bluuebunny/crossref_metadata_2025 huggingface dataset:
New information technologies and their impact on the humanitarian sector
Authors: Meier Patrick
Published: September 2012

New information and communication technologies are impacting the humanitarian sector in profound ways. Both crisis-affected communities and global volunteer networks are becoming increasingly digital. This means that the former are increasingly the source of relevant crisis information, while the latter are becoming more adept at managing and visualizing this information on live crisis maps. This article introduces the field of crisis mapping and provides key examples from Haiti, Russia, Libya, and Somalia to demonstrate how digitally empowered affected communities and volunteer networks are reshaping humanitarian response in the twenty-first century.
What future role for local organizations? A reflection on the need for humanitarian capacity-building
Authors: Audet François
Published: September 2012

While treating the humanitarian organizations themselves as rational actors, this article considers the factors that influence the decisions and the current logic of Western humanitarian organizations in their dealings with local organizations. This reflection necessarily leads to a re-examination of the current structure of these organizations and to proposed scenarios to identify the best methods for the future, particularly in the relational framework between international organizations and their local partners. Ultimately, the humanitarian organization interventional model must be broadened, taking local humanitarian capacity-building into greater consideration.
Heritability of Ambulatory and Beat-to-Beat Office Blood Pressure in Large Multigenerational Arab Pedigrees: The ‘Oman Family Study’
Authors: Albarwani Sulayma , Muñoz M. Loretto , Voruganti V. Saroja , Jaju Deepali , Al-Yahyaee V. Saeed , Rizvi Syed G. , Lopez-Alvarenga Juan C. , Al-Anqoudi Zahir M , Bayoumi Riad A. , Comuzzie Anthony G. , Snieder Harold , Hassan Mohammed O.
Published: September 2012

Objective: To estimate the heritability of ambulatory blood pressure (BP), heart rate (HR), and beat-to-beat office BP and HR in an isolated, environmentally and genetically homogeneous Omani Arab population. Methods: Ambulatory BP measurements were recorded in 1,124 subjects with a mean age of 33.8 ± 16.2 years, using the auscultatory mode of the validated Schiller ambulatory BP Monitor. Beat-to-beat BP and HR were recorded by the Task Force Monitor. Heritability was estimated using quantitative genetic analysis. This was achieved by applying the maximum-likelihood-based variance decomposition method implemented in SOLAR software. Results: We detected statistically significant heritability estimates for office beat-to-beat, 24-hour, daytime, and sleep HR of 0.31, 0.21, 0.20, and 0.07, respectively. Heritability estimates in the abovementioned conditions for systolic BP (SBP)/diastolic BP (DBP)/mean BP (MBP) were all significant and estimated at 0.19/0.19/0.19, 0.30/0.44/0.41, 0.28/0.38/0.39, and 0.21/0.18/0.20, respectively. Heritability estimates for 24-hour and daytime ambulatory SBP, DBP, and MBP ranged from 0.28 to 0.44, and were higher than the heritability estimates for beat-to-beat recordings and sleep periods, which were estimated within a narrow range of 0.18–0.21. Conclusion: In this cohort, because shared environments are common to all, the environmental influence that occurs is primarily due to the variation in non-shared environment that is unique to the individual. We demonstrated significant heritability estimates for both beat-to-beat office and ambulatory BP and HR recordings, but 24-hour and daytime ambulatory heritabilities are higher than those from beat-to-beat resting levels and ambulatory night-time recordings.
Teaching an old dogma new tricks: twenty years of Shc adaptor signalling
Authors: Wills Melanie K. B. , Jones Nina
Published: September 2012

Shc (Src homology and collagen homology) proteins are considered prototypical signalling adaptors in mammalian cells. Consisting of four unique members, ShcA, B, C and D, and multiple splice isoforms, the family is represented in nearly every cell type in the body, where it engages in an array of fundamental processes to transduce environmental stimuli. Two decades of investigation have begun to illuminate the mechanisms of the flagship ShcA protein, whereas much remains to be learned about the newest discovery, ShcD. It is clear, however, that the distinctive modular architecture of Shc proteins, their promiscuous phosphotyrosine-based interactions with a multitude of membrane receptors, involvement in central cascades including MAPK (mitogen-activated protein kinase) and Akt, and unconventional contributions to oxidative stress and apoptosis all require intricate regulation, and underlie diverse physiological function. From early cardiovascular development and neuronal differentiation to lifespan determination and tumorigenesis, Shc adaptors have proven to be more ubiquitous, versatile and dynamic than their structures alone suggest.
Magnetic pinning effects of epitaxial LaxSr1−xMnO3 nanostructured thin films on YBa2Cu3O7−δ layers
Authors: Petrisor T. , Gabor M. S. , Tiusan C. , Galluzzi V. , Celentano G. , Popa S. , Boulle A. , Petrisor T.
Published: September 2012

The present paper presents the effects of a nanostructured, ferromagnetic La1−xSrxMnO3(LSMO) thin film on the pinning characteristics of an epitaxial YBa2Cu3O7(YBCO) thin film deposited on top. Ordered arrays of LSMO grains were obtained upon growing the film on a terraced (001) SrTiO3 substrate. The analyses of magnetic measurements revealed the presence of a complex vortex pinning mechanism within the YBCO film. With respect to a reference single YBCO layer, an additional pinning potential was observed. Its temperature evolution suggests that a magnetic pinning mechanism is responsible for improved pinning characteristics in the high temperature and field region. Based on the morphology of the underlying LSMO buffer, a strong pinning force is expected to arise due to the anti-dot formations, where a high magnetization gradient exists.
Coupling scanning tunneling microscope and supersonic molecular beams: A unique tool for in situ investigation of the morphology of activated systems
Authors: Smerieri M. , Reichelt R. , Savio L. , Vattuone L. , Rocca M.
Published: September 2012

We report here on a new experimental apparatus combining a commercial low temperature scanning tunneling microscope with a supersonic molecular beam. This setup provides a unique tool for the in situ investigation of the topography of activated adsorption systems and opens thus new interesting perspectives. It has been tested towards the formation of the O/Ag(110) added rows reconstruction and of their hydroxylation, comparing data recorded upon O2 exposure at thermal and hyperthermal energies.
Response to “Comment on ‘Geometric phase of the gyromotion for charged particles in a time-dependent magnetic field’” [Phys. Plasmas 19, 094701 (2012)]
Authors: Liu Jian , Qin Hong
Published: September 2012

The reformulation of our analysis on the geometric phase of the gyromotion [J. Liu and H. Qin, Phys. Plasmas 18, 072505 (2011)] in terms of spatial angles presented in the comment by Brizard and Guillebon is interesting and correct. The subtlety of whether the adiabatic term associated with the long term average of the variation of pitch angle completely disappears after the gyrophase average is related to where valid approximations are applied. But it has no impact on the main conclusions.
Transport properties of Ni, Co, Fe, Mn doped Cu0.01Bi2Te2.7Se0.3 for thermoelectric device applications
Authors: Lukas K. C. , Liu W. S. , Ren Z. F. , Opeil C. P.
Published: September 2012

Bi2Te3 based thermoelectric devices typically use a nickel layer as a diffusion barrier to block the diffusion of solder or copper atoms from the electrode into the thermoelectric material. Previous studies have shown degradation in the efficiency of these thermoelectric devices may be due to the diffusion of the barrier layer into the thermoelectric material. In this work, Ni, Co, Fe, and Mn are intentionally doped into Cu0.01Bi2Te2.7Se0.3 in order to understand their effects on the thermoelectric material. Thermoelectric transport properties including the Seebeck coefficient, thermal conductivity, electrical resistivity, carrier concentration, and carrier mobility of Cu0.01Bi2Te2.7Se0.3 doped with 2 atomic percent M (M = Ni, Co, Fe, Mn) as Cu0.01Bi2Te2.7Se0.3M0.02 are studied in a temperature range of 5-525 K. It is seen that the introduction of Ni, Co, Fe, or Mn does not affect the overall figure of merit, and therefore demonstrates that the diffusion barrier is not leading to device degradation as previously hypothesized. Any of these elements may be used as a diffusion barrier with Co being the best candidate based on both its electrical and mechanical properties.
Switching dynamics and charge transport studies of resistive random access memory devices
Authors: Long Branden , Li Yibo , Mandal Saptarshi , Jha Rashmi , Leedy Kevin
Published: September 2012

We report the switching dynamics and charge transport studies on Ru/HfO2/TiOx/Ru resistive random access memory devices in low resistance state (LRS), high resistance state (HRS), and virgin resistance state (VRS). The charge transport in LRS is governed by Ohmic conduction of electrons through local filamentary paths while it is governed by a combination of Frenkel-Poole emission and trap assisted tunneling process in HRS and VRS. The area of the filament in LRS is extracted and related to the compliance current. The thickness of the re-oxidized filament is extracted and related to the reset voltage in HRS. The energy consumed during the reset process was analyzed on the time-scale to experimentally demonstrate joule-heating mediated oxidation dynamics of filament during device reset.
Layering and temperature-dependent magnetization and anisotropy of naturally produced Ni/NiO multilayers
Authors: Pappas S. D. , Kapaklis V. , Delimitis A. , Jönsson P. E. , Th. Papaioannou E. , Poulopoulos P. , Fumagalli P. , Trachylis D. , Velgakis M. J. , Politis C.
Published: September 2012

Ni/NiO multilayers were grown by magnetron sputtering at room temperature, with the aid of the natural oxidation procedure. That is, at the end of the deposition of each single Ni layer, air is let to flow into the vacuum chamber through a leak valve. Then, a very thin NiO layer (∼1.2 nm) is formed. Simulated x-ray reflectivity patterns reveal that layering is excellent for individual Ni-layer thickness larger than 2.5 nm, which is attributed to the intercalation of amorphous NiO between the polycrystalline Ni layers. The magnetization of the films, measured at temperatures 5–300 K, has almost bulk-like value, whereas the films exhibit a trend to perpendicular magnetic anisotropy (PMA) with an unusual significant positive interface anisotropy contribution, which presents a weak temperature dependence. The power-law behavior of the multilayers indicates a non-negligible contribution of higher order anisotropies in the uniaxial anisotropy. Bloch-law fittings for the temperature dependence of the magnetization in the spin-wave regime show that the magnetization in the multilayers decreases faster as a function of temperature than the one of bulk Ni. Finally, when the individual Ni-layer thickness decreases below 2 nm, the multilayer stacking vanishes, resulting in a dramatic decrease of the interface magnetic anisotropy and consequently in a decrease of the perpendicular magnetic anisotropy.
Study and optimization of negative polarity rod pinch diode as flash radiography source at 4.5 MV
Authors: Etchessahar Bertrand , Bernigaud Virgile , Caron Michel , Cartier Frédéric , Cartier Stéphanie , Hourdin Laurent , Magnin Laurent , Nicolas Rémi , Poulet Frédéric , Rosol Rodolphe , Tailleur Yaël , Toury Martial , Compant La Fontaine Antoine , Bicrel Béatrice , Cassany Bruno , Desanlis Thierry , Voisin Luc , Hébert David , Delbos Christophe , Garrigues Alain , Soleilhavoup Isabelle
Published: September 2012

The negative polarity rod pinch diode (NPRPD) is a potential millimeter spot size radiography source for high voltage generators (4 to 8 MV) [Cooperstein et al., “Considerations of rod-pinch diode operation in negative polarity for radiography,” in Proceedings of the 14th IEEE Pulsed Power Conference, 2003, pp. 975–978]. The NPRPD consists of a small diameter (few mm) cylindrical anode extending from the front end of the vacuum cell through a thin annular cathode, held by a central conductor. The polarity has been inverted when compared to the original rod pinch diode [Cooperstein et al., “Theoretical modeling and experimental characterization of a rod-pinch diode,” Phys. Plasmas 8(10), 4618–4636 (2001)] in order to take advantage from the maximal x-ray emission toward the anode holder at such a voltage [Swanekamp et al., “Evaluation of self-magnetically pinched diodes up to 10 MV as high resolution flash X-ray sources,” IEEE Trans. Plasma Sci. 32(5), 2004–2016 (2004). We have studied this diode at 4.5 MV, driven by the ASTERIX generator [Raboisson et al., “ASTERIX, a high intensity X-ray generator,” in Proceedings of the 7th IEEE Pulsed Power Conference, 1989, pp. 567–570.]. This generator, made up of a capacitor bank and a Blumlein line, was initially designed to test the behavior of electronic devices under irradiation. In our experiments, the vacuum diode has been modified in order to set up flash a radiographic diode [Etchessahar et al., “Negative polarity rod pinch diode experiments on the ASTERIX generator,” in Conference Records–Abstracts, 37th IEEE International Conference on Plasma Science, 2010]. The experiments and numerical simulations presented here allowed the observation and analysis of various physical phenomena associated with the diode operation. Also, the influence of several experimental parameters, such as cathode and anode diameters, materials and surface states, was examined. In order to achieve the most comprehensive characterization of the diode, both optical and x-ray diagnostics were used, including high speed multi-image ICCD (intensified CCD) cameras, streak camera, dosimeters, spot size measurements, and pinhole cameras. A set of new results have been obtained through this study. The plasma emission from the anode and cathode surfaces and its expansion appear to be critical for the diode functioning. Also, for the first time, potential sources of diode instability were identified. Finally, an optimal and stable diode configuration was found with the following parameters: 52 rad at 1 m (in Al) and 2.2 mm spot size.
Effect of target composition on proton acceleration in ultraintense laser-thin foil interaction
Authors: Liu Qingcao , Liu Meng , Yu Tongpu , Ding Pengji , Liu Zuoye , Sun Shaohua , Liu Xiaoliang , Lu Xing , Guo Zeqin , Hu Bitao
Published: September 2012

The interactions of ultraintense circularly polarized laser pulses with a mixed solid target and a double-layer target are studied by two-dimensional particle-in-cell simulations. Different carbon and proton compositions in the targets are used in the simulations. It is shown that the proton acceleration mechanisms in both targets are very sensitive to the ion density ratios between protons and carbon ions. For a mixed solid target, a relatively low proton density gives rise to monoenergetic peaks in the proton energy spectrum while a high proton density leads to a large cut-off energy and wide energy spread. With the increase of the ratio, the so-called directed-Coulomb-explosion becomes dominated over the radiation pressure. Surprisingly, for a double-layer target with a front proton layer and an ultrathin rear carbon layer, a highly monoenergetic proton beam with a peak energy of 1.7 GeV/u, an energy spread of ∼4%, and a divergency angle of 2° can be obtained, which might have diverse applications in medical therepy and proton imaging in future.
Depth profiling and imaging capabilities of an ultrashort pulse laser ablation time of flight mass spectrometer
Authors: Cui Yang , Moore Jerry F. , Milasinovic Slobodan , Liu Yaoming , Gordon Robert J. , Hanley Luke
Published: September 2012

An ultrafast laser ablation time-of-flight mass spectrometer (AToF-MS) and associated data acquisition software that permits imaging at micron-scale resolution and sub-micron-scale depth profiling are described. The ion funnel-based source of this instrument can be operated at pressures ranging from 10−8 to ∼0.3 mbar. Mass spectra may be collected and stored at a rate of 1 kHz by the data acquisition system, allowing the instrument to be coupled with standard commercial Ti:sapphire lasers. The capabilities of the AToF-MS instrument are demonstrated on metal foils and semiconductor wafers using a Ti:sapphire laser emitting 800 nm, ∼75 fs pulses at 1 kHz. Results show that elemental quantification and depth profiling are feasible with this instrument.
Influence of equilibrium shear flow on peeling-ballooning instability and edge localized mode crash
Authors: Xi P. W. , Xu X. Q. , Wang X. G. , Xia T. Y.
Published: September 2012

The E × B shear flow plays a dual role on peeling-ballooning modes and their subsequently triggered edge localized mode (ELM) crashes. On one hand, the flow shear can stabilize high-n modes and twist the mode in the poloidal direction, constraining the mode's radial extent and reducing the size of the corresponding ELM. On the other hand, the shear flow also introduces the Kelvin-Helmholtz drive, which can destabilize peeling-ballooning modes. The overall effect of equilibrium shear flow on peeling-ballooning modes and ELM crashes depends on the competition between these two effects. When the flow shear is either small or very large, it can reduce ELM size. However, for moderate values of flow shear, the destabilizing effect from the Kelvin-Helmholtz term is dominant and leads to larger ELM crashes.
Solid films and transports in cellular foams
Authors: Tan Hoang Minh , Perrot Camille
Published: September 2012

We show that critical path ideas lead to the identification of two local characteristic sizes for the long wavelength acoustic properties in cellular solids, the pore and throat sizes. Application of the model to real foam samples, which may contain solid films or membranes yields quantitative agreement between a finite-element numerical homogenization approach and experimental results. From three routinely available laboratory measurements: the open porosity ϕ, the static viscous permeability k0, and the average struts length Lm obtained from microscopy analysis; asymptotic transport parameters at high-frequencies and the normal incidence sound absorption coefficient are derived with no adjustable parameters.
On the influence of nanometer-thin antiferromagnetic surface layer on ferromagnetic CrO2
Authors: Das P. , Bajpai A. , Ohno Y. , Ohno H. , Müller J.
Published: September 2012

We investigate the influence of naturally grown 2–5 nm thin surface layer of antiferromagnetic (AFM) Cr2O3 on the half metallic ferromagnet CrO2 by measuring the magnetic behavior of a single micro-crystal. The temperature variation of the magnetic stray fields of the micro-crystal measured by micro-Hall magnetometry shows an anomalous increase below ∼60 K. We find clear evidence that this behavior is due to the influence of the AFM surface layer. The average amplitude of the Barkahausen jumps exhibits a similar temperature dependence indicating that the AFM surface layer plays a role in defining the potential landscape seen by the domain configuration in the ferromagnetic grain.
Generation of high-energy (>15 MeV) neutrons using short pulse high intensity lasers
Authors: Petrov G. M. , Higginson D. P. , Davis J. , Petrova Tz. B. , McNaney J. M. , McGuffey C. , Qiao B. , Beg F. N.
Published: September 2012

A roadmap is suggested and demonstrated experimentally for the production of high-energy (>15 MeV) neutrons using short pulse lasers. Investigation with a 3D Monte Carlo model has been employed to quantify the production of energetic neutrons. Numerical simulations have been performed for three nuclear reactions, d(d,n)3He, 7Li(d,n)8Be, and 7Li(p,n)7Be, driven by monoenergetic ion beams. Quantitative estimates for the driver ion beam energy and number have been made and the neutron spectra and yield in the ion propagation direction have been evaluated for various incident ion energies. In order to generate neutron fluence above a detection limit of 106 neutrons/sr, either ∼1010 protons with energy 20–30 MeV or comparable amount of deuterons with energy 5–10 MeV are required. Experimental verification of the concept with deuterons driven by the Titan laser (peak intensity 2 × 1019 W/cm2, pulse duration of 9 ps, wavelength 1.05 μm, and energy of 360 J) is provided with the generation of neutrons with energy of up to 18 MeV from 7Li(d,n)8Be reactions. Future research will focus on optimized schemes for ion acceleration for production of high-energy neutrons, which will involve efficient target design, laser parameter optimization, and converter material.
Design, construction, and testing of a parabolic trough solar concentrator for hot water and low enthalpy steam generation
Authors: Venegas-Reyes E. , Jaramillo O. A. , Castrejón-García R. , Aguilar J. O. , Sosa-Montemayor F.
Published: September 2012

This paper reports the design, construction, and evaluation of a solar parabolic trough concentrator (PTC) with a rim angle of 45°, a length of 4.88 m, and an aperture area of 5.8 m2. The PTC is made of aluminium in such a way that both the manufacturing and assembly processes do not require complicated technology or skilled labour. Since the PTC is for low enthalpy steam generation and hot water, it is designed with an unshielded receiver and without a glass cover in order to reduce both production and transportation costs. A finite element stress analysis is conducted to determine the mechanical behaviour of the PTC under various simulated wind loads on the structure. A simple solar tracking system is employed when it is oriented in a North-to-South direction. The optical efficiency of the collector is also reported. Said efficiency depends on the optical properties of the materials involved, the geometry of the collector, and the various imperfections arising from the construction of the collector. The thermal performance of the PTC was determined according to the Standard ASHRAE 93-1986 (RA 91). Peak efficiencies close to 60% were obtained.
Studies of sheath characteristics in a double plasma device with a negatively biased separating grid and a magnetic filter field
Authors: Das B. K. , Chakraborty M. , Bandyopadhyay M.
Published: September 2012

A double plasma device has two regions: Source region and target region. These two regions are divided by a magnetic filter field. A grid is placed coplanar to the magnetic filter. To study the sheath structure in the target region, a metallic plate is placed at the center, which can be biased with respect to the chamber (ground) potential. Plasma is created in the source region by filament discharge technique. Plasma diffusing from the source region to the target region is subjected to the magnetic filter field and also an electric field applied on the grid. Plasma thus obtained in the target region forms a sheath on the biased plate. The influence of both the magnetic filter field and the electric field, applied between the grid and the chamber wall, on the sheath structure formed on the biased plate is studied. It is found that the magnetic filter field and the electric field change the sheath structure in different ways.
Single-mode lasing of GaN nanowire-pairs
Authors: Xu Huiwen , Wright Jeremy B. , Luk Ting-Shan , Figiel Jeffery J. , Cross Karen , Lester Luke F. , Balakrishnan Ganesh , Wang George T. , Brener Igal , Li Qiming
Published: September 2012

Stable single-mode lasing operation from a pair of coupled GaN nanowires is demonstrated through optical pumping. GaN nanowires with different lengths were placed side-by-side in contact to form a coupled cavity through nanoprobe manipulation. Unlike individual nanowire lasers, which operate in a combined multiple transverse and multiple longitude mode oscillation, a coupled nanowire-pair provides a mode selection mechanism through the Vernier effect, which can strongly enhance the free spectrum range between adjacent resonant modes and generate a stable single-mode operation with a high side-mode suppression ratio.
Vortices of self-gravitating grains in dusty plasmas
Authors: Nebbat E. , Annou R.
Published: September 2012

Vortices are an attractive expression of the non-linear dynamics of fluids along with plasmas. In complex plasmas, Nebbat and Annou [Phys. Plasmas 17, 093702 (2010)] proposed a time dependent non-linear model that considers vortices as a consequence of an instability. The model is augmented hereafter by incorporating the gravitational grain-grain attraction, particle drift due to self-gravity field, self-consistent inter-particle distance, the permeability of grains along with the grain charge excess due to the non-linear dependence of the grain capacitance on its size. Effects of the latter parameters as well as the effect of grain mass to charge ratio on the characteristics of the vortex such as density are investigated.
The acoustic velocity, refractive index, and equation of state of liquid ammonia dihydrate under high pressure and high temperature
Authors: Ma Chunli , Wu Xiaoxin , Huang Fengxian , Zhou Qiang , Li Fangfei , Cui Qiliang
Published: September 2012

High-pressure and high-temperature Brillouin scattering studies have been performed on liquid of composition corresponding to the ammonia dihydrate stoichiometry (NH3·2H2O) in a diamond anvil cell. Using the measured Brillouin frequency shifts from 180° back- and 60° platelet-scattering geometries, the acoustic velocity, refractive index, density, and adiabatic bulk modulus have been determined under pressure up to freezing point along the 296, 338, 376, and 407 K isotherms. Along these four isotherms, the acoustic velocities increase smoothly with increasing pressure but decrease with the increased temperature. However, the pressure dependence of the refractive indexes on the four isotherms exhibits a change in slope around 1.5 GPa. The bulk modulus increases linearly with pressure and its slope, dB/dP, decreases from 6.83 at 296 K to 4.41 at 407 K. These new datasets improve our understanding of the pressure- and temperature-induced molecular structure changes in the ammonia-water binary system.
The structural and piezoresponse properties of c-axis-oriented Aurivillius phase Bi5Ti3FeO15 thin films deposited by atomic vapor deposition
Authors: Zhang P. F. , Deepak N. , Keeney L. , Pemble M. E. , Whatmore R. W.
Published: September 2012

The deposition by atomic vapor deposition of highly c-axis-oriented Aurivillius phase Bi5Ti3FeO15 (BTFO) thin films on (100) Si substrates is reported. Partially crystallized BTFO films with c-axis perpendicular to the substrate surface were first deposited at 610 °C (8% excess Bi), and subsequently annealed at 820 °C to get stoichiometric composition. After annealing, the films were highly c-axis-oriented, showing only (00l) peaks in x-ray diffraction (XRD), up to (0024). Transmission electron microscopy (TEM) confirms the BTFO film has a clear layered structure, and the bismuth oxide layer interleaves the four-block pseudoperovskite layer, indicating the n = 4 Aurivillius phase structure. Piezoresponse force microscopy measurements indicate strong in-plane piezoelectric response, consistent with the c-axis layered structure, shown by XRD and TEM.
Ultra-relativistic ion acceleration in the laser-plasma interactions
Authors: Huang Yongsheng , Wang Naiyan , Tang Xiuzhang , Shi Yijin , Xueqing Yan
Published: September 2012

An analytical relativistic model is proposed to describe the relativistic ion acceleration in the interaction of ultra-intense laser pulses with thin-foil plasmas. It is found that there is a critical value of the ion momentum to make sure that the ions are trapped by the light sail and accelerated in the radiation pressure acceleration (RPA) region. If the initial ion momentum is smaller than the critical value, that is in the classical case of RPA, the potential has a deep well and traps the ions to be accelerated, as the same described before by simulation results [Eliasson et al., New J. Phys. 11, 073006 (2009)]. There is a new ion acceleration region different from RPA, called ultra-relativistic acceleration, if the ion momentum exceeds the critical value. In this case, ions will experience a potential downhill. The dependence of the ion momentum and the self-similar variable at the ion front on the acceleration time has been obtained. In the ultra-relativistic limit, the ion momentum at the ion front is proportional to t4/5, where t is the acceleration time. In our analytical hydrodynamical model, it is naturally predicted that the ion distribution from RPA is not monoenergetic, although the phase-stable acceleration mechanism is effective. The critical conditions of the laser and plasma parameters which identify the two acceleration modes have been achieved.
The microstructure network and thermoelectric properties of bulk (Bi,Sb)2Te3
Authors: Xie Wenjie , Hitchcock Dale A. , Kang Hye J. , He Jian , Tang Xinfeng , Laver Mark , Hammouda Boualem
Published: September 2012

We report small-angle neutron scattering studies on the microstructure network in bulk (Bi,Sb)2Te3 synthesized by the melt-spinning (MS) and the spark-plasma-sintering (SPS) process. We find that rough interfaces of multiscale microstructures generated by the MS are responsible for the large reduction of both lattice thermal conductivity and electrical conductivity. Our study also finds that subsequent SPS forms a microstructure network of ∼10 nm thick lamellae and smooth interfaces between them. This nanoscale microstructure network with smooth interfaces increases electrical conductivity while keeping a low thermal conductivity, making it an ideal microstructure for high thermoelectric efficiency.
Thermal stability of exchange-biased NiFe/FeMn multilayered thin films
Authors: Chen H. Y. , Phuoc Nguyen N. , Ong C. K.
Published: September 2012

A systematic study of the effect of ferromagnetic thickness on magnetic and microwave properties of exchange-biased NiFe/FeMn multilayered thin films was carried out with regards to thermal stability. The temperature-dependent microwave characteristics of the films were obtained from the near-field microwave microscopy technique and analysed based on Landau-Lifshitz-Gilbert equation. The complex microwave permeability spectra of the magnetic thin films up to 5 GHz in the temperature range from room temperature to 420 K were measured. It was found that thicker ferromagnetic layers helped to reduce the dependence of the magnetic properties on temperature, leading to better thermal stability. The saturation magnetization MS, dynamic magnetic anisotropy field HKdyn, and ferromagnetic resonance frequency fFMR were found to decrease with temperature, while the effective damping coefficient αeff was increased with temperature. We also investigate the rotational magnetic anisotropy field HKrot with temperature which gives a measure of the rotatable magnetization of the antiferromagnetic layers and its thermal stability.
Giant coercivity in perpendicularly magnetized cobalt monolayer
Authors: Lin D. C. , Song C. , Cui B. , Wang Y. Y. , Wang G. Y. , Pan F.
Published: September 2012

We report giant coercivity (HC) up to 35 kOe at 4 K, measured by the anomalous Hall effect, in perpendicularly magnetized Co (∼0.3 nm) films, where Co is approximately one monolayer. The HC is dramatically reduced with huge applied current, due to Joule heating rather than Rashba effect. It is also sensitive to temperatures, producing almost zero HC at 200 K. The Curie temperature of the Co monolayer is ∼275 K, far lower than that of bulk Co. The giant HC could be explained by the strong interaction at Co/Pd interface, providing a promising paradise: one monolayer, one permanent magnet.
Performance improvement of micro-fuel cell by manipulating the charged diffuse layer
Authors: Sprague Isaac B. , Dutta Prashanta
Published: September 2012

A fuel cell device is presented based on a counter-flow microfluidic fuel cell (CFMFC) with nano-porous electrodes by developing an advection flux of ions within the electric double layer (EDL). Typically, in a microfluidic fuel cell, advection in the EDL is negligible because the near wall electrolyte velocity is zero. However, by using nano-pores, a non-negligible ion flux due to advection can be developed in the charged regions of the EDL which affects the structure of the EDL. In this article, we use a mathematical model to study how advection in the EDL affects the kinetic performance of fuel cells. Our model predicts that the peak power density can be increased by more than 2 fold in a CFMFC using this approach to kinetic enhancement.
Testing the variability of chloroplast sequences for plant phylogeography
Authors: Byrne M. , Hankinson M.
Published: September 2012

Phylogeography in plants is hampered by lack of DNA-sequence regions that detect sufficient variation in intra-specific lineages to reveal historical patterns. We tested 13 putatively highly variable non-coding chloroplast regions in six species complexes, from four different angiosperm families, where phylogeographic patterns have previously been identified using restriction fragment length polymorphism analysis of the chloroplast genome. All regions tested amplified in most of the species. The intergenic spacer regions trnQ–rps16, trnS–trnG, psbA–trnH, psbD–trnT and ndhC–trnV were the five most promising regions for phylogeographic analysis in terms of variability, and petB and rpl16 were variable, given the utility of being amplified in a single reaction. The trnQ–rps16 and psbA–trnH intergenic spacer regions and the rpl16 D4-loop intron showed variation between known lineages in all species. The psbA–trnH intergenic spacer that has been suggested as a suitable barcoding gene for plants, generally showed a level of variation similar to that in other variable regions in the species investigated here, suggesting that some caution is required in the use of this region for barcoding applications. The present analysis identified a set of seven chloroplast regions that are a useful basis for informed selection of sequences for assessment of phylogeographic structure in plants.
Optimising vitrification of human oocytes using multiple cryoprotectants and morphological and functional assessment
Authors: Seet V. Y. K. , Al-Samerria S. , Wong J. , Stanger J. , Yovich J. L. , Almahbobi G.
Published: September 2012

Oocyte vitrification is a clinical practice that allows preservation of fertility potential in women. Vitrification involves quick cooling using high concentrations of cryoprotectants to minimise freezing injuries. However, high concentrations of cryoprotectants have detrimental effects on oocyte quality and eventually the offspring. In addition, current assessment of oocyte quality after vitrification is commonly based only on the morphological appearance of the oocyte, raising concerns regarding its efficiency. Using both morphological and functional assessments, the present study investigated whether combinations of cryoprotectants at lower individual concentrations result in better cryosurvival rates than single cryoprotectants at higher concentrations. Surplus oocytes from IVF patients were vitrified within 24 h after retrieval using the Cryotop method with several cryoprotectants, either individually or in combination. The morphological and functional quality of the vitrified oocytes was investigated using light microscopy and computer-based quantification of mitochondrial integrity, respectively. Oocyte quality was significantly higher using a combination of cryoprotectants than vitrification with individual cryoprotectants. In addition, the quality of vitrified oocyte varied depending on the cryoprotectants and type of combination used. The results of the present study indicate that observations based purely on the morphological appearance of the oocyte to assess the cryosurvival rate are insufficient and sometimes misleading. The outcome will have a significant implication in the area of human oocyte cryopreservation as an important approach for fertility preservation.
Does fire regime affect both temporal patterns and drivers of vegetation recovery in a resilient Mediterranean landscape? A remote sensing approach at two observation levels
Authors: Lozano F. Javier , Suárez-Seoane Susana , de Luis-Calabuig Estanislao
Published: September 2012

We investigate how fire regime may influence both temporal patterns and drivers of vegetation regeneration in a Natural Park (NW Spain) affected by a long history of fire events and human activities. To address this issue, we evaluate the suitability of five spectral indices derived from Landsat imagery (for the period 1992–2005) for estimating biophysical properties of vegetation and monitoring post-fire recovery. Complementarily, we assess the role of the observation level (pixel and patch) on the results, identifying which of them is more informative for land management. Tasselled Cap Wetness was the best-performing index and total cover was the vegetation property more closely related to spectral data. Most post-fire recovery occurred within the 2 years following the fire event. Fire recurrence did not influence patch extent or shape nor did it affect ecosystem resilience. However, patch extent and shape affected resilience. The relevance of the environmental drivers behind vegetation recovery was not related to fire recurrence and changed over time. Prior vegetation status and rainfall were the most important drivers, while topography and vegetation type had a more secondary role. Our results advocate the consideration of patches as the most appropriate organisational unit when monitoring vegetation recovery.
Fire activity projections in the SRES A2 and B2 climatic scenarios in peninsular Spain
Authors: Vázquez de la Cueva A. , Quintana José R. , Cañellas Isabel
Published: September 2012

Climate change is affecting the meteorological and climatic conditions in which forest vegetation develops. These conditions are also determinant in present and future forest fire activity. In order to quantify the expected alterations in future fire activity, we built linear regression models using monthly meteorological variables and the recorded fire activity in peninsular Spain. These models were developed for 15 territories and for the number of fires, the forest area burned and the wooded forest area burned. The meteorological variables used as predictors are derived from a Regional Climate Model covering the period 1961–90 as the control scenario and 2071–2100 as the future scenario. In the 13 territories with valid models, the explained variance ranged from 20 to 68% for the number of fires, from 12 to 66% for the forest area burned, and from 12 to 62% for the wooded forest area burned. Based on these models, we calculated the ratios between the estimations for the climatic scenarios SRES A2 and B2 and the estimates for the control period. For the entire area and for the A2/control and B2/control respectively, the ratios are 2.5 and 2 times for the number of fires, 4.6 and 3.4 for the forest area burned and 3.9 and 3 times for the wooded forest area burned. In spite of the uncertainties regarding future climatic scenarios as well as the simplicity of the model, the results nevertheless point to a very significant increase in fire activity. Forest management should therefore be focussed on adaptation procedures as well as on ecosystem resilience. This strategy will promote a more sustainable coexistence of forests and fires in altered fire regimes.
Simulating effects of climate change and ecological restoration on fire behaviour in a south-western USA ponderosa pine forest
Authors: Honig Kristen A. , Fulé Peter Z.
Published: September 2012

Global climate change has the potential to affect future wildfire activity, particularly in south-western USA ponderosa pine forests that have been substantially altered by land-use practices and aggressive fire suppression. Using two regional general circulation models for the A1B greenhouse gas emission scenario, Australia’s CSIRO:MK3 and Germany’s MPIM:ECHAM5, we predicted fire behaviour under the 80th, 90th and 97th percentiles of future fire-weather conditions at a study site on the Kaibab National Forest, Arizona. We then altered the fuel structure by simulating alternative ecological restoration treatments: a full treatment (FULL), a full treatment with a 40.6-cm-diameter restriction on tree removal (16″ CAP) and a full treatment with a 25.4-cm-diameter restriction on tree removal (10″ CAP). Model results show that differences in fire weather (temperature and fuel moistures) expected by the end of the 21st century were not influential enough to alter fire behaviour significantly, but treatments did significantly reduce severe burning. Alteration of fuel structure through the 16″ CAP and FULL ecological restoration treatments caused significant declines in fire behaviour and crown fire activity under all climate scenarios. The 10″ CAP substantially reduced treatment effectiveness.
Modelling the effects of surface and crown fire behaviour on serotinous cone opening in jack pine and lodgepole pine forests
Authors: Alexander M. E. , Cruz M. G.
Published: September 2012

A methodology has been developed for defining the various threshold conditions required for the opening of serotinous cones and viable seed release in the overstorey canopies in jack pine (Pinus banksiana) and lodgepole pine (Pinus contorta var. latifolia) forests on the basis of fireline intensity and, in turn, rate of fire spread and fuel consumption. The extent of the effects to the overstorey canopy (i.e. crown scorch height and flame defoliation) and the type of fire (i.e. low- to high-intensity surface, intermittent crown and active crown) vary at any given fireline intensity level and are principally a function of foliar moisture content, canopy base height, stand height and canopy bulk density. The viability of the seed stored in serotinous cones of the two pine species begins to decreases once the flame-front residence time at the ground level of an active crown fire exceeds 50 s.
Parameter-free model discrimination criterion based on steady-state coplanarity
Authors: Harrington Heather A. , Ho Kenneth L. , Thorne Thomas , Stumpf Michael P.H.
Published: September 2012

We introduce a procedure for deciding when a mass-action model is incompatible with observed steady-state data that does not require any parameter estimation. Thus, we avoid the difficulties of nonlinear optimization typically associated with methods based on parameter fitting. Instead, we borrow ideas from algebraic geometry to construct a transformation of the model variables such that any set of steady states of the model under that transformation lies on a common plane, irrespective of the values of the model parameters. Model rejection can then be performed by assessing the degree to which the transformed data deviate from coplanarity. We demonstrate our method by applying it to models of multisite phosphorylation and cell death signaling. Our framework offers a parameter-free perspective on the statistical model selection problem, which can complement conventional statistical methods in certain classes of problems where inference has to be based on steady-state data and the model structures allow for suitable algebraic relationships among the steady-state solutions.
Dataglove measurement of joint angles in sign language handshapes
Authors: Eccarius Petra , Bour Rebecca , Scheidt Robert A.
Published: September 2012

In sign language research, we understand little about articulatory factors involved in shaping phonemic boundaries or the amount (and articulatory nature) of acceptable phonetic variation between handshapes. To date, there exists no comprehensive analysis of handshape based on the quantitative measurement of joint angles during sign production. The purpose of our work is to develop a methodology for collecting and visualizing quantitative handshape data in an attempt to better understand how handshapes are produced at a phonetic level. In this pursuit, we seek to quantify the flexion and abduction angles of the finger joints using a commercial data glove (CyberGlove; Immersion Inc.). We present calibration procedures used to convert raw glove signals into joint angles. We then implement those procedures and evaluate their ability to accurately predict joint angle. Finally, we provide examples of how our recording techniques might inform current research questions.
Location in ASL
Authors: Mauk Claude E. , Tyrone Martha E.
Published: September 2012

Recent work on location variation led us to investigate whether phonetic effects influence the lowering of certain forehead located signs in American Sign Language. We found that signing speed and the location of adjacent signs did affect these forehead signs in ways that conform to general principals of coarticulation. In this paper, we use those results as a basis to illustrate additional approaches to the evaluation of the phonetics of location. In particular, we suggest that finer grained analyses of location values may provide insights into directionality of coarticulatory effects, that changes in body posture assist in the achievement of location values, and that kinematic data can be used to describe the use of the signing space in a global sense. Previous work in sign phonetics has provided a solid foundation and new research is progressing well, but there is much work yet to be done.
Complexity in two-handed signs in Kenyan Sign Language
Authors: Morgan Hope E. , Mayberry Rachel I.
Published: September 2012

This paper investigates whether two-handed signs in Kenyan Sign Language, a relatively young school-based sign language, conform to the same constraints on combinations of movement and handshape that hold in other sign languages. An analysis of 467 two-handed signs, separated into four types based on complexity, found that KSL is highly constrained, with only a few signs that violate proposed conditions. Three hypotheses to account for handshape restrictions on the non-dominant hand in highly complex signs are tested. Findings show that a universal unmarked set accounts for most of these handshapes; a language-specific unmarked set does no better; and a constraint on markedness at the featural level essentially accounts for all the signs. Further analyses discover that a preference for unmarked handshapes in the most complex signs extends to all two-handed signs to some degree. Finally, a phonotactic preference for the G/1 handshape on the dominant hand in complex signs is uncovered. Some evidence suggests that this tendency may surface in other languages as well.