bluuebunny/crossref_metadata_2025 huggingface dataset:
Incidence and clinical implications of stent fractures of the Xpert self-expanding nitinol stent in infrainguinal arteries
Authors: Keo  , Kickuth  , Diehm  , Baumgartner  , Dai-Do
Published: February 2009

Background: Different stents in infrainguinal arteries have recently been associated with stent fractures and unfavorable clinical outcome, although data is limited regarding fractures of the Xpert selfexpanding nitinol stent. Thus, purpose of the present investigation was to evaluate its incidence and clinical implications in lower limb arteries. Patients and methods: Fifty-three consecutive patients (53 limbs) with peripheral arterial disease underwent secondary Xpert stent implantation due to suboptimal primary balloon angioplasty (PTA). Median age was 76 years. Stent fractures were evaluated by plain X-ray at median follow-up of 16 months. Stent patency was assessed by duplex ultrasound and sustained clinical improvement was defined as improvement of the ABI of ≥ 0.10 together with improvement of at least one Rutherford class above the baseline finding throughout follow-up. Results: Median length of femoropopliteal and infrapopliteal lesion was 3.0 and 2.3 cm, respectively. Sixtyfive stents were implanted in 43 limbs with femoropopliteal and 10 stents in 10 limbs with infrapopliteal lesion, respectively. Stent fractures occurred in 3 of 43 limbs (7.0%) of patients with femoropopliteal lesion with stent-based fracture rate of 4.6%. All fractured stents showed multiple struts fractures and occurred in the distal and middle superficial femoral artery. No stent fracture was observed in infrapopliteal lesions. The fractured stents were not associated with any clinical deterioration. Sustained clinical improvement was 71.0% and 54.6% for femoropopliteal and infrapopliteal lesions, respectively. Stent patency assessed by duplex was 65.2 and 63.9% for femoropopliteal and infrapopliteal lesions, respectively. Conclusions: Fractures of the Xpert stent were seldom and not associated with unfavorable clinical outcome at midterm follow-up.
Mechanical compression versus haemostatic wound dressing after femoral artery sheath removal: A prospective, randomized study
Authors: Schwarz  , Rastan  , Pochert  , Sixt  , Schwarzwälder  , Bürgelin  , Büttner  , Müller  , Neumann  , Zeller
Published: February 2009

Background: Bleeding complications in the groin are one of the major disadvantages of femoral catheter procedures. The immobilisation of the patient and the compression bandages can jeopardize the patients’ comfort. Aim of the study was a randomized comparison of safety and patient comfort of mechanical pressure followed by pressure bandage overnight using two different haemostatic pads after femoral artery sheath removal. Patients and methods: Nine hundred and eight consecutive patients undergoing diagnostic or therapeutic procedures via a 5 or 6 F femoral sheath were randomly selected either for mechanical compression therapy followed by a compression bandage (302 patients, group 1), or manual compression with application of a calcium ion releasing device (compression bandage only after application of > 5000 IU of heparin; 303 patients; group 2), or manual compression with a thrombin covered PAD without compression bandage (303 patients, group 3). Results: No major hemorrhage or death occurred. A false aneurysm was found in 10 (3.3%), 13 (4.3%), and 10 patients (3.3%) of group 1, 2, and 3, respectively (p = 0.38). Three patients (0.3%) needed surgical treatment. 69 (22.7%) patients in thrombin covered PAD-group required a compression bandage overnight due to seeping hemorrhage after 15 minutes. In the calcium ion releasing PAD-group 124 (40.9%) patients had continued bandaging, 46 (15.2%) due to seeping hemorrhage after 15 min, and 78 (25.7%) due to application of heparin > 5000 IU. Conclusions: The use of mechanical compression combined with a pressure bandage, and the use of haemostatic wound dressing assisted sheath removal technique offer a comparable level of safety. Patient comfort is improved with the usage of PAD devices, however the technical failure rate of the PAD should be taken into account.
Human iliac vein replacement with a tissue-engineered graft
Authors: Teebken  , Puschmann  , Rohde  , Burgwitz  , Winkler  , Pichlmaier  , Weidemann  , Haverich
Published: February 2009

The modification of a previously described technique to generate venous conduits in a lamb model from a decellularised matrix and autologous cells and its application to human tissue is described. A 49-year-old woman underwent surgery for a large malignant pelvic tumour (carcinoma of unknown primary) involving the right iliac artery and vein. The right iliac artery was reconstructed with a cryopreserved human arterial allograft. For iliac vein reconstruction a tissue-engineered neo-vein was developed utilising a decellularised cryopreserved vein allograft that was reseeded in a bioreactor with autologous endothelial cells derived from the recipient’s great saphenous vein. Both interposition grafts were patent initially, after 3, 6, 12, and 24 months, but the tissue-engineered neo-vein had become obstructed due to evolving disease four month postoperatively. Tissue engineered neo-veins may be a therapeutic option in selected cases with symptomatic vein stenosis or obstruction not curable with interventional methods or standard prosthetic replacement.
Emergency endovascular treatment of a ruptured internal iliac artery aneurysm long after abdominal aortic aneurysm surgical repair
Authors: Borioni  , De Luca  , Maspes  , Sciuto  , Garofalo
Published: February 2009

The purpose of this report is to describe the endovascular exclusion of an internal iliac artery (IIA) aneurysm in emergency setting, long after abdominal aortic aneurysm surgical repair. An 85-year-old male presented with a contained rupture of a huge IIA aneurysm, ten years after aortoiliac bifurcated grafting. Because of poor clinical conditions an emergency endovascular treatment was planned. A stent-graft was positioned from the proximal right branch of the bifurcated surgical prosthesis to the distal external iliac artery, covering the hypogastric aneurysm neck. One month after the procedure, CT scan demonstrated the complete exclusion of the aneurysm. Endovascular treatment of IIA aneurysms is an excellent option to reduce perioperative morbidity and mortality in high risk patients, particularly in an emergency setting.
Turbulent exchange coefficients for the ice/ocean interface in case of rapid melting
Authors: Sirevaag Anders
Published: February 2009

In the marginal ice zones, drifting sea ice encounters large ocean heat fluxes and melting rates. However, as found from modelling studies and observations of ice melting, double diffusive effects at the ice/ocean interface limit the melting rates. In this paper, direct measurements of turbulent heat and salt fluxes from the marginal ice zone during rapid melting are presented. The strength of double diffusion is found to be significant and close to the range suggested from other studies. Calculated melting rates when double diffusive effects are present are compared to melting rates calculated from a traditional bulk parameterization of ocean heat flux for a range of temperatures and friction velocities often encountered within the marginal ice zones. This comparison shows that by ignoring double diffusive effects, melting rates are overestimated by several cm per day, which may have a significant impact on a predicted future ice cover.
Combining remote sensing data and an inundation model to map tidal mudflat regions and improve flood predictions: A proof of concept demonstration in Cook Inlet, Alaska
Authors: Ezer Tal , Liu Hua
Published: February 2009

Accurate flood predictions require high resolution inundation numerical models and detailed coastal and land topography data. However, such data are not always available. A new method to obtain topographic information of flood zones from remote sensing data is demonstrated here for Cook Inlet, Alaska, where tidal range reaches 8–10 m. The moving shoreline is detected from analysis of water coverage in satellite images taken at different tidal stages, and then the shoreline data from different times are combined with water level data from observations and models to produce new topographic maps of previously unobserved mudflats. The remote sensing‐based analysis provides for the first time a way to evaluate the flood predictions of the inundation model of the inlet. The new flood‐zone topography obtained from the remote sensing data will help to construct a more accurate inundation model in the future.
Secondary organic aerosol formation in urban air: Temporal variations and possible contributions from unidentified hydrocarbons
Authors: Matsui H. , Koike M. , Takegawa N. , Kondo Y. , Griffin R. J. , Miyazaki Y. , Yokouchi Y. , Ohara T.
Published: February 2009

Quantitative evaluation of the performance of one of the most advanced mechanistic secondary organic aerosol (SOA) modules/models, the Model of Aerosol Dynamics, Reaction, Ionization, and Dissolution 2 (MADRID2) in the three‐dimensional Models‐3/Community Multiscale Air Quality (CMAQ), in urban air is made. Model calculations are compared for the Tokyo, Japan, metropolitan area with measurements made using an Aerodyne quadrupole aerosol mass spectrometer (Q‐AMS) at an urban site for 9 days in July and August 2003. In general, model calculations reproduced absolute values and temporal variations of meteorological parameters, C2–C8 volatile organic compounds (VOCs), NOx (NO + NO2), inorganic aerosols, and O3 concentrations reasonably well at this site. However, model‐calculated SOA concentrations are a factor of 5 smaller than observed oxygenated organic aerosol (OOA) concentrations, and calculated total organic aerosol (OA = SOA + primary organic aerosol) concentrations are smaller by a factor of 2, indicating missing processes or sources in the current organic aerosol model calculations. On the other hand, observed features of diurnal and day‐to‐day variations of OOA were captured by our model calculations. Because of the large quantity of unidentified total nonmethane VOCs (NMVOCs) in urban air, a possible contribution of SOA formation from high‐molecular‐weight VOCs is examined through simple sensitivity studies, in which emissions are increased to account for unidentified NMVOCs. It is found that they are potentially one of the missing SOA sources, demonstrating the importance of reliable measurements of high‐molecular‐weight VOCs and total NMVOCs. Relationships between SOA and O3, including regional (∼150 × 150 km2) enhancements around the Tokyo metropolitan area, are also discussed.
Interpreting discrepancies between discharge and precipitation in high‐altitude area of Chile's Norte Chico region (26–32°S)
Authors: Favier Vincent , Falvey Mark , Rabatel Antoine , Praderio Estelle , López David
Published: February 2009

The water resources of high‐altitude areas of Chile's semiarid Norte Chico region (26–32°S) are studied using surface hydrological observations (from 59 rain gauges and 38 hydrological stations), remotely sensed data, and output from atmospheric prediction models. At high elevations, the observed discharge is very high in comparison with precipitation. Runoff coefficients exceed 100% in many of the highest watersheds. A glacier inventory performed with aerial photographs and ASTER images was combined with information from past studies, suggesting that glacier retreat could contribute between 5% and 10% of the discharge at 3000 m in the most glacierized catchment of the region. Snow extent was studied using MOD10A2 data. Results show that snow is present during 4 months at above 3000 m, suggesting that snow processes are crucial. The mean annual sublimation (∼80 mm a−1 at 4000 m) was estimated from the regional circulation model (WRF) and data from past studies. Finally, spatial distribution of precipitation was derived from available surface data and the global forecast system (GFS) atmospheric prediction model. Results suggest that annual precipitation is three to five times higher near the peak of the Andes than in the lowlands to the west. The GFS model suggests that daily precipitation rates in the mountains are similar to those in the coastal region, but precipitation events are more frequent and tend to last longer. Underestimation of summer precipitation may also explain part of the excess in discharge. Simple calculations show that consideration of GFS precipitation distributions, sublimation, and glacier melt leads to a better hydrological balance.
Culture-independent identification of gut bacteria correlated with the onset of diabetes in a rat model
Authors: Roesch Luiz F W , Lorca Graciela L , Casella George , Giongo Adriana , Naranjo Andres , Pionzio Arianna M , Li Nan , Mai Volker , Wasserfall Clive H , Schatz Desmond , Atkinson Mark A , Neu Josef , Triplett Eric W
Published: February 2009

Bacteria associated with the onset of type 1 diabetes in a rat model system were identified. In two experiments, stool samples were collected at three time points after birth from bio-breeding diabetes-prone (BB-DP) and bio-breeding diabetes-resistant (BB-DR) rats. DNA was isolated from these samples and the 16S rRNA gene was amplified using universal primer sets. In the first experiment, bands specific to BB-DP and BB-DR genotypes were identified by automated ribosomal intergenic spacer analysis at the time of diabetes onset in BB-DP. Lactobacillus and Bacteroides strains were identified in the BB-DR- and BB-DP-specific bands, respectively. Sanger sequencing showed that the BB-DP and BB-DR bacterial communities differed significantly but too few reads were available to identify significant differences at the genus or species levels. A second experiment confirmed these results using higher throughput pyrosequencing and quantitative PCR of 16S rRNA with more rats per genotype. An average of 4541 and 3381 16S rRNA bacterial reads were obtained from each of the 10 BB-DR and 10 BB-DP samples collected at time of diabetes onset. Nine genera were more abundant in BB-DP whereas another nine genera were more abundant in BB-DR. Thirteen and eleven species were more abundant in BB-DP and BB-DR, respectively. An average of 23% and 10% of all reads could be classified at the genus and species levels, respectively. Quantitative PCR verified the higher abundance of Lactobacillus and Bifidobacterium in the BB-DR samples. Whether these changes are caused by diabetes or are involved in the development of the disease is unknown.
Diversity of iron oxidizers in wetland soils revealed by novel 16S rRNA primers targeting Gallionella-related bacteria
Authors: Wang Juanjuan , Muyzer Gerard , Bodelier Paul L E , Laanbroek Hendrikus J
Published: February 2009

Neutrophilic iron-oxidizing bacteria (FeOB) are important catalysts of iron cycling in wetland environments. However, little is known about their diversity and distribution in various environments. The aim of this study was to develop a PCR-DGGE assay enabling the detection of neutrophilic iron oxidizers in wetland habitats. Gradient tubes were used to enrich FeOB. From these enrichments, a clone library was established on the basis of the almost complete 16S rRNA gene using the universal bacterial primers 27f and 1492r. This clone library consisted of mainly α- and β-Proteobacteria, among which two major clusters were closely related to Gallionella spp. Specific probes and primers were developed on the basis of this 16S rRNA gene clone library. The newly designed Gallionella-specific 16S rRNA gene primer set 122f/998r was applied to community DNA obtained from three contrasting wetland environments, followed by Denaturing Gradient Gel Electrophoresis (DGGE) analysis. A second 16S rRNA gene clone library was constructed using the PCR products from one of our sampling sites amplified with the newly developed primer set 122f/998r. The cloned 16S rRNA gene sequences all represented novel culturable iron oxidizers most closely related to Gallionella sp. On the basis of their nucleotide sequences, four groups could be identified that were comparable to the DGGE banding pattern obtained before with the same PCR products as used for the second clone library. Using these Gallionella-specific 16S rRNA gene-based primers, in combination with DGGE, first insights into the diversity and distribution of these bacteria in wetland soils were obtained.
In situ transcriptomic analysis of the globally important keystone N2-fixing taxon Crocosphaera watsonii
Authors: Hewson Ian , Poretsky Rachel S , Beinart Roxanne A , White Angelicque E , Shi Tuo , Bench Shellie R , Moisander Pia H , Paerl Ryan W , Tripp H James , Montoya Joseph P , Moran Mary Ann , Zehr Jonathan P
Published: February 2009

The diazotrophic cyanobacterium Crocosphaera watsonii supplies fixed nitrogen (N) to N-depleted surface waters of the tropical oceans, but the factors that determine its distribution and contribution to global N2 fixation are not well constrained for natural populations. Despite the heterogeneity of the marine environment, the genome of C. watsonii is highly conserved in nucleotide sequence in contrast to sympatric planktonic cyanobacteria. We applied a whole assemblage shotgun transcript sequencing approach to samples collected from a bloom of C. watsonii observed in the South Pacific to understand the genomic mechanisms that may lead to high population densities. We obtained 999 C. watsonii transcript reads from two metatranscriptomes prepared from mixed assemblage RNA collected in the day and at night. The C. watsonii population had unexpectedly high transcription of hypothetical protein genes (31% of protein-encoding genes) and transposases (12%). Furthermore, genes were expressed that are necessary for living in the oligotrophic ocean, including the nitrogenase cluster and the iron-stress-induced protein A (isiA) that functions to protect photosystem I from high-light-induced damage. C. watsonii transcripts retrieved from metatranscriptomes at other locations in the southwest Pacific Ocean, station ALOHA and the equatorial Atlantic Ocean were similar in composition to those recovered in the enriched population. Quantitative PCR and quantitative reverse transcriptase PCR were used to confirm the high expression of these genes within the bloom, but transcription patterns varied at shallower and deeper horizons. These data represent the first transcript study of a rare individual microorganism in situ and provide insight into the mechanisms of genome diversification and the ecophysiology of natural populations of keystone organisms that are important in global nitrogen cycling.
A behavioral model of axisymmetrically configured magnetorheological fluid using Lekner summation
Authors: Jang Kyung-In , Seok Jongwon , Min Byung-Kwon , Lee Sang Jo
Published: February 2009

This study presents a new behavioral model for the magnetorheological (MR) fluid used in cylindrical rectilinear dampers. The model predicts variations in the magnetic energy density, shear stress, and viscoelastic behavior against an imposed strain along the axial direction under an axisymmetric magnetic field. Using the Lekner summation method, slow convergent magnetic interaction energy functions are transformed into rapidly convergent ones. The Maxwell constitutive model is coupled to the static model to take into account the viscoelastic behavior of the MR fluid.
Nonequilibrium quantum dynamics in ferromagnetic nanoparticles: Conditions for Bose–Einstein condensation
Authors: Johnson P. R. , Della Torre E. , Bennett L. H. , Watson R. E.
Published: February 2009

Nanoparticles provide a system where the nonequilibrium dynamics of magnons can be engineered, varied, and studied over many orders of magnitude. This paper describes the conditions for quasiequilibrium phases with either more or less magnons than predicted by Bloch’s law, including, if certain conditions hold, a Bose–Einstein condensate phase whose existence should strongly depend on system size.
Role of spin-orbit coupling in spin-spiral structures in Fe monolayer on W(110): A first-principles noncollinear magnetism study
Authors: Nakamura Kohji , Akiyama Toru , Ito Tomonori , Freeman A. J.
Published: February 2009

The stability of spin-spiral structures in an Fe monolayer on a W(110) substrate is investigated by means of the first-principles film full-potential linearized augmented plane-wave method, and the role of spin-orbit coupling (SOC) on the spin-spiral structures is determined. Our calculations demonstrate that without SOC, the spin-spiral structures are energetically favored over the ferromagnetic (FM) state, but that when the strong SOC at the Fe/W(110) interface is introduced, the formation of the spin-spiral structures is suppressed. Thus, the ground state of the system appears to be the FM state—as observed in experiments.
Mössbauer studies for spinel-type ACr2S4 (A=Cd and Fe)
Authors: Son Bae Soon , Lee Bo Wha , Kim Chul Sung
Published: February 2009

Magnetic ordering of Cd1−xFexCr2S4 (0.0≤x≤1.0) with Cd replaced by Fe on tetrahedral (A) site is studied by Mössbauer spectroscopy and vibrating sample magnetometer as a function of temperature and external magnetic field. We find that all Fe ion states are ferrous ions with a tetrahedral coordination from isomer shift values at room temperature. The Curie temperatures (TC) for the Cd1−xFexCr2S4 (0.0≤x≤1.0) increase with Cd replaced by Fe at tetrahedral site. The magnetic behavior can be explained with ion configuration and spin interaction between either tetrahedral-octahedral sites or intra-atoms. The magnetic structure changes from ferromagnetic to ferrimagnetic with increasing Fe ions on tetrahedral site, which is caused by the magnetic order becoming antiparallel with increasing Fe ions. The Mössbauer spectrum at 4.2 K is asymmetric for all the samples. It can be explained by ferrous ion of Jahn–Teller ion induced distortion. Furthermore, the contribution of angular moment of Fe2+ enhances the asymmetric line of Mössbauer spectra at 4.2 K.
Magnetic and optical properties of rf-sputtered zinc ferrite thin films
Authors: Sultan M. , Singh R.
Published: February 2009

Zn-ferrite (ZnFe2O4) thin films were deposited by rf-magnetron sputtering on glass substrates at room temperature (RT) in pure oxygen environment. The as-deposited films were investigated by x-ray diffraction to show that single phase nanocrystalline spinel patterns belong to zinc ferrite. The magnetization shows ferrimagnetic behavior, and it strongly depends on oxygen working pressure. The maximum magnetization of 230 emu/cm3 (42 emu/g) at RT is obtained for the film deposited at 27 mTorr of oxygen pressure. The oxygen vacancy concentration and random distribution of Zn2+ and Fe3+ on both tetrahedral and octahedral sites are the possible reasons of high magnetization due to rapid cooling of sputtered vapors to form solid state film. The optical properties of the films show 85% transparency above 550 nm wavelength. The estimated values of direct and indirect band gaps are 2.5 and 1.9 eV, respectively.
Schloegl’s second model for autocatalysis with particle diffusion: Lattice-gas realization exhibiting generic two-phase coexistence
Authors: Guo Xiaofang , Liu Da-Jiang , Evans J. W.
Published: February 2009

We analyze a discontinuous nonequilibrium phase transition between an active (or reactive) state and a poisoned (or extinguished) state occurring in a stochastic lattice-gas realization of Schloegl’s second model for autocatalysis. This realization, also known as the quadratic contact process, involves spontaneous annihilation, autocatalytic creation, and diffusion of particles on a square lattice, where creation at empty sites requires a suitable nearby pair of particles. The poisoned state exists for all annihilation rates p>0 and is an absorbing particle-free “vacuum” state. The populated active steady state exists only for p below a critical value, pe. If pf denotes the critical value below which a finite population can survive, then we show that pf<pe. This strict inequality contrasts a postulate of Durrett, and is a direct consequence of the occurrence of coexisting stable active and poisoned states for a finite range pf≤p≤pe (which shrinks with increasing diffusivity). This so-called generic two-phase coexistence markedly contrasts behavior in thermodynamic systems. However, one still finds metastability and nucleation phenomena similar to those in discontinuous equilibrium transitions.
Inelastic x-ray scattering from high pressure fluids in a diamond anvil cell
Authors: Gorelli F. A. , Santoro M. , Scopigno T. , Krisch M. , Bryk T. , Ruocco G. , Ballerini R.
Published: February 2009

We present an experimental setup to study terahertz dynamics in fluids under high pressure, employing inelastic x-ray scattering and diamond anvil cell techniques. The use of a carefully designed vacuum chamber and the minimization and control of sources of parasitic scattering allowed circumventing previous limitations due to important empty cell contributions to the scattering signal. The successful implementation of our setup is demonstrated in the case of supercritical fluid argon, for which a full viscoelastic analysis yields the dispersion relation of sound waves, the generalized heat capacity ratio, and longitudinal viscosity. Our results are in excellent agreement with available experimental observables and molecular dynamics simulations.
Controlling internal barrier in low loss BaTiO3 supercapacitors
Authors: Chung U-C. , Elissalde C. , Mornet S. , Maglione M. , Estournès C.
Published: February 2009

Supercapacitor behavior has been reported in a number of oxides including reduced BaTiO3 ferroelectric ceramics. These so-called giant properties are however not easily controlled. We show here that the continuous coating of individual BaTiO3 grains by a silica shell in combination with spark plasma sintering is a way to process bulk composites having supercapacitor features with low dielectric losses and temperature stability. The silica shell acts both as an oxidation barrier during the processing and as a dielectric barrier in the final composite.
Calculation of semiconductor band gaps with the M06-L density functional
Authors: Zhao Yan , Truhlar Donald G.
Published: February 2009

The performance of the M06-L density functional has been tested for band gaps in seven semiconductors plus diamond and MgO. Comparison with the local spin density approximation (LSDA), Becke-Lee-Yang-Parr (BLYP), Perdew-Burke-Eernzerhof (PBE), Tao-Perdew-Staroverov-Scuseria (TPSS), and Heyd-Scuseria-Ernzerhof (HSE) functionals shows that M06-L has improved performance for calculating band gaps as compared to other local functionals, but it is less accurate than the screened hybrid HSE functional for band gaps.
New more accurate calculations of the ground state potential energy surface of H3+
Authors: Pavanello Michele , Tung Wei-Cheng , Leonarski Filip , Adamowicz Ludwik
Published: February 2009

Explicitly correlated Gaussian functions with floating centers have been employed to recalculate the ground state potential energy surface (PES) of the H3+ ion with much higher accuracy than it was done before. The nonlinear parameters of the Gaussians (i.e., the exponents and the centers) have been variationally optimized with a procedure employing the analytical gradient of the energy with respect to these parameters. The basis sets for calculating new PES points were guessed from the points already calculated. This allowed us to considerably speed up the calculations and achieve very high accuracy of the results.
Luminescence behavior of Ce3+ and Dy3+ codoped oxyfluoride glasses and glass ceramics containing LaF3 nanocrystals
Authors: Luo Qun , Qiao Xvsheng , Fan Xianping , Yang Hui , Zhang Xianghua , Cui Shou , Wang Ling , Wang Gang
Published: February 2009

The Ce3+ and Dy3+ codoped oxyfluoride glasses and glass ceramics containing LaF3 nanocrystals have been prepared in the reducing atmosphere. The emission intensity and Commission International de I'Eclairage (CIE) chromaticity coordinates of the Ce3+ and Dy3+ codoped glasses significantly changed with concentration ratio of Ce3+ to Dy3+. The emission intensity of both Ce3+ ions and Dy3+ ions in the 3.0% Ce3+ and 3.0% Dy3+ codoped glass ceramics increased significantly in comparison with that in the glass. The glasses and glass ceramics could emit bright white light by adjusting the concentration ratio of Ce3+ to Dy3+.
Noninvasive probing of the human body with electromagnetic pulses: Modeling of the signal path
Authors: Thiel F. , Seifert F.
Published: February 2009

The biomedical applications of ultrawideband (UWB) radar promise a very important means to remotely monitor physiological signatures such as myocardial deformation and respiration. Accurate numerical and analytical techniques to predict the propagation of UWB signals in biological tissue are of great interests to researchers as an aid in developing signal processing algorithms. We propose applying an analytic transmit/receive signal path model considering the antennas, the human body, and the signal processing part of the UWB unit. Furthermore, the frequency dependency of the different biological tissues’ dielectric properties and the individual continuous motion of intrathoracic tissue layers are incorporated.
Quantitative analysis of plasma ablation using inverse wire array Z pinches
Authors: Harvey-Thompson A. J. , Lebedev S. V. , Bland S. N. , Chittenden J. P. , Hall G. N. , Marocchino A. , Suzuki-Vidal F. , Bott S. C. , Palmer J. B. A. , Ning C.
Published: February 2009

An inverse (exploding) wire array configuration, in which the wires form a cylinder around a current carrying electrode on axis, was used to study the ablation phase of the wires. This configuration allows the parameters of the plasma from individual wires of the array to be measured as the ablated plasma streams propagate in the outward radial direction. The density distribution and the evolution of the natural mode of modulation of the ablation flow was measured with interferometry and soft x-ray imaging. Measurements of the voltage across the array, which in this configuration is determined by the private magnetic flux around the individual wires, allow information on the localization of the current to be obtained. Results are compared to three-dimensional magnetohydrodynamics simulations.
Effects of symmetry, shape, and structural parameters of two-dimensional SiNx photonic crystal on the extracted light from Y2O3:Eu3+ film
Authors: Oh Jeong Rok , Lee Young Kwang , Park Hoo Keun , Do Young Rag
Published: February 2009

This study examined the effects of the triangular- and square-lattice symmetries as well as the nanorod and airhole shapes of two-dimensional (2D) SiNx photonic crystal layers (PCLs) on the light extraction efficiency of thin-film phosphors (TFPs) in an attempt to improve the light extraction efficiency from the phosphor side of an Y2O3:Eu3+ thin film. Triangular-lattice and square-lattice 2D SiNx nanorods/airholes were fabricated as PCLs on sol-gel derived Y2O3:Eu3+ TFPs using different combinations of the following processes: nanosphere lithography or laser interfering lithography, mask fabrication, and reactive ion etching. The integrated light efficiency of the triangular lattice was approximately 1.33 and 1.64 times as high as that of the square lattice for the nanorods and airholes. The greatest improvement in the phosphor-side extraction efficiency of the Y2O3:Eu3+ TFPs was obtained by adding triangular-lattice 2D SiNx airhole PCL arrays. The angular distribution of the light emitted from the various types of 2D SiNx PCL-coated Y2O3:Eu3+ TFPs was also investigated to better understand the effects of the symmetry and shape of the 2D PCLs on the viewing angle of the light emitted from the Y2O3:Eu3+ thin films. Moreover, the effects of structural parameters, including the dielectric-areal fill factor and lattice parameter (below cutoff size and above 1.0 μm size, as well as the optimum size of triangular lattice) of the 2D SiNx PC arrays, on the extraction efficiency of the Y2O3:Eu3+ TFPs were investigated to improve the scattering capability of the leaky modes as a function of the structural parameters. This enhanced extraction efficiency was attributed to the scattering of the forward emission excited directly by inward UV and the scattering of re-excited forward emission by backscattered UV through the leaky and/or Bragg scattering produced by the 2D periodic array.
Properties of GaAs(001) surfaces thermally annealed in vacuum
Authors: Morota Hiroaki , Adachi Sadao
Published: February 2009

Thermal degradation of GaAs(001) surfaces has been studied using spectroscopic ellipsometry (SE), optical microscopy, ex situ atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) techniques. The SE data suggest that thermal annealing causes no or little influence on the surface native oxide layer at temperatures T≤500 °C. Microscopic roughening starts to occur on GaAs surface at T>500 °C, giving maximum AFM roughness (rms∼14 nm) at 540 °C, and then tends to smoothened at T>540 °C (rms∼2.5 nm at 580 °C). Macroscopically roughened surfaces are observed at T>500 °C, becoming more pronounced at higher annealing temperature. The Ga droplets are also observed at T≥600 °C that lead to catastrophically damaged surfaces and make SE measurement impossible. The XPS data indicate thinning of the native GaAs oxide in the limited temperature range 450<T<580 °C; however, annealing at T≥580 °C leads to coverage with thermal oxides (Ga2O and As2O3). The naturally grown GaAs oxide is also found to act as a good passivation film against annealing-induced PL degradation.
Temperature dependent electrical transport in p-ZnO/n-Si heterojunction formed by pulsed laser deposition
Authors: Majumdar S. , Banerji P.
Published: February 2009

ZnO film, with urea as nitrogen source to dope its p-type, is deposited by pulsed laser on n-type (100) Si substrate to fabricate p-ZnO/n-Si heterojunctions. The current-voltage (I-V) characteristics of the heterojunction have been studied in the temperature range 140–300 K. The turn on voltage decreased with increasing temperature while the breakdown voltage is increased slightly. The forward current is greatly increased with increasing temperature, while the reverse current is increased nominally. Both the decrease in barrier height and the increase in ideality factor with decrease in temperature are indicative of deviation from the pure thermionic emission-diffusion mechanism. The ln(I0) versus 1/kT plot exhibits the linear portion corresponding to an activation energy of 0.07 eV. Temperature-dependent forward current measurements suggest that trap-assisted multistep tunneling is the dominant carrier transport mechanism in this heterojunction. C-V analysis indicates an abrupt interface and band bending of 0.96 V in silicon. Heterojunction band diagram for p-ZnO/n-Si is proposed. The hysteresis in the high frequency capacitance voltage (C-V) curve indicates the presence of trapped charges at the interface.
Nonpolar m-plane InGaN multiple quantum well laser diodes with a lasing wavelength of 499.8 nm
Authors: Okamoto Kuniyoshi , Kashiwagi Junich , Tanaka Taketoshi , Kubota Masashi
Published: February 2009

We demonstrated nonpolar m-plane InGaN multiple quantum well laser diodes (LDs) under continuous-wave (cw) operation with a lasing wavelength of 499.8 nm, which is the longest reported for GaN-based LDs. A maximum optical output power of 15 mW was achieved, with the threshold current and the corresponding threshold current density (Jth) of 46 mA and 3.1 kA/cm2, respectively. The correlation between lasing wavelength shift and electrical input power (Pin) under cw operation was investigated using LDs of which reflectivity of front facet were varied from 70% to 97%. The lasing wavelength increased with increasing Pin with a slope of 4.56 and 4.34 nm/W for 70% and 97% mirror, respectively. The result suggested that the redshift due to self-heating is more predominant than the blueshift due to band filling above Jth even at near green region for nonpolar GaN-based LDs and reduction in Pin is indispensable to improve wavelength stabilization.
Light-induced domain reversal in doped lithium niobate crystals
Authors: Wang Wenjie , Kong Yongfa , Liu Hongde , Hu Qian , Liu Shiguo , Chen Shaolin , Xu Jingjun
Published: February 2009

Light-induced domain reversals of Mg-doped, Zr-doped, and nominally pure LiNbO3 crystals were investigated with focused 514.5 nm laser beams. It was found the light-reduced values of electric field for domain reversal are almost the same, about 3 kV/mm. Inverted domains always first nucleate on the −c surface within the illuminated region but appear at the edge of the spot on the +c surface. The light-induced inverted domains are hard to be reversed by application of a reverse electric field or by heating to temperatures as high as 600 °C. According to these experimental results, we present a qualitative model on the light-induced domain reversal process in LiNbO3.
Propagation of an atmospheric pressure plasma plume
Authors: Lu X. , Xiong Q. , Xiong Z. , Hu J. , Zhou F. , Gong W. , Xian Y. , Zou C. , Tang Z. , Jiang Z. , Pan Y.
Published: February 2009

The “plasma bullet” behavior of atmospheric pressure plasma plumes has recently attracted significant interest. In this paper, a specially designed plasma jet device is used to study this phenomenon. It is found that a helium primary plasma can propagate through the wall of a dielectric tube and keep propagating inside the dielectric tube (secondary plasma). High-speed photographs show that the primary plasma disappears before the secondary plasma starts to propagate. Both plumes propagate at a hypersonic speed. Detailed studies on the dynamics of the plasma plumes show that the local electric field induced by the charges on the surface of the dielectric tube plays an important role in the ignition of the secondary plasma. This indicates that the propagation of the plasma plumes may be attributed to the local electric field induced by the charges in the bulletlike plasma volume.
The influence of annealing conditions on the growth and structure of embedded Pt nanocrystals
Authors: Giulian R. , Araujo L. L. , Kluth P. , Sprouster D. J. , Schnohr C. S. , Johannessen B. , Foran G. J. , Ridgway M. C.
Published: February 2009

The growth and structure of Pt nanocrystals (NCs) formed by ion implantation in a-SiO2 has been investigated as a function of the annealing conditions. Transmission electron microscopy and small-angle x-ray scattering measurements demonstrate that the annealing ambient has a significant influence on NC size. Samples annealed in either Ar, O2, or forming gas (95% N2: 5% H2) at temperatures ranging from 500 °C–1300 °C form spherical NCs with mean diameters ranging from 1–14 nm. For a given temperature, annealing in Ar yields the smallest NCs. O2 and forming gas ambients produce NCs of comparable size though the latter induces H chemisorption at 1100 °C and above, as verified with x-ray absorption spectroscopy. This H intake is accompanied by a bond-length expansion and increased structural disorder in NCs of diameter >3 nm.
Modeling of degradation behavior of InGaP/GaAs/Ge triple-junction space solar cell exposed to charged particles
Authors: Sato Shin-ichiro , Ohshima Takeshi , Imaizumi Mitsuru
Published: February 2009

Degradation modeling of InGaP/GaAs/Ge triple-junction (3J) space solar cells, which are exposed to charged particles (protons and electrons), is introduced using a one-dimensional optical device simulator: PC1D. The proposed method can reproduce the electrical degradation of 3J solar cells from fitting the external quantum efficiencies for subcells. In this modeling, carrier removal rate of base layer (RC) and damage coefficient of minority carrier diffusion length (KL) in each subcell are considered as radiation degradation parameters. Nonionizing energy loss (NIEL) analysis for both radiation degradation parameters is discussed. The radiation degradation of a 3J solar cell can be predicted from the results of degradation level in the each subcell estimated from correlativity between NIEL and both radiation degradation parameters.
Selective optical charge generation, storage, and readout in a single self-assembled quantum dot
Authors: Heiss D. , Jovanov V. , Caesar M. , Bichler M. , Abstreiter G. , Finley J. J.
Published: February 2009

We report the investigation of a single quantum dot charge storage device. The device allows selective optical charging of a single dot with electrons; storage of these charges over timescales much longer than microseconds. Reliable readout of the charge occupancy is realized by the time gated photoluminescence technique. This device enables us to investigate the tunneling escape of electrons at high electric fields up to several microseconds and, therefore, demonstrates that with more elaborate pulse sequences such structures can be used to investigate charge and spin dynamics in single quantum dots.
Thermal conductivity measurement of fluids using the 3ω method
Authors: Lee Seung-Min
Published: February 2009

We have developed a procedure to measure the thermal conductivity of dielectric liquids and gases using a steady state ac hot wire method in which a thin metal wire is used as a heater and thermometer. The temperature response of the heater wire was measured in a four-probe geometry using an electronic circuit developed for the conventional 3ω method. The measurements have been performed in the frequency range from 1 mHz to 1 kHz. We devised a method to transform the raw data into well-known linear logarithmic frequency dependence plot. After the transformation, an optimal frequency region of the thermal conductivity data was clearly determined as has been done with the data from thin metal film heater. The method was tested with air, water, ethanol, mono-, and tetraethylene glycol. Volumetric heat capacity of the fluids was also calculated with uncertainty and the capability as a probe for metal-liquid thermal boundary conductance was discussed.
Origin of reverse leakage current in n-type nanocrystalline diamond/p-type silicon heterojunction diodes
Authors: Ikeda Tomohiro , Teii Kungen
Published: February 2009

The reverse leakage current in n-type nanodiamond film/p-type silicon wafer heterojunction diodes is examined as a function of the film conductivity. We observe that as the delocalization of carriers in the films becomes stronger, the leakage current becomes larger (from 10−3 to 101 A cm−2). The major leakage source is attributed to the minority carriers from the π defect bands introduced by sp2 carbon. Both a current injection barrier and a dielectric barrier at the interface are found to be small (∼0.6 eV). The simultaneous reduction in leakage current and turn-on voltage for low-loss diodes needs optimization of the interfacial valence band connection.
Three-dimensional composite metallodielectric nanostructure for enhanced surface plasmon resonance sensing
Authors: Chen Haiping Matthew , Pang Lin , Kher Aditya , Fainman Yeshaiahu
Published: February 2009

The authors simulated, fabricated, and characterized a mushroomlike composite metallodielectric nanostructure that shows improved characteristics for surface plasmon resonance sensing applications with an enhancement in the normal electric field compared to the conventional nanohole structure. A fabrication method is introduced to give controllable linewidth by an oblique metal deposition process. A sensor built with the composite nanostructure was then used to determine the hydrophilicity of its surface by monitoring the resonant wavelength shift and computing the corresponding adsorption thickness.
Room temperature photoinduced magnetization of manganese zinc ferrite
Authors: Bettinger J. S. , Chopdekar R. V. , Suzuki Y.
Published: February 2009

We have grown samples of (Mn,Zn,Fe)3O4 on (100) Si substrates that are photomagnetic at room temperature. The samples were grown with cation concentrations containing zero crossings of the first order anisotropy constant K1 near room temperature. Photomagnetic measurements with and without HeNe illumination show an increase in initial magnetization up to 8.1% at 100 Oe due to a significant increase in the initial permeability of these samples. This photomagnetic effect is explained by an intervalence charge transfer occurring when K1 is small. The magnitude of the photoinduced magnetization increases with decreasing nanocrystallite size.
Electron mobility in scaled silicon metal-oxide-semiconductor field-effect transistors on off-axis substrates
Authors: Qin Guoxuan , Zhou Han , Ramayya Edwin B. , Ma Zhenqiang , Knezevic Irena
Published: February 2009

Off-axis silicon wafers promise monolithic integration of III-V optoelectronics with silicon microelectronics. However, it is unclear how miniaturization affects electronic device performance on off-axis substrates. We present the fabrication and characterization of metal-oxide-semiconductor field-effect transistors (MOSFETs) with different gate lengths on regular Si(100) and 4° off-axis wafers. The field-effect electron mobility in the off-axis devices is lower than in their (100)-wafer counterparts with equivalent gate length. Monte Carlo simulations have reproduced the experimental data and demonstrated that the mobility degradation in off-axis devices stems from enhanced electron scattering from the Si/SiO2 surface roughness. Short-channel MOSFETs on (100) and off-axis substrates perform comparably.
Thermal equation of state of copper studied by high P-T synchrotron x-ray diffraction
Authors: Wang Yuejian , Zhang Jianzhong , Xu Hongwu , Lin Zhijun , Daemen Luke L. , Zhao Yusheng , Wang Liping
Published: February 2009

The unit-cell volume of copper (Cu) has been measured by synchrotron x-ray at pressures and temperatures of up to 8.1 GPa and 1100 K. From pressure-volume-temperature (P-V-T) measurements, thermoelastic parameters of Cu were derived based on a modified high-T Birch–Murnaghan equation of state and a thermal pressure approach. The ambient bulk modulus derived from this work is comparable to previously reported value, whereas all other thermoelastic parameters of Cu have never been determined before. These results extend our knowledge of the fundamental thermophysical properties on Cu.
Tuning of threshold voltage of organic field-effect transistors by space charge polarization
Authors: Sakai Heisuke , Konno Koudai , Murata Hideyuki
Published: February 2009

We demonstrate a tunable threshold voltage in an organic field-effect transistor (OFET) using an ion-dispersed gate dielectric. By applying an external electric field (Vex) to the gate dielectrics, the dispersed ions in the gate dielectric are separated by electrophoresis and form space charge polarization. The drain current of the OFET increases more than 1.9 times, and the threshold voltage (Vth) decreases by 22 V (from −35.1 to −13.1 V). The direction and the magnitude of Vth shift are tunable with the applied Vex. The origin of the Vth shift is attributed to the polarization of the gate dielectric.
The structural quality of AlxGa1−xN epitaxial layers grown by digitally alloyed modulated precursor epitaxy determined by transmission electron microscopy
Authors: Hawkridge M. E. , Liliental-Weber Z. , Kim Hee Jin , Choi Suk , Yoo Dongwon , Ryou Jae-Hyun , Dupuis Russell D.
Published: February 2009

Al x Ga 1 − x N layers of varying composition (0.5<xAl<1.0) grown in the digitally alloyed modulated precursor epitaxial regime employing AlN and GaN binary sublayers by metal organic chemical vapor deposition on AlN templates were characterized by transmission electron microscopy techniques. Fine lamellae were observed in bright field images that indicate a possible variation in composition due to the modulated nature of growth. In higher Ga content samples (xAl<0.75), a compositional inhomogeneity associated with thicker island regions was observed, which is determined to be due to large Ga-rich areas formed at the base of the layer. Possible causes for the separation of Ga-rich material are discussed in the context of the growth regime used.