Formulation and evaluation of controlled-release transdermal patches of theophylline-salbutamol sulfate.

Transdermal formulations containing theophylline and salbutamol sulfate (SS) were formulated using hydroxypropylmethylcellulose. Theophylline was loaded by adsorption with the aid of the coadsorbate sodium chloride. The formulations were subjected to in vitro release studies, and the dose of salbutamol and theophylline was optimized to yield the desired flux. The films were uniform and 93 +/- 5.4 microm thick. The in vitro fluxes of theophylline and salbutamol sulfate from the formulation were 1.22 +/- 0.4 mg/h/cm2 and 13.36 +/- 1.02 microg/h/cm2, respectively. The formulation was subjected to pharmacodynamic studies in guinea pigs. The preconvulsive time (PCT) of guinea pigs increased significantly after 4 h, and the same was observed even after 24 h Pharmacokinetic studies were carried out in healthy human volunteers. Theophylline was analyzed in saliva, and salbutamol was analyzed in the blood plasma. The Tmax of the drugs was 3 h, and appreciable concentrations of the drugs above their MEC could be analyzed even after 12 h. The elimination half-life of the drugs was significantly prolonged compared to that for tablets. There were no signs of erythema or edema in the volunteers during observation for a period of 7 days.     

Synergism of microwave irradiation and enzyme catalysis in synthesis of isoniazid

Isoniazid is a useful antitubercular drug widely employed in combination therapy with rifampicin. The synthesis of isoniazid from ethyl isonicotinate and hydrazine hydrate was studied in non‐aqueous media via lipase‐catalyzed hydrazinolysis under both conventional heating and microwave irradiation by using different supported lipases. Among three different commercial lipases used, namely Novozym 435 (Candida antarctica lipase), Lipozyme RM IM (Rhizomucor miehei lipase) and Lipozyme TL IM (Thermomyces lanuginosus lipase), Novozym 435 was found to be the most effective, with conversion of 54% for equimolar concentrations at 50 °C in 4 h. The rate of reaction as well as final conversion increased synergistically under microwave irradiation in comparison with conventional heating, which showed 36.4% conversion, even after 24 h, for the control experiment. Effects of various process parameters such as speed of agitation, catalyst loading, substrate concentration, product concentration and temperature were studied. A kinetic model is also described. Copyright © 2007 Society of Chemical Industry     

Numerical Study and Experimental Validation of Effect of Varying Fiber Crack Density on Stiffness Reduction in CFRP Composites

Representative volume element (RVE) has commonly been used to predict the stiffness of undamaged composite materials using finite element analysis (FEA). However, never has been an independently measured true microstructural damage quantity used in FEA to predict composite stiffness. Hence, in this work, measured fiber crack density in unidirectional fiber composite (generated using controlled fatigue loading) was used to predict reduction in stiffness using a RVE. It was found that the stiffness changes with change in depth of the volume element along the fiber direction and asymptotically reaches a constant value beyond a critical length called representative depth. It was argued that this representative depth should be more than the minimum of two characteristic length scales, twice of ineffective length and average length of broken fibers. Effective stiffness obtained from FEA of the optimum-sized RVE was in excellent agreement with the experimental results for given microstructural damage state.     

Shear Reversible Alumina Gels for Direct Writing

Phase diagram of alumina sol has been investigated, wherein a unique region of shear reversible gels has been discovered. In this region, rapid transformation from gel to sol was observed, where the viscosity shows a sudden drop by six orders of magnitude on application of shear stress. The sol to gel transformation was observed to depend on the composition of the sol and could be tuned in the range of few seconds to hours. These gels are suitable for fabricating complex three‐dimensional structures using advanced technology of direct write and ink‐jet printing.     

Determinants of metabolic acidosis among hemodialysis patients

Metabolic acidosis is frequently present, poorly controlled, and associated with adverse effects among hemodialysis patients. Potential determinants of metabolic acidosis include endogenous acid production, administration of alkali, neutralization of acid by buffers, dilution of serum bicarbonate by interdialytic fluid gain, and loss of bicarbonate in stool. Understanding the relative importance of these determinants may help guide efforts to manage metabolic acidosis. We used chart abstraction, patient interviews, and laboratory testing to assess variables related to acid production (protein breakdown), alkali administration (dialysis dose, missed treatments, dialysate bicarbonate concentration, oral bicarbonate supplements), acid buffering (phosphorus binders), dilution of bicarbonate (interdialytic weight gain), and loss of bicarbonate in stool (diarrhea) for 190 randomly selected patients from 44 hemodialysis facilities. We used multivariate analyses to determine which potential determinants were independently associated with predialysis serum bicarbonate levels. Of all patients, 30% had metabolic acidosis (serum bicarbonate level <22 mEq/L). On multivariate analysis, metabolic acidosis was more likely with increased protein nitrogen appearance (odds ratio [OR] 1.60 per 0.2 g/kg/day, p=0.001) and less likely with increased Kt/V (OR 0.61 per 0.20 increase in Kt/V, p<0.001) and with increased calcium carbonate use (OR 0.38 per 2 g/day, p=0.003). Key determinants of metabolic acidosis among hemodialysis patients are protein breakdown, dialysis dose, and specific phosphorus binders. Further work is needed to develop interventions to address these determinants.     

Solid lipid nanoparticles of ondansetron HCl for intranasal delivery: development, optimization and evaluation

The present investigation deals with the development and statistical optimization of solid lipid nanoparticles (SLNs) of ondansetron HCl (OND) for intranasal (i.n.) delivery. SLNs were prepared using the solvent diffusion technique and a 2(3) factorial design. The concentrations of lipid, surfactant and cosurfactant were independent variables in this design, whereas, particle size and entrapment efficiency (EE) were dependent variables. The particle size of the SLNs was found to be 320-498?nm, and the EE was between 32.89 and 56.56?%. The influence of the lipid, surfactant and cosurfactant on the particle size and EE was studied. A histological study revealed no adverse response of SLNs on sheep nasal mucosa. Transmission electron microscopic analysis showed spherical shape particles. Differential scanning calorimetry and X-ray diffraction studies indicated that the drug was completely encapsulated in a lipid matrix. In vitro drug release studies carried out in phosphate buffer (pH 6.6) indicated that the drug transport was of Fickian type. Gamma scintigraphic imaging in rabbits after i.n. administration showed rapid localization of the drug in the brain. Hence, OND SLNs is a promising nasal delivery system for rapid and direct nose-to-brain delivery.     

Analysis of couple stress nanofluid flow under convective condition in the temperature-dependent fluid properties and Lorentz forces

In recent years, a great deal of interest has been generated in modern micro- and nanotechnologies for micro/nano-electronic devices. These technologies are increasingly utilizing sophisticated fluid media to enhance performance. Among the new trends is the simultaneous adoption of nanofluids and biological micro-organisms. Motivated by bio-nanofluid vertical channel oxygenators in medical engineering, in the current work, a mathematical model is developed to examine the flow of mixed convective couple-stress nanofluids in a vertical channel with a transverse magnetic field, fluid viscosity that changes with temperature, and thermal conductivity. The non-Newtonian model follows Brownian motion and heat spread by nanoparticles in a fluid under coupled stress. Highly linked, nonlinear regulating equations are translated into nondimensional equations using relevant variables. The governing equations are then turned into a form with no dimensions. The Keller-box technique, a second-order finite difference method for solving second-order equations, is used to solve them numerically. On the other hand, the effects of different non-Newtonian flow parameters, such as the couple stress fluid parameter, the magnetic parameter, the variable fluid viscosity, the variable thermal conductivity parameters, the Brinkman number, the nanofluid and buoyancy parameters, and the rate of chemical reaction parameter, are carefully studied. The velocity, temperature, and concentration fields are calculated over a wide range of possible values for the relevant parameters.     

Combined dimension reduction and tabulation strategy using ISAT–RCCE–GALI for the efficient implementation of combustion chemistry

Computations of turbulent combustion flows using detailed chemistry involving a large number of species and reactions are computationally prohibitive, even on a distributed computing system. Here, we present a new combined dimension reduction and tabulation methodology for the efficient implementation of combustion chemistry. In this study, the dimension reduction is performed using the rate controlled constrained-equilibrium (RCCE) method, and tabulation of the reduced space is performed using the in situ adaptive tabulation (ISAT) algorithm. The dimension reduction using RCCE is performed by specifying a set of represented (constrained) species, which in this study is selected using a new Greedy Algorithm with Local Improvement (GALI) (based on the greedy algorithm). This combined approach is found to be particularly fruitful in the probability density function (PDF) approach, wherein the chemical composition is represented by a large number of particles in the solution domain. In this work, the combined approach has been tested and compared to reduced and skeletal mechanisms using a partially-stirred reactor (PaSR) for premixed combustion of (i) methane/air (using the 31-species GRI-Mech 1.2 detailed mechanism and the 16-species ARM1 reduced mechanism) and (ii) ethylene/air (using the 111-species USC-Mech II detailed mechanism, a 38-species skeletal mechanism and a 24-species reduced mechanism). Results are presented to quantify the relative accuracy and efficiency of three different ways of representing the chemistry: (i) ISAT alone (with a detailed mechanism); (ii) ISAT (with a reduced or skeletal mechanism); and (iii) ISAT–RCCE with represented species selected using GALI. We show for methane/air: ISAT (with ARM1 reduced mechanism) incurs 6% error, while ISAT–RCCE incurs the same error using just 8 or more represented species, and less than 1% error using 11 or more represented species, with a twofold speedup relative to using ISAT alone with the GRI-Mech 1.2 detailed mechanism. And we show for ethylene/air: ISAT incurs 7% and 3% errors with the reduced and skeletal mechanisms, respectively, while ISAT–RCCE achieves the same levels of error 7% with just 18 and 3% with just 25 represented species, and also provides 15-fold speedup relative to using ISAT alone with the USC-Mech II detailed mechanism. With fewer species to track in the CFD code, this combined ISAT–RCCE–GALI reduction–tabulation algorithm provides an accurate and efficient way to represent combustion chemistry.     

Convective nanofluid flow over a vertical cone with a rough surface

In recent literature, the analysis of a combined convective flow over a cone has received a lot of attention. To explore the convection effects of flow over a cone in greater detail, in this investigation, we have considered a cone with a rough surface, which is entirely a new flow problem. Recent studies have shown the influence of roughness on fluid flow over several geometries, but flow over a rough conical surface has not been studied so far. In addition, we have analyzed the effects of nanoparticles, magnetohydrodynamic (MHD), and suction/blowing, which could have significant impacts on characteristics of fluid flow over the cone with a rough surface. Initially, the governing equations, which are partial differential equations with a high degree of nonlinearity, are nondimensionalized through Mangler's transformations. Later, linear equations are obtained via the method of quasilinearization, which is then solved numerically through finite difference approximations. The roughness of the cone's surface has notable effects on fluid flow, that too away from the origin. In fact, the roughness increases the friction at the cone's surface. Furthermore, the magnetic field applied at the wall increases the surface friction. Thus, the combination of roughness and MHD helps delay the boundary layer separation. On the other hand, the suction reduces the temperature of the fluid and increases the energy transport strength, while the thermophoresis parameter exhibits the contrary nature. Therefore, the combined consideration of these two could enhance energy transport strength in several industrial applications.     

Zirconium based bulk metallic glass / tungsten fibre composite — fabrication and characterization

The aim of the present work was to fabricate and characterize a composite consisting of Zr based bulk metallic glass as the matrix and W fibres as the reinforcement. This kind of composite because of its very high impact toughness has got widespread applications including in some strategic areas. The glass forming Zr₅₂Ti₆Al₁₀Cu₁₈Ni₁₄ (at%) alloy was selected for this purpose because of its high glass forming ability and tungsten was selected as the reinforcing medium because of its high melting point, non reactivity with the liquid phase and high strength. The composite was fabricated in a unique way where a preform of W wires was made and the glass forming alloy was vitrified with this preform as reinforcement using the copper mold casting technique The composite produced was characterized using optical microscopy and EPMA studies. Compression testing was done to evaluate the mechanical properties of the composite.