769 research outputs found
Dilatonic global strings
We examine the field equations of a self-gravitating global string in low
energy superstring gravity, allowing for an arbitrary coupling of the global
string to the dilaton. Massive and massless dilatons are considered. For the
massive dilaton the spacetime is similar to the recently discovered
non-singular time-dependent Einstein self-gravitating global string, but the
massless dilaton generically gives a singular spacetime, even allowing for
time-dependence. We also demonstrate a time-dependent non-singular
string/anti-string configuration, in which the string pair causes a
compactification of two of the spatial dimensions, albeit on a very large
scale.Comment: 18 pages RevTeX, 3 figures, references amende
Comparison of s- and d-wave gap symmetry in nonequilibrium superconductivity
Recent application of ultrafast pump/probe optical techniques to
superconductors has renewed interest in nonequilibrium superconductivity and
the predictions that would be available for novel superconductors, such as the
high-Tc cuprates. We have reexamined two of the classical models which have
been used in the past to interpret nonequilibrium experiments with some
success: the mu* model of Owen and Scalapino and the T* model of Parker.
Predictions depend on pairing symmetry. For instance, the gap suppression due
to excess quasiparticle density n in the mu* model, varies as n^{3/2} in d-wave
as opposed to n for s-wave. Finally, we consider these models in the context of
S-I-N tunneling and optical excitation experiments. While we confirm that
recent pump/probe experiments in YBCO, as presently interpreted, are in
conflict with d-wave pairing, we refute the further claim that they agree with
s-wave.Comment: 14 pages, 11 figure
Phenotypic plasticity, seasonal climate and the population biology of Bicyclus butterflies (Satyridae) in Malawi
Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe
From the Allerød to the mid-Holocene: Palynological evidence from the south basin of the Caspian Sea
This article has been made available through the Brunel Open Access Publishing Fund. Copyright @ The Authors. This is an open-access article distributed under the terms of the Creative
Commons Attribution-NonCommercial-No Derivative Works License, which permits
non-commercial use, distribution, and reproduction in any medium, provided
the original author and source are credited.Pollen and dinoflagellate cysts have been analysed in a core from the south basin of the Caspian Sea, providing a picture of respectively past vegetation and water salinity for the Late Pleistocene to middle Holocene. A relatively sharp lithological change at 0.86 m depth reflects a shift from detrital silts to carbonates-rich fine silts. From this depth upwards, a Holocene chronology is built based on ten radiocarbon dates on ostracod shells and bulk carbonates. From the vegetation point of view, the Late Pleistocene deserts and steppes were partially replaced in the most sheltered areas by an open woodland with Pinus, Juniperus-Hippophae-Elaeagnus and even Alnus-Quercus-Pterocarya and Fraxinus, related to the Allerød palynozone. This was interrupted by the Younger Dryas palynozone when Artemisia reaches a maximum in a first instance followed by a very dry phase with only a slight return of Pinus and Quercus and the rare presence of Ulmus-Zelkova. From 11.5 to 8.4 cal. ka BP, an open landscape dominated by shrubs such as Ephedra and progressively increasing Quercus appeared. The final spread of diverse evergreen and deciduous trees is delayed and occurs after 8.4 cal. ka BP. It is suggested that this delay is caused by an arid climate in the Early Holocene linked to high insolation and perhaps to a lake effect. The dinocyst assemblages fluctuate between slightly brackish (Pyxidinopsis psilata and Spiniferites cruciformis, 7 psu and lower) and more brackish (Impagidinium caspienense, ∼13 psu). In the Lateglacial (Khvalynian highstand), the assemblages remained dominated by relative low salinity taxa. A late and brief increase of salinity occurred prior to 11.2 cal. ka BP associated with the Mangyshlak lowstand. It is suggested that it was caused by a brief drop in meltwater flow from both the north and the southeast (Uzboy) and a likely evaporation increase. This lowstand occurs quasi at the same time as the end of a longer lowstand in the Black Sea. The freshest waters are then inferred as having occurred between 8.4 and ≤4.4 cal. ka BP, linked to a connection with the Amu Darya and the melting glaciers on the Pamir Mountains. The Caspian Sea is a sensitive environment, easily perturbed by global climatic changes, such as the Allerød and Holocene warming, and the Lateglacial and Younger Dryas cooling, as well as by regional changes in its hydrography, such as shifts in the Eurasian meltwater and the Volga and Amu Darya inflows.Centre National de la Recherche Scientifique, Franc
Genetic and Phenotypic Features of Schizophrenia in the UK Biobank
IMPORTANCE Large-scale biobanks provide important opportunities for mental health
research, but selection biases raise questions regarding the comparability of individuals
with those in clinical research settings.
OBJECTIVE To compare the genetic liability to psychiatric disorders in individuals with
schizophrenia in the UK Biobank with individuals in the Psychiatric Genomics Consortium
(PGC) and to compare genetic liability and phenotypic features with participants recruited
from clinical settings.
DESIGN, SETTING, AND PARTICIPANTS This cross-sectional study included participants from
the population-based UK Biobank and schizophrenia samples recruited from clinical settings
(CLOZUK, CardiffCOGS, Cardiff F-Series, and Cardiff Affected Sib-Pairs). Data were collected
between January 1993 and July 2021. Data analysis was conducted between July 2021
and June 2023.
MAIN OUTCOMES AND MEASURES A genome-wide association study of UK Biobank
schizophrenia case-control status was conducted, and the results were compared with
those from the PGC via genetic correlations. To test for differences with the clinical samples,
polygenic risk scores (PRS) were calculated for schizophrenia, bipolar disorder, depression,
and intelligence using PRS-CS. PRS and phenotypic comparisons were conducted using
pairwise logistic regressions. The proportions of individuals with copy number variants
associated with schizophrenia were compared using Firth logistic regression.
RESULTS The sample of 517 375 participants included 1438 UK Biobank participants with
schizophrenia (550 [38.2%] female; mean [SD] age, 54.7 [8.3] years), 499 475 UK Biobank
controls (271 884 [54.4%] female; mean [SD] age, 56.5 [8.1] years), and 4 schizophrenia
research samples (4758 [28.9%] female; mean [SD] age, 38.2 [21.0] years). Liability to
schizophrenia in UK Biobank was highly correlated with the latest genome-wide association
study from the PGC (genetic correlation, 0.98; SE, 0.18) and showed the expected patterns
of correlations with other psychiatric disorders. The schizophrenia PRS explained 6.8% of the
variance in liability for schizophrenia case status in UK Biobank. UK Biobank participants with
schizophrenia had significantly lower schizophrenia PRS than 3 of the clinically ascertained
samples and significantly lower rates of schizophrenia-associated copy number variants than
the CLOZUK sample. UK Biobank participants with schizophrenia had higher educational
attainment and employment rates than the clinically ascertained schizophrenia samples,
lower rates of smoking, and a later age of onset of psychosis.
CONCLUSIONS AND RELEVANCE Individuals with schizophrenia in the UK Biobank, and likely
other volunteer-based biobanks, represent those less severely affected. Their inclusion in
wider studies should enhance the representation of the full spectrum of illness severity
Specificity of polygenic signatures across symptom dimensions in bipolar disorder: an analysis of UK Bipolar Disorder Research Network data
Background
Current definitions and clinical heterogeneity in bipolar disorder are major concerns as they obstruct aetiological research and impede drug development. Therefore, stratification of bipolar disorder is a high priority. To inform stratification, our analysis aimed to examine the patterns and relationships between polygenic liability for bipolar disorder, major depressive disorder (MDD), and schizophrenia with multidimensional symptom representations of bipolar disorder.
Methods
In this analysis, data from the UK Bipolar Disorder Research Network (BDRN) were assessed with the Operational Checklist for Psychotic Disorders. Individuals with bipolar disorder as defined in DSM-IV, of European ancestry (self-reported), aged 18 years or older at time of interview, living in the UK, and registered with the BDRN were eligible for inclusion. Psychopathological variables obtained via interview by trained research psychologists or psychiatrists and psychiatric case notes were used to identify statistically distinct symptom dimensions, calibrated with exploratory factor analysis and validated with confirmatory factor analysis (CFA). CFA was extended to include three polygenic risk scores (PRSs) indexing liability for bipolar disorder, MDD, and schizophrenia in a multiple indicator multiple cause (MIMIC) structural equation model to estimate PRS relationships with symptom dimensions.
Findings
Of 4198 individuals potentially eligible for inclusion, 4148 (2804 [67·6%] female individuals and 1344 [32·4%] male individuals) with a mean age at interview of 45 years (SD 12·03) were available for analysis. Three reliable dimensions (mania, depression, and psychosis) were identified. The MIMIC model fitted the data well (root mean square error of approximation 0·021, 90% CI 0·019–0·023; comparative fit index 0·99) and suggests statistically distinct symptom dimensions also have distinct polygenic profiles. The PRS for MDD was strongly associated with the depression dimension (standardised β 0·125, 95% CI 0·080–0·171) and the PRS for schizophrenia was strongly associated with the psychosis dimension (0·108, 0·082–0·175). For the mania dimension, the PRS for bipolar disorder was weakly associated (0·050, 0·002–0·097).
Interpretation
Our findings support the hypothesis that genetic heterogeneity underpins clinical heterogeneity, suggesting that different symptom dimensions within bipolar disorder have partly distinct causes. Furthermore, our results suggest that a specific symptom dimension has a similar cause regardless of the primary psychiatric diagnosis, supporting the use of symptom dimensions in precision psychiatry
Active Galactic Nuclei at the Crossroads of Astrophysics
Over the last five decades, AGN studies have produced a number of spectacular
examples of synergies and multifaceted approaches in astrophysics. The field of
AGN research now spans the entire spectral range and covers more than twelve
orders of magnitude in the spatial and temporal domains. The next generation of
astrophysical facilities will open up new possibilities for AGN studies,
especially in the areas of high-resolution and high-fidelity imaging and
spectroscopy of nuclear regions in the X-ray, optical, and radio bands. These
studies will address in detail a number of critical issues in AGN research such
as processes in the immediate vicinity of supermassive black holes, physical
conditions of broad-line and narrow-line regions, formation and evolution of
accretion disks and relativistic outflows, and the connection between nuclear
activity and galaxy evolution.Comment: 16 pages, 5 figures; review contribution; "Exploring the Cosmic
Frontier: Astrophysical Instruments for the 21st Century", ESO Astrophysical
Symposia Serie
- …