Determination of liquid-vapor equilibrium and critical properties of fatty acids for biodiesel production through molecular dynamics.

In recent years, biodiesel production has emerged as an option for renewable and green fuel generation due to the constant reduction of fossil fuel reservoirs. Biofuels as biodiesel also show valuable attributes, environmentally speaking, due to their low environmental impact, contributing to the achievement of sustainability. However, costs are not allowable for large-scale production. Thereby, several novel processes have been proposed (e.g., reactive distillation) to solve this issue. An inconvenience for the development of these processes is the little information in the literature about the critical properties of fatty acids, which are precursors of biodiesel. Determination of critical properties for fatty acids through experimentation is difficult. The reason is that fatty acids tend to self-associate (to dimerize) due to carboxylic groups presence through hydrogen bonds, and consequently, have higher boiling points than other compounds of similar molecular mass (e.g., hydrocarbons, esters). Therefore, alternative methods for this determination are required. One choice is the group-contribution method, which is based on the structure of the molecule; however, results can significantly vary among different group-contribution approaches. Another alternative (and the focus of this research) for the determination of these properties is molecular simulation techniques. In this work, the liquid-vapor equilibrium as a function of temperature and the surface tension of three pure fatty acids of long chain (linoleic, oleic, and palmitic acid) have been calculated. Simulations have been performed by molecular dynamics using the method of direct determination of phase coexistence with the software GROMACS; in which the transferable potentials for phase equilibria united atom forcefield (TraPPE-UA) have been implemented for these specific molecules. Orthobaric densities and surface tension values have been reported at temperatures near the critical point (from 650 K to 800 K). Critical properties (temperature, pressure, density) have been extrapolated from trajectories obtained in these simulations using scaling law relations. Critical properties for these compounds are not available experimentally, therefore, group contribution calculations from the literature were used as a reference. In this comparison, the palmitic acid properties calculated in this work, show the best agreement among the three substances investigated.

Sleep Phases in Crayfish: Relationship Between Brain Electrical Activity and Autonomic Variables.

In vertebrates like mammals and birds, two types of sleep have been identified: rapid eye movement and non-rapid eye movement sleep. Each one is associated with specific electroencephalogram patterns and is accompanied by variations in cardiac and respiratory frequencies. Sleep has been demonstrated only in a handful of invertebrates, and evidence for different sleep stages remains elusive. Previous results show that crayfish sleeps while lying on one side on the surface of the water, but it is not known if this animal has sleep phases. Heart rate and respiratory frequency are modified by diverse changes in the crayfish environment during wakefulness, and previously, we showed that variations in these variables are present during sleep despite that there are no autonomic anatomical structures described in this animal. Here, we conducted experiments to search for sleep phases in crayfish and the relationships between sleep and cardiorespiratory activity. We used the wavelet transform, grouping analysis with k-means clustering, and principal component analysis, to analyze brain and cardiorespiratory electrical activity. Our results show that (a) crayfish can sleep lying on one side or when it is motionless and (b) the depth of sleep (measured as the power of electroencephalographic activity) changes over time and is accompanied by oscillations in cardiorespiratory signal amplitude and power. Finally, we propose that in crayfish there are at least three phases of sleep.

Clinical-therapeutic study on the efficacy and safety of thalidomide in the management of discoid lupus erythematosus. A single-centre, retrospective study.

Thalidomide is a second-line treatment for discoid lupus erythematosus (DLE). The efficacy of this treatment, the minimum effective doses, and safety is poorly documented in the literature. The aim of the study was to determine the efficacy and tolerance of thalidomide as first or second line of therapy for discoid lupus erythematosus. We present a retrospective single-centre study of 68 patients with DLE treated with thalidomide from 2003 to 2019. The inclusion criteria were the presence of clinical lesions suggestive of DLE, confirmed by histological examination and direct immunofluorescence. The mean age at diagnosis was 37.45 years (range 18-65 years). Thalidomide was started an average of 2.25 years after the diagnosis of DLE, as second-line therapy in 85% of the cases (58 patients), and as first-line therapy in 10 patients (15%). Fifty-six patients improved with thalidomide (82%), 39 cases achieved complete remission and 17 partial remissions. The mean duration of follow-up with thalidomide was 8.4 months (range 3-25 months). Five patients discontinued thalidomide due to adverse events. The most frequent side effect was headache (23.5%). Thalidomide is effective and safe in DLE patients as first or second-line treatment with a good safety profile.

Solution structure of the inhibitor of cysteine proteases 1 from Entamoeba histolytica reveals a possible auto regulatory mechanism.

The genome of Entamoeba histolytica encodes approximately 50 Cysteine Proteases (CPs) whose activity is regulated by two Inhibitors of Cysteine Proteases (ICPs), EhICP1 and EhICP2. The main difference between both EhICPs is the acquisition of a 17 N-terminal targeting signal in EhICP2 and three exposed cysteine residues in EhICP1. The three exposed cysteines in EhICP1 potentiate the formation of cross-linking species that drive heterogeneity. Here we solved the NMR structure of EhICP1 using a mutant protein without accessible cysteines. Our structural data shows that EhICP1 adopts an immunoglobulin fold composed of seven ß-strands, and three solvent exposed loops that resemble the structures of EhICP2 and chagasin. EhICP1 and EhICP2 are able to inhibit the archetypical cysteine protease papain by intercalating their BC loops into the protease active site independently of the character of the residue (serine or threonine) responsible to interact with the active site of papain. EhICP1 and EhICP2 present signals of functional divergence as they clustered in different clades. Two of the three exposed cysteines in EhICP1 are located at the DE loop that intercalates into the CP substrate-binding cleft. We propose that the solvent exposed cysteines of EhICP1 play a role in regulating its inhibitory activity and that in oxidative conditions, the cysteines of EhICP1 react to form intra and intermolecular disulfide bonds that render an inactive inhibitor. EhICP2 is not subject to redox regulation, as this inhibitor does not contain a single cysteine residue. This proposed redox regulation may be related to the differential cellular localization between EhICP1 and EhICP2.

Hierarchical complex self-assembly in binary nanoparticle mixtures.

Hierarchical self-assembly of soft matter provides a powerful route to create complex materials with enhanced physical properties. The understanding of the fundamental processes leading to such organization can provide design rules to create new functional materials. In this work, we use a simple model of polymer-grafted nanoparticles to explore the self-assembly of binary mixtures. By using Monte Carlo simulations we study the interplay of composition, density and particle sizes on the self-organization of such nanoparticle systems. It is found that complex hierarchical organization can take place for conditions where one-component systems form simple lattices. In particular, a mixture where one component forms a structure with 18-fold symmetry in a sea of an apparent disordered phase of the second component is observed to emerge for certain parameter combinations.

Who is the boss? Individual recognition memory and social hierarchy formation in crayfish.

Under laboratory conditions, crayfish establish hierarchical orders through agonistic encounters whose outcome defines the dominant one and one, or more, submissive animals. These agonistic encounters are ritualistic, based on threats, pushes, attacks, grabs, and avoidance behaviors that include retreats and escape responses. Agonistic behavior in a triad of unfamiliar, size-matched animals is intense on the first day of social interaction and the intensity fades on daily repetitions. The dominant animal keeps its status for long periods, and the submissive ones seem to remember 'who the boss is'. It has been assumed that animals remember and recognize their hierarchical status by urine signals, but the putative substance mediating this recognition has not been reported. The aim of this work was to characterize this hierarchical recognition memory. Triads of unfamiliar crayfish (male animals, size and weight-matched) were faced during standardized agonistic protocols for five consecutive days to analyze memory acquisition dynamics (Experiment 1). In Experiment 2, dominant crayfish were shifted among triads to disclose whether hierarchy depended upon individual recognition memory or recognition of status. The maintenance of the hierarchical structure without behavioral reinforcement was assessed by immobilizing the dominant animal during eleven daily agonistic encounters, and considering any shift in the dominance order (Experiment 3). Standard amnesic treatments (anisomycin, scopolamine or cold-anesthesia) were given to all members of the triads immediately after the first interaction session to prevent individual recognition memory consolidation and evaluate its effect on the hierarchical order (Experiment 4). Acquisition of hierarchical recognition occurs at the first agonistic encounter and agonistic behavior gradually diminishes in the following days; animals keep their hierarchical order despite the inability of the dominant crayfish to attack the submissive ones. Finally, blocking of protein synthesis or muscarinic receptors and cold anesthesia impair memory consolidation. These findings suggest that agonistic encounters induces the acquisition of a robust and lasting social recognition memory in crayfish.

Disruption of behavior and brain metabolism in artificially reared rats.

Early adverse life stress has been associated to behavioral disorders that can manifest as inappropriate or aggressive responses to social challenges. In this study, we analyzed the effects of artificial rearing on the open field and burial behavioral tests and on GFAP, c-Fos immunoreactivity, and glucose metabolism measured in anxiety-related brain areas. Artificial rearing of male rats was performed by supplying artificial milk through a cheek cannula and tactile stimulation, mimicking the mother's licking to rat pups from the fourth postnatal day until weaning. Tactile stimulation was applied twice a day, at morning and at night, by means of a camel brush on the rat anogenital area. As compared to mother reared rats, greater aggressiveness, and boldness, stereotyped behavior (burial conduct) was observed in artificially reared rats which occurred in parallel to a reduction of GFAP immunoreactivity in somatosensory cortex, c-Fos immunoreactivity at the amygdala and primary somatosensory cortex, and lower metabolism in amygdala (as measured by 2-deoxi-2-[18 fluoro]-d-glucose uptake, assessed by microPET imaging). These results could suggest that tactile and/or chemical stimuli from the mother and littermates carry relevant information for the proper development of the central nervous system, particularly in brain areas involved with emotions and social relationships of the rat. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 77: 1413-1429, 2017.

Sleep in invertebrates: crayfish.

Although sleep is a very conspicuous behavior in all animals that we are frequently in contact with and possibly in many others, its scientific study was for many years restricted to very few of them. However, since the end of the XX century there have been studies about sleep in several animals and currently many of them attempt to found, first, if all animals sleep and second, if their sleep is similar to that of other animals. An important objective of this search is to identify the animal species in which sleep originated, which might gives us clues about the need that was fulfilled by such behavior. The search started with insects, among the most developed arthropods, but has now been expanded to include other invertebrates, among them crustaceans. In this work we review some aspects of sleep in invertebrates, focusing on the crustacean crayfish, animals in which both, behavioral and electrophysiological studies have been conducted and whose results show surprising similarities with sleep in mammals.

Slow waves during sleep in crayfish. Origin and spread.

Previous results show that when unrestrained crayfish sleep, the electrical activity of the brain changes from multiple spikes (frequencies above 300 Hz) on a flat baseline to continuous slow waves at a frequency of 15-20 Hz. To study the temporal organization of such activity, we developed a tethered crayfish preparation that allows us to place electrodes on visually identified regions of the brain. Recording the electrical activity of different brain areas shows that when the animal is active (awake), slow waves are present only in the central complex. However, simultaneously with the animal becoming limp (sleeping), slow waves spread first to deuto- and then to protocerebrum, suggesting that the central complex of the crayfish brain acts as the sleep generator.

Rehabilitación de niños y jóvenes farmacodependientes a través de un Programa Comunitário de Consulta Externa / Rehabilitation of pharmacodependent children and adolescents though a Community Program in out patient clinic

En 1977 se inició un Programa Piloto, basado en el modelo de "La Familia Enseñante", dirigido inicialmente a niños inhaladores de disolventes industriales entre los 7 y 13 años de edad, y posteriormente a jóvenes polifarmacodependientes entre los 14 y 25 años de edad, con la variante de brindar el tratamiento bajo una modalidad de consulta externa con el fin de atender a un mayor número de casos. Desde el año de 1982, el Programa Piloto cuenta con tres alternativas de tratamiento, las cuales difieren entre sí en cuanto a su aproximación al problema del abuso de drogas, a su duración y a la intensidad del tratamiento, aunque todas ellas se ofrecen bajo la misma modalidad de consulta externa dentro de un Centro Comunitario ubicado en una zona de alto riesgo. La primera alternativa es el Tratamiento a Largo Plazo. La segunda alternativa es el Tratamiento a Corto Plazo y la tercera alternativa es el Tratamiento Combinado. A fin de evaluar experimentalmente el grado de efectividad de cada una de estas alternativas de tratamiento, durante el año de 1983 se seleccionó una muestra de 60 sujetos farmacodependientes divididos en cuatro grupos (tres grupos experimentales y un grupo sin tratamiento) compuestos de 15 sujetos cada uno. Los instrumentos empleados para este estudio fueron los siguientes: a) Entrevista Inicial, de la cual se obtuvieron básicamente las características sociodemográficas de los sujetos; b) Autoreporte sobre Delincuencia y Farmacodependencia, del cual se obtuvieron los patrones del consumo de drogas de los sujetos, y c) Entrevista de Seguimiento a través de los Padres, de la cual se obtuvieron las medidas subjetivas sobre la efectividad del tratamiento y el grado de satisfacción reportado por los padres. Los resultados son presentados de acuerdo a la siguiente clasificación: Características generales de los sujetos. Características relacionadas con la farmacodependencia. Efectividad de las alternativas de tratamiento. Se encontró que el Tratamiento Combinado fue en el que se registro la menor deserción de sujetos durante el tratamiento (20%), siguiéndole el tratamiento a Corto Plazo (26.6%) y finalmente el Tratamiento a Largo Plazo (33.3%)