bluuebunny/crossref_metadata_2025 huggingface dataset:
Stability of Adiposity Phenotypes from Childhood and Adolescence into Young Adulthood with Contribution of Parental Measures
Authors: Campbell Peter T. , Katzmarzyk Peter T. , Malina Robert M. , Rao D. C. , Pérusse Louis , Bouchard Claude
Published: April 2008

Objective: The stability of several indicators of body composition and adipose tissue distribution over 12 years was quantified.

Research Methods and Procedures: The participants were 77 boys and 76 girls who were evaluated along with their parents at baseline as children and adolescents (8 to 18 years of age) and remeasured as young adults 12 years later. Indicators of body composition included the body mass index, fat mass, fat free mass, percentage of body fat, sum of six skinfolds (SF6), and the first principal component of six age‐adjusted skinfold residuals. Relative adipose tissue distribution was represented by the second principal component of skinfold residuals and a trunk‐to‐extremity skinfold ratio, adjusted for SF6.

Results: Partial interage correlations, controlling for initial age and length of follow‐up, were 0.65 and 0.59 for the body mass index, 0.59 and 0.64 for fat mass, 0.65 and 0.57 for fat free mass, 0.50 and 0.57 for percentage of body fat, 0.66 and 0.44 for SF6, 0.64 and 0.42 for the first principal component of six age‐adjusted skinfold residuals, 0.19 and 0.31 for the second principal component of skinfold residuals, and 0.41 and 0.47 for trunk‐to‐extremity skinfold ratio, adjusted for SF6, in men and women, respectively. Multiple regression analyses indicated that the significant partial R2 values of parental measurements on the prediction of their offspring in young adulthood ranged from 2% to 9%.

Discussion: The results indicate moderately high stability of indicators of body composition and somewhat lower stability of measures of adipose tissue distribution. Overall, parental measures offer less predictive value than do measures of childhood and adolescent body composition and adipose tissue distribution.
Leptin Levels Are Associated with Fat Oxidation and Dietary‐Induced Weight Loss in Obesity
Authors: Verdich Camilla , Toubro Søren , Buemann Benjamin , Holst Jens Juul , Bülow Jens , Simonsen Lene , Søndergaard Susanne Bonnichsen , Christensen Niels Juel , Astrup Arne
Published: April 2008

Objective: To examine the relationship between fasting plasma leptin and 24‐hour energy expenditure (EE), substrate oxidation, and spontaneous physical activity (SPA) in obese subjects before and after a major weight reduction compared with normal weight controls. To test fasting plasma leptin, substrate oxidations, and SPA as predictive markers of success during a standardized weight loss intervention.

Research Methods and Procedures: Twenty‐one nondiabetic obese (body mass index: 33.9 to 43.8 kg/m2) and 13 lean (body mass index: 20.4 to 24.7 kg/m2) men matched for age and height were included in the study. All obese subjects were reexamined after a mean weight loss of 19.2 kg (95% confidence interval: 15.1–23.4 kg) achieved by 16 weeks of dietary intervention followed by 8 weeks of weight stability. Twenty‐four‐hour EE and substrate oxidations were measured by whole‐body indirect calorimetry. SPA was assessed by microwave radar.

Results: In lean subjects, leptin adjusted for fat mass (FM) was correlated to 24‐hour EE before (r = −0.56, p < 0.05) but not after adjustment for fat free mass. In obese subjects, leptin correlated inversely with 24‐hour and resting nonprotein respiratory quotient (r = −0.47, p < 0.05 and r = −0.50, p < 0.05) both before and after adjustments for energy balance. Baseline plasma leptin concentration, adjusted for differences in FM, was inversely related to the size of weight loss after 8 weeks (r = −0.41, p = 0.07), 16 weeks (r = −0.51, p < 0.05), and 24 weeks (r = −0.50, p < 0.05).

Discussion: The present study suggests that leptin may have a stimulating effect on fat oxidation in obese subjects. A low leptin level for a given FM was associated with a greater weight loss, suggesting that obese subjects with greater leptin sensitivities are more successful in reducing weight.
Impact of Weight Reduction on Early Carotid Atherosclerosis in Obese Premenopausal Women
Authors: Mavri Alenka , Stegnar Mojca , Sentočnik Jožica T. , Videčnik Viktor
Published: April 2008

Objective: To investigate the extent of carotid atherosclerosis and the effect of weight loss on carotid intima‐media thickness (IMT) in obese premenopausal women.

Research Methods and Procedures: In 43 obese premenopausal women who participated in a 3‐month weight reduction program with a hypocaloric diet, IMT was measured by B‐mode high‐resolution ultrasound at entry and after 5 months of follow‐up. Blood samples were analyzed at entry, after intervention, and after 5 months of follow‐up. Nineteen lean women served as control subjects.

Results: At entry, common carotid IMT (0.72 vs. 0.59 mm), carotid bulb IMT (0.90 vs. 0.71 mm), and overall mean IMT (0.81 vs. 0.65 mm) were greater in obese women than in lean women (all p < 0.01). After dietary intervention decreases in blood pressure, low density lipoprotein to high density lipoprotein cholesterol ratio, triglycerides, fibrinogen, plasminogen activator inhibitor‐1, and an increase in tissue‐type plasminogen activator activity levels were observed. These effects persisted after follow‐up in 14 women who maintained reduced weight. Reduction in carotid bulb IMT (to 0.81 mm, p < 0.01) and overall mean IMT (to 0.79 mm, p < 0.05) was observed in this subgroup. No significant change of carotid IMT was detected in eight women who regained weight. Changes in IMT were associated independently and significantly with changes in body mass index, low density lipoprotein to high density lipoprotein cholesterol ratio, and plasminogen activator inhibitor‐1 antigen.

Discussion: Obese premenopausal women had greater IMT than did age‐matched lean controls. It seems that this early atherosclerotic changes may be reversed by normalization of body weight.
Independent Influences of Central Fat and Skeletal Muscle Lipids on Insulin Sensitivity
Authors: Furler Stuart M. , Poynten Ann M. , Kriketos Adamandia D. , Lowy Andrew J. , Ellis Bronwyn A. , Maclean Elizabeth L. , Courtenay Brett G. , Kraegen Edward W. , Campbell Lesley V. , Chisholm Donald J.
Published: April 2008

Objective: Insulin resistance is closely associated with two disparate aspects of lipid storage: the intracellular lipid content of skeletal muscle and the magnitude of central adipose beds. Our aim was to determine their relative contribution to impaired insulin action.

Research Methods and Procedures: Eighteen older (56 to 75 years of age) men were studied before elective knee surgery. Insulin sensitivity (M/ΔI) was determined by hyperinsulinemic–euglycemic clamp. Central abdominal fat (CF) was assessed by DXA. Skeletal muscle was excised at surgery and assayed for content of metabolically active long‐chain acyl‐CoA esters (LCAC).

Results: Significant inverse relationships were observed between LCAC and M/ΔI (R2 = 0.34, p = 0.01) and between CF and M/ΔI (R2 = 0.38, p = 0.006), but not between CF and LCAC (R2 = 0.0005, p = 0.93). In a multiple regression model (R2 = 0.71, p < 0.0001), both CF (p = 0.0006) and LCAC (p = 0.0009) were independent statistical predictors of M/ΔI. Leptin levels correlated inversely with M/ΔI (R2 = 0.60, p = 0.0002) and positively with central (R2 = 0.41, p = 0.006) and total body fat (R2 = 0.63, p = 0.0001).

Discussion: The mechanisms by which altered lipid metabolism in skeletal muscle influences insulin action may not be related directly to those linking central fat and insulin sensitivity. In particular, it is unlikely that muscle accumulation of lipids directly derived from labile central fat depots is a principal contributor to peripheral insulin resistance. Instead, our results imply that circulating factors, other than nonesterified fatty acids or triglyceride, mediate between central fat depots and skeletal muscle tissue. Leptin was not exclusively associated with central fat, but other factors, secreted specifically from central fat cells, could modulate muscle insulin sensitivity.
Lifestyle Treatments in Randomized Clinical Trials of Pharmacotherapies for Obesity
Authors: Poston Walker S. Carlos , Haddock C. Keith , Dill Patricia L. , Thayer Beth , Foreyt John P.
Published: April 2008

Objective:This meta‐analysis evaluated the types of lifestyle treatments used in published obesity drug studies and assessed their contribution to weight losses associated with pharmacological interventions.

Research Methods and Procedures:Randomized, placebo‐controlled, double‐blind clinical trials of anti‐obesity agents that are/were Food and Drug Administration‐approved for the treatment of obesity (both prescription and over‐the‐counter), and drugs that are Food and Drug Administration‐approved and are used off‐label for obesity were included. Studies were located by computer searches of databases (e.g., Medline, PsychInfo) and reviewing tables of content/reference sections of journals, abstracts, previous reviews, past empirical studies, relevant book chapters, and recent issues of journals that regularly publish obesity research. In addition, a number of individuals who regularly publish in the obesity literature were asked to provide personal lists of obesity‐drug studies. Based on the above criteria, a total of 108 randomized clinical trials were located.

Results:Balanced‐deficit diets, low‐calorie diets, and self‐monitoring were the most used lifestyle treatments in published obesity studies. They were incorporated into 40.7%, 25%, and 23.1% of pharmacotherapy studies, respectively. Physical activity and other behavioral or psychotherapeutic interventions rarely were used. A substantial portion of weight loss experienced by patients was attributable to both “placebo effects” and to the lifestyle treatments.

Discussion:Obesity‐pharmacotherapy trials do not use lifestyle treatments with the frequency expected based on the official positions of most professional organizations concerned with the comprehensive management of obesity.
Influence of Leptin on Changes in Body Fat during Growth in African American and White Children
Authors: Johnson Maria S. , Huang Terry T‐K. , Figueroa‐Colon Reinaldo , Dwyer James H. , Goran Michael I.
Published: April 2008

Objective: The aim of this study was to determine whether initial levels or temporal changes in fasting leptin were associated with longitudinal changes in body‐fat mass in children.

Research Methods and Procedures: The study group consisted of 85 children (42 white and 43 African American) with a mean initial age of 8.1 ± 0.1 years. The children had between three and six annual visits for repeated measurements of body composition by DXA and fasting leptin level. Fat mass and fasting leptin level were not normally distributed and were log‐transformed. Data were analyzed using SAS Proc mixed growth models, with log fat as the dependent variable.

Results: Initial leptin level was a significant predictor of the change in fat mass over time (p < 0.0001), with high initial leptin levels resulting in increased fat gain, independent of initial fat levels. This relationship remained significant when the data were analyzed separately by race (whites, p < 0.0001; African Americans, p = 0.008). The relationship between the initial level of leptin and the change in fat mass was not modified by race, sex, or Tanner Stage. The rate of change in leptin during the study was significantly related to the rate of change in fat mass in African Americans (p = 0.008) but not in whites (p = 0.490).

Discussion: In conclusion, high fasting leptin level at the start of the study was significantly associated with increasing fat mass in this cohort, indicating that the children may be developing resistance to the effects of leptin.
QT Dispersion in Uncomplicated Human Obesity
Authors: Girola Andrea , Enrini Riccardo , Garbetta Francesca , Tufano Antonietta , Caviezel Francesco
Published: April 2008

Objective: Because obese patients generally may be prone to ventricular arrhythmias, this study was designed to measure the interval between Q‐ and T‐waves of the electrocardiogram (QT) interval dispersion (QTD) in uncomplicated overweight and obese patients. QTD is an electrocardiographic parameter whose prolongation is thought to be predictive of the possibility of sudden death caused by ventricular arrhythmias. To better evaluate the association between obesity per se and QTD, the study population was intentionally selected because they were free of complications.

Research Methods and Procedures: QTD (defined as the difference between the maximum and the minimum QT corrected interval [QTc] across the 12‐lead electrocardiogram) was measured manually in 54 obese patients (Group A: mean body mass index [BMI] of 38.1 ± 0.9 kg/m2 [SEM], 15 males and 39 females), 35 overweight patients (Group B: mean BMI of 27.3 ± 0.2 kg/m2, 10 males and 25 females), and 57 normal weight healthy control subjects (Group C: mean BMI of 21.9 ± 0.2 kg/m2, 17 males and 40 females). The obese and overweight patients had no heart disease, hypertension, diabetes, or impaired glucose tolerance and did not have any hormonal, hepatic, renal or electrolyte disorders. The study subjects were matched in terms of age (mean age 38.4 ± 1.2 years) and sex.

Results: The QTDs were comparable among the three groups: Group A, 56.4 ± 2.6 ms; Group B, 56.7 ± 2.1 ms; and Group C, 59.4 ± 2.1 ms; not significant. The QTc intervals of Group A and Group B were similar to that of Group C (411.8 ± 3.3, 407.2 ± 3.9, and 410.3 ± 3.9 ms, respectively [not significant]) and did not correlate with BMI. An association was found between QTD and QTc (r = 0.24, p < 0.005). Using multivariate stepwise regression analysis of the study population, QTD did not correlate with age, BMI, waist circumference, or abdominal sagittal diameter.

Discussion: These data suggest that QTD in uncomplicated obese or overweight subjects is comparable with that in age‐ and sex‐matched normal weight healthy controls. In this study population, no association was found between QTD and anthropometric parameters reflecting body fat distribution.
Sterol Regulatory Element Binding Protein 1c (SREBP‐1c) Expression in Human Obesity
Authors: Kolehmainen Marjukka , Vidal Hubert , Alhava Esko , Uusitupa Matti I.J.
Published: April 2008

Objective: Investigation of the expression of sterol regulatory element binding protein‐1c (SREBP‐1c) in different adipose tissue depots in morbidly obese subjects before and after 1 year of weight loss induced by gastric banding operation.

Research Methods and Procedures: SREBP‐1c expression was studied in 20 massively obese subjects (6 men and 14 women; age: 41 ± 9 years; weight: 148 ± 34 kg; percentage of body fat: 42 ± 4; mean ± SD) using reverse transcription competitive polymerase chain reaction. Adipose tissue biopsies were taken from omental, subcutaneous abdominal, and femoral depots before weight loss, and from subcutaneous depots after weight loss. Subcutaneous samples were taken also from 6 normal weight subjects.

Results: The level of SREBP‐1c mRNA was significantly lower in omental (1.8 ± 0.2 amol/μg of total RNA) than in subcutaneous abdominal (3.7 ± 0.4 amol/μg of total RNA) or femoral (3.9 ± 0.4 amol/μg of total RNA; p < 0.001, mean ± SEM) depots. The values in subcutaneous depots were about twice as high in normal weight (7.4 ± 2.5 for abdominal and 6.5 ± 1.5 for femoral, p < 0.01) as in obese subjects. After weight loss, the mRNA levels of SREBP‐1c increased in obese subjects, both in subcutaneous abdominal (5.3 ± 0.7, p < 0.01) and in femoral (4.8 ± 0.8, p < 0.05) tissue.

Discussion: SREBP‐1c mRNA expression was lower in omental adipose tissue than in subcutaneous depots in obese subjects before weight loss. Furthermore, the expression of SREBP‐1c in obese subjects was clearly lower than in normal weight subjects, but mRNA levels increased along with weight reduction. Weight reduction was associated with increased mRNA levels of SREBP‐1c in obese subjects. The reduced expression of SREBP‐1c in obesity could be ascribed to lowered action or concentration of insulin, changeable along with weight reduction. However, changes in SREBP‐1c expression after weight reduction could also be ascribed to the changes in calorie intake or nutritional habits after gastric banding operation.
Handbook of Surface Plasmon Resonance
Authors: Kooyman Rob P H , Corn Robert M , Wark Alastair , Lee Hye Jin , Gedig Erk , Engbers Gerard , Walstrom Lennart , de Mol Nico J , Hall Damien R , Yager Paul , Chinowsky Timothy , Fu Elain , Nelson Kjell , McWhirter Alan , Fischer Marcel J E , Lokate Angelique M C , Beusink J Bianca , Pruijn Ger J M , Knoll Wolfgang , Kasry Amal , Liu Jing , Neumann Thomas , Niu Lifang , Park Hyeyoung , Paulsen Harald , Robelek Rudolf , Yu Fang , Schuck Peter , Frazier Richard A
Published: April 2008

Surface plasmon resonance (SPR) plays a dominant role in real-time interaction sensing of biomolecular binding events. This book focuses on a total system description including optics, fluidics and sensor surfaces. It covers all commercial SPR systems in the market. It is the first of its kind and fills a gap in the technical literature as no other handbook on SPR is currently available. The final chapter discussed new trends and a vision is given for future developments and needs of the SPR market. This excellent handbook provides comprehensive information with easy to use, stand-alone chapters and will be of great use to anyone one working with or affiliated to the technology.
Relaxation of caloric curves on complex potential energy surfaces
Authors: Calvo F. , Wales D. J.
Published: April 2008

Time-dependent caloric curves of model systems with complex energy landscapes are calculated by solving master equation kinetics in stepwise heating or cooling protocols. By considering in detail a simple two-state harmonic model, we show that both the transition temperature and the associated latent heat vary significantly if the sampling time is not long enough. Microcanonical characteristics, including possible S-bends in the caloric curve, are also qualitatively affected by insufficient sampling. The geometry of S-bends as a function of the observation time agrees quantitatively with the predictions of catastrophe theory. For two Lennard–Jones clusters with 13 and 31 atoms the relations between the transition temperatures and the sampling time are shown to follow scaling laws, in agreement with the results of molecular dynamics simulations [J. Chem. Phys. 113, 1315 (2000)].
The influence of rotation on the βN threshold for the 2∕1 neoclassical tearing mode in DIII-D
Authors: Buttery R. J. , La Haye R. J. , Gohil P. , Jackson G. L. , Reimerdes H. , Strait E. J. ,   the DIII-D Team
Published: April 2008

Utilizing a capability to vary neutral beam torque injection in the DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] tokamak, m∕n=2∕1 neoclassical tearing mode onset thresholds are found to fall by about one unit in βN, from ∼3 to ∼2, in ITER-like sawtoothing high-energy confinement modes of plasma operation [R. Aymar, Plasma Phys. Control. Fusion 42, B385 (2000)] as “co-injected” torque and rotation are reduced. However, increasing levels of torque and rotation in the counter-direction do not lead to corresponding rises in βN thresholds. More encouragingly, error field sensitivity is not found to increase in low rotation plasmas, as might be expected theoretically. These results pose an interesting physics problem, as well as raising concern for future devices such as ITER. Further analyses have explored possible physics origins of the behavior. They suggest many of the usual effects expected to lead to a rotation dependence (mode coupling, wall drag, ion polarization currents) are not significant, with instead models that depend on the size and sign of rotation shear playing a role. Onset behavior suggests the mode is close to being intrinsically (classically) unstable when it appears, and a conceptual explanation is offered for a mechanism by which rotation shear feeds into the onset process through changes to the classical tearing stability index, Δ′. Further parameter extensions and studies are desirable to fully resolve the underlying physics of this interesting process.
The role of chromatin conformations in diffusional transport of chromatin-binding proteins: Cartesian lattice simulations
Authors: Wedemeier Annika , Zhang Ting , Merlitz Holger , Wu Chen-Xu , Langowski Jörg
Published: April 2008

In this paper, a lattice model for the diffusional transport of chromatin-binding particles in the interphase cell nucleus is proposed. Sliding effects are studied in dense networks of chromatin fibers created by three different methods: Randomly distributed, noninterconnected obstacles, a random walk chain model with an attractive step potential, and a self-avoiding random walk chain model with a hard repulsive core and attractive surroundings. By comparing a discrete and continuous version of the random walk chain model, we demonstrate that lattice discretization does not alter the diffusion of chromatin-binding particles. The influence of conformational properties of the fiber network on the particle sliding is investigated in detail while varying occupation volume, sliding probability, chain length, and persistence length. It is observed that adjacency of the monomers, the excluded volume effect incorporated in the self-avoiding random walk model, and the persistence length affect the chromatin-binding particle diffusion. It is demonstrated that sliding particles sense local chain structures. When plotting the diffusion coefficient as a function of the accessible volume for diffusing particles, the data fall onto master curves depending on the persistence length. However, once intersegment transfer is involved, chromatin-binding proteins no longer perceive local chain structures.
The phase dynamics and wetting layer formation mechanisms in two-step surface-directed spinodal decomposition
Authors: Yan Li-Tang , Xie Xu-Ming
Published: April 2008

The two-step quench process of surface-directed spinodal decomposition is numerically investigated by coupling the Flory–Huggins–de Gennes equation with the Cahn–Hilliard–Cook equation. The phase dynamics and formation mechanisms of the wetting layer in two-step surface-directed spinodal decomposition have been concerned in detail. The results demonstrate that a parallel strip structure forms near the wetting layer and propagates into the bulk, when the first quench depth is very shallow and the bulk does not undergo phase separation, and the second quench depths are various points with deeper quench depths. In this case, the wetting layer turns to be unchangeable at the intermediate and later stages of the second quench process, compared to the growth with a time exponent 1∕2 during the first quench process. When the first quench depth is deeper and phase separation occurs in the bulk during the first quench process, it is found that a deeper second quench depth can stimulate a more obvious secondary domain structure, and the formation mechanism of the wetting layer changes from logarithmic growth law to Lifshitz–Slyozov growth law.
Intensity scaling of hot electron energy coupling in cone-guided fast ignition
Authors: Chrisman B. , Sentoku Y. , Kemp A. J.
Published: April 2008

A critical issue for the fast ignition of inertial fusion targets, where compressed fuel is ignited by injection of an intense short laser pulse, is whether the hot electrons produced in the interaction are in an energy range conducive to efficient heating of the core. This work presents the first comprehensive two-dimensional kinetic simulation of the cone-guided approach to fast ignition. Simulation results predict the hot electron temperature to be much lower than previously expected, which indicates the possibility of using them for optimum core heating. Furthermore, the roles of collisional versus kinetic processes for transport and heating mechanisms of the core plasmas are clarified. The core heating efficiency scales linearly with intensity at ranges of 1019–1020W∕cm2, but falls below this range due to deflection of hot electrons in strong magnetic filaments behind the cone target.
Statics, linear, and nonlinear dynamics of entangled polystyrene melts simulated through the primitive chain network model
Authors: Yaoita Takatoshi , Isaki Takeharu , Masubuchi Yuichi , Watanabe Hiroshi , Ianniruberto Giovanni , Greco Francesco , Marrucci Giuseppe
Published: April 2008

Simulation results of the primitive chain network (PCN) model for entangled polymers are compared here to existing data of diffusion coefficient, linear and nonlinear shear and elongational rheology of monodisperse polystyrene melts. Since the plateau modulus of polystyrene is well known from the literature, the quantitative comparison between the whole set of data and simulations only requires a single adjustable parameter, namely, a basic time. The latter, however, must be consistent with the known rheology of unentangled polystyrene melts, i.e., with Rouse behavior, and is therefore not really an adjustable parameter. The PCN model adopted here is a refined version of the original model, incorporating among other things a more accurate description of chain end dynamics as well as finite extensibility effects. In the new version, we find good agreement with linear rheology, virtually without adjustable parameters. It is also shown that, at equilibrium, Gaussian statistics are well obeyed in the simulated network. In the nonlinear range, excellent agreement with data is found in shear, whereas discrepancies and possible inadequacies of the model emerge in fast uniaxial elongational flows, even when accounting for finite extensibility of the network strands.
Structural optimization for heat detection of DNA thermosequencing platform using finite element analysis
Authors: Esfandyarpour Hesaam , Zheng Bo , Pease R. Fabian W. , Davis Ronald W.
Published: April 2008

For the past three decades, Sanger’s method has been the primary DNA sequencing technology; however, inherent limitations in cost and complexity have limited its usage in personalized medicine and ecological studies. A new technology called “thermosequencing” can potentially reduce both the cost and complexity of DNA sequencing by using a microfluidic platform [Esfandyarpour, Pease, and Davis, J. Vac. Sci. Technol. B26, 661 (2008)]. To optimize the efficiency of the technology, finite element analysis was used to model the thermosequencing system by simulating the DNA incorporation reaction series and the resulting product concentration and heat production. Different models of the thermosequencing platform were created to simulate the effects of the materials surrounding the system, to optimize the geometry of the system, and to concentrate reaction heat into specific regions for detection in the real system. The resulting concentrations of reaction products were used to calibrate the reaction speed and to design the heat sensors in the thermosequencing technology. We recommend a modified gated structure for the microfluidic detection platform by using control valves and show how this new platform could dramatically improve the detection efficiency.
Laser beam filamentation and stochastic electron heating at upper hybrid layer
Authors: Sharma Prerana , Mahmoud S. T. , Gupta M. K. , Sharma R. P.
Published: April 2008

This paper presents an investigation of the filamentation (single hot spot) of an ultrahigh-power laser beam in homogeneous plasma. Upper hybrid wave (UHW) coupling in these filaments has been studied. We have discussed two extreme scenarios: (1) The laser beam has ultrahigh power so that relativistic and ponderomotive nonlinearities are operative; and (2) the laser beam power is moderate, therefore only ponderomotive nonlinearity dominates. At ultrahigh laser powers, relativistic and ponderomotive nonlinearities lead to filamentation of the laser beam. In these filamentary regions, the UHW gets coupled to the laser beam, and a large fraction of the pump (laser beam) energy gets transferred to UHW and this excited UHW can accelerate the electrons. In the second case, nonlinear coupling between the laser beam and the upper hybrid wave leads to the localization of the UHW. Electrons interacting with the localized fields of the UHW demonstrate chaotic motion. The simulation result confirms the presence of chaotic fields, and interaction of these fields with electrons leads to velocity space diffusion, which is accompanied by particle heating. Using the Fokker–Planck equation, the heating of electrons has been estimated. The effect of the change of background magnetic field strength on heating has also been discussed.
A sodium atom in a large water cluster: Electron delocalization and infrared spectra
Authors: Cwiklik Lukasz , Buck Udo , Kulig Waldemar , Kubisiak Piotr , Jungwirth Pavel
Published: April 2008

Ab initio molecular dynamics simulations modeling low-energy collisions of a sodium atom with a cluster with more than 30 water molecules are presented. We follow the dynamics of the atom-cluster interaction and the delocalization of the valence electron of sodium together with the changes in the electron binding energy. This electron tends to be shared by the nascent sodium cation and the water cluster. IR spectra of the sodium-water cluster are both computationally and experimentally obtained, with a good agreement between the two approaches.
Studies on waves and instabilities in a plasma sheath formed on the outer surface of a space craft
Authors: Aria Anil K. , Malik Hitendra K.
Published: April 2008

Using the normal mode analysis, the number of possible modes is obtained in a magnetized inhomogeneous plasma sheath formed during the motion of a space craft which consists of negative ions (due to dust) along with the positive ions and the isothermal electrons. In addition to three propagating modes with phase velocities λ1, λ2, and λ3 such that λ1<λ2<λ3, two types of instabilities with growth rates γ1 and γ2 also occur in such a plasma sheath. The growth rate γ1 is increased with the negative to positive ion density ratio r0, ion temperature T, and obliqueness θ of the magnetic field B0. The growth rate γ2 of the other instability gets lower with the density ratio r0 but gets higher with the temperature T. The growth rate γ2 is sensitive to the temperature T, whereas the growth rate γ1 gets prominently changed with the density ratio r0. The increase in the growth rate γ1 with the obliqueness θ is more pronounced under the effect of stronger magnetic field. On other hand, the phase velocity λ1 shows weak dependence on r0 and T (though it gets larger) but it gets significantly changed (increased) for the larger obliqueness θ. The phase velocity λ2 gets larger with r0, B0, and θ and becomes lower for the higher temperature T. The phase velocity λ3 is decreased for the higher values of r0 and B0 and is increased for the larger values of T and θ.
A cryostat and temperature control system optimized for measuring relaxations of glass-forming liquids
Authors: Igarashi Brian , Christensen Tage , Larsen Ebbe H. , Olsen Niels Boye , Pedersen Ib H. , Rasmussen Torben , Dyre Jeppe C.
Published: April 2008

An experimental setup, including a cryostat and a temperature control system, has been constructed to meet the demands of measuring linear and nonlinear macroscopic relaxation properties of glass-forming liquids in the extremely viscous state approaching the glass transition. In order to be able to measure such frequency-dependent response functions accurately (including dielectric permittivity, specific heat, thermal expansivity, and shear and bulk moduli), as well as nonlinear relaxations following a temperature jump, one must have the ability to hold temperatures of liquids steady over the span of several days or even several weeks. To maximize temperature stability, special care is taken to thermally isolate the sample chamber of the cryostat. The main temperature control system is capable of maintaining temperatures within a few millikelvins. If liquid is deposited into a special transducer assembly that includes a subcryostat unit, the temperature of liquids can be maintained even more precisely, within a few tenths of a millikelvin. This subcryostat unit is more responsive to temperature changes because (i) it is equipped with a Peltier element that provides secondary heating and cooling, (ii) the transducer contains a layer of liquid that is only 50μm thick, and (iii) feedback proportional-integral-derivative temperature control is implemented by a fully analog circuit. The subcryostat permits us to change and stabilize temperatures quickly; it takes only 10s to stabilize the temperature within tenths of a millikelvin after a jump of 1K, for example, a capability that is highly advantageous for accurately observing relaxation processes following a temperature step.
An impedance-measurement setup optimized for measuring relaxations of glass-forming liquids
Authors: Igarashi Brian , Christensen Tage , Larsen Ebbe H. , Olsen Niels Boye , Pedersen Ib H. , Rasmussen Torben , Dyre Jeppe C.
Published: April 2008

An electronics system has been assembled to measure frequency-dependent response functions of glass-forming liquids in the extremely viscous state approaching the glass transition. We determine response functions such as dielectric permittivity and shear and bulk moduli by measuring electrical impedances of liquid-filled transducers, and this technique requires frequency generators capable of producing signals that are reproducible over the span of several days or even several weeks. To this end, we have constructed a frequency generator that produces low-frequency (1mHz–100Hz) sinusoidal signals with voltages that are reproducible within 10ppm. Two factors that partly account for this precision are that signals originate from voltages stored in a look-up table and that only coil-less filters are used in this unit, which significantly reduces fluctuations of output caused by changes of temperatures of circuits. This generator also includes a special triggering facility that makes it possible to measure up to 512 voltages per cycle that are spaced apart at uniform phase intervals. Fourier transformations of such data yield precise determinations of complex amplitudes of voltages and currents applied to a transducer, which ultimately allows us to determine electrical impedances of transducers with a reproducibility error that is only a few parts per hundred thousand. This equipment is used in tandem with a commercial LCR meter and/or impedance analyzer that give(s) impedance measurements at higher frequencies, up to 1MHz. The experimental setup allows measurements of the transducer impedance over nine decades of frequency within a single run.
Resonant transmission spectroscopy on the p to p transitions of a charge tunable InGaAs quantum dot
Authors: Seidl S. , Kroner M. , Lux C. , Holleitner A. W. , Karrai K. , Warburton R. J. , Badolato A. , Petroff P. M.
Published: April 2008

We have performed resonant interband transmission spectroscopy on the transitions between the s-shells and the p-shells of a single charge tunable InGaAs quantum dot (QD). In contrast to the s-shell spectroscopy, investigating p-shell transitions allows the study of a QD charged with up to four electrons. The exciton charging state is clearly identified as a function of gate voltage ranges. In contrast to the s-shell, the p-shell electronic states show a strong tunnel coupling to the Fermi sea of the back contact.
High-speed all-optical modulation using polycrystalline silicon microring resonators
Authors: Preston Kyle , Dong Po , Schmidt Bradley , Lipson Michal
Published: April 2008

We experimentally demonstrate on-chip active photonic devices fabricated from deposited polycrystalline silicon, which can be used for monolithic three-dimensional integration of optical networks. The demonstrated modulator is based on all-optical carrier injection in a micrometer-size resonator and has a modulation depth of 10dB and a temporal response of 135ps. Grain boundaries in the polycrystalline silicon (polysilicon) material result in faster electron-hole recombination, enabling a shortened carrier lifetime and a faster optical switching time compared to similar devices based on crystalline silicon.
A piezoelectric single crystal traveling wave step motor for low-temperature application
Authors: Dong Shuxiang , Yan Li , Viehland D. , Jiang Xiaoning , Hackenberger Wesley S.
Published: April 2008

A piezoelectric Pb(Mg1∕3Nb2∕3)O3-PbTiO3 single crystal traveling wave rotary motor operated in a stepping motion for cryogenic actuations was developed and characterized. This single crystal stepping motor had a torque of ⩾1.5kgcm, an excess of 1800 steps per revolution about its axis, and a power consumption of ≦2W by using a step motion with 25% duty cycle. We then show that this single crystal motor can successfully operate at 77K (liquid nitrogen) under a load.
Spectral and temporal response of liquid-crystal-on-silicon spatial light modulators
Authors: Bock Martin , Kumar Das Susanta , Grunwald Ruediger , Osten Stefan , Staudt Peter , Stibenz Gero
Published: April 2008

Spectral and temporal phase response of selected types of liquid-crystal-on-silicon spatial light modulators were studied using femtosecond pulses, determining specific transfer functions of the devices. The phase response resulting from programed gray level distributions was detected by analyzing the diffraction characteristics and by spectral phase interferometry for direct electric-field reconstruction. The results indicate the appearance of distinct parameter ranges that enable minimum spatiotemporal distortion. Weak oscillations in the spectral phase are explained by Gires–Tournois resonances [F. Gires and P. Tournois, Acad. Sci. Paris, C. R. 258, 6112 (1964)].
Effect of internal surface area on the performance of ZnO∕In2S3∕CuSCN solar cells with extremely thin absorber
Authors: Kieven D. , Dittrich T. , Belaidi A. , Tornow J. , Schwarzburg K. , Allsop N. , Lux-Steiner M.
Published: April 2008

Solar cells with an extremely thin light absorber were realized by wet chemical preparation on arrays of ZnO nanorods. The absorber consisted of an In2S3 layer (∼20nm thickness) and its interface region with a transparent CuSCN hole conductor. By changing the length of the nanorods (0–3.3μm) and keeping the In2S3 layer thickness constant at ∼20nm, the short circuit current increased from about 2–10mA∕cm2. A marked increase of the external quantum efficiency at longer wavelengths is attributed to light scattering and a solar energy conversion efficiency of 2.5% has been demonstrated.
Barium-functionalized multiwalled carbon nanotube yarns as low-work-function thermionic cathodes
Authors: Xiao Lin , Liu Peng , Liu Liang , Jiang Kaili , Feng Xiaofeng , Wei Yang , Qian Li , Fan Shoushan , Zhang Taihua
Published: April 2008

Barium-functionalized multiwalled carbon nanotube yarns were fabricated by drawing and twisting multiwalled carbon nanotube forests through a solution containing barium nitrate. After heat activation under vacuum, the functionalized yarns were enriched in barium oxide due to the high surface-to-volume ratio of the nanotubes. The cathodes exhibited good thermionic properties, with a work function as low as 1.73–2.06eV and thermionic current density that exceeded 185mA∕cm2 in a field of 850V∕5mm at 1317K. The barium-functionalized yarns had high tensile strength of up to 420MPa and retained strength of ∼250MPa after a 2h activation process.
Wideband 15THz response using organic electro-optic polymer emitter-sensor pairs at telecommunication wavelengths
Authors: McLaughlin Colin V. , Hayden L. Michael , Polishak Brent , Huang Su , Luo Jingdong , Kim Tae-Dong , Jen Alex K.-Y.
Published: April 2008

Poled polymer films are employed in terahertz emission and detection using telecommunication wavelength femtosecond pulses. Films 10–15μm thick with electro-optic coefficients as high as 160pm∕V at 1300nm are used to generate and sense subpicosecond pulses with continuous bandwidth up to 15THz. Terahertz emission from a poled polymer film is compared to terahertz emission from the organic crystal DAST. The use of a poled polymer as the terahertz sensor allows the identification of DAST phonons at 1.1, 3.0, 5.3, 8.5, and 12.5THz.
Self-thickening, cross-slip deformation twinning model
Authors: Narayan J. , Zhu Y. T.
Published: April 2008

We propose a cross-slip deformation twinning model based upon our experimental in situ deformation of Cu–Ge alloys using a transmission electron microscope. During the deformation, Shockley partials are emitted from the grain boundaries, which encounter an obstacle within the grain and split to nucleate deformation twins in the cross slip as well as primary planes. Upon further deformation a thickening process for twins is directly observed. The proposed model provides a dislocation mechanism for the observed simultaneous twin thickening in both the cross-slip and primary planes. The role of the proposed mechanism in the deformation of nanocrystalline materials is discussed.
Piezoelectric property in morphotropic phase boundary Bi0.5(Na0.82K0.18)0.5TiO3 lead free thick film deposited by screen printing
Authors: Zhang Haibo , Jiang Shenglin , Zeng Yike
Published: April 2008

Piezoelectric Bi0.5(Na0.82K0.18)0.5TiO3 thick films were screen printed on Pt electroded alumina substrates. The resulting 38μm thick films sintered at 1100°C for 0.5h have maximum relative permittivity of 810, dielectric loss of 2.0% (at 10kHz), remanent polarization of 28.3μC∕cm2, coercive field of 62kV∕cm, and longitudinal effective piezoelectric coefficient d33eff of 109pm∕V. The temperature dependence of the dielectric constant shows two clear peaks that were associated with phase transitions. The performance of this lead free piezoelectric thick film could be comparable to the corresponding bulk ceramics.
Endogenous steroids and financial risk taking on a London trading floor
Authors: Coates J. M. , Herbert J.
Published: April 2008

Little is known about the role of the endocrine system in financial risk taking. Here, we report the findings of a study in which we sampled, under real working conditions, endogenous steroids from a group of male traders in the City of London. We found that a trader's morning testosterone level predicts his day's profitability. We also found that a trader's cortisol rises with both the variance of his trading results and the volatility of the market. Our results suggest that higher testosterone may contribute to economic return, whereas cortisol is increased by risk. Our results point to a further possibility: testosterone and cortisol are known to have cognitive and behavioral effects, so if the acutely elevated steroids we observed were to persist or increase as volatility rises, they may shift risk preferences and even affect a trader's ability to engage in rational choice.
The influence of cochlear shape on low-frequency hearing
Authors: Manoussaki Daphne , Chadwick Richard S. , Ketten Darlene R. , Arruda Julie , Dimitriadis Emilios K. , O'Malley Jen T.
Published: April 2008

The conventional theory about the snail shell shape of the mammalian cochlea is that it evolved essentially and perhaps solely to conserve space inside the skull. Recently, a theory proposed that the spiral's graded curvature enhances the cochlea's mechanical response to low frequencies. This article provides a multispecies analysis of cochlear shape to test this theory and demonstrates that the ratio of the radii of curvature from the outermost and innermost turns of the cochlear spiral is a significant cochlear feature that correlates strongly with low-frequency hearing limits. The ratio, which is a measure of curvature gradient, is a reflection of the ability of cochlear curvature to focus acoustic energy at the outer wall of the cochlear canal as the wave propagates toward the apex of the cochlea.
Global regulatory logic for specification of an embryonic cell lineage
Authors: Oliveri Paola , Tu Qiang , Davidson Eric H.
Published: April 2008

Explanation of a process of development must ultimately be couched in the terms of the genomic regulatory code. Specification of an embryonic cell lineage is driven by a network of interactions among genes encoding transcription factors. Here, we present the gene regulatory network (GRN) that directs the specification of the skeletogenic micromere lineage of the sea urchin embryo. The GRN now includes all regulatory genes expressed in this lineage up to late blastula stage, as identified in a genomewide survey. The architecture of the GRN was established by a large-scale perturbation analysis in which the expression of each gene in the GRN was cut off by use of morpholinos, and the effects on all other genes were measured quantitatively. Several
cis
-regulatory analyses provided additional evidence. The explanatory power of the GRN suffices to provide a causal explanation for all observable developmental functions of the micromere lineage during the specification period. These functions are: (
i
) initial acquisition of identity through transcriptional interpretation of localized maternal cues; (
ii
) activation of specific regulatory genes by use of a double negative gate; (
iii
) dynamic stabilization of the regulatory state by activation of a feedback subcircuit; (
iv
) exclusion of alternative regulatory states; (
v
) presentation of a signal required by the micromeres themselves and of two different signals required for development of adjacent endomesodermal lineages; and (
vi
) lineage-specific activation of batteries of skeletogenic genes. The GRN precisely predicts gene expression responses and provides a coherent explanation of the biology of specification.
Transfer of a large gene regulatory apparatus to a new developmental address in echinoid evolution
Authors: Gao Feng , Davidson Eric H.
Published: April 2008

Of the five echinoderm classes, only the modern sea urchins (euechinoids) generate a precociously specified embryonic micromere lineage that ingresses before gastrulation and then secretes the biomineral embryonic skeleton. The gene regulatory network (GRN) underlying the specification and differentiation of this lineage is now known. Many of the same differentiation genes as are used in the biomineralization of the embryo skeleton are also used to make the similar biomineral of the spines and test plates of the adult body. Here, we determine the components of the regulatory state upstream of these differentiation genes that are shared between embryonic and adult skeletogenesis. An abrupt “break point” in the micromere GRN is thus revealed, on one side of which most of the regulatory genes are used in both, and on the other side of which the regulatory apparatus is entirely micromere-specific. This reveals the specific linkages of the micromere GRN forged in the evolutionary process by which the skeletogenic gene batteries were caused to be activated in the embryonic micromere lineage. We also show, by comparison with adult skeletogenesis in the sea star, a distant echinoderm outgroup, that the regulatory apparatus responsible for driving the skeletogenic differentiation gene batteries is an ancient pleisiomorphic aspect of the echinoderm-specific regulatory heritage.
Adenovirus E1A targets p400 to induce the cellular oncoprotein Myc
Authors: Tworkowski Kathryn A. , Chakraborty Abhishek A. , Samuelson Andrew V. , Seger Yvette R. , Narita Masako , Hannon Gregory J. , Lowe Scott W. , Tansey William P.
Published: April 2008

Adenovirus E1A drives oncogenesis by targeting key regulatory pathways that are critical for cellular growth control. The interaction of E1A with p400 is essential for many E1A activities, but the downstream target of this interaction is unknown. Here, we present evidence that the oncoprotein transcription factor Myc is the target of this interaction. We show that E1A stabilizes Myc protein via p400 and promotes the coassociation of Myc and p400 at Myc target genes, leading to their transcriptional induction. We also show that E1A requires Myc for its ability to activate Myc-dependent gene expression and induce apoptosis, and that forced expression of Myc is sufficient to rescue the activity of an E1A-mutant defective in p400 binding. Together, these findings establish that Myc, via p400, is an essential downstream target of E1A.