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El contexto universitario constituye un escenario complejo que puede potenciar el desarrollo personal de los estudiantes, pero también puede estimular la experimentación de emociones negativas. El estudio presentado en este artículo se orientó a explorar la afectividad negativa en estudiantes universitarios. Se realizó un muestreo probabilístico. La muestra estuvo compuesta por 1.377 estudiantes a los que se les administró el Autorreporte Vivencial. Se utilizó el análisis descriptivo univariante y también el análisis de conglomerados en 2 etapas, el análisis categórico de componentes principales y los árboles de decisión. Los resultados revelaron bajos niveles de afecto negativo. Los estudiantes se dividieron en 2 grupos que se diferencian en la intensidad con la que experimentan las diferentes emociones negativas, con mayor presencia de las mujeres en el conglomerado de peores resultados. Se identificó que la tristeza y la angustia demostraron ser los mejores predictores de la afectividad negativa en los estudiantes universitarios. Los resultados alcanzados constituyen los primeros pasos para el diseño de estrategias preventivas y de promoción de la salud mental en el contexto universitario.

Increasing global food demand requires the exploration of agricultural production systems that minimise the conflict between food production and biodiversity conservation. Cattle ranching is a main land-use in tropical and sub-tropical South American semi-arid ecosystems, such as the Chaco eco-region of sub-tropical Argentina, one of the most active frontiers of land-use change. Despite open habits being a key component of the Chaco landscape, conservation studies and policies have focussed on forests. In this study, bird and mammal communities of three different open-canopy livestock-producing systems in the semi-arid Argentinian Chaco: natural grasslands, sown non-native pastures and silvopastoral systems are discussed. Diversity (Inverse Simpson index) and species composition (multivariate ordinations) were measured and species identified that characterise each system (indicator species). The three livestock systems did not significantly differ in terms of diversity but showed differences in the composition of bird communities. Natural grasslands had the highest number of bird and mammal indicator species (including Myrmecophaga tridactyla, a high conservation-value species). These results highlight natural grasslands as a landscape unit with a high conservation value and indicate that they should be explicitly targeted by conservation and land-use policies, particularly because they represent a small and rapidly decreasing proportion of the semi-arid Argentinian Chaco.

There are several classification problems, which are difficult to solve using a single classifier because of the complexity of the decision boundary. Whereas a wide variety of multiple classifier systems have been built with the purpose of improving the recognition process, there is no universal method performing the best. This paper provides a review of different multi-classifiers and some application of them. Also it is shown a novel model of combining classifiers and its application to predicting human immunodeficiency virus drug resistance from genotype. The proposal is based on the use of different classifier models. It clusters the dataset considering the performance of the base classifiers. The system learns how to decide from the groups, by using a meta-classifier, which are the best classifiers for a given pattern. The proposed model is compared with well-known classifier ensembles and individual classifiers as well resulting the novel model in similar or even better performance.

Polymers that exhibit physicochemical responses to stimuli have been widely explored as potential drug delivery systems. Different kind of stimuli investigated to date includes, for example, chemical substances and changes in temperature, pH and electric fields. Polymers that exhibit dramatic changes in their behavior in an aqueous solution at temperatures close to the body temperature are of particular interest in drug delivery and biomedical applications. Thermosensitive polymers have a wide range of applications, specially, the thermosensitive triblock copolymers because they exhibit unique aqueous solution properties, biodegradability and biocompatibility. These copolymers can be designed to be used as potential drug delivery systems for therapeutic protein drugs or poorly water soluble drugs. This article reviews the applications of polymer solutions with the ability to form in situ implants under temperature changes, in areas of interest to biomedical, pharmacist and engineer scientists. Recent advantages on thermosensitive and biodegradable polymers are discussed to give a wide overview of the available strategies to modify them in order to make them suitable for potential applications in health products.

Pegylation technologies have improved since chemistry and purification processes have advanced over the years. Furthermore, a gradual better understanding of the clinical responses has spurred the need for more effective therapeutic agents. Nowadays, it is necessary to early identify therapy needs and technical capabilities to develop customized, innovative products that reach the market successfully. Consequently, the main technical efforts are directed to solve some intricate problems associated with the drug delivery where improved solubility, in vivo stability, targeted delivery, and enhanced efficacy and safety are the major challenges. Too many alternative approaches for too many needs open up the possibility for follow-on developers and competitors, and provide opportunities for innovation that provoke an intense worldwide competition in a complex intellectual property environment. This paper presents an overview of general trends and patents supporting PEGylation platforms. Since the golden rule is that PEGylation has to be tailored to each specific drug and application, the review format is structured by specific conjugated species alphabetically sorted within the following groups: PEG-protein conjugates, PEG-antibody and antibody fragment conjugates, PEG-oligonucleotide conjugates, PEG-small molecule drug conjugates, and PEGylated materials and miscellaneous applications.

Abstract: A plausible architecture of an ancient genetic code is derived from an extended base triplet vector space over the Galois field of the extended base alphabet {D,A,C,G,U}, where symbol D represents one or more hypothetical bases with unspecific pairings. We hypothesized that the high degeneration of a primeval genetic code with five bases and the gradual origin and improvement of a primeval DNA repair system could make possible the transition from ancient to modern genetic codes. Our results suggest that the Watson–Crick base pairing G≡C and A=U and the non-specific base pairing of the hypothetical ancestral base D used to define the sum and product operations are enough features to determine the coding constraints of the primeval and the modern genetic code, as well as, the transition from the former to the latter. Geometrical and algebraic properties of this vector space reveal that the present codon assignment of the standard genetic code could be induced from a primeval codon assignment. Besides, the Fourier spectrum of the extended DNA genome sequences derived from the multiple sequence alignment suggests that the called period-3 property of the present coding DNA sequences could also exist in the ancient coding DNA sequences. The phylogenetic analyses achieved with metrics defined in the N-dimensional vector space of DNA sequences and with the new evolutionary model presented here also suggest that an ancient DNA coding sequence with five or more bases does not contradict the expected evolutionary history. [Copyright &y& Elsevier]

A series of new N-acetylated non-ionic and cationic gemini surfactants (3a–f) having dimeric structures derived from primary and tertiary amines with variably long tails (C8–C12–C18) were synthesized. In addition, N-acetylated monomeric analogues 6aand 6bwere prepared and their antifungal potency and surface properties were also determined. Critical micelle concentration (CMC), effectiveness of surface tension reduction (?CMC), surface excess concentration (G), and area per molecule at the interface (A) were also determined and the resulting values indicate that the cationic series is characterized by good surface-active and self-aggregation properties. For the first time, all surfactants were tested to evaluate their antifungal properties using the method for the broth macrodilution test (M27-A2, NCCLS). Four microbial strains were used to perform the study: Candida parapsilosis(ATCC 22019), C. albicans(ATCC 64548), and a wild-type strain of C. parasilosisand Saccharomyces cerevisiae(ATCC 9763). The antimicrobial activity was measured by yeast growth inhibition expressed as minimum inhibitory concentration (MIC) values. Results were compared to those obtained for their monomeric analogues and for a commercially available reference compound (Fluconazole). Gemini 3b, 3eand 3fwere found to be the most potent compounds. The results show S. cerevisiaeas the most sensitive strain. In contrast, the wild strain of C. parapsilosiswas resistant.

Bond-based quadratic indices, new TOMOCOMD-CARDD molecular descriptors, and linear discriminant analysis (LDA) were used to discover novel lead trichomonacidals. The obtained LDA-based quantitative structure-activity relationships (QSAR) models, using nonstochastic and stochastic indices, were able to classify correctly 87.91% (87.50%) and 89.01% (84.38%) of the chemicals in training (test) sets, respectively. They showed large Matthews correlation coefficients of 0.75 (0.71) and 0.78 (0.65) for the training (test) sets, correspondingly. Later, both models were applied to the virtual screening of 21 chemicals to find new lead antitrichomonal agents. Predictions agreed with experimental results to a great extent because a correct classification for both models of 95.24% (20 of 21) of the chemicals was obtained. Of the 21 compounds that were screened and synthesized, 2 molecules (chemicals G-1, UC-245) showed high to moderate cytocidal activity at the concentration of 10 μg/ml, another 2 compounds (G-0 and CRIS-148) showed high cytocidal activity only at the concentration of 100 μg/ml, and the remaining chemicals (from CRIS-105 to CRIS-153, except CRIS-148) were inactive at these assayed concentrations. Finally, the best candidate, G-1 (cytocidal activity of 100% at 10 μg/ml) was in vivo assayed in ovariectomized Wistar rats achieving promising results as a trichomonacidal drug-like compound.

Abstract: Neutral and cationic series of new trimeric β-hydroxy amino or ammonium surfactants were synthesized via a two-step process involving the Williamson etherification and regioselective oxirane ring opening with primary and tertiary amines, which afforded good to excellent yields. The synthesized compounds were obtained in high purity by a simple purification procedure on column chromatography. The critical micelle concentration (CMC), effectiveness of surface tension reduction (γ CMC), surface excess concentration (Γ), and area per molecule at the interface (A) were determined and values indicate that the cationic series is characterized by good surface-active and self-aggregation properties. The antimicrobial activities are reported for the first time against representative bacteria and fungi for trimeric compounds. The antimicrobial potency was found to be dependent on the target microorganism (Gram-positive bacteria > fungi > Gram-negative bacteria), as well as both the neutral or ionic nature (cationic > neutral) and alkyl chain length (tri-C12 > tri-C18 > tri-C8) of the compounds. The tri-C8 and tri-C18 compounds were found to be almost inactive and the tri-C12 compounds, the most potent antimicrobial surface-active agents from the synthesized series. The trimeric C12 cationic compound was found to be comparable to benzalkonium chloride against Gram-positive bacteria and fungi, in vitro. The antimicrobial effectiveness of this new compound and the facile two-step procedure for synthesizing it with an excellent overall yield (92%) provide a cost effective trimeric gemini surfactant.

Abstract: Starting from the four DNA bases order in the Boolean lattice, a novel Lie Algebra of the genetic code is proposed. Here, the main partitions of the genetic code table were obtained as equivalent classes of quotient spaces of the genetic code vector space over the Galois field of the four DNA bases. The new algebraic structure shows strong connections among algebraic relationships, codon assignments and physicochemical properties of amino acids. Moreover, a distance defined between codons expresses a physicochemical meaning. It was also noticed that the distance between wild type and mutant codons tends to be small in mutational variants of four genes: human phenylalanine hydroxylase, human β-globin, HIV-1 protease and HIV-1 reverse transcriptase. These results strongly suggest that deterministic rules in genetic code origin must be involved. [Copyright &y& Elsevier]

A novel algebraic structure of the genetic code is proposed. Here, the principal partitions of the genetic code table were obtained as equivalent classes of quotient spaces of the genetic code vector space over the Galois field of the four DNA bases. The new algebraic structure shows strong connections among algebraic relationships, codon assignment and physicochemical properties of amino acids. Moreover, a distance function defined between the codon binary representations in the vector space was demonstrated to have a linear behavior respect to physical variables such as the mean of amino acids interaction energies in proteins. It was also noticed that the distance between wild type and mutant codons approach to smaller values in mutational variants of four genes, i.e., human phenylalanine hydroxylase, human β-globin, HIV-1 protease and HIV-1 reverse transcriptase. These results strongly suggest that deterministic rules must be involved in the genetic code origin.A novel algebraic structure of the genetic code is proposed. Here, the principal partitions of the genetic code table were obtained as equivalent classes of quotient spaces of the genetic code vector space over the Galois field of the four DNA bases. The new algebraic structure shows strong connections among algebraic relationships, codon assignment and physicochemical properties of amino acids. Moreover, a distance function defined between the codon binary representations in the vector space was demonstrated to have a linear behavior respect to physical variables such as the mean of amino acids interaction energies in proteins. It was also noticed that the distance between wild type and mutant codons approach to smaller values in mutational variants of four genes, i.e., human phenylalanine hydroxylase, human β-globin, HIV-1 protease and HIV-1 reverse transcriptase. These results strongly suggest that deterministic rules must be involved in the genetic code origin.

The hydrogenation of limonene, using 5% Pd/C, 5% Pd/Al2O3and 0.5% Pd/Al2O3catalysts, was studied in a stirred slurry minireactor in a temperature range of 273–323 K, at 106.65 kPa of hydrogen pressure. In the absence of extraparticle and intraparticle mass transfer effects, side products, such as terpinolene, γ-terpinene and p-cymene, were formed besides p-menthene and p-menthane. A significant presence of terpinolene and γ-terpinene indicates that an extensive isomerization precedes hydrogenation, while the presence of p-cymene shows that a dehydrogenation occurs simultaneously. The virtual absence of intermediates, such as α-phellandrene, β-phellandrene and α-terpinene, can be attributed to the fact that conjugated cyclic dienes are too strongly adsorbed to desorb before reacting further. Possible mechanisms of reaction are discussed: the involvement of π-allyl-adsorbed species explains the isomerization process over palladium, but greater isomerization activity observed for alumina-supported catalysts is explained by mechanisms involving Lewis acid sites provided by the alumina. Two possible pathways for isomerization on alumina are recognized: one of them involves the formation of carbonium ions and the other may comprise double-bond migration via allyl route including carbanions. The results suggest that, over alumina, limonene isomerizes via the π-allylic mechanism, whereas terpinolene and terpinene isomerize via the carbonium ion mechanism.

An extension of Silvestri et al.'s (1968, 1970) treatment to extimate kinetic parameters in complex pseudomonomolecular reaction systems including several irreversible reaction steps is proposed. The method allows a considerable reduction of the experimental work while the required computational work is minimal.As an application, the kinetic modelling of the reaction network for the catalytic hydrogenation of methyl linoleate in liquid phase at 398-443 K and 370-647 kPa is presented. Accurate estimates of the various global pseudo-first order rate constants are thus obtained. It is also shown that the apparent co-hydrogenation of double bonds of the methyl linoleate to yield methyl stearate is a mere artifact related only to non-equilibrium chemisorptions.

Mass transfer through cylindrical semipermeable walls is analyzed. The solution is obtained in terms of integral equations. Despite the existence of a non-homogeneous boundary condition on the semipermeable wall, the solution thus obtained is particularly advantageous since the associated eigenvalue problem is independent of the Sherwood number. This parameter takes into account the main conductances at the tube wall.The approach is applied to the case of mass transfer from the interior of a capillary tube with semipermeable walls to an external fluid. The flow in the tube is laminar, and the external flow is assumed turbulent.The mathematical methodology employed provides a framework to develop numerical schemes of fast and sure convergence.

Precise values of the intrinsic selectivities and yields for the hydrogenation products of methyl linolenate (Ln) and methyl linoleate (L) obtained under carefully controlled conditions using a commercial Ni catalyst are presented and analyzed in detail. The existence of a preferential adsorption of Ln and a significant co-hydrogenation of its double bonds are confirmed as being the dominant features under typical vegetable oil processing conditions. It is shown that the values of the selectivities that are obtained from the classical consecutive reactions network account for the intrinsic selectivity of the catalyst only while hydrogenating feedstocks with moderate to low (<10%) contents of Ln.

Hydrogenation of vegetable oils is one of the earliest commercial gas-liquid- solid heterogeneous catalytic processes. usually employed to reduce the degree of unsaturation of the naturally occurring triglycerides so as to obtain new, attractive organoleptic changes, and a greater chemical stability. Due to its intrinsic challenge and to its commercial importance, the process has drawn the attention of numerous scholars. Accordingly, there exists a great deal of work which has both generated empirical rules and allowed us to tackle many of the theoretical aspects of the problem as well.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.