bluuebunny/crossref_metadata_2025_split huggingface dataset:
A simple conceptual model of cirrus horizontal inhomogeneity and cloud fraction
Authors: Smith S. A. , Del Genio A. D. 
Published: January 2003

AbstractA simple conceptual model of horizontal inhomogeneity and cloud amount in cirrus clouds has been formulated on the basis that internal horizontal inhomogeneity in the ice mixing ratio is due to variations in the cloud depth, which are assumed to be Gaussian. The use of such a model was justified by the observed relationship between the normalized variability of cloud depth and both the cloud amount and the normalized variability of the ice‐water mixing ratio (and extinction).Using radar cloud‐depth data as input, the model reproduced well the in‐cloud ice‐water mixing ratio histograms obtained from horizontal aircraft runs during the FIRE‐II cirrus campaign. For totally overcast cases the histograms were almost Gaussian, but changed as cloud amount decreased to distributions which peaked at the lowest non‐zero ice value and decreased rapidly and monotonically towards higher ice values for cloud amounts below 90%. Cloud amounts and average ice‐water mixing ratios for cases with observed distributions of cloud depth were predicted by the model to within 15% and 31% of the observed values. This model could be used as a starting point in the development of a GCM parametrization of the ice mixing‐ratio probability distribution function and cloud amount, if a means of diagnosing the depth of the saturated layer and the standard deviation of cloud depth from basic large‐scale meteorological parameters could be determined. Copyright © 2002 Royal Meteorological Society.
VHF radar measurements and model simulations of mountain waves over Wales
Authors: Vosper S. B. , Worthington R. M. 
Published: January 2003

AbstractVery high frequency (VHF) radar measurements of mountain waves over Aberystwyth, Wales, during 29 November 1997 are presented and compared with the predictions made by a three‐dimensional numerical model which is based on the linearized equations of motion. The radar height–time plot of vertical velocity reveals a wave field in the troposphere and lower stratosphere which changes significantly throughout the day. Four separate radiosonde soundings taken during the day are used to represent the steady background flow in the numerical model. In this case the steady‐state model wave fields are shown to compare qualitatively well with the radar measurements and the three‐dimensional information provided by the model is used to help explain the changes in the wave field observed by the radar throughout the day.The radiosonde profiles are interpolated in time to provide approximate basic‐state data at two‐hour intervals. Model steady‐state vertical‐velocity fields, based on each of these 13 approximate basic‐state profiles are used to generate a model time–height vertical‐velocity plot which is qualitatively similar to that obtained from the radar measurements, indicating that, to a reasonable approximation, the evolving wave field can be regarded as a sequence of independent steady states. This is generally true if the basic‐state flow remains steady over the time taken for wave packets to propagate over several wavelengths. Group‐velocity arguments are used to show that, for typical mountain waves in the troposphere, such time‐scales are generally less than one hour.Model simulations in which the basic‐state flow is allowed to vary in time continually (based on either the interpolated radiosonde soundings or the radar horizontal‐wind measurements) are conducted. In this case the simulated wave fields are always unsteady; the waves show a tendency to drift in response to changes in the basic‐state wind field. For example, during instances when the wind speed at a given level decreases (whilst the wind direction remains the same) the waves show an upwind phase propagation with a typical phase speed of the order of 1 m s−1. The consequence of this unsteadiness for the propagation of the waves is discussed. Copyright © 2002 Royal Meteorological Society.
Transient and asymptotic perturbation growth in a simple model
Authors: Gelaro Ronald , Reynolds Carolyn A. , Errico Ronald M. 
Published: January 2003

AbstractThe relationship between asymptotic and finite‐interval instabilities in nonlinear, time‐dependent flows is examined in the context of a quasi‐geostrophic model. For a chosen interval and metric, perturbation growth is related to the singular vectors (SVs) of the linear propagator, while long‐term or asymptotic growth is determined by the leading Lyapunov vector (LV), which is independent of metric and grows at the mean rate of the leading Lyapunov exponent. It is shown that the growth rates of the leading LVs vary significantly about their mean values over periods of a few days. For the leading LV, episodes of greater (or lesser) growth correspond to significant variations in vertical structure, and are highly correlated with its projection onto the leading SVs optimized for short (e.g. 24‐hour) intervals. The LV exhibits maximum growth over east Asia and the Pacific, where its projection onto rapidly growing SVs in the vicinity of the Pacific storm track is greatest. For a given 24‐hour interval, the 30 leading SVs at initial time account for only a few per cent of the total variance of the LV, but account for most of its growth. Filtering these leading SV components from the evolving LV structure over successive intervals reduces its mean (asymptotic) growth rate dramatically in a piecewise continuous sense. The results make clear the importance of transient growth in maintaining the positive mean growth rates of the leading LVs, and in determining the asymptotic stability properties of time‐dependent flows. Copyright © 2002 Royal Meteorological Society.
Implementation and validation of a new prognostic large‐scale cloud and precipitation scheme for climate and data‐assimilation purposes
Authors: Lopez Philippe 
Published: January 2003

AbstractA large‐scale condensation scheme, able to treat separately both atmospheric cloud condensate and precipitation content in a prognostic way, has been implemented and validated in Météo‐France's operational global model, ARPEGE. The proposed scheme can be used for climate simulations and short‐range numerical weather prediction, although it was originally designed for the future variational assimilation of cloud and precipitation observations.The main originalities of the scheme, compared with other existing schemes having a similar moderate level of complexity, lie in the inclusion of a prognostic variable for rain and snow content, and in the use of a simple semi‐Lagrangian treatment of the fall of precipitation. The calculations of large‐scale condensation/evapora tion and cloud fraction are based on probability‐density functions, and the parametrized microphysical processes that involve precipitation are autoconversion, collection, and evaporation/sublimation.Various observations, which include satellite data from METEOSAT and from the Defense Meteorological Satellite Program's Special Sensor Microwave Imager, have been used for validating the cloud scheme within three‐dimensional ARPEGE simulations at operational resolution for cases from the Fronts and Atlantic Storm‐Track Experiment. These ARPEGE simulations have also been compared with 10 km runs obtained with the Met Office's Unified Model and with the French Méso‐NH research model. In addition, cloud radar, ceilometer, and lidar observations from the Atmospheric Radiation Measurement project have been utilized for validating the simulation of a synoptic winter cloud system over the southern Great Plains in the USA. The behaviour of the scheme was then assessed at a coarser resolution, with a particular focus on the zonal‐mean radiative budget of the earth and the zonal‐mean cloud cover.Finally, the question of the sensitivity of the results from the new scheme to various parameters has been addressed, including the time step and the specification of the fall velocities for rain and snow. Copyright © 2002 Royal Meteorological Society.
A refined semi‐Lagrangian vertical trajectory scheme applied to a hydrostatic atmospheric model
Authors: Gospodinov I. , Spiridonov V. , Bénard P. , Geleyn J.‐F. 
Published: January 2003

AbstractAn explicit estimate of the vertical acceleration in a hydrostatic atmospheric model is necessary in order to extend the application of the uniform acceleration two‐time‐level semi‐Lagrangian trajectory scheme of Gospodinov et al. to the vertical direction. It has been diagnosed from the continuity equation. The trajectory scheme proposed, together with the vertical acceleration, has been tested for the so‐called ‘Baltic jet’ case which is dominated by horizontal advection. Enhanced quality has been demonstrated. Copyright © 2002 Royal Meteorological Society.
Investigation of risk factors in children with arterial ischemic stroke
Authors: Ganesan Vijeya , Prengler Mara , McShane Michael A. , Wade Angela M. , Kirkham Fenella J. 
Published: January 2003

AbstractWe present data on the known risk factors encountered in children presenting with a first arterial ischemic stroke to a single tertiary center over 22 years. Two hundred twelve patients (54% male; median age, 5 years) were identified. One hundred fifteen (54%) were previously healthy. Cerebral arterial imaging was undertaken in 185 patients (87%) and was abnormal in 79%. Of 104 previously healthy patients investigated with echocardiography, only 8 had abnormal studies. Genetic or acquired conditions causing thrombophilia were rare. Forty percent of patients were anemic, and 21% either had elevated total plasma homocysteine or were homozygous for the t‐MTHFR mutation. Trauma and previous varicella zoster infection were significantly more common in the previously healthy group. There was a significant association between cerebral arterial abnormalities and systolic blood pressure greater than 90th percentile and a trend for an association with varicella within the previous year. Clinical history and examination usually identify underlying risk factors and precipitating triggers for arterial ischemic stroke in childhood. Cerebral arterial imaging is usually abnormal, but echocardiography and prothrombotic screening are commonly negative. Ann Neurol 2003
Assessing the onset of structural change in familial Alzheimer's disease
Authors: Schott Jonathan M. , Fox Nick C. , Frost Chris , Scahill Rachael I. , Janssen John C. , Chan Dennis , Jenkins Rhian , Rossor Martin N. 
Published: January 2003

AbstractRegional and global cerebral atrophy are inevitable features of Alzheimer's disease (AD). We assessed volumes and atrophy rates of brain structures in patients with familial AD during the period that they developed symptoms. Five patients with presymptomatic AD and 20 controls had two or more annual volumetric MRI brain scans. Volumes of brain, ventricles, temporal lobes, hippocampi, and entorhinal cortices (ECs) were measured. Rates of volume change were calculated from serial scans. There were no significant differences in baseline measures of whole brain, temporal lobe, or ventricular volume between patients and controls; averaged volumes of medial temporal lobe structures (both hippocampi and ECs) were 16.6% (95% confidence interval [CI], 3.3–28.0%) lower in patients. Atrophy rates for brain, temporal lobe, hippocampus, and EC were significantly increased in patients compared with controls (p < 0.05). Averaged atrophy rates from both hippocampi and ECs were 5.1% (95% CI, 3.0–7.1%) greater in patients than controls. Linear extrapolation backward suggested medial temporal lobe atrophy commenced 3.5 years (95% CI, 0.7–7.5 years) before onset, when all patients were asymptomatic. We conclude that increased medial temporal lobe atrophy rates are an early and distinguishing feature of AD and that pathological atrophy probably is occurring several years before the onset of symptoms. Ann Neurol 2003;53:000–000
Magnetic resonance cerebral metabolic rate of oxygen utilization in hyperacute stroke patients
Authors: Lee Jin‐Moo , Vo Katie D. , An Hongyu , Celik Azim , Lee Yueh , Hsu Chung Y. , Lin Weili 
Published: January 2003

AbstractThe purpose of this study was to explore the feasibility of obtaining magnetic resonance–measured cerebral metabolic rate of oxygen utilization (MR‐CMRO2) in acute ischemic stroke patients. Seven stroke patients were serially imaged: 4.5 ± 0.9 hours (tp1), 3 to 5 days (tp2), and 1 to 3 months (tp3) after symptom onset. Diffusion‐weighted, perfusion‐weighted, and multiecho gradient‐echo/spin‐echo images were acquired; cerebral blood flow and oxygen extraction fraction maps were obtained from which CMRO2 was calculated as the product of cerebral blood flow and oxygen extraction fraction. The final infarct lesions obtained from tp3 T2‐weighted images and the “penumbra” obtained from the tp1 perfusion‐weighted image–defined lesion were coregistered onto tp1 CMRO2 maps. CMRO2 values in the region of brain that eventually infarcted were reduced to 0.40 ± 0.24 of the respective region on the contralateral hemisphere. The “salvaged penumbra” defined by the area of mismatch between the final infarct and the tp1 perfusion‐weighted lesion demonstrated an average CMRO2 value of 0.55 ± 0.11 of the contralateral hemisphere. Although our results are preliminary and require further evaluation, the ability to obtain in vivo measurements of MR‐CMRO2 noninvasively potentially can provide information for determining brain tissue viability in acute ischemic stroke patients.
Consequences of a novel caveolin‐3 mutation in a large German family
Authors: Fischer Dirk , Schroers Anja , Blümcke Ingmar , Urbach Horst , Zerres Klaus , Mortier Wilhelm , Vorgerd Matthias , Schröder Rolf 
Published: January 2003

AbstractMutations in the human caveolin‐3 gene (cav‐3) on chromosome 3p25 have been described in limb girdle muscular dystrophy, rippling muscle disease, hyperCKemia, and distal myopathy. Here, we describe the genetic, myopathological, and clinical findings in a large German family harboring a novel heterozygous mutation (GAC→GAA) in codon 27 of the cav‐3 gene. This missense mutation causes an amino acid change from asparagine to glutamate (Asp27Glu) in the N‐terminal region of the Cav‐3 protein, which leads to a drastic decrease of Cav‐3 protein expression in skeletal muscle tissue. In keeping with an autosomal dominant mode of inheritance, this novel cav‐3 mutation was found to cosegregate with neuromuscular involvement in the reported family. Ultrastructural analysis of Cav‐3–deficient muscle showed an abnormal folding of the plasma membrane as well as multiple vesicular structures in the subsarcolemmal region. Neurological examination of all nine subjects from three generations harboring the novel cav‐3 mutation showed clear evidence of rippling muscle disease. However, only two of these nine patients showed isolated signs of rippling muscle disease without muscle weakness or atrophy, whereas five had additional signs of a distal myopathy and two fulfilled the diagnostic criteria of a coexisting limb girdle muscular dystrophy. These findings indicate that mutations in the human cav‐3 gene can lead to different and overlapping clinical phenotypes even within the same family. Different clinical phenotypes in caveolinopathies may be attributed to so far unidentified modifying factors/genes in the individual genetic background of affected patients. Ann Neurol 2003
Blockers of sodium and calcium entry protect axons from nitric oxide‐mediated degeneration
Authors: Kapoor Raju , Davies Meirion , Blaker Paul A. , Hall Susan M. , Smith Kenneth J. 
Published: January 2003

AbstractAxonal degeneration can be an important cause of permanent disability in neurological disorders in which inflammation is prominent, including multiple sclerosis and Guillain–Barré syndrome. The mechanisms responsible for the degeneration remain unclear, but it is likely that axons succumb to factors produced at the site of inflammation, such as nitric oxide (NO). We previously have shown that axons exposed to NO in vivo can undergo degeneration, especially if the axons are electrically active during NO exposure. The axons may degenerate because NO can inhibit mitochondrial respiration, leading to intraaxonal accumulation of Na+ and Ca2+ ions. Here, we show that axons can be protected from NO‐mediated damage using low concentrations of Na+ channel blockers, or an inhibitor of Na+/Ca2+ exchange. Our findings suggest a new strategy for axonal protection in an inflammatory environment, which may be effective in preventing the accumulation of permanent disability in patients with neuroinflammatory disorders. Ann Neurol 2003
The neurobiology, diagnosis, and treatment of narcolepsy
Authors: Scammell Thomas E. 
Published: January 2003

AbstractNarcolepsy is a common cause of chronic sleepiness distinguished by intrusions into wakefulness of physiological aspects of rapid eye movement sleep such as cataplexy and hallucinations. Recent advances provide compelling evidence that narcolepsy may be a neurodegenerative or autoimmune disorder resulting in a loss of hypothalamic neurons containing the neuropeptide orexin (also known as hypocretin). Because orexin promotes wakefulness and inhibits rapid eye movement sleep, its absence may permit inappropriate transitions between wakefulness and sleep. These discoveries have considerably improved our understanding of the neurobiology of sleep and should foster the development of rational treatments for a variety of sleep disorders. Ann Neurol 2003
Axonal injury within language network in primary progressive aphasia
Authors: Catani Marco , Piccirilli Massimo , Cherubini Antonio , Tarducci Roberto , Sciarma Tiziana , Gobbi Gianni , Pelliccioli Gianpiero , Petrillo Stefania Maria , Senin Umberto , Mecocci Patrizia 
Published: January 2003

AbstractPrimary progressive aphasia (PPA) is characterized by an isolated progressive impairment of word use and comprehension reflecting the distribution of pathological processes within the left hemisphere. We used proton magnetic resonance spectroscopy (1H‐MRS) to study in vivo the integrity of axonal fibers connecting perisylvian language areas in 11 patients with PPA, 11 subjects with Alzheimer's disease, and 22 controls. Brain metabolites (N‐acetylaspartate, myoinositol, choline, creatine) were measured bilaterally within a volume of interest located in the central portion of the superior longitudinal fasciculus, a long associative bundle connecting Broca's area with Wernicke's area, and other language regions of the temporal lobe. In the PPA group, there was an asymmetrical N‐acetylaspartate to creatine ratio reduction compared with Alzheimer's disease and controls, with greater changes on the left side. The myoinositol to creatine ratio was increased in the PPA group bilaterally compared with controls. The choline to creatine ratio did not differ among the three groups. These results indicate an asymmetrical focal axonal injury within the language network in PPA. The marked difference in the distribution of N‐acetylaspartate to creatine between PPA and Alzheimer's disease suggests that proton magnetic resonance spectroscopy may help to differentiate between these two conditions. Ann Neurol 2003;53:000–000
Magnetic resonance imaging and neurosphere therapy of stroke in rat
Authors: Zhang Zheng Gang , Jiang Quan , Zhang Ruilan , Zhang Li , Wang Lei , Zhang Lijei , Arniego Polly , Ho Khang‐Loon , Chopp Michael 
Published: January 2003

AbstractWe intracisternally transplanted subventricular zone (SVZ) cells labeled by ferromagnetic particles into stroked rats. Migration of transplanted cells was non‐invasively tracked using magnetic resonance imaging (MRI). We found that transplanted cells selectively migrated towards the ischemic parenchyma at a mean speed of 65 ± 14.6 μm/hr in living rats. Migration of transplanted cells in the brain was also measured histopathologically. Rats transplanted with SVZ cells exhibited significant improvement of neurological function. Our data suggest that intracisternal transplantation of SVZ cells provides an avenue for cell therapy of stroke and that MRI can be used to track grafted cells in the brain. Ann Neurol 2003
Transient suppression of tinnitus by transcranial magnetic stimulation
Authors: Plewnia Christian , Bartels Mathias , Gerloff Christian 
Published: January 2003

AbstractIt has been proposed that tinnitus is associated with an irregular activation of the temporoparietal cortex. If this activity is a functionally relevant component of the tinnitus‐related network, a virtual temporary lesion of this area should result in transient reduction of tinnitus. To test this hypothesis, we applied 10Hz repetitive transcranial magnetic stimulation to eight scalp and four control positions in 14 patients with chronic tinnitus. Stimulation of left temporoparietal cortex significantly reduced tinnitus (Friedman analysis of variance, p < 0.05; compared with control), indicating that secondary auditory areas can be critical for tinnitus perception, perhaps as a consequence of maladaptive cortical reorganization. Ann Neurol 2003
Expression of cyclooxygenase‐2 in embryonic and fetal tissues during organogenesis and late pregnancy
Authors: Stanfield K.M. , Bell R.R. , Lisowski A.R. , English M.L. , Saldeen S.S. , Khan K. Nasir M. 
Published: January 2003

AbstractBACKGROUNDCyclooxygenase (COX) catalyzes the committed step in prostaglandin biosynthesis and exists as two related but unique isoforms, COX‐1 (constitutive) and COX‐2 (inducible). Prostaglandins (PGs) are known to have many important functions in reproduction, such as placentation and decidualization. Studies with the COX‐1 and COX‐2 knockout mice have demonstrated that COX‐2, but not COX‐1, is crucial for normal ovulation, implantation, and decidualization, suggesting that COX‐2–derived PGs are important during the initial stages of pregnancy. Although the COX‐2 knockout mice did not exhibit any abnormalities at birth, relatively little information exists with regard to the expression of COX‐2 in the fetus during development.METHODSIn order to understand the role of COX‐2 throughout pregnancy, we characterized the cell type and the temporal expression of inducible COX‐2 throughout embryonic and fetal development in the rat (n = 22) by immunohistochemistry and in situ hybridization.RESULTSHigh levels of COX‐2 expression were seen in decidualized uterine tissue on gestation days 7–13 and then in the fetal membranes on gestation days 17–20. Cyclooxygenase‐2 expression was not detectable in any tissues from developing embryos during gestation days 7–13, but was observed in the fetal growth period (gestation days 15–20) in the skin, heart, cartilage, and the kidney.CONCLUSIONSNo COX‐2 expression was seen in fetal tissues at days 7–13 of gestation, but was seen in various tissues at days 15–17 of gestation. These observations suggest that COX‐2 may be important in mid to late pregnancy through an effect on fetal organ growth, but not in the organogenetic phase of fetal development. Birth Defects Research (Part A) 67:54–58, 2003. © 2003 Wiley‐Liss, Inc.