bluuebunny/crossref_metadata_2025 huggingface dataset:
Bacterial diversity in rhizosphere soil from Antarctic vascular plants of Admiralty Bay, maritime Antarctica
Authors: Teixeira Lia C R S , Peixoto Raquel S , Cury Juliano C , Sul Woo Jun , Pellizari Vivian H , Tiedje James , Rosado Alexandre S
Published: April 2010

The Antarctic is a pristine environment that contributes to the maintenance of the global climate equilibrium. The harsh conditions of this habitat are fundamental to selecting those organisms able to survive in such an extreme habitat and able to support the relatively simple ecosystems. The DNA of the microbial community associated with the rhizospheres of Deschampsia antarctica Desv (Poaceae) and Colobanthus quitensis (Kunth) BartI (Caryophyllaceae), the only two native vascular plants that are found in Antarctic ecosystems, was evaluated using a 16S rRNA multiplex 454 pyrosequencing approach. This analysis revealed similar patterns of bacterial diversity between the two plant species from different locations, arguing against the hypothesis that there would be differences between the rhizosphere communities of different plants. Furthermore, the phylum distribution presented a peculiar pattern, with a bacterial community structure different from those reported of many other soils. Firmicutes was the most abundant phylum in almost all the analyzed samples, and there were high levels of anaerobic representatives. Also, some phyla that are dominant in most temperate and tropical soils, such as Acidobacteria, were rarely found in the analyzed samples. Analyzing all the sample libraries together, the predominant genera found were Bifidobacterium (phylum Actinobacteria), Arcobacter (phylum Proteobacteria) and Faecalibacterium (phylum Firmicutes). To the best of our knowledge, this is the first major bacterial sequencing effort of this kind of soil, and it revealed more than expected diversity within these rhizospheres of both maritime Antarctica vascular plants in Admiralty Bay, King George Island, which is part of the South Shetlands archipelago.
The LAILAPS Search Engine: A Feature Model for Relevance Ranking in Life Science Databases
Authors: Lange Matthias , Spies Karl , Colmsee Christian , Flemming Steffen , Klapperstück Matthias , Scholz Uwe
Published: April 2010

Efficient and effective information retrieval in life sciences is one of the most pressing challenge in bioinformatics. The incredible growth of life science databases to a vast network of interconnected information systems is to the same extent a big challenge and a great chance for life science research. The knowledge found in the Web, in particular in life-science databases, are a valuable major resource. In order to bring it to the scientist desktop, it is essential to have well performing search engines. Thereby, not the response time nor the number of results is important. The most crucial factor for millions of query results is the relevance ranking. In this paper, we present a feature model for relevance ranking in life science databases and its implementation in the LAILAPS search engine. Motivated by the observation of user behavior during their inspection of search engine result, we condensed a set of 9 relevance discriminating features. These features are intuitively used by scientists, who briefly screen database entries for potential relevance. The features are both sufficient to estimate the potential relevance, and efficiently quantifiable. The derivation of a relevance prediction function that computes the relevance from this features constitutes a regression problem. To solve this problem, we used artificial neural networks that have been trained with a reference set of relevant database entries for 19 protein queries. Supporting a flexible text index and a simple data import format, this concepts are implemented in the LAILAPS search engine. It can easily be used both as search engine for comprehensive integrated life science databases and for small in-house project databases. LAILAPS is publicly available for SWISSPROT data at http://lailaps.ipk-gatersleben.de
The Effect of Obesity and Weight Loss on Aortic Pulse Wave Velocity as Assessed by Magnetic Resonance Imaging
Authors: Rider Oliver J. , Tayal Upasana , Francis Jane M. , Ali Mohammed K. , Robinson Monique R. , Byrne James P. , Clarke Kieran , Neubauer Stefan
Published: April 2010

Obesity is an escalating global health problem associated with both an increased risk of death and an increased risk of cardiovascular events. Our goal was to use magnetic resonance imaging (MRI) to determine the effect of obesity and weight loss, in the absence of the traditional cardiovascular risk factors, on aortic pulse wave velocity (PWV) a reliable, reproducible, and accurate clinical measure of aortic stiffness linked to increased mortality. Fifty obese (BMI 38.3 ± 6.8 kg/m2) and eighteen normal‐weight controls (BMI 22.0 ± 1.7 kg/m2) with no identifiable cardiovascular risk factors underwent vascular MRI to assess PWV between the ascending aorta at the level of the pulmonary artery and the abdominal aorta (AA). Twenty‐eight subjects underwent repeat imaging after a 1‐year period of weight loss. Both groups were well matched for age, systolic blood pressure, fasting glucose, and total cholesterol. Obesity was associated with a 14% increase in PWV (P = 0.021), and with elevated C‐reactive protein (CRP) (P < 0.01) and leptin levels (P < 0.001) factors known to cause increase arterial stiffness. Weight loss (average 50% excess weight) was associated with a 14% improvement in PWV (P = 0.03), and with reductions in serum leptin levels (P < 0.01). Obesity, in the absence of the traditional cardiovascular risk factors, is associated with increased aortic PWV, a noninvasive clinical measure of aortic stiffness independently predictive of cardiovascular mortality. Significant weight loss results in improvements in aortic PWV. This may provide a potential link between both obesity and increased mortality, and the reduction in mortality that occurs with weight loss.
Adiposity in Childhood Is Related to C‐Reactive Protein and Adiponectin in Young Adulthood: From the Bogalusa Heart Study
Authors: Toprak Demet , Toprak Ahmet , Chen Wei , Xu Ji Hua , Srinivasan Sathanur , Berenson Gerald S.
Published: April 2010

To determine the association between cardiovascular (CV) risk factors in childhood and high‐sensitivity C‐reactive protein (hsCRP) and adiponectin in adulthood, 835 eligible white and African‐American young adult subjects (age range 24–42 years, average 34 years, 43% men, 31% African Americans) who had CV risk‐factor variable data from their childhood (20 years earlier, age range 5–18 years, average 14 years) were selected. Stepwise linear regression models revealed that mean logarithmic hsCRP level in adulthood was 0.02 greater with every increase of 1 mm in skinfold thickness in childhood, 0.25 greater for African Americans than whites, 0.36 greater for girls than boys, and 0.15 greater for every unit increase in BMI z score. Mean logarithmic adiponectin level in adulthood was 0.36 greater for girls than boys, 0.22 greater for whites than African Americans, and 0.01 less with every increase of 1 mm of childhood skinfold thickness. Seventy participants (8%) were overweight or obese in their childhood, and 64 of these (91%) remained obese in their young adulthood. In conclusion, childhood adiposity and African‐American race were associated with higher hsCRP and lower adiponectin levels in their adulthood. Skinfold thickness and BMI z score in childhood were the main obesity determinants for higher hsCRP and lower adiponectin levels in young adulthood.
Incorporating Computer-Aided Language Sample Analysis Into Clinical Practice
Authors: Price Lisa Hammett , Hendricks Sean , Cook Colleen
Published: April 2010

Purpose

During the evaluation of language abilities, the needs of the child are best served when multiple types and sources of data are included in the evaluation process. Current educational policies and practice guidelines further dictate the use of authentic assessment data to inform diagnosis and treatment planning. Language sampling and analysis (LSA) offers an important clinical tool for gathering such authentic assessment data, and computer-aided methods of LSA make it clinically feasible. The purpose of this tutorial is to provide step-by-step procedures for computer-aided LSA (CLSA).

Method

This tutorial includes instructions for a 4-step CLSA process: (a) eliciting a representative sample of the child’s language and recording it directly onto the computer; (b) transcribing the language sample; (c) analyzing the language sample and interpreting the results using a readily available software program, Systematic Analysis of Language Transcripts (SALT; J. Miller & A. Iglesias, 2006); and (d) using the results to plan the child’s treatment goals and activities. A case study is provided to illustrate this process.

Implications

Digital technologies can dramatically improve the feasibility of LSA, potentially transforming clinical practice by providing a quantifiable but naturalistic measure of language. This tutorial will facilitate the integration of useful technologies into clinical practice and provide information regarding the application of CLSA data.
Clinical Application of the Mean Babbling Level and Syllable Structure Level
Authors: Morris Sherrill R.
Published: April 2010

Purpose

This clinical exchange reviews two independent phonological assessment measures: mean babbling level (MBL) and syllable structure level (SSL). Both measures summarize phonetic inventory and syllable shape in a calculated average and have been used in research to describe the phonological abilities of children ages 9 to 36 months. An example of the measures' clinical use is presented.

Method

Six studies reporting MBL and SSL were reviewed. Combined, the studies included 207 participants. One hundred twenty-eight of those were developing language as expected, and 79 were identified as having speech-language impairment.

Conclusion

Overall, the studies indicate that SSL is a reliable measure that increases as children develop. Children with language impairment exhibit lower SSL scores than children with typical language skills. Further, a lower than expected MBL is predictive of a lack of meaningful speech at 24 months of age.

Implication

MBL and SSL have clinical application in terms of initial evaluation as well as progress monitoring. Recommendations for standardized corpus inclusion procedures are presented.
Identification of Clinical Markers of Specific Language Impairment in Adults
Authors: Poll Gerard H. , Betz Stacy K. , Miller Carol A.
Published: April 2010

Purpose

To investigate the usefulness of 3 tasks known to be effective diagnostic clinical markers of specific language impairment (SLI) in children: (a) nonword repetition, (b) sentence repetition, and (c) grammaticality judgments of finiteness marking.

Method

Two groups of young adults, 13 with SLI and 18 with typical language, completed 3 experimental tasks: (a) nonword repetition, (b) sentence repetition, and (c) grammaticality judgments of sentences that were either correct or contained an omitted finiteness marker, an overt agreement error, or an omitted progressive –
ing
. Analyses included receiver operating characteristic curve analyses and computation of likelihood ratios associated with the use of each task as a clinical marker for SLI, as well as development of a logistic regression model that used multiple tasks as predictors.

Results

Each marker task significantly contributed to classification of adults as affected or unaffected by SLI, with moderate positive and negative likelihood ratios. A combination of the 3 marker tasks was the best predictor of affectedness status with moderate to large likelihood ratios.

Conclusions

The results suggest that SLI persists into adulthood and that effective clinical markers of this disorder are similar to those used to identify SLI in children. Refinement of these tasks to increase their likelihood ratios will improve their usefulness in diagnosing SLI in adults.
Acoustic Analysis of the Voiced-Voiceless Distinction in Dutch Tracheoesophageal Speech
Authors: Jongmans Petra , Wempe Ton G. , van Tinteren Harm , Hilgers Frans J. M. , Pols Louis C. W. , van As-Brooks Corina J.
Published: April 2010

Purpose

Confusions between voiced and voiceless plosives and voiced and voiceless fricatives are common in Dutch tracheoesophageal (TE) speech. This study investigates (a) which acoustic measures are found to convey a correct voicing contrast in TE speech and (b) whether different measures are found in TE speech than in normal laryngeal (NL) speech. The main focus was on plosives.

Method

Nine TE and 5 NL speakers were included in this study. Fourteen acoustic measures were selected and analyzed. Comparisons were made between voiced and voiceless for the groups separately and between TE and NL speakers. Conditional inference trees were used to establish the most important distinguishing cue.

Results

TE speakers do not differ significantly from NL speakers, except for pitch-related measures. For plosives, all measures distinguished between voiced and voiceless for both speaker groups. The main distinguishing measure for the plosives was relative phonation time in the closure.

Conclusions

TE and NL speakers differ less in the way the voiced-voiceless distinction is conveyed than expected. Further research is needed to show whether the main acoustic cue is also perceptually most relevant.
On the bound of the Lyapunov exponents for the fractional differential systems
Authors: Li Changpin , Gong Ziqing , Qian Deliang , Chen YangQuan
Published: April 2010

In recent years, fractional(-order) differential equations have attracted increasing interests due to their applications in modeling anomalous diffusion, time dependent materials and processes with long range dependence, allometric scaling laws, and complex networks. Although an autonomous system cannot define a dynamical system in the sense of semigroup because of the memory property determined by the fractional derivative, we can still use the Lyapunov exponents to discuss its dynamical evolution. In this paper, we first define the Lyapunov exponents for fractional differential systems then estimate the bound of the corresponding Lyapunov exponents. For linear fractional differential system, the bounds of its Lyapunov exponents are conveniently derived which can be regarded as an example for the theoretical results established in this paper. Numerical example is also included which supports the theoretical analysis.
Conformal linear gravity in de Sitter space
Authors: Takook M. V. , Tanhayi M. R. , Fatemi S.
Published: April 2010

It has been shown that the theory of linear conformal quantum gravity must include a tensor field of rank-3 and mixed symmetry [Binegar et al., Phys. Rev. D 27, 2249 (1983)]. In this paper, we obtain the corresponding field equation in de Sitter space. Then, in order to relate this field with the symmetric tensor field of rank-2, Kαβ related to graviton, we will define homomorphisms between them. Our main result is that if one insists Kαβ to be a unitary irreducible representation of de Sitter and conformal groups, it must satisfy a field equation of order of 6, which is obtained.
Direct multiscale coupling of a transport code to gyrokinetic turbulence codes
Authors: Barnes M. , Abel I. G. , Dorland W. , Görler T. , Hammett G. W. , Jenko F.
Published: April 2010

Direct coupling between a transport solver and local, nonlinear gyrokinetic calculations using the multiscale gyrokinetic code TRINITY [M. Barnes, “TRINITY: A unified treatment of turbulence, transport, and heating in magnetized plasmas,” Ph.D. thesis, University of Maryland, 2008 (eprint arXiv:0901.2868)] is described. The coupling of the microscopic and macroscopic physics is done within the framework of multiscale gyrokinetic theory, of which we present the assumptions and key results. An assumption of scale separation in space and time allows for the simulation of turbulence in small regions of the space-time grid, which are embedded in a coarse grid on which the transport equations are implicitly evolved. This leads to a reduction in computational expense of several orders of magnitude, making first-principles simulations of the full fusion device volume over the confinement time feasible on current computing resources. Numerical results from TRINITY simulations are presented and compared with experimental data from JET [M. Keilhacker, Plasma Phys. Controlled Fusion 41, B1 (1999)] and ASDEX Upgrade [O. Gruber, Nucl. Fusion 47, S622 (2007)] plasmas.
Evolution of helicity in fluid flows
Authors: Scofield D. F. , Huq Pablo
Published: April 2010

An invariant helicity integral and a differential helicity evolution equation are found for viscous fluid flows. A geometrodynamical approach is used, which includes a vortex field. The vortex field is derivable from a vector potential A. The vector potential is then used to characterize the evolution of flow topology. The source of the helicity is found to be the topological parity k=2λω⋅ζ and the moving boundary surfaces of the fluid. Here, ω and ζ are the vorticity and swirl components of the vortex field {ω,ζ} and λ is a constitutive or material parameter of the fluid. Our first result using the vector calculus identifies the scalar helicity as ht=Aω. This result is then generalized using the calculus of differential forms, yielding other results including the existence of a helicity current vector proportional to (ϕω−λA×ζ).
Nonlinear Wood anomalies in the reflectivity of layered superconductors
Authors: Apostolov S. S. , Maizelis Z. A. , Sorokina M. A. , Yampol’skiĭ V. A.
Published: April 2010

The excitation of nonlinear surface Josephson plasma waves in slabs of layered superconductors is studied theoretically by means of incident plane waves using the prism method in the Otto configuration. The bilateral excitation symmetric with respect to the magnetic field is considered. The excitation leads to the resonant suppression of the specular reflection, i.e. to the Wood anomalies. Due to the nonlinearity the reflectivity resonantly depends not only on the wave frequency ω and the incident angle θ but on the wave amplitude h as well. It is shown that total suppression of reflectivity can be attained by an appropriate choice of ω, θ, h, and other parameters of the problem. The results of the analytical calculations are supported by numerical simulations.
The evidence of a new magnetic anomaly in Zn-doped LSCO cuprates
Authors: Nadareishvili M. M. , Kvavadze K. A.
Published: April 2010

The low-temperature heat capacity in pure (y=0) and Zn-doped La1.84Sr0.16Cu1−yZnyO4 samples (y=0.033 and 0.06) have been performed in the temperature interval 1.8–60K by the method of high-precision pulsed differential calorimetry, providing measurements under the equilibrium conditions in contrast to commonly used differential scanning calorimeters. For these systems a new heat capacity anomaly was observed in the nonsuperconducting state, which is related with Zn impurities and has the form of single wide peak. The anomaly does not show a phonon character as it strongly shifts towards higher temperatures with increasing Zn content, as is characteristic for a magnetic anomaly. The anomaly increases almost linearly with the impurity concentration.
Effect of Cd content on the kinetics of low-temperature structural transformation in In–Cd alloy
Authors: Pal’-Val’ P. P. , Pal’-Val’ L. N. , Ostapovets A. A. , Vanek P.
Published: April 2010

The effect of the Cd concentration on the kinetics of a spontaneous low-temperature structural phase transformation previously observed in the martensite phase of the solid solution In–Cd is investigated. Acoustic, resistive, and calorimetric measurements are performed in the temperature interval 100–340K on samples containing 4.3, 5.5, and 6.6at.% Cd. It is established that the transformation rate increases considerably with increasing Cd concentration. The empirical activation parameters of the transformation are obtained: activation energy U0=0.43eV and period of attempts τ0=5⋅10−9s. It is shown that this transformation has the characteristic features of a first-order phase transition. It is suggested that the low-temperature isothermal instability of the macroscopic properties of the alloy is due to the decomposition of the In-based solid solution. The substantial increase of the decomposition rate with increasing Cd concentration could be due to an increase of the driving force of this process.
Dynamic transitions in a three dimensional associating lattice gas model
Authors: Szortyka Marcia M. , Girardi Mauricio , Henriques Vera B. , Barbosa Marcia C.
Published: April 2010

We investigate the thermodynamic and dynamic properties of a three dimensional associating lattice gas (ALG) model through Monte Carlo simulations. The ALG model combines a soft core potential and orientational degrees of freedom. The competition of directional attractive forces and the soft core potential results in two coexisting liquid phases which are also connected through order-disorder critical transitions. The model presents structural order, density, and diffusion anomalies. Our study suggests that the dynamic fragile-to-strong transitions are associated to changes in structural order.
Epitaxial lift-off for sample preparation of x-ray absorption fine structure
Authors: Higashi Kotaro , Ishikawa Fumitaro , Handa Katsumi , Emura Shuichi , Kondow Masahiko
Published: April 2010

We propose a simple sample preparation technique of x-ray absorption fine structure (XAFS) for its application to the individual layer of practical compound semiconductor devices. An epitaxial lift-off process enables the investigation of pure uppermost thin epitaxial layer without containing information of the bottom-side layers as well as substrate. The plain procedure offers smooth thin film with desired thickness preserving its crystallographic structure, suitable for the measurement. We carry out XAFS measurements for 2.0 and 0.2 μm thick GaAs epitaxial layer at transmission and fluorescence mode, respectively. Clear extended-XAFS oscillation is obtained, and the radial distribution function of which deduces accurate first nearest-neighbor Ga–As bond length to be 2.46 Å for both the samples. That shows the feasibility of the proposed technique for the analysis of the precise atomic configurations of thin film semiconductors.
Strong symmetrical non-Oberbeck–Boussinesq turbulent convection and the role of compressibility
Authors: Burnishev Yuri , Segre Enrico , Steinberg Victor
Published: April 2010

Strong non-Oberbeck–Boussinesq (OB) effects in turbulent convection were investigated experimentally in SF6 in the vicinity of its gas-liquid critical point (CP). The temperature and density dependencies of the thermodynamic and kinetic properties of SF6 near its CP and at the average critical density lead to strong but symmetric vertical variations of the main physical properties, which enter into the control parameters of turbulent convection. This produces an up-down symmetry in the temperature drops across the upper and lower half of the cell, while the temperature in the middle of the cell remains equal to the average value. Thus, in spite of the strong variations of the fluid properties across the cell height, the up-down symmetry remains like in the OB case. The distinctive feature of the symmetric non-OB turbulent convection is that the heat transport scales with the Rayleigh number Ra like in the OB turbulent convection. At the same time, it shows a much stronger dependence on the Prandtl number Pr. We singled out the influence of the non-OB effect on the heat transport and found that, for the same Pr, an eightfold larger non-OB effect does not alter either the value of the Nusselt number, Nu, nor its scaling with respect to the Rayleigh number, Nu∝Raγ. The conclusion is that the strong symmetric non-OB effect by itself is not responsible for the strong Pr dependence of the heat transport near CP. The possible source of this Pr dependence is the strongly enhanced isothermal compressibility in the vicinity of CP, which can affect the dynamics of plumes and so the heat transport close to the CP, and manifests itself in a dependence of Nu on Pr much steeper than in the OB case.
From brain to earth and climate systems: Small-world interaction networks or not?
Authors: Bialonski Stephan , Horstmann Marie-Therese , Lehnertz Klaus
Published: April 2010

We consider recent reports on small-world topologies of interaction networks derived from the dynamics of spatially extended systems that are investigated in diverse scientific fields such as neurosciences, geophysics, or meteorology. With numerical simulations that mimic typical experimental situations, we have identified an important constraint when characterizing such networks: indications of a small-world topology can be expected solely due to the spatial sampling of the system along with the commonly used time series analysis based approaches to network characterization.
Hidden imperfect synchronization of wall turbulence
Authors: Tardu Sedat F.
Published: April 2010

Instantaneous amplitude and phase concept emerging from analytical signal formulation is applied to the wavelet coefficients of streamwise velocity fluctuations in the buffer layer of a near wall turbulent flow. Experiments and direct numerical simulations show both the existence of long periods of inert zones wherein the local phase is constant. These regions are separated by random phase jumps. The local amplitude is globally highly intermittent, but not in the phase locked regions wherein it varies smoothly. These behaviors are reminiscent of phase synchronization phenomena observed in stochastic chaotic systems. The lengths of the constant phase inert (laminar) zones reveal a type I intermittency behavior, in concordance with saddle-node bifurcation, and the periodic orbits of saddle nature recently identified in Couette turbulence. The imperfect synchronization is related to the footprint of coherent Reynolds shear stress producing eddies convecting in the low buffer.
The dynamics of laser droplet generation
Authors: Krese Blaž , Perc Matjaž , Govekar Edvard
Published: April 2010

We propose an experimental setup allowing for the characterization of laser droplet generation in terms of the underlying dynamics, primarily showing that the latter is deterministically chaotic by means of nonlinear time series analysis methods. In particular, we use a laser pulse to melt the end of a properly fed vertically placed metal wire. Due to the interplay of surface tension, gravity force, and light-metal interaction, undulating pendant droplets are formed at the molten end, which eventually completely detach from the wire as a consequence of their increasing mass. We capture the dynamics of this process by employing a high-speed infrared camera, thereby indirectly measuring the temperature of the wire end and the pendant droplets. The time series is subsequently generated as the mean value over the pixel intensity of every infrared snapshot. Finally, we employ methods of nonlinear time series analysis to reconstruct the phase space from the observed variable and test it against determinism and stationarity. After establishing that the observed laser droplet generation is a deterministic and dynamically stationary process, we calculate the spectra of Lyapunov exponents. We obtain a positive largest Lyapunov exponent and a negative divergence, i.e., sum of all the exponents, thus indicating that the observed dynamics is deterministically chaotic with an attractor as solution in the phase space. In addition to characterizing the dynamics of laser droplet generation, we outline industrial applications of the process and point out the significance of our findings for future attempts at mathematical modeling.
Neutral-gas depletion and repletion in plasmas
Authors: Fruchtman A. , Rax J.-M.
Published: April 2010

Repletion of neutrals, an unexpected increase in the neutral-gas density when ionization is intense, has been recently predicted to occur in a gas discharge when a thermalized neutral gas is collisionless enough, so that its inertia dominates over the drag by collisions with ions. A parameter is identified here that determines which process should occur, neutral-gas repletion or the more expected neutral-gas depletion. The particle and momentum balance equations of the plasma and neutrals are solved, and it is demonstrated how when this parameter is varied, the neutral-gas density exhibits a transition between depletion and repletion.
Liquid/vapor coexistence and surface tension of the Sutherland fluid with a variable range of interaction: Computer simulation and perturbation theory studies
Authors: Melnyk Roman , Orea Pedro , Nezbeda Ivo , Trokhymchuk Andrij
Published: April 2010

The liquid-vapor phase diagram and surface tension for the Sutherland fluids with a variable range of interaction have been determined by canonical Monte Carlo simulations and compared with the augmented van der Waals analytic theory. The theory, based on a short-range Yukawa reference, performs well for medium-range models but its accuracy deteriorates with the shortening range due to deteriorating accuracy of the underlined analytic mean spherical approximation solution for the reference Yukawa potential. The simulation results are also analyzed from the point of the extended principle of corresponding states and it is shown that the surface tension and also, to a certain degree of accuracy, the vapor-liquid coexistence curve satisfy the principle.
Statistics of mixing in three-dimensional Rayleigh–Taylor turbulence at low Atwood number and Prandtl number one
Authors: Boffetta G. , Mazzino A. , Musacchio S. , Vozella L.
Published: April 2010

Three-dimensional miscible Rayleigh–Taylor (RT) turbulence at small Atwood number and at Prandtl number one is investigated by means of high resolution direct numerical simulations of the Boussinesq equations. RT turbulence is a paradigmatic time-dependent turbulent system in which the integral scale grows in time following the evolution of the mixing region. In order to fully characterize the statistical properties of the flow, both temporal and spatial behaviors of relevant statistical indicators have been analyzed. Scaling of both global quantities (e.g., Rayleigh, Nusselt, and Reynolds numbers) and scale dependent observables built in terms of velocity and temperature fluctuations are considered. We extend the mean-field analysis for velocity and temperature fluctuations to take into account intermittency, both in time and space domains. We show that the resulting scaling exponents are compatible with that of the classical Navier–Stokes turbulence advecting a passive scalar at comparable Reynolds number. Our results support the scenario of universality of turbulence with respect to both the injection mechanism and the geometry of the flow.
Clustering effects in Ga(AsBi)
Authors: Imhof Sebastian , Thränhardt Angela , Chernikov Alexej , Koch Martin , Köster Niko S. , Kolata Kolja , Chatterjee Sangam , Koch Stephan W. , Lu Xianfeng , Johnson Shane R. , Beaton Dan A. , Tiedje Thomas , Rubel Oleg
Published: April 2010

The photoluminescence from a Ga(AsBi) sample is investigated as a function of pump power and lattice temperature. The disorder-related features are analyzed using a Monte Carlo simulation technique. A two-scale approach is introduced to separately account for cluster localization and alloy disorder effects. The corresponding characteristic energy scales of 11 and 45 meV are deduced from the detailed comparison between experiment and simulation.
Influence of different dielectrics on the first layer grain sizes and its effect on the mobility of pentacene-based thin-film transistors
Authors: Hu Yuanyuan , Qi Qiong , Jiang Chao
Published: April 2010

Pentacene thin-film transistors using different dielectrics including thermal oxide SiO2 and a series of bilayered dielectrics that are polymethyl methacrylate/SiO2, polycarbonate/SiO2, and polystyrene/SiO2 were fabricated. Atomic force microscopic measurements indicated that grain sizes of the submonolayer films were drastically different with the various dielectrics. Dielectrics with lower surface energy lead to larger grain sizes at the first monolayer and consequently higher mobility of the fabricated transistors. The correlation between the mobility and the grain sizes at the first monolayer of the pentacene films could be explained by utilizing a microscopic mobility model relating to the grains and grain boundaries.
Control of spin-polarized current in a scanning tunneling microscope by single-atom transfer
Authors: Ziegler M. , Ruppelt N. , Néel N. , Kröger J. , Berndt R.
Published: April 2010

The spin polarization of the tunneling current between a Cr-covered scanning tunneling microscope tip and a Fe-covered W(110) surface was controllably modified by transferring single Cr atoms from the tip to the surface. Reproducible reversal of the spin polarization enables the discrimination of magnetic from electronic properties without the need of an external magnetic field.
Magnetic and transport properties of epitaxial (LaBa)Co2O5.5+δ thin films on (001) SrTiO3
Authors: Liu M. , Liu J. , Collins G. , Ma C. R. , Chen C. L. , He J. , Jiang J. C. , Meletis E. I. , Jacobson A. J. , Zhang Q. Y.
Published: April 2010

The (LaBa)Co2O5+δ thin films were grown on (001) SrTiO3 single crystal substrates by using pulsed laser deposition. Microstructure studies from x-ray diffraction and electron microscopy show that the films have good epitaxial quality with a-axis orientation and sharp atomic interface. Transport property and isothermal magnetoresistance measurements have been used to understand the physical properties of the films with anomalous magnetic phenomena and the largest reported magnetoresistance value of 19% at 40 K.
Spin polarized electron transport through a graphene nanojunction
Authors: Lü Xiaoling , Zheng Yisong , Xin Huanwen , Jiang Liwei
Published: April 2010

The electronic transmission spectrum of a graphene nanojunction formed by interconnecting two armchair-edged graphene nanoribbons is obtained by the first principle calculation. We find that in such a simple structure the electronic transmission is remarkably spin-polarized when its size is not very small. By calculating the local density of states and electron occupation numbers on some typical atoms at the scattering region, we conclude that the origin of the spin-polarization is the antiresonance effect, generated by the edge state localized at the zigzag-edged shoulder of the nanojunction.
Effect of integral proteins in the phase stability of a lipid bilayer: Application to raft formation in cell membranes
Authors: Gómez Jordi , Sagués Francesc , Reigada Ramon
Published: April 2010

The existence of lipid rafts is a controversial issue. The affinity of cholesterol for saturated lipids is manifested in macroscopic phase separation in model membranes, and is believed to be the thermodynamic driving force for raft formation. However, there is no clear reason to explain the small (nanometric) size of raft domains in cell membranes. In a recent paper Yethiraj and Weisshaar [Biophys. J. 93, 3113 (2007)] proposed that the effect of neutral integral membrane proteins may prevent from the formation of large lipid domains. In this paper we extend this approach by studying the effect of the protein size, as well as the lipid-protein interaction. Depending on these factors, two different mechanisms for nanodomain stabilization are shown to be possible for static proteins. The application of these results to a biological context is discussed.
A multiyear comparison of the male reproductive biology of the brown treesnake (Boiga irregularis) from Guam and the native range
Authors: Aldridge Robert D. , Siegel Dustin S. , Bufalino Angelo P. , Wisniewski Samantha S. , Jellen Benjamin C.
Published: April 2010

Previous studies have suggested that reproduction in the brown treesnake (Boiga irregularis) is reduced on Guam because of elevated stress hormones caused by limited food availability. This study examined the reproductive anatomy of male brown treesnakes on Guam over a 15-year period (1985–99) to determine whether the size at maturity and development of the testis and sexual segment of the kidney varied between years and to compare these data to those for snakes collected from the native range. On Guam, the average snout–vent length and body mass of B. irregularis has decreased from its high in 1985 and remained stable from 1989 to 1999. The snout–vent length at maturity was similar between years. Mean diameters of the seminiferous tubule and the sexual segment of the kidney were not significantly different between years. However, the number of sexual segment tubules hypertrophied per snake varied greatly. Snakes from the native range matured at smaller snout–vent lengths and had significantly more hypertrophied sexual segment tubules per kidney than populations on Guam. These data suggest that elevated plasma levels of corticosterone, potentially due to an increase in male–male interactions as a result the explosive population growth experienced on Guam, may be negatively influencing male reproduction.
The use of den trees by the squirrel glider (Petaurus norfolcensis) in temperate Australian woodlands
Authors: Crane Mason J. , Lindenmayer David B. , Cunningham Ross B.
Published: April 2010

Effective conservation relies on understanding the biology of particular species and how they use key resources. For many arboreal mammals, tree hollows are a key den site. We examined the use of tree hollows by the squirrel glider (Petaurus norfolcensis) in south-eastern Australia. Over a five-month study, individual squirrel gliders used multiple hollow trees (average = 7) as den sites. Den sites were often adjacent to areas where nocturnal activities took place. The average distance between den sites used by individual gliders on successive days was 218 m. Dens were often shared by an adult pair and a juvenile. Den trees were disproportionably used, with gliders showing preference for 1–2 primary den trees often located on steep slopes. Our findings have implications for the number and spatial arrangement of den trees needed to promote the conservation of populations of the squirrel glider, particularly where land is used for agriculture and livestock grazing.
Modification of divertor heat and particle flux profiles with applied 3D fields in NSTX H-mode plasmas
Authors: Ahn J.-W. , Canik J.M. , Soukhanovskii V.A. , Maingi R. , Battaglia D.J.
Published: April 2010

Externally imposed non-axisymmetric magnetic perturbations are observed to alter divertor heat and particle flux profiles in the National Spherical Torus Experiment (NSTX). The divertor profiles are found to have a modest level of multiple local peaks, characteristic of strike point splitting or the ‘magnetic lobe’ structure, even before the application of the 3D fields in some (but not all) NSTX discharges. This is thought to be due to the intrinsic error fields. The applied 3D fields augmented the intrinsic strike point splitting, making the amplitude of local peaks and valleys larger in the divertor profile and striations at the divertor surface brighter. The measured heat flux profile shows that the radial location and spacing of the striations are qualitatively consistent with a vacuum field tracing calculation. 3D field application did not change the peak divertor heat and particle fluxes at the toroidal location of measurement. Spatial characteristics of the observed patterns are also reported in the paper.
On the endofiniteness of a key module over pure semisimple rings
Authors: Dung Nguyen , García José
Published: April 2010

Let

R
R

be a left pure semisimple ring such that there are no non-zero homomorphisms from preinjective modules to non-preinjective indecomposable modules in

R
R

-mod, and let

W
W

be the left key

R
R

-module; i.e.,

W
W

is the direct sum of all non-isomorphic non-preinjective indecomposable direct summands of products of preinjective left

R
R

-modules. We show that if the module

W
W

is endofinite, then

R
R

is a ring of finite representation type. This settles a question considered in [L. Angeleri Hügel, A key module over pure-semisimple hereditary rings, J. Algebra 307 (2007), 361-376] for hereditary rings.
Approximation by strongly annular solutions of functional equations
Authors: Daquila R.
Published: April 2010

A major result of this paper is that the set of all functions

g
(
z
)

g(z)

such that

g
g

is strongly annular and is a solution of a Mahler type of functional equation given by

g
(
z
)
=
q
(
z
)
g
(

z
p

)

g(z)=q(z)g(z^p)

where

p
≥
2

p\ge 2

is an integer and

q
q

is a polynomial with

q
(
0
)
=
1

q(0)=1

is a dense first category set in the set of all holomorphic functions on the open unit disk with the topology of almost uniform convergence. A second result is that strongly annular solutions of these types of functional equations are dense in the space of holomorphic functions with Maclaurin coefficients of

±
1

\pm 1

with the same topology.
On the degree of rapid decay
Authors: Nica Bogdan
Published: April 2010

A finitely generated group

Γ
\Gamma

equipped with a word-length is said to satisfy property RD if there are

C
,
s
≥
0

C, s\geq 0

such that, for all non-negative integers

n
n

, we have

‖
a
‖
≤
C
(
1
+
n

)
s

‖
a

‖
2

\|a\|\leq C (1+n)^s \|a\|_2

whenever

a
∈

C

Γ

a\in \mathbb {C}\Gamma

is supported on elements of length at most

n
n

.

We show that, for infinite

Γ
\Gamma

, the degree

s
s

is at least

1

/

2

1/2

.
The real plank problem and some applications
Authors: Muñoz-Fernández G. , Sarantopoulos Y. , Seoane-Sepúlveda J.
Published: April 2010

K. Ball has proved the “complex plank problem”: if(xk)k=1n\left (x_{k}\right )_{k=1}^{n}is a sequence of norm11vectors in acomplexHilbert space(H,⟨⋅,⋅⟩)\left (H, \, \langle \cdot ,\cdot \rangle \right ), then there exists a unit vectorxxfor which\[|⟨x,xk⟩|≥1/n,k=1,…,n.\left |\langle {x}, x_{k}\rangle \right |\geq 1/\sqrt {n}\,,\quad k=1, \ldots , n\,.\]In general, this result is not true onrealHilbert spaces. However, in special cases we prove that the same result holds true. In general, for some unit vectorxxwe have derived the estimate\[<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="StartAbsoluteValue mathematical left-angle x comma x Subscript k Baseline mathematical right-angle EndAbsoluteValue greater-than-or-equal-to max left-brace right-brace comma slash slash lamda 1 n comma slash slash 1 times times lamda nn comma">|⟨x,xk⟩|≥max{λ1/n,1/λnn},\left |\langle {x}, x_{k}\rangle \right | \geq \max \left \{\sqrt {\lambda _{1}/n},\, 1/\sqrt {\lambda _{n}n}\right \}\,,\]whereλ1\lambda _{1}is the smallest andλn\lambda _{n}is the largest eigenvalue of the Hermitian matrixA=[⟨xj,xk⟩]A=\left [\langle {x_{j}}, x_{k}\rangle \right ],j,k=1,…,nj, k=1, \ldots , n. We have also improved known estimates for the norms of homogeneous polynomials which are products of linear forms on real Hilbert spaces.
On identities involving the sixth order mock theta functions
Authors: Lovejoy Jeremy
Published: April 2010

We present

q
q

-series proofs of four identities involving sixth order mock theta functions from Ramanujan’s lost notebook. We also show how Ramanujan’s identities can be used to give a quick proof of four sixth order identities of Berndt and Chan.
On a symplectic generalization of Petrie’s conjecture
Authors: Tolman Susan
Published: April 2010

Motivated by the Petrie conjecture, we consider the following questions: Let a circle act in a Hamiltonian fashion on a compact symplectic manifold

(
M
,
ω
)

(M,\omega )

which satisfies
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper H Superscript 2 i Baseline left-parenthesis upper M semicolon double-struck upper R right-parenthesis equals upper H Superscript 2 i Baseline left-parenthesis double-struck upper C double-struck upper P Superscript n Baseline comma double-struck upper R right-parenthesis">

H

2
i

(
M
;

R

)
=

H

2
i

(

C

P

n

,

R

)

H^{2i}(M;\mathbb {R}) = H^{2i}({\mathbb C}{\mathbb P}^n,\mathbb {R})

for all

i
i

. Is
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper H Superscript j Baseline left-parenthesis upper M semicolon double-struck upper Z right-parenthesis equals upper H Superscript j Baseline left-parenthesis double-struck upper C double-struck upper P Superscript n Baseline semicolon double-struck upper Z right-parenthesis">

H
j

(
M
;

Z

)
=

H
j

(

C

P

n

;

Z

)

H^j(M;\mathbb {Z}) = H^j({\mathbb C}{\mathbb P}^n;\mathbb {Z})

for all

j
j

? Is the total Chern class of

M
M

determined by the cohomology ring

H
∗

(
M
;

Z

)

H^*(M;\mathbb {Z})

? We answer these questions in the six-dimensional case by showing that

H
j

(
M
;

Z

)

H^j(M;\mathbb {Z})

is equal to

H
j

(

C

P

3

;

Z

)

H^j({\mathbb C}{\mathbb P}^3;\mathbb {Z})

for all

j
j

, by proving that only four cohomology rings can arise, and by computing the total Chern class in each case. We also prove that there are no exotic actions. More precisely, if

H
∗

(
M
;

Z

)

H^*(M;\mathbb {Z})

is isomorphic to

H
∗

(

C

P

3

;

Z

)

H^*({\mathbb C}{\mathbb P}^3;\mathbb {Z})

or
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper H Superscript asterisk Baseline left-parenthesis ModifyingAbove upper G With tilde Subscript 2 Baseline left-parenthesis double-struck upper R Superscript 5 Baseline right-parenthesis semicolon double-struck upper Z right-parenthesis">

H
∗

(

G
~

2

(

R

5

)
;

Z

)

H^*(\widetilde {G}_2(\mathbb {R}^5);\mathbb {Z})

, then the representations at the fixed components are compatible with one of the standard actions; in the remaining two cases, the representation is strictly determined by the cohomology ring. Finally, our results suggest a natural question: Do the remaining two cohomology rings actually arise? This question is closely related to some interesting problems in symplectic topology, such as embeddings of ellipsoids.
The Ethanol Extract of Fructus trichosanthis Promotes Fetal Hemoglobin Production via p38 MAPK Activation and ERK Inactivation in K562 Cells
Authors: Li Hui , Ko Chun Hay , Tsang Suk Ying , Leung Ping Chung , Fung Ming Chui , Fung Kwok Pui
Published: April 2010

Pharmacological stimulation of fetal hemoglobin (HbF) expression may be a promising approach for the treatment of beta‐thalassemia. In this study, the effects of Fructus trichosanthis (FT) were investigated in human erythroleukemic K562 cells for their gamma‐globin mRNA and HbF‐induction activities. The role of signaling pathways, including extracellular regulated protein kinase (ERK) and p38 mitogen‐activated protein kinase (MAPK), was also investigated. It was found that the ethanol extract of FT significantly increased gamma‐globin mRNA and HbF levels, determined by real‐time reverse transcription polymerase chain reaction and enzyme linked immunosorbent assay, respectively, in dose‐ and time‐dependent manner. Total Hb (THb) levels were also elevated in the concentrations without cytotoxicity (<80 μg mL−1). Pre‐treatment with p38 MAPK inhibitor SB203580 blocked the stimulatory effects of FT extract in total and HbF induction. In contrast, no change in HbF was observed when treated with ERK inhibitor PD98059. Furthermore, FT ethanol extract activated p38 MAPK and inhibited ERK signaling pathways in K562 cells, as revealed in western blotting analysis. In addition, SB203580 significantly abolished p38 MAPK activation when the cells were treated with FT. In summary, the ethanol extract of FT was found to be a potent inducer of HbF synthesis in K562 cells. The present data delineated the role of ERK and p38 MAPK signaling as molecular targets for pharmacologic stimulation of HbF production upon FT treatment.