bluuebunny/crossref_metadata_2025 huggingface dataset:
An electric arc in a transverse magnetic field: a theory for low power gradient
Authors: Lord W. T.
Published: March 2006

A uniform electric arc column is held at rest against an imposed low-speed flow perpendicular to its length by an applied magnetic field transverse to both the arc and the flow. The situation is represented mathematically by two regions separated by an isothermal boundary, the arc periphery, across which certain gas properties change discontinuously. It is assumed that the arc has low power gradient so that the Nusselt number is small compared with unity. The Reynolds number is then small also and the methods of the theory of flow at low Reynolds number are used to obtain solutions for the temperature, magnetic field, velocity and pressure inside and outside the arc. It is found that the periphery of the arc is a circle and its radius is determined by heat transfer. The flow near the periphery, and the drag of the arc, are found to depend on a final boundary condition at the periphery, the form of which is not yet clear. Several examples of possible flow patterns are given, and it is shown that the arc may be likened to a slippery porous body for which the slipperiness and porousness are governed by the final boundary condition. The electric and magnetic characteristics of the arc are derived and shown to be amenable to examination by experiment and to empirical extension for arcs of higher power gradient.
Gas diffusion from ascending gas bubbles
Authors: Leblond Paul H.
Published: March 2006

General qualitative rules are derived for the behaviour of the volume of an ascending spherical bubble and of the gas pressure within it. Three modes of behaviour are discerned, corresponding to as many possible orderings of the relative influences of ascent velocity, gas leakage and surface tension on the volume and the pressure balance. These general results are nearly independent of the particular forms of the ascent velocity and gas exchange functions. Quantitative results are presented for the Stokes law régime.
The fluid mechanics of the aortic valve
Authors: Bellhouse B. J. , Talbot L.
Published: March 2006

The closure mechanism of the human aortic valve is investigated experimentally with a rigid-walled model placed in a pulsatile water-tunnel. It is shown that the valve is controlled by a fluid feed-back system incorporating a stagnation point at the downstream end of each sinus and a trapped vortex within it, and that threequarters of the valve's closure is accomplished during forward flow, requiring only very little reversed flow to seal it. The experiments are complemented by solutions of the inviscid-flow equations, based on a Hill spherical vortex model.
The measurement of skin friction in turbulent boundary layers with adverse pressure gradients
Authors: Brown K. C. , Joubert P. N.
Published: March 2006

This paper describes a floating-element skin friction meter which has been designed for use in adverse pressure gradients. The effects of secondary forces on the element, which arise from the pressure gradient, are examined in some detail. The limitations of various methods of measuring wall shear stress are discussed and the results from the floating element device are compared with measurements taken in a two-dimensional boundary layer using Preston tubes and velocity profiles. As it is planned to use the instrument later for direct measurements of the shear stress in three-dimensional boundary layers, the relevance of the instrument to this situation is also discussed.
Inviscid reacting flow near a stagnation point
Authors: Conti Raul , Dyke Milton Van
Published: March 2006

A reacting flow free of molecular transport exhibits noteworthy behaviour in the neighbourhood of a blunt, symmetrical stagnation point. A local analytical study using the Lighthill-Freeman gas model reveals the basic structure of such a flow. Chemical activity is found to affect some, but not all, of the local characteristics of the flow. Unaffected are the pressure and velocity fields near the stagnation point, where the pressure varies quadratically and the velocity varies linearly as in an inert flow. In addition, the stagnation point is found to be in chemical equilibrium for all non-zero reaction rates. On the other hand the density, temperature, and concentration fields are affected by the non-equilibrium reactions. The extent of this effect can be predicted on the basis of a reaction parameter that measures the rate of reaction in terms of the velocity gradient at the stagnation point. A rapidly reacting flow (with reaction parameter greater than unity) approaches the stagnation point with vanishing gradients of density and temperature, whereas a slowly reacting flow approaches with infinite gradients. The flow field is represented mathematically by functions that are regular along the body but non-analytic in the normal direction. Numerical computations support the validity of the local closed-form solution, and provide information on the local effects of the chemical history of the flow.
The generation of continental shelf waves
Authors: Adams J. K. , Buchwald V. T.
Published: March 2006

Assuming zero divergence, the equations of forced long waves in a uniformly rotating, homogeneous ocean are reduced to a single partial differential equation for the stream function. A shelf of exponential slope between a rigid continent and a sea of uniform depth is taken as a model, and certain other assumptions are made which appear physically reasonable. Calculations made on the basis of this simplified theory are in good qualitative agreement with observations of shelf waves, indicating that these waves are generated by the stress of the longshore component of the geostrophic wind.
Reliability of a tympanic thermometer in measuring temperatures in children after minor ear surgery
Authors: Pandey A , Ingrams D R , Jones M , Raman R , Marks N D
Published: March 2006

Aim: To evaluate the reliability of infrared tympanic thermometry in children who have undergone myringotomy with grommet insertion.

Method: Forty children who had undergone myringotomy with at least one grommet insertion had the tympanic temperature of each ear and the axillary temperature measured on admission and 30 minutes post-operatively.

Result: No difference was found between the pre- and post-operative temperatures measured by either method (p > 0.05, paired t-test, hypothesized difference of 0).

Conclusion: Infrared tympanic thermometry is reliable in monitoring body temperature in children who have had minor ear surgery.
Angiolymphoid hyperplasia with eosinophilia of the auricle: progression of histopathological changes
Authors: Effat K G
Published: March 2006

Angiolymphoid hyperplasia with eosinophilia is a rare condition that demonstrates dermal or subcutaneous proliferation of endothelial cells associated with an inflammatory cell infiltrate. A case is reported, with emphasis on the histopathological features on repeated biopsies. The report serves to stress the importance of considering this condition in the differential diagnosis of lesions in and around the ear.
The influence of adversity and perceived social support on the outcome of major depressive disorder in subjects with different levels of depressive symptoms
Authors: LESKELÄ ULLA , RYTSÄLÄ HEIKKI , KOMULAINEN ERKKI , MELARTIN TARJA , SOKERO PETTERI , LESTELÄ-MIELONEN PAULA , ISOMETSÄ ERKKI
Published: March 2006

Background. Adverse life events and social support may influence the outcome of major depressive disorder (MDD). We hypothesized that outcome would depend on the level of depressive symptoms present at the outset, with those in partial remission being particularly vulnerable.

Method. In the Vantaa Depression Study (VDS), patients with DSM-IV MDD were interviewed at baseline, and at 6 and 18 months. Life events were investigated with the Interview for Recent Life Events (IRLE) and social support with the Interview Measure of Social Relationships (IMSR) and the Perceived Social Support Scale – Revised (PSSS-R). The patients were divided into three subgroups at 6 months, those in full remission (n=68), partial remission (n=75) or major depressive episode (MDE) (n=50). The influence of social support and negative life events during the next 12 months on the level of depressive symptoms, measured by the Hamilton Rating Scale for Depression (HAMD), was investigated at endpoint.

Results. The severity of life events and perceived social support influenced the outcome of depression overall, even after adjusting for baseline level of depression and neuroticism. In the full remission subgroup, both severity of life events and subjective social support significantly predicted outcome. However, in the partial remission group, only the severity of events, and in the MDE group, the level of social support were significant predictors.

Conclusions. Adverse life events and/or poor perceived social support influence the medium-term outcome of all psychiatric patients with MDD. These factors appear to have the strongest predictive value in the subgroup of patients currently in full remission.
Clinical and neuropsychological characteristics of child and adolescent bipolar disorder
Authors: KYTE ZOË A. , CARLSON GABRIELLE A. , GOODYER IAN M.
Published: March 2006

Background. The diagnosis of bipolar disorder in pre-pubertal populations remains difficult and often controversial. Consequently, the clinical and neuropsychological characteristics of mania in the child and adolescent years remain poorly defined. This review provides a clinical account of childhood and adolescent bipolar disorder and compares the neuropsychology and neuroanatomy of young BPD patients compared with adult BPD and childhood syndromes of attention deficit hyperactivity disorder (ADHD) and conduct disorder (CD).

Method. Literature review based on Pubmed searches.

Results. Early- and adult-onset mania and BPD may share a common pattern of neurobiological characteristics despite developmental variations in the clinical presentation. In contrast, important distinctions are apparent between the child-onset syndromes of BPD, ADHD and CD, specifically at the neural level.

Conclusions. Disorders of affect dysregulation in childhood deserve closer neuroscientific and phenotypic scrutiny than given hitherto.
A recursive approach for the analysis of snake robots using Kane's equations
Authors: Nia H. Tavakoli , Pishkenari H. N. , Meghdari A.
Published: March 2006

This paper presents a recursive approach for solving kinematic and dynamic problems in snake-like robots using Kane's equations. An n-link model with n-nonholonomic constraints is used as the snake robot model in our analysis. The proposed algorithm which is used to derive kinematic and dynamic equations recursively, enhances the computational efficiency of our analysis. Using this method we can determine the number of additions and multiplications as a function of n. The proposed method is compared with the Lagrange and Newton-Euler's method in three different aspects: Number of operations, CPU time and error in the computational procedures.
Fourier-based optimal excitation trajectories for the dynamic identification of robots
Authors: Park Kyung-Jo
Published: March 2006

This paper describes a new approach to the parameterization of robot excitation trajectories for optimal robot identification. The trajectory parameterization is based on a combined Fourier series and polynomial functions. The coefficients of the Fourier series are optimized for minimal sensitivity of the identification to measurement disturbances, which is measured as the d-optimality criterion, taking into account motion constraints in joint and Cartesian space. This parameterization satisfies both the guarantees of convergence by adding terms and the matching of the boundary conditions. Application of the method for the identification of the CRS A465 industrial robot proves the validity of the proposed approach.
Optimal settings of fingerprint-type analysing computer software for the analysis of enterohaemorrhagic Escherichia coli pulsed-field gel electrophoresis patterns
Authors: YOKOYAMA E. , UCHIMURA M.
Published: March 2006

Settings of fingerprint-type analysing computer software were optimized for analysis of enterohaemorrhagic Escherichia coli (EHEC) pulsed-field gel electrophoresis (PFGE) patterns. Under the lowest values of parameters, maximum value of similarities calculated using the Dice coefficient were obtained between PFGE patterns from one EHEC strain on the same gel when reference lanes for calibration of distortions during electrophoresis were set to every fourth lane. PFGE patterns of 15 EHEC strains on different gels were investigated. Similarity values calculated using the Pearson product-moment correlation coefficient (Pearson correlation) were significantly higher than those using the Dice coefficient with optimal values of parameters determined by the program (P<0·01). When PFGE patterns of 45 EHEC strains were analysed by the computer program, EHEC strains from one mass outbreak and three intra-family outbreaks were each clustered and the similarity values within the clusters were >90% using Pearson correlation.
Neurochemistry of severe dementia
Authors: Sharp Sally I , Francis Paul T , Ballard Clive G
Published: March 2006

Severe dementia is associated with frequent psychiatric and behavioural disturbances in addition to marked cognitive and functional deficits. Research to determine a neurochemical understanding of dementia over the last three decades has generated therapeutic strategies which improve patients' cognition and activities of daily living. Different key dementia syndromes have been shown to have distinct neurotransmitter biochemical patho-logy, with important implications for therapy. The current review focuses predominantly upon excitatory neurotransmitter systems.
Hydrographic observations during the 2002 IOC Contaminant Baseline Survey in the western Pacific Ocean
Authors: Measures C. I. , Cutter G. A. , Landing W. M. , Powell R. T.
Published: March 2006

The 2002 IOC Contaminant Baseline Survey in the western Pacific Ocean was the fourth in a series of cruises intended to establish the contemporary concentrations of trace elements and other materials in the major water masses of the ocean and to illuminate the pathways by which materials delivered to the surface ocean are incorporated in the subsurface waters. The expedition occupied 9 vertical profile stations encompassing the subtropical and subarctic gyre of the western North Pacific. In addition, underway surface water samples were collected during transits between the stations. This paper uses the temperature, salinity, nutrient, oxygen, and chlorophyll data to set the hydrographic and biological background for the other papers in this theme.
Sulfur, sea salt, and radionuclide aerosols in GISS ModelE
Authors: Koch Dorothy , Schmidt Gavin A. , Field Christy V.
Published: March 2006

We simulate a suite of aerosols in the new GISS ModelE GCM: present‐day sulfur species and the natural species sea salt, radionuclides 7Be (stratospheric source), and 210Pb (derived from 222Rn from soils). The natural species are used to test the model and to help diagnose the anthropogenic sulfur species. Model improvements over previous versions include increased vertical resolution, addition of a stratiform dissolved species budget (DSB), better tracer coupling to the boundary layer, and an improved relative humidity‐dependent radiative scheme. The DSB reduces the loads of most soluble species since it increases stratiform precipitation scavenging. We compare the model with extensive surface and aircraft concentration measurements in the troposphere and stratosphere. We compare three different formulations of the 222Rn emissions and find that a scheme with reduced radon flux at high latitudes of the Northern Hemisphere for all seasons gives the best 210Pb results. Although the 222Rn emissions appear to be approximately the right order of magnitude, model 210Pb is too large. Conversely, our 7Be source is too small (since concentrations in the upper troposphere and stratosphere are deficient), while the 7Be surface concentrations are as observed. These radionuclide results suggests that model scavenging (by moist convection) is deficient. Our new model uses increased natural sulfur emissions; however, the DSB causes sulfate to be generally less than observed and indicates a need for additional sulfur oxidation mechanisms. Model radiative forcing for sulfate and sea salt are −0.54 and −1.1 W m−2, respectively. The anthropogenic sulfate forcing is −0.25 W m−2, less than the −0.68 W m−2 in our previous model mainly owing to an 18% decrease in industrial emissions.
Antarctic snow accumulation mapped using polarization of 4.3‐cm wavelength microwave emission
Authors: Arthern Robert J. , Winebrenner Dale P. , Vaughan David G.
Published: March 2006

Different parts of Antarctica receive different amounts of snowfall each year. In this paper we map the variations of the mean annual snow accumulation across the ice sheet. We also quantify the uncertainty in our estimates more objectively than has been possible for earlier maps. The new map is produced using observations from satellites and ground‐based measurements. After a logarithmic transformation, these are combined using the geostatistical method of continuous‐part universal kriging to give an estimate of the snow accumulation within each cell of a rectangular grid covering Antarctica. We also derive spatial averages over the major drainage systems of the ice sheet, along with their confidence intervals. We obtain a value of 143 ± 4 kg m−2 a−1 for the average rate of snow accumulation upon the grounded ice sheet of Antarctica.
Influence of trench width on subduction hinge retreat rates in 3‐D models of slab rollback
Authors: Stegman D. R. , Freeman J. , Schellart W. P. , Moresi L. , May D.
Published: March 2006

Subduction of tectonic plates limited in lateral extent and with a free‐trailing tail, i.e., “free subduction,” is modeled in a three‐dimensional (3‐D) geometry. The models use a nonlinear viscoplastic rheology for the subducting plate and exhibit a wide range of behaviors depending on such plate characteristics as strength, width, and thickness. We investigate the time evolution of this progressive rollback subduction, measure the accompanying return flow in the upper mantle, and quantify the plate kinematics. Due to the 3‐D geometry, flow is allowed to accompany slab rollback around the lateral edges of the slab (the toroidal component), as opposed to 2‐D geometry, where material is forced to flow underneath the slab tip (the poloidal component). A simple force balance is provided which relates the speed of backward trench migration to the resistive forces of generating flow and weakening the plate. Our results indicate most of the gravitational energy of the system (i.e., the negative buoyancy of the subducting slab) is converted into a toroidal flow (∼69%), a much smaller amount goes into weakening the plate (∼18%), and the remaining amount goes into driving flow parallel to displacement of the slab (∼13%). For the trench widths (W) we investigate (≤1500 km), a maximum trench retreat rate occurs for trenches 600 km wide, which is attributed to the interaction between a plate of finite width and the induced flow (which has a lengthscale in the horizontal direction). These numerical results quantitatively agree with comparable 3‐D laboratory experiments using analogue models with a purely viscous plate material (Schellart, 2004a, 2004b), including correlations between increasing retreat rate with increasing plate thickness, trench width for maximum retreat rate (500 km), and estimated amount of slab buoyancy used to drive rollback‐induced flow (∼70%). Several implications for plate tectonics on Earth result from these models such as rollback subduction providing a physical mechanism for ephemeral slab graveyards situated above the more viscous lower mantle (and endothermic phase transition) prior to a flushing event into the lower mantle (mantle avalanche).
A high‐resolution investigation of temperature, salinity, and upwelling activity proxies in corals
Authors: Ourbak Timothée , Corrège Thierry , Malaizé Bruno , Le Cornec Florence , Charlier Karine , Peypouquet Jean Pierre
Published: March 2006

We present a high‐resolution study of five geochemical components of a New Caledonia coral core. Minor and trace elements (Sr/Ca, U/Ca, Mg/Ca, Ba/Ca), together with oxygen isotopes (δ18O), were investigated at near‐fortnightly resolution. Geochemical measurements were compared to sea surface temperature (SSTTSG) and salinity (SSSTSG) recorded by a thermosalinograph (TSG) located less than 10 m from the coral. Results show that Sr/Ca, Mg/Ca, and δ18O are temperature‐dependent (correlation coefficient to local SSTTSG between 0.74 and 0.84). Their robustness as SST tracers is tested against a satellite‐based data set for a 4 year validation period. U/Ca has a more complex behavior and appears to be linked to both SSTTSG and SSSTSG, despite relatively small local SSS variations. For the first time this salinity‐related imprint is quantified in a U/Ca coralline ratio. In addition to SST and SSS tracers, Ba/Ca measurements provide a possible way to investigate upwelling activity occurrences.
Narrow‐band extremely low frequency (ELF) wave phenomena observed at South Pole Station
Authors: Kim Hyomin , Lessard Marc R. , LaBelle James , Johnson Jay R.
Published: March 2006

Extremely low frequency (ELF) magnetic pulsations which show a whistler‐like spectral structure have been measured at South Pole Station. An initial survey of the first 70 days of data revealed narrow‐band ELF pulsations with slowly varying frequency over time. The narrow‐band (a few Hz) signatures maintain their bandwidth as their frequencies decrease from 110 to 50 Hz (and their second harmonics) over the course of 40–90 s. Although the narrow‐band ELF waves have a signature somewhat similar to very low frequency (VLF) whistlers, their duration and frequency range are much different from those of whistlers; they also show an unusual characteristic where their frequency often increases before it decreases. These events show a peak in their magnetic local time (MLT) occurrence distribution near the pre‐midnight region, a result that contrasts sharply with the only three previously published studies of these waves. Two possibilities of generation mechanism are discussed.
A GCM study of the influence of equatorial winds on the timing of sudden stratospheric warmings
Authors: Pascoe C. L. , Gray L. J. , Scaife A. A.
Published: March 2006

A full troposphere‐stratosphere‐mesosphere global circulation model is used in a set of idealised experiments to investigate the sensitivity of the Northern Hemisphere winter stratospheric flow to improvements in the equatorial zonal winds. The model shows significant sensitivity to variability in the upper equatorial stratosphere, the imposition of SAO and QBO like variability in this region advances the timing of midwinter sudden warmings by about one month. Perturbations to the lower equatorial stratosphere are mainly found to influence early winter polar variability. These results suggest that it is important to pay attention to the capability of models to simulate realistic variability in the upper equatorial stratosphere.
Possible influences of Asian dust aerosols on cloud properties and radiative forcing observed from MODIS and CERES
Authors: Huang Jianping , Minnis Patrick , Lin Bing , Wang Tianhe , Yi Yuhong , Hu Yongxiang , Sun‐Mack Sunny , Ayers Kirk
Published: March 2006

The effects of dust storms on cloud properties and Radiative Forcing (RF) are analyzed over Northwestern China from April 2001 to June 2004 using data collected by the MODerate Resolution Imaging Spectroradiometer (MODIS) and Clouds and the Earth's Radiant Energy System (CERES) instruments on the Aqua and Terra satellites. On average, ice cloud effective particle diameter, optical depth and ice water path of cirrus clouds under dust polluted conditions are 11%, 32.8%, and 42% less, respectively, than those derived from ice clouds in dust‐free atmospheric environments. Due to changes in cloud microphysics, the instantaneous net RF is increased from −161.6 W/m2 for dust‐free clouds to −118.6 W/m2 for dust‐contaminated clouds.
Sliding of outrunner blocks from submarine landslides
Authors: De Blasio Fabio Vittorio , Engvik Lars Enok , Elverhøi Anders
Published: March 2006

Outrunner blocks are nearly intact pieces of debris that detach from a slowing‐down submarine landslide and flow ahead of the front. Data gathered from different sliding areas highlight some properties of outrunner blocks and in particular their inordinate mobility reflected in runouts of up to 25 kilometres, even on very gentle slopes. Blocks may produce an erosion glide track on the sea floor few centimetres to several metres deep, which in some cases exhibits regularly spaced grooves along the flow direction. Understanding the dynamics of outrunner blocks may shed light on the flow and lubrication of submarine landslides. We develop a simple hydrodynamic model of a rigid block interacting with ambient water and subject to lubrication with the sea floor, and calculate numerically the equation of motion for the block. We find that as a consequence of lift forces and water lubrication, the block may reach long runouts, in agreement with data. When the block is moving at high speed, we find an oscillating solution to the equations of motion which could explain the creation of dashed grooves.
Climate sensitivity and cloud response of a GCM with a superparameterization
Authors: Wyant Matthew C. , Khairoutdinov Marat , Bretherton Christopher S.
Published: March 2006

The climate sensitivity of an atmospheric GCM that uses a cloud‐resolving model as a convective superparameterization is analyzed by comparing simulations with specified climatological sea surface temperature (SST) and with the SST increased by 2 K. The model has weaker climate sensitivity than most GCMs, but comparable climate sensitivity to recent aqua‐planet simulations of a global cloud‐resolving model. The weak sensitivity is primarily due to an increase in low cloud fraction and liquid water in tropical regions of moderate subsidence as well as substantial increases in high‐latitude cloud fraction.
Subtle precursors of volcanic eruptions at Piton de la Fournaise detected by extensometers
Authors: Peltier A. , Staudacher T. , Catherine P. , Ricard L.‐P. , Kowalski P. , Bachèlery P.
Published: March 2006

The highly active Piton de la Fournaise volcano is an excellent field laboratory to develop and test, in a short time span, new methods for detecting volcanic precursors. Since 1995, a network of four extensometers has been installed and has detected extensional, shear and vertical movements of fractures in relation to ground deformations of the volcano. This study describes new insights in the distribution of stresses in the volcanic edifice between eruptions and during magma intrusions. Continuous measurements show that all eruptions were preceded several months before by significant fracture movements: a constant opening associated with a dextral movement on the south flank and a sinistral movement on the north flank of the volcano. These movements can be attributed to a shallow pressure source below the summit craters.
Drastic decrease in sediment supply from the Yangtze River and its challenge to coastal wetland management
Authors: Yang S. L. , Li M. , Dai S. B. , Liu Z. , Zhang J. , Ding P. X.
Published: March 2006

The 1951–2004 time series of annual sediment supply from the Yangtze were analyzed using the wavelet method. Coastal bathymetric data were processed using the Arc‐GIS software. A typical intertidal flat was measured from May 2002 to August 2005 for comparison of bed levels before and after the Three Gorges Dam (TGD). There is a significant decreasing trend in riverine sediment supply since late 1960s, which is attributed mainly to the dam constructions. TGD reduced the sediment load to147 mt/yr in 2004, only 35% of the average. In response to this drastic decrease, the deltaic coast is turning from progradation to recession. We predict that the Yangtze sediment supply will further decrease and coastal erosion will be intensified in the coming decades, which poses a great challenge to coastal management.
Constraining the magnitude of the global dust cycle by minimizing the difference between a model and observations
Authors: Cakmur R. V. , Miller R. L. , Perlwitz J. , Geogdzhayev I. V. , Ginoux P. , Koch D. , Kohfeld K. E. , Tegen I. , Zender C. S.
Published: March 2006

Current estimates of global dust emission vary by over a factor of two. Here, we use multiple data types and a worldwide array of stations combined with a dust model to constrain the magnitude of the global dust cycle for particles with radii between 0.1 and 8 μm. An optimal value of global emission is calculated by minimizing the difference between the model dust distribution and observations. The optimal global emission is most sensitive to the prescription of the dust source region. Depending upon the assumed source, the agreement with observations is greatest for global, annual emission ranging from 1500 to 2600 Tg. However, global annual emission between 1000 and 3000 Tg remains in agreement with the observations, given small changes in the method of optimization. Both ranges include values that are substantially larger than calculated by current dust models. In contrast, the optimal fraction of clay particles (whose radii are less than 1 μm) is lower than current model estimates. The optimal solution identified by a combination of data sets is different from that identified by any single data set and is more robust. Uncertainty is introduced into the optimal emission by model biases and the uncertain contribution of other aerosol species to the observations.
Mineral dust aerosols in the NASA Goddard Institute for Space Sciences ModelE atmospheric general circulation model
Authors: Miller R. L. , Cakmur R. V. , Perlwitz J. , Geogdzhayev I. V. , Ginoux P. , Koch D. , Kohfeld K. E. , Prigent C. , Ruedy R. , Schmidt G. A. , Tegen I.
Published: March 2006

We describe an updated model of the dust aerosol cycle embedded within the NASA Goddard Institute for Space Studies ‘ModelE’ atmospheric general circulation model (AGCM). The model dust distribution is compared to observations ranging from aerosol optical thickness and surface concentration to deposition and size distribution. The agreement with observations is improved compared to previous distributions computed by either an older version of the GISS AGCM or an offline tracer transport model. The largest improvement is in dust transport over the Atlantic due to increased emission over the Sahara. This increase comes from subgrid wind fluctuations associated with dry convective eddies driven by intense summertime heating. Representation of ‘preferred sources’ of soil dust particles is also fundamental to the improvement. The observations suggest that deposition is too efficient in the model, partly due to AGCM rainfall errors.
Estimating uncertainty of the WMO mole fraction scale for carbon dioxide in air
Authors: Zhao Cong Long , Tans Pieter P.
Published: March 2006

The current WMO CO2Mole Fraction Scale consists of a set of 15 CO2‐in‐air primary standard calibration gases ranging in CO2mole fraction from 250 to 520 μmol mol−1. Since the WMO CO2Expert Group transferred responsibility for maintaining the WMO Scale from the Scripps Institution of Oceanography (SIO) to the Climate Monitoring and Diagnostics Laboratory (CMDL) in 1995, the 15 WMO primary standards have been calibrated, first at SIO and then at regular intervals, between 1 and 2 years, by the CMDL manometric system. The uncertainty of the 15 primary standards was estimated to be 0.069 μmol mol−1(one‐sigma) in the absolute sense. Manometric calibrations results indicate that there is no evidence of overall drift of the Primaries from 1996 to 2004. In order to lengthen the useful life of the Primary standards, CMDL has always transferred the scale via NDIR analyzers to the secondary standards. The uncertainties arising from the analyzer random error and the propagation error due to the uncertainty of the reference gas mole fraction are discussed. Precision of NDIR transfer calibrations was about 0.014 μmol mol−1from 1979 to present. Propagation of the uncertainty was calculated theoretically. In the case of interpolation the propagation error was estimated to be between 0.06 and 0.07 μmol mol−1when the Primaries were used as the reference gases via NDIR transfer calibrations. The CMDL secondary standard calibrations are transferred via NDIR analyzers to the working standards, which are used routinely for measuring atmospheric CO2mole fraction in the WMO Global Atmosphere Watch monitoring program. The uncertainty of the working standards was estimated to be 0.071 μmol mol−1in the one‐sigma absolute scale. Consistency among the working standards is determined by the random errors of downward transfer calibrations at each level and is about 0.02 μmol mol−1. For comparison with an independent absolute scale, the five gravimetric standards from the National Institute for the Environmental Studies (NIES) in Tsukuba, Japan, ranging in CO2mole fraction from 350 to 390 μmol mol−1have been calibrated relative to the CMDL secondary standards. The average and standard deviation of the differences between the NIES gravimetric and CMDL analyzed CO2mole fraction are 0.004 ± 0.03 μmol mol−1.
Validation of stratospheric nitric acid profiles observed by Improved Limb Atmospheric Spectrometer (ILAS)–II
Authors: Irie H. , Sugita T. , Nakajima H. , Yokota T. , Oelhaf H. , Wetzel G. , Toon G. C. , Sen B. , Santee M. L. , Terao Y. , Saitoh N. , Ejiri M. K. , Tanaka T. , Kondo Y. , Kanzawa H. , Kobayashi H. , Sasano Y.
Published: March 2006

The Improved Limb Atmospheric Spectrometer‐II (ILAS‐II) was launched aboard the Advanced Earth Observing Satellite‐II (ADEOS‐II) in December 2002. Stratospheric vertical profiles of nitric acid (HNO3) concentration observed by ILAS‐II (version 1.4) are validated using coincident HNO3 measurements by balloon‐borne instruments (MIPAS‐B2 and MkIV) in March and April 2003. Further validation is performed by making climatological comparisons of lower stratospheric HNO3‐ozone (O3) correlations obtained by ILAS‐II and ILAS (the predecessor of ILAS‐II) for specific potential vorticity‐based equivalent latitudes and seasons where and when ILAS data showed very compact correlations in 1997. The reduced scatter of ILAS‐II HNO3 values around the reference HNO3, which is derived from ILAS‐II O3 using the ILAS HNO3‐O3 correlation, shows that the precision of the ILAS‐II HNO3 data is better than 13–14%, 5%, and 1% at 15, 20, and 25 km, respectively. Combining all of the comparisons made in the present study, the accuracy of the ILAS‐II HNO3 profiles at 15–25 km is estimated to be better than −13%/+26%.
Effect of cirrus clouds on the diurnal cycle of tropical deep convective clouds
Authors: Hong Gang , Heygster Georg , Rodriguez Carlos Augusto Morales
Published: March 2006

The cirrus clouds tightly connected with tropical deep convective clouds can extend and persist for some hours after the deep convective clouds themselves dissipate. This can result in time lags of the diurnal cycle of deep convective clouds detected from infrared satellite measurements with different brightness temperature thresholds because different amounts of cirrus clouds contaminate the measurement. The diurnal cycles of rain from the Tropical Ocean–Global Atmosphere (TOGA) radar during the Tropical Rainfall Measuring Mission (TRMM) Wet Season Atmospheric Mesoscale Campaign (WETAMC) Large‐Scale Biosphere Atmosphere (LBA) Experiment in Amazonia and the diurnal cycles of deep convective clouds and high cold clouds from the Precipitation Radar (PR), Visible and Infrared Scanner (VIRS) onboard the TRMM satellite over the tropics (30°S–30°N) from November 1998 to April 1999 are investigated to study the influence of cirrus clouds on the observed diurnal cycle of tropical deep convective clouds. A 2‐hour time lag of the diurnal cycle of deep convective clouds from the VIRS with respect to that from the PR is found over land. Over ocean the cirrus clouds generated by deep convective clouds enhance the diurnal cycle of the deep convective clouds from the VIRS, and a time lag similar to that over land also occurs. The influence of cirrus clouds leads the diurnal cycle of the deep convective clouds from the VIRS to depend strongly on the selected IR threshold and to be very different from that of the PR over the maritime continent. Moreover, over ocean and the maritime continent, from late afternoon to midnight the strong increase of the deep convective clouds from the VIRS is mainly due to the developing cirrus clouds near and above the tropical tropopause layer.
Transfer of the solar signal from the stratosphere to the troposphere: Northern winter
Authors: Matthes Katja , Kuroda Yuhji , Kodera Kunihiko , Langematz Ulrike
Published: March 2006

The atmospheric response to the solar cycle has been previously investigated with the Freie Universität Berlin Climate Middle Atmosphere Model (FUB‐CMAM) using prescribed spectral solar UV and ozone changes as well as prescribed equatorial, QBO‐like winds. The solar signal is transferred from the upper to the lower stratosphere through a modulation of the polar night jet and the Brewer‐Dobson circulation. These model experiments are further investigated here to show the transfer of the solar signal from the lower stratosphere to the troposphere and down to the surface during Northern Hemisphere winter. Analysis focuses on the transition from significant stratospheric effects in October and November to significant tropospheric effects in December and January. The results highlight the importance of stratospheric circulation changes for the troposphere. Together with the poleward‐downward movement of zonal wind anomalies and enhanced equatorward planetary wave propagation, an AO‐like pattern develops in the troposphere in December and January during solar maximum. In the middle of November, one third of eddy‐forced tropospheric mean meridional circulation and surface pressure tendency changes can be attributed to the stratosphere, whereas most of the polar surface pressure tendency changes from the end of November through the middle of December are related to tropospheric mechanical forcing changes. The weakening of the Brewer‐Dobson circulation during solar maximum leads to dynamical heating in the tropical lower stratosphere, inducing circulation changes in the tropical troposphere and down to the surface that are strongest in January. The simulated tropospheric effects are identified as indirect effects from the stratosphere because the sea surface temperatures are identical in the solar maximum and minimum experiment. These results confirm those from other simplified model studies as well as results from observations.
Seasonal and interannual variations of carbon and oxygen isotopes of respired CO2 in a tallgrass prairie: Measurements and modeling results from 3 years with contrasting water availability
Authors: Lai Chun‐Ta , Riley William , Owensby Clenton , Ham Jay , Schauer Andrew , Ehleringer James R.
Published: March 2006

We made weekly measurements of carbon (δ13C) and oxygen (δ18O) isotopes of atmospheric CO2 in a C3/C4 tallgrass prairie during the growing season for 3 years with contrasting soil moisture conditions. Air samples above and within canopies were collected using 100‐ml flasks at night to characterize isotopic composition of ecosystem respiration. We used a two‐source mixing line (Keeling plot) approach to estimate isotope ratios of ecosystem respired CO2 for both carbon (δ13CR) and oxygen (δ18OR). Measured net ecosystem CO2 exchange (NEE) showed the largest net carbon uptake in 2004, followed by 2003 and 2002. This interannual difference in NEE strongly depends on the amount and distribution of precipitation received by this tallgrass prairie. Precipitation also affects the timing of the seasonal transition from C3 dominance in spring to C4 dominance in summer. Variations of δ13CR showed that C4 plants dominated ecosystem respiration in 2003 and 2004, except in early spring when C3 plants were more active. In contrast, contributions of C3 plants were relatively higher for an extended period in the summer of 2002, when a severe drought occurred. Typically, C3 forbs extract water and nutrients from soil layers below that of the C4 grasses and remain photosynthetically active in periods when C4 grasses have water stress that limits photosynthesis. Drought‐reduced C4 grass photosynthesis was lower than temperature‐limited C3 forb growth during this period. We used an integrated isotope land surface model (ISOLSM) to simulate (and compare to measurements) net CO2 fluxes, δ18O values of leaf and soil water, and δ18O values of aboveground and soil respiration. The Keeling plot analysis becomes less reliable for estimating δ18OR values when the surface soil is dry. We suspect this is due to low CO2 production in the soil when water is limiting, in which case the invasion (abiotic) effect is more significant. ISOLSM reasonably captured seasonal variations of measured δ18OR in all 3 years, indicating the model's consistency of predicting δ18OR in different soil water conditions. Model simulations also showed that nighttime δ18O values of aboveground respiration were variable, often becoming very positive in water‐stressed conditions primarily because of the low relative humidity and resultant elevated δ18O values of leaf water.
Lack of ceramide generation and altered sphingolipid composition are associated with drug resistance in human ovarian carcinoma cells
Authors: Prinetti Alessandro , Millimaggi Danilo , D'Ascenzo Sandra , Clarkson Matilda , Bettiga Arianna , Chigorno Vanna , Sonnino Sandro , Pavan Antonio , Dolo Vincenza
Published: March 2006

PTX (Paclitaxel®) is an antimitotic agent used in the treatment of a number of major solid tumours, particularly in breast and ovarian cancer. This study was undertaken to gain insight into the molecular alterations producing PTX resistance in ovarian cancer. PTX treatment is able to induce apoptosis in the human ovarian carcinoma cell line, CABA I. PTX-induced apoptosis in CABA I cells was accompanied by an increase in the cellular Cer (ceramide) levels and a decrease in the sphingomyelin levels, due to the activation of sphingomyelinases. The inhibition of acid sphingomyelinase decreased PTX-induced apoptosis. Under the same experimental conditions, PTX had no effect on Cer and sphingomyelin levels in the stable PTX-resistant ovarian carcinoma cell line, CABA-PTX.

The acquisition of the PTX-resistant phenotype is accompanied by unique alterations in the complex sphingolipid pattern found on lipid extraction. In the drug-resistant cell line, the levels of sphingomyelin and neutral glycosphingolipids were unchanged compared with the drug-sensitive cell line. The ganglioside pattern in CABA I cells is more complex compared with that of CABA-PTX cells. Specifically, we found that the total ganglioside content in CABA-PTX cells was approximately half of that in CABA I cells, and GM3 ganglioside content was remarkably higher in the drug-resistant cell line.

Taken together our findings indicate that: i) Cer generated by acid sphingomyelinase is involved in PTX-induced apoptosis in ovarian carcinoma cells, and PTX-resistant cells are characterized by their lack of increased Cer upon drug treatment, ii) PTX resistance might be correlated with an alteration in metabolic Cer patterns specifically affecting cellular ganglioside composition.
Bile acids alter the subcellular localization of CNT2 (concentrative nucleoside cotransporter) and increase CNT2-related transport activity in liver parenchymal cells
Authors: Fernández-Veledo Sonia , Huber-Ruano Isabel , Aymerich Ivette , Duflot Sylvie , Casado F. Javier , Pastor-Anglada Marçal
Published: March 2006

CNT2 (concentrative nucleoside cotransporter) is a plasma membrane high-affinity Na+-coupled adenosine transporter, also localized in intracellular structures. This transporter protein may play additional roles other than nucleoside salvage, since it has recently been shown to be under purinergic control via KATP channels, by a mechanism that does not seem to involve changes in its subcellular localization. In an attempt to identify the agents that promote CNT2 trafficking, bile acids were found to increase CNT2-related transport activity in a KATP channel-independent manner in both Fao hepatoma and rat liver parenchymal cells. A maximum effect was recorded after treatment with hydrophilic anions such as TCA (taurocholate). However, this effect did not involve changes in the amount of CNT2 protein, it was instead associated with a subcellular redistribution of CNT2, resulting in an accumulation of the transporter at the plasma membrane. This was deduced from subcellular fractionation studies, biotinylation of plasma membrane proteins and subsequent CNT2 detection in streptavidin precipitates and in vivo confocal microscopic analysis of the distribution of a YFP (yellow fluorescent protein)–CNT2 construct. The induction of CNT2 translocation, triggered by TCA, was inhibited by wortmannin, dibutyryl-AMPc, PD98059 and colchicine, thus suggesting the involvement of the PI3K/ERK (phosphoinositide 3-kinase/extracellular-signal related kinase) pathway in microtubule-dependent activation of recombinant CNT2. These are novel effects of bile-acid physiology and provide the first evidence for short-term regulation of CNT2 translocation into and from the plasma membrane.
Bcl-2 overexpression prevents calcium overload and subsequent apoptosis in dystrophic myotubes
Authors: Basset Olivier , Boittin François-Xavier , Cognard Christian , Constantin Bruno , Ruegg Urs T.
Published: March 2006

Duchenne muscular dystrophy (DMD) is a lethal disease caused by the lack of the cytoskeletal protein dystrophin. Altered calcium homoeostasis and increased calcium concentrations in dystrophic fibres may be responsible for the degeneration of muscle occurring in DMD. In the present study, we used subsarcolemmal- and mitochondrial-targeted aequorin to study the effect of the antiapoptotic Bcl-2 protein overexpression on carbachol-induced near-plasma membrane and mitochondrial calcium responses in myotubes derived from control C57 and dystrophic (mdx) mice. We show that Bcl-2 overexpression decreases subsarcolemmal and mitochondrial calcium overload that occurs during activation of nicotinic acetylcholine receptors in dystrophic myotubes. Moreover, our results suggest that overexpressed Bcl-2 protein may prevent near-plasma membrane and mitochondrial calcium overload by inhibiting IP3Rs (inositol 1,4,5-trisphosphate receptors), which we have shown previously to be involved in abnormal calcium homoeostasis in dystrophic myotubes. Most likely as a consequence, the inhibition of IP3R function by Bcl-2 also inhibits calcium-dependent apoptosis in these cells.