A Sturm-Liouville equation on the crossroads of continuous and discrete hypercomplex analysis

The paper studies discrete structural properties of polynomials that play an important role in the theory of spherical harmonics in any dimensions. These polynomials have their origin in the research on problems of harmonic analysis by means of generalized holomorphic (monogenic) functions of hypercomplex analysis. The Sturm-Liouville equation that occurs in this context supplements the knowledge about generalized Vietoris number sequences Vn, first encountered as a special sequence (corresponding to n=2) by Vietoris in connection with positivity of trigonometric sums. Using methods of the calculus of holonomic differential equations, we obtain a general recurrence relation for Vn, and we derive an exponential generating function of Vn expressed by Kummer's confluent hypergeometric function.This work was supported by Portuguese funds through the CMAT—Research Centre of Mathematics of University of Minho—and through the CIDMA-Center of Research and Development in Mathematics and Applications (University of Aveiro) and the Portuguese Foundation for Science and Technology (“FCT - Fundação para a Ciência e Tecnologia”), within projects UIDB/00013/2020, UIDP/00013/2020, UIDB/04106/2020 , and UIDP/04106/2020

How Will the Hematopoietic System Deal with Space Radiation on the Way to Mars?

Traveling through deep space raises challenges to biological systems that have not been fully appreciated or addressed. In addition to the lack of gravity, the space environment includes exposure to charged remnants of supernova explosions beyond our solar system that travels with enormous velocities and energies, called HZE (high atomic number Z and energy E) particles and have the potential to disrupt chemical bonds within the human body though ionization. As a process, the collision of charged particles with matter is not new to physicists and biologists on Earth, and we have extensive data on low-linear energy transfer (LET) ionizing radiation from both accidental and deliberate exposures, dating back to the discovery of radioactive isotopes by Madame Curie. One of the primary morbidities associated with radiation exposure is the challenge to the hematopoietic system. The purpose of the current review is to discuss some of the basic tenants of hierarchical tissue systems by elaborating the effects of radiation damage to the hematopoietic stem cell and how terrestrial radiation and space radiation differ.The last few decades of research in the field of space radiation, which consists of high-LET ions of 4He, 12C, 16O, 28Si, 48Ti, and 56Fe, and low-LET protons, have shown that there is a significantly more deleterious impact on the hematopoietic system by the high-LET ions compared to protons, X-rays, and γ-rays. Ground-based high-LET radiation experiments have shown not only in vitro and in vivo adverse effects on hematopoietic stem cells, but also that human leukemia can be induced in humanized mouse models.High-LET space radiation is more lethal to hematopoietic stem cells compared to low-LET radiation, but further research is required in order to understand the impact of high-LET radiation on hematopoietic malignancies. Most of the ground-based studies, because of technical difficulties and cost issues, have been carried out at high dose rates with only one ion species at a time. What remains to be clearly described, however, is the potential damage to the hematopoietic system from exposure to the more complex types of radiation at low dose rates that will occur during space travel and how space agencies can sufficiently protect our astronauts

The Magmatic Gas Signature of Pacaya Volcano, With Implications for the Volcanic CO2Flux From Guatemala

Pacaya volcano in Guatemala is one of the most active volcanoes of the Central American Volcanic Arc (CAVA). However, its magmatic gas signature and volatile output have received little attention to date. Here, we present novel volcanic gas information from in-situ (Multi-GAS) and remote (UV camera) plume observations in January 2016. We find in-plume H2O/SO2and CO2/SO2ratios of 2-20 and 0.6-10.5, and an end-member magmatic gas signature of 80.5 mol. % H2O, 10.4 mol. % CO2, and 9.0 mol. % SO2. The SO2flux is evaluated at 885 ± 550 tons/d. This, combined with co-acquired volcanic plume composition, leads to H2O and CO2fluxes of 2,230 ± 1,390 and 700 ± 440, and a total volatile flux of ∼3,800 tons/d. We use these results in tandem with previous SO2flux budgets for Fuego and Santiaguito to estimate the total volcanic CO2flux from Guatemala at ∼1,160 ± 600 tons/day. This calculation is based upon CO2/total S (St) ratios for Fuego (1.5 ± 0.75) and Santiaguito (1.4 ± 0.75) inferred from a gas (CO2/Stratio) versus trace-element (Ba/La ratio) CAVA relationship. The H2O-poor and low CO2/Stratio (∼1.0-1.5) signature of Pacaya gas suggests dominant mantle-wedge derivation of the emitted volatiles. This is consistent with3He/4He ratios in olivine hosted fluid inclusions (FIs), which range between 8.4 and 9.0 Ra (being Ra the atmospheric3He/4He ratio) at the upper limit of MORB range (8 ± 1 Ra). These values are the highest ever measured in CAVA and among the highest ever recorded in arc volcanoes worldwide, indicating negligible4He contributions from the crust/slab