Microcanonical versus Canonical Analysis of Protein Folding

The microcanonical analysis is shown to be a powerful tool to characterize the protein folding transition and to neatly distinguish between good and bad folders. An off-lattice model with parameter chosen to represent polymers of these two types is used to illustrate this approach. Both canonical and microcanonical ensembles are employed. The required calculations were performed using parallel tempering Monte Carlo simulations. The most revealing features of the folding transition are related to its first-order-like character, namely, the S-bend pattern in the caloric curve, which gives rise to negative microcanonical specific heats, and the bimodality of the energy distribution function at the transition temperatures. Models for a good folder are shown to be quite robust against perturbations in the interaction potential parameters.Comment: 4 pages, 4 figure

Pattern-induced anchoring transitions in nematic liquid crystals

In this paper we revisit the problem of a nematic liquid crystal in contact with patterned substrates. The substrate is modelled as a periodic array of parallel infinite grooves of well-defined cross section sculpted on a chemically homogeneous substrate which favors local homeotropic anchoring of the nematic. We consider three cases: a sawtooth, a crenellated and a sinusoidal substrate. We analyse this problem within the modified Frank-Oseen formalism. We argue that, for substrate periodicities much larger than the extrapolation length, the existence of different nematic textures with distinct far-field orientations, as well as the anchoring transitions between them, are associated with the presence of topological defects either on or close to the substrate. For the sawtooth and sinusoidal case, we observe a homeotropic to planar anchoring transition as the substrate roughness is increased. On the other hand, a homeotropic to oblique anchoring transition is observed for crenellated substrates. In this case, the anchoring phase diagram shows a complex dependence on the substrate roughness and substrate anchoring strength.Comment: 36 pages, 15 figures, revised version submitted to Journal of Physics: Condensed Matte

Binding of SARS-CoV-2 to cell receptors: a tale of molecular evolution

The magnified infectious power of the SARS-CoV-2 virus compared to its precursor SARS-CoV is intimately linked to an enhanced ability in the mutated virus to find available hydrogen bond sites in the host cells. This characteristic is acquired during virus evolution because of the selective pressure exerted at the molecular level. We pinpoint the specific residue (in the virus) to residue (in the cell) contacts during the initial recognition and binding and show that the virus\ub7 \ub7 \ub7 cell interaction is mainly due to an extensive network of hydrogen bonds and to a large surface of non-covalent interactions. In addition to the formal quantum characterization of bonding interactions, computation of absorption spectra for the specific virus\ub7 \ub7 \ub7 cell interacting residues yields significant shifts of 06\u3bb max = 47 and 66 nm in the wavelength for maximum absorption in the complex with respect to the isolated host and virus, respectively

Inverting Adversarially Robust Networks for Image Synthesis

Recent research in adversarially robust classifiers suggests their representations tend to be aligned with human perception, which makes them attractive for image synthesis and restoration applications. Despite favorable empirical results on a few downstream tasks, their advantages are limited to slow and sensitive optimization-based techniques. Moreover, their use on generative models remains unexplored. This work proposes the use of robust representations as a perceptual primitive for feature inversion models, and show its benefits with respect to standard non-robust image features. We empirically show that adopting robust representations as an image prior significantly improves the reconstruction accuracy of CNN-based feature inversion models. Furthermore, it allows reconstructing images at multiple scales out-of-the-box. Following these findings, we propose an encoding-decoding network based on robust representations and show its advantages for applications such as anomaly detection, style transfer and image denoising

Ring Vibrations to Sense Anionic Ibuprofen in Aqueous Solution as Revealed by Resonance Raman

We unravel the potentialities of resonance Raman spectroscopy to detect ibuprofen in diluted aqueous solutions. In particular, we exploit a fully polarizable quantum mechanics/molecular mechanics (QM/MM) methodology based on fluctuating charges coupled to molecular dynamics (MD) in order to take into account the dynamical aspects of the solvation phenomenon. Our findings, which are discussed in light of a natural bond orbital (NBO) analysis, reveal that a selective enhancement of the Raman signal due to the normal mode associated with the C–C stretching in the ring, νC=C, can be achieved by properly tuning the incident wavelength, thus facilitating the recognition of ibuprofen in water samples

Making Vision Transformers Truly Shift-Equivariant

For computer vision, Vision Transformers (ViTs) have become one of the go-to deep net architectures. Despite being inspired by Convolutional Neural Networks (CNNs), ViTs' output remains sensitive to small spatial shifts in the input, i.e., not shift invariant. To address this shortcoming, we introduce novel data-adaptive designs for each of the modules in ViTs, such as tokenization, self-attention, patch merging, and positional encoding. With our proposed modules, we achieve true shift-equivariance on four well-established ViTs, namely, Swin, SwinV2, CvT, and MViTv2. Empirically, we evaluate the proposed adaptive models on image classification and semantic segmentation tasks. These models achieve competitive performance across three different datasets while maintaining 100% shift consistency

Hemoglobin Mass, Blood Volume and VO₂max of Trained and Untrained Children and Adolescents Living at Different Altitudes

Introduction: To a considerable extent, the magnitude of blood volume (BV) and hemoglobin mass (Hbmass) contribute to the maximum O(2)-uptake (VO(2)max), especially in endurance-trained athletes. However, the development of Hbmass and BV and their relationships with VO(2)max during childhood are unknown. The aim of the present cross-sectional study was to investigate Hbmass and BV and their relationships with VO(2)max in children and adolescents. In addition, the possible influence of endurance training and chronic hypoxia was evaluated. Methods: A total of 475 differently trained children and adolescents (girls n = 217, boys n = 258; untrained n = 171, endurance trained n = 304) living at two different altitudes (∼1,000 m, n = 204, ∼2,600 m, n = 271) and 9–18 years old participated in the study. The stage of puberty was determined according to Tanner; Hbmass and BV were determined by CO rebreathing; and VO(2)max was determined by cycle ergometry and for runners on the treadmill. Results: Before puberty, there was no association between training status and Hbmass or BV. During and after puberty, we found 7–10% higher values in the trained groups. Living at a moderate altitude had a uniformly positive effect of ∼7% on Hbmass in all groups and no effect on BV. The VO(2)max before, during and after puberty was strongly associated with training (pre/early puberty: boys +27%, girls +26%; mid puberty: +42% and +45%; late puberty: +43% and +47%) but not with altitude. The associated effects of training in the pre/early pubertal groups were independent of Hbmass and BV, while in the mid- and late pubertal groups, 25% of the training effect could be attributed to the elevated Hbmass. Conclusions: The associated effects of training on Hbmass and BV, resulting in increased VO(2)max, can only be observed after the onset of puberty

Minerales de Mn-Co-Ni en las lateritas De Cuba oriental: resultados preliminares

En los yacimientos de lateritas niquelíferas, el Ni y Co pueden ser incorporados en óxidos e hidróxido s de Mn, donde han precipitados mediante reacciones redox (Elias et al., 1981). Además de asbolanas (ricas en Ni y ricas en Co), otros minerales que contienen Co son heterogenita y litioforita (Chukhrov et al., 1 983; Manceau et al., 1987; Llorca y Monchoux, 1991)

Calidad de vida relacionada con salud en la población Colombiana: ¿cómo valoran los colombianos su estado de salud?

Objetivo Determinar la percepción sobre la calidad de vida relacionada con salud (CVrS) que tiene la población adulta en Colombia.Métodos encuesta poblacional en una muestra representativa de la población rural y urbana, de 18 y más años. Se midió la CVrS con el instrumento EQ5D-3L y la escala visual análoga, como parte de la cuarta Encuesta Nacional de Salud Mental. Las estimacionesfueron ajustadas por el diseño de muestreo y se acompañan de intervalos de confianza al 95 %.Resultados 1 0867 personas completaron la medición; 69,7 % (IC95 % 66,9 a 68,9) de la población reporto estar en “salud completa”; la mayor proporción de personas valoraronsu salud por encima de 80 puntos. La presencia de “moderado dolor o malestar”, seguida de estar “moderadamente angustiado o deprimido” fueron las alteraciones más frecuentes. Los adultos jóvenes tienden a valorar mejor su salud que los adultosmayores. No hay diferencias en la percepción de la salud entre regiones del país.Conclusiones La calidad de vida relacionada con salud en la población colombiana  es mayor de 80 puntos en una escala de 1 a 100. Las alteraciones como angustia y depresión y la percepción del dolor, fueron las más comúnmente reportadas por los colombianos. La situación de pobreza y el bajo nivel educacional son determinantes de la valoración que hacen los colombianos de su CVrS.Objective To determine the perception about quality of life related to health in the adult population of Colombia.Methods Population-based survey applied on a representative sample of the Colombian rural and urban population, aged 18 years or more. Quality of life related to health was measured using the generic EQ5D instrument and the analogue visual scale aspart of the fourth National Mental Health Survey. Estimates were accompanied by 95 % confidence intervals and were adjusted by the sampling design.Results 10 867 people aged 18 years or older completed the measurement. 69.7 % (CI95 %; 66.9-68.9) of the population reported being "completely healthy". Most of the population rated their health condition above 80 points. The presence of "moderatepain or discomfort", followed by being "moderately distressed or depressed" were the most frequent alterations. Young adults tend to perceive their health better than older adults. There is no difference in the perception of health between regions of the country.Conclusions Quality of life related to health in the Colombian population is greater than 80 points on a scale of 1 to 100. Alterations such as angst and depression and the perception of pain were the most frequently reported by Colombians. Poverty and alow level of education are determinants of the perception of Colombians regarding their quality of life related to health

Flujo en medio poroso no saturado con conductividad hidráulica discontinua (planteamiento del problema)

When studying the flow in an unsaturated porous medium from a point recharge, two phenomena are identified: In the first the residual soil retention conditions are negligible, the mass of water available to flow is constant in time, for So the dimensional analysis considering first order self similarity is sufficient to solve the known diffusion equation. Conversely, if residual soil retention is taken into account, the mass of water available to flow is variable over time because the capillary forces retain some of the water in the pores, so that the mass does not comply with a law Of conservation and the assumption of previous self similarity is not valid. Then another type of self-similar assumption is called the second order, in which the so-called anomalous exponents appear. Under these conditions the equation to be solved is nonlinear with discontinuous coefficient and is called the Baremblatt Equation. The dimensional analysis is not enough to obtain the complete solution one goes to other different techniques, in this case to solve a problem of self value. In the second part will present the numerical solution and the application of this problemCuando se estudia elflujo en un medio poroso no saturado a partir de una recarga puntual, seidentifican dos fenómenos: En el primero las condiciones de retención residual del suelo sondespreciables, la masa de agua disponible para fluir es constante en el tiempo, por lo tanto elanálisis dimensional considerando autosimilaridad de primer orden es suficientepara solucionarla conocida Ecuación de difusión. Por el contrario, si se tiene en cuenta la retención residualdel suelo, la masa de agua disponible para fluir es variable con el tiempo debido a que lasfuerzas de capilaridad retienen parte del agua en los poros, por lo tanto la masa no cumple unaley de conservación y la suposición de autosimilaridad anterior no es válida. Se consideraentonces otro tipo de suposición autosimilar llamada de segundo orden, en la cual aparecen losllamados exponentes anómalos. Bajo estas condiciones la ecuación a solucionar es no linealcon coeficiente discontinuo y recibe el nombre deEcuación de Baremblatt. El análisis dimensionalno es suficientepara obtener la solución completa y se acude a otras técnicas diferentes, en estecaso a resolver un problema de autovalor. En la segunda parte sepresentara la solución numericay la aplicación de este problema