Faculty Publications

Permanent URI for this collectionhttps://hdl.handle.net/10361/28424

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A 4D spacetime embedded in a 5D pseudo-Euclidean space describing interior of compact stars
(© 2017, Springer New York LLC, 2/1/2017) Singh, Ksh Newton; Murad, Mohammad Hassan; Pant, Neeraj; Department of Mathematics and Natural Sciences
The present paper provides a new model of compact stars satisfying the Karmarkar condition. The model is obtained by assuming a new type of metric potential for gr r from the condition of embedding class I. The model parameters are obtained accordingly by employing the metric potentials to Einstein's field equations. Our model is free from geometric singularity and satisfies all the physical conditions. The obtained mass and radius of the compact stars Cen X-3, EXO 1785-248 and SAX 1808.4-3658 obtained from the model are consistent with the observational data of T. Gangopadhyay et al. Detailed analyses of these neutron stars (Cen X-3, EXO 1785-248 and SAX 1808.4-3658) are also given with the help of graphical representations.
Accurate numerical simulation of the far-field tsunami caused by the 2011 Tohoku earthquake, including the effects of Boussinesq dispersion, seawater density stratification, elastic loading, and gravitational potential change
(© 2017 Elsevier Ltd, 3/1/2017) Baba, Toshitaka; Allgeyer, Sébastien; Hossen, Md. Jakir; Cummins, Phil R.; Tsushima, Hiroaki; Imai, Kentaro; Yamashita, Kei; Kato, Toshihiro; Department of Mathematics and Natural Sciences
In this study, we considered the accurate calculation of far-field tsunami waveforms by using the shallow water equations and accounting for the effects of Boussinesq dispersion, seawater density stratification, elastic loading, and gravitational potential change in a finite difference scheme. By comparing numerical simulations that included and excluded each of these effects with the observed waveforms of the 2011 Tohoku tsunami, we found that all of these effects are significant and resolvable in the far field by the current generation of deep ocean-bottom pressure gauges. Our calculations using previously published, high-resolution models of the 2011 Tohoku tsunami source exhibited excellent agreement with the observed waveforms to a degree that has previously been possible only with near-field or regional observations. We suggest that the ability to model far-field tsunamis with high accuracy has important implications for tsunami source and hazard studies.
A study on the microbiological status of mineral drinking water
(© 2017 Bentham Science Publishers B.V., 4/1/2017) Aditi, Faria Y.; Rahman, Shafkat Shamim; Hossain, Md Manjur; Department of Mathematics and Natural Sciences
Introduction: Water-borne diseases constitute a major health burden in Bangladesh. The objective of this study was to assess the overall quality of mineral water samples that obtained from different shops of Dhaka city. Material and Methods: To achieve the above-mentioned objective, methods of heterotrophic plate count (HPC) and total coliform count (TCC) were applied. Moreover, isolated colony from mineral water samples were characterized by using biochemical and antimicrobial susceptibility tests. Results: Different water samples showed different HPC ranged from 1.0×10 to 8.00×102. Antimicrobial sensitivity test of some selected bacteria viz S. intermedius, S. aureus, S. felis and S. Saccharolyticus were performed. It was observed that Staphylococcus spp. isolates were susceptible to erythromycin, tetracycline, norfloxacin and ciprofloxacin. Furthermore, a few Staphylococcus spp. isolates were intermediate resistant to penicillin and oxacillin. However, most of the Staphylococcus spp. isolates were resistant to cefixime. Conclusion: The results indicate that mineral water serves as a reservoir of various bacteria and that people in Dhaka city, who are the consumers of these water, might get diseases. This study emphasizes the need for elaborated microbiological examinations of mineral drinking water commonly used in Dhaka city.
Protection against shigellosis caused by shigella dysenteriae serotype 4 in Guinea pigs using escherichia albertii dm104 as a live vaccine candidate strain
(© 2017 Akadémiai Kiadó, 2017-06) Chowdhury, Fatema Moni; Rahman, Mohammed Ziaur; Sarkar, Md Murshed Hasan; Rabbi, Fazle A.; Khan, Sirajulislam; Ahsan, Chowdhury Rafiqul; Birkeland, Nils Kåre; Department of Mathematics and Natural Sciences
Recently, we reported the induction of protective immunity by environmental Escherichia albertii strain DM104 against Shigella dysenteriae in Guinea pig model. In this study, we assessed three different immunization routes, such as intranasal, oral, and intrarectal routes, and revealed differences in immune responses by measuring both the serum IgG and mucosal IgA antibody titers. Protective efficacy of different routes of immunization was also determined by challenging immunized Guinea pigs against live S. dysenteriae. It was found that intranasal immunization showed promising results in terms of antibody response and protective efficacy. All these results reconfirm our previous findings and additionally point out that the intranasal immunization of the environmental E. albertii strain DM104 in Guinea pig model can be a better live vaccine candidate against shigellosis.
Calculation of the bandwidth of a graded-index optical fiber using experimentally measured quantities
(© 2007 Dhaka University Journal of Science, 2007-01) Alam, Shaif-ul; Abedin, Kazi Monowar; Haider, A F M Yusuf; Department of Mathematics and Natural Sciences
Effect of Fluctuating surface heat and mass flux on natural convection flow along a vertical flat plate
(© 2015 Hindawi Publishing Corporation, 2015) Hussain, Sharmina; Roy, Nepal Chandra; Hossain, Md. Anwar; Saha, Suvash Chandra; Department of Mathematics and Natural Sciences
An investigation has been carried on double diffusive effect on boundary layer flow due to small amplitude oscillation in surface heat and mass flux. Extensive parametric simulations were performed in order to elucidate the effects of some important parameters, that is, Prandtl number, Schmidt number, and Buoyancy ratio parameter on flow field in conjunction with heat and mass transfer. Asymptotic solutions for low and high frequencies are obtained for the conveniently transformed governing coupled equations. Solutions are also obtained for wide ranged value of the frequency parameters. Comparisons between the asymptotic and wide ranged values are made in terms of the amplitudes and phases of the shear stress, surface heat transfer, and surface mass transfer. It has been found that the amplitudes and phase angles obtained from asymptotic solutions are found in good agreement with the finite difference solutions obtained for wide ranged value of the frequency parameter.
Unsteady laminar mixed convection boundary layer flow near a vertical wedge due to oscillations in the free-stream and surface temperature
(© 2016 De Gruyter Open Ltd., 2016) Roy, Nepal Chandra; Hossain, Md. Anwar; Hussain, Sharmina; Department of Mathematics and Natural Sciences
The unsteady laminar boundary layer characteristics of mixed convection flow past a vertical wedge have been investigated numerically. The free-stream velocity and surface temperature are assumed to be oscillating in the magnitude but not in the direction of the oncoming flow velocity. The governing equations have been solved by two distinct methods, namely, the straightforward finite difference method for the entire frequency range, and the extended series solution for low frequency range and the asymptotic series expansion method for high frequency range. The results demonstrate the effects of the Richardson number, Ri, introduced to quantify the influence of mixed convection and the Prandtl number, Pr, on the amplitudes and phase angles of the skin friction and heat transfer. In addition, the effects of these parameters are examined in terms of the transient skin friction and heat transfer.
In vitro shoot micro propagation of medicinal applications and ornamental value of Cestrum nocturnum L.
(© 2016 Indian Society for Education and Environment, 2016) Sarkar, Mohammad Khairul Islam; Jahan, Miskat Ara Akhter; Roy, Chapol Kumar; Hossain, Khaled; Rahman, Shafkat Shamim; Mia, Md Rubel; Islam, Mohammad Rafiqul; Azim, Dewan Anwarul; Department of Mathematics and Natural Sciences
Background/Objectives: Cestrum nocturnum L. a night Blooming jasmine belongs to Solanaceae family widely circulated all over tropical as well as subtropical areas of the World. It is mainly popular for ornamental fragrant flowering and hedge plant but also sometimes for traditional medicinal purpose. Due to strongest smelling characteristics of the plants, it is used in many industries for making Perfumes, essential Oils, Soaps, Candles, Body Oils, etc. The existence of natural plants of economic importance are threatened due to rapid urban development, including industrialization, residential development, educational, commercial etc., reduce the land for cultivation. Hence plant tissue culture protocol may be adapted for production and utilization of economically popular plants, including C. nocturnum involving limited space and short period of time. Methods: Shoot tip explants of naturally grown C. nocturnum were excised sterilized and endued on 'Murashige and Skoog' (MS) medium enriched changed concentration of BA, NAA, as well as GA3 singly or in combination. Excised micro shoots were examined for root development on 0.5 MS using IBA, NAA as well as IAA separately. Findings: The highest amount of multiple bud were observed in low concentration of BA (01.50 milligram × l-1), resulted no. of shoot 4.40 as well as 4.20/explant, no. of leaves 15.40 as well as 4.20/explant as well as size of different shoot 5.360 as well as 4.860 cm. The concentration of IBA and IAA were found to be best for root formation in micro shoots (13.20, 6.80 roots/micro shoots) as well as root size (8.39, 5.73 cm) individually. Application: There are many opportunity of plant tissue culture which offer marvelous chances in plant propagation, plant development as well as creation of plants with necessary agronomical features. Finally often hardening plantlets were gradually adjusted to natural condition and acclimatized with 90% success. This established protocol could help plant cell biotechnology, horticulture, medical and industrial sector of the country.
Designing novel antibacterials: application of omics science
(© 2013 AVES Ibrahim Kara, 2013) Zaman, Aubhishek M.; Razzaque, Samsad; Department of Mathematics and Natural Sciences
Antibacterials are agents that act against pernicious bacterial pathogens by killing or inactivating them. At present, designing antibacterials have been assisted greatly by omics sciences-genomics, proteomics, metabolomics and interactomics. This review discusses different aspects of the omics sciences in simple to complex hierarchies. From the simplest of sequence analysis to more complex on the pyramid -structural, functional and interactional analysisall comprises the grand ambit of omics science. Sequence comparison can reveal novel information about drug resistance in the bacteria and thus can be of momentous significance for designing improved antibacterials. On the other hand, sequence characterization of the host protein can lead to production of effective antibiotic synthetically. Nowadays, structure based molecular designing, using computational docking techniques, has become a widely accepted routine work in drug designing processes. Moreover, new high-throughput data from microarray expression, protein-protein interaction assay are opening up a new vista for detecting more and more drug targets. Extensive focus put on to understand host-pathogen interaction on systems level has greatly accelerated the process of designing effective antibacterials against tuberculosis and many such complex diseases. Summarizing, this review exemplifies various different ways how increasingly omics science is transforming the paradigm of discovering novel antibacterials; omics approach is all set to speed up the process and bring down the expenses of the antibacterials even more in time to come.
Kaposi's sarcoma: a computational approach through protein-protein interaction and gene regulatory networks analysis
(© 2012 Springer Science+Business Media New York, 2013) Zaman, Aubhishek M.; Rahaman, Md. Habibur; Razzaque, Samsad; Department of Mathematics and Natural Sciences
Interactomic data for Kaposi's Sarcoma Associated Herpes virus (KSHV) - the causative agent of vascular origin tumor called Kaposi's sarcoma - is relatively modest to date. The objective of this study was to assign functions to the previously uncharacterized ORFs in the virus using computational approaches and subsequently fit them to the host interactome landscape on protein, gene, and cellular level. On the basis of expression data, predicted RNA interference data, reported experimental data, and sequence based functional annotation we also tried to hypothesize the ORFs role in lytic and latent cycle during viral infection. We studied 17 previously uncharacterized ORFs in KSHV and the host-virus interplay seems to work in three major functional pathways - cell division, transport, metabolic and enzymatic in general. Studying the host-virus crosstalk for lytic phase predicts ORF 10 and ORF 11 as a predicted virus hub whereas PCNA is predicted as a host hub. On the other hand, ORF31 has been predicted as a latent phase inducible protein. KSHV invests a lion's share of its coding potential to suppress host immune response; various inflammatory mediators such as IFN-γ, TNF, IL-6, and IL-8 are negatively regulated by the ORFs while Il-10 secretion is stimulated in contrast. Although, like any other computational prediction, the study requires further validation, keeping into account the reproducibility and vast sample size of the systems biology approach the study allows us to propose an integrated network for host-virus interaction with good confidence. We hope that the study, in the long run, would help us identify effective dug against potential molecular targets.
Combination of community-based vulnerability and adaptation to storm surges in coastal regions of Bangladesh
(© 2014 World Scientific Publishing Co. Pte Ltd, 2014) Younus, Md. Aboul Fazal; Sharna, Sabrina Shahrin; Department of Mathematics and Natural Sciences
Bangladesh has been identified as one of the countries most vulnerable to climate change and rising sea-level. This is because it is located at the northern end of the funnel-shaped Bay of Bengal, and as a consequence it has experienced a number of severe storm surges in the last three decades. The inhabitants of the coastal region are very poor, and the surges have pushed them to a "tipping-point"; that is, the point of desperation which is exacerbating the socio-economic threats to their existence. The study reported here aimed to explore the perceptions of coastal communities with regard to vulnerability and adaptation (V & A) strategies in four different areas of Bangladesh in order to reduce their vulnerability to future storm surges. After reviewing the impact assessment guidelines of the Intergovernmental Panel on Climate Change (IPCC), United States Country Studies Program (USCSP) and United Nations Environment Programme (UNEP), the researchers applied the Participatory Rapid Appraisal (PRA) method (a behavioural environmental decision-making tool) to survey 160 participants in four case-study areas, with 20 participants in two sessions in each case. The evaluation of V & A was implemented and prioritised in this study by a measuring scale, called the "weighted matrix index". This study not only considered the integrated assessment of V & A but it also classified the levels of vulnerability and adaptation in different categories. Additionally, it provides a comparative picture of the vulnerabilities for similar risks in different types of communities. These key aspects demonstrate and emphasise that adaptation policy needs to be implemented immediately in Bangladesh in order to reduce and manage future vulnerability in the coastal region under the potential climate change regimes.
Power allocation for the network coded cognitive cooperative network
(© 2011 IEEE, 2011) Kaiser, Moritz Shamim; Department of Mathematics and Natural Sciences
Demand for higher data rate wireless applications has led to scarcity in radio frequency spectrum. This article focuses the power allocation for the network coded cognitive cooperative network (NCCCN). Analog network coded (ANC) Orthogonal-Frequency-Division-Multiplexing (OFDM) improves the capacity of the cognitive cooperative network (CCN). Moreover, CCN enhances the spectrum utilization efficiency. A power allocation optimization problem have been formed that maximizes the data transmission rate of the NCCCN under the total transmit and peak-interference powers or the total transmit and average-interference powers. The spectral efficiency of the proposed network is compared with the spectral efficiency of CCN without ANC. Simulation results show that the proposed NCCCN enhances spectral efficiency in compared to the CCN without ANC.
Neuro-fuzzy-based hand-off and opportunistic spectrum access for cognitive cooperative network
(© 2012 Inderscience Enterprises, 2012-04) Kaiser, Moritz Shamim; Ahmed, Kazi Mohiuddin; Department of Mathematics and Natural Sciences
This paper investigates neuro-fuzzy (NF)-based opportunistic spectrum access and spectrum hand-off (HO) for a cognitive cooperative network (CCN). The main aim is to increase the average throughput of the CCN. Secondary users (SUs) in the CCN are scheduled using α-proportional scheduling. The NF α-based algorithm enables each SU to determine the most appropriate channel for its data transmission. SUs keep their transmission power below the interference temperature through power control and do not interfere with the normal operation of primary radio network (PRN). If the quality of service (QoS) of the SU is not obtained, a HO occurs. Mamdani-adaptive neuro-fuzzy inference system (M-ANFIS) is used to construct spectrum access and HO controllers. The proposed algorithm is compared with the existing algorithms. Performance evaluations clearly reveal that the outage probability is reduced and average throughput of the CCN isincreased.
Evaluation of three immunological tests for the diagnosis of pulmonary tuberculosis in a rural endemic area of Bangladesh
(© 2014 Elsevier Ltd, 2014-06) Islam, Mohammad Tariqul; Rabbi, Fazle; Ferdous, Shameema; Parvin, Ummey Shahnaz; Hossain, Akram; Hossain, Mohammad Sorowar; Department of Mathematics and Natural Sciences
Objective: Bangladesh is a high tuberculosis burden country. It is always challenging to diagnose active pulmonary tuberculosis (PTB) cases in rural areas where the setting up of conventional microscopic and cultural diagnostic tools is difficult. The objective of the present study is to find a feasible, reliable and easily accessible alternative diagnostic approach for PTB in the rural areas of Bangladesh. Methods: A total of 86 sputum samples were collected from clinically suspected PTB patients of Anantapur village, an underdeveloped remote area of Netrokona district, Bangladesh. Sputum samples were screened by Ziehl-Neelsen (Z-N) and fluorescence staining methods and were categorized as smear-positive active PTB cases (n= 50) and smear-negative controls (n= 36); then the performance of three popular immunological tests were evaluated, including ICT, ELISA and Mantoux tests (MT). Results: The sensitivity of ICT, ELISA, and MT (10. mm induration size) was 68%, 84% and 96%, respectively, and the specificity of these tests was 94.4%, 80.6% and 52.8%, respectively. When the cut-off size of induration in MT was changed from 10 to ≥15. mm, the sensitivity and specificity of MT became 92% and 83.3%, respectively. It was also found that the interpretation of MT was not significantly affected by BCG vaccination when ≥15. mm induration was taken as a cut-off value. Conclusion: Considering the resource-constraints of rural and remote areas, the Mantoux test could be an alternative tool for the diagnosis of active PTB.
Isolation of yeasts from raisins and Palm-juice and ethanol production in molasses medium
(© 2016 Indian Society for Education and Environment, 2016) Rahman, Shafkat Shamim; Islam, Sarkar Mohammad Khairul; Rafiqul, Islam Mohammad; Khaled, Hossain; Kamrun, Nahar; Kumar, Roy Chapol; Uddin, Md Ekhlas; Choudhury, Naiyyum; Department of Mathematics and Natural Sciences
The alternative fuels are expected to satisfy the progressive demand for energy on the wake of the negative effects of fossil fuel on the atmosphere and resultant universal warming. In this study two ethanol fermenting Saccharomyces cerevisae were isolated from Palm juice and Raisins. Method/Statistical Analysis: Both isolates were grown in Yeast extract Peptone Dextrose (YEPD) medium and characterized for alcoholic fermentation using molasses medium and optimized for pH, thermo-, osmo-, ethanol tolerance and sugar concentration. Findings: Results showed for ethanol fermentation, 31°C temperature, 6.01 pH and 6.50% sugar concentration is the prime condition. Raisin-isolate emerged as highly thermophilic and stress tolerant in nature. Under optimized conditions, S. cerevisae isolated from Palmjuice produced 9.85% of ethanol in the medium. Application/Improvements: Creation of ethanol through fermentation appears to be a potential other fossil fuel and can be used as exclusive fuel in vehicles with dedicated engines or in fuel blends.
A class of relativistic anisotropic charged stellar models in isotropic coordinates
(© 2014, Springer Science+Business Media Dordrecht., 2014) Pant, Neeraj; Pradhan, Nirakar; Murad, Mohammad Hassan; Department of Mathematics and Natural Sciences
In this present paper, we present a class of static, spherically symmetric charged anisotropic fluid models of super dense stars in isotropic coordinates by considering a particular type of metric potential, a specific choice of electric field intensity E and pressure anisotropy factor Δ which involve parameters K (charge) and α (anisotropy) respectively. The solutions so obtained are utilized to construct the models for super-dense stars like neutron stars and strange quark stars. Our solutions are well behaved within the following ranges of different constant parameters: 4<n≤21.6, 0<K<0.2499, 0≤α≤0.068 and Schwarzschild parameter, 0≤u=GM/c2R≤0.334. With Δ=0 we rediscover the isotropic model of Pant et al. (Astrophys. Space Sci. 352:135, 2014) and with α=0 and K=0 we rediscover the isotropic neutral model of Murad and Pant (Astrophys. Space Sci. 350:349, 2014). It has been observed that with the increase of α maximum mass decreases. We also present models of super dense star like neutron and quark star based on the particular solution taking n=4.35, α=0.002, K=0.2062 for which u has maximum value umax=0.306. By assuming surface density ρb=4.6888×1014 g cm−3 the resulting well behaved solution has a maximum quark star mass M=2.02 M⊙ and radius R=9.78 km; and the choice ρb=2.7×1014 g cm−3 results charged fluid ball of maximum mass M=2.66 M⊙ and radius R=12.89 km.
A class of super dense stars models using charged analogues of Hajj-Boutros type relativistic fluid solutions
(© 2014, Springer Science+Business Media New York, 2014-10) Pant, Neeraj; Pradhan, Nirakar; Murad, Mohammad Hassan; Department of Mathematics and Natural Sciences
We present a spherically symmetric solution of the general relativistic field equations in isotropic coordinates for perfect charged fluid, compatible with a super dense star modeling. The solution is well behaved for all the values of Schwarzschild parameter u lying in the range 0 < u < 0.1727 for the maximum value of charge parameter K = 0.08163. The maximum mass of the fluid distribution is calculated by using stellar surface density as ρb = 4.6888×1014g cm−3. Corresponding to K = 0.08 and umax = 0.1732, the resulting well behaved solution has a maximum mass M = 0.9324M⊙ and radius R = 8.00 and by assuming ρb = 2×1014g cm−3 the solution results a stellar configuration with maximum mass M = 1.43M⊙ and radius Rb = 12.25 km. The maximum mass is found increasing with increasing K up to 0.08. The well behaved class of relativistic stellar models obtained in this work might has astrophysical significance in the study of internal structure of compact star such as neutron star or self-bound strange quark star like Her X-1.
Anisotropic charged stellar models in Generalized Tolman IV spacetime
(© 2015, Società Italiana di Fisica and Springer-Verlag Berlin Heidelberg, 2015) Murad, Mohammad Hassan; Fatema, Saba; Department of Mathematics and Natural Sciences
With the presence of electric charge and pressure anisotropy some anisotropic stellar models have been developed. An algorithm recently presented by Herrera et al. (Phys. Rev. D 77, 027502 (2008)) to generate static spherically symmetric anisotropic solutions of Einstein's equations has been used to derive relativistic anisotropic charged fluid spheres. In the absence of pressure anisotropy the fluid spheres reduce to some well-known Generalized Tolman IV exact metrics. The astrophysical significance of the resulting equations of state (EOS) for a particular case (Wyman-Leibovitz-Adler) for the anisotropic charged matter distribution has been discussed. Physical analysis shows that the relativistic stellar structure obtained in this work may reasonably model an electrically charged compact star, whose energy density associated with the electric fields is on the same order of magnitude as the energy density of fluid matter itself like electrically charged bare strange quark stars.
Growing electrostatic modes in the isothermal pair plasma of the pulsar magnetosphere
(© 2011 Springer Science+Business Media B.V., 2012) U. A., Mofiz; Amin, Md. Ruhul; Shukła, Padma Kant; Department of Mathematics and Natural Sciences
It is shown that a strongly magnetized isothermal pair plasma near the surface of a pulsar supports low-frequency (in comparison to electron cyclotron frequency) toroidal electrostatic plasma modes in the equatorial region. Physically, the thermal pressure coupled with the magnetic pressure creates the low frequency oscillations which may grow for particular case of inhomogeneities of the equilibrium magnetic field and the pair plasma density.
Optical solitons in negative-index meta-materials
(© 2013 IEEE, 2013) U. A., Mofiz; Department of Mathematics and Natural Sciences
The nonlinear propagation of gigahertz electromagnetic wave propagation in the resonant region of a negative index meta-material is investigated. It is found that the negative refractive index is maintained within a narrow band of frequency which is more narrowed down with the intensity of the radiation. In the high frequency response, the nonlinear field dependent dispersion relation is obtained, and the corresponding group velocity is determined. In the low frequency response, coupled nonlinear Schrödinger equations are obtained which show the creation of bright and dark optical solitons. The bright soliton is a fast mode and it is modulationally unstable. The dark soliton is a slow mode and it is modulationally stable. Applications of these results to terahertz spectrums and in the photonic crystals are mentioned.

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