Experimental Test of Higher-Order Electron-Capture Processes in Collisions of Fast Protons with Atomic Hydrogen

We present measurements of the angular distribution of fast hydrogen atoms formed by electron capture of 2.8- and 5.0-MeV protons in atomic hydrogen. In the angular region of the Thomas peak (0.47 mrad) the experimental results obtained with this pure three-body collision system are in reasonable agreement with a strong-potential Born calculation and the impulse approximation, but not with other higher-order theories

Resonant Transfer and Excitation in Li-Like F Colliding with H₂

We have measured coincidences between x rays and projectiles that have captured one electron in F6+ + H2 collisions at projectile energies between 15 and 33 MeV. The cross sections for capture and simultaneous x-ray emission as a function of projectile energy show clear structures. Indications of an unexpectedly high population of high-n states predominantly formed by resonant transfer and excitation (RTE) were found. Above the Kln (n\u3e1) RTE resonance energies another maximum was observed

Repurposing the Electron Transfer Reactant Phenazine Methosulfate (PMS) for the Apoptotic Elimination of Malignant Melanoma Cells through Induction of Lethal Oxidative and Mitochondriotoxic Stress

Redox-directed pharmacophores have shown potential for the apoptotic elimination of cancer cells through chemotherapeutic induction of oxidative stress. Phenazine methosulfate (PMS), a N-alkylphenazinium cation-based redox cycler, is used widely as an electron transfer reactant coupling NAD(P)H generation to the reduction of tetrazolium salts in biochemical cell viability assays. Here, we have explored feasibility of repurposing the redox cycler PMS as a superoxide generating chemotherapeutic for the pro-oxidant induction of cancer cell apoptosis. In a panel of malignant human melanoma cells (A375, G361, LOX), low micromolar concentrations of PMS (1-10 μM, 24 h) displayed pronounced apoptogenicity as detected by annexin V-ITC/propidium iodide flow cytometry, and PMS-induced cell death was suppressed by antioxidant (NAC) or pan-caspase inhibitor (zVAD-fmk) cotreatment. Gene expression array analysis in A375 melanoma cells (PMS, 10 µM; 6 h) revealed transcriptional upregulation of heat shock (HSPA6, HSPA1A), oxidative (HMOX1) and genotoxic (EGR1, GADD45A) stress responses, confirmed by immunoblot detection demonstrating upregulation of redox regulators (NRF2, HO-1, HSP70) and modulation of pro- (BAX, PUMA) and anti-apoptotic factors (Bcl-2, Mcl-1). PMS-induced oxidative stress and glutathione depletion preceded induction of apoptotic cell death. Furthermore, the mitochondrial origin of PMS-induced superoxide production was substantiated by MitoSOX-Red live cell fluorescence imaging, and PMS-induced mitochondriotoxicity (as evidenced by diminished transmembrane potential and oxygen consumption rate) was observable at early time points. After demonstrating NADPH-driven (SOD-suppressible) superoxide radical anion generation by PMS employing a chemical NBT reduction assay, PMS-induction of oxidative genotoxic stress was substantiated by quantitative Comet analysis that confirmed the introduction of formamido-pyrimidine DNA glycosylase (Fpg)-sensitive oxidative DNA lesions in A375 melanoma cells. Taken together, these data suggest feasibility of repurposing the biochemical reactant PMS as an experimental pro-oxidant targeting mitochondrial integrity and redox homeostasis for the apoptotic elimination of malignant melanoma cells.National Institutes of Health [1R01CA229418, 1R03CA230949, ES007091, ES006694]; National Institutes of Health (Arizona Cancer Center Support Grant) [CA023074]Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Recomendaciones para la evaluación en entornos virtuales

Los procesos de enseñanza y aprendizaje que tienen lugar en entornos virtuales ponen tanto a enseñantes como estudiantes, frente a nuevos desafíos y a una revisión de las formas de enseñar, aprender y evaluar. La enseñanza a través de aulas virtuales requiere explicar conceptos en forma clara, proponer la realización de prácticas de aprendizaje que promuevan la participación, promover conversaciones, dar indicaciones sobre cómo abordar la bibliografía, evaluar tareas que exijan la construcción de una respuesta elaborada. Sin embargo, el escaso tiempo que se ha tenido en este tiempo de pandemia para “virtualizar” los contenidos, las prácticas de aprendizaje, el diálogo y el ambiente de la clase, llevan a tener ciertos recaudos en la puesta en marcha de esta modalidad de enseñanza a través de soportes digitales.Fil: Castillo, B. Universidad Nacional de Córdoba. Facultad de Odontología. Asesoría Pedagógica; Argentina.Fil: Tessio Conca, A. Universidad Nacional de Córdoba. Facultad de Odontología. Asesoría Pedagógica; Argentina.Fil: Rezzónico, M. S. Universidad Nacional de Córdoba. Facultad de Odontología. Asesoría Pedagógica; Argentina.Fil: Allende Posse, M. Universidad Nacional de Córdoba. Facultad de Odontología. Asesoría Pedagógica; Argentina.Fil: Justiniano, M. S. Universidad Nacional de Córdoba. Facultad de Odontología. Asesoría Pedagógica; Argentina

Pautas pedagógicas y comunicacionales para la educación en tiempos de emergencia: la enseñanza en la virtualidad

La medida de aislamiento establecida ante la propagación del coronavirus nos sorprendió a todos. Bajo la consigna de dar continuidad a la actividad docente en el grado, sin la posibilidad de una mínima organización y sin demasiada experiencia previa, debimos asumir el desarrollo de la enseñanza en espacios virtuales. Nos encontramos ahora ante la proximidad del inicio del segundo semestre del año, que se estima se desarrollará bajo condiciones de una “nueva normalidad”. Esto implicará el regreso a las aulas bajo condiciones restrictivas en cuanto a espacios y cantidad de personas presentes por clase, lo cual dará lugar a la continuidad de la enseñanza virtual, bien sea a través de un formato totalmente en línea, o bajo la posibilidad de un formato mixto, que combine instancias presenciales y en línea. Estamos, por tanto, ante el desafío de planear una propuesta que suponga la genuina integración de ambas instancias.publishedVersionRezzónico, M. S. Universidad Nacional de Córdoba. Facultad de Odontología. Asesoría Pedagógica; Argentina.Castillo, B. Universidad Nacional de Córdoba. Facultad de Odontología. Asesoría Pedagógica; Argentina.Tessio Conca, A. Universidad Nacional de Córdoba. Facultad de Odontología. Asesoría Pedagógica; Argentina.Allende Posse, M. Universidad Nacional de Córdoba. Facultad de Odontología. Asesoría Pedagógica; Argentina.Justiniano, M. S. Universidad Nacional de Córdoba. Facultad de Odontología. Asesoría Pedagógica; Argentina

Population of Highly Excited Intermediate Resonance States by Electron Transfer and Excitation

Coincidences between two sulfur K x rays were detected from collisions of hydrogenlike S ions with H2 gas in the projectile energy range between 150 and 225 MeV. These K x rays are emitted in the decay of doubly excited states formed in the collisions via transfer and excitation. The excitation function for two coincident Kβ transitions peaks at about 175 MeV, slightly above the expected KMM resonance energy for resonant transfer and excitation (RTE). This demonstrates the occurrence of ΔN≥2 transitions (i.e., KMM and higher resonances) in the RTE process. The cross sections for the population of the very highly excited states are higher than those predicted by theoretical calculations that use dielectronic recombination rates folded with the Compton profile for the bound electrons

Multiphoton radiative recombination of electron assisted by laser field

In the presence of an intensive laser field the radiative recombination of the continuum electron into an atomic bound state generally is accompanied by absorption or emission of several laser quanta. The spectrum of emitted photons represents an equidistant pattern with the spacing equal to the laser frequency. The distribution of intensities in this spectrum is studied employing the Keldysh-type approximation, i.e. neglecting interaction of the impact electron with the atomic core in the initial continuum state. Within the adiabatic approximation the scale of emitted photon frequencies is subdivided into classically allowed and classically forbidden domains. The highest intensities correspond to emission frequencies close to the edges of classically allowed domain. The total cross section of electron recombination summed over all emitted photon channels exhibits negligible dependence on the laser field intensity.Comment: 14 pages, 5 figures (Figs.2-5 have "a" and "b" parts), Phys.Rev.A accepted for publication. Fig.2b is presented correctl

Ecological-economic sustainability of the Baltic cod fisheries under ocean warming and acidification

Human-induced climate change such as ocean warming and acidification, threatens marine ecosystems and associated fisheries. In the Western Baltic cod stock socio-ecological links are particularly important, with many relying on cod for their livelihoods. A series of recent experiments revealed that cod populations are negatively affected by climate change, but an ecological-economic assessment of the combined effects, and advice on optimal adaptive management are still missing. For Western Baltic cod, the increase in larval mortality due to ocean acidification has experimentally been quantified. Time-series analysis allows calculating the temperature effect on recruitment. Here, we include both processes in a stock-recruitment relationship, which is part of an ecological-economic optimization model. The goal was to quantify the effects of climate change on the triple bottom line (ecological, economic, social) of the Western Baltic cod fishery. Ocean warming has an overall negative effect on cod recruitment in the Baltic. Optimal management would react by lowering fishing mortality with increasing temperature, to create a buffer against climate change impacts. The negative effects cannot be fully compensated, but even at 3 °C warming above the 2014 level, a reduced but viable fishery would be possible. However, when accounting for combined effects of ocean warming and acidification, even optimal fisheries management cannot adapt to changes beyond a warming of +1.5° above the current level. Our results highlight the need for multi-factorial climate change research, in order to provide the best available, most realistic, and precautionary advice for conservation of exploited species as well as their connected socio-economic systems