bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationship between δ18O and minor element composition of Terebratalia transversa
Authors: Cusack Maggie , Parkinson David , Pérez-Huerta Alberto , England Jennifer , Curry Gordon B. , Fallick Anthony E.
Published: August 2008

With their extensive fossil record and shells of stable low-Mg calcite, rhynchonelliform brachiopods are attractive sources of climate information via seawater temperature proxies such as stable oxygen isotope composition. In Terebratalia transversa (Sowerby) there is a progression towards oxygen isotope equilibrium in the calcite of the innermost secondary layer. This study confirms the lack of any vital effects influencing oxygen isotope composition of T. transversa, even in specialised areas of the innermost secondary layer. Calcite Mg/Ca ratio is another potential seawater temperature proxy, that has the advantage of not being influenced by salinity. Mg concentrations measured by electron microprobe analyses indicate that there is no concomitant decrease in Mg concentration towards the inner secondary layer, associated with the progressive shift towards oxygen isotope equilibrium. Mg distribution is heterogeneous throughout the shell and correlates with that of sulphur, which may be a proxy for organic components, suggesting that some of the Mg may not be in the calcite lattice. It is essential therefore, to determine the chemical environment of the magnesium ions to avoid any erroneous temperature extrapolations in brachiopods or any other calcite biomineral.
Venous thromboembolism: Contemporary diagnostic and therapeutic aspects
Authors: Bounameaux  , Righini  , Perrier
Published: August 2008

To discuss new features that were published during the past few years on diagnosis and treatment of venous thromboembolism (VTE). Progress has been made in assessing clinical probability of pulmonary embolism (PE), in addressing the particular aspects of PE diagnosis in the elderly, in evaluating the diagnostic performance of single- and multi-detector row helical computed tomography (hCT), and in looking at the role of D-dimer measurement and lower limb venous compression ultrasonography in the diagnostic work-up of PE. New therapeutic options have also been proposed. Diagnosing VTE depends upon several, mainly non-invasive diagnostic tools that must be used sequentially, depending on the clinical situation and the local expertise. In the vast majority of patients, a noninvasive work-up is feasible and the diagnostic algorithms are becoming simpler. We focused on new developments of clinical probability assessment, PE in the elderly, potential new uses of D-dimer measurement, advent of multidetector row helical computed tomography and utility of ultrasonography to detect deep vein thrombosis in PE suspected patients. Treatment of acute venous thromboembolism consists of parenteral administration of heparin (usually low-molecular-weight heparin or, more recently, fondaparinux) overlapped and followed by oral vitamin K antagonists that will be administered for a certain period of time (usually 3 to 12 months), depending upon the estimated risks of recurrence and bleeding in each individual patient. Contemporary features include the controversial possibility of reducing the intensity of oral anticoagulant treatment (INR 1.5–2) after an initial full-intensity treatment (INR 2–3) period of 3 to 12 months, and the emergence of new anticoagulant drugs such as direct oral synthetic inhibitors of thrombin or factor Xa.
Distribution pattern of infrageniculate arterial obstructions in patients with diabetes mellitus and renal insufficiency – implications for revascularization
Authors: Diehm  , Rohrer  , Baumgartner  , Keo  , Do  , Kalka
Published: August 2008

Background: Diabetes mellitus (DM) and renal insufficiency (RI) were shown to be associated with an obstructive lesion pattern favouring distal lower limb arterial segments in patients with peripheral arterial disease (PAD). We hypothesized that presence of DM is associated with pronounced involvement of the tibioperoneal arteries, whereas RI predominantly affects the pedal arch. Patients and methods: A consecutive series of PAD patients (mean age 75 ± 10 years, 40 women) with RI alone (n = 15), RI and DM (n = 25), DM alone (n = 25) and without RI or DM (n = 25) underwent diagnostic angiography. We analyzed the obstructive burden of different segments of the infrageniculate arterial tree using the Bollinger score as well as accessibility of pedal arteries for bypass surgery. Results: In patients with DM and in patients with RI the mean total obstructive burden was higher in pedal as compared to tibioperoneal arteries (9.79 ± 4.60 vs. 6.99 ± 3.45, p = 0.03;10.50 ± 5.53 vs. 6.88 ± 4.12, p = 0.05, respectively). However, rates of patency of at least one pedal artery were significantly lower in patients with RI and RI/DM as compared to controls (47% and 48% vs. 80%, respectively; p = 0.007), whereas patency was comparable between patients with diabetes alone and controls (72% vs. 80%, ns). Rates of viability of pedal arteries as an attachment site for distal bypass was 80%, 68%, 47% and 44% in controls, patients with DM alone, RI alone and RI/DM, respectively (p = 0.0042). Conclusions: In contrast to previous anecdotal observations, both DM and RI are associated with a high atherosclerotic burden of the pedal arch in the present angiographic series. The presence of RI, however, is associated with a lower patency of the pedal arch as compared to the presence of DM alone, and more than fifty percent patients are unsuitable for distal bypass grafting.
Endoscopic mucosal resection for recurrent gastric antral vascular ectasia
Authors: Katsinelos  , Chatzimavroudis  , Katsinelos  , Panagiotopoulou  , Kotakidou  , Tsolkas  , Triantafillidis  , Papaziogas
Published: August 2008

Gastric antral vascular ectasia (GAVE) is an overt or occult source of gastrointestinal bleeding. Despite several therapeutic approaches have been successfully tested for preventing chronic bleeding, some patients present recurrence of GAVE lesions. To the best of our knowledge, we report the first case, of a 86-year-old woman who presented severe iron-deficiency anemia due to GAVE and showed recurrence of GAVE lesion despite the intensive argon plasma coagulation treatment. We performed endoscopic mucosal resection of bleeding GAVE with resolution of anemia.
Median sternotomy for an unexpected complication of permanent hemodialysis catheters: "stuck catheter"
Authors: Akgun  , Ak  , Tugrular  , Civelek  , Isbir  , Arsan
Published: August 2008

Cuffed tunneled venous access catheters are commonly used for temporary and permanent access in patients undergoing hemodialysis. These catheters play an essential role in providing permanent access in patients in whom all other access options have been exhausted. However, they are prone to several complications like catheter thrombosis, catheter fibrin sheating and infection. Herein, we report two uncommon cases of stuck hemodialysis cuffed tunneled catheters causing stenosis and thrombosis in central veins which needed to be removed by median sternotomy.
An investigation of GSWP‐2 Mississippi River basin surface water and energy budgets
Authors: Feng Xia , Houser Paul
Published: August 2008

This paper demonstrates the usefulness of watershed‐scale surface water and energy budget analysis for evaluating model skill and deficiencies. Mississippi river basin land surface model water and energy budget simulations from the Second Global Soil Wetness Project (GSWP‐2) are compared with available observations from 1986 to 1995. Forced by the same meteorological parameters, the evaluated GSWP‐2 land surface models (SSiB, Noah and CLM2‐TOP) exhibit similarities and differences in depicting basin averaged water and energy balance components. The CLM2‐TOP evaporation approaches the reanalysis and runoff is closer to the gauge measurement, while the Noah model's evaporation is underestimated and the corresponding runoff is overestimated, which could be related to the limitation in the parameterization of turbulent flux and infiltration process. The energy components of the three land surface models have a similar seasonal cycle but with different magnitudes. Despite the seasonal differences, the interannual variations of water and energy budget components are comparable and correlated. Overall, the more complex CLM2‐TOP model outperforms the SSiB and Noah models in reproducing watershed‐scale seasonal and interannual water and energy variations. All three models consistently reveal that the most extreme hydrological events are associated with El Niño‐Southern Oscillation (ENSO) phases. However, the relationship of surface water components to ENSO varies geographically. For future studies, land‐atmosphere coupled processes need to be included to determine the ability of land surface models to represent surface water and energy processes.
Development of a statistical downscaling model for projecting monthly rainfall over East Asia from a general circulation model output
Authors: Paul Sahana , Liu C. M. , Chen J. M. , Lin S. H.
Published: August 2008

The objective of this paper is to describe a statistical downscaling model based on established links between large scale variables from a general circulation model (GCM) and regional rainfall to project climate change over East Asia in the 21st century. We develop a SVD (singular value decomposition)‐based regression model to downscale the GCM data. In order to establish a link between monthly regional precipitation and large scale variable (mean sea level pressure, 10 m wind speed, or 2 m temperature), we used the IS92a scenario data of ECHAM4/OPCY3 and the data from the Climate Research Unit from 1901 to 1990. In the 20th century, their connections have remained unchanged over time for all seasons. The continuity of these relationships to the next century is tested by checking the similarity in the main SVD modes of predictors and the empirical orthogonal functions of predictors throughout the 20th and 21st century. Furthermore, comparing the SVD‐downscaled and ECHAM4‐projected changes of precipitation in the 2090s with respect to the 1990s reveals similar patterns over most areas with much more detailed regional characteristics, although the magnitude of change is not compatible. In all, the annual rainfall over East Asia is projected to increase over northern China and the Indochina peninsula and to decrease over the coast of southern China by the end of the 21st century.
Parameterization of cloud droplet activation using a simplified treatment of the aerosol number size distribution
Authors: Kivekäs Niku , Kerminen Veli‐Matti , Anttila Tatu , Korhonen Hannele , Lihavainen Heikki , Komppula Mika , Kulmala Markku
Published: August 2008

The number‐to‐volume concentration ratio, R, defined as the number concentration of particles larger than a certain cut‐off diameter divided by the total particle volume concentration, can be used for expressing aerosol number size distributions in a simplified way. Earlier studies have shown that R shows less variability than random size distributions would produce. In this article the parameter R was used to develop a new parameterization for estimating the cloud droplet number concentration (CDNC). The parameterization is a function of four input parameters: the total submicron volume concentration (Vtot), number‐to‐volume concentration ratio with a 0.1‐μm cut‐off diameter (R(0.1 μm)), soluble fraction of the particle volume (ɛ) and air updraft velocity (vup). The parameterization was derived by finding the best fit to a series of simulations made with an adiabatic air parcel model simulating cloud droplet activation, and the model input parameters were varied over a range typical for northern European background air. Results from the parameterization were compared with cloud droplet concentrations measured in Northern Finland, and a good agreement was found. The new parameterization demonstrates that if the value of R(0.1 μm) can be estimated or parameterized without knowing the whole particle number size distribution, cloud droplet number concentrations can be estimated relatively accurately by using only the four parameters mentioned above. This would reduce significantly the computer resources needed for calculating CDNC in large‐scale atmospheric models.
Estimating ice content and extinction in precipitating cloud systems from CloudSat radar measurements
Authors: Matrosov Sergey Y. , Heymsfield Andrew J.
Published: August 2008

Relations between W band radar reflectivity and ice cloud water content and visible extinction coefficient are developed using a large microphysical data set. These relations are specifically tuned for CloudSat radar to derive ice content and optical thickness of ice parts of precipitating systems where other types of measurements have limitations. Accounting for nonsphericity is essential for larger particles, which produce higher reflectivities (Ze > 0 dBZ) and often dominate ice content of precipitating clouds. Typical values of median sizes in such clouds are about 1–2 mm, and they vary modestly. The modest particle size variability and strong non‐Rayleigh scattering reduce data scatter in the derived relations and increase an exponent in best fit power law approximations for ice water content–reflectivity and extinction‐reflectivity relations. The data scatter for high‐reflectivity clouds is smaller than for low‐reflectivity nonprecipitating clouds. It is about 33% for the reflectivity‐ice water content relation, and it is about 50% for the reflectivity‐extinction relation. For higher reflectivities, the temperature dependence of the ice water content‐reflectivity relations is not very distinct, and uncertainties due to temperature variations are not expected to be high compared to possible errors due to particle shape variability. Uncertainties in particle aspect ratio, mass‐size relation assumptions, and underrepresentation of smaller particles in samples can produce additional retrieval errors, so cloud ice content estimates can have uncertainties of about 50%, and extinction estimates can have uncertainties as large as a factor of 2.
Sensitivity of the simulated East Asian summer monsoon climatology to four convective parameterization schemes
Authors: Kang Hyun‐Suk , Hong Song‐You
Published: August 2008

This study attempts to clarify the effects of parameterized convection on a simulated East Asian summer monsoon climatology from 1997 to 2006 within a regional climate model (RCM) framework. Four different convective parameterized schemes (CPSs) were chosen in the National Centers for the Environmental Prediction regional spectral model, the Simplified Arakawa‐Schubert (SAS), Relaxed Arakawa‐Schubert (RAS), NCAR Community Climate Model version 3 (CCM), and new Kain‐Fritsch (KF2) schemes. On the whole, there is no single scheme that outperforms the other in all aspects of the simulated climatology. The results show that the SAS and KF2 schemes are capable of reproducing the 10‐year June–July–August climatology with a certain wet bias over land and dry bias over the oceans. The SAS scheme is capable of resolving the interannual variations of the monsoon precipitation, and the KF2 is able to capture the intraseasonal variation. The RAS scheme significantly reduces precipitation over land compared to other schemes, but interannual variabilities are reasonably reproduced. On the contrary, the CCM scheme significantly overestimates the precipitation over land as well as ocean. Discernable differences among four CPSs are found in the distribution of the spatial spectrum, in which the KF2 scheme is the most effective in adding regional details to an external large‐scale forcing. The feasibility of a physics ensemble using different convection schemes and the impacts of domain size are also discussed.
Geologic, structural, and thermochronologic constraints on the tectonic evolution of the Sierra Mazatán core complex, Sonora, Mexico: New insights into metamorphic core complex formation
Authors: Wong Martin S. , Gans Phillip B.
Published: August 2008

The Sierra Mazatán in northwestern Mexico is the southernmost metamorphic core complex in the North American Cordillera. Large‐magnitude Tertiary extension at Sierra Mazatán involved both ductile and brittle slip along a major normal fault that presently dips 10°–15° west. Extension was polyphase and involved an early period of extension from 25 to 23 Ma followed by major slip from 21 to 16 Ma. Total slip was ≤20 km and occurred at rates of 3–4 mm/a. This extension predated the plate boundary change to transtension at ∼12 Ma and was largely decoupled from relative Pacific–North American plate motion. Numerous lines of evidence suggest that the presently low‐angle normal fault initiated at a steep dip (50°–60°) and was rotated to lower angles during slip. When corrected for this tilting, fault corrugations at Sierra Mazatán had a similar geometry to the segmentation of many active normal faults, which is compatible with their origin as primary fault features. Many aspects of the Sierra Mazatán are comparable to large active normal faults, indicating that this core complex formed owing to prolonged extension on an otherwise typical high‐angle normal fault. Therefore, core complexes need not represent a fundamentally unique mode of crustal extension.
An analysis of nonpayment of water services in Nuevo Laredo, Mexico
Authors: Aguilar‐Benitez Ismael , Saphores Jean‐Daniel
Published: August 2008

In many developing and developed cities, nonpayment for water services undermines the financial health of water utilities; in poorer areas, it also hinders the water utilities' ability to serve poor households. However, nonpayment has not received much attention in the literature so far. In this paper, we analyze nonpayment for a unique data set of households from Nuevo Laredo, Mexico. Our fieldwork and basic statistics indicate that nonpayment is very common and affects both poor and affluent households, so ability to pay may only partly explain nonpayment. Using panel data models to control for unobserved household characteristics (to avoid omitted variable bias) and after accounting for monthly effects, we find that long‐term delinquent households consume ∼3% more water than do other families; this number is larger for households who are retired and affluent, which further compounds the adverse consequences of nonpayment.
Evaluating catchment‐scale hydrological modeling by means of terrestrial gravity observations
Authors: Hasan Shaakeel , Troch Peter A. , Bogaart Patrick W. , Kroner Corinna
Published: August 2008

In a previous study (Hasan et al., 2006) we applied time series analysis and distributed hydrological modeling techniques to investigate the effect of hydrological processes on observed terrestrial gravity residuals. In this study we apply terrestrial gravity observations (measured in one location) to constrain simple hydrological models in a catchment around the gravimeter. A superconducting gravimeter observes with high frequency (1 Hz) the temporal variations in the gravity field with high accuracy (sub nm s−2 for hourly variation) near Moxa, Germany since 1999. Hourly gravity residuals are derived by filtering and reducing for Earth tides, polar motion, barometric pressure variations, and instrumental drift. These gravity residuals show significant response to hydrological processes (precipitation, evaporation, surface and subsurface flow) in the catchment surrounding the observatory. We can thus consider the observed gravity change as an integrator of catchment‐scale hydrological response (similar in nature as discharge measurements), and therefore use it to constrain catchment‐scale hydrologic models. We test a set of simple water balance models against measured discharge, and employ observed gravity residuals to evaluate model parameters. Results indicate that a lumped water balance model for unsaturated storage and fluxes, coupled with a semidistributed hydraulic groundwater model for saturated storage and fluxes, successfully reproduces both gravity and discharge dynamics.
Bayesian modeling of the assimilative capacity component of nutrient total maximum daily loads
Authors: Faulkner B. R.
Published: August 2008

Implementing stream restoration techniques and best management practices to reduce nonpoint source nutrients implies enhancement of the assimilative capacity for the stream system. In this paper, a Bayesian method for evaluating this component of a total maximum daily load (TMDL) load capacity is developed and applied. The joint distribution of nutrient retention metrics from a literature review of 495 measurements was used for Monte Carlo sampling with a process transfer function for nutrient attenuation. Using the resulting histograms of nutrient retention, reference prior distributions were developed for sites in which some of the metrics contributing to the transfer function were measured. Contributing metrics for the prior include stream discharge, cross‐sectional area, fraction of storage volume to free stream volume, denitrification rate constant, storage zone mass transfer rate, dispersion coefficient, and others. Confidence of compliance (CC) that any given level of nutrient retention has been achieved is also determined using this approach. The shape of the CC curve is dependent on the metrics measured and serves in part as a measure of the information provided by the metrics to predict nutrient retention. It is also a direct measurement, with a margin of safety, of the fraction of export load that can be reduced through changing retention metrics. For an impaired stream in western Oklahoma, a combination of prior information and measurement of nutrient attenuation was used to illustrate the proposed approach. This method may be considered for TMDL implementation.
Density‐driven exchange flow between open water and an aquatic canopy
Authors: Zhang Xueyan , Nepf Heidi M.
Published: August 2008

Differences in water density can drive an exchange flow between the vegetated and open regions of surface water systems. A laboratory experiment has been conducted to investigate this exchange flow, using a random array of rigid, emergent cylinders to represent the canopy region. The flow pattern was captured using a CCD camera. The velocity of the current entering the canopy and the volume discharge both decrease with increasing vegetative drag and also decrease gradually over time. Theoretical predictions for velocity and discharge rate are developed and verified with experimental observations. Extensions to field conditions are also discussed.
Memory effects induced by dependence on initial conditions and ergodicity of transport in heterogeneous media
Authors: Suciu N. , Vamoş C. , Vereecken H. , Sabelfeld K. , Knabner P.
Published: August 2008

For transport in statistically homogeneous random velocity fields with properties that are routinely assumed in stochastic groundwater models, the one‐particle dispersion (i.e., second central moment of the ensemble average concentration for a point source) is a “memory‐free” quantity independent of initial conditions. Nonergodic behavior of large initial plumes, as manifest in deviations of actual solute dispersion from one‐particle dispersion, is associated with a “memory term” consisting of correlations between initial positions and displacements of solute molecules. Reliable numerical experiments show that increasing the source dimensions has two opposite effects: it reduces the uncertainty related to the randomness of center of mass, but, at the same time, it yields large memory terms. The memory effects increase with the source dimension and depend on its shape and orientation. Large narrow sources oriented transverse to the mean flow direction yield ergodic behavior with respect to the one‐particle dispersion of the longitudinal dispersion and nonergodic behavior of the transverse dispersion, whereas for large longitudinal sources, the longitudinal dispersion behaves nonergodically, and the transverse dispersion behaves ergodically. Such memory effects are significantly large over hundreds of heterogeneity scales and should therefore be considered in practical applications, for instance, calibration of model parameters, forecasting, and identification of the contaminant source.
New Gravity Field for the Arctic
Authors: Kenyon Steve , Forsberg Rene , Coakley Bernard
Published: August 2008

The study of the Arctic Ocean has been hampered by incomplete basic knowledge of the basin and its structure. An improved gravity anomaly map (Figure 1) and grid have been developed that complement the new International Chart of the Arctic Ocean [Jakobsson et al., 2008]. This article announces the availability of the Arctic Gravity Project (ArcGP) grid version 2.0 and discusses the genesis of the project.
Community Modeling in Hydrologic Science: Scoping Workshop on a Community Hydrologic Modeling Platform (CHyMP); Washington, D.C., 26–27 March 2008
Authors: Famiglietti James , Murdoch Larry , Lakshmi Venkat , Hooper Rick
Published: August 2008

As one of two major new initiatives for its next 5‐year phase, the Consortium of Universities for the Advancement of Hydrologic Science, Inc. (CUAHSI), is proposing to launch a major effort toward the development of a Community Hydrologic Modeling Platform (CHyMP), which will support a range of research and applications in water cycle science.
Parker Lecturers Gather at Joint Assembly
Authors: Crooker Nancy
Published: August 2008

Present and past Parker Lecturers, who are Bowie Lecturers of AGU's Space Physics and Aeronomy (SPA) section, gathered at the Joint Assembly in Fort Lauderdale, Fla., on the occasion of the fiftieth anniversary of the publication of Eugene Parker's famous paper predicting the existence of the supersonic solar wind (see Figure 1).
AMSSpin: A LabVIEW program for measuring the anisotropy of magnetic susceptibility with the Kappabridge KLY‐4S
Authors: Gee Jeffrey S. , Tauxe Lisa , Constable Cathy
Published: August 2008

Anisotropy of magnetic susceptibility (AMS) data are widely used as a petrofabric tool because the technique is rapid and nondestructive and because static measurement systems are capable of determining small degrees of anisotropy. The Kappabridge KLY‐4S provides high resolution as a result of the large number of measurements acquired while rotating the sample about three orthogonal axes. Here we describe a graphical‐based program called AMSSpin for acquiring AMS data with this instrument as well as a modified specimen holder that should further enhance the utility of this instrument. We also outline a method for analysis of the data (that differs in several ways from that of the software supplied with the instrument) and demonstrate that the measurement errors are suitable for using linear perturbation analysis to statistically characterize the results. Differences in the susceptibility tensors determined by our new program and the SUFAR program supplied with the instrument are small, typically less than or comparable to deviations between multiple measurements of the same specimen.
Depth‐shifting cores incompletely recovered from the upper oceanic crust, IODP Hole 1256D
Authors: Gilbert Lisa A. , Burke Andrea
Published: August 2008

Seafloor drilling operations, especially those in crustal rocks, yield incomplete recovery of drilled sections, and depths of the recovered core pieces are assigned with some uncertainty. Here we present a new depth‐shifting method that is simple and rapid, requires little subjective input, and is applicable to any core‐log integration problem where sufficient comparable data have been collected in both the open hole and from the recovered core. Over the depth range for which both core and log data have been collected, an automatic algorithm selected the best new depth for each piece. The criteria for determining the best depth were as follows: (1) find new depths for as many pieces as possible, and (2) minimize the difference between core density and log density. In this study, depth‐shifting is applied at Integrated Ocean Drilling Program (IODP) Hole 1256D, which is our first opportunity to study a section of intact, in situ upper ocean crust drilled down to gabbro. The new depths significantly improve the agreement between an independent data set and the logging record.
Short‐term variability of the Mediterranean in‐ and out‐flows
Authors: Millot Claude
Published: August 2008

A re‐analysis of CTD profiles collected in the Strait of Gibraltar during the 1985‐1986 Gibraltar Experiment shows that a large variability can occur, within a 10‐day interval, in the nature of the Atlantic Water found in the sill surroundings and expected to flow into the Mediterranean Sea, and in the set of Mediterranean Waters outflowing from the sea. Since both strongly mix together within the strait, the outflow in the Atlantic Ocean can display a tremendous short‐term variability mainly due to the variability of the inflow. Specifying any nominal characteristic for the outflow all its way downstream, a fortiori any nominal characteristic for the various veins into which it is split, thus needs monitoring the whole water column within the strait.
Effect of meteor ionization on sporadic‐E observed at Jicamarca
Authors: Malhotra Akshay , Mathews John D. , Urbina Julio
Published: August 2008

Relatively little progress has been made in the study of equatorial Sporadic‐E when compared to the study of mid‐latitude Sporadic‐E. Indeed, it is unclear if Sporadic‐E has been observed at all near the geomagnetic equator using any technique other than the ionosonde. In particular, there have been no reports of Sporadic‐E observed using the Jicamarca Radio Observatory (JRO) 50 MHz radar. The overwhelming—in SNR terms—presence of the nearly ubiquitous Equatorial Electrojet (EEJ) is the likely reason Sporadic‐E has not been reported at JRO as well as at other similar radars near the geomagnetic equator. We present here what we believe to be the first Sporadic‐E (defined here as altitude‐narrow E‐region layers that last tens of minutes) observations from JRO. The structure and characteristics of these equatorial Sporadic‐E layers is compared with their mid‐latitude counterparts. We also demonstrate the immediate effect of meteor‐produced ionization on the formation and evolution of the equatorial Sporadic‐E layers.
An analysis of sudden impulses at geosynchronous orbit
Authors: Villante U. , Piersanti M.
Published: August 2008

An analysis of sudden impulses (SI) at geosynchronous orbit (2000–2004) confirms a general dependence of the SI amplitude on the variation of the square root of the solar wind pressure, together with an explicit LT dependence, with greater responses at satellites located closer to noon meridian. In the dayside hemisphere the magnetospheric response, which mostly influences the Bz component, is well consistent with the magnetic field jump expected for changes of the magnetopause current alone, driven by changes of the solar wind pressure. In the dark hemisphere, where the changes of the Bx component are often relevant, the competing contributions of several current systems (from the magnetopause, cross‐tail current, ring current, Birkeland current) determine a large variety of responses that cannot be interpreted in a statistical sense. Depending on the solar wind conditions, different situations emerge for nightside events. We present a case in which a remarkable magnetospheric compression determined field variations which can be interpreted in terms of a strongly dominant contribution of the magnetopause current even in the midnight sector, while in other cases the observed features are consistent with the predictions of the global current system. We also speculated that additional elements (such as the geocentric distance of the hinging point, the separation point between closed and open field lines in the geomagnetic tail) might play a crucial role in determining the aspects of the magnetospheric response. The correspondence between model predictions and observations persists even in cases of moderate Southward orientations of the IMF.
Ecohydrological model of flow duration curves and annual minima
Authors: Botter Gianluca , Zanardo Stefano , Porporato Amilcare , Rodriguez‐Iturbe Ignacio , Rinaldo Andrea
Published: August 2008

To address streamflow variability in river basins, Botter et al. (2007a) recently provided an analytical solution for the seasonal probability distribution function of daily streamflows on the basis of a stochastic description of soil moisture dynamics at basin scales. In this paper the above model is extended to the annual timescale to derive analytical expressions for the long‐term flow duration curve on the basis of a few climatic, ecohydrologic, and geomorphic parameters of the basin. A novel analytical expression for the cumulative probability distribution of the annual minima is also derived from the “troughs under threshold” theory. The expressions derived provide a physically based linkage between flow duration curves and the distribution of annual minima through geomorphic, climatic, and ecological features of the basin. Our theoretical results prove in good agreement with observational streamflow data in a 50 km2 vegetated basin located in North Carolina (USA), suggesting that the model developed may represent a valid tool for estimating low‐flow statistics in gauged and ungauged basins.
Molecular mimicry between IL‐33 and KSHV for attachment to chromatin through the H2A–H2B acidic pocket
Authors: Roussel Lucie , Erard Monique , Cayrol Corinne , Girard Jean‐Philippe
Published: August 2008

Interleukin‐33 (IL‐33) is an IL‐1‐like ligand for the ST2 receptor that stimulates the production of Th2‐associated cytokines. Recently, we showed that IL‐33 is a chromatin‐associated factor in the nucleus of endothelial cells in vivo. Here, we report the identification of a short IL‐33 chromatin‐binding peptide that shares striking similarities with a motif found in Kaposi sarcoma herpesvirus LANA (latency‐associated nuclear antigen), which is responsible for the attachment of viral genomes to mitotic chromosomes. Similar to LANA, the IL‐33 peptide docks into the acidic pocket formed by the H2A–H2B dimer at the nucleosomal surface and regulates chromatin compaction by promoting nucleosome–nucleosome interactions. Taken together, our data provide important new insights into the nuclear roles of IL‐33, and show a unique example of molecular mimicry of a chromatin‐associated cytokine by a DNA tumour virus. In addition, the data provide, to the best of our knowledge, the first demonstration of the existence of non‐histone cellular factors that bind to the acidic pocket of the nucleosome.
Control of DNA polymerase λ stability by phosphorylation and ubiquitination during the cell cycle
Authors: Wimmer Ursula , Ferrari Elena , Hunziker Peter , Hübscher Ulrich
Published: August 2008

DNA polymerase (Pol) λ is a DNA repair enzyme involved in base excision repair, non‐homologous end joining and translesion synthesis. Recently, we identified Pol λ as an interaction partner of cyclin‐dependent kinase 2 (CDK2) that is central to the cell cycle G1/S transition and S‐phase progression. This interaction leads to in vitro phosphorylation of Pol λ, and its in vivo phosphorylation pattern during cell cycle progression mimics the modulation of CDK2/cyclin A. Here, we identify several phosphorylation sites of Pol λ. Experiments with phosphorylation‐defective mutants suggest that phosphorylation of Thr 553 is important for maintaining Pol λ stability, as it is targeted to the proteasomal degradation pathway through ubiquitination unless this residue is phosphorylated. In particular, Pol λ is stabilized during cell cycle progression in the late S and G2 phases. This most likely allows Pol λ to correctly conduct repair of damaged DNA during and after S phase.
Do in vivo Experimental Models Reflect Human Cerebral Small Vessel Disease? a Systematic Review
Authors: Hainsworth Atticus H , Markus Hugh S
Published: August 2008

Cerebral small vessel disease (SVD) is a major cause of stroke and dementia. Pathologically, three lesions are seen: small vessel arteriopathy, lacunar infarction, and diffuse white matter injury (leukoaraiosis). Appropriate experimental models would aid in understanding these pathologic states and also in preclinical testing of therapies. The objective was to perform a systematic review of animal models of SVD and determine whether these resemble four key clinicopathologic features: (1) small, discrete infarcts; (2) small vessel arteriopathy; (3) diffuse white matter damage; (4) cognitive impairment. Fifteen different models were included, under four categories: (1) embolic injuries (injected blood clot, photochemical, detergent-evoked); (2) hypoperfusion/ischaemic injury (bilateral common carotid occlusion/stenosis, striatal endothelin-1 injection, striatal mitotoxin 3-NPA); (3) hypertension-based injuries (surgical narrowing of the aorta, or genetic mutations, usually in the renin-angiotensin system); (4) blood vessel damage (injected proteases, endothelium-targeting viral infection, or genetic mutations affecting vessel walls). Chronic hypertensive models resembled most key features of SVD, and shared the major risk factors of hypertension and age with human SVD. The most-used model was the stroke-prone spontaneously hypertensive rat (SHR-SP). No model described all features of the human disease. The optimal choice of model depends on the aspect of pathophysiology being studied.
Left ventricular systolic and diastolic dyssynchrony in coronary artery disease with preserved ejection fraction
Authors: Lee Pui-Wai , Zhang Qing , Yip Gabriel Wai-Kwok , Wu LiWen , Lam Yat-yin , Wu Eugene B. , Yu Cheuk-Man
Published: August 2008

The present study aims to evaluate LV (left ventricular) mechanical dyssynchrony in CAD (coronary artery disease) with preserved and depressed EF (ejection fraction). Echocardiography with TDI (tissue Doppler imaging) was performed in 311 consecutive CAD patients (94 had preserved EF ≥50% and 217 had depressed EF <50%) and 117 healthy subjects to determine LV systolic and diastolic dyssynchrony by measuring Ts-SD (S.D. of time to peak myocardial systolic velocity during the ejection period) and Te-SD (S.D. of time to peak myocardial early diastolic velocity during the filling period) respectively, using a six-basal/six-mid-segmental model. In CAD patients with preserved EF, both Ts-SD (32.2±17.3 compared with 17.7±8.6 ms; P<0.05) and Te-SD (26.2±13.6 compared with 20.3±8.1 ms; P<0.05) were significantly prolonged when compared with controls, although they were less prolonged than CAD patients with depressed EF (Ts-SD, 37.8±16.5 ms; and Te-SD, 36.0±23.9 ms; both P<0.005). Patients with preserved EF who had no prior MI (myocardial infarction) had Ts-SD (32.9±17.5 ms) and Te-SD (28.6±14.8 ms) prolonged to a similar extent (P=not significant) to those with prior MI (Ts-SD, 28.4±16.8 ms; and Te-SD, 25.5±15.0 ms). Patients with class III/IV angina or multi-vessel disease were associated with more severe mechanical dyssynchrony (P<0.05). Furthermore, the majority of patients with mechanical dyssynchrony had narrow QRS complexes in those with preserved EF. This is in contrast with patients with depressed EF in whom systolic and diastolic dyssynchrony were more commonly associated with wide QRS complexes. In conclusion, LV mechanical dyssynchrony is evident in CAD patients with preserved EF, although it was less prevalent than those with depressed EF. In addition, mechanical dyssynchrony occurred in CAD patients without prior MI and narrow QRS complexes.
Stability and electronic properties of native defects and substitutional impurities in GaN nanotubes
Authors: Colussi M. L. , Baierle R. J. , Miwa R. H.
Published: August 2008

Spin-polarized density functional theory is used to investigate the stability and electronic properties of vacancies, antisites, and substitutional Si and C in zigzag and armchair GaN nanotubes. Antisites and vacancies present lower formation energies as compared with their counterparts in the bulk GaN system, introducing localized electronic levels within the nanotube band gap. For vacancy systems in the neutral charge state the defective levels present a spin splitting giving rise to a net magnetic moment of 1 μB. Substitutional Si and C in the Ga site have the lowest formation energy and exhibit donor properties, suggesting the formation of defect-induced n-type GaN nanotubes. Our calculated formation energies for charged defects indicate that the neutral charge states are present for all the studied defects, thus suggesting a different picture for those defects in nanotube systems when compared with their counterparts in the bulk phase.
Rotational dynamics and polymerization of C60 in C60-cubane crystals: A molecular dynamics study
Authors: Coluci V. R. , Sato F. , Braga S. F. , Skaf M. S. , Galvão D. S.
Published: August 2008

We report classical and tight-binding molecular dynamics simulations of the C60 fullerene and cubane molecular crystal in order to investigate the intermolecular dynamics and polymerization processes. Our results show that, for 200 and 400 K, cubane molecules remain basically fixed, presenting only thermal vibrations, while C60 fullerenes show rotational motions. Fullerenes perform “free” rotational motions at short times (≲1 ps), small amplitude hindered rotational motions (librations) at intermediate times, and rotational diffusive dynamics at long times (≳10 ps). The mechanisms underlying these dynamics are presented. Random copolymerizations among cubanes and fullerenes were observed when temperature is increased, leading to the formation of a disordered structure. Changes in the radial distribution function and electronic density of states indicate the coexistence of amorphous and crystalline phases. The different conformational phases that cubanes and fullerenes undergo during the copolymerization process are discussed.
Selection of a single femtosecond high-order harmonic using a zone plate based monochromator
Authors: Gaudin J. , Rehbein S. , Guttmann P. , Godé S. , Schneider G. , Wernet Ph. , Eberhardt W.
Published: August 2008

We report the use of zone plate optics as a monochromator for the spectral selection of a single high-order harmonic of a femtosecond laser generated in a rare gas medium. We show that this is a convenient way of monochromatizing the vacuum ultraviolet (VUV) pulses in the photon energy range from 30 up to 70 eV while keeping the pulse duration in the femtosecond range. We measure the emission spectra with a typical energy resolution of E/ΔE=60. Comparably high transmission and diffraction efficiencies allow the record of images of different harmonics using a camera within a few seconds of acquisition time. This is our first step toward a VUV microscope with a submicrometer spatial resolution and femtosecond time resolution. Possible applications of this setup are also discussed.
Low roll-off efficiency green phosphorescent organic light-emitting devices with simple double emissive layer structure
Authors: Jeon Woo Sik , Park Tae Jin , Kim Sun Young , Pode Ramchandra , Jang Jin , Kwon Jang Hyuk
Published: August 2008

Using an Ir(ppy)3 metal complex doped in 4,4′4″-tris(N-carbazolyl)-triphenylamine hole and bis[2-(2-hydroxyphenyl)-pyridine]beryllium electron transport host materials, simple three layer green phosphorescent organic light-emitting devices comprising double emissive layers have been fabricated. A low driving voltage value of 3.3 V to reach a luminance of 1000 cd/m2 and maximum current- and power-efficiency values of 58.7 cd/A and 65.1 lm/W, and maximum external quantum efficiency (EQE) value of 18.6% are reported in this device. EQE exceeding 15% over a wide range of current density from 0.03 to 25 mA/cm2 is noticed. We demonstrate a low roll-off current efficiency value of 12% at a luminance of 10 000 cd/m2 in a highly efficient simple double emissive layer device, imperative to high brightness applications.
Catalytic organometallic anticancer complexes
Authors: Dougan Sarah J. , Habtemariam Abraha , McHale Sarah E. , Parsons Simon , Sadler Peter J.
Published: August 2008

Organometallic complexes offer chemistry that is not accessible to purely organic molecules and, hence, potentially new mechanisms of drug action. We show here that the presence of both an iodido ligand and a σ-donor/π-acceptor phenylazopyridine ligand confers remarkable inertness toward ligand substitution on the half-sandwich “piano-stool” ruthenium arene complexes [(η
6
-arene)Ru(azpy)I]
+
(where arene =
p
-cymene or biphenyl, and azpy =
N
,
N
-dimethylphenyl- or hydroxyphenyl-azopyridine) in aqueous solution. Surprisingly, despite this inertness, these complexes are highly cytotoxic to human ovarian A2780 and human lung A549 cancer cells. Fluorescence-trapping experiments in A549 cells suggest that the cytotoxicity arises from an increase in reactive oxygen species. Redox activity of these azopyridine Ru
II
complexes was confirmed by electrochemical measurements. The first one-electron reduction step (half-wave potential −0.2 to −0.4 V) is assignable to reduction of the azo group of the ligand. In contrast, the unbound azopyridine ligands are not readily reduced. Intriguingly the ruthenium complex acted as a catalyst in reactions with the tripeptide glutathione (γ-
l
-Glu-
l
-Cys-Gly), a strong reducing agent present in cells at millimolar concentrations; millimolar amounts of glutathione were oxidized to glutathione disulfide in the presence of micromolar ruthenium concentrations. A redox cycle involving glutathione attack on the azo bond of coordinated azopyridine is proposed. Such ligand-based redox reactions provide new concepts for the design of catalytic drugs.
Cluster reactivity experiments: Employing mass spectrometry to investigate the molecular level details of catalytic oxidation reactions
Authors: Johnson Grant E. , Tyo Eric C. , Castleman A. W.
Published: August 2008

Mass spectrometry is the most widely used tool in the study of the properties and reactivity of clusters in the gas phase. In this article, we demonstrate its use in investigating the molecular-level details of oxidation reactions occurring on the surfaces of heterogeneous catalysts via cluster reactivity experiments. Guided ion beam mass spectrometry (GIB-MS) employing a quadrupole–octopole–quadrupole (Q–O–Q) configuration enables mass-selected cluster ions to be reacted with various chemicals, providing insight into the effect of size, stoichiometry, and ionic charge state on the reactivity of catalyst materials. For positively charged tungsten oxide clusters, it is shown that species having the same stoichiometry as the bulk, WO
3
+
, W
2
O
6
+
, and W
3
O
9
+
, exhibit enhanced activity and selectivity for the transfer of a single oxygen atom to propylene (C
3
H
6
), suggesting the formation of propylene oxide (C
3
H
6
O), an important monomer used, for example, in the industrial production of plastics. Furthermore, the same stoichiometric clusters are demonstrated to be active for the oxidation of CO to CO
2
, a reaction of significance to environmental pollution abatement. The findings reported herein suggest that the enhanced oxidation reactivity of these stoichiometric clusters may be due to the presence of radical oxygen centers (W–O●) with elongated metal–oxygen bonds. The unique insights gained into bulk-phase oxidation catalysis through the application of mass spectrometry to cluster reactivity experiments are discussed.