection of data occurred in the spring and early summer and consisted of an online survey. The second set of data was collected towards late summer and early fall (autumn). The second set of data was collected via hard-copy surveys that were mailed in by respondents who were recruited via email and in person at large wildland fires. Through confirmatory factor analyses, a three-factor, higher-order, multidimensional structure of leadership in wildland fire was supported. The Crewmember Perceived Leadership Scale consists of perceptions of competent decision-making, personal genuineness and integrity of supervisors as seen by their subordinates. Initial evidence of reliability and validity was supported during the first study of this research. Results from Study 1 indicate that higher rankings of fire leaders by their crewmembers was related to higher worker engagement and job satisfaction. The second study included an additional five items to rate fire leaders; the structure of the three leadership components was again supported. Implications for leadership development in wildland fire, future research and practice are discussed.
First record of limb preferences in monotremes (Zaglossus spp.)
Authors: Giljov Andrey , Karenina Karina , Hawkins Margaret , Malashichev Yegor
Published: October 2015

Lateralisation in forelimb use at the population and/or individual level has been found in a wide variety of vertebrate species. However, some large taxa have not yet been investigated and that limits a proper evolutionary interpretation of forelimb preferences. Among mammals lateralised use of the forelimbs has been shown for both placentals and marsupials, but nothing is known about behavioural lateralisation in monotremes. Here we examined lateral preferences in forelimb use in four long-beaked echidnas (male and female Zaglossus bruijni, and male and female Z. bartoni) in captivity. Three individuals showed significant forelimb preferences in unimanual behaviours associated with feeding. When stepping on an eminence with one forelimb first, the lateralisation at the individual level was found only in males of both species. During male–female interactions, the male Z. bartoni significantly preferred to put one of the forelimbs on the female’s back. In both males, the direction of preferences was consistent across different types of behaviour. Our results confirm that manual lateralisation, at least at the individual level, is widespread among mammals. Further research is needed to investigate whether the monotremes display population-level lateralisation in forelimb use.
p27
kip1
controls H-Ras/MAPK activation and cell cycle entry via modulation of MT stability
Authors: Fabris Linda , Berton Stefania , Pellizzari Ilenia , Segatto Ilenia , D’Andrea Sara , Armenia Joshua , Bomben Riccardo , Schiappacassi Monica , Gattei Valter , Philips Mark R. , Vecchione Andrea , Belletti Barbara , Baldassarre Gustavo
Published: October 2015

Significance

Different functions have been ascribed to p27
kip1
, originally identified as a universal cyclin-dependent kinase (CDK) inhibitor, fundamental for the control of cell proliferation and tumor progression. Yet, not all p27 functions can be explained by its ability to bind and inhibit CDKs. Here, we demonstrate that p27
kip1
controls cell cycle entry also through a CDK-independent function, by regulating microtubule stability. Following growth factor stimulation, p27
kip1
prevents full activation of H-Ras, acting on its subcellular compartmentalization, eventually restraining the activation of the MAPK pathway. Our work provides additional understanding of the mechanisms regulating the cell cycle and anticipates potential implications in diseases characterized by deregulated proliferation, such as cancer.
Extreme electron polaron spatial delocalization in π-conjugated materials
Authors: Rawson Jeff , Angiolillo Paul J. , Therien Michael J.
Published: October 2015

Significance

π-Conjugated organic molecules offer an added dimension to traditional inorganic materials in transistors, solar cells, and light-emitting diodes. The spatial extent over which charges are spread within an organic structure is associated with a material’s suitability for these applications. Here, using two experimental spectroscopic techniques, coupled with computational analysis, we determine the distribution of negative charges within designed organic molecules comprised of multiple π-conjugated repeat units. We find that negative charges in these highly conjugated organic structures are dispersed over greater areas relative to any other organic material that has been studied to date. This discovery is significant, as the design of organic materials that adeptly accommodate and transmit negative charges remains a significant challenge in materials science.
KH domain protein RCF3 is a tissue-biased regulator of the plant miRNA biogenesis cofactor HYL1
Authors: Karlsson Patricia , Christie Michael Danger , Seymour Danelle K. , Wang Huan , Wang Xi , Hagmann Jörg , Kulcheski Franceli , Manavella Pablo Andrés
Published: October 2015

Significance

Micro RNAs (miRNAs) are small RNA molecules that regulate gene expression posttranscriptionally in a process known as gene silencing. Fine-tuning the production of miRNAs is essential for correct silencing of their targets, which in turn is important for homeostasis and development. To fine-tune the production of miRNAs, plants deploy a combination of proteins that act as cofactors of the miRNA-processing machinery. Here, we describe REGULATOR OF CBF GENE EXPRESSION 3 (RCF3) as a tissue-specific regulator of miRNA biogenesis in plants. RCF3 interacts with the phosphatases C-TERMINAL DOMAIN PHOSPHATASE-LIKE1 and 2 (CPL1 and CPL2), ultimately affecting the phosphorylation of one of the main DICER-LIKE1 (DCL1) accessory proteins, HYPONASTIC LEAVES1 (HYL1), with a concomitant effect on miRNA production.
Structure and two-metal mechanism of a eukaryal nick-sealing RNA ligase
Authors: Unciuleac Mihaela-Carmen , Goldgur Yehuda , Shuman Stewart
Published: October 2015

Significance

Polynucleotide ligases are an ancient superfamily of nucleic acid repair enzymes that join 3′-OH and 5′-PO
4
DNA or RNA ends. Ligases react with ATP or NAD
+
to form a covalent enzyme–adenylate intermediate in which AMP is linked via a P–N bond to a lysine side-chain. This paper reports crystal structures of a eukaryal ATP-dependent RNA ligase (
Naegleria gruberi
RNA ligase, NgrRnl) that illuminate the stereochemistry and two-metal catalytic mechanism of the lysine adenylylation reaction. A signature N-terminal domain of NgrRnl binds the ATP γ-phosphate and orients the pyrophosphate leaving group apical to the lysine nucleophile. NgrRnl is the founder of a distinct RNA ligase clade, with homologs in diverse bacterial, viral, and eukaryal proteomes.
The engagement policies of the European Union, Georgia and Russia towards Abkhazia
Authors: Kereselidze Nino
Published: October 2015

Three major actors in the context of the conflict in Abkhazia have opted for different policies towards the de facto entity. This article argues that although Georgia and the EU have so far adhered to engagement without recognition policies towards Abkhazia (and South Ossetia), governance practices nurturing nation- and state-building in these entities, coupled with the Russian policy of recognition, constitute challenges to conflict resolution. Over 20 years since the wars in Georgia, present-day Abkhazia, despite limited community capacity, is asserting itself with nascent trends of state-building. To mitigate its isolation, the EU and Georgia need to develop a substantially different policy of engagement vis-à-vis Abkhazia embedding incentives towards a political solution of the conflict. This article draws heavily on interviews, documentaries and observational evidence, building on limited primary and secondary sources.
Angiotensin II down-regulates nephrin–Akt signaling and induces podocyte injury: role of c-Abl
Authors: Yang Qian , Ma Yiqiong , Liu Yipeng , Liang Wei , Chen Xinghua , Ren Zhilong , Wang Huiming , Singhal Pravin C. , Ding Guohua
Published: October 2015

Recent studies have shown that nephrin plays a vital role in angiotensin II (Ang II)–induced podocyte injury and thus contributes to the onset of proteinuria and the progression of renal diseases, but its specific mechanism remains unclear. c-Abl is an SH2/SH3 domain–containing nonreceptor tyrosine kinase that is involved in cell survival and regulation of the cytoskeleton. Phosphorylated nephrin is able to interact with molecules containing SH2/SH3 domains, suggesting that c-Abl may be a downstream molecule of nephrin signaling. Here we report that Ang II–infused rats developed proteinuria and podocyte damage accompanied by nephrin dephosphorylation and minimal interaction between nephrin and c-Abl. In vitro, Ang II induced podocyte injury and nephrin and Akt dephosphorylation, which occurred in tandem with minimal interaction between nephrin and c-Abl. Moreover, Ang II promoted c-Abl phosphorylation and interaction between c-Abl and SH2 domain–containing 5′-inositol phosphatase 2 (SHIP2). c-Abl small interfering RNA (siRNA) and STI571 (c-Abl inhibitor) provided protection against Ang II–induced podocyte injury, suppressed the Ang II-induced c-Abl–SHIP2 interaction and SHIP2 phosphorylation, and maintained a stable level of nephrin phosphorylation. These results indicate that c-Abl is a molecular chaperone of nephrin signaling and the SHIP2-Akt pathway and that the released c-Abl contributes to Ang II–induced podocyte injury.
OCRL1 engages with the F-BAR protein pacsin 2 to promote biogenesis of membrane-trafficking intermediates
Authors: Billcliff Peter G. , Noakes Christopher J. , Mehta Zenobia B. , Yan Guanhua , Mak LokHang , Woscholski Rudiger , Lowe Martin
Published: October 2015

Mutation of the inositol 5-phosphatase OCRL1 causes Lowe syndrome and Dent-2 disease. Loss of OCRL1 function perturbs several cellular processes, including membrane traffic, but the underlying mechanisms remain poorly defined. Here we show that OCRL1 is part of the membrane-trafficking machinery operating at the trans-Golgi network (TGN)/endosome interface. OCRL1 interacts via IPIP27A with the F-BAR protein pacsin 2. OCRL1 and IPIP27A localize to mannose 6-phosphate receptor (MPR)–containing trafficking intermediates, and loss of either protein leads to defective MPR carrier biogenesis at the TGN and endosomes. OCRL1 5-phosphatase activity, which is membrane curvature sensitive, is stimulated by IPIP27A-mediated engagement of OCRL1 with pacsin 2 and promotes scission of MPR-containing carriers. Our data indicate a role for OCRL1, via IPIP27A, in regulating the formation of pacsin 2–dependent trafficking intermediates and reveal a mechanism for coupling PtdIns(4,5)P2hydrolysis with carrier biogenesis on endomembranes.
How nontraditional model systems can save us
Authors: Gladfelter Amy S.
Published: October 2015

In this essay I would like to highlight how work in nontraditional model systems is an imperative for our society to prepare for problems we do not even know exist. I present examples of how discovery in nontraditional systems has been critical for fundamental advancement in cell biology. I also discuss how as a collective we might harvest both new questions and new solutions to old problems from the underexplored reservoir of diversity in the biosphere. With advancements in genomics, proteomics, and genome editing, it is now technically feasible for even a single research group to introduce a new model system. I aim here to inspire people to think beyond their familiar model systems and to press funding agencies to support the establishment of new model systems.
A LAPF/phafin1-like protein regulates TORC1 and lysosomal membrane permeabilization in response to endoplasmic reticulum membrane stress
Authors: Kim Adam , Cunningham Kyle W.
Published: October 2015

Lysosomal membrane permeabilization (LMP) is a poorly understood regulator of programmed cell death that involves leakage of luminal lysosomal or vacuolar hydrolases into the cytoplasm. In Saccharomyces cerevisiae, LMP can be induced by antifungals and endoplasmic reticulum stressors when calcineurin also has been inactivated. A genome-wide screen revealed Pib2, a relative of LAPF/phafin1 that regulates LMP in mammals, as a pro-LMP protein in yeast. Pib2 associated with vacuolar and endosomal limiting membranes in unstressed cells in a manner that depended on its FYVE domain and on phosphatidylinositol 3-phosphate (PI(3)P) biosynthesis. Genetic experiments suggest that Pib2 stimulates the activity of TORC1, a vacuole-associated protein kinase that is sensitive to rapamycin, in a pathway parallel to the Ragulator/EGO complex containing the GTPases Gtr1 and Gtr2. A hyperactivating mutation in the catalytic subunit of TORC1 restored LMP to the gtr1∆ and pib2∆ mutants and also prevented the synthetic lethality of the double mutants. These findings show novel roles of PI(3)P and Pib2 in the regulation of TORC1, which in turn promoted LMP and nonapoptotic death of stressed cells. Rapamycin prevented the death of the pathogenic yeast Candida albicans during exposure to fluconazole plus a calcineurin inhibitor, suggesting that TORC1 broadly promotes sensitivity to fungistats in yeasts.
Better Overeducated than Unemployed? The Short- and Long-Term Effects of an Overeducated Labour Market Re-entry
Authors: Voßemer Jonas , Schuck Bettina
Published: October 2015

Previous studies have shown that overeducation is inferior to adequate employment. For example, overeducated workers have lower earnings, participate less often in continuing education and training, and are less satisfied with their jobs. This article changes perspectives by asking whether it is better for the unemployed to take up a job for which they are overeducated or to remain unemployed and continue the search for adequate employment. Theoretically, we rely on the established confrontation of the stepping-stone and trap hypotheses, which make opposing predictions in terms of long-term employment chances and job quality. Using the German Socio-Economic Panel (1984–2012) and applying a dynamic propensity score matching approach, the analyses reveal an interesting trade-off. Although an overeducated re-entry increases the long-term employment chances persistently, it also implies strong lock-in effects into overeducation for up to 5 years after re-employment. In sum, the results support the stepping-stone hypothesis in terms of future employment chances, but also highlight non-negligible risks of remaining trapped in a job that is below one’s level of educational qualification.
Mysterious misalignments between geomagnetic and stellar reference frames seen in CHAMP and Swarm satellite measurements
Authors: Maus Stefan
Published: October 2015

The orientation of a spacecraft in Low Earth Orbit can be determined accurately from either magnetic field measurements or star camera images. Ideally, the independently computed spacecraft attitudes should agree. However, we find that the German CHAMP and European Space Agency triple-satellite Swarm geomagnetic satellites exhibit consistent misalignments between the stellar and geomagnetic reference frames, which oscillate with the local time of the orbit. Having an amplitude of 20 arcsec, these oscillations are more than an order of magnitude larger than the stability of the optical bench, which cohosts the magnetometers and star cameras. The misalignments could originate either from the magnetometer or star camera measurements. On one hand, as-yet-unknown external magnetic field contributions could appear as a rotation of the geomagnetic reference frame. On the other hand, the observed misalignments agree in amplitude and phase with the effects of stellar aberration, caused by the movement of the star cameras relative to the light rays emitted by the stars. This is surprising because stellar aberration is allegedly already corrected for by the star image processing system. Resolving these mysterious misalignments is key to fulfilling the measurement accuracy requirements and science objectives of the ongoing Swarm mission. If caused by stellar aberration, fully correcting for this effect could significantly improve the attitude accuracy not only of CHAMP and Swarm, but also of several other past and ongoing scientific satellite missions.
Whole-genome bisulfite sequencing maps from multiple human tissues reveal novel CpG islands associated with tissue-specific regulation
Authors: Mendizabal Isabel , Yi Soojin V.
Published: October 2015

CpG islands (CGIs) are one of the most widely studied regulatory features of the human genome, with critical roles in development and disease. Despite such significance and the original epigenetic definition, currently used CGI sets are typically predicted from DNA sequence characteristics. Although CGIs are deeply implicated in practical analyses of DNA methylation, recent studies have shown that such computational annotations suffer from inaccuracies. Here we used whole-genome bisulfite sequencing from 10 diverse human tissues to identify a comprehensive, experimentally obtained, single-base resolution CGI catalog. In addition to the unparalleled annotation precision, our method is free from potential bias due to arbitrary sequence features or probe affinity differences. In addition to clarifying substantial false positives in the widely used University of California Santa Cruz (UCSC) annotations, our study identifies numerous novel epigenetic loci. In particular, we reveal significant impact of transposable elements on the epigenetic regulatory landscape of the human genome and demonstrate ubiquitous presence of transcription initiation at CGIs, including alternative promoters in gene bodies and non-coding RNAs in intergenic regions. Moreover, coordinated DNA methylation and chromatin modifications mark tissue-specific enhancers at novel CGIs. Enrichment of specific transcription factor binding from ChIP-seq supports mechanistic roles of CGIs on the regulation of tissue-specific transcription. The new CGI catalog provides a comprehensive and integrated list of genomic hotspots of epigenetic regulation.