bluuebunny/crossref_metadata_2025 huggingface dataset:
A high carrier injection terahertz quantum cascade laser based on indirectly pumped scheme
Authors: Razavipour S. G. , Dupont E. , Chan C. W. I. , Xu C. , Wasilewski Z. R. , Laframboise S. R. , Hu Q. , Ban D.
Published: January 2014

A Terahertz quantum cascade laser with a rather high injection coupling strength based on an indirectly pumped scheme is designed and experimentally implemented. To effectively suppress leakage current, the chosen quantum cascade module of the device is based on a five-well GaAs/Al0.25Ga0.75As structure. The device lases up to 151 K with a lasing frequency of 2.67 THz. This study shows that the effect of higher energy states in carrier transport and the long-range tunnel coupling between states that belong to non-neighbouring modules have to be considered in quantum design of structures with a narrow injector barrier. Moreover, the effect of interface roughness scattering between the lasing states on threshold current is crucial.
${\mathbbm {C}}$
C
-Graded vertex algebras and conformal flow
Authors: Laber Rob , Mason Geoffrey
Published: January 2014

We consider $\mathbbm {C}$C-graded vertex algebras, which are vertex algebras V with a $\mathbbm {C}$C-grading such that V is an admissible V-module generated by “lowest weight vectors.” We show that such vertex algebras have a “good” representation theory in the sense that there is a Zhu algebra A(V) and a bijection between simple admissible V-modules and simple A(V)-modules. We also consider pseudo vertex operator algebras (PVOAs), which are $\mathbbm {C}$C-graded vertex algebras with a conformal vector such that the homogeneous subspaces of V are generalized eigenspaces for L(0); essentially, these are VOAs that lack any semisimplicity or integrality assumptions on L(0). As a motivating example, we show that deformation of the conformal structure (conformal flow) of a strongly regular VOA (e.g., a lattice theory, or Wess-Zumino-Witten model) is a path in a space whose points are PVOAs.
Significant electrical control of amorphous oxide thin film transistors by an ultrathin Ti surface polarity modifier
Authors: Cho Byungsu , Choi Yonghyuk , Jeon Heeyoung , Shin Seokyoon , Seo Hyungtak , Jeon Hyeongtag
Published: January 2014

We demonstrate an enhanced electrical stability through a Ti oxide (TiOx) layer on the amorphous InGaZnO (a-IGZO) back-channel; this layer acts as a surface polarity modifier. Ultrathin Ti deposited on the a-IGZO existed as a TiOx thin film, resulting in oxygen cross-binding with a-IGZO surface. The electrical properties of a-IGZO thin film transistors (TFTs) with TiOx depend on the surface polarity change and electronic band structure evolution. This result indicates that TiOx on the back-channel serves as not only a passivation layer protecting the channel from ambient molecules or process variables but also a control layer of TFT device parameters.
Gamma radiation induced effects in floppy and rigid Ge-containing chalcogenide thin films
Authors: Ailavajhala Mahesh S. , Gonzalez-Velo Yago , Poweleit Christian , Barnaby Hugh , Kozicki Michael N. , Holbert Keith , Butt Darryl P. , Mitkova Maria
Published: January 2014

We explore the radiation induced effects in thin films from the Ge-Se to Ge-Te systems accompanied with silver radiation induced diffusion within these films, emphasizing two distinctive compositional representatives from both systems containing a high concentration of chalcogen or high concentration of Ge. The studies are conducted on blanket chalcogenide films or on device structures containing also a silver source. Data about the electrical conductivity as a function of the radiation dose were collected and discussed based on material characterization analysis. Raman Spectroscopy, X-ray Diffraction Spectroscopy, and Energy Dispersive X-ray Spectroscopy provided us with data about the structure, structural changes occurring as a result of radiation, molecular formations after Ag diffusion into the chalcogenide films, Ag lateral diffusion as a function of radiation and the level of oxidation of the studied films. Analysis of the electrical testing suggests application possibilities of the studied devices for radiation sensing for various conditions.
Control of epitaxial growth of Fe-based nanocrystals on Si substrates using well-controlled nanometer-sized interface
Authors: Nakamura Yoshiaki , Sugimoto Ryota , Ishibe Takafumi , Matsui Hideki , Kikkawa Jun , Sakai Akira
Published: January 2014

We have developed an epitaxial growth technique for Fe-based nanocrystals (NCs) on Si substrates with high selectivity of their crystal structure. Ge NCs with controlled shape and strain were initially epitaxially grown on Si substrates covered with an ultrathin SiO2 film. Using these well-controlled Ge NCs as nucleation sites, Fe-based NCs could be formed with crystal-structure selectivity. In Fe deposition on the Ge NCs at room temperature, bcc-Fe NCs were formed, where epitaxial growth was influenced by the Ge NC shapes related to surface coverage. For Fe deposition at 250–300 °C, Fe-Ge alloying occurred without intermixing with Si. The epitaxially grown crystal structures were determined by the strain state of the Ge NCs: Fe1.7Ge NCs with a B82 structure for spherical strain-relaxed Ge NCs with a lattice constant close to that of bulk Ge, and ε-FeGe NCs with a B20 structure for flattened strained Ge NCs with a lattice constant close to that of bulk Si. All the NCs had sharp interfaces, where interfacial alloying in the Fe-Si-Ge system was well controlled. This growth technique can be used as a general technique enabling epitaxial growth of well-controlled transition metal-based films and nanostructures.
A generalized Debye source approach to electromagnetic scattering in layered media
Authors: O’Neil Michael
Published: January 2014

The standard solution to time-harmonic electromagnetic scattering problems in homogeneous layered media relies on the use of the electric field dyadic Green's function. However, for small values of the governing angular frequency ω, evaluation of the electric field using this Green's function exhibits numerical instability. In this short note, we provide an alternative approach which is immune from this low-frequency breakdown as ω → 0. Our approach is based on the generalized Debye source representation of Maxwell fields. Using this formulation, the electric and magnetic fields gracefully decouple in the static limit, a behavior similar to that of the classical Lorenz-Debye-Mie representation of Maxwell fields in spherical geometries. We derive extensions of both the generalized Deybe source and Lorenz-Debye-Mie representations to planar geometries, as well as provide equations for the solution of scattering from a perfectly conducting half-space and in layered media using a Sommerfeld-like approach. These formulas are stable as ω tends to zero, and offer alternatives to the electric field dyadic Green's function.
Harvesting of drifting filamentous macroalgae in the Baltic Sea: An energy assessment
Authors: Risén Emma , Tatarchenko Olena , Gröndahl Fredrik , Malmström Maria E.
Published: January 2014

Eutrophication combined with climate change has caused ephemeral filamentous macroalgae to increase and drifts of seaweed cover large areas of some Baltic Sea sites during summer. In ongoing projects, these mass occurrences of drifting filamentous macroalgae are being harvested to mitigate eutrophication, with preliminary results indicating considerable nutrient reduction potential. In the present study, an energy assessment was made of biogas production from the retrieved biomass for a Baltic Sea pilot case. Use of different indicators revealed a positive energy balance. The energy requirements corresponded to about 30%–40% of the energy content in the end products. The net energy gain was 530–800 MJ primary energy per ton wet weight of algae for small-scale and large-scale scenarios, where 6 000 and 13 000 tonnes dwt were harvested, respectively. However, the exergy efficiency differed from the energy efficiency, emphasising the importance of taking energy quality into consideration when evaluating energy systems. An uncertainty analysis indicated parametric uncertainty of about 25%–40%, which we consider to be acceptable given the generally high sensitivity of the indicators to changes in input data, allocation method, and system design. Overall, our evaluation indicated that biogas production may be a viable handling strategy for retrieved biomass, while harvesting other types of macroalgae than red filamentous species considered here may render a better energy balance due to higher methane yields.
Wave power calculations for a wave energy conversion device connected to a drogue
Authors: Nolte Jerica D. , Ertekin R. C.
Published: January 2014

We present the numerical modeling of a heaving, point-source wave energy conversion (WEC) device, previously tested by the University of Hawaii at Manoa. The WEC device converts the vertical heave displacements into a rotational motion to generate electrical power; the heave displacements converted are from the WEC system rising with the incoming waves relative to an anchoring system. Two anchoring methods of the WEC device are referred to as the single-body case (moored system) and double-body case (drogue anchored system). The numerical model performs hydrodynamic analysis in the time domain in irregular seas for the single-body or double-body case. We then compare the predictions with the available in-ocean experiments. The computer program written for this purpose solves for the individual body motion and predicts the WEC device's power production over the time series. Moreover, we present the results of the study that shows the effect of the device-damping characteristics and the size and the depth of operation of the drogue on wave-power predictions.
Repeated load relaxation testing of pure polycrystalline nickel at room temperature using nanoindentation
Authors: Stegall D. E. , Mamun M. A. , Crawford B. , Elmustafa A. A.
Published: January 2014

We present the results of repeated relaxation tests using nanoindentation to derive the activation volume of the dislocation velocity and the ratios of the dislocation density and dislocation velocity. An experimental technique, based on classical uniaxial relaxation experiments, was developed to establish a constant strain during repeated load relaxation transients and then to calculate the stiffness of unloading, and therefore the hardness, across the transients with acceptable results. We found that the activation volume of the dislocation velocity from our nanoindentation methodology was in good agreement when compared to the same reported for uniaxial experiments.
Effect of hydrostatic pressure on magnetic and magnetocaloric properties of Mn-site doped perovskite manganites Pr0.6Ca0.4Mn0.96B0.04O3 (B=Co and Cr)
Authors: Thiyagarajan R. , Esakki Muthu S. , Mahendiran R. , Arumugam S.
Published: January 2014

We have investigated the effect of hydrostatic pressure on magnetization and magnetocaloric properties of Pr0.6Ca0.4Mn0.96B0.04O3 (B = Co and Cr) polycrystals. At ambient pressure, both the systems undergo a first-order paramagnetic insulator to ferromagnetic metallic transition. On increasing the hydrostatic pressure, the ferromagnetic Curie temperature (TC) shifts towards high temperature at a rate of dTC/dP = 34 K/GPa (23.15 K/GPa) and 31.1 K/GPa (20.7 K/GPa) during cooling (warming) for B = Co and Cr, respectively. While the hysteresis in magnetization decreases with increasing pressure, P = 1 GPa is insufficient to completely suppress the first order transition. The magnetic entropy change (ΔSM) was calculated for various pressures up to 1 GPa and under a magnetic field of μ0H = 1-5 T. The application of pressure, as well as the magnetic field, shifts the peak in ΔSM(T) towards a higher temperature. The maximum value of ΔSM (ΔSMmax) is increased by the magnetic field but decreased by the pressure. It is also observed that while the magnetic field increases the Relative Cooling Power (RCP) of both samples, pressure decreases the RCP of Co doped but does not affect the RCP of Cr doped sample.
Effect of the computational domain on direct simulations of turbulent channels up to Reτ = 4200
Authors: Lozano-Durán Adrián , Jiménez Javier
Published: January 2014

The effect of domain size on direct numerical simulations of turbulent channels with periodic boundary conditions is studied. New simulations are presented up to Reτ = 4179 in boxes with streamwise and spanwise sizes of 2πh × πh, where h is the channel half-height. It is found that this domain is large enough to reproduce the one-point statistics of larger boxes. A simulation in a box of size 60πh × 6πh is used to show that a contour of the two-dimensional premultiplied spectrum of the streamwise velocity containing 80% of the kinetic energy closes at λx ≈ 100h.
Phase-field model for dielectric breakdown in solids
Authors: Chaitanya Pitike Krishna , Hong Wei
Published: January 2014

Using an analogy between dielectric breakdown and fracture of solids, this paper develops a phase field model for the electric damage initiation and propagation in dielectric solids during breakdown. Instead of explicitly tracing the growth of a conductive channel, the model introduces a continuous phase field to characterize the degree of damage, and the conductive channel is represented by a localized region of fully damaged material. Similar as in the classic theory of fracture mechanics, an energetic criterion is taken: The conductive channel will grow only if the electrostatic energy released per unit length of the channel is greater than that dissipated through damage. Such an approach circumvents the detailed analysis on the complex microscopic processes near the tip of a conductive channel and provides a means of quantitatively predicting breakdown phenomena in materials, composites, and devices. This model is implemented into a finite-element code, and several numerical examples are solved. With randomly distributed defects, the model recovers the inverse power relation between breakdown strength and sample thickness. Finally, the effect of the layered structure in a breakdown-resistant laminate is demonstrated through a numerical example.
Angular dependence of light trapping in In0.3Ga0.7As/GaAs quantum-well solar cells
Authors: Li X. H. , Li P. C. , Hu D. Z. , Schaadt D. M. , Yu E. T.
Published: January 2014

The dependence of light trapping effects in In0.3Ga0.7As/GaAs quantum-well solar cells on wavelength and incident angle is experimentally characterized and analyzed. Separation of active device layers from their epitaxial growth substrate enables integration of thin-film semiconductor device layers with nanostructured metal/dielectric rear contacts to increase optical absorption via coupling to both Fabry-Perot resonances and guided lateral propagation modes in the semiconductor. The roles of Fabry-Perot resonances and coupling to guided modes are analyzed via photocurrent response measurements and numerical modeling for light incident at angles of 0° (normal incidence) to 30° off normal. Light trapping enables external quantum efficiency at long wavelengths as high as 2.9% per quantum well to be achieved experimentally, substantially exceeding the ∼1% per quantum well level typically observed. Increased long wavelength quantum efficiency is shown in experimental measurements to persist with increasing angle of incidence and is explained as a consequence of the large number of guided modes available in the device structure.
Phase stability and property evolution of biphasic Ti–Ni–Sn alloys for use in thermoelectric applications
Authors: Douglas Jason E. , Birkel Christina S. , Verma Nisha , Miller Victoria M. , Miao Mao-Sheng , Stucky Galen D. , Pollock Tresa M. , Seshadri Ram
Published: January 2014

Thermoelectric properties and phase evolution have been studied in biphasic Ti–Ni–Sn materials containing full-Heusler TiNi2Sn embedded within half-Heusler thermoelectric TiNiSn. Materials, prepared by levitation induction melting followed by annealing, were of the nominal starting composition of TiNi1+xSn, with x between 0.00 and 0.25. Phases and microstructure were determined using synchrotron X-ray diffraction and optical and electron microscopy. The full-Heusler phase is observed to be semi-coherent with the half-Heusler majority phase. Differential thermal analysis was performed to determine melting temperatures of the end-member compounds. The thermal conductivity is reduced with the introduction of a dispersed, full-Heusler phase within the half-Heusler material. This leads to an increased thermoelectric figure of merit, ZT, from 0.35 for the stoichiometric compound to 0.44 for TiNi1.15Sn. Beyond x = 0.15 ZT decreases due to a rise in thermal conductivity. Density functional theory calculations using hybrid functionals were performed to determine band alignments between the half- and full-Heusler compounds, as well as comparative energies of formation. The hybrid functional band structure of TiNiSn is presented as well.
Thermally-driven H interaction with HfO2 films deposited on Ge(100) and Si(100)
Authors: Soares G. V. , Feijó T. O. , Baumvol I. J. R. , Aguzzoli C. , Krug C. , Radtke C.
Published: January 2014

In the present work, we investigated the thermally-driven H incorporation in HfO2 films deposited on Si and Ge substrates. Two regimes for deuterium (D) uptake were identified, attributed to D bonded near the HfO2/substrate interface region (at 300 °C) and through the whole HfO2 layer (400–600 °C). Films deposited on Si presented higher D amounts for all investigated temperatures, as well as, a higher resistance for D desorption. Moreover, HfO2 films underwent structural changes during annealings, influencing D incorporation. The semiconductor substrate plays a key role in this process.
Characteristics of a micro-hydro turbine
Authors: Schleicher W. , Ma H. , Riglin J. , Kraybill Z. , Wei W. , Klein R. , Oztekin A.
Published: January 2014

Computational Fluid Dynamics, a crucial tool in exploring designs of hydraulic machinery, is used to evaluate the design of a non-uniform Archimedean spiral rotor. A transient simulation method is implemented using a frame of reference change between time-steps to capture the flow field correctly. The boundary conditions for this method are discussed and are validated with previously published experimental data using a flat plate propeller turbine. A spectral and temporal convergence study for the non-uniform Archimedean spiral rotor is performed to verify solution independence of mesh and time-step selection. Performance characteristics of the rotor are provided over a wide range of volumetric flow rates and rotation rates. The best hydraulic efficiency point is determined to be 72% for the presented rotor design and is compared with the performance of similar micro-hydro turbines.
X-ray photoelectron spectroscopic study of silicon surface passivation in alcoholic iodine and bromine solutions
Authors: Batra Neha , Vandana  , Kumar Praveen , Srivastava S. K. , Singh P. K.
Published: January 2014

We report an X-ray photoelectron spectroscopic (XPS) study of silicon surfaces passivation using alcoholic solutions of iodine and bromine where different behavior with two systems is observed. The minority carrier lifetime determined by microwave photoconductive decay method showed better surface passivation for iodine-alcoholic system with HF preconditioning step. The iodine–ethanol (I–E) passivated samples show strong Si–I bonding (two times) in Si core level spectra for the samples without oxide (25.5%) compared with oxide (10.2%) counterpart. However, bromine–ethanol (B–E) passivated samples show higher Si–Br bonding strength in the samples with oxide (24.7%) compared to without oxide specimens (12.0%). This may be the reason of difference in passivation behavior of I–E and B–E systems. Higher O–Br bonding in O core level spectra of B–E passivated samples with oxide (35.8%), compared to without oxide (20.7%), results in comparable lifetime values in both with and without preconditioning. To understand the effect of solvent on the passivation, experiments are performed using iodine–methanol (I–M) and bromine–methanol (B–M) solutions and XPS analysis shows similar Si–I, Si–Br, and O–Br bonding trends.
1.3 μm photoluminescence of Ge/GaAs multi-quantum-well structure
Authors: Aleshkin V. Ya. , Dubinov A. A. , Kudryavtsev K. E. , Rumyantsev V. V. , Tonkikh A. A. , Zakharov N. D. , Zvonkov B. N.
Published: January 2014

In this paper, we report on photoluminescence studies of a multiple quantum well Ge/GaAs heterostructure grown by laser-assisted sputtering. A broad luminescence peak is found at about 1.3 μm at room temperature. We attribute this peak to the direct band gap transitions between Γ-valley electrons in the GaAs matrix and valence band heavy holes in Ge quantum wells.
Light harvesting with Ge quantum dots embedded in SiO2 or Si3N4
Authors: Cosentino Salvatore , Sungur Ozen Emel , Raciti Rosario , Mio Antonio M. , Nicotra Giuseppe , Simone Francesca , Crupi Isodiana , Turan Rasit , Terrasi Antonio , Aydinli Atilla , Mirabella Salvo
Published: January 2014

Germanium quantum dots (QDs) embedded in SiO2 or in Si3N4 have been studied for light harvesting purposes. SiGeO or SiGeN thin films, produced by plasma enhanced chemical vapor deposition, have been annealed up to 850 °C to induce Ge QD precipitation in Si based matrices. By varying the Ge content, the QD diameter can be tuned in the 3–9 nm range in the SiO2 matrix, or in the 1–2 nm range in the Si3N4 matrix, as measured by transmission electron microscopy. Thus, Si3N4 matrix hosts Ge QDs at higher density and more closely spaced than SiO2 matrix. Raman spectroscopy revealed a higher threshold for amorphous-to-crystalline transition for Ge QDs embedded in Si3N4 matrix in comparison with those in the SiO2 host. Light absorption by Ge QDs is shown to be more effective in Si3N4 matrix, due to the optical bandgap (0.9–1.6 eV) being lower than in SiO2 matrix (1.2–2.2 eV). Significant photoresponse with a large measured internal quantum efficiency has been observed for Ge QDs in Si3N4 matrix when they are used as a sensitive layer in a photodetector device. These data will be presented and discussed, opening new routes for application of Ge QDs in light harvesting devices.
Efficient gradient field generation providing a multi-dimensional arbitrary shifted field-free point for magnetic particle imaging
Authors: Kaethner Christian , Ahlborg Mandy , Knopp Tobias , Sattel Timo F. , Buzug Thorsten M.
Published: January 2014

Magnetic Particle Imaging (MPI) is a tomographic imaging modality capable to visualize tracers using magnetic fields. A high magnetic gradient strength is mandatory, to achieve a reasonable image quality. Therefore, a power optimization of the coil configuration is essential. In order to realize a multi-dimensional efficient gradient field generator, the following improvements compared to conventionally used Maxwell coil configurations are proposed: (i) curved rectangular coils, (ii) interleaved coils, and (iii) multi-layered coils. Combining these adaptions results in total power reduction of three orders of magnitude, which is an essential step for the feasibility of building full-body human MPI scanners.
Ultrafast photoconductivity of crystalline, polycrystalline, and nanocomposite ZnSe material systems for terahertz applications
Authors: Collier C. M. , Holzman J. F.
Published: January 2014

Ultrafast photoconductivity is studied for crystalline (bulk), polycrystalline (microstructure), and nanocomposite (nanostructure) ZnSe material systems. Spectral transmission analyses show a pronounced red-shift of the absorption edge for only the nanocomposite ZnSe (being comprised of 500 nm nanoparticles in a polymer host). Ultrafast transient analyses show respective 6 ns, 1.5 ns, and 95 ps charge-carrier lifetimes for the respective material systems. The results are interpreted with a diffusion-recombination model, showing distinct regimes for bulk diffusion and surface recombination. Nanocomposite ZnSe is shown to be particularly advantageous for terahertz applications seeking ultrafast photoconductivity with high dielectric breakdown strengths and ultrashort charge-carrier lifetimes.
A programmable quantum current standard from the Josephson and the quantum Hall effects
Authors: Poirier W. , Lafont F. , Djordjevic S. , Schopfer F. , Devoille L.
Published: January 2014

We propose a way to realize a programmable quantum current standard (PQCS) from the Josephson voltage standard and the quantum Hall resistance standard (QHR) exploiting the multiple connection technique provided by the quantum Hall effect (QHE) and the exactness of the cryogenic current comparator. The PQCS could lead to breakthroughs in electrical metrology like the realization of a programmable quantum current source, a quantum ampere-meter, and a simplified closure of the quantum metrological triangle. Moreover, very accurate universality tests of the QHE could be performed by comparing PQCS based on different QHRs.
Monolayer-induced band shifts at Si(100) and Si(111) surfaces
Authors: Mäkinen A. J. , Kim Chul-Soo , Kushto G. P.
Published: January 2014

We report our study of the interfacial electronic structure of Si(100) and Si(111) surfaces that have been chemically modified with various organic monolayers, including octadecene and two para-substituted benzene derivatives. X-ray photoelectron spectroscopy reveals an upward band shift, associated with the assembly of these organic monolayers on the Si substrates, that does not correlate with either the dipole moment or the electron withdrawing/donating character of the molecular moieties. This suggests that the nature and quality of the self-assembled monolayer and the intrinsic electronic structure of the semiconductor material define the interfacial electronic structure of the functionalized Si(100) and Si(111) surfaces.
Epitaxial two-dimensional nitrogen atomic sheet in GaAs
Authors: Harada Yukihiro , Yamamoto Masuki , Baba Takeshi , Kita Takashi
Published: January 2014

We have grown an epitaxial two-dimensional nitrogen (N) atomic sheet in GaAs by using the site-controlled N δ-doping technique. We observed a change of the electronic states in N δ-doped GaAs from the isolated impurity centers to the delocalized impurity band at 1.49 eV with increasing N-doping density. According to the excitation-power- and temperature-dependent photoluminescence (PL) spectra, the emission related to localized levels below the impurity band edge was dominant at low excitation power and temperature, whereas the effects of the localized levels can be neglected by increasing the excitation power and temperature. Furthermore, a clear Landau shift of the PL-peak energy was observed at several Tesla in the Faraday configuration, in contrast to the case in the impurity limit.
Ni80Fe20 film with periodically modulated thickness as a reconfigurable one-dimensional magnonic crystal
Authors: Kakazei G. N. , Liu X. M. , Ding J. , Adeyeye A. O.
Published: January 2014

Magnonic crystals with periodically modulated thickness were fabricated using deep ultraviolet lithography by covering Ni80Fe20 nanowire arrays with continuous Ni80Fe20 film. It is shown that the magnetization reversal and ferromagnetic resonance fields can be tuned either varying the film thickness (t) or the stripe width (w). For t ≥ 20 nm, two different stable magnetic configurations in zero external field were obtained. These configurations are characterized by noticeably different frequencies of ferromagnetic resonance up to 1 GHz and can be switched by applying magnetic pulses of proper amplitude and polarity.
Nanoparticle-induced rectification in a single cylindrical nanopore: Net currents from zero time-average potentials
Authors: Ali Mubarak , Ramirez Patricio , Nasir Saima , Nguyen Quoc-Hung , Ensinger Wolfgang , Mafe Salvador
Published: January 2014

Rectification in nanopores is usually achieved by a fixed asymmetry in the pore geometry and charge distribution. We show here that nanoparticle blocking of a cylindrical pore induces rectifying properties that can support significant net currents with zero time-average potentials. To describe experimentally this effect, the steady-state current-voltage curves of a single nanopore are obtained for different charge states and relative sizes of the pore and the charged nanoparticles, which are present only on one side. The rectification phenomena observed can find applications in the area of nanofluidics and involves physical concepts that are also characteristic of the blocking of protein ion channels by ionic drugs.
Atmosphere controlled conductivity and Maxwell-Wagner relaxation in Bi0.5K0.5TiO3—BiFeO3 ceramics
Authors: Morozov Maxim I. , Einarsrud Mari-Ann , Grande Tor
Published: January 2014

Here, we report on a giant dielectric relaxation in (1 − x)Bi0.5K0.5TiO3—xBiFeO3 ceramics below ∼300 °C, which becomes more pronounced with increasing BiFeO3 content. The relaxation was shown to be of Maxwell-Wagner type and associated with charge depletion at the electroded interfaces. It was also shown that the relaxation could be controlled or, eventually, removed by heat treatment in controlled partial pressure of oxygen. This was rationalized by the relationship between the electrical conductivity and variation in the oxidation state of Fe, which is strongly coupled to the partial pressure of oxygen. The results are discussed with emphasis on oxygen diffusion and point defect equilibria involving oxygen vacancies and iron in divalent and tetravalent state. Finally, the barrier-free dielectric properties of the (1 − x)Bi0.5K0.5TiO3—xBiFeO3 ceramics are reported.
State Rescaling and the Making of City-Regions in the Pearl River Delta, China
Authors: Li Zhigang , Xu Jiang , Yeh Anthony G O
Published: January 2014

This study empirically tests the theory of state rescaling with a study of recent city-region making in China. The implementation of two interjurisdictional projects, the Pearl River Delta Intercity Railway and the Guangzhou–Foshan Metro, are critically investigated to probe the restructuring states in the transitional Pearl River Delta. We argue that the principle of scale theory is relevant to China, where scalar reconfiguration of states has been identified in the process of city-region making. To implement the projects, governments at various geographical scales engage in numerous activities of flexible competition, cooperation, and negotiation. The paper draws on a detailed empirical observation of the actual process, to broaden the theoretical framework of state rescaling, showing four dimensions of state-rescaling categories of restructuring: upscaling, downscaling, statization, and destatization. The paper also highlights the creation of the city-region—that is, state space—as both a de jure and de facto political instrument to rearticulate state power. With an emphasis on the concomitant trend of centralization or upscaling, it also contributes to the existing literature on state rescaling in China by denaturalizing the trend of decentralization, or downscaling.
Variance component analysis of body mass in a wild population of deer (Odocoileus virginianus): results from two decades of research
Authors: Webb Stephen L. , Gee Kenneth L. , DeYoung Randy W. , Harju Seth M.
Published: January 2014

Context
Long-term studies of large, vertebrate mammals using capture–recapture data are scarce, even though long-term ecological studies are requisite to understanding quantitative genetics and evolutionary processes that can be applied as part of management programs.

Aims
Objectives were to (1) partition components of variation in body mass to understand the differential effects of environmental variation on the sexes during ontogeny, to better prescribe habitat-improvement projects, and (2) estimate repeatability to assess potential for selection on body mass.

Methods
We used a 23-year dataset (1983–2005) of capture–recapture records of wild white-tailed deer (Odocoileus virginianus) to estimate components of variance and repeatability of body mass. We used an animal-model approach that employed the use of general linear mixed models and restricted maximum likelihood to adjust for the effects of age (i.e. fixed effect), and to partition the total phenotypic variance into among-individual (i.e. the deer), permanent environmental (i.e. year of birth) and temporary environmental (i.e. year of measurement and residual) effects (all modelled as random effects).

Key results
We found that body mass increased with age in both sexes, repeatability of body mass was 0.595 for females and 0.716 for males, and among-individual variation was more influential on body mass than were permanent and temporary environmental effects combined. Year of birth was more important in males than females, but changed during the course of ontogeny for both sexes. Year of measurement did not influence post-rut body mass in males, but did contribute to variation in body mass of females.

Conclusions
These long-term data offer insights into the sources of variation that influence body mass of deer, which can be used to understand how environmental sources of variation influence phenotypic traits, and for developing management plans and making selection decisions.

Implications
Knowledge of repeatability (as an upper limit to heritability) can be used to make management decisions related to selection, culling and breeding, whereas understanding environmental effects can lead to better management recommendations (e.g. habitat-improvement projects).
Captive husbandry and veterinary care of northern New Zealand dotterels (Charadrius obscurus aquilonius) during the CV Rena oil-spill response
Authors: Gartrell B. D. , Collen R. , Dowding J. E. , Gummer H. , Hunter S. , King E. J. , Laurenson L. , Lilley C. D. , Morgan K. J. , McConnell H. M. , Simpson K. , Ward J. M.
Published: January 2014

Context
Oil spills cause significant detrimental impacts on many shoreline species. There is limited information in the scientific literature about the management and response of shorebirds to oil spills. Northern New Zealand dotterels (Charadrius obscurus aquilonius) were pre-emptively captured as part of the oiled wildlife response to the container vessel Rena oil spill, to ensure the survival of a regional population should there be a catastrophic release of oil. Previous attempts to hold dotterels in captivity have resulted in high mortality.

Aims
To describe the captive husbandry and veterinary management of wild-caught adult dotterels, to outline the common problems encountered, and make recommendations for future captive management.

Methods
The dotterels were caught by noose mat on beaches at risk of further contamination by oil. Initially, dotterels were kept individually indoors and force-fed until they converted to self-feeding on a diet of an artificial insect analogue, ox heart and mealworms. Once self-feeding, the birds were shifted to individual outdoor aviaries.

Key results
Sixty dotterels were caught. About half of birds had oil contamination of the legs, nine birds had light oil staining of feathers and only three of these birds required washing. The degree of oiling and washing did not affect survival. Dotterels took a median of 5 days (range 1–15 days) to convert to the captive diet. Common problems encountered in captivity included carpal and beak abrasions (61.7%) and pododermatitis (75%); however, these did not affect survival. Seven birds (11.7%) developed respiratory disease and six of these died from aspergillosis. The incidence of aspergillosis increased with length of time in captivity and was largely refractory to treatment. The 54 surviving birds were released at their capture sites after a median time of 49 days in captivity (with a range of 39–61 days).

Conclusions
The captive management of the dotterels achieved a 90% survival rate over a period of about 2 months. Deaths were solely due to respiratory aspergillosis, but intensive captive husbandry was required to convert the birds to a captive diet, to minimise traumatic injuries and to manage pododermatitis.

Implications
Although the captive management of shorebird species as a pre-emptive strategy to minimise the effects of oil spills carries significant costs and risks to the birds, it should be considered in the emergency management of high-priority species.
Dysfunctional dichotomies? Deflating bipolar constructions of curriculum and pedagogy through case studies from music and history
Authors: Cain Tim , Chapman Arthur
Published: January 2014

Recent public discussions of curriculum and pedagogy that have accompanied the English National Curriculum review have been structured around clichéd dichotomies that generate more heat than light and that, as Robin Alexander has argued, reduce complex educational debates to oppositional and incompatible slogans. This paper begins by exploring the ways in which these dichotomies have structured recent debates and goes on to critically explore arguments in two contemporary debates, in the fields of history education and music education, assessing how these debates have been framed and the extent to which the debates can be considered fruitful and progressive. In the first case, we seek to show, through a discussion of ‘knowledge’ and ‘skill’ in history, that bipolar thinking is both inadequate and dysfunctional in relation to the matters under discussion. A third term — disciplinary understanding — is advocated and explored. In the second case, we demonstrate that dichotomous thinking about formal and informal music education has generated a debate that has become more sophisticated as various authors have problematised and critiqued informal learning. Analysis of these debates suggests that dichotomous thinking is pernicious when dichotomies are used only as slogans, although dichotomies can be generative when they are used as starting points to open discussion, not to close it. The paper suggests that the difference between the debates might be explained by the varying degrees of political involvement in them.
The relationship between religion and the state: the institution of ‘Commandment of the Faithful’ in Morocco
Authors: Khamlichi Ahmed Al
Published: January 2014

The term ‘Amir al-Mou’mineen’ (Commander of the Faithful) and ‘caliph’ were first bestowed on Omar Bin al-Khattab who became the successor of the Prophet (Peace be upon him) two-and-a-half years after he passed away. By virtue of the political and religious connotations of the term, the title conveyed overarching political authority – a kind of absolute power. The notion of Commander of the Faithful facilitated oppression of those who held different views, directly or indirectly, through employing fatawa, that is religious interpretations and edicts, in addition to mobilizing religious followers and devotees. This excess of political power is based on the definition of Imarat al-Mu’mineen (Commandment of the Faithful) or the Caliphate common in religious jurisprudence. This definition was coined by Ibn Khaldoun, and may be translated as: ‘making people abide by the view of Shar (the Law of God in Islam) regarding their temporal and afterlife interests’. Morocco has been no different from the rest of the Islamic world over the centuries, and now two distinct phenomena are apparent. First, the emergence of different groups, each with its own ideology and claims to be defending religion and pursuing its implementation. Such groups consider all other ways of thinking as apostasy that must be eliminated; while juxtaposed to them, there exist intellectual currents calling for the continued separation of religion and the state and its laws. During the past two decades this phenomenon has led to tragic situations in a considerable number of Islamic states, whose prospects now seem very gloomy. Second, a tight regulation of state institutions, together with constitutional guarantees of individual rights and freedoms, can prevent the manipulation of the state in the name of religion, and its use for tyranny and the oppression of individuals and minorities, be it in the name of Commandment of the Faithful or any other term. It seems that Morocco is aware of the power of these two phenomena, especially after it faced social unrest in 1992 and 2001, which almost destroyed its stability.
The Syrian Crisis: a systemic framework
Authors: Khashanah Khaldoun
Published: January 2014

There is as yet no framework for understanding the Syrian Crisis (herein referred to as ‘the Syrian Crisis’; the Syrian Crisis or simply ‘the Crisis’) or more generally the Arab Spring. There are many arguments that are often inconsistent. A framework can help further socio-political and economic analysis and synthesis and will facilitate the convergence of conflicting views on a solution. This article is intended to provide a systemic framework for the Syrian Crisis that can be extended to other Arab experiences. Syrians have split into three main categories vis-à-vis the Crisis: pro-government, pro-revolt and a silent middle. The contention here that, regardless of classification or intentions, events on the ground and the accompanying political manoeuvres point collectively to the conclusion that the revolt became a tool in the toolbox for Syrian realignment ideologically and geopolitically under the pretence of a just revolt. The argument advanced is that there is a plan for the realignment of Syria that uses the revolt as an entrance point and a tool in this strategy – whether the Syrians engaged in revolt know it or not. The Syrian people, the Syrian government and the rebels have borne the entire risk throughout the induced Crisis with no control over aspects of its trajectory. The complexity of the Syrian Crisis comes from two simultaneous confluences: an ideological confluence and geopolitical confluence. In his exposition of this strategy the author posits that, for the plan to succeed, it may be necessary to destroy the fabric of Syrian society by discrediting Syrian nationalism, Arab nationalism and moderate Islamism through supporting sectarianism, subnationalism, regionalism and Islamic fundamentalism to achieve the desired realignment under the banner of humanitarian intervention. The course of action adopted by the external opposition does not align with a revolution for the people of Syria. The sponsors of the plan discerned here deployed Islamist Jihadism as a universal catalytic enabler of Syria’s destruction without appearing to be supporting terrorism for regime change in Syria. The losers are the Syrian people, their infrastructure, their unity and possibly their statehood, and many innocent lives. The author introduces two new analytic tools to facilitate the discussion: the ‘ideogram’ and the ‘geogram’.
A note on special values of 𝐿-functions
Authors: Gun Sanoli , Murty M. , Rath Purusottam
Published: January 2014

In this paper, we link the nature of special values of certain Dirichlet

L
L

-functions to those of multiple gamma values.
On the Gorenstein and cohomological dimension of groups
Authors: Talelli Olympia
Published: January 2014

Here we relate the Gorenstein dimension of a group

G
G

,

G
c
d

R

G

\mathrm {Gcd}_{R}G

, over

Z

\mathbb Z

and

Q

\mathbb Q

to the cohomological dimension of

G
G

,

c
d

R

G

\mathrm {cd}_{R}G

, over

Z

\mathbb Z

and

Q

\mathbb Q

, and show that if

G
G

is in

L
H

F

{\scriptstyle \bf {LH}}\mathfrak F

, a large class of groups defined by Kropholler, then

c
d

Q

G
=

G
c
d

Q

G

\mathrm {cd}_{\mathbb Q}G=\mathrm {Gcd}_{\mathbb Q}G

and if

G
G

is torsion free, then

G
c
d

Z

G
=

c
d

Z

G

\mathrm {Gcd}_{\mathbb Z}G= \mathrm {cd}_{\mathbb Z}G

. We also show that for any group

G
G

,

G
c
d

Q

G
≤

G
c
d

Z

G

\mathrm {Gcd}_{\mathbb Q}G\leq \mathrm {Gcd}_{\mathbb Z}G

.
Kaplansky Theorem for completely regular spaces
Authors: Li Lei , Wong Ngai-Ching
Published: January 2014

Let

X
,
Y

X, Y

be realcompact spaces or completely regular spaces consisting of

G
δ

G_\delta

-points. Let

ϕ
\phi

be a linear bijective map from

C
(
X
)

C(X)

(resp.

C
b

(
X
)

C^b(X)

) onto

C
(
Y
)

C(Y)

(resp.

C
b

(
Y
)

C^b(Y)

). We show that if

ϕ
\phi

preserves nonvanishing functions, that is,
\[
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="f left-parenthesis x right-parenthesis not-equals 0 comma for-all x element-of upper X comma long left right double arrow phi left-parenthesis f right-parenthesis left-parenthesis y right-parenthesis not-equals 0 comma for-all y element-of upper Y comma">

f
(
x
)
≠
0
,
∀

x
∈
X
,

⟺

ϕ
(
f
)
(
y
)
≠
0
,
∀

y
∈
Y
,

f(x)\neq 0,\forall \, x\in X, \quad \Longleftrightarrow \quad \phi (f)(y)\neq 0, \forall \, y\in Y,

\]
then

ϕ
\phi

is a weighted composition operator
\[

ϕ
(
f
)
=
ϕ
(
1
)
⋅
f
∘
τ
,

\phi (f)=\phi (1)\cdot f\circ \tau ,

\]
arising from a homeomorphism

τ
\tau

from

Y
Y

onto

X
X

. This result is applied also to other nice function spaces, e.g., uniformly or Lipschitz continuous functions on metric spaces.
Automorphisms of affine smooth varieties
Authors: Jelonek Zbigniew , Lenarcik Tomasz
Published: January 2014

Let

k
k

be an algebraically closed field. If

X
X

is a smooth projective variety over

k
k

and

H
⊂
X

H\subset X

is a very ample hypersurface without ruled components, then the group

A
u
t

(
X
∖
H
)

\mathrm {Aut}(X\setminus H)

is finite and equal to
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="normal upper S normal t normal a normal b Subscript upper X Baseline left-parenthesis upper H right-parenthesis equals StartSet phi element-of normal upper A normal u normal t left-parenthesis upper X right-parenthesis colon phi left-parenthesis upper H right-parenthesis equals upper H EndSet period">

S
t
a
b

X

(
H
)
=
{
ϕ
∈

A
u
t

(
X
)
:
ϕ
(
H
)
=
H
}
.

\mathrm {Stab}_X(H)=\{ \phi \in \mathrm {Aut}(X): \phi (H)=H\}.
On exotic affine 3-spheres
Authors: Dubouloz Adrien , Finston David
Published: February 2014

Every

A

1

\mathbb {A}^{1}

-bundle over

A

∗

2

,

\mathbb {A}_{\ast }^{2},

the complex affine plane punctured at the origin, is trivial in the differentiable category, but there are infinitely many distinct isomorphy classes of algebraic bundles. Isomorphy types of total spaces of such algebraic bundles are considered; in particular, the complex affine

3
3

-sphere

S

C

3

,

\mathbb {S}_{\mathbb {C}}^{3},

given by

z

1

2

+

z

2

2

+

z

3

2

+

z

4

2

=
1
,

z_{1}^{2}+z_{2}^{2}+z_{3}^{2}+z_{4}^{2}=1,

admits such a structure with an additional homogeneity property. Total spaces of nontrivial homogeneous

A

1

\mathbb {A}^{1}

-bundles over

A

∗

2

\mathbb {A}_{\ast }^{2}

are classified up to

G

m

\mathbb {G}_{m}

-equivariant algebraic isomorphism, and a criterion for nonisomorphy is given. In fact

S

C

3

\mathbb {S}_{\mathbb {C}}^{3}

is not isomorphic as an abstract variety to the total space of any

A

1

\mathbb {A}^{1}

-bundle over

A

∗

2

\mathbb {A}_{\ast }^{2}

of different homogeneous degree, which gives rise to the existence of exotic spheres, a phenomenon that first arises in dimension three. As a byproduct, an example is given of two biholomorphic but not algebraically isomorphic threefolds, both with a trivial Makar-Limanov invariant, and with isomorphic cylinders.
Conventional transmission electron microscopy
Authors: Winey Mark , Meehl Janet B. , O'Toole Eileen T. , Giddings Thomas H.
Published: January 2014

Researchers have used transmission electron microscopy (TEM) to make contributions to cell biology for well over 50 years, and TEM continues to be an important technology in our field. We briefly present for the neophyte the components of a TEM-based study, beginning with sample preparation through imaging of the samples. We point out the limitations of TEM and issues to be considered during experimental design. Advanced electron microscopy techniques are listed as well. Finally, we point potential new users of TEM to resources to help launch their project.