Interfacial chemistry on carboxylate-functionalized monolayer assemblies

Deposition of trichlorosilanes with ester groups at their remote termini provides a convenient entry to carboxylic acid-bearing siloxane-anchored self-assembled monolayers. The de-esterification of these esters has been optimized to minimize monolayer damage, and their quantitative re-esterification provides clear evidence for the stability of these systems. Both the structure of the ester-terminated monolayer and its de-esterification/esterification chemistry can be easily monitored by FTIR-ATR measurements. This spectroscopic tool, together with a liquid cell that enables IR spectra to be measured in an aqueous environment, enables a detailed structural analysis of the carboxylic acid-bearing siloxane-anchored self-assembled monolayers and an assessment of their acid/base behavior (by in situ titration). The use of D₂O instead of H₂O for the in situ titration experiments also improves the available IR window. Both monomeric and dimeric/oligomeric acid groups are seen, and the relative ease of deprotonation of these various species can be directly monitored. Monomers of alkyl carboxylic acids that are hydrogen bonded only to surrounding water molecules have a pK_a = 4.9, while the pK_a for the aggregated molecules is 9.3. Similar behavior is seen for surface-bound benzoic acids, where the two pK_a values are 4.7 and 9.0. The influence of temperature on these structures and their chemistry has been explored to a limited extent as well. When the alkylcarboxylic acid system is cooled to 10 °C, the pK_a value for the acid monomers is reduced from 4.9 to 4.5 and increases from 9.3 to 10.3 for the aggregates.     

Capsaicinoids quantification in chili peppers cultivated in the state of Yucatan,Mexico

Capsaicinoids are a group of 12 or more related alkaloids responsible of the pungent sensation in fruits of the genus Capsicum. Capsaicin [(E)-N-(4-hydroxy-3-methoxybenzyl)-8-methyl-6-nonenamide] and dihydrocapsaicin are responsible for more than 90% of the pungency. This work describes the quantitative analyses by gas chromatography of the content of capsaicin and dihydrocapsaicin in the pericarp, placenta, and seeds of seven cultivars of chili peppers cultivated in the state of Yucatan, Mexico [chawa, dulce, sukurre, xcat’ik (Capsicum annuum L. var. annuum), maax (Capsicum annuum L. var. aviculare), and habanero orange and habanero white (Capsicum chinense Jacq.)]. Capsaicin content was higher, as expected, in the fruits of habanero orange and habanero white, followed by sukurre, chawa, xkat’ik, and maax. Dihydrocapsaicin content did not follow the same scheme, being higher in the fruits of sukurre, followed by chawa, habanero white, habanero orange, and maax. Xcat’ik showed minor quantities of dihydrocapsaicin, while dulce chili contained only traces of these two alkaloids.     

Transversal moving-front patterns: Criteria and simulations for two-bed and cylindrical shell packed-bed reactors

We show that a moving-front solution in a cylindrical shell packed-bed catalyzing a first-order activated reaction may bifurcate into transversal patterns when Pe_C/Pe_T<ΔT_ad/ΔT_m, i.e. when the ratio of the mass to heat Pe numbers is smaller than the ratio of the adiabatic to maximal temperature rises. This coincides with the previous condition of transversal patterns to emerge in stationary fronts [Pe_C/Pe_T<1 [Viswanathan, G., Bindal, A., Khinast, J., Luss, D., 2005. Stationary transversal hot zones in adiabatic packed-bed reactors. A.I.Ch.E. Journal 51, 3028-3038]] and extends the bifurcations condition to the case of moving fronts. The novel condition cannot be satisfied in a downstream propagating front (ΔT_m/ΔT_ad>1), but for an upstream propagating front (toward the cold reactor inlet) ΔT_m/ΔT_ad<1 and the symmetry breaking can be obtained within a feasible domain of operating conditions (Pe_C/Pe_T>1). It was also assumed that the axial and the transversal Pe numbers vary consistently, i.e. κ_C=Pe_C⊥/Pe_C=κ_T=Pe_T⊥/Pe_T. A similar condition was also obtained using a simplified model composed of two 1-D beds with heat and mass exchange between them.Bifurcation diagram showing domains of transversal patterns is constructed using a learning two-bed model. These predictions are verified by direct numerical simulations of the continuous 2-D cylindrical shell model showing various types of moving transversal patterns within a feasible domain of the state parameters with Pe_C>Pe_T. In the case of varying ratio (κ_C≠κ_T) the pattern domain can be significantly extended toward larger Pe_C/Pe_T.     

Growth and Adhesion Enhancement of Diamond Films Deposited on Steel Substrates by a Cr–N Interlayer

Diamond film deposition onto iron-based substrates by chemical vapor deposition methods is complicated by the formation of black carbon or graphitic soot on the substrate surface prior to diamond nucleation and growth, by fast diffusion of carbon into the iron substrate, and by poor adhesion of the deposited film. These complications suggested the use of a buffer layer between the deposited diamond film and the iron-based substrate. We review different methods used to improve the adhesion of diamond film to steel substrates. In particular we describe in detail our own studies which involve the use of a Cr-N interlayer. The use of a chromium nitride interlayer has been found to improve significantly the adhesion of diamond films deposited on ferrous substrates. This is achieved by hindering diffusion processes of carbon and iron, very stable mechanical and chemical bonding between the interlayer and the diamond film, and good adhesion of the interlayer to the steel substrate. We also report on our studies related to residual stress present in the films, as well as a correlation between the interlayer properties and adhesion strength of deposited films.     

Quality attributes of a heart healthy yogurt

The objective was to study the effect of heart healthy nutrients on the physico-chemical, microbiological and sensory characteristics of yogurt. Thiamine (vitamin B₁), riboflavin (vitamin B₂), niacin (vitamin B₃), folic acid (vitamin B₉), manganese and magnesium were added during mix preparation at 0%, 30%, 60% and 90% of their respective recommended dietary allowance (RDA). Fiber (Ceolus Fiber DF-17) was added at a constant rate of 176 g/7.570 kg yogurt mix in all the treatments. Total solids in the control were kept constant with non-fat dry milk. Incorporation of the heart healthy nutrients at the 30%, 60% and 90% RDA significantly decreased syneresis, pH, L*, a* values but significantly increased b* value. Product viscosity was significantly increased by the incorporation of the nutrients at 60% of their respective RDA's. The incorporation of the above heart healthy vitamins and minerals at any of the studied rates in yogurts did not significantly affect flavor, appearance, body and texture and microbial counts of the product. Although there were subtle yet significant changes in instrumental color and viscosity these slight changes could not be detected by sensory evaluation. Yogurts can successfully be manufactured with the above heart healthy nutrients.     

Averaging analysis of periodically forced fluid networks

For a lumped parameter model of a flow network driven by a periodic generator, we apply averaging to find an approximate solution and analyze its stability. The approximate solution has three parts: mean flow due to the resistive effects of branches, a time-periodic part due to “inductive” effects, and a mean flow average correction due to the interaction of nonlinear and time varying effects. We present an example that may explain the scenario leading to venous diseases. It is shown that the widening of a branch in a venous network leads to an increase in the AC flow and a decrease in the DC flow through that branch, thus increasing the stress on venous valves, and consequently leading to a further increase in the effective width of the vein.     

Botanical features for identification of Gymnosporia arenicola dried leaf

Gymnosporia arenicola Jordaan (Celastraceae) is a shrub or small tree, which naturally occurs in coastal sand dunes of Southern Mozambique and South Africa. Its dried leaf is often used in traditional medicine for the treatment of infectious and inflammatory diseases. Hereby, we present results of studies carried out according to the pharmacopoeia standards for the identification of herbal drugs, in the whole, fragmented, and powdered plant material. These results were complemented with scanning electron microscopy and histochemical techniques. The leaf microscopic analysis revealed a typical dorsiventral mesophyll with a corresponding spongy parenchyma–palisade parenchyma ratio of 0.60, anomocytic and paracytic stomata, papillate cells with a diameter of 4.00 ± 0.40 µm, multicellular uniseriate nonglandular trichomes with a length of 27.00 ± 4.10 µm and cristalliferous idioblasts containing calcium oxalate cluster crystals with a diameter of 23.04 ± 5.84 µm. The present findings demonstrate that the G. arenicola leaf has both nonglandular trichomes and hypoderm, features not previously described in the corresponding botanical section (Gymnosporia sect. Buxifoliae Jordaan). The establishment of these new botanical markers for the identification of G. arenicola leaf is essential for quality, safety and efficacy reasons. Microsc. Res. Tech. 78:1001–1009, 2015. © 2015 Wiley Periodicals, Inc.     

Water purification from metal ions using carbon nanoparticle-conjugated polymer nanocomposites

The paper deals with a novel method of obtaining nanocarbon-conjugated polymer nanocomposites (NCPC) using nanocarbon colloids (NCC) and polyethylenimine (PEI) for water purification from metal ions. Size of NCC, process of NCPC synthesis, its chemical characteristics, ratio of NCC and PEI in NCPC, speed of coagulation of NCPC, mechanism of interaction of metal ions with NCPC, ability of removing metal ions from water by NCPC against pH have been studied. NCPC has a bonding capacity of 4.0-5.7 mmol/g at pH 6 for most of the divalent metal ions. Percent of sorption of Zn²⁺, Cd²⁺, Cu²⁺, Hg²⁺, Ni²⁺, Cr⁶⁺ ions is higher than 99%. Lifetime of NCPC before coagulation in the treated water is 1 s-1000 min and depends on the ratio of polymeric molecules and carbon nanoparticle concentrations. Results of laboratory tests of the method are described.     

Development of a new procedure for precise determination of viral aerosol lethal dose (ALD50) for birds

This paper describes a new method for precise determination of viral aerosol lethal dose (ALD₅₀) and reports the results obtained for birds exposed by H5N1 Avian influenza A strain under controlled laboratory conditions. The reported method utilizes our recently developed personal bioaerosol sampler capable of monitoring viable virus concentration in the ambient air. Up to six laboratory animals could be located in a specially designed aerosol chamber and exposed in parallel by an airborne strain of interest to generate the amount of data sufficient for representative statistical analysis. A concentration of viable airborne virus was measured by the personal aerosol samplers directly in the breathing zone of each particular bird. The results show a very low inter-sampler variation used for each particular run, which was confirmed by a single factor ANOVA test undertaken for all six personal samplers involved in each experiment. As was shown, the difference in amount of viruses collected by all samplers during each particular run was not statistically significant. It was found that the ALD₅₀ for approximately 400-g birds exposed to H5N1 Avian influenza A strain A/Chicken/Suzdalka/Nov-11/2005 was around 26.5 FFU (focus forming units).