bluuebunny/crossref_metadata_2025 huggingface dataset:
Global ocean heat content 1955–2008 in light of recently revealed instrumentation problems
Authors: Levitus S. , Antonov J. I. , Boyer T. P. , Locarnini R. A. , Garcia H. E. , Mishonov A. V.
Published: April 2009

We provide estimates of the warming of the world ocean for 1955–2008 based on historical data not previously available, additional modern data, correcting for instrumental biases of bathythermograph data, and correcting or excluding some Argo float data. The strong interdecadal variability of global ocean heat content reported previously by us is reduced in magnitude but the linear trend in ocean heat content remain similar to our earlier estimate.
Transpolar potential and reconnection voltage of the Earth from global MHD simulations
Authors: Peng Z. , Lai H. R. , Hu Y. Q.
Published: April 2009

The ionospheric transpolar potential (Vpc) and the magnetospheric reconnection voltage (Vr) of the Earth are investigated in terms of global MHD simulations of the solar wind‐magnetosphere‐ionosphere (SMI) system. A spherical shell approximation is used for the ionosphere with a uniform Pedersen conductance and a zero Hall conductance, the interplanetary magnetic field is due southward, and quasi‐steady solutions are obtained for the system. Each solution is characterized by the following four parameters: the ionospheric Pedersen conductance ΣP, the solar wind electric field Esw, ram pressure Psw, and Alfvén Mach number MA. More than 100 cases are treated separately and Vpc and Vr are calculated in each case. It is found that both Vpc and Vr increase monotonically with increasing Psw and decreasing MA regardless of the magnitude of Esw. The simulation results are well organized by a combined parameter f = EswPswMA−1/2 and approximately fitted by functions of f and ΣP. When the units are S for ΣP, kV for Vpc and Vr, mV/m for Esw, and nPa for Psw, the functions are found to be Vpc = 2.3 × 103 (f + 0.8)(ΣP + 2)−1/(f + 8.2) and Vr = 1.8 × 103[f + 0.45(ΣP1/2 + 1.2)] (ΣP1/2 + 0.45)−1/(f + 15.5). Three conclusions are made as follows: (1) Both Vpc and Vr saturate with respect to the increase of f; any variation of the interplanetary conditions in favor of the increase of f may cause the saturation. (2) The saturation point is found to be fc = 6.6 for Vpc and fc = 14.4 − 0.9ΣP1/2 for Vr, whereas the value of ΣP controls the saturation levels. (3) The two potentials, Vpc and Vr, stem from the SMI coupling and exhibit similar saturation behaviors. They are positively correlated because of sharing the same driving source and the close coupling between the ionosphere and the magnetosphere.
Contact analyses and permeability measurements of polished fracture surfaces in Sambagawa metapelitic schists and Ryoke mylonites from the Median Tectonic Line, Japan
Authors: Uehara Shin‐ichi , Shimamoto Toshihiko
Published: April 2009

Fractures play a vital role in fluid flow through rocks, and highly fractured zones can be the most permeable part of a fault zone. However, the evaluation of the hydraulic properties of natural fractured rocks at great depths is not easy because of the complexity of fracture geometry and the scaling problem from laboratory to nature. As a first step toward the estimation of flow rate through fractured zones at depth, this paper examines the issue of permeability estimation in the case of flow between polished surfaces of known topography (or roughness) via an integrated study of permeability measurements at effective pressures up to 180 MPa, surface roughness measurements, and contact analyses using the Hertzian theory of surface asperities of fractures as a function of stress. Apertures between two polished surfaces in specimens of Sambagawa pelitic schist and Ryoke mylonite were estimated from permeability measurements assuming the cubic law. The aperture of contacting surfaces has also been calculated from contact analyses of representative asperities. Despite some imperfections in the agreement between these two approaches, the overall features of progressive reduction in aperture upon an increase in effective pressure were successfully predicted. Deviations between the two approaches are probably due to complex deformation of multiple contacting asperities or limitations of our contact analysis method.
Photochemically induced carbon dioxide production as a mechanism for carbon loss from plant litter in arid ecosystems
Authors: Brandt L. A. , Bohnet C. , King J. Y.
Published: April 2009

We investigated the potential for abiotic mineralization to carbon dioxide (CO2) via photodegradation to account for carbon (C) loss from plant litter under conditions typical of arid ecosystems. We exposed five species of grass and oak litter collected from arid and mesic sites to a factorial design of ultraviolet (UV) radiation (UV pass, UV block), and sterilization under dry conditions in the laboratory. UV pass treatments produced 10 times the amount of CO2 produced in UV block treatments. CO2 production rates were unaffected by litter chemistry or sterilization. We also exposed litter to natural solar radiation outdoors on clear, sunny days close to the summer solstice at midlatitudes and found that UV radiation (280–400 nm) accounted for 55% of photochemically induced CO2 production, while shortwave visible radiation (400–500 nm) accounted for 45% of CO2 production. Rates of photochemically induced CO2 production on a per‐unit‐mass basis decreased with litter density, indicating that rates depend on litter surface area. We found no evidence for leaching, methane production, or facilitation of microbial decomposition as alternative mechanisms for significant photochemically induced C loss from litter. We conclude that abiotic mineralization to CO2 is the primary mechanism by which C is lost from litter during photodegradation. We estimate that CO2 production via photodegradation could be between 1 and 4 g C m−2 a−1 in arid ecosystems in the southwestern United States. Taken together with low levels of litter production in arid systems, photochemical mineralization to CO2 could account for a significant proportion of annual carbon loss from litter in arid ecosystems.
Rain cell size distribution inferred from rain gauge and radar data in the UK
Authors: Begum Sahena , Otung Ifiok E.
Published: April 2009

Knowledge of rain cell size distribution is relevant for the modeling and design of Earth‐space communication systems. Long‐term rain rate time series were processed to determine the spatial structure of rain cells by applying the synthetic storm technique assuming some known value of storm translation speed. Using a 3 1/2 year record of rain rate at Sparsholt, UK, the size distributions of rain fields were determined using rain cell translation speeds derived from analysis of radar plan position indicator scans. The results were compared with distributions of rain cell sizes determined directly from 66 radar reflectivity scans performed in seven rain events and found to give cell sizes in the region of 10 km for rain cells of threshold ≥ 20 mm/h.
Reducing ship emissions along U.S. coastline
Authors: Showstack Randy
Published: April 2009

The United States has called for reducing harmful ship emissions by asking the International Maritime Organization (IMO), a United Nations agency, to create a 370‐kilometer‐wide emissions control area (ECA) around the U.S. coastline, the U.S. Environmental Protection Agency (EPA) announced on 30 March. IMO will begin reviewing the proposal in July, and approval could occur as early as next year.
Carlson Receives 2008 Norman L. Bowen Award
Authors: Shirley Steven B. , Carlson Richard W.
Published: April 2009

Richard W. Carlson received the Norman L. Bowen Award at the 2008 AGU Fall Meeting Honors Ceremony, held 17 December in San Francisco, Calif. The award recognizes outstanding contributions to volcanology, geochemistry, or petrology.
Frequency of cool summers in interior North America over the past three centuries
Authors: Girardin Martin P. , Tardif Jacques C. , Epp Brock , Conciatori France
Published: April 2009

An innovative technique utilizes a tree‐ring marker to investigate long‐term changes in the frequency of cool summers in Interior North America (INA), a region that currently suffers important gaps in knowledge concerning annual to secular temperature changes. Using multivariate adaptive regression splines (MARS), we established a threshold for the formation of climatically‐induced light rings recorded in Pinus banksiana trees from INA. Then, we used the MARS model to reconstruct negative departures in summer maximum temperatures (April–September) from 1717 to 2007. The estimates explain 45% of the variance in instrumental temperature data. The reconstruction indicates the presence of significant multidecadal changes in the frequency of cool summers, with maximums in 1780, 1900 and 1960 and minimums in 1740, 1860, 1920 and 2000. No evidence of secular changes was found.
Winter Northern Hemisphere weather patterns remember summer Arctic sea‐ice extent
Authors: Francis Jennifer A. , Chan Weihan , Leathers Daniel J. , Miller James R. , Veron Dana E.
Published: April 2009

The dramatic decline in Arctic summer sea‐ice cover is a compelling indicator of change in the global climate system and has been attributed to a combination of natural and anthropogenic effects. Through its role in regulating the exchange of energy between the ocean and atmosphere, ice loss is anticipated to influence atmospheric circulation and weather patterns. By combining satellite measurements of sea‐ice extent and conventional atmospheric observations, we find that varying summer ice conditions are associated with large‐scale atmospheric features during the following autumn and winter well beyond the Arctic's boundary. Mechanisms by which the atmosphere “remembers” a reduction in summer ice cover include warming and destabilization of the lower troposphere, increased cloudiness, and slackening of the poleward thickness gradient that weakens the polar jet stream. This ice‐atmosphere relationship suggests a potential long‐range outlook for weather patterns in the northern hemisphere.
Observations of an interplanetary switch‐on shock driven by a magnetic cloud
Authors: Feng H. Q. , Lin C. C. , Chao J. K. , Wu D. J. , Lyu L. H. , Lee L. C.
Published: April 2009

A possible interplanetary switch‐on shock event prior to a trailing magnetic cloud was observed on August 1, 2002 at 1 AU. We fit the data with the Rankine‐Hugoniot (R‐H) relations based on both oblique and switch‐on shock models. It is found that both models are consistent with the observed data, and the best fit solutions of the two models are close to one another. For the oblique shock model, the best fit upstream shock normal angle, θBN1 (= cos−1(Bt1/B1)), is as small as 5.55°. The shock has the following characteristics: (1) plasma density, plasma temperature, and the magnetic field strength all increase across the shock, (2) protons are thermalized very efficiently across the shock, but it is not the case for electrons, (3) the fast‐mode Mach number is greater than unity in the preshock region and less than unity in the postshock region, and (4) from the oblique shock model we find that the normal Alfvén Mach number is very close to unity in the postshock region, while from the switch‐on shock model we obtain a solution of unity normal Alfvén Mach number. Our results clearly demonstrate the MHD character of a fast shock propagating along the ambient magnetic field.
Do hurricanes cause significant interannual variability in the air‐sea CO2 flux of the subtropical North Atlantic?
Authors: Koch Jennifer , McKinley Galen A. , Bennington Val , Ullman David
Published: April 2009

Observations at Bermuda and in the Caribbean Sea indicate that hurricanes influence surface ocean pCO2 (pCO2ocean) and air‐sea CO2 fluxes at short time scales. We use a regional version of the MIT ocean general circulation model to study impacts on interannual variability in air‐sea CO2 fluxes in the North Atlantic subtropical gyre (25–40N). Consistent with observations, enhanced wind speeds dominate the hurricane's effect on the flux, driving CO2 out of the ocean due to the negative air‐sea gradient in pCO2 (pCO2atm < pCO2ocean) that occurs in response to warm sea surface temperatures (SSTs) during hurricane season. With a storm, vertical mixing causes negative SST anomalies that depress pCO2ocean, but not enough to reverse the gradient. Though hurricanes drive a substantial local CO2 efflux, we find no evidence for a relationship between year‐to‐year variability in hurricane frequency and variability in basin‐integrated air‐sea CO2 fluxes across the subtropical North Atlantic.
An unusual current sheet in an ICME: Possible association with C/2006 P1 (McNaught)
Authors: Russell C. T. , Jian L. K. , Luhmann J. G.
Published: April 2009

On December 15, 2006, a strong ICME crossed the twin STEREO spacecraft while they were still close together in near‐Earth space. In the midst of this traversal, a strong current sheet was observed in the magnetic records, whose properties are inconsistent with our present understanding of the magnetic structure of an interplanetary coronal mass ejection (ICME). A possible cause of this current sheet is the extended dust trail of C/2006 P1 (McNaught), whose orbital plane the ICME traversed close to the Sun. If this association is correct, then charged dust can produce twists in the interplanetary magnetic field that can persist for an AU or longer. Further, as a result of this electromagnetic interaction, small dust particles can be carried out of the solar system.
Rhizobitoxine producers gain more poly-3-hydroxybutyrate in symbiosis than do competing rhizobia, but reduce plant growth
Authors: Ratcliff William C , Denison R Ford
Published: April 2009

Legume sanctions against rhizobia that fix less nitrogen should exert a strong selection for more beneficial genotypes of rhizobia, but strains providing little host benefit are common. One reason may be that some rhizobia chemically manipulate the host, undermining the efficacy of sanctions. Here we show that the ethylene inhibitor, rhizobitoxine (Rtx), is an example of such a manipulation. Rtx-producing rhizobia decreased legume growth, but benefited relative to an isogenic, non-producing strain on the same plant by accumulating 47% more of the storage lipid poly-3-hydroxybutyrate (PHB).
Childbirth Moderates the Genetic and Environmental Influences on BMI in Adult Twins
Authors: Rebollo‐Mesa Irene , Ordoñana Juan R.
Published: April 2009

We report a study of the moderating role that the number of childbirths has on the genetic and environmental influences on BMI variation. We used a classical twin design with a sample of 704 adult female twins (334 monozygotic and 370 dizygotic). A gene–environment interaction (G × E) model was applied to estimate the moderating effects of childbearing. Results show that age and number of children exert a significant positive main effect on BMI. Furthermore, we found significant moderating effects of childbearing, with a larger number of children associated with an increased sensitivity to environmental factors.
Triglyceride Levels and Not Adipokine Concentrations Are Closely Related to Severity of Nonalcoholic Fatty Liver Disease in an Obesity Surgery Cohort
Authors: Kashyap Sangeeta R. , Diab Dima L. , Baker Allison R. , Yerian Lisa , Bajaj Harpreet , Gray‐McGuire Courtney , Schauer Philip R. , Gupta Manjula , Feldstein Ariel E. , Hazen Stanley L. , Stein Catherine M.
Published: April 2009

Although nonalcoholic fatty liver disease (NAFLD) is frequent in obesity, the metabolic determinants of advanced liver disease remain unclear. Adipokines reflect inflammation and insulin resistance associated with obesity and may identify advanced NAFLD. At the time of obesity surgery, 142 consecutive patients underwent liver biopsy and had their preoperative demographic and clinical data obtained. Liver histology was scored by the NAFLD activity score, and patients subdivided into four groups. Concentrations of retinol‐binding protein 4 (RBP4), adiponectin, tumor necrosis factor‐α (TNF‐α), and leptin were determined ∼1 week prior to surgery and results were related to liver histology. The prevalence of no NAFLD was 30%, simple steatosis 23%, borderline nonalcoholic steatohepatitis (NASH) 28%, and definitive NASH 18%. Type 2 diabetes mellitus (T2DM) and metabolic syndrome (MS) prevalence were 39 and 75%, respectively, and did not differ across the four histological groups (P = NS). Triglyceride (TG) and alanine transaminase (ALT) levels, strongly associated with advanced stages of NAFLD and NASH (P = 0.04). TG levels >150 mg/dl, increased the likelihood of NASH 3.4‐fold, whereas high‐density lipoprotein (HDL) levels predicted no NAFLD (P < 0.01). Concentrations of TNF‐α, leptin, and RBP4 did not differ among histological groups and thus did not identify NASH; however, there was a trend for adiponectin to be lower in NASH vs. no NAFLD (P = 0.061). In summary, both TG and ALT levels assist in identification of NASH in an obesity surgery cohort. These findings underscore the importance of fatty acid delivery mechanisms to NASH development in severely obese individuals.
INSIG2 SNPs Associated With Obesity and Glucose Homeostasis Traits in Hispanics: The IRAS Family Study
Authors: Talbert Matthew E. , Langefeld Carl D. , Ziegler Julie T. , Haffner Steven M. , Norris Jill M. , Bowden Donald W.
Published: April 2009

The genome‐wide association study by Herbert et al. identified the INSIG2 single‐nucleotide polymorphism (SNP) rs7566605 as contributing to increased BMI in ethnically distinct cohorts. The present study sought to further clarify the matter, by testing whether SNPs of INSIG2 influenced quantitative adiposity or glucose homeostasis traits in Hispanics of the Insulin Resistance Atherosclerosis Family Study (IRASFS). Using a tagging SNP approach, rs7566605 and 31 additional SNPs were genotyped in 1,425 IRASFS Hispanics. SNPs were tested for association with six adiposity measures: BMI, waist circumference (WAIST), waist‐to‐hip ratio (WHR), subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), and VAT to SAT ratio (VSR). SNPs were also tested for association with fasting glucose (GFAST), fasting insulin (FINS), and three measures obtained from the frequently sampled intravenous glucose tolerance test: insulin sensitivity (SI), acute insulin response (AIR), and disposition index (DI). Most prominent association was observed with direct computed tomography (CT)‐measured adiposity phenotypes, including VAT, SAT, and VSR (P values range from 0.007 to 0.044 for rs17586756, rs17047718, rs17047731, rs9308762, rs12623648, and rs11673900). Multiple SNP associations were observed with all glucose homeostasis traits (P values range from 0.001 to 0.031 for rs17047718, rs17047731, rs2161829, rs10490625, rs889904, and rs12623648). Using BMI as a covariate in evaluation of glucose homeostasis traits slightly reduced their association. However, association with adiposity and glucose homeostasis phenotypes is not significant following multiple comparisons adjustment. Trending association after multiple comparisons adjustment remains suggestive of a role for genetic variation of INSIG2 in obesity, but these results require validation.
Potential Contribution of Adipose Tissue to Elevated Serum Cystatin C in Human Obesity
Authors: Naour Nadia , Fellahi Soraya , Renucci Jean‐François , Poitou Christine , Rouault Christine , Basdevant Arnaud , Dutour Anne , Alessi Marie‐Christine , Bastard Jean‐Philippe , Clément Karine , Guerre‐Millo Michèle
Published: April 2009

Cystatin C, an endogenous inhibitor of cathepsin proteases has emerged as a biomarker of cardiovascular risk and reduced renal function. Epidemiological studies indicate that serum cystatin C increased in human obesity. Here, we evaluated the contribution of adipose tissue to this elevation, based on our previous observation that cystatin C is produced by in vitro differentiated human adipocytes. We measured serum cystatin C in 237 nonobese (age: 51 ± 0.8 years; BMI: 22.8 ± 0.11 kg/m2) and 248 obese subjects (age: 50 ± 0.8 years; BMI: 34.7 ± 0.29 kg/m2). Creatinine‐based estimated glomerular filtration rate (eGFR) was calculated to account for renal status. Cystatin C gene expression and secretion were determined on surgical adipose tissue biopsies in a distinct group of subjects. Serum cystatin C is elevated in obese subjects of both genders, independently of reduced eGFR. Cystatin C mRNA is expressed in subcutaneous and omental adipose tissue, at twice higher levels in nonadipose than in adipose cells. Gene expression and cystatin C release by adipose tissue explants increase two‐ to threefold in obesity. These data confirm elevation of serum cystatin C in human obesity and strongly argue for a contribution of increased production of cystatin C by enlarged adipose tissue. Because cystatin C has the potential to affect adipose tissue and vascular homeostasis through local and/or systemic inhibition of cathepsins, this study adds a new factor to the list of adipose tissue secreted bioactive molecules implicated in obesity and obesity‐linked complications.
Entry Into Romantic Partnership Is Associated With Obesity
Authors: The Natalie S. , Gordon‐Larsen Penny
Published: April 2009

BMI is highly correlated between spouses; however, less is understood about the underlying mechanism(s) by which the development of obesity in one individual increases the risk of obesity in his/her spouse. The objective of this study is to investigate whether romantic partnership and duration of cohabitation are related to incident obesity and obesity‐promoting behaviors. We used two data sets from the National Longitudinal Study of Adolescent Health: (i) 6,949 US adolescents (wave II, 1996) followed into adulthood (wave III, 2001–2002) and (ii) 1,293 dating, cohabiting, and married romantic couples from wave III, including measured anthropometry and self‐report behavior data. In the longitudinal cohort, we used sex‐stratified logistic regression models to examine the risk of incident obesity by longitudinal romantic relationship status and duration of time spent living with a romantic partner. In the Couples Sample, we used multinomial logistic regression to predict concordance in outcomes: obesity, moderate‐to‐vigorous physical activity, and screen time by romantic partnership and duration of time living with a romantic partner. Individuals who transitioned from single/dating to cohabiting or married were more likely to become obese than those who were dating at both waves. Partner concordance for negative, obesity‐related behaviors was strongest for married couples and couples who lived together ≥2 years. The shared household environment may increase the likelihood of becoming obese, influence partner concordance, and may be an important target for obesity intervention.
The tumour suppressor Pdcd4: recent advances in the elucidation of function and regulation
Authors: Lankat‐Buttgereit Brigitte , Göke Rüdiger
Published: April 2009

Pdcd4 (programmed cell death 4) has been known as a tumour suppressor gene and potential target for anticancer therapies for several years. Initially, Pdcd4 was identified as a gene that is up‐regulated during apoptosis, but its precise role still remains to be defined. However, there is increasing evidence that Pdcd4 levels influence transcription, as well as translation, modulate different signal transduction pathways and might act as a tumour suppressor. Interestingly, recent data suggest that Pdcd4 function may depend on cell type and/or genetic background. This review summarizes the current knowledge regarding the function and regulation of Pdcd4.
Protein phosphatase 2A plays a role in hydrogen peroxide-induced disruption of tight junctions in Caco-2 cell monolayers
Authors: Sheth Parimal , Samak Geetha , Shull J. Andrew , Seth Ankur , Rao Radhakrishna
Published: April 2009

Evidence indicates that PP2A (protein phosphatase 2A) interacts with epithelial tight junctions and negatively regulates the integrity of the tight junction. In the present study, the role of PP2A in the hydrogen peroxide-induced disruption of the tight junction was examined in Caco-2 cell monolayers. Hydrogen peroxide-induced decrease in electrical resistance and increase in inulin permeability was associated with the dephosphorylation of occludin on threonine residues. The hydrogen peroxide-induced decrease in electrical resistance, increase in inulin permeability and redistribution of occludin and ZO (zonula occludens)-1 from the intercellular junctions were significantly attenuated by selective inhibitors of PP2A (okadaic acid and fostriecin) and by knockdown of PP2A-Cα (the catalytic subunit of PP2A). The PP2A-Cα protein and PP2A activity were co-immunoprecipitated with occludin, and this co-immunoprecipitation was rapidly increased by hydrogen peroxide. Hydrogen peroxideinduced increase in co-immunoprecipitation of PP2A-Cα with occludin was prevented by PP2, a Src kinase inhibitor. GST (glutathione transferase)-pull down assays using recombinant GST–Occludin-C (C-terminal tail of occludin) and the purified PP2A showed that PP2A binds to the C-terminal domain of occludin; Src-induced tyrosine phosphorylation of GST–Occludin-C enhanced this binding. The present study shows that hydrogen peroxide increases the association of PP2A with occludin by a Src kinase-dependent mechanism, and that PP2A activity is involved in hydrogen peroxide-induced disruption of tight junctions in Caco-2 cell monolayers.
Emic Perspectives on Quality of Life: The Case of the Danish Wadden Sea Festival
Authors: Liburd Janne J. , Derkzen Petra
Published: April 2009

This paper sets out to probe how a cultural festival can enhance quality of life (QoL) and identifies possible drivers in the process. The Wadden Sea Festival in Denmark is based on the idea of integrating the coastal environment in the presentation of contemporary art. Specifically, unique tidal differences are utilised to stage a range of performances. The Wadden Sea Festival was designed to create regional, national and international liaisons between artists and cultural institutions and to enhance local residents'sense of place and collective identity while also attracting visitors to the region. Recognising the articulated aims of the festival, we explore how a cultural festival, and more specifically contemporary art, may positively influence the QoL of participants, residents and visitors alike. Participant-observation and in-depth interviews formed the basis for this exploratory research. We elicit and illustrate how the festival generated feelings of positive energy and integrity among individual artists and discuss these elements in relation to theoretical conceptualisations of QoL. Adopting a highly contextualised and qualitative approach, we argue that emic perspectives are needed to understand the immaterial elements of QoL.

Further, an emic approach allows for deep narratives and opens up for multidimensional perspectives that could be applied in different cultural settings.
Emerging Green Tourists in Australia: Their Behaviours and Attitudes
Authors: Bergin-Seers Suzanne , Mair Judith
Published: April 2009

Concern about environmental sustainability and climate change has increased dramatically in the past decade and is affecting the way consumers behave. This change has led to a greater focus on green consumerism, and for the tourism industry, a greater interest in green tourists. Although debate about green tourist behaviour exists, it is accepted that some tourists have stronger views than others about environmental issues and are also more active in addressing these concerns with regard to how they live their lives. There is still much to learn about green consumerism and this study aimed to identify and profile green tourists to raise awareness about their attitudes and behaviours and to recognise this market for driving change. A group identified as emerging green tourists was distinguished by their environmental behaviour at home, their information seeking and purchasing intentions. However, there is little clear evidence that these intentions have translated into actual purchases.
Magnetotransmission spectra in La0.7Pb0.3MnO3−δ epitaxial thin film with colossal magnetoresistance effect
Authors: Malak Sidney T. , Clayton-Cox Ryan , Scheuermann James R. , Stehlik Jiri , Wang Jian-Qing
Published: April 2009

The magnetorefractive effect in transmission modes (MT-MRE) of epitaxial grown La0.7Pb0.3MnO3−δ was measured and studied. The studied film had a colossal magnetoresistance value up to 80% (at 5.5 tesla) at room temperature. In addition, the MT-MRE spectra in the range of 350–15 000 cm−1 in magnetic fields up to 1.0 tesla were obtained, and it was observed that the MT-MRE scaled proportionally with the applied magnetic field and was largest at lower frequencies below 3000 cm−1. The maximum observed MT-MRE value was 4.0% at 1.0 tesla. Beyond far infrared (FIR) range, the MT-MRE curves monotonically decrease with frequency until the effect vanishes at 11 400 cm−1. Such crossover of magnetospectroscopic responses from FIR to near IR frequencies is the first evidence of gradual disappearance of the magnetodynamics at higher frequencies, resulting from the dynamic Jahn–Teller effect.
Spin wave scattering and interface magnetism in superconducting-ferromagnet-superconducting hybrid structures
Authors: Alvarez G. A. , Wang X. L. , Puzzer T. , Peleckis G. , Dou S. X.
Published: April 2009

In this work we report on interlayer spin-polarized transport studies carried out on YBa2Cu3O7-δ/La2/3Sr1/3MnO3/YBa2Cu3O7-δ thin film multilayers. Anisotropic YBa2Cu3O7-δ high-temperature superconductors (YBCO) and the manganite La2/3Sr1/3MnO3 (LSMO) are layered metallic systems where the c-axis interlayer current transport occurs via sequential tunneling of charge carriers. The temperature dependence of the resistance R(T) for different applied fields shows that these heterostructures are clearly influenced by both the insulator-to-metal transition of the LSMO layers at ∼320 K and the stripe fluctuations in the conductivity of the YBCO layers at the onset of electronic inhomogeneity at ∼210 K. Furthermore, the tunneling of spin-polarized charge carriers between the YBCO layers through LSMO showed sharp switching between the high and low resistance states, which we assume corresponds to antiparallel and parallel alignments of the magnetic (spin) moments of these hybrid structures. The investigation of these promising hybrid structures is aimed at understanding the science of the new spin-based devices, laying the foundation for a new generation of ultrafast, nonvolatile electronics.
The effect of the sputtering gas (Ar, Xe) on FePt clusters formation: structural and magnetic properties
Authors: Cantelli V. , Grenzer J. , von Borany J. , Fassbender J.
Published: April 2009

It will be reported about the effect of the sputtering gases, Ar and Xe, on FePt clusters formation by magnetron sputtering deposition at high working pressures. All layers, with bulk equivalent thicknesses between 3 to 5 nm, were realized at RT by a sequential layer by layer deposition or a co-deposition of Fe and Pt. After rapid thermal annealing at 500 °C, the highest L10 fraction was found using Xe as sputtering gas: Xe decreases the transformation activation energy and therefore, reduces the critical thickness necessary to obtain the high anistropic ferromagnetic phase. Ar assisted growths lead to FePt clusters in the L10 phase only if the sequential layer deposition is used, whereas for Xe no differences in the deposition techniques were observed.
The noncommutative sine-Gordon breather
Authors: Fischer André , Lechtenfeld Olaf
Published: April 2009

As shown by Lechtenfeld et al. [Nucl. Phys. B 705, 447 (2005)], there exists a noncommutative deformation of the sine-Gordon model which remains (classically) integrable but features a second scalar field. We employ the dressing method (adapted to the Moyal-deformed situation) for constructing the deformed kink-antikink and breather configurations. Explicit results and plots are presented for the leading noncommutativity correction to the breather. Its temporal periodicity is unchanged.
Persistent subplasma-frequency kinetic electrostatic electron nonlinear waves
Authors: Johnston T. W. , Tyshetskiy Y. , Ghizzo A. , Bertrand P.
Published: April 2009

Driving a one-dimensional collisionless Maxwellian (Vlasov) plasma with a sufficiently strong longitudinal ponderomotive driver for a sufficiently long time results in a self-sustaining nonsinusoidal wave train with well-trapped electrons even for frequencies well below the plasma frequency, i.e., in the plasma wave spectral gap. Typical phase velocities of these waves are somewhat above the electron thermal velocity. This new nonlinear wave is being termed a kinetic electrostatic electron nonlinear (KEEN) wave. The drive duration must exceed the bounce period τB of the trapped electrons subject to the drive, as calculated from the drive force and the linear plasma response to the drive. For a given wavenumber a wide range of KEEN wave frequencies can be readily excited. The basic KEEN structure is essentially kinetic, with the trapped electron density variation being almost completely shielded by the free electrons, leaving just enough net charge to support the wave.
Nonferromagnetic nanocrystalline ZnO:Co thin films doped with Zn interstitials
Authors: Knies Christoph , Elm Matthias T. , Klar Peter J. , Stehr Jan , Hofmann Detlev M. , Romanov Nikolai , Kammermeier Tom , Ney Andreas
Published: April 2009

ZnCoO thin films were synthesized via a wet chemical route and subsequently annealed in Zn vapor to increase the conductivity by introducing Zn interstitials. All samples show small hysteresis loops close to the detection limit of the magnetometer. Thus the samples were thoroughly investigated to obtain evidence for further ferromagneticlike behavior. Optical and magneto-optical experiments show the crystal field transitions of Co2+ in the near infrared and visible spectral range. At energies above 2.8 eV a charge transfer transition of Co2+ is observed. The results of magnetotransport measurements are explained by the formation of an impurity band situated below the conduction band. No further evidence for ferromagnetism is obtained.
Synchronization of coupled single-electron circuits based on nanoparticles and tunneling junctions
Authors: Cervera Javier , Manzanares José A. , Mafé Salvador
Published: April 2009

We explore theoretically the synchronization properties of a device composed of coupled single-electron circuits whose building blocks are nanoparticles interconnected with tunneling junctions. Elementary nanoscillators can be achieved by a single-electron tunneling cell where the relaxation oscillation is induced by the tunneling. We develop a model to describe the synchronization of the nanoscillators and present sample calculations to demonstrate that the idea is feasible and could readily find applications. Instead of considering a particular system, we analyze the general properties of the device making use of an ideal model that emphasizes the essential characteristics of the concept. We define an order parameter for the system as a whole and demonstrate phase synchronization for sufficiently high values of the coupling resistance.
Spatiotemporal multiscaling analysis of impurity transport in plasma turbulence using proper orthogonal decomposition
Authors: Futatani S. , Benkadda S. , del-Castillo-Negrete D.
Published: April 2009

The spatiotemporal multiscale dynamics of the turbulent transport of impurities is studied in the context of the collisional drift wave turbulence. Two turbulence regimes are considered: a quasihydrodynamic regime and a quasiadiabatic regime. The impurity is assumed to be a passive scalar advected by the corresponding E×B turbulent flow in the presence of diffusion. Two mixing scenarios are studied: a freely decaying case, and a forced case in which the scalar is forced by an externally imposed gradient. The results of the direct numerical simulations are analyzed using proper orthogonal decomposition (POD) techniques. The multiscale analysis is based on a space-time separable POD of the impurity field. The low rank spatial POD eigenfunctions capture the large scale coherent structures and the high rank eigenfunctions capture the small scale fluctuations. The temporal evolution at each scale is dictated by the corresponding temporal POD eigenfunctions. Contrary to the decaying case in which the POD spectrum decays fast, the spectrum in the forced case is relatively flat. The most striking difference between these two mixing scenarios is in the temporal dynamics of the small scale structures. In the decaying case the POD reveals the presence of “bursty” dynamics in which successively small (high POD rank) scales are intermittently activated during the mixing process. On the other hand, in the forced simulations the temporal dynamics exhibits stationary fluctuations. Spatial intermittency or “patchiness” in the mixing process characterizes the distribution of the passive tracer in the decaying quasihydrodynamic regime. In particular, in this case the probability distribution function of the low rank POD spatial reconstruction error is non-Gaussian. The spatiotemporal POD scales exhibit a diffusive-type scaling in the quasiadiabatic regime. However, this scaling seems to be absent in the quasihydrodynamic regime that shows no scaling (in the decaying case) or two different superdiffusive-type scaling regimes (in the forced case).
The performance of minima hopping and evolutionary algorithms for cluster structure prediction
Authors: Schönborn Sandro E. , Goedecker Stefan , Roy Shantanu , Oganov Artem R.
Published: April 2009

We compare evolutionary algorithms with minima hopping for global optimization in the field of cluster structure prediction. We introduce a new average offspring recombination operator and compare it with previously used operators. Minima hopping is improved with a softening method and a stronger feedback mechanism. Test systems are atomic clusters with Lennard-Jones interaction as well as silicon and gold clusters described by force fields. The improved minima hopping is found to be well-suited to all these homoatomic problems. The evolutionary algorithm is more efficient for systems with compact and symmetric ground states, including LJ150, but it fails for systems with very complex energy landscapes and asymmetric ground states, such as LJ75 and silicon clusters with more than 30 atoms. Both successes and failures of the evolutionary algorithm suggest ways for its improvement.
On nonholonomic systems and variational principles
Authors: Cronström Christofer , Raita Tommi
Published: April 2009

We consider the compatibility of the equations of motion which follow from d’Alembert’s principle in the case of a general autonomous nonholonomic mechanical system in N dimensions with those equations which follow for the same system by assuming the validity of a specific variational action principle, in which the nonholonomic conditions are implemented by means of the multiplication rule in the calculus of variations. The equations of motion which follow from the principle of d’Alembert are not identical to the equations which follow from the variational action principle. We give a proof that the solutions to the equations of motion which follow from d’Alembert’s principle do not in general satisfy the equations which follow from the action principle with nonholonomic constraints. Thus the principle of d’Alembert and the minimal action principle involving the multiplication rule are not compatible in the case of systems with nonholonomic constraints. For simplicity the proof is given for autonomous systems only, with one general nonholonomic constraint, which is linear in the generalized velocities of the system.
Ratchet-induced anisotropic behavior of superparamagnetic microdroplet
Authors: Zhang Jihua , Cheng Zhongjun , Zheng Yongmei , Jiang Lei
Published: April 2009

Microscale ratchet structured surfaces were coated with nanoparticles, which resulted in anisotropic behavior of superparamagnetic microdroplet by magnetic field actuation. This ratchet structure enables superparamagnetic microdroplets to generate the anisotropic behavior through the alternative external magnetic field. A tuning behavior was revealed by changing the height of ratchet, the numbers of superparamagnetic nanoparticles, and the size of microdroplets. It is significant to understand the wetting properties on superhydrophobic surfaces with anisotropic structure.
Energy transfer between laser beams crossing in ignition hohlraums
Authors: Michel P. , Divol L. , Williams E. A. , Thomas C. A. , Callahan D. A. , Weber S. , Haan S. W. , Salmonson J. D. , Meezan N. B. , Landen O. L. , Dixit S. , Hinkel D. E. , Edwards M. J. , MacGowan B. J. , Lindl J. D. , Glenzer S. H. , Suter L. J.
Published: April 2009

The full scale modeling of power transfer between laser beams crossing in plasmas is presented. A new model was developed, allowing calculations of the propagation and coupling of pairs of laser beams with their associated plasma wave in three dimensions. The complete set of laser beam smoothing techniques used in ignition experiments is modeled and their effects on crossed-beam energy transfer are investigated. A shift in wavelength between the beams can move the instability in or out of resonance and hence allows tuning of the energy transfer. The effects of energy transfer on the effective beam pointing and on symmetry have been investigated. Several ignition designs have been analyzed and compared, indicating that a wavelength shift of up to 2 Å between cones of beams should be sufficient to control energy transfer in ignition experiments.
First-order phase transition and high energy cyclonic spots in a shallow water model on a rapidly rotating sphere
Authors: Ding Xueru , Lim Chjan C.
Published: April 2009

A statistical equilibrium theory based on the Lagrangian of the rotating shallow water equations is presented with applications to cooperative properties of large-scale features in the Jovian atmosphere when the flows have pronounced hemispherical asymmetry. Large planetary spin is shown to play a significant role in the orientation asymmetry or energy gap between cyclonic and anticyclonic vorticity distributions. This suggests that angular momentum is the key physical factor behind the statistical preference for a cyclonic vorticity distribution at high levels of flow energy. Simulation results reported here show that for a range of high energy-to-enstrophy ratios at Jupiter’s parameters, a broad-based cyclonic vortex forms in one of the hemisphere with few other coherent spots. Evidence that this cooperative phenomenon arise from a first-order phase transition is discussed.
The electronic spectrum of vanadium monoxide across the visible: New bands and new insight
Authors: Hopkins W. Scott , Hamilton Suzanne M. , Mackenzie Stuart R.
Published: April 2009

Resonance enhanced multiphoton ionization spectra of vanadium monoxide (VO) have been measured in the 16 000–23 300 cm−1 region. A series of intense peaks, identified as the VO C Σ4−(v′)−X Σ4− (v″=0) progression, has been recorded up to v′=7 and vibrational and rotational parameters have been extracted by simulation of the rotationally resolved spectra. Additional weak transitions in the spectrum are assigned to the 2 Π2−X Σ4− spin-forbidden band system allowing the first direct determination of a spin-orbit coupling constant within the doublet spin manifold of VO. Together, the spectra provide absolute energies for several doublet electronic states with respect to the X Σ4− ground state. A further vibronic progression observed at 22 000 cm−1 is assigned as a second spin-forbidden excitation from the X Σ4− ground state to a Π2 state which has not previously been characterized.
Enhanced photon-induced carrier density in silicon-on-insulator via surface recombination suppression for increasing plasma dispersion effect
Authors: Hsieh Ming-Kai , Ku Kai-Ning , Lee Ming-Chang M.
Published: April 2009

The authors studied enhancement of photon-induced carrier density in silicon-on-insulator (SOI) by suppressing surface recombination. Through applying electric field at the top silicon surface or at the Si/SiO2 interface, either electrons or holes are depleted near the interface, reducing the possibility of recombination. We examined enhanced photon-induced carrier density depending on the thickness of the SOI layer and the polarity of the applied field. The results show that the enhanced carrier density is prominent for thin SOI and increases with applied voltage. The effective photon-induced carrier density is magnified by three times with surface bias simultaneously at the top and bottom interfaces of SOI. The corresponding plasma dispersion effect is also estimated.
Possible formation of interlayer nano-p-n junctions and quantum dot in double-walled carbon nanotube with electrode contacts to different layers
Authors: Shimizu T. , Haruyama J. , Nozawa K. , Sugai T. , Shinohara H.
Published: April 2009

We report findings on the asymmetrical current properties on both the source-drain and back-gate voltage (VBG) dependence (unconventional ambipolar behavior) found in a double-walled carbon nanotube (DWNT) field-effect transistor, which has electrode contacts to different layers. We also find Coulomb oscillations with a large charging energy observable only in +VBG region at low temperature. As origins for these phenomena, we discuss the possible presence of outer p- and inner n-type semiconducting layers, a corresponding interlayer nano-p-n junction, and a small quantum dot region in the inner n-layer exposed from the outer layer. Annealing of the DWNT in air atmosphere after synthesis allows change in only outer layer to p-type, remaining n-type behavior in the inner layer.
Effect of β-sheet propensity on peptide aggregation
Authors: Bellesia Giovanni , Shea Joan-Emma
Published: April 2009

The effect of β-sheet propensity on the structural features of peptide aggregates was investigated using an off-lattice coarse-grained peptide model. A phase diagram as a function of temperature and β-sheet propensity reveals a diverse family of supramolecular assemblies. Highly rigid peptides (peptides with high β-sheet propensity) are seen to assemble predominantly into fibrillar structures. Increasing the flexibility of the peptide (reducing β-sheet propensity) leads to a variety of structures, including fibrils, β-barrel structures, and amorphous aggregates. Nonfibrillar entities have been suggested as primary causative agents in amyloid diseases and our simulations indicate that mutations that decrease β-sheet propensity will decrease fibril formation and favor the formation of such toxic oligomers. Parallels between β-sheet aggregates and nematic liquid crystals are discussed.
Electron Compton-like quasielastic scattering from H2, D2, and HD
Authors: Bonham R. A. , Cooper G. , Hitchcock A. P.
Published: April 2009

A significant anomaly in the ratio of the cross sections for quasielastic scattering of D2 to H2 in a 50:50 mixture has been reported recently [Phys. Rev. Lett. 100, 043204 (2008)]. In particular, the interpretation of quasielastic scattering provided in that work predicts that the signals should be based on the elemental content and not on the molecular structure, and thus the spectrum for HD and that for the 50:50 mixture should be effectively the same, aside from minor line shape differences. In fact the signal from H in the mixture was low by 31(4)% (or that from D was correspondingly high) when compared to the signal from H in HD. Here, an attempt is made to explain this anomaly by scattering theory calculations based on the first Born and Born–Oppenheimer approximations. The relative contributions of translational, vibrational, and rotational excitations are computed for several temperatures. The computed signals are compared to the experimental spectra of HD and the 50:50 H2/D2 mixture and to pure H2 and D2, which were reported previously. Good agreement is found for the spectral line shapes. The predicted peak positions are also found to be in good agreement with experiment except for a slight shift in the case of D2. However the anomalous cross section ratio of D2 to H2 experimentally observed in the 50:50 mixture could not be explained by this approach.