bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic profiling of the glucose metabolic network in fasted rat hepatocytes using [1,2-13C2]glucose
Authors: MARIN Silvia , LEE W.-N. Paul , BASSILIAN Sara , LIM Shu , BOROS Laszlo G. , CENTELLES Josep J. , FERNÁNDEZ-NOVELL Josep Maria , GUINOVART Joan J. , CASCANTE Marta
Published: June 2004

Recent studies in metabolic profiling have underscored the importance of the concept of a metabolic network of pathways with special functional characteristics that differ from those of simple reaction sequences. The characterization of metabolic functions requires the simultaneous measurement of substrate fluxes of interconnecting pathways. Here we present a novel stable isotope method by which the forward and reverse fluxes of the futile cycles of the hepatic glucose metabolic network are simultaneously determined. Unlike previous radio-isotope methods, a single tracer [1,2-13C2]D-glucose and mass isotopomer analysis is used. Changes in fluxes of substrate cycles, in response to several gluconeogenic substrates, in isolated fasted hepatocytes from male Wistar rats were measured simultaneously. Incubation with these substrates resulted in a change in glucose-6-phosphatase/glucokinase and glycolytic/gluconeogenic flux ratios. Different net redistributions of intermediates in the glucose network were observed, resulting in distinct metabolic phenotypes of the fasted hepatocytes in response to each substrate condition. Our experimental observations show that the constraints of concentrations of shared intermediates, and enzyme kinetics of intersecting pathways of the metabolic network determine substrate redistribution throughout the network when it is perturbed. These results support the systems-biology notion that network analysis provides an integrated view of the physiological state. Interaction between metabolic intermediates and glycolytic/gluconeogenic pathways is a basic element of cross-talk in hepatocytes, and may explain some of the difficulties in genotype and phenotype correlation.
Identification of a dehydrogenase acting on D-2-hydroxyglutarate
Authors: ACHOURI Younes , NOËL Gaëtane , VERTOMMEN Didier , RIDER Mark H. , VEIGA-DA-CUNHA Maria , van SCHAFTINGEN Emile
Published: June 2004

Extracts of frozen rat liver were found to catalyse the formation of 3H2O from DL-2-hydroxy[2-3H]glutarate. Three peaks of enzyme activities were observed on separation by chromatography on DEAE-Sepharose. The first and second peaks corresponded to an enzyme acting on L-2-hydroxyglutarate and the third peak corresponded to an enzyme acting on D-2-hydroxyglutarate, as indicated by competitive inhibition of the detritiation of the racemic radioactive compound by the unlabelled L- and D-isomers respectively. The enzyme acting on the D-form was further characterized. It was independent of NAD or NADP and it converted D-2-hydroxyglutarate into α-ketoglutarate, transferring electrons to artificial electron acceptors. It also oxidized D-lactate, D-malate and meso-tartrate and was stimulated by Zn2+, Co2+ and Mn2+, but not by Mg2+ or Ca2+. Subcellular fractionation indicated that it was present in the mitochondrial fraction. The enzyme was further purified by chromatography on Blue Trisacryl and phenyl-Sepharose, up to a stage where only a few bands were still visible by SDS/ PAGE. Among the four candidate polypeptides that were identified by MS, one corresponded to a predicted mitochondrial protein homologous with FAD-dependent D-lactate dehydrogenase. The corresponding human protein was expressed in HEK-293 cells and it was shown to catalyse the detritiation of DL-2-hydroxy[2-3H]glutarate with similar properties as the purified rat enzyme.
Thimerosal stimulates Ca2+ flux through inositol 1,4,5-trisphosphate receptor type 1, but not type 3, via modulation of an isoform-specific Ca2+-dependent intramolecular interaction
Authors: BULTYNCK Geert , SZLUFCIK Karolina , KASRI Nael Nadif , ASSEFA Zerihun , CALLEWAERT Geert , MISSIAEN Ludwig , PARYS Jan B. , DE SMEDT Humbert
Published: June 2004

Thiol-reactive agents such as thimerosal have been shown to modulate the Ca2+-flux properties of IP3 (inositol 1,4,5-trisphosphate) receptor (IP3R) via an as yet unidentified mechanism [Parys, Missiaen, De Smedt, Droogmans and Casteels (1993) Pflügers Arch. 424, 516–522; Kaplin, Ferris, Voglmaier and Snyder (1994) J. Biol. Chem. 269, 28972–28978; Missiaen, Taylor and Berridge (1992) J. Physiol. (Cambridge, U.K.) 455, 623–640; Missiaen, Parys, Sienaert, Maes, Kunzelmann, Takahashi, Tanzawa and De Smedt (1998) J. Biol. Chem. 273, 8983–8986]. In the present study, we show that thimerosal potentiated IICR (IP3-induced Ca2+ release) and IP3-binding activity of IP3R1, expressed in triple IP3R-knockout R23-11 cells derived from DT40 chicken B lymphoma cells, but not of IP3R3 or [Δ1–225]-IP3R1, which lacks the N-terminal suppressor domain. Using a 45Ca2+-flux technique in permeabilized A7r5 smooth-muscle cells, we have shown that Ca2+ shifted the stimulatory effect of thimerosal on IICR to lower concentrations of thimerosal and thereby increased the extent of Ca2+ release. This suggests that Ca2+ and thimerosal synergetically regulate IP3R1. Glutathione S-transferase pull-down experiments elucidated an interaction between amino acids 1–225 (suppressor domain) and amino acids 226–604 (IP3-binding core) of IP3R1, and this interaction was strengthened by both Ca2+ and thimerosal. In contrast, calmodulin and sCaBP-1 (short Ca2+-binding protein-1), both having binding sites in the 1–225 region, weakened the interaction. This interaction was not found for IP3R3, in agreement with the lack of functional stimulation of this isoform by thimerosal. The interaction between the IP3-binding and transmembrane domains (amino acids 1–604 and 2170–2749 respectively) was not affected by thimerosal and Ca2+, but it was significantly inhibited by IP3 and adenophostin A. Our results demonstrate that thimerosal and Ca2+ induce isoform-specific conformational changes in the N-terminal part of IP3R1, leading to the formation of a highly IP3-sensitive Ca2+-release channel.
Regulation of cytosolic prostaglandin E synthase by phosphorylation
Authors: KOBAYASHI Tsuyoshi , NAKATANI Yoshihito , TANIOKA Toshihiro , TSUJIMOTO Masafumi , NAKAJO Shigeo , NAKAYA Kazuyasu , MURAKAMI Makoto , KUDO Ichiro
Published: June 2004

cPGES [cytosolic PG (prostaglandin) E synthase] is constitutively expressed in various cells and can regulate COX (cyclo-oxygenase)-1-dependent immediate PGE2 generation. In the present study, we found that cPGES underwent serine phosphorylation, which was accelerated transiently after cell activation. Several lines of evidence suggest that a cPGES-activating protein kinase is CK-II (casein kinase II). Recombinant cPGES was phosphorylated directly by and associated with CK-II in vitro, resulting in marked reduction of the Km for the substrate PGH2. In activated cells, cPGES phosphorylation occurred in parallel with increased cPGES enzymic activity and PGE2 production from exogenous and endogenous arachidonic acid, and these processes were facilitated by Hsp90 (heat-shock protein 90), a molecular chaperone that formed a tertiary complex with cPGES and CK-II. Treatment of cells with inhibitors of CK-II and Hsp90 and with a dominant-negative CK-II attenuated the formation of the cPGES–CK-II–Hsp90 complex and attendant cPGES phosphorylation and activation. Mutations of either of two predicted CK-II phosphorylation sites on cPGES (Ser113 and Ser118) abrogated its phosphorylation and activation both in vitro and in vivo. Moreover, the CK-II–Hsp90-mediated activation of cPGES was ameliorated by the p38 mitogen-activated protein kinase inhibitor SB20358 or by the anti-inflammatory glucocorticoid dexamethasone. Taken together, the results of the present study have provided the first evidence that the cellular function of this eicosanoid-biosynthetic enzyme is under the control of a molecular chaperone and its client protein kinase.
Reversion of protein aggregation mediated by Sso7d in cell extracts of Sulfolobus solfataricus
Authors: GUAGLIARDI Annamaria , MANCUSI Lucia , ROSSI Mosè
Published: June 2004

In eukaryotic cells and in Escherichia coli, reversion of protein aggregation is mediated by the network of chaperones belonging to Hsp70 and Hsp100 families [Weibezahn, Bukau and Mogk (2004) Microb. Cell Fact. 3, 1–12]. The thermophilic prokaryotes of the archaea domain lack homologues of these chaperone families, and the mechanisms they use to rescue aggregated proteins are unknown [Macario, Malz and Conway de Macario (2004) Front. Biosci. 9, 1318–1332]. In the present study, we show that stable protein aggregates can be detected in extracts of starved cells of the thermophilic archaeon Sulfolobus solfataricus, and that the protein Sso7d interacts with the aggregates and mediates the disassembly of the aggregates and the re-activation of insolubilized β-glycosidase in the presence of ATP hydrolysis. Furthermore, we report that heat-induced protein aggregates in extracts of exponential cells of S. solfataricus contain Sso7d that rescues insolubilized proteins in the presence of ATP hydrolysis. Results of these experiments performed in cell extracts are consistent with an in vivo role of Sso7d in reverting protein aggregation.
Requirements for superoxide-dependent tyrosine hydroperoxide formation in peptides
Authors: WINTERBOURN Christine C. , PARSONS-MAIR Helena N. , GEBICKI Silvia , GEBICKI Janusz M. , DAVIES Michael J.
Published: June 2004

Superoxide reacts rapidly with other radicals, but these reactions have received little attention in the context of oxidative stress. For tyrosyl radicals, reaction with superoxide is 3-fold faster than dimerization, and forms the addition product tyrosine hydroperoxide. We have explored structural requirements for hydroperoxide formation using tyrosine analogues and di- and tri-peptides. Superoxide and phenoxyl radicals were generated using xanthine oxidase, peroxidase and the respective tyrosine derivative, or by γ-radiation. Peroxides were measured using FeSO4/Xylenol Orange. Tyrosine and tyramine formed stable hydroperoxides, but N-acetyltyrosine and p-hydroxyphenylacetic acid did not, demonstrating a requirement for a free amino group. Using [14C]tyrosine, the hydroperoxide and dityrosine were formed at a molar ratio of 1.8:1. Studies with pre-formed hydroperoxides, and measurements of substrate losses, indicated that, in the absence of a free amino group, reaction with superoxide resulted primarily in restitution of the parent compound. With dipeptides, hydroperoxides were formed only on N-terminal tyrosines. However, adjacent lysines promoted hydroperoxide formation, as did addition of free lysine or ethanolamine. Results are compatible with a mechanism [d'Alessandro, Bianchi, Fang, Jin, Schuchmann and von Sonntag (2000) J. Chem. Soc. Perkin Trans. II, 1862–1867] in which the phenoxyl radicals react initially with superoxide by addition, and the intermediate formed either releases oxygen to regenerate the parent compound or is converted into a hydroperoxide. Amino groups favour hydroperoxide formation through Michael addition to the tyrosyl ring. These studies indicate that tyrosyl hydroperoxides should be formed in proteins where there is a basic molecular environment. The contribution of these radical reactions to oxidative stress warrants further investigation.
Charting gene regulatory networks: strategies, challenges and perspectives
Authors: WEI Gong-Hong , LIU De-Pei , LIANG Chih-Chuan
Published: June 2004

One of the foremost challenges in the post-genomic era will be to chart the gene regulatory networks of cells, including aspects such as genome annotation, identification of cis-regulatory elements and transcription factors, information on protein–DNA and protein–protein interactions, and data mining and integration. Some of these broad sets of data have already been assembled for building networks of gene regulation. Even though these datasets are still far from comprehensive, and the approach faces many important and difficult challenges, some strategies have begun to make connections between disparate regulatory events and to foster new hypotheses. In this article we review several different genomics and proteomics technologies, and present bioinformatics methods for exploring these data in order to make novel discoveries.
Cyan-emitting and orange-emitting fluorescent proteins as a donor/acceptor pair for fluorescence resonance energy transfer
Authors: KARASAWA Satoshi , ARAKI Toshio , NAGAI Takeharu , MIZUNO Hideaki , MIYAWAKI Atsushi
Published: June 2004

GFP (green fluorescent protein)-based FRET (fluorescence resonance energy transfer) technology has facilitated the exploration of the spatio-temporal patterns of cellular signalling. While most studies have used cyan- and yellow-emitting FPs (fluorescent proteins) as FRET donors and acceptors respectively, this pair of proteins suffers from problems of pH-sensitivity and bleeding between channels. In the present paper, we demonstrate the use of an alternative additional donor/acceptor pair. We have cloned two genes encoding FPs from stony corals. We isolated a cyan-emitting FP from Acropara sp., whose tentacles exhibit cyan coloration. Similar to GFP from Renilla reniformis, the cyan FP forms a tight dimeric complex. We also discovered an orange-emitting FP from Fungia concinna. As the orange FP exists in a complex oligomeric structure, we converted this protein into a monomeric form through the introduction of three amino acid substitutions, recently reported to be effective for converting DsRed into a monomer (Clontech). We used the cyan FP and monomeric orange FP as a donor/acceptor pair to monitor the activity of caspase 3 during apoptosis. Due to the close spectral overlap of the donor emission and acceptor absorption (a large Förster distance), substantial pH-resistance of the donor fluorescence quantum yield and the acceptor absorbance, as well as good separation of the donor and acceptor signals, the new pair can be used for more effective quantitative FRET imaging.
The ErbB2/Neu/HER2 receptor is a new calmodulin-binding protein
Authors: LI Hongbing , SÁNCHEZ-TORRES Juan , del CARPIO Alan , SALAS Valentina , VILLALOBO Antonio
Published: June 2004

We have demonstrated previously that the EGFR (epidermal growth factor receptor) is a calmodulin (CaM)-binding protein. To establish whether or not the related receptor ErbB2/Neu/HER2 also binds CaM, we used human breast adenocarcinoma SK-BR-3 cells, because these cells overexpress this receptor thus facilitating the detection of this interaction. In the present paper, we show that ErbB2 could be pulled-down using CaM–agarose beads in a Ca2+-dependent manner, as detected by Western blot analysis using an anti-ErbB2 antibody. ErbB2 was also isolated by Ca2+-dependent CaM-affinity chromatography. We also demonstrate using an overlay technique with biotinylated CaM that CaM binds directly to the immunoprecipitated ErbB2. The binding of biotinylated CaM to ErbB2 depends strictly on the presence of Ca2+, since it was prevented by the presence of EGTA. Moreover, the addition of an excess of free CaM prevents the binding of its biotinylated form, demonstrating that this was a specific process. We excluded any interference with the EGFR, as SK-BR-3 cells express considerably lower levels of this receptor, and no detectable EGFR signal was observed by Western blot analysis in the immunoprecipitated ErbB2 preparations used to perform the overlay assays with biotinylated CaM. We also demonstrate that treating living cells with W7 [N-(6-aminohexyl)-5-chloro-1-naphthalenesulphonamide], a cell-permeant CaM antagonist, down-regulates ErbB2 phosphorylation, and show that W7 does not interfere non-specifically with the activity of ErbB tyrosine kinases. We also show that W7 inhibits the phosphorylation (activation) of both ERK1/2 (extracellular-signal-regulated kinases 1 and 2) and Akt/PKB (protein kinase B), in accordance with the inhibition observed in ErbB2 phosphorylation. In contrast, W7 treatment increased the phosphorylation (activation) of CREB (cAMP-response-element-binding protein) and ATF1 (activating transcription factor-1), two Ca2+-sensitive transcription factors that operate downstream of these ErbB2 signalling pathways, most likely because of the absence of calcineurin activity. We conclude that ErbB2 is a new CaM-binding protein, and that CaM plays a role in the regulation of this receptor and its downstream signalling pathways in vivo.
A novel role of Mgm1p, a dynamin-related GTPase, in ATP synthase assembly and cristae formation/maintenance
Authors: AMUTHA Boominathan , GORDON Donna M. , GU Yajuan , PAIN Debkumar
Published: June 2004

In Saccharomyces cerevisiae, two mitochondrial inner-membrane proteins play critical roles in organellar morphology. One is a dynamin-related GTPase, Mgm1p, which participates in mitochondrial fusion. Another is Tim11p, which is required for oligomeric assembly of F1Fo-ATP synthase, which generates ATP through oxidative phosphorylation. Our data bring these findings together and define a novel role for Mgm1p in the formation and maintenance of mitochondrial cristae. We show that Mgm1p serves as an upstream regulator of Tim11p protein stability, ATP synthase assembly, cristae morphology and cytochrome c storage within cristae.
Pustulöse Hauterkrankungen des Neugeborenen
Authors: Fölster‐Holst Regina , Höger Peter
Published: June 2004

Das Spektrum pustulöser Hauterkrankungen im Neugeborenenalter ist groß. Es reicht von harmlosen, transitorischen Adaptationsstörungen bis zu systemischen, lebensbedrohlichen Erkrankungen. Bei 30 – 60 % der Neugeborenen treten Pusteln im Rahmen des harmlosen Erythema toxicum auf, dessen Genese bis heute nicht geklärt ist. Differentialdiagnostisch gilt es, hiervon die behandlungsbedürftigen pustulösen Hauterkrankungen abzugrenzen, die sowohl infektiöser als auch nicht‐infektiöser Genese sein können. Typische Erreger sind Malassezia furfur, Staphylokokken, Streptokokken, Candida spp. und Viren der Herpesgruppe.
Longitudinale Melanonychie bei Einnahme von Hydroxycarbamid
Authors: Neynaber Sven , Wolff Hans , Plewig Gerd , Wienecke Ralf
Published: June 2004

Vier Fallberichte von Patienten mit myeloproliferativem Syndrom, die zur Therapie Hydroxycarbamid (Synonyme: Hydroxyurea, Hydroxyharnstoff; Handelsnamen: Litalir®, Syrea®) einnehmen, und bei denen es einige Monate nach Beginn der Therapie zum Auftreten striärer, longitudinaler Pigmentierungen der Finger‐ und Fußnägel kommt.

Hintergrund: Pigmentierungen von Finger‐ und Fußnägeln eröffnen ein weites Feld der Differentialdiagnosen. Sie können mikrobiologischer, melanozytärer, stoffwechselbedingter oder exogener Ursache sein.

Patienten und Methodik: Wir berichten über drei weibliche und einen männlichen Patienten im Alter zwischen 62 und 87 Jahren mit myeloproliferativem Syndrom oder chronisch myeloischer Leukämie, die zur Behandlung über fünf bis zwölf Jahre Hydroxycarbamid Synonyme: Hydroxyurea, Hydroxyharnstoff; Handelsnamen: Litalir®, Syrea®) einnahmen oder noch einnehmen. Die vier Patienten haben einen Hauttyp II nach Fitzpatrick.

Ergebnisse: Mehrere Monate nach Beginn der Einnahme kam es zu striären, longitudinalen Pigmentierungen an Finger‐ und Fußnägeln. Bei zwei Patienten wurde dieser Befund als Zufallsbefund diagnostiziert, während sich die anderen beiden Patienten wegen der Nagelpigmentierungen in hautfachärztliche Behandlung begaben.

Bei zwei der Patienten kam es wenige Monate nach Absetzen von Hydroxycarbamid zum Verschwinden der longitudinalen Pigmentierung während bei einem Patienten die Melanonychie der Finger‐ und Fußnägel bestehen blieb. Eine Patientin konnte wegen fehlenden Kontaktes nicht nachkontrolliert werden.

Schlußfolgerung: Beim Auftreten longitudinaler Melanonychie bei hämato‐onkologischen Patienten ist eine genaue Anamnese, insbesondere bezüglich der Medikamente wichtig, da durch Hydroxyharnstoff Pigmentierungen der Finger‐ und Fußnägel auftreten können. Nach wie vor müssen jegliche melanozytäre Pigmentierungen der Akren, die Ausdruck eines akrolentiginösen Melanoms sein können, diagnostisch ausgeschlossen werden.
Structural transformation induced improved luminescent properties for LaVO4:Eu nanocrystals
Authors: Jia Chun-Jiang , Sun Ling-Dong , Luo Feng , Jiang Xiao-Cheng , Wei Liu-He , Yan Chun-Hua
Published: June 2004

To develop a good host material for red phosphors as well as a model for clarifying the underlying correlation between structure and properties, tetragonal phased LaVO4:Eu was synthesized via an ethylenediamine tetra-acetic acid (EDTA) assisted hydrothermal method. The challenging transformation from monazite to the metastable zircon structure for LaVO4:Eu resulted in a remarkable improvement of the luminescent properties. This improvement was rationally analyzed and the impact of structure on luminescent properties was explored. Based on these results, structural transformation-induced luminescent properties improvement was proposed as an efficient means to improve the performance of doped-insulators.
Sensitivity and gigahertz counting performance of NbN superconducting single-photon detectors
Authors: Korneev A. , Kouminov P. , Matvienko V. , Chulkova G. , Smirnov K. , Voronov B. , Gol’tsman G. N. , Currie M. , Lo W. , Wilsher K. , Zhang J. , Słysz W. , Pearlman A. , Verevkin A. , Sobolewski Roman
Published: June 2004

We have measured the quantum efficiency (QE), GHz counting rate, jitter, and noise-equivalent power (NEP) of nanostructured NbN superconducting single-photon detectors (SSPDs) in the visible to infrared radiation range. Our 3.5-nm-thick and 100- to 200-nm-wide meander-type devices (total area 10×10μm2), operating at 4.2K, exhibit an experimental QE of up to 20% in the visible range and ∼10% at 1.3 to 1.55μm wavelength and are potentially sensitive up to midinfrared (∼10μm) radiation. The SSPD counting rate was measured to be above 2GHz with jitter <18ps, independent of the wavelength. The devices’ NEP varies from ∼10−17W∕Hz1∕2 for 1.55μm photons to ∼10−20W∕Hz1∕2 for visible radiation. Lowering the SSPD operating temperature to 2.3K significantly enhanced its performance, by increasing the QE to ∼20% and lowering the NEP level to ∼3×10−22W∕Hz1∕2, both measured at 1.26μm wavelength.
Fabrication of 5nm linewidth and 14nm pitch features by nanoimprint lithography
Authors: Austin Michael D. , Ge Haixiong , Wu Wei , Li Mingtao , Yu Zhaoning , Wasserman D. , Lyon S. A. , Chou Stephen Y.
Published: June 2004

We report advances in nanoimprint lithography, its application in nanogap metal contacts, and related fabrication yield. We have demonstrated 5nm linewidth and 14nm linepitch in resist using nanoimprint lithography at room temperature with a pressure less than 15psi. We fabricated gold contacts (for the application of single macromolecule devices) with 5nm separation by nanoimprint in resist and lift-off of metal. Finally, the uniformity and manufacturability of nanoimprint over a 4in. wafer were demonstrated.
Controlled carbon nanotube sheathing on ultrafine InP nanowires
Authors: Yin L. W. , Bando Y. , Zhu Y. C. , Li M. S.
Published: June 2004

Controlled carbon nanotube sheathing on ultrafine InP nanowires has been realized through a simple vapor–solid process. The synthesized InP–C nanocables were composed of crystalline InP core about 13–15nm in diameter and parallel carbon sheath layers about several nanometers in thickness. The growth of the C layers takes place via a layer-by-layer process. The carbon tube sheathing can be controlled from several to more than 10 parallel layers by adjusting the deposition time. Both the carbon tube sheath and InP nanowire core show a higher degree of crystalline perfection. Graphitic carbon could act as chemically inert protecting layers for the ultrafine InP nanowires. This method could be applied to a wide range of materials and result in various hetrostructures, which may serve as potential building blocks in various nanodevices.
Formation of regular arrays of submicron GaAs dots on silicon
Authors: Beach J. D. , Veauvy C. , Caputo R. , Collins R. T. , Khandekar A. A. , Kuech T. F. , Inoki C. K. , Kuan T. S. , Hollingsworth R. E.
Published: June 2004

A combination of photolithography written with a near-field scanning optical microscope, gallium electrodeposition, and arsine annealing was used to produce regular arrays of submicron GaAs dots on a silicon substrate. Electrodeposition on a patterned Si surface produced an array of roughly hemispherical Ga dots. Annealing in arsine converted the gallium to GaAs, and caused the dots to develop faceted features. Transmission electron microscope measurements showed that the GaAs dots were polycrystalline, but had only a few grains. The dots did not have a preferred orientation relative to the substrate. Metalorganic chemical vapor deposition growth occurred selectively on these dots, forming regular arrays of GaAs disks up to 20μm in diameter. The GaAs disks exhibited characteristic GaAs low-temperature photoluminescence. This method has application for precisely positioning semiconductor dots or tailoring the grain size of polycrystalline films.
Decomposition of SiN interlayer during thermal annealing of HfAlOx∕SiN∕Si(001) structure
Authors: Kundu Manisha , Miyata Noriyuki , Morita Yukinori , Horikawa Tsuyoshi , Nabatame Toshihide , Ichikawa Masakazu , Toriumi Akira
Published: June 2004

We investigated the effects of postdeposition annealing (PDA) on a 3.1-nm-HfAlOx∕0.45-nm-SiN∕Si(001) structure under ultrahigh vacuum conditions. PDA caused the SiN interlayer (IL) to decompose, which was followed by N incorporation into the HfAlOx film. A detailed assessment of temperature and time dependencies during the PDA of the structure indicated that the SiN IL decomposed with an activation energy of 0.7eV, which was much lower than that of bulk β-phase Si3N4. We suggest that the presence of oxygen-deficient metal oxide sites at the internal dielectric interface of the structure was responsible for catalyzing IL decomposition during PDA.
Systematic enhancement of in-field critical current density with rare-earth ion size variance in superconducting rare-earth barium cuprate films
Authors: MacManus-Driscoll J. L. , Foltyn S. R. , Jia Q. X. , Wang H. , Serquis A. , Maiorov B. , Civale L. , Lin Y. , Hawley M. E. , Maley M. P. , Peterson D. E.
Published: June 2004

Enhanced in-field critical current densities (Jc’s) have been obtained in epitaxial superconducting (RE1,RE2)Ba2Cu3O7−x (RE1=rare-earthion 1, and RE2=rare earth ion 2) films grown on both single crystal and buffered metallic substrates. For a constant average RE ionic radius (equal to that of yttrium), there is a systematic dependence of the in-field Jc on the RE ion size variance, with a small, but nonzero, variance being optimum. Compared to the standard YBa2Cu3O7−x composition, a factor of two improvement in Jc(75.5K) is reproducibly observed at 0.2T(‖c) for the composition Dy1∕3Ho2∕3Ba2Cu3O7−x on both single crystal and buffered-metallic substrates. Angular dependent magnetic field studies and transmission electron microscopy indicate the presence of additional pointlike random defects.
Cryogenic magnetic field sensor based on the magnetoresistive effect in bulk Bi2212+USr2CaO6
Authors: Ionescu M. , Winton B. , Silver T. , Dou S. X. , Ramer R.
Published: June 2004

A large magnetoresistive (MR) effect was observed in melt-textured (MT) Bi2212 in which USr2CaO6 was added in a proportion of 6wt%. The resistivity measurements of MT Bi2212+6wt% USr2CaO6 show high sensitivity to applied dc fields, as compared to pure Bi2212, in particular at low fields, below 3T, and in a temperature range between 45K and 85K. In this temperature range, the MR effect of MT Bi2212+6wt% USr2CaO6 is two orders of magnitude larger than the MR effect in pure Bi2212, and display a maximum that may be tuned to a particular temperature within the above range, by changing the amount of added nonsuperconducting compound. A cryogenic sensor was built and tested at 77K in low fields. It shows a good sensitivity and small (∼1%) hysteresis of resistivity when the applied field was cycled between 0T and 1T.
Dip-pen nanolithography with magnetic Fe2O3 nanocrystals
Authors: Gundiah Gautam , John Neena Susan , Thomas P. John , Kulkarni G. U. , Rao C. N. R. , Heun S.
Published: June 2004

Dip-pen nanolithography has been employed to obtain magnetic nanopatterns of γ-Fe2O3 nanocrystals on mica and silicon substrates. The chemical and magnetic nature of the patterns have been characterized employing low-energy electron microscopy, x-ray photoemission electron microscopy, and magnetic force microscopy measurements.
Thermoelectric devices using InN and Al1−xInxN thin films prepared by reactive radio-frequency sputtering
Authors: Yamaguchi Shigeo , Izaki Ryohei , Kaiwa Nakaba , Sugimura Satoshi , Yamamoto Atsushi
Published: June 2004

We have fabricated thermoelectric devices using InN and Al0.25In0.75N prepared by radio-frequency sputtering. The devices are composed of (a) Al0.25In0.75N–chromel of 20 pairs on SiO2 glass, (b) InN–chromel of 20 pairs on SiO2 glass, and (c) InN-chromel of 20 pairs on polyimide film. The maximum output power and the open output voltage were (a) 1.6×10−6W and 0.21V at the temperature difference ΔT=345K, 263×10−12W and 2.7×10−3V at ΔT=4.8K, (b) 3.9×10−6W and 0.22V at ΔT=332K, 282×10−12W and 2.4×10−3V at ΔT=4.1K, and (c) 0.33×10−6W and 0.089V at ΔT=280K, 63×10−12W and 1.4×10−3V at ΔT=4.5K, respectively.
Inherent charge transfer layer formation at La0.6Sr0.4FeO3∕La0.6Sr0.4MnO3 heterointerface
Authors: Kumigashira H. , Kobayashi D. , Hashimoto R. , Chikamatsu A. , Oshima M. , Nakagawa N. , Ohnishi T. , Lippmaa M. , Wadati H. , Fujimori A. , Ono K. , Kawasaki M. , Koinuma H.
Published: June 2004

We have investigated the Mn3d spectral function in La0.6Sr0.4FeO3(LSFO)∕La0.6Sr0.4MnO3(LSMO) heterointerfaces as well as of La1−xSrxMnO3 films using Mn2p−3d resonant photoemission spectroscopy. The strong enhancement of the Mn3d spectra at the Mn2p−3d threshold enables us to extract the Mn3d spectra of LSMO layers in the vicinity of the interface with the LSFO overlayers. We have found that the spectral intensity of eg↑ states near the Fermi level is gradually reduced with increasing LSFO overlayer thickness and is finally saturated at 5–7ML. The close similarity in reduction of the intensity of the eg↑ states between the LSFO∕LSMO interface and hole-doped LSMO films indicates the occurrence of charge transfer at the interface between the LSMO and LSFO layers.
All-optical multiphoton absorption figures of merit: Polydiacetylene poly (bis para-toluene sulfonate) of 2,4-hexadiyne-1,6diol
Authors: Yoshino Fumiyo , Polyakov Sergey , Stegeman George I.
Published: June 2004

The all-optical switching figures of merit are reported for the single crystal PTS (polydiacetylene poly (bis para-toluene sulfonate) of 2,4-hexadiyne-1,6 diol). Included are the effects of the absorption mechanisms from linear up to four-photon over the wavelength range 1.2–2.2μm.
Cancer treatment by ultrasound: Increasing the depth of necrosis
Authors: Melodelima David , Cathignol Dominique
Published: June 2004

Tissue coagulation by high-intensity ultrasound is a well-established method of cancer treatment. It suffers, however, from insufficient depth of action in the case of deep-seated tumors where endoscopic or interstitial applicators are used. It is demonstrated here that this depth can be increased by temporarily creating cavitation bubbles in such a way that ultrasound attenuation becomes stronger in the zone where tissue heating is insufficient. In vitro experiments in liver tissue confirm that bubbles are indeed located in this zone and that the effective depth of coagulation necrosis is doubled.
Pinning phenomena in a superconducting film with a square lattice of artificial pinning centers
Authors: Jiang Z. , Dikin D. A. , Chandrasekhar V. , Metlushko V. V. , Moshchalkov V. V.
Published: June 2004

We study the transport properties of a superconducting Nb film with a square lattice of artificial pinning centers (APCs) as a function of dc current, at a temperature close to the superconducting transition temperature of the film. We find that, at low dc currents, the differential resistance of the film shows the standard matching field anomaly, that is, the differential resistance has a local minimum at magnetic fields corresponding to an integer number of flux lines per APC. However, at higher dc currents, the differential resistance at each matching field turns to a local maximum, which is exactly opposite to the low current behavior. This effect might indicate that the flux lines in the APC system change their flow mode as the dc current is increased.
Percolation network of growing V2O5 nanowires
Authors: Chang Yu Jin , Kang Byung Hyun , Kim Gyu Tae , Park Sung Joon , Ha Jeong Sook
Published: June 2004

Percolation network of the growing V2O5 nanowires was demonstrated by devising a simple but practical method to investigate the percolation phenomena. As the reaction proceeded in the ammonium(meta)vanadate solution at room temperature, the lengths of V2O5 nanowires increased at a speed of 0.13μm∕day at an early stage of the growth and 0.03μm∕day on the average up to 3 months. Percolation network was made by abruptly freezing the homogeneously dispersed aqueous solutions of V2O5 nanowires in liquid nitrogen. After 7h of aging time, an abrupt increase of the conductance was observed, revealing the satisfaction of the percolation threshold (pc∼0.17) at the average wire length of 40nm.
A printable form of silicon for high performance thin film transistors on plastic substrates
Authors: Menard E. , Lee K. J. , Khang D.-Y. , Nuzzo R. G. , Rogers J. A.
Published: June 2004

Free-standing micro- and nanoscale objects of single crystal silicon can be fabricated from silicon-on-insulator wafers by lithographic patterning of resist, etching of the exposed top silicon, and removing the underlying SiO2 to lift-off the remaining silicon. A large collection of such objects constitutes a type of material that can be deposited and patterned, by dry transfer printing or solution casting, onto plastic substrates to yield mechanically flexible thin film transistors that have excellent electrical properties. Effective mobilities of devices built with this material, which we refer to as microstructured silicon (μs-Si), are demonstrated to be as high as 180cm2∕Vs on plastic substrates. This form of “top down” microtechnology might represent an attractive route to high performance flexible electronic systems.
Eu
2
+
-doped Ca-α-SiAlON: A yellow phosphor for white light-emitting diodes
Authors: Xie Rong-Jun , Hirosaki Naoto , Sakuma Ken , Yamamoto Yoshinobu , Mitomo Mamoru
Published: June 2004

In this letter, a yellow oxynitride phosphor α-SiAlON with compositions of Ca0.625EuxSi0.75−3xAl1.25+3xOxN16−x (Ca-α-SiAlON:Eu, x=0–25) was prepared by gas pressure sintering. The diffuse reflection spectrum, photoluminescence spectrum, and chromaticity of the powder phosphors were presented. It absorbs light efficiently in the UV–visible spectral region, and shows a single intense broadband emission at 583–603nm. This phosphor may become a good candidate for creating white light, typically warm white light, when coupled to a blue light-emitting diode (λem=450nm).
Formation of Ge nanocrystals in HfAlO high-k dielectric and application in memory device
Authors: Wang Ying Qian , Chen Jing Hao , Yoo Won Jong , Yeo Yee-Chia , Kim Sun Jung , Gupta Rohit , Tan Zerlinda Y. L. , Kwong Dim-Lee , Du An Yan , Balasubramanian N.
Published: June 2004

Formation of Ge nanocrystals embedded in HfAlO high-k dielectric by co-sputtering of HfO2, Al2O3, and Ge, followed by rapid thermal annealing was demonstrated. Analysis by transmission electron microscopy and x-ray photoelectron spectroscopy confirmed the formation of nonoxidized Ge nanocrystals with a minimum size of about 5nm embedded in HfAlO dielectric. We also demonstrated the application of such nanocrystals in nonvolatile memory devices, achieving a 2.2V memory window as obtained from the C–V characterization of the memory device.
Improvements of InGaN∕GaN quantum-well interfaces and radiative efficiency with InN interfacial layers
Authors: Cheng Yung-Chen , Wu Cheng-Ming , Chen Meng-Kuo , Yang C. C. , Feng Zhe-Chuan , Li Gang Alan , Yang Jer-Ren , Rosenauer Andreas , Ma Kung-Je
Published: June 2004

The optical properties and nanostructures of two InGaN∕GaN quantum-well (QW) samples of slightly different structures are compared. In one of the samples, InN interfacial layers of a few monolayers are added to the structure between wells and barriers for improving the QW interface quality. Compared with the standard barrier-doped QW sample, the addition of the InN interfacial layers does improve the QW interface quality and hence the photon emission efficiency. The strain state analysis images show the high contrast between the clear QW interface in the sample with InN layers and the diffusive QW boundaries in the reference sample. The detection-energy-dependent photoluminescence excitation data reveal the consistent results.
Temperature stability of permittivity and dielectric relaxationin multilayered thin films of (Ba0.80Sr0.20)(Ti1−xZrx)O3with a compositionally graded layer
Authors: Cheng B. L. , Wang Can , Wang S. Y. , Button T. W. , Lu H. B. , Zhou Y. L. , Chen Z. H. , Yang G. Z.
Published: June 2004

Mutilayered thin (Ba0.80Sr0.20)(Ti1−xZrx)O3 (BSTZ) films with various compositional graded layers (CGL) have been successfully fabricated on Nb doped SrTiO3 substrates by pulsed-laser deposition technique with four BSTZ ceramic targets (x=0.36,0.18,0.08,0). The gradients of compositions are artificially tailored in multilayered thin films by varying the CGL, and x-ray diffraction indicates that the internal stress is modulated in the multilayered films. Influence of the composition gradient on the dielectric properties has been investigated at the temperature range from 120 to 440K. Temperature stability of permittivity of the multilayered films is found to be improved with the increase of the gradients of compositions. Moreover, a dielectric relaxation process with activation energy of 1.02eV is observed, which is also related to the composition gradient, and can be described to motion of oxygen vacancies. The results show that the temperature stability of permittivity can be tailed by the design of multilayered film with CGL, and the internal stress induced by the gradients of composition could influence the relaxation process.
NMR line broadening in He3–4He heterophase solid mixtures below 50 mK
Authors: Mikhin N. P.
Published: June 2004

The possible causes of the previously observed low-temperature decrease in the spin–spin relaxation time in phase-separated He3–4He solid mixtures are analyzed. It is shown that the jump in magnetic susceptibility at the boundary between the nuclear paramagnet He3 and the diamagnetic He4 matrix gives rise to appreciable local gradients of the external magnetic field at low temperatures in He3 clusters several microns in size, effectively broadening the NMR line. The results of the calculations give a good description of the experimental data.
Evolution of a pulse of noninteracting quasiparticles with dispersion and initial angular width
Authors: Adamenko I. N. , Nemchenko K. E. , Slipko V. A. , Wyatt A. F. G.
Published: June 2004

The evolution of a pulse of noninteracting quasiparticles, caused by their different velocities and angular distribution of momenta, is studied theoretically. Equations are found that describe the shape of the pulse surface at any time. The times of the beginning and end and the duration of the quasiparticle energy flux density is determined at a general spatial point. The quasiparticle energy density is considered at all times and positions, and it is shown that in the region of high energy density, in the middle of the pulse, it is equal to the initial energy density under certain conditions. These theoretical results are discussed in relation to experimental data on the evolution of a pulse of noninteracting phonons in superfluid helium.
Hysteresis of the magnetic properties and the irreversibility line in Bi2Sr2CaCu2Oy layered superconductors
Authors: Vashakidze Yu. M. , Shaposhnikova T. S. , Talanov Yu. I.
Published: June 2004

Measurements of the irreversibility line in Bi2Sr2CaCu2Oy single crystals are made by three experimental methods: by dc magnetization measurements, microwave absorption measurements, and registration of the harmonics in the high-frequency response of the superconductor. It is found that the position of the irreversibility line on the magnetic phase diagram depends substantially on the method of measurement and the frequency used. Analysis of the results shows that the discrepancy in the irreversibility lines is due to both a difference in the mechanisms of hysteresis of the magnetic properties and to the different scales of the measurement times. It is shown that the position of the irreversibility line is determined at low temperatures by the limiting value of the vortex creep rate for the given method of registration and at high temperatures by the time required for two-dimensional vortices to overcome the surface barrier. It is concluded that the irreversibility line is a dynamic phase transition. The first experimental evidence of the presence of a surface barrier for 2D vortices is obtained.
Simultaneous mapping of filamentous actin flow and turnover in migrating cells by quantitative fluorescent speckle microscopy
Authors: Vallotton Pascal , Gupton Stephanie L. , Waterman-Storer Clare M. , Danuser Gaudenz
Published: June 2004

We report advances in quantitative fluorescent speckle microscopy to generate simultaneous maps of cytoskeleton flow and rates of net assembly and disassembly in living cells. We apply this tool to analyze the filamentous actin (F-actin) dynamics at the front of migrating cells. F-actin turnover and flow are both known to be factors of cell locomotion. However, how they are orchestrated to produce directed cell movements is poorly understood. Our approach to data analysis allows us to examine their interdependence. Our maps confirm the previously described organization of flow into a lamellipodium and a lamellum, both exhibiting retrograde flow; and a convergence zone, where lamellum retrograde flow meets with slow anterograde flow of cortical F-actin at the ventral side of the cell body. The turnover maps show the well known actin polymerization at the leading edge, but also indicate that ≈90% of the polymer disassembles at the lamellipodium–lamellum junction. Strong depolymerization is also found in the convergence zone, where meshwork contraction is prominent. To determine whether contraction and depolymerization are coupled events, we have treated cells with calyculin A, which is known to promote myosin activity. Stimulated contraction was accompanied by accelerated retrograde flow and increased depolymerization throughout the lamellum, whereas disassembly at the lamellipodium–lamellum junction remained unaffected. There appear to be two distinct depolymerization mechanisms, of which one depends directly on meshwork contraction.
Contribution of inhibitory mechanisms to direction selectivity and response normalization in macaque middle temporal area
Authors: Thiele A. , Distler C. , Korbmacher H. , Hoffmann K.-P.
Published: June 2004

Inhibitory mechanisms contribute to directional tuning in primary visual cortex, and it has been suggested that, in the primate brain, the middle temporal area (MT) inherits most of its directional information from primary visual cortex (V1). To test the validity of this hierarchical scheme, we investigated whether directional tuning in MT was present upon blockade of local γ-aminobutyratergic (GABAergic) inhibitory mechanisms. Direction selectivity during the initial 50 ms after response onset was abolished in many MT cells when the local inhibitory network was inactivated whereas direction selectivity in later response periods was largely unaffected. Thus, direction selectivity during early response periods is often generated autonomously within MT whereas direction selectivity during later response periods is either inherited from other visual areas or locally mediated by mechanisms other than γ-aminobutyric acid type A receptor (GABA
A
) inhibition. GABAergic inhibition may also mediate contrast normalization. Our data suggest that GABA
A
inhibition implements a local direction-selective static nonlinearity, rather than a full normalization in MT. These findings put constraints on strict hierarchical models according to which MT performs more complex computations based on local motion measurements provided by earlier areas, arguing for more distributed and independent information processing.
The loss function of sensorimotor learning
Authors: Körding Konrad Paul , Wolpert Daniel M.
Published: June 2004

Motor learning can be defined as changing performance so as to optimize some function of the task, such as accuracy. The measure of accuracy that is optimized is called a loss function and specifies how the CNS rates the relative success or cost of a particular movement outcome. Models of pointing in sensorimotor control and learning usually assume a quadratic loss function in which the mean squared error is minimized. Here we develop a technique for measuring the loss associated with errors. Subjects were required to perform a task while we experimentally controlled the skewness of the distribution of errors they experienced. Based on the change in the subjects' average performance, we infer the loss function. We show that people use a loss function in which the cost increases approximately quadratically with error for small errors and significantly less than quadratically for large errors. The system is thus robust to outliers. This suggests that models of sensorimotor control and learning that have assumed minimizing squared error are a good approximation but tend to penalize large errors excessively.
Cells release prions in association with exosomes
Authors: Fevrier Benoit , Vilette Didier , Archer Fabienne , Loew Damarys , Faigle Wolfgang , Vidal Michel , Laude Hubert , Raposo Graça
Published: June 2004

Prion diseases are infectious neurodegenerative disorders linked to the accumulation in the central nervous system of the abnormally folded prion protein (PrP) scrapie (PrPsc), which is thought to be the infectious agent. Once present, PrPsc catalyzes the conversion of naturally occurring cellular PrP (PrPc) to PrPsc. Prion infection is usually initiated in peripheral organs, but the mechanisms involved in infectious spread to the brain are unclear. We found that both PrPc and PrPsc were actively released into the extracellular environment by PrP-expressing cells before and after infection with sheep prions, respectively. Based on Western blot with specific markers, MS, and morphological analysis, our data revealed that PrPc and PrPsc in the medium are associated with exosomes, membranous vesicles that are secreted upon fusion of multivesicular endosomes with the plasma membrane. Furthermore, we found that exosomes bearing PrPsc are infectious. Our data suggest that exosomes may contribute to intercellular membrane exchange and the spread of prions throughout the organism.