bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficacy of Postoperative Transarterial Chemoembolization and Portal Vein Chemotherapy for Patients with Hepatocellular Carcinoma Complicated by Portal Vein Tumor Thrombosis—a Randomized Study
Authors: Li Q. , Wang J. , Sun Y. , Cui Y.L. , Juzi J.T. , Li H.X. , Qian B.Y. , Hao X.S.
Published: October 2006

Objectives

The aim of this single, randomized study was to explore the efficacy of postoperative transarterial chemoembolization (TACE) and portal vein chemotherapy (PVC) for patients with hepatocellular carcinoma (HCC) complicated by portal vein tumor thrombosis (PVTT) and to evaluate prognostic factors.

Methods

The study cohort consisted of 112 patients with HCC and PVTT randomly divided into three groups: Group A (37 patients), operation only; Group B (35 patients), operation plus TACE; Group C (40 patients), operation plus TACE and PVC. Disease‐free survival rates and prognostic factors were analyzed.

Results

Most of the side effects and complications were related to the operation, catheters, and local chemotherapy and included liver decompensation (15.0%), catheter obstruction (11.6%), and nausea and loss of appetite (22.1%). The disease‐free survival curve was significantly different among the three groups, as estimated by the Kaplan‐Meier method (both P < 0.05). Group C showed a significantly higher disease‐free survival rate than Group A (P < 0.05), but no statistical differences were found between group A and group B, and group B and group C (both P > 0.05). Tumor size, tumor number, PVTT location, and treatment modalities were independent prognostic factors (P < 0.05).

Conclusion

Postoperative TACE combined with PVC may benefit the survival of patients with HCC complicated by PVTT in the short‐term (less than 60 months), but long‐term efficacy is not yet certain and needs to be confirmed by further studies.
PP2Cγ‐mediated S‐phase accumulation induced by the proteasome‐dependent degradation of p21WAF1/CIP1
Authors: Suh Eun-Jung , Kim Tae-Yoon , Kim Sang Hoon
Published: October 2006

Serine/threonine phosphatases such as PP1, PP2A, and PP2B are well known to regulate the transition phase of the cell cycle. However, the function of PP2Cγ in cell cycle progression is still unclear. In the present study, we report the characterization of PP2Cγ in mammalian cells during the cell cycle. After release of synchronized cells from thymidine block, over‐expression of PP2Cγ led to accumulation in the S phase. The amount of endogenous p21WAF1/CIP1 protein was markedly reduced by the expression of PP2Cγ. The degradation of p21WAF1/CIP1 induced by PP2Cγ was mediated in a proteasome‐dependent manner. In addition, the phosphatase activity of PP2Cγ was capable of repressing the level of p21WAF1/CIP1 protein. Phosphorylation of Rb was also reduced in cells expressing PP2Cγ. Taken together, these results indicate that PP2Cγ‐induced S phase accumulation may be associated with proteasome‐directed p21WAF1/CIP1 degradation.
SURNAMES AS ALLELES: SPATIAL DISTRIBUTION OF SURNAMES IN A PROVINCE OF THE ITALIAN ALPS
Authors: CARAVELLO G. U. , TASSO M.
Published: October 2006

The present paper seeks to analyse the spatial distribution of surnames in the province of Belluno in the Italian Alps, and describes the internal mobility of the population taking into consideration one of the most important and ancient roads in the area. The study is based on the analysis of the similarity of the frequencies of some autochthonous surnames depending on their geographical distance apart. The population considered turned out to be basically sedentary. When forced to migrate, the population preferred to go far from their homeland rather than inside the area: this happened probably because the opportunities that the province of Belluno could offer were quite scarce throughout the whole territory, and people hoped to improve their economic situation by going abroad.
Early childhood factors associated with the development of post-traumatic stress disorder: results from a longitudinal birth cohort
Authors: KOENEN KARESTAN C. , MOFFITT TERRIE E. , POULTON RICHIE , MARTIN JUDITH , CASPI AVSHALOM
Published: October 2006

Background. Childhood factors have been associated with increased risk of developing post-traumatic stress disorder (PTSD). Previous studies assessed only a limited number of childhood factors retrospectively. We examined the association between childhood neurodevelopmental, temperamental, behavioral and family environmental characteristics assessed before age 11 years and the development of PTSD up to age 32 years in a birth cohort.

Method. Members of a 1972–73 New Zealand birth cohort (n=1037) who were assessed at ages 26 and 32 years for PTSD as defined by DSM-IV.

Results. We identified two sets of childhood risk factors. The first set of risk factors was associated both with increased risk of trauma exposure and with PTSD assessed at age 26. These included childhood externalizing characteristics and family environmental stressors, specifically maternal distress and loss of a parent. The second set of risk factors affected risk for PTSD only and included low IQ and chronic environmental adversity. The effect of cumulative childhood factors on risk of PTSD at age 26 was substantial; over 58% of cohort members in the highest risk quartile for three developmental factors had PTSD as compared to only 25% of those not at high risk on any factors. Low IQ at age 5, antisocial behavior, and poverty before age 11 continued to predict PTSD related to traumatic events that occurred between the ages of 26 and 32.

Conclusions. Developmental capacities and conditions of early childhood may increase both risk of trauma exposure and the risk that individuals will respond adversely to traumatic exposures. Rather than being solely a response to trauma, PTSD may have developmental origins.
Swearing Voices: An Experimental Investigation of the Suppression of Hostile Hallucinations
Authors: Rassin Eric , van der Heiden Simone
Published: October 2006

Generally, the suppression of unwanted thoughts is found to be ineffective. Moreover, in the longer run, suppression attempts may backfire in that they produce a delayed increase in unwanted thoughts (i.e. a rebound effect). This ineffectiveness and paradox have been observed in various studies, and with various targets, such as neutral thoughts, obsessive intrusions, worries, addictive urges, and phobia-related cognitions. The present study sought to explore the effect of suppression of a different intrusion, namely a hallucination. Healthy undergraduates were exposed to a laboratory procedure that was to provoke hallucinations. Half of the participants were additionally given instructions to suppress the hallucinations. Results indicated that suppression was somewhat effective in the short run, but ineffective in the long run. However, no rebound effect was observed.
Oxygen minimum zone expansion in the eastern tropical North Pacific during deglaciation
Authors: Hendy I. L. , Pedersen T. F.
Published: October 2006

During deglaciation at ∼17 ka the intensity and footprint of the oxygen minimum zone (OMZ) increased in the Eastern Tropical North Pacific (ETNP) before a subsequent expansion on the California Margin. Evidence for the earlier increase is found in trace metal concentrations, lamination preservation and δ15N values from cores located between 540–750 m water depth in the Gulf of Tehuantepec, Southern Mexico. These results differ from similar proxies found even 5°N of the site, where there is evidence for OMZ changes related to rapid climate change in the Northern Hemisphere. Instead, OMZ expansion in the Gulf was contemporaneous with changes in sea ice extent and zonal wind shifts around Antarctica, pointing to Subantarctic Mode Water and Antarctic Intermediate Water as likely sources of oxygen‐depleted water. These observations reinforce the importance of the Southern Ocean as a primary modulator of northern hemisphere ocean climate, as far as 15°N in the ETNP.
Planktivorous auklet Ptychoramphus aleuticus responses to ocean climate, 2005: Unusual atmospheric blocking?
Authors: Sydeman William J. , Bradley Russell W. , Warzybok Pete , Abraham Christine L. , Jahncke Jaime , Hyrenbach K. David , Kousky Vernon , Hipfner J. Mark , Ohman Mark D.
Published: October 2006

In spring‐summer 2005, anomalous atmospheric‐oceanographic coupling caused unprecedented reproductive failures and redistribution of a planktivorous marine bird in both central California (37°N) and southern British Columbia (50°N). At SE Farallon Island, CA, the birds abandoned the breeding colony en masse between 10–20 May, a unique behavioral response; for the first time in 35 years, reproductive success was zero. At Triangle Island, B.C., only 8% of the nesting pairs were successful, the worst year on record. Surveys of birds at sea revealed a peak in relative abundance south of Point Conception (34°N) in summer and fall, suggestive of emigration from the north. Prey (euphausiid crustacean) biomass in the Gulf of the Farallones was reduced, but remained high south of Point Conception. Change in predator and prey may be explained, in part, by unusual atmospheric blocking in the Gulf of Alaska in May, which caused the jet stream to shift southwards resulting in poor upwelling‐favorable winds and anomalously warm SST. This study demonstrates the deleterious consequences of this climate event for a top marine predator in the central‐northern California Current System.
Application of airborne LiDAR to mapping seismogenic faults in forested mountainous terrain, southeastern Alps, Slovenia
Authors: Cunningham Dickson , Grebby Stephen , Tansey Kevin , Gosar Andrej , Kastelic Vanja
Published: October 2006

Results are presented of the first airborne LiDAR survey ever flown in Europe for the purpose of mapping the surface expression of earthquake‐prone faults. Detailed topographic images derived from LiDAR data of the Idrija and Ravne strike‐slip faults in NW Slovenia reveal geomorphological and structural features that shed light on the overall architecture and kinematic history of both fault systems. The 1998 MW = 5.6, and 2004 MW = 5.2 Ravne Fault earthquakes and the historically devastating 1511 M = 6.8 Idrija earthquake indicate that both systems pose a serious seismic hazard in the region. Because both fault systems occur within forested terrain, a tree removal algorithm was applied to the data; the resulting images reveal surface scarps and tectonic landforms in unprecedented detail. Importantly, two sites were discovered to be potentially suitable for fault trenching and palaeo‐seismological analysis. This study highlights the potential contribution of LiDAR surveying in both low‐relief valley terrain and high‐relief mountainous terrain to a regional seismic hazard assessment programme. Geoscientists working in other tectonically active regions of the world where earthquake‐prone faults are obscured by forest cover would also benefit from LiDAR maps that have been processed to remove the canopy return and reveal the forest floor topography.
Global lifetime of elemental mercury against oxidation by atomic bromine in the free troposphere
Authors: Holmes Christopher D. , Jacob Daniel J. , Yang Xin
Published: October 2006

We calculate the global mean atmospheric lifetime of elemental mercury (Hg0) against oxidation by atomic bromine (Br) in the troposphere by combining recent kinetic data for the Hg‐Br system with modeled global concentrations of tropospheric Br. We obtain a lifetime of 0.5–1.7 years based on the range of kinetic data, implying that oxidation of Hg0 by Br is a major, and possibly dominant, global sink for Hg0. Most of the oxidation takes place in the middle and upper troposphere, where Br concentrations are high and where cold temperatures suppress thermal decomposition of the HgBr intermediate. This oxidation mechanism is consistent with mercury observations, including in particular high gaseous Hg(II) concentrations in Antarctic summer. Better free‐tropospheric measurements of bromine radicals and further kinetic study of the Hg‐Br system are essential to more accurately assess the global importance of Br as an oxidant of atmospheric Hg0.
Application of the CACM and MPMPO modules using the CMAQ model for the eastern United States
Authors: Chen Jianjun , Mao Huiting , Talbot Robert W. , Griffin Robert J.
Published: October 2006

The Caltech Atmospheric Chemistry Mechanism (CACM) and the Model to Predict the Multiphase Partitioning of Organics (MPMPO) have been updated with a detailed treatment of the oxidation mechanisms and secondary organic aerosol (SOA) formation potentials of α‐pinene, β‐pinene, and d‐limonene. The updated CACM and MPMPO modules have been incorporated into the Community Multiscale Air Quality (CMAQ) model. The revised CMAQ model was used to simulate air quality over the eastern United States, with a particular focus on New England (NE) for the period 3–4 August 2004, which was part of the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) campaign. On 3 August, 24‐hour‐average organic aerosol (OA) and PM2.5 concentrations were approximately 7.0 μg m−3 and 13.0 μg m−3, respectively, at Thompson Farm (TF), a rural site in southeastern New Hampshire. The model results (e.g., ozone (O3), PM2.5, and individual PM2.5 chemical components) were compared against various observational data sets (e.g., AIRMAP, IMPROVE, SEARCH, and AIRNOW), as well as CMAQ model predictions using the CB‐IV gas‐phase mechanism and the SORGAM SOA module. Both CMAQ model simulations with CACM/MPMPO and with CB‐IV/SORGAM predicted O3, PM2.5, sulfate, and ammonium reasonably well but underestimated elemental and organic carbon aerosol. SOA predictions from CACM/MPMPO and from CB‐IV/SORGAM were very close for the sites where OA concentrations were available on 4 August, though sensitivity of SOA predictions at TF to domain‐wide NOx emissions and temperature variations differed significantly. Additionally, on the basis of the predicted chemical composition of OA from CMAQ with CACM/MPMPO, 24‐hour averages of the ratio of the organic mass to organic carbon were determined to be in the range of 1.1 to 1.9, depending on the relative abundance of SOA and primary organics.
Evaluation of bacteria‐facilitated cadmium transport in gravel columns using the HYDRUS colloid‐facilitated solute transport model
Authors: Pang Liping , Šimůnek Jirka
Published: October 2006

The colloid‐facilitated solute transport model, based on HYDRUS‐1D, was evaluated using the column experimental data of Pang et al. (2005) for cadmium (Cd) transport facilitated by B. subtilis spores or E. coli in saturated coarse alluvial gravels. We simulated Cd transport involving convection, dispersion, kinetic adsorption/desorption to/from the aquifer media and to/from mobile/immobile bacteria, and kinetic attachment/detachment of the bacteria to/from the aquifer media. To reduce the number of parameters to be optimized, we independently estimated Cd sorption/desorption rates to mobile bacteria from a batch study. The model described the collected experimental data reasonably well. Extensive sensitivity analysis to various reaction parameters was carried out to obtain an understanding of the relative importance of individual model parameters on model predictions. Our modeling results suggest that the rates of Cd sorption or desorption differ not only between different bacterial species but also between unattached and deposited bacteria. The results of the sensitivity analysis indicated that the Cd sorption rate to unattached bacteria had a significantly greater impact on the model results than its sorption rate to deposited bacteria. For the experimental system investigated here, model results were most sensitive to parameters describing interactions between Cd‐aquifer media, bacteria‐aquifer media, and Cd‐mobile bacteria, and they were less sensitive to interactions between Cd‐immobile bacteria and desorption rate from mobile bacteria.
Development of an in situ peak intensity measurement method for ultraintense single shot laser-plasma experiments at the Sandia Z petawatt facility
Authors: Link Anthony , Chowdhury Enam A. , Morrison John T. , Ovchinnikov Vladimir M. , Offermann Dustin , Van Woerkom Linn , Freeman Richard R. , Pasley John , Shipton Erik , Beg Farhat , Rambo Patrick , Schwarz Jens , Geissel Matthias , Edens Aaron , Porter John L.
Published: October 2006

Using the physical process of ultraintense field ionization of high charge states of inert gas ions, we have developed a method of peak intensity measurement at the focus of high energy short pulse lasers operating in single shot mode. The technique involves detecting ionization products created from a low pressure gas target at the laser focus via time of flight detector. The observation of high ion charge states collected by the detector yields peak intensity at the focus when compared with the results obtained from well established tunnel ionization models. An initial peak intensity measurement of 5×1016Wcm−2 was obtained for a 1.053μm center wavelength, 0.4J pulse with 1ps pulse duration focused with an f∕5.5 off-axis parabola. Experiments with multijoule level, 500fs laser pulses are on the way.
New reflectometer design for density profile measurements on JET
Authors: Meneses L. , Cupido L. , Ferreira A. A. , Hacquin S. , Manso M. ,   JET EFDA Contributors
Published: October 2006

New transmission lines and antennas recently installed at Join European Torus (JET) under the European Fusion Development Agreement enhancement project millimeter wave access meet the performance requirements of broadband reflectometry for density profile measurements. A fast swept frequency modulation continuous wave [H. Bottollier, Curtet-et al., Rev. Sci. Instrum. 58, 539 (1987); F. Simonet et al., ibid. 56, 664 (1985); A. Silva et al., ibid. 70, 664 (1999); S. Hacquin et al., ibid. 75, 3834 (2004)] using coherent detection of the reflected signal was developed to probe the midplane plasma in the X-mode polarization in the 50–75 GHz frequency range, aiming at measuring the edge density profile in the JET advanced scenarios with an axial magnetic field of 2.4 T. The operating principles of the new system are described and some preliminary results obtained with it are presented. Special attention is given to the capability of operating on bistatic antenna arrangements over long waveguides using a local generated reference, as these will be the conditions proposed for the ITER reflectometers.
Noncovalent interactions between organometallic metallocene complexes and single-walled carbon nanotubes
Authors: Sceats Emma L. , Green Jennifer C.
Published: October 2006

First principles density functional pseudopotential calculations have been used to investigate the nature of interactions between single-walled carbon nanotubes (SWNTs) and intercalated transition metal metallocene complexes, M(η-C5H5)2 (MCp2). Three composites, MCp2-graphene (dt=∞), MCp2@(17,0) (dt=1.33nm), and MCp2@(12,0) (dt=0.94nm) (where M=Fe,Co), have been studied to probe the influence of the nanotube diameter (dt) on the nature and magnitude of the interactions. Theoretical results presented here demonstrate that these MCp2@SWNT composites are stabilized by weak π-stacking and CH⋯π interactions, and in the case of the CoCp2@SWNT composites there is an additional electrostatic contribution as a result of charge transfer from CoCp2 to the nanotube. The extent of charge transfer (MCp2→SWNT) can be rationalized in terms of the electronic structures of the two fragments, or more specifically, the relative positions of the metallocene highest occupied molecular orbital and the conduction band of the nanotube in the electronic structure of the composite.
Ultrafast millimeter-wave frequency-modulated continuous-wave reflectometry for NSTX
Authors: Kubota S. , Peebles W. A. , Nguyen X. V. , Crocker N. A. , Roquemore A. L.
Published: October 2006

The millimeter-wave frequency-modulated continuous-wave (FM-CW) reflectometer on NSTX is a multichannel system providing electron density profile measurements with a frequency coverage of 13–53GHz [corresponding O-mode density range of (0.21–3.5)×1013cm−3]. Recently, this system has been modified to allow ultrafast full-band sweeps for repetition intervals down to 10μs. For this system to function as a fluctuation diagnostic it is crucial to eliminate artifacts in the phase derivative caused by nonlinearities in the frequency sweep; we introduce a simple hardware technique for reducing these artifacts to ≃0.3%. For NSTX, the additional bandwidth (⩽100kHz) greatly enhances the capability of the FM-CW reflectometer as a diagnostic for low frequency magnetohydrodynamics instabilities (e.g., internal kinks, resistive wall modes, neoclassical tearing modes, as well as fast-particle driven fishbones and low frequency toroidal Alfvén eigenmodes).
Structure of liquid water at ambient temperature from ab initio molecular dynamics performed in the complete basis set limit
Authors: Lee Hee-Seung , Tuckerman Mark E.
Published: October 2006

Structural properties of liquid water at ambient temperature were studied using Car-Parrinello [Phys. Rev. Lett. 55, 2471 (1985)] ab initio molecular dynamics (CPAIMD) simulations combined with the Kohn-Sham (KS) density functional theory and the BLYP exchange-correlation functional for the electronic structure. Unlike other recent work on the same subject, where plane-wave (PW) or hybrid Gaussian/plane-wave basis sets were employed, in the present paper, a discrete variable representation (DVR) basis set is used to expand the KS orbitals, so that with the real-space grid adapted in the present work, the properties of liquid water could be obtained very near the complete basis set limit. Structural properties of liquid water were extracted from a 30ps CPAIMD-BLYP/DVR trajectory at 300K. The radial distribution functions (RDFs), spatial distribution functions, and hydrogen bond geometry obtained from the CPAIMD-BLYP/DVR simulation are generally in good agreement with the most up to date experimental measurements. Compared to recent ab initio MD simulations based on PW basis sets, less significant overstructuring was found in the RDFs and the distributions of hydrogen bond angles, suggesting that previous plane-wave and Gaussian basis set calculations have exaggerated the tendency toward overstructuring.
Imaging nanostructures with scanning photoionization microscopy
Authors: Monti Oliver L. A. , Baker Thomas A. , Nesbitt David J.
Published: October 2006

We report detailed studies of local electronic properties in nanostructured thin metallic films using scanning photoionization microscopy. This novel form of microscopy combines the advantages of diffraction-limited optical excitation with the ability to detect both photons and low kinetic energy photoelectrons, permitting sensitive characterization of heterogeneous surfaces under vacuum conditions. Using this technique, correlated measurements of multiphoton photoemission cross section and optical penetration depth are reported for Au films supported on Pt. These results present a first step toward combining confocal fluorescence or Raman microscopy with time-resolved photoelectron imaging spectroscopy in complex metal film environments, which should be ideally suited to investigating local plasmonic effects in nanostructures.
Contact transfer of aligned carbon nanotube arrays onto conducting substrates
Authors: Kumar Ashavani , Pushparaj Victor L. , Kar Swastik , Nalamasu Omkaram , Ajayan Pulickel M. , Baskaran Rajashree
Published: October 2006

The authors demonstrate the fabrication of different architectures of carbon nanotubes on conducting substrates via contact transfer of nanotubes using low temperature solders. Lithographically patterned multiwalled carbon nanotube arrays grown on silica substrates by chemical vapor deposition methods are transferred onto solder coated substrates. Both negative and positive patterns can be obtained by changing the printing parameters. Good wetting and electrical contacts are confirmed by measuring their field emission properties. This method can be used to construct nanotube structures of different shapes and dimensions over large areas on substrates of choice and could be a feasible process to integrate nanotubes into various devices.
Two-dimensional mesoscale simulations of quasielastic reloading and unloading in shock compressed aluminum
Authors: Dwivedi S. K. , Asay J. R. , Gupta Y. M.
Published: October 2006

Two-dimensional (2D) mesoscale simulations of planar shock compression, followed by either reloading or unloading, are presented to examine and understand the quasielastic response observed experimentally in shocked polycrystalline aluminum. The simulations included a realistic representation of the grain ensembles in polycrystalline samples to identify heterogeneous deformation features deemed important to model the continuum measurements. The simulations were carried out using a 2D Lagrangian finite element code (ISP-TROTP) that incorporated elastic-plastic deformation in grain interiors and utilized a contact/cohesive methodology to analyze the response of finite strength grain boundaries. Local heterogeneous response due to mesoscale features was quantified by calculating appropriate material variables along in situ Lagrangian tracer lines and comparing the temporal variation of their mean values with results from 2D continuum simulations. A series of initial calculations ruled out effects due to finite element size and width of the representative volume element used in our simulations. Simulations using a variety of heterogeneities were performed to identify the heterogeneities that were most important for simulating the experimentally observed quasielastic response. These were inclusions, hardened grain boundaries, and microporosity. Mesoscale simulations incorporating these effects demonstrate that the shock-deformed state in polycrystalline aluminum is strongly heterogeneous with considerable variations in lateral stresses. The simulated velocity profiles for a representative reloading and unloading experimental configuration were found to agree well with experimental data, and suggest that hardened grain boundaries are the most likely source of mesoscale heterogeneities in shocked 6061-T6 aluminum. The calculated shear strength and shear stresses were also found to be in good agreement with the reported experimental values.
Temperature and structural changes of water clusters in vacuum due to evaporation
Authors: Caleman Carl , van der Spoel David
Published: October 2006

This paper presents a study on evaporation of pure water clusters. Molecular dynamics simulations between 20ns and 3μs of clusters ranging from 125to4096molecules in vacuum were performed. Three different models (SPC, TIP4P, and TIP5P) were used to simulate water, starting at temperatures of 250, 275, and 300K. We monitored the temperature, the number of hydrogen bonds, the tetrahedral order, the evaporation, the radial distribution functions, and the diffusion coefficients. The three models behave very similarly as far as temperature and evaporation are concerned. Clusters starting at a higher temperature show a higher initial evaporation rate and therefore reach the point where evaporation stop (around 240K) sooner. The radius of the clusters is decreased by 0.16–0.22nm after 0.5μs (larger clusters tend to decrease their radius slightly more), which corresponds to around one evaporated molecule per nm2. The cluster temperature seems to converge towards 215K independent of cluster size, when starting at 275K. We observe only small structural changes, but the clusters modeled by TIP5P show a larger percentage of molecules with low diffusion coefficient as t→∞, than those using the two other water models. TIP4P seems to be more structured and more hydrogen bonds are formed than in the other models as the temperature falls. The cooling rates are in good agreement with experimental results, and evaporation rates agree well with a phenomenological expression based on experimental observations.
Single phase nanocrystalline GaMnN thin films with high Mn content
Authors: Granville S. , Budde F. , Ruck B. J. , Trodahl H. J. , Williams G. V. M. , Bittar A. , Ryan M. , Kennedy J. , Markwitz A. , Metson J. B. , Prince K. E. , Cairney J. M. , Ridgway M. C.
Published: October 2006

Ga 1 − x Mn x N thin films with a Mn content as high as x=0.18 have been grown using ion-assisted deposition and a combination of Rutherford backscattering spectroscopy and nuclear reaction analysis was used to determine their composition. The structure of the films was determined from x-ray diffraction, transmission electron microscopy, and extended x-ray absorption fine structure (EXAFS). The films are comprised of nanocrystals of random stacked GaMnN and there is no evidence of Mn-rich secondary phases or clusters. EXAFS measurements at the Mn and Ga edge are almost identical to those at the Ga edge from Mn-free nanocrystalline GaN films, showing that the Mn occupies the Ga lattice sites, and simulated radial distribution functions of possible Mn-rich impurity phases bear no resemblance to the experimental data. The results indicate that these are the most heavily Mn-doped single phase GaN films studied to date.
Plasticizer effect on the dynamics of polyvinylchloride studied by dielectric spectroscopy and quasielastic neutron scattering
Authors: Zorn Reiner , Monkenbusch Michael , Richter Dieter , Alegría Angel , Colmenero Juan , Farago Bela
Published: October 2006

We have studied the influence of plasticization on the microscopic dynamics of a glass-forming polymer. For this purpose we studied polyvinylchloride (PVC) with and without the commercially used plasticizer dioctylphthalate (DOP). We used dielectric spectroscopy and inelastic neutron scattering employing the neutron spin echo (NSE) technique. For both kinds of spectra the α relaxation could be consistently described by a model involving a distribution of individual relaxations of the Kohlrausch type. In contrast to earlier studies it turned out that an asymmetric distribution is necessary to fit the data at the lower temperatures investigated here. The shape parameters of the distribution (width, skewness) for PVC and PVC/DOP turned out to coincide when the characteristic relaxation times were the same. This means that the plasticizer only induces a remapping of the temperature dependence of the α relaxation. Comparison of NSE spectra S(Q,t)∕S(Q) at different scattering vectors Q gave the result that the slowing down at the structure factor peak Qmax is surprisingly small for PVC while it is in the normal range for PVC/DOP.
Surface core-level shifts of strontium observed in photoemission of barium strontium titanate thin films
Authors: Baniecki J. D. , Ishii M. , Shioga T. , Kurihara K. , Miyahara S.
Published: October 2006

Angle resolved x-ray photoelectron spectroscopy was used to investigate the surface electronic structure of barium strontium titanate (BST) films. In contrast to previous photoemission studies which identified two chemical states associated with only Ba in the near surface region, the authors have resolved core-level features from surface Sr atoms which provide new insight into the surface electronic structure of BST thin films. The surface Sr 3d features are found to lie approximately 1eV higher in binding energy than the bulk derived peaks. The effects of aqueous and annealing surface treatments and the origin of the Sr surface core-level shifts are discussed.
An EDS approach to the inverse problem in the calculus of variations
Authors: Aldridge J. E. , Prince G. E. , Sarlet W. , Thompson G.
Published: October 2006

The inverse problem in the calculus of variations for a given set of second-order ordinary differential equations consists of deciding whether their solutions are those of Euler–Lagrange equations and whether the Lagrangian, if it exists, is unique. This paper discusses the exterior differential systems approach to this problem. In particular, it proposes an algorithmic procedure towards the construction of a certain differential ideal. The emphasis is not so much on obtaining a complete set of integrability conditions for the problem, but rather on producing a minimal set to expedite the differential ideal process.
Refrigerant capacity of FeCrMoCuGaPCB amorphous alloys
Authors: Franco V. , Borrego J. M. , Conde C. F. , Conde A. , Stoica M. , Roth S.
Published: October 2006

The magnetocaloric effect of the FeCrMoCuGaPCB alloy series, suitable for being prepared as bulk amorphous alloys, has been studied. Optimal refrigeration cycles have a cold reservoir close to room temperature. The refrigerant capacity of these alloys is comparable to that of a Mo-containing Finemet-type alloy and is ∼40% bigger than that of other bulk amorphous alloys with comparable working temperatures. Analysis of the field dependence of the magnetic entropy change evidences a power law for all the magnetic regimes.
Cs
Eu
Br
3
: Crystal structure and its role in the photostimulation of CsBr:Eu2+
Authors: Hesse S. , Zimmermann J. , von Seggern H. , Ehrenberg H. , Fuess H. , Fasel C. , Riedel R.
Published: October 2006

Cs Br : Eu 2 + has recently been investigated as a photostimulable x-ray storage phosphor with great potential for application in high-resolution image plates. In a recent paper Hackenschmied et al. [J. Appl. Phys. 93, 5109 (2003)] suggested that segregations of CsEuBr3 or Cs4EuBr6 formed within CsBr:Eu2+ during annealing are responsible for an increase in the photostimulated luminescence (PSL) yield. In this work single crystals of CsEuBr3 were prepared by a one step synthesis and identified by x-ray diffraction (XRD) analysis as single phase perovskites. It was concluded that, after preparation, CsEuBr3 degrades in normal atmosphere into at least two phases, one of which is the orthorhombic structure of Cs2EuBr5∙10H2O. The XRD powder diffraction pattern of this compound is very similar to that of the segregations observed within CsBr:Eu2+ and reported by Hackenschmied et al. However, the increased PSL yield in CsBr:Eu2+ after annealing cannot be due to the segregations, because the trivalent nature of the europium in the segregations renders them PSL inactive.
Probing Feshbach resonances in F+H2(j=1)→HF+H: Dynamical effect of single quantum H2-rotation
Authors: Ren Zefeng , Che Li , Qiu Minghui , Wang Xingan , Dai Dongxu , Harich Steven A. , Wang Xiuyan , Yang Xueming , Xu Chuanxiu , Xie Daiqian , Sun Zhigang , Zhang Dong H.
Published: October 2006

Full quantum state resolved scattering of the F atom reaction with H2(j=0) and H2(j=1) was investigated at the collision energies of 0.19 and 0.56kcal∕mol. Dramatic difference between the dynamics for the F+H2(j=0,1) reactions at both collision energies have been observed. Forward scattering HF(v′=2) products have been observed unambiguously for the F+H2(j=1) reaction at low collision energies, which was attributed to the Feshbach resonances. This study provides a unique case of reaction resonances involving a rotationally excited reagent.
Closed-form expressions for correlated density matrices: Application to dispersive interactions and example of He2
Authors: Ragot Sébastien , Becker Pierre J.
Published: October 2006

Empirically correlated density matrices of N-electron systems are investigated. Closed-form expressions are derived for the one- and two-electron reduced density matrices from a pairwise correlated wave function. Approximate expressions are then proposed which reflect dispersive interactions between closed-shell centrosymmetric subsystems. Said expressions clearly illustrate the consequences of second-order correlation effects on the reduced density matrices. Application is made to a simple example: the He2 system. Reduced density matrices are explicitly calculated, correct to second order in correlation, and compared with approximations of independent electrons and independent electron pairs. The models proposed allow for variational calculations of interaction energies and equilibrium distance as well as a clear interpretation of dispersive effects on electron distributions. Both exchange and second order correlation effects are shown to play a critical role on the quality of the results.
High-frequency electron drift instability in the cross-field configuration of Hall thrusters
Authors: Ducrocq A. , Adam J. C. , Héron A. , Laval G.
Published: October 2006

A systematic study of a high-frequency electron drift instability is presented. It has very large wave numbers corresponding to wavelengths close to the electron gyroradius. The three-dimensional dispersion relation is derived for a model of a crossed electric and magnetic field configuration existing in the Hall thruster. It is shown that the instability develops in packets of oblique unstable modes perpendicular to the magnetic field. The evolution of the instability is also studied for distorted electron distribution functions obtained in particle-in-cell simulations.
Extraction of nitride trap density from stress induced leakage current in silicon-oxide-nitride-oxide-silicon flash memory
Authors: Gu Shaw-Hung , Wang Tahui , Lu Wen-Pin , Ku Yen-Hui Joseph , Lu Chih-Yuan
Published: October 2006

The authors propose a technique to extract a silicon nitride trap density from stress induced leakage current in a polycrystalline silicon-oxide-nitride-oxide-silicon flash memory cell. An analytical model based on the Frenkel-Poole emission is developed to correlate a nitride trap density with stress induced leakage current. The extracted nitride trap density is 7.0×1012cm−2eV−1. They find that nitride trapped charges have a rather uniform distribution in an energy range of measurement (∼0.2eV).
Absorption and fluorescence of single molecules
Authors: Butter J. Y. P. , Hecht B. , Crenshaw B. R. , Weder C.
Published: October 2006

Simultaneous detection of single molecules by absorption and fluorescence is demonstrated using confocal microscopy at cryogenic temperature. Dynamical processes such as blinking and spectral jumping of single emitters are observed in both detection channels. The relative magnitude of fluorescence and absorption varies between molecules. In particular, we observe molecules that do not emit detectable Stokes-shifted fluorescence but show a strong absorption signal. The fact that coherent resonant scattering underlies the absorption process is demonstrated by a correlation between small linewidth and large absorption amplitude.
Transport in carbon nanotube p-i-n diodes
Authors: Bosnick Ken , Gabor Nathan , McEuen Paul
Published: October 2006

Single-walled carbon nanotube diodes are fabricated in a split-gate geometry with electron (n) and hole (p) regions separated by a central region. With the central region gated p or n type the diodes “leak” at low voltages, likely due to tunneling across the smaller depletion region. With the central region intrinsic, nearly ideal diode behavior is observed. Comparison to theory for a one-dimensional diode yields the band gap of the tube and the transmission coefficient through the junction. In reverse bias, the breakdown voltage depends weakly on temperature and nanotube diameter. Comparisons are made to predictions for Zener tunneling and avalanche breakdown.
Low loss contacts for organic semiconductor lasers
Authors: Görrn P. , Rabe T. , Riedl T. , Kowalsky W. , Galbrecht F. , Scherf U.
Published: October 2006

For the realization of electrically driven organic semiconductor lasers low loss contacts for charge injection are essential. The authors show that the addition of thin, highly transparent conducting layers (thickness on the order of 10–20nm) of aluminum doped zinc oxide to a planar waveguide structure formed by a 145nm thick polymer active layer leaves the threshold for the onset of amplified spontaneous emission almost unchanged. This finding paves the way towards electrically driven organic lasers without the need for unrealistically thick organic spacers to keep the waveguide mode away from the contacts.
Submicrosecond pulsed atmospheric glow discharges sustained without dielectric barriers at kilohertz frequencies
Authors: Walsh J. L. , Shi J. J. , Kong M. G.
Published: October 2006

In this letter, the authors report the experimental observation of a large-volume atmospheric glow discharge sustained without dielectric barriers at 1kHz. This barrier-free mode of operation is made possible with a submicrosecond pulsed excitation instead of the usual sinusoidal excitation. Its current-voltage characteristics are shown to be very different from conventional atmospheric dielectric barrier discharges, and its generation mechanism is studied with nanosecond resolved optical emission spectroscopy. The pulsed barrier-free atmospheric plasma is shown to produce very intense atomic oxygen emission line at 777nm, up to one magnitude more intensive than that of a comparable atmospheric dielectric barrier discharge.
Lateral reduction of random percolative networks formed by nanocrystals: Possibilities for a new concept electronic device?
Authors: Pennelli Giovanni
Published: October 2006

Percolative threshold dependence on the reduction of lateral dimension in random site networks is investigated by Monte Carlo simulations. Conductance of a large amount of random grain (nanocrystal) sets has been calculated as a function of the transverse dimension. Effect of a transverse applied field, acting on the grain charging energies, is evaluated and compared with the lateral reduction. Active devices (transistors) based on this concept could be fabricated and employed for multilevel device integration.
Mn-doped 0.71Pb(Mg1∕3Nb2∕3)O3–0.29PbTiO3 pyroelectric crystals for uncooled infrared focal plane arrays applications
Authors: Tang Yanxue , Luo Laihui , Jia Yanmin , Luo Haosu , Zhao Xiangyong , Xu Haiqing , Lin Di , Sun Jinglan , Meng Xiangjian , Zhu Junhao , Es-Souni Mohammed
Published: October 2006

3 mol % Mn -doped 0.71Pb(Mg1∕3Nb2∕3)O3–0.29PbTiO3 single crystals were grown by a modified Bridgman technique. The pyroelectric properties and thermal stability of the crystals were investigated. Mn substitution resulted in an enhanced pyroelectric coefficient and a lower dielectric loss, which led to the improvement of the detectivity figure of merit of doped crystals by about a factor of 4 at 50Hz compared with that of pure crystals. Moreover, the thermal stability was enhanced by Mn substitution. The mechanism of doping effect is explained by the fact that the domain walls are pinned by the dopant dipolar defects, which optimizes the pyroelectric performance of 0.71Pb(Mg1∕3Nb2∕3)O3–0.29PbTiO3 for uncooled infrared focal plane arrays applications.
Correlation between grain size and domain size distributions in ferroelectric media for probe storage applications
Authors: Kim Yunseok , Cho Youngsang , Hong Seungbum , Bühlmann Simon , Park Hongsik , Min Dong-Ki , Kim Seung-Hyun , No Kwangsoo
Published: October 2006

The relationship between grain size and domain size distributions has been studied by piezoelectric force microscopy in ferroelectric films with average grain size of 150nm. As the ratio of domain size to grain size increases, the domain size deviation decreases in a 1∕xn-type function, where n is 1.105. Extrapolation of the model shows that in order to obtain 10% domain size deviation in 1Tbit∕in.2 media, a grain size smaller than 14nm is required. The obtained results imply that either nanograin or single crystalline/epitaxial films provide reliable domain distributions for probe storage applications.
Large electro-optic effect in tensile strained Ge-on-Si films
Authors: Jongthammanurak Samerkhae , Liu Jifeng , Wada Kazumi , Cannon Douglas D. , Danielson David T. , Pan Dong , Kimerling Lionel C. , Michel Jurgen
Published: October 2006

The authors report the first observation of a large, strain-enhanced, electro-optic effect in the weakly absorbing regime for Ge epitaxial films grown directly on Si substrates. The field dependence of absorption in the Ge films was measured from spectral responsivity measurements of Ge-on-Si p-i-n diodes. The experimental data were analyzed using the generalized Franz-Keldysh formalism [H. Shen and F. H. Pollak, Phys. Ref. B 42, 7097 (1990)] and the valence band edge shifts of the light- and heavy-hole energy positions were in response to biaxial stress. With measured Δα∕α∼3 and derived Δn∕F=280pm∕V, the material has significant potential for field-induced phase or electroabsorption modulator devices.
High intensity light propagation in InAs
Authors: Krishnamurthy Srinivasan , Yu Zhi Gang , Guha Shekhar , Gonzalez Leo
Published: October 2006

The authors present their experimental and theoretical results on nonlinear absorption of light in InAs. The nonlinear variation of output intensity as a function of input intensity and time are calculated by solving four coupled rate equations simultaneously. All required quantities, including two-photon absorption, free-carrier absorption, Auger and radiative recombination lifetimes, and intrinsic carrier densities, have been obtained from the underlying band structures. The calculated thickness and energy-dependent output intensities in InAs agree very well with the values measured in their pump-probe experiments.
In situ studies of semiconductor nanowire growth using optical reflectometry
Authors: Clement T. , Ingole S. , Ketharanathan S. , Drucker Jeff , Picraux S. T.
Published: October 2006

The authors report the use of in situ optical reflectometry to determine the incubation time for the onset of growth, mean growth rate, and average length of Si nanowires during chemical vapor deposition vapor-liquid-solid synthesis. Results for the constructive and destructive interferences of 635nm linearly polarized laser light scattering from growing nanowire layers are compared to simulations. This real time optical reflectance approach is shown to quantitatively determine nanowire growth rates as well as reveal a pressure dependence for the time to nucleate nanowire growth.
Physics of ultrathin photovoltaics
Authors: Karpov V. G. , Cooray M. L. C. , Shvydka Diana
Published: October 2006

The authors consider physical properties of ultrathin photovoltaics with thickness (≲1μm) smaller than both the depletion width and diffusion length, applicable to the cases of amorphous, polycrystalline, and nanostructured devices. Three phenomena underlie the unique physics of such systems: (1) lateral screening by conducting electrodes, (2) leakiness due to defect assisted tunneling, and (3) gigantic capacitive energy conducive to shunting breakdown. The authors give numerical estimates and discuss practical implications of these phenomena.
Synchronizabilities of networks: A new index
Authors: Yang Huijie , Zhao Fangcui , Wang Binghong
Published: October 2006

The random matrix theory is used to bridge the network structures and the dynamical processes defined on them. We propose a possible dynamical mechanism for the enhancement effect of network structures on synchronization processes, based upon which a dynamic-based index of the synchronizability is introduced in the present paper.
Molded electromechanical shift register memories
Authors: McClelland Gary M. , Atmaja Bayu
Published: October 2006

Synchronous, nonvolatile, shift register memories storing >1000 data bits can be constructed of a series of bistable mechanical levers, interacting electrostatically and actuated by a single electrode. An entire memory can be formed by a single molding step. A working laboratory-scale model has been constructed, and two submicron designs have been modeled. In one design using conducting levers, momentum briefly carries information. In another design using charged levers, information is passed between primary and secondary portions of a memory cell. Input and output, error propagation, fabrication tolerance, and memory integration are discussed.