Spatial analysis of thunderstorms and lightning casualties in Bangladesh     

Md. Mahabubur Rahman  Tasnim Ara  Mohiuddin Ibn Shafique  Md. Abdur Rahman  Mohammad Lutfor Rahman 《Singapore journal of tropical geography》2023,44(3):499-518

Considering the adverse outcomes of thunderstorm-mediated lightning in recent years, this study aimed to identify the most thunderstorm-and-casualty prone regions and seasons in Bangladesh, via geospatial mapping. We attempted to forecast the number of yearly thunderstorm (TS) days for each meteorological station and district-level lightning casualties by using TS days as a proxy variable. Data on TS days and lightning casualties were collected from Bangladesh Meteorological Department and Network for Information, Response And Preparedness Activities on Disaster respectively. This study analysed 629 fatalities and 232 injuries. The Integrated Nested Laplace Approximation with Matern covariance function was employed to assess the spatial pattern of TS days. Polynomial regressions were used to forecast the number of TS days and the single clustered Generalized Estimating Equations method was employed to explore the relationship between the number of TS days and lightning casualties. The results indicated that the mean number of TS days per station increased in recent years, particularly in February, March, April, and September. We found the months of April, May, June, and September to be the most threatening months due to TS events and related casualties. The northeast region was identified as the most TS-prone region with the highest number of casualties in Bangladesh. Our analysis suggests that it might remain the most hazardous region in coming years.  相似文献   

Post-Cyclone Sidr illness patterns in coastal Bangladesh: an empirical study     

Bimal Kanti Paul  Munshi Khaledur Rahman  Bankim Chandra Rakshit 《Natural Hazards》2011,56(3):841-852

After the landfall of Cyclone Sidr along the southwestern coast of Bangladesh on November 15, 2007, emergency and public health personnel within and beyond Bangladesh anticipated a massive outbreak of water-borne and other diseases in most affected areas. Fortunately, such an outbreak did not occur. The objectives of this paper are to examine the extent and pattern of illnesses experienced by Cyclone Sidr survivors in the aftermath of its landfall and to investigate household and individual-level factors associated with such illnesses. Based on face-to-face interviews conducted among 277 randomly selected Sidr survivors living in the four most severely impacted coastal districts, this study found that the post-cyclone incidence of water-borne, respiratory, and other diseases was not unusually high. Only 52 persons suffered Sidr-related illnesses, and their illnesses were significantly associated with household income, and gender and age of the Sidr survivors. A major outbreak of such diseases was largely avoided because of the proper distribution of food and safe drinking water, as well as the timely implementation of health care intervention measures. This important finding will aid relevant authorities in successfully responding to outbreaks of diseases following a future extreme event in Bangladesh and perhaps elsewhere.  相似文献   

Passive earth pressure on embedded vertical plate anchors in sand   总被引：1，自引：1，他引：0  

Adel Hanna  Farhana Rahman  Tahar Ayadat 《Acta Geotechnica》2011,6(1):21-29

Passive earth pressure on embedded anchor plates constitutes a viable resisting force for the design of underground structures. In the current practice, these forces are empirically calculated, ignoring the effects of the depth of embedment and the level of consolidation of the surrounding soil, which takes place during plate installation on the in situ stress levels. Accordingly, wide discrepancies between predicted and measured pullout capacities of these plates were reported in the literature. Numerical model was developed using finite-element technique and the constitutive law of Mohr?CCoulomb to simulate the case of a retaining wall partially supported by an embedded anchor plate in sand. The results produced in this investigation showed that the passive earth pressure acting on anchor plates increases due to the increase of angle of shearing resistance and the overconsolidation ratio of sand, and it decreases due to an increase of the embedment depth of anchor. Design theories were developed for the case of embedded anchor plate in overconsolidated sand. The theories developed will satisfy the design needed in terms of allowable pullout load and/or displacement.  相似文献   

Salinity impacts on agro-biodiversity in three coastal, rural villages of Bangladesh     

M.H. Rahman  T. Lund  I. Bryceson 《Ocean & Coastal Management》2011,54(6):455-468

Salinity increase has been one of the major problems for traditional agricultural practices in coastal Bangladesh for several decades, but very few studies have been conducted on effects of salinity on agro-biodiversity in this area. This study investigated the salinity effects on agro-biodiversity in rice (Oryza sativa L.), vegetables, and fruit trees in three coastal, rural villages; Putia (Satkhira district), Srifaltala (Bagerhat district) and Hogolbunia (Khulna district). Information was collected by participatory rural appraisal methods including transect walks, group discussions, key informant interviews, and 121 personal interviews from July to December 2006. The study revealed that increased salinity had significant negative impacts on the overall agro-biodiversity. From 1975 to 2006 the number of indigenous rice varieties declined from seventeen to zero in Putia, from twelve to nine in Hogolbunia and from fifteen to two in Srifaltala. The encroachment of shrimp ponds near the homestead, and cultivation of high yielding, salt-tolerant rice varieties contributed to the decline of indigenous rice varieties. The occurrence of vegetable and fruit tree species declined from 1975 to 1990. The farmers appeared generally unaware of the importance of conservation of seeds and local landraces. This paper highlights factors directly and indirectly influencing farmers’ agricultural practices, and contributes to the discussion as to how environmental changes influence agro-biodiversity conservation and food production. The large reduction in agro-biodiversity, largely induced by increasing salinity, is alarming and threatens the Bangladeshi farmers’ ability to continue crop cultivation and thus their livelihood.  相似文献   

Solitary and rogue waves in Fermi-Dirac plasmas: relativistic degeneracy effects     

Ata-ur Rahman  S. Ali 《Astrophysics and Space Science》2014,351(1):165-172

Ion acoustic (IA) solitary and rogue waves are studied in an unmagnetized plasma consisting of non-degenerate warm ions, relativistically degenerate electrons and positrons. By using the reductive perturbation technique, the evolution of IA solitary waves is described by the Korteweg-de Vries (KdV) equation. However, when the frequency of the carrier wave is much smaller than the ion plasma frequency then the KdV equation is also used to study the nonlinear evolution of modulationally unstable modified IA wavepackets through the derivation of nonlinear Schrödinger equation. It is found that the characteristics of the IA solitary and rogue waves are substantially influenced by the intrinsic plasma parameters. The relevance of the present investigation involving IA solitary and rogue waves in astrophysical plasma environments is also highlighted.  相似文献   

Some electrically charged relativistic stellar models in general relativity     

A. H. M. Mahbubur Rahman  Mohammad Hassan Murad 《Astrophysics and Space Science》2014,351(1):255-265

Some new families of electrically charged stellar models of ultra-compact star have been studied. With the help of particular form of one of the metric potentials the Einstein–Maxwell field equations in general relativity have been transformed to a system of ordinary differential equations. The interior matter pressure, energy–density, and the adiabatic sound speed are expressed in terms of simple algebraic functions. The constant parameters involved in the solution have been set so that certain physical criteria satisfied. Based on the analytic model developed in the present work, the values of the relevant physical quantities have been calculated by assuming the estimated masses and radii of some well known potential strange star candidates like X-ray pulsar Her X-1, millisecond X-ray pulsar SAX J 1808.4-3658, and 4U 1820-30. The analytical equations of state of the charged matter distribution may play a significant role in the study of the internal structure of highly compact charged stellar objects in general relativity.  相似文献   

Electron capture strength on odd-A nucleus 59Co in explosive astrophysical environment     

Muneeb-Ur Rahman  Jameel-Un Nabi 《Astrophysics and Space Science》2014,351(1):235-242

The Gamow-Teller (GT) transitions within massive stars play sumptuous role in the dynamics of core collapse supernovae. GT strength distributions and electron capture rates have been calculated for odd-A nucleus ⁵⁹Co within the proton-neutron quasiparticles random phase approximation (pn-QRPA) formalism. The pn-QRPA results are compared with other model calculations and (n,p) reaction experiment carried out at TRIUMF charge-exchange facility. The pn-QRPA calculated a total B(GT ₊) strength of 3.3 for ⁵⁹Co to be compared with the shell model value of 2.5 and the 1.9±0.1 in the (n,p) charge-exchange reaction. Aufderheide et al. (1993) extracted total strength equaling 2.4±0.3. The placement of GT centroid at 5.6 MeV by the pn-QRPA model is in reasonable agreement with the shell model centroid at 5.1 MeV whereas the measured GT centroid was placed at 4.4±0.3 MeV in the (n,p) experiment. Fuller, Fowler and Newman (FFN) (1980, 1982a, 1982b), placed the GT centroid at too low excitation energy of 2.0 MeV in the daughter nucleus ⁵⁹Fe, and this misplacement led to the enhancement of FFN rates. The suppressed pn-QRPA and shell model electron capture rates are in good agreement with each other. The rates are suggestive of higher value of Y _e (electron-to-baryon ratio) and may contribute to a more massive homologously collapsing core resulting in a more energetic shock. It might be interesting for the simulators to check the effect of these suppressed rates on the fine-tuning of the time rate of Y _e , the concomitant heavy element nucleosynthesis, and, on the energetics of the subsequent shock wave.  相似文献   

Diamond xenolith and matrix organic matter in the Sutter's Mill meteorite measured by C‐XANES     

Yoko Kebukawa  Michael E. Zolensky  A. L. David Kilcoyne  Zia Rahman  Peter Jenniskens  George D. Cody 《Meteoritics & planetary science》2014,49(11):2095-2103

The Sutter's Mill (SM) meteorite fell in El Dorado County, California, on April 22, 2012. This meteorite is a regolith breccia composed of CM chondrite material and at least one xenolithic phase: oldhamite. The meteorite studied here, SM2 (subsample 5), was one of three meteorites collected before it rained extensively on the debris site, thus preserving the original asteroid regolith mineralogy. Two relatively large (10 μm sized) possible diamond grains were observed in SM2‐5 surrounded by fine‐grained matrix. In the present work, we analyzed a focused ion beam (FIB) milled thin section that transected a region containing these two potential diamond grains as well as the surrounding fine‐grained matrix employing carbon and nitrogen X‐ray absorption near‐edge structure (C‐XANES and N‐XANES) spectroscopy using a scanning transmission X‐ray microscope (STXM) (Beamline 5.3.2 at the Advanced Light Source, Lawrence Berkeley National Laboratory). The STXM analysis revealed that the matrix of SM2‐5 contains C‐rich grains, possibly organic nanoglobules. A single carbonate grain was also detected. The C‐XANES spectrum of the matrix is similar to that of insoluble organic matter (IOM) found in other CM chondrites. However, no significant nitrogen‐bearing functional groups were observed with N‐XANES. One of the possible diamond grains contains a Ca‐bearing inclusion that is not carbonate. C‐XANES features of the diamond‐edges suggest that the diamond might have formed by the CVD process, or in a high‐temperature and ‐pressure environment in the interior of a much larger parent body.  相似文献   

Mineralogy and petrography of C asteroid regolith: The Sutter's Mill CM meteorite     

Michael Zolensky  Takashi Mikouchi  Marc Fries  Robert Bodnar  Peter Jenniskens  Qing‐zhu Yin  Kenji Hagiya  Kazumasa Ohsumi  Mutsumi Komatsu  Matthew Colbert  Romy Hanna  Jessie Maisano  Richard Ketcham  Yoko Kebukawa  Tomoki Nakamura  Moe Matsuoka  Sho Sasaki  Akira Tsuchiyama  Matthieu Gounelle  Loan Le  James Martinez  Kent Ross  Zia Rahman 《Meteoritics & planetary science》2014,49(11):1997-2016

Based upon our characterization of three separate stones by electron and X‐ray beam analyses, computed X‐ray microtomography, Raman microspectrometry, and visible‐IR spectrometry, Sutter's Mill is a unique regolith breccia consisting mainly of various CM lithologies. Most samples resemble existing available CM2 chondrites, consisting of chondrules and calcium‐aluminum‐rich inclusion (CAI) set within phyllosilicate‐dominated matrix (mainly serpentine), pyrrhotite, pentlandite, tochilinite, and variable amounts of Ca‐Mg‐Fe carbonates. Some lithologies have witnessed sufficient thermal metamorphism to transform phyllosilicates into fine‐grained olivine, tochilinite into troilite, and destroy carbonates. One finely comminuted lithology contains xenolithic materials (enstatite, Fe‐Cr phosphides) suggesting impact of a reduced asteroid (E or M class) onto the main Sutter's Mill parent asteroid, which was probably a C class asteroid. One can use Sutter's Mill to help predict what will be found on the surfaces of C class asteroids such as Ceres and the target asteroids of the OSIRIS‐REx and Hayabusa 2 sample return missions (which will visit predominantly primitive asteroids). C class asteroid regolith may well contain a mixture of hydrated and thermally dehydrated indigenous materials as well as a significant admixture of exogenous material would be essential to the successful interpretation of mineralogical and bulk compositional data.  相似文献   

Measuring shapes of galaxy images – II. Morphology of 2MASS galaxies     

Nurur Rahman  Sergei F. Shandarin 《Monthly notices of the Royal Astronomical Society》2004,354(1):235-251

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