On total internal reflection investigation of nanoparticles by integrated micro-fluidic system

We report on a novel sensor for characterization of nanoparticles colloidal suspensions. We employ a diffraction grating under total internal reflection for investigation of nanodisperse fluids passing through an integrated microfluidic channel. Dispersions containing polymeric, metallic, and ferromagnetic nanoparticles are studied. Using this device, we can accurately determine in real-time the specific refractive index for the nanoparticle suspension and the nanoparticle concentration. The nanoparticle concentrations can be calculated with a resolution of 0.3-0.5 wt% for polymeric nanoparticles, 0.03-0.05 wt% for metallic nanoparticles, and 0.05-0.1 wt% for ferromagnetic nanoparticles. This translates to an effective refractive index that can be determined with an accuracy of 7 x 10(-4) for the polymeric and 2 x 10(-4) for the metallic and ferromagnetic dispersions.     

Application of surface response analysis to the optimisation of nitric passivation of cp titanium and Ti6Al4V

Passivation of Ti6Al4V and cp Ti by mean of nitric acid treatment are used to reduce their surface reactivity, and consequently increasing resistance to corrosion, in physiological media.

In this work, the response surface methodology was employed to know the effects of operating parameters of the nitric passivation (HNO₃ content, temperature of solution and passivation period) on the corrosion resistance of commercially pure (cp) titanium and Ti6Al4V alloy in Ringer's solution. The experiment included two 3³ factorial designs. According to the responses from the experimental designs, the effects of each variable were calculated and the interactions between them were determined. The statistical test has revealed that the main effect of the nitric acid content is the most significant factor. The surface response methodology was applied to graphically determine the optimal working conditions.

Different electrochemical techniques (OCP, Rp and cyclic polarisation tests) were used to compare the electrochemical behaviour of cp Ti and Ti6Al4V, with and without passivation.     

Microemulsion Radical Polymerization of Alkyl Acrylates

The oil/water microemulsion polymerizations of alkyl (methyl (MA), ethyl (EA), butyl (BA), hexyl (HA) and 2-ethylhexyl (EHA)) acrylates initiated by a water-soluble (ammonium peroxodisulphate (APS)) initiator were investigated. The rate of polymerization versus conversion curve shows two inconstant intervals. The maximum rate of polymerization of MA, EA, BA and EHA is found to be proportional to the 0·53, 0·17, 0·46 and 0·59 powers of the APS concentration and to the first power of the monomer (MA, BA and EHA) concentration. Homogeneous (solution) radical polymerization is operative in the MA, BA and EHA systems. The strong rate dependence on the EA monomer concentration is assumed to be caused by both the polymerization within the micelle core and the gel effect. The particle size was observed to increase with conversion in the EA and BA runs and to decrease in the EHA and HA runs. The number of particles increased with conversion during the whole polymerization. The polymer particles grow by recruiting monomer and emulsifier from the free monomer-swollen micelles and dead particles. © 1997 SCI.     

Alignment of adjacent picture frames captured by a CLSM

Mosaicking a picture from its adjacent parts (called picture frames or tiles) is encountered in different fields of research and technology, e.g., photogrammetry, remote sensing, microscopy, etc. It is applied whenever the object of investigation is too large for the field of view of the sensor, e.g. a microscope, We describe mosaicking with a confocal laser-scanning microscope (CLSM) Bio-Rad, MRC 600 (U.K.). Aligning neighboring picture tiles was accomplished by registering the overlapped border areas of these tiles. Such registration procedures are constrained by: the limited size of the registered samples (windows); anisotropy of the form of the windows (usually narrow rectangles); and the content of the windows, including changes of their intensity scale. Focusing on the latter problem, methods of registration were discussed and the robustness of the following three similarity based methods was studied with regard to the distortions of the intensity scales of the tiles to be registered: the sum of absolute valued differences (SAVD); normalized correlation coefficient (NCC); and the mutual information function (MIF). Pilot experiments were extended to three-dimensional (3-D) stacks of pictures encountered in the framework of 3-D object rendering and visualization. MIF was found in most cases to be the most robust; however, it also demanded the most computational power. It is discussed how to choose a cost-effective method of the registration with regard to the content (texture, contrast, intensity scale distortion) of the tiles     

Polymerization of butyl acrylate in microemulsion. Locus of initiation

The locus of initiation in the microemulsion polymerization of butyl acrylate initiated by water-soluble ammonium peroxodisulfate, partially water-soluble azoisobutyronitrile and oil-soluble dibenzoyl peroxide is determined almost exclusively by the initiator solubility in respective phases of the reaction system, regardless of the overall character of the system. This conclusion was drawn taking into account the results of the microemulsion study in comparison with those from inverse microemulsion polymerizations. The polymerization experiments were carried out in the presence of stable nitroxyl radicals acting as polymerization inhibitors of different solubility in water. The consumption of the inhibitor radicals by the combination with radicals from initiator decomposition was followed by electron spin resonance spectrometer.     

The influence of salt intake on glomerular count in compensatory kidney hypertrophy in rats of different ages

Drinking saline instead of water elevated the glomerular count in hypertrophied kidneys of rats uninephrectomized as adults. No changes occurred in glomerular concentration in kidney tissue indicating a more marked increase of other kidney structures. This procedure was ineffective in immature animals.     

Merry christma: an early network worm

A computer worm disguised as a benign holiday greeting spread rapidly via email and clogged up networks worldwide. The story is all too common today, but this happened to corporate and university mainframes in 1987, in the infancy of the computer virus problem, even before the famous Internet, or Morris, worm. This article reviews 1987's relevant global networking environment, the way the Christma worm spread, the events surrounding its worldwide propagation, and the surprising effect it had once it got inside IBM.     

Noninvasive measurement of cardiac output using partial CO2 rebreathing

A noninvasive algorithm for estimating cardiac output is discussed. The technique is based on a differential form of the CO₂ Fick equation applied during normal ventilation and a 30-s period of partial rebreathing using additional deadspace. Using the Fick equation in a differential form eliminates the need to estimate mixed venous pCO₂, also the sensitivity of the cardiac output estimate to changes in the alveolar deadspace fraction is greatly reduced. The procedure is fully automated, requires minimal staff supervision, and provides cardiac output estimates every 3 1/2-min. Estimates of cardiac output when compared to thermodilution yielded a correlation coefficient of 0.92 with a linear regression slope of 0.92 ( n=451). Temporary increases in alveolar deadspace did not significantly alter this relationship. Cardiac output estimates obtained during period of increased pulmonary shunt due to oleic acid infusion yielded a correlation coefficient of 0.90 with a linear regression slope of 0.92 when compared to direct thermodilution measurements     

Dispersion polymerization of styrene and methyl methacrylate initiated by poly(oxyethylene) macromonomeric azoinitiators

Macromonomeric poly(oxyethylene) azoinitiators (macroinimers) MIM-400 and MIM-1500 were synthesized and characterized by IR and NMR spectroscopy and DSC techniques. The dispersion polymerizations of styrene and methyl methacrylate (MMA) initiated by poly(oxyethylene) macroinimers (MIM-400 and MIM-1500) in water/ethanol were investigated at 60°C. The rate of polymerization was found to increase with increasing concentration of MIM and the increase was more pronounced in the styrene system. In the range of medium conversions the rate of polymerization was found to be proportional to the 1.7th and 1.6th power of [MIM-400] and [MIM-1500] for MMA and to the 2.5th power of [MIM-400] for styrene, respectively.