Isolation of experimental anti-AIDS glycerophospholipids by micro-preparative reversed-phase high-performance liquid chromatography.

The experimental anti-AIDS glycerophosphatidic acid: nucleoside (sn-1/sn-2 diacylglycerol:dideoxynucleotide) drugs 3'-azido-3'-deoxythymidine monophosphate diglyceride (AZT-MP-DG) and 2',3'-dideoxycytidine monophosphate diglyceride (ddC-MP-DG) were isolated and purified by reversed-phase high-performance liquid chromatography (HPLC). The chromatographic separation was based on the glycerophospholipid moiety of the drugs and detection of the nucleoside component. The separations were optimized on method development columns packed with the stationary phase to be used in the micro-preparative column and monitored by a UV detector. Fractions were collected and analyzed for purity by analytical-scale HPLC and by thin-layer chromatography (TLC). The purity of the recovered drugs based on UV and light-scattering detection and on TLC was greater than 99%. The purified compounds were isolated for studies on structure confirmation, physical, biophysical and formulation properties and anti-HIV efficacy in culture.     

Modification of isotactic polypropylene film by radiation-induced graft copolymerization

In the present communication we report on the radiation induced grafting of methyl methacrylate (MMA) onto irradiated isotactic polypropylene film (IPP) by Peroxidation method to prepared grafted membrane (IPP-g-MMA). The radioactive isotope ⁶⁰Co was used as the source of gamma radiation. A plausible mechanism of grafting has been proposed. Optimum conditions pertaining to maximum percentage of grafting were evaluated as a function of different reaction parameters such as radiation dose, inhibitor concentration, monomer concentration, reaction time and reaction temperature respectively. Maximum percentage of grafting (85%) was obtained at [radiation dose] = 25 kGy, [inhibitor concentration] = 0.04 wt%, [MMA] = 6 wt%, [Reaction Temperature] = 60 °C in a [Reaction time] of 120 min. The evidence of grafted membrane was characterized by Fourier transform infrared spectroscopy, Atomic force microscopy method, Scanning electron microscopy which indicates that MMA has been grafted onto IPP. Hydrolysis of the grafted membranes in 1 N NaOH transformed ester groups of the grafted membranes to carboxylic acid and hydroxyl groups to form hydrolyzed grafted membranes. Hydrolyzed grafted membranes were investigated for their swelling behavior. Swelling properties of the hydrolyzed grafted membranes were performed in different solvents such as water, N,N-dimethylformamide (DMF) and dimethylsulfoxide (DMSO). Maximum percentage swelling value of IPP-g-MMA was observed in pure DMSO, followed by DMF and water.     

A Smoluchowski model of crystallization dynamics of small colloidal clusters

We investigate the dynamics of colloidal crystallization in a 32-particle system at a fixed value of interparticle depletion attraction that produces coexisting fluid and solid phases. Free energy landscapes (FELs) and diffusivity landscapes (DLs) are obtained as coefficients of 1D Smoluchowski equations using as order parameters either the radius of gyration or the average crystallinity. FELs and DLs are estimated by fitting the Smoluchowski equations to Brownian dynamics (BD) simulations using either linear fits to locally initiated trajectories or global fits to unbiased trajectories using Bayesian inference. The resulting FELs are compared to Monte Carlo Umbrella Sampling results. The accuracy of the FELs and DLs for modeling colloidal crystallization dynamics is evaluated by comparing mean first-passage times from BD simulations with analytical predictions using the FEL and DL models. While the 1D models accurately capture dynamics near the free energy minimum fluid and crystal configurations, predictions near the transition region are not quantitatively accurate. A preliminary investigation of ensemble averaged 2D order parameter trajectories suggests that 2D models are required to capture crystallization dynamics in the transition region.     

A Family of Semi-Regular Divisible Difference Sets

We give a construction of semi-regular divisible difference sets with parametersm = p2a(r–1)+2b (pr – 1)/(p – 1), n = pr, k = p(2a+1)(r–1)+2b (pr – 1)/(p – 1)1 = p(2a+1)(r–1)+2b (pr–1 – 1)/(p-1), 2 = p2(a+1)(r–1)–r+2b (pr – 1)/(p – 1)where p is a prime and r a + 1.     

An alternative approach to determine the spot-size of a multi-mode laser beam and its application to diode laser beams

An alternative approach is suggested to determine the spot-size of a multi-mode laser beam. It has been shown by simulations that the suggested approach can give the beam quality factor and characteristic radius with less than 5% error. Unlike the power content method, the proposed method is applicable to the beams even with diameter one tenth of the CCD size. The new approach has been applied to a multi-mode diode laser output and it is shown that the ABCD matrix analysis can be used for beam propagation, with the measured parameters of the laser.