bluuebunny/crossref_metadata_2025 huggingface dataset:
Hyperoxia‐mediated oxidative stress increases expression of UCP3 mRNA and protein in skeletal muscle
Authors: Flandin Pierre , Donati Yves , Barazzone-Argiroffo Constance , Muzzin Patrick
Published: May 2005

The uncoupling protein‐3 (UCP3) is a mitochondrial protein expressed mainly in skeletal muscle. Among several hypotheses for its physiological function, UCP3 has been proposed to prevent excessive production of reactive oxygen species. In the present study, we evaluated the effect of an oxidative stress induced by hyperoxia on UCP3 expression in mouse skeletal muscle and C2C12 myotubes. We found that the hyperoxia‐mediated oxidative stress was associated with a 5‐fold and 3‐fold increase of UCP3 mRNA and protein levels, respectively, in mouse muscle. Hyperoxia also enhanced reactive oxygen species production and UCP3 mRNA expression in C2C12 myotubes. Our findings support the view that both in vivo and in vitro UCP3 may modulate reactive oxygen species production in response to an oxidative stress.
Degradation of HMG‐CoA reductase in rat liver is cholesterol and ubiquitin independent
Authors: Ness Gene C. , Holland Reed C.
Published: May 2005

In contrast with the accelerated degradation observed in tumor cells in response to sterols, hepatic 3‐hydroxy‐3‐methylglutaryl coenzyme A (HMG‐CoA) reductase turnover in whole animals was not increased by dietary cholesterol. Furthermore, treating rats with lovastatin to lower hepatic cholesterol levels did not decrease the rate of degradation. The half‐life remained in the 6 h range. Co‐immunoprecipitation studies revealed that the amount of ubiquitin associated with the reductase was entirely dependent upon the amount of microsomal protein subjected to immunoprecipitation. The results indicate that in liver, neither the rate of reductase protein degradation nor the ubiquitin‐proteasome system appear to play roles in mediating changes in HMG‐CoA reductase protein levels in response to dietary cholesterol.
SNAT2 silencing prevents the osmotic induction of transport system A and hinders cell recovery from hypertonic stress
Authors: Bevilacqua Elena , Bussolati Ovidio , Dall‧Asta Valeria , Gaccioli Francesca , Sala Roberto , Gazzola Gian C. , Franchi-Gazzola Renata
Published: May 2005

Under hypertonic conditions the induction of SLC38A2/SNAT2 leads to the stimulation of transport system A and to the increase in the cell content of amino acids. In hypertonically stressed human fibroblasts transfection with two siRNAs for SNAT2 suppressed the increase in SNAT2 mRNA and the stimulation of system A transport activity. Under the same condition, the expansion of the intracellular amino acid pool was significantly lowered and cell volume recovery markedly delayed. It is concluded that the up‐regulation of SNAT2 is essential for the rapid restoration of cell volume after hypertonic stress.
Up‐regulation of lactosylceramide synthase in MDR1 overexpressing human liver tumour cells
Authors: Hummel Ina , Klappe Karin , Kok Jan Willem
Published: May 2005

HepG2 cells, stably transfected with MDR1 cDNA, encoding the P‐glycoprotein multidrug resistance efflux pump, display an altered sphingolipid composition compared to control cells, stably transfected with empty vector. The MDR1 overexpressing cells display a ∼3‐fold increased level of lactosylceramide and an increased ganglioside mass. Both the mRNA and the activity of lactosylceramide synthase were increased in HepG2/MDR1 cells. In conclusion, the increased glycolipid content in MDR1‐transfected HepG2 cells is caused by a transcriptional up‐regulation of the enzyme lactosylceramide synthase.
Redox potential of cytochrome c550 in the cyanobacterium Thermosynechococcus elongates
Authors: Ishikita Hiroshi , Knapp Ernst-Walter
Published: May 2005

Cytochrome c550 (cyt c550) from photosystem II (PSII) exists in the PSII‐bound form but can be released from PSII by treatment with divalent cations or Tris, yielding the isolated form. We calculated heme redox potentials (E
m) based on the crystal structures of cyt c550 by solving the Poisson–Boltzmann equation. In the isolated form, the calculated E
m are −240 mV at pH 6.0 and −352 mV at pH 9.0. This pH‐dependence is predominantly due to deprotonation of the heme‐propionic group near Asn‐49. In the PSII‐bound form, the calculated E
m was up‐shifted by 160 mV versus the isolated form due to a conformational change of protein backbone, yielding E
m
= −84 mV.
Amino acid residues associated with cluster N3 in the NuoF subunit of the proton‐translocating NADH‐quinone oxidoreductase from Escherichia coli
Authors: Velazquez Isabel , Nakamaru-Ogiso Eiko , Yano Takahiro , Ohnishi Tomoko , Yagi Takao
Published: May 2005

The NuoF subunit, which harbors NADH‐binding site, of Escherichia coli NADH‐quinone oxidoreductase (NDH‐1) contains five conserved cysteine residues, four of which are predicted to ligate cluster N3. To determine this coordination, we overexpressed and purified the NuoF subunit and NuoF + E subcomplex in E. coli. We detected two distinct EPR spectra, arising from a [4Fe–4S] cluster (g

x,y,z

= 1.90, 1.95, and 2.05) in NuoF, and a [2Fe–2S] cluster (g

x,y,z

= 1.92, 1.95, and 2.01) in NuoE subunit. These clusters were assigned to clusters N3 and N1a, respectively. Based on the site‐directed mutagenesis experiments, we identified that cluster N3 is ligated to the 351Cx2Cx2Cx40C398 motif.
Amphiphilic β‐sheet cobra cardiotoxin targets mitochondria and disrupts its network
Authors: Wang Chia-Hui , Wu Wen-guey
Published: May 2005

Recent advance in understanding the role of toxin proteins in controlling cell death has revealed that pro‐apoptotic viral proteins targeting mitochondria contain amphiphilic α‐helices with pore‐forming properties. Herein, we describe that the pore‐forming amphiphilic β‐sheet cardiotoxins (or cytotoxins, CTXs) from Taiwan cobra (Naja atra) also target mitochondrial membrane after internalization and act synergistically with CTX‐induced cytosolic calcium increase to disrupt mitochondria network. It is suggested that CTX‐induced fragmentation of mitochondria play a role in controlling CTX‐induced necrosis of myocytes and cause severe tissue necrosis in the victims.
Microsomal triglyceride transfer protein expression in adipocytes: A new component in fat metabolism
Authors: Swift Larry L. , Kakkad Bharati , Boone Cordelia , Jovanovska Aneta , Jerome W. Gray , Mohler Peter J. , Ong David E.
Published: May 2005

Microsomal triglyceride transfer protein (MTP) is a carrier of triglyceride essential for the assembly of apolipoprotein (apo)B‐containing lipoproteins by the liver and the small intestine. Its role in triglyceride transfer in tissues that do not secrete lipoproteins has not been explored. In particular, MTP would seem to be a candidate for a role in triglyceride metabolism within the adipocyte. To test this hypothesis, we probed adipocytes for the presence of MTP. Immunohistochemical and biochemical studies demonstrate MTP in adipocytes from brown and white fat depots of mice and human, as well as in 3T3‐L1 cells. Confocal microscopy revealed MTP throughout 3T3 cells; however, MTP fluorescence was prominent in juxtanuclear areas. In differentiated 3T3 cells MTP fluorescence was very striking around lipid droplets. In vitro lipid transfer assays demonstrated the presence of triglyceride transfer activity within microsomal fractions isolated from rat adipose tissue. In addition, quantitative rtPCR studies showed that MTP expression in mouse white fat depots was approximately 1% of MTP expression in mouse liver. MTP mRNA in differentiated 3T3 cells was approximately 13% of liver expression. Our results provide unequivocal evidence for the presence of MTP in adipocytes and present new possibilities for defining the mechanisms by which triglyceride is stored and/or hydrolyzed and mobilized.
HIV infection among pregnant women in Nigeria
Authors: Sagay A.S. , Kapiga S.H. , Imade G.E. , Sankale J.L. , Idoko J. , Kanki P.
Published: May 2005

Objectives: To determine risk factors for HIV among pregnant women (N = 2657) receiving antenatal services in Jos, Plateau state, Nigeria. Methods: Information about potential risk factors was obtained at interview. Biological samples were collected for detection of HIV and other sexually transmitted infections (STIs). Results: The prevalence of HIV was 8.2%. Women aged 20–29 years had more than 4‐fold increased risk of HIV. Women of Catholic (adjusted odds ratio (AOR) = 1.72, 95% CI = 1.01–2.95) and Pentecostal (AOR = 2.57, 95% CI = 1.46–4.52) denominations were more likely to be HIV‐infected when compared to Moslem women. The risk of HIV was also increased among women with multiple marriages and in women married to a banker/accountant. Other predictors of HIV were having a husband with other partners, perceived risk of HIV, STIs, candidiasis and bacterial vaginosis. Conclusions: Development of effective interventions, including behavioral change, expansion of perinatal HIV prevention services and STI control, should be given the highest priority.
In vitro alterations in cytoskeletal tensional homeostasis control gene expression in tendon cells
Authors: Lavagnino Michael , Arnoczky Steven P.
Published: May 2005

An in vitro collagen gel system was used to determine the effect of alterations in cytoskeletal tensional homeostasis on gene expression in tendon cells. Collagen gel matrices, seeded with rat tail tendon cells, underwent cytochalasin D and gel contraction treatments designed to alter the internal cytoskeletal homeostasis of the cells. Gels were examined for cytoskeletal organization using a rhodamine phalloidin stain for actin. The effect of altered cytoskeletal organization on mRNA expression of a catabolic (interstitial collagenase) and anabolic (α1(I) collagen) gene was examined using northern blot analysis. Tendon cells in adhered gels demonstrated a highly organized cytoskeleton and showed evidence of α1(I) collagen mRNA expression but no evidence of collagenase mRNA expression. Treatment of the attached gel with cytochalasin D disrupted the cytoskeletal organization and resulted in the upregulation of collagenase mRNA and the inhibition of α1(I) collagen mRNA expression. Release of the gels resulted in a cell mediated gel contraction, an immediate loss of cytoskeletal organization, and an mRNA expression pattern similar to that seen with cytochalasin D treatment. Isometric contraction of the gel on itself or around a 3‐point traction device resulted in an mRNA expression pattern similar to the adhered gel. Gene expression in the contracted gels could be reversed through chemical cytoskeletal disruption or removal of the traction device which permitted further gel contraction. The results of the study suggest that tendon cells can establish an internal cytoskeletal tension through interactions with their local extracellular environment. Alterations in this tension appear to control the expression of both catabolic and anabolic genes in a reciprocal manner. © 2005 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.
Effect of trunk flexion on cervical muscle EMG to rear impacts
Authors: Kumar Shrawan , Ferrari Robert , Narayan Yogesh
Published: May 2005

Objective: To determine the effect of occupant positioning on the response of the cervical muscles to whiplash‐type posterolateral impacts.

Methods: Twenty healthy volunteers underwent left posterolateral whiplash‐type impacts with the volunteers seated “out‐of position”. Electromyograms of the cervical muscles were recorded.

Results: Whether having the trunk flexed to the left or right at the time of impact, the muscle responses were low in magnitude, showing a trend to increasing EMG responses with increasing acceleration (P > 0.05). The time to onset and time to peak electromyogram for most muscles showed a trend to progressively decrease with increasing levels of acceleration. With the subject flexed to the left, all muscles generated 31% or less of the maximal voluntary contraction electromyogram. With the subject flexed to the right, all muscles generated 27% or less of their maximal electromyogram. In both positions, the trapezii were the most active (P < 0.05). Thus, having the trunk flexed out of neutral posture at the time of impact produces a very low magnitude cervical muscle response compared to impacts with the trunk in neutral posture.

Conclusions: In the absence of bodily impact, the flexed trunk posture appears to produce a biomechanical response that would probably decrease the likelihood of cervical muscle injury in low velocity posterolateral impacts. © 2005 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.
Coulomb stress changes caused by repeated normal faulting earthquakes during the 1997 Umbria‐Marche (central Italy) seismic sequence
Authors: Nostro Concetta , Chiaraluce Lauro , Cocco Massimo , Baumont David , Scotti Oona
Published: May 2005

We investigate fault interaction through elastic stress transfer among a sequence of moderate‐magnitude main shocks (5 < Mw < 6) which ruptured distinct normal fault segments during a seismic sequence in the Umbria‐Marche region (central Apennines). We also model the spatial pattern of aftershocks and their faulting mechanisms through Coulomb stress changes. We compute stress perturbations caused by earthquake dislocations in a homogeneous half‐space. Our modeling results show that seven out of eight main shocks of the sequence occur in areas of enhanced Coulomb stress, implying that elastic stress transfer may have promoted the occurrence of these moderate‐magnitude events. Our modeling results show that stress changes caused by normal faulting events reactivated and inverted the slip of a secondary N‐S trending strike‐slip fault inherited from compressional tectonics in its shallowest part (1–3 km). Of the 1517 available aftershocks, 82% are located in areas of positive stress changes for optimally oriented planes (OOPs) for Coulomb failure. However, only 45% of the 322 available fault plane solutions computed from polarity data is consistent with corresponding focal mechanisms associated with the OOPs. The comparison does not improve if we compute the optimally oriented planes for Coulomb failure by fixing the strike orientation of OOPs using information derived from structural geology. Our interpretation of these modeling results is that elastic stress transfer alone cannot jointly explain the aftershock spatial distribution and their focal mechanisms.
Forecasting the evolution of seismicity in southern California: Animations built on earthquake stress transfer
Authors: Toda Shinji , Stein Ross S. , Richards‐Dinger Keith , Bozkurt Serkan B.
Published: May 2005

We develop a forecast model to reproduce the distribution of main shocks, aftershocks and surrounding seismicity observed during 1986–2003 in a 300 × 310 km area centered on the 1992 M = 7.3 Landers earthquake. To parse the catalog into frames with equal numbers of aftershocks, we animate seismicity in log time increments that lengthen after each main shock; this reveals aftershock zone migration, expansion, and densification. We implement a rate/state algorithm that incorporates the static stress transferred by each M ≥ 6 shock and then evolves. Coulomb stress changes amplify the background seismicity, so small stress changes produce large changes in seismicity rate in areas of high background seismicity. Similarly, seismicity rate declines in the stress shadows are evident only in areas with previously high seismicity rates. Thus a key constituent of the model is the background seismicity rate, which we smooth from 1981 to 1986 seismicity. The mean correlation coefficient between observed and predicted M ≥ 1.4 shocks (the minimum magnitude of completeness) is 0.52 for 1986–2003 and 0.63 for 1992–2003; a control standard aftershock model yields 0.54 and 0.52 for the same periods. Four M ≥ 6.0 shocks struck during the test period; three are located at sites where the expected seismicity rate falls above the 92 percentile, and one is located above the 75 percentile. The model thus reproduces much, but certainly not all, of the observed spatial and temporal seismicity, from which we infer that the decaying effect of stress transferred by successive main shocks influences seismicity for decades. Finally, we offer a M ≥ 5 earthquake forecast for 2005–2015, assigning probabilities to 324 10 × 10 km cells.
Cluster analysis of cloud regimes and characteristic dynamics of midlatitude synoptic systems in observations and a model
Authors: Gordon Neil D. , Norris Joel R. , Weaver Christopher P. , Klein Stephen A.
Published: May 2005

Global climate models typically do not correctly simulate cloudiness associated with midlatitude synoptic systems because coarse grid spacing prevents them from resolving dynamics occurring at smaller scales and there exist no adequate parameterizations for the effects of these subgrid‐scale dynamics. Comparison of modeled and observed cloud properties averaged over similar regimes (e.g., compositing) aids the diagnosis of simulation errors and identification of meteorological forcing responsible for producing particular cloud conditions. This study uses a k‐means clustering algorithm to objectively classify satellite cloud scenes into distinct regimes based on grid box mean cloud fraction, cloud reflectivity, and cloud top pressure. The spatial domain is the densely instrumented southern Great Plains site of the Atmospheric Radiation Measurement Program, and the time period is the cool season months (November–March) of 1999–2001. As a complement to the satellite retrievals of cloud properties, lidar and cloud radar data are analyzed to examine the vertical structure of the cloud layers. Meteorological data from the constraint variational analysis is averaged for each cluster to provide insight on the large‐scale dynamics and advective tendencies coincident with specific cloud types. Meteorological conditions associated with high and low subgrid spatial variability are also investigated for each cluster. Cloud outputs from a single‐column model version of the GFDL AM2 atmospheric model forced with meteorological boundary conditions derived from observations and a numerical weather prediction model were compared to observations for each cluster in order to determine the accuracy with which the model reproduces attributes of specific cloud regimes.
Interannual consistency of bi‐monthly differences in diurnal variations of the ground‐level, vertical electric field
Authors: Burns G. B. , Frank‐Kamenetsky A. V. , Troshichev O. A. , Bering E. A. , Reddell B. D.
Published: May 2005

Interyear consistency is demonstrated in the bi‐monthly average diurnal vertical electric field measured over ∼720 “fair‐weather” days collected during a 5‐year interval (1998 to 2002) at Vostok (78.5°S, 107°E; magnetic latitude 83.6°S), Antarctica. After correcting for the influence of polar‐cap convection, seasonal peaks in the average electric field values occur around July‐August with a diurnal maximum at ∼ 2050 UT while lowest average magnitudes are measured near November‐December when the associated diurnal maximum occurs at ∼1830 UT. These variations are consistent with expected seasonal changes in global thunderstorm activity. Comparisons of ground‐level vertical electric field measurements (Vm−1) with Weimer‐1996 model cross‐polar cap potentials above Vostok (kV) for individual UT hours yield significant correlations over all hours but with reduced standard errors around local magnetic noon (∼1300 UT). This implies a more direct linkage between solar wind parameters and the cross‐polar cap potential near magnetic noon, for this site (magnetic latitude: 83.6°S). An all hours–all seasons linkage factor of 0.76 ± 0.06 Vm−1 per kV is determined, broadly consistent with an average ionosphere‐ground potential difference of ∼250 kV and a measured average vertical electric field of 185 Vm−1. Evidence is presented supporting a seasonal variation in this linkage factor, with generally lower magnitudes in the austral winter (May to August).
Trends in positive and negative ozone laminae in the Northern Hemisphere
Authors: Krizan P. , Lastovicka J.
Published: May 2005

The measured ozone profile is often not a smooth curve with a maximum in the stratosphere. It exhibits narrow layers of enhanced ozone concentration (positive laminae) and of depleted ozone (negative laminae). Here we deal with the trends in ozone laminae characteristics. All sufficiently long data series of ozonesonde soundings from the Northern Hemisphere poleward of 30°N are analyzed separately for Europe, northern America, Japan, and the Arctic. The trends in ozone laminae are quite strong, much stronger than those in total ozone at middle latitudes. A reversal in trends in the ozone laminae characteristics, mainly in the overall ozone content (deficit) in positive (negative) laminae per profile and the number of laminae per profile, is found to have occurred in the mid‐1990s. Whereas a negative trend was observed before the mid‐1990s, a positive trend was observed after about 1995. We assume this change in the ozone laminae trend to be caused predominantly by a change in the trends in circulation in the middle atmosphere.
Implementation of a gravity wave source spectrum parameterization dependent on the properties of convection in the Whole Atmosphere Community Climate Model (WACCM)
Authors: Beres Jadwiga H. , Garcia Rolando R. , Boville Byron A. , Sassi Fabrizio
Published: May 2005

This article describes the implementation of a new source spectrum parameterization for convectively generated gravity waves in the Whole Atmosphere Community Climate Model, version 2 (WACCM2). This parameterization is active in the tropics and is interactive with the underlying convection. The gravity wave spectrum at each model grid point and time step is determined based on the convective heating depth, tropospheric wind, and the convective heating rate. This parameterization introduces more realistic spatial and temporal distributions of gravity wave activity and yields gravity wave characteristics related to the underlying wave source. We present the estimated gravity wave momentum flux phase speed spectra at 100 hPa as well as the gravity wave drag in the middle and upper atmosphere using the new source spectrum representation. We also show the effects of this more physically based parameterization on the structure of the stratospheric and mesospheric semi‐annual oscillations of the zonal wind compared to a simulation with uniform gravity wave distribution. We conclude that the interaction of the gravity wave parameterization with tropospheric characteristics is a positive step toward a more physical representation of the middle and upper atmosphere.
Sulfate formation in sea‐salt aerosols: Constraints from oxygen isotopes
Authors: Alexander B. , Park R. J. , Jacob D. J. , Li Q. B. , Yantosca R. M. , Savarino J. , Lee C. C. W. , Thiemens M. H.
Published: May 2005

We use observations of the mass‐independent oxygen isotopic composition (Δ17O) of sulfate in the marine boundary layer (MBL) to quantify the sulfate source from aqueous SO2 (S(IV)) oxidation by O3 in alkaline sea‐salt aerosols. Oxidation by O3 imparts a large Δ17O signature to the resulting sulfate (8.8‰) relative to oxidation by H2O2 (0.9‰) or by OH or O2 (0‰). Ship data from two Indian Ocean Experiment (INDOEX) cruises in the Indian Ocean indicate Δ17O values usually <1‰ in the submicron sulfate aerosol but considerable variability in the supermicron sulfate with frequent occurrences above 1‰ and up to 6.7‰. The large Δ17O values are associated with high concentrations of sea‐salt aerosols, providing evidence for the S(IV) + O3 pathway. We use a global chemical transport model (GEOS‐CHEM) to interpret quantitatively the INDOEX observations and to assess the global importance of sulfate production in sea‐salt aerosols. The model accounts for titration of sea‐salt alkalinity in the MBL by uptake of acid gases (SO2, H2SO4, and HNO3), shutting down the S(IV) + O3 pathway. We find that this titration occurs rapidly over much of the oceans except at high latitudes (strong sea‐salt emission) and is due to both the S(IV) + O3 reaction and HNO3 (g) condensation; that is, sulfate formation in sea‐salt aerosols is limited by the alkalinity flux from the ocean and by competition for this alkalinity supply from HNO3 (g). The model is consistent with the Δ17O magnitudes and patterns in the INDOEX data. Titration of alkalinity is critical for the success of the model simulation. Regeneration of sea‐salt aerosol alkalinity by OH uptake is inconsistent with the Δ17O observations in INDOEX. Model results indicate that sulfate production in sea‐salt aerosols decreases MBL SO2 concentrations and gas phase H2SO4 production rates by typically 10–30% (up to >70%) and increases MBL sulfate concentrations by typically >10% (up to 30%). Globally, this mechanism contributes 9% of atmospheric sulfate production and 1% of the sulfate burden. The impact on H2SO4 (g) formation and implications for the potential formation of new particles in the MBL warrants inclusion in models examining the radiative effects of sulfate aerosols.
Postcorrelation ripple removal and radio frequency interference rejection for Parkes Telescope survey data
Authors: Barnes D. G. , Briggs F. H. , Calabretta M. R.
Published: May 2005

The 21 cm multibeam receiver on the Parkes telescope has been used for many neutral hydrogen (HI) imaging projects, for example, the HI Parkes All Sky Survey (HIPASS) and the Southern Galactic Plane Survey. In many experiments to date, basic radio frequency interference (RFI) rejection has been accomplished on a per‐feed basis, using the median statistic throughout the processing, which eliminates outliers in a nonparametric fashion at the expense of increased statistical noise. The classic 21 cm baseline ripple problem has been largely ignored, except for the subtraction of a coarse template which is calculated independently of feed, time, telescope elevation, and receiver rotation. The ripple is especially strong during the daytime, when the Sun acts as a broadband RFI noise source. Here we report on new techniques that we are developing, for application to raw, postcorrelation multibeam data, which handle RFI rejection and ripple suppression in more sophisticated ways. RFI can be identified by the presence of coincident outliers on multiple feeds, by sharp increases or decreases in flux time series that are inconsistent with a beam‐smeared sky, and by the presence of highly polarized flux. We present our progress with this approach and highlight some remaining difficulties. We also present a novel technique for modeling the variation during telescope scans of 21 cm baseline ripple caused by stray continuum radiation undergoing multiple reflections in the telescope cavity and demonstrate its application to HIPASS data; this may increase the usefulness of daytime spectral line observing.
Interdecadal variations of the coastal Oyashio from the 1970s to the early 1990s
Authors: Tatebe Hiroaki , Yasuda Ichiro
Published: May 2005

The interdecadal migration of the southernmost latitude of the coastal Oyashio is investigated using a simple layered model. Being influenced by the changes of the Aleutian low which shows two dominant oscillations with bi‐decadal and penta‐decadal periods, the southernmost latitude gradually migrated southward from the 1970s to the early 1990s with less bi‐decadal signals. The westward baroclinic Rossby waves on the be‐decadal period could be attenuated effectively by the local wind stress anomalies which changed their signs on the characteristics of the Rossby waves. As a result, only the penta‐decadal signal can survive and reach the western boundary region, and the coastal Oyashio can be affected. In the analyzed period from the 1970s to the 1990s, the transient responses of the North Pacific ocean to the interdecadal changes of the Aleutian low could play a role in cutting off the bi‐decadal signals.
Decreasing river discharge in northern Canada
Authors: Déry Stephen J. , Wood E. F.
Published: May 2005

Freshwater discharge to high‐latitude oceans in 64 Canadian rivers is investigated. The mean annual discharge rate attains 1252 km3 yr−1 for an area of 5.6 × 106 km2, equating to a sink of 225 mm yr−1 in the surface water budget of northern Canada (excluding the Arctic Archipelago where insufficient data exist). Application of the Mann‐Kendall test to the data reveals a 10% decrease (−125 km3 yr−1 or −22 mm yr−1) in the total annual river discharge to the Arctic and North Atlantic Oceans from 1964 to 2003. This trend in river runoff is consistent with a 21 mm yr−1 decline in observed precipitation over northern Canada between 1964 and 2000. We find evidence of statistically‐significant links between the Arctic Oscillation, El Niño/Southern Oscillation, and the Pacific Decadal Oscillation to the total annual freshwater discharge in northern Canada's rivers at interannual‐to‐decadal timescales.
Vertical segregation in granular mass flows: A shear cell study
Authors: Cagnoli B. , Manga M.
Published: May 2005

Non‐fluidised, dry granular mass flows are obtained with rock fragments located on a rough rotating disk. In these flows that develop a quasi‐rigid upper layer and a basal layer of colliding particles, dense clasts sink whereas light ones rise when surrounded by particles with intermediate density. Our experiments demonstrate that the presence of a quasi‐rigid upper layer in granular mass flows does not prevent vertical segregation and that the formation of coarse‐tail grading in pyroclastic flows does not require fluidising gases. High‐speed videos reveal that vertical segregation in granular mass flow of rock fragments is generated by inertia differences between segregating clasts and matrix when they are both pushed upward by collisions with the basal layer. Coarse‐tail grading occurs because the average segregation velocity of smaller clasts is smaller than that of larger clasts.
Asymptotics of regulated field commutators for Einstein-Rosen waves
Authors: Barbero G. J. Fernando , Mena Marugán Guillermo A. , Villaseñor Eduardo J. S.
Published: May 2005

We discuss the asymptotic behavior of regulated field commutators for linearly polarized, cylindrically symmetric gravitational waves and the mathematical techniques needed for this analysis. We concentrate our attention on the effects brought about by the introduction of a physical cutoff in the study of the microcausality of the model and describe how the different physically relevant regimes are affected by its presence. Specifically we discuss how genuine quantum gravity effects can be disentangled from those originating in the introduction of a regulator.
Collective dielectric relaxation in smectic A and smectic C⋆ phases near transition temperature of electroclinic liquid crystals
Authors: Thakur A. K. , Chadha G. K. , Kaur S. , Bawa S. S. , Biradar A. M.
Published: May 2005

The collective dielectric relaxation processes of electroclinic liquid-crystal materials have been investigated in a thin (3.5μm) planar cell in the frequency range of 1 Hz–10 MHz. Measurement of complex dielectric permittivity versus temperature has been taken on aligned samples filled with different electroclinic liquid-crystal materials. The dielectric data were collected by using the measuring electric field perpendicular to the smectic layer planes. The behavior of the collective dielectric modes has been studied in smectic C*(SmC*) and smectic A(SmA) phases. However, near the transition temperature of SmC*-SmA phase, the dielectric permittivity due to the Goldstone mode and soft mode could not be separated. It has also been observed that the dielectric permittivity increases with temperature before the transition temperature of SmC*-SmA phase under bias field. Temperature dependence of dielectric increments before the transition temperature under bias field and relaxation frequency suggests that the electroclinic liquid crystal shows transitional behavior over a wide temperature range and does not obey the Curie–Weiss law near the transition temperature like in other ferroelectric liquid-crystal materials.
A spectral method for the nonconserved surface evolution of nanocrystalline gratings below the roughening transition
Authors: Ramasubramaniam A. , Shenoy V. B.
Published: May 2005

The evolution of nanoscale gratings on high-symmetry crystalline surfaces is studied below the roughening temperature in the nonconserved regime, where mass transport takes place via evaporation and condensation of atoms from the vapor to atomic-height surface steps. Since the equation for surface evolution is singular at a facet orientation, a modeling approach based on a weak formulation using a Fourier series expansion is employed. Our method allows for the consideration of a wide range of morphologies ranging from simple sinusoidal one-dimensional (1D) and two-dimensional (2D) gratings to more disordered sputter ripples, and gratings on vicinal surfaces where steps are introduced due to miscut from a facet orientation. Extensions of previous analyses of the decay of 1D sinusoids on vicinal surfaces are discussed; the miscut is seen to lead to the formation of flat regions of low step density at the profile extrema. We also suggest a tighter bound for the maximum miscut beyond which faceting does not occur. In distinct contrast to the case of conserved dynamics, 2D sinusoids do not show shape-invariant relaxation, but instead peaks and valleys shrink simultaneously leaving fourfold hypocycloidal regions around the saddle points. We, however, find that radially symmetric Gaussian bumps remain shape invariant during nonconserved relaxation. Our simulations on sputter ripples show lack of faceting during relaxation while the amplitude is found to decay, for a significant duration, in inverse proportion to the square root of the relaxation time, as observed in recent experiments on Ge(001) surfaces. We also consider relaxation experiments of sinusoids on Si(001) and find good agreement of the profiles observed at high temperature with our nonconserved calculations although the decay behavior at moderately high temperatures (900–1100 °C) is found to be consistent with the case where both conserved and nonconserved modes of mass transport are comparable.
Self-diffusion of molecular hydrogen in clathrasils compared: Dodecasil 3C versus sodalite
Authors: van den Berg A. W. C. , Flikkema E. , Jansen J. C. , Bromley S. T.
Published: May 2005

The self-diffusion coefficient of molecular hydrogen through the all-silica microporous dodecasil 3C structure is calculated by means of molecular-dynamics (MD) calculations, allowing for full framework flexibility, in order to assess the material’s feasibility as a hydrogen storage medium. The hydrogen uptake rate into dodecasil 3C is compared to that previously calculated for sodalite and it is found that the latter performs significantly better. The reason for this variation in performance is found to lie in intrinsic topological differences between each framework type. This is explicitly demonstrated by means of a simplified version of transition state theory helping to succinctly rationalize the MD data.
Calculation of electric-field gradients based on higher-order generalized Douglas–Kroll transformations
Authors: Neese Frank , Wolf Alexander , Fleig Timo , Reiher Markus , Hess Bernd Artur
Published: May 2005

In this paper, the calculation of electric-field-like properties based on higher-order Douglas–Kroll–Hess (DKH) transformations is discussed. The electric-field gradient calculated within the Hartree–Fock self-consistent field framework is used as a representative property. The properties are expressed as an analytic first derivative of the four-component Dirac energy and the nth-order DKH energy, respectively. The differences between a “forward” transformation of the relativistic energy or the “back transformation” of the wave function is discussed in some detail. Detailed test calculations were carried out on the electric-field gradient at the halogen nucleus in the series HX (X=F,Cl,Br,I,At) for which extensive reference data are available. The DKH method is shown to reproduce (spin-free) four-component Dirac–Fock results to an accuracy of better than 99% which is significantly closer than previous DKH studies. The calculations of both the Hamiltonian and the property operator are shown to be essentially converged after the second-order transformation, even for elements as heavy as At. In addition, we have obtained results within the density-functional framework using the DKHZ and zeroth-order regular approximation (ZORA) methods. The latter results included picture-change effects at the scalar relativistic variant of the ZORA-4 level and were shown to be in quantitative agreement with earlier results obtained by van Lenthe and Baerends. The picture-change effects are somewhat smaller for the ZORA method compared to DKH. For heavier elements significant differences in the field gradients predicted by the two methods were found. Based on comparison with four-component Dirac–Kohn–Sham calculations, the DKH results are more accurate. Compared to the spin-free Dirac–Kohn–Sham reference values, the ZORA-4 formalism did not improve the results of the ZORA calculations.
Electronic structure, reactivity, and spectroscopy of dihydrides of group-IB metals
Authors: Guitou-Guichemerre M. , Chambaud G.
Published: May 2005

Atomic pseudopotentials and highly correlated wave functions, including spin-orbit interactions, have been used to evaluate the electronic structure, stability, and spectroscopy of triatomic molecule MH2, with a metal M belonging to group IB (Cu, Ag, and Au). CuH2 and AuH2 have been recently observed by IR spectroscopy in solid hydrogen and bending anharmonic wave numbers have been assigned to these two systems. The AgH2 molecule has not been detected nor experimentally characterized, despite several theoretical works arguing on its stability. Our results confirm that the MH2 radicals have a metastable bent ground state separated from the dissociation into [M+H2] ground state by barriers which have been evaluated to 1.43, 0.78, and 0.80eV, for Cu, Ag, and Au compounds, respectively. These barriers are calculated smaller than in previous determinations but still large enough to stabilize the MH2 systems. Spectroscopic data are calculated for these radicals.
Two-phase planar and regular lamellar coupled growth along the univariant eutectic reaction in ternary alloys: An analytical approach and application to the Al–Cu–Ag system
Authors: De Wilde J. , Froyen L. , Witusiewicz V. T. , Hecht U.
Published: May 2005

Unidirectional solidification of ternary eutectic alloys with a composition close to the univariant eutectic reaction under certain conditions leads to two-phase planar growth, showing a lamellar morphology similar to what is known from binary (invariant) eutectic growth. In the latter case, the most applied analytical description is the Jackson–Hunt model. The present paper extends this model to steady-state two-phase planar and regular lamellar coupled growth in the case of the univariant eutectic reaction in ternary alloys as obtained during unidirectional solidification. It is shown that during steady state, a similar expression between the lamellar spacing λ and the growth velocity v, i.e., λ2v= constant, describes the spacing selection whenever minimum undercooling is assumed. The constant is only dependent on the material properties of the selected alloy. The theory is applied to growth along the univariant reaction L→α(Al)+θ-Al2Cu in Al–Cu–Ag alloys resulting in a good agreement between the calculations and the experimental results. However, some uncertainties concerning the variation of the material properties, in particular, the interfacial properties, remain when going from the binary system towards ternary univariant growth. So, finally a sensitivity analysis is made, being a good solution to show the effect of a change in alloy and material properties on the eutectic growth morphology, e.g., by a change in the amount of the alloying elements.
Investigating the properties of supported vesicular layers on titanium dioxide by quartz crystal microbalance with dissipation measurements
Authors: Reviakine Ilya , Rossetti Fernanda F. , Morozov Alexander N. , Textor Marcus
Published: May 2005

Adsorption of phospholipid vesicles on titanium dioxide was studied by a combination of quartz crystal microbalance with dissipation (QCM-D) and atomic force microscopy techniques. Vesicle size, concentration in solution, and bilayer composition were systematically varied. A strong dependence of the QCM-D response (magnitude of the frequency and dissipation factor shifts) on the vesicle concentration in solution was observed. QCM-D data were compared with a linear viscoelastic model based on the Voight element to determine layer thickness, density, elastic modulus, and viscosity. Based on the results of this comparison, it is proposed that (i) layer thickness and density, as sensed by QCM-D, saturate much earlier (in time) than the actual surface coverage of the vesicles (number of vesicles per unit area); (ii) changes in surface coverage that occur after the density and thickness, as sensed by QCM-D, have saturated, are interpreted by the model as changes in the layer’s viscoelastic properties. This is caused by the replacement of the viscous media (water) between the vesicles by viscoelastic media of similar density (vesicles); (iii) viscoelastic properties of layers formed at different vesicle concentrations differ significantly, while the vesicle surface coverage in those layers does not. Based on the comparison between the atomic force microscopy images and QCM-D data acquired at various vesicle concentrations it is proposed that QCM-D response is not directly related to the surface coverage of the vesicles.
Modeling of twinning in epitaxial (001)-oriented La0.67Sr0.33MnO3 thin films
Authors: Farag N. , Bobeth M. , Pompe W. , Romanov A. E. , Speck J. S.
Published: May 2005

Twinning, i.e., the formation of structural domains, in La1−xSrxMnO3 thin films, which grow coherently on (001)-oriented cubic substrates, is explained as a result of shear strain relaxation within the distorted rhombohedral La1−xSrxMnO3 crystal lattice. A one-dimensional periodic model structure of twins is proposed and the nonuniform elastic strains within twinned La1−xSrxMnO3 films are calculated by applying the coherency-defect technique. The strain field depends on the ratio of the domain width and film thickness and exhibits maxima at the triple junctions of the domain boundaries and the film/substrate interface. The equilibrium domain width is derived as a function of the film thickness by minimizing the total energy of the system including contributions from elastic strain and domain-wall energy. From comparison of the theoretical results with recent electron microscope observations of twins the domain-wall energy can be predicted. From the observed average domain width in La0.67Sr0.33MnO3 films, the domain-wall energy of 1.35mJ∕m2 is suggested. The possibility of a preferred nucleation of the ferromagnetic phase at triple junctions due to spatial strain variations is discussed.
A self-consistent theoretical model for macropore growth in n-type silicon
Authors: Barillaro G. , Pieri F.
Published: May 2005

In this work, a theoretical study on the growth of macropores fabricated from n-type silicon by photoelectrochemical etching in HF-based electrolytes is reported. By solving the diffusion equation into the pores, we deduce a self-consistent model which can be used for quantitative prediction of the growth speed and pore depth. The limiting factor of the growth, i.e., the HF concentration at the pore tip, is shown to be a nonlinear function of the pore depth, a fact not accounted for by the current literature. A reduced model with a closed analytical solution is presented as well. Finally, the predictions of the full and reduced models are compared with the experimental data.
A self-closed thermal model for laser shock peening under the water confinement regime configuration and comparisons to experiments
Authors: Wu Benxin , Shin Yung C.
Published: May 2005

Laser shock peening (LSP) is emerging as a competitive alternative technology to classical treatments to improve fatigue and corrosion properties of metals for a variety of important applications. LSP under a water confinement regime (WCR) can produce plasma pressures on the target surface four times higher and two to three times longer than those under direct regime configurations. However, most of the published thermal models for LSP under WCR are not self-closed, and have free variables which have to come from experimental measurements under the same conditions. In this paper, a self-closed thermal model for LSP under WCR configurations is presented. This model has considered most of the relevant physical processes for laser ablation and plasma formation and expansion, and there are no free variables in the model. The simulation results for pressures from the model are compared with the available experimental results in literature under a variety of laser-pulse conditions, and good agreements are found.
Solvatochromic behavior of phenol blue in CO2+ethanol and CO2+n-pentane mixtures in the critical region and local composition enhancement
Authors: Chen Jiawei , Shen Dong , Wu Weize , Han Buxing , Wang Bo , Sun Donghai
Published: May 2005

The UV-Vis spectra of probe phenol blue in CO2+ethanol and CO2+n-pentane binary mixtures were studied at 308.15 K and different pressures. The experiments were conducted in both supercritical region and subcritical region of the mixtures by changing the compositions of the mixed solvents. On the basis of the experimental results the local compositions of the solvents about phenol blue were estimated by neglecting the size difference of CO2 and the cosolvents. Then the local composition data were corrected by a method proposed in this work, which is mainly based on Lennard-Jones sphere model. It was demonstrated that the local mole fraction of the cosolvents is higher than that in the bulk solution at all the experimental conditions. In the near critical region of the mixed solvents the local composition enhancement, defined as the ratio of cosolvent mole fraction about the solute to that in the bulk solution, increased significantly as pressure approached the phase boundary from high pressure. The local composition enhancement was not considerable as pressure was much higher than the critical pressure. In addition, in subcritical region the degree of composition enhancement was much smaller and was not sensitive to pressure in the entire pressure range as the concentration of the cosolvents in the mixed solvents was much higher than the concentration at the critical point of the mixtures.
Selection of temperature intervals for parallel-tempering simulations
Authors: Kone Aminata , Kofke David A.
Published: May 2005

A heuristic is developed specifying that temperatures in replica-exchange simulations should be spaced such that about 20% of the phase-swap attempts are accepted. The result is found to be independent of the heat capacity, suggesting that it may be applied generally despite being based on an assumption of (piecewise-) constant heat capacity.
Optical characterization of porous alumina from vacuum ultraviolet to midinfrared
Authors: Thompson Daniel W. , Snyder Paul G. , Castro Leon , Yan Li , Kaipa Prasuna , Woollam John A.
Published: May 2005

Porous alumina was fabricated and optically characterized over a wide spectral range. Layers were formed electrochemically in oxalic acid solution from 10-μm-thick aluminum films evaporated onto silicon wafers. The layer formation was monitored with in situ spectroscopic ellipsometry in the visible and near-infrared wavelength range to accurately determine the thickness and dielectric functions. Anisotropy due to the columnar nature of the porous structure was determined using optical modeling. The porous alumina layer was found to have a small but significant absorption tail throughout the visible region. Atomic force microscopy and scanning electron microscopy were used throughout the process to assess the quality of pore formation. The mean pore center-to-center spacing was approximately 100 nm with thicknesses up to 5μm. The infrared spectra revealed absorption peaks previously seen in ceramic alumina and peaks not associated with bulk alumina.