Influence of solar activity on hydrological processes

International audienceThe relationship between solar activity and the water volumes of lakes is searched here by means of correlational and spectral analysis methods. The level of two lakes, Pátzcuaro in México and Tchudskoye in Russia, together with solar activity indexes are used for the analysis. It is found that the source of the oscillation mechanism of the level of those lakes is the solar activity cycle through its influence on the magnetosphere and the terrestrial atmosphere. The present study allows for the development of long-period prognostic of water volumes of big lakes

Relativistic proton production at the sun in the October 28th, 2003 solar event

Abstract In order to infer about the origin of solar relativistic particles (SRP) from the particle event of October 28th, 2003, we proceed to do a confrontation of the experimental energy spectra with the theoretical spectra derived from a transport equation for stochastic acceleration. On basis to a two-source model of particle generation, one of which is associated with an expanding magnetic loop, we solve the transport equation including adiabatic losses simultaneously with the stochastic acceleration process. The confrontation shows that there are two different populations during this event, one of which, the so-called ''delayed component'' may be correctly described by stochastic acceleration, but not the so-called ''prompt component''. We found that the required acceleration efficiencies turn to be very high, so that for this particular event, adiabatic cooling is practically negligible as far as the energy spectrum is concerned. Qualitative inferences point toward a dominated Alfven accelerating turbulence. Our results provide a new support to the existence of two relativistic particle populations in some solar relativistic particle events

Characterization of endogenous Kv1.3 channel isoforms in T cells

Producción CientíficaVoltage-dependent potassium channel Kv1.3 plays a key role on T-cell activation; however, lack of reliable antibodies has prevented its accurate detection under endogenous circumstances. To overcome this limitation, we created a Jurkat T-cell line with endogenous Kv1.3 channel tagged, to determine the expression, location, and changes upon activation of the native Kv1.3 channels. CRISPR-Cas9 technique was used to insert a Flag-Myc peptide at the C terminus of the KCNA3 gene. Basal or activated channel expression was studied using western blot analysis and imaging techniques. We identified two isoforms of Kv1.3 other than the canonical channel (54 KDa) differing on their N terminus: a longer isoform (70 KDa) and a truncated isoform (43 KDa). All three isoforms were upregulated after T-cell activation. We focused on the functional characterization of the truncated isoform (short form, SF), because it has not been previously described and could be present in the available Kv1.3−/− mice models. Overexpression of SF in HEK cells elicited small amplitude Kv1.3-like currents, which, contrary to canonical Kv1.3, did not induce HEK proliferation. To explore the role of endogenous SF isoform in a native system, we generated both a knockout Jurkat clone and a clone expressing only the SF isoform. Although the canonical isoform (long form) localizes mainly at the plasma membrane, SF remains intracellular, accumulating perinuclearly. Accordingly, SF Jurkat cells did not show Kv1.3 currents and exhibited depolarized resting membrane potential (VM), decreased Ca2+ influx, and a reduction in the [Ca2+]i increase upon stimulation. Functional characterization of these Kv1.3 channel isoforms showed their differential contribution to signaling pathways involved in formation of the immunological synapse. We conclude that alternative translation initiation generates at least three endogenous Kv1.3 channel isoforms in T cells that exhibit different functional roles. For some of these functions, Kv1.3 proteins do not need to form functional plasma membrane channels.Ministerio de Economía y Competitividad (grant PID 2020‐118517RB‐I00)Junta de Castilla y León (grants VA172P20) and (CLU-2019-02)Funds from Institut Curie, INSERM,Agence Nationale de la Recherche RetroTact (ANR‐20CE15‐0009‐01,ANR‐10‐IDEX‐0001‐02 PSL*, and ANR‐11‐LABX‐0043)Fondation pour la Recherche Médicale FRM (EQU202003010280

P-P Total Cross Sections at VHE from Accelerator Data

Comparison of P-P total cross-sections estimations at very high energies - from accelerators and cosmic rays - shows a disagreement amounting to more than 10 %, a discrepancy which is beyond statistical errors. Here we use a phenomenological model based on the Multiple-Diffraction approach to successfully describe data at accelerator energies. The predictions of the model are compared with data On the basis of regression analysis we determine confident error bands, analyzing the sensitivity of our predictions to the employed data for extrapolation. : using data at 546 and 1.8 TeV, our extrapolations for p-p total cross-sections are only compatible with the Akeno cosmic ray data, predicting a slower rise with energy than other cosmic ray results and other extrapolation methods. We discuss our results within the context of constraints in the light of future accelerator and cosmic ray experimental results.Comment: 26 pages aqnd 11 figure

The role of fluctuational acceleration in the generation of solar particles

La aceleración estocástica de partículas es fundamentalmente un proceso de difusión en el espacio fase de energía. A pesar del comportamiento estadístico del proceso de difusión, se establece una tendencia promedio de ganancia de energía de carácter determinístico, que es usualmente designada como aceleración sistemática. En el caso particular de la Física de Rayos Cósmicos, a menudo se considera solamente la tasa de aceleración sistemática, ignorándose los efectos de dispersión en el espacio de energía, los cuales son identificados como una tasa fluctuacional de aceleración. Sin embargo, ha sido demostrado por varios autores que, dependiendo de las propiedades de la turbulencia involucrada en la aceleración, la tasa de aceleración sistemática puede ser ineficiente en algunos casos, e incluso ser nulificada por procesos competitivos de perdida de energía, de tal forma que la producción de partículas energéticas es debida exclusivamente a los efectos de dispersión en energía. En este trabajo se calcula separadamente la contribución de ambas tasas de cambio de energía, para evaluar su importancia en la producción de partículas energéticas. Se consideran dos mecanismos de aceleración, el proceso Fermi y la aceleración resonante por turbulencia magnetosónica (cuando el armónico S=O). Se resuelve analíticamente la ecuación de transporte para el caso estacionario y para el caso dependiente del tiempo. Se encuentra que la contribución de los efectos de dispersión en energía al espectro de partículas al nivel de sus fuentes no puede ser considerada como una mera fluctuación en el flujo de partículas, sino que representa en algunos casos una importante sobre-producción de partículas y en otros casos una importante depresión de partículas en el espectro de aceleración. La relevancia de esos efectos de difusión en energía depende principalmente de la eficiencia del proceso acelerador, la correlación entre la población inicial de partículas con el espectro de velocidades de la turbulencia, y de la proporción relativa entre las diferentes clases de interacciones de las partículas con los agentes aceleradores. Se establecen los límites bajo los cuales los efectos de difusión en energía podrán ser ignorados relativos a la tasa de aceleración sistemática. Se concluye que, con algunas excepciones, en el caso estacionario el espectro de energía derivado exclusivamente con base en la tasa sistemática no describe el flujo real de las partículas aceleradas, y que el apelativo de tasa fluctuacional de aceleración no es apropiado. El calculo de flujo de radiación secundaria con base al espectro de las partículas aceleradas debe de tomar en consideración la limitante de considerar únicamente la tasa de aceleración sistemática. doi: https://doi.org/10.22201/igeof.00167169p.1994.33.2.47

Prediction of interplanetary shock waves using cosmic ray fluctuations

En el trabajo se propone usar métodos espectrales y autorregresivos para mejorar los procesos de detección de variaciones en la composición espectral de la intensidad de rayos cósmicos y de la componente Bz del campo magnético interplanetario. Usando esta metodología, se determinaron algunas regularidades en la variación del espectro de potencias de la intensidad de los rayos cósmicos antes del arribo de una onda de choque a la Tierra. Así, el arribo de la onda de choque es precedido por la aparición de una onda con período de 4 a 8 horas en el espectro de potencias de la componente Bz del campo magnético. Los resultados confirman la posibilidad de usar los rayos cósmicos y la actividad geomagnética para el diagnóstico del medio interplanetario y la predicción del arribo de ondas de choque a la Tierra, con una anticipación de 1 a 2 días. doi: https://doi.org/10.22201/igeof.00167169p.1998.37.2.39

The neuroprotective transcription factor ATF5 is decreased and sequestered into polyglutamine inclusions in Huntington’s disease

Activating transcription factor-5 (ATF5) is a stress-response transcription factor induced upon different cell stressors like fasting, amino-acid limitation, cadmium or arsenite. ATF5 is also induced, and promotes transcription of anti-apoptotic target genes like MCL1, during the unfolded protein response (UPR) triggered by endoplasmic reticulum stress. In the brain, high ATF5 levels are found in gliomas and also in neural progenitor cells, which need to decrease their ATF5 levels for differentiation into mature neurons or glia. This initially led to believe that ATF5 is not expressed in adult neurons. More recently, we reported basal neuronal ATF5 expression in adult mouse brain and its neuroprotective induction during UPR in a mouse model of status epilepticus. Here we aimed to explore whether ATF5 is also expressed by neurons in human brain both in basal conditions and in Huntington’s disease (HD), where UPR has been described to be partially impaired due to defective ATF6 processing. Apart from confirming that ATF5 is present in human adult neurons, here we report accumulation of ATF5 within the characteristic polyglutamine-containing neuronal nuclear inclusions in brains of HD patients and mice. This correlates with decreased levels of soluble ATF5 and of its antiapoptotic target MCL1. We then confirmed the deleterious effect of ATF5 deficiency in a Caenorhabditis elegans model of polyglutamine-induced toxicity. Finally, ATF5 overexpression attenuated polyglutamine-induced apoptosis in a cell model of HD. These results reflect that decreased ATF5 in HD—probably secondary to sequestration into inclusions—renders neurons more vulnerable to mutant huntingtin-induced apoptosis and that ATF5-increasing interventions might have therapeutic potential for HD.CiberNed-ISCIII collaborative Grants PI2013/09-2 and PI2015-2/06-3 and by grants from Spanish Ministry of Economy and Competitiveness (MINECO): SAF2009-08233 and SAF2015-65371-R to JJL, by Fundación BBVA and by Fundación Ramón Arece