Proper Motion of Pulsar B1800-21

We report high angular resolution, multi-epoch radio observations of the young pulsar PSR B1800-21. Using two pairs of data sets, each pair spanning approximately a ten year period, we calculate the proper motion of the pulsar. We obtain a proper motion of mu_alpha=11.6 +- 1.8 mas/yr, mu_delta=14.8 +- 2.3 mas/yr, which clearly indicates a birth position at the extreme edge of the W30 supernova remnant. Although this does not definitively rule out an association of W30 and PSR B1800-21, it does not support an association.Comment: 13 pages, 1 color figure. Replaced with version accepted for publication in Astrophysical Journa

Hyperspherical Close-Coupling Calculations for Electron-Capture Cross Sections in Low-Energy Ne¹⁰⁺ +H (1s) Collisions

We present total and partial electron-capture cross sections for Ne¹⁰⁺ +H (1s) collisions at energies from 0.01 eV to 1 keV using the hyperspherical close-coupling method. Good agreements with the previous calculations by the classical-trajectory Monte-Carlo method are found for total capture cross section, but not for partial cross sections, especially below about 200 eV/amu. We found that the total cross section is mainly due to the population of n=7 channels and only at energies above 50 eV/amu n = 5,6 channels begin to contribute to the total cross section

Conhecimento dos professores de matemáticas em formação sobre os produtos notáveis

La presente investigación indaga sobre el conocimiento de futuros profesores de matemáticas en relación con los productos notables. El estudio de corte cualitativo y descriptivo se desarrolla con estudiantes universitarios que cursan un programa de formación de profesores de matemáticas para el nivel bachillerato. Se utilizaron criterios de análisis relativos al Conocimiento Matemático para la Enseñanza como elementos teóricos que permitieron, a partir de la aplicación de un cuestionario, analizar los conocimientos manifestados por los profesores en formación. Se proporciona evidencia de la actividad matemática que realizan los estudiantes para profesor, al resolver tareas que involucran a los productos notables y su enseñanza. Los resultados informan de las inconsistencias en los conocimientos de los futuros docentes y sobre las fortalezas que manifiestan en los subdominios del Conocimiento Matemático para la Enseñanza, lo que permite establecer áreas de desarrollo en su formación.This paper studies preservice math teachers' knowledge regarding notable products. The qualitative and descriptive study is conducted with university students in a program for high school mathematics teachers. The theoretical elements used were analysis criteria related to Mathematical Knowledge for Teaching. This theoretical foundation allowed the analysis of the preservice teachers' knowledge through a questionnaire. The paper presents evidence of the mathematical activity of preservice teachers when solving tasks and lessons involving notable products. Results report the inconsistencies in preservice teachers' knowledge and the strengths that they manifest in the subdomains of Mathematical Knowledge for Teaching. These results suggest areas of development necessary for teacher training.Esta pesquisa investiga o conhecimento de futuros professores de matemática em relação a produtos notáveis. O estudo qualitativo e descritivo é realizado com estudantes universitários que cursam um programa de formação de professores de matemática para o nível de bacharelado. Foram utilizados critérios de análise relacionados ao Conhecimento Matemático para o Ensino como elementos teóricos que permitiram, a partir da aplicação de um questionário, analisar o conhecimento manifestado pelos professores em formação. É fornecida evidência da atividade matemática que os alunos para professor realizam ao resolver tarefas que envolvem produtos notáveis e seu ensino. Os resultados informam as inconsistências no conhecimento de futuros professores e sobre as fortalezas que manifestam nos subdomínios do Conhecimento Matemático para o Ensino, o que permite estabelecer áreas de desenvolvimento em sua formação

Fifty-year study of microplastics ingested by brachyuran and fish larvae in the central English North Sea

\ua9 2023 The Authors. Microplastics (MPs) are ubiquitous pollutants in marine environments. Among the many detrimental consequences of microplastic pollution, its consumption by marine biota is of particular relevance for human health, due to exposure through the food web. Long-term time-series biotic samples are overlooked sources of information for microplastics research. These collections are extremely valuable for the detection and monitoring of changes in marine environments. However, there are very few long-term studies (>10 years) of the uptake of microplastics by biota. Here, we used Dove Time Series planktonic samples (from 1971 to 2020) to assess the presence and prevalence of microplastics in the English North Sea coast over time. Fish and brachyuran larvae were selected due to their commercial importance and consequent implications for human health. A custom enzymatic digestion method was used to extract microplastics for FTIR-ATR polymer identification. An increasing cumulative trend in MP ingestion was identified. Cellophane and polyethylene terephthalate were the polymer types found most frequently in both taxa. Although a total higher microplastics uptake was observed in fish, consumption was not significantly different between taxa over time. Equally, results were not clearly related to microplastics shape or polymer type. This work did not find significant long-term evidence on the increasing uptake of microplastic particles by zooplankton over time. However, the results of this report identified additives, plasticisers, and other more complex and hazardous compounds that should not be released to the environment (e.g., bis-(2-hydroxyethyl) dimerate, propylene glycol ricinoleate) inside marine biota. The study detailed herein provides a case study for the use of long-term time-series in providing accurate assessments of microplastic pollution in marine biota

Non-singular Universes a la Palatini

It has recently been shown that f(R) theories formulated in the Palatini variational formalism are able to avoid the big bang singularity yielding instead a bouncing solution. The mechanism responsible for this behavior is similar to that observed in the effective dynamics of loop quantum cosmology and an f(R) theory exactly reproducing that dynamics has been found. I will show here that considering more general actions, with quadratic contributions of the Ricci tensor, results in a much richer phenomenology that yields bouncing solutions even in anisotropic (Bianchi I) scenarios. Some implications of these results are discussed.Comment: 4 pages, no figures. Contribution to the Spanish Relativity Meeting (ERE2010), 6-10 Sept. Granada, Spai

Peculiar outburst of A 0535+26 observed with INTEGRAL, RXTE and Suzaku

A normal outburst of the Be/X-ray binary system A0535+26 has taken place in August 2009. It is the fourth in a series of normal outbursts that have occured around the periastron passage of the source, but is unusual by starting at an earlier orbital phase and by presenting a peculiar double-peaked light curve. A first "flare" (lasting about 9 days from MJD 55043 on) reached a flux of 440 mCrab. The flux then decreased to less than 220 mCrab, and increased again reaching 440 mCrab around the periastron at MJD 55057. Target of Opportunity observations have been performed with INTEGRAL, RXTE and Suzaku. First results of these observations are presented, with special emphasis on the cyclotron lines present in the X-ray spectrum of the source, as well as in the pulse period and energy dependent pulse profiles of the source.Comment: 6 pages, Accepted for publication on PoS, Proceedings of "The Extreme sky: Sampling the Universe above 10 keV", held in Otranto (Italy) in October 200

CR1 Knops blood group alleles are not associated with severe malaria in the Gambia

The Knops blood group antigen erythrocyte polymorphisms have been associated with reduced falciparum malaria-based in vitro rosette formation (putative malaria virulence factor). Having previously identified single-nucleotide polymorphisms (SNPs) in the human complement receptor 1 (CR1/CD35) gene underlying the Knops antithetical antigens Sl1/Sl2 and McC(a)/McC(b), we have now performed genotype comparisons to test associations between these two molecular variants and severe malaria in West African children living in the Gambia. While SNPs associated with Sl:2 and McC(b+) were equally distributed among malaria-infected children with severe malaria and control children not infected with malaria parasites, high allele frequencies for Sl 2 (0.800, 1,365/1,706) and McC(b) (0.385, 658/1706) were observed. Further, when compared to the Sl 1/McC(a) allele observed in all populations, the African Sl 2/McC(b) allele appears to have evolved as a result of positive selection (modified Nei-Gojobori test Ka-Ks/s.e.=1.77, P-value <0.05). Given the role of CR1 in host defense, our findings suggest that Sl 2 and McC(b) have arisen to confer a selective advantage against infectious disease that, in view of these case-control study data, was not solely Plasmodium falciparum malaria. Factors underlying the lack of association between Sl 2 and McC(b) with severe malaria may involve variation in CR1 expression levels

Psychedelics Promote Structural and Functional Neural Plasticity.

Atrophy of neurons in the prefrontal cortex (PFC) plays a key role in the pathophysiology of depression and related disorders. The ability to promote both structural and functional plasticity in the PFC has been hypothesized to underlie the fast-acting antidepressant properties of the dissociative anesthetic ketamine. Here, we report that, like ketamine, serotonergic psychedelics are capable of robustly increasing neuritogenesis and/or spinogenesis both in vitro and in vivo. These changes in neuronal structure are accompanied by increased synapse number and function, as measured by fluorescence microscopy and electrophysiology. The structural changes induced by psychedelics appear to result from stimulation of the TrkB, mTOR, and 5-HT2A signaling pathways and could possibly explain the clinical effectiveness of these compounds. Our results underscore the therapeutic potential of psychedelics and, importantly, identify several lead scaffolds for medicinal chemistry efforts focused on developing plasticity-promoting compounds as safe, effective, and fast-acting treatments for depression and related disorders

Últimos avances sobre los mecanismos reguladores de la absorción de fósforo

P as an essential nutrient has been researched for many years, but now, due to the polluting effect of this mineral, that is released into the environment through the manure of domestic animals, new research lines has come up with the aim to identify nutritional requirements and determine the factors affecting excretion. Absorption is perhaps one of the factors that influence the metabolic kinetics of P, and this in turn, is influenced by several factors to keep its homeostasis. There are differences between ruminant and monogastric animals in relation to the way P is metabolized in the body, however intestinal absorption systems have similar characteristics. The discovery of several P transport systems in the intestinal epithelial cell membranes, and several substances that affect it, has helped to clarify the metabolism of this mineral and why is completely linked to Ca metabolism. Therefore, is interesting to consider these features to increase the use of P in different physiological stages of domestic animals, avoiding its excessive excretion, when the absorption capacity is diminished, or increasing dietary P, when the absorption is increased in stages mineral replacement.Como nutriente esencial el P ha sido investigado durante muchos años, pero en la actualidad, debido al efecto contaminante de este mineral, liberado en el ambiente a través de las excretas de los animales domésticos, nuevas líneas de investigación han aparecido con miras a determinar las exigencias nutricionales y a determinar los factores que afectan la excreción. La absorción es tal vez uno de los factores que más influencia la cinética metabólica del P, y esta a su vez, es influenciada por varios factores para mantener estable su homeostasis. Existen diferencias entre los animales rumiantes y monogástricos en relación a la forma como el P es metabolizado en el organismo, sin embargo los sistemas de absorción intestinal poseen características semejantes. El descubrimiento de varios sistemas de transporte del P en las membranas celulares del epitelio intestinal, y de varias sustancias que lo afectan, ha contribuido a esclarecer el metabolismo de este mineral y de porqué está completamente acoplado al metabolismo del Ca. Por lo tanto, resulta interesante considerar estas características para aumentar la utilización del P en las diferentes etapas fisiológicas de los animales domésticos, evitando su excesiva excreción, cuando la capacidad de absorción esta disminuida, o incrementando el P dietético, cuando su absorción se encuentra aumenta en las etapas de reposición mineral

Study of the many fluorescent lines and the absorption variability in GX 301-2 with XMM-Newton

We present an in-depth study of the High Mass X-ray Binary (HMXB) GX 301-2 during its pre-periastron flare using data from the XMM-Newton satellite. The energy spectrum shows a power law continuum absorbed by a large equivalent hydrogen column on the order of 10^24 cm^2 and a prominent Fe K-alpha fluorescent emission line. Besides the Fe K-alpha line, evidence for Fe K-beta, Ni K-alpha, Ni K-beta, S K-alpha, Ar K-alpha, Ca K-alpha, and Cr K-alpha fluorescent lines is found. The observed line strengths are consistent with fluorescence in a cold absorber. This is the first time that a Cr K-alpha line is seen in emission in the X-ray spectrum of a HMXB. In addition to the modulation by the strong pulse period of ~685 sec the source is highly variable and shows different states of activity. We perform time-resolved as well as pulse-to-pulse resolved spectroscopy to investigate differences between these states of activity. We find that the fluorescent line fluxes are strongly variable and generally follow the overall flux. The N_H value is variable by a factor of 2, but not correlated to the continuum normalization. We find an interval of low flux in the light curve in which the pulsations cease almost completely, without any indication of an increasing absorption column. We investigate this dip in detail and argue that it is most likely that during the dip the accretion ceased and the afterglow of the fluorescent iron accounted for the main portion of the X-ray flux. A similar dip was found earlier in RXTE data, and we compare our findings to these resultsComment: 13 pages, 13 Figures, published in A&