778 research outputs found
Localization of Atiyah classes
We construct the Atiyah classes of holomorphic vector bundles using (1,0)-connections and developing a Chern–Weil type theory, allowing us to effectively compare Chern and Atiyah forms. Combining this point of view with the Čech–Dolbeault cohomology, we prove several results about vanishing and localization of Atiyah classes, and give some applications. In particular, we prove a Bott type vanishing theorem for (not necessarily involutive) holomorphic distributions. As an example we also present an explicit computation of the residue of a singular distribution on the normal bundle of an invariant submanifold that arises from the Camacho–Sad type localization
Fibrations of genus two on complex surfaces
We consider fibrations of genus 2 over complex surfaces. The purpose of this
paper is primarily to provide a geometric description of the possible
structures of the fibration on a neighborhood of a singular fiber. In
particular it is shown that the "geometric data" of the singular fiber
determines the fibration on its neighborhood up to a transversely holomorphic
-diffeomorphism. The method employed is quite flexible and it
applies to good extent to fibrations of arbitrary genus.Comment: This is the final version, June 201
Sociodemographic predictors of depression among survivors of armed conflict with posttraumatic stress disorder in Dogonahawa, north central Nigeria
Background: Survivors of mass violence are at high risk of developing a wide range of psychological disorders. Nevertheless, little is known about the impact of trauma in post conflict low-income countries where armed conflict abounds.Objective: This study was carried out to assess the prevalence of comorbid depression among victims of armed- conflict in Dogonahawa, north-central Nigeria who developed posttraumatic stress disorder (PTSD) and those who did not. It also assessed the socio-demographic predictors for comorbid depression among those who developed PTSD.Method: A cross-sectional study that employed a multi stage sampling technique to select eligible subjects in Dogonahawa, north-central Nigeria. The PTSD module of Mini International Neuropsychiatric Interview (MINI) was used to assess for current symptoms of PTSD, while the Beck Depression Inventory-II (BDI-II) was used to assess for depression.Results: The results showed that 55.5% and 44.7% of the respondents had PTSD and PTSD with comorbid depression respectively. The difference in prevalence was statistically significant with adults diagnosed with PTSD in this community being significantly more likely to experience comorbid depression than those without PTSD (p< 0.001). Being a female gender and being the head of household were found to be the predictors for comorbid depression among respondents with PTSD.Conclusions: Mental health consequences of conflict continued to endure four years after the armed conflict. In the light of the above, mental health emergency interventions after exposure to traumatic event need to be developed to enhance healing and recovery.KeyWords: PTSD, co-morbid depression, sociodemographic predictors, depression, Armed, Conflict, Dogonahaw
An approximate theory for substructure propagation in clusters
The existence of dark matter can be proved in an astrophysical context by the
discovery of a system in which the observed baryons and the inferred dark
matter are spatially segregated, such as the bullet cluster (1E0657-558). The
full descriptions of the dark matter halo and X-ray gas substructure motions
are necessary to forecast the location of the dark halo from X-ray maps, which
can be confirmed by the detection of a galaxy concentration or by gravitational
lensing. We present an analytical hydrodynamic model to determine the distance
between the X-ray and dark-matter components and the Mach number of the merger
shock. An approximate solution is given for the problem of the substructure
propagation in merging clusters. A new method to predict the position of a dark
matter halo in clusters, where there is a separation between the X-ray gas and
the dark halo, is proposed and applied to the clusters 1E0657-558 and Abell
1763.Comment: Accepted for publication in Astronomy & Astrophysic
Interacting Ricci Dark Energy and its Statefinder Description
In this paper we have considered an interacting Ricci dark energy in flat FRW
universe. We have reconstructed the Hubble's parameter under this interaction.
Also, we have investigated the statefinder diagnostics. It has been revealed
that the equation of state parameter behaves like quintessence in this
interaction and from the statefinder diagnostics it has been concluded that the
interacting Ricci dark energy interpolates between dust and CDM stages
of the universe.Comment: 9 pages, 3 figure
Higher Order Corrections to the Primordial Gravitational Wave Spectrum and its Impact on Parameter Estimates for Inflation
We study the impact of the use of the power series expression for the
primordial tensor spectrum on parameter estimation from future direct detection
gravitational wave experiments. The spectrum approximated by the power series
expansion may give large deviation from the true (fiducial) value when it is
normalized at CMB scale because of the large separation between CMB and direct
detection scales. We derive the coefficients of the higher order terms of the
expansion up to the sixth order within the framework of the slow-roll
approximation and investigate how well the inclusion of higher order terms
improves the analytic prediction of the spectrum amplitude by comparing with
numerical results. Using the power series expression, we consider future
constraints on inflationary parameters expected from direct detection
experiments of the inflationary gravitational wave background and show that the
truncation of the higher order terms can lead to incorrect evaluation of the
parameters. We present two example models; a quadratic chaotic inflation model
and mixed inflaton and curvaton model with a quartic inflaton potential.Comment: 25 pages, 7 figures, revised version accepted by JCA
Hard X-ray Bursts from Collapse of the Super Massive Stars
The very first stars in the Universe can be very massive, up to
. They would leave behind massive black holes that could act as
seeds for growing super massive black holes of active galactic nuclei. Given
the anticipated fast rotation such stars would end their live as super massive
collapsars and drive powerful magnetically-dominated jets. In this paper we
investigate the possibility of observing the bursts of high-energy emission
similar to the Long Gamma Ray Bursts associated with normal collapsars. We show
that during the collapse of supercollapsars, the Blandford-Znajek mechanism can
produce jets as powerful as fewerg/s and release up to
erg of the black hole rotational energy. Due to the higher intrinsic
time scale and higher redshift the initial bright phase of the burst can last
for about seconds whereas the central engine would remain active for
about 10 days. Due to the high redshift the burst spectrum is expected to be
soft, with the spectral energy distribution peaking at around 60keV. The peak
total flux density is relatively low, few,
but not prohibitive. The such events should be rear 0.03 year, the
observations needs long term program and could be done in future.Comment: 4 pages, 2 figures. proceedings of workshop "Many faces of GRB
phenomena - optics vs high energy", SAO Russia, October 12-16, 2009
Tunable Emergent Heterostructures in a Prototypical Correlated Metal
At the interface between two distinct materials desirable properties, such as
superconductivity, can be greatly enhanced, or entirely new functionalities may
emerge. Similar to in artificially engineered heterostructures, clean
functional interfaces alternatively exist in electronically textured bulk
materials. Electronic textures emerge spontaneously due to competing
atomic-scale interactions, the control of which, would enable a top-down
approach for designing tunable intrinsic heterostructures. This is particularly
attractive for correlated electron materials, where spontaneous
heterostructures strongly affect the interplay between charge and spin degrees
of freedom. Here we report high-resolution neutron spectroscopy on the
prototypical strongly-correlated metal CeRhIn5, revealing competition between
magnetic frustration and easy-axis anisotropy -- a well-established mechanism
for generating spontaneous superstructures. Because the observed easy-axis
anisotropy is field-induced and anomalously large, it can be controlled
efficiently with small magnetic fields. The resulting field-controlled magnetic
superstructure is closely tied to the formation of superconducting and
electronic nematic textures in CeRhIn5, suggesting that in-situ tunable
heterostructures can be realized in correlated electron materials
A systematic review of protocol studies on conceptual design cognition
This paper reports the first systematic review and synthesis of protocol studies on conceptual design cognition. 47 protocol studies from the domains of architectural design, engineering design, and product de-sign engineering were reviewed towards answering the following re-search question: What is our current understanding of the cognitive processes involved in conceptual design tasks carried out by individual designers? Studies were found to reflect three viewpoints on the cognitive nature of designing, namely: design as search; design as ex-ploration; and design activities. Synthesising the findings of individual studies yielded a classification of cognitive processes involved in con-ceptual design tasks, described in different terms across different viewpoints. Towards a common terminology, these processes are posi-tioned within the cognitive psychology literature, revealing seven basic types of process that appear to be fundamental to designing across all viewpoints: memory (working and long term); visual perception; men-tal imagery; attention; semantic association; cognitive control; and higher-order processes, e.g. analysis and reasoning. The development of common cognitive models of conceptual design, grounded in a sci-entifically rigorous understanding of design cognition, is identified as an avenue for future research
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