bluuebunny/crossref_metadata_2025 huggingface dataset:
Cladistic analysis of morphological characters in the eulophine tribe Cirrospilini (Hymenoptera: Eulophidae)
Authors: UBAIDILLAH Rosichon , LASALLE John , QUICKE Donald L. J. , KOJIMA Jun‐ichi
Published: December 2003

A total of 56 morphological characters were analyzed for 53 cirrospiline species that represent all of the 17 described genera of the tribe. The other taxa of the Eulophinae included in the analysis were six species of six representative genera in the tribe Eulophini, a species of Elasmus (the only genus comprising the tribe Elasmini), and a species of Trichospilus (unplaced). Trichospilus and two of the six genera of Eulophini examined were placed within Cirrospilini. Monophyly of Cirrospilini (when these two genera of Eulophini and Trichospilus are included) and of the cirrospiline genera for which more than one species were examined was supported, but the relationships between the genera were poorly resolved. An exception was Cirrospilus, the largest genus in the Cirrospilini, monophyly of which was not supported to any extent.
Thienopyridine‐linked thrombotic microangiopathy: association with endothelial cell apoptosis and activation of MAP kinase signalling cascades
Authors: Mauro Michael , Zlatopolskiy Andrey , Raife Thomas J. , Laurence Jeffrey
Published: December 2003

The thienopyridine platelet antagonist ticlopidine is associated with development of thrombotic thrombocytopenic purpura (TTP) but the pathophysiology of this link is unclear. Severe deficiency of disintegrin and metalloproteinase with thrombospondin motif‐13 (ADAMTS13), described in familial cases and a significant fraction of idiopathic TTP, has been reported in only a few ticlopidine‐linked cases. As ticlopidine can disrupt production of extracellular matrix (ECM) components critical to microvascular endothelial cell (MVEC) integrity in vitro, we explored the hypotheses that ticlopidine and ticlopidine‐linked TTP plasmas induce MVEC apoptosis in a manner similar to that of idiopathic TTP plasmas, and that ECM components and related mitogen‐activated protein kinase (MAPK) signalling cascades may be involved in this process. Replicating the activity of plasmas from patients with idiopathic TTP, plasma from five ticlopidine‐linked TTP patients induced apoptosis of primary human dermal, glomerular and hepatic MVEC, but had no effect on pulmonary MVEC or large vessel endothelial cells (EC). Pharmacological levels of ticlopidine initiated apoptosis with similar EC lineage restriction. In parallel, ticlopidine and plasmas from idiopathic and ticlopidine‐TTP patients decreased transcripts for the ECM component thrombospondin‐1 in MVEC, but not in large vessel EC. These changes were accompanied by prolonged induction of MAPKs extracellular signal‐related kinase (ERK)‐1/2 and p38 only in TTP susceptible MVEC. Induction of apoptosis by ticlopidine and TTP plasma was abrogated by inhibitors of ERK‐1/2 and p38 phosphorylation. In conclusion, MVEC apoptosis related to altered ECM–MVEC interactions may be a key part of the pathology of ticlopidine‐linked and idiopathic TTP.
Elevation of serum hepatocyte growth factor during granulocyte colony‐stimulating factor‐induced peripheral blood stem cell mobilization
Authors: Fujii Keiko , Ishimaru Fumihiko , Kozuka Teruhiko , Matsuo Keitaro , Nakase Koichi , Kataoka Itaru , Tabayashi Takayuki , Shinagawa Katsuji , Ikeda Kazuma , Harada Mine , Tanimoto Mitsune
Published: December 2003

We examined serum levels of the angiogenic factors, vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and hepatocyte growth factor (HGF), in normal donors for allogeneic peripheral blood stem cell (PBSC) transplantation. Granulocyte colony‐stimulating factor (G‐CSF) (filgrastim 400 μg/m2/d) was administered to 23 donors for 5 d and aphereses were performed on days 4 and 5. Although bFGF remained at similar levels after G‐CSF treatment, serum VEGF and HGF levels increased 1·5‐fold (n = 13; P = 0·02) and 6·8‐fold (n = 23; P < 0·0001) respectively. The serum HGF level before G‐CSF administration on day 1 correlated inversely with mobilized CD34+ cell numbers. Time course kinetics of HGF showed that on the day after G‐CSF administration (day 2), serum HGF levels increased to 3678 pg/ml. For auto PBSC mobilization with chemotherapy and G‐CSF 200 μg/m2/d (n = 8), we observed similar HGF elevation, which appeared to be dose‐dependent on the G‐CSF administered.
Diffuse large B‐cell lymphoma: clinical implications of extranodal versus nodal presentation – a population‐based study of 1575 cases
Authors: Møller Michael B. , Pedersen Niels T. , Christensen Bjarne E.
Published: December 2003

Differences in genetic origin between nodal and extranodal diffuse large B‐cell lymphomas (DLBCL) exist. Using population‐based data from the registry of the Danish Lymphoma Group, the present study is the first to analyse clinical implications of nodal versus extranodal presentation of DLBCL. Of 4786 newly diagnosed non‐Hodgkin's lymphoma patients in a 16‐year period, 1575 (33%) had DLBCL. The annual incidence rate was 2·9 per 100 000; 40% were extranodal. The clinical profile of patients with extranodal DLBCL was different from the nodal DLBCL patients. Extranodal DLBCL was associated with older age and poorer performance score, but also lower tumour burden. In extranodal DLBCL, 51% of the cases were stage I and 36% were stage IV, whereas the patients were relatively equally distributed between the four stages in nodal DLBCL. For stage I patients, extranodal DLBCL was independently associated with poor survival (P = 0·003). In contrast, among stage IV patients those with extranodal DLBCL survived longer (P = 0·009). We conclude that there are important clinical differences between nodal and extranodal DLBCL. The addition of these clinical results to the existing aetiological and genetic data suggests that the distinction between nodal and extranodal DLBCL is not only pathogenetically but also clinically important.
BAT‐25 and BAT‐26, two mononucleotide microsatellites, are not sensitive markers of microsatellite instability in acute myeloid leukaemia
Authors: Faulkner Rowena D. , Seedhouse Claire H. , Das‐Gupta Emma P. , Russell Nigel H.
Published: December 2003

BAT‐25 and BAT‐26 are mononucleotide microsatellites with quasi‐monomorphic allele length distribution in healthy controls but unstable, shortened alleles in solid organ tumours with a mutator phenotype (RER+). Both markers are highly sensitive and specific for RER+ colorectal cancer. This study evaluated three mononucleotide microsatellites, BAT‐25, BAT‐26 and BAT‐40 (a polymorphic mononucleotide microsatellite) in RER+ acute myeloid leukaemia (AML). Sixteen [six therapy‐related AML (t‐AML), 10 de novo AML] known RER+ AML, 22 healthy controls and five known RER− AML samples were analysed. In healthy controls and RER− AML, BAT‐25 and BAT‐26 were quasi‐monomorphic and BAT‐40 was polymorphic. Of the RER+ AML samples, 0 of 16 had microsatellite instability (MSI) at BAT‐25, 0 of 16 had MSI at BAT‐26 and three of 16 had MSI at BAT‐40. We conclude that BAT‐25, BAT‐26 and BAT‐40 microsatellites are insensitive to RER+ AML. Further studies are required to determine a consensus panel of sensitive microsatellites for use in AML.
Decrease of Smad4 gene expression in patients with essential thrombocythaemia may cause an escape from suppression of megakaryopoiesis by transforming growth factor‐β1
Authors: Kuroda Hiroyuki , Matsunaga Takuya , Terui Takeshi , Tanaka Ikuta , Takimoto Rishu , Fujikawa Koshi , Takayama Tetsuji , Kato Junji , Hirayama Yasuo , Sakamaki Sumio , Kohda Kyuhei , Niitsu Yoshiro
Published: December 2003

Essential thrombocythaemia (ET) is characterized by the abnormal and sustained proliferation of megakaryocytes. The mechanism for this lineage‐specific expansion in ET, remains unclear. We have previously reported that transforming growth factor‐β1 (TGF‐β1) is involved in negative feedback regulation of megakaryopoiesis in both healthy volunteers (HV) and patients with idiopathic thrombocytopenic purpura (ITP). The present study found that megakaryocyte colony‐forming units (CFU‐MK) of ET patients were less sensitive to TGF‐β1 than those of HV. The expression of Smad4 (Sma‐ and Mad‐related protein‐4) in CFU‐MK of ET patients was reduced in comparison with that of HV. Finally, to confirm that the impaired TGF‐β1 sensitivity was caused by reduced expression of Smad4, we examined Smad4‐transfected CFU‐MK from ET patients in the presence of TGF‐β1, and verified that the transfectants were indeed as susceptible as CFU‐MK from HV to TGF‐β1. Thus it was surmised that one of the mechanisms for impaired sensitivity of CFU‐MK to TGF‐β1 is the reduced expression of Smad4.
A rapid and specific whole blood HPA‐1 phenotyping by flow cytometry using two commercialized monoclonal antibodies directed against GP IIIa and GP IIb‐IIIa complexes
Authors: Sorel Nathalie , Brabant Severine , Christiaens Luc , Brizard Andre , Mauco Gerard , Macchi Laurent
Published: December 2003

The human platelet antigen 1 (HPA‐1) system has been implicated in rare but severe diseases, such as neonatal alloimmune thrombocytopenic purpura, post‐transfusion purpura and immune platelet refractoriness. We developed a flow cytometry assay for HPA‐1 phenotyping using two commercial monoclonal antibodies, P2 and SZ21, directed against glycoprotein (GP) IIb–IIIa and GP IIIa respectively. One hundred and twenty‐seven healthy controls were studied and ratios of mean fluorescence intensity for P2 and SZ21 discriminated between HPA‐1a homozygotes and heterozygotes. These two monoclonal antibodies, coupled with flow cytometry represent a rapid and reliable tool for platelet HPA‐1 typing to aid diagnosis.
Apicidin potentiates the imatinib‐induced apoptosis of Bcr–Abl‐positive human leukaemia cells by enhancing the activation of mitochondria‐dependent caspase cascades
Authors: Kim Jin Seok , Jeung Hoi Kyung , Cheong June‐Won , Maeng Hoyoung , Lee Seung Tae , Hahn Jee Sook , Ko Yun Woong , Min Yoo Hong
Published: December 2003

Apicidin, a histone deacetylase inhibitor, is a novel cyclic tetrapeptide with potent antiproliferative activity against various cancer cells. We examined whether apicidin potentiates the imatinib‐induced apoptosis of Bcr–Abl‐positive human leukaemia cells. In K562 cells, the co‐administration of minimally toxic concentrations of imatinib and apicidin (imatinib/apicidin) for 48 h produced a marked increase in mitochondrial damage, processing of caspase cascades and apoptosis. Similar results were observed in leukaemic blasts obtained from patients with chronic myeloid leukaemia in blast crisis. Imatinib/apicidin co‐treatment for 48 h resulted in a near complete loss of the full‐length XIAP (X‐linked inhibitor of apoptosis) protein, with a corresponding increase in the 29‐kDa XIAP cleavage product. Both the degradation of XIAP and increased release of second mitochondria‐derived activator of caspase/direct IAP‐binding protein with low pI (Smac/DIABLO) into the cytosol were abrogated by pretreatment with the caspase‐3 inhibitor DEVD‐CHO. Imatinib/apicidin co‐treatment for 48 h produced a prominent decrease in Bcr–Abl protein levels in a caspase‐dependent manner. In summary, these data indicate that apicidin potentiates the imatinib‐induced apoptosis of Bcr–Abl‐positive leukaemia cells through the enhanced activation of the mitochondria‐dependent caspase cascades, accompanied by caspase‐dependent downregulation of Bcr–Abl and XIAP. These findings generate a rationale for further investigation of apicidin and imatinib as a potential therapeutic strategy in Bcr–Abl‐positive leukaemias.
Altered expression of Tfg and Dap3 in Ikaros‐defective T‐cell lymphomas induced by X‐irradiation in B6C3F1 mice
Authors: Yasumura Kyoko , Sugimura Isamu , Igarashi Kazuei , Kakinuma Shizuko , Nishimura Mayumi , Doi Masahiro , Shimada Yoshiya
Published: December 2003

Ikaros is a Kruppel‐type zinc finger protein that is essential for normal lymphocyte development and differentiation. Recently, it has been demonstrated that Ikaros is frequently inactivated in both human and mouse leukaemias/lymphomas. Although this inactivation is thought to be involved in leukaemogenesis, little is known about the molecular mechanisms that lead to neoplastic transformation. To identify the genes that may be controlled by Ikaros, we performed differential display analysis of RNAs from mouse 3T3‐L1 cells that had been transfected with the Ikaros gene. Two cDNAs, the Trk‐fused gene (Tfg) and death‐associated protein 3 gene (Dap3) were upregulated in Ikaros‐transfected cells. Expression of Tfg and Dap3 was consistently downregulated in radiation‐induced T‐cell lymphomas that exhibited defective Ikaros expression. These results suggest that Tfg and Dap3 function downstream of Ikaros and may be involved in radiation‐induced lymphomagenesis.
Feature Environmental geophysics: a site characterization tool for urban regeneration in the post‐mining era
Authors: Styles Peter
Published: December 2003

The closure and decay of industrial activity involving mining, chemical or light industrial operations has scarred the landscape of urban areas. The Government has major initiatives in urban regeneration to remediate these ‘brown‐field sites’.
Atomic Spectral Tables for the Chandra X-Ray Observatory. Part I S VIII–S XIV
Authors: Podobedova L. I. , Musgrove A. , Kelleher D. E. , Reader J. , Wiese W. L.
Published: December 2003

Tables of critically compiled wavelengths, energy levels, line classifications, and transition probabilities are given for spectra of ionized sulfur (S VIII–S XIV) in the region 21–170 Å. These tables provide data of interest for the Emission Line Project in support of the analysis of astronomical data from the Chandra X-Ray Observatory. They will also be useful for the diagnostics of plasmas encountered in fusion energy research. The transition probabilities were obtained mainly from recent sophisticated calculations carried out with complex computer codes.
Ultrasonic Parameters as a Function of Absolute Hydrostatic Pressure. I. A Review of the Data for Organic Liquids
Authors: Oakley Barbara A. , Barber Gary , Worden Tony , Hanna Darrin
Published: December 2003

This review provides an overview of experimental results involving ultrasonic parameters as a function of absolute hydrostatic pressure in organic liquids. Major topics of discussion include the pioneering work of Litovitz and Carnevale involving deduction of the chemical and structural properties of liquids from acoustical properties as a function of pressure; modern general ultrasonic studies of a broad range of organic liquids; work accomplished by Russians and others from the former Soviet block countries, particularly the work headed by Otpuschennikov at the Kursk Pedagogical Institute; the studies involving refrigerants published by Takagi at the Kyoto Institute of Technology; tribological and petroleum industry studies related to oils; Brillouin scattering experiments; and thermodynamic methods of B/A measurement. The importance of ultrasonic parameters as a function of pressure to the understanding of a variety of processes is highlighted. A table of 325 liquids and liquid mixtures with a total of 366 entries indexed by chemical name is provided. Publications involving a specific liquid are cited within the table under the entry for that liquid, with the author’s name, aim of the study (e.g., speed of sound or absorption studies), methodology, and pressure/temperature ranges of the experimentation also given (197 references).
Ultrasonic Parameters as a Function of Absolute Hydrostatic Pressure. II. Mathematical Models of the Speed of Sound in Organic Liquids
Authors: Oakley Barbara A. , Hanna Darrin , Shillor Meir , Barber Gary
Published: December 2003

Polynomial expressions for the speed of sound as a function of pressure for 68 different organic liquids are presented in tabular form. (The liquids form a subset of those discussed in the companion paper: Ultrasonic parameters as a function of absolute hydrostatic pressure. I. A review of the data for organic liquids.) The polynomial expressions are based upon the experimental results reported by many different researchers. For some common liquids, such as benzene, hexane, ethanol, and carbon tetrachloride, the results of as many as five different researchers are reported. These results sometimes vary widely—far more than would be expected from calculated experimental uncertainties. An analysis is presented of how well pressure-dependent polynomials fit the experimental data when the number of coefficients is increased. The error in the polynomial fit is also explored when both pressure and temperature dependencies are present. Finally, differences between ultrasonic and Brillouin scattering experimental results are discussed.
Correlations for Vapor Nucleating Critical Embryo Parameters
Authors: Magnusson Lars-Erik , Koropchak John A. , Anisimov Michael P. , Poznjakovskiy Valeriy M. , de la Mora Juan Fernandez
Published: December 2003

Condensation nucleation light scattering detection in principle works by converting the effluent of the chromatographic separation into an aerosol and then selectively evaporating the mobile phase, leaving less volatile analytes and nonvolatile impurities as dry aerosol particles. The dry particles produced are then exposed to an environment that is saturated with the vapors of an organic solvent (commonly n-butanol). The blend of aerosol particles and organic vapor is then cooled so that conditions of vapor supersaturation are achieved. In principle, the vapor then condenses onto the dry particles, growing each particle (ideally) from as small as a few nanometers in diameter into a droplet with a diameter up to about 10 μm. The grown droplets are then passed through a beam of light, and the light scattered by the droplets is detected and used as the detector response. This growth and detection step is generally carried out using commercial continuous-flow condensation nucleus counters. In the present research, the possibility of using other fluids than the commonly used n-butanol is investigated. The Kelvin equation and the Nucleation theorem [Anisimov et al. (1978)] are used to evaluate a range of fluids for efficacy of growing small particles by condensation nucleation. Using the available experimental data on vapor nucleation, the correlations of Kelvin diameters (the critical embryo sizes) and the bulk surface tension with dielectric constants of working liquids are found. A simple method for choosing the most efficient fluid, within a class of fluids, for growth of small particles is suggested.
Recommended Critical Temperatures. Part I. Aliphatic Hydrocarbons
Authors: Owczarek Iwona , Blazej Krystyna
Published: December 2003

This work deals with the critical temperature (Tc) for saturated and unsaturated aliphatic hydrocarbons. For 175 hydrocarbons (branched alkanes, branched and unbranched alkenes, and alkynes), an existing lack of critical temperature values have been complemented. Prediction methods have been used, the usefulness of which for specific groups and subgroups of the above mentioned hydrocarbons had been previously critically evaluated. The evaluation of accuracy of the relevant aspects of these methods is given in this study. An additional result of this work is the creation of a set of recommended experimental data on critical temperatures and normal boiling points for aliphatic hydrocarbons. Such a set has been created mainly for the purpose of evaluation of prediction methods applied in this study.
Recommended Vapor–Liquid Equilibrium Data. Part 2: Binary Alkanol–Alkane Systems
Authors: Góral Marian , Oracz Paweł , Skrzecz Adam , Bok Andrzej , Ma̧czyński Andrzej
Published: December 2003

The recommended vapor–liquid equilibrium (VLE) data for 36 binary systems involving primary, secondary, and tertiary alcohols with n-alkanes and isoalkanes [with the exception of 1-alkanols–n-alkane systems, which were presented in Part 1 of this series—J. Phys. Chem. Ref. Data 31(3), 702 (2002)] have been obtained after critical evaluation of all data (744 data sets) reported in the open literature up to the middle of 2002. The evaluation procedure consisted in combining the thermodynamic consistency tests, data correlation, comparison with enthalpy of mixing data, and comparison of VLE data for various mixtures. The data were correlated with equations based on local compositions concept as well as with equation of state appended with chemical term (EoSC) proposed by Góral. The recommended data are presented in the form of sheets containing tables of data, figures and auxiliary information. Each sheet corresponds to one system and contains three isotherms (spaced by at least 15 K) and one isobar (preferably at 101.32 kPa). Experimental gaps were completed with the predicted data.
A Comprehensive and Critical Compilation, Evaluation, and Selection of Physical–Chemical Property Data for Selected Polychlorinated Biphenyls
Authors: Li Nanqin , Wania Frank , Lei Ying D. , Daly Gillian L.
Published: December 2003

Accurate physical–chemical properties (aqueous solubility SW, octanol–water partition coefficient KOW, vapor pressure P, Henry’s law constant H, octanol–air partition coefficient KOA, octanol solubility SO) are of fundamental importance for modeling the transport and fate of organic pollutants in the environment. Energies of phase transfer are used to describe the temperature dependence of these properties. When trying to quantify the behavior of contaminant mixtures such as the polychlorinated biphenyls, consistent physical–chemical properties are required for each individual congener. A complete set of temperature dependent property data for sixteen polychlorinated biphenyls (PCB-3, 8, 15, 28, 29, 31, 52, 61, 101, 105, 118, 138, 153, 155, 180, 194) was derived, based on all experimentally obtained values reported for these congeners in the literature. Log mean values derived from the experimental data were adjusted to yield an internally consistent set of data for each congener. These adjusted data also show a greater degree of interhomologue consistency, which can be illustrated with the help of simple quantitative structure-property relationships that use molar mass and the number of chlorine substitutions in ortho-positions as descriptors. The extent of the required adjustment gives an indication of the uncertainty of the averaged measured values and is typically lower than might be expected from the range of the reported measured values.
Vapor Pressure and Critical Point of Tritium Oxide
Authors: Xiang H. W.
Published: December 2003

A simple general corresponding-states principle has been developed to represent the vapor pressure of tritium oxide from its triple point to its critical point, to describe the available experimental data, and to extrapolate beyond their range. This work takes advantage of the adoptions of the ITS-90 temperature scale and of the new critical parameters obtained from the extended corresponding-states principle. The vapor pressure data are described within their scatter in the entire temperature range. Comparisons with the available experimental data show that the extended corresponding-states principle for vapor pressure can calculate values with good accuracy. The substance-dependent characteristic parameters are given, such as critical temperature, critical density, critical pressure, and acentric factor. The values of the pressures, along with their first and second derivatives, as a function of temperature over the entire region from the triple point to the critical point are tabulated and recommended for scientific and practical uses.
Thermochemical Properties, ΔfH°(298.15 K), S°(298.15 K), and Cp°(T), of 1,4-Dioxin, 2,3-Benzodioxin, Furan, 2,3-Benzofuran, and Twelve Monochloro and Dichloro Dibenzo-p-dioxins and Dibenzofurans
Authors: Zhu Li , Bozzelli Joseph W.
Published: December 2003

Values for ΔfH°(298.15 K), S°(298.15 K), and Cp°(T) (5⩽T/K⩽6000) are computed by density functional B3LYP/6-31G(d,p) and B3LYP/6-311+G(3df,2p) calculation methods for 12 monochloro and dichloro dibenzo-p-dioxins and dibenzofurans: 1-chloro dibenzo-p-dioxin, 2-chloro dibenzo-p-dioxin, 1,6-dichloro dibenzo-p-dioxin, 1,8-dichloro dibenzo-p-dioxin, 1,9-dichloro dibenzo-p-dioxin, 2,8-dichloro dibenzo-p-dioxin, 3-chloro dibenzofuran, 4-chloro dibenzofuran, 1,6-dichloro dibenzofuran, 3,6-dichloro dibenzofuran, 3,7-dichloro dibenzofuran, and 4,6-dichloro dibenzofuran. Molecular structures and vibration frequencies are determined at the B3LYP/6-31G(d,p) level of theory. Isodesmic reactions are utilized at each calculation level to determine the enthalpy of formation of each species. Contributions to the entropy and the heat capacity from translation, vibration, and external rotations are calculated using the rigid-rotor-harmonic-oscillator approximation based on the B3LYP/6-31G(d,p) structures. The enthalpies of formation for 1,4-dioxin, furan, 2,3-benzodioxin, 2,3-benzofuran, dibenzo-p-dioxin, and dibenzofuran are also calculated. Thermochemical properties of two composite central atom groups and four interaction groups are derived for use in a group additivity scheme to calculate these thermochemical properties of polychlorinated dibenzo-p-dioxins and dibenzofurans.
Electrical contact resistance theory for conductive rough surfaces separated by a thin insulating film
Authors: Kogut L. , Komvopoulos K.
Published: December 2003

An electrical contact resistance (ECR) theory is presented for conductive and rough (fractal) surfaces separated by a thin insulating film, which is treated as an energy barrier that impedes current flow due to the electric-tunnel effect. The analysis yields insight into the effects of film properties, current flow, surface topography, mechanical properties, and contact load on the ECR. It is shown that the variation of ECR with the contact load is less pronounced than that observed in the absence of an insulating layer due to the intrinsic voltage dependence of the tunnel resistance and the associated voltage compensation mechanism. The effect of nonohmic behavior on the relationships of the ECR with the contact load and the real contact area is discussed and results are compared with approximate analytical relationships developed herein. The relationship between the real contact area and the ECR depends on the current intensity and film properties and is independent of the surface topography and mechanical properties. Approaches for determining the surface roughness, mechanical properties, insulating film properties, and real contact area from ECR measurements are interpreted in light of the theory developed.
Growth and electrical properties of atomic-layer deposited ZrO2/Si-nitride stack gate dielectrics
Authors: Ishii Hiroyuki , Nakajima Anri , Yokoyama Shin
Published: December 2003

We deposited ZrO2 thin films by atomic-layer deposition (ALD) using zirconium tertiary–butoxide [Zr(t-OC4H9)4, (ZTB)] and H2O source gases on Si substrates at low temperatures. We grew ZrO2 films layer by layer in a temperature range of 175–250 °C to minimize surface roughness. The deposited ZrO2 film thickness had self-limiting properties with the exposure time of ZTB and vapor pressures of ZTB and H2O. The deposition rate per cycle was independent of the vapor pressure of ZTB from 0.01 kPa to 0.04 kPa. Transmission electron microscopy revealed that the formation of an SiOx interfacial layer could be suppressed by using an ALD ZrO2/ALD Si-nitride (∼0.5 nm) stack structure. We found the fixed charge, interface trap density, and leakage current density in the ALD ZrO2/ALD Si-nitride stack dielectrics to be less than those in ALD ZrO2 dielectrics. In spite of the same equivalent oxide thickness of 1.6 nm, the relative dielectric constant εr (11.5) of the ALD ZrO2/ALD Si-nitride stack capacitor was higher than that (10.5) of the ALD ZrO2 capacitor due to the suppression of formation of the interfacial SiOx layer (1.0–1.5 nm) by an ultrathin ALD Si nitride (∼0.5 nm). The current conduction mechanism is identified as direct tunneling of electron except at very low dielectric fields. Comparing structural and electrical properties, ALD ZrO2/ALD Si-nitride stack dielectrics are promising candidates for sub-0.1-μm metal–oxide–semiconductor field-effect transistors.
Patterned magnetic tunnel junctions with Al conduction layers: Fabrication and reduction of pinhole effect
Authors: Han X. F. , Yu Andrew C. C.
Published: December 2003

Magnetic tunnel junctions (MTJs), Ta(5 nm)/Al(20 nm)/Ni79Fe21 (5 nm)/Ir22Mn78 (10 nm)/Co75Fe25 (4 nm)/Al(x nm)-oxide/Co75Fe25 (4 nm)/Ni79Fe21 (20 nm)/Ta (5 nm) [x=0.8 and 0.9 nm], with 20 nm thick Al conduction layers were fabricated using magnetron sputtering deposition. Due to the surface roughness of the Al conduction layer, metallic pinholes could easily occur at the barrier layer. Remedies for such a pinhole issue can be solved by a critical underoxidation condition for the Al-oxide tunneling barriers and a postfabrication annealing process of the MTJs at 300 °C. A high magnetoresistance ratio of 45%, low resistance-area product of around 10 kΩ μm2, and sensing layer coercivity of approximately 20 Oe were obtained at room temperature for the annealed MTJs. The results suggest that pinhole defects could be eliminated or significantly reduced with a critical Al-oxide layer fabrication condition together with the annealing process. The MTJ structure after further structural and patterning modifications can be adopted as the cell elements for magnetoresistive random access memory based on the Al wring interconnection in semiconductor integrated circuit techniques.
Lock-in by molecular multiplication
Authors: Braun Dieter , Libchaber Albert
Published: December 2003

A lock-in amplifier is physically realized at the level of fluorescent dye molecules. It is based on the general property that the emission of a fluorescent dye is the product of quantum efficiency and illumination intensity. For each pixel of a microscopic image, we measure in amplitude and phase an environment property of the dye, such as conformation, membrane voltage, or temperature. This lock-in implementation is highly parallel and reaches the ultimate photon shot noise limit. Using fast temperature oscillations, we apply it to measure the opening/closing kinetics of a molecular beacon (DNA hairpin) at 5 μs resolution.
Silicon-based near-infrared tunable filters filled with positive or negative dielectric anisotropic liquid crystals
Authors: Pucker G. , Mezzetti A. , Crivellari M. , Bellutti P. , Lui A. , Daldosso N. , Pavesi L.
Published: December 2003

Complementary metal-oxide-semiconductor-compatible tunable Fabry–Pérot microcavities filled with liquid crystals (LCs) were realized and studied in the near-infrared region. The microcavities were produced by chip bonding technique, which allows one to infill LC between two [SiO2/Si]3λ/4 (λ=1.5 μm) dielectric Bragg reflectors separated by 950-nm-thick SiO2 posts. Liquid crystals with positive and negative dielectric anisotropy were used, i.e. MerckE7 (Δε=13.8) and Merck-6608 LC (Δε=−4.2). Mirror-integrated electrodes allow an external bias to induce an electric field and to tune the LC properties and, hence, the microcavity resonance. Electric-field-induced shifts of the second-order cavity modes of 127 and 49 nm were obtained for Merck-E7 and Merck-6608 LC, with driving potentials of 5 and 10 V, respectively.
Fast line-based experiment timing system for LabVIEW
Authors: Owen Scott F. , Hall David S.
Published: December 2003

We have developed a line-based computer control system that is embedded within the commercially available program LabVIEW. The program translates a sequence of C++ commands into an array of values for the programming of hardware devices, including digital and analog I/O boards and a GPIB controller. These commands are executed with 1 μs resolution upon receipt of an external triggering signal. We have successfully applied this system to the generation of Bose–Einstein condensates in a dilute gas of Rb87.
Characteristics of electron cyclotron resonance plasma generated in a rectangular waveguide by high-power microwave
Authors: Mishra Lekha Nath , Shibata Kanetoshi , Ito Hiroaki , Yugami Noboru , Nishida Yasushi
Published: December 2003

A new source for the generation of overdense plasma is developed using an electron cyclotron resonance (ECR) technique in a rectangular waveguide by a high-power (1 kW) microwave of frequency 2.45 GHz. The characteristics of the plasma for Ar gas are presented, including a large surface area to fill the entire waveguide of length 100 cm with uniformity ±3% over 50 cm. With the help of a Langmuir probe, plasma density about 1012 cm−3 and electron temperature of 8–12 eV are observed, and their dependence on the background gas pressure and magnetic field are also examined. It is shown that these parameters can be controlled by adjusting the gas pressure, magnetic fields, and/or microwave power. Such a plasma could be useful in plasma processing and in background plasma for the concept of plasma-based particle accelerators as well.
Temperature and bias dependence of dynamic conductance—low resistive magnetic tunnel junctions
Authors: Oliver Bryan , Nowak Janusz
Published: December 2003

I–V curves of magnetic tunnel junctions were measured in a temperature range of 5–305 K. Effective barrier parameters were estimated by fitting the dynamical conductance G(V) with the Brinkman–Dynes–Rowell model and fitting the temperature dependence of zero-bias conductance G(T) with the Stratton model. A large discrepancy was discovered when comparing barrier parameters predicted by the two models. The inconsistency between the models can be explained by the presence of an inelastic, spin-independent conductance that is strongly dependent on both temperature and voltage as described by Glazman–Matveev theory of electron hopping. This additional hopping conductance helps explain the observed temperature dependence and bias dependence of magnetic tunnel junction conductance.
Effect of grain size on electric resistivity and thermopower of (Ca2.6Bi0.4)Co4O9 thin films
Authors: Zhou Yuqin , Matsubara Ichiro , Shin Woosuck , Izu Noriya , Murayama Norimitsu
Published: December 2003

( Ca 2.6 Bi 0.4 ) Co 4 O 9 thin films were deposited on MgO single crystal substrates by the spin coating method. Films with different grain sizes (50–500 nm) were obtained by preparing at different temperatures. Films were polycrystalline in nature and oriented preferentially in the (001) direction. Electrical resistivity and thermopower were measured to study the effect of the grain size on the thermoelectric properties. Hall carrier concentrations of the films are dependent on the grain size. The film with a smaller grain size has a lower carrier concentration, a larger resistivity, and a higher thermopower. The thermoelectric power factor is related to the grain size and shows a maximum for the film with grain size of about 100 nm.
Stress, texture, and microstructure in niobium thin films sputter deposited onto amorphous substrates
Authors: Okolo B. , Lamparter P. , Welzel U. , Mittemeijer E. J.
Published: December 2003

Nb films with thicknesses 5, 20, 100, and 500 nm were deposited by magnetron sputtering onto Si wafers covered with amorphous layers of SiO2 and Si3N4. The substrates were used in the as-received and sputter cleaned conditions. Various methods were applied for an extensive investigation of the physical properties of the Nb films: they were analyzed with respect to morphology (by focused ion beam imaging and by atomic force microscopy), chemical composition (by x-ray photoelectron spectroscopy sputter depth profiling and by x-ray reflectometry) and texture, (macro) stress and microstrain (by x-ray diffraction methods). An explanation for the strong dependence of the sharpness of the dominant {110} fiber texture in the Nb films on the type of substrate, the cleaning conditions, and the film thickness is presented. X-ray diffraction stress analysis revealed strong compressive stress parallel to the surface of the order of a few gigapascal within a layer close to the film surface. This was ascribed to the formation of oxides at the boundaries of the columnar grains after exposure of the films to air. By grazing incidence x-ray diffraction the existence of a stress gradient in the Nb films was confirmed. The growth stress and the microstrain, determined by line profile analysis, could be correlated with the sharpness of the texture of the Nb films.
Theoretical phonon thermal conductivity of Si/Ge superlattice nanowires
Authors: Dames C. , Chen G.
Published: December 2003

An incoherent particle model has been developed to calculate the phonon thermal conductivity of superlattice nanowires. This is an extension of the photon net-radiation method and Schuster–Schwarzschild approximation to dispersive acoustic phonons in a gray medium. By comparing the roughness and geometric variations of typical nanowires to the characteristic phonon wavelength (∼1 nm at 300 K), diffuse scattering and incoherent three-dimensional dispersion are justified. An isotropic sine-type (Born–von Karman) dispersion is used, which requires only the sound velocity, atomic number density, and bulk conductivity to fully describe a material. A simple picture is also given in terms of Matthiessen’s rule and three effective mean free paths. Agreement with available experimental data is poor at the smallest diameters, but good above 30 nm diameter. Compared to a conventional superlattice, calculations show that the additional sidewall scattering in a superlattice nanowire can reduce the thermal conductivity by a factor of 2 or more.
Atomistic model of limited-thickness Si(001) epitaxy at low temperatures
Authors: Shintani K. , Nakajima T. , Kameoka S.
Published: December 2003

Limited-thickness homoepitaxial growth on a Si(001) surface at low temperatures is investigated by using the classical molecular-dynamics method with the Stillinger-Weber potential. The simulation begins with preliminary equilibration of the substrate at a specified temperature. 256 silicon atoms with the energy of 0.2 eV are then deposited one by one on the substrate. The simulations are performed at the temperatures 300, 500, 700, and 1000 K. At 300 and 500 K, the initial three or four monolayers grow epitaxially, and the subsequent layers form amorphouslike structures. At 700 and 1000 K, the deposited atoms form epitaxial structures throughout the simulation. In the epitaxial growth mode, 2×1 dimer rows are observed to align along alternately perpendicular 〈110〉 directions in successive atomic layers. Tracking a few atoms on the substrate surface reveals that these transient anisotropic surface structures are created by the breaking and reconstruction of dimers due to the impingement of deposited atoms even if the diffusion length of the adatoms is small. We conclude that breakdown of epitaxy occurs when such renewal of surface dimers ceases to be repeated.
Hydrogen isotope exchange and the surface barrier in p-type gallium nitride
Authors: Myers S. M. , Seager C. H.
Published: December 2003

Fourier-transform infrared spectroscopy was used to examine the replacement of one H isotope by another within p-type, Mg-doped GaN during heating in H2 gas at 700 °C. A central objective was further mechanistic understanding of the surface-barrier effect that has previously been shown to limit H release during postgrowth thermal activation of H-passivated Mg acceptors. Ambient H21 or H22 was found to accelerate the removal of the other isotope by orders of magnitude, consistent with recombinative desorption of H2 being rate limiting. The results agree closely with a predictive model describing the interrelated behaviors of H within the semiconductor and on the surface. The saturation concentration of H decreased during the heat treatments, presumably indicating a reduction in the effective level of p-type doping, which is provisionally ascribed to compensation by N vacancies.
Magneto-optical properties of Fe/Cr/Fe/MgO/Fe structures epitaxially grown on GaAs(001)
Authors: Przybylski M. , Grabowski J. , Wulfhekel W. , Rams M. , Tomala K. , Kirschner J.
Published: December 2003

Fe/Cr/Fe trilayers were epitaxially grown on atomically flat GaAs(001). For the thickness of Cr spacer layer corresponding to antiferromagnetic coupling, “reversed” minor hysteresis loops were measured with longitudinal magneto-optical Kerr effect (MOKE), i.e., a negative “magnetization” signal was detected when the thicker bottom Fe layer was saturated along the applied field. This behavior is interpreted by depth variations of the MOKE sensitivity. Magnetization reversal shows that both antiferromagnetic switching and spin–flop transition fields depend on the ratio of both Fe film thicknesses. The shape of the MOKE loops becomes more complex with further deposition of MgO and Fe layers on the top of the Fe/Cr/F/GaAs(001) stack. Superconducting quantum interference device measurements confirm the interpretation of the MOKE loops and demonstrate homogeneity and sharpness of the interfaces in the structures.
Stress effects in sol-gel derived ferroelectric thin films
Authors: Lian L. , Sottos N. R.
Published: December 2003

Residual stress development during processing of sol-gel derived ferroelectric thin films influences electromechanical properties and performance. The present work investigates the effects of stress on field-induced polarization switching in ferroelectric Pb(Zr0.52Ti0.48)O3 (PZT) (52/48) thin films. Film response is measured as a function of externally applied mechanical stress using a double-beam laser-Doppler heterodyne interferometer. This apparatus successfully eliminates any displacement contribution from flexural vibration of the substrate and enables measurement of the strain-electric field hysteresis loops as a function of applied stress. The field-induced strain in the PZT film increases with increasing compressive stress, while the opposite trend is observed for applied tensile stress. The dependence of electromechanical response on the external stress is attributed to the initial tensile residual stress state in the film. Tensile stress creates an in-plane clamping effect on the domains in the film, hindering polarization switching. The application of a compressive stress reduces tensile residual stress in the film and the constraint on the domains, leading to higher field-induced strains. Applied tensile stress amplifies the clamping effect, leading to lower field-induced strains.
Thermal conductivity of SiC fine particles reinforced Al alloy matrix composite with dispersed particle size
Authors: Xu Yibin , Tanaka Yoshihisa , Goto Masahiro , Zhou You , Yagi Koichi
Published: December 2003

The thermal conductivity of 10, 20, 30, and 40 vol % silicon-carbide-particulate-reinforced aluminum matrix composite was determined as a function of the volume fraction of SiC. The microstructures of the composites were examined with a scanning electron microscope. The size distributions of SiC particles were obtained by analyzing the micrographs. The interfacial thermal conductance was calculated with consideration of the particle size distribution. Both the thermal conductivity and interfacial thermal conductance decreased as the volume fraction of SiC increased.
Magnetic properties of PbFe2/3W1/3O3-PbTiO3 solid solutions
Authors: Mitoseriu Liliana , Marré Daniele , Siri Antonio Sergio , Nanni Paolo
Published: December 2003

The magnetic properties of the ferroic (1−x)PbFe2/3W1/3O3–xPbTiO3 system with various compositions in the range x∈(0,0.50) were investigated. A magnetodielectric coupling is proved by an anomaly of the magnetic hysteresis loop found in the Curie range of temperatures for the relaxor PbFe2/3W1/3O3 ceramic. Two types of superexchange magnetic interactions and a succession of magnetic transitions with Néel temperatures dependent on the composition were found in the system. The present results confirm the hypothesis of a relationship between the magnetic properties and the nanopolar ordering in the relaxor–ferroelectric system.
Surface photovoltage effect and its time dependence in GaAs–GaAsP superlattice studied with combination of synchrotron and laser radiation
Authors: Tanaka S. , Nishitani T. , Nakanishi T. , Moré S. D. , Azuma J. , Takahashi K. , Watanabe O. , Kamada M.
Published: December 2003

The surface photovoltage (SPV) effect and its temporal profiles in a GaAs–GaAsP superlattice (SL) were measured by core-level photoelectron spectroscopy with the combination of synchrotron radiation and laser. It was found that the SPV effect in the SL is remarkably suppressed as compared with that in a bulk GaAs. The difference in the temporal profile of the SPV between SL and bulk samples was observed in microsecond range. The suppression of the SPV effect in the negative electron affinity surfaces of the SL was also observed. It is concluded that the SL with a high-doping surface layer is suitable for the spin-polarized electron source without the SPV effect.
Nanostructural zinc oxide and its electrical and optical properties
Authors: Xu C. X. , Sun X. W. , Chen B. J. , Shum P. , Li S. , Hu X.
Published: December 2003

Nanostructural zinc oxide fibers have been fabricated by a simple vapor transport method of heating the mixture of zinc oxide, gallium oxide, and carbon powders in air. The zinc oxide nanofibers showed cauliflower-like, disordered, vertically and horizontally aligned morphologies in different temperature regions. The aligned nanofibers were composed of hexagonal zinc oxide with good crystallinity. Gallium was doped into zinc oxide with a concentration of 0.73 at. %. The growth process and the characteristics can be interpreted by a vapor-liquid-solid mechanism. The field emission of the vertically aligned zinc oxide fiber array showed a low field emission threshold, high current density, rapid surge, and high field enhancement factor. The threshold electric field is about 2.4 V/μm at a current density of 0.1 μA/cm−2. The field enhancement factor was 2991. The emission current density and the electric field followed the Fowler–Nordheim relationship.
Effects of annealing on the color, absorption spectra, and light yield of Ce:YAlO3 single crystal grown by the temperature gradient technique
Authors: Zeng Xionghui , Zhao Guangjun , Xu Jun , He Xiaoming
Published: December 2003

YAlO 3 single crystal doped with Ce3+ at concentration 1% was grown by the temperature gradient technique. The as-grown crystal was pink. After H2 annealing or air annealing at 1400 °C for 20 h, the crystal was turned into colorless. We concluded there were two kinds of color centers in the as-grown crystal. One is F+ center attributed to absorption band peaking at about 530 nm, the other is O− center attributed to absorption band peaking at about 390 nm. This color centers model can be applied in explaining the experiment phenomena including the color changes, the absorption spectra changes, and the light yield changes of Ce:YAP crystals before and after annealing.
Brightness of carbon nanotube electron sources
Authors: de Jonge Niels
Published: December 2003

The virtual source sizes of individual multiwalled carbon nanotube electron emitters were investigated with a point projection microscope. The average radius of the virtual source size was found to be 2.6 nm, which does not correspond to the standard model of a field emitter. Instead, a model based on a flattened cap or an open cap seems to provide a more realistic description. The broadening effect of Coulomb interactions on the virtual source was calculated. The reduced angular current density was measured at the maximum current at which stable emission was obtained and arrived at an average of 30 nA sr−1 V−1. The reduced brightness values obtained for two emitters were (2.5±1)×109 and (1.3±0.5)×109 A m−2 sr−1 V−1, respectively. These values are an order of magnitude larger than the values of state-of-the-art commercial sources.