bluuebunny/crossref_metadata_2025 huggingface dataset:
Improvement of the self-field critical current of a high-Tc superconducting tape by the edge cover from soft ferromagnetic material
Authors: Gömöry F.
Published: September 2006

Improvement of the electrical transport capability is analyzed for a superconducting wire with elliptic section, when its edges have been covered by a soft ferromagnetic material. Numerical calculations have been carried out to find the distributions of electrical current and magnetic field when reaching the critical current. The dependence of critical current density on local magnetic field and its orientation has been taken into consideration. For an arrangement that resembles a typical commercial tape from high-temperature superconductor Bi2Sr2Ca2Cu3O10 covered by a Ni sheath at edges, an increase of self-field critical current could reach 10%.
1
μ
m
saturable absorber with recovery time reduced by lattice mismatch
Authors: Suomalainen S. , Guina M. , Hakulinen T. , Okhotnikov O. G. , Euser T. G. , Marcinkevicius S.
Published: September 2006

Metamorphic growth of lattice mismatched InGaP on GaAs has been used to fabricate a fast semiconductor saturable absorber mirror operating at the 1060nm wavelength range. The absorption recovery time could be reduced to ∼5ps without deteriorating the nonlinear absorption properties. The device was used to demonstrate self-starting operation of a mode-locked Yb-doped fiber laser and obtain high quality picosecond pulses.
Conformational flexibility and its effect on the vibrationally resolved absorption and fluorescence spectra of oligofluorenes
Authors: Song Jian , Liang Wan Zhen , Zhao Yi , Yang Jinlong
Published: September 2006

The authors present a first-principles density-functional theory study on the electronic excitation of oligofluorenes. Their results indicate that the strong electron-nuclear coupling results in a dynamic structural distortion in the S1 state, which extends over eight monomers in the center of the long chain and contributes a relaxation energy of ∼0.23eV. The field-induced density matrices evidence that the excitons localize in the regions where the structural alternations occur. The asymmetry of absorption and fluorescence spectra of oligofluorenes is significantly pronounced. The experimentally observed spectroscopic features are reasonably reproduced by properly taking into account the anharmonic torsional potentials without any adjustable parameters.
Schottky barrier height of ferromagnet/Si(001) junctions
Authors: Sugiura Kuniaki , Nakane Ryosho , Sugahara Satoshi , Tanaka Masaaki
Published: September 2006

The Schottky barrier height of ferromagnetic metal/semiconductor junctions is one of the most important parameters for the performance of semiconductor-based spin-electronic devices. The authors investigated the Schottky barrier height ϕB of ferromagnet/Si(001) junctions with various ferromagnetic metals (CoFe, CoFeB, and MnAs), and found that ϕB of epitaxial MnAs∕Si(001) junctions fabricated by molecular beam epitaxy was 0.16eV for electrons, which is much lower than ϕB (∼0.7eV) of CoFe∕Si(001) and CoFeB∕Si(001) junctions. This implies that MnAs is a promising ferromagnetic material for Si-based spin-electronic devices, especially for the source and drain of spin metal-oxide-semiconductor field effect transistors.
The behavior of reorientational correlation functions of water at the water-lipid bilayer interface
Authors: Bhide Shreyas Y. , Berkowitz Max L.
Published: September 2006

We studied the effects of confinement and the head group motion on the behavior of the reorientational correlation functions for water molecules at the water∕lipid bilayer interface. The correlation functions were calculated from the data obtained from two molecular dynamics simulations: one with a flexible bilayer and the other with a frozen bilayer. In our present analysis the water molecules were separated into spatial regions according to their distance from the bilayer surface and into population groups, according to the length of their stay in the corresponding regions. We estimate that for most of the water molecules that are in a strongly confined environment of the transition region between the head groups and tails, and that solvate carbonyl groups, the decay time of their reorientational correlation functions is of the order of a few tens of picoseconds. Water molecules that stay inside the transition region for long periods of time can display longer time decay (of the order of hundreds of picoseconds). This latter long time decay is determined by the dynamics of the phospholipids, it is substantially reduced when the bilayer is frozen. The decay of the correlation functions for the interfacial water molecules that are solvating the head groups is also slowed down when compared to bulk, but just by factors of 3–4.
Calculation of two-photon absorption spectra of donor-π-acceptor compounds in solution using quadratic response time-dependent density functional theory
Authors: Day Paul N. , Nguyen Kiet A. , Pachter Ruth
Published: September 2006

Linear and quadratic response time-dependent density functional theories have been applied to calculate the photophysical properties of donor-π-acceptor molecules which are known to have large nonlinear absorption. The linear absorption and two-photon absorption spectra predicted using hybrid functionals, including the Coulomb-attenuated model, with continuum solvation models are reported and compared to experiment and to previous theoretical predictions. While the quadratic response with these functionals overestimated the TPA cross sections relative to experiment when a Gaussian linewidth function was used, a fairly good agreement was obtained when a Lorentzian linewidth function was applied. In addition, the comparison of the TPA cross sections calculated by the sum over states with those calculated by the two-state approximation indicates the importance of the higher energy states in TPA, particularly in nondegenerate experiments.
Simple method to obtain symmetry harmonics of point groups
Authors: Boiko D. L. , Féron P. , Besnard P.
Published: September 2006

We propose a simple, self-consistent method to obtain basis functions of irreducible representations of a finite point group. Our method is based on eigenproblem formulation of a projection operator represented as a nonhomogeneous polynomial of angular momentum L̂. The method is shown to be more efficient than the usual numerical methods when applied to the analysis of high-order symmetry harmonics in cubic and icosahedral groups. For low-order symmetry harmonics the method provides rational coefficients of expansion in the YL,M basis.
Is weak pseudo-Hermiticity weaker than pseudo-Hermiticity?
Authors: Mostafazadeh Ali
Published: September 2006

For a weakly pseudo-Hermitian linear operator, we give a spectral condition that ensures its pseudo-Hermiticity. This condition is always satisfied whenever the operator acts in a finite-dimensional Hilbert space. Hence weak pseudo-Hermiticity and pseudo-Hermiticity are equivalent in finite-dimensions. This equivalence extends to a much larger class of operators. Quantum systems whose Hamiltonian is selected from among these operators correspond to pseudo-Hermitian quantum systems possessing certain symmetries.
The anisotropic hard-sphere crystal-melt interfacial free energy from fluctuations
Authors: Davidchack Ruslan L. , Morris James R. , Laird Brian B.
Published: September 2006

We have calculated the interfacial free energy for the hard-sphere system, as a function of crystal interface orientation, using a method that examines the fluctuations in the height of the interface during molecular dynamics simulations. The approach is particularly sensitive for the anisotropy of the interfacial free energy. We find an average interfacial free energy of γ=0.56±0.02kBTσ−2. This value is lower than earlier results based upon direct calculations of the free energy [R. L. Davidchack and B. B. Laird, Phys. Rev. Lett. 85, 4751 (2000)]. However, both the average value and the anisotropy agree with the recent values obtained by extrapolation from direct calculations for a series of the inverse-power potentials [R. L. Davidchack and B. B. Laird, Phys. Rev. Lett. 94, 086102 (2005)].
Fast electronic and thermal processes in femtosecond laser ablation of Au
Authors: Dachraoui Hatem , Husinsky Wolfgang
Published: September 2006

Velocity distribution, pulse width dependence studies, and two-pulse correlation measurements have been used to study the possibility of the occurrence of ultrafast electronic and thermal ablation processes in Au exposed to ultrashort laser pulses in the femtosecond to picosecond time domain. Three distinct different velocity groups (5.5, 1.5, and 0.25eV) have been observed and can be attributed to two ultrafast electronic processes (Coulomb explosion and rapid plasma formation) and a thermal process. The buildup of a rapid plasma favors the laser energy absorption around 400fs after the beginning of the laser-matter interaction.
Correlation between the atomic structures and the misorientation angles of [0001]-tilt grain boundaries at triple junctions in ZnO thin films grown on Si substrates
Authors: Shin J. W. , Lee J. Y. , No Y. S. , Kim T. W. , Choi W. K.
Published: September 2006

The correlation between the atomic structures and the misorientation angles of [0001]-tilt grain boundaries at triple junctions in ZnO thin films grown on Si substrates was investigated by using high-resolution transmission electron microscopy (HRTEM) measurements. The HRTEM images showed three symmetric grain boundaries and one asymmetric grain boundary around the triple junction in the ZnO film. The correlation between the atomic structures and the misorientation angles of the grain boundaries at triple junctions in ZnO films is described on the basis of the HRTEM results.
All-dimensional subwavelength cavities made with metamaterials
Authors: Li Hongqiang , Hao Jiaming , Zhou Lei , Wei Zeyong , Gong Lingkan , Chen Hong , Chan C. T.
Published: September 2006

By exploiting the reflection phase properties of metamaterial reflectors, the authors propose a method to break the size restrictions imposed strictly on conventional cavities. They design the all-dimensional subwavelength cavities and perform experiments and simulations to demonstrate their subwavelength functionalities. For the smallest cavity that they fabricated, each dimension is only a quarter of the resonance wavelength.
Lithium manganese oxide as an effective buffer layer between organic and metal layers in organic light-emitting devices
Authors: Liu Tswen-Hsin
Published: September 2006

Tris(8-hydroxyquinolinato)aluminum (Alq3)-based organic light-emitting devices using a thermally deposited lithium manganese oxide layer between aluminum (Al) cathode and Alq3 have been fabricated. The highest luminance efficiency obtained with a 1-nm-thick LiMnxOy layer is very similar to that of the device with 1-nm-thick LiF. However, the device with an 18nm LiMnxOy layer obtained a longer operational stability although the luminance efficiency is lower. The improvements are attributed to lithium extractions of the lithium manganese oxide layer and the interfacial properties between Alq3 and Al are discussed.
One-step solution fabrication of magnetic chains consisting of jingle-bell-shaped cobalt mesospheres
Authors: Liang Fang , Guo Lin , Zhong QunPeng , Wen Xiaogang , Yang Shihe , Zheng Wangzhi , Chen Chinping , Zhang Nina , Chu Weiguo
Published: September 2006

Using a one-step solution phase approach, the authors have synthesized uniform jingle bell-shaped cobalt mesopheres (550–750nm) and assembled the mesospheres into long magnetic chains (20–30μm). All of the cobalt spheres are hollow with ∼40nm thick shells but each contains an ∼200nm diameter solid ball. The nano- to mesoscale structures were realized via reaction of CoCl2∙6H2O and N2H4∙H2O in the presence of polyvinylpyrrolidone (PVP) in an ethylene glycol solution. Magnetic measurements show a coercivity of about 75Oe with a remnance of 9.6emu∕g at 300K. We propose a possible mechanism for the formation of the nanoto mesoscale structures.
Influence of a controllable scatterer on the lasing properties of an ultralow threshold Raman microlaser
Authors: Mazzei A. , Krauter H. , Benson Oliver , Götzinger Stephan
Published: September 2006

The authors investigate Raman lasing in a spherical high-Q glass microresonator with the help of a near-field optical scanning probe. Scattered photons are utilized to perform mode mapping of both pump and lasing modes. Single mode lasing with a record low threshold of 4.3μW is observed. They investigate the position dependent quenching of the laser emission by the additional loss introduced by the subwavelength scanning probe and derive an estimation of the mechanical force gradient acting on the probe. They generalize a theoretical model of Raman lasing in microresonators to describe these effects.
Application of density functional theory for studies of excited states and phosphorescence of platinum(II) acetylides
Authors: Minaev Boris , Jansson Emil , Lindgren Mikael
Published: September 2006

The electronic states of different conformations of platinum acetylides Pt(PH3)2(CC–Ph)2 and Pt(PH3)2(CC–PhCC–Ph)2 (PE1 and PE2) were calculated with density functional theory (DFT) using effective core potential basis sets. Time dependent DFT calculations of UV absorption spectra showed strong dependence of the intense absorption band maxima on mutual orientation of the phenyl rings with respect to the P–Pt–P axis. Geometry optimization of the first excited triplet state (T1) indicates broken symmetry structure with the excitation being localized in one ligand. This splits the two substitution ligands into a nondistorted aromatic ring with the CC–Ph bonds for one side and into a quinoid structure with a cumulenic CCC link on the other side. Quadratic response (QR) calculations of spin-orbit coupling and phosphorescence radiative lifetime (τR) indicated a good agreement with experimental τR values reported for solid PE1 and PE2 and PE2 capped with dendrimers in tetrahydrofuran solutions. The QR calculations reproduced an increase of τR upon prolongation of π chain of ligands and concommittant redshift of the phosphorescence. Moreover, it is shown how the phosphorescence borrows intensity from σ→π* transitions localized at the CC–Pt–P fragments and that there is no intensity borrowing from delocalized π→π* transitions.
Single-polarization polarization maintaining optical fiber with large stress birefringence and high homogeneity
Authors: Li M. C. , Liu L. H. , Xiao T. P. , Xue J. J. , Liang L. T. , Wang H. L. , Xiong M.
Published: September 2006

A type of high-birefringence polarization maintaining (PM) fiber was designed and fabricated using a modified chemical vapor deposition (MCVD) process. Different from conventional stress-applied PM fibers, the shape of the stress jacket is like a “capsule.” By study of the cross sectional component distribution and a calculation of stress birefringence using the finite element method, the structure and composition of capsule PM fiber were optimized and the hybrid MCVD process was developed. With advantages in homogeneity and temperature performance, capsule fiber has great potential in applications such as fiber gyroscopes, fiber hydrophones, and other optical fiber sensors.
Joule heating induced negative differential resistance in freestanding metallic carbon nanotubes
Authors: Kuroda Marcelo A. , Leburton Jean-Pierre
Published: September 2006

The features of the IV characteristics of metallic carbon nanotubes (m-CNTs) in different experimental setups are studied using semiclassical Boltzmann transport equation together with the heat dissipation equation to account for significant thermal effects at high electric bias. The model predicts that the shape of the m-CNT characteristics is basically controlled by heat removal mechanisms. In particular, the authors show that the onset of negative differential resistance in freestanding nanotubes finds its origins in strong transport nonlinearities associated with poor heat removal unlike in substrate-supported nanotubes.
Plasmonic coupling between a metallic nanosphere and a thin metallic wire
Authors: Hao F. , Nordlander P.
Published: September 2006

Using the plasmon hybridization method the authors examine light-induced coupling between the localized plasmons of a metallic nanosphere and the propagating plasmons of an infinite metallic wire. The plasmon resonances of the coupled system are found to be shifted in frequency relative to the plasmonic structure of the isolated nanoparticles. The magnitude of the shifts depends on the polarization of the incident light and the system geometry. In the limit of a thin wire, it is shown that the nanosphere can serve as an efficient nanoantenna which can couple incident electromagnetic radiation into low-energy propagating wire plasmons.
Structure and optical properties of Lu2SiO5:Ce phosphor thin films
Authors: Lee J.-K. , Muenchausen R. E. , Lee Jang-Sik , Jia Q. X. , Nastasi M. , Valdez J. A. , Bennett B. L. , Cooke D. W. , Lee Sang Yeol
Published: September 2006

Luminescent, cerium doped Lu2SiO5 thin films with C2∕c symmetry have been prepared by pulsed laser deposition (PLD) at temperatures much lower than the crystallization temperature (2150°C) of the corresponding bulk crystals. The PLD grown films show the typical luminescence resulting from the Ce3+ 5d-4f transition. Maximum luminescence efficiency was observed for films prepared at an oxygen partial pressure of 200mTorr at 600°C. These conditions reflect a balance between Ce4+∕Ce3+ interconversion and the crystalline quality of the films. The results indicate that PLD offers a low temperature deposition technique for complex oxide phosphor materials.
Effect of a thin optical Kerr medium on a Laguerre-Gaussian beam
Authors: Zhang Weiya , Kuzyk Mark G.
Published: September 2006

Using a generalized Gaussian beam decomposition method the authors determine the propagation of a Laguerre-Gaussian (LG) beam that has passed through a thin nonlinear optical Kerr medium. The orbital angular momentum per photon of the beam is found to be conserved while the component beams change. As an illustration of applications, the authors propose and demonstrate a Z-scan experiment using a LG01 beam and a dye-doped polymer film.
Nuclear magnetic resonance study of the Ru∕Mn valence states and magnetic interactions in SrRu0.9Mn0.1O3
Authors: Han Z. H. , Budnick J. I. , Hines W. A. , Dabrowski B. , Maxwell T.
Published: September 2006

The substitution of Mn for Ru in SrRuO3 suppresses the ferromagnetic (FM) order monotonically at low concentration (<0.39) and induces antiferromagnetic (AFM) order at high concentration (>0.39). In an attempt to understand how the Mn substitution initially modifies the magnetic interactions in SrRu1−xMnxO3, a polycrystalline SrRu0.9Mn0.1O3 sample was prepared and studied by Mn55 and Ru99,101 spin-echo nuclear magnetic resonance (NMR). Mn55 NMR reveals that the Mn dopants are in an intermediate Mn3+∕4+ valence state due to fast electron hopping. The magnetic interaction between the Mn ions is FM, mediated by the double exchange mechanism. The Ru4+ hyperfine field is reduced due to an AFM coupling with the Mn moments, which shifts the Ru NMR peaks to lower frequencies. The suppression of the FM ordering temperature in SrRu1−xMnxO3 is attributed to the interruption of the itinerancy of the Ru 4d electrons by Mn substitution.
Bias-dependent electron spin lifetimes in n-GaAs and the role of donor impact ionization
Authors: Furis M. , Smith D. L. , Crooker S. A. , Reno J. L.
Published: September 2006

In bulk n-GaAs epilayers doped near the metal-insulator transition, the authors study the evolution of electron spin lifetime τs as a function of applied lateral electrical bias Ex. τs is measured via the Hanle effect using magneto-optical Kerr rotation. At low temperatures (T<10K, where electrons are partially localized and τs>100ns at zero bias), a marked collapse of τs is observed when Ex exceeds the donor impact ionization threshold at ∼10V∕cm. A steep increase in the concentration of warm delocalized electrons—subject to Dyakonov-Perel spin relaxation [Sov. Phys. Solid State 13, 3023 (1972)]—accounts for the rapid collapse of τs and strongly influences electron spin transport in this regime.
Electronic memory effects in diodes from a zinc oxide nanoparticle-polystyrene hybrid material
Authors: Verbakel Frank , Meskers Stefan C. J. , Janssen René A. J.
Published: September 2006

Current-voltage characteristics of diode structures with an active layer of a zinc oxide nanoparticle-polystyrene hybrid material (1:2 by weight) deposited by spin coating from solution were investigated. Aluminum and poly(3,4-ethylenedioxythiophene):polystyrene-sulfonate were used as electrodes. After a forming step, the conduction under reversed bias voltage can be raised or lowered in a gradual and reversible manner by applying forward and reverse bias voltages, respectively. Electrically induced switching between states with high and lower conductivities is possible on a time scale of 100ms and the conduction levels remain stable for over 1h.
Impedance spectroscopy of distinct electrical responses in TlH2PO4
Authors: Kim S. H. , Lee K. W. , Lee Cheol Eui , Lee K.-S. , Kim D. H. , Jang D. Y.
Published: September 2006

The ferroelastic phase in hydrogen-bonded TlH2PO4 was investigated by means of impedance spectroscopy. The high-temperature dielectric susceptibility revealed the corresponding Curie-Weiss temperature to be far above the antiferroelectric phase transition temperature, and a phase boundary has been identified and confirmed by the distinct electric field dependencies of the polarization.
High-quality-factor photonic crystal heterostructure laser
Authors: Shih M. H. , Kuang Wan , Mock Adam , Bagheri Mahmood , Hwang E. H. , O’Brien J. D. , Dapkus P. D.
Published: September 2006

A high-quality-factor (Q) photonic crystal heterostructure laser was designed and characterized. Good agreement was obtained between the experimental lasing data and three-dimensional finite-difference time-domain numerical predictions.
Freezing-in and production of entropy in vitrification
Authors: Möller Jörg , Gutzow Ivan , Schmelzer Jürn W. P.
Published: September 2006

Following the classical concepts developed by Simon [Z. Anorg. Allg. Chem. 203, 219 (1931)], vitrification in the cooling of glass-forming melts is commonly interpreted as the transformation of a thermodynamically (meta)stable equilibrium system into a frozen-in, thermodynamically nonequilibrium system, the glass. Hereby it is assumed that the transformation takes place at some well-defined sharp temperature, the glass transition temperature Tg. However, a more detailed experimental and theoretical analysis shows that the transition to a glass proceeds in a broader temperature range, where the characteristic times of change of temperature, τT=−(T∕Ṫ), and relaxation times, τ, of the system to the respective equilibrium states are of similar order of magnitude. In this transition interval, the interplay of relaxation and change of external control parameters determines the value of the structural order parameters. In addition, irreversible processes take place in the transition interval, resulting both in an entropy freezing-in as well as in an irreversible increase of entropy and, as a result, in significant changes of all other thermodynamic parameters of the vitrifying systems. The effect of entropy production on glass transition and on the properties of glasses is analyzed here for the first time. In this analysis, the structural order-parameter concept as developed by de Donder and van Rysselberghe [Thermodynamic Theory of Affinity (Stanford University Press, Stanford, 1936)] and Prigogine and Defay [Chemical Thermodynamics (Longmans, London, 1954)] is employed. In the framework of this approach we obtain general expressions for the thermodynamic properties of vitrifying systems such as heat capacity, enthalpy, entropy, and Gibbs’ free energy, and for the entropy production. As one of the general conclusions we show that entropy production has a single maximum upon cooling and two maxima upon heating in the glass transition interval. The theoretical concepts developed allow us to explain in addition to the thermodynamic parameters also specific features of the kinetic parameters of glass-forming melts such as the viscosity. Experimental results are presented which confirm the theoretical conclusions. Further experiments are suggested, allowing one to test several additional predictions of the theory.
Adsorption of model surfactantlike copolymers on nanopatterned surfaces
Authors: Striolo Alberto
Published: September 2006

The adsorption of polymers, copolymers, surfactants, and biopolymers is often used to engineer surfaces. Towards improving our understanding of polymer adsorption we report simulation results for the adsorption of model copolymers, resembling surfactants, on nanoscale patterned hydrophobic surfaces at infinitely dilute concentrations. The surfactants are composed by a hydrophobic tail and a hydrophilic head. Surfactant adsorption on the hydrophobic surface occurs in the tail-down configuration in which the tail segments are in contact with the surface. We investigate how the presence of a solid hard mask, used to create the nanoscale pattern on the underlying hydrophobic surface, affects the surfactant adsorption. We find that surfactant adsorption on the underlying hydrophobic surface is prevented when the characteristic dimensions of the solid hard mask are less than twice the radius of gyration. We also show that details about mask-surfactant head effective interactions have the potential to alter the characteristics of adsorption. When the mask repels the head segments, the surfactants hardly adsorb on the underlying hydrophobic surface. When the mask strongly attracts the surfactant heads, the surfactants may preferentially adsorb on the mask rather than on the underlying hydrophobic surface. Under these latter circumstances the adsorbed surfactants in some cases assume a head-down configuration in which the head segments are in contact with the mask and the tail segments extend towards the bulk solution. We explain our results in terms of enthalpy and entropy of adsorption and discuss practical implications.
Infrared spectra of HC2−∙(C2H2)n and O2−∙(C2H2)n clusters (n=2–5)
Authors: Schneider Holger , Weber J. Mathias
Published: September 2006

We study the solvation of HC2− and O2− with acetylene ligands by means of midinfrared photodissociation spectroscopy in the CH stretching region, monitoring C2H2 evaporation upon infrared photon absorption by the parent cluster ions. Our findings are interpreted with the help of density functional theory. The infrared spectra indicate that while the binding generally occurs through ionic H bonds, there are two different classes of ligands which differ in their binding strength. This holds true for both core ions, even though their electronic structures and charge distributions are very different.
Confined optical modes and amplified spontaneous emission from a microtube cavity formed by vacuum assisted filtration
Authors: Balakrishnan S. , Gun’ko Y. , Rakovich Yu. P. , Donegan J. F. , Perova T. S. , Moore R. A.
Published: October 2006

The authors demonstrate a new route to the fabrication of individual aluminosilicate microtubes that can act as micron-scale optical cylindrical resonators. The microtubes were prepared using a simple vacuum assisted wetting and filtration through a microchannel glass matrix. Microphotoluminescence spectra of the microtube cavity show sharp resonant modes with quality factors up to 3200. A strong reduction of the emission decay time at high excitation power confirms the occurrence of amplified spontaneous emission from a single microtube.
Combinatorial study of Ni–Ti–Pt ternary metal gate electrodes on HfO2 for the advanced gate stack
Authors: Chang K.-S. , Green M. L. , Suehle J. , Vogel E. M. , Xiong H. , Hattrick-Simpers J. , Takeuchi I. , Famodu O. , Ohmori K. , Ahmet P. , Chikyow T. , Majhi P. , Lee B.-H. , Gardner M.
Published: October 2006

The authors have fabricated combinatorial Ni–Ti–Pt ternary metal gate thin film libraries on HfO2 using magnetron co-sputtering to investigate flatband voltage shift (ΔVfb), work function (Φm), and leakage current density (JL) variations. A more negative ΔVfb is observed close to the Ti-rich corner than at the Ni- and Pt-rich corners, implying smaller Φm near the Ti-rich corners and higher Φm near the Ni- and Pt-rich corners. In addition, measured JL values can be explained consistently with the observed Φm variations. Combinatorial methodologies prove to be useful in surveying the large compositional space of ternary alloy metal gate electrode systems.
Electrical bistability in a xanthene class molecule: Conduction mechanisms
Authors: Rath Arup K. , Sahu Satyajit , Pal Amlan J.
Published: October 2006

The author study conduction mechanism in two conducting states of a bistable device at 10–300K range. They find that in the electrical bistable devices, electrical switching is associated with a change in the conduction mechanism. Device current in the low-conducting state follows an injection-limited mechanism. The current in the high-conducting state conforms a bulk-dominated mechanism, namely, space-charge limited conduction with an exponential distribution of traps. The bistability has an associated memory phenomenon. The devices exhibit read-only and random-access memory applications for several hours.
Effect of fire retardant application on phosphorus leaching from Mediterranean forest soil: short-term laboratory-scale study
Authors: Pappa A. , Tzamtzis N. , Koufopoulou S.
Published: September 2006

The application of fire retardants for forest fire prevention purposes can result in chemicals leaching from soil to the drainage water during the annual rainfall period. In addition, wildland fires can have an impact on the leaching of various chemicals from treated forest soils. In leachates, large concentrations of phosphorus (P) – one of the major components of long-term retardants – could affect the groundwater quality. In this present study, the leaching of phosphorus (contained in FIRE-TROL 931 – a long-term fire retardant based on polyphosphates) from a typical Mediterranean forest soil, was studied at the laboratory scale. The concentrations of P from the application of retardant in the resulting leachates from pots, containing forest soil and pine trees (Pinus halepensis), alone and in combination with fire, were determined by an inductively coupled plasma analytical method. The leaching of P, under the conditions used, was found to be a small percentage of the initially applied P quantities. However, it was different among the treated samples affected by both plant and fire conditions.
Fire regime and post-fire Normalized Difference Vegetation Index changes in the eastern Iberian peninsula (Mediterranean basin)
Authors: Abdel Malak Dania , Pausas Juli G.
Published: September 2006

Fire occurrence in Mediterranean landscapes has been studied widely. Despite this, a specific monitoring of vegetation recovery after recurrent fires by means of satellite images has been developed to a lesser extent. With the use of Satellite Remote Sensing (SRS) techniques and multi-temporal Landsat images of the area of Ayora (287 700 ha) in Valencia (Eastern Spain), between the years 1984 and 1999, we studied the post-fire regeneration of the Normalized Difference Vegetation Index (NDVI) in areas subjected to different fire recurrences. Emphasis is given to the effect of time since fire, precipitation, and bedrock types on post-fire NDVI changes. Results suggest that for the first 7 years after a single fire, NDVI depends mainly on the time since fire (post-fire regeneration), whereas environmental parameters (precipitation and bedrock type) are of little relevance. After this period, precipitation begins to have a direct influence on the NDVI. In patches burned twice, with fire intervals of 8 and 9 years, NDVI is also controlled by the time since fire. Furthermore, NDVI recovery is faster after the first fire than after the second fire, suggesting that fire recurrence has a negative impact on the resilience of these communities. Bedrock type did not show any effect on NDVI after fire. These findings contribute to the understanding of Mediterranean landscape dynamics and provide evidence for the usefulness of NDVI in post-fire regeneration assessment, and the possible negative effects of the increasing fire recurrences observed in the last decades.
Time series of chaparral live fuel moisture maps derived from MODIS satellite data
Authors: Stow Douglas , Niphadkar Madhura , Kaiser John
Published: September 2006

Wildfires in chaparral shrublands of southern California are a major hazard and important ecological disturbance agent. Fire managers typically monitor fuel moisture of chaparral shrublands to assess the risk of wildfires, using field-based sampling methods for a few small study areas located sparsely throughout southern California. Remote sensing provides the potential for deriving spatially explicit and temporally frequent data on live fuel moisture (LFM) conditions. The objective of this present study was to explore the potential for monitoring LFM with maps derived from Moderate Resolution Imaging Spectroradiometer (MODIS) data on the National Aeronautics and Space Administration (NASA) Terra Earth-observing satellite. A time series of MODIS surface reflectance data (MOD-09_A1) for San Diego County, California from Fall 2000 through 2003 was used to derive normalized difference indices, which were regressed against LFM data. A high degree of temporal co-variability was found, with three MODIS indices providing similar predictability. Regression relationships were inverted and applied to MODIS images to map LFM interval classes for chaparral areas of San Diego County. The spatial–temporal patterns of LFM maps suggest that, at a minimum, the MODIS can provide spatially explicit information that extends the utility of ground-based measurements of LFM data at a few sites.
A 229-year dendroclimatic-inferred record of forest fire activity for the Boreal Shield of Canada
Authors: Girardin Martin P. , Bergeron Yves , Tardif Jacques C. , Gauthier Sylvie , Flannigan Mike D. , Mudelsee Manfred
Published: September 2006

Six independent tree-ring reconstructions of summer drought were calibrated against instrumental fire data to develop a 229-year dendroclimatic-inferred record of fire activity (annual area burned and fire occurrence) on the Boreal Shield, Canada. As a means of validating the statistical reconstructions of the fire activity, a comparison was made with a stand age distribution derived from a regional time-since-last-fire map for an area located at the transition between the mixedwood and coniferous boreal forests of south-western Quebec. Calibration statistics indicated that 31% of the area burned variance and 45% of the fire occurrence variance could be accounted for by the six drought reconstructions. The verification statistics indicated a tendency for the statistical reconstructions of the fire activity to reproduce with confidence both high and relatively low frequency variations in fire. Episodes of succeeding years with important fire activity were estimated for 1789–1796, 1820–1823, 1837–1841, 1862–1866, 1906–1912, 1919–1922, 1933–1938, and 1974–1977. Also estimated were periods of reduced forest fire activity, particularly in the occurrence rate of extreme fire years, from c. 1850 to 1900 and again during the second half of the 20th century. Correlation analysis between the statistical reconstruction of the area burned and the stand age distribution suggested that both proxies shared similar information on the fire activity. Correlation maps, however, indicated that variability in the statistical reconstructions was not necessarily representative of fire activity in all regions of the Boreal Shield.
Temporal and spatial characteristics of forest fires in South Korea between 1970 and 2003
Authors: Lee Byungdoo , Park Pil Sun , Chung Joosang
Published: September 2006

Information on the temporal and spatial patterns of forest fires can contribute to efficient forest fire management. To evaluate the readjustment of forest fire precautionary periods and to provide information for forest fire prevention and suppression strategies, the temporal and spatial characteristics of forest fire occurrences and spread in Korea were analysed using statistics from 1970 to 2003. Monthly forest fire occurrences and burned area were examined using time-series analysis, and F-tests were conducted among forest fire occurrences, burned area, and fire area growth rate to understand monthly forest fire characteristics. To understand the spatial characteristics of forest fires, cities and counties with similar forest fire characteristics were grouped based on cluster analysis of forest fire occurrences and spread characteristics. A seasonal exponential smoothing model was selected for forest fire occurrences and burned area. The number of mean annual forest fire occurrences was 429, and mean annual burned area was 2908 ha year–1 in Korea. The seasonal differences in forest fire characteristics were clearly distinguished, with 61% of total forest fire occurrences and 90% of total burned area being in March and April. Forest fire precautionary periods are suggested based on forest fire occurrence patterns. A total of 226 cities and counties throughout the country were classified into three groups. Group 1, which had frequent forest fire occurrences with smaller burned areas and slower fire growth area rates, was distributed in the western part of Korea and metropolitan regions. Group 3, which had a relatively small number of forest fire occurrences but larger burned areas and fast growth rates, was located in the central inland region and the eastern part of the Taeback Mountain Range. Group 2 had characteristics intermediate between those of group 1 and group 3.
Indications of vigor loss after fire in Caribbean pine (Pinus caribaea) from electrical resistance measurements
Authors: Paysen Timothy E. , Koonce Andrea L. , Taylor Edwin , Rodriquez Maria Ouxiliadora
Published: September 2006

In May 1993, electrical resistance measurements were performed on trees in burned and unburned stands of Caribbean pine (Pinus caribaea Mor.) in north-eastern Nicaragua to determine whether tree vigor was affected by fire. An Osmose model OZ-67 Shigometer with digital readout was used to collect the sample electrical resistance data. Computer-simulated randomization techniques were used to evaluate the significance of differences in electrical resistance between living trees of burned and unburned stands of various ages. Electrical resistance was used as an index of the general metabolic activity of the tree – our chosen definition of tree vigor. Results indicate a loss of tree vigor in stands that burned in comparison with those that did not.
Remote sensing techniques to assess active fire characteristics and post-fire effects
Authors: Lentile Leigh B. , Holden Zachary A. , Smith Alistair M. S. , Falkowski Michael J. , Hudak Andrew T. , Morgan Penelope , Lewis Sarah A. , Gessler Paul E. , Benson Nate C.
Published: September 2006

Space and airborne sensors have been used to map area burned, assess characteristics of active fires, and characterize post-fire ecological effects. Confusion about fire intensity, fire severity, burn severity, and related terms can result in the potential misuse of the inferred information by land managers and remote sensing practitioners who require unambiguous remote sensing products for fire management. The objective of the present paper is to provide a comprehensive review of current and potential remote sensing methods used to assess fire behavior and effects and ecological responses to fire. We clarify the terminology to facilitate development and interpretation of comprehensible and defensible remote sensing products, present the potential and limitations of a variety of approaches for remotely measuring active fires and their post-fire ecological effects, and discuss challenges and future directions of fire-related remote sensing research.
In situ measurements of water vapor, heat, and CO2 fluxes within a prescribed grass fire
Authors: Clements Craig B. , Potter Brian E. , Zhong Shiyuan
Published: September 2006

Fluxes of water vapor, heat, and carbon dioxide associated with a prescribed grass fire were documented quantitatively using a 43-m instrumented flux tower within the burn perimeter and a tethered balloon sounding system immediately downwind of the fire. The measurements revealed significant increases of temperature (up to 20°C), heat flux (greater than 1000 W m–2), and CO2 (larger than 2000 parts per million by volume) within the smoke plumes, as well as an intensification of turbulent mixing. Furthermore, the observations revealed an increase in water vapor mixing ratio of more than 2 g kg–1, or nearly 30% over the ambient air, which is in good agreement with theoretical estimates of the amount of water vapor release expected as a combustion by-product from a grass fire. These observations provide direct evidence that natural fuel-load grass-fire plumes may modify the dynamic environment of the lower atmosphere through not only heat release and intense mixing, but also large addition of water vapor.
Evaluation of forest fire retardant removal from forest fuels by rainfall
Authors: Xanthopoulos Gavriil , Ghosn Dany , Kazakis George
Published: September 2006

Long-term forest fire retardants for fire prevention purposes are currently used, or are under consideration, in many parts of the world. Their use requires, among other things, knowledge about weathering of retardants with time, which may lead to the need for re-application. Rainfall is a factor that can lead to retardant depletion from the fuels. In this study, the rate of depletion was evaluated experimentally using Aleppo pine (Pinus halepensis) needles. The needles were made into small bundles and immersed in retardant, which was FIRE-TROL 936 concentrate, diluted to 20% (v/v) with water. The retardant-treated needles, after drying, were exposed to natural rain in three different rainfall events, and retardant depletion was measured. A regression equation was developed with percentage retardant removal as the dependent variable. The natural logarithm of rainfall quantity, expressed in mm of rain, and the duration of rain, expressed in min, were the two independent variables. A simple equation can be used to support pre-suppression planning and to assess environmental effects.
Fire history in ponderosa pine landscapes of Grand Canyon National Park: is it reliable enough for management and restoration?
Authors: Baker William L.
Published: September 2006

Reconstructing fire regimes of the past can provide a valuable frame of reference for understanding the impact of human land uses on contemporary fire and forest structure, but methods for reconstructing past fire regimes are under re-evaluation. In the present article, a common method of characterizing surface fire regimes, using composite fire intervals from fire scars, is shown to significantly underestimate the length of the fire rotation and population mean fire interval in Grand Canyon landscapes where these parameters are known. Also, the evidence and interpretation that past high-severity fire was uncommon in ponderosa pine landscapes in Grand Canyon National Park are challenged. Together, these two concerns mean that an alternative characterization of the fire regime, which has very different implications, cannot be excluded. Management aimed at lowering fire risk, as a means of restoration, does not presently have a sound scientific basis, if it uses the composite fire interval as a measure of the fire regime or is based on fire history research that lacks adequate analysis of past high-severity fire.
CHOICE AND LONG-TERM CARE IN OECD COUNTRIES: CARE OUTCOMES, EMPLOYMENT AND FISCAL SUSTAINABILITY
Authors: Lundsgaard Jens
Published: September 2006

As the number of older people in need of long-term care increases, efforts to support older people remaining in their home are intensified in most OECD countries. In this context, there is a movement towards allowing more individual choice for older people receiving publicly funded long-term care at home. Having more flexibility in terms of how to receive care can increase the older person's self-determination and that of his/her informal caregivers. Having a choice among alternative care providers can empower older people as consumers and may help strengthen the role of households in the care-management process. The main aims of this article are (i) to categorise and analyse different types of arrangements allowing home care users more choice and map the prevalence of such arrangements in OECD countries, (ii) to give an overview of some country-specific outcomes in terms of care quality for care recipients, and (iii) to discuss some implications for employment and fiscal sustainability.
CONSTRUCTING THE CARE CONSUMER: FREE CHOICE OF HOME CARE FOR THE ELDERLY IN DENMARK
Authors: Rostgaard Tine
Published: September 2006

Traditional welfare institutions are challenged by the desire to design our own individual welfare packages. Politically, the response can be to introduce choice in social policy, also from the aim that the pacified welfare client should re-materialise as an active welfare consumer. This paper analyses the development of the form and concept of consumerism in social policy, taking the domiciliary care for the elderly in Denmark as an example. It seems that consumerism has become part of the logic of governance, and new forms of responsibility have been created which not only empower but also condition the individual citizen. The consumerist approach implies a new social construction of social policy; a second-generation do-it-yourself social policy in which the imperative is to secure the right to choose, more than equality of opportunity to choose or equality of outcome.
Escape from fatal fusion
Authors: Williams Ruth
Published: September 2006

In 1971, a seminal paper from the laboratory of Philip D'Arcy Hart reported that the intracellular pathogen Mycobacterium tuberculosis avoids destruction in the cell's lysosomes by avoiding these organelles altogether—a trick now known to be used by many other intracellular pathogens.
FoldUnfold: web server for the prediction of disordered regions in protein chain
Authors: Galzitskaya Oxana V. , Garbuzynskiy Sergiy O. , Lobanov Michail Yu.
Published: October 2006

Summary: Identification of disordered regions in polypeptide chains is very important because such regions are essential for protein function. A new parameter, namely mean packing density of residues has been introduced to detect disordered regions in a protein sequence. We have demonstrated that regions with weak expected packing density would be responsible for the appearance of disordered regions. Our method (FoldUnfold) has been tested on datasets of globular proteins (559 proteins) and long disordered protein segments (129 proteins) and showed improved performance over some other widely used methods, such as DISOPRED, PONDR VL3H, IUPred and GlobPlot.

Availability: The FoldUnfold server is available for users at . There is a link to our server through the web site of DisProt ().

Contact:  ogalzit@vega.protres.ru