bluuebunny/crossref_metadata_2025 huggingface dataset:
COMMUTE TIMES AND THE EFFECTIVE RESISTANCES OF RANDOM TREES
Authors: Al-Awadhi Fahimah , Konsowa Mokhtar , Najeh Zainab
Published: July 2009

In this article we study the commute and hitting times of simple random walks on spherically symmetric random trees in which every vertex of levelnhas outdegree 1 with probability 1−qnand outdegree 2 with probabilityqn. Our argument relies on the link between the commute times and the effective resistances of the associated electric networks when 1 unit of resistance is assigned to each edge of the tree.
STOCHASTICALLY SCALABLE FLOW CONTROL
Authors: Voice Thomas
Published: July 2009

Recent advances in the mathematical analysis of flow control have prompted the creation of the Scalable TCP (STCP) and Exponential RED (E-RED) algorithms. These are designed to be scalable under the popular deterministic delay stability modeling framework. In this article, we analyze stochastic models of STCP and STCP combined with E-RED link behavior. We find that under certain plausible network conditions, these probabilistic models also exhibit scalable behavior. In particular, we derive parameter choice schemes for which the equilibrium coefficients of variation of flow rates are bounded, however large, fast, or complex the network. Our model is shown to exhibit behavior similar to the mean field convergence that has recently been observed in TCP.
Analysis of phenotype, genotype and serotype distribution in erythromycin-resistant group B streptococci isolated from vaginal flora in Southern Ireland
Authors: KIELY R. A. , LUCEY B. , COTTER L.
Published: July 2009

The screening of 2000 women of childbearing age in Cork between 2004 and 2006 produced 37 erythromycin-resistant group B streptococcus (GBS) isolates. PCR analysis was performed to determine the basis for erythromycin resistance. The ermTR gene was most frequently expressed (n=19), followed by the ermB gene (n=8). Four isolates harboured the mefA gene. Six isolates yielded no PCR products. Some phenotype–genotype correlation was observed. All isolates expressing the mefA gene displayed the M phenotype whilst all those expressing ermB displayed the constitutive macrolide resistance (cMLSB) phenotype. Of 19 isolates that expressed the ermTR gene, 16 displayed the inducible macrolide resistance (iMLSB) phenotype. Serotype analysis revealed that serotypes III and V predominated in these isolates. The identification of two erythromycin-resistant serotype VIII isolates among this collection represents the first reported finding of erythromycin resistance in this serotype. A single isolate was non-typable using two latex agglutination serotyping kits.
Globalization: A Historical Perspective
Authors: Wesseling Henk L.
Published: July 2009

The term globalization has been accepted very quickly. Until the 1990’s virtually unknown, the word is now on everybody’s lips. The phenomenon of globalization however is much older than the concept. It started at the end of the 15th century with the beginnings of European expansion and was dramatically increased by the industrialization of the world since the late 18th century. Over the last 30 years or so it has accelerated so much that one can speak of a new stage of globalization.
Academia Europaea: Origin and Early Days
Authors: Burgen Arnold
Published: July 2009

The Academia Europaea had its origin in a proposal that came in 1984 from the UK Department of Education and Science. This led to a Foundation Meeting in Cambridge in September 1988 attended by 54 of the Founding Members. They set up the formal framework and this provided the basis of the first Plenary Meeting held in London in June 1989.
The European Research Council: A Revolutionary Excellence Initiative for Europe
Authors: Antonoyiannakis Manolis , Kafatos Fotis C.
Published: July 2009

Launched in 2007, the European Research Council (ERC) aims at pulling out all the stops in supporting ambitious research projects in frontier research by the most talented scientists and scholars. The ERC grants are generous, open to nationals from any country in the world, and subject to one criterion alone: peer-reviewed excellence. We outline the central strategic priorities of the ERC, and briefly describe some impressions from the first two calls.
Apologies, Regrets, and Reparations
Authors: Engerman Stanley L.
Published: July 2009

The concept of reparations-payments made for damages inflicted by one individual upon another have long been regarded as appropriate social policy. It has only been in the 20th century that the concept has been broadened to deal with evils committed in earlier generations for which payments have been requested, the most discussed of these being the request for reparations for today’s blacks for suffering attributable to slavery that ended over one hundred years ago. Other examples include payments by Germany and other European nations for crimes committed in the Second World War. Starting about 1990, there have been frequent apologies for past and present crimes, which acknowledge wrongs committed but without any financial payment. Many nations, churches, and private groups have recently made such apologies, which have seemed to come politically acceptable.
Cognitive recovery and predictors of functional outcome 1 year after traumatic brain injury
Authors: SIGURDARDOTTIR SOLRUN , ANDELIC NADA , ROE CECILIE , SCHANKE ANNE-KRISTINE
Published: July 2009

Outcome studies on traumatic brain injury (TBI) have shown that functional status can be predicted by demographic, injury severity, and trauma-related factors. Concurrent cognitive functions as one of the determinants of functional outcome is less documented. This study evaluated the effects of concurrent neuropsychological measures on functional outcome 1 year after injury. Neuropsychological data, employment status, self-reported fatigue, and the Glasgow Outcome Scale-Extended (GOSE) were collected from 115 persons with TBI (ranging from mild to severe) at 3 and 12 months postinjury. Principal components analysis was conducted with the neuropsychological measures and three components emerged. Multiple regression analysis, controlling for demographic and injury severity related factors, was used to test the effects of cognitive components at 12 months on functional outcome (GOSE). One year after injury, 64% were categorized as “good recovery” and 36% as “moderate disability” according to GOSE. Good functional recovery depended on shorter duration of posttraumatic amnesia, less fatigue, absence of intracranial pathology, higher education, and better performance on cognitive measures. The predictive values of Verbal/Reasoning and Visual/Perception components are supported; each added significantly and improved prediction of functional outcome. The Memory/Speed component showed a near-significant relationship to outcome. (JINS, 2009, 15, 740–750)
Heat-initiated prebiotic formation of peptides from glycine/aspartic acid and glycine/valine in aqueous environment and clay suspension
Authors: Pant Chandra Kala , Lata Hem , Pathak Hari Datt , Mehata Mohan Singh
Published: July 2009

The effect of heat on the reaction system of glycine/aspartic acid and glycine/valine in the aqueous environment as well as in montmorillonite clay suspension with or without divalent cations (Ca2+, Mg2+ and Ni2+) has been investigated at 85°C±5°C for varying periods under prebiotic drying and wetting conditions. The resulting products were analysed and characterized by chromatographic and spectroscopic methods. Peptide formation appears to depend on the duration of heat effect, nature of reactant amino acids and, to some extent, on montmorillonite clay incorporated with divalent cations. In the glycine/aspartic acid system, oligomerization of glycine was limited up to trimer level (Gly)3 along with the formation of glycyl-aspartic acid, while linear and cyclic peptides of aspartic acid were not formed, whereas the glycine/valine system preferentially elongated homo-oligopeptide of glycine up to pentamer level (Gly)5 along with formation of hetero-peptides (Gly-Val and Val-Gly). These studies are relevant in the context of the prebiotic origin of proteins and the role of clay and metal ions in condensation and oligomerization of amino acids. The length of the bio-oligomer chain depends upon the reaction conditions. However, condensation into even a small length seems significant, as the same process would have taken millions of years in the primitive era of the Earth, leading to the first proteins.
Altersbilder und Gesundheitsverhalten
Authors: Huy Christina , Thiel Ansgar
Published: July 2009

Zusammenfassung. Klassische Gesundheitsverhaltensmodelle berücksichtigen vor allem die drei zentralen psychologischen Einflussvariablen Risikowahrnehmung, wahrgenommener Nutzen und Selbstwirksamkeit. Bisher gibt es jedoch kaum Untersuchungen zum Einfluss von individuellen Vorstellungen und Einstellungen zum Alter(n). Die vorliegende Studie untersucht daher den Zusammenhang zwischen Alterseinstellungen und dem Gesundheitsverhalten. 2002 Personen zwischen 50 und 70 Jahren wurden in computer-assistierten Telefoninterviews befragt. Altersbilder wurden mittels Faktoren- und Clusteranalyse identifiziert; Einflüsse auf das Gesundheitsverhalten wurden mit einer multiplen Regressionsanalyse ermittelt. Es fanden sich drei unterschiedliche Altersbilder: die „fitten Leistungshungrigen” (n = 808), die „Klassischen” (n = 618) und die „unbekümmert Engagierten” (n = 576). Personen mit einer positiven stereotypen Wahrnehmung vom Alter wiesen ein signifikant besseres Gesundheitsverhalten auf als Personen, die sich mit dem „klassischen” Altersbild identifizierten. Die Vorstellung, selbst etwas für seine Gesundheit tun zu können, hatte neben sozioökonomischen Faktoren den größten Einfluss auf das Gesundheitsverhalten. Die Ergebnisse sprechen für die Notwendigkeit von „Gesundheitsbildung”. Dabei müssen besonders Personen, die sich mit dem „klassischen”, eher negativ getönten Altersbild identifizieren, gezielt von Präventionsprogrammen angesprochen werden.
Current state, scales of variability, and trends of biogeochemical properties in the northern Adriatic Sea
Authors: Solidoro Cosimo , Bastianini Mauro , Bandelj Vinko , Codermatz Raffaella , Cossarini Gianpiero , Melaku Canu Donata , Ravagnan Elisa , Salon Stefano , Trevisani Sebastiano
Published: July 2009

This paper illustrates the main results of a statistical analysis performed on a data set obtained by integrating experimental observations collected during many oceanographic research projects on the northern Adriatic Sea (NAS). The observations cover the last 20 years and provide a robust base for the assessment of the current state and scales of variability for temperature, salinity, nutrients, dissolved oxygen, and chlorophyll. The results confirmed a clear seasonal cycle and marked spatial gradients for most parameters in all seasons. The largest proportion of the river Po input flows south along the coast, but significant eastward freshwater fluxes are also present in all seasons, more markedly in winter. The coastal belt south of the Lagoon of Venice is the most eutrophic area, mainly because of river inputs, while an oligotrophic condition prevails along the eastern part of the basin. Small‐scale structures, including eddies and jets, are permanent features of the system. In order to test the existence of significant trends of variation in the physical and biogeochemical parameters, the data set has been enlarged by including observations from 1976. Analyses of trends over 30 years show an increase in salinity, which might be a consequence of both reduced outflows from rivers and a more sustained inflow of water along eastern coast, and a clear reduction in concentrations of phosphate and ammonia in coastal areas, probably due to new regulations regarding the control of nutrient loads and possibly suggesting the occurrence of cultural oligotrophication. No decrease is instead observed for concentration of nitrate.
THEMIS high‐resolution digital terrain: Topographic and thermophysical mapping of Gusev Crater, Mars
Authors: Cushing G. E. , Titus T. N. , Soderblom L. A. , Kirk R. L.
Published: July 2009

We discuss a new technique to generate high‐resolution digital terrain models (DTMs) and to quantitatively derive and map slope‐corrected thermophysical properties such as albedo, thermal inertia, and surface temperatures. This investigation is a continuation of work started by Kirk et al. (2005), who empirically deconvolved Thermal Emission Imaging System (THEMIS) visible and thermal infrared data of this area, isolating topographic information that produced an accurate DTM. Surface temperatures change as a function of many variables such as slope, albedo, thermal inertia, time, season, and atmospheric opacity. We constrain each of these variables to construct a DTM and maps of slope‐corrected albedo, slope‐ and albedo‐corrected thermal inertia, and surface temperatures across the scene for any time of day or year and at any atmospheric opacity. DTMs greatly facilitate analyses of the Martian surface, and the MOLA global data set is not finely scaled enough (128 pixels per degree, ∼0.5 km per pixel near the equator) to be combined with newer data sets (e.g., High Resolution Imaging Science Experiment, Context Camera, and Compact Reconnaissance Imaging Spectrometer for Mars at ∼0.25, ∼6, and ∼20 m per pixel, respectively), so new techniques to derive high‐resolution DTMs are always being explored. This paper discusses our technique of combining a set of THEMIS visible and thermal infrared observations such that albedo and thermal inertia variations within the scene are eliminated and only topographic variations remain. This enables us to produce a high‐resolution DTM via photoclinometry techniques that are largely free of albedo‐induced errors. With this DTM, THEMIS observations, and a subsurface thermal diffusion model, we generate slope‐corrected maps of albedo, thermal inertia, and surface temperatures. In addition to greater accuracy, these products allow thermophysical properties to be directly compared with topography.
One‐dimensional solute transport in a permeable reactive barrier–aquifer system
Authors: Park Eungyu , Zhan Hongbin
Published: July 2009

Transient semianalytical and steady state analytical solutions to assess solute transport in a permeable reactive barrier (PRB)–aquifer system are developed on the basis of a multidomain approach of an up‐gradient PRB and a down‐gradient aquifer. Sensitivity analysis of input parameters in the solution is addressed through mathematical modeling. A designing equation from the developed steady state closed‐form analytical solution is derived, and the accuracy of the equation is tested. The results confirm that the thickness and the first‐order reaction capability of the PRB are two of the most important design considerations. Through sensitivity analysis, the reduction of the reactive capability of the PRB has a significant impact on the PRB performance. The aquifer reaction capability is found to be nonnegligible for the determination of the required thickness of the PRB, and its importance becomes greater when the PRB porosity becomes smaller because of mineral fouling.
Receiver function study of the Cascadia megathrust: Evidence for localized serpentinization
Authors: Nikulin Alex , Levin Vadim , Park Jeffrey
Published: July 2009

We characterize the crustal and upper mantle structure of the Cascadian fore arc using receiver function analysis of data from long‐running observatories located along the North American margin in Oregon and Washington. We identify coherent SV‐polarized phases consistent with P‐S conversion from the top of the subducting Juan de Fuca plate throughout the area west of the volcanic arc. In many instances we also find evidence for deeper features, likely associated with the subducted oceanic crust. At many locations SH‐polarized energy in receiver functions is associated with the surface of the subducting plate. These SH‐polarized phases display significant directional variation and show clear polarity reversals, consistent with the presence of seismic anisotropy. Previously, a layer of serpentinized material within the megathrust has been proposed to explain an anisotropic, low‐velocity, high Poisson's ratio layer identified by receiver function analysis at Corvallis, Oregon (Global Seismic Network station COR). Our new results suggest that this feature is widespread in Cascadia, but the specific receiver function signature varies. This anisotropic supraslab layer is supported by receiver function estimates beneath seismic stations which, similar to COR, are ∼100 km from the coast and ∼40 km above the slab surface. However, the orientation of rock fabric implied by the anisotropy varies greatly from station to station. Modeling with synthetic seismograms supports the existence of serpentinite beneath station GNW (Green Mountain, Washington). Closer to the coast, where the slab is shallower, an anisotropic layer is likely beneath some stations, but the evidence is less conclusive. We propose that the anisotropic signature beneath the inland stations is related to serpentinization of the mantle wedge at greater depths, best explained by the presence of the polymorph antigorite. Hypothetically suctioned upward by slab rollback, a deformed sliver of serpentinite‐rich rock above the slab interface would likely display the observed large spatial variation in anisotropic symmetry axis within the layer, consistent with our observations.
Parametric instabilities of circularly polarized Alfvén waves in plasmas with beam protons
Authors: Nariyuki Y. , Hada T. , Tsubouchi K.
Published: July 2009

The proton velocity distribution functions (VDFs) observed in the solar wind often show beam components. In this study, by means of one‐dimensional hybrid simulation, parametric instabilities of circularly polarized Alfvén waves in core proton‐electron‐beam proton plasmas are discussed. Numerical results show that nonlinear evolution of parametric instabilities in core proton‐electron‐beam proton plasmas are different from those in core proton‐electron plasmas. Furthermore, numerical solutions of the linear dispersion relations suggest the importance of the proton kinetic effects, which agrees with the past studies. In the case that the beams are stable, according to the excitation of the broadband Alfvén waves by the parametric instabilities, protons are diffused in the velocity space, resulting in the scattering and broadening of the beam components. Such time evolution of the proton VDFs changes the wave dispersion relation and affects the properties of the parametric instabilities, in agreement with the past theoretical studies. As a result, even if a decay instability is dominant at the linear stage, the parent wave can mainly be dissipated by the modulational instability at the nonlinear stage. Phase coherent turbulence is generated corresponding to the occurrence of the modulational instability. Parametric instabilities are also observed in plasmas with unstable beams. When left‐hand polarized (LH‐) Alfvén wave is initially given, both backward propagating right‐hand polarized (RH‐) and LH‐ Alfvén waves are excited by the decay instabilities in our runs. As time elapses, phase coherent turbulence is generated by the modulational instabilities, as in the case of stable beams. Some of the beam protons are perpendicularly accelerated by cyclotron resonance with the primary wave.
Technical Note: The Use of RNA-interference as a Tool to Find Proteins Involved in Melanosome Formation or Transport
Authors: Amsen Eva , Rotin Daniela
Published: July 2009

Melanosomes are lysosome-related organelles that produce and transport the pigment melanin within melanocytes. Mutations in proteins required for melanosome transport and formation lead to a range of pigmentation defects, manifested at the cellular level as perinuclear clustering of melanosomes, or reduced sorting of melanosomal cargo such as tyrosinase-related protein 1 (TYRP1). A pilot screen was carried out to investigate whether a combination of cellular imaging and RNA interference could be used to identify new proteins involved in pigmentation pathways. In this study, eleven genes known to play a role in melanosome transport/formation or other pigmentation properties were knocked down in mouse melanocytes with shRNAmir constructs. The investigated genes were TYRP1, pallidin, cappuccino, dysbindin, HPS5, LYST, Myosin Va, melanophilin, RhoA, UBPY and mahogunin. In a blinded confocal imaging experiment, the only reproducible change observed in cells in which these targets were knocked down was a decrease in TYRP1 levels upon transfection with knockdown constructs against TYRP1 itself, or one of three constructs targeting HPS5 (Hermansky-Pudlak Syndrome 5). Upon analysis with high-content imaging software, only the knockdown construct against TYRP1 itself was detected. RT-PCR analysis showed that many of the shRNAmir constructs did not reduce mRNA and proteins levels enough to detect effects on melanosome properties. This was further examined for melanophilin, a protein necessary for melanosome transport. Altogether, the data show that this system is currently not sensitive enough for use in a screen for unknown regulators of melanosome transport and formation. The main obstacle appears to be incomplete reduction of target protein levels. Our observation that a ~50% reduction in mRNA level is not sufficient to elicit an effect is supported by the fact that heterozygous carriers of melanosomal transport disorders (Griscelli Syndrome, Hermansky-Pudlak Syndrome) do not display diseases phenotypes. A further reduction in protein levels, for example by viral infection of shRNA, may be required.
Asporin competes with decorin for collagen binding, binds calcium and promotes osteoblast collagen mineralization
Authors: Kalamajski Sebastian , Aspberg Anders , Lindblom Karin , Heinegård Dick , Oldberg Åke
Published: July 2009

The interactions of the ECM (extracellular matrix) protein asporin with ECM components have previously not been investigated. Here, we show that asporin binds collagen type I. This binding is inhibited by recombinant asporin fragment LRR (leucine-rich repeat) 10–12 and by full-length decorin, but not by biglycan. We demonstrate that the polyaspartate domain binds calcium and regulates hydroxyapatite formation in vitro. In the presence of asporin, the number of collagen nodules, and mRNA of osteoblastic markers Osterix and Runx2, were increased. Moreover, decorin or the collagen-binding asporin fragment LRR 10–12 inhibited the pro-osteoblastic activity of full-length asporin. Our results suggest that asporin and decorin compete for binding to collagen and that the polyaspartate in asporin directly regulates collagen mineralization. Therefore asporin has a role in osteoblast-driven collagen biomineralization activity. We also show that asporin can be expressed in Escherichia coli (Rosetta-gami™) with correctly positioned cysteine bridges, and a similar system can possibly be used for the expression of other SLRPs (small LRR proteoglycans/proteins).
Laryngeal Laser Surgery for Recurrent Respiratory Papillomatosis, Cancer and Dysplasia: Operating Room and Office
Authors: Zeitels Steven M. , Hillman Robert E.
Published: July 2009

Since their introduction in laryngology over 30 years ago, lasers have facilitated critically-important innovations that have now evolved into office-based surgery. Recent advances include the application of angiolytic lasers that treat vocal fold lesions by ablating vasculature and the use of the thulium laser as a more efficient and versatile tissue dissector. In our experience, the 532nm pulsed KTP laser has emerged thus far as the optimal angiolytic laser to treat vocal-fold lesions both in the operating room and in the clinic setting. Despite the fact that the skill-sets to adopt office-based laser treatment are an easy transition for most laryngological surgeons, the primary impediment to widespread adoption is the cost of the technology. Furthermore, critical development of these new lasers will occur with broader use of these lasers in other surgical disciplines, which should diminish costs for all surgeons and thereby promote better outcomes for individuals with voice disorders.
Mechanisms of flexoelectric switching in a zenithally bistable nematic device
Authors: Parry-Jones L. A. , Meyer R. B. , Elston S. J.
Published: July 2009

Flexoelectric effects in nematic liquid crystals are well known to occur through combinations of either the sum or the difference of the splay and bend polarizations. In this work we examine the role of both mechanisms in the switching of zenithally bistable nematic devices, and conclude that both can cause bistable switching. Interestingly, we find that the most important flexoelectric coefficient (in terms of reducing the switching threshold voltage) can be either the splay or bend coefficient, depending purely on the relative dielectric permittivities of the grating and liquid crystal materials.
On the delamination dynamic of sputtered amorphous carbon nitride films
Authors: Peponas S. , Benlahsen M. , Guedda M.
Published: July 2009

We present in this study a spectroscopic investigation of spontaneous delamination of amorphous carbon nitride (a-CNx) films deposited on silicon substrates (Si) by rf magnetron sputtering of a graphite target in pure Ar/N2 gas mixture. The microstructural properties of the films were determined in their as-deposited state using infrared absorption and Raman spectroscopy experiments. Various shapes of debonding patterns have been observed. Based on the present experimental evidence, a description of nitrogen incorporation and the resulting hybridization states of the CN bonds in the a-CNx films prior and after delamination are proposed to elucidate the microstructural origin of this delamination occurring along the a-CNx/Si interface and the physicochemical mechanism that governed its dynamic.
Origin of low Gilbert damping in half metals
Authors: Liu Chunsheng , Mewes Claudia K. A. , Chshiev Mairbek , Mewes Tim , Butler William H.
Published: July 2009

Using a combination of first-principles calculations and an extended Hückel tight binding model this letter reports on the origin of the low Gilbert damping in half metals. This approach enables the prediction of the lower limit for the magnetization relaxation in a wide variety of material systems relevant for future spintronic applications. For the two model systems Co2MnGe and Co2MnSi minimal damping parameters of 1.9×10−4 and 0.6×10−4 are predicted.
Fractional Fokker–Planck equation approach for the interconversion between dielectric and mechanical measurements
Authors: Garcia-Bernabé A. , Sanchis M. J. , Díaz-Calleja R. , del Castillo L. F.
Published: July 2009

This work describes a model of interconversion between mechanical and dielectric measurement. A previous version of this model has been proposed in the hereafter called “previous paper” [Díaz-Calleja, et al.Phys. Rev. E 72, 051505 (2005)], starting from a scaling relation between the translational and rotational viscosities present in a glass forming liquid near the glass transition temperature. Now, in order to improve the previous procedure, the following modifications have been made: (1) a definition of the rotational viscosity obtained from a fractional Fokker–Planck equation has been used, (2) the complex translational viscosity is taken as a non-Newtonian one, (3) a careful splitting of α and β relaxations is necessary, because the interconversión algorithm depends on the underlying molecular mechanism of each relaxation, and (4) the modulus and phase angle of complex viscosities were analyzed instead of real and imaginary parts of the complex viscosities. The proposed interconversion model, in the interval of frequencies 10−2–10+5 Hz, shows that the obtained results are more accurate than those one obtained in the previous paper.
Discharge characteristics of an atmospheric-pressure argon plasma column generated with a single-electrode configuration
Authors: Li Shou-Zhe , Huang Wen-Tong , Zhang Jialiang , Wang Dezhen
Published: July 2009

An atmospheric-pressure argon discharge plasma column is generated by making use of a single-electrode configuration with the power supply operating at a frequency of 45 kHz. It is observed that corona, glowlike plume, and filamentary discharges evolve individually with increasing applied voltage. It is in the filamentary state with average electron density of order 1012 cm−3 that plasma column grows up in the tube with increasing applied voltage. Its discharge characteristics are determined by measuring electrical parameters (voltage, conduction current, and average absorbed power) and optical emission spectroscopy.
Strain-induced localized states within the matrix continuum of self-assembled quantum dots
Authors: Popescu Voicu , Bester Gabriel , Zunger Alex
Published: July 2009

Quantum dot-based infrared detectors often involve transitions from confined states of the dot to states above the minimum of the conduction band continuum of the matrix. We discuss the existence of two types of resonant states within this continuum in self-assembled dots: (i) virtual bound states, which characterize square wells even without strain and (ii) strain-induced localized states. The latter emerge due to the appearance of “potential wings” near the dot, related to the curvature of the dots. While states (i) do couple to the continuum, states (ii) are sheltered by the wings, giving rise to sharp absorption peaks.
Detection and depth analyses of deep levels generated by ion implantation in n- and p-type 4H-SiC
Authors: Kawahara Koutarou , Alfieri Giovanni , Kimoto Tsunenobu
Published: July 2009

The authors investigated deep levels in the whole energy range of bandgap of 4H-SiC, which are generated by low-dose N+, P+, and Al+ implantation, by deep level transient spectroscopy (DLTS). Ne+-implanted samples have been also prepared to investigate the pure implantation damage. In the n-type as-grown material, the Z1∕2 (EC−0.63eV) and EH6∕7 (EC−1.6eV) centers are dominant deep levels. At least, seven peaks (IN1, IN3–IN6, IN8, and IN9) have emerged by implantation and annealing at 1000°C in the DLTS spectra from all n-type samples, irrespective of the implanted species. After high-temperature annealing at 1700°C, however, most DLTS peaks disappeared, and two peaks, IN3 and IN9, which may be assigned to Z1∕2 and EH6∕7, respectively, survive with a high concentration over the implanted atom concentration. In the p-type as-grown material, the D (EV+0.40eV) and HK4 (EV+1.4eV) centers are dominant. Two peaks (IP1 and IP3) have emerged by implantation and annealing at 1000°C, and four traps IP2 (EV+0.39eV), IP4 (EV+0.72eV), IP7 (EV+1.3eV), and IP8 (EV+1.4eV) are dominant after annealing at 1700°C in all p-type samples. The IP2 and IP8 may be assigned to the HS1 and HK4 centers, respectively. The depth analyses have revealed that the major deep levels are generated in the much deeper region than the implant profile.
Plasma sheath physics and dose uniformity in enhanced glow discharge plasma immersion ion implantation and deposition
Authors: Li Liuhe , Li Jianhui , Kwok Dixon T. K. , Wang Zhuo , Chu Paul K.
Published: July 2009

Based on the multiple-grid particle-in-cell code, an advanced simulation model is established to study the sheath physics and dose uniformity along the sample stage in order to provide the theoretical basis for further improvement of enhanced glow discharge plasma immersion ion implantation and deposition. At t=7.0 μs, the expansion of the sheath in the horizontal direction is hindered by the dielectric cage. The electron focusing effect is demonstrated by this model. Most of the ions at the inside wall of the cage are implanted into the edge of the sample stage and a relatively uniform ion fluence distribution with a large peak is observed at the end. Compared to the results obtained from the previous model, a higher implant fluence and larger area of uniformity are disclosed.
Poisson structure on a space with linear SU(2) fuzziness
Authors: Khorrami Mohammad , Fatollahi Amir H. , Shariati Ahmad
Published: July 2009

The Poisson structure is constructed for a model in which spatial coordinates of configuration space are noncommutative and satisfy the commutation relations of a Lie algebra. The case is specialized to that of the group SU(2), for which the counterpart of the angular momentum as well as the Euler parametrization of the phase space are introduced. SU(2)-invariant classical systems are discussed, and it is observed that the path of particle can be obtained by the solution of a first-order equation, as the case with such models on commutative spaces. The examples of free particle, rotationally invariant potentials, and specially the isotropic harmonic oscillator are investigated in more detail.
Nonequilibrium characterization of spinodal points using short time dynamics
Authors: Loscar Ernesto S. , Ferrero Ezequiel E. , Grigera Tomás S. , Cannas Sergio A.
Published: July 2009

Although intuitively appealing, the concept of spinodal is rigorously defined only in systems with infinite range interactions (mean-field systems). In short-range systems, a pseudospinodal can be defined by extrapolation of metastable measurements, but the point itself is not reachable because it lies beyond the metastability limit. In this work we show that a sensible definition of spinodal points can be obtained through the short time dynamical behavior of the system deep inside the metastable phase by looking for a point where the system shows critical behavior. We show that spinodal points obtained by this method agree both with the thermodynamical spinodal point in mean-field systems and with the pseudospinodal point obtained by extrapolation of metaequilibrium behavior in short-range systems. With this definition, a practical determination can be achieved without regard for equilibration issues.
Magnetic imaging with femtosecond temporal resolution
Authors: Li Jie , Lee Min-Sang , He Wei , Redeker Björn , Remhof Arndt , Amaladass Edward , Hassel Christoph , Eimüller Thomas
Published: July 2009

A scanning Kerr microscope with a temporal resolution of <230 fs and a spatial resolution of 210 nm is presented. Equipped with a large temporal and spatial scanning range of 8 ns and 320 μm, respectively, the microscope allows studying nonuniform magnetization dynamics on many different time scales over a large area. For demonstration, we study the magnetization dynamics in Fe/Gd multilayer dot arrays exhibiting a spin reorientation transition (SRT) on three different time scales, namely, femtosecond, picosecond, and nanosecond scales. The dynamics on all time scales varies from one dot to another. This is attributed to the high sensitivity of the SRT to the variations of the layer thicknesses and the Fe/Gd interface structure.
High energy electron crystal spectrometer
Authors: Kudyakov T. , Jochmann A. , Zeil K. , Kraft S. , Finken K. H. , Schramm U. , Willi O.
Published: July 2009

A spectrometer has been developed to measure relativistic electrons produced in different types of plasmas, such as tokamak plasmas and laser produced plasmas. The spectrometer consists of nine Y2SiO5:Ce crystals, which are shielded by stainless steel filters. The absolute calibration of the spectrometer was performed at the superconducting electron linear accelerator Electron Linac for beams with high Brilliance and low Emittance. The spectrometer can provide information about energy distribution of electrons and their numbers for the energy range between 4 and 30 MeV. The spectrum is analyzed by means of the Monte Carlo three-dimensional GEANT4 code. An energy resolution of about 10% is achieved.
Mechanical stability of proteins
Authors: Gabovich A. M. , Li Mai Suan
Published: July 2009

A number of experiments and experimentally based simulations showed that β-proteins are mechanically more stable than α-proteins. However, the theory that might explain this evidence is still lacking. In this paper we have developed a simple elastic theory, which allows to estimate critical forces for stretching both kinds of proteins. It has been shown that unfolding of β-proteins does really require notably higher forces as compared to the stretching of α-proteins.
Spin-forbidden and spin-enabled 4f14→4f135d1 transitions of Yb2+-doped CsCaBr3
Authors: Sánchez-Sanz Goar , Seijo Luis , Barandiarán Zoila
Published: July 2009

The lowest part of the 4f→5d absorption spectrum of Yb2+-doped CsCaBr3 crystals has been calculated using methods of quantum chemistry and it is presented here. A first, low-intensity band is found on the low energy side of the spectrum, followed by several strong absorption bands, in agreement with experimental observations in trivalent and divalent lanthanide ions of the second half of the lanthanide series, doped in crystals. Based on Hund’s rule, these transitions are usually interpreted as “spin-forbidden” and “spin-allowed” transitions, but this interpretation has been recently questioned in the literature. Here, a two-step relativistic method has been used which reveals the spin composition of the excited state wave functions. The forbidden band is found to be due to spin-forbidden transitions involving “high-spin” excited states because their 1 T31u character is 90%. However, the allowed bands cannot be described as spin-allowed transitions involving “low-spin” excited states. Rather, they correspond to “spin-enabled” transitions because they get their intensity from limited (smaller than 45%) electric dipole enabling low-spin T11u character. Calculations using a spin-free Hamiltonian revealed that the difference in their electronic structures is related to the fact that the 4f135d(t2g)1 manifold is split by an energy gap which separates the lowest (high-spin) 1 T31u from the rest of terms, which, in turn, lie very close in energy from each other. As a consequence, the lowest spin-orbit components of 1 T31u are shown to remain 90% pure when spin-orbit coupling is considered, whereas a strong spin-orbit coupling exists between the remaining 4f135d(t2g)1 terms, among which the 1–3 T11u enabling ones lie. As a result, there is a widespread electric dipole enabling T11u character, which, although never higher than 45%, leads to a number of spin-enabled absorption bands.
Ordered Si nanoaperture arrays for the measurement of ion currents across lipid membranes
Authors: Koynov Svetoslav , Brandt Martin S. , Stutzmann Martin
Published: July 2009

Confined arrays of highly ordered microchannels in silicon with apertures as small as 100 nm and flat ridges between them are manufactured using electrochemically defined Si macropores whose orifices are reduced by deposition of dielectric SiOx thin films. The formation of continuous fluid lipid membranes over these channel arrays is achieved by vesicle fusion. This structure should allow a large choice of lipid membranes to be investigated by spatially resolved ion current measurements.
A novel weighted density functional theory for adsorption, fluid-solid interfacial tension, and disjoining properties of simple liquid films on planar solid surfaces
Authors: Yu Yang-Xin
Published: July 2009

A novel weighted density functional theory (WDFT) for an inhomogeneous 12-6 Lennard-Jones fluid is proposed based on the modified fundamental measure theory for repulsive contribution, the mean-field approximation for attractive contribution, and the first-order mean-spherical approximation with a weighted density for correlation contribution. Extensive comparisons of the theoretical results with molecular simulation and experimental data indicate that the new WDFT yields accurate density profiles, adsorption isotherms, fluid-solid interfacial tensions, as well as disjoining potentials and pressures of simple gases such as argon, nitrogen, methane, ethane, and neon confined in slitlike pores or near graphitic solid surfaces. The present WDFT performs better than the nonlocal density functional theory, which is frequently used in the study of adsorption on porous materials. Since the proposed theory possesses a good dimensional crossover and is able to correctly reduce to two-dimensional case, it performs very well even in very narrow pores. In addition, the present WDFT reproduces very well the supercritical fluid-solid interfacial tensions, whereas the theory of Sweatman underestimates them at high bulk densities. The present WDFT predicts that the increase in the fluid-wall attraction may change the sign of the interfacial tension and hence may make the wall from “phobic” to “philic” with respect to the fluid. The new WDFT is computationally as simple and efficient as the mean-field theory and avoids the second-order direct correlation function as an input. It provides a universal way to construct the excess Helmholtz free-energy functional for inhomogeneous fluids such as Yukawa, square-well, and Sutherland fluids.
Dynamics starting at a conical intersection: Application to the photochemistry of pyrrole
Authors: Sellner Bernhard , Barbatti Mario , Lischka Hans
Published: July 2009

The photochemical ring opening process in pyrrole has been investigated by performing classical on-the-fly dynamics using the multiconfiguration self-consistent field method for the computation of energies and energy gradients. As starting point for the dynamics the conical intersection corresponding to the ring-puckered ring-opened structure, determined previously [Barbatti et al., J. Chem. Phys. 125, 164323 (2006)], has been chosen. Two sets of initial conditions for the nuclear velocities were constructed: (i) nuclear velocities in the branching (g,h) plane of the conical intersection and (ii) statistical distribution for all atoms. Both sets of initial conditions show very similar results. Reactive trajectories are only found in a very limited sector in the (g,h) plane and reaction products are very similar. Within the simulation time of 1 ps, ring opening of pyrrole to the biradical NH=CH–CH•–CH=CH• chain followed by ring closure to a substituted cyclopropene structure (NH=CH–C3H3) is observed. The computed structural data correlate well with the experimentally observed dissociation products.
Polarization switching kinetics of ferroelectric nanomesas of vinylidene fluoride-trifluoroethylene copolymer
Authors: Gaynutdinov R. V. , Lysova O. A. , Yudin S. G. , Tolstikhina A. L. , Kholkin A. L. , Fridkin V. M. , Ducharme Stephen
Published: July 2009

The polarization switching kinetics of ferroelectric polymer nanomesas was investigated using piezoresponse force microscopy. The nanomesas were made by self-organization from Langmuir–Blodgett films of a 70% vinylidene fluoride and 30% trifluoroethylene copolymer. The polarization switching time exhibits an exponential dependence on reciprocal voltage that is consistent with nucleation-type switching dynamics.
Integration of reduced graphene oxide into organic field-effect transistors as conducting electrodes and as a metal modification layer
Authors: Lee Chen-Guan , Park Sungjin , Ruoff Rodney S. , Dodabalapur Ananth
Published: July 2009

The characteristics of thin-film transistors (TFTs) with pentacene active layers and source/drain contact layers consisting of either Au, Au coated with highly reduced graphene oxide (HRG), or plain HRG, are compared. It is shown that the incorporation of HRG as an interfacial material between gold source/drain contacts and pentacene in TFT devices results in improved electrical characteristics. The effect of the HRG layer is to improve the gold/pentacene interface leading to better charge injection, lower losses at the interface, and, consequently, higher effective carrier mobility.
Microstrip circuit analog of a complex diffraction phenomenon
Authors: Fernández-Prieto A. , Medina F. , Mesa F.
Published: July 2009

This letter presents a methodology to reproduce at microwave frequencies the physical behavior of certain diffraction structures that have been investigated in the optics community. The methodology will be exemplified with a microstrip circuit implementation of a transmission line system exhibiting an electromagnetic response that mimics the response of simple and compound diffraction gratings. The identification of such “bridge” circuit analogies could be very fruitful for the understanding and development of design strategies to devise practical components based on phenomena employed in the affine areas of optics and microwave engineering.
Pinning control of threshold coupled chaotic neuronal maps
Authors: Shrimali Manish Dev
Published: July 2009

Chaotic neuronal maps are studied with threshold activated coupling at selected pinning sites with increasing pinning density. A transition from spatiotemporal chaos to a fixed spatial profile with synchronized temporal cycles is observed. There is an optimal fraction of sites where it is necessary to apply the control algorithm in order to effectively suppress chaotic dynamics.
Current-gain cutoff frequencies above 10 MHz for organic thin-film transistors with high mobility and low parasitic capacitance
Authors: Kitamura Masatoshi , Arakawa Yasuhiko
Published: July 2009

The current-gain cutoff frequency for bottom contact n-channel C60 thin-film transistors (TFTs) with channel lengths of 2–10 μm has been investigated. Patterned gate electrodes were adopted to reduce parasitic capacitance of the TFTs. The cutoff frequency was estimated by direct measurement of the gate and drain modulation currents. The estimated cutoff frequency increases consistently with reducing channel length. A maximum cutoff frequency of 20.0 MHz was obtained from a C60 TFT with a channel length of 2 μm and a saturation mobility of 1.11 cm2/V s.
Magnetically actuated microrotors with individual pumping speed and direction control
Authors: Kavčič B. , Babič D. , Osterman N. , Podobnik B. , Poberaj I.
Published: July 2009

We demonstrate an experimental realization of a microscale pump self-assembled from superparamagnetic colloidal spheres and driven by an external magnetic field, where a system of microelectrodes controls the pump rotor by dielectrophoretic force. Whereas an external magnetic field is used to assemble and drive the rotor, which allows parallel fabrication and actuation of many such devices, the microelectrodes enable control of an individual rotor and thus regulate pumping speed and direction of any single pump in the microfluidic device. Dielectrophoretically controlled micropumps can be fabricated with existing microfabrication techniques and can be easily integrated into complex microfluidic devices.
Morphological instability of spherical soft particles induced by surface charges
Authors: Li Bo , Feng Xi-Qiao , Li Yue , Wang Gang-Feng
Published: July 2009

We here demonstrate that surface charges on a spherical soft particle may induce its morphology instability. It is found that various patterns can be obtained by varying the surface charge density. The critical condition for the occurrence of surface instability and the wavelength of the induced surface patterns are derived analytically and, thereby, the morphological phase diagram of soft particles can be provided easily. Besides the electric stress, surface tension also plays a significant role in the surface evolution process. In addition, the morphological evolution behavior of a soft particle is demonstrated to exhibit distinct dependence on its size.
A widely voltage-tunable quantum cascade laser based on “two-step” coupling
Authors: Yao Yu , Franz Kale J. , Wang Xiaojun , Fan Jen-Yu , Gmachl Claire
Published: July 2009

A novel quantum cascade laser design with “two-step” coupling between the injector and the upper laser state is demonstrated to achieve a widely voltage-tunable laser spectrum. Electroluminescence from this design can be tuned over a range of more than 200 cm−1 with a tuning coefficient of ∼700 cm−1/V per stage. Lasers based on this design provide a tuning range of ∼100 cm−1 (8.3–9 μm) above threshold with a tuning coefficient of ∼900 cm−1/V per stage at a constant temperature of 295 K.