946 research outputs found

    Study of the tidal variations in mesospheric temperature at low and mid latitudes from WINDII and potassium lidar observations

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    Zonal mean daytime temperatures from the Wind Imaging Interferometer (WINDII) on the Upper Atmosphere Research Satellite (UARS) and nightly temperatures from a potassium (K) lidar are employed in the study of the tidal variations in mesospheric temperature at low and mid latitudes in the Northern Hemisphere. The analysis is applied to observations at 89km height for winter solstice, December to February (DJF), at 55° N, and for May and November at 28° N. The WINDII results are based on observations from 1991 to 1997. The K-lidar observations for DJF at Kühlungsborn (54° N) were from 1996–1999, while those for May and November at Tenerife 28° N were from 1999. To avoid possible effects from year-to-year variability in the temperatures observed, as well as differences due to instrument calibration and observation periods, the mean temperature field is removed from the respective data sets, assuming that only tidal and planetary scale perturbations remain in the temperature residuals. The latter are then binned in 0.5h periods and the individual data sets are fitted in a least-mean square sense to 12-h and 8-h harmonics, to infer semidiurnal and terdiurnal tidal parameters. Both the K-lidar and WINDII independently observed a strong semidiurnal tide in November, with amplitudes of 13K and 7.4K, respectively. Good agreement was also found in the tidal parameters derived from the two data sets for DJF and May. It was recognized that insufficient local time coverage of the two separate data sets could lead to an overestimation of the semidiurnal tidal amplitude. A combined ground-based/satellite data set with full diurnal local time coverage was created which was fitted to 24h+12h+8h harmonics and a novel method applied to account for possible differences between the daytime and nighttime means. The results still yielded a strong semidiurnal tide in November at 28° N with an amplitude of 8.8K which is twice the SD amplitude in May and DJF. The diurnal tidal parameters were practically the same at 28° N and 55° N, in November and DJF, respectively, with an amplitude of 6.5K and peaking at ~9h. The diurnal and semidiurnal amplitudes in May were about the same, 4K, and 4.6K, while the terdiurnal tide had the same amplitudes and phases in May and November at 28° N. Good agreement is found with other experimental data while models tend to underestimate the amplitudes.<br><br><b> Key words.</b> Atmospheric composition and structure (pressure, density and temperature) – Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides

    Accumulated environmental risk in young refugees – A prospective evaluation

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    Background: Recently, we reported a strong, disease-independent relationship between accumulated pre-adult environmental risks and violent aggression later in life. Risk factors were interchangeable, and migration was among the explored risks. Alarmed by these data, we assessed collected risk loadin young ‘healthy’ refugees as a specifics group of current migration streams and evaluated first signals of behavioral abnormalities. Methods: In 9 German refugee centers, n=133 young refugees, not previously in contact with the health system, were recruited, many of them unaccompanied minors. Risk factors experienced apart from migration/refuge were carefully assessed: Traumatic experiences before/during/after flight (including war,genocide, human trafficking, torture, murder, slavery, terrorist attacks), urbanicity, physical and sexual abuse, problematic alcohol and cannabis use (lifetime). Evaluation comprised physical exam and psychopathology screening. Findings: Refugees arrived in Germany via Eastern Mediterranean/Balkanroute (34.6%), from Africa via Central Mediterranean route (39.1%), by plane (17.3%) or other routes, such as Western Mediterranean or Atlantic (9.0%). Flight reasons were war/expulsion (25.6%), persecution/threats to life (51.9%), economical/others (22.5%). Interpretation: refugees from hosting countries with alarming 'risk burden', should be considered as highly vulnerable towards development of global functional deficits, behavioral abnormalities, and neuropsychiatric disorders. Rapid proactive integration or sustainable support of those who will return to rebuild their countries are mandatory

    Odor naming and interpretation performance in 881 schizophrenia subjects: association with clinical parameters

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    BACKGROUND: Olfactory function tests are sensitive tools for assessing sensory-cognitive processing in schizophrenia. However, associations of central olfactory measures with clinical outcome parameters have not been simultaneously studied in large samples of schizophrenia patients. METHODS: In the framework of the comprehensive phenotyping of the GRAS (Göttingen Research Association for Schizophrenia) cohort, we modified and extended existing odor naming (active memory retrieval) and interpretation (attribute assignment) tasks to evaluate them in 881 schizophrenia patients and 102 healthy controls matched for age, gender and smoking behavior. Associations with emotional processing, neuropsychological test performance and disease outcome were studied. RESULTS: Schizophrenia patients underperformed controls in both olfactory tasks. Odor naming deficits were primarily associated with compromised cognition, interpretation deficits with positive symptom severity and general alertness. Contrasting schizophrenia extreme performers of odor interpretation (best versus worst percentile; N=88 each) and healthy individuals (N=102) underscores the obvious relationship between impaired odor interpretation and psychopathology, cognitive dysfunctioning, and emotional processing (all p<0.004). CONCLUSIONS: The strong association of performance in higher olfactory measures, odor naming and interpretation, with lead symptoms of schizophrenia and determinants of disease severity highlights their clinical and scientific significance. Based on the results obtained here in an exploratory fashion in a large patient sample, the development of an easy-to-use clinical test with improved psychometric properties may be encouraged

    The importance of initial-final state correlations for the formation of fragments in heavy ion collisions

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    Using quantum molecular dynamics simulations, we investigate the formation of fragments in symmetric reactions between beam energies of E=30AMeV and 600AMeV. After a comparison with existing data we investigate some observables relevant to tackle equilibration: dsigma/dErat, the double differential cross section dsigma/pt.dpz.dpt,... Apart maybe from very energetic E>400AMeV and very central reactions, none of our simulations gives evidence that the system passes through a state of equilibrium. Later, we address the production mechanisms and find that, whatever the energy, nucleons finally entrained in a fragment exhibit strong initial-final state correlations, in coordinate as well as in momentum space. At high energy those correlations resemble the ones obtained in the participant-spectator model. At low energy the correlations are equally strong, but more complicated; they are a consequence of the Pauli blocking of the nucleon-nucleon collisions, the geometry, and the excitation energy. Studying a second set of time-dependent variables (radii, densities,...), we investigate in details how those correlations survive the reaction especially in central reactions where the nucleons have to pass through the whole system. It appears that some fragments are made of nucleons which were initially correlated, whereas others are formed by nucleons scattered during the reaction into the vicinity of a group of previously correlated nucleons.Comment: 45 pages text + 20 postscript figures Accepted for publication in Physical Review

    Detectability of dirty dust grains in brown dwarf atmospheres

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    Dust clouds influence the atmospheric structure of brown dwarfs, and they affect the heat transfer and change the gas-phase chemistry. However, the physics of their formation and evolution is not well understood. In this letter, we predict dust signatures and propose a potential observational test of the physics of dust formation in brown dwarf atmosphere based on the spectral features of the different solid components predicted by dust formation theory. A momentum method for the formation of dirty dust grains (nucleation, growth, evaporation, drift) is used in application to a static brown dwarf atmosphere structure to compute the dust grain properties, in particular the heterogeneous grain composition and the grain size. Effective medium and Mie theory are used to compute the extinction of these spherical grains. Dust formation results in grains whose composition differs from that of grains formed at equilibrium. Our kinetic model predicts that solid amorphous SiO2[s] (silica) is one of the most abundant solid component followed by amorphous MgSiO4[s] and MgSiO3[s], while SiO2[s] is absent in equilibrium models because it is a metastable solid. Solid amorphous SiO2[s] possesses a strong broad absorption feature centered at 8.7mum, while amorphous Mg2SiO4[s]/MgSiO3[s] absorb at 9.7mum beside other absorption features at longer wavelength. Those features at lambda < 15mum are detectable in absorption if grains are small (radius < 0.2mum) in the upper atmosphere as suggested by our model. We suggest that the detection of a feature at 8.7mum in deep infrared spectra could provide evidence for non-equilibrium dust formation that yields grains composed of metastable solids in brown dwarf atmospheres. This feature will shift towards 10mum and broaden if silicates (e.g. fosterite) are much more abundant.Comment: A&A Letter, accepte

    A benzene interference single-electron transistor

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    Interference effects strongly affect the transport characteristics of a benzene single-electron transistor (SET) and for this reason we call it interference SET (I-SET). We focus on the effects of degeneracies between many-body states of the isolated benzene. We show that the particular current blocking and selective conductance suppression occurring in the benzene I-SET are due to interference effects between the orbitally degenerate states. Further we study the impact of reduced symmetry due to anchor groups or potential drop over the molecule. We identify in the quasi-degeneracy of the involved molecular states the necessary condition for the robustness of the results.Comment: 17pages, 9 figures, revised versio

    Preadult polytoxicomania—strong environmental underpinnings and first genetic hints

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    Considering the immense societal and personal costs and suffering associated with multiple drug use or “polytoxicomania”, better understanding of environmental and genetic causes is crucial. While previous studies focused on single risk factors and selected drugs, effects of early-accumulated environmental risks on polytoxicomania were never addressed. Similarly, evidence of genetic susceptibility to particular drugs is abundant, while genetic predisposition to polytoxicomania is unexplored. We exploited the GRAS data collection, comprising information on N~2000 deep-phenotyped schizophrenia patients, to investigate effects of early-life environmental risk accumulation on polytoxicomania and additionally provide first genetic insight. Preadult accumulation of environmental risks (physical or sexual abuse, urbanicity, migration, cannabis, alcohol) was strongly associated with lifetime polytoxicomania (p  = 1.5 × 10−45; OR = 31.4), preadult polytoxicomania with OR = 226.6 (p = 1.0 × 10−33) and adult polytoxicomania with OR = 17.5 (p = 3.4 × 10−24). Parallel accessibility of genetic data from GRAS patients and N~2100 controls for genome-wide association (GWAS) and phenotype-based genetic association studies (PGAS) permitted the creation of a novel multiple GWAS–PGAS approach. This approach yielded 41 intuitively interesting SNPs, potentially conferring liability to preadult polytoxicomania, which await replication upon availability of suitable deep-phenotyped cohorts anywhere world-wide. Concisely, juvenile environmental risk accumulation, including cannabis and alcohol as starter/gateway drugs, strongly predicts polytoxicomania during adolescence and adulthood. This pivotal message should launch more effective sociopolitical measures to prevent this deleterious psychiatric condition

    The neurobiological characterization of distinct cognitive subtypes in early-phase schizophrenia-spectrum disorders

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    INTRODUCTION: Cognitive deficits are present in some, but not all patients with schizophrenia-spectrum disorders (SSD). We and others have demonstrated three cognitive clusters: cognitively intact patients, patients with deficits in a few domains and those with global cognitive deficits. This study aimed to identify cognitive subtypes of early-phase SSD with matched controls as a reference group, and evaluated cognitive subgroups regarding clinical and brain volumetric measures. METHODS: Eighty-six early-phase SSD patients were included. Hierarchical cluster analysis was conducted using global performance on the Brief Assessment of Cognition in Schizophrenia (BACS). Cognitive subgroups were subsequently related to clinical and brain volumetric measures (cortical, subcortical and cortical thickness) using ANCOVA. RESULTS: Three distinct cognitive clusters emerged: relative to controls we found one cluster of patients with preserved cognition (n = 25), one moderately impaired cluster (n = 38) and one severely impaired cluster (n = 23). Cognitive subgroups were characterized by differences in volume of the left postcentral gyrus, left middle caudal frontal gyrus and left insula, while differences in cortical thickness were predominantly found in fronto-parietal regions. No differences were demonstrated in subcortical brain volume. DISCUSSION: Current results replicate the existence of three distinct cognitive subgroups including one relatively large group with preserved cognitive function. Cognitive subgroups were characterized by differences in cortical regional brain volume and cortical thickness, suggesting associations with cortical, but not subcortical development and cognitive functioning such as attention, executive functions and speed of processing

    Mid-Infrared Imaging and Modelling of the Dust Shell around Post-AGB star HD 187885 (IRAS 19500-1709)

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    We present 10 and 20 micron images of IRAS 19500-1709 taken with the mid-infrared camera, OSCIR, mounted on the Gemini North Telescope. We use a 2-D dust radiation transport code to fit the spectral energy distribution from UV to sub-mm wavelengths and to simulate the images.Comment: 4 pages, 5 figures. To appear in "Asymmetric Planetary Nebulae III", eds. M.Meixner, J.Kastner, N.Soker & B.Balick. 2004, ASP Conference Serie
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