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Search Results: 1 - 10 of 14584 matches for " Mohammad Rezaul Karim "
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Synthesis and Characterizations of Poly(3-hexylthiophene) and Modified Carbon Nanotube Composites
Mohammad Rezaul Karim
Journal of Nanomaterials , 2012, DOI: 10.1155/2012/174353
Abstract: Poly(3-hexylthiophene) and modified (functionalized and silanized) multiwall carbon nanotube (MWNT) nanocomposites have been prepared through in situ polymerization process in chloroform medium with FeCl3 oxidant at room temperature. The composites are characterized through Fourier transfer infrared spectroscopy (FT-IR), Raman, and X-ray diffraction (XRD) measurements to probe the nature of interaction between the moieties. Optical properties of the composites are measured from ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectroscopy. Conductivity of the composites is followed by four probe techniques to understand the conduction mechanism. The change (if any) in C=C symmetric and antisymmetric stretching frequencies in FT-IR, the shift in G band frequencies in Raman, any alterations in max of UV-Vis, and PL spectroscopic measurements are monitored with modified MWNT loading in the polymer matrix.
Determination of hemoglobin adduct of a musk xylene metabolite in trout as biomarker of exposure by gas chromatography mass spectrometry
MOTTALEB Mohammad Abdul,KARIM Mohammad Rezaul,
MOTTALEB Mohammad Abdul
,KARIM Mohammad Rezaul

环境科学学报(英文版) , 2005,
Abstract: Musk xylene(MX) is frequently used as fragrances in formulation of personal care products. Quantification of a bound 4-amino-MX(4-AMX) as cysteine adducts in trout hemoglobin(Hb) was made by gas chromatography-ion trap-mass spectrometry(GC/MS). The Hb samples were collected from trout after 24 h exposure to MX at 10 microg/g, and or menhaden oil(control). The formation of cysteine-Hb adduct was observed from nitroso derivative of MX, released by alkaline hydrolysis. The released 4-AMX metabolite was extracted in n-hexane. The extract was then reduced by evaporation, and analyzed by GC/MS. When similar agreement of mass spectral features and retention time of 4-AMX were obtained in both standard and sample solutions, the presence of 4-AMX metabolite in the Hb was confirmed. The concentration of 4-AMX was found to be 3.1 x 10(-6)--6.9 x 10(-6) mg/g in the Hb solution. Quantitation was made based on an internal standard, a calibration plot, and response factor. In the non-hydrolyzed and laboratory blank extracts, the 4-AMX metabolite was not detected. Additionally, coeluting and interfering ions were observed in the biological samples.
Thermal Behavior with Mechanical Property of Fluorinated Silane Functionalized Superhydrophobic Pullulan/Poly(vinyl alcohol) Blends by Electrospinning Method
Mohammad Rezaul Karim,Md. Shahidul Islam
Journal of Nanomaterials , 2011, DOI: 10.1155/2011/979458
Abstract: Fluorinated silane functionalized superhydrophobic pullulan/poly(vinyl alcohol) (PULL/PVA) blend membrane with water contact angle larger than 150° has been prepared by the electrospinning method. The morphology, thermal stability, and mechanical property of the membranes are characterized using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and ZWICK materials testing machine, respectively. Interactions between PULL and PVA and PULL/PVA blends with perfluorooctyltriethoxysilane (PFOTES) of the membranes are analyzed using differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR). Contact angles and water drops on the surface of the membrane are measured by video microscopy. The study shows that the addition of minor quantity of PVA with PULL results in improvement in thermal stability and mechanical property (tensile strength) of the PULL membranes. 1. Introduction The wettability of a solid surface is an interesting property of a material and is described as the contact angle between a liquid and a solid surface. When the contact angle between water and a solid surface is larger than 150°, this solid surface is called a superhydrophobic surface [1]. Superhydrophobic surfaces are widely found in nature. For example, the surface of a lotus leaf is observed to be an array of nanoscale buds [2]. Water drops on the surface of the leaf tend to slide down, rendering its self-cleaning property. The surfaces which mimic “lotus effect” have triggered extensive interests for their potential applications involving water repellency, self-cleaning, and antifouling properties [3–6]. Generally, the hydrophobicity of surfaces depends on both their chemical composition and surface geometrical structure [7]. In terms of chemical composition, hydrophobicity can only be increased by introducing a component with low surface energy such as fluorinated methyl groups. However, this method to increase hydrophobicity is limited. The maximum contact angle that can be reached by coating fluorinated methyl groups onto a flat solid surface is only 120°, which can be hardly called superhydrophobic [8]. Therefore, a hierarchical structure is introduced into the solid surface to achieve superhydrophobicity. A number of methods have been used to make a hierarchical superhydrophobic surface including phase separation [9], electrochemical deposition [10], chemical vapor deposition [11], crystallization control [12], photolithography [13], assembly [14], sol-gel methods [15], solution-immersion methods [16], and array of nanotubes/nanofibers [17,
Analysis of ASE and Intraband Crosstalk Limitations in FBG-OC-Based Bidirectional Optical Cross Connects in a WDM Ring Network
Mohammad Rezaul Karim,S. P. Majumder
International Journal of Electronics, Computer and Communications Technologies , 2012,
Abstract: We investigate the effects of optical amplifiers in the presence of intraband crosstalk arises in FBG-OC-based bidirectional optical cross connects (BOXCs) for bidirectional WDM ring networks (BWRNs). Theoretical analysis is carried out to evaluate the performance limitations due to ASE of optical amplifiers in bidirectional WDM ring networks. We analyzed here two configurations of FBG-OC-based BOXCs: 2 × 2 BOXC and 4 × 4 BOXC in the presence of optical preamplifiers for bidirectional WDM ring networks and evaluate the bit-error rate (BER) and power penalty (PP) due to intraband crosstalk and ASE noise. Receiver sensitivity is significantly degraded which causes additional BER and power penalty due to signal-ASE beat noise induced in optical amplifiers in the presence of intraband crosstalk arises in BOXC. It is found that BER and power penalty, due to ASE-signal beat noise accumulated through multiple nodes along with intraband crosstalk induced by fiber Bragg gratings, are worsen significantly not only with the number of wavelength channel increased for both bar and cross state of BOXC but also with the number of amplifier increased. BER and power penalty are not affected with the position number of the wavelength channels in the bar state while in the cross state, if the position number of the wavelength channels is increased, the BER and power penalty both are increased.
2,9-Bis(1,3-benzothiazol-2-yl)-1,10-phenanthroline dichloromethane disolvate
Jesmin Akther,Sergey Lindeman,Mohammad Rezaul Karim
Acta Crystallographica Section E , 2008, DOI: 10.1107/s1600536808019995
Abstract: In the title compound, C26H14N4S2·2CH2Cl2, the two pendant benzothiazole groups are slightly twisted with respect to the phenanthroline core [dihedral angles = 1.03 (7) and 9.05 (5)°]. Weak intermolecular C—H...N and C—H...Cl interactions occur in the crystal structure.
Investigation of Heavy Metals and Radionuclide’s Impact on Environment Due to The Waste Products of Different Iron Processing Industries in Chittagong, Bangladesh  [PDF]
Mohammad Saifur Rahman, Bijoy Sonker Barua, Md. Rezaul Karim, Masud Kamal
Journal of Environmental Protection (JEP) , 2017, DOI: 10.4236/jep.2017.89061
Abstract: The waste products, such as induction furnace slag, ladle furnace slag, air pollution control dust, and ramming mass collected from major iron processing industries in Chittagong, Bangladesh were analyzed for heavy metals and naturally radioactive elements. The concentrations of heavy metals Fe, Cr, Mn, Co, Cd, Ni, Pb, Cu and Zn were obtained from atomic absorption spectrophotometer (AAS) analysis with flame atomizer and the radioactivities due to 226Ra, 232Th and 40K were determined using high purity germanium (HPGe) detector of well shielded gamma-ray counting system. From the mean specific activities of the above three natural radionuclides in the investigated samples, the radium equivalent activity (Raeq) and the external hazard index (Hex) were calculated. The study showed the prospect of contamination of environmental materials (viz., soil, water, air, plant) due to many of these investigated elements by using the collected waste products in landfill. The chemical process of ion exchange indicates that the elevated heavy metals in soil can play a role to increase the natural radioactivity of the soil. The obtained Raeq as well as Hex indicated the insignificant radiation hazard due to the activities of primordial radionuclides found in the investigated samples.
Some Novel Schiff Bases from Pyruvic Acid with Amines Containing N & S Donor Atoms: Synthesis, Spectral Studies and X-Ray Crystal Structures  [PDF]
Abdul Azim Jambol, Malai Haniti Sheikh Abdul Hamid, Aminul Huq Mirza, Md. Shafiqul Islam, Mohammad Rezaul Karim
International Journal of Organic Chemistry (IJOC) , 2017, DOI: 10.4236/ijoc.2017.71005
Abstract: Four Schiff bases, from pyruvic acid (1) with amines containing N and S donor atoms, thiocarbohydrazide (2, 61%), 2-methyl-3-thiosemicarbazide (3, 26%), S-benzyldithiocarbazate (4, 51%) and S-n-octyldithiocarbazate (5, 63%) have been successfully synthesized. The conventional method was used and a series of novel linear and cyclic Schiff bases were obtained with or without catalyst. All the Schiff bases were fully characterized by CHN elemental analysis, FT-IR, 1H & 13C NMR, EI-MS and two of the Schiff bases were further characterized by X-ray crystallographic structure analysis. Compound 2 crystallizes in the triclinic space group P-1 and unit cell dimensions are: a = 4.1777(8), b = 5.9538(11), c = 13.458(3) Å, α = 92.759(6), β = 90.813(6), γ = 100.040(6)°, R1 = 0.0439. Compound 3 crystallizes in the orthorhombic space group P n a 2(1) and unit cell dimensions are: a = 5.5992(2), b = 11.3962(5), c = 10.6473(5), α = 92.759(6), β = 90.813(6), γ = 100.040(6)°, R1 = 0.0285. Compounds 2 and 3 were obtained as cyclic Schiff bases which are triazine derivatives.
Quasi Solid-State Dye-Sensitized Solar Cell Incorporating Highly Conducting Polythiophene-Coated Carbon Nanotube Composites in Ionic Liquid
Mohammad Rezaul Karim,Ashraful Islam,Surya Prakash Singh,Liyuan Han
Advances in OptoElectronics , 2011, DOI: 10.1155/2011/357974
Abstract: Conducting polythiophene (PTh) composites with the host filler multiwalled carbon nanotube (MWNT) have been used, for the first time, in the dye-sensitized solar cells (DSCs). A quasi solid-state DSCs with the hybrid MWNT-PTh composites, an ionic liquid of 1-methyl-3-propyl imidazolium iodide (PMII), was placed between the dye-sensitized porous TiO2 and the Pt counter electrode without adding iodine and higher cell efficiency (4.76%) was achieved, as compared to that containing bare PMII (0.29%). The MWNT-PTh nanoparticles are exploited as the extended electron transfer materials and serve simultaneously as catalyst for the electrochemical reduction of I ? 3 . 1. Introduction Dye-sensitized solar cells (DSCs) have attracted significant attention as promising solar-to-electricity power conversion devices because of their higher energy conversion and potential for low-cost production [1–6]. In general, DSCs comprise an electrode consisting of nanocrystalline titanium dioxide (TiO2) films modified with a dye, a platinum counterelectrode, and an electrolyte solution in between the electrodes. Photoexcitation of the dye results in the injection of an electron into the conduction band of the oxide. The original state of the dye is subsequently restored by electron donation from a redox system, such as the iodide/triiodide (I?/I3??) couple. At the present, DSCs are mainly constructed by using liquid electrolyte as a charge transport material. The charge transport in these liquid electrolytes is typically achieved by using I?/I3?? redox reaction in electrolyte solution. Therefore, long-term durability of DSCs is limited by leakage and the volatilization of organic solvent-based electrolytes. Numerous investigations have been conferred to overcome this drawback, replacing the liquid electrolyte by organic and inorganic hole transport materials [7–9], polymer and gel electrolytes [10–14], and nanocomposite ionic liquid (IL) electrolytes [15–20] resulting in solid-state and quasi solid-state DSCs. Imperfect pour filling of the dye-coated nanocrystalline TiO2 film with organic and inorganic hole transport materials results in a poor device efficiency. Moreover, the ionic conductivity for the majority of the amorphous polymer electrolytes is too low (<10?5?S?cm?1), limiting the device efficiency. Although nanocomposite IL electrolyte can reduce leakages, it is not satisfactory, because of the high concentration of corrosive and volatile iodine present in the electrolyte. The introduction of I2 into the electrolytes could increase the conductivity of the electrolyte
Multiwall Carbon Nanotube Coated with Conducting Polyaniline Nanocomposites for Quasi-Solid-State Dye-Sensitized Solar Cells
Mohammad Rezaul Karim,Ashraful Islam,M. D. Akhtaruzzaman,Liyuan Han
Journal of Chemistry , 2013, DOI: 10.1155/2013/962387
Abstract:
Mammalian Fauna and Conservational Issues of the Baraiyadhala National Park in Chittagong, Bangladesh  [PDF]
Rezaul Karim, Farid Ahsan
Open Journal of Forestry (OJF) , 2016, DOI: 10.4236/ojf.2016.62011
Abstract: Mammals were studied at the Baraiyadhala National Park, Chittagong from August 2012 to July 2013. Twenty nine species of mammals belonging to 26 genera, 17 families and 9 orders were recorded. Of the recorded species, 2 were primates, 10 rodents, 1 lagomorph (hare), 5 chiropterans (bats), 1 manid, 7 carnivores and 3 ungulates. Rodentia appeared as the largest family contained 10 speices. The overall mammalian population density was 239.12/km2. Irrawardy squirrel (Callosciurus pygerythrus) scored the highest density (112.97/km2) and several species attained the lowest (1/km2 each). Local status (relative abundance) of mammals assessed where 15 (51.72%) species were rare, and according to National Conservation Status, 13 (44.82%) were remarked as threatened species of that area. There were some major threats to the park such as forest fire, encroachment of forest and forest edges by both tribal and landless people, illegal exploitation of forest resources, grazing of livestock and unavailable water reservoirs.
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