A simple model for the semicontinuous heterophase polymerization: Ethyl methacrylate as a case example

A simple but comprehensive model considering homogeneous and micellar nucleation, coagulation, entry of radicals to particles and to micelles and radicals' exit from particles, is presented. The model is validated, in a starved semicontinuous heterophase polymerization of ethyl methacrylate, at three monomer addition rates. The model accurately describes the overall and instantaneous conversion, the average particle density and diameter, and the number and weight average molar masses evolutions over time. It is found that even though the average number of radicals is much smaller than 0.5, the system is not 0-1. An empirical function was used to describe the gel effect. The homogeneous nucleation was the prevailing mechanism for particle formation and large exit rates of radicals were observed. POLYM. ENG. SCI., 60: 223–232, 2019. © 2019 Society of Plastics Engineers     

A “four-ferrocene” modified stem-loop structure as a probe for sensitive detection and single-base mismatch discrimination of DNA

We report the use of a four-ferrocene modified oligonucleotide as a probe for DNA detection with a gold electrode microsystem. This oligonucleotide is synthesized by automated solid-phase synthesis with four successive ferrocene moieties at the 5′-end and a C6-thiol modifier group at the 3′-end. The grafting of this 4Fc-DNA probe on a gold electrode microsystem results in the appearance of the ferrocene redox couple in cyclic voltammetry. The probe sequence is a stem-loop structure that folds efficiently on the electrode, thus optimizing electron transfer. Such architecture serves as sensor for DNA detection which is based on hybridization. The resulting disposable voltammetric sensor allowed direct, reagentless DNA detection in a small volume (20 μL). Electrochemical response upon hybridization with complementary short sequence (30-base length) and long sequence (50-base length) strands was observed by differential pulse voltammetry. Current variations were compared. The longer the sequence, the greater the decrease in current. The system's detection limit was estimated at 3.5 pM (0.07 fmol in 20 μL) with the 50-base length target and provided a dynamic detection range between 3.5 pM and 5 nM. Single mismatch detection showed a good level of sensitivity. The system was regenerated twice with no significant loss of Fc signal. Finally, 1 pM sensitivity was reached with a long chain analog of DNA PCR products of Influenza virus.     

Virulence-resistance plasmids (pUO-StVR2-like) in meat isolates of Salmonella enterica serovar Typhimurium

During a screening of Salmonella enterica in foods of animal origin four isolates of serovar Typhimurium carrying hybrid virulence-resistance plasmids were detected. Three of them, one from pork and two from chicken meat, contained pUO-StVR2, a derivative of the pSLT virulence plasmid with the bla_OXA-1, catA1, aadA1, sulI and tet(B) genes, which confer resistance to ampicillin, chloramphenicol, streptomycin-spectinomycin, sulfonamides and tetracycline, respectively. The fourth isolate, from pork, harbored a pUO-StVR2 variant (termed ν8) with an additional dfrA10 gene responsible for resistance to trimethoprim. This gene is part of the orf513-dfrA10-qacEΔ1-sul1 element characteristically found in complex class 1 integrons. Pulsed-field gel electrophoresis identified two XbaI-BlnI combined profiles: X2-B2 generated from the three pUO-StVR2 isolates, and X12-B17 shown by the pUO-StVR2-ν8 isolate. The same profiles have also been found in clinical and ill pig isolates, supporting chicken and pork meat as vehicles for transmission of Typhimurium carrying pUO-StVR2-like plasmids.     

Bioaccessibility of calcium, iron and zinc from three legume samples

Legumes can be a source of mineral elements but also of antinutritional factors which can affect their absorption. An in vitro method including gastrointestinal digestion was used to estimate mineral bioavailability. Soluble (bioaccessible) and insoluble calcium, iron and zinc from white beans, chickpeas and lentils were determined after gastrointestinal digestion. The influence of the original sample weight on the soluble mineral fraction was also estimated. The results obtained show that white beans are the legumes with the highest bioaccessible calcium and iron contents. Lentils have a high iron content but its bioaccessibility is much lower than that of iron from white beans and chickpeas. An increase in sample weight increases the amount of bioaccessible element available for intake, but the increase is not always proportional.     

Yeast on the milky way: genetics,physiology and biotechnology of Kluyveromyces lactis

The milk yeast Kluyveromyces lactis has a life cycle similar to that of Saccharomyces cerevisiae and can be employed as a model eukaryote using classical genetics, such as the combination of desired traits, by crossing and tetrad analysis. Likewise, a growing set of vectors, marker cassettes and tags for fluorescence microscopy are available for manipulation by genetic engineering and investigating its basic cell biology. We here summarize these applications, as well as the current knowledge regarding its central metabolism, glucose and extracellular stress signalling pathways. A short overview on the biotechnological potential of K. lactis concludes this review. Copyright © 2013 John Wiley & Sons, Ltd.     

Electroporation of single cells and tissues with an electrolyte-filled capillary

We show how an electrolyte-filled capillary (EFC) coupled to a high-voltage power supply can be used as a versatile electroporation tool for the delivery of dyes, drugs, and biomolecules to the cytoplasm of single cells and cells in tissues. A large-voltage pulse applied across the EFC (fused silica, 30 cm long, 375-microm o.d., 30-microm i.d.) gives rise to a small electric field outside the terminus of the EFC, which causes pore formation in cell membranes and induces an electroosmotic flow of electrolyte. When the EFC contains cell-loading agents, then the electroosmotic flow delivers the agents at the site of pore formation. The combination of pore formation and delivery enables loading of materials into the cytoplasm. By patch-clamp and fluorescence microscopy, formation of pores was observed at estimated transmembrane voltages of <85 mV with half-maximum values around 206 mV. The electroporation protocol was demonstrated by introduction of fluorogenic dyes into single NG108-15 cells, cellular processes, and small populations of cells in organotypic hippocampal cultures. Preliminary results are shown in which this protocol was employed for in vivo electroporation of ventral mesencephalon in rat brains. The technique was also used to access organelle-based detection systems inside cells. As a demonstration, 1,4,5-inositoltriphosphate was added to the electrolyte and detected by intracellular organelles in electroporated cells.     

Stability of the lipid fraction of milk‐based infant formulas during storage

A study is made of the effects of storage (time and temperature) on the lipid fraction of four milk‐based adapted infant formulas with basically the same composition, though differing in the iron salt added (lactate or sulfate) and/or the vitamin E source (α‐tocopherol or α‐tocopherol acetate). Peroxide value, hydroperoxide C₁₈ percentage and thiobarbituric acid‐reactive substance (TBARS) content were used as indicators of lipid peroxidation. Fat contents remained stable throughout storage. Peroxide values increased from the first storage month and were affected by storage time, although they exhibited irregular behavior. Storage time and temperature affected hydroperoxide percentage, which was seen to be the earliest indicator of lipid oxidation, being measurable in newly manufactured formulas. TBARS values were only affected by storage time. No statistically significant differences were found among the four infant formulas for any of the lipid oxidation indicators.     

Fabrication and performance of InP-based heterostructure barriervaractors in a 250-GHz waveguide tripler

High-performance InGaAs-InAlAs-AlAs heterostructure barrier varactors (HBV's) have been designed, fabricated, and RF tested in a 250-GHz tripler block. The devices with two barriers stacked on the same epitaxy are planar integrated with coaxial-, coplanar-, and strip-type configurations. They exhibit state-of-the-art capacitance voltage characteristics with a zero-bias capacitance C₃⁰ of 1 fF/μm² and a capacitance ratio of 6:1. Experiments in a waveguide tripler mount show a 9.8-dBm (9.55-mW) output power for 10.7% conversion efficiency at 247.5 GHz. This is the highest output power and efficiency reported from an HBV device at J-band (220-325 GHz)     

Baked product development based fermented legumes and cereals for schoolchildren snack

The objective of this work was to develop three foodstuffs based on mixes of wheat and fermented and non-fermented legumes, for the purpose of contributing with a healthy alternative for school snacks. To this aim, refined wheat flour was partially substituted with whole legume flours for the preparation of cakes, brownies and cookies, foodstuffs traditionally consumed by school age children. Cakes were formulated substituting 20% of wheat flour with Phaseolus vulgaris flour, brownies with 30% of Cajanus cajan flour and cookies with 30% of Vigna sinensis flour, using fermented and non-fermented legumes in the three products. When these products were subjected to sensorial evaluation through a test of degree of acceptability and using a hedonic scale of 7 points, values higher than 5 in the attributes taste, color and overall appraisal were found for all the products. In addition, the preference was measured with a group of 90 school children, corroborating the results obtained at laboratory level. Chemical characterization showed protein contents between 12 and 13% for the cake, 10 and 11% for the brownies and 10% for the cookies and protein digestibilities in vitro of 91%, 87% and 93%, respectively. The calorie supply, calculated per portion was of 199 kcal, 246 kcal and 237 kcal, for cakes, brownies and cookies, respectively. It was concluded that it is technically possible to incorporate fermented and non-fermented Phaseolus vulgaris, Vigna sinensis and Cajanus cajan, to highly consumed products such as cakes, brownies and cookies with a higher nutritional content and well-accepted by school-age children.     

Dynamic range of an optical amplifier cascade in an ASK system withsignificant phase noise

The authors present detailed results concerning the dynamic range of an amplitude-shift keyed (ASK) heterodyne optical communication system where the transmitted signal is impaired by significant amounts of laser phase noise. Theoretical results are evaluated for a system with up to ten in-line optical amplifiers and a significant influence of the laser phase noise is found for the maximum allowable transmission span and the dynamic range. With ten amplifiers, a linewidth of 11% of the bit rate causes the span to be reduced by 12.2 dB and the dynamic range to be reduced by 5.7 dB. The results have been confirmed using two amplifiers in a field trial experiment at a bit rate of 636 Mb/s with an IF linewidth of 70 MHz