bluuebunny/crossref_metadata_2025 huggingface dataset:
Defying the economists: a decrease in heart rate improves not only cardiac but also endothelial function
Authors: Triggle C R
Published: April 2008

Ivabradine has proven therapeutic efficacy for cardiac ischaemia and, until proved otherwise, is a very specific inhibitor of the cardiac sinoatrial node If current. In the current issue of the British Journal of Pharmacology, Drouin et al. demonstrated that chronic treatment of the human apoB‐100 transgene dyslipidaemic mouse with ivabradine significantly improved endothelium‐dependent vasodilatation to ACh in renal and cerebral arteries and that the beneficial effects of ivabradine result secondarily to the lowering of heart rate. These data suggest that drugs that target the If current have potential benefits not only as anti‐ischaemics but also as agents for the treatment of endothelial dysfunction.

British Journal of Pharmacology (2008) 154, 727–728; doi:10.1038/bjp.2008.116; published online 28 April 2008
Mutational analysis of conserved glycine residues 142, 143 and 146 reveals Gly142 is critical for tetramerization of CTP synthase from Escherichia coli
Authors: Lunn Faylene A. , MacLeod Travis J. , Bearne Stephen L.
Published: April 2008

CTPS (cytidine 5′-triphosphate synthase) catalyses the ATP-dependent formation of CTP from UTP using either ammonia or L-glutamine as the nitrogen source. Binding of the substrates ATP and UTP, or the product CTP, promotes oligomerization of CTPS from inactive dimers to active tetramers. In the present study, site-directed mutagenesis was used to replace the fully conserved glycine residues 142 and 143 within the UTP-binding site and 146 within the CTP-binding site of Escherchia coli CTPS. CD spectral analyses of wild-type CTPS and the glycine mutants showed a slight reduction of ∼15% in α-helical content for G142A and G143A relative to G146A and wild-type CTPS, suggesting some local alterations in structure. Relative to wild-type CTPS, the values of kcat/Km for ammonia-dependent and glutamine-dependent CTP formation catalysed by G143A were reduced 22- and 16-fold respectively, whereas the corresponding values for G146A were reduced only 1.4- and 1.8-fold respectively. The glutaminase activity (kcat) of G146A was similar to that exhibited by the wild-type enzyme, whereas that of G143A was reduced 7.5-fold. G146A exhibited substrate inhibition at high concentrations of ammonia and a partial uncoupling of glutamine hydrolysis from CTP production. Although the apparent affinity (1/[S]0.5) of G143A and G146A for UTP was reduced ∼4-fold, G146A exhibited increased co-operativity with respect to UTP. Thus mutations in the CTP-binding site can affect UTP-dependent activity. Surprisingly, G142A was inactive with both ammonia and glutamine as substrates. Gel-filtration HPLC experiments revealed that both G143A and G146A were able to form active tetramers in the presence of ATP and UTP; however, nucleotide-dependent tetramerization of G142A was significantly impaired. Our observations highlight the sensitivity of the structure of CTPS to mutations in the UTP- and CTP-binding sites, with Gly142 being critical for nucleotide-dependent oligomerization of CTPS to active tetramers. This ‘structural sensitivity’ may limit the number and/or types of mutations that could be selected for during the development of resistance to cytotoxic pyrimidine nucleotide analogues.
The yeast Tsa1 peroxiredoxin is a ribosome-associated antioxidant
Authors: Trotter Eleanor W. , Rand Jonathan D. , Vickerstaff Jill , Grant Chris M.
Published: April 2008

The yeast Tsa1 peroxiredoxin, like other 2-Cys peroxiredoxins, has dual activities as a peroxidase and as a molecular chaperone. Its peroxidase function predominates in lower-molecular-mass forms, whereas a super-chaperone form predominates in high-molecular-mass complexes. Loss of TSA1 results in aggregation of ribosomal proteins, indicating that Tsa1 functions to maintain the integrity of the translation apparatus. In the present study we report that Tsa1 functions as an antioxidant on actively translating ribosomes. Its peroxidase activity is required for ribosomal function, since mutation of the peroxidatic cysteine residue, which inactivates peroxidase but not chaperone activity, results in sensitivity to translation inhibitors. The peroxidatic cysteine residue is also required for a shift from ribosomes to its high-molecular-mass form in response to peroxide stress. Thus Tsa1 appears to function predominantly as an antioxidant in protecting both the cytosol and actively translating ribosomes against endogenous ROS (reactive oxygen species), but shifts towards its chaperone function in response to oxidative stress conditions. Analysis of the distribution of Tsa1 in thioredoxin system mutants revealed that the ribosome-associated form of Tsa1 is increased in mutants lacking thioredoxin reductase (trr1) and thioredoxins (trx1 trx2) in parallel with the general increase in total Tsa1 levels which is observed in these mutants. In the present study we show that deregulation of Tsa1 in the trr1 mutant specifically promotes translation defects including hypersensitivity to translation inhibitors, increased translational error-rates and ribosomal protein aggregation. These results have important implications for the role of peroxiredoxins in stress and growth control, since peroxiredoxins are likely to be deregulated in a similar manner during many different disease states.
DNA topology influences p53 sequence-specific DNA binding through structural transitions within the target sites
Authors: Jagelská Eva B. , Brázda Václav , Pečinka Petr , Paleček Emil , Fojta Miroslav
Published: April 2008

The tumour suppressor protein p53 is one of the most important factors regulating cell proliferation, differentiation and programmed cell death in response to a variety of cellular stress signals. P53 is a nuclear phosphoprotein and its biochemical function is closely associated with its ability to bind DNA in a sequence-specific manner and operate as a transcription factor. Using a competition assay, we investigated the effect of DNA topology on the DNA binding of human wild-type p53 protein. We prepared sets of topoisomers of plasmid DNA with and without p53 target sequences, differing in their internal symmetry. Binding of p53 to DNA increased with increasing negative superhelix density (−σ). At −σ≤0.03, the relative effect of DNA supercoiling on protein–DNA binding was similar for DNA containing both symmetrical and non-symmetrical target sites. On the other hand, at higher −σ, target sites with a perfect inverted repeat sequence exhibited a more significant enhancement of p53 binding as a result of increasing levels of negative DNA supercoiling. For −σ=0.07, an approx. 3-fold additional increase in binding was observed for a symmetrical target site compared with a non-symmetrical target site. The p53 target sequences possessing the inverted repeat symmetry were shown to form a cruciform structure in sufficiently negative supercoiled DNA. We show that formation of cruciforms in DNA topoisomers at −σ≥0.05 correlates with the extra enhancement of p53–DNA binding.
Calsenilin and CALP interact with the cytoplasmic tail of UDP-Gal:GA2/GM2/GD2 β-1,3-galactosyltransferase
Authors: Quintero Cristián A. , Valdez-Taubas Javier , Ferrari Mariana L. , Haedo Sergio D. , Maccioni Hugo J. F.
Published: April 2008

GalT2 (UDP-Gal:GA2/GM2/GD2 β-1,3-galactosyltransferase) is a Golgi-resident type II membrane protein that participates in the synthesis of glycosphingolipids. The molecular determinants for traffic and localization of this and other glycosyltransferases are still poorly characterized. Considering the possibility that interactions with other proteins may influence these processes, in the present study we carried out a yeast two-hybrid screening using elements of the N-terminal domain of GalT2 as bait. In this screening, we identified calsenilin and its close homologue CALP (calsenilin-like protein), both members of the recoverin-NCS (neuronal calcium sensor) family of calcium-binding proteins. In vitro, GalT2 binds to immobilized recombinant CALP, and CALP binds to immobilized peptides with the GalT2 cytoplasmic tail sequence. GalT2 and calsenilin interact physically when co-expressed in CHO (Chinese-hamster ovary)-K1 cells. The expression of CALP or calsenilin affect Golgi localization of GalT2, and of two other glycosyltransferases, SialT2 (CMP-NeuAc:GM3 sialyltransferase) and GalNAcT (UDP-GalNAc:lactosylceramide/GM3/GD3 β1-4 N-acetylgalactosaminyltransferase), by redistributing them from the Golgi to the ER (endoplasmic reticulum), whereas the localization of the VSV-G (G-protein of the vesicular stomatitis virus) or the Golgin GM130 was essentially unaffected. Conversely, the expression of GalT2 affects the localization of calsenilin and CALP by shifting a fraction of the molecules from being mostly diffuse in the cytosol, to clustered structures in the perinuclear region. These combined in vivo and in vitro results suggest that CALP and calsenilin are involved in the trafficking of Golgi glycosyltransferases.
On the kinetics of photodegradation in transparent silicones
Authors: Zimmermann Claus G.
Published: April 2008

The photodegradation behavior of three different transparent silicone elastomers, primarily used in space, was investigated experimentally. Samples were irradiated by an artificial ultraviolet (UV) light source, whose spectrum was split into five discrete wavelength bands in the range from 200 to 400 nm. The transmittance of the samples was measured for various UV doses up to an equivalent of 10 000 sun hours in space. A model was developed in order to predict the sample transmittance in this two parameter space of UV dose and wavelength and was found to be in good agreement with the measured data. This not only allowed for a concise characterization of the degradation behavior of the silicones by the microscopic model parameters, but more importantly allowed us to extrapolate the sample transmittance to UV doses not accessible by experiment. Since the model only uses minimal assumptions with regard to the UV induced chemistry, a potential wider applicability to other polymer systems is suggested.
Temporal asymmetry of fluctuations in nonequilibrium steady states: Links with correlation functions and nonlinear response
Authors: Paneni Carlo , Searles Debra J. , Rondoni Lamberto
Published: April 2008

The presence of temporal asymmetries in fluctuation paths of nonequilibrium systems has recently been confirmed numerically in nonequilibrium molecular dynamics simulations of particular deterministic systems. Here we show that this is a common feature of homogeneously driven and thermostatted, reversible, deterministic, chaotic, nonequilibrium systems of interacting particles. This is done by expressing fluctuation paths as correlation functions. The theoretical arguments look rather general, and we expect them to easily extend to other forms of driving and thermostats. The emergence of asymmetry is also justified using the transient time correlation function expression of nonlinear response theory. Numerical simulations are used to verify our arguments.
Ion irradiation induced hollow and sandwiched nanoparticles
Authors: Ren Feng , Cai Guang Xu , Xiao Xiang Heng , Fan Li Xia , Liu Chang , Fu De Jun , Wang Jian Bo , Jiang Chang Zhong
Published: April 2008

We report on the fabrication of hollow and sandwiched nanoparticles by ion irradiation. Ag nanoparticles embedded in silica were irradiated by N+, Si+, Ar+, and Cu+ ions at 300keV to a fluence of 5×1016ions∕cm2, by Cu+ ions at varying energies from 110to500keV to a fluence of 5×1016ions∕cm2, and by Cu+ ions at 400keV to fluences varied from 1×1016to1×1017ions∕cm2. The size of the irradiation-induced nanovoids increases with increasing ion mass and energy. The formation of nanovoids depends on the electronic and nuclear energy loss of the irradiation ions. The formation of irradiation-induced sandwiched nanoparticles is because of the capture of knocked-out Ag atoms from nanoshells by nanovoids. The size of the inner nanoparticles within the sandwiched structure increases with increasing fluence.
High-refractive-index TiO2-nanoparticle-loaded encapsulants for light-emitting diodes
Authors: Mont Frank W. , Kim Jong Kyu , Schubert Martin F. , Schubert E. Fred , Siegel Richard W.
Published: April 2008

A high-refractive-index (high-n) encapsulant is highly desirable because it can result in enhancement of light-extraction efficiency from high-n semiconductor light-emitting diode (LED) chips. A uniform dispersion of TiO2 nanoparticles in epoxy for LED encapsulation is demonstrated for surfactant-coated TiO2 nanoparticles by drying, mixing with a solvent, refluxing, centrifuging, and mixing with epoxy. The refractive index of surfactant-coated TiO2-nanoparticle-loaded epoxy is 1.67 at 500nm, significantly higher than that of conventional epoxy (n=1.53). Theoretical analysis of optical scattering in nanoparticle-loaded encapsulants reveals that the diameter of nanoparticles and the volume loading fraction of nanoparticles are of critical importance for optical scattering. Quasispecular transparency of the encapsulant film can be achieved if the thickness of the film is kept below the optical scattering length. A graded-refractive-index multilayer encapsulation structure with the thickness of each layer being less than the mean optical scattering length is proposed in order to reduce optical losses from scattering and Fresnel reflection. Furthermore, three-dimensional optical ray-tracing simulations demonstrate that encapsulants with an optimized scattering coefficient, ks, benefit from optical scattering by extracting deterministic trapped modes. Theoretical light-extraction enhancements larger than 50% are found when comparing scattering-free to scattering encapsulation materials.
Simulation of α-channeling in mirror machines
Authors: Zhmoginov A. I. , Fisch N. J.
Published: April 2008

Applying α-channeling techniques to mirror machines can significantly increase their effective reactivity, thus making open configurations more advantageous for practical fusion. A large fraction of α-particle energy can be extracted using rf waves. Effects employed to cool α particles can also in principle be used to heat the fusion ions; the possibility to design a configuration of rf waves that could be used to perform both tasks is demonstrated.
Effect of texture dispersion on the effective biaxial modulus of fiber-textured hexagonal, tetragonal, and orthorhombic films
Authors: Wu Huaping , Wu Linzhi , Du Shanyi
Published: April 2008

The effective biaxial modulus (Meff) of fiber-textured hexagonal, tetragonal, and orthorhombic films is estimated by using the Voigt–Reuss–Hill and Vook–Witt grain-interaction models. The orientation distribution function with Gaussian distributions of the two Euler angles θ and ϕ is adopted to analyze the effect of texture dispersion degree on Meff. Numerical results that are based on ZnO, BaTiO3, and yttrium barium copper oxide (YBCO) materials show that the Vook–Witt average of Meff is identical to the Voigt–Reuss–Hill average of Meff for the (001) plane of ideally fiber-textured hexagonal and tetragonal films. The ϕ distribution has no influence on Meff of the (hkl)-fiber-textured hexagonal film at any θ distribution in terms of the isotropy in the plane perpendicular to the [001] direction. Comparably, tetragonal and orthorhombic films represent considerable actions of ϕ dispersion on Meff, and the effect of ϕ dispersion on Meff of a (001)-fiber-textured YBCO film is smaller than that for a (001)-fiber-textured BaTiO3 film since the shear anisotropic factor in the (001) shear plane of a YBCO film more closely approaches 1. Enhanced θ and ϕ distributions destroy the perfect fiber textures, and as a result, the films exhibit an evolution from ideal (hkl) fiber textures to random textures with varying full widths at half maximums of θ and ϕ.
Properties of Coulomb crystals: Rigorous results
Authors: Cioslowski Jerzy
Published: April 2008

Rigorous equalities and bounds for several properties of Coulomb crystals are presented. The energy eN per particle pair is shown to be a nondecreasing function of the particle number N for all clusters described by double-power-law pairwise-additive potentials ϵ(r) that are unbound at both r→0 and r→∞. A lower bound for the ratio of the mean reciprocal crystal radius and eN is derived. The leading term in the asymptotic expression for the shell capacity that appears in the recently introduced approximate model of Coulomb crystals is obtained, providing in turn explicit large-N asymptotics for eN and the mean crystal radius. In addition, properties of the harmonic vibrational spectra are investigated, producing an upper bound for the zero-point energy.
Waves in a bounded two component electron-dust plasma
Authors: Tian Shi-Ling , Tang Rong-An , Xue Ju-Kui
Published: April 2008

Taking into account the boundary, the dust charge variation, the dust size and particle density effects, waves in a two component electron-dust plasma, bounded by a cylindrical domain, are presented. The dispersion relation for the waves is obtained and investigated analytically. Some limiting cases are also discussed. It is shown that the mentioned effects have a strong influence on the dispersion properties of the waves. The finite geometry not only modifies the frequencies of the excited modes, but it also has significant influence on the damping rate of the long waves.
Shear-induced particle migration in binary colloidal suspensions
Authors: Semwogerere Denis , Weeks Eric R.
Published: April 2008

We present experimental investigations of the spatial and temporal evolution of particle migration in pressure driven flows of Brownian particle suspensions. Binary suspensions of 1.4 and 3.0μm diameter colloidal particles are pumped through a 50×500μm2 rectangular-cross-section capillary tube. Shear rate gradients caused by the resulting parabolic velocity profile drive the particles away from the walls toward the center of the channel, where the shear rate is lowest. The flows are directly imaged using high-speed laser scanning confocal microscopy. Size segregation of the particles is observed. Depending on the conditions, either the large or the small particles enrich the center. We measure the development of the size segregation by tracking the evolution of the cross-stream concentrations of the particles.
Magnetic measurements and crystal field investigation of Tm3+ in Tm(CF3SO3)3⋅9H2O
Authors: Bisui D. , Chattopadhyay K. N. , Mallick P. K. , Ghosh M. , Chakrabarti P. K.
Published: April 2008

Single crystals of thulium trifluoromethanesulfonate (TmTFMS) were grown and the principal magnetic susceptibility χ⊥ and magnetic anisotropy Δχ(=χ∥−χ⊥) were measured in the temperature range of 300–13.5K and 300–80K, respectively. Though the value of χ⊥ is found to rapidly increase with the decrease in temperature, the value of χ∥ slowly increases with the lowering of temperature down to ∼110K, below which it slowly decreases. The hexagonal crystal structure of TmTFMS is similar to that of the isostructural series of hydrated rare earth ethylsulfates and the non-Kramers Tm3+ ion occupies a site of C3h symmetry. Our observed magnetic data were analyzed using crystal field (CF) analyses where the Hamiltonian includes the atomic free ion and (CF) (one-electron) interaction terms. The computed and measured paramagnetic susceptibilities of TmTFMS agree well in the temperature range of our study. Smooth variation of χ⊥ down to 13.5K does not indicate any structural phase transition or symmetry breaking, at least down to 13.5K. The computed nuclear quadruple splitting and electronic heat capacities give some interesting results. In order to substantiate the theoretical calculation, the Raman spectra of the compound were recorded in the wavenumber range of 10–1800cm−1. It has been found that the theoretical values of the CF Stark energies in the ground multiplet are in good agreement with the Raman data.
Probing of electric field in pentacene using microscopic optical second harmonic generation
Authors: Yamada Daisuke , Manaka Takaaki , Lim Eunju , Tamura Ryousuke , Iwamoto Mitsumasa
Published: April 2008

The electric field distribution in a pentacene field effect transistor (FET) was examined by using microscopic optical second harmonic generation (SHG) measurements. Results showed that the enhanced SHG signal changes depending on biasing conditions. The SHG profile was estimated by analyzing a Laplace field formed in organic FET (OFET) using conformal mapping and other methods. Results showed that the observed SHG profile is in good agreement with the obtained profile, indicating that our microscopic SHG data describe the electric field distribution in OFETs with high accuracy. The decrease in the SHG intensity was also discussed based on a Poisson field formation, caused by carriers injected from a source electrode. These results show that the SHG technique is effective for probing of electric fields formed in organic materials.
Self-organization of jets in electrospinning from free liquid surface: A generalized approach
Authors: Lukas David , Sarkar Arindam , Pokorny Pavel
Published: April 2008

Electrospinning has enabled creation of excellent materials for a great number of applications. Previously, it was based on less productive capillary spinners. The present study is based on recent efforts to elevate electrospinning technology to an industrial level by simultaneously provoking innumerable polymeric jets from a sufficiently large liquid surface to increase productivity. Particularly, it deals with electrospinning from free surface of conductive liquids and validates a formulated hypothesis that explains self-organization of jets on one-dimensional free liquid surfaces in terms of electrohydrodynamic instability of surface waves. Here, it is shown how the hypothesis, based on a profound analysis of a dispersion law, explains that above a certain critical value of applied electric field intensity∕field strength the system starts to be self-organized in mesocopic scale due to the mechanism of the “fastest forming instability.” The mechanism plays a key role in selecting a particular wave with a characteristic wavelength whose amplitude boundlessly grows faster than the others. The fastest growing stationary wave, according to the hypothesis, marks the onset of electrospinning from a free liquid surface with its jets originating from the wave crests. Singularity of this approach lies in predicting critical values of the phenomenon, viz., critical field strength and corresponding critical interjet distance. The critical field strength, will, thereafter, be used in defining a unique dimensionless electrospinning number. It will, subsequently, be shown how the critical interjet distance, i.e., the maximal distance between the neighboring jets, simply depends on the capillary length. The capillary length represents a latent characteristic spatial scale of the system. The theory also predicts interjet distance for field strengths above the critical value. The said prediction is universally applicable for all conductive liquids if it is expressed in terms of the dimensionless parameters of the interjet distance and the electrospinning number. The theory also predicts relaxation time, necessary for spontaneous jetting after a high voltage is applied. The theoretical considerations are eventually compared to that of Zeleny’s, obtained for capillary electrospinner to demonstrate universality of the approach. Eventually, jetting from free liquid surface on specially designed linear cleft electrospinner are observed, analyzed, and compared to the theoretical predictions obtaining satisfactory results.
The energy coupling efficiency of multiwavelength laser pulses to damage initiating defects in deuterated KH2PO4 nonlinear crystals
Authors: DeMange P. , Negres R. A. , Rubenchik A. M. , Radousky H. B. , Feit M. D. , Demos S. G.
Published: April 2008

The bulk damage performance of potassium dihydrogen phosphate crystals under simultaneous exposure to 1064, 532, and 355nm nanosecond-laser pulses is investigated in order to probe the mechanisms governing damage initiation during frequency conversion. The results provide insight into the dependence on laser parameters of the defect-assisted excitation process responsible for coupling of the laser energy into the lattice under exposure to high power laser light. In addition, it is suggested that the damage performance can be directly related to and predicted from the damage behavior of the crystal at each wavelength separately.
Development of a control system for pulsed-electron spin resonance spectrometers
Authors: Mizuta Yukio , Kazama Shunji , Ohba Yasunori , Sakai Naoko , Yamamoto Yukio , Shimoyama Yuhei
Published: April 2008

A pulse control and data acquisition system with high time resolution of 300ps and data-averaging rate of 100kHz for a pulsed-ESR spectrometer was constructed. The system consists of two sets of 3.34GHz data timing generator and a dual-channel analog-to-digital converter with 1GHz samples, both of which are commercially available. We developed a scheme and software to control these equipments with high efficiency in pulsing design, data acquisition, and accurate synchronization of the devices. The system was developed at Ku band (17.5GHz) and demonstrated some examples of electron spin echo and double quantum measurements.
Percolative model of the effect of disorder on the resistive peak broadening in La2∕3Ca1∕3MnO3 near the metal-insulator transition
Authors: Egilmez M. , Chow K. H. , Jung J.
Published: April 2008

The effect of the lattice disorder on the resistivity of La1−xCaxMnO3 (LCMO) near x=13 at the metal-insulator transition was studied by using a percolation model. The percolation model was applied to calculate the temperature dependence of the resistivity ρ(T) of the mixed state, where metallic ferromagnetic and insulating paramagnetic clusters simultaneously exist. The temperature dependence of the fraction of the metallic phase was obtained by assuming a Gaussian distribution of random transition temperatures, whose width increases with an increasing lattice disorder. The resistivity ρ(T) calculated from the model reproduces well the experimental ones for LCMO crystals and disordered films.
Theoretical study of the potential energy surface for the interaction of cisplatin and their aquated species with water
Authors: Lopes Juliana Fedoce , Rocha Willian R. , Dos Santos Hélio F. , De Almeida Wagner B.
Published: April 2008

In this work, a systematic study of the interaction of neutral cisplatin ([Pt(NH3)2Cl2]) and their charged aquated species ([Pt(NH3)2Cl(H2O)]+ and [Pt(NH3)2(H2O)2]2+) with water was carried out. The potential energy surface (PES) was analyzed by considering 35 spatial orientations for the interacting species. The calculations were performed at various levels of theory including Møller–Plesset fourth order perturbation theory and density functional theory (DFT-B3LYP) using extended basis sets. Lennard–Jones (12-6) plus Coulomb classical potential was also used to assess the repulsion-dispersion and electrostatic contributions. The effect of atomic charges on the interaction energies is discussed using Mülliken, charges from electrostatic potential grid method and natural bond orbital schemes. The outcomes show that the electrostatic term plays a primary role on the calculation of interaction energies, with the absolute values of atomic charges from different approaches significantly affecting the overall interaction. Unusual results were revealed by basis set superposition error calculations for the structures located on the platinum-water PES.
High internal quantum efficiency ZnO nanorods prepared at low temperature
Authors: Chen Jie , Aé L. , Aichele Ch. , Lux-Steiner M. Ch.
Published: April 2008

A preparation process for ZnO nanorods (or nanowires) by use of electrochemical deposition in an aqueous solution of zinc nitrate and nitric acid at temperatures 75°C was established. The surface morphologies of ZnO nanostructures can be adjusted with constant high internal quantum efficiency (IQE). The as-grown ZnO nanostructures exhibit a dominant and intense near-band-edge emission. The ZnO nanostructures present an IQE of ∼28% measured by a He–Cd laser under excitation power density of ∼22W∕cm2 at a wavelength of 325nm.
Negative-zero-positive metamaterial with omega-type metal inclusions
Authors: Zhang Fuli , Houzet Gregory , Lheurette Eric , Lippens Didier , Chaubet Michel , Zhao Xiaopeng
Published: April 2008

We report on a negative-zero-positive metamaterial based on an omega-type microstructure with special attention on the nonvanishing group velocity for a zero refractive index. We first investigate the dispersion characteristics by full wave analysis, by stressing the necessary conditions of equality between the electric and magnetic plasma frequencies which are characteristic of the dispersion of the effective permittivity and permeability. Also, tuning of the gapless transition frequency between the left and right-handed dispersion branches was analyzed when the permittivity of the host substrate is changed. Last, we demonstrate experimentally the balanced composite character of the dispersion by frequency and angle-resolved transmission measurements, carried out at centimeter wavelengths on slabs and wedge-type prototypes, respectively.
The numerical mirage method for photothermal characterization of materials
Authors: Demko Michael T. , Hostler Stephen R. , Abramson Alexis R.
Published: April 2008

Noncontact thermal measurement techniques offer rapid thermal characterization without modification or destruction of the sample being studied. A simple and versatile method has been developed, termed the “numerical mirage method,” that utilizes the transient photothermal deflection of a laser beam traversing a modulated temperature gradient. This method expands the range and simplifies the experimental procedure of traditional mirage methods. A numerical solver is used to create accurate deflection profile models and a linear curve fitting routine is developed, from which the thermal diffusivity of a material may be determined. This method allows for rapid modification of sample and heating configurations. Verification of the method is performed on bismuth and fused quartz reference samples, and good agreement with literature is obtained.
Continuously tunable laser emission from a wedge-shaped organic microcavity
Authors: Schütte B. , Gothe H. , Hintschich S. I. , Sudzius M. , Fröb H. , Lyssenko V. G. , Leo K.
Published: April 2008

We present an organic microcavity laser with wide tunability in the range of 595–650nm, having a threshold as low as 2nJ/pulse. The active medium consists of the organic composite tris(8-hydroxy quinoline) aluminum (Alq3) and 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) embedded in between two distributed Bragg reflectors. The inhomogeneously broadened emission from DCM is exploited for lasing by means of a tunable Fabry–Perot-type interferometer. Continuous tuning is achieved by varying the thickness of the active layer. The device shows a high photostability under direct excitation in the absorption band of the guest molecule, thus, allowing to monitor the optical gain spectrum of the active medium.
Single-crystal epitaxial thin films of SrFeO2 with FeO2 “infinite layers”
Authors: Inoue Satoru , Kawai Masanori , Shimakawa Yuichi , Mizumaki Masaichiro , Kawamura Naomi , Watanabe Takashi , Tsujimoto Yoshihiro , Kageyama Hiroshi , Yoshimura Kazuyoshi
Published: April 2008

Single-crystal thin films of SrFeO2, which is an oxygen-deficient perovskite with “infinite layers” of Fe2+O2, were prepared by using CaH2 for low-temperature reduction of epitaxial SrFeO2.5 single-crystal films deposited on KTaO3 substrates. This reduction process, removing oxygen ions from the perovskite structure framework and causing rearrangements of oxygen ions, topotactically transforms the brownmillerite SrFeO2.5 to the c-axis oriented SrFeO2.
Graphoepitaxy of sexithiophene and orientation control by surface treatment
Authors: Ikeda Susumu , Saiki Koichiro , Wada Yasuo , Inaba Katsuhiko , Ito Yoshiyasu , Kikuchi Hirokazu , Terashima Kazuo , Shimada Toshihiro
Published: April 2008

The factors influencing the graphoepitaxy of organic semiconductor α-sexithiophene (6T) on thermally oxidized silicon substrates were studied and it was discovered that a wider pitch in the microgrooves decreased the degree of graphoepitaxy. A more significant finding was that in-plane orientation could be changed by simple surface treatment. On UV∕ozone-treated substrates (hydrophilic condition), the b-axis of 6T was parallel to the grooves. Further surface treatment with hexamethyl-disiloxane (under hydrophobic conditions) changed this in-plane orientation by 90°. This change is due to the interaction between the topmost chemical species (functional groups) of the groove walls and organic molecules, a behavior peculiar to organic graphoepitaxy and exploitable for optimal orientation control in device processing. The nucleation and growth processes that cause the graphoepitaxy are discussed, based on the experimental results.
Thermally stable thermoelectric Zn4Sb3 by zone-melting synthesis
Authors: Pedersen B. L. , Iversen B. B.
Published: April 2008

The thermal stability of thermoelectric Zn4Sb3 has been investigated on samples produced by a new zone-melting technique, as well as by the conventional quench method. The multitemperature synchrotron powder diffraction data reveal that while conventionally synthesized, Zn4Sb3 samples have almost 40% degradation in the first heating cycle at 625K, samples prepared by zone melting only have 3% degradation. Repeated thermal cycling induces additional degradation of the quenched sample of up to 58%, compared to ∼9% degradation in the zone-melted sample. Thus, zone-melting produces Zn4Sb3 samples that are significantly more thermally stable, which make them promising for commercial implementation.
Air-stable organic-based semiconducting room temperature thin film magnet for spintronics applications
Authors: Carlegrim Elin , Kanciurzewska Anna , Nordblad Per , Fahlman Mats
Published: April 2008

Herein, we report on a preparation method of vanadium tetracyanoethylene, V(TCNE)x, an organic-based semiconducting room temperature thin film magnet. Previously, this compound has been reported to be extremely air sensitive but this preparation method leads to V(TCNE)x, which can retain its magnetic ordering at least several weeks in air. The electronic structure has been studied by photoelectron spectroscopy and the magnetic properties by superconducting quantum interference device. The properties mentioned above, in combination with complete spin polarization, makes this air-stable V(TCNE)x a very promising material for spintronic devices.
Scanning confocal fluorescence imaging and micro-Raman investigations of oxygen implanted channel waveguides in Nd:MgO:LiNbO3
Authors: Jaque D. , Chen Feng , Tan Yang
Published: April 2008

The spatial variation of the spectroscopic properties of Nd3+ ions in oxygen implanted Nd:MgO:LiNbO3 channel waveguides have been investigated by scanning confocal microluminescence experiments. Although the radiative probabilities of Nd3+ ions were unaffected by the waveguide fabrication procedure, slight changes (in terms of spectral position and width of the emission lines) have been found in the electronic damage region. Raman spectra have been also analyzed in order to get a further understanding on the possible relation of these spectral changes with the micro-modifications induced during the waveguide formation.
Coaxial ultrasound-modulated optical spectroscopy in scattering medium
Authors: Hisaka Masaki , Sasakura Yu
Published: April 2008

Ultrasound-modulated optical spectroscopy within a coaxial system capable of attaining submillimeter spatial resolution has been developed to investigate scattering media spectroscopic properties at depths of several centimeters. By using stroboscopic illumination methods, a broad spectral bandwidth pulsed laser and a focused ultrasound pulse simultaneously irradiated a biological tissue phantom containing oxyhemoglobin and deoxyhemoglobin absorbers. The ultrasound-modulated optical spectroscopic images were synchronously acquired by a fiber optic spectrometer scanning in two dimensions. We have obtained the wavelength dependent ultrasound-modulated optical signals produced by the ultrasound interactions changing the distribution of scattered light through several different mechanisms and evaluated the proposed system.
Mechanical properties, glass transition temperature, and bond enthalpy trends of high metalloid Fe-based bulk metallic glasses
Authors: Gu X. J. , Poon S. Joseph , Shiflet Gary J. , Widom Michael
Published: April 2008

Mechanical properties and glass transition temperatures (Tg) of Fe–Cr–Mo–P–C–B bulk metallic glasses containing up to 27at.% metalloids have been studied. The shear modulus (G) is found to decrease with increasing metalloid content and a maximum plastic strain of ∼3% is obtained, despite the increase in the number of strong metal-metalloid bonds. Also, Tg increases with the decrease in G, in contrast to usual behavior. By employing first-principles calculations, the results are discussed in light of atomic bonding and connectivity in the amorphous network. The findings are relevant to understanding ductility and glass transition of metallic glasses.
Size-dependent polarization distribution in ferroelectric nanostructures: Phase field simulations
Authors: Wang Jie , Kamlah Marc , Zhang Tong-Yi , Li Yulan , Chen Long-Qing
Published: April 2008

From phase field simulations, we investigate the size-dependent polarization distribution in ferroelectric nanostructures embedded in a nonferroelectric medium. The simulation results exhibit that vortex structures of polarizations and single-domain structures are formed in ferroelectric nanodots and nanowires, respectively. Furthermore, a single-vortex structure is formed in the ferroelectric nanodots if the aspect ratio of thickness to lateral size is less than a critical value, whereas the ferroelectric nanodots are in a multivortex state if the aspect ratio exceeds the critical value. When the aspect ratio approaches infinity, nanodots will become nanowires, in which polarizations are homogeneous.
Influence of water acidity on ozone decay time and its applications
Authors: Lee Han Y. , Uhm Han S. , Hong Yi F. , Park Yun H.
Published: April 2008

The increase in ozone decay time by lowering the pH value of water from pH=7to3 is observed. The decay time drastically decreases as the ethanol concentration increases. It is also noted that the ozone decay times in the electrolyzed ozone water and in the acidic ozone water are identical to each other if they have the same pH value. A simple analytical estimation of viable microbe number after contact with acidic ozone water agrees remarkably well with experimental data, demonstrating the capability of cleaning a large surface area contaminated by toxic biological agents.
Oxidation of archaeal peroxiredoxin involves a hypervalent sulfur intermediate
Authors: Nakamura Tsutomu , Yamamoto Takahiko , Abe Manabu , Matsumura Hiroyoshi , Hagihara Yoshihisa , Goto Tadashi , Yamaguchi Takafumi , Inoue Tsuyoshi
Published: April 2008

The oxidation of thiol groups in proteins is a common event in biochemical processes involving disulfide bond formation and in response to an increased level of reactive oxygen species. It has been widely accepted that the oxidation of a cysteine side chain is initiated by the formation of cysteine sulfenic acid (Cys-SOH). Here, we demonstrate a mechanism of thiol oxidation through a hypervalent sulfur intermediate by presenting crystallographic evidence from an archaeal peroxiredoxin (Prx), the thioredoxin peroxidase from
Aeropyrum pernix
K1 (ApTPx). The reaction of Prx, which is the reduction of a peroxide, depends on the redox active cysteine side chains. Oxidation by hydrogen peroxide converted the active site peroxidatic Cys-50 of ApTPx to a cysteine sulfenic acid derivative, followed by further oxidation to cysteine sulfinic and sulfonic acids. The crystal structure of the cysteine sulfenic acid derivative was refined to 1.77 Å resolution with
R
cryst
and
R
free
values of 18.8% and 22.0%, respectively. The refined structure, together with quantum chemical calculations, revealed that the sulfenic acid derivative is a type of sulfurane, a hypervalent sulfur compound, and that the S
γ
atom is covalently linked to the N
δ1
atom of the neighboring His-42. The reaction mechanism is revealed by the hydrogen bond network around the peroxidatic cysteine and the motion of the flexible loop covering the active site and by quantum chemical calculations. This study provides evidence that a hypervalent sulfur compound occupies an important position in biochemical processes.
Simulation of talking faces in the human brain improves auditory speech recognition
Authors: von Kriegstein Katharina , Dogan Özgür , Grüter Martina , Giraud Anne-Lise , Kell Christian A. , Grüter Thomas , Kleinschmidt Andreas , Kiebel Stefan J.
Published: April 2008

Human face-to-face communication is essentially audiovisual. Typically, people talk to us face-to-face, providing concurrent auditory and visual input. Understanding someone is easier when there is visual input, because visual cues like mouth and tongue movements provide complementary information about speech content. Here, we hypothesized that, even in the absence of visual input, the brain optimizes both auditory-only speech and speaker recognition by harvesting speaker-specific predictions and constraints from distinct visual face-processing areas. To test this hypothesis, we performed behavioral and neuroimaging experiments in two groups: subjects with a face recognition deficit (prosopagnosia) and matched controls. The results show that observing a specific person talking for 2 min improves subsequent auditory-only speech and speaker recognition for this person. In both prosopagnosics and controls, behavioral improvement in auditory-only speech recognition was based on an area typically involved in face-movement processing. Improvement in speaker recognition was only present in controls and was based on an area involved in face-identity processing. These findings challenge current unisensory models of speech processing, because they show that, in auditory-only speech, the brain exploits previously encoded audiovisual correlations to optimize communication. We suggest that this optimization is based on speaker-specific audiovisual internal models, which are used to simulate a talking face.
Younger Dryas “black mats” and the Rancholabrean termination in North America
Authors: Haynes C. Vance
Published: April 2008

Of the 97 geoarchaeological sites of this study that bridge the Pleistocene-Holocene transition (last deglaciation), approximately two thirds have a black organic-rich layer or “black mat” in the form of mollic paleosols, aquolls, diatomites, or algal mats with radiocarbon ages suggesting they are stratigraphic manifestations of the Younger Dryas cooling episode 10,900 B.P. to 9,800 B.P. (radiocarbon years). This layer or mat covers the Clovis-age landscape or surface on which the last remnants of the terminal Pleistocene megafauna are recorded. Stratigraphically and chronologically the extinction appears to have been catastrophic, seemingly too sudden and extensive for either human predation or climate change to have been the primary cause. This sudden Rancholabrean termination at 10,900 ± 50 B.P. appears to have coincided with the sudden climatic switch from Allerød warming to Younger Dryas cooling. Recent evidence for extraterrestrial impact, although not yet compelling, needs further testing because a remarkable major perturbation occurred at 10,900 B.P. that needs to be explained.
Judicial systems in contact
Authors: Berk-Seligson Susan
Published: April 2008

The Quichua of Ecuador, along with other indigenous peoples of Latin America, have been struggling to attain the right to use their ancestral language and their traditional ways of administering justice in an effort to gain greater autonomy in a variety of sociopolitical spheres of life. Based on interviews with 93 Ecuadorians — judges, magistrates, lawyers, justices of the peace, interpreters, translators, and local and national political leaders — the study finds an ideological splintering of views on this subject. Among the disparate Quichua communities and among State justice providers (largely comprising the hegemonic mestizo/blanco sector of society) there is a lack of agreement on how justice is to be carried out and what role the Quichua language should play in it. Despite the heterogeneity of views, however, there is tacit agreement on one de facto language policy, namely, the use of untrained, ad hoc interpreters in judicial settings.
The right to linguistic non-discrimination and Creole language situations
Authors: Brown-Blake Celia
Published: April 2008

There has been a proposal to include language as a basis upon which discrimination should be proscribed in the Constitution of Jamaica. The proposal was considered in 2001 by a parliamentary committee which articulated certain concerns largely about the legal ramifications of a right not to be discriminated against on the ground of language. Central to the committee’s concerns are the nature and extent of the legal obligations that may arise for the state in a situation in which English is the de facto official language but in which Jamaican Creole, a largely oral, low status vernacular, not highly mutually intelligible with English, is the dominant language for a majority of Jamaicans. This article explores the concerns of the parliamentary committee. It draws upon legal decisions and principles from other jurisdictions in the area of discrimination involving language and attempts an assessment of the applicability of such principles to the Jamaican language situation and Creole language situations in general.
Multifunctionality in Pitkern-Norf’k and Tok Pisin
Authors: Mühlhäusler Peter
Published: April 2008

This paper investigates claims as to the role of categorial multifunctionality in the Pitkern-Norf’k (PN) language. It concludes that the grammar of this construction is far less productive than that of either English or Tahitian (the principal substratum language). Essentially, multifunctionality in PN is a subset of English. In this, it is very different from Tok Pisin, which developed an independent system of categorial multifunctionality over the first 80 years of its existence. The paper makes some suggestions as to why the productivity of the derivational lexicon is so different in the two languages.
An analysis of progressive aspect in French and Dutch in terms of Variation and Specialization
Authors: Mortier Liesbeth
Published: April 2008

This paper tackles the concepts of ‘Variation’ and ‘Specialization’, frequently used in grammaticalization theory, within the context of progressive aspectual periphrases and from a comparative perspective French-Dutch. Drawing on historical and contemporary data, it is shown that these periphrases (i) have a disambiguating function, (ii) vary as to the level of Specialization operating on them, and (iii) manifest a relatively high level of formal fusion and semantic uniformity, due to processes of ‘metaphorization’, ‘reanalysis’ and ‘desemanticization’. The synergy between ‘Variation’ and ‘Specialization’ as proposed in this analysis allows for a comprehensive account of linguistic phenomena which are subject to (especially incipient) grammaticalization.