This work probes the relevance of oxygen vacancies in the formation of local ferromagnetic coupling between Fe ions at octahedral sites in zinc ferrites. This coupling gives rise to a ferrimagnetic ...ordering with the Curie temperatures above room temperature in an otherwise antiferromagnetic compound. This conclusion is based on experimental results from x-ray magnetic circular dichroism measurements at the Fc L sub(2,3) edges and magnetization measurements performed on zinc ferrites, nanoparticles, and films, with different cation distributions and oxygen vacancy concentrations. Our observations are confirmed by density-functional-theory calculations and indicate that the enhanced ferrimagnetic response observed in some nominally nonmagnetic or antiferromagnetic ferrites can be taken as a further example of the defect-induced magnetism phenomenon.
Coffee is one of the most important commercial traded commodities in the international market, as well as the most popular beverage around the world. In Mexico, organic coffee cultivation ...(specifically, Arabica coffee crops) is a highly demanded that generates up to 500,000 employments in 14 federal entities. Among various coffee producers, Chiapas, Veracruz, and Oaxaca are responsible of 80% of the total coffee production in the country. Currently, Mexico is the leading producer of organic coffee in the world. However, there have been a slow recovery due to the large production losses since 2012, caused by earlier and highly aggressive outbreaks of coffee leaf rust (CLR), in the country, where the infectious agent is known as Hemileia vastatrix (HV). This phenomenon is becoming frequent, and climate change effects could be the main contributors. This spontaneous proliferation was generated in Mexico, due to the precipitation and temperature variability, during the last decade. As result, in Mexico, the biological interaction between coffee crops and their environment has been harmed and crucial characteristics, as crop yield and quality, are particularly being affected, directly by the negative effects of the greenhouse phenomenon, and indirectly, through diseases as CLR. Therefore, this review discusses the contribution of climate change effects in the early development of CLR in Mexico. The focus is also given on possible schemes and actions taken around the world as control measures to adapt the vulnerable coffee varieties to tackle this challenging issue.
Display omitted
•Mexico is the leading producer worldwide regarding organic coffee.•Climate change has a strong relationship with the early development of Hemileia vastatrix.•The variabilities generated in the rainfall and temperature patterns are presented.•More technological strategies and breeding programs must be implemented.
Inconsistent associations between smoking status and prostate cancer (PC) could be due to exposure assessment error. Reconstructing smoking behaviors over the life course could reduce exposure ...assessment error.
As part of a case-control study, we identified 402 incident and histologically confirmed PC cases that were matched by age (±5 years) to 805 population controls. Through direct interview, we obtained information about: age at smoking onset, intensity and frequency of cigarette smoking at different life stages, and smoking cessation age. Smoking status at interview and average smoking index over the lifetime (packs/year) were estimated. Life course smoking patterns were obtained applying the k-means+ method for longitudinal data to the smoking index (pack/year) for each life stage.
Two life-course smoking patterns were identified among ever smokers: "pattern A" characterized by males who reported low and constant smoking intensity (87.8%), and "pattern B" (12.2%) males with an initial period of low intensity, followed by an increase during the second period. Compared to never smokers, pattern B was associated with higher poorly differentiated PC, (OR 2.30; 95% CI 1.21-4.38). No association was observed with average smoking index.
Life course smoking patterns seem to capture the smoking variability during life course and reduce the likelihood of reverse causation. Using this assessment strategy our findings support the potential role of tobacco smoking in PC, particularly poorly differentiated PC. Prospective studies with comprehensive smoking history during the lifetime are needed to confirm these findings.
A mutator is a variant in a population of organisms whose mutation rate is higher than the average mutation rate in the population. For genetic and population dynamics reasons, mutators are produced ...and survive with much greater frequency than anti-mutators (variants with a lower-than-average mutation rate). This strong asymmetry is a consequence of both fundamental genetics and natural selection; it can lead to a ratchet-like increase in the mutation rate. The rate at which mutators appear is, therefore, a parameter that should be of great interest to evolutionary biologists generally; for example, it can influence: (1) the survival duration of a species, especially asexual species (which are known to be short-lived), (2) the evolution of recombination, a process that can ameliorate the deleterious effects of mutator abundance, (3) the rate at which cancer appears, (4) the ability of pathogens to escape immune surveillance in their hosts, (5) the long-term fate of mitochondria, etc. In spite of its great relevance to basic and applied science, the rate of mutation to a mutator phenotype continues to be essentially unknown. The reasons for this gap in our knowledge are largely methodological; in general, a mutator phenotype cannot be observed directly, but must instead be inferred from the numbers of some neutral “marker” mutation that can be observed directly: different mutation-rate variants will produce this marker mutation at different rates. Here, we derive the expected distribution of the numbers of the marker mutants observed, accounting for the fact that some of the mutants will have been produced by a mutator phenotype that itself arose by mutation during the growth of the culture. These developments, together with previous enhancements of the Luria–Delbrück assay (by one of us, dubbed the “Jones protocol”), make possible a novel experimental protocol for estimating the rate of mutation to a mutator phenotype. Simulated experiments using biologically reasonable parameters that employ this protocol show that such experiments in the lab can give us fairly accurate estimates of the rate of mutation to a mutator phenotype. Although our ability to estimate mutation-to-mutator rates from simulated experiments is promising, we view this study as a proof-of-concept study and an important first step towards practical empirical estimation.
B-cell acute lymphoblastic leukemia (B-ALL) is one of the most common childhood cancers worldwide. Although most cases are sporadic, some familial forms, inherited as autosomal dominant traits with ...incomplete penetrance, have been described over the last few years. Germline pathogenic variants in transcription factors such as
, and
have been identified as causal in familial forms. The proband was a 7-year-old Mexican girl diagnosed with high-risk B-ALL at five years and 11 months of age. Family history showed that the proband's mother had high-risk B-ALL at 16 months of age. She received chemotherapy and was discharged at nine years of age without any evidence of recurrence of leukemia. The proband's father was outside the family nucleus, but no history of leukemia or cancer was present up to the last contact with the mother. We performed exome sequencing on the proband and the proband's mother and identified the
variant NM_016734.3:c.963del: p.(Ala322LeufsTer11), located in the transactivation domain of the PAX5 protein. The variant was classified as probably pathogenic according to the ACMG criteria. To the best of our knowledge, this is the first Mexican family with an inherited increased risk of childhood B-ALL caused by a novel germline pathogenic variant of
. Identifying individuals with a hereditary predisposition to cancer is essential for modern oncological practice. Individuals at high risk of leukemia would benefit from hematopoietic stem cell transplantation, but family members carrying the pathogenic variant should be excluded as hematopoietic stem cell donors.
Batoid (rays and skates) populations are declining worldwide, with unknown ecological consequences due to lacking consolidated data on the trophic ecology of these species. Such trends are ...particularly disconcerting in Mexican waters, where batoids are heavily exploited by commercial fisheries. To assess the current state of knowledge of batoid diet in this region, we conducted a meta‐analysis of 54 published stomach content analysis studies. Trophic niche was assessed from 44 total species, including variations due to sex, ontogeny, season, and region, as well as trophic overlap among species. The species assessed belonged to the taxonomic families Urotrygonidae, Dasyatidae, Potamotrygonidae, Mobulidae, Rhinopteridae, Aetobatidae, Gymnuridae, Rhinobatidae, Rajidae, Arhyncobatidae, and Narcinidae. Most of the diet studies to date were conducted in the Mexican Pacific (n = 24), whereas only three studies have come from the Mexican Atlantic, with 27 additional studies coming from other American countries from the tropical and subtropical region. Crustaceans were reported in more than 50% of the species assessed and were also generally the most important prey item, with either high (76%–100%) and medium‐high (51%–75%) importance based on dietary indices from the literature reviewed. While the diet of 40 species (91%) consisted of more than one prey type, feeding strategy analysis (Levin and Shannon–Wiener indices) of 27 species indicated that 25 were specialists and two generalists. Species diets varied with ontogeny (20%), sex (11%), region (11%), and seasonality (9%). According to the reviewed studies, interspecific diet overlap was evident in 36% of species, mainly in the family Urotrygonidae. Batoids were grouped into four trophic guilds: crustacivores (68.1%), annelidivores (primarily polychaetes) (13.6%), molluscivores (11.3%), and piscivores (6.8%), based on the literature reviewed. This study showed that most of the batoids had a specialist crustacean‐based diet. Future research should focus on species devoid of dietary data to encapsulate the trophic niche breadth of this group in Mexican waters, particularly from the Mexican Atlantic and surrounding regions.
Display omitted
•Ru(phpy)(phen)(MeCN)2+ mediated the living radical polymerization of three monomers.•Addition of small amounts of a second cyclometalated Ru catalyst improved the control.•Block ...copolymers synthesis based on these catalytical system was carried out.•It was possible to obtain block copolymers started from different macroinitiators.•Triblock copolymer of PSt-b-PMMA-b-PBA was successfully synthesized.
Living radical polymerizations of three representative monomers, styrene (St), methyl methacrylate (MMA) and n-butyl acrylate (BA) catalyzed by cyclometalated ruthenium(II) complex, cis-Ru(o-C6H4-2-py)(phen)(MeCN)2PF6, has been investigated. It has been shown, that the control over all three homo-polymerizations may be significantly improved in the presence of small amounts of another ruthenium(II) complex, Ru(o-C6H4-2-py)(phen)2PF6, bearing strongly bound bidentate ligands. Although the mechanism of the phenomenon is rather different in the case of St and in the case of MMA and BA polymerizations. The best control was achieved in polymerization of St, while BA polymerization remained the worst controlled. The possibility of formation of sequential di- and tri-block copolymers from these monomers has been demonstrated.
In a disordered system, a quantity is self-averaging when the ratio between its variance for disorder realizations and the square of its mean decreases as the system size increases. Here, we consider ...a chaotic disordered many-body quantum system and search for a relationship between self-averaging behavior and the properties of the distributions over disorder realizations of various quantities and at different timescales. An exponential distribution, as found for the survival probability at long times, explains its lack of self-averaging, since the mean and the dispersion are equal. Gaussian distributions, however, are obtained for both self-averaging and non-self-averaging quantities. Our studies show also that one can make conclusions about the self-averaging behavior of one quantity based on the distribution of another related quantity. This strategy allows for semianalytical results, and thus circumvents the limitations of numerical scaling analysis, which are restricted to few system sizes.
ResumenDesde la publicación en 2008 de las guías de diagnóstico y tratamiento de la enfermedad diverticular del colon de la Asociación Mexicana de Gastroenterología ha habido avances significativos ...en el conocimiento de esta enfermedad. Se realizó una revisión sistemática de la literatura en PubMed de enero de 2008 a julio de 2018 con el fin de revisar y actualizar las guías 2008 y proporcionar nuevas recomendaciones basadas en la evidencia. Se incluyeron todas las publicaciones en español e inglés, de alta calidad. Se redactaron los enunciados, que fueron votados utilizando el método Delphi. Se estableció la calidad de la evidencia y la fuerza de las recomendaciones según el sistema GRADE para cada enunciado. Cuarenta y tres enunciados fueron finalmente votados y calificados. Se informan nuevos datos sobre definición, clasificación, epidemiología, fisiopatología y factores de riesgo. Se revisó con especial énfasis la utilidad de la tomografía computarizada y de la colonoscopia, así como los métodos endoscópicos para el control de la hemorragia. Se discutió sobre el tratamiento ambulatorio de la diverticulitis no complicada, el papel de la rifaximina y la mesalazina, en el manejo de la diverticulitis aguda complicada tanto en sus alternativas mínimamente invasivas hasta las opciones quirúrgicas con énfasis en sus indicaciones, limitaciones y contraindicaciones. Los nuevos enunciados proporcionan directrices basadas en la evidencia actualizada. Se presentan la discusión, el grado y la fuerza de la recomendación de cada uno de ellos.
Fiber type composition, organization, and distribution are key elements in muscle functioning. These properties can be modified by intrinsic and/or extrinsic factors, such as undernutrition and ...injuries. Currently, there is no methodology to quantitatively analyze such modifications. On one hand, we propose a fractal approach to determine fiber type organization, using the fractal correlation method in software Fractalyse. On the other hand, we applied the kernel methodology from machine learning to build radial-basis functions for the spatial distribution of fibers (distribution functions), by dividing into square cells a two-dimensional binary image for the spatial distribution of fibers from a muscle fascicle and mounting on each cell a radial-basis function in such a way that the sum of all cell functions creates a smooth version of the fiber histogram on the cell grid. The distribution functions thus created belong in a reproducing kernel Hilbert space which permits us to regard them as vectors and measure distances and angles between them. In the present study, we analyze fiber type organization and distribution in fascicles (F2, F3, F4, and F5) of the
extensor digitorum longus
muscle (EDLm) from control and undernourished male rats. Fibers were classified according to the ATPase activity in slow, intermediate, and fast. Then, (
x, y
) coordinates of fibers were used to build binary images and distribution functions for each fiber type and both conditions. The fractal organization analysis showed that fast and intermediate fibers, from both groups, had a fractal organization within the four fascicles, i.e., the fiber assembly is distributed in clusters. We also show that chronic undernutrition altered the organization of fast fibers in the F3, although it still is considered a fractal organization. Distribution function analysis showed that each fiber type (slow, intermediate, and fast) has a unique distribution within the fascicles, in both conditions. However, chronic undernutrition modified the intra-fascicular fiber type distributions, except in the F2. Altogether, these results showed that the methodology herein proposed allows for analyzing fiber type organization and distribution modifications. On the other side, we show that chronic undernutrition alters not only the fiber type composition but also the organization and distribution, which could affect the muscle functioning, and ultimately, its behavior (e.g., locomotion).
PDF
