Microfluidic motion for a direct investigation of solvent interactions with PDMS microchannels

Solid surface/liquid interactions play an important role in microfluidics and particularly in manipulation of films, drops and bubbles, a basic requirement for a number of lab-on-chip applications. The behavior of solvents in coated microchannels is difficult to be predicted considering theories; therefore, experimental methods able to estimate the properties at the interface in real time and during the operational regime are amenable. Here, we propose to use an experimental setup to evaluate the effective dynamics of solvents inside PDMS microchannels. The influence of the solvent properties as well as of the channel wall’s wettability on the fluid movements was evaluated. Modification of the channel properties was achieved by introducing Teflon coatings that allow producing stable hydrophobic microchannel walls. The results were fitted according to Washburn-type power-law and compared with theoretical calculations of the parameter β that expresses the dependence of capillary dynamics on surface tension γ, liquid viscosity η, contact angles θ and the hydraulic radius R _H. A comparison between the calculated and the experimental values reveled that parameters other than the contemplated ones influenced the measurements. The main parameter that affects the flow of solvents such as water, methanol ethanol, dimethylformamide, acetonitrile and acetone was found to be the γ/η ratio. Considering these results, the investigation tool described here is believed to be promising to predict the dynamics of common organic solvents inside integrated functional fluidic devices and to accurately control solvent flow, particularly in capillary-driven pumpless systems, a basic requirement for widening the application range of PDMS lab-on-chip devices.     

Batch treatment of liquid fraction of pig slurry by intermittent aeration: process simulation and microbial community analysis

BACKGROUND: Manure treatment in intensive livestock farming is required to reduce the risk of negative environmental impacts by nitrogen disposal. Biological removal through intermittent aeration in a single bioreactor is a suitable method for this purpose. The characteristic operation based on the alternation of oxic/anoxic phases confers these systems with certain particularities in terms of process modelling and of understanding the microbial interactions. RESULTS: The performance of a sequencing batch reactor (SBR) treating raw liquid fraction of pig slurry (LFPS) under loading rates of 0.13 g N L^?1 d^?1 was studied. Three different aeration strategies were applied: (1) constant airflow; (2) dissolved oxygen (DO) set‐point; and (3) DO‐based real‐time control. The comparatively low aeration intensity applied throughout the third strategy resulted in the process being performed mainly via nitrite, implying a reduction on the requirements of organic carbon and oxygen. However, a decrease in the nitrification rate was observed under those conditions. Experimental results were satisfactorily simulated by a mathematical model focused on organic carbon and nitrogen removal. Microbial community structure analysis through denaturing gradient gel electrophoretic profiling of 16S rDNA genes showed that the aeration exerted a strong influence on the dominant microbial populations. The presence of the ammonia‐oxidizing species Nitrosomonas europaea, and of denitrifying bacteria related to Thauera sp. and Ralstonia sp., was detected in the strategy at low DO. CONCLUSION: Dependence of model statement and parameter values on the bioreactor operational patterns and piggery wastewater composition was evidenced. Oxygen limitation was responsible for a significant microbial shift in SBR treating LFPS. Copyright © 2009 Society of Chemical Industry     

The mental health of men with a psychiatric disorder or traumatic brain injury: Wives' labeling and husbands' perceived control.

Objective: To investigate the relations among wives' labeling of their husbands' psychiatric disorder or brain injury as an organic illness, the husbands' perceived control over their disabilities, and the husbands' mental health. Participants: 57 male clients of the Department of Rehabilitation, Israel's Ministry of Defence (26 with a psychiatric disorder and 31 with a traumatic brain injury) and their wives. Measures: Illness Labeling Questionnaire, the Perceived Control Over Illness Questionnaire, and the Mental Health Inventory. Results: Husbands' mental health was low but did not differ according to disability; wives' labeling of husbands' condition was negatively related to the husbands' mental health; husbands' perceived control was positively related to their mental health for both disabilities. Conclusion: Organic illness labels, even when adopted by the wives of the persons with the disability, seem to be negatively related to that person's mental health, whereas perceived control over a mental disorder or a brain injury seems to contribute positively to mental health, independently of how the disorder or injury is labeled. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of polyvinylchloride films and edible starch coatings on quality aspects of refrigerated Brussels sprouts

To extend shelf life, the effects of polyvinylchloride film (PVC) and edible coatings on quality aspects of refrigerated Brussels sprouts were studied. Starch-based coatings were formulated using glycerol (G), sorbitol (S) or glycerol plus sunflower oil (O). Sprouts so treated as well as uncoated ones were placed on expanded polystyrene trays. Combinations of PVC and coatings (treatments named G-PVC, S-PVC and O-PVC) were also tested. Uncovered trays were maintained as controls. All packages were stored at 0 °C for 42 days and samples were removed every 14 days to determine commercial acceptability, weight loss, surface colour (of sprouts’ heads and bases) and texture. Sprouts in all treatments maintained optimum quality conditions over the first 14 days. At the end of storage, browning of cut zones and losses in weight and firmness were minimised in PVC-packaged sprouts, particularly in G-PVC. Therefore, PVC and G-PVC treatments were selected to evaluate some nutritional quality components. Ascorbic acid and total flavonoid contents remained almost constant while radical scavenging activity increased after 42 days of storage. Thus, PVC and G-PVC treatments showed the best performance for long-term refrigerated storage of Brussels sprouts.     

Evaluation of the mechanical properties and diffusion coefficients of osmodehydrated melon cubes

The objective of this work was to evaluate the influence of osmotic agents, their concentration and temperature, on the mass transfer kinetics and mechanical properties of osmodehydrated melon cubes. Samples were immersed in a hypertonic solution of sucrose or maltose up to 8 h under controlled temperature and agitation. Water loss, sugar gain and mechanical properties were analysed throughout the process. Mass transfer kinetics was modelled according to Peleg and Fick equations. Higher water loss, lower sugar uptake and stress at rupture values more similar to fresh fruit were observed in samples treated with maltose solutions. Peleg’s model showed the best adjustment to all the experimental data, however the k₁ and k₂ parameters did not show a clear trend with the solution concentration or temperature increase. The effective diffusivity obtained using Fick’s equation varied from 3.93 × 10^?9 to 6.45 × 10^?9m² s^?1 for water loss and from 7.57 × 10^?10 to 3.14 × 10^?9m² s^?1 for sugar gain.     

Thiocyanate Ion Promoted E ⇌ Z Isomerization of a-Bromo-β,β-Diactivated Electrophilic Olefins: An Apparent High Nucleofugality of NCS−

(E)-β-Chloro-α-phenylcinnamaldehyde and (E)- and (Z)-methyl α-tert-butoxycarbonyl-p-nitro-β-bromocinnamates in the presence of NCS⁻ ion in acetonitrile undergo an (E) ⇌ (Z) isomerization which is faster than the vinylic substitution. (E)- and (Z)-methyl α-cyano-β-mesyloxy- (and β-chloro-) p-nitrocinnamates undergo substitution under similar conditions without preceding isomerization. MO calculations gave the energy differences between the eclipsed and the perpendicular conformers of carbanions ⁻CH₂CH₂X and (NC)₂ČH₂X (X = Cl, NCS). These rotational barriers denote the hyperconjugation stabilization energy resulting from interaction of the C-X bond and the 2p(C⁻) orbital. Both HCA values are high, those for X = Cl being 15–20% higher than for X = NCS. The limited literature data on the nucleofugality of NCS⁻ suggests that it can have a nucleofugality which is not much lower than that of Cl⁻ or Br⁻. Consequently, NCS⁻-catalyzed isomerizations of electrophilic vinyl chlorides and bromides, which involve a 180° internal rotation followed by a faster expulsion of NCS⁻ than of Cl⁻ from the initially formed intermediate carbanion Y'Y⁻C-C(R)(Cl)SCN, are not unreasonable, especially if solvation, which was not included in the calculations, plays an important role in the nucleofuge expulsion process.     

Semivolatile organic compounds in window films from lower Manhattan after the September 11th World Trade Center attacks

The September 11th World Trade Center (WTC) terrorist attacks resulted in the large-scale release of contaminants that were deposited on the environment of New York City (NYC). Six weeks after the attacks, samples of an organic film on window surfaces were collected and analyzed for polybrominated diphenyl ethers (PBDE), polychlorinated biphenyls (PCB), polychlorinated naphthalenes (PCN), polycyclic aromatic hydrocarbons (PAH), and organochlorine pesticides (OCPs). Concentrations dropped by an order of magnitude within 1 km of the WTC and reached background concentrations by 3.5 km. Concentrations within 1 km of the WTC averaged 3280 ng/m2 for sigmaPBDE, 900 ng/m2 for sigmaPCB, 33 ng/m2 for sigmaPCN, and 77100 ng/m2 for sigmaPAH. Congener profiles of the sites nearest the WTC suggested a combination of combustion and evaporative sources of all compounds, whereas the background sites exhibited profiles consistent with evaporative sources. PBDE profiles showed enrichment in lower molecular weight congeners near the WTC, suggesting that these congeners were formed as a result of the combustion conditions. Homologue fractions of PCN combustion markers were approximately 2-9 times greater at near WTC sites compared to background NYC. Gas-phase air concentrations were back-calculated from measured film concentrations using the film-air partition coefficient (KFA), and calculated air concentrations followed spatial trends observed in films.     

Acetylcholine receptor at neuromuscular junctions by EM autoradiography using mask analysis and linear sources

Several methods of analyzing EM autoradiograms are now available. Two such procedures, the grain density distribution (or histogram) method and the mask method use the resolution of the EM autoradiographic technique to generate grain distributions expected from postulated sources, and compare these with the observed grains in the autoradiograms. These two methods are here compared in the analysis of label on linear sources: the distribution of labeled acetylcholine receptor (AChR) down the postjunctional folds of lizard and frog neuromuscular junctions. The receptors were labeled with I-25-α-bungarotoxin and the autoradiograms coated with the high resolution Kodak emulsion 129–01. We found that both methods gave similar results in confirming that the bulk of the AChR is concentrated on the thickened region of the membrane at the top ∼2000 A of the junctional folds, and that there may be a gradient of receptor concentration down the folds. The grain density distribution method is simpler, but does not lend itself easily to quantifying the extent of deviation from simple models. Although computer graphics is not necessary for either method, its use allows the expected grains from linear sources to be generated quickly, making the mask analysis a feasible routine method for assigning the extent of label in different membrane regions.     

Synthesis,structure and electrochemical properties of the cationic complex tris-(imidazolidine-1,10-phenanthroline)iron(II)

The complex [Fe^II(Imz-phen)₃](PF₆)₂, (Imz-phen = imidazolidine-[4,5-f]-1,10-phenanthroline) has been prepared and characterized using X-ray diffraction, UV–vis and IR spectroscopy, elemental analysis, fast atomic bombardment (FAB) mass spectrometry, and cyclic voltammetry. Its crystal lattice includes acetonitrile (π–π bound to phenanthroline), methanol, and water molecules. Scanning continuously between 1000 mV and 1650 mV in CH₃CN, a modified electrode that includes the iron (II) complex is obtained; after the 25th continuous cycle a stable film is formed that is electrocatalytically active in the reduction of sulfur oxoanions. When the electrocatalytic properties are evaluated in ethanol/water solution, the current achieved from the electroreduction of these sulfur species is linearly dependent on the respective concentrations, suggesting potential application in sulfite determination.     

Consideration of the influence of aging process,type of wine and oenological classic parameters on the levels of wood volatile compounds present in red wines

The contents of the volatile compounds extracted from wood: cis- and trans-whiskylactones, vanillin, syringaldehyde, furfural, 5-methylfurfural, eugenol, guaiacol, p-ethyl-phenol and p-ethylguaicol have been studied in 12 single-variety wines aged in new American oak barrels. The concentration of these compounds were determined after the following combinations of time in wood and time in bottle: 0 months in wood plus 18 months in bottle, 4 months in wood  + 14 months in bottle, 9 months in wood + 9 moths in bottle and 12 months in wood + 6 months in bottle. According to the composition of the wines, it is possible to conclude in general, that, the extraction of these compounds was faster during the first four or 9 months of aging in wood, depending on the wines. After 12 months of oak maturation, the extraction of these compounds slowed down. Furthermore, the final concentrations of these volatile compounds were different among studied wines. These differences could be related to some of the values of some of their oenological parameters, such as the contents of tartaric acid and sulphur dioxide of each wine.