Instituto Politécnico Nacional

About: Instituto Politécnico Nacional is a education organization based out in Mexico City, Mexico. It is known for research contribution in the topics: Population & Control theory. The organization has 43351 authors who have published 63315 publications receiving 938532 citations. The organization is also known as: Instituto Politécnico Nacional & Instituto Politecnico Nacional.

Contact mechanics and rubber friction for randomly rough surfaces with anisotropic statistical properties.

Abstract: In this paper we extend the theory of contact mechanics and rubber friction developed by one of us (B.N.J. Persson, J. Chem. Phys. 115, 3840 (2001)) to the case of surfaces with anisotropic surface roughness. As an application we calculate the viscoelastic contribution to the rubber friction. We show that the friction coefficient may depend significantly on the sliding direction, while the area of contact depends weakly on the sliding direction. We have carried out experiments for rubber blocks sliding on unidirectionally polished steel surfaces. The experimental data are in a good qualitative agreement with the theory.

Methylome analysis reveals an important role for epigenetic changes in the regulation of the Arabidopsis response to phosphate starvation

Abstract: Phosphate (Pi) availability is a significant limiting factor for plant growth and productivity in both natural and agricultural systems. To cope with such limiting conditions, plants have evolved a myriad of developmental and biochemical strategies to enhance the efficiency of Pi acquisition and assimilation to avoid nutrient starvation. In the past decade, these responses have been studied in detail at the level of gene expression; however, the possible epigenetic components modulating plant Pi starvation responses have not been thoroughly investigated. Here, we report that an extensive remodeling of global DNA methylation occurs in Arabidopsis plants exposed to low Pi availability, and in many instances, this effect is related to changes in gene expression. Modifications in methylation patterns within genic regions were often associated with transcriptional activation or repression, revealing the important role of dynamic methylation changes in modulating the expression of genes in response to Pi starvation. Moreover, Arabidopsis mutants affected in DNA methylation showed that changes in DNA methylation patterns are required for the accurate regulation of a number of Pi-starvation–responsive genes and that DNA methylation is necessary to establish proper morphological and physiological phosphate starvation responses.

EmoSenticSpace: a novel framework for affective common-sense reasoning

Abstract: Emotions play a key role in natural language understanding and sensemaking. Pure machine learning usually fails to recognize and interpret emotions in text accurately. The need for knowledge bases that give access to semantics and sentics (the conceptual and affective information) associated with natural language is growing exponentially in the context of big social data analysis. To this end, this paper proposes EmoSenticSpace, a new framework for affective common-sense reasoning that extends WordNet-Affect and SenticNet by providing both emotion labels and polarity scores for a large set of natural language concepts. The framework is built by means of fuzzy c-means clustering and support-vector-machine classification, and takes into account a number of similarity measures, including point-wise mutual information and emotional affinity. EmoSenticSpace was tested on three emotion-related natural language processing tasks, namely sentiment analysis, emotion recognition, and personality detection. In all cases, the proposed framework outperforms the state-of-the-art. In particular, the direct evaluation of EmoSenticSpace against psychological features provided in the benchmark ISEAR dataset shows a 92.15% agreement.

Optimized Analysis of Organic Acids in Edible Mushrooms from Portugal by Ultra Fast Liquid Chromatography and Photodiode Array Detection

Abstract: Organic acid profiles of different mushroom species were obtained by ultra fast liquid chromatography, by means of photodiode array detector. The chromatographic separation was achieved using a SphereClone (Phenomenex) reverse phase C18 column using an isocratic elution with sulphuric acid (3.6 mM) at a flow rate of 0.8 mL/min. All the compounds were separated in 8 min. The method was optimized using Agaricus bisporus sample and proved to be reproducible and accurate. Organic acid profiles were quite homogeneous for all mushroom samples; oxalic, malic and fumaric acids were the main organic acids; some samples also presented quinic and citric acids. Sarcondon imbricatus was the species that presented the highest total content (254.09 mg/g dry weight (dw)), while Bovista nigrescens presented the lowest concentration (1.33 mg/g dw). The high amounts of organic acids present in all the species may suggest that they could be related to the antioxidant activity found in these species and previously reported by us.