bluuebunny/crossref_metadata_2025 huggingface dataset:
Excessive ventilation during early phase of exercise: A new predictor of poor long‐term outcome in patients with chronic heart failure
Authors: Jankowska Ewa A. , Witkowski Tomasz , Ponikowska Beata , Reczuch Krzysztof , Borodulin‐Nadzieja Ludmila , Anker Stefan D. , Piepoli Massimo F. , Banasiak Waldemar , Ponikowski Piotr
Published: August 2007

Background:

Studies demonstrating prognostic value of excessive exercise ventilation in chronic heart failure (CHF) have focused on data derived from the whole cardiopulmonary exercise test (CPET). Whether ventilatory response to early phase of exercise is useful for risk stratification in CHF is unknown.

Methods and results:

We evaluated 216 patients with systolic CHF who underwent CPET (age: 60±11 years, NYHA class [I/II/III/IV]: 18/104/77/17). Ventilatory response to exercise (slope of regression line relating ventilation to carbon dioxide production) was calculated from the whole exercise test (VE‐VCO2‐all) and from the first 3min of exercise (early phase — VE‐VCO2‐3min). During follow‐up (mean: 40± 20months, >3years in survivors), 89 (41%) CHF patients died. High VE‐VCO2‐all and VE‐VCO2‐3min predicted poor outcome in single predictor analyses, and in multivariable models when adjusted for prognosticators (age, NYHA class, ejection fraction, peak VO2) (P<0.0001). In receiver operating characteristic curve analysis, areas under curve for 3‐year follow‐up were similar for VE‐VCO2‐all and VE‐VCO2‐3min. VE‐VCO2‐3min maintained its prognostic value in patients taking β‐blockers (P<0.0001) and those unable to perform maximal CPET (P=0.0009).

Conclusions:

In CHF patients, excessive ventilation assessed over the first 3min predicts poor outcome. Assessment of ventilatory response to exercise for prognostic stratification may be extended to patients unable to perform maximal CPET.
Dobutamine stress echocardiography and the effect of revascularization on outcome in diabetic and non‐diabetic patients with chronic ischaemic left ventricular dysfunction
Authors: Cortigiani Lauro , Sicari Rosa , Desideri Alessandro , Bigi Riccardo , Bovenzi Francesco , Picano Eugenio ,   on behalf of the VIDA (Viability Identification with Dobutamine Administration) Study Group
Published: August 2007

Aim:

To evaluate the interaction between prognostic effect of revascularization and viability in diabetic and non‐diabetic patients with ischaemic left ventricular dysfunction.

Methods:

612 patients with angiographically proven coronary artery disease and left ventricular ejection fraction <35% underwent dobutamine stress echocardiography to assess viability (peak‐rest wall motion score index >0.4). 262 patients (75 diabetics, 187 non‐diabetics) underwent revascularization and 350 (88 diabetics, 262 non‐diabetics) were on medical therapy.

Results:

During follow‐up 215 patients died. Independent predictors of mortality in revascularized patients were resting left ventricular ejection fraction (HR=0.93, 95% CI 0.89–0.97, p<0.0001), Δ WMSI>40 (HR=0.44, 95% CI 0.23–0.85, p=0.01), and age (HR=1.03, 95% CI 1.00–1.06, p=0.04). In medically treated patients, independent predictors of mortality were diabetes mellitus (HR=1.64, 95% CI 1.13–2.38, p=0.009), number of diseased vessels (HR=1.27, 95% CI 1.03–1.56, p=0.02), and age (HR–1.02, 95% CI 1.00=1.04, p–0.03). In revascularized patients, 4‐year mortality was 15% in those with viability and 26% in those without viability (p=0.04), there was no difference between diabetics and non‐diabetics (24% vs 22%; p=0.24).

Conclusions:

Viability at dobutamine stress echocardiography independently predicts improved outcome following revascularization in non‐diabetics as well as diabetic patients with ischaemic left ventricular dysfunction.
The reactivation of DnaA(L366K) requires less acidic phospholipids supporting their role in the initiation of chromosome replication in Escherichia coli
Authors: Aranovich Alexander , Parola Abraham H. , Fishov Itzhak
Published: August 2007

DnaA(L366K), in concert with a wild‐type DnaA (wtDnaA) protein, restores the growth of Escherichia coli cells arrested in the absence of adequate levels of cellular acidic phospholipids. In vitro and in vivo studies showed that DnaA(L366K) alone does not induce the initiation of replication, and wtDnaA must also be present. Hitherto the different behavior of wt and mutant DnaA were not understood. We now demonstrate that this mutant may be activated at significantly lower concentrations of acidic phospholipids than the wild‐type protein, and this may explain the observed growth restoration in vivo.
Myotonic dystrophy CTG repeat expansion alters Ca2+ channel functional expression in PC12 cells
Authors: Andrade Arturo , de León Mario Bermúdez , Hernández-Hernández Oscar , Cisneros Bulmaro , Felix Ricardo
Published: August 2007

We previously reported that expression of myotonic dystrophy (DM1) expanded CUG repeats impedes NGF‐induced differentiation in a PC12 clone (CTG90 cells). Here, we present evidence for changes in the fractional contribution of distinct voltage‐gated Ca2+ channels, key elements in neurotrophin‐promoted differentiation, to the total Ca2+ current in the CTG90 cells. Patch‐clamp recordings showed that the relative proportion of pharmacologically isolated Ca2+ channel types differed between control and CTG90 cells. Particularly, the functional expression of N‐type channels was significantly reduced. Though quantitative real‐time RT‐PCR revealed that transcripts for the pore‐forming subunit encoding the N‐type channels remained unchanged, the protein level analyzed by semi‐quantitative Western blotting was down‐regulated in the CTG90 cells. These data suggest modifications in the processing of N‐type Ca2+ channels in PC12 cells expressing the DM1 mutation.
Human manganese superoxide dismutase suppresses HER2/neu‐mediated breast cancer malignancy
Authors: Chuang Tzu-Chao , Liu Jah-Yao , Lin Chi-Tsai , Tang Ya-Ting , Yeh Ming-Han , Chang Su-Chien , Li Jhy-Wei , Kao Ming-Ching
Published: August 2007

The up‐regulation of HER2/neu is associated with human malignancies and is a useful target for developing anticancer drugs. Overexpression of human manganese superoxide dismutase (MnSOD) has been demonstrated to effectively suppress various carcinoma cells, including breast carcinomas, in vitro and in vivo. This study demonstrates that MnSOD effectively suppresses HER2/neu oncogene expression at the transcriptional level. Additionally, stable transfection was used and the MnSOD‐transfected human breast cancer clones were found to be able to down‐regulate the endogenous production of p185HER2/neu. Furthermore, the MnSOD‐overexpressing stable transfectants exhibited reduced soft‐agarose colony‐forming ability and metastatic properties, unlike control cell lines. These data suggest that MnSOD may be useful in treating HER2/neu‐mediated human breast tumor malignancy.
Delayed Treatment of Persistent Radial Nerve Paralysis Associated with Fractures of the Middle Third of Humerus: Review and Evaluation of the Long-Term Results of 52 Cases
Authors: VERGA M. , DI CAPRIO A. PERI , BOCCHIOTTI M. A. , BATTISTELLA F. , BRUSCHI S. , PETROLATI M.
Published: August 2007

This study was undertaken to determine the efficacy of delayed surgical treatment in cases of persistent radial nerve paralysis after fractures of the middle third of the humerus. We have limited this study to patients who had absolutely no functional recovery of the radial nerve 3 to 4 months after middle third humeral fractures. The fractures were treated by a variety of orthopaedic methods, conservative and surgical, in other departments and hospitals. Surgical exploration of the radial nerve was carried out 3 to 4 months after primary orthopaedic treatment. The outcome of this study concurs with data in the literature in showing that delayed nerve surgery (neurolysis or nerve grafts) in the absence of functional recovery of the radial nerve after humeral fracture can be useful in achieving good functional recovery and subjectively satisfying results.
Use of Modified Tension Band Sutures for Fingernail Disruptions
Authors: PATANKAR H. S.
Published: August 2007

A series of 66 patients, aged between 1 and 70 years, with 70 disruptive injuries to finger nails was reviewed. The injuries were treated by cleaning of the finger, evacuation of haematoma and anatomical replacement of the nail plate, or a substitute, which was secured with a modified dorsal tension band suture without formal repair of the nail bed. K-wire fixation of the distal phalanx was employed only in the event of displaced fracture of the distal phalanx, complete absence of the nail plate and laceration extending to the distal pulp. This simple method, which bypasses the injured and friable, but vital nail structures resulted in uncomplicated reformation of the normal nail plate in all of the cases. Removal of the nail plate and formal repair of the nail bed is not necessary in any age group with finger nail disruptions.
A Russia that can say “no”?
Authors: Connor Walter D.
Published: August 2007

A rather consistent picture of Russian domestic politics and foreign policy in Putin's second presidential term emerges from the four works discussed. Elements of authoritarian rule, welcome or at least acceptable to large segments of a public weary of the political and economic disorder of Yeltsin's time, combine with Russia's growing energy-driven economic strength to provide a stable environment, and broad support for the regime. These strengths are expressed externally in a more assertive foreign policy, whose manifestations in both trade and security areas pose challenges for the US, and its EU and NATO allies.
Politics without frontiers: The impact of Hungarian domestic politics on the minority question in Romania
Authors: Kulcsár László J. , Bradatan Cristina
Published: August 2007

Throughout the past years, substantial discussions have dealt with the factors associated with ethnic conflicts such as institutional designs, group dynamics and the influence of external peacemakers. However, one area remains largely uncovered: this is how the domestic politics of a nation state shape minority issues from the same ethnicity in another country. In this paper we discuss the dynamics of Hungarian politics relative to the Hungarian minority in Romania, and identify factors that resulted in exporting domestic political contention to another country.
A 3-month, double-blind, controlled trial of feeding with sucrose polyester in human volunteers
Authors: Kelly Sean M. , Shorthouse Maria , Cotterell Josephine C. , Riordan Alex M. , Lee Alison J. , Thurnham David I. , Hanka Rudolf , Hunter John O.
Published: August 2007

Sucrose polyester (SPE) is a tasteless, odourless substance which reduces plasma cholesterol concentrations and may therefore be valuable as a fat substitute in human foodstuffs. It has recently been approved for use in snack foods by the United States Federal Drug Administration. The current study was designed to investigate its effects on gastrointestinal physiology and nutrient absorption in human subjects. A 6-month (2×3-month periods) double-blind, lacebo-controlled, randomized, cross-over trial of SPE and control fat was performed in healthy free-living volunteers. Subjects consumed 20–40 g of SPE daily (mean 26·8 (se 6·8) g) which reduced the intake of total and saturated fat but had no effect on energy intake or body weight. Plasma cholesterol and triacylglycerols were reduced. The frequency of bowel movements and their urgency were increased and anal leakage occured in 7·2% of subjects. Abdominal pain was more frequent in subjects receiving SPE and was significantly greater than in the control group after 8 weeks feeding. The plasma concentrations of vitamin E and six carotenoids were significantly reduced. Routine haematology and biochemistry, other vitamins, intestinal biopsies, bile-salt retention, rectal prostaglandins, fractional Ca absorption and aminopyrine metabolism were unaffected. The ingestion of foods containing 20–40 g SPE daily provoked significant gastro-intestinal problems. This intake is greater than that to be expected from the use of SPE in savoury snack foods, for which it has been approved by the United States Federal Drug Administration. However, the favourable effects on lipid profiles must be balanced against the reduction in the concentrations of vitamins and carotenoids, as these compounds may have beneficial effects on health through protection from free-radical oxidative stress.
The effect of 13 weeks of running training followed by 9 d of detraining on postprandial lipaemia
Authors: Herd Sara L. , Hardman Adrianne E. , Boobis Leslie H. , Cairns Caroline J.
Published: August 2007

The present study examined the influence of training, followed by a short period of detraining, on postprandial lipaemia. Fourteen normolipidaemic, recreationally active young adults aged 18–31 years participated, in two self-selected groups: three men and five women (BMI 21·7–27·6 kg/m2) completed 13 weeks of running training, after which they refrained from exercise for 9 d; three men and three women (BMI 21·5–25·6 kg/m2) maintained their usual lifestyle. Oral fat tolerance tests were conducted at baseline and again 15 h, 60 h and 9 d after the runners' last training session. Blood samples were drawn after an overnight fast and at intervals for 6 h after consumption of a high-fat meal (1·2 g fat, 1·4 g carbohydrate, 70·6 kJ energy/kg body mass). Heparin was then administered (100 IU/kg) and a further blood sample was drawn for measurement of plasma lipoprotein lipase (EC3.1.1.34; LPL) activity. Endurance fitness improved in runners, relative to controls (maximal O2uptake +3·2 (SE 1·1) ml/kg per minv.− 1·3 (SE 1·2) ml/kg per min; P < 0·05). In the absence of the acute effect of exercise, i.e. 60 h after the last training session, there was no effect of training on either postprandial lipaemia or on post-heparin LPL activity. However, changes during 9 d of detraining in both these variables differed significantly between groups; after 2 d without exercise (60 h test), the runners' lipaemic response was 37% higher than it was the morning after their last training session (15 h test; runnersv.controlsP< 0·05), with a reciprocal decrease in post-heparin LPL activity (P< 0·01). These findings suggest that improved fitness does not necessarily confer an effect on postprandial lipaemia above that attributable to a single session of exercise.
Dietary recommendations and prevailing food and nutrient intakes in Germany
Authors: Hermann-Kunz Edelgard , Thamm Michael
Published: August 2007

Dietary recommendations on nutrient intakes as published by the German Society of Nutrition are only met by a very small proportion of the adult population in East and in West Germany. Dietary data from the Nutrition Survey and Risk Factor Analysis Study in West Germany and from the National Health Survey in East Germany were used to identify differences in nutrient intakes and in food consumption patterns between subgroups of the study participants that were close to, or failed to meet the dietary guidelines. The subgroups were created by dividing subjects into quartiles on the basis of their daily intakes of total fat (%energy), saturated fatty acids (%energy), fibre (g/d) and the food group fruit and vegetables (g/d). Comparisons of the consumption patterns between subjects in the first and in the fourth quartile of intake of the nutrients under study were performed. Differences in food and nutrient intakes were seen among those more compliant and less compliant with the recommendations. The presented analysis provides first indications for future improvements of the existing food-based dietary guidelines in Germany.
An approach to the development of food-based dietary guidelines for Ireland
Authors: Flynn Mary A. T. , Kearney John M.
Published: August 2007

The aim of the present study was to analyse the different food and nutrient intakes of the adult Irish population from the lowest and highest quartiles of intake for total fat (%energy) dietary fibre (g/MJ) and fruit and vegetables (g/day). Data on Irish adults (n = 715) from the Irish National Nutrition Survey conducted in 1989 were used for the analyses and showed that the average diet is low in dietary fibre, with fruit and vegetables being only half the recommended level of 400 g. Comparisons of people with low or high intakes (from lowest and highest quartiles) of total fat (%energy), dietary fibre (g/MJ) and fruit and vegetables (g/day) show patterns of food intake differing in both the percentage of consumers and in the mean intakes among consumers only. This analysis provides data which may be useful as a first step towards the development of food-based dietary guidelines for Ireland. In particular, the low intake of fruit and vegetables in the adult Irish population deserves special attention.
Patterns of food and nutrient intakes in Italy and their application to the development of food-based dietary guidelines
Authors: Turrini Aida , Leclercq Catherine , D'Amicis Amleto
Published: August 2007

Patterns of food and nutrient intakes in Italy were estimated starting from a nationwide food survey carried out by the National Institute of Nutrition (NIN) in 1994–6, called INN-CA 1995. The present analysis looks at food and nutrient intakes of the subsample of the adults (18–60-year-old individuals). In particular, the two extreme quartiles of the distribution of total fat intake expressed as percentage of energy were considered in the analysis. The results showed that the subjects included in the fourth quartile (high-fat consumers) consumed fewer vegetables than the subjects in the first quartile (low-fat consumers). Furthermore, high-fat consumers had a tendency to have an unbalanced diet, whereas the low-fat consumers present a better pattern. In synthesis, 50% of the adults reach the goal of at least 400g of vegetables and fruit daily, and 25% consume less than 30 % of energy from total fats. Convincing that part of the population whose diet does not comply with dietary goals to come back to the Mediterranean tradition might be a priority for nutrition education in Italy.
Atteintes du pied dans les maladies metaboliques
Authors: Gerster
Published: August 2007

Dans la phase aiguë la goutte touche le plus souvent l'hallux, plus rarement le médiotarse ou le tendon d'Achille. Le diagnostic de certitude repose sur la mise en évidence de cristaux typiques. Le traitement de la crise aiguë ou subaiguë avec la colchicine est une bonne alternative aux AINS s'il n'y a pas d'insuffisance rénale. Le traitement hypo-uricémiant (allopurinol ou agents uricosuriques) est à commencer à distance d'une crise aiguë, car il comporte le risque d'une exacerbation de l'inflammation. Le losartan et le fénofibrate ont une action uricosurique. L'hémochromatose se manifeste principalement sous forme d'une atteinte chondrocalcinosique, en particulier au talon. L'enthésopathie hyperostosante diffuse peut causer une talalgie sévère par une ossification à l'insertion de la fascia plantaire ou du tendon calcanéen. L'hypercholestérolémie peut se manifester par des xanthomes des tendons d'Achille à localisation bilatérale. Un rhumatisme apatitique peut survenir chez les patients en hémodialyse chronique.
Chlorinated Diphenyl Ethers in Sediments, Biota, and the Water Column from Coastal British Columbia, Canada
Authors: Rayne Sierra , Michael Ikonomou , Garrett Chris
Published: August 2007

Polychlorinated diphenyl ethers (PCDEs) are impurities in technical chlorophenol mixtures, are used as dielectric fluids in capacitors and as herbicides, antiseptics, food preservatives, and papers and textiles, and can be formed through the chlorination of organics in water and wastewater streams. Samples from semipermeable membrane devices (SPMDs), sediments, English sole, mussels, and Dungeness crab were collected from urban/industrial and remote sites along the marine coast of British Columbia and analyzed by congener-specific GC-MS analysis for mono- through deca-substituted PCDEs. Higher concentrations in biota and sediments were observed near urban/industrial areas, with evidence for food-chain biomagnification within major harbours. Correlations between size distributions and PCDE levels indicate these hydrophobic contaminants tend to preferentially partition into sediments with higher clay/silt fractions. Multivariate analysis of congener patterns shows distinct PCDE profiles among different species and environmental matrices, and evidence for favoured dechlorination pathways among the most commonly observed congeners in aquatic systems.
Preferential accumulation of bubbles in Couette-Taylor flow patterns
Authors: Climent Eric , Simonnet Marie , Magnaudet Jacques
Published: August 2007

We investigate the migration of bubbles in several flow patterns occurring within the gap between a rotating inner cylinder and a concentric fixed outer cylinder. The time-dependent evolution of the two-phase flow is predicted through three-dimensional Euler-Lagrange simulations. Lagrangian tracking of spherical bubbles is coupled with direct numerical simulation of the Navier-Stokes equations. We assume that bubbles do not influence the background flow (one-way coupling simulations). The force balance on each bubble takes into account buoyancy, added-mass, viscous drag, and shear-induced lift forces. For increasing velocities of the rotating inner cylinder, the flow in the fluid gap evolves from the purely azimuthal steady Couette flow to Taylor toroidal vortices and eventually a wavy vortex flow. The migration of bubbles is highly dependent on the balance between buoyancy and centripetal forces (mostly due to the centripetal pressure gradient) directed toward the inner cylinder and the vortex cores. Depending on the rotation rate of the inner cylinder, bubbles tend to accumulate alternatively along the inner wall, inside the core of Taylor vortices or at particular locations within the wavy vortices. A stability analysis of the fixed points associated with bubble trajectories provides a clear understanding of their migration and preferential accumulation. The location of the accumulation points is parameterized by two dimensionless parameters expressing the balance of buoyancy, centripetal attraction toward the inner rotating cylinder, and entrapment in Taylor vortices. A complete phase diagram summarizing the various regimes of bubble migration is built. Several experimental conditions considered by Djéridi, Gabillet, and Billard [Phys. Fluids 16, 128 (2004)] are reproduced; the numerical results reveal a very good agreement with the experiments. When the rotation rate is increased further, the numerical results indicate the formation of oscillating bubble strings, as observed experimentally by Djéridi et al. [Exp. Fluids 26, 233 (1999)]. After a transient state, bubbles collect at the crests or troughs of the wavy vortices. An analysis of the flow characteristics clearly indicates that bubbles accumulate in the low-pressure regions of the flow field.
Numerical experiments of the planar equal-mass three-body problem: The effects of rotation
Authors: Kuwabara Kenji Hiro , Tanikawa Kiyotaka
Published: August 2007

The planar three-body problem with angular momentum is numerically and systematically studied as a generalization of the free-fall problem (i.e., the three-body problem with zero initial velocities). The initial conditions in the configuration space exhaust all possible forms of a triangle, whereas the initial conditions in the momentum space are chosen so that position vectors and momentum vectors are orthogonal. Numerical results are organized according to the value of virial ratio k defined as the ratio of the total kinetic energy to the total potential energy. Final motions are mapped in the initial value space. Several interesting features are found. Among others, binary collision curves seem to spiral into the Lagrange point, and for large k, binary collision curves connect the Lagrange point and the Euler point. The existence of a lunar periodic orbit and a periodic orbit of petal-type is suggested. The number of escape orbits as a function of the escape time is analyzed for different k. The behavior of this number for different time and k shows most remarkably the effects of rotation of triple systems. The number of escape orbits increases exponentially for k⩽0.1, the number seems to saturate for k=0.3−0.5, and most of the escape orbits escape quickly for k=0.9. The area of chaotic motion is small for k=0.9.
Continuum limit semiclassical initial value representation for dissipative systems
Authors: Pollak Eli
Published: August 2007

In this paper, we consider a dissipative system in which the system is coupled linearly to a harmonic bath. In the continuum limit, the bath is defined via a spectral density and the classical system dynamics is given in terms of a generalized Langevin equation. Using the path integral formulation and factorized initial conditions, it is well known that one can integrate out the harmonic bath, leaving only a path integral over the system degrees of freedom. However, the semiclassical initial value representation treatment of dissipative systems has usually been limited to a discretized treatment of the bath in terms of a finite number of bath oscillators. In this paper, the continuum limit of the semiclassical initial value representation is derived for dissipative systems. As in the path integral, the action is modified with an added nonlocal term, which expresses the influence of the bath on the dynamics. The first order correction term to the semiclassical initial value approximation is also derived in the continuum limit.
The effect of diffusion-limited lifetime on implied current voltage curves based on photoluminescence data
Authors: Abbott M. D. , Bardos R. A. , Trupke T. , Fisher K. C. , Pink E.
Published: August 2007

Quasi-steady-state photoconductance measurements and Suns-photoluminescence are useful techniques in predicting the electrical terminal characteristics of partially finished solar cells in contactless mode even prior to the junction formation. In both techniques, a measured average minority carrier density in the bulk is correlated with the carrier density at the edge of the junction and thereby with an implied voltage. This paper discusses experimental artifacts in such experiments that can be caused by the diffusion-limited effective minority carrier lifetime. Here these effects are discussed theoretically and demonstrated experimentally in relation to the Suns-photoluminescence technique only, because the range of implied voltages that is affected is generally not accessible via photoconductance measurements. A simple technique is proposed to correct the curves and increase the range of voltages measured accurately by the Suns-photoluminescence technique. It is concluded that the influence of diffusion-limited lifetime must be considered when interpreting Suns-photoluminescence curves, particularly in samples with a surface that is passivated by a shunted junction.
Sampling of states for estimating the folding funnel entropy and energy landscape of a model alpha-helical hairpin peptide
Authors: Chapagain Prem P. , Parra Jose L. , Gerstman Bernard S. , Liu Yanxin
Published: August 2007

Protein folding times are many orders of magnitude shorter than would occur if the peptide chain randomly sampled possible configurations, which implies that protein folding is a directed process. The detailed shape of protein’s energy landscape determines the rate and reliability of folding to the native state, but the large number of structural degrees of freedom generates an energy landscape that is hard to visualize because of its high dimensionality. A commonly used picture is that of an energy funnel leading from high energy random coil state down to the low energy native state. As lattice computer models of protein dynamics become more realistic, the number of possible configurations becomes too large to count directly. Statistical mechanic and thermodynamic approaches allow us to count states in an approximate manner to quantify the entropy and energy of the energy landscape within a folding funnel for an α-helical protein. We also discuss the problems that arise in attempting to count the huge number of individual states of the random coil at the top of the funnel.
A term-by-term direct numerical simulation validation study of the multi-environment conditional probability-density-function model for turbulent reacting flows
Authors: Smith S. T. , Fox R. O.
Published: August 2007

The multi-environment conditional probability-density-function (MECPDF) approach for modeling extinction and re-ignition in turbulent nonpremixed reacting flows is analyzed. A unique derivation of the model is given, which makes use of numerical Gaussian quadrature in addition to physical assumptions. The new derivation offers insight into the physical meaning of model terms and offers a more rigorous method for model validation. The assumptions required to close the dissipation terms are validated term by term using data from direct numerical simulations of an inert and a reacting scalar in decaying isotropic turbulence. Results show convergence of the numerical quadrature with an increasing number of quadrature points. Also, good agreement is shown for the physical model assumptions required to close the mixed dissipation and the progress-variable dissipation terms. The MECPDF method is also demonstrated to offer the flexibility to incorporate either micromixing or otherwise more sophisticated models for the mixing between regions of the flow that exhibit differing degrees of extinction.
Spontaneous generation of vortex crystals from forced two-dimensional homogeneous turbulence
Authors: Jiménez Javier , Guegan Alan
Published: August 2007

The long-term limit of statistically stationary two-dimensional turbulence is shown to depend on the form of the large-scale forcing, in agreement with previous results. That effect is studied systematically by continuously varying the forcing from deterministic to Brownian in direct numerical simulations in doubly periodic boxes. As expected, this switches on or off the enstrophy cascade and the presence of strong coherent structures, but the transition is not monotonic. Under intermediate forcing conditions, the flow evolves to a stationary vortex crystal with triangular lattice, which appears to be stable and to last indefinitely. Deterministic forcings frustrate crystallization through the formation of fast-moving dipoles, and very random ones melt the crystal. The dispersion properties of the different regimes are studied, and it is shown that efficient particle dispersion depends on the presence of multiscale turbulence. The relation with other two-dimensional systems is discussed.
A novel low inertia shear flow instability triggered by a chemical reaction
Authors: Burghelea Teodor , Wielage-Burchard Kerstin , Frigaard Ian , Martinez D. Mark , Feng James J.
Published: August 2007

We present an experimental investigation of a novel low Reynolds number shear flow instability triggered by a chemical reaction. An acid-base reaction taking place at the interface between a Newtonian fluid and carbopol-940 solution leads to a strong viscosity stratification, which locally destabilizes the flow. Our experimental observations are made in the context of a miscible displacement flow, for which the flow instability promotes local mixing and subsequently improves the displacement efficiency. The experimental study is complemented by a simplified normal mode analysis to shed light on the origin of the instability.
Unsteady draining flows from a rectangular tank
Authors: Forbes Lawrence K. , Hocking Graeme C.
Published: August 2007

Two-dimensional, unsteady flow of a two-layer fluid in a tank is considered. Each fluid is inviscid and flows irrotationally. The lower, denser fluid flows with constant speed out through a drain hole of finite width in the bottom of the tank. The upper, lighter fluid is recharged at the top of the tank, with an input volume flux that matches the outward flux through the drain. As a result, the interface between the two fluids moves uniformly downwards, and is eventually withdrawn through the drain hole. However, waves are present at the interface, and they have a strong effect on the time at which the interface is first drawn into the drain. A linearized theory valid for small extraction rates is presented. Fully nonlinear, unsteady solutions are computed by means of a novel numerical technique based on Fourier series. For impulsive start of the drain, the nonlinear results are found to agree with the linearized theory initially, but the two theories differ markedly as the interface approaches the drain and nonlinear effects dominate. For wide drains, curvature singularities appear to form at the interface within finite time.
Alternative linear-scaling methodology for the second-order Møller-Plesset perturbation calculation based on the divide-and-conquer method
Authors: Kobayashi Masato , Imamura Yutaka , Nakai Hiromi
Published: August 2007

A new scheme for obtaining the approximate correlation energy in the divide-and-conquer (DC) method of Yang [Phys. Rev. Lett. 66, 1438 (1991)] is presented. In this method, the correlation energy of the total system is evaluated by summing up subsystem contributions, which are calculated from subsystem orbitals based on a scheme for partitioning the correlation energy. We applied this method to the second-order Møller-Plesset perturbation theory (MP2), which we call DC-MP2. Numerical assessment revealed that this scheme provides a reliable correlation energy with significantly less computational cost than the conventional MP2 calculation.
Submillimeter-wave spectroscopy of DCO+ in the excited vibrational states: Does the Stark effect cause anomalies in the (022) state?
Authors: Hirao T. , Yu Shanshan , Amano T.
Published: August 2007

The lowest two rotational transitions of (0220) were not detected in previous investigations. This nonobservation was ascribed to the Stark broadening caused by the electric field in a hollow cathode discharge and an extended negative glow discharge. However, rotational lines of symmetric-top ions such as CH3CNH+ and SD3+ were observed in extended negative glow discharges with no such Stark effect. Also, no anomalies were observed for similar lines for HCN and HNC produced in an extended negative glow discharge. In the present investigation, we extended the measurements of DCO+ up to 800GHz. The DCO+ ions were produced in an extended negative glow discharge in a gas mixture of D2 and CO (a couple of millitorr each) in Ar buffer (∼12mTorr). The measurements were made mostly at liquid nitrogen temperature. Our observations confirmed that the lowest rotational lines in (0220) within our frequency coverage, J=4-3, were too weak to be detected. However, a most notable result obtained in the present investigation is that the J=5-4 and J=6-5 lines of (0220) and the J=5-4 line of (0420) have been detected in induced emission. This observation implies that the previous nonobservation of low-J lines in (0220) may not be due to the Stark effect. The l-type splitting in (0330) has been observed for the J=9-8 transition and higher. However, the splittings for the J=7-6 and J=8-7 lines that are expected to be large enough have not been resolved. The reason for this “narrowing” has been unexplained at the present stage. The population inversion suggests that, initially, DCO+ is formed predominantly in stretching vibrational states, and, subsequently, the energy transfer to bending vibrational states takes place through collisional relaxation processes.
On the Knudsen transport of gases in nanochannels
Authors: Li Zhigang , Hong Ling
Published: August 2007

We investigate the diffusion of gas molecules in nanochannels under the combinational effect of the vibration of the channel, gas-wall binding energy, and channel size through molecular dynamics simulations. It is found that the molecular vibration of the channel plays a critical role in gas transport process when the gas-wall binding energy is strong. For small binding energies, the influence of the flexibility of the wall can be neglected. In rigid channels, the gas self-diffusion coefficient increases with increasing gas-wall binding energy, while it decreases in nonrigid channels. The effect of the channel size on the self-diffusion coefficient is not significant except that a local maximum in the gas self-diffusion coefficient is found in 2nm channels due to the strong repulsive force caused by the surface curvature of the channels.
In situ imaging of electromigration-induced nanogap formation by transmission electron microscopy
Authors: Heersche Hubert B. , Lientschnig Günther , O’Neill Kevin , van der Zant Herre S. J. , Zandbergen Henny W.
Published: August 2007

The authors imaged electromigration-induced nanogap formation in situ by transmission electron microscopy. Real-time video recordings show that edge voids form near the cathode side. The polycrystalline gold wires narrow down until a single-grain boundary intersects the constriction along which the breaking continues. During the last 50ms of the break, a relatively large deformation of the constriction’s geometry occurs. The shape of the anode (blunt) and the cathode (sharp) is asymmetric when the wire breaks with a bias voltage applied, but symmetric when a narrow constriction breaks spontaneously.
Adsorption-controlled molecular-beam epitaxial growth of BiFeO3
Authors: Ihlefeld J. F. , Kumar A. , Gopalan V. , Schlom D. G. , Chen Y. B. , Pan X. Q. , Heeg T. , Schubert J. , Ke X. , Schiffer P. , Orenstein J. , Martin L. W. , Chu Y. H. , Ramesh R.
Published: August 2007

Bi Fe O 3 thin films have been deposited on (111) SrTiO3 single crystal substrates by reactive molecular-beam epitaxy in an adsorption-controlled growth regime. This is achieved by supplying a bismuth overpressure and utilizing the differential vapor pressures between bismuth oxides and BiFeO3 to control stoichiometry. Four-circle x-ray diffraction reveals phase-pure, untwinned, epitaxial, (0001)-oriented films with rocking curve full width at half maximum values as narrow as 25arcsec (0.007°). Second harmonic generation polar plots combined with diffraction establish the crystallographic point group of these untwinned epitaxial films to be 3m at room temperature.
Hydration properties of magnesium and calcium ions from constrained first principles molecular dynamics
Authors: Ikeda Takashi , Boero Mauro , Terakura Kiyoyuki
Published: August 2007

We studied the solvation structures of the divalent metal cations Mg2+ and Ca2+ in ambient water by applying a Car-Parrinello-based constrained molecular dynamics method. By employing the metal-water oxygen coordination number as a reaction coordinate, we could identify distinct aqua complexes characterized by structural variations of the first coordination shell. In particular, our estimated free-energy profile clearly shows that the global minimum for Mg2+ is represented by a rather stable sixfold coordination in the octahedral arrangement, in agreement with experiments. Conversely, for Ca2+ the free-energy curve shows several shallow local minima, suggesting that the hydration structure of Ca2+ is highly variable. Implications for water exchange reactions are also discussed.
Relation between the critical current and the n value of ReBCO thin films: A scaling law for flux pinning of ReBCO thin films
Authors: Oh Sangjun , Choi Heekyung , Lee Chulhee , Lee Sangmoo , Yoo Jaeun , Youm Dojun , Yamada H. , Yamasaki H.
Published: August 2007

Detailed field and angle dependencies of the critical current and the n value for a SmBCO coated conductor have been measured. It was found that the field dependence of the n value can be fitted by an empirical power law with three parameters including the irreversibility field. We also found that there is a correlation between the critical current and the n value which can be described by the Kramer model including thermal activation. The model fits the field dependence of the empirical critical current data at various angles and temperatures with three fitting parameters, the pinning force maximum, the g factor, and the upper critical field. The upper critical field found from fitting was higher than the irreversibility field, and the angular dependence of the upper critical field is in agreement with the Tinkham model. The pinning force maxima do not show a correlation with the upper critical or the irreversibility fields, which is attributed to the difference in the pinning mechanism with a variation of the angle. It was further shown that the angular dependence of the critical current can be calculated by the Kramer model including thermal activation with empirical angular dependence expressions for each parameter. The critical current data reported by Yamada et al. [Supercond. Sci. Technol. 17, S25 (2004)] for YBCO thin films on various substrates deposited by pulsed laser deposition method can also be described by the Kramer model including thermal activation and the angular dependencies of each parameter were compared with the SmBCO coated conductor fitting results.
The C1s core line in irradiated graphite
Authors: Speranza Giorgio , Minati Luca , Anderle Mariano
Published: August 2007

Recently, plasma deposited amorphous carbon films have been the subject of extensive experimental and theoretical investigations aimed at correlating their electronic, structural, and mechanical properties to growth parameters. To investigate these properties, different spectral parameters reflecting the electronic structure of carbon-based materials are proposed in literature. The effects of various electronic configurations on the carbon photoelectron spectra are analyzed here with particular attention to C1s core line with the aim to better interpret its structure. The latter is commonly fitted under the assumption that it can be described by using just two spectral components related to sp2 and sp3 hybrids. Their relative intensities are then used to estimate the sp2 and sp3 phases. We show that, in the presence of an amorphous network, the C1s line shape is the result of a more complex mixture of electronic states. Ar+ irradiated graphite and successive oxidation was used to identify spectral features to better describe the C1s line shape.
Dielectrophoresis force driven dynamics of carbon nanotubes in liquid crystal medium
Authors: Srivastava Anoop Kumar , Jeong Seok Jin , Lee Myong-Hoon , Lee Seung Hee , Jeong Seok Ho , Lee Young Hee
Published: August 2007

This work reports the translation motion of carbon nanotubes (CNTs) dispersed in nematic liquid crystal (NLC) under an ac electric field. This effect was studied for homogeneously and vertically aligned NLC cells driven by in-plane field and vertical electric field, respectively. Long axis of the CNTs is aligned along the liquid crystal director, and above the critical field, the director of the NLC is distorted due to translation motion of CNTs in NLC. The amplitude of this translation motion decreases with increasing frequency, whereas the critical field increases with increasing frequency. We present the mechanism of translation motion of CNTs and model this observed phenomenon based on dielectrophoretic force.
Effects of Pb(Zn1∕3Nb2∕3)O3 addition and postannealing temperature on the electrical properties of Pb(ZrxTi1−x)O3 thick films prepared by aerosol deposition method
Authors: Choi Jong-Jin , Hahn Byung-Dong , Ryu Jungho , Yoon Woon-Ha , Park Dong-Soo
Published: August 2007

Effects of the lead zinc niobate (PZN) addition and postannealing temperature on the electrical properties of the lead zirconate titanate (PZT) films were observed to improve electrical properties of the PZT film. The PZN content was varied from 0% to 40%, and the postannealing temperature was varied from 500to900°C. The as-deposited film had a fairly dense microstructure without any cracking and showed a single perovskite phase formed with nanosized grains. Meanwhile, rapid grain growth was observed when the postannealing temperature was increased from 700to900°C. The PZN-added PZT film showed poorer electrical properties than the pure PZT film did when the films were annealed at 700°C but higher remnant polarization, dielectric constant, and piezoelectric response when the films were annealed at 900°C. Remnant polarization value, relative dielectric constant, and piezoelectric constant of the 20% PZN-added PZT films annealed at 900°C were 50.0μC∕cm2, 1643, and 200pC∕N, respectively, which are values sufficiently high to be comparable with the bulk specimen sintered at 1200°C.
Nucleation and growth of carbon nanotubes in catalytic chemical vapor deposition
Authors: Moshkalev Stanislav A. , Verissimo Carla
Published: August 2007

The process of nucleation of multiwall carbon nanotubes in chemical vapor deposition process with nickel as catalyst and methane as a carbon precursor is analyzed. The nucleation is considered as a specific instability developed on the surface of a metal catalyst particle supersaturated with carbon. The energy released in graphitization of carbon from the metal-carbon solution is shown to be crucial for the nanotube nucleation. The energy released may be high enough for substantial metal heating resulting in partial liquefaction of the catalyst particle. The proposed mechanism can be called vapor-solid-liquid-solid (VSLS) as the catalyst particle may be in a mixed solid-liquid (or liquidlike) state during nucleation and unstable phases of nanotube growth.
Linear and nonlinear electrodynamic responses of bulk CaC6 in the microwave regime
Authors: Andreone A. , Cifariello G. , Di Gennaro E. , Lamura G. , Emery N. , Hérold C. , Marêché J. F. , Lagrange P.
Published: August 2007

The linear and nonlinear responses to a microwave electromagnetic field of two c-axis oriented polycrystalline samples of the recently discovered superconductor CaC6 (TC≈11.5K) is studied in the superconducting state down to 2K. The surface resistance RS and the third order intermodulation distortion, arising from a two-tone excitation, have been measured as a function of temperature and microwave circulating power. Experiments are carried out using a dielectrically loaded copper cavity operating at 7GHz in a “hot finger” configuration. The results confirm recent experimental findings that CaC6 behaves as a weakly coupled, fully gapped, superconductor.
Spectroscopy, energy transfer, and frequency upconversion in Tm3+-doped TeO2-PbO glass
Authors: Rai Vineet Kumar , Menezes Leonardo de S. , de Araújo Cid B.
Published: August 2007

Absorption and luminescence experiments were performed in thulium (Tm3+)-doped TeO2-PbO glass samples. Spectroscopic quantities such as transition probabilities, branching ratios, and radiative lifetimes related to the Tm3+ ions were determined using the Judd-Ofelt theory. Luminescence properties were studied by exciting the samples using a pulsed laser operating at 590 nm. Stokes luminescence centered at 792 nm and frequency upconversion (UC) to the blue (≈457 nm) were observed. The intensity and the time evolution of both emissions were studied for different concentrations of Tm3+ ions. The results indicate that the dipole-dipole interaction provides the most important contribution for energy transfer among the Tm3+ ions. The origin of the UC process is attributed to energy transfer among Tm3+ ions in pairs.