bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical and experimental investigation on self-terminating and recombination lasers in univalent ions of calcium and strontium
Authors: Pan Bai-Liang , Chen Gang , Chen Xing , Yao Zhi-Xin
Published: June 2004

A concise computer model has been developed to simulate the plasma kinetics of the self-terminating and recombination lasers in single strontium ions excited by longitudinal pulsed discharge. The results predicted by the model indicate that the univalent ions of calcium and strontium are the ideal lasing substances both for self-terminating laser and recombination laser. With the improvement of the discharge circuit, the structure of the laser cavity, and the discharge tube, the alternate oscillations of the two class lasers were successively realized by longitudinal pulsed discharge in mixture vapors of helium and single strontium or calcium ions. The dependence of laser performance on working parameters, together with the characteristics of the photoelectric pulse waveforms, were measured and analyzed.
Effect of La, B doping on the electrical resistivity and magnetic susceptibility of nanocrystalline vanadium nitride
Authors: Sudhakar N. , Ningthoujam R. S. , Rajeev K. P. , Nigam A. K. , Weissmüller J. , Gajbhiye N. S.
Published: June 2004

High resolution electrical resistivity and magnetic susceptibility measurements on nanocrystalline VN samples doped with 0.2 at. % B and La, and 0.5 at. % B and La (crystallite size ∼6–11 nm) were done to study their normal state and superconducting properties. We analyze the resistivity data in the light of the existing theoretical framework. The resistivity of the former sample follows a Tn behavior at low temperature with n≈4 suggesting that electron-phonon scattering play a significant role in determining the low temperature normal state resistivity. While the latter follows a more complicated behavior with a negative temperature coefficient of resistivity indicating that electron-electron scattering in addition to disorder enhanced electron interaction determine the normal state resistivity. We observe that the system is driven towards a disordered state with increasing doping levels of B and La. The superconducting transition is found in the electrical resistivity and magnetic susceptibility studies. The susceptibility follows a Curie-like behavior above the superconducting transition temperature (Tc).
Epitaxial growth of pentacene films on Cu(110)
Authors: Söhnchen S. , Lukas S. , Witte G.
Published: June 2004

The molecular structure of thin pentacene (C22H14) films grown on a Cu(110) surface has been studied by means of He atom scattering, low energy electron diffraction, thermal desorption spectroscopy, x-ray photoelectron spectroscopy, and x-ray absorption spectroscopy. Depending on the actual film thickness three different crystalline phases have been identified which reveal a characteristic reorientation of the molecular plane relative to the substrate surface. In the monolayer regime the molecules form a highly ordered commensurate (6.5×2) structure with a planar adsorption geometry. For thin multilayers (thickness <2 nm) a second phase is observed which is characterized by a lateral (−0.65 5.69  1.90 1.37) structure and a tilting of the molecular plane of about 28° around their long axis which remains parallel to the surface. Finally, when exceeding a thickness of about 2 nm subsequent growth proceeds with an upright molecular orientation and leads to the formation of crystalline films which are epitaxially oriented with respect to the substrate. The present study thus demonstrates that also on metal substrates highly ordered pentacene films with an upright orientation of the molecular planes can be grown. Photoelectron spectroscopy data indicate further that thick films do not grow in a layer-by-layer mode but reveal a significant degree of roughness.
Modeling diffusion in miscible polymer blend films
Authors: Indrakanti Ananth , Ramesh Narayan , Duda J. Larry , Kumar Sanat K.
Published: June 2004

Recent experiments designed to probe polymer transport in the bulk and in the vicinity of surfaces have examined the interdiffusion of multilayer sandwiches of isotopically labeled polymers. The measured time dependent concentration profiles normal to the surface are typically fit to Fick’s law, with a single fitting parameter, the mutual binary diffusion coefficient (MBDC). The resulting MBDCs are found to vary over a broad range of film thicknesses and time, with the time dependence being viewed as a unique signature of the reptation mechanism of long chain motion, and the thickness dependence being attributed to the slowing down of chain dynamics near surfaces. Since the experiments are conducted at finite concentration, the MBDC, which is a product of the bare mobility and the concentration derivative of the chemical potential, could be dominated by the time and thickness dependence of this second term (which is ignored in Fick’s law). To quantify this conjecture we consider the more rigorous Cahn formulation of the diffusion problem in terms of chemical potential gradients. We use square gradient theory to evaluate chemical potentials, and fit the resulting time dependent concentration profiles to the analytical solution of Fick’s law. By thus mimicking the experimental analysis we find that the apparent MBDCs vary with time as t−1/2 at short times, in good agreement with existing experiments. We show that this time dependence reflects the system’s desire to minimize concentration gradients, a fact ignored in Fick’s law. Since these arguments make no reference to the mechanism of chain motion, we argue that the time dependence of MBDC derived from interdiffusion experiments does not provide unequivocal support for the reptation mechanism of long chain transport. The MBDC values, which also vary with the degree of confinement, are predicted to increase with decreasing thickness for model parameters corresponding to experimental systems. In contrast, since the experimental fits yield an opposite trend, we suggest that the bare mobility of the chains decreases strongly with decreasing thickness. These findings strongly support the idea that the chains are “pinned” irreversibly to the surfaces, in good agreement with other, independent experiments.
Modeling of an induction plasma under transient turbulent flow conditions
Authors: Ye R. , Ishigaki T. , Boulos M. I.
Published: June 2004

A renormalization group (RNG) k-ε turbulence model was employed to investigate the role of turbulence for the transient behavior of the radio frequency induction plasma discharge. Time-dependent conservation equations for the plasma and turbulence under local thermal equilibrium (LTE) conditions were solved numerically in two-dimensional, axisymmetric coordinates. Responses of energy, momentum, and turbulence to steplike and pulsed power changes in an Ar-H2 plasma with a hydrogen volume concentration of 10.9%, and a total gas flow rate of 104.0 slpm were studied. The corresponding Reynolds number at the inlet of the discharge cavity was 2667. The turbulence model was validated qualitatively by comparing the predicted results with experimental observations under pulsed power conditions. It is found the transient behavior of the plasma energy and momentum are mainly governed by radial convection, while that of the turbulence is primarily determined by axial convection. These gave rise to a 5–10 ms delay in the response of the turbulence lagging behind the temperature field, for sudden power changes, under current operating conditions. A comparison between the results predicted using the RNG k-ε turbulence model and those obtained using the laminar model indicates the presence of turbulence leads to a longer relaxation time of plasma. Under pulsed power conditions, the plasma temperature responds to power changes almost instantaneously, and it is always in a transient state. In contrast, variation in the relative turbulent viscosity is insignificant and it is concluded that the turbulence is in a quasisteady state when the period of a pulse is between 10 and 15 ms. By comparing the predicted results with images obtained using a high-speed camera (0.67 ms/frame) under the same operating conditions, we found that the turbulence model predicted a more accurate transient behavior in terms of plasma volume and temperature than the laminar model does.
Radial distribution function analyses of amorphous carbon thin films containing various levels of silicon and hydrogen
Authors: Evans R. D. , Bentley J. , More K. L. , Doll G. L. , Glass J. T.
Published: June 2004

Short-range order in amorphous carbon thin films containing silicon and hydrogen (Si-aC:H) was characterized using radial distribution functions (RDFs). RDFs describe the average number of neighbors located a distance r away from an arbitrary atom in the sample. Two methods in the transmission electron microscope (TEM) were used in this study to obtain RDFs: energy-filtered convergent-beam electron diffraction (EFCBED) and extended electron energy-loss fine structure (EXELFS) analyses. Four Si-aC:H film samples were prepared in cross section for TEM using a focused ion beam system. Both EFCBED and EXELFS techniques were used to study the same samples. RDF interpretation included estimation and comparison of near-neighbor distances, average bond angles, and coordination numbers as a function of sample composition. Key RDF characteristics were correlated to thin film material properties.
Fabrication of focused poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE) copolymer 40–50 MHz ultrasound transducers on curved surfaces
Authors: Robert Michelle , Molingou Gilbert , Snook Kevin , Cannata Jonathan , Shung K. Kirk
Published: June 2004

Copolymer films such as poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE) have lower acoustic impedance compared to their ceramic counterparts, allowing for a better acoustic match to tissues in the human body. Because of this, copolymer ultrasonic transducers are capable of yielding the desirable characteristics of broad bandwidth and short pulse duration that allow better image resolution to be achieved. In the past, such transducers in the frequency range from 40 to 80 MHz have frequently been fabricated by spin coating the copolymer film onto a flat substrate and then applying the film to a curved backing using an adhesive layer. The adhesive layer may cause spurious signals at these frequencies, in addition to the film damage that may occur as a result of such processing. In order to avoid these problems, a copolymer film can be directly spin coated onto a curved substrate. The resulting devices had an operating frequency of over 40 MHz and approximately a 75% bandwidth. The potential of several approaches that could be further explored to increase the level of performance of such devices is also discussed.
Nearest-neighbor distances in strained thin films of random pseudobinary semiconductor alloys: A calculational methodology
Authors: d’Acapito F.
Published: June 2004

A method, based on macroscopic elastic theory, is presented, which predicts the nearest-neighbor distances in strained pseudobinary semiconductor thin films. The method applies to films grown on the (001) face of substrates with the zincblende or diamond structure. Based on crystallographic and elastic parameters, the bond lengths are determined through minimization of the elastic energy calculated in the framework of the valence force field method. Good agreement with experimental data is obtained by considering only bond stretching terms. The effectiveness of this method is shown in a number of cases taken from literature.
Fabrication and characterization of single-grain organic field-effect transistor of pentacene
Authors: Minari Takeo , Nemoto Takashi , Isoda Seiji
Published: June 2004

A single-grain pentacene field-effect transistor with ordinary top-contact structure is fabricated, and its electrical properties are characterized at various temperatures. The device exhibits field-effect mobility as high as 2 cm2/V s at 300 K, although mobility is dependent on gate voltage. This value for field-effect mobility is about one order of magnitude higher than that of a polycrystalline device made from the same pentacene film. The activation energy obtained from an Arrhenius plot of mobility is nearly constant with varying gate voltage, whereas the activation energy of the polycrystalline device decreases as gate voltage increases. Such behavior of the activation energy suggests that intrinsic carrier transport in an organic grain can be described by thermally activated hopping of molecular polarons while extrinsic transport across grain boundaries can be described by the trap model.
Transparent conducting Zn1−xMgxO:(Al,In) thin films
Authors: Cohen D. J. , Ruthe K. C. , Barnett S. A.
Published: June 2004

Zn 1−x Mg x O:Al thin films have been grown epitaxially on c-plane sapphire substrates by direct current reactive magnetron sputtering. Structural evaluation indicated that the ZnMgO films had similar crystalline perfection as ZnO films grown under similar conditions. Postdeposition annealing with in situ In doping was done at 415 °C for 4 h in H2/Ar mixtures, resulting in improved electrical properties. Increasing the Mg content from 0 to 20 at. % increased the band gap but decreased the conductivity, mobility, and electron density in annealed films. The decrease in mobility was explained by a combination of increasing electron effective mass and alloy disorder scattering. Increasing the Al dopant content in ZnMgO had similar effects as in pure ZnO, increasing the carrier density and optical band gap but decreasing the mobility. Band gaps of 3.76 eV were achieved in the Zn0.8Mg0.2O:(Al,In) films with a corresponding resistivity of 2×10−2 Ω cm, a carrier concentration of 4×1019 cm−3, and a mobility of 7 cm2/V s.
Electron transport mechanisms in thin boron-doped diamond films
Authors: Yater J. E. , Shih A. , Butler J. E. , Pehrsson P. E.
Published: June 2004

Electron transmission spectroscopy is used to examine the effect of transport distance, diamond nanostructure, and electron affinity on the cold emission characteristics of thin nanocrystalline diamond films. Energy distribution and intensity measurements are taken from films having different thicknesses (∼0.15, 2, and 4 μm) and surface properties (hydrogenated, cesiated), and two distinct transmission regimes are identified that exhibit fundamentally different characteristics. In measurements taken at sufficiently high beam energy Eo, electrons are transported through the conduction band of the diamond and emitted at a low-affinity surface, with transmission yields generally greater than 1. In this regime, the dependence on Eo results from the finite escape depth of the conduction-band electrons, which is determined to be ∼1 μm for these films based on a Monte Carlo analysis of the incident electron range. In measurements taken at lower values of Eo, electrons are generated outside of this escape range and are unable to reach the surface via conduction-band transport. In this regime, the transmission data are dominated by a much broader, low-intensity distribution, and the transmission yields are substantially lower than 1. The transmission is furthermore completely insensitive to changes in the surface properties of the diamond. Based on the nanostructure of the films, electrons are most likely transported along grain boundaries that propagate through the films.
Three-dimensional effects for two-dimensional samples in plasma immersion ion implantation
Authors: Manova D. , Neumann H. , Mändl S. , Rauschenbach B.
Published: June 2004

Plasma immersion ion implantation is a fast method for ion implantation into complex-shaped three-dimensional objects as the ions are accelerated from the receding plasma sheath edge towards the substrate during the negative high-voltage pulses. Except for the region near the edges, homogeneous implantation can be obtained for the surface of flat samples. Here, it is shown that a much larger absolute dose and a much larger dose variation is observed on the back side of rectangular stainless steel samples—resulting in highly localized corrosion—due to the interference of the supporting rod connected to the high voltage-feed through.
General equivalent circuit for intermediate band devices: Potentials, currents and electroluminescence
Authors: Luque A. , Martı́ A. , Stanley C. , López N. , Cuadra L. , Zhou D. , Pearson J. L. , McKee A.
Published: June 2004

A general model to describe the operation of intermediate band solar cells (IBSCs), incorporating a significant number of physical effects such as radiative coupling between bands, and impact ionization and Auger recombination mechanisms, is presented in equivalent circuit form. The model is applied to IBSC prototypes fabricated from InAs quantum dots structures to determine the value of the circuit elements involved. The analysis shows evidence of splitting between the conduction and intermediate band quasi-Fermi levels, one of the fundamental working hypotheses on which operation of the IBSC depends. The model is also used to discuss the limitations and potential of this type of cell.
Mechanism of bending electrostriction in thermoplastic polyurethane
Authors: Zhou Y. , Wong Y. W. , Shin F. G.
Published: June 2004

The mechanism of bending electrostriction in polyurethane films is discussed and elucidated through a numerical calculation. The simulations are carried out on a model in which charge carriers are assumed to be electrons injected from the cathode by the Schottky effect, and the positive charges are immobile. Under a dc field, our simulation results show that the electrons go out of the anode, leaving behind a large quantity of positive charge around the anode. As a result, the electric field near the anode eventually becomes much larger than that near the cathode. The asymmetrical electric field distribution leads to an asymmetrical stress distribution through the electrostriction effect and thus to bending of the polyurethane film under the application of a dc electric field. The results can also explain the gradual change in bending direction after reversing the polarity of the electric field.
Effects of FeCl3 doping on polymer-based thin film transistors
Authors: Chen Y. , Shih I. , Xiao S.
Published: June 2004

Polymer-based thin film transistors (PTFTs) were fabricated on glass substrates with anodized Al2O3 as gate insulators. RR-P3HT (regioregular poly–3-hexylthiophene) and MEH-PPV [poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene)] were respectively used as semiconducting active layers for the transistors. A two orders of magnitude increase in field effect mobility (from 7.2×10−4 cm2/V s to 7.4×10−2 cm2/V s) deduced from electrical data of transistors fabricated using FeCl3 doped RR-P3HT was observed. This increase is believed to be mainly due to a large reduction in contact resistance (from 108 Ω to 103 Ω) to the source and drain Au contacts. The conductivity of RR-P3HT was found to increase only slightly with the doping. For MEH-PPV, doping with FeCl3 also decreased its contact resistance. However, it (4 GΩ) was still much larger than the channel (polymer) resistance (1 MΩ), leading to a slight improvement in its field effect mobility. Theoretically, contacts between Au and P3HT should have very small energy barrier heights (<0.2 eV) for hole injection. We believe that a negative vacuum level shift introduced by metal to organic interfacial dipoles might be the origin of this large energy barrier, as well as to large contact resistance.
Sb surfactant effect on GaInAs/GaAs highly strained quantum well lasers emitting at 1200 nm range grown by molecular beam epitaxy
Authors: Kageyama Takeo , Miyamoto Tomoyuki , Ohta Masataka , Matsuura Tetsuya , Matsui Yasutaka , Furuhata Tatsuya , Koyama Fumio
Published: June 2004

A surfactant effect of antimony (Sb) on highly strained GaInAs quantum wells (QWs) was studied by molecular beam epitaxy. Noticeable improvement of the photoluminescence (PL) was observed by adding the dilute Sb. The QWs showed an increased PL intensity and narrow linewidth of 23 meV for the wavelength range up to 1180 nm. An atomic force microscope study showed a flattened surface morphology by the introduction of the Sb. Broad-area lasers with a GaInAsSb/GaAs double-QW active layer emitting at 1170 nm showed a low threshold current density of 125 A/cm2 per well for an infinite cavity length.
A regression technique to analyze the second-order nonlinear optical response of thin films
Authors: Siltanen Mikael , Cattaneo Stefano , Vuorimaa Elina , Lemmetyinen Helge , Katz Thomas J. , Phillips Karen E. S. , Kauranen Martti
Published: June 2004

We present a new technique, based on regression analysis, to determine the second-order nonlinear optical susceptibility tensor of thin films. The technique does not require the absolute levels or phases of measured signals to be mutually calibrated. In addition it yields indicators that address the quality of theoretical models describing the sample. We use the technique to determine the susceptibility tensor of samples of a nonracemic chiral material which have very low symmetry (both chiral and anisotropic) and have many independent tensor components. The results show the importance of using detailed theoretical models that account for the linear optical properties of the sample.
Heteroduplex rejection during single-strand annealing requires Sgs1 helicase and mismatch repair proteins Msh2 and Msh6 but not Pms1
Authors: Sugawara Neal , Goldfarb Tamara , Studamire Barbara , Alani Eric , Haber James E.
Published: June 2004

Recombination between moderately divergent DNA sequences is impaired compared with identical sequences. In yeast, an HO endonuclease-induced double-strand break can be repaired by single-strand annealing (SSA) between flanking homologous sequences. A 3% sequence divergence between 205-bp sequences flanking the double-strand break caused a 6-fold reduction in repair compared with identical sequences. This reduction in heteroduplex rejection was suppressed in a mismatch repair-defective
msh6
Δ strain and partially suppressed in an
msh2
separation-of-function mutant. In
mlh1
Δ strains, heteroduplex rejection was greater than in
msh6
Δ strains but less than in wild type. Deleting
PMS1, MLH2
,or
MLH3
had no effect on heteroduplex rejection, but a
pms1
Δ
mlh2
Δ
mlh3
Δ triple mutant resembled
mlh1
Δ. However, correction of the mismatches within heteroduplex SSA intermediates required
PMS1
and
MLH1
to the same extent as
MSH2
and
MSH6
. An SSA competition assay in which either diverged or identical repeats can be used for repair showed that heteroduplex DNA is likely to be unwound rather than degraded. This conclusion is supported by the finding that deleting the
SGS1
helicase also suppressed heteroduplex rejection.
TRPC3 channels confer cellular memory of recent neuromuscular activity
Authors: Rosenberg Paul , Hawkins April , Stiber Jonathan , Shelton John M. , Hutcheson Kelley , Bassel-Duby Rhonda , Shin Dong Min , Yan Zhen , Williams R. Sanders
Published: June 2004

Skeletal muscle adapts to different patterns of motor nerve activity by alterations in gene expression that match specialized properties of contraction, metabolism, and muscle mass to changing work demands (muscle plasticity). Calcineurin, a calcium/calmodulin-dependent, serine–threonine protein phosphatase, has been shown to control programs of gene expression in skeletal muscles, as in other cell types, through the transcription factor nuclear factor of activated T cells (NFAT). This study provides evidence that the function of NFAT as a transcriptional activator is regulated by neuromuscular stimulation in muscles of intact animals and that calcium influx from the transient receptor potential (TRPC3) channel is an important determinant of NFAT activity. Expression of TRPC3 channels in skeletal myocytes is up-regulated by neuromuscular activity in a calcineurin-dependent manner. These data suggest a mechanism for cellular memory in skeletal muscles whereby repeated bouts of contractile activity drive progressively greater remodeling events.
Extracellular ATP induces oscillations of intracellular Ca2+and membrane potential and promotes transcription of IL-6 in macrophages
Authors: Hanley Peter J. , Musset Boris , Renigunta Vijay , Limberg Sven H. , Dalpke Alexander H. , Sus Rainer , Heeg Klaus M. , Preisig-Müller Regina , Daut Jürgen
Published: June 2004

The effects of low concentrations of extracellular ATP on cytosolic Ca2+, membrane potential, and transcription of IL-6 were studied in monocyte-derived human macrophages. During inflammation or infection many cells secrete ATP. We show here that application of 10 μM ATP or 10 μM UTP induces oscillations in cytosolic Ca2+with a frequency of ≈12 min-1and oscillations in membrane potential. RT-PCR analysis showed expression of P2Y1, P2Y2, P2Y11, P2X1, P2X4, and P2X7receptors, large-conductance (KCNMA1andKCNMB1–4), and intermediate-conductance (KCNN4) Ca2+-activated K+channels. The Ca2+oscillations were unchanged after removal of extracellular Ca2+, indicating that they were mainly due to movements of Ca2+between intracellular compartments. Comparison of the effects of different nucleotides suggests that the Ca2+oscillations were elicited by activation of P2Y2receptors coupled to phospholipase C. Patch–clamp experiments showed that ATP induced a transient depolarization, probably mediated by activation of P2X4receptors, followed by membrane potential oscillations due to opening of Ca2+-activated K+channels. We also found that 10 μM ATPγS increased transcription of IL-6 ≈40-fold within 2 h. This effect was abolished by blockade of P2Y receptors with 100 μM suramin. Our results suggest that ATP released from inflamed, damaged, or metabolically impaired cells represents a “danger signal” that plays a major role in activating the innate immune system.
Identification of a domain within the multifunctional
Vibrio cholerae
RTX toxin that covalently cross-links actin
Authors: Sheahan Kerri-Lynn , Cordero Christina L. , Fullner Satchell Karla J.
Published: June 2004

The Gram-negative pathogen
Vibrio cholerae
causes diarrheal disease through the export of enterotoxins. The
V. cholerae
RTX toxin was previously identified and characterized by its ability to round human laryngeal epithelial (HEp-2) cells. Further investigation determined that cell rounding is caused by the depolymerization of actin stress fibers, through the unique mechanism of covalent actin cross-linking. In this study, we identify a domain within the full-length RTX toxin that is capable of mediating the cross-linking reaction when transiently expressed within eukaryotic cells. A structure/function analysis of the actin cross-linking domain (ACD) reveals that a 412-aa, or a 47.8-kDa, region is essential for cross-linking activity. When this domain is deleted from the full-length toxin gene, actin cross-linking, but not cell rounding, is eliminated, indicating that this toxin carries multiple dissociable activities. The ACD shares 59% amino acid identity with a hypothetical protein from
V. cholerae
, VC1416, and transient expression of the C-terminal domain of VC1416 also results in actin cross-linking in eukaryotic cells. The presence of this second ACD linked to an
Rhs
-like element suggests that
V. cholerae
acquired the domain by horizontal gene transfer and the ACD was inserted into the RTX toxin by gene duplication through the evolution of
V. cholerae
.
Binocularity and brain evolution in primates
Authors: Barton R. A.
Published: June 2004

Primates are distinguished by frontally directed, highly convergent orbits, which are associated with stereoscopic vision. Although stereoscopic vision requires specialized neural mechanisms, its implications for brain evolution are unknown. Using phylogenetic comparative analysis, I show that evolutionary increases among primate taxa in the degree of orbital convergence correlate with expansion of visual brain structures and, as a consequence, with the overall size of the brain. This pattern is found across the whole primate order and is also repeated within each of the two major primate subtaxa. The visual expansion associated with increased binocularity is specific to the parvocellular visual pathway, consistent with recent evidence implicating this pathway in fine-grained stereopsis. The results support the hypothesis that brain size evolution in primates was associated with visual specialization.
A chlamydial type III translocated protein is tyrosine-phosphorylated at the site of entry and associated with recruitment of actin
Authors: Clifton D. R. , Fields K. A. , Grieshaber S. S. , Dooley C. A. , Fischer E. R. , Mead D. J. , Carabeo R. A. , Hackstadt T.
Published: June 2004

The obligate intracellular bacteriumChlamydia trachomatisrapidly induces its own entry into host cells. Initial attachment is mediated by electrostatic interactions to heparan sulfate moieties on the host cell, followed by irreversible binding to an unknown secondary receptor. This secondary binding leads to the recruitment of actin to the site of attachment, formation of an actin-rich, pedestallike structure, and finally internalization of the bacteria. How chlamydiae induce this process is unknown. We have identified a high-molecular-mass tyrosine-phosphorylated protein that is rapidly phosphorylated on attachment to the host cell. Immunoelectron microscopy studies revealed that this tyrosine-phosphorylated protein is localized to the cytoplasmic face of the plasma membrane at the site of attachment of surface-associated chlamydiae. The phosphoprotein was isolated by immunoprecipitation with the antiphosphotyrosine antibody 4G10 and identified as the chlamydial protein CT456, a hypothetical protein with unknown function. The chlamydial protein (Tarp) appears to be translocated into the host cell by type III secretion because it is exported in aYersiniaheterologous expression assay. Phosphotyrosine signaling across the plasma membrane preceded the recruitment of actin to the site of chlamydial attachment and may represent the initial signal transduced from pathogen to the host cell. These results suggest thatC. trachomatisinternalization is mediated by a chlamydial type III-secreted effector protein.
High-resolution characterization of the pancreatic adenocarcinoma genome
Authors: Aguirre Andrew J. , Brennan Cameron , Bailey Gerald , Sinha Raktim , Feng Bin , Leo Christopher , Zhang Yunyu , Zhang Jean , Gans Joseph D. , Bardeesy Nabeel , Cauwels Craig , Cordon-Cardo Carlos , Redston Mark S. , DePinho Ronald A. , Chin Lynda
Published: June 2004

The pancreatic adenocarcinoma genome harbors multiple amplifications and deletions, pointing to the existence of numerous oncogenes and tumor suppressor genes driving the genesis and progression of this lethal cancer. Here, array comparative genomic hybridization on a cDNA microarray platform and informatics tools have been used to define the copy number alterations in a panel of 24 pancreatic adenocarcinoma cell lines and 13 primary tumor specimens. This high-resolution genomic analysis has identified all known regional gains and losses as well as many previously uncharacterized highly recurrent copy number alterations. A systematic prioritization scheme has selected 64 focal minimal common regions (MCRs) of recurrent copy number change. These MCRs possess a median size of 2.7 megabases (Mb), with 21 (33%) MCRs spanning 1 Mb or less (median of 0.33 Mb) and possessing an average of 15 annotated genes. Furthermore, complementary expression profile analysis of a significant fraction of the genes residing within these 64 prioritized MCRs has enabled the identification of a subset of candidates with statistically significant association between gene dosage and mRNA expression. Thus, the integration of DNA and RNA profiles provides a highly productive entry point for the discovery of genes involved in the pathogenesis of pancreatic adenocarcinoma.
Integration of transcriptomics and metabolomics for understanding of global responses to nutritional stresses in
Arabidopsis thaliana
Authors: Hirai Masami Yokota , Yano Mitsuru , Goodenowe Dayan B. , Kanaya Shigehiko , Kimura Tomoko , Awazuhara Motoko , Arita Masanori , Fujiwara Toru , Saito Kazuki
Published: June 2004

Plant metabolism is a complex set of processes that produce a wide diversity of foods, woods, and medicines. With the genome sequences of
Arabidopsis
and rice in hands, postgenomics studies integrating all “omics” sciences can depict precise pictures of a whole-cellular process. Here, we present, to our knowledge, the first report of investigation for gene-to-metabolite networks regulating sulfur and nitrogen nutrition and secondary metabolism in
Arabidopsis
, with integration of metabolomics and transcriptomics. Transcriptome and metabolome analyses were carried out, respectively, with DNA macroarray and several chemical analytical methods, including ultra high-resolution Fourier transform-ion cyclotron MS. Mathematical analyses, including principal component analysis and batch-learning self-organizing map analysis of transcriptome and metabolome data suggested the presence of general responses to sulfur and nitrogen deficiencies. In addition, specific responses to either sulfur or nitrogen deficiency were observed in several metabolic pathways: in particular, the genes and metabolites involved in glucosinolate metabolism were shown to be coordinately modulated. Understanding such gene-to-metabolite networks in primary and secondary metabolism through integration of transcriptomics and metabolomics can lead to identification of gene function and subsequent improvement of production of useful compounds in plants.
Methionine sulfoxide reductase A is important for lens cell viability and resistance to oxidative stress
Authors: Kantorow Marc , Hawse John R. , Cowell Tracy L. , Benhamed Sonia , Pizarro Gresin O. , Reddy Venkat N. , Hejtmancik J. F.
Published: June 2004

Age-related cataract, an opacity of the eye lens, is the leading cause of visual impairment in the elderly, the etiology of which is related to oxidative stress damage. Oxidation of methionine to methionine sulfoxide is a major oxidative stress product that reaches levels as high as 60% in cataract while being essentially absent from clear lenses. Methionine oxidation results in loss of protein function that can be reversed through the action of methionine sulfoxide reductase A (MsrA), which is implicated in oxidative stress protection and is an essential regulator of longevity in species ranging from
Escherichia coli
to mice. To establish a role for MsrA in lens protection against oxidative stress, we have examined the levels and spatial expression patterns of MsrA in the human lens and have tested the ability of MsrA to protect lens cells directly against oxidative stress. In the present report, we establish that MsrA is present throughout the human lens, where it is likely to defend lens cells and their components against methionine oxidation. We demonstrate that overexpression of MsrA protects lens cells against oxidative stress damage, whereas silencing of the MsrA gene renders lens cells more sensitive to oxidative stress damage. We also provide evidence that MsrA is important for lens cell function in the absence of exogenous stress. Collectively, these data implicate MsrA as a key player in lens cell viability and resistance to oxidative stress, a major factor in the etiology of age-related cataract.
BERA at 30. Have we come of age?†
Authors: Furlong John
Published: June 2004

The increasing demand for research‐based evidence in the development of policy and practice presents the research community with new opportunities and challenges. We are still troubled by accusations of poor quality and lack of impact. A national research policy, designed to respond to these criticisms, has emerged recently which promotes a ‘big science’ model of research. This increasingly silences other approaches and opens up unhelpful divisions; a particular problem is the re‐emergence of epistemological divisions—the paradigm wars. A ‘big science’ policy for research is also inappropriate in a world where practitioners increasingly want and need to engage in research themselves as a key strategy in ‘knowledge transfer’. The paper concludes by arguing that we need to defend a rich and diverse range of approaches to research, promoting debate about quality within different sub‐communities and encouraging open discussion across epistemological and methodological boundaries.
Reasoning as a scientist: ways of helping children to use language to learn science
Authors: Mercer Neil , Dawes Lyn , Wegerif Rupert , Sams Claire
Published: June 2004

Sociocultural researchers have claimed that students' learning of science is a discursive process, with scientific concepts and ways of reasoning being learned through engagement in practical enquiry and social interaction as well as individualized activity. It is also often claimed that interacting with partners while carrying out scientific investigations is beneficial to students' learning and the development of their understanding. The research we describe investigated the validity of these claims and explored their educational implications. An experimental teaching programme was designed to enable children in British primary schools to talk and reason together and to apply these skills in their study of science. The results obtained indicate that (a) children can be enabled to use talk more effectively as a tool for reasoning and (b) talk‐based activities can have a useful function in scaffolding the development of reasoning and scientific understanding. The implications of the findings for educational policy and practice are discussed.
Theorising how student teachers form their identities in initial teacher education
Authors: Atkinson Dennis
Published: June 2004

This article investigates the forming of student teacher identities in initial teacher education. By analysing student narratives of school experiences the article argues that although reflective, reflexive and critical discourses are helpful interrogatory tools, they presuppose a prior subjectivity which fails to acknowledge the idea that it is through such discursive practices that subjectivity emerges. Such discourses also suggest an emancipatory project grounded in rationality. The article demonstrates that these reflective discourses fail to take into account non‐symbolizable and non‐rational aspects of experiencing that have powerful ontological effects on subjectivity and identity. Such aspects are structured in student narratives through fantasy, which allows students to understand their experiences as consistent and meaningful.
Interactive whole class teaching in the National Literacy and Numercy Strategies
Authors: Smith Fay , Hardman Frank , Wall Kate , Mroz Maria
Published: June 2004

The study set out to investigate the impact of the official endorsement of ‘interactive whole class teaching’ on the interaction and discourse styles of primary teachers while teaching the National Literacy and Numeracy Strategies. In both strategies, interactive whole class teaching is seen as an ‘active teaching’ model promoting high quality dialogue and discussion between teachers and pupils. Pupils are expected to play an active part in discussion by asking questions, contributing ideas and explaining and demonstrating their thinking to the class. Using computerized systematic classroom observation, discourse analysis of transcripts and a questionnaire, the project looked specifically at the discourse strategies currently used by a national sample of primary teachers when teaching the literacy and numeracy strategies and their perceptions of current practices. The findings suggest that traditional patterns of whole class interaction have not been dramatically transformed by the strategies. The implications of the findings for classroom pedagogy, teachers' professional development and future research priorities are considered.
The emotional impact of performance‐related pay on teachers in England
Authors: Mahony Pat , Menter Ian , Hextall Ian
Published: June 2004

This article reports on the emotional impact of Threshold Assessment on teachers and schools. Using data from an ESRC funded project, ‘The impact of Performance Threshold Assessment on teachers’ work' (ESRC R000239286), we seek to contribute to a growing literature on teachers' emotions by sharing some of the insights gained from 76 interviews undertaken in nine case study primary and secondary schools between 2001–2003. The research has revealed a number of (apparently) unintended consequences of Threshold Assessment as well as considerable variability of experience. We underline the significance of contextual factors in the way that the policy was handled in schools and in the degrees of vulnerability and exposure experienced by teachers as they struggled to come to terms with the demands of ‘performativity’.

…social policy needs a subject in which mind and body, reason and passion, self and other, agent and object are held simultaneously in mind without splitting one from the other. (Hoggett, 2000a, p. 143)
Making the case for the BRAT (British Regiment Attached Traveller)
Authors: Clifton Grace
Published: June 2004

Military brats and other global nomads (Book 1) M. G. Ender (Ed.), 2002

The military family (Book 2) J. A. Martin, L. N. Rosen & L. R. Sparacino (Eds), 2000

The military child—mobility and education (Book 3) M. M. Keller & G. T. Decoteau, 2000
Endovascular treatment of venous malformations in extremities: results of sclerotherapy and the quality of life after treatment
Authors: Rautio R. , Saarinen J. , Laranne J. , Salenius J.‐P. , Keski‐Nisula L.
Published: June 2004

Purpose: To evaluate the long‐term results of endovascular sclerotherapy in treating venous extremity malformations and to assess the quality of life after treatment.

Material and Methods: Twenty‐four patients were included who had completed treatment with ethanol sclerotherapy and a minimum of one year observation period. Nineteen patients attended a clinical control. To evaluate the quality of life after treatment, 23 patients filled in a questionnaire which included 20 multiple‐choice questions exploring four dimensions: psychological, physical and social functioning, and pain.

Results: At the clinical control seven patients had no clinical symptoms related to the malformation, six had slight, four moderate, and two severe symptoms. In 16 patients the symptoms had diminished after treatment. No deterioration of the initial situation was observed. The results concerning quality of life showed that most patients did well after endovascular treatment. Pain was the most important injurious factor for state of health among the four different dimensions. The poorest outcome was found in malformations that filled the whole muscle or muscle compartment and in larger lesions. The patients whose malformation at the clinical control caused swelling to the extremity affected had poorer quality indices than others.

Conclusion: Endovascular treatment for venous malformations is an effective treatment.
Diabetic retinopathy: sonographically measured hemodynamic alterations in ocular, carotid, and vertebral arteries
Authors: Päivänsalo M. , Pelkonen O. , Rajala U. , Keinanen‐Kiukaanniemi S. , Suramo I.
Published: June 2004

Purpose: To compare local ophthalmic blood flow changes with flow changes in carotid and vertebral arteries in diabetic patients with retinopathy of different grades.

Material and Methods: Ten patients with proliferative or preproliferative retinopathy, 10 with mild retinopathy, and 10 matched controls were prospectively studied with ultrasound. Color and duplex Doppler imaging was used to quantitate blood flow in the central retinal arteries (CRA), ophthalmic arteries (OA), common carotid (CCA) and vertebral arteries (VA). Peak systolic velocity (PSV), mean velocity (MV), and resistance index (RI) in CRA, OA, CCA and VA, and volume flow (VF) were measured in CCA and VA.

Results: There was a non‐significant increase in the CRA and OA velocities in mild retinopathies, a decrease of about 30% in MV, and a slightly increased RI in proliferative or preproliferative retinopathies. There was a decrease of about 15% in the carotid MV and a 20% decrease in the vertebral MV and a decrease of about 30% in VF in the CCA and VA in severe retinopathies. The MV ratio of CRA/CCA was lower in the severe retinopathy group than in the controls.

Conclusion: The study showed a non‐significant increase of ocular blood flow velocities in mild diabetic retinopathy and a significant decrease of flow velocities in severe diabetic retinopathy. This decrease in flow primarily seems to reflect the general decrease of blood flow in the cervical arteries.
Can computed tomography scout radiography replace plain film in the evaluation of patients with acute urinary tract colic?
Authors: Ege G. , Akman H. , Kuzucu K. , Yildiz S.
Published: June 2004

Purpose: To determine the sensitivity of computed tomography (CT) scout view in detecting ureteral stones and whether CT scout radiography can replace plain film in the evaluation of patients with acute urinary tract colic.

Material and Methods: Between January 2000 and 2002, 110 patients with ureterolithiasis were prospectively evaluated for the detection of ureteral stones on CT scout radiographs. The findings were compared with those of plain films. All patients were examined with plain film, CT scout radiography, and unenhanced helical CT. CT scans were performed within 24 h of plain films. Each CT scout radiograph was interpreted without knowledge of the findings on plain film.

Results: 111 stones were detected by unenhanced helical CT. Mean stone size was 3.9 mm (range 1–10 mm). Of all stones, 57 (52%) were visible on plain film; 44 (40%) were seen on CT radiographs. The sensitivity of 79 small stones (<5 mm) on CT scout radiography was 29% and of abdominal radiography 37%. For 32 big stones (>5 mm), the sensitivity of CT scout radiography was 66% and of abdominal radiography 87.5%.

Conclusion: In this study, plain film was more sensitive than CT scout radiography in revealing ureteral calculi. However, the detection of stones 5 mm or larger had a sensitivity of 66% on CT scout radiographs; 77% (44/57) of the stones visible on plain films were also seen on CT scout radiographs. We therefore believe that CT scout radiography can be used as a baseline study in most patients with big ureteral stones.
Magnetic resonance imaging of the rotator cuff in destroyed rheumatoid shoulder: comparison with findings during shoulder replacement
Authors: Soini I. , Belt E. A. , Niemitukia L. , Mäenpää H. M. , Kautiainen H. J.
Published: June 2004

Purpose: To evaluate the predictive value of preoperative magnetic resonance imaging (MRI) with respect to rotator cuff ruptures.

Material and Methods: Thirty‐one patients with rheumatic disease underwent preoperative MRI before shoulder arthroplasty. The scans were reviewed independently by two experienced radiologists. Three surgeons performed all the replacements (hemiarthroplasties), and the condition of the rotator cuff was assessed. Complete and massive tears of the rotator cuff were recorded and compared at surgery and on MRI.

Results: With MRI, 21 shoulders (68%) were classified as having complete or massive tears of the rotator cuff and at surgery 14 shoulders (45%). Cohen's kappa coefficient was 0.44 (95% CI: 0.16 to 0.72) and accuracy 0.71 (95% CI: 0.52 to 0.86).

Conclusion: In severely destroyed rheumatoid shoulder, the findings of soft tissues were incoherent both with MRI and at surgery. The integrity of tendons could not readily be elucidated with MRI because of an inflammatory process and scarred tissues; in surgery, too, changes were frequently difficult to categorize. Preoperative MRI of severely destroyed rheumatoid shoulder before arthroplasty turned out to be of only minor importance.