766 research outputs found
Paracingulate sulcus morphology is associated with hallucinations in the human brain
Hallucinations are common in psychiatric disorders, and are also experienced by many individuals who are not mentally ill. Here, in 153 participants, we investigate brain structural markers that predict the occurrence of hallucinations by comparing patients with schizophrenia who have experienced hallucinations against patients who have not, matched on a number of demographic and clinical variables. Using both newly validated visual classification techniques and automated, data-driven methods, hallucinations were associated with specific brain morphology differences in the paracingulate sulcus, a fold in the medial prefrontal cortex, with a 1 cm reduction in sulcal length increasing the likelihood of hallucinations by 19.9%, regardless of the sensory modality in which they were experienced. The findings suggest a specific morphological basis for a pervasive feature of typical and atypical human experience
Spatial variability of the Purbeck–Wight Fault Zone—a long-lived tectonic element in the southern UK
New seamless onshore to offshore bedrock (1:10 k scale) mapping for the Lyme Bay area is used to resolve the westward termination of the Purbeck–Wight Fault Zone (PWFZ) structure, comprising one of the most prominent, long-lived (Variscan–Cimmerian–Alpine) structural lineaments in the southern UK. The study area lies south of the Variscan Frontal Thrust and overlays the basement Variscide Rhenohercynian Zone, in a region of dominant E-W tectonic fabric and a secondary conjugate NW-SE/NE-SW fabric. The PWFZ comprises one of the E-W major structures, with a typical history including Permian to early Cretaceous growth movement (relating to basement Variscan Thrust reactivation) followed by significant Alpine (Helvetic) inversion. Previous interpretations of the PWFZ have been limited by the low resolution (1:250 k scale) of the available offshore BGS mapping, and our study fills this gap. We describe a significant change in structural style of the fault zone from east to west. In the Weymouth Bay area, previous studies demonstrate the development of focussed strain associated with the PWFZ, accompanied by distributed strain, N-S fault development, and potential basement uplift in its hangingwall. In the Lyme Bay area to the west, faulting is dominantly E-W, with N-S faulting absent. Comparison of the newly mapped faulting networks to gravity data suggests a spatial relationship between this faulting variation and basement variability and uplift
Probing the time dependence of dark energy
A new method to investigate a possible time-dependence of the dark energy
equation of state is proposed. We apply this methodology to two of the most
recent data sets of type Ia supernova (Union2 and SDSS) and the baryon acoustic
oscillation peak at . For some combinations of these data, we show
that there is a clear departure from the standard CDM model at
intermediary redshifts, although a non-evolving dark energy component () cannot be ruled out by these data. The approach developed here may be
useful to probe a possible evolving dark energy component when applied to
upcoming observational data.Comment: 6 pages, 3 figures, LaTe
Thermomagnetic history effects in SmMnGe
The intermetallic compound SmMnGe, displaying multiple magnetic phase
transitions, is being investigated in detail for its magnetization behavior
near the 145 K first order ferromagnetic to antiferromagnetic transition
occuring on cooling, in particular for thermomagnetic history effects in the
magnetization data. The most unusual finding is that the thermomagnetic
irreversibility, [= M(T)-M(T)] at 135 K is higher in
intermediate magnetic field strengths. By studying the response of the sample
(i.e., thermomagnetic irreversibility and thermal hysteresis) to different
histories of application of magnetic field and temperature, we demonstrate how
the supercooling and superheating of the metastable magnetic phases across the
first order transition at 145 K contribute to overall thermomagnetic
irreversibility.Comment: 15 pages, 5 figures, to appear in Physical Review
4f spin density in the reentrant ferromagnet SmMn2Ge2
The spin contribution to the magnetic moment in SmMn2Ge2 has been measured by
magnetic Compton scattering in both the low and high temperature ferromagnetic
phases. At low temperature, the Sm site is shown to possess a large 4f spin
moment of 3.4 +/- 0.1 Bohr magnetons, aligned antiparallel to the total
magnetic moment. At high temperature, the data show conclusively that ordered
magnetic moments are present on the samarium site.Comment: 5 pages, 2 figures, transferred from PRL to PRB (Rapid Comm.
Open Issues on the Synthesis of Evolved Stellar Populations at Ultraviolet Wavelengths
In this paper we briefly review three topics that have motivated our (and
others') investigations in recent years within the context of evolutionary
population synthesis techniques. These are: The origin of the FUV up-turn in
elliptical galaxies, the age-metallicity degeneracy, and the study of the
mid-UV rest-frame spectra of distant red galaxies. We summarize some of our
results and present a very preliminary application of a UV grid of theoretical
spectra in the analysis of integrated properties of aged stellar populations.
At the end, we concisely suggest how these topics can be tackled once the World
Space Observatory enters into operation in the midst of this decade.Comment: 8 pages, 4 figures, accepted for publication in Astrophysics & Space
Science, UV Universe special issu
Elastic Scattering of Pions From the Three-nucleon System
We examine the scattering of charged pions from the trinucleon system at a
pion energy of 180 MeV. The motivation for this study is the structure seen in
the experimental angular distribution of back-angle scattering for pi+ 3He and
pi- 3H but for neither pi- 3He nor pi+ 3H. We consider the addition of a double
spin flip term to an optical model treatment and find that, though the
contribution of this term is non-negligible at large angles for pi+ 3He and pi-
3H, it does not reproduce the structure seen in the experiment.Comment: 15 pages + 5 figure
Current lookback time-redshift bounds on dark energy
We investigate observational constraints on dark energy models from lookback
time (LT) estimates of 32 old passive galaxies distributed over the redshift
interval . To build up our LT sample we combine the age
measurements for these 32 objects with estimates of the total age of the
Universe, as obtained from current CMB data. We show that LT data may provide
bounds on the cosmological parameters with accuracy competitive with type Ia
Supernova methods. In order to break possible degeneracies between models
parameters, we also discuss the bounds when our lookback time versus redshift
sample is combined with with the recent measurement of the baryonic acoustic
oscillation peak and the derived age of the Universe from current CMB
measurements.Comment: 6 pages, 4 figures, LaTe
Charge Form Factor and Cluster Structure of Li Nucleus
The charge form factor of Li nucleus is considered on the basis of its
cluster structure. The charge density of Li is presented as a
superposition of two terms. One of them is a folded density and the second one
is a sum of He and the deuteron densities. Using the available
experimental data for He and deuteron charge form factors, a good
agreement of the calculations within the suggested scheme is obtained with the
experimental data for the charge form factor of Li, including those in
the region of large transferred momenta.Comment: 12 pages 5 figure
Charge-Symmetry Violation in Pion Scattering from Three-Body Nuclei
We discuss the experimental and theoretical status of charge-symmetry
violation (CSV) in the elastic scattering of pi+ and pi- on 3H and 3He.
Analysis of the experimental data for the ratios r1, r2, and R at Tpi = 142,
180, 220, and 256 MeV provides evidence for the presence of CSV. We describe
pion scattering from the three-nucleon system in terms of single- and
double-scattering amplitudes. External and internal Coulomb interactions as
well as the Delta-mass splitting are taken into account as sources of CSV.
Reasonable agreement between our theoretical calculations and the experimental
data is obtained for Tpi = 180, 220, and 256 MeV. For these energies, it is
found that the Delta-mass splitting and the internal Coulomb interaction are
the most important contributions for CSV in the three-nucleon system. The CSV
effects are rather sensitive to the choice of pion-nuclear scattering
mechanisms, but at the same time, our theoretical predictions are much less
sensitive to the choice of the nuclear wave function. It is found, however,
that data for r2 and R at Tpi = 142 MeV do not agree with the predictions of
our model, which may indicate that there are additional mechanisms for CSV
which are important only at lower energies.Comment: 26 pages of RevTeX, 16 postscript figure
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