bluuebunny/crossref_metadata_2025 huggingface dataset:
Baseline logical elements on the basis of DNA
Authors: Lakhno V. D. , Sultanov V. B.
Published: April 2008

DNA possesses unique electronic properties which may be of utility for devising electronic elements of nanometer size. We present some examples of double‐stranded oligonucleotides with control electrodes which realize logical elements NOT, OR, AND, and XOR basic for Boolean logic. The logical gates constructed are nondissipative which solves the well‐known problem of huge energy consumption by electronic systems of ultrahigh density. We demonstrate that DNA‐based electronic computing circuits can be created in principle. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Nondynamical correlation energy in model molecular systems
Authors: Chojnacki Henryk
Published: April 2008

The hypersurfaces for the deprotonation processes have been studied at the nonempirical level for H3O+, NH, PH, and H3S+ cations within their correlation consistent basis set. The potential energy curves were calculated and nondynamical correlation energies analyzed. We have found that the restricted Hartree‐Fock wavefunction leads to the improper dissociation limit and, in the three latest cases requires multireference description. We conclude that these systems may be treated as a good models for interpretation of the proton transfer mechanism as well as for testing one‐determinantal or multireference cases. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Long‐term transportation, by road and air, of Devil‐ray (Mobula mobular), Meagre (Argyrosomus regius), and Ocean Sunfish (Mola mola)
Authors: Correia João P. S. , Graça José T. C. , Hirofumi Morikawa
Published: April 2008

Between September 2006 and April 2007 the authors transported one 0.9 m wingspan Mobula mobular from Olhão (South of Portugal) to Valencia (East of Spain), 12 ∼1.0 m long Argyrosomus regius to Tarragona (Northeast of Spain) and four ∼0.4 m long Mola mola to Atlanta (GA, USA). These journeys had a total “water to water” duration of 17, 22 and 33 hr, respectively. The first two transports were conducted by road whereas the third involved a combination of road and air travel. Water quality parameters—specifically dissolved oxygen, temperature, pH and ammonia—were monitored continuously throughout the duration of the trips and were maintained at optimum levels through the use of battery‐powered filtration and chemical supplements. All animals arrived alive and well at their destinations. This paper reports on the specific transport regime adopted in each case and provides some insight for potential improvements in future similar transports. Zoo Biol 27:234–250, 2008. © 2008 Wiley‐Liss, Inc.
The contribution of self‐efficacy and depression to disability and work status in chronic pain patients: A comparison between Australian and Brazilian samples
Authors: Sardá Jamir , Nicholas Michael K. , Asghari Ali , Pimenta Cibele A.M.
Published: April 2008

There is evidence that cognitions (beliefs) and mood contribute to physical disability and work status in people with chronic pain. However, most of the current evidence comes from North America and Europe. This study examined the contribution of demographic, pain and psychosocial factors to disability and work status in chronic pain patients in two matched samples from quite different countries (Australia and Brazil). Data were collected from 311 chronic pain patients in each country.

The results suggest that although demographic and pain variables (especially pain levels) contribute to disability, self‐efficacy beliefs made a significant contribution to disability in both samples. Age and educational level also contributed to unemployment in both samples. But there were some differences, with self‐efficacy and physical disability contributing to work status only in the Brazilian sample. In contrast, depression was the only psychological risk factor for unemployment in the Australian sample. Catastrophising and pain acceptance did not contribute to disability or unemployment in either sample. These findings confirm key aspects of biopsychosocial models of pain in two culturally and linguistically different chronic pain samples from different countries. They suggest that different chronic pain populations may share more similarities than differences.
Poiseuille flow in a fluid overlying a porous medium
Authors: HILL ANTONY A. , STRAUGHAN BRIAN
Published: April 2008

This paper numerically investigates the instability of Poiseuille flow in a fluid overlying a porous medium saturated with the same fluid. A three-layer configuration is adopted. Namely, a Newtonian fluid overlying a Brinkman porous transition layer, which in turn overlies a layer of Darcy-type porous material. It is shown that there are two modes of instability corresponding to the fluid and porous layers, respectively. The key parameters which affect the stability characteristics of the system are the depth ratio between the porous and fluid layers and the transition layer depth.
Shallow-water modons on thef-plane
Authors: KIZNER Z. , REZNIK G. , FRIDMAN B. , KHVOLES R. , McWILLIAMS J.
Published: April 2008

Solutions for steadily translating localized vortical structures, or modons, are sought in the framework of a 1½-layer rotating shallow-water (RSW) model on thef-plane. In this model, the fluid is assumed to rotate at a constant rate and to be composed of an active finite-depth layer and a passive infinitely deep layer. The focus is on the smooth intense modons, in which the potential vorticity field is continuous, and the pressure (hence, the active-layer thickness) and velocity are smooth, while inertial effects and deviations of the active-layer thickness from the static level are considerable. The problem is solved numerically employing a Newton--Kantorovich iterative procedure, Fourier–Chebyshev spectral expansion and collocations. The numerics are preceded by a theoretical modon design discussion that includes: derivation of fundamental modon invariants; distinction between the flow in the trapped-fluid region and the flow outside it; and the boundary conditions at the separatrix, the streamline demarcating the two regions. Also, some basic distinctions from the quasi-geostrophic modons are discussed, and an asymptotic analysis of the RSW modon far-field characteristics is carried out. This analysis reveals that an RSW modon must propagate more slowly than inertia–gravity waves. In smooth modons, the requirement that the active-layer thickness should be positive imposes an even stronger restriction on the allowed translational speed. To enable the use of Fourier–Chebyshev series, only the modons with circular separatrices are considered. The numerical iterative procedure is initialized by an analytical quasi-geostrophic dipolar modon solution; accordingly, the obtained RSW modons appear as cyclone–anticyclone pairs. Computations show that the allowed maximal translational speed monotonically decreases as a function of the modon size and, for reasonable sizes, is appreciably smaller than the gravity-wave limit. As distinct from quasi-geostrophic modons, the RSW modons with circular separatrices display nonlinearity of the potential vorticity (PV)vs. streamfunction relation, and the cyclone–anticyclone asymmetry: while the integral mass anomaly in the modon is zero, the cyclone is more intense and compact than the anticyclone.
The influence of secondary flows induced by normal stress differences on the shear-induced migration of particles in concentrated suspensions
Authors: RAMACHANDRAN ARUN , LEIGHTON DAVID T.
Published: April 2008

It was first demonstrated experimentally by H. Giesekus in 1965 that the second normal stress difference in polymers can induce a secondary flow within the cross-section of a non-axisymmetric conduit. In this paper, we show through simulations that the same may be true for suspensions of rigid non-colloidal particles that are known to exhibit a strong negative second normal stress difference. Typically, the magnitudes of the transverse velocity components are small compared to the average axial velocity of the suspension; but the ratio of this transverse convective velocity to the shear-induced migration velocity is characterized by the shear-induced migration Péclet number χ which scales as B2/a2, B being the characteristic length scale of the cross-section and a being the particle radius. Since this Péclet number is kept high in suspension experiments (typically 100 to 2500), the influence of the weak circulation currents on the concentration profile can be very strong, a result that has not been appreciated in previous work. The principal effect of secondary flows on the concentration distribution as determined from simulations using the suspension balance model of Nott & Brady (J. Fluid Mech. vol. 275, 1994, p. 157) and the constitutive equations of Zarraga et al. (J. Rheol. vol. 44, 2000, p. 185) is three-fold. First, the steady-state particle concentration distribution is no longer independent of particle size; rather, it depends on the aspect ratio B/a. Secondly, the direction of the secondary flow is such that particles are swept out of regions of high streamsurface curvature, e.g. particle concentrations in corners reach a minimum rather than the local maximum predicted in the absence of such flows. Finally, the second normal stress differences lead to instabilities even in such simple geometries as plane-Poiseuille flow.
Convective instability and transient growth in flow over a backward-facing step
Authors: BLACKBURN H. M. , BARKLEY D. , SHERWIN S. J.
Published: April 2008

Transient energy growths of two- and three-dimensional optimal linear perturbations to two-dimensional flow in a rectangular backward-facing-step geometry with expansion ratio two are presented. Reynolds numbers based on the step height and peak inflow speed are considered in the range 0–500, which is below the value for the onset of three-dimensional asymptotic instability. As is well known, the flow has a strong local convective instability, and the maximum linear transient energy growth values computed here are of order 80×103 at Re = 500. The critical Reynolds number below which there is no growth over any time interval is determined to be Re = 57.7 in the two-dimensional case. The centroidal location of the energy distribution for maximum transient growth is typically downstream of all the stagnation/reattachment points of the steady base flow. Sub-optimal transient modes are also computed and discussed. A direct study of weakly nonlinear effects demonstrates that nonlinearity is stablizing at Re = 500. The optimal three-dimensional disturbances have spanwise wavelength of order ten step heights. Though they have slightly larger growths than two-dimensional cases, they are broadly similar in character. When the inflow of the full nonlinear system is perturbed with white noise, narrowband random velocity perturbations are observed in the downstream channel at locations corresponding to maximum linear transient growth. The centre frequency of this response matches that computed from the streamwise wavelength and mean advection speed of the predicted optimal disturbance. Linkage between the response of the driven flow and the optimal disturbance is further demonstrated by a partition of response energy into velocity components.
Anthropological communities of interpretation for Burma: An overview
Authors: Chit Hlaing U
Published: April 2008

This paper surveys the history of anthropological work on Burma, dealing both with Burman and other ethnic groups. It focuses upon the relations between anthropology and other disciplines, and upon the relationship of such work to the development of anthropological theory. It tries to show how anthropology has contributed to an overall understanding of Burma as a field of study and, conversely, how work on Burma has influenced the development of anthropology as a subject. It also tries to relate the way in which anthropology helps place Burma in the broader context of Southeast Asia.
Retroperitoneale Fibrose, Morbus Ormond, chronische Periaortitis, ...?
Authors: Vogt Bruno , Meier Pascal , Burnier Michel
Published: April 2008

Die retroperitoneale Fibrose oder Morbus Ormond ist eine seltene Krankheit charakterisiert durch eine entzündliche Fibrose des Retroperitoneums und der abdominalen Aorta, welche sich häufig bis in die iliacae communes Arterien erstreckt. Die abdominale Aorta kann aneurysmatisch verändert sein, weshalb die retroperitoneale Fibrose in solche mit oder ohne Aneurysma der Aorta abdominalis aufgeteilt werden kann. Typischerweise weisst die idiopathische retroperitoneale Fibrose keine aneurysmatische Erweiterung der Baucharterie auf. Die klinische Präsentation ist nicht spezifisch und beinhaltet unklare Abdomen-, Flanken- oder Rückenschmerzen sowie Allgemeinsymptome wie Müdigkeit, Fieber und Gewichtsverlust. Die Ursache und die pathophysiologischen Mechanismen sind nicht klar, jedoch deuten viele Faktoren auf autoimmune Mechanismen hin. Die wichtigste Komplikation der retroperitonealen Fibrose ist die Harnleiterstauung mit Hydronephrose, welche ein- oder beidseitig auftreten kann und entlastet werden muss. Da die Ursache dieser Erkrankung nicht bekannt ist, gibt es keine kausale Therapie. Wegen der Seltenheit aber auch der sehr heterogenen Präsentation der Erkrankung gibt es auch keine randomisierte prospektive Studie zur Behandlung. Die medikamentöse Therapie beschränkt sich auf Steroide alleine oder in Kombination mit weiteren immunsuppressiven Medikamenten. Das Ansprechen auf die Therapie ist sehr individuell. Als gute Verlaufsparameter eignen sich der Allgemeinzustand, die Blutsenkungsreaktion und CT- oder MRI-Untersuchungen.
Experimental and numerical studies on excess‐air formation in quasi‐saturated porous media
Authors: Klump Stephan , Cirpka Olaf A. , Surbeck Heinz , Kipfer Rolf
Published: April 2008

The concentrations of conservative groundwater components of atmospheric origin often exceed the concentrations in equilibrium with the atmosphere. This phenomenon, called “excess air”, is caused by gas exchange between entrapped gas and groundwater. We present experimental results from a horizontal quasi‐saturated sand column, in which we have analyzed excess‐air formation by noble‐gas analysis and measurement of the total dissolved gas pressure. The experimental results agree with a numerical model based on kinetic dissolution of spherical gas bubbles. Parameter studies show that the dissolution of entrapped gas is controlled by gas‐transfer kinetics only when the contact time between the water and gas phases is relatively short. In natural systems, this could be the case for gas exchange within the hyporheic zone of natural rivers. In the typical situation of excess‐air formation upon regional groundwater recharge, it seems acceptable to apply gas‐transfer models assuming local equilibrium. Additional parameter studies show that the direction of flow considerably affects the evolution of dissolution fronts. Our experimental and numerical results show that apparently unfractionated excess air is formed in the presence of a progressively dissolving gas phase, that is, the excess‐air component has an elemental composition similar to that of free atmospheric air. This observation contradicts the common conceptual model that unfractionated excess air indicates the complete dissolution of entrapped air, as formulated in the unfractionated excess air (UA) model (Heaton and Vogel, 1981) which is also contained as a special case in the closed‐system equilibrium (CE) model of Aeschbach‐Hertig et al. (2000). We conjecture that the estimated fractionation factor, F, and amount of initial gas, A, determined by fitting the CE model to noble‐gas concentrations, are biased when F is zero (apparently unfractionated excess air) and A corresponds to initial gas saturations smaller than one per cent.
A large eddy in the central Arctic Ocean
Authors: Aagaard Knut , Andersen Roger , Swift James , Johnson James
Published: April 2008

Long‐term moored measurements of temperature, salinity, and velocity over the abyssal plain near the North Pole show a rich array of eddy‐like structures over a wide range of depths. Here we demonstrate an anticyclone that extends from the surface to at least 1700 m, is about 60 km across, and has a likely origin along the Eurasian continental margin.
First satellite observations of lower tropospheric ammonia and methanol
Authors: Beer Reinhard , Shephard Mark W. , Kulawik Susan S. , Clough Shepard A. , Eldering Annmarie , Bowman Kevin W. , Sander Stanley P. , Fisher Brendan M. , Payne Vivienne H. , Luo Mingzhao , Osterman Gregory B. , Worden John R.
Published: April 2008

The Tropospheric Emission Spectrometer (TES) on the EOS Aura satellite makes global measurements of infrared radiances which are used to derive profiles of species such as O3, CO, H2O, HDO and CH4 as routine standard products. In addition, TES has a variety of special modes that provide denser spatial mapping over a limited geographical area. A continuous‐coverage mode (called “transect”, about 460 km long) has now been used to detect additional molecules indicative of regional air pollution. On 10 July 2007 at about 05:37 UTC (13:24 LMST) TES conducted such a transect observation over the Beijing area in northeast China. Examination of the residual spectral radiances following the retrieval of the TES standard products revealed surprisingly strong features attributable to enhanced concentrations of ammonia (NH3) and methanol (CH3OH), well above the normal background levels. This is the first time that these molecules have been detected in space‐based nadir viewing measurements that penetrate into the lower atmosphere.
Comparison of Personal Versus Fictional Narratives of Children With Language Impairment
Authors: McCabe Allyssa , Bliss Lynn , Barra Gabriela , Bennett MariBeth
Published: April 2008

Purpose

Personal narratives are common in children’s conversations, recommended as the appropriate genre for early writing by educators, and part of many high-stakes tests, possibly because they tend to be better formed than fictional narratives. However, current practice in the field of speech-language pathology employs fictional narratives in assessment, intervention, and study of children with impaired language development. This article explored performance on personal versus fictional narratives by children with language impairment (LI), hypothesizing that performance on the former would be better and a minimal relationship between performances in the 2 genres.

Method

Twenty-seven children age 7;0–9;9 (years;months) with LI orally produced personal and fictional narratives (responses to a wordless picture book). Narratives were analyzed by raters blind to experimental hypotheses using high-point analysis and an analysis derived from scoring of a high-stakes composition for 4th grade.

Results

High-point ratings of personal significantly exceeded those of fictional narratives. Disproportionate fictional stories did not meet minimal narrative criteria. However, more personal narratives than would be expected by chance did. The analyses were significantly correlated. Quality of a child’s performance of personal was minimally related to that of fictional narratives.

Conclusions

Clinicians may want to consider functional aspects of personal narratives.
Ion current on a small spherical attractive probe in a weakly ionized plasma with ion-neutral collisions (kinetic approach)
Authors: Zobnin A. V. , Usachev A. D. , Petrov O. F. , Fortov V. E.
Published: April 2008

The ion flux on a small attractive sphere (the sphere radius is much less than the Debye length) and the electric potential distribution around the sphere charged in a stationary weakly ionized plasma are calculated by the direct solution of the kinetic equation with the Bhatnagar–Gross–Krook collision term. Only a weak dependence of the ion flux on the electron temperature is found. An analytical approximation of the calculated ion current–voltage characteristics is proposed for intermediate collisionalities, where neither a collisionless theory nor a continuum fluid approach is valid. This approximation was used for calculation of the floating sphere potential. A reasonable agreement of the calculated floating sphere potential with prior numerical calculations is found.
Simulating electron spin resonance spectra of nitroxide spin labels from molecular dynamics and stochastic trajectories
Authors: Sezer Deniz , Freed Jack H. , Roux Benoît
Published: April 2008

Simulating electron spin resonance spectra of nitroxide spin labels from motional models is necessary for the quantitative analysis of experimental spectra. We present a framework for modeling the spin label dynamics by using trajectories such as those from molecular dynamics (MD) simulations combined with stochastic treatment of the global protein tumbling. This is achieved in the time domain after two efficient numerical integrators are developed: One for the quantal dynamics of the spins and the other for the classical rotational diffusion. For the quantal dynamics, we propagate the relevant part of the spin density matrix in Hilbert space. For the diffusional tumbling, we work with quaternions, which enables the treatment of anisotropic diffusion in a potential expanded as a sum of spherical harmonics. Time-averaging arguments are invoked to bridge the gap between the smaller time step of the MD trajectories and the larger time steps appropriate for the rotational diffusion and/or quantal spin dynamics.
Simulating ion beam extraction from a single aperture triode acceleration column: A comparison of the beam transport codes IGUN and PBGUNS with test stand data
Authors: Patel A. , Wills J. S. C. , Diamond W. T.
Published: April 2008

Ion beam extraction from two different ion sources with single aperture triode extraction columns was simulated with the particle beam transport codes PBGUNS and IGUN. For each ion source, the simulation results are compared to experimental data generated on well-equipped test stands. Both codes reproduced the qualitative behavior of the extracted ion beams to incremental and scaled changes to the extraction electrode geometry observed on the test stands. Numerical values of optimum beam currents and beam emittance generated by the simulations also agree well with test stand data.
Effects of ordering degree on the dielectric and ferroelectric behaviors of relaxor ferroelectric Pb(Sc1/2Nb1/2)O3 ceramics
Authors: Zhu Mankang , Chen Chuan , Tang Jianlan , Hou Yudong , Wang Hao , Yan Hui , Zhang Weihong , Chen Jian , Zhang Wenjun
Published: April 2008

Relaxor ferroelectric Pb(Sc0.5Nb0.5)O3 ceramics were synthesized by a modified solid oxide reaction method. The x-ray diffraction and Raman scattering analysis affirmed that annealing dominated the ordering degree of PSN samples. The measurements on dielectric response and ferroelectric behavior indicate the prominent impact of the ordering degree. The dielectric response of a relaxor ferroelectric is determined by the growing and freezing behaviors of the polar regions, which is correlated with the ordering degree. In addition, the behavior of the ferroelectric phase transition was controlled by the lattice distortion in ordered domain due to the displacement of Pb and ferroelectrically active Nb cations in the PSN lattice.
Ion streaming instability in a quantum dusty magnetoplasma
Authors: Shukla Nitin , Shukla P. K. , Brodin G. , Stenflo L.
Published: April 2008

It is shown that a relative drift between the ions and the charged dust particles in a magnetized quantum dusty plasma can produce an oscillatory instability in a quantum dust acousticlike wave. The threshold and growth rate of the instability are presented. The result may explain the origin of low-frequency electrostatic fluctuations in semiconductors quantum wells.
Microstructure and depletion forces in polymer-colloid mixtures from an interfacial statistical associating fluid theory
Authors: Bymaster Adam , Jain Shekhar , Chapman Walter G.
Published: April 2008

By using a classical density functional theory (interfacial statistical associating fluid theory), we investigate the structure and effective forces in nonadsorbing polymer-colloid mixtures. The theory is tested under a wide range of conditions and performs very well in comparison to simulation data. A comprehensive study is conducted characterizing the role of polymer concentration, particle/polymer-segment size ratio, and polymer chain length on the structure, polymer induced depletion forces, and the colloid-colloid osmotic second virial coefficient. The theory correctly captures a depletion layer on two different length scales, one on the order of the segment diameter (semidilute regime) and the other on the order of the polymer radius of gyration (dilute regime). The particle/polymer-segment size ratio is demonstrated to play a significant role on the polymer structure near the particle surface at low polymer concentrations, but this effect diminishes at higher polymer concentrations. Results for the polymer-mediated mean force between colloidal particles show that increasing the concentration of the polymer solution encourages particle-particle attraction, while decreasing the range of depletion attraction. At intermediate to high concentrations, depletion attraction can be coupled to a midrange repulsion, especially for colloids in solutions of short chains. Colloid-colloid second virial coefficient calculations indicate that the net repulsion between colloids at low polymer densities gives way to net attraction at higher densities, in agreement with available simulation data. Furthermore, the results indicate a higher tendency toward colloidal aggregation for larger colloids in solutions of longer chains.
Suspension properties at finite Reynolds number from simulated shear flow
Authors: Kulkarni Pandurang M. , Morris Jeffrey F.
Published: April 2008

This work examines the role of particle-scale inertia in a monodisperse suspension of non-Brownian and neutrally buoyant spherical particles subjected to simple-shear flow. The dimensionless parameters governing the problem are the solid-volume fraction ϕ and the Reynolds number defined Re=ργ̇a2∕μ, where a is the sphere radius, γ̇ is the shear rate, and μ and ρ are the viscosity and density of the fluid, respectively. Using numerical simulations in a wall-bounded domain via the lattice-Boltzmann method, the bulk rheological properties of relative viscosity, normal stress differences, and particle pressure are reported for 0.01⩽Re<5 and 0.05⩽ϕ⩽0.3. The anisotropy in microstructure at finite Re is studied through the pair distribution function g(r). Also presented are the probability density functions of particle velocity fluctuations in gradient and vorticity directions. Comparisons to low Reynolds number theory and simulations are provided wherever possible.
Squeezing of a periodic emulsion through a cubic lattice of spheres
Authors: Zinchenko Alexander Z. , Davis Robert H.
Published: April 2008

Squeezing of a periodic, highly concentrated emulsion of deformable drops through a dense, simple cubic array of solid spherical particles at zero Reynolds number is simulated by considering one drop in a periodic cell. The particles are rigidly held in space. The drops with nondeformed diameter comparable with the particle size (and considerably larger than the interparticle constrictions) squeeze under a specified average pressure gradient. This three dimensional problem serves as a useful prototype model of drop-solid interaction for emulsion flow through granular materials. The solution allows us to study permeabilities for both phases in detail and determine the critical conditions when the drop phase flow stops due to blockage in the pores by capillary forces. The algorithm employs a boundary-integral formulation with periodic Green’s function, Hebeker representation for solid-particle contributions, and recent desingularization tools [A. Z. Zinchenko and R. H. Davis, J. Fluid Mech. 564, 227 (2006)] to alleviate difficulties with lubrication. Calculations are challenging in that tens of thousands of boundary elements per surface and 10 000–20 000 time steps are required for near-critical squeezing conditions, and the use of multipole acceleration is crucial to make such simulations feasible. The results are presented for 36% and 50% concentrated emulsions flowing through an array of almost packed particles, at drop-to-medium viscosity ratios of 1 and 4. Scaling for the squeezing time of the drop phase at near-criticial capillary numbers is extracted from the calculations. For all the simulated cases, the drops move, on average, faster than the continuous phase.
Cylindrical bubble dynamics: Exact and direct numerical simulation results
Authors: Delale Can F. , Tryggvason Gretar , Nas Selman
Published: April 2008

The axially symmetric collapse and growth of a cylindrical bubble are considered. A universal law of cylindrical bubble dynamics is obtained when the pressure at the boundary and that inside the bubble satisfy certain conditions. Both vapor bubbles having constant pressure and gas bubbles obeying the isothermal law are considered. Moreover, for gas bubbles, the energy equation within the bubble is considered in the uniform pressure approximation for the effect of heat conduction through the bubble wall, and an exact particular solution, leading to explicit gas pressure and gas temperature expressions, is obtained. Finally, the findings are validated by direct numerical simulations by using the front tracking/finite volume method.
Abnormal ferroelectric response and enhancement of piezoelectricity of PbTiO3 under uniaxial compression
Authors: Duan Yifeng , Li Jingbo , Li Shu-Shen , Xia Jian-Bai , Chen Changqing
Published: April 2008

The ferroelectricity of rhombohedral PbTiO3 under uniaxial compression is investigated from first-principles study. Upon compression, the ferroelectricity decreases until a critical stress of −29 GPa and then increases with a further increase of the magnitude of the uniaxial compressive stress. We also find that uniaxial compression could enhance piezoelectricity and that the maximum piezoelectric coefficient d33 occurs at σ33=−49 GPa, which supports the experimentally observed piezoelectric behavior in rhombohedral Pb(Mg1/3Nb2/3O3)−0.32PbTiO3 [Q. Wan, C. Chen, and Y. P. Shen, J. Appl. Phys. 98, 024103 (2005)]. Our calculated results show that the Pb, Ti, and O atoms have different contributions to the total polarization with increasing the magnitude of uniaxial compressive stress, and that when −σ33>55 GPa, the Ti atoms no longer have contributions to the polarization, which leads to the changes of ferroelectricity and piezoelectricity.
Precise measurement of the resolution in light microscopy using Fourier transform
Authors: Vainrub Arnold
Published: April 2008

The resolution power of light microscope has been accurately measured (±5%) by Fourier transform of various object images and further evaluation of the highest spatial frequency in Fourier spectrum. Any unknown shape plane object with a shape feature’s size smaller than the resolution to be measured was shown to provide a reliable resolution test. This simple method gives a direct measurement of the resolution power as defined by Abbe [Archiv. F. Mikroskopische Anat. 9, 413 (1873)]. The results have been justified by comparison to a standard resolution measurement by using calibrated periodic line patterns. Notably, the approach is applicable in super-resolution light microscopy (transmission, reflection, and fluorescence), where calibrated resolution targets do not occur. It was conveniently implemented by using a compact disk as a test object and free IMAGEJ imaging software.
A stochastic simulation of nonisothermal nucleation
Authors: Barrett Jonathan C.
Published: April 2008

The results of stochastic simulations of growth and evaporation of small clusters in vapor are reported. Energy dependent growth rates are determined from the monomer-cluster collision rate and decay rates are found from a detailed balance, with the equilibrium size and energy distribution of clusters calculated using the capillarity approximation and the equilibrium vapor pressure. These rates are used in simulations of two-dimensional random walks in size and energy space to determine the fraction of clusters in supersaturated vapor of size (imin+1) that reach a size imax. By assuming that clusters of size imin are in equilibrium, this fraction can be related to the nonisothermal nucleation rate. The simulated rates show good agreement with the previously published analytical results. In the absence of an inert carrier gas, the nonisothermal nucleation rates are typically between 1% and 5% of the isothermal rates.
Ge
O
x
interface layer reduction upon Al-gate deposition on a HfO2∕GeOx∕Ge(001) stack
Authors: Rangan Sylvie , Bersch Eric , Bartynski Robert Allen , Garfunkel Eric , Vescovo Elio
Published: April 2008

The metallization of HfO2∕Ge by Al at room temperature was studied using photoemission and inverse photoemission. Upon deposition, Al reduces the GeOx interfacial layer between Ge and HfO2, and a thin Al2O3 layer is formed at the Al∕HfO2 interface. The band alignment across the Al∕HfO2∕Ge stacks is also addressed.
1
nm
equivalent oxide thickness in Ga2O3(Gd2O3)∕In0.2Ga0.8As metal-oxide-semiconductor capacitors
Authors: Shiu K. H. , Chiang T. H. , Chang P. , Tung L. T. , Hong M. , Kwo J. , Tsai W.
Published: April 2008

An equivalent oxide thickness about 1nm for Ga2O3(Gd2O3) (GGO) on In0.2Ga0.8As has been achieved by employing a thin in situ deposited 3nm thick Al2O3 protection layer. The dual gate oxide stacks of the Al2O3∕GGO (33, 20, 10, 8.5, and 4.5nm)/In0.2Ga0.8As∕GaAs metal-oxide-semiconductor (MOS) capacitors remain amorphous after rapid thermal annealing up to 800–850°C, accompanied with atomically sharp smooth oxide/semiconductor interfaces. Well behaved capacitance-voltage (C-V) curves of the MOS diodes have shown sharp transition from depletion to accumulation with small flatband voltage (1.1V for Au metal gate and 0.1V for Al), and weak frequency dispersion (1.5%–5.4%) between 10 and 500kHz at accumulation capacitance. Low leakage current densities [3.1×10−5 and 2.5×10−9A∕cm2 at V=Vfb+1V for Al2O3(3nm)∕GGO(4.5 and 8.5nm)], a high dielectric constant around 14–16 of GGO for all tested thicknesses, and a low interfacial density of states (Dit) in the low 1011cm−2eV−1 have also been accomplished.
Indium stability on InGaAs during atomic H surface cleaning
Authors: Aguirre-Tostado F. S. , Milojevic M. , Hinkle C. L. , Vogel E. M. , Wallace R. M. , McDonnell S. , Hughes G. J.
Published: April 2008

Atomic H exposure of a GaAs surface at 390°C is a relatively simple method for removing the native oxides without altering the surface stoichiometry. In-situ reflection high energy electron diffraction and angle-resolved x-ray photoelectron spectroscopy have been used to show that this procedure applied to In0.2Ga0.8As effectively removes the native oxides resulting in an atomically clean surface. However, the bulk InGaAs stoichiometry is not preserved from this treatment. The In:Ga ratio from the substrate is found to decrease by 33%. The implications for high-mobility channel applications are discussed as the carrier mobility increases nearly linearly with the In content.
The pronunciation of Hong Kong English
Authors: Deterding David , Wong Jennie , Kirkpatrick Andy
Published: April 2008

This paper provides a detailed description of the pronunciation of English by fifteen fourth-year undergraduates at the Hong Kong Institute of Education. First, the occurrence of American features of pronunciation is considered. Then there is an analysis of the pronunciation of initial TH, initial and final consonant clusters, L-vocalisation, conflation between initial [n] and [l], monophthong vowels, the vowels in FACE and GOAT, vowel reduction, rhythm and sentence stress. Finally, the status of Hong Kong English is considered, particularly the extent of its continuing alignment with an exonormative standard.
An Occurrence of Multiple Carcinomas in Both Kidneys of a 5-year-old Female Cynomolgus Monkey (Macaca fascicularis)
Authors: Yamaguchi Yuko , Hoshiya Toru , Horiguchi Kosuke , Tamura Kazutoshi
Published: April 2008

An occurrence of multiple carcinoma in both kidneys of a 5-year-old female cynomolgus monkey is described in the present paper. Macroscopically, the kidneys were enlarged with multiple solid and grayish-white masses and cysts mainly in the cortex and outer medulla. Light microscopically, carcinomas showed either tubulopapillary or tubulosolid growth patterns. Carcinoma cells were pleomorphic cuboidal to columnar cells. Cytoplasm was abundant and either granular and eosinophilic or clear, and nuclei were large and vesicular with prominent nucleoli. Electron microscopy revealed the existence of a brush border-like structure on the cell surface of carcinoma cells, suggesting that carcinoma cells arose from proximal tubular epithelial cells. Small foci of tubular epithelial cell hyperplasia and adenomas were also observed independently of carcinomas. There was no evidence of transition from adenoma to carcinoma, and no metastases were detected.
A Critical Comparison of Murine Pathology and Epidemiological Data of TCDD, PCB126, and PeCDF
Authors: Yoshizawa Katsuhiko , Heatherly Allison , Malarkey David E. , Walker Nigel J. , Nyska Abraham
Published: April 2008

2,3,7,8-Tetrachlorodibenzo- p-dioxin (TCDD, or dioxin) and dioxin-like compounds (DLCs) induce numerous toxicities, including developmental, endocrine, immunological, and multi-organ carcinogenic, in animals and/or humans. Multiple studies completed by the National Toxicology Program (NTP) focused on the effects caused in Harlan Sprague-Dawley rats by specific DLCs, among them the prototypical dioxin, TCDD. Because humans are exposed daily to a combination of DLCs, primarily via ingestion of food, the Toxic Equivalency Factor (TEF) was developed in order to evaluate health hazards caused by these mixtures. Herein we review the pathological effects reported in humans exposed to TCDD; 3,3′,4,4′,5-pentachlorobiphenyl (PCB 126); and 2,3,4,7,8,-pentachlorodibenzofuran (PeCDF) and compare them to similar changes seen in NTP murine studies performed with the same compounds. While there were differences in specific pathologies observed, clear consistency in the target organs affected (liver, oral cavity, cardiovascular system, immune system, thyroid, pancreas, and lung) could be seen in both human studies and rodent toxicity and carcinogenicity investigations.
Mouse Skin Models for Carcinogenic Hazard Identification: Utilities and Challenges
Authors: Lynch Dave , Svoboda Jessica , Putta Sumanth , Hofland Hans E. J. , Chern Wendy H. , Hansen Laura A.
Published: April 2008

This report addresses 1) the predictability of mouse skin models for carcinogenic hazard identification, 2) the association between early changes in the skin and later tumorigenic responses, and 3) the relative sensitivity of three mouse models of skin tumorigenesis; i.e. the genetically-initiated Tg.AC and RasH2 lines and the SENCAR mouse model. All three mouse models responded similarly, with mild inflammation and epidermal hyperplasia, to several weeks of treatment with a topical agent. Based on our previous research experience, we hypothesized that inflammation, irritation, proliferation, and/or hyperplasia in the skin would precede and predict the appearance of tumors in these sensitive mouse skin models. Consistent with our hypothesis, the test agent caused a low but significant tumorigenic response in Tg.AC mice. We propose that inflammation, irritation, and hyperplasia are sensitive predictors of a later tumorigenic response in Tg.AC mice. Further studies are needed, however, to better determine the relative sensitivity of these 3 models to a wider variety of agents.
Novel Vascular Lesions in Mice Given a Non-Peptide Vitronectin Receptor Antagonist
Authors: Rehm Sabine , Thomas Roberta A. , Smith Kim S. , Mirabile Rosanna C. , Gales Tracy L. , Eustis Scot L. , Boyce Rogely W.
Published: April 2008

Novel vascular lesions were observed in mice given an αvβ3, αvβ5 receptor antagonist (SB-273005) for up to 3 months. Vascular smooth muscle cell (VSMC) necrosis was observed in aorta and renal hilar arteries approximately 6 hours after dosing followed by loss of VSMC, adaptive medial thickening by VSMC hypertrophy and deposition of PAS-positive matrix and collagen. Renal hilar and arcuate arteries developed delayed and transient fibrinoid necrosis and inflammation. Vascular regeneration was not evident following drug-withdrawal after 3 days of dosing. Vascular lesions were associated with necrosis, regeneration and fibrosis of heart, kidney and spleen consistent with initial ischemic injury followed by tissue repair. VSMC toxicity was likely not related to integrin antagonism because lesions were not observed with related compounds and no vascular changes were observed in other preclinical species. In vitro studies failed to demonstrate a direct toxic effect of SB-273005 on VSMC or unique species sensitivity of murine VSMC. In conclusion, SB-273005 caused VSMC necrosis in aorta and renal arteries of mice. Lesions did not progress or recover, but there was medial hypertrophic adaptation even with continued dosing. This is considered direct species-specific VSMC toxicity of unknown mechanism and unrelated to vitronectin receptor antagonism.
Mesial Temporal Lobe Epilepsy: Pathogenesis, Induced Rodent Models and Lesions
Authors: Sharma Alok K. , Reams Rachel Y. , Jordan William H. , Miller Margaret A. , Thacker H. Leon , Snyder Paul W.
Published: April 2008

Mesial temporal lobe epilepsy (MTLE), the most common epilepsy in adults, is generally intractable and is suspected to be the result of recurrent excitation or inhibition circuitry. Recurrent excitation and the development of seizures have been associated with aberrant mossy fiber sprouting in the hippocampus. Of the animal models developed to investigate the pathogenesis of MTLE, post-status epilepticus models have received the greatest acceptance because they are characterized by a latency period, the development of spontaneous motor seizures, and a spectrum of lesions like those of MTLE. Among post-status epilepticus models, induction of systemic kainic acid or pilocarpine-induced epilepsy is less labor-intensive than electrical-stimulation models and these models mirror the clinicopathologic features of MTLE more closely than do kindling, tetanus toxin, hyperthermia, post-traumatic, and perinatal hypoxia/ischemia models. Unfortunately, spontaneous motor seizures do not develop in kindling or adult hyperthermia models and are not a consistent finding in tetanus toxin-induced or perinatal hypoxia/ischemia models. This review presents the mechanistic hypotheses for seizure induction, means of model induction, and associated pathology, especially as compared to MTLE patients. Animal models are valuable tools not only to study the pathogenesis of MTLE, but also to evaluate potential antiepileptogenic drugs.
Interactions among Ytm1, Erb1, and Nop7 Required for Assembly of the Nop7-Subcomplex in Yeast Preribosomes
Authors: Tang Lan , Sahasranaman Aarti , Jakovljevic Jelena , Schleifman Erica , Woolford John L.
Published: April 2008

In Saccharomyces cerevisiae, more than 180 assembly factors associate with preribosomes to enable folding of pre-rRNA, recruitment of ribosomal proteins, and processing of pre-rRNAs to produce mature ribosomes. To examine the molecular architecture of preribosomes and to connect this structure to functions of each assembly factor, assembly subcomplexes have been purified from preribosomal particles. The Nop7-subcomplex contains three assembly factors: Nop7, Erb1, and Ytm1, each of which is necessary for conversion of 27SA3 pre-rRNA to 27SBS pre-rRNA. However, interactions among these three proteins and mechanisms of their recruitment and function in pre-rRNPs are poorly understood. Here we show that Ytm1, Erb1, and Nop7 assemble into preribosomes in an interdependent manner. We identified which domains within Ytm1, Erb1, and Nop7 are necessary for their interaction with each other and are sufficient for recruitment of each protein into preribosomes. Dominant negative effects on growth and ribosome biogenesis caused by overexpressing truncated Ytm1, Erb1, or Nop7 constructs, and recessive phenotypes of the truncated proteins revealed not only interaction domains but also other domains potentially important for each protein to function in ribosome biogenesis. Our data suggest a model for the architecture of the Nop7-subcomplex and provide potential functions of domains of each protein.
Vulnerable Multiracial Families and Early Years Services: Concerns, Challenges and Opportunities
Authors: Boushel Margaret
Published: April 2008

In Britain, very young mixed‐parentage children are more likely to receive state care than any other children. However, despite a dramatic increase in the number of multiracial families, their experiences have received little research attention. This article reviews the research on the experiences of vulnerable and poor multiracial families. Three areas of concern emerge—the relationship between family structure, locality and racism, disadvantage and oppression; the impact on family life of structurally reinforced and culturally defined gender roles; and the strengths and limitations of current early years research and practice. Suggestions are made about ways in which early years professionals might develop their practice with young vulnerable multiracial families.
Induction of leukemia‐specific antibodies by immunotherapy with leukemia‐cell‐derived heat shock protein 70
Authors: Jimbo Junko , Sato Kazuya , Hosoki Takaaki , Shindo Motohiro , Ikuta Katsuya , Torimoto Yoshihiro , Kohgo Yutaka
Published: April 2008

Cancer immunotherapy using heat shock protein (HSP) derived from autologous tumor requires cluster of differentiation (CD)4+ as well as CD8+ T‐cells for the prolongation of patient survival, suggesting that a humoral immune response through CD4+ T‐cells is important in addition to cellular immunity. However, the role of humoral responses in HSP‐based autologous tumor immunotherapy remains unclear. In the present study, we investigated whether leukemia‐specific antibodies and antibody‐mediated cytotoxicity against autologous leukemia cells have a crucial role in a mouse A20 leukemia model by immunizing A20‐derived HSP70. Immunization with A20‐derived HSP70 induced the production of anti‐A20‐antibodies and the antibodies recognized HSP70‐binding peptides derived from A20. One of those was a major histocompatibility complex (MHC) class‐I binding peptide, which has been clarified as the target peptide of CD8+ cytotoxic T‐cells (CTL) against A20. The anti‐A20‐antibodies produced by immunization with A20‐derived HSP70 induced complement‐dependent cytotoxicity (CDC) against A20 in vitro. In addition, immunization with A20‐derived HSP70 increased intracellular interleukin‐4 (IL4)‐production of CD4+ T‐cells, confirming the activation of type‐2 helper T‐cells. Taken together, immunization with leukemia‐cell‐derived HSP70 induces antibodies against leukemia‐cell‐specific peptides and might play a crucial role in the eradication of leukemia cells by CDC in mice. These findings will enable future establishment of a novel therapeutic strategy using antileukemia antibodies in HSP‐based autologous tumor immunotherapy. (Cancer Sci 2008; 99: 1427–1434)