Latex Fractionation by Sedimentation and Colloidal Crystallization: The Case of Poly(styrene-co-acrylamide)

Poly(styrene-co-acrylamide) (PS-AAM) latex was prepared, fractionated by sedimentation under gravity, and characterized by PCS, infrared spectra, secondary and backscattered electron imaging in the scanning electron microscope, and electron spectroscopy imaging in an analytical transmission electron microscope. Three latex fractions were obtained. The lower fraction was opalescent and its particles were the more uniform, concerning size, chemical composition, and topochemical features. This lower fraction was still further fractionated by zonal centrifugation in a density gradient, yielding two fractions with similar macrocrystal-forming abilities but different sizes and chemical compositions. These results confirm those previously obtained for the PS-HEMA latex. Copyright 2000 Academic Press.     

Electrical biosensing with synthetic nanopores and nanochannels

The integration of constriction structures such as nanopores and nanochannels into fluidic devices discloses powerful biosensing capabilities that can be tuned to a wide range of analytes through conceptually simple size calibrations. The practical implementation of this tuning requires a nontrivial manipulation of matter at nanoscale with further requirements for low complexity and low-cost procedures that may be adapted to industrial production. Here, we review the recent progress on the fabrication techniques of nanopores and nanochannels, together with the efforts to realize their full biosensing potential by understanding and amending the problems still afflicting the measurement performed during operation.     

Calcul de la fonction correlation de phonon pour la diffraction d'une particule par un solide

A method of calculating expressions of the type $\text{<T exp[?i}\text{k}{}_1\text{u}{}_{\ln }\text{(t}{}_1\text{)] ... exp [?i}\text{k}{}_{\mathrm{n}}\text{u}{}_{\ln }\text{(t}{}_{\mathrm{n}}\text{>}$ which is simpler than that based on Wick's theorem is proposed. Expressions of the above type are widely used in studying the effects of temperature in electron and neutron diffraction.     

Detection of hypophosphite, phosphite, and orthophosphate in natural geothermal water by ion chromatography

Current doctrine states that phosphorus is incorporated into cells in the pentavalent(V) oxidation state as orthophosphate. However, recent studies show that microorganisms contain enzymes used to metabolize reduced forms of phosphorous, including phosphite(III) and hypophosphite(I), which suggests that there is a natural source for these chemical species. This paper will discuss suppressed conductivity ion chromatography methods developed to detect hypophosphite, phosphite, and orthophosphate in a geothermal water matrix containing fluoride, chloride, bromide, nitrate, hydrogen carbonate and sulfate. All peaks were clearly resolved, and calibrations were linear with estimated 3sigma detection limits of 0.83, 0.39, and 0.35 microM for hypophosphite, phosphite, and orthophosphate, respectively.     

Early out-of-equilibrium beam-plasma evolution

We solve analytically the out-of-equilibrium initial stage that follows the injection of a radially finite electron beam into a plasma at rest and test it against particle-in-cell simulations. For initial large beam edge gradients and not too large beam radius, compared to the electron skin depth, the electron beam is shown to evolve into a ring structure. For low enough transverse temperatures, the filamentation instability eventually proceeds and saturates when transverse isotropy is reached. The analysis accounts for the variety of very recent experimental beam transverse observations.