bluuebunny/crossref_metadata_2025 huggingface dataset:
Priming of Depth-Rotated Objects Depends on Attention and Part Changes
Authors: Thoma Volker , Davidoff Jules
Published: January 2006

Three priming experiments investigated the role of attention and view changes when common objects were rotated in depth. Objects were shown in prime-probe trial pairs. Experiment 1 extended findings by Stankiewicz, Hummel, and Cooper (1998 ) showing that attended objects primed themselves in the same but not in a reflected view, whereas ignored objects only primed themselves in the same view. In Experiment 2, depth-rotations produced changes in the visible part structure between prime and probe view of an object. Priming after depth-rotation was more reduced for attended objects than for ignored objects. Experiment 3 showed that other depth rotations that did not change the perceived part structure revealed a priming pattern similar to that in Experiment 1, with equivalent reduction in priming for attended and ignored objects. These data indicate that recognition of attended objects is mediated by a part-based (analytic) representation together with a view-based (holistic) representation, whereas ignored images are recognized in a strictly view-dependent fashion.
Spatial Associations in Number-Related Tasks
Authors: Schwarz Wolf , Müller Dana
Published: January 2006

Bimanual parity judgments of numerically small (large) digits are faster with the left (right) hand (the SNARC effect; Dehaene, Bossini, & Giraux, 1993 ). According to one explanation, this effect is culturally derived and reflects ontogenetic influences such as the direction of written language; it might therefore be limited to, or at least be larger with, pairs of lateralized effectors which are instrumental to the production and comprehension of written language. We report two experiments which test for SNARC effects with pedal responses, and compare these effects to manual results. Pedal responses yielded highly systematic SNARC effects; furthermore, these effects did not differ from manual SNARC effects. These results argue against accounts in which the SNARC effect is specific for effectors that are habitually associated with the production or comprehension of written language.
Effects of Belief and Logic on Syllogistic Reasoning
Authors: Ball Linden J. , Phillips Peter , Wade Caroline N. , Quayle Jeremy D.
Published: January 2006

Studies of syllogistic reasoning have demonstrated a nonlogical tendency for people to endorse more believable conclusions than unbelievable ones. This belief bias effect is more dominant on invalid syllogisms than valid ones, giving rise to a logic by belief interaction. We report an experiment in which participants’ eye movements were recorded in order to provide insights into the nature and time course of the reasoning processes associated with manipulations of conclusion validity and believability. Our main dependent measure was people’s inspection times for syllogistic premises, and we tested predictions deriving from three contemporary mental-models accounts of the logic by belief interaction. Results supported recent “selective processing” theories of belief bias (e.g., Evans, 2000 ; Klauer, Musch, & Naumer, 2000 ), which assume that the believability of a conclusion biases model construction processes, rather than biasing the search for falsifying models (e.g., Oakhill & Johnson-Laird, 1985 ) or a response stage of reasoning arising from subjective uncertainty (e.g., Quayle & Ball, 2000 ). We conclude by suggesting that the eye-movement analyses in reasoning research may provide a useful adjunct to other process-tracing techniques such as verbal protocol analysis.
Mars Global Surveyor and Mars Odyssey Accelerometer observations of the Martian upper atmosphere during aerobraking
Authors: Withers Paul
Published: January 2006

Mars Global Surveyor and Mars Odyssey accelerometer measurements of martian upper atmospheric densities reveal the large‐scale and small‐scale structure of the thermosphere in unprecedented detail. Meridional density gradients, which are seasonally dependent, are greater on the dayside than the nightside, indicating stronger meridional winds on the dayside. Density scale heights do not vary greatly with latitude. Densities and density scale heights are lower on the nightside than on the dayside, but the day‐night contrast is not as great as at Venus. Thus atmospheric circulation plays a greater role in determining the state of the thermosphere on Mars than on Venus. Oscillations in density along individual density profiles, probably due to gravity waves, are common and their amplitudes are tens of percent. Step‐like changes in density are also observed, but their origin is less clear. Data coverage is extensive enough to permit studies of weather, not just climate.
Polar survey of magnetic field in near tail: Reconnection rare inside 9 RE
Authors: Ge Y. S. , Russell C. T.
Published: January 2006

We have examined the magnetic field at the apogee of the Polar spacecraft for three seasons during which time apogee was close to the equatorial plane and within 2 hours of midnight. The magnetic field magnitude in this region is rarely below 5 nT. However, when it is low, the magnetic field is very dynamic, with current sheet thinnings, plasma sheet expansions, and magnetic field dipolarizations. At times of low magnetic field strength we have examined the component normal to the magnetospheric equator for the presence of southward magnetic fields. However, in the period studied only northward fields were present in this region with one brief exception due to a bent current layer and not due to local reconnection. Thus it is very rare that the neutral point is as close as 9 RE.
Detection‐attribution of global warming at the regional scale: How to deal with precipitation variability?
Authors: Douville H.
Published: January 2006

Given the strong natural variability of precipitation, detection of anthropogenic climate change has been mainly based on surface thermal indicators. It is here argued that precipitation variability, whatever its natural or anthropogenic origin, is likely to affect surface temperature and, thereby, to hamper the detection‐attribution of climate change at the regional scale. This issue is illustrated over Sudan and Sahel using the outputs of eleven coupled general circulation models having participated in the latest IPCC simulations. Like in situ observations, models show a strong relationship between detrended seasonal anomalies of surface air temperature and precipitation during the summer monsoon season. Linear regressions are then used to remove the precipitation influence on observed and simulated linear trends in surface air temperature. The results indicate that this strategy is efficient to reduce the spread in the simulated surface warming and make it more consistent with the instrumental record over recent decades.
Have anthropogenic aerosols delayed a greenhouse gas‐induced weakening of the North Atlantic thermohaline circulation?
Authors: Delworth Thomas L. , Dixon Keith W.
Published: January 2006

In many climate model simulations using realistic, time‐varying climate change forcing agents for the 20th and 21st centuries, the North Atlantic thermohaline circulation (THC) weakens in the 21st century, with little change in the 20th century. Here we use a comprehensive climate model to explore the impact of various climate change forcing agents on the THC. We conduct ensembles of integrations with subsets of climate change forcing agents. Increasing greenhouse gases – in isolation – produce a significant THC weakening in the late 20th century, but this change is partially offset by increasing anthropogenic aerosols, which tend to strengthen the THC. The competition between increasing greenhouse gases and anthropogenic aerosols thus produces no significant THC change in our 20th century simulations when all climate forcings are included. The THC weakening becomes significant several decades into the 21st century, when the effects of increasing greenhouse gases overwhelm the aerosol effects.
Hurricane‐induced storm surges, currents and destratification in a semi‐enclosed bay
Authors: Li Ming , Zhong Liejun , Boicourt William C. , Zhang Shunli , Zhang Da‐Lin
Published: January 2006

Semi‐enclosed bays and estuaries are usually protected from hurricane‐generated storm surges. When a hurricane travels on the land side, however, it may induce high storm surges, strong currents and destratification in the water column. Real‐time observations and numerical model prediction both show a slab‐like sloshing in Chesapeake Bay when it was hit by Hurricane Isabel in September 2003. Strong southeasterly winds in the right front quadrant of the storm forced water in Chesapeake Bay to move northward as a single layer, producing high sea levels and flooding in the northern Bay region including Baltimore and Annapolis. Furthermore, the strong landward winds erased water‐column stratification and caused a strong intrusion of high‐salinity shelf water into the Bay. After Isabel's passage, the longitudinal salinity gradient produces restratification and two‐layer circulation in the Bay.
Wind‐wave development under alternating wind jets and wakes induced by orographic effects
Authors: Shimada Teruhisa , Kawamura Hiroshi
Published: January 2006

We investigate fetch‐limited wind‐wave development under alternating coastal wind jets and wakes induced by orographic effects. Synthetic Aperture Radar and scatterometer resolve wind jets and wakes with widths of 5–40 km. Using the wind field and a third‐generation wave model, we simulate the nearshore wave field. As a result, broader directional wave spectra are seen in wakes while we can find evolution of the directional wave spectrum with offshore distance in both wind jets and wakes. Especially within the offshore distance of 40 km, directional wave spectra have two peaks. These characteristics are well reflected in the overall directional spreading field. The overall directional spreading closely corresponds to the wind speed distribution, and is small/large in wind jet/wake region. The results mean that wave energies that come from neighboring wind jet regions cross in wake regions and combine with wave energy generated by local wind in wake regions.
Revised spherical cap harmonic analysis (R‐SCHA): Validation and properties
Authors: Thébault E. , Schott J. J. , Mandea M.
Published: January 2006

We recently proposed a technique able to represent the spatial variations of the magnetic field at regional scales. However, we pointed out that these preliminary developments were not suited for the complete representation of the geomagnetic field. In this paper, we propose a complete revision, the revised spherical cap harmonic analysis (R‐SCHA), which introduces slight changes in order to rectify the previous shortcomings. In addition, some discussions shed a new light on the former spherical cap harmonic analysis (SCHA) and help us to demonstrate its deficiencies and approximations. We finally show that R‐SCHA now fully satisfies the natural properties of potential fields. R‐SCHA also yields analytical relationships with the spherical harmonics. Taking advantage of the mathematical equivalence of both representations, we explore the relevance of fundamental concepts like spectrum, minimum wavelength, or internal/external field separation. We conclude that these concepts are misleading and must be handled with care in regional modeling. A prime goal being the ability of R‐SCHA to represent real data sets, we also investigate and illustrate the effect of finite series expansions. A norm for the regularization of the inverse problem is proposed as well. The conclusions drawn in this paper allow us to validate the method and to assert that the present proposal is suited for modeling and studying the lithospheric magnetic field from ground to satellite altitudes at regional scales.
Circulation of Tampa Bay driven by buoyancy, tides, and winds, as simulated using a finite volume coastal ocean model
Authors: Weisberg Robert H. , Zheng Lianyuan
Published: January 2006

The circulation of Tampa Bay is investigated using a high‐resolution, three‐dimensional, density‐dependent, finite volume coastal ocean model (FVCOM) that includes Tampa Bay, the intracoastal waterway, and the inner portion of the west Florida continental shelf. Model performance over the three‐month interval, September to November 2001, is assessed against available tide gauge and velocity profiler data before using the model to describe the circulation as driven by rivers, tides, and winds. Because of a mean wind velocity vector directed down the estuary axis, we ran a parallel model experiment without winds to distinguish the estuarine circulation by gravitational convection from the mean wind effects. With or without winds, Tampa Bay exhibits a robust, two‐layered estuarine circulation that concentrates on the deep channels. The mean outflow at the surface tends to converge on the channels where the free surface elevation is locally minimum. The mean inflow near the bottom also concentrates in the channels where the baroclinic pressure gradient force is largest. Geometry thus guides the mean circulation and salinity distributions. At the Tampa Bay mouth, mean outflows exist both in the deeper Egmont Channel and the shallower South Pass, whereas a mean inflow is limited to the Egmont Channel. A residence time based on the Egmont Channel influx is estimated to be about 100 days. Consistent with previous studies we conclude that gravitational convection is a major contributor to the water property distributions of Tampa Bay, and that the FVCOM is suitable for estuary/shelf interaction studies.
Altimeter dual‐frequency observations of surface winds, waves, and rain rate in tropical cyclone Isabel
Authors: Quilfen Y. , Tournadre J. , Chapron B.
Published: January 2006

Extreme weather events such as tropical cyclones are difficult to observe with conventional means. Satellite‐based observations provide essential measurements of key parameters governing tropical cyclones. They are critical for short‐term forecasting. Radiometers onboard the Defense Meteorological Satellite Program satellite series, WindSat and Tropical Rainfall Measuring Mission satellites, scatterometers onboard the ERS, ADEOS, and QuikScat satellites offer unprecedented synoptic observations of surface wind and atmospheric liquid water content, revealing the storm structures with good accuracy. However, satellite estimates do not provide direct measurements of geophysical parameters and can suffer from limitations linked to the sensors characteristics, such as the signal wavelength and polarization or the measurement incidence angle. For example, measurements at Ku band are strongly affected by rain. Still, each observing system can offer specific information that can be combined with the others. In particular, we highlight the capabilities of dual‐frequency altimeter to provide very high resolution measurements of rain rate, surface wind speed, and wave characteristics. A method is proposed to obtain continuous along‐track 5 km resolution measurements of these parameters in the tropical cyclone Isabel. The results shows that dual‐frequency altimeters can provide useful information to complement and validate the operational fields provided by the atmospheric numerical models and by NOAA observing systems.
Propagation of a gravity current in a two‐layer stratified environment
Authors: Samothrakis P. , Cotel A. J.
Published: January 2006

Gravity currents are created by a continuous release of dense fluid along a 6° inclined ramp. The surrounding fluid is composed of a two‐layer stably stratified environment. A chemical (phenolphthalein) reaction technique and Planar Laser Induced Fluorescence (PLIF) are used to measure the entrainment rate of lower fluid into the gravity current. The change of volume in the head of the gravity current quantifies the entrainment and mixing. Their dependence on the Richardson number, based on the gravity current head size and velocity and the initial density difference between the current and bottom layer fluids, is determined using chemically reacting PLIF. To further understand the entrainment process and to quantify the effect of the interface on the internal structure of the gravity current, Particle Image Velocimetry (PIV) measurements are performed. Both instantaneous velocity and vorticity fields are quantified. In addition, vertical profiles of velocity and vorticity are computed at two different locations, upstream and downstream of the impingement region. The vortical structure of the gravity current is clearly affected by the presence of the stratified interface. The level of restructuring depends on the Richardson number, based on the density difference across the interface. At low Ri, vorticity increases following the impingement, whereas at higher Ri, a decrease in vorticity is observed as well as a significant change in the head structure of the gravity current.
Transport of carbon monoxide from the tropics to the extratropics
Authors: Bowman Kenneth P.
Published: January 2006

Global observations of carbon monoxide (CO) from the Measurements of Pollution in the Troposphere (MOPITT) instrument on the NASA Terra satellite and three‐dimensional trajectories computed from analyzed winds are used independently to study the transport of air from the tropics to the extratropics. During southern hemisphere spring (September through November), biomass burning in the southern tropics produces large‐scale plumes of CO. These plumes can be easily distinguished from the clean air of the southern hemisphere extratropics. Both total column CO maps and latitude‐height cross‐sections of CO show a strong gradient of CO between 30 and 40°S. Climatological trajectory calculations show that air originating in the lower troposphere near the tropical biomass‐burning regions generally rises into the middle and upper troposphere, where it is entrained in the equatorward side of the subtropical jet. While the zonal dispersion of air parcels within the tropics and subtropics is relatively rapid, air disperses rather slowly across the jet. The MOPITT CO data thus confirm the results from the trajectory analysis that transport from the tropics to the extratropics is a comparatively slow process. This gives rise to the appearance of “transport barriers” in the subtropics.
Near‐ and mid‐infrared microspectroscopy of the Ronda peridotite
Authors: Klima Rachel L. , Pieters Carlé M.
Published: January 2006

Microspectroscopy is a potentially useful tool for planetary applications, as individual mineral grains can be targeted and measured in situ. A series of closely coupled experiments was designed to investigate and compare the laboratory measurement of optical properties of a peridotite sample in the macroscale and microscale. The Ronda peridotite consists largely of olivine with significant orthopyroxene and minor clinoproxene and serpentine. Microscopic transmission spectra of unmounted thin sections produce strong, well‐defined absorption features in the near infrared, and band positions can be directly compared to macroscopic and microscopic reflectance spectra. For near‐infrared reflectance, where photons are multiply scattered by different grains, measurement of a microscopic target means most photons are scattered out of the field of view and few photons return to the detector from the target area. This precludes most microspectroscopic reflectance measurements of small features in the near infrared. In the mid‐infrared, where reflectance measurements involve only surface interactions, microspectroscopic measurements detect well‐defined absorption features for most samples. Although the intensity of absorption features varies between grains, band positions are consistent with macroscopic diffuse reflectance and emittance measurements of bulk samples, and can be used to extract general chemical information such as iron/magnesium ratios of olivines.
On the limits of Antarctic and marine climate records synchronization: Lag estimates during marine isotopic stages 5d and 5c
Authors: Landais A. , Waelbroeck C. , Masson‐Delmotte V.
Published: January 2006

North Atlantic sediment records (MD95‐2042), Greenland (Greenland Ice Core Project (GRIP)) and Antarctica (Byrd and Vostok) ice core climate records have been synchronized over marine isotopic stage 3 (MIS 3) (64 to 24 kyr B.P.) (Shackleton et al., 2000). The resulting common timescale suggested that MD95‐2042 δ18Obenthic fluctuations were synchronous with temperature changes in Antarctica (δDice or δ18Oice records). In order to assess the persistency of this result we have used here the recent Greenland NorthGRIP ice core covering the last glacial inception. We transfer the Antarctic Vostok GT4 timescale to NorthGRIP δ18Oice and MD95‐2042 δ18Oplanktonic records and precisely quantify all the relative timing uncertainties. During the rapid warming of Dansgaard‐Oeschger 24, MD95‐2042 δ18Obenthic decrease is in phase with δ18Oplanktonic decrease and therefore with NorthGRIP temperature increase, but it takes place 1700 ± 1100 years after the Antarctic warming. Thus the present study reveals that the results obtained previously for MIS 3 cannot be generalized and demonstrates the need to improve common chronologies for marine and polar archives.
Structural architecture of the southern and middle Urals foreland from reflection seismic profiles
Authors: Brown D. , Juhlin C. , Tryggvason A. , Friberg M. , Rybalka A. , Puchkov V. , Petrov G.
Published: January 2006

The Urals Seismic Experiment and Integrated Studies (URSEIS), Mikhailovsky, and Europrobe's Seismic Reflection Profiling in the Urals (ESRU) reflection seismic profiles provide constraints for the construction of balanced and restored geological cross sections across the southern and middle Urals foreland. The profiles image the transition from the undeformed foreland basin to the frontal structure of the foreland thrust and fold belt, the location of the basal detachment, and the location of the ramp down into the middle or lower crust. In the URSEIS and ESRU profiles, the transition into the undeformed foreland basin is imaged as an emergent west‐vergent thrust that deforms a westward thickening package of reflections related to synorogenic sediments, whereas in the Mikhailovsky profile, it is a buried system of imbricate thrusts. In all three data sets, the western flank of the foreland thrust and fold belt is imaged in the seismic data as an imbricate thrust system developed above a basal detachment located in either the upper part of the Neoproterozoic basement sediments or the lower part of the Paleozoic continental margin sediments. Truncation of reflections related to the undeformed sediments in the footwall to the imbricate thrust system mark the location of the ramp down of the basal detachment into the middle or lower crust beneath the basement‐cored anticlines along the eastern flank of the thrust belt. The URSEIS and ESRU profiles image the basement‐cored anticlines as predominantly east dipping reflections that extend into the middle and lower crust. Rocks in these anticlines record at least one phase of pre‐Uralide deformation and, at least in part, the reflectivity is due to this deformation event. Balanced and restored cross sections constructed along the three profiles indicate that the minimum shortening is about 20–25 km.
Dynamic subgrid‐scale models for momentum and scalar fluxes in large‐eddy simulations of neutrally stratified atmospheric boundary layers over heterogeneous terrain
Authors: Stoll Rob , Porté‐Agel Fernando
Published: January 2006

The accuracy of large‐eddy simulations (LESs) of the atmospheric boundary layer (ABL) over complex terrain relies on the ability of the subgrid‐scale (SGS) models to capture the effect of subgrid turbulent fluxes on the resolved fields of velocity and scalars (e.g., heat, water vapor, and pollutants). A common approach consists of parameterizing the SGS stresses and fluxes using eddy viscosity and eddy diffusivity models, respectively. These models require the specification of two parameters: the Smagorinsky coefficient in the eddy viscosity model and, in addition, the SGS Schmidt/Prandtl number in the eddy diffusivity model. This is complicated by the dependence of the coefficients on local conditions such as distance to the ground, mean shear, and atmospheric stability. In this study, scale‐dependent dynamic SGS models are used in conjunction with Lagrangian averaging to compute both the Smagorinsky coefficient and the SGS Schmidt (or Prandtl) number dynamically as the flow evolves in both space and time based on the local dynamics of the resolved scales. These tuning‐free models are implemented in LES of both homogeneous and heterogeneous neutral atmospheric boundary layers with surface fluxes of a passive scalar. In the homogeneous simulations the models are shown to accurately predict the resolved flow statistics (mean profiles and spectra of velocity and scalar concentration) and spatial distributions of the SGS model coefficients and parameters. In simulations over heterogeneous surfaces both coefficients adjust in a self‐consistent way to horizontal flow inhomogeneities associated with changes in surface conditions. For smooth‐to‐rough (rough‐to‐smooth) abrupt changes in surface roughness the Smagorinsky coefficient decreases (increases) in response to increased (decreased) mean shear and flow anisotropy associated with these transitions. The SGS Schmidt number also adjusts to inhomogeneities in the scalar field associated with changes in surface scalar flux. This illustrates the need for local calculation of model coefficients and brings into question the common practice of using a constant SGS Schmidt/Prandtl number in LES of the ABL.
Pore‐scale mechanisms of colloid deposition and mobilization during steady and transient flow through unsaturated granular media
Authors: Gao Bin , Saiers James E. , Ryan Joseph
Published: January 2006

The distribution of colloid‐associated contaminants and colloid‐sized microorganisms within the vadose zone is controlled, in part, by mobilization and retention processes. In this work, we present pore‐scale observations of colloid mobilization, transport, and retention within a transparent flow cell packed with partially saturated quartz sand. Our results show that colloid retention is dominated by adhesion to insular air bubbles at high moisture content and a combination of thin‐film straining and immobile water storage at low moisture content. Mobilization of retained colloids under steady flow is governed by slow exchange between zones of immobile and mobile water. During transient flow, characterized by increases in flow rate and moisture content, strained colloids are released from expanding thin films of water and from immobile water zones that reconnect with advecting pore water regions. On the basis of our observations we infer that colloid mobilization and retention within the vadose zone reflects contributions from multiple mechanisms that are sensitive to moisture content and flow regime.
Multiple signalling pathways involved in β2‐adrenoceptor‐mediated glucose uptake in rat skeletal muscle cells
Authors: Nevzorova Julia , Evans Bronwyn A , Bengtsson Tore , Summers Roger J
Published: January 2006

β‐adrenoceptor (AR) agonists increase 2‐deoxy‐[3H]‐D‐glucose uptake (GU) via β2‐AR in rat L6 cells. The β‐AR agonists, zinterol (β2‐AR) and (−)‐isoprenaline, increased cAMP accumulation in a concentration‐dependent manner (pEC50=9.1±0.02 and 7.8±0.02). Cholera toxin (% max increase 141.8±2.5) and the cAMP analogues, 8‐bromo‐cAMP (8Br‐cAMP) and dibutyryl cAMP (dbcAMP), also increased GU (196.8±13.5 and 196.4±17.3%).

The adenylate cyclase inhibitor, 2′,5′‐dideoxyadenosine (50 μM), significantly reduced cAMP accumulation to zinterol (100 nM) (109.7+35.0 to 21.6+4.5 pmol well−1), or forskolin (10 μM) (230.1±58.0 to 107.2±26.3 pmol well−1), and partially inhibited zinterol‐stimulated GU (217±26.3 to 176.1±20.4%). The protein kinase A (PKA) inhibitor, 4‐cyano‐3‐methylisoquinoline (100 nM), did not inhibit zinterol‐stimulated GU. The PDE4 inhibitor, rolipram (10 μM), increased cAMP accumulation to zinterol or forskolin, and sensitised the GU response to zinterol, indicating a stimulatory role of cAMP in GU.

cAMP accumulation studies indicated that the β2‐AR was desensitised by prolonged stimulation with zinterol, but not forskolin, whereas GU responses to zinterol increased with time, suggesting that receptor desensitisation may be involved in GU. Receptor desensitisation was not reversed by inhibition of PKA or Gi.

PTX pretreatment (100 ng ml−1) inhibited insulin or zinterol‐stimulated but not 8Br‐cAMP or dbcAMP‐stimulated GU. The PI3K inhibitor, LY294002 (1 μM), inhibited insulin‐ (174.9±5.9 to 142.7±2.7%) and zinterol‐ (166.9±7.6 to 141.1±8.1%) but not 8 Br‐cAMP‐stimulated GU. In contrast to insulin, zinterol did not cause phosphorylation of Akt.

The results suggest that GU in L6 cells involves three mechanisms: (1) an insulin‐dependent pathway involving PI3K, (2) a β2‐AR‐mediated pathway involving both cAMP and PI3K, and (3) a receptor‐independent pathway suggested by cAMP analogues that increase GU independently of PI3K. PKA appears to negatively regulate β2‐AR‐mediated GU.

British Journal of Pharmacology (2006) 147, 446–454. doi:10.1038/sj.bjp.0706626
Actions of flecainide on susceptibility to phase‐2 ventricular arrhythmias during infarct evolution in rat isolated perfused hearts
Authors: Clements‐Jewery Hugh , Kanaganayagam Gajen Sunthar , Kabra Ruchi , Curtis Michael J
Published: January 2006

The mechanism of flecainide‐induced unexpected death remains uncertain. Phase‐2 ventricular arrhythmias occur during infarct evolution. We examined whether flecainide (0.74 and 1.48 μM, representing the peak unbound plasma and total blood concentrations, respectively, at ‘therapeutic’ dosage) has proarrhythmic activity on phase‐2 arrhythmia susceptibility during infarct evolution.

To achieve this, we used the Langendorff‐perfused rat heart preparation (n=8 per group) in which baseline phase‐2 arrhythmia susceptibility is low. Left main coronary occlusion evoked phase‐1 (acute ischaemia‐induced) ventricular arrhythmias including fibrillation (VF) in all hearts. By 90 min, hearts were relatively arrhythmia‐free.

Randomized and blinded switch of perfusion to flecainide at 90 min caused no increase over baseline in the incidence of VF, tachycardia (VT) or premature beats (VPB) during the following 150 min of ischaemia, or during reperfusion (begun 240 min after the onset of ischaemia).

In separate hearts, catecholamines (313 nM norepinephrine and 75 nM epinephrine) were co‐perfused with flecainide from 90 min of ischaemia. Catecholamine perfusion increased heart rate, coronary flow and QT interval, and shortened PR interval (all P<0.05), actions that were not altered by flecainide. Catecholamine perfusion caused a weak nonsignificant increase in phase‐2 VPB, VT and VF incidence, but there was no proarrhythmic interaction with flecainide.

In conclusion, the present findings suggest that the increased risk of death associated with clinical use of flecainide is not due to facilitation of phase‐2 ventricular arrhythmias.

British Journal of Pharmacology (2006) 147, 468–475. doi:10.1038/sj.bjp.0706633
Depletion of intracellular Ca2+ stores enhances flow‐induced vascular dilatation in rat small mesenteric artery
Authors: Liu Cuiling , Ngai Ching‐Yuen , Huang Yu , Ko Wing‐Hung , Wu Min , He Guo‐Wei , Garland Christopher J , Dora Kim A , Yao Xiaoqiang
Published: January 2006

The effect of depleting intracellular Ca2+ stores on flow‐induced vascular dilatation and the mechanism responsible for the vasodilatation were examined in rat isolated small mesenteric arteries.

The arteries were pressurized to 50 mmHg and preconstricted with phenylephrine. Intraluminal flow reversed the effect of phenylephrine, resulting in vasodilatation. Flow dilatation consisted of an initial transient peak followed by a sustained plateau phase. The magnitude of dilatation was markedly reduced by removing Ca2+ from the intraluminal flow medium.

Depletion of intracellular Ca2+ stores with either cyclopiazonic acid (CPA, 2 μM) or 1,4‐dihydroxy‐2,5‐di‐tert‐butylbenzene (BHQ, 10 μM) significantly augmented the magnitude of flow dilatation. Flow‐induced endothelial cell Ca2+ influx was also markedly enhanced in arteries pretreated with CPA or BHQ.

Flow‐induced dilatation was insensitive to Nw‐nitro‐L‐arginine methyl ester (100 μM) plus indomethacin (3 μM) or to oxyhemoglobin (3 μM), but was markedly reduced by 30 mM extracellular K+ or 2 mM tetrabutylammonium (TBA), suggesting an involvement of EDHF.

Catalase at 1200 U ml−1 abolished the flow‐induced dilatation, while the application of exogenous H2O2 (90–220 μM) induced relaxation in phenylephrine‐preconstricted arteries. Relaxation to exogenous H2O2 was blocked in the presence of 30 mM extracellular K+, and H2O2 (90 μM) hyperpolarized the smooth muscle cells, indicating that H2O2 can act as an EDHF.

In conclusion, flow‐induced dilatation in rat mesenteric arteries can be markedly enhanced by prior depletion of intracellular Ca2+ stores. Furthermore, these data are consistent with a role for H2O2 as the vasodilator involved.

British Journal of Pharmacology (2006) 147, 506–515. doi:10.1038/sj.bjp.0706639
Activation of insulin‐like growth factor I receptor‐mediated pathway by ginsenoside Rg1
Authors: Chen Wen‐Fang , Lau Wai‐Sum , Cheung Pik‐Yuen , Guo De‐An , Wong Man‐Sau
Published: January 2006

Ginsenoside Rg1, an active ingredient in ginseng, was previously shown to be a novel class of potent phytoestrogen. The present study aims at investigating the molecular mechanisms involved in mediating its actions in human breast cancer (MCF‐7) cells.

Rg1 (1 pM) stimulates cell proliferation (P<0.01) and estrogen‐responsive pS2 mRNA expression (P<0.05) without alteration of estrogen receptor alpha (ERα) protein or mRNA expression in MCF‐7 cells. In addition, 10−14–10−4 M of Rg1 does not demonstrate specific binding to ERα.

We hypothesize that Rg1 may exert its actions in MCF‐7 cell via the activation of crosstalk between ER‐ and insulin growth factor I receptor (IGF‐IR)‐dependent pathways.

The results indicate that Rg1 significantly increases IGF‐IR expression and IGF‐IR promoter activity in MCF‐7 cells (P<0.05). Cotreatment of MCF‐7 cells with 1 μM of estrogen antagonist ICI 182,780 completely abolishes the effects of Rg1 on IGF‐IR expression.

Furthermore, Rg1 enhances tyrosine phosphorylation of IRS‐1 in MCF‐7 cells upon IGF‐I stimulation and the activation of IRS‐1 phosphorylation is also ER‐dependent.

Taken together, our results suggest that Rg1 not only increases IGF‐IR expression but also enhances IGF‐IR‐mediated signaling pathways in MCF‐7 cells. The stimulation of IGF‐IR expression by Rg1 in MCF‐7 cells appears to require ER, and its actions might involve ligand‐independent activation of ER.

British Journal of Pharmacology (2006) 147, 542–551. doi:10.1038/sj.bjp.0706640
Endothelium‐dependent relaxation evoked by ATP and UTP in the aorta of P2Y2‐deficient mice
Authors: Guns Pieter‐Jan D F , Van Assche Tim , Fransen Paul , Robaye Bernard , Boeynaems Jean‐Marie , Bult Hidde
Published: January 2006

Based on pharmacological criteria, we previously suggested that in the mouse aorta, endothelium‐dependent relaxation by nucleotides is mediated by P2Y1(adenosine diphosphate (ADP)), P2Y2(adenosine triphosphate (ATP)) and P2Y6(uridine diphosphate (UDP)) receptors. For UTP, it was unclear whether P2Y2, P2Y6or yet another subtype was involved. Therefore, in view of the lack of selective purinergic agonists and antagonists, we used P2Y2‐deficient mice to clarify the action of UTP.

Thoracic aorta segments (width 2 mm) of P2Y2‐deficient and wild‐type (WT) mice were mounted in organ baths to measure isometric force development and intracellular calcium signalling.

Relaxations evoked by ADP, UDP and acetylcholine were identical in knockout and WT mice, indicating that the receptors for these agonists function normally.

P2Y2‐deficient mice showed impaired ATP‐ and adenosine 5′[γ‐thio] triphosphate (ATPγS)‐evoked relaxation, suggesting that in WT mice, ATP and ATPγS activate predominantly the P2Y2subtype.

The ATP/ATPγS‐evoked relaxation and calcium signals in the knockout mice were partially rescued by P2Y1, as they were sensitive to 2′‐deoxy‐N6‐methyladenosine 3′,5′‐bisphosphate (MRS2179), a P2Y1‐selective antagonist.

In contrast to ATP, the UTP‐evoked relaxation was not different between knockout and WT mice. Moreover, the action of UTP was not sensitive to MRS2179. Therefore, the action of UTP is probably mediated mainly by a P2Y6(like) receptor subtype.

In conclusion, we demonstrated that ATP‐evoked relaxation of the murine aorta is mainly mediated by P2Y2. But this P2Y2receptor has apparently no major role in UTP‐evoked relaxation. The vasodilator effect of UTP is probably mediated mainly by a P2Y6(like) receptor.

British Journal of Pharmacology(2006)147, 569–574. doi:10.1038/sj.bjp.0706642
Vasorelaxant effects of oleamide in rat small mesenteric artery indicate action at a novel cannabinoid receptor
Authors: Hoi Pui Man , Hiley C Robin
Published: January 2006

Oleamide (cis‐9‐octadecenoamide) exhibits some cannabimimetic responses despite its low affinities at the currently known cannabinoid receptors. Here we have investigated whether or not it is a vasorelaxant in rat small mesenteric arteries.

Oleamide elicited vasorelaxation (EC50=1.2±0.2 μM,Rmax=99.1±3.9%,n=8) which was reduced by endothelial removal. Nitric oxide synthase inhibition reduced the response (EC50=5.3±1.6 μM,Rmax=59.2±7.7%,n=7;P<0.01) as did blockade of Ca2+‐sensitive K+channels (KCa) with apamin plus charybdotoxin (both 50 nM) (EC50=2.1±0.2 μM,Rmax=58.4±1.9%,n=5;P<0.05). Desensitisation of vanilloid receptors with capsaicin (10 μMfor 30 min) shifted the oleamide concentration–response curve ∼30‐fold to the right (n=7;P<0.01). Pertussis toxin (400 ng ml−1for 2 h) caused a two‐fold shift in the response curve (EC50=2.2±0.4 μM,Rmax=66.8±4.5%,n=6;P<0.01).

Rimonabant (CB1cannabinoid receptor antagonist; SR141716A; 3 μM) significantly inhibited relaxation induced by oleamide (EC50=3.5±0.3 μM,Rmax=75.1±1.9%;n=8;P<0.05). In contrast, neither the more selective CB1receptor antagonist, AM251 (1 μM), nor the CB2antagonist, SR144528 (1 μM), had significant effects. O‐1918 (10 μM), a putative antagonist at a novel endothelial cannabinoid receptor (abnormal‐cannabidiol site), markedly reduced the relaxation to oleamide (n=7;P<0.01).

It is concluded that oleamide responses in the rat isolated small mesenteric artery are partly dependent on the presence of the endothelium, activation of Ca2+‐sensitive K+channels (KCa) and involve capsaicin‐sensitive sensory nerves. Oleamide may share a receptor (sensitive to rimonabant and O‐1918, and coupled toKCaandGi/o) with anandamide in this vessel. This might be distinct from both of the known cannabinoid receptors and the novel abnormal‐cannabidiol site.

British Journal of Pharmacology(2006)147, 560–568. doi:10.1038/sj.bjp.0706643
A3 adenosine receptor antagonists delay irreversible synaptic failure caused by oxygen and glucose deprivation in the rat CA1 hippocampus in vitro
Authors: Pugliese Anna Maria , Coppi Elisabetta , Spalluto Giampiero , Corradetti Renato , Pedata Felicita
Published: January 2006

The role of adenosine A3 receptor activation during ischaemia‐like conditions produced by oxygen and glucose deprivation (OGD) was evaluated with extracellular recordings from the CA1 region of rat hippocampal slices. In all, 7 min of OGD evoked tissue anoxic depolarisation (AD, peak at ∼7 min from OGD start, n=20) and were invariably followed by irreversible loss of electrically evoked field epsps (fepsps, n=42).

The selective adenosine A3 antagonists 3‐propyl‐6‐ethyl‐5[(ethylthio)carbonyl]‐2‐phenyl‐4‐propyl‐3‐pyridinecarboxylate (MRS 1523, 1–100 nM, n=31), N‐[9‐chloro‐2‐(2‐furanyl)[1,2,4]‐triazolo[1,5‐c]quinazolin‐5‐yl]benzeneacetamide (MRS 1220, 100 nM, n=7), N‐(2‐methoxyphenyl)‐N′‐[2‐(3‐pyrindinyl)‐4‐quinazolinyl]‐urea, (VUF 5574, 100 nM, n=3) and 5‐[[(4‐pyridyl)amino]carbonyl]amino‐8‐methyl‐2‐(2‐furyl)‐pyrazolo[4,3‐e]1,2,4‐triazolo[1,5‐c]pyrimidine hydrochloride (1 nM, n=4), prevented the irreversible failure of neurotransmission induced by 7 min OGD (n=45) and the development of AD in 20 out of 22 monitored slices.

When tested on OGD episodes of longer duration (8–10 min, n=18), 100 nM MRS 1523 prevented or delayed the appearance of AD and exerted a protective effect on neurotransmission for episodes of up to 9 min duration. In the absence of AD, the fepsp recovery was almost total, regardless of OGD episode duration.

These findings support the notion that A3 receptor stimulation is deleterious during ischaemia and suggest that selective A3 receptor block may substantially increase the resistance of the CA1 hippocampal region to ischaemic damage.

British Journal of Pharmacology (2006) 147, 524–532. doi:10.1038/sj.bjp.0706646
Kerr effect as a tool for the investigation of dynamic heterogeneities
Authors: Häberle Uli , Diezemann Gregor
Published: January 2006

We propose a dynamic Kerr effect experiment for the distinction between dynamic heterogeneous and homogeneous relaxations in glassy systems. The possibility of this distinction is due to the inherent nonlinearity of the Kerr effect signal. We model the slow reorientational molecular motion in supercooled liquids in terms of noninertial rotational diffusion. The Kerr effect response, consisting of two terms, is calculated for heterogeneous and for homogeneous variants of the stochastic model. It turns out that the experiment is able to distinguish between the two scenarios. We furthermore show that exchange between relatively “slow” and “fast” environments does not affect the possibility of frequency-selective modifications. It is demonstrated how information about changes in the width of the relaxation-time distribution can be obtained from experimental results.
Stretching of hydrogen-bonded OH in the lowest singlet excited electronic state of water dimer
Authors: Chipman Daniel M.
Published: January 2006

The lowest singlet excited electronic state of water monomer in the gas phase is strictly dissociative along a OH stretch coordinate but changes its nature when the stretched OH moiety is hydrogen bonded to a neighboring water molecule. This work extends previous exploration of the water dimer excited singlet potential-energy surface, using computational methods that are reliable even at geometries well removed from the ground-state equilibrium. First, the hydrogen-bonded OH moiety is stretched far enough to establish the existence of a barrier that is sufficient to support a quasibound vibrational state of the OH oscillator near the Franck-Condon region. Second, the constraint of an icelike structure is relaxed, and it is found that a substantial fraction of liquidlike structures also supports a quasibound vibrational state. These potential-energy explorations on stretching of the hydrogen-bonded OH moiety in a water dimer are discussed as a model for understanding the initial dynamics upon excitation into the lowest excited singlet state of condensed water. The possibility is raised that the excited-state lifetime may be long enough to allow for exciton migration, which would provide a mechanism for energy transport in condensed water phases.
Engineering clusters for table-top acceleration of ions
Authors: Jha J. , Mathur D. , Krishnamurthy M.
Published: January 2006

Upon irradiation by ultrashort, intense laser light, inert gas clusters show an uncanny ability to absorb nearly all the incident optical energy, and to subsequently disburse this energy by producing very energetic ions and electrons. Practical realization of a table-top accelerator requires such a laser-cluster “ion source” to demonstrate sufficiency in terms of brightness, ion yield, and charge state. We show that by “engineering” the constituents of the cluster, using low ionization energy dopants, it is possible to significantly enhance the high-energy ion yield and ion charge states.
Controlling magnetic vortices through exchange bias
Authors: Sort J. , Salazar-Alvarez G. , Baró M. D. , Dieny B. , Hoffmann A. , Novosad V. , Nogués J.
Published: January 2006

The magnetization reversal in Permalloy (Py) and Py-IrMn disks (1μm diameter) is investigated. The Py disks reverse their magnetization via vortex state formation. Conversely, if the Py-IrMn disks are field cooled from above the blocking temperature TB, a critical angle with respect to the cooling direction is set, beyond which the vortex no longer nucleates. This angle can be experimentally tuned by varying the magnitude of the exchange bias field. Furthermore, the coupling with IrMn can also induce an enhancement of the vortex stability when the disks are zero-field cooled from above TB.
Investigation of transition dynamics in a quantum-dot laser optically pumped by femtosecond pulses
Authors: Rafailov E. U. , McRobbie A. D. , Cataluna M. A. , O’Faolain L. , Sibbett W. , Livshits D. A.
Published: January 2006

The behavior of a quantum-dot edge-emitting laser, optically pumped by femtosecond pulses, has been investigated. It has been observed that pulses generated by the laser from ground-state transitions have longer durations than those generated from the excited states. Interestingly, the shortest pulses were generated when the transitions from the first excited-state were dominant.
Enhancement of photoluminescence from Yb and Er co-doped Al2O3 films by an asymmetric metal cavity
Authors: Managaki Nobuto , Fujii Minoru , Nakamura Toshihiro , Usui Yoshiko , Hayashi Shinji
Published: January 2006

The effects of Au thin layers on luminescence properties of Er and Yb co-doped Al2O3 films were studied. The 1.54μm emission of Er3+ excited by the energy transfer from Yb3+ is found to be strongly enhanced by placing a Au layer on top of the films. Photoluminescence excitation spectra of the 1.54μm PL of Er3+ and time transients of the 980nm emission of Yb3+ revealed that PL enhancement arises from two different mechanisms. The first one is the enhancement of local electric fields accompanied by the excitation of surface plasmons of rough Au surfaces. The other one is the enhancement of energy transfer rate from Yb3+ to Er3+ caused by the modification of the local photonic mode density at the position of the Yb–Er coupled system.
Simultaneous direct detection of sub keV molecular and atomic ions with a delta-doped charge-coupled device at the focal plane of a miniature mass spectrometer
Authors: Jewell April D. , Jones Todd J. , Sinha Mahadeva P. , Nikzad Shouleh
Published: January 2006

A delta-doped charge-coupled device (CCD) was used for the simultaneous and direct detection of low-energy atomic and molecular ions dispersed along the focal plane of a miniature mass spectrometer (MMS). The measured detection threshold for charged particles with a delta-doped CCD has been extended down to 700eV, representing over an order of magnitude improvement compared to conventional solid-state detectors. We report the direct detection of 700eV energy ions by the mass spectral measurements of species such as iron pentacarbonyl. The combination of delta-doped CCD and MMS enables high-speed, precision mass spectrometry of ions and molecules on a small scale suitable for field and space applications.