bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of the contaminant concentration variability among Lake Geneva Arctic char using stable isotopic composition (δ15N and δ13C)
Authors: Dufour Elise , Gerdeaux Daniel , Corvi Claude , Khim‐Heang Sophal , Mariotti André
Published: August 2002

Measurements of organochlorine [polychlorinated biphenyls (PCBs) and dichlorodiphenyl‐dichloroethylene (DDE)] and Hg concentrations and nitrogen and carbon stable isotopic compositions (δ15N and δ13C) were performed on 63 Arctic char (Salvelinus alpinus) from Lake Geneva. Fish exhibited a high interindividual variablity in pollutant concentrations. Since the accumulation of such persistent contaminants is obtained from food, the co‐occurrence of dietary differentiation leading to the contaminant interindividual variability was suspected. δ15N and δ13C were used for assessing trophic position and food source differences among Arctic char. The low ranges of δ15N and δ13C could not explain the interindividual variability in pollutant concentrations. The lack of relation between δ15N and contaminant concentration did not suggest a trophic level biomagnification of PCB, DDE, and Hg. Lake Geneva spatial variability in pollutants may be an important factor of variability within the Arctic char population. The bioaccumulation pattern occurring for Hg was not apparent for PCB and DDE. Organochlorines are hydrophobic contaminants, and their bioaccumulation pattern may be masked by seasonal variations in fish lipid content. © 2001 John Wiley & Sons, Inc. Environ Toxicol 16: 185–191, 2001
Environmental Guidelines for Power Plants in India and Other Nations
Authors: Sinha Subrato
Published: August 2002

The emissions guidelines for power plants in India are comparable to those of many other developed and
developing nations, and in some cases are more stringent. But India's environmental impact assessment and
enforcement practices need to be improved. © 2001 John Wiley & Sons, Inc.
Integrated energy balance analysis of a stand‐alone wind power system for various typical Aegean Sea regions
Authors: Kaldellis J. K. , Tsesmelis M.
Published: August 2002

The wind power industry is nowadays a mature energy production sector disposing to market commercial wind converters from 50 W up to 5 MW. In the present work the possibility of using stand‐alone electricity production systems based on a small wind turbine in order to meet the electricity requirements of remote consumers is analysed for selected Aegean Sea regions possessing representative wind potential types. The proposed configuration results from an extensive long‐term meteorological data analysis on a no‐load rejection condition basis during the entire time period examined. Accordingly, an integrated energy balance analysis is carried out for the whole time period investigated, including also the system battery depth‐of‐discharge distribution versus time. Finally, the predicted optimum system configuration is compared to other existing technoeconomic alternatives on a simplified total production cost basis. The results support the viability of similar solutions, especially for areas of high or medium wind potential. Copyright © 2002 John Wiley & Sons, Ltd.
Size and origin of the escape peak in various Si(Li) detectors
Authors: Papp T. , Campbell J. L.
Published: August 2002

The variation of the escape peak to parent peak intensity ratio among nine Si(Li) detectors was studied using an 55Fe source. We selected detectors of widely different overall lineshape response, all from commercial suppliers. We used a sophisticated non‐linear fitting code to model the underlying background and the demonstrably variable low‐energy tailing features. The resulting escape to parent peak ratio exhibits considerable variation for the different detectors. Copyright © 2001 John Wiley & Sons, Ltd.
Double K‐photoionization of S and Ar
Authors: Sánchez Héctor Jorge
Published: August 2002

Experimental evidence of double photoionizations at core levels of S (Z = 16) and Ar (Z = 18) is presented. Measurements of Kα line intensities were carried out in the region of the double‐photoionization K‐edge energy using monochromatic synchrotron radiation. From these measurements, double K‐ionization energies were obtained and double‐photoionization K‐edge jumps were calculated for these elements. A discussion on the effects of double K vacancies on XRF analysis is presented, and some approaches to the treatment of multiple vacancies in XRF are pointed out. Copyright © 2001 John Wiley & Sons, Ltd.
First results of TXRF measurements of low‐Z elements on Si wafer surfaces at the PTB plane grating monochromator beamline for undulator radiation at BESSY II
Authors: Streli C. , Wobrauschek P. , Beckhoff B. , Ulm G. , Fabry L. , Pahlke S.
Published: August 2002

First measurements of low‐Z elements on Si wafer surfaces with undulator and wiggler radiation excited total reflection x‐ray fluorescence (TXRF) spectrometry were performed at the PTB plane grating monochromator beamline for undulator radiation at the electron storage ring BESSY II. The synchrotron radiation (SR) TXRF spectrometer for low‐Z elements of the Atominstitut was used, equipped with a down‐looking Ge(HP) detector with a 300 nm NORWAR window, with the wafer positioned horizontally. Experiments were performed with excitation energies above 0.7 keV in the wiggler mode and with excitation energies below 0.7 keV in the undulator mode of the PTB insertion device U180. For droplet samples on Si wafer surfaces detection limits for Na down to C were found to be in the low‐picogram range. Copyright © 2001 John Wiley & Sons, Ltd.
Evaluation of preconcentration methods for the determination of trace amounts of rare earth elements by x‐ray fluorescence analysis using a conventional x‐ray tube system and a synchrotron radiation source
Authors: De Vito I. , Perez C. A. , Bueno M. I. Maretti S. , Olsina R. , Masi A.
Published: August 2002

Trace amounts of rare earth elements (REE) were preconcentrated by chemofiltration methods using the organic reagents o‐(3,6‐disulfo‐2‐hydroxy‐1‐naphthylazo)benzenearsonic acid (Thorin) and 2,2′‐(1,8‐dihydroxy‐3,6‐disulfonaphthylene‐2,7‐bisazo)bisbenzenearsonic acid (Arsenazo III) as complexing agents for the REE. The resulting specimens (thin film) were then analyzed by an x‐ray fluorescence method using two different instruments: a conventional x‐ray tube system and a synchrotron radiation source. The results from these two systems were compared with respect to radiation damage, accuracy, detection limits and ease of analysis. Copyright © 2001 John Wiley & Sons, Ltd.
Computer microtomography using a laboratory x‐ray fluorescence microbeam spectrometer—A feasibility study
Authors: Wȩgrzynek Dariusz
Published: August 2002

Absorption tomography imaging of small objects was performed using parallel beam geometry and a laboratory microbeam x‐ray fluorescence (µ‐XRF) spectrometer. Two x‐ray tubes, with Mo and Cr anodes, were used to perform tomographic imaging with different energies, namely 5.411 and 17.5 keV. The primary beam was collimated–focused using a tapered single glass capillary with an exit diameter of about 12 µm. The spatial resolution of the collimated x‐ray beam was about 25 µm (FWHM). The attenuated primary beam was measured using a standard Si(Li) energy‐dispersive detector. Depending on the beam intensity, two measuring modes were utilized: direct measurement of the transmitted beam and measurement of the secondary radiation excited by the transmitted beam in the yttrium target. The tomographic images of several small objects were obtained, namely a glass capillary, the tip of a match, a burned wooden stick and the head of a fly. The limitations of computer microtomography imaging using laboratory µ‐XRF are discussed and the solutions to the approached problems are presented. Copyright © 2001 John Wiley & Sons, Ltd.
Ypt protein prenylation depends on the interplay among levels of Rab escort protein and geranylgeranyl diphosphate in yeast cells
Authors: Miaczynska Marta , Wagner Wolfgang , Bauer Bettina E. , Schweyen Rudolf J. , Ragnini Antonella
Published: August 2002

Farnesyl diphosphate (FPP), an intermediate of the sterol biosynthetic pathway, is used by farnesyl transferase to farnesylate, among others, the Ras proteins, and by geranylgeranyl diphosphate synthase to produce geranylgeranyl diphosphate (GGPP). GGPP is then transferred by geranylgeranyl transferase II (GGTase II) to Rab/Ypt members of the Ras superfamily known to be required at all stages of vesicle transport in both mammals and yeast. Formation of a complex between a Rab/Ypt protein and an accessory protein named the Rab escort protein (REP) is a prerequisite for GGTase II substrate recognition. Little is known about the factors that regulate GGTase II activity in living cells but, based on available data, it seems possible that vesicle transport in higher eukaryotes is regulated by the levels of prenylated Rab/Ypt proteins in the cells. Here we show that the levels of REP play an important role in regulating GGTase II activity in yeast cells if sufficient substrates are present. Moreover, overexpression of REP causes, directly or indirectly, an increased level of Ypt substrates available for prenylation, which in turn leads to the depletion of the GGPP pool in the cell. Overall our data suggest that the levels of REP and the availability of GGPP play a role in regulating Ypt protein prenylation. Copyright © 2001 John Wiley & Sons, Ltd.
Isolation and sequence analysis of the gene encoding triose phosphate isomerase from Zygosaccharomyces bailii
Authors: Merico Annamaria , Rodrigues Fernando , Côrte‐Real Manuela , Porro Danilo , Maria Ranzi Bianca , Compagno Concetta
Published: August 2002

The ZbTPI1 gene encoding triose phosphate isomerase (TIM) was cloned from a Zygosaccharomyces bailii genomic library by complementation of the Saccharomyces cerevisiae tpi1 mutant strain. The nucleotide sequence of a 1.5 kb fragment showed an open reading frame (ORF) of 746 bp, encoding a protein of 248 amino acid residues. The deduced amino acid sequence shares a high degree of homology with TIMs from other yeast species, including some highly conserved regions. The analysis of the promoter sequence of the ZbTPI1 revealed the presence of putative motifs known to have regulatory functions in S. cerevisiae. The GenBank Accession No. of ZbTPI1 is AF325852. Copyright © 2001 John Wiley & Sons, Ltd.
Kluyveromyces lactis cytoplasmic plasmid pGKL2: heterologous expression of Orf3p and proof of guanylyltransferase and mRNA–triphosphatase activities
Authors: Tiggemann Markus , Jeske Stefanie , Larsen Michael , Meinhardt Friedhelm
Published: August 2002

The predicted ORF3 polypeptide (Orf3p) of the linear genetic element pGKL2 from Kluyveromyces lactis was expressed in Bacillus megaterium as a fusion protein with a His(6X)‐tag at the C‐terminus for isolation by Ni‐affinity chromatography. This is the first time that a yeast cytoplasmic gene product has been expressed heterologously as a functional protein in a bacterial system. The purified protein was found to display both RNA 5′‐triphosphatase and guanylyltransferase activities. When the lysine residue present at position 177 of the protein within the sequence motif (KXDG), highly conserved in capping enzymes and other nucleotidyl transferases, was substituted by alanine, the guanylyltransferase activity was lost, thereby proving an important role for the transfer of GMP from GTP to the 5′‐diphosphate end of the mRNA. Our in vitro data provides the first direct evidence that the polypeptide encoded by ORF3 of the cytoplasmic yeast plasmid pGKL2 functions as a plasmid‐specific capping enzyme. Since genes equivalent to ORF3 of pGKL2 have been identified in all autonomous cytoplasmic yeast DNA elements investigated so far, our findings are of general significance for these widely distributed yeast extranuclear genetic elements. Copyright © 2001 John Wiley & Sons, Ltd.
Cloning and sequence analysis of the LEU2 homologue gene from Pichia anomala
Authors: De la Rosa José M. , Pérez José A. , Gutiérrez Fernando , González José M. , Ruiz Teresa , Rodríguez Luis
Published: August 2002

The Pichia anomala LEU2 gene (PaLEU2) was isolated by complementation of a leu2 Saccharomyces cerevisiae mutant. The cloned gene also allowed growth of a Escherichia coli leuB mutant in leucine‐lacking medium, indicating that it encodes a product able to complement the β‐isopropylmalate dehydrogenase deficiency of the mutants. The sequenced DNA fragment contains a complete ORF of 1092 bp, and the deduced polypeptide shares significant homologies with the products of the LEU2 genes from S. cerevisiae (84% identity) and other yeast species. A sequence resembling the GC‐rich palindrome motif identified in the 5′ region of S. cerevisiae LEU2 gene as the binding site for the transcription activating factor encoded by the LEU3 gene was found at the promoter region. In addition, upstream of the PaLEU2 the 3′‐terminal half of a gene of the same orientation, encoding a homologue of the S. cerevisiae NFS1/SPL1 gene that encodes a mitochondrial cysteine desulphurase involved in both tRNA processing and mitochondrial metabolism, was found. The genomic organization of the PaNFS1–PaLEU2 gene pair is similar to that found in several other yeast species, including S. cerevisiae and Candida albicans, except that in some of them the LEU2 gene appears in the reverse orientation. The nucleotide sequence has been submitted to the EMBL database under Accession No. AJ294714. Copyright © 2001 John Wiley & Sons, Ltd.
Lipid composition, fatty acid profiles, and lipid‐soluble antioxidants of eggs of the Hermann’s tortoise (Testudo hermanni boettgeri)
Authors: Speake Brian K. , Surai Peter F. , Gore Mauvis
Published: August 2002

The major lipid classes, their fatty acid profiles, and the amounts of the lipid‐soluble components, vitamin E, vitamin A, and carotenoids, were determined for egg yolks of the Hermann’s tortoise (Testudo hermanni boettgeri) with the aim of identifying any features that may potentially impair the adaptation of this endangered species to deteriorations in habitat. Total lipid formed 16% (wt/wt) of the fresh yolk and consisted of (wt/wt) 74.4% triacylglycerol, 18.1% phospholipid, 3.0% cholesteryl ester, and 3.4% free cholesterol. Despite a diet based on green plants, contributing α‐linolenic acid as the main polyunsaturate, this fatty acid formed only 3.8% of the total mass of fatty acid of the total lipid. The main acyl component of the yolk lipids was the monounsaturated fatty acid, oleic acid, which formed 45.6% of the total. The most striking feature of the yolk composition was the almost complete lack of two nutrients, docosahexaenoic acid and vitamin A, which are essential for the developing embryo. Although it is feasible that the embryo synthesizes docosahexaenoic acid from yolk‐derived α‐linolenic acid and also converts yolk‐derived β‐carotene to vitamin A, the yolk is poorly endowed with both these precursors. The stringencies displayed by the yolk composition in this species may limit the flexibility to adapt to changes in the availability of food items when the habitat is threatened. Zoo Biol 20:75–87, 2001. © 2001 Wiley‐Liss, Inc.
Disease risk and inter‐institutional transfer of specimens in cooperative breeding programs: Herpes and the elephant species survival plans
Authors: Ryan Sadie J. , Thompson Steven D.
Published: August 2002

Managers of cooperative breeding programs and re‐introduction projects are increasingly concerned with the risk of disease transmission when specimens are transferred among facilities or between facilities and the natural environment. We used data maintained in North American studbooks to estimate the potential risks of disease transmission by direct and indirect contact of specimens in the American Zoo and Aquarium Association’s Elephant Species Survival Plan. Histological evidence for a novel herpesvirus disease transmitted between and within elephant species housed in North American facilities prompted an examination of the scope of possible transmission routes within the captive population. We found that, compared with other species managed through Species Survival Plans, elephants experience relatively few transfers between zoos. Nevertheless, the number of direct contacts with other elephants born during the study period of 1983–1996 (excluding stillbirths) was much higher than we had anticipated (μ = 25 ± 27; N = 59) and the number of potential indirect contacts was surprisingly large (μ = 143 ± 92; N = 59). Although these high rates of potential contacts complicate exact identification of infection pathways for herpesvirus, we were able to propose potential routes of transmission for the histologically identified cases. Furthermore, the extraction of data from studbooks allowed us to readily identify other specimens that did not succumb to the disease despite similar exposure. Moreover, we were able to identify other possible cases to recommend for histological examination. Herein we reveal the possibilities of multiple disease transmission pathways and demonstrate how complex the patterns of transmission can be, confounded by the unknown latency of this novel herpesvirus. This emphasizes the need for zoo veterinarians and cooperative breeding programs to consider the full potential for disease transmission associated with each and every inter‐zoo transfer of specimens. Zoo Biol 20:89–101, 2001. © 2001 Wiley‐Liss, Inc.
Evaluation of the Maruyama Computer Program Accuracy for Preoperative Estimation of Lymph Node Metastases from Gastric Cancer
Authors: Guadagni Stefano , de Manzoni Giovanni , Catarci Marco , Valenti Marco , Amicucci Gianfranco , De Bernardinis Giancarlo , Cordiano Claudio , Carboni Manlio , Maruyama Keiichi
Published: August 2002

Controversy still exists about the optimal lymph node (LN) dissection for potentially curable gastric cancer. For rational LN dissection it is important to know the incidence of metastasis at each LN station. For this purpose a computer program was developed using data from 4302 primary gastric cancers treated at the National Cancer Center Hospital in Tokyo between 1969 and 1989. To evaluate the accuracy of the computer program, the differences between the individual reports generated by the computer and the stored data were investigated in 282 Italian patients submitted to curative gastrectomy and D2 or more extended LN dissections for gastric cancer. Receiver operating characteristic (ROC) analysis was used to assess the sensitivity and specificity of the program for predicting LN metastases in each of the 16 regional LN stations. The computer program showed good predictive ability for LN metastases in most of the 16 LN stations, as the areas under the curve ranged from 0.741 (station 15) to 0.944 (station 8), with a mean of 0.856. A critical cutoff point of 18% of the program's expected percentage was the value maximizing the validity of the prediction. Using an “absolute” cutoff point of 0%, the overall rate of false‐negative (FN) predictions in 176 N+ patients was 11.9%; of these, 11 (6.2%) were absolute FNs, in which the program totally failed to estimate LN metastases; the remaining 10 cases (5.7%) were relative FNs because the specific prediction was positive for a different depth of stomach invasion. The low number of D3/D4 lymphadenectomies in the historical database may affect the low estimate of metastases to N3/N4 nodes generated by the program. Based on these data, the program predicts with good accuracy the extent of LN metastases from gastric cancer, but it is not recommended for directing the surgeon to perform more extensive lymphadenectomy.
Vascular Imaging before, during, and after Endovascular Repair
Authors: White Rodney A. , Donayre Carlos E. , Kopchok George E. , Walot Irwin , Mehinger C. Mark , Wilson Eric P. , deVirgilio Christian
Published: August 2002

Endovascular techniques for repair of vascular lesions are developing rapidly. Imaging modalities are critical in this evolution from several perspectives. Device development and evaluation rely on precise imaging to ensure fixation of devices, isolation of lesions, and assessment of healing at various intervals. Clinical implementation of endovascular techniques requires a spectrum of imaging methods to choose patients appropriately for procedures, to deploy devices expediently and precisely, and to evaluate long‐term efficacy in a minimally invasive manner. This paper reviews the utility of available imaging methods for performing these assessments.
Surgical Strategy for Management of Deep Venous Thrombosis of the Lower Extremities
Authors: Meissner Alfred J. , Huszcza Sławomir
Published: August 2002

Clinical experience proves that there is a considerable group of patients with acute proximal deep vein thrombosis (DVT) of the legs who have absolute or relative contraindications to anticoagulants or thrombolytic agents but require immediate medical treatment. The aim here is to present our strategy for qualifying patients for venous thrombectomy and the technique of the operation in patients with acute iliofemoral DVT. A total of 268 patients with DVT were evaluated. A proximal thrombosis was diagnosed in 225 cases (84%), and acute thrombosis was found in 126 (56%) of these 225 patients. Venous thrombectomy with temporary arteriovenous fistula was performed in 30 patients. In the remaining patients initial treatment included heparin, acenocumarol, or both in 61, thrombolytic agents in 26, and other therapy in 9 cases. Three patients died during the early postoperative period. Minor nonhemorrhagic complications were observed in four operated patients. One patient developed wound hematoma. In all but three operated cases the patency of the iliac and femoral veins with leg swelling in 16 patients was observed 1 year after fistula closure. There were no episodes of rethrombosis during this period. None of the thrombectomized patient had leg ulcers. Eight patients were free of clinical symptoms related to DVT. We believe that venous thrombectomy provides a good chance for satisfactory restoration of venous outflow in patients with acute proximal DVT. Venous thrombectomy with temporary arteriovenous fistula represents the treatment of choice in patients with acute, proximal DVT and with contraindications to heparin treatment.
Assessing the Suitability of Gastric Carcinoma for Limited Resection: Histologic Differentiation of Endoscopic Biopsy
Authors: Namieno Tsutomu , Koito Kazumitsu , Higashi Tsunemi , Shimamura Tsuyoshi , Yamashita Kenichiro , Sato Naoki , Kondo Yukifumi
Published: August 2002

Histologically differentiated adenocarcinoma satisfies one of the criteria for limited surgery for mucosal carcinoma of the stomach; however, the histology of the endoscopic biopsy specimen is often different from that of the resected specimen. The medical records of 1018 early gastric carcinomas were retrospectively analyzed to investigate the relation between the histologies of biopsy and resected specimens. Regression analysis showed that the histologies of biopsy specimens were significantly related to those of resected specimens (r= 0.916,n= 5, p= 0.0288) for the mucosal carcinomas, but their relation was not significant for the submucosal carcinomas (r= 0.677, n= 5,p= 0.2091). By analyzing the 344 differentiated mucosal carcinomas, moderately differentiated tubular adenocarcinomas were seen to be frequently less differentiated at resection. The histology of the biopsy specimens from mucosal carcinoma of the stomach grossly satisfies one of the criteria for limited surgery, but moderately differentiated adenocarcinoma may not be suitable for this treatment.
Options and Strategies for the Management of Choledocholithiasis
Authors: Rosenthal Raul J. , Rossi Ricardo L. , Martin Ronald F.
Published: August 2002

The introduction of laparoscopic techniques for the management of biliary stone disease has expanded the therapeutic choices for surgeons confronted with choledocholithiasis. As new strategies emerge, the treatment of cholelithiasis and choledocholithiasis remains controversial. This paper discusses the options available for the treatment of common bile duct stones. Diagnostic and therapeutic algorithms are proposed. The treatment of these patients must be individualized, taking into consideration the condition of the patient, associated diseases, secondary complications of the gallstones, and the surgical expertise and resources of the institution.
The coupling of dynamics in coupled map lattices
Authors: Chen J. Y. , Wong K. W. , Zheng H. Y. , Shuai J. W.
Published: August 2002

We investigate the coupling of dynamics in coupled map lattices (CMLs) which is not only related to coupled parameter, but also the asynchronization among different mean fields in the lattices. Computer simulations show that the optimal coupling among mean fields can be found from the maximum coupling of dynamics in various CMLs. As a consequence, the application areas of coupled systems may be broadened due to the better understanding of their dynamics.
Protein Import Into Mitochondria
Authors: Paschen Stefan A. , Neupert Walter
Published: August 2002

Most mitochondrial proteins are encoded by the nuclear genome and thus have to be imported into mitochondria from the cytosol. Protein translocation across and into the mitochondrial membranes is a multistep process facilitated by the coordinated action of at least four specialized translocation systems in the outer and inner membranes of mitochondria. The outer membrane contains one general translocase, the TOM complex, whereas three distinct translocases are located in the inner membrane, which facilitates translocation of different classes of preproteins. The TIM23 complex mediates import of matrix‐targeted preproteins with N ‐terminal presequences, whereas hydrophobic preproteins with internal targeting signals are inserted into the inner membrane via the TIM22 complex. The OXA translocase mediates the insertion of preproteins from the matrix space into the inner membrane. This review focuses on the structural organization and function of the import machinery of the model organisms of Saccharomyces cerevisiae and Neurospora crassa . In addition, the molecular basis of a new human mitochondrial disorder is discussed, the Mohr‐Tranebjaerg syndrome. This is the first known disease, which is caused by an impaired mitochondrial protein import machinery leading to progressive neurodegeneration.
Studies of the laser evaporation process and unipolar arcing inside a scanning electron microscope
Authors: W Pompe  , P Siemroth  , H Muller  , K Wetzig  , H -J Weiss
Published: August 2002

The beam of a Q-switched Nd-glass laser has been guided into a scanning electron microscope with the aim of observing target erosion in situ. The erosion caused by one shot was found to be highly inhomogeneous, with craters distributed irregularly across the irradiated spot. The ion energy distribution, ion density, and electron temperature of the plasma cloud emanating from the Cu, Ti, and YBa2Cu3O7targets were measured by means of a Langmuir probe. The ion energy distributions turned out to be nearly Maxwellian, with an average energy of about 20 eV, which is higher than expected from laser heating but similar to the energy of ions emitted from cathode spots of vacuum arcs. From their observations the authors conclude that, with incident power densities of 107-108W cm-2, target erosion is increased by unipolar arcing.
The relativistic fifth-order geometrical aberrations of a combined focusing-deflection system
Authors: Yu Li  , Shuangqi Kuang  , Zhiqiang Feng  , Tingyu Liu
Published: August 2002

The relativistic fifth-order geometrical aberrations of the combined focusing-deflection system and their coefficients have been derived. The variational functions and some of their gradients are given as are all aberrations and the fundamental method of derivation with software REDUCE.
An improved analysis of the thermophoretic force on a small particle suspended in a rarefied plasma
Authors: Xi Chen  , Xin Tao
Published: August 2002

In Brock's (1964) analysis concerning the thermophoretic force on a small particle suspended in a rarefied plasma with a temperature gradient, the effect of the presence of an external magnetic field on the ion and electron components of the thermophoretic force was demonstrated. The particle suspended in the plasma was assumed to be electrically neutral, which is obviously not realistic. Consequently, Brock obtained similar expressions for the thermophoretic force components due to, respectively, atoms, ions and electrons for the case without the external magnetic field. The present paper improves Brock's analysis by taking the charging of the suspended particle into account and obtains somewhat different expressions from his results for the thermophoretic force components due to ions and electrons.
A kinetic model of time-dependent dielectric breakdown for polymers
Authors: Ding Hong-Zhi  , Xing Xiu-San  , Zhu He-Sun
Published: August 2002

A kinetic model of time-dependent dielectric breakdown for polymers is presented. The micromechanism of thermally activated bond-breakdown is developed for polymers to account for the dynamical process of dielectric breakdown. We first prove that the thermally activated polymer bond-breakdown processes can explain not only the burst of a conducting pathway nucleated in any defect and the following successive propagation, but also the time-dependent dielectric breakdown strength of polymers. The formulae for conducting microcrack growth rate and time to failure are derived and applied to the experimental data for polyethylene terephthalate films.
An X-ray diffraction study of implantation damage in InSb reduced by a magnetic field
Authors: E Gartstein  , Y Khait  , V Richter
Published: August 2002

First results of an X-ray diffraction study of a newly found substantial reduction in radiation damage by permanent magnetic fields in InSb single crystals during implantation with In+ions are discussed. The data indicate that, in the presence of a permanent magnetic field, there is a decrease in formation of point defects, and in their trend to form clusters. These observations are supported by Rutherford backscattering measurements. A scheme to perform grazing-incidence measurements using a diffractometer equipped with parallel beam optics is presented.
Monte Carlo analysis of the electrons' motion in a segmented hollow cathode discharge
Authors: Z Donkó  , K Rózsa  , R C Tobin
Published: August 2002

We have investigated the motion of electrons in a new, high voltage segmented hollow cathode discharge, which is known to be an efficient pumping source for charge-transfer excited UV metal ion lasers. We have studied the spatial distribution of ion production, electron energy distributions, statistics of electron avalanches, the fraction of oscillating electrons, and the distribution of the fast electrons' current on the anode surface in a helium discharge having four electrode segments. We have found that the ion production is strongly peaked in the centre of the discharge due to the focusing cathode geometry. The effect of magnetic field on the characteristics of the discharge was also studied. With increasing magnetic field the peak of the spatial distribution of ionization was split into two regions of high ionization rate. Furthermore, due to the magnetic field, at fixed discharge current the number of high-energy electrons absorbed on the anode increased considerably, and a higher number of primary electrons were absorbed by the anode without making any ionization. At constant discharge voltage the fraction of oscillating electrons was found to decrease, due to the applied longitudinal magnetic field. The magnetic field dependence of the spatial distribution of ion production, the energy distribution of electrons absorbed by the anode and the fraction of oscillating electrons at different discharge conditions were also studied in a discharge having six electrode segments.
Attenuation of thermal neutrons by an imperfect single crystal
Authors: K Naguib  , M Adib
Published: August 2002

A semi-empirical formula is given which allows one to calculate the total thermal cross section of an imperfect single crystal as a function of crystal constants, temperature and neutron energy E, in the energy range between 3 meV and 10 eV. The formula also includes the contribution of the parasitic Bragg scattering to the total cross section that takes into account the crystal mosaic spread value and its orientation with respect to the neutron beam direction. A computer program (ISCANF) was developed to calculate the total attenuation of neutrons using the proposed formula. The ISCANF program was applied to investigate the neutron attenuation through a copper single crystal. The calculated values of the neutron transmission through the imperfect copper single crystal were fitted to the measured ones in the energy range 3 - 40 meV at different crystal orientations. The result of fitting shows that use of the computer program ISCANF allows one to predict the behaviour of the total cross section of an imperfect copper single crystal for the whole energy range.
Non-equilibrium properties of a flowing hydrogen cascaded arc plasma: kinetic modelling
Authors: V P Silakov  , A A Matveyev  , A V Chebotarev  , D K Otorbaev
Published: August 2002

A new kinetic scheme of the non-equilibrium gas discharge plasma is employed to describe the characteristics of a low-pressure cascaded arc plasma in pure hydrogen. The presented kinetic model includes the dynamics of the following plasma components: vibrationally excited hydrogen molecules in the ground electronic state, hydrogen atoms in the ground and electronically excited states (H(n), n=1,2,...) and electrons, positive and negative hydrogen ions. It has been shown that the low-pressure hydrogen cascaded arc plasma is characterized by high degrees of ionization and dissociation, and can generate high-density fluxes of vibrationally excited hydrogen molecules and negative ions.
Detailed threshold analysis of UV-emitting nitride vertical-cavity surface-emitting lasers
Authors: Pawel Mackowiak  , Wlodzimierz Nakwaski
Published: August 2002

In the present paper a detailed (but simple from a mathematical point of view) threshold analysis of room-temperature pulse operation of ultraviolet light (UV) emitting GaN/AlGaN/AlN vertical-cavity electrically pumped surface-emitting lasers (VCSELs) is carried out to examine the possible use of this semiconductor injection laser configuration in future mass application. Several VCSEL structures are considered. An index-guided nitride single quantum well (SQW) VCSEL structure ensures the best laser performance, as expected, particularly in the case of small-size devices. But surprisingly, gain-guided SQW VCSELs are found to exhibit comparable thresholds with much simpler double-heterostructure (DH) VCSELs of bulk active regions. Moreover, thresholds of DH nitride VCSELs are proved to be much less sensitive to all optical losses (for example material absorption as well as diffraction, scattering, and end losses) than their SQW counterparts. Therefore the SQW VCSELs need more advanced technology (making possible achievement of lower dislocation densities and/or higher facet reflectivities) to be superior to DH ones.
Acceleration of conducting polymer-coated latex particles as projectiles in hypervelocity impact experiments
Authors: M J Burchell  , M J Cole  , S F Lascelles  , M A Khan  , C Barthet  , S A Wilson  , D B Cairns  , S P Armes
Published: August 2002

A series of sterically-stabilized polystyrene latex particles in the size range 0.1-5.0 µm have been coated with ultrathin (<50 nm) overlayers of either polypyrrole, polyaniline or poly(3,4-ethylenedioxythiophene). In each case the conducting polymer overlayer allows the latex particles to acquire surface charge and hence be accelerated up to hypervelocities (>1 km s-1) using a Van de Graaff accelerator. These coated latexes have two main advantages compared to the sterically-stabilized polypyrrole particles of 0.1-0.3 µm diameter reported previously. First, a wider particle size range can be accessed. Second, the particle size distributions of the coated latexes are much narrower than those of the pure polypyrrole particles reported earlier.

Preliminary studies confirm that, after charging and acceleration, these conducting polymer-coated latex particles have very similar mass-velocity profiles to those reported for colloidal iron particles in the hypervelocity literature. The hypervelocity impact generated ionization has been measured for latex spheres impacting copper targets. This is compared to previous work for impact ionization by iron particles, thus demonstrating the ability to study the dependence of impact ionization on widely different projectile materials.
Breakdown delay times and memory effects in helium at low pressure
Authors: V Kudrle  , E LeDuc  , M Fitaire
Published: August 2002

When the series of voltage pulses is applied to a gas-filled discharge tube, one observes that a breakdown and the subsequent discharge will influence the probability of the next breakdown. Repeating the measurement of the breakdown delay timemany times we can determine the distribution ofand subsequently decompose breakdown delay time into a formative time lag and the statistical delay time. Our measurements show that even a measurement taken 10 min after the last breakdown is influenced by it. The processes in a volume being unimportant due to a flow mode of operation, it is proposed that the memory effect is caused by some surface processes. The experiments are carried out in a discharge tube with two plane-parallel electrodes separated by 2 cm in a pressure range of several Torr. In this paper, dependences of both statistical delay time and formative time lag on the repetition rate, discharge duration and anode voltage are presented.
The covariance function, bilocal approximation and homogenization of chiral-in-chiral composite materials
Authors: Bernhard Michel  , Akhlesh Lakhtakia
Published: August 2002

In continuation of an earlier paper on the application of the bilocal approximation (BA) within the framework of the strong property fluctuation theory (SPFT), an important restriction on the covariance function is lifted and the consequences numerically examined.
Nonlinear stress-strain behaviour and stress relaxation of
PZFNTU ceramics in the three-point bending test
Authors: Haitao Huang  , Peter Hing
Published: August 2002

A nonlinear stress-strain behaviour at room temperature was observed in the ferroelectric Pb(Zr0.58
Fe0.20
Nb0.2
Ti0.02
)0.994
U0.006
O3
(PZFNTU) ceramic beams in the three-point bending test. This nonlinear phenomenon is attributed to the ferroelectric domain reorientation during bending. A stress relaxation behaviour which obeys perfectly a logarithmic time law has also been found. This relation is similar to the ageing of the dielectric constant. A Weibull analysis showed that the batch of the sintered PZT ceramic samples tested had a high Weibull modulus and a high flexural strength.
Raman scattering study on anatase TiO2nanocrystals
Authors: W F Zhang  , Y L He  , M S Zhang  , Z Yin  , Q Chen
Published: August 2002

Titanium dioxide (TiO2) nanocrystals are prepared by a hydrolysis process of tetrabutyl titanate. Nanocrystal samples with various sizes of 6.8-27.9 nm are obtained after annealing from 100 to 650 °C. The crystal structures and the average particle sizes are examined using x-ray diffraction. Raman scattering was employed to investigate the evolution of the anatase phase in the nanocrystals during annealing. Phonon confinement and non-stoichiometry effects are responsible for the blueshift and broadening of the lowest-frequency EgRaman mode. The influence of interfacial vibrations on the Raman linewidth is also discussed.
Proof and analysis of the pendulum motion of beam electrons in a hollow cathode discharge
Authors: G Stockhausen  , M Kock
Published: August 2002

The pendulum motion of electrons in a hollow cathode discharge accelerated in the cathode fall is demonstrated with the use of a femtosecond laser pulse and the so-called fast optogalvanic effect. The signals are described quantitatively using a Monte Carlo model for various pressure and current levels. As a result the discharge can be described by the model from start-up to high-current operation.
The physics and applications of ion beam erosion
Authors: G Carter
Published: August 2002

Energetic ion bombardment of solid targets can lead to the production of atomic recoils and defects within the solid and the ejection or sputtering of atoms from the surface with the consequent erosion of the solid. The yield of sputtered atoms per ion depends on a number of ion and target parameters but, particularly, on the gradient of the surface with respect to the incident ion flux, the surface curvature and higher spatial derivatives of the height. As a result of these dependences of the local erosion rate, the morphology of a surface can be modified. But, in addition, surface atomic relaxation effects which may be mediated by the irradiation can occur and so the evolution of the surface may be complex. If the nature of these, often competing, processes is understood and can be suitably controlled by selection of experimental conditions, ion beam erosion can be employed to generate useful surface geometries.

This review briefly summarizes current understanding of the sputtering process and the origin of the above dependences and describes how, if only a surface gradient related mechanism dominates, the evolution of surface geometry can be accurately predicted. The higher-order and surface relaxation processes are then considered in both a deterministic approach and in a stochastic approach and these are shown to lead to fine spatial scale modifications to evolving surfaces. In both these areas, the physical models are supported by experimental observations. It is then shown how the lowest and higher orders and competing mechanisms can be selected in order to produce the desired surface morphologies in several application areas, including depth profiling of impurities in solids, ion milling and polishing, and the creation of repetitive surface structures.
Reactive re-oxidation of reduced TiO2(110) surfaces demonstrated by high temperature STM movies
Authors: P Stone  , R A Bennett  , M Bowker
Published: August 2002

The re-oxidation of slightly reduced TiO2(110) surfaces by exposure to an oxygen pressure of ~2 × 10-7mbar in the temperature range 473-1000 K occurs by re-growth of TiO2overlayers by diffusion of Tin+interstitials from the bulk. Starting with a (1 × 2) reconstructed surface, scanning tunnelling microscope images of the surface reacting under these conditions show that the (1 × 1) islands nucleate within the (1 × 2) layer and grow laterally. As the islands reach a critical size, which is temperature dependent, a new (1 × 2) layer begins to nucleate and grow. At both extremes of the temperature range nucleation of the second layer occurs before coalescence of the (1 × 1) islands, however, at temperatures between 673 and 773 K large areas of (1 × 1) surface form before growth of the second layer. The reaction is cyclic and several layers of TiO2can be grown in this way.
Quantum carpets woven by Wigner functions
Authors: Friesch O M , Marzoli I , Schleich W P
Published: August 2002

The dynamics of many different quantum systems is characterized by a regular net of minima and maxima of probability stretching out in a spacetime representation. We offer an explanation to this phenomenon in terms of the Wigner function. This approach illustrates very clearly the crucial role played by interference.
Use
of composite rotations to
correct systematic errors in
NMR quantum computation
Authors: Cummins H K , Jones J A
Published: August 2002

We implement an ensemble quantum counting algorithm on three NMR spectrometers with 1
H resonance frequencies of 500, 600 and 750 MHz. At higher frequencies, the results deviate markedly from naive theoretical predictions. These systematic errors can be attributed almost entirely to off-resonance effects, which can be substantially corrected for using fully compensating composite rotation pulse sequences originally developed by Tycko. We also derive an analytic expression for generating such sequences with arbitrary rotation angles.
Transport of cold atoms in a miniature guide
Authors: Key M , Rooijakkers W , Hinds E A
Published: August 2002

We have developed a waveguide for atoms based on magnetic confinement within a hollow glass fibre. Weak-field-seeking atoms are transported along a central hole and are prevented from hitting the wall by the magnetic field due to four current-carrying wires embedded in the fibre. A 'pinch' coil wound around the fibre plugs the guide at one end with a magnetic field strong enough to reflect the weak-field-seeking atoms. We have demonstrated that all the positivemFsublevels of the85RbF= 3 ground state are guided and have made a movie of the atom dynamics.
Interfacial dynamics in 3D binary fluid demixing: animation studies*
Authors: Pagonabarraga I , Desplat J-C , Wagner A J , Cates M E
Published: August 2002

The late-stage phase ordering, in three dimensions, of fully symmetric binary fluid mixtures is studied via a lattice Boltzmann method. We present time-resolved maps of the fluid velocity fields and also animated visualizations of the interfacial motion. These show distinct features corresponding to regimes where viscous, crossover and inertial hydrodynamic scaling have previously been identified. Specifically, while the interface is overdamped in the viscous regime, it exhibits recoil after topological reconnection at intermediate and higher inertia; and in our most inertial runs the interface shows extensive underdamped capillary disturbances not attributable to topological reconnection events. The advantages and practicality of presenting such dynamical data in fully animated form are demonstrated and briefly discussed.

This paper's animations are available from theMultimedia Enhancements pageas individual files and also packed into archives (two formats).
Progressive Massive Fibrosis Identified at Federally Funded Black Lung Clinics in the US
Authors: Harris Drew A. , Almberg Kirsten S. , Blackley David J. , Cohen Robert A. , Edwards Chesnee , Johnson Bradley , Hall Noemi B.
Published: January 2024

This study of US Black Lung Clinics (established to treat coal miners) reports the prevalence of progressive massive fibrosis identified through June 2023.
Introduction to JAMA Climate Change and Health Series
Authors: Ebi Kristie L. , Hess Jeremy J.
Published: January 2024

This JAMA Insights introduces the new series on climate change intended to inform readers about the associations between climate change and health.