National Autonomous University of Mexico

About: National Autonomous University of Mexico is a education organization based out in Mexico City, Distrito Federal, Mexico. It is known for research contribution in the topics: Population & Galaxy. The organization has 72868 authors who have published 127797 publications receiving 2285543 citations. The organization is also known as: UNAM & Universidad Nacional Autónoma de México.

Some aspects of source characteristics of the 19 September 1985 Michoacan earthquake and ground motion amplification in and near Mexico City from strong motion data

Abstract: The Fourier amplitude ratio of the 19 September ( M s = 8.1) to the 21 September 1985 ( M s = 7.6), Michoacan earthquakes obtained from data in and near Mexico City increases from about 3.5 at 0.5 Hz to about 10 at 0.2 Hz. This increase is neither seen in the coastal data nor in the teleseismic broadband GDSN P -wave spectra. It is also not predicted by ω −2 or Gusev9s scaling laws. We tentatively attribute the increase at frequencies of less than 0.5 Hz to a special path and/or a depth of energy release effect for the 19 September earthquake. The damage to Mexico City is mostly related to 0.5 Hz energy. Since at f ≧ 0.5 Hz, the Fourier amplitude ratios in and near Mexico City, along the coast, and at teleseismic distances are nearly equal; we attribute this energy to the source characteristics of the 19 September earthquake. The evidence suggests that the 19 September was about twice more energetic at f ≃ 0.5 Hz than expected from scaling laws and from spectral regression of coastal earthquakes recorded in Mexico City. The analysis of strong motion data recorded in Mexico City shows that the ground motions in the lake bed zone are amplified by 8 to 50 times with respect to a hill zone site in Ciudad Universitaria. The frequency at which the maximum relative amplification occurs varies from site to site and lies between 0.2 and 0.7 Hz. The data suggest that f o = β/4 H , where f o = frequency at which maximum relative amplitude occurs, and β and H are the shear wave velocity and the thickness of the clay layer, respectively. Relatively small, if any, nonlinear behavior of the clay is found at strains of about 0.2 per cent during the great 19 September earthquake. For a given lake bed site, maximum relative amplitude and f o are roughly constant, independent of magnitude, depth, and azimuth of sources located more than about 200 km. Ground motion at lake bed sites in Mexico City with f o ≃ 0.5 Hz appear to be amplified 75 times with respect to hard-rock coastal sites at equal distances from the source. This is also confirmed by M L calculation of the 19 and 21 September earthquakes. For the 19 and 21 September earthquakes, the average values of M L at hard-rock coastal sites (100 ≦ distance ≦ 250 km) are 7.4 and 6.7, whereas they are 8.7 and 8.4 in the lake bed zone (distance ∼300 km), respectively.

CircRNA accumulation in the aging mouse brain.

Abstract: Circular RNAs (circRNAs) are a newly appreciated class of RNAs expressed across diverse phyla. These enigmatic transcripts are most commonly generated by back-splicing events from exons of protein-coding genes. This results in highly stable RNAs due to the lack of free 5' and 3' ends. CircRNAs are enriched in neural tissues, suggesting that they might have neural functions. Here, we sought to determine whether circRNA accumulation occurs during aging in mice. Total RNA-seq profiling of young (1 month old) and aged (22 month old) cortex, hippocampus and heart samples was performed. This led to the confident detection of 6,791 distinct circRNAs across these samples, including 675 novel circRNAs. Analysis uncovered a strong bias for circRNA upregulation during aging in neural tissues. These age-accumulation trends were verified for individual circRNAs by RT-qPCR and Northern analysis. In contrast, comparison of aged versus young hearts failed to reveal a global trend for circRNA upregulation. Age-accumulation of circRNAs in brain tissues was found to be largely independent from linear RNA expression of host genes. These findings suggest that circRNAs might play biological roles relevant to the aging nervous system.

Electronic and optical properties of strained graphene and other strained 2D materials: a review

Abstract: This review presents the state of the art in strain and ripple-induced effects on the electronic and optical properties of graphene. It starts by providing the crystallographic description of mechanical deformations, as well as the diffraction pattern for different kinds of representative deformation fields. Then, the focus turns to the unique elastic properties of graphene, and to how strain is produced. Thereafter, various theoretical approaches used to study the electronic properties of strained graphene are examined, discussing the advantages of each. These approaches provide a platform to describe exotic properties, such as a fractal spectrum related with quasicrystals, a mixed Dirac-Schrodinger behavior, emergent gravity, topological insulator states, in molecular graphene and other 2D discrete lattices. The physical consequences of strain on the optical properties are reviewed next, with a focus on the Raman spectrum. At the same time, recent advances to tune the optical conductivity of graphene by strain engineering are given, which open new paths in device applications. Finally, a brief review of strain effects in multilayered graphene and other promising 2D materials like silicene and materials based on other group-IV elements, phosphorene, dichalcogenide- and monochalcogenide-monolayers is presented, with a brief discussion of interplays among strain, thermal effects, and illumination in the latter material family.

Differences in Perception of Everyday Odors: a Japanese-German Cross-cultural Study

Abstract: There is a growing appreciation that experience with odors may strongly influence their perception. To further investigate this, the responses of 40 Japanese and 44 age-matched German women to everyday odorants were compared. Subjects were presented with 18 stimuli in squeeze bottles and asked to rate them according to intensity, familiarity, pleasantness and edibility, to describe associations elicited by them and, if possible, to name them. One-third of the odorants were presumed to be familiar to the Japanese only, one-third to the Germans and one-third to both populations. Significant differences were found between the two populations on all measures. Better performance by the Japanese in providing appropriate descriptors for 'Japanese' odorants and by the Germans for 'European' odorants supported the pre-selection of stimuli as culture-typical. Particularly clear differences between the two populations were found in pleasantness ratings. In general, a positive relationship was found between pleasantness and judgement of stimuli as edible, suggesting that culture-specific experiences-particularly of foods-may significantly influence odor perception. Somewhat unexpectedly, significant differences were also found between the two populations in intensity ratings for some odorants. These differences did not seem simply to be artefacts of the test situation and raise the possibility that experience may even influence such basic aspects of odor perception as stimulus intensity.

A computational methodology for accurate predictions of rate constants in solution: application to the assessment of primary antioxidant activity.

Abstract: The accurate prediction of rate constants for chemical reactions in solution, using computational methods, is a challenging task. In this work, a computational protocol designed to be a reliable tool in the study of radical-molecule reactions in solution is presented. It is referred to as quantum mechanics-based test for overall free radical scavenging activity (QM-ORSA) because it is mainly intended to provide a universal and quantitative way of evaluating the free radical scavenging activity of chemical compounds. That is, its primary antioxidant activity. However, it can also be successfully applied to obtain accurate kinetic data for other chemical reactions in solution. The QM-ORSA protocol has been validated by comparison with experimental results, and its uncertainties have been proven to be no larger than those arising from experiments. Further applications of QM-ORSA are expected to contribute increasing the kinetic data for free radical-molecule reactions relevant to oxidative stress, which is currently rather scarce.