Altering Bubble Dynamics via In Situ Vapor Extraction

Spatiotemporal cooling of electronics using latent energy might be achieved by closely spaced, rapid departure of small bubbles. One means to achieve small diameters during boiling is to provide an additional upward force during bubble formation, such as that from vapor extraction. Experiments were conducted of bubble extraction using constant flow rates of both air and vapor that ranged from 30 to 90 mm³/s. Extraction was achieved with a hydrophobic porous membrane sealed to a tube in which a vacuum was drawn. The gap between the extraction and supply surface was varied from 0.5 to 3.25 mm. Only individual bubbles that ruptured at the top surface while still attached to the supply surface were considered. Bubble departure diameters are approximately 80% of the gap height. As with unconfined bubbles in pool boiling, the bubble frequency varies inversely with departure diameter. Correlations for bubble rupture, bubble departure, and bubble frequency are presented as a function of gap height. Using the three distinct regimes identified in the experimental study, namely, growth only, growth with extraction, and extraction only, an effective bubble diameter model and an appropriate static force balance were developed. These were used to predict bubble departure frequencies and diameters, respectively, under confined extraction conditions.     

Implications of the negative capacitance observed at forward bias in nanocomposite and polycrystalline solar cells

Four different types of solar cells prepared in different laboratories have been characterized by impedance spectroscopy (IS): thin-film CdS/CdTe devices, an extremely thin absorber (eta) solar cell made with microporous TiO2/In(OH)xSy/PbS/PEDOT, an eta-solar cell of nanowire ZnO/CdSe/CuSCN, and a solid-state dye-sensitized solar cell (DSSC) with Spiro-OMeTAD as the transparent hole conductor. A negative capacitance behavior has been observed in all of them at high forward bias, independent of material type (organic and inorganic), configuration, and geometry of the cells studied. The experiments suggest a universality of the underlying phenomenon giving rise to this effect in a broad range of solar cell devices. An equivalent circuit model is suggested to explain the impedance and capacitance spectra, with an inductive recombination pathway that is activated at forward bias. The deleterious effect of negative capacitance on the device performance is discussed, by comparison of the results obtained for a conventional monocrystalline Si solar cell showing the positive chemical capacitance expected in the ideal IS model of a solar cell.     

Properties of a variable-delay polarization modulator

We investigate the polarization modulation properties of a variable-delay polarization modulator (VPM). The VPM modulates polarization via a variable separation between a polarizing grid and a parallel mirror. We find that in the limit where the wavelength is much larger than the diameter of the metal wires that comprise the grid, the phase delay derived from the geometric separation between the mirror and the grid is sufficient to characterize the device. However, outside of this range, additional parameters describing the polarizing grid geometry must be included to fully characterize the modulator response. In this paper, we report test results of a VPM at wavelengths of 350 μm and 3 mm. Electromagnetic simulations of wire grid polarizers were performed and are summarized using a simple circuit model that incorporates the loss and polarization properties of the device.     

Use of β-cyclodextrin to decrease the level of cholesterol in milk fat

This study was carried out to determine optimum conditions (β-cyclodextrin concentration, mixing time, and holding time) for cholesterol removal from pasteurized nonhomogenized milk at 4°C on a commercial scale by adding β-cyclodextrin in a specially designed bulk mixer tank. The β-cyclodextrin (0.4, 0.6, 0.8, and 1.0%) removed from 65.42 to 95.31% of cholesterol at 4°C in 20 min. Treatment of milk with 0.8 and 1.0% (wt/vol) β-cyclodextrin was no better than treatment with 0.6% β-cyclodextrin. Maximum cholesterol removal was seen with 6 h of treatment. The β-cyclodextrin cholesterol complex was precipitated from milk during 20 min without stirring at 4°C and removed by centrifugation. After separating the milk, approximately 0.35% of residual β-cyclodextrin remained in the skim fraction and 0.1% in the cream from milk treated with 0.6% β-cyclodextrin. The rest of the β-cyclodextrin was complexed with the cholesterol and eliminated via the discharger of the separator. Individual fatty acid and triglyceride compositions did not differ between control milk and milk treated with 0.6% β-cyclodextrin.     

Voluntary alcohol consumption in vervet monkeys: individual, sex, and age differences

The patterns of voluntary alcohol consumption were studied in 35 vervet monkeys (Cercopithecus aethiops), classified into four groups. Each monkey showed a fairly steady rate during the studied period, resulting in individual differences that became more evident as the treatment evolved. Females showed higher alcohol intake frequencies than males. This sexual difference was maintained among adults and juveniles. Age differences were also observed: juveniles showed higher frequencies of intake than adults, both in general and in each sex group. Intake frequency was not related to age in prepubertal subjects, neither in general nor in each particular sex. The origin of these sex and age alcohol consumption differences remains to be studied, but differences in alcohol metabolism and factors related to puberty are possible influences.     

Automated analysis of two- and three-color fluorescent Elispot (Fluorospot) assays for cytokine secretion

The Elispot effectively measures the frequencies of cells secreting particular molecules, especially low-frequency cells such as antigen-specific T cells. The Fluorospot assay adapted this analysis to two products per cell, and this has now been extended to three-color measurement of both mouse and human cytokine-secreting cells. Due to the increased data complexity, and particularly the need to define single-, double- and triple-producing cells, it is critical to objectively quantify spot number, size, intensity, and coincidence with other spots. An automated counting program, Exploraspot, was therefore developed to detect and quantify Fluorospots in automated fluorescence microscope images. Morphological parameters, including size, intensity, location, circularity and others are calculated for each spot, exported in FCS format, and further analyzed by gating and graphical display in popular flow cytometry analysis programs. The utility of Exploraspot is demonstrated by identification of single-, double- and triple-secreting T cells; tolerance of variable background fluorescence; and estimation of the numbers of genuine versus random multiple events.     

Overall composition, nitrogen fractions and fat characteristics of Cabrales cheese during ripening

Summary Changes in the global composition, textural parameters, nitrogen fractions, fats characteristics and casein breakdown in Cabrales cheese were studied over a maturation period of four months. Extensive proteolysis and lipolysis occurred. Approximately 88 % of the total nitrogen in the mature cheese was water-soluble and nearly 79% of the water-soluble nitrogen was non-protein nitrogen. Degradation of _s- andß-caseins was complete at the end of ripening, and at this stage the total free fatty acid (FFA) content was 33 153 mg/kg. Correlation coefficients were calculated for all variables and stepwise discriminant analysis was applied in order to classify Cabrales cheeses according to ripening time.

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Zusammensetzung der Stickstoff-Fraktionen und die Fett-Charakteristik der Cabrales-Käse während der Reifung

Zusammenfassung Es wurde der Wechsel in der Zusammensetzung der Textur, der Stickstofffraktionen, der Fettbestandteile und eine Caseinhydrolyse des Cabrales-Käses während viermonatiger Reifelagerung studiert. Zusätzlich gibt es auch eine starke Lipolyse. Ungefähr 88% des gesamten Stickstoffs und fast 79% des löslichen Stickstoffs waren Nicht-Protein-Stickstoff. Der Abbau des _s-casein undß-casein war am Ende der Reifung vollständig und in dieser Zeit war der Gehalt an freien Fettsäuren 33 153 mg/kg. Der Korrelationskoeffizient wurde für alle Variable bestimmt und die Diskriminationsanalyse wurde angewandt, um alle Cabrales-Käse entsprechend der Reifungszeit zu klassifizieren.

     

Biochemical characteristics of a semi-hard ewe's-milk cheese

Physicochemical, organoleptic and microbiological characteristics of three batches of industrial semihard ewe's milk cheeses were studied over a 90-day ripening period. Cheeses were made with a selected starter containingLactococcus lactis subsp.lactis and subsp.cremoris. The total microbial count was normal throughout manufacture and the ripening period. The level of noncasein nitrogen (NCN) was moderate (23.8% of the total nitrogen, TN) but non-protein nitrogen and amino-acid nitrogen were high: 73.6 (% NCN) and 1.92 (% TN) respectively. Breakdown of _s-(66%) and-caseins (17%) at 90 days provided the cheeses with excellent textural and sensory characteristics.

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Biochemische Charakteristik eines halbharten Schafskäse

Zusammenfassung Die physiko-chemische, sensorische und mikrobiologische Charakteristik von drei industriellhalb-reifen Schafskäsen wurde während der 90-Tage-Reifungszeit untersucht. Die Käse wurden mit einem ausgewählten Starter mitLactococcus lactis subsp.lactis und subsp.cremoris hergestellt. Die gesamte Keimzahl war während der Herstellung und Reifungszeit normal. Der Nicht-Cascin-Stickstoff (NCN) war mittelmäßig (23,8% des Gesamt-Stickstoffes, TN), aber der Aminosäure-Stickstoff war hoch (73,6% NCN und 1,92% TN). Der Abbau von _s-(66%) und-Cascinen (17%) nach 90 Tagen ist verantwortlich für die gute Texture und Sensorik des Käses.

     

Fourier Thermal Analysis of the Eutectic Formed in Pb-Sn Alloys

The effect of the presence of two different primary phases on the microstructural characteristics and solidification kinetics of Pb-Sn eutectic was analyzed using Fourier thermal analysis method (FTA) and microstructural characterization. Three Pb-Sn alloys, a hypoeutectic, an eutectic, and a hypereutectic alloy, were melted in an electric furnace under an argon atmosphere and poured into sand molds. Cooling curves were obtained and numerically processed using FTA. Microstructural observations of the probes indicate a lamellar morphology for the eutectic microconstituent of the hypereutectic alloy; the eutectic alloy shows the presence of both lamellar and anomalous eutectic and the hypoeutectic alloy shows only the presence of anomalous eutectic. FTA results indicate that in the case of the probes showing the presence of anomalous eutectic, there is a primary eutectic formed during recalescence at high undercooling and a secondary eutectic yielded at low undercooling at the eutectic plateau temperature. This result shows that the cause behind the observed differences in the eutectic morphologies of the experimental alloys lies on the nucleating ability of the primary phase available as a potential substrate for nucleation of the eutectic microconstituent.