Synthesis of colloidal solutions with silicon nanocrystals from porous silicon

In this work, we have obtained colloidal solutions of Si nanocrystals (Si-ncs), starting from free-standing porous silicon (PSi) layers. PSi layers were synthesized using a two-electrode Teflon electrochemical cell; the etching solution contained hydrogen peroxide 30%, hydrofluoric acid 40% (HF), and methanol. The anodizing current density was varied to 250 mA cm^-2, 1 A cm^-2, and 1.2 A cm^-2. Thus obtained, PSi was mechanically pulverized in a mortar agate; then, the PSi powders were poured into different solutions to get the final Si-ncs colloidal solutions. The different optical, morphological, and structural characteristics of the colloidal solutions with Si-ncs were measured and studied. These Si-ncs colloidal solutions, measured by photoluminescence (PL), revealed efficient blue-green or violet emission intensities. The results of X-ray diffraction (XRD) indicate that the colloidal solutions are mainly composed of silicon nanocrystallites. The result of UV–vis transmittance indicates that the optical bandgap energies of the colloidal solutions varied from 2.3 to 3.5 eV for colloids prepared in methanol, ethanol, and acetone. The transmission electron microscopy (TEM) images showed the size of the nanocrystals in the colloidal solutions. Fourier transform infrared spectroscopy (FTIR) spectra showed different types of chemical bonds such as Si-O-Si, Si-CH₂, and SiH _x , as well as some kind of defects.

PACS

61.46Df.-a; 61.43.Gt; 61.05.cp; 78.55.-m; 81.15.Gh     

Production of first generation adenoviral vectors for preclinical protocols: amplification, purification and functional titration

Gene therapy represents a promising approach in the treatment of several diseases. Currently, the ideal vector has yet to be designed; though, adenoviral vectors (Ad-v) have provided the most utilized tool for gene transfer due principally to their simple production, among other specific characteristics. Ad-v viability represents a critical variable that may be affected by storage or shipping conditions and therefore it is advisable to be assessed previously to protocol performance. The present work is unique in this matter, as the complete detailed process to obtain Ad-v of preclinical grade is explained. Amplification in permissive HEK-293 cells, purification in CsCl gradients in a period of 10 h, spectrophotometric titration of viral particles (VP) and titration of infectious units (IU), yielding batches of AdβGal, AdGFP, AdHuPA and AdMMP8, of approximately 1013-101? VP and 1012-1013 IU were carried out. In vivo functionality of therapeutic AdHuPA and AdMMP8 was evidenced in rats presenting CCl?-induced fibrosis, as more than 60% of fibrosis was eliminated in livers after systemic delivery through iliac vein in comparison with irrelevant AdβGal. Time required to accomplish the whole Ad-v production steps, including IU titration was 20 to 30 days. We conclude that production of Ad-v following standard operating procedures assuring vector functionality and the possibility to effectively evaluate experimental gene therapy results, leaving aside the use of high-cost commercial kits or sophisticated instrumentation, can be performed in a conventional laboratory of cell culture.     

Enzymatic Interesterification Between Pine Seed Oil and a Hydrogenated Fat to Prepare Semi-Solid Fats Rich in Pinolenic Acid and Other Polyunsaturated Fatty Acids

Enzyme catalyzed interesterification (EIE) of pine seed oil (PSO) and a fully hydrogenated soybean oil (FHSBO) were studied in batch reactors in solvent-free media to prepare different semisolid fats rich in polyunsaturated fatty acids (PUFA). Optimal operation conditions found were: 10 % (w/w) enzyme loading, 75 °C and magnetic agitation at 300 rpm. Quasi-equilibrium conditions were reached after 2, 3 and 6 h, when immobilized lipases from Thermomyces lanuginosus (Lipozyme^® TL IM), Candida antarctica B. (Novozym^® 435) and Rhizomucor miehei (Lipozyme^® RM IM) from Novozymes A/S (Bagsvaerd, Denmark) were employed, respectively. Similar distributions of unsaturated to saturated fatty acid (UFA/SFA) residues along the glycerol backbone of the fat products were obtained with both non-selective and sn-1(3) regioselective lipases due to significant spontaneous acyl migration during the reaction. The products had higher UFA/SFA ratios at the sn-2 position (2.4–2.5, 1.4–1.7, and 0.5–0.8 for the trials involving 20, 40 and 70 % FHSBO, w/w, respectively) than the corresponding physical blends (0.8, 0.4 and 0.5, respectively). Fat products containing 3.1–11.6 % (w/w) pinolenic acid (Pn) and 16.1–35.7 % (w/w) linoleic acid (L) at the sn-2 position were prepared. The free acid contents of EIE products prepared with Lipozyme^® TL IM and Novozym^® 435 were 6.1–6.4 and 2.5–2.6, respectively. Residual activities of Lipozyme^® TL IM and Novozym^® 435 diminish by ca. 20 % after 9 reaction cycles.     

Prediction of the density and viscosity in biodiesel blends at various temperatures

Biodiesel defined as mono-alkyl esters of vegetable oils and animal fats, has had a considerable development and great acceptance as an alternative fuel for diesel engines. Density and viscosity are two important physical properties to affect the utilization of biodiesel as fuel. In this work, mixtures of biodiesel and ultra low sulfur diesel (ULSD) were used to study the variation of density (ρ) and kinematic viscosity (η) as a function of percent volume (V) and temperature (T), experimental measurements were carried out for six biodiesel blends at nine temperatures in the range of 293.15-373.15 K. Both, density and viscosity increases because of the increase in the concentration of biodiesel in the blend, and both of them decrease as temperature increases. One empirical correlation was proposed to estimate the density: ρ = α·V + β·T + δ; and three empirical correlations were developed to predict the kinematic viscosity: η = exp[ln(γ) + ?·V + ω/T + λ·V/T²], η = exp[ln(γ) + ω/T + λ·V/T²] and η = exp[ln(γ) + ω/T + λ·V/T]. The corresponding parameters were optimized by the Levenberg-Marquardt method. The estimated values of density and viscosity are in good agreement with the experimental data because absolute average prediction errors of 0.02% and 2.10% were obtained in the Biodiesel(1) + ULSD(2) system studied in this work.     

Implementation of Neural Machine Translation for Nahuatl as a Web Platform: A Focus on Text Translation

Programming and Computer Software - There are few on-line platforms related to Natural Language Processing and zero services of machine translation for Nahuatl as a low-resource language. However,...     

Automatic transformation from TIDES to TimeML annotation

Until recently, most systems performing temporal extraction and reasoning from text have focused on recognizing and normalizing temporal expressions alone, for which the TIDES annotation scheme has been adopted. Temporal awareness of a text, however, involves not only identifying the temporal expressions, but the events which these expressions anchor, as well as other events which must be ordered relative to them. Because of these broader concerns, TimeML has been developed as an annotation specification that encompasses not only temporal expressions, but all temporally relevant aspects of a text. The annotation schemes, however, are not interchangeable, resulting in incompatible corpora and accompanying extraction algorithms for each standard. In this paper, we describe an automatic migration process from the TIMEX2 tags of TIDES to the TIMEX3 tags of TimeML. This transformation procedure has been implemented and evaluated with two different corpora, obtaining 93.3 and 89.2% overall F-Measure respectively.     

Relationship of Adiposity and Insulin Resistance Mediated by Inflammation in a Group of Overweight and Obese Chilean Adolescents

The mild chronic inflammatory state associated with obesity may be an important link between adiposity and insulin resistance (IR). In a sample of 137 overweight and obese Chilean adolescents, we assessed associations between high-sensitivity C-reactive protein (hs-CRP), IR and adiposity; explored sex differences; and evaluated whether hs-CRP mediated the relationship between adiposity and IR. Positive relationships between hs-CRP, IR and 2 measures of adiposity were found. Hs-CRP was associated with waist circumference (WC) in boys and fat mass index (FMI) in girls. Using path analysis, we found that hs-CRP mediated the relationship between adiposity (WC and FMI) and the homeostatic model assessment of insulin resistance (HOMA-IR) (p < 0.05) in both sexes. Our novel finding is that inflammation statistically mediated the well described link between increased adiposity and IR.     

Influence of monomeric concentration on mechanical and electrical properties of poly(styrene-co-acrylonitrile) and poly(styrene-co-acrylonitrile/acrylic acid) yarns electrospun

Two series of copolymers were synthesized by emulsion polymerization: poly(styrene-co-acrylonitrile) P(S:AN) and P(S:AN-acrylic acid) P(S:AN-AA). The monomeric concentrations in both series were: 0:100, 20:80, 40:60, 50:50 (wt%:wt%), and 1 wt% of AA. The copolymers were dissolved in N,N-dimethylformamide (4–10 wt%) and were electrospun. Polymeric yarns were collected using a blade collector. The synthesized and fabricated materials were characterized by known techniques. Mechanical and electrical properties of polymeric yarns indicated a dependence of monomeric concentration. Elastic modulus increases as acrylonitrile concentration increases (up to 30 MPa). Yarns were submitted to degradation process into saline solution, where the acrylic acid content kept a constant elastic modulus at long times. The electrical current into yarns was higher when the concentration is 50:50 wt%:wt% (1.2 mA). The cytotoxicity results showed a cell viability close to 100% for yarns without AA.     

Selective Synthesis of Diacylglycerols of Conjugated Linoleic Acid

Quasi-quantitative selective production of diacylglycerols (DAG) rich in polyunsaturated fatty acids (PUFA) was demonstrated using a Penicillium camembertii lipase. Under optimal initial conditions [60 °C, 10% (w/w) biocatalyst based on total reactants, 5:1 molar ratio of free conjugated linoleic acid (CLA) to hydroxyl groups in partial glycerides consisting of ca. 90% (w/w) monoacylglycerols (MAG) and ca. 10% (w/w) diacylglycerols (DAG)], reaction for only 4.5 h gave 98.62% DAG and 1.38% MAG. The DAG contained >95% unsaturated fatty acid residues. Predominant DAG were LnLn, LnL and LL, although LO and LP were also significant (Ln = linolenic; L = linoleic; O = oleic; P = palmitic). Effects of the acylating agent (free CLA), solvent, and temperature on undesirable side reactions were determined. Reaction selectivities were similar in n-hexane and solvent-free media. The re-esterified products contained less than 7% saturated fatty acids and a higher ratio of unsaturated to saturated fatty acid residues (19.00) than the precursor soybean oil (5.22). The biocatalyst retained 55% of its initial activity after use in three consecutive reaction/extraction cycles.     

Mycoflora and Co-Occurrence of Fumonisins and Aflatoxins in Freshly Harvested Corn in Different Regions of Brazil

Natural mycoflora and co-occurrence of fumonisins (FB₁, FB₂) and aflatoxins (AFB₁, AFB₂, AFG₁ and AFG₂) in freshly harvested corn grain samples from four regions of Brazil were investigated. Fusarium verticillioides was predominant in all samples. Analysis of fumonisins showed that 98% of the samples were contaminated with FB₁ and 74.5% with FB₁ + FB₂, with toxin levels ranging from 0.015 to 9.67 μg/g for FB₁ and from 0.015 to 3.16 μg/g for FB₂. Twenty-one (10.5%) samples were contaminated with AFB₁, seven (3.5%) with AFB₂ and only one (0.5%) with AFG₁ and AFG₂ Co-contamination with aflatoxins and fumonisins was observed in 7% of the samples. The highest contamination of fumonisins and aflatoxins was observed in Nova Odessa (SP) and Várzea Grande (MT), respectively. The lowest contamination of these mycotoxins was found in Várzea Grande and Nova Odessa, respectively.