Nano-mixing of dipyridamole drug and excipient nanoparticles by sonication in liquid CO2

Nanoparticles (about 200 nm thick and 600–12000 nm long flakes) of dipyridamole, a poorly water-soluble anti-thrombosis drug, are produced by supercritical antisolvent solvent with enhanced mass transfer method. Applicability of sonication in liquid CO₂ for mixing of drug and excipient nanoparticles is demonstrated for several binary mixtures of drug and excipient. The drug particles are mixed with three different excipients: silica nanoparticles, lactose microparticles, and polyvinylpyrrolidone nanoparticles. To intimately mix at nanoscale, macro mixtures of dipyridamole and excipient particles are sonicated in liquid carbon dioxide. The effects of ultrasonic energy, amplitude, and component weight ratio are studied for the binary mixtures. Characterization of mixing is done using several methods. Scanning electron microscopy is used as a primary method for microscopic analysis. Two macroscopic effects, drug dissolution and blend homogeneity (relative standard deviation), are used to characterize mixing quality of drug/lactose mixture. Results of drug dissolution and blend homogeneity show effectiveness of the proposed mixing method for fine size particles. Material handling properties of drug/silica and lactose/silica mixtures were examined. Upon mixing, the handling properties are significantly improved as measured by compressibility index and Hausner ratio. Liquid CO₂ offers an environmentally benign media for mixing. In addition, the mixture obtained does not contain any residual solvent as compared to the sonication in organic liquids. Upon depressurization, CO₂ is easily removed from the mixture providing a facile recovery of the product.     

Electrical behavior of silver particulate films deposited on 8 MeV electron beam irradiated softened polystyrene substrates

Results of the investigations carried out on the electrical behavior of silver particulate films deposited on electron beam irradiated polystyrene (PS) coated substrates held at a temperature of 455 K in a vacuum of 8 × 10⁻⁶ torr at a constant deposition rate of 0.4 nm/s are reported. It is known that when metals are evaporated on to softened polymer substrates, subsurface particulate structures are formed whose morphology is dependent on deposition parameters. Further, it was shown that the morphology is dependent on polymer-metal interaction. The present work demonstrates that the polymer-metal interaction can be brought about in inert polymers like PS by electron irradiation. The results indicate that the films deposited on PS irradiated to a dose of 20 and 25 kGy gives rise to smaller clusters with smaller inter-cluster separation, better suited for sensor applications. The induced polymer-metal interaction is attributed to the creation of free radicals due to the 8 MeV electron irradiation.     

Production and recovery of poly‐3‐hydroxybutyrate from Methylobacterium sp V49

Bacterial polyesters have shown potential as biodegradable plastics. Microorganisms capable of producing these polyesters from cheaper carbon sources and methods for their efficient recovery are widely studied worldwide. Methylobacterium sp V49, an environmental isolate, was cultivated on a mineral salts medium containing different carbon sources. Maximum accumulation of poly‐3‐hydroxybutyrate (PHB) within the bacterial cell was observed with glucose as the carbon source. Methanol and sugars such as sucrose and lactose also induced PHB accumulation. The effect of C:N ratio on polymer accumulation was studied. Different strategies for the extraction and recovery of the polymer from the cells were compared. A non‐solvent‐based method using a high‐pressure homogenizer in the presence of SDS was found to be the most satisfactory. Maximum recovery of 98% was achieved by homogenizing the cells at 400 kgcm^?2 in 5% SDS solution. © 2002 Society of Chemical Industry     

H2 Energy Estimate of Boundary Controlled Vibrating Hybrid Structure Subject to Uncertain Forces

We study here a model hybrid system consisting of a flexible rectangular space structure such as a solar cell array, hoisted at one end by a movable rigid hub, set to vibration from certain initial conditions, but subject to uncertain disturbing forces distributed along its length. Assuming that the control of vibrations is sought by a damper at the hub end proportional to a general nonlinear function of the velocity of the point, we obtain an H2 energy estimate of vibrations over a time interval [0,T] in terms of initial energy of the system and the time integral of the L2 norm of the disturbance over the length of the panel. From this, estimates of tolerance level of the disturbances are obtained. Both torsional and flexural modes of vibration are considered.     

Preparation of high surface area nickel electrodeposit using a liquid crystal template technique

We show in this work that template electrodeposition of nickel at room temperature from a nickel sulphamate bath prepared in a new hexagonal liquid crystalline phase of water-Triton X-100-poly (acrylic acid) results in a highly porous surface. The roughness factor value of about 3620 obtained for this coating is the highest value reported in the literature for any electrodeposited nickel. The scanning electron microscopy (SEM) and scanning tunneling microscopy (STM) pictures show the formation of porous deposit with granular features in between the pores. The single electrode double layer capacitance value measured for the deposit is 338 mF cm⁻², which translates into a specific capacitance of 50 F g⁻¹ without any post-thermal treatment of the electrode, suggesting its utility in super capacitors. Electrochemical studies using cyclic voltammetry (CV), Tafel plots and electrochemical impedance spectroscopy (EIS) and comparison of these results with some existing high surface area Ni catalysts show that the material has potential application as an excellent hydrogen evolving cathode.     

Solid state reactions of cordierite precursor oxides and effect of CaO doping on the thermal expansion behaviour of cordierite honeycomb structures

The extruded cordierite honeycomb structure from a stoichiometric formulation of talc, kaolinite, and alumina was subjected to TGA-DSC, dilatometric and XRD investigations. The experimental observations were made to identify the phase transformation sequence in order to understand the solid state reactions involved in the cordierite formation. A maximum cordierite content of 90% was achieved for the samples sintered at 1693 K with a soaking time of 4 h, corresponding to a lowest coefficient of thermal expansion (CTE) of 0.74 × 10^–6/K (along the direction of extrusion) was observed. Attempts were made to establish correlations with cordierite content, processing temperature and CTE of the samples. A few mechanisms are proposed to explain our observations. Attempts are also made to rationalize the low CTE observed along the direction of extrusion on the basis of orientation of anisotropic cordierite crystals as revealed by the transverse I-ratio calculated from the XRD patterns. Effect of CaO doping on CTE of cordierite has been studied in the present work. It was observed that though there is an increase in bulk thermal expansion of cordierite honeycombs on CaO doping due to the absence of micro-cracks as reveled by thermal cycling hysteresis, axial anisotropy was found to be reduced significantly.     

Structure‐Guided Design of Thiazolidine Derivatives as Mycobacterium tuberculosis Pantothenate Synthetase Inhibitors

The pantothenate biosynthetic pathway is essential for the persistent growth and virulence of Mycobacterium tuberculosis (Mtb) and one of the enzymes in the pathway, pantothenate synthetase (PS, EC: 6.3.2.1), encoded by the panC gene, has become an appropriate target for new therapeutics to treat tuberculosis. Herein, we report nanomolar thiazolidine inhibitors of Mtb PS developed by a rational inhibitor design approach. The thiazolidine compounds were discovered by using energy‐based pharmacophore modelling and subsequent in vitro screening, which resulted in compounds with a half maximal inhibitory concentration (IC₅₀) value of (1.12±0.12) μM . These compounds were subsequently optimised by a combination of modelling and synthetic chemistry. Hit expansion of the lead by chemical synthesis led to an improved inhibitor with an IC₅₀ value of 350 nM and an Mtb minimum inhibitory concentration (MIC) of 1.55 μM . Some of these compounds also showed good activity against dormant Mtb cells.     

Studies on structural,dielectric and charge transport properties of PVA:LiBr solid polymer electrolyte films

In the present study, solid polymer electrolytes (SPEs) based on poly (vinyl alcohol) (PVA) doped with lithium bromide (LiBr) were prepared by solution casting method. Fourier transform infrared spectroscopy results affirm the complexation of LiBr with PVA. X-ray diffraction results exhibit the increase of amorphous nature of the polymer electrolytes, which is also observed in scanning electron microscopy images and atomic force microscopy topographs. Thermogravimetric analysis thermographs endorse the increase of thermal stability of the polymer due to doping. Dielectric studies exhibit non-Debye nature of the polymer electrolytes. Conductivity spectra reveal the maximum ionic conductivity (1.15 × 10⁻⁴ S/cm) for 20 wt% LiBr/PVA electrolyte at ambient temperature. Impedance analysis reveals the decrease of ionic relaxation in the polymer electrolytes and the studied transport properties of the electrolyte show that the major contribution to the conduction in this polymer electrolyte is ions.     

The Role of Hyperexcitability in Gliomagenesis

Glioblastoma is the most common malignant primary brain tumor. Recent studies have demonstrated that excitatory or activity-dependent signaling—both synaptic and non-synaptic—contribute to the progression of glioblastoma. Glutamatergic receptors may be stimulated via neuron–tumor synapses or release of glutamate by the tumor itself. Ion currents generated by these receptors directly alter the structure of membrane adhesion molecules and cytoskeletal proteins to promote migratory behavior. Additionally, the hyperexcitable milieu surrounding glioma increases the rate at which tumor cells proliferate and drive recurrent disease. Inhibition of excitatory signaling has shown to effectively reduce its pro-migratory and -proliferative effects.