bluuebunny/crossref_metadata_2025 huggingface dataset:
Unusual size-dependent magnetization in near hemispherical Co nanomagnets on SiO2 from fast pulsed laser processing
Authors: Krishna H. , Miller C. , Longstreth-Spoor L. , Nussinov Z. , Gangopadhyay A. K. , Kalyanaraman R.
Published: April 2008

Nanosecond pulsed laser melting of ultrathin metal films can lead to self-organized arrays of spherical nanoparticles. We have applied this technique to assemble arrays of nanoparticles of the soft elemental ferromagnet Co on SiO2. Surface morphology studies by using scanning electron microscopy and atomic force microscopy established that the nanoparticles were nearly hemispherical with an average contact angle of ∼104±22°. Magnetic properties of these nanoparticles in the size range of 30–250nm diameter were investigated by magnetic force microscopy under zero applied field in conjunction with simulations of the magnetic tip-particle interaction. Particles up to 180nm diameter were found to be single domain with the magnetization direction oriented predominantly in-plane for the smaller particles (⩽75nm) and out-of-plane for the larger particles (⩽180nm). Multidomain behavior was observed for particles larger than 180nm. Magnetic hysteresis measurements at room temperature confirmed that the arrays consisted of a mixture of in-plane and out-of-plane orientations. Microstructural analysis by transmission electron microscopy revealed that the nanoparticles had a granular microstructure with the average grain size increasing with particle size. This size-dependent magnetic orientation is inconsistent with the expected in-plane orientation due to shape anisotropy. We suggest that a size-dependent residual strain and the microstructure formed by rapid laser processing determine the orientation of nanomagnets. This idea was supported by the significant increase in in-plane orientation of larger particles following thermal annealing. These studies suggest that anisotropic nanomagnets of near hemispherical polycrystalline particles with desired magnetic orientation can be prepared by fast laser thermal processing.
Evaluation of the efficiency potential of intermediate band solar cells based on thin-film chalcopyrite materials
Authors: Martí Antonio , Marrón David Fuertes , Luque Antonio
Published: April 2008

This paper discusses the potential of the intermediate band solar cell (IBSC) concept to improve the efficiency of thin-film chalcopyrite solar cells. The results show that solar cells based on CuGaS2, with a radiative limiting efficiency of 46.7%, exhibit the highest potential. A simple method for the identification of transition elements that when incorporated in CuGaS2 could possibly introduce an intermediate band is also described. The IBSC concept is also applied under the assumptions that thin-film solar cells are not to be operated under concentrated light and that a non-negligible contribution of nonradiative recombination exists.
Multiferroic properties of sputtered BiFeO3 thin films
Authors: Li Yibin , Sritharan Thirumany , Zhang Sam , He Xiaodong , Liu Yang , Chen Tupei
Published: April 2008

A cosputtering method was used to deposit BiFeO3 thin films on Pt∕Ti∕SiO2∕Si substrates. It was confirmed as a polycrystalline film with a tetragonal crystal structure in the annealed state. Both Fe2+ and Fe3+ ions were found to coexist in the film. The leakage current density is as low as 10−3A∕cm2 at 120kV∕cm. This sputtered film shows multiferroic properties exhibiting a saturated ferroelectric loop with a large remnant polarization of 37μC∕cm2 and a saturated ferromagnetic loop with saturation magnetization of 21emu∕cm3 at room temperature.
Interaction of gold nanoparticles with protein: A spectroscopic study to monitor protein conformational changes
Authors: Wangoo Nishima , Suri C. Raman , Shekhawat G.
Published: April 2008

Gold nanoparticles (GNPs) conjugated with biomolecules are promising building blocks for assembly into nanostructured functional materials for developing biomarker platforms because of their size dependent optical and electrical properties. Biocompatible GNPs were synthesized using glutamic acid as a reducing agent and the interaction between bovine serum albumin (BSA) and GNPs was investigated using fluorescence and circular dichroism (CD) spectroscopies. The binding constant (Kb) of protein (BSA) to GNPs was determined by measuring the quenching of the fluorescence intensity of tryptophan residues of the protein molecules after conjugation. The conformational change in BSA at its native form after conjugation with GNPs confirmed that protein undergoes a more flexible conformational state on the boundary surface of GNPs after bioconjugation. The CD studies further showed a decrease in the α-helical content after conjugation. The results confirmed that the change in conformation was larger at higher concentrations of GNPs.
Thermodynamic analysis and phase field modeling of domain structures in bilayer ferroelectric thin films
Authors: Artemev A. , Geddes B. , Slutsker J. , Roytburd A.
Published: April 2008

The domain structure in bilayer ferroelectric films was studied by using an analytical thermodynamic theory and computer simulations utilizing the phase field model. It is demonstrated that in a low applied field, a self-poled state can be produced in a bilayer film with one layer in a polydomain state and the other layer in a single-domain state. The presence of the layer with a polydomain structure results in a higher dielectric constant and lower coercive field as compared to a bilayer in a single-domain state. The increase in the applied field results in the transition to a single-domain state in the whole bilayer. The thermodynamic potentials of the layers and the energies of electrostatic and elastic interactions determine the critical fields which can control the transitions between single-domain and polydomain states as well as polarization switching of bilayers. Different thermodynamic hysteresis loops are obtained depending on the relationship between these critical fields and the amplitude of the applied ac field. The phase field model of the domain structure produces results that confirm main predictions of the analytical theory.
Propagation of Rayleigh-type surface waves in a transversely isotropic piezoelectric layer on a piezomagnetic half-space
Authors: Pang Yu , Liu Jin-Xi , Wang Yue-Sheng , Zhao Xiao-Fang
Published: April 2008

Propagation of Rayleigh-type surface waves in a piezoelectric-piezomagnetic layered half-space is investigated. The materials are assumed to be transversely isotropic crystals. The dispersion relations have been numerically derived and computed by considering the coupling piezoelectric and piezomagnetic behaviors. The phase velocities are obtained for four kinds of electric-magnetic boundary conditions at the free surface. The variations of mechanical displacements, electric and magnetic potentials along the thickness direction of the layer are obtained. The effects of different electric-magnetic boundary conditions on the phase velocity and mode shapes of displacements, electric and magnetic potentials have been discussed. The results show that the lowest mode is Rayleigh mode and that the phase velocities of the higher modes tend to the shear wave velocity of the piezoelectric layer as the frequency increases. The electric boundary conditions dominate the phase velocity. The magnetic boundary conditions have a significant effect on the mode shapes of the displacements, electric and magnetic potentials of the first mode. It is also found that piezoelectric material properties have an important effect on wave propagation. The result is relevant to the analysis and design of various acoustic surface wave devices constructed from piezoelectric and piezomagnetic materials.
High temperature thermoelectric transport properties of p-type Ba8Ga16AlxGe30−x type-I clathrates with high performance
Authors: Deng Shukang , Tang Xinfeng , Li Peng , Zhang Qingjie
Published: April 2008

Using group-III atom Al as doping element, Ba8Ga16AlxGe30−x (x=1.0, 2.0, 3.0, 4.0, and 5.0) type-I clathrates with different Al content were synthesized by combining melting reaction with spark plasma sintering method. The effects of Al content on thermoelectric properties are investigated. X-ray diffraction patterns and Rietveld analysis reveal that the compounds prepared by this method are type-I clathrates and Al atom preference for the 6c site. The Al substitutions do not affect the atomic displacement parameters (ADPs) of framework atoms (Ge∕Ga) and filled atoms (Ba) compared to that of Ba8Ga16Ge30, and the ADPs of Al are nearly equivalent to that of other framework Ge∕Ga atoms. All specimens exhibit the behavior of the p-type conduction. The carrier concentration and electrical conductivity increase while Seebeck coefficient decreases with the increasing Al content for the specimens with ⩽4.0. Ba8Ga16Al3.0Ge27.0 compound possesses the relatively lower lattice thermal conductivity κL due to the mass fluctuation between Al atoms and other atoms in the framework; it is as low as 0.96W∕mK at 300K. The maximum ZT value of 0.61 is obtained at 760K for Ba8Ga16Al3.0Ge27.0.
Band offsets of InGaP∕GaAs heterojunctions by scanning tunneling spectroscopy
Authors: Dong Y. , Feenstra R. M. , Semtsiv M. P. , Masselink W. T.
Published: April 2008

Scanning tunneling microscopy and spectroscopy are used to study InGaP∕GaAs heterojunctions with InGaAs-like interfaces. Band offsets are probed using conductance spectra, with tip-induced band bending accounted for using three-dimensional electrostatic potential simulations together with a planar computation of the tunnel current. Curve fitting of theory to experiment is performed. Using an InGaP band gap of 1.90eV, which is appropriate to the disordered InGaP alloy, a valence band offset of 0.38±0.01eV is deduced along with the corresponding conduction band offset of 0.10±0.01eV (type I band alignment).
Magnetic coupling properties of Mn-doped ZnO nanowires: First-principles calculations
Authors: Shi Hongliang , Duan Yifeng
Published: April 2008

Based on the density functional theory, we study the magnetic coupling properties of Mn-doped ZnO nanowires. For the nanowires with passivated surfaces, the antiferromagnetic state is found and the Mn atoms have a clustering tendency. When the distance between two Mn atoms is large, the system energetically favors the paramagnetic or spin-glass state. For the nanowires with unpassivated surfaces, the ferromagnetic (FM) coupling states appear between the two nearest Mn atoms, and the zinc vacancies can further stabilize the FM states between them. The electrons with enough concentration possibly mediate the FM coupling due to the negative exchange splitting of conduction band minimum induced by the s-d coupling, which could be useful in nanomaterial design for spintronics.
Photoluminescence and electrical properties of highly transparent (Bi,Eu)4Ti3O12 ferroelectric thin films on indium-tin-oxide-coated glass substrates
Authors: Ruan Kaibin , Chen Xinman , Liang Tong , Wu Guangheng , Bao Dinghua
Published: April 2008

Highly transparent (Bi,Eu)4Ti3O12 (BEuT) ferroelectric thin films were prepared on indium-tin-oxide (ITO)-coated glass substrates by using chemical solution deposition technique, and the photoluminescence and electrical properties of the thin films were investigated in terms of annealing temperature and concentration of europium ions. The BEuT thin films had a polycrystalline bismuth-layered perovskite structure and exhibited excellent optical transmittance. Photoluminescence spectra of the thin films included two strong peaks which originated from two transitions of D05→F17 (594nm) and D05→F27 (617nm). The emission intensity of two peaks increases with increasing annealing temperature due to improved crystallinity of the thin films. An unusual composition quenching effect of photoluminescence was found in the rare earth doped bismuth titanate thin films. In addition, the BEuT thin films also showed ferroelectric properties comparable to those of BEuT thin films deposited on Pt∕Ti∕SiO2∕Si substrates. These results suggest that BEuT thin films can be considered as a promising multifunctional material which can find applications in transparent optoelectronic devices.
The effect of molecule-molecule and molecule-substrate interaction in the formation of Pt-octaethyl porphyrin self-assembled monolayers
Authors: Oncel Nuri , Bernasek Steven L.
Published: April 2008

The adsorption of Pt-octaethyl porphyrin (Pt-OEP) molecules on highly ordered pyrolytic graphite (HOPG) and on 5-(octadecyloxy) isophthalic acid covered HOPG was studied with scanning tunneling microscopy at the solid-liquid interface. Pt-octaethyl porphyrin molecules lie flat on both surfaces and form a hexagonal lattice with an internal angle of about 60° and a lattice spacing of approximately 1.2nm. The similar overlayer structure observed on the dramatically different substrates suggests that molecular packing in the Pt-OEP layer controls the structure.
Magnetocaloric effect in melt spun Ni50.3Mn35.5Sn14.4 ribbons
Authors: Hernando B. , Sánchez Llamazares J. L. , Santos J. D. , Prida V. M. , Baldomir D. , Serantes D. , Varga R. , González J.
Published: April 2008

We determined the magnetic entropy change and refrigerant capacity of melt spun Ni50.3Mn35.5Sn14.4 ribbons around both the structural and the magnetic transitions for a field of 20kOe. The maximum entropy changes at the structural and magnetic transitions were of 4.1 and −1.1Jkg−1K−1. Ribbons studied show a larger refrigerant capacity around the magnetic transition (46Jkg−1) than around the structural transition (26Jkg−1), suggesting that the temperature range at the magnetic transition is more adequate for a refrigerant cycle than that at the structural transition.
Experimental evidence for the flatband voltage shift of high-k metal-oxide-semiconductor devices due to the dipole formation at the high-k∕SiO2 interface
Authors: Iwamoto Kunihiko , Kamimuta Yuuichi , Ogawa Arito , Watanabe Yukimune , Migita Shinji , Mizubayashi Wataru , Morita Yukinori , Takahashi Masashi , Ota Hiroyuki , Nabatame Toshihide , Toriumi Akira
Published: April 2008

We have examined an origin of the flatband voltage (VFB) shift in metal-oxide-semiconductor capacitors by employing bilayer high-k gate dielectrics consisting of HfO2 and Al2O3 on the interfacial SiO2 layer. We found that the high-k∕SiO2 interface affects the VFB shift through an electrical dipole layer formation at its interface, regardless of the gate electrode materials. Furthermore, we demonstrated that the VFB shift in the metal/high-k gate stack is determined only by the dipole at high-k∕SiO2 interface, while for the Si-based gate it is determined by both gate/high-k and high-k∕SiO2 interfaces.
Metal-insulator transition, specific heat, and grain-boundary-induced disorder in Sm0.55Sr0.45MnO3
Authors: Egilmez M. , Chow K. H. , Jung J. , Fan I. , Mansour A. I. , Salman Z.
Published: April 2008

The effects of the grain-boundary-induced lattice disorder on the resistivity, the magnetization, and the specific heat of a prototypical manganite Sm0.55Sr0.45MnO3 near half doping were investigated at temperatures near the metal-insulator transition. An increasing lattice disorder softens the magnetic phase transition from a first order phase transition into a second order transition. Furthermore, the peaks in the resistivity and specific heat are broaden and there is an increase in the charge-carrier scattering rates in the metallic and insulating states. The origin of these phenomena is discussed.
Chiral selective tunneling induced negative differential resistance in zigzag graphene nanoribbon: A theoretical study
Authors: Wang Z. F. , Li Qunxiang , Shi Q. W. , Wang Xiaoping , Yang Jinlong , Hou J. G. , Chen Jie
Published: April 2008

The electronic and phase-coherent transport properties of a doped zigzag graphene nanoribbon are studied theoretically in this paper. The I-V curve of the device shows an interesting negative differential resistance (NDR) phenomenon. We found that the NDR is caused by the chiral tunneling of graphene, which is attributed to the symmetry of the eigenstates of individual subbands. This new physics finding is helpful for us to gain more insights about carrier transport in graphene nanoribbons and to design graphene-based nanoelectronic devices.
Nanoscale surface displacement detection in high absorbing solids by time-resolved thermal mirror
Authors: Malacarne L. C. , Sato F. , Pedreira P. R. B. , Bento A. C. , Mendes R. S. , Baesso M. L. , Astrath N. G. C. , Shen J.
Published: April 2008

Nanoscale surface displacement is used to determine thermo-optical–mechanical properties of high absorbing solids by means of the time-resolved thermal mirror method. The thermoelastic equation for the surface displacement and an expression for the probe beam intensity at the detector plane were derived. Experiments were performed in a high absorbing TiO2-doped low silica calcium aluminosilicate glass, and obtained the valuable values of the fluorescence quantum efficiency and thermal properties. The results indicate that this method is reliable for the characterization of semitransparent, high absorbing, and opaque materials.
Two-dimensional vortex-pinning phenomena in YBa2Cu3Oy films
Authors: Horii S. , Takamura M. , Mukaida M. , Ichinose A. , Yamada K. , Teranishi R. , Matsumoto K. , Kita R. , Yoshida Y. , Shimoyama J. , Kishio K.
Published: April 2008

Anomalous superconducting properties were demonstrated in anisotropic high-critical-temperature superconductors (HTSCs) by simultaneously introducing two different planar types of vortex-pinning centers. The nanostructure, magnetic field, and field-angle dependency of critical current properties for an a-axis-grown multilayered film consisting of superconducting and semiconducting layers were characterized. Semiconductive layers running perpendicular to CuO2 superconducting layers behave as novel two-dimensional vortex-pinning centers that reverse the typical magnetic response in the superconducting state observed for conventional HTSCs. The results indicate that the vortex behavior in nanostructured HTSCs can be controlled; therefore, significant potential exists for further improvement of the critical current properties.
Nanowire sensor response to reactive gas environment
Authors: Cvelbar Uroš , Ostrikov Kostya (Ken) , Drenik Aleksander , Mozetic Miran
Published: April 2008

The response of an originally developed catalytic sensor with a Nb2O5 nanowire array at its outer surface to the varying density of O atoms is experimentally and numerically studied. This technique can be used to measure one order of magnitude lower densities of O atoms and achieve a stable linear response in a significantly broader pressure range compared to conventional catalytic probes with a flat surface. The nanostructured outer surface also acts as a thermal barrier against sensor overheating. This approach is generic and can be used for reactive species detection in other reactive gas environments.
High capacitance density metal-insulator-metal structures based on a high-κ HfNxOy–SiO2–HfTiOy laminate stack
Authors: Mikhelashvili V. , Thangadurai P. , Kaplan W. D. , Eisenstein G.
Published: April 2008

We demonstrate a metal-insulator-metal (MIM) capacitor containing five laminate films of HfNxOy, SiO2, and HfTiOy. The MIM capacitors exhibit capacitance densities and dielectric constants of 16fF∕μm2 and 27 in the as-deposited state and 11fF∕μm2 and 30 after thermal annealing. The tangent loss of the annealed structures measured at room temperature and at 0.1MHz is 0.0055. Low leakage current densities (1.5×10−7A∕cm2 at 2V), linear and quadratic capacitance voltage coefficients of 19ppm∕V and 235ppm∕V2, respectively, as well as a capacitance temperature coefficient of 650ppm∕°C were demonstrated.
Ni-induced destabilization dynamics of crystalline zinc borohydride
Authors: Choudhury Pabitra , Bhethanabotla Venkat R. , Stefanakos Elias
Published: April 2008

Fundamental understanding of the role of Ni additives in promoting the dehydrogenation mechanism of hydrogen desorption in zinc borohydride [Zn(BH4)2] is a key factor for using this material in hydrogen storage. A systematic theoretical study of the energetics and hydrogen dynamics was carried out to understand this dehydrogenation mechanism. The energetic calculations reveal that Ni substitutes Zn in preference to B. H atoms are pulled toward these doped Ni atoms, which introduce instability via the breaking of multiple B–H bonds in the complex borohydride. The mechanistic understanding gained from this study can be applied to the design of better hydrogen storage materials.
Thermal transport across nanoscale solid-fluid interfaces
Authors: Murad Sohail , Puri Ishwar K.
Published: April 2008

An explanation for the effective thermal resistance RK can be based on the impedance to the passage of thermal phonons across an interface. We conjecture that (1) increasing the fluid pressure, and (2) making an interface more hydrophilic should facilitate better acoustic matching and thus lower RK. Our molecular dynamics simulations confirm this. Overall, RK decreases with increasing temperature and is inversely proportional to the heat flux.
Incorporation of Ga in ZnO∕GaN epitaxial films
Authors: Schneider R. , Schirra M. , Reiser A. , Prinz G. M. , Limmer W. , Sauer R. , Thonke K. , Biskupek J. , Kaiser U.
Published: April 2008

Growth of zinc oxide (ZnO) layers on gallium nitride (GaN) substrates benefits from the small lattice mismatch of these two materials. We report on spatially resolved cathodoluminescence studies of ZnO layers grown by a modified chemical vapor deposition process on GaN templates deposited on sapphire substrates. Line scans across the ZnO∕GaN interface reveal the incorporation of gallium from the template into the ZnO layer. Transmission electron microscopy and micro-Raman measurements both indicate that strain relaxation occurs within a distance of a few nanometers from the ZnO∕GaN interface. The diffusion coefficient of gallium in ZnO is determined.
Obtaining the glass transition temperature by measuring the crack healing process of glassformers
Authors: Zhang J. L. , Wu W. H. , Zhou H. W. , Guo X. Z. , Huang Y. N.
Published: April 2008

By the study of a series of molecular liquids of fragilities covering almost the entire known range by the mechanical spectroscopy of quantitatively monitoring the healing of stress-induced microcracks recently developed by W. H. Wu et al. [Appl. Phys. Lett. 92, 011918 (2008)], we show that the cracking healing temperature coincides with the onset glass temperature Tg, quite independent of the liquid fragility. Another interesting observation is that the major part of the modulus recovery occurs below Tg. Thus, our study establishes an additional approach to the study of the glass dynamics and glass transition which lends itself to a variety of potential applications.
Differential scanning calorimetry measurements of kinetic factors involved in salicide process
Authors: Hoummada K. , Portavoce A. , Perrin-Pellegrino C. , Mangelinck D. , Bergman C.
Published: April 2008

Experimental procedure allowing the measurement of kinetic factors controlling the reaction of a nanometric film with a monocrystalline substrate by differential scanning calorimetry (DSC) is described. This technique is shown to be of great interest for characterization of silicide formation during microelectronic industrial processes. Combining both in situ x-ray diffraction measurements (crystal structure) and DSC measurements (formation enthalpy), the interface reaction coefficient Kr and the effective diffusion coefficient Kd characterizing Pd2Si growth have been measured.
Dissolution and off-stoichiometric formation of compound layers in solid state reactions
Authors: Erdélyi Zoltán , Beke Dezső L. , Taranovskyy Andriy
Published: April 2008

In many technological processes, intermediate phases are produced by solid state reactions (SSRs) of pure materials initially layered onto each other. It is generally accepted that during heat treatments of such structures, stoichiometric compound films form and then grow, or if such a layer already exists then it growths further. We show that in many realistic cases the compound layer forms and starts to grow highly off stoichiometrically. Moreover, an initially existing stoichiometric compound layer may dissolve then off stoichiometrically reform. Our findings are of primary importance for nanotechnologies where early stages of SSR are utilized; e.g., metallization for silicon-based devices in micro-/nanoelectronics.
Determination of spin polarization in InAs∕GaAs self-assembled quantum dots
Authors: Hernandez F. G. G. , Mayer Alegre T. P. , Medeiros-Ribeiro G.
Published: April 2008

The spin polarization of electrons trapped in InAs self-assembled quantum dot ensembles is investigated. A statistical approach for the population of the spin levels allows one to infer the spin polarization from the measured values of the addition energies. From the magnetocapacitance spectroscopy data, the authors found a fully polarized ensemble of electronic spins above 10T when B∥[001] and at 2.8K. Finally, by including the g-tensor anisotropy, the angular dependence of the spin polarization with the magnetic field B orientation and strength could be determined.
High quality anatase TiO2 film: Field-effect transistor based on anatase TiO2
Authors: Katayama Masao , Ikesaka Shinya , Kuwano Jun , Koinuma Hideomi , Matsumoto Yuji
Published: April 2008

We proposed an oxygen modulation method for the growth of high crystalline and insulative anatase films. The cycle of deposition under low oxygen pressure and annealing under high oxygen pressure was repeated every 1nm thick growth. The sharp reflection high-energy electron diffraction pattern and step-and-terrace surface morphology confirmed high crystallinity of the obtained anatase film; the resistivity reached as high as 1.8MΩcm. As a result, the present anatase film exhibited high performance in a field-effect transistor as an active channel. On-to-off current ratio and field-effect mobility exceeded 105 and 0.3cm2∕Vs, respectively.
Nanoscale epitaxial cobalt salicide bitlines for charge trapping memory cells
Authors: Kleint C. A. , Mueller T. , Teichert S. , Fitz C. , Nagel N. , Kuesters K. H.
Published: April 2008

An epitaxial CoSi2 process is presented, which allows the self-aligned formation of bitlines with only a few tens of nanometer width for Twin Flash memory cells in the 63nm generation. The bitlines show a good thermal stability and low resistance for widths down to 35nm, where polycrystalline CoSi2 is known to exhibit a strong narrow linewidth effect. Transmission electron microscopy studies revealed a cube-on-cube epitaxy with only a few twins depending on the annealing conditions. The low bitline resistance results in a linear drain voltage dependence of the programing characteristics and a suppression of secondary electron injection during programing.
Distinguishing self-gated rectification action from ordinary diode rectification in back-gated carbon nanotube devices
Authors: Li Jiantong , Zhang Zhi-Bin , Östling Mikael , Zhang Shi-Li
Published: April 2008

Self-gating leading to rectification action is frequently observed in two-terminal devices built from individual or networked single-walled carbon nanotubes (SWCNTs) on oxidized Si substrates. The current-voltage (I-V) curves of these SWCNT devices remain unaltered when switching the measurement probes. For ordinary diodes, the I-V curves are symmetric about the origin of the coordinates when exchanging the probes. Numerical simulations suggest that the self-gated rectification action should result from the floating semiconducting substrate which acts as a back gate. Self-gating effect is clearly not unique for SWCNT devices. As expected, it is absent for devices fabricated on insulating substrates.
ZnO nanorods for solar cells: Hydrothermal growth versus vapor deposition
Authors: Hsu Y. F. , Xi Y. Y. , Djurišić A. B. , Chan W. K.
Published: April 2008

Performance of dye-sensitized solar cells (DSSCs) based on ZnO nanorods prepared by hydrothermal and vapor-deposition methods has been investigated. In spite of their inferior optical properties, DSSCs based on hydrothermally grown rods exhibit higher power conversion efficiency, which can be attributed to the higher dye adsorption. Hydrothermally grown and vapor deposited nanorods also exhibit different dependence of photovoltaic performance on the annealing conditions of the rods, indicating significant effect of the native defects on the achievable photocurrent and power conversion efficiency. Efficiency of 0.22% is obtained for both as grown hydrothermally grown nanorods and vapor deposited nanorods annealed in oxygen at 200°C.
Intrinsic stress evolution in nanocrystalline diamond thin films with deposition temperature
Authors: Xiao X. , Sheldon B. W. , Qi Y. , Kothari A. K.
Published: April 2008

The stress evolution in nanocrystalline diamond (NCD) films deposited at different temperatures (from 800to400°C) was investigated. Results showed that the intrinsic stress gradually changed from tensile to compressive with decreasing deposition temperature. Most importantly, the intrinsic stress can be tailored to zero by adjusting the deposition temperature, which is critical to many applications. It has been proven that more H as well as sp2 bonded carbon was incorporated into the grain boundaries, which was responsible for the evolution of stress and other mechanical properties with deposition temperature. Moreover, all the NCD films showed excellent mechanical properties.
Taxonomy of Echium (Boraginaceae) species from Cape Verde Islands
Authors: Romeiras Maria M. , Ascensão Lia , Duarte Maria C. , Diniz Maria A. , Pais Maria S.
Published: April 2008

The morphological variation of endemic species from the Macaronesian Islands has long attracted attention of many taxonomists. The taxonomy of the endemic Echium L. species (E. hypertropicum Webb, E. stenosiphon Webb and E. vulcanorum A.Chev.) from Cape Verde Islands was revised, on the basis of in situ collected material and on herbarium specimens. Our results revealed that the patterns of morphological variation correspond closely to the geographic localisation of the islands groups, and that habit and floral morphology are important for distinguishing the two southern taxa, E. hypertropicum and E. vulcanorum, from the northern species, E. stenosiphon. This species has the same ecological preferences (e.g. altitude; exposition; soil type) in São Nicolau, São Vicente and Santo Antão Islands. However, the differences in indumentum observed among E. stenosiphon specimens account for the occurrence of different taxonomic groups distributed in these Northern Islands. The two southern species, E. hypertropicum and E. vulcanorum, are morphologically similar, but have different ecological preferences, a pattern of variation similar to other Macaronesian Echium species. Furthermore, the morphological variation observed among the three Cape Verde species, discussed within the general context of Echium taxonomy and closely related genera (e.g. Lobostemon, Echiostachys and Pontechium), suggests that the systematic relationships are beyond the actual circumscription of these genera.
New species of dictyostelid cellular slime moulds from Australia
Authors: Landolt John C. , Cavender James C. , Stephenson Steven L. , Vadell Eduardo M.
Published: April 2008

During the 2001–2006 field seasons, samples for isolation of dictyostelid cellular slime moulds were collected at several localities in Queensland, the Northern Territory, Western Australia and Victoria. The majority of these samples were collected from the soil–litter layer on the ground, but some additional samples were obtained from the layer of organic matter (‘canopy soil’) associated with the bases of vascular epiphytes on the trunks and branches of trees in the tropical forests of northern Queensland. Many of the forms recovered from these samples could be assigned to described taxa, including such cosmopolitan species as Dictyostelium mucoroides, Polysphondylium pallidum, P. violaceum and D. giganteum. However, several others appear to represent new species, and eight of these (D. boomeransporum, D. flexuosum, D. granulosum, D. myxobasis, D. radiculatum, D. rotatum, P. australicum and P. stolonicoideum) are described herein. The large number of apparently undescribed forms suggests that the dictyostelid biota of Australia is relatively distinct when compared with that of any other continent.
Expected gene-order distances and model selection in bacteria
Authors: Dalevi Daniel , Eriksen Niklas
Published: April 2008

Motivation: The evolutionary distance inferred from gene-order comparisons of related bacteria is dependent on the model. Therefore, it is highly important to establish reliable assumptions before inferring its magnitude.

Results: We investigate the patterns of dotplots between species of bacteria with the purpose of model selection in gene-order problems. We find several categories of data which can be explained by carefully weighing the contributions of reversals, transpositions, symmetrical reversals, single gene transpositions and single gene reversals. We also derive method of moments distance estimates for some previously uncomputed cases, such as symmetrical reversals, single gene reversals and their combinations, as well as the single gene transpositions edit distance.

Contact:  ner@math.chalmers.se

Supplementary information:  Supplementary data are available at Bioinformatics online.
FT-COMAR: fault tolerant three-dimensional structure reconstruction from protein contact maps
Authors: Vassura Marco , Margara Luciano , Di Lena Pietro , Medri Filippo , Fariselli Piero , Casadio Rita
Published: April 2008

Summary: Fault Tolerant Contact Map Reconstruction (FT-COMAR) is a heuristic algorithm for the reconstruction of the protein three-dimensional structure from (possibly) incomplete (i.e. containing unknown entries) and noisy contact maps. FT-COMAR runs within minutes, allowing its application to a large-scale number of predictions.

Availability:  http://bioinformatics.cs.unibo.it/FT-COMAR

Contact:  vassura@cs.unibo.it

Supplementary information: Supplementary data are available on Bioinformatics online.
Does habituation to humans influence predator discrimination in Gunther's dik-diks (
Madoqua guentheri
)?
Authors: Coleman Andrea , Richardson Dominique , Schechter Robin , Blumstein Daniel T
Published: April 2008

Animals living around humans may habituate to us, but little is known about the consequences of this habituation. Some wildlife managers assume that habituation to humans makes individuals less likely to respond to natural predators, which is something to be avoided in captive breeding programmes where animals are destined for release. We conducted a playback experiment where we broadcast the sounds of a terrestrial predator and the song from a non-threatening bird to Gunther's dik-diks (
Madoqua guentheri
), a small ungulate that is vulnerable to many predators, in areas where dik-diks were and were not habituated to humans. Contrary to our expectation, habituated dik-diks discriminated the predator sounds from the birdsong, while unhabituated dik-diks failed to make this discrimination. Our results demonstrate that humans may influence predation hazard assessment, but we should not generally assume that human-habituated animals will be especially vulnerable to predators.
Intermittent transformation between radial breathing and flexural vibration modes in a single-walled carbon nanotube
Authors: Li Q.M , Shi M.X
Published: April 2008

Based on an equivalent continuum cylindrical shell model, we have predicted the intermittent transformation between radial breathing and flexural vibration modes in a single-walled carbon nanotube. It is found that the radial breathing and flexural vibration modes may appear intermittently, in certain circumstances, when the dominant parameters of the problem are in the instable region of the Mathieu stability diagram. The coupled nonlinear differential equations of the radial breathing and the flexural vibration modes are presented to a fourth-order approximation, which is then solved using a finite series expansion method. Intermittent transformation between radial breathing and flexural vibration modes is predicted, which may influence the physical properties of the carbon nanotube and the Raman spectroscope measurements.
Further investigation of crystal hardening inequalities in (110) channel die compression
Authors: Havner Kerry S
Published: April 2008

A set of geometrically based FCC crystal slip-systems hardening inequalities is analytically investigated in (110) channel die compression for all lateral constraint directions betweenand, following previous analyses of the other two distinct orientation ranges in (110) compression. With all critical slip systems active, it is proved that these inequalities uniquely predict initial lattice stability and finite crystal shearing only in the horizontal channel plane, consistent with experiments for this range of orientations. (The earlier analyses had predicted load-axis stability in both orientation ranges, and lattice stability in one, also commonly found experimentally.) Moreover, it is established that the lateral constraint stress predicted by the hardening inequalities will be less than that given by classic Taylor hardening as this stress evolves with deformation. It is further shown, taking into account experimental stress–strain curves and latent hardening experiments for aluminium and copper, that lattice stability generally can be expected to very large deformations, except perhaps for lateral constraint orientations near theend of the range, which result is consistent with experiment. In appendix A, the possibilities of solutions with a critical slip system inactive are investigated, and predictions of a power law rate-dependent plasticity model are analysed for comparison with the results based on the hardening inequalities.
New serotype of mutans streptococci isolated from pig oral cavity
Authors: Takada Kazuko , Igarashi Mitsuhiko , Yamaguchi Yasutaka , Hirasawa Masatomo
Published: April 2008

Gram‐positive streptococcal mutans‐like strains, but with clearly different colony formation than S. orisuis on Mitis Salivarius agar, were isolated from the pig oral cavity and identified by 16S rRNA sequencing, G+C content, DNA‐DNA homology and extensive biochemical and serological testing. The phenotypic data showed that the strains were similar to S. orisuis except for susceptibility to bacitracin. DNA‐DNA homology between the isolates and S. orisuis was 72∼81%. However, serological data showed that they have a different sero‐specific antigen from S. orisuis and other mutans streptococci. A new serotype, designated p, strains are classified in a serovar of S. orisuis, one of mutans streptococci.
Hsa, an adhesin of Streptococcus gordonii DL1, binds to α2‐3‐linked sialic acid on glycophorin A of the erythrocyte membrane
Authors: Yajima Ayako , Urano‐Tashiro Yumiko , Shimazu Kisaki , Takashima Eizo , Takahashi Yukihiro , Konishi Kiyoshi
Published: April 2008

Bacterial recognition of host sialic acid‐containing receptors plays an important role in microbial colonization of the human oral cavity. The aggregation of human platelets by Streptococcus gordonii DL1 is implicated in the pathogenesis of infective endocarditis. In addition, we consider that hemagglutination of this organism may act as an additive factor to increase the severity of this disease. We previously reported that this interaction requires the bacterial expression of a 203‐kDa protein (Hsa), which has sialic acid‐binding activity. In the present study, we confirmed that erythrocyte surface sialoglycoproteins are the receptors for Hsa. We examined the effects of proteinase K, chymotrypsin, phospholipase C, and α(2‐3) or α(2‐3, 6, 8) neuraminidase on hemagglutination activity and found that the interaction occurs between Hsa and α2‐3‐linked sialic acid‐containing proteins of erythrocytes. We expressed recombinant NR2, which is the putative binding domain of Hsa, fused with GST in Escherichia coli BL21. Dot‐blot analysis demonstrated that GST‐HsaNR2 binds both glycophorin A (GPA) and band 3. Moreover, GPA and a small amount of band 3 were detected by GST pull‐down assays. These findings indicate that S. gordonii Hsa specifically binds to GPA and band 3, α2‐3‐linked sialic acid membrane glycoproteins.
Generation and characterization of human monoclonal antibodies to G5, a linear neutralization epitope on glycoprotein of rabies virus, by phage display technology
Authors: Zhao Xiao‐Ling , Yin Jun , Chen Wei‐Qiang , Jiang Ming , Yang Guan , Yang Zhi‐Hua
Published: April 2008

The aim of the present study was to discover distinct human MAbs to RV with high neutralizing potency and a broad neutralization spectrum. A phage display technology was used to produce human scFv to G5, a conserved linear neutralization epitope on Gp of RV. A phage display scFv library with 6 × 107 members was constructed and the phage‐scFv with ‘antigen‐binding’ activities were selected with synthetic peptide G5‐24. The obtained scFv genes were cloned into pET22b(+)/BL21(DE3) and from this we prepared purified scFv fragments. The assay of the specificity characteristics and neutralization capacity showed that two distinct clones with new human immunoglobulin V genes can recognize G5 specifically as well as neutralize different RV strains. They have potential for inclusion in an antibodies combination aimed for use in rabies PEP.
Disruption of the association of 73 kDa heat shock cognate protein with transporters associated with antigen processing (TAP) decreases TAP‐dependent translocation of antigenic peptides into the endoplasmic reticulum
Authors: Kamiguchi Kenjiro , Torigoe Toshihiko , Fujiwara Osamutaro , Ohshima Shin , Hirohashi Yoshihiko , Sahara Hiroeki , Hirai Itaru , Kohgo Yutaka , Sato Noriyuki
Published: April 2008

Major histocompatibility complex class I‐bound antigenic peptides generated in the cytosol are translocated into the ER by TAP. In the present study, the physical association of HSC73 with TAP in human lymphoblastoid T1 cells was demonstrated. The dissociation was induced in the presence of 10 mM ATP, indicating that the ADP‐binding form of HSC73 might be associated with TAP. We found that HSC73‐binding immunosuppressant, MeDSG disrupted the HSC73‐TAP association, whereas it did not affect the binding of HSC73 to a substrate protein. MHC class I expression on the cell surface was also downregulated. Then, the effect of MeDSG on the TAP‐mediated ER translocation was examined using two homologous model peptides, NGT‐Bw4 and NGT‐Bw6, which had distinct binding affinity to HSC73. Although high‐affinity peptide NGT‐Bw4 was translocated by TAP, low‐affinity peptide NGT‐Bw6 was not. The TAP‐dependent translocation of NGT‐Bw4 was abolished in the presence of MeDSG. Decreased presentation on the cell surface was shown for the human leukocyte antigen (HLA)‐A31‐restricted natural antigenic peptide F4.2, which had high affinity to HSC73, in the presence of MeDSG. It was indicated that disruption of the HSC73‐TAP association resulted in inhibition of TAP‐dependent translocation of HSC73‐bound peptides. Our findings highlighted an important role of HSC73 for feeding antigenic peptides to TAP, and suggested a possibility that a synthetic polyamine might inhibit the function of HSC73, thereby suppressing MHC class I‐restricted presentation of HSC73‐bound antigenic peptides.
Late Carboniferous foreland basin formation and Early Carboniferous stretching in Northwestern Europe: inferences from quantitative subsidence analyses in the Netherlands
Authors: Kombrink Henk , Leever Karen A. , Van Wees Jan‐Diederik , Van Bergen Frank , David Petra , Wong Theo E.
Published: April 2008

The large thickness of Upper Carboniferous strata found in the Netherlands suggests that the area was subject to long‐term subsidence. However, the mechanisms responsible for subsidence are not quantified and are poorly known. In the area north of the London Brabant Massif, onshore United Kingdom, subsidence during the Namurian–Westphalian B has been explained by Dinantian rifting, followed by thermal subsidence. In contrast, south and east of the Netherlands, along the southern margin of the Northwest European Carboniferous Basin, flexural subsidence caused the development of a foreland basin. It has been proposed that foreland flexure due to Variscan orogenic loading was also responsible for Late Carboniferous subsidence in the Netherlands. In the first part of this paper, we present a series of modelling results in which the geometry and location of the Variscan foreland basin was calculated on the basis of kinematic reconstructions of the Variscan thrust system. Although several uncertainties exist, it is concluded that most subsidence calculated from well data in the Netherlands cannot be explained by flexural subsidence alone. Therefore, we investigated whether a Dinantian rifting event could adequately explain the observed subsidence by inverse modelling. The results show that if only a Dinantian rifting event is assumed, such as is found in the United Kingdom, a very high palaeowater depth at the end of the Dinantian is required to accommodate the Namurian–Westphalian B sedimentary sequence. To better explain the observed subsidence curves, we propose (1) an additional stretching event during the Namurian and (2) a model incorporating an extra dynamic component, which might well explain the very high wavelength of the observed subsidence compared with the wavelength of the predicted flexural foreland basin.
Spider silk fibres in artificial nerve constructs promote peripheral nerve regeneration
Authors: Allmeling C. , Jokuszies A. , Reimers K. , Kall S. , Choi C. Y. , Brandes G. , Kasper C. , Scheper T. , Guggenheim M. , Vogt P. M.
Published: April 2008

Abstract.  Objective: In our study, we describe the use of spider silk fibres as a new material in nerve tissue engineering, in a 20‐mm sciatic nerve defect in rats. Materials and methods: We compared isogenic nerve grafts to vein grafts with spider silk fibres, either alone or supplemented with Schwann cells, or Schwann cells and matrigel. Controls, consisting of veins and matrigel, were transplanted. After 6 months, regeneration was evaluated for clinical outcome, as well as for histological and morphometrical performance. Results: Nerve regeneration was achieved with isogenic nerve grafts as well as with all constructs, but not in the control group. Effective regeneration by isogenic nerve grafts and grafts containing spider silk was corroborated by diminished degeneration of the gastrocnemius muscle and by good histological evaluation results. Nerves stained for S‐100 and neurofilament indicated existence of Schwann cells and axonal re‐growth. Axons were aligned regularly and had a healthy appearance on ultrastructural examination. Interestingly, in contrast to recently published studies, we found that bridging an extensive gap by cell‐free constructs based on vein and spider silk was highly effective in nerve regeneration. Conclusion: We conclude that spider silk is a viable guiding material for Schwann cell migration and proliferation as well as for axonal re‐growth in a long‐distance model for peripheral nerve regeneration.