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Articles by A. Ahmad
Total Records ( 17 ) for A. Ahmad
  R. Omar , N.A. Rahim and A. Ahmad
  Problem statement: Voltage disturbances are the most common power quality problem due to the increased use of a large numbers of sophisticated electronic equipment in industrial distribution system. The voltage disturbances such as voltage sags, swells, harmonics, unbalance and flickers. High quality in the power supply is needed, since failures due to such disturbances usually have a high impact on production cost. There are many different solutions to compensate voltage disturbances but the use of a DVR is considered to be the most cost effective method. The objective of this study is to propose a new topology of a DVR in order to mitigate voltage swells using a powerful power custom device namely the Dynamic Voltage Restorer (DVR). Approach: New configuration of a DVR with an improvement of a controller based on direct-quadrature-zero method has been introduced to compensate voltage swells in the network. Results: The effectiveness of the DVR with its controller were verify using Matlab/Simulink’s SimPower Toolbox and then implemented using 5KVA DVR experimental setup. Simulations and experimental results demonstrate the effective dynamic performance of the proposed configuration. Conclusion: The implimentation of the proposed DVR validate the capabilities in mitigating of voltage swells effectiveness.During voltage swells, the DVR injects an appropriate voltage to maintain the load voltage at its nominal value.
  A. Ahmad , M. Chaudhary , A. Soni , A. Payasi and V.K. Dwivedi
  In the present study, the researchers have tried to determine the toxicity of a novel fixed dose combination of ofloxacin plus ornidazole (mebatic) vs. ofloxacin, ornidazole and metronidazole alone drugs in the plasma of Wister rats. Total thirty Wister rats were randomly selected and divided into five groups of six rats each. Group I was control normal saline (0.9% NaCl) treated group where as rest of four groups were treated with respective drugs. The drugs were given to animals intravenously for 24 days and blood samples were collected on 12th and 24th day after treatment for the measurement of biochemical parameters. Present results showed that there was insignificant increase in hemoglobin level on 12th and 24th day in mebatic treated group as compared with other treated groups. The levels of uric acid, alkaline phosphatase, creatinine, bilirubin and hepatic enzymes were found to be lowered but insignificant in mebatic treated group on 12th and 24th day treatment in comparison to ofloxacin, ornidazole as well as metronidazole alone treated groups. These levels were found to be almost near to normal level in mebatic treated group. When ofloxacin, ornidazole as well as metronidazole alone treated groups were compared to control group, these hepatic and renal parameters were significantly increased except in mebatic treated group. The level of free radical mediated damage was also significantly decreased in mebatic treated group in comparison to other treated groups. Therefore, these findings concluded that mebatic drug is less toxic and most effective than ofloxacin, ornidazole and metronidazole alone which improved hepatic and renal enzymes and free radical mediated damage.
  Jugah B. Kadir , A. Ahmad , M. Sariah and A.S. Juraimi
  The possibility of using an indigenous plant pathogen to control itchgrass (Rottboellia cochichinensis) was investigated in this study. A fungal pathogen of itchgrass, Exserohilum longirostratum, was determined in the laboratory and greenhouse as a potential bioherbicide. The disease symptoms on inoculated plants appeared 24 h post inoculation as discrete spot with watery dark border, eventually expand and cause extensive necrosis on the leaves, resulted in burnt-like symptom. When applied as a post emergence foliar spray, the fungus inflicted high percentage of mortality to young itch grass seedlings It did not killed older plants but was capable of reducing biomass by about 56% when the plants were inoculated with 3.5x105 conidia mL-1. Media containing carbon: nitrogen ratio of 10:1 as in V8 juice agar and PDA produced more conidia compared to medium (CMA) containing carbon:nitrogen ratio of 40:1. Light and temperature had major influence on fungal sporulation, exposing the fungus to longer duration (12 h) of light significantly increases conidia production. The optimal temperature for growth and sporulation of this fungus is in the range of 25 to 30°C.
  M.R. Siddiqui , A. Tariq , A. Ahmad , M. Chaudhary , S.M. Shrivastava and R.K. Singh
  Two simple, rapid and sensitive spectrophotometric methods have been proposed for the determination of milrinone in pharmaceutical formulations. The first method is based on the charge transfer complexation reaction of milrinone with 2, 3-Dichloro-5, 6-Dicyanobenzoquinone, DDQ while the second method is based on charge transfer reaction of milrinone with p-Chloranilic Acid (pCA). Under the optimized experimental conditions Beer's law is obeyed in the concentration range of 2-40 μg mL-1 for method A and 5-100, 2-40 μg mL-1 for method B. The recovery ranged from 100.06 -100.11 for method A and from 99.34 -99.97 for method B. The coefficient of correlation was found to be 0.9998 for A and 0.9999 for B and the detection limit for method A and method B was found to be 0.765 and 3.35, respectively. Both the methods have been applied to determination of milrinone in the pharmaceutical formulation. Results of the analysis are validated statistically.
  P.K. Lo , C.Y. Tan , O. Hassan , A. Ahmad , N.M. Mahadi and R.M. Illias
  In the study presented, Design of Experiments (DOE) was combined with statistical analysis such as fractional factorial design and small central composite design Response Surface Methodology (RSM) to significantly increase the extracelullar recombinant CGTase yields in fermentation flasks. The new medium obtained by the statistical analysis for the significant medium components comprised of 12 g L-1 NZ Amine A, 24 g L-1 yeast extract, 9.44 g L-1 KH2PO4, 4.4 g L-1 K2HPO4, 4.58 mL L-1 glycerol, 7 mg L-1 sucrose and 3 mg L-1 CuCl2. Yields were improved about 68% from 9.54 to 16.07 kU mL-1 in flasks when using the optimized cultivation medium. The results suggest that the overexpression level of recombinant CGTase excreted into the culture medium using the recombinant Escherichia coli could be improved through medium optimization.
  A. Lloyd , B. Nafees , S. Gavriel , M. D. Rousculp , K. S. Boye and A. Ahmad

Aims Different estimates exist regarding the impact of diabetic retinopathy (DR) on health utility. A previously reported prospective observational study has reported much larger decrements in self-reported utility than generic utility data from the UK Prospective Diabetes Study and the Lipids in Diabetes Study. The present study was designed to estimate utility loss using multiple methods.

Methods Detailed health state descriptions reflecting declining DR (five different visual acuity levels), neuropathy and nephropathy were validated with patients and used to elicit utility values from people with DR, people with diabetes and members of the UK general public using standard gamble. In addition, a larger sample of people with retinopathy completed different health-related quality of life measures in an interview [EuroQoL (EQ-5D), Health State Utilities Index (HUI)-3, and National Eye Institute Visual Functioning Questionnaire-25].

Results The utility scores from the standard gamble interviews were not significantly different between the three groups. There was a decline in utility from 6/6 vision to counting fingers of −0.244. The utility data derived from the generic measures revealed an equivalent decline of −0.41 on both the EQ-5D single index and the HUI-3.

Conclusions This study has re-examined the utility decrements associated with DR and has identified much larger declines in utility than previously reported. The study has also reported the utility values of patients with retinopathy as assessed by standard gamble. We believe that this may be the first study to report utility values for health states associated with vision loss which have been elicited from patients with vision loss.

  N.H. Abdul Hamid , A. Ahmad , M.S. Ahmad , Y.C. Alicia Tang and A. Mustapha
  Simulation is a way of doing thought experiments besides the deduction and induction methods. Agent-based Simulation (ABS) falls under the domain of artificial intelligence when agent is used to perform certain tasks such as behaviour prediction, optimization of functions or time-constrained work-flow management. This work discussed the use of ABS on a computational normative framework based on a set of empirical characteristics that influence agents’ performance in time-constrained environment. The ABS simulates a domain called the Examination Preparation and Moderation Process (EPMP) which entails document submission processes with deadlines. The simulation is conducted in six different environments and the results of the agent performance in each environment are presented and discussed. The results indicate that the simulation conducted in the EPMP is suitable and effective for evaluating normative agent-based systems.
  V.K. Dwivedi , A. Soni , A. Payasi , A. Ahmad , Shambhu P. Singh and M. Chaudhary
  The aim of present study was to evaluate the effect of levofloxacin and potentox drugs in osteomyelitis -induced rat model. Staphylococcus aureus 100 μL (1x106 CFU mL-1) was inoculated into the proximal metaphysis of the tibia for induction of osteomyelitis. Body weight and temperature of osteomyelitis-induced rats were monitored every 4th day for three weeks before and after treatment with levofloxacin and potentox. Levofloxacin and potentox were given to animals by intravenously for 21 days. To determine the biochemical parameters (Protein, CRP, Na, Phosphorus, Calcium levels), hepatic enzymes as well as renal function test along with cytokines and malondialdehyde (MDA), myeloperoxidase (MPO) levels in the serum of osteomyelitis-induced untreated and treated groups. Our results showed that the levels of biochemical parameters as well as renal function test along with malondialdehyde, myeloperoxidase levels were significantly altered in the untreated group as compared to levofloxacin and potentox treated groups. When levofloxacin treated group was compared to potentox-treated group, the renal function test and levels of biochemical parameters along with malondialdehyde, myeloperoxidase levels and cytokines were significantly improved in the serum of potentox-treated group. The hepatic enzyme activity was found to be higher in levofloxacin treated group in comparison to potentox-treated group. These study concluded that potentox act as an antioxidant by improving free radical mediated damage and prevents osteomyelitis infection and hepatoxicity in comparison to levofloxacin, caused by Staphylococcus aureus microorganism.
  V.K. Dwivedi , M. Chaudhary , A. Soni , J. Yadav , A. Tariq , M.R. Siddiqui , A. Ahmad and P.S. Negi
  The present study was to investigate the comparative efficacy of ceftriaxone and a fixed dose combination of ceftriaxone plus sulbactam along with VRP1034 (Sulbactomax) in cerebrospinal fluid (CSF) of meningitis induced rat model. Eighteen rats were divided into three groups of six rats each. Meningitis were induced by MRSA strain (log 106 cfu mL-1). Group I was infected group; whereas group II and III were ceftriaxone and sulbactomax treated groups. Drugs were analyzed in CSF by high performance liquid chromatography. Some biochemical parameters were studied in infected and treated groups. Present results showed that the mean level of ceftriaxone drug concentration was increased significantly in sulbactomax treated group in comparison to ceftriaxone alone treated group. Glucose level was increased in sulbactomax treated group as compared to ceftriaxone alone treated group. The levels of protein, calcium and phosphorus were significantly lowered in both treated group as compared to infected group. These biochemical parameters were decreased along with increased glucose level in sulbactomax treated group in comparison to ceftriaxone alone treated group. Present findings concluded that sulbactomax enhanced the penetration rate in CSF than ceftriaxone alone due to VRP1034. It plays a therapeutic role in crossing blood brain barrier and helps in prevention of bacterial meningitis infection.
  M. Mohamad , M.W. Ali and A. Ahmad
  A mass transfer model of major phytochemical components from Eurycoma longifolia was developed in order to describe the solid-liquid extraction process. The yield of the extraction normally depends on the operating parameters such as solvent to raw material ratio, extraction time, temperature and agitation speed. In this study, the model was developed taking into account the two-way mass transfer of solute into liquid phase and the solvent into solid system. The influence of processing variables such as extraction temperature, solvent to raw material ratio and agitation speed was simulated by the model. Several assumptions were made in the theoretical approach to solve the simulation algorithm in order to predict the performance of the solid-liquid extraction system. From the study, it can be concluded that when the extraction temperature was increased, the yield of extraction also increased and this has reduced the extraction time. The best agitation speed was found to be at 400 rpm.
  S.M.W. Ali , A. Ripin and A. Ahmad
  Recovery of used lubricating oil by extraction produced organic sludge and recovered base oil, but this oil has metallic content such as magnesium and zinc. In this study, purification of recovered base oil by using adsorption process to remove heavy metals was performed. Zeolite was used as an adsorbent. The parameters studied were contact time, amount of zeolite, temperature and their interactions. The results showed that zinc removal was higher than that of the magnesium. The optimum magnesium and zinc removal obtained were 50 and 62%, respectively. The most influential parameter affecting the magnesium and zinc removal was the time of adsorption. Further investigations on the optimum conditions will be performed.
  S.M. Jamil , M.W. Ali , A. Ripin and A. Ahmad
  It was common to use solvent extraction to recover base oil from used lubricants. Although, significant amount of contaminants removal was achieved by using solvent extraction, some problems arised which need to be resolved. The recovered base oil from solvent extraction was still in the darkish color with stink odor and only minimum heavy metals were removed. As an alternative, an adsorption method which used chitosan to remove metals and contaminants was being investigated. This paper presents the application of experimental design on the study of metals removal from the recovered base oil using adsorption process. Four parameters namely temperature, contact time, chitosan grain size and chitosan dosage on the performance of chitosan to adsorb metals were studied. It was found that the most influential parameter effecting the metals removal was the chitosan grain size. The metals removals also greatly depended on the temperature of the process and chitosan dosage. The performance of these parameters will be further investigated.
  A. Ahmad and S.D. Hutagalung
  One-dimensional silicon nanostructures were synthesized via thermal evaporation technique using nickel catalyst. Effects of nickel catalyst and silicon substrate position on the formation of silicon nanostructure were studied extensively. Silicon powder that used as silicon source was evaporated at 900-1000°C for 1 h using tube furnace under controlled environment. The uncoated and nickel-coated silicon substrates were positioned at 3-12 cm from the silicon powder at downstream nitrogen gas flow. It was found that on the substrate without nickel catalyst have no traces of silicon nanostructures. However, on the nickel-coated silicon substrate obtained nanowires and needle-like nanostructures with various diameter and length. These results prove that nickel catalyst is playing an important role on the growth of silicon nanostructures on silicon substrate. Most of the grown one-dimensional silicon nanostructures are not in vertical alignment but bends to the certain direction. This bent-shaped formation might be due to the applied force of carrier gas flow during thermal evaporation. The nickel catalyst at the tip of silicon nanowires could be confirmed the growth mechanism of one-dimensional silicon nanostructures is similar to vapor-liquid-solid mechanism.
  Sheikh, M.A. , S. Khanum , A. Ahmad , T. Iqbal , Z. Hydair and Shakeela Naz
  Levofloxacin is a quinolone antimicrobial which acts through the inhibition of bacterial topoisomerases that has been developed mostly for clinical use in human medicine. Its protein binding was investigated in human beings under indigenous conditions. Drug concentration of 1, 2, 3, 4 and 5 g/ml were added to the plasma and binding of levofloxacin was determined by ultrafiltration and its concentration in ultrafiltrates was determined by microbiological assay. The binding of levofloxacin showed positive correlation between drug concentration and percentage bound drug and maximum binding was observed at 5 g/ml and 59% in human beings. The pH of plasma also affected the binding, being highest at 7.4 in human beings, and it was 53%. In vitro binding of levofloxacin was maximum at normal level of blood protein.
  D.S. Kushwah , M.T. Salman , P. Singh , V.K. Verma and A. Ahmad
  Paracetamol overdose causes serious liver necrosis. Hepatoprotective activity of ethanolic extract of Nigella sativa in Paracetamol induced acute hepatotoxicity was investigated in rats. Fasted male Wistar rats were orally treated with Nigella sativa extract in graded doses for 5 days followed by Nigella sativa extract and paracetamol 3 g kg-1 on 6 and 7th day. Circulatory liver markers and reduced glutathione (GSH) levels were estimated and histopathological study of liver performed. Paracetamol caused a significant increase in serum alkaline phosphatase, glutamic oxaloacetic transaminase, glutamic pyruvic transaminase and total Bilirubin and a significant decrease in GSH compared to control. Nigella sativa pretreatment significantly prevented the increase in liver enzymes and total bilirubin and decrease in GSH level as compared to paracetamol group. Liver histopathology showed marked reduction in sinusoidal dilatation, midzonal necrosis, portal triaditis and occasional apoptosis in Nigella sativa extract treated groups as compared to group receiving only paracetamol. Nigella sativa extract possesses hepatoprotective action against paracetamol induced acute hepatoxicity. Further research is needed to advocate its prophylactic use for drug induced hepatotoxicity.
  N. Rasheed , A. Ahmad and A. Alghasham
  Dopamine (DA) exerts powerful effects on the central regulation of motor and behavioral activities during stressful conditions. This study aimed to evaluate the response of dopaminergic system in Acute Stress (AS) and Chronic Unpredictable Stress (CUS) by measuring dopamine receptor (D1 and D2) gene expression and distribution in the frontal cortex, striatum, hippocampus and amygdala brain regions of rats and also investigated the corresponding changes in the expression of immediate early gene (cfos) in the all selected brain regions. Involvement of D1 receptor in AS and CUS was examined by using A68930 (a D1 selective agonist). Rats were exposed to AS (single immobilization for 150 min) and CUS (two different stressors for 7 days). The results showed that under baseline condition cfos gene was distributed in the brain, with the highest density in the frontal cortex followed by amygdala, striatum and hippocampus. We also found that AS and CUS caused an induction of cfos gene in frontal cortex, striatum and amygdala. Importantly the increased cfos mRNA expression remains up regulated following the treatment of A68930 at 0.25 mg kg-1 dose suggested that neurons in these brain structures are activated. D1 receptor gene was also found to be distributed in the brain, with the highest density in the striatum followed by amygdala, frontal cortex and hippocampus. In case of D2 receptor gene, the highest density was found in the striatum followed by amygdala, hippocampus and frontal cortex. Whereas, D1 receptor gene was found to be elevated in the striatum and hippocampus in both stressed models, but this was normalized by A68930 treatment. On the other hand, D1 receptor mRNA level was reduced in the frontal cortex and amygdala regions in CUS group only. Whereas, the expression D2 receptor remains unchanged in these regions. These changes in gene expression of D1/D2 receptor and cfos, clearly indicating their diverse role in various central nervous system functions operated in particular brain regions.
  M.A.S. Mohamed Arip , D.N. Kamaruzaman , A. Roslan , A. Ahmad and M.R. Abd Rahman
  The aim of this study were to develop and validate a self-rating scale, student stress inventory or SSI for the assessment of stress among Malaysian youth. There are four sub-scales measured in SSI. First, physical stress which contains 10 negative items. Second, interpersonal relationship consists of 10 negative items. Third, academic stress with 10 negative items. The last sub-scales is environmental stress which contains 10 negative items. Content validity was valued by 9 experts which are 5 lecturers and 4 practitioners. The 50 respondents from undergraduate students of an educational university in Peninsular Malaysia were involved for the reliability test. SSI obtained high validity for overall which is 8.05 (80.5%) and for sub-scale of physical: 8.07, interpersonal relationship: 7.89, academic: 8.22 and environmental: 8.02. Reliability analysis also showed high level of reliability which is 0.857 while sub-scale analysis showed moderate where physical: 0.680, interpersonal: 0.620, academic: 0.842 and environmental: 0.806. By this finding, it showed that SSI has a high score of reliability and validity, thus, it can be used in Malaysia context to measure the level of stress among university students. SSI would be beneficial in giving information to educators, counselors, psychologists and researchers who are striving in enhancing students psychological wellness.
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