bluuebunny/crossref_metadata_2025 huggingface dataset:
Internal and External Cues of Meal Cessation: The French Paradox Redux?
Authors: Wansink Brian , Payne Collin R. , Chandon Pierre
Published: July 2008

Objective: Our objective was to investigate whether people who use internal cues of satiation when eating a meal are likely to weigh less than people who instead rely on external cues. In addition to exploring the role that internal and external cues play in meal cessation, this study raises an overlooked explanation of the French paradox.

Research Methods and Procedures: A demographically‐matched student sample of 133 Parisians and 145 Chicagoans completed a brief survey on meal cessation that asked the extent to which they agreed with statements associated with internal cessation cues and statements with external cessation cues. Their answers to these were compared across BMI levels and across countries.

Results: Normal‐weight people indicated that they were more likely to be influenced by internal cues of meal cessation (p = 0.043), while overweight people indicated that they were more influenced by external cues (p = 0.005). Similarly, while the French were influenced by internal cues of meal cessation (p < 0.001), Americans were more influenced by external cues (p < 0.001).

Discussion: This research revisits Schachter's externality hypothesis and suggests that one's over‐reliance on external cues may prove useful in offering a partial explanation of why BMI might vary across people and potentially across cultures. Relying on internal cues for meal cessation, rather than on external cues, may improve eating patterns over the long term.
Interaction Between High‐Fat Diet and Alcohol Dehydrogenase on Ethanol‐Elicited Cardiac Depression in Murine Myocytes
Authors: Ren Jun
Published: July 2008

Objective:Consumption of high‐fat diet and alcohol is associated with obesity, leading to enhanced morbidity and mortality. This study was designed to examine the interaction between high‐fat diet and the alcohol metabolizing enzyme alcohol dehydrogenase (ADH) on ethanol‐induced cardiac depression.

Research Methods and Procedures:Mechanical and intracellular Ca2+properties were measured in cardiomyocytes from ADH transgenic and Friend Virus‐B type (FVB) mice fed a low‐ or high‐fat diet for 16 weeks. Expression of protein kinase B (Akt) and Foxo3a, two proteins essential for cardiac survival, was evaluated by Western blot. Cardiac damage was determined by carbonyl formation.

Results:High fat but not ADH induced obesity without hyperglycemia or hypertension, prolonged time‐to‐90% relengthening (TR90), and depressed peak shortening (PS) and maximal velocity of shortening/relengthening (± dL/dt) without affecting intracellular Ca2+properties. Ethanol suppressed PS and intracellular Ca2+rise in low‐fat‐fed FVB mouse cardiomyocytes. ADH but not high‐fat diet shifted the threshold of ethanol‐induced inhibition of PS and ± dL/dt to lower levels. The amplitude of ethanol‐induced cardiac depression was greater in the high‐fat but not the ADH group without additive effects. Ethanol down‐ and up‐regulated Akt and Foxo3a expression, respectively, and depressed intracellular Ca2+rise, the effects of which were exaggerated by ADH, high‐fat, or both. High‐fat diet, but not ADH, enhanced Foxo3a expression and carbonyl content in non‐ethanol‐treated mice. Ethanol challenge significantly enhanced protein carbonyl formation, with the response being augmented by ADH, high‐fat, or both.

Discussion:Our data suggest that high‐fat diet and ADH transgene may exaggerate ethanol‐induced cardiac depression and protein damage in response to ethanol.
Polybrominated Diphenyl Ethers as Endocrine Disruptors of Adipocyte Metabolism
Authors: Hoppe Andrea A. , Carey Gale B.
Published: July 2008

Objective: Obesity is thought to result from poor diet and insufficient exercise. An additional factor may be endocrine‐disrupting environmental chemicals that contaminate the air, water, and food supply. We tested the hypothesis that a class of lipid‐soluble flame retardant chemicals known to accumulate in adipose tissue, polybrominated diphenyl ethers (PBDEs), disrupts insulin and isoproterenol sensitivity of isolated rat adipocytes.

Research Methods and Procedures: Six‐week‐old Sprague‐Dawley rats were gavaged daily with 14 mg/kg body weight (BW) pentabrominated diphenyl ether (penta‐BDE) in corn oil (n = 24) or corn oil alone (n = 24). At 2 and 4 weeks of treatment, epididymal fat pad adipocytes were isolated, and isoproterenol‐stimulated lipolysis, insulin‐stimulated glucose oxidation, and adipocyte size were measured.

Results: There was no alteration in adipocyte metabolism after 2 weeks of in vivo penta‐BDE treatment, but after 4 weeks of treatment, adipocytes averaged a 30% increase in isoproterenol‐stimulated lipolysis and a 59% decrease in insulin‐stimulated glucose oxidation, compared with control. There were no differences in average rat BW and adipocyte size between treated and control rats, but plasma total thyroxine level in 2‐ and 4‐week treated rats was 30% of control.

Discussion: Daily exposure of rats to 14 mg/kg BW penta‐BDE for 4 weeks has no effect on animal or adipocyte size but significantly alters insulin and isoproterenol‐stimulated metabolism of isolated adipocytes. These alterations, hallmark features of metabolic obesity, suggest the need for further research on the contribution of lipid‐soluble, endocrine‐disrupting environmental chemicals to the obesity epidemic.
Association between Gastric Electromechanical Activity and Satiation in Dogs
Authors: Sanmiguel Claudia P. , Aviv Ricardo , Policker Shai , Haddad Walid , Brody Fredrick , Soffer Edy E.
Published: July 2008

Objective: The objective of this study was to validate the use of impedance for measurement of antral contractions and to determine the relationship between food‐induced changes in gastric motility and satiation.

Research Methods and Procedures: In Experiment 1, three dogs were implanted with an antral strain gauge and bipolar electrodes for measurement of local tissue impedance. Impedance and strain gauge recordings were obtained simultaneously during antral contractions to correlate impedance changes with contractile events. In Experiment 2, seven dogs were implanted with two pairs of gastric electrodes for simultaneous recording of slow wave activity and impedance. The changes in the rate of slow waves and of antral contractions assessed by impedance during food intake were characterized.

Results: Variations in strain gauge amplitude were highly correlated with changes in antral impedance (R2: 0.70 to 0.82, p < 0.05). In Experiment 2, slow wave rate was significantly reduced after food intake and reached a nadir at satiation (5.0 ± 0.3 vs. 3.8 ± 0.5 events/min, p < 0.001). Likewise, the amplitude of antral contractions assessed by variations in impedance was significantly increased after food intake, peaking at satiation (5.3 ± 1.4 vs. 12.2 ± 4.3 Ohms, p < 0.01).

Discussion: Measurement of impedance is a reliable tool for assessing gastric contractility. Food ingestion significantly reduces slow wave rate and enhances antral contractions. Peak changes in these two variables occur at the time of satiation. Electrical measurements of both slow waves and impedance may be used to estimate gastric motility and satiation.
Breakfast Cereals and Risk of Type 2 Diabetes in the Physicians’ Health Study I
Authors: Kochar Jinesh , Djoussé Luc , Gaziano J. Michael
Published: July 2008

Objective: To examine the association between breakfast cereal consumption and the risk of type 2 diabetes (DM).

Research Methods and Procedures: We analyzed prospectively data from 21,152 male participants of the Physicians’ Health Study I. Consumption of breakfast cereals was estimated using an abbreviated food questionnaire, and incident DM was ascertained through yearly follow‐up questionnaires.

Results: The average age was 53.6 ± 9.4 years (range, 39.7 to 85.9) during the initial assessment of cereal intake (1981 to 1983). During a mean follow‐up of 19.1 years, 1958 cases of DM occurred. The crude incidence rates of DM were 57.7, 53.8, 43.5, and 35.4 cases/10,000 person‐years for people reporting breakfast cereal intake of 0, ≤1, 2 to 6, and ≥7 servings/wk, respectively. In a Cox regression model adjusting for age, cigarette smoking, BMI, physical activity, vegetable consumption, and alcohol intake, hazard ratios (95% confidence interval) for DM were 1.0 (reference), 0.89 (0.79 to 1.00), 0.76 (0.67 to 0.86), and 0.63 (0.55 to 0.72) from the lowest to the highest category of cereal consumption, respectively (p for trend < 0.0001). In secondary analyses, the inverse association between cereal intake and DM was stronger with whole‐grain than refined cereals.

Discussion: These results suggest that intake of breakfast cereals might confer a lower risk of DM. Consumption of whole‐grain products may help lower the risk of DM.
Consistent Self‐monitoring of Weight: A Key Component of Successful Weight Loss Maintenance
Authors: Butryn Meghan L. , Phelan Suzanne , Hill James O. , Wing Rena R.
Published: July 2008

Objective: The objectives were to investigate the characteristics associated with frequent self‐weighing and the relationship between self‐weighing and weight loss maintenance.

Research Methods and Procedures: Participants (n = 3003) were members of the National Weight Control Registry (NWCR) who had lost ≥30 lbs, kept it off for ≥1 year, and had been administered the self‐weighing frequency assessment used for this study at baseline (i.e., entry to the NWCR). Of these, 82% also completed the one‐year follow‐up assessment.

Results: At baseline, 36.2% of participants reported weighing themselves at least once per day, and more frequent weighing was associated with lower BMI and higher scores on disinhibition and cognitive restraint, although both scores remained within normal ranges. Weight gain at 1‐year follow‐up was significantly greater for participants whose self‐weighing frequency decreased between baseline and one year (4.0 ± 6.3 kg) compared with those whose frequency increased (1.1 ± 6.5 kg) or remained the same (1.8 ± 5.3 kg). Participants who decreased their frequency of self‐weighing were more likely to report increases in their percentage of caloric intake from fat and in disinhibition, and decreases in cognitive restraint. However, change in self‐weighing frequency was independently associated with weight change.

Discussion: Consistent self‐weighing may help individuals maintain their successful weight loss by allowing them to catch weight gains before they escalate and make behavior changes to prevent additional weight gain. While change in self‐weighing frequency is a marker for changes in other parameters of weight control, decreasing self‐weighing frequency is also independently associated with greater weight gain.
Cardiorespiratory Fitness, Different Measures of Adiposity, and Cancer Mortality in Men
Authors: Farrell Stephen W. , Cortese Gina M. , LaMonte Michael J. , Blair Steven N.
Published: July 2008

Objective: The purpose was to examine the prospective relationship among cardiorespiratory fitness level (CRF), different measures of adiposity, and cancer mortality in men.

Research Methods and Procedures: Participants were 38,410 apparently healthy men who completed a comprehensive baseline health examination between 1970 and 2001. Clinical measures included BMI, waist circumference (WC), percent body fat, and CRF quantified as duration of a maximal treadmill exercise test. Participants were divided into fifths of CRF, BMI, WC, and percent body fat. Hazard ratios were computed with Cox regression analysis.

Results: During a mean follow‐up period of 17.2 ± 7.9 years, 1037 cancer deaths occurred. Adjusted hazard ratios across incremental BMI quintiles were 1.0, 1.23, 1.15, 1.39, and 1.72; those of WC were 1.0, 1.05, 1.03, 1.31, and 1.64; those of percent body fat were 1.0, 1.24, 1.17, 1.23, and 1.50; and those of CRF were 1.0, 0.70, 0.67, 0.70, and 0.49 (trend p < 0.01 for each). Further adjustment for CRF eliminated the significant trend in mortality risk across percent body fat groups and attenuated the trend in risk across BMI and WC groups. Adjustment of CRF for adiposity measures had little effect on mortality risk. When grouped into categories of fit and unfit (upper 80% and lower 20% of CRF distribution, respectively), mortality rates (per 10,000 man‐years) were significantly lower in fit compared with unfit men within each stratum of BMI, WC, and percent body fat.

Discussion: Higher levels of CRF are associated with lower cancer mortality risk in men, independently of several adiposity measures.
Four‐year Follow‐up of School‐based Intervention on Overweight Children: The KOPS Study
Authors: Plachta‐Danielzik Sandra , Pust Svenja , Asbeck Inga , Czerwinski‐Mast Mareike , Langnäse Kristina , Fischer Carina , Bosy‐Westphal Anja , Kriwy Peter , Müller Manfred J.
Published: July 2008

Objective: To evaluate the 4‐year outcome of a school‐based health promotion on weight status as part of the Kiel Obesity Prevention Study (KOPS).

Research Methods and Procedures: Within a cluster‐sampled quasi‐randomized controlled trial, 1764 children at 6 and 10 years of age were assessed between 1996 and 2005 in 32 primary schools in Kiel, North Germany. Six nutrition units followed by 20‐minute running games were performed within the first year at school. Prevalence, incidence, and remission of overweight were main outcome measures.

Results: The 4‐year change in BMI was +11.6%, with increases in prevalence of overweight and obesity from 5.2% to 11.1% and 3.9% to 5.1%, respectively. Cumulative 4‐year incidence of overweight and obesity was 9.2% and 3.1%, respectively. Intervention had no effect on mean BMI. The effect on prevalence was significant in children from families with high socioeconomic status [odds ratio (OR), 0.35; 95% confidence interval (CI), 0.14 to 0.91] and marginally significant in children of normal‐weight mothers (OR, 0.57; 95% CI, 0.33 to 1.00). Cumulative 4‐year incidence of overweight was lower only in intervention children from families with high socioeconomic status (OR, 0.26; 95% CI, 0.07 to 0.87). Remission of overweight was most pronounced in children of normal‐weight mothers (OR, 5.43; 95% CI, 1.28 to 23.01). Prevalence of underweight was unchanged. The intervention had minor but favorable effects on lifestyle.

Discussion: A school‐based health promotion has sustainable effects on remission and incidence of overweight; it was most pronounced in children of normal‐weight mothers and children from families with high socioeconomic status. There was no effect on obesity. The data argue in favor of additional measures of prevention.
Using treemaps for variable selection in spatio-temporal visualisation
Authors: Slingsby Aidan , Dykes Jason , Wood Jo
Published: July 2008

We demonstrate and reflect upon the use of enhanced treemaps that incorporate spatial and temporal ordering for exploring a large multivariate spatio-temporal data set. The resulting data-dense views summarise and simultaneously present hundreds of space-, time-, and variable-constrained subsets of a large multivariate data set in a structure that facilitates their meaningful comparison and supports visual analysis. Interactive techniques allow localised patterns to be explored and subsets of interest selected and compared with the spatial aggregate. Spatial variation is considered through interactive raster maps and high-resolution local road maps. The techniques are developed in the context of 42.2 million records of vehicular activity in a 98 km2 area of central London and informally evaluated through a design used in the exploratory visualisation of this data set. The main advantages of our technique are the means to simultaneously display hundreds of summaries of the data and to interactively browse hundreds of variable combinations with ordering and symbolism that are consistent and appropriate for space- and time-based variables. These capabilities are difficult to achieve in the case of spatio-temporal data with categorical attributes using existing geovisualisation methods. We acknowledge limitations in the treemap representation but enhance the cognitive plausibility of this popular layout through our two-dimensional ordering algorithm and interactions. Patterns that are expected (e.g. more traffic in central London), interesting (e.g. the spatial and temporal distribution of particular vehicle types) and anomalous (e.g. low speeds on particular road sections) are detected at various scales and locations using the approach. In many cases, anomalies identify biases that may have implications for future use of the data set for analyses and applications. Ordered treemaps appear to have potential as interactive interfaces for variable selection in spatio-temporal visualisation.
Generation of electromagnetic structures via modulational instability of drift waves
Authors: Smolyakov A. I. , Krasheninnikov S. I.
Published: July 2008

Generation mechanism for large scale electromagnetic structures (blobs) is considered by employing the technique of four-wave interactions (modulational instability). It is shown that primary electrostatic turbulence may generate elongated electromagnetic structures with poloidal modulations. Such structures are principally related to drift-Alfvén waves. The analysis fully takes into account finite ion temperature effects and associated diamagnetic contributions to Reynolds stress. The turbulent generation of blobs has instability growth rates which scale similar to the zonal flow instabilities, γ∼⟨qṼ⟩, where q is a characteristic wave vector of large scale modes, and Ṽ is a characteristic amplitude of the velocity of turbulent fluctuations. This analysis is shown to be fully consistent with results of an earlier analysis by using the wave kinetic equation.
Propagation of transverse domain walls in homogeneous magnetic nanowires
Authors: Allende S. , Altbir D. , Salcedo E. , Bahiana M. , Sinnecker J. P.
Published: July 2008

The field driven nucleation and propagation of transverse domain walls in a uniform Ni nanowire is examined by means of Monte Carlo simulations combined with a scaling technique. Simulations show a nonlinear behavior followed by the simultaneous nucleation of several domain walls. Also we study the angular dependence of the propagation of the transverse domain wall with external field. Results are analyzed in terms of the classical relaxation model for interface dynamics.
Improved thermoelectric performance in the Zintl phase compounds YbZn2−xMnxSb2 via isoelectronic substitution in the anionic framework
Authors: Yu C. , Zhu T. J. , Zhang S. N. , Zhao X. B. , He J. , Su Z. , Tritt Terry M.
Published: July 2008

It has been shown previously that the thermoelectric properties of the Zintl phase compound, YbZn2Sb2 can be finely tuned via substitution at the cationic Yb-site. Here we report the results of the investigation of isoelectronic substitution of Zn by Mn in the anionic (Zn2Sb2)2− framework. The p-type YbZn2−xMnxSb2 (0.0⩽x⩽0.4) samples have been synthesized via a solid-state reaction followed by suitable cooling, annealing, grounding, and hot-pressing densification processes. In samples with x=0.0, 0.05, 0.10, 0.15, 0.2, 0.3, and 0.4, the electrical conductivity, Seebeck coefficient, and thermal conductivity measurements have been performed as a function of temperature from 300to750K. It is found that the Mn substitution effectively lowers the thermal conductivity for all samples, while it significantly increases the power factor for x⩽0.15. As a result, a dimensionless figure of merit ZT of ∼0.61–0.65 has been attained at 726K for x=0.05–0.15 as compared to the ZT of ∼0.48 in the unsubstituted YbZn2Sb2.
Laser ablation-induced spectral plasma characteristics in optical far- and near fields
Authors: Hwang David J. , Jeon Hojeong , Grigoropoulos Costas P. , Yoo Jong , Russo Richard E.
Published: July 2008

The aim of this work is to elucidate the ablation-induced plasma physics for chemical species analysis by laser-induced breakdown spectroscopy at higher spatial resolution. To accomplish this, the effect of the laser spot size on the laser ablation-induced plasma characteristics is experimentally investigated, both in optical far-field and near-field ablation configurations, utilizing a Cr thin film of ∼200 nm thickness on quartz substrate as a target. The far-field ablation is affected under tight focusing conditions, wherein nanosecond laser pulses of 532 nm wavelength are focused to laser focal spot diameters of ∼7 and 1.5 μm. The measured results show that the ablation-induced plasma from sub-10 μm ablation craters exhibits complex three-dimensional behavior, leading to greatly reduced laser-plasma interaction and an order of magnitude shorter plasma lifetime. Nanosecond laser pulses of 532 nm wavelength are also coupled to a pulled fiber based near-field scanning optical microscopy probe. Due to the sharp tip presence in close proximity of the ablation craters, entirely different plasma evolution behavior is observed, highlighted by orders of magnitude shorter plasma lifetime and strongly directional material ejection. The ablation-induced plasma from reduced lateral crater dimensions both in far- and near-field shows improved contrast of atomic transition signals with respect to the wide-spectrum background, hence confirming the potential for laser-induced breakdown spectroscopy with high spatial resolution.
Laser-rf creation and diagnostics of seeded atmospheric pressure air and nitrogen plasmas
Authors: Luo Siqi , Denning C. Mark , Scharer John E.
Published: July 2008

A laser initiation and radio frequency (rf) sustainment technique has been developed and improved from our previous work to create and sustain large-volume, high-pressure air and nitrogen plasmas. This technique utilizes a laser-initiated, 15 mTorr partial pressure tetrakis (dimethylamino) ethylene seed plasma with a 75 Torr background gas pressure to achieve high-pressure air/nitrogen plasma breakdown and reduce the rf power requirement needed to sustain the plasma. Upon the laser plasma initiation, the chamber pressure is raised to 760 Torr in 0.5 s through a pulsed gas valve, and the end of the chamber is subsequently opened to the ambient air. The atmospheric-pressure plasma is then maintained with the 13.56 MHz rf power. Using this technique, large-volume (1000 cm3), high electron density (on the order of 1011–12 cm−3), 760 Torr air and nitrogen plasmas have been created while rf power reflection is minimized during the entire plasma pulse utilizing a dynamic matching method. This plasma can project far away from the antenna region (30 cm), and the rf power budget is 5 W/cm3. Temporal evolution of the plasma electron density and total electron-neutral collision frequency during the pulsed plasma is diagnosed using millimeter wave interferometry. Optical emission spectroscopy (OES) aided by SPECAIR, a special OES simulation program for air-constituent plasmas, is used to analyze the radiating species and thermodynamic characteristics of the plasma. Rotational and vibrational temperatures of 4400–4600±100 K are obtained from the emission spectra from the N2(2+) and N2+(1−) transitions by matching the experimental spectrum results with the SPECAIR simulation results. Based on the relation between the electron collision frequency and the neutral density, utilizing millimeter wave interferometry, the electron temperature of the 760 Torr nitrogen plasma is found to be 8700±100 K (0.75±0.1 eV). Therefore, the plasma deviates significantly from local thermal equilibrium.
Optical characterization of erbium doped LiNbO3 poling properties
Authors: Paturzo M. , Grilli S. , Ferraro P. , Finizio A. , De Natale P. , Argiolas N. , Bazzan M. , Ciampolillo M. V. , Sada C.
Published: July 2008

We investigate the characteristics of the poling process of two samples of Er:LiNbO3 grown by the Chzocralski technique by comparing their optical properties. The first has a multidomain structure and shows some optical inhomogeneities probably due to lattice defects; the second, poled at the high temperature just after the growth, has a ferroelectric monodomain structure. Moreover, in order to highlight the effect of the high temperature poling, a further poling process was performed on both the samples at room temperature and was monitored in real time through a simple optical setup in order to evidence whether the erbium inclusion influences the poling process and which are the differences between the poling dynamics of the two samples. The results show that the erbium causes a change of the coercive field value with respect to the pure congruent LiNbO3 crystals, and that the multidomain structure influences strongly the poling dynamics.
Effect of local electrical properties on the electrostatic discharge withstand capability of multilayered chip ZnO varistors
Authors: Hirose Sakyo , Yamamoto Yoji , Niimi Hideaki
Published: July 2008

The local electrical properties at individual grain boundaries of multilayered chip varistors composed of ZnO–Bi2O3 (Bi–ZnO) and ZnO–Pr6O11 (Pr–ZnO) ceramics have been investigated using a scanning probe microscope (SPM) to clarify their effect on the electrostatic discharge (ESD) withstand capabilities. Pr–ZnO varistors exhibit a higher ESD withstand capability compared to Bi–ZnO varistors, although both types of devices exhibit similar electrical nonlinearity and surge current withstand capabilities. Bi–ZnO varistors exhibit asymmetric current-voltage (I-V) characteristics after the application of ESD pulses; their breakdown voltage decreases from 9 to 4 V and the leakage current increases. This indicates that the ESD pulses destroy some electrical potential barriers. Scanning surface potential microscopy (SSPM) measurements of a Bi–ZnO varistor reveal the existence of high electrical potential barriers at grain boundaries and electrode interfaces, and high-resistance secondary phases. In contrast, SSPM measurements of a Pr–ZnO varistor reveal that electrical potential barriers exist only at grain boundaries. This suggests that the difference in ESD withstand capabilities between the Bi–ZnO and Pr–ZnO varistors is reasonably due to the differences in their local electrical properties.
Reflectance analysis of a multilayer one-dimensional porous silicon structure: Theory and experiment
Authors: Saarinen Jarkko J. , Weiss Sharon M. , Fauchet Philippe M. , Sipe J. E.
Published: July 2008

We present a method for treating birefringent effects in layered media and apply the formalism to analyze reflectance from a multilayer one-dimensional (1D) porous silicon (PS) structure at off-normal incidence. The approach is to characterize the fields in terms of s- and p-polarized amplitudes in each layer, and the calculations then naturally employ Fresnel reflection and transmission coefficients for the uniaxially anisotropic media. We observe an excellent agreement between the theoretical and experimental curves by including optical absorption and macroscale waviness of the PS layers, and the resolution of the spectrophotometer. In particular, we point out the importance of birefringent effects that cause the splitting of the resonance wavelengths between two different polarizations. The investigated 1D PS structure can be used, for example, as a polarization sensitive optical switch.
Application of coordinate transformation in bent waveguides
Authors: Huangfu Jiangtao , Xi Sheng , Kong Fanmin , Zhang Jingjing , Chen Hongsheng , Wang Dongxing , Wu Bae-Ian , Ran Lixin , Kong Jin Au
Published: July 2008

We apply coordinate transformations in the design of waveguides with bent geometry to reduce reflection at the incident port. It was found that in the case of metallic waveguides, by applying the transformation to the medium inside a right-angle bent waveguide, low reflection can be obtained. For the case of dielectric waveguides, this can also be done by applying the same transformation to the bent region containing both the dielectric core and its claddings. Our proposed technique provides an alternative method for designing bent waveguides with low insertion loss.
Effect of intensity noise of semiconductor lasers on the digital modulation characteristics and the bit error rate of optical communication systems
Authors: Ahmed Moustafa , Yamada Minoru
Published: July 2008

This paper presents theoretical evaluation of the digital modulation performance of semiconductor lasers in digital communication systems with gigabit rates. The study is based on numerical integration of the rate equations augmented by a nonreturn-to-zero (NRZ) bit generator. For solitary semiconductor lasers, the performance is evaluated in terms of the eye diagram, turn-on delay jitter (TOJ), and signal-to-noise ratio. In communication systems, the performance is evaluated by the bit error rate (BER) and power penalty induced by the laser noise. Contributions of both the intrinsic fluctuations and bit pattern to the TOJ and BER are assessed. The results show that when the modulation current is low and the semiconductor laser is biased relatively above threshold, the power penalty decreases although the eye diagram is not well open. When the modulation current is high enough, biasing the semiconductor laser far-above threshold achieves both lower power penalty and higher eye-diagram quality.
Space-charge-controlled electro-optic effect: Optical beam deflection by electro-optic effect and space-charge-controlled electrical conduction
Authors: Nakamura Koichiro , Miyazu Jun , Sasaki Yuzo , Imai Tadayuki , Sasaura Masahiro , Fujiura Kazuo
Published: July 2008

This paper describes the experimental and theoretical studies of an anomalous optical beam deflection phenomenon based on electrooptic effect and space-charge-controlled electrical conduction. In the experiment, a large deflection angle of 250mrad (=14.3°) has been observed by applying ±250V to a 0.5-mm-thick KTa1−xNbxO3 crystal with a short interaction length of 5.0mm. The crystal has a rectangular shape with uniform electrodes and there is no prism shape involved which is a common geometrical shape of crystal, electrode, or ferroelectric domain in the conventional electro-optic deflectors. The operating principle is investigated and it is found that the space-charge-controlled electrical conduction in the crystal plays an essential role in this deflection phenomenon. The electrical conduction is carried by electrons injected from the Ohmic contact of the electrode with the crystal. The injected electrons induce the space-charge effect and the electric field becomes nonuniform between the electrodes. The theoretical analysis shows that the electric field has a square-root dependence on the distance from the cathode. As a result, a linearly graded refractive index is induced by the electrooptic Kerr effect of the crystal and the optical beam is cumulatively deflected as it propagates in the crystal. We named this effect the “space-charge-controlled electro-optic effect” and the factors related to the onset of this effect are also discussed.
Deformation pathway to high-pressure phases of silicon during nanoindentation
Authors: Kim Dong Earn , Oh Soo Ik
Published: July 2008

The deformation pathway of silicon induced by nanoindentation is investigated in detail at the atomic level using molecular dynamics. Due to the complex stresses associated with the directional loading along a specific crystallographic orientation, the initial Si I lattice is transformed into two different high-pressure phases, namely, Si II and BCT5-Si. The Si II phase, where atoms have the six nearest neighbors, is generated through the tetragonal deformation caused by the compressive loading along the [001] direction. In contrast, the BCT5-Si phase, where each silicon atom has the five nearest neighbors, is formed by flattening the initially stepped sixfold rings of the diamond lattice onto the (110) plane of the BCT lattice. These reconstructive transformations are accomplished only by adding additional bonds and do not involve any bond breaking.
Impact of velocity space distribution on hybrid kinetic-magnetohydrodynamic simulation of the (1,1) mode
Authors: Kim Charlson C. ,   the NIMROD team
Published: July 2008

Numeric studies of the impact of the velocity space distribution on the stabilization of (1,1) internal kink mode and excitation of the fishbone mode are performed with a hybrid kinetic-magnetohydrodynamic model. These simulations demonstrate an extension of the physics capabilities of NIMROD [C. R. Sovinec et al., J. Comput. Phys. 195, 355 (2004)], a three-dimensional extended magnetohydrodynamic (MHD) code, to include the kinetic effects of an energetic minority ion species. Kinetic effects are captured by a modification of the usual MHD momentum equation to include a pressure tensor calculated from the δf particle-in-cell method [S. E. Parker and W. W. Lee, Phys. Fluids B 5, 77 (1993)]. The particles are advanced in the self-consistent NIMROD fields. We outline the implementation and present simulation results of energetic minority ion stabilization of the (1,1) internal kink mode and excitation of the fishbone mode. A benchmark of the linear growth rate and real frequency is shown to agree well with another code. The impact of the details of the velocity space distribution is examined; particularly extending the velocity space cutoff of the simulation particles. Modestly increasing the cutoff strongly impacts the (1,1) mode. Numeric experiments are performed to study the impact of passing versus trapped particles. Observations of these numeric experiments suggest that assumptions of energetic particle effects should be re-examined.
Ion beam driven ion-acoustic waves in a plasma cylinder with negative ions
Authors: Sharma Suresh C. , Gahlot Ajay
Published: July 2008

An ion beam propagating through a magnetized plasma cylinder containing K+ positive ions, electrons, and SF6− negative ions drives electrostatic ion-acoustic (IA) waves to instability via Cerenkov interaction. Two electrostatic IA wave modes in presence of K+ and SF6− ions are studied. The phase velocity of the sound wave in presence of positive and negative ions increase with the relative density of negative ions. The unstable wave frequencies and the growth rate of both the modes in presence of positive and negative ions increase with the relative density of negative ions. The growth rate of both the unstable modes in presence of SF6− and K+ ions scales as the one-third power of the beam density. Numerical calculations of the phase velocity, growth rate, and mode frequencies have been carried out for the parameters of the experiment of Song et al. [Phys. Fluids B 3, 284 (1991)].
Stabilizing spiral waves by noninvasive structural perturbations
Authors: Liu Fang , Yu Dongchuan , Liu Jun
Published: July 2008

We suggest a promising engineering approach to structural perturbation that in principle generates arbitrary additional connections artificially. We show that this structural perturbation method can be applied to stabilize spiral waves noninvasively. Furthermore, the stabilization performance is improved dramatically using proper delay for each additional connection to be created. This structural perturbation method with proper parameters can also be considered as a noninvasive adaptive pinning control that obtains better control performance than the typical constant pinning control. Remarkably, we numerically illustrate that a few additional connections (i.e., small structural perturbation) may result in stabilization of spiral waves. All methods suggested are motivated and illustrated with a FitzHugh–Nagumo model.
The inequality of charge and spin diffusion coefficients
Authors: Pramanik Sandipan , Bandyopadhyay Supriyo , Cahay Marc
Published: July 2008

Since spin and charge are both carried by electrons (or holes) in a solid, it is natural to assume that charge and spin diffusion coefficients will be the same. Drift-diffusion models of spin transport typically assume so. Here, we show analytically that the two diffusion coefficients can be vastly different in quantum wires. Although we do not consider quantum wells or bulk systems, it is likely that the two coefficients will be different in those systems as well. Thus, it is important to distinguish between them in transport models, particularly those applied to quantum wire based devices.
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-rich deposition conditions and growth mechanism of tetrahedral amorphous carbon films deposited using filtered arc
Authors: Zhu Jiaqi , Han Jiecai , Han Xiao , Schlaberg H. Inaki , Wang Jiazhi
Published: July 2008

Tetrahedral amorphous carbon (ta-C) films with many superior properties approaching those of diamond crystal were prepared using filtered cathodic vacuum arc technology. To ascertain the sp3-rich deposition condition, the dependence of the film microstructure on the deposition energy was investigated by means of visible Raman spectroscopy, x-ray photoelectron spectroscopy, electron energy loss spectroscopy, x-ray reflectivity, and nanoindentation. The maximum hardness and Young’s modulus are achieved at a bias of −80V, at which the maximum sp3 fraction of about 82% is obtained. Under this condition, the most symmetric Raman line shape, the highest x-ray photoemission C 1s core level position and a π* transition peak with the smallest integral area in the K-edge spectra are simultaneously achieved. The structural properties are found to be strongly correlated with the mass density of the films. At the optimal substrate bias of −80V, the film mass density reaches its maximum value. The cross section of the films is characterized with a layered distribution in mass density. A surface layer with low density is an intrinsic feature and experimental evidence of the subplantation growth of the films.
A model for liquid transfer between two approaching gas bearing surfaces through coupled evaporation-condensation and migration dynamics
Authors: Wu Lin
Published: July 2008

A model for transfer of liquid coated on one surface to another approaching surface through evaporation-condensation has been constructed for a gas bearing system. The evaporation-condensation process is dynamically coupled to the migration of already condensed liquid film. An equation based on mass transport principle is derived to calculate the partial vapor phase pressure distribution of evaporated liquid material within the sandwiched gas bearing layer. The controlling parameters in the evaporation-condensation and migration dynamics are identified to be the electric potential difference between the surfaces, liquid molecular weight, disjoining pressure, air shearing stresses, thickness of liquid film coated on one wall, and the wall-to-wall separation. Application of the model to the study of disk-to-slider lubricant transfer in a hard disk drive system shows very rich nonlinear dynamics of the coupled evaporation-condensation and migration of lubricants within the head-disk interface. Disk-slider lubricant bridges are formed when the disk-slider electric potential difference is above a critical value.
High temperature thermoelectric transport properties of double-atom-filled clathrate compounds YbxBa8−xGa16Ge30
Authors: Tang Xinfeng , Li Peng , Deng Shukang , Zhang Qingjie
Published: July 2008

Type-I clathrates YbxBa8−xGa16Ge30 (x=0–1.3) filled by ytterbium and barium were synthesized by melting reaction method combined with spark plasma sintering method. The structure and thermoelectric properties of double-atoms-filled clathrate compounds are investigated. X-ray diffraction patterns and Rietveld analysis reveal that the compounds prepared by this method are type-I clathrates. The filling atoms exhibit atomic displacement parameters that are larger than that of framework atoms. All specimens show n-type conduction and the room temperature carrier concentration (Np) increases with the increasing Yb content. The electrical conductivity of the compounds increases at first and then decreases with the increasing Yb content. When x=0.7, it reaches the maximum. The Seebeck coefficient decreases gradually with the increasing x. The substituting of Yb atoms for Ba leads to significant influence on the lattice thermal conductivity of the compounds. The lattice thermal conductivity decreases gradually with the increasing x. Of all the YbxBa8−xGa16Ge30 compounds, Yb0.5Ba7.5Ga16Ge30 compound has the greatest ZT value and its maximal ZT value reaches 1.1 at about 950K. Compared with the Ba8Ga16Ge30 sample, it increases by 90% at the same temperature.
Effects of UV/ozone treatment of a polymer dielectric surface on the properties of pentacene thin films for organic transistors
Authors: Han Seung Jin , Kim Jae-Hoon , Won Kim Jeong , Min Chang-Ki , Hong Sa-Hwan , Kim Dal-Hyun , Baek Kyu-Ha , Kim Gi-Heon , Do Lee-Mi , Park Y.
Published: July 2008

Ultraviolet photoelectron spectroscopy and atomic force microscopy (AFM) were used to investigate the energy level alignment and growth morphology of pentacene (Pn) films deposited on a PMMA derivative-based dielectric surface with and without ultraviolet/ozone treatment. The treated surface exhibited higher offset values for the highest occupied molecular orbital levels between Pn and the polymer, which would result in higher threshold voltages for the device. However, aligned vacuum levels of the treated surface and the Pn at the interface were observed, suggesting that the dipole field would be reduced in the Pn film on the treated surface. The hydrophilic nature of the treated surface, observed by water contact angle measurement, allowed for a larger grain size of the Pn film, as confirmed by the AFM measurements, which will also favorably contribute to device mobility.
The double Gaussian distribution of barrier heights in Al/TiO2/p-Si (metal-insulator-semiconductor) structures at low temperatures
Authors: Pakma O. , Serin N. , Serin T. , Altındal Ş.
Published: July 2008

The current-voltage (I-V) characteristics of Al/TiO2/p-Si metal-insulator-semiconductor (MIS) structures have been investigated in the temperature range of 80–300 K. An abnormal decrease in the zero bias barrier height (BH) (ϕb0) and an increase in the ideality factor (n) with decreasing temperature have been explained on the basis of the thermionic emission (TE) theory with Gaussian distribution (GD) of the BHs due to the BH inhomogeneities. The temperature dependence of the experimental I-V data of the Al/TiO2/p-Si (MIS) structures has revealed the existence of a double GD with mean BH values (ϕ¯b0) of 1.089 and 0.622 eV and standard deviations σs of 0.137 and 0.075 V, respectively. Thus, the modified ln(I0/T2)−q2σ02/2(kT)2 versus q/kT plot gives ϕ¯b0 values and Richardson constants (A∗) as 1.108 and 0.634 eV and 31.42 and 23.83 A/cm2 K2, respectively, without using the temperature coefficient of the BH. The value of the effective Richardson constant of 31.42 A/cm2 K2 is very close to the theoretical value of 32 A/cm2 K2 for p-Si. As a result, the temperature dependence of the forward bias I-V characteristics of the Al/TiO2/p-Si (MIS) structure can be successfully explained on the basis of the TE mechanism with a double GD of the BHs.
Reactor prospect of spheromak concept by electrostatic helicity injection
Authors: Tang X. Z. , Boozer A. H.
Published: July 2008

The highest performing spheromaks in the laboratory are formed by electrostatic helicity injection. Discharges with up to 1MA plasma current and core electron temperature as high as 500eV have been recently obtained. For such a scheme to scale-up to a reactor, however, a much higher current multiplication factor (plasma current over injector current) must be achieved. It is shown here that spheromak current multiplication is linearly proportional to flux amplification (ratio of poloidal fluxes inside and outside the separatrix of the mean field). Hence, spheromak optimization is centered around achieving high flux amplification, which is provided by linear or nonlinear resonant coupling between helicity injector and the spheromak force-free eigenmode. The nonlinear resonant field amplification is the most promising route to high flux amplification in a realistic plasma that often significantly deviates from the Taylor state. Accessing such nonlinear resonant field amplification can be facilitated by auxiliary current drive around the magnetic axis and auxiliary heating to break the electron temperature constraint on flux amplification.
The effect of dislocations on crack propagation in wrinkled gold film deposited on polydimethylsiloxane
Authors: Lin C. B. , Lin C. C. , Lee Sanboh , Chou Y. T.
Published: July 2008

Crack propagation in a wrinkled thin film of gold deposited on polydimethylsiloxane (PDMS) was affected by the presence of folding defects—the ripple dislocations. The ripple pattern, ripple dislocations, and the crack were simultaneously formed after the tensile load applied on the PDMS substrate was removed. The crack, however, was unstable and propagated forward. The propagation rate increased when the crack passed by the ripple dislocations, but less significantly when it advanced near a ripple dislocation dipole. Such crack dislocation interaction implies that the ripple dislocation has an internal stress field. The measured data of the rate process were analyzed based on the theory of fracture mechanics, and an empirical relationship between the crack velocity and the crack extension force was presented.
Magnetization and Raman scattering studies of (Co,Mn) codoped ZnO nanoparticles
Authors: Duan L. B. , Rao G. H. , Wang Y. C. , Yu J. , Wang T.
Published: July 2008

Single-phase (Co,Mn) codoped ZnO nanoparticles were synthesized by an autocombustion method. Hysteresis loop was observed at 300 K for the sample Zn0.98Co0.01Mn0.01O with a low coercivity (40±5 Oe). Temperature dependence of magnetization rules out the possibility of superparamagnetism or spin-glass behavior. Raman scattering studies manifested that there might exist a defect annihilation arising from the (Co,Mn) codoped into ZnO host lattice. As the ferromagnetism of diluted magnetic semiconductors is closely related to the dopant-defect hybridization, the ferromagnetic ordering was significantly enhanced in the sample Zn0.98Co0.01Mn0.01O by the (Co,Mn) codoping, in comparison to the Zn0.99Co0.01O and Zn0.99Mn0.01O fabricated by the same method.
Nonadiabatic corrections to the wave function and energy
Authors: Pachucki Krzysztof , Komasa Jacek
Published: July 2008

Nonadiabatic corrections in molecules composed of a few atoms are considered. It is demonstrated that a systematic perturbative expansion around the adiabatic solution is possible, with the expansion parameter being the electron-nucleus mass ratio to the 3/4 power. Closed form formulas for the leading corrections to the wave function and to the energy are derived. Their applicability is demonstrated by a comparison of numerical results for the hydrogen molecule with the former nonadiabatic calculations and the experimental values. Good agreement with the recent experiment is achieved for the ground state dissociation energy of both H2 and D2.
Optimization and improvement of Halbach cylinder design
Authors: Bjørk R. , Bahl C. R. H. , Smith A. , Pryds N.
Published: July 2008

In this paper we describe the results of a parameter survey of a 16 segmented Halbach cylinder in three dimensions in which the parameters internal radius, rin, external radius, rex, and length, L, have been varied. Optimal values of rex and L were found for a Halbach cylinder with the least possible volume of magnets with a given mean flux density in the cylinder bore. The volume of the cylinder bore could also be significantly increased by only slightly increasing the volume of the magnets, for a fixed mean flux density. Placing additional blocks of magnets on the end faces of the Halbach cylinder also improved the mean flux density in the cylinder bore, especially so for short Halbach cylinders with large rex. Moreover, magnetic cooling as an application for Halbach cylinders was considered. A magnetic cooling quality parameter, Λcool, was introduced and results showed that this parameter was optimal for long Halbach cylinders with small rex. Using the previously mentioned additional blocks of magnets can improve the parameter by as much as 15% as well as improve the homogeneity of the field in the cylinder bore.