bluuebunny/crossref_metadata_2025 huggingface dataset:
Two cysteine protease inhibitors, EhICP1 and 2, localized in distinct compartments, negatively regulate secretion in Entamoeba histolytica
Authors: Sato Dan , Nakada-Tsukui Kumiko , Okada Mami , Nozaki Tomoyoshi
Published: September 2006

The enteric protozoan parasite Entamoeba histolytica uniquely possesses two isotypes of ICPs, a novel class of inhibitors for cysteine proteases. These two EhICPs showed a remarkable difference in the ability to inhibit cysteine protease (CP) 5, a well‐established virulence determinant, whereas they equally inhibited CP1 and CP2. Immunofluorescence imaging and cellular fractionation showed that EhICP1 and EhICP2 are localized to distinct compartments. While EhICP1 is localized to the soluble cytosolic fraction, EhICP2 is targeted from lysosomes to phagosomes upon erythrocyte engulfment. Overexpression of either EhICP1 or EhICP2 caused reduction of intracellular CP activity, but not the amount of CP, and decrease in the secretion of all major CPs, suggesting that both EhICPs are involved in the trafficking and/or interference with the major CP activity. These data indicate that the two EhICPs, present in distinct subcellular compartments, negatively regulate CP secretion, and, thus, the virulence of this parasite.
Quantitative comparison of the efficiency of antibodies against S1 and S2 subunit of SARS coronavirus spike protein in virus neutralization and blocking of receptor binding: Implications for the functional roles of S2 subunit
Authors: Zeng Fanya , Hon Chung Chau , Yip Chi Wai , Law Ka Man , Yeung Yin Shan , Chan Kwok Hung , Malik Peiris Joseph S. , Leung Frederick Chi Ching
Published: September 2006

Neutralizing effects of antibodies targeting the C‐terminal stalk (S2) subunit of the spike protein of severe acute respiratory syndrome coronavirus have previously been reported, although its mechanism remained elusive. In this study, high titered mouse antisera against the N‐terminal globular (S1) and S2 subunits of the S protein were generated and total immunoglobulin G (IgG) was purified from these antisera. The efficiency of these purified IgGs in virus neutralization and blocking of receptor binding were compared quantitatively using virus neutralization assay and a previously developed cell‐based receptor binding assay, respectively. We demonstrated that anti‐S1 IgG neutralizes the virus and binds to the membrane associated S protein more efficiently than anti‐S2 IgG does. Moreover, both anti‐S1 and anti‐S2 IgGs were able to abolish the binding between S protein and its cellular receptor(s), although anti‐S1 IgG showed a significantly higher blocking efficiency. The unexpected blocking ability of anti‐S2 IgG towards the receptor binding implied a possible role of the S2 subunit in virus docking process and argues against the current hypothesis of viral entry. On the other hand, the functional roles of the previously reported neutralizing epitopes within S2 subunit were investigated using an antigen specific antibody depletion assay. Depletion of antibodies against these regions significantly diminished, though not completely abolished, the neutralizing effects of anti‐S2 IgG. It suggests the absence of a major neutralizing domain on S2 protein. The possible ways of anti‐S2 IgGs to abolish the receptor binding and the factors restricting anti‐S2 IgGs to neutralize the virus are discussed.
Disruption of parental‐specific expression of imprinted genes in uniparental fetuses
Authors: Ogawa Hidehiko , Wu Qiong , Komiyama Junichi , Obata Yayoi , Kono Tomohiro
Published: September 2006

In mammals, imprinted genes show parental origin‐dependent expression based on epigenetic modifications called genomic imprinting (GI), which are established independently during spermatogenesis or oogenesis. Due to GI, uniparental fetuses never develop to term. To determine whether such expression of imprinted genes is maintained in uniparental mouse fetuses, we analyzed the expression of 20 paternally and 11 maternally expressed genes in androgenetic and parthenogenetic fetuses. Four genes of each type were expressed in both groups of fetuses. Furthermore, quantitative analysis showed that expression levels deviated from the presumed levels for some imprinted genes. These results suggest that mechanisms acting in trans between paternal and maternal alleles are involved in the appropriate expression of some imprinted genes.
The effects of charge‐neutralizing mutation D6.30N on the functions of CB1 and CB2 cannabinoid receptors
Authors: Nebane Ntsang M. , Kellie Brandon , Song Zhao-Hui
Published: September 2006

Charge‐neutralizing mutation D6.30N of the human cannabinoid receptor subtype 1 (CB1) and cannabinoid receptor subtype 2 (CB2) cannabinoid receptors was made to test two hypotheses: (1) D6.30 may be crucial for the functions of CB1 and CB2 receptors. (2) D6.30 may participate in an ionic lock with R3.50 that keeps the receptors in an inactive conformation. Specific ligand binding and ligand‐induced inhibition of forskolin‐stimulated cAMP accumulation were observed with human embryonic kidney epithelial cell line (HEK293) cells expressing wild‐type CB1 and CB2, as well as CB1D6.30N and CB2D6.30N mutant receptors. There was however a decrease in maximum response of the mutant receptors compared to their wild‐type counterparts, suggesting that D6.30 is essential for full activation of both CB1 and CB2 receptors. Both CB1D6.30N and CB2D6.30N demonstrated a level of constitutive activity no greater than that of their wild‐type counterparts, indicating that either D6.30 does not participate in a salt bridge with R3.50, or the salt bridge is not critical for keeping cannabinoid receptors in the inactive conformation.
JNK mediates TGF‐β1‐induced epithelial mesenchymal transdifferentiation of mouse transformed keratinocytes
Authors: Santibañez Juan F.
Published: September 2006

In this study we analyzed the role of the c‐Jun N‐terminal kinases (JNK) pathway in the TGF‐β1 stimulation of urokinase‐type plasminogen activator (uPA), initial stages of epithelial‐mesenchymal transdifferentiation (EMT) and cell migration. TGF‐β1 induces JNK phosphorylation, c‐Jun transactivation and AP1 activation. The involvement of JNK was evaluated using dominant negative mutants SEK‐1 AL, JNK and cJun, depletion of JNK1,2 proteins by treatment of cells with antisense oligonucleotides, as well as the chemical inhibitor SP600125. Our results demonstrated that the JNK pathway is required in the TGF‐β1 enhancement of uPA, fibronectin, E‐cadherin delocalization, actin re‐organization and vimentin expression, concomitant with the induction of cell migration. These results allow us to suggest a role of JNK in the TGF‐β1 induction of EMT in relation with the stimulation of malignant properties of mouse transformed keratinocytes.
Directed evolution of a bacterial efflux pump: Adaptation of the E. coli TolC exit duct to the Pseudomonas MexAB translocase
Authors: Bokma Evert , Koronakis Eva , Lobedanz Sune , Hughes Colin , Koronakis Vassilis
Published: September 2006

Bacterial multidrug efflux pumps operate by periplasmic recruitment and opening of TolC family outer membrane exit ducts by cognate inner membrane translocases. Directed evolution of active hybrid pumps was achieved by challenging a library of mutated, shuffled TolC variants to adapt to the non‐cognate Pseudomonas MexAB translocase, and confer resistance to the efflux substrate novobiocin. Amino acid substitutions in MexAB‐adapted TolC variants that endowed high resistance were recreated independently, and revealed that MexAB‐adaptation was conferred only by substitutions located in the lower α‐helical barrel of TolC, specifically the periplasmic equatorial domain and entrance coiled coils. These changes converge to the native MexAB partner OprM, and indicate an interface key to the function and diversity of efflux pumps.
Cutaneous haemangiosarcoma of the lower eyelid in an elderly white cat
Authors: Hartley Claudia , Ladlow Jane , Smith Ken C.
Published: September 2006

A case of cutaneous haemangiosarcoma of the left lower eyelid in a 15-year-old white domestic shorthair cat is reported. A protuberant red mass occupying one-third of the lower eyelid margin length was present. Intermittent haemorrhage occurred from the mass surface. Surgical biopsy had revealed a locally invasive tumour composed of numerous irregular blood-filled spaces lined by a single layer of plump endothelial cells and separated by thin fibrous septa. Mitotic activity was rare and the appearance was consistent with a low-grade haemangiosarcoma. The mass continued to enlarge and referral was sought. Due to financial constraints and the owner's wish for a single procedure, enucleation with an axial pattern flap based on the superficial temporal artery was undertaken. Histopathology of the excised tissue confirmed the presence of a well-differentiated haemangiosarcoma. Tumour-free excisional margins were confirmed, the surgical area healed uneventfully, and there has been no recurrence during the subsequent 16 months.
Einflussfaktoren auf den Alkoholkonsum Jugendlicher: Zur Rolle von Gen-Umwelt Wechselwirkungen
Authors: Hinckers Anne S. , Frank Josef , Heinz Andreas , Schumann Gunter , Schmidt Martin H. , Laucht Manfred
Published: September 2006

Zusammenfassung: Fragestellung: Übermäßiger Alkoholkonsum im Jugendalter erhöht das Risiko einer späteren Alkoholerkrankung. Geeignete präventive Maßnahmen bedürfen eines ätiologischen Modells, in das sowohl genetische als auch Umweltfaktoren eingehen. Welche Rolle dabei Wechselwirkungen zwischen Genotyp und Umwelt zukommt, soll in einer Literaturübersicht geprüft werden. Methodik: Mit Hilfe der Datenbank Medline Advanced wurden themenbezogene Artikel gesucht. Diese wurden auf ihre Relevanz überprüft und nach genetischen Faktoren, Umweltfaktoren und deren Wechselwirkung geordnet. Ergebnisse: Eine Vielzahl von Faktoren beeinflusst, isoliert und in Kombination mit anderen, den Alkoholkonsum Jugendlicher. Dabei erklärt jede einzelne Variable nur einen geringen Anteil der Variation des Konsumverhaltens. Schlussfolgerungen: Die vielfältigen Möglichkeiten von Wechselwirkungen zwischen einzelnen Faktoren werden deutlich. Der Bedarf an umfassenden Modellen zum erhöhten Alkoholkonsum Jugendlicher und der Integration bisheriger Ergebnisse in diese Modelle ist groß.
Assessing the Big Five
Authors: Schulze Ralf , Roberts Richard D.
Published: September 2006

Abstract. A new measure of the Big Five personality constructs, the Openness Conscientiousness Extraversion Agreeableness Neuroticism Index Condensed (OCEANIC), was developed and validated. In Study 1 (N = 166), the convergent validity with the Big Five as assessed by the NEO-FFI was established. Study 2 (N = 3 808) served to investigate the structure of the instrument with stepwise exploratory factor analysis and confirmatory factor analysis. The incremental predictive validity with respect to objective university grades was examined in Study 3 (N = 145). The results show that a) the scales of the initial item pool converge with those of an established measure of the Big Five, b) the Big Five factor model fits the data both at the item and facet level and both for subsamples of students and workers, and c) consistent with previous research, the Conscientiousness factor of the OCEANIC predicts university grades beyond intelligence measures.
Beanspruchungswirkungen von Selbstkontrollanforderungen und Kontrollmöglichkeiten bei der Arbeit
Authors: Neubach Barbara , Schmidt Klaus-Helmut
Published: September 2006

Zusammenfassung. An zunehmend mehr Arbeitsplätzen wird heute ein hohes Ausmaß an Selbstkontrolle von den Beschäftigten gefordert. In Anlehnung an das “Demands-Control“-Modell von Karasek (1979) wurde untersucht, ob die beanspruchenden Wirkungen dieser bisher wenig untersuchten Form der Arbeitsbelastung durch situative Spielräume der Kontrolle und Einflussnahme abgeschwächt bzw. moderiert werden. Untersuchungsteilnehmer waren 260 Altenpflegekräfte. Es konnte gezeigt werden, dass zunehmende Selbstkontrollanforderungen mit einer signifikanten Abnahme der Arbeitszufriedenheit sowie mit einem signifikanten Anstieg der emotionalen Erschöpfung und der gesundheitlichen Beschwerden einhergehen, wenn die situativen Spielräume der Kontrolle und Einflussnahme gering ausgeprägt sind. Bestehen dagegen große situative Spielräume, wird dieser ungünstige Beanspruchungseffekt der Selbstkontrollanforderungen vollständig aufgehoben. Dieser Effekt ließ sich auch in Bezug auf objektive Indikatoren der Beanspruchungen - Fehlzeiten der Mitarbeiter im Jahreszeitraum nach der Befragung - nachweisen.
Wie gut können Scheidungen vorhergesagt werden?
Authors: Lutz Wolfgang , Weinmann-Lutz Birgit
Published: September 2006

Zusammenfassung. Die Vorhersagerichtigkeit von Scheidungen und daraus abgeleitet Angaben zur paarspezifischen Vorhersagegenauigkeit tauchen häufig in Fachpublikationen und Presse auf - mit Raten zwischen 80 und 90%. Ziel dieser Arbeit ist es, den Einfluss von Basisraten von Scheidung auf die Vorhersagegenauigkeit und die Bedeutung von Kreuzvalidierungen zur Verbesserung der Vorhersagen aufzuzeigen. Basierend auf zwei Subsamples von Querschnittsdatensätzen (Swiss Household Panel SHP: N = 5156; US-Krankenkasse COMPASS: N = 9941) wurden hierarchisch logistische Regressionen zur Bestimmung der Prädiktoren angewandt, welche dann den Ausgangspunkt für Kreuzvalidierungen mit Basisratenkorrekturen darstellten. Die Abhängigkeit der Vorhersagegüte von der Basisrate und das Absinken der Vorhersagegüte bei Kreuzvalidierungen konnte belegt werden. Die Rate der richtigen Scheidungsvorhersagen (positiv prädiktiver Wert) liegt in einer Größenordnung zwischen 20 und 40%. Eine größere Genauigkeit und Vorsicht gegenüber Vorhersageraten von Scheidungen erscheint angebracht, besonders in der Kommunikation wissenschaftlicher Ergebnisse an die Öffentlichkeit oder in Interventionen.
Die Relevanz psychophysiologischer Reaktionen und Prozesse für das Erbringen von Höchstleistungen am Beispiel des konzertierenden Musikers
Authors: Ferstl Elisabeth
Published: September 2006

Zusammenfassung. So heilend Musik an sich in der Angst- und Schmerzlinderung wirken kann, so sehr kann das Musizieren unter permanentem Leistungsdruck Ängste auslösen, Schmerzen verursachen und die Gesundheit der Musiker gefährden. Im Rahmen einer Pilotstudie mit 24 Streichern der Universität Mozarteum Salzburg wurden durch psychophysiologisches Monitoring während der Auftritte der Probanden die Parameter Hautwiderstand, Hautpotential und EMG erfasst und mittels Zeitreihenanalyse analysiert, um so weitgehend objektive Informationen über vegetativ-emotionale, nerval-kognitive und motorisch-muskuläre Prozesse der Musiker in der Stress-Leistungssituation des Auftritts zu erhalten. Im vorliegenden Beitrag werden konträr verlaufende psychophysiologische Reaktionen am Beispiel von Probanden unterschiedlichen Leistungsvermögens und mit unterschiedlichen Bewältigungsstrategien hinsichtlich der Stresssituation demonstriert und Fragen nach denkbaren “Therapie“-Möglichkeiten zur Verbesserung der Konstitution und Optimierung der musikalischen Qualität aufgeworfen sowie Zusammenhänge mit den Faktoren Körperbeherrschung, Praktizieren von Entspannungstechniken, Schlafqualität etc. dargestellt.
Eine Methode zur Klassifizierung von Regelvorgängen biologischer und musikalischer Prozesse mit Hilfe eines künstlichen neuronalen Netzes und ihre Relevanz im Bereich der Musikwirkungsforschung
Authors: Fritz Florentina Maria
Published: September 2006

Zusammenfassung. Die Wirkung von Musik auf den Menschen ist unumstritten und kann mit Hilfe naturwissenschaftlicher Methoden untersucht werden. Eine neu entwickelte Methode zur Analyse der Synchronisation zwischen Musik und Hörer bzw. Musiker soll in Folge unterstützt durch ein künstliches neuronales Netz dargestellt werden. Dieser Ansatz ermöglicht einen direkten Vergleich zwischen physiologischen und musikalischen Daten und schafft dadurch eine Möglichkeit, die Wirkung von Musik auf den Menschen zu untersuchen. Künstliche neuronale Netze lassen sich sehr vielseitig einsetzen, so beispielsweise im Bereich der Mustererkennung. Im Speziellen ist es Aufgabe des eingesetzten neuronalen Netzes, biologische Zustände vegetativer Funktionen des Menschen (vegetativ-emotionale Reaktionen, charakterisiert durch den Parameter Hautwiderstand, vegetativ-nervale Reaktionen, bestimmt durch den Parameter Hautpotenzial, und motorisch-muskuläre Reaktionen, bestimmt durch den Parameter EMG) und “musikalische Zustände“ in musikalischen Parametern (durchschnittlicher Lautstärkewechsel, aufsummiert normiertes Frequenzdichtespektrum und Tonfolgedichte) zu klassifizieren. Zu diesem Zwecke wird zunächst die Methodik der Chronobiologischen Regulationsdiagnostik nach Hecht/Balzer beschrieben, welche sich im Wesentlichen mit der Analyse von Perioden und Rhythmen in Zeitreihen befasst, und im weiteren Verlauf dieses Beitrags in weiterentwickelter Form als Grundlage für die Klassifizierung durch das neuronale Netz dient. Die Ergebnisse des entwickelten neuronalen Netzes werden evaluiert und erste praktische Anwendungsbeispiele des Netzes aus dem Bereich Musikwirkung präsentiert sowie eine Relevanz der vorgestellten Methodik im Bereich der Musiktherapie angesprochen.
Mechanisms of midlatitude cross‐tropopause transport using a potential vorticity budget approach
Authors: Gray S. L.
Published: September 2006

A potential vorticity (PV) budget method has been used to attribute vertical transport across the near‐tropopause (1 PVU surface) in extratropical weather systems to radiative, latent heating and cooling, and mixing processes. Sources and sinks of PV due to nonconservative processes are calculated online and advected as passive tracers. There is reasonable agreement between the spatial distribution of transport determined from the PV budget method and the transport across the 1–2 PVU zone from a passive tracer and trajectories, but different aspects of exchange can be diagnosed with each method. Stratosphere‐to‐troposphere transport occurred in the broad upper level PV anomalies and was attributed mainly to latent heating and cooling processes; troposphere‐to‐stratosphere transport occurred toward the tail of a PV filament and in a ridge region and was attributed mainly to radiative processes. The contribution of mixing processes to transport was comparatively small. Using the PV budget method, the domain integrated exchange across the 1 PVU surface was from stratosphere to troposphere, and the magnitude of 1 × 1015 kg over a 2 day winter integration in a large North Atlantic domain is consistent with stratosphere‐troposphere exchange calculations from other studies. This exchange arises from an approximate balance between the dominant stratosphere‐to‐troposphere transport due to latent heating and cooling processes and troposphere‐to‐stratosphere transport due to radiative processes. The direction of transport across the tropopause in a fold was found to be critically dependent on the PV surface considered to represent the tropopause.
Aerosol characteristics at a high‐altitude location in central Himalayas: Optical properties and radiative forcing
Authors: Pant P. , Hegde P. , Dumka U. C. , Sagar Ram , Satheesh S. K. , Moorthy K. Krishna , Saha Auromeet , Srivastava M. K.
Published: September 2006

Collocated measurements of the mass concentrations of aerosol black carbon (BC) and composite aerosols near the surface were carried out along with spectral aerosol optical depths (AODs) from a high‐altitude station, Manora Peak in central Himalayas, during a comprehensive aerosol field campaign in December 2004. Despite being a pristine location in the Shivalik Ranges of central Himalayas and having a monthly mean AOD (at 500 nm) of 0.059 ± 0.033 (typical to this site), total suspended particulate (TSP) concentration was in the range 15–40 μg m−3 (mean value 27.1 ± 8.3 μg m−3). Interestingly, aerosol BC had a mean concentration of 1.36 ± 0.99 μg m−3 and contributed ∼5.0 ± 1.3% to the composite aerosol mass. This large abundance of BC is found to have linkages to the human activities in the adjoining valley and to the boundary layer dynamics. Consequently, the inferred single scattering albedo lies in the range of 0.87 to 0.94 (mean value 0.90 ± 0.03), indicating significant aerosol absorption. The estimated aerosol radiative forcing was as low as −4.2 W m−2 at the surface, +0.7 W m−2 at the top of the atmosphere, implying an atmospheric forcing of +4.9 W m−2. Though absolute value of the atmospheric forcing is quite small, which arises primarily from the very low AOD (or the column abundance of aerosols), the forcing efficiency (forcing per unit optical depth) was ∼88 W m−2, which is attributed to the high BC mass fraction.
Role of surface evaporation in surface rainfall processes
Authors: Cui Xiaopeng , Li Xiaofan
Published: September 2006

The roles of surface evaporation in tropical surface rainfall processes in rainfall regions (raining stratiform and convective regions) and rainfall‐free regions (nonraining stratiform and clear‐sky regions) are investigated on the basis of the data from a series of two‐dimensional cloud‐resolving simulations. The model is integrated for 21 days with imposed zonally uniform vertical velocity, zonal wind, horizontal temperature, and vapor advection, as well as sea surface temperature from the Tropical Ocean–Global Atmosphere Coupled Ocean‐Atmosphere Response Experiment (TOGA COARE). The model is also integrated to equilibrium states for 40 days with imposed zero vertical velocity, constant zonal wind, and sea surface temperatures of 31°C and 29°C for two separate experiments. The time‐ and zonal‐mean surface evaporation mainly comes from rainfall‐free regions, where the surface evaporation is largely balanced by the vapor divergence associated with the subsidence. In rainfall regions the vapor convergence determines the convective rainfall while the surface evaporation plays a negligible role. Thus surface evaporation pumps water vapor into rainfall‐free regions, and the divergence transports the vapor from rainfall‐free regions to rainfall regions, which supports the rainfall. Imposed forcing and sea surface temperature do not change the role of surface evaporation in rainfall processes.
A combined microscopic and macroscopic approach to modeling the transport of pathogenic microorganisms from nonpoint sources of pollution
Authors: Yeghiazarian L. L. , Walker M. J. , Binning P. , Parlange J.‐Y. , Montemagno C. D.
Published: September 2006

Recent outbreaks of cryptosporidiosis raise serious concerns about the effectiveness of watershed management in controlling the risk of contamination by pathogens. A modeling strategy that takes into account the inherent randomness of the occurrence and transport of pathogens in surface water is important for accurate risk assessment and prediction of water contamination events. This paper presents a stochastic Markov model of microorganism transport, with distinct states of microorganism behavior capturing the microbial partitioning between solid and aqueous phases in runoff and soil surface, including the partitioning among soil particles of various sizes. A connection between the soil sediment and microbial transport is established through the incorporation of an erosion model (WEPP) into the microorganism transport model. Probability distribution functions of microorganism occurrence in time and space are constructed, and their properties are analyzed. A deterministic mathematical model of coupled pathogen and sediment transport is developed in parallel to parameterize the Markov process. The numerical values for the Markov model parameters were derived from two sets of experimental data. Model results show that areas with clay soils are more likely than sandy soils to contribute to contamination events and that the most influential transport parameters are the saturated hydraulic conductivity, rainfall intensity, and topographic slope.
Multicriterion decision analysis approach to assess the utility of watershed modeling for management decisions
Authors: Elshorbagy Amin
Published: September 2006

This paper employs the multicriterion decision analysis (MCDA) technique in a novel way to address the efficiency of watershed instrumentation programs and the efficacy of watershed modeling. A case study of reconstructed watersheds in northern Alberta, Canada, is used to illustrate the proposed usage of the MCDA technique. The watersheds have been disturbed as a result of oil sands mining activities. Assessing the performance of the reconstructed watersheds with regard to restoring the hydrology of the disturbed watershed is a crucial issue for both the mining industry and other stakeholders. The problem is formulated in a multicriterion context. A payoff matrix containing seven evaluation criteria and three different soil covers as feasible alternatives is constructed. The system dynamics watershed (SDW) model is used to simulate the reconstructed watersheds over a period of 61 years using historical meteorological records. Accordingly, 61 payoff matrices that are populated using the results of the SDW model are evaluated. A multicriterion decision analysis framework is implemented to evaluate the different alternatives with respect to the chosen set of criteria. The three alternatives are ranked every year, and accordingly, the probability that a certain alternative dominates others is estimated. The alternative that has the highest probability of occupying the top rank over the period of analysis is indicated as the best alternative. The probability value is called the probability of making the right decision (PMRD). Various types of uncertainty analyses are conducted to evaluate the sensitivity of the final decision to changes in the scores of the evaluation matrices. An index, named the confidence in the PMRD, is developed to quantify the reliability of the results of the watershed model. The results highlight the utility of modeling as a possible alternative to some components of the intensive instrumentation program. Moreover, areas of deficiency and inaccuracies in the watershed model are identified for further improvements.
Ionospheric signatures of a plasmaspheric plume over Europe
Authors: Yizengaw Endawoke , Moldwin Mark B. , Galvan David A.
Published: September 2006

Previously, ionospheric signatures of plasmaspheric plumes were reported only at the North American longitude sector. This led to the hypothesis that the geomagnetic field configuration at those longitudes played a vital role in the observation of plasmaspheric plume signatures only over the American continent. Combining ground‐based GPS total electron content (TEC), EISCAT incoherent scattering radar (ISR), and DMSP F15 ion drift meter observations we have observed greatly elevated density over the European continent during storm recovery phase on 12 September 2005. The TEC seen over Europe has a tongue of enhanced ionization extending to higher latitudes, which is identical to the plasmaspheric plume signatures that have been often observed over North America. Therefore, our observations clearly demonstrate that ionospheric signatures of plasmaspheric plumes are not limited to the North American sector and suggest that they may be observed at any longitude as long as a dense array of instruments are available to identify these signatures.
Severe ozone depletion in the cold Arctic winter 2004–05
Authors: von Hobe M. , Ulanovsky A. , Volk C. M. , Grooß J.‐U. , Tilmes S. , Konopka P. , Günther G. , Werner A. , Spelten N. , Shur G. , Yushkov V. , Ravegnani F. , Schiller C. , Müller R. , Stroh F.
Published: September 2006

During a flight of the M55 Geophysica into the Arctic polar vortex on 7 March 2005, ozone, halogen species, tracers and water vapor were measured. Up to 90% chlorine activation and up to 60% ozone loss were found above 14 km, reflecting the low temperatures and extensive PSC formation prevalent in the Arctic stratosphere over the 2004/05 winter. Observations are generally well reproduced by CLaMS model simulations. The observed levels of active chlorine can only be reproduced by assuming significant denitrification of about 70%. Moderate dehydration up to 0.5 ppm is observed in some locations. We deduce a partial column ozone loss of 62 (+8/−17) DU below 19 km on 7 March.
Observation of O2 1.27 μm dayglow by SPICAM IR: Seasonal distribution for the first Martian year of Mars Express
Authors: Fedorova Anna , Korablev Oleg , Perrier Severine , Bertaux Jean‐Loup , Lefevre Frank , Rodin Alexander
Published: September 2006

The O2(a1Δg) molecule is a result of the photodissociation of ozone in the Martian atmosphere and may be used as a tracer for atmospheric ozone mostly above ∼20 km since the singlet delta state is quenched by carbon dioxide at lower altitudes. The SPICAM IR acousto‐optic tunable filter (AOTF) spectrometer is a part of the SPICAM experiment onboard Mars Express. It is able to measure the O2 singlet delta emission band at 1.27 μm with a resolving power of ∼2200. We present the first seasonal map of the O2 emission covering the entire Martian year. Maximal values of O2 emission are observed during late winter to early spring at high latitudes in both hemispheres. We report the highest dayglow intensity of 30 MR in the southern hemisphere (70°–80°S latitudes) at Ls = 185°–195° and of 26 MR in the north polar regions (latitudes 70°–80°N) at Ls = 10°–20°. The lowest emissions are measured during the southern hemisphere summer near perihelion (Ls = 270°–330°), with an upper limit of 1–2 MR. At low latitudes (30°S–30°N) the seasonal evolution of the O2 emission shows a distinct maximum (5–7 MR) near aphelion. This is consistent with the maximum in O3 occurring at this time of the year, which has been reported from Earth, from satellite, or by modeling studies. The comparison of our results with previous measurements carried out from Earth shows quantitative differences that can be attributed to differences in local time of the observation or interannual variability of the Martian ozone layer.
Protein SUMOylation is Massively Increased in Hibernation Torpor and is Critical for the Cytoprotection Provided by Ischemic Preconditioning and Hypothermia in SHSY5Y Cells
Authors: Lee Yang-ja , Miyake Shin-ichi , Wakita Hideaki , McMullen David C , Azuma Yoshiaki , Auh Sungyoung , Hallenbeck John M
Published: September 2006

Hibernation torpor provides an excellent natural model of tolerance to profound reductions in blood flow to the brain and other organs. Here, we report that during torpor of 13-lined ground squirrels, massive SUMOylation occurs in the brain, liver, and kidney. The level of small ubiquitin-related modifier (SUMO) conjugation coincides with the expression level of Ubc9, the SUMO specific E2-conjugating enzyme. Hypothermia alone also increased SUMO conjugation, but not as markedly as hibernation torpor. Increased SUMO conjugation (induced by Ubc9 overexpression, ischemic preconditioning (PC) ± hypothermia) was necessary and sufficient for tolerance of SHSY5Y neuroblastoma cells to oxygen/glucose deprivation (OGD) (‘ in vitro ischemia‘); decreased SUMO conjugation (induced by a dominant-negative Ubc9) severely reduced tolerance to OGD in these cells. These data indicate that post-translational modification of proteins by SUMOylation is a prominent feature of hibernation torpor and is critical for cytoprotection by ischemic PC ± hypothermia in SHSY5Y cells subjected to OGD.
Reduction in Oxidative Stress by Superoxide Dismutase Overexpression Attenuates Acute Brain Injury after Subarachnoid Hemorrhage via Activation of Akt/Glycogen Synthase Kinase-3β Survival Signaling
Authors: Endo Hidenori , Nito Chikako , Kamada Hiroshi , Yu Fengshan , Chan Pak H
Published: September 2006

Recent studies have revealed that oxidative stress has detrimental effects in several models of neurodegenerative diseases, including subarachnoid hemorrhage (SAH). However, how oxidative stress affects acute brain injury after SAH remains unknown. We have previously reported that overexpression of copper/zinc-superoxide dismutase (SOD1) reduces oxidative stress and subsequent neuronal injury after cerebral ischemia. In this study, we investigated the relationship between oxidative stress and acute brain injury after SAH using SOD1 transgenic (Tg) rats. SAH was produced by endovascular perforation in wild-type (Wt) and SOD1 Tg rats. Apoptotic cell death at 24 h, detected by a cell death assay, was significantly decreased in the cerebral cortex of the SOD1 Tg rats compared with the Wt rats. The mortality rate at 24 h was also significantly decreased in the SOD1 Tg rats. A hydroethidine study demonstrated that superoxide anion production after SAH was reduced in the cerebral cortex of the SOD1 Tg rats. Moreover, phosphorylation of Akt and glycogen synthase kinase-3β (GSK3β), which are survival signals in apoptotic cell death, was more enhanced in the cerebral cortex of the SOD1 Tg rats after SAH using Western blot analysis and immunohistochemistry. We conclude that reduction in oxidative stress by SOD1 overexpression may attenuate acute brain injury after SAH via activation of Akt/GSK3β survival signaling.
Effect of testosterone on ex vivo vascular reactivity in man
Authors: Malkin Christopher J. , Jones Richard D. , Jones T. Hugh , Channer Kevin S.
Published: September 2006

Testosterone is reported to have an acute vasodilating action in vitro, an effect that may impart a favourable haemodynamic response in patients with chronic heart failure. However, the effect of chronic testosterone exposure on general vascular reactivity is poorly described. In the present study, fresh subcutaneous resistance arteries were obtained from patients with heart failure (n=10), healthy controls (n=9) and men with androgen-deficiency (n=17). All arteries were studied using a wire myograph to examine the effect of cumulative additions of testosterone (1 nmol/l–100 μmol/l) compared with vehicle control following maximal pre-constriction with KCl (1–100 μmol/l). The vascular reactivity of arteries from androgen-deficient patients was examined further by recording tension concentration curves to cumulative additions of noradrenaline (1 nmol/l–100 μmol/l) and U46619 (1–300 nmol/l), followed by relaxation concentration curves to additions of ACh (acetylcholine; 10 nmol/l–30 μmol/l) and SNP (sodium nitroprusside; 10 nmol–30 μmol/l) respectively. In all cases, statistical analysis was performed by ANOVA. Patients with proven androgen-deficiency were treated according to clinical recommendations for a minimum of 3 months and further arteries (n=19) were taken for experimentation using the same protocol. In all groups, testosterone was confirmed to be an acute concentration-dependent vasodilator at concentrations ≥1 μmol/l (P=0.0001). The dilating effect of testosterone was augmented in patients with androgen-deficiency prior to treatment, and this effect was abrogated following appropriate testosterone replacement. Testosterone therapy significantly reduced the normal vascular dilating response to ACh and SNP (P<0.01) and significantly increased the contractile response to noradrenaline (P<0.01), but not U46619. Testosterone is an acute dose-dependent vasodilator of resistance arteries. Physiological testosterone replacement attenuates general vascular reactivity in androgen-deficient subjects. The numerous perceived benefits of testosterone replacement may be offset by a decline in vascular reactivity and, therefore, further studies and careful monitoring of patients is recommended.
Signal transduction therapy in haematological malignancies: identification and targeting of tyrosine kinases
Authors: Chase Andrew , Cross Nicholas C. P.
Published: September 2006

Tyrosine kinases play key roles in cell proliferation, survival and differentiation. Their aberrant activation, caused either by the formation of fusion genes by chromosome translocation or by intragenic changes, such as point mutations or internal duplications, is of major importance in the development of many haematological malignancies. An understanding of the mechanisms by which BCR-ABL contributes to the pathogenesis of chronic myeloid leukaemia led to the development of imatinib, the first of several tyrosine kinase inhibitors to enter clinical trials. Although the development of resistance has been problematic, particularly in aggressive disease, the development of novel inhibitors and combination with other forms of therapy shows promise.
Au-assisted growth approach for vertically aligned ZnO nanowires on Si substrate
Authors: Zhang Guoqiang , Nakamura Atsushi , Aoki Toru , Temmyo Jiro , Matsui Yoshio
Published: September 2006

We have described a Au-assisted approach for growth of vertically aligned ZnO nanowires on Si substrate by metal-organic chemical vapor deposition. By employing an annealed Au∕Si substrate, on which Au nanoislands are homogeneously distributed, vertically aligned ZnO nanowires on a Si substrate are resulted. Photoluminescence measurement shows that the near-band emission intensity of these ZnO nanowires is significantly improved compared with the ZnO film grown directly on a Si substrate. Extensive characterization by transmission electron microscopy has been made and the growth mechanism of these ZnO nanowires is discussed.
On estimates of Lyapunov exponents of synchronized coupled systems
Authors: Zhou Tianshou , Chen Guanrong , Lu Qishao , Xiong Xiaohua
Published: September 2006

Lyapunov exponents of a synchronized coupled system consist of those of the underlying individual systems and the transverse systems, based on a mode decomposition along the synchronization manifold. Estimates of bounds on the Lyapunov exponents (including transverse Lyapunov exponents) are derived. Several examples are used to validate the theoretical estimates.
Symbolic synchronization and the detection of global properties of coupled dynamics from local information
Authors: Jalan Sarika , Jost Jürgen , Atay Fatihcan M.
Published: September 2006

We study coupled dynamics on networks using symbolic dynamics. The symbolic dynamics is defined by dividing the state space into a small number of regions (typically 2), and considering the relative frequencies of the transitions between those regions. It turns out that the global qualitative properties of the coupled dynamics can be classified into three different phases based on the synchronization of the variables and the homogeneity of the symbolic dynamics. Of particular interest is the homogeneous unsynchronized phase, where the coupled dynamics is in a chaotic unsynchronized state, but exhibits qualitative similar symbolic dynamics at all the nodes in the network. We refer to this dynamical behavior as symbolic synchronization. In this phase, the local symbolic dynamics of any arbitrarily selected node reflects global properties of the coupled dynamics, such as qualitative behavior of the largest Lyapunov exponent and phase synchronization. This phase depends mainly on the network architecture, and only to a smaller extent on the local chaotic dynamical function. We present results for two model dynamics, iterations of the one-dimensional logistic map and the two-dimensional Hénon map, as local dynamical function.
Generalized projective synchronization of chaotic systems with unknown dead-zone input: Observer-based approach
Authors: Hung Yung-Ching , Hwang Chi-Chuan , Liao Teh-Lu , Yan Jun-Juh
Published: September 2006

In this paper we investigate the synchronization problem of drive-response chaotic systems with a scalar coupling signal. By using the scalar transmitted signal from the drive chaotic system, an observer-based response chaotic system with dead-zone nonlinear input is designed. An output feedback control technique is derived to achieve generalized projective synchronization between the drive system and the response system. Furthermore, an adaptive control law is established that guarantees generalized projective synchronization without the knowledge of system nonlinearity, and/or system parameters as well as that of parameters in dead-zone input nonlinearity. Two illustrative examples are given to demonstrate the effectiveness of the proposed synchronization scheme.
Higher-dimensional knotlike topological defects in local non-Abelian topological tensor currents
Authors: Duan Yi-shi , Wu Shao-feng , Zhang Peng-ming
Published: September 2006

We present the novel topological tensor currents to describe the infinitesimal thin higher-dimensional topological defects in the local SO(n) gauge theory. The topological quantization of defects and the inner structure of the currents are obtained. As the generalization of Nielsen-Olesen local U(1) field theory for Nambu string, the local SO(n) gauge-invariant Lagrangian and the motion equation of the higher-dimensional topological defects are derived. Moreover, for closed defects, we study their important topological configuration, i.e., the higher-dimensional knotlike structures. Using the topological tensor currents and their preimages, we construct a series of metric independent integrals and prove their gauge independence. Similar to the helicity integral characterizing one-dimensional knotlike vortex filament, these topological invariants are evaluated to the generalized linking numbers of higher-dimensional knotlike defects.
Perpendicular anisotropy in electrodeposited, Co-rich Co–Pt films by use of Ru underlayers
Authors: Pattanaik G. , Zangari G. , Weston J.
Published: September 2006

Co-rich Co–Pt alloys were electrodeposited from an amino-citrate-based solution on a Si (011)∕Cu(111)∕Ru(0001) seed layer. Such a template provides an appropriate interface structure for the growth of a (0002)-oriented hexagonal phase, stabilized at larger thickness by the electrolyte chemistry, providing for a columnar structure with no detectable grain coarsening. This results in as-deposited Co–Pt films exhibiting perpendicular anisotropy (anisotropy constant up to 1.2MJ∕m3) and hard magnetic properties (coercivity up to 358.2kA∕m) in a wide thickness range, from 5to2000nm. Crystalline, magnetoelastic, and interface effects are discussed as possible origins of the observed perpendicular anisotropy.
Structural model for bulk amorphous alloys
Authors: Fan Cang , Liaw P. K. , Wilson T. W. , Dmowski W. , Choo H. , Liu C. T. , Richardson J. W. , Proffen Th.
Published: September 2006

A structural model is proposed for bulk amorphous alloys based on the pair distribution functions (PDFs) measured using neutron scattering at ambient and cryogenic temperatures and different structural states. Reverse Monte Carlo (RMC) simulations were performed, in which icosahedral and cubic structures were used as the initial structures for the PDF refinement. The combined PDF and RMC studies show that strongly bonded clusters, with atomic-bond lengths shorter than their crystalline counterpart structures, are randomly distributed and strongly connected in the amorphous matrix. An attempt has also been made to identify the relationship between amorphous structures and their mechanical properties.
Preparation and dielectric characterization of ferroelectric (PbxSr1−x)TiO3 glass ceramics doped with La2O3
Authors: Kumar Devendra , Gautam C. R. , Parkash Om
Published: September 2006

Perovskite lead strontium titanate solid solution phase has been crystallized in the presence of La2O3 in the system [(PbxSr1−x)O∙TiO2]–[2SiO2∙B2O3]–[K2O]–[BaO]–[La2O3] (1⩽x⩽0.5). La2O3 is a donor dopant for (Pb,Sr)TiO3 and can make crystalline phase semiconducting in the glass ceramics. Dispersion of semiconducting perovskite phase in insulating glassy matrix may lead to space charge polarization around crystal glass interface, imparting high value of effective dielectric constant. Glass ceramic samples show a broad Curie peak in their dielectric constant versus temperature plots. The dissipation factor versus temperature plots also show a relaxation peak, which shifts to higher temperature with increasing frequency.
Stable fiber-based Fabry-Pérot cavity
Authors: Steinmetz T. , Colombe Y. , Hunger D. , Hänsch T. W. , Balocchi A. , Warburton R. J. , Reichel J.
Published: September 2006

The development of a fiber-based, tunable optical cavity with open access is reported. The cavity is of the Fabry-Pérot type and is formed with miniature spherical mirrors positioned on the end of single- or multimode optical fibers by a transfer technique, which involves lifting a high-quality mirror from a smooth convex substrate, either a ball lens or microlens. The cavities typically have a finesse of ∼1000 and a mode volume of 600μm3. The detection of small ensembles of cold Rb atoms guided through such a cavity on an atom chip is demonstrated.
Mitigation of fast ions from laser-produced Sn plasma for an extreme ultraviolet lithography source
Authors: Tao Y. , Tillack M. S.
Published: September 2006

The authors present evidence of the reduction of fast ion energy from laser-produced Sn plasma by introducing a low energy prepulse. The energy of Sn ions was reduced from more than 5keV to less than 150eV nearly without loss of the in-band conversion from laser to 13.5nm extreme ultraviolet (EUV) emission as compared with that of a single pulse. The reason may come from the interaction of the main pulse with preplasma instead of the full density solid surface. This makes it possible to use the full density Sn target in the practical EUV lithography source.
Built-in field effect on the electron mobility in AlN∕GaN∕AlN quantum wells
Authors: Pokatilov E. P. , Nika D. L. , Balandin A. A.
Published: September 2006

The authors demonstrated theoretically that compensation of the built-in electric field in AlN∕GaN∕AlN heterostructures with the externally applied perpendicular electric field may lead to the increase of the in-plane electron drift mobility. It has been shown that two- to fourfold increase of the room temperature mobility can be achieved for both nondegenerate and degenerate electron densities. Their calculations clarified the role of the intersubband electron transitions mediated by optical phonons in limiting the carrier mobility in GaN-based heterostructures. The tuning of the electron mobility with the perpendicular electric field may impact design of the high-power GaN∕AlGaN heterostructure field-effect transistors.
Efficiency enhancement in Si solar cells by textured photonic crystal back reflector
Authors: Zeng L. , Yi Y. , Hong C. , Liu J. , Feng N. , Duan X. , Kimerling L. C. , Alamariu B. A.
Published: September 2006

An efficient light-trapping scheme is developed for solar cells that can enhance the optical path length by several orders of magnitude using a textured photonic crystal as a backside reflector. It comprises a reflection grating etched on the backside of the substrate and a one-dimensional photonic crystal deposited on the grating. Top-contacted crystalline Si solar cells integrated with the textured photonic crystal back reflector were designed and fabricated. External quantum efficiency was significantly improved between the wavelengths of 1000 and 1200nm (enhancement up to 135 times), and the overall power conversion efficiency was considerably increased.
High-quality nonpolar 4H-AlN grown on 4H-SiC (112¯) substrate by molecular-beam epitaxy
Authors: Horita Masahiro , Suda Jun , Kimoto Tsunenobu
Published: September 2006

Growth of very high-quality nonpolar (112¯0) a-plane face 4H-AlN on 4H-SiC (112¯0) substrate was investigated. Nonpolar 4H-AlN (112¯0) was isopolytypically grown on 4H-SiC (112¯0) substrate by molecular-beam epitaxy. A reduction of defects such as stacking faults and threading dislocations was achieved by keeping the growing surface flat. To this end, the SiC substrate was HCl gas etched and the V/III ratio was optimized for AlN growth. A full width at half maximum of symmetrical x-ray diffraction ω scan of the 4H-AlN layer was 40arcsec. Transmission electron microscopy revealed the stacking fault density to be 2×105cm−1, and the partial and perfect threading dislocation densities to be 7×107 and 1×107cm−2, respectively.