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匹配条件: “Ashraful Alam” ,找到相关结果约1718条。
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Emerging Ideas in Nanocantilever based Biological Sensors
Ankit Jain,Muhammad Ashraful Alam
Physics , 2013,
Abstract: In this review article, we focus on emerging nanocantilever based biological sensors and discuss the response of nanocantilevers towards bio-molecules capture. The article guides the reader through various modes of operation (e.g., static or dynamic) to detect the change in characteristics (e.g., mass, stiffness, and/or surface stress) of cantilever due to adsorption of bio-molecules on cantilever surface. First, we explain the classical linear resonant mode mass sensors and static stress based sensors. The effect of operating the cantilever in nonlinear regime is then illustrated through examples of bifurcation based mass sensors and electromechanical coupling based Flexure-FET biosensors. We believe that a new class of nonlinear sensors, with their extraordinary sensitivity towards bio-molecules capture, could be the potential candidate for low cost point-of-care applications.
Prospects of Hysteresis-Free Abrupt Switching (0mV/dec) in Landau Switches
Ankit Jain,Muhammad Ashraful Alam
Physics , 2013, DOI: 10.1109/TED.2013.2286997
Abstract: Sub-threshold swing (S) defines the sharpness of ON-OFF switching of a Field Effect Transistor (FET) with S=0 corresponding to abrupt switching characteristics. While thermodynamics dictates S to be greater than or equal to 60mV/dec for classical FETs, "Landau switches" use inherently unstable gate insulators to achieve abrupt switching. Unfortunately, S=0 switching is always achieved at the expense of an intrinsic hysteresis, making these switches unsuitable for low-power applications. The fundamental question therefore remains: Under what condition, hysteresis-free abrupt switching can be achieved in a Landau switch? In this paper, we first provide an intuitive classification of all charge based switches in terms of their energy landscapes and identify two-well energy landscape as the characteristic feature of Landau switches. We then use nanoelectromechanical field effect transistor (NEMFET) as an illustrative example of a Landau switch and conclude that a flat energy landscape is essential for hysteresis-free abrupt switching. In contrast, a hysteresis-free smooth sub-60mV/dec switching is obtained by stabilizing the unstable gate insulator in its unstable regime. Our conclusions have broad implications and may considerably simplify the design of next charge based logic switch.
Naringin Improves Diet-Induced Cardiovascular Dysfunction and Obesity in High Carbohydrate, High Fat Diet-Fed Rats
Md. Ashraful Alam,Kathleen Kauter,Lindsay Brown
Nutrients , 2013, DOI: 10.3390/nu5030637
Abstract: Obesity, insulin resistance, hypertension and fatty liver, together termed metabolic syndrome, are key risk factors for cardiovascular disease. Chronic feeding of a diet high in saturated fats and simple sugars, such as fructose and glucose, induces these changes in rats. Naturally occurring compounds could be a cost-effective intervention to reverse these changes. Flavonoids are ubiquitous secondary plant metabolites; naringin gives the bitter taste to grapefruit. This study has evaluated the effect of naringin on diet-induced obesity and cardiovascular dysfunction in high carbohydrate, high fat-fed rats. These rats developed increased body weight, glucose intolerance, increased plasma lipid concentrations, hypertension, left ventricular hypertrophy and fibrosis, liver inflammation and steatosis with compromised mitochondrial respiratory chain activity. Dietary supplementation with naringin (approximately 100 mg/kg/day) improved glucose intolerance and liver mitochondrial dysfunction, lowered plasma lipid concentrations and improved the structure and function of the heart and liver without decreasing total body weight. Naringin normalised systolic blood pressure and improved vascular dysfunction and ventricular diastolic dysfunction in high carbohydrate, high fat-fed rats. These beneficial effects of naringin may be mediated by reduced inflammatory cell infiltration, reduced oxidative stress, lowered plasma lipid concentrations and improved liver mitochondrial function in rats.
Protein binding interaction of warfarin and acetaminophen in presence of arsenic and of the biological system
Md. Ashraful Alam,Riaz Uddin,Shamsul Haque
Bangladesh Journal of Pharmacology , 2008,
Abstract: Equilibrium dialysis was used to study in vitro binding of warfarin at physiological pH and temperature in bovine serum albumin (BSA) along with the increasing concentration of acetaminophen and there interaction with the protein in presence of arsenic. The free fractions were determined by UV spectrophotometric technique. The binding of warfarin to BSA depended on both drug and arsenic concentrations. Free warfarin concentration increased due to addition of acetaminophen which reduced the binding of warfarin to BSA. Free warfarin concentration also increased accordingly by increasing the concentra-tion of acetaminophen when only the BSA was present. When the binding site was blocked by sufficient amount of arsenic the increment of free concentration of warfarin decreased to a lower extent. This suggests that in the presence of arsenic the warfarin being slowly displaced from its high affinity binding site with increasing acetamino-phen concentration.
Markov-Chain Formulation of Reaction-Diffusion Model and its Implications for Statistical Distribution of Interface Defects in Nanoscale Transistors
Ahmad Ehteshamul Islam,Muhammad Ashraful Alam
Physics , 2010,
Abstract: Continued scaling of nanoscale transistors leads to broad device-to-device fluctuation of parameters due to random dopant effects, channel length variation, interface trap generation, etc. In this paper, we obtain the statistics of negative bias temperature instability (NBTI)-induced interface defect generation in ultra-scaled MOSFET by Markov Chain Monte-Carlo (MCMC) solution of Reaction-Diffusion (R-D) model. Our results show that the interface defect generation at a particular stress time, i.e., NIT}@tSTS in small transistors should follow a skew-normal distribution and that the generation and annealing of interface defects are strongly correlated. Next, we use a random percolative network to demonstrate (which is also consistent with previously published results in literature based on separate techniques) that the distribution of threshold voltage shift for single interface defect, i.e., {\Delta}VT@NIT is exponential, with finite number of transistors having zero {\Delta}VT. Finally, we show that the statistics of {\Delta}VT@tSTS - based on the convolution of NIT@tSTS and {\Delta}VT@NIT - is broadly consistent with the available experimental data in literature.
Market Depth and Risk Return Analysis of Dhaka Stock Exchange: An Empirical Test of Market Efficiency
Md. Mahmudul Alam, Kazi Ashraful Alam, Md. Gazi Salah Uddin
ASA University Review , DOI: -
Abstract: It is customary that when security prices fully reflect all available information, the markets for those securities are said to be efficient. And if markets are inefficient, investors can use available information ignored by the market to earn abnormally high returns on their investments. In this context this paper tries to find evidence supporting the reality of weak-form efficiency of the Dhaka Stock Exchange (DSE) by examining the issues of market risk-return relationship and market depth or liquidity for DSE. The study uses a data set of daily market index and returns for the period of 1994 to 2005 and weekly market capital turnover in proportion of total market capital for the period of 1994 to 2005. The paper also looks about the market risk (systemic risk) and return where it is found that market rate of return of DSE is very low or sometimes negative. Eventually Capital Asset Pricing Model (CAPM), which envisages the relationship between risk and the expected rate of return on a risky security, is found unrelated in DSE market. As proper risk-return relationships of the market is seems to be deficient in DSE and the market is not liquid, interest of the available investors are bring into being very insignificant. All these issues are very noteworthy to the security analysts, investors and security exchange regulatory bodies in their policy making decisions to progress the market condition.
Phytochemical and Cytotoxic Investigation of Codiaeum variegatum Linn. Leaf
Nadia Saffoon,Md. Ashraful Alam,Golam Mezbah Uddin
Stamford Journal of Pharmaceutical Sciences , 2010,
Abstract:
Activity of Trypsin Adsorbed on Temperature and pH-Responsive Micron-Sized PS/P(NIPAM-MAA-MBAAm) Composite Polymer Particles
M. Ashraful Alam,M.A. Jalil Miah,Hasan Ahmad
Journal of Applied Sciences , 2008,
Abstract: Micron-sized polystyrene (PS) seed particles were prepared by dispersion polymerization of styrene in ethanol-water media. Seeded copolymerization of N-isopropyl acrylamide (NIPAM), methacrylic acid (MAA) and N,N`-methylene-bis-acrylamide (MBAAm) was then carried out in presence of PS seed particles. The produced PS/P(NIPAM-MAA-MBAAm) composite polymer particles exhibited volume phase transition to small changes in temperature and pH, respectively. Specific activities of trypsin aqueous solution (free trypsin) and trypsin in presence of PS seed and composite polymer particles were measured under identical conditions. Relative study suggested that trypsin adsorbed on PS/P(NIPAM-MAA-MBAAm) composite polymer particles retained their native conformation.
A COMPARATIVE QUALITY CONTROL STUDY ON CONVENTIONAL IBUPROFEN TABLETS AVAILABLE IN BANGLADESHI PHARMA MARKET
Syed Masudur Rahman Dewan,Ashraful Alam,Sayed Koushik Ahamed
International Research Journal of Pharmacy , 2013,
Abstract: The quality of a pharmaceutical product is essential to ensure the safety of the patients. Different parameters of quality control of pharmaceutical products can guarantee the quality and bioavailability and optimal therapeutic activity. Therefore, the present study was undertaken with the aim of assuring the quality and the therapeutic activity of ibuprofen tablets available in the Bangladeshi drug market. Different quality control parameters, i.e., the variation of weight, friability, content uniformity, disintegration time and dissolution profiles were assessed in vitro. To demonstrate the differences between the products, the difference (f1) and similarity (f2) data were analyzed. The results showed that all products fulfill the given specification selected by Pharmacopeia (USP-NF).
In-vitro free radical scavenging activity of Ixora coccinea L
Moni Rani Saha,Md. Ashraful Alam,Raushanara Akter,Rumana Jahangir
Bangladesh Journal of Pharmacology , 2008,
Abstract: Antioxidant activity of the methanol extract of Ixora coccinea L. was determined by DPPH free radical scavenging assay, reducing power and total antioxidant capacity using phosphomolybdenum method. Preliminary phytochemical screening revealed that the extract of the flower of I. coccinea possesses flavonoids, steroids and tannin materials. The extract showed significant activities in all antioxidant assays compared to the standard antioxidant in a dose dependent manner and remarkable activities to scavenge reactive oxygen species (ROS) may be attributed to the high amount of hydrophilic phenolics. In DPPH radical scavenging assay the IC50 value of the extract was found to be 100.53 μg/mL while ascorbic acid had the IC50 value 58.92 μg/mL. Moreover, I. coccinea extract showed strong reducing power and total antioxidant capacity.
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