bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and photovoltaic properties of dithieno[3,2-b:2′,3′-d]silole-based conjugated copolymers
Authors: Wen Shanpeng , Wang Chen , Ma Pengfei , Zhao Ying-Xuan , Li Chang , Ruan Shengping
Published: May 2015

Efficient polymer solar cells were fabricated by blending PDTS-DTffBT with PC71BM, and the power conversion efficiency reached 5.26%.
Preparation of a graphene-based composite aerogel and the effects of carbon nanotubes on preserving the porous structure of the aerogel and improving its capacitor performance
Authors: Ma Zhihua , Zhao Xiaowei , Gong Chunhong , Zhang Jingwei , Zhang Jiwei , Gu Xiufang , Tong Lei , Zhou Jingfang , Zhang Zhijun
Published: May 2015

Carbon nanotube supported 3D graphene-based composite aerogel was prepared, which exhibited high pore volume, conductivity, and great capacitor performance.
Soft and hard templating of graphitic carbon nitride
Authors: Yang Zhao , Zhang Yuanjian , Schnepp Zoe
Published: May 2015

This article reviews recent advances in templating of graphitic carbon nitride materials, with a particular focus on applications in photocatalysis.
Safer salts for CdTe nanocrystal solution processed solar cells: the dual roles of ligand exchange and grain growth
Authors: Townsend Troy K. , Heuer William B. , Foos Edward E. , Kowalski Eric , Yoon Woojun , Tischler Joseph G.
Published: May 2015

The dual role of salt treatment was revealed by replacing conventional CdCl2 with non-toxic NH4Cl to simultaneously exchange native ligands and promote grain growth in inorganic CdTe nanocrystal solar cells.
One-pot synthesis of BiPO4 functionalized reduced graphene oxide with enhanced photoelectrochemical performance for selective and sensitive detection of chlorpyrifos
Authors: Qian Jing , Yang Zhenting , Wang Chengquan , Wang Kan , Liu Qian , Jiang Ding , Yan Yuting , Wang Kun
Published: May 2015

BiPO4–rGO NCs proved to be an excellent photoactive material and have been used for selective PEC sensing of chlorpyrifos.
A facile and rapid preparation of highly crumpled nitrogen-doped graphene-like nanosheets for high-performance supercapacitors
Authors: Peng Hui , Ma Guofu , Sun Kanjun , Zhang Zhiguo , Yang Qian , Ran Feitian , Lei Ziqiang
Published: May 2015

Highly crumpled nitrogen-doped graphene-like nanosheets (CN-GLSs) with a high specific surface area (1169 m2 g−1) and large pore volume (2.58 cm3 g−1) are prepared from a macroporous resin via simultaneous urea gasification expansion and CaCl2 activation methods.
Tough and fully recoverable hydrogels
Authors: Wei Junhua , Wang Jilong , Su Siheng , Wang Shiren , Qiu Jingjing
Published: May 2015

In natural cartilage, collagen fibers form the extracellular matrix, while aggrecan entangles with these fibers and provides cartilage with its osmotic properties, which are critical to resist cyclic compressive loads.
Synthesis, characterization and electrical properties of silicon-doped graphene films
Authors: Wang Zegao , Li Pingjian , Chen Yuanfu , Liu Jingbo , Zhang Wanli , Guo Zheng , Dong Mingdong , Li Yanrong
Published: May 2015

A silicon-doped graphene film was synthesized by CVD using triphenylsilane as a sole carbon and silicon source. The silicon-doped graphene exhibits a strong p-type feature and has a large hole mobility of 660 cm2 V−1 s−1.
Bane to boon: tailored defect induced bright red luminescence from cuprous iodide nanophosphors for on-demand rare-earth-free energy-saving lighting applications
Authors: Saha Subhajit , Das Swati , Sen Dipayan , Ghorai Uttam Kumar , Mazumder Nilesh , Gupta Bipin Kumar , Chattopadhyay Kalyan Kumar
Published: May 2015

Ultra-high red luminescence is demonstrated from rare-earth free as well as nontoxic cuprous iodide nanophosphors through controlled defect level engineering.
Study on the internal field and conduction mechanism of atomic layer deposited ferroelectric Hf0.5Zr0.5O2 thin films
Authors: Park M. H. , Kim H. J. , Kim Y. J. , Moon T. , Kim K. D. , Lee Y. H. , Hyun S. D. , Hwang C. S.
Published: May 2015

The effects of the internal field and conduction mechanism of carriers in ferroelectric Hf0.5Zr0.5O2 thin films are systematically investigated by controlling the in-depth profile of oxygen vacancy concentrations.
Highly-sensitive epinephrine sensors based on organic electrochemical transistors with carbon nanomaterial modified gate electrodes
Authors: Mak Chun Hin , Liao Caizhi , Fu Ying , Zhang Meng , Tang Chun Yin , Tsang Yuen Hong , Chan Helen L. W. , Yan Feng
Published: May 2015

The sensitivity of OECT-based epinephrine sensors has been dramatically improved by modifying carbon nanomaterials on the Pt gate electrodes.
Novel blue and green phosphors obtained from K2ZrSi3O9:Eu2+ compounds with different charge compensation ions for LEDs under near-UV excitation
Authors: Ding Xin , Zhu Ge , Geng Wanying , Mikami Masayoshi , Wang Yuhua
Published: May 2015

Novel blue and green phosphors obtained from K2ZrSi3O9:Eu2+ compound by co-doping Al3+ and Sc3+ for LEDs under NUV excitation.
Tail wags the dog: activity of krait natriuretic peptide is determined by its C-terminal tail in a natriuretic peptide receptor-independent manner
Authors: Sridharan Sindhuja , Kini R. Manjunatha
Published: May 2015

Natriuretic peptides (NPs) are potent vasoactive hormones, which maintain pressure–volume homoeostasis. Snake venom NPs exhibit distinct biological activity compared with mammalian NPs due to subtle changes in their sequences. We recently identified a new NP from krait venom (KNP), with an unusual 38-residue long C-terminal tail, which has a propensity to form an α-helix. KNP mediates vasodilation via NP receptor (NPR) independent mechanisms on pre-contracted aortic strips in contrast with classical NPs. The infusion of KNP in anaesthetized rats resulted in a prolonged and sustained drop in blood pressure (BP) and heart rate (HR) with no renal effects in contrast with mammalian counterparts. Deletion mutant studies have revealed the presence of two functional segments in KNP, namely Ring and Helix. Although the Ring interacts with NPR, its contribution to the activity of KNP is shown to be negligible as both KNP and Helix elicit equipotent endothelium-dependent vasorelaxation. Further, KNP and Helix signalled through endothelial nitric oxide (NO) to mediate NPR-independent vasodilation. Thus, KNP exhibits non-canonical characteristics through its C-terminal tail, despite a functional NP ring. The present study has altered the paradigm of NP biology through the understanding of structure–function relationships and may serve as a lead for the design of novel hypotensive agents.
Modulation of the extracellular matrix patterning of thrombospondins by actin dynamics and thrombospondin oligomer state
Authors: Hellewell Andrew L. , Gong Xianyun , Schärich Karsten , Christofidou Elena D. , Adams Josephine C.
Published: May 2015

Thrombospondins (TSPs) are evolutionarily-conserved, secreted glycoproteins that interact with cell surfaces and extracellular matrix (ECM) and have complex roles in cell interactions. Unlike the structural components of the ECM that form networks or fibrils, TSPs are deposited into ECM as arrays of nanoscale puncta. The cellular and molecular mechanisms for the patterning of TSPs in ECM are poorly understood. In the present study, we investigated whether the mechanisms of TSP patterning in cell-derived ECM involves actin cytoskeletal pathways or TSP oligomer state. From tests of a suite of pharmacological inhibitors of small GTPases, actomyosin-based contractility, or actin microfilament integrity and dynamics, cytochalasin D and jasplakinolide treatment of cells were identified to result in altered ECM patterning of a model TSP1 trimer. The strong effect of cytochalasin D indicated that mechanisms controlling puncta patterning depend on global F-actin dynamics. Similar spatial changes were obtained with endogenous TSPs after cytochalasin D treatment, implicating physiological relevance. Under matched experimental conditions with ectopically-expressed TSPs, the magnitude of the effect was markedly lower for pentameric TSP5 and Drosophila TSP, than for trimeric TSP1 or dimeric Ciona TSPA. To distinguish between the variables of protein sequence or oligomer state, we generated novel, chimeric pentamers of TSP1. These proteins accumulated within ECM at higher levels than TSP1 trimers, yet the effect of cytochalasin D on the spatial distribution of puncta was reduced. These findings introduce a novel concept that F-actin dynamics modulate the patterning of TSPs in ECM and that TSP oligomer state is a key determinant of this process.
The regulation of mitochondrial transcription factor A (Tfam) expression during skeletal muscle cell differentiation
Authors: Collu-Marchese Melania , Shuen Michael , Pauly Marion , Saleem Ayesha , Hood David A.
Published: May 2015

The ATP demand required for muscle development is accommodated by elevations in mitochondrial biogenesis, through the co-ordinated activities of the nuclear and mitochondrial genomes. The most important transcriptional activator of the mitochondrial genome is mitochondrial transcription factor A (Tfam); however, the regulation of Tfam expression during muscle differentiation is not known. Thus, we measured Tfam mRNA levels, mRNA stability, protein expression and localization and Tfam transcription during the progression of muscle differentiation. Parallel 2-fold increases in Tfam protein and mRNA were observed, corresponding with 2–3-fold increases in mitochondrial content. Transcriptional activity of a 2051 bp promoter increased during this differentiation period and this was accompanied by a 3-fold greater Tfam mRNA stabilization. Interestingly, truncations of the promoter at 1706 bp, 978 bp and 393 bp promoter all exhibited 2–3-fold higher transcriptional activity than the 2051 bp construct, indicating the presence of negative regulatory elements within the distal 350 bp of the promoter. Activation of AMP kinase augmented Tfam transcription within the proximal promoter, suggesting the presence of binding sites for transcription factors that are responsive to cellular energy state. During differentiation, the accumulating Tfam protein was progressively distributed to the mitochondrial matrix where it augmented the expression of mtDNA and COX (cytochrome c oxidase) subunit I, an mtDNA gene product. Our data suggest that, during muscle differentiation, Tfam protein levels are regulated by the availability of Tfam mRNA, which is controlled by both transcription and mRNA stability. Changes in energy state and Tfam localization also affect Tfam expression and action in differentiating myotubes.
Homocysteine facilitates LOX-1 activation and endothelial death through the PKCβ and SIRT1/HSF1 mechanism: relevance to human hyperhomocysteinaemia
Authors: Hung Ching-Hsia , Chan Shih-Hung , Chu Pei-Ming , Tsai Kun-Ling
Published: May 2015

HHcy (hyperhomocysteinaemia) is one of the major risk factors for cardiovascular diseases. A high concentration of Hcy (homocysteine) induces endothelial dysfunction by activating endothelial oxidative stress. LOX-1 (lectin-like oxidized low-density lipoprotein receptor 1) plays a vital role in regulating the progression of atherosclerotic lesions. LOX-1 activation causes endothelial apoptosis and inflammation. The mechanism is still unclear as to whether Hcy affects human endothelial LOX-1 expression. LOX-1 expression level was confirmed by Western blotting assay in Hcy-treated endothelial cells. L-Methionine was used for HHcy induction in animals. Our results suggested that Hcy increased PKCβ (protein kinase Cβ) activation to enhance the LOX-1 expression level. The up-regulation of PKCβ phosphorylation subsequently causes ROS (reactive oxygen species) formation and SIRT1 (sirtuin 1) degradation through a proteasome-dependent mechanism, thereby mitigating the activity of SIRT1 by deacetylating HSF1 (heat-shock transcription factor 1). We also found that NOX2 is a key NAPDH oxidase isoform responsible for the Hcy-caused ROS formation. The overexpression of SIRT1 and HSF1 reduced the Hcy-induced LOX-1 activation. Silencing PKCβ function also reduced LOX-1 activation and endothelial apoptosis caused by Hcy. Our hypothesis was supported by analysing the data from methionine-induced HHcy-affected animals. Our data indicate a new direction for LOX-1 regulation by the modulation of the PKCβ/NAPDH oxidase/SIRT1/HSF1 mechanism. Our findings might provide a novel route for developing new therapeutic treatments for HHcy.
A Comparison of Two Methods for Measuring Listening Effort As Part of an Audiologic Test Battery
Authors: Johnson Jani , Xu Jingjing , Cox Robyn , Pendergraft Paul
Published: May 2015

Purpose

We evaluated 2 measures of listening effort (a self-report measure and a word recall measure) regarding their suitability for inclusion in a comprehensive audiologic testing protocol. The relationship between the 2 measures was explored, and both measures were examined with regard to validity, sensitivity, and effect on speech intelligibility performance.

Method

Thirty adults with normal hearing participated. Speech intelligibility performance was evaluated at 4 signal-to-noise ratios by using keywords embedded in both high- and low-context sentences. Listening effort was evaluated at set intervals throughout the speech intelligibility task.

Results

Results obtained with the 2 measures were consistent with expected changes in listening effort. However, data obtained with the self-report method demonstrated greater sensitivity to these changes. The 2 measures were uncorrelated. Under certain conditions, speech intelligibility performance was more negatively affected when the word recall measure was used. Exploration of additional theoretical and practical considerations supported a conclusion that the self-report measure was preferable for measuring listening effort simultaneously with speech intelligibility.

Conclusion

The results of this study provide a rationale for preferring the self-report measure of listening effort over the word recall measure when testing audiologic outcomes.
Mandibular Symphyseal/Parasymphyseal Fracture with Incisor Tooth Loss: Preventing Lower Arch Constriction
Authors: Rahpeyma Amin , Khajehahmadi Saeedeh , Abdollahpour Somayeh
Published: May 2015

Mandibular fractures are the second most common fractures of the face after the nasal bone. Mandibular symphyseal/parasymphyseal fracture comprises 15.6 to 29.3% of mandibular fractures. Tooth loss in the fracture line is a known phenomenon, but space loss has not been evaluated comprehensively in the literature. In a retrospective study, patients with mandibular symphyseal/parasymphyseal fractures, who had been treated from 2012 to 2013 in Mashhad University, Iran, Emdadi Hospital, were recalled. Patients with mandibular incisor tooth/teeth loss were included in the study. Space loss, the technique used to replace the lost tooth/teeth, upper and lower dental midline relationship, combination fracture or fractures in other facial skeleton, and type of treatment were evaluated. Of 98 patients with mandibular symphyseal/parasymphyseal fractures, 22.5% had incisor tooth/teeth loss. In this group, 73% had space loss. Only four patients had replaced the lost tooth/teeth. Dental midlines did not match each other in patients whose feature was evaluated. Open reduction and internal fixation with miniplates were used in symphyseal/parasymphyseal fractures except one. Space loss after mandibular symphyseal/parasymphyseal fracture with incisor tooth loss is a common error. The most important factor to prevent complications related to space loss following mandibular symphyseal/parasymphyseal fracture accompanying incisor tooth loss is space preservation.
Bioactive-glass in Oral and Maxillofacial Surgery
Authors: Profeta AndreaCorrado , Huppa Christoph
Published: May 2015

The use of synthetic materials to repair craniofacial defects is increasing today and will increase further in the future. Because of the complexity of the anatomy in the head and neck region, reconstruction and augmentation of this area pose a challenge to the surgeon. This review discusses key facts and applications of traditional reconstruction bone substitutes, also offering comparative information. It then describes the properties and clinical applications of bioactive-glass (B-G) and its variants in oral and maxillofacial surgery, and provides clinical findings. The discussion of each compound includes a description of its composition and structure, the advantages and shortcomings of the material, and its current uses in the field of osteoplastic and reconstructive surgery. With a better understanding of the available alloplastic implants, the surgeon can make a more informed decision as to which implant would be most suitable in a particular patient.
Transorbital Orbitocranial Penetrating Injury with an Iron Rod
Authors: Agrawal Amit , Reddy V.Umamaheswara , Kumar S.Satish , Hegde Kishor V. , Rao G.Malleswara
Published: May 2015

Transorbital orbitocranial penetrating injuries (TOPIs) are relatively rare, can be caused by high-speed projectile foreign bodies to low-energy trauma (which is rarer), and account for 24% of penetrating head injuries in adults and approximately 45% in children. We report an uncommon nonfatal case of TOPI where a 16-year-old male child sustained injury due to accidental penetration of metal bar into the forehead. A bicoronal flap was raised to remove the metal bar. The patient recovered well, had normal vision, and doing well at follow-up.
Microscopic conductivity of lattice fermions at equilibrium. I. Non-interacting particles
Authors: Bru J.-B. , de Siqueira Pedra W. , Hertling C.
Published: May 2015

We consider free lattice fermions subjected to a static bounded potential and a time- and space-dependent electric field. For any bounded convex region ℛ ⊂ ℝd (d ≥ 1) of space, electric fields E within R drive currents. At leading order, uniformly with respect to the volume R of R and the particular choice of the static potential, the dependency on E of the current is linear and described by a conductivity (tempered, operator-valued) distribution. Because of the positivity of the heat production, the real part of its Fourier transform is a positive measure, named here (microscopic) conductivity measure of R, in accordance with Ohm’s law in Fourier space. This finite measure is the Fourier transform of a time-correlation function of current fluctuations, i.e., the conductivity distribution satisfies Green–Kubo relations. We additionally show that this measure can also be seen as the boundary value of the Laplace–Fourier transform of a so-called quantum current viscosity. The real and imaginary parts of conductivity distributions are related to each other via the Hilbert transform, i.e., they satisfy Kramers–Kronig relations. At leading order, uniformly with respect to parameters, the heat production is the classical work performed by electric fields on the system in presence of currents. The conductivity measure is uniformly bounded with respect to parameters of the system and it is never the trivial measure 0 dν. Therefore, electric fields generally produce heat in such systems. In fact, the conductivity measure defines a quadratic form in the space of Schwartz functions, the Legendre–Fenchel transform of which describes the resistivity of the system. This leads to Joule’s law, i.e., the heat produced by currents is proportional to the resistivity and the square of currents.
Exploring the potential energy landscape of the Thomson problem via Newton homotopies
Authors: Mehta Dhagash , Chen Tianran , Morgan John W. R. , Wales David J.
Published: May 2015

Locating the stationary points of a real-valued multivariate potential energy function is an important problem in many areas of science. This task generally amounts to solving simultaneous nonlinear systems of equations. While there are several numerical methods that can find many or all stationary points, they each exhibit characteristic problems. Moreover, traditional methods tend to perform poorly near degenerate stationary points with additional zero Hessian eigenvalues. We propose an efficient and robust implementation of the Newton homotopy method, which is capable of quickly sampling a large number of stationary points of a wide range of indices, as well as degenerate stationary points. We demonstrate our approach by applying it to the Thomson problem. We also briefly discuss a possible connection between the present work and Smale’s 7th problem.
Reconstruction of steps on the Cu(111) surface induced by sulfur
Authors: Walen Holly , Liu Da-Jiang , Oh Junepyo , Lim Hyunseob , Evans J. W. , Kim Yousoo , Thiel P. A.
Published: May 2015

A rich menagerie of structures is identified at 5 K following adsorption of low coverages (≤0.05 monolayers) of S on Cu(111) at room temperature. This paper emphasizes the reconstructions at the steps. The A-type close-packed step has 1 row of S atoms along its lower edge, where S atoms occupy alternating pseudo-fourfold-hollow (p4fh) sites. Additionally, there are 2 rows of S atoms of equal density on the upper edge, bridging a row of extra Cu atoms, together creating an extended chain. The B-type close-packed step exhibits an even more complex reconstruction, in which triangle-shaped groups of Cu atoms shift out of their original sites and form a base for S adsorption at (mostly) 4fh sites. We propose a mechanism by which these triangles could generate Cu–S complexes and short chains like those observed on the terraces.
Periodic local MP2 method employing orbital specific virtuals
Authors: Usvyat Denis , Maschio Lorenzo , Schütz Martin
Published: May 2015

We introduce orbital specific virtuals (OSVs) to represent the truncated pair-specific virtual space in periodic local Møller-Plesset perturbation theory of second order (LMP2). The OSVs are constructed by diagonalization of the LMP2 amplitude matrices which correspond to diagonal Wannier-function (WF) pairs. Only a subset of these OSVs is adopted for the subsequent OSV-LMP2 calculation, namely, those with largest contribution to the diagonal pair correlation energy and with the accumulated value of these contributions reaching a certain accuracy. The virtual space for a general (non diagonal) pair is spanned by the union of the two OSV sets related to the individual WFs of the pair. In the periodic LMP2 method, the diagonal LMP2 amplitude matrices needed for the construction of the OSVs are calculated in the basis of projected atomic orbitals (PAOs), employing very large PAO domains. It turns out that the OSVs are excellent to describe short range correlation, yet less appropriate for long range van der Waals correlation. In order to compensate for this bias towards short range correlation, we augment the virtual space spanned by the OSVs by the most diffuse PAOs of the corresponding minimal PAO domain. The Fock and overlap matrices in OSV basis are constructed in the reciprocal space. The 4-index electron repulsion integrals are calculated by local density fitting and, for distant pairs, via multipole approximation. New procedures for determining the fit-domains and the distant-pair lists, leading to higher efficiency in the 4-index integral evaluation, have been implemented. Generally, and in contrast to our previous PAO based periodic LMP2 method, the OSV-LMP2 method does not require anymore great care in the specification of the individual domains (to get a balanced description when calculating energy differences) and is in that sense a black box procedure. Discontinuities in potential energy surfaces, which may occur for PAO-based calculations if one is not careful, virtually disappear for OSV-LMP2. Moreover, due to much increased compactness of the pair-specific virtual spaces, the OSV-LMP2 calculations are faster and require much less memory than PAO-LMP2 calculations, despite the noticeable overhead of the initial OSV construction procedure.
Cryogenic preamplification of a single-electron-transistor using a silicon-germanium heterojunction-bipolar-transistor
Authors: Curry M. J. , England T. D. , Bishop N. C. , Ten-Eyck G. , Wendt J. R. , Pluym T. , Lilly M. P. , Carr S. M. , Carroll M. S.
Published: May 2015

We examine a silicon-germanium heterojunction bipolar transistor (HBT) for cryogenic pre-amplification of a single electron transistor (SET). The SET current modulates the base current of the HBT directly. The HBT-SET circuit is immersed in liquid helium, and its frequency response from low frequency to several MHz is measured. The current gain and the noise spectrum with the HBT result in a signal-to-noise-ratio (SNR) that is a factor of 10–100 larger than without the HBT at lower frequencies. The transition frequency defined by SNR = 1 has been extended by as much as a factor of 10 compared to without the HBT amplification. The power dissipated by the HBT cryogenic pre-amplifier is approximately 5 nW to 5 μW for the investigated range of operation. The circuit is also operated in a single electron charge read-out configuration in the time-domain as a proof-of-principle demonstration of the amplification approach for single spin read-out.
Potentials of the Heun class: The triconfluent case
Authors: Batic D. , Mills-Howell D. , Nowakowski M.
Published: May 2015

We study special classes of potentials for which the one-dimensional (or radial) Schrödinger equation can be reduced to a triconfluent Heun equation by a suitable coordinate transformation together with an additional transformation of the wave function. In particular, we analyze the behaviour of those subclasses of the potential arising when the ordinary differential equation governing the coordinate transformation admits explicit analytic solutions in terms of the radial variable. Furthermore, we obtain formulae for solutions of the eigenvalue problem of the associated radial Schrödinger operator. Last but not least, using methods of supersymmetric quantum mechanics we relate the considered potentials to a new class of exactly solvable ones.
Closing the pressure gap in x-ray photoelectron spectroscopy by membrane hydrogenation
Authors: Delmelle Renaud , Probst Benjamin , Alberto Roger , Züttel Andreas , Bleiner Davide , Borgschulte Andreas
Published: May 2015

Comprehensive studies of gas-solid reactions require the in-situ interaction of the gas at a pressure beyond the operating pressure of ultrahigh vacuum (UHV) X-ray photoelectron spectroscopy (XPS). The recent progress of near ambient pressure XPS allows to dose gases to the sample up to a pressure of 20 mbar. The present work describes an alternative to this experimental challenge, with a focus on H2 as the interacting gas. Instead of exposing the sample under investigation to gaseous hydrogen, the sample is in contact with a hydrogen permeation membrane, through which hydrogen is transported from the outside to the sample as atomic hydrogen. Thereby, we can reach local hydrogen concentrations at the sample inside an UHV chamber, which is equipped with surface science tools, and this corresponds to a hydrogen pressure up to 1 bar without affecting the sensitivity or energy resolution of the spectrometer. This experimental approach is validated by two examples, that is, the reduction of a catalyst precursor for CO2 hydrogenation and the hydrogenation of a water reduction catalyst for photocatalytic H2 production, but it opens the possibility of the new in situ characterisation of energy materials and catalysts.
Tunable and efficient terahertz radiation generation by photomixing of two super Gaussian laser pulses in a corrugated magnetized plasma
Authors: Varshney Prateek , Sajal Vivek , Singh Kunwar Pal , Kumar Ravindra , Sharma Navneet K.
Published: May 2015

A scheme of terahertz (THz) radiation generation is investigated by photo-mixing of two super Gaussian laser beams having different frequencies (ω1, ω2) and wave numbers (k→1, k→2) in a performed corrugated plasma embedded with transverse dc magnetic field. Lasers exert a nonlinear ponderomotive force, imparting an oscillatory velocity to plasma electrons that couples with the density corrugations (n′=nα0eiαz) to generate a strong transient nonlinear current, that resonantly derives THz radiation of frequency ∼ωh (upper hybrid frequency). The periodicity of density corrugations is suitably chosen to transfer maximum momentum from lasers to THz radiation at phase matching conditions ω=ω1−ω2 and k→=k→1−k→2+α→. The efficiency, power, beam quality, and tunability of the present scheme exhibit high dependency upon the applied transverse dc magnetic field along with q-indices and beam width parameters (a0) of super Gaussian lasers. In the present scheme, efficiency ∼10−2 is achieved with the optimization of all these parameters.
Oxygen octahedra distortion induced structural and magnetic phase transitions in Bi1−xCaxFe1−xMnxO3 ceramics
Authors: Kumar Pawan , Shankhwar Nisha , Srinivasan A. , Kar Manoranjan
Published: May 2015

The co-doping of Ca and Mn in respective Bi and Fe-sites of BiFeO3 lattice leads to structural transition from rhombohedral (R3c space group) to orthorhombic (Pbnm space group) crystal symmetry. The tilt angle for anti-phase rotation of the oxygen octahedra of BiFeO3 at room temperature is observed to be ∼13.8°. It decreases with the increase in the co-doping percentage which suggests the composition-driven structural phase transition. The remnant magnetization for sample with 15% of co-doping becomes about 16 times that of BiFeO3. It may be attributed to the suppression of cycloid spin structure and uncompensated spins at the surface of nanocrystallites. Further increase in co-doping percentage results in the sharp reduction of remnant magnetization due to the dominant contribution from the collinear antiferromagnetic ordering in the Pbnm space group. The Arrott plot analysis clearly indicates the composition-driven crossover from the antiferromagnetic to weak ferromagnetic ordering and vice versa. Electron spin resonance results provide the evidence for the composition-driven phase transitions from an incommensurate spin cycloidal modulated state to one with nearly homogeneous spin order. The band gap (2.17 eV) of BiFeO3 measured using UV-Vis spectra was supported by the resonance Raman spectra.
Burst design and signal processing for the speed of sound measurement of fluids with the pulse-echo technique
Authors: Dubberke Frithjof H. , Baumhögger Elmar , Vrabec Jadran
Published: May 2015

The pulse-echo technique determines the propagation time of acoustic wave bursts in a fluid over a known propagation distance. It is limited by the signal quality of the received echoes of the acoustic wave bursts, which degrades with decreasing density of the fluid due to acoustic impedance and attenuation effects. Signal sampling is significantly improved in this work by burst design and signal processing such that a wider range of thermodynamic states can be investigated. Applying a Fourier transformation based digital filter on acoustic wave signals increases their signal-to-noise ratio and enhances their time and amplitude resolutions, improving the overall measurement accuracy. In addition, burst design leads to technical advantages for determining the propagation time due to the associated conditioning of the echo. It is shown that the according operation procedure enlarges the measuring range of the pulse-echo technique for supercritical argon and nitrogen at 300 K down to 5 MPa, where it was limited to around 20 MPa before.
Angular distribution of ions and extreme ultraviolet emission in laser-produced tin droplet plasma
Authors: Chen Hong , Wang Xinbing , Duan Lian , Lan Hui , Chen Ziqi , Zuo Duluo , Lu Peixiang
Published: May 2015

Angular-resolved ion time-of-flight spectra as well as extreme ultraviolet radiation in laser-produced tin droplet plasma are investigated experimentally and theoretically. Tin droplets with a diameter of 150 μm are irradiated by a pulsed Nd:YAG laser. The ion time-of-flight spectra measured from the plasma formed by laser irradiation of the tin droplets are interpreted in terms of a theoretical elliptical Druyvesteyn distribution to deduce ion density distributions including kinetic temperatures of the plasma. The opacity of the plasma for extreme ultraviolet radiation is calculated based on the deduced ion densities and temperatures, and the angular distribution of extreme ultraviolet radiation is expressed as a function of the opacity using the Beer–Lambert law. Our results show that the calculated angular distribution of extreme ultraviolet radiation is in satisfactory agreement with the experimental data.
Communication: Saturated CO2 absorption near 1.6 μm for kilohertz-accuracy transition frequencies
Authors: Burkart Johannes , Sala Tommaso , Romanini Daniele , Marangoni Marco , Campargue Alain , Kassi Samir
Published: May 2015

Doppler-free saturated-absorption Lamb dips were measured on weak rovibrational lines of 12C16O2 between 6189 and 6215 cm−1 at sub-Pa pressures using optical feedback frequency stabilized cavity ring-down spectroscopy. By referencing the laser source to an optical frequency comb, transition frequencies for ten lines of the 30013←00001 band P-branch and two lines of the 31113←01101 hot band R-branch were determined with an accuracy of a few parts in 1011. Involving rotational quantum numbers up to 42, the data were used for improving the upper level spectroscopic constants. These results provide a highly accurate reference frequency grid over the spectral interval from 1599 to 1616 nm.
A dielectrophoretic-gravity driven particle focusing technique for digital microfluidic systems
Authors: Samiei Ehsan , Rezaei Nejad Hojatollah , Hoorfar Mina
Published: May 2015

In the present study, a particle focusing technique functioning based on the cumulative effects of gravity and negative dielectrophoresis (nDEP) is developed for digital microfluidic (DMF) systems. This technique works using the conventional electrodes used for droplet manipulation without a need for geometrical modification. Particle manipulation is performed by applying an AC voltage to the electrode above which there is the droplet containing the non-buoyant particles. The particles sediment due to the difference between the gravitational and the vertical component of the nDEP forces, while the horizontal component of the nDEP force concentrates them on the center of the electrode. Therefore, the magnitude of the voltage must be kept within an effective range to have simultaneous effects of sedimentation (dominated by gravity) and concentration (due to the horizontal component of the nDEP force). The physics of the phenomenon is explained using simulation. The effects of the magnitude of the applied voltage, the particle size and density, and the electrode size on the focusing behavior of the particles are studied. Finally, a potential application of the present technique is illustrated for particle concentration in DMF.
Demonstration of isotype GaN/AlN/GaN heterobarrier diodes by NH3-molecular beam epitaxy
Authors: Fireman Micha N. , Browne David A. , Mazumder Baishakhi , Speck James S. , Mishra Umesh K.
Published: May 2015

The results of vertical transport through nitride heterobarrier structures grown by ammonia molecular beam epitaxy are presented. Structures are designed with binary layers to avoid the effects of random alloy fluctuations in ternary nitride barriers. The unintentional incorporation of Ga in the AlN growth is investigated by atom probe tomography and is shown to be strongly dependent on both the NH3 flowrate and substrate temperature growth parameters. Once nominally pure AlN layer growth conditions are achieved, structures consisting of unintentionally doped (UID) GaN spacer layers adjacent to a nominally pure AlN are grown between two layers of n+ GaN, from which isotype diodes are fabricated. Varying the design parameters of AlN layer thickness, UID spacer layer thickness, and threading dislocation density show marked effects on the vertical transport characteristics of these structures. The lack of significant temperature dependence, coupled with Fowler-Nordheim and/or Milliken-Lauritsen analysis, point to a prevalently tunneling field emission mechanism through the AlN barrier. Once flatband conditions in the UID layer are achieved, electrons leave the barrier with significant energy. This transport mechanism is of great interest for applications in hot electron structures.
Financing the agrarian transition? The Clean Development Mechanism and agricultural change in Latin America
Authors: Wittman Hannah , Powell Lisa Jordan , Corbera Esteve
Published: May 2015

The food crisis of 2007–08 generated widespread global concerns about land consolidation and agricultural transition, with renewed attention on foreign land investments and growing global markets for meat and biofuels. As part of and alongside this process, agriculture and land-use projects registered in the Kyoto Protocol's Clean Development Mechanism (CDM) continued to rise, representing almost a third of global projects and almost 50% of projects in Latin America. In this paper we conduct an analysis of the sustainable development claims of Latin American CDM projects, focusing particularly on their implications for land consolidation, regional food security, and agrarian justice. Our analysis suggests that in Latin America those benefiting most from the development and sale of carbon-offset projects have, to date, been large-scale corporations investing in industrial carbon projects such as large tree plantations, sugarcane, and large-scale, export-oriented livestock production. As such, we argue that the carbonization of agriculture through the CDM serves as a driver of ‘global green grabbing’ and that the scope and financialization of CDM projects in the agriculture and forestry sectors in Latin America may contribute to the maintenance of an agrarian system of ‘climate injustice’ rather than foster sustainable development across the region.
Ghosts in the Delta: USAID and the historical geographies of Vietnam's ‘other’ war
Authors: Attewell Wesley
Published: May 2015

This paper will provide historical and geographical nuance to Eyal Weizman's concept of the ‘humanitarian present’ through an interrogation of the United States Agency for International Development's (USAID) entanglement in Cold War counterinsurgency. Specifically, it focuses on Cold War Vietnam, where USAID, through its Offices of Rural Affairs and Public Safety, spearheaded the ‘other’ war for rural ‘hearts and minds’ through two distinct, yet related, suites of spatial interventions. First, it sought to indirectly ‘conduct the conduct’ of the South Vietnamese people by providing technical assistance and commodity support to the Strategic Hamlet and Revolutionary Development programs. USAID's counterinsurgency programming, however, was not only traversed by a ‘will to improve’: it was also marked by a ‘will to police’. Here, I am specifically referring to the central role that USAID's Office of Public Safety played in helping the government of South Vietnam establish a functioning National Police whose ‘internal security’ mandate eventually encompassed both a biopolitics of population control as well as a necropolitics of neutralization. Over the course of this essay I will theorize these two tracks of counterinsurgency programming as the Janus faces of a broader ‘war–police’ nexus geared towards catalyzing the fabrication of a modern social order in the Vietnamese countryside.
A transformation-grammar-based methodology for the adaptation of existing housetypes: the case of the ‘rabo-de-bacalhau’
Authors: Eloy Sara , Duarte José Pinto
Published: May 2015

The research presented here aims to develop a methodology for rehabilitating the existing housing stock to meet the new needs of dwellers in the current information society and the consequent need to integrate information, communication, and automation technology into living areas. This paper focuses on the use of a transformation grammar in the rehabilitation methodology as a tool for identifying and encoding the principles and rules behind the adaptation of existing houses, and on space syntax as a tool for evaluating the spatial properties of the proposed designs, both in the final layout and during the transformation.
A land-use allocation optimization model to mitigate potential seismic damages
Authors: Wang Chih-Hao , Guldmann Jean-Michel
Published: May 2015

Seismic hazard mitigation is becoming an important consideration in planning for disaster-resilient cities. Seismic hazard and urban vulnerability are the two major factors in the assessment of seismic risk. Peak ground acceleration (PGA) and peak ground displacement (PGD) are the two major measures of seismic hazards, and land-use and building patterns characterize urban vulnerability. A set of pseudodata is generated by an earthquake-engineering simulation model for the city of Taichung, Taiwan, using twenty-two significant historical seismic events. A seismic damage model is first statistically estimated, relating monetary building damages to seismic impacts (PGA and PGD) and building inventories (residential, commercial, industrial, government). This damage function is then incorporated into a seismic land-use optimization model to allocate future land uses to the available land while minimizing aggregate seismic damages. Solving the model under the twenty-two seismic events and under different regional growth scenarios generates robust site rankings, pointing to priority locations for future activities away from the most severe historical earthquakes. These rankings can help decision makers allocate future activities under the uncertainty of both regional development and seismic hazard.
Coevolution of urban form and built form: a new typomorphological model for Tehran
Authors: Shayesteh Homeira , Steadman Philip
Published: May 2015

The paper brings analytical and typological models to the study of the coevolution of urban form and built form in Tehran. It follows the transformation of housing at both urban and architectural scales. At the urban scale, residential areas in Tehran have evolved from small irregular blocks to larger regular grids. At the architectural scale, residential units have evolved from courtyard houses, to terraced houses with south-facing courts, to multistorey apartment units. How do these two processes of evolution relate to each other? Are they entangled in a coevolutionary pattern, or do they remain independent evolutionary developments circumstantially brought together? The paper answers this question by looking at a series of stereotypical built forms for housing in Tehran over time, and by developing a model that brings together parameters of urban structure including block and plot size, and ground coverage ratio, with parameters of built form including access frontage, day-lit depth, and plan shape. In order to build the model and quantify its parameters, three areas of Tehran, representative of its three key stages of growth, are analysed using GIS. The model is found to be capable of approximating reality. During a process of design experiments with blocks of the same dimensions, it is found that alternative built forms are possible, all conforming to similar ratios of ground coverage, floor space index, day lighting, and road access.
Assessing neighbourhood destination access for children: development of the NDAI-C audit tool
Authors: Badland Hannah , Donovan Phil , Mavoa Suzanne , Oliver Melody , Chaudhury Moushumi , Witten Karen
Published: May 2015

Considerable societal changes across many countries have altered how children interact with their local environment, yet child-specific destination data have not been translated into a child-related destination accessibility index to further understand how neighbourhood locations support or hinder child mobility. Using data sourced from 238 9–11 year-old children living in Auckland, New Zealand, we aimed to: identify common destinations children travelled to; and develop a spatially derived objective index to quantify access to destinations that may support child mobility in the neighbourhood. Our findings show that children accessed a wide range of destinations during their daily activities, and the neighbourhoods that supported children's mobility tended to be located in more established areas, rather than newer greenfield developments.
Topologies of vulnerability and the proliferation of camp life
Authors: Debrix François
Published: May 2015

An important theoretical insight in critical geography of late has been the conceptual reevaluation of space topologically, in a manner that moves us away from an insistence on topographical priority. Unlike topography that relies on fixity, placement, grounding, and mapping, topology approaches space as a matter of relationality, redistribution, layering, transformation, or virtuality. The camp has been a ubiquitous geographical figure of late-modern life that has been subjected to topographical representations and rationalities. Recently, we have been encouraged to rethink the camp as a series of topological relations between the potentiality of spatial conditions of power and the capacity of bodies to be captured by regimes of sovereign exception. This paper examines two theorists who have made the space of the camp intelligible topologically: Agamben and Butler. These theorists help us to understand that what manifests itself topographically is often the result of topological dispositions that invest bodies with various forms of becoming. Whereas Agamben's camp topology allows us to see how political power can be ‘virtually everywhere’, Butler extends this theorizing by being more open to the presence of differential regimes of exposure to vulnerability. In this manner, Butler still finds a use for some form of critical topography.
Improvement in primary school adherence to the NSW Healthy School Canteen Strategy in 2007 and 2010
Authors: Hills Anne , Nathan Nicole , Robinson Keira , Fox Danushka , Wolfenden Luke
Published: May 2015

Issue addressed

Since 2005, a government‐endorsed strategy guiding food sold in New South Wales school canteens has been in place. This study describes the changes in school canteen food between 2007 and 2010 and characterises schools most likely to adhere to strategy guidelines.

Methods

Menus obtained from a cohort of primary and central schools in the Hunter New England region of New South Wales were audited using a traffic light system of classification. Energy dense, nutrient‐poor or ‘red’ items are restricted; ‘amber’ are to be selected carefully and healthier ‘green’ items are encouraged.

Results

In 2007, 7% of schools had no red items on their menu. In 2010, this improved to 22% (P < 0.05). In 2010, small schools (OR = 1.9, 95% CI = 1.25–3.05, P = 0.003); lower socioeconomic schools (OR = 1.3, 95% CI = 1.02–1.78, P = 0.03); non‐government (OR = 1.7, 95% CI = 1.22–2.23, P = 0.001) and rural schools (OR = 1.7, 95% CI = 1.30–2.25, P < 0.001) had higher odds of having red items on the menu. No significant change occurred in the proportion of green foods listed for sale between 2007 and 2010.

Conclusions

Proportion of schools adhering to strategy guidelines had increased slightly, however, most continue to list red items for regular sale.