bluuebunny/crossref_metadata_2025 huggingface dataset:
Helium transport in sediment pore fluids of the Congo‐Angola margin
Authors: Chaduteau Carine , Jean‐Baptiste Philippe , Fourré Elise , Charlou Jean‐Luc , Donval Jean‐Pierre
Published: January 2009

During the ZaïRov2 cruise of the ZaïAngo project (1998–2000) on the passive Congo‐Angola margin, several gravity cores were analyzed for helium isotopic composition of sedimentary pore waters in two cold fluid seepage zones: the Astrid slide area and the Regab giant pockmark. Gas concentration and isotopic composition are presented along with thermal data in terms of the origin and circulation of fluids. Helium isotope data lie on a mixing line between bottom seawater and an almost pure radiogenic. Helium and temperature vertical profiles are well described by the classic diffusion‐advection equation. On the basis of He profiles, we estimate the advection rate on the rim of the pockmark between 1.2 and 2.3 mm/a. The He flux derived for a pure diffusive regime (2.4 × 10−8 mol/m2/a) can favorably be compared to literature data and contrasts with the flux computed close to the pockmark center (1.9 × 10−7 mol/m2/a). Helium depth profiles turned to be more sensitive to advection rate than temperature profiles are.
Tongue‐shaped frontal structure and warm water intrusion in the southern Yellow Sea in winter
Authors: Lie Heung‐Jae , Cho Cheol‐Ho , Lee Seok
Published: January 2009

In winter, a thermohaline front forms at the Yellow Sea (YS) entrance where the warm and saline Cheju Warm Current (CWC) water meets cold coastal water. The frontal structure, as well as the northwestward intrusion of the warm water, was investigated by analyzing conductivity‐temperature‐depth (CTD) data, tracks of drifting floats, moored current data, and satellite images. The CWC water advances westward as a tongue with its tip heading westward across the YS entrance, not intruding northward along the deepest part of the YS trough, whereas a secondary warm water band is developed northwestward along the western flank of the trough. Floats in the warm tongue moved northwestward across the western frontal zone where the frontal structure was weak, reflecting the northwestward intrusion along the 50–70 m isobaths through the frontal zone. Currents in the trough do not always meet the upwind flow theory that, in an elongated basin, the wind‐driven flow is upwind in the deep channel, but rather show the predominance of the southward downwind flow. Model experiments show that on the western flank of the trough, both the southeastward tide‐induced residual flow and the southeastward flow due to the nonlinear effect between tide and wind are generated at the same time. Thus the intermittent intrusion of the CWC across the western frontal zone may be closely associated with the predominance of the upwind flow over the southeastward nonlinear interacted flow.
Pressure gradient effect on a particle velocity distribution
Authors: Lui A. T. Y.
Published: January 2009

In space plasma missions, measurements of the three‐dimensional particle velocity distribution are used to examine the dynamical evolution of plasmas. The first velocity moment of the measured particle velocity distribution is often regarded as the bulk flow of the population. Accurate determination of bulk flows is crucial if the frozen‐in‐condition is judged by E + V × B = 0, where E is the electric field, V is the bulk flow, and B is the magnetic field. In this paper, we show that this first velocity moment computed from the measured particle velocity distribution can deviate substantially from the bulk motion of the particle population when a significant pressure gradient exists near the measurement location. The discrepancy, which arises from the diamagnetic drift with a finite Larmor radius effect, increases with increasing energy range used in the computation. The result calls for caution in the proper interpretation of this velocity moment and suggests a means to avoid error in the determination of bulk flow due to pressure gradient effects.
When do particles follow field lines?
Authors: Minnie J. , Matthaeus W. H. , Bieber J. W. , Ruffolo D. , Burger R. A.
Published: January 2009

We examine charged particle transport perpendicular to the large scale magnetic field. We find that the limit of an infinite parallel mean free path of particles diffusing along the large scale magnetic field is a necessary condition for which the diffusive spread of the magnetic field lines leads to a proportional spread of the particles. When it occurs this requires that parallel mean free path is well in excess of the smaller of the system size and the turbulence ultrascale. However, there are alternative situations in which particles may diffuse, but field lines do not. In the latter cases the asymptotic behavior is that which persists after the parallel mean free path exceeds some multiple of the correlation scales. This phenomenon of diffusing particles/non‐diffusing field lines is typically determined by the 2D turbulence spectrum, where the diffusion coefficient of the magnetic field due to 2D turbulence can diverge if the spectrum of the 2D fluctuations is not well behaved at small wave numbers. We also show that the classical relation between parallel and perpendicular diffusion for high energy particles is consistent with the field line random walk description of particle diffusion.
A geological fingerprint of low‐viscosity fault fluids mobilized during an earthquake
Authors: Brodsky E. E. , Rowe C. D. , Meneghini F. , Moore J. C.
Published: January 2009

The absolute value of stress on a fault during slip is a critical unknown quantity in earthquake physics. One of the reasons for the uncertainty is a lack of geological constraints in real faults. Here we calculate the slip rate and stress on an ancient fault in a new way based on rocks preserved in an unusual exposure. The study area consists of a fault core on Kodiak Island that has a series of asymmetrical intrusions of ultrafine‐grained fault rock into the surrounding cataclasite. The intrusive structures have ductile textures and emanate upward from a low‐density layer. We interpret the intrusions as products of a gravitational (Rayleigh‐Taylor) instability where the spacing between intrusions reflects the preferred wavelength of the flow. The spacing between intrusions is 1.4 ± 0.5 times the thickness of the layer. This low spacing‐to‐thickness ratio cannot be explained by a low Reynolds number flow but can be generated by one with moderate Reynolds numbers. Using a range of density contrasts and the geometry of the outcrop as constraints, we find that the distance between intrusions is best explained by moderately inertial flow with fluid velocities on the order of 10 cm/s. The angle that the intrusions are bent over implies that the horizontal slip velocity was comparable to the vertical rise velocity, and therefore, the fault was slipping at a speed of order 10 cm/s during emplacement. These slip velocities are typical of an earthquake or its immediate afterslip and thus require a coseismic origin. The Reynolds number of the buoyant flow requires a low viscous stress of at most 20 Pa during an earthquake.
Frictional and transport properties of the Chelungpu fault from shallow borehole data and their correlation with seismic behavior during the 1999 Chi‐Chi earthquake
Authors: Tanikawa Wataru , Shimamoto Toshihiko
Published: January 2009

We carried out low‐ and high‐velocity friction tests on fault rock samples from shallow boreholes on the Taiwan Chelungpu fault and measured their fluid transport properties under high pressure, with the objective of explaining the different seismic behaviors in the northern and southern sections of the fault during the 1999 Chi‐Chi earthquake. Our results of low‐velocity friction tests demonstrate that fault gouge from the southern section of the fault exhibits velocity‐weakening frictional behavior, whereas gouge from the northern section exhibits velocity‐strengthening friction. Friction in the northern gouge decreased strongly with increasing wetness, whereas friction in southern gouge samples was not affected by wetness. A rapid reduction of friction was observed immediately after the onset of slip in high‐velocity friction tests. The results of high‐velocity friction tests were similar for all fault gouge samples tested, although permeability in the northern fault zone was lower than that in the south. Numerical modeling indicated that thermal pressurization in the northern fault zone promoted stress reduction and fault instability during slip, whereas it did not in the south. This contrasting seismic behavior between north and south is caused mainly by differences in fluid transport properties of the slip zones. More efficient thermal pressurization in the north explains the large slip displacement there. The results of our low‐velocity friction tests are consistent with nucleation of the Chi‐Chi earthquake in the south and propagation of the rupture from south to north.
Regional three‐dimensional seismic velocity model of the crust and uppermost mantle of northern California
Authors: Thurber Clifford , Zhang Haijiang , Brocher Thomas , Langenheim Victoria
Published: January 2009

We present a three‐dimensional (3D) tomographic model of the P wave velocity (Vp) structure of northern California. We employed a regional‐scale double‐difference tomography algorithm that incorporates a finite‐difference travel time calculator and spatial smoothing constraints. Arrival times from earthquakes and travel times from controlled‐source explosions, recorded at network and/or temporary stations, were inverted for Vp on a 3D grid with horizontal node spacing of 10 to 20 km and vertical node spacing of 3 to 8 km. Our model provides an unprecedented, comprehensive view of the regional‐scale structure of northern California, putting many previously identified features into a broader regional context and improving the resolution of a number of them and revealing a number of new features, especially in the middle and lower crust, that have never before been reported. Examples of the former include the complex subducting Gorda slab, a steep, deeply penetrating fault beneath the Sacramento River Delta, crustal low‐velocity zones beneath Geysers‐Clear Lake and Long Valley, and the high‐velocity ophiolite body underlying the Great Valley. Examples of the latter include mid‐crustal low‐velocity zones beneath Mount Shasta and north of Lake Tahoe.
Seismic structure beneath the Rivera subduction zone from finite‐frequency seismic tomography
Authors: Yang Ting , Grand Stephen P. , Wilson David , Guzman‐Speziale Marco , Gomez‐Gonzalez Juan Martin , Dominguez‐Reyes Tonatiuh , Ni James
Published: January 2009

The subduction zone of western Mexico is a unique region on Earth where microplate capture and overriding plate disruption are occurring today. The young, small Rivera plate and the adjacent Cocos plate are subducting beneath the Jalisco block of Mexico. Here, we present aPwave tomographic model of the upper mantle to 400 km depth beneath the Jalisco block and surrounding regions using teleseismicPwaves recorded by the Mapping the Rivera Subduction Zone (MARS) and Colima Volcano Deep Seismic Experiment (CODEX) seismic arrays. The inversion used 12,188Pwave residuals and finite‐frequency theory to backproject the 3‐D traveltime sensitivity kernels through the model. Below a depth of 150 km, the tomography model shows a clear gap between the Rivera and Cocos slabs that increases in size with depth. The gap between the plates lies beneath the northern part of the Colima graben and may be responsible for the location of Colima volcano. The images indicate that the deep Rivera plate is subducting more steeply than does the adjacent Cocos plate and also has a more northerly trajection. At a depth of about 100 km, both the Rivera and Cocos slabs have increased dips such that the slabs are deeper than 200 km beneath the Trans‐Mexican Volcanic Belt (TMVB). It is also found that the Rivera plate is at roughly 140‐km depth beneath the young central Jalisco Volcanic lineament. Our images suggest that the Rivera plate and westernmost Cocos plate have recently rolled back toward the trench. This scenario may explain the unusual magmatic activity seen in the TMVB.
Generation of internal waves by a supercritical stratified plume
Authors: Stashchuk Nataliya , Vlasenko Vasiliy
Published: January 2009

The generation of internal waves by a propagating river plume is studied in the framework of a fully nonlinear nonhydrostatic numerical model. The vertical fluid stratification, parameters of tide, river discharge, and the bottom topography were taken close to those observed near the Columbia River mouth. It was found that in the beginning of the ebb tidal phase the river water intruding into the sea behaves as a surface jet stream. It collides with the stagnant shelf waters and sinks down in the area of the outer plume boundary, forming a head of the gravity current. In supercritical conditions which are normally realized at the first stage of the ebb tidal phase, internal waves are arrested in the head of the gravity current because their phase speed is smaller than the velocity of the plume. They are released and radiate from the plume when the speed of the decelerating front becomes smaller than the internal wave phase speed. This mechanism of the wave generation is sensitive to the stratification of the ambient shelf waters. It was found that dramatic decay of the buoyancy frequency profile from the surface to the bottom provides the most favorable conditions for the efficient disintegration of the head of the gravity current into a packet of internal waves and their fast separation from the plume. In the case when the fluid stratification on the shelf is close to monotonous, the disintegration of the head of the gravity current into a packet of solitary internal waves is not expected.
Global distribution of atmospheric waves in the equatorial upper troposphere and lower stratosphere: AGCM simulation of sources and propagation
Authors: Kawatani Yoshio , Takahashi Masaaki , Sato Kaoru , Alexander Simon P. , Tsuda Toshitaka
Published: January 2009

The global distribution, sources, and propagation of atmospheric waves in the equatorial upper troposphere and lower stratosphere were investigated using an atmospheric general circulation model with T106L60 resolution (120‐km horizontal and 550‐m vertical resolution). The quasibiennial oscillation (QBO) with a period of ∼1.5–2 years was simulated well without gravity wave drag parameterization. The zonal wave number versus the frequency spectra of simulated precipitation represent realistic signals of convectively coupled equatorial trapped waves (EQWs). The temperature spectra in the stratosphere also indicate dominant signals of EQWs. EQWs with equivalent depths in the range of 8–90 m from the n = −1 mode to n = 2 mode were extracted separately. Each EQW in the stratosphere generally corresponded well with the source of each convectively coupled EQW activity in the troposphere. The propagations of Kelvin waves and n = 0 eastward/westward propagating EQWs are strongly influenced by the Walker circulation and the phase of the QBO. Potential energy associated with EQWs is generally larger in the westerly than in the easterly shear phase of the QBO. EQWs with vertical wavelengths ≤ 7 km contribute up to ∼30% of total potential energy ≤ 7 km over the equator at an altitude of 20–30 km. Gravity waves generated by cumulus convection with periods ≤ 24 h are clearly visible over areas of Africa, the Amazon, and around Indonesia, and result in localized PE distributions in areas short distances from the source region. Comparisons of the model results and recent satellite observations are discussed.
Effect of changes in climate and emissions on future sulfate‐nitrate‐ammonium aerosol levels in the United States
Authors: Pye H. O. T. , Liao H. , Wu S. , Mickley L. J. , Jacob D. J. , Henze D. K. , Seinfeld J. H.
Published: January 2009

Global simulations of sulfate, nitrate, and ammonium aerosols are performed for the present day and 2050 using the chemical transport model GEOS‐Chem. Changes in climate and emissions projected by the IPCC A1B scenario are imposed separately and together, with the primary focus of the work on future inorganic aerosol levels over the United States. Climate change alone is predicted to lead to decreases in levels of sulfate and ammonium in the southeast U.S. but increases in the Midwest and northeast U.S. Nitrate concentrations are projected to decrease across the U.S. as a result of climate change alone. In the U.S., climate change alone can cause changes in annually averaged sulfate‐nitrate‐ammonium of up to 0.61 μg/m3, with seasonal changes often being much larger in magnitude. When changes in anthropogenic emissions are considered (with or without changes in climate), domestic sulfate concentrations are projected to decrease because of sulfur dioxide emission reductions, and nitrate concentrations are predicted to generally increase because of higher ammonia emissions combined with decreases in sulfate despite reductions in emissions of nitrogen oxides. The ammonium burden is projected to increase from 0.24 to 0.36 Tg, and the sulfate burden to increase from 0.28 to 0.40 Tg S as a result of globally higher ammonia and sulfate emissions in the future. The global nitrate burden is predicted to remain essentially constant at 0.35 Tg, with changes in both emissions and climate as a result of the competing effects of higher precursor emissions and increased temperature.
Near‐surface soil moisture assimilation for quantifying effective soil hydraulic properties using genetic algorithms: 2. Using airborne remote sensing during SGP97 and SMEX02
Authors: Ines Amor V. M. , Mohanty Binayak P.
Published: January 2009

Pixel‐based effective soil hydraulic parameters are crucial inputs for large‐scale hydroclimatic modeling. In this paper, we extend/apply a genetic algorithm (GA) approach for estimating these parameters at the scale of an airborne remote sensing (RS) footprint. To estimate these parameters, we used a time series of near‐surface RS soil moisture data to invert a physically based soil‐water‐atmosphere‐plant (SWAP) model with a (multipopulated) modified‐microGA. Uncertainties in the solutions were examined in two ways: (1) by solving the inverse problem under various combinations of modeling conditions in a respective way; and (2) the same as the first method but the inverse solutions were determined in a collective way aimed at finding the robust solutions for all the modeling conditions (ensembles). A cross validation of the derived soil hydraulic parameters was done to check their effectiveness for all the modeling conditions used. For our case studies, we considered three electronically scanned thinned array radiometer (ESTAR) footprints in Oklahoma and four polarimetric scanning radiometer (PSR) footprints in Iowa during the Southern Great Plains 1997 (SGP97) Hydrology Experiment and Soil Moisture Experiment 2002 (SMEX02) campaigns, respectively. The results clearly showed the promising potentials of near‐surface RS soil moisture data combined with inverse modeling for determining average soil hydrologic properties at the footprint scale. Our cross validation showed that parameters derived by method 1 under water table (bottom boundary) conditions are applicable also for free‐draining conditions. However, parameters derived under free‐draining conditions generally produced too wet near‐surface soil moisture when applied under water table conditions. Method 2, on the other hand, produced robust parameter sets applicable for all modeling conditions used. These results were validated using distributed in situ soil moisture and soil hydraulic properties measurements, and texture‐based data from the UNSODA database. In this study, we conclude that inverse modeling of RS soil moisture data is a promising approach for parameter estimation at large measurement support scale. Nevertheless, the derived effective soil hydraulic parameters are subject to the uncertainties of remotely sensed soil moisture data and from the assumptions used in the soil‐water‐atmosphere‐plant modeling. Method 2 provides a flexible framework for accounting these sources of uncertainties in the inverse estimation of large‐scale soil hydraulic properties. We have illustrated this flexibility by combining multiple data sources and various modeling conditions in our large‐scale inverse modeling.
Impact Cratering and Its Planetary and Environmental Effects: Large Meteorite Impacts and Planetary Evolution IV; Vredefort Dome, South Africa, 17–21 August 2008
Authors: Morrow Jared , Gibson Roger , Reimold Wolf Uwe
Published: January 2009

The Fourth Conference on Large Meteorite Impacts and Planetary Evolution (LMI IV) was held near the town of Parys in the Vredefort Dome, the center of Earth's oldest and largest preserved impact structure. The Vredefort Dome, approximately 120 kilometers southwest of Johannesburg, South Africa, presents a superb cross section through deep levels of the impact structure. The Dome also provides exposures of the exceptionally well preserved Archean and Paleoproterozoic (>3.1 to 2.1 billion year old) rocks of the Kaapvaal craton. In July 2005, the northwestern part of the Dome was declared a World Heritage Site. Work is under way to strengthen the tourism infrastructure at the site, including construction of a visitor center.
Special Presentation: Bras Awarded 2007 Robert E. Horton Medal
Authors: Rodriguez‐Iturbe Ignacio , Bras Rafael L.
Published: January 2009

Rafael L. Bras was awarded the 2007 Robert E. Horton Medal during a special presentation at the AGU Fall Meeting Honors Ceremony, held 17 December 2008 in San Francisco, Calif. The medal is for “outstanding contributions to hydrology.”
Your Dues
Authors: Spilhaus Fred
Published: January 2009

Your AGU dues, at $20, are truly a bargain and have been so for 40 years. It would be difficult to point to the primary driver for the extraordinary growth in AGU membership during the past 40 years, but surely the low and stable dues have been a major contributor. The low entry fee brings a diverse, worldwide community of scientists into our network. It is also consistent with AGU's commitment to the public good, which is the basis for the tax‐exempt status the Union enjoys in the United States.
Viral lysis of Phaeocystis pouchetii: Implications for algal population dynamics and heterotrophic C, N and P cycling
Authors: Haaber Jakob , Middelboe Mathias
Published: January 2009

A model ecosystem with two autotrophic flagellates, Phaeocystis pouchetii and Rhodomonas salina, a virus specific to P. pouchetii (PpV) and bacteria and heterotrophic nanoflagellates was used to investigate effects of viral lysis on algal population dynamics and heterotrophic nitrogen and phosphorus mineralization. Lysis of P. pouchetii by PpV had strong positive effects on bacterial and HNF abundance, and the mass balance of C, N and P suggested an efficient transfer of organic material from P. pouchetii to bacterial and HNF biomass through viral lysis. At the same time, the degradation of P. pouchetii lysates was associated with significant regeneration of inorganic N and P resulting in 148 μg N l−1 and 7 μg P l−1, corresponding to 78% and 26% of lysate N and P being mineralized to NH4+ and PO43−, respectively. These results showed that the turnover of viral lysates in the microbial food web was associated with significant N and P mineralization, supporting the current view that viral lysates can be an important source of inorganic nutrients in marine systems. In the presence of R. salina, the generated NH4+ supported 11% of the observed R. salina growth. Regrowth of virus-resistant P. pouchetii following cell lysis was observed in long-term incubations (150 days), and possibly influenced by nutrient availability and competition from R. salina. The observed impact of viral activity on autotrophic and heterotrophic processes provides direct experimental evidence for virus-driven nutrient generation and emphasizes the potential importance of the viral activity in supporting marine primary production.
Association Between Adult Attention Deficit/Hyperactivity Disorder and Obesity in the US Population
Authors: Pagoto Sherry L. , Curtin Carol , Lemon Stephenie C. , Bandini Linda G. , Schneider Kristin L. , Bodenlos Jamie S. , Ma Yunsheng
Published: January 2009

Attention deficit hyperactivity disorder (ADHD) is a neurobehavioral disorder that affects ∼2.9–4.7% of US adults. Studies have revealed high rates of ADHD (26–61%) in patients seeking weight loss treatment suggesting an association between ADHD and obesity. The objective of the present study was to test the association between ADHD and overweight and obesity in the US population. Cross‐sectional data from the Collaborative Psychiatric Epidemiology Surveys were used. Participants were 6,735 US residents (63.9% white; 51.6% female) aged 18–44 years. A retrospective assessment of childhood ADHD and a self‐report assessment of adult ADHD were administered. Diagnosis was defined by three categories: never met diagnostic criteria, met full childhood criteria with no current symptoms, and met full childhood criteria with current symptoms. The prevalence of overweight and obesity was 33.9 and 29.4%, respectively, among adults with ADHD, and 28.8 and 21.6%, respectively, among persons with no history of ADHD. Adult ADHD was associated with greater likelihood of overweight, (odds ratio (OR) = 1.58; 95% confidence interval (CI) = 1.05, 2.38) and obesity (OR = 1.81; 95% CI = 1.14, 2.64). Results were similar when adjusting for demographic characteristics and depression. Mediation analyses suggest that binge eating disorder (BED), but not depression, partially mediates the associations between ADHD and both overweight and obesity. Results suggest that adult ADHD is associated with overweight and obesity.
Peroxiredoxin 5 confers protection against oxidative stress and apoptosis and also promotes longevity in Drosophila
Authors: Radyuk Svetlana N. , Michalak Katarzyna , Klichko Vladimir I. , Benes Judith , Rebrin Igor , Sohal Rajindar S. , Orr William C.
Published: January 2009

Peroxiredoxin 5 is a distinct isoform of the peroxiredoxin gene family. The antioxidative and anti-apoptotic functions of peroxiredoxin 5 have been extensively demonstrated in cell culture experiments. In the present paper, we provide the first functional analysis of peroxiredoxin 5 in a multicellular organism, Drosophila melanogaster. Similar to its mammalian, yeast or human counterparts, dPrx5 (Drosophila peroxiredoxin 5) is expressed in several cellular compartments, including the cytosol, nucleus and the mitochondrion. Global overexpression of dPrx5 in flies increased resistance to oxidative stress and extended their life span by up to 30% under normal conditions. The dprx5−/− null flies were comparatively more susceptible to oxidative stress, had higher incidence of apoptosis, and a shortened life span. TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling) analysis revealed that the dprx5−/− null mutant had discernible tissue-specific apoptotic patterns, similar to those observed in control flies exposed to paraquat. In addition, apoptosis was particularly notable in oenocytes. During development the dPrx5 levels co-varied with ecdysone pulses, suggesting inter-relationship between ecdystreroids and dPrx5 expression. The importance of dPrx5 for development was further underscored by the embryonic lethal phenotype of progeny derived from the dprx5−/− null mutant. Results from the present study suggest that the antioxidant and anti-apoptotic activities of dPrx5 play a critical role in development and aging of the fly.
End-organ dysfunction and cardiovascular outcomes: the role of the microcirculation
Authors: Lockhart Christopher J. , Hamilton Paul K. , Quinn Cathy E. , McVeigh Gary E.
Published: January 2009

Risk factors for cardiovascular disease mediate their effects by altering the structure and function of wall and endothelial components of arterial blood vessels. A pathological change in the microcirculation plays a pivotal role in promoting end-organ dysfunction that not only predisposes to further organ damage, but also increases the risk for future macrovascular events. The microcirculation is recognized as the site where the earliest manifestations of cardiovascular disease, especially inflammatory responses, occur that may play a pivotal role in driving the atherosclerotic process in conduit vessels. Furthermore, the vast surface area of the endothelium compared with conduit vessels means that the vascular effects of endothelial dysfunction or activation will be most apparent in this section of the vasculature. Current techniques providing indices of vascular health focus on large arteries without providing insight into the structure and function of small vessels. Techniques capable of detecting microvascular damage and monitoring the response to therapeutic interventions, especially in vulnerable target organs of interest, may improve risk stratification and represent a valuable surrogate for future cardiovascular outcome.
PPARγ and its ligands: therapeutic implications in cardiovascular disease
Authors: Villacorta Luis , Schopfer Francisco J. , Zhang Jifeng , Freeman Bruce A. , Chen Y. Eugene
Published: January 2009

The relevance of PPARγ (peroxisome-proliferator-activated receptor γ) as an important therapeutic target for the treatment of diabetes arises from its hypoglycaemic effects in diabetic patients and also from the critical role in the regulation of cardiovascular functions. From a clinical perspective, differences between current FDA (Food and Drug Administration)-approved PPARγ drugs have been observed in terms of atherosclerosis and cardiac and stroke events. The adverse effects of PPARγ-specific treatments that hamper their cardiovascular protective roles, affirm the strong need to evaluate the efficacy of the current drugs. Therefore active research is directed towards high-throughput screening and pharmacological testing of a plethora of newly identified natural or synthetic compounds. In the present review we describe the rationale behind drug design strategies targeting PPARγ, based on current knowledge regarding the effects of such drugs in experimental animal models, as well as in clinical practice. Regarding endogenous PPARγ ligands, several fatty acid derivatives bind PPARγ with different affinities, although the physiological relevance of these interactions is not always evident. Recently, NO-derived unsaturated fatty acids were found to be potent agonists of PPARs, with preferential affinity for PPARγ, compared with oxidized fatty acid derivatives. Nitroalkenes exert important bioactivities of relevance for the cardiovascular system including anti-inflammatory and antiplatelet actions, and are important mediators of vascular tone. A new generation of insulin sensitizers with PPARγ function for the treatment of diabetes may serve to limit patients from the increased cardiovascular burden of this disease.
Effect of ischaemic exercise training of a normal limb on angiogenesis of a pathological ischaemic limb in rabbits
Authors: Shen Mei , Gao Jing , Li Jianan , Su Juan
Published: January 2009

The present study was designed to test the hypothesis that local exercise of a normal limb can promote angiogenesis in a pathological ischaemic limb. New Zealand White rabbits underwent left femoral artery ligation (Lig) and electrode implantation on the right sciatic nerve. The rabbits were randomly assigned to four groups: (i) Lig-N group, which did not receive ES (electrical stimulation); (ii) Lig-High group, which received high-intensity ES (2.5 mA, 40Hz for 1 ms) on the right hindlimb; (iii) Lig-Low group, which received low-intensity ES (0.3 mA, 40Hz for 1 ms) on the right hindlimb; (iv) Double-Lig-High group, which underwent femoral artery ligation on both hindlimbs and received high-intensity ES (2.5 mA, 40Hz for 1 ms) on the right hindlimb. The ES procedure included 5 min of stimulation, followed by 5 min of rest, and was repeated eight times a day for 4 weeks. Collateral circulation was examined grossly by angiography, resting blood flow was measured using the microspheres technique, and capillary supply was evaluated by immunohistochemistry. VEGF (vascular endothelial growth factor) mRNA and protein were analysed by real-time RT (reverse transcription)–PCR and Western blotting respectively. Collateral blood flow in all of the major muscles of the left hindlimb in the Lig-High group was highest among the four groups (P<0.01). Capillary supply (P<0.001), VEGF mRNA (P<0.01) and VEGF protein (P<0.01) in the gastrocnemius muscle increased remarkably in the Lig-High group; no statistically significant difference was observed among the other three groups. In conclusion, angiogenesis associated with an up-regulation of VEGF expression in pathological ischaemic limb may be facilitated by 4 weeks of physiological ischaemic exercise training in a normal limb.
Prenatal programming of renal sodium handling in the rat
Authors: Alwasel Saleh H. , Ashton Nick
Published: January 2009

Prenatally programmed hypertension induced by maternal protein restriction is associated with increased expression of the renal tubular Na+/K+/2Cl− co-transporter (NKCC2) and the Na+/Cl− co-transporter (NCC). This has led to the suggestion that renal Na+ retention contributes to the development of hypertension in the LP rat (offspring exposed to a maternal low-protein diet in utero). However, this hypothesis has not been tested in vivo. Renal clearance measurements in hypertensive 4-week-old male and female LP rats showed that, although the glomerular filtration rate remained unaltered, urine flow (P<0.01) and urinary Na+ excretion rates (1.6±0.3 and 3.0±0.4 μmol·min−1·100 g−1 of body weight in control male and LP male respectively; P<0.001) were increased. Na+ excretion was positively correlated with mean arterial pressure in both males (P<0.01) and females (P<0.05), but neither the slope nor the intercept differed between control and LP rats. Fractional excretion of Na+ was increased in male (1.5±0.2 and 3.0±0.5% in control and LP rats respectively; P<0.001) and female LP rats, implying reduced tubular reabsorption of Na+. Western blotting and quantitative PCR showed that NKCC2 expression was increased, whereas NCC mRNA was not up-regulated. Na+/K+ ATPase α1 subunit expression did not differ from controls; however, there was a significant reduction in whole kidney pump activity (23.4±1.8 and 17.7±1.2 nmol of phosphate·μg−1 of protein·h−1 in control male and male LP rats respectively; P<0.001); immunohistochemistry showed that the α1 subunit was virtually absent from the inner medulla. The greater Na+ excretion of LP rats can be explained, in part, by a pressure–natriuresis mechanism; however, the loss of the Na+/K+ ATPase α1 subunit from the inner medulla and up-regulation of NKCC2 suggests that altered renal Na+ handling is also programmed prenatally.
Effects of HCV co-infection on apoptosis of CD4+ T-cells in HIV-positive patients
Authors: Körner Christian , Krämer Benjamin , Schulte Daniela , Coenen Martin , Mauss Stefan , Fätkenheuer Gerd , Oldenburg Johannes , Nattermann Jacob , Rockstroh Jürgen K. , Spengler Ulrich
Published: January 2009

Apoptosis importantly contributes to loss of CD4+ T-cells in HIV infection, and modification of their apoptosis may explain why HIV/HCV (hepatitis C virus)-co-infected patients are more likely to die from liver-related causes, although the effects of HCV on HIV infection remain unclear. In the present study, we studied in a cross-sectional and serial analysis spontaneous ex vivo CD4+ T-cell apoptosis in HIV/HCV-co-infected and HIV-mono-infected patients before and after HAART (highly active antiretroviral therapy). Apoptosis of peripheral blood CD4+ T-cells was measured by both a PARP [poly(ADP-ribose) polymerase] and TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling) assay to detect cells with irreversible apoptosis. Although hepatitis C alone did not increase CD4+ T-cell apoptosis, HCV co-infection disproportionately increased elevated rates of apoptosis in CD4+ T-cells from untreated HIV-positive patients. Increased CD4+ T-cell apoptosis was closely correlated with HIV, but not HCV, viral loads. Under HAART, increased rates of CD4+ T-cell apoptosis rapidly decreased both in HIV-mono-infected and HIV/HCV-co-infected patients, without any significant difference in apoptosis rates between the two patient groups after 4 weeks of therapy. Nevertheless residual CD4+ T-cell apoptosis did not reach the normal levels seen in healthy controls and remained higher in HIV patients receiving protease inhibitors than in patients with other antiretroviral regimens. The results of the present study suggest that HCV co-infection sensitizes CD4+ T-cells towards apoptosis in untreated HIV-positive patients. However, this effect is rapidly lost under effective antiretroviral therapy.
Comparison of the transport properties of high quality AlGaN/AlN/GaN and AlInN/AlN/GaN two-dimensional electron gas heterostructures
Authors: Tülek Remziye , Ilgaz Aykut , Gökden Sibel , Teke Ali , Öztürk Mustafa K. , Kasap Mehmet , Özçelik Süleyman , Arslan Engin , Özbay Ekmel
Published: January 2009

The transport properties of high mobility AlGaN/AlN/GaN and high sheet electron density AlInN/AlN/GaN two-dimensional electron gas (2DEG) heterostructures were studied. The samples were grown by metal-organic chemical vapor deposition on c-plane sapphire substrates. The room temperature electron mobility was measured as 1700 cm2/V s along with 8.44×1012 cm−2 electron density, which resulted in a two-dimensional sheet resistance of 435 Ω/◻ for the Al0.2Ga0.8N/AlN/GaN heterostructure. The sample designed with an Al0.88In0.12N barrier exhibited very high sheet electron density of 4.23×1013 cm−2 with a corresponding electron mobility of 812 cm2/V s at room temperature. A record two-dimensional sheet resistance of 182 Ω/◻ was obtained in the respective sample. In order to understand the observed transport properties, various scattering mechanisms such as acoustic and optical phonons, interface roughness, and alloy disordering were included in the theoretical model that was applied to the temperature dependent mobility data. It was found that the interface roughness scattering in turn reduces the room temperature mobility of the Al0.88In0.12N/AlN/GaN heterostructure. The observed high 2DEG density was attributed to the larger polarization fields that exist in the sample with an Al0.88In0.12N barrier layer. From these analyses, it can be argued that the AlInN/AlN/GaN high electron mobility transistors (HEMTs), after further optimization of the growth and design parameters, could show better transistor performance compared to AlGaN/AlN/GaN based HEMTs.
Microfluidic electrospinning of biphasic nanofibers with Janus morphology
Authors: Srivastava Yasmin , Marquez Manuel , Thorsen Todd
Published: January 2009

In this paper a method of electrospinning conducting and nonconducting biphasic Janus nanofibers using microfluidic polydimethylsiloxane (PDMS)-based manifolds is described. Key benefits of using microfluidic devices for nanofiber synthesis include rapid prototyping, ease of fabrication, and the ability to spin multiple Janus fibers in parallel through arrays of individual microchannels. Biphasic Janus nanofibers of polyvinylpyrrolidone (PVP)+polypyrrole (PPy)/PVP nanofibers with an average diameter of 250nm were successfully fabricated using elastomeric microfluidic devices. Fiber characterization and confirmation of the Janus morphology was subsequently carried out using a combination of scanning electron microscopy, energy dispersion spectroscopy, and transmission electron microscopy.
Study of a liquid crystal structure with improved electro-optical characteristics
Authors: Lim Ji-Hun , Oh Byeong-Yun , Kim Byoung-Yong , Kim Young-Hwan , Lee Kang-Min , Han Jeoung-Min , Lee Sang-Keuk , Seo Dae-Shik
Published: January 2009

This paper introduces the vertically aligned twisted nematic in-plane switching (VPS) structure, and compares the electro-optical (EO) characteristics of VPS liquid crystal displays (LCDs) and in-plane switching (IPS) LCDs. Various VPS-LCD pretilt angles were induced, and ion beam (IB) irradiation was used to enhance the EO properties. An x-ray photoelectron spectroscopic analysis of the IB-irradiated polymer surface confirmed that the intensity of C=O bonding as a function of exposure time traced the pretilt angles. The pretilt angle effect on optical properties was first analyzed in the experimental results. While multidomain vertical alignment LCDs and IPS-LCDs only resolve one difficulty, the VPS-LCDs described here overcome several viewing angle and transmittance curve problems.
Superintegrability with third order integrals of motion, cubic algebras, and supersymmetric quantum mechanics. I. Rational function potentials
Authors: Marquette Ian
Published: January 2009

We consider a superintegrable Hamiltonian system in a two-dimensional space with a scalar potential that allows one quadratic and one cubic integrals of motion. We construct the most general cubic algebra and we present specific realizations. We use them to calculate the energy spectrum. All classical and quantum superintegrable potentials separable in Cartesian coordinates with a third order integral are known. The general formalism is applied to quantum reducible and irreducible rational potentials separable in Cartesian coordinates in E2. We also discuss these potentials from the point of view of supersymmetric and PT-symmetric quantum mechanics.
Field electron emission enhancement of amorphous carbon through a niobium carbide buffer layer
Authors: Xu L. , Wang C. , Hu C. Q. , Zhao Z. D. , Yu W. X. , Zheng W. T.
Published: January 2009

We investigate the field electron emission for amorphous carbon (a-C) films deposited on Si (100) substrates through a niobium carbide buffer layer with different structures and find that the niobium carbide buffer layer can substantially improve the electron field emission properties of a-C films, which can be attributed to an increase in the enhancement factor β on the surface of a-C films after the insertion of the niobium carbide layer in between a-C film and substrate. Moreover, a phase transition for niobium carbide layer from hexagonal (Nb2C) to cubic (NbC) structure, revealed by x-ray diffraction, further enhances the electron field emission. The first-principles calculated results show that the work function of NbC is lower than that of Nb2C, which is the reason why the electron emission of a-C is further enhanced.
Integrability of a nonlinear evolution equation derived from isoperimetric plane curve motion
Authors: Brunelli J. C.
Published: January 2009

We provide a geometrical interpretation for the series of transformations used by Sakovich [Phys. Lett. A 314, 232 (2003)] to map the third-order nonlinear evolution equation obtained by Chou and Qu [Physica D 162, 9 (2002)] to the mKdV equation. We also discuss its bi-Hamiltonian integrability as well as integrable equations associated with this system.
The octapolic ellipsoidal term in magnetoencephalography
Authors: Dassios George , Hadjiloizi Demetra , Kariotou Fotini
Published: January 2009

The forward problem of magnetoencephalography (MEG) in ellipsoidal geometry has been studied by Dassios and Kariotou [“Magnetoencephalography in ellipsoidal geometry,” J. Math. Phys. 44, 220 (2003)] using the theory of ellipsoidal harmonics. In fact, the analytic solution of the quadrupolic term for the magnetic induction field has been calculated in the case of a dipolar neuronal current. Nevertheless, since the quadrupolic term is only the leading nonvanishing term in the multipole expansion of the magnetic field, it contains not enough information for the construction of an effective algorithm to solve the inverse MEG problem, i.e., to recover the position and the orientation of a dipole from measurements of the magnetic field outside the head. For this task, the next multipole of the magnetic field is also needed. The present work provides exactly this octapolic contribution of the dipolar current to the expansion of the magnetic induction field. The octapolic term is expressed in terms of the ellipsoidal harmonics of the third degree, and therefore it provides the highest order terms that can be expressed in closed form using long but reasonable analytic and algebraic manipulations. In principle, the knowledge of the quadrupolic and the octapolic terms is enough to solve the inverse problem of identifying a dipole inside an ellipsoid. Nevertheless, a simple inversion algorithm for this problem is not yet known.
A vapor cell based on dispensers for laser spectroscopy
Authors: Bridge E. M. , Millen J. , Adams C. S. , Jones M. P. A.
Published: January 2009

We describe a simple strontium vapor cell for laser spectroscopy experiments. Strontium vapor is produced using an electrically heated commercial dispenser source. The sealed cell operates at room temperature, and without a buffer gas or vacuum pump. The cell was characterized using laser spectroscopy, and was found to offer stable and robust operation, with an estimated lifetime of >10 000 h. By changing the dispenser, this technique can be readily extended to other alkali and alkaline earth elements.
Investigation of Förster-type energy transfer in organic light-emitting devices with 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethy ljulolidin-4-yl-vinyl)-4H-pyran doped cohost emitting layer
Authors: Yu Li-Zhen , Jiang Xue-Yin , Zhang Zhi-Lin , Lou Li-Ren , Lee Ching-Ting
Published: January 2009

Organic light-emitting devices (OLEDs) with cohosted emitter, which is composed of 9,10-di(2-naphthyl)anthracene (ADN) and tris(8-hydroxy-quinolinato) aluminum (Alq3) and doped with 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethy ljulolidin-4-yl-vinyl)-4H-pyran (DCJTB), were fabricated and studied. The efficiency of OLEDs with a cohost emitter was higher than that with a single host emitter. For the cohost emitter with ADN/Alq3 weight ratio of 75:25, the 3.4 cd/A efficiency of the resulted OLEDs was obtained. It is found that the absorption spectra of DCJTB and the emission spectra of Alq3 changed with the composition of the emitter. This phenomenon is attributed to the polarization effect. On the basis of the Förster’s theory, the resulted overlap integral exhibits the highest value for this cohost emitter. The experimental results reveal that the cascade energy transfer plays an important role in the luminance efficiency enhancement of the cohost emitter in OLEDs.
Transport of parallel momentum by drift-Alfvén turbulence
Authors: McDevitt C. J. , Diamond P. H.
Published: January 2009

An electromagnetic gyrokinetic formulation is utilized to calculate the turbulent radial flux of parallel momentum for a strongly magnetized plasma in the large aspect ratio limit. For low-β plasmas, excluding regions of steep density gradients, the level of momentum transport induced by microturbulence is found to be well described within the electrostatic approximation. However, near regions of steep equilibrium profile gradients, strong electromagnetic contributions to the momentum flux are predicted. In particular, for sufficiently steep density gradient, the magnitude of transport induced by the off-diagonal residual stress component of the momentum flux induced by drift wave turbulence can be quenched. This quenching mechanism, which results from shielding of the parallel electric field by the inductive term, is distinct from E×B shear decorrelation, since it allows for the level of off-diagonal turbulent transport to be strongly reduced without extinguishing the underlying microturbulence. In contrast, the level of transport induced by a given Alfvénic branch of the drift-Alfvén dispersion relationship typically increases as the density gradient steepens, allowing an alternate channel for momentum transport. A calculation of the momentum transport induced by Alfvénic turbulence in a homogeneous medium suggests that an imbalance in Elsasser populations is required in order to introduce a finite level of off-diagonal momentum transport for the case of the simplified geometry considered.