bluuebunny/crossref_metadata_2025 huggingface dataset:
A Surprising Link Between the Energetics of Ovariectomy‐induced Weight Gain and Mammary Tumor Progression in Obese Rats
Authors: MacLean Paul S. , Giles Erin D. , Johnson Ginger C. , McDaniel Shauntae M. , Fleming‐Elder Brooke K. , Gilman Kaite A. , Andrianakos Anna G. , Jackman Matthew R. , Shroyer Kenneth R. , Schedin Pepper J.
Published: October 2009

Obesity increases the risk for postmenopausal breast cancer. We have modeled this metabolic context using female Wistar rats that differ in their polygenic predisposition for obesity under conditions of high‐fat feeding and limited physical activity. At 52 days of age, rats were injected with 1‐methyl‐1‐nitrosourea (MNU, 50 mg/kg) and placed in an obesogenic environment. At 19 weeks of age, the rats were separated into lean, mid‐weight, and obese rats, based upon their weight gained during this time. The rats were ovariectomized (OVX) at ∼24 weeks of age and the change in tumor multiplicity and burden, weight gain, energy intake, tumor estrogen receptor (ER) status, and humoral metabolite and cytokine profiles were examined. The survival and growth of tumors increased in obese rats in response to OVX. OVX induced a high rate of weight gain during post‐OVX weeks 1–3, compared to SHAM‐operated controls. During this time, feed efficiency (mg gain/kcal intake) was lower in obese rats, and this reduced storage efficiency of ingested fuels predicted the OVX‐induced changes in tumor multiplicity (r = −0.64, P < 0.001) and burden (r = −0.57, P < 0.001). Tumors from obese rats contained more cells that expressed ERα, and post‐OVX plasma from rats with the lowest feed efficiency had lower interleukin (IL)‐2 and IL‐4 levels. Our observations suggest a novel link between obesity and mammary tumor promotion that involves impaired fuel metabolism during OVX‐induced weight gain. The metabolically inflexible state of obesity and its inability to appropriately respond to the OVX‐induced energy imbalance provides a plausible explanation for this relationship and the emergence of obesity's impact on breast cancer risk after menopause.
The Effect of Mannan Oligosaccharide Supplementation on Body Weight Gain and Fat Accrual in C57Bl/6J Mice
Authors: Smith Daniel L. , Nagy Tim R. , Wilson Landon S. , Dong Shengli , Barnes Stephen , Allison David B.
Published: October 2009

The prevalence of obesity in industrialized societies has become markedly elevated. In contrast, model organism research shows that reducing caloric intake below ad libitum levels provides many health and longevity benefits. Despite these benefits, few people are willing and able to reduce caloric intake over prolonged periods. Prior research suggests that mannooligosaccharide (MOS or mannan) supplementation can increase lifespan of some livestock and in rodents can reduce visceral fat without reducing caloric intake. Hence, we tested the effect of MOS supplementation as a possible calorie restriction (CR) mimetic (CRM) in mice. C57Bl/6J male mice were fed a high‐fat “western” type diet with or without 1% MOS (by weight) supplementation (n = 24/group) from 8 to 20 weeks of age. Animals were housed individually and provided 95% of ad libitum food intake throughout the study. Body weight was measured weekly and body composition (lean and fat mass) measured noninvasively every 3 weeks. Individual fat depot weights were acquired by dissection at study completion. Supplementation of a high‐fat diet with 1% MOS tended to reduce total food intake (mean ± s.d.; control (CON): 293.69 ± 10.53 g, MOS: 288.10 ± 11.82 g; P = 0.09) during the study. Moreover, MOS supplementation had no significant effect on final body weight (CON: 25.21 ± 2.31 g, MOS: 25.28 ± 1.49 g; P = 0.91), total fat (CON: 4.72 ± 0.90 g, MOS: 4.82 ± 0.83 g; P = 0.69), or visceral fat (CON: 1.048 ± 0.276 g, MOS: 1.004 ± 0.247 g; P = 0.57). Contrary to previous research, MOS supplementation had no discernable effect on body weight gain or composition during this 12‐week study, challenging the potential use of MOS as a CRM or body composition enhancer.
Environmental and Genetic Factors Influence the Relationship Between Circulating IL‐10 and Obesity Phenotypes
Authors: Bassols Judit , Botas Patricia , Moreno‐Navarrete Jose M. , Delgado Elias , Ortega Francisco , Ricart Wifredo , Fernandez‐Real Jose M.
Published: October 2009

Interleukin‐10 (IL‐10) is a centrally operating anti‐inflammatory cytokine that plays a crucial role in the regulation of the innate immune system. It has strong inactivating properties on the inflammatory host response and has been related with viral persistence. We aimed to evaluate the association among circulating IL‐10, obesity phenotypes, IL‐10 and IL‐10R1 gene polymorphisms, and the environmental exposure to viral infection. IL‐10 −819C/T gene promoter and IL‐10 receptor‐1 −243A/G gene polymorphisms were studied in 760 subjects, whereas the former was also investigated in a replication study of 676 subjects. The association of circulating IL‐10 levels (enzyme‐linked immunosorbent assay) with the serum IgG against adenoviruses and enteroviruses was evaluated in a subset of 189 subjects. Circulating levels of IL‐10 were increased in obese people and were positively associated with weight, BMI, waist, waist‐to‐hip ratio, fat mass, systolic pressure, and, interestingly, the titer of adenoviruses and enteroviruses. Obese subjects with adenovirus titer over the median had the highest circulating IL‐10 concentration. Both obesity and adenovirus titer were independently associated with IL‐10 variance. Nonmorbid obese T carriers for the −819CT IL‐10 gene polymorphism had significantly higher BMI and waist circumference, and those with normal fasting glucose had increased fasting triglycerides. G carriers for the −536AG IL‐10R1 gene polymorphism had higher systolic and diastolic pressures, and IL‐10 levels; and obese G carriers had an increased waist‐to‐hip ratio. In summary, circulating IL‐10 levels were associated not only with obesity status but also with genetic factors and with the exposure to environmental pathogens.
Is There Really a “Cushion Effect”?: A Biomechanical Investigation of Crash Injury Mechanisms in the Obese
Authors: Kent Richard W. , Forman Jason L. , Bostrom Ola
Published: October 2009

The objective of this study was to document the motion and potential injury mechanisms of obese occupants in frontal car crashes compared to a control group of nonobese occupants in controlled laboratory impacts. Eight cadavers were divided into obese (n = 3) and a nonobese (n = 5) groups and exposed to a 48 km/h impact. High speed digital video documented the motion of the belted subjects. Compared to the nonobese cohort, the obese exhibited a characteristically different set of motions. As expected, the obese (heavier) subjects experienced greater maximum forward displacement (excursion) before their motion was arrested by the restraint. In addition, the obese exhibited a different distribution of excursions among body segments. The primary difference between the cohorts was substantially larger hip excursion in the obese (452 ± 83 mm vs. 203 ± 42 mm, P < 0.01), which was the proximate cause of a tendency of the obese cadavers' torsos to pitch forward less during impact. Some of the published epidemiology can be elucidated by the results reported here. The increased hip excursion and concomitant decreased torso pitch may reduce the risk of the head striking some component of the vehicle interior. Furthermore, the reclined torso during belt loading may increase the risk of rib and pulmonary trauma because the load is concentrated on the compliant and vulnerable lower thorax and less on the stiff upper ribs and clavicle. The lower extremities also experience increased excursion as a result of this hip excursion, and thus an increased risk of a hard contact and resulting injury.
Comparison of Lipid and Fatty Acid Composition of the Liver, Subcutaneous and Intra‐abdominal Adipose Tissue, and Serum
Authors: Kotronen Anna , Seppänen‐Laakso Tuulikki , Westerbacka Jukka , Kiviluoto Tuula , Arola Johanna , Ruskeepää Anna‐Liisa , Yki‐Järvinen Hannele , Orešič Matej
Published: October 2009

Ceramides may mediate saturated fat–induced insulin resistance, but there are no data comparing ceramide concentrations between human tissues. We therefore performed lipidomic analysis of human subcutaneous (SCfat) and intra‐abdominal (IAfat) adipose tissue, the liver, and serum in eight subjects. The liver contained (nmol/mg tissue) significantly more ceramides (1.5–3‐fold), sphingomyelins (7–8‐fold), phosphatidylethanolamines (10–11‐fold), lysophosphatidylcholines (7–12‐fold), less ether‐linked phosphatidylcholines (2–2.5‐fold) but similar amounts of diacylglycerols as compared to SCfat and IAfat. The amounts of ceramides and their synthetic precursors, such as palmitic (16:0) free fatty acids and sphingomyelins, differed considerably between the tissues. The liver contained proportionally more palmitic, stearic (18:0), and long polyunsaturated fatty acids than adipose tissues. Stearoyl‐CoA desaturase 1 (SCD1) activity reflected by serum, estimated from the 16:1/16:0‐ratio, was closely related to that in the liver (r = 0.86, P = 0.024) but not adipose tissues. This was also true for estimated elongase (18:1/16:1, r = 0.89, P = 0.01), and Δ5 (20:4/20:3, r = 0.89, P = 0.012) and Δ6 (18:3[n‐6]/18:2, r = 1.0, P < 0.001) desaturase activities. We conclude that the human liver contains higher concentrations of ceramides and saturated free fatty acids than either SCfat or IAfat.
Retracted: In Bangladesh, overweight individuals have fewer symptoms of depression than nonoverweight individuals
Authors: Asghar Shaheen , Magnusson Andres , Khan Azad , Ali Keramat , Hussain Akhtar
Published: October 2009

The aim of this study was to examine whether the association between overweight and depression usually found in western societies would also be found in locations where overweight is not stigmatized. A total of 1,271 individuals from rural Bangladesh were randomly selected; the response rate was 76%. Depressive symptoms were measured with the Montgomery‐Åsberg Depression Rating Scale (MADRS). The sum MADRS scores were 13.4 (s.d. = 5.8) and 18.5 (8.1) for overweight vs. nonoverweight (t = 6.6; P < 0.000) men, respectively, and 19.7 (7.8) and 23.2 (7.9) for overweight vs. nonoverweight women, respectively (t = 4.2; P < 0.000). Thus the MADRS score was lower in overweight individuals. After adjusting for sex and age, BMI significantly predicted the MADRS score (β = −0.3; t = 10.2; P < 0.000). These findings suggest that overweight may be related to fewer depressive symptoms in non western cultures.
A constitutively active and uninhibitable caspase-3 zymogen efficiently induces apoptosis
Authors: Walters Jad , Pop Cristina , Scott Fiona L. , Drag Marcin , Swartz Paul , Mattos Carla , Salvesen Guy S. , Clark A. Clay
Published: October 2009

The caspase-3 zymogen has essentially zero activity until it is cleaved by initiator caspases during apoptosis. However, a mutation of V266E in the dimer interface activates the protease in the absence of chain cleavage. We show that low concentrations of the pseudo-activated procaspase-3 kill mammalian cells rapidly and, importantly, this protein is not cleaved nor is it inhibited efficiently by the endogenous regulator XIAP (X-linked inhibitor of apoptosis). The 1.63 Å (1 Å = 0.1 nm) structure of the variant demonstrates that the mutation is accommodated at the dimer interface to generate an enzyme with substantially the same activity and specificity as wild-type caspase-3. Structural modelling predicts that the interface mutation prevents the intersubunit linker from binding in the dimer interface, allowing the active sites to form in the procaspase in the absence of cleavage. The direct activation of procaspase-3 through a conformational switch rather than by chain cleavage may lead to novel therapeutic strategies for inducing cell death.
The plant endoplasmic reticulum: a cell-wide web
Authors: Sparkes Imogen A. , Frigerio Lorenzo , Tolley Nicholas , Hawes Chris
Published: October 2009

The ER (endoplasmic reticulum) in higher plants forms a pleomorphic web of membrane tubules and small cisternae that pervade the cytoplasm, but in particular form a polygonal network at the cortex of the cell which may be anchored to the plasma membrane. The network is associated with the actin cytoskeleton and demonstrates extensive mobility, which is most likely to be dependent on myosin motors. The ER is characterized by a number of domains which may be associated with specific functions such as protein storage, or with direct interaction with other organelles such as the Golgi apparatus, peroxisomes and plastids. In the present review we discuss the nature of the network, the role of shape-forming molecules such as the recently described reticulon family of proteins and the function of some of the major domains within the ER network.
Positive contribution of ERdj5/JPDI to endoplasmic reticulum protein quality control in the salivary gland
Authors: Hosoda Akira , Tokuda Mio , Akai Ryoko , Kohno Kenji , Iwawaki Takao
Published: October 2009

In eukaryotic cells, most membrane and secretory proteins are modified post-translationally in the ER (endoplasmic reticulum) for correct folding and assembly. Disulfide-bond formation is one of the important modifications affecting folding and is catalysed by the PDI (protein disulfide isomerase) family proteins. ERdj5 [also known as JPDI (J-domain-containing PDI-like protein)] is a member of the PDI family proteins and has been reported to act as a reductase in ERAD (ER-associated degradation). However, the role of ERdj5 at the whole-body level remains unclear. Therefore in the present study we generated ERdj5-knockout mice {the mouse gene of ERdj5 is known as Dnajc10 [DnaJ (Hsp40) homologue, subfamily C, member 10]} and analysed them. Although ERdj5-knockout mice were viable and healthy, the ER stress response was activated in the salivary gland of the knockout mice more than that of control mice. Furthermore, in ERdj5-knockout cells, the expression of exogenous ERdj5 mitigated the ER stress caused by overproduction of α-amylase, which is one of the most abundant proteins in saliva and has five intramolecular disulfide bonds. This effect was dependent on the thioredoxin-like motifs of ERdj5. Thus we suggest that ERdj5 contributes to ER protein quality control in the salivary gland.
Comparison of gene expression profiling between bovine subcutaneous and intramuscular adipose tissues by serial analysis of gene expression
Authors: Bong Jong Jing , Cho Keun Kwang , Baik Myunggi
Published: October 2009

The deposition of intramuscular adipose fat is an important factor in the quality of beef, particularly in Korean cattle and Japanese cattle. A better understanding of the differential mechanisms regulating the deposition and release of fat between intramuscular and external adipose tissues, particularly subcutaneous adipose tissues, would prove vital in understanding the deposition of intramuscular fat. A SAGE (serial analysis of gene expression) method was used to identify functionally active genes in adipose tissues and to compare the global gene expression profile between the subcutaneous and the intramuscular adipose tissues in Korean cattle. We detected 11268 tags, representing 3761 transcripts in the SAGE library of the subcutaneous adipose tissues. We detected 10830 tags, representing 2918 transcripts in the intramuscular adipose tissues. Comparison of gene expression patterns between subcutaneous adipose tissues and intramuscular adipose tissues revealed that 82 genes were differentially expressed at >2‐fold levels. Among them, expression levels of 50 genes were higher in subcutaneous adipose tissues compared with intramuscular tissues, whereas those of 32 genes were higher in intramuscular adipose tissues. The genes that displayed >2‐fold higher expression in subcutaneous adipose tissues included secreted protein acidic and rich in cysteine, annexin II, thyroid hormone receptor interactor 1, ferritin heavy chain polypeptide 1, cofilin, diacylglycerol O‐acyltransferase and thymosin beta 4. Those that showed >2‐fold higher expression levels in intramuscular adipose tissues included troponin t3, heat shock 70 kDa protein 1 and NMT2 (N‐myristoyltransferase 2). Expression patterns of NMT2 and troponin t3 genes were examined during differentiation of 3T3‐LI preadipocytes. NMT2 gene was actively expressed at both the growing stage of preadipocytes and the initial stage of differentiation of 3T3‐L1 adipocytes, but its expression was reduced at the active stage of adipocyte differentiation. Troponin t3 gene was not expressed at the growing stage of preadipocyte, but it was actively expressed during differentiation of adipocytes. This implies that troponin t3 may play a positive role in intramuscular fat deposition of beef. Our SAGE experiment provides a differential gene expression profile in subcutaneous and intramuscular adipose tissues of Korean cattle. This information will be useful in developing method(s) to produce high‐marble beef.
A Survey of Multiple Tree Visualisation
Authors: Graham Martin , Kennedy Jessie
Published: October 2009

This article summarises the current state of research into multiple tree visualisations. It discusses the spectrum of current representation techniques used on single trees, pairs of trees and finally multiple trees, in order to identify which representations are best suited to particular tasks and to find gaps in the representation space, in which opportunities for future multiple tree visualisation research may exist. The application areas from where multiple tree data are derived are enumerated, and the distinct structures that multiple trees make in combination with each other and the effect on subsequent approaches to their visualisation are discussed, along with the basic high-level goals of existing multiple tree visualisations.
In situ study of the formation of silicide phases in amorphous Ni–Si mixed layers
Authors: Van Bockstael C. , Detavernier C. , Van Meirhaeghe R. L. , Jordan-Sweet J. L. , Lavoie C.
Published: October 2009

In this paper, we investigated Ni silicide phase formation when Si is added within an as deposited 50 nm Ni film. A series of 22 samples with a Si content varying from 0 to 50 at. % was prepared and systematically investigated with in situ x-ray diffraction. The inert oxide substrate was used to identify the phases which first crystallize in an amorphous Ni–Si mixture of a given concentration. The noncongruent silicides Ni3Si and Ni3Si2 are never observed to crystallize readily out of the mixture. A remarkable observation is the initial crystallization at low temperature of a hexagonal Ni-silicide, observed over a broad mixed layer composition [35–49%Si]; this hexagonal phase nucleates readily as a single phase [39–47%Si] or together with Ni2Si [35–38%Si] or NiSi [49%Si]. This low-temperature phase is related to the high temperature θ-phase, but covers a wide composition range up to 47%Si. For the same Ni–Si films deposited on Si(100), the initial nucleation of the Ni(Si) mixture is similar as for the samples deposited on SiO2, such that the complex sequence of metal-rich Ni-silicide phases typically observed during Ni/Si reactions is modified. For samples containing more than 21%Si, a simpler sequential phase formation was observed upon annealing. From pole figures, the phase formation sequence was observed to have a significant influence on the texture of the technologically relevant NiSi phase. For mixture composition ranging from 38% to 43%Si, the initial transient θ-phase appears extremely textured on Si(100). The observed transient appearance of a hexagonal phase is of importance in understanding the phase formation mechanisms in the Ni–Si system.
Electron dynamics in GaN wafers with an inhomogeneous distribution of defects in the depth direction
Authors: Ohashi Yuji , Katayama Kenji , Shen Qing , Toyoda Taro
Published: October 2009

The dynamics of photoexcited electrons in a GaN wafer with an inhomogeneous dislocation density distribution in the depth direction was measured by the near-field heterodyne transient grating method. We investigated the dependence of the interfaces with different dislocation densities, the dependence on the pump wavelength for a sample with a decaying distribution of dislocation density, which gives information on the depth dependence on the carrier dynamics. In the latter experiment, the observed depth region was continuously changed by tuning the wavelength around the band gap of GaN. The responses of the electron dynamics can be fitted with the sum of two exponential decays for all the experiments and only the slower component decayed faster as the dislocation density increased. It was concluded that the faster component corresponded to the trap process of electrons by deep states due to inherent defects in the GaN wafer and the slower component corresponded to the recombination of the trapped electrons at the defect states by dislocation defects.
Prediction of breakdown in ultrathin SiO2 films with fractal distribution of traps
Authors: Russo F. , Badolato G. , Irrera F.
Published: October 2009

An approach to modeling of thin SiO2 film degradation based on fractal distribution of traps is presented, which shows a high predictive power for ultrathin oxides breakdown. The fractal patterns of traps are produced by a modified version of the diffusion limited aggregation (DLA) model introduced in literature as to describe irreversible colloidal aggregation. In the present version of the DLA model, the trap generation in SiO2 is not random. It occurs at an interface or the trap aggregates to another existing trap. The movement probabilities of particles creating traps are defined through two parameters, which describe the lateral and straight movement. The two parameter values have been set as to obtain a certain fractal dimension (1.7) derived from optical inspections on dielectrics already reported in literature. The model has been calibrated using breakdown data obtained on samples fabricated ad hoc. It is coherent with the Weibull statistics describing the oxide film failure. Finally, the results of the model have been compared with experimental data of breakdown taken from literature.
Elimination of phase separation in metalorganic chemical vapor deposition-grown GaInP epilayers by compositionally step-graded Ga1−xInxP multilayers
Authors: Tsai Yu-Li , Horng Ray-Hua , Liu Po-Liang , Tseng Ming-Chun , Lin Der-Yuh , Wuu Dong-Sing
Published: October 2009

In this paper, we report on the influence of compositionally step-graded Ga1−xInxP multilayers on the microstructural and optical properties of In-rich Ga0.46In0.54P film grown on a GaAs substrate. Based on the transmission electron microscope observation, the growth of Ga0.46In0.54P on GaAs was found to result in phase separation, which was due to the strain-induced composition pulling effect. This phase separation could be successfully eliminated by the step-graded Ga1−xInxP multilayers with optimized thickness. The elimination was caused by the sufficient moderation of compressive strain in the subsequently grown Ga0.46In0.54P film. The employment of step-graded Ga1−xInxP multilayers was also helpful in improving compositional uniformity and photoluminescence property of the subsequently grown film. The compositional dependence of the film structure and the ab initio elastic constants were used to show that Ga1−xInxP multilayers with a systematic increase in the In-rich compositional regime exhibit epitaxial stability.
Phase change mechanisms during femtosecond laser pulse train ablation of nickel thin films
Authors: Li Xin , Jiang Lan , Tsai Hai-Lung
Published: October 2009

The mechanisms of nickel thin films irradiated by femtosecond laser pulse trains are studied by a model using molecular dynamics simulations and two-temperature model. It is found that the pulse train technology can change energy transport and corresponding phase change processes. Compared with single pulse ablation at the same total fluence, the pulse trains lead to (1) lower ablation rate with more and smaller uniform nanoparticles, (2) higher film surface temperatures and longer thermalization time, (3) much lower electron thermal conductivity that can further control heat-affected zone, (4) significantly smaller film compressive stresses and tensile stresses which reduce microcracks, and (5) a transition from phase explosion to the critical point phase separation which favors small uniform nanoparticle generation.
Charge spectroscopy of Si nanocrystallites embedded in a SiO2 matrix
Authors: Antonova Irina V. , Volodin Vladimir A. , Neustroev Efim P. , Smagulova Svetlana A. , Jedrzejewsi Jedrzej , Balberg Isaac
Published: October 2009

In the present work we have determined the electronic levels in systems of Si nanocrystallites (NCs) embedded in the insulating matrix of silicon dioxide, SiO2, by employing the charge deep-level transient spectroscopy (Q-DLTS) technique. We have clearly shown that these levels are associated with the NCs. Correspondingly, we suggest that the levels that we found are associated mainly with two quantum confinement energies, 0.14 and 0.19 eV. These energies are shown to be consistent with the corresponding theoretical estimates for the presently studied Si–NCs/SiO2 systems. The fact that these levels are almost fixed for the various samples studied suggests the importance of the bulk-surface coupling under quantum confinement conditions.
Symmetry of residual stress fields of ZnO below an indent measured by three-dimensional Raman spectroscopy
Authors: Wermelinger Thomas , Spolenak Ralph
Published: October 2009

ZnO is a wide gap semiconductor with interesting properties for applications in nanoelectronics as well as nanophotonics and can be used for ultraviolet nanolasers. The optical and electrical properties of ZnO are strongly influenced by residual stresses, defects, as well as microstructural changes. This work presents a detailed study of the residual stresses and the microstructure in three dimensional (3D) around a Vickers microindent placed on the prism plane of a ZnO single crystal. The biaxial stress field on the surface of the indent was measured using a confocal Raman microscope. The deformed microstructure around the indent was examined by 3D Raman and cathodoluminescence measurements. Further, a cross section extracted from the center of the indent was studied by transmission electron microscopy. The results show that the symmetry of the residual stress field on the surface depends not on the geometry of the indent but on the deformation mechanism of the crystal. The 3D Raman measurements allow calculating the volume of high-dislocation density in the vicinity of the indent.
Processing and properties of large grain Y–Ba–Cu–O containing Y2Ba4CuWOy and Ag second phase inclusions
Authors: Pathak S. K. , Babu N. H. , Iida K. , Strasik M. , Cardwell David
Published: October 2009

Second phase nanoinclusions of composition Y2Ba4CuWOy (Y-24W1) have been incorporated into the YBa2Cu3O7−δ (Y-123) superconducting matrix to form effective artificial flux pinning sites. A remarkable improvement in critical current density Jc has been observed at both self- and higher applied fields in these samples, in contrast to the effect that the presence of Y2BaCuO5 (Y-211) second phase inclusions has on Jc, particularly at low field. The field trapping ability of samples containing the Y-24W1 phase has been improved by adding silver to the nanocomposite precursor composition in an attempt to reduce the formation of c-axis microcracks in the sample microstructure. The combined effect of the Y-24W1 artificial defects and the addition of silver produce enhanced trapped fields in these samples.
Dielectric properties of Li2O–3B2O3 glasses
Authors: Vaish Rahul , Varma K. B. R.
Published: October 2009

The frequency and temperature dependences of the dielectric constant and the electrical conductivity of the transparent glasses in the composition Li2O–3B2O3 were investigated in the 100 Hz–10 MHz frequency range. The dielectric constant and the loss in the low frequency regime were electrode material dependent. Dielectric and electrical relaxations were, respectively, analyzed using the Cole–Cole and electric modulus formalisms. The dielectric relaxation mechanism was discussed in the framework of electrode and charge carrier (hopping of the ions) related polarization using generalized Cole–Cole expression. The frequency dependent electrical conductivity was rationalized using Jonscher’s power law. The activation energy associated with the dc conductivity was 0.80±0.02 eV, which was ascribed to the motion of Li+ ions in the glass matrix. The activation energy associated with dielectric relaxation was almost equal to that of the dc conductivity, indicating that the same species took part in both the processes. Temperature dependent behavior of the frequency exponent (n) suggested that the correlated barrier hopping model was the most apposite to rationalize the electrical transport phenomenon in Li2O–3B2O3 glasses. These glasses on heating at 933 K/10 h resulted in the known nonlinear optical phase LiB3O5.
Production of planar-type overdense plasma with resonant excitation of surface plasmon polaritons
Authors: Chen Zhaoquan , Liu Minghai , Tang Liang , Lv Jianhong , Wen Yuanfang , Hu Xiwei
Published: October 2009

The present study presents a plasma source, capable of generating overdense plasma below the whole quartz plate while exciting surface plasmon polaritons (SPPs) by means of a subwavelength diffraction grating. The wavelength of surface wave, calculated on either the discharge image or the simulated electric field distribution graph, is about 5.7 cm, which approximates the theoretical value by a calculation of the SPP dispersion equation in overdense plasma. The operation mechanism of plasma heating is attributed to the resonant excitation of SPPs and its dissipation in plasma.
Study of SF6 adsorption on graphite using infrared spectroscopy
Authors: Thomas Petros , Xia Yu , Boyd David A. , Hopkins Todd A. , Hess George B.
Published: October 2009

We report an experimental study of adsorbed monolayers of SF6 on graphite using infrared reflection absorption spectroscopy supplemented by ellipsometry. The asymmetric S–F stretch mode ν3 near 948 cm−1 in the gas is strongly blueshifted in the film by dynamic dipole coupling. This blueshift is very sensitive to the intermolecular spacing in the SF6 layer. We convert the measured frequency ν3 to a lattice spacing a, using a self-consistent field calculation, calibrated by the frequency in the commensurate phase. The resolution in lattice spacing is 0.002 Å, although there is a larger systematic uncertainty associated with nondynamic-dipole contributions to the frequency shift. We map the commensurate-incommensurate transition, a transition between two incommensurate phases, and the melting transition. These results are compared to previous x-ray data. We provide a new determination of the layer critical point (156 K), the layer condensation line down to 110 K, and the spreading pressure at saturation in this temperature range.
Conductivity and scaling properties of chemically grown granular silver films
Authors: Peterson M. S. M. , Deutsch M.
Published: October 2009

We address room-temperature conductivities of chemically grown silver films. Disordered, granular silver films are grown using a modified Tollens reaction. Thick, polycrystalline films are transparent at visible wavelengths, with crystallinity similar to that of silver powders. The measured conductivities are close to those measured by I. V. Antonets, L. N. Kotov, S. V. Nekipelov, and Ye. A. Golubev, Tech. Phys. 49, 306 (2004) in amorphous silver films, however the thickness where bulk conductivity is reached is anomalously high. While measured resistance values do not obey a scaling relation in thickness, accounting for the films’ structural porosity through geometrical rescaling of the thickness leads to emergence of the well-known percolation power-law scaling, albeit that of two-dimensional percolating films.
Hybrid-anvil: A suitable anvil for large volume cubic high pressure apparatus
Authors: Han Qi-gang , Ma Hong-an , Huang Guo-feng , Zhang Cong , Li Zhan-chang , Jia Xiao-peng
Published: October 2009

A hybrid-anvil used in cubic high pressure apparatus is presented, which makes it possible to pressurize samples of 36 mm3 volume up to 5.5 GPa and to heat simultaneously up to 1350–1400 °C for routine operation. The hybrid-anvil has been designed based on the theory of multilayered pressure vessels and massive support, which can save weight about 60.00% compared to the traditional anvil. We note from 10 000 times of experiments that the rate of failure crack decreases about 16.67% and the cost of anvil saves about 66.40% after the modification of the anvil. This represents a relatively simple and inexpensive anvil for material synthesis and research.
Relativistic performance analysis of a high current density magnetron injection gun
Authors: Barnett L. R. , Luhmann N. C. , Chiu C. C. , Chu K. R.
Published: October 2009

Electron beam quality is essential to the performance of millimeter-wave gyroamplifiers, particularly the gyrotron traveling-wave tube amplifier, which is extremely sensitive to the electron velocity spread and emission uniformity. As one moves up in power and frequency, the quality of the electron beam becomes even more critical. One aspect of the electron beam formation technology which has received relatively little attention has been the performance analysis of the electron beam itself. In this study, a 100 kV, 8 A magnetron injection gun with a calculated perpendicular-to-parallel velocity ratio of 1.4 and axial velocity spread of 3.5% has been designed, tested, and analyzed. It is shown that the equipment precision and a fully relativistic data analysis model afford sufficient resolution to allow a verification of the theoretical predictions as well as a quantitative inference to the surface roughness of the cathode used.
High-energy monoenergetic proton bunch from laser interaction with a complex target
Authors: Wang Fengchao , Shen Baifei , Zhang Xiaomei , Jin Zhangying , Wen Meng , Ji Liangliang , Wang Wenpeng , Xu Jiancai , Yu M. Y. , Cary J.
Published: October 2009

Generation of high-energy proton bunch in the interaction of a high-power laser pulse with a complex target consisting of a front horizontal slice adjoining a conventional heavy ion and proton double-layer slab is investigated using two-dimensional particle-in-cell simulation. The laser pulse propagates along both sides of the slice. A large number of hot electrons are generated and accelerated by the surface ponderomotive force, and transported through the double layer, forming a backside sheath field which is considerably stronger and more localized than that produced by the electrons from a simple double layer. As a result, the protons in the proton layer can be accelerated to energies more than three times, and the energy spread halved, that from the simple double layer.
Accurate prediction of higher-level electronic structure energies for large databases using neural networks, Hartree–Fock energies, and small subsets of the database
Authors: Malshe M. , Pukrittayakamee A. , Raff L. M. , Hagan M. , Bukkapatnam S. , Komanduri R.
Published: October 2009

A novel method is presented that significantly reduces the computational bottleneck of executing high-level, electronic structure calculations of the energies and their gradients for a large database that adequately samples the configuration space of importance for systems containing more than four atoms that are undergoing multiple, simultaneous reactions in several energetically open channels. The basis of the method is the high-degree of correlation that generally exists between the Hartree–Fock (HF) and higher-level electronic structure energies. It is shown that if the input vector to a neural network (NN) includes both the configuration coordinates and the HF energies of a small subset of the database, MP4(SDQ) energies with the same basis set can be predicted for the entire database using only the HF and MP4(SDQ) energies for the small subset and the HF energies for the remainder of the database. The predictive error is shown to be less than or equal to the NN fitting error if a NN is fitted to the entire database of higher-level electronic structure energies. The general method is applied to the computation of MP4(SDQ) energies of 68 308 configurations that comprise the database for the simultaneous, unimolecular decomposition of vinyl bromide into six different reaction channels. The predictive accuracy of the method is investigated by employing successively smaller subsets of the database to train the NN to predict the MP4(SDQ) energies of the remaining configurations of the database. The results indicate that for this system, the subset can be as small as 8% of the total number of configurations in the database without loss of accuracy beyond that expected if a NN is employed to fit the higher-level energies for the entire database. The utilization of this procedure is shown to save about 78% of the total computational time required for the execution of the MP4(SDQ) calculations. The sampling error involved with selection of the subset is shown to be about 10% of the predictive error for the higher-level energies. A practical procedure for utilization of the method is outlined. It is suggested that the method will be equally applicable to the prediction of electronic structure energies computed using even higher-level methods than MP4(SDQ).
Dissociative adsorption of hydrogen fluoride onto amorphous solid water
Authors: Ayotte Patrick , Rafiei Zohreh , Porzio François , Marchand Patrick
Published: October 2009

Adsorption of hydrogen fluoride (HF) onto amorphous solid water films at 50 K is reported to yield a strong absorbance continuum in their reflection-absorption infrared spectra (RAIRS). This and other complex features observed in the RAIRS spectra of stratified binary composite HF:H2O nanoscopic films deposited onto Pt(111) are interpreted quantitatively using a classical optics model. Comparison with experimental data allows us to determine that the absorbance continuum is due to absorption within the film (as opposed to trivial optical effects) and that the extent of intermixing and uptake is mostly limited to the first few molecular layers. Furthermore, extensive isotope scrambling is demonstrated by the observation of similar Zundel continua upon codeposition of neat HF, or DF, and H2O vapors onto Pt(111) at 50 K. These observations are consistent with those expected from extensive ionic dissociation of HF upon dissolution within, and adsorption onto, ASW at 50 K.
Stray light correction for solar measurements using array spectrometers
Authors: Kreuter Axel , Blumthaler Mario
Published: October 2009

A stray light matrix correction method for array spectrometers is presented that is specifically tailored for solar spectral measurements. A stray light distribution function based on a single laser line measurement is approximated by an analytical function using three parameters only. This function is the basis for the stray light correction matrix. One cutoff filter is then used to adjust an offset parameter such that stray light corrected data are spectrally flat and around zero below the cutoff wavelength. This parameter also accounts for the IR contribution and has to be adjusted individually for each type of spectrum. A solid validation is given by intercomparison of calibrated solar spectra with a double-monochromator spectroradiometer. An agreement of 5% for wavelengths down to 307 nm and solar zenith angle smaller than 70° is achieved.
Limiting current enhancements for a relativistic electron beam propagating through coaxial cylinders
Authors: Baedke W. C.
Published: October 2009

An investigation of the space-charge-limited (SCL) currents for un-neutralized relativistic electron beams drifting through an infinitely long dielectrically lined coaxial cylindrical structure with a biased inner conductor is presented. To begin, an approximate limiting current expression is developed for an un-neutralized finite-width relativistic electron beam drifting through a biased coaxial cylindrical structure, which contains no dielectric liner. The SCL currents are then numerically calculated and compared to the approximation and it is shown that there is good agreement between the two. Building on this, the SCL currents are then numerically calculated when a dielectric liner, which encloses the finite-width electron beam, is present. It is shown that when a dielectric liner is present, there is a point at which increases in the SCL currents saturate and increasing the relative dielectric constant provides no additional increase in the expected SCL currents. In addition, it is demonstrated that the dielectric liner, in conjunction with the biased inner conductor, provides significant SCL current enhancements when compared to a system with no dielectric liner and no biased inner conductor. Finally, the possibility of dielectric breakdown is addressed as well as the amount of accumulated charge at the vacuum-dielectric interface.
Improving upon the accuracy for doubly excited states within the coupled cluster singles and doubles theory
Authors: Kuś Tomasz , Bartlett Rodney J.
Published: October 2009

An alternative strategy of computations for double character excited states has been examined. The basic idea is to employ the reference function specific to the excited state of interest, as opposed to the traditionally used reference function, usually corresponding to the ground state, specific to the entire spectrum of a molecule. The procedure is used within the framework of the coupled cluster singles and doubles (CCSD) method. The conventional spin-conserving CC approach as well as its spin-flip (SF) extension has been analyzed. For the latter, two variants are considered, changing the Sz value of the reference function by one [equation-of-motion (EOM)-SF] and two (EOM-2SF). The accuracy of the methods is benchmarked for the C2 and C4 molecules and referred to the full configuration interaction (FCI) or CC singles, doubles, and triples results. The vertical and adiabatic excitation energies, equilibrium geometries, and harmonic frequencies are studied. A significant improvement is demonstrated for the excitation energies of doubly excited states. Comparing these values with the FCI method, the errors of the conventional EOM CCSD method of about 1.7–2.2 eV are reduced to about 0.0–0.4 eV for the SF method. An improvement is also shown for the equilibrium geometries and harmonic frequencies.
Accurate ab initio potential energy curves for the classic Li–F ionic-covalent interaction by extrapolation to the complete basis set limit and modeling of the radial nonadiabatic coupling
Authors: Varandas A. J. C.
Published: October 2009

Multireference configuration interaction calculations using large correlation consistent basis sets and full configuration interaction calculations with the smallest of such basis are utilized to describe the ionic-neutral curve crossing for the title system. The results of the former calculations have then been extrapolated to the complete basis set limit using the uniform singlet- and triplet-pair extrapolation scheme. A recent suggestion for locating the nonadiabatic matrix terms at the point where the dynamical correlation split vanishes has also been tested. Additionally, a consistent formalism is suggested to model the radial dependence of the nonadiabatic matrix terms that warrants an overlap dependence away from the crossing. When applied to LiF, the overall approach yields results in excellent agreement with the commonly accepted values for the geometric and energetic attributes at both the equilibrium and diabatic crossing regions.
Control of unsteady flow separation over a circular cylinder using dielectric-barrier-discharge surface plasma
Authors: Jukes Timothy N. , Choi Kwing-So
Published: October 2009

Dielectric-barrier-discharge plasma actuators have been used to control the unsteady flow separation over a circular cylinder at Re=15 000 with a view to maximizing the lift with a minimum drag increase. The flow structure was studied using time-resolved particle image velocimetry and flow visualization, while the dynamic lift and drag were simultaneously measured with a two-component force balance. Our results show that the lift can be dramatically increased by a single, short-duration pulse of plasma at carefully chosen location and timing. A peak lift coefficient of 1.24 was observed, showing that the plasma can increase lift by over 300%, with less than 25% increase in drag. Optimal conditions occurred when the actuator was located at 75° from the streamwise axis, with plasma forcing timed to coincide with the retreat of the separation point. This corresponds to the actuator being located 7° upstream of the natural separation point. The peak lift was relatively insensitive to the duration of the plasma.
Structure and thermodynamics of colloidal protein cluster formation: Comparison of square-well and simple dipolar models
Authors: Young Teresa M. , Roberts Christopher J.
Published: October 2009

Reversible formation of weakly associated protein oligomers or clusters is a key early step in processes such as protein aggregation and colloidal phase separation. A previously developed cell-based, quasichemical model for lattice fluids [T. M. Young and C. J. Roberts, J. Chem. Phys. 127, 165101 (2007)] is extended here to treat continuous-space systems. It is illustrated using two simplified limiting cases for globular proteins at the isoelectric point: spherical square-well (SW) particles with an isotropic short-ranged attraction and screened dipolar particles with SW attractions and square-shoulder repulsions. Cluster free energies (ΔAi) and structures are analyzed as a function of the reduced second virial coefficient b2∗. ΔAi values and the average structures of clusters up to pentamers have distinct differences due to the anisotropic nature of the dipolar interactions. However, ΔAi values can be mapped semiquantitatively between the two cases if compared at common values of b2∗. Free energy landscapes of oligomerization are constructed, illustrating significant differences in landscape ruggedness for small clusters of dipolar versus SW fluids, and suggesting a possible molecular interpretation for empirical models of nucleation-dependent aggregation of proteins.
A connection between domain-averaged Fermi hole orbitals and electron number distribution functions in real space
Authors: Francisco E. , Martín Pendás A. , Blanco M. A.
Published: October 2009

We show in this article how for single-determinant wave functions the one-electron functions derived from the diagonalization of the Fermi hole, averaged over an arbitrary domain Ω of real space, and expressed in terms of the occupied canonical orbitals, describe coarse-grained statistically independent electrons. With these domain-averaged Fermi hole (DAFH) orbitals, the full electron number distribution function (EDF) is given by a simple product of one-electron events. This useful property follows from the simultaneous orthogonality of the DAFH orbitals in Ω, Ω′=R3−Ω, and R3. We also show how the interfragment (shared electron) delocalization index, δΩ,Ω′, transforms into a sum of one-electron DAFH contributions. Description of chemical bonding in terms of DAFH orbitals provides a vivid picture relating bonding and delocalization in real space. DAFH and EDF analyses are performed on several test systems to illustrate the close relationship between both concepts. Finally, these analyses clearly prove how DAFH orbitals well localized in Ω or Ω′ can be simply ignored in computing the EDFs and/or δΩ,Ω′, and thus do not contribute to the chemical bonding between the two fragments.