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.     

Packing cylinders on a cylinder with contact constraints

The problem of cylinder packing is investigated. The specific problem is to determine the maximum number of congruent cylinders that can be packed around a core cylinder of arbitrary dimensions. The constraint is that their circular face must keep in contact with the core cylinder and there may be no overlapping. Only right circular cylinders are considered. Mathematically, a lower and upper bound is determined. A quantitative result is also found using a modified genetic algorithm. The algorithm was found to reproduce the published results for the top and bottom circular faces of the core which reduces to the problem of packing congruent circles within a circle. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Nanoscale dendritic organoplatinum antitumor drugs

Organoplatinum compounds exhibit broad antitumor activity. Cisplatin [cis- dichlorodiammine platinum (II)] is the most prominent of this family and is currently the most prescribed cancer drug. It is widely used for the treatment of human testicular, ovarian, bladder, head and neck carcinomas. However, it is an extremely toxic compound and side effects such as nephrotoxicity and myelotoxicity are major drawbacks for its use in clinical applications. A way to combat the side effects associated with the administration of platinum drugs would be to generate a prodrug conjugate that, when present in the extracellular fluid, would slowly release active platinum species at a level below the threshold for side effects. Traditionally, linear hydrophilic polymers have been examined for potential application as carrier platforms for these drugs. The advent of dendrimers, which are highly branched macromolecules with precisely controlled nanoscale size, shape and end-group functionality, has provided an excellent opportunity to design and formulate novel multivalent time-release drug systems. For example, treatment of a generation 4.5 (carboxylate surface) poly(amidoamine) [PAMAM] dendrimer with diaquo(1,2-diaminocyclohexane) platinum(II) generates a nanoparticle with forty platinum moieties attached at the surface. This polymer-drug conjugate displays a very good release profile for the platinum species. Under physiological conditions about 80% of the platinum units are released over the first 24 hours. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Conductance of tetraethylammonium halides in ethylene glycol

Conductance measurements on tetraethylammonium halides in ethylene glycol at different temperatures and concentrations are reported. Experimental data are analysed on the basis of Onsager's equation and the Onsager—Fuoss—Skinner equation. The ion-size parameter a(Å) obtained from the Onsager—Fuoss—Skinner equation is reported at different temperatures. The temperature dependence of the Walden products of the salt solutions in ethyleneglycol is also discussed in terms of the structure-breaking/making characteristics of the salt.     

Gas holdup in three-phase immobilized-cell bioreactors

A number of studies in the published literature deal with gas holdup in three-phase reactors. However, very few address the cases in which the solid density approaches that of the liquid phases and in which low gas velocities are involved. These conditions are commonly encountered in immobilized-cell bubble columns and in fluidized-bed bioreactors. This paper reports the effect of gas and liquid velocity upon gas holdup and bed expansion in fluidized-bed bioreactors. For liquid-fluidization of low-density alginate beads in the absence of gas, the terminal sedimentation velocity (vT) of the particles is a constant, and expansion of the bed follows Richardson and Zaki’s correlation. In the presence of gas, however, the apparent terminal sedimentation velocity value is affected by the velocity of the gas and liquid phases. For gas velocities above a minimum value, the calculated value of vT depends on liquid velocity only, and a constant bed expansion was observed for a range of gas and liquid flow rates. For the gas-liquid interactions, a modified drift-flux model was found to be valid. For superficial gas velocities between 5 and 17 cm/min, the modified drift-flux velocity was observed to be a function of gas velocity, suggesting the prevalence of a coalescence regime.     

Anion receptor functions of lanthanide tris(beta-diketonate) complexes: naked eye detection and ion-selective electrode determination of Cl- anion

Lanthanide tris(fluorinated beta-diketonates) acted as effective receptors of Cl- anion in luminescence sensing and ion-selective electrode systems via highly coordinated complexation.     

Redox potential in acetone-butanol fermentations

In batch and continuous cultivations ofClostridium acetobutylicum ATCC 824 on lactose, a strong relationship was observed between redox potential of broth and the cellular metabolism. The specific productivity of butanol as well as of butyric acid was found to be maximum at a redox potential of -250 mV. The specific production rate of butyric acid decreased rapidly at redox potentials. For butanol, however, it achieved a lower but stable value. This was true for dynamic as well as steady states. The continuous fermentations involving lactose exhibited sustained oscillations at low dilution rates. These oscillations appear to be related to butanol toxicity to the growth of cells. At higher dilution rates where butanol concentrations were relatively low, no such oscillations were observed. It can be concluded that broth redox potential is an excellent indicator of the resulting fermentation product partitioning.     

Novel nitroimidazo[2,1-b]oxazole formation from reaction of 2,4(5)-dinitroimidazole with oxiranes

A novel reaction for the synthesis of 2,3-dihydroimidazo[2,1-b]oxazoles has been described by condensation of 2,4(5)-dinitroimidazole with a series of oxiranes.