Thin shell wormhole due to dyadosphere of a charged black hole

To explain Gamma Ray Bursts, Ruffini argued that the event horizon of a charged black hole is surrounded by a special region called, the Dyadosphere where electric field exceeds the critical value for $e^+$ $e^-$ pair production. In the present work, we construct a thin shell wormhole by performing a thought surgery between two dadospheres. Several physical properties of this thin shell wormhole have been analyzed.Comment: 10 pages, 2 figures. Accepted in Mod.Phys.Lett.

Some new class of Chaplygin Wormholes

Some new class of Chaplygin wormholes are investigated in the framework of a Chaplygin gas with equation of state $p = - \frac{A}{\rho}$, $A>0$. Since empty spacetime ($p = \rho = 0$) does not follow Chaplygin gas, so the interior Chaplygin wormhole solutions will never asymptotically flat. For this reason, we have to match our interior wormhole solution with an exterior vacuum solution i.e. Schwarzschild solution at some junction interface, say $r = a$. We also discuss the total amount of matter characterized by Chaplygin gas that supplies fuel to construct a wormhole.Comment: 14 pages, 12 figures, Accepted for publication in Mod.Phys.Lett.

Arid hydrological modeling at Wadi Alaqiq, Madinah, Saudi Arabia

Madinah is one of the urban centers that have experienced several devastating floods during the past 50 years. The objectives of this study are to estimate the flood hydrograph and peak discharge in the Wadi Alaqiq in Madinah and its major sub-catchments based on daily rainfall distribution. Daily annual maximum records are chosen for rainfall distribution in the study area. Wadi Alaqiq is located in the western part of the Madinah city and consists of five major sub-catchments, namely, Aqiq, Ruwawah, Reem, Al-Yutmah and Annaqi. The HEC-HMS and modified Talbot models are applied to estimate design flood for various average recurrence intervals (ARI). The analysis involves two stages, where stage one is concerned with modeling of the Wadi Alaqiq sub-catchment and comparison of the peak flow values obtained by previous studies and empirical formulae based on rainfall distribution analysis. In the second stage, the HEC-HMS is run separately for the five sub-catchments of Wadi Alaqiq. The model parameter values are then used to simulate for 25-year, 50-year and 100-year flood hydrographs. The HEC-HMS model is used to analyze the hydrologic behaviour of the wadi catchments. Initial and constant rate loss method is used to determine the hydrologic loss and the excess rainfall was transformed using the Clark\x92s Unit Hydrograph. The peak flow simulations are very close with reported values and those derived by modified Talbot. Also, the peak discharges are applied to model discharges from the HEC-HMS and modified Talbot equations of the five sub-catchments for a set of selected return periods. The direct runoff ratio for Madinah region in wadis Al-Yutmah, Annaqi, Aqiq, Reem and Ruwawah ranged from 25 to 28 of the total rainfall. This is due to topography condition, wadi catchment area and the use of predicted maximum daily rainfall results. The model results are reasonable for rainfall-runoff application and can be used for wadi corridor management in arid region

Case studies of six CBFM-2 water bodies

The case studies report on how CBFM-2 interventions have affected aquatic productivity, income, employment and livelihoods in six case study sites, Beelbhora beel cluster (Kishoreganj), Sholuar beel (Narail), Chapundaha beel (Rangpur), Hamil beel (Tangail), Kutir beel (Kishoreganj) and Dikshi beel (Pabna).

Graphene as a buffer layer for silicon carbide-on-insulator structures

We report an innovative technique for growing the silicon carbide-on-insulator (SiCOI) structure by utilizing polycrystalline single layer graphene (SLG) as a buffer layer. The epitaxial growth was carried out using a hot-mesh chemical vapor deposition (HM-CVD) technique. Cubic SiC (3C-SiC) thin film in (111) domain was realized at relatively low substrate temperature of 750 °C. 3C-SiC energy bandgap of 2.2 eV was confirmed. The Si-O absorption band observed in the grown film can be caused by the out-diffusion of the oxygen atom from SiO2 substrate or oxygen doping during the cleaning process. Further experimental works by optimizing the cleaning process, growth parameters of the present growth method, or by using other growth methods, as well, are expected to realize a high quality SiCOI structure, thereby opening up the way for a breakthrough in the development of advanced ULSIs with multifunctionalities

Continuous quality assessment; development of a simple computer based model for audit

Objective: Accurate assessment of quality of care is a fundamental first step in the process of quality improvement. The vast amount of data generated in a hospital mandates some form of computerization for management of information. We describe a locally developed simple computer based program to access relevant information from a hospital patient management network. The objective was to reduce the amount of manual work involved for busy clinicians attempting to audit quality of care.Methods: A single surgical procedure, Laparoscopic Cholecystectomy was chosen. Quality indicators were identified by literature review as conversion rate from laparoscopic to open cholecystectomy and length of hospital stay (LOS). A simple query was developed to extract the required information from hospital database. Commercially available spreadsheet software (Microsoft Excel) was used to calculate the rates. Outliers were defined as LOS more than 1 standard deviation from the mean. The second part of the study involved a manual review of case notes to validate the program and determine the causes for deviation from the mean.Results: The program was able to access and process data as planned. In a one-year period from March 1997 to February 1998, two hundred and thirty one laparoscopic cholecystectomies were attempted. Twenty-three were converted to open procedures given a conversion rate of 9.96%. On manual review of case notes no false positives or false negatives were found. The reasons for conversion were similar to those described in the literature. The mean length of stay for laparoscopic cholecystectomy was 3.39 days and 7.17 days for converted cases. The commonest reason for delay in discharge was noted to be non-availability of elective operating time.CONCLUSION: We have successfully developed and used a simple computer based program to access information stored in hospital patient management systems. Quality of care indicators identified from literature were used as standards. Outliers with respect to these were reviewed in detail to identify causes for deviation. The program was validated by manual review