Papers by Abdul Rahman Khan
Journal of Liquid Chromatography & Related Technologies, 2015
cBergenia ciliata (Paashanbheda, Saxifragraceae) has been used for centuries in Ayurvedic formula... more cBergenia ciliata (Paashanbheda, Saxifragraceae) has been used for centuries in Ayurvedic formulations for a number of ailments related to antiurolithiasis, as an anti-inflamatory, for antitussive activity, and as an antioxidant. In the present communication, four samples of Bergenia ciliata were collected from varying altitudes of Uttrakhand, India, and an analytical HPLC method was developed and validated for the separation and quantification of Bergenin, Epicatechin, (þ)-Catechin, and Gallicin (A-D) in Bergenia ciliata. HPLC analysis was carried out onto a reverse phase column (Reodein; RP-C 18 ; size 4.5 Â 250 mm, 5.0 µm) with mobile phase started with gradient composition prepared from water:phosphoric acid 99.6:0.3 (component A) and acetonitrile:water:phosphoric acid 79.6:20:0.3 (component B). Scanning wavelength kmax 280 nm was used in the determination of compounds using HPLC. The contents of targeted compounds A-D were found positively correlated with the altitudes of collecting site. However, good correlation was only found in compound A and B contents (r ¼ 0.6892, 0.6398) compared to compound C and D contents (r ¼ 0.1297, 0.3245).
Advanced Science, Engineering and Medicine, 2015
ABSTRACT Many common gram-positive pathogens such as Staphylococcus aureus, Enterococcus species,... more ABSTRACT Many common gram-positive pathogens such as Staphylococcus aureus, Enterococcus species, and Streptococcus pneumoniae have become increasingly resistant to antibacterial agents. Consequently potent new drugs with activity against gram positive bacteria are immediately needed. Oxazolidinones which represent a promising new class of potent antibacterial agent have a unique mechanism of inhibiting bacterial protein synthesis. The commercial success of linezolid, the only FDA approved oxazolidinone have significant efforts to developed new antibacterial agents in the oxazolidinone class. Linezolid shows promise as an alternative to glycopeptides and streptogramins to treat serious infections due to resistant gram positive pathogens such as methicillin resistant Staphylococcus aureus, vancomycin resistant enterococci, and penicillin resistant Streptococcus pneumoniae. New agents with greater potency and new spectra of activity could arise from further modification of the oxazolidinone rings. Three oxazolidinones are currently undergoing clinical trials. Cubist Pharmaceuticals has announced that its new drug application (NDA) for tedizolid phosphate (TR-701) has been accepted by the US FDA for priority review. TR-701 used for the treatment of acute bacterial skin and skin structure infections (ABSSSI). TR-701 is a once daily oxazolidinone being developed for both intravenous and oral administration for the treatment of serious Gram positive infections, including those caused by methicillin-resistant Staphylococcus aureus (MRSA). Rib-X Pharmaceuticals Reports Positive Phase 2 Study Results for Radezolid in Community Acquired Pneumonia. Sutezolid (PNU-100480, PF-02341272) has shown promising efficacy in a phase IIa study in patients suffering from TB in South Africa. AstraZeneca finish phase 2a clinical trials in December 2013 and work ongoing to position AZD5847 for phase 2b by mid 2014 for the treatment of tuberculosis. This review makes an attempt to summarize the work carried out in the period from 2000 until 2013.
An environmentally friendly method for the disposal of scrap tires is currently unavailable; as a... more An environmentally friendly method for the disposal of scrap tires is currently unavailable; as a result, ultimate disposal of used vehicle tires continues to be a major challenge around the world. In the United States (US), during the past two decades, scrap tires have been generated at the rate of approximately one tire per person per year (i.e., approximately 290 million new scrap tires every year). It is estimated that there are currently 2 billion tires stockpiled in the US. Due to various problems involved in the disposal of scrap tires, different alternatives for recycle and reuse have been examined; however, one concern is the leaching of different tire constituents (organic and inorganic) with time, and their subsequent potential harmful impacts on the environment.
ABSTRACT The permeability of uniform and mixed-size (volume based) tire chips under various overb... more ABSTRACT The permeability of uniform and mixed-size (volume based) tire chips under various overburden pressures is determined. Tire chips sizes of 5.08, 10.16, and 15.24cm are used. The permeability tests are conducted using sample layers of 15.24-, 30.48-, and 45.72-cm thickness. The vertical and lateral permeability data of uniformly sized chips under no overburden are in the range of coarse gravel. The mixed-size tire chips have permeability in the range of coarse to very coarse gravel under no overburden. Under overburden, the compressibility of the uniformly sized tire chips increases with tire-chip size and decreases with layer thickness. There is a general trend of decrease in permeability with increase in overburden pressure. In the case of uniformly sized chips under overburden, the 5.08-cm chips have the highest permeability and the 15.24-cm chips have the lowest permeability. The mixed-size tire chips have higher permeability than the uniformly sized tire chips. In general, the permeability of uniform and mixed-size tire chips is in the range of coarse gravel.
ABSTRACT Results are presented from an experimental study of the stage discharge relationship for... more ABSTRACT Results are presented from an experimental study of the stage discharge relationship for a porous pipe buried under loose laid aggregate. A series of steady-state experiments were performed in which the depth of flow over the pipe was measured for a given pipe discharge. The stage-discharge relationship for the entire system is well described by an orifice equation when the water surface in the aggregate trench was horizontal and the pipe was running full at the outlet. An energy equation analysis shows that the dominant energy losses are due to flow through the small side wall orifices into the pipe and from friction losses along the pipe. Friction losses in the aggregate are shown to be negligible, which again supports the orifice equation model. Discharge coefficients are reported for three commonly available porous pipes. The results of this research can be used in the sizing and placement of subsurface drains in aggregate filled storm water infiltration practices such as infiltration trenches and porous pavements. (C) 2014 American Society of Civil Engineers.
"A numerical model is proposed for the solution of one-dimensional shall... more "A numerical model is proposed for the solution of one-dimensional shallow water flow equations for natural rivers. This model is based on the total variation diminishing Runge-Kutta discontinuous Galerkin finite element method. In natural rivers, the cross-section shape and bed slope can be quite irregular, which requires a compatible discretization scheme for the bed slope term and net pressure force term. Therefore, in this model, the hydrostatic pressure force term and the wall pressure force term are combined and a new discretization for the resulting term is introduced. This formulation is shown to prevent unphysical flow due to improper treatment of bottom slope term. The mass and momentum flux term are calculated by HLL Riemann solver. A scheme is presented to model flow over dry bed. To evaluate the numerical scheme, tests are conducted for idealized dambreak problems in parabolic (with wet and dry beds), and rectangular channels, hydraulic jump in a rectangular channel, dambreak in the Teton River (Idaho, USA) and the Toce River (Northern Alps, Italy), and flooding event in the East Fork River (Wyoming, USA). The comparison of the computational results with analytical and laboratory results of dam break flows shows that the model is capable of handling flow over dry areas. The simulation results for hydraulic jump show the discharge conservation property and shock prediction capability of the model. The dambreak and flood simulations in natural channels show that the model is capable of handling flows in highly varying bed topography and channel geometry. Keywords: Runge-Kutta discontinuous Galerkin; total variation diminishing; shallow water flows; Saint-Venant equations; natural rivers "
. Gravity-driven fluid mud flow. Top-(a) and side-view (b, c) photographs of the fluid mud gravit... more . Gravity-driven fluid mud flow. Top-(a) and side-view (b, c) photographs of the fluid mud gravity current are presented. In these photographs, lobe-cleft patterns at the leading edge of the current (a), nose and billows above and behind the head of the current (b), and decay/breakdown of billows (c) behind the nose can be seen.
"A numerical model is proposed for the solution of one-dimensional shall... more "A numerical model is proposed for the solution of one-dimensional shallow water flow equations for natural rivers. This model is based on the total variation diminishing Runge-Kutta discontinuous Galerkin finite element method. In natural rivers, the cross-section shape and bed slope can be quite irregular, which requires a compatible discretization scheme for the bed slope term and net pressure force term. Therefore, in this model, the hydrostatic pressure force term and the wall pressure force term are combined and a new discretization for the resulting term is introduced. This formulation is shown to prevent unphysical flow due to improper treatment of bottom slope term. The mass and momentum flux term are calculated by HLL Riemann solver. A scheme is presented to model flow over dry bed. To evaluate the numerical scheme, tests are conducted for idealized dambreak problems in parabolic (with wet and dry beds), and rectangular channels, hydraulic jump in a rectangular channel, dambreak in the Teton River (Idaho, USA) and the Toce River (Northern Alps, Italy), and flooding event in the East Fork River (Wyoming, USA). The comparison of the computational results with analytical and laboratory results of dam break flows shows that the model is capable of handling flow over dry areas. The simulation results for hydraulic jump show the discharge conservation property and shock prediction capability of the model. The dambreak and flood simulations in natural channels show that the model is capable of handling flows in highly varying bed topography and channel geometry. Keywords: Runge-Kutta discontinuous Galerkin; total variation diminishing; shallow water flows; Saint-Venant equations; natural rivers "
Uploads
Papers by Abdul Rahman Khan