bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic structures inside boundary layers of magnetic clouds
Authors: Wei Fengsi , Liu Rui , Feng Xueshang , Zhong Dingkun , Yang Fang
Published: December 2003

We analyze 23 magnetic cloud boundary layers (BLs) in Feb. 1995–Oct. 1998 and find that: (1) the distribution functions of fluctuations in the southward field component inside the boundary layer, ΔBzL, is very different from ΔBzS in the background solar wind and ΔBzM inside the cloud, with the enhancement in the fluctuation amplitude and the variation of the magnitude and direction of the average field. (2) in the maximum variance plane (MVP) composed of the maximum and medium variance directions, the walk of the tips of the magnetic field vectors in the BL could be classified into two types based on: (a) field vectors vibrate along a circle arc, which is possibly related with Alfven fluctuations inside the BL; (b) field vectors walk randomly in the MVP, which could be correlated with the turbulence inside the BL. (3) In the ϕ‐θ plane, fields inside the BL exhibits a ‘U’ or inverse ‘U’ shape with a spacing of about 180 degree in the azimuthal angle, which indicate the existence of a field reverse region and are often associated with the Alfvenic fluctuations. The results above suggest that the cloud's BL owns the magnetic structure different from that in the solar wind and cloud body, which is a manifestation for the interaction of the magnetic cloud (MC) with the solar wind (SW).
Plasma distribution at Venus and Ionospheric magnetic fields: Implication for Mars
Authors: Dwivedi A. K. , Mahajan K. K.
Published: December 2003

Magnetometer measurements on the Pioneer Venus Orbiter, (PVO), have shown the presence of large‐scale steady horizontal magnetic fields in the dayside ionosphere of Venus during episodes of high solar wind dynamic pressure, Psw. These horizontal magnetic fields are expected to inhibit plasma diffusion and modify the plasma distribution from a diffusive equilibrium type profile to a “depressed” type profile. We have analyzed electron and ion density profiles measured by the electron temperature probe and ion mass spectrometer for several orbits having large scale horizontal magnetic fields. We find that the observed density profiles are nearly similar to those expected under diffusive equilibrium, thereby suggesting that these fields perhaps do not inhibit diffusion. This observation has a major consequence for Mars ionosphere where the observed electron density profiles are of “depressed” type and have been explained on the basis of horizontal magnetic fields measured by the MAG/ER experiment on Mars Global Surveyor, spacecraft.
Numerical simulation of caldera formation due to collapse of a magma chamber
Authors: Kusumoto Shigekazu , Takemura Keiji
Published: December 2003

The caldera structure after collapse of the magma chamber was estimated by numerical simulation. In the simulation, the collapse of the magma chamber was approximated by the contraction of a small sphere in the elastic medium, and the distribution of plastic and/or rupturing area was calculated using the Coulomb failure criterion under the assumption of an elastic‐perfectly‐plastic material. Given an undefined or isotropic regional stress field, the plastic area (caldera) was found to develop as a circular depression on the surface, appearing funnelform in cross section. Under an anisotropic regional stress field, the caldera developed in the direction of the maximum compression (or minimum extension) axis. In all simulations, the collapse of the magma chamber resulted in the formation of an outward dipping reverse ring fault around the area above the chamber, and an inward dipping normal ring fault at the periphery of the caldera.
Isotopic variation in Indian Monsoon precipitation: Records from Bombay and New Delhi
Authors: Bhattacharya S. K. , Froehlich K. , Aggarwal P. K. , Kulkarni K. M.
Published: December 2003

The stable isotope composition and the tritium content of precipitation analysed within the framework of the IAEA/WMO Global Network for Isotopes in Precipitation (GNIP) have been evaluated for the Indian stations Bombay and New Delhi representing two different regions of the Indian Monsoon. The rainfall at New Delhi is controlled by north‐west moving depressions with diverse routes and variable transit times over the land subsequent to their formation at the head of Bay of Bengal. In contrast, Bombay rains are caused by spatially locked cyclonic vortices on the west coast of India with continuous supply of oceanic moisture resulting in negligible isotopic variation over the rainy months. The evaluation of the long‐term isotope data of the two stations provided specific information on monsoon rain formation mechanism and the moisture source of the monsoon rains. The average isotope ratios clearly represent an imprint of oceanic moisture during the summer monsoon and of continental moisture during the winter monsoon period. The rainout efficiency is about 30% in case of Bombay (representative of west coast region) and about 56% in case of New Delhi (representative of north Indian Plains). Furthermore, the isotope data indicate that the moisture for low‐intensity rains during the post‐monsoon phase originates from the Asian continent.
Insolation forcing of the Australian monsoon as controls of Pleistocene mega‐lake events
Authors: Wyrwoll Karl‐Heinz , Valdes Paul
Published: December 2003

During the last c. 300,000 years mega‐lakes with areas an order of magnitude greater than those of today occurred in the monsoon region of northern Australia. The results of an Atmosphere Global Circulation Model (AGCM) sensitivity experiment show that the repeated occurrence of mega‐lake phases during the Pleistocene, and the strong monsoon flow that this implies, can be related to Milankovitch insolation forcing. The AGCM experiment is centred on the Southern Hemisphere low‐latitude, summer insolation high of 115,000 years ago. The details of the results indicate a strong response of the Australian monsoon to the higher insolation at that time, with a longer monsoon season, increased precipitation and higher resultant runoff than at present.
The shape of convective rain cells
Authors: von Hardenberg J. , Ferraris L. , Provenzale A.
Published: December 2003

The shape of rainfall cells is a crucial ingredient of stochastic point‐process models that describe intense precipitation events. Here we study the shape of the individual rain cells measured during the TOGA/COARE and GATE radar experiments. We find that, on average, rainfall intensity decreases exponentially from the cell's center. An exponential profile provides a good estimate of the precipitation intensity in the bulk of the cell. By contrast, the standard assumption of a Gaussian shape leads to significant underestimation of the precipitation intensity in the central portion of the cell and of the associated hydrologic response.
Roles of tropospheric and boundary layer forcing in the diurnal cycle of convection in the U.S. southern great plains
Authors: Zhang Guang J.
Published: December 2003

This study examines the roles of the tropospheric large‐scale forcing, surface sensible and latent heat fluxes and convective inhibition in the diurnal variation of convection in the U.S. Southern Great Plains using data from the Atmospheric Radiation Measurement program. It is shown that the diurnal variation of the tropospheric large‐scale forcing has a strong in‐phase relationship with convection, whereas the diurnal variations of surface sensible and latent heat fluxes as well as the thermodynamic properties of the near‐surface air are nearly out of phase with that of convection. Both the single column version and the full global model of the NCAR CCM3 are used to test the roles of the tropospheric and boundary layer forcing in the observed diurnal variation of convection. When convection is parameterized based on the tropospheric large‐scale forcing, the diurnal variation of convection is in good agreement with the observations.
Link between major flank slip and 2002–2003 eruption at Mt. Etna (Italy)
Authors: Acocella Valerio , Behncke Boris , Neri Marco , D'Amico Salvatore
Published: December 2003

The 2002–2003 Etna eruption is studied through earthquake distributions and surface fracturing. In September 2002, earthquake‐induced surface rupture (sinistral offset ∼0.48 m) occurred along the E‐W striking Pernicana Fault (PF), on the NE flank. In late October, a flank eruption accompanied further (∼0.77 m) surface rupturing, reaching a total sinistral offset of 1.25 m; the deformation then propagated for 18 km eastwards to the coastline (sinistral offset 0.03 m) and southwards, along the NW‐SE striking Timpe (dextral offset 0.04 m) and, later, Trecastagni faults (dextral offset 0.035 m). Seismicity (<4 km bsl) on the E flank accompanied surface fracturing: fault plane solutions indicate an overall ESE‐WNW extension direction, consistent with ESE slip of the E flank also revealed by ground fractures. A three‐stage model of flank slip is proposed: inception (September earthquake), climax (accelerated slip and eruption) and propagation (E and S migration of the deformation).
The effects of non‐sphericity on geostationary satellite retrievals of dust aerosols
Authors: Wang Jun , Liu Xiong , Christopher Sundar A. , Reid Jeffrey S. , Reid Elizabeth , Maring Hal
Published: December 2003

Using data collected during the Puerto Rico Dust Experiment (PRIDE), we examine the effect of non‐spherical phase functions on dust aerosol retrievals from geostationary satellites. We utilize a statistical model based on Scanning Electron Micrograph (SEM) analysis of individual dust particles. Using T‐matrix calculations and assuming that dust particles are randomly‐orientated oblate spheroids we compute the dust phase function and scattering properties. Although the non‐spherical function developed in this study compares well with the synthetic non‐spherical phase functions [Liu et al., 2003], new retrievals using the non‐spherical phase function only show slight improvement at scattering angles (Θ) from 110° ∼ 150°, and become worse for Θ between 150° ∼ 170°. However the retrievals are greatly improved at all angles when retrieval algorithms account for the combined effect of both spherical and non‐spherical phase functions.
The 600–750 hPa relative humidity minimum observed during PEM‐Tropics B
Authors: Yasunaga K. , Kida H. , Satomura T.
Published: December 2003

The height where cumulus convection over tropical oceans directly transports air from the boundary layer is statistically investigated, making use of the NASA Pacific Exploratory Mission‐Tropics B (PEM‐Tropics B) observed data. The cumulus convection detrainment levels are inferred by high CH3I concentrations and relative humidity. The relationship between the injection height and stability is also discussed. Tropical cumulus convection directly transported boundary layer air to the 350–600 hPa and 750–800 hPa levels. These pressure levels coincided with the heights where stable layers were frequently observed. On the other hand, the cumulus convection infrequently transported boundary layer air directly to the 600–750 hPa levels, being consistent with the fact that stability around these levels was weak.
A significant CO2 sink in the tropical Atlantic Ocean associated with the Amazon River plume
Authors: Körtzinger Arne
Published: December 2003

During Meteor cruise 55 a strong undersaturation of surface seawater with respect to atmospheric CO2 was found in the Amazon River plume which is advected into the surface circulation of the tropical Atlantic. A conservative estimate of the plume‐related CO2 sink in the tropical Atlantic yields a net air‐sea flux of 0.014 ± 0.005 Pg C yr−1. The corresponding average CO2 flux density of 1.35 mmol m−2 d−1 is of similar magnitude but opposite sign as found elsewhere in the slightly supersaturated tropical Atlantic illustrating the significant impact of the Amazon on the biogeochemistry of large ocean areas. The dramatic change of the CO2 saturation state from highly supersaturated river waters to markedly undersaturated surface waters in the plume can be explained by a combination of the effects of CO2 outgassing from river water, of mixing between river and ocean water on the CO2 system properties, and of strong biological carbon drawdown in the plume.
Effects of pure silica coatings on thermal emission spectra of basaltic rocks: Considerations for Martian surface mineralogy
Authors: Kraft Michael D. , Michalski Joseph R. , Sharp Thomas G.
Published: December 2003

On Mars, silica derived from chemical weathering could precipitate to coat rocks and particles. We suggest that rock coatings of secondary amorphous silica may account for a widespread Martian surface spectral unit previously modeled as andesite or weathered basalt. In a laboratory study, we investigated the effects of synthetic silica coatings on thermal infrared (TIR) spectroscopic measurements. Secondary amorphous silica is spectrally similar to silicate glass and clay spectra used in previous spectroscopic models. Silica coating and substrate spectra combine nonlinearly to produce a composite spectrum of a coated rock. Silica coatings <10 μm thick effectively mask the spectral contribution of a silicate substrate. Therefore, the capability of volumetrically small amounts of silica present as thin coatings on rocks should be considered when seeking explanations for spectral variability of Martian surface materials.
Martian Layered Fluvial Deposits: Implications for Noachian Climate Scenarios
Authors: Moore Jeffrey M. , Howard Alan D. , Dietrich William E. , Schenk Paul M.
Published: December 2003

Fluvial deposits in a basin north of Holden crater exhibiting a sinuous, anabranching pattern are of deltaic or fan origin. Channel width and meander wavelength indicate persistent flow magnitudes of about 700 m3/s. If these flows were produced by quasi‐periodic climate episodes involving typical terrestrial‐style precipitation, the deposit required thousands to millions of years to accumulate. However, a scenario of deposition during a few short episodes of constant heavy precipitation resulting from large impacts cannot be excluded.
Impact of historical land cover change on the July climate of the United States
Authors: Baidya Roy Somnath , Hurtt George C. , Weaver Christopher P. , Pacala Stephen W.
Published: December 2003

We used the Regional Atmospheric Modeling System (RAMS) model to investigate the possible impact of land cover change on the July climate of the coterminous United States over the last 290 years. Vegetation data were estimated using the Ecosystem Demography model. The observed change in land cover leads to a weak warming along the Atlantic coast and a strong cooling of more than 1 K over the Midwest and the Great Plains region. The precipitation signal is weaker and shows some reduction in the Midwest because of changes in the patterns of large‐scale moisture advection.
First inversions of observed submillimeter limb sounding radiances by neural networks
Authors: Jiménez Carlos , Eriksson Patrick , Murtagh Donal
Published: December 2003

First inversions of observed limb sounding data by a very fast neural network technique are presented. The technique is based on training a set of multilayer perceptrons. The training set was built by random generation of atmospheric states followed by forward model calculations to derive the corresponding radiances. A novel spectral reduction technique was used to reduce the dimensionality of the spectral space, allowing the setting up of multilayer perceptrons with a practical topology. For training, an algorithm that relies on Bayesian techniques was applied in order to favor generalization. The technique was tested by inverting measured radiances from the Odin‐SMR submillimeter radiometer and judged by comparing with similar inversions from an optimal estimation code. The neural network technique resulted in much faster inversions than the optimal estimation code, but biases between the optimal estimation and neural network retrievals were found. The problem was tracked down to the presence of spectral artifacts in the measured radiances. The optimal estimation inversions were also affected but seemed less sensitive. Nevertheless, the results were promising and opened the possibility of implementing a very fast processing algorithm for the Odin‐SMR data.
Seasonal and QBO variations of ascent rate in the tropical lower stratosphere as inferred from UARS HALOE trace gas data
Authors: Niwano Masanori , Yamazaki Koji , Shiotani Masato
Published: December 2003

Seasonal and interannual variations in ascent rates are investigated as a function of latitude and height, using water vapor (H2O) and methane (CH4) data from the stratospheric measurements of the Halogen Occultation Experiment (HALOE). The ascent rate is inferred from the ascending signal of variations in the entry value of [H2O] + 2[CH4] (Ĥ). Within ±15° of the equator the derived ascent rate exhibits two kinds of dominant variations with a clear latitudinal structure, seasonal variation, and the quasi‐biennial oscillation (QBO). The seasonal cycle exhibits a vertically in‐phase variation, with a northern winter maximum of 0.2–0.4 mm s−1 and a summer minimum of ∼0.2 mm s−1 in the 20–60 hPa layer. The latitudinal structure is characterized by an early appearance of a subtropical summer maximum of the ascent rate and by double peaks at 10–15°N and S during the northern winter season. The QBO component of the ascent rate shows tropically confined anomalies with a rapid downward propagation, but mass attenuation anomalies estimated from the ascent rate show a much slower downward propagation. The descent anomalies exhibit a well‐structured and equatorially symmetric variation, while the ascent anomalies have a tendency to propagate latitudinally. This might be connected with the phase dependency of the QBO acceleration. An examination of the phase and amplitude of the ascent rate and temperature for both the seasonal and QBO components emphasizes that the radiative damping timescale is considerably long (40–100 days) below 40 hPa.
A sensitivity study of climate and energy balance simulations with use of satellite‐derived emissivity data over Northern Africa and the Arabian Peninsula
Authors: Zhou L. , Dickinson R. E. , Tian Y. , Jin M. , Ogawa K. , Yu H. , Schmugge T.
Published: December 2003

This paper analyzes the sensitivity of simulated climate and energy balance to changes in soil emissivity over Northern Africa and the Arabian Peninsula and considers how this information may be used to improve emissivity parameterizations in climate models. Analysis of satellite observations suggests that the soil emissivity in current models is too high over this region. Sensitivity tests based on the recently developed Community Land Model indicate that this bias could produce significant errors in the model simulated ground and air temperature, net and upward longwave radiation, and sensible heat flux. There is a linear relationship between changes in emissivity and changes in these variables. Statistical results show that, on average for the study region, a decrease of soil emissivity by 0.1 will increase ground and air temperature by about 1.1°C and 0.8°C and decrease net and upward longwave radiation by about 6.6 Wm−2 and 8.1 Wm−2, respectively, at the ground surface. The decreased net longwave radiation (less emission) is mainly balanced by an increase of sensible heat flux of about 5.9 Wm−2. These relations vary seasonally and diurnally. The temperature increases are slightly higher in winter than in summer and twice as large during nighttime as during daytime, while the sensible heat flux and longwave radiation show more change in summer/daytime than in winter/nighttime. Our experimental results are consistent with our theoretical energy balance analyses. When a more realistic emissivity value is used, the model cold bias over the Sahara in comparison with land surface air temperature observations could be partially reduced. These results indicate that the simple representations of the land surface emissivity in climate models, especially for bare soil, need improvements based on satellite and in situ observations.
Considerations for effusive cryovolcanism on Europa: The post‐Galileo perspective
Authors: Fagents Sarah A.
Published: December 2003

Cryovolcanic resurfacing is a popular mechanism to explain relatively young surface units on icy satellites of Jupiter, Saturn, Uranus, and Neptune. Prior to the Galileo data acquired between 1996 and 2001, Europa was thought to have undergone significant cryovolcanic resurfacing, facilitated by a global ocean beneath the icy surface. However, close examination of Galileo data at resolutions much better than those of Voyager images show that many of the features previously thought to be cryovolcanic are commonly best explained by other formative mechanisms, including tectonism and diapirism. In this study, I present an examination of the characteristics of a variety of Europan surface features for which effusive cryovolcanism is a possible origin, including apparently lobate “flows,” certain elliptical to circular lenticulae, and low‐lying, smooth, low‐albedo surfaces. A review of cryovolcanic eruption theory, together with Galileo data analysis of Europan surface geology and composition, indicates that cryovolcanism is a viable, though not unequivocal, explanation for some of these features. Some constraints on cryomagma properties and lithospheric structure are offered for these cases. The presence of small‐volume, low‐viscosity effusions is supported by observations and modeling. Some positive relief lenticulae could represent more viscous effusions, although diapirism may be a preferable explanation. However, strong evidence is lacking for cryovolcanic resurfacing on a large scale. On the basis of our experience with Galileo images of Europa (and Ganymede), Voyager‐era inferences for widespread cryovolcanism on icy satellites may be overstated and will need to be carefully reexamined in the light of new data from upcoming spacecraft missions.
High‐resolution topomapping of candidate MER landing sites with Mars Orbiter Camera narrow‐angle images
Authors: Kirk Randolph L. , Howington‐Kraus Elpitha , Redding Bonnie , Galuszka Donna , Hare Trent M. , Archinal Brent A. , Soderblom Laurence A. , Barrett Janet M.
Published: December 2003

We analyzed narrow‐angle Mars Orbiter Camera (MOC‐NA) images to produce high‐resolution digital elevation models (DEMs) in order to provide topographic and slope information needed to assess the safety of candidate landing sites for the Mars Exploration Rovers (MER) and to assess the accuracy of our results by a variety of tests. The mapping techniques developed also support geoscientific studies and can be used with all present and planned Mars‐orbiting scanner cameras. Photogrammetric analysis of MOC stereopairs yields DEMs with 3‐pixel (typically 10 m) horizontal resolution, vertical precision consistent with ∼0.22 pixel matching errors (typically a few meters), and slope errors of 1–3°. These DEMs are controlled to the Mars Orbiter Laser Altimeter (MOLA) global data set and consistent with it at the limits of resolution. Photoclinometry yields DEMs with single‐pixel (typically ∼3 m) horizontal resolution and submeter vertical precision. Where the surface albedo is uniform, the dominant error is 10–20% relative uncertainty in the amplitude of topography and slopes after “calibrating” photoclinometry against a stereo DEM to account for the influence of atmospheric haze. We mapped portions of seven candidate MER sites and the Mars Pathfinder site. Safety of the final four sites (Elysium, Gusev, Isidis, and Meridiani) was assessed by mission engineers by simulating landings on our DEMs of “hazard units” mapped in the sites, with results weighted by the probability of landing on those units; summary slope statistics show that most hazard units are smooth, with only small areas of etched terrain in Gusev crater posing a slope hazard.
Recurrent ponded infiltration into structured soil: A magnetic resonance imaging study
Authors: Votrubová Jana , Císlerová Milena , Gao Amin M. H. , Hall Laurance D.
Published: December 2003

Recurrent ponded infiltration (RPI) was applied to two undisturbed samples (5.4‐cm diameter, 9‐cm height) of coarse sandy loam (Korkusova Hut', CR). The water distribution within the samples during RPI was monitored using magnetic resonance imaging (MRI); the soil internal structure was visualized by X‐ray computed tomography (CT). Preferential flow and a decrease of the steady state infiltration rate between two successive infiltrations of RPI are typical for the soil studied. During the MRI‐monitored experiment these phenomena were pronounced only in one sample, which facilitated their linking to specific features in the MRI results; the flow rate decrease was related to a reduction of the MRI‐detected water content and a change of the spectrum of T1 (a characteristic related to the water surface‐to‐volume ratio). The MRI methods employed could detect water in low‐density regions and thereby captured potential preferential pathways; however, one‐dimensional (1‐D) MRI demonstrated that some results may be affected by fast flow.
Unusual form of neurocysticercosis associated with HIV infection
Authors: Delobel P. , Signate A. , El Guedj M. , Couppie P. , Gueye M. , Smadja D. , Pradinaud R.
Published: December 2003

Concurrent infection with Taenia solium and HIV would be expected to occur more frequently because of the increasing frequency of HIV infection in endemic areas of cysticercosis. However, little is known about the influence of HIV infection on the frequency and the clinical course of cysticercosis. Giant cysts and racemose forms of neurocysticercosis seem to be more frequent in HIV‐infected patients and may be secondary to an uncontrolled parasitic growth because of an impaired cell‐mediated immune response. We report an unusual case of epidural spinal racemose neurocysticercosis revealed by compression of cauda equina in an HIV‐infected man and discuss the potential interactions between T. solium and HIV infections.
Differences in cerebrospinal fluid dynamics do not affect the levels of biochemical markers in ventricular CSF from patients with aqueductal stenosis and idiopathic normal pressure hydrocephalus
Authors: Tisell M. , Tullberg M. , Månsson J.‐E. , Fredman P. , Blennow K. , Wikkelsø C.
Published: December 2003

To compare levels of biochemical markers in ventricular cerebrospinal fluid (vCSF) between patients with aqueductal stenosis (AS) and idiopathic normal pressure hydrocephalus (INPH) and relate these results to clinical outcome after surgery. Neurofilament light protein, tau protein, sulfatide, vasoactive intestinal peptide (VIP), neuropeptide PYY (NPY) and CSF/serum albumin ratio were measured in vCSF from 18 consecutive AS and 19 consecutive INPH patients. Clinical outcome was evaluated after surgery by standardized indices. The levels of markers were related to clinical outcome. No differences in any of the markers were found between AS and INPH patients. The concentration of sulfatide and albumin ratio correlated inversely with psychometric improvement, whilst VIP and NPY correlated inversely with improvement in alertness. The similar levels of biochemical markers in vCSF from AS and INPH patients indicate similarities in pathophysiology and turnover rate of vCSF despite differences in CSF dynamics. High albumin ratio and sulfatide concentrations in vCSF in hydrocephalus patients have negative implications for surgical outcome and might indicate concomitant cerebrovascular disorder.
Etiology of and risk factors for cerebral infarction in young adults in western Norway: a population‐based case‐control study
Authors: Naess H. , Nyland H. I. , Thomassen L. , Aarseth J. , Myhr K.‐M.
Published: December 2003

We sought to study the etiology of and risk factors for cerebral infarction in young adults in Hordaland County, Norway. All patients aged 15–49 years living in Hordaland County with a first‐ever cerebral infarction during 1988–97 were included. Etiology was analyzed in subgroups defined by sex, age (<40 years versus 40 years), circulation territory (anterior versus posterior circulation) and short‐term functional outcome [modified Rankin score (mRS)  2 versus mRS > 2]. A questionnaire was used to evaluate possible risk factors amongst the patients compared with an age‐ and sex‐matched control group. The distribution of etiology was significantly different in all subgroups. Atherosclerosis was frequent amongst men (22.8% vs. 4.2%) and patients  40 years (20.8% vs. 2.7%). All patients with microangiopathy had favorable short‐term outcome. Significant risk factors were smoking more than 15 cigarettes per day (P < 0.001), hypertension (P = 0.001), and myocardial infarction (P = 0.035). Modifiable risk factors were frequent.
Rapidly reversible dementia in cerebral amyloid inflammatory vasculopathy
Authors: Harkness K. A. C. , Coles A. , Pohl U. , Xuereb J. H. , Baron J. C. , Lennox G. G.
Published: December 2003

This report discusses a biopsy proven case of cerebral amyloid angiopathy, with additional prominent vascular inflammatory features, characterized by a rapidly progressive dementia and leukoencephalopathy, where the clinical and radiological abnormalities resolved rapidly with minimal therapeutic intervention. We propose the term cerebral amyloid inflammatory vasculopathy (CAIV) to describe this condition.
Early CT changes and outcome of ischemic stroke
Authors: Aronovich B. D. , Reider‐Groswasser I. I. , Segev Y. , Bornstein N. M.
Published: December 2003

Although recombinant tissue plasminogen activator (rt‐PA) was rapidly implemented as part of the emergency care of acute stroke, its use in daily clinical practice still remains controversial in many countries. The most important question is criteria for careful selection of subgroup of patients for this treatment. It has been hypothesized that early computed tomography (CT) changes of ischemia are risk factors for symptomatic intracerebral hemorrhage and poor outcome. We conducted a prospective outcome study of patients with acute ischemic stroke (IS) admitted to the hospital within 6 h of symptom onset. Experienced neuroradiologists blind to the clinical outcome of the patients read all CT scans carried out in the emergency room. Early CT changes were defined as in European Cooperative Acute Stroke Study (ECASS) 2. There were 150 patients (75 males, mean age 72.5 ± 9.0) with acute IS (54.7% with mild stroke and 45.3% with severe stroke). Early CT changes were presented with tissue hypodensity – 55.7%, effacement of sulci – 41.3%, hyperdensity of middle cerebral artery (MCA) – 13.3%, hypodensity of lentiform – 20.7%, loss of insular ribbon sign – 28.7%. Follow‐up after 30 days showed that 44% of the patients were discharged home, 20% were discharged to rehabilitation facilities, 22% were discharged to chronic care institutions and 14% died. Data were statistically analyzed. Our data suggest that early signs on CT scan could not predict outcome of patients with acute IS.
The sensitivity of 18‐fluorodopa positron emission tomography and magnetic resonance imaging in Parkinson's disease
Authors: Heiss W.‐D. , Hilker R.
Published: December 2003

Parkinson's disease (PD) as the most important movement disorder is characterized by a progressive loss of nigral dopamine neurons and a subsequent degeneration within several other transmitter systems. Functional brain imaging with positron emission tomography (PET) and the radiotracer 18‐fluorodopa (FDOPA) is capable to quantify the deficiency of dopamine synthesis and storage within pre‐synaptic striatal nerve terminals. Therefore, FDOPA‐PET allows the diagnosis of PD in early disease stages and the differentiation of clinically unclear cases from other movement disorders, e.g. essential tremor. Additionally, FDOPA‐PET imaging permits the follow‐up of disease progression, the assessment of medical and surgical PD therapy strategies with possible neuroprotective properties and the detection of pre‐clinical disease in subjects at risk for the disorder. The classical domain of morphological magnetic resonance imaging (MRI) is the differentiation of symptomatic Parkinsonism from PD. However, recent advances in MRI data acquisition and analysis techniques demonstrated MRI to be also a valuable tool for detection of nigral pathology in PD and for differentiation of neurodegenerative disorders with atypical Parkinsonism.
Pneumonia and urinary tract infection after acute ischaemic stroke: a tertiary analysis of the GAIN International trial
Authors: Aslanyan S. , Weir C. J. , Diener H.‐C. , Kaste M. , Lees K. R. ,   the GAIN International Steering Committee and Investigators
Published: December 2003

The third most common stroke complication is infection. We studied the rates of aspiration pneumonia and urinary tract infection (UTI), their risk factors and their effect on outcome in the 1455 Glycine Antagonist (Gavestinel) in Neuroprotection (GAIN) International patients with ischaemic stroke. Forward stepwise logistic regression and Cox proportional hazards modelling identified baseline factors that predicted events and the independent effect of events up to day 7 on poor stroke outcome at 3 months in patients alive at day 7, after correcting for prognostic factors. Higher baseline National Institute of Health Stroke Scale (NIHSS) and age, male gender, history of diabetes and stroke subtype predicted pneumonia, which occurred in 13.6% of patients. Female gender and higher baseline NIHSS and age predicted UTI, which occurred in 17.2% of patients. Pneumonia was associated with poor outcome by mortality (hazard ratio, 2.2; 95% confidence interval, 1.5–3.3), Barthel index (<60) (odds ratio, 3.8; 2.2–6.7), NIHSS (4.9; 1.7–14) and Rankin scale (≥2) (3.4; 1.4–8.3). UTI was associated with Barthel index (1.9; 1.2–2.9), NIHSS (2.2; 1.2–4.0) and Rankin scale (3.1; 1.6–4.9). Pneumonia and UTI are independently associated with stroke poor outcome. Patients with identified risk factors must be closely monitored for infection.
Concentration dependence of the diffusion coefficient in separating dilute solid mixtures of He4 in 3He
Authors: Grigor’ev V. N. , Maı̆danov V. A. , Penzev A. A. , Rudavskiı̆ É. Ya. , Rybalko A. S. , Syrnikov Ye. V.
Published: December 2003

The kinetics of the separation of dilute solid mixtures of 4He in 3He is investigated in the ranges of temperature 100–200 mK, 4He concentration x=2.2–3.3%, and pressure 32–35 bar. It is found that the characteristic time τ required for the separating mixture to come to equilibrium depends substantially on the degree of supercooling. When the mixture is supercooled by more than 40–50 mK relative to the separation temperature of the initial mixture, the characteristic time τ<103 s and remains practically unchanged as the temperature is lowered further. At low supercoolings the values of τ reach 4×104 s and decrease noticeably with further decrease in temperature. A relation between the measured values of τ and the effective coefficient of mass diffusion is established using the solution of the diffusion problem with allowance for the surface resistance arising when the 4He impurity atoms leave the solution and enter new-phase inclusions. It is shown that an adequate description of the experimental data in the framework of the kinetic theory of tunneling transport of impurities under conditions of an appreciable interaction between them can be obtained under the assumption that the diffusion coefficient of 4He in 3He is proportional to x−4/3. The concentration of nuclei and the average size of the region associated to each nucleus are determined. Analysis of the experimental results on the kinetics of nucleation in phase separation shows that they can be explained by the theory of homogeneous nucleation. The values thus obtained for the coefficient of interphase surface tension agree with the existing data. The relaxation time due to the finite resistance to the penetration of an impurity through the boundary between the matrix and new-phase inclusion is determined for the first time.
Coupling of the magnetic layers and electron spin polarization in four-layer structures of amplitude and nonmagnetic semiconductors
Authors: Zorchenko V. V. , Sipatov A. Yu. , Volobuev V. V.
Published: December 2003

The electron energy spectrum, the energy Em of the exchange coupling between magnetic layers, and the relative polarization β of the electron spins in semiconductor structures with two ferromagnetic barriers and nonmagnetic layers acting as potential wells for electrons are considered. For the example of EuS/PbS(001) structures it is shown that in the case of Fermi statistics Em is a sign-varying oscillatory function of the width a of the potential well between barriers, and with increasing electron density n0 in the wells and increasing thickness d of the nonmagnetic sublayers between the barrier and substrate, the extrema of Em are shifted to smaller a and their amplitudes rapidly increase. As the temperature is lowered from the Curie point, the energy Em, depending on a, n0, and d, can increase (in modulus) monotonically or nonmonotonically, change sign from positive to negative, or change sign twice. The polarization β decreases with increasing a, n0, and d, undergoing sharp jumps when Em changes sign. For Boltzmann statistics only a ferromagnetic orientation of the barrier magnetizations (Em<0) is possible.
Spin–plasma wave in a one-dimensional metal
Authors: Gokhfeld V. M.
Published: December 2003

It is shown that a new type weakly damped acoustic plasmons can propagate in a quasi-one-dimensional conductor in an external static magnetic field H. These are due to the presence of spin subbands in the electron spectrum and are accompanied by forced oscillations of the magnetic moment of the sample. The dependence of the velocity and amplitude of these waves on the magnetic field strength H is found.
Setup for calorimetric measurements at temperatures below 1 K
Authors: Eropkin V. N. , Chagovets T. V.
Published: December 2003

A compact, top-loading He3 evaporation refrigerator is built for doing heat-capacity studies on various samples at temperatures below 1 K. It uses adsorption pumping and utilizes a portable helium Dewar of the STG-40 type as the cryostat. A calorimetric cell is built which permits investigation of the heat capacity of samples with masses of less than one gram. The lowest measurement temperature is 0.32 K. The dependence of the temperature of the He3 evaporation chamber on the power delivered to it is established. The refrigerator can operate continuously for two hours at a heat load of 50 μW.
Phonon Raman scattering in LaMn1−xCoxO3 (x=0, 0.2, 0.3, 0.4, and 1.0)
Authors: Gnezdilov V. P. , Yeremenko A. V. , Pashkevich Yu. G. , Lemmens P. , Güntherodt G. , Shiryaev S. V. , Bychkov G. L. , Barilo S. N.
Published: December 2003

The Raman-active phonons in perovskite-like LaMn1−xCoxO3 (x=0, 0.2, 0.3, 0.4, and 1.0) are studied by measuring the Raman spectra at temperatures of 295 and 5 K. The changes in the spectra with Co doping are correlated with the decrease of the orthorhombic distortions. Surprisingly, more phonon lines are observed than are allowed for the rhombohedral LaCoO3 structure.
Solvent-free simulations of fluid membrane bilayers
Authors: Brannigan Grace , Brown Frank L. H.
Published: December 2003

A molecular level model for lipid bilayers is presented. Lipids are represented by rigid, asymmetric, soft spherocylinders in implicit solvent. A simple three parameter potential between pairs of lipids gives rise to a rich assortment of phases including (but not limited to) micelles, fluid bilayers, and gel-like bilayers. Monte Carlo simulations have been carried out to verify self-assembly, characterize the phases corresponding to different potential parametrizations, and to quantify the physical properties associated with those parameter sets corresponding to fluid bilayer behavior. The studied fluid bilayers have compressibility moduli in agreement with experimental systems, but display bending moduli at least three times larger than typical biological membranes without cholesterol.
Time-dependent quantum wave packet calculation for nonadiabatic F(2P3/2,2P1/2)+H2 reaction
Authors: Zhang Yan , Xie Ting-Xian , Han Ke-Li , Zhang John Z. H.
Published: December 2003

In this paper we present a time-dependent quantum wave packet calculation for the reaction of F(2P3/2,2P1/2)+H2 on the Alexander–Stark–Werner potential energy surface. The reaction probabilities and the integral cross sections for the reaction of F(2P3/2,2P1/2)+H2 (v=j=0) are computed using time-dependent quantum methods with the centrifugal sudden approximate. The results are compared with recent time-independent quantum calculations. The two-surface reaction probability for the initial ground spin–orbit state of J=0.5 is similar to the time-independent result obtained by Alexander et al. [J. Chem. Phys. 113, 11084 (2000)]. Our calculation also shows that electronic coupling has a relatively minor effect on the reactivity from the P3/22 state but a non-negligible one from the P1/22 state. By comparison with exact time-independent calculations, it is found that the Coriolis coupling plays a relatively minor role. In addition, most of the reactivity of the excited state of fluorine atom results from the spin–orbit coupling.
Theoretical study of the electronic states of niobium trimer (Nb3) and its anion (Nb3−)
Authors: Majumdar D. , Balasubramanian K.
Published: December 2003

Geometries and energy separations of the various low-lying electronic states of niobium trimer (Nb3) and its anion (Nb3−) with triangular and linear structural arrangements have been investigated. The complete active space multiconfiguration self-consistent field method followed by multireference singles plus doubles configuration interaction (MRSDCI) that included up to 48 million configuration spin functions have been used to compute several electronic states of these clusters. The geometries of ground and excited states of Nb3 and Nb3− are triangular. The ground states of both Nb3 (2B1) and Nb3− (1A1) have been found to be of low spin. The low-lying electronic states with degenerate symmetries in the D3h group are distorted to the C2v structure (from the ideal D3h) due to the Jahn–Teller effect. On the basis of the energy separations of our computed electronic states of Nb3, we have assigned the observed photoelectron spectrum of Nb3−. We have also compared our MRSDCI results with density functional calculations. The electron affinity, ionization potential, dissociation and atomization energies of Nb3 have been calculated and the results have been found to be in excellent agreement with the experiment.
Ab initio potential energy and dipole moment surfaces, infrared spectra, and vibrational predissociation dynamics of the Cl−35⋯H2/D2 complexes
Authors: Buchachenko A. A. , Grinev T. A. , Kłos J. , Bieske E. J. , Szczȩśniak M. M. , Chałasiński G.
Published: December 2003

Three-dimensional potential energy and dipole moment surfaces of the Cl−–H2 system are calculated ab initio by means of a coupled cluster method with single and double excitations and noniterative correction to triple excitations with augmented correlation consistent quadruple-zeta basis set supplemented with bond functions, and represented in analytical forms. Variational calculations of the energy levels up to the total angular momentum J=25 provide accurate estimations of the measured rotational spectroscopic constants of the ground van der Waals levels n=0 of the Cl−⋯H2/D2 complexes although they underestimate the red shifts of the mid-infrared spectra with v=0→v=1 vibrational excitation of the monomer. They also attest to the accuracy of effective radial interaction potentials extracted previously from experimental data using the rotational RKR procedure. Vibrational predissociation of the Cl−⋯H2/D2(v=1) complexes is shown to follow near-resonant vibrational-to-rotational energy transfer mechanism so that more than 97% of the product monomers are formed in the highest accessible rotational level. This mechanism explains the strong variation of the predissociation rate with isotopic content and nuclear spin form of the complex. Strong deviation of the observed relative abundances of ortho and para forms of the complexes from those of the monomers is qualitatively explained by the secondary ligand exchange reactions in the ionic beam, within the simple thermal equilibrium model. Positions and intensities of the hot v=0, n=1→v=1, n=1 and combination v=0, n=0→v=1, n=1 bands are predicted, and implications to the photoelectron spectroscopy of the complex are briefly discussed.
The effect of conformation on the ionization energetics of n-butylbenzene. I. A threshold ionization study
Authors: Tong Xin , Ford Mark S. , Dessent Caroline E. H. , Müller-Dethlefs Klaus
Published: December 2003

Conformational isomers of the aromatic hydrocarbon n-butylbenzene have been studied using two-color REMPI (resonance enhanced multiphoton ionization) and MATI (mass analyzed threshold ionization) spectroscopy to explore the effect of conformation on ionization dynamics. Gauche- and anti-cationic conformers were selectively produced by two-color excitation via the respective S1 origins. Adiabatic ionization potentials of the gauche- and anti-conformations were determined to be 70 148 and 69 955±5 cm−1, respectively. Analysis of the REMPI and MATI spectra allowed the determination of the S0 (38 cm−1), S1 (100 cm−1), and D0 (−155 cm−1) gauche- and anti-conformer energy differences. Spectral features and vibrational modes are interpreted with the aid of MP2/cc-pVDZ ab initio calculations, and ionization-induced changes in the molecular conformations discussed.
The effect of conformation on the ionization energetics of n-butylbenzene. II. A zero electron kinetic energy photoelectron spectroscopy study with partial rotational resolution
Authors: Ford Mark S. , Tong Xin , Dessent Caroline E. H. , Müller-Dethlefs Klaus
Published: December 2003

Rotationally resolved zero electron kinetic energy (ZEKE) spectra of n-butylbenzene have been investigated using a spectator orbital model to compare the ionization energetics of two molecular conformers. A new ZEKE electron detection scheme was employed to record ZEKE excitation spectra as a function of the S1←S0 excitation laser photon energy, with fixed photon energy of the ionization laser. These ZEKE excitation spectra are a sensitive probe of the rotational constants of all three states involved, the S0 and S1 of the neutral and the D0 of the cation. For gauche-conformer I, the rotational constants of the cation have been determined as A+=2330.6±2.3 MHz, B+=772.4±1.5 MHz, and C+=741.61±0.72 MHz. The rotational constants for the anti-conformer, V, were determined as A+=3410.4±3.3 MHz, B+=577.7±1.9 MHz, and C+=524.79±0.50 MHz. This is the first time that the geometric structures of two cationic conformers have been identified using a rotational analysis. The inertial defects derived from the rotational constants provide detailed information relating to the geometric changes experienced by the conformers upon S1←S0 excitation and D0←S1 ionization. Despite the relatively small difference in geometry between the two conformers, they are observed to display dramatically different ionization cross sections. The differences in ionization dynamics of the conformers are interpreted in terms of conformationally dependent electronic structure changes, with reference to excess charge delocalization from the aromatic ring to the side chain in the cations, resulting in higher angular momentum contributions in the spectator orbital of conformer V compared to conformer I. These higher spectator electron orbital angular momentum components result in a reduced ionization cross section for conformer V compared to conformer I.