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Fabrication and Characterization on Physico-Mechanical and Structural Properties of Sawdust Reinforced Acrylonitrile Butadiene Styrene (ABS) Composites

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Materials Sciences and Applications 2020年第9期11卷 644-658页

作者： Budrun Neher Nabila tasnim Nova Rakib Hossain M. A. Gafur Farid ahmed Department of Physics Jahangirnagar University Dhaka Bangladesh Department of Physics Bangabandhu Sheikh Mujibur Rahman Science & Technology University Gopalganj Bangladesh PP and PDC Bangladesh Council of Scientific and Industrial Research Dhaka Bangladesh

The sawdust reinforced Acrylonitrile Butadiene Styrene (ABS) composites were prepared by using hot press molding machine for five different wt% (0%, 5%, 10%, 15% and 20%) at 180°C temperature and 50 KN load. Sawdust was collected from local saw mill of Savar, Dhaka, Bangladesh and ABS polymer was collected from local market of Dhaka, Bangladesh. In this study, different properties of composites like physical (bulk density and water absorption), mechanical (tensile properties and hardness) and structural (Fourier Transform Infrared Spectroscopy) properties were studied. The bulk density of composites was not altered consistently and it gave greater value for 5% and 20% composites. The water absorption enhanced for all composites with the accumulation of fiber content and soaking time. The reduction of tensile strength and Leeb’s rebound hardness of the composites were observed with the increase of the fiber content in all compositions. Maximum (%) of elongation was found for 5% composite, and then it gradually decreased;however, elastic modulus increased with the increased of fiber content in composites. Fourier Transform Infrared (FTIR) spectroscopy study was done for structural characterization. It was found that there was a new bond (C≡C) stretching formed for 20% composite;moreover, C-H rocking for 0% composite was broken for all other composites after the addition of sawdust in ABS polymer matrix.

关键词： Sawdust-ABS Composite Hot Press Molding Machine Tensile Strength Leeb’s Rebound Hardness FTIR Spectroscopy

Structural and Dielectric Properties of (Bi₂O₃Fe₂O₃)_0.4(Nb₂O₅)_0.6 for Different Sintering Temperature

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Materials Sciences and Applications 2016年第8期7卷 421-429页

作者： Sadia tasnim Mowri M. A. Gafur Quazi Delwar Hossain Aninda Nafis ahmed Muhammad Shahriar Bashar Electrical and Electronic Engineering Department Chittagong University of Engineering and Technology Chittagong Bangladesh Pilot Plant & Process Development Centre Bangladesh Council of Scientific and Industrial Research Dhaka Bangladesh Institute of Fuel Research & Development Bangladesh Council of Scientific and Industrial Research Dhaka Bangladesh

In this research work, (Bi2O3Fe2O3)0.4(Nb2O5)0.6 was made by the solid state reaction method. Samples were sintered at four different temperatures (850°C, 925°C, 1000°C and 1150°C) to study the effect of sintering temperature on the various properties of the samples. X-ray diffraction analysis confirmed that single phase Bi1.721δ0.089Fe1.056Nb1.134O7 was found when sintering temperature increased. At the same time, larger grain size was found when sintering temperature increased. From variation of dielectric loss with respect to frequency, a small peak was found when sample was sintered at higher temperature (1150°C). Dielectric constant of the sample decreases with the increase of frequency for all the samples. With the variation of temperature, DC resistivity of the samples showed that resistivity decreases with the increase of measuring temperature which indicates semiconducting nature.

关键词： XRD Niobium SEM Dielectric Constant Dielectric Loss Loss Tangent Bismuth Ferrite Resistivity

<i>gyrA</i>Gene Mutation Conferring Phenotypic Cross-Resistance among Fluoroquinolones (Ofloxacin, Levofloxacin and Gatifloxacin) in Multidrug Resistant <i>Mycobacterium tuberculosis</i>Strains Isolated from Pulmonary MDR-TB Patients in Bangladesh

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Journal of Tuberculosis Research 2018年第3期6卷 227-237页

作者： Tamanna tasnim Fatema Mohammad Alam S. M. Ali ahmed Shirin Tarafder S. M. Mostofa Kamal Shamim Hossain Department of Microbiology and Immunology Bangabandhu Sheikh Mujib Medical University (BSMMU) Dhaka Bangladesh National Tuberculosis Reference Laboratory (NTRL) National Institute of Diseases of the Chest and Hospital (NIDCH) Dhaka Bangladesh

Background and objectives: Fluoroquinolones (FLQs) are an essential component of multidrug resistant-tuberculosis (MDR-TB) treatment regimen but unfortunately the emergence of FLQ resistant MDR-TB cases is challenging the current MDR-TB treatment regimen. FLQ resistance is mainly caused by gyrA gene mutation and phenotypic cross-resistance may occur among the different FLQs. A limited number of data exists regarding the cross-resistance phenomenon among FLQs and it appears that resistance to the present class representative FLQ, ofloxacin (OFX), may or may not correlate with complete cross-resistance to other FLQs. So the study was designed to observe if gyrA gene mutations confer to the phenotypic cross-resistance among FLQs [OFX, Levofloxacin (LFX) and Gatifloxacin (GFX)] tested. Methodology: Sputum samples from 68 diagnosed pulmonary MDR-TB cases were collected. All samples were subjected to Multiplex Real-time PCR for the detection of gyrA gene mutations and conventional culture on Lowenstein-Jensen (L-J) media followed by drug sensitivity testing (DST) of culture isolates (MDR-TB strains) by indirect proportion method for the detection of phenotypic resistance pattern to OFX, LFX and GFX. Results: Out of the 68 MDR-TB sputum samples 13 (19.11%) had MDR-TB bacilli with mutations in the gyrA gene and 11(16.18%) of the MDR-TB culture isolates were found to have resistance to FLQs by DST. The study observed that 11 MDR-TB samples with gyrA gene mutations showed complete phenotypic cross-resistance among OFX, LFX and GFX. Conclusion: This study found that mutation in the gyrA gene of the MDR-TB bacilli results in the complete cross-resistance among the FLQs (OFX, LFX and GFX) tested. It is therefore of utmost importance to carry out the base line resistance and cross-resistance tests for the individual FLQs prior to initiating the treatment of MDR-TB cases in Bangladesh for successful clinical outcomes.

关键词： Multidrug Resistant-Tuberculosis (MDR-TB) gyrA Gene Mutations Fluoroquinolones (FLQs) Cross-Resistance

A Review on D 614G Mutation with Bangladesh Scenario

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Advances in Infectious Diseases 2020年第3期10卷 249-255页

作者： Arifa Akram Mohammad Jahidur Rahman Khan Md. Bayzid Bin Monir Md. Reaz Uddin Chowdhury Mahmuda Yeasmin Md. Maruf ahmed Molla tasnim Nafisa Department of Virology National Institute of Laboratory Medicine and Referral Center Dhaka Bangladesh Department of Microbiology Shaheed Suhrawardy Medical College Dhaka Bangladesh Department of Microbiology National Institute of Laboratory Medicine and Referral Center Dhaka Bangladesh Abdul Malek Ukil Medical College Noakhali Bangladesh

With the COVID-19 pandemic, disparities between the infection rate and death rate in different countries become a major concern. In some countries, lower mortality rate compared to others can be explained by better testing capacity and intensive care facilities. Complete SARS-CoV-2 genome sequences from different countries of the world are continually submitted to Global Initiative for Sharing All Influenza Data using Next Generation Sequencing method. A SARS-CoV-2 variant with a D 614G Mutation in the spike (S) protein has become the most dominant form in the global pandemic. There are a number of ongoing studies trying to relate this mutation with the infectivity, mortality, transmissibility of the virus and its impact on vaccine development. This review aims to accumulate the major findings from some of these studies and focus its future implication. Some studies suggested D 614G strain has increased binding capacity, it affects more cells at a faster rate, so has a high transmissibility. Patients infected with this strain were found with high viral load. But still now there is no such evidence that this strain produces more severe disease as well as increased mortality. The structural change of spike protein produced by D 614G mutation was minor and did not hamper the vaccine efficacy. Some studies showed antibodies produced against D614 strain can neutralize G614 strain and vice versa. Whenever a mutation occurs in spike protein there are always chances of affecting the infectivity, transmissibility, vaccine efficacy. Therefore, more studies are required to find out the overall effect of D 614G mutation.

关键词： Coronavirus D 614G Mutation SARS-CoV-2 Spike Protein Global Initiative for Sharing All Influenza Data (GISAID)

Pathogenesis of the Chikungunya virus and the host immunity response

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Life Research 2021年第2期4卷 1-10页

作者： Tasnia ahmed Syed Abdullah Ibn Asaduzzaman Rehman Tanvir Zobayda Nahar Nishat tasnim Chandrika Saha Rashed Noor Department of Microbiology Stamford University Bangladesh51 Siddeswari RoadDhaka 1217Bangladesh Department of Life Sciences(DLS) School of Environment and Life Sciences(SELS)Independent UniversityBangladesh(IUB)Plot 16Block BAftabuddin Ahmed RoadBashundhara R/ADhaka 1212Bangladesh

Along with the running COVID-19 pandemic by the severe acute respiratory syndrome coronavirus 2,the Chikungunya virus is already known as the causative agent of re-emerging Chikungunya fever in many countries after several years of latency;and it’s certainly one of the most important clinical issues possibly due to the lack of appropriate ***,continuous study and monitoring of this disease outbreak demand attention by the relevant health *** review has been written in the light of the recently available reports on the Chikungunya virus *** genomic structure and its impact on the viral epidemiology,the possible protective immunity,and the infection mitigation strategies have been ***’s already well known that the Chikungunya virus can start infection after getting entrance into the blood circulation through the mosquito bites followed by the dissemination into the major organs like liver,brain,eye,joints and lymph nodes in order to inaugurate the ***,the occurrence of death is very rare but the extreme fatality and morbidity may occur if the patient has other underlying disease *** molecular aspects of the virus,the site-specific damages caused by the viral infection,and finally,the public awareness of such viral infection as discussed in the current review would help to maintain the public health sustainability especially in the developing countries whereby the knowledge on the required hygiene is poor.

关键词： Chikungunya virus infection Re-emerging diseases Public health Host immunity