bluuebunny/crossref_metadata_2025 huggingface dataset:
“Writing Reform” in Early Twentieth-Century Los Angeles: The Sonoratown Anthologies
Authors: LEWTHWAITE STEPHANIE
Published: July 2007

In early twentieth-century Los Angeles, Anglo-American women writers documented the emergence of a metropolis. Perceptions of race, ethnicity and culture became embedded in the struggle to depict and interpret a new urbanism. In capturing the changing cityscape, women writers constructed Sonoratown, the old Mexican Quarter of Los Angeles, as a place in the social imagination. This article examines representations of Sonoratown and its Mexican inhabitants in two anthologies. Women writers, many of whom moved in civic and reform-minded circles, rendered Sonoratown ambiguously: as a “picturesque” place to be preserved and yet a space earmarked for renewal, Sonoratown became entwined with the drive for social reform, assimilation and urban development.
“I Improvised behind Him…Ahead of Time”: Charles Mingus, Kenneth Patchen and Jazz/Poetry Fusion Art
Authors: FARRINGTON HOLLY
Published: July 2007

In the last two weeks of March 1959, the jazz bassist Charlie Mingus and the beat poet Kenneth Patchen performed on stage together at the Living Theatre in New York City. Mingus and his band improvised to jazz themes at the back, while Patchen read simultaneously from his poetry at the front. This article examines in detail both Patchen's and Mingus's work with jazz/poetry fusion art and positions these collaborations within the context of the wider movement. It explores the artistic relationship between Mingus and Patchen and examines and contextualizes these performances within the jazz aesthetic.
Ghetto Formation and Armed Resistance in East St. Louis, Illinois
Authors: McLAUGHLIN MALCOLM
Published: July 2007

This article explores African American armed resistance during the 1917 East St. Louis race riot in the context of black migration and ghetto formation. In particular it considers the significance of the development of the black urban community, composed of an emerging working class and a dynamic, militant and increasingly influential middle class. It was that community which came under attack by white mobs in 1917, and this work illuminates the infrastructure of resistance in the city, showing how African Americans drew upon the resources of the nascent ghetto and older traditions of self-defence to protect their homes and families.
Successful computer-assisted cognitive remediation therapy in patients with unipolar depression: a proof of principle study
Authors: ELGAMAL SAFA , McKINNON MARGARET C. , RAMAKRISHNAN KARUNA , JOFFE RUSSELL T. , MacQUEEN GLENDA
Published: July 2007

Background

Despite increasing awareness of the extent and severity of cognitive deficits in major depressive disorder (MDD), trials of cognitive remediation have not been conducted. We conducted a 10-week course of cognitive remediation in patients with long-term MDD to probe whether deficits in four targeted cognitive domains, (i) memory, (ii) attention, (iii) executive functioning and (iv) psychomotor speed, could be improved by this intervention.

Method

We administered a computerized cognitive retraining package (PSSCogReHab) with demonstrated efficacy to 12 stable patients with recurrent MDD. Twelve matched patients with MDD and a group of healthy control participants were included for comparison; neither comparator group received the intervention that involved stimulation of cognitive functions through targeted, repetitive exercises in each domain.

Results

Patients who received cognitive training improved on a range of neuropsychological tests targeting attention, verbal learning and memory, psychomotor speed and executive function. This improvement exceeded that observed over the same time period in a group of matched comparisons. There was no change in depressive symptom scores over the course of the trial, thus improvement in cognitive performance occurred independent of other illness variables.

Conclusions

These results provide preliminary evidence that improvement of cognitive functions through targeted, repetitive exercises is a viable method of cognitive remediation in patients with recurrent MDD.
Bifurcating energy-angular spectrum of electrons accelerated by intense laser pulse
Authors: Lin D. , HO Y.K. , Kong Q. , Chen Z. , Wang P.X. , Xu J.J. , Kawata S.
Published: July 2007

Bifurcation phenomenon in the energy-angular correlation spectrum of the vacuum laser acceleration has been observed with computer simulation. Concerning a focused laser pulse, the classical single-valued energy-angular correlation spectrum for a plane wave is, besides broadened to a band, bifurcated with the classical value in between the two branches. Analytic expression to describe the correlation has been derived and physical explanations based on the ponderomotive potential model and Lorentz-Newton force analyses are presented. The theoretical results are supported by numerical simulations which have been compared with the experimental results. This study is helpful in designing vacuum laser acceleration experiments.
Collimated attosecond GeV electron bunches from ionization of high-Z material by radially polarized ultra-relativistic laser pulses
Authors: Karmakar A. , Pukhov A.
Published: July 2007

Three dimensional Particle-in-Cell (3D-PIC) simulations of electron acceleration in vacuum with radially polarized ultra-intense laser beams have been performed. It is shown that single-cycle laser pulses efficiently accelerate a single attosecond electron bunch to GeV energies. When multi-cycle laser pulses are used, one has to employ ionization of high-Z materials to inject electrons in the accelerating phase at the laser pulse maximum. In this case, a train of highly collimated attosecond electron bunches with a quasi-monoenergetic spectra is produced. A comparison with electron acceleration by Gaussian laser pulses has been done. It is shown that the radially polarized laser pulses are superior both in the maximum energy gain and in the quality of the produced electron beams.
Adult pertussis vaccination strategies and their impact on pertussis in the United States: evaluation of routine and targeted (cocoon) strategies
Authors: COUDEVILLE L. , VAN RIE A. , ANDRE P.
Published: July 2007

A compartmental, age-structured mathematical model was developed and recent US pertussis epidemiology data were used to evaluate the impact on pertussis infection rates of routine and targeted adult immunization strategies. Model simulations predict that the implementation of adolescent immunization only could reverse the current rise in pertussis infection rates but may lead to a resurgence of pertussis in subsequent decades. In contrast, inclusion of a routine adult strategy is likely to lead to sustained control of pertussis. Routine adult vaccination could control the disease even with relatively low coverage rates of 40% for routine vaccination of all adults every 10 years, or 65% for a targeted vaccination of close contacts of newborns completed by one booster dose for all adults. The model also predicts that the optimal age for this booster dose is 40 years. These results support the 2006 American Academy of Immunization Practices' recommendations for adolescent and adult vaccination against pertussis.
A Note on Freĭman's Theorem in Vector Spaces
Authors: SANDERS T.
Published: July 2007

A famous result of Freĭman describes the sets A, of integers, for which |A+A| ≤ K|A|. In this short note we address the analogous question for subsets of vector spaces over $\mathbb{F}_2$. Specifically we show that if A is a subset of a vector space over $\mathbb{F}_2$ with |A+A| ≤ K|A| then A is contained in a coset of size at most 2O(K3/2 log K)|A|, which improves upon the previous best, due to Green and Ruzsa, of 2O(K2)|A|. A simple example shows that the size may need to be at least 2Ω(K)|A|.
Potential renal acid load in the diet of children and adolescents: impact of food groups, age and time trends
Authors: Alexy Ute , Kersting Mathilde , Remer Thomas
Published: July 2007

Objective

The impact of acid–base balance on health is widely accepted. Here, we describe the potential renal acid load (PRAL) in the diet of healthy German children and adolescents.

Design

The Dortmund Nutritional and Anthropometric Longitudinally Designed (DONALD) Study is an ongoing longitudinal (open cohort) study (start 1985) collecting detailed data on diet, growth, development and metabolism in infants, children and adolescents.

Setting

Research Institute of Child Nutrition, Dortmund.

Subjects

Seven hundred and twenty children and adolescents (351 boys and 369 girls), aged 3–18 years, provided 4187 yearly collected 3-day dietary records between 1995 and 2005.

Results

Mean daily PRAL was positive in all age/sex groups (6–21 mEq day−1), and significantly higher in boys than in girls after the age of 8 years, even when calculated as mEq MJ−1. Fruits, vegetables and potatoes had a negative impact on PRAL; cheese, dairy products, cereals/bread and meat/fish/eggs had a positive impact. In a mixed linear model, PRAL, expressed as mEq day−1 and mEq MJ−1, remained stable during the study period, since time trends of PRAL-relevant food groups countervail each other. PRAL intake (mEq MJ−1) was significantly positively associated (P < 0.0001) with fat intake (% of energy intake, %E), but negatively with carbohydrate intake (%E; P < 0.0001).

Conclusions

The analysis of dietary habits in our sample of German children and adolescents showed a moderate excess of acidity. Especially older boys should be encouraged to eat more potatoes and vegetables as good sources of dietary alkalinity. The PRAL concept is compatible with current concepts for a healthy diet.
Unique patterns of dietary adequacy in three cultures of Canadian Arctic indigenous peoples
Authors: Kuhnlein Harriet V , Receveur Olivier , Soueida Rula , Berti Peter R
Published: July 2007

Background

Information is needed on dietary adequacy of Arctic indigenous populations in Canada. Extensive work has been completed on composition of Arctic food and food use, and dietary reference intakes are available.

Objective

To complete the first comprehensive dietary adequacy assessment of three populations of adult Arctic indigenous people.

Setting and subjects

Dietary assessment interviews were conducted with randomly selected indigenous adults during two seasons in 44 representative communities of Yukon First Nations (n= 797), Dene/Métis, (n= 1007) and Inuit (n= 1525).

Methods

Twenty-four-hour recalls were used to derive adjusted distributions of usual nutrient intakes in four age/gender groups for assessment of dietary adequacy for carbohydrate, dietary fibre, protein,n–3 fatty acids,n–6 fatty acids, calcium, copper, iron, magnesium, manganese, phosphorus, selenium, zinc, vitamin A, riboflavin, folate, vitamin B6, vitamin C, vitamin D and vitamin E.

Results

Nutrients with high prevalence of adequacy for most age/gender groups in all three cultures were protein, carbohydrate,n–3 fatty acids, iron, copper, zinc, manganese, selenium, riboflavin and vitamin B6; some individuals exceeded the upper intake level for iron, zinc, selenium, vitamin A and vitamin D. Estimated average requirement nutrients of concern for adequacy were magnesium, folate, vitamin A, vitamin C and vitamin E; however, a few age/gender groups were exceptions. Prevalence of inadequacy for AI nutrients which may be undesirably high were fibre,n–6 fatty acids and calcium. Vitamin D was more adequate in Inuit women and men than for Yukon First Nations or Dene/Métis.

Conclusions

Unique patterns of dietary adequacy exist among Arctic indigenous peoples. Local wildlife food sources and market food sources should be maximised for their nutrient contributions to Arctic diets.
Inadequate intakes of dietary zinc among pregnant women from subsistence households in Sidama, Southern Ethiopia
Authors: Abebe Yewelsew , Bogale Alemtsehay , Hambidge K Michael , Stoecker Barbara J , Arbide Isabel , Teshome Akilu , Krebs Nancy F , Westcott Jamie E , Bailey Karl B , Gibson Rosalind S
Published: July 2007

Objective

To assess the prevalence of zinc inadequacy based on dietary intakes and plasma zinc concentrations and, simultaneously, the prevalence of inadequate intakes of energy, protein, calcium and iron.

Design

A cross-sectional study of a convenience sample of subsistence farming households in Sidama, Southern Ethiopia.

Subjects

Dietary intakes were calculated from 1-day weighed food records and 40 repeats from 99 pregnant women in the third trimester using analysed values of major staple foods for zinc, iron, calcium and phytate. The distribution of observed intakes was adjusted for usual intakes and the prevalence of inadequacy estimated using the estimated average requirement (EAR) cutpoint method. Prevalence of inadequacy for zinc, protein and iron intakes were compared with those based on biochemical measures.

Results

Prevalence of zinc inadequacy was very high: 99% for US FNB EAR and 100% for IZiNCG EAR compared to 72% based on low plasma zinc concentrations. Corresponding prevalence estimates for iron were much lower: 4% for inadequate intakes based on US FNB EAR vs.8.7% for iron deficiency anaemia (haemoglobin < 110 g l−1; ferritin < 12 μg l−1) and 32.3% for low storage iron. Prevalence of inadequacy for protein was 100% for adjusted intakes and 91% for serum albumin < 32 g l−1. For calcium, 74% were at risk for inadequate intakes.

Conclusion

The high prevalence of inadequate intakes of zinc and protein was reasonably consistent with those based on biochemical measures. Such dietary deficits could be overcome by regular consumption of cellular animal protein. In contrast, both dietary and biochemical measures of iron inadequacy were low.
Seven distinct dietary patterns identified among pregnant Finnish women – associations with nutrient intake and sociodemographic factors
Authors: Arkkola Tuula , Uusitalo Ulla , Kronberg-Kippilä Carina , Männistö Satu , Virtanen Mikko , Kenward Michael G , Veijola Riitta , Knip Mikael , Ovaskainen Marja-Leena , Virtanen Suvi M
Published: July 2007

Objectives

To identify and describe dietary patterns in a cohort of pregnant women and investigate whether the dietary patterns are associated with dietary intake and sociodemographic factors.

Design

Mothers entering the Finnish Type 1 Diabetes Prediction and Prevention (DIPP) Nutrition Study in 1997–2002 were retrospectively asked to complete a food-frequency questionnaire concerning their diet during pregnancy. Principal components analysis was used to identify dietary patterns.

Setting

Finland.

Subjects

Subjects were 3730 women with a newborn infant carrying increased genetic susceptibility to type 1 diabetes mellitus.

Results

Seven factors were identified and named. Energy intake correlated positively with ‘Healthy’, ‘Fast food’, ‘Traditional bread’, ‘Traditional meat’ and ‘Coffee’ patterns and inversely with the ‘Alcohol and butter’ pattern. Intake of dietary fibre correlated positively with ‘Healthy’, ‘Traditional bread’ and ‘Low-fat foods’ patterns and inversely with the ‘Alcohol and butter’ pattern. The seven dietary patterns seemed to account for relatively large proportions of the variance in energy and nutrient intakes except for the intake of vitamin D, vitamin C, carotenoids and calcium. Maternal age and higher level of education were associated with higher scores on ‘Healthy’, ‘Low-fat foods’ and ‘Alcohol and butter’ patterns.

Conclusion

Principal components analysis produced seven dietary patterns which may be useful for further research concerning maternal diet and health outcomes among both mothers and their offspring.
Rio de la Plata estuary response to wind variability in synoptic to intraseasonal scales: 2. Currents' vertical structure and its implications for the salt wedge structure
Authors: Simionato C. G. , Meccia V. L. , Guerrero R. , Dragani W. C. , Nuñez M.
Published: July 2007

The first acoustic Doppler current profiler current data collected at two locations of the Río de la Plata salt wedge during a period of around 6 months and salinity profiles gathered at and around those locations are used to study the vertical structure of currents' response to wind variability in synoptic to intraseasonal timescales and its implications for stratification. Results indicate that the estuary rapidly responds to prevailing southwesterlies/northeasterlies with currents that decay toward the bottom with only little rotation in depth. For the less frequent southeasterlies/northwesterlies the estuary develops a strong vertical structure with a defined inversion in current direction between surface and bottom layers. These patterns derive from the estuary's geometry and bathymetry. Results have important implications for the salinity vertical structure that are verified on the analyzed profiles. First, the combination of the bathymetry and coastline with the prevailing wind variability is highly favorable to the maintenance of a salt wedge structure in this estuary. Second, weakening and eventually breakdown of stratification can only occur for intense and/or persistent southeasterly winds, which even can be very strong, are not frequent. This can explain why the Río de la Plata displays the unusual feature of being an area of spawning and a nursery for a number of coastal species that use the wedge as an essential element for their reproduction. Results show that stratification is highly affected by short‐term wind variability, which is its major characteristic in the area, changing the classical concept of summer‐winter seasonality as the main feature of estuarine variability.
3‐D aerosol‐cloud radiative interaction observed in collocated MODIS and ASTER images of cumulus cloud fields
Authors: Wen Guoyong , Marshak Alexander , Cahalan Robert F. , Remer Lorraine A. , Kleidman Richard G.
Published: July 2007

Three‐dimensional (3‐D) aerosol‐cloud interaction is examined by analyzing two images containing cumulus clouds in biomass‐burning regions in Brazil. The research consists of two parts. The first part focuses on identifying 3‐D cloud impacts on reflectances for the pixels selected for the MODIS aerosol retrieval based purely on observations. The second part of the research combines the observations with radiative transfer computations to identify key parameters in the 3‐D aerosol‐cloud interaction. We find that 3‐D cloud‐induced enhancement depends on the optical properties of nearby clouds as well as on wavelength. The enhancement is too large to be ignored. Associated bias error in one‐dimensional (1‐D) aerosol optical thickness retrieval ranges from 50 to 140% depending on wavelength and the optical depth of nearby clouds, as well as aerosol optical thickness. We caution the community to be prudent when applying 1‐D approximations in computing solar radiation in clear regions adjacent to clouds or when using traditional retrieved aerosol optical thickness in aerosol indirect effect research.
Origin of neutron flux increases observed in correlation with lightning
Authors: Babich Leonid P. , Roussel‐Dupré Robert A.
Published: July 2007

The past decade of research into the phenomenon of lightning has seen an accumulation of evidence for the existence of penetrating radiation (X‐ and γ‐rays) in direct association with many forms of discharges. As a result, our basic understanding of the mechanisms that produce lightning has shifted from the present paradigm based on conventional breakdown to a picture that incorporates the acceleration and avalanche of energetic particles. Experiments conducted at high mountainous facilities in Gulmarg, India, have further confirmed the need for a paradigm shift. These measurements have shown an enhancement in neutron flux in the atmosphere in correlation with lightning electromagnetic pulses. We demonstrate here that the prevailing neutron generation theory based on synthesis of deuterium nuclei in the lightning channel is not feasible. Instead, this phenomenon is most likely connected with photonuclear reactions produced as part of the recently elaborated theory of relativistic runaway breakdown.
Buoy monitors ocean acidification
Authors: Zielinski Sarah
Published: July 2007

A new Gulf of Alaska buoy installed on 7 June is the first to provide data that will help scientists study ocean acidification caused by the absorption of atmospheric carbon dioxide. Sensors attached to the buoy are measuring key climate indicators in the atmosphere and ocean, including surface acidity and the air‐sea exchange of carbon dioxide. The buoy was installed in collaboration with the Line P program, which has provided decades of continuous measurements from a series of oceanographic stations along line P which extends from the mouth of the Juan de Fuca Strait south of Vancouver Island to Pacific Ocean Station Papa, where the new buoy was installed.The buoy is part of a project conducted by scientists from NOAAs Pacific Marine Environmental Laboratory; the University of Washington, Seattle; Fisheries and Oceans Canada; and the Institute of Ocean Sciences in Sydney, British Columbia.
U.S. national estuaries in “fair” condition
Authors: Zielinski Sarah
Published: July 2007

The first report to evaluate the condition of the U.S. National Estuary Program finds that the 28 NEP estuaries are in “fair condition” and generally doing better or equal to non‐NEP U.S. estuaries despite significant human population pressures. The estuaries were rated for water and sediment quality, benthic zone health, and fish tissue contaminants. NEP estuaries in the southeast received the highest ratings, and those in the northeast and Puerto Rico the lowest. The most common concerns for NEP estuaries include habitat loss and alteration, species loss and decline, nutrients, toxics, and pathogens. The “National Estuary Program Coastal Condition Report” is available at http://www.epa.gov/owow/oceans/nepccr/
A scientific synthesis and assessment of the Arctic Carbon Cycle
Authors: Hayes Daniel J. , Guo Laodong , McGuire A. David
Published: July 2007

The Arctic Monitoring and Assessment Programme (AMAP), along with the Climate and Cryosphere (CliC) Project and the International Arctic Science Committee (IASC), sponsored the Arctic Carbon Cycle Assessment Workshop, at the Red Lion Hotel in Seattle, Wash., between 27 February and 1 March 2007. The workshop was held in a general effort toward the scientific synthesis and assessment of the Arctic system carbon cycle, as well as to generate feedback on the working draft of an assessment document. The initial assessment was prepared by the Arctic carbon cycle assessment writing team, which is led by A. David McGuire (University of Alaska Fairbanks) and includes Leif Anderson (Goteborg University, Sweden), Torben Christensen (Lund University, Sweden), Scott Dallimore (Natural Resources Canada), Laodong Guo (University of Southern Mississippi), Martin Heimann (Max Planck Institute, Germany), Robie MacDonald (Department of Fisheries and Oceans, Canada), and Nigel Roulet (McGill University, Canada).

The workshop brought together leading researchers in the fields of terrestrial, marine, and atmospheric science to report on and discuss the current state of knowledge on contemporary carbon stocks and fluxes in the Artie and their potential responses to a changing climate. The workshop was attended by 35 scientists representing institutions from 10 countries in addition to two representatives of the sponsor agencies (John Calder for AMAP and Diane Verseghy for CliC).
Fellows celebrated at Joint Assembly
Authors: Anonymous
Published: July 2007

The 2007 AGU Fellows were presented at the recent Joint Assembly in Acupulco, Mexico. A formal ceremony ws held on 25 May 2007, where President Tim Killeen introduced each Fellow and read a brief statement of the achievements for which each had been selected. The presentations were followed by an honors fiesta at which family members and close colleagues further feted the honorees.
Review of Immunoinformatic approaches to in-silico B-cell epitope prediction
Authors: Reitmaier Rick
Published: July 2007

In this paper, the current state of in-silico, B-cell epitope prediction is discussed. Recommendations for improving some of the approaches encountered are outlined, along with the presentation of an entirely novel technique, which uses molecular mechanics for epitope classification, evaluation and prediction.
Sharing Detailed Research Data Is Associated with Increased Citation Rate
Authors: Piwowar Heather
Published: July 2007

Presentation based on the publication here:Piwowar HA, Day RS, Fridsma DB (2007) Sharing Detailed Research Data Is Associated with Increased Citation Rate. PLoS ONE 2(3): e308. doi:10.1371/journal.pone.0000308Sharing research data provides benefit to the general scientific community, but the benefit is less obvious for the investigator who makes his or her data available.We examined the citation history of 85 cancer microarray clinical trial publications with respect to the availability of their data. The 48% of trials with publicly available microarray data received 85% of the aggregate citations. Publicly available data was significantly (p = 0.006) associated with a 69% increase in citations, independently of journal impact factor, date of publication, and author country of origin using linear regression.This correlation between publicly available data and increased literature impact may further motivate investigators to share their detailed research data.
A dynamic global-coefficient subgrid-scale eddy-viscosity model for large-eddy simulation in complex geometries
Authors: You Donghyun , Moin Parviz
Published: July 2007

An improvement of the dynamic procedure of Park et al. [Phys. Fluids 18, 125109 (2006)] for closure of the subgrid-scale eddy-viscosity model developed by Vreman [Phys. Fluids 16, 3670 (2004)] is proposed. The model coefficient which is globally constant in space but varies in time is dynamically determined assuming the “global equilibrium” between the subgrid-scale dissipation and the viscous dissipation of which utilization was proposed by Park et al. Like the Vreman model with a fixed coefficient and the dynamic-coefficient model of Park et al., the present model predicts zero eddy-viscosity in regions where the vanishing eddy viscosity is theoretically expected. The present dynamic model is especially suitable for large-eddy simulation in complex geometries since it does not require any ad hoc spatial and temporal averaging or clipping of the model coefficient for numerical stabilization and more importantly, requires only a single-level test filter in contrast to the dynamic model of Park et al., which employs two-level test filters.
Molecular beam optical Stark study of rhodium mononitride
Authors: Ma Tongmei , Gengler Jamie , Wang Zhong , Wang Hailing , Steimle Timothy C.
Published: July 2007

The optical Stark effect in the Q(1) and R(0) lines of the [15.1]1-XΣ+1 (1,0) band of rhodium mononitride (RhN) were recorded and analyzed to determine the permanent electric dipole moments μ for the XΣ+1(υ=0) and [15.1]1(υ=1) states to be 2.43(5) and 1.75(1)D, respectively. The determined dipole moments are compared to predicted values obtained from density functional theory [Stevens et al., Chem. Phys. Lett. 421, 281 (2006)] and an all-electron ab initio calculation [Shim et al., J. Mol. Struct. THEOCHEM 393, 127 (1997)]. A simple single configuration molecular orbital correlation diagram is used to rationalize the relative values of μ for the 4d mononitrides and RhO. An electronic configuration for the [15.1]1 state is proposed based on the interpretation of the Rh103 and N14 magnetic hyperfine interactions.
Nonequilibrium reaction rates in the macroscopic chemistry method for direct simulation Monte Carlo calculations
Authors: Goldsworthy M. J. , Macrossan M. N. , Abdel-jawad M. M.
Published: July 2007

The direct simulation Monte Carlo (DSMC) method is used to simulate the flow of rarefied gases. In the macroscopic chemistry method (MCM) for DSMC, chemical reaction rates calculated from local macroscopic flow properties are enforced in each cell. Unlike the standard total collision energy (TCE) chemistry model for DSMC, the new method is not restricted to an Arrhenius form of the reaction rate coefficient, nor is it restricted to a collision cross section which yields a simple power-law viscosity. For reaction rates of interest in aerospace applications, chemically reacting collisions are generally infrequent events and, as such, local equilibrium conditions are established before a significant number of chemical reactions occur. Hence, the reaction rates which have been used in MCM have been calculated from the reaction rate data which are expected to be correct only for conditions of thermal equilibrium. Here we consider artificially high reaction rates so that the fraction of reacting collisions is not small and propose a simple method of estimating the rates of chemical reactions which can be used in the MCM in both equilibrium and nonequilibrium conditions. Two tests are presented: (1) The dissociation rates under conditions of thermal nonequilibrium are determined from a zero-dimensional Monte Carlo sampling procedure which simulates “intramodal” nonequilibrium; that is, equilibrium distributions in each of the translational, rotational, and vibrational modes but with different temperatures for each mode; (2) the 2D hypersonic flow of molecular oxygen over a vertical plate at Mach 30 is calculated. In both cases the new method produces results in close agreement with those given by the standard TCE model in the same highly nonequilibrium conditions. We conclude that the general method of estimating the nonequilibrium reaction rate is a simple means by which information contained within nonequilibrium distribution functions predicted by the DSMC method can be included in the macroscopic chemistry method.
Morphological study into the temperature dependence of solid ammonia under astrochemical conditions using vacuum ultraviolet and Fourier-transform infrared spectroscopy
Authors: Dawes Anita , Mukerji Robin J. , Davis Michael P. , Holtom Philip D. , Webb Sarah M. , Sivaraman Bhalamurugan , Hoffmann Søren V. , Shaw David A. , Mason Nigel J.
Published: July 2007

The authors present the results of a morphological study of solid ammonia using both Fourier-transform infrared and vacuum ultraviolet (VUV) spectroscopy. Dramatic changes in the VUV and infrared spectra at temperatures between 65 and 85K provide a deeper insight into the structure of ammonia ice particularly with the observation of an exciton transition at 194nm (6.39eV) in the VUV spectrum, revealing a structure that is composed of crystallites. A complementary structure is observed in the IR spectrum at 1100cm−1 which is assigned to the symmetric deformation of ammonia molecules at the surfaces of the crystallites. Such spectral signatures may be used to identify the environment within which the ammonia ice is formed and provide a new route for obtaining information on the physical and chemical conditions occurring within the interstellar medium, on the surfaces of planetary bodies, and in Kuiper belt objects.
Determining landscape-based criteria for freezing of liquids
Authors: Chakraborty Somendra Nath , Chakravarty Charusita
Published: July 2007

The correlation between statistical properties of the energy landscape and the number of accessible configurational states, as measured by the exponential of the excess entropy (eSe), are studied in the case of a simple Lennard-Jones-type liquid in the neighborhood of the thermodynamic freezing transition. The excess entropy Se is defined as the difference between the entropy of the liquid and that of the ideal gas under identical temperature and pressure conditions and is estimated using the pair correlation contribution, S2. Landscape properties associated with three categories of configurations are considered: instantaneous configurations, inherent saddles, and inherent minima. Landscape properties studied include the energy and the key parameters of the Hessian eigenvalue distribution as well as the mean distances between instantaneous configurations and the corresponding inherent saddles and minima. The signatures of the thermodynamic freezing transition are clearest in the case of inherent structure properties which show, as a function of eS2, a pronounced change in slope in the vicinity of the solid-liquid coexistence. The mean distance between instantaneous and saddle configurations also shows a similar change in slope when the system crosses from the stable to the supercooled regime. In the case of inherent saddles, the minimum eigenvalue acts as a similar indicator of the thermodynamic freezing transition but the average and maximum eigenvalues do not carry similar signatures. In the case of instantaneous configurations, a weak indicator of the thermodynamic freezing transition is seen in the behavior of the fraction of negative curvature directions as a function of the exponential of the excess entropy.
Electrical behavior and vacuum ultraviolet radiation efficiency of monofilamentary xenon dielectric barrier discharges
Authors: Merbahi N. , Ledru G. , Sewraj N. , Marchal F.
Published: July 2007

In this paper we report the experimental investigation of a pure xenon monofilamentary dielectric barrier discharge (DBD), using a high voltage power supply. Stable microdischarges were achieved and studied in the pressure range of 100–400Torr, at frequencies between 10 and 40kHz. Successive 3ns exposure time snapshots of the discharge clearly show how it built up. Its diameter was about 0.26mm. The discharge voltage and current were determined from the measurement of the supply voltage and current. Compared to those in argon, the current pulses were shorter (less than 30ns, above 200Torr) and had much higher peak values. Ignition voltages were also higher in the heavier gas. Electrical energy and vacuum ultraviolet radiation energy of the second continuum of xenon were both independent of frequency. They both varied almost linearly with pressure. The measured DBD vuv efficiency of a single xenon microdischarge reported here was between 55% and 60%, and the maximum value was reached for 200Torr. These values were twice those reported for multifilamentary discharges working with a sinusoidal supply. They were similar to those obtained for multifilamentary dielectric barrier discharges excited with short voltage pulses.
Microphase separation induced by interfacial segregation of isotropic, spherical nanoparticles
Authors: Hore Michael J. A. , Laradji Mohamed
Published: July 2007

In a recent experiment by Chung et al. [Nano Lett. 5, 1878 (2005)] and simulation by Stratford et al. [Science 309, 2198 (2005)] on immiscible blends containing nanoscale particles, it was shown that the phase separation of the two polymers can be prevented as a result of the aggregation of the nanoparticles at the interfaces between the two polymers. Motivated by these studies, we performed large scale systematic simulations, based on the dissipative particle dynamics approach, on immiscible binary (A-B) fluids containing moderate volume fractions of isotropic nanoscale spherical particles N. The nanoparticles preferentially segregate at the interfaces between the two fluids if the pairwise interactions between the three components are such that χAB>∣χAN−χBN∣. We find that at later times, the average domain size saturates to a value, L∼RN∕ϕN, where RN and ϕN are the radius and volume fraction of the nanoparticles, respectively. For small nanoparticles, however, full phase separation is observed.
Electron paramagnetic resonance study of hydrogen-incorporated ultrananocrystalline diamond thin films
Authors: Liu Chao , Xiao Xingcheng , Wang Hsien-Hau , Auciello Orlando , Carlisle John A.
Published: July 2007

Hydrogen-incorporated ultrananocrystalline diamond (UNCD) thin films have been deposited in microwave plasma enhanced chemical vapor deposition (MPECVD) system with various hydrogen concentrations in the Ar/CH4 gas mixture, and characterized by several techniques including electron paramagnetic resonance (EPR), Raman spectroscopy, scanning electron microscope (SEM), and dc conductivity measurements. The EPR spectrum of diamond film was composed of two Lorentzian lines with different g factors. When hydrogen concentration in the plasma increased during diamond growth, the spin density of the narrow line decreased, whereas the spin density of the broad signal remained roughly constant. We propose that the two EPR components can be attributed to two different phases in the diamond film, i.e., the narrow line is originated from the highly defective grain boundary region and the broad line is related to the defects in the diamond grains.
High resolution electron energy loss measurements of Na∕Cu(111) and H2O∕Na∕Cu(111): Dependence of water reactivity as a function of Na coverage
Authors: Politano A. , Agostino R. G. , Colavita E. , Formoso V. , Chiarello G.
Published: July 2007

Collective electronic excitations occurring in Na layers grown on Cu(111) and in H2O∕Na∕Cu(111) have been investigated at room temperature by high resolution electron energy loss spectroscopy. Loss spectra taken for a coverage between 0.55 and 0.70 ML of Na are characterized by a feature at 3.0eV assigned to a Mie resonance. Further increasing the Na coverage leads to the appearance of the Na surface plasmon at 3.9eV. Water molecules dissociate on Na layers as shown by the appearance of the OH–Na vibration. Upon water adsorption, relevant effects on both electronic excitations and vibrational modes were observed as a function of Na coverage.
Ab initio vibrational predissociation dynamics of He–I2(B) complex
Authors: Valdés Álvaro , Prosmiti Rita , Villarreal Pablo , Delgado-Barrio Gerardo , Lemoine Didier , Lepetit Bruno
Published: July 2007

Three-dimensional quantum mechanical calculations on the vibrational predissociation dynamics of HeI2B state complex are performed using a potential energy surface accurately fitted to unrestricted open-shell coupled cluster ab initio data, further enabling extrapolation for large I2 bond lengths. A Lanczos iterative method with an optimized complex absorbing potential is used to determine energies and lifetimes of the vibrationally predissociating He,I2(B,v′) complex for v′⩽26 of I2 vibrational excitations. The calculated predissociating state energies agree with recent experimental results within 0.5cm−1. This excellent agreement is remarkable since no adjustment was made with respect to the experiments. The present ab initio approach, however, shows its limitations in the fact that the computed lifetimes that are highly sensitive to subtle details of the potential energy surfaces such as anisotropy, are a factor of 1.5 larger than the available experimental data.
Optical properties of Y2O3 thin films doped with spatially controlled Er3+ by atomic layer deposition
Authors: Hoang J. , Van T. T. , Sawkar-Mathur M. , Hoex B. , Van de Sanden M. C. M. , Kessels W. M. M. , Ostroumov R. , Wang K. L. , Bargar J. R. , Chang J. P.
Published: July 2007

We report in this work the optical properties of Er3+-doped Y2O3, deposited by radical enhanced atomic layer deposition. Specifically, the 1.53μm absorption cross section of Er3+ in Y2O3 was measured by cavity ring-down spectroscopy to be (1.9±0.5)×10−20cm2, about two times that for Er3+ in SiO2. This is consistent with the larger Er3+ effective absorption cross section at 488nm, determined based on the 1.53μm photoluminescence yield as a function of the pump power. X-ray photoelectron spectroscopy and Rutherford backscattering spectroscopy were used to determine the film composition, which in turn was used to analyze the extended x-ray absorption fine structure data, showing that Er was locally coordinated to only O in the first shell and its second shell was a mixture of Y and Er. These results demonstrated that the optical properties of Er3+-doped Y2O3 are enhanced, likely due to the fully oxygen coordinated, spatially controlled, and uniformly distributed Er3+ dopants in the host. These findings are likely universal in rare-earth doped oxide materials, making it possible to design materials with improved optical properties for their use in optoelectronic devices.
In situ pressure calibration for piston cylinder cells via ruby fluorescence with fiber optics
Authors: Koyama-Nakazawa Kazuko , Koeda Masahito , Hedo Masato , Uwatoko Yoshiya
Published: July 2007

A fiber-optic measurement technique is developed for estimating the pressure inside a piston cylinder cell up to ∼4GPa, based on the pressure-induced R1 fluorescence line shift of ruby (ruby scale). Ruby scale and a conventional technique (calibration on phase transitions of bismuth) were simultaneously applied to the cell filled with a pressure transmitting medium of isopropyl alcohol. The pressure readings of the two methods were consistent with each other, and no pressure gradient was observed. The ruby scale has the advantages of real time estimation and easy installation in a small space. Because of these advantages, three fibers were simultaneously introduced in the sample space at the same time, and pressure distribution was measured for Fluorinert (FC70:FC77=1:1), Daphne oil 7373, and Fomblin oil (YHVAC 130∕14).
Enhanced radiation tolerance in nanocrystalline MgGa2O4
Authors: Shen Tong D. , Feng Shihai , Tang Ming , Valdez James A. , Wang Yongqiang , Sickafus Kurt E.
Published: July 2007

The authors demonstrate a substantial enhancement in radiation-induced amorphization resistance for single-phased nanocrystalline (NC) versus large-grained polycrystalline MgGa2O4. NC and large-grained MgGa2O4 were irradiated at ∼100K with 300keV Kr++ ions to fluences ranging between 5×1019 and 4×1020Kr∕m2. Large-grained MgGa2O4 samples began to amorphize by a fluence of 5×1019Kr∕m2, while NC MgGa2O4 remained crystalline with no evidence for structural changes (other than moderate grain growth in the lowermost implanted region), to a fluence of 4×1020Kr∕m2. To our knowledge, this is the first experimental study to reveal enhanced amorphization resistance in an irradiated, single-phase, NC material.
Direct fabrication of twisted nanofibers by electrospinning
Authors: Gu Bon Kang , Shin Min Kyoon , Sohn Ki Won , Kim Sun I. , Kim Seon Jeong , Kim Sung-Kyoung , Lee Haiwon , Park Joon Shik
Published: July 2007

The authors have fabricated artificial twisted nanofibers that resemble naturally twisted fiber structures, such as collagen fibril and double-strand DNA, using a modified conventional electrospinning system to directly develop the twisted nanofibers. The system modification allowed for the fabrication of twisted nanofibers by controlling the whipping jet using a modified electric field from an auxiliary electrode. Moreover, the authors calculated the magnitude of the electric field strength vectors using the Maxwell software program to identify the effect of the rotating electric field on the auxiliary electrode. Twisted nanofibers have a potential application in biomimetics, such as in artificial muscles, actuators, and nanoelectromechanical systems.
Magnetic and structural properties of Gd-implanted zinc-blende GaN
Authors: Lo F.-Y. , Melnikov A. , Reuter D. , Wieck A. D. , Ney V. , Kammermeier T. , Ney A. , Schörmann J. , Potthast S. , As D. J. , Lischka K.
Published: July 2007

Zinc-blende GaN layers grown by molecular beam epitaxy were uniformly focused-ion-beam implanted with 300keV Gd3+ ions for doses ranging from 1×1012to1×1015cm−2, and their structural and magnetic properties were studied. The implanted samples were not subjected to any annealing treatment. Only Gd incorporation into zinc-blende GaN was observed by x-ray diffraction. Magnetic investigations using superconducting quantum interference device magnetometry reveal a (super)paramagneticlike behavior with an ordering temperature around 60K for the sample with the highest implantation dose. Our experimental studies indicate that the spontaneous electric polarization in wurtzite GaN is the crucial mechanism for its ferromagneticlike behavior upon Gd doping.
‘Fair Trade’ with Africa
Authors: Barratt Brown Michael
Published: July 2007

The origin of Africa's current failure to benefit from the expansion of world trade lies in the colonial division of labour, the consequences of which persist in economic structures far more than in other continents. The consequent economic distortions emphasising export of primary products have been preserved by external forces and are now being reinforced by free markets. The ‘fair trade’ concept seeks to ensure a measure of surplus for some producers that the market – dominated by middle-men and oligopsonistic Western corporations – denies them. A leading force in the movement, TWIN, originated in London in the 1980s, and the movement now has worldwide trade approaching £1 billion, mainly in coffee, cocoa and tea, but also in rice and cotton. African countries have been prime beneficiaries. Although growth of ‘fair trade’ is extremely high, it is unlikely ever to displace ‘free trade’ in importance, but it may nevertheless promote a way out of poverty (including dependence on the commodities in question) for many people otherwise trapped in the hangover of colonial power. This may be through gaining increasing control over the commodity chains of which at present they are only the first, fragmented element.
The Burundi Peace Negotiations: An African Experience of Peace–making
Authors: Daley Patricia
Published: July 2007

Contemporary peace negotiations in Africa reflect perceived changes in the nature of warfare in the post-Cold War, neo-liberal era. ‘New wars’ are characterised as predominantly civil warfare that is non-ideological, fuelled by identity-politics and driven by greed or grievance. Neo-liberal approaches to conflict resolution involve a multiplicity of state and non-state actors, both protagonists and mediators, and promote universally-applicable solutions, such as power-sharing and the extension of market-based economic systems. These have had limited success in Africa because they have been unable to transform the social system within which violence and inequalities are embedded. Through an examination of the Burundi peace process, particularly, the Arusha peace negotiations – their origins, actors, debates, agreements and recommendations – this article highlights the discursive practices of neo-liberal peace-making and exposes its inherent limitations in creating any meaningful transformation of the political space. It is argued here that peace negotiations can be perceived as political struggles, beyond that envisaged between the belligerents, due to the prevalence of a multitude of supporting actors seeking to promote vested interests. Consequently, the resulting peace agreement is not necessarily consensual or reflective of a compromise for the sake of peace; it marks, essentially, a temporary stalemate in the power play between international, regional and local actors and their competing visions of peace. This explains why the ‘liberal’ peace that is attained through these manoeuvrings is one that appears to uphold the sovereignty of the state, but is not transformative with regards to the security of the people.