1,494 research outputs found
Effective action for the field equations of charged black holes
In this article, we consistently reduce the equations of motion for the
bosonic N = 2 supergravity action, using a multi-centered black hole ansatz for
the metric. This reduction is done in a general, non-supersymmetric setup, in
which we extend concepts of BPS black hole technology. First of all we obtain a
more general form of the black hole potential, as part of an effective action
for both the scalars and the vectors in the supergravity theory. Furthermore,
we show that there are extra constraints specifying the solution, which we
calculate explicitly. In the literature, these constraints have already been
studied in the one-center case. We also show that the effective action we
obtain for non-static metrics, can be linked to the "entropy function" for the
spherically symmetric case, as defined by Sen and Cardoso et al.Comment: 18 pages, (v2: small corrections, version to be published in CQG
Seagrass mapping synthesis: a resource for coastal management in the Great Barrier Reef World Heritage Area
This project provides an up to date synthesis of the available information on seagrass in the Great Barrier Reef World Heritage Area (GBRWHA). It brings together more than 30 years of spatial information and data collection into easy to use spatial GIS layers that provide key information on species, meadow type and age and reliability of the data.
The project provides:
Seagrass site and meadow-specific data in Geographic Information System (GIS) layers to provide seagrass data to inform research analysis and management advice.
A site layer that includes >66,000 individual survey sites with information including latitude/longitude, Natural Resource Management region, site depth, seagrass presence/absence, dominant seagrass species, presence/absence of individual species, survey date, survey method, and data custodian.
A meadow layer that includes 1169 individual and/or composite seagrass meadows with information including individual meadow persistence, meadow location (intertidal/subtidal), meadow density based on mean biomass and/or mean percent cover, meadow area, dominant seagrass species, seagrass species present, range of survey dates, survey method, and data custodian.
Metadata to enable interpretation of the information and to identify the original data custodians for assistance with interpretation.
Outcomes:
This study consolidates all available seagrass spatial data for the GBRWHA collected from 1984 to December 2014 by the TropWATER Seagrass Group and CSIRO in a GIS database.
It assembles and documents the state of spatial knowledge of seagrass in the GBRWHA.
The spatial data is based on methods developed by TropWATER and CSIRO for seagrass habitat surveys of subtidal meadows, and TropWATER methods for intertidal surveys. Methods include sampling by boat (free divers, underwater video camera, grabs, sled with net sampling), helicopter and walking.
447,530 hectares of seagrasses were mapped (modelled deep water seagrass areas are not included in area figures in this report) within the GBRWHA; much of which provides habitat for commercial and traditional fishery species, and an important food resource for dugong and green turtle populations.
Data is included for twelve seagrass species from three families. Seagrass was present at 39% of all sites visited.
The study identifies areas where much of the data available for management is more than 20 years old or where there are specific habitats unsurveyed. Large areas of central and northern Queensland require updating. Several key habitat types such as reef platform seagrass meadows are poorly represented in the data
Non-supersymmetric Attractors in Born-Infeld Black Holes with a Cosmological Constant
We investigate the attractor mechanism for spherically symmetric extremal
black holes in Einstein-Born-Infeld-dilaton theory of gravity in
four-dimensions, in the presence of a cosmological constant. We look for
solutions analytic near the horizon by using perturbation method. It is shown
that the values of the scalar fields at the horizon are only dependent on the
charges carried by the black hole and are irrelevant in their asymptotic
values. This analysis supports the validity of non-supersymmetric attractors in
the presence of higher derivative interactions in the gauge fields part and in
non-asymptotically flat spacetime.Comment: 18 pages, no figu
Diffraction Grating and Periodic Surface on Porous Silicon
Fabrication of micrometer size laser-induced periodic surface structures (ripples)on single crystalline silicon by laser beam irradiation of wavelength (810 nm) in HFelectrolyte has been reported. Nonlinear changes of the refractive index are observeddue to the interaction of laser light with silicon nanoparticles. Spatial self-phasemodulated optical fringes were used to study the nonlinear optical response ofnanocrystalline silicon produced by laser-induced etching process
Preparation and characterization of activated carbon from plantain peel and coconut shell using biological activators
A concern over the toxicity of chemicals used during the activation stage in the
preparation of activated carbon is beginning to gain attention. The study
therefore looked into the possibility of using bio-activators (lemon juice and
potash leached from the peel of unripe plantain) as activating chemicals, for
environmentally friendly activated carbon. Coconut shell and the peel from
unripe plantain were used as feedstock and pyrolyzed at 400 and 450 0c. An
impregnation ratio of 0.25:1 was used while laboratory grade potassium
hydroxide was used as a base activating agent as a control setup.
Characterization of the activated carbon was carried out using parameters like
bulk density and yield which were obtained using standard procedures. Results
showed that activating carbon using bio-activators as activating agents had very
good characteristics when compared with the control. Bio-activators are
therefore recommended for the production of bio based activated carbon
especially in the fields of medicine, food and pharmaceuticals. The effect of
carbonization temperature on adsorption efficiency and pore structure were
investigated using methylene blue as adsorbate and SEM respectively
Multi-Centered Black Hole Flows
We describe the systematical construction of the first order formalism for
multi-centered black holes with flat three dimensional base-space, within the
so-called model of N=2, D=4 ungauged Maxwell-Einstein supergravity. The
three possible flow classes (BPS, composite non-BPS and almost-BPS) are
analyzed in detail, and various solutions, such as single-centered (static or
under-rotating) and all known multi-centered black holes, are recovered in this
unified framework. We also consider the possibility of obtaining new solutions.
The almost-BPS class is proved to split into two general sub-classes,
corresponding to a positive or negative value of the duality-invariant
polynomial for the total charge; the well known almost BPS system is shown to
be a particular solution of the second sub-class.Comment: 17 pages,no figure
Helicobacter pylori Infection in Various ABO Blood Groups of Kashmiri Population
Aim: This study was carried out to assess the prevalence of Helicobacter pylori infection
in various ABO blood groups of people of Kashmir
MRI-Diagnosed Tumour Deposits and EMVI Status Have Superior Prognostic Accuracy to Current Clinical TNM Staging in Rectal Cancer.
BACKGROUND DATA: MRI assessment of rectal cancer not only assesses tumour depth and surgical resectability but also extramural disease which affects prognosis. We have observed that non-nodal tumour nodules (tumour deposits; mrTDs) have a distinct MRI appearance compared to lymph node metastases (mrLNMs). OBJECTIVE: We aimed to assess whether mrTDs and mrLNMs have different prognostic implications and compare these to other known prognostic markers. METHODS: This was a retrospective cohort study of 233 patients undergoing resection for rectal cancer from January 2007-October 2015. Data were obtained from electronic records and MRIs blindly re-reported. Survival was determined using Kaplan-Meier method. Prognostic markers were evaluated using Cox regression and competing risks analysis. Inter-observer agreement for mrTD was measured using Cohen's Kappa. RESULTS: On multivariable analysis, baseline mrTD/mrEMVI (extramural venous invasion) status was the only significant MRI factor for adverse survival (HR 2.36 (1.54-3.61) for OS, 2.37 (1.47-3.80) for DFS (both p < 0.001), superseding T and N categories. mrLNMs were associated with good prognosis (HR 0.50 (0.31-0.80)p= 0.004 for OS, 0.60 (0.40-0.90)p = 0.014 for DFS). On multivariable analysis, mrTDs/mrEMVI were strongly associated with distant recurrence (HR 6.53 (2.52-16.91) p = < 0.001) whereas T and N category were not. In a subgroup analysis of post-treatment MRIs in post-chemoradiotherapy (CRT) patients, mrTD/mrEMVI status was again the only significant prognostic factor; furthermore those who showed a good treatment response had a prognosis similar to patients who were negative at baseline. Inter-observer agreement for detection of mrTDs was κ0.77 and κ0.83. CONCLUSION: Current MRI staging predicting T and N status does not adequately predict prognosis. Positive mrTD/mrEMVI status has greater prognostic accuracy and would be superior in determining treatment and follow-up protocols. CRT may be a highly effective treatment strategy in mrTD/mrEMVI positive patients
Stationary Dyonic Regular and Black Hole Solutions
We consider globally regular and black hole solutions in SU(2)
Einstein-Yang-Mills-Higgs theory, coupled to a dilaton field. The basic
solutions represent magnetic monopoles, monopole-antimonopole systems or black
holes with monopole or dipole hair. When the globally regular solutions carry
additionally electric charge, an angular momentum density results, except in
the simplest spherically symmetric case. We evaluate the global charges of the
solutions and their effective action, and analyze their dependence on the
gravitational coupling strength. We show, that in the presence of a dilaton
field, the black hole solutions satisfy a generalized Smarr type mass formula.Comment: 23 pages, 4 figure
Continuity Culture: A Key Factor for Building Resilience and Sound Recovery Capabilities
This article investigates the extent to which Jordanian service organizations seek to establish continuity culture through testing, training, and updating of their business continuity plans. A survey strategy was adopted in this research. Primary and secondary data were used. Semistructured interviews were conducted with five senior managers from five large Jordanian service organizations registered with the Amman Stock Exchange. The selection of organizations was made on the basis of simple random sampling. Interviews targeted the headquarters only in order to obtain a homogenous sample. Three out of five organizations could be regarded as crisis prepared and have better chances for recovery. The other two organizations exhibited characteristics of standard practice that only emphasizes the recovery aspect of business continuity management (BCM), while paying less attention to establishing resilient cultures and embedding BCM. The findings reveal that the ability to recover following major incidents can be improved by embedding BCM in the culture of the organization and by making BCM an enterprise-wide process. This is one of few meticulous studies that have been undertaken in the Middle East and the first in Jordan to investigate the extent to which service organizations focus on embedding BCM in the organizational culture
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