bluuebunny/crossref_metadata_2025 huggingface dataset:
Freshwater pulses in the eastern Arctic Ocean during Saalian and Early Weichselian ice-sheet collapse
Authors: Knies Jochen , Vogt Christoph
Published: November 2003

Improved multiparameter records from the northern Barents Sea margin show two prominent freshwater pulses into the Arctic Ocean during MIS 5 that significantly disturbed the regional oceanic regime and probably affected global climate. Both pulses are associated with major iceberg-rafted debris (IRD) events, revealing intensive iceberg/sea ice melting. The older meltwater pulse occurred near the MIS 5/6 boundary (∼131,000 yr ago); its ∼2000 year duration and high IRD input accompanied by high illite content suggest a collapse of large-scale Saalian Glaciation in the Arctic Ocean. Movement of this meltwater with the Transpolar Drift current into the Fram Strait probably promoted freshening of Nordic Seas surface water, which may have increased sea-ice formation and significantly reduced deep-water formation. A second pulse of freshwater occurred within MIS 5a (∼77,000 yr ago); its high smectite content and relatively short duration is possibly consistent with sudden discharge of Early Weichselian ice-dammed lakes in northern Siberia as suggested by terrestrial glacial geologic data. The influence of this MIS 5a meltwater pulse has been observed at a number of sites along the Transpolar Drift, through Fram Strait, and into the Nordic Seas; it may well have been a trigger for the North Atlantic cooling event C20.
Late Holocene climates of the Near East deduced from Dead Sea level variations and modern regional winter rainfall
Authors: Enzel Yehouda , Bookman (Ken Tor) Revital , Sharon David , Gvirtzman Haim , Dayan Uri , Ziv Baruch , Stein Mordechai
Published: November 2003

The Dead Sea is a terminal lake of one of the largest hydrological systems in the Levant and may thus be viewed as a large rain gauge for the region. Variations of its level are indicative of the climate variations in the region. Here, we present the decadal- to centennial-resolution Holocene lake-level curve of the Dead Sea. Then we determine the regional hydroclimatology that affected level variations. To achieve this goal we compare modern natural lake-level variations and instrumental rainfall records and quantify the hydrology relative to lake-level rise, fall, or stability. To quantify that relationship under natural conditions, rainfall data pre-dating the artificial Dead Sea level drop since the 1960s are used. In this respect, Jerusalem station offers the longest uninterrupted pre-1960s rainfall record and Jerusalem rains serve as an adequate proxy for the Dead Sea headwaters rainfall. Principal component analysis indicates that temporal variations of annual precipitation in all stations in Israel north of the current 200 mm yr−1 average isohyet during 1940–1990 are largely synchronous and in phase (∼70% of the total variance explained by PC1). This station also represents well northern Jordan and the area all the way to Beirut, Lebanon, especially during extreme drought and wet spells. We (a) determine the modern, and propose the past regional hydrology and Eastern Mediterranean (EM) climatology that affected the severity and length of droughts/wet spells associated with multiyear episodes of Dead Sea level falls/rises and (b) determine that EM cyclone tracks were different in average number and latitude in wet and dry years in Jerusalem. The mean composite sea level pressure and 500-mb height anomalies indicate that the potential causes for wet and dry episodes span the entire EM and are rooted in the larger-scale northern hemisphere atmospheric circulation. We also identified remarkably close association (within radiocarbon resolution) between climatic changes in the Levant, reflected by level changes, and culture shifts in this region.
Amino acids and hexosamines in the Hess Rise core during the past 220,000 years
Authors: Gupta Lallan Prasad , Kawahata Hodaka
Published: November 2003

Core sediment samples collected from the Hess Rise, North Pacific, were analyzed for 20 common amino acids (AA) and two hexosamines (HA) to understand the relation between glacial–interglacial variations and deposition/preservation of sedimentary organic matter (OM). The sediments are predominantly carbonaceous (carbonates 35–80%). AA-based parameters—aspartic acid/glycine ratio and serine+threonine relative mole content—suggest that calcareous plankton was the major source of OM in these sediments. This inference is supported by the similarity in distribution patterns of AA and HA contents with that of organic carbon. Low values of AA/HA and glucosamine/galactosamine ratios (average 4.4 and 1.1, respectively) imply that much of the planktonic OM was replaced by microbial OM. The relative molar concentration of two nonprotein AA (β-alanine and γ-aminobutyric acid) varied with age of sediments; i.e., they were less abundant in recent sediments and more abundant in the oldest sediments. This trend is an indicator of extremely slow but continuous enzymatic degradation of proteinaceous OM within the sediments. So far, bulk OM has been believed to be one of the best proxies for estimation of primary productivity. However, it may be an underestimate, even for the late Quaternary sediments. Comparison of AA and HA content variations with SPECMAP stack revealed their enhanced deposition and preservation during glacial periods relative to interglacial periods. This, in turn, affected not only the planktonic production in surface waters but also the benthic community, including bacteria on the seafloor.
Calibrated, late Quaternary age indices using clast rubification and soil development on alluvial surfaces in Pilot Knob Valley, Mojave Desert, southeastern California
Authors: Helms John G. , McGill Sally F. , Rockwell Thomas K.
Published: November 2003

The orange coating (varnish) that forms on the undersides (ventral sides) of clasts in desert pavements constitutes a potential relative-age indicator. Using Munsell color notation, we semiquantified the color of the orange, ventral varnish on the undersides of clasts from 15 different alluvial fan and terrace surfaces of various ages ranging from less than 500 to about 25,000 yr. All of the surfaces studied are located along the central portion of the left-lateral Garlock fault, in the Mojave Desert of southern California. The amount of left-lateral offset may be used to determine the relative ages of the surfaces. The previously published slip rate of the fault may also be used to estimate the absolute age of each surface. The color of the ventral varnish is strongly correlated with surface age and appears to be a more reliable age-indicator than the percentage coverage of dorsal varnish. Soil development indices also were not as strongly correlated with age, as were the colors of the ventral varnish. In particular, rubification appears to be more useful than soils for distinguishing relative ages among Holocene surfaces. Humidity sensors indicated that the undersides of clasts condensed moisture nightly for a period of several days to over a week after each rain. These frequent wet-dry cycles may be responsible for the rapid development of clast rubification on Holocene surfaces.
Prediction of the binding site on E1 in the assembly of the pyruvate dehydrogenase multienzyme complex of Bacillus stearothermophilus
Authors: Jung Hyo-Il , Perham Richard N
Published: November 2003

The β‐subunit (E1β) of the pyruvate decarboxylase (E1, α2β2) component of the Bacillus stearothermophilus pyruvate dehydrogenase complex was comparatively modelled based on the crystal structures of the homologous 2‐oxoisovalerate decarboxylase of Pseudomonas putida and Homo sapiens. Based on this homology modelling, alanine‐scanning mutagenesis studies revealed that the negatively charged side chain of Glu285 and the hydrophobic side chain of Phe324 are of particular importance in the interaction with the peripheral subunit‐binding domain of the dihydrolipoyl acetyltransferase component of the complex. These results help to identify the site of interaction on the E1β subunit and are consistent with thermodynamic evidence of a mixture of electrostatic and hydrophobic interactions being involved.
Structural basis of calcium and galactose recognition by the lectin PA‐IL of Pseudomonas aeruginosa
Authors: Cioci Gianluca , Mitchell Edward P , Gautier Catherine , Wimmerová Michaela , Sudakevitz Dvora , Pérez Serge , Gilboa-Garber Nechama , Imberty Anne
Published: November 2003

The structure of the tetrameric Pseudomonas aeruginosa lectin I (PA‐IL) in complex with galactose and calcium was determined at 1.6 Å resolution, and the native protein was solved at 2.4 Å resolution. Each monomer adopts a β‐sandwich fold with ligand binding site at the apex. All galactose hydroxyl groups, except O1, are involved in a hydrogen bond network with the protein and O3 and O4 also participate in the co‐ordination of the calcium ion. The stereochemistry of calcium galactose binding is reminiscent of that observed in some animal C‐type lectins. The structure of the complex provides a framework for future design of anti‐bacterial compounds.
The function of conserved cysteine residues in the extracellular domain of human receptor‐activity‐modifying protein 1
Authors: Steiner Sarah , Born Walter , Fischer Jan A. , Muff Roman
Published: November 2003

The receptor‐activity‐modifying protein (RAMP) 1 is a single‐transmembrane‐domain protein associated with the calcitonin‐like receptor (CLR) to reveal a calcitonin gene‐related peptide (CGRP) receptor. The extracellular region of RAMP1 contains six conserved cysteines. Here, Cys27 in myc‐tagged human (h) RAMP1 was deleted (hRAMP1Δ1), and Cys40, Cys57, Cys72, Cys82 and Cys104 were each replaced by Ala. In COS‐7 cells expressing hCLR/myc‐hRAMP1Δ1 or ‐C82A, cell surface expression, [125I]hαCGRP binding and cAMP formation in response to hαCGRP were similar to those of hCLR/myc‐hRAMP1. Cell surface expression of myc‐hRAMP1‐C72A was reduced to 24±7% of myc‐hRAMP1, and that of ‐C40A, ‐C57A and ‐C104A was below 10%. [125I]hαCGRP binding of hCLR/myc‐hRAMP1‐C72A was 13±3% of hCLR/myc‐hRAMP1 and it was undetectable in hCLR/myc‐hRAMP1‐C40A‐, ‐C57A‐ and ‐C104A‐expressing cells. Maximal cAMP stimulation by hαCGRP in hCLR/myc‐hRAMP1‐C40A‐ and ‐C72A‐expressing cells was 14±1% and 33±2% of that of the hCLR/myc‐hRAMP1 with comparable EC50. But cAMP stimulation was abolished in cells expressing hCLR/myc‐hRAMP1‐C57A and ‐C104A. In conclusion, CGRP receptor function was not affected by the deletion of Cys27 or the substitution of Cys82 by Ala in hRAMP1, but it was impaired by the substitution of Cys40, Cys57, Cys72 and Cys104 by Ala. These four cysteines are required for the transport of hRAMP1 together with the CLR to the cell surface.
Coordinate expression of the α and β subunits of heterotrimeric G proteins involves regulation of protein degradation in CHO cells
Authors: Lee Yun-Il , Kim So-Young , Cho Chin-Ho , Seo MiRan , Cho Du-Hyong , Kwak Sahng-June , Juhnn Yong-Sung
Published: November 2003

Individual cell types express a characteristic balance between heterotrimeric G protein α and βγ subunits, but little is known about the regulatory mechanism. We systemically examined the regulatory mechanism in CHO cells. We found that expression of Gαs, Gαi2, and Gαq proteins increased in direct proportion to the increase of Gβ1γ2 overexpressed transiently. Expression of Gβ protein also increased following overexpression of Gαs, Gαi2, and Gαq. The Gβγ overexpression stimulated degradation of Gβ in contrast to reduction of Gαs degradation. We conclude that coordinate expression of the G protein subunits involves regulation of protein degradation via proteasome in CHO cells.
PIAS1 enhances SUMO‐1 modification and the transactivation activity of the major immediate–early IE2 protein of human cytomegalovirus
Authors: Lee Jang-Mi , Kang Hee-Jung , Lee Hye-Ra , Choi Cheol Yong , Jang Won-Jong , Ahn Jin-Hyun
Published: November 2003

The protein inhibitor of activated STAT1 (PIAS1), known to be a small ubiquitin‐like modifier (SUMO) E3 ligase, was found to interact with the human cytomegalovirus IE2 protein. We found that the sumoylation of IE2 was markedly enhanced by wild‐type PIAS1 but not by a mutant containing a Cys to Ser substitution at position 351 (C351S) within the RING finger‐like domain. In target reporter gene assays, wild‐type PIAS1, but not the C351S mutant, enhanced the IE2‐mediated transactivations of viral polymerase promoter and cellular cyclin E promoter and this augmentation required the intact sumoylation sites of IE2. Our results suggest that PIAS1 acts as a SUMO E3 ligase toward IE2 and that it may regulate the transactivation function of IE2. To our knowledge, IE2 is the first viral target found to be regulated by a SUMO E3 ligase.
A PERIOD inhibitor buffer introduces a delay mechanism for CLK/CYC‐activated transcription
Authors: Weber Frank , Kay Steve A
Published: November 2003

We investigated the functions of clock genes period (per) and timeless (tim) in establishing negative feedback on circadian transcription factors clock/cycle (Clk/cyc) in Drosophila. We show that PER protein persists for several hours after rapid degradation of TIM in the morning. We observed in cell culture that isolated PER inhibits CLK/CYC‐activated transcription in the absence of TIM and we further demonstrated for the first time in vivo that PER accumulation in a tim loss‐of‐function mutant background causes efficient inhibition of CLK/CYC‐dependent transcription. These results identify PER to be the main inhibitor for CLK/CYC and they suggest a delay mechanism during early morning, when PER protein, after degradation of TIM, forms an inhibitor buffer for CLK/CYC that attenuates the restart of the next cycle of CLK/CYC‐activated transcription. While TIM likely enhances the inhibition of CLK/CYC by PER in the dark, our results suggest a reduction of PER‐mediated inhibition by TIM in light.
Simultaneous activation of apoptosis and inflammation in pathogenesis of septic shock: a hypothesis1
Authors: Joshi Vishwas D , Kalvakolanu Dhananjaya V , Cross Alan S
Published: November 2003

Sepsis, a widely prevalent disease with increasing morbidity and mortality, is thought to result from uncontrolled inflammatory responses to microbial infection and/or components. However, failure of several experimental anti‐inflammatory therapies has necessitated re‐evaluation of the paradigm underlying the pathogenesis of this complex disorder. Apoptotic cell death forms a second dominant feature of septic shock in patients and animal models. Anti‐apoptotic strategies may protect animals from septic death. However, simultaneous occurrence of apoptosis and inflammation is necessary for septic death. At the cellular level, apoptosis plays a central role in the development of the lymphoid system and regulation of immune responses. Immune activation renders cells refractory to apoptosis while apoptosis of activated lymphocytes is an important immunoregulatory mechanism. Factors such as complement factor 5a, caspase‐1 and mitogen‐activated protein kinase, which participate in apoptosis as well as pro‐inflammatory pathways, may be responsible for simultaneous activation of apoptosis and inflammation in sepsis. Further identification of other similar biochemical events capable of co‐activating inflammation and apoptosis may provide new targets for therapy of this hitherto untreatable disease.
Presence of the inositol 1,4,5‐triphosphate receptor isoforms in the nucleoplasm
Authors: Huh Yang Hoon , Yoo Seung Hyun
Published: November 2003

Although the inositol 1,4,5‐triphosphate (IP3)‐induced nuclear Ca2+ release has been shown to play key roles in nuclear functions, the presence of IP3 receptor (IP3R)/Ca2+ channels in the nucleoplasm has not been found. Recently, the IP3R/Ca2+ channels were reported to exist in the nucleoplasmic reticulum structure, an extension of the nuclear envelope. Here we investigated the potential existence of the IP3Rs in the nucleoplasm and found the presence of all three IP3R isoforms in neuroendocrine and non‐neuroendocrine cells. The IP3Rs were widely scattered in the nucleoplasm, localizing in both the heterochromatin and euchromatin regions.
Intracellular trafficking of CLN3, the protein underlying the childhood neurodegenerative disease, Batten disease
Authors: Mao Qinwen , Xia Haibin , Davidson Beverly L
Published: November 2003

Juvenile neuronal ceroid lipofuscinoses (Batten disease) is a progressive neurodegenerative disorder resulting from mutations in the CLN3 gene, which encodes a hydrophobic 438 amino acid protein of unknown function. Prior studies have shown that CLN3 is expressed in multiple tissues, with highest levels in brain and testis. Experiments using cells overexpressing CLN3 indicate that CLN3 is a lysosomal resident protein. However, studies to date have not addressed trafficking of endogenous CLN3. As such, the purpose of the present study was two‐fold. First, to develop a culture model to allow evaluation of native CLN3 transport. Second, to utilize available epitope‐specific antibodies to determine if CLN3 reaches the plasma membrane en route to the lysosome. Our data using a NCCIT (embryonic testicular carcinoma) cell model coupled with surface biotinylation and antibody trapping demonstrated that at least a proportion of CLN3 trafficks to the lysosome via the cell membrane. Moreover, inhibition of the μ3A subunit of the AP‐3 adapter protein complex increased levels of CLN3 at the cell surface.
Plant mitochondrial nucleoside diphosphate kinase is attached to the membrane through interaction with the adenine nucleotide translocator
Authors: Knorpp Carina , Johansson Monika , Baird Anne-Marie
Published: November 2003

This study shows that the plant mitochondrial nucleoside diphosphate kinase (mNDPK) localizes to both the intermembrane space and to the mitochondrial inner membrane. We show that mNDPK is very firmly attached to the membrane. Co‐immunoprecipitation experiments identified the adenine nucleotide translocator as an interaction partner. This is the first report showing a direct association between these two proteins, although previous studies have shown metabolic cooperation between them. Possible consequences for mitochondrial energy metabolism are discussed.
Antagonism of botulinum toxin type A‐induced cleavage of SNAP‐25 in rat cerebral synaptosome by toosendanin
Authors: Zhou Jian-Ying , Wang Zhong-Feng , Ren Xiao-Mei , Tang Mian-Zhi , Shi Yu-Liang
Published: November 2003

Toosendanin (TSN), a triterpenoid derivative extracted from Chinese traditional medicine, has been demonstrated to be an effective cure for experimental botulism. This study is designed to explore its antibotulismic mechanism by Western blotting. The results showed that TSN incubation did not change the electrophoresis pattern and the amounts of synaptosomal‐associated protein of 25 kDa (SNAP‐25), syntaxin and synaptobrevin/vesicle‐associated membrane protein in rat cerebral synaptosomes, but made the synaptosomes completely resistant to botulinum neurotoxin A (BoNT/A)‐mediated cleavage of SNAP‐25. After binding of BoNT/A to synaptosomes, TSN still partially antagonized the toxin‐mediated cleavage of SNAP‐25. However, TSN‐incubated synaptosomal membrane fraction did not resist the cleavage of SNAP‐25 by the light chain of BoNT/A. It is suggested that the antibotulismic effect of TSN results from blocking the toxin's approach to its enzymatic substrate.
A left‐handed 31 helical conformation in the Alzheimer Aβ(12–28) peptide
Authors: Jarvet J , Damberg P , Danielsson J , Johansson I , Eriksson L.E.G , Gräslund A
Published: November 2003

We show for the first time that the secondary structure of the Alzheimer β‐peptide is in a temperature‐dependent equilibrium between an extended left‐handed 31 helix and a flexible random coil conformation. Circular dichroism spectra, recorded at 0.03 mM peptide concentration, show that the equilibrium is shifted towards increasing left‐handed 31 helix structure towards lower temperatures. High resolution nuclear magnetic resonance (NMR) spectroscopy has been used to study the Alzheimer peptide fragment Aβ(12–28) in aqueous solution at 0°C and higher temperatures. NMR translation diffusion measurements show that the observed peptide is in monomeric form. The chemical shift dispersion of the amide protons increases towards lower temperatures, in agreement with the increased population of a well‐ordered secondary structure. The solvent exchange rates of the amide protons at 0°C and pH 4.5 vary within at least two orders of magnitude. The lowest exchange rates (0.03–0.04 min−1) imply that the corresponding amide protons may be involved in hydrogen bonding with neighboring side chains.
Caspase 8 mediated apoptotic cell death induced by β‐sheet forming polyalanine peptides
Authors: Giri Kalyan , Ghosh Utpal , Bhattacharyya Nitai P , Basak Soumen
Published: November 2003

Expansion of a polyalanine stretch from 10 to 12–17 residues in the N‐terminus of the protein PABP2 has been implicated in the genetically acquired disease oculopharyngeal muscular dystrophy, characterized by nuclear protein deposits. Here we report a correlation between the structural properties and cell toxicity of two peptides mimicking the N‐terminal domain of PABP2: one containing seven and the other 11 uninterrupted alanine residues. Consistent with earlier observations, the longer peptide (11‐ala) was found to adopt β‐sheet structure while the shorter one (7‐ala) formed α‐helix over a wide range of concentrations (∼20–500 μM). We observed that treatment with 11‐ala resulted in significantly enhanced death of Chinese hamster V79 cells, compared to the effect of treatment with 7‐ala, via the cytochrome c mediated apoptotic pathway. Increases in caspase 8 and caspase 3 activity were also observed in human cells (K562) treated with 11‐ala. These results indicate that the toxicity of pathogenic peptides is directly linked to their β‐sheet structure and also support recent observations that small oligomeric species of peptides and proteins are the key toxic elements in causing protein aggregation diseases.
TIMP‐3 inhibits aggrecanase‐mediated glycosaminoglycan release from cartilage explants stimulated by catabolic factors
Authors: Gendron Christi , Kashiwagi Masahide , Hughes Clare , Caterson Bruce , Nagase Hideaki
Published: November 2003

Aggrecanases are considered to play a key role in the destruction of articular cartilage during the progression of arthritis. Here we report that the N‐terminal inhibitory domain of tissue inhibitor of metalloproteinases 3 (N‐TIMP‐3), but not TIMP‐1 or TIMP‐2, inhibits glycosaminoglycan release from bovine nasal and porcine articular cartilage explants stimulated with interleukin‐1α or retinoic acid in a dose‐dependent manner. This inhibition is due to the blocking of aggrecanase activity induced by the catabolic factors. Little apoptosis of primary porcine chondrocytes is observed at an effective concentration of N‐TIMP‐3. These results suggest that TIMP‐3 may be a candidate agent for use against cartilage degradation.
Inhibition of ubiquitin/proteasome‐dependent proteolysis in Saccharomyces cerevisiae by a Gly‐Ala repeat
Authors: Heessen Stijn , Dantuma Nico P. , Tessarz Peter , Jellne Marianne , Masucci Maria G.
Published: November 2003

The glycine‐alanine (GA) repeat of the Epstein–Barr virus nuclear antigen‐1 inhibits in cis ubiquitin‐dependent proteolysis in mammalian cells through a yet unknown mechanism. In the present study we demonstrate that the GA repeat targets an evolutionarily conserved step in proteolysis since it can prevent the degradation of proteasomal substrates in the yeast Saccharomyces cerevisiae. Insertion of yeast codon‐optimised recombinant GA (rGA) repeats of different length in green fluorescent protein reporters harbouring N‐end rule or ubiquitin fusion degradation signals resulted in efficient stabilisation of these substrates. Protection was also achieved in rpn10Δ yeast suggesting that this polyubiquitin binding protein is not required for the rGA effect. The conserved effect of the GA repeat in yeast opens the possibility for the use of genetic screens to unravel its mode of action.
The effect of experienced emotions on preschoolers’ narration *This research was conducted at the University of Geneva between 1991 and 1996, directed by Professor D. N. Stern, M. D., Swiss National Science Foundation grant No 32-30804.91
Authors: Favez Nicolas , de Roten Yves , Stern Daniel N. , Bonvin Patrick
Published: November 2003

This paper presents a study of the relationship between emotions and autobiographical narratives by preschoolers (aged 3 to 5 years). The children (N = 39) actively participate in a short scenario (the Geneva Emotion-Eliciting Scenario, GEES), whose central theme is the separation of two friends. The children were then asked to narrate this event. The emotions experienced by the child throughout the scenario were analyzed by means of facial expression coding (KIDIES). Coding of childrens’ narratives was based on a content analysis. The analyses showed that the expression of emotions congruent to the events is not related to the content of the narrative, except in the case of the specific separation event.
Measuring attitudinal change in repeated cross-sectional surveys: beliefs about the self, life, and society among Swiss elders (1979-1994) * Author note. This study was funded by the Swiss National Science Foundation PNR “Vieillesses” (No 4032-35728). The authors would like to thank Jean-François Bickel, Carole Maystre, Nathalie Vollenwyder for their collaboration on this study, and Nathalie Ducommun for her editorial assistance.
Authors: Spini Dario , d’Epinay Christian Laliv
Published: November 2003

In this paper three ways of measuring and defining change in cross-sectional designs are presented. The first measure of change concerns structural stability: continuity in the organisation of a set of variables across time. The second is level stability: the comparison of means in different groups differing on age or socio-cultural dimensions. The third is based one the changing parameter model ( Firebaugh, 1997 ). In this model, it is the interaction between ageing effects or socio-cultural factors (period and cohort effects) and another variable that is assessed. These three approaches of change are illustrated on the basis of beliefs about the self, life and society assessed in representative populations of elders in two regions of Switzerland (Geneva and Central Valais) in 1979 (N = 1608) and 1994 (N = 2101).
Experiments important to Carver and Scheier’s self- regulation theory are not replicable
Authors: Dahme Gisela , Eichstaedt Jan , Rudolph Udo
Published: November 2003

Four experiments with 45, 53, 40 and 60 participants were conducted to test an effect predicted by Carver and Scheier’s (1998) theory and which has been confirmed in four independent studies by Carver and coworkers. With favorable expectations of success, participants low in self-awareness should be less persistent (measured by time until explicitly giving up an intractable task) than participants high in self-awareness. The opposite should be true for unfavorable expectancy. Empirical evidence reported in this paper shows that various theory-consistent ways of manipulating expectancies and self-awareness as well as subtracting periods of mental disengagement from time on task did not yield this predicted interaction. It is discussed whether self-awareness theory ( Duval & Wicklund, 1972 ) can better explain the pattern of results found in the present as well as in Carver’s studies than self-regulation theory.
Aging characteristics of nickel contact on p-type silicon
Authors: Chattopadhyay P.
Published: November 2003

The effect of aging on the electrical properties of a Ni–p-Si contact was studied by measuring the electrical characteristics at different intervals of time. The current–voltage characteristics measured show a decrease in the current over time for the first few measurements at different aging times followed by an insignificant change for longer aging. The barrier height extracted from I−V characteristics was found to increase from an initial value to a final higher value after a prolonged period of aging. This is the opposite of those normally exhibited by an aging Al−SiO2−p-Si system [H. C. Card, IEEE Trans. Electron Devices ED-23, 538 (1976)]. Similar to the case of current, the device conductance and capacitance were also found to decrease with the aging time until they become saturated after longer periods of aging. The features of aging are explained by a theoretical model which considers the existence of an interfacial SiO2 layer and Si traps in the interfacial region. It is shown that the concentration of silicon traps decays exponentially over time. The interpretation of the aging characteristics of a Ni–p-Si contact on the basis of exponential decay in the silicon trap concentration is in contrast to an Al−SiO2−p-Si system where the aging behavior was accounted for in terms of the net growth in silicon concentration over time followed by saturation after longer aging. Analyses of the low and high frequency capacitance reveal two types of interface state that have different time constants and density. The time constants of these states were found to be dependent on the aging time via surface potential at the contact.
The role of electronic symmetry in charge-transfer-to-solvent reactions: Quantum nonadiabatic computer simulation of photoexcited sodium anions
Authors: Smallwood C. Jay , Bosma Wayne B. , Larsen Ross E. , Schwartz Benjamin J.
Published: November 2003

Since charge-transfer-to-solvent (CTTS) reactions represent the simplest class of solvent-driven electron transfer reactions, there has been considerable interest in understanding the solvent motions responsible for electron ejection. The major question that we explore in this paper is what role the symmetry of the electronic states plays in determining the solvent motions that account for CTTS. To this end, we have performed a series of one-electron mixed quantum/classical nonadiabatic molecular dynamics simulations of the CTTS dynamics of sodide, Na−, which has its ground-state electron in an s orbital and solvent-supported CTTS excited states of p-like symmetry. We compare our simulations to previous theoretical work on the CTTS dynamics of the aqueous halides, in which the ground state has the electron in a p orbital and the CTTS excited state has s-like symmetry. We find that the key motions for Na− relaxation involve translations of solvent molecules into the node of the p-like CTTS excited state. This solvation of the electronic node leads to migration of the excited CTTS electron, leaving one of the p-like lobes pinned to the sodium atom core and the other extended into the solvent; this nodal migration causes a breakdown of linear response. Most importantly, for the nonadiabatic transition out of the CTTS excited state and the subsequent return to equilibrium, we find dramatic differences between the relaxation dynamics of sodide and the halides that result directly from differences in electronic symmetry. Since the ground state of the ejected electron is s-like, detachment from the s-like CTTS excited state of the halides occurs directly, but detachment cannot occur from the p-like CTTS excited state of Na− without a nonadiabatic transition to remove the node. Thus, unlike the halides, CTTS electron detachment from sodide occurs only after relaxation to the ground state and is a relatively rare event. In addition, the fact that the electronic symmetry of sodide is the same as for the hydrated electron enables us to directly study the effect of a stabilizing atomic core on the properties and solvation dynamics of solvent-supported electronic states. All the results are compared to experimental work on Na− CTTS dynamics, and a unified picture for the electronic relaxation for solvent-supported excited states of any symmetry is presented.
Direct numerical simulation of turbulent channel flow with wall velocity disturbances
Authors: Orlandi P. , Leonardi S. , Tuzi R. , Antonia R. A.
Published: November 2003

This paper considers the effect of applying nonzero velocity fluctuations along a flat smooth wall, mainly with the aim of understanding how conditions at the wall interact with the outer turbulent flow. Such a study is expected to be of use in formulating effective strategies for wall turbulence control. Three direct numerical simulations of a turbulent plane channel flow are carried out, starting with a flow field with no-slip conditions. Each simulation evolves by imposing (on one wall) only one nonzero velocity component. When a nonzero longitudinal velocity fluctuation u1 is applied, drag reduction occurs. With a nonzero spanwise velocity fluctuation u3, the flow is very similar to that in an unperturbed channel. However, the use of a nonzero wall-normal velocity fluctuation u2 results in structural changes similar to those observed in a direct numerical simulation of a turbulent flow over a rough surface. From the present simplified simulations, the inference is that the salient characteristics of rough wall flows reflect mainly the presence of a nonzero wall-normal normal velocity distribution at the interface between the roughness cavities and the external flow.
Spectral analysis of localized disturbances in boundary layer at subcritical Reynolds numbers
Authors: Boiko A. V. , Grek G. R. , Sboev D. S.
Published: November 2003

A flat plate boundary layer disturbance in the form of a streak is excited by a vortex of limited spanwise extent generated upstream of the plate leading edge. Frequency-wave spectral analysis of the streamwise velocity component of the streak is performed. The most part of energy in the spectrum is contained in low-frequency waves with the angles of their wave vector inclination to streamwise direction more than 85°. Spanwise wave numbers, peculiarities of amplitude growth, as well as streamwise velocity profiles of the most powerful spectral components of the streak are in a good agreement with known theoretical data on linear transient growth. However, behavior of the total energy of the streak is not corresponding to that of theoretical “optimal” transient structures. We suspect that, to make the theoretical results concerning the streak energy valid, details of the receptivity process must be taken into consideration. As the frequency grows, dispersion characteristics and decrements of the spectral components approach results of stability theory for Tollmien–Schlichting waves.
Translocation of a polymer chain across a nanopore: A Brownian dynamics simulation study
Authors: Tian Pu , Smith Grant D.
Published: November 2003

We carried out Brownian dynamics simulation studies of the translocation of single polymer chains across a nanosized pore under the driving of an applied field (chemical potential gradient). The translocation process can be either dominated by the entropic barrier resulted from restricted motion of flexible polymer chains or by applied forces (or chemical gradient across the wall), we focused on the latter case in our studies. Calculation of radius of gyrations at the two opposite sides of the wall shows that the polymer chains are not in equilibrium during the translocation process. Despite this fact, our results show that the one-dimensional diffusion and the nucleation model provide an excellent description of the dependence of average translocation time on the chemical potential gradients, the polymer chain length and the solvent viscosity. In good agreement with experimental results and theoretical predictions, the translocation time distribution of our simple model shows strong non-Gaussian characteristics. It is observed that even for this simple tubelike pore geometry, more than one peak of translocation time distribution can be generated for proper pore diameter and applied field strengths. Both repulsive Weeks–Chandler–Anderson and attractive Lennard-Jones polymer–nanopore interaction were studied, attraction facilitates the translocation process by shortening the total translocation time and dramatically improve the capturing of polymer chain. The width of the translocation time distribution was found to decrease with increasing temperature, increasing field strength, and decreasing pore diameter.
Methane chemistry involved in a low-pressure electron cyclotron wave resonant plasma discharge
Authors: Morrison N. A. , William C. , Milne W. I.
Published: November 2003

Radio frequency (rf) generated methane plasmas are commonly employed in the deposition of hydrogenated amorphous carbon (a-C:H) thin films. However, very little is known about the rf discharge chemistry and how it relates to the deposition process. Consequently, we have characterized a low-pressure methane plasma and compared the results with those obtained theoretically by considering the steady-state kinetics of the chemical processes present in a low-pressure plasma reactor, in order to elucidate the dominant reaction channels responsible for the generation of the active precursors required for film growth. Mass spectrometry measurements of the gas phase indicated little variation in the plasma chemistry with increasing electron temperature. This was later attributed to the partial saturation of the electron-impact dissociation and ionization rate constants at electron temperatures in excess of ∼4 eV. The ion densities in the plasma were also found to be strongly dependent upon the parent neutral concentration in the gas phase, indicating that direct electron-impact reactions exerted greater influence on the plasma chemistry than secondary ion–neutral reactions.
Nitric acid oxidation of Si to form ultrathin silicon dioxide layers with a low leakage current density
Authors: Kobayashi Asuha Hikaru , Maida Osamu , Takahashi Masao , Iwasa Hitoo
Published: November 2003

Ultrathin silicon dioxide (SiO2) layers with excellent electrical characteristics can be formed using the nitric acid oxidation of Si (NAOS) method, i.e., by immersion of Si in nitric acid (HNO3) solutions. The SiO2 layer formed with 61 wt % HNO3 at its boiling temperature of 113 °C has a 1.3 nm thickness with a considerably high density leakage current. When the SiO2 layer is formed in 68 wt % HNO3 (i.e., azeotropic mixture with water), on the other hand, the leakage current density (e.g., 1.5 A/cm2 at the forward gate bias, VG, of 1 V) becomes as low as that of thermally grown SiO2 layers, in spite of the nearly identical SiO2 thickness of 1.4 nm. Due to the relatively low leakage current density of the NAOS oxide layer, capacitance–voltage (C–V) curves can be measured in spite of the ultrathin oxide thickness. However, a hump is present in the C–V curve, indicating the presence of high-density interface states. Fourier transformed infrared absorption measurements show that the atomic density of the SiO2 layers increases by 7% with an increase in the HNO3 concentration from 61 to 68 wt %. Measurements of valence band spectra clarify that this concentration increase causes the enhancement of the valence band discontinuity at the Si/SiO2 interface from 4.1 to 4.3 eV. When postmetallization annealing (PMA) treatment is performed at 400 °C in hydrogen on 〈aluminum (Al)/chemical SiO2/Si(100)〉 metal–oxide–semiconductor diodes, the leakage current density markedly increases, and this increase is attributed to a reaction between the Al electrode and the chemical SiO2 layer, resulting in a decrease in the SiO2 thickness. With PMA at 200 °C in hydrogen, on the other hand, the SiO2 thickness decreases only slightly to 1.3 nm. In this case, the leakage current density greatly decreases (e.g., 0.4 A/cm2 at VG=1 V and 5×10−3 A/cm2 at VG=−1 V), and consequently it becomes 1/3–1/10 of those for thermally grown SiO2 layers with the same thickness. The hump in the C–V curves disappears after PMA at 200 °C, indicating the elimination of interface states, and the interface state passivation is attributed to one of the reasons for the decrease in the leakage current density. Measurements of the valence band spectra show that another reason for the decrease in the leakage current density by PMA are an increase in the band discontinuity at the Si/SiO2 interface, and the elimination of SiO2 gap states.
Motional states of magnetic molecules and their coherent superposition
Authors: Mainos C. , Baudon J. , Karam J.-C. , Perales F. , Robert J. , Pirani F. , Aquilanti V.
Published: November 2003

We study the coherent superposition of motional states in magnetic molecules. The distinct time evolution of each motional state in the presence of an external magnetic field and the dynamics of the molecular rotation are found to be interrelated by a molecular orientation correlation function. The correlation of two distinct molecular orientations is then investigated in terms of a dimensionless time variable and is found to reflect the inertia of the reorientation process. The relative phase in the coherent superposition gives evidence of a continuous redistribution of the interaction energy among the motional states of the superposition. Numerical simulations are provided for the prototypical magnetic molecule O2 in its ground state. Relevance is indicated for experiments on molecular interferometry, coherent control, and quantum information.
Structural and electronic properties of iron monoxide clusters FenO and FenO− (n=2–6): A combined photoelectron spectroscopy and density functional theory study
Authors: Gutsev Gennady L. , Bauschlicher Charles W. , Zhai Hua-Jin , Wang Lai-Sheng
Published: November 2003

We report a combined anion photoelectron spectroscopy and density functional theory (DFT) study on a series of iron monoxide clusters, FenO (n=2–6). Well-resolved photoelectron spectra were obtained for FenO− at variable detachment energies, allowing the ground state and numerous low-lying excited states of FenO to be observed. Sharp threshold photoelectron features were obtained for each species, which suggest rather small geometry changes between the anion and neutral ground states for the monoxide clusters and allows the electron affinities of the neutral clusters to be measured accurately. Extensive DFT calculations using the generalized gradient approximation were carried out for both FenO and FenO−. Optimized geometries of the ground and lowest excited states of both the anion and neutral species are reported along with the ground-state vibrational frequencies and fragmentation energies. Theoretical electron affinities were compared with the experimental measurements to verify the ground states of the iron monoxide clusters obtained from the DFT calculations.
Mean drift induced by free and forced dilational waves
Authors: Weber Jan Erik , Christensen Kai Haakon
Published: November 2003

The mean drift velocity induced by longitudinal dilational waves in an elastic film is studied theoretically on the basis of a Lagrangian description of motion. The film is horizontal and situated at the interface between two viscous fluids. For time-damped dilational waves we let the film (i) move freely with the mean fluid velocity at the interface, and (ii) be kept fixed, i.e., having no mean motion. In the latter case the mean Lagrangian drift velocity in both fluids becomes oppositely directed to the wave propagation direction after a very short time. This is due to the fact that a fixed film initially generates a strong source of negative Eulerian second order mean momentum at the interface. This effect becomes even more pronounced when we consider forced dilational waves in a fixed film. Now a suitably arranged shear stress in the upper fluid prevents wave amplitude decay in the film. Accordingly, the negative mean Eulerian momentum at the interface becomes independent of time, and the backward drift will propagate deeper and deeper into the lower fluid. For a no-slip bottom at finite depth we may have a stationary drift solution with negative Lagrangian drift velocity everywhere in the fluid.
Critical properties of molecular fluids from the virial series
Authors: MacDowell L. G. , Menduiña C. , Vega C. , de Miguel E.
Published: November 2003

We present results for the fourth virial coefficient of quadrupolar Lennard-Jones diatomics for several quadrupole moments and elongations. The coefficients are employed to predict the critical properties from two different truncated virial series. The first one employs the exact second and third virial coefficients, calculated in our previous work. The second includes also the exact fourth virial coefficient as obtained in this work. It is found that the first method yields already fairly good predictions. The second method significantly improves on the first one, however, yielding good results for both the critical temperature and pressure. Particularly, when compared with predictions from perturbation theories available in the literature, the virial series to fourth order compares favorably for the critical temperature. The results suggest that the failure of perturbation theories to predict the critical temperature and pressure is not only related to the neglect of density fluctuations, but also to poor prediction of the virial coefficients.
Molecular dynamics simulation of ion transport in moderately dense gases in an electrostatic field
Authors: Balla Georgia , Koutselos Andreas D.
Published: November 2003

The motion of ions in moderately dense gases under the action of an electrostatic field is simulated through a nonequlibrium molecular dynamics method. The method is developed through consideration of multiple ion-neutral collisions in a previously established procedure for low-density gases. The first two moments of the ion velocity distribution function for the representative system of K+ in Ar are calculated at various gas densities and field strengths and through them the mobility and two effective temperatures, parallel and perpendicular to the field. Additional tests for the accuracy of analytic expressions for the effective temperatures in terms of drift velocity and differential mobility derived from a three-temperature treatment of the Boltzmann kinetic equation were successful supporting the extension of use of generalized Einstein relations in this area. The procedure is easily extendable to the case of molecular ions with internal degrees of freedom.
Collisional energy transfer probabilities of highly excited molecules from KCSI. III. Azulene: P(E′,E) and moments of energy transfer for energies up to 40 000 cm−1 via self-calibrating experiments
Authors: Hold Uwe , Lenzer Thomas , Luther Klaus , Symonds Andrew C.
Published: November 2003

Complete experimental transition probability density functions P(E′,E) have been determined for collisions between highly vibrationally excited azulene and several bath gases over a wide energy range. This was achieved by applying 2-color “kinetically controlled selective ionization (KCSI)” [U. Hold, T. Lenzer, K. Luther, K. Reihs, and A. C. Symonds, J. Chem. Phys. 112, 4076 (2000)]. The results are “self-calibrating,” i.e., independent of any empirical calibration curve, as usually needed in traditional energy transfer experiments like time-resolved ultraviolet absorption or infrared fluorescence. The complete data set can be described by our recently introduced monoexponential 3-parameter P(E′,E) form with a parametric exponent Y in the argument, P(E′,E)∝exp[−{(E−E′)/(C0+C1⋅E)}Y]. For small colliders (helium, argon, xenon, N2, and CO2) the P(E′,E) show increased amplitudes in the wings compared to a monoexponential form (Y<1). For larger colliders, the wings of P(E′,E) have an even smaller amplitude (Y>1) than that provided by a monoexponential. Approximate simulations show that the wings of P(E′,E) at amplitudes <1×10−6 (cm−1)−1 have a nearly negligible influence on the population distributions and the net energy transfer. All optimized P(E′,E) representations exhibit a linear energy dependence of the collision parameter α1(E)=C0+C1⋅E, which also results in an (approximately) linear dependence of 〈ΔE〉 and 〈ΔE2〉1/2. The energy transfer parameters presented in this study have benchmark character in certainty and accuracy, e.g., with only 2%–5% uncertainty for our 〈ΔE〉 data below 25 000 cm−1. Deviations of previously reported first moment data from ultraviolet absorption and infrared fluorescence measurements can be traced back to either the influence of azulene self-collisions or well-known uncertainties in calibration curves.