bluuebunny/crossref_metadata_2025 huggingface dataset:
Inertial-range intermittency and accuracy of direct numerical simulation for turbulence and passive scalar turbulence
Authors: WATANABE TAKESHI , GOTOH TOSHIYUKI
Published: October 2007

We examine the effects of the variation in dissipation-range resolution on the accuracy of inertial-range statistics and intermittency in terms of the direct numerical simulations of homogeneous turbulence and passive-scalar turbulence by changing the spatial resolution up to 20483 grid points while maintaining a constant Reynolds number at Rλ ≃ 180 or ≃ 420 and Schmidt number at Sc = 1. Although large fluctuations of the derivative fields depended strongly on Kmaxη and were underestimated when Kmaxη≃1, where Kmax is the maximum wavenumber in the computations and η is the mean Kolmogorov length, the behaviour of the spectra and the scaling exponents of the structure functions up to the eighth order in the range of scales greater than 10η was insensitive to variations in Kmaxη, even when Kmaxη≃1. The relationship between the spatial resolution and asymptotic tail of the probability density functions of the energy dissipation fields was studied using the multifractal model for dissipation, and the results were confirmed by comparison to the simulation data. Degradation of the statistics arises from modifications to the flow dynamics due to the finite wavenumber cutoff and the use of a coarser filter width for the data, which is obtained using a reasonable accuracy criterion for the flow dynamics. The effect of the former was less than that of the latter for the low-to-moderate-order statistics when Kmaxη≥1. We also discuss the universality of the inertial-range statistics with respect to variations in the dissipation-range characteristics.
Internal gravity waves generated by a turbulent bottom Ekman layer
Authors: TAYLOR JOHN R. , SARKAR SUTANU
Published: October 2007

Internal gravity waves excited by the turbulent motions in a bottom Ekman layer are examined using large-eddy simulation. The outer flow is steady and uniformly stratified while the density gradient is set to zero at the flat lower wall. After initializing with a linear density profile, a mixed layer forms near the wall separated from the ambient stratification by a pycnocline. Two types of internal wave are observed. Waves with frequencies larger than the free-stream buoyancy frequency are seen in the pycnocline, and vertically propagating internal waves are observed in the outer layer with characteristic frequency and wavenumber spectra. Since a signature of the pycnocline waves is observed in the frequency spectrum of the mixed layer, these waves may affect the boundary-layer turbulence. The dominant outer-layer waves have a group velocity directed 35-60° from the vertical axis, which is consistent with previous laboratory studies. The energy flux associated with the radiated waves is small compared to the integrated dissipation in the boundary layer, but is of the same order as the integrated buoyancy flux. A linear model is proposed to estimate the decay in wave amplitude owing to viscous effects. Starting from the observed wave amplitudes at the bottom of the pycnocline, the model prediction for the spectral distribution of the outer layer wave amplitude compares favourably with the simulation results.
Drag on spheres in micropolar fluids with non-zero boundary conditions for microrotations
Authors: HOFFMANN KARL-HEINZ , MARX DAVID , BOTKIN NIKOLAI D.
Published: October 2007

The Stokes formula for the resistance force exerted on a sphere moving with constant velocity in a fluid is extended to the case of micropolar fluids. A non-homogeneous boundary condition for the micro-rotation vector is used: the micro-rotation on the boundary of the sphere is assumed proportional to the rotation rate of the velocity field on the boundary.
Experimental investigations of turbulent drag reduction by surface-embedded grooves
Authors: FROHNAPFEL B. , JOVANOVIĆ J. , DELGADO A.
Published: October 2007

Consideration of near-wall turbulence in the functional space that emphasizes the level of anisotropy of the velocity fluctuations not only provides an understanding of th causative physics behind remarkable effects of turbulent drag reduction, but also lead to the logical design of a surface topology which is shown experimentally to be capable o producing a significant reduction of viscous drag which far exceeds what has been achieved so far.
A randomized controlled trial with 4-month follow-up of adjunctive repetitive transcranial magnetic stimulation of the left prefrontal cortex for depression
Authors: Mogg A. , Pluck G. , Eranti S. V. , Landau S. , Purvis R. , Brown R. G. , Curtis V. , Howard R. , Philpot M. , McLoughlin D. M.
Published: October 2007

Background

Effectiveness of repetitive transcranial magnetic stimulation (rTMS) for major depression is unclear. The authors performed a randomized controlled trial comparing real and sham adjunctive rTMS with 4-month follow-up.

Method

Fifty-nine patients with major depression were randomly assigned to a 10-day course of either real (n=29) or sham (n=30) rTMS of the left dorsolateral prefrontal cortex (DLPFC). Primary outcome measures were the 17-item Hamilton Depression Rating Scale (HAMD) and proportions of patients meeting criteria for response (⩾50% reduction in HAMD) and remission (HAMD⩽8) after treatment. Secondary outcomes included mood self-ratings on Beck Depression Inventory-II and visual analogue mood scales, Brief Psychiatric Rating Scale (BPRS) score, and both self-reported and observer-rated cognitive changes. Patients had 6-week and 4-month follow-ups.

Results

Overall, Hamilton Depression Rating Scale (HAMD) scores were modestly reduced in both groups but with no significant group×time interaction (p=0.09) or group main effect (p=0.85); the mean difference in HAMD change scores was −0.3 (95% CI −3.4 to 2.8). At end-of-treatment time-point, 32% of the real group were responders compared with 10% of the sham group (p=0.06); 25% of the real group met the remission criterion compared with 10% of the sham group (p=0.2); the mean difference in HAMD change scores was 2.9 (95% CI −0.7 to 6.5). There were no significant differences between the two groups on any secondary outcome measures. Blinding was difficult to maintain for both patients and raters.

Conclusions

Adjunctive rTMS of the left DLPFC could not be shown to be more effective than sham rTMS for treating depression.
Towards further understanding of the co-morbidity between attention deficit hyperactivity disorder and bipolar disorder: a MRI study of brain volumes
Authors: Biederman J. , Makris N. , Valera E. M. , Monuteaux M. C. , Goldstein J. M. , Buka S. , Boriel D. L. , Bandyopadhyay S. , Kennedy D. N. , Caviness V. S. , Bush G. , Aleardi M. , Hammerness P. , Faraone S. V. , Seidman L. J.
Published: October 2007

Background

Although attention deficit hyperactivity disorder (ADHD) and bipolar disorder (BPD) co-occur frequently and represent a particularly morbid clinical form of both disorders, neuroimaging research addressing this co-morbidity is scarce. Our aim was to evaluate the morphometric magnetic resonance imaging (MRI) underpinnings of the co-morbidity of ADHD with BPD, testing the hypothesis that subjects with this co-morbidity would have neuroanatomical correlates of both disorders.

Method

Morphometric MRI findings were compared between 31 adults with ADHD and BPD and with those of 18 with BPD, 26 with ADHD, and 23 healthy controls. The volumes (cm3) of our regions of interest (ROIs) were estimated as a function of ADHD status, BPD status, age, sex, and omnibus brain volume using linear regression models.

Results

When BPD was associated with a significantly smaller orbital prefrontal cortex and larger right thalamus, this pattern was found in co-morbid subjects with ADHD plus BPD. Likewise, when ADHD was associated with significantly less neocortical gray matter, less overall frontal lobe and superior prefrontal cortex volumes, a smaller right anterior cingulate cortex and less cerebellar gray matter, so did co-morbid ADHD plus BPD subjects.

Conclusions

Our results support the hypothesis that ADHD and BPD independently contribute to volumetric alterations of selective and distinct brain structures. In the co-morbid state of ADHD plus BPD, the profile of brain volumetric abnormalities consists of structures that are altered in both disorders individually. Attention to co-morbidity is necessary to help clarify the heterogeneous neuroanatomy of both BPD and ADHD.
A genetically informative developmental study of the relationship between conduct disorder and peer deviance in males
Authors: Kendler K. S. , Jacobson K. , Myers J. M. , Eaves L. J.
Published: October 2007

Background

Conduct disorder (CD) and peer deviance (PD) both powerfully predict future externalizing behaviors. Although levels of CD and PD are strongly correlated, the causal relationship between them has remained controversial and has not been examined by a genetically informative study.

Method

Levels of CD and PD were assessed in 746 adult male–male twin pairs at personal interview for ages 8–11, 12–14 and 15–17 years using a life history calendar. Model fitting was performed using the Mx program.

Results

The best-fit model indicated an active developmental relationship between CD and PD including forward transmission of both traits over time and strong causal relationships between CD and PD within time periods. The best-fit model indicated that the causal relationship for genetic risk factors was from CD to PD and was constant over time. For common environmental factors, the causal pathways ran from PD to CD and were stronger in earlier than later age periods.

Conclusion

A genetically informative model revealed causal pathways difficult to elucidate by other methods. Genes influence risk for CD, which, through social selection, impacts on the deviance of peers. Shared environment, through family and community processes, encourages or discourages adolescent deviant behavior, which, via social influence, alters risk for CD. Social influence is more important than social selection in childhood, but by late adolescence social selection becomes predominant. These findings have implications for prevention efforts for CD and associated externalizing disorders.
An electron-beam accelerator based on spiral water PFL
Authors: Liu J.L. , Yin Yi , Ge Bin , Zhan T.W. , Chen X.B. , Feng J.H. , Shu Ting , ZHANG J.D. , Wang X. Xinxin
Published: October 2007

An electron-beam accelerator based on spiral water pulse forming line which consists of a primary storage capacitor system, an air core spiral strip transformer, a spiral pulse forming line of water dielectric, and a field-emission diode, is described. The experimental results showed that the diode voltage is more than 500 kV, the electron beam current of diode is about 24 kA, and the pulse duration is about 200 ns. The main parameters of the accelerator were calculated theoretically. The distributions for electrical field in the pulse forming line were obtained by the simulations. In addition, the process of the accelerator charging a spiral pulse forming line was simulated through the Pspice software to get the waveforms of charging voltage of pulse forming line, the diode voltage and diode current of accelerator. The theoretical and simulated results agree with the experimental results. This accelerator is very compact and works stably and reliably.
Saturation effect at high laser pulse energies in laser-induced breakdown spectroscopy for elemental analysis in water
Authors: Fang Xiao , Rafi Ahmad S.
Published: October 2007

Saturation effects in laser-induced breakdown spectroscopy in water for elemental analysis have been investigated. Existing theoretical model of laser-induced plasma in solids has been applied to liquid phase under some simplifying assumptions to take account of the laser pulse energy dependence of atomic emissions from Na and Cu in aqueous solution. The theory was found to explain the emission process for laser energies up to but below the saturation level. The saturation limit of the emission with laser pulse energy corresponds well with that of the plasma temperature deduced from blackbody emission considerations. The saturation energies for atomic emissions were found to be lower for bulk excitations compared to water jet excitations. The dependence of signal strength on sample concentration indicated that the concentration values at saturation are lower at higher laser energies, as is expected from the theoretical model.
Race and food store availability in an inner-city neighbourhood
Authors: Galvez Maida P , Morland Kimberly , Raines Cherita , Kobil Jessica , Siskind Jodi , Godbold James , Brenner Barbara
Published: October 2007

Background

A growing body of research has shown that disparities in resources, including food stores, exist at the neighbourhood level and the greatest disparities are seen in minority neighbourhoods, the same neighbourhoods at increased risk of obesity and diabetes. Less is known about whether differences in availability of resources by African American or Latino race/ethnicity exist within a single minority community.

Objective

The present study examined whether census blocks either 75% African American (AA) or 75% Latino (L) are associated with food store availability, as compared with racially mixed (RM) census blocks, in East Harlem, New York.

Design/methods

A cross-sectional study utilising a walking survey of East Harlem was performed. Food stores were classified into: supermarkets, grocery stores, convenience stores, specialty stores, full-service restaurants and fast-food stores.

Results

One hundred and sixty-five East Harlem census blocks were examined; 17 were AA, 34 were L and 114 were RM. Of AA census blocks, 100% had neither supermarkets nor grocery stores. AA census blocks were less likely to have convenience stores (prevalence ratio (PR) = 0.25, 95% confidence interval (CI) 0.07–0.86) compared with RM census blocks. In contrast, predominantly L census blocks were more likely to have convenience stores (PR = 1.8, 95% CI 1.20–2.70), specialty food stores (PR = 3.74, 95% CI 2.06–7.15), full-service restaurants (PR = 1.87, 95% CI 1.04–3.38) and fast-food restaurants (PR = 2.14, 95% CI 1.33–3.44) compared with RM census blocks.

Conclusions

We found that inequities in food store availability exist by race/ethnicity in East Harlem, New York. This has implications for racial/ethnic differences in dietary quality, obesity and obesity-related disorders.
Is cooking food in iron pots an appropriate solution for the control of anaemia in developing countries? A randomised clinical trial in Benin
Authors: Sharieff Waseem , Dofonsou Joyce , Zlotkin Stanley
Published: October 2007

Objective

To evaluate the effect of two types of iron pots on haemoglobin (Hb) and serum ferritin (SF) concentrations in young children (6–24 months), adolescent girls (11–15 years) and women of reproductive age (15–44 years), whose households were provided with iron pots for cooking food over a period of 6 months, compared with controls.

Design and methods

We randomly assigned 161 households including 339 individuals from the three subgroups to cast iron pots, blue steel pots or oral iron supplements (control). In the control group, children received micronutrient Sprinkles™, and adolescent girls and women received iron tablets daily for 6 months. We measured Hb, SF and C-reactive protein concentrations at baseline and 6 months, and compared groups using regression models.

Results

Anaemia prevalence (Hb < 110 g l−1in infants, Hb < 120 g l−1in girls or women) was 47% (cast iron group), 50% (blue steel group) and 50% (control) at baseline. At 6 months, there were no significant differences in Hb concentrations among groups; however, differences in SF concentrations were significant (P< 0.0001) – the control group had higher SF concentrations compared with the groups using iron pots. Also, differences in the prevalence of iron-deficiency anaemia (IDA; anaemia plus SF < 15 μg l−1) were almost significant between cast iron and control groups (P= 0.08), and blue steel and control groups (P= 0.05).

Conclusion

There is no evidence that iron cooking pots are effective against IDA. Further research is warranted to determine whether the iron leached from the pots is bioavailable.
Modeling and Parameter Identification of the Simultaneous Saccharification‐Fermentation Process for Ethanol Production
Authors: Ochoa Silvia , Yoo Ahrim , Repke Jens‐Uwe , Wozny Günter , Yang Dae Ryook
Published: October 2007

Despite many environmental advantages of using alcohol as a fuel, there are still serious questions about its economical feasibility when compared with oil‐based fuels. The bioethanol industry needs to be more competitive, and therefore, all stages of its production process must be simple, inexpensive, efficient, and “easy” to control. In recent years, there have been significant improvements in process design, such as in the purification technologies for ethanol dehydration (molecular sieves, pressure swing adsorption, pervaporation, etc.) and in genetic modifications of microbial strains. However, a lot of research effort is still required in optimization and control, where the first step is the development of suitable models of the process, which can be used as a simulated plant, as a soft sensor or as part of the control algorithm. Thus, toward developing good, reliable, and simple but highly predictive models that can be used in the future for optimization and process control applications, in this paper an unstructured and a cybernetic model are proposed and compared for the simultaneous saccharification‐fermentation process (SSF) for the production of ethanol from starch by a recombinant Saccharomyces cerevisiae strain. The cybernetic model proposed is a new one that considers the degradation of starch not only into glucose but also into dextrins (reducing sugars) and takes into account the intracellular reactions occurring inside the cells, giving a more detailed description of the process. Furthermore, an identification procedure based on the Metropolis Monte Carlo optimization method coupled with a sensitivity analysis is proposed for the identification of the modelapos;s parameters, employing experimental data reported in the literature.
Modeling of Effects of Nutrient Gradients on Cell Proliferation in Microfluidic Bioreactor
Authors: Hu Guoqing , Quaranta Vito , Li Dongqing
Published: October 2007

Precise control of the microenvironment is highly desirable in cell culture to study the cell biology. Microfluidic based bioreactors provide a promising method for the spatial and temporal control of cell growth and stimuli. A three‐dimensional nutrient transport model, incorporating the monolayer cell growth model, has been developed to investigate the influence of gradients of oxygen and epidermal growth factor (EGF) on the cell culture in the continuous‐flow microchannel bioreactor. Our results demonstrate that applying inlet concentration gradients of oxygen and EGF can induce variations of cell density in the y‐direction. It is further found that compared to the oxygen gradients the EGF concentration gradients are more efficient in regulating the cell growth.
Nitrate uptake at photic zone depths is not important for export in the subtropical ocean
Authors: Painter Stuart C. , Sanders Richard , Poulton Alex J. , Woodward E. Malcolm S. , Lucas Mike , Chamberlain Katie
Published: October 2007

Observations of nitrate (NO3−) uptake across the photic zone of the tropical and subtropical Atlantic Ocean are described. High NO3− uptake rates were commonly found at depth (>75 m), coincident with the deep chlorophyll maximum and the nitracline, whereas highest rates of carbon fixation were found in near‐surface waters (0−50 m). Thus NO3− based estimates of in situ new production (NO3− uptake × 6.6) at depth are in excess of in situ measurements of carbon fixation implying NO3− uptake exceeds production requirements. Such surplus NO3− uptake may ultimately result in the production of dissolved organic nitrogen with its measurement within the particulate phase representing a transient enrichment. When only upper euphotic zone (to 14% irradiance depth) rates of NO3− uptake and carbon fixation are considered, new production is less than total carbon fixation, suggesting, as expected, that additional nitrogen sources are required to support the observed production levels. Comparison of the deep NO3− uptake rates with literature estimates of seasonal NO3− drawdown within the nitracline suggests that the drawdown observed represents only 1% of the actual NO3− uptake occurring in this region of the water column, and hence most NO3− uptake must be recycled locally rather than exported.
An evaluation of MODIS 250‐m data for green LAI estimation in crops
Authors: Gitelson Anatoly A. , Wardlow Brian D. , Keydan Galina P. , Leavitt Bryan
Published: October 2007

Green leaf area index (LAI) is an important variable for climate modeling, estimates of primary production, agricultural yield forecasting, and many other diverse applications. Remotely sensed data provide considerable potential for estimating LAI at local, regional, and global scales. The goal of this study was to retrieve green LAI from MODIS 250‐m vegetation index (VI) data for irrigated and rainfed maize and soybeans. The performance of both MODIS‐derived NDVI and Wide Dynamic Range Vegetation Index (WDRVI) were evaluated across three growing seasons (2002 through 2004) over a wide range of LAI and also compared to the performance of NDVI and WDRVI derived from reflectance data collected at close‐range across the same field locations. The NDVI vs. LAI relationship showed asymptotic behavior with a sharp decrease in the sensitivity of the NDVI to LAI exceeding 2 m2/m2 for both crops. WDRVI vs. LAI relation was linear across the entire range of LAI variation with determination coefficients above 0.93. Importantly, the coefficients of the close‐range WDRVI vs. LAI equation and the MODIS‐retrieved WDRVI vs. LAI equation were very close. The WDRVI was found to be capable of accurately estimating LAI across a much greater LAI range than the NDVI and can be used for assessing even slight variations in LAI, which are indicative of the early stages of plant stress. These results demonstrate the new possibilities for analyzing the spatio‐temporal variation of the LAI of crops using multi‐temporal MODIS 250‐m imagery.
Effect of charged dust particles on the ion cyclotron and firehose instabilities
Authors: de Juli M. C. , Schneider R. S. , Ziebell L. F. , Gaelzer R.
Published: October 2007

Effects due to the presence of charged dust particles on the growth rate of instabilities of low frequency electromagnetic waves propagating along the ambient magnetic field are investigated, using a kinetic theory which takes into account the collisional charging of the dust particles. For perpendicular ion temperature larger than the parallel ion temperature the dustless plasma features the proton cyclotron anisotropy instability, which is gradually reduced by the presence of the dust population, until complete disappearance for sufficiently large dust density. For perpendicular ion temperature smaller than the parallel ion temperature the dustless plasma features the proton fire‐hose instability, which is also reduced by the presence of the dust population. The results obtained show that the fire‐hose instability is more easily quenched by the presence of the dust than the proton cyclotron instability. For both instabilities, the presence of the dust affects the dispersion relation by the charge imbalance produced by the electron capture by the dust particles, and by the damping effect originated from the collisional charging of the dust particles.
Temperature anomaly reemergence in seasonally frozen soils
Authors: Schaefer Kevin M. , Zhang Tingjun , Tans Pieter P. , Stöckli Reto
Published: October 2007

In cold regions where soils experience seasonally freezing and thawing, past soil temperature anomalies are stored as variations in the amount of ground ice and can reemerge at the surface after frozen soils thaw. Warmer soils in autumn result in shallower freeze depths in winter, requiring less energy to thaw in spring, and resulting in warmer soils the following summer. We identified reemergence from in situ soil temperature data across the former Soviet Union and simulated reemergence using a soil heat transfer model with phase change. Reemergence is triggered by a sudden drop in the apparent soil specific heat associated with the latent heat of fusion of water. Past soil temperature anomalies persisting just below the maximum freeze depth, which varies from less than one to three meters, amplify the reemergence signal. Reemergence strength increases with soil water content and does not occur if the soil never freezes. To simulate the reemergence, models need a soil column at least 7 m deep with enough vertical resolution to accurately capture variability in the frozen layer. Reemergence of past soil temperature anomalies is a new class of time delayed, land‐atmosphere feedbacks that can potentially help to explain observed variability in climate and improve seasonal climate prediction in regions with seasonally frozen soils.
Detrital zircon age and Hf isotopic studies for metasedimentary rocks from the Chinese Altai: Implications for the Early Paleozoic tectonic evolution of the Central Asian Orogenic Belt
Authors: Long Xiaoping , Sun Min , Yuan Chao , Xiao Wenjiao , Lin Shoufa , Wu Fuyuan , Xia Xiaoping , Cai Keda
Published: October 2007

The Chinese Altai, a typical region of the Central Asian Orogenic Belt (CAOB), has been envisaged as subduction‐accretion complex or Precambrian microcontinent. Thick metasedimentary rocks crop out extensively in the Central Altai and Qiongkuer domains, but their depositional age is not well constrained. Most workers have regarded these sedimentary rocks as passive continental margin sediments deposited on a Precambrian microcontinent. However, our studies of U‐Pb and Hf isotopes of detrital zircons separated from these rocks reveal that a predominant population has 206Pb/238U ages between 460 and 540 Ma and most grains of this population possess positive ɛHf(t) values. Zircons of the population have oscillatory zoning, possess high Th/U ratios, and are enhedral to subhedral crystals with sharp edges, showing short distance of transportation from an igneous provenance. The above results indicate that these metasedimentary rocks were deposited on an active continental margin not prior to the Middle Ordovician. Therefore the Chinese Altai orogen was an active continental margin in the Early Paleozoic, which is inconsistent with a Precambrian microcontinent model and reveals an arc accretionary history.
Increased antiviral activity of microscale‐purified HuIFNα8 (human interferon α8) over HuIFNα2b in Hep‐2 cells challenged with Mengo virus
Authors: García Julio César Sánchez , Ariza Alejandro Miranda , Lasa Alexis Musacchio , González Luis Javier , Perez Vladimir Besada
Published: October 2007

Human proteins are not routinely expressed at high levels in Escherichia coli for, among other reasons, different codon usage. Several purification procedures have been applied to recover recombinant proteins for further biological characterization. However, the vast majority involve costly chromatography procedures. In the present study, both HuIFNα2b (human interferon α2b) and HuIFNα8 were expressed efficiently in E. coli BL21‐codonplus‐RIL. Subsequently, both recombinant proteins were purified to homogeneity by passive elution from reverse‐stained SDS/PAGE gels, a cost‐effective purification procedure. After purification, both recovered proteins were biologically active. The HuIFNα8 subtype induced 1.46‐fold more antiviral activity than HuIFNα2b using Hep‐2 human laryngeal carcinoma cell challenged with Mengo virus.
Proton quantum coherence observed in water confined in silica nanopores
Authors: Garbuio V. , Andreani C. , Imberti S. , Pietropaolo A. , Reiter G. F. , Senesi R. , Ricci M. A.
Published: October 2007

Deep inelastic neutron scattering measurements of water confined in nanoporous xerogel powders, with average pore diameters of 24 and 82Å, have been carried out for pore fillings ranging from 76% to nearly full coverage. DINS measurements provide direct information on the momentum distribution n(p) of protons, probing the local structure of the molecular system. The observed scattering is interpreted within the framework of the impulse approximation and the longitudinal momentum distribution determined using a model independent approach. The results show that the proton momentum distribution is highly non-Gaussian. A bimodal distribution appears in the 24Å pore, indicating coherent motion of the proton over distances d of approximately 0.3Å. The proton mean kinetic energy ⟨EK⟩W of the confined water molecule is determined from the second moment of n(p). The ⟨EK⟩W values, higher than in bulk water, are ascribed to changes of the proton dynamics induced by the interaction between interfacial water and the confining surface.
q
-quaternions and q-deformed su(2) instantons
Authors: Fiore Gaetano
Published: October 2007

We construct (anti-)instanton solutions of a would-be q-deformed su(2) Yang-Mills theory on the quantum Euclidean space Rq4 [the SOq(4)-covariant noncommutative space] by reinterpreting the function algebra on the latter as a q-quaternion bialgebra. Since the (anti-)self-duality equations are covariant under the quantum group of deformed rotations, translations, and scale change, by applying the latter we can generate new solutions from the one centered at the origin and with unit size. We also construct multi-instanton solutions. As they depend on noncommuting parameters playing the roles of “sizes” and “coordinates of the centers” of the instantons, this indicates that the moduli space of a complete theory should be a noncommutative manifold. Similarly, gauge transformations should be allowed to depend on additional noncommutative parameters.
Suppression of longitudinal modes in two-sectioned, coupled-cavity GaAs∕(Al,Ga)As terahertz quantum-cascade lasers
Authors: Giehler M. , Kostial H. , Hey R. , Grahn H. T.
Published: October 2007

The spectra of two-sectioned, coupled-cavity (TSCC) terahertz quantum-cascade lasers exhibit a number of longitudinal modes, which are periodically suppressed due to interference effects. The number of suppressed modes is equal to the ratio of the lengths of the two subcavities. At maximum laser output, the mode suppression disappears due to optical saturation, and a switching between TSCC and single-cavity-like mode features appears for certain delays between the current pulses through the individual subcavities. A transfer-matrix approach reproduces the mode spacings very well, but predicts a smaller modulation of the mode heights and does not describe the observed mode switching.
Ferroelectrical properties of W-doped lead zirconate titanate
Authors: Zhang Zhen , Lu Li , Shu Chang , Wu Ping , Song Wendong
Published: October 2007

Effects of the dopant W on the ferroelectric properties of Pb(Zr0.3Ti0.7)O3 (PZT) have been studied. The PZT and PZT doped with W (PZTW) thin films were deposited on LaNiO3 bottom electrodes by pulsed laser deposition at an oxygen partial pressure of 300mTorr. X-ray diffraction of PZTW films revealed pure perovskite structure with increased (110) orientation, compared to that of PZT films with high (l00) orientation. Both secondary ion mass spectrometry and x-ray photoelectron spectra tests confirmed the existence of W ions in the PZTW films. Although the PZTW film showed decreased remnant polarization, the saturation polarization is increased and the coercive field was greatly lowered. Moreover, the PZTW film demonstrated an improved fatigue behavior than PZT film. The W dopants are believed to contribute to the improvement of the ferroelectric behavior of PZT thin films. Ab initio calculation indicated that the formation energy of the oxygen vacancies in PZT lattice under Pb-deficient conditions can be greatly increased by doping W, leading to a suppression of oxygen vacancy concentration. Furthermore, the W 5d states share the conduction band minimum with Ti 3d states, which helps reduce the occupation of Ti 3d states by the electrons released from oxygen vacancies. Therefore, the PZTW is less susceptible to fatigue.
Honeycomblike large area LaB6 plasma source for Multi-Purpose Plasma facility
Authors: Woo Hyun-Jong , Chung Kyu-Sun , You Hyun-Jong , Lee Myoung-Jae , Lho Taihyeop , Choh Kwon Kook , Yoon Jung-Sik , Jung Yong Ho , Lee Bongju , Yoo Suk Jae , Kwon Myeon
Published: October 2007

A Multi-Purpose Plasma (MP2) facility has been renovated from Hanbit mirror device [Kwon et al., Nucl. Fusion 43, 686 (2003)] by adopting the same philosophy of diversified plasma simulator (DiPS) [Chung et al., Contrib. Plasma Phys. 46, 354 (2006)] by installing two plasma sources: LaB6 (dc) and helicon (rf) plasma sources; and making three distinct simulators: divertor plasma simulator, space propulsion simulator, and astrophysics simulator. During the first renovation stage, a honeycomblike large area LaB6 (HLA-LaB6) cathode was developed for the divertor plasma simulator to improve the resistance against the thermal shock fragility for large and high density plasma generation. A HLA-LaB6 cathode is composed of the one inner cathode with 4in. diameter and the six outer cathodes with 2in. diameter along with separate graphite heaters. The first plasma is generated with Ar gas and its properties are measured by the electric probes with various discharge currents and magnetic field configurations. Plasma density at the middle of central cell reaches up to 2.6×1012cm−3, while the electron temperature remains around 3–3.5eV at the low discharge current of less than 45A, and the magnetic field intensity of 870G. Unique features of electric property of heaters, plasma density profiles, is explained comparing with those of single LaB6 cathode with 4in. diameter in DiPS.
X-ray absorption and magnetic circular dichroism characterizations of Mn doped ZnO
Authors: Thakur P. , Chae K. H. , Kim J.-Y. , Subramanian M. , Jayavel R. , Asokan K.
Published: October 2007

We report the near-edge x-ray absorption fine structure (NEXAFS) and x-ray magnetic circular dichroism (XMCD) experiments on well characterized Mn doped ZnO thin films that show ferromagnetism at room temperature. The NEXAFS measurements at O K edge clearly exhibit a preedge spectral feature which evolves with Mn doping, similar to one observed in hole-doped cuprates and manganites. The Mn L3,2 edge NEXAFS spectra exhibit divalent Mn apart from mixed valent Mn3+∕Mn4+ states. The spectral features of XMCD at Mn L3,2 edge demonstrate that ferromagnetism comes from Mn2+ ions and its dichroism shape is independent of Mn concentration.
Magnetic field modeling of a dual-magnet configuration
Authors: Teo Tat Joo , Chen I-Ming , Yang Guilin , Lin Wei
Published: October 2007

This paper presents the theoretical and experimental studies of a dual-magnet (DM) configuration that forms the electromagnetic circuit of a nanopositioning actuator. Motivation of this work arises when an accurate prediction of the magnetic field behavior within the DM configuration is required to achieve ultrahigh precision motion control. In the theoretical modeling, the DM configuration is decomposed into several regions where each region is treated as a boundary-value problem. A method, termed superposition of the boundary conditions, is used to obtain the field solution of an air gap that is influenced by two magnetic sources. Consequently, a two-dimensional (2D) analytical model that accurately predicts the magnetic field behavior of the DM configuration is presented. In the experimental investigations, the magnetic flux density measured from a DM configuration prototype is used to validate the accuracy of the 2D analytical model. These experimental data were also compared against the magnetic flux density collected from a conventional single-magnet configuration prototype. Such comparisons verify the claimed features of the DM configuration, i.e., providing 40% increase in the magnetic flux density and offering an evenly distributed magnetic field through the entire air gap of 11mm.
Hot-electron recirculation in ultraintense laser pulse interactions with thin foils
Authors: Huang Yong-sheng , Lan Xiao-fei , Duan Xiao-jiao , Tan Zhi-xin , Wang Nai-yan , Shi Yi-jin , Tang Xiu-zhang , He Ye-xi
Published: October 2007

A model, called the Step Model, is proposed to describe hot-electron recirculation. A formula to estimate electron density at the rear side sheath is described. With a fixed initial hot-electron density for some target thicknesses, the results from the Step Model are compared with several experiments. The influences of laser pulse absorption efficiency, laser pulse duration, the opening angle of hot-electrons, hot-electron recirculation, and target thickness on the ion acceleration are discussed. When the target thickness is far less than the laser focus radius, the initial electron density will be proportional to the laser pulse absorption efficiency, and the angular effect and the thickness effect can both be ignored. For any target thickness, the maximum ion velocity accelerated by the rear side sheath can be calculated using the Step Model. As an application to some experiments, the Step Model provides a half-analytic method to achieve the dependence of the laser pulse absorption efficiency on target thickness and the influence of amplified spontaneous emission (ASE) duration on the laser absorption efficiency.
Coherent and intense multibeam generation by the apex of sharp nano-objects: Electron half-circular prism
Authors: Cho B. , Ishikawa T. , Oshima C.
Published: October 2007

Mutually coherent multiple electron beams (multibeam) were generated from diffraction at the apex of sharp nano-objects, especially carbon nanotubes, in a field emission projection microscope. Simulation using a simple scalar diffraction model showed that the apex of sharp nano-objects played the role of an electron half-circular prism, deflecting an electron beam through a constant angle toward the prism axis. The multibeam diffraction pattern gave a high visibility of ∼0.8 and high intensity.
Continuum visible spectra from InBr discharge excited in a microwave resonant cavity
Authors: Chen Yuming , Chen Dahua
Published: October 2007

Emissions from InBr radiation have been investigated in a microwave resonant cavity system. We demonstrate that with proper operation the emission spectra of InBr can be a continuum in the visible range and can be suitable for lighting applications. The continuum spectra are stronger with an increase in input microwave power. In our system, a high color rendering index of 97 can be obtained from the bulb with 25mg InBr and 800W input microwave power. The spectral lines 410.1 and 451.1nm from InI play an important role to balance the spectral distribution for lighting requirements. The continuum spectra may be due to the transition of Rydberg states to the C state of InBr molecules.
High porosity metallic glass foam: A powder metallurgy route
Authors: Demetriou Marios D. , Schramm Joseph P. , Veazey Chris , Johnson William L. , Hanan Jay C. , Phelps Nicholas B.
Published: October 2007

A powder metallurgy route to the fabrication of metallic glass foam is introduced. The method involves consolidating metallic glass powder blended with blowing agent particulates to produce expandable precursors, capable of yielding foams with porosities as high as 86%. The foams are found to inherit the strength of the parent metallic glass and to be able to deform heavily toward full densification absorbing high amounts of energy.
Absolute frequency stabilization of a diode laser to cesium atom-molecular hyperfine transitions via modulating molecules
Authors: Ma Jie , Wang Lirong , Zhao Yanting , Xiao Liantuan , Jia Suotang
Published: October 2007

We have demonstrated a robust method of directly stabilizing diode laser frequency to the cesium atom-molecular hyperfine transitions. The trap loss fluorescence spectroscopy was applied to yield the error signal based on modulating molecules with ultralow modulation frequency of 1.2Hz. The excursions over 300s of the frequency of the laser were bounded by 1.5MHz. The root of Allan variance of the error signals reached a minimum of 4.8×10−11 for an averaging time of 100s.
Effect of backing layer thickness on adhesion of single-level elastomer fiber arrays
Authors: Kim Seok , Sitti Metin , Hui Chung-Yuen , Long Rong , Jagota Anand
Published: October 2007

The effect of the backing layer thickness on adhesion was investigated for single-level elastomer fibrillar adhesives. Polyurethane microfiber arrays with spatulated tips on a 160μm thick backing layer show nine times greater adhesion strength (around 22N∕cm2) than those with a 1120μm thick backing. A theoretical model is proposed to explain this difference in which very thin backing layers promote equal load sharing, maximizing adhesion, while very thick backings can lead to reduced adhesion due to edge stress concentration. Therefore, backing layer thickness should be considered as a significant parameter for design of high performance fibrillar adhesives.
Experts in Their Fields: Farmer — Expert Knowledges and Environmentally Friendly Farming Practices
Authors: Riley Mark
Published: October 2007

Through a focus on farming practices this paper considers farmer–science knowledges and explores three interrelated issues. First is the hitherto neglected issue of temporal dynamicity—the paper gives attention to how past history and time are constructed, organised, and drawn upon both in the way farmers develop and understand their own practices as well as in how they understand and negotiate those practices that they are now being asked to undertake in contemporary agrienvironment schemes. Second, the paper considers the way in which farmers draw on context-specific experiential understandings in completing their practices, and how these understandings conflict with, and are negotiated alongside, those understandings embedded within conservation schemes and their ‘prescriptions’. Third, the paper develops recent suggestions relating to the potential role of farmers within agrienvironment schemes by illustrating how, when approached through the appropriate methodology, farmers' localised understandings may be usefully incorporated within the discussion of hay-meadow management for conservation.
Fractal Analysis of Street Vistas: A Potential Tool for Assessing Levels of Visual Variety in Everyday Street Scenes
Authors: Cooper Jon , Oskrochi Reza
Published: October 2007

Fractal analysis and the calculation of fractal dimension offer the potential for the numerical characterisation of places by providing a synthetic measurement of place complexity. This paper provides a fractal analysis of street vistas linking the calculation of fractal dimension to the perception of levels of visual variety present in everyday urban streets. A technique for calculating street vista fractal dimensions of textures extracted from greyscale images is presented, and correlations between the resultant fractal dimension and scores for perceived visual variety are discussed.
Effects of body size and lifestyle on evolution of mammal life histories
Authors: Sibly Richard M. , Brown James H.
Published: October 2007

It has recently been proposed that life-history evolution is subject to a fundamental size-dependent constraint. This constraint limits the rate at which biomass can be produced so that production per unit of body mass is inevitably slower in larger organisms than in smaller ones. Here we derive predictions for how changes in body size and production rates evolve in different lifestyles subject to this constraint. Predictions are tested by using data on the mass of neonate tissue produced per adult per year in 637 placental mammal species and are generally supported. Compared with terrestrial insectivores with generalized primitive traits, mammals that have evolved more specialized lifestyles have divergent mass-specific production rates: (i) increased in groups that specialize on abundant and reliable foods: grazing and browsing herbivores (artiodactyls, lagomorphs, perissodactyls, and folivorous rodents) and flesh-eating marine mammals (pinnipeds, cetaceans); and (ii) decreased in groups that have lifestyles with reduced death rates: bats, primates, arboreal, fossorial, and desert rodents, bears, elephants, and rhinos. Convergent evolution of groups with similar lifestyles is common, so patterns of productivity across mammalian taxa reflect both ecology and phylogeny. The overall result is that groups with different lifestyles have parallel but offset relationships between production rate and body size. These results shed light on the evolution of the fast–slow life-history continuum, suggesting that variation occurs along two axes corresponding to body size and lifestyle.
Demethylation of a specific hypersensitive site in the Th2 locus control region
Authors: Kim Sean T. , Fields Patrick E. , Flavell Richard A.
Published: October 2007

A growing body of literature has examined and implicated DNA methylation as a critical epigenetic modification in T helper (Th) cell differentiation. The absence of DNA methyltransferases or methyl-binding proteins derepresses many cytokine loci, allowing their ectopic expression, while methylation of specific CpG residues is sufficient to prevent expression. Here, we characterize demethylation events of the Th2 cytokine locus control region (LCR).rad50hypersensitive site 7 (RHS7), a hypersensitive site within this LCR, becomes demethylated in a STAT6-dependent manner and only in cells stimulated under type 2 conditions. Robust demethylation appears to require signaling contributions from both IL-4 receptor, via STAT6, and CD28, but it cannot be effected by GATA3. Finally, RHS7 is demethylated independently of cell division, consistent with an “active,” rather than passive, mechanism. Taken together, these findings firmly connect RHS7 demethylation and Th2 LCR activation in the type 2 differentiation program.
InterProSurf: a web server for predicting interacting sites on protein surfaces
Authors: Negi Surendra S. , Schein Catherine H. , Oezguen Numan , Power Trevor D. , Braun Werner
Published: October 2007

Summary: A new web server, InterProSurf, predicts interacting amino acid residues in proteins that are most likely to interact with other proteins, given the 3D structures of subunits of a protein complex. The prediction method is based on solvent accessible surface area of residues in the isolated subunits, a propensity scale for interface residues and a clustering algorithm to identify surface regions with residues of high interface propensities. Here we illustrate the application of InterProSurf to determine which areas of Bacillus anthracis toxins and measles virus hemagglutinin protein interact with their respective cell surface receptors. The computationally predicted regions overlap with those regions previously identified as interface regions by sequence analysis and mutagenesis experiments.

Availability: The InterProSurf web server is available at http://curie.utmb.edu/

Contact:  webraun@utmb.edu

Supplementary information: Other test examples are available as Supplementary Material at Bioinformatics online.